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The coordination of pyridine-2-amino(methyl)dimethylsilane ligands to ruthenium has afforded access to a family of novel complexes that display multicenter Ru-H-Si interactions according to the number of incorporated ligands. The new complexes Ru[κ-Si,N-(SiMe2)N(Me)(C5H4N)](η(4)-C8H12)(η(3)-C8H11) (1), Ru2(μ-H)2(H)2[κ-Si,N-(SiMe2)N(Me)(C5H4N)]4 (2), and Ru(H)[κ-Si,N-(SiMe2)N(Me)(C5H4N)]3 (3) were isolated and fully characterized. The complexes exhibit different degrees of Si-H activation: complete Si-H cleavage, secondary interactions between the atoms (SISHA), and η(2)-Si-H coordination. Reversible protonation of 3 leading to the cationic complex [RuH{(η(2)-H-SiMe2)N(Me)κ-N-(C5H4N)}{κ-Si,N-(SiMe2)N(Me)(C5H4N)}2](+)[BAr(F)4](-) (5) was also demonstrated. The coordination modes in these systems were carefully studied with a combination of X-ray and neutron diffraction analysis, DFT geometry optimization, and multinuclear NMR spectroscopy.

Unexpected room temperature luminescence is observed and rationalized by highly challenging excited state calculations for a functionalized phosphine ligand coordinated on the [Ru(bpy)(tpy)](2+) core.

The reactivity of the (o-phosphinophenyl)(amino)borane compound HB(N(i)Pr(2))C(6)H(4)(o-PPh(2)) prepared from Li(C(6)H(4))PPh(2) and HBCl(N(i)Pr(2)) toward the bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1) was studied by a combination of DFT, X-ray, and multinuclear NMR techniques including solid-state NMR, a technique rarely employed in organometallic chemistry. The study showed that the complex RuH(2){HB(N(i)Pr(2))C(6)H(4)(o-PPh(2))}(PCy(3))(2) (3), isolated in excellent yield as yellow crystals and characterized by X-ray diffraction, led in solution to PCy(3) dissociation and formation of an unsaturated 16-electron complex RuH(2){HB(N(i)Pr(2))C(6)H(4)(o-PPh(2))}(PCy(3)) (4), with a hydride trans to a vacant site. In both cases, the (phosphinoaryl)(amino)borane acts as a bifunctional ligand through the phosphine moiety and a Ru-H-B interaction, thus featuring an agostic interaction.

An uncommon synergism in the concerted action of OH- and PR3 toward the simple Ru(II) complex Ru(CO)3Cl2(thf) allows a highly efficient reduction of the metal in ethanol or acetonitrile solution at 0 degrees C, with selective production of the corresponding Roper's-type Ru(0) complexes Ru(CO)2(PR3)3 in high yields within 10 min.

A novel reactivity of 5‐barbiturate imidazo[1,5‐a]pyridinium 1⋅H with [Ru(2‐methylallyl)2(COD)] was explored which led to the formation of an uncommon, zwitterionic complex [Ru(1')(1⋅H)], composed of the NHC ligand 1', cyclometallated at one ortho‐methyl position of the N‐mesityl substituent, and the zwitterionic precursor 1⋅H. Barbiturate moieties coordinate either through a η3 mode or through coordination of the anionic oxygen atom to ensure the coordination saturation and stability to the complex. The addition of pivalic acid results in the protonolysis of the Ru‐Calkyl bond and demetallation of the N‐mesityl, while triphenylphosphine and pyridine are able to displace the rather labile 1⋅H ligand. Attempts to incorporate an alkylidene fragment from these complexes led to the isolation of a rare complex 7 bearing an alkylidene tethered to a η5‐cyclopentadienyl ligand formed by phenylacetylene tetramerization. [ABSTRACT FROM AUTHOR]

Three Hoveyda‐Grubbs complexes supported by N‐(9‐alkylfluorenyl)imidazol‐2‐ylidene ligands (alkyl=methyl, ethyl or benzyl) have been synthesized. With the aim to generate chelating, cyclometalated (C,CNHC) ruthenium complexes for Z‐selective olefin metathesis, the C(sp3)‐H activation of the dangling alkyl group has been studied. While the methyl derivative leads to the expected cyclometalated complex, a C(sp2)‐H activation of the fluorenyl moiety and no evolution/transformation are observed for the ethyl and benzyl derivatives, respectively. Although highly fragile under catalytic conditions, the cyclometalated complex leads to Z/E stereoselectivity up to 94/6. An unprecedented insertion of the alkylidene moiety into the Ru‐CNHC bond leading to ruthenium N‐heterocyclic olefin complexes is also observed and supported by calculations of the corresponding reaction pathway. [ABSTRACT FROM AUTHOR]

