Dinuclear Bis(1,2-diaryl-1,2-ethylenedithiolato)iron Complexes: [Fe<sup>III</sup><sub>2</sub>(L)<sub>4</sub>]<i><sup>n</sup></i><sup></sup> (<i>n</i> = 2−, 1−, 0, 1+)
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The electronic structures of four members of the electron-transfer series [Fe2(1L)4]n (n = 2−, 1−, 0, 1+) have been elucidated in some detail by electronic absorption, IR, X-band electron paramagnetic resonance (EPR), and Mössbauer spectroscopies where (1L)2- represents the ligand 1,2-bis(4-tert-butylphenyl)-1,2-ethylenedithiolate(2−) and (1L•)- is its π-radical monoanion. It is conclusively shown that all redox processes are ligand-centered and that high-valent iron(IV) is not accessible. The following complexes have been synthesized: [FeIII2(1L•)2(1L)2]0 (1), [FeIII2(2L•)2(2L)2]·2CH2Cl2 (1‘) where (2L)2- is 1,2-bis(p-tolyl)-1,2-ethylenedithiolate(2−) and (2L•)- represents its π-radical monoanion, [Cp2Co][FeIII2(1L•)(1L)3]·4(toluene)·0.5Et2O (2), and [Cp2Co]2[FeIII2(1L)4]·2(toluene) (3). The crystal structures of 1‘ and 2 have been determined by single-crystal X-ray crystallography at 100 K. The ground states of complexes have been determined by temperature-dependent magnetic susceptibility measurements and EPR spectroscopy: 1‘ and 1 are diamagnetic (St = 0); 2 (St = 1/2); 3 (St = 0); the monocation [FeIII2(1L•)3(1L)]+ possesses an St = 1/2 ground state (St = total spin ground state of dinuclear species). All species contain pairs of intermediate-spin ferric ions (SFe = 3/2), which are strongly antiferromagnetically coupled (H = −2JS1·S2, where S1 = S2 = 3/2 and J = ∼−250 cm-1).
