title: Increased Lewis acidity in hafnium-substituted polyoxotungstates.
abstract: Monolacunary polyoxotungstates [alpha(1)-P(2)W(17)O(61)](10-) and [alpha-PW(11)O(39)](7-) react with HfCl(4) to yield [alpha(1)-HfP(2)W(17)O(61)](6-) and [alpha-Hf(OH)PW(11)O(39)](4-), isolated as organo-soluble tetrabutylammonium (TBA) salts. Subsequent analyses, including mass spectrometry, show that they are stronger Lewis acids than (TBA)(5)H(2)[alpha(1)-YbP(2)W(17)O(61)]. The new polyoxotungstates catalyze Lewis acid mediated organic reactions, such as Mukaiyama aldol and Mannich-type additions. In particular, reactions with aldehydes, which were impossible with lanthanide polyoxotungstates, are made possible. Thus these modifications of the polyoxometalate composition allowed fine tuning of the Lewis acidity. The catalysts could be easily recovered and reused.
authors: Université Pierre et Marie Curie-Paris 6, Laboratoire de chimie organique (UMR CNRS 7611), Institut de chimie moléculaire (FR 2769), C. 229, 4 place Jussieu, 75005 Paris, France.
authors: Cécile
authors: C
authors: Boglio
authors: Kevin
authors: K
authors: Micoine
authors: Pauline
authors: P
authors: Rémy
authors: Bernold
authors: B
authors: Hasenknopf
authors: Serge
authors: S
authors: Thorimbert
authors: Emmanuel
authors: E
authors: Lacôte
authors: Max
authors: M
authors: Malacria
authors: Carlos
authors: C
authors: Afonso
authors: Jean-Claude
authors: JC
authors: Tabet