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Reaction of the alkenyl complex OsCl(E-CH=CHPh)(CO)(PiPr3)2 (1) with phenyllithium gives OsH-{C6H4-2-(E-CH=CHPh)}(CO)(PiPr 3)2 (2). The structure of 2 (isomer 2a) has been determined by X-ray diffraction: triclinic, P1, a = 9.230(1) Å, b = 10.092(1) Å, c = 18.525(2) Å, α = 88.667(7)°, β = 87.172(7)°. γ = 71.110(6)°, V = 1630.6(3), Z = 2, R (F, Fo ≥ 4σ(Fo)) = 4.01, wR (F2, all reflections) = 9.94%. The geometry around the osmium can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying two relative trans positions. The remaining perpendicular plane is formed by the carbonyl and the 2-(E-1′-styryl)-phenyl ligands mutually trans disposed, the hydride ligand and one olefinic hydrogen of the 2-(E-1′-styryl)phenyl ligand, which shows an agostic interaction with the osmium atom (distance 2.05(7) Å). The solutions of 2 show equilibria between the agostic isomer (2a) and a nonagostic isomer (2b). The thermodynamic magnitudes involved in the equilibrium as well as the activation parameters for the conversion between the two isomers were determined in toluene-d8 by 1H NMR spectroscopy. The values obtained were ΔH° = -1.6 (±0.1) Kcal mol-1 and ΔS° = -9.6 (±0.6) cal K-1 mol-1 for the formation of the agostic isomer, whereas the activation parameters for the breaking of the agostic interaction were ΔH‡ = 7.6 (±0.2) Kcal mol-1 and ΔS† = -1.0 (±0.7) cal K-1 mol-1. 2 reacts with CO to give the octahedral complex OsH{C6H4-2-(E-CH=CHPh)}(CO)2(P iPr3)2 (3). Reactions of 1 with methyllithium and CD3Li give OsH{C6H4-2-(E-CH=CHCH3)}(CO)(P iPr3)2 (4) and OsH{C6H4-2-(E-CH=CHCD3)}-(CO)(P iPr3)2 (4-d3), respectively. The spectra of these complexes indicate that in solution they also show equilibria between agostic and nonagostic isomers. Reactions of 4 with P(OMe)3 and CO afford OsH{C6H4-2-(E-CH=CHCH3)(CO){P(OMe) 3}(PiPr3)2 (5) and OsH{C6H4-2-(E-CH=CHCH3)}(CO)2(P iPr3)2 (6), respectively, in which the incoming ligands coordinate trans to the hydride. 4 and 4-d3 isomerize in solution to give OsH(η3-CH2CHCHPh)-(CO)(PiPr 3)2 (11) and OsD(η3-CD2CHCHPh)(CO)(PiPr 3)2 (11-d3), respectively. Reaction of 11 with CO leads to OsH(η1-CH2CH=CHPh)(CO)2(P iPr3)2 (12). The first order constants kobs and kobs-d3 for the isomerization of 4 and 4-d3 to 11 and 11-d3 were obtained in CDCl3, giving activation parameters of ΔH‡ = 20.8 (±1.7) Kcal mol-1 and ΔS‡ = -2.8 (±2.0) cal K-1 mol-1 for the isomerization of 4 to 11 and a relation kobs/kobs-d3 = 3.6 at 303 K., We thank the D.G.I.C.Y.T. (Project PB 92-0092, Programa de Promoción General del Conocimiento) and E.U. (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the Diputación General de Aragón (D.G.A.) for a grant.

