2-Amino­benzoxazole–oxalic acid (2/1)

In the title compound, 2C₇H₇N₂O⁺·C₂O₄²⁻, proton transfer from oxalic acid to the N atom of the heterocycle has occurred to form a 2:1 molecular salt. In the extended structure, N—H...O hydrogen bonds link the components into [100] chains, which feature R²₂(8) and R⁴₄(14) loops.

Key indicators

Structure: I

• Single-crystal X-ray study
• T = 293 K
• R factor = 0.045
• wR factor = 0.132
• Data-to-parameter ratio = 11.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT250_ALERT_2_C Large U3/U1 Ratio for <U(i,j)> Tensor(Resd    3)        2.6 Note
PLAT911_ALERT_3_C Missing FCF Refl Between Thmin & STh/L=    0.600          9 Report
                1  6  0,   7  5  2,   0  7  3,   6  1  4,   2  3  6,   4  4 12,
               -5  8 12,  -5  0 13,   0  2 16,

Alert level G
PLAT002_ALERT_2_G Number of Distance or Angle Restraints on AtSite         10 Note
PLAT012_ALERT_1_G No       _shelx_res_checksum Found in CIF ......     Please Check
PLAT172_ALERT_4_G The CIF-Embedded .res File Contains DFIX Records          1 Report
PLAT199_ALERT_1_G Reported _cell_measurement_temperature ..... (K)        293 Check
PLAT200_ALERT_1_G Reported   _diffrn_ambient_temperature ..... (K)        293 Check
PLAT398_ALERT_2_G Deviating  C-O-C   Angle From 120 for O1       .      105.9 Degree
PLAT398_ALERT_2_G Deviating  C-O-C   Angle From 120 for O2       .      105.3 Degree
PLAT480_ALERT_4_G Long H...A H-Bond Reported H2       ..O1       .       2.65 Ang.
PLAT790_ALERT_4_G Centre of Gravity not Within Unit Cell: Resd.  #          2 Note
              C7 H7 N2 O
PLAT860_ALERT_3_G Number of Least-Squares Restraints .............          6 Note
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600         31 Note
PLAT953_ALERT_1_G Reported (CIF) and Actual (FCF) Hmax Differ by .          1 Units
PLAT969_ALERT_5_G The 'Henn et al.' R-Factor-gap value ...........       2.11 Note
              Predicted wR2: Based on SigI   2  6.24 or SHELX Weight 13.33       
PLAT978_ALERT_2_G Number C-C Bonds with Positive Residual Density.          2 Info

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

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

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Computing details

Bis(2-aminobenzoxazol-3-ium) oxalate

Crystal data

2C7H7N2O^+·C2O4^2^−	F(000) = 744
Mr = 358.31	Dx = 1.541 Mg m^−3
Monoclinic, P21/n	Cu Kα radiation, λ = 1.54184 Å
a = 6.5080 (2) Å	Cell parameters from 2449 reflections
b = 17.6943 (7) Å	θ = 4.1–70.3°
c = 13.6264 (5) Å	µ = 1.03 mm^−1
β = 100.200 (4)°	T = 293 K
V = 1544.34 (10) Å^3	Needle, light yellow
Z = 4	0.17 × 0.14 × 0.12 mm

Data collection

XtaLAB Synergy, Single source at home/near, HyPix3000 diffractometer	2960 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Cu) X-ray Source	2288 reflections with I > 2σ(I)
Mirror monochromator	Rint = 0.031
Detector resolution: 10.0000 pixels mm^-1	θmax = 71.4°, θmin = 4.1°
ω scans	h = −8→7
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2020)	k = −20→21
Tmin = 0.157, Tmax = 1.000	l = −13→16
2960 measured reflections

Refinement

Refinement on F^2	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.045	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.132	w = 1/[σ^2(Fo^2) + (0.0724P)^2 + 0.1538P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
2960 reflections	Δρmax = 0.23 e Å^−3
259 parameters	Δρmin = −0.20 e Å^−3
6 restraints

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.

