Crystal structure of {3-[3,5-bis(2,6-dimethylphenyl)-1,2-phenylene]-1-(2,6,2′′,6′′-tetramethyl-1,1′:3′,1′′-terphenyl-5′-yl)imidazol-2-ylidene}chlorido(η6-p-cymene)ruthenium(II) benzene disolvate

The title compound, [Ru(C47H43N2)Cl(C10H14)]·2C6H6, crystallized with two independent molecules of benzene. One of the N-aryl moieties of the N-heterocyclic carbene (NHC) ligand underwent cyclometallation to form a five-membered ruthenacycle. The complex has a three-legged piano-stool structure with two C atoms incorporated in the five-membered ruthenacycle and a Cl atom as legs. The ruthenacycle is essentially coplanar with the imidazole ring of the NHC ligand, making a dihedral angle of 0.85 (8)°.


S1. Comment
Transition metal complexes bearing N-heterocyclic carbene (NHC) ligands have been broadly utilized in the catalytic reactions. It has been known that the catalytic performance largely depends on not only the electronic property of the ligand but also steric environment around the metal center. Since these properties can be tuned with changing the substituents on the nitrogen atoms and the carbene ring, a variety of NHCs have been synthesized. In the course of our studies on development of cavity-shaped ligands, we have reported an NHC based on a m-phenylene dendrimer framework and its palladium complexes (Yamashita et al., 2005). Herein, the crystal structure of a ruthenium(II) complex bearing the cavity-shaped NHC is reported, where an aromatic ring on the nitrogen of the NHC ligand underwent cyclometallation to form a five-membered ruthenacycle. Related ruthenacycles bearing an NHC ligand have been reported in the literatures (Hong et al., 2007;Karabıyık et al., 2008;Zhang et al., 2009).
The title compound was synthesized by the reaction of dichloro-(p-cymene)-ruthenium(II) dimer with 1,3-bis(2,2",6,6"tetramethyl-m-terphenyl-5′-yl)imidazol-2-ylidene. The molecular structure of the title compound is shown in Fig. 1. It was found that one of N-aryl moieties underwent cyclometallation to form a ruthenacycle, which is almost coplanar with the imidazole ring. The bond length of Ru-C(carbene) is 2.0163 (15) Å, which is slightly shorter than that of Ru-

S2. Experimental
In a dry box under an argon atmosphere, dichloro-(p-cymeme)-ruthenium(II) (36.3 mg, 0.0593 mmol) was added to a solution of 1,3-bis(2,2",6,6"-tetramethyl-m-terphenyl-5′-yl)imidazol-2-ylidene (75.5 mg, 0.119 mmol) in benzene (1 ml) at room temperature. After the reaction mixture was stirred for 1 h at room temperature, the solution was evaporated in vacuo to afford orange solids, which was put out from the dry box. To the solids was added benzene, and the resulting mixture was subjected to centrifugal separation, and the supernatant was evaporated in vacuo. The resulting orange solids were separated by silica gel chromatography (hexane:ethyl acetate = 3:1) to afford the title compound (66.2 mg, 0.0731 mmol, 61%). Single crystals suitable for X-ray diffraction were obtained by recrystallization from a benzene/hexane solution.

S3. Refinement
H atoms were treated as riding with C-H = 0.95-1.00 Å and with U iso (H) = 1.2 (1.5 for methyl groups) times U eq (C).  The asymmetric unit of the title compound with 50% probability displacement ellipsoids (arbitrary spheres for H atoms).
Special details 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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.