Mono- and polynuclear Ag(I) complexes of N-functionalized bis(diphenylphosphino)amine DPPA-type ligands: synthesis, solid-state structures and reactivity
Résumé
The reactivity of the N-functionalized DPPA-type ligands (Ph2P)2N(p-Z)C6H4 [Z = H (1a), SMe (1b), OMe (1c)] with AgBF4 was investigated and revealed an unexpected influence of the para substituent Z of the N-aryl ligand. In acetone, the mononuclear bis-chelated [Ag{(1a–1c)-P,P}2]BF4 (2a·BF4–2c·BF4) and dinuclear bridged [Ag2{μ2-(1a–1c)-P,P}2](BF4)2 [3a·(BF4)2–3c·(BF4)2] complexes were obtained with a 1 : 2 and 1 : 1 AgBF4/ligand molar ratio, respectively. While the molecular structures of 2a·BF4 and 2b·BF4 determined in the solid-state by X-ray diffraction revealed their mononuclear nature and the absence of cation/anion interaction, complexes 3b·(BF4)2 and 3c·(BF4)2 form 2D coordination polymers through intermolecular Ag–S or Ag–O interactions, respectively, involving the N-function of the respective DPPA-type ligand, and display direct interactions between one BF4 anion and both Ag(I) cations. Surprisingly, the equimolar reaction between ligands 1a–1c and AgBF4 in CH2Cl2 led to different proportions of the dinuclear complexes 3a·(BF4)2–3c·(BF4)2 and clusters [Ag3(μ3-Cl)2{μ2-(1b–1c)-P,P}3]BF4 (4b·BF4–4c·BF4), depending on the nature of the para substituent Z of the N-aryl ligand. The trinuclear complexes resulted from C–Cl bond activation of the chlorinated solvent and were characterized by NMR spectroscopy and X-ray diffraction, and could be selectively produced by addition of 2/3 equiv. of [NMe4]Cl to the corresponding dinuclear complexes or by a one-pot procedure involving the correct amount of each reagent. A series of experiments and kinetic NMR investigations were performed to gain further insight into the formation of the trinuclear Ag3Cl2 core clusters.