Different cation-protonation patterns in mol­ecular salts of unsymmetrical dimethyhydrazine: C2H9N2·Br and C2H9N2·H2PO3

Katinaitė, J.; Harrison, W.T.A.

doi:10.1107/S2056989016011993

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ISSN: 2056-9890

Volume 72| Part 8| August 2016| Pages 1206-1210

https://doi.org/10.1107/S2056989016011993

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Different cation-protonation patterns in molecular salts of unsymmetrical dimethyhydrazine: C₂H₉N₂·Br and C₂H₉N₂·H₂PO₃

Judita Katinaitė ^a and William T. A. Harrison ^a ^*

^aDepartment of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland
^*Correspondence e-mail: w.harrison@abdn.ac.uk

Edited by H. Stoeckli-Evans, University of Neuchâtel, Switzerland (Received 19 July 2016; accepted 22 July 2016; online 29 July 2016)

We describe the syntheses and crystal structures of two molecular salts containing the 1,1-dimethylhydrazinium cation, namely 1,1-dimethylhydrazin-1-ium bromide, C₂H₉N₂⁺·Br⁻, (I), and 2,2-dimethylhydrazin-1-ium dihydrogen phosphite, C₂H₉N₂⁺·H₂PO₃⁻, (II). In (I), the cation is protonated at the methylated N atom and N—H⋯Br hydrogen bonds generate [010] chains in the crystal. In (II), the cation is protonated at the terminal N atom and cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds generate (001) sheets.

Keywords: crystal structure; unsymmetrical dimethylhydrazine; protonation pattern; hydrogen bonds.

CCDC references: 1495475; 1495474

1. Chemical context

Unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine; C₂H₈N₂; UDMH) is a colourless liquid at room temperature and pressure with a strong and unpleasant ammonia-like or fishy smell. The best known application of this compound is the fuel (reducing agent) in hypergolic rocket fuels (Edwards, 2003 ), where it can be used alone or mixed with hydrazine: the latter formulation (trade name `Aerozine 50') was used by the Apollo lunar modules to begin their homeward journeys from the moon.

Chemically, both nitrogen atoms in UDMH bear lone pairs of electrons, which can act as weak bases to accept protons and therefore result in the formation of molecular salts when reacted with acids. The first crystal structure of a UDMH salt was reported by Klapötke et al. (1999 ), who prepared 1,1-dimetylhydrazinium azide as a possible high-energy-density material with military applications; the methylated UDMH nitrogen atom is protonated and the components are linked by strong N—H⋯N hydrogen bonds in the crystal. However, this salt exhibited pronounced hygroscopic behaviour and had a low melting point of 311 K, which deemed it unsuitable for such uses. The nitrate salt of UDMH, which may be a decomposition product of hypergolic fuels, was prepared soon afterwards by the same workers (De Bonn et al., 2001 ) by a low-temperature, non-aqueous synthesis: anhydrous nitric acid and UDMH were separately dissolved in dichloromethane at 195 K and the solutions mixed at the same temperature. The resulting hygroscopic salt, 1,1-dimethylhydrazinium nitrate, is protonated at the methylated nitrogen atom and features N—H⋯O hydrogen bonds in its crystal structure.

Merkoulov et al. (2005 ) synthesized 1,1-dimethylhydrazinium chloride by reacting liquid UDMH with HCl dissolved in diethyl ether: its crystal structure consists of two independent cations and two chloride anions in the asymmetric unit. The cation is protonated at the methylated nitrogen atom and a dense network of strong N—H⋯Cl and weak C—H⋯Cl hydrogen bonds helps to consolidate the packing in the crystal. A salt with a more complicated counter-ion was synthesised by Mu et al. (2011 ): the addition of liquid UDMH to a solution of picric acid in ethanol at room temperature yielded 1,1-dimethylhydrazinium picrate. As before, the UDMH protonates at the methylated nitrogen atom and cation-to-anion N—H⋯O hydrogen bonds help to establish the packing.

As an extension of these studies, we now describe the syntheses and crystal structures of 1,1-dimethylhydrazin-1-ium bromide, C₂H₉N₂⁺·Br⁻ (I) and 2,2-dimethylhydrazin-1-ium dihydrogen phosphite, C₂H₉N₂⁺·H₂PO₃⁻ (II).

