The Molecular and Electronic Structure of the Electron Transfer Series [Fe₂(NO)₂(S₂C₂R₂)₃]<i>^z</i> (<i>z</i> = 0, −1, −2; R = phenyl, <i>p</i>-tolyl, <i>p</i>-<i>tert</i>-butylphenyl)^†

Three dinuclear (nitrosyl)iron complexes containing three 1,2-di(phenyl)ethylene-1,2-dithiolate ligands have been prepared ([Fe2(NO)2(S2C2R2)3]0 (R = phenyl, 1a; p-tolyl, 2a; (4-tert-butyl)phenyl, 3a)). Each of these compounds represents the first member of a three-membered electron-transfer series: [Fe2(NO)2(S2C2R2)3]z (z = 0, −1, , −2). The salt [Co(Cp)2][Fe2(NO)2(L3)3] has also been isolated. The molecular structures of 2a and 3a have been determined by X-ray crystallography. Both neutral complexes contain two nearly linear FeNO units, one of which is S,S‘-coordinated to two dithiolene ligands yielding a square-based pyramidal Fe(NO)S4 polyhedron; the second FeNO moiety forms two (μ2-S)-bridges to the first unit and is S,S‘-coordinated to a third dithiolate radical yielding also a square-based pyramidal Fe(NO)S4 polyhedron. The electronic structures of the neutral, monoanionic, and dianionic species have been elucidated spectroscopically (UV−vis, IR, EPR, Mössbauer): [{FeII(NO+)}(L•){FeII(ṄO)}(L)2]0 (S = 0); [{FeII(ṄO)}(L•){FeII(ṄO)}(L)2]1- (S = 1/2); and [{FeII(ṄO)}(L){FeII(ṄO)}(L)2]2- (S = 0), where (L)2- represents the corresponding closed-shell dithiolate dianion and (L•)- is its monoanionic radical.