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 K2[(mtEt)3B–B(mtEt)3] cannot be prepared from B2(NMe2)4/4 HmtEt/2 KmtEt, because the stable intramolecular diadduct (mtEt)B(μ-mtEt)2B(mtEt) is generated instead (HmtEt = 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 K2[(mtEt)3B-(m-C6H4)-B(mtEt)3] and K2[(mtEt)3B-(p-C6H4)-B(mtEt)3] become readily accessible. These ligands react with [(p-cym)RuCl2]2 to give the dinuclear RuII complexes [(p-cym)Ru(mtEt)3B-(m-C6H4)-B(mtEt)3Ru(p-cym)]Cl2 and [(p-cym)Ru(mtEt)3B-(p-C6H4)-B(mtEt)3Ru(p-cym)]Cl2 (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.