Comparative Structural Studies of Ni vs. Au Metal Bis‐dithiolene Complexes with a Thiazole Backbone [M(R‐thiazdt)₂]

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

“…This Bu 4 N + salt is isostructural with the Et 4 N + one, but the limited increase of the unit cell volume (from 971 to 1016 Å 3 ) indicates a sub-stoichiometry in the Bu 4 N + cation, hence the formulation [Bu 4 N] x [Ni­(Me-thiazds) 2 ] 2 with 0 < x < 1 (see below for details). The obtention of mixed-valence salts comes here in strong contrast with N -ethyl dithiolene and diselenolene, [Ni­(Et-thiazdt) 2 ] 0 and [Ni­(Et-thiazds) 2 ] 0 , as well as N -methyl dithiolene [Ni­(Me-thiazdt) 2 ] 0 , all isolated as neutral, single-component species. ,, …”

“…Then, through electrochemical oxidation, the neutral species are most often isolated as single-component molecular conductors, either with nickel as the closed shell species [Ni­(R-thiazdt) 2 ] 0 or with gold as radical complexes [Au­(R-thiazdt) 2 ] • . Such neutral Ni bis­(dithiolene) complexes exhibit, given their closed shell nature, semi-conducting behavior for [Ni­(R-thiazdt)] (R = Me, Et, and Pr). , We previously showed, however, that [Ni­(Et-thiazdt) 2 ] 0 (R = Et) turns metallic under pressure in the low temperature range when the pressure reaches 4.4 GPa and in the whole temperature range for pressures above 6.9 GPa . In the gold series, we have shown that the presence of a substituent smaller than the ethyl one on the ligand allowed us to go from a Mott insulator material for [Au­(Et-thiazdt) 2 ] • to a metallic system for [Au­(Me-thiazdt) 2 ] • .…”