Metformindiium dibromide

Pérez-Benítez, A.; Hernández Márquez, L.E.; Arroyo-Carmona, R.E.; Bernès, S.

doi:10.1107/S2414314626007911

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 8| August 2026| x260791

https://doi.org/10.1107/S2414314626007911

Open

access

Metformindiium dibromide

Aarón Pérez-Benítez,^a Luis E. Hernández Márquez,^a Rosa Elena Arroyo-Carmona ^a ^* and Sylvain Bernès ^b ^*

^aFacultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, 72570 Puebla, Pue., Mexico, and ^bInstituto de Física Luis Rivera Terrazas, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, 72570 Puebla, Pue., Mexico
^*Correspondence e-mail: [email protected], [email protected]

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 31 July 2026; accepted 2 August 2026; online 11 August 2026)

The crystal structure of the title salt, C₄H₁₃N₅²⁺·2Br⁻, is reported in space group P2₁/c, with Z = 4. Unexpectedly, this crystal is not isomorphous to the dichloride analogue, which has been reported in space group P2₁ (Z = 2). This originates from the shift of one halide anion in the asymmetric unit, which modifies the network of N—H⋯halide hydrogen bonds. For the here-reported structure, centrosymmetric R₄²(8) ring motifs are formed, affording a one-dimensional structure along [100], and the network is further expanded to a three-dimensional structure including larger ring motifs. This report is an example of a routine refinement carried out using now well-established techniques of quantum crystallography.

Keywords: crystal structure; metformin; dibromide salt; hydrogen bonds; QTAIM.

CCDC reference: 2578518

Structure description

In a recent article, Hill & Boeré (2025 ) argue in favour of wider application of quantum crystallography methods in routine chemical crystallography. Nowadays, experimental data quality is enough, even at room temperature, to fit the observed structure factors against non-spherical features of the electronic density map ρ(r). As a result, refined structures are closer to those expected from neutron diffraction data. Most significantly, accurate positions for H atoms can be obtained, frequently with anisotropic displacement parameters. Such a precision is inherently unachievable in the context of an IAM (Independent Atom Model), since structure factors only include spherical scattering factors. In fact, the default SFAC command in SHELXL still refers to Cromer–Mann scattering factors for neutral atoms, taken from the 1992 edition of the International Tables (Wilson & Geist, 1992 ; Sheldrick, 2015b ). In opposition, the ‘Hirshfeld Atom Refinement' approach (HAR; Capelli et al., 2014 ; Kleemiss et al., 2021 ) uses non-spherical form factors for each atom in the model. The computed map ρ(r) is then suitable for studying atoms, bonds, and lone pairs, using the concepts devised by Richard Bader in the QTAIM theory (Quantum Theory of Atoms in Molecules; Bader, 2005 ). Indeed, some such ‘routine' structures have already been published in repository journals like Acta Cryst. C or IUCrData (e.g. Jones, 2025 ; Samson et al., 2025 ). We report here the HAR refinement for a new metforminium(2+) salt.

The title compound, abbreviated H₂Mf²⁺·2Br⁻, is the dibromide salt of metformin [IUPAC name: [amino(dimethyliminio)methyl](diaminomethylidene)ammonium dibromide]. Metformin, Mf, is the first-line oral medication used to lower blood sugar in patients diagnosed with type-2 diabetes, and is sold in form of chlorhydrate, HMf⁺·Cl⁻. On the other hand, the monocation HMf⁺ and dication H₂Mf²⁺ have been used as counter-ions for vanadium clusters, which are also probed as medication against diabetes (e.g. Polito-Lucas et al., 2021 ; Chatkon et al., 2022 ).

