Synthesis and characterization of cobalt(II) complexes of croconate and dicyanomethylene-substituted derivatives

The crystal structures of cobalt(II) complexes of croconate [CoL1(H2O)(3)] 1 (L-1 = C5O52-) and croconate violet K-2[CoL22(H2O)(2)]. 2H(2)O 2 [L-2 = 3 ,5-bis(dicyanomethylene)cyclopentane-1,2,4-trionate] have been determined. Complex 1 consists of infinite zig-zag chains constituted by one metal atom , one croconate acting as a bridge and three water molecules. Moreover thes e chains, parallel to the c axis, are stacked with metal-metal distances of 7.9891(3) Angstrom inside a chain and 5.0035(6) Angstrom between chains. C omplex 2 consists of dianionic and mononuclear entities in which the ligand is O-co-ordinated. The magnetic properties of 1 and 2 have been investigat ed in the 4-300 K temperature range (mu(eff) = 3.65 to 5.02 mu(B) for 1 and mu(eff) = 4.80 to 4.90 mu(B) for 2). Their redox properties are discussed and compared to those of the free ligands.