Metal complexes based on extended TTF (tetrathiafulvalene) ligands, [M(dmdt)(2)](2-), [M(tmdt)(2)](2-) (dmdt = dimethyltetrathiafulvalenedithiolate, tmdt = trimethylenetetrathiafulvalenedithiolate) (M = Ni, Pd, Pt, etc) were synthesized. The newly developed nickel complexes such as [Ni(dmdt)(2)](2-) and [Ni(tmdt)(2)](2-) are easily oxidized to neutral state by electrochemical oxidation and the microcrystals of these neutral complexes exhibit high conductivity (100-500 S cm(-1)). The crystal structure of [Ni(tmdt)(2)], one of these neutral complexes, was finally determined, which supports the metallic behavior of resistivity of this neutral metal complex.