Reaction of Copper(II) Chloroacetate with Pyrazole. Synthesis of a One-Dimensional Coordination Polymer and Unexpected Dehydrochlorination Reaction

The reaction of copper(II) chloroacetate (1d) with pyrazole (Hpz) mainly yielded the mononuclear compound [Cu(mu-ClCH2COO)(2)(Hpz)(2)] (2m), which self-assembled generating a one-dimensional coordination polymer. Moreover, the concomitant isolation of the tetranuclear [{Cu-2(mu-pz)(mu-OCH2COO)(Hpz)(MeOH)}(2)(mu-ClCH2COO)(2)] (3t) and hexanudear [{Cu-3(mu-OH)(mu-pz)(3)(Hpz)(2)}(2)(mu-ClCH2COO)(2)](Cl)(2) (4h) species evidenced the occurrence of a peculiar, previously unreported, dehydrochlorination reaction and the formation of the trinuclear triangular moiety [Cu-3(mu(3)-OH)(mu-pz)(3)]. Theoretical calculations based on density functional theory including solvation effects indicate a possible pathway for the formation of 3t. Interestingly, besides the energy minimum corresponding to 3t, a further relative energy minimum is found for a species which can be considered a possible reaction intermediate.