Investigation of Structural Transformation of a Chain-like Silver(I) Pyrazolate into a Triangular Isomer

Four silver(I) pyrazolato complexes, namely, [Ag(mdnpz)](n), [(Ag(mdnpz)(NCCH3)](n), [Ag(mdnpz)](3)center dot 2.5H(2)O, and [Ag(mdnpz)](3)center dot C7H8, were synthesized and structurally characterized by single-crystal X-ray diffraction, where mdnpz- denotes 4-methyl-3,5-dinitro-pyrazolate and C7H8 stands for toluene. The chain-like [Ag(mdnpz)](n) can be prepared by mixing 4-methyl-3,5-dinitro-pyrazole and AgNO3 in methanol. [(Ag(mdnpz)(NCCH3)](n), adopting a helical chain structure, was isolated from an acetonitrile solution of [Ag(mdnpz)](n), which may be a key intermediate in the structural transformation. The triangular species can be obtained as adducts with water or toluene from the aforementioned CH3CN solution. On the basis of the experimental observations, crystal structures, mass spectrum, and theoretical investigation, the isomeric transformation can be described as a solvent-assisted, acid-base interaction promoted, thermodynamically favored process.