Mixed-Valence Conductors from Ni Bis(diselenolene) Complexes with a Thiazoline Backbone.

Highly conducting, mixed-valence, multi-component nickel bis( diselenolene ) salts were obtained by electrocrystallization of the monoanionic species [Ni(Me-thiazds) 2 ] -1 (Me-thiazds: N -methyl-1,3-thiazoline-2-thione-4,5-diselenolate), with 1:2 and 1:3 stoichiometries depending of the counter ion used (Et 4 N + and n Bu 4 N + vs Ph 4 P + , respectively). This behavior strongly differs from that of the corresponding monoanionic dithiolene complexes whose oxidation afforded the single component neutral species. This provides additional rare examples of mixed-valence conducting salts of nickel diselenolene complexes, only known in two examples with the dsit (1,3-dithiole-2-thione-4,5-diselenolate) and dsise (1,3-dithiole-2-selone-4,5-diselenolate) ligands. The mixed-valence salts form highly dimerized or trimerized bi- and trimetallic units, rarely seen with such nickel complexes. Transport measurements under a high pressure (up to 10 GPa) and band structure calculations confirm the semiconducting character of [Ph 4 P][Ni(Me-thiazds) 2 ] 3 and the quasi metallic character of [Et 4 N][Ni(Me-thiazds) 2 ] 2 and [NBu 4 ] x [Ni(Me-thiazds) 2 ] 2 salts (0 < x < 1).