Crystal Structure and Spectroscopic Properties of trans-Dibromobis(1,2-ethanediamine)chromium(III) Perchlorate.

The crystal structure of trans-[Cr(en)2Br2]ClO4 (en = 1,2-ethanediamine) has been determined by a single-crystal X-ray diffraction study at 150 K. The complex crystallizes in the space group $$ P\overline{1} $$ of the triclinic system with two mononuclear formula units in a cell of dimensions a = 6.853(4), b = 8.109(5), c = 12.475(8) Å, α = 81.006(10)° , β = 77.005(10)° and γ = 74.981(10)°. The Cr atom is in a slightly distorted octahedral environment, coordinated by four nitrogen atoms of two en ligands and two bromine atoms in trans axial positions. The mean Cr–N(en) and Cr–Br bond lengths are 2.079(3) and 2.4743(10)Å, respectively. The five-membered rings are in stable gauche conformations with N1–Cr1–N2 and N3–Cr2–N4 angles of 82.81(11)° and 83.67(11)°, respectively. The crystal packing is stabilized by a network of N–H···O and N–H···Br hydrogen bonds. The infrared and electronic absorption spectra are consistent with the results of X-ray crystallography. The spectroscopic properties of the title complex are in good agreement with the result of X-ray crystallography, which shows that the chromium atom is in an octahedral environment, coordinated by two bidentate 1,2-ethanediamine ligands and two bromine atoms in trans positions.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]