Bridging Hydrido Ligands Research Articles

Stoichiometric and Catalytic Reduction of Carbon Dioxide by a Sterically Encumbered Amidinato Magnesium Hydride

AbstractA sterically encumbered dinuclear amidinato magnesium hydride 3 with bridging hydrido ligands was synthesized from the metalation of the corresponding amidine 1 with dibutylmagnesium and subsequent treatment with phenylsilane. This complex reacts stoichiometrically with 1 atm of carbon dioxide at room temperature in tetrahydrofuran (THF) to the corresponding bis(thf) adduct of the dinuclear formate complex 4‐2 thf with bridging formate anions. This complex is stable in THF at 60 °C for more than 16 hours but decomposes into the amidine 1 upon removal of ligated thf ligands. Complex 3 efficiently catalyzes the reduction of carbon dioxide with 9‐BBN, yielding bis(boryl)acetal (R2BO)2CH2, and with silanes H4‐nSiPhn (n=1, 2, and 3). The bis(silyl)acetal is quantitatively accessible for Ph3SiH (n=3) whereas during the reduction of CO2 with hydrogen‐richer silanes (n=1, 2) siloxanes form and methane evolves.

Alkyne Coupling and Cyclization on Metal Cluster Complexes. Additions and Couplings of Dimethyl acetylenedicarboxylate to Ru6(μ6-C)(CO)14(μ3-η4-C4H4)

Reactions of the hexaruthenium cluster complex Ru6(μ6-C)(CO)14(μ3−η4−C4H4), 2 with dimethyl acetylenedicarboxylate (DMAD) at 25 °C yielded five new compounds: Ru6(μ5-C)(CO)16(μ−η4−C4H4), 3; Ru6(μ6-C)(CO)14[η6-1,2-C6H4(CO2Me)2], 4; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 5; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 6 and Ru6(μ6-C)(CO)14[μ3−η6−1,2−C6H4(CO2Me)2], 7. Compounds 4 and 7 are isomers that contain the six-membered arene, dimethyl phthalate, 1,2−C6H4(CO2Me)2, as a ligand. Compound 3 was formed as a side product in low yield (6%) by the simple addition of CO to 2. The addition of CO to 2 causes the cluster to open to that of a spiked, square pyramid. Direct reaction of CO to 2 provided 3 in a good yield (72%). A DMAD ligand was added to the cluster of 2 as a simple triply-bridging ligand to form open Ru6 clusters in compounds 5 and 6. Addition of DMAD to 3 yielded the DMAD derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)[μ−C2(CO2Me)2], 8 which contains a DMAD ligand bridging a basal edge of an opened spiked-square pyramidal Ru6 cluster. Compound 5 was thermally converted to the new complex Ru6(μ5-C)(CO)14[μ4−η6−CHCHCHCC(CO2Me)C(CO2Me)](μ-H), 9 that contains a bridging CHCHCHCC(CO2Me)C(CO2Me) ligand formed by a coupling of the DMAD ligand to the bridging C4H4 ligand in 5 accompanied by a cleavage of one CH bond and formation of a bridging hydrido ligand. Decarbonylation of 3 with Me3NO yielded the NMe3 derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)(NMe3), 10 in which the NMe3 ligand is coordinated to the spiked metal atom on the square-pyramidal Ru5 cluster. Treatment of 4 and 7 with CO at 25 °C induced elimination of the 1,2−C6H4(CO2Me)2 ligand to yield free dimethyl phthalate, 11 and formation of the known parent carbonyl complex Ru6(μ6-C)(CO)17. All of the new cluster compounds were characterized by single-crystal X-ray diffraction analyses.

