Structure and Reactivity of Dinitrogen Rhodium Complexes Containing N-Heterocyclic Carbene Ligands

The rhodium bis-carbene complex [Rh(IPr)(2)(N-2)Cl], where IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, has been synthesized and characterized. The complex is a rare example of a four-coordinate rhodium complex featuring nitrogen bound end-on. While quite stable as a solid under inert atmosphere, in solution the N-2 ligand has been found to be quite labile. This lability has been exploited in the synthesis of complexes with the formula [Rh(IPr)(2)(XY)Cl], where XY = O-2, H-2 and CO. Interestingly, the dihydride coordination leads to oxidation of the metal centre to Rh-III, even though previous studies from our lab have shown that Rh remains in the +1 oxidation state upon coordination of dioxygen. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)