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The organic molecule 2-(1-phenyl-1-(pyridin-2-yl)ethyl)-6-(3-(1-phenyl-1-(pyridin-2-yl)ethyl)phenyl)pyridine (H3L) has been designed, prepared, and employed to synthesize the encapsulated-type pseudo-tris(heteroleptic) iridium(III) derivative Ir(κ6-fac-C,C′,C″-fac-N,N′,N″-L). Its formation takes place as a result of the coordination of the heterocycles to the iridium center and the ortho-CH bond activation of the phenyl groups. Dimer [Ir(μ-Cl)(η4-COD)]2 is suitable for the preparation of this compound of class [Ir(9h)] (9h = 9-electron donor hexadentate ligand), but Ir(acac)3 is a more appropriate starting material. Reactions were carried out in 1-phenylethanol. In contrast to the latter, 2-ethoxyethanol promotes the metal carbonylation, inhibiting the full coordination of H3L. Complex Ir(κ6-fac-C,C′,C″-fac-N,N′,N″-L) is a phosphorescent emitter upon photoexcitation, which has been employed to fabricate four yellow emitting devices with 1931 CIE (x:y) ∼ (0.52:0.48) and a maximum wavelength at 576 nm. These devices display luminous efficacies, external quantum efficiencies, and power efficacies at 600 cd m–2, which lie in the ranges 21.4–31.3 cd A–1, 7.8–11.3%, and 10.2–14.1 lm W1–, respectively, depending on the device configuration., Financial support from 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 CESGA Supercomputing Center and BIFI Institute are also acknowledged for the use of their computational resources.

The preparation of three families of phosphorescent iridium(III) emitters, including iridaoxazole derivatives, hydroxycarbene compounds, and

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.

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 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 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)(η

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 wide range of ruthenium complexes stabilized by the POP-pincer ligand xant(PiPr2)2 (9,9-dimethyl-4,5- bis(diisopropylphosphino)xanthene) were prepared starting from cis-RuCl 2{κ-S-(DMSO)4} (1; DMSO = dimethyl sulfoxide). Treatment of toluene solutions of this adduct with the diphosphine under reflux leads to RuCl2{xant(PiPr2)2} (κ-S-DMSO) (2), which reacts with H2 in the presence of a Brønsted base. The reaction in the presence of Et3N affords RuHCl{xant(PiPr2)2}(κ-S-DMSO) (3), whereas NaH removes both chloride ligands to give RuH2{xant(P iPr2)2}(κ-S-DMSO) (4). The stirring of 3 in 2-propanol under 3 atm of H2 for a long time produces the elimination of DMSO and the coordination of H2 to yield the dihydrogen derivative, RuHCl(η2-H2){xant(P iPr2)2} (5). In contrast to H2, PPh3 easily displaces DMSO from the metal center of 3 to afford RuHCl{xant(PiPr2)2}(PPh3) (6), which can be also obtained starting from RuHCl(PPh3)3 (7) and xant(PiPr2)2. In contrast to 3, complex 4 does not undergo DMSO elimination to give RuH2(η2-H 2){xant(PiPr2)2} (8) under a H 2 atmosphere. However, the latter can be prepared by hydrogenation of Ru(COD)(COT) (9; COD = 1,5-cyclooctadiene and COT = 1,3,5-cyclooctatriene) in the presence of xant(PiPr2)2. A more efficient procedure to obtain 8 involves the sequential hydrogenation with ammonia borane of the allenylidene derivative RuCl2(i=Ci=Ci=CPh2) {xant(PiPr2)2} (10), which is formed from the reaction of 2 with 1,1-diphenyl-2-propyn-1-ol. The hydrogenation initially gives RuCl2(i=Ci=CHCHPh2){xant(PiPr 2)2} (11), which undergoes the subsequent reduction of the Ru-C double bond to yield the hydride-tetrahydroborate complex, RuH(η2-H2BH2){xant(PiPr 2)2} (12). The osmium complex, OsCl 2{xant(PiPr2)2}(κ-S-DMSO) (13), reacts with 1,1-diphenyl-2-propyn-1-ol in a similar manner to its ruthenium counterpart 2 to yield the allenylidene derivative, OsCl 2(i=Ci=Ci=CPh2){xant(PiPr2) 2} (14). Ammonia borane also reduces the Cβ-C γ double bond of the allenylidene of 14. However, the resulting vinylidene species, OsCl2(i=Ci=CHCHPh2){xant(P iPr2)2} (15), is inert. Complex 12 is an efficient catalyst precursor for the hydrogen transfer from 2-propanol to ketones, the α-alkylations of phenylacetonitrile and acetophenone with alcohols, and the regio- and stereoselective head-to-head (Z) dimerization of terminal alkynes. © 2014 American Chemical Society., Financial support from the Spanish MINECO (CTQ2011-23459) and Consolider Ingenio 2010 (CSD2007-00006), the DGA (E35), and the European Social Fund (FSE) is acknowledged. T.B. thanks the Spanish MINECO for funding through the Juan de la Cierva programme. J.A. acknowledges support via a predoctoral fellowship from the DGA.

A wide range of osmium-polyhydride complexes stabilized by the POP-pincer ligand xant(PiPr2)2 (9,9-dimethyl-4,5- bis(diisopropylphosphino)xanthene) have been synthesized through cis-OsCl 2{κ-S-(DMSO)4} (1, DMSO = dimethyl sulfoxide). Treatment of toluene solutions of this adduct with the diphosphine, under reflux, leads to OsCl2{xant(PiPr2) 2}(κ-S-DMSO) (2). The reaction of 2 with H2 in the presence of Et3N affords OsH3Cl{xant(PiPr 2)2} (3), which can be also prepared by addition of xant(PiPr2)2 to toluene solutions of the unsaturated d4-trihydride OsH3Cl(PiPr 3)2 (5). Complex 3 reductively eliminates H2 in toluene at 90 °C. In the presence of dimethyl sulfoxide, the resulting monohydride is trapped by the S-donor molecule to give OsHCl{xant(P iPr2)2}(κ-S-DMSO) (6). The reaction of 2 with H2 is sensible to the Brønsted base. Thus, in contrast to Et3N, NaH removes both chloride ligands and the hexahydride OsH 6{xant(PiPr2)2} (7), containing a κ2-P-binding diphosphine, is formed under 3 atm of hydrogen at 50 C. Complex 7 releases a H2 molecule to yield the tetrahydride OsH4{xant(PiPr2)2} (8), which can be also prepared by reaction of OsH6(PiPr3) 2 (9) with xant(PiPr2)2. Complex 8 reduces H+ to give, in addition to H2, the oxidized OsH4-species [OsH4(OTf){xant(PiPr 2)2}]+ (10, OTf = trifluoromethanesulfonate). The redox process occurs in two stages via the OsH5-cation [OsH 5{xant(PiPr2)2}]+ (11). The metal oxidation state four can be recovered. The addition of acetonitrile to 10 leads to [OsH2(η2-H2)(CH 3CN){xant(PiPr2)2}]2+ (12). The deprotonation of 12 yields the osmium(IV) trihydride [OsH 3(CH3CN){xant(PiPr2) 2}]+ (13), which is also formed by addition of HOTf to the acetonitrile solutions of 8. The latter is further an efficient catalyst precursor for the head-to-head (Z)-dimerization of phenylacetylene and tert-butylacetylene. During the activation process of the tetrahydride, the bis(alkynyl)vinylidene derivatives Os(C≡CR)2(=C=CHR) {xant(PiPr2)2} (R = Ph (14), tBu (15)) are formed. © 2013 American Chemical Society., Financial support from the Spanish MINECO (Projects CTQ2011-23459 and Consolider Ingenio 2010 (CSD2007-00006)), the DGA (E35) and the European Social Fund (FSE) is acknowledged. T.B. thanks Spanish MINECO for funding through the Juan de la Cierva programme. J.A. acknowledges support via a predoctoral fellowship from the DGA.

