N,N-Di­methyl­biguanidium nitrate

The cation in the title compound, C₄H₁₂N₅⁺·NO₃⁻, is protonated at one imino group, and through this an intramolecular N—H...N hydrogen bond is formed, which stabilizes the conformation of the cation in the structure. The dihedral angle between the two guanidine groups is 51.7 (1)°.

Key indicators

• Single-crystal X-ray study
• T = 184 K
• Mean [sigma](O-N) = 0.003 Å
• R factor = 0.054
• wR factor = 0.129
• Data-to-parameter ratio = 10.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Metformin is an antihyperglycemic agent which improves glucose tolerance in type-2 diabetic patients, lowering both basal and postprandial plasma glucose levels. There are some benefits for these diabetic patients who use it in order to control their plasma glucose levels. From pharmacological studies, metformin acts by improving peripheral sensitivity to insulin, inhibiting gastrointestinal absorption of glucose, and decreasing hepatic glucose production. Researchers indicate that metformin alone does not produce hypoglycemia in either diabetic or nondiabetic individuals (Davidson & Peters, 1997; Jackson et al., 1987; Klip et al., 1990). In previous reports, we studied that the structures of metformin formed the complexes with Zn²⁺, Cu²⁺ and Ni²⁺ (Zhu et al., 2002, 2002a,b). Magnesium, a ubiquitous element that plays a fundamental role in many cellular reactions, is involved in more than 300 enzymatic reactions in which food is catabolized and new chemical products are formed, such as glycogen breakdown, fat oxidation, protein synthesis, ATP synthesis, and the second messenger system (Lukaski, 2000). In order to obtain the information regarding interaction between metformin and magnesium ions, magnesium(II) nitrate is employed in our current research. However, the title compound, (I), is obtained instead of the Mg²⁺ complex. Compared with (C₄H₁₂N₅)[TlBr₄] (He et al., 2002) and C₄H₁₂N₅⁺·Cl⁻ (Hariharan et al., 1989), the anion of (I) is NO₃⁻ here.

Selected geometric parameters are listed in Table 1, and a perspective view of the structure is shown in Fig. 1. In the structure of (I), the two guanidine groups form two planes with a 51.7 (1)° planar angle. Atoms C1 and C2 are −0.042 (3) and −0.019 (3) Å out of planes N1/N2/N3/C1 and N3/N4/N5/C2, respectively. The C—N bond distances of (I) in the range of 1.324 (3)–1.336 (3) Å are shorter than a single and longer than the double bond, indicating a delocalization of π-electron density across the biguanide group. In other words, the position of the single and double bond is not strictly located inside the molecule. 1,1-Dimethylbiguanide as a form of cation appears in several compounds, such as (C₄H₁₂N₅)[ZnCl₃] (Zhu et al., 2002), and previously mentioned. Compared with the cation form of these compounds, a notable difference can be drawn from the packing diagrams. As shown in Fig. 2, two molecules are connected by two N5—H···N3 hydrogen bonds, forming an elongated hexagon. The hydrogen bonding information is given in Table 2 and a packing diagram is shown in Fig. 3. In addition, the molecules in the crystal are held together by van der Waals forces by a number of intermolecular N—H···O interactions. A weak N—H···N intramolecular hydrogen bond stabilizes the cation conformation (Fig. 1).

S2. Experimental

Crystals of (I) were grown from an aqueous solution of magnesium(II) nitrate hexahydrate (100.0 mmol) and N-dimethylbiguanide hydrochloride (100.0 mmol). The solution was left at room temperature and crystals formed after a few days. The elemental analysis result was in agreement with the structural composition of (I).

S3. Refinement

H atoms attached to C and N atoms were located in difference Fourier maps and refined with a global U_iso value. The C—H and N—H distances were in the ranges 0.93 (3)–0.98 (3) and 0.84 (3)–0.91 (3) Å, respectively.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. A view of the asymmetric unit of (I), with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radii. Dotted lines represent hydrogen bonds.
	Fig. 2. The crystal structure of (I) as a dimer formed via hydrogen bonds. Dotted lines represent hydrogen bonds.
	Fig. 3. A packing diagram of the structure of the title compound.

