metal-organic compounds
Bis[μ-2-(2H-benzotriazol-2-yl)-4-methylphenolato]bis[dimethylaluminium(III)]
aDepartment of Chemistry, Chung Yuan Christian University, Chung-Li 320, Taiwan
*Correspondence e-mail: btko@cycu.edu.tw
The title complex, [Al2(CH3)4(C13H10N3O)2], is dimeric, bridged through the O atoms of the phenolate anions. The 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); Wu et al. (2006). For related structures, see: Lewinski et al. (2003); Tsai et al. (2009).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2008); cell SAINT (Bruker, 2008); data reduction: SAINT; 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.
Supporting information
10.1107/S1600536809018492/rk2147sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809018492/rk2147Isup2.hkl
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 δ 7.04–8.14 (14H, m, ArH), 2.40 (6H, s, CH3), -0.57 (12H, s, AlCH3).
was cooled to 273 K, yielding yellow crystals. Yield: 0.24 g (86%). 1H NMR (CDCl3, p.p.m.):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).
Data collection: APEX2 (Bruker, 2008); cell
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).[Al2(CH3)4(C13H10N3O)2] | Z = 1 |
Mr = 562.58 | F(000) = 296 |
Triclinic, P1 | Dx = 1.320 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.4220 (4) Å | Cell parameters from 7401 reflections |
b = 9.7120 (5) Å | θ = 2.5–28.2° |
c = 11.6331 (6) Å | µ = 0.14 mm−1 |
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 |
Bruker APEXII CCD diffractometer | 3405 independent reflections |
Radiation source: fine-focus sealed tube | 2923 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.017 |
ϕ and ω scans | θmax = 28.2°, θmin = 2.0° |
Absorption correction: multi-scan (SADABS; Bruker, 2008) | h = −9→8 |
Tmin = 0.937, Tmax = 0.966 | k = −12→12 |
11757 measured reflections | l = −14→15 |
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)] = 0.039 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0679P)2 + 0.1915P] where P = (Fo2 + 2Fc2)/3 |
3405 reflections | (Δ/σ)max = 0.001 |
182 parameters | Δρmax = 0.28 e Å−3 |
0 restraints | Δρmin = −0.26 e Å−3 |
[Al2(CH3)4(C13H10N3O)2] | γ = 109.574 (2)° |
Mr = 562.58 | V = 707.79 (7) Å3 |
Triclinic, P1 | Z = 1 |
a = 7.4220 (4) Å | Mo Kα radiation |
b = 9.7120 (5) Å | µ = 0.14 mm−1 |
c = 11.6331 (6) Å | T = 296 K |
α = 112.517 (2)° | 0.48 × 0.25 × 0.25 mm |
β = 94.824 (3)° |
Bruker APEXII CCD diffractometer | 3405 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2008) | 2923 reflections with I > 2σ(I) |
