Vibrational spectra of halogen-bridged systems. Part III. The infrared spectra (450—80 cm.–1) of binuclear palladium, platinum (M2X4L2), and rhodium (Rh2X2L4) complexes

Abstract

Infrared absorption frequencies (450–80 cm.^–1) are given for 46 palladium and platinum compounds of the type M₂X₄L₂(X = Cl, Br, l; L = neutral donor ligand), and for some halogen-bridged rhodium compounds, Rh₂X₂L₄. The predicted number of absorptions due to terminal and bridge bond stretching vibrations has been found, and their ranges are suggested for use as correlations. The lower of the two bridge modes for the platinum and palladium complexes is markedly sensitive to change of L, varying in a similar order (that of the trans-effect of L) to that previously found for mononuclear complexes cis-[PtX₂L₂]. A clear distinction can be made, on the basis of halogen-sensitive bands, between halogen-bridged and sulphide-bridged complexes M₂X₄(SR₂)₂. Assignments for ν(M—L)(L = S, P, As, Te) are discussed. For the rhodium complexes, the number of bands found in the ν(Rh—X)_b region allows distinction to be made between planar and bent bridges.