Coordination polymers from mild condition reactions of copper(II) carboxylates with pyrazole (Hpz). Influence of carboxylate basicity on the self-assembly of the [Cu3(μ3-OH)(μ-pz)3]2+ secondary building unit

The reaction of some saturated and unsaturated aliphatic copper(II) monocarboxylates, Cu(RCOO)2 [R = C6H5CH2 (phenylacetate, Phac), CH2[dbnd]CHCH2 (vinylacetate, Vnac), C6H5CH[dbnd]CH (3-trans-phenylacrylate, Phacr), C6H5(CH2)2 (3-phenylpropionate, Phpr), c-C6H11 (ciclo–hexylcarboxylate, c-Hexc), CH3(CH2)10 (laurate, Lau), CH3(CH2)12 (myristate, Myr), (CH3)3C (pivalate, Piv)] with pyrazole (Hpz) and water in protic solvents, yielded trinuclear triangular derivatives based on the [Cu3(μ3-OH)(μ-pz)3] fragment whose double positive charge is balanced by two coordinated carboxylate ions, actually [Cu3(μ3-OH)(μ-pz)3(Phac)2], 1, [Cu3(μ3-OH)(μ-pz)3(Vnac)2(Hpz)], 2, [Cu3(μ3-OH)(μ-pz)3(Phacr)2], 3, [Cu3(μ3-OH)(μ-pz)3(Phpr)2(Hpz)Cu3(μ3-OH)(μ-pz)3(Phpr)2(Hpz)(H2O)]·xH2O·yMeOH, 4, [Cu3(μ3-OH)(μ-pz)3(c-Hexc)2], 5, [Cu3(μ3-OH)(μ-pz)3(Lau)2], 6, [Cu3(μ3-OH)(μ-pz)3(Myr)2], 7, [Cu3(μ3-OH)(μ-pz)3(Piv)2(HPz)(HPiv)2], 8. This behavior is consistent with some previously observed features and evidences that the basicity of carboxylate ions is the key for the deprotonation of Hpz and water, leading to the formation of pz− and OH− ions, which are determinant for the self-assembly of the trinuclear triangular species. Single crystal XRD determinations evidenced that in compounds 1, 2 and 5 the trinuclear moieties further self-assemble generating monodimensional coordination polymers or, in one case (compound 4), a dodecanuclear discrete assembly.