Abstract
The cationic d10 metal complexes [(bdz)Cu(PPh3)2+]+ of the π accepting bidiazine (bdz) chelate ligands 3,3′-bipyridazine, 2,2′-bipyrazine, 2,2′- and 4,4′-bipyrimidine were synthesized and compared with the analogous complex of 2,2′-bipyridine. The long wavelength metal-to-ligand charge transfer (MLCT) absorption maxima and the reduction potentials indicate relatively little π* orbital stabilization by +Cu(PPh3)2. The particular d orbital splitting in a tetrahedral ligand field results in an additional contribution from △t to the energy difference between the first and second MLCT band. Only the most easily reduced complexes of 4,4′-bipyrimidine and 2,2′-bipyrazine yield neutral radical complexes (“Cu(0)”) which were characterized by ESR spectroscopy.

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