The here reported crystal structure for H₂Mf²⁺·2Br⁻ is not isostructural to H₂Mf²⁺·2Cl⁻ (Xia, 2023 ; Hitchings et al., 2025 ). The dichloride salt crystallizes in space group P2₁, with Z = 2, while the dibromide salt gives crystals in space group P2₁/c, with Z = 4 (Fig. 1). Metrics for the dication H₂Mf²⁺ are however similar in both salts, and its twisted conformation is maintained, regardless of the counter-ion (Table 1). An overlay between both dications gives an rms deviation of 0.06 Å. The introduction of a c glide plane in the case of the dibromide salt should thus result from different positions of the halide ions in the asymmetric units. In turn, these positions should determine different networks of hydrogen bonds. This is indeed the case, as shown in Fig. 2: the halide ions interact directly with the guanidine moiety of H₂Mf²⁺, through charge-assisted (Cl⁻/Br⁻)⋯(H₂N)⁺ contacts. Cl1/Br1 ions have the same position in the asymmetric units, and behave as acceptors with H2E as donor (Table 2, entry 1). The key difference relates for Cl2/Br2 position: in the dichloride salt, Cl2 gives a double-acceptor hydrogen bond, with H4A and H5A as donors (Fig. 2, top). In the case of the dibromide salt, only one hydrogen bond is formed, N4—H4A⋯Br2 (Fig. 2, bottom; Table 2, entry 2).

Table 1
Bond lengths (Å) and valence angles (°) observed in dication H₂Mf²⁺ for the dichloride (Xia, 2023) and dibromide salts

Parameter	H₂Mf²⁺·2Cl^−a	H₂Mf²⁺·2Br⁻/SHELXL^b	H₂Mf²⁺·2Br⁻/NoSpherA2 ^c
Bonds
N1—C1	1.473 (4)	1.463 (3)	1.455 (3)
N1—C2	1.469 (4)	1.462 (4)	1.459 (4)
N1—C3	1.335 (4)	1.304 (3)	1.309 (3)
N2—C3	1.321 (4)	1.315 (3)	1.315 (3)
N3—C3	1.386 (3)	1.392 (3)	1.392 (3)
N3—C4	1.378 (3)	1.362 (3)	1.362 (3)
N4—C4	1.325 (4)	1.306 (4)	1.309 (4)
N5—C4	1.310 (4)	1.304 (4)	1.311 (3)
Angles
C1—N1—C2	115.7 (3)	115.1 (3)	115.2 (3)
C1—N1—C3	122.9 (2)	123.2 (2)	123.3 (3)
C2—N1—C3	120.0 (3)	120.9 (2)	120.7 (2)
N1—C3—N2	123.3 (2)	123.6 (2)	123.5 (2)
N1—C3—N3	118.2 (2)	119.5 (2)	119.2 (2)
N2—C3—N3	118.3 (3)	116.8 (2)	117.3 (2)
C3—N3—C4	125.0 (2)	124.8 (2)	124.4 (2)
N3—C4—N4	118.1 (3)	118.0 (3)	117.9 (3)
N3—C4—N5	120.4 (3)	119.5 (2)	119.6 (2)
N4—C4—N5	121.6 (3)	122.5 (3)	122.4 (3)
Torsion angles
N1—C3—N3—C4	−139.2 (3)	−133.1 (3)	−133.4 (2)
N2—C3—N3—C4	45.6 (4)	49.7 (4)	49.6 (3)
Notes: (a) Xia (2023); (b) SHELXL refinement: isotropic H atoms; free coordinates and displacement parameters for all atoms (152 parameters, R₁ = 3.14% for observed reflections, wR₂ = 7.84% for all reflections); (c) refinement details in Table 3.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2E⋯Br1	0.89 (5)	2.46 (4)	3.343 (3)	168 (3)
N4—H4A⋯Br2	0.91 (5)	2.48 (4)	3.355 (3)	163 (3)
N2—H2D⋯Br1ⁱ	0.99 (4)	2.45 (4)	3.341 (3)	149 (3)
N3—H3⋯Br1ⁱⁱ	0.94 (4)	2.42 (4)	3.321 (2)	160 (4)
N4—H4B⋯Br1ⁱⁱⁱ	1.01 (5)	2.48 (5)	3.350 (3)	144 (4)
N5—H5A⋯Br2^iv	0.90 (5)	2.49 (5)	3.346 (3)	157 (5)
N5—H5B⋯Br2^v	0.99 (4)	2.34 (4)	3.322 (3)	172 (3)
Symmetry codes: (i) ; (ii) ; (iii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iv) $[x, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ ; (v) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 1
Molecular structure of the title compound, with displacement ellipsoids at 30% probability level. The asymmetric unit and the labelling scheme are those adopted by Xia (2023

) in the dichloride analogue. The inset shows a representative crystal with a maximum dimension of ca. 4 mm, obtained by evaporation of an aqueous solution.

