Crystal structure and spectroscopic properties of bis[trans-dichlorobis(2,2-dimethylpropane-1,3-diamine)chromium(III)] tetrachlorozincate

The structure of trans-[Cr(Me(2)tn)(2)Cl(2)](2)ZnCl(4) (Me(2)tn = 2,2-dimethylpropane-1,3-diamine) was determined by a single-crystal X-ray diffraction study at 173 K. The analysis reveals that there are three crystallographically independent chromium(III) complex cations in the title compound. The chromium(III) atoms are coordinated by four nitrogen atoms of Me(2)tn and two chlorine atoms in a trans arrangement, displaying a distorted octahedral geometry. The two six-membered chelate rings in three complex cations are oriented in an anti chair-chair conformation with respect to each other. The Cr-N and Cr-Cl bond lengths average 2.0862(2) and 2.3112(6) angstrom, respectively. The ZnCl(4)(2) have slightly distorted tetrahedral arrangement with Zn-Cl lengths and the Cl-Zn-Cl angles are influenced by hydrogen bonding. The resolved absorption maxima in the electronic d-d spectrum were fitted with a secular determinant for a quartet energy state of the d(3) configuration in a tetragonal field. It is confirmed that the nitrogen atoms of the Me(2)tn ligand are strong sigma donors, but the chloro ligands have weak sigma- and pi donor properties toward the chromium(III) ion.