Synthesis and Characterization of N-Heterocyclic Carbene Substituted Phosphine and Phosphite Rhodium Complexes and their Catalytic Properties in Hydrogenation Reactions

✍ Scribed by Wolfgang A. Herrmann; Guido D. Frey; Eberhardt Herdtweck; Martin Steinbeck

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 318 KB
• Volume: 349
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.200700079

✦ Synopsis

Abstract

Mixed N‐heterocyclic carbene‐substituted phosphine and phosphite complexes of rhodium were prepared, starting from [Rh(COE)~2~Cl]~2~ (COE=cyclooctene) by addition of free N‐heterocyclic carbenes (NHC) and PR~3~. All new complexes were characterized by spectroscopy. In addition, the structures of trans‐chloro(1,3‐dicyclohexylimidazol‐2‐ylidene)‐bis(triphenylphosphite)rhodium(I) (5), chloro‐trans‐bis(1,3‐dicyclohexylimidazol‐2‐ylidene) (triphenylphosphine)rhodium(I) (6), and chloro(η^4^‐1,5‐cyclooctadiene)(1,3‐di‐[(1__R,2__S,5__R__)‐2‐isopropyl‐5‐menthylcyclohex‐1‐yl]imidazol‐2‐ylidene)rhodium(I) (8) were determined by single crystal X‐ray analyses. The hydrogenation of cyclohexene using molecular hydrogen has been optimized for some N‐heterocyclic carbene‐substituted phosphine and phosphite rhodium complexes by variation of the reaction conditions.