Phosphane lone-pair energies as a measure of ligand donor strengths and relation to activation energies

Using density-functional theory as implemented in the projector-augmented w ave method, we have calculated structures, energy levels, structures of the protonated forms, and proton affinities of the phosphanes PH3, PF3, P(CF3) (3), PMe3, P(NMe2)(3), P(C6H5)(3), P(p-C6H4OMe)(3), and P(P-C6H4NMe2)(3) Th e donor strengths of the phosphanes are discussed in terms of lone-pair ene rgies and proton affinities. The influence of the donor ability of the phos phane ligands on the protonolytic cleavage of the metal-carbon bond in [NiC l(CH2CH2NH3)(PR3)(2)](+) complexes has been studied. A linear relationship between the lone-pair energies of the phosphanes and the activation barrier has been established. (C) 2000 Elsevier Science B.V. All rights reserved.