A review on 1,1-bis(diphenylphosphino)methane bridged homo- and heterobimetallic complexes for anticancer applications: Synthesis, structure, and cytotoxicity

Herein, we review developments in synthesis, structure, and biological (anti-cancer) activities of 1,1-bis(diphenylphosphino)methane (dppm) bridged homo- and heterobimetallic systems of the type LmM(μ2-dppm)M’Ln (M and M′ are transition metals which may be different or the same and Ln,m are co-ligands) since the first such reported bimetallic system in 1987 until the present time (2020). As the simplest diphosphine, dppm enables facile formation of bimetallic complexes, where, given the short spacer between the PPh2 groups, close spatial proximity of the metal centres is ensured. We concentrate on complexes bearing no M–M interaction and contrast biological activities of these complexes with mononuclear counterparts and positive control agents such as cisplatin, in an attempt to elucidate patterns in the biological activities of these complexes.