N,N-dimethylbiguanidium nitrate

Crystal data

C4H12N5^+·NO3^−	Z = 2
Mr = 192.20	F(000) = 204
Triclinic, P1	Dx = 1.418 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.204 (3) Å	Cell parameters from 2484 reflections
b = 7.534 (3) Å	θ = 2.8–24.7°
c = 8.821 (4) Å	µ = 0.12 mm^−1
α = 78.109 (5)°	T = 184 K
β = 73.979 (6)°	Block, colorless
γ = 85.353 (6)°	0.30 × 0.20 × 0.10 mm
V = 450.1 (3) Å^3

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1559 independent reflections
Radiation source: fine-focus sealed tube	1181 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scans	θmax = 25.0°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	h = −5→8
Tmin = 0.965, Tmax = 0.988	k = −7→8
1875 measured reflections	l = −10→10

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.129	All H-atom parameters refined
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0627P)^2] where P = (Fo^2 + 2Fc^2)/3
1559 reflections	(Δ/σ)max = 0.002
155 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.20 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.

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

	x	y	z	Uiso*/Ueq
C1	0.3203 (3)	0.1619 (3)	0.7195 (3)	0.0232 (6)
C2	0.3318 (4)	0.2505 (3)	0.9550 (3)	0.0236 (6)
C3	0.2488 (5)	0.0584 (4)	0.4995 (3)	0.0315 (7)
C4	0.1365 (6)	−0.1112 (4)	0.7791 (4)	0.0477 (9)
N1	0.2468 (3)	0.0374 (3)	0.6676 (2)	0.0251 (5)
N2	0.3802 (3)	0.3163 (3)	0.6177 (3)	0.0290 (6)
N3	0.3490 (3)	0.1233 (2)	0.8670 (2)	0.0262 (5)
N4	0.2262 (3)	0.4036 (3)	0.9364 (3)	0.0309 (6)
N5	0.4182 (3)	0.2203 (3)	1.0727 (3)	0.0342 (6)
N6	0.1893 (3)	0.5910 (3)	0.3001 (3)	0.0316 (6)
O1	0.3340 (3)	0.4826 (2)	0.2927 (2)	0.0312 (5)
O2	0.1352 (3)	0.6691 (3)	0.4143 (3)	0.0542 (6)
O3	0.1053 (3)	0.6168 (3)	0.1917 (2)	0.0534 (6)
H21	0.347 (4)	0.357 (4)	0.529 (4)	0.051 (3)*
H22	0.451 (4)	0.388 (4)	0.646 (3)	0.051 (3)*
H41	0.219 (4)	0.468 (4)	1.005 (4)	0.051 (3)*
H42	0.151 (5)	0.418 (4)	0.868 (4)	0.051 (3)*
H51	0.499 (4)	0.123 (4)	1.084 (3)	0.051 (3)*
H52	0.401 (4)	0.294 (4)	1.138 (4)	0.051 (3)*
H3A	0.368 (5)	0.110 (4)	0.435 (4)	0.051 (3)*
H4A	0.006 (5)	−0.095 (4)	0.782 (4)	0.051 (3)*
H3B	0.147 (4)	0.141 (4)	0.472 (3)	0.051 (3)*
H4B	0.170 (4)	−0.224 (4)	0.745 (3)	0.051 (3)*
H3C	0.231 (4)	−0.060 (4)	0.476 (3)	0.051 (3)*
H4C	0.146 (4)	−0.119 (4)	0.885 (4)	0.051 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0173 (13)	0.0265 (13)	0.0250 (13)	0.0027 (11)	−0.0048 (11)	−0.0056 (10)
C2	0.0249 (14)	0.0258 (13)	0.0191 (12)	−0.0013 (11)	−0.0055 (11)	−0.0025 (10)
C3	0.0318 (17)	0.0356 (16)	0.0318 (15)	0.0009 (13)	−0.0132 (13)	−0.0113 (12)
C4	0.065 (2)	0.0401 (18)	0.0394 (18)	−0.0224 (18)	−0.0158 (18)	−0.0008 (14)
N1	0.0258 (12)	0.0255 (11)	0.0256 (11)	−0.0022 (9)	−0.0083 (9)	−0.0059 (9)
N2	0.0345 (14)	0.0287 (12)	0.0260 (12)	−0.0060 (10)	−0.0142 (11)	−0.0001 (9)
N3	0.0320 (13)	0.0250 (11)	0.0242 (11)	0.0030 (9)	−0.0126 (10)	−0.0052 (8)
N4	0.0342 (14)	0.0313 (13)	0.0323 (13)	0.0088 (10)	−0.0159 (11)	−0.0118 (10)
N5	0.0455 (16)	0.0329 (13)	0.0322 (13)	0.0131 (11)	−0.0219 (12)	−0.0141 (10)
N6	0.0275 (13)	0.0372 (13)	0.0345 (13)	0.0011 (11)	−0.0112 (11)	−0.0135 (10)
O1	0.0291 (10)	0.0319 (10)	0.0367 (11)	0.0084 (8)	−0.0137 (8)	−0.0126 (8)
O2	0.0514 (14)	0.0640 (14)	0.0607 (14)	0.0165 (11)	−0.0200 (12)	−0.0422 (12)
O3	0.0410 (13)	0.0811 (16)	0.0530 (13)	0.0201 (11)	−0.0317 (11)	−0.0286 (11)