The activation and transformations of vinyl acetate at a dirhenium carbonyl center

The reaction of Re2(CO)8(μ-C6H5)(μ-H), 1 with vinyl acetate in methylene chloride by heating at 40 °C yielded three new products: Re3(CO)13(μ-η2-C2H3), 3, (24% yield), Re2(CO)8(μ-η2-O2CCH3)(μ-H), 4, (9% yield) and Re2(CO)8(μ-η2-CHCHO2CCH3)(μ-H), 5, (13% yield). Compound 3 was also obtained in a similar yield from the reaction of Re2(CO)8(μ-H)[μ-η2-C(H) = C(H)Bun], 2 with vinyl acetate, but compounds 4 and 5 were not obtained. All of the products were characterized structurally by single-crystal X-ray diffraction analysis. Compound 3 consists of an open trirhenium cluster containing two rhenium – rhenium bonds. One of the rhenium – rhenium bonds contains a μ-η2-(σ+π)-coordinated C2H3 (vinyl) ligand. Compound 4 contains two rhenium atoms with a bridging η2-acetate ligand and a bridging hydrido ligand. Compound 5 contains two mutually bonded Re–Re atoms with a bridging (σ+π)-coordinated acetate-substituted vinyl group and a bridging hydrido ligand by the cleavage of one of the CH bonds on the β–carbon atom of the vinyl group of the vinyl acetate. The reaction of compound 3 with I2 resulted in cleavage of the Re(CO)5 group to yield the known complex Re(CO)5I and the new dirhenium complex Re2(CO)8I(μ-η2-C2H3), 6 containing a μ-η2-(σ+π)-coordinated vinyl group.

Reductive coupling of diisopropylcarbodiimide by a dirhenium carbonyl complex

The reaction of Re2(CO)8(μ-H)[μ-η2-C(H) = C(H)Bun] with N,N′-diisopropylcarbodiimide yielded the new rhenium diamidinate complex [Re(CO)4]2[(μ-C2(N{iPr})4], 2, in 59% yield that was formed by the reductive coupling of two of carbodiimide molecules at the central carbon atom. The diamidinate ligand is nonplanar and four iminyl nitrogen atoms are coordinated to two Re(CO)4 groups in two chelating groups that have formed five-membered rings. Density functional molecular orbital analyses were used to explain the bonding of the diamidinate ligand to the two rhenium atoms. A second product Re2(CO)8(μ-OH)(μ-H), 3 was obtained from the reaction of N,N′-diisopropylcarbodiimide and Re2(CO)8(μ-C6H5)(μ-H), 1. Compound 3 was subsequently found to be a product of the reaction of 1 with traces of H2O in the original reaction and was independently obtained in 60% yield from the reaction of 1 with H2O. Compound 3 contains a bridging hydroxo ligand and a bridging hydrido ligand across the Re–Re bond between two mutually bonded Re(CO)4 groups. Both new compounds were characterized structurally by single-crystal X-ray diffraction analysis.

The coordination and activation of azobenzene by Ru5(μ5-C) cluster complexes

The reaction of Ru5(μ5-C)(CO)15, 1 with azobenzene, PhN = NPh, yielded the pentaruthenium carbido cluster compound Ru5C(CO)13(C6H4N=NC6H5)[μ-H], 4 containing a chelating ortho-metalated azobenzene ligand on one of the ruthenium atoms in a opened square-pyramidal Ru5C cluster. Compound 4 is electronically unsaturated and it readily adds one CO ligand at 25 °C to yield the electronically saturated complex Ru5C(CO)14(C6H4N=NC6H5)[μ-H], 5. Ru5C(CO)13(μ-η2-Ph)[μ-Au(NHC)], 3 reacts with azobenzene to yield the azobenzene complex Ru5C(CO)13(μ−η2−PhN = NPh)(η1−Ph)[μ−Au(NHC)], 6, NHC = 1,3-bis(2,6-diisopropylphenyl-imidazole-2ylidene), which contains a novel bridging di-σ-η2-N,N-coordinated azobenzene ligand across an open edge of an Ru5C cluster. Compound 6 eliminated benzene and was transformed to the new compound Ru5C(CO)13(C6H4N=NC6H5)[μ−Au(NHC)], 7 when heated to 105 °C for 3 h. Compound 7 is similar to 4 except that it has an Au(NHC) group in the place of the bridging hydrido ligand in 4. Compound 7 is also formally electronically unsaturated like 4. All of the new compounds were characterized by single-crystal X-ray diffraction analyses. The structures, bonding and reactivity of the complexes are discussed.

