Counter-anion role in the formation of two supramolecular complexes: [Ag₂(DPP)₂](ClO₄)₂·CH₃CN and [Ag₂(DPP)₂(NO₃)₂] {DPP isN-[(diphenylphosphanyl)methyl]pyridin-4-amine}

Abstract

The title compounds, bis{μ-N-[(diphenylphosphanyl)methyl]pyridin-4-amine-κ(2)N(1):P}disilver bis(perchlorate) acetonitrile monosolvate, [Ag2(C18H17N2P)2](ClO4)2·CH3CN, (1), and bis{μ-N-[(diphenylphosphanyl)methyl]pyridin-4-amine-κ(2)N(1):P}bis[(nitrato-κ(2)O,O)silver], [Ag2(C18H17N2P)2(NO3)2], (2), each contain disilver macrocyclic [Ag2(C18H17N2P)2](2+) cations lying about inversion centres. The cations are constructed by two N-[(diphenylphosphanyl)methyl]pyridin-4-amine (DPP) ligands linking two Ag(+) cations in a head-to-tail fashion. In (1), the unique Ag(+) cation has a near-linear coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands. Two ClO4(-) anions doubly bridge two metallomacrocycles through Ag···O and N-H···O weak interactions to form a chain extending in the c direction. The half-occupancy acetonitrile molecule lies with its methyl C atom on a twofold axis and makes a weak N···Ag contact. In (2), there are two independent [Ag(C18H17N2P)](+) cations. The nitrate anions weakly chelate to each Ag(+) cation, leading to each Ag(+) cation having a distorted tetrahedral coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands, and two chelating nitrate O atoms. Each dinuclear [Ag2(C18H17N2P)2(NO3)2] molecule acts as a four-node to bridge four adjacent equivalent molecules through N-H···O interactions, forming a two-dimensional sheet parallel to the bc plane. Each sheet contains dinuclear molecules involving just Ag1 or Ag2 and these two types of sheet are stacked in an alternating fashion. The sheets containing Ag1 all lie near x = 1/2, 3/2, 5/2 etc, while those containing Ag2 all lie near x = 0, 1, 2 etc. Thus, the two independent sheets are arranged in an alternating sequence at x = 0, 1/2, 1, 3/2 etc. These two different supramolecular structures result from the different geometric conformations of the templating anions which direct the self-assembly of the cations and anions.