Combining organometallic and Werner-type coordination sites in highly preorganized heterobimetallic systems

A first example of a novel class of preorganized bimetallic complexes is reported, in which both an organometallic CpMn(CO)2 fragment and a classical Werner-type coordination site are arranged in close proximity by means of a bridging pyrazolate. The synthetic route starts from N-protected bis(chloromethyl)pyrazole and involves sequential attachment of the manganese part and the chelating N-donor compartment, bis(pyridylmethyl)amine, at the different sides of the ligand backbone. Pyrazole binding to the manganese(I) is achieved by photoinduced substitution of CO, and the adjacent N4-coordination pocket is suited to accommodate a second metal ion. The heterodinuclear MnZn complex 4 is characterized crystallographically and its redox chemistry investigated by spectroelectrochemical methods.