Ditopic tris(2-mercaptoimidazol-1-yl) borate ligands and their coordination behavior toward [Ru(p-cymene)]2+

The ditopic tris(2-mercaptoimidazol-1-yl) borate ligand K-2[(mt(Et))(3)B-B(mt(Et))(3)] cannot be prepared from B-2(NMe2)(4)/4 Hmt(Et)/2 Kmt(Et), because the stable intramolecular diadduct (mt(Et))B(mu-mt(Et))(2)B(mt(Et)) is generated instead (Hmt(Et) = 2-mercapto-1-ethylimidazole). Introduction of a meta-or para-phenylene spacer between the two boron atoms precludes the 2-mercaptoimidazol-1-yl groups from adopting a bridging position so that the potassium salts K-2[(mt(Et))(3)B-(m-C6H4)-B(mt(Et))(3)] and K-2[(mt(Et))(3)B-(p-C6H4)-B(mt(Et))(3)] become readily accessible. These ligands react with [(p-cym) RuCl2](2) to give the dinuclear Ru-II complexes [(p-cym) Ru(mt(Et))(3)B-(m-C6H4)-B(mt(Et))(3)Ru(p-cym)]Cl-2 and [(p-cym) Ru(mt(Et))(3)B-(p-C6H4)-B(mt(Et))(3)Ru(p-cym)] Cl-2 (p-cym = p-cymene). After the exchange of the Cl counterions for [PF6], both complexes have been crystallized and structurally characterized by X-ray diffraction. (C) 2011 Elsevier B. V. All rights reserved.