Tricarbonylrhenium(I) Complexes of Dinucleating Redox-Active Pincer Ligands

Abstract

Two homobimetallic tricarbonylrhenium(I) complexes of new redox-active dinucleating pincer ligands have been prepared to assess the impact of spacer size on the first oxidation potentials with respect to mononucleating analogues and on intramolecular electronic communication. The new pincer ligands feature two tridentate NNN- sites each composed of two pyrazolyl flanking donors and a diarylamido anchor that are either directly linked (to form a central benzidene core, H2(L1)) or linked via a para-phenylene group (to form a para-terphenyldiamine core, H2(L2)). The bimetallic complexes of the deprotonated ligands, [fac-Re(CO)3]2(μ-L1), 1, and [fac-Re(CO)3]2(μ-L2), 2, were fully characterized in solution and the solid state including by single-crystal X-ray diffraction for 1. The electrochemical properties of each depended strongly on solvent and electrolyte. Complex 1 exhibits two one-electron oxidations in all electrolyte-containing solutions but with separations between first and second oxidation potentia...