A highly conducting mixed-valence nickel bis(dithiolene) salt [Et 4 N][Ni(Me-thiazSe-dt) 2 ] 2 with selone substitution.

The prototypical [Ni(dmit) 2 ] complex (dmit: 1,3-dithiole-2-thione-4,5-dithiolate) is modified here by combining the N-R substitution found in [Ni(R-thiazdt) 2 ] complexes (R-thiazdt: N -alkyl-thiazoline-2-thione-4,5-dithiolate) and the selone substitution found in [Ni(dmiSe) 2 ] complex (dmiSe: 1,3-dithiole-2-selone-4,5-dithiolate) to give a novel N -methyl substituted, radical anionic complex formulated as [Ni(Me-thiazSe-dt) 2 ] 1- (Me-thiazSe-dt: N -methyl-thiazoline-2-selone-4,5-dithiolate). Both this anionic complex and its mixed-valence Et 4 N + salt crystallize with a rare cis arrangement of the two dithiolene ligands around the Ni atom. In the 1 : 2 [Et 4 N][Ni(Me-thiazSe-dt) 2 ] 2 salt, the complexes organize into dimerized chains well isolated from each other, giving the salt a strong one-dimensional character. It shows however a high RT conductivity of 4.6 S cm -1 and small activation energy of 33 meV, indicating a possible Mott insulator behavior, which is not suppressed under pressures up to 10 GPa.