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Immobilization of rhodium complexes in chiral organic–inorganic hybrid materials
Author(s) -
Adima Augustin,
Moreau Joël J.E.,
Man Michel Wong Chi
Publication year - 2000
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/(sici)1520-636x(2000)12:5/6<411::aid-chir21>3.0.co;2-x
Subject(s) - chemistry , rhodium , catalysis , acetophenone , enantioselective synthesis , hybrid material , heterogeneous catalysis , hydrolysis , sorption , organic chemistry , adsorption
Two new alkoxysilylated derivatives of (−)‐(1R,2R)‐1,2‐diaminocyclohexane: M = N‐[(triethoxysilyl)propyl]‐(−)‐(1R,2R)‐1,2‐diaminocyclohexane and B = N,N'‐bis[(triethoxysilyl)propyl]‐(−)‐(1R,2R)‐1,2‐diaminocyclohexane have been synthesized. Their complexation with [Rh(cod)Cl] 2 in the presence of TEOS = Si(OEt) 4 , followed by sol‐gel hydrolysis‐condensation, afforded new catalytic chiral hybrid materials. Evidence for the presence of the organic moieties complexed by rhodium in these solids was obtained by UV‐visible spectroscopy, FT‐IR studies, solid state 13 C and 29 Si CP‐MAS NMR analysis, energy‐dispersive X‐ray (EDX) techniques, and elemental analysis. The nitrogen sorption studies and BET analyses ranged these solid gels from nonporous to highly porous materials. The catalytic activities and selectivities of the solid materials have been studied in the asymmetric hydrogen‐transfer reduction of prochiral ketones and compared to that of the homogeneous rhodium complexes of the ligands M and B . The hybrid materials appeared interesting supports for enantioselective heterogeneous catalysis leading to chiral alcohols with ee up to 58% in the reduction of acetophenone and up to 98% in the case of the more hindered related ketones. The catalytic properties as a function of the nature of chiral hybrid solid are discussed. Chirality 12:411–420, 2000. © 2000 Wiley‐Liss, Inc.