Tmin = 0.937, Tmax = 0.966 | Rint = 0.017 |
11757 measured reflections |
R[F2 > 2σ(F2)] = 0.039 | 0 restraints |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.28 e Å−3 |
3405 reflections | Δρmin = −0.26 e Å−3 |
182 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Al | 0.05537 (5) | 0.05266 (4) | 0.89433 (3) | 0.03495 (10) | |
O | 0.05448 (13) | 0.14683 (10) | 1.06417 (8) | 0.0383 (2) | |
N1 | 0.16914 (16) | 0.28879 (13) | 0.90600 (11) | 0.0394 (2) | |
N2 | 0.20710 (15) | 0.42899 (12) | 1.00733 (10) | 0.0366 (2) | |
N3 | 0.28396 (18) | 0.56192 (13) | 0.98973 (12) | 0.0457 (3) | |
C1 | 0.10477 (17) | 0.30216 (14) | 1.15315 (12) | 0.0347 (3) | |
C2 | 0.17660 (18) | 0.44012 (14) | 1.12950 (12) | 0.0348 (3) | |
C3 | 0.2281 (2) | 0.59650 (15) | 1.22664 (13) | 0.0420 (3) | |
H3B | 0.2737 | 0.6849 | 1.2076 | 0.050* | |
C4 | 0.2129 (2) | 0.62320 (16) | 1.35011 (13) | 0.0435 (3) | |
C5 | 0.1424 (2) | 0.48768 (17) | 1.37431 (13) | 0.0432 (3) | |
H5A | 0.1312 | 0.5018 | 1.4567 | 0.052* | |
C6 | 0.0886 (2) | 0.33235 (16) | 1.27846 (13) | 0.0421 (3) | |
H6A | 0.0399 | 0.2447 | 1.2982 | 0.051* | |
C7 | 0.22611 (19) | 0.33415 (16) | 0.81377 (13) | 0.0409 (3) | |
C8 | 0.2240 (2) | 0.2418 (2) | 0.68526 (15) | 0.0546 (4) | |
H8A | 0.1766 | 0.1290 | 0.6486 | 0.065* | |
C9 | 0.2959 (2) | 0.3281 (2) | 0.61786 (16) | 0.0588 (4) | |
H9A | 0.2961 | 0.2715 | 0.5328 | 0.071* | |
C10 | 0.3694 (2) | 0.4988 (2) | 0.67200 (16) | 0.0566 (4) | |
H10A | 0.4178 | 0.5511 | 0.6219 | 0.068* | |
C11 | 0.3719 (2) | 0.5895 (2) | 0.79461 (16) | 0.0534 (4) | |
H11A | 0.4203 | 0.7023 | 0.8297 | 0.064* | |
C12 | 0.29715 (19) | 0.50377 (16) | 0.86672 (14) | 0.0416 (3) | |
C13 | 0.2747 (3) | 0.7923 (2) | 1.45629 (17) | 0.0637 (5) | |
H13A | 0.3229 | 0.8706 | 1.4231 | 0.096* | |
H13B | 0.3771 | 0.8112 | 1.5237 | 0.096* | |
H13C | 0.1635 | 0.8026 | 1.4896 | 0.096* | |
C14 | −0.1914 (2) | −0.00914 (18) | 0.77213 (15) | 0.0490 (3) | |
H14A | −0.2766 | −0.1197 | 0.7492 | 0.073* | |
H14B | −0.1613 | 0.0013 | 0.6964 | 0.073* | |
H14C | −0.2562 | 0.0610 | 0.8114 | 0.073* | |
C15 | 0.2981 (2) | 0.02143 (18) | 0.86005 (16) | 0.0501 (3) | |
H15A | 0.2845 | −0.0846 | 0.8501 | 0.075* | |
H15B | 0.4081 | 0.1025 | 0.9306 | 0.075* | |
H15C | 0.3199 | 0.0312 | 0.7828 | 0.075* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Al | 0.03920 (19) | 0.03075 (17) | 0.03427 (18) | 0.01356 (14) | 0.01205 (14) | 0.01332 (13) |
O | 0.0501 (5) | 0.0270 (4) | 0.0362 (4) | 0.0132 (3) | 0.0149 (4) | 0.0131 (3) |
N1 | 0.0451 (5) | 0.0326 (5) | 0.0389 (5) | 0.0130 (4) | 0.0134 (4) | 0.0155 (4) |
