Silyl Complexes Research Articles

A Stable Silylene in a Reactive Environment: Synthesis, Reactivity, and Silicon Extrusion Chemistry of a Coordinatively Unsaturated Ruthenium Silylene Complex Containing Chloride and η3-P−C−P Ligands

Reaction of [(dcypb)ClRu(μ-Cl)3Ru(dcypb)(N2)] (1) with 4 equiv of the stable silylene 1,3-di-tert-butyl-1,3,2-diazasilol-2-ylidene (SiLN2) yields coordinatively unsaturated RuCl(η3-dcypb)(SiLN2) (2...

A theoretical study of the reaction products created by irradiation of the carbonyl iron silyl complexes Cp(CO) 2FeSiH 2Me and Cp(CO) 2FeCH 2SiH 3

The theoretical reaction pathways of the irradiation of Cp(CO) 2FeSiH 2CH 3 and Cp(CO) 2FeCH 2SiH 3 have been studied by means of DFT calculations using the BPW91/6-311G* method. Although the calculated characteristic vibrational modes of the metal ligand unit for the various photoproducts are significantly different in constitution, they are very similar in wavenumbers, which did not simplify their identification. In spite of this, the theoretical results are found to be consistent with recent experimental findings obtained by the matrix isolation technique.

Organolutetium Complexes in σ-Bond Metathesis Reactions Involving Silicon. Catalysts for the Hydrogenolysis of Si−C Bonds

The lutetium hydride complex [Cp*2Lu(μ-H)]2 (1) efficiently cleaves the Si−C bond of PhSiH3 to produce benzene and cross-linked polysilanes (SiHx)y. The Si−C bond cleavage appears to proceed via the lutetium phenyl complex Cp*2LuPh (2). This is supported by the reaction of PhSiH3 with 2, which results in the formation of benzene. Moreover, activation of the Si−C bond of C6F5SiH3 by 1 yields the related lutetium aryl complex Cp*2LuC6F5 (4) and oligosilanes. The reaction of 1 with o-MeOC6H4SiH3, on the other hand, results in the formation of dihydrogen and the neutral lutetium silyl complex (5). The solid-state structure of 5 was determined by X-ray crystallography. Reactions of arylsilanes with the lutetium methyl complex [Cp*2LuMe]2 (3) are less selective than the corresponding reactions of 1 and lead to competitive Si−C and Si−H bond activations. Complex 1 acts as an efficient catalyst for organosilane hydrogenolysis. Thus, addition of excess phenyl- or hexylsilane to solutions of 1 under an atmosphere o...

Activation of Water and of Dioxygen by a Bis(diphenylphosphinopropyl)silyl (biPSi) Complex of Ruthenium(II): Formation of Bis(diphenylphosphinopropyl)siloxo Cage Complexes. Concomitant Oxygen Atom Insertion into a Silicon−Carbon Bond

The coordinatively saturated hydrido complex RuH(biPSi)(CO)2 (1), biPSi = −Si(Me)(CH2CH2CH2PPh2)2, reacts slowly with either water/piperidine or dioxygen to afford the novel “anchored” siloxo complexes (3, L = CO) and (6, L = CO), respectively, which undergo carbonyl displacement to yield analogues in which L = P(OMe)3 that are crystalline (5 or 7, respectively) and for which anti stereochemistry (i.e., H at Ru vs Me or OMe at Si) has been identified by using X-ray crystallography (i.e., products 5-a, 7-a respectively). Complex 1 catalyzes autoxidation of cyclohexene (mainly to cyclohexenone, cyclohexenol:TTO ≈ 300, 4 h).

Effective Control of Two Elimination Processes from a Hydridobis(silyl)iron(IV) Complex

Abstract A novel hydridobis(silyl)iron(IV) complex Cp*(CO)Fe(H){SiMe2O(2-C5H4N)}2 (1) (Cp*=η5-C5Me5) was synthesized in high yield. Two elimination processes from 1 were effectively controlled by the reaction conditions: HSiMe2O(2-C5H4N) is eliminated on heating or UV-irradiation, whereas HO(2-C5H4N) is eliminated in the presence of Et3Al. The latter reaction was applied to a “silylene introduction” toward a silyl complex producing a silyl(silylene) complex.

