Modulation of Multimetal Complexation Behavior of Tetraoxime Ligand by Covalent Transformation of Olefinic Functionalities

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• 作者：Shigehisa Akine ; Satoko Kagiyama ; Tatsuya Nabeshima
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：March 1, 2010
• 年：2010
• 卷：49
• 期：5
• 页码：2141-2152
• 全文大小：1273K
• 年卷期：v.49,no.5(March 1, 2010)
• ISSN：1520-510X

文摘

A new multimetal complexation system that can change its complexation behavior by C−C bond formation has been developed. The acyclic tetraoxime ligand H₄L¹ having two terminal allyl groups was synthesized. The olefin metathesis of H₄L¹ selectively produced trans-H₄L² while the reaction of [L¹Zn₂Ca] exclusively afforded cis-H₄L². The saturated analogue H₄L³ was synthesized by hydrogenation. The complexation of the ligands H₄L (L = L¹, trans-L², cis-L², L³) with zinc(II) acetate (3 equiv) yielded the trinuclear complexes [LZn₃] with a similar trinuclear core bridged by acetato ligands. Whereas the formation process of [L¹Zn₃] having an acyclic ligand was highly cooperative, the macrocyclic analogues [LZn₃] (L = trans-L², cis-L², L³) were formed in a stepwise fashion via the intermediate 2:3 complex [(HL)₂Zn₃]. The trinuclear complexes [LZn₃] (L = L¹, trans-L², cis-L², L³) can recognize alkaline earth metal ions via site-selective metal exchange. The acyclic [L¹Zn₃] selectively recognizes Ca²⁺, while the cyclic [trans-L²Zn₃] showed a Ba²⁺ selectivity. The metal exchange of [LZn₃] (L = L¹, trans-L², cis-L², L³) with La³⁺ efficiently occurred to give [LZn₂La], but the trans-olefin linker of the [trans-L²Zn₂La] significantly deforms the structure in such a way that one of the salicylaldoxime moieties does not participate in the coordination. Consequently, the chemical transformation of the olefinic moiety significantly affects the multimetal complexation behavior of the tetraoxime ligands.