Trivalent iron and ruthenium complexes with a redox noninnocent (2-mercaptophenylimino)-methyl-4,6-di-tert-butylphenolate(2-) ligand.

The 3,5-di-tert-butyl substituted N-(salicylidene)-o-mercaptoaniline (H(2)L) ligand reacted with equimolar amounts of FeBr(2) and 2 equiv of triethylamine in air affords [Fe(III)(L-L)Br](0) (1), where (L-L)(2-) is a pentacoordinate ligand formed from the oxidative dimerization of L(2-) via disulfide bridge formation. Reaction of H(2)L with RuCl(3) x H(2)O and NEt(3) gives a dark green-brown dinuclear complex, [Ru(III)(2)(L)(2)Cl(2)(NCCH(3))(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 Mossbauer 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 [Ru(III)(2)(L(*))(L)Cl(2)(NCCH(3))(2)](+), [2](+) (S = (1)/(2)), and [Ru(III)(2)(L(*))(2)Cl(2)(NCCH(3))(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.