Trivalent Iron and Ruthenium Complexes with a Redox Noninnocent (2-Mercaptophenylimino)-methyl-4,6-di-<i>tert</i>-butylphenolate(2-) Ligand

The 3,5-di-tert-butyl substituted N-(salicylidene)-o-mercaptoaniline (H2L) ligand reacted with equimolar amounts of FeBr2 and 2 equiv of triethylamine in air affords [FeIII(L−L)Br]0 (1), where (L−L)2− is a pentacoordinate ligand formed from the oxidative dimerization of L2− via disulfide bridge formation. Reaction of H2L with RuCl3·H2O and NEt3 gives a dark green-brown dinuclear complex, [RuIII2(L)2Cl2(NCCH3)2]0 (2). Both complexes have been characterized by X-ray crystallography. A Ru−Ru single bond is evident in 2. Complex 1 has also been characterized by electron paramagnetic resonance and Mössbauer spectroscopies and magnetic susceptibility measurements that identify a high-spin Fe(III) (S = 5/2) center. Diamagnetic 2 is successively twice reversibly one-electron oxidized to produce [RuIII2(L•)(L)Cl2(NCCH3)2]+, [2]+ (S = 1/2), and [RuIII2(L•)2Cl2(NCCH3)2]2+, [2]2+ (S = 0). Spectroelectrochemical and electron paramagnetic resonance measurements identify these as ligand-based oxidations affording o-coordinated phenoxyl radicals. DFT calculations on the electron transfer series corroborate this result and that the Ru−Ru single bond is retained throughout this series.