Crystal structure of bis(methyltributylammonium) penta-μ-bromo-di-μ₅-bromo-pentacuprate(I), a compound containing a discrete [Cu₅Br₇]²⁻ aggregate

Abstract

The structure of the title compound has been determined from single-crystal X-ray diffraction data. [N(CH₃)(C₄H₉)₃]₂[Cu₅Br₇] crystallizes in space groupP¯1, witha=12.276(15),b=14.903(23),c=11.777(16) Å,α=105.1(1),β=95.0(1), γ=92.8(1)°, andZ=2. Full-matrix least-squares refinement of 361 structural parameters gaveR=0.067 for 3618 observed [I>3σ(I)] reflections, measured at 170 K. Bis(methyltributylammonium) penta-μ-bromo-di-μ ₅-bromo-pentacuprate(I) contains a discrete [Cu₅Br₇]²⁻ anion that can be described as a distorted pentagonal bipyramidal cage of bromide ions, containing copper(I) ions in tetrahedral holes, i.e., as being composed of five face-sharing Cu-Br tetrahedra. The coordination polyhedra associated with all five copper(I) centers are, however, severely distorted, a more adequate description of the copper(I) coordination in this anion thus being 2×(2+2) and 3×(3+1). Cu-Br distances range from 2.296(5) to 3.534(6) Å, and Cu⋯Cu contacts from 2.566(7) to 2.637(6) Å.