Figure 2
Comparison of the asymmetric units for H₂Mf²⁺·2Cl⁻ (Xia, 2023

; space group P2₁; top) and H₂Mf²⁺·2Br⁻ (this work; space group P2₁/c; bottom). The guanidine moiety in the cation and halides ions are shown using a spacefill representation (Macrae et al., 2020

This difference for the position of one anion is reflected in different supramolecular features. The smallest ring motifs found in H₂Mf²⁺·2Br⁻ have graph set R₄²(8) and are centrosymmetric. Cations are connected through these rings, forming a one-dimensional network oriented along [100]. The remaining amine groups, N3 and N5, give other efficient N—H⋯Br interactions, to build a complex three-dimensional framework (Fig. 3). A different image is obtained in the case of the dichloride salt: the bifurcated hydrogen bond including Cl2 affords an R₂¹(6) ring motif, which is not present in the dibromide salt. The complete crystal structure is essentially diperiodic, and expands to a three-dimensional framework, documented in the supplementary information file available from the CrystEngComm article (Hitchings et al., 2025; see Table S5 and Figure S3).

Figure 3
Part of the crystal structure of the title compound, emphasizing R₄²(8) rings building the one-dimensional framework (yellow areas). Br atom interactions with N3 and N5 afford a three-dimensional supramolecular structure.

Synthesis and crystallization

The title compound was synthesized by reacting at room temperature 3.4 g (20.5 mmol) of metforminium chloride dissolved in 15 ml of distilled water, with 6 ml of 48% HBr (53.0 mmol). After 15 min. of magnetic stirring, the solvent was evaporated at ambient conditions for about three weeks, to yield large polyhedric colourless single crystals (Fig. 1, inset).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The structure was first refined with SHELXL (Sheldrick, 2015b) and then with OLEX2.refine using the GUI OLEX2 (Bourhis et al., 2015 ; Dolomanov et al., 2009 ). Further refinements were carried out using NoSpherA2 in the same GUI (Kleemiss et al., 2021) and ORCA for DFT computations (Neese, 2022 ). The last cycles for refining non-spherical scattering factors were based on a tetrameric model, [C₄H₁₃N₅Br₂]₄, in order to take in account non-covalent bonds, using the PBE0 functional in conjunction with the def2-TZVPD basis set, including the DKH2 correction for relativistic effects. Coordinates and anisotropic displacement parameters were refined for all atoms, without restraints nor constraints. A batch of 12 cycles of refinement for this 96-atom model including 568 electrons is completed in a few hours on an unsophisticated desktop PC (i7–6700 CPU @3.40 GHz, 8 threads, 8 Gb RAM).

Table 3
Experimental details

Crystal data
Chemical formula	C₄H₁₃N₅²⁺·2Br⁻
M_r	290.99
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	295
a, b, c (Å)	10.3335 (3), 15.0443 (4), 6.4977 (2)
β (°)	95.427 (2)
V (Å³)	1005.61 (5)
Z	4
Radiation type	Ag Kα, λ = 0.56083 Å
μ (mm⁻¹)	4.29
Crystal size (mm)	0.29 × 0.20 × 0.07

Data collection
Diffractometer	Stoe Stadivari
Absorption correction	Multi-scan (LANA; Folkers-Karlsson et al., 2026 )
T_min, T_max	0.288, 0.741
No. of measured, independent and observed [I > 2σ(I)] reflections	31050, 3212, 2465
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.725

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.070, 1.04
No. of reflections	3212
No. of parameters	217
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.85, −0.57
Computer programs: X-AREA Pilatus3SV (Stoe, 2025 ), X-AREA Recipe (Folkers-Karlsson et al., 2026), X-AREA Integrate3D and LANA (Folkers-Karlsson et al., 2026), SHELXT2018/2 (Sheldrick, 2015a ), OLEX2.refine (Bourhis et al., 2015), XP in SHELXTL-Plus (Sheldrick, 2008 ), Mercury (Macrae et al., 2020 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 2578518

