Hexa­methyl­enetetraminium 2,4,6-tri­nitro­phenolate

In the title complex, the 1:1 ionic adduct of hexa­methyl­enetetraminium and 2,4,6-tri­nitro­phenolate, C₆H₁₃N₄⁺·­C₆H₂N₃O₇⁻, the cation acts as a donor for bifurcated hydrogen bonds to the O atoms of the phenolate and one of the nitro groups of the 2,4,6-tri­nitro­phenolate anion. The crystal structure is built from sheets of cations and anions, and is stabilized by intermolecular C—H...O and C—H...π interactions.

S1. Comment

The crystal structures of the adducts of hexamethylenetetramine (HMT) and mono-, di-, or tri-phenol derivatives have been investigated intensively (Jordan & Mak, 1970; Mak et al., 1977, 1978; Mahmoud & Wallwork, 1979; Coupar, Glidewell & Ferguson, 1997; Coupar, Ferguson et al., 1997; Ng et al., 2001; Usman et al., 2001). Although HMT usually acts as an acceptor of up to three O—H···N hydrogen bonds (Jordan & Mak, 1970; Mak et al., 1977, 1978; Mahmoud & Wallwork, 1979; Coupar, Glidewell & Ferguson, 1997; Coupar, Ferguson et al., 1997), or partially acts as a hydrogen bond donor with 4-nitrophenol (Ng et al., 2001), recently we have shown that HMT can also act solely as an N—H···O hydrogen donor in the presence of 2,4-dinitrophenol (Usman et al., 2001). In this HMT-2,4-dinitrophenol complex, the phenolic H atom is transferred to the HMT. This H-atom transfer process occurs because 2,4-dinitrophenol is a stronger acid than the other phenols investigated. This unusual behaviour of HMT in the solid state is of interest, and led us to the title adduct where 2,4,6-trinitrophenol (TNP) also acts as a stronger acid.

Scheme 1

In the title complex, the TNP also transfers an H atom from the hydroxy group to the HMT moiety to form the 2,4,6-trinitrophenolate anion (TNP^-), making the HMT positively charged.

The bond lengths and angles (Table 1) within the hexamethylenetetraminium cation (HMT⁺) are comparable with those of HMT⁺ in the 143 K polymorph of hexamethylenetetraminium-2,4-dinitrophenolate (Usman et al., 2001), while those within the TNP^- anion are comparable with those of TNP^- in potassium- and ammonium-2,4,6-trinitrophenolate (Maartmann-Moe, 1969). For instance, in the title complex the mean N—O bond length [1.224 (5) Å] and the C—O bond length agree with the mean N—C and C—O bond lengths in the two 2,4,6-trinitrophenolate derivatives reported by Maartmann-Moe (1969) [N—C 1.224 (6) Å and C—O 1.241 (7) Å].

In the HMT⁺ cation, the N—C bond distances around the N4 atom are elongated due to the positive charge localized on the protonated N4 atom. The N4—C7, N4—C8 and N4—C9 bond distances [mean value of 1.518 (2) Å] are equivalent to the length of the typical N—C single bond in the trimethylammonium ion (Allen et al., 1987). The protonated N4 atom also slightly affects the π-electron distribution in the surrounding atoms, which can be seen in the shortening by about 0.03 Å of the N5—C7, N6—C8, and N7—C9 bond distances compared with the other two N5—C, N6—C and N7—C bonds.

In the title adduct, the TNP^- anion is nearly planar, with the nitro groups slightly twisted about their C—N bonds so that the angles between the aromatic ring plane and those of the CNO₂ groupings containing N1, N2 and N3 are 11.06 (1), 7.96 (9) and 5.46 (10)°, respectively. The nitro-O atoms deviate from the aromatic ring plane by 0.287 (2) O2, -0.114 (2) O3, -0.307 (1) O4, -0.062 (2) O5, 0.175 (2) O6 and -0.017 (2) Å O7. For the HMT⁺ cation, all of the six-membered NCNCNC rings adopt a chair conformation, as shown by their puckering parameters (Cremer & Pople, 1975) (see Table 3).

The crystal structure of the title adduct is built from sheets of HMT⁺ cations and separate sheets of TNP^- anions stacked alternately along the a axis. The HMT⁺ cation acts as an N—H···O hydrogen bond donor and forms bifurcated interionic hydrogen bonds with both the phenolate-O atom and a nitro-O atom of the same adjacent TNP^- anion (Table 2). These interactions link the HMT⁺ and TNP^- ions into ion pairs. Interionic C12—H12A···O7 and C12—H12B···O4 interactions interconnect the ion pairs into infinite two dimensional networks which lie perpendicular to the c axis (Fig. 2). An interionic C5—H5···π interaction involving the centroid of the aromatic ring of the TNP^- anion was also observed (Table 2).

