9-Ethynyl-1,2-dimethyl-1,2-dicarba-closo-dodeca­borane (1,2-Me₂-9-HC[triple bond]C-closo-1,2-C₂B₁₀H₉)

The asymmetric unit of the title compound, C₆H₁₆B₁₀, contains one mol­ecule that is close to possessing a non-crystallographic plane of mirror symmetry in the space group Pna2₁. The orientation of the mol­ecules in the ortho­rhom­bic cell shows that the structure can not be described in the space group Pnma, which has the same systematic absence conditions. The long inner-cluster C—C distance of 1.510 (5) Å is typical for {1,2-Me₂-closo-1,2-C₂B₁₀} derivatives.

Key indicators

• Single-crystal X-ray study
• T = 290 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.056
• wR factor = 0.104
• Data-to-parameter ratio = 7.9

checkCIF/PLATON results

No syntax errors found






Alert level C
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       7.87
PLAT340_ALERT_3_C Low Bond Precision on  C-C Bonds (x 1000) Ang ..          6
PLAT367_ALERT_2_C Long?  C(sp?)-C(sp?) Bond  C1     -   C2     ...       1.68 Ang.

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           24.99
           From the CIF: _reflns_number_total               1181
           Count of symmetry unique reflns         1182
           Completeness (_total/calc)             99.92%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no
PLAT343_ALERT_2_G Check sp?     Angle Range in Main Residue for ..        C1
PLAT343_ALERT_2_G Check sp?     Angle Range in Main Residue for ..        C2

   3 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The interest in functionalized dicarba-closo-dodecaboranes as building blocks for a broad range of applications is steadily increasing because of their high chemical and thermal stability as well as the diversity of their substitution patterns at the boron cage (Bregadze, 1992; Kalinin & Ol'shevskaya, 2008). The synthesis of {closo-C₂B₁₀} clusters with alkynyl groups bonded to boron is achieved by Pd-catalyzed Kumada-type cross-coupling reactions using the iodinated clusters and alkynyl Grignard reagents as precursors (Zakharkin et al., 1981; Himmelspach & Finze, 2010a). The title compound 1,2-dimethyl-9-ethynyl-1,2-dicarba-closo-dodecaborane, which is the first structurally characterized monoethynyldicarba-closo-dodecaborane with a B_cluster—C≡C—H unit, crystallizes in the orthorhombic acentric space group Pna2₁ with one complete molecule in the asymmetric unit. The bond lengths and angles of the {closo-1,2-C₂B₁₀} cage of 1,2-Me₂-9-HC≡C-closo-1,2- C₂B₁₀H₉ are similar to those reported for the related bis(trimethylsilylalkynyl) substituted derivative 1,2-Me₂ -9,12-(Me₃SiC≡C)₂-closo-1,2-C₂B₁₀H₉ (Himmelspach & Finze, 2010a). The B—C and C≡C distances are similar to values reported for the diethynyldicarba-closo-dodecaboranes 9,12-(HC≡C)₂-closo-1,2-C₂B₁₀H₁₀ and 9,10-(HC≡C)₂-closo-1,7-C₂B₁₀H₁₀ (Himmelspach & Finze, 2010a) and the related anionic monocarba-closo-dodecaborate anions [12-HC≡ C-closo-1-CB₁₁H₁₁]^- and [7,12-(HC≡C)₂–closo-1-CB₁₁H₁₀]^- (Himmelspach & Finze, 2010b).

Related literature

For a general overview of the functionalization of dicarba-closo-dodecaboranes, see: Bregadze (1992); Kalinin & Ol'shevskaya (2008). For the synthesis and properties of {closo-1,2-C₂B₁₀} clusters with ethynyl groups bonded to boron, see: Zakharkin et al. (1981); Himmelspach & Finze (2010a). For structures of related icosahedral boron cages with alkynyl groups bonded to boron, see: Finze (2008); Himmelspach & Finze (2010b). For intensity statistics of Friedel opposites for all non-centrosymmetric space groups, see: Shmueli et al. (2008).

S2. Experimental

1,2-Me₂-9-HC≡C-closo-1,2-C₂B₁₀H₉ was synthesized according to a published procedure and the spectroscopic data have been reported earlier (Himmelspach & Finze, 2010a). The compound was dissolved in acetonitrile and slow evaporation of the solvent resulted in colorless crystals.

S3. Refinement

All hydrogen atom positions were obtained from difference fourier maps. The hydrogen atoms of the methyl groups were included in the latest stages of the refinement with a riding model and for each methyl group a common U_iso value was refined. The hydrogen atoms bonded to the carborane cluster were included in the refinement with a riding model (AFIX 153) and their U_iso values were set to 1.2 of the equivalent isotropic displacement parameter of the corresponding parent atom. The hydrogen atom of the ethynyl group was positioned using a riding model (AFIX 163) and its U_iso was refined freely. In the absence of significant anomalous scattering effects, Friedel pairs were averaged, resulting in a low reflection to parameter ratio (Shmueli et al., 2008).

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND Brandenburg, 2010); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. : Hydrogen atoms are drawn with arbitrary radii and the displacement ellipsoids are shown at the 35% probability level.
	Fig. 2. : Packing of the title compound along [0–10] showing that the non-crystallographic mirror symmetry of the molecule is not consistent with the metric and the symmetry of the true space group Pna21.

9-Ethynyl-1,2-dimethyl-1,2-dicarba-closo-dodecaborane

Crystal data

C6H16B10	F(000) = 408
Mr = 196.29	Dx = 1.021 Mg m^−3
Orthorhombic, Pna21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 6575 reflections
a = 14.5368 (8) Å	θ = 3.2–27.2°
b = 7.0085 (3) Å	µ = 0.05 mm^−1
c = 12.5373 (5) Å	T = 290 K
V = 1277.32 (10) Å^3	Prism, colourless
Z = 4	0.4 × 0.2 × 0.2 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	1049 reflections with I > 2σ(I)
Radiation source: Enhance (Mo) X-ray Source	Rint = 0.042
Graphite monochromator	θmax = 25.0°, θmin = 3.2°
Detector resolution: 16.2711 pixels mm^-1	h = −17→17
ω scans	k = −8→8
11327 measured reflections	l = −14→14
1181 independent reflections

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)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.104	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.005P)^2 + 0.630P] where P = (Fo^2 + 2Fc^2)/3
1181 reflections	(Δ/σ)max = 0.010
150 parameters	Δρmax = 0.14 e Å^−3
1 restraint	Δρmin = −0.18 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	0.1554 (3)	1.0151 (6)	0.6353 (3)	0.0654 (11)
C3	0.0608 (3)	1.0836 (9)	0.6036 (4)	0.1134 (19)
H3A	0.0361	1.1629	0.6592	0.175 (15)*
H3B	0.0211	0.9757	0.5929	0.175 (15)*
H3C	0.0649	1.1557	0.5387	0.175 (15)*
C2	0.1709 (2)	0.9362 (5)	0.7606 (3)	0.0603 (10)
C4	0.0899 (3)	0.9387 (7)	0.8384 (4)	0.0973 (16)
H4A	0.1076	0.8772	0.9037	0.171 (14)*
H4B	0.0388	0.8721	0.8074	0.171 (14)*
H4C	0.0726	1.0683	0.8529	0.171 (14)*
B3	0.1682 (3)	0.7752 (7)	0.6574 (3)	0.0651 (12)
H3	0.1130	0.6699	0.6457	0.078*
B4	0.2219 (3)	0.8917 (6)	0.5497 (3)	0.0600 (11)
H4	0.2023	0.8613	0.4667	0.072*
B5	0.2525 (3)	1.1224 (7)	0.5909 (4)	0.0641 (12)
H5	0.2533	1.2426	0.5346	0.077*
B6	0.2166 (3)	1.1519 (6)	0.7254 (4)	0.0655 (12)
H6	0.1929	1.2898	0.7573	0.079*
B7	0.2479 (3)	0.7542 (7)	0.7621 (4)	0.0641 (11)
H7	0.2458	0.6335	0.8182	0.077*
B8	0.2840 (3)	0.7257 (6)	0.6277 (4)	0.0618 (11)
H8	0.3061	0.5870	0.5957	0.074*
B9	0.3368 (3)	0.9424 (6)	0.5869 (3)	0.0569 (10)
B10	0.3323 (3)	1.1052 (7)	0.6967 (4)	0.0641 (12)
H10	0.3859	1.2134	0.7098	0.077*
B11	0.2770 (3)	0.9867 (7)	0.8032 (4)	0.0634 (11)
H11	0.2940	1.0175	0.8869	0.076*
B12	0.3516 (3)	0.8587 (7)	0.7199 (4)	0.0654 (12)
H12	0.4185	0.8061	0.7485	0.078*
C5	0.4156 (3)	0.9438 (6)	0.5044 (4)	0.0741 (11)
C6	0.4772 (3)	0.9437 (7)	0.4438 (5)	0.1044 (17)
H1	0.5260	0.9435	0.3958	0.15 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.061 (2)	0.078 (3)	0.058 (2)	0.009 (2)	−0.0032 (19)	0.000 (2)
C3	0.082 (3)	0.156 (5)	0.102 (4)	0.045 (3)	−0.009 (3)	0.001 (4)
C2	0.063 (2)	0.066 (2)	0.052 (2)	−0.0107 (18)	0.0106 (19)	−0.007 (2)
C4	0.090 (3)	0.120 (4)	0.082 (3)	−0.026 (3)	0.033 (3)	−0.013 (3)
B3	0.072 (3)	0.062 (3)	0.061 (3)	−0.020 (2)	0.001 (2)	−0.012 (2)
B4	0.067 (2)	0.070 (3)	0.044 (2)	−0.003 (2)	−0.005 (2)	−0.007 (2)
B5	0.086 (3)	0.056 (2)	0.051 (2)	0.002 (2)	0.005 (2)	0.004 (2)
B6	0.081 (3)	0.053 (2)	0.062 (3)	−0.006 (2)	0.015 (2)	−0.010 (2)
B7	0.091 (3)	0.053 (2)	0.048 (2)	−0.006 (2)	0.002 (2)	0.007 (2)
B8	0.082 (3)	0.047 (2)	0.057 (2)	0.005 (2)	0.005 (2)	−0.001 (2)
B9	0.059 (2)	0.062 (2)	0.050 (2)	−0.003 (2)	0.003 (2)	−0.001 (2)
B10	0.065 (3)	0.067 (3)	0.061 (3)	−0.023 (2)	0.002 (2)	−0.007 (3)
B11	0.075 (3)	0.070 (3)	0.045 (2)	−0.014 (2)	−0.002 (2)	−0.006 (2)
B12	0.061 (2)	0.080 (3)	0.056 (3)	0.005 (2)	−0.009 (2)	0.001 (2)
C5	0.072 (2)	0.081 (3)	0.070 (3)	−0.002 (2)	0.015 (2)	−0.002 (2)
C6	0.094 (3)	0.119 (4)	0.101 (3)	−0.004 (3)	0.042 (3)	−0.003 (3)

Geometric parameters (Å, º)

C1—C3	1.510 (5)	B5—B9	1.759 (6)
C1—C2	1.680 (5)	B5—B10	1.766 (6)
C1—B4	1.684 (6)	B5—B6	1.778 (6)
C1—B5	1.693 (6)	B5—H5	1.1000
C1—B3	1.714 (6)	B6—B11	1.750 (7)
C1—B6	1.728 (6)	B6—B10	1.751 (6)
C3—H3A	0.9600	B6—H6	1.1000
C3—H3B	0.9600	B7—B11	1.760 (6)
C3—H3C	0.9600	B7—B12	1.757 (6)
C2—C4	1.529 (5)	B7—B8	1.776 (6)
C2—B11	1.670 (6)	B7—H7	1.1000
C2—B7	1.697 (6)	B8—B9	1.777 (6)
C2—B6	1.709 (6)	B8—B12	1.781 (6)
C2—B3	1.717 (5)	B8—H8	1.1000
C4—H4A	0.9600	B9—C5	1.544 (5)
C4—H4B	0.9600	B9—B12	1.780 (6)
C4—H4C	0.9600	B9—B10	1.789 (6)
B3—B7	1.758 (6)	B10—B11	1.765 (7)
B3—B8	1.758 (6)	B10—B12	1.774 (7)
B3—B4	1.760 (6)	B10—H10	1.1000
B3—H3	1.1000	B11—B12	1.752 (6)
B4—B5	1.755 (6)	B11—H11	1.1000
B4—B8	1.767 (6)	B12—H12	1.1000
B4—B9	1.769 (6)	C5—C6	1.175 (6)
B4—H4	1.1000	C6—H1	0.9300
C3—C1—C2	118.2 (3)	C2—B6—H6	124.2
C3—C1—B4	121.2 (4)	C1—B6—H6	124.3
C2—C1—B4	110.5 (3)	B11—B6—H6	122.4
C3—C1—B5	122.1 (4)	B10—B6—H6	122.6
C2—C1—B5	110.0 (3)	B5—B6—H6	122.6
B4—C1—B5	62.6 (2)	C2—B7—B11	57.7 (2)
C3—C1—B3	116.9 (4)	C2—B7—B3	59.6 (2)
C2—C1—B3	60.8 (2)	B11—B7—B3	107.4 (3)
B4—C1—B3	62.4 (3)	C2—B7—B12	104.4 (3)
B5—C1—B3	113.5 (3)	B11—B7—B12	59.7 (3)
C3—C1—B6	117.7 (4)	B3—B7—B12	107.8 (3)
C2—C1—B6	60.2 (2)	C2—B7—B8	105.6 (3)
B4—C1—B6	114.0 (3)	B11—B7—B8	108.1 (3)
B5—C1—B6	62.6 (3)	B3—B7—B8	59.7 (3)
B3—C1—B6	112.5 (3)	B12—B7—B8	60.5 (3)
C1—C3—H3A	109.5	C2—B7—H7	124.5
C1—C3—H3B	109.5	B11—B7—H7	122.1
H3A—C3—H3B	109.5	B3—B7—H7	121.6
C1—C3—H3C	109.5	B12—B7—H7	122.4
H3A—C3—H3C	109.5	B8—B7—H7	121.9
H3B—C3—H3C	109.5	B3—B8—B4	59.9 (3)
C4—C2—B11	120.3 (3)	B3—B8—B9	107.8 (3)
C4—C2—C1	119.3 (3)	B4—B8—B9	59.9 (2)
B11—C2—C1	110.7 (3)	B3—B8—B7	59.6 (2)
C4—C2—B7	120.6 (4)	B4—B8—B7	107.5 (3)
B11—C2—B7	63.0 (2)	B9—B8—B7	107.7 (3)
C1—C2—B7	110.3 (3)	B3—B8—B12	106.7 (3)
C4—C2—B6	116.9 (3)	B4—B8—B12	107.2 (3)
B11—C2—B6	62.4 (3)	B9—B8—B12	60.1 (2)
C1—C2—B6	61.3 (2)	B7—B8—B12	59.2 (3)
B7—C2—B6	114.3 (3)	B3—B8—H8	122.2
C4—C2—B3	118.0 (3)	B4—B8—H8	122.0
B11—C2—B3	113.7 (3)	B9—B8—H8	121.6
C1—C2—B3	60.6 (2)	B7—B8—H8	122.1
B7—C2—B3	62.0 (2)	B12—B8—H8	122.5
B6—C2—B3	113.3 (3)	C5—B9—B5	122.1 (3)
C2—C4—H4A	109.5	C5—B9—B4	121.7 (3)
C2—C4—H4B	109.5	B5—B9—B4	59.7 (2)
H4A—C4—H4B	109.5	C5—B9—B8	121.3 (3)
C2—C4—H4C	109.5	B5—B9—B8	107.7 (3)
H4A—C4—H4C	109.5	B4—B9—B8	59.8 (3)
H4B—C4—H4C	109.5	C5—B9—B12	122.6 (3)
C1—B3—C2	58.6 (2)	B5—B9—B12	107.1 (3)
C1—B3—B7	105.9 (3)	B4—B9—B12	107.1 (3)
C2—B3—B7	58.4 (2)	B8—B9—B12	60.1 (2)
C1—B3—B8	105.3 (3)	C5—B9—B10	122.6 (3)
C2—B3—B8	105.5 (3)	B5—B9—B10	59.7 (3)
B7—B3—B8	60.7 (3)	B4—B9—B10	107.3 (3)
C1—B3—B4	58.0 (2)	B8—B9—B10	107.9 (3)
C2—B3—B4	105.2 (3)	B12—B9—B10	59.6 (3)
B7—B3—B4	108.6 (3)	B6—B10—B5	60.7 (3)
B8—B3—B4	60.3 (2)	B6—B10—B11	59.7 (3)
C1—B3—H3	123.9	B5—B10—B11	107.5 (3)
C2—B3—H3	124.0	B6—B10—B12	107.5 (3)
B7—B3—H3	121.6	B5—B10—B12	107.0 (3)
B8—B3—H3	122.5	B11—B10—B12	59.3 (3)
B4—B3—H3	122.2	B6—B10—B9	108.2 (3)
C1—B4—B5	59.0 (2)	B5—B10—B9	59.3 (3)
C1—B4—B3	59.6 (3)	B11—B10—B9	107.4 (3)
B5—B4—B3	108.3 (3)	B12—B10—B9	60.0 (2)
C1—B4—B8	106.2 (3)	B6—B10—H10	121.4
B5—B4—B8	108.3 (3)	B5—B10—H10	122.0
B3—B4—B8	59.8 (3)	B11—B10—H10	122.3
C1—B4—B9	105.7 (3)	B12—B10—H10	122.3
B5—B4—B9	59.9 (3)	B9—B10—H10	121.9
B3—B4—B9	108.1 (3)	C2—B11—B6	59.9 (2)
B8—B4—B9	60.3 (2)	C2—B11—B7	59.2 (3)
C1—B4—H4	123.6	B6—B11—B7	109.2 (3)
B5—B4—H4	121.5	C2—B11—B12	105.8 (3)
B3—B4—H4	121.4	B6—B11—B12	108.5 (3)
B8—B4—H4	121.9	B7—B11—B12	60.0 (3)
B9—B4—H4	122.2	C2—B11—B10	106.2 (3)
C1—B5—B4	58.4 (2)	B6—B11—B10	59.8 (3)
C1—B5—B9	105.8 (3)	B7—B11—B10	108.9 (3)
B4—B5—B9	60.5 (2)	B12—B11—B10	60.6 (3)
C1—B5—B10	105.7 (3)	C2—B11—H11	123.6
B4—B5—B10	109.0 (3)	B6—B11—H11	121.0
B9—B5—B10	61.0 (3)	B7—B11—H11	121.0
C1—B5—B6	59.7 (3)	B12—B11—H11	122.0
B4—B5—B6	108.2 (3)	B10—B11—H11	121.8
B9—B5—B6	108.4 (3)	B11—B12—B7	60.2 (3)
B10—B5—B6	59.2 (3)	B11—B12—B10	60.1 (3)
C1—B5—H5	124.1	B7—B12—B10	108.6 (3)
B4—B5—H5	121.3	B11—B12—B9	108.3 (3)
B9—B5—H5	121.6	B7—B12—B9	108.4 (3)
B10—B5—H5	121.9	B10—B12—B9	60.4 (3)
B6—B5—H5	121.5	B11—B12—B8	108.2 (3)
C2—B6—C1	58.5 (2)	B7—B12—B8	60.3 (2)
C2—B6—B11	57.7 (2)	B10—B12—B8	108.4 (3)
C1—B6—B11	104.8 (3)	B9—B12—B8	59.9 (2)
C2—B6—B10	105.1 (3)	B11—B12—H12	121.6
C1—B6—B10	104.8 (3)	B7—B12—H12	121.3
B11—B6—B10	60.5 (3)	B10—B12—H12	121.3
C2—B6—B5	104.8 (3)	B9—B12—H12	121.5
C1—B6—B5	57.7 (3)	B8—B12—H12	121.6
B11—B6—B5	107.7 (3)	C6—C5—B9	178.2 (5)
B10—B6—B5	60.0 (3)	C5—C6—H1	180.0