Short inter­molecular N—Br...O=C contacts in 1,3-dibromo-5,5-dimethyl­imidazolidine-2,4-dione

In the title compound, C₅H₆Br₂N₂O₂, all atoms except for the methyl group lie on a mirror plane in the space group Pnma (No. 62). All bond lengths are normal and the five-membered ring is planar by symmetry. Two short inter­molecular N—Br...O=C contacts [Br...O = 2.787 (2) and 2.8431 (19) Å] are present, originating primarily from the O-atom lone pairs donating electron density to the anti­bonding orbitals of the N—Br bonds (delocalization energy transfers 3.27 and 2.11 kcal mol⁻¹). The total stabilization energies of the Br...O inter­actions are 3.4828 and 2.3504 kcal mol⁻¹.

S1. Comment

In the search for uncommon intermolecular interactions in the solid state, our interest has focused on compounds containing short X···O intermolecular contacts (X = halogen). The structure of the title compound, dibromantin, (I), is presented here and is a unique example of short intermolecular N—Br···O═C contacts. Dibromantin (1,3-dibromo-5,5-dimethylhydantoin or 1,3-dibromo-5,5-dimethyl-2,4-imidazolidinedione) is a commercially available analytical reagent used in the pharmaceutical sciences (de Bertorello et al., 1967; Hilp, 2002a,b), as a brominating reagent (an alternative to N-bromosuccinimide and its derivatives; Jolles, 1966), as a drinking water purifier and as a popular water treatment biocide (Unhoch & Vore, 2004).

All intramolecular bond lengths and angles in (I) are normal (Fig. 1). All atoms except the methyl group lie on the special position c with site symmetry m. Thus, the five-membered ring is planar by symmetry (and without disorder).

The structure of (I) in the solid state has interesting features. There are short intermolecular N—Br···O═C contacts of 2.787 (2) Å (Br1···O2ⁱ and O2···Br1ⁱⁱ) and 2.8431 (19) Å (Br2···O1ⁱⁱⁱ and O1···Br2^iv), distinctly (>10%) shorter than the sum of the van der Waals radii (3.35 Å; Reference?) [symmetry codes: (i) x - 1, y, z; (ii) x + 1, y, z; (iii) x + 1/2, y, -z + 1/2; (iv) x - 1/2, y, -z + 1/2]. Moreover, although Br···O short contacts have been extensively studied over the past few decades (Hassel & Romming, 1962; Leser & Rabinovich, 1978; Ramasubbu et al., 1986), only one structure with a similar N—Br···O═C short contact is known, namely N-bromosuccinimide, (II) (Jabay et al., 1977), where the Br···O distance is 2.80 Å. Additionally, several structures have been reported with other halogen atoms involved in analogous short contacts: methyl 2-(3-oxo-1-phenylbenzo[c-1,5]aziodolin-2-yl)propanoate (NI···OC = 2.781 Å; Zhdankin et al., 2003), 1-acetoxy-1,2-benziodazole-3(1H)-one (NI···OC = 2.867 Å; Zhdankin et al., 1997), N-iodosuccinimide (NI···OC = 2.580 Å; Padmanabhan et al., 1990), N-chlorosuccinimide, (III) (NCl···OC = 2.880 Å; Brown, 1961), N-chloro-N-(2,6-dichlorophenyl)trichloroacetamide (NCl···OC = 2.829 Å; Gowda et al., 1996), 1,3-dichloro-1,3-diazetidine-2,4-dione (NCl···OC = 2.948 Å; Belaj et al., 1991) and N-chlorophthalimide (NCl···OC = 2.946 Å; Ghassemzadeh et al., 1994).

In compound (I), the N—Br···O angles of 179.24 (9) and 160.70 (9)°, and the Br···O═C angles of 170.9 (2) and 148.9 (2)°, are comparable with those in (II) (169.5° and 140.9°, respectively). In both compounds, the five-membered rings are in a trans arrangement to the Br···O interaction, but in (I) the rings are coplanar, while in (II) they are inclined at 127°. The contacts extend molecules of (I) into a one-dimensional ladder-type double chain along the a axis direction (Fig. 2) with an R³₃(12) motif (Bernstein et al., 1995).

