Synthesis and ligand properties towards gold and silver of the ferrocenylamidobenzimidazole ligand

The treatment of FcCOCl (Fc = (C5H5)Fe(C5H4)) with aminobenzimidazole in 1:1 or 2:1 ratio gives the ferrocenyl-amido derivatives FcCO(benzimNH2) or (FcCO)2(NHbenzim), respectively. The reactivity of FcCO(benzimNH2) with silver or gold complexes has been studied. The reaction with the basic gold compounds [Au(acac)(PPh3)] or [O(AuPPh3)3]ClO4 occurs with deprotonation of the NH2 group and coordination of one or three gold(phosphine) fragments. The treatment of this ligand with silver compounds, such as Ag(OTf) or [Ag(OTf)(PPh3)], gives the complexes of stoichiometry [Ag(OTf)L] or [Ag(OTf)(PPh3)L]. The ligand FcCO(benzimNH2) and the complex [Ag(OTf){FcCO(benzimNH2)}(PPh3)] have been characterized by X-ray diffraction studies. DFT calculations were performed on models of this dimeric silver complex and showed that dimerization is energetically favourable, because Ag(I) achieves a four coordination environment, despite some bonds being relatively weak.