
Supporting information
![]() | Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801013095/bt6073sup1.cif |
![]() | Structure factor file (CIF format) https://doi.org/10.1107/S1600536801013095/bt6073Isup2.hkl |
CCDC reference: 172188
Under an inert atmosphere of argon gas, mesitylaldehyde (0.35 g, 2.36 mmol) was added dropwise to a 195 K cooled solution of Me3Al (2.4 mmol of a 2M solution in toluene) in 3 ml of toluene, producing a yellow solution. The reaction mixture was allowed to warm slowly to ambient temperature with constant stirring and stirred for a further 20 h. All toluene was removed in vacuo, the residue was dissolved in 5 ml of hexane and a crystalline product was obtained on cooling the mixture to 245 K for 24 h. Yield: 0.153 g, 29.5%; m.p. 417–419 K. 1H NMR (C6D6, 400 MHz): δ 6.66 (broad s, 2H, m-H, Ph), 5.58 (q, J = 6.8 Hz, 1H, HCO), 2.54 (broad s, 3H, o-Me, Ph), 2.14 (broad s, 3H, o-Me, Ph), 2.01 (m, 3H, p-Me, Ph), 1.36 (m, 3H, Me), -0.44, -0.53, -0.62 (s, 6H, Me—Al). The presence of three signals for the methyl groups attached to the metal and the broad resonances obtained for some of the ligand H atoms indicates that a dynamic process is in operation in solution.
The high-angle data (θ = 60–67.5°) are incomplete because of restrictions imposed by the low-temperature device; data up to θ = 60° are 98% complete. H atoms were placed geometrically and refined with a riding model (including free rotation about C—C bonds), and with Uiso constrained to be 1.2 (1.5 for methyl groups) times Ueq of the carrier atom.
Data collection: DIF4 (Stoe & Cie, 1988); cell refinement: DIF4; data reduction: local programs; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.
![]() | Fig. 1. The molecular structure of (I) with unique atom labels and 50% probability ellipsoids for non-H atoms. |
[Al(CH3)2(C12H18O)2] | F(000) = 480 |
Mr = 440.56 | Dx = 1.110 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54184 Å |
a = 7.224 (3) Å | Cell parameters from 32 reflections |
b = 15.380 (6) Å | θ = 19.0–28.0° |
c = 12.204 (5) Å | µ = 1.12 mm−1 |
β = 103.48 (4)° | T = 160 K |
V = 1318.6 (9) Å3 | Block, colourless |
Z = 2 | 0.7 × 0.7 × 0.6 mm |
Stoe-Siemens diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 67.5°, θmin = 4.7° |
Graphite monochromator | h = −7→8 |
ω/θ scans | k = −14→18 |
2201 measured reflections | l = −10→14 |
2201 independent reflections | 5 standard reflections every 60 min |
1912 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.077 | H-atom parameters constrained |
wR(F2) = 0.217 | w = 1/[σ2(Fo2) + (0.1463P)2 + 0.8656P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max = 0.003 |