Photochemistry of bridged disilyldiiron complexes (SiMe 2)[(η 5-C 5H 4)Fe(CO) 2SiMe 2SiMe 2R] 2, R=Me, Ph

Photochemical irradiation of the new bimetallic disilyliron complexes (SiMe 2)[(η 5-C 5H 4)Fe(CO) 2SiMe 2SiMe 2R] 2, R=Me, Ph, results in silylene elimination chemistry, as observed for the mono-metallic analogs, resulting in the formation of complexes (SiMe 2)[(η 5-C 5H 4)Fe(CO) 2SiMe 2R] 2. The intermediate silyl(silylene) complexes can be intercepted with HMPA. Apart from a very reactive minor product that we have been unable to identify at this time, the proximity of the two transition metal centers has little impact upon the observed chemistry.

An Observable Silene/Silylene Rearrangement in a Cationic Iridium Complex

The iridium complex Cp*(PMe3)Ir(Me)(SiMe2OTf) (2) reacts with LiB(C6F5)4(Et2O)2 to form a mixture of the silene complex [Cp*(PMe3)Ir(η2-CH2SiMe2)(H)][B(C6F5)4] (3) and the base-stabilized silylene complex [Cp*(PMe3)Ir(Me)(SiMe2(Et2O))][B(C6F5)4] (4). The silene complex 3 has been crystallographically characterized. Addition of pyridine to this mixture affords Cp*(PMe3)Ir(Me)(SiMe2(L)][B(C6F5)4] (5a, L = pyridine) in good yield, whereas addition of CO or ethylene results in clean formation of Cp*(PMe3)Ir(L)(SiMe3)][B(C6F5)4] (8a, L = CO; 8b, L = C2H4).

Stereomutation at an Octahedral Transition-Metal Center: Energetics of Hydride Transit between Syn and Anti Faces of the Bis(diphenylphosphinopropyl)(methyl)silyl (biPSi) Complex RuH(biPSi)(CO)2

Reaction of SiH(Me)(CH2CH2CH2PPh2)2, “biPSiH”, with Ru(PPh3)2(CO)3 affords quantitatively the phosphinoalkylsilyl complex RuH(biPSi)(CO)2, as a mixture of the crystallographically characterized syn diastereomer 3-s and its anti correspondent 3-a; subsequent treatment with CCl4 then LiAl2H4 provides access to the deuterioisotopomer Ru2H(biPSi)(CO)2, 3-d1. Slow stereomutation of pure 3-s to an equilibrium mixture 3-s/3-a (4.5:1, 295 K) occurs with ΔG⧧295, 102(5) kJ mol-1; ΔH⧧295, 113(7) kJ mol-1; ΔS⧧295, 37(2) J K-1 mol-1; this is not accompanied by incorporation of external 13CO, shows only a minor isotope effect vs 3-d1, and is concluded to be nondissociative.

Theoretical investigation of substituent effects on the silicon–metal bond for a series of transition metal-substituted base-stabilized silylene complexes

Hartree–Fock ab initio calculations were used to investigate the effects of various silicon substituents on the silicon–ruthenium bond for four transition metal-substituted base-stabilized silylene complexes. To provide comparison information, one silyl complex, Cp*(PMe 3) 2Ru–Si[S(Tol- p)] 3, and four base-free silylene complexes ([Cp*(PMe 3) 2RuSiMe 2]BPh 4, Cp*(PMe 3) 2RuSi[S(Tol- p)][Os(CO) 4], a bis(silylene)nickel compound and [ trans-(P(Cy 3) 2(H)PtSi(SEt) 2]BPh 4) were also studied. Results of the calculations indicate that the order of promotion of silylene character for base groups is NCMe>OTf≫S(Tol- p). Of those considered, the best substituent group in terms of transition metal–silicon double bond promotion is methyl followed by triflate. The worst group with respect to this property is S(Tol- p).

