Synthesis and Structural Features of Rhodium Complexes of Expanded Ring N-Heterocyclic Carbenes

The rhodium complexes [Rh(NHC)(COD)Cl] and cis-[Rh(NHC)(CO)(2)Cl] of seven-membered N-heterocyclic carbenes (NHC) bearing aromatic N-substituents (mesityl, xylyl and o-tolyl) were synthesised, and a comparison of their steric and electronic properties with those of the analogous five- and six-membered NHC complexes was made on the basis of infrared and solid-state data. The X-ray structures for the complexes Rh(6-Mes)(COD)Cl, Rh(7-Mes)(COD)Cl and Rh(7-oTol)(COD)Cl were determined. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)