2201 reflections | Δρmax = 0.54 e Å−3 |
143 parameters | Δρmin = −0.84 e Å−3 |
0 restraints | Extinction correction: SHELXTL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.011 (2) |
[Al(CH3)2(C12H18O)2] | V = 1318.6 (9) Å3 |
Mr = 440.56 | Z = 2 |
Monoclinic, P21/c | Cu Kα radiation |
a = 7.224 (3) Å | µ = 1.12 mm−1 |
b = 15.380 (6) Å | T = 160 K |
c = 12.204 (5) Å | 0.7 × 0.7 × 0.6 mm |
β = 103.48 (4)° |
Stoe-Siemens diffractometer | Rint = 0.000 |
2201 measured reflections | 5 standard reflections every 60 min |
2201 independent reflections | intensity decay: none |
1912 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.077 | 0 restraints |
wR(F2) = 0.217 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.54 e Å−3 |
2201 reflections | Δρmin = −0.84 e Å−3 |
143 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Al | 0.44345 (12) | 0.55944 (5) | 0.07415 (7) | 0.0324 (4) | |
O | 0.4687 (3) | 0.44128 (12) | 0.05642 (16) | 0.0322 (5) | |
C1 | 0.6373 (5) | 0.6039 (2) | 0.2005 (3) | 0.0477 (9) | |
H1A | 0.6204 | 0.6667 | 0.2075 | 0.072* | |
H1B | 0.7639 | 0.5923 | 0.1875 | 0.072* | |
H1C | 0.6252 | 0.5750 | 0.2701 | 0.072* | |
C2 | 0.1802 (5) | 0.5975 (2) | 0.0545 (3) | 0.0480 (8) | |
H2A | 0.1353 | 0.5831 | 0.1221 | 0.072* | |
H2B | 0.1003 | 0.5680 | −0.0109 | 0.072* | |
H2C | 0.1727 | 0.6605 | 0.0423 | 0.072* | |
C3 | 0.3788 (4) | 0.36716 (19) | 0.0958 (3) | 0.0352 (7) | |
H3 | 0.2566 | 0.3560 | 0.0393 | 0.042* | |
C4 | 0.3290 (5) | 0.3876 (2) | 0.2072 (3) | 0.0497 (9) | |
H4A | 0.4458 | 0.4000 | 0.2644 | 0.075* | |
H4B | 0.2643 | 0.3375 | 0.2311 | 0.075* | |
H4C | 0.2448 | 0.4383 | 0.1981 | 0.075* | |
C5 | 0.5027 (4) | 0.28651 (18) | 0.0991 (2) | 0.0334 (7) | |
C6 | 0.6914 (4) | 0.28329 (19) | 0.1616 (2) | 0.0364 (7) | |
C7 | 0.8002 (4) | 0.2092 (2) | 0.1550 (3) | 0.0386 (7) | |
H7 | 0.9283 | 0.2072 | 0.1974 | 0.046* | |
C8 | 0.7267 (5) | 0.13858 (19) | 0.0884 (3) | 0.0381 (7) | |
C9 | 0.5395 (5) | 0.14193 (19) | 0.0308 (3) | 0.0384 (7) | |
H9 | 0.4863 | 0.0933 | −0.0135 | 0.046* | |
C10 | 0.4243 (4) | 0.21397 (19) | 0.0350 (2) | 0.0356 (7) | |
C11 | 0.7867 (5) | 0.3558 (2) | 0.2392 (3) | 0.0491 (9) | |
H11A | 0.7576 | 0.3490 | 0.3133 | 0.074* | |
H11B | 0.7390 | 0.4121 | 0.2070 | 0.074* | |
H11C | 0.9247 | 0.3530 | 0.2474 | 0.074* | |
C12 | 0.8498 (6) | 0.0601 (2) | 0.0815 (3) | 0.0514 (9) | |
H12A | 0.9802 | 0.0792 | 0.0840 | 0.077* | |
H12B | 0.7989 | 0.0291 | 0.0107 | 0.077* | |
H12C | 0.8500 | 0.0213 | 0.1452 | 0.077* | |
C13 | 0.2174 (5) | 0.2098 (2) | −0.0277 (3) | 0.0444 (8) | |
H13A | 0.1361 | 0.2198 | 0.0251 | 0.067* | |
H13B | 0.1899 | 0.1523 | −0.0624 | 0.067* | |
