η³-silapropargyl/alkynylsilyl molybdenum complexes: Synthesis, structure, and reactivity toward methanol

(Chemical Equation Presented) Novel η³-silapropargyl/ alkynylsilyl complexes Cp*(CO)₂Mo(η³-Ph ₂SiCCR) (3a, R = ^tBu; 3b, R = ⁱPr) were synthesized by the reactions of Cp*(CO)₂(MeCN)MoMe (1) with alkynylsilanes HPh₂SiC≡CR. The structures of 3a and 3b were fully characterized by NMR spectroscopy and X-ray crystallography. The reaction of 3a with MeOH at room temperature gave the stable four-membered metallacycle Cp*(CO)₂MoC(=CH^tBu)SiPh₂OMe (5a), while the corresponding reaction of 3b led to the formation of the η³-allyl complex Cp*(CO)₂Mo{η³- (MeOPh₂Si) HCCHCMe₂} (7) via Cp*(CO) ₂MoC(=CHiPr)SiPh₂OMe (5b).