Quaternization of the bridgehead nitrogen in silatranylosmium(II) complexes and reestablishment of the transannular N-Si bond following migratory insertion of the silatranyl ligand

The Si-N distance in the five-coordinate silatranyl complex Os(Si{OCH2CH2}(3)N)Cl(CQ)(PPh3)(2) (1a, Q = O) is very long, and the geometry about nitrogen is planar. Accordingly, the nitrogen atom readily undergoes methylation, or protonation, and this increases the Si-N separation even further. On addition of CO to 1b (O = S), the coordinated CS inserts into the Os-Si bond and the normal silatrane N-Si interaction is restored in, the product, Os(eta(2)-C{S}Si{OCH2CH2}(3)N)Cl(CO)(PPh3)(2) (4).