Titanium(IV) Complexes of Disulfide-Linked Schiff Bases

With the goal of preparing Ti­(IV) complexes bearing a sulfur-based redox function of possible use in electrocatalytic oxidations of alcohols at electrode surfaces, a series of seven 2,2′-dithiodianiline Schiff-base derivatives, including two new variations, were tested in reactions with Ti­(OR)4 (R = iPr, tBu). Instead of the expected dimetallic products of general formula [LTi­(OR)2]2, mononuclear species LTi­(OR)2 were obtained, confirmed by crystallographic determinations to have an unprecedented, symmetrical, and macrocyclic arrangement with four-point binding to the metal center and with the disulfide moieties remaining uncoordinated. Cyclic voltammetry performed in CH2Cl2 displayed oxidations at potentials useful for fuel cells (+1.1–1.5 V vs Ag/AgCl), but despite the uncoordinated disulfide moieties, the complexes were reticent to engage in reduction processes.