On the bonding, structure and thermodynamics of phosphorus halide boron halide complexes X3P·BY3 (X, Y=Cl, Br, I)

Abstract

Donor–acceptor complexes X3P·BY3 (X, Y=Cl, Br, I) and their fragments have been studied using density functional (B3LYP) and ab initio methods (MP2, CCSD(T)) with effective core potentials. The bonding, charge transfer and structure of all X3P·BY3 is discussed on the basis of natural bond orbital (NBO) analysis. The estimated free molecular enthalpies of dissociation indicate that all X3P·BY3 represent thermodynamically labile species which are stabilized by the lattice energies in the solid state. The total distortion energy increases in accordance with the decreasing complex dissociation enthalpy. With regard to halogen exchange between the PX3 and BY3 moiety in X3P·BY3 (g) adducts, only the complexes where Y=X and where X represents a heavier halogen than Y are thermodynamically stable.