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Complex OsH4{κ3-P,O,P-[xant(PiPr2)2]} (1) activates the Si–H bond of triethylsilane, triphenylsilane, and 1,1,1,3,5,5,5-heptamethyltrisiloxane to give the silyl-osmium(IV)-trihydride derivatives OsH3(SiR3){κ3-P,O,P-[xant(PiPr2)2]} [SiR3 = SiEt3 (2), SiPh3 (3), SiMe(OSiMe3)2 (4)] and H2. The activation takes place via an unsaturated tetrahydride intermediate, resulting from the dissociation of the oxygen atom of the pincer ligand 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(PiPr2)2). This intermediate, which has been trapped to form OsH4{κ2-P,P-[xant(PiPr2)2]}(PiPr3) (5), coordinates the Si–H bond of the silanes to subsequently undergo a homolytic cleavage. Kinetics of the reaction along with the observed primary isotope effect demonstrates that the Si–H rupture is the rate-determining step of the activation. Complex 2 reacts with 1,1-diphenyl-2-propyn-1-ol and 1-phenyl-1-propyne. The reaction with the former affords Os{C≡CC(OH)Ph2}2{═C═CHC(OH)Ph2}{κ3-P,O,P-[xant(PiPr2)2]} (6), which catalyzes the conversion of the propargylic alcohol into (E)-2-(5,5-diphenylfuran-2(5H)-ylidene)-1,1-diphenylethan-1-ol, via (Z)-enynediol. In methanol, the hydroxyvinylidene ligand of 6 dehydrates to allenylidene, generating Os{C≡CC(OH)Ph2}2{═C═C═CPh2}{κ3-P,O,P-[xant(PiPr2)2]} (7). The reaction of 2 with 1-phenyl-1-propyne leads to OsH{κ1-C,η2-[C6H4CH2CH═CH2]}{κ3-P,O,P-[xant(PiPr2)2]} (8) and PhCH2CH═CH(SiEt3)., Financial support from the MICIN/AEI/10.13039/501100011033 (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged.

The reaction of the hexahydride OsH6(PiPr3)2 with a P,Ge,P-germylene-diphosphine affords an osmium tetrahydride derivative bearing a Ge,P-chelate, which arises from the hydrogenolysis of a P–C(sp3) bond. This Os(IV)–Ge(II) compound is a pioneering example of a bifunctional catalyst based on the coordination of a σ-donor acid, which is active in the dehydrogenation of formic acid to H2 and CO2. The kinetics of the dehydrogenation, the characterization of the resting state of the catalysis, and DFT calculations point out that the hydrogen formation (the fast stage) exclusively occurs on the coordination sphere of the basic metal center, whereas both the metal center and the σ-donor Lewis acid cooperatively participate in the CO2 release (the rate-determining step). During the process, the formate group pivots around the germanium to approach its hydrogen atom to the osmium center, which allows its transfer to the metal and the CO2 release., Financial support was provided by the MICINN of Spain (PID2020-115286GB-I00/AEI/10.13039/501100011033, RED2018-102387-T, and PID2019-104652GB-I00), Gobierno de Aragón (E06_20R and LMP148_18), FEDER, and FSE.

The silylation of a phosphine of OsH6(PiPr3)2 is performed via net-metathesis between Si−C(spn) and H−C(sp3) σ-bonds (n=2, 3). Complex OsH6(PiPr3)2 activates the Si−H bond of Et3SiH and Ph3SiH to give OsH5(SiR3)(PiPr3)2, which yield OsH4{κ1-P,η2-SiH-[iPr2PCH(Me)CH2SiR2H]}(PiPr3) and R−H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first-order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state. It displays selectivity, releasing the hydrocarbon resulting from the rupture of the weakest Si-substituent bond, when the silyl ligand bears different substituents. Accordingly, reactions of OsH6(PiPr3)2 with dimethylphenylsilane, and 1,1,1,3,5,5,5-heptamethyltrisiloxane afford OsH5(SiR2R′)(PiPr3)2, which evolve into OsH4{κ1-P,η2-GeH-[iPr2PCH(Me)CH2SiR2H]}(PiPr3) (R=Me, OSiMe3) and R′−H (R′=Ph, Me). Exchange reaction is extended to Et3GeH. The latter reacts with OsH6(PiPr3)2 to give OsH5(GeEt3)(PiPr3)2, which loses ethane to form OsH4{κ1-P,η2-GeH-[iPr2PCH(Me)CH2GeEt2H]}(PiPr3)., Financial support from the MCIN/AEI/10.13039/501100011033 (Projects PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and LMP23_21), FEDER, and the European Social Fund is gratefully acknowledged. E. R. thanks the MCIN for her FPI contract (PRE2018-085398, “ESF investing in your future”).

To prepare new phosphorescent iridium(III) emitters, 2-phenyl-6-(1-phenyl-1-(pyridin-2-yl)ethyl)pyridine (H2L) has been designed and its reactions with [Ir(μ-Cl)(η4-COD)]2 (1, COD = 1,5-cyclooctadiene) have been studied. The products obtained depend on the refluxing temperature of the solvent. Thus, complexes Ir(κ4-C,C′,N,N′-L)Cl(CO) (2), [Ir(η4-COD)(κ2-N,N′-H2L)][IrCl2(η4-COD)] (3), and [Ir(μ-Cl)(κ4-C,C′,N,N′-L)]2 (4) have been formed in 2-ethoxyethanol, propan-2-ol, and 1-phenylethanol, respectively. Complex 4 reacts with K(acac) to give the acetylacetonate derivative Ir(κ4-C,C′,N,N′-L)(acac) (5). Complexes 2 and 5 are efficient blue-green and green emitters of classes [6tt+1m+2m] and [6tt+3b], respectively. They display lifetimes in the range of 1.1–4.5 μs and high quantum yields (0.54–0.87) in both PMMA films and 2-MeTHF at room temperature., Financial support from the MINECO of Spain [Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T], Gobierno de Aragón (Group E06_20R and Project LMP148_18), FEDER, and the European Social Fund is acknowledged.

The transformation of alkyl nitriles to symmetrical and asymmetrical secondary aliphatic amines promoted by the hexahydride complex OsH6(PiPr3)2 (1) is described, and the mechanisms of the reactions involved are established. Complex 1 catalyzes the aforementioned transformations of aryl-, pyridyl-, and alkoxy-functionalized alkyl nitriles with linear or branched chains. The formation of the secondary amines involves primary imines, primary amines, and secondary imines as organic intermediates. The reactions take place under mild conditions (toluene, 100 °C, and 4 bar of H2). Stoichiometric reactions of 1 with pivalonitrile and 2-methoxyacetonitrile have allowed us to isolate the trihydride azavinylidene derivatives OsH3{═N═CHR}(PiPr3)2 (R = tBu (3), CH2OMe (4)). Their formation involves the insertion of the N–C triple bond of the substrates into an Os–H bond of the unsaturated tetrahydride OsH4(PiPr3)2 (A), which is generated by reductive elimination of H2 from the hexahydride precursor. The reaction of these trihydride azavinylidene species with H2 is the key step for the reduction of the N–C triple bond of the nitriles. In the absence of H2, the attack of A to the azavinylidene ligand produces the rupture of its C(sp2)–C(sp3) bond. As a consequence of this attack and the presence of primary imines and amines in the reaction media, the binuclear complexes (PiPr3)2H4Os(μ-CN)OsH3{κ1-N-(NH═CHCH2OMe)}(PiPr3)2 (5) and (PiPr3)2H4Os(μ-CN)OsH3{κ1-N-(NH2CH2CH2OMe)}(PiPr3)2 (6) have been isolated and characterized by X-ray diffraction analysis, for 2-methoxyacetonitrile. DFT calculations reveal noticeable similarities between the hydrogenations of nitriles to primary imines and those of primary imines to primary amines., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

Reactions of the hexahydride OsH6(PiPr3)2 (1) with 2-butyne and 3-hexyne and the behavior of the resulting species toward pinacolborane (pinBH) have been investigated in the search for new hydroboration processes. Complex 1 reacts with 2-butyne to give 1-butene and the osmacyclopropene OsH2(η2-C2Me2)(PiPr3)2 (2). In toluene, at 80 °C, the coordinated hydrocarbon isomerizes into a η4-butenediyl form to afford OsH2(η4-CH2CHCHCH2)(PiPr3)2 (3). Isotopic labeling experiments indicate that the isomerization involves Me-to-COs hydrogen 1,2-shifts, which take place through the metal. The reaction of 1 with 3-hexyne gives 1-hexene and OsH2(η2-C2Et2)(PiPr3)2 (4). Similarly to 2, complex 4 evolves to η4-butenediyl derivatives OsH2(η4-CH2CHCHCHEt)(PiPr3)2 (5) and OsH2(η4-MeCHCHCHCHMe)(PiPr3)2 (6). In the presence of pinBH, complex 2 generates 2-pinacolboryl-1-butene and OsH{κ2-H,H-(H2Bpin)}(η2-HBpin)(PiPr3)2 (7). According to the formation of the borylated olefin, complex 2 is a catalyst precursor for the migratory hydroboration of 2-butyne and 3-hexyne to 2-pinacolboryl-1-butene and 4-pinacolboryl-1-hexene. During the hydroboration, complex 7 is the main osmium species. The hexahydride 1 also acts as a catalyst precursor, but it requires an induction period that causes the loss of 2 equiv of alkyne per equiv of osmium., Financial support from the MICIN/AEI/10.13039/ 501100011033 of Spain (Projects PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged.

