Silver(I) complexes of fixed, polytopic bis(pyrazolyl)methane ligands: Influence of ligand geometry on the formation of discrete metallacycles and coordination polymers

Reactions of the arene-linked bis(pyrazolyl) methane ligands m-bis[bis(1-pyrazolyl)methyl]benzene, (m-[CH(pz)(2)](2)C6H4, L-m), p-bis[bis(1-pyrazolyl)methyl]benzene, (p-[CH(pz)(2)](2)C6H4, L-p), and 1,3,5-tris[bis(1-pyrazolyl)methyl] benzene (1,3,5- CH(pz)(2)](3)C6H3, L-3) with AgX salts (pz = 1-pyrazolyl; X = BF4- or PF6-) yield two types of molecular motifs depending on the arrangement of the ligating sites about the central arene ring. Reactions of the m-phenylene-linked L-m with AgBF4 and AgPF6 afford complexes consisting of discrete, metallacyclic dications: [Ag-2(mu-L-m)(2)]- BF4)(2) (1) and [Ag-2(mu-L-m)(2)](PF6)(2) (2). When the p-phenylene-linked L-p is treated with AgBF4 and AgPF6, acyclic, cationic coordination polymers are obtained: {[Ag(mu-L-p)]BF4}(infinity) (3) and {[Ag(mu-L-p)]PF6}(infinity) (4). Reaction of the ligand L-3, containing three bis( pyrazolyl) methane units in a meta arrangement, with an equimolar amount of AgBF4 again yields discrete metallacyclic dications in which one bis( pyrazolyl) methane unit on each ligand remains unbound: [Ag-2(mu-L-3)(2)](BF4)(2) (5). Treatment of L-3 with an excess of AgBF4 affords a polymer of metallacycles, {[Ag-3(mu-L-3)(2)]- BF4)(3)}(infinity) (6), with one of the bis( pyrazolyl) methane units on each ligand bound to a silver cation bridging two metallacycles. The supramolecular structures of the silver(I) complexes 1-6 are organized by noncovalent interactions, including weak hydrogen bonding, pi-pi, and anion-pi interactions.