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Crystal Structure and Spectroscopic Properties of Bis[trans-dichlorobis(2,2-dimethylpropane-1,3-diamine)chromium(III)] Tetrachlorozincate


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The structure of trans-[Cr(Me2tn)2Cl2]2ZnCl4 (Me2tn = 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 Me2tn 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) Å, respectively. The ZnCl42– 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 d3 configuration in a tetragonal field. It is confirmed that the nitrogen atoms of the Me2tn ligand are strong σ donors, but the chloro ligands have weak σ- and π donor properties toward the chromium(III) ion.