C−H Activation Reactions on Rh(I)−Ethylene Complexes of the Hydrotris(3,5-dimethylpyrazolyl)borate Ligand, Tp^Me_²

Abstract

N-donor Lewis bases such as acetonitrile or pyridine react with the Rh(I) compound TpMe2Rh(C2H4)2 (1) to give the Rh(III) derivatives TpMe2Rh(CHCH2)(C2H5)(L) (2, 3) as the kinetic products of the reactions. Upon heating at 60 °C, the acetonitrile adduct 2 converts into TpMe2Rh(C2H4)(NCMe) (5). Under similar conditions, 2 is able to induce the activation of one of the C−H bonds of C6H6, in a process that involves the intermediacy of 1, as demonstrated by isotopic labeling studies. The phosphine adducts TpMe2Rh(C2H4)(PR3) (R = Me, Et) are also efficient reagents for the C−H bond activation of C6H6, py, or thiophene. In the latter case, rupture of the C−S bond is also detected, although the C−S bond activation complexes are thermodynamically disfavored with respect to those derived from the cleavage of one of the α-C−H bonds.