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The title molecule is dimeric,
i.e. di-
-trimethylsiloxy-bis(dichloroaluminium), [Al
2Cl
4(C
3H
9Si)
2], and possesses exact crystallographic inversion symmetry. The O atoms of the trimethylsiloxy groups bridge the two Al atoms to form a four-membered ring. The Si-O bond distance [1.711 (3) Å], the Al-O mean bond distance [1.806 (4) Å] and the mean Si-C bond distance [1.875 (6) Å] appear to agree well with standard data. Mean values for C-Si-C, O-Si-C, and Si-O-Al angles are 112.9 (3), 105.8 (2), and 131.8 (2)° repectively. The two ring angles O-Al-O and Al-O-Al are 84.43 (16) and 95.57 (16)°, respectively.
Supporting information
CCDC reference: 156201
A solution of (SiMe3)2O (1.74 g, 10.7 mmol) in CH2Cl2 was added to a suspension of AlCl3 (1.43 g, 10.7 mmol) in CH2Cl2 (40 ml). The resulting solution was stirred for 12 h and then filtered. Upon distillation of the solvent, the compound was isolated as a colourless precipitate (1.062 g, 53.1% yield). The sample used for the diffraction experiments was prepared by slow sublimation under vacuum. The calculated powder diffraction pattern of the crystal was identical with that of the bulk material.
Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: XS in SHELXTL (Sheldrick, 1997); program(s) used to refine structure: XL in SHELXTL (Sheldrick, 1997); software used to prepare material for publication: XL in SHELXTL.
Crystal data top
[Al2Cl4(C3H9Si)2] | F(000) = 384 |
Mr = 374.14 | Dx = 1.359 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 6.7860 (14) Å | Cell parameters from 24 reflections |
b = 9.1740 (18) Å | θ = 13–15° |
c = 14.982 (3) Å | µ = 0.86 mm−1 |
β = 101.42 (3)° | T = 176 K |
V = 914.2 (3) Å3 | Cleaved fragment, colourless |
Z = 2 | 0.25 × 0.20 × 0.15 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1128 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.000 |
Graphite monochromator | θmax = 25.0°, θmin = 2.6° |
θ–2θ scans | h = 0→8 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→10 |
Tmin = 0.806, Tmax = 0.879 | l = −17→17 |
1602 measured reflections | 3 standard reflections every 60 min |
1602 independent reflections | intensity decay: none |
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)] = 0.054 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.155 | H-atom parameters constrained |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0658P)2 + 1.6734P] where P = (Fo2 + 2Fc2)/3 |
1602 reflections | (Δ/σ)max < 0.001 |
73 parameters | Δρmax = 0.63 e Å−3 |
0 restraints | Δρmin = −0.35 e Å−3 |
Crystal data top
[Al2Cl4(C3H9Si)2] | V = 914.2 (3) Å3 |
Mr = 374.14 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 6.7860 (14) Å | µ = 0.86 mm−1 |
b = 9.1740 (18) Å | T = 176 K |
c = 14.982 (3) Å | 0.25 × 0.20 × 0.15 mm |
β = 101.42 (3)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 1128 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.000 |
Tmin = 0.806, Tmax = 0.879 | 3 standard reflections every 60 min |
1602 measured reflections | intensity decay: none |
1602 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.054 | 0 restraints |
wR(F2) = 0.155 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.63 e Å−3 |
1602 reflections | Δρmin = −0.35 e Å−3 |
73 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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Cl1 | 0.4080 (2) | 0.02238 (18) | 0.12259 (11) | 0.0519 (5) | |
Cl2 | −0.0163 (2) | 0.23542 (17) | 0.13926 (10) | 0.0521 (4) | |
Si | 0.0717 (2) | 0.23544 (16) | −0.12069 (10) | 0.0364 (4) | |
Al | 0.1068 (2) | 0.07089 (17) | 0.07154 (10) | 0.0310 (4) | |
