Structures of silver pyrazolates in hydrocarbon solutions via vapor-pressure osmometry

Molecular weights of {3,5-(CF 3) 2Pz]Ag} 3, {3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, and {3,5-( i-Pr) 2Pz]Ag} 3 at various solution concentrations have been investigated using vapor-pressure osmometry. Depending on the concentration, the trinuclear {3,5-(CF 3) 2Pz]Ag} 3 either dissociates into mono- and dinuclear moieties or remains trinuclear or aggregates to hexanuclear species in toluene. In contrast, {3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, which has a bulky and relatively electron-rich pyrazolate, retains the trinuclear form even at low concentrations in toluene. Both {3,5-(CF 3) 2Pz]Ag} 3 and {3,5-( i-Pr) 2Pz]Ag} 3 adopt trinuclear structures in heptane at low concentrations. At higher concentrations, {3,5-( i-Pr) 2Pz]Ag} 3 forms hexanuclear species. The aggregation-segregation points are rather sharp and are reminiscent of the all-or-none character of phase transitions. Remarkably, at higher concentrations, the aggregation states of these silver pyrazolates are similar to those expected based on solid-state data.