The Cambridge Structural Database (Version 5.28; Allen, 2002) was searched for C—Br···O═C contacts shorter than 3.2 Å (as N—Br···O═C interactions are rare). The number of reported Br···O interactions decreases as the Br···O distance shortens, the C—Br···O angle adopts values in the range 140–180° with no single maximum, and the Br···O═C angle adopts values in the range 90–180° (maximum value 144°). Thus, the preferred angles are neither orthogonal nor linear. Examination of the two-dimensional contour plots of angle versus distance (Fig. 3) reveals two preferred pairs of C—Br···O angle and Br···O distance, 162.4° and 3.167 Å, and 172.0° and 3.052 Å, and three preferred pairs of Br···O═C angle and Br···O distance, 117.7° and 3.170 Å, 136.9° and 3.113 Å, and 141.0° and 3.087 Å. The values in (I) (as + symbols in Fig. 3) have been removed from the pairs.

For compound (III) (N-chlorosuccinimide), it was proposed that electrostatic attraction exists between the N—Cl and O═C groups because of the large polarization of these groups (Brown, 1961) as N^δ-—Cl^δ+···O^δ-═C^δ+. Due to the chemical similarity of the interactions in (I) and (III), electrostatic attraction can also be proposed for (I), and in order to confirm this assumption quantum mechanical calculations were performed. The molecular electronic properties have been calculated at a single point for both the diffraction-derived coordinates and the optimized structure, and these are comparable to within three standard deviations. The intermolecular interactions were calculated for sets containing bewteen three and 23 molecules; further details are available in the archived CIF.

The calculations show that the existence of intermolecular interactions leads to a decrease of p character in the N,O atom hybrids and increasing p character in the Br,C atom hybrids. This agrees with the increased polarization of the aforementioned bonds and the larger charges on the interacting atoms (Table 2). The N, O and methyl group C atoms have δ^- charges and the remainder of the atoms have δ⁺ charges, confirming the Brown (1961) postulates about polarization. The intermolecular interactions affect only the charges of the N—Br···O═C atoms (Table 2). Additionally, it is observed that the N—Br bond in the interacting molecules is created by less electron density than in non-interacting molecules. The energies of the intermolecular interaction are 3.4828 and 2.3504 kcal mol^-1 (1 kcal mol^-1 = 4.184 kJ mol^-1) for Br1···O2 and Br2···O1, respectively [including the basis-set superposition error (Boys & Bernardi, 1970) of 0.1147 kcal mol^-1]. The second-order perturbation theory analysis of the Fock matrix in the natural bond orbital (NBO) basis sets leads to the conclusion that these interactions are formed mostly by the O lone pairs donating electron density to the antibonding orbitals of the N—Br bonds, with delocalization energies of 3.27 and 2.11 kcal mol^-1, respectively, as above, proving that electrostatic attraction between the largely polarized groups is not responsible for these interactions. Noteworthy is the fact that, in separate molecules, there is no 2p_y coefficient in the h_C1(σ bond) and the h_O1(σ bond) hybrids. This is caused by coupling of the N1 and N2 atom lone-pair electrons with the antibonding C1—O1 orbital (interaction energies 83.39 and 54.13 kcal mol^-1, respectively). For the C2—O2 bond, only one such interaction is available with the N2 atom lone pair (interaction energy 76.04 kcal mol^-1). In sets containing the Br···O interactions, the diminishing 2p_y coefficient is not observed, due to the O1 atom electron-density changes (and, in consequence, changes in the natural orbital composition) caused by the intermolecular interactions.

The ab initio calculations prove that the N—Br···O═C interaction is bonding in character, but it is weak and its energy is comparable with weak C—H···O hydrogen bonds (Desiraju & Steiner, 1999).

Related literature

For related literature, see: Allen (2002); Belaj et al. (1991); Bernstein et al. (1995); Boys & Bernardi (1970); Brown (1961); Desiraju & Steiner (1999); Ghassemzadeh et al. (1994); Gowda et al. (1996); Hassel & Romming (1962); Hilp (2002a, 2002b); Jabay et al. (1977); Jolles (1966); Leser & Rabinovich (1978); Markish & Arrad (1995); Padmanabhan et al. (1990); Ramasubbu et al. (1986); Sheldrick (1997); Unhoch & Vore (2004); Zhdankin et al. (1997, 2003); de Bertorello (1967).

