2,4,6-Trichloro-1,3,5-trimethyl­borazine

Weinmann, M.; Nuss, J.; Jansen, M.

doi:10.1107/S1600536807047241

2,4,6-Trichloro-1,3,5-trimethylborazine

The title compound, (CH₃NBCl)₃ or C₃H₉B₃Cl₃N₃, is the first crystallographically characterized trialkyltrichloroborazine derivative. It crystallizes with two independent molecules in the asymmetric unit. The B₃N₃ rings are essentially planar, with B—N distances ranging from 1.428 (5) to 1.449 (4) Å, and with B—N—B and N—B—N angles in the ranges 118.4 (3)–119.4 (3) and 120.7 (3)–121.8 (3)°, respectively. The two independent molecules are staggered parallel along [x, 0, 0] and [x, ${1 \over 2}$ , ${1 \over 2}$ ], most probably due to the formation of weak intermolecular C—H

Cl hydrogen bonds.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807047241/wm2148sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536807047241/wm2148Isup2.hkl Contains datablock I

CCDC reference: 667292

checkCIF report

Key indicators

Single-crystal X-ray study
T = 100 K
Mean (N-B) = 0.004 Å
R factor = 0.061
wR factor = 0.173
Data-to-parameter ratio = 24.7

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H13A   ..  CL12    ..       3.04 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H21C   ..  CL13    ..       2.97 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H22C   ..  CL13    ..       2.99 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H21A   ..  CL23    ..       3.01 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H22B   ..  CL21    ..       3.03 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H23C   ..  CL22    ..       3.09 Ang.
PLAT481_ALERT_4_C Long D...A H-Bond Reported C23    ..  CL22    ..       4.02 Ang.

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

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

Comment top

We recently reported on the first approach towards the continuous synthesis of molecular precursors of high-temperature Si/C/B/N ceramics. Cl₃SiN(Me)BCl₂ (DMTA, dichloroborylmethyltrichlorosilylamine) was obtained in a straightforward reaction from silicontetrachloride, methylamine, and borontrichloride (Kroschel, 2001; Kroschel & Jansen, 2002; Weinmann et al., 2007). DMTA is thermally instable. At elevated temperature it decomposes by SiCl₄ elimination to yield B,B',B''-trichloro-N,N',N''-trimethylborazine, (CH₃NBCl)₃ (Scheme 2).

The title compound was first obtained by Burg & Kuljian (1950) by chance from equal gas volumes of MeN(SiH₃)₂ and BCl₃. Initially, Me(SiH₃)NBCl₂ formed at 195 K but on warming to room temperature it lost ClSiH₃ and quantitatively converted into (CH₃NBCl)₃. Similarly, (CH₃NBCl)₃ was obtained by Nöth & Sprague (1970) from MeN(SiMe₃)₂ and BCl₃. The N atom in DMTA is clearly less basic than those in Me(SiH₃)NBCl₂ or Me(SiMe₃)NBCl₂. Therefore, decomposition (i.e. SiCl₄ elimination) proceeds slower and requires higher temperatures. On the other hand the retarded degradation results in the formation of single crystals of (CH₃NBCl)₃ which accumulate as colorless needles.

Figure 1 shows the structures of the two independent molecules which are nearly identical. B, N, C, and Cl atoms are in a strictly planar arrangement with B and N atoms spanning an almost perfect hexagon. In average, the B—N distances measure 1.437 and 1.435 Å; the maximum deviations from these values are 0.012 and 0.008 Å, respectively. The B—N bonds are thus only slightly longer than those found in (HNBCl)₃ (1.413 Å; Coursen & Hoard, 1952) and (Ph₃NBCl)₃ (1.428 Å; Schwarz et al., 1977). In contrast, there is neither evidence for distortion such as in (CH₃NB(NMe₂))₃ (Rodriguez & Borek, 2006) nor for the existence of "long" and "short" B—N bonds as reported for (ClNBCl)₃ (1.398 versus 1.451 Å; Haasnoot et al., 1972), indicating a perfect π-delocalization of the N electron lone pairs. This is reflected by the B—N—B and N—B—N bond angles which approach 120°. However, the former (average 118.8 and 118.9°) are slightly smaller than the latter (121.1°). B—Cl and N—C bond lengths are similar to those reported in the literature for other B-chloro and N-methyl borazine derivatives. From Figure 2 it is evident that molecules 1 and 2 are staggered parallel along [a, 0, 0] and [a, 1/2, 1/2], respectively. H···Cl separations of ca 3 Å (H···Cl distances are thus within the sum of the Van-der-Vaals radii of hydrogen and chlorine) indicate that weak H···Cl hydrogen bridges enforce the special arrangement (see Table).

