1308
Organometallics 2007, 26, 1308-1310
A Cyclopropenylaluminum Derivative from Hydrolysis and
Alcoholysis of an Aluminacyclobutenone
Yihua Gao, Xiaoyan Cheng, Haibin Song, Jianying Zhang, and Chunming Cui*
State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai UniVersity, Tianjin 300071,
People’s Republic of China
ReceiVed January 11, 2007
Summary: Hydrolysis and alcoholysis of the cyclic aluminum
acyl LAl[C(O)C(SiMe3)C(SiMe3)] (1; L ) HC[(CMe)(NAr)]2,
Ar ) 2,6-iPr2C6H3) resulted in the formation of the cyclopro-
penylaluminum deriVatiVe LAl{[C3(SiMe3)2]C(O)C(SiMe3)C-
(SiMe3)} (2) with the elimination of aluminum hydroxides
LAlOH(OR) (R ) H, Et, tBu).
Thus, hydrolysis of 1 was conducted in toluene at low
temperature.6 The 1H NMR spectrum of the crude product
indicates almost quantitative formation of two products in a 1:1
ratio (Scheme 1). Compound 2 was obtained as orange crystals
in modest yield by crystallization of the crude product from
n-hexane, and colorless crystals of 3 could be isolated in low
yield (ca. 20%) by repeated crystallization of the remaining solid
from n-hexane. Compound 2 has been fully characterized by
1H and 13C NMR, UV-vis, and IR spectroscopy, by elemental
analysis, and by X-ray single-crystal analysis.6,7 The formation
In recent years, strained rings that incorporate heavier main-
group elements have been intensely investigated, owing to their
unusual chemical and physical properties.1 It has been shown
that AlC2 ring compounds are highly reactive and display diverse
reaction patterns because of the ring strain and relatively weak
Al-C bonds.2 Despite the fact that several AlC2 ring compounds
have been studied, the chemistry of AlC3 ring systems has
received less attention. Recently, we reported on the first
synthesis of the cyclic aluminum acyl complex LAl[C(O)C-
(SiMe3)C(SiMe3)] (1) by a CO insertion reaction with LAl[η2-
(Me3SiC2SiMe3)] (L ) HC[(CMe)(NAr)]2, Ar ) 2,6-iPr2C6H3).3
This AlC3 ring species contains two different Al-C bonds, and
their relative reactivities are of fundamental interest. On the other
hand, well-defined aluminum acyl compounds are very rare4
and the nature of Al-C(O) bonds has been essentially unex-
plored. It has been reported that compound 1 is readily oxidized
by molecular oxygen at low temperature, resulting in the
selective insertion of one oxygen atom into the Al-C(O) bond.3
Herein we report on the unexpected formation of the first
cyclopropenylaluminum complex via hydrolysis and alcoholysis
of 1.
1
of 3 was confirmed by H and 13C NMR and IR spectroscopy
and X-ray structural analysis. 3 was previously prepared by
hydrolysis of LAlI2 in a two-phase ammonia/toluene system or
in the presence of an N-heterocyclic carbene and has been fully
characterized.8
1
The H NMR spectrum of 2 displays three singlets for the
SiMe3 groups, and the total integration is doubled compared to
that of 1, indicating the transfer of the C2(SiMe3)2 moiety from
one molecule of 1 to the other. The 13C NMR spectrum of 2
shows the resonances for the carbonyl group at δ 212.6 ppm
and for the olefinic carbons in the cyclopropene subunit at δ
(6) To a solution of LAl[C(O)C(SiMe3)C(SiMe3)] (0.13 g, 0.20 mmol)
in n-hexane (10 mL) was added a solution of water (1.8 µL, 0.10 mmol) in
toluene (2 mL) at -78 °C. The mixture was warmed to room temperature.
All volatiles were removed under vacuum, and the remaining solid was
crystallized from n-hexane at -20 °C to yield 2 as yellow crystals (0.05 g,
59%). Anal. Calcd for C47H77AlN2OSi4 (825.45): C, 68.39; H, 9.32; N,
3.39. Found: C, 68.31; H, 8.95; N, 3.37. 1H NMR (C6D6): δ -0.02 (s,
18H, SiMe3), 0.51, 0.52 (s, 2 × 9H, SiMe3), 1.00 (d, 6H, J ) 6.80 Hz,
CHMe2), 1.17 (d, 12H, J ) 6.80 Hz, CHMe2), 1.21 (d, 6H, J ) 6.80 Hz,
6H, CHMe2), 1.31 (s, 6H, Me), 2.97, 3.09 (sept, 2 × 2H, J ) 6.80 Hz,
CHMe2), 5.07 (s, 1H, γ-CH), 7.01-7.09 (m, 6H, Ar H). 13C NMR (C6D6):
δ 0.79, 3.85, 4.64 (SiMe3), 24.30, 24.69, 25.21, 26.00, 26.57 (CHMe2, Me),
27.90, 28.69 (CHMe2), 102.36 (γ-CH), 102.47 (Al-C in the C3 ring), 123.57
(Al-C(SiMe3)-C(SiMe3)),124.98, 125.77, 134.20, 141.93, 143.63, 145.18
(Ar C), 171.81 (CdN), 183.23 (Al-CC2(SiMe3)2), 196.60 (br, Al-
C(SiMe3)), 212.57 (CO). IR: ν/cm-1 1715 (m, CdC), 1611 (s, CO), 1536
We recently demonstrated a high-yield route for the prepara-
tion of an aluminum hydroxide by controlled hydrolysis of LAl-
[η2-(Me3SiC2SiMe3)].5 The selective cleavage of the Al-C bond
in the small-ring system prompted us to investigate the relative
reactivity of the two different Al-C bonds of 1 toward H2O.