Alkynyl ligands stabilize dimers [Ir(μ-X)(3b)2]2 with a cis disposition of the heterocycles of the 3b ligands, in contrast to chloride. Thus, the complexes of this class─cis-[Ir(μ2-η2-C≡CPh){κ2-C,N-(C6H4-Isoqui)}2]2 (Isoqui = isoquinoline) and cis-[Ir(μ2-η2-C≡CR){κ2-C,N-(MeC6H3-py)}2]2 (R = Ph, tBu)─have been prepared in high yields, starting from the dihydroxo-bridged dimers trans-[Ir(μ-OH){κ2-C,N-(C6H4-Isoqui)}2]2 and trans-[Ir(μ-OH){κ2-C,N-(MeC6H3-py)}2]2 and terminal alkynes. Subsequently, the acetylide ligands have been employed as building blocks to prepare the orange and green iridium(III) phosphorescent emitters, Ir{κ2-C,N-[C(CH2Ph)Npy]}{κ2-C,N-(C6H4-Isoqui)}2 and Ir{κ2-C,N-[C(CH2R)Npy]}{κ2-C,N-(MeC6H3-py)}2 (R = Ph, tBu), respectively, with an octahedral structure of fac carbon and nitrogen atoms. The green emitter Ir{κ2-C,N-[C(CH2tBu)Npy]}{κ2-C,N-(MeC6H3-py)}2 reaches 100% of quantum yield in both the poly(methyl methacrylate) (PMMA) film and 2-MeTHF at room temperature. In organic light-emitting diode (OLED) devices, it demonstrates very saturated green emission at a peak wavelength of 500 nm, with an external quantum efficiency (EQE) of over 12% or luminous efficacy of 30.7 cd/A., Financial support from the MICIN/AEI/10.13039/501100011033 (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged.

The C–H bond activation of methylquinolines, quinoline, 3-methoxyquinoline, and 3-(trifluoromethyl)quinoline promoted by the square-planar rhodium(I) complex RhH{κ3-P,O,P-[xant(PiPr2)2]} [1; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene] has been systematically studied. Results reveal that the activation of the heteroring is preferred over the activation of the carbocycle, and the activated position depends upon the position of the substituent in the substrate. Thus, 3-, 4-, and 5-methylquinoline reacts with 1 to quantitatively form square-planar rhodium(I)-(2-quinolinyl) derivatives, whereas 2-, 6-, and 7-methylquinoline quantitatively leads to rhodium(I)-(4-quinolinyl) species. By contrast, quinoline and 8-methylquinoline afford mixtures of the respective rhodium(I)-(2-quinolinyl) and -(4-quinolinyl) complexes. 3-Methoxyquinoline displays the same behavior as that of 3-methylquinoline, while 3-(trifluoromethyl)quinoline yields a mixture of rhodium(I)-(2-quinolinyl), -(4-quinolinyl), -(6-quinolinyl), and -(7-quinolinyl) isomers., Financial support from the MICIN/AEI/10.13039/501100011033 (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged. L.A.d.l.H. thanks the MECD for her FPU contract (FPU17/04813, “ESF investing in your future”).

A cycle of stoichiometric elemental reactions defining the direct arylation promoted by a redox-pair Rh(I)–Rh(III) is reported. Starting from the rhodium(I)-aryl complex RhPh{κ3-P,O,P-[xant(PiPr2)2]} (xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene), the reactions include C–Cl oxidative addition of organic chlorides, halide abstraction from the resulting six-coordinate rhodium(III) derivatives, C–C reductive coupling between the initial aryl ligand and the added organic group, oxidative addition of a C–H bond of a new arene, and deprotonation of the generated hydride-rhodium(III)-aryl species to form a new rhodium(I)-aryl derivative. In this context, the kinetics of the oxidative additions of 2-chloropyridine, chlorobenzene, benzyl chloride, and dichloromethane to RhPh{κ3-P,O,P-[xant(PiPr2)2]} and the C–C reductive eliminations of biphenyl and benzylbenzene from [RhPh2{κ3-P,O,P-[xant(PiPr2)2]}]BF4 and [RhPh(CH2Ph){κ3-P,O,P-[xant(PiPr2)2]}]BF4, respectively, have been studied. The oxidative additions generally involve the cis addition of the C–Cl bond of the organic chloride to the rhodium(I) complex, being kinetically controlled by the C–Cl bond dissociation energy; the weakest C–Cl bond is faster added. The C–C reductive elimination is kinetically governed by the dissociation energy of the formed bond. The C(sp3)–C(sp2) coupling to give benzylbenzene is faster than the C(sp2)–C(sp2) bond formation to afford biphenyl. In spite of that a most demanding orientation requirement is needed for the C(sp3)–C(sp2) coupling than for the C(sp2)–C(sp2) bond formation, the energetic effort for the pregeneration of the C(sp3)–C(sp2) bond is lower. As a result, the weakest C–C bond is formed faster., Financial support from the MICIN/AEI/10.13039/501100011033 (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and LMP23_21), FEDER, and the European Social Fund is acknowledged. L.A.d.l.H. thanks the MECD for her FPU contract (FPU17/04813, “ESF investing in your future”).

The study of the reactions of IrH5(PiPr3)2 (1) with 2,6-diphenylpyridine and 2-phenoxy-6-phenylpyridine and the photophysical characterization of some of the resulting compounds, as well as their osmium counterparts, reveal that the bite angle of dianionic C,N,C-pincer ligands has a marked influence on the chemical and photophysical properties of iridium(III) and osmium(IV) hydride complexes. Complex 1 promotes a double o-CH bond activation of both disubstituted pyridines. The reaction with 2,6-diphenylpyridine directly leads to IrH{κ3-C,N,C-(C6H4-py-C6H4)}(PiPr3)2 (2), whereas the activation of 2-phenoxy-6-phenylpyridine is sequential and slower. Initially, the phenyl activation gives IrH2{κ2-C,N-(C6H4-py-OPh)}(PiPr3)2 (3), which subsequently evolves to IrH{κ3-C,N,C-(C6H4-py-OC6H4)}(PiPr3)2 (4). Complexes 2 and 4 are Brønsted bases, which react with HBF4·OEt2. The protonation of the hydride position is elusive; the proton of the acid is selectively added to one of the metalated substituents. Thus, the reaction with 2 affords [IrH{κ3-C,N,(C–H)-(C6H4-py-Ph)}(PiPr3)2]BF4 (5), in which the C–H bond formed remains coordinated. The protonation of 4 selectively occurs at the phenoxy substituent to give the five-coordinate cationic complex [IrH{κ2-C,N-(C6H4-py-OPh)}(PiPr3)2]BF4 (6) bearing a free OPh group. In contrast to 5, complex 6 inserts acetylene and phenylacetylene into the Ir–H bond to yield [Ir{(E)-CH═CHR}{κ2-C,N-(C6H4-py-OPh)}(PiPr3)2]BF4 (R = H (7), Ph (8)). Complexes 2 and 4 and their osmium(IV) counterparts OsH2{κ3-C,N,C-(C6H4-py-C6H4)}(PiPr3)2 (A) and OsH2{κ3-C,N,C-(C6H4-py-OC6H4)}(PiPr3)2 (B) are phosphorescent emitters, which display emission wavelengths between 473 and 619 nm and quantum yields between 0.03 and 0.96 depending upon the metal center and the presence or absence of an oxygen atom in the pincer ligand., Financial support from the MINECO of Spain (Project CTQ2017-82935-P (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(η4-C8H12)]2 (M = Rh (1), Ir (2)) and [M(μ-OH)(η4-C8H12)]2 (M = Rh (3), Ir (4)) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1, the mononuclear derivative RhCl(η4-C8H12){κ1-Npy-(HBMePHI)} (5), and the binuclear species [RhCl(η4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (6). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η4-C8H12){κ1-Npy-(HBMePHI)} (7) and [IrCl(η4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (8). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(η4-C8H12)]2(μ-OH){μ-Npy,Niso-(BMePHI)} (M = Rh (9), Ir (10)), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KOtBu, the [BMePHI]− ligand undergoes three different degradations: alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core., Financial support from the MCI, projects CTQ2017-82935-P, PID2019-108429RB-I00, and RED2018-102387-T, the Gobierno de Aragón (Group E06_17R), Fundación Ramón Areces (XVIII Concurso Nacional de Ayudas a la Investigación en Ciencias de la Vida y de la Materia CIVP18A3938), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged. A.I.N. and A.C. thank the MINECO (Spain) for a predoctoral fellowship and Juan de la Cierva-Incorporación Fellowship, respectively.

Reactions of the aryl complexes Rh(aryl){κ3-P,O,P-[xant(PiPr2)2]} (1; aryl = 3,5-Me2C6H3 (a), C6H5 (b), 3,5-Cl2C6H3 (c), 3-FC6H4 (d); xant(PiPr2)2 = 9,9-dimethyl-4,5-bis-(diisopropylphosphino)xanthene) with O2, CO, and MeO2CC≡CCO2Me have been performed. Under 1 atm of O2, the pentane solutions of complexes 1 afford the dinuclear peroxide derivatives [Rh(aryl){κ2-P,P-xant(PiPr2)2}]2(μ-O2)2 (2a–2d) as yellow solids. In solution, these species are unstable. In dichloromethane, at room temperature, they are transformed into the dioxygen adducts Rh(aryl)(η2-O2){κ3-P,O,P-[xant(PiPr2)2]} (3a–3d), as a result of the rupture of the double peroxide bridge and the reduction of the metal center. Complex 3b decomposes in benzene, at 50 °C, to give diphosphine oxide, phenol, and biphenyl. Complexes 1 react with CO to give the square-planar mono carbonyl derivatives Rh(aryl)(CO){κ2-P,P-[xant(PiPr2)2]} (4a–4d), which under carbon monoxide atmosphere evolve to benzoyl species Rh{C(O)aryl}(CO){κ2-P,P-[xant(PiPr2)2]} (5a–5d), resulting from the migratory insertion of CO into the Rh-aryl bond and the coordination of a second CO molecule. The transformation is reversible; under vacuum, complexes 5 regenerate the precursors 4. The addition of the activated alkyne to complexes 1b and 1d initially leads to the π-alkyne intermediates Rh(aryl){η2-C(CO2Me)≡C(CO2Me)}{κ3-P,O,P-[xant(PiPr2)2]} (6b, 6d), which evolve to the alkenyl derivatives Rh{(E)-C(CO2Me)=C(CO2Me)aryl}{κ3-P,O,P-[xant(PiPr2)2]} (7b, 7d). The diphosphine adapts its coordination mode to the stability requirements of the different complexes, coordinating cis-κ2-P,P in complexes 2, fac-κ3-P,O,P in compounds 3, trans-κ2-P,P in the mono carbonyl derivatives 4 and 5, and mer-κ3-P,O,P in products 6 and 7., Financial support from the MINECO of Spain (Project CTQ2017-82935-P (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged. L.A.d.l.H. thanks the MECD for her FPU contract (FPU17/04813).

