Hypercoordinate Silacycloalkanes: Step-by-Step Tuning of N→Si Interactions

The silacycloalkanes (ON)2Si(CH2)n (ON = 8-oxyquinolinate, n = 3, 4, 5, 6) reveal stepwise decreasing N→Si coordination with increasing ring size. Whereas for n = 3 and 4 hexacoordinate silicon compounds were found at room temperature, n = 5 supports an equilibrium that allowed for the isolation of two coordination isomers (CN 4 and 6) as crystalline solids, and n = 6 causes the equilibrium to shift toward the tetracoordinate Si compound.