Refinement. The hydrogen atoms of amino groups and protonated nitro­gen atoms of oxzole groups were located in difference - Fourier maps and refined with restrained distances of 0.85±(1) Å. The H atoms of the benzene ring were calculated geometrically with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.1212 (2)	0.44529 (8)	0.33805 (10)	0.0428 (3)
N1	0.4453 (2)	0.48755 (9)	0.38019 (11)	0.0381 (4)
H1	0.545 (3)	0.5203 (13)	0.3995 (19)	0.082 (9)*
C1	0.4597 (3)	0.41299 (11)	0.34764 (13)	0.0366 (4)
O2	1.3397 (2)	0.94256 (8)	0.42539 (10)	0.0410 (3)
N2	0.1639 (3)	0.56637 (11)	0.39934 (16)	0.0521 (5)
H2A	0.0351 (19)	0.5701 (15)	0.4069 (18)	0.069 (8)*
H2B	0.252 (3)	0.6021 (11)	0.4168 (18)	0.069 (8)*
C2	0.6255 (3)	0.36637 (12)	0.34088 (15)	0.0439 (5)
H2	0.762934	0.382283	0.360114	0.053*
O3	0.4839 (2)	0.67161 (8)	0.42640 (12)	0.0540 (4)
N3	1.0284 (2)	0.88951 (9)	0.42134 (12)	0.0381 (4)
H3A	0.927 (3)	0.8578 (14)	0.427 (2)	0.090 (10)*
C3	0.5769 (4)	0.29442 (12)	0.30389 (16)	0.0518 (5)
H3	0.685094	0.261048	0.299092	0.062*
O4	0.7441 (2)	0.58949 (7)	0.42948 (10)	0.0432 (3)
N4	1.3345 (3)	0.81860 (10)	0.47545 (14)	0.0470 (4)
H4A	1.4629 (19)	0.8123 (15)	0.4680 (17)	0.061 (7)*
H4B	1.258 (3)	0.7797 (10)	0.4805 (18)	0.064 (8)*
C4	0.3719 (4)	0.27030 (13)	0.27364 (17)	0.0533 (6)
H4	0.346243	0.222044	0.247253	0.064*
O5	0.7522 (2)	0.78759 (8)	0.43539 (12)	0.0517 (4)
C5	0.2049 (3)	0.31731 (12)	0.28231 (16)	0.0497 (5)
H5	0.066961	0.301904	0.263314	0.060*
O6	1.0164 (2)	0.70685 (9)	0.46759 (14)	0.0624 (5)
C6	0.2561 (3)	0.38746 (11)	0.32045 (13)	0.0394 (4)
C7	0.2444 (3)	0.50366 (11)	0.37490 (13)	0.0383 (4)
C8	0.9941 (3)	0.96341 (10)	0.38748 (13)	0.0350 (4)
C9	0.8136 (3)	1.00364 (12)	0.35338 (13)	0.0420 (4)
H9	0.682079	0.982192	0.350086	0.050*
C10	0.8389 (3)	1.07772 (13)	0.32431 (15)	0.0490 (5)
H10	0.720945	1.106402	0.300336	0.059*
C11	1.0345 (4)	1.11046 (13)	0.32983 (16)	0.0531 (5)
H11	1.044476	1.160508	0.310364	0.064*
C12	1.2147 (3)	1.06995 (12)	0.36377 (16)	0.0483 (5)
H12	1.346707	1.091225	0.368116	0.058*
C13	1.1870 (3)	0.99662 (11)	0.39057 (13)	0.0377 (4)