2. Structural commentary

Compound (I) crystallizes in space group I2/a (non-standard setting of C2/c) with one cation and one bromide anion in the asymmetric unit (Fig. 1). The cation is protonated at the central N2 atom, as seen in previous UDMH salts referred to above. The N1—N2 bond length [1.4478 (19) Å] is slightly shorter than the C—N bond lengths [1.482 (2) and 1.485 (2) Å]. N2 is displaced from N1, C1 and C2 by 0.4834 (16) Å and the C—N—C bond angle [111.38 (14)°] is slightly greater than the C—N—N angles [108.93 (12) and 108.97 (14)°]. The H atoms attached to N1 point away from the carbon atoms [C1—N2—N1—H2n = −175.7 (2); C2—N2—N1—H1n = 178.0 (2)°] and the N2—H3n bond bisects the N1H₂ group [H3n—N2—N1—H1n = 61 (2)°].

Figure 1
The molecular structure of (I)

, showing 50% displacement ellipsoids. The N—H⋯Br hydrogen bond is indicated by a double-dashed line (Table 1

Compound (II) crystallizes in space group Pna2₁ with one cation and one dihydrogen phosphite anion in the asymmetric unit (Fig. 2). In this case, the cation is protonated at the terminal N atom rather than the central N atom, which has not been seen previously in UDMH salts. The N1—N2 bond length is 1.454 (3) Å and the C—N bond lengths are 1.462 (3) and 1.463 (3) Å. The geometry about N2 is pyramidal and this atom is displaced from N1, C1 and C2 by 0.504 (2) Å. The bond angles about N2 show the same trend as those in (I): C—N—C = 110.69 (18); C—N—N = 107.62 (17) and 107.94 (18)°. Two of the H atoms attached to N1 have almost the same locations as the corresponding atoms in (I), whereas the third bisects the C1—N2—C2 grouping [C1—N2—N1—H3n = −62°]. In the anion, the P1—O3 bond length of 1.5638 (16) Å is typical (Harrison, 2003 ) for the protonated O atom in a dihydrogen phosphite group whereas P1—O1 [1.4982 (15) Å] and P1—O2 [1.5003 (16) Å] are almost the same length, indicating the expected delocalization (resonance) of the negative charge over these two O atoms. The O—P—O bond angle for the unprotonated oxygen atoms [116.76 (9)°] is significantly larger than the O—P—OH angles [106.37 (9) and 111.46 (9)°], as seen previously for similar species (Harrison, 2003). P1 is displaced from its attached O atoms by 0.4510 (13) Å.

Figure 2
The molecular structure of (II)

, showing 50% displacement ellipsoids. The N—H⋯O hydrogen bond is indicated by a double-dashed line (Table 2

3. Supramolecular features

In the crystal of (I), N—H⋯Br hydrogen bonds (Table 1) link the components into [010] chains (Fig. 3): each Br⁻ ion accepts three N—H⋯Br bonds and alternating, centrosymmetric R₄²(8) and R₄²(10) loops occur within the chain. The N2 bond is significantly shorter than the N1 bonds, which may be due to the positive charge residing on N2: this was also observed in the structure of the nitrate salt (de Bonn et al., 2001). There are also several weak C—H⋯Br contacts (Table 1) in (I); the weak and strong interactions result in each bromide ion accepting a total of seven hydrogen bonds (Fig. 4).

Table 1
Hydrogen-bond geometry (Å, °) for (I)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1n⋯Br1ⁱ	0.89 (2)	2.68 (3)	3.5666 (15)	170.7 (18)
N1—H2n⋯Br1	0.89 (2)	2.62 (2)	3.5117 (14)	175.0 (19)
N2—H3n⋯Br1ⁱⁱ	0.87 (2)	2.39 (2)	3.2490 (13)	173.3 (17)
C1—H1a⋯Br1ⁱ	0.98	3.11	3.9690 (18)	148
C1—H1b⋯Br1ⁱⁱⁱ	0.98	3.09	4.0175 (19)	158
C1—H1c⋯Br1^iv	0.98	2.90	3.8682 (17)	168
C2—H2c⋯Br1ⁱⁱⁱ	0.98	3.07	3.9843 (18)	156
Symmetry codes: (i) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[-x+{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iv) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ .

Figure 3
Partial packing diagram for (I)

, showing the formation of [010] chains linked by N—H⋯Br hydrogen bonds. C-bound H atoms are omitted for clarity. Symmetry codes as in Table 1

Figure 4
The environment of the bromide ion in the crystal of (I)

. [Symmetry codes: (i) $[{1\over 2}]$ − x, $[{3\over 2}]$ − y, $[{1\over 2}]$ − z; (ii) $[{1\over 2}]$ − x, $[{1\over 2}]$ − y, $[{1\over 2}]$ − z; (iii) −x, $[{1\over 2}]$ + y, $[{1\over 2}]$ − y; (iv) x, $[{3\over 2}]$ − y, z − $[{1\over 2}]$ .] Note that each of the five cations has a different bonding mode: η¹ N1, N2 and C1 and η² N1 + C1 and C1 + C2.

The crystal structure of (II) appears to correlate with the novel protonation pattern of the C₂H₉N₂⁺ cation: the three H atoms attached to N1 each partake in a strong, near-linear N—H⋯O hydrogen bond to nearby H₂PO₃⁻ anions (Table 2). The anions are linked into [100] chains by O—H⋯O hydrogen bonds with adjacent anions in the chain related by a-glide symmetry. Together, these interactions generate (001) sheets (Fig. 5) As usual (Harrison, 2001 ), the P—H grouping of the anion does not participate in hydrogen bonds and the H atom points into the inter-layer region.

Table 2
Hydrogen-bond geometry (Å, °) for (II)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1n⋯O1ⁱ	0.91	1.83	2.736 (2)	176
N1—H2n⋯O1ⁱⁱ	0.91	1.85	2.762 (2)	176
N1—H3n⋯O2	0.91	1.91	2.814 (2)	175
O3—H1o⋯O2ⁱ	0.87	1.74	2.568 (2)	159
Symmetry codes: (i) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z]$ ; (ii) x, y+1, z.

Figure 5
Partial packing diagram for (II)

, showing part of an (001) sheet. Symmetry codes as in Table 2

4. Database survey

A search of the Cambridge Structural Database (CSD; Groom et al., 2016 ) revealed the crystal structures of the four UDMH derivatives cited above: refcodes for the azide, nitrate, chloride and picrate salts are CORRUW, IBOLOA, FOHLUK and AZUXID, respectively.

5. Synthesis and crystallization

Caution! UDMH is toxic, potentially carcinogenic and may form explosive mixtures with oxidizing agents: all appropriate safety measures must be put in place when handling this compound.

To prepare (I), aqueous solutions of UDMH (10 ml, 1.0 M) and hydrobromic acid (10 ml, 1.0 M) were mixed at room temperature to yield a colourless solution and colourless rods (to ∼1 mm in length) of (I) grew as the solvent evaporated in a watch glass. These crystals are extremely hygroscopic and should be immediately transferred to a desiccator for storage: if left in air, they absorb enough water to completely dissolve within an hour or two.

To prepare (II), aqueous solutions of UDMH (10 ml, 1.0 M) and phosphorus acid (10 ml, 1.0 M) were mixed at room temperature to yield a colourless solution and yellowish slabs of (II) grew as the increasingly viscous solvent slowly evaporated over several days in a watch glass. These crystals are hygroscopic and should be stored in a desiccator. IR: 2383 cm⁻¹ (P—H stretch).

The IR spectra of UDMH, (I) and (II) are available as supporting information.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The N-bound H atoms in (I) were located in difference maps and their positions freely refined; those in (II) were relocated to idealized locations and refined as riding atoms. The O-bound H atom in (II) was located in a difference map and refined as riding, in its as-found relative position. The methyl H atoms were geometrically placed (C—H = 0.98 Å): the –CH₃ groups were allowed to rotate, but not to tip, to best fit the electron density. The constraint U_iso(H) = 1.2U_eq(carrier) or 1.5U_eq(methyl carrier) was applied in all cases.

