Gold (I) Complexes of 2,2'-Biimidazolate Ligand: Syntheses and Spectral Properties of Hetero-polymetallic Complexes Having Ru2Au2 Core

The reaction of [Ru(L)2(H2biim)](ClO4)2 [L1 = 2,2¢-bipyridine (bpy) or L2 =  2-(phenylazo)pyridine (pap) and H2biim = 2,2¢-biimidazole] with Au(tht)Cl (tht = tetrahydrothiophene) in presence of base in methanol produced a terametallic cationic complex [{Ru(L)2(biim)}2Au2]2+, [1]2+ which was isolated as its perchlorate salt. The compounds were characterized by various spectroscopic techniques. ESIMS data of these fully corroborate with their formulation. Spectral data of all the polymetallic systems are reported and compared. The redox properties of the complexes are interesting. The complex [{Ru(bpy)2(biim)}2Au2](ClO4)2 showed one irreversible metal based oxidation at 1.43 V whereas the compound [{Ru(pap)2(biim)}2Au2](ClO4)2 showed one irreversible ligand based oxidation at 1.34 V. This type of binding mode of the biimidazolate anion containing Ru2Au2 core is rare in the literature. ‘Metal complex as ligand’ strategy provides a platform for the synthesis novel polymetallic complexes of gold(I).