N2 | 0.0380 (5) | 0.0293 (4) | 0.0405 (5) | 0.0110 (4) | 0.0075 (4) | 0.0160 (4) |
N3 | 0.0533 (6) | 0.0335 (5) | 0.0504 (6) | 0.0124 (5) | 0.0101 (5) | 0.0231 (5) |
C1 | 0.0349 (5) | 0.0294 (5) | 0.0369 (6) | 0.0121 (4) | 0.0098 (4) | 0.0122 (4) |
C2 | 0.0354 (5) | 0.0312 (5) | 0.0362 (6) | 0.0136 (4) | 0.0064 (4) | 0.0132 (4) |
C3 | 0.0457 (7) | 0.0305 (5) | 0.0440 (7) | 0.0144 (5) | 0.0041 (5) | 0.0128 (5) |
C4 | 0.0436 (6) | 0.0354 (6) | 0.0414 (7) | 0.0166 (5) | 0.0031 (5) | 0.0074 (5) |
C5 | 0.0450 (7) | 0.0433 (6) | 0.0353 (6) | 0.0178 (5) | 0.0108 (5) | 0.0110 (5) |
C6 | 0.0473 (7) | 0.0382 (6) | 0.0403 (6) | 0.0158 (5) | 0.0156 (5) | 0.0167 (5) |
C7 | 0.0398 (6) | 0.0427 (6) | 0.0441 (6) | 0.0150 (5) | 0.0134 (5) | 0.0234 (5) |
C8 | 0.0635 (9) | 0.0543 (8) | 0.0464 (7) | 0.0219 (7) | 0.0219 (7) | 0.0223 (6) |
C9 | 0.0581 (8) | 0.0775 (10) | 0.0476 (8) | 0.0259 (8) | 0.0207 (6) | 0.0338 (7) |
C10 | 0.0463 (7) | 0.0758 (9) | 0.0619 (9) | 0.0192 (7) | 0.0156 (6) | 0.0483 (7) |
C11 | 0.0506 (8) | 0.0551 (7) | 0.0636 (9) | 0.0157 (6) | 0.0132 (6) | 0.0395 (7) |
C12 | 0.0382 (6) | 0.0427 (6) | 0.0481 (7) | 0.0141 (5) | 0.0086 (5) | 0.0261 (5) |
C13 | 0.0802 (11) | 0.0409 (8) | 0.0481 (9) | 0.0224 (8) | 0.0030 (8) | 0.0019 (6) |
C14 | 0.0484 (7) | 0.0451 (7) | 0.0506 (8) | 0.0163 (6) | 0.0066 (6) | 0.0213 (6) |
C15 | 0.0452 (7) | 0.0443 (7) | 0.0595 (8) | 0.0189 (6) | 0.0192 (6) | 0.0192 (6) |
Al—O | 1.8337 (10) | C6—H6A | 0.9300 |
Al—C15 | 1.9725 (15) | C7—C12 | 1.3991 (19) |
Al—C14 | 1.9767 (15) | C7—C8 | 1.414 (2) |
Al—Oi | 2.0918 (10) | C8—C9 | 1.370 (2) |
Al—N1 | 2.1060 (11) | C8—H8A | 0.9300 |
O—C1 | 1.3595 (14) | C9—C10 | 1.407 (2) |
O—Ali | 2.0918 (10) | C9—H9A | 0.9300 |
N1—N2 | 1.3344 (15) | C10—C11 | 1.354 (2) |
N1—C7 | 1.3556 (18) | C10—H10A | 0.9300 |
N2—N3 | 1.3277 (15) | C11—C12 | 1.417 (2) |
N2—C2 | 1.4268 (17) | C11—H11A | 0.9300 |
N3—C12 | 1.3483 (19) | C13—H13A | 0.9600 |
C1—C6 | 1.3967 (18) | C13—H13B | 0.9600 |
C1—C2 | 1.4084 (18) | C13—H13C | 0.9600 |
C2—C3 | 1.3978 (17) | C14—H14A | 0.9600 |
C3—C4 | 1.380 (2) | C14—H14B | 0.9600 |
C3—H3B | 0.9300 | C14—H14C | 0.9600 |
C4—C5 | 1.390 (2) | C15—H15A | 0.9600 |
C4—C13 | 1.5098 (19) | C15—H15B | 0.9600 |
C5—C6 | 1.3826 (18) | C15—H15C | 0.9600 |
C5—H5A | 0.9300 | ||
O—Al—C15 | 115.55 (6) | C1—C6—H6A | 118.8 |
O—Al—C14 | 114.97 (6) | N1—C7—C12 | 107.66 (12) |
C15—Al—C14 | 129.44 (7) | N1—C7—C8 | 131.38 (13) |
O—Al—Oi | 76.96 (4) | C12—C7—C8 | 120.97 (13) |
C15—Al—Oi | 94.55 (6) | C9—C8—C7 | 116.14 (15) |
