Molecular and Electronic Structures of Iron Complexes Containing N,S-Coordinated, Open-Shell o-Iminothionebenzosemiquinonate(1−) π Radicals

The reaction of the dinuclear species (μ-NH,NH)[FeIII(LIP)(LAP)]2 dissolved in CH2Cl2 with dioxygen affords black microcrystals of diamagnetic (μ-S,S)[FeIII(LIP)(LISQ)]2·n-hexane (6) upon the addition of n-hexane, where (LIP)2- represents the dianion of 4,6-di-tert-butyl-2-aminothiophenol, (LAP)- is the corresponding monoanion, and (LISQ)- is the corresponding o-iminothionebenzosemiquinonate(1−) π radical monoanion; similarly, the dianion (‘H2N2S2‘)2- is derived from 1,2-ethanediamine-N,N‘-bis(2-benzenethiol), and (‘N2S2‘)3- is its monoradical trianion. The above reaction in a CH2Cl2/CH3OH (1:1) mixture yields the diamagnetic isomer (μ-NH,NH)[FeIII(LIP)(LISQ)]2·5CH3OH (7), whereas air oxidation of (μ-S,S)[FeII(‘H2N2S2‘)]2 in CH3CN yields diamagnetic (μ-S,S)[FeIII(‘N2S2‘)]2 (8). Complexes 6 and 8 were shown to undergo addition reactions with phosphines, phosphites, or cyanide affording the following complexes:  trans-[FeII(LISQ)2(P(OPh)3)] (9; St = 0) and [N(n-Bu)4][FeII(LISQ)2(CN)] (St = 0). Oxidation of 6 in CH2Cl2 with iodine, bromine, and chlorine respectively yields black microcrystals of [FeIII(LISQ)2X] (X = I, Br, or Cl) with St = 1/2. The structures of complexes 69 have been determined by X-ray crystallography at 100 K. The oxidation level of the ligands and iron ions in all complexes has been unequivocally established, as indicated by crystallography; electron paramagnetic resonance, UV−vis, and Mössbauer spectroscopies; and magnetic-susceptibility measurements. The N,S-coordinated o-iminothionebenzosemiquinonate(1−) π radicals have been identified in all new complexes. The electronic structures of the new complexes have been determined, and it is shown that no evidence for iron oxidation states >III is found in this chemistry.