An unusual 1,3-hydrogen shift from the metal center to the Cβ atom of the C3-chain of the allenylidene ligand in a hydride-osmium(II)-allenylidene complex is the beginning of several interesting transformations in the cumulene. The hydride-osmium(II)-allenylidene complex was prepared in two steps, starting from the tetrahydride dimer [(Os(H···H){κ3-P,O,P-[xant(PiPr2)2]})2(μ-Cl)2][BF4]2 (1). Complex 1 reacts with 1,1-diphenyl-2-propyn-1-ol to give the hydride-osmium(II)-alkenylcarbyne [OsHCl(≡CCH═CPh2){κ3-P,O,P-[xant(PiPr2)2]}]BF4 (2), which yields OsHCl(═C═C═CPh2){κ3-P,O,P-[xant(PiPr2)2]} (3) by selective abstraction of the Cβ–H hydrogen atom of the alkenylcarbyne ligand with KtBuO. Complex 3 is metastable. According to results of DFT calculations, the migration of the hydride ligand to the Cβ atom of the cumulene has an activation energy too high to occur in a concerted manner. However, the migration can be catalyzed by water, alcohols, and aldehydes. The resulting alkenylcarbyne-osmium(0) intermediate is unstable and evolves into a 7:3 mixture of the hydride-osmium(II)-indenylidene OsHCl(═CIndPh){κ3-P,O,P-[xant(PiPr2)2]} (4) and the osmanaphthalene OsCl(C9H6Ph){κ3-P,O,P-[xant(PiPr2)2]} (5). Protonation of 4 with HBF4 leads to the elongated dihydrogen complex [OsCl(η2-H2)(═CIndPh){κ3-P,O,P-[xant(PiPr2)2]}]BF4 (6), while the protonation of 5 regenerates 2. In contrast to 4, complex 6 evolves to a half-sandwich indenyl derivative, [Os(η5-IndPh)H{κ3-P,O,P-[xant(PiPr2)2]}][BF4]Cl (7). Phenylacetylene also provokes the 1,3-hydrogen shift in 3. However, it does not participate in the migration. In contrast to water, alcohols, and aldehydes, it stabilizes the resulting alkenylcarbyne to afford [Os(≡CCH═CPh2)(η2-HC≡CPh){κ3-P,O,P-[xant(PiPr2)2]}]Cl (8)., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and RED2018-102387-T (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

1-Phenyl-3-(1-phenyl-1-(pyridin-2-yl)ethyl)isoquinoline (H2MeL) has been prepared by Pd(N-XantPhos)-catalyzed “deprotonative cross-coupling processes” to synthesize new phosphorescent red iridium(III) emitters (601–732 nm), including the carbonyl derivative Ir(κ4-cis-C,C′-cis-N,N′-MeL)Cl(CO) and the acetylacetonate compound Ir(κ4-cis-C,C′-cis-N,N′-MeL)(acac). The tetradentate 6e-donor ligand (6tt′) of these complexes is formed by two different bidentate units, namely, an orthometalated 2-phenylisoquinoline and an orthometalated 2-benzylpyridine. The link between the bidentate units reduces the number of possible stereoisomers of the structures [6tt′ + 3b] (3b = bidentate 3e-donor ligand), with respect to a [3b + 3b′ + 3b″] emitter containing three free bidentate units, and it permits a noticeable stereocontrol. Thus, the isomers fac-Ir(κ4-cis-C,C′-cis-N,N′-MeL){κ2-C,N-(C6H4-py)}, mer-Ir(κ4-cis-C,C′-cis-N,N′-MeL){κ2-C,N-(C6H3R-py)}, and mer-Ir(κ4-trans-C,C′-cis-N,N′-MeL){κ2-C,N-(C6HR-py)} (R = H, Me) have also been selectively obtained. The new emitters display short lifetimes (0.7–4.6 μs) and quantum yields in a doped poly(methyl methacrylate) film at 5 wt % and 2-methyltetrahydrofuran at room temperature between 0.08 and 0.58. The acetylacetonate complex Ir(κ4-cis-C,C′-cis-N,N′-MeL)(acac) has been used as a dopant for a red PhOLED device with an electroluminescence λmax of 672 nm and an external quantum efficiency of 3.4% at 10 mA/cm2., Financial support was provided by MINECO of Spain [CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T], Gobierno de Aragón (E06_20R and LMP148_18), FEDER, and the European Social Fund. The CESGA Supercomputing Center and BIFI Institute are also acknowledged for the use of their computational resources.

The C,N,N′-donor aryl-diimineborate pincer ligand of the complexes OsH2{κ3-C,N,N-[C6H3RCH═NB(cat)N═CHC6H4R]}(PiPr3)2 (R = H, Me) has been generated in a one-pot procedure, by the reaction of the hexahydride OsH6(PiPr3)2 with catecholborane (catBH) and two molecules of the corresponding aryl nitrile. The osmium–pincer bonding situation has been analyzed by means of atoms in molecules (AIM), natural bond orbital (NBO), and energy decomposition analysis coupled with the natural orbitals for chemical valence (EDA-NOCV) methods. According to the results, the complexes exhibit a rather strong electron-sharing Os–C bond, two weaker donor–acceptor N–Os bonds, and two π-back-donations from the transition metal to vacant π* orbitals of the formed metallacycles. In addition, spectroscopic findings and DFT calculations reveal that the donor units of the pincer are incorporated in a sequential manner. First, the central Os–N bond is formed, by the reaction of the dihydrideborate ligand of the intermediate OsH3{κ2-H,H-(H2Bcat)}(PiPr3)2 with one of the aryl nitriles. The subsequent oxidative addition of the o-C–H bond of the aryl substituent of the resulting κ1-N-(N-boryl-arylaldimine) affords the Os–C bond. Finally, the second Os–N bond is generated from a hydride, an ortho-metalated N-boryl-arylaldimine, and the second aryl nitrile., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE), CTQ2016-78205-P, PID2019-106184GB-I00, and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

The hexahydride complex OsH6(PiPr3)2 promotes the C–H bond activation of the 1,3-disubstituted phenyl group of the [BF4]− and [BPh4]− salts of the cations 1-(3-(isoquinolin-1-yl)phenyl)-3-methylimidazolium and 1-(3-(isoquinolin-1-yl)phenyl)-3-methylbenzimidazolium. The reactions selectively afford neutral and cationic trihydride-osmium(IV) derivatives bearing κ2-C,N- or κ2-C,C-chelating ligands, a cationic dihydride-osmium(IV) complex stabilized by a κ3-C,C,N-pincer group, and a bimetallic hexahydride formed by two trihydride-osmium(IV) fragments. The metal centers of the hexahydride are separated by a bridging ligand, composed of κ2-C,N- and κ2-C,C-chelating moieties, which allows electronic communication between the metal centers. The wide variety of obtained compounds and the high selectivity observed in their formation is a consequence of the main role of the azolium group during the activation and of the existence of significant differences in behavior between the azolium groups. The azolium role is governed by the anion of the salt, whereas the azolium behavior depends upon its imidazolium or benzimidazolium nature. While [BF4]− inhibits the azolium reactions, [BPh4]− favors the azolium participation in the activation process. In contrast to benzimidazolylidene, the imidazolylidene resulting from the deprotonation of the imidazolium substituent coordinates in an abnormal fashion to direct the phenyl C–H bond activation to the 2-position. The hydride ligands of the cationic dihydride-osmium(IV) pincer complex display intense quantum mechanical exchange coupling. Furthermore, this salt is a red phosphorescent emitter upon photoexcitation and displays a noticeable catalytic activity for the dehydrogenation of 1-phenylethanol to acetophenone and of 1,2-phenylenedimethanol to 1-isobenzofuranone. The bimetallic hexahydride shows catalytic synergism between the metals, in the dehydrogenation of 1,2,3,4-tetrahydroisoquinoline and alcohols., Financial support from the MICIN of Spain (PID2020-115286GB-I00/AEI/10.13039/501100011033 and RED2018-102387-T), Gobierno de Aragón (E06_20R), FEDER, and the European Social Fund is acknowledged.

The orthometalated phenyl groups of the dimer [Ir(μ-Cl){κ2-C,N-(C6H3Me-py)}2]2 have been selectively brominated, at para-position with regard to the Ir–C bonds, with N-bromosuccinimide. The bromination leads to [Ir(μ-Cl){κ2-C,N-(C6H2MeBr-py)}2]2, which affords the mononuclear derivatives Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,N-[OC(O)-py]}, Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,O-(acac)}, and Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-C,N-[C6H4-Mepy]} by replacement of the chloride bridges by a picolinate anion, an acac group, and an orthometalated 2-phenyl-5-methylpyridine ligand, respectively. Complexes Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,O-(acac)} and Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-C,N-[C6H4-Mepy]} have been subsequently postfunctionalized by means of palladium-catalyzed Suzuki–Miyaura cross-coupling to give Ir{κ2-C,N-(C6H2MeR-py)}2{κ2-O,O-(acac)} (R = Me, Ph) and Ir{κ2-C,N-(C6H2Me2-py)}2{κ2-C,N-[C6H4-Mepy]}. These [3b + 3b + 3b′] mononuclear compounds are green-yellow emitters (488–580 nm) upon photoexcitation, in doped poly(methyl methacrylate) (PMMA) film at 5 wt % at room temperature and 2-methyltetrahydrofuran (2-MeTHF) at room temperature and at 77 K. They display lifetimes in the range 1.0–5.0 μs and quantum yields in PMMA films and in 2-MeTHF at room temperature between 0.84 and 0.40., Financial support from the MINECO of Spain (PID2020-115286GB-I00 and RED2018-102387-T (AEI/FEDER, UE), Gobierno de Aragón (E06_20R and LMP148_18), FEDER, and the European Social Fund is acknowledged.

The hexahydride OsH6(PiPr3)2 competently catalyzes the hydration of aliphatic nitriles to amides. The main metal species under the catalytic conditions are the trihydride osmium(IV) amidate derivatives OsH3{κ2-N,O-[HNC(O)R]}(PiPr3)2, which have been isolated and fully characterized for R = iPr and tBu. The rate of hydration is proportional to the concentrations of the catalyst precursor, nitrile, and water. When these experimental findings and density functional theory calculations are combined, the mechanism of catalysis has been established. Complexes OsH3{κ2-N,O-[HNC(O)R]}(PiPr3)2 dissociate the carbonyl group of the chelate to afford κ1-N-amidate derivatives, which coordinate the nitrile. The subsequent attack of an external water molecule to both the C(sp) atom of the nitrile and the N atom of the amidate affords the amide and regenerates the κ1-N-amidate catalysts. The attack is concerted and takes place through a cyclic six-membered transition state, which involves Cnitrile···O–H···Namidate interactions. Before the attack, the free carbonyl group of the κ1-N-amidate ligand fixes the water molecule in the vicinity of the C(sp) atom of the nitrile., Financial support was provided by MINECO of Spain [CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T], Gobierno de Aragón (E06_20R and LMP148_18), FEDER, and the European Social.

