Literature DB >> 26279884

Crystal structures of 4-chloro-pyridine-2-carbo-nitrile and 6-chloro-pyridine-2-carbo-nitrile exhibit different inter-molecular π-stacking, C-H⋯Nnitrile and C-H⋯Npyridine inter-actions.

Matthew J Montgomery1, Thomas J O'Connor1, Joseph M Tanski1.   

Abstract

The two title compounds are isomers of C6H3ClN2 containing a n class="Chemical">pyridine ring, a nitrile group, and a chloro substituent. The mol-ecules of each compound pack together in the solid state with offset face-to-face π-stacking, and inter-molecular C-H⋯Nnitrile and C-H⋯Npyridine inter-actions. 4-Chloro-pyridine-2-carbo-nitrile, (I), exhibits pairwise centrosymmetric head-to-head C-H⋯Nnitrile and C-H⋯Npyridine inter-actions, forming one-dimensional chains, which are π-stacked in an offset face-to-face fashion. The inter-molecular packing of the isomeric 6-chloro-pyridine-2-carbo-nitrile, (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 inter-actions, 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 mol-ecules with alternating orientations of the chloro and nitrile substituents.

Entities:  

Keywords:  C—H⋯N inter­actions; chloro­cyano­pyridine; crystal structure; π-stacking

Year:  2015        PMID: 26279884      PMCID: PMC4518955          DOI: 10.1107/S2056989015011767

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Chloro­n class="Chemical">pyridine­carbo­nitriles 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 ▸). 6-Chloro­n class="Chemical">pyridine-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

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 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 ▸] and 4-cyano­pyridine [1.137 (8) Å; Laing et al., 1971 ▸] 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) 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 ▸).
Figure 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

A view of 6-chloro­pyridine-2-carbo­nitrile, (II), with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.

Both (I) and (II) 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 n class="Chemical">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

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⋯n class="Chemical">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⋯n class="Chemical">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).
Figure 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.]

Table 1

Hydrogen-bond geometry (Å, °) for (I)

D—H⋯A D—HH⋯A DA D—H⋯A
C3—H3A⋯N2i 0.952.643.462 (5)146
C6—H6A⋯N1ii 0.952.753.493 (5)136

Symmetry codes: (i) ; (ii) .

Figure 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.]

In contrast to (I), the mol­ecules of (II) pack together via head-to-tail C—H⋯Nnitrile and C—H⋯n class="Chemical">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 ▸).
Figure 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 + , y − , −z + .]

Table 2

Hydrogen-bond geometry (Å, °) for (II)

D—H⋯A D—HH⋯A DA D—H⋯A
C4—H4A⋯N1i 0.952.493.4099 (15)164
C5—H5A⋯N2ii 0.952.703.5651 (17)152

Symmetry codes: (i) ; (ii) .

Figure 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 + , −y + , z + .]

Notably, there are no significant Cl⋯Cl contacts in (I) or (II), in contrast to 2-n class="Chemical">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 halidehalide contacts, see Pedireddi et al. (1994 ▸) and Jelsch et al. (2015 ▸).

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.

Refinement

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 U iso(H) = 1.2U eq(C) of the aryl C atoms.
Table 3

Experimental details

 (I)(II)
Crystal data
Chemical formulaC6H3ClN2 C6H3ClN2
M r 138.55138.55
Crystal system, space groupMonoclinic, P21/n Monoclinic, 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)
Z 44
Radiation typeMo KαMo Kα
μ (mm−1)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)
T min, T max 0.67, 0.980.82, 0.98
No. of measured, independent and observed [I > 2σ(I)] reflections12191, 1852, 149815460, 1868, 1657
R int 0.0630.031
(sin θ/λ)max−1)0.7150.717
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.050, 0.135, 1.120.028, 0.082, 1.09
No. of reflections18521868
No. of parameters8282
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.53, −0.370.48, −0.19