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314626007911/bt4203sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626007911/bt4203Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314626007911/bt4203Isup3.cml

checkCIF report

Computing details top

[Amino(dimethyliminio)methyl](diaminomethylidene)ammonium dibromide top

Crystal data top

C₄H₁₃N₅²⁺·2Br⁻	F(000) = 569.890
M_r = 290.99	D_x = 1.922 Mg m⁻³
Monoclinic, P2₁/c	Ag Kα radiation, λ = 0.56083 Å
a = 10.3335 (3) Å	Cell parameters from 22061 reflections
b = 15.0443 (4) Å	θ = 2.7–29.9°
c = 6.4977 (2) Å	µ = 4.29 mm⁻¹
β = 95.427 (2)°	T = 295 K
V = 1005.61 (5) Å³	Plate, colourless
Z = 4	0.29 × 0.2 × 0.07 mm

Data collection top

Stoe Stadivari diffractometer	3212 independent reflections
Radiation source: Sealed X-ray tube, Axo Astix-f Microfocus source	2465 reflections with I > 2σ(I)
Graded multilayer mirror monochromator	R_int = 0.031
Detector resolution: 5.81 pixels mm^-1	θ_max = 24.0°, θ_min = 2.7°
ω scans	h = −14→14
Absorption correction: multi-scan (LANA;Folkers-Karlsson et al., 2026)	k = −21→21
T_min = 0.288, T_max = 0.741	l = −9→9
31050 measured reflections

Refinement top

Refinement on F²	0 constraints
Least-squares matrix: full	Primary atom site location: dual
R[F² > 2σ(F²)] = 0.030	Secondary atom site location: difference Fourier map
wR(F²) = 0.070	All H-atom parameters refined
S = 1.04	w = 1/[σ²(F_o²) + (0.0267P)² + 1.1908P] where P = (F_o² + 2F_c²)/3
3212 reflections	(Δ/σ)_max = 0.001
217 parameters	Δρ_max = 0.85 e Å⁻³
0 restraints	Δρ_min = −0.57 e Å⁻³

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

	x	y	z	U_iso*/U_eq
Br1	0.90769 (3)	0.642983 (18)	−0.06038 (4)	0.03418 (8)
Br2	0.44558 (3)	0.85428 (2)	0.28006 (5)	0.04693 (9)
N1	0.81449 (19)	0.41933 (14)	0.5843 (3)	0.0288 (4)
N2	0.8743 (3)	0.48014 (19)	0.2806 (4)	0.0341 (5)
H2D	0.916 (4)	0.426 (3)	0.231 (5)	0.048 (10)
H2E	0.881 (4)	0.529 (3)	0.205 (6)	0.061 (12)
N3	0.7614 (2)	0.56611 (16)	0.4982 (3)	0.0307 (5)
H3	0.783 (4)	0.585 (3)	0.635 (7)	0.065 (12)
N4	0.6770 (3)	0.70012 (18)	0.3858 (5)	0.0377 (5)
H4A	0.612 (4)	0.736 (3)	0.330 (7)	0.058 (12)
H4B	0.749 (4)	0.735 (3)	0.465 (8)	0.079 (15)
N5	0.6060 (3)	0.5722 (2)	0.2185 (4)	0.0354 (5)
H5A	0.568 (3)	0.608 (4)	0.118 (8)	0.078 (15)
H5B	0.600 (4)	0.506 (3)	0.215 (5)	0.046 (10)
C1	0.7302 (4)	0.4179 (3)	0.7514 (6)	0.0441 (7)
H1A	0.671 (5)	0.360 (3)	0.730 (7)	0.080 (15)
H1B	0.675 (5)	0.468 (3)	0.748 (7)	0.102 (18)
H1C	0.780 (5)	0.402 (4)	0.878 (6)	0.12 (2)
C2	0.8806 (4)	0.3358 (2)	0.5493 (6)	0.0424 (7)
H2A	0.910 (6)	0.306 (4)	0.683 (8)	0.13 (2)
H2B	0.964 (7)	0.343 (3)	0.475 (12)	0.14 (3)
H2C	0.824 (5)	0.295 (4)	0.451 (12)	0.15 (3)
C3	0.8168 (2)	0.48498 (16)	0.4524 (3)	0.0241 (4)
C4	0.6799 (2)	0.61371 (16)	0.3628 (4)	0.0257 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.03867 (13)	0.03190 (14)	0.03194 (12)	0.00332 (10)	0.00313 (9)	−0.00091 (10)
Br2	0.05447 (18)	0.04031 (17)	0.04234 (15)	0.01947 (13)	−0.01468 (12)	−0.00801 (12)
N1	0.0322 (10)	0.0297 (11)	0.0238 (9)	0.0024 (8)	−0.0007 (7)	0.0022 (8)
N2	0.0430 (13)	0.0310 (13)	0.0294 (11)	0.0084 (11)	0.0104 (10)	0.0042 (10)
H2D	0.06 (3)	0.05 (3)	0.04 (2)	0.03 (2)	0.017 (19)	0.01 (2)
H2E	0.06 (3)	0.08 (3)	0.05 (3)	−0.02 (2)	0.01 (2)	0.00 (2)
N3	0.0358 (11)	0.0285 (11)	0.0262 (10)	0.0087 (9)	−0.0055 (8)	−0.0039 (9)
H3	0.08 (3)	0.03 (2)	0.09 (3)	0.01 (2)	−0.01 (3)	0.01 (2)
N4	0.0376 (13)	0.0237 (12)	0.0518 (16)	0.0065 (10)	0.0042 (11)	0.0007 (11)
H4A	0.08 (3)	0.02 (2)	0.08 (3)	0.01 (2)	0.03 (2)	−0.01 (2)
H4B	0.06 (3)	0.06 (3)	0.11 (4)	0.03 (3)	−0.03 (3)	0.00 (3)
N5	0.0348 (12)	0.0298 (13)	0.0391 (13)	0.0012 (10)	−0.0091 (10)	0.0038 (11)
H5A	0.02 (2)	0.11 (4)	0.11 (4)	0.00 (2)	0.02 (2)	0.01 (3)
H5B	0.07 (3)	0.04 (2)	0.019 (18)	0.00 (2)	−0.016 (17)	0.007 (17)
C1	0.0488 (18)	0.052 (2)	0.0331 (15)	−0.0020 (16)	0.0106 (13)	0.0068 (15)
H1A	0.09 (3)	0.07 (3)	0.08 (3)	−0.05 (3)	0.02 (3)	0.00 (2)
H1B	0.16 (4)	0.07 (3)	0.09 (3)	0.05 (3)	0.08 (3)	0.05 (3)
H1C	0.15 (5)	0.18 (6)	0.04 (2)	0.03 (4)	0.06 (3)	0.03 (3)
C2	0.057 (2)	0.0293 (15)	0.0398 (16)	0.0100 (14)	0.0006 (14)	0.0062 (12)
H2A	0.17 (6)	0.12 (5)	0.09 (4)	0.04 (4)	−0.04 (4)	0.03 (4)
H2B	0.17 (6)	0.07 (4)	0.18 (6)	0.06 (4)	0.07 (6)	0.05 (4)
H2C	0.06 (3)	0.12 (5)	0.25 (7)	−0.01 (3)	−0.04 (4)	−0.09 (5)
C3	0.0247 (10)	0.0249 (11)	0.0219 (9)	0.0021 (8)	−0.0015 (8)	−0.0024 (8)
C4	0.0262 (10)	0.0215 (10)	0.0293 (10)	0.0036 (9)	0.0020 (8)	0.0008 (9)

Geometric parameters (Å, º) top

N1—C1	1.455 (3)	N4—C4	1.309 (4)
N1—C2	1.459 (4)	N5—H5A	0.90 (5)
N1—C3	1.309 (3)	N5—H5B	0.99 (4)
N2—H2D	0.99 (4)	N5—C4	1.311 (3)
N2—H2E	0.89 (5)	C1—H1A	1.06 (4)
N2—C3	1.315 (3)	C1—H1B	0.95 (4)
N3—H3	0.94 (4)	C1—H1C	0.96 (5)
N3—C3	1.392 (3)	C2—H2A	1.00 (5)
N3—C4	1.362 (3)	C2—H2B	1.04 (6)
N4—H4A	0.91 (5)	C2—H2C	1.02 (5)
N4—H4B	1.01 (5)

