CC Coupling of N‐Heterocycles at the fac ‐Re(CO) 3 Fragment: Synthesis of Pyridylimidazole and Bipyridine Ligands

A new family of cationic rhenium tricarbonyl complexes with either two N‐alkylimidazole (N‐RIm) and one pyridine (Py) ligand, or two pyridine and one N‐RIm ligand, [Re(CO) 3 (N‐RIm) (3− x ) (Py) x ] + , has been prepared. The reaction of these complexes with a strong base, followed by an oxidant, selectively afforded 2,2’‐pyridylimidazole complexes as the result of intramolecular dehydrogenative CC coupling reactions. For tris(pyridine) complexes [Re(CO) 3 (Py) 3 ] + the reaction pattern upon a deprotonation/oxidation sequence is maintained, which allows the generation of complexes with 2,2’‐bipyridine ligands. In the particular combination of two different types of pyridine ligand in the cationic fac ‐Re(CO) 3 complexes only the cross‐coupling products with asymmetric 2,2’‐bipyridine ligands were obtained; the homocoupling products were not observed.