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Acta Crystallogr Sect E Struct Rep Online. 2009 June 1; 65(Pt 6): m670.
Published online 2009 May 23. doi:  10.1107/S1600536809018492
PMCID: PMC2969717

Bis[μ-2-(2H-benzotriazol-2-yl)-4-methyl­phenolato]bis­[dimethyl­aluminium(III)]

Abstract

The title complex, [Al2(CH3)4(C13H10N3O)2], is dimeric, bridged through the O atoms of the phenolate anions. The asymmetric unit contains one half of the mol­ecule and there is a crystallographic inversion centre in this mol­ecule. Each Al atom is penta­coordinated by one N atom and two bridging O atoms of two N,O-bidentate benzotriazolylphenolate ligands and by two C atoms from two methyl groups, forming a distorted trigonal–bipyramidal environment.

Related literature

For background information, see: Liu et al. (2001 [triangle]); Wu et al. (2006 [triangle]). For related structures, see: Lewinski et al. (2003 [triangle]); Tsai et al. (2009 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-0m670-scheme1.jpg

Experimental

Crystal data

  • [Al2(CH3)4(C13H10N3O)2]
  • M r = 562.58
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-0m670-efi1.jpg
  • a = 7.4220 (4) Å
  • b = 9.7120 (5) Å
  • c = 11.6331 (6) Å
  • α = 112.517 (2)°
  • β = 94.824 (3)°
  • γ = 109.574 (2)°
  • V = 707.79 (7) Å3
  • Z = 1
  • Mo Kα radiation
  • μ = 0.14 mm−1
  • T = 296 K
  • 0.48 × 0.25 × 0.25 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2008 [triangle]) T min = 0.937, T max = 0.966
  • 11757 measured reflections
  • 3405 independent reflections
  • 2923 reflections with I > 2σ(I)
  • R int = 0.017

Refinement

  • R[F 2 > 2σ(F 2)] = 0.039
  • wR(F 2) = 0.122
  • S = 1.03
  • 3405 reflections
  • 182 parameters
  • H-atom parameters constrained
  • Δρmax = 0.28 e Å−3
  • Δρmin = −0.26 e Å−3

Data collection: APEX2 (Bruker, 2008 [triangle]); cell refinement: SAINT (Bruker, 2008 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809018492/rk2147sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809018492/rk2147Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors gratefully acknowledge financial support from the National Science Council, Taiwan (grant No. NSC97-2113-M-033-005-MY2) and from the Project of the Specific Research Fields in Chung Yuan Christian University, Taiwan (grant No. CYCU-97-CR-CH).

supplementary crystallographic information

Comment

Due to the biodegradable, biocompatible, and permeable properties, aliphatic polyesters, such as poly(ε-caprolactone) - (PCL), poly(lactide) - (PLA) and their co-polymers have been widely used in the biomedical and pharmaceutical fields. Therefore, it has been of great interest to develop new catalytic/initiating systems for the preparation of PCL and PLA. Metal complex-catalyzed ring-opening polymerization (ROP) of lactones/lactides has been proven to be the most promising method to synthesize these polymers (Wu et al., 2006). Among them, a variety of main group metal complexes, such as magnesium, zinc, tin, lithium, and calcium as well as aluminum complexes have been reported to be efficient initiators/catalysts. In particular, Liu with co-workers, (2001) have reported the aluminum alkoxide complexes supported by the bulky bisphenol ligand and these complexes have been demonstrated as efficient initiators to catalyze ROP of caprolactones and lactides. Recently, our group is interested in the synthesis and preparation of various metal complexes derived from the benzotriazol-phenol ligands. For instance, we have successfully synthesized and structural characterized a Pd(II) complex with 4-methyl-2-(2H-benzotriazol-2-yl)-phenolate ligands (Tsai et al., 2009). We report herein the synthesis and crystal structure of N,O-bidentate benzotriazol-phenolate ligands incorporated AlIII complex (I), a potential catalyst for the ROP of cyclic esters in the presence of alcohols (Scheme 1).

