Octahedral HSiCl₃ and HSiCl₂Me Adducts with Pyridines

Stable solid adducts of substituted pyridines (Rpy) with HSiCl3 and HSiCl2Me were prepared in high yields under aprotic and anaerobic conditions at room temperature. The octahedral complexes of HSiCl3 underwent dismutation reactions in polar solvents. In contrast, the HSiCl2Me(Rpy)2 adducts were not susceptible to dismutation under comparable conditions, but they tended to dissociate more easily because of the reduced Lewis acidity of HSiCl2Me relative to HSiCl3. The bonding between silicon and its surrounding ligands is highly ionic, as can be seen from QTAIM and charge distribution analyses. 29Si CP/MAS spectra in combination with quantum-chemical calculations show that the lowest shielding is along the Cl−Si−Cl axis. The other two components of the shielding tensor are oriented along the N−Si−N and H−Si−Cl/Me axes. It is known that many reactions of (hydrido)chlorosilanes are catalyzed by pyridine bases. Therefore, the results presented here provide a basis for better control of these reactions, especially chlorine substitution and hydrosilylation.