(η6-Benzophenone)(η5-pentamethylcyclopentadienyl)ruthenium(II) tetraphenylborate

The structure of the title compound, [Ru(C10H15)(C13H10O)](C24H20B), consists of discrete [Cp*Ru(II)benzophenone] cations and tetraphenylborate anions (Cp* = pentamethylcyclopentadienyl). Tethering the Cp*Ru group to one aryl ring of benzophenone results in average values of 1.42 (1) and 1.38 (1) Å for the C—C bond lengths in the Ru-tethered and untethered phenyl rings, respectively. The dihedral angle between the benzene and phenyl rings of the benzophenone group is 50.5 (1)°.


Experimental
Crystal data [Ru(C 10   The compound crystallizes as discrete cations and anions (Fig. 1). No significant C-H···O interactions are observed between the phenyl and methyl protons and the ketone oxygen. The dihedral angle between the two aryl rings of the benzophenone is 50.5 (1)° and comparable to the value of 53.75 (6)° reported for the parent monoclinic benzophenone (Moncol & Coppens, 2004). The Ru-C bond lengths in the cation are also similar to those reported for other [Cp*Ru(arene)] + complexes (Gemel et al., 1996;Loughrey et al., 2008). The average value of 1.42 (1)Å for the C-C bond lengths in the Ru tethered phenyl ring (C11-C16) is 0.04Å longer than the average value of 1.38 (1)Å observed for the free phenyl ring (C18-C23), the latter being marginally shorter than the value of 1.392 (5)Å for the parent benzophenone.

Experimental
Benzophenone (0.8 g, 4.39 mmol) and HCp* (0.3 ml, 1.88 mmol) were added to a solution of ruthenium trichloride hydrate (0.20 g, 0.76 mmol) in ethanol (20 ml) under argon. The resulting solution was heated under reflux conditions for a period of 10 h to yield a golden brown coloured solution. The solvent was concentrated in vacuo with the remaining residue being redissolved in an ether/water partition (20 ml/20 ml). The aqueous portion was retained and washed with a further three aliquots of diethyl ether (20 ml). The aqueous layer was mixed slowly with an aqueous solution of sodium tetraphenylborate (5 ml, 0.30 M). The resulting cream coloured precipitate was filtered from solution and redissolved in a minimum quantity of acetone. This solution was filtered through a short alumina column (neutral, 150 mesh) using acetone as the eluent. The solution was concentrated in vacuo and the product recrystallized through addition of a minimum quantity of cold water. The resulting crystalline precipitate was then filtered from solution and dried in vacuo. Yield = 0.273 g, 48.7%. Crystals suitable for X-ray diffraction studies were grown by slow diffusion of diethyl ether into a solution of the compound in acetone.

Refinement
H atoms attached to carbon were constrained as riding atoms, with C-H set to 0.94-96 Å. U iso (H) values were set to 1.2U eq (aromatic) and 1.5U eq (alkyl) of the parent atom. Fig. 1. The asymmetric unit of (I), with atom labels and 40% probability displacement ellipsoids for the non-H atoms.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.