Dihydride silyl complexes Cp*(CO)2W(H)2(SiHPhR) (R = Ph, 7; H, 8) were synthesized by treating the donor-stabilized silylene complexes cis-Cp*(CO)2(H)W=SiRPh·Do (R = Ph, H; Do = Py, THF) with LiAlH4, to give Li[Cp*(CO)2W(H)(SiHPhR)] (R = Ph, 5; H, 6) followed by protonation using CF3-COOH. X-ray analyses of the crystals of 7 and 8 revealed that the former adopts a distorted pseudooctahedral structure (7a), while the latter possesses a pseudo-trigonal-prismatic structure (8b). In solution, both complexes exist as equilibrium mixtures of these two structural isomers: the distorted pseudooctahedral isomer (7a/8a) and the pseudo-trigonal-prismatic isomer (7b/8b). In addition to this interconversion process, two dynamic processes involving site exchanges of hydride and silyl ligands in the pseudo-trigonal-prismatic isomer were shown for 8b by detailed NMR studies. The addition of HCl to cis-Cp*(CO)2(H)W=SiHPh·THF afforded Cp*(CO)2W(H)2(SiHPhCl) (9), which also gave an equilibrium mixture of the distorted pseudo-octahedral isomer (9a) and the pseudo-trigonal-prismatic isomer (9b). The presence of an additional dynamic process, hydride site exchange in the distorted pseudooctahedral isomer, was revealed for 9a due to its chiral silicon center.
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