Ab initio calculations of Cl2SO center dot nAlCl(3) complexes (n=1,2)

Fragments of the potential energy surfaces (PES) for the SOCl2 . nAlCl(3) (n = 1, 2) complexes were calculated by the ab initio MO LCAO method using the RHF approximation for the STO-3G basis set adding a 3d-AO for the S atom, as well as the semiempirical MNDO method. Two local minima, assigned to the donor-acceptor complex Cl2SO-->AlCl3 (1a) and to Cl3SOAlCl2 (1b) were located on the PES at n = 1. Two local minima corresponding to two donor-acceptor complexes Cl2SO-->Al2Cl(6) and [GRAPHICS] were also located on the PES at n = 2. An analysis of the enthalpies of cation formation in the SOCl2 + nAlCl(3) (n = 1-3) systems calculated by the ab initio method shows that the enthalpy of formation of the SOCl+ cation at n = 2 is 17 kcal mol(-1) less than that at n = 1; the structure of the Cl2SOAlCl2+ cation with two strong electrophilic centers at the Al and S atoms becomes more favorable energetically at n = 3. The results of calculations for Cl2SO.nAlCl(3) complexes by the MNDO method are in agreement with those obtained by the ab initio method except for the geometry of complexes containing the Cl3SO fragment and the charge values on the S atoms.