Four‐, Five‐, and Six‐Coordinate Silicon(IV) Complexes: Reactivity of the Donor‐Stabilized Silylenes [iPrNC(Ph)NiPr]2Si and [iPrNC(NiPr2)NiPr]2Si Towards Me3SiN3 and PhSCH2N3

Bis(amidinato)silylene 1 and the analogous bis(guanidinato)silylene 2 reacted with Me3SiN3 to form compounds 3 [a five-coordinate silicon(IV) complex with an Si=N double bond] and 4 [a four-coordinate silicon(IV) complex with an Si=N double bond], respectively. For compound 3, a dynamic equilibrium between a five- and four-coordinate silicon(IV) species in solution was observed (at –95 °C, these species are stable on the NMR spectroscopic timescale), whereas 4 is four-coordinate in solution. Treatment of 1 with PhSCH2N3 afforded compound 5 (isolated as 5a·5b·0.5n-C6H14), which is a cocrystallizate of the diastereomers 5a and 5b with half an n-hexane molecule in the asymmetric unit. The diastereomers 5a and 5b [six-coordinate silicon(IV) complexes with an unsubstituted methyleneamido ligand and an SiN5S skeleton] differ only in their interchanged positions of their thiophenolato and methyleneamido ligands. In solution, a dynamic equilibrium between 5a and 5b was observed.