Six-coordinate NbF5 and TaF5 complexes with tertiary mono-phosphine and -arsine ligands

The syntheses of the extremely moisture sensitive, neutral [MF5(PR3)] (M = Nb or Ta, R = Me or Ph) and [MF5(AsR3')] (R' = Me or Et), from reaction of the ligands with MF5 in anhydrous diethyl ether solution are reported. Attempts to isolate analogous complexes with SbMe3 were unsuccessful. The products are characterised by IR and mutinuclear NMR (H-1, F-19{H-1), P-31{H-1} and Nb-93) spectroscopic studies. These are the first examples of six-coordinate phosphine or arsine complexes of the Group 5 pentafluorides. The ionic species, trans-[MF4(PMe3)(2)][MF6], are obtained from diethyl ether solution of [MF5(PMe3)] containing excess PMe3 and similarly characterised. All complexes are extremely moisture and oxygen sensitive and decomposed by many common solvents. In solution in toluene the [MF5(PMe3)] (M = Nb or Ta) and [MF5(AsR3')] are extensively dissociated at ambient temperatures. The [MF5(PPh3)] dissolve in CH2Cl2 with decomposition to form [PPh3H][MF6]. Attempts to isolate phosphine complexes of NbOF3 were unsuccessful. (C) 2015 The Authors. Published by Elsevier B.V.