S2. Experimental

1.40 g (10 mmol) of hexamethylenetetramine and 2.29 g (10 mmol) of 2,4,6-trinitrophenol were thoroughly mixed and then dissolved in 50 ml of acetone with drops of water. The mixture was warmed until a clear solution was obtained. The solution was filtered off and left to evaporate slowly in air. Yellow single crystals suitable for X-ray data collection were obtained from the solution after a few days.

S3. Refinement

The H14N atom was located in a difference Fourier map and was refined freely as an isotropic atom. After checking for H atoms in the difference map, the positions of all remaining H atoms were geometrically idealized and allowed to ride on their parent atoms with C—H distances in the range 0.93–0.97 Å and fixed displacement parameters defined by U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PARST (Nardelli, 1995) and PLATON (Spek, 1990).

Figures

	Fig. 1. The structure of the title ionic adduct showing 50% probability displacement ellipsoids and the atom numbering scheme.
	Fig. 2. Packing diagram of the title ionic adduct viewed down the c axis. The dashed lines denote the interionic hydrogen bond interactions.

Hexamethylenetetramine-2,4,6-trinitrophenol

Crystal data

C6H13N4^+·C6H2N3O7^−	F(000) = 768
Mr = 369.31	Dx = 1.661 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.4995 (2) Å	Cell parameters from 6652 reflections
b = 6.6344 (1) Å	θ = 3.2–28.3°
c = 18.6203 (2) Å	µ = 0.14 mm^−1
β = 107.022 (1)°	T = 183 K
V = 1476.48 (4) Å^3	Block, yellow
Z = 4	0.40 × 0.40 × 0.32 mm

Data collection

Siemens SMART CCD area detector diffractometer	3575 independent reflections
Radiation source: fine-focus sealed tube	2697 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.069
Detector resolution: 8.33 pixels mm^-1	θmax = 28.3°, θmin = 3.2°
ω scans	h = −16→16
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	k = −8→7
Tmin = 0.947, Tmax = 0.957	l = −24→16
8504 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.058	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.154	w = 1/[σ^2(Fo^2) + (0.0807P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.95	(Δ/σ)max < 0.001
3575 reflections	Δρmax = 0.43 e Å^−3
240 parameters	Δρmin = −0.43 e Å^−3
0 restraints	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.033 (4)

Special details

Experimental. The data collection covered over a hemisphere of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0, 88 and 180°) for the crystal and each exposure of 10 s covered 0.3° in ω. The crystal-to-detector distance was 5 cm and the detector swing angle was -35°. Crystal decay was monitored by repeating fifty initial frames at the end of data collection and analysing the intensity of duplicate reflections, and was found to be negligible.

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.

