Crystal structures of dinuclear copper(II) and oxovanadium(IV) complexes of N,N,N',N'-tetrakis(2-pyridylmethyl)-6,6'-bis(aminomethyl)-2,2'-bipyridine

Two dinuclear transition-metal complexes of the polypyridine ligand N,N,N',N'-tetrakis(2-pyridylmethyl)-6,6'-bis(aminomethyl)-2,2'-bipyridine (btpa) have been prepared and structurally characterized. The crystal structure of [Cu-2(SO4)(2)(btpa)](0.68(1))[Cu-2(SO4)(2)(H2O)(2)(btpa)](0.32(1)). 6.64(2)H2O (1) is triclinic, beta = 90.95(2), gamma = 93.41(1)degrees with one formula unit in the cell. The structure refined to a final R-value of 0.058 for 1686 reflexions. There is a square-planar arrangement of an oxygen atom of the sulfate ion and three nitrogen atoms of the btpa ligand which bridges the two copper atoms of the centrosymmetric complex cation, Cu Cu ... 7.718(4) Angstrom. The structure is disordered with a water molecule sometimes coordinating to the copper atom. The crystal structure of [(VO)(2)(mu-SO4)(btpa)](ClO4)(2) . 4.99(8)H2O (2) is triclinic, space group P<P(1)over bar>, with a = 16.710(3), b = 10.813(2), c = 13.845(2) Angstrom, alpha = 100.76(1), beta = 95.42(1), gamma = 102.89(1)degrees with two formula units in the cell. The structure refined to a final R-value of 0.064 for 4120 reflexions. The vanadyl groups of the complex dimer are bridged by btpa and by a sulfate ion, V ... V=4.328(2) Angstrom. The vanadium atoms are octahedrally coordinated by a vanadyl oxygen atom, an oxygen of the sulfate ion and four nitrogen atoms of btpa. Magnetic measurements show no magnetic interaction between the metal centers in 1 or in 2.