Bis-triphenylphosphonio-isophosphindolide salts 1[X] react with Cu(I)-halides CuX to give isolable products of composition [(1)Cu2X3 ]. X-ray crystal structure analyses confirmed that for X = Br, Cl dinuclear complexes [(μ-1 )(μ-X)Cu2X2] with μ2, η1(P)-bridging cations 1 are formed, while for X = I a solid phase containing a salt (1)2[Cu4I6] and a complex [(1)2Cu4I6] with a terminal η1(P)-coordinated ligand 1 was obtained. The bonding parameters in the two types of complexes suggest that l i s a hybrid between a phosphenium cation and a phospholide anion whose π-system is less nucleophilic than the phosphorus lone-pair.31P NMR studies revealed that in solution in all cases binuclear complexes [(1)Cu2X3] are in dynamic equilibrium with small amounts of mononuclear species and free 1. The same equilibria were detected in the system 1[OTf]/CuOTf. NMR studies of ligand exchange reactions indicated that the stability of complexes [(1)Cu2X3 ] increases in the order X = OTf < I < Br, Cl, and titration of [(1)Cu2Br3] with Et4NBr allowed to determine the equilibrium constant of the complex formation reaction.