Efficient Synthesis of a NHC-Coordinated Trisilacyclopropylidene and Its Coordination Behavior.

With a co-reduction procedure using 2 equivalents Mes2 SiCl2 and 1 equivalent NHCiPr2Me2 →SiCl4 an NHC-adduct of a trisilacyclopropylidene (SiMes2 )2 SiNHCiPr2Me2 1 was synthesized. Addition of NHCMe4 to 1 results in quantitative carbene exchange under release of NHCiPr2Me2 to yield (SiMes2 )2 SiNHCMe4 2. Both NHC-coordinated trisilacyclopropylidenes coordinate to BH3 . In reaction of 1 with SiMe3 N3 a NHC-coordinated trisilane with an exocyclic Si=N double bond is formed. With diphenylacetylene 1 undergoes a ring expansion at room temperature to afford a five-membered ring compound with an NHC-coordinated silylene functionality.