Far-infrared spectroscopy of some halide complexes.

A survey of the published data on M-X bond vibrations (M = Pt, Pd; X = Cl, Br, I) highlighted several gaps in the information. A full assignment of the infrared spectra of anionic bridged complexes of platinum and palladium identified stretching modes in terminal and bridged positions and bending modes. These assignments provide the basis for an extended examination of substituted halogen-bridged complexes of Pt(II), Pd(Il) and Rh(l). The terminal and higher bridge (MX) have relatively constant frequencies, whilst the lower bridge mode varies with the nature of the ligand, L. In the first systematic study of Pt (IV) complexes, the infrared spectra of cis- and trans- [PtX4L2] are assigned. The number of (PtX) and (PtL) modes observed relate to the stereochemistry of the complexes and distinguish between cis- and trans- isomers. In [PtX4L2], (PtX) is ligand insensitive whereas for the cis- complexes, vibrations of the Pt-X bonds trans to L show a marked ligand dependence. From an extensive review of M-L bond vibrations (L = S, Se, Te, As, P, py, olefin) and the corresponding low-frequency ligand spectra, assignments of (ML) and (LML) are made for the platinum, palladium and rhodium complexes. Finally the first assignments of infrared- active metal-metal bond vibrations are recorded for transition metal-tin complexes.