Crystal structure of tert-butyl-N-phenylcarbonitrilium tetrachloridoaluminate

The nitrilium cations of the title compound adopt a slightly distorted linear configuration and are linked through π–π interactions. The nitrilium cations and tetraaluminate anions are arranged in alternating planes parallel to the (011) plane.


Structural commentary
The asymmetric unit of the crystal (Fig. 1) contains one nitrilium cation and one tetrachloridoaluminate anion, which are ion-separated. The nitrilium cation adopts a slightly distorted linear configuration [C-N C = 178.87 (16) and N C-C = 179.13 (17) ] and features an N C bond length of 1.1353 (19) Å , which is in the range of previously reported nitrilium ions (see Database survey). The tetrachloridoaluminate anion has an approximately tetrahedral geometry and is in the range of those reported previously (Bezombes et al., 2004).

Supramolecular features
In the unit cell, pairs of inversion-related nitrilium cations are linked throughinteractions with an inter-centroid ISSN 1600-5368 distance of 3.8091 (13) Å . There is a plane-to-plane shift of the phenyl rings of 1.563 (3) Å . The nitrilium cations and tetrachloridoaluminate anions are arranged in alternating planes parallel to (011).

Synthesis and crystallization
This experiment was performed under an atmosphere of dry nitrogen using standard Schlenk-line and glovebox techniques. NMR spectra were recorded at 300 K on a Bruker Advance 500 and referenced internally to residual solvent resonance of CD 2 Cl 2 , 1 H at 5.32, 13 C{ 1 H} at 53.84. The melting point was measured in a sealed capillary on a Stuart Scientific SMP3 melting point apparatus and is uncorrected. The IR spectrum was recorded on a Shimadzu FTIR-8400S spectrophotometer. Solvents were distilled from the appropriate drying agents CaH 2 (DCM), NaK/benzophenone (diethyl ether), and P 2 O 5 (CD 2 Cl 2 ), and kept under an inert atmosphere of dry nitrogen.
The title compound was obtained as follows: to a suspension of AlCl 3 (3.00 g, 22.4 mmol) in DCM (10 ml) cooled to 195 K, an equimolar amount of N-phenylpivalimidoyl chloride (4.38 g, 22.4 mmol) in DCM (25 ml) was added dropwise, after which the reaction mixture was warmed to room temperature and stirred for 16 h. All volatiles were removed in vacuo, after which the product was redissolved in DCM (60 ml), layered with diethyl ether (90 ml) and cooled to 193 K for 48 h. The analytically pure product was isolated as a grey crystalline solid (6.23 g, 18.9 mmol, 85%). Recrystallization from DCM at 278 K yielded crystals suitable for X-ray crystallography. The crystals were coated with paratone oil and mounted on a glass fibre in the cooled nitrogen stream of the diffractometer. M.p.

Special details
Experimental. Corrections were done with the SADABS program, utilizing the none merged raw data obtained from the integration process. Integration and final cell refinement were done with SAINT. SADABS reports ratio of Tmin/Tmax = 0.797049 Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.