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(μ-ClCH 2 COO) 2 (Hpz) 2 ] ( 2m ), which self-assembled generating a one-dimensional coordination polymer. Moreover, the concomitant isolation of the tetranuclear [{Cu 2 (μ-pz)(μ-OCH 2 COO)(Hpz)(MeOH)} 2 (μ-ClCH 2 COO) 2 ] ( 3t ) and hexanuclear [{Cu 3 (μ 3 -OH)(μ-pz) 3 (Hpz) 2 } 2 (μ-ClCH 2 COO) 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 (μ 3 -OH)(μ-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.