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) (<b>3</b>) was synthesized by the reaction of Cp*Mo­(CO)₂(py)­Me with Ph₂HSiCHCMe₂. Reactions of <b>3</b> with primary amines RNH₂ (R = ^<i>t</i>Bu, ^<i>i</i>Pr, Et) gave Mo–N–Si three-membered cyclic complexes Cp*Mo­(CO)₂(κ²-<i>N</i>,<i>Si</i>-RHNSiPh₂) (<b>5a</b>, R = ^<i>t</i>Bu; <b>5b</b>, R = ^<i>i</i>Pr; <b>5c</b>, R = Et) with elimination of isobutene. In NMR tube reactions using ^<i>i</i>PrNH₂ and EtNH₂, the Mo–N–Si–C four-membered cyclic complexes Cp*Mo­(CO)₂(κ²-<i>N</i>,<i>C</i>-RHNSiPh₂CH^<i>i</i>Pr) (<b>4b</b>, R = ^<i>i</i>Pr; <b>4c</b>, R = Et) were observed as intermediates leading to <b>5b</b> and <b>5c</b>, respectively. Complex <b>4c</b> was successfully isolated in a preparative reaction. The molecular structures of <b>3</b>, <b>4c</b>, and <b>5b</b> were determined by X-ray crystal analyses. Interestingly, the contribution of silylene character was suggested for the SiPh₂ moiety of <b>5b</b> from the X-ray structure. The reaction of <b>5b</b> with MeOH gave the dinuclear complex Cp*­(CO)₂Mo­(μ-OMe)­(μ-H)­Mo­(CO)₂Cp* as a major product