A series of polypyridyl ruthenium(II) complexes has been synthesized and characterized by ³H-NMR, electronic absorption and voltammetric techniques. Among this series, hexafluorophosphate salts of eight ruthenium(II) complexes were newly prepared. Due to the well-known ability of this class of compounds to assist electro- and photocatalytic reductive processes (such as the reduction of CO2, H+ and NAD(P)+ models), particular attention has been paid to investigate the nature of their one- and two-electron reduced species through computational and spectroscopic techniques. [ABSTRACT FROM AUTHOR]

The incorporation of a nitrile function ortho to the B(sp2)HN iPr2 group to obtain cyano(aryl)boranes and subsequent ruthenium-catalyzed transformation of these cyano(aryl)boranes under a dihydrogen atmosphere (0.1 MPa) provided direct access to NH-containing 1 H-2,1-benzazaboroles as BN analogues of indene under very mild conditions (i.e., room temperature). The BN heterocycle could be functionalized from the corresponding lithium amide either by N-elementation with various p-block (C, Si, P, B) electrophiles or by palladium-catalyzed N-arylation with aryl bromides thus to provide a new and powerful protocol for B−N bond decoration. [ABSTRACT FROM AUTHOR]

We recently disclosed a new ruthenium-catalyzed dehydrogenative cyclization process (CDC) of diamine-monoboranes leading to cyclic diaminoboranes. In the present study, the CDC reaction has been successfully extended to a larger number of diamine-monoboranes ( 4- 7) and to one amine-borane alcohol precursor ( 8). The corresponding NB(H)N- and NB(H)O-containing cyclic diaminoboranes ( 12- 15) and oxazaborolidine ( 16) were obtained in good to high yields. Multiple substitution patterns on the starting amine-borane substrates were evaluated and the reaction was also performed with chiral substrates. Efforts have been spent to understand the mechanism of the ruthenium CDC process. In addition to a computational approach, a strategy enabling the kinetic discrimination on successive events of the catalytic process leading to the formation of the NB(H)N linkage was performed on the six-carbon chain diamine-monoborane 21 and completed with a 15N NMR study. The long-life bis-σ-borane ruthenium intermediate 23 possessing a reactive NHMe ending was characterized in situ and proved to catalyze the dehydrogenative cyclization of 1, ascertaining that bis σ-borane ruthenium complexes are key intermediates in the CDC process. [ABSTRACT FROM AUTHOR]

Comparedwith the reactivity of o-Ph2P(C6H4–CH2)BH(NiPr2) with [RuH2(η2-H2)2(PCy3)2], the behaviorof the phosphinoborane Ph2P(CH2–C6H4)BH(NiPr2) is radically different. No agostic σ-B–H complexcould be observed, the reaction leading to the isolation of a newbis-σ borane aryl-ruthenium complex via B–C bond cleavageand Ru–C bond formation. Reactivity studies of this complexwith dihydrogen and/or HBArF4as a proton sourceenable the formation of a tethered chiral-at-Ru piano-stool cationiccomplex. [ABSTRACT FROM AUTHOR]

Tuning the nature of the linker in a L∼BHR phosphinoborane compound led to the isolation of a ruthenium complex stabilized by two adjacent, δ-CH and ε-Bsp2H, agostic interactions. Such a unique coordination mode stabilizes a 14-electron 'RuH2P2' fragment through connected σ-bonds of different polarity, and affords selective BH, CH, and BC bond activation as illustrated by reactivity studies with H2 and boranes. [ABSTRACT FROM AUTHOR]

Functionalization of CO2 is a challenging goal and precedents exist for the generation of HCOOH, CO, CH3OH, and CH4 in mild conditions. In this series, CH2O, a very reactive molecule, remains an elementary C1 building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO2 catalyzed by a polyhydride ruthenium complex. Guided by mechanistic studies, we disclose the selective trapping of formaldehyde by in situ condensation with a primary amine into the corresponding imine in very mild conditions. Subsequent hydrolysis into amine and a formalin solution demonstrates for the first time that CO2 can be used as a C1 feedstock to produce formaldehyde. [ABSTRACT FROM AUTHOR]

