Synthesis, structure, and electronic and EPR spectra of copper(II) complexes containing the [CuBr4]2- anion and triphenylarsine oxide

Article abstract of DOI:10.1021/ic00036a012

The preparation and characterization of (Ph₃AsOH)₂[CuBr₄] and [Cu(Ph₃AsO)₄][CuBr₄] are reported (Ph₃AsO = triphenylarsine oxide). Crystallographic analysis of the monoclinic crystals of (Ph₃AsOH)₂[CuBr₄] (space group C2/c, a = 17.569 (3) ?, b = 13.090 (2) ?, c = 16.933 (2) ?, and β = 105.64 (2)°, R = 0.055 and R_w = 0.057) revealed the presence of compressed [CuBr₄]^2- tetrahedra of C₂ symmetry with Cu-Br distances of 2.340 (1) and 2.437 (1) ? and trans-Br-Cu-Br angles of 139.2 (1) and 122.4 (1)°. The oxonium cations hydrogen bond to the bromine atoms involved in the longer Cu-Br bonds and the smaller trans-Br-Cu-Br angle. Single-crystal electronic and EPR spectra are interpreted in terms of the observed [CuBr₄]^2- geometry. Analysis of the electronic and EPR spectra of [Cu(Ph₃AsO)₄][CuBr₄] led to the postulation of the presence of planar [Cu(Ph₃AsO)₄]²⁺ cations and distorted tetrahedral [CuBr₄]^2- anions.