The five-coordinate complex [RuHCl(CO)(PPri 3)2] (1) reacts with cyclopentadiene in methanol under reflux to give [RuH(η5-C5H5)(CO)(PPri 3)] (2) and [HPPri 3]Cl. The protonation of 2 in dichloromethane-d2 leads to the dihydrogen complex [Ru(η5-C5H5)(η5-H 2)(CO)(PPri 3)]-BF4 (3) in equilibrium with traces of the dihydrido tautomer [RuH2(η5-C5H5)(CO)(PPr i 3)]-BF4 (4). The reaction of 2 with HBF4·Et2O in acetone affords the solvated complex [Ru(η5-C5H5)(CO){η 1-OC(CH3)2}(PPri 3)]BF4 (5), which reacts with CO, dimethyl acetylenedicarboxylate, and NaCl to give [Ru(η5-C5H5)(CO)2(PPr i 3)]BF4 (6), [Ru(η5-C5H5){η2-C 2(CO2CH3)2}(CO)(PPri 3)]-BF4 (7), and [Ru(η5-C5H5)Cl(CO)(PPri 3)] (8), respectively. Complex 5 also reacts with alkyn-1-ols. The reaction with 1,1-diphenyl-2-propyn-1-ol leads to the allenylidene complex [Ru(η5-C5H5)(C=C=CPh 2)(CO)(PPri 3)]BF4 (9), which affords [Ru(η5-C5H5){C(OH)CH=CPh 2}-(CO)(PPri 3)]BF4 (10) by reaction with water. 10 is converted into the acyl derivative [Ru-(η5-C5H5){C(O)CH=CPh 2}(CO)(PPri 3)] (11), when a CH2Cl2 solution of 10 is passed through an Al2O3 column. The structure of 11 was determined by an X-ray investigation. The reaction of 5 with 2-propyn-1-ol leads to the α,β-unsaturated hydroxycarbene complex [Ru-(η5-C5H5){C(OH)CH=CH 2}(CO)(PPri 3)]BF4 (12). Similarly to 10, 12 is converted into [Ru-(η5-C5H5){C(O)CH=CH 2}(CO)(PPri 3)] (13), when the solutions of 12 are passed through an Al2O3 column. Treatment of 5 with 1-ethynyl-1-cyclohexanol leads to a mixture of organometallic compounds including [Ru(η5-C5H5){C(OH)CH=C(CH2) 4CH2}(CO)(PPri 3)]BF4 (14). Chromatography of the mixture affords [Ru(η5-C5H5){C(O)CH=C(CH2) 4CH2}(CO)-(PPri 3)] (15) and [Ru(η5-C5H5){C≡CC=CH(CH 2)3CH2}(CO)(PPri 3)] (16). 9 reacts with alcohols and thiols to give [Ru(η5-C5H5){C(ER)CH=CPh 2}(CO)(PPri 3)]BF4 (ER = OMe (17), OEt (18), SPrn (21)), which by treatment with NaOMe afford [Ru(η5-C5H5){C(ER)=C=CPh 2}(CO)-(PPri 3)] (ER = OMe (19), OEt (20), SPrn (22)). Similarly, the reaction of 9 with benzophenone imine leads to [Ru(η5-C5H5){C(CH=CPh 2)=N=CPh2}(CO)(PPri 3)]BF4 (23), which by reaction with NaOMe gives [Ru(η5-C5H5){C(N=CPh 2)=C=CPh2}(CO)(PPri 3)] (24). The structure of 23 was also determined by an X-ray investigation. The C=N bond lengths are 1.283(9) and 1.252(9) Å, while the C-N-C angle is 149.9(6)°., We thank the DGICYT (Project PB-95-0806, Programa de Promoción General del Conocimiento) and the EU (European Union) (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support.

The monoolefin complex Rh(acac)(cyclooctene)(PCy3) (1) reacts with HGeEt3 to give Rh(acac)H(GeEt3)(PCy3) (2). On treatment of 2 with methyl propiolate and phenylacetylene the complexes Rh(acac){η2-CH(GeEt3)=CHR}(PCy3) (R = CO2Me (3), Ph (4)) are obtained. The X-ray crystal structure analysis of 3 reveals that the coordination geometry around the rhodium center is almost square-planar with the olefin disposed perpendicular to the coordination plane of the rhodium atom. Complex 1 also reacts with HSnPh3. The reaction leads to Rh(acsc)H(SnPh3)(PCy3) (5). In the presence of methyl propiolate, phenylacetylene, and (trimethylsilyl)acetylene complex 5 affords the alkenyl compounds Rh-(acac){(E)-CH=CHR}(SnPh3)(PCy3) (R = CO2Me (6), Ph (7), SiMe3 (8)). Similarly, the reactions of 5 with diethyl acetylenedicarboxylate and diphenylacetylene yield Rh(acac)-(CR=CHR)(SnPh3)(PCy3) (R = CO2Et (9), Ph (10)). The addition of 1 equiv of 1-ethynyl-1-cyclohexanol to a pentane suspension of 5 leads to the hydroxyalkenyl derivative Rh(acac)-{(E)-CH=CHC(OH)(CH2)4CH2}(SnPh 3)(PCy3) (11). The structure of 11 was determined by X-ray analysis. The coordination geometry around the metal center can be rationalized as a square pyramid with the stannyl ligand in the apical position. Although the hydroxyalkenyl ligand of 11 is stable and does not dehydrate to give the corresponding α,β-unsaturated alkenyl compound, complexes of this type can be prepared from enynes. Thus, the reaction of 5 with 2-methyl-1-buten-3-yne leads to the α,β-unsaturated alkenyl complex Rh(acac){(E)-CH=CHC(CH3)=CH2}(SnPh3)(PCy 3) (12), whereas in the presence of 1,1-diphenyl-2-propyn-1-ol complex 5 affords the allenyl derivative Rh(acac)(CH=C=CPh2(SnPh3)(PCy3) (13)., We thank the DGICYT (Proyet PB 92-0092, Programa de Promoción General del Conocimiento, and EU Project Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant. L.R. thanks the Spanish Government for a grant (Programa de Formación Científica para Iberoamérica).

