Force-constant calculations for Ni(PF 3) 4, Pd(PF 3) 4 and Pt(PF 3) 4

Abstract

Force constants for a SVFF approximation have been obtained for the compounds Ni(PF 3) 4, Pd(PF 3) 4 and Pt(PF 3) 4 using the FG matrix method and vibrational assignments ( A 1, E and F 2 symmetry species) on the basis of regular tetrahedral symmetry, point group T d . Six primary force constants involving bond stretching and bond angle changes and five interaction force constants were used to simultaneously fit the observed wavenumbers. The PF stretching force constant differs by only ± 3% for all three compounds and for the free ligand, PF 3. The metal—phosphorus stretching force constant, however, increases significantly in the order Ni < Pd < Pt, and is 65% larger for Pt(PF 3) 4 than for Ni(PF 3) 4. These changes are discussed in terms of the metal—phosphorus—fluorine bonding in M(PF 3) 4 compounds.