Crystal structure of N-[3-(benzo[d]thiazol-2-yl)-6-bromo-2H-chromen-2-ylidene]-4-methylbenzenamine

In the crystal structure of the title compound, the C=N—C angle is wide [125.28 (8)°]. The benzothiazole and chromene ring systems are almost coplanar and lie parallel to (1 0); the toluene ring system is rotated by ca 40° out of the chromene plane.


Structural commentary
The molecule of 7 is shown in Fig. 2. The structure determination makes clear that the unexpected product is a chromene derivative with an exocyclic imino function rather than a quinoline with an exocyclic oxo function. Bond lengths and angles may be regarded as normal, except that the C9 N9-C17 angle is very wide at 125.28 (8) ; selected values are given in Table 1. The benzothiazole and chromene ring systems are almost coplanar, with an interplanar angle of 7.59 (2) ; associated with this is a short intramolecular contact S1Á Á ÁN9 2.7570 (8) Å . The toluene ring system is appreciably rotated out of the chromene plane, with an interplanar angle of 40.38 (2) .

Database survey
The searches employed the routine ConQuest (Bruno et al., 2002), part of Version 2022.3.0 of the CSD (Groom et al., 2016). We recently reported the structure of the mixed coumarin/ benzo[d]thiazole derivative 3-(benzo[d]thiazol-2-yl)-2Hchromen-2-one [3-(1,3-benzothiazol-2-yl)-2H-1-benzopyran-2-one] (Abdallah et al., 2022). The structure of the 4-oxo isomer had already been published by Lohar et al. (2018). Two more related structures were published by others at the same time (Singh et al., 2022). The current structure, however, bears an imine ( NAr) rather than an oxo substituent at atom C2 of the chromene (and thus is strictly not a coumarin). Only one other such structure was found in the database; its substituent at the imine nitrogen atom is pyridin-2-ethyl (refcode ITEVAF; Ahamed & Ghosh, 2011) and its C N-C angle is much narrower than in 7 at 118.5 (7) . A further search was therefore performed for structures with an NAr group at the 2-position of a chromene ring system. This gave 18 hits with a considerable spread of C N-C angles, namely 120.5-127.9 , mean value 123.4 (24) . Nine of these structures appeared in the same publication (Shishkina et al., 2019), and, like 7, none of them had an interplanar angle close to the calculated gas-phase optimum of 0 .

Figure 3
Layer structure of compound 7 (without hydrogen atoms) showing the asymmetric unit (indicated by the label O1) and further translationrelated molecules viewed perpendicular to the plane (110). A second layer is related to the first by inversion.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The methyl group was included as an idealized rigid group allowed to rotate but not tip (C-H 0.98 Å , H-C-H 109.5 ). Other hydrogen atoms were included using a riding model starting from calculated positions, with C-H 0.95 Å . The U(H) values were fixed at 1.5 Â U eq of the parent carbon atoms for methyl H atoms and 1.2 Â U eq for other hydrogen atoms.    (Rigaku OD, 2022); program(s) used to solve structure: SHELXT (Sheldrick, 2015b); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015a); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015a).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Short intramolecular contact: 2.7570 (0.0008) S1 -N9 Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 6.9114 (

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.45005 (