SYNTHESIS, STRUCTURE AND METAL REDOX OF ALKOXIDE BOUND OXOVANADIUM(V)COMPLEXES INCORPORATING N-SALICYLIDENE N-NAPHTHALIDENE-ALPHA-AMINOALCOHOLS/

In the title families the ONO ligands are deprotonated forms of N-(1-h ydroxyethyl) salicylaldimine(H2L1), N-(1-hydroxy-2-methylpropyl)salicy laldimine (H2L2), N-(1-hydroxyethyl)naphthaldimine(H2L3), N-(1-hydroxy -2-methylpropyl)naphthaldimine(H2L4). The ON ligand is deprotonated 8- quinolinol(Hhq). The complexes VO(L)(hq) (L=L-1-L-4) have been synthes ized in excellent yields from {VO(L)}(x) and 8-quinolinol in methanol (oxidant is aerial oxygen). The crystal structure of VO(L-2)(hq) has r evealed tridentate ONO and bidentate ON binding by [L-2](2-) and hq(-) , respectively. The V--O(phenolate) bond length is longer than V--O(al koxidic) by similar to 0.09 Angstrom. In CDCl3 solution the H-1 NMR sp ectrum of the VOL2(hq) shows that the binding nature in solid state is also retained in solution. The complexes display the quasi-reversible one-electron couple VO(L)(hq)-VO(L)(hq)(-) near -0.43 V vs saturated calomel electrode. This lowering of potentials indicate considerable V O3+ stabilization due to alkoxide binding. Electrogenerated solution o f VO(L)(hq)(-) are EPR-active corresponding to a d(xy)(1) configuratio n. (C) 1997 Elsevier Science Ltd.