Complexes of vanadium(IV) oxide difluoride with neutral N- and O-donor ligands

Abstract

A convenient new synthesis for complexes of VOF2 with N-donor ligands is via the reaction of VF4 with the ligand in water, either under reflux or using hydrothermal conditions. The complexes, mer-[VOF2(terpy)]·3H2O (terpy=2,2′6′,2‴-terpyridyl), [VOF2(bipy)(H2O)], [VOF2(phen)(H2O)], [VOF2(py)2(H2O)], [VOF2(py)2(H2O)]·H2O, [V2O2F4(py)4] and [pyH]2[V2O2F6(H2O)2], along with the O-donor, pyridine N-oxide (pyNO) complex, [V2O2F4(H2O)2(pyNO)2], have been isolated and characterised. The controlled hydrolysis of VF4 in water produces the hydrate [VOF2(H2O)2]·H2O. The complex [VOF2(Me3tacn)] (Me3tacn=1,4,7-trimethyl-1,4,7-triazacyclononane) was prepared by the reaction of [VOF2(py)2(H2O)] and Me3tacn in MeCN. The new complexes have been characterised by microanalysis and single crystal X-ray diffraction. Powder X-ray diffraction (PXRD) data were recorded for the bulk samples and compared with the PXRD patterns simulated from the single crystal data to confirm that the latter were representative of the bulk products. All the complexes contain six-coordinate vanadium(IV), with extensive H-bonding and (in the pyridyl ligand complexes) π-stacking interactions present. IR and UV–visible spectroscopic data and magnetic measurements are also reported and discussed. Attempts to obtain phosphine oxide or ether complexes by similar routes were unsuccessful. Unless the temperature is carefully controlled, the hydrothermal route yields mixtures of VIV and VV complexes.