Diverse Ag(I) complexes constructed from asymmetric pyridyl and pyrimidyl amide ligands: roles of Ag•••Ag and π-π interactions

Reactions of silver(I) salts with the isomeric pyridyl amide ligands methyl-4-(pyridin-2-ylcarbamoyl) benzoate (L-1), methyl-4-(pyridin-3-ylcarbamoyl) benzoate (L-2) and methyl-4-(pyridin-4-ylcarbamoyl) benzoate (L-3) and the pyrimidyl amide ligand methyl-4-(pyrimidin-2-ylcarbamoyl) benzoate (L-4) afforded the complexes Ag-4(L-1)(4)(NO3)(4), 1, [Ag(L-2)(2)][Ag(NO3)(2)], 2, [Ag(L-2)(2)](ClO4), 3, [Ag(L-2)(2)](ClO4)center dot 2CH(3)CN, 4, [Ag(L-3)(2)](NO3), 5, [Ag(L-3)(2)](ClO4)center dot CH3CN, 6, and [Ag(L-4)(2)](X) (X = ClO4-, 7; BF4-, 8; PF6-, 9), which were structurally characterized by X-ray crystallography. The L-1-L-3 ligands in 1-6 adopt monodentate bonding modes, which coordinate to the metal centers through the pyridyl nitrogen atoms, whereas the L-4 ligands of 7-9 adopt a bidentate mode, featuring chelation through one pyrimidyl nitrogen atom and the amide oxygen atom. All nine complexes adopt discrete structures with 1 being tetranuclear and 2-9 being mononuclear. Moreover, Ag center dot center dot center dot Ag short contacts, pi center dot center dot center dot pi stacking interactions and/or Ag center dot center dot center dot O interactions are found in these complexes which extend the dimensionalities of the structures. The changes of the donor atom positions and counteranions significantly affect the supramolecular structures of these complexes and the L-1-L-4 ligands are sufficiently flexible to adopt the cis and/or trans conformations.