Synthesis, chemistry and structures of complexes of the dioxovanadium(v) halides VO2F and VO2Cl

Abstract

[VO₂F(L–L)] (L–L = 2,2′-bipyridyl, 1,10-phenanthroline, Me₂N(CH₂)₂NMe₂) and [VO₂F(py)₂] (py = pyridine) have been prepared from the corresponding [VOF₃(L–L)] or [VOF₃(py)₂] and O(SiMe₃)₂ in MeCN solution. VO₂F (itself made from VOF₃ and O(SiMe₃)₂ in MeCN) forms [Me₄N][VO₂F₂] with [Me₄N]F, but does not react with neutral N- or O-donor ligands. VO₂Cl, prepared from VOCl₃ and ozone, reacts with 2,2′-bipyridyl or 1,10-phenanthroline to form [VO₂Cl(L–L)], with pyridine or pyridine-N-oxide (L) to produce [VO₂Cl(L)₂], and with OPPh₃ or OAsPh₃ (L′) gives [VO₂Cl(L′)]. A second product from the OPPh₃ system is the ionic [VO₂(OPPh₃)₃][VO₂Cl₂] containing a trigonal bipyramidal cation. Neither VO₂F nor VO₂Cl form isolable complexes with MeCN, thf or MeO(CH₂)₂OMe, and both are reduced by P-, As-, S- or Se-donor ligands. [Ph₄As][VO₂X₂] (X = F or Cl) react with 2,2′-bipyridyl to form [VO₂X(2,2′-bipyridyl)], but similar reactions with weaker O-donor ligands fail. The complexes have been characterised by IR, multinuclear NMR (¹H, ¹⁹F, ⁵¹V or ³¹P) and UV-visible spectroscopy. X-ray crystal structures are reported for [VO₂F(py)₂], [VO₂Cl(L)₂] (L = py or pyNO) and [VO₂(OPPh₃)₃][VO₂Cl₂].