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ISSN: 2056-9890
Volume 71| Part 7| July 2015| Pages 852-856

Crystal structures of 4-chloro­pyridine-2-carbo­nitrile and 6-chloro­pyridine-2-carbo­nitrile exhibit different inter­molecular π-stacking, C—H⋯Nnitrile and C—H⋯Npyridine inter­actions

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aDepartment of Chemistry, Vassar College, Poughkeepsie, NY 12604, USA
*Correspondence e-mail: jotanski@vassar.edu

Edited by C. Rizzoli, Universita degli Studi di Parma, Italy (Received 11 June 2015; accepted 18 June 2015; online 27 June 2015)

The two title compounds are isomers of C6H3ClN2 containing a pyridine ring, a nitrile group, and a chloro substituent. The mol­ecules of each compound pack together in the solid state with offset face-to-face π-stacking, and inter­molecular C—H⋯Nnitrile and C—H⋯Npyridine inter­actions. 4-Chloro­pyridine-2-carbo­nitrile, (I), exhibits pairwise centrosymmetric head-to-head C—H⋯Nnitrile and C—H⋯Npyridine inter­actions, forming one-dimensional chains, which are π-stacked in an offset face-to-face fashion. The inter­molecular packing of the isomeric 6-chloro­pyridine-2-carbo­nitrile, (II), which differs only in the position of the chloro substituent on the pyridine ring, exhibits head-to-tail C—H⋯Nnitrile and C—H⋯Npyridine inter­actions, forming two-dimensional sheets which are π-stacked in an offset face-to-face fashion. In contrast to (I), the offset face-to-face π-stacking in (II) is formed between mol­ecules with alternating orientations of the chloro and nitrile substituents.

1. Chemical context

Chloro­pyridine­carbo­nitriles are members of a class of compounds containing the ubiquitous six-membered nitro­gen-containing heterocycle pyridine. The pyridine heterocycle features prominently in many valuable synthetic compounds (Bull et al., 2012[Bull, J. A., Mousseau, J. J., Pelletier, G. & Charette, A. B. (2012). Chem. Rev. 112, 2642-2713.]). While several of the ten possible isomers of chloro­pyridine­carbo­nitrile are commercially available, none of their crystal structures have been reported in the literature, although the structure of 2-chloro­pyridine-4-carbo­nitrile has been deposited in the Cambridge Structural Database (Version 5.31, June 2015 with updates; Groom & Allen, 2014[Groom, C. R. & Allen, F. H. (2014). Angew. Chem. Int. Ed. 53, 662-671.]) as a private communication (refcode LOBVIJ). The title compounds represent two isomers of chloro­pyridine-2-carbo­nitrile, namely 4-chloro­pyridine-2-carbo­nitrile, (I)[link], and 6-chloro­pyridine-2-carbo­nitrile, (II)[link]. In both cases, the intra­molecular packing exhibits weak inter­molecular C—H⋯N inter­actions, which are well documented (Desiraju & Steiner, 1999[Desiraju, G. R. & Steiner, T. (1999). In The Weak Hydrogen Bond in Structural Chemistry and Biology. Oxford University Press.]), as well as aromatic π-stacking inter­actions (Hunter & Saunders, 1990[Hunter, C. A. & Saunders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525-5534.]; Lueckheide et al., 2013[Lueckheide, M., Rothman, N., Ko, B. & Tanski, J. M. (2013). Polyhedron, 58, 79-84.]).

[Scheme 1]

4-Chloro­pyridine-2-carbo­nitrile, (I)[link], may be synthesized by the cyanation of 4-chloro­pyridine N-oxide with tri­methyl­silanecarbo­nitrile (TMSCN) (Sakamoto et al., 1985[Sakamoto, T., Kaneda, S.-I., Nishimura, S. & Yamanaka, H. (1985). Chem. Pharm. Bull. 2, 565-571.]). More recently, it has been shown that (I)[link] can be prepared in a one-step process from 4-nitro­pyridine N-oxide with ethyl chloro­formate and TMSCN (Veerareddy et al., 2011[Veerareddy, A., Surendrareddy, G. & Dubey, P. K. (2011). J. Heterocycl. Chem. 48, 961-964.]). (I)[link] has found use as a building block for a family of chiral catalysts (Busto et al., 2005[Busto, E., Gotor-Fernandez, V. & Gotor, V. (2005). Tetrahedron Asymmetry, 16, 3427-3425.]).

6-Chloro­pyridine-2-carbo­nitrile, (II)[link], may be synthesized by the vapor-phase chlorination of 2-cyano­pyridine (Ruetman & Taplin, 1971[Ruetman, S. H. & Taplin, W. H. (1971). US Patent 3591597 A.]), or by the cyanation of 2-chloro­pyridine N-oxide hydro­chloride with sodium cyanide (Tsukamoto et al., 2009[Tsukamoto, I., Koshio, H., Kuramochi, T., Saitoh, C., Yanai-Inamura, H., Kitada-Nozawa, C., Yamamoto, E., Yatsu, T., Shimada, Y., Sakamoto, S. & Tsukamoto, S.-I. (2009). Bioorg. Med. Chem. 17, 3130-3141.]). This compound has found applications in the preparation of biologically active or pharmaceutical compounds, such as heteroaromatic carb­oxy­lic acids (Kiener et al., 1996[Kiener, A., Roduit, J.-P. & Glockler, R. (1996). Eur. Patent Appl. EP747486A119961211.]) and 2-aryl­amino-substituted pyridinyl nitriles (Guo et al., 2013[Guo, S., Wang, Y., Sun, C., Li, J., Zou, D., Wu, Y. & Wu, Y. (2013). Tetrahedron Lett. 54, 3233-3237.]).