Synthesis, Characterization, and Reactivity of a High-Spin Iron(II) Hydrido Complex Supported by a PNP Pincer Ligand and Its Application as a Homogenous Catalyst for the Hydrogenation of Alkenes.

This study focused on the synthesis and characterization of a range of low-valent, high-spin iron(II) complexes supported by a carbazole-based PNP pincer-type ligand. The addition of the lithiated ligand (PNP)Li to FeCl2(THF)1.5 yielded the chlorido complex (PNP)FeCl (1), which could be readily converted to the four-coordinate iron(II) alkyl complexes (PNP)FeR [R = CH2SiMe3 (3a), Me (3b), CH2Ph (3c)]. These iron(II) complexes were fully characterized by X-ray analysis and a comprehensive, density-functional-theory-assisted study with complete assignment of their paramagnetic 1H and 13C NMR spectra. Treatment of 1 with KHBEt3 or the addition of molecular hydrogen to (PNP)FeR afforded a high-spin iron(II) PNP hydrido complex, which was identified as the dimer [(PNP)Fe(μ-H)]2 (4) with two bridging hydrido ligands between the iron centers. Exposing complexes 1 and 4 to carbon monoxide led to the corresponding six-coordinate, diamagnetic complexes (PNP)Fe(CO)2Cl (2) and (PNP)Fe(CO)2H (5), of which 2 was present as cis/trans isomers. Furthermore, 4 was found to be an active catalyst for the hydrogenation of alkenes.

Synthesis and Reactivity of Thiolate‐Bridged NiIIMI Heterodinuclear Complexes (M = Rh, Ir) with an S‐Bidentate NiP2S2 Metalloligand

The mononuclear complex [Ni(meppp)] {H2meppp = meso‐1,3‐bis[(2‐mercaptoethyl)(phenyl)phosphino]propane} was used as an S‐bidentate NiP2S2 metalloligand to prepare a series of NiIIMI complexes with various neutral ligands, namely, [Ni(µ‐meppp)ML2]PF6 [M = Rh, L = 1/2cod (1a; cod = 1,5‐cycloocatadiene), CO (1b), XylNC (1c; Xyl = 2,6‐dimethylphenyl), P(OPh)3 (1d); M = Ir, L = 1/2cod (2a), CO (2b), XylNC (2c)]. The reactivities of 1 and 2 toward methyl iodide and tertiary hydrosilanes were examined. Complexes 1c, 2a, and 2b reacted with MeI to afford the oxidative addition products [Ni(µ‐meppp)M(L)2(Me)(I)]PF6 [M = Rh, L = XylNC (3c); M = Ir, L = 1/2cod (4a)] and [Ni(µ‐meppp)Ir(CO)(Me)(I)2] (5). In the reactions with hydrosilanes, only 2c exhibited an interesting reactivity to afford the NiII(µ‐H)IrIII silyl complexes [Ni(µ‐meppp)(µ‐H)Ir(XylNC)2(Si)]PF6 [Si = SiEt3 (6a), SiMe2Ph (6b), SiMePh2 (6c), SiPh3 (6d)]. The reaction proceeded via the intermediate isomers [Ni(meppp)(µ‐H)Ir(XylNC)2(Si)]PF6 (7); intermediate 7d (Si = SiPh3) was characterized and has an NiII(µ‐H)IrIII silyl structure with the hydrido ligand nesting in the reverse side of the Ni(µ‐S)2Ir pocket to that of 6d. These results demonstrated that the reactivities of the bis(thiolate)‐bridged NiIIMI heterodinuclear complexes can be tuned by changing the metal ions and ancillary ligands. In addition, the S‐bidentate NiP2S2 metalloligand [Ni(meppp)] plays an important role in the stabilization of the bridging hydrido ligand in both pockets of the NiII(µ‐H)IrIII core owing to the flexibility of the hinged Ni(µ‐SR)2Ir structure.

Formyl C-H activation in N,N-Dimethylformamide by a dirhenium carbonyl complex

The reaction of Re2(CO)8[μ-η2-C(H)=C(H)Bun](μ-H), 1 with N,N-dimethylformamide (DMF) at 70 C for 6 h has yielded three new compounds: Re2(CO)8(μ-η2-O=CNMe2)(μ-H), 2, (16% yield), Re2(CO)7(NHMe2)(μ-η2-O=CNMe2)(μ-H), 3, (30% yield), Re2(CO)9(NHMe2), 4 (14% yield). Compounds 2 and 3 contain a C,O-η2-bridging formamido (O=CNMe2) ligand and a bridging hydrido ligand that were formed by the elimination of hexene from 1 and the oxidative addition of the formyl C-H bond of the DMF to the dirhenium group of 1. Compound 3 also contains an NHMe2 ligand that was apparently formed by the decarbonylation of DMF and the transfer of the formyl hydrogen atom to the NMe2 group. Compound 4 contains a similarly formed NHMe2 ligand. Compound 2 was also obtained by the reaction of 3 with CO and compound 3 was obtained by the reaction of 2 with DMF. Compound 4 was obtained independently in a high yield by the reaction of Re2(CO)9(NCMe) with NHMe2. Compounds 2, 3 and 4 were characterized structurally by single-crystal X-ray diffraction analyses.

Bridging phenyl ligands. Unsaturated mercury-triosmium carbonyl cluster complexes containing bridging phenyl ligands

The gold phosphine group in the complex Os3(CO)10(μ-η1-Ph)(μ-AuPPh3), 1 can be replaced by mercury halide groups by reactions with mercury halides. The reaction of 1 with HgI2 yielded the new compound [Os3(CO)10(μ-η1-Ph)(μ-HgI)]4, 2 in 19% yield. The reaction of 1 with HgCl2 yielded the new compound Os4(CO)13(μ-η1-Ph)(μ-Cl)3, 3 in 18% yield. When heated to reflux in cyclohexane solvent, compound 2 was converted into the compound [Os3(CO)9(μ3-C6H4)(μ-H)(μ3-Hg)]2Os(CO)4, 4 in 11% yield. All new compounds were characterized by single-crystal X-ray diffraction analyses. Compound 2 is a tetramer of the unit “Os3(CO)10(μ-η1-Ph)(μ-HgI)” that is held together by a cubane-like Hg4I4 core having D2 symmetry. Each triosmium cluster is formally electronically unsaturated and contains one edge-bridging phenyl ligand. Compound 3 contains a Os3(CO)10(μ-η1-Ph)(μ-Hg) cluster, but in this case the Hg atom bridges to an additional Os(CO)3 group via three bridging chloride ligands. Compound 4 contains two Os3(CO)9(μ3-C6H4)(μ-H)(μ3-Hg) clusters that are linked by a bridging Os(CO)4 group. Each Os3 cluster in 4 contains a triply bridging C6H4 benzyne ligand and one bridging hydrido ligand.

Facile CH Bond Formation by Reductive Elimination at a Dinuclear Metal Site

AbstractThe electronically unsaturated dirhenium complex [Re2(CO)8(µ‐AuPPh3)(µ‐Ph)] (1) was obtained from the reaction of [Re2(CO)8{µ‐η2‐C(H)C(H)nBu}(µ‐H)] with [Au(PPh3)Ph]. The bridging {AuPPh3} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re2(CO)8(µ‐H)(µ‐Ph)] (2) by reaction of 1 with HSnPh3. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 °C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses.

Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: synthesis, structures, C-Si bond activation and catalytic activity in ethylene polymerization.

The reaction of Ap(9Me)Lu(CH2SiMe3)2(thf) (Ap(9Me) = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap(9Me)Ln(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*-Y(1A)-CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)3(μ(2)-H)3(μ(3)-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ(3)- and μ(2)-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(thf)3](+)[B(C6F5)4](-) as well as [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions.

Reactivity of Yttrium Carboxylates Toward Alkylaluminum Hydrides

Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(μ-H)AlMe2(μ-H)AlMe2(μ-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of δ=-88.1 ppm (R=CH2SiMe3) and δ=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments.

Synthesis and structures of new tetrairidium carbonyl clusters containing phenylgermanium ligands

The reaction of Ir4(CO)11(PPh3) with GePh3H in the presence of Me3NO at room temperature has yielded a new complex Ir4(CO)10(PPh3)(GePh3)(μ-H), 1 in 54% yield by decarbonylation and oxidative addition of the GeH bond of the GePh3H to the cluster. The structure of 1 consists of a tetrahedral Ir4 cluster with a terminal GePh3 ligand and a bridging hydrido ligand. Compound 1 was converted to the GePh2-bridged complex Ir4(CO)10(PPh3)(μ-GePh2), 2 in 95% yield when heated to 40 °C, by the cleavage of a phenyl ring from the GePh3 ligand and the elimination of a molecule of benzene. The reaction of 2 with GePh3H at 65 °C yielded the new tetrahedral Ir4 complex Ir4(CO)7(PPh3)(GePh2)(GePh3)(μ3-η2-GePhC6H4)(μ-H)2, 3 which contains an ortho-metallated bridging μ3-η2-GePh(C6H4) ligand, a terminal GePh3 ligand, a bridging GePh2 ligand and two bridging hydrido ligands. Compound 3 was converted to the complex Ir4(CO)7(PPh3)(GePh2)2(μ3-η2-GePhC6H4)(μ-H), 5 cleavage of a phenyl ring from the GePh3 ligand and the elimination of a molecule of benzene. The structure of 5 consists of a tetrahedral Ir4 cluster with an ortho-metallated bridging μ3-η2-GePh(C6H4) group, two bridging GePh2 ligands and one bridging hydrido ligand. The reaction of 2 with GePh2H2 at 40 °C yielded the tetrairidium complex Ir4(CO)6(PPh3)(GePh2)3(GePh2H)(μ-H)3, 6 with three bridging GePh2 ligands, a terminal GePh2H ligand and three bridging hydrido ligands. All new compounds were fully characterized by IR and 1H NMR spectroscopy, single-crystal X-ray diffraction analyses, and mass spectrometry.

Reactions of Bis(tri-tert-butylphosphine)platinum with Metal Hydride Complexes. The Reactions of Pt(P-t-Bu3)2 with HRe(CO)4SbPh3

Pt(P-t-Bu3)2 reacts with the rhenium hydride complex HRe(CO)4(SbPh3), 1, at 25 °C to give the complex PtRe(CO)4(Ph)(P-t-Bu3)(μ-SbPh2)(μ-H), 2, in 75% yield by the oxidative-addition of a Sb−C bond on the SbPh3 ligand of 1 to a Pt(P-t-Bu3) group generated by loss of a P-t-Bu3 ligand from Pt(P-t-Bu3)2. Compound 2 contains a Pt−Re bond [Pt(1)−Re(1) = 3.0971(7) Å] with a bridging SbPh2 ligand and a bridging hydrido ligand. At 98 °C, Pt(P-t-Bu3)2 reacts with two equivalents of 1 to yield the compounds PtRe2(CO)8[PH(t-Bu2)](Ph)(μ-SbPh2)2(μ-H), 3, PtRe2(CO)8(SbPh3)(Ph)(μ-SbPh2)2(μ-H), 4, and PtRe2(P-t-Bu3)(μ-SbPh2)2(μ-SbPh), 5. Compounds 3 and 4 both contain five-membered Re2Sb2Pt rings formed from two mutually bonded Re(CO)4 groups and two bridging SbPh2 ligands that are both bonded to the Pt atom. Compound 4 was obtained from 2 independently by reaction with 1. Pt(P-t-Bu3)2 reacts with 1 at 68 °C under a hydrogen atmosphere to yield 2, 4, and the new compound, HPtRe2(CO)8(P-t-Bu3)(μ-SbPh2)2(μ-H), 6, which also contains a five-membered Re2Sb2Pt ring similar to those found in 3 and 4. Five compounds were obtained in low yields when 2 was thermally decomposed under nitrogen at 100 °C: 5 (4%); Re2(CO)8(μ-SbPh2)2, 7 (6% yield); RePh(CO)4SbPh3, 10 (4%); Re2(CO)8[PtH(CO)(P-t-Bu3)](μ3-SbPh)(μ-SbPh2), 11 (4%); RePh(CO)4[PtH(CO)P(t-Bu)3](μ-SbPh2), 12 (7%). Of these, only 12 is new. Compound 12 is a CO adduct of 2 and was obtained independently by the addition of CO to 2. The CO ligand was added to the platinum atom, the Pt−Re bond of 2 was cleaved, and the phenyl group was shifted to the rhenium atom. The two metal atoms are linked solely by the bridging SbPh2 ligand. Seven compounds, 5 (9% yield), 7 (26%), Pt3(CO)3(P-t-Bu3)3, 9 (71%), 11 (7%), 12 (8%), PtRe2(CO)9P(t-Bu)3(μ-H)2, 13 (13%), and Re3(CO)13(μ3-SbPh)(μ-SbPh2), 14 (18%), were obtained when 2 was allowed to react with CO at room temperature. Of these, only compound 14 is new. Compound 14 contains no platinum atoms. The structure of 14 contains two Re(CO)4 groups linked by a bridging SbPh2 ligand and a bridging SbPh ligand. The bridging SbPh ligand also contains a pendant Re(CO)5 group.

