Reduction of Disulfides with Magnesium(II) and Gallium(II) Complexes of a Redox‐Active Diimine Ligand

Abstract

Abstract The reactions of (dpp‐bian)Mg(thf) 3 ( 1 ) {dpp‐bian = 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene} with 0.5 molar equivalents of RS–SR (R = Bz, s Bu, C(S)NMe 2 ) occur with a cleavage of the S–S bond to afford monosulfide complexes (dpp‐bian)Mg(SBz)(dme) ( 2 ), (dpp‐bian)Mg[S( s Bu)](dme) ( 3 ), and (dpp‐bian)Mg[SC(S)NMe 2 ](thf) ( 4 ). Compounds 2 , 3 , and 4 are paramagnetic due to the presence of dpp‐bian radical‐anions that are formed in the course of one‐electron transfer from the dpp‐bian dianion in 1 to the sulfur‐containing substrate. Reduction of BzS–SBz with gallane (dpp‐bian)Ga–Ga(dpp‐bian) ( 5 ) gives a mononuclear Ga III complex with the dpp‐bian radical‐anion, (dpp‐bian)Ga(SBz) 2 ( 6 ). The reaction of 5 with RS–SR (R = C(S)NMe 2 ) proceeds with a cleavage of the S–S and Ga–Ga bonds and affords (dpp‐bian)Ga[SC(S)NMe 2 ] ( 7 ), in which the dpp‐bian ligand retains its dianionic state. Complexes 2 , 3 , 4 , and 6 have been characterized by ESR and IR spectroscopy, and complex 7 has been studied by 1 H MNR spectroscopy. The molecular structures of 2 – 4 , 6 , and 7 have been determined by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)