New Mono- and Polynuclear Iron Silylene and Stannylene Complexes

The mono- and dinuclear stannylene reagents [Sn(μ-NtBu)2SiMe2] (4) and [Sn(OtBu)(μ-OtBu)]2 (6) were reacted with the amine-stabilized bis(dimethylamino)silylene complex [Fe{Si(NMe2)2(NHMe2)}(CO)4] ...

ChemInform Abstract: The Chemistry of Organo(silyl)platinum(II) Complexes Relevant to Catalysis

A variety of silylplatinum complexes cis- and trans-PtR(SiYPh2)L2 (R=Me, Et, Pr, Bu, vinyl, phenyl, phenylethynyl; Y=Ph, Me, H, F, OMe; L=PMePh2, PMe2Ph), cis-Pt(SiR3)(SnMe3)(PMe2Ph)2 (SiR3=SiMe3, SiMe2Ph, SiMePh2, SiPh3), and cis-Pt(SiR3)2(PMe2Ph)2 (SiR3=SiMe2Ph, SiMePh2, SiPh3) have been prepared, and their structures and reactivities toward CSi bond formation and phenylacetylene insertion have been examined by X-ray diffraction analysis, NMR spectroscopy, and kinetic experiments. Three types of processes are operative for CSi bond formation from cis-PtR(SiYPh2)L2 complexes giving RSiYPh2. One is the direct CSi reductive elimination; most of the complexes follow this process. The second type involves isomerization of cis-PtR(SiYPh2)L2 to cis-PtY(SiRPh2)L2, followed by YSi reductive elimination; this process has been observed for cis-PtR(SiPh3)L2 (R=Et, Pr, Bu) and cis-PtR(SiHPh2)L2 (R=Me, Et, Pr, Bu). Reactions of alkyl–silyl complexes with hydrosilanes also afford the corresponding alkylsilanes quantitatively, constituting the third type of process. Insertion of phenylacetylene into the PtSi bond of PtR(SiPh3)L2 complexes takes place only for the cis isomers. Silyl–stannyl complexes undergo competitive insertion of phenylacetylene into the PtSi and PtSn bonds under kinetic conditions, whereas the insertion into the PtSi bond predominates under thermodynamic conditions. Reactivities of four PtSiR3 bonds toward insertion relative to the PtSnMe3 bond have been evaluated: SiMe3 (>49)>SiMe2Ph (1.9)>SiMePh2 (0.69)>SiPh3 (0.075). Bis-silyl complexes exhibit a rather intricate dependence of the insertion reactivity upon the sorts of silyl ligands, not simply correlated with the reactivity of PtSiR3 bonds, owing to the insertion process involving prior dissociation of a phosphine ligand. The bis-silyl complexes have a twisted square planar structure significantly distorted from planarity, and the rate of phosphine dissociation is highly sensitive to this distortion.

Reactivity of the Base-Stabilized Bis(silylene)iron Complex (η5-C5H5)Fe(CO)(η2-SiMe2-OtBu-SiMe2): Elevated Temperature Trapping of SiMe2 by R3EH (R = Me3Si, E = Si, Ge) and Elimination of Me2(OtBu)SiSiMe2H by n-Bu3SnH

The base-stabilized silylene complex (η5-C5H5)Fe(CO)(η2-SiMe2-OtBu-SiMe2) is unreactive toward (Me3Si)3EH (E = Si, Ge) under photochemical irradiation or at room temperature. However, at 80 °C it reacts, presumably via the equilibrium concentration of base-free complex (η5-C5H5)Fe(CO)(SiMe2OtBu)(SiMe2), to transfer the silylene group and form (Me3Si)3ESiMe2H. Attempts to transfer the SiMe2 group to tributyltin hydride led to formation of bis(tributylstannyl)iron complexes.

A Triangular Triplatinum Complex with Electron-Releasing SiPh2 and PMe3 Ligands: [{Pt(-SiPh2)(PMe3)}3

A platinum–silylene complex is implicated in the generation of the triangular platinum cluster 1 by thermolysis of a bis(silyl)-PtII complex. Although 1 contains only electron-releasing ligands, X-ray structural data, NMR studies, and MO calculations on a model complex are consistent with the presence of Pt0 centers and metal–metal bonds.

