Polarized reflection, electrical conductivity, magnetic susceptibility measurements and X-ray crystal structure predetermination have been carried out on one- dimensional iodo-bridged binuclear metal dithioacetato complexes, M2(dta)4I (M=Pt and Ni; dta=CH3CS2−) in order to elucidate their electronic property. The chain structure consists of -M2-5+-M2,5+-I-M2-5+-M2-5+- with no Peierls distortion, and two metal atoms in binuclear moieties are bridged by four dithioacetato ligands to give a cage structure. The magnetic behavior of these compounds revealed very strong anti ferromagnetic coupling between electronic spins (S=1/2) localized on the M-M dimers. They show semi conducting behavior with high conductivities and small activation energies compared with those of the MX compounds. From these results, it may be concluded that the compounds are one-dimensional Mott-Hubbard insulators, in contrast to Peierls insulators of R4[Pt2(pop)4X].nH20 complexes (…M2+-M2+…X-M3+-M3+-X‥).