S2. Experimental

Compound (I) was synthesized by the method of Markish & Arrad (1995). To a solution (200 ml) [Solvent?] containing NaOH (5.00 g) and 5,5-dimethylhydantoin (8.40 g), Br₂ (22.050 g) was added dropwise over a period of 1 h. The reaction temperature was kept at 284.4 (3) K and the reagents were stirred for 2 h. The resulting precipitate was filtered using a Buchner funnel and washed with cold water [275 (1) K] until bromine was not detected in the filtrate. The resulting fine crystalline dibromantin was dried in a vacuum desiccator for 24 h (yield 97.3%; purity 99.8%, determined by the iodometric method). Colourless crystals of (I) suitable for X-ray diffraction were obtained by recrystallization from a saturated solution in water (0.22 g in 100 g H₂O) at 297 (1) K (7 weeks). This may seem to be a poor solvent as dibromantin has a low solubility in water, but usage of organic solvents (especially alcohols) causes dibromantin to decompose to 5,5-dimethylhydantoin before crystals can be obtained. Attempts to recrystallize (even from water) commercially available dibromantin always led to growth of 5,5-dimethylhydantoin. This was probably caused by decomposition catalyzed by small amounts of decomposition products always present in commercial dibromantin (3% w/w Fluka, 2% w/w Aldrich).

S3. Refinement

The H atoms were placed in calculated positions and were refined as riding on their parent C atoms, with C—H = 0.96 Å and with U_iso(H) = 1.5U_eq(C). The methyl groups were allowed to rotate about their local threefold axis [using AFIX 137 (SHELXL97; Sheldrick, 1997)].

Computing details

Data collection: CrysAlis CCD (Kuma Diffraction, 2000); cell refinement: CrysAlis RED (Kuma Diffraction, 2000); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/PC (Sheldrick, 1990b), Mercury (Version 1.4; Macrae et al., 2006) and VISC-II (Izumi & Dilanian, 2005); software used to prepare material for publication: Please provide missing information.

Figures

	Fig. 1. The molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. Part of the molecular packing of (I), showing (a) the short intermolecular contacts (dashed lines) and (b) the overlapping of the van der Waals spheres.
	Fig. 3. (a) Contour plot showing the relationship between the C—Br···O angle and the Br···O distance. (b) Contour plot showing the relationship between the Br···O═C angle and the Br···O distance. In both plots, the values for (I) are indicated by + symbols.

1,3-Dibromo-5,5-dimethyl-2,4-imidazolidinedione

Crystal data

C5H6Br2N2O2	F(000) = 544
Mr = 285.94	Dx = 2.258 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 1000 reflections
a = 7.9749 (2) Å	θ = 2–25°
b = 7.9205 (2) Å	µ = 9.59 mm^−1
c = 13.3152 (3) Å	T = 291 K
V = 841.06 (4) Å^3	Prism, colourless
Z = 4	0.12 × 0.08 × 0.06 mm

Data collection

Kuma KM4 CCD area-detector diffractometer	815 independent reflections
Radiation source: fine-focus sealed tube	750 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
ω scans	θmax = 25.1°, θmin = 3.0°
Absorption correction: numerical (X-RED; Stoe & Cie, 1999)	h = −7→9
Tmin = 0.399, Tmax = 0.558	k = −9→9
8337 measured reflections	l = −15→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.016	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.040	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.022P)^2 + 0.3072P] where P = (Fo^2 + 2Fc^2)/3
815 reflections	(Δ/σ)max < 0.001
65 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.56 e Å^−3

Special details

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Ab initio calculations on (I) ============================= The molecular electronic properties have been calculated at a single point for the coordinates determined from X-ray diffraction as well as for the optimized structure. The optimized geometric parameters were in agreement with those found from the diffraction measurements to within three standard deviations. The intermolecular interactions were calculated for sets containing between three and 23 molecules (further details below). The basis set superposition error (BSSE) was estimated using the counterpoize method (Boys & Bernardi, 1970).

