Cu(I) and Ag(I) complexes of chalcogenide derivatives of the organometallic ligand dppf and the dppa analogue

New Cu(I) and Ag(I) complexes were prepared by reaction of [M(NCCH3)4][X] (M = Cu or Ag; X = BF4 or PF6) with the bidentate chalcogenide ligands Ph2P(E)NHP(E)Ph2 (E = S, S2dppa; E = Se, Se2dppa), and dpspf (1,1′-bis(diphenylselenophosphoryl)ferrocene). Copper and silver behaved differently. While three molecules of either S2dppa and Se2dppa bind to a distorted tetrahedral Cu4 cluster, with deprotonation of the ligand, 1:2 complexes of the neutral ligands are formed with Ag(I), with a tetrahedral coordination of the metal. The [Cu4{Ph2P(Se)NP(Se)Ph2}3]+ clusters assemble as dimers, held together by weak Se⋯Se distances interactions. Another dimer was observed for the [Ag(dpspf)]+ cation, with two short Ag⋯Se distances. DFT and MP2 calculations indicated the presence of attracting interactions, reflected in positive Mayer indices (MI). The electrochemistry study of this species showed that both oxidation and reduction took place at silver.