2. Structural commentary

4-Chloro­pyridine-2-carbo­nitrile, (I)[link] (Fig. 1[link]), and 6-chloro­pyridine-2-carbo­nitrile, (II)[link] (Fig. 2[link]), exhibit similar metrical parameters. The nitrile bond length C1—N2 of 1.156 (3) Å in (I)[link] and 1.138 (2) Å in (II)[link] are similar to those seen in the related structure 2-chloro­pyridine-4-carbo­nitrile, with the nitrile C≡N distance is 1.141 Å (CSD refcode LOBVIJ). The nitrile bond lengths in 2- and 3-cyano­pyridine [1.145 (2) and 1.150 (1) Å, respectively; Kubiak et al., 2002[Kubiak, R., Janczak, J. & Śledź, M. (2002). J. Mol. Struct. 610, 59-64.]] and 4-cyano­pyridine [1.137 (8) Å; Laing et al., 1971[Laing, M., Sparrow, N. & Sommerville, P. (1971). Acta Cryst. B27, 1986-1990.]] are also similar to those found in the title compounds. The aromatic chlorine bond lengths, viz. C4—Cl and C6—Cl of 1.740 (3) Å in (I)[link] and 1.740 (1) Å in (II)[link], are similar to those seen in the related structures 2-chloro­pyridine-4-carbo­nitrile (1.732 Å; CSD refcode LOBVIJ), 2- and 3-chloro­pyridine hydro­chloride (1.710 and 1.727 Å, respectively; Freytag & Jones, 2001[Freytag, M. & Jones, P. G. (2001). Z. Naturforsch. Teil B, 56, 889-896.]), and 4-chloro­pyridine hydro­chloride (1.730 Å; Freytag et al., 1999[Freytag, M., Jones, P. G., Aherns, B. & Fischer, A. K. (1999). New J. Chem. 23, 1137-1139.]).

[Figure 1]
Figure 1
A view of 4-chloro­pyridine-2-carbo­nitrile, (I)[link], with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.
[Figure 2]
Figure 2
A view of 6-chloro­pyridine-2-carbo­nitrile, (II)[link], with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.

Both (I)[link] and (II)[link] are almost planar, with r.m.s. deviations from the mean planes of all non-H atoms of 0.0077 and 0.0161 Å, respectively. As may be expected, the heterocyclic rings are slightly wedge shaped as the pyridine C—N bond are shorter than the C—C bonds in each aromatic ring. In (I)[link], the ring C2—N1 and C6—N1 bond lengths of 1.361 (3) and 1.350 (3) Å are similar to those found in (II)[link] of 1.349 (1) and 1.322 (1) Å. The average ring C—C bond lengths are 1.403 (2) Å in (I)[link] and 1.391 (5) Å in (II)[link]. The lengths are comparable to those found in the parent compound, pyridine, with C—N of 1.34 Å and C—C of 1.38 Å (Mootz & Wussow, 1981[Mootz, D. & Wussow, H. G. (1981). J. Chem. Phys. 75, 1517-1522.]), and in the related structure 2-chloro­pyridine-4-carbo­nitrile, with C—N bond lengths of 1.328 and 1.340 Å, and an average C—C bond length of 1.377 (7) Å (CSD refcode LOBVIJ).

3. Supra­molecular features

The mol­ecules of each of the title compounds pack together in the solid state with π-stacking, and inter­molecular C—H⋯Nnitrile and C—H⋯Npyridine inter­actions, however, the packing motifs are unique, and also different than those found in the related structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ). For a discussion of weak C—H⋯X inter­actions, see Desiraju & Steiner (1999[Desiraju, G. R. & Steiner, T. (1999). In The Weak Hydrogen Bond in Structural Chemistry and Biology. Oxford University Press.]).

The mol­ecules of (I)[link] pack together in the solid state via alternating centrosymmetric head-to-head inter­molecular C—H⋯Nnitrile and C—H⋯Npyridine inter­actions to form a one-dimensional zigzag chain (Fig. 3[link] and Table 1[link]). The chains further pack together through offset face-to-face π-stacking (Fig. 4[link]). This π-stacking is characterized by a centroid-to-centroid distance of 3.813 (5) Å, a plane-to-centroid distance of 3.454 (4) Å, and a ring offset or ring-slippage distance of 1.615 (3) Å (Hunter & Saunders, 1990[Hunter, C. A. & Saunders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525-5534.]; Lueckheide et al., 2013[Lueckheide, M., Rothman, N., Ko, B. & Tanski, J. M. (2013). Polyhedron, 58, 79-84.]). The π-stacking in (I)[link] is similar to that found in the related unpublished structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ).

Table 1
Hydrogen-bond geometry (Å, °) for (I)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
C3—H3A⋯N2i 0.95 2.64 3.462 (5) 146
C6—H6A⋯N1ii 0.95 2.75 3.493 (5) 136
Symmetry codes: (i) -x-1, -y+1, -z; (ii) -x, -y+1, -z+1.
[Figure 3]
Figure 3
A view of the inter­molecular C—H⋯Nnitrile and C—H⋯Npyridine contacts (dashed lines) in 4-chloro­pyridine-2-carbo­nitrile, (I)[link], that form a one-dimensional chain. [Symmetry codes: (i) −x − 1, −y + 1, −z; (ii) −x, −y + 1, −z + 1.]
[Figure 4]
Figure 4
A view of the offset face-to-face π-stacking in 4-chloro­pyridine-2-carbo­nitrile, (I)[link], with the thick dashed line indicating a centroid-to-centroid inter­action. [Symmetry code: (i) x + 1, y, z.]