C14—Al—Oi | 94.85 (5) | C9—C8—H8A | 121.9 |
O—Al—N1 | 87.28 (4) | C7—C8—H8A | 121.9 |
C15—Al—N1 | 92.11 (6) | C8—C9—C10 | 122.70 (16) |
C14—Al—N1 | 91.89 (6) | C8—C9—H9A | 118.7 |
Oi—Al—N1 | 164.24 (4) | C10—C9—H9A | 118.7 |
C1—O—Al | 134.46 (8) | C11—C10—C9 | 122.11 (15) |
C1—O—Ali | 122.50 (8) | C11—C10—H10A | 118.9 |
Al—O—Ali | 103.04 (4) | C9—C10—H10A | 118.9 |
N2—N1—C7 | 103.95 (11) | C10—C11—C12 | 116.60 (15) |
N2—N1—Al | 127.89 (9) | C10—C11—H11A | 121.7 |
C7—N1—Al | 128.13 (9) | C12—C11—H11A | 121.7 |
N3—N2—N1 | 115.67 (11) | N3—C12—C7 | 109.19 (12) |
N3—N2—C2 | 120.79 (11) | N3—C12—C11 | 129.32 (13) |
N1—N2—C2 | 123.49 (10) | C7—C12—C11 | 121.48 (14) |
N2—N3—C12 | 103.53 (11) | C4—C13—H13A | 109.5 |
O—C1—C6 | 119.56 (11) | C4—C13—H13B | 109.5 |
O—C1—C2 | 124.65 (11) | H13A—C13—H13B | 109.5 |
C6—C1—C2 | 115.79 (11) | C4—C13—H13C | 109.5 |
C3—C2—C1 | 121.32 (12) | H13A—C13—H13C | 109.5 |
C3—C2—N2 | 116.43 (11) | H13B—C13—H13C | 109.5 |
C1—C2—N2 | 122.22 (11) | Al—C14—H14A | 109.5 |
C4—C3—C2 | 121.75 (13) | Al—C14—H14B | 109.5 |
C4—C3—H3B | 119.1 | H14A—C14—H14B | 109.5 |
C2—C3—H3B | 119.1 | Al—C14—H14C | 109.5 |
C3—C4—C5 | 117.29 (12) | H14A—C14—H14C | 109.5 |
C3—C4—C13 | 121.89 (14) | H14B—C14—H14C | 109.5 |
C5—C4—C13 | 120.80 (14) | Al—C15—H15A | 109.5 |
C6—C5—C4 | 121.39 (13) | Al—C15—H15B | 109.5 |
C6—C5—H5A | 119.3 | H15A—C15—H15B | 109.5 |
C4—C5—H5A | 119.3 | Al—C15—H15C | 109.5 |
C5—C6—C1 | 122.45 (13) | H15A—C15—H15C | 109.5 |
C5—C6—H6A | 118.8 | H15B—C15—H15C | 109.5 |
Symmetry code: (i) −x, −y, −z+2. |
Experimental details
Crystal data | |
Chemical formula | [Al2(CH3)4(C13H10N3O)2] |
Mr | 562.58 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 296 |
a, b, c (Å) | 7.4220 (4), 9.7120 (5), 11.6331 (6) |
α, β, γ (°) | 112.517 (2), 94.824 (3), 109.574 (2) |
V (Å3) | 707.79 (7) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 0.14 |
Crystal size (mm) | 0.48 × 0.25 × 0.25 |
Data collection | |
Diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2008) |
Tmin, Tmax | 0.937, 0.966 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11757, 3405, 2923 |
Rint | 0.017 |
(sin θ/λ)max (Å−1) | 0.665 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.122, 1.03 |
No. of reflections | 3405 |
No. of parameters | 182 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.28, −0.26 |
Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Acknowledgements
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
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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.