RELATIONSHIP BETWEEN OXO-BRIDGED DIMER FORMATION AND STRUCTURE OF VANADIUM(III) AMINO POLYCARBOXYLATES

The structures of vanadium(III) complexes with several amino polycarbo xylates in the solid state as well as in aqueous solution have been in vestigated using electronic and Raman spectrophotometry and H-1 NMR re laxation time. The amino polycarboxylates employed were dtpa (diethyle netriamine-N,N,N',N'',N''-pentaacetate), edta (ethylenediamine-N,N,N', N'-tetraacetate) cydta (1,2-cyclohexanediamine-N,N,N',N'-tetraacetate) , 1,3-pdta (1,3-propanediamine-N,N,N',N'-tetraacetate), S,S'-edds (S,S '-ethylenediamine-N,N-disuccinate), eddda ylenediamine-N,N'-diacetate- N,N'-di-3-propionate), tcta (1,4,7-triazacyclononane-1,4,7-triacetate) , eed3a (N-ethylethylenediamine-N,N',N',-triacetate), nta (nitrilotria cetate), and ida (iminodiacetate). The dtpa, tcta, and ida complexes, in addition to the edta, cydta, and nta complexes, the structures of w hich have been determined earlier, adopt heptacoordination in the soli d state. The S,S'-edds and eddda complexes adopt hexacoordination as f ound for the 1,3-pdta complex. In aqueous solution, the hexacoordinate complexes yield the ore-bridged dinuclear vanadium(III) complexes by hydrolysis, but the heptacoordinate ones do not. The vanadium(III) com plex with eed3a, Na-2[V(eed3a)(SO4)], is also found to adopt heptacoor dination in the solid state, but it changes to the hexacoordinate comp lex in aqueous solution by releasing the sulfate ion.