Biguanidinium dichloride

Portalone, G.

doi:10.1107/S1600536808006144

organic compounds

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Volume 64| Part 4| April 2008| Page o683

doi:10.1107/S1600536808006144

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Biguanidinium dichloride

Gustavo Portalone ^a ^*

^aChemistry Department, `Sapienza' University of Rome, P. le A. Moro, 5, I-00185 Rome, Italy
^*Correspondence e-mail: g.portalone@caspur.it

(Received 4 March 2008; accepted 5 March 2008; online 7 March 2008)

The asymmetric unit of the title compound, C₂H₉N₅²⁺·2Cl⁻, is composed of one diprotonated biguanidinium cation and two chloride anions. The diprotonated cation consists of two planar halves twisted by 36.42 (6)°. The ions are associated in the crystal structure by extensive hydrogen bonding into a three-dimensional network; the diprotonated biguanidinium cation is hydrogen bonded to the chloride anions.

Related literature

For a general approach to the use of multiple-hydrogen-bonding DNA/RNA nucleobases as potential supramolecular reagents, see: Portalone & Colapietro (2004 , 2007 and references therein). For related crystal structures, see: Ernst (1977 ); Pinkerton & Schwarzenbach (1978 ); Martin & Pinkerton (1996 ); Martin et al. (1996 , 1997 ); Kurzer & Pitchfork (1968 ).

Experimental

Crystal data

C₂H₉N₅²⁺·2Cl⁻
M_r = 174.04
Monoclinic, P 2₁ /c
a = 6.43693 (9) Å
b = 16.93420 (18) Å
c = 6.65260 (8) Å
β = 98.6878 (12)°
V = 716.84 (1) Å³
Z = 4
Mo Kα radiation
μ = 0.83 mm⁻¹
T = 298 (2) K
0.20 × 0.20 × 0.15 mm

Data collection

Oxford Diffraction Xcalibur S CCD diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ) T_min = 0.852, T_max = 0.886
80724 measured reflections
2456 independent reflections
2349 reflections with I > 2σ(I)
R_int = 0.020

Refinement

R[F² > 2σ(F²)] = 0.027
wR(F²) = 0.070
S = 1.14
2456 reflections
119 parameters
All H-atom parameters refined
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯Cl2	0.819 (18)	2.279 (18)	3.0796 (9)	166.0 (16)
N2—H21⋯Cl1ⁱ	0.833 (18)	2.530 (18)	3.2557 (10)	146.4 (15)
N2—H22⋯Cl2ⁱⁱ	0.852 (19)	2.34 (2)	3.1714 (10)	167.1 (17)
N3—H31⋯Cl2ⁱ	0.823 (19)	2.787 (19)	3.5098 (12)	147.8 (16)
N3—H32⋯Cl1ⁱⁱⁱ	0.857 (19)	2.599 (19)	3.1933 (10)	127.4 (15)
N3—H32⋯Cl2	0.857 (19)	2.835 (19)	3.5454 (12)	141.3 (15)
N4—H41⋯Cl1	0.88 (2)	2.703 (19)	3.4178 (11)	139.4 (16)
N4—H42⋯Cl1^iv	0.846 (19)	2.412 (19)	3.2295 (10)	162.8 (17)
N5—H51⋯Cl2^v	0.853 (19)	2.413 (19)	3.2404 (12)	163.7 (16)
N5—H52⋯Cl1	0.874 (19)	2.369 (19)	3.1905 (11)	156.7 (17)
Symmetry codes: (i) x-1, y, z; (ii) $[x-1, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iv) -x+1, -y, -z; (v) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ; cell refinement: CrysAlis RED (Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ; data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808006144/kp2161sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808006144/kp2161Isup2.hkl

