Bis(piperidin-1-yl)methanone

The title compound, C11H20N2O, is a urea derivative bearing two piperidine moieties in place of the amino groups. The molecule shows approximate non-crystallographic C 2 symmetry. The six-membered rings adopt 1 C 4 and 4 C 1 conformations and their mean planes make a dihedral angle of 35.87 (5)°. In the crystal, intermolecular C—H⋯O contacts connect the molecules into infinite strands along the a axis.


D-HÁ
Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009  Dipiperidin-1-ylmethanone -also known as carbodipiperidid or bis(pentamethylene)urea -is a derivative of urea bearing two piperidine moieties. Given its N,O set of donor atoms, it can act as a mono-or a bidentate ligand. Despite this versatility, the coordination chemistry of the title compound has remained nearly unexplored. In a larger study to determine the coordination behaviour of nitrogen-and oxygen-containing ligands, it seemed of interest to determine the structure of the free ligand to enable comparative studies.
The two six-membered rings are present in 1 C 4 and 4 C 1 conformation, respectively. The least-square planes defined by their atoms intersect at an angle of 35.87 (5)°. The distance between the two nitrogen atoms was found to be approximately 2.35 Å while both N-O distances were measured around 2.28 Å ( Figure 1).
In the crystal structure, C-H···O contacts are observed. If only those contacts are taken into account whose range falls more than 0.2 Å below the sum of van-der-Waals radii of the corresponding atoms, the molecules are connected to infinite strands along the crystallographic a axis. The contacts originate from one of the hydrogen atoms in beta-position to the nitrogen atom of the same six-membered ring ( Figure 2). In terms of graph-set analysis, the unitary descriptor of this intermolecular interaction is C 1 1 (6).
The molecular packing of the compound is shown in Figure 3.

Experimental
The structural analysis was done on a single-crystal taken from a commercially obtained (EGA Chemicals) batch of the title compound.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.99 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).