Ab Initio Calculations of Complexes of Tetrachlorides of Group IVA Elements: VIII.1 Structure of SiCl4 Complexes with Hexamethylphosphoric Triamide and Dynamics of Their Formation

摘要

Quantum-chemical calculations of the systems SiCl4<-OP[N(CH3)2]3 and SiCl4<-20P[N(CH3)2]3 with complete optimization of their geometry at various SH-0 distances were performed by the RHF/6-31G(d) method.The first system was also calculated by the MP2/6-31G(d) method.The calculations of the systems with the complete geometry optimization resulted in trigonal-bipyramidal and trans-octahedral structures,respectively,having energy minima.When the components of the latter system approach each other,first their mutual polarization occurs,and then it is accompanied by electron density transfer from the H and P atoms of the electron-donor molecules to the Cl atoms of the acceptor.The results of the calculation of the trans-octahedral complex agree with the experimental ~(35)Cl NQR data.The electron density of Cl atoms increases upon complex formation,mainly due to an increase in their p_(sigma) electron density.