The preparation of aromatic hydride-osmaoxazolium and hydride-oxazole compounds is reported and their reactivity toward phenylacetylene investigated. Complex [OsH(OH)(≡CPh)(IPr)(PiPr3)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene, OTf = CF3SO3) reacts with acetonitrile and benzonitrile to give [OsH{κ2-C,O-[C(Ph)NHC(R)O]}(NCR)(IPr)(PiPr3)]OTf (R = Me (2), Ph (3)) via amidate intermediates, which are generated by addition of the hydroxide ligand to the nitrile. In agreement with this, the addition of 2-phenylacetamide to acetonitrile solutions of 1 gives [OsH{κ2-C,O-[C(Ph)NHC(CH2Ph)O]}(NCCH3)(IPr)(PiPr3)]OTf (4). The deprotonation of the osmaoxazolium ring of 2 and 4 leads to the oxazole derivatives OsH{κ2-C,O-[C(Ph)NC(R)O]}(IPr)(PiPr3) (R = Me (5), CH2Ph (6)). Complexes 2 and 4 add their Os–H and Os–C bonds to the C–C triple bond of phenylacetylene to afford [Os{η3-C3,κ1-O-[CH2C(Ph)C(Ph)NHC(R)O]}(NCCH3)2(IPr)]OTf (R = Me (7), CH2Ph (8)), bearing a tridentate amide-N-functionalized allyl ligand, while complexes 5 and 6 undergo a vicarious nucleophilic substitution of the hydride at the metal center with the alkyne, via the compressed dihydride adduct intermediates OsH2(C≡CPh){κ2-C,O-[C(Ph)NC(R)O]}(IPr)(PiPr3) (R = Me (9), CH2Ph (10)), which reductively eliminate H2 to yield the acetylide-osmaoxazoles Os(C≡CPh){κ2-C,O-[C(Ph)NC(R)O]}(IPr)(PiPr3) (R = Me (11), CH2Ph (12))., Financial support was provided by the MICINN of Spain (PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (E06_20R and predoctoral contract to N.R.P.), FEDER, and FSE.

Complex OsH6(PiPr3)2 is an efficient catalyst precursor for the addition of pinacolborane and catecholborane to the C–N triple bond of alkyl nitriles. In this way, a variety of N,N-diborylamines have been isolated and fully characterized, including 13 derivatives not described so far. The range of nitriles used is wide and comprises substrates having unfunctionalized linear and branched chains, and functionalized chains with methoxide, trifluoromethyl, aryl, pyridyl, benzoyl, or cyanide groups. Kinetic studies demonstrate that the overall process consists of two consecutive irreversible reactions: the catalytic metal-promoted monohydroboration of the nitrile to afford the borylimine and the metal-free stoichiometric hydroboration of the latter to give the diborylamine. The mechanism of the hydroboration has been established by combining the kinetic analysis of the catalysis, stoichiometric reactions, and DFT calculations. The rate-determining step of the catalysis is the insertion of the C–N triple bond of the nitrile into the Os–B bond of an osmium-σ-borane intermediate and is regiodirected by the nucleophilicity of the nitrogen atom and the electrophilicity of the carbon atom of the nitrile., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE), CTQ2016-78205-P, PID2019-106184GB-I00, and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

A synthetic methodology to prepare iridium(III) emitters of the class [3b+3b+3b′] with two ortho-metalated 1-phenylisoquinolines and an asymmetrical β-diketonate has been discovered. The abstraction of the chloride ligands of the dimer [Ir(μ-Cl){κ2-C,N-(C6H4-isoqui)}2]2 (1, C6H5-isoqui = 1-phenylisoquinoline) with AgBF4 in acetone and the subsequent addition of water to the resulting solution affords the water solvate mononuclear complex [Ir{κ2-C,N-(C6H4-isoqui)}2(H2O)2]BF4 (2), which reacts with KOH to give the dihydroxo-bridged dimer [Ir(μ-OH){κ2-C,N-(C6H4-isoqui)}2]2 (3). Treatment of the latter with dimethyl acetylenedicarboxylate leads to Ir{κ2-C,N-(C6H4-isoqui)}2{κ2-O,O-[OC(CO2CH3)CHC(OCH3)O]} (4), as a result of the anti-addition of the O–H bond of a mononuclear [Ir(OH){κ2-C,N-(C6H4-isoqui)}2] fragment to the C–C triple bond of the alkyne and the coordination of one of the carboxylate substituents to the metal center. Complex 3 also reacts with α,β-unsaturated ketones. The reaction with 3-(4-methylphenyl)-1-phenylprop-2-en-1-one affords Ir{κ2-C,N-(C6H4-isoqui)}2{κ2-O,O-[OC(C6H5)CHC(p-C6H4Me)O]} (5), whereas methyl vinyl ketone gives a mixture of Ir{κ2-C,N-(C6H4-isoqui)}2{κ2-O,O-[OC(CH3)CHCHO]} (6) and Ir{κ2-C,N-(C6H4-isoqui)}2{κ2-O,O-[OC(CH3)CHC(CH═CH2)O]} (7). Complexes 5 and 6 are the result of the addition of the O–H bond of the mononuclear [Ir(OH){κ2-C,N-(C6H4-isoqui)}2] fragment to the C–C double bond of the α,β-unsaturated ketones and the coordination of the carbonyl group to the iridium center, to generate O,O-chelates which lose molecular hydrogen to aromatize into the asymmetrical β-diketonate ligands. Complexes 4–7 are phosphorescent emitters in the red spectral region (599–672 nm) in doped poly(methyl methacrylate) (PMMA) film at 5 wt % at room temperature and 2-methyltetrahydrofuran at room temperature and 77 K. They display short lifetimes (0.8–2.5 μs) and quantum yields in both doped PMMA films and in 2-methyltetrahydrofuran at room temperature depending on the substituents of the β-diketonate: about 0.6–0.5 for 4 and 6 and ca. 0.35 for 5 and 7., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged

The discovery of cycloosmathioborane compounds is reported. These species, which are prepared by the simultaneous dehydrogenation of a trihydride hydrogensulfide osmium(IV) complex and a BH3NHR2 amine–borane, bear an Os–S–B three-membered ring, being a manifestation of the 4n + 2 Hückel aromaticity in which n = 0 and where the two π electrons of the ring are provided by the S atom., We thank MINECO of Spain (Projects CTQ2017-82935-P, CTQ2016-78205-P, and Red de Excelencia Consolider CTQ2016-81797-REDC), Diputación General de Aragón (No. E06_17R), FEDER, and the European Social Fund for financial support.

The saturated trihydride IrH3{κ3‐P,O,P‐[xant(PiPr2)2]} (1; xant(PiPr2)2=9,9‐dimethyl‐4,5‐bis(diisopropylphosphino)xanthene) activates the B−H bond of two molecules of pinacolborane (HBpin) to give H2, the hydride‐boryl derivatives IrH2(Bpin){κ3‐P,O,P‐[xant(PiPr2)2]} (2) and IrH(Bpin)2{κ3‐P,O,P‐[xant(PiPr2)2]} (3) in a sequential manner. Complex 3 activates a C−H bond of two molecules of benzene to form PhBpin and regenerates 2 and 1, also in a sequential manner. Thus, complexes 1, 2, and 3 define two cycles for the catalytic direct C−H borylation of arenes with HBpin, which have dihydride 2 as a common intermediate. C−H bond activation of the arenes is the rate‐determining step of both cycles, as the C−H oxidative addition to 3 is faster than to 2. The results from a kinetic study of the reactions of 1 and 2 with HBpin support a cooperative function of the hydride ligands in the B−H bond activation. The addition of the boron atom of the borane to a hydride facilitates the coordination of the B−H bond through the formation of κ1‐ and κ2‐dihydrideborate intermediates., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and RED2018-102387-T (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_20R, project LMP148_18, and predoctoral contract to A.M.), FEDER, and the European Social Fund is acknowledged.

The preparation of the hydroxo-osmium(IV) complex OsH3(OH){xant(PiPr2)2} (xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) and its catalytic efficiency for the dehydrogenation of formic acid to H2 and CO2 are reported. The mechanism of the dehydrogenation has been unambiguously stablished by combining the kinetic analysis of the catalysis, the isolation of the intermediates and the kinetic analysis of their decomposition, and density functional theory (DFT) calculations on the rate-determining step. Under catalytic conditions, the trihydride-hydroxo complex reacts with formic acid to afford OsH3{κ1-O-(HCO2)}{xant(PiPr2)2}, which isomerizes into OsH3{κ1-H-(HCO2)}{xant(PiPr2)2} by means of the slippage of the metal center through a formate O–C–H path. The κ1-H-formate intermediate releases CO2 to give the previously reported tetrahydride OsH4{xant(PiPr2)2}, which undergoes protonation with formic acid. The resulting OsH5 cation exists as an equilibrium mixture of the tautomers trihydride-compressed dihydride [OsH3(H···H){xant(PiPr2)2}]+ and hydride-compressed dihydride–dihydrogen [OsH(H···H)(η2-H2){xant(PiPr2)2}]+. The dissociation of H2 from the latter leads to [OsH3{xant(PiPr2)2}]+, which coordinates HCO2– to regenerate the trihydride-(κ1-O-formate) complex and close the cycle. The release of CO2 from the κ1-H-formate intermediate is the rate-determining step of the catalysis., We thank MINECO of Spain (Project No. CTQ2017-82935-P) and Red de Excelencia Consolider (No. CTQ2016-81797-REDC), Diputacion General de Aragon (No. E06_17R), FEDER, and the European Social Fund for financial support.