Both restricted Hartree–Fock and density functional methods in the triple zeta 6–311++G(3df,3dp) basis set were used, as implemented in GAUSSIAN03 (Frisch et al., 2004). The differences in electronic properties and energies originating from the different number of molecules used in the calculations and the differences between the methods used are given in parentheses as standard deviations. If no deviation is given the values were the same in the range of reported precision. The electron density and intermolecular interactions were also described by natural bond orbital theory (NBO) (Foster & Weinhold, 1980; Reed & Weinhold, 1985; Reed et al., 1988), because the natural atomic orbitals (NAO) are extensions of the elementary Lewis structure concept and this allows discussion of the interactions in terms of `classical' orbital–orbital interactions.

The interacting N—Br and C1═O1 groups bonds can be expressed as σ_N1—Br1 (1.98387 e) = 0.8128(sp^3.26)_N1 + 0.5825(sp^10.57)_Br1, σ_C2═O2 (1.99375 e) = 0.5873(sp^1.90)_C2 + 0.8094(sp^1.28)_O2, π_C2═O2 (1.99375 e) = 0.5036(p)_C2 + 0.8639(p)_O2. σ_N2—Br2 (1.98405 e) = 0.8217(sp^3.10)_N2 + 0.5699(sp^10.74)_Br2, σ_C1═O1 (1.99335 e) = 0.5936(sp^1.72)_C1 + 0.8048(sp^1.32)_O1, π_C1═O1 (1.99554 e) = 0.4912(p)_C1 + 0.8710(p)_O1, and are created by hybrids h_N1 ≈ 0.4838(2 s)_N1 + 0.1382(2p_x)_N1 + 0.8632(2p_y)_N1, h_Br1 ≈ 0.2785(4 s)_Br1 - 0.1438(4p_x)_Br1 - 0.9365(4p_y)_Br1, h_{C2(σ bond)} ≈ 0.5846(2 s)_C2 + 0.2827(2p_x)_C2 - 0.7555(2p_y)_C2, h_{O2(σ bond)} ≈ 0.6621(2 s)_O2 - 0.2833(2p_x)_O2 + 0.6924(2p_y)_O2, h_{C2(π bond)} ≈ 0.9940(2p_z)_C2, h_{O2(π bond)} ≈ 0.9993(2p_z)_O2, h_N2 ≈ 0.4938(2 s)_N2 - 0.2963(2p_x)_N2 - 0.8165(2p_y)_N2, h_Br2 ≈ 0.2745(4 s)_Br2 + 0.2831(4p_x)_Br2 + 0.9044(4p_y)_Br2, h_{C1(σ bond)} ≈ 0.6046(2 s)_C1 + 0.1185(2p_x)_C1 + 0.7847(2p_y)_C1, h_{O1(σ bond)} ≈ 0.6558(2 s)_O1 - 0.1092(2p_x)_O1 - 0.74554(2p_y)_O1, h_{C1(π bond)} ≈ 0.9930(2p_z)_C1, h_{O1(π bond)} ≈ 0.9992(2p_z)_O1.

