Silyl Hydride Complexes Research Articles

C−H and Si−H Activation on Palladium(II) and Platinum(II) Complexes with a New Methoxyalkyl-Substituted Diimine Ligand

Electrophilic 1,4-bis(methoxypropyl)-2,3-dimethyl-1,4-diazabutadiene Pd(II) and Pt(II) cations 2a,b with a BArF counteranion have been prepared. Complex 2a undergoes intramolecular C−H activation to form tricyclic 5, and complex 2b adds to Et3SiH to form an octahedral diimine Pt(IV) silyl hydride complex, 7.

Silyl-Komplexe des Molybdäns und Wolframs. Synthese, Reaktivität und Struktur

The photochemical reaction of Cp 2MH 2 (M=Mo, 1; W, 2) with several hydridosilanes HSiR 3 produces the corresponding silyl hydride complexes Cp 2M(H)(SiR 3) (M=Mo: SiR 3SiEt 3, 3; SiCl 3, 4; Si(OEt) 3, 5; SiH 2(C 5Me 5), 6; SiH 2(C 5Me 4H) 2, 7; SiH(C 5Me 4H) 2, 8; SiH 2[2-(Me 2NCH 2)C 6H 4], 9; M=W: SiR 3SiCl 3, 10) by a reductive elimination/oxidative addition process. Analogous photolysis of 1 in the presence of (C 5Me 5) 2SiHCl or (C 5Me 5) 2SiH 2 does not yield the corresponding complexes Cp 2Mo(H)(SiR 3) (SiR 3SiCl(C 5Me 5) 2; SiH(C 5Me 5) 2). Treatment of 4 and 6, respectively, with LiAlH 4 leads to the hydridosilyl complex Cp 2Mo(H)(SiH 3) 11. Compounds 6–8 and 11 are expected to be single-source precursors for generation of molybdenum silicides. The hydride complexes 4, 5, and 6 are readily converted to the chloro compounds Cp 2Mo(Cl)(SiR 3) (SiR 3SiCl 3, 12; Si(OEt) 3, 13; SiH 2(C 5Me 5), 14). The reaction of 11 with CCl 4 yields complex 12 under exchange of each non-C-bound hydrogen atom. Spectroscopic data of the metallosilanes are discussed and compared with the ones of the parent silanes. An intramolecular N-donor coordination of the functionalized aryl substituent is indicated for 9 by means of 29Si NMR spectroscopy. 6 undergoes fast sigmatropic rearrangements within the Si–(C 5Me 5) fragment as proved by a variable temperature 1H NMR investigation. The structures of 6, 7, 8, and 12 have been determined by single-crystal X-ray diffractometry. Bonding parameters of these typical bent–sandwich complexes are discussed taking account of electronic and steric influences.

Synthesis and Reactivity of 16-Electron Hafnocene Silyl Hydride Complexes

The synthesis and reactivity of monomeric, 16-electron hafnocene silyl hydride complexes are described. The complex CpCp*Hf[Si(SiMe3)3]H (1; Cp* = η5-C5Me5), prepared by the reaction of CpCp*Hf(H)Cl with (THF)3LiSi(SiMe3)3, reacts rapidly with both ethylene and diphenylacetylene with elimination of HSi(SiMe3)3 to afford the corresponding hafnacyclopentane and tetraphenylhafnacyclopentadiene complexes. Complex 1 reacts with acetone to give the insertion product CpCp*Hf(OCHMe2)[Si(SiMe3)3] (4). Reaction of 1 with the secondary silane H2Si(SiMe3)2 proceeds smoothly to the new silyl hydride complex CpCp*Hf[SiH(SiMe3)2]H (5), which was characterized by X-ray crystallography. Deuterium labeling experiments indicate that the latter reaction occurs with significant scrambling of label between the SiH and HfH positions. The tertiary silane Ph3SiH does not react under comparable conditions. The silane H2Si(SiMe3)2 undergoes a similar σ-bond metathesis reaction with CpCp*Hf[Si(SiMe3)3]Cl, to give CpCp*Hf[SiH(SiMe3)2...

Silyl and bis(silyl)hydride complexes of ruthenium: Effect of ancillary groups on the oxidative addition of Si-H bonds