Related literature top

The title compound was first obtained by Burg & Kuljian (1950) and Nöth & Sprague (1970) via different reaction routes. For the synthesis of the borazine precursor compound dichloroborylmethyltrichlorosilylamine used in the present study, see: Kroschel (2001); Kroschel & Jansen (2002); Weinmann et al. (2007). For structure determinations of the related compounds (HNBCl)₃, (Ph₃NBCl)₃, [CH₃NB(NMe₂)]₃ and (ClNBCl)₃, see: Coursen & Hoard (1952); Schwarz et al. (1977); Rodriguez & Borek (2006); Haasnoot et al. (1972).

Experimental top

DMTA was synthesized by a continuous gas phase procedure starting from SiCl₄ and MeNH₂. As-obtained Cl₃SiNHMe was directly reacted with BCl₃. Solid amine hydrochloride byproducts were removed by filtration through inductively heated ceramic filters. Details of the experimental setup are found elsewhere (Weinmann et al., 2007). Raw DMTA was purified by fractional distillation. Subsequent heating to 323–343 K over 4–6 weeks resulted in partial decomposition by SiCl₄ elimination and formation of crystalline (CH₃NBCl)₃.

Structure description top

Computing details top

Data collection: SMART (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2005); software used to prepare material for publication: enCIFer (Allen et al., 2004).

Figures top

	Fig. 1. Structure of the two independent (CH₃NBCl)₃ molecules, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Packing diagram of (MeNBCl)₃.
	Fig. 3. The formation of the title compound.

2,4,6-Trichloro-1,3,5-trimethylborazine top

Crystal data top

C₃H₉B₃Cl₃N₃	Z = 4
M_r = 225.91	F(000) = 456
Triclinic, P1	D_x = 1.547 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.720 (4) Å	Cell parameters from 4305 reflections
b = 9.167 (5) Å	θ = 2.4–30.9°
c = 15.054 (8) Å	µ = 0.89 mm⁻¹
α = 90.446 (12)°	T = 100 K
β = 91.727 (12)°	Plate, colourless
γ = 114.38 (1)°	0.50 × 0.20 × 0.05 mm
V = 969.7 (9) Å³

Data collection top

Bruker SMART APEX CCD diffractometer	5513 independent reflections
Radiation source: fine-focus sealed tube	3775 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.060
ω scans	θ_max = 30.0°, θ_min = 1.4°
Absorption correction: multi-scan (SADABS; Bruker, 2007)	h = −10→10
T_min = 0.665, T_max = 0.957	k = −12→12
9812 measured reflections	l = −20→21

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.061	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.173	H-atom parameters constrained
S = 1.02	w = 1/[σ²(F_o²) + (0.0958P)² + 0.0723P] where P = (F_o² + 2F_c²)/3
5513 reflections	(Δ/σ)_max = 0.001
223 parameters	Δρ_max = 0.89 e Å⁻³
0 restraints	Δρ_min = −0.59 e Å⁻³

Crystal data top

C₃H₉B₃Cl₃N₃	γ = 114.38 (1)°
M_r = 225.91	V = 969.7 (9) Å³
Triclinic, P1	Z = 4
a = 7.720 (4) Å	Mo Kα radiation
b = 9.167 (5) Å	µ = 0.89 mm⁻¹
c = 15.054 (8) Å	T = 100 K
α = 90.446 (12)°	0.50 × 0.20 × 0.05 mm
β = 91.727 (12)°

Data collection top

Bruker SMART APEX CCD diffractometer	5513 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2007)	3775 reflections with I > 2σ(I)
T_min = 0.665, T_max = 0.957	R_int = 0.060
9812 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.061	0 restraints
wR(F²) = 0.173	H-atom parameters constrained
S = 1.02	Δρ_max = 0.89 e Å⁻³
5513 reflections	Δρ_min = −0.59 e Å⁻³
223 parameters

Special details top

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. H atoms were placed geometrically applying restrains of isotropic displacement parameters 1.5 times of the attached carbon atom.

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

	x	y	z	U_iso*/U_eq
Cl11	0.73512 (13)	0.15475 (10)	0.43707 (5)	0.0267 (2)
Cl12	0.82179 (13)	0.78156 (10)	0.37427 (5)	0.0277 (2)
Cl13	0.68452 (13)	0.53493 (10)	0.71585 (5)	0.0266 (2)
N11	0.7664 (4)	0.4683 (3)	0.41615 (16)	0.0196 (5)
N12	0.7499 (4)	0.6409 (3)	0.54139 (16)	0.0202 (5)
N13	0.7120 (4)	0.3594 (3)	0.56975 (16)	0.0194 (5)
B11	0.7372 (5)	0.3398 (4)	0.4775 (2)	0.0189 (6)
B12	0.7754 (5)	0.6179 (4)	0.4491 (2)	0.0195 (6)
B13	0.7169 (5)	0.5096 (4)	0.6006 (2)	0.0197 (6)
C11	0.7896 (6)	0.4449 (4)	0.32036 (19)	0.0260 (7)
H11A	0.9217	0.4625	0.3106	0.039*
H11B	0.7581	0.5213	0.2857	0.039*
H11C	0.7044	0.3354	0.3015	0.039*
C12	0.7621 (6)	0.7972 (4)	0.5763 (2)	0.0269 (7)
H12A	0.7591	0.8645	0.5265	0.040*
H12B	0.8813	0.8511	0.6114	0.040*
H12C	0.6541	0.7789	0.6140	0.040*
C13	0.6809 (5)	0.2273 (4)	0.6338 (2)	0.0256 (7)
H13A	0.5563	0.1959	0.6601	0.038*
H13B	0.7808	0.2648	0.6809	0.038*
H13C	0.6852	0.1350	0.6023	0.038*
Cl21	0.56506 (13)	0.33268 (10)	1.08219 (5)	0.0285 (2)
Cl22	0.00324 (13)	−0.28065 (10)	1.13894 (5)	0.02597 (19)
Cl23	0.17428 (14)	−0.06954 (11)	0.79348 (5)	0.0287 (2)
N21	0.2749 (4)	0.0253 (3)	1.09944 (15)	0.0195 (5)
N22	0.1009 (4)	−0.1550 (3)	0.97015 (16)	0.0199 (5)
N23	0.3520 (4)	0.1197 (3)	0.94460 (16)	0.0208 (5)
B21	0.3843 (5)	0.1462 (4)	1.0388 (2)	0.0196 (6)
B22	0.1358 (5)	−0.1254 (4)	1.0643 (2)	0.0183 (6)
B23	0.2113 (6)	−0.0326 (4)	0.9112 (2)	0.0211 (7)
C21	0.3086 (5)	0.0565 (4)	1.19702 (19)	0.0255 (7)
H21A	0.4276	0.0493	1.2155	0.038*
H21B	0.2028	−0.0232	1.2284	0.038*
H21C	0.3177	0.1640	1.2114	0.038*
C22	−0.0423 (5)	−0.3115 (4)	0.9340 (2)	0.0264 (7)
H22A	−0.1314	−0.3666	0.9802	0.040*
H22B	0.0226	−0.3778	0.9149	0.040*
H22C	−0.1123	−0.2930	0.8831	0.040*
C23	0.4641 (5)	0.2474 (4)	0.8818 (2)	0.0272 (7)
H23A	0.5060	0.3526	0.9113	0.041*
H23B	0.3841	0.2427	0.8291	0.041*
H23C	0.5754	0.2303	0.8639	0.041*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl11	0.0341 (5)	0.0167 (4)	0.0302 (4)	0.0115 (3)	0.0014 (3)	−0.0038 (3)
Cl12	0.0372 (5)	0.0175 (4)	0.0258 (4)	0.0086 (3)	0.0025 (3)	0.0054 (3)
Cl13	0.0358 (5)	0.0223 (4)	0.0191 (3)	0.0093 (4)	0.0019 (3)	−0.0017 (3)
N11	0.0208 (14)	0.0157 (13)	0.0197 (11)	0.0049 (11)	0.0006 (9)	−0.0004 (9)
N12	0.0253 (15)	0.0128 (12)	0.0214 (11)	0.0068 (11)	−0.0011 (9)	−0.0033 (9)
N13	0.0200 (14)	0.0157 (13)	0.0209 (11)	0.0058 (11)	−0.0008 (9)	0.0011 (9)
B11	0.0184 (17)	0.0146 (16)	0.0228 (15)	0.0060 (13)	−0.0003 (11)	−0.0018 (12)
B12	0.0191 (17)	0.0178 (16)	0.0201 (14)	0.0061 (14)	0.0002 (11)	0.0018 (12)
B13	0.0204 (18)	0.0160 (16)	0.0208 (14)	0.0059 (14)	−0.0018 (11)	−0.0012 (11)
C11	0.033 (2)	0.0240 (17)	0.0197 (13)	0.0105 (15)	0.0014 (12)	−0.0019 (11)
C12	0.031 (2)	0.0136 (16)	0.0336 (16)	0.0066 (14)	0.0007 (13)	−0.0059 (12)
C13	0.0322 (19)	0.0210 (17)	0.0236 (14)	0.0110 (15)	0.0011 (12)	0.0055 (12)
Cl21	0.0276 (5)	0.0161 (4)	0.0356 (4)	0.0031 (3)	−0.0027 (3)	−0.0027 (3)
Cl22	0.0296 (5)	0.0193 (4)	0.0248 (3)	0.0056 (3)	0.0044 (3)	0.0049 (3)
Cl23	0.0404 (5)	0.0282 (4)	0.0186 (3)	0.0153 (4)	0.0003 (3)	−0.0011 (3)
N21	0.0236 (15)	0.0160 (13)	0.0185 (11)	0.0080 (11)	−0.0014 (9)	−0.0013 (9)
N22	0.0229 (15)	0.0140 (13)	0.0212 (11)	0.0063 (11)	−0.0031 (9)	−0.0025 (9)
N23	0.0239 (15)	0.0158 (13)	0.0227 (12)	0.0081 (11)	0.0040 (10)	0.0024 (9)
B21	0.0184 (18)	0.0125 (16)	0.0269 (16)	0.0058 (14)	−0.0009 (12)	−0.0013 (12)
B22	0.0216 (18)	0.0112 (15)	0.0237 (15)	0.0084 (14)	0.0018 (12)	0.0009 (11)
B23	0.0254 (19)	0.0194 (17)	0.0195 (14)	0.0103 (15)	0.0009 (12)	−0.0010 (12)
C21	0.035 (2)	0.0230 (17)	0.0175 (13)	0.0106 (15)	−0.0006 (12)	−0.0017 (11)
C22	0.031 (2)	0.0170 (16)	0.0275 (15)	0.0065 (15)	−0.0030 (13)	−0.0045 (12)
C23	0.032 (2)	0.0180 (16)	0.0299 (16)	0.0085 (15)	0.0066 (13)	0.0049 (12)