In contrast to (I)[link], the mol­ecules of (II)[link] pack together via head-to-tail C—H⋯Nnitrile and C—H⋯Npyridine inter­actions to form two-dimensional sheets that are parallel to the (001) plane (Fig. 5[link] and Table 2[link]). As in (I)[link], the parallel planes of the mol­ecules engage in offset face-to-face π-stacking between the two-dimensional sheets, which is characterized by a ring centroid-to-centroid distance of 3.7204 (7) Å, a centroid-to-plane distance of 3.41 (1) Å, and a ring-offset slippage of 1.48 (2) Å (Fig. 6[link]). However, in constrast to (I)[link], the π-stacking in (II)[link] is formed between mol­ecules with alternating orientations of the chloro and nitrile substituents with a plane-to-plane angle of 0.23 (5)°. For a more thorough description of π-stacking, see Hunter & Saunders (1990[Hunter, C. A. & Saunders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525-5534.]) and Lueckheide et al. (2013[Lueckheide, M., Rothman, N., Ko, B. & Tanski, J. M. (2013). Polyhedron, 58, 79-84.]).

Table 2
Hydrogen-bond geometry (Å, °) for (II)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
C4—H4A⋯N1i 0.95 2.49 3.4099 (15) 164
C5—H5A⋯N2ii 0.95 2.70 3.5651 (17) 152
Symmetry codes: (i) x-1, y, z; (ii) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}].
[Figure 5]
Figure 5
A view of the inter­molecular C—H⋯Nnitrile and C—H⋯Npyridine contacts (dashed lines) in 6-chloro­pyridine-2-carbo­nitrile, (I)[link], that form a two-dimensional sheet. [Symmetry codes: (i) x − 1, y, z; (ii) −x + [{3\over 2}], y − [{1\over 2}], −z + [{3\over 2}].]
[Figure 6]
Figure 6
A view of the alternating offset face-to-face π-stacking in 6-chloro­pyridine-2-carbo­nitrile, (II)[link], with the thick dashed line indicating a centroid-to-centroid inter­action. [Symmetry code: (i) x + [{1\over 2}], −y + [{1\over 2}], z + [{1\over 2}].]

Notably, there are no significant Cl⋯Cl contacts in (I)[link] or (II)[link], in contrast to 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ), which exhibits a Cl⋯Cl contact distance of 3.371 Å that is shorter than the sum of the van der Waals radius of chlorine (3.5 Å; Bondi, 1964[Bondi, A. (1964). J. Phys. Chem. 68, 441-451 .]). For more information on halide–halide contacts, see Pedireddi et al. (1994[Pedireddi, V. R., Reddy, D. S., Goud, B. S., Craig, D. C., Rae, A. D. & Desiraju, G. R. (1994). J. Chem. Soc. Perkin Trans. 2, pp. 2353-2360.]) and Jelsch et al. (2015[Jelsch, C., Soudani, S. & Ben Nasr, C. (2015). IUCrJ, 2, 327-340.]).

4. Synthesis and crystallization

4-Chloro­pyridine-2-carbo­nitrile (97%) and 6-chloro­pyridine-2-carbo­nitrile (96%) were purchased from Aldrich Chemical Company, USA. 4-Chloro­pyridine-2-carbo­nitrile was recrystallized from 95% ethanol.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3[link]. H atoms on C atoms were included in calculated positions and refined using a riding model, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C) of the aryl C atoms.

Table 3
Experimental details

  (I) (II)
Crystal data
Chemical formula C6H3ClN2 C6H3ClN2
Mr 138.55 138.55
Crystal system, space group Monoclinic, P21/n Monoclinic, P21/n
Temperature (K) 125 125
a, b, c (Å) 3.813 (5), 14.047 (19), 11.356 (15) 6.1739 (15), 15.238 (4), 7.0123 (18)
β (°) 96.806 (19) 112.492 (4)
V3) 604.0 (14) 609.5 (3)
Z 4 4
Radiation type Mo Kα Mo Kα
μ (mm−1) 0.52 0.52
Crystal size (mm) 0.25 × 0.10 × 0.04 0.20 × 0.15 × 0.03
 
Data collection
Diffractometer Bruker APEXII CCD Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2013[Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Multi-scan (SADABS; Bruker, 2013[Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.67, 0.98 0.82, 0.98
No. of measured, independent and observed [I > 2σ(I)] reflections 12191, 1852, 1498 15460, 1868, 1657
Rint 0.063 0.031
(sin θ/λ)max−1) 0.715 0.717
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.135, 1.12 0.028, 0.082, 1.09
No. of reflections 1852 1868
No. of parameters 82 82
H-atom treatment H-atom parameters constrained H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.53, −0.37 0.48, −0.19
Computer programs: APEX2 and SAINT (Bruker, 2013[Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXS2014 and SHELXTL2014 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]).

Supporting information


Chemical context top

Chloro­pyridine­carbo­nitriles are members of a class of compounds containing the ubiquitous six-membered nitro­gen-containing heterocycle pyridine. The pyridine heterocycle features prominently in many valuable synthetic compounds (Bull et al., 2012). While several of the ten possible isomers of chloro­pyridine­carbo­nitrile are commercially available, none of their crystal structures have been reported in the literature, although the structure of 2-chloro­pyridine-4-carbo­nitrile has been deposited in the Cambridge Structural Database (Version 5.31, June 2015 with updates; Groom & Allen, 2014) as a private communication (refcode LOBVIJ). The title compounds represent two isomers of chloro­pyridine-2-carbo­nitrile, namely 4-chloro­pyridine-2-carbo­nitrile, (I), and 6-chloro­pyridine-2-carbo­nitrile, (II). In both cases, the intra­molecular packing exhibits weak inter­molecular C—H···N inter­actions, which are well documented (Desiraju & Steiner, 1999), as well as aromatic π-stacking inter­actions (Hunter & Saunders, 1990; Lueckheide et al., 2013).

