Selective formation of a unique diphosphonium-diphosphine from a tetraphosphine double protonation induced by zirconium salts.

A mixed ferrocenyl diphosphonium-diphosphine cation, associated with two [ZrCl(5).thf](-) anions, is obtained from a ferrocenyl tetraphosphine, as a unique didentate ionic metalloligand in a perfectly selective reaction induced by ZrCl(4) in THF.