Reactivity studies of LAlH2 (L = HC(CMeNAr)2, Ar = 2,6-i Pr2C6H3) with 2-aminobenzenethiol, 2-aminophenol, and 1,4-dithiane-2,5-diol

Article abstract of DOI:10.1021/om300577j

The reaction of LAlH₂ (L = HC(CMeNAr)₂, Ar = 2,6-iPr₂C₆H₃) (1) with 2-aminobenzenethiol, 2-aminophenol, and 1,4-dithiane-2,5-diol resulted in the compounds LAl[(μ-N)(μ-S)](o-C₆H₄) (2), LAl[(μ-O)(o-C ₆H₄)(NH₂)]₂ (3), and LAl(μ-O)₂(p-dithiane) (4), respectively. Compound 2 features an organic-inorganic hybrid containing an NAlSC₂ five-membered ring, while compound 3 exhibits a C-O-Al-O-C chain structure. Compound 4 forms a basket-like molecule with the C₄S₂ unit as the bottom part and O₂Al as the handle. Complexes 2, 3, and 4 were characterized by ¹H NMR, elemental analysis, and single-crystal X-ray diffraction studies.

Full text of DOI:10.1021/om300577j

Note
pubs.acs.org/Organometallics
Reactivity Studies of LAlH2 (L = HC(CMeNAr)2, Ar = 2,6‑iPr2C6H3) with
2‑Aminobenzenethiol, 2‑Aminophenol, and 1,4-Dithiane-2,5-diol
Zhi Yang,*,† Pengfei Hao,† Zhihong Liu,† Xiaoli Ma,† Herbert W. Roesky,*,‡ Kening Sun,† and Jiarong Li†
†School of Chemical Engineering and Environment, Beijing Institute of Technology, 100081 Beijing, China
‡Institut fur Anorganische Chemie der Georg-August-Universitat Gottingen, Tammannstrasse 4, D-37077 Gottingen, Germany
̈
̈
̈
̈
S
* Supporting Information
ABSTRACT: The reaction of LAlH2 (L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) (1) with 2-
aminobenzenethiol, 2-aminophenol, and 1,4-dithiane-2,5-diol resulted in the compounds LAl[(μ-
N)(μ-S)](o-C6H4) (2), LAl[(μ-O)(o-C6H4)(NH2)]2 (3), and LAl(μ-O)2(p-dithiane) (4),
respectively. Compound 2 features an organic−inorganic hybrid containing an NAlSC2 five-
membered ring, while compound 3 exhibits a C−O−Al−O−C chain structure. Compound 4
forms a basket-like molecule with the C4S2 unit as the bottom part and O2Al as the handle.
Complexes 2, 3, and 4 were characterized by 1H NMR, elemental analysis, and single-crystal X-ray
diffraction studies.
benzenethiol, 2-aminophenol, and 1,4-dithiane-2,5-diol, respec-
tively.
INTRODUCTION
■
Owing to the strong Lewis acidity and inexpensiveness, the
aluminum complexes attract considerable attention for organic
synthesis1 and polymerization.2 Aluminum compounds con-
taining Al−S−C moieties have not been well studied when
compared with those containing Al−O−C cores. This is mainly
due to the thermodynamic stability of the latter species.
Aluminum sulfides with the [AlS]n core are either planar (n =
2), cubic (n = 4), or drum-like (n = 6) or possess more complex
structures with an Al:S molar ratio different from that of 1:1.3
In 2003 Jancik et al. reported on the preparation of the unique
monomeric aluminum moiety comprising two terminal S−H
groups.4 Henceforth, more and more aluminum compounds
containing the Al−S−C core were reported.5 It is noteworthy
to mention that aluminum nitrides possessing the Al−N−C
core are associated with far-ranging applications such as Al−N-
based semiconductors and Al−N-based ceramics.6 However,
compounds containing the S−Al−N moiety are very rare.7−9
Thus, we became interested in preparing organoaluminum
heterocycles containing both the Al−S−C core and the Al−N−
C skeleton. Meanwhile, aluminoxane exhibits excellent initiator
properties for the ring-opening polymerization of lactone.10
Main group metal hydrides supported by organic ligands are
important in organometallic chemistry. Previously,11−15 we
reported on a series of organoaluminum heterocycles by the
reaction of organic aluminum precursors with organic
compounds containing reactive groups. Due to the converse
polarity of the hydrides in 1 and the protons in C−XH (X = S,
N, O), these systems facilitate reactions under hydrogen
elimination. Herein, we report on three structures bearing the
Al−X−C moiety by the reaction of 1 with 2-amino-
RESULTS AND DISCUSSION
■
The reaction of 1 with 2-aminobenzenethiol, 2-aminophenol,
and 1,4-dithiane-2,5-diol (Scheme 1) in a molar ratio of 1:1,
1:2, and 1:1 resulted in products LAl[(μ-N)(μ-S)](o-C6H4)
(2), LAl[(μ-O)(o-C6H4)(NH2)]2 (3), and LAl(μ-O)2(p-
dithiane) (4), respectively. During the course of these reactions
hydrogen gas evolution was observed, which proceeds under
the elimination of 2 equiv of hydrogen. Compound 2 was
crystallized from THF, 3 from toluene, and 4 from n-hexane.
All products are soluble in toluene, benzene, THF, and
trichloromethane, respectively.
1
Compounds 2, 3, and 4 were characterized by H NMR
investigation in CDCl3 and by elemental analysis. The 1H NMR
spectra of 3 and 4 exhibit one set of resonances for the aryl
group on sulfur, nitrogen, carbon, and the ligand, indicating
symmetric molecules. The IR spectrum of compound 2 shows a
strong absorption band at v 3309 cm−1, which is quite close to
̅
that (v 3398 and v 3220 cm−1) reported in refs 8 and 9 with the
proton bound to nitrogen.
̅
̅
Compound 2 crystallizes in the orthorhombic space group
Cmca, 3 in the monoclinic P21/c, and 4 in the orthorhombic
Pbca. The molecular structures are shown in Figures 1, 2, and 3,
respectively. For the structure of 2, two carbon atoms, one
aluminum atom, one nitrogen atom, and one sulfur atom form
a five-membered planar C2AlNS ring. The central aluminum
Received: June 27, 2012
Published: August 10, 2012
© 2012 American Chemical Society
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Organometallics
Note
Scheme 1. Preparation of Compounds 2, 3, and 4
Figure 2. Molecular structure of 3. Thermal ellipsoids are drawn at the
50% level, and hydrogen atoms attached to the benzene nitrogens are
shown. Selected bond distances (Å) and angles (deg): Al(1)−N(1)
1.868(4), Al(1)−N(2) 1.878(4), Al(1)−O(1) 1.716(3), Al(1)−O(2)
1.705(3); O(1)−Al(1)−N(1) 111.26(18), O(1)−Al(1)−N(2)
114.93(18), O(2)−Al(1)−O(1) 109.80(18), O(2)−Al(1)−N(1)
113.18(18), O(2)−Al(1)−N(2) 108.80(18), N(1)−Al(1)−N(2)
98.53(17).
Figure 3. Molecular structure of 4. Thermal ellipsoids are drawn at the
50% level. The solvent molecule and the hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): Al(1)−N(1)
1.888(2), Al(1)−N(2) 1.892(2), Al(1)−O(1) 1.724(2), Al(1)−O(2)
1.730(2), O(1)−C(30) 1.375(8), O(2)−C(31) 1.405(17), C(31)−
S(1) 1.853(15), C(36)−S(1) 1.811(6), C(30)−S(2) 1.816(7),
C(32)−S(2) 1.822(7), C(32)−C(31) 1.573(16), C(30)−C(36)
1.542(8); O(1)−Al(1)−N(1) 111.40(10), O(2)−Al(1)−N(2)
112.74(11), O(1)−Al(1)−O(2) 111.67(10), N(1)−Al(1)−N(2),
96.74(10), C(30)−O(1)−Al(1) 127.6(3), C(31)−O(2)−Al(1)
125.2(8), O(1)−C(30)−C(36) 110.2(5), O(1)−C(30)−S(2)
112.9(5), C(36)−C(30)−S(2) 110.6(5), C(31)−C(32)−S(2)
115.4(8), O(2)−C(31)−C(32) 14.8(10), O(2)−C(31)−S(1)
110.5(10), C(32)−C(31)−S(1) 106.2(10), C(30)−C(36)−S(1)
113.4(4), C(36)−S(1)−C(31) 104.0(6), C(30)−S(2)−C(32)
101.2(3).
Figure 1. Molecular structure of 2. Thermal ellipsoids are drawn at the
50% level. The solvent molecule and the hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): Al(1)−N(1)
1.877(2), Al(1)−N(2) 1.877(2), Al(1)−N(3) 1.799(4), Al(1)−S(1)
2.2274(15), N(3)−C(21) 1.387(5), S(1)−C(16) 1.778(4), C(16)−
C(21) 1.406(6); N(1)−Al(1)−N(2) 97.49(14), N(3)−Al(1)−N(1)
116.83(10), N(3)−Al(1)−N(2) 116.83(10), N(1)−Al(1)−S(1)
116.88(8), N(2)−Al(1)−S(1) 116.88(8), C(16)−S(1)−Al(1)
92.21(14), N(3)−Al(1)−S(1) 93.52(12), C(21)−C(16)−S(1)
118.5(3), C(21)−N(3)−Al(1) 116.8(3), N(3)−C(21)−C(16)
119.0(4).