Complex OsH 6(P iPr 3) 2 (1) reacts with 1-methylthymine and 1-methyluracil to give OsH 3(P iPr 3) 2(nucleobase') (2, 3) containing the deprotonated nucleobases (nucleobase') 2-N,O coordinated by the nitrogen atom at position 3 and the oxygen bonded to the carbon atom of the ring at position 4. Similarly, the reactions of 1 with thymidine, 5-methyluridine, deoxyuridine, and uridine lead to OsH 3(P iPr 3) 2(nucleoside') (4-7) with the deprotonated nucleoside (nucleoside') 2-N,O coordinated by the nitrogen atom at position 3 and the oxygen bonded to the carbon atom at position 4 of the nucleobases. Treatment of complexes 5 and 7, containing nucleosides derived from ribose, with OsH 2Cl 2(P iPr 3) 2 (8) in the presence of Et 3N affords dinuclear species OsH 3(P iPr 3) 2(nucleobase')-(ribose)(P iPr 3) 2H 2Os (9, 10) formed by two different metal fragments. Complex 1 also promotes the cleavage of the N-C bond of 2-7 to give the dinuclear species {OsH 3(P iPr 3) 2} 2(nucleobase'') (11, 12) with the nucleobase skeleton (nucleobase'') 2-N,O coordinated to both metal fragments. These compounds can be also prepared by reaction of 1 with 0.5 equiv of thymine and uracil. The use of 1:1 hexahydride:nucleobase molar ratios gives rise to the preferred formation of the mononuclear complexes OsH 3(P iPr 3) 2(nucleobase''') (13, 14; nucleobase''' = monodeprotonated thymine or uracil). The X-ray structures of complexes 6, 11, and 14 are also reported. © 2012 American Chemical Society., Financial support from the MINECO of Spain (Projects CTQ2011-23459 and Consolider Ingenio 2010 CSD2007- 00006), the Diputación General de Aragón (E35), and FEDER is acknowledged.

A metal-promoted degradation of 2-azetidinones to afford CC′N-pincer ligands is reported. The hexahydride complex OsH6(PiPr3)2 (1) reacts with (±)-cis-1-(4-methoxyphenyl)-3-phenoxy-4-(pyridin-2-yl)azetidin-2-one (I), (±)-cis-1-(4-methoxyphenyl)-3-phenoxy-4-(isoquinolin-2-yl)azetidin-2-one (II), and (±)-cis-1-(4-methoxyphenyl)-3-phenoxy-4-(quinolin-2-yl)azetidin-2-one (III) to give the respective OsH2(PiPr3)2(CC′N) (2–4) complexes, which add HBF4·OEt2 to yield [OsH2(PiPr3)2(CC″N)]BF4 (5–7). These salts are the result of the addition of the proton of the acid to the dianionic CC′N-pincer ligand. The hydride ligands of these compounds undergo quantum mechanical exchange coupling, which has been experimentally quantified according to a two-dimensional harmonic oscillator model, where Jex is determined by the separation between the hydrides, their hard sphere radius, and a ν parameter describing the H–M–H vibrational wag mode allowing the movement along the H–H vector. The comparison of the results reveals that the phenomenon is particularly intense for 5–7. Furthermore, in these compounds, the separation between the hydrides is ∼0.1 Å shorter than in the respective neutral species 2–4, whereas the hydride hard sphere radius increases by ∼10%, and the ν value decreases by ∼20%., Financial support from the Spanish MINECO (Project Nos. CTQ2013-46459-C2-01-P, CTQ2014-52799-P, and CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged.

