(η6‐Arene)ruthenium(N‐heterocyclic carbene) Complexes for the Chelation‐Assisted Arylation and Deuteration of Arylpyridines: Catalytic Studies and Mechanistic Insights

A series of (η6‐arene)ruthenium complexes have been tested in the arylation of arylpyridines. One (η6‐p‐cymene)ruthenium(N‐heterocyclic carbene) complex (labelled as 1 in the text) was found to be the most effective, being capable of arylating a wide set of substantially different arylpyridines. Complex 1 is also able to promote the regioselective deuteration of a series of arylated N‐heterocycles, via a nitrogen‐directed mechanism. Two of the deuterated amines were used to measure the kinetic isotope effect (KIE) in the arylation process. The detection of an inverse KIE, together with the observation that the CH activation process does not require the addition of a base, suggest that the rate‐limiting step in the arylation process may be different to that of previously reported studies.