4-Chloro­pyridine-2-carbo­nitrile, (I), may be synthesized by the cyanation of 4-chloro­pyridine N-oxide with tri­methyl­silanecarbo­nitrile (TMSCN) (Sakamoto et al., 1985). More recently, it has been shown that (I) can be prepared in a one-step process from 4-nitro­pyridine N-oxide with ethyl chloro­formate and TMSCN (Veerareddy et al., 2011). (I) has found use as a building block for a family of chiral catalysts (Busto et al., 2005) and in the synthesis of 2-aryl­amino-substituted pyridinyl nitriles (Guo et al., 2013).

6-Chloro­pyridine-2-carbo­nitrile, (II), may be synthesized by the vapor-phase chlorination of 2-cyano­pyridine (Ruetman & Taplin, 1971), or by the cyanation of 2-chloro­pyridine N-oxide hydro­chloride with sodium cyanide (Tsukamoto et al., 2009). This compound has found applications in the preparation of biologically active or pharmaceutical compounds, such as heteroaromatic carb­oxy­lic acids (Kiener et al., 1996) and 2-aryl­amino substituted pyridinyl nitriles (Guo et al., 2013).

Structural commentary top

4-Chloro­pyridine-2-carbo­nitrile, (I) (Fig. 1), and 6-chloro­pyridine-2-carbo­nitrile, (II) (Fig. 2), exhibit similar metrical parameters. The nitrile bond length C1—N2 of 1.156 (3) Å in (I) and 1.138 (2) Å in (II) are similar to those seen in the related structure 2-chloro­pyridine-4-carbo­nitrile, with the nitrile CN distance is 1.141 Å (CSD refcode LOBVIJ). The nitrile bond lengths in 2- and 3-cyano­pyridine [1.145 (2) and 1.150 (1) Å, respectively; Kubiak et al., 2002] and 4-cyano­pyridine [1.137 (8) Å; Laing et al., 1971] are also similar to those found in the title compounds. The aromatic chloride bond lengths, viz. C4—Cl and C6—Cl of 1.740 (3) Å in (I) and 1.740 (1) Å in (II), are similar to those seen in the related structures 2-chloro­pyridine-4-carbo­nitrile (1.732 Å; CSD refcode LOBVIJ), 2- and 3-chloro­pyridine hydro­chloride (1.710 and 1.727 Å, respectively; Freytag & Jones, 2001), and 4-chloro­pyridine hydro­chloride (1.730 Å; Freytag et al., 1999).

Both (I) and (II) are planar, with r.m.s. deviations from the mean planes of all non-H atoms of 0.0077 and 0.0161 Å, respectively. As may be expected, the heterocyclic rings are slightly wedge shaped as the pyridine C—N bond are shorter than the C—C bonds in each aromatic ring. In (I), the ring C2—N1 and C6—N1 bond lengths of 1.361 (3) and 1.350 (3) Å are similar to those found in (II) of 1.349 (1) and 1.322 (1) Å. The average ring C—C bond lengths are 1.403 (2) Å in (I) and 1.391 (5) Å in (II). The lengths are comparable to those found in the parent compound, pyridine, with C—N of 1.34 Å and C—C of 1.38 Å (Mootz & Wussow, 1981), and in the related structure 2-chloro­pyridine-4-carbo­nitrile, with C—N bond lengths of 1.328 and 1.340 Å, and an average C—C bond length of 1.377 (7) Å (CSD refcode LOBVIJ).

Supra­molecular features top

The molecules of each of the title compound pack together in the solid state with π-stacking, and inter­molecular C—H···Nnitrile and C—H···Npyridine inter­actions, however, the packing motifs are unique, and also different than those found in the related structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ). For a discussion of weak C—H···X inter­actions, see Desiraju & Steiner (1999).

The molecules of (I) pack together in the solid state via alternating centrosymmetric head-to-head inter­molecular C—H···Nnitrile and C—H···Npyridine inter­actions to form a one-dimensional zigzag chain (Fig. 3 and Table 1). The chains further pack together through offset face-to-face π-stacking (Fig. 4). This π-stacking is characterized by a centroid-to-centroid distance of 3.813 (5) Å, a plane-to-centroid distance of 3.454 (4) Å, and a ring offset or ring-slippage distance of 1.615 (3) Å (Hunter & Saunders, 1990; Lueckheide et al., 2013). The π-stacking in (I) is similar to that found in the related unpublished structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ).

In contrast to (I), the molecules of (II) pack together via head-to-tail C—H···Nnitrile and C—H···Npyridine inter­actions to form two-dimensional sheets that are parallel to the (001) plane (Fig. 5 and Table 2). As in (I), the parallel planes of the molecules engage in offset face-to-face π-stacking between the two-dimensional sheets, which is characterized by a ring centroid-to-centroid distance of 3.7204 (7) Å, a centroid-to-plane distance of 3.41 (1) Å, and a ring-offset slippage of 1.48 (2) Å (Fig. 6). However, in constrast to (I), the π-stacking in (II) is formed between molecules with alternating orientations of the chloro and nitrile substituents with a plane-to-plane angle of 0.23 (5)°. For a more thorough description of π-stacking, see Hunter & Saunders (1990) and Lueckheide et al. (2013).

Notably, there are no significant Cl···Cl contacts in (I) or (II), in contrast to 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ), which exhibits a Cl···Cl contact distance of 3.371 Å that is shorter than the sum of the van der Waals radius of chlorine (3.5 Å; Bondi, 1964). For more information on halide–halide contacts, see Pedireddi et al. (1994) and Jelsch et al. (2015).

