OXYGEN ABSTRACTION REACTIONS OF N-SUBSTITUTED HYDROXAMIC ACIDS WITH MOLYBDENUM(V) AND VANADIUM(III) AND VANADIUM(IV) COMPOUNDS

A wide range of N-substituted mono- and dihydroxamic acids undergo oxy gen abstraction on reaction with V(III), V(IV), and Mo(V) compounds to form hydroxamates of V(V) and Mo(VI) respectively together with the c orresponding amides and diamides. The molybdenyl and vanadyl hydroxama tes form metal-oxygen clusters under FABMS conditions. The X-ray cryst al structures of [MoO2{CH3(CH2)(n)C(O)N(C6H5)O}(2) (1 and 2) (n = 4, 5 ) show monomeric structures with structural trans effects and conseque nt weakening of the Mo-O(ligand) bonds which may account for the tende ncy to form clusters in FABMS. In constrast, the electrospray MS of th e vanadyl dihydroxamates, VO(OH)[PhN(O)C(O)(CH2)(n)C(O)N(O)Ph] (n = 3, 5) and VO(OH)[p-CH3C6C4N(O)C(O) (CH2)(n)C(O)N(O)C6H4-CH3) (n = 2, 4) show the presence of dimers in solution.