Force constant calculations for phosphorus(III) methyl, tetrakistrimethylphosphine-nickel(0) and -platinum(0), PMe3, Ni(PMe)3)4 and Pt(PMe3)4

Force constants for an SVFF approximation have been calculated for the molecules Ni[P(CH3)3]4, Pt[P(CH3)3]4 and P(CH3)3 using an FG matrix method and vibrational assignments with the assumption of methyl point masses. The observed wavenumbers of the M[P(CH3)3]4 species were fitted using six primary and eight interaction force constants. The vibrational assignments for the Ni[P(CH3)4]4 and Pt[P(CH3)3]4 species are confirmed by the force constant calculations. Comparisons are made with the force constants for the related molecules Ni(PF3)4, Pt(PF3)4 and Ni(PCl3)4. The metal—phosphorus stretching force constant in Pt(PF3)4 is 3.5 times larger than the corresponding value in Ni(PMe3)4. Changes in the force constants are discussed in terms of the metal—phosphorus—methyl bonding in the M[P(CH3)3]4 species.