For a separate molecule (calculated for both optimized and non-optimized structure), these bonds and hybrids are σ_N1—Br1 (1.98533 e) = 0.8006(sp^3.44)_N1 + 0.5992(sp^9.17)_Br1, σ_C2═O2 (1.99376 e) = 0.5910(sp^1.88)_C2 + 0.8067(sp^1.31)_O2, π_C2═O2 (1.99313 e) = 0.5178(p)_C1 + 0.8555(p)_O1, σ_N2—Br2 (1.98504 e) = 0.8111(sp^3.24)_N2 + 0.5849(sp^9.57)_Br2, σ_C1═O1 (1.99344 e) = 0.5968(sp^1.71)_C1 + 0.8024(sp^1.36)_O1, π_C1═O1 (1.99521 e) = 0.5968(p)_C1 + 0.8652(p)_O1, h_N1 ≈ 0.4741(2 s)_N1 + 0.2556(2p_x)_N1 - 0.8414(2p_y)_N1, h_Br1 ≈ 0.3010(4 s)_Br1 - 0.2764(4p_x)_Br1 + 0.9000(4p_y)_Br1, h_{C2(σ bond)} ≈ 0.5870(2 s)_C2 - 0.5843(2p_x)_C2 + 0.5538(2p_y)_C2, h_{O2(σ bond)} ≈ 0.6567(2 s)_O2 - 0.5593(2p_x)_O2 - 0.5040(2p_y)_O2, h_{C2(π bond)} ≈ 0.9939(2p_z)_C2, h_{O1(π bond)} ≈ 0.9992(2p_z)_O1, h_N2 ≈ 0.4851(2 s)_N2 + 0.3685(2p_x)_N2 + 0.7918(2p_y)_N2, h_Br2 ≈ 0.2932(4 s)_Br2 - 0.4210(4p_x)_Br2 - 0.8438(4p_y)_Br2, h_{C1(σ bond)} ≈ 0.6063(2 s)_C1 + 0.7918(2p_x)_C1 h_{O1(σ bond)} ≈ 0.6508(2 s)_O1 - 0.7575(2p_x)_O1 h_{C1(π bond)} ≈ 0.9929(2p_z)_C1 h_{O1(π bond)} ≈ 0.9992(2p_z)_O1

which shows that the existence of intermolecular interactions leads to a decrease in the p character of N,O atom hybrids and an increase in the p character of Br,C atom hybrids. This is in agreement with the increased polarization of the bonds considered and the larger charges on the interacting atoms (Table 2). The N, O and methyl C atoms have δ^- charges and the remaining atoms have δ⁺ charges, which confirms the above-mentioned Brown (1961) postulate about polarization.

The intermolecular interactions only affect the charges of N—Br···O═C atoms (Table 2). Additionally, it is found that the N—Br bond in interacting molecules is created by less electron density than in non-interacting molecules. The energies of intermolecular interaction are 3.4828 and 2.3504 kcal mol^-1, respectively, for Br1···O2 and Br2···O1 (including a BSSE of 0.1147 kcal mol^-1). The second-order perturbation theory analysis of the Fock matrix on the NBO basis leads to the conclusion that the interactions discussed are formed mostly by O lone pairs donating electron density to the antibonding orbitals of N—Br bonds, and these `delocalization' energies are 3.27 and 2.11 kcal mol^-1, respectively, as above, which proves that electric attraction between largely polarized groups is not responsible for the interaction discussed.

Noteworthy is the fact that, in a separate molecule, there is no 2p_y coefficient in the h_{C1(σ bond)} and h_{O1(σ bond)} hybrids. This is caused by coupling of the lone pair electrons of atoms N1 and N2 with the antibonding C1—O1 orbital (interaction energies are 83.39 and 54.13 kcal mol^-1, respectively).

For the C2—O2 bond, only one such interaction is available, with the lone pair of atom N2 (interaction energy 76.04 kcal mol^-1). In sets containing Br···O interactions, a diminution of the 2p_y coefficient is not observed due to electron density changes on atom O1 (and in consequence changes in the composition of the natural orbitals) caused by the above-mentioned intermolecular interactions. Ab initio calculations prove that N—Br···O═C is a bonding interaction, but it is very weak and its energy is comparable with those found for weak C—H···O hydrogen bonds (Desiraju & Steiner, 1999).

Boys, S. F. & Bernardi, F. (1970). Mol. Phys. 19, 553–566.

Brown, R. N. (1961). Acta Cryst. 14, 711–715.

Desiraju, G. R. & Steiner, T. (1999). The Weak Hydrogen Bond in Structural Chemistry and Biology. IUCr Monograph on Crystallography 9, pp. 73–80. Oxford University Press.

Foster, J. P. & Weinhold, F. A. (1980). J. Am. Chem. Soc. 102, 7211–7218.

Frisch, M. J. et al. (2004). GAUSSIAN03. Revision C.02. Gaussian Inc., Wallingford, Connecticut, USA.

Reed, A. E., Curtis, L. A. & Weinhold, F. A. (1988). Chem. Rev. 88, 899–926.

Reed, A. E. & Weinhold, F. A. (1985). J. Chem. Phys. 83, 1736–1740.

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

	x	y	z	Uiso*/Ueq
N1	0.5798 (3)	0.2500	0.53142 (18)	0.0416 (7)
C1	0.6446 (3)	0.2500	0.4381 (2)	0.0303 (7)
N2	0.8202 (3)	0.2500	0.45268 (17)	0.0330 (6)
C2	0.8663 (4)	0.2500	0.5512 (2)	0.0327 (7)
C3	0.7043 (3)	0.2500	0.6130 (2)	0.0304 (7)
Br1	0.35168 (4)	0.2500	0.55164 (2)	0.03606 (12)
O1	0.5750 (3)	0.2500	0.35850 (14)	0.0452 (6)
Br2	0.96142 (4)	0.2500	0.34390 (2)	0.04022 (12)
O2	1.0067 (3)	0.2500	0.58505 (18)	0.0545 (7)
C4	0.6928 (3)	0.0910 (3)	0.67636 (17)	0.0400 (5)
H4A	0.5899	0.0919	0.7137	0.060*
H4B	0.7859	0.0868	0.7220	0.060*
H4C	0.6954	−0.0063	0.6334	0.060*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0139 (12)	0.090 (2)	0.0213 (13)	0.000	0.0006 (10)	0.000
C1	0.0241 (15)	0.0431 (18)	0.0238 (16)	0.000	0.0011 (12)	0.000
N2	0.0202 (13)	0.0558 (17)	0.0232 (13)	0.000	0.0050 (10)	0.000
C2	0.0207 (16)	0.051 (2)	0.0264 (15)	0.000	0.0008 (12)	0.000
C3	0.0186 (14)	0.0527 (19)	0.0198 (14)	0.000	−0.0020 (12)	0.000
Br1	0.01779 (16)	0.0591 (2)	0.03126 (18)	0.000	0.00092 (12)	0.000
O1	0.0347 (12)	0.0794 (19)	0.0214 (12)	0.000	−0.0064 (10)	0.000
Br2	0.0353 (2)	0.0529 (2)	0.03251 (19)	0.000	0.01512 (14)	0.000
O2	0.0196 (11)	0.107 (2)	0.0369 (13)	0.000	−0.0019 (10)	0.000
C4	0.0372 (13)	0.0474 (14)	0.0354 (12)	−0.0001 (11)	0.0005 (10)	0.0017 (11)

Geometric parameters (Å, º)

N1—C1	1.346 (4)	C2—O2	1.207 (3)
N1—C3	1.472 (4)	C2—C3	1.533 (4)
N1—Br1	1.839 (3)	C3—C4^i	1.518 (3)
C1—O1	1.196 (3)	C3—C4	1.518 (3)
C1—N2	1.414 (4)	C4—H4A	0.9600
N2—C2	1.362 (4)	C4—H4B	0.9600
N2—Br2	1.835 (2)	C4—H4C	0.9600
C1—N1—C3	115.0 (2)	N1—C3—C4^i	111.67 (15)
C1—N1—Br1	121.0 (2)	N1—C3—C4	111.67 (15)
C3—N1—Br1	124.00 (19)	C4^i—C3—C4	112.1 (3)
O1—C1—N1	129.8 (3)	N1—C3—C2	99.9 (2)
O1—C1—N2	125.5 (3)	C4^i—C3—C2	110.44 (16)
N1—C1—N2	104.7 (2)	C4—C3—C2	110.44 (16)
C2—N2—C1	113.6 (2)	C3—C4—H4A	109.5
C2—N2—Br2	126.4 (2)	C3—C4—H4B	109.5
C1—N2—Br2	119.98 (19)	H4A—C4—H4B	109.5
O2—C2—N2	127.6 (3)	C3—C4—H4C	109.5
O2—C2—C3	125.5 (3)	H4A—C4—H4C	109.5
N2—C2—C3	106.8 (2)	H4B—C4—H4C	109.5

Symmetry code: (i) x, −y+1/2, z.