Crystal structures of 6-chloroindan-1-one and 6-bromoindan-1-one exhibit different intermolecular packing interactions

The structures of two haloindanones are reported and differences in their intermolecular packing interactions are explored.


Chemical context
Halogenated derivatives of the common bicyclic organic framework 1-indanone have been shown to be useful in a variety of synthetic and biologically related applications (Ruiz et al., 2004). A search of the Cambridge Structural Database (Version 5.31, September 2016 with updates; Groom et al., 2016) returns four simple arylhalide substituted 1-indanones, although several more are commercially available. The title compounds represent two analogs of 6-haloindan-1-one that are notably not isomorphous. In addition, they are not isomorphous with the fluorine derivative 6-fluoroindan-1-one, which is one of the four that has previously been reported (Slaw & Tanski, 2014). In the chloro analog, 6-chloroindan-1one (I), the molecules pack together via a series of C-HÁ Á ÁO interactions. C-HÁ Á ÁX interactions are common and have been discussed in the literature (Desiraju & Steiner, 1999), as well as specifically in the case of 1-indanone itself (Ruiz et al., 2004). The bromo derivative 6-bromoindan-1-one (II) packs with offset face-to-face -stacking (Hunter & Saunders, 1990;Lueckheide et al., 2013) and several different intermolecular contacts including C-HÁ Á ÁO, C-HÁ Á ÁBr weak hydrogen bonds and BrÁ Á ÁO interactions. ISSN 2056-9890 The compounds 6-chloroindan-1-one (I) and 6-bromoindan-1-one (II) may be synthesized by the microwave or ultrasound-aided ring closure of 4-chloro-or 4-bromobenzenepropanoic acid, respectively, catalyzed by triflic acid in dichloromethane (Oliverio et al., 2014). 6-Haloindan-1-ones have featured in the synthesis of biologically or pharmacologically active compounds. In recent examples, 6-chloroindan-1-one (I) has been employed in the total synthesis of the anticancer natural product chartarin (Unzner et al., 2016), and in the synthesis of triazole-quinoline derivatives that are acetylcholinesterase inhibitors relevant to the treatment of Alzheimer's disease (Mantoani et al., 2016). 6-Bromoindan-1one has been used as the starting material for the synthesis of small molecules that inhibit cell entry by HIV-1 (Melillo et al., 2016), and both 6-chloroindan-1-one and 6-bromoindan-1-one have been used as the starting material for the preparation of C-7 substituted 3,4-dihydroisoquinolin-1(2H)-one analogues that selectively inhibit unique poly-ADP-ribose polymerases (Morgan et al., 2015).

Supramolecular features
In the crystal structure of 6-chloroindan-1-one (I), the molecules pack together via van der Waals contacts, specifically C-HÁ Á ÁO interactions, without any -stacking. The C-HÁ Á ÁO interactions ( Fig. 3 and Table 1) connect the indanone oxygen atom with methylene hydrogen atoms on neighboring molecules into a two-molecule-thick sheet parallel to the (100) plane (Fig. 4). These sheets further pack together without any notable intermolecular contacts. The closest ClÁ Á ÁCl contact between the sheets, 3.728 Å , is somewhat longer than the sum of the van der Waals radii of chlorine, 3.50 Å (Bondi, 1964).  A view of 6-chloroindan-1-one (I) with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.

Figure 4
A view of the sheet structure in 6-chloroindan-1-one (I) formed by C-HÁ Á ÁO contacts. See Table 1 for symmetry codes (i) and (ii).

Figure 5
A view of the alternating offset face-to-face -stacking and C-HÁ Á ÁBr interaction in 6-bromoindan-1-one (II) with the thick black line indicating a centroid-to-centroid interaction. See Table 2 for symmetry code (iii).

(I) 6-Chloroindan-1-one
Crystal data 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1 0.44180 (2) 0.68505 (5)      where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 1.15 e Å −3 Δρ min = −1.15 e Å −3 Special details Experimental. BASF 0.0762 (5) 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.