H13C | 0.1921 | 0.2545 | −0.0865 | 0.067* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Al | 0.0411 (7) | 0.0270 (5) | 0.0326 (6) | 0.0017 (3) | 0.0156 (4) | −0.0041 (3) |
O | 0.0418 (12) | 0.0272 (10) | 0.0307 (10) | 0.0014 (8) | 0.0145 (9) | −0.0001 (7) |
C1 | 0.060 (2) | 0.0455 (19) | 0.0394 (17) | −0.0086 (15) | 0.0158 (15) | −0.0112 (14) |
C2 | 0.054 (2) | 0.0391 (17) | 0.057 (2) | 0.0090 (15) | 0.0259 (16) | 0.0015 (15) |
C3 | 0.0392 (17) | 0.0300 (14) | 0.0407 (16) | 0.0009 (12) | 0.0178 (13) | 0.0018 (11) |
C4 | 0.065 (2) | 0.0439 (19) | 0.0506 (19) | 0.0099 (16) | 0.0354 (17) | 0.0080 (15) |
C5 | 0.0413 (17) | 0.0258 (14) | 0.0359 (14) | 0.0030 (12) | 0.0144 (12) | 0.0048 (11) |
C6 | 0.0440 (18) | 0.0336 (15) | 0.0338 (14) | −0.0013 (13) | 0.0137 (12) | 0.0035 (11) |
C7 | 0.0403 (17) | 0.0358 (16) | 0.0401 (15) | 0.0049 (13) | 0.0098 (13) | 0.0058 (12) |
C8 | 0.0494 (19) | 0.0299 (15) | 0.0392 (16) | 0.0060 (13) | 0.0183 (13) | 0.0074 (12) |
C9 | 0.0492 (19) | 0.0291 (15) | 0.0406 (16) | −0.0009 (12) | 0.0182 (14) | 0.0010 (12) |
C10 | 0.0420 (18) | 0.0322 (15) | 0.0353 (15) | −0.0012 (12) | 0.0142 (12) | 0.0025 (12) |
C11 | 0.051 (2) | 0.0446 (19) | 0.0481 (19) | 0.0016 (15) | 0.0040 (15) | −0.0079 (14) |
C12 | 0.058 (2) | 0.0350 (17) | 0.065 (2) | 0.0098 (14) | 0.0218 (18) | 0.0042 (15) |
C13 | 0.0428 (19) | 0.0386 (17) | 0.0508 (19) | −0.0020 (14) | 0.0087 (15) | −0.0006 (14) |
Al—O | 1.844 (2) | C5—C10 | 1.404 (4) |
Al—Oi | 1.848 (2) | C6—C7 | 1.397 (4) |
Al—C1 | 1.950 (3) | C6—C11 | 1.520 (4) |
Al—C2 | 1.950 (4) | C7—C8 | 1.386 (4) |
O—C3 | 1.448 (3) | C7—H7 | 0.950 |
O—Ali | 1.848 (2) | C8—C9 | 1.372 (5) |
C1—H1A | 0.980 | C8—C12 | 1.512 (4) |
C1—H1B | 0.980 | C9—C10 | 1.394 (4) |
C1—H1C | 0.980 | C9—H9 | 0.950 |
C2—H2A | 0.980 | C10—C13 | 1.514 (4) |
C2—H2B | 0.980 | C11—H11A | 0.980 |
C2—H2C | 0.980 | C11—H11B | 0.980 |
C3—C4 | 1.518 (4) | C11—H11C | 0.980 |
C3—C5 | 1.525 (4) | C12—H12A | 0.980 |
C3—H3 | 1.000 | C12—H12B | 0.980 |
C4—H4A | 0.980 | C12—H12C | 0.980 |
C4—H4B | 0.980 | C13—H13A | 0.980 |
C4—H4C | 0.980 | C13—H13B | 0.980 |
C5—C6 | 1.399 (4) | C13—H13C | 0.980 |
O—Al—Oi | 80.20 (9) | C10—C5—C3 | 118.3 (3) |
O—Al—C1 | 111.46 (13) | C7—C6—C5 | 119.2 (3) |
Oi—Al—C1 | 110.88 (13) | C7—C6—C11 | 117.1 (3) |
O—Al—C2 | 113.67 (13) | C5—C6—C11 | 123.8 (3) |
Oi—Al—C2 | 114.63 (13) | C8—C7—C6 | 122.0 (3) |
C1—Al—C2 | 119.49 (16) | C8—C7—H7 | 119.0 |
C3—O—Al | 132.26 (17) | C6—C7—H7 | 119.0 |
C3—O—Ali | 123.53 (16) | C9—C8—C7 | 117.9 (3) |
Al—O—Ali | 99.80 (9) | C9—C8—C12 | 121.6 (3) |
Al—C1—H1A | 109.5 | C7—C8—C12 | 120.6 (3) |
Al—C1—H1B | 109.5 | C8—C9—C10 | 122.5 (3) |