The solid structure of title compound (I) reveals a dimeric AlIII complex (Fig. 1), doubly bridged through the O atoms of the phenolate anions. It was found that the asymmetric unit has one half of molecule and there exists a crystallographic inversion centre of symmetry in this molecule. The geometry around each Al atom is penta-coordinated with a distorted trigonal bipyramidal environment in which one N atom and two bridging O atoms come from N,O–bidentate benzotriazol-phenolate ligand and two C atoms are from two methyl groups. The sums of bond angles around Al center are 359.97 (7)°. The bond distances between the Al atom and O, N1, Oi (symmetry code: (i) -x, -y, -z + 2), C14 and C15 are 1.8338 (11), 2.1061 (13), 2.0918 (11), 1.9767 (17), 1.9725 (17) Å, respectively. These bond distances are longer than those found in other Schiff base AlIII complexes with four-coordinated geometry (Lewinski et al., 2003). It is interesting to note that the six-member ring formed from the bidentate benzotriazol-phenolate ligand and Al atom is almost coplanar with the mean deviation of 0.006 (2) Å.

Experimental

The title compound I was synthesized by the following procedures (see Fig. 2): to a rapidly stirred solution of 4-methyl-2-(2H-benzotriazol-2-yl)phenol (0.22 g, 1.0 mmol) in toluene (20 ml) was slowly added AlMe3 (0.5 ml, 1.0 mmol). The mixture was further stirred at room temperature for 2 h and then dried under vacuum. The residue was extracted with hot toluene (10 ml) and the saturated solution was cooled to 273 K, yielding yellow crystals. Yield: 0.24 g (86%). 1H NMR (CDCl3, p.p.m.): δ 7.04–8.14 (14H, m, ArH), 2.40 (6H, s, CH3), -0.57 (12H, s, AlCH3).

Refinement

The H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C—H = 0.93 Å and 0.96 Å with Uiso(H) = 1.2 and 1.5Ueq(C).

Figures

Fig. 1.
A view of the molecular structure of I with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius. Symmetry code: (i) -x, -y, -z + 2.
Fig. 2.
The preparation pass for the title compound I.

Crystal data

[Al2(CH3)4(C13H10N3O)2]Z = 1
Mr = 562.58F(000) = 296
Triclinic, P1Dx = 1.320 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.4220 (4) ÅCell parameters from 7401 reflections
b = 9.7120 (5) Åθ = 2.5–28.2°
c = 11.6331 (6) ŵ = 0.14 mm1
α = 112.517 (2)°T = 296 K
β = 94.824 (3)°Block, yellow
γ = 109.574 (2)°0.48 × 0.25 × 0.25 mm
V = 707.79 (7) Å3

Data collection

Bruker APEXII CCD diffractometer3405 independent reflections
Radiation source: fine-focus sealed tube2923 reflections with I > 2σ(I)
graphiteRint = 0.017
[var phi] and ω scansθmax = 28.2°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Bruker, 2008)h = −9→8
Tmin = 0.937, Tmax = 0.966k = −12→12
11757 measured reflectionsl = −14→15

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.122H-atom parameters constrained
S = 1.03w = 1/[σ2(Fo2) + (0.0679P)2 + 0.1915P] where P = (Fo2 + 2Fc2)/3
3405 reflections(Δ/σ)max = 0.001
182 parametersΔρmax = 0.28 e Å3
0 restraintsΔρmin = −0.26 e Å3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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)

