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The title compound, 6-pyridyl-4-aza-arachno-nonaborane(11), C5H16B8N2, has an arachno nine-vertex {4-NB8H11} cluster structure with a pyridine ligand in the exo-6-position. The cluster has close geometric similarities to the thia­borane and carbaborane analogues.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100002742/br1272sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100002742/br1272Isup2.hkl
Contains datablock I

Comment top

There is current interest in smaller heteroboranes. (Davison et al., 1999) Our own interest in the nine-vertex azaboranes stems firstly from that (a) these species are not well investigated in an absolute sense, but clearly have potentially very interesting chemistry (Dörfler et al., 1997) and also in that (b) nine-vertex arachno species in general have a propensity to couple upon simple heating to give big-borane 'macropolyhedral' clusters, as in thiaborane, platinaborane and iridaborane chemistry. (Bould, Clegg, Teat, Barton, Rath, Thornton-Pett & Kennedy, 1999) In main-group heteroborane chemistry in particular, [6-(SMe2)-arachno-4-SB8H10] gives the interesting species [S2B17H19(SMe2)] with a hexagonal pyramidal structural feature. (Kaur et al., 1996) The nine-vertex thiaboranes [6-L-arachno-4-SB8H10] and carbaboranes [6-L-arachno-4-CB8H12] are well characterized structurally. (Holub, Kennedy & Štíbr, 1994; Holub et al., 1994; Plešek et al., 1994) Several corresponding azaborane analogues [6-L-arachno-4-NB8H11], where L is a two-electron ligand, are known (Jelinek, Štíbr & Kennedy, 1994). However, structural work on these azaboranes is lacking, although the related 'parent' non-ligand species [arachno-4-NB8H13] itself was examined crystallographically some time ago. (Baše et al., 1975; Ragatz et al., 1975) Here we report the structure of the pyridine derivative [6-(C5H5N)-arachno-4-NB8H11].

The molecular structure (Fig. 1) closely resembles those of the thiaborane and carbaborane analogues [SB8H10(N4C6H6)] and [CB8H12(N4C6H6)], where N4C6H6 is hexamethylene tetramine. Apart from the variation of the nitrogen ligands between NC5H5 and N4C6H6, which does not affect the cluster interatomic distances significantly, the compounds differ in the isolobal cluster constuents, CH2, NH and S in the 4-position. There are obvious corresponding differences in the boron-to-heteroatom distances, but the other interatomic distances within the clusters are very similar. For all three classes of compound, there appears to be an asymmetry in the bonding of the bridging hydrogen atoms, with the shorter distances being towards B8, although this is not so marked for H78 in the title compound. A similar asymmetry is also noted for the four bridging hydrogen atoms in the parent non-ligand analogue NB8H13 (Ragatz. et al., 1975).

Experimental top

The title compound may be prepared by the action of pyridine on [arachno-4-NB8H13], following a previously detailed procedure. (Jelínek, Štíbr & Kennedy, 1994) The crystallographic sample was obtained from CHCl3 / pentane

Refinement top

The direction of the polar axis is ambiguous since the structure does not possess significant anomolous scatterers of Mo—Kα radiation. Pyridine hydrogen atoms were constrained to calculated positions with isotropic displacement parameters equal to 1.2 × Ueq of the parent carbon atom. Cluster-associated hydrogen atoms were located via Fourier difference syntheses and all associated parameters were refined freely.

Computing details top

Data collection: KCCD (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1996); data reduction: DENZO-SMN (Otwinowski & Minor, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEX5 (McArdle, 1995); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1] Fig. 1. Perspective view of a single molecule of 6-(C5H5N)-arachno-4-NB8H11 drawn with 40% probability ellipsoids and with H atoms shown as small circles of artificial radius for clarity.
systematic name to be included here top
Crystal data top
C5H16B8N2F(000) = 400
Mr = 190.68Dx = 1.113 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
a = 14.3618 (1) ŵ = 0.06 mm1
b = 10.4600 (1) ÅT = 190 K
c = 7.5779 (1) ÅPrism, yellow
V = 1138.39 (2) Å30.24 × 0.18 × 0.06 mm
Z = 4
Data collection top
Nonius KappaCCD area detector
diffractometer
3204 independent reflections
Radiation source: fine-focus sealed tube3077 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.042
Detector resolution: 9.091 pixels mm-1θmax = 30.5°, θmin = 2.4°
Area–detector ϕ and ω scansh = 2020
Absorption correction: multi-scan
(Blessing, 1995)
k = 1414
Tmin = 0.987, Tmax = 0.997l = 1010
26404 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.035H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.093 w = 1/[σ2(Fo2) + (0.0562P)2 + 0.0813P]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max = 0.001
3204 reflectionsΔρmax = 0.14 e Å3
185 parametersΔρmin = 0.16 e Å3
1 restraintAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 1.5 (11)
Crystal data top
C5H16B8N2V = 1138.39 (2) Å3
Mr = 190.68Z = 4
Orthorhombic, Pna21Mo Kα radiation
a = 14.3618 (1) ŵ = 0.06 mm1
b = 10.4600 (1) ÅT = 190 K
c = 7.5779 (1) Å0.24 × 0.18 × 0.06 mm
Data collection top
Nonius KappaCCD area detector
diffractometer
3204 independent reflections
Absorption correction: multi-scan
(Blessing, 1995)
3077 reflections with I > 2σ(I)
Tmin = 0.987, Tmax = 0.997Rint = 0.042
26404 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.035H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.093Δρmax = 0.14 e Å3
S = 1.07Δρmin = 0.16 e Å3
3204 reflectionsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
185 parametersAbsolute structure parameter: 1.5 (11)
1 restraint
Special details top

Experimental. PLEASE NOTE cell_measurement_ fields are not relevant to area detector data, the entire data set is used to refine the cell, which is indexed from all observed reflections in a 10 degree phi range.

Data were collected using a mixture area-detector ο and ϕ- exposures with the CCD detector positioned 25 mm from the sample. The title compound crystallizes in the polar, orthorhombic, space group Pna21.