H1A—C1—H1B | 109.5 | C8—C9—H9 | 118.8 |
Al—C1—H1C | 109.5 | C10—C9—H9 | 118.8 |
H1A—C1—H1C | 109.5 | C9—C10—C5 | 119.0 (3) |
H1B—C1—H1C | 109.5 | C9—C10—C13 | 118.4 (3) |
Al—C2—H2A | 109.5 | C5—C10—C13 | 122.6 (3) |
Al—C2—H2B | 109.5 | C6—C11—H11A | 109.5 |
H2A—C2—H2B | 109.5 | C6—C11—H11B | 109.5 |
Al—C2—H2C | 109.5 | H11A—C11—H11B | 109.5 |
H2A—C2—H2C | 109.5 | C6—C11—H11C | 109.5 |
H2B—C2—H2C | 109.5 | H11A—C11—H11C | 109.5 |
O—C3—C4 | 110.7 (2) | H11B—C11—H11C | 109.5 |
O—C3—C5 | 110.1 (2) | C8—C12—H12A | 109.5 |
C4—C3—C5 | 113.9 (2) | C8—C12—H12B | 109.5 |
O—C3—H3 | 107.3 | H12A—C12—H12B | 109.5 |
C4—C3—H3 | 107.3 | C8—C12—H12C | 109.5 |
C5—C3—H3 | 107.3 | H12A—C12—H12C | 109.5 |
C3—C4—H4A | 109.5 | H12B—C12—H12C | 109.5 |
C3—C4—H4B | 109.5 | C10—C13—H13A | 109.5 |
H4A—C4—H4B | 109.5 | C10—C13—H13B | 109.5 |
C3—C4—H4C | 109.5 | H13A—C13—H13B | 109.5 |
H4A—C4—H4C | 109.5 | C10—C13—H13C | 109.5 |
H4B—C4—H4C | 109.5 | H13A—C13—H13C | 109.5 |
C6—C5—C10 | 119.4 (3) | H13B—C13—H13C | 109.5 |
C6—C5—C3 | 122.3 (3) | ||
Oi—Al—O—C3 | −156.1 (3) | C3—C5—C6—C7 | −176.0 (3) |
C1—Al—O—C3 | 95.2 (3) | C10—C5—C6—C11 | −176.2 (3) |
C2—Al—O—C3 | −43.4 (3) | C3—C5—C6—C11 | 5.1 (4) |
Oi—Al—O—Ali | 0.0 | C5—C6—C7—C8 | −0.1 (4) |
C1—Al—O—Ali | −108.71 (14) | C11—C6—C7—C8 | 178.9 (3) |
C2—Al—O—Ali | 112.71 (15) | C6—C7—C8—C9 | −2.1 (4) |
Al—O—C3—C4 | −30.5 (4) | C6—C7—C8—C12 | 178.8 (3) |
Ali—O—C3—C4 | 178.1 (2) | C7—C8—C9—C10 | 1.7 (4) |
Al—O—C3—C5 | −157.29 (19) | C12—C8—C9—C10 | −179.2 (3) |
Ali—O—C3—C5 | 51.3 (3) | C8—C9—C10—C5 | 0.9 (4) |
O—C3—C5—C6 | 57.3 (3) | C8—C9—C10—C13 | −177.5 (3) |
C4—C3—C5—C6 | −67.7 (4) | C6—C5—C10—C9 | −3.1 (4) |
O—C3—C5—C10 | −121.4 (3) | C3—C5—C10—C9 | 175.6 (2) |
C4—C3—C5—C10 | 113.6 (3) | C6—C5—C10—C13 | 175.3 (3) |
C10—C5—C6—C7 | 2.7 (4) | C3—C5—C10—C13 | −6.0 (4) |
Symmetry code: (i) −x+1, −y+1, −z. |
Experimental details
Crystal data | |
Chemical formula | [Al(CH3)2(C12H18O)2] |
Mr | 440.56 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 160 |
a, b, c (Å) | 7.224 (3), 15.380 (6), 12.204 (5) |
β (°) | 103.48 (4) |
V (Å3) | 1318.6 (9) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 1.12 |
Crystal size (mm) | 0.7 × 0.7 × 0.6 |
Data collection | |
Diffractometer | Stoe-Siemens diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2201, 2201, 1912 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.599 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.077, 0.217, 1.05 |
No. of reflections | 2201 |
No. of parameters | 143 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.54, −0.84 |
Computer programs: DIF4 (Stoe & Cie, 1988), DIF4, SHELXTL (Sheldrick, 1997), SHELXTL and local programs.
