Manipulating Self-Assembly in Silver(I) Complexes of 1,3-Di-N-pyrazolylorganyls

A series of ligands with two pyrazolyls (pz) linked by either a propyl (pz(2)prop), a benzyl (pz(2)Bn or pzBnpz*, where Bn = benzyl and pz* = 3,5-dimethylpyrazolyl), or a 1,8-naphthyl (pz(2)naphth) spacer and their silver(I) tetrafluoroborate complexes have been prepared with the intent of evaluating how the conformational flexibility of the ligands would affect the supramolecular assembly of the 1:1 [Ag(ligand)](BF4) complexes and their capacity for promoting short Ag center dot center dot center dot Ag interactions. The noncoordinating nature of the tetrafluoroborate anion ensured low coordination numbers to the silver(I) centers, thereby allowing the metal ion to participate in multiple noncovalent interactions that dictate the ligand conformations and supramolecular isomerism observed in the solid state. In the solid state, the complex [Ag(CH3CN)(pz(2)prop)](BF4) forms a cyclic bimetallic cation that assembles into one-dimensional chains as a result of Ag-pi and CH center dot center dot center dot F noncovalent interactions, in a manner distinct from the known nitrate derivative. With [Ag(pz(2)Bn)](BF4), either cyclic bimetallic cations or coordination polymers can be formed depending on the solvents used for crystallization, where acetone promotes the formation of the former while acetonitrile gives the latter. The complex [Ag(pzBnpz*)](BF4) forms two different one-dimensional coordination polymers in the same flask during crystallization from acetone/Et2O, where the presence or absence of the included solvent dictates the differences in the secondary coordination sphere of (and noncovalent interactions involving) silver(I). In all the above cases, neighboring silver atoms are separated beyond van der Waals contact. In contrast, the complex [Ag(pz(2)naphth)](BF4)center dot 2CH(3)CN forms discrete cyclic bimetallic cations where the rigid ligand enforces a short (3.19 angstrom) Ag center dot center dot center dot Ag contact. All complexes are extensively dissociated in a CH3CN solution, as indicated from a combination of H-1 NMR and positive-ion electrospray ionization mass spectral data.