Novel binuclear vanadium( V )–Schiff base cations containing single fluorine bridges and the structure of difluorodioxovanadate(1–)

The complex [VO (salen)][H2salen =N,N′-ethylenebis(salicylideneimine)] reacted with HBF4·Et2O in air to produce the novel linear species [{VO (salen)}2(µ-F)]+, the structure of which has been determined as its BF4– and [VO2F2]– salts. The perchlorate and triflate (O3SCF3)– salts have been characterised spectroscopically and analytically, as well as the tetrafluoroborate homologues from salicylaldehyde and 2-methylpropylenediamine, and from ethylenediamine and 3-methoxysalicylaldehyde. The [VO2F2]– is mononuclear in the above salt, as well as in [PPh4][VO2F2], compared to a polynuclear form found in [NH4][VO2F2]. The mononuclear anion was also fully characterised by 19F and 51V NMR spectroscopy.