An Air‐Stable Heterobimetallic Si 2 M 2 Tetrahedral Cluster

Air‐ and moisture‐stable heterobimetallic tetrahedral clusters [Cp(CO) 2 MSiR] 2 (M=Mo or W; R=Si t Bu 3 ) were isolated from the reaction of N‐heterocyclic carbene (NHC) stabilized silyl(silylidene) metal complexes Cp(CO) 2 M=Si(Si t Bu 3 )NHC with a mild Lewis acid (BPh 3 ). Alternatively, treatment of the NHC‐stabilized silylidene complex Cp(CO) 2 W=Si(Si t Bu 3 )NHC with stronger Lewis acids such as AlCl 3 or B(C 6 F 5 ) 3 resulted in the reversible coordination of the Lewis acid to one of the carbonyl ligands. Computational investigations revealed that the dimerization of the intermediate metal silylidyne (M≡Si) complex to a tetrahedral cluster instead of a planar four‐membered ring is due to steric bulk.