Formation of mono-, bi-, tri-, and tetranuclear Ag(I) complexes of C3-symmetric tripodal benzimidazole ligands

The C-3-symmetric tripodal ligand tris(2-benzimidazolylmethyl)amine (ntb) and its alkyl-substituted;dd derivatives tris(N-R-benzimidazol-2-ylmethyl)amine (R = methyl, Mentb; R = ethyl, Etntb; R = propyl, Pmtb) react with various silver(I) salts to afford mononuclear [AE(Pmtb)(CF3SO3)].0.25H(2)O, 1, binuclear [Ag-2(Mentb)(2)](CF3SO3)(2). H2O, 2, trinuclear [Ag-3(Etntb)(2)] (ClO4)(3). CH3OH, 3, and tetranuclear [Ag-4(ntb)(2)(CH3CN)(2)(CF3CO2)(2)] (CF3-CO2)(2). 2H(2)O, 4. All four complexes have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. The Ag(I) ion in 1 is coordinated to the three imine nitrogen atoms pf the Prntb ligand and one oxygen atom of the trifluoroinethanesulfonate anion in a distorted tetrahedral environment. Dinuclear 2 has C-2 symmetry with each Ag(I) atom trigonally coordinated by;two arms of one Mentb and one arm of another, Trinuclear 3 has C-3 symmetry with a Ag-3 regular triangle sandwiched between a pair of Etntb ligands such that one arm of each ligand is involved in linear coordination about an Ag(I) atom. in the tetranuclear complex 4, two linearly coordinated Ag(I) atoms lying on the molecular C-2 axis-are bridged by a pair of nth ligands and the remaining pendant arm of each ntb ligand;is attached to another Ag(I) atom whose tetrahedral coordination sphere is completed by an acetonitrile molecule and a chelating trifluoroacetate anion. Complexes 2 and 3 may be regarded as an aggregation of two tridentate ligands by a silver dimer and a trinuclear cluster with weak Ag Ag interactions, respectively, while in 4 the aggregation of two tripodal ligands by four Ag(I) ions affords a multicomponent internal cavity. The packing modes of complexes 1-3 are dominated by weak supramolecular pi . . . pi and CH . . . pi interactions. Hexagonal or square channels are generated in 1 and 2, and a honeycomb layer structure is formed in 3 with solvate molecules and counteranions occupying the voids. The crystal structure of 4 consists of a three-dimensional network consolidated by NH . . .O and OH . . .O hydrogen bonds.