(η6-Benzene)dichlorido(dicyclohexylphenylphosphane)ruthenium(II) benzene sesquisolvate

The asymmetric unit of the title compound, [RuCl2(C6H6)(C18H27P)]·1.5C6H6, contains one molecule of the RuII complex and one and a half solvent molecules as one of these is located about a centre of inversion. The RuII atom has a classical three-legged piano-stool environment being coordinated by an η6-benzene ligand [Ru—centroid = 1.6964 (6) Å], two chloride ligands with an average Ru—Cl bond length of 2.4138 (3) Å and a dicyclohexylphenylphosphane ligand [Ru—P = 2.3786 (3) Å]. The effective cone angle for the phosphane was calculated to be 158°. In the crystal, weak C—H⋯Cl hydrogen bonds link the RuII complexes into centrosymmetric dimers. The crystal packing exhibits intra- and intermolecular C—H⋯π interactions resulting in a zigzag pattern in the [101] direction.

The asymmetric unit of the title compound, [RuCl 2 (C 6 H 6 )-(C 18 H 27 P)]Á1.5C 6 H 6 , contains one molecule of the Ru II complex and one and a half solvent molecules as one of these is located about a centre of inversion. The Ru II atom has a classical three-legged piano-stool environment being coordinated by an 6 -benzene ligand [Ru-centroid = 1.6964 (6) Å ], two chloride ligands with an average Ru-Cl bond length of 2.4138 (3) Å and a dicyclohexylphenylphosphane ligand [Ru-P = 2.3786 (3) Å ]. The effective cone angle for the phosphane was calculated to be 158 . In the crystal, weak C-HÁ Á ÁCl hydrogen bonds link the Ru II complexes into centrosymmetric dimers. The crystal packing exhibits intraand intermolecular C-HÁ Á Á interactions resulting in a zigzag pattern in the [101] direction.
Cg1 and Cg2 are the centroids of the C19-C24 and C31-C33/C31 0 -C33 0 ) benzene rings. The activity of the half-sandwich Ru(II)-arene complexes are well known in the catalytic transfer hydrogenation of carbonyl compounds (Chen et al., 2002;Crochet et al., 2003;Aydemir et al., 2011;Wang et al., 2011) and for ringopening metathesis polymerization (Stumpf et al., 1995). Reported here is the η 6 -Ru compound containing the phosphane, PCy 2 Ph, where Cy = C 6 H 11 and Ph = C 6 H 5 as part of our ongoing structural investigation into these type of complexes.
The title compound crystallizes in the triclinic space group P1 (Z=2), with its molecules adopting a classical threelegged piano-stool environment observed for these type of complexes. Each Ru complex co-crystallizes with sesqui benzene solvate molecules due to one of the solvate being situated on an inversion centre (see Fig. 1). The coordination sphere of the ruthenium is occupied by a benzene, dicyclohexylphenylphosphane and two chloride atoms. The distance between Ru and the centroid of the π-bonded η 6 -benzene ligand is 1.6964 (6) Å and the mean Ru-C bond distance is 2.2099 (13) Å. The coordination of the remaining ligands to the Ru atom shows a slight deviation from the typical octahedral geometry with Cl-Ru-Cl = 88.07 (11) and Cl-Ru-P = 87.12 (11), 90.97 (2)°. The bond distances of Ru-P = 2.3786 (3) and Ru-Cl(avg.) = 2.4138 (3) Å are within normal ranges (Allen, 2002).
The steric demand of phosphane ligands is usually described with the use of the Tolman cone angle model (Tolman, 1977). In the present study we make use of an adaptation of this model whereby the geometry obtained from the title compound (and adjusting the Ru-P bond distance to 2.28 Å) is used to calculate an effective cone angle (Otto, 2001).
The value obtained with this method is 158°, which is marginally smaller that the average effective cone angle value calculated from literature observations of the phosphane ligand. Data extracted from the Cambridge Structural Database (Allen, 2002) shows an average cone angle of 165° for the phosphane from 31 hits, containing 45 useable observations with a standard deviation of ±6° and a spread from 148° to 180°.
The slightly smaller cone angle value obtained for the phosphane ligand in the title compound could be due to a crowded metal coordination environment as well as several C-H···Cl and C-H···π interactions that are observed (see Fig.   2, Table 1 for a graphical representation of the interactions).

Experimental
[(C 6 H 6 )RuCl 2 ] 2 (50.0 mg, 0.10 mmol) and dicyclohexylphenylphosphane (60.2 mg, 0.22 mmol) in benzene (25 ml) were refluxed under argon for 4 h. The resulting red solution was cooled and filtered to obtain the title complex as orange needles suitable for a single-crystal X-ray study.

Refinement
The aromatic, methine and methylene H atoms were placed in geometrically idealized positions (C-H = 0.95-1.00) and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (C).

Figure 1
A view of the title complex, showing the atom-numbering scheme and 50% probability displacement ellipsoids. Accented lettering indicate atoms generated by symmetry code: 1 -x,1 -y,1 -z.  Packing diagram showing the C-H···Cl/π interactions (indicated by red dashed lines). Special details Experimental. The intensity data was collected on a Bruker Apex DUO 4 K CCD diffractometer using an exposure time of 10 s/frame. A total of 3975 frames were collected with a frame width of 0.5° covering up to θ = 28.39° with 99.8% completeness accomplished. 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.