Ruthenium alkyl complexes Cp(PMe 3) 2 RuCH 2SiMe 3 ( 2) and Cp(PPh 3) 2RuMe ( 3) reacted with hydrosilanes forming ruthenium silyl and/or bis(silyl)hydride complexes. Complex 2 reacted with HSiR 3 at 100°C forming the corresponding silyl complexes Cp(PMe 3) 2RuSiR 3[SiR 3 = SiCl 3 ( 4), SiMeCl 2 ( 5), SiMe 2Cl ( 6)] in high yields. At 125–150°C, 2 reacted with HSiEt 3 giving a mixture of the silyl Cp(PMe 3) 2RuSiEt 3 ( 7) and the bis(silyl)hydride Cp(PMe 3)Ru(SiEt 3) 2H ( 8); this mixture can be converted solely to 7 upon reaction with PMe 3. Complex 3 reacted with HSiEt 3 at 100°C forming Cp(PPh 3) 2RuSiEt 3 ( 9). The reaction of 3 with neat HSiCl 3 at 100°C forms a mixture of Cp(PPh 3)Ru(SiCl 3) 2H ( 10) and Cp(PPh 3) 2RuSiCl 3 ( 11), with 10 being the major product. At lower concentrations of HSiCl 3 (< 2 M), the reaction with 3 forms mixtures of 10 and 11 but with 11 being the major product. Mixtures of 10 and 11 can be converted to 11 upon reaction with excess PPh 3. Similarly, 11 reacts with neat HSiCl 3 to generate a mixture of 10 and 11. The effects of the ancillary ligands on ruthenium and the nature of the hydrosilane on the rate and course of reaction are also discussed.

Preparation and X-ray Structure of Cp2Ti(Ph2SiH2)(PMe3)

Abstract : The synthesis and X-ray structure determination of the novel complex, Cp2Ti(Ph2SiH2)(PMe3), 4 is reported. The spectroscopic and structural data indicate that 4 is best described as being a hybrid between a titanium(IV) (silyl)hydride complex and a titanium(II) silane complex. Complex 4 reacts reversibly with N2 to form the bridging dinitrogen complex 5 and, in the presence of norbornene, 4 catalytically dimerizes Ph2SiH2 in quantitative yield. Silane complex, Titanium

Reaction of primary silanes with dinuclear rhodium hydride complexes: silane coupling reactions

The reaction of the dinuclear rhodium hydride dimer [(dippe)Rh] 2(μ-H) 2 (dippe=l,2-bis(diisopropylphosphino)ethane) with primary silanes is described. In the presence of two equivalents of RSiH 3 (R=Bu n and Tol P), dinuclear bis(μ-silylene) complexes of the formula [(dippe)Rh] 2(μ-SiHR) 2 result. Attempts to generate silylhydride complexes of the formula [(dippe)Rh] 2(μ-H)(μ-H-SiHR) by the addition of one equiv. of RSiH 3 failed. The bis(μ-silylene) complexes react with hydrogen to form adducts wherein two equivalents of H 2 per dimer unit have been activated; on the basis of NMR spectral studies these complexes are proposed to have the following formula: [(dippe)RhH] 2(μ-H-SiHR) 2. These molecules are extremely fluxional and lose H 2 rather readily. Addition of more than three equivalents of primary silane to 1 generated dinuclear rhodium derivatives with three silicon-containing ligands, having the formula [(dippe)Rh] 2(μ-SiHR)(μ-H-SiHR) 2. In the presence of excess primary silane, the dinuclear rhodium hydride 1 acts as a catalyst precursor for the dehydrogenative coupling of silanes. With the p-tolylsilane, dimerization does occur but the process is complicated by dispro- portionation reactions to generate (Tol P) 2SiH 2 and (Tol P) 3SiH; with butylsilane, SiSi chains with up to five silicons have been produced with no evidence of disproportionation. Crystals of [(dippe)Rh] 2(μ-SiHBu n) 2 ( 2a) are monoclinic, a=10.889(1), b=13.105(2), c=16.676(2) Å,β=104.06(1)°, Z=2, space group P2 1/n.; and those of [(dippe)Rh] 2(μ-η 2-H-SiHTol P) 2(μ-SiHTol P) ( 4b) are monoctinic, a=25.839(4), b=13.084(3), c=17.133(3) Å, β=107.10(1)°, Z=4, space group P21/ a. The structures were solved by Patterson ( 2a) and direct ( 4b) methods and were refined by full-matrix least-squares procedures to R=0.035 and 0.047 ( R w=0.030 and 0.060) for 3184 and 5997 reflections with 1⩾3η( I), respectively.

Silicon-hydrogen, silicon-silicon, and carbon-hydrogen bond activation by coordinatively unsaturated rhodium phosphine RhCl(PH3)2: ab initio molecular orbital study

SiH bond activation, oxidative addition of the SiH bond of SiH 4 to coordinatively unsaturated RhCl (PH 3 ) 2 , was theoretically investigated with an ab initio molecular orbital (MO) method, and its potential energy profile was compared with that for CH bond activation, oxidative addition of the CH bond of CH 4 . All the stationary point were determined at the MP2 level. While CH bond activation passes through an η 2 -CH 4 complex and a three-centered transition state, SiH bond activation is downhill and the η 2 -SiH 4 complex is a transition state for intramolecular rearrangement connecting two silyl hydride complexes, the product of SiH bond activation

Synthesis, characterization, and reactivity of zirconocene and hafnocene silyl hydride complexes

Synthesis, characterization, and reactivity of zirconocene and hafnocene silyl hydride complexes