Base stabilization of functionalized silylene transition metal complexes

Article abstract of DOI:10.1021/om00004a019

The dehydrogenative coupling reaction of primary silanes ArSiH₃ [Ar = [2-(Me₂NCH₂)C₆H₄], [8-(Me₂NCH₂)C₁₀H₆], [8-(Me₂N)C₆H₄]] with Fe(CO)₅, Cr(CO)₆, CpCo(CO)₂, and RCpMn(CO)₃ (R = H, CH₃) under photolytic conditions affords an effective access to intramolecular base-stabilized functionalized silanediyl-transition metal complexes of general formula [ArHSi=MLn]. ²⁹Si-NMR investigations of the photochemical reaction of PhSiH₃ with Fe-(CO)₅ in the presence of 1,3-dimethyl-2-imidazolidinone (DMI) or hexamethylphosphoric triamide indicates a two-step mechanism for the formation of base-stabilized silanediyl-transition metal complexes. The carbonyl displacement reactions of the complex [2-(Me₂-NCH₂)C₆H₄]HSi=Cr(CO) ₅ in the presence of PPh₃ or P(OMe)₃ lead to the formation of trans-(PPh₃)₂Cr(CO)₄ or trans-[P(OMe₎3]₂Cr(CO)₄, respectively, either by photolysis or by thermolysis. Photochemical displacement reaction with (diphenylphosphino)ethane furnished [2-(Me₂-NCH₂)C₆H₄]HSi=Cr[Ph ₂P(CH₂)₂PPh₂](CO)₃ by subsequent displacement of two carbonyls of the metal moiety. Exchange reactions of the complex [2-(Me₂NCH₂)C₆H₄]HSi=Cr(CO) ₅ with Ph₃CX (X = Cl, BF₄, OSO₂CF₃) or CH₃COX′ (X′ = Cl, Br) provide a direct entry to a series of functionalized complexes [2-(Me₂NCH₂)C₆H₄]XSi=Cr(CO) ₅. The liberated silylenes from complexes ArHSi(B)=Fe(CO)₄ (Ar = Ph, 1-Np) (B = DMI) can be trapped in the presence of tert-butyl alcohol or methanol to give di-tert-butoxysilanes or trimethoxysilanes, respectively.