N‑Metallacycles from [Cp*MX2]2 and Alkynylpyridines: Synthesis, Reaction Pathway, and Aromaticity

The reaction of [Cp*MX2]2 (M = Rh or Ir, X = Cl, Br, or I) with alkynylpyridines afforded halogen-substituted N-metallacyclic complexes. The reaction pathway has been examined through deuterium labeling and other experiments and computational studies and is proposed to proceed via halide dissociation followed by attack at the alkyne. These N-metallacycles exhibit aromaticity and undergo Sonogashira coupling reactions.