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

	x	y	z	Uiso*/Ueq
O1	0.60294 (10)	0.5516 (2)	0.07795 (8)	0.0320 (3)
O2	0.45903 (14)	0.8527 (2)	0.04912 (12)	0.0550 (5)
O3	0.29116 (13)	0.7894 (3)	0.04515 (12)	0.0615 (6)
O4	0.18616 (10)	0.2220 (2)	0.15681 (8)	0.0312 (4)
O5	0.30662 (12)	−0.0030 (2)	0.21338 (10)	0.0438 (4)
O6	0.67789 (12)	0.0254 (2)	0.20283 (10)	0.0431 (4)
O7	0.73586 (11)	0.2486 (2)	0.14037 (10)	0.0408 (4)
N3	0.66203 (12)	0.1781 (2)	0.16407 (9)	0.0223 (3)
N2	0.28268 (12)	0.1539 (2)	0.17746 (8)	0.0227 (3)
N1	0.38972 (12)	0.7422 (2)	0.06093 (9)	0.0243 (3)
N4	0.81992 (11)	0.61547 (19)	0.09625 (7)	0.0149 (3)
N5	0.97556 (10)	0.7577 (2)	0.19366 (7)	0.0157 (3)
N6	1.00739 (11)	0.59303 (19)	0.08449 (8)	0.0160 (3)
N7	0.91067 (11)	0.91728 (19)	0.07003 (8)	0.0151 (3)
C1	0.53481 (13)	0.4662 (2)	0.10504 (9)	0.0182 (3)
C2	0.42297 (13)	0.5466 (2)	0.09739 (9)	0.0171 (3)
C3	0.34367 (13)	0.4483 (2)	0.12158 (9)	0.0168 (3)
H3A	0.2733	0.5054	0.1143	0.020*
C4	0.36892 (13)	0.2631 (2)	0.15695 (9)	0.0170 (3)
C5	0.47419 (13)	0.1785 (2)	0.17098 (9)	0.0175 (3)
H5A	0.4908	0.0567	0.1966	0.021*
C6	0.55404 (13)	0.2770 (2)	0.14654 (9)	0.0176 (3)
C7	0.86933 (13)	0.6544 (2)	0.17982 (9)	0.0167 (3)
H7A	0.8181	0.7361	0.1978	0.020*
H7B	0.8802	0.5274	0.2068	0.020*
C8	0.90167 (14)	0.4883 (2)	0.06953 (9)	0.0174 (3)
H8A	0.9127	0.3597	0.0954	0.021*
H8B	0.8717	0.4629	0.0161	0.021*
C9	0.80422 (13)	0.8160 (2)	0.05523 (9)	0.0162 (3)
H9A	0.7730	0.7938	0.0017	0.019*
H9B	0.7524	0.8994	0.0720	0.019*
C10	1.05185 (13)	0.6316 (2)	0.16567 (9)	0.0181 (3)
H10A	1.1237	0.6986	0.1758	0.022*
H10B	1.0635	0.5042	0.1924	0.022*
C11	0.98830 (13)	0.7876 (2)	0.04477 (9)	0.0173 (3)
H11A	0.9580	0.7635	−0.0087	0.021*
H11B	1.0593	0.8568	0.0532	0.021*
C12	0.95718 (13)	0.9492 (2)	0.15161 (9)	0.0169 (3)
H12A	0.9062	1.0326	0.1691	0.020*
H12B	1.0277	1.0207	0.1615	0.020*
H1N4	0.751 (2)	0.550 (3)	0.0879 (14)	0.046 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0130 (6)	0.0422 (8)	0.0414 (8)	−0.0030 (5)	0.0087 (6)	0.0185 (6)
O2	0.0472 (10)	0.0246 (8)	0.1038 (16)	−0.0003 (7)	0.0387 (10)	0.0197 (8)
O3	0.0211 (8)	0.0479 (10)	0.1066 (16)	0.0081 (7)	0.0046 (9)	0.0446 (10)
O4	0.0117 (6)	0.0399 (8)	0.0434 (8)	0.0009 (5)	0.0104 (6)	0.0099 (6)
O5	0.0277 (8)	0.0465 (9)	0.0591 (10)	0.0008 (6)	0.0156 (7)	0.0337 (8)
O6	0.0261 (8)	0.0465 (9)	0.0603 (11)	0.0174 (6)	0.0181 (7)	0.0281 (8)
O7	0.0222 (7)	0.0264 (7)	0.0838 (13)	0.0037 (5)	0.0310 (8)	0.0089 (7)
N3	0.0146 (7)	0.0219 (7)	0.0309 (8)	0.0009 (5)	0.0074 (6)	−0.0016 (6)
N2	0.0145 (7)	0.0314 (8)	0.0226 (7)	−0.0016 (6)	0.0062 (6)	0.0078 (6)
N1	0.0219 (8)	0.0202 (7)	0.0281 (8)	−0.0014 (6)	0.0032 (6)	0.0033 (6)
N4	0.0103 (6)	0.0165 (6)	0.0183 (7)	−0.0016 (5)	0.0048 (5)	0.0009 (5)
N5	0.0119 (6)	0.0188 (6)	0.0160 (6)	0.0006 (5)	0.0033 (5)	0.0012 (5)
N6	0.0148 (7)	0.0172 (6)	0.0183 (7)	0.0019 (5)	0.0082 (5)	0.0020 (5)
N7	0.0143 (6)	0.0144 (6)	0.0175 (6)	0.0007 (5)	0.0058 (5)	0.0019 (5)
C1	0.0115 (7)	0.0242 (8)	0.0181 (8)	−0.0041 (6)	0.0030 (6)	−0.0002 (6)
C2	0.0139 (8)	0.0174 (7)	0.0184 (8)	−0.0014 (6)	0.0022 (6)	0.0011 (6)
C3	0.0117 (7)	0.0219 (8)	0.0165 (7)	0.0001 (6)	0.0035 (6)	−0.0013 (6)
C4	0.0116 (8)	0.0229 (8)	0.0176 (8)	−0.0023 (6)	0.0062 (6)	0.0021 (6)
C5	0.0143 (8)	0.0190 (7)	0.0181 (8)	0.0000 (6)	0.0031 (6)	0.0012 (6)
C6	0.0099 (7)	0.0218 (8)	0.0204 (8)	0.0006 (6)	0.0033 (6)	−0.0016 (6)
C7	0.0158 (8)	0.0218 (8)	0.0145 (7)	−0.0005 (6)	0.0078 (6)	0.0019 (6)
C8	0.0188 (8)	0.0142 (7)	0.0208 (8)	0.0001 (6)	0.0083 (6)	−0.0020 (6)
C9	0.0118 (7)	0.0185 (7)	0.0166 (7)	0.0026 (5)	0.0016 (6)	0.0020 (6)
C10	0.0124 (7)	0.0223 (8)	0.0189 (8)	0.0044 (6)	0.0034 (6)	0.0039 (6)
C11	0.0164 (8)	0.0193 (8)	0.0192 (8)	0.0014 (6)	0.0099 (6)	0.0031 (6)
C12	0.0159 (7)	0.0141 (7)	0.0204 (8)	−0.0018 (5)	0.0049 (6)	−0.0023 (6)

