Niobium-93 nuclear magnetic resonance studies of the solvolysis of NbCl5 by alcohols

Abstract

Niobium-93 and ¹H NMR spectroscopy have been used to identify the substitution products NbCl_5–x-(OMe)_x formed by the stepwise substitution of NbCl₅ by MeOH in non-co-ordinating solvents. This reveals evidence for all of the possible substitution products, NbCl_5–x(OMe)_x′ whilst phase equilibria favour the formation of [NbCl₄(OMe)]₂ and [NbCl₂(OMe)₃]₂ dimer species over [NbCl₃(OMe)₂]₂ in mixed MeOH–aromatic solvents. In co-ordinating solvents such as acetonitrile ⁹³Nb NMR spectroscopy distinguishes between the unco-ordinated dimeric [NbCl_5–x(OMe)_x]₂ species and the monomeric adduct species NbCl_5–x(OMe)_x·MeCN. Monitoring of NbCl₅ solvolysis in ROH (R = Me, Et or Prⁱ) by ⁹³Nb NMR spectroscopy thus identifies all NbCl_5–x(OR)_x species present and reveals that the solution composition is both concentration and temperature dependent.