Table 3
Experimental details

	(I)	(II)
Crystal data
Chemical formula	C₂H₉N₂⁺·Br⁻	C₂H₉N₂⁺·H₂PO₃⁻
M_r	141.02	142.10
Crystal system, space group	Monoclinic, I2/a	Orthorhombic, Pna2₁
Temperature (K)	100	100
a, b, c (Å)	13.2423 (2), 5.1239 (1), 16.1839 (3)	8.0690 (2), 6.9970 (2), 11.7001 (6)
α, β, γ (°)	90, 94.838 (2), 90	90, 90, 90
V (Å³)	1094.20 (3)	660.57 (4)
Z	8	4
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	7.36	0.35
Crystal size (mm)	0.23 × 0.09 × 0.09	0.18 × 0.18 × 0.02

Data collection
Diffractometer	Rigaku Mercury CCD	Rigaku Mercury CCD
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2012 )	–
T_min, T_max	0.282, 0.557	–
No. of measured, independent and observed [I > 2σ(I)] reflections	6485, 1258, 1224	5347, 1395, 1365
R_int	0.029	0.023
(sin θ/λ)_max (Å⁻¹)	0.649	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.051, 1.12	0.025, 0.065, 1.09
No. of reflections	1258	1395
No. of parameters	58	77
No. of restraints	0	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.50, −0.48	0.24, −0.28
Absolute structure	–	Refined as an inversion twin.
Absolute structure parameter	–	0.15 (14)
Computer programs: CrystalClear (Rigaku, 2012), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), ORTEP-3 for Windows (Farrugia, 2012 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 1495475; 1495474

Crystal structure: contains datablocks I, II, global. DOI: https://doi.org/10.1107/S2056989016011993/su5314sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016011993/su5314Isup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989016011993/su5314IIsup3.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989016011993/su5314Isup4.cml

Supporting information file. DOI: https://doi.org/10.1107/S2056989016011993/su5314IIsup5.cml

checkCIF report

Computing details top

For both compounds, data collection: CrystalClear (Rigaku, 2012); cell refinement: CrystalClear (Rigaku, 2012); data reduction: CrystalClear (Rigaku, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: publCIF (Westrip, 2010).

(I) 1,1-Dimethylhydrazin-1-ium bromide top

Crystal data top

C₂H₉N₂⁺·Br⁻	F(000) = 560
M_r = 141.02	D_x = 1.712 Mg m⁻³
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
a = 13.2423 (2) Å	Cell parameters from 5743 reflections
b = 5.1239 (1) Å	θ = 2.5–27.5°
c = 16.1839 (3) Å	µ = 7.36 mm⁻¹
β = 94.838 (2)°	T = 100 K
V = 1094.20 (3) Å³	Rod, colourless
Z = 8	0.23 × 0.09 × 0.09 mm

Data collection top

Rigaku Mercury CCD diffractometer	1224 reflections with I > 2σ(I)
ω scans	R_int = 0.029
Absorption correction: multi-scan (CrystalClear; Rigaku, 2012)	θ_max = 27.5°, θ_min = 2.5°
T_min = 0.282, T_max = 0.557	h = −17→17
6485 measured reflections	k = −6→5
1258 independent reflections	l = −20→19

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.020	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.051	w = 1/[σ²(F_o²) + (0.0349P)² + 0.3874P] where P = (F_o² + 2F_c²)/3
S = 1.12	(Δ/σ)_max = 0.001
1258 reflections	Δρ_max = 0.50 e Å⁻³
58 parameters	Δρ_min = −0.48 e Å⁻³
0 restraints	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0151 (6)

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.13506 (11)	0.3029 (3)	0.30499 (9)	0.0197 (3)
H1n	0.1888 (17)	0.204 (4)	0.3204 (13)	0.024*
H2n	0.1477 (17)	0.393 (3)	0.2599 (15)	0.024*
N2	0.13068 (10)	0.4851 (2)	0.37297 (8)	0.0170 (3)
H3n	0.1867 (17)	0.574 (4)	0.3765 (12)	0.020*
C1	0.11750 (14)	0.3372 (3)	0.45000 (11)	0.0191 (3)
H1a	0.1708	0.2047	0.4582	0.029*
H1b	0.0510	0.2519	0.4454	0.029*
H1c	0.1220	0.4571	0.4973	0.029*
C2	0.04544 (15)	0.6693 (3)	0.35325 (15)	0.0278 (4)
H2a	0.0567	0.7656	0.3025	0.042*
H2b	0.0416	0.7925	0.3992	0.042*
H2c	−0.0182	0.5715	0.3450	0.042*
Br1	0.17057 (2)	0.64136 (3)	0.12100 (2)	0.01501 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0198 (7)	0.0244 (6)	0.0150 (7)	0.0014 (6)	0.0030 (5)	0.0027 (5)
N2	0.0120 (6)	0.0147 (6)	0.0240 (7)	−0.0019 (5)	−0.0004 (5)	0.0017 (5)
C1	0.0195 (8)	0.0226 (8)	0.0151 (8)	−0.0015 (5)	0.0010 (6)	−0.0008 (5)
C2	0.0175 (9)	0.0173 (8)	0.0479 (12)	0.0030 (6)	−0.0014 (8)	0.0067 (7)
Br1	0.01199 (13)	0.01558 (14)	0.01745 (14)	−0.00069 (4)	0.00116 (7)	0.00263 (4)

Geometric parameters (Å, º) top

N1—N2	1.4478 (19)	C1—H1a	0.98
N1—H1n	0.89 (2)	C1—H1b	0.98
N1—H2n	0.89 (2)	C1—H1c	0.98
N2—C1	1.482 (2)	C2—H2a	0.98
N2—C2	1.485 (2)	C2—H2b	0.98
N2—H3n	0.87 (2)	C2—H2c	0.98

N2—N1—H1n	103.6 (14)	H1a—C1—H1b	109.5
N2—N1—H2n	108.0 (12)	N2—C1—H1c	109.5
H1n—N1—H2n	108.8 (19)	H1a—C1—H1c	109.5
N1—N2—C1	108.93 (12)	H1b—C1—H1c	109.5
N1—N2—C2	108.97 (14)	N2—C2—H2a	109.5
C1—N2—C2	111.38 (14)	N2—C2—H2b	109.5
N1—N2—H3n	107.4 (13)	H2a—C2—H2b	109.5
C1—N2—H3n	111.9 (13)	N2—C2—H2c	109.5
C2—N2—H3n	108.1 (13)	H2a—C2—H2c	109.5
N2—C1—H1a	109.5	H2b—C2—H2c	109.5
N2—C1—H1b	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1n···Br1ⁱ	0.89 (2)	2.68 (3)	3.5666 (15)	170.7 (18)
N1—H2n···Br1	0.89 (2)	2.62 (2)	3.5117 (14)	175.0 (19)
N2—H3n···Br1ⁱⁱ	0.87 (2)	2.39 (2)	3.2490 (13)	173.3 (17)
C1—H1a···Br1ⁱ	0.98	3.11	3.9690 (18)	148
C1—H1b···Br1ⁱⁱⁱ	0.98	3.09	4.0175 (19)	158
C1—H1c···Br1^iv	0.98	2.90	3.8682 (17)	168
C2—H2c···Br1ⁱⁱⁱ	0.98	3.07	3.9843 (18)	156

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

(II) 2,2-Dimethylhydrazin-1-ium dihydrogen phosphite top

Crystal data top

C₂H₉N₂⁺·H₂PO₃⁻	D_x = 1.429 Mg m⁻³
M_r = 142.10	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pna2₁	Cell parameters from 4031 reflections
a = 8.0690 (2) Å	θ = 3.4–27.5°
b = 6.9970 (2) Å	µ = 0.35 mm⁻¹
c = 11.7001 (6) Å	T = 100 K
V = 660.57 (4) Å³	Plate, yellow
Z = 4	0.18 × 0.18 × 0.02 mm
F(000) = 304

Data collection top

Rigaku Mercury CCD diffractometer	R_int = 0.023
ω scans	θ_max = 27.5°, θ_min = 3.4°
5347 measured reflections	h = −8→10
1395 independent reflections	k = −8→9
1365 reflections with I > 2σ(I)	l = −15→13

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.025	H-atom parameters constrained
wR(F²) = 0.065	w = 1/[σ²(F_o²) + (0.0374P)² + 0.203P] where P = (F_o² + 2F_c²)/3
S = 1.09	(Δ/σ)_max < 0.001
1395 reflections	Δρ_max = 0.24 e Å⁻³
77 parameters	Δρ_min = −0.28 e Å⁻³
1 restraint	Absolute structure: Refined as an inversion twin.
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.15 (14)

