Dioxidovanadium(V) complexes with pyridoxal aminoguanidine derivative: synthesis and spectral and structural characterization.

Three square-pyramidal complexes of dioxidovanadium(V) with {[(3-hydroxy-5-(hydroxymethyl)-2-methyl-4-pyridyl)methylene]amino}guanidine (PLAG), of the formulas NH4[VO2(PLAG-2H)]·H2O (1), VO2 (PLAG-H) (2) and K[VO2 (PLAG-2H)]·H2O (3) were synthesized and characterized by IR and electronic spectra, and in case of 1 and 3 by X-ray crystallography as well. The reaction of aqueous ammoniacal solution of NH4VO3 and PLAG resulted in formation of 1, which in MeOH undergoes spontaneous transformation into 2, which, in turn, in the reaction with KOH transforms into 3. In these complexes, PLAG is coordinated in a common tridentate ONN mode, via the phenoxide oxygen atom and the nitrogen atoms of the azomethine and imino groups of the aminoguanidine fragment. In all previously characterized complexes, PLAG was coordinated in the neutral form. However, here it was proven that this ligand could be coordinated in both mono- (2) and doubly-deprotonated forms (1 and 3) as well. [ABSTRACT FROM AUTHOR]