Assembly and Properties of Heterobimetallic CoII/III/CaII Complexes with Aquo and Hydroxo Ligands

详细信息    查看全文

• 作者：David C. Lacy ; Young Jun Park ; Joseph W. Ziller ; Junko Yano ; A. S. Borovik
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：October 24, 2012
• 年：2012
• 卷：134
• 期：42
• 页码：17526-17535
• 全文大小：447K
• 年卷期：v.134,no.42(October 24, 2012)
• ISSN：1520-5126

文摘

The use of water as a reagent in redox-driven reactions is advantageous because it is abundant and environmentally compatible. The conversion of water to dioxygen in photosynthesis illustrates one example, in which a redox-inactive Ca^II ion and four manganese ions are required for function. In this report we describe the stepwise formation of two new heterobimetallic complexes containing Co^II/III and Ca^II ions and either hydroxo or aquo ligands. The preparation of a four-coordinate Co^II synthon was achieved with the tripodal ligand, N,N鈥?N鈥?[2,2鈥?2鈥?nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido, [MST]^{3鈥?/sup>. Water binds to [CoIIMST]鈭?/sup> to form the five-coordinate [CoIIMST(OH₂)]鈭?/sup> complex that was used to prepare the CoII/CaII complex [CoIIMST(渭-OH₂)CaII15-crown-5(OH₂)]+ ([CoII(渭-OH₂)CaIIOH₂]+). [CoII(渭-OH₂)CaOH₂]+ contained two aquo ligands, one bonded to the CaII ion and one bridging between the two metal ions, and thus represents an unusual example of a heterobimetallic complex containing two aquo ligands spanning different metal ions. Both aquo ligands formed intramolecular hydrogen bonds with the [MST]3鈥?/sup> ligand. [CoIIMST(OH₂)]鈭?/sup> was oxidized to form [CoIIIMST(OH₂)] that was further converted to [CoIIIMST(渭-OH)CaII15-crown-5]+ ([CoIII(渭-OH)CaII]+) in the presence of base and CaIIOTf₂/15-crown-5. [CoIII(渭-OH)CaII]+ was also synthesized from the oxidation of [CoIIMST]鈭?/sup> with iodosylbenzene (PhIO) in the presence of CaIIOTf₂/15-crown-5. Allowing [CoIII(渭-OH)CaII]+ to react with diphenylhydrazine afforded [CoII(渭-OH₂)CaIIOH₂]+ and azobenzene. Additionally, the characterization of [CoIII(渭-OH)CaII]+ provides another formulation for the previously reported CoIV鈥搊xo complex, [(TMG₃tren)CoIV(渭-O)ScIII(OTf)₃]2+ to one that instead could contain a CoIII鈥揙H unit.}