The bis(alkynyl) complex [Os(C2Ph)2(CO)(PiPr3)2] (1) reacts with benzophenone imine to give [Os(C2Ph)2(CO)(NH=CPh2)(PiPr3) 2] (2) as a mixture of two isomers, cis-bis(alkynyl) (2a) and trans-bis(alkynyl) (2b). In toluene under reflux, this mixture is converted into [Os(C2-Ph){NH=C(Ph)C6H4}(CO)(PiPr 3)2] (3) and phenylacetylene. The X-ray crystal structure of 3 has been determined (triclinic, space group P1 with a = 11.078(1) Å, b = 18.910(2) Å, c = 20.290(2) Å, α = 67.562(7)°, β = 89.427(9)°, γ = 87.289(9)°, and Z = 4). 3 reacts with HBF4 in diethyl ether to give phenylacetylene and [Os{NH=C(Ph)C6H4}(CO)(OH2)(PiPr 3)2]BF4 (4), which by reaction with CH3Li affords [Os(CH3){NH=C(Ph)C6H4}(CO)(PiPr 3)2] (5). © 1995 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks Diputación General de Aragón (DGA) for a grant.

The five-coordinate complexes Os{(E)-CH=CHR}Cl(CO)(PiPr3)2 (R = Ph (3), H (6)) react with CH2=CHMgBr to give the osmium(0) derivatives Os(η4-C4H5R)(CO)(PiPr3) 2 (R = Ph (5), H (7)). The molecular structure of 5 has been determined by X-ray crystallography. The coordination around the osmium atom can be described as a distorted square pyramid with a triisopropylphosphine ligand located at the apex. The base is formed by the carbonyl group and the other triisopropylphosphine ligand mutually cis disposed and by the midpoints of both terminal carbon-carbon bonds of the diene. The reaction of the chloro-styrylruthenium(II) complex Ru{(E)-CH=CHPh}Cl(CO)(PiPr3)2 (4) with CH2=CHMgBr leads to Ru{(E)-CH=CHPh}(CH=CH2)(CO)(PiPr3)2 (10), which affords Ru(η4-C4H5Ph)(CO)(PiPr3) 2 (11) by stirring in hexane at 50°C. 10 reacts with carbon monoxide to give Ru{(E)CH=CHPh}(CH=CH2)(CO)2(PiPr3)2 (12), which can be also prepared by reaction of Ru{(E)-CH=CHPh}Cl(CO)2(PiPr3)2 (13) with CH2=CHMgBr. © 1995 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the Diputación General de Aragón (DGA) for a grant.

The complexes Ir(acac)(cyclooctene)(PR3) (PR3 = PiPr3 (2), PCy3 (3)), which are prepared by reaction of Ir(acac)(cyclooctene)2 (1) with the corresponding phosphine, react with carbon monoxide and acetylenedicarboxylic methyl ester to give Ir(acac)(CO)(PR3) (PR3 = PiPr3 (4), PCy3 (5)) and Ir(acac)(η2-CH3O2C-C≡C-CO 2CH3)(PR3) (PR3 = PiPr3 (6), PCy3 (7)). The reactions of 6 and 7 with H2SiPh2 afford Ir(acac){C[CH(OCH3)OSiPh2]=CHCO2CH 3}(PR3) (PR3 = PiPr3 (8), PCy3 (9)). The X-ray crystal structure analysis of 9 (monoclinic, space group P21/c with a = 21.408(1) Å, b = 10.246(1) Å, c = 18.983(1) Å, and β = 106.89(1)°) reveals that the bonding situation in the Ir-Si-O sequence could be described as an intermediate state between metal-silylene stabilized by an oxygen base and a tetrahedral silicon. © 1995 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project, Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant. L. R. thanks the Spanish Government for a grant (Programa de Formación Científica para Iberoamérica).

