Investigation of the structure and catalytic activity in olefin cyclopropanation of neutral and cationic dicopper complexes of 3,5-bis(pyridinylimino)benzoic acid

Three neutral and one cationic copper(I) complexes with 3,5-bis(pyridinylimino)benzoic acid are synthesized and characterized in solution and in the solid state by a variety of spectroscopic techniques and X-ray crystallography. The compounds are monomeric in nature possessing two Cu(I) centers each coordinated to one of the two diimine sites of the ligand. The chromophores are either N2PX, where X is a halide (Cl, Br or I) for the neutral or N2P2 for the ionic compounds, respectively. The phosphorus donor is triphenylphosphane. The crystal structures of the isostructural bromido and iodido compounds are solved and discussed. The compounds are tested for their catalytic activity in olefin cyclopropanation reactions by means of ethyl diazoacetate decomposition and prove to be moderately active with the ionic one being the most active and the most promising since for cyclohexene it reveals a considerable diastereoselectivity and a 90:10 exo:endo ratio of the final product.