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

Crystal structure: contains datablock(s) global, I, II. DOI: 10.1107/S2056989015011767/rz5161sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015011767/rz5161Isup2.hkl Structure factors: contains datablock(s) II. DOI: 10.1107/S2056989015011767/rz5161IIsup3.hkl Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989015011767/rz5161Isup4.cml Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989015011767/rz5161IIsup5.cml CCDC references: 1407613, 1407612 Additional supporting information: crystallographic information; 3D view; checkCIF report
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
Bruker APEXII CCD diffractometer1852 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 = −5→5
Absorption correction: multi-scan (SADABS; Bruker, 2013)k = −20→19
Tmin = 0.67, Tmax = 0.98l = −16→16
12191 measured reflections
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) = 0.135w = 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
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.
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)
N2−0.4067 (5)0.39592 (13)0.09730 (18)0.0253 (4)
C1−0.2642 (5)0.45592 (15)0.15388 (19)0.0204 (4)
C2−0.0811 (5)0.53460 (14)0.22134 (18)0.0173 (4)
C3−0.0084 (5)0.61731 (14)0.15971 (18)0.0177 (4)
H3A−0.07580.62350.07680.021*
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*
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)
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—C3−0.1 (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—C6−179.07 (16)
C1—C2—C3—C4−179.48 (18)C2—N1—C6—C5−0.1 (3)
C2—C3—C4—C5−0.3 (3)C4—C5—C6—N10.1 (3)
D—H···AD—HH···AD···AD—H···A
C3—H3A···N2i0.952.643.462 (5)146
C6—H6A···N1ii0.952.753.493 (5)136
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
Bruker APEXII CCD diffractometer1868 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 = −8→8
Absorption correction: multi-scan (SADABS; Bruker, 2013)k = −21→21
Tmin = 0.82, Tmax = 0.98l = −10→9
15460 measured reflections
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) = 0.082w = 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
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.
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)
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)
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—C6−0.07 (15)
C6—N1—C2—C1−178.24 (8)C2—N1—C6—C50.12 (15)
N1—C2—C3—C4−1.03 (15)C2—N1—C6—Cl179.80 (7)
C1—C2—C3—C4177.74 (9)C4—C5—C6—N1−0.38 (15)
C2—C3—C4—C50.71 (15)C4—C5—C6—Cl179.96 (7)
D—H···AD—HH···AD···AD—H···A
C4—H4A···N1i0.952.493.4099 (15)164
C5—H5A···N2ii0.952.703.5651 (17)152
  6 in total

Review 1.  Synthesis of pyridine and dihydropyridine derivatives by regio- and stereoselective addition to N-activated pyridines.

Authors:  James A Bull; James J Mousseau; Guillaume Pelletier; André B Charette
Journal:  Chem Rev       Date:  2012-02-21       Impact factor: 60.622

2.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

3.  The Cambridge Structural Database in retrospect and prospect.

Authors:  Colin R Groom; Frank H Allen
Journal:  Angew Chem Int Ed Engl       Date:  2014-01-02       Impact factor: 15.336

4.  Synthesis and structure-activity relationships of amide derivatives of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetic acid as selective arginine vasopressin V2 receptor agonists.

Authors:  Issei Tsukamoto; Hiroyuki Koshio; Takahiro Kuramochi; Chikashi Saitoh; Hiroko Yanai-Inamura; Chika Kitada-Nozawa; Eisaku Yamamoto; Takeyuki Yatsu; Yoshiaki Shimada; Shuichi Sakamoto; Shin-ichi Tsukamoto
Journal:  Bioorg Med Chem       Date:  2009-03-09       Impact factor: 3.641

5.  Likelihood of atom-atom contacts in crystal structures of halogenated organic compounds.

Authors:  Christian Jelsch; Sarra Soudani; Cherif Ben Nasr
Journal:  IUCrJ       Date:  2015-04-10       Impact factor: 4.769

6.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

  6 in total

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