Geometric parameters (Å, º)

C1—N1	1.327 (3)	C4—H4B	0.95 (3)
C1—N2	1.335 (3)	C4—H4C	0.95 (3)
C1—N3	1.343 (3)	N2—H21	0.87 (3)
C2—N5	1.324 (3)	N2—H22	0.89 (3)
C2—N3	1.331 (3)	N4—H41	0.84 (3)
C2—N4	1.336 (3)	N4—H42	0.90 (3)
C3—N1	1.455 (3)	N5—H51	0.91 (3)
C3—H3A	0.95 (3)	N5—H52	0.85 (3)
C3—H3B	0.98 (3)	N6—O2	1.226 (3)
C3—H3C	0.98 (3)	N6—O3	1.241 (3)
C4—N1	1.453 (4)	N6—O1	1.266 (3)
C4—H4A	0.93 (3)
N1—C1—N2	118.7 (2)	H4B—C4—H4C	111 (2)
N1—C1—N3	119.4 (2)	C1—N1—C4	121.3 (2)
N2—C1—N3	121.6 (2)	C1—N1—C3	121.2 (2)
N5—C2—N3	118.1 (2)	C4—N1—C3	116.8 (2)
N5—C2—N4	117.8 (2)	C1—N2—H21	125.2 (19)
N3—C2—N4	124.1 (2)	C1—N2—H22	118.1 (19)
N1—C3—H3A	108.3 (17)	H21—N2—H22	117 (3)
N1—C3—H3B	112.5 (17)	C2—N3—C1	121.5 (2)
H3A—C3—H3B	107 (2)	C2—N4—H41	115 (2)
N1—C3—H3C	109.4 (16)	C2—N4—H42	118.8 (18)
H3A—C3—H3C	112 (2)	H41—N4—H42	125 (3)
H3B—C3—H3C	108 (2)	C2—N5—H51	120.1 (18)
N1—C4—H4A	110.5 (19)	C2—N5—H52	120 (2)
N1—C4—H4B	112.4 (18)	H51—N5—H52	119 (3)
H4A—C4—H4B	103 (3)	O2—N6—O3	121.2 (2)
N1—C4—H4C	111.9 (17)	O2—N6—O1	119.2 (2)
H4A—C4—H4C	107 (3)	O3—N6—O1	119.6 (2)
N2—C1—N1—C4	−164.5 (3)	N5—C2—N3—C1	−159.1 (2)
N3—C1—N1—C4	21.6 (4)	N4—C2—N3—C1	23.8 (4)
N2—C1—N1—C3	6.3 (4)	N1—C1—N3—C2	−147.5 (2)
N3—C1—N1—C3	−167.6 (2)	N2—C1—N3—C2	38.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N5—H52···O1^i	0.85 (3)	2.11 (3)	2.962 (3)	175 (3)
N5—H51···N3^ii	0.91 (3)	2.10 (3)	3.003 (3)	171 (3)
N4—H41···O3^i	0.84 (3)	2.12 (3)	2.932 (3)	162 (3)
N2—H21···O1	0.87 (3)	2.13 (3)	2.980 (3)	166 (3)
N2—H22···O1^iii	0.89 (3)	2.14 (3)	3.009 (3)	168 (3)
N4—H42···O3^iv	0.90 (3)	2.10 (3)	2.936 (3)	153 (3)
N4—H42···N2	0.90 (3)	2.58 (3)	2.913 (3)	103 (2)

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