The dihydrido-olefin complex OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2) (2) reacts with H(2)SiPh(2) to give OsH(3)(SiHPh(2))(CO)(P(i)Pr(3))(2) (3). The molecular structure of 3 has been determined by X-ray diffraction (monoclinic, space group P2(1)/c with a = 16.375(2) A, b = 11.670(1) A, c =18.806(2) A, beta = 107.67(1) degrees, and Z = 4) together with ab initio calculations on the model compound OsH(3)(SiH(3))(CO)(PH(3))(2). The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydrido ligand and the carbonyl group in the axial positions. The two other hydrido ligands lie in the equatorial plane, one between the phosphine ligands and the other between the SiHPh(2) group and one of the phosphine ligands. Complex 3 can also be prepared by reaction of OsH(eta(2)-H(2)BH(2))(CO)(P(i)Pr(3))(2) (4) with H(2)SiPh(2). Similarly, the treatment of 4 with HSiPh(3) affords OsH(3)(SiPh(3))(CO)(P(i)Pr(3))(2) (5), while the addition of H(3)SiPh to 4 in methanol yields OsH(3){Si(OMe)(2)Ph}(CO)(P(i)Pr(3))(2) (6). Complex 2 also reacts with HGeR(3) and HSnR(3) to give OsH(3)(GeR(3))(CO)(P(i)Pr(3))(2) (GeR(3) = GeHPh(2) (7), GePh(3) (8), GeEt(3) (9)) and OsH(3)(SnR(3))(CO)(P(i)Pr(3))(2) (R = Ph (10), (n)Bu (11)), respectively. In solution, compounds 3 and 5-11 are fluxional and display similar (1)H and (31)P{(1)H} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.

The dihydrido-dichloro complex OsH2Cl2(P-z'-Pr3)2 (1) reacts with 2,2,-biimidazole (H2bim) to give the dihydrogen derivative [OsCl(»?2-H2)(H2bim)(P-!-Pr3)2]Cl (2). The molecular structure of 2 has been determined by X-ray investigation. 2 crystallizes with a dichloromethane molecule in the triclinic space group with a = 12.133(1)k,b = 16.034(1) A, c = 18.321(1) A, a = 105.10(1)°, ß = 90.01(1)°, y = 93.87(1)°, and Z = 4. The coordination geometry around the osmium center can be rationalized as a distorted octahedron with the two phosphine ligands disposed mutually trans. The remaining coordination sites of the octahedron are occupied by the dihydrogen ligand, the chloride atom, and by two nitrogen atoms of the chelate 2,2'-biimidazole ligand. One of the two acidic NH groups of the 2,2,-biimidazole ligand of 2 can be deprotonated by NaBH4 to give [OsCl(i)2-H2)(Hbim)(P-¡-Pr3)2] (3). Similarly the 2,2'-biimidazole ligand of 2 is deprotonated by dimers of the type [M(/u-OMe)(diolefin)]2 to form the heterobimetallic compounds [(P-i-Pr3)2(t;2-H2)C10s(/u-Hbim)RhCl(COD)] (COD = 1,5-cyclooctadiene, 4), [(P-i-Pr3)2(j)2-H2)C10s(M-Hbim)IrCl(C0D)] (5), and [(P-z-Pr3)2(r,2-H2)C10s(M-Hbim)IrCl(TFB)] (TFB = tetrafluorobenzobarrelene, 6). The addition of pyrazole to 1 leads to the complex trans-dichloro-[OsCl2(i72-H2)-(Hpz)(P-(-Pr3)2] (7), which is transformed into its isomer cis-dichloro- [OsCl2(i?2-H2)(Hpz)(P-z-Pr3)2] (8) by stirring in hexane at 60 °C. The molecular structure of 8 has also been determinated. 8 crystallizes with a pyrazole molecule in the monoclinic space group C2/c (No. 15) with a = 21.575(3) k,b = 8.743(1) A, c = 31.341(9) A, ß = 90.98(2)°, and Z = 8. The coordination geometry around the osmium center could be described as based on a distorted octahedron with the two phosphine ligands occuping the apical positions. The equatorial plane is formed by the dihydrogen and the pyrazole ligands mutually ris-disposed and the two chloride atoms are also ris-disposed., We thank Dr. E. Sola for T1 measurements and the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) for financial support.

