Complexes of mixed silicon halides with 4-picoline

The reaction products of an addition reaction of five different silicon tetrahalides with the aromatic nitro­gen base 4-methyl­pyridine are presented. The following five structures are isomorphous: (I) tetra­chloro­bis(4-methyl­pyridine)­silicon, C₁₂H₁₄­Cl₄­N₂Si, (II) bromo­tri­chloro­bis(4-methyl­pyridine)­silicon, C₁₂H₁₄­Br­Cl₃N₂Si, (III) di­bromo­di­chloro­bis(4-methyl­pyridine)­silicon, C₁₂H₁₄­Br₂­Cl₂N₂Si, (IV) tri­bromo­chloro­bis(4-methyl­pyridine)­silicon, C₁₂H₁₄Br₃­Cl­N₂Si, and (V) tetra­bromo­bis(4-methyl­pyridine)­silicon, C₁₂H₁₄Br₄N₂Si. The mol­ecules of (I) and (V), with D_2h symmetry, have crystallographic C_2h symmetry, while the molecules of (II), (III) and (IV) have a lower molecular symmetry, but as a result of the disorder of the halogen ligands, they appear to be of the same crystallographic symmetry. The environment around the Si atom can be described as a slightly distorted octahedron with the methyl­pyridine ligands occupying axial positions and the four halogen ligands in the equatorial plane. In spite of the different substitution pattern of the silicon centre, there are only insignificant differences between these five structures.

S1. Comment

In recent years the extension of the coordination sphere of silicon in complexes with organic nitrogen bases has been the subject of numerous studies (Bechstein et al., 1990; Chuit et al., 1993; Kane et al., 1998; Hensen et al., 1998; Hensen et al. 2000). Several complexes of silicon halides are already known, but only little is known about adducts of mixed silicon halides, because exchange reactions have to be taken into account. This kind of exchange reaction between silicon tetrahalides at high temperatures and pressures have been described by Forbes & Anderson (1944) and were recently proved (Hensen et al., 2000) at ambient conditions. Furthermore, it was presumed (Wannagat et al., 1954) that pyridine or comparable ligands catalyze halogen exchange reactions of silicon halides. This would mean that during the reaction of mixed silicon halides with nitrogen bases not only the Lewis acid-base reaction, but also base-catalyzed dismutations have to be taken into account (Hass & Bechstein, 1981; Bassindale et al., 1995; Kost et al., 1995; Herzog et al., 1996; Boudjouk et al., 1998). We present in this work the first crystal structures of complexes in which the silicon centre carries different halogen ligands. \sch

All five compounds form isomorphous crystals and the cell parameters show only minor differences. However, the following trends are noticeable: in the line from SiCl₄ to SiBr₄ the c axis is shorter, whereas the a and the b axis are longer.

Compounds (I) and (V) belong to the symmetry point group C_{2 h} (deviating only slightly from molecular D_{2 h} symmetry). (II), (III) and (IV) are of lower molecular symmetry, but as a result of the disorder of the halogen ligands, they display the same crystallographic symmetry as (I) and (V). The Si atom is located on a special position of site symmetry 2/m and the picoline moieties lie on a crystallographic mirror plane. Only the halogen ligands and two H atoms of each methyl group occupy a general position. The silicon centre appears in a nearly ideal octahedral environment, where the two picoline ligands occupy axial positions and the four halogen ligands lie in the equatorial plane. There are only minor deviations from the perfect octahedral coordination. The planes of the methylpyridine rings bisect the Hal-Si-Hal angle almost exactly. As a result of the crystallographic symmetry the N—Si—N bond angles and the Hal-Si-Hal bond angles of opposite halogen atoms are exactly 180°. The remaining bond angles at Si differ only insignificantly from 90°. In spite of the different substitution pattern of the silicon centre, comparable geometric parameters are nearly identical in all five structures: the mean value of the Si—N bond length is 1.980 (4) Å. The C—N—C angle [mean value is 117.6 (1)°] is not affected by the different substitution pattern of the silicon centre, either. The crystallographic symmetry requires that there is only a quarter of the molecule in the asymmetric unit. As a result of that, the halogen atoms in (II), (III) and (IV) are disordered and they cannot be distinguished (see experimental section).

The molecules crystallize in planes perpendicular to the crystallographic a axis. The distance between these planes is a/2. A view onto these planes demonstrates (Fig. 4), that the aromatic residues are nearly perfectly stacked and the Si-Hal₄ moieties fill the remaining gaps.

The structures presented in this paper are isostructural with trans-tetrachlorobis(4-methylpyridine)titanium (Hensen et al., 1999). The presence of an aromatic base during the reaction to synthesize these compounds did not considerably stimulate the halogen exchange, a fact that has already been observed (Hensen et al., 2000). As a result of that, no dismutation could be detected and each of the reaction products could be recrystallized. This result could also be attributed to the high dilution of the substance in the solvent and the fact that the complexes are extremely poorly soluble.

S2. Experimental

To the respective silicon halide (5 mmol) in chloroform (25 ml) 4-picoline was added and the reaction was monitored by measuring the temperature. After approximately 3 h, the precipitated solid was isolated, washed and dried. Crystals of (V) were obtained by heating the powder in an evacuated glas ampul for 2 h to 500 K, then for 5 h to 445 K and cooling down the sample to room temperature within 4 h. (I) to (IV) were dissolved in hot chloroform and crystals appeared within 10 to 15 h at room temperature. Elemental analyses: (II), C₁₂H₁₄BrCl₃Si: calculated: C 36.0, H 3.5, Br 19.9, Cl 26.5, N 7.0%; found: C 36.3, H 3.7, Br 18.9, Cl 25.7, N 7.0%; (III), C₁₂H₁₄Br₂Cl₂Si: calculated: C 32.4, H 3.2, Br 35.9, Cl 15.9, N 6.3%; found: C 33.0, H 3.3, Br 36.3, Cl 16.1, N 6.3%; (IV), C₁₂H₁₄Br₃ClSi: calculated: C 30.9, H 3.4, Br 47.5, Cl 7.0, N 5.6%; found: C 30.1, H 3.4, Br 48.8, Cl 6.1, N 5.8%.

S3. Refinement

All H atoms were initially located by difference Fourier synthesis. Subsequently their positions were idealized and constrained to ride on their parent atoms with C—H(aromatic) = 0.95 and C—H(methyl = 0.98 Å, and fixed individual displacement parameters [U(H) = 1.2U_eq(C_aromatic) or U(H) = 1.5U_eq(C_methyl)]. The hydrogen atoms of the methyl groups are disordered. Two orientations differing by a 60° rotation about the C_aromatic—C_methyl bond could be identified.