C14	1.2326 (3)	0.87935 (11)	0.44171 (13)	0.0372 (4)
C15	0.6703 (3)	0.65540 (10)	0.43310 (13)	0.0354 (4)
C16	0.8301 (3)	0.72137 (11)	0.44698 (14)	0.0379 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0305 (7)	0.0392 (7)	0.0574 (8)	−0.0051 (5)	0.0037 (5)	−0.0028 (6)
N1	0.0284 (8)	0.0363 (9)	0.0492 (8)	−0.0048 (6)	0.0058 (6)	−0.0030 (7)
C1	0.0356 (10)	0.0348 (10)	0.0396 (9)	−0.0046 (8)	0.0071 (7)	0.0037 (7)
O2	0.0322 (7)	0.0382 (7)	0.0536 (8)	−0.0047 (5)	0.0098 (5)	0.0007 (6)
N2	0.0331 (9)	0.0404 (10)	0.0844 (13)	−0.0023 (8)	0.0144 (9)	−0.0085 (9)
C2	0.0377 (11)	0.0428 (11)	0.0523 (11)	0.0007 (8)	0.0110 (8)	0.0039 (9)
O3	0.0292 (7)	0.0391 (8)	0.0945 (11)	−0.0031 (6)	0.0131 (7)	−0.0047 (8)
N3	0.0298 (8)	0.0342 (9)	0.0515 (9)	−0.0049 (7)	0.0101 (6)	−0.0018 (7)
C3	0.0567 (14)	0.0396 (11)	0.0626 (13)	0.0058 (10)	0.0202 (10)	0.0046 (10)
O4	0.0327 (7)	0.0323 (7)	0.0645 (8)	−0.0021 (5)	0.0086 (6)	−0.0027 (6)
N4	0.0360 (10)	0.0392 (10)	0.0663 (11)	0.0014 (8)	0.0102 (8)	0.0037 (8)
C4	0.0648 (15)	0.0344 (11)	0.0637 (13)	−0.0072 (10)	0.0199 (11)	−0.0045 (10)
O5	0.0324 (7)	0.0332 (7)	0.0900 (11)	−0.0013 (6)	0.0120 (7)	0.0054 (7)
C5	0.0486 (12)	0.0430 (12)	0.0579 (12)	−0.0135 (9)	0.0105 (9)	−0.0027 (9)
O6	0.0291 (8)	0.0397 (9)	0.1155 (14)	−0.0015 (6)	0.0047 (8)	0.0032 (8)
C6	0.0351 (10)	0.0378 (10)	0.0451 (10)	−0.0019 (8)	0.0063 (7)	0.0037 (8)
C7	0.0328 (9)	0.0344 (10)	0.0477 (10)	−0.0039 (7)	0.0066 (7)	0.0009 (8)
C8	0.0355 (10)	0.0337 (10)	0.0367 (8)	−0.0029 (7)	0.0093 (7)	−0.0032 (7)
C9	0.0353 (10)	0.0433 (11)	0.0476 (10)	0.0004 (8)	0.0082 (8)	−0.0014 (9)
C10	0.0491 (12)	0.0459 (12)	0.0525 (11)	0.0074 (9)	0.0102 (9)	0.0043 (9)
C11	0.0620 (14)	0.0383 (12)	0.0616 (13)	−0.0022 (10)	0.0180 (10)	0.0085 (10)
C12	0.0476 (12)	0.0418 (12)	0.0576 (12)	−0.0100 (9)	0.0154 (9)	0.0013 (9)
C13	0.0361 (10)	0.0357 (10)	0.0423 (9)	−0.0014 (8)	0.0098 (7)	−0.0029 (8)
C14	0.0330 (10)	0.0340 (10)	0.0453 (9)	−0.0050 (7)	0.0090 (7)	−0.0041 (8)
C15	0.0304 (9)	0.0343 (10)	0.0420 (9)	−0.0025 (7)	0.0079 (7)	0.0009 (8)
C16	0.0305 (9)	0.0336 (10)	0.0498 (10)	−0.0033 (7)	0.0077 (7)	0.0007 (8)

