Benzamidinium tetra­hydro­penta­borate sesquihydrate

Gustavo Portalone

doi:10.1107/S1600536808017522

. 2008 Jun 19;64(Pt 7):o1282–o1283. doi: 10.1107/S1600536808017522

Benzamidinium tetrahydropentaborate sesquihydrate

Gustavo Portalone ^a,^*

PMCID: PMC2961702 PMID: 21202914

Abstract

The asymmetric unit of the title compound [systematic name: benzamidinium 3,3′,5,5′-tetrahydroxy-1,1′-spirobi[2,4,6-trioxa-1,3,5-triboracyclohexane](1−) sesquihydrate], C₇H₉N₂ ⁺·B₅H₄O₁₀ ⁻·1.5H₂O, is composed of two protonated benzamidinium cations, two tetrahydropentaborate anions and three water molecules of crystallization. The ions and water molecules are associated in the crystal structure by an extensive three-dimensional hydrogen-bonding network, which consists mainly of cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds.

Related literature

For crystal structure determinations of the tetrahydropentaborate anion, see: Loboda et al., (1993 ▶, 1994 ▶); Wiebcke et al. (1993 ▶); Turdybekov et al. (1992 ▶); Freyhardt et al. (1994 ▶); Baber et al. (2004 ▶). For the computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990 ▶); Bernstein et al. (1995 ▶); Motherwell et al. (1999 ▶). For hydration in molecular crystals, see: Gillon et al. (2003 ▶).

Experimental

Crystal data

C₇H₉N₂ ⁺·B₅H₄O₁₀ ⁻·1.5H₂O
M _r = 366.27
Triclinic,
a = 8.22314 (19) Å
b = 10.7814 (2) Å
c = 19.1997 (3) Å
α = 75.9475 (11)°
β = 85.4458 (16)°
γ = 73.6979 (13)°
V = 1584.74 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.14 mm⁻¹
T = 298 (2) K
0.15 × 0.12 × 0.10 mm

Data collection

Oxford Diffraction Xcalibur S CCD diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 ▶) T _min = 0.975, T _max = 0.988
142668 measured reflections
9063 independent reflections
5688 reflections with I > 2σ(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.098
S = 0.99
9063 reflections
542 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction 2006 ▶); cell refinement: CrysAlis RED(Oxford Diffraction 2006 ▶); 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 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808017522/rz2220sup1.cif

e-64-o1282-sup1.cif^{(28.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808017522/rz2220Isup2.hkl

e-64-o1282-Isup2.hkl^{(434.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3ⁱ	0.83 (2)	2.04 (2)	2.8562 (13)	167.4 (18)
O4—H4⋯O6Aⁱⁱ	0.87 (2)	2.00 (2)	2.8361 (13)	161.3 (18)
O7—H7⋯O5Aⁱⁱⁱ	0.89 (2)	1.80 (2)	2.6877 (13)	177 (2)
O9—H9⋯O1A^iv	0.87 (2)	1.91 (2)	2.7784 (14)	174.6 (19)
O2A—H2A⋯O10^iv	0.87 (2)	1.84 (2)	2.7050 (14)	174.5 (17)
O4A—H4A⋯O6ⁱⁱⁱ	0.89 (2)	1.79 (2)	2.6735 (13)	178 (2)
O7A—H7A⋯O5ⁱⁱ	0.92 (2)	1.93 (2)	2.8085 (15)	160 (2)
O9A—H9A⋯O2W	0.87 (2)	2.18 (2)	2.9474 (16)	147.4 (18)
N1—H11⋯O1W	0.870 (18)	2.059 (18)	2.8756 (18)	156.0 (16)
N1—H12⋯O2A^v	0.872 (18)	1.996 (18)	2.8484 (15)	165.7 (15)
N2—H21⋯O1W	0.893 (17)	2.330 (17)	3.0892 (18)	142.8 (14)
N2—H22⋯O4A	0.858 (17)	2.025 (18)	2.8772 (16)	172.0 (15)
N1A—H11A⋯O10A	0.869 (19)	2.238 (19)	3.0084 (18)	147.7 (16)
N1A—H12A⋯O8	0.892 (19)	2.12 (2)	2.9646 (17)	157.4 (16)
N2A—H21A⋯O2W^iv	0.86 (2)	2.01 (2)	2.8703 (18)	175.0 (18)
N2A—H22A⋯O9	0.891 (19)	2.181 (19)	3.0717 (16)	178.4 (16)
O1W—H11W⋯O1^vi	0.82 (2)	2.10 (2)	2.9180 (15)	173 (2)
O1W—H12W⋯O4^vii	0.85 (2)	2.22 (2)	3.0033 (18)	153 (2)
O2W—H21W⋯O3W	0.93 (2)	1.92 (2)	2.8199 (19)	163 (2)
O2W—H22W⋯O7^viii	0.91 (2)	1.90 (2)	2.8016 (14)	169.3 (19)
O3W—H31W⋯O3W^ix	0.72 (3)	2.488 (10)	3.003 (3)	130.5 (17)
O3W—H32W⋯O7A	0.98 (3)	2.05 (3)	2.983 (2)	159 (2)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) .

Acknowledgments

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

supplementary crystallographic information

Comment

The asymmetric unit of the title compound (Fig. 1) comprises two planar benzamidinium cations, two tetrahydropentaborate anions and three water molecules of crystallization. The anions consist of a central BO₄ tetrahedron fused to four trigonal planar BO₃(OH) units. Both cations and the anions show normal geometric parameters (Table 1). Analysis of the crystal packing (Fig. 2) shows that adjacent [B₅O₆(OH)₄]^- units are hydrogen bonded to form eight-membered rings of graph set R²₂(8) (Etter et al., 1990; Bernstein et al., 1995; Motherwell et al., 1999). This anion-to-anion hydrogen-bonding framework is supplemented by the formation of five hydrogen bonds from each benzamidinium cation to adjacent [B₅O₆(OH)₄]^- anions (Table 2). Interestingly, two of the three water molecules of crystallization form hydrogen bonds which involve all the available hydrogen-bond donor/acceptor sites, at variance with what has been found in a survey of 3315 organic hydrate crystal structures. In this study (Gillon et al., 2003) it has been shown that the most common environment is one in which water forms three hydrogen bonds, two as donor and one as acceptor.

Experimental

B(OH)₃ (90 mg, 0.15 mmol, Sigma Aldrich at 99.5% purity) was added to a stirred solution of benzamidine, C₇H₈N₂, (12 mg, 0.1 mmol, Fluka at 95% purity) in water (10 ml) and heated under reflux for 3 h. After cooling the solution to ambient temperature, crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent over several days.