Halogen-bonded network of trinuclear copper(II) 4-iodopyrazolate complexes formed by mutual breakdown of chloroform and nanojars

Crystals of bis(tetrabutylammonium) di-mu(3)-chlorido-tris(mu(2)-4-iodopyrazolato-kappa N-2:N')tris[chloridocuprate(II)] 1,4-dioxane hemisolvate, (C16H36N)(2)[Cu-3(C3H2-IN2)(3)Cl-5]center dot 0.5C(4)H(8)O or (Bu4N)(2)[Cu-3(II)(mu(3)-Cl)(2)(mu-4-I-pz)(3)Cl-3]center dot 0.5C(4)H(8)O, were obtained by evaporating a solution of (Bu4N)(2)[{Cu-II(mu-OH)(mu-4-I-pz)}(n)CO3] (n = 27-31) nanojars in chloroform/1,4-dioxane. The decomposition of chloroform in the presence of oxygen and moisture provides HCl, which leads to the breakdown of nanojars to the title trinuclear copper(II) pyrazolate complex, and possibly Cu-II ions and free 4-iodopyrazole. Cu-II ions, in turn, act as catalyst for the accelerated decomposition of chloroform, ultimately leading to the complete breakdown of nanojars. The crystal structure presented here provides the first structural description of a trinuclear copper(II) pyrazolate complex with iodine substituted pyrazoles. In contrast to related trinuclear complexes based on differently substituted 4-R-pyrazoles (R = H, Cl, Br, Me), the [Cu-3(mu-4-I-pz)(3)Cl-3] core in the title complex is nearly planar. This difference is likely a result of the presence of the iodine substituent, which provides a unique, novel feature in copper pyrazolate chemistry. Thus, the iodine atoms form halogen bonds with the terminal chlorido ligands of the surrounding complexes [mean length of I center dot center dot center dot Cl contacts = 3.48 (1) angstrom], leading to an extended two-dimensional, halogen-bonded network along ((1) over bar 10). The cavities within this framework are filled by centrosymmetric 1,4-dioxane solvent molecules, which create further bridges via C-H center dot center dot center dot Cl hydrogen bonds with terminal chlorido ligands of the trinuclear complex not involved in halogen bonding.