Geometric parameters (Å, º)

O1—C6	1.397 (2)	N4—H4A	0.866 (10)
O1—C7	1.349 (2)	N4—H4B	0.858 (10)
N1—H1	0.876 (10)	N4—C14	1.303 (3)
N1—C1	1.400 (3)	C4—H4	0.9300
N1—C7	1.328 (2)	C4—C5	1.390 (3)
C1—C2	1.374 (3)	O5—C16	1.276 (2)
C1—C6	1.386 (3)	C5—H5	0.9300
O2—C13	1.400 (2)	C5—C6	1.364 (3)
O2—C14	1.357 (2)	O6—C16	1.222 (2)
N2—H2A	0.865 (10)	C8—C9	1.382 (3)
N2—H2B	0.857 (10)	C8—C13	1.380 (3)
N2—C7	1.296 (3)	C9—H9	0.9300
C2—H2	0.9300	C9—C10	1.388 (3)
C2—C3	1.385 (3)	C10—H10	0.9300
O3—C15	1.234 (2)	C10—C11	1.388 (3)
N3—H3A	0.877 (10)	C11—H11	0.9300
N3—C8	1.391 (2)	C11—C12	1.382 (3)
N3—C14	1.321 (2)	C12—H12	0.9300
C3—H3	0.9300	C12—C13	1.369 (3)
C3—C4	1.392 (3)	C15—C16	1.553 (3)
O4—C15	1.266 (2)
C7—O1—C6	105.93 (14)	C5—C6—C1	123.77 (19)
C1—N1—H1	129 (2)	N1—C7—O1	111.77 (16)
C7—N1—H1	123 (2)	N2—C7—O1	120.69 (17)
C7—N1—C1	107.77 (15)	N2—C7—N1	127.53 (18)
C2—C1—N1	133.15 (18)	C9—C8—N3	132.26 (18)
C2—C1—C6	120.73 (18)	C13—C8—N3	107.36 (16)
C6—C1—N1	106.12 (16)	C13—C8—C9	120.37 (18)
C14—O2—C13	105.31 (14)	C8—C9—H9	121.8
H2A—N2—H2B	122 (3)	C8—C9—C10	116.46 (19)
C7—N2—H2A	122.7 (18)	C10—C9—H9	121.8
C7—N2—H2B	115.0 (19)	C9—C10—H10	118.9
C1—C2—H2	121.8	C9—C10—C11	122.2 (2)
C1—C2—C3	116.40 (19)	C11—C10—H10	118.9
C3—C2—H2	121.8	C10—C11—H11	119.4
C8—N3—H3A	123 (2)	C12—C11—C10	121.1 (2)
C14—N3—H3A	129 (2)	C12—C11—H11	119.4
C14—N3—C8	107.10 (15)	C11—C12—H12	122.1
C2—C3—H3	118.8	C13—C12—C11	115.9 (2)
C2—C3—C4	122.3 (2)	C13—C12—H12	122.1
C4—C3—H3	118.8	C8—C13—O2	107.87 (16)
H4A—N4—H4B	119 (2)	C12—C13—O2	128.21 (18)
C14—N4—H4A	120.4 (17)	C12—C13—C8	123.92 (19)
C14—N4—H4B	115.1 (18)	N3—C14—O2	112.34 (16)
C3—C4—H4	119.5	N4—C14—O2	119.57 (17)
C5—C4—C3	120.9 (2)	N4—C14—N3	128.08 (18)
C5—C4—H4	119.5	O3—C15—O4	125.89 (17)
C4—C5—H5	122.1	O3—C15—C16	117.56 (16)
C6—C5—C4	115.8 (2)	O4—C15—C16	116.55 (16)
C6—C5—H5	122.1	O5—C16—C15	115.62 (16)
C1—C6—O1	108.39 (16)	O6—C16—O5	125.33 (18)
C5—C6—O1	127.84 (18)	O6—C16—C15	119.06 (17)
N1—C1—C2—C3	−179.9 (2)	C6—C1—C2—C3	1.4 (3)
N1—C1—C6—O1	−1.0 (2)	C7—O1—C6—C1	0.03 (19)
N1—C1—C6—C5	178.36 (18)	C7—O1—C6—C5	−179.3 (2)
C1—N1—C7—O1	−1.8 (2)	C7—N1—C1—C2	−177.2 (2)
C1—N1—C7—N2	179.0 (2)	C7—N1—C1—C6	1.7 (2)
C1—C2—C3—C4	0.9 (3)	C8—N3—C14—O2	1.1 (2)
C2—C1—C6—O1	178.00 (16)	C8—N3—C14—N4	179.93 (19)
C2—C1—C6—C5	−2.6 (3)	C8—C9—C10—C11	−0.6 (3)
C2—C3—C4—C5	−2.0 (3)	C9—C8—C13—O2	−178.45 (16)
O3—C15—C16—O5	−10.1 (3)	C9—C8—C13—C12	1.8 (3)
O3—C15—C16—O6	169.97 (19)	C9—C10—C11—C12	0.8 (3)
N3—C8—C9—C10	−179.46 (19)	C10—C11—C12—C13	0.3 (3)
N3—C8—C13—O2	0.65 (19)	C11—C12—C13—O2	178.73 (18)
N3—C8—C13—C12	−179.10 (18)	C11—C12—C13—C8	−1.6 (3)
C3—C4—C5—C6	0.9 (3)	C13—O2—C14—N3	−0.71 (19)
O4—C15—C16—O5	169.79 (17)	C13—O2—C14—N4	−179.63 (17)
O4—C15—C16—O6	−10.2 (3)	C13—C8—C9—C10	−0.6 (3)
C4—C5—C6—O1	−179.32 (18)	C14—O2—C13—C8	0.00 (18)
C4—C5—C6—C1	1.4 (3)	C14—O2—C13—C12	179.74 (19)
C6—O1—C7—N1	1.1 (2)	C14—N3—C8—C9	177.88 (19)
C6—O1—C7—N2	−179.66 (18)	C14—N3—C8—C13	−1.07 (19)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O4	0.88 (1)	1.78 (1)	2.650 (2)	176 (3)
N2—H2A···O4^i	0.87 (1)	2.00 (1)	2.863 (2)	174 (3)
N2—H2B···O3	0.86 (1)	1.94 (1)	2.770 (2)	164 (2)
C2—H2···O1^ii	0.93	2.65	3.522 (2)	157
N3—H3A···O5	0.88 (1)	1.71 (1)	2.577 (2)	173 (3)
N4—H4A···O5^ii	0.87 (1)	2.06 (1)	2.918 (2)	172 (2)
N4—H4B···O6	0.86 (1)	2.02 (1)	2.851 (2)	163 (2)

Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z.