Steric and electronic effects on acetate-assisted cyclometallation of 2-phenylpyridines at [MCl2Cp*]2 (M = Ir, Rh)

The reactions of substituted 2-phenylpyridines at [MCl2Cp*](2) dimers (M = Ir, Rh) in the presence of NaOAc form cyclometallated complexes Cp*M(Phpyr)Cl. H/D exchange experiments and substrate competition experiments show that kinetic selectivity favours electron donating substituents whilst substrates with electron withdrawing substituents are favoured thermodynamically. Experiments with Ir are mostly irreversible under the conditions used whilst those for Rh are more easily reversible. For meta-substituted phenylpyridines steric effects are important, larger substituents leading to formation of the para-substituted cyclometallated product.