Silylation of ethylene by the chlorosilanes HSiMe2Cl and HSiMeCl2was catalysed by the bis(dihydrogen) complex RuH2(η2-H2)2(PCy3)2(1). Dehydrogenative silylation leading to the formation of the corresponding vinylsilanes was in competition with hydrosilylation. The rate and selectivity of the reactions were influenced by the number of chloro substituents and the ethylene pressure. A comparative mechanistic study was performed in toluene-d8with the two chlorosilanes. Reaction of 1with an excess of HSiMe2Cl (10 equiv.) produced the σ-silane complexes RuH2(η2-H2)(η2-HSiMe2Cl)(PCy3)2(2Me2Cl), RuH2(η2-HSiMe2Cl)2(PCy3)2(3Me2Cl) and the silyl complex RuCl(SiMe2Cl)(η2-H2)(PCy3)2(4Me2Cl), all characterised by multinuclear NMR spectroscopy. Complexes 2Me2Cland 3Me2Cladopt a cisconfiguration for the two bulky phosphine ligands as a result of stabilising SISHA (Secondary Interactions between Silicon and Hydrogen Atoms) interactions. Complex 4Me2Clresulted from the stoichiometric reaction of HSiMe2Cl with 1producing RuHCl(η2-H2)(PCy3)2in situwhich further reacted with evolution of H2and formation of 4Me2Cl. When reacting 1with 10 equiv. of HSiMeCl2, the corresponding complexes 3MeCl2and 4MeCl2were detected as well as traces of 2MeCl2. The reactivity toward ethylene was then examined. Under catalytic conditions (excess silane in toluene-d8, ethylene atmosphere) only two compounds could be characterised: free PCy3and the new (η6-aryl)(disilyl) complexes of the general formula Ru(η6-C6D5CD3)(SiMe3−nCln)2(PCy3) (6Me3−nCln-d8, n= 1,2). The X-ray structure of 6MeCl2was obtained on a single-crystal at 160 K. When only 2 equiv. of HSiMe2Cl were added, the ethylene(silyl) complex RuH(SiMe2Cl)(C2H4)(PCy3)2(7Me2Cl) was obtained in addition to the organic products resulting from catalytic hydrogenation, hydrosilylation and dehydrogenative silylation, i.e.C2H6(major one), C2H3SiMe2Cl and C2H5SiMe2Cl. In the case of 2 equiv. of HSiMeCl2, upon ethylene addition, 7MeCl2was formed in minority compared to a new disilyl complex Ru(SiMeCl2)2(PCy3)2(8MeCl2) characterised by NMR spectroscopy and X-ray diffraction on a single crystal at 160 K. In 8MeCl2, a formal 14-electron species, stabilisation through two agostic C–H bonds of the cyclohexyl groups was ascertained by DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and crystal structures of two new phosphine ruthenium polypyridine complexes [Ru(tpy)(bpy)(PR3)]2+ with R=Ph (1), Cy (2) are reported. Their geometrical parameters are intimately related to the electronic and steric properties of the phosphine ligand. Electrochemical and UV–Vis analyses showed the influence of the substituents of the coordinated phosphorus atom on the RuIII/RuII potential and on the frontier orbitals energy gap. The results are discussed in terms of steric effects and net donor power of the phosphine ligands. [Copyright &y& Elsevier]