atom is located in the spirocyclic center of the fused six-
membered ring (C3N2Al) and the five-membered ring
(C2AlNS). The sum of the inner angles of the C2AlO2 five-
membered ring in 2 is 539.99°, which is quite close to the ideal
planar ring of 540°. Compound 3 exhibits a C−O−Al−O−C
framework with the unreacted protons on the ortho-nitrogen
atoms. The Al(1)−O(1) bond length of 3 (av 1.716 Å) is
slightly longer when compared with the normal Al−OH bond
distance (av 1.705 Å) in LAl(OH)2.16 It is interesting that the
structure of 3 is quite different from that of 2. This is
independent of the precursor ratio of 1:1 or 1:2 (1 to 2-
aminobenzenethiol or 2-aminophenol). For this different
behavior we assume that the thermodynamic Al−O bond
energy in 3 favors the formation of the two Al−O bonds, while
in 2 the more flexible Al−S−C bond angle of 92.21(14)°
prefers the formation of the five-membered AlNC2S ring. The
formation of LAl[(μ-S)(o-C6H4)(NH2)]2 instead of 2 was not
observed. For comparing the rigid compounds 2 and 3 the
product with the more flexible 1,4-dithiane-2,5-diol precursor
was prepared. Compound 4 contains the organic−inorganic
hybrid with the AlO2C3S seven-membered rings, which show a
structure similar to a basket with the O−Al−O as the handle
and C4S2 as the bottom. During the reaction the 2,5-dithiazole
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Organometallics
Note
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six-membered ring turned from the chair conformation to a
boat configuration under elimination of hydrogen and
formation of two Al−O bonds. The Al−O bond length in 4
(av 1.727 Å) is longer when compared with that of LAl(OH)2
(av 1.705 Å). This might be due to the electron-donating ligand
bound at the aluminum.
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Figure 4. Core molecular structure of 4. Thermal ellipsoids are drawn
at the 50% level. The solvent molecule and the hydrogen atoms are
omitted for clarity. The molecular structure of the latter shows as the
lower part a basket-like arrangement.
́
4528−4530. (h) Rascon-Cruz, F.; Huerta-Lavorie, R.; Jancik, V.;
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SUMMARY
■
Three compounds containing the Al−X−C (X = S, N, O)
structural motif have been prepared by the facile reaction of
aluminum hydride with 2-aminobenzenethiol, 2-aminophenol,
and 1,4-dithiane-2,5-diol, respectively. These compounds have
novel aluminum-containing acyclic or cyclic building blocks
with O, S, and N elements. Presently we are investigating their
catalytic properties for ring-opening polymerization of cyclic
esters and rac-lactide.
ASSOCIATED CONTENT
* Supporting Information
Table, cif files for compounds 2, 3, and 4, and full experimental
procedures are available free of charge via the Internet at
http://pubs.acs.org.
■
S
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N. J.; Kostalik, H. A.; Lobkovsky, E. B.; Mutolo, P. F.; Abruna, H. D.;
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A. L.; Kopilov, J.; Goldberg, I.; Coates, G. W.; Kol, M. Chem. Commun.
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AUTHOR INFORMATION
Corresponding Author
*Fax: (+86) 10-68911040 (Z.Y.), (+49) 551-393-373
(H.W.R.). E-mail: zhiyang@bit.edu.cn (Z.Y.), hroesky@gwdg.
de (H.W.R.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(11) Yang, Z.; Ma, X.; Oswald, R. B.; Roesky, H. W.; Zhu, H.;
Schulzke, C.; Starke, K.; Baldus, M.; Schmidt, H.-G.; Noltemeyer, M.
Angew. Chem., Int. Ed. 2005, 44, 7072−7074; Angew. Chem. 2005, 117,
7234−7236.
(12) (a) Yang, Z.; Ma, X.; Oswald, R. B.; Roesky, H. W.; Noltemeyer,
M. J. Am. Chem. Soc. 2006, 128, 12406−12407. (b) Yang, Z.; Ma, X.;
Jancik, V.; Zhang, Z.; Roesky, H. W.; Magull, J.; Noltemeyer, M.;
Schmidt, H.-G.; Cea-Olivares, R.; Toscano, R. A. Inorg. Chem. 2006,
45, 3312−3315.
(13) Yang, Z.; Ma, X.; Roesky, H. W.; Yang, Y.; Magull, J.; Ringe, A.
Inorg. Chem. 2007, 46, 7093−7096.
(14) Yang, Z.; Ma, X.; Zhang, Z.; Roesky, H. W.; Magull, J.; Ringe, A.
Z. Anorg. Allg. Chem. 2008, 634, 2740−2742.
This work was supported by the National Nature Science
Foundation of China (21001016, 20901009); the Research
Fund for the Doctoral Program of Higher Education of China
(2009110112043); the Program of NCET-10-0050; and
International S&T Cooperation Program of China.
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