A Triangular Triplatinum Complex with Electron-Releasing SiPh2 and PMe3 Ligands: [{Pt(μ-SiPh2)(PMe3)}3

A platinum–silylene complex is implicated in the generation of the triangular platinum cluster 1 by thermolysis of a bis(silyl)-PtII complex. Although 1 contains only electron-releasing ligands, X-ray structural data, NMR studies, and MO calculations on a model complex are consistent with the presence of Pt0 centers and metal–metal bonds.

Synthesis and Reactivity of (Pentamethylcyclopentadienyl)ruthenium Complexes of the Stable Neutral Silylene Si(tBuNCHCHNtBu)

The coordination chemistry of the stable silylene (1) in Cp*Ru complexes has been investigated. Silylene 1 reacts with 0.25 equiv of [Cp*RuCl]4 to give the 16-electron Ru silylene complex (2). This...

The chemistry of organo(silyl)platinum(II) complexes relevant to catalysis

A variety of silylplatinum complexes cis- and trans-PtR(SiYPh 2)L 2 (R=Me, Et, Pr, Bu, vinyl, phenyl, phenylethynyl; Y=Ph, Me, H, F, OMe; L=PMePh 2, PMe 2Ph), cis-Pt(SiR 3)(SnMe 3)(PMe 2Ph) 2 (SiR 3=SiMe 3, SiMe 2Ph, SiMePh 2, SiPh 3), and cis-Pt(SiR 3) 2(PMe 2Ph) 2 (SiR 3=SiMe 2Ph, SiMePh 2, SiPh 3) have been prepared, and their structures and reactivities toward CSi bond formation and phenylacetylene insertion have been examined by X-ray diffraction analysis, NMR spectroscopy, and kinetic experiments. Three types of processes are operative for CSi bond formation from cis-PtR(SiYPh 2)L 2 complexes giving RSiYPh 2. One is the direct CSi reductive elimination; most of the complexes follow this process. The second type involves isomerization of cis-PtR(SiYPh 2)L 2 to cis-PtY(SiRPh 2)L 2, followed by YSi reductive elimination; this process has been observed for cis-PtR(SiPh 3)L 2 (R=Et, Pr, Bu) and cis-PtR(SiHPh 2)L 2 (R=Me, Et, Pr, Bu). Reactions of alkyl–silyl complexes with hydrosilanes also afford the corresponding alkylsilanes quantitatively, constituting the third type of process. Insertion of phenylacetylene into the PtSi bond of PtR(SiPh 3)L 2 complexes takes place only for the cis isomers. Silyl–stannyl complexes undergo competitive insertion of phenylacetylene into the PtSi and PtSn bonds under kinetic conditions, whereas the insertion into the PtSi bond predominates under thermodynamic conditions. Reactivities of four PtSiR 3 bonds toward insertion relative to the PtSnMe 3 bond have been evaluated: SiMe 3 (>49)>SiMe 2Ph (1.9)>SiMePh 2 (0.69)>SiPh 3 (0.075). Bis-silyl complexes exhibit a rather intricate dependence of the insertion reactivity upon the sorts of silyl ligands, not simply correlated with the reactivity of PtSiR 3 bonds, owing to the insertion process involving prior dissociation of a phosphine ligand. The bis-silyl complexes have a twisted square planar structure significantly distorted from planarity, and the rate of phosphine dissociation is highly sensitive to this distortion.

Reactions of a novel quadruply chelated molybdenum–silyl complex with β-dicarbonyl compounds

The novel molybdenum–silyl complex [MoH 3{[Ph 2PCH 2CH 2P(Ph)–C 6H 4- o] 2(Ar)Si -P,P,P,P, Si}] ( 1) reacted with 2,4-pentanedione to give eight-coordinate dihydrido complex 2 ( a, Ar=Ph; b, Ar= o-tolyl) with a chelated 2,4-pentanedionato ligand as a result of repelling one of four Mo–P bonds in 1. On the other hand, the reaction between 1 and dialkyl malonates gave an η 1- O-enolato type complex in which the quadruply chelated P–P–Si–P–P framework was found to be kept intact. The structure of 2a was confirmed by X-ray crystallographic structure analysis.