Synthesis and crystallization top

4-Chloro­pyridine-2-carbo­nitrile (97%) and 6-chloro­pyridine-2-carbo­nitrile (96%) were purchased from Aldrich Chemical Company, USA. 4-Chloro­pyridine-2-carbo­nitrile was recrystallized from 95% ethanol.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms on C atoms were included in calculated positions and refined using a riding model, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C) of the aryl C matoms.

Structure description top

Chloro­pyridine­carbo­nitriles are members of a class of compounds containing the ubiquitous six-membered nitro­gen-containing heterocycle pyridine. The pyridine heterocycle features prominently in many valuable synthetic compounds (Bull et al., 2012). While several of the ten possible isomers of chloro­pyridine­carbo­nitrile are commercially available, none of their crystal structures have been reported in the literature, although the structure of 2-chloro­pyridine-4-carbo­nitrile has been deposited in the Cambridge Structural Database (Version 5.31, June 2015 with updates; Groom & Allen, 2014) as a private communication (refcode LOBVIJ). The title compounds represent two isomers of chloro­pyridine-2-carbo­nitrile, namely 4-chloro­pyridine-2-carbo­nitrile, (I), and 6-chloro­pyridine-2-carbo­nitrile, (II). In both cases, the intra­molecular packing exhibits weak inter­molecular C—H···N inter­actions, which are well documented (Desiraju & Steiner, 1999), as well as aromatic π-stacking inter­actions (Hunter & Saunders, 1990; Lueckheide et al., 2013).

4-Chloro­pyridine-2-carbo­nitrile, (I), may be synthesized by the cyanation of 4-chloro­pyridine N-oxide with tri­methyl­silanecarbo­nitrile (TMSCN) (Sakamoto et al., 1985). More recently, it has been shown that (I) can be prepared in a one-step process from 4-nitro­pyridine N-oxide with ethyl chloro­formate and TMSCN (Veerareddy et al., 2011). (I) has found use as a building block for a family of chiral catalysts (Busto et al., 2005) and in the synthesis of 2-aryl­amino-substituted pyridinyl nitriles (Guo et al., 2013).

6-Chloro­pyridine-2-carbo­nitrile, (II), may be synthesized by the vapor-phase chlorination of 2-cyano­pyridine (Ruetman & Taplin, 1971), or by the cyanation of 2-chloro­pyridine N-oxide hydro­chloride with sodium cyanide (Tsukamoto et al., 2009). This compound has found applications in the preparation of biologically active or pharmaceutical compounds, such as heteroaromatic carb­oxy­lic acids (Kiener et al., 1996) and 2-aryl­amino substituted pyridinyl nitriles (Guo et al., 2013).

4-Chloro­pyridine-2-carbo­nitrile, (I) (Fig. 1), and 6-chloro­pyridine-2-carbo­nitrile, (II) (Fig. 2), exhibit similar metrical parameters. The nitrile bond length C1—N2 of 1.156 (3) Å in (I) and 1.138 (2) Å in (II) are similar to those seen in the related structure 2-chloro­pyridine-4-carbo­nitrile, with the nitrile CN distance is 1.141 Å (CSD refcode LOBVIJ). The nitrile bond lengths in 2- and 3-cyano­pyridine [1.145 (2) and 1.150 (1) Å, respectively; Kubiak et al., 2002] and 4-cyano­pyridine [1.137 (8) Å; Laing et al., 1971] are also similar to those found in the title compounds. The aromatic chloride bond lengths, viz. C4—Cl and C6—Cl of 1.740 (3) Å in (I) and 1.740 (1) Å in (II), are similar to those seen in the related structures 2-chloro­pyridine-4-carbo­nitrile (1.732 Å; CSD refcode LOBVIJ), 2- and 3-chloro­pyridine hydro­chloride (1.710 and 1.727 Å, respectively; Freytag & Jones, 2001), and 4-chloro­pyridine hydro­chloride (1.730 Å; Freytag et al., 1999).

Both (I) and (II) are planar, with r.m.s. deviations from the mean planes of all non-H atoms of 0.0077 and 0.0161 Å, respectively. As may be expected, the heterocyclic rings are slightly wedge shaped as the pyridine C—N bond are shorter than the C—C bonds in each aromatic ring. In (I), the ring C2—N1 and C6—N1 bond lengths of 1.361 (3) and 1.350 (3) Å are similar to those found in (II) of 1.349 (1) and 1.322 (1) Å. The average ring C—C bond lengths are 1.403 (2) Å in (I) and 1.391 (5) Å in (II). The lengths are comparable to those found in the parent compound, pyridine, with C—N of 1.34 Å and C—C of 1.38 Å (Mootz & Wussow, 1981), and in the related structure 2-chloro­pyridine-4-carbo­nitrile, with C—N bond lengths of 1.328 and 1.340 Å, and an average C—C bond length of 1.377 (7) Å (CSD refcode LOBVIJ).

The molecules of each of the title compound pack together in the solid state with π-stacking, and inter­molecular C—H···Nnitrile and C—H···Npyridine inter­actions, however, the packing motifs are unique, and also different than those found in the related structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ). For a discussion of weak C—H···X inter­actions, see Desiraju & Steiner (1999).

The molecules of (I) pack together in the solid state via alternating centrosymmetric head-to-head inter­molecular C—H···Nnitrile and C—H···Npyridine inter­actions to form a one-dimensional zigzag chain (Fig. 3 and Table 1). The chains further pack together through offset face-to-face π-stacking (Fig. 4). This π-stacking is characterized by a centroid-to-centroid distance of 3.813 (5) Å, a plane-to-centroid distance of 3.454 (4) Å, and a ring offset or ring-slippage distance of 1.615 (3) Å (Hunter & Saunders, 1990; Lueckheide et al., 2013). The π-stacking in (I) is similar to that found in the related unpublished structure 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ).

