EDGE-SHARING OF 2 5-MEMBERED METAL CHELATE RINGS - STRUCTURES AND MAGNETISM OF MO0-COMPLEXES, CUI-COMPLEXES, AND COII-COMPLEXES WITH THE S-FRAME LIGAND AZO-2,2'-PYRIDINE

Edge-sharing of two alpha-iminoazo five-membered chelate rings in dinuclear complexes of the S-frame ligand azo-2,2'-pyridine (apy) gives rise to short distances between coplanar molecule-bridged metal centers. An intramolecular Cu-Cu distance of 493.7 pm was found for {(mu,eta-4-apy)[Cu(PPh3)2]2}2+ in the crystal with BF4- anions. Despite such relatively short metal-metal distances the corresponding Co(II) dimer (mu,eta-4-apy)[Co(hfacac)2]2 (hfacac: hexafluoroacetylacetonate) does not exhibit unusual magnetic coupling between the high-spin d7 centers. The mononuclear complex (apy)Mo(CO)4 contains a not completely coplanar apy ligand; the free pyridyl group is rotated in such a fashion as to minimize steric repulsion and possibly coordinate weakly to the metal.