Complex RuCl{(E)-CH=CHPh}(CO)2(PiPr3)2 (1) reacts with CH3Li in toluene at room temperature to give Ru(CH3){(E)-CH=CHPh}(CO)2(PiPr 3)2 (2). The structure of 2 was determined by an X-ray investigation. The coordination geometry around the ruthenium atom is octahedral with the phosphine ligands occupying trans positions. The perpendicular plane is formed by the methyl and styryl ligands mutually cis disposed and by two additional carbonyl groups. The reaction of 2 with HBF4•OEt2 leads to styrene and the cationic five-coordinate complex [Ru(CH3)(CO)2(PiPr3) 2]BF4 (3), which adds carbon monoxide to give the corresponding derivative [Ru(CH3)(CO)3(PiPr3) 2]BF4 (5). The related styryl complex [Ru-{(E)-CH=CHPh}(CO)3(PiPr3) 2]BF4 (6) can be prepared by reaction of 1 with AgBF4 under a carbon monoxide atmosphere. Complex 3 also reacts with NaCl, NaI, LiOPh, and LiC≡CPh. The reaction with NaCl leads to the η1-acyl carbonyl Ru{C(O)CH3}Cl(CO)(PiPr3)2 (7). The structure of 7 was also determined by an X ray investigation. The geometry of 7 can be rationalized as a square pyramid with the acyl ligand located at the apex. The reaction of 3 with NaI gives a mixture of the methyl dicarbonyl Ru(CH3)I(CO)2(PiPr3)2 (8) and the η1-acyl-carbonyl Ru{C(O)CH3}I(CO)(PiPr3)2 (9). Similarly, the treatment of 3 with LiOPh results in a rapidly established equilibrium mixture of the methyl dicarbonyl Ru(CH3)(OPh)(CO)2(Pi-Pr3) 2 (12) and the η1-acyl carbonyl Ru{C(O)CH3}(OPh)(CO)(PiPr3)2 (13), while the reaction of 3 with LiC≡CPh affords Ru(CH3)(C≡CPh)(CO)2(PiPr 3)2 (14). Under a CO atmosphere 14 is quantitatively converted into Ru{C(O)CH3}(C≡CPh)(CO)2(PiPr 3)2 (15). Under a CO atmosphere, 2 is in equilibrium with Ru{C(O)CH3}{(E)-CH=CHPh}(CO)2(PiPr 3)2 (17). © 1995 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the Diputación General de Aragón (DGA) for a grant.

We thank the DGICYT (Project PB-92-0092, Programa de Promoción General del Conocimiento) and the EU (Project Selective Processes and Catalysis involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant.

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.

The synthesis of the azavinylidene and azavinylidene-bridged compounds Ir(=N=CPli2)-(diolefinXPCys) (5, diolefin =tetrafluorobenzobarrelene (TFB); 6, diolefin =1,5-cyclooctadiene (COD)) and [Ir(M-N=CPh2)(diolefin)]2 (7, diolefin = COD; 8, diolefin = TFB) is described. The azavinyhdene derivatives 5 and 6 were prepared by reaction of the corresponding squareplanar methoxy complex Ir(OMe)(diolefin)(PCys) with benzophenone imine, whereas the azavinylidene-bridged 7 and 8 were similarly obtained from [Ir(/z-OMeXdiolefin)]2 (diolefin = COD, TFB). The complexes 7 and 8 react with CO to give [Ir(M-N=CPh2)(CO)2]2 (9), which affords [Ir(M-N=CPh2)(CO)(PCy3)]2 (10) in the presence of PCys. The preparation of the related compounds [Rh(/t-N=CPh2)(diolefin)]2 (diolefin = COD (13), TFB (14)), [Rh(«-N=CPh2)(CO)2]2 (15), Rh2(/t-N=CPh2)2(CO)3PCy3 (16), and [Rh(/t-N=CPh2)(CO)(PCy3)]2 (17) is also reported. The structure of 14 was determined by an X-ray investigation. 14 crystallizes in the space group PI with a =16.468(5) k,b = 16.569(5) A, c =18.139(5) Á, a =66.03(1)°, ß —74.32(2)°, y=89.71(2)°, and Z = 4. The molecular structure reveals that the core of the molecule is formed by a Rh2N2 skeleton in a bent configuration., We thank the DGICYT (Project PB92-0092, Programa de Promoción General del Conocimiento) and the EU (Project: Selective Processes and Catalysis involving Small Molecules). M.O. and E.O. thank the Diputación General de Aragón (DGA) for grants.

