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Chiral NHC‐Complexes with Dioxolane Backbone Heterogenized on MCM‐41. Catalytic Activity
Author(s) -
Villaverde Gonzalo,
Corma Avelino,
Iglesias Marta,
Sánchez Félix
Publication year - 2011
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201100119
Subject(s) - benzonitrile , rhodium , palladium , catalysis , chemistry , dioxolane , selectivity , asymmetric hydrogenation , organic chemistry , heterogeneous catalysis , enantioselective synthesis , combinatorial chemistry , polymer chemistry
Rhodium, palladium, and gold complexes of chiral (NHC)–dioxolane–amino ligands were prepared. Herein, new methods for the heterogenization of NHC‐chiral complexes on porous silica supports are demonstrated for the facile recovery and recycling of these expensive catalysts. Activity, selectivity, and recyclability were investigated and compared to that of the analogous homogeneous catalysts for asymmetric hydrogenation reactions. The compounds were characterized by using a variety of methods, including solid state cross‐polarization magic‐angle spinning (CP MAS) 13 C NMR, FT‐IR spectroscopy, and elemental analysis. Heterogenized rhodium(I) and palladium(II) catalysts could be used at least four times without loss of activity or enantioselectivity. (NHC)–gold(I) complexes were easily immobilized and recycled by a treatment with benzonitrile during the washing steps between cycles. This washing maintained the activity and enantioselectivity.