Geometric parameters (Å, º) top

Cl11—B11	1.791 (4)	Cl21—B21	1.804 (4)
Cl12—B12	1.804 (3)	Cl22—B22	1.796 (3)
Cl13—B13	1.787 (3)	Cl23—B23	1.793 (4)
N11—B12	1.428 (5)	N21—B21	1.437 (4)
N11—B11	1.449 (4)	N21—B22	1.440 (5)
N11—C11	1.483 (4)	N21—C21	1.489 (4)
N12—B12	1.436 (4)	N22—B23	1.430 (4)
N12—B13	1.445 (4)	N22—B22	1.437 (4)
N12—C12	1.487 (4)	N22—C22	1.489 (4)
N13—B11	1.429 (4)	N23—B21	1.434 (4)
N13—B13	1.435 (4)	N23—B23	1.444 (5)
N13—C13	1.498 (4)	N23—C23	1.498 (4)
C11—H11A	0.9800	C21—H21A	0.9800
C11—H11B	0.9800	C21—H21B	0.9800
C11—H11C	0.9800	C21—H21C	0.9800
C12—H12A	0.9800	C22—H22A	0.9800
C12—H12B	0.9800	C22—H22B	0.9800
C12—H12C	0.9800	C22—H22C	0.9800
C13—H13A	0.9800	C23—H23A	0.9800
C13—H13B	0.9800	C23—H23B	0.9800
C13—H13C	0.9800	C23—H23C	0.9800

