Simple General Method of Generating Non-oxo, Non-amavadine Model Octacoordinated Vanadium(IV) Complexes of Some Tetradentate ONNO Chelating Ligands from Various Oxovanadium(IV/V) Compounds and Structural Characterization of One of Them

A simple general route of obtaining very stable octacoordinated non-oxovanadium(IV) complexes of the general formula VL₂ (where H₂L is a tetradentate ONNO donor) is presented. Six such complexes (1−6) are adequately characterized by elemental analysis, mass spectrometry, and various spectroscopic techniques. One of these compounds (1) has been structurally characterized. The molecule has crystallographic 4̄ symmetry and has a dodecahedral structure existing in a tetragonal space group P4̄n2. The non-oxo character and VL₂ stoichiometry for all of the complexes are established from analytical and mass spectrometric data. In addition, the non-oxo character is clearly indicated by the complete absence of the strong ν_VO band in the 925−1025 cm^-1 region, which is a signature of all oxovanadium species. The complexes are quite stable in open air in the solid state and in solution, a phenomenon rarely observed in non-oxovanadium(IV) or bare vanadium(IV) complexes.