C2—N1—C1	115.2 (3)	H1B—C1—H1A	108 (4)
C3—N1—C1	123.3 (3)	H1C—C1—N1	109 (3)
C3—N1—C2	120.7 (2)	H1C—C1—H1A	99 (4)
H2E—N2—H2D	116 (3)	H1C—C1—H1B	120 (4)
C3—N2—H2D	125 (2)	H2A—C2—N1	111 (3)
C3—N2—H2E	119 (3)	H2B—C2—N1	114 (3)
C3—N3—H3	114 (2)	H2B—C2—H2A	105 (5)
C4—N3—H3	122 (2)	H2C—C2—N1	111 (3)
C4—N3—C3	124.4 (2)	H2C—C2—H2A	113 (5)
H4B—N4—H4A	113 (4)	H2C—C2—H2B	103 (5)
C4—N4—H4A	125 (3)	N2—C3—N1	123.5 (2)
C4—N4—H4B	123 (2)	N3—C3—N1	119.2 (2)
H5B—N5—H5A	123 (4)	N3—C3—N2	117.3 (2)
C4—N5—H5A	115 (3)	N4—C4—N3	117.9 (3)
C4—N5—H5B	121.7 (19)	N5—C4—N3	119.6 (2)
H1A—C1—N1	107 (2)	N5—C4—N4	122.4 (3)
H1B—C1—N1	112 (2)

N1—C3—N3—C4	−133.4 (2)	N2—C3—N3—C4	49.6 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2E···Br1	0.89 (5)	2.46 (4)	3.343 (3)	168 (3)
N4—H4A···Br2	0.91 (5)	2.48 (4)	3.355 (3)	163 (3)
N2—H2D···Br1ⁱ	0.99 (4)	2.45 (4)	3.341 (3)	149 (3)
N3—H3···Br1ⁱⁱ	0.94 (4)	2.42 (4)	3.321 (2)	160 (4)
N4—H4A···N4ⁱⁱⁱ	0.91 (5)	3.18 (4)	3.579 (2)	109 (3)
N4—H4B···Br1^iv	1.01 (5)	2.48 (5)	3.350 (3)	144 (4)
N4—H4B···N4^iv	1.01 (5)	3.06 (5)	3.579 (2)	113 (3)
N5—H5A···Br2ⁱⁱⁱ	0.90 (5)	2.49 (5)	3.346 (3)	157 (5)
N5—H5B···Br2^v	0.99 (4)	2.34 (4)	3.322 (3)	172 (3)
C1—H1A···N5^vi	1.06 (4)	3.08 (5)	3.501 (5)	104 (3)
C1—H1B···N3	0.95 (4)	2.43 (4)	2.808 (5)	104 (3)
C1—H1B···N5^vi	0.95 (4)	2.99 (5)	3.501 (5)	115 (4)
C2—H2A···Br1^vii	1.00 (5)	3.24 (6)	3.630 (3)	105 (4)

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

Bond lengths (Å) and valence angles (°) observed in dication H₂Mf²⁺ for the dichloride (Xia, 2023) and dibromide salts top

Parameter	H₂Mf²⁺·2Cl^- ^a	H₂Mf²⁺·2Br^-/SHELXL^b	H₂Mf²⁺·2Br^-/NoSpherA2 ^c
Bonds
N1—C1	1.473 (4)	1.463 (3)	1.455 (3)
N1—C2	1.469 (4)	1.462 (4)	1.459 (4)
N1—C3	1.335 (4)	1.304 (3)	1.309 (3)
N2—C3	1.321 (4)	1.315 (3)	1.315 (3)
N3—C3	1.386 (3)	1.392 (3)	1.392 (3)
N3—C4	1.378 (3)	1.362 (3)	1.362 (3)
N4—C4	1.325 (4)	1.306 (4)	1.309 (4)
N5—C4	1.310 (4)	1.304 (4)	1.311 (3)
Angles
C1—N1—C2	115.7 (3)	115.1 (3)	115.2 (3)
C1—N1—C3	122.9 (2)	123.2 (2)	123.3 (3)
C2—N1—C3	120.0 (3)	120.9 (2)	120.7 (2)
N1—C3—N2	123.3 (2)	123.6 (2)	123.5 (2)
N1—C3—N3	118.2 (2)	119.5 (2)	119.2 (2)
N2—C3—N3	118.3 (3)	116.8 (2)	117.3 (2)
C3—N3—C4	125.0 (2)	124.8 (2)	124.4 (2)
N3—C4—N4	118.1 (3)	118.0 (3)	117.9 (3)
N3—C4—N5	120.4 (3)	119.5 (2)	119.6 (2)
N4—C4—N5	121.6 (3)	122.5 (3)	122.4 (3)
Torsion angles
N1—C3—N3—C4	-139.2 (3)	-133.1 (3)	-133.4 (2)
N2—C3—N3—C4	45.6 (4)	49.7 (4)	49.6 (3)

