35Cl NQR spectra of phosphorus chlorides and their molecular conformations in crystals.: Part 2.: Steric effects in ArPCl2 and RPCl2 molecules

The MNDO, HF and MP2 calculations showed that in the molecules of both types, RPCl2 (R = CH3, ClCH2, CF3, CCl3) and ArPCl2 increasing of steric interactions between R and kr radicals and chlorine atoms of the PCl2 group leads to enhancement of s-character of LP2 orbital of the chlorine atoms. In the series RPCl2, in contradistinction to the series ArPCl2, increasing of steric interactions leads to decreasing of percentage of s-character of LP3 hybrid orbital of the chlorine atoms and increasing of LP3 donor-acceptor interactions with antibonding orbital of the P-C bond. The difference in coefficients of linear dependencies between Cl-35 NQR frequencies of the chlorine atoms Of PCl2 group and atomic charges on these atoms in the series RPCl2 and ArPCl2 are explained by the above mentioned distinctions. Cl-35 NQR spectrum at 77 K of CCl3PCl2 have been obtained: v(C-Cl) = 38.853(2), 39.469(1) MHz, v(P-Cl) = 27.306 MHz. (C) 2001 Elsevier Science B.V. All rights reserved.