checkCIF report

Comment top

Biguanidine derivatives, characterized by multiple hydrogen-bond donor sites, are good candidates to be coupled in the crystal with carefully selected molecules having multiple hydrogen-bond acceptor sites (Portalone & Colapietro, 2004, 2007). As a part of a more general study of multiple-hydrogen-bonding DNA/RNA nucleobases as potential supramolecular reagents, this paper reports the crystal structure of the title compound, (I), BIGH₂²⁺2Cl^-. The asymmetric unit of (I) (Fig. 1) consists of a diprotonated biguanidinium cation (BIGH₂²⁺) and two chloride anions; protonation occurs at the bridge N atom and the imino N atom of the biguanidine molecule. The structure of the delocalized cation is very similar to those previously reported for the carbonate (BIGH₂)CO₃ and the sulfates (BIGH₂)SO₄.2H₂O and (BIGH₂)SO₄.H₂O (Pinkerton & Schwarzenbach, 1978), the dinitrate (BIGH₂)NO₃ (Martin et al., 1996), the diperchlorate (BIGH₂)2ClO₄ (Martin & Pinkerton, 1996), the bis-dinitramide (BIGH₂)(DN)₂ and (BIGH₂)(DN)₂.H₂O (Martin et al., 1997). BIGH₂²⁺ is composed of two planar halves sharing the atom N(1). These two planar parts are twisted with respect to each other by 36.42 (6)°. The C—N terminal bond lengths are shorter due to delocalization of π-electron density through the planar fragments. The lack of complete planarity of the cation is due to steric interaction between the hydrogen atoms. This interaction induces a strain in the molecule which is manifested by the opening of the angle at the bridging N atom [C1—N1—C2, 127.9 (1)°]. The weakening of the bridges bonds is due to the lowered basicity of the bridge N atom on protonation [pk_a^I = 11.5; pk_a^II = 2.9 (Kurzer & Pitchfork, 1968)] and is manifested by the longer C—N1 bridging bonds [1.363 (1) - 1.372 (1) Å] and the shorter terminal C—N bonds [1.306 (1) - 1.321 (1) Å], comparing with the corresponding ones reported for BIGH⁺Cl^- (Ernst, 1977). Analysis of the crystal packing of (I) (Fig. 2) shows that the structure is stabilized by ten hydrogen bonds N—H···Cl^- involving all protons (Table 1) which account for the relatively high density (D_x = 1.61 Mg m^-3).

Related literature top

For a general approach to the use of multiple-hydrogen-bonding DNA/RNA nucleobases as potential supramolecular reagents, see: Portalone & Colapietro (2004, 2007 and references therein). For related crystal structures, see: Ernst (1977); Pinkerton & Schwarzenbach (1978); Martin & Pinkerton (1996); Martin et al. (1996, 1997).

For related literature, see: Kurzer & Pitchfork (1968).

Experimental top

Biguanide (0.1 mmol, Sigma Aldrich at 98% purity) was dissolved in water (9 ml) and heated under reflux for 2 h. After cooling a solution to an ambient temperature, while stirring, HCl (6 mol L^-1) was added dropwise until the pH = 2. Crystals suitable for single-crystal X-ray diffraction were obtained by slow evaporation of the solvent after a few days.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. The molecular structure of (I) showing the atom-labelling scheme. Displacements ellipsoids are at the 50% probability level.
	Fig. 2. Crystal packing diagram for (I) viewed approximately down a. All atoms are shown as small spheres of arbitrary radii. Hydrogen bonding is indicated by dashed lines.

Biguanidinium dichloride top

Crystal data top

C₂H₉N₅²⁺·2Cl⁻	F(000) = 360
M_r = 174.04	D_x = 1.613 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 80724 reflections
a = 6.43693 (9) Å	θ = 3.2–32.0°
b = 16.93420 (18) Å	µ = 0.83 mm⁻¹
c = 6.65260 (8) Å	T = 298 K
β = 98.6878 (12)°	Plate, colourless
V = 716.84 (2) Å³	0.20 × 0.20 × 0.15 mm
Z = 4

Data collection top

Oxford Diffraction Xcalibur S CCD diffractometer	2456 independent reflections
Radiation source: Enhance (Mo) X-ray source	2349 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.020
Detector resolution: 16.0696 pixels mm^-1	θ_max = 32.0°, θ_min = 3.2°
ω and ϕ scans	h = −9→9
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	k = −25→25
T_min = 0.852, T_max = 0.886	l = −9→9
80724 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.027	All H-atom parameters refined
wR(F²) = 0.071	w = 1/[σ²(F_o²) + (0.0293P)² + 0.2376P] where P = (F_o² + 2F_c²)/3
S = 1.14	(Δ/σ)_max < 0.001
2456 reflections	Δρ_max = 0.14 e Å⁻³
119 parameters	Δρ_min = −0.14 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.110 (6)

