rac-cis-Dicarbonylchlorido{1-[2-(diphenylphosphanyl-κP)benzyl]-3-(phenyl-κC 1)imidazol-2-ylidene-κC 2}ruthenium(II) dichloromethane monosolvate

In the title compound, [Ru(C28H22N2P)Cl(CO)2]·CH2Cl2, the RuII atom exhibits a distorted octahedral coordination geometry. The N-phenyl group of the ligand has undergone orthometalation; as a result, the tridentate phosphane-functionalized N-heterocyclic carbene ligand is coordinating in a meridional fashion. This complex is of interest with respect to transfer hydrogenation catalysis and also provides an example of C—H activation behavior in late transition metal complexes. The dichloromethane solvent molecule is disordered over two sets of sites with an occupancy ratio of 0.873 (14):0.127 (14).

In the title compound, [Ru(C 28 H 22 N 2 P)Cl(CO) 2 ]ÁCH 2 Cl 2 , the Ru II atom exhibits a distorted octahedral coordination geometry. The N-phenyl group of the ligand has undergone orthometalation; as a result, the tridentate phosphanefunctionalized N-heterocyclic carbene ligand is coordinating in a meridional fashion. This complex is of interest with respect to transfer hydrogenation catalysis and also provides an example of C-H activation behavior in late transition metal complexes. The dichloromethane solvent molecule is disordered over two sets of sites with an occupancy ratio of 0.873 (14):0.127 (14).

Related literature
For a review of transition metal catalysts supported by donorfunctionalized N-heterocyclic carbenes, see: Cavell & Normand (2008). For the first reported synthesis of the imidazolium chloride pro-ligand, see: Wang et al. (2005). For the structure of a similar molecule bearing an N-mesityl moiety that has not undergone orthometalation, see: Domski et al. (2012).

Experimental
Crystal data [Ru(C 28 Table 1 Selected bond lengths (Å ). to extensive overlapping of peaks in the aromatic regions. In order to establish the three-dimensional structure of this molecule we grew single crystals of the title complex and collected X-ray diffraction data. Upon solving the structure we were surprised to find that the N-phenyl moiety of the ligand had undergone orthometalation. While C-H activation by ruthenium(II) is not without precedent, we had not expected this to happen; it would have been difficult to elucidate this behavior without the aid of X-ray crystallography.
In the solid state, the geometry about ruthenium was distorted octahedral with a C(3)-Ru-C(11) bond angle of 77.79 (12)°. The Ru-carbonyl distances were inequivalent with the Ru-C(2) distance being 0.072 (0) Å longer than the Ru-C(1) distance; this observation is consistent with the stronger trans-influence of the NHC relative to chloride.

Experimental
Single crystals suitable for X-ray diffraction studies were grown by vapor diffusion of diethyl ether onto a saturated dichloromethane solution of the title compound.

Refinement
The preliminary model of the structure was obtained using XS, a direct methods program. Least-squares refining of the model versus. the data was performed with XL computer program. Illustrations were made with the XP program and tables were made with the XCIF program. All are in the SHELXTL v6.1 package. Thermal ellipsoids shown in the illustrations are at the 50% level unless otherwise noted. All non-hydrogen atoms were refined with anisotropic thermal parameters. A disordered dichloromethane molecule is included in the structure. The relative occupancy refined to 0.873 (14):0.127 (14). The two disorder sites were restrained to have the same conformation, Uaniso(C51)=Uaniso(C51′).
The anisotropic displacement parameters were restrained with the rigid body(DELU) restraint and the similarity (SIMU) restraint. All H atoms were included with the riding model using the XL program default values. No further restraints or constraints were imposed on the refinement model.

Figure 1
The molecular structure of the title complex with ellipsoids drawn at the 50% probability level. Hydrogen atoms and a dichloromethane molecule of crystallization were omitted for clarity.

rac-cis-Dicarbonylchlorido{1-[2-(diphenylphosphanyl-κP)benzyl]-3-(phenyl-κC 1 )imidazol-2-ylidene-
Special details Experimental. The title compound was prepared by allowing 1-phenyl-3-(2-diphenylphosphinobenzyl)-1H-imidazol-3ium chloride (0.4997 g) (Wang et al., 2005) to react with Ag 2 O (0.2502 g) in dry, degassed dichloromethane under a nitrogen atmosphere in the absence of light; 4 Å molecular sieves (approximately 0.5 g) were added to the mixture at the beginning of the reaction. After 24 h, the reaction mixture was filtered through Celite TM under an atmosphere of nitrogen into a flask containing [Ru(CO) 3 Cl 2 ] 2 (0.1340 g); the reaction mixture was allowed to stir for 24 h in the dark. After stirring overnight, the reaction mixture was filtered through Celite TM under an atmosphere of dry nitrogen and all volatiles were removed in vacuo. The solid residue was purified via column chromatography (SiO 2 , 40:1 CH 2 Cl 2 /MeOH) to furnish a yellow solid. Single crystals of the title compound were grown by dissolving the crude product in the minimum amount of dichloromethane and allowing diethyl ether to slowly evaporate, condense, and diffuse into the dichloromethane solution. 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. Several low angle reflections were omitted from the final cycles of refinement due to beam-stop shadowing effects. A disordered dichloromethane molecule is included in the structure. The relative occupancy refined to 0.873 (14):0.127 (14). The two disorder sites were restrained to have the same conformation, Uaniso(C41)=Uaniso(C41′). The anisotropic displacement parameters were restrained with the rigid body restraint and the simu restraint.

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