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 (Å2) top
xyzUiso*/Ueq
B20.61305 (7)0.11540 (10)0.12282 (16)0.0329 (2)
H20.6101 (9)0.0783 (14)0.014 (2)0.039 (3)*
B30.71392 (8)0.10069 (12)0.26392 (18)0.0380 (2)
H30.7796 (9)0.0459 (14)0.229 (2)0.048 (4)*
B60.56286 (7)0.26681 (9)0.15134 (14)0.03049 (19)
H60.5426 (8)0.3282 (11)0.2630 (17)0.031 (3)*
N610.51072 (5)0.31278 (7)0.01888 (11)0.03052 (17)
C620.55371 (8)0.32651 (11)0.17561 (15)0.0383 (2)
H620.61810.30660.18480.051 (4)*
C630.50672 (8)0.36869 (11)0.32277 (14)0.0429 (2)
H630.53820.37620.43250.062 (5)*
C640.41320 (8)0.40017 (10)0.31025 (15)0.0411 (2)
H640.38010.43090.41010.058 (4)*
C650.36940 (7)0.38594 (11)0.14964 (16)0.0404 (2)
H650.30530.40650.13730.062 (5)*
C660.41948 (7)0.34166 (10)0.00739 (14)0.0360 (2)
H660.38870.33110.10260.043 (4)*
B70.68635 (7)0.25299 (10)0.15570 (17)0.0351 (2)
H70.7337 (9)0.2899 (13)0.0493 (19)0.042 (3)*
H780.6994 (10)0.3280 (13)0.288 (2)0.044 (4)*
B80.73358 (8)0.24070 (13)0.38385 (18)0.0416 (3)
H890.6850 (11)0.2616 (16)0.505 (2)0.062 (5)*
H80.8076 (10)0.2610 (14)0.416 (2)0.047 (4)*
N40.55926 (6)0.10322 (8)0.44236 (11)0.03517 (19)
H40.5261 (10)0.0624 (18)0.532 (2)0.061 (5)*
B50.51709 (7)0.12431 (11)0.26099 (15)0.0329 (2)
H50.4459 (9)0.0917 (14)0.241 (2)0.043 (4)*
B90.66180 (8)0.11060 (12)0.47779 (17)0.0395 (2)
H90.6863 (9)0.0686 (14)0.6000 (19)0.042 (3)*
B10.60906 (8)0.01135 (11)0.30112 (16)0.0373 (2)
H10.6026 (9)0.0968 (15)0.299 (2)0.054 (4)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
B20.0326 (5)0.0325 (4)0.0337 (5)0.0004 (4)0.0034 (4)0.0000 (4)
B30.0301 (5)0.0401 (5)0.0438 (6)0.0025 (4)0.0021 (4)0.0082 (5)
B60.0294 (4)0.0333 (4)0.0287 (4)0.0010 (4)0.0005 (4)0.0003 (4)
N610.0302 (4)0.0315 (4)0.0299 (3)0.0006 (3)0.0010 (3)0.0001 (3)
C620.0390 (5)0.0435 (5)0.0325 (4)0.0033 (4)0.0050 (4)0.0029 (4)
C630.0520 (6)0.0444 (5)0.0322 (5)0.0018 (4)0.0026 (4)0.0033 (4)
C640.0485 (6)0.0366 (5)0.0382 (5)0.0026 (4)0.0111 (4)0.0043 (4)
C650.0348 (4)0.0422 (5)0.0440 (5)0.0008 (4)0.0053 (4)0.0045 (4)
C660.0309 (4)0.0413 (5)0.0360 (4)0.0000 (3)0.0004 (4)0.0015 (4)
B70.0299 (4)0.0366 (5)0.0389 (5)0.0024 (4)0.0006 (4)0.0051 (4)
B80.0328 (5)0.0472 (6)0.0449 (6)0.0073 (4)0.0072 (5)0.0069 (5)
N40.0328 (4)0.0407 (4)0.0320 (4)0.0041 (3)0.0020 (3)0.0052 (4)
B50.0297 (4)0.0360 (5)0.0332 (5)0.0036 (4)0.0014 (4)0.0009 (4)
B90.0351 (5)0.0461 (6)0.0372 (5)0.0037 (4)0.0025 (4)0.0086 (5)
B10.0369 (5)0.0345 (5)0.0405 (6)0.0019 (4)0.0027 (4)0.0038 (5)
Geometric parameters (Å, º) top
B2—B51.7333 (15)C64—C651.3781 (17)
B2—B11.7360 (16)C65—C661.3762 (15)
B2—B61.7535 (15)B7—B81.8616 (18)
B2—B71.8004 (15)B7—H71.124 (14)
B2—B31.8071 (17)B7—H781.287 (15)
B2—H21.109 (16)B8—B91.8497 (17)
B3—B81.7466 (18)B8—H781.267 (14)
B3—B91.7882 (18)B8—H891.171 (18)
B3—B11.7946 (17)B8—H81.112 (15)
B3—B71.8350 (16)N4—B91.4989 (14)
B3—H31.134 (14)N4—B51.5180 (14)
B6—N611.5671 (13)N4—B11.6064 (15)
B6—B71.7798 (14)N4—H40.935 (17)
B6—B51.8287 (15)B5—B11.7982 (16)
B6—H61.101 (13)B5—H51.088 (13)
N61—C621.3462 (13)B9—B11.8557 (18)
N61—C661.3475 (12)B9—H891.627 (16)
C62—C631.3762 (16)B9—H91.084 (14)
C63—C641.3861 (17)B1—H11.135 (15)
B5—B2—B162.44 (7)H7—B7—H78105.1 (10)
B5—B2—B663.26 (6)B3—B8—B959.55 (7)
B1—B2—B6117.18 (8)B3—B8—B761.04 (7)
B5—B2—B7109.78 (8)B9—B8—B7101.84 (8)
B1—B2—B7114.38 (8)B3—B8—H78104.1 (7)
B6—B2—B760.09 (6)B9—B8—H78122.4 (6)
B5—B2—B3106.53 (8)B7—B8—H7843.6 (7)
B1—B2—B360.82 (7)B3—B8—H89117.8 (8)
B6—B2—B3109.49 (8)B9—B8—H8960.3 (8)
B7—B2—B361.15 (6)B7—B8—H89119.7 (8)
B5—B2—H2123.7 (7)H78—B8—H8994.7 (10)
B1—B2—H2120.5 (7)B3—B8—H8115.5 (8)
B6—B2—H2114.6 (7)B9—B8—H8126.0 (8)
B7—B2—H2115.5 (7)B7—B8—H8122.7 (8)
B3—B2—H2123.7 (7)H78—B8—H8111.1 (10)
B8—B3—B963.09 (7)H89—B8—H8111.2 (11)
B8—B3—B1119.38 (9)B9—N4—B5123.13 (8)
B9—B3—B162.39 (7)B9—N4—B173.30 (7)
B8—B3—B2111.47 (8)B5—N4—B170.20 (7)
B9—B3—B2101.29 (7)B9—N4—H4113.1 (10)
B1—B3—B257.63 (6)B5—N4—H4121.6 (10)
B8—B3—B762.58 (7)B1—N4—H4116.1 (11)
B9—B3—B7105.33 (8)N4—B5—B2102.82 (8)
B1—B3—B7109.95 (8)N4—B5—B157.20 (6)
B2—B3—B759.24 (6)B2—B5—B158.86 (6)
B8—B3—H3114.2 (7)N4—B5—B6112.74 (8)
B9—B3—H3126.0 (8)B2—B5—B658.91 (6)
B1—B3—H3118.1 (7)B1—B5—B6110.39 (7)
B2—B3—H3124.9 (8)N4—B5—H5117.0 (8)
B7—B3—H3121.0 (8)B2—B5—H5130.3 (8)
N61—B6—B2111.84 (8)B1—B5—H5120.5 (8)
N61—B6—B7121.09 (8)B6—B5—H5122.0 (8)
B2—B6—B761.26 (6)N4—B9—B3104.24 (9)
N61—B6—B5116.90 (7)N4—B9—B8121.10 (9)
B2—B6—B557.83 (6)B3—B9—B857.36 (7)
B7—B6—B5106.47 (7)N4—B9—B156.01 (6)
N61—B6—H6109.1 (6)B3—B9—B158.97 (7)
B2—B6—H6136.9 (6)B8—B9—B1111.19 (8)
B7—B6—H6107.2 (6)N4—B9—H89105.9 (6)
B5—B6—H691.8 (6)B3—B9—H8994.8 (6)
C62—N61—C66118.62 (9)B8—B9—H8938.7 (6)
C62—N61—B6122.67 (8)B1—B9—H89135.8 (6)
C66—N61—B6118.70 (9)N4—B9—H9116.8 (7)
N61—C62—C63121.61 (10)B3—B9—H9128.0 (7)
C62—C63—C64119.73 (10)B8—B9—H9116.5 (7)
C65—C64—C63118.49 (10)B1—B9—H9121.5 (8)
C66—C65—C64119.32 (10)H89—B9—H9102.7 (10)
N61—C66—C65122.21 (10)N4—B1—B299.10 (8)
B6—B7—B258.65 (6)N4—B1—B399.60 (8)
B6—B7—B3107.09 (7)B2—B1—B361.55 (7)
B2—B7—B359.61 (6)N4—B1—B552.59 (6)
B6—B7—B8112.70 (8)B2—B1—B558.71 (6)
B2—B7—B8106.64 (8)B3—B1—B5104.34 (8)
B3—B7—B856.39 (7)N4—B1—B950.69 (6)
B6—B7—H7124.2 (7)B2—B1—B9101.38 (8)
B2—B7—H7122.0 (7)B3—B1—B958.64 (7)
B3—B7—H7119.2 (7)B5—B1—B993.11 (8)
B8—B7—H7118.0 (7)N4—B1—H1124.8 (9)
B6—B7—H7896.3 (6)B2—B1—H1128.0 (9)
B2—B7—H78132.9 (6)B3—B1—H1125.8 (7)
B3—B7—H7898.6 (6)B5—B1—H1126.3 (7)
B8—B7—H7842.8 (6)B9—B1—H1127.0 (9)