Due to the crystallographic symmetry of these structures, the halogen atoms of (II), (III) and (IV) are disordered. The resolution of the data did not allow for distinguishing two distinct positions for Cl and Br. Only one peak was found in the respective difference maps. Thus, Br and Cl were refined with a site occupation factor fixed to the appropriate value (according to the elemental analyses) and a restrained bond length of 2.383 (1) Å and 2.203 (1) Å for Si—Br and Si—Cl, respectively. A search in the Cambridge Crystallographic Database (Version 5.18, October 1999; Allen & Kennard, 1993) for the fragment SiN₂X₄ (X = any group 7 A element) yielded only one comparable structure: tetrachlorodipyridylsilane (Bechstein et al., 1990) which was measured at room temperature. Thus, we employed the values found in (I) and (V) as restraints for the Si—Cl and Si—Br lengths. For (II) the anisotropic displacement parameters of Cl and Br were restrained to have the same U^ij components with an effective standard deviation of 0.001.

Computing details

For all compounds, data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (in SHELXTL-Plus, 1991).

Figures

	Fig. 1. Perspective view of (I) with the atom numbering; only symmetry independent atoms are labelled; displacement ellipsoids are at the 50% probability level.
	Fig. 2. Perspective view of (II) with the atom numbering; only symmetry independent atoms are labelled; displacement ellipsoids are at the 50% probability level. The crystallographic symmetry imposes Br/Cl disorder at the site of each halogen ligand. This figure is also representative of the structures of (III) and (IV).
	Fig. 3. Perspective view of (V) with the atom numbering; only symmetry independent atoms are labelled; displacement ellipsoids are at the 50% probability level.
	Fig. 4. Packing diagram of (I) representative for all five structures; view perpendicular to the b/c plane.

(I) ;

Crystal data

C12H14Cl4N2Si	F(000) = 364
Mr = 356.14	Dx = 1.524 Mg m^−3
Orthorhombic, Pmna	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2	Cell parameters from 8192 reflections
a = 7.1766 (1) Å	θ = 1–25°
b = 7.8911 (1) Å	µ = 0.83 mm^−1
c = 13.7036 (1) Å	T = 173 K
V = 776.05 (2) Å^3	Block, colourless
Z = 2	0.60 × 0.40 × 0.40 mm

Data collection

Siemens CCD three-circle diffractometer	853 independent reflections
Radiation source: fine-focus sealed tube	815 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
ω scans	θmax = 26.3°, θmin = 2.6°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −8→8
Tmin = 0.637, Tmax = 0.733	k = −9→9
10172 measured reflections	l = −16→16

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)] = 0.020	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.058	H atoms treated by a mixture of independent and constrained refinement
S = 1.15	w = 1/[σ^2(Fo^2) + (0.0314P)^2 + 0.2249P] where P = (Fo^2 + 2Fc^2)/3
853 reflections	(Δ/σ)max < 0.001
56 parameters	Δρmax = 0.26 e Å^−3
0 restraints	Δρmin = −0.18 e Å^−3

Special details

Experimental. The data collection nominally covered a sphere of reciprocal space, by a combination of seven, for (I), (III), (IV) and (V), and eight, for (II), sets of exposures; each set had a different ϕ angle for the crystal and each exposure covered 0.3° in ω. The crystal-to-detector distance was 4 cm for (II) and (IV), 5 cm for (III) and 6 cm for (I) and (V). Coverage of the unique set for all structures is 100% complete to at least 25.0° in θ. Crystal decay was monitored by repeating the initial frames at the end of data collection and analyzing the duplicate reflections.

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	Occ. (<1)
Si1	0.0000	0.5000	0.5000	0.01946 (16)
Cl1	0.21877 (5)	0.33821 (4)	0.43645 (2)	0.03014 (14)
N1	0.0000	0.64104 (17)	0.38019 (10)	0.0208 (3)
C2	0.0000	0.8127 (2)	0.38592 (13)	0.0245 (4)
H2	0.0000	0.8642	0.4486	0.029*
C3	0.0000	0.9155 (2)	0.30441 (13)	0.0263 (4)
H3	0.0000	1.0352	0.3118	0.032*
C4	0.0000	0.8439 (2)	0.21074 (13)	0.0237 (4)
C41	0.0000	0.9519 (2)	0.11990 (13)	0.0313 (4)
H41A	0.0000	0.8795	0.0618	0.047*	0.50
H41B	0.1106	1.0248	0.1195	0.047*	0.50
H41C	0.0000	1.0722	0.1377	0.047*	0.50
H41D	0.1083	0.9268	0.0814	0.047*	0.50
C5	0.0000	0.6671 (2)	0.20496 (13)	0.0251 (4)
H5	0.0000	0.6129	0.1430	0.030*
C6	0.0000	0.5706 (2)	0.28969 (12)	0.0249 (4)
H6	0.0000	0.4506	0.2842	0.030*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.0231 (3)	0.0158 (3)	0.0195 (3)	0.000	0.000	0.0019 (2)
Cl1	0.0340 (2)	0.0270 (2)	0.0295 (2)	0.01011 (12)	0.00782 (12)	0.00549 (11)
N1	0.0242 (7)	0.0178 (6)	0.0205 (7)	0.000	0.000	0.0023 (5)
C2	0.0307 (9)	0.0193 (8)	0.0234 (8)	0.000	0.000	−0.0003 (6)
C3	0.0312 (9)	0.0185 (8)	0.0292 (9)	0.000	0.000	0.0040 (7)
C4	0.0196 (8)	0.0263 (9)	0.0253 (9)	0.000	0.000	0.0076 (7)
C41	0.0337 (10)	0.0325 (9)	0.0275 (9)	0.000	0.000	0.0114 (8)
C5	0.0282 (9)	0.0264 (9)	0.0206 (8)	0.000	0.000	0.0006 (6)
C6	0.0309 (9)	0.0196 (8)	0.0242 (8)	0.000	0.000	0.0006 (7)

Geometric parameters (Å, º)