Complex OsH{η5-C5H4(CH 2)2NMe2}(PiPr3) 2 (1) reacts with 1 equiv of trifluoromethanesulfonic acid (HOTf) and trifluoromethanesulfonic acid-d1 (DOTf) to produce the dihydride and hydride-deuteride complexes, [OsHE{η5-C5H 4(CH2)2NMe2}(PiPr 3)2]OTf (E = H (2), D (2-d1)), respectively. Treatment of 2 and 2-d1 with a second equivalent of HOTf gives [OsHE[η5-C5H4(CH2) 2NHMe2}(PiPr3)2][OTf] 2 (E = H (3), D (3-d1)) as a result of the protonation of the nitrogen atom. While the hydride and deutende ligands of 2, 2-d1, 3, and 3-d1 do not undergo any H/D exchange process with the solvent, in acetone-d6 the NH proton of 3 and 3-d1 changes places with a deuterium atom of the solvent to yield [OsHE{η5- C5H4(CH2)2NDMe2}(P iPr3)2][OTf]2 (E = H (3-Nd 1), D (3-d2)). Complex 3-Nd1 can also be obtained from the treatment of complex 2 with DOTf in dichloromethane. No exchange process between the hydride and the ND positions in 3-Nd1 or between the deuteride and NH positions in 3-d1 has been observed. Treatment of 3-Nd1 and 3-d1 with sodium methoxide results in a selective reaction of the base with the ammonium group to regenerate 2 and 2-d1, respectively. Complex 1 also reacts with methyl and methyl-d3 trifluoromethanesulfonate (CH3OTf and CD 3OTf, respectively) to give [OsH{η5-C 5H4(CH2)2NMe2CE 3}(PiPr3)2]OTf (E = H (4), D (4-d3)) as a result of the addition of the CE3 (E = H, D) group to the nitrogen atom. Complex 4 has been characterized by an X-ray diffraction analysis. It reacts with a second molecule of CH3OTf or CD3OTf to produce [OsH{η5-C5H 4(CH2)2-NMe3}{CH 2CH(CH3)PiPr2}(PiPr 3)][OTf]2 (5). Similarly, complex 4-d3 reacts with a second molecule of CH3OTf or CD3OTf to yield [OsH{η5-C5H4(CH2) 2NMe2CD3}{CH2CH(CH 3)PiPr2}(PiPr3)][OTf] 2 (5-d3). In acetonitrile, complex 5 evolves to an equilibrium mixture of the acetonitrile adducts [Os{η5-C 5H4(CH2)2NMe3}(NCCH 3)(PiPr3)2][OTf]2 (7) and [Os{η5-C5H4(CH2) 2NMe3}(NCCH3)2(PiPr 3)][OTf]2 (8). In methanol or methanol-d4, complex 4 is not stable and loses trimethylamine to give the vinylcyclopentadienyl derivatives [OsHE(η5-C5H 4CH=CH2)(PiPr3)2]OTf (E = H (9), D (9-d1)) as a result of the protonation or deuteration of the metallic center and a subsequent Hofmann elimination. Protonation of 4 with HOTf gives the dihydride-trimethylammonium derivative [OsH2{η 5-C5H4(CH2)2NMe 3}(PiPr3)2]-[OTf]2 (10). Treatment of 9 with sodium methoxide produces OsH(η5-C 5H4CH=CH2)(PiPr3) 2 (11). © 2005 American Chemical Society., Financial support from the MCYT of Spain (Projects BQU2002-00606) is acknowledged.

