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An Al4(OH)4 Eight-Membered Ring in a Molecular Aluminopolysiloxane and Its Behavior with Bases.

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[lo] S. G. Blanco. M. P. Gomez-Sal, S. M Carreras, M. Mena, P. Royo, R. Serrano. J Chrm. Sor. Chem. Commun. 1986, 1572.
[ l l ] P. Gbmez-Sal. A Martin, M. Mena, C. Yelamos, Inorg. Chem. 1996,35,242.
[12] E H M O calculations were carried out using standard programs and
parameters a) J. Howell, A. Rossi. D. Wallace, K. Haraki. R. Hoffmann,
FORTICONN QCPE 1977,II. 344. Bond lengths and angles were taken from
X-ray crystallographic data and idealized for T, symmetry.
[13] a) F. Bottoniley, F. Grein. Inorg. Chsm. 1982, 21, 4170; b) P. D. Williams,
M D. Curtis. [hid.1986, 25, 4562; c) F. Botromley, D. E. Paez, P. S. White,
F. H. Kohler. R C. Thompson, N. P. C. Westwood. Organometullics 1990, 9,
2443: d ) C. D Abernethy, F. Bottomley, A. Decken, T. S. Cameron, ibid. 1996,
1s. 1758
[I41 Initial rate method (97k 1 C). k , = 4.03(7) x 10-‘sC1 for 1 and k , =
1.47(1) x 1 0 - O
for [D,]-I. k,,!k, = 2.7.
[15] C. McDade. J C. Green, J. E. Bercaw, Orgunometullics 1982, 12, 1629.
[16] J. D Meinhart. E. V Anslyn, R. H. Grubbs, Orgunometdlics 1989.8, 583.
[17] L. Li. M Hung. Z. Xue, J. Am. Chem. Suc. 1995, 117, 12746, and references
therein. L . Li. Z. Xuc. G P. A Yap, A . L. Rheingold, Orgunometallics 1995,
14. 49911.
[18] a ) T.Wettling. J. Schneider. 0. Wagner, C. G. Kreiter, M. Regitz, Angew.
Chrm. 1989. 101. 1035; Angew. Cl7em Int. Ed. Engl. 1989, 28, 1013; b) P. B.
Hitchcock, J. A. Johnson, J. F. Nixon, ibid. 1993, 105, 86 and 1993, 32. 103:
c ) R. Streubel. ihid 1995, 107,478 and 1995,34,436; d) J. F. Nixon, Chem. Soc.
RCV 1995. 24. i t 9
+
Ph3Si0H.
‘
tBu
0
(Ph,SiO),Al’
AI(OSiPh&
’
0
‘
tBu
2
[tBuOAIH,],
1
Ph,Si-
I
0 - SiPh,
I
0
-2tBuOH
-2 H2
Ph,Si-
0-Al-
I
I
I
7
Ph,Si
I
0-AI-0
I
-SiPh,
I
P
-0 - SiPh,
3
Scheme 1.
An A14(0H), Eight-Membered Ring
in a Molecular Aluminopolysiloxane and
Its Behavior with Bases**
Michael Veith,* M a r i a Jarczyk, and Volker Huch
Dedicuted to Profkssor Roger Blachnik
on the occusion of his 60th birthday
In the last few years many research groups, especially that of
H. W. Roesky, have shown that aluminopolysiloxanes that are
soluble in organic solvents are surprisingly simple to synthesize.“. 21 The compounds known to date have a polycyclic
framework consisting of Al, Si, and 0;the silicon atoms bear a
further organic or amine ligand. A molecular sodium aluminosilicate has also been synthesized and characterized.[’I
We recently reported the structure of tert-butoxyaluminum
hydride ( I ) .[31 Herein we describe related aluminopolysiloxanes,
which we obtained while investigating the reactivity of 1 with
triphenylsilanol and diphenylsilanediol. Surprisingly, the reaction with diphenylsilanediol results in a n alurninosiloxane that
contains a central A1,0, ring. To our knowledge, a structural
unit of this type had hitherto not been detected in natural aluminosilicates.
The alkoxydihydride 1 reacts with Ph,SiOH with elimination
of hydrogen to provide the aluminum alkoxydisilanolate 2 in
nearly quantitative yield (Scheme
According to the X-ray
structure a n a l y ~ i s ‘the
~ ] molecule is dimeric with distorted tetrahedral coordination at aluminum and a central, planar A1,0,
four-membered ring (point symmetry C,, Figure 1). As expected, the oxygen atoms of the tert-butoxy ligands function as
bridging atoms between the aluminum atoms, whereas the
triphenylsilanolate groups are terminally bound. The large
[*I
[**I
Prof. M. Veith, bl Jarczyk. Dr V. Huch
lnstitut fur Anorganische Chemie der Universitit des Saarlandes
Postfach 15 11 50, D-66041 Saarbrucken (Germany)
Fax: Int. code +1681)302-3995
This work was wpported by the Fonds der Chemischen Industrie and the
Deutschen Forschungsgemeinschaft (SFB 277, “Grenzeflichenbestimrnte Materialien”).
Angsn.. Cheni. I n ! . Ed Engl. 1997, 36, No. l i 2
Figure 1. Ball-and-stick representation of 2 in the crystal [ 5 ] . Important bond
lengths [A] and angles
AILO(1) 1.827(2), AILO(1’) 1.824(2), AI-O(2) 1.686(3),
AI-0(3) 1.694(3), Si(l)-O(2) 1.607(3), Si(2)-0(3) 1.620(3); O(1)-AlLO(1‘) 81.0(1),
O(I)-A1-0(2) 112.4(1), 0(1)-A1-0(3) 115.7(1), Al-O(l)-Al’ 99.0(1), Si(l)-O(2)-AI
177.6(2), Si(2)-0(3)-AI 153 5 ( 2 )
[’I:
Si-0-A1 angles (Si(2)-0(3)-Al 153.5(2), Si(l)-0(2)-AI 177.6(2)”)
are typical for sterically demanding R-0-A1 ligandst6I
Treatment of 1 with two equivalents of Ph,Si(OH), in diethyl
ether (Scheme 1) led to the crystalline compound 3 in acceptable
yield. In addition to the evolution of hydrogen, the formation of
tert-butanol is detected by ‘H N M R spectroscopy. The 27Aland
29Si N M R spectra of 3 each show one signal. The ‘ H N M R
spectrum displays a sharp singlet at 6 = 6.1 7 for an OH group.
Accordingly, the solid-state IR spectrum of 3 contains an unusually narrow band at 3619 cm-’ accompanied by a less intense band at 3560cm-’. Both bands are assigned to 0 - H
stretches; the splitting of the signals can be explained by the
crystal structure (see below). The OSi(Ph,)OSi(Ph,)O units
present in the molecule can be attributed to the Lewis acid
catalyzed condensation of Ph,Si(OH), monomers. Although
the reactions of Ph,Si(OH), with trialkylalanes could lead to
OAlOAlOSi chains o r Al,Si,O, rings, no such observation was
made.[71
As seen in the crystal structure analysis,[’] 3 is an isolated
aluminopolysiloxane, which crystallizes with four molecules of
ether (Figure 2). There is an AI,(OH), eight-membered ring in
the center of the structure; the AI(0H)AI edges are spanned by
four disiloxane bridges. This results in a framework of five annelated eight-membered rings, and the molecule has approxi-
C, VCH Verlagsgesellschaft mbH, 0-69451 Weinheim. 1997
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Ph
Ph
Ph
Ph'
014'1
\
\
Ph'
Ph
Figure 2. Ball-and-stick representation of 3 in the crystal [ 5 ] .Forclarity, the phenyl
groups are indicated by Ph. The fourth diethyl ether molecule is a space filler
between the molecules and does not interact with the OH groups. Important bond
lengths [A] and angles I"]: Al(1)-O(1) 1.797(3), A1(1)-0(4) 1.802(3), A1(2)-0(1)
1.796(3), A1(2)-0(2) 1.806(3), A1(3)-0(2) 1.789(1), A1(3)-0(3) 1.807(3), A1(4)-0(3)
1.814(3), Al(4)-O(4) 1.787(3); mean values: Si-O,, 1.604(3), Si-0,, 1.631(3); Si-0-Si
144.8(2), Si-0-AI 157.6(2), AI-O,, 1.698(3), A I - 0 - A I 130.8.
mately S, point symmetry. The annelated rings form an average
angle of 131.So(0-A1 . . .Al) with the central four-membered
Al, ring. The S, symmetry is disrupted because only three of the
four molecules of diethyl ether are coordinated through their
oxygen atoms to the hydrogen atoms of the central OH groups
in the Al,(OH), unit. The fourth diethyl ether molecule acts
only as a space filler in the van der Waals lattice. The coordination of the ether molecules is indirect evidence of the presence of
OH groups in the central eight-membered ring; the 0-0 distances of the 0 - H . . 0 bridges lie in the range of 2.60-2.70 A,
and indicate strong hydrogen bonding.['] The Al-0-A1 bridges
are virtually symmetrical (Al-0 1.787(3)-1.814(3) A), and, as
expected, the other distances in the side rings are