Crystal structure of (η4-cyclooctadiene)(3,3′-dimesityl-1,1′-methylenediimidazoline-2,2′-diylidene)nickel(0) tetrahydrofuran monosolvate

The complex at 100 K has monoclinic (P21/c) symmetry and a distorted tetrahedral geometry around the nickel center, with the cyclooctadiene ligand coordinated in a κ2,η2 fashion. The bidentate NHC ligand is not planar, with a C(carbene)—Ni—C(carbene) angle of 91.51 (12)°, resulting in the mesityl groups being on the same side of the cyclooctadiene (COD) ligand.


Supramolecular features
Four molecules of ( Mes NHC 2 Me)Ni(COD) and THF are present in the unit cell, as depicted in Fig. 3. The molecules are oriented such that the COD ligands from neighboring molecules are adjacent to each other, with distances of 2.61 and 2.95 Å between nearest hydrogen atoms (H28AÁ Á ÁH32A and H27BÁ Á ÁH31B, respectively). Standard deviations for distances including hydrogen atoms are not listed because hydrogen atoms were positionally fixed. The methyl group at the para position of the mesityl fragment is oriented towards the aryl ring of the mesityl of the neighboring molecule, with a distance of 2.72 Å between the aryl ring centroid (C8-C13) and the nearest methyl hydrogen atom (H15C). The THF molecule is closest to the backbone of the ( Mes NHC 2 Me) ligand, such that the molecules are 3.527 (17)   View of one molecule of ( Mes NHC 2 Me)Ni(COD) with 50% probability ellipsoids. The THF molecules and H atoms are omitted for clarity.  View of ( Mes NHC 2 Me)Ni(COD)ÁTHF with 50% probability ellipsoids, showing the THF disorder.

Database survey
A survey of the Cambridge Structural Database (Web accessed August 9, 2018; Groom et al., 2016) and SciFinder (SciFinder, 2018) yielded no exact matches for this complex, but related complexes with slightly varied ligands, such as ( tBu NHC 2 Me)Ni(COD) (tBu = tert-butyl) and ( Dipp NHC 2-Me)Ni(COD) (Dipp = 2,6-di(isopropyl)phenyl) (Brendel et al., 2014) have been reported. The crystal structures of both these complexes have generally similar structural characteristics. The main difference is that the COD ligand in ( tBu NHC 2 Me)Ni(COD) is coordinated in a 1 , 2 fashion.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Most hydrogen atoms were placed in calculated positions using the AFIX commands of SHELXL and refined as riding with distances of 0.95 Å for C-H, 0.99 Å for CH 2 and 0.98 Å for CH 3 . Methyl H atoms were allowed to rotate but not to tip to best fit the experimental electron density. U iso values of riding H atoms were set to 1.2 times U eq (C) for CH and CH 2 , and 1.5 times U eq (C) for CH 3 . The positions of the hydrogen atoms on the portions of the COD ligand directly bound to nickel and attached to C26, C29, C30, and C33 were determined from the difference map.
Positions and isotropic displacement parameters were refined, but the associated C-H atom distances were restrained to be similar to each other by using a SADI command of SHELXL (for C26-H26A, C29-H29A, C30-H30A, and C33-H33A). The two moieties of the disordered THF molecule were restrained to have similar geometries (a SAME command in SHELXL was applied for O1 0 through C37 0 and O1 through C34 to make bond distances and angles equivalent with standard deviations of 0.02 and 0.04 Å for 1,2-and 1,3 distances, respectively). U ij components of ADPs of the disordered atoms were restrained to be similar to each other with an esd of 0.01 Å 2 for atoms closer to each other than 2.0 Å (SIMU command of SHELXL), resulting in a final close-to-equal site occupancy ratio of 0.502 (13) to 0.498 (13).  Data collection: APEX3 (Bruker, 2017); cell refinement: SAINT (Bruker, 2017); data reduction: SAINT (Bruker, 2017); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (