2-Aza­niumylcarba-closo-dodeca­borate ethanol monosolvate

Alexander Himmelspach; Guido J Reiss; Maik Finze

doi:10.1107/S1600536811006222

. 2011 Feb 26;67(Pt 3):o704. doi: 10.1107/S1600536811006222

2-Azaniumylcarba-closo-dodecaborate ethanol monosolvate

Alexander Himmelspach ^a, Guido J Reiss ^a, Maik Finze ^a,^*

PMCID: PMC3051930 PMID: 21522448

Abstract

Two formula units of the title compound, 2-H₃N-closo-1-CB₁₁H₁₁·CH₃CH₂OH or CH₁₄B₁₁N·C₂H₅OH, form a ring motif of R ₄ ²(8) type in the solid state that surrounds a crystallographic center of symmetry. The ring motif is a result of N—H⋯O hydrogen bonds. In contrast to many structures of {closo-1-CB₁₁} clusters, the assignment of the position of the cluster C atom in the structure of the title compound is unambigious. The relatively long B—N bond length [1.5396 (10) Å] documents the absence of any B—N π-interaction in the title compound although this was observed for a related 2-aminocarba-closo-dodecaborate.

Related literature

For a general overview on monocarba-closo-dodecaborates, see: Körbe et al. (2006 ▶). For the synthesis and properties of 2-amino- and 2-azaniumylcarba-closo-dodecaboron clusters, see: Finze (2009 ▶). For structures and properties of related {closo-1-CB₁₁} clusters with NH₂ and NH₃ groups, see: Jelínek et al. (1986 ▶); Finze (2007 ▶); Finze et al. (2007 ▶); Finze & Sprenger (2010 ▶). For hydrogen-bond motifs, see: Etter (1990 ▶).

Experimental

Crystal data

CH₁₄B₁₁N·C₂H₆O
M _r = 205.11
Monoclinic,
a = 9.5753 (2) Å
b = 9.2549 (2) Å
c = 13.9095 (5) Å
β = 97.519 (3)°
V = 1222.04 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.06 mm⁻¹
T = 120 K
0.28 × 0.26 × 0.20 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009 ▶) T _min = 0.729, T _max = 1.000
61096 measured reflections
3561 independent reflections
3199 reflections with I > 2σ(I)
R _int = 0.030
3 standard reflections every 60 min intensity decay: none

Refinement

R[F ² > 2σ(F ²)] = 0.029
wR(F ²) = 0.069
S = 1.02
3561 reflections
208 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2011) ▶; software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811006222/br2161sup1.cif

e-67-0o704-sup1.cif^{(21KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811006222/br2161Isup2.hkl

e-67-0o704-Isup2.hkl^{(174.7KB, 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
N1—H1B⋯O1	0.900 (12)	2.006 (12)	2.8937 (9)	168.5 (10)
N1—H1A⋯O1ⁱ	0.898 (12)	2.065 (12)	2.9446 (9)	166.1 (10)

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Symmetry code: (i) Inline graphic .

Acknowledgments

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) and by the Fonds der Chemischen Industrie (FCI).

supplementary crystallographic information

Comment

Icosahedral monocarba-closo-dodecaborates with functional groups, for example amino or ammonio that are bonded to the cluster atoms are building blocks for a broad range of applications (Körbe et al., 2006). The properties and the reactivity of the amino groups depend on (i) the further substituents of the {closo-1-CB₁₁} cluster and (ii) the type of the cluster atom, either carbon or boron that it is bonded to. The influence of the substituents is evident from a comparison of the properties of [1-H₂N-closo-1-CB₁₁X₁₁]^- with X equal to either H or F. The non-fluorinated anion is indefinitely stable in concentrated aqueous bases and acids whereas the fluorinated anion decomposes in acidic aqueous solutions and undergoes substituent exchange reactions in basic aqueous solutions (Finze et al., 2007). Furthermore, [1-H₂N-closo-1-CB₁₁F₁₁]^- reacts with strong non-nucleophilic bases under aprotic conditions to result in a cluster rearrangement that so far was observed for highly fluorinated aminocarba-closo-dodecaborates only (Finze, 2007). The difference in the properties of amino groups that are either bonded to the cluster carbon atom or to one of the boron atoms is demonstrated by a comparison of the pK_avalue of 1-H₃N-closo-CB₁₁H₁₁ 6.0 (Jelínek et al., 1986) and of 2-H₃N-closo-CB₁₁H₁₁ >10.5 (Finze, 2009).

The inner salt 2-H₃N-closo-1-CB₁₁H₁₁ crystallizes as ethanol solvate in the monoclinic space group P2₁/c with one complete molecule and one ethanol molecule in the asymmetric unit. The cluster carbon atom is unambiguously assigned as evident from comparative refinements (Figure 1). Furthermore, the experimental inner cluster carbon-boron and boron-boron bond lengths are in excellent agreement to values derived from DFT calculations at the B3LYP/6–311++G(d,p) and at the MP2/6–311++G(d,p) level of theory, which were reported earlier (Finze, 2009). In this earlier contribution it was concluded on the basis of experimental inner-cluster d(C—B) and d(B—B) of the related {closo-1-CB₁₁} species [1-Ph-2-H₂N-closo-1-CB₁₁H₁₀]^- and 1-Ph-2-Me₃N-closo-1-CB₁₁H₁₀ in conjunction with theoretical bond lengths of [2-H₂N-closo-1-CB₁₁H₁₁]^- and 2-H₃N-closo-1-CB₁₁H₁₁ that there is a small amount of B—N π-interaction for the amino derivatives whereas for the ammonio derivatives this π-interaction was not observed. The d(B2—N1) of 1.5396 (10) Å in the structure of the title compound supports these previous results. As a consequence of this weakened B2—N1 bond the inner-cluster C1—B2 bond is strengthened as documented by d(C1—B2) of 1.6872 (11) Å.

The title compound 2-H₃N-closo-1-CB₁₁H₁₁.CH₃CH₂OH forms dimers in the solid state (Table 1, Figure 2). The hydrogen-bonded ring consists of two ammonio derivatives and two ethanol molecules and has to be described as R²₄(8) (Etter, 1990). A very similar hydrogen-bonded system was previously found for the related ammonio substituted carborane 1-H₃N-2-F-closo-1-CB₁₁H₁₀ in the structure of its acetone solvate (Finze & Sprenger, 2010).

Experimental

2-H₃N-closo-1-CB₁₁H₁₁ was synthesized according to a published procedure that also includes the spectroscopic data (Finze, 2009). The title compound was dissolved in a minimum amount of diethyl ether, ethanol, and chloroform (20:1:1). The clear colorless solution was stored at 3 °C in a refrigerator resulting in colorless crystals within two days.

A single crystal suitable for structure determination was harvested under a dry nitrogen atmosphere and was directly transferred into the cooling stream of an Oxford-Xcalibur diffractometer equipped with an EOS-CCD detector.