Geometric parameters (Å, º)

O1—C1	1.2456 (19)	N7—C12	1.474 (2)
O2—N1	1.2037 (19)	C1—C6	1.457 (2)
O3—N1	1.221 (2)	C1—C2	1.464 (2)
O4—N2	1.2393 (18)	C2—C3	1.368 (2)
O5—N2	1.2258 (19)	C3—C4	1.386 (2)
O6—N3	1.226 (2)	C3—H3A	0.9300
O7—N3	1.2262 (18)	C4—C5	1.383 (2)
N3—C6	1.449 (2)	C5—C6	1.377 (2)
N2—C4	1.4403 (19)	C5—H5A	0.9300
N1—C2	1.467 (2)	C7—H7A	0.9700
N4—C8	1.517 (2)	C7—H7B	0.9700
N4—C9	1.5181 (19)	C8—H8A	0.9700
N4—C7	1.519 (2)	C8—H8B	0.9700
N4—H1N4	0.94 (3)	C9—H9A	0.9700
N5—C7	1.4488 (19)	C9—H9B	0.9700
N5—C10	1.4737 (19)	C10—H10A	0.9700
N5—C12	1.474 (2)	C10—H10B	0.9700
N6—C8	1.446 (2)	C11—H11A	0.9700
N6—C11	1.4719 (19)	C11—H11B	0.9700
N6—C10	1.472 (2)	C12—H12A	0.9700
N7—C9	1.4431 (19)	C12—H12B	0.9700
N7—C11	1.4733 (19)
O6—N3—O7	121.20 (15)	C5—C6—N3	115.37 (14)
O6—N3—C6	119.06 (14)	C5—C6—C1	124.14 (14)
O7—N3—C6	119.74 (14)	N3—C6—C1	120.49 (14)
O5—N2—O4	122.60 (14)	N5—C7—N4	109.83 (12)
O5—N2—C4	119.32 (14)	N5—C7—H7A	109.7
O4—N2—C4	118.07 (14)	N4—C7—H7A	109.7
O2—N1—O3	121.94 (16)	N5—C7—H7B	109.7
O2—N1—C2	120.14 (15)	N4—C7—H7B	109.7
O3—N1—C2	117.89 (14)	H7A—C7—H7B	108.2
C8—N4—C9	108.82 (12)	N6—C8—N4	109.58 (12)
C8—N4—C7	108.64 (12)	N6—C8—H8A	109.8
C9—N4—C7	108.69 (12)	N4—C8—H8A	109.8
C8—N4—H1N4	111.3 (14)	N6—C8—H8B	109.8
C9—N4—H1N4	110.2 (15)	N4—C8—H8B	109.8
C7—N4—H1N4	109.2 (15)	H8A—C8—H8B	108.2
C7—N5—C10	108.83 (12)	N7—C9—N4	109.62 (12)
C7—N5—C12	108.73 (12)	N7—C9—H9A	109.7
C10—N5—C12	108.51 (12)	N4—C9—H9A	109.7
C8—N6—C11	108.66 (12)	N7—C9—H9B	109.7
C8—N6—C10	109.30 (12)	N4—C9—H9B	109.7
C11—N6—C10	108.68 (12)	H9A—C9—H9B	108.2
C9—N7—C11	108.89 (12)	N6—C10—N5	111.90 (12)
C9—N7—C12	109.09 (12)	N6—C10—H10A	109.2
C11—N7—C12	108.35 (12)	N5—C10—H10A	109.2
O1—C1—C6	125.47 (15)	N6—C10—H10B	109.2
O1—C1—C2	122.79 (15)	N5—C10—H10B	109.2
C6—C1—C2	111.73 (13)	H10A—C10—H10B	107.9
C3—C2—C1	123.88 (15)	N6—C11—N7	112.14 (12)
C3—C2—N1	116.08 (14)	N6—C11—H11A	109.2
