Co-ordination complexes of niobium and tantalum. Part XV. Sulphoxide complexes of oxobis(oxalato)niobates(V)

Abstract

The preparation and properties of crystalline colourless complexes of the composition M^I[NbO(C₂O₄)₂(dmso)₂](M = NH₄, K, Rb, or Cs; dmso = dimethyl sulphoxide), and M^I[NbO(C₂O₄)₂(tmso)₂](M = NH₄, K, Rb; tmso = tetramethylene sulphoxide) are described. The complexes were prepared by dissolving the corresponding M^I salts of oxobis(oxalato)aquoniobates in dmso and tmso, respectively. Stability trends and i.r. spectra of these oxobis-(oxalato) bis(sulphoxide)niobate(V) series of complexes are discussed. According to chemical and i.r. evidence the complexes contain two oxygen-bonded sulphoxide ligands and the presence of seven-co-ordinate niobium(V) in these complexes is assumed.