In contrast to (I), the molecules of (II) pack together via head-to-tail C—H···Nnitrile and C—H···Npyridine inter­actions to form two-dimensional sheets that are parallel to the (001) plane (Fig. 5 and Table 2). As in (I), the parallel planes of the molecules engage in offset face-to-face π-stacking between the two-dimensional sheets, which is characterized by a ring centroid-to-centroid distance of 3.7204 (7) Å, a centroid-to-plane distance of 3.41 (1) Å, and a ring-offset slippage of 1.48 (2) Å (Fig. 6). However, in constrast to (I), the π-stacking in (II) is formed between molecules with alternating orientations of the chloro and nitrile substituents with a plane-to-plane angle of 0.23 (5)°. For a more thorough description of π-stacking, see Hunter & Saunders (1990) and Lueckheide et al. (2013).

Notably, there are no significant Cl···Cl contacts in (I) or (II), in contrast to 2-chloro­pyridine-4-carbo­nitrile (CSD refcode LOBVIJ), which exhibits a Cl···Cl contact distance of 3.371 Å that is shorter than the sum of the van der Waals radius of chlorine (3.5 Å; Bondi, 1964). For more information on halide–halide contacts, see Pedireddi et al. (1994) and Jelsch et al. (2015).

Synthesis and crystallization top

4-Chloro­pyridine-2-carbo­nitrile (97%) and 6-chloro­pyridine-2-carbo­nitrile (96%) were purchased from Aldrich Chemical Company, USA. 4-Chloro­pyridine-2-carbo­nitrile was recrystallized from 95% ethanol.

Refinement details top

Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms on C atoms were included in calculated positions and refined using a riding model, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C) of the aryl C matoms.

Computing details top

For both compounds, data collection: APEX2 (Bruker, 2013); cell refinement: APEX2 (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL2014 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL2014 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008).

