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• 作者：Debbie C. Crans ; Feilong Jiang ; John Chen ; Oren P. Anderson ; and Mary M. Miller
• 刊名：Inorganic Chemistry
• 出版年：1997
• 出版时间：March 12, 1997
• 年：1997
• 卷：36
• 期：6
• 页码：1038 - 1047
• 全文大小：262K
• 年卷期：v.36,no.6(March 12, 1997)
• ISSN：1520-510X

文摘

Tetranuclear vanadium complexes with alkoxy ligands,[V₄O₄{,,₃-(OCH₂)₃CCH₃}₂(OCH₃)₆](1) and [V₄O₄{-(OCH₂)₃CCH₃}{,₃-(OCH₂)₃CCH₃}{,,₃-(OCH₂)₃CCH₃}(OR)₃](R = C₂H₅ (2), R =CH(CH₃)₂ (3), R =CH₃(4)), were synthesized by reacting VO(OR)₃ andH₃thme (H₃thme =1,1,1-tris(hydroxymethyl)ethane) in alcohol.Complex 1 crystallized in the monoclinic space groupP2₁/n with a =9.646(4) Å, b = 11.502(3) Å, c =11.960(3) Å, = 90.20(3), V = 1326.9 (7)ų, Z = 2 and R (wR₂)= 0.045 (0.143). Complex 2 also crystallizedinthe monoclinic space group P2₁/n witha = 8.290(8) Å, b = 12.237(2) Å,c = 29.118(4) Å, = 89.455(9),V= 2954(3) ų, Z = 4, and R(wR₂) = 0.049 (0.126). Both 1 and2 are neutral, discrete complexes possessing acommon [V₄O₁₆]^12-core, which consists of four vanadium(V) atoms chelated by two(1) or three (2) tridentatethme^3- ligands and by six (1) orthree (2) RO^- groups. Compound1 exhibits a crystallographically requiredinversion center; in contrast, complex 2 exhibits nocrystallographically imposed symmetry, and its threetrialkoxyligands each coordinate differently (onethme^3- is coordinated in a new coordinationmode with the oxygens ina terminal, doubly-bridging and triply-bridging mode). Bothcompounds 1 and 2 maintain their structuresinsolution, although compound 1 also forms a second minorspecies upon dissolution. Sequential exchanges of theRO^- groups in complexes 2 and 3were investigated by ⁵¹V and ¹H NMRspectroscopy. For example,[V₄O₄(thme)₃(OC₂H₅)₃]will react with CH₃OH to generate[V₄O₄(thme)₃(OCH₃)₃](4). These reactions werefound to be reversible. The time scale of the alcohol exchangereactions were found to vary depending on thevanadium center that is undergoing the exchange.