Methyl 3,4-dibromo-2-(triisopropyl­silyl)-1H-pyrrole-1-carboxyl­ate

Banwell, M.G.; Holden, K.E.; Willis, A.C.

doi:10.1107/S1600536807037774

Methyl 3,4-dibromo-2-(triisopropylsilyl)-1H-pyrrole-1-carboxylate

M. G. Banwell, K. E. Holden and A. C. Willis

The title compound, C₁₅H₂₅Br₂NO₂Si, represents a rare example of a C2-silylated pyrrole for which a single-crystal X-ray analysis has been completed. The molecule adopts an s-transoid conformation about the N-CO bond of the carbamate residue.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807037774/hg2268sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536807037774/hg2268Isup2.hkl Contains datablock I

CCDC reference: 660212

checkCIF report

Key indicators

Single-crystal X-ray study
T = 200 K
Mean (C-C) = 0.004 Å
R factor = 0.024
wR factor = 0.027
Data-to-parameter ratio = 9.8

checkCIF/PLATON results

No syntax errors found



Alert level C
REFNR01_ALERT_3_C  Ratio of reflections to parameters is < 10 for a
            centrosymmetric structure
            sine(theta)/lambda                0.6497
            Proportion of unique data used    0.6008
            Ratio reflections to parameters   9.8302
PLAT088_ALERT_3_C Poor Data / Parameter Ratio ....................       9.83
PLAT164_ALERT_4_C Nr. of Refined C-H H-Atoms in Heavy-At Struct...         25
PLAT391_ALERT_3_C Deviating Methyl C15     H-C-H Bond Angle ......     100.00 Deg.
PLAT431_ALERT_2_C Short Inter HL..A Contact  Br21   ..  O7      ..       3.11 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 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
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 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

Comment top

During attempts to prepare compound (I) by sequential treatment of the known tribromide (II) (Bray et al., 1990) with phenyllithium then methyl chloroformate an isomeric product was sometimes formed (and occasionally to the exclusion of the desired material). The isomer was subjected to a single-crystal X-ray analysis and thus establishing it was the title compound (III). This previously unreported tetra-substituted pyrrole most likely arises from an initial and selective lithium-for-bromine exchange reaction between phenyllithium and tribromide (II) and so forming the corresponding C2-lithiated compound. This last species presumably undergoes silyl group migration to give the more stable N1-lithiated isomer that then reacts with added methyl chloroformate and so affording the observed product. The silyl group migration proved to be a temperature sensitive process that could be suppressed by strict maintenance of the reaction temperature at 195 K and with the result that the desired compound, (I), was formed in preparatively useful yields.

Compound (III) represents the first example of a C2-triisopropylsilyl-substituted pyrrole for which a single-crystal X-ray analysis has been reported although a few such analyses of other types of C2-silylated pyrroles have been described (König et al., 1995; Frenzel et al., 1996; Kang et al., 1999; Liu et al., 2000; Kang et al., 2000; Couzijn et al., 2004; Marsh, 2004). All of the non-hydrogen-containing bond lengths and angles (Table 1) associated with compound (III) fall within the expected ranges. The most conspicuous feature associated with the structure is the s-transoid arrangement adopted by the carbomethoxy group about the C6–N1 bond and this undoubtedly results from the steric effects exerted by the adjacent and bulky triisopropylsilyl group. The C2–C3 bond is notably longer than its C4–C5 counterpart (1.382 (3) vs 1.342 (3) Å) and may reflect the repulsive effectsoperating between the C2-triisopropylsilyl and C3-bromine groups attached to the carbons of the former bond. The N1–C2 bond is also longer than the equivalent N1–C5 bond (1.423 vs 1.385 Å) and this situation is probably the result of similar effects. In contrast the C3- and C4-bromine bonds are of similar length (1.879 (2) vs 1.871 (2) Å).

Related literature top

For related literature, see: Bray et al. (1990); Couzijn et al. (2004); Frenzel et al. (1996); König et al. (1995); Kang et al. (1999, 2000); Liu et al. (2000); Marsh (2004).

Experimental top

Phenyllithium (0.41 ml of a 1.8 M solution in cyclohexane/diethyl ether, 0.74 mmol, ex Aldrich Chemical Co.) was added, dropwise, to a magnetically stirred solution of tribromopyrrole (II) (341 mg, 0.74 mmol) in dry THF (15 ml) maintained at 195 K under a nitrogen atmosphere. After 0.25 h unchilled methyl chloroformate (60 µl, 0.78 mmol) was added to the reaction mixture and then the cooling bath removed. Once the reaction mixture had warmed to 291 K it was diluted with water (10 ml) and extracted with ethyl acetate (3 × 15 ml). The combined organic extracts were then dried (MgSO₄), filtered and concentrated under reduced pressure. Subjection of the ensuing light-yellow oil to flash chromatography (silica, hexane elution) and concentration of the relevant fractions (R_f = 1/5) under reduced pressure afforded a white solid. Recrystallization of this material (methanol or THF) then gave the title compound (III) (42 mg, 13%) as colourless needles, m.p. 366–367 K [Found: (M – C₃H₇^.)⁺, 393.9485. C₁₅H₂₅⁷⁹Br₂NO₂Si requires (M – C₃H₇^.)⁺, 393.9474]. ¹H NMR (300 MHz, CDCl₃): δ 7.53 (s, 1H), 3.94 (s, 3H), 1.84 (septet, J = 7.5 Hz, 3H), 1.10 (d, J = 7.5 Hz, 18H); ¹³C NMR (75 MHz, CDCl₃): δ 150.4 (C), 130.7 (C), 125.1 (CH), 117.7 (C), 106.3 (C), 54.7 (CH₃), 19.2 (6 × CH₃), 12.8 (3 × CH); IR (KBr, ν_max, cm^-1): 2945, 2866, 1757, 1440, 1353, 1302, 1280, 1215, 1127, 1036; MS (EI, 70 eV): 398, 396 and 394 [(M – C₃H₇^.)⁺, 70, 100 and 69%].

Structure description top

For related literature, see: Bray et al. (1990); Couzijn et al. (2004); Frenzel et al. (1996); König et al. (1995); Kang et al. (1999, 2000); Liu et al. (2000); Marsh (2004).

Computing details top

Data collection: COLLECT (Nonius, 1997); cell refinement: DENZO/SCALEPACK; data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 2003); molecular graphics: ORTEPII (Johnson, 1976) in TEXSAN (Molecular Structure Corporation, 1997); software used to prepare material for publication: CRYSTALS.

Figures top

	Fig. 1. Molecular structure of (III) with labelling of selected atoms. Anisotropic displacement ellipsoids show 30% probability levels. Hydrogen atoms are drawn as circles with small radii.
	Fig. 2. Unit cell packing diagram of (III) projected down the b axis. Hydrogen atoms are drawn as circles with small radii.
	Fig. 3. Compounds (I), (II) and (III).

Methyl 3,4-dibromo-2-(triisopropylsilyl)-1H-pyrrole-1-carboxylate top

Crystal data top

C₁₅H₂₅Br₂NO₂Si	F(000) = 888
M_r = 439.26	D_x = 1.547 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 92459 reflections
a = 14.6807 (4) Å	θ = 3–27°
b = 7.3800 (2) Å	µ = 4.37 mm⁻¹
c = 17.4291 (5) Å	T = 200 K
β = 92.8487 (15)°	Needle, colourless
V = 1886.00 (9) Å³	0.36 × 0.10 × 0.07 mm
Z = 4

Data collection top

Nonius KappaCCD diffractometer	2605 reflections with I > 3σ(I)
Graphite monochromator	R_int = 0.059
φ and ω scans with CCD	θ_max = 27.5°, θ_min = 3.1°
Absorption correction: integration [via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999)]	h = −19→19
T_min = 0.447, T_max = 0.762	k = −8→9
41120 measured reflections	l = −22→22
4336 independent reflections

Refinement top

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.024	Only H-atom coordinates refined
wR(F²) = 0.027	Method, part 1, Chebychev polynomial [Carruthers & Watkin (1979). Acta Cryst. A35, 698–699; Prince (1982). Mathematical Techniques in Crystallography and Materials Science. New York: Springer–Verlag] [weight] = 1/[A₀T₀(x) + A₁T₁(x) ··· + A_n-1]*T_n-1(x)] where A_i are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight][1-(δF/6σF)²]², A_i are: 2.01 -0.979 2.14 -0.341 0.473
S = 1.15	(Δ/σ)_max = 0.002
2605 reflections	Δρ_max = 0.33 e Å⁻³
265 parameters	Δρ_min = −0.49 e Å⁻³
0 restraints

Crystal data top

C₁₅H₂₅Br₂NO₂Si	V = 1886.00 (9) Å³
M_r = 439.26	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 14.6807 (4) Å	µ = 4.37 mm⁻¹
b = 7.3800 (2) Å	T = 200 K
c = 17.4291 (5) Å	0.36 × 0.10 × 0.07 mm
β = 92.8487 (15)°

Data collection top

Nonius KappaCCD diffractometer	4336 independent reflections
Absorption correction: integration [via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999)]	2605 reflections with I > 3σ(I)
T_min = 0.447, T_max = 0.762	R_int = 0.059
41120 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.024	0 restraints
wR(F²) = 0.027	Only H-atom coordinates refined
S = 1.15	Δρ_max = 0.33 e Å⁻³
2605 reflections	Δρ_min = −0.49 e Å⁻³
265 parameters

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

	x	y	z	U_iso*/U_eq
N1	0.36958 (13)	0.5984 (3)	0.44081 (10)	0.0297
C2	0.28285 (16)	0.5206 (3)	0.45316 (12)	0.0311
C3	0.26276 (17)	0.5898 (4)	0.52402 (13)	0.0359
C4	0.33465 (18)	0.7017 (3)	0.55408 (13)	0.0362
C5	0.39939 (18)	0.7052 (4)	0.50238 (13)	0.0354
C6	0.41628 (16)	0.5914 (3)	0.37249 (13)	0.0313
O7	0.38537 (12)	0.5309 (2)	0.31321 (9)	0.0383
O8	0.49883 (12)	0.6636 (3)	0.38432 (10)	0.0445
C9	0.5537 (2)	0.6726 (5)	0.3175 (2)	0.0534
Si10	0.22018 (4)	0.35292 (9)	0.38468 (3)	0.0298
C11	0.16792 (19)	0.4966 (4)	0.30420 (14)	0.0388
C12	0.0864 (2)	0.6051 (5)	0.3294 (2)	0.0580
C13	0.1456 (3)	0.3964 (5)	0.22850 (17)	0.0550
C14	0.12861 (19)	0.2398 (4)	0.44087 (15)	0.0421
C15	0.1679 (3)	0.1198 (5)	0.5064 (2)	0.0597
C16	0.0573 (2)	0.1367 (5)	0.3905 (2)	0.0555
C17	0.30387 (18)	0.1785 (4)	0.34943 (15)	0.0389
C18	0.3822 (2)	0.1358 (5)	0.4070 (2)	0.0571
C19	0.2602 (3)	0.0001 (4)	0.3208 (2)	0.0539
Br20	0.15689 (2)	0.56204 (5)	0.579168 (18)	0.0638
Br21	0.34204 (2)	0.82451 (4)	0.648093 (14)	0.0502
H51	0.452 (2)	0.765 (4)	0.5030 (16)	0.0425*
H91	0.609 (3)	0.718 (5)	0.3363 (19)	0.0648*
H92	0.565 (2)	0.564 (5)	0.301 (2)	0.0648*
H93	0.521 (2)	0.745 (5)	0.280 (2)	0.0648*
H111	0.215 (2)	0.581 (4)	0.2954 (16)	0.0462*
H121	0.068 (2)	0.691 (5)	0.291 (2)	0.0692*
H122	0.094 (3)	0.661 (5)	0.376 (2)	0.0692*
H123	0.035 (3)	0.524 (5)	0.332 (2)	0.0692*
H131	0.121 (2)	0.477 (5)	0.191 (2)	0.0654*
H132	0.198 (3)	0.336 (5)	0.211 (2)	0.0654*
H133	0.100 (2)	0.308 (5)	0.237 (2)	0.0654*
H141	0.097 (2)	0.340 (4)	0.4636 (18)	0.0510*
H151	0.218 (3)	0.180 (5)	0.540 (2)	0.0720*
H152	0.189 (3)	0.011 (6)	0.487 (2)	0.0720*
H153	0.119 (3)	0.076 (5)	0.536 (2)	0.0720*
H161	0.025 (2)	0.218 (5)	0.349 (2)	0.0665*
H162	0.087 (3)	0.033 (5)	0.369 (2)	0.0665*
H163	0.014 (2)	0.089 (5)	0.422 (2)	0.0665*
H171	0.330 (2)	0.235 (4)	0.3058 (17)	0.0468*
H181	0.417 (2)	0.244 (6)	0.423 (2)	0.0683*
H182	0.424 (2)	0.046 (5)	0.382 (2)	0.0683*
H183	0.363 (2)	0.080 (5)	0.454 (2)	0.0683*
H191	0.211 (3)	0.021 (5)	0.282 (2)	0.0649*
H192	0.307 (2)	−0.077 (5)	0.296 (2)	0.0649*
H193	0.241 (2)	−0.066 (5)	0.361 (2)	0.0649*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0299 (10)	0.0344 (10)	0.0250 (8)	−0.0019 (8)	0.0032 (7)	−0.0007 (8)
C2	0.0346 (12)	0.0344 (12)	0.0246 (10)	−0.0012 (10)	0.0044 (9)	0.0009 (9)
C3	0.0422 (14)	0.0371 (13)	0.0288 (11)	−0.0024 (11)	0.0062 (10)	−0.0026 (10)
C4	0.0484 (15)	0.0337 (13)	0.0262 (10)	0.0012 (11)	−0.0007 (10)	−0.0015 (9)
C5	0.0402 (14)	0.0359 (14)	0.0298 (11)	−0.0039 (11)	−0.0015 (10)	−0.0008 (9)
C6	0.0355 (12)	0.0279 (12)	0.0308 (11)	0.0016 (10)	0.0056 (9)	0.0047 (9)
O7	0.0454 (10)	0.0455 (10)	0.0243 (8)	−0.0084 (8)	0.0061 (7)	−0.0006 (7)
O8	0.0348 (9)	0.0565 (12)	0.0430 (9)	−0.0121 (9)	0.0105 (7)	−0.0059 (9)
C9	0.0472 (17)	0.0580 (19)	0.0571 (18)	−0.0137 (16)	0.0232 (14)	−0.0044 (16)
Si10	0.0305 (3)	0.0318 (3)	0.0271 (3)	−0.0021 (3)	0.0026 (2)	−0.0004 (2)
C11	0.0380 (14)	0.0409 (14)	0.0368 (12)	−0.0017 (12)	−0.0047 (10)	0.0031 (11)
C12	0.0503 (18)	0.055 (2)	0.068 (2)	0.0140 (16)	−0.0045 (16)	0.0031 (17)
C13	0.060 (2)	0.067 (2)	0.0368 (14)	−0.0038 (18)	−0.0100 (14)	0.0001 (14)
C14	0.0426 (15)	0.0432 (15)	0.0412 (13)	−0.0079 (13)	0.0094 (11)	−0.0042 (12)
C15	0.071 (2)	0.060 (2)	0.0494 (17)	−0.0170 (17)	0.0144 (16)	0.0175 (15)
C16	0.0421 (16)	0.058 (2)	0.067 (2)	−0.0181 (15)	0.0087 (15)	−0.0077 (16)
C17	0.0395 (13)	0.0332 (13)	0.0445 (13)	−0.0016 (11)	0.0075 (11)	−0.0029 (11)
C18	0.0496 (18)	0.0403 (17)	0.081 (2)	0.0089 (14)	−0.0040 (17)	0.0041 (16)
C19	0.060 (2)	0.0400 (16)	0.0632 (19)	−0.0017 (15)	0.0128 (16)	−0.0114 (14)
Br20	0.06063 (19)	0.0831 (3)	0.05041 (17)	−0.01778 (18)	0.03013 (14)	−0.02307 (16)
Br21	0.0718 (2)	0.04899 (16)	0.03003 (12)	−0.00375 (15)	0.00367 (11)	−0.01156 (11)

Geometric parameters (Å, º) top

N1—C2	1.423 (3)	C12—H122	0.91 (4)
N1—C5	1.385 (3)	C12—H123	0.96 (4)
N1—C6	1.404 (3)	C13—H131	0.94 (4)
C2—C3	1.382 (3)	C13—H132	0.95 (4)
C2—Si10	1.922 (2)	C13—H133	0.95 (4)
C3—C4	1.419 (4)	C14—C15	1.535 (4)
C3—Br20	1.879 (2)	C14—C16	1.535 (4)
C4—C5	1.342 (3)	C14—H141	0.97 (3)
C4—Br21	1.871 (2)	C15—H151	1.02 (4)
C5—H51	0.89 (3)	C15—H152	0.93 (4)
C6—O7	1.194 (3)	C15—H153	0.96 (4)
C6—O8	1.331 (3)	C16—H161	1.04 (4)
O8—C9	1.450 (3)	C16—H162	0.97 (4)
C9—H91	0.93 (4)	C16—H163	0.93 (4)
C9—H92	0.88 (4)	C17—C18	1.521 (4)
C9—H93	0.95 (4)	C17—C19	1.537 (4)
Si10—C11	1.890 (3)	C17—H171	0.96 (3)
Si10—C14	1.896 (3)	C18—H181	0.98 (4)
Si10—C17	1.902 (3)	C18—H182	1.02 (4)
C11—C12	1.523 (4)	C18—H183	0.98 (4)
C11—C13	1.534 (4)	C19—H191	0.98 (4)
C11—H111	0.95 (3)	C19—H192	1.00 (4)
C12—H121	0.95 (4)	C19—H193	0.91 (4)

Br21···O7ⁱ	3.105 (2)	C5···C18ⁱⁱ	3.589 (5)

C2—N1—C5	111.29 (18)	C11—C13—H131	110 (2)
C2—N1—C6	126.27 (19)	C11—C13—H132	111 (2)
C5—N1—C6	122.0 (2)	H131—C13—H132	111 (3)
N1—C2—C3	102.6 (2)	C11—C13—H133	109 (2)
N1—C2—Si10	124.77 (15)	H131—C13—H133	107 (3)
C3—C2—Si10	132.56 (18)	H132—C13—H133	109 (3)
C2—C3—C4	110.9 (2)	Si10—C14—C15	112.8 (2)
C2—C3—Br20	129.47 (19)	Si10—C14—C16	113.8 (2)
C4—C3—Br20	119.57 (17)	C15—C14—C16	111.1 (3)
C3—C4—C5	107.6 (2)	Si10—C14—H141	104.0 (18)
C3—C4—Br21	127.93 (18)	C15—C14—H141	107.8 (18)
C5—C4—Br21	124.5 (2)	C16—C14—H141	106.7 (18)
N1—C5—C4	107.6 (2)	C14—C15—H151	114 (2)
N1—C5—H51	122.1 (18)	C14—C15—H152	110 (2)
C4—C5—H51	130.3 (19)	H151—C15—H152	110 (3)
N1—C6—O7	124.5 (2)	C14—C15—H153	109 (2)
N1—C6—O8	109.5 (2)	H151—C15—H153	112 (3)
O7—C6—O8	126.0 (2)	H152—C15—H153	100 (3)
C6—O8—C9	115.6 (2)	C14—C16—H161	113 (2)
O8—C9—H91	104 (2)	C14—C16—H162	108 (2)
O8—C9—H92	111 (2)	H161—C16—H162	113 (3)
H91—C9—H92	106 (3)	C14—C16—H163	109 (2)
O8—C9—H93	107 (2)	H161—C16—H163	108 (3)
H91—C9—H93	116 (3)	H162—C16—H163	105 (3)
H92—C9—H93	113 (3)	Si10—C17—C18	114.0 (2)
C2—Si10—C11	105.30 (11)	Si10—C17—C19	114.7 (2)
C2—Si10—C14	107.01 (11)	C18—C17—C19	109.0 (3)
C11—Si10—C14	110.99 (13)	Si10—C17—H171	104.3 (18)
C2—Si10—C17	109.84 (11)	C18—C17—H171	107.2 (17)
C11—Si10—C17	112.63 (12)	C19—C17—H171	107.0 (18)
C14—Si10—C17	110.78 (13)	C17—C18—H181	113 (2)
Si10—C11—C12	112.1 (2)	C17—C18—H182	107 (2)
Si10—C11—C13	115.4 (2)	H181—C18—H182	109 (3)
C12—C11—C13	111.4 (3)	C17—C18—H183	114 (2)
Si10—C11—H111	102.3 (18)	H181—C18—H183	106 (3)
C12—C11—H111	107.2 (18)	H182—C18—H183	107 (3)
C13—C11—H111	107.6 (18)	C17—C19—H191	112 (2)
C11—C12—H121	110 (2)	C17—C19—H192	110 (2)
C11—C12—H122	116 (2)	H191—C19—H192	107 (3)
H121—C12—H122	110 (3)	C17—C19—H193	110 (2)
C11—C12—H123	108 (2)	H191—C19—H193	112 (3)
H121—C12—H123	105 (3)	H192—C19—H193	106 (3)
H122—C12—H123	108 (3)

Br20—C3—C2—Si10	−6.5 (4)	C2—Si10—C14—C16	165.9 (2)
Br20—C3—C2—N1	176.4 (2)	C2—Si10—C17—C18	31.0 (2)
Br20—C3—C4—Br21	3.2 (3)	C2—Si10—C17—C19	157.7 (2)
Br20—C3—C4—C5	−177.1 (2)	C2—N1—C5—C4	−0.8 (3)
Br21—C4—C3—C2	−179.1 (2)	C2—C3—C4—C5	0.7 (3)
Br21—C4—C5—N1	179.8 (2)	C3—C2—Si10—C11	104.7 (3)
Si10—C2—N1—C5	−176.3 (2)	C3—C2—Si10—C14	−13.4 (3)
Si10—C2—N1—C6	11.5 (3)	C3—C2—Si10—C17	−133.8 (2)
Si10—C2—C3—C4	176.1 (2)	C3—C2—N1—C5	1.1 (3)
O7—C6—O8—C9	1.9 (4)	C3—C2—N1—C6	−171.1 (2)
O7—C6—N1—C2	6.5 (4)	C4—C5—N1—C6	171.9 (2)
O7—C6—N1—C5	−165.0 (2)	C11—Si10—C14—C15	179.4 (2)
O8—C6—N1—C2	−174.1 (2)	C11—Si10—C14—C16	51.5 (2)
O8—C6—N1—C5	14.4 (3)	C11—Si10—C17—C18	148.0 (2)
N1—C2—Si10—C11	−78.7 (2)	C11—Si10—C17—C19	−85.3 (2)
N1—C2—Si10—C14	163.2 (2)	C12—C11—Si10—C14	42.3 (2)
N1—C2—Si10—C17	42.8 (2)	C12—C11—Si10—C17	167.1 (2)
N1—C2—C3—C4	−1.1 (3)	C13—C11—Si10—C14	−86.7 (3)
N1—C5—C4—C3	0.1 (3)	C13—C11—Si10—C17	38.2 (3)
N1—C6—O8—C9	−177.5 (2)	C14—Si10—C17—C18	−87.1 (2)
C2—Si10—C11—C12	−73.2 (2)	C14—Si10—C17—C19	39.7 (2)
C2—Si10—C11—C13	157.8 (2)	C15—C14—Si10—C17	53.5 (2)
C2—Si10—C14—C15	−66.2 (2)	C16—C14—Si10—C17	−74.4 (2)

Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, y+1, z.

Experimental details

Crystal data
Chemical formula	C₁₅H₂₅Br₂NO₂Si
M_r	439.26
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	200
a, b, c (Å)	14.6807 (4), 7.3800 (2), 17.4291 (5)
β (°)	92.8487 (15)
V (Å³)	1886.00 (9)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	4.37
Crystal size (mm)	0.36 × 0.10 × 0.07

Data collection
Diffractometer	Nonius KappaCCD
Absorption correction	Integration [via Gaussian method (Coppens, 1970) implemented in maXus (Mackay et al., 1999)]
T_min, T_max	0.447, 0.762
No. of measured, independent and observed [I > 3σ(I)] reflections	41120, 4336, 2605
R_int	0.059
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.024, 0.027, 1.15
No. of reflections	2605
No. of parameters	265
H-atom treatment	Only H-atom coordinates refined
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.49

Computer programs: COLLECT (Nonius, 1997), DENZO/SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), CRYSTALS (Watkin et al., 2003), ORTEPII (Johnson, 1976) in TEXSAN (Molecular Structure Corporation, 1997), CRYSTALS.