Single-crystal-to-single-crystal structural transformations of two sandwich-like Cu(ii) pyrazolate complexes and their excellent catalytic performances in MMA polymerization.

Reactions of Cu(OAc)(2)·H(2)O with dmnpzH in EtOH produce a heptanuclear copper(ii) pyrazolate complex [Cu(7)(OH)(2)(OAc)(6)(dmnpz)(6)(EtOH)(6)], which is able to undergo a SCSC structural transformation from a lower symmetry structure to a higher symmetry structure via replacement of ligated-EtOH molecules with MeOH; both complexes along with the solvent-free species exhibit high catalytic activity in the polymerization of MMA.