The mechanism and selectivity of terminal alkyne coupling reactions promoted by rhodium(I) complexes of NHC‐based CNC pincer ligands have been investigated. Synthetic and kinetic experiments support E‐ and gem‐enyne formation through a common reaction sequence involving hydrometallation and rate‐determining C−C bond reductive elimination. The latter is significantly affected by the ligand topology: Employment of a macrocyclic variant enforced exclusive head‐to‐head coupling, contrasting the high selectivity for head‐to‐tail coupling observed for the corresponding acyclic pincer ligand.

Silver(i) and copper(i) complexes of a macrocyclic NHC-based pincer ligand, bearing a central lutidine donor and a dodecamethylene spacer, have been prepared and evaluated under equivalent conditions in transmetallation reactions.

Two catalysts for the price of one: a shape changing rhodium catalyst enables preparation of unusual isobenzenes using a one-pot procedure.