(Bis{2-[3-(2,4,6-trimethylbenzyl)imidazolin-2-yliden-1-yl-κC 2]-4-methylphenyl}amido-κN)chloridopalladium(II)

The coordination geometry about the Pd centre in the title compound, [Pd(C40H42N5)Cl], is approximately square-planar. The CNC pincer-type N-heterocyclic carbene ligand binds to the Pd atom in a tridentate fashion by the amido N atom and the two carbene atoms and generates two six-membered chelate rings, completing the coordination.

The coordination geometry about the Pd centre in the title compound, [Pd(C 40 H 42 N 5 )Cl], is approximately square-planar. The CNC pincer-type N-heterocyclic carbene ligand binds to the Pd atom in a tridentate fashion by the amido N atom and the two carbene atoms and generates two six-membered chelate rings, completing the coordination.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: KJ2138).
the recently emerging PNP ligands with a diarylamido backbone have become attractive due to their unusual reactivity in activation of inert chemical bonds (Liang et al., 2003;Fan et al., 2004;Loch et al., 2002). Therefore, it is surprising to us that no pincer-type bis-NHC ligands based on a diarylamido backbone have been described. Guided by the explorations of the PNP ligand by Liang (Liang et al., 2003), we envisaged that replacement of phosphine arms in the ligand with NHCs would produce new CNC pincer-type ligands that may display useful properties for many challenging catalytic applications, especially for those requiring harsh reaction conditions. We reported the synthesis and catalytic activity of several new pincer-type NHC-Pd complexes (Wei et al., 2008). Though the title compound was synthesized previously by us, the crystal was obtained just recently by growing from dichloromethane and diethyl ether. The crystal structure of the title compound is present here for comparing it with the crystal structure of [bis(2-(3-benzylimidazolin-2-yliden-1-yl)-4methylphenyl)amido]\ chloropalladium(II) that has been reported earlier (Wei et al., 2008). It is obvious that there are some differences in the coordination geometries at Pd and in the dihedral angles between the two benzene rings of the diarylamido backone and those between the two NHC rings.
The molecular structure of the title compound is depicted in Figure 1. As expected, the monoanionic ligand is coordinated to palladium in a tridentate fashion by the amido nitrogen and the two carbene atoms, forming two six-membered chelate rings. The geometry about Pd is approximately square planar, with the C28-Pd-C11 angle of 170.1 (2)° and the N3-Pd-Cl1 angle of 177.98 (14)°. The two benzene rings of the diarylamido backone form a dihedral angle of 67.50 (16)°.
The dihedral angle of the two NHC rings is 80.72 (19)°. There is no H-bond observed in the crystal structure.
[PdCl 2 (MeCN) 2 ] (25.8 mg, 0.100 mmol) in CH 2 Cl 2 (3 ml) was added to the resulting solution and stirred at room temperature for 2 h. The reaction mixture was filtered and washed with CH 2 Cl 2 (10 ml). The combined solution was evaporated under reduced pressure to leave a raw product, which was purified by flash chromatography on silica gel (dichloromethane) to give a yellow solid. Yellow single crystals suitable for an X-ray diffraction study were obtained at ambient temperature by slow evaporation of dichloromethane and diethyl ether solution over a period of several days. supplementary materials sup-2 Refinement All H atom were positioned geometrically with C-H = 0.93, 0.96 and 0.97 Å for aromatic/imidazole, methyl and methylene H and refined using a riding model with displacement parameters of 1.5 U eq (C) for methyl and U iso (H) = 1.2 U eq (C, O) for others. Initial refinements showed the presence of a severely disordered diethylether solvent molecule. Since no satisfactory model could be obtained, the contribution of this disordered density to the final model was taken into account using the SQUEEZE procedure as incorporated in PLATON (Spek, 2009). Using this method we found a total number of 39.0, 36.9, 36.8 and 39.1 electrons in each of four symmetry-related cavities with a volume of 209.0, 208.9, 209.0 and 209.0 Å 3 , respectively. Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

Figures
Crystal data [Pd(C 40