* To whom correspondence should be addressed. E-mail: cmcui@
nankai.edu.cn.
(1) For reviews, see: (a) Sekiguchi, A.; Lee, V. Y. Chem. ReV. 2003,
103, 1429. (b) Escudie´, J.; Couret, C.; Ranaivonjatovo, H.; Satge, J. Coord.
Chem. ReV. 1994, 130, 427. (c) Driess, M.; Gru¨tzmacher, H. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 828. (d) Tsumuraya, T.; Batcheller, S. A.;
Masamune, S. Angew. Chem., Int. Ed. Engl. 1991, 30, 902.
(2) (a) Zhu, H.; Oswald, R. B.; Fan, H.; Roesky, H. W.; Ma, Q.; Yang,
Z.; Schmidt, H.-G.; Noltemeyer, M.; Starke, K.; Hosmane, N. S. J. Am.
Chem. Soc. 2006, 128, 5100. (b) Zhu, H.; Chai, J.; Fan, H.; Roesky, H.
W.; He, C.; Jancik, V.; Schmidt, H.-G.; Noltemeyer, M.; Merrill, W. A.;
Power, P. P. Angew. Chem., Int. Ed. 2005, 44, 5090. (c) Cui, C.; Ko¨pke,
S.; Herbst-Irmer, R.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.;
Wrackmeyer, B. J. Am. Chem. Soc. 2001, 123, 9091. (d) Uhl, W.; Spies,
T.; Koch, R.; Saak, W. Organometallics 1999, 18, 4598. (e) Li, X.; Song,
H.; Duan, L.; Cui, C.; Roesky, H. W. Inorg. Chem. 2006, 45, 1912. (f)
Zhu, H.; Chai, J.; Ma, Q.; Jancik, V.; Roesky, H. W.; Fan, H.; Herbst-
Irmer, R. J. Am. Chem. Soc. 2004, 126, 10194.
(s, CdC). UV-vis (hexanes): λmax/nm 345 (shoulder). LAl(OH)2 was
obtained by repeated crystallization of the remaining solid from n-hexane.
The spectroscopic data are the same as those reported.8 Reactions of 1 with
EtOH and tBuOH were conducted similarly. Compound 2 was isolated by
crystallization from n-hexane in ca. 50% yield for both of the reactions.
Hydroxyaluminum alkoxides 4 and 5 can not be isolated in pure form by
repeated crystallization. The NMR spectra of 4 and 5 containing small
amount of 2 indicate their formation. Selected 1H NMR (C6D6) data for 5:
δ 0.53 (s, 1H, OH), 0.83 (s, 9H, tBu), 1.06, 1.16, 1.35, 1.45 (d, 4 × 6H, J
) 6.80 Hz, CHMe2), 1.55 (s, 6H, Me), 3.36, 3.47 (sept, 2 × 2H, J ) 7.20
Hz, CHMe2), 4.84 (s, 1H, γ-CH). IR: ν/cm-1 3744 (OH).
(7) Crystallographic data for 2: Mo KR (λ ) 0.710 73 Å) radiation at
113(2) K, monoclinic, space group P121/n1, a ) 11.1041(7) Å, b ) 38.623-
(2) Å, c ) 12.8542(8) Å, â ) 115.449(2)°, Z ) 4, GOF ) 1.061, R1 )
0.0481, wR2 ) 0.1095 for 11 848 reflections (I > 2σ(I)); R1 ) 0.0583,
wR2 ) 0.1157 for all data. CCDC-620154 contains the supplementary
crystallographic data for this paper.
(8) (a) Zhu, H.; Chai, J.; He, C.; Bai, G.; Roesky, H. W.; Schmidt, H.-
G.; Noltemeyer, M. Organometallics 2005, 24, 380. (b) Bai, G.; Peng, Y.;
Roesky, H. W.; Li, J.; Schmidt, H.-G.; Noltemeyer, M. Angew. Chem., Int.
Ed. 2003, 42, 1132.
(3) Li, X.; Ni, C.; Song, H.; Cui, C. Chem. Commun. 2006, 1763.
(4) Mason, M. R.; Song, B.; Kirschbaum, K. J. Am. Chem. Soc. 2004,
126, 11812.
(5) Li, X.; Duan, L.; Song, H.; Ni, C.; Cui, C. Organometallics 2006,
25, 5665.
10.1021/om070028k CCC: $37.00 © 2007 American Chemical Society
Publication on Web 02/16/2007