Si1—N1^i	1.9835 (13)	C3—H3	0.9500
Si1—N1	1.9835 (13)	C4—C5	1.397 (2)
Si1—Cl1^ii	2.2030 (3)	C4—C41	1.509 (2)
Si1—Cl1^iii	2.2030 (3)	C41—H41A	0.9800
Si1—Cl1^i	2.2030 (3)	C41—H41B	0.9800
Si1—Cl1	2.2030 (3)	C41—H41C	0.9800
N1—C2	1.357 (2)	C41—H41D	0.9600
N1—C6	1.359 (2)	C5—C6	1.389 (2)
C2—C3	1.381 (2)	C5—H5	0.9500
C2—H2	0.9500	C6—H6	0.9500
C3—C4	1.403 (3)
N1^i—Si1—N1	180.000 (1)	C2—C3—H3	119.9
N1^i—Si1—Cl1^ii	90.12 (3)	C4—C3—H3	119.9
N1—Si1—Cl1^ii	89.88 (3)	C5—C4—C3	117.03 (16)
N1^i—Si1—Cl1^iii	89.88 (3)	C5—C4—C41	121.17 (17)
N1—Si1—Cl1^iii	90.12 (3)	C3—C4—C41	121.80 (15)
Cl1^ii—Si1—Cl1^iii	180.0	C4—C41—H41A	109.9
N1^i—Si1—Cl1^i	89.88 (3)	C4—C41—H41B	109.7
N1—Si1—Cl1^i	90.12 (3)	H41A—C41—H41B	109.7
Cl1^ii—Si1—Cl1^i	89.098 (18)	C4—C41—H41C	110.0
Cl1^iii—Si1—Cl1^i	90.902 (18)	H41A—C41—H41C	140.1
N1^i—Si1—Cl1	90.12 (3)	H41B—C41—H41C	55.5
N1—Si1—Cl1	89.88 (3)	C4—C41—H41D	109.7
Cl1^ii—Si1—Cl1	90.902 (18)	H41A—C41—H41D	55.5
Cl1^iii—Si1—Cl1	89.098 (18)	H41B—C41—H41D	57.4
Cl1^i—Si1—Cl1	179.999 (12)	H41C—C41—H41D	109.7
C2—N1—C6	117.47 (14)	C6—C5—C4	120.01 (17)
C2—N1—Si1	120.81 (12)	C6—C5—H5	120.0
C6—N1—Si1	121.72 (11)	C4—C5—H5	120.0
N1—C2—C3	122.68 (16)	N1—C6—C5	122.59 (15)
N1—C2—H2	118.7	N1—C6—H6	118.7
C3—C2—H2	118.7	C5—C6—H6	118.7
C2—C3—C4	120.22 (15)
N1^i—Si1—N1—C2	0.0 (2)	C6—N1—C2—C3	0.0
Cl1^ii—Si1—N1—C2	134.549 (9)	Si1—N1—C2—C3	180.0
Cl1^iii—Si1—N1—C2	−45.451 (9)	N1—C2—C3—C4	0.0
Cl1^i—Si1—N1—C2	45.451 (9)	C2—C3—C4—C5	0.0
Cl1—Si1—N1—C2	−134.548 (9)	C2—C3—C4—C41	180.0
N1^i—Si1—N1—C6	180.0 (2)	C3—C4—C5—C6	0.0
Cl1^ii—Si1—N1—C6	−45.451 (9)	C41—C4—C5—C6	180.0
Cl1^iii—Si1—N1—C6	134.549 (9)	C2—N1—C6—C5	0.0
Cl1^i—Si1—N1—C6	−134.549 (9)	Si1—N1—C6—C5	180.0
Cl1—Si1—N1—C6	45.452 (9)	C4—C5—C6—N1	0.0

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

(II) ;

Crystal data

C12H14BrCl3N2Si	F(000) = 400
Mr = 400.60	Dx = 1.717 Mg m^−3
Orthorhombic, Pmna	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2	Cell parameters from 8192 reflections
a = 7.177 (1) Å	θ = 1–25°
b = 7.962 (1) Å	µ = 3.24 mm^−1
c = 13.557 (1) Å	T = 173 K
V = 774.69 (16) Å^3	Plate, colourless
Z = 2	0.40 × 0.30 × 0.10 mm

Data collection

Siemens CCD three-circle diffractometer	1278 independent reflections
Radiation source: fine-focus sealed tube	1051 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
ω scans	θmax = 30.5°, θmin = 2.6°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.358, Tmax = 0.738	k = −11→11
24114 measured reflections	l = −19→19

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0576P)^2 + 0.7835P] where P = (Fo^2 + 2Fc^2)/3
1278 reflections	(Δ/σ)max < 0.001
65 parameters	Δρmax = 0.65 e Å^−3
8 restraints	Δρmin = −1.14 e Å^−3

Special details

Experimental. ;

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	Occ. (<1)
Br1	0.7267 (10)	0.1751 (10)	0.4254 (6)	0.0279 (7)	0.25
Cl1	0.7230 (7)	0.1548 (8)	0.4385 (5)	0.0236 (5)	0.75
Si1	0.5000	0.0000	0.5000	0.0172 (3)
N1	0.5000	0.1414 (4)	0.6195 (2)	0.0185 (6)
C2	0.5000	0.3104 (5)	0.6123 (3)	0.0219 (7)
H2	0.5000	0.3600	0.5486	0.026*
C3	0.5000	0.4138 (5)	0.6940 (3)	0.0234 (8)
H3	0.5000	0.5323	0.6857	0.028*
C4	0.5000	0.3448 (5)	0.7886 (3)	0.0202 (7)
C41	0.5000	0.4528 (6)	0.8791 (3)	0.0291 (9)
H41A	0.5000	0.5667	0.8613	0.044*	0.50
H41B	0.3975	0.4223	0.9200	0.044*	0.50
H41C	0.5000	0.3880	0.9384	0.044*	0.50
H41D	0.3929	0.5222	0.8774	0.044*	0.50
C5	0.5000	0.1699 (5)	0.7956 (3)	0.0228 (8)
H5	0.5000	0.1174	0.8585	0.027*
C6	0.5000	0.0735 (5)	0.7111 (3)	0.0220 (7)
H6	0.5000	−0.0454	0.7173	0.026*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0369 (7)	0.0240 (16)	0.0227 (19)	−0.0067 (7)	0.0049 (8)	0.0017 (11)
Cl1	0.0324 (5)	0.0195 (12)	0.0190 (14)	−0.0103 (6)	0.0087 (6)	0.0009 (8)
Si1	0.0221 (7)	0.0139 (6)	0.0156 (6)	0.000	0.000	−0.0020 (5)
N1	0.0233 (14)	0.0164 (13)	0.0157 (14)	0.000	0.000	−0.0025 (11)
C2	0.0284 (19)	0.0187 (16)	0.0187 (17)	0.000	0.000	0.0001 (13)
C3	0.0308 (19)	0.0177 (16)	0.0215 (18)	0.000	0.000	−0.0038 (14)
C4	0.0192 (16)	0.0222 (17)	0.0191 (17)	0.000	0.000	−0.0067 (14)
C41	0.032 (2)	0.033 (2)	0.0217 (19)	0.000	0.000	−0.0109 (16)
C5	0.0268 (18)	0.0249 (18)	0.0168 (17)	0.000	0.000	−0.0014 (14)
C6	0.0292 (18)	0.0181 (16)	0.0187 (17)	0.000	0.000	0.0003 (13)

Geometric parameters (Å, º)

Br1—Si1	2.3695 (11)	C2—H2	0.9500
Cl1—Si1	2.1856 (10)	C3—C4	1.396 (5)
Si1—N1	1.973 (3)	C3—H3	0.9500
Si1—N1^i	1.973 (3)	C4—C5	1.396 (5)
Si1—Cl1^i	2.1855 (10)	C4—C41	1.498 (5)
Si1—Cl1^ii	2.1855 (10)	C41—H41A	0.9381
Si1—Cl1^iii	2.1856 (10)	C41—H41B	0.9532
Si1—Br1^i	2.3695 (11)	C41—H41C	0.9553
Si1—Br1^ii	2.3695 (11)	C41—H41D	0.9471
Si1—Br1^iii	2.3695 (11)	C5—C6	1.380 (5)
N1—C2	1.349 (5)	C5—H5	0.9500
N1—C6	1.354 (5)	C6—H6	0.9500
C2—C3	1.380 (5)
N1—Si1—N1^i	180.0	N1^i—Si1—Br1^iii	89.1 (2)
N1—Si1—Cl1^i	90.5 (2)	Cl1^i—Si1—Br1^iii	89.52 (6)
N1^i—Si1—Cl1^i	89.5 (2)	Cl1^ii—Si1—Br1^iii	176.1 (4)
N1—Si1—Cl1^ii	90.5 (2)	Cl1—Si1—Br1^iii	90.48 (6)
N1^i—Si1—Cl1^ii	89.5 (2)	Cl1^iii—Si1—Br1^iii	3.9 (4)
Cl1^i—Si1—Cl1^ii	94.2 (4)	Br1^i—Si1—Br1^iii	93.2 (5)
N1—Si1—Cl1	89.5 (2)	Br1^ii—Si1—Br1^iii	179.999 (1)
N1^i—Si1—Cl1	90.5 (2)	Br1—Si1—Br1^iii	86.8 (5)
Cl1^i—Si1—Cl1	180.0	C2—N1—C6	117.7 (3)
Cl1^ii—Si1—Cl1	85.8 (4)	C2—N1—Si1	120.7 (3)
N1—Si1—Cl1^iii	89.5 (2)	C6—N1—Si1	121.6 (2)
N1^i—Si1—Cl1^iii	90.5 (2)	N1—C2—C3	122.5 (4)
Cl1^i—Si1—Cl1^iii	85.8 (4)	N1—C2—H2	118.7
Cl1^ii—Si1—Cl1^iii	180.0 (3)	C3—C2—H2	118.7
Cl1—Si1—Cl1^iii	94.2 (4)	C2—C3—C4	120.2 (3)
N1—Si1—Br1^i	89.1 (2)	C2—C3—H3	119.9
N1^i—Si1—Br1^i	90.9 (2)	C4—C3—H3	119.9
Cl1^i—Si1—Br1^i	3.9 (4)	C3—C4—C5	117.1 (3)
Cl1^ii—Si1—Br1^i	90.48 (6)	C3—C4—C41	121.8 (3)
Cl1—Si1—Br1^i	176.1 (4)	C5—C4—C41	121.1 (4)
Cl1^iii—Si1—Br1^i	89.52 (6)	C4—C41—H41A	110.2
N1—Si1—Br1^ii	89.1 (2)	C4—C41—H41B	109.3
N1^i—Si1—Br1^ii	90.9 (2)	H41A—C41—H41B	113.3
Cl1^i—Si1—Br1^ii	90.48 (6)	C4—C41—H41C	112.3
Cl1^ii—Si1—Br1^ii	3.9 (4)	H41A—C41—H41C	137.6
Cl1—Si1—Br1^ii	89.52 (6)	H41B—C41—H41C	51.1
Cl1^iii—Si1—Br1^ii	176.1 (4)	C4—C41—H41D	108.4
Br1^i—Si1—Br1^ii	86.8 (5)	H41A—C41—H41D	55.2
N1—Si1—Br1	90.9 (2)	H41B—C41—H41D	62.3
N1^i—Si1—Br1	89.1 (2)	H41C—C41—H41D	109.6
Cl1^i—Si1—Br1	176.1 (4)	C6—C5—C4	119.9 (4)
Cl1^ii—Si1—Br1	89.52 (6)	C6—C5—H5	120.0
Cl1—Si1—Br1	3.9 (4)	C4—C5—H5	120.0
Cl1^iii—Si1—Br1	90.48 (6)	N1—C6—C5	122.6 (3)
Br1^i—Si1—Br1	180.0	N1—C6—H6	118.7
Br1^ii—Si1—Br1	93.2 (5)	C5—C6—H6	118.7
N1—Si1—Br1^iii	90.9 (2)
N1^i—Si1—N1—C2	−1 (100)	Br1^i—Si1—N1—C6	43.4 (2)
Cl1^i—Si1—N1—C2	−132.91 (19)	Br1^ii—Si1—N1—C6	−43.4 (2)
Cl1^ii—Si1—N1—C2	132.91 (19)	Br1—Si1—N1—C6	−136.6 (2)
Cl1—Si1—N1—C2	47.09 (19)	Br1^iii—Si1—N1—C6	136.6 (2)
Cl1^iii—Si1—N1—C2	−47.09 (19)	C6—N1—C2—C3	0.000 (2)
Br1^i—Si1—N1—C2	−136.6 (2)	Si1—N1—C2—C3	180.000 (1)
Br1^ii—Si1—N1—C2	136.6 (2)	N1—C2—C3—C4	0.000 (2)
Br1—Si1—N1—C2	43.4 (2)	C2—C3—C4—C5	0.000 (2)
Br1^iii—Si1—N1—C2	−43.4 (2)	C2—C3—C4—C41	180.000 (2)
N1^i—Si1—N1—C6	179.4 (5)	C3—C4—C5—C6	0.000 (2)
Cl1^i—Si1—N1—C6	47.09 (19)	C41—C4—C5—C6	180.000 (2)
Cl1^ii—Si1—N1—C6	−47.09 (19)	C2—N1—C6—C5	0.000 (2)
Cl1—Si1—N1—C6	−132.91 (19)	Si1—N1—C6—C5	180.000 (1)
Cl1^iii—Si1—N1—C6	132.91 (19)	C4—C5—C6—N1	0.000 (2)

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

(III) ;

Crystal data

C12H14Br2Cl2N2Si	F(000) = 436
Mr = 445.06	Dx = 1.854 Mg m^−3
Orthorhombic, Pmna	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2	Cell parameters from 7725 reflections
a = 7.252 (2) Å	θ = 1–25°
b = 8.120 (2) Å	µ = 5.48 mm^−1
c = 13.540 (3) Å	T = 173 K
V = 797.3 (3) Å^3	Block, colourless
Z = 2	0.35 × 0.30 × 0.12 mm