Notes: (a) Xia (2023); (b) SHELXL refinement: isotropic H atoms; free coordinates and displacement parameters for all atoms (152 parameters, R₁ = 3.14 % for observed reflections, wR₂ = 7.84 % for all reflections); (c) refinement details in Table 3.

Funding information

Funding for this research was provided by: Vicerrectoría de Investigación y Estudios de Posgrado, BUAP (grant No. 00118-PVG/2026; studentship to Luis E. Hernández-Márquez (Program Haciendo Ciencia en la BUAP Primavera 2026)); Consejo Nacional de Ciencia y Tecnología (grant No. 268178).

References

Bader, R. F. W. (2005). Monatsh. Chem. 136, 819–854. Web of Science CrossRef CAS Google Scholar
Bourhis, L. J., Dolomanov, O. V., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2015). Acta Cryst. A71, 59–75. Web of Science CrossRef IUCr Journals Google Scholar
Capelli, S. C., Bürgi, H.-B., Dittrich, B., Grabowsky, S. & Jayatilaka, D. (2014). IUCrJ 1, 361–379. Web of Science CSD CrossRef CAS PubMed IUCr Journals Google Scholar
Chatkon, A., Haller, J. P. & Haller, K. J. (2022). Acta Cryst. B78, 798–808. CrossRef IUCr Journals Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Folkers-Karlsson, L. C., Celani, P., Hahn, F. & Richter, J. (2026). Z. Kristallogr. 241, 41–51. CAS Google Scholar
Hill, N. D. D. & Boeré, R. T. (2025). Chem. Methods 5, e202400052. Web of Science CrossRef Google Scholar
Hitchings, T. J., School Project Students, Shepherd, A., Alfredsson, M. & Saines, P. J. (2025). CrystEngComm 27, 7785–7791. CrossRef CAS Google Scholar
Jones, P. G. (2025). Acta Cryst. C81, 455–461. Web of Science CSD CrossRef IUCr Journals Google Scholar
Kleemiss, F., Dolomanov, O. V., Bodensteiner, M., Peyerimhoff, N., Midgley, L., Bourhis, L. J., Genoni, A., Malaspina, L. A., Jayatilaka, D., Spencer, J. L., White, F., Grundkötter-Stock, B., Steinhauer, S., Lentz, D., Puschmann, H. & Grabowsky, S. (2021). Chem. Sci. 12, 1675–1692. Web of Science CSD CrossRef CAS Google Scholar
Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226–235. Web of Science CrossRef CAS IUCr Journals Google Scholar
Neese, F. (2022). WIREs Comput. Mol. Sci. 12, e1606. Google Scholar
Polito-Lucas, J. A., Núñez-Ávila, J. A., Bernès, S. & Pérez-Benítez, A. (2021). IUCrData 6, x210634. Google Scholar
Samson, L., Banwart, L., Silwal, S. & Bond, M. R. (2025). IUCrData 10, x250747. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Stoe (2025). X-AREA Pilatus3SV. Stoe & Cie, Darmstadt, Germany. Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wilson, A. J. C. & Geist, V. (1992). International Tables for Crystallography Vol. C, Mathematical, Physical and Chemical Tables. Dordrecht, Boston, London: Kluwer Academic Publishers. Google Scholar
Xia, Y.-P. (2023). Z. Kristallogr. New Cryst. Struct. 238, 799–800. CrossRef Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 8| August 2026| x260791

https://doi.org/10.1107/S2414314626007911

Open

access

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Search IUCr Journals		doi		Advanced search
Author		volume	page

organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Metformindiium dibromide

Structure description

Synthesis and crystallization

Refinement

Structural data

Funding information

References

organic compounds