Electrostatically Driven Complexes of SiF4 With Amines

摘要

Some SiF4-polyamine complexes that have recently been prepared are investigated computationally and compared to their counterparts involving NH3. The formation of these systems can be explained satisfactorily in terms of electrostatic interactions between positive sigma-holes on the silicon, on the extensions of the F-Si bonds, and the lone pairs of the amino nitrogens. The displacement of an F- ion en route to complexes with three amino groups can be understood as a means of avoiding an excessive and destabilizing accumulation of negative charge in the central portion of the system. Very good overall agreement is found between crystallographic and the corresponding computed structural data. The sigma-hole interpretationa is fully compatible with initial sp(3) -> d(2)sp(3) rehybridization of the silicon, but it is not necessary to invoke the latter.