C1—C2—N1	120.03 (14)	N7—C11—H11A	109.2
C2—C3—C4	119.52 (15)	N6—C11—H11B	109.2
C2—C3—H3A	120.2	N7—C11—H11B	109.2
C4—C3—H3A	120.2	H11A—C11—H11B	107.9
C5—C4—C3	121.41 (14)	N7—C12—N5	112.13 (12)
C5—C4—N2	119.35 (14)	N7—C12—H12A	109.2
C3—C4—N2	119.21 (14)	N5—C12—H12A	109.2
C6—C5—C4	119.11 (15)	N7—C12—H12B	109.2
C6—C5—H5A	120.4	N5—C12—H12B	109.2
C4—C5—H5A	120.4	H12A—C12—H12B	107.9
O1—C1—C2—C3	174.80 (16)	O1—C1—C6—N3	4.4 (3)
C6—C1—C2—C3	−4.4 (2)	C2—C1—C6—N3	−176.45 (14)
O1—C1—C2—N1	−4.2 (3)	C10—N5—C7—N4	−59.11 (16)
C6—C1—C2—N1	176.62 (14)	C12—N5—C7—N4	58.91 (15)
O2—N1—C2—C3	167.90 (18)	C8—N4—C7—N5	59.14 (15)
O3—N1—C2—C3	−10.3 (2)	C9—N4—C7—N5	−59.12 (15)
O2—N1—C2—C1	−13.0 (3)	C11—N6—C8—N4	−59.31 (16)
O3—N1—C2—C1	168.81 (18)	C10—N6—C8—N4	59.14 (16)
C1—C2—C3—C4	1.3 (3)	C9—N4—C8—N6	59.25 (16)
N1—C2—C3—C4	−179.67 (14)	C7—N4—C8—N6	−58.93 (15)
C2—C3—C4—C5	2.5 (2)	C11—N7—C9—N4	58.91 (16)
C2—C3—C4—N2	−175.61 (15)	C12—N7—C9—N4	−59.16 (15)
O5—N2—C4—C5	6.9 (2)	C8—N4—C9—N7	−59.03 (16)
O4—N2—C4—C5	−172.03 (15)	C7—N4—C9—N7	59.12 (15)
O5—N2—C4—C3	−174.93 (17)	C8—N6—C10—N5	−60.44 (16)
O4—N2—C4—C3	6.1 (2)	C11—N6—C10—N5	57.99 (16)
C3—C4—C5—C6	−2.6 (3)	C7—N5—C10—N6	60.22 (16)
N2—C4—C5—C6	175.49 (14)	C12—N5—C10—N6	−57.94 (16)
C4—C5—C6—N3	179.64 (14)	C8—N6—C11—N7	60.76 (16)
C4—C5—C6—C1	−1.0 (3)	C10—N6—C11—N7	−58.08 (16)
O6—N3—C6—C5	−4.9 (2)	C9—N7—C11—N6	−60.66 (17)
O7—N3—C6—C5	175.43 (17)	C12—N7—C11—N6	57.88 (16)
O6—N3—C6—C1	175.74 (16)	C9—N7—C12—N5	60.49 (16)
O7—N3—C6—C1	−3.9 (3)	C11—N7—C12—N5	−57.92 (16)
O1—C1—C6—C5	−174.91 (17)	C7—N5—C12—N7	−60.16 (16)
C2—C1—C6—C5	4.3 (2)	C10—N5—C12—N7	58.06 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H14N···O1	0.94 (2)	1.81 (3)	2.666 (2)	152 (2)
N4—H14N···O7	0.94 (2)	2.26 (2)	2.865 (2)	122 (2)
C12—H12A···O7^i	0.97	2.49	3.362 (2)	149
C12—H12B···O4^ii	0.97	2.41	3.364 (2)	167
C5—H5A···Cg^iii	0.93	3.30	4.07	142

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