A neutral bis(diethylthiotetrathiafulvalenyldiselenolato)nickel complex: asuperior organic conductor to the corresponding dithiolato derivative

The tetra-n-hexylammonium salt of the bis(diethylthiotetrathiafulvalenyldis elenolato)nickelate complex monoanion (1b) was obtained by the reaction of bis(tetra-n-hexylammonium) diethylthiotetrathiafulvalenyldiselenolate with nickel(ii) acetylacetonate. X-Ray structure analysis of 1b showed that the molecular skeleton, except for the four ethyl groups, is almost planar, wit h the six sulfur and two selenium atoms on each ligand being essentially lo cated in the same plane and with the geometry around the nickel atom being square-planar. From the SQUID and EPR measurements, the unpaired spin in 1b is located primarily on the nickel atom, which is best described as a Ni(I II) (S = 1/2) metal center. Iodine oxidation of 1b gave the corresponding n eutral complex 1a as microcrystals. A compressed pellet of 1a exhibited a r oom-temperature electrical conductivity of 2.8 cm(-1), which is higher by c a. 60 times, than that for the corresponding dithiolato complex 2a (5.0 x 1 0(-2) cm(-1)) obtained by iodine oxidation of tetra-n-hexylammonium bis(die thylthiotetrathiafulvalenyldithiolato)nickelate 2b. The temperature depende nce of the electrical conductivity was as expected for a semiconductor, but the activation energy was very low (0.014 eV).