Low-temperature crystal structure of 4-chloro-1H-pyrazole

The crystal structure of 4-chloro-1H-pyrazole has been determined at 170 K, showing a hydrogen-bonded trimeric mol­ecular assembly that is isostructural to its bromo analogue, 4-bromo-1H-pyrazole.

Key indicators

• Single-crystal X-ray study
• T = 170 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.033
• wR factor = 0.092
• Data-to-parameter ratio = 18.5

checkCIF/PLATON results

No syntax errors found



Alert level G
PLAT007_ALERT_5_G Number of Unrefined Donor-H Atoms ..............          3 Report
PLAT300_ALERT_4_G Atom Site Occupancy of H1A        Constrained at        0.5 Check
PLAT300_ALERT_4_G Atom Site Occupancy of H2         Constrained at        0.5 Check
PLAT300_ALERT_4_G Atom Site Occupancy of H3A        Constrained at        0.5 Check
PLAT978_ALERT_2_G Number C-C Bonds with Positive Residual Density.          3 Info

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   0 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   5 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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Computing details

Data collection: APEX3 (Bruker, 2020); cell refinement: CrysAlis PRO (Rigaku OD, 2019); data reduction: CrysAlis PRO (Rigaku OD, 2019); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

4-Chloro-1H-pyrazole

Crystal data

C3H3ClN2	Dx = 1.557 Mg m^−3
Mr = 102.52	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 6701 reflections
a = 14.9122 (10) Å	θ = 2.3–30.2°
b = 17.6410 (9) Å	µ = 0.69 mm^−1
c = 4.9878 (3) Å	T = 170 K
V = 1312.13 (14) Å^3	Rect. Prism, clear colourless
Z = 12	0.28 × 0.14 × 0.08 mm
F(000) = 624

Data collection

Bruker D8 CMOS diffractometer	1481 reflections with I > 2σ(I)
ω scans	Rint = 0.043
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2019)	θmax = 29.0°, θmin = 2.3°
Tmin = 0.760, Tmax = 1.000	h = −20→20
25891 measured reflections	k = −23→23
1798 independent reflections	l = −6→6

Refinement

Refinement on F^2	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.033	Hydrogen site location: mixed
wR(F^2) = 0.092	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0418P)^2 + 0.5547P] where P = (Fo^2 + 2Fc^2)/3
1798 reflections	(Δ/σ)max = 0.001
97 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.65912 (3)	0.45830 (2)	0.73672 (9)	0.04510 (15)
C1	0.66638 (11)	0.61504 (9)	0.6893 (4)	0.0375 (3)
C2	0.63595 (10)	0.54554 (8)	0.6008 (3)	0.0330 (3)
N1	0.63427 (9)	0.66822 (7)	0.5248 (3)	0.0390 (3)
H1A	0.644141	0.717242	0.538844	0.047*	0.5
C3	0.58468 (11)	0.56001 (10)	0.3776 (3)	0.0389 (4)
N2	0.58435 (9)	0.63462 (8)	0.3340 (3)	0.0405 (3)
H2	0.556236	0.657939	0.202649	0.049*	0.5
Cl2	0.70256 (4)	0.250000	0.59928 (11)	0.03892 (16)
C5	0.62343 (15)	0.250000	0.3495 (4)	0.0326 (4)
N3	0.52730 (9)	0.28813 (7)	0.0432 (3)	0.0395 (3)
H3A	0.494432	0.317237	−0.061095	0.047*	0.5
C4	0.58543 (12)	0.31226 (10)	0.2276 (3)	0.0396 (4)
H3	0.5571 (14)	0.5266 (11)	0.253 (4)	0.043 (5)*
H1	0.7031 (12)	0.6279 (11)	0.839 (4)	0.040 (5)*
H4	0.5962 (12)	0.3661 (12)	0.261 (4)	0.051 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0525 (3)	0.0303 (2)	0.0525 (3)	0.00392 (16)	−0.00952 (19)	0.00342 (16)
C1	0.0379 (8)	0.0335 (8)	0.0412 (8)	−0.0017 (6)	−0.0027 (7)	−0.0020 (7)
C2	0.0340 (7)	0.0281 (7)	0.0371 (8)	0.0020 (6)	0.0008 (6)	−0.0006 (6)
N1	0.0408 (7)	0.0330 (6)	0.0431 (7)	−0.0007 (6)	0.0017 (6)	−0.0012 (6)
C3	0.0429 (9)	0.0345 (8)	0.0391 (8)	0.0028 (6)	−0.0053 (7)	−0.0032 (7)
N2	0.0450 (8)	0.0383 (7)	0.0384 (7)	0.0053 (6)	−0.0022 (6)	0.0028 (6)
Cl2	0.0416 (3)	0.0395 (3)	0.0356 (3)	0.000	−0.0053 (2)	0.000
C5	0.0359 (11)	0.0311 (10)	0.0309 (10)	0.000	−0.0011 (9)	0.000
N3	0.0432 (7)	0.0370 (7)	0.0384 (7)	0.0068 (6)	−0.0036 (6)	−0.0001 (6)
C4	0.0483 (10)	0.0306 (8)	0.0401 (8)	0.0052 (7)	−0.0035 (7)	−0.0040 (7)