The range of processes of degradation–transformation of NHC ligands in the coordination sphere of a transition metal has been enlarged. The NHC-acyl ligand of the complex Os{κ2-C,C-[C(O)CH2ImMe]}Cl(PiPr3)2 (1) undergoes a complex rearrangement promoted by internal alkynes to give Os{κ2-C,N-[CH2ImMe]}Cl(CO)(PiPr3)2 (2). Mechanistic studies have revealed that the degradation involves a catalytic alkyne-mediated deinsertion of CO from the acyl moiety to afford Os{κ2-C,C-[CH2ImMe]}Cl(CO)(PiPr3)2 (3), followed by a thermally activated stoichiometric 1,2-methylene shift from N to C. The catalytic activity of the alkynes depends upon their substituents, decreasing in the sequence diphenylacetylene > 1-phenyl-1-propyne > 3-hexyne > 2-butyne. Phenylacetylene tautomerizes in the metal coordination sphere to afford the stable vinylidene Os{κ2-C,C-[C(O)CH2ImMe]}Cl(═C═CHPh)(PiPr3)2 (4), which experiences the coupling of the acyl moiety and the vinylidene ligand under a carbon monoxide atmosphere. The addition of HBF4·OEt2 to the resulting complex Os{κ2-C,C-[C(═CHPh)C(O)CH2ImMe]}Cl(CO)2(PiPr3) (5) leads to [Os{κ2-O,C-[O═C(CH═CHPh)CH2ImMe]}Cl(CO)2(PiPr3)]BF4 (6) containing an NHC-(α,β-unsaturated ketone) ligand., Financial support from the MINECO of Spain (Project CTQ2017-82935-P), Gobierno de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged. M.P.G. thanks the Spanish MINECO for her FPI fellowship.

A novel type of catalyst precursors for the dehydrogenation of hydrogen carriers based on organic liquids has been discovered. Complexes OsH6(PiPr3)2 (1) and OsH(OH)(CO)(PiPr3)2 (2) react with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePI) to give OsH3{κ2-Npy,Nimine-(BMePI)}(PiPr3)2 (3) and OsH{κ2-Npy,Nimine-(BMePI)}(CO)(PiPr3)2 (4). The unprecedented κ2-Npy,Nimine coordination mode of BMePI is thermodynamically preferred with Os(IV) and Os(II) metal fragments and allows for preparation of BMePI-based dinuclear metal cations. Treatment of OsH2Cl2(PiPr3)2 (5) with 0.5 equiv of HBMePI in the presence of KOtBu affords the chloride salt of the bis(osmium(IV)) dinuclear cation [{OsH3(PiPr3)2}2{μ-(κ2-Npy,Nimine)2-BMePI}]+ (6). Related homoleptic bis(osmium(II)) complexes have been also synthesized. Complex 4 reacts with the bis(solvento) [OsH(CO){κ1-O-[OCMe2]2}(PiPr3)2]BF4 to give [{OsH(CO)(PiPr3)2}2{μ-(κ2-Npy,Nimine)2-BMePI}]BF4 (7), whereas the addition of 0.5 equiv of HBMePI to {OsCl(η6-C6H6)}2(μ–Cl)2 (8) affords [{OsCl(η6-C6H6)}2{μ-(κ2-Npy,Nimine)2-BMePI}]Cl (9). The reactions of 4 with 8 and {OsCl(η6-p-cymene)}2(μ–Cl)2 (10) lead to the heteroleptic cations [(PiPr3)2(CO)HOs{μ-(κ2-Npy,Nimine)2-BMePI}OsCl(η6-arene)]+ (arene = C6H6 (11), p-cymene (12)). The electronic structrure and electrochemical properties of the dinuclear complexes were also studied. Complexes 3 and 4 are efficient catalyst precursors for the acceptorless and base-free dehydrogenation of secondary and primary alcohols and cyclic and lineal amines. The primary alcohols afford aldehydes. The amount of H2 released per gram of heterocycle depends upon the presence of a methyl group adjacent to the nitrogen atom, the position of the nitrogen atom in the heterocycle, and the size of the heterocycle., Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects CTQ2017-82935-P, Red de Excelencia Consolider CTQ2016-81797-REDC), the Gobierno de Aragón (E35), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged.

Molecular phosphorescent heteroleptic bis-tridentate iridium(III) emitters have been prepared via η1-arene intermediates. In the presence of 4.0 mol of AgOTf, the complex [(IrCl{κ3-N,C,N-(pyC6HMe2py)})(μ-Cl)]2 (1; pyC6H2Me2py=1,3-di(2-pyridyl)-4,6-dimethylbenzene) reacted with 9-(6-phenylpyridin-2-yl)-9H-carbazole (PhpyCzH) and 2-phenoxy-6-phenylpyridine (PhpyOPh) to give [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCzH)}]OTf (2) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOPh)}]OTf (3). The X-ray diffraction structures of 2 and 3 reveal that the carbazolyl and phenoxy substituents of the C,N,C′ ligand coordinate to the metal center to form an η1-arene π bond. Treatment of 2 and 3 with KOtBu led to the deprotonation of the coordinated carbon atom of the η1-arene group to afford the molecular phosphorescent [5t+4t′] heteroleptic iridium(III) complexes [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCz)}] (4) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOC6H4)}] (5). These complexes are green emitters that display short lifetimes and high quantum yields of 0.73 (4) and 0.87 (5) in the solid state., Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects CTQ2014-52799-P, Red de Excelencia Consolider CTQ2016-81797-REDC), the Gobierno deAragón (E35), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged.

The preparation of new osmium hydride complexes, starting from OsH6(PiPr3)2 (1) and OsH2Cl2(PiPr3)2 (2), and their catalytic activity in acceptorless dehydrogenative coupling of alcohols and amines and in dehydrogenation of cyclic amines are reported. Complex 1 reacts with acetylacetone (Hacac) to give the classical trihydride OsH3(acac)(PiPr3)2 (3). The protonation of 3 with triflic acid (HOTf) produces the release of H2 and the formation of the unsaturated osmium(IV) dihydride [OsH2(acac)(PiPr3)2]OTf (4), which is also prepared by starting from 2 via the intermediate OsH2Cl(acac)(PiPr3)2 (5). Treatment of an acetylacetone solution of 5 with KOH affords Os(acac)2(PiPr3)2 (6). In the presence of 5 mol % of KOH, complexes 3–6 promote the coupling of benzyl alcohol and aniline to give N-benzylideneaniline and H2. Under the same conditions, complex 3 catalyzes a wide range of analogous couplings to afford a variety of imines, including aliphatic imines, with yields between 90 and 40% after 1–48 h. Complex 3 also catalyzes the dehydrogenation of cyclic amines. According to the amount of H2 released by each 1 g of employed substrate, the amines have been classified into three classes: poor (1,2,3,4-tetrahydroquinaldine, 2-methylindoline, and 2,6-dimethylpiperidine), moderate (1,2,3,4-tetrahydroquinoline and 6-methyl-1,2,3,4-tetrahydroquinoline), and good hydrogen donors (1,2,3,4-tetrahydroisoquinoline)., Financial support from the MINECO of Spain (Projects CTQ2014-52799-P and CTQ2016-81797-REDC), the Diputacion General de Aragón (E-35), FEDER, and the European Social Fund is acknowledged.

The elusive C–H bond activation of an organic fragment contained in many biologically active molecules and the use of the resulting noninnocent ligand in bimetallic catalysis applied to the acceptorless and base-free dehydrogenation of secondary alcohols has been performed by using the polyhydrides IrH5(PiPr3)2 (1) and OsH6(PiPr3)2 (2). Complex 1 activates the N–H bond of 1,3-bis(6′-methylpyridyl-2′-imino)isoindoline (HBMePHI) to give the mononuclear complex IrH2{κ2-Npy,Nimine(BMePHI)}(PiPr3)2 (3). Both 1 and 2 activate the C(sp2)–H bond at position 4 of the core isoindoline of the BMePHI ligand of 3. The reactions lead to the homobinuclear complex (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}IrH2(PiPr3)2 (4) and the heterobinuclear compound (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}OsH3(PiPr3)2 (5), respectively. The metalated carbon atom of 4 and 5 has a marked nucleophilic character. Thus, it adds the proton of alcohols to afford the respective cations [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}IrH2(PiPr3)2]+ (6) and [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}OsH3(PiPr3)2]+ (7), and the corresponding alkoxide. The mononuclear complex 3 and the binuclear compounds 4 and 5 are efficient catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. The binuclear complexes 4 and 5 are significantly more active than 3. The catalytic synergism is a consequence of the mutual electronic influence of the metals through the bridge. X-ray diffraction analysis data of the structures of 3–5 and the reactivity of 4 and 5 support a noninnocent character of the bridging ligand., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged. A.I.N. thanks the MINECO for his predoctoral fellowship.

The saturated trihydride IrH3{κ3-P,O,P-[xant(PiPr2)2]} (1; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) coordinates the Si–H bond of triethylsilane, 1,1,1,3,5,5,5-heptamethyltrisiloxane, and triphenylsilane to give the σ-complexes IrH3(η2-H-SiR3){κ2-cis-P,P-[xant(PiPr2)2]}, which evolve to the dihydride-silyl derivatives IrH2(SiR3){κ3-P,O,P-[xant(PiPr2)2]} (SiR3 = SiEt3 (2), SiMe(OSiMe3)2 (3), SiPh3 (4)) by means of the oxidative addition of the coordinated bond and the subsequent reductive elimination of H2. Complexes 2–4 activate a C–H bond of symmetrically and asymmetrically substituted arenes to form silylated arenes and to regenerate 1. This sequence of reactions defines a cycle for the catalytic direct C–H silylation of arenes. Stoichiometric isotopic experiments and the kinetic analysis of the transformations demonstrate that the C–H bond rupture is the rate-determining step of the catalysis. As a consequence, the selectivity of the silylation of substituted arenes is generally governed by ligand–substrate steric interactions., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and RED2018-102387-T (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_20R, project LMP148_18, and predoctoral contract to AM.), FEDER, and the European Social Fund is acknowledged.