The bis(alkynyl) complex [Os(C2Ph)2(CO)(PiPr3)2] (1) reacts with CH3CO2H to give the vinylacetato derivative [Os(C2Ph){C(=CHPh)OC(O)CH3}(CO)(PiPr3) 2] (3). The protonation of 3 with HBF4 in diethyl ether leads to the carbene compound [Os(C2Ph){=C(CH2Ph)OC(O)CH3}(CO)(PiPr 3)2]BF4 (4). On the other hand, reaction of the analogous ruthenium complex [Ru(C2Ph)2(CO)(PiPr3)2] (2) with CH3CO2H affords [Ru(C2Ph)(η2-O2CCH 3)(CO)(PiPr3)2] (5) and phenylacetylene. 5 reacts with HBF4 in acetone to give [Ru{C(=CHPh)OC(O)CH3}(CO){η1-OC(CH3) 2}(PiPr3)2]BF4 (6). The molecular structure of 6 has been determined by an X-ray investigation. 6 crystallizes in the monoclinic space group C2/m with a = 16.399(2) Å, b = 14.870(5) Å, c = 16.855(3) Å, β = 105.98(2)°, and Z = 4. The coordination geometry around the ruthenium atom could be described as based on a distorted octahedron with the two phosphine ligands occupying relative irons positions. The perpendicular coordination plane is formed by the atoms of the vinyl ester ligand (O and C), the oxygen atom of the acetone molecule, and the carbonyl ligand. The coordinated acetone molecule of 6 can be displaced by anions such as [PhC≡C]- and Cl- to give the complexes [Ru(C2Ph){C(=CHPh)OC(O)CH3}(CO)(PiPr3) 2] (9) and [Ru{C(=CHPh)OC(O)CH3}Cl(CO)(PiPr3)2] (10), respectively. 9 reacts with HBF4 in acetone as solvent to give 6 and phenylacetylene. The reaction of 10 with HBF4 leads to the carbene cationic complex [RuCl{=C(CH2Ph)OC(O)CH3}(CO)(PiPr3) 2]BF4 (11). 10 also reacts with CH3CO2H; in this case the reaction affords cis-PhCH=CHOC(O)CH3 and [RuCl{η1-OC(O)CH3}(CO)2(PiPr 3)2] (12). The compound [Ru(η2-O2CCH3)(CO)2(PiPr 3)2]BF4 (13) and cis-PhCH=CHOC(O)CH3 were similarly obtained from 6 and CH3CO2H. The reactivity of the six-coordinate bis(alkynyl) complexes [Ru(C2Ph)2(CO)(NCCH3)(PiPr3) 2] (14) and [Ru(C2Ph)2(CO)2(PiPr3)2] (15) toward HBF4 was also investigated. These compounds react in coordinating solvents with HBF4 to give [Ru(C2Ph)(CO)(NCCH3)2(PiPr3) 2]BF4 (16) or [Ru(C2Ph)(CO)2{η1-OC(CH3) 2}(PiPr3)2]BF4 (17) and phenylacetylene. In dichloromethane 17 releases the acetone ligand to give [Ru(C2Ph)(CO)2(PiPr3)2]BF 4 (18). Starting from 18 the hexacoordination can be achieved by addition of acetonitrile and carbon monoxide. These reactions lead to [Ru(C2Ph)(CO)2(NCCH3)(PiPr3) 2]BF4 (19) and [Ru(C2Ph)(CO)3(PiPr3)2]BF 4 (20). Complexes 16 and 17 react with CH3CO2H to give [Ru{C(=CHPh)OC(O)CH3}(CO)(NCCH3)(PiPr3) 2]BF4 (21) and [Ru{C(=CHPh)OC(O)CH3}(CO)2(PiPr3) 2]BF4 (22), which can be also prepared from 6 by reaction with acetonitrile and carbon monoxide, respectively. © 1994 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project: Selective Process and Catalysis Involving Small Molecules) for financial support. E.O. thanks Diputación General de Aragón (DGA) for a grant.

