N,N,N-Tributylbutan-1-aminium (T-4)-(cyano-κC)trihydroborate

In the crystal structure of the title salt, C16H36N+·CH3BN−, the tetra-n-butylammonium cations and [BH3(CN)]− anions are connected via weak C—H⋯N interactions, forming chains along the b-axis direction. The anion is almost linear with an N—C—B angle of 178.7 (2)°. The C—N—C angle values at the core of the tetra-n-butylammonium cation range from 105.74 (11) to 111.35 (11)° with an average of 109.49 (11)°, close to the ideal tetrahedral value.


Comment
Despite the fact the title compound (I) is a common reagent used for example as a reducing agent (Hutchins & Kandasamy, 1973), its crystal structure has not yet been reported.
The structure contains distinctive N(Bu) 4 cations and BH 3 CN anions lying in general positions (figure 1). The anion is almost linear with a N-C-B angle of 178.7 (2)°. The C-N-C angle values at the core of the tetra-n-butylammonium cation range from 105.74 (11)° to 111.35 (11)° with an average of 109.49 (11)° close to the ideal tetrahedral value.
The n-butyl chains are fully extended with an all-trans conformations, giving for the tetra-n-butylammonium cation a distorted D 2d point group symmetry (Alder et al., 1990).
Each anion is surrounded by two cations linked through three weak C-H···N hydrogen bonds; these define chains along the b-axis (figure 2) with a distance separation between the nitrogen atoms of 4.404 (2) Å and 4.491 (2) Å.

Experimental
Compound (I) is commercially available from Sigma-Aldrich and a crystalline specimen has been extracted directly from the commercial flask.

Refinement
H-atoms were placed in calculated positions (C-H 0.98-0.99 Å, B-H 0.99 Å) and were included in the refinement in the riding model approximation, with U iso (H) = 1.2Ueq(C) for methylene or 1.5Ueq(C) for methyl groups and the hydrogen atoms linked to the boron atom.  The molecular structure of the title compound, with atomic numbering scheme and 50% probability displacement ellipsoids for non-hydrogen atoms. Hydrogen atoms are drawn as spheres of arbitrary radius with hydrogen bonds drawn as dashed lines.  Projection along the a-axis showing the chains running along the b-axis made by the weak C-H···N interactions (dashed lines). Hydrogen atoms not involved in these interactions have been removed for clarity.

Special details
Experimental. X-ray crystallographic data for I were collected from a single-crystal sample, which was mounted on a loop fiber. Data were collected using a Bruker microstar diffractometer equipped with a Platinum 135 CCD Detector, a Helios optics and a Kappa goniometer. The crystal-to-detector distance was 4.0 cm, and the data collection was carried out in 512 x 512 pixel mode. The initial unit-cell parameters were determined by a least-squares fit of the angular setting of strong reflections, collected by a 110.0 degree scan in 110 frames over three different parts of the reciprocal space Geometry. All e.s.   (7) 0.0062 (7) 0.0027 (6)  C12 0.0387 (9) 0.0298 (10) 0.0215 (8) 0.0001 (8) 0.0049 (7) 0.0009 (7)  C13 0.0203 (7) 0.0143 (7) 0.0203 (7) 0.0001 (6)