B12—N11—B11	119.4 (3)	B21—N21—B22	119.0 (3)
B12—N11—C11	120.5 (2)	B21—N21—C21	119.8 (3)
B11—N11—C11	120.1 (3)	B22—N21—C21	121.1 (3)
B12—N12—B13	118.4 (3)	B23—N22—B22	118.6 (3)
B12—N12—C12	121.2 (3)	B23—N22—C22	120.2 (3)
B13—N12—C12	120.4 (3)	B22—N22—C22	121.1 (3)
B11—N13—B13	118.5 (3)	B21—N23—B23	119.0 (3)
B11—N13—C13	121.5 (3)	B21—N23—C23	120.5 (3)
B13—N13—C13	120.0 (3)	B23—N23—C23	120.5 (3)
N13—B11—N11	120.9 (3)	N23—B21—N21	120.7 (3)
N13—B11—Cl11	119.6 (2)	N23—B21—Cl21	119.9 (2)
N11—B11—Cl11	119.5 (2)	N21—B21—Cl21	119.4 (2)
N11—B12—N12	120.9 (3)	N22—B22—N21	121.2 (3)
N11—B12—Cl12	119.8 (2)	N22—B22—Cl22	119.0 (3)
N12—B12—Cl12	119.2 (3)	N21—B22—Cl22	119.7 (2)
N13—B13—N12	121.8 (3)	N22—B23—N23	121.3 (3)
N13—B13—Cl13	118.8 (2)	N22—B23—Cl23	119.2 (3)
N12—B13—Cl13	119.3 (2)	N23—B23—Cl23	119.5 (2)
N11—C11—H11A	109.5	N21—C21—H21A	109.5
N11—C11—H11B	109.5	N21—C21—H21B	109.5
H11A—C11—H11B	109.5	H21A—C21—H21B	109.5
N11—C11—H11C	109.5	N21—C21—H21C	109.5
H11A—C11—H11C	109.5	H21A—C21—H21C	109.5
H11B—C11—H11C	109.5	H21B—C21—H21C	109.5
N12—C12—H12A	109.5	N22—C22—H22A	109.5
N12—C12—H12B	109.5	N22—C22—H22B	109.5
H12A—C12—H12B	109.5	H22A—C22—H22B	109.5
N12—C12—H12C	109.5	N22—C22—H22C	109.5
H12A—C12—H12C	109.5	H22A—C22—H22C	109.5
H12B—C12—H12C	109.5	H22B—C22—H22C	109.5
N13—C13—H13A	109.5	N23—C23—H23A	109.5
N13—C13—H13B	109.5	N23—C23—H23B	109.5
H13A—C13—H13B	109.5	H23A—C23—H23B	109.5
N13—C13—H13C	109.5	N23—C23—H23C	109.5
H13A—C13—H13C	109.5	H23A—C23—H23C	109.5
H13B—C13—H13C	109.5	H23B—C23—H23C	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C13—H13A···Cl12ⁱ	0.98	3.04	3.846 (4)	140
C21—H21C···Cl13ⁱⁱ	0.98	2.97	3.938 (4)	170
C22—H22C···Cl13ⁱⁱⁱ	0.98	2.99	3.778 (4)	138
C21—H21A···Cl23^iv	0.98	3.01	3.942 (4)	160
C22—H22B···Cl21^iv	0.98	3.03	3.783 (4)	134
C23—H23C···Cl22^iv	0.98	3.09	4.018 (5)	158

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+1, −z+2; (iii) x−1, y−1, z; (iv) −x+1, −y, −z+2.

Experimental details

Crystal data
Chemical formula	C₃H₉B₃Cl₃N₃
M_r	225.91
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	7.720 (4), 9.167 (5), 15.054 (8)
α, β, γ (°)	90.446 (12), 91.727 (12), 114.38 (1)
V (Å³)	969.7 (9)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.89
Crystal size (mm)	0.50 × 0.20 × 0.05

Data collection
Diffractometer	Bruker SMART APEX CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2007)
T_min, T_max	0.665, 0.957
No. of measured, independent and observed [I > 2σ(I)] reflections	9812, 5513, 3775
R_int	0.060
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.061, 0.173, 1.02
No. of reflections	5513
No. of parameters	223
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.89, −0.59

Computer programs: SMART (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 2005), enCIFer (Allen et al., 2004).

Selected bond lengths (Å) top

Cl11—B11	1.791 (4)	Cl21—B21	1.804 (4)
Cl12—B12	1.804 (3)	Cl22—B22	1.796 (3)
Cl13—B13	1.787 (3)	Cl23—B23	1.793 (4)
N11—B12	1.428 (5)	N21—B21	1.437 (4)
N11—B11	1.449 (4)	N21—B22	1.440 (5)
N11—C11	1.483 (4)	N21—C21	1.489 (4)
N12—B12	1.436 (4)	N22—B23	1.430 (4)
N12—B13	1.445 (4)	N22—B22	1.437 (4)
N12—C12	1.487 (4)	N22—C22	1.489 (4)
N13—B11	1.429 (4)	N23—B21	1.434 (4)
N13—B13	1.435 (4)	N23—B23	1.444 (5)
N13—C13	1.498 (4)	N23—C23	1.498 (4)