The dihydrido-olefin complex OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2) (2) reacts with H(2)SiPh(2) to give OsH(3)(SiHPh(2))(CO)(P(i)Pr(3))(2) (3). The molecular structure of 3 has been determined by X-ray diffraction (monoclinic, space group P2(1)/c with a = 16.375(2) Å, b = 11.670(1) Å, c =18.806(2) Å, beta = 107.67(1) degrees, and Z = 4) together with ab initio calculations on the model compound OsH(3)(SiH(3))(CO)(PH(3))(2). The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydrido ligand and the carbonyl group in the axial positions. The two other hydrido ligands lie in the equatorial plane, one between the phosphine ligands and the other between the SiHPh(2) group and one of the phosphine ligands. Complex 3 can also be prepared by reaction of OsH(eta(2)-H(2)BH(2))(CO)(P(i)Pr(3))(2) (4) with H(2)SiPh(2). Similarly, the treatment of 4 with HSiPh(3) affords OsH(3)(SiPh(3))(CO)(P(i)Pr(3))(2) (5), while the addition of H(3)SiPh to 4 in methanol yields OsH(3){Si(OMe)(2)Ph}(CO)(P(i)Pr(3))(2) (6). Complex 2 also reacts with HGeR(3) and HSnR(3) to give OsH(3)(GeR(3))(CO)(P(i)Pr(3))(2) (GeR(3) = GeHPh(2) (7), GePh(3) (8), GeEt(3) (9)) and OsH(3)(SnR(3))(CO)(P(i)Pr(3))(2) (R = Ph (10), (n)Bu (11)), respectively. In solution, compounds 3 and 5-11 are fluxional and display similar (1)H and (31)P{(1)H} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.

The complexes IrH2(η2-O2CR)(PPh3)2 (R = (S)-CH(NaphOMe)Me (2), (R)-CH(OMe)Ph (3), (R)-C(CF3)(OMe)Ph (4), (S)-CHOC(=O)CH2CH2 (5)) have been prepared by reaction of IrH5(PPh3)2 (1) with the corresponding carboxylic acid RCO2H. The reactivity of these compounds toward acetylenedicarboxylic dimethyl ester and HBF4 has been studied. 2-5 react with acetylenedicarboxylic dimethyl ester to afford the hydrido-vinyl complexes IrH-{C(CO2Me)=CH(CO2Me)}(η2-O 2CR)(PPh3)2 (R = (S)-CH(NaphOMe)Me (6), (R)-CH(OMe)Ph (7), (R)-C(CF3)(OMe)Ph (8), (S)-CHOC(=O)CH2CH2 (9)) by insertion of the alkyne into one of the two Ir-H bonds of the starting complexes. Reactions of 2 and 3 with HBF4 in diethyl ether lead to the hydrido-bridged dinuclear complexes [Ir2H2(PPh3)4(μ-H)2 (μ-η2-O2CR)]BF4 (R = (S)-CH(NaphOMe)Me (10), (R)-CH(OMe)Ph (11)). The molecular structure of 11 was determined by an X-ray investigation. Compound 11 crystallizes in the orthorhombic system, space group P212121, with cell dimensions a = 14.082(1) Å, b = 23.169(2) Å, and c = 25.291(3) Å, and Z = 4. The structure was refined to the following R and Rw values: 0.0414 and 0.0389 for 8343 observed reflections. The cation of 11 can be described as a dinuclear species of 32 valence electrons. Electron counting, to satisfy the 18-electron rule, suggests the presence of an iridium-iridium double bond which is consistent with the observed iridium-iridium distance (2.6592(6) Å). EHT-MO calculations on the model [Ir2H2(PH3)4(μ-H) 2(μ-η2-O2CH)]+ suggests the existence of a >partial> double bond between the metal atoms. However, the interaction between metals is not based on the direct overlap of the iridium orbitals, but on the three center bonds formed by the bridging system. © 1994 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Projet: Selective Processes and Catalysis involving Small Molecules) for financial support. M.M. and E.O.thank the DGA (Diputación General de Aragón) for a grant.