A mixed valence Cu(I)/Cu(II) chain compound: crystal structure of 1,4,8,11-tetraazacyclotetradecane copper(II) tribromocuprate(I)

The essentially anaerobic reaction of CuBr2 and 14ane-N-4 in water/acetone solvent (14ane-N-4 =1,4,8,11-tetraazacyclotetradecane) yields a mixed valen ce Cu(I)/Cu(II) compound. The compound is orthorhombic, space group Pcnn, w ith a = 23.6310(1) Angstrom, b = 23.6429(2) Angstrom, c = 12.4537(1) Angstr om and V = 6957.95(9) Angstrom (3) with Z = 16, for rho (calc) = 2.349 g/cc . Refinement of a twinned crystal with 8,504 unique reflections yielded fin al values of R-1 = 0.0725 (\F\ > 2 sigma) and wR(2) = 0.114 and a goodness of fit of 1.448. The compound contains chains of Cu(14ane-N-4)(2+) cations and CuBa32- anions, which are linked together by long semicoordinate Cu(II) Br bonds. The chains run perpendicular to the c axis and are arranged in l ayers in which the chains alternately run parallel to the (1 1 0) and to th r (1 -1 0) crystal directions. The Cu(II) ion is coordinated by the tetrade ntate macrocycle to yield an approximate square planar coordination. The Cu Br32- anions have a nearly trigonal planar with Cu-Br(ave) = 2.38(1) Angstr om.