Crystal data top

C₂H₉N₅²⁺·2Cl⁻	V = 716.84 (2) Å³
M_r = 174.04	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 6.43693 (9) Å	µ = 0.83 mm⁻¹
b = 16.93420 (18) Å	T = 298 K
c = 6.65260 (8) Å	0.20 × 0.20 × 0.15 mm
β = 98.6878 (12)°

Data collection top

Oxford Diffraction Xcalibur S CCD diffractometer	2456 independent reflections
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	2349 reflections with I > 2σ(I)
T_min = 0.852, T_max = 0.886	R_int = 0.020
80724 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.027	0 restraints
wR(F²) = 0.071	All H-atom parameters refined
S = 1.14	Δρ_max = 0.14 e Å⁻³
2456 reflections	Δρ_min = −0.14 e Å⁻³
119 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	0.86502 (5)	−0.053995 (15)	0.27026 (4)	0.03288 (9)
Cl2	0.62775 (5)	0.315420 (18)	0.37349 (5)	0.03605 (9)
N1	0.35152 (13)	0.16618 (5)	0.32041 (15)	0.02556 (17)
H1	0.430 (3)	0.2034 (10)	0.356 (3)	0.039 (4)*
N2	0.00539 (15)	0.12772 (6)	0.20409 (16)	0.02955 (19)
H21	0.025 (3)	0.0812 (11)	0.243 (3)	0.038 (4)*
H22	−0.109 (3)	0.1408 (11)	0.130 (3)	0.048 (5)*
N3	0.09938 (18)	0.25798 (6)	0.21118 (17)	0.0335 (2)
H31	−0.025 (3)	0.2708 (11)	0.195 (3)	0.046 (5)*
H32	0.193 (3)	0.2941 (11)	0.232 (3)	0.044 (5)*
N4	0.38953 (17)	0.03968 (6)	0.18533 (15)	0.0304 (2)
H41	0.461 (3)	−0.0045 (12)	0.196 (3)	0.050 (5)*
H42	0.308 (3)	0.0513 (11)	0.078 (3)	0.047 (5)*
N5	0.62338 (15)	0.08686 (7)	0.45410 (16)	0.0324 (2)
H51	0.646 (3)	0.1178 (11)	0.556 (3)	0.044 (5)*
H52	0.711 (3)	0.0485 (11)	0.440 (3)	0.051 (5)*
C1	0.14797 (15)	0.18273 (5)	0.24248 (14)	0.02118 (17)
C2	0.45468 (15)	0.09538 (6)	0.31785 (15)	0.02354 (18)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.04007 (15)	0.02213 (13)	0.03406 (15)	0.00402 (9)	−0.00208 (10)	−0.00296 (9)
Cl2	0.03243 (14)	0.03940 (16)	0.03375 (15)	−0.01269 (10)	−0.00333 (10)	0.00083 (10)
N1	0.0205 (4)	0.0213 (4)	0.0344 (4)	−0.0012 (3)	0.0024 (3)	−0.0021 (3)
N2	0.0220 (4)	0.0256 (4)	0.0390 (5)	−0.0017 (3)	−0.0020 (3)	0.0058 (4)
N3	0.0368 (5)	0.0215 (4)	0.0420 (6)	0.0052 (4)	0.0055 (4)	0.0047 (4)
N4	0.0379 (5)	0.0269 (4)	0.0257 (4)	0.0089 (4)	0.0022 (4)	−0.0017 (3)
N5	0.0253 (4)	0.0399 (5)	0.0312 (5)	0.0067 (4)	0.0010 (3)	0.0010 (4)
C1	0.0229 (4)	0.0203 (4)	0.0208 (4)	0.0012 (3)	0.0047 (3)	0.0022 (3)
C2	0.0218 (4)	0.0261 (4)	0.0238 (4)	0.0022 (3)	0.0068 (3)	0.0031 (3)

Geometric parameters (Å, º) top

N1—C1	1.3634 (13)	N3—H32	0.857 (19)
N1—C2	1.3719 (13)	N4—C2	1.3156 (14)
N1—H1	0.819 (18)	N4—H41	0.88 (2)
N2—C1	1.3056 (13)	N4—H42	0.846 (19)
N2—H21	0.833 (18)	N5—C2	1.3131 (14)
N2—H22	0.852 (19)	N5—H51	0.853 (19)
N3—C1	1.3211 (13)	N5—H52	0.874 (19)
N3—H31	0.823 (19)