Reactivity of borate ligand derived from CS 2 with κ2- N,S -chelated ruthenium borate complexes, [Ph 3 P(κ2- N,S -L)Ru{κ3- H,S,S ′-H 2 B(L) 2 }], (L = C 7 H 4 NS 2 , C 5 H 4 NS) has been demonstrated that led to the formation of ruthenium dithioformate and trithia-borinane complexes. [Display omitted] The reactivity of κ2 - N,S -chelated ruthenium borate complexes, [Ph 3 P(κ2 - N,S -L)Ru{ κ3 - H,S,S ′-H 2 B(L) 2 }], (L = C 5 H 4 NS, C 7 H 4 NS 2) 1 and 3 with borate ligand derived from CS 2 has been investigated. The thermolysis of [Ph 3 P(κ2 - N,S -C 5 H 4 NS)Ru{ κ3 - H,S,S ′-H 2 B(C 5 H 4 NS) 2 }], 1 with Na[BH 3 (SCHS)] led to the formation of ruthenium dithioformate complexes, [PPh 3 (κ3 - H,S,S ′-H 2 B(C 5 H 4 NS)}Ru{(η 2-SCHS)}], trans- 2 and [PPh 3 (κ3 - H,S,S ′-H 2 B(C 5 H 4 NS)}Ru{(η 2-SCHS)}], cis- 2. Further, to study the reactivity of the same borate ligand derived from CS 2 , we have performed the reaction of [Ph 3 P(κ2 - N,S -C 7 H 4 NS 2)Ru{ κ3 - H,S,S ′-H 2 B(C 7 H 4 NS 2) 2 }], 3 with Na[BH 3 (SCHS)] that yielded ruthenium dithioformate, [Ph 3 P(κ2 - N,S -C 5 H 4 NS)Ru{(η 2-SCHS)}], cis- 4 and 1,3,5-trithia-2-borinane, [PPh 3 Ru{ κ3 - H,S,S′ -H 2 B(NC 7 H 4 S 2) 2 }]{(SCH 2) 2 SBH}], 5 complexes. All these studies show that cis- 4 is analogous to trans- 2 and cis- 2. The solid-state X-ray structure of 5 shows that the ruthenium center is stabilized by diborate, phosphine and six-membered ruthenacycle [RuSBNCS] ring that is fused with a {C 2 S 3 B} ring. The synthesized complexes have been thoroughly characterized by various spectroscopic techniques and single-crystal X-ray diffraction analysis of trans- 2 , cis- 2 and 5. Density functional theory (DFT) calculations further provided an insight into the electronic structures of the complexes. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of tert-butylborane with the bis(dihydrogen) complex RuH2(η2-H2)2(PCy3)2 leads to the corresponding bis σ-borane complex which is the first example of a monoalkylborane ruthenium bis σ-complex. An alternative route involves the reaction of RuHCl(η2-H2)(PCy3)2 with lithium tert-butylborohydride. [Copyright &y& Elsevier]

Three new N-heterocyclic-silazane compounds, 1a--c, were prepared and employed as bidentate ligands to ruthenium, resulting in a series of [Ru(H){(κ-Si,N- (SiMe2-N-heterocycle)}3] complexes (3a--c) featuring the same RuSi3H motif. Detailed structural characterization of the RuSi3H complexes with X-ray diffraction, and in the case of triazabicyclo complex [Ru(H){κ-Si,N-(SiMe2)(C7-H12N3)}3] (3a), neutron diffraction, enabled a reliable description of the molecular geometry. The hydride ligand of (3a) is located closer to two of the silicon atoms than it is to the third. Such a geometry differs from that of the previously reported complex [Ru(H){(κ-Si,N-(SiMe2)N(SiMe2H)(CsH4N)}3] (3d), also characterized by neutron diffraction, where the hydride was found to be equidistant from all three silicon atoms. A DFT study revealed that the symmetric and less regular isomers are essentially degenerate. Information on the dynamics and on the Ru•••H•••Si interactions was gained from multinuclear solid-state (¹H wPMLG, 29Si CP MAS, and 2D ¹H-39Si dipolar HETCOR experiments) and solution NMR studies. The corresponding intermediate complexes, [Ru{κ-Si,N-(SiMe2-N-heterocycle)}(η4-C8H12)(η³-C8H11)] (2a--c), involving a single silazane ligand were isolated and characterized by multinuclear NMR and X-ray diffraction. Protonation of the RuSi3H complexes was also studied. Reaction of 3a with NH4PF6 gave rise to [Ru(H)(η²-H -- SiMe2)κ-N-(C7H12N3){κ-Si,N- (SiMe2)(C7H12N3)}2]+[PF6]-(4aPF6) which was isolated and characterized by NMR spectroscopy, X-ray crystallography, and DFT studies. The nature of the Si--H interactions in this silazane series was analyzed in detail. [ABSTRACT FROM AUTHOR]

