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 (micro2-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, M?ssbauer): [[FeII(NO+)](L*)[FeII(NO)](L)2]0 (S = 0); [[FeII(NO)](L*)[FeII(NO)](L)2]1- (S = 1/2); and [[FeII(NO)](L)[FeII(NO)](L)2]2- (S = 0), where (L)2- represents the corresponding closed-shell dithiolate dianion and (L*)- is its monoanionic radical.
Crystallography, X-Ray Electron Spin Resonance Spectroscopy