abstract
The tetrahexylammonium (THA) salt of the peroxocomplex [W(2)O(3)(O(2))(4)](2-) was used as catalyst for the oxidation of cis-cyclooctene, geraniol and cyclooctane, with hydrogen peroxide, in acetonitrile. High catalytic activity for all substrates, with high efficiency of use of hydrogen peroxide, was found. Under the conditions used, the oxidation of cyclooctane gives rise to cyclooctanone, cyclooctanol and cyclooctyl hydroperoxide, with 90% and 97% of conversion after 6 and 12 h, respectively, reaching turnover numbers higher than 600. A possible mechanism for the oxidation of cyclooctane is proposed. The oxidation of cis-cyclooctene gives the corresponding epoxide with 100% conversion after 4 h, whereas geraniol yields mainly the 2,3-epoxide (94% selectivity) with 88% of conversion after 5 h of reaction. The crystal structure of (THA)(2)[W(2)O(3)(O(2))(4)] is reported. The anion has two types of coordinated peroxide ligands, namely symmetrical and unsymmetrical bridging peroxo groups. This study indicates that the peroxocomplex [W(2)O(3)(O(2))(4)](2-) is catalytically active both in epoxidation reactions in acetonitrile and in the oxyfunctionalization of a cycloalkane. (C) 2008 Elsevier B.V. All rights reserved.
keywords
KEGGIN-TYPE POLYOXOTUNGSTATES; X-RAY STRUCTURE; ALLYLIC ALCOHOLS; HETEROPOLYOXOPEROXO COMPLEXES; DINUCLEAR PEROXOTUNGSTATE; SELECTIVE OXIDATION; BIPHASE MEDIUM; EPOXIDATION; CRYSTAL; OLEFINS
subject category
Chemistry; Environmental Sciences & Ecology
authors
Santos, ICMS; Paz, FAA; Simoes, MMQ; Neves, MGPMS; Cavaleiro, JAS; Klinowski, J; Cavaleiro, AMV
our authors
Ana Maria Vieira Silva Viana Cavaleiro
Full professor
Filipe Alexandre Almeida Paz
Principal Researcher
Isabel Cristina Maia da Silva Santos Vieira
Junior Researcheracknowledgements
Thanks are due to the University of Aveiro, Fundacao para a Ciencia e a Tecnologia (FCT) and FEDER for funding. I.C.M.S. Santos is also grateful to FCT for her grant.