The way to prepare molecular emitters [5t + 4t′] of iridium(III) with a 5t ligand derived from the abstraction of the hydrogen atom at position 2 of the aryl group of 1,3-di(2-pyridyl)benzene (dpybH) is shown. In addition, the photophysical properties of the new emitters are compared with those of their counterparts resulting from the deprotonation of 1,3-di(2-pyridyl)-4,6-dimethylbenzene (dpyMebH), at the same position, which are also synthesized. Treatment of 0.5 equiv of the dimer [Ir(μ-Cl)(η2-COE)2]2 (COE = cyclooctene) with 1.0 equiv of Hg(dpyb)Cl leads to the iridium(III) derivative IrCl2{κ3-N,C,N-(dpyb)}(η2-COE) (3), which reacts with 2-(1H-imidazol-2-yl)-6-phenylpyridine (HNImpyC6H5) and 2-(1H-benzimidazol-2-yl)-6-phenylpyridine (HNBzimpyC6H5) in the presence of Na2CO3 to give Ir{κ3-C,N,N-(NImpyC6H4)}{κ3-N,C,N-(dpyb)} (4) and Ir{κ3-C,N,N-(NBzimpyC6H4)}{κ3-N,C,N-(dpyb)} (5), respectively. Similar reactions of the Williams’s dimer [IrCl(μ-Cl){κ3-N,C,N-(dpyMeb)}]2 with HNImpyC6H5 and HNBzimpyC6H5 in the presence of Na2CO3 afford the dimethylated counterparts Ir{κ3-C,N,N-(NImpyC6H4)}{κ3-N,C,N-(dpyMeb)} (6) and Ir{κ3-C,N,N-(NBzimpyC6H4)}{κ3-N,C,N-(dpyMeb)} (7), whereas 2-(6-phenylpyridine-2-yl)-1H-indole (HIndpyC6H5) initially gives IrH{κ2-N,N-(IndpyC6H5)}{κ3-N,C,N-(dpyMeb)} (8) and subsequently Ir{κ3-C,N,N-(IndpyC6H4)}{κ3-N,C,N-(dpyMeb)} (9). Complexes 4–7 are phosphorescent green emitters (λem 490–550 nm), whereas 9 is greenish yellow emissive (λem 547–624 nm). They display lifetimes in the range 0.5–9.7 μs and quantum yields in both doped poly(methyl)methacrylate films and in 2-methyltetrahydrofuran at room temperature depending upon the ligands: 0.5–0.7 for 6 and 7, about 0.4 for 4 and 5, and 0.3–0.2 for 9., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

Chapter Two.-- Edited by Pedro J. Pérez., Unsaturated osmium(IV)-hydride complexes are diamagnetic six-coordinate d4 species, which undergo distortion from the octahedral geometry to form unusual D4d or C2v geometries. They display a notable ability to activate HH, BH, CH, CC, CO, CBr, SiH, SnH, NH, or OH bonds of a wide range of inorganic, organic, and organometallic molecules, including: molecular hydrogen, boranes, phosphines, heterocycles, olefins, dienes, enynes, allenes, allenedienes, alkynamides, alkylhalides, silanes, stannanes, diamines, oximes, metal-nucleosides, or molecular oxygen. The activations yield, among other organometallic derivatives, dihydrogen, borane, borinium, alkylidene, alkylidyne, vinylidene, NHC, silylene, stannyl, osmafuran, osmaisobenzofuran, osmabenzimidazolium, or azavinylidene complexes. A characteristic of these activation processes is that they do not result in an increase of the formal oxidation state of the metal center. Given the wide range of σ-bond activations promoted by these compounds and the wide variety of complexes formed, future interesting applications for them can be anticipated., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and RED2018-102387-T (AEI/FEDER, UE)), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

OsH6(PiPr3)2 has been used to selectively activate C–H, O–H, and C–C sigma bonds in nucleobases and nucleosides, including derivatives of 6-phenylpurine and 4-phenylpyrimidine, leading to cyclometalated mononuclear Os–trihydride complexes, in excellent yields and as single products. Additionally, OsH6(PiPr3)2 promotes the efficient dehydrogenative decarbonylation of primary alcohols in nucleosides having unprotected sugar moieties. The incorporation of OsH2Cl2(PiPr3)2 in the structure of cyclometalated Ir(III) and Rh(III) half-sandwich complexes derived from nucleosides allows the preparation of a class of heterobimetallic bioorganometallic complexes having at least one M–C bond. These methodologies could be used in the future as a way for the orthogonal functionalization of oligonucleotides., Financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades (MICIyU) (Projects CTQ2016-77555C2-1-R to M.A.S., CTQ2017-82935-P to M.A.E., Red de Excelencia Consolider (RED2018-102387-T), Fundación Ramon Areces (CIVP18A3938, to M.A.S.), the Gobierno de Aragón (Group E06_17R and Project LMP148_18, to M.A.E.), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged.

The d2-hexahydride complex OsH6(PiPr3)2 (1) promotes the activation of C–H bonds of 2,2′-bipyridines and related heterocycles. The study of the same reactions with the deuteride counterpart OsD6(PiPr3)2 (1-d) reveals that the activation of the C–H bonds situated in the sterically less hindered positions is kinetically preferred. However, the isolated products are the result of the thermodynamic control of the reactions. Thus, reactions of 1 with 2,2′-bipyridine, 6-phenyl-2,2′-bipyridine, and 6-methyl-2,2′-bipyridine give the “rollover cyclometalation” products OsH3{κ2-C,N-[C5(R)H2N-py]}(PiPr3)2 (R = H (2), Ph (3), Me (4)), whereas 3,5-dimethyl-6-phenyl-2,2′-bipyridine affords OsH2{κ3-C,N,C-[C5H3N-(Me)2py-C5H4]}(PiPr3)2 (5), containing a dianionic C,N,C-pincer ligand. The behavior of substrates pyridyl-benzimidazolium and -imidazolium is similar. Reaction of 1 with 3-methyl-1-(6-phenylpyridin-2-yl)-1H-benzimidazolium tetrafluoroborate leads to OsH3{κ2-C,C-[MeBzim-C5(Ph)H2N]}(PiPr3)2 (6), bearing an anionic Cpy,CNHC-chelate. On the other hand, 3-methyl-1-(6-phenylpyridin-2-yl)-1H-imidazolium tetrafluoroborate yields [OsH2{κ3-C,N,C-(MeIm-py-C6H4)}(PiPr3)2]BF4 (7), containing a monoanionic C,N,C-pincer with a NHC-unit coordinated in an abnormal fashion. The reactivity pattern of these substrates is also observed with the d4-iridium-pentahydride IrH5(PiPr3)2 (8), which has generated IrH2{κ2-C,N-[C5(R)H2N-py]}(PiPr3)2 (R = H, (9), Ph (10)) and IrH{κ3-C,N,C-[C5H3N-(Me2)py-C5H4]}(PiPr3)2 (11). The osmium(IV)–carbon bonds display a higher degree of covalency than the iridium(III)–carbon bonds. In contrast to 2, the metalated carbon atom of 9 undergoes the addition of a proton of methanol to give [IrH2{κ2-N,N-(bipy)}(PiPr3)2]BF4 (12)., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

The discovery of a reaction which allows preparation of boroxide complexes of platinum group metals and study of their behavior under CO atmosphere is described. The trihydride-osmium(IV)-hydroxo complex OsH3(OH){κ3-P,O,P-[xant(PiPr2)2]} (1, xant(PiPr2)2 = 4,5-bis(diisopropylphosphino)xanthene) reacts with the amino-boranes iPr(H)NBCy2 and iPr(H)NBBN to give the osmium(IV)-boroxide derivatives OsH3(OBR2){κ3-P,O,P-[xant(PiPr2)2]} (BR2 = BCy2 (2), BBN (3); BBN = 9-borabicyclo[3.5.1]nonane) and iPrNH2 as a consequence of the addition of the O–H bond of the hydroxo ligand of 1 to the B–N bond of the amino-boranes. At room temperature under CO atmosphere, complexes 2 and 3 eliminate H2 to afford the osmium(II)–boroxide compounds OsH(OBR2)(CO)2{κ2-P,P-[xant(PiPr2)2]} (BR2 = BCy2 (4), BBN (5)) bearing a κ2-P,P-coordinated ether-diphosphine. The subsequent reductive elimination of the borinic acids R2BOH needs heating and a long duration and leads to the tricarbonyl-osmium(0) derivative Os(CO)3{κ2-P,P-[xant(PiPr2)2]} (6) with the phosphorus atoms of the diphosphine lying in the equatorial plane of a pentagonal bypyramid of donor atoms around the metal center. In contrast to 2 and 3, under CO atmosphere, precursor 1 eliminates water to initially give the trans-dihydride OsH2(CO){κ3-P,O,P-[xant(PiPr2)2]} (7), which subsequently evolves to the cis-dihydride-cis-dicarbonyl derivative OsH2(CO)2{κ2-P,P-[xant(PiPr2)2]} (8) and finally into the tricarbonyl 6., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P, CTQ2016-77614-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged. A.R. acknowledges a postdoctoral contract funded by the “Plan Propio de I + D + i” of the Universidad de Castilla-La Mancha.

This is an open access article published under an ACS AuthorChoice License., Square-planar alkylidyne and five-coordinate alkylidene mixed iPr3P–Os–IPr (IPr = 1,3-bis(diisopropylphenyl)imidazolylidene) complexes have been discovered and characterized, and their formation has been rationalized. The cationic five-coordinate hydride-alkylidyne compounds [OsHX(≡CPh)(IPr)(PiPr3)]OTf (X = Cl (1), F (4); OTf = CF3SO3) undergo deprotonation with KOtBu to afford the trans-halide-alkylidyne square-planar derivatives OsX(≡CPh)(IPr)(PiPr3) (X = Cl (2), F (5)). Oxidative addition of the C(sp)–H bond of phenylacetylene and methyl propiolate along the Cl–Os–CPh axis of 2 with the hydrogen atom directed to the alkylidyne leads to alkynyl-cis-hydride-alkylidyne intermediates, which rapidly evolve into the five-coordinate alkylidene complexes Os(C≡CR)Cl(═CHPh)(IPr)(PiPr3) (R = Ph (6), CO2Me (7)) as a consequence of the migration of the hydride from the metal center to the Cα atom of the alkylidyne. Oxidative addition of the C(sp)–H bond of methyl propiolate along the X–Os–CPh axis of 2 and 5 with the hydrogen atom directed to the halide gives the alkynyl-trans-hydride-alkylidyne derivatives OsH(C≡CCO2Me)X(≡CPh)(IPr)(PiPr3) (X = Cl (8), F (9)). Complex 8 evolves into 7. However, complex 9 containing the stronger π-donor fluoride is stable. The oxidative addition of HCl to 2 selectively yields the cis-hydride-alkylidyne compound OsHCl2(≡CPh)(IPr)(PiPr3) (10), which is also stable., Financial support from the Spanish MINECO (Projects CTQ2014-52799-P, Red de Excelencia Consolider CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged. J.J.F.C. acknowledges support via a predoctoral fellowship from the DGA.