C1—N1—C2	127.89 (9)	H41—N4—H42	121.2 (17)
C1—N1—H1	117.6 (12)	C2—N5—H51	120.4 (12)
C2—N1—H1	113.6 (12)	C2—N5—H52	119.2 (13)
C1—N2—H21	122.9 (12)	H51—N5—H52	120.4 (17)
C1—N2—H22	116.6 (13)	N2—C1—N3	120.97 (10)
H21—N2—H22	120.4 (17)	N2—C1—N1	122.31 (9)
C1—N3—H31	118.5 (13)	N3—C1—N1	116.70 (9)
C1—N3—H32	121.3 (12)	N5—C2—N4	122.04 (10)
H31—N3—H32	119.0 (17)	N5—C2—N1	116.03 (10)
C2—N4—H41	116.7 (12)	N4—C2—N1	121.93 (9)
C2—N4—H42	119.7 (12)

C2—N1—C1—N2	19.96 (17)	C1—N1—C2—N5	−159.12 (10)
C2—N1—C1—N3	−161.49 (10)	C1—N1—C2—N4	21.55 (17)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl2	0.819 (18)	2.279 (18)	3.0796 (9)	166.0 (16)
N2—H21···Cl1ⁱ	0.833 (18)	2.530 (18)	3.2557 (10)	146.4 (15)
N2—H22···Cl2ⁱⁱ	0.852 (19)	2.34 (2)	3.1714 (10)	167.1 (17)
N3—H31···Cl2ⁱ	0.823 (19)	2.787 (19)	3.5098 (12)	147.8 (16)
N3—H32···Cl1ⁱⁱⁱ	0.857 (19)	2.599 (19)	3.1933 (10)	127.4 (15)
N3—H32···Cl2	0.857 (19)	2.835 (19)	3.5454 (12)	141.3 (15)
N4—H41···Cl1	0.88 (2)	2.703 (19)	3.4178 (11)	139.4 (16)
N4—H42···Cl1^iv	0.846 (19)	2.412 (19)	3.2295 (10)	162.8 (17)
N5—H51···Cl2^v	0.853 (19)	2.413 (19)	3.2404 (12)	163.7 (16)
N5—H52···Cl1	0.874 (19)	2.369 (19)	3.1905 (11)	156.7 (17)

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

Experimental details

Crystal data
Chemical formula	C₂H₉N₅²⁺·2Cl⁻
M_r	174.04
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	298
a, b, c (Å)	6.43693 (9), 16.93420 (18), 6.65260 (8)
β (°)	98.6878 (12)
V (Å³)	716.84 (2)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.83
Crystal size (mm)	0.20 × 0.20 × 0.15

Data collection
Diffractometer	Oxford Diffraction Xcalibur S CCD diffractometer
Absorption correction	Multi-scan (CrysAlis RED; Oxford Diffraction, 2006)
T_min, T_max	0.852, 0.886
No. of measured, independent and observed [I > 2σ(I)] reflections	80724, 2456, 2349
R_int	0.020
(sin θ/λ)_max (Å⁻¹)	0.745

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.027, 0.071, 1.14
No. of reflections	2456
No. of parameters	119
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.14, −0.14

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl2	0.819 (18)	2.279 (18)	3.0796 (9)	166.0 (16)
N2—H21···Cl1ⁱ	0.833 (18)	2.530 (18)	3.2557 (10)	146.4 (15)
N2—H22···Cl2ⁱⁱ	0.852 (19)	2.34 (2)	3.1714 (10)	167.1 (17)
N3—H31···Cl2ⁱ	0.823 (19)	2.787 (19)	3.5098 (12)	147.8 (16)
N3—H32···Cl1ⁱⁱⁱ	0.857 (19)	2.599 (19)	3.1933 (10)	127.4 (15)
N3—H32···Cl2	0.857 (19)	2.835 (19)	3.5454 (12)	141.3 (15)
N4—H41···Cl1	0.88 (2)	2.703 (19)	3.4178 (11)	139.4 (16)
N4—H42···Cl1^iv	0.846 (19)	2.412 (19)	3.2295 (10)	162.8 (17)
N5—H51···Cl2^v	0.853 (19)	2.413 (19)	3.2404 (12)	163.7 (16)
N5—H52···Cl1	0.874 (19)	2.369 (19)	3.1905 (11)	156.7 (17)

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

Acknowledgements

We thank MIUR (Rome) for 2006 financial support of the project `X-ray diffractometry and spectrometry'.

References

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