Reaction of copper(l) chloride and bromide, CuX (X = Cl or Br), with triphenylarsine in acetonitrile solution has resulted in two adducts, respectively, of 2:11, [(Ph3As)(2)Cu(mu-Cl)(2)Cu(AsPh3)(NCMe)] (1), and 1:1:2 stoichiometry, [(Ph3As)(MeCN)Cu(mu-Br)(2)Cu(NCMe)(AsPh3)] (.) 2MeCN (2), characterized by elemental analysis, IR, ESI MS and NMR spectroscopy, and room temperature single crystal X-ray structure determinations. The environments of the two four-coordinate copper(l) atoms in 1 are different, being As2Cu(mu-Cl)(2) and As,NCu(mu-Cl)(2). (2) is also binuclear, being a centrosymmetric dimer with the two four-coordinate, symmetry-related copper atoms having As,NCu(mu-Br)(2)-environments. (c) 2005 Elsevier B.V. All rights reserved.