A new mixed valence copper complex Cu-II(Me(5)dien)Cl-2((CuCl)-Cl-I) (2) was obtained from the reaction of CuCl with Cu-II(Me(5)dien)Cl-2 (1) in acetonitrile. The structures of 1 and 2 have been determined by single-crystal X-ray diffraction analyses. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.374(5) Angstrom, b = 17.155(3) Angstrom, c = 23.806(5) Angstrom, beta = 94.40(4)degrees, Z = 8, and V = 3398(1) Angstrom(3) while compound 2 crystallizes in orthorhombic space group Pbcn with a = 14.71(1) Angstrom, b = 16.06(2) Angstrom, c = 13.38(1) Angstrom, Z = 8, and V = 3159(5) Angstrom. The Cu-II(Me(5)dien)Cl-2 unit in both compounds has a similar distorted square-pyramidal geometry. The (CuCl)-Cl-1 moiety in 2 is attached to the Cu-II unit via two bridging chlorine atoms and has a distorted trigonal planar geometry. UV-vis and EPR spectroscopic studies and molecular orbital calculations established the presence of significant perturbation of the (CuCl)-Cl-1 unit to the electronic structure of the Cu(II) ion in compound 2.