Trinuclear, Antiferromagnetically Coupled Cu^II Complex with an EPR Spectrum of Mononuclear Cu^II: Effect of Alcoholic Solvents

A rigid trinuclear copper pyrazolato framework supports the solvolytic exchange of μ3-X by μ3-OR ligands (X = Cl and Br; R = alkyl group), converting the trinuclear ferromagnetically coupled S = 3/2 system to antiferromagnetically coupled S = 1/2 in the solid state. In contrast, we propose that, in alcoholic solutions, solvolysis results in unsymmetrical coordination of the Cu3 cluster, magnetically decoupling one Cu center from the other two. This disguises the intact triangular CuII3 system as a mononuclear CuII complex in its electron paramagnetic resonance spectrum.