Iminophosphorane-based synthesis of multinuclear ferrocenyl urea, thiourea and guanidine derivatives and exploration of their anion sensing properties

One-flask preparation of bisferrocenyl-substituted urea and thiourea and trisferrocenyl-substituted guanidine have been achieved from the iminophosphorane derived from ferrocenemethyl azide by using aza-Wittig reactions with carbon dioxide and carbon disulfide. Electrochemical studies indicate that there is no electronic communications between the peripheral ferrocene units and only one reversible redox wave is observed, which underwent a remarkable cathodic shift (ΔE1/2=100–170 mV) in the presence of dihydrogenphosphate anion.