Selective alcohol oxidation with molecular oxygen catalyzed by Os-Cr and Ru-Cr complexes

Citation
Pa. Shapley et al., Selective alcohol oxidation with molecular oxygen catalyzed by Os-Cr and Ru-Cr complexes, J AM CHEM S, 122(6), 2000, pp. 1079-1091
Citations number
92
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry & Analysis",Chemistry
Journal title
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
ISSN journal
0002-7863 → ACNP
Volume
122
Issue
6
Year of publication
2000
Pages
1079 - 1091
Database
ISI
SICI code
0002-7863(20000216)122:6<1079:SAOWMO>2.0.ZU;2-E
Abstract
The heterobimetallic complexes [Y] [M(N)R-2(mu-O)(2)CrO2] (where Y is eithe r N(n-Bu)(4)(+) or PPh4+; M is either Ru or Os; and R is an alkyl or aryl l igand) catalyze the selective oxidation of alcohols with molecular oxygen. The rate of the reaction is higher with a ruthenium-containing complex than with an analogous osmium-containing catalyst. The rate decreases with ster ic bulk in either the catalyst or substrate. Single-crystal X-ray diffracti on studies of [N(n-Bu)4][Ru(N)(CH2SiMe3)(2)(mu-O)(2)CrO2] and [PPh4] [Os(N) Me(CH2SiMe3)(mu-O)(2)CrO2] show the chromate group coordinated to each nitr ido(dialkyl)metal center through two oxo ligands. The oxidation of benzyl a lcohol by [N(n-Bu)(4)][Os(N)(CH2SiMe3)(2)(mu-O)(2)CrO2] was examinined in d etail. It is first order in alcohol and substrate, and, when oxygen partial pressure is low, the rate depends directly on the O-2 partial pressure. A mechanism in which alcohol coordinates to the osmium center and is oxidized by P-hydrogen elimination is consistent with the data. [N(n-Bu)(4)][Os(N)( CH2SiMe3)(2)(mu-O)(2)CrO2] catalyzes the oxidation of dppe with Oz through a different pathway.