xyzUiso*/Ueq
Al0.05537 (5)0.05266 (4)0.89433 (3)0.03495 (10)
O0.05448 (13)0.14683 (10)1.06417 (8)0.0383 (2)
N10.16914 (16)0.28879 (13)0.90600 (11)0.0394 (2)
N20.20710 (15)0.42899 (12)1.00733 (10)0.0366 (2)
N30.28396 (18)0.56192 (13)0.98973 (12)0.0457 (3)
C10.10477 (17)0.30216 (14)1.15315 (12)0.0347 (3)
C20.17660 (18)0.44012 (14)1.12950 (12)0.0348 (3)
C30.2281 (2)0.59650 (15)1.22664 (13)0.0420 (3)
H3B0.27370.68491.20760.050*
C40.2129 (2)0.62320 (16)1.35011 (13)0.0435 (3)
C50.1424 (2)0.48768 (17)1.37431 (13)0.0432 (3)
H5A0.13120.50181.45670.052*
C60.0886 (2)0.33235 (16)1.27846 (13)0.0421 (3)
H6A0.03990.24471.29820.051*
C70.22611 (19)0.33415 (16)0.81377 (13)0.0409 (3)
C80.2240 (2)0.2418 (2)0.68526 (15)0.0546 (4)
H8A0.17660.12900.64860.065*
C90.2959 (2)0.3281 (2)0.61786 (16)0.0588 (4)
H9A0.29610.27150.53280.071*
C100.3694 (2)0.4988 (2)0.67200 (16)0.0566 (4)
H10A0.41780.55110.62190.068*
C110.3719 (2)0.5895 (2)0.79461 (16)0.0534 (4)
H11A0.42030.70230.82970.064*
C120.29715 (19)0.50377 (16)0.86672 (14)0.0416 (3)
C130.2747 (3)0.7923 (2)1.45629 (17)0.0637 (5)
H13A0.32290.87061.42310.096*
H13B0.37710.81121.52370.096*
H13C0.16350.80261.48960.096*
C14−0.1914 (2)−0.00914 (18)0.77213 (15)0.0490 (3)
H14A−0.2766−0.11970.74920.073*
H14B−0.16130.00130.69640.073*
H14C−0.25620.06100.81140.073*
C150.2981 (2)0.02143 (18)0.86005 (16)0.0501 (3)
H15A0.2845−0.08460.85010.075*
H15B0.40810.10250.93060.075*
H15C0.31990.03120.78280.075*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Al0.03920 (19)0.03075 (17)0.03427 (18)0.01356 (14)0.01205 (14)0.01332 (13)
O0.0501 (5)0.0270 (4)0.0362 (4)0.0132 (3)0.0149 (4)0.0131 (3)
N10.0451 (5)0.0326 (5)0.0389 (5)0.0130 (4)0.0134 (4)0.0155 (4)
N20.0380 (5)0.0293 (4)0.0405 (5)0.0110 (4)0.0075 (4)0.0160 (4)
N30.0533 (6)0.0335 (5)0.0504 (6)0.0124 (5)0.0101 (5)0.0231 (5)
C10.0349 (5)0.0294 (5)0.0369 (6)0.0121 (4)0.0098 (4)0.0122 (4)
C20.0354 (5)0.0312 (5)0.0362 (6)0.0136 (4)0.0064 (4)0.0132 (4)
C30.0457 (7)0.0305 (5)0.0440 (7)0.0144 (5)0.0041 (5)0.0128 (5)
C40.0436 (6)0.0354 (6)0.0414 (7)0.0166 (5)0.0031 (5)0.0074 (5)
C50.0450 (7)0.0433 (6)0.0353 (6)0.0178 (5)0.0108 (5)0.0110 (5)
C60.0473 (7)0.0382 (6)0.0403 (6)0.0158 (5)0.0156 (5)0.0167 (5)
C70.0398 (6)0.0427 (6)0.0441 (6)0.0150 (5)0.0134 (5)0.0234 (5)
C80.0635 (9)0.0543 (8)0.0464 (7)0.0219 (7)0.0219 (7)0.0223 (6)
C90.0581 (8)0.0775 (10)0.0476 (8)0.0259 (8)0.0207 (6)0.0338 (7)
C100.0463 (7)0.0758 (9)0.0619 (9)0.0192 (7)0.0156 (6)0.0483 (7)
C110.0506 (8)0.0551 (7)0.0636 (9)0.0157 (6)0.0132 (6)0.0395 (7)
C120.0382 (6)0.0427 (6)0.0481 (7)0.0141 (5)0.0086 (5)0.0261 (5)
C130.0802 (11)0.0409 (8)0.0481 (9)0.0224 (8)0.0030 (8)0.0019 (6)
C140.0484 (7)0.0451 (7)0.0506 (8)0.0163 (6)0.0066 (6)0.0213 (6)
C150.0452 (7)0.0443 (7)0.0595 (8)0.0189 (6)0.0192 (6)0.0192 (6)

Geometric parameters (Å, °)

Al—O1.8337 (10)C6—H6A0.9300
Al—C151.9725 (15)C7—C121.3991 (19)
Al—C141.9767 (15)C7—C81.414 (2)
Al—Oi2.0918 (10)C8—C91.370 (2)
Al—N12.1060 (11)C8—H8A0.9300
O—C11.3595 (14)C9—C101.407 (2)
O—Ali2.0918 (10)C9—H9A0.9300
N1—N21.3344 (15)C10—C111.354 (2)
N1—C71.3556 (18)C10—H10A0.9300
N2—N31.3277 (15)C11—C121.417 (2)
N2—C21.4268 (17)C11—H11A0.9300
N3—C121.3483 (19)C13—H13A0.9600
C1—C61.3967 (18)C13—H13B0.9600
C1—C21.4084 (18)C13—H13C0.9600
C2—C31.3978 (17)C14—H14A0.9600
C3—C41.380 (2)C14—H14B0.9600
C3—H3B0.9300C14—H14C0.9600
C4—C51.390 (2)C15—H15A0.9600
C4—C131.5098 (19)C15—H15B0.9600
C5—C61.3826 (18)C15—H15C0.9600
C5—H5A0.9300
O—Al—C15115.55 (6)C1—C6—H6A118.8
O—Al—C14114.97 (6)N1—C7—C12107.66 (12)
C15—Al—C14129.44 (7)N1—C7—C8131.38 (13)
O—Al—Oi76.96 (4)C12—C7—C8120.97 (13)
C15—Al—Oi94.55 (6)C9—C8—C7116.14 (15)
C14—Al—Oi94.85 (5)C9—C8—H8A121.9
O—Al—N187.28 (4)C7—C8—H8A121.9
C15—Al—N192.11 (6)C8—C9—C10122.70 (16)
C14—Al—N191.89 (6)C8—C9—H9A118.7
Oi—Al—N1164.24 (4)C10—C9—H9A118.7
C1—O—Al134.46 (8)C11—C10—C9122.11 (15)
C1—O—Ali122.50 (8)C11—C10—H10A118.9
Al—O—Ali103.04 (4)C9—C10—H10A118.9
N2—N1—C7103.95 (11)C10—C11—C12116.60 (15)
N2—N1—Al127.89 (9)C10—C11—H11A121.7
C7—N1—Al128.13 (9)C12—C11—H11A121.7
N3—N2—N1115.67 (11)N3—C12—C7109.19 (12)
N3—N2—C2120.79 (11)N3—C12—C11129.32 (13)
N1—N2—C2123.49 (10)C7—C12—C11121.48 (14)
N2—N3—C12103.53 (11)C4—C13—H13A109.5
O—C1—C6119.56 (11)C4—C13—H13B109.5
O—C1—C2124.65 (11)H13A—C13—H13B109.5
C6—C1—C2115.79 (11)C4—C13—H13C109.5
C3—C2—C1121.32 (12)H13A—C13—H13C109.5
C3—C2—N2116.43 (11)H13B—C13—H13C109.5
C1—C2—N2122.22 (11)Al—C14—H14A109.5
C4—C3—C2121.75 (13)Al—C14—H14B109.5
C4—C3—H3B119.1H14A—C14—H14B109.5
C2—C3—H3B119.1Al—C14—H14C109.5
C3—C4—C5117.29 (12)H14A—C14—H14C109.5
C3—C4—C13121.89 (14)H14B—C14—H14C109.5
C5—C4—C13120.80 (14)Al—C15—H15A109.5
C6—C5—C4121.39 (13)Al—C15—H15B109.5
C6—C5—H5A119.3H15A—C15—H15B109.5
C4—C5—H5A119.3Al—C15—H15C109.5
C5—C6—C1122.45 (13)H15A—C15—H15C109.5
C5—C6—H6A118.8H15B—C15—H15C109.5

Symmetry codes: (i) −x, −y, −z+2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RK2147).

References

  • Bruker (2008). APEX2, SADABS and SAINT Bruker AXS Inc., Madison, Wisconsin, USA.
  • Lewinski, J., Zachara, J., Starowieyski, K. B., Ochal, Z., Justyniak, I., Kopec, T., Stolarzewicz, P. & Dranka, M. (2003). Organometallics, 22, 3773–3780.
  • Liu, Y.-C., Ko, B.-T. & Lin, C.-C. (2001). Macromolecules, 34, 6196–6201.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Tsai, C.-Y., Lin, C.-H. & Ko, B.-T. (2009). Acta Cryst. E65, m619. [PMC free article] [PubMed]
  • Wu, J., Yu, T.-L., Chen, C.-T. & Lin, C.-C. (2006). Coord. Chem. Rev.250, 602–626.

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