5,11-Dimethyldibenzo[b,f][1,5]diazocine-6,12(5H,11H)-dione

In the molecule of the title compound, C16H14N2O2, an N,N′-dimethyldianthranilide, the two methyl groups are disordered over two positions; site occupation factors were kept fixed as 0.75:0.25 and 0.65:0.35. The dihedral angle between the two benzene rings is 75.57 (3)°.

In the molecule of the title compound, C 16 H 14 N 2 O 2 , an N,N 0dimethyldianthranilide, the two methyl groups are disordered over two positions; site occupation factors were kept fixed as 0.75:0.25 and 0.65:0.35. The dihedral angle between the two benzene rings is 75.57 (3) .

S1. Comment
Several structures of the unsubstituted dianthranilide (i.e., lacking methyl groups on the nitrogen atoms) are present in the literature, including ethanol, DMF and pyridine solvates of racemic material (Gordon-Wylie et al., 2004) as well as a DMSO solvate of racemic material, unsolvated racemate and a DMSO solvate of enantiomerically pure crystals (Olszewska et al., 2004).
In the molecule of the title compound, (I), (Fig. 1) the bond lengths and angles are within normal ranges. When the crystal structure was solved, the two methyl groups were found to be disordered. The dihedral angle between the two benzene rings is 75.57 (3)°.
The X-ray crystal structures of three N,N′-disubstituted dianthranilides have also been reported and in all cases they have a smaller dihedral angle between the two aryl rings of the dianthranilide in comparison with the structures of the unsubstituted compounds. The N, N′-di[1-(N-t-butylcarbamoyl)-1-(cyclohexyl)-methyl] (Ebert et al., 1998), N,N′-dibenzyl (Nonnenmacher et al., 2000) and N,N′-dicamphanoyl derivatives (Olszewska et al., 2004) have dihedral angles of 78.2, 83.9 and 77.5°, respectively.

S2. Experimental
The title compound was prepared according to the literature procedure (Nadkarni & Hosangadi, 1988) in 89% yield.
Single crystals of (I) were produced from slow evaporation of a dichloromethane solution.

S3. Refinement
When the crystal structure was solved, the two methyl groups were found to be disordered. They were each modelled with disorder over two positions with a common carbon atom. One was assigned a 75:25 split occupancy, the other 65:35.
A rotating refinement was used for each methyl position giving staggered orientations for each. H atoms were positioned geometrically, with C-H = 0.95 and 0.98 Å for aromatic and methyl H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C).  The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
Synthetic scheme for the synthesis of (I).  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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (