Diacetonitrile[N,N′-bis(2,6-diisopropylphenyl)ethane-1,2-diimine]dichloridochromium(II) acetonitrile solvate

The title compound, [CrCl2(CH3CN)2(C26H36N2)]·CH3CN, was synthesized by the reaction of CrCl2(THF)2 with N,N′-bis(2,6-diisopropylphenyl)ethane-1,2-diimine in dichloromethane/acetonitrile. The chromium center is coordinated by two N atoms of the chelating diimine ligand, two chloride ions in a trans configuration with respect to each other, and by two N atoms of two acetonitrile molecules in a distorted octahedral geometry.

This work was supported by the Leibniz-Institut fü r Katalyse e. V. an der Universitä t Rostock.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: IM2148). Diacetonitrile[N, (Turki et al., 2006;Ghosh et al., 2008). Dimerization of isoprene (tom Dieck et al., 1979) and polymerization of ethene (Bart et al., 2004;Huang et al., 2007) are examples for catalytic investigations with this type of ligand. The shortest metal-metal bond at that time was observed in a dinuclear chromium complex with this ligand (Kreisel et al., 2007).
We became interested in chromium complexes with this ligand during our studies on the selective oligomerization of ethylene via transition-metal catalyzed tri-or tetramerization, yielding 1-hexene or 1-octene (Wöhl et al., 2009). Derived thereof we wanted to examine the N,N'-chelating ligand in combination with chromium in order to find differences and similarities in coordination and catalysis compared to other oligomerization systems. We deployed a simple preparation procedure that is described here, to obtain the complex for our screening experiments.
The molecular structure of the title compound shows that the chromium(II) center is coordinated by two N atoms of the chelating diazabutadiene ligand, (i-Pr) 2 C 6 H 3 -N═C(H)C(H)═N-C 6 H 3 (i-Pr) 2 , two chloride ions in trans-configuration with respect to each other and two acetonitrile molecules (Fig. 1). Its coordination geometry can be best described as distorted octahedral. Furthermore, the chelating ligand and the metal form a five-membered ring Cr(N═C-C═N), which is folded along the NN-axis by an angle of 162.5 (1)°. The asymmetric unit contains additionally one solvent molecule acetonitrile.

Refinement
The H atoms were placed in idealized positions with d(C-H) = 0.98 (CH 3 ) and 0.95-1.00 Å (CH) and refined using a riding model with U iso (H) fixed at 1.5 U eq (C) for CH 3 and 1.2 U eq (C) for CH. Fig. 1. The molecular structure of the title compound showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted for clarity. The asymmetric unit additionally contains one solvent molecule acetonitrile which is not shown.