Data collection

Siemens CCD three-circle diffractometer	1110 independent reflections
Radiation source: fine-focus sealed tube	969 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.042
ω scans	θmax = 28.7°, θmin = 2.5°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.162, Tmax = 0.520	k = −10→10
14499 measured reflections	l = −16→18

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.027	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.063	w = 1/[σ^2(Fo^2) + (0.0269P)^2 + 0.6549P] where P = (Fo^2 + 2Fc^2)/3
S = 1.12	(Δ/σ)max = 0.005
1110 reflections	Δρmax = 0.38 e Å^−3
66 parameters	Δρmin = −0.37 e Å^−3
2 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0048 (9)

Special details

Experimental. ;

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	Occ. (<1)
Br1	0.2298 (6)	0.1680 (6)	0.4263 (4)	0.0274 (4)	0.50
Cl1	0.2237 (13)	0.1512 (14)	0.4383 (9)	0.0247 (8)	0.50
Si1	0.0000	0.0000	0.5000	0.0185 (2)
N1	0.0000	0.1419 (3)	0.61919 (17)	0.0194 (5)
C2	0.0000	0.3083 (4)	0.6110 (2)	0.0234 (6)
H2	0.0000	0.3559	0.5469	0.028*
C3	0.0000	0.4114 (4)	0.6923 (2)	0.0239 (6)
H3	0.0000	0.5274	0.6833	0.029*
C4	0.0000	0.3450 (4)	0.7877 (2)	0.0223 (6)
C41	0.0000	0.4530 (4)	0.8779 (2)	0.0308 (7)
H41A	0.0000	0.5669	0.8602	0.046*	0.50
H41B	−0.1025	0.4225	0.9189	0.046*	0.50
H41C	0.0000	0.3882	0.9372	0.046*	0.50
H41D	−0.1071	0.5224	0.8763	0.046*	0.50
C5	0.0000	0.1736 (4)	0.7959 (2)	0.0236 (6)
H5	0.0000	0.1234	0.8593	0.028*
C6	0.0000	0.0765 (4)	0.7116 (2)	0.0224 (6)
H6	0.0000	−0.0399	0.7187	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0322 (6)	0.0237 (9)	0.0263 (12)	−0.0079 (3)	0.0068 (5)	−0.0018 (6)
Cl1	0.0340 (11)	0.0212 (18)	0.0189 (18)	−0.0115 (10)	0.0101 (9)	−0.0018 (13)
Si1	0.0243 (5)	0.0139 (5)	0.0173 (5)	0.000	0.000	−0.0025 (4)
N1	0.0248 (12)	0.0164 (11)	0.0170 (11)	0.000	0.000	−0.0023 (9)
C2	0.0319 (16)	0.0171 (13)	0.0212 (14)	0.000	0.000	−0.0003 (11)
C3	0.0290 (15)	0.0165 (13)	0.0263 (15)	0.000	0.000	−0.0061 (11)
C4	0.0205 (13)	0.0240 (14)	0.0224 (13)	0.000	0.000	−0.0073 (12)
C41	0.0367 (18)	0.0312 (17)	0.0246 (16)	0.000	0.000	−0.0134 (13)
C5	0.0282 (15)	0.0251 (14)	0.0176 (14)	0.000	0.000	−0.0011 (11)
C6	0.0303 (15)	0.0165 (13)	0.0205 (13)	0.000	0.000	−0.0008 (11)

Geometric parameters (Å, º)

Br1—Si1	2.3734 (8)	C2—H2	0.9500
Cl1—Si1	2.1994 (11)	C3—C4	1.399 (4)
Si1—N1	1.983 (2)	C3—H3	0.9500
Si1—N1^i	1.983 (2)	C4—C5	1.397 (4)
Si1—Cl1^i	2.1993 (11)	C4—C41	1.504 (4)
Si1—Cl1^ii	2.1993 (11)	C41—H41A	0.9555
Si1—Cl1^iii	2.1994 (11)	C41—H41B	0.9600
Si1—Br1^i	2.3734 (8)	C41—H41C	0.9600
Si1—Br1^ii	2.3734 (8)	C41—H41D	0.9600
Si1—Br1^iii	2.3734 (8)	C5—C6	1.388 (4)
N1—C2	1.355 (4)	C5—H5	0.9500
N1—C6	1.359 (4)	C6—H6	0.9500
C2—C3	1.382 (4)
N1—Si1—N1^i	180.0	N1^i—Si1—Br1^iii	89.54 (15)
N1—Si1—Cl1^i	90.9 (3)	Cl1^i—Si1—Br1^iii	87.8 (2)
N1^i—Si1—Cl1^i	89.1 (3)	Cl1^ii—Si1—Br1^iii	176.8 (5)
N1—Si1—Cl1^ii	90.9 (3)	Cl1^iii—Si1—Br1^iii	3.2 (5)
N1^i—Si1—Cl1^ii	89.1 (3)	Cl1—Si1—Br1^iii	92.2 (2)
Cl1^i—Si1—Cl1^ii	95.1 (7)	Br1^i—Si1—Br1^iii	90.8 (3)
N1—Si1—Cl1^iii	89.1 (3)	Br1^ii—Si1—Br1^iii	179.999 (1)
N1^i—Si1—Cl1^iii	90.9 (3)	Br1—Si1—Br1^iii	89.2 (3)
Cl1^i—Si1—Cl1^iii	84.9 (7)	C2—N1—C6	117.7 (2)
Cl1^ii—Si1—Cl1^iii	179.998 (2)	C2—N1—Si1	120.8 (2)
N1—Si1—Cl1	89.1 (3)	C6—N1—Si1	121.47 (19)
N1^i—Si1—Cl1	90.9 (3)	N1—C2—C3	122.6 (3)
Cl1^i—Si1—Cl1	179.998 (1)	N1—C2—H2	118.7
Cl1^ii—Si1—Cl1	84.9 (7)	C3—C2—H2	118.7
Cl1^iii—Si1—Cl1	95.1 (7)	C2—C3—C4	120.1 (3)
N1—Si1—Br1^i	89.54 (15)	C2—C3—H3	120.0
N1^i—Si1—Br1^i	90.46 (15)	C4—C3—H3	120.0
Cl1^i—Si1—Br1^i	3.2 (5)	C5—C4—C3	117.2 (3)
Cl1^ii—Si1—Br1^i	92.2 (2)	C5—C4—C41	121.1 (3)
Cl1^iii—Si1—Br1^i	87.8 (2)	C3—C4—C41	121.7 (3)
Cl1—Si1—Br1^i	176.8 (5)	C4—C41—H41A	111.1
N1—Si1—Br1^ii	89.54 (14)	C4—C41—H41B	108.6
N1^i—Si1—Br1^ii	90.46 (14)	H41A—C41—H41B	113.3
Cl1^i—Si1—Br1^ii	92.2 (2)	C4—C41—H41C	111.1
Cl1^ii—Si1—Br1^ii	3.2 (5)	H41A—C41—H41C	137.8
Cl1^iii—Si1—Br1^ii	176.8 (5)	H41B—C41—H41C	51.4
Cl1—Si1—Br1^ii	87.8 (2)	C4—C41—H41D	108.9
Br1^i—Si1—Br1^ii	89.2 (3)	H41A—C41—H41D	55.0
N1—Si1—Br1	90.46 (15)	H41B—C41—H41D	62.5
N1^i—Si1—Br1	89.54 (14)	H41C—C41—H41D	110.0
Cl1^i—Si1—Br1	176.8 (5)	C6—C5—C4	120.0 (3)
Cl1^ii—Si1—Br1	87.8 (2)	C6—C5—H5	120.0
Cl1^iii—Si1—Br1	92.2 (2)	C4—C5—H5	120.0
Cl1—Si1—Br1	3.2 (5)	N1—C6—C5	122.4 (3)
Br1^i—Si1—Br1	180.0	N1—C6—H6	118.8
Br1^ii—Si1—Br1	90.8 (3)	C5—C6—H6	118.8
N1—Si1—Br1^iii	90.46 (14)
N1^i—Si1—N1—C2	0 (100)	Br1^i—Si1—N1—C6	44.60 (14)
Cl1^i—Si1—N1—C2	−132.5 (4)	Br1^ii—Si1—N1—C6	−44.60 (14)
Cl1^ii—Si1—N1—C2	132.5 (4)	Br1—Si1—N1—C6	−135.40 (14)
Cl1^iii—Si1—N1—C2	−47.5 (4)	Br1^iii—Si1—N1—C6	135.40 (14)
Cl1—Si1—N1—C2	47.5 (4)	C6—N1—C2—C3	0.000 (1)
Br1^i—Si1—N1—C2	−135.40 (14)	Si1—N1—C2—C3	180.0
Br1^ii—Si1—N1—C2	135.40 (14)	N1—C2—C3—C4	0.000 (1)
Br1—Si1—N1—C2	44.60 (14)	C2—C3—C4—C5	0.000 (1)
Br1^iii—Si1—N1—C2	−44.60 (14)	C2—C3—C4—C41	180.000 (1)
N1^i—Si1—N1—C6	180.0 (4)	C3—C4—C5—C6	0.000 (1)
Cl1^i—Si1—N1—C6	47.5 (4)	C41—C4—C5—C6	180.000 (1)
Cl1^ii—Si1—N1—C6	−47.5 (4)	C2—N1—C6—C5	0.000 (1)
Cl1^iii—Si1—N1—C6	132.5 (4)	Si1—N1—C6—C5	180.0
Cl1—Si1—N1—C6	−132.5 (4)	C4—C5—C6—N1	0.000 (1)

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

(IV) ;

Crystal data

C12H14Br3ClN2Si	F(000) = 472
Mr = 489.52	Dx = 2.014 Mg m^−3
Orthorhombic, Pmna	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2	Cell parameters from 4418 reflections
a = 7.296 (1) Å	θ = 1–25°
b = 8.211 (1) Å	µ = 7.73 mm^−1
c = 13.472 (1) Å	T = 173 K
V = 807.07 (16) Å^3	Block, colourless
Z = 2	0.25 × 0.15 × 0.10 mm

Data collection

Siemens CCD three-circle diffractometer	1005 independent reflections
Radiation source: fine-focus sealed tube	823 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.048
ω scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.224, Tmax = 0.462	k = −10→10
11697 measured reflections	l = −17→17

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.024	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.052	w = 1/[σ^2(Fo^2) + (0.0222P)^2 + 0.3546P] where P = (Fo^2 + 2Fc^2)/3
S = 1.16	(Δ/σ)max = 0.001
1005 reflections	Δρmax = 0.35 e Å^−3
66 parameters	Δρmin = −0.35 e Å^−3
2 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0044 (6)

Special details

Experimental. ;

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	Occ. (<1)
Br1	0.7312 (2)	0.1639 (3)	0.4262 (2)	0.0262 (3)	0.75
Cl1	0.7222 (18)	0.151 (2)	0.4391 (15)	0.0301 (19)	0.25
Si1	0.5000	0.0000	0.5000	0.0167 (3)
N1	0.5000	0.1418 (3)	0.61899 (19)	0.0175 (6)
C2	0.5000	0.3059 (4)	0.6099 (2)	0.0213 (7)
H2	0.5000	0.3521	0.5452	0.026*
C3	0.5000	0.4091 (4)	0.6909 (2)	0.0226 (7)
H3	0.5000	0.5237	0.6813	0.027*
C4	0.5000	0.3451 (4)	0.7868 (3)	0.0205 (7)
C41	0.5000	0.4524 (4)	0.8769 (3)	0.0293 (8)
H41A	0.5000	0.5660	0.8608	0.044*	0.50
H41B	0.3975	0.4217	0.9195	0.044*	0.50
H41C	0.5000	0.3873	0.9378	0.044*	0.50
H41D	0.3929	0.5216	0.8769	0.044*	0.50
C5	0.5000	0.1763 (4)	0.7955 (2)	0.0219 (7)
H5	0.5000	0.1276	0.8595	0.026*
C6	0.5000	0.0793 (4)	0.7124 (2)	0.0202 (7)
H6	0.5000	−0.0356	0.7205	0.024*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0282 (4)	0.0239 (4)	0.0266 (8)	−0.0081 (3)	0.0074 (3)	−0.0045 (3)
Cl1	0.044 (3)	0.032 (3)	0.014 (3)	−0.017 (2)	0.0137 (17)	−0.004 (2)
Si1	0.0211 (6)	0.0135 (6)	0.0154 (5)	0.000	0.000	−0.0028 (5)
N1	0.0212 (13)	0.0152 (14)	0.0161 (12)	0.000	0.000	−0.0035 (11)
C2	0.0299 (18)	0.0155 (16)	0.0184 (15)	0.000	0.000	0.0005 (13)
C3	0.0286 (18)	0.0132 (15)	0.0260 (18)	0.000	0.000	−0.0044 (14)
C4	0.0158 (15)	0.0222 (17)	0.0235 (15)	0.000	0.000	−0.0088 (14)
C41	0.035 (2)	0.027 (2)	0.0262 (18)	0.000	0.000	−0.0124 (15)
C5	0.0266 (17)	0.0229 (17)	0.0163 (15)	0.000	0.000	−0.0015 (14)
C6	0.0262 (17)	0.0128 (16)	0.0218 (15)	0.000	0.000	0.0000 (14)

