(η6-Benzene)dichlorido(chlorodicyclohexylphosphane-κP)ruthenium(II) chloroform monosolvate

The title compound, [RuCl2(η6-C6H6)(C12H22ClP)]·CHCl3, was prepared by reaction of [RuCl2(η6-C6H6)]2 with chlorodicyclohexylphosphane in CHCl3 at 323 K under argon. The RuII atom is surrounded by one arene ligand, two Cl atoms and a phosphane ligand in a piano-stool geometry. The phosphane ligand is linked by the P atom, with an Ru—P bond length of 2.3247 (4) Å. Both cyclohexyl rings at the P atom adopt a chair conformation. In the crystal, the RuII complex molecule and the chloroform solvent molecule are linked by a bifurcated C—H⋯(Cl,Cl) hydrogen bond. Intramolecular C—H⋯Cl hydrogen bonds are also observed.

Supporting information for this paper is available from the IUCr electronic archives (Reference: IS5363).

Comment
The half-sandwich (η 6 -C 6 H 6 )-dichlorido(chlorodicyclohexylphosphane)ruthenium(II) complex was formed by reaction of one equivalent of [RuCl 2 (η 6 -C 6 H 6 )] 2 with two equivalents of (Cy 2 P(1-naphthoyl)) ligand under hydrogenation conditions (CHCl 3 , 60 bar of H 2 , 353 K, 3 hrs) as a side product. The cleavage of the 1-naphthoyl group from [RuCl 2 (η 6 -C 6 H 6 ) (Cy 2 P(1-naphthoyl)] complex forms firstly [RuCl 2 (η 6 -C 6 H 6 )(Cy 2 PH)] and subsequent chlorination of the dicyclohexylphosphane unit due to CHCl 3 yields the title compound in poor yield. Additionally, we could not observe any trace amount of title compound by using non-chlorinated solvents such as MeOH. The substitution of hydrogen next to phosphane by chlorine coming from solvent molecules is also described for the formation of a Ru-complex with the related chlorodiphenylphosphane ligand by Torres-Lubián et al. (1999). More specifically, the title complex was formed by reaction of [RuCl 2 (η 6 -C 6 H 6 )] 2 with chlorodicyclohexylphosphane in CHCl 3 at 323 K under argon in 41% yield.
Crystals suitable for X-ray crystal structure analysis could be obtained by crystallization from a chloroform/heptane mixture. In the 31 P NMR spectrum of the complex the signal for the phosphorus was observed at 156.3 p.p.m., whereas free ligand signal appears at 128.8 p.p.m.. The title compound shows the three legged piano-stool geometry at the ruthenium centre with the arene, chlorodicyclohexylphosphane and two chlorine ligands in the coordination sphere ( Fig.   1). The phosphane ligand is linked by the phosphorus with a Ru-P bond length of 2.3247 (4) Å. Both cyclohexyl rings at the phosphorus atom adopt a chair conformation. The Ru complex is co-crystallized with CHCl 3 .

Experimental
A 50 ml round bottom flask with inert gas valve was charged with 0.05 mmol (25 mg) [RuCl 2 (η 6 -C 6 H 6 )] 2 and 4 ml CHCl 3 under argon atmosphere. To this suspension 0.105 mmol (21 µL) chlorodicyclohexylphosphane was added and the reaction mixture was allowed to react 3 h at 323 K. A clear red brown solution has been formed and the volume was reduced carefully in high vacuum to ca 1 ml. Next 20 ml heptane was added to the reaction mixture and cooled for 1 h with ice bath. The precipitate was washed with heptane (3 × 5 ml) to yield the title compound as an orange brown solid (20 mg, 41%). Red single crystals were grown in CHCl 3 /heptane mixture at 245 K for 1 day. 1 H NMR (300 MHz),

Refinement
H atoms were placed in idealized positions with C-H = 0.95-1.00 Å (CH), 0.99 Å (CH 2 ) and refined using a riding model with U iso (H) fixed at 1.2U eq (C).  The molecular structure of the title compound with 30% displacement ellipsoids. Hydrogen atoms are omitted for clarity.  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.