Dioxidovanadium(V) complexes with pyridoxalaminoguanidine: Synthesis, spectral and structural characterization

Three square-pyramidal complexes of dioxidovanadium(V) with pyridoxalaminoguanidine (PLAG), of the formulas NH4[VO2(PLAG−2H)]∙H2O (1), VO2(PLAG−H) (2) and K[VO2(PLAG−2H)]∙H2O (3) have been synthesized and characterized by IR and UV-Vis spectral analysis 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 phenoxide oxygen atom and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In all previously characterized complexes PLAG was coordinated in neutral form. However, here we have proven that this ligand can be coordinated in both mono- (2) and doubly deprotonated form (1 and 3) as well. [Projekat Ministarstva nauke Republike Srbije, br. 172014]

Transition metal complexes with thiosemicarbazide-based ligands. Part 58. Synthesis, spectral and structural characterization of dioxovanadium(V) complexes with salicylaldehyde thiosemicarbazone

The first two complexes of dioxovanadium(V) with salicylaldehyde thiosemicarbazone (SALTSC), of the coordination formulas [VO2(SALTSC––H)]∙H2O (1) and NH4[VO2(SALTSC–2H] (2), were synthesized and characterized by elemental analysis, conductometric measurements, IR and UV–Vis spectroscopy and X-ray analysis. The complexes were obtained in the reaction of an aqueous ammoniacal solution of NH4VO3 and SALTSC. The results of the characterization showed that SALTSC was coordinated in the usual ONS tridentate mode as monoanion in complex 1 and dianion in complex 2. In both complexes, the vanadium atom is in a deformed square-pyramidal environment and is slightly shifted towards the apical oxo-ligand (» 0.52 Å)