Synthesis, Structure Characterization, and Reversible Transformation of a Cobalt Salt of a Dilacunary 纬-Keggin Silicotungstate and Sandwich-Type Di- and Tetracobalt-Containing Silicotungstate Dimers
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- 作者：Yuji Kikukawa ; Kosuke Suzuki ; Kazuya Yamaguchi ; Noritaka Mizuno
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：August 5, 2013
- 年：2013
- 卷：52
- 期：15
- 页码：8644-8652
- 全文大小：419K
- 年卷期：v.52,no.15(August 5, 2013)
- ISSN：1520-510X
文摘
A cobalt salt of a 纬-Keggin dilacunary silicotungstate, {CoL5}2[纬-SiW10O34L2] [Co-SiW10; L = N,N-dimethylformamide (DMF) or H2O], could be synthesized by the cation-exchange reaction of TBA4[纬-H4SiW10O36] (TBA = tetra-n-butylammonium) with 2 equiv of Co(NO3)2 with respect to TBA4[纬-H4SiW10O36] in a mixed solvent of DMF and acetone (97% yield). Each Co-SiW10 was linked by water molecules via a hydrogen-bonding network. Besides Co-SiW10, various kinds of isostructural M-SiW10 could be synthesized via the same procedure as that for Co-SiW10 (M = Mn2+, Fe2+, Ni2+, Cu2+, Zn2+, and Cd2+). By the reaction of Co-SiW10 with 1 equiv of TBA6[纬-H2SiW10O36] in acetone, a silicotungstate dimer pillared by two cobalt cations with a significantly slipped dimer configuration, TBA6[Co2(纬-H3SiW10O36)2]路3H2O (Co2), could be synthesized. By the reaction of Co-SiW10 with 3 equiv of TBAOH in acetone, a tetracobalt-containing sandwich-type silicotungstate, TBA6[{Co(H2O)}2(渭3-OH)2{Co(H2O)2}2(纬-H2SiW10O36)2]路5H2O (Co4), could be synthesized. Compound Co4 possessed the tetracobalt鈥搊xygen core, [{Co(H2O)}2(渭3-OH)2{Co(H2O)2}2]6+, identical with those of previously reported Weakley-type sandwich polyoxometalates, [Co4(H2O)2(XM9O34)2]n鈭?/sup> (X = P5+, Si4+, Ge4+, As5+ or V5+; M = Mo6+ or W6+). The reversible transformation between these three compounds (Co-SiW10 Co2, Co-SiW10 Co4, and Co2 Co4) took place by the addition and/or subtraction of required components in appropriate solvents, affording the desired products in high yields (71鈥?3% yields).