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首页> 外文期刊>Journal of Inorganic Biochemistry: An Interdisciplinary Journal >Vanadium(V) complex with Schiff-base ligand containing a flexible amino side chain: Synthesis, structure and reactivity
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Vanadium(V) complex with Schiff-base ligand containing a flexible amino side chain: Synthesis, structure and reactivity

机译:带有柔性氨基侧链的席夫碱配体的钒(V)配合物:合成,结构和反应活性

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The Schiff-base ligand (H(2)salhyhNH(3))Cl (1) derived from salicylaldehyde and 6-aminohexanoic acid hydrazide hydrochloride reacts with ammonium metavanadate in methanol solution to yield the dioxidovanadium(V) complex [VO2(salhyhNH(3))] (2). The utilized hydrazone ligand contains a flexible and protonated amino side chain. Crystallization from methanol affords complex 2 in the monoclinic space group P2(1), whereas crystallization from a methanol/water mixture 1:1 yields crystals, containing a water molecule of crystallization per two formula units (2.1/2H(2)O), in the orthorhombic space group Pbcn. In both cases the protonated amino group compensates the negative charge on the dioxidovanadium moiety and is involved in an extensive hydrogen bonding network particularly including the oxido groups from neighboring vanadium complexes. The reactivity of complex 2 toward protonation in aqueous solution has been investigated by spectrophotometric titrations and is characterized by two subsequent protonation steps at the hydrazide nitrogen atom of the ligand system and an oxido group leading to the formation of an oxidohydroxidovanadium(V) species with corresponding pK(a) values of 3.2 and 2.9, respectively. With larger excess of acid the oxidohydroxidovanadium(V) species starts to form the corresponding anhydride. The formation of the anhydride is strongly favored in the presence of methanol. The reaction of complex 2 with hydrogen peroxide in methanol solution leads to the formation of an oxidoperoxidovanadium(V) species, whereas in aqueous solution the addition of one equivalent of acid is required. Complex 2 catalyzes the oxidation of methylphenylsulfane to the corresponding sulfoxide in methanol/dichloromethane mixture using hydrogen peroxide as oxidant at room temperature. (C) 2015 Elsevier Inc. All rights reserved.
机译:从水杨醛和6-氨基己酸酰肼盐酸盐衍生的席夫碱配体(H(2)salhyhNH(3))Cl(1)与偏钒酸铵在甲醇溶液中反应生成二氧化钒(V)络合物[VO2(salhyhNH(3) ))](2)。所利用的ligand配体包含挠性和质子化的氨基侧链。从甲醇中结晶可得到单斜空间群P2(1)/ n中的络合物2,而从甲醇/水混合物1:1中结晶可得到晶体,每两个分子式单位(2.1 / 2H(2)O ),在正交空间群Pbcn中。在两种情况下,质子化的氨基都补偿了二氧化钒基团上的负电荷,并参与了广泛的氢键网络,特别是包括来自相邻钒配合物的氧化基团。已通过分光光度滴定法研究了配合物2在水溶液中对质子化的反应性,其特征是在配体系统的酰肼氮原子和一个氧化基团上进行了两个随后的质子化步骤,从而导致形成氧化羟基氧化钒(V)物种, pK(a)值分别为3.2和2.9。随着更多过量的酸,氧化羟基氧化钒(V)物质开始形成相应的酸酐。在甲醇存在下强烈促进酸酐的形成。配合物2与过氧化氢在甲醇溶液中的反应导致形成氧化过氧化物钒(V)物质,而在水溶液中则需要添加一当量的酸。在室温下,使用过氧化氢作为氧化剂,配合物2在甲醇/二氯甲烷混合物中催化甲基苯基硫烷氧化为相应的亚砜。 (C)2015 Elsevier Inc.保留所有权利。

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