Crystal structure of tris(dimethylamido-κN)bis(dimethylamine-κN)zirconium(IV) iodide

The crystal structure of tris(dimethylamido)bis(dimethylamine) zirconium(IV) iodide is reported.


Chemical context
Zirconium amide complexes are widely used in the synthesis of other zirconium complexes and solid oxide fuel cells (SOFCs). Additionally, many zirconium amide complexes are precatalysts for hydroamination/cyclization of unactivated aminoalkenes (Luconi et al., 2013, Manna et al., 2013 andreferences therein). Perhaps one of the most well known zirconium amide complexes is tetrakis(dimethylamido)zirconium(IV). The title compound serendipitously formed from the reaction of an excess of tetrakis(dimethylamido)zirconium(IV) and a bis(imidazolium) salt that we routinely perform, as illustrated in the Scheme below.

Structural commentary
The zirconium complex has a slightly distorted trigonalbipyramidal geometry with three dimethamido ligands in equatorial positions and two dimethyamine ligands in axial positions (Fig. 1). Iodide provides a counterbalancing charge for the cationic zirconium complex. The Zr-amine bonds 2.3730 (13)

Supramolecular features
NÁ Á ÁI contacts of 3.6153 (15) and 3.5922 (14) Å are consistent with the presence of N-HÁ Á ÁI interactions ( Table 1). The 'twist' of the second dimethylamido ligand away from the first is consistent with interaction with a symmetry-related I À atom (H2-N2-N1-H1 À 114 ; Fig. 2). The N-HÁ Á ÁI interactions link the complex cations and iodide anions into extended chains that propagate parallel to the a axis.

Database survey
The synthesis or crystal structure of tris(dimethylamido)bis-(dimethylamine)zirconium(IV) iodide has not been reported as of 22 April 2015 based on a comprehensive WebCSD and Scifinder Scholar search. Similar compounds have been characterized crystallographically, for example tetrakis(dimethylamido)zirconium(IV) and its lithium dimethylamido adduct (Chisholm et al., 1988) and several more zirconium-amide iodide complexes (Lehn & Hoffman, 2002).

Synthesis and crystallization
1,3-Bis(3 0 -hexylimidazol-1 0 -yl)benzene diiodide (301 mg, 0.475 mmol), tetrakis(dimethylamido)zirconium(IV) (317 mg, 1.24 mmol) and dry toluene (2.8 mL) were combined in an inert atmosphere of Ar and heated at 383 K for 5 min in a sealed screw-cap vial. While heating, the reaction mixture became homogeneous. Upon cooling to room temperature, an oil formed. The top layer was removed and the oil was washed with toluene (3 Â 3 mL). The toluene washings were combined and allowed to sit at room temperature. Colorless crystals formed after 2 months. The mother liquor was decanted and the crystals were covered with paratone oil after using a few crystals for 1 H NMR spectroscopy. 1 H NMR spectra of the samples indicated that Displacement ellipsoid plot of the title compound. All hydrogens except the amine H atoms have been omitted for clarity. Ellipsoids are shown at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ). Symmetry code: (i) x À 1 2 ; Ày þ 3 2 ; Àz þ 1.

Figure 2
A packing plot of the unit cell viewed approximately down the b axis, illustrating the N-HÁ Á ÁI interactions (grey dotted lines). All hydrogen atoms except the amine H atoms have been omitted for clarity. Displacement ellipsoids are shown at the 50% probability level.
crystallized in the form of needles, which were not suitable for single-crystal X-ray diffraction. However, a suitable tabletshaped crystal of tris(dimethylamido)bis(dimethylammine)zirconium(IV) iodide was selected, mounted, and analyzed.

Special details
Experimental. wR2(int) was 0.0590 before and 0.0411 after absorption correction. The ratio of minimum to maximum transmission is 0.8806. The λ/2 correction factor is 0.00150. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.