The cationic Rh(I) dicarbonyl complex [{Rh(bim)(CO)2}+BPh4–] 1, containing a bidentate bisimidazolylmethane ligand [bim refers to bis(N-methylimidazol-2-yl)methane] acts as a catalyst for the cyclization of alkynyl amides to produce lactams and N-acyl heterocyclic compounds.