Synthesis of Heterometallic Trinuclear Polyhydrido Clusters Containing Ruthenium and Osmium and Their Electronic and Structural Deviation from Homometallic Systems

A trinuclear heterometallic pentahydrido complex, (Cp*Ru)2(Cp*Os)(μ-H)5 (3), was synthesized by dehydrogenative coupling between a diruthenium tetrahydride complex, Cp*Ru(μ-H)4RuCp*, and an osmium pentahydride, Cp*OsH5; an analogous complex, (Cp*Ru)(Cp*Os)2(μ-H)5 (4), was obtained by the reaction of a dimeric ruthenium methoxo complex, Cp*Ru(μ-OMe)2RuCp*, with a diosmium tetrahydride complex, Cp*Os(μ-H)4OsCp*, under an atmospheric pressure of dihydrogen. Complexes 3 and 4 were sufficiently basic to be protonated with HBF4, leading to the formation of corresponding hexahydrido cations, [(Cp*Ru)2(Cp*Os)(μ-H)6]+ (7) and [(Cp*Ru)(Cp*Os)2(μ-H)6]+ (8), respectively. An experiment on proton transfer between the two heterometallic systems 7 and 4 showed that the RuOs2 pentahydride was more basic than the Ru2Os pentahydride. Optimized structures of the heterometallic polyhydrido complexes 3, 4, 7, and 8 were derived using their C5H5 analogues as model compounds. Unlike the Ru3 system, the complex (CpRu)n(CpOs)3−n(μ-H)5 (3a: n = 2, 4a: n = 1), which has five doubly bridging hydrido ligands, was the most stable. Although X-ray structural studies of these complexes were conducted using a labeled cyclopentadienyl group, C5EtMe4, in all cases, their structures were disordered with respect to metal atoms. The most plausible structures of these complexes were obtained by solving simultaneous equations for metal−metal bond lengths. The estimated lengths were fully consistent with structures optimized by density functional theory calculations.

