Ionothermal synthesis and crystal structure of a new organic-inorganic hybrid compound: catena-poly[bis(1-ethyl-3-methylimidazolium) [hepta-μ-bromido-pentacuprate(I)]]

A new organic-inorganic hybrid compound, catena-poly[bis(1-ethyl-3-methylimidazolium) [mu(5)-bromido-tri-mu(3)-bromido-tri-mu(2)-bromido-pentacuprate(I)]], {(C6H11N2)(2)[Cu5Br7]}(n), has been obtained under ionothermal conditions from a reaction mixture containing Ba(OH)(2)center dot 8H(2)O, Cu(OH)(2)center dot 2H(2)O, As2O5, 1-ethyl-3-methylimidazolium bromide and distilled water. The crystal structure consists of complex [Cu5Br7](2-) anions arranged in sinusoidal {[Cu5Br7](2-)}(n) chains running along the a axis, which are surrounded by 1-ethyl-3-methylimidazolium cations. Three of the five unique Br atoms and one of the three Cu-I atoms occupy special positions with half-occupancy (a mirror plane perpendicular to the b axis, site symmetry m). The Cu-I ions are in a distorted tetrahedral coordination environment, with four Br atoms at distances ranging from 2.3667 (10) to 2.6197 (13) angstrom, and an outlier at 3.0283 (12) angstrom, exceptionally elongated and with a small contribution to the bond-valence sum of only 6.7%. Short C-H center dot center dot center dot Br contacts build up a three-dimensional network. The Cu center dot center dot center dot Cu distances within the chain range from 2.8390 (12) to 3.0805 (17) angstrom, indicating the existence of weak Cu-I center dot center dot center dot Cu-I cuprophilic interactions.