Complexes of niobium(V) and tantalum(V) with phosphorus and arsenic ligands

Abstract

Complexation reactions between [M 2Cl 10] (M = Nb, Ta) and some phosphine, phosphite and arsine ligands have been investigated. Complexes [MCl 5L 2] {M = Nb, L 2 = (PMe 2Ph) 2, (P(OPh) 3) 2, (dmpe) 2 dppe and dpae; M = Ta, L 2 = (PMe 2Ph) 2, dmpe, dppe and dpae} have been isolated and characterised by analysis, IR and 1H NMR spectroscopy and, in three cases, by 31P NMR spectroscopy. Reactions of other phosphines (PMePh 2, PPh 3) and phosphites {P(OEt) 3, P(OPh) 3} with [M 2Cl 10] have also been studied. The nature of the phosphorus complexes appears to be sterically controlled and depends on the cone angles of the ligands. Products [M(C 6F 5) xCl 5-x] (x = 2–3, M = Nb, Ta) are formed by [M 2Cl 10] and pentafluorophenyllithium and these have been investigated by analysis, IR and 19F NMR spectroscopy. A ditertiary arsine adduct, [Nb(C 6F 5) 2Cl 3(dpae)], has also been isolated and characterised.