Figures top
[Figure 1] Fig. 1. A view of 4-chloropyridine-2-carbonitrile, (I), with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. A view of 6-chloropyridine-2-carbonitrile, (II), with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.
[Figure 3] Fig. 3. A view of the intermolecular C—H···Nnitrile and C—H···Npyridine contacts (dashed lines) in 4-chloropyridine-2-carbonitrile, (I), that form a one-dimensional chain. [Symmetry codes: (i) -x-1, -y+1, -z; (ii) -x, -y+1, -z+1.]
[Figure 4] Fig. 4. A view of the offset face-to-face π-stacking in 4-chloropyridine-2-carbonitrile, (I), with the thick dashed line indicating a centroid-to-centroid interaction. [Symmetry code: (i) x+1, y, z.]
[Figure 5] Fig. 5. A view of the intermolecular C—H···Nnitrile and C—H···Npyridine contacts (dashed lines) in 6-chloropyridine-2-carbonitrile, (I), that form a two-dimensional sheet. [Symmetry codes: (i) x-1, y, z; (ii) -x+3/2, y-1/2, -z+3/2.]
[Figure 6] Fig. 6. A view of the alternating offset face-to-face π-stacking in 6-chloropyridine-2-carbonitrile, (II), with the thick dashed line indicating a centroid-to-centroid interaction. [Symmetry code: (i) x+1/2, -y+1/2, z+1/2.]
(I) 4-Chloropyridine-2-carbonitrile top
Crystal data top
C6H3ClN2F(000) = 280
Mr = 138.55Dx = 1.524 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 3.813 (5) ÅCell parameters from 3637 reflections
b = 14.047 (19) Åθ = 2.9–30.3°
c = 11.356 (15) ŵ = 0.52 mm1
β = 96.806 (19)°T = 125 K
V = 604.0 (14) Å3Plate, colourless
Z = 40.25 × 0.10 × 0.04 mm
Data collection top
Bruker APEXII CCD
diffractometer
1852 independent reflections
Radiation source: fine-focus sealed tube1498 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.063
Detector resolution: 8.3333 pixels mm-1θmax = 30.6°, θmin = 2.3°
φ and ω scansh = 55
Absorption correction: multi-scan
(SADABS; Bruker, 2013)
k = 2019
Tmin = 0.67, Tmax = 0.98l = 1616
12191 measured reflections
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.050H-atom parameters constrained
wR(F2) = 0.135 w = 1/[σ2(Fo2) + (0.0646P)2 + 0.4268P]
where P = (Fo2 + 2Fc2)/3
S = 1.12(Δ/σ)max < 0.001
1852 reflectionsΔρmax = 0.53 e Å3
82 parametersΔρmin = 0.37 e Å3
Crystal data top
C6H3ClN2V = 604.0 (14) Å3
Mr = 138.55Z = 4
Monoclinic, P21/nMo Kα radiation
a = 3.813 (5) ŵ = 0.52 mm1
b = 14.047 (19) ÅT = 125 K
c = 11.356 (15) Å0.25 × 0.10 × 0.04 mm
β = 96.806 (19)°
Data collection top
Bruker APEXII CCD
diffractometer
1852 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2013)
1498 reflections with I > 2σ(I)
Tmin = 0.67, Tmax = 0.98Rint = 0.063
12191 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0500 restraints
wR(F2) = 0.135H-atom parameters constrained
S = 1.12Δρmax = 0.53 e Å3
1852 reflectionsΔρmin = 0.37 e Å3
82 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cl0.27576 (14)0.79489 (4)0.15624 (5)0.02207 (17)
N10.0055 (5)0.52050 (12)0.33977 (16)0.0197 (4)
N20.4067 (5)0.39592 (13)0.09730 (18)0.0253 (4)
C10.2642 (5)0.45592 (15)0.15388 (19)0.0204 (4)
C20.0811 (5)0.53460 (14)0.22134 (18)0.0173 (4)
C30.0084 (5)0.61731 (14)0.15971 (18)0.0177 (4)
H3A0.07580.62350.07680.021*
C40.1688 (5)0.69050 (13)0.22646 (18)0.0163 (4)
C50.2634 (5)0.67930 (15)0.34888 (18)0.0192 (4)
H5A0.3830.72830.39530.023*
C60.1748 (6)0.59298 (15)0.40037 (19)0.0207 (4)
H6A0.23820.58510.48320.025*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl0.0217 (3)0.0212 (3)0.0227 (3)0.00411 (18)0.00040 (18)0.00357 (18)
N10.0200 (8)0.0197 (8)0.0191 (9)0.0004 (6)0.0016 (7)0.0014 (7)
N20.0261 (9)0.0245 (9)0.0247 (10)0.0046 (7)0.0003 (8)0.0011 (7)
C10.0176 (9)0.0218 (9)0.0216 (10)0.0002 (7)0.0019 (8)0.0027 (8)
C20.0141 (8)0.0180 (9)0.0199 (10)0.0012 (7)0.0021 (7)0.0016 (7)
C30.0161 (9)0.0217 (9)0.0153 (9)0.0004 (7)0.0020 (7)0.0001 (7)
C40.0144 (8)0.0169 (8)0.0180 (9)0.0012 (7)0.0032 (7)0.0018 (7)
C50.0185 (9)0.0201 (9)0.0185 (10)0.0003 (7)0.0002 (8)0.0024 (7)
C60.0236 (10)0.0230 (10)0.0152 (9)0.0012 (8)0.0020 (8)0.0004 (7)
Geometric parameters (Å, º) top
Cl—C41.740 (3)C3—C41.402 (3)
N1—C61.350 (3)C3—H3A0.95
N1—C21.361 (3)C4—C51.403 (3)
N2—C11.156 (3)C5—C61.405 (3)
C1—C21.473 (3)C5—H5A0.95
C2—C31.401 (3)C6—H6A0.95
C6—N1—C2116.07 (19)C3—C4—Cl119.61 (18)
N2—C1—C2177.6 (2)C5—C4—Cl120.11 (16)
N1—C2—C3125.12 (19)C4—C5—C6117.58 (19)
N1—C2—C1116.70 (19)C4—C5—H5A121.2
C3—C2—C1118.2 (2)C6—C5—H5A121.2
C2—C3—C4116.7 (2)N1—C6—C5124.3 (2)
C2—C3—H3A121.7N1—C6—H6A117.9
C4—C3—H3A121.7C5—C6—H6A117.9
C3—C4—C5120.27 (19)
C6—N1—C2—C30.1 (3)C2—C3—C4—Cl178.93 (15)
C6—N1—C2—C1179.66 (19)C3—C4—C5—C60.1 (3)
N1—C2—C3—C40.3 (3)Cl—C4—C5—C6179.07 (16)
C1—C2—C3—C4179.48 (18)C2—N1—C6—C50.1 (3)
C2—C3—C4—C50.3 (3)C4—C5—C6—N10.1 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C3—H3A···N2i0.952.643.462 (5)146
C6—H6A···N1ii0.952.753.493 (5)136
Symmetry codes: (i) x1, y+1, z; (ii) x, y+1, z+1.
(II) 6-Chloropyridine-2-carbonitrile top
Crystal data top
C6H3ClN2F(000) = 280
Mr = 138.55Dx = 1.510 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 6.1739 (15) ÅCell parameters from 9960 reflections
b = 15.238 (4) Åθ = 2.7–30.5°
c = 7.0123 (18) ŵ = 0.52 mm1
β = 112.492 (4)°T = 125 K
V = 609.5 (3) Å3Plate, colourless
Z = 40.20 × 0.15 × 0.03 mm
Data collection top
Bruker APEXII CCD
diffractometer
1868 independent reflections
Radiation source: fine-focus sealed tube1657 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.031
Detector resolution: 8.3333 pixels mm-1θmax = 30.6°, θmin = 2.7°
φ and ω scansh = 88
Absorption correction: multi-scan
(SADABS; Bruker, 2013)
k = 2121
Tmin = 0.82, Tmax = 0.98l = 109
15460 measured reflections
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.028H-atom parameters constrained
wR(F2) = 0.082 w = 1/[σ2(Fo2) + (0.0424P)2 + 0.1697P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max = 0.001
1868 reflectionsΔρmax = 0.48 e Å3
82 parametersΔρmin = 0.19 e Å3
Crystal data top
C6H3ClN2V = 609.5 (3) Å3
Mr = 138.55Z = 4
Monoclinic, P21/nMo Kα radiation
a = 6.1739 (15) ŵ = 0.52 mm1
b = 15.238 (4) ÅT = 125 K
c = 7.0123 (18) Å0.20 × 0.15 × 0.03 mm
β = 112.492 (4)°
Data collection top
Bruker APEXII CCD
diffractometer
1868 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2013)
1657 reflections with I > 2σ(I)
Tmin = 0.82, Tmax = 0.98Rint = 0.031
15460 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.082H-atom parameters constrained
S = 1.09Δρmax = 0.48 e Å3
1868 reflectionsΔρmin = 0.19 e Å3
82 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cl1.01050 (5)0.09596 (2)0.82065 (4)0.02803 (10)
N10.98012 (14)0.26545 (6)0.82258 (13)0.01720 (17)
N21.10287 (19)0.47889 (7)0.79286 (18)0.0351 (2)
C11.00059 (18)0.41966 (8)0.81170 (17)0.0232 (2)
C20.87412 (16)0.34169 (7)0.83298 (15)0.01728 (19)
C30.66223 (17)0.34787 (7)0.85770 (15)0.0198 (2)
H3A0.59580.40320.86640.024*
C40.55044 (17)0.26976 (8)0.86928 (16)0.0210 (2)
H4A0.40410.2710.88460.025*
C50.65405 (17)0.19009 (7)0.85828 (15)0.0205 (2)
H5A0.58180.13590.86590.025*
C60.86897 (17)0.19295 (7)0.83550 (15)0.01759 (19)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl0.03124 (16)0.02096 (15)0.03084 (16)0.00422 (9)0.01070 (11)0.00400 (9)
N10.0135 (3)0.0212 (4)0.0168 (4)0.0004 (3)0.0058 (3)0.0014 (3)
N20.0343 (5)0.0294 (5)0.0430 (6)0.0068 (4)0.0164 (5)0.0013 (4)
C10.0207 (5)0.0237 (5)0.0250 (5)0.0006 (4)0.0085 (4)0.0006 (4)
C20.0148 (4)0.0199 (4)0.0167 (4)0.0007 (3)0.0055 (3)0.0001 (3)
C30.0154 (4)0.0238 (5)0.0204 (4)0.0035 (3)0.0071 (3)0.0010 (4)
C40.0135 (4)0.0317 (5)0.0187 (4)0.0012 (4)0.0072 (3)0.0010 (4)
C50.0182 (4)0.0246 (5)0.0186 (4)0.0051 (3)0.0068 (3)0.0004 (4)
C60.0175 (4)0.0193 (4)0.0151 (4)0.0004 (3)0.0052 (3)0.0012 (3)
Geometric parameters (Å, º) top
Cl—C61.7402 (11)C3—C41.3938 (15)
N1—C61.3218 (13)C3—H3A0.95
N1—C21.3490 (13)C4—C51.3881 (16)
N2—C11.1378 (16)C4—H4A0.95
C1—C21.4604 (15)C5—C61.3965 (14)
C2—C31.3870 (14)C5—H5A0.95
C6—N1—C2116.15 (9)C5—C4—H4A120.2
N2—C1—C2177.99 (12)C3—C4—H4A120.2
N1—C2—C3124.44 (9)C4—C5—C6117.21 (9)
N1—C2—C1113.94 (9)C4—C5—H5A121.4
C3—C2—C1121.62 (9)C6—C5—H5A121.4
C2—C3—C4117.46 (9)N1—C6—C5125.09 (9)
C2—C3—H3A121.3N1—C6—Cl114.83 (8)
C4—C3—H3A121.3C5—C6—Cl120.07 (8)
C5—C4—C3119.65 (9)
C6—N1—C2—C30.62 (14)C3—C4—C5—C60.07 (15)
C6—N1—C2—C1178.24 (8)C2—N1—C6—C50.12 (15)
N1—C2—C3—C41.03 (15)C2—N1—C6—Cl179.80 (7)
C1—C2—C3—C4177.74 (9)C4—C5—C6—N10.38 (15)
C2—C3—C4—C50.71 (15)C4—C5—C6—Cl179.96 (7)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···N1i0.952.493.4099 (15)164
C5—H5A···N2ii0.952.703.5651 (17)152
Symmetry codes: (i) x1, y, z; (ii) x+3/2, y1/2, z+3/2.
Hydrogen-bond geometry (Å, º) for (I) top
D—H···AD—HH···AD···AD—H···A
C3—H3A···N2i0.952.643.462 (5)145.5
C6—H6A···N1ii0.952.753.493 (5)136.0
Symmetry codes: (i) x1, y+1, z; (ii) x, y+1, z+1.
Hydrogen-bond geometry (Å, º) for (II) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···N1i0.952.493.4099 (15)164.4
C5—H5A···N2ii0.952.703.5651 (17)151.7
Symmetry codes: (i) x1, y, z; (ii) x+3/2, y1/2, z+3/2.

