Si-H and Si-C Bond Activation of a Triorganosilane Promoted by [RhCl{P(i-Pr)3}2]. Synthesis and Structure of a Dinuclear Rh(IV) Complex with μ-Silylene Ligands

Article abstract of DOI:10.1246/bcsj.70.189

[RhCIL₂] (L = P(i-Pr)₃) reacts with tris(2-phenylethyl)silane in pentane to give a dinuclear Rh(IV) complex, [LRh-(H)₂{μ-Si(CH₂CH₂Ph)₂} ₂Rh(H)₂L] (1), and several organic products including ethylbenzene, chloro{tris(2-phenylethyl)}silane, and tetrakis(2-phenylethyl)silane. Results of X-ray crystallography and NMR study of 1 indicate a symmetrical molecular structure containing two Rh(IV) centers which are bonded to each other through two bridging silylene ligands. [1, triclinic, space group P1 with a = 12.886(4), b = 13.217(3), c = 10.388(3) A, α = 104.78(2), β = 106.50(2), γ = 61.70(2)°, V = 1478 A³, Z = 1, R = 0.073. R_w = 0.081 for 3930 reflections with I > 3σ(I) and 289 variables]. The initial reaction products contain mononuclear Rh(III) complexes, [RhCl(H)₂L₂] (2) and [RhCl(H) {Si(CH₂CH₂Ph)₃}L₂] (3), the latter of which is turned into 1 on further stirring. Reactions of tribenzylsilane and of tris(p-methylbenzyl)silane with [RhClL₂] cause immediate separation of [RhL(R₃Si)H(μ-Cl)₂RhH(SiR₃)L] (4: R = CH₂Ph, 5: R = CH₂C₆H₄Me-p). X-Ray crystallography of 4 has revealed the structure containing two Rh(III) centers with distorted trigonal bipyramidal coordination [4, monoclinic, space group P2₂/n with a = 11.513(3), b = 28.227(9), c = 20.883(5) A, β = 94.14(2)°, V = 6769 A³, Z = 4, R = 0.071, R_w = 0.066 for 4249 reflections with I > 3σ(I) and 637 variables]. A prolonged reaction of tribenzylsilane leads to formation of chlorotribenzylsilane.