1,1′-(4,4′-Bipiperidine-1,1′-diyl)bis(2,2,2-trifluoroethanone)

The title compound, C14H18F6N2O2, has a central center of symmetry with both piperidine rings occurring in regular chair conformations. Even though the structure is fairly compact with no sizable voids, the shortest H⋯O distance is as long as 2.58 Å.

The title compound, C 14 H 18 F 6 N 2 O 2 , has a central center of symmetry with both piperidine rings occurring in regular chair conformations. Even though the structure is fairly compact with no sizable voids, the shortest HÁ Á ÁO distance is as long as 2.58 Å .
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG5179).

Experimental
The compound (I) was prepared by the procedure reported for piperidine by Schenck et al. (2004). The 4,4'-bipiperidyl dihydrochloride (0.5 g, 2.07 mmol) and triethyl amine (1.2 ml, 8.6 mmol) mixed together at 0 °C in 20 ml of dry diethyl ether, stirred the mixture for 10 min. and added trifluoro acetic anhydride (0.61 ml, 4.3 mmol) dropwise, continued stirring at room temperature for 3 h., added 1 ml of 2M HCl and stirred for 10 min., filtered the solid residue and washed with fresh diethyl ether.
The highly stable X-ray quality crystals were obtained by slow evaporation of dichloromethane. A rather large specimen (maximum dimension 1.00 mm) was used for data collection to get high diffraction intensitites. Previous investigations indicate that this does not represent a problem for a light-atom-only structure (see Görbitz, 1999).

Refinement
The hydrogen atoms were placed at calculated position with C-H = 0.99 Å for CH 2 and 1.00 Å for CH. For all H atoms U iso (H) values were fixed at 1.2U eq of the carrier atom.  1,1'-(4,4'-Bipiperidine-1,1'-diyl)bis(2,2,2-trifluoroethanone) 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 Rfactors(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.