Geometric parameters (Å, º)

Cl1—C2	1.7169 (15)	N2—H2	0.8800
C1—C2	1.380 (2)	Cl2—C5	1.716 (2)
C1—N1	1.335 (2)	C5—C4	1.377 (2)
C1—H1	0.952 (19)	C5—C4^i	1.377 (2)
C2—C3	1.374 (2)	N3—N3^i	1.345 (3)
N1—H1A	0.8800	N3—H3A	0.8800
N1—N2	1.3457 (19)	N3—C4	1.334 (2)
C3—N2	1.334 (2)	C4—H4	0.98 (2)
C3—H3	0.951 (19)
C2—C1—H1	130.6 (11)	N1—N2—H2	125.7
N1—C1—C2	108.04 (14)	C3—N2—N1	108.50 (14)
N1—C1—H1	121.4 (11)	C3—N2—H2	125.7
C1—C2—Cl1	127.15 (13)	C4^i—C5—Cl2	127.11 (10)
C3—C2—Cl1	126.74 (12)	C4—C5—Cl2	127.11 (10)
C3—C2—C1	106.09 (14)	C4—C5—C4^i	105.8 (2)
C1—N1—H1A	125.6	N3^i—N3—H3A	125.7
C1—N1—N2	108.87 (13)	C4—N3—N3^i	108.61 (9)
N2—N1—H1A	125.6	C4—N3—H3A	125.7
C2—C3—H3	131.0 (12)	C5—C4—H4	129.2 (11)
N2—C3—C2	108.49 (15)	N3—C4—C5	108.50 (15)
N2—C3—H3	120.2 (12)	N3—C4—H4	122.3 (11)
Cl1—C2—C3—N2	−178.73 (13)	N1—C1—C2—Cl1	178.76 (12)
C1—C2—C3—N2	0.03 (19)	N1—C1—C2—C3	0.01 (18)
C1—N1—N2—C3	0.07 (18)	Cl2—C5—C4—N3	179.74 (15)
C2—C1—N1—N2	−0.05 (18)	N3^i—N3—C4—C5	−0.20 (16)
C2—C3—N2—N1	−0.06 (19)	C4^i—C5—C4—N3	0.3 (3)

Symmetry code: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···N1^ii	0.88	2.03	2.885 (3)	165
N2—H2···N3^iii	0.88	1.99	2.8582 (19)	169
N3—H3A···N2^iii	0.88	1.99	2.8582 (19)	169

Symmetry codes: (ii) x, −y+3/2, z; (iii) −x+1, −y+1, −z.