η³-silaallyl/alkenylsilyl molybdenum complex: Synthesis, structure, and reactivity toward primary amines to form Mo-N-Si three-membered cyclic complexes

The new η³-silaallyl/alkenylsilyl molybdenum complex Cp∗Mo(CO)₂(η³-Ph₂SiCHCMe₂) (3) was synthesized by the reaction of Cp∗Mo(CO)₂(py)Me with Ph₂HSiCH-CMe₂. Reactions of 3 with primary amines RNH₂ (R = ^tBu, ⁱPr, Et) gave Mo-N-Si three-membered cyclic complexes Cp∗Mo(CO)₂(η²-N,Si-RHNSiPh₂) (5a, R = ^tBu; 5b, R = ⁱPr; 5c, R = Et) with elimination of isobutene. In NMR tube reactions using ⁱPrNH₂ and EtNH₂, the Mo-N-Si-C four-membered cyclic complexes Cp∗Mo(CO)₂(η²-N,C-RHNSiPh₂CHⁱPr) (4b, R = ⁱPr; 4c, R = Et) were observed as intermediates leading to 5b and 5c, respectively. Complex 4c was successfully isolated in a preparative reaction. The molecular structures of 3, 4c, and 5b were determined by X-ray crystal analyses. Interestingly, the contribution of silylene character was suggested for the SiPh₂ moiety of 5b from the X-ray structure. The reaction of 5b with MeOH gave the dinuclear complex Cp∗(CO)₂Mo(η-OMe)(η -H)Mo(CO)₂Cp∗ as a major product.