Geometric parameters (Å, º)

Br1—Si1	2.3758 (6)	C2—H2	0.9500
Cl1—Si1	2.2021 (11)	C3—C4	1.394 (5)
Si1—N1^i	1.981 (2)	C3—H3	0.9500
Si1—N1	1.981 (2)	C4—C5	1.391 (4)
Si1—Cl1^ii	2.2021 (11)	C4—C41	1.500 (5)
Si1—Cl1^i	2.2022 (11)	C41—H41A	0.9578
Si1—Cl1^iii	2.2022 (11)	C41—H41B	0.9759
Si1—Br1^ii	2.3758 (6)	C41—H41C	0.9794
Si1—Br1^i	2.3758 (6)	C41—H41D	0.9659
Si1—Br1^iii	2.3758 (6)	C5—C6	1.374 (5)
N1—C2	1.353 (4)	C5—H5	0.9500
N1—C6	1.359 (4)	C6—H6	0.9500
C2—C3	1.382 (4)
N1^i—Si1—N1	180.0	N1—Si1—Br1^iii	89.68 (9)
N1^i—Si1—Cl1	91.7 (6)	Cl1—Si1—Br1^iii	87.3 (4)
N1—Si1—Cl1	88.3 (6)	Cl1^ii—Si1—Br1^iii	177.0 (6)
N1^i—Si1—Cl1^ii	91.7 (6)	Cl1^i—Si1—Br1^iii	92.7 (4)
N1—Si1—Cl1^ii	88.3 (6)	Cl1^iii—Si1—Br1^iii	3.0 (6)
Cl1—Si1—Cl1^ii	94.8 (10)	Br1^ii—Si1—Br1^iii	180.0
N1^i—Si1—Cl1^i	88.3 (6)	Br1—Si1—Br1^iii	89.53 (11)
N1—Si1—Cl1^i	91.7 (6)	Br1^i—Si1—Br1^iii	90.47 (11)
Cl1—Si1—Cl1^i	180.0	C2—N1—C6	117.4 (3)
Cl1^ii—Si1—Cl1^i	85.2 (10)	C2—N1—Si1	120.8 (2)
N1^i—Si1—Cl1^iii	88.3 (6)	C6—N1—Si1	121.8 (2)
N1—Si1—Cl1^iii	91.7 (6)	N1—C2—C3	122.6 (3)
Cl1—Si1—Cl1^iii	85.2 (10)	N1—C2—H2	118.7
Cl1^ii—Si1—Cl1^iii	179.998 (3)	C3—C2—H2	118.7
Cl1^i—Si1—Cl1^iii	94.8 (10)	C2—C3—C4	120.1 (3)
N1^i—Si1—Br1^ii	89.68 (9)	C2—C3—H3	120.0
N1—Si1—Br1^ii	90.32 (9)	C4—C3—H3	120.0
Cl1—Si1—Br1^ii	92.7 (4)	C5—C4—C3	117.0 (3)
Cl1^ii—Si1—Br1^ii	3.0 (6)	C5—C4—C41	121.1 (3)
Cl1^i—Si1—Br1^ii	87.3 (4)	C3—C4—C41	121.9 (3)
Cl1^iii—Si1—Br1^ii	177.0 (6)	C4—C41—H41A	112.8
N1^i—Si1—Br1	89.68 (9)	C4—C41—H41B	108.9
N1—Si1—Br1	90.32 (9)	H41A—C41—H41B	112.7
Cl1—Si1—Br1	3.0 (6)	C4—C41—H41C	111.0
Cl1^ii—Si1—Br1	92.7 (4)	H41A—C41—H41C	136.2
Cl1^i—Si1—Br1	177.0 (6)	H41B—C41—H41C	50.7
Cl1^iii—Si1—Br1	87.3 (4)	C4—C41—H41D	110.2
Br1^ii—Si1—Br1	90.47 (11)	H41A—C41—H41D	55.1
N1^i—Si1—Br1^i	90.32 (9)	H41B—C41—H41D	62.1
N1—Si1—Br1^i	89.68 (9)	H41C—C41—H41D	108.7
Cl1—Si1—Br1^i	177.0 (6)	C6—C5—C4	120.6 (3)
Cl1^ii—Si1—Br1^i	87.3 (4)	C6—C5—H5	119.7
Cl1^i—Si1—Br1^i	3.0 (6)	C4—C5—H5	119.7
Cl1^iii—Si1—Br1^i	92.7 (4)	N1—C6—C5	122.4 (3)
Br1^ii—Si1—Br1^i	89.53 (11)	N1—C6—H6	118.8
Br1—Si1—Br1^i	180.0	C5—C6—H6	118.8
N1^i—Si1—Br1^iii	90.32 (9)
N1^i—Si1—N1—C2	−179.7 (7)	Br1^ii—Si1—N1—C6	134.76 (5)
Cl1—Si1—N1—C2	47.4 (5)	Br1—Si1—N1—C6	−134.76 (5)
Cl1^ii—Si1—N1—C2	−47.4 (5)	Br1^i—Si1—N1—C6	45.24 (5)
Cl1^i—Si1—N1—C2	−132.6 (5)	Br1^iii—Si1—N1—C6	−45.24 (5)
Cl1^iii—Si1—N1—C2	132.6 (5)	C6—N1—C2—C3	0.000 (1)
Br1^ii—Si1—N1—C2	−45.24 (5)	Si1—N1—C2—C3	180.000 (1)
Br1—Si1—N1—C2	45.24 (5)	N1—C2—C3—C4	0.000 (2)
Br1^i—Si1—N1—C2	−134.76 (5)	C2—C3—C4—C5	0.000 (2)
Br1^iii—Si1—N1—C2	134.76 (5)	C2—C3—C4—C41	180.000 (1)
N1^i—Si1—N1—C6	0 (100)	C3—C4—C5—C6	0.000 (2)
Cl1—Si1—N1—C6	−132.6 (5)	C41—C4—C5—C6	180.000 (1)
Cl1^ii—Si1—N1—C6	132.6 (5)	C2—N1—C6—C5	0.000 (1)
Cl1^i—Si1—N1—C6	47.4 (5)	Si1—N1—C6—C5	180.0
Cl1^iii—Si1—N1—C6	−47.4 (5)	C4—C5—C6—N1	0.000 (2)

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

(V) ;

Crystal data

C12H14Br4N2Si	F(000) = 508
Mr = 533.98	Dx = 2.178 Mg m^−3
Orthorhombic, Pmna	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2	Cell parameters from 7725 reflections
a = 7.3298 (2) Å	θ = 1–25°
b = 8.2819 (3) Å	µ = 9.95 mm^−1
c = 13.4126 (3) Å	T = 143 K
V = 814.21 (4) Å^3	Block, colourless
Z = 2	0.30 × 0.20 × 0.05 mm

