Synthesis, Structural Characterization, and Density Functional Study of Homo- and Heteropolyhalide Complexes of CuII with Dien and Dpta Ligands: Crystal Structure of [Bis(3-aminopropyl)amine](bromo)(diiodobromo)copper(II)

Polyhalide mononuclear [CuX(L)(XY2)] and dinuclear [{CuX(L)}2(μ‐XY2X)] CuII complexes [L = diethylenetriamine (dien) or dipropylenetriamine (dpta); X = Cl, Br and Y = Br, I] have been obtained by treating the precursor [CuX2(L)] complexes with Br2 or I2 in 1:1 and 2:1 molar ratios. The new homo‐ and heteropolyhalide CuII complexes, either mononuclear or dinuclear, were predicted to be five‐coordinate CuII complexes exhibiting a distorted square‐pyramidal configuration. DFT calculations at the B3LYP level of theory provided a satisfactory description of the structures of all complexes, while the distorted square‐pyramidal structure of a representative complex, namely [CuBr(dpta)(BrI2)], was further substantiated by a single‐crystal X‐ray diffraction study. In the square‐pyramidal structure of [CuBr(dpta)(BrI2)], the basal plane of the pyramid involves three Cu–N contacts [1.990(7), 2.065(7), and 1.989(7) Å] from dpta and the Br(1) atom, while Br(2), which participates in the formation of the terminal [BrI2]– ligand, occupies the apical position. The Cu–Br(1) and Cu–Br(2) bond lengths were found to be 2.5797(14) Å (terminal) and 2.735(14) Å (bridging), respectively, while the Br1–Cu–Br2 bond angle is 98.83(5)°. The terminal [BrI2]– ligand is almost linear [Br–I–I bond angle of 174.48(3)°]. DFT calculations, spectroscopic measurements, including far‐IR and EPR studies, and magnetic measurements of the dinuclear complexes predict that the bridging tetrahalide XY2X moiety adopts a linear configuration as well. The bonding, electronic, and related properties of the complexes are also discussed in the framework of density functional theory. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)