O1 | 0.0414 (5) | 0.0933 (3) | −0.0506 (2) | 0.0286 (8) | |
C1 | 0.0834 (9) | 0.1502 (6) | −0.2316 (4) | 0.0457 (15) | |
H1A | −0.0434 | 0.1054 | −0.2564 | 0.069* | |
H1B | 0.1873 | 0.0775 | −0.2230 | 0.069* | |
H1C | 0.1125 | 0.2234 | −0.2729 | 0.069* | |
C2 | −0.1491 (8) | 0.3583 (6) | −0.1255 (4) | 0.0398 (13) | |
H2A | −0.2691 | 0.3088 | −0.1548 | 0.060* | |
H2B | −0.1312 | 0.4446 | −0.1593 | 0.060* | |
H2C | −0.1608 | 0.3850 | −0.0648 | 0.060* | |
C3 | 0.3144 (7) | 0.3295 (5) | −0.0635 (4) | 0.0317 (12) | |
H3A | 0.4255 | 0.2642 | −0.0619 | 0.048* | |
H3B | 0.3056 | 0.3565 | −0.0025 | 0.048* | |
H3C | 0.3342 | 0.4153 | −0.0973 | 0.048* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cl1 | 0.0369 (7) | 0.0560 (9) | 0.0563 (9) | 0.0054 (7) | −0.0063 (6) | −0.0102 (7) |
Cl2 | 0.0641 (10) | 0.0414 (8) | 0.0539 (9) | 0.0035 (7) | 0.0192 (7) | −0.0145 (7) |
Si | 0.0391 (8) | 0.0285 (8) | 0.0441 (9) | 0.0018 (6) | 0.0146 (6) | 0.0060 (6) |
Al | 0.0341 (8) | 0.0271 (8) | 0.0306 (8) | 0.0001 (7) | 0.0033 (6) | −0.0040 (6) |
O1 | 0.0307 (18) | 0.0218 (17) | 0.0329 (19) | −0.0004 (14) | 0.0050 (14) | 0.0014 (14) |
C1 | 0.054 (3) | 0.048 (3) | 0.041 (3) | 0.016 (3) | 0.024 (3) | 0.015 (3) |
C2 | 0.041 (3) | 0.032 (3) | 0.047 (3) | 0.009 (2) | 0.013 (3) | 0.012 (2) |
C3 | 0.019 (2) | 0.015 (2) | 0.062 (3) | −0.0109 (19) | 0.011 (2) | 0.001 (2) |
Geometric parameters (Å, º) top
Cl1—Al | 2.083 (2) | Si—C3 | 1.906 (5) |
Cl2—Al | 2.084 (2) | Al—O1i | 1.804 (3) |
Si—O1 | 1.711 (3) | Al—O1 | 1.808 (3) |
Si—C1 | 1.853 (6) | Al—Ali | 2.675 (3) |
Si—C2 | 1.865 (5) | O1—Ali | 1.804 (3) |
| | | |
O1—Si—C1 | 105.1 (2) | O1—Al—Cl2 | 111.65 (13) |
O1—Si—C2 | 106.9 (2) | Cl1—Al—Cl2 | 115.76 (9) |
C1—Si—C2 | 113.4 (3) | O1i—Al—Ali | 42.27 (11) |
O1—Si—C3 | 105.5 (2) | O1—Al—Ali | 42.16 (11) |
C1—Si—C3 | 114.1 (3) | Cl1—Al—Ali | 121.79 (10) |
C2—Si—C3 | 111.1 (2) | Cl2—Al—Ali | 122.45 (10) |
O1i—Al—O1 | 84.43 (16) | Si—O1—Ali | 131.3 (2) |
O1i—Al—Cl1 | 110.97 (13) | Si—O1—Al | 132.3 (2) |
O1—Al—Cl1 | 114.98 (14) | Ali—O1—Al | 95.57 (16) |
O1i—Al—Cl2 | 115.21 (13) | | |
Symmetry code: (i) −x, −y, −z. |
Experimental details
Crystal data |
Chemical formula | [Al2Cl4(C3H9Si)2] |
Mr | 374.14 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 176 |
a, b, c (Å) | 6.7860 (14), 9.1740 (18), 14.982 (3) |
β (°) | 101.42 (3) |
V (Å3) | 914.2 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.86 |
Crystal size (mm) | 0.25 × 0.20 × 0.15 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.806, 0.879 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1602, 1602, 1128 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.594 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.054, 0.155, 1.10 |
No. of reflections | 1602 |
No. of parameters | 73 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.63, −0.35 |
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We are interested in the dimer, (I), of dichlorotrimethylsiloxyaluminum, because we intend to explore its reactions with a variety of nucleophiles, such as amides and azides, to prepare new precursors to Sialons (silicon–aluminium–oxygen–nitrogen ceramics) or related alloys. Previous work (Schmidbaur et al., 1964) indicated that the molecule is dimeric and it was proposed that the O atoms of the trimethylsiloxy group, rather than the Cl ligands, bridge the Al atoms to form the dimer. Our X-ray analysis confirmed the suggested structure. At a later time, we discovered that the structure of (Me3SiOAlBr2)2, the bromine analogue, has been determined (Bonamico & Dessy, 1967) and is essentially identical to (Me3SiOAlCl2)2. \scheme