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Acta Cryst. (2009). E65, m670    [ doi:10.1107/S1600536809018492 ]

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

C.-Y. Li, C.-H. Lin and B.-T. Ko

Abstract top

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.

Comment top

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.

Related literature top

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

Experimental top

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 top

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).

Computing details top

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

Figures top
[Figure 1] 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.
[Figure 2] Fig. 2. The preparation pass for the title compound I.
Bis[µ-2-(2H-benzotriazol-2-yl)-4- methylphenolato]bis[dimethylaluminium(III)] top
Crystal data top
[Al2(CH3)4(C13H10N3O)2]Z = 1
Mr = 562.58F000 = 296
Triclinic, P1Dx = 1.320 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 7.4220 (4) ÅCell parameters from 7401 reflections
b = 9.7120 (5) Åθ = 2.5–28.2º
c = 11.6331 (6) ŵ = 0.14 mm−1
α = 112.517 (2)ºT = 296 K
β = 94.824 (3)ºBlock, yellow
γ = 109.574 (2)º0.48 × 0.25 × 0.25 mm
V = 707.79 (7) Å3
Data collection top
Bruker APEXII CCD
diffractometer		3405 independent reflections
Radiation source: fine-focus sealed tube2923 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.017
T = 296 Kθmax = 28.2º
φ and ω scansθmin = 2.0º
Absorption correction: multi-scan
(SADABS; Bruker, 2008)		h = −9→8
Tmin = 0.937, Tmax = 0.966k = −12→12
11757 measured reflectionsl = −14→15
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039H-atom parameters constrained
wR(F2) = 0.122  w = 1/[σ2(Fo2) + (0.0679P)2 + 0.1915P]
where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max = 0.001
3405 reflectionsΔρmax = 0.28 e Å−3
182 parametersΔρmin = −0.26 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
[Al2(CH3)4(C13H10N3O)2]γ = 109.574 (2)º
Mr = 562.58V = 707.79 (7) Å3
Triclinic, P1Z = 1
a = 7.4220 (4) ÅMo Kα
b = 9.7120 (5) ŵ = 0.14 mm−1
c = 11.6331 (6) ÅT = 296 K
α = 112.517 (2)º0.48 × 0.25 × 0.25 mm
β = 94.824 (3)º
Data collection top
Bruker APEXII CCD
diffractometer		3405 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2008)		2923 reflections with I > 2σ(I)
Tmin = 0.937, Tmax = 0.966Rint = 0.017
11757 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.039182 parameters
wR(F2) = 0.122H-atom parameters constrained
S = 1.03Δρmax = 0.28 e Å−3
3405 reflectionsΔρmin = −0.26 e Å−3
Special details top

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) top
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) top
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, °) top
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.
Acknowledgements top

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).

references
References top

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