Infrared spectra (1200–200 cm.–1) of trimethylphosphine oxide and trimethylamine oxide metal complexes

Abstract

The infrared spectra have been recorded, in the region 1200–200 cm.^–1, for trimethylamine oxide and trimethylphosphine oxide complexes of the types (i) ML₂X₂, where X = Cl, Br, or l, and M = Co or Zn, and (ii) SnL₂X₄, where X = F, Cl, Br, or l. Assignments have been made for ν(N–O), ν(P–O), ν(M–O), and ν(M–X) stretching frequencies. These data are discussed in relation to the stereochemistry of the complexes and the relative bonding properties of the amine oxide and phosphine oxide and other oxo-ligands. The relatively high ν(M–O) values of 575–520 cm.^–1 which have been assigned for the amine oxide complexes indicate that this ligand is a stronger donor than both trimethylphosphine oxide [with ν(M–O) at 470–400 cm.^–1] and pyridine N-oxide [with ν(M–O) at 450–300 cm.^–1].