The alkynyl complexes [Rh2(p-OOCCH3) (µV1:v1 2-C2R)(CO)2(PCy3)2] (R = Ph (1), C02CH3 (3), SiMe3 (6)) react withHBFrOEt2 to give the vinylidene-bridged rhodium derivatives [Rh2(p-OOCCH3)(p-C=CHR)(CO)2-(.PCy3)2¡BF4 (R = Ph (2), C02CH3 (4), H (5)). The molecular structure of complex 2 has been determined; crystals of 2 are monoclinic, space group P2i/n with a = 10.377(12) A,b = 28.526(2) A,c = 17.155(2) ,ß = 91.53-(l)°,andZ = 4. On the basis of X-ray analysis, the cation of 2 can be described as a dinuclear species of 30 valence electrons, which contains a single rhodium-rhodium bond (d(Rh-Rh) = 2.6557(5) A). Additionally, the metal centers are bridged by a vinylidene ligand and a carboxylate group., We thank the DGICYT (Project PB 89-0055; Programa de Promoción General del Conocimiento) for its financial support. L.R. thanks Programa de Cooperación Científica con Iberoamérica for a grant.

The dihydride-dichloro complex OsH2Cl2(PiPr3)2 (1) reacts with cyclohexanone oxime in toluene under reflux to give after 12 h OsHCl2{N=C(CH2)4CH2}(P iPr3)2 (2), which can be also obtained by reaction of the oximate compound, OsH2Cl{κ-N,κ-O[ON=C(CH2)4CH 2]}(PiPr3)2 (3) with HCl. Complex OsHCl2{N=C(CH3)2}(PiPr 3)2 (4) has been similarly prepared by treatment of compound OsH2Cl{κ-N,κ-O[ON=C(CH3)2]}(P iPr3)2 (5) with HCl. When the reaction of 1 and cyclohexanone oxime, in toluene under reflux, was quenched after 1 h, a mixture of 1, 2, 3, and the trichloroazavinylidene OsCl3{N=C(CH2)4CH2}(P iPr3)2 (6) was obtained. The structures in the solid state of 2 and 6 have been determined by X-ray diffraction studies. In both cases, the geometry around the metal center can be described as a distorted octahedron with the phosphorus atoms of the phosphines occupying trans positions and the C=N group and the carbon atoms bonded to this group lying in a plane that is parallel to the Cl-Os-Cl plane. CCSD(T)//B3LYP calculations on the model complexes OsXCl2(N=CH2)(PH3)2 [X = H (2t), X = Cl (6t)] state that the above-mentioned conformation is 15.3 (2t) or 12.1 (6t) kcal mol-1 more stable than that with the azavinylidene ligand parallel to the P-Os-P plane. In solution the azavinylidene ligands of 2 and 4 rotate around the Os-N-C axis. The activation parameters of the process are ΔH = 14.4 ± 0.8 kcal mol-1 and ΔS = -1.1 ± 1.3 cal mol-1 K-1 for 2 and ΔH = 13.1 ± 0.8 kcal mol-1 and ΔS = 0.0 ± 2.8 cal mol-1 K-1 for 4. © 2000 American Chemical Society., Financial support from the DGES of Spain (Projects PB98-0916-02-01 and PB98-1591) is acknowledged. J.T. acknowledges the “Direcció General de Recerca de la Generalitat de Catalunya” for a grant. R.C. thanks also the “Ministerio de Educación y Cultura” for a grant.

Financial support from the DGES of Spain (Projects PB98-1591 and PB98-0916-C02-01) is acknowledged. R. C. thanks the ‘‘Ministerio de Ciencia y Tecnologia’’ for a grant.

The monohydrido complex RuHCl(CO)(PiPr3)2 (1) reacts with HC=CC(OH)R1R2 to give the hydroxyvinyl compounds RuCl{(E)-CH=CHC(OH)R1R2}(CO)(PiPr3)2 (R1 = R2 = H (2); R1 = H, R2 = Ph (3); R1 = R2 = Ph (4)), which by reaction with HBF4 afford [RuCl-(=CHCH=CR1R2)(CO)(PiPr3) 2]BF4 (R1 = H, R2 = Ph (5); R1 = R2 = Ph (6)). The former cationic compounds react with NaCl to give RuCl2(=CHCH=CR1R2)(CO)(PiPr3) 2 (R1 = H, R2 = Ph (7); R1 = R2 = Ph (8)). The molecular structure of 6 was determined by X-ray crystallography. Crystals of 6 are orthorhombic, space group Pna21, with unit cell dimensions a = 16.681(1) Å, b = 18.876(1) Å, and c = 11.967(1) Å. The structure was solved and refined using 6457 observed reflections; R = 0.0273 and Rw, = 0.0281. The geometry around the ruthenium atom can be described as a square pyramid with the alkylidene ligand located in the apex. The base is formed by the carbonyl ligand and the chlorine atom mutually trans disposed, with two triisopropylphosphine groups. The complexes 2-4 react with CO to give the cis-dicarbonyl compounds RuCl{(E)-CH=CHC(OH)R1R2}(CO)2(PiPr 3)2 (R1 = R2 = H (9); R1 = H, R2 = Ph (10); R1 = R2 = Ph (11)). The reaction of 1 with 1-ethynyl-1-cyclohexanol affords RuCl{(E)-CH=CHC(OH)(CH2)4CH2}(CO)(PiPr 3)2 (12), which after 4 days in toluene at 60°C gives RuCl{(E)-CH=CHC=CH(CH2)3CH2}(CO)(PiPr 3)2 (13). The reaction of 13 with HBF4 leads to [RuCl{=CHCH=C(CH2)4CH2}(CO)(PiPr 3)2]BF4 (14), which can also be obtained from the reaction of 12 with HBF4. © 1994 American Chemical Society., We thank the DGICYT (Project PB 92-0092, Programa de Promoción General del Conocimiento) and EU (Project: Selective Processes and Catalysis Involving Small Molecules) for financial support. E. O. thanks the DGA (Diputación General de Aragón) for a grant.