The novel disilazane compound 2-pyridinetetramethyldisilazane (1) has been synthesized. The competition between N-pyridine coordination and Si-H bond activation was studied through its reactivity with two ruthenium complexes. The reaction between. 1 and RuH2(H2)2(PCy3)2 led to the isolation of the new complex RuH2{(η²-HSiMe2)N(KN-C5H4N)(SiMe2H)}(PCy3)2 (2) resulting from the loss of two dihydrogen ligands and coordination of 1 to the ruthenium center via a K²N,(η²-Si-H) mode. Complex 2 has been characterized by multinuclear NMR experiments (¹H, 31P, 13C, 29Si), X-ray diffraction and DFT studies. In particular, the HMBC 29Si-¹H spectrum supports the presence of two different silicon environments: one Si-H bond is dangling, whereas the other one is η²-coordinated to the ruthenium with a JSIH value of 50 Hz. DFT calculations (B3PW91) were also carried out to evaluate the stability of the agostic species versus a formulation corresponding to a bis(σ-Si-H) isomer and confirmed that N-coordination overcomes any stabilization that could be gained by the establishment of SISHA interactions. There is no exchange between the two Si-H bonds present in 2, as demonstrated by deuterium-labeling experiments. Heating 2 at 70 °C under vacuum for 24 h, leads to the formal loss of one equivalent of H2 from 2 and formation of the 16- electron complex RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}(PCy3)2 (3) formulated as a hydrido(silyl) species on the basis of multinuclear NMR experiments. The dehydrogenation reaction is fully reversible under dihydrogen atmosphere. Reaction of Ru(COD)(COT) with 3 equiv of 1 under a H2 pressure led to the isolation of the new complex RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}3 (4) characterized as a hydridotrisilyl complex by multinuclear NMR techniques, X-ray and neutron diffractions, as well as DFT calculations. The 29Si HMBC experiments confirm the presence of two different silicon atoms in 4, with a signal at -14.64 ppm for three dangling Si-Me2H fragments and a signal at 64.94 ppm (correlating with the hydride signal) assigned to three Si-Me2N groups bound to Ru. Comparison of DFT and neutron parameters involving the hydride clearly indicates an excellent correlation. The Si-H distance of ∼2.15 Å is much shorter than the sum of the van der Waals radii and typically in the range of a significant interaction between a silicon and a hydrogen atom (SISHA interactions). In 4, three dangling Si-H groups remain accessible for further functionalization. [ABSTRACT FROM AUTHOR]

Abstract: The diastereoselective κ2-P,N-coordination of a chiral tricyclic β-iminophosphine ligand to the half-sandwich ruthenium(II) fragments [RuCl(η6-arene)]+ (arene=C6H6, p-cymene, 1,3,5-C6H3Me3, C6Me6), [Ru(η6-p-cymene)(NCMe)]2+ and [Ru(η5-C5H5)(NCMe)]+ is described. The structures of the resulting mono- and dicationic cymene derivatives have been confirmed by X-ray crystallography. Studies on the catalytic activity of these Ru(II) compounds in Diels–Alder cycloaddition processes are also reported. [Copyright &y& Elsevier]

The phosphinosilane compound PPh2CH2OSiMe2H is potentially a bifunctional P∼Si-H ligand. By treatment with the RuIIprecursor RuH2(H2)2(PCy3)2, the complex Ru(PPh2CH2OSiMe2H)3 (2), resulting from the coordination of three ligands and the displacement of two PCy3 and two dihydrogen ligands, was formed. The different bonding modes for each of the three bifunctional P∼Si-H ligands are discussed on the basis of multinuclear NMR, X-ray diffraction, and density functional theory studies. One ligand acts as a monodentate phosphine ligand with a pendant Si-H group, whereas the two others act as bidentate ligands with different Si-H bond activations. Indeed, an intermediate structure between two arrested forms 2a and 2b can be proposed: a dihydrido(disilyl)- ruthenium(IV) species (form 2a) resulting from two Si-H oxidative additions or a hydrido(silyl)ruthenium(ll) species (form 2b) presenting an agostic Si-H bond and only one oxidative addition. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the catalytic activities of benzonitrile reduction by 2 and use of ruthenium for nitrile hydrogenation. It mentions that the study uses THF-d8 and peforms experiments in catalytic and stoichiometric levels to determine the mechanism reaction of benzonitrile. The results of the study indicate that the mild condition with bis(dihydrogen) complex 2 contributes to achieve the benzonitrile hydrogenation into benzylamine.

The article discusses the study which examines the reaction of mesitylborane with a chlorohydrido(dihydrogen) ruthenium complex leading to the isolation of the first terminal borylene ruthenium complex. It shows the reversible release of dihydrogen. Base from the preliminary results, the researchers expect a versatile reactivity from the new borylene at ruthenium by analogy to the development of carbene ruthenium chemistry.

Diamine-monoboranes and one amine-borane alcohol precursor are utilized for cyclization reactions affording the corresponding NB(H)N- and NB(H)O-containing cyclic diaminoboranes and oxazaborolidine, resp. Efforts to understand the mechanism of the ruthenium catalyzed dehydrogenative cyclization process are presented. [ABSTRACT FROM AUTHOR]