2-Chloro-1,1-di­methyl-2-phenyl-2,3-di­hydro-1H-1,2-benzazoniaborolate

In the crystal structure of the title compound, C₁₅H₁₇BClN, the coordination around both B and N is distorted tetrahedral. The five-membered heterocycle adopts a folded conformation.

Key indicators

• Single-crystal X-ray study
• T = 180 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.068
• wR factor = 0.139
• Data-to-parameter ratio = 14.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Organoboron chemistry is intriguing from a number of points of view: structural (bornane clusters), bond theoretical (multicenter bonding) and practical (hydroboration and carbaboration). Boron is found in a large number of saturated and unsaturated heterocycles, in segments such as C—B—C, C—B—N, N—B—N, O—B—O, C—B—O, C—B—S, etc.

Recently, we have synthesized, in high yield, the title compound, (I), containing the C—B—N fragment. This compound has been characterized by single-crystal X-ray diffraction analysis.

The geometric parameters of the heterocyclic moiety of (I) are listed in Table 1 and the molecular structure is illustrated in Fig. 1. The five-membered heterocyclic ring adopts a folded conformation. The angle between the C1/B/N and C1/C2/C7/N planes is 29.1 (5)°. The torsion angles Cl—B—N—C7 [−84.4 (2) Å] and Cl—B—C1—C2 [82.2 (3) Å] indicate that the B—Cl bond is almost perpendicular to the heterocyclic ring.

Both the B and N atoms are sp³ hybridized and coordination around each is distorted tetrahedral. The B—C bond length [1.608 (4) Å] agrees well with the value of 1.597 (22) Å for a four-coordinate B atom bonded to a Csp³ atom (Allen et al., 1987). The B—N bond is much longer [1.685 (4) Å]. A search of the Cambridge Structural Database (CSD; Allen, 2002) found four comparable compounds with a five-membered BNC₃ ring and four-coordinate B and N atoms. These entries and the values of the B—N bond lengths are: 1.720 (3) Å in KISZIV (Köster et al., 1991), 1.716 (5) Å in RISHAC (Ashe et al., 1997), 1.682 (4) and 1.684 (4) Å in WOPBEI (Schumann et al., 2000) and 1.702 Å in YAXFUY (Köster et al., 1993).

S2. Experimental

n-Butyllithium (molar ratio 1:1) was added dropwise to a solution of N,N-dimethyl-o-toluidine in hexane at 273 K, and the temperature was allowed to rise to room temperature. The mixture was stirred for more than 5 h and then chlorotrimethylsilane (molar ratio 1:1) was added at 273 K. The resulting mixture was warmed slowly to room temperature and stirred for a further 12 h to yield a white precipitate (LiCl). The mixture was filtered and the title compound, (I), was isolated by distilling the filtrate as a colorless oil. A solution of (I) in toluene was cooled to 273 K and dichlorophenylborane added (ratio 1:1). The mixture was warmed slowly to room temperature and the solution refluxed for a further 12 h, eliminating chlorotrimethylsilane. A pale-white solid was obtained, which was dissolved in CH₂Cl₂ (10 ml). The solution was concentrated carefully under vacuum, yielding a colorless crystal of the title compound. All reactions were performed under argon, using standard Schlenk techniques. The hexane was dried by distilling with a sodium–potassium alloy, CH₂Cl₂ was distilled from CaH₂ and toluene was distilled with sodium.

S3. Refinement

All H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry, with C—H distances of 0.98 Å and U_iso(H) = 1.5U_eq(C), but each group was allowed to rotate freely about the C—N bond. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.95–1.00 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented by small spheres of arbitrary radii.
	Fig. 2. A packing diagram of the title molecule, viewed down the a axis. For clarity, all H atoms have been omitted.

(I)

Crystal data

C15H17BClN	F(000) = 544
Mr = 257.56	Dx = 1.276 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 7.4639 (11) Å	Cell parameters from 1487 reflections
b = 14.798 (2) Å	θ = 2.8–26.3°
c = 12.2356 (18) Å	µ = 0.27 mm^−1
β = 97.180 (2)°	T = 180 K
V = 1340.8 (3) Å^3	Block, colorless
Z = 4	0.40 × 0.30 × 0.30 mm

Data collection

Bruker SMART APEC CCD area-detector diffractometer	2355 independent reflections
Radiation source: fine-focus sealed tube	1905 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
ω scans	θmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→8
Tmin = 0.902, Tmax = 0.925	k = −17→14
5435 measured reflections	l = −14→11

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)] = 0.068	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.139	H-atom parameters constrained
S = 1.16	w = 1/[σ^2(Fo^2) + (0.0512P)^2 + 0.4704P] where P = (Fo^2 + 2Fc^2)/3
2355 reflections	(Δ/σ)max < 0.001
165 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.29 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
Cl	−0.01009 (10)	0.74719 (5)	0.05040 (7)	0.0334 (3)
B	0.2168 (5)	0.7602 (2)	−0.0039 (3)	0.0248 (8)
N	0.3654 (3)	0.78433 (16)	0.10747 (19)	0.0217 (6)
C1	0.2162 (4)	0.85511 (19)	−0.0680 (3)	0.0275 (8)
H1A	0.3050	0.8553	−0.1194	0.033*
H1B	0.0981	0.8676	−0.1077	0.033*
C2	0.2635 (4)	0.92258 (19)	0.0219 (2)	0.0240 (7)
C3	0.2368 (4)	1.0150 (2)	0.0214 (3)	0.0297 (8)
H3	0.1806	1.0433	−0.0416	0.036*
C4	0.2933 (4)	1.0656 (2)	0.1144 (3)	0.0303 (8)
H4	0.2729	1.1276	0.1136	0.036*
C5	0.3797 (4)	1.0255 (2)	0.2087 (3)	0.0320 (8)
H5	0.4197	1.0607	0.2698	0.038*
C6	0.4066 (4)	0.9326 (2)	0.2121 (3)	0.0291 (8)
H6	0.4634	0.9044	0.2750	0.035*
C7	0.3463 (4)	0.88399 (19)	0.1191 (2)	0.0227 (7)
C8	0.5538 (4)	0.7665 (2)	0.0831 (3)	0.0289 (8)
H8A	0.5717	0.7949	0.0148	0.043*
H8B	0.5721	0.7026	0.0776	0.043*
H8C	0.6383	0.7907	0.1414	0.043*
C9	0.3399 (5)	0.7351 (2)	0.2102 (3)	0.0323 (8)
H9A	0.4371	0.7495	0.2665	0.048*
H9B	0.3388	0.6712	0.1964	0.048*
H9C	0.2273	0.7528	0.2340	0.048*
C10	0.2694 (4)	0.66752 (19)	−0.0612 (2)	0.0232 (7)
C11	0.2196 (4)	0.5825 (2)	−0.0253 (3)	0.0305 (8)
H11	0.1511	0.5791	0.0331	0.037*
C12	0.2691 (5)	0.5030 (2)	−0.0738 (3)	0.0380 (9)
H12	0.2357	0.4475	−0.0470	0.046*
C13	0.3676 (5)	0.5063 (2)	−0.1618 (3)	0.0412 (10)
H13	0.3996	0.4531	−0.1950	0.049*
C14	0.4187 (5)	0.5892 (2)	−0.2004 (3)	0.0376 (9)
H14	0.4854	0.5921	−0.2596	0.045*
C15	0.3698 (4)	0.6678 (2)	−0.1504 (3)	0.0316 (8)
H15	0.4052	0.7229	−0.1772	0.038*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl	0.0235 (4)	0.0319 (5)	0.0449 (5)	−0.0001 (3)	0.0049 (3)	−0.0011 (4)
B	0.0221 (19)	0.030 (2)	0.0208 (19)	0.0002 (15)	−0.0042 (15)	0.0005 (16)
N	0.0226 (14)	0.0214 (13)	0.0204 (14)	0.0012 (10)	−0.0008 (11)	0.0022 (11)
C1	0.0288 (19)	0.0257 (17)	0.0259 (18)	0.0006 (14)	−0.0048 (14)	0.0007 (14)
C2	0.0221 (17)	0.0253 (17)	0.0245 (17)	−0.0011 (13)	0.0024 (13)	0.0015 (14)
C3	0.034 (2)	0.0265 (18)	0.0280 (18)	0.0006 (14)	0.0003 (15)	0.0075 (15)
C4	0.036 (2)	0.0211 (17)	0.034 (2)	0.0028 (14)	0.0068 (16)	−0.0002 (15)
C5	0.034 (2)	0.0304 (19)	0.031 (2)	−0.0009 (15)	0.0016 (15)	−0.0080 (15)
C6	0.032 (2)	0.0297 (19)	0.0243 (18)	0.0038 (15)	−0.0019 (15)	−0.0005 (14)
C7	0.0218 (17)	0.0214 (16)	0.0254 (18)	0.0002 (12)	0.0050 (14)	0.0003 (13)
C8	0.0260 (18)	0.0269 (18)	0.0330 (19)	0.0011 (13)	0.0001 (14)	−0.0014 (14)
C9	0.041 (2)	0.0273 (19)	0.0278 (19)	0.0029 (15)	0.0011 (15)	0.0085 (15)
C10	0.0234 (17)	0.0225 (17)	0.0217 (17)	−0.0016 (13)	−0.0042 (13)	−0.0012 (13)
C11	0.031 (2)	0.035 (2)	0.0247 (18)	0.0026 (15)	−0.0005 (15)	−0.0009 (15)
C12	0.045 (2)	0.026 (2)	0.040 (2)	0.0029 (16)	−0.0057 (18)	−0.0026 (17)
C13	0.044 (2)	0.036 (2)	0.039 (2)	0.0129 (17)	−0.0106 (18)	−0.0145 (18)
C14	0.035 (2)	0.048 (2)	0.029 (2)	0.0054 (17)	0.0020 (16)	−0.0079 (18)
C15	0.0320 (19)	0.0335 (19)	0.0279 (19)	−0.0007 (15)	−0.0023 (15)	−0.0014 (15)

Geometric parameters (Å, º)

Cl—B	1.905 (4)	C6—H6	0.9300
B—C1	1.608 (4)	C8—H8A	0.9600
B—C10	1.611 (4)	C8—H8B	0.9600
B—N	1.685 (4)	C8—H8C	0.9600
N—C9	1.485 (4)	C9—H9A	0.9600
N—C7	1.490 (4)	C9—H9B	0.9600
N—C8	1.497 (4)	C9—H9C	0.9600
C1—C2	1.495 (4)	C10—C11	1.398 (4)
C1—H1A	0.9700	C10—C15	1.400 (4)
C1—H1B	0.9700	C11—C12	1.388 (4)
C2—C3	1.382 (4)	C11—H11	0.9300
C2—C7	1.392 (4)	C12—C13	1.378 (5)
C3—C4	1.384 (4)	C12—H12	0.9300
C3—H3	0.9300	C13—C14	1.386 (5)
C4—C5	1.383 (4)	C13—H13	0.9300
C4—H4	0.9300	C14—C15	1.383 (4)
C5—C6	1.388 (4)	C14—H14	0.9300
C5—H5	0.9300	C15—H15	0.9300
C6—C7	1.374 (4)
C1—B—C10	121.2 (3)	C6—C7—C2	123.8 (3)
C1—B—N	99.8 (2)	C6—C7—N	124.9 (3)
C10—B—N	111.1 (2)	C2—C7—N	111.2 (2)
C1—B—Cl	108.1 (2)	N—C8—H8A	109.5
C10—B—Cl	110.0 (2)	N—C8—H8B	109.5
N—B—Cl	105.3 (2)	H8A—C8—H8B	109.5
C9—N—C7	112.4 (2)	N—C8—H8C	109.5
C9—N—C8	107.8 (2)	H8A—C8—H8C	109.5
C7—N—C8	107.3 (2)	H8B—C8—H8C	109.5
C9—N—B	116.1 (2)	N—C9—H9A	109.5
C7—N—B	103.0 (2)	N—C9—H9B	109.5
C8—N—B	110.0 (2)	H9A—C9—H9B	109.5
C2—C1—B	103.8 (2)	N—C9—H9C	109.5
C2—C1—H1A	111.0	H9A—C9—H9C	109.5
B—C1—H1A	111.0	H9B—C9—H9C	109.5
C2—C1—H1B	111.0	C11—C10—C15	115.9 (3)
B—C1—H1B	111.0	C11—C10—B	122.7 (3)
H1A—C1—H1B	109.0	C15—C10—B	121.4 (3)
C3—C2—C7	117.3 (3)	C12—C11—C10	122.2 (3)
C3—C2—C1	129.6 (3)	C12—C11—H11	118.9
C7—C2—C1	113.2 (2)	C10—C11—H11	118.9
C2—C3—C4	120.2 (3)	C13—C12—C11	120.1 (3)
C2—C3—H3	119.9	C13—C12—H12	120.0
C4—C3—H3	119.9	C11—C12—H12	120.0
C5—C4—C3	121.0 (3)	C12—C13—C14	119.6 (3)
C5—C4—H4	119.5	C12—C13—H13	120.2
C3—C4—H4	119.5	C14—C13—H13	120.2
C4—C5—C6	120.1 (3)	C15—C14—C13	119.6 (3)
C4—C5—H5	120.0	C15—C14—H14	120.2
C6—C5—H5	120.0	C13—C14—H14	120.2
C7—C6—C5	117.5 (3)	C14—C15—C10	122.7 (3)
C7—C6—H6	121.2	C14—C15—H15	118.7
C5—C6—H6	121.2	C10—C15—H15	118.7
C1—B—N—C9	150.8 (2)	C3—C2—C7—N	179.8 (3)
C10—B—N—C9	−80.1 (3)	C1—C2—C7—N	−0.2 (4)
Cl—B—N—C9	38.9 (3)	C9—N—C7—C6	37.9 (4)
C1—B—N—C7	27.6 (3)	C8—N—C7—C6	−80.4 (3)
C10—B—N—C7	156.6 (2)	B—N—C7—C6	163.6 (3)
Cl—B—N—C7	−84.4 (2)	C9—N—C7—C2	−143.8 (3)
C1—B—N—C8	−86.5 (3)	C8—N—C7—C2	97.9 (3)
C10—B—N—C8	42.6 (3)	B—N—C7—C2	−18.1 (3)
Cl—B—N—C8	161.56 (19)	C1—B—C10—C11	−159.6 (3)
C10—B—C1—C2	−149.7 (3)	N—B—C10—C11	83.8 (3)
N—B—C1—C2	−27.5 (3)	Cl—B—C10—C11	−32.3 (3)
Cl—B—C1—C2	82.2 (3)	C1—B—C10—C15	20.8 (4)
B—C1—C2—C3	−160.6 (3)	N—B—C10—C15	−95.8 (3)
B—C1—C2—C7	19.4 (3)	Cl—B—C10—C15	148.1 (2)
C7—C2—C3—C4	0.8 (5)	C15—C10—C11—C12	1.0 (4)
C1—C2—C3—C4	−179.3 (3)	B—C10—C11—C12	−178.6 (3)
C2—C3—C4—C5	1.0 (5)	C10—C11—C12—C13	−1.3 (5)
C3—C4—C5—C6	−1.7 (5)	C11—C12—C13—C14	0.8 (5)
C4—C5—C6—C7	0.6 (5)	C12—C13—C14—C15	−0.1 (5)
C5—C6—C7—C2	1.2 (5)	C13—C14—C15—C10	−0.1 (5)
C5—C6—C7—N	179.3 (3)	C11—C10—C15—C14	−0.3 (4)
C3—C2—C7—C6	−1.9 (5)	B—C10—C15—C14	179.3 (3)
C1—C2—C7—C6	178.1 (3)