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Title
Japanese:Strategic Design and Refinement of Lewis Acid-Base Catalysis by Rare-Earth-Metal-Containing Polyoxometalates. 
English:Strategic Design and Refinement of Lewis Acid-Base Catalysis by Rare-Earth-Metal-Containing Polyoxometalates. 
Author
Japanese: Kosuke Suzuki, Midori Sugawa, Yuji Kikukawa, Keigo Kamata, Kazuya Yamaguchi, Noritaka. Mizuno.  
English: Kosuke Suzuki, Midori Sugawa, Yuji Kikukawa, Keigo Kamata, Kazuya Yamaguchi, Noritaka. Mizuno.  
Language English 
Journal/Book name
Japanese:Inorganic Chemistry 
English:Inorganic Chemistry 
Volume, Number, Page Vol. 51    No. 12    pp. 6953-6961
Published date 2012 
Publisher
Japanese:American Chemical Society 
English:American Chemical Society 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
DOI https://doi.org/10.1021/ic3008365
Abstract Efficient polyoxometalate (POM)-based Lewis acid-base catalysts of the rare-earth-metal-contg. POMs (TBA6RE-POM, RE = Y3+, Nd3+, Eu3+, Gd3+, Tb3+, or Dy3+) were designed and synthesized by reactions of (TBA)4H4[ﾎｳ-SiW10O36] (TBA = Bu4N) with RE(acac)3 (acac = acetylacetonato). TBA6RE-POM consisted of two silicotungstate units pillared by two rare-earth-metal cations. Nucleophilic O-enriched surfaces of neg. charged POMs and the incorporated rare-earth-metal cations could work as Lewis bases and Lewis acids, resp. Consequently, cyanosilylation of carbonyl compds. with trimethylsilyl cyanide ((TMS)CN) was efficiently promoted in the presence of the rare-earth-metal-contg. POMs via the simultaneous activation of coupling partners on the same POM mols. POMs with larger metal cations showed higher catalytic activities for cyanosilylation because of the higher activation ability of C=O bonds (higher Lewis acidities) and sterically less hindered Lewis acid sites. Among the POM catalysts examd., the Nd-contg. POM showed remarkable catalytic performance for cyanosilylation of various kinds of structurally diverse ketones and aldehydes, giving the corresponding cyanohydrin trimethylsilyl ethers in high yields (13 substrates, 94-99%). In particular, the turnover frequency (714,000 h-1) and the turnover no. (23,800) for the cyanosilylation of n-hexanal were of the highest level among those of previously reported catalysts. [on SciFinder(R)]

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