Molecular vibrations of complex with trigonal ligands

A normal coordinate analysis was performed for the compound [Pt(NH3)4]2+ which has a square planar framework structure (PtN4 with local symmetry D4h) and tetrahedral NH3 groups (local symmetry C3v). C4h over-all structure was assumed (two opposite animine groups are considered to be in staggered position). Two general valence force fields which reproduce satisfactorily the observed frequencies for the whole complex as well as the H/D isotopic derivative have been developped. These calculations for the whole complex (C4h) are compared with the point mass model approximation (PtN'4, D4h with mN', = mNH3 ), the validity of which is confirmed. Finally the refined force field for [Pt(NH3)4]2+ was used to calculate the frequencies of various isotopes (14N/15N, H/D) and the mean amplitudes at absolute zero and 298 °K of the mother molecule