Metal-mediated direct C–H bond activation at the 8-position of quinolines, which is the essential step for the functionalization of this bond, is promoted by the hexahydride OsH6(PiPr3)2. This complex activates quinoline and 2-, 3-, 6-, and 7-methylquinoline to afford the classical trihydride derivatives OsH3{κ2-C8,N-(quinolinyl)}(PiPr3)2 and OsH3{κ2-C8,N-(quinolinyl-n-Me)}(PiPr3)2 (n = 2, 3, 6, 7), containing a four-membered heterometalla ring., Financial support from the MINECO of Spain (Projects CTQ2014-52799-P and CTQ2014-51912-REDC), the Diputación General de Aragón (E-35), FEDER, and the European Social Fund is acknowledged.

The preparation, photophysical properties, and applicability to the fabrication of organic light-emitting diodes (OLEDs) of new phosphorescent bis(tridentate) [5t + 4t′] iridium(III) molecules are described. Treatment of [Ir(μ-OMe)(η4-COD)]2 (1; COD = 1,5-cyclooctadiene) with 5-tert-butyl-1,3-bis(3-isopropylimidazolium)benzene diiodide ([iPrHImC6H3(5-tBu)HImiPr][I]2), in the presence of KI, leads to [IrI(μ-I){κ3-C,C,C-[iPrImC6H2(5-tBu)ImiPr]}]2 (2). This complex reacts with 2-(1H-imidazol-2-yl)-6-phenylpyridine (HNImpyC6H5) and 2-(1H-benzimidazol-2-yl)-6-phenylpyridine (HNBzimpyC6H5), in the presence of Na2CO3, to afford the bis(tridentate) derivatives Ir{κ3-C,C,C-[iPrImC6H2(5-tBu)ImiPr]}{κ3-N,N,C-[NImpyC6H4]} (4) and Ir{κ3-C,C,C-[iPrImC6H2(5-tBu)ImiPr]}{κ3-N,N,C-[NBzimpyC6H4]} (5). Complexes 4 and 5 are phosphorescent emitters (λem 482–590 nm), which display observed lifetimes in the range 1.2–11.7 μs. They show high quantum yields in both doped poly(methyl methacrylate) films and in 2-methyltetrahydrofuran at room temperature (ϕ = 0.73–0.49). Complex 5 has been demonstrated to be suitable for use as a reasonably efficient phosphorescent greenish yellow emitter for OLED devices with an electroluminescence λmax of 552 nm and a maximum external quantum efficiency (EQE) of 12%., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), Gobierno de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

Complex Rh(Bpin){κ3-P,O,P-[xant(PiPr2)2]} (Bpin = pinacolboryl; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) catalyzes the addition of B2pin2 to 3-hexyne and 4-octyne to give equimolecular mixtures of conjugated boryldienes and borylolefins, as a result of the addition of the B–B bond of the diborane to different molecules of alkynes and hydride transfer from one to the other. Both the dehydrogenative borylation and hydroborylation reactions form a catalytic cycle that has been deduced on the basis of stoichiometric studies. Complex Rh(Bpin){κ3-P,O,P-[xant(PiPr2)2]} promotes the dehydrogenative borylation of alkynes by means of reactions of insertion of the alkyne into the Rh–B bond, Z–E isomerization of the β-borylalkenyl ligand of the resulting Rh–alkenyl species, and Cγ–H bond activation of the alkyl substituent attached to the alkenyl Cα atom. As a consequence of the formation of boryldienes, the monohydride RhH{κ3-P,O,P-[xant(PiPr2)2]} is generated. The latter in a sequential manner reacts with the alkynes and the diborane to give the borylolefin hydroborylation products, via Rh–alkenyl intermediates, and regenerates the initial Rh–boryl compound. The latter also promotes stoichiometric cycles to prepare diboryl-2-olefins via allyl intermediates. In addition, the stoichiometric rhodium-mediated formation of 1-boryl-2-olefins is shown., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged.

The reduction of the N≡C bond of benzonitriles promoted by OsH6(PiPr3)2 (1) has been studied. Complex 1 releases a H2 molecule and coordinates 2,6-dimethylbenzonitrile to afford the tetrahydride OsH4{κ1-N-(N≡CC6H3Me2)}(PiPr3)2 (2), which is thermally stable toward the insertion of the nitrile into one of the Os–H bonds. In contrast to 2,6-dimethylbenzonitrile, benzonitrile and 2-methylbenzonitrile undergo insertion, via Os(η2-N≡CR) intermediates, to give the azavinylidene derivatives OsH3(═N═CC6H4R)(PiPr3)2 [R = H (3) or Me (4)]. The analysis by means of computational tools (EDA–NOCV) of the bonding situation in these compounds suggests that the donor–acceptor nature of the osmium azavinylidene bond dominates over the mixed electron-sharing/donor–acceptor and pure electron-sharing bonding modes. The N atom is strongly nucleophilic, whereas one of the hydrides is electrophilic. In spite of the different nature of these centers, the migration of the latter to the N atom is kinetically prevented. However, the use of water as a proton shuttle allows hydride migration, as a consequence of a significant decrease in the activation barrier. The resulting phenylaldimine intermediates evolve by means of orthometalation to give OsH3{κ2-N,C-(NH═CHC6H3R)}(PiPr3)2 [R = H (5) or Me (6)]. The presence of electrophilic and nucleophilic centers in 3 confers upon it the ability to activate σ-bonds, including H2 and pinacolborane (HBpin). The reaction with the latter gives OsH3{κ2-N,C-[N(Bpin)═CHC6H4]}(PiPr3)2 (7)., Financial support from the Spanish MINECO (Projects CTQ2017-82935-P, CTQ2016-78205-P, and Red de Excelencia Consolider CTQ2016-81797-REDC), Gobierno de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund (FSE) is acknowledged.

The complex Ir(acac){κ2-C,N-[C6BrH3-py]}{κ2-C,N-[C6H4-py]} (2) is a green emitter, which displays short lifetimes (0.9–4.9 μs) and quantum yields of 0.32 in poly(methyl methacrylate) films at 5 wt % and 0.41 in 2-methyltetrahydrofuran at room temperature. Its Pd(OAc)2/4 PPh3-catalyzed cross-coupling reactions with RB(OH)2 afford Ir(acac){κ2-C,N-[C6RH3-py]}{κ2-C,N-[C6H4-py]} (R = Me (3), Ph (4)), which show almost identical emissions with quantum yields in the range 0.98–0.82., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged.

A new class of phosphorescent tris-heteroleptic iridium(III) complexes has been discovered. The addition of PhMeImAgI (PhMeIm = 1-phenyl-3-methylimidazolylidene) to the dimer [Ir(μ-Cl)(COD)]2 (1; COD = 1,5-cyclooctadiene) affords IrCl(COD)(PhMeIm) (2), which reacts with 1-phenylisoquinoline, 2-phenylpyridine, and 2-(2,4-difluorophenyl)pyridine to give the respective dimers [Ir(μ-Cl){κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-isoqui)}]2 (3), [Ir(μ-Cl){κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-py)}]2 (4), and [Ir(μ-Cl){κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6F2H2-py)}]2 (5), as a result of the N-heterocyclic carbene (NHC)- and N-heterocycle-supported o-CH bond activation of the aryl substituents and the hydrogenation of a C–C double bond of the coordinated diene. In solution, these dimers exist as a mixture of isomers a (Im trans to N) and b (Im trans to Cl), which lie in a dynamic equilibrium. The treatment of 3–5 with Kacac (acac = acetylacetonate) yields isomers a (Im trans to N) and b (Im trans to O) of Ir{κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-isoqui)}(κ2-O,O-acac) (6a and 6b), Ir{κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-py)}(κ2-O,O-acac) (7a and 7b), and Ir{κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6F2H4-py)}(κ2-O,O-acac) (8a and 8b), which were separated by column chromatography. The treatment of 6a with HX in acetone–water produces the protonation of the acac ligand and the formation of the bis(aquo) complex [Ir{κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-isoqui)}(H2O)2]X [X = BF4 (9a[BF4]), OTf (9a[OTf])]. The salt 9a[BF4] reacts with 2-(2-pinacolborylphenyl)-5-methylpyridine in the presence of 40 equiv of K3PO4 to afford Ir{κ2-C,C-(C6H4-ImMe)}{κ2-C,N-(C6H4-isoqui)}{κ2-C,N-(C6H4-Mepy)} (10a). Complexes 6a, 6b, 7a, 7b, 8a, 8b, and 10a are phosphorescent emitters (λem = 465–655 nm), which display short lifetimes in the range of 0.2–5.6 μs. They show high quantum yields both in doped poly(methyl methacrylate) films (0.34–0.87) and in 2-methyltetrahydrofuran at room temperature (0.40–0.93). From the point of view of their applicability to the fabrication of organic-light-emitting-diode devices, a notable improvement with regard to those containing two cyclometalated C,N ligands is achieved. The introduction of the cyclometalated aryl-NHC group allows one to reach a brightness of 1000 cd/m2 at a lower voltage and appears to give rise to higher luminous efficacy and power efficacy., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged.

A novel osmium-catalyzed cyclization of o-alkynyl phenethylamines to give 3-benzazepines is reported. The procedure allows the straightforward preparation of a broad range of dopaminergic 3-benzazepine derivatives. Mechanistic investigations revealed that the process takes place via osmacyclopropene intermediates, which were isolated and characterized by X-ray crystallography., This research was supported by the MICINN (projects CTQ2011-28258, CTQ2014-52799-P, and CTQ2014-51912REDC), Xunta de Galicia and the European Regional Development Fund (projects GRC2014/032 and EM 2012/051), the DGA (E-35), and the European Social Fund (SFE). A.A.-P.and C.G.-R. thank the Spanish MICINN for a pre-doctoral FPI fellowship and Juan de la Cierva Contract (JCI-2011-09946), respectively.