Diruthenium−Tin Complexes from the Reaction of Ph2SnH2 with Ru(CO)5 and Their Reactions with Bis(tri-tert-butylphosphine)platinum

Ph2SnH2 reacts with 2 equiv of Ru(CO)5 to give the compound [Ru(CO)4H]2(μ-SnPh2) (1) in 57% yield by loss of CO from each molecule of Ru(CO)5 and by an oxidative addition of an Sn−H bond to each ruthenium atom. When compound 1 was irradiated with visible radiation, the compound Ru2(CO)8(μ-SnPh2) (2) was obtained by loss of hydrogen. A mechanism involving loss of CO followed by loss of H2 and readdition of CO is supported by isotopic labeling studies. Compound 1 reacts with Pt(PBut3)2 to yield the new trimetallic compound Ru2(CO)7(μ-SnPh2)(μ-H)2(μ-PtPBut3) (3). Compound 3 contains a Pt(CO)(PBut3) group bridging the Ru−Ru bond and two bridging hydrido ligands. Compound 2 reacts with Pt(PBut3)2 to yield the two products PtRu2(CO)8)(PBut3)(μ-SnPh2) (4; 78% yield) and Pt2Ru2(CO)8(PBut3)2(μ-SnPh2) (5; 15% yield) by the addition of one and two Pt(PBut3) groups to the metal−metal bonds of 2. The first Pt(PBut3) addition occurs at the Ru−Ru bond to form 4. The second Pt(PBut3) addition occurs at one of the Ru−Sn b...

Cleavage of tert-Butyl Groups from the Tri-tert-butylphosphine Ligand in Osmium−Platinum Carbonyl Cluster Complexes

Two products, Pt2Os3(CO)10(PBut3)(PBut2CMe2CH2)(µ-H) (1) and Pt2Os3(CO)9(PBut3)(µ-PBut2)(µ-H)(µ3-CCMe2) (2), were obtained from the reaction of Os3(CO)12 with Pt(PBut3)2 at 97 °C. Compound 2 is new and consists of a square-pyramidal cluster of five metal atoms with a bridging PBut2 ligand, a bridging hydrido ligand, and a triply bridging dimethylvinylidene ligand C═CMe2 formed by transformations of a tri-tert-butylphosphine ligand. Compound 1 was transformed into 2 at 125 °C, and compound 2 was transformed into two new compounds, PtOs3(CO)7(PBut3)(µ-PBut2)(µ4-CHCMeCH) (3) and Pt4Os3(CO)12(µ-PBut2)2 (4), at 174 °C. Compound 3 contains a bridging PBut2 ligand and a quadruply bridging CHCMeCH ligand in a butterfly cluster of four metal atoms. Compound 4 contains four platinum atoms and three osmium atoms. The metal atoms are arranged in the form of a doubly capped square pyramid with the four platinum atoms in the square base. Two triangles of the square pyramid are capped by Os(CO)3 groups. The molecule also contains two bridging di-tert-butylphosphido ligands on opposite sides of the Pt4 square base. Compound 3 is electron-deficient by the amount of four electrons, and it reacts reversibly with CO to form the new compound PtOs3(CO)8(PBut3)(µ-PBut2)(µ4-CHCMeCH) (5) by the addition of one CO ligand to the platinum atom. The electronic structures of 3−5 were investigated by Fenske–Hall molecular orbital calculations.

Acid–Base Bifunction and Umpolung of the Bridging Hydride in a Coordinatively Unsaturated Mesylimido- and Hydrido-Bridged Diiridium Complex

The mono(mesylamido)-bridged diiridium(III) complex [(Cp*IrCl)2(μ2-H)(μ2-NHMs)] (Cp* = η5-C5(CH3)5, Ms = SO2CH3) undergoes reversible dehydrochlorination to afford the unsaturated imido-bridged dinuclear complex [Cp*Ir(μ2-H)(μ2-NMs)IrClCp*] (2). The reaction of 2 with trimethylphosphine gives the simple adduct [Cp*Ir{P(CH3)3}(μ2-H)(μ2-NMs)IrClCp*], while the reaction with CO results in sequential formation of the mono- and dicarbonyl Ir(II) complexes [Cp*Ir(CO)(μ2-NHMs)IrClCp*] and [{Cp*Ir(CO)}2(μ2-NMs)] with concomitant umpolung of the bridging hydrido ligand in 2 to the amido proton.

Facile cleavage of a phenyl group from SbPh 3 by dirhenium carbonyl complexes

The complex Re 2(CO) 8[μ-η 2-C(H) C(H)Bu n ](μ-H) ( 1) reacts with SbPh 3 at 68 °C to yield the new σ-phenyl dirhenium complex Re 2(CO) 8(SbPh 3)(Ph)(μ-SbPh 2) ( 4) in 72% yield. Compound 4 contains two rhenium atoms held together by a bridging SbPh 2 ligand. One rhenium atom contains a σ-phenyl group. The other rhenium atom contains a SbPh 3 ligand. Compound 4 was also obtained in 34% yield from the reaction of Re 2(CO) 10 with SbPh 3 in the presence of UV–Vis irradiation together with some monorhenium products: HRe(CO) 4SbPh 3 ( 5), Re(Ph)(CO) 4SbPh 3 ( 6) and fac-Re(Ph)(CO) 3(SbPh 3) 2 ( 7) in low yields. Complex 4 is split by reaction with an additional quantity of SbPh 3 to yield the monorhenium SbPh 3 complexes 6, 7 and mer-Re(Ph)(CO) 3(SbPh 3) 2 ( 8) that contain a σ-phenyl ligand. When 4 was treated with hydrogen, the phenyl ligand was eliminated as benzene and the dirhenium complexes Re 2(CO) 8(μ-SbPh 2)(μ-H) ( 10), and Re 2(CO) 7(SbPh 3)(μ-SbPh 2)(μ-H) ( 11), were formed that contain a bridging hydrido ligand. The doubly SbPh 2-bridged dirhenium complex Re 2(CO) 7(SbPh 3)(μ-SbPh 2) 2 ( 9) that has no metal–metal bond was also formed in these two reactions.

Facile activation of hydrogen by unsaturated platinum–osmium carbonyl cluster complexes

The electronically unsaturated cluster complex Os 3Pt 2(CO) 10(PBu t 3) 2 ( 10) was obtained from the reaction of Os 3(CO) 10(NCMe) 2 with Pt(PBu t 3) 2. Three side products: PtOs 3(CO) 10(PBu t 2)CMe 2CH 2(μ-H) ( 13), Os 3(CO) 10(PBu t 3) 2 ( 14) and Pt 2Os 3(CO) 10(PBu t 3)(PBu t 2)CMe 2CH 2(μ-H) ( 15) were also obtained from this reaction. The three osmium atoms in 10 lie in the equatorial plane of a trigonal bipyramid. The platinum atoms occupy the apical positions. When heated, compound 10 was converted to 15 by metallation of one of the methyl groups of one of the PBu t 3 ligands at the platinum atom to which it is coordinated. The platinum atom then shifted to an edge of the Os 3 triangle by cleaving one of its Pt–Os bonds. Compound 13 also contains a metallated PBu t 3 ligand attached to the platinum atom of the tetrahedral PtOs 3 cluster. Compound 10 reacts with hydrogen at 0 °C to yield the di- and tetra-hydrido compounds Os 3Pt 2(CO) 10(PBu t 3) 2(μ-H) 2 ( 11) and Os 3Pt 2(CO) 10(PBu t 3) 2(μ-H) 4 ( 12) with the hydrido ligands bridging Os–Pt and Os–Os bonds. With each addition of hydrogen, one of the platinum atoms in the cluster was shifted to an edge of the Os 3triangle. When solutions of 12 at 25 °C were purged with nitrogen, hydrogen was eliminated and the compounds 10 and 11 were regenerated. The electronic structures of 10 and 11 were also investigated by Fenske–Hall molecular orbital theory. When compound 10 was exposed to hydrogen for 2.5 h, compound 12 was formed together with the new tetranuclear metal cluster complexes PtOs 3(CO) 10(PBu t 3)(μ-H) 2 ( 16), PtOs 3(CO) 9(PBu t 3)(μ-H) 4 ( 17) and PtOs 3(CO) 8(PBu t 3) 2(μ-H) 4 ( 18). Compounds 16– 18 contain tetrahedrally shaped clusters of four metal atoms with bridging hydrido ligands. All new compounds were characterized structurally by single-crystal X-ray diffraction methods.