Special details top

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.5416 (2)	0.5852 (2)	0.22552 (17)	0.0132 (4)
H1n	0.6455	0.5972	0.1962	0.016*
H2n	0.4779	0.6848	0.2016	0.016*
H3n	0.4960	0.4735	0.2011	0.016*
N2	0.5499 (2)	0.5853 (3)	0.34964 (17)	0.0145 (4)
C1	0.3807 (3)	0.5724 (3)	0.3936 (3)	0.0189 (5)
H1a	0.3169	0.6834	0.3677	0.028*
H1b	0.3832	0.5699	0.4773	0.028*
H1c	0.3286	0.4551	0.3652	0.028*
C2	0.6471 (3)	0.4186 (3)	0.3845 (2)	0.0206 (5)
H2a	0.7575	0.4255	0.3499	0.031*
H2b	0.5912	0.3018	0.3590	0.031*
H2c	0.6576	0.4169	0.4679	0.031*
P1	0.45797 (6)	0.05934 (7)	0.10615 (6)	0.01209 (15)
H1	0.4666	0.0529	−0.0064	0.015*
O1	0.35870 (18)	−0.1101 (2)	0.14409 (14)	0.0153 (3)
O2	0.39202 (17)	0.2526 (2)	0.13797 (14)	0.0165 (4)
O3	0.63746 (19)	0.0285 (2)	0.15307 (17)	0.0196 (4)
H1o	0.7059	0.1224	0.1417	0.024*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0099 (8)	0.0108 (8)	0.0189 (10)	0.0002 (6)	−0.0001 (7)	−0.0003 (7)
N2	0.0114 (9)	0.0142 (9)	0.0180 (11)	0.0005 (6)	−0.0007 (7)	−0.0007 (8)
C1	0.0124 (10)	0.0206 (11)	0.0236 (13)	−0.0007 (8)	0.0021 (10)	−0.0016 (9)
C2	0.0172 (11)	0.0209 (12)	0.0237 (13)	0.0050 (8)	−0.0028 (10)	0.0023 (10)
P1	0.0074 (2)	0.0095 (2)	0.0194 (3)	0.00031 (18)	0.0003 (3)	0.0004 (2)
O1	0.0097 (6)	0.0100 (7)	0.0263 (9)	−0.0005 (6)	0.0011 (6)	0.0013 (6)
O2	0.0097 (6)	0.0112 (7)	0.0286 (10)	0.0017 (6)	−0.0011 (6)	−0.0023 (6)
O3	0.0075 (6)	0.0127 (7)	0.0386 (10)	−0.0009 (6)	−0.0030 (7)	0.0040 (7)

Geometric parameters (Å, º) top

N1—N2	1.454 (3)	C2—H2a	0.98
N1—H1n	0.91	C2—H2b	0.98
N1—H2n	0.91	C2—H2c	0.98
N1—H3n	0.91	P1—O1	1.4982 (15)
N2—C1	1.462 (3)	P1—O2	1.5003 (16)
N2—C2	1.463 (3)	P1—O3	1.5638 (16)
C1—H1a	0.98	P1—H1	1.32
C1—H1b	0.98	O3—H1o	0.8689
C1—H1c	0.98

N2—N1—H1n	109.5	H1b—C1—H1c	109.5
N2—N1—H2n	109.5	N2—C2—H2a	109.5
H1n—N1—H2n	109.5	N2—C2—H2b	109.5
N2—N1—H3n	109.5	H2a—C2—H2b	109.5
H1n—N1—H3n	109.5	N2—C2—H2c	109.5
H2n—N1—H3n	109.5	H2a—C2—H2c	109.5
N1—N2—C1	107.94 (18)	H2b—C2—H2c	109.5
N1—N2—C2	107.62 (17)	O1—P1—O2	116.76 (9)
C1—N2—C2	110.69 (18)	O1—P1—O3	106.37 (9)
N2—C1—H1a	109.5	O2—P1—O3	111.46 (9)
N2—C1—H1b	109.5	O1—P1—H1	107.3
H1a—C1—H1b	109.5	O2—P1—H1	107.3
N2—C1—H1c	109.5	O3—P1—H1	107.3
H1a—C1—H1c	109.5	P1—O3—H1o	115.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1n···O1ⁱ	0.91	1.83	2.736 (2)	176
N1—H2n···O1ⁱⁱ	0.91	1.85	2.762 (2)	176
N1—H3n···O2	0.91	1.91	2.814 (2)	175
O3—H1o···O2ⁱ	0.87	1.74	2.568 (2)	159

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

Acknowledgements

We thank the EPSRC National Crystallography Service (University of Southampton) for the data collections.

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