Experimental details

Crystal data
Chemical formulaC5H16B8N2
Mr190.68
Crystal system, space groupOrthorhombic, Pna21
Temperature (K)190
a, b, c (Å)14.3618 (1), 10.4600 (1), 7.5779 (1)
V3)1138.39 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.06
Crystal size (mm)0.24 × 0.18 × 0.06
Data collection
DiffractometerNonius KappaCCD area detector
diffractometer
Absorption correctionMulti-scan
(Blessing, 1995)
Tmin, Tmax0.987, 0.997
No. of measured, independent and
observed [I > 2σ(I)] reflections
26404, 3204, 3077
Rint0.042
(sin θ/λ)max1)0.714
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.093, 1.07
No. of reflections3204
No. of parameters185
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.14, 0.16
Absolute structureFlack H D (1983), Acta Cryst. A39, 876-881
Absolute structure parameter1.5 (11)

Computer programs: KCCD (Nonius, 1998), DENZO-SMN (Otwinowski & Minor, 1996), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEX5 (McArdle, 1995).

Selected geometric parameters (Å, º) top
B6—N611.5671 (13)B8—B91.8497 (17)
B6—B71.7798 (14)N4—B91.4989 (14)
B6—B51.8287 (15)N4—B51.5180 (14)
B7—B81.8616 (18)N4—B11.6064 (15)
N61—B6—B7121.09 (8)B9—N4—B5123.13 (8)
N61—B6—B5116.90 (7)B9—N4—B173.30 (7)
B7—B6—B5106.47 (7)B5—N4—B170.20 (7)
B6—B7—B8112.70 (8)N4—B5—B6112.74 (8)
B9—B8—B7101.84 (8)N4—B9—B8121.10 (9)
 

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