Experimental details

(I)(II)
Crystal data
Chemical formulaC6H3ClN2C6H3ClN2
Mr138.55138.55
Crystal system, space groupMonoclinic, P21/nMonoclinic, P21/n
Temperature (K)125125
a, b, c (Å)3.813 (5), 14.047 (19), 11.356 (15)6.1739 (15), 15.238 (4), 7.0123 (18)
β (°) 96.806 (19) 112.492 (4)
V3)604.0 (14)609.5 (3)
Z44
Radiation typeMo KαMo Kα
µ (mm1)0.520.52
Crystal size (mm)0.25 × 0.10 × 0.040.20 × 0.15 × 0.03
Data collection
DiffractometerBruker APEXII CCDBruker APEXII CCD
Absorption correctionMulti-scan
(SADABS; Bruker, 2013)
Multi-scan
(SADABS; Bruker, 2013)
Tmin, Tmax0.67, 0.980.82, 0.98
No. of measured, independent and
observed [I > 2σ(I)] reflections
12191, 1852, 1498 15460, 1868, 1657
Rint0.0630.031
(sin θ/λ)max1)0.7150.717
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.135, 1.12 0.028, 0.082, 1.09
No. of reflections18521868
No. of parameters8282
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.53, 0.370.48, 0.19

Computer programs: APEX2 (Bruker, 2013), SAINT (Bruker, 2013), SHELXS2014 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), SHELXTL2014 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008).

 

Acknowledgements

This work was supported by Vassar College. X-ray facilities were provided by the US National Science Foundation (grant No. 0521237 to JMT).

References

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First citationBruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBull, J. A., Mousseau, J. J., Pelletier, G. & Charette, A. B. (2012). Chem. Rev. 112, 2642–2713.  CrossRef CAS PubMed Google Scholar
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Volume 71| Part 7| July 2015| Pages 852-856
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