Data collection

Siemens CCD three-circle diffractometer	907 independent reflections
Radiation source: fine-focus sealed tube	728 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
ω scans	θmax = 26.4°, θmin = 2.9°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.105, Tmax = 0.609	k = −10→10
7079 measured reflections	l = −14→16

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.065	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0342P)^2 + 0.9192P] where P = (Fo^2 + 2Fc^2)/3
907 reflections	(Δ/σ)max = 0.001
56 parameters	Δρmax = 0.63 e Å^−3
0 restraints	Δρmin = −0.48 e Å^−3

Special details

Experimental. ;

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	Occ. (<1)
Br1	0.23257 (4)	0.16177 (4)	0.42619 (3)	0.02330 (15)
Si1	0.0000	0.0000	0.5000	0.0150 (4)
N1	0.0000	0.1415 (5)	0.6189 (3)	0.0168 (9)
C2	0.0000	0.3052 (6)	0.6088 (4)	0.0176 (10)
H2	0.0000	0.3504	0.5437	0.021*
C3	0.0000	0.4080 (6)	0.6901 (4)	0.0204 (11)
H3	0.0000	0.5215	0.6800	0.024*
C4	0.0000	0.3460 (6)	0.7870 (4)	0.0197 (10)
C41	0.0000	0.4520 (6)	0.8766 (4)	0.0264 (12)
H41A	0.0000	0.5668	0.8598	0.040*	0.50
H41B	−0.1025	0.4225	0.9185	0.040*	0.50
H41C	0.0000	0.3881	0.9369	0.040*	0.50
H41D	−0.1071	0.5224	0.8759	0.040*	0.50
C5	0.0000	0.1782 (6)	0.7964 (4)	0.0199 (10)
H5	0.0000	0.1307	0.8608	0.024*
C6	0.0000	0.0803 (6)	0.7130 (4)	0.0191 (10)
H6	0.0000	−0.0335	0.7217	0.023*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0237 (2)	0.0194 (2)	0.0268 (2)	−0.00750 (14)	0.00648 (14)	−0.00455 (15)
Si1	0.0161 (8)	0.0109 (9)	0.0181 (9)	0.000	0.000	−0.0023 (8)
N1	0.0179 (19)	0.014 (2)	0.018 (2)	0.000	0.000	−0.0035 (17)
C2	0.020 (2)	0.010 (2)	0.022 (3)	0.000	0.000	0.0035 (19)
C3	0.026 (3)	0.010 (2)	0.025 (3)	0.000	0.000	−0.002 (2)
C4	0.013 (2)	0.020 (3)	0.026 (2)	0.000	0.000	−0.008 (2)
C41	0.027 (3)	0.026 (3)	0.026 (3)	0.000	0.000	−0.010 (2)
C5	0.020 (2)	0.023 (3)	0.017 (3)	0.000	0.000	−0.004 (2)
C6	0.026 (2)	0.012 (2)	0.019 (2)	0.000	0.000	0.000 (2)

Geometric parameters (Å, º)

Br1—Si1	2.3835 (3)	C3—H3	0.9500
Si1—N1	1.979 (4)	C4—C5	1.396 (7)
Si1—N1^i	1.979 (4)	C4—C41	1.488 (7)
Si1—Br1^i	2.3835 (3)	C41—H41A	0.9777
Si1—Br1^ii	2.3835 (3)	C41—H41B	0.9698
Si1—Br1^iii	2.3835 (3)	C41—H41C	0.9657
N1—C6	1.360 (6)	C41—H41D	0.9781
N1—C2	1.363 (6)	C5—C6	1.381 (7)
C2—C3	1.384 (7)	C5—H5	0.9500
C2—H2	0.9500	C6—H6	0.9500
C3—C4	1.397 (7)
N1—Si1—N1^i	180.0	C2—C3—H3	119.8
N1—Si1—Br1^i	89.89 (8)	C4—C3—H3	119.8
N1^i—Si1—Br1^i	90.11 (8)	C5—C4—C3	116.7 (5)
N1—Si1—Br1^ii	89.89 (8)	C5—C4—C41	121.0 (5)
N1^i—Si1—Br1^ii	90.11 (8)	C3—C4—C41	122.3 (5)
Br1^i—Si1—Br1^ii	91.320 (17)	C4—C41—H41A	112.8
N1—Si1—Br1^iii	90.11 (8)	C4—C41—H41B	108.6
N1^i—Si1—Br1^iii	89.89 (8)	H41A—C41—H41B	112.2
Br1^i—Si1—Br1^iii	88.680 (17)	C4—C41—H41C	110.7
Br1^ii—Si1—Br1^iii	180.0	H41A—C41—H41C	136.5
N1—Si1—Br1	90.11 (8)	H41B—C41—H41C	51.5
N1^i—Si1—Br1	89.89 (8)	C4—C41—H41D	110.1
Br1^i—Si1—Br1	180.0	H41A—C41—H41D	54.4
Br1^ii—Si1—Br1	88.680 (17)	H41B—C41—H41D	62.2
Br1^iii—Si1—Br1	91.320 (17)	H41C—C41—H41D	109.5
C6—N1—C2	117.6 (4)	C6—C5—C4	120.8 (5)
C6—N1—Si1	121.8 (3)	C6—C5—H5	119.6
C2—N1—Si1	120.6 (3)	C4—C5—H5	119.6
N1—C2—C3	122.2 (5)	N1—C6—C5	122.2 (4)
N1—C2—H2	118.9	N1—C6—H6	118.9
C3—C2—H2	118.9	C5—C6—H6	118.9
C2—C3—C4	120.5 (5)
N1^i—Si1—N1—C6	180.0 (6)	C6—N1—C2—C3	0.000 (2)
Br1^i—Si1—N1—C6	45.660 (9)	Si1—N1—C2—C3	180.000 (2)
Br1^ii—Si1—N1—C6	−45.660 (9)	N1—C2—C3—C4	0.000 (2)
Br1^iii—Si1—N1—C6	134.340 (9)	C2—C3—C4—C5	0.000 (2)
Br1—Si1—N1—C6	−134.340 (9)	C2—C3—C4—C41	180.000 (2)
N1^i—Si1—N1—C2	0 (100)	C3—C4—C5—C6	0.000 (2)
Br1^i—Si1—N1—C2	−134.340 (9)	C41—C4—C5—C6	180.000 (2)
Br1^ii—Si1—N1—C2	134.340 (9)	C2—N1—C6—C5	0.000 (2)
Br1^iii—Si1—N1—C2	−45.660 (9)	Si1—N1—C6—C5	180.000 (1)
Br1—Si1—N1—C2	45.660 (9)	C4—C5—C6—N1	0.000 (2)

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