Communication.-- Titulo del pdf: Making Easier the β-Lactam Fragmentation via Metal-Assistance: Mechanistic Insight., The mechanism of OsH6(PiPr3)2-mediated fragmentation of a 4-(2 pyridyl)-2-azetidinone has been investigated by DFT calculations. The addition of the C4-H bond of the substrate to OsH2(PiPr3)2 allows the active participation of an osmium lone pair in the B-type b-lactam fragmentation process. This new mechanism makes the N1-C4/C2-C3 fragmentation of the lactamic core thermally accessible through a stepwise process., Financial support from the Spanish MINECO and FEDER (Projects CTQ2013-46459-C2-01-P, CTQ2014-52799-P, CTQ2014-54071-P, and CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged

This is an open access article published under an ACS AuthorChoice License., The hexahydride complex OsH6(PiPr3)2 activates the C−OMe bond of 1-(2-methoxy-2-oxoethyl)-3-methylimidazolium chloride, in addition to promoting the direct metalation of the imidazolium group, to afford a fivecoordinate OsCl(acyl-NHC)(PiPr3)2 compound. The latter coordinates carbon monoxide, oxygen, and molecular hydrogen to give the corresponding carbonyl, dioxygen, and dihydrogen derivatives. Complex 3 also promotes the heterolytic bond activation of pinacolborane (HBpin), using the acyl oxygen atom as a pendant Lewis base. The hydride ligand and the Bpin substituent of the Fischer-type carbene of the resulting complex 7 activate the O−H bond of alcohols and water. As a consequence, complex 3 is a metal ligand cooperating catalyst for the generation of molecular hydrogen, by means of both the alcoholysis and hydrolysis of pinacolborane, via the intermediates 7 and 6., Financial support from the MINECO of Spain (Projects CTQ2014-52799-P and CTQ2014-51912-REDC), the Diputación General de Aragón (E-35), and the European Social Fund (FSE) and FEDER. M.P.G. thanks the Spanish MINECO for her FPI fellowship. T.B. thanks the Spanish MINECO for funding through the Juan de la Cierva program.

This is an open access article published under a Creative Commons Attribution (CC-BY) License., The capacity of the hexahydride complex OsH6(PiPr3)2 (1) to discern between the nitrogen atom and the NH unit in the azole assisted aryl C−H bond activation has been investigated. Complex 1 reacts with 2-phenylimidazole to give OsH3{κ2-C,N-(C6H4-imidazole)}(PiPr3)2 (2), which has been characterized by X-ray diffraction analysis. The structure proves the higher affinity of the metal center for the N atom in the presence of the NH unit, which remains unchanged, and reveals that in the solid state the molecules of this complex form infinite chains by means of intermolecular asymmetric 3-center bifurcated dihydrogen bonds. In solution, 1HDOSY NMR experiments suggest that the association degree decreases as the temperature increases. The fused six-membered ring of benzimidazole weakens the NH bond, enhancing its reactivity. As a consequence, complex 1 cannot discern between the N atom and the NH unit of 2-phenylbenzimidazole. Thus, the treatment of 1 with this substrate leads to a mixture of OsH3{κ2-C,N-(C6H4-benzimidazole)}(PiPr3)2 (3) and the dinuclear species (PiPr3)2H3Os(C6H4-benzimidazolate)OsH(η2-H2)(PiPr3)2 (4). The latter is the result of a N-assisted ortho-C−H bond activation of the phenyl group promoted by 0.5 equiv of 1 and the N−H bond activation promoted by the remaining 0.5 equiv of hexahydride 1 along with the agostic coordination of the remaining ortho-C−H bond to the metal center of the unsaturated fragment OsH(η 2-H2)(PiPr3)2. The comparison of the redox properties of 3 and 4 suggests that the interaction between the metal centers in the dinuclear compound is negligible. The replacement of the NH group of the azoles by a sulfur atom does not modify the behavior of the substrates. Thus, the reactions of 1 with 2-phenylthiazole and 2-phenylbenzothiazole afford OsH3{κ 2-C,N-(C6H4-thiazole)}(PiPr3)2 (5) and OsH3{κ2-C,N-(C6H4-benzothiazole)}(PiPr3)2 (6). In turn, complexes 2, 3, 5, and 6 are phosphorescent., Financial support from the Spanish MINECO and FEDER (Projects CTQ2013-46459-C2-01-P to M.A.S., CTQ2014-52799-P to M.A.E., CTQ2013-44303-P to I.F., CTQ2014-54071-P to A.L., and CTQ2014-51912-REDC, the DGA (E35), and the European Social Fund (FSE) is acknowledged.

The metal fragment Os(CO)(PiPr3)2 stabilizes boryl-dihydrideborate species, which can be viewed as snapshots of states of B–H oxidative addition of a R2BH molecule and frustrated B–H bond activation of a second one. Complex OsH2(η2-CH2═CHEt)(CO)(PiPr3)2 (2) shows a tendency to dissociate the olefin. The resulting dihydride OsH2(CO)(PiPr3)2 (3) rapidly coordinates catecholborane (HBcat) and pinacolborane (HBpin) to give the corresponding σ-borane derivatives OsH2(η2-HBR2)(CO)(PiPr3)2 (BR2 = Bcat (4), Bpin (5)). Complex 4 reacts with a second molecule of HBcat to release H2 and to afford the octahedral boryl dihydride borate derivative Os(Bcat)(κ2-H2Bcat)(CO)(PiPr3)2 (6), which undergoes a thermally activated Bcat site exchange process in solution. Borane displaces catecholborane from the dihydride-borate of 6 to generate the boryl-tetrahydrideborate Os(Bcat)(κ2-H2BH2)(CO)(PiPr3)2 (7). This compound and the Bpin counterpart Os(Bpin)(κ2-H2BH2)(CO)(PiPr3)2 (8) have also been prepared by reaction of the corresponding Os(BR2)Cl(CO)(PiPr3)2 with Na[BH4]., Financial support from the Spanish MINECO (Projects CTQ2011-23459 and CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged. M.M. thanks the Spanish MEC for her FPU grant.

The elemental steps for the preparation of (E)-pinBC(Me)═C(Me)Bpin (Bpin = pinacolboryl) by means of the anti addition of B2pin2 to 2-butyne, promoted by the boryl complex Rh(Bpin){xant(PiPr2)2} (1; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene), have been analyzed from a kinetic point of view, and the intermediates of the process, the β-borylakenyl complexes Rh{(Z)-C(Me)═C(Me)Bpin}{xant(PiPr2)2} (2) and Rh{(E)-C(Me)═C(Me)Bpin}{xant(PiPr2)2} (3), have been isolated and fully characterized. The key step for the formation of the diborylalkene is the transformation of 2 into 3 as a result of the Z–E isomerization of the β-borylalkenyl group, which takes place via metallacyclopropene intermediates. The isomerization is sterically controlled, and the pincer diphosphine adapts its coordination mode to the requirements of the process happening to act as κ2-P,P. The Z–E isomerization of the β-borylalkenyl ligand of 2 is slower than the oxidative addition of the diborane to 1. As a consequence, under catalytic conditions, the formation of the syn-addition product (Z)-pinBC(Me)═C(Me)Bpin is favored, although the intermediate Rh(Bpin)3{xant(PiPr2)2} is much less stable than 2., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputacion General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged.

The preparation of a N,N,N-osmaligand, its coordination to iridium to afford an efficient catalyst precursor, and the catalytic activity of the latter in dehydrogenation reactions of hydrogen carriers based on alcohols are reported. Complex OsH2Cl2(PiPr3)2 (1) reacts with 3-(2-pyridyl)pyrazol to give the osmium(II) complex 2H, which contains an acidic hydrogen atom. Deprotonation of the latter by the bridging methoxy groups of the dimer [Ir(μ-OMe)(η4-COD)]2 (COD = 1,5-cyclooctadiene) leads to Ir(2)(η4-COD) (3), where osmaligand 2 has a free-nitrogen atom. Iridium complex 3 catalyzes the dehydrogenation of secondary and primary alcohols to ketones and aldehydes or esters, respectively, and the dehydrogenation of diols to lactones. Cyclooctatriene is detected during the catalysis by GC-MS, suggesting that the true catalyst of the reactions is a dihydride IrH2(2)-species with osmaligand 2 acting as N,N,N-pincer. The presence of a phenyl group in the substrates favors the catalytic processes. The dehydrogenative homocoupling of primary alcohols to esters appears to take place via the transitory formation of hemiacetals., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged.

Complexes [Ir(μ-Cl)(η2-C8H14)2]2 (1) and [Ir(μ-Cl)(η4-C8H12)]2 (2) promote the pyridyl-directed ortho-CH and ortho-CBr activations of the phenyl substituent of 2-(2-bromophenyl)pyridine. The formed products depend upon the olefin of the dimer, which governs the kinetic preference of the activation. The cyclooctene complex 1 reacts with the substituted heterocycle to give (η2-C8H14)2Ir(μ-Cl)2Ir{κ2-C,N-[C6BrH3-py]}2 (3), in acetone, at room temperature. Treatment of 3 with K(acac) affords Ir(acac)(η2-C8H14)2 (4) and Ir(acac){κ2-C,N-[C6BrH3-py]}2 (5; acac = acetylacetone). Under more severe conditions, 2-ethoxyethanol under reflux, the reaction of 1 with the heterocycle gives a yellow solid, which yields a 5:82:7 mixture of 5, Ir(acac){κ2-C,N-[C6BrH3-py]}{κ2-C,N-[C6H4-py]} (6), and Ir(acac){κ2-C,N-[C6H4-py]}2 (7) by reaction with K(acac). In acetone or toluene, at room temperature, 2-(2-bromophenyl)pyridine breaks the chloride bridges of dimer 2 to form IrCl(η4-C8H12){κ1-N-[py-C6BrH4]} (8), which evolves into IrClBr{κ2-C,N-[C6H4-py]}(η4-C8H12) (9) as a result of the oxidative addition of the ortho-CBr of the phenyl substituent to the metal center. Treatment of 9 with Ag2O in acetylacetone leads to Ir(acac){κ2-C,N-[C6H4-py]}{κ1-C, η2-[C8H12-(C3-acac)]} (10), as a consequence of the replacement of the halides by an O,O-chelate acac ligand and the outside to metal nucleophilic attack of a second acac group to the diene C–C double bond disposed trans to bromide., Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputación General de Aragón (E06_17R), FEDER, and the European Social Fund is acknowledged.