Reaction of the hexahydride complex OsH6(PiPr3)2 (1) with pyridine-2-thiol leads to the trihydride derivative OsH3{κ-N,κ-S-(2-Spy)}(PiPr3)2 (2). The structure of 2 has been determined by X-ray diffraction. The geometry around the osmium atom can be described as a distorted pentagonal bipyramid with the phosphine ligands occupying axial positions. The equatorial plane contains the pyridine-2-thiolato group, attached through a bite angle of 65.7(1)°, and the three hydride ligands. The theoretical structure determination of the model complex OsH3{κ-N,κ-S-(2-Spy)}(PH3)2 (2a) reveals that the hydride ligands form a triangle with sides of 1.623, 1.714, and 2.873 Å, respectively. A topological analysis of the electron density of 2a indicates that there is no significant electron density connecting the hydrogen atoms of the OsH3 unit. In solution, the hydride ligands of 2 undergo two different thermally activated site exchange processes, which involve the central hydride with each hydride ligand situated close to the donor atoms of the chelate group. The activation barriers of both processes are similar. Theoretical calculations suggest that the transition states have a cis-hydride−dihydrogen nature. In addition to the thermally activated exchange processes, complex 2 shows quantum exchange coupling between the central hydride and the one situated close to the sulfur atom of the pyridine-2-thiolato group. The reactions of 1 with l-valine and 2-hydroxypyridine afford OsH3{κ-N,κ-O-OC(O)CH[CH(CH3)2]NH2}(PiPr3)2 (3) and OsH3{κ-N,κ-O-(2-Opy)}(PiPr3)2 (4) respectively, which according to their spectroscopic data have a similar structure to that of 2. In solution, the hydride ligands of 3 and 4 also undergo two different thermally activated site exchange processes. However, they do not show quantum exchange coupling. The tetranuclear complexes [(PiPr3)2H3Os(μ-biim)M(TFB)]2 [M = Rh (5), Ir (6); H2biim = 2, 2‘-biimidazole; TFB = tetrafluorobenzobarrelene] have been prepared by reaction of OsH3(Hbiim)(PiPr3)2 with the dimers [M(μ-OMe)(TFB)]2 (M = Rh, Ir). In solution the hydride ligands of these complexes, which form two chemically equivalent unsymmetrical OsH3 units, undergo two thermally activated site exchanges and show two different quantum exchange coupling processes., We thank the DGICYT of Spain (Projects PB95-0806 and PB95-0639-CO2-01, Programa de Promocion General del Conocimiento).

