Synthesis, crystal structure and spectroscopic properties of trans-dibromidobis(2,2-dimethylpropane-1,3-diamine-κ(2)N,N')chromium(III) perchlorate.

The title complex salt, trans-anti-[CrBr2(Me2tn)2]ClO4 (where Me2tn = 2,2-dimethylpropane-1,3-diamine, C5H14N2), was prepared and its structure determined by single-crystal X-ray diffraction at 100 K. The asymmetric unit contains three conformationally similar complex cations and three perchlorate anions. In each complex cation, the Cr(III) centre is coordinated by four N atoms of two chelating Me2tn ligands in the equatorial plane and by two Br atoms in a trans-axial arrangement, to give a distorted octahedral geometry. Interionic contacts are dominated by extensive hydrogen bonding, involving the NH groups of the Me2tn ligand as donors and the anion O atoms or coordinated Br atoms as acceptors, resulting in two-dimensional layers in the bc plane. Ligand field analysis based on the angular overlap model, and IR and electronic spectroscopic properties, are also discussed.