Diversification of ligand families through ferroin-neocuproin metal-binding domain manipulation

Derivatization of 5,5'-bis(3-hydroxyphenyl)-2,2'-bipyridine to give two new ligands, 3 and 4, which possess terminal alkene functionalities is described. The syntheses and characterization of the palladium(II) complexes [Pd(3)(2)][BF4](2) and [Pd(4)(2)][BF4](2), and the related [Pd(2)(2)][BF4](2) in which 2 is 5,5'-bis(3-methoxyphenyl)-2,2'-bipyridine are reported. The labile nature of the ligand leads to [Pd(2)(2)][BF4](2) co-crystallizing with the free ligand as [Pd(2)(2)][BF4](2)center dot 2; in the solid state, the ligands in the [Pd(2)(2)](2+) cation distort (a 'bow-incline' distortion) to alleviate bpy H-6 center dot center dot center dot H-6 repulsions. Compound 2 has been converted to 5,5'-bis(3-methoxyphenyl)-6-methyl-2,2'-bipyridine (5) and 5,5'-bis(3-methoxyphenyl)-6,6'-dimethyl-2,2'-bipyridine (6) to produce ligands suited to forming air-stable, copper(I) complexes of type [CuL2](+). [Cu(5)(2)][PF6] and [Cu(6)(2)][PF6] have been prepared and characterized, and the single crystal structures of 6 and [Cu(5)(2)][PF6]center dot 0.1C(2)H(4)Cl(2)center dot 0.15CH(2)Cl(2) are described. By altering the conditions under which 2 is methylated, competitive formation of 5,5', 5 '', 5'''-tetrakis(3-methoxyphenyl)-2,2':3', 3 '':2 '', 2'''-quaterpyridine occurs