The acetylacetonato complex Ir(acac)(cyclooctene)(PCy3) (1) reacts with molecular hydrogen in the presence of 1 equiv of PCy3 to give Ir(acac)H2(PCy3)2 (2). The addition of 1 equiv of PhC≡CH to a benzene-d6 solution of 1 causes the displacement of the coordinated olefin and the formation of Ir(acac)(η2-PhC≡CH)(PCy3) (3). The addition of hexane to this solution reverses the reaction and precipitates 1. The treatment of 1 with 3 equiv of PhC≡CH affords Ir{κ3-CH=C(Ph)CH[C(O)CH3]2}(C 2Ph)(CPh=CH2)(PCy3) (4), which is a result of the oxidative addition of the HC≡ bond of an alkyne, the insertion of a second alkyne into an Ir-C3(acac) bond, and the subsequent insertion of a third alkyne into the Ir-H bond, previously formed. The structure of 4 was determined by an X-ray investigation. The coordination geometry around the iridium atom can be rationalized as a distorted octahedron with the bicyclic ligand occupying three coordination sites of a octahedral face. In the presence of PCy3 the reaction of 1 and PhC≡CH leads to Ir(acac)H(C2Ph)(PCy3)2 (5). Under the same conditions, CyC=CH and Me3SiC≡CH afford the corresponding hydrido-alkynyl derivatives Ir(acac)H-(C2R)(PCy3)2 (R = Cy (6), Me3Si (7)). The addition of silanes HSiR3 to 1 gives Ir(acac)H-(SiR3)(PCy3) (SiR3 = SiEt3 (8), SiPh3 (9), SiHPh2 (10)). The structure of 8 was also determined by an X-ray analysis. The coordination geometry around the metallic center of 8 can be rationalized as a square pyramid with the triethylsilyl group located at the apex. In the presence of PCy3, the reactions of 1 with silanes lead to Ir(acac)H(SiR3)(PCy3)2 (SiR3 = SiEt3 (11), SiHPh2 (12), SiH2Ph (13)). Complex 1 also reacts with HSnPh3. In the absence of PCy3 the reaction product is Ir(acac)H(SnPh3)(PCy3) (14), while in the presence of PCy3 the six-coordinate derivative Ir(acac)H(SnPh3)(PCy3)2 (15) is obtained. Under atmospheric pressure of hydrogen, complex 8 is converted into the trihydrido-silyl-iridium(V) derivative Ir(acac)H3(SiEt3)(PCy3) (32). In solution, this complex is fluxional with values of ΔH# and ΔS# of 12.23 (± 0.76) kcal mol-1 and 1.45 (± 1.84) cal K-1 mol-1, respectively. Complex 8 has also been found to be an active catalyst for the addition of HSiEt3 to PhC≡CH. In all experiments, PhCH=CH2, PhC≡CSiEt3, cis-PhCH=CH(SiEt3), trans-PhCH=CH(SiEt3), and Ph(SiEt3)C=CH2 were obtained. The major product in all cases is the thermodynamically less stable cis-PhCH=CH(SiEt3), resulting from the anti-addition of the silane to the alkyne. This product is selectively formed in approximately 70% yield., We thank the DGICYT (Projet PB 92-0092, Programa de Promoción General del Conocimiento, and EU Projet Selective Processes and Catalysis Involving Small Molecules) for financial suport. E.O. thanks the DGA (Diputación General de Aragón) for a grant. L.R. thanks the Spanish Government for a grant (Programa de Formación Científica para Iberoamérica).

The monohydride complex OsHCl(CO)(PiPr3)2 (1) reacts with 2-propyn-1-ol to give the vinyl compound Os(CH=CHCH2OH)Cl(CO)(PiPr3)2 (2a). The reaction of 1 with 1-phenyl-2-propyn-1-ol leads to a mixture of products, from which the complexes OsCl2(=CHCH=CHPh)(CO)(PiPr3)2 (3a) and Os(CHCHC(O)Ph)Cl(CO)(PiPr3)2 (4a) were separated. The molecular structures of complexes 3a and 4a were determined by X-ray crystallography. Crystals of 3a are monoclinic, space group P21/c, with unit cell dimensions a = 15.671(3) Å, b = 12.507(2) Å, c = 16.632(3) Å, and β = 108.95(1°). The structure was refined to the R and Rw values 0.0202 and 0.0239 on 5080 observed data. The coordination around the osmium atom can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying trans positions; the perpendicular plane is defined by the vinylcarbene and a carbonyl ligand, mutually cis disposed, and by two chloride atoms. Crystals of 4a are orthorhombic, space group P212121, with a = 8.797(1) Å, b = 15.268(2) Å and c = 22.275(3) Å. The structure was refined to the R and Rw values 0.0198 and 0.0223 on 5532 reflections. The osmium coordination environment can also be rationalized as a distorted octahedron with the two phosphine ligands disposed mutually irons. The remaining coordination sites of the octahedron are occupied by the carbonyl ligand, the chloride atom, and the chelate CHCHC(O)Ph ligand. The reaction of 1 with 1,1-diphenyl-2-propyn-1-ol also leads to a mixture of products, from which the complex OsCl2(=CHCH=CPh2)(CO)(PiPr3)2 (3b) was isolated and characterized. © 1994 American Chemical Society., We thank the DGICYT (Project BP 92-0092, Programa de Promoción General del Conocimiento) for financial support. B. Z. thanks the Ministerio de Educación y Ciencia and E. 0. the Diputación General de Aragón (DGA) for a grant.