[M(R-dmet)2] Bis(1,2-dithiolenes): a Promising New Class Intermediate between [M(dmit)2] and [M(R,R'-timdt)2] (M = Ni, Pd, Pt)

We report the first examples of metal dithiolenes belonging to the class [M(R-dmet)2] [R-dmet ) formally monoreduced N-substituted thiazolidine-2,4,5-trithione; R ) Et, M ) Ni (1), Pd (2), Pt (3)]. A comparative spectroscopic, electrochemical, and density functional theory theoretical investigation indicates that [M(R-dmet)2] complexes show features intermediate between those of the dithiolenes belonging to the previously reported classes [M(R,R¢-timdt)2] and [M(dmit)2] (R,R¢-timdt ) formally monoreduced N,N¢-disubstituted imidazolidine-2,4,5-trithione; dmit ) 2-thioxo-1,3-dithiole-4,5-dithiolato). UV-vis-near-IR spectroscopy and cyclic voltammetry/ differential pulsed voltammetry measurements performed on 1 and 3 proved that the new dithiolenes are stable as neutral, monoanionic, and bianionic species and feature a near-IR electrochromic absorption falling at about 1000 and 1250 nm for neutral and monoanionic species, respectively.