Al—O | 1.844 (2) | Al—C2 | 1.950 (4) |
Al—Oi | 1.848 (2) | O—C3 | 1.448 (3) |
Al—C1 | 1.950 (3) | ||
O—Al—Oi | 80.20 (9) | C1—Al—C2 | 119.49 (16) |
O—Al—C1 | 111.46 (13) | C3—O—Al | 132.26 (17) |
Oi—Al—C1 | 110.88 (13) | C3—O—Ali | 123.53 (16) |
O—Al—C2 | 113.67 (13) | Al—O—Ali | 99.80 (9) |
Oi—Al—C2 | 114.63 (13) |
Symmetry code: (i) −x+1, −y+1, −z. |
For many years, aluminium alkoxides and aryloxides have been utilized as reagents in organic synthesis (Zietz et al., 1983). However, the development of heterobimetallic reagents for use in asymmetric transformations has led to an increased awareness of the importance of aluminium in synthesis (Yamamoto & Maruoka, 1988; Saito & Yamamoto, 1997; Saito et al., 1998; Saito et al., 1999; Cogan & Ellman, 1999). In this regard, we have recently reported the syntheses and solid-state structures of dimethylaluminium enolates and aryloxides, produced from the reactions of trimethylaluminium and aromatic methyl ketones (Allan et al., 2000). The unexpected formation of enolate species was found to be a consequence of steric crowding in the ketones, when both the 2- and 6-positions of the aromatic rings carried methyl groups. We report here the structure of the title compound, (I), which is produced from the addition reaction between trimethylaluminium and 2,4,6-trimethylbenzaldehyde (mesitylaldehyde).
As can be seen from Fig. 1, complex (I) adopts a dimeric structure with a planar central Al2O2 ring core. The molecule is crystallographically centrosymmetric. Each Al atom is tetracoordinate by bonding to two methyl groups and two bridging O atoms. Although the average of the angles around each metal is 108.4°, these vary from 80.20 (9)° for O—Al—Oi to 119.49 (16)° for C1—Al—C2, giving a highly distorted pseudo-tetrahedral geometry at aluminium [symmetry code: (i) 1 - x, 1 - y, -z]. The internal Al2O2 ring angles at the metal atoms are smaller than at the oxygen atoms [80.20 (9) and 99.80 (9)°, respectively], which is consistent with sp2 hybridization for the bridging O atoms (van der Steen et al., 1991). The two independent Al—O distances are essentially the same at 1.844 (2) and 1.848 (2) Å for Al—O and Al—Oi respectively. Similarly, the remaining bond lengths and angles within (I) are in accord with those found in related systems (Schumann et al., 1996; Hitchcock et al., 1990; Sierra et al., 1989).
It is notable that the α-carbon atom C3 lies 0.434 Å out of the Al2O2 ring plane, and that the groups attached to this atom are staggered with respect to the ring, with torsion angles of -30.5 (4), 86.3 and -157.3 (2)° for Al—O—C3—C4, Al—O—C3—H3, Al—O—C3—C5, respectively. These differ markedly from those found in the closely related enolate analogue [Me2AlOC(2,4,6-Me3C6H2)=CH2], (II), where the olefin bond lies close the Al2O2 ring plane (Allan et al., 2000). This difference is most likely a consequence of the sp3 versus sp2 hybridization of the α-carbons in (I) and (II), respectively, which alters the minimum energy orientation of the attached groups.