RESUMO
A novel C3-symmetric propeller-shaped vanadium(IV/V) oxide cluster complex, [V8O19(4,4'- tBubpy)3] (V8'), has been synthesized from the reaction of the windmill-shaped vanadium(V) oxide cluster complex [V8O20(4,4'- tBubpy)4] (V8) with PPh3 under N2, whereas refluxing V8 in methanol or ethanol under N2 provides tetranuclear oxido(alkoxido)vanadium(IV/V) complexes [V4O6(OR)6(4,4'- tBubpy)2] [R = Me (V4'-Me) and Et (V4'-Et)]. The mixed-valent vanadium(IV/V) clusters V8' and V4' are converted back to V8 under O2. Interconversions of V4' and the oxido(alkoxido)vanadium(V) complexes [V4O8(OMe)4(4,4'- tBubpy)2] (V4) and [V7O17(OEt)(4,4'- tBubpy)3] (V7-Et) are also presented.
RESUMO
The octanuclear oxidovanadium(V) complex [V8O20(4,4'-(t)Bubpy)4] (1; 4,4'-(t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine) was synthesized in multigram-scale quantities by the reaction of VOSO4 with 4,4'-(t)Bubpy in the presence of sodium benzoate under O2. The reaction of 1 with MeOH under air afforded the tetranuclear oxidovanadium(V) complex [V4O8(OMe)4(4,4'-(t)Bubpy)2] (2) selectively. In contrast, treatment of 1 with EtOH or MeOC2H4OH under air gave the heptanuclear oxidovanadium(V) complexes [V7O17(OR)(4,4'-(t)Bubpy)3] (R = Et (3a), MeOC2H4 (3b)) having an unprecedented neutral V7O17(OR) core. Although 3a and 3b are relatively stable in CH2Cl2, slow diffusion of Et2O into the solution of 3a in CH2Cl2 afforded 1 as yellow crystals. Complex 2 was also converted into 1 by recrystallization from CHCl3-CH2Cl2/Et2O. (1)H and (51)V NMR as well as electrospray ionization mass spectrometry studies of the behavior of 2 in CD2Cl2 suggested the formation of the methoxido analogue of 3 (3c, R = Me), which is considered to be an intermediate species in the conversion of 2 to 1. The present results provide a rare example of interconversion among neutral vanadium(V) oxide cluster complexes by changing the solvent systems.
RESUMO
A novel octanuclear vanadium(V) oxide cluster complex, [V8O20(4,4'-(t)Bubpy)4] (1), was synthesized and characterized by single-crystal X-ray structure analysis to reveal that 1 has an unprecedented neutral V8O20 core. An unexpected interconversion between 1 and the methoxo(oxo)vanadium(V) cluster complex, [V4O8(OMe)4(4,4'-(t)Bubpy)2] (2), was observed upon changes in the solvent systems.
