Coordination chemistry of di-2-pyridylmethane and related bridging ligands with silver(I), copper(II), palladium(II) and zinc(II)

Di-2-pyridylmethane (1) and the bridging ligands 1,1,2,2-tetra(2-pyridyl)ethane (2), 1,1,2,2-tetra(2-pyridyl)ethan-2-ol (3) and tetra(2-pyridyl)ethene (4) chelate to metal atoms with the formation of 6-membered chelate rings. The utility of these ligands in coordination chemistry and as metallosupramolecular synthons was probed by reaction with silver, copper, palladium and zinc salts. On reaction with AgNO3 the model ligand, 1, formed a 1-D coordination polymer with an unusual bridging mode and with Cu(NO3)2 underwent oxidation to produce a Cu6(L)4(L =5, di-2pyridylmethanediol) complex. The bridging ligands 2 and 4 formed several discrete dinuclear complexes, a [2 + 2]-dimetallomacrocycle and a 1-D coordination polymer. Ligand 3 was demonstrated to be less stable and underwent three different solvolysis reactions to give a range of products that were characterised by X-ray crystallography.