Synthesis and Characterization of Tantalum Silyl and Disilyl Imido Complexes That Do Not Contain Anionic π-Ligands

Tantalum disilyl and silyl complexes [(Me3Si)2N](Me3SiN)Ta(SiPh2But)2 (1) and [(Me3Si)2N](Me2N)(Me3SiN)Ta(SiPh2But) (2) have been prepared and characterized. They are, to our knowledge, the first k...

Homogeneous catalyst systems with organosilicon components for olefin metathesis

Two silicon-containing catalyst systems for the olefin metathesis reaction are described. The first system, WCl 6/Ph 2SiH 2, is active for all kinds of olefinic substrates: acyclic, cyclic and functionalized olefins, and alkadienes. The second system, W(CO) 6/Ph 2SiH 2, is active for the metathesis of terminal olefins, but only under UV irradiation. Upon reaction between the catalyst components, a tungsten–silylene intermediate is formed as the precursor of the active species for metathesis. The product of a [2+2] cycloaddition of the tungsten–silylene complex was isolated. It showed catalytic activity for the metathesis of 1-hexene under UV irradiation, or at elevated temperature, when tungsten–silylene species could be generated from [W(CO) 4] 2[μ 2-Si(C 6H 5) 2] 2. This is the first example of olefin metathesis with metal–silylene activation.

Stoichiometric and Catalytic Activation of Si−H Bonds by a Triruthenium Carbonyl Cluster, (μ3,η2:η3:η5-acenaphthylene)Ru3(CO)7: Isolation of the Oxidative Adducts, Catalytic Hydrosilylation of Aldehydes, Ketones, and Acetals, and Catalytic Polymerization of Cyclic Ethers

Treatment of the ruthenium cluster (μ3,η2:η3:η5-acenaphthylene)Ru3(CO)7 (1) with stoichiometric amounts of trialkylsilanes results in liberation of a CO ligand followed by oxidative addition of a Si−H bond. The trinuclear silyl complexes (μ3,η2:η3:η5-acenaphthylene)Ru3(H)(SiR3)(CO)6 (2) were isolated in good yield. They were characterized by NMR spectroscopy and X-ray crystallography. Compound 1 catalyzes the hydrosilylation of olefins, acetylenes, ketones, and aldehydes. In particular, the reactions of aldehydes and ketones proceed at room temperature to form the corresponding silyl ethers in good yield; the catalytic activities are superior to those with RhCl(PPh3)3. The RhCl(PPh3)3-catalyzed hydrosilylation of ketones with Me2(H)SiCH2CH2Si(H)Me2 results in selective reaction of only one Si−H terminus, while similar reactions, when catalyzed by 1, allow utilization of both Si−H groups. Significantly different regio- and stereoselectivities, compared with those obtained in reactions catalyzed by RhCl(PPh3)3, also were observed in the hydrosilylation of α,β-unsaturated carbonyl compounds and 4-tert-butylcyclohexanone, respectively. The reactions with acetals and cyclic ethers also take place under similar conditions. The reaction of trialkylsilanes with an excess of a cyclic ether resulted in ring-opening polymerization. Polymerization of THF was investigated as a representative example. Treatment of trialkylsilanes with an excess of THF (10−102 equiv with respect to silanes) in the presence of a catalytic amount of 1 resulted in production of polytetrahydrofuran with Mn = 1000−200 000 and Mw/Mn = 1.3−2.0. Changing the ratio of THF to HSiR3 can control the molecular weight. NMR studies suggested that the structure of the polymer is R3SiO−[(CH2)4O]n−CH2CH2CH2CH3. Mechanistic considerations based on differences in the catalytic activities between the catalysts 1 and 2 are discussed.