Co-ordination complexes of niobium and tantalum. Part VIII. Complexes of niobium(IV), niobium(V), and tantalum(V) with mixed oxo, halogeno, alkoxy, and 2,2′-bipyridyl ligands

Abstract

Reaction of 2,2′-bipyridyl (bipy) under various conditions with NbX₅(X = F, Cl, or Br), TaX₅(X = Cl or Br), and niobium oxide trichloride gives different types of mixed ligand complexes. Solutions of metal pentahalides and niobium oxide trichloride in benzene under anhydrous conditions gave crystalline compounds of general formula MX₅(bipy) and NbOCl₃(bipy). Solutions of metal pentachlorides in ether under anhydrous conditions gave crystalline complexes of formula Nb₂OCl₈(bipy)₂ and Ta₄OCl₁₈(bipy)₄. Solutions of niobium pentachloride in alcohols, containing a small, controlled amount of water gave stable crystalline compounds of formula NbOCl₂(OR)(bipy). Electrolytically reduced solutions of niobium pentachloride and bipyridyl in alcohol gave crystalline paramagnetic complexes of formula Nb₂Cl₅(OR)₃(bipy)₂. The compounds were characterized by analysis, X-ray powder photographs, i.r. spectra, and magnetic susceptibility measurements.