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The title mol­ecule is dimeric, i.e. di-[mu]-tri­methyl­siloxy-bis­(di­chloro­aluminium), [Al2Cl4(C3H9Si)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

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100017261/qa0441sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100017261/qa0441Isup2.hkl
Contains datablock I

CCDC reference: 156201

Comment top

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

Experimental top

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.

Computing details top

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.

(I) top
Crystal data top
[Al2Cl4(C3H9Si)2]F(000) = 384
Mr = 374.14Dx = 1.359 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 6.7860 (14) ÅCell parameters from 24 reflections
b = 9.1740 (18) Åθ = 13–15°
c = 14.982 (3) ŵ = 0.86 mm1
β = 101.42 (3)°T = 176 K
V = 914.2 (3) Å3Cleaved fragment, colourless
Z = 20.25 × 0.20 × 0.15 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1128 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.000
Graphite monochromatorθmax = 25.0°, θmin = 2.6°
θ–2θ scansh = 08
Absorption correction: ψ scan
(North et al., 1968)
k = 010
Tmin = 0.806, Tmax = 0.879l = 1717
1602 measured reflections3 standard reflections every 60 min
1602 independent reflections intensity decay: none
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.054Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.155H-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 parametersΔρmax = 0.63 e Å3
0 restraintsΔρmin = 0.35 e Å3
Crystal data top
[Al2Cl4(C3H9Si)2]V = 914.2 (3) Å3
Mr = 374.14Z = 2
Monoclinic, P21/nMo Kα radiation
a = 6.7860 (14) ŵ = 0.86 mm1
b = 9.1740 (18) ÅT = 176 K
c = 14.982 (3) Å0.25 × 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 = 0.8793 standard reflections every 60 min
1602 measured reflections intensity decay: none
1602 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0540 restraints
wR(F2) = 0.155H-atom parameters constrained
S = 1.10Δρmax = 0.63 e Å3
1602 reflectionsΔρmin = 0.35 e Å3
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
xyzUiso*/Ueq
Cl10.4080 (2)0.02238 (18)0.12259 (11)0.0519 (5)
Cl20.0163 (2)0.23542 (17)0.13926 (10)0.0521 (4)
Si0.0717 (2)0.23544 (16)0.12069 (10)0.0364 (4)
Al0.1068 (2)0.07089 (17)0.07154 (10)0.0310 (4)
O10.0414 (5)0.0933 (3)0.0506 (2)0.0286 (8)
C10.0834 (9)0.1502 (6)0.2316 (4)0.0457 (15)
H1A0.04340.10540.25640.069*
H1B0.18730.07750.22300.069*
H1C0.11250.22340.27290.069*
C20.1491 (8)0.3583 (6)0.1255 (4)0.0398 (13)
H2A0.26910.30880.15480.060*
H2B0.13120.44460.15930.060*
H2C0.16080.38500.06480.060*
C30.3144 (7)0.3295 (5)0.0635 (4)0.0317 (12)
H3A0.42550.26420.06190.048*
H3B0.30560.35650.00250.048*
H3C0.33420.41530.09730.048*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0369 (7)0.0560 (9)0.0563 (9)0.0054 (7)0.0063 (6)0.0102 (7)
Cl20.0641 (10)0.0414 (8)0.0539 (9)0.0035 (7)0.0192 (7)0.0145 (7)
Si0.0391 (8)0.0285 (8)0.0441 (9)0.0018 (6)0.0146 (6)0.0060 (6)
Al0.0341 (8)0.0271 (8)0.0306 (8)0.0001 (7)0.0033 (6)0.0040 (6)
O10.0307 (18)0.0218 (17)0.0329 (19)0.0004 (14)0.0050 (14)0.0014 (14)
C10.054 (3)0.048 (3)0.041 (3)0.016 (3)0.024 (3)0.015 (3)
C20.041 (3)0.032 (3)0.047 (3)0.009 (2)0.013 (3)0.012 (2)
C30.019 (2)0.015 (2)0.062 (3)0.0109 (19)0.011 (2)0.001 (2)
Geometric parameters (Å, º) top
Cl1—Al2.083 (2)Si—C31.906 (5)
Cl2—Al2.084 (2)Al—O1i1.804 (3)
Si—O11.711 (3)Al—O11.808 (3)
Si—C11.853 (6)Al—Ali2.675 (3)
Si—C21.865 (5)O1—Ali1.804 (3)
O1—Si—C1105.1 (2)O1—Al—Cl2111.65 (13)
O1—Si—C2106.9 (2)Cl1—Al—Cl2115.76 (9)
C1—Si—C2113.4 (3)O1i—Al—Ali42.27 (11)
O1—Si—C3105.5 (2)O1—Al—Ali42.16 (11)
C1—Si—C3114.1 (3)Cl1—Al—Ali121.79 (10)
C2—Si—C3111.1 (2)Cl2—Al—Ali122.45 (10)
O1i—Al—O184.43 (16)Si—O1—Ali131.3 (2)
O1i—Al—Cl1110.97 (13)Si—O1—Al132.3 (2)
O1—Al—Cl1114.98 (14)Ali—O1—Al95.57 (16)
O1i—Al—Cl2115.21 (13)
Symmetry code: (i) x, y, z.

Experimental details

Crystal data
Chemical formula[Al2Cl4(C3H9Si)2]
Mr374.14
Crystal system, space groupMonoclinic, P21/n
Temperature (K)176
a, b, c (Å)6.7860 (14), 9.1740 (18), 14.982 (3)
β (°) 101.42 (3)
V3)914.2 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.86
Crystal size (mm)0.25 × 0.20 × 0.15
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.806, 0.879
No. of measured, independent and
observed [I > 2σ(I)] reflections
1602, 1602, 1128
Rint0.000
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.054, 0.155, 1.10
No. of reflections1602
No. of parameters73
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.63, 0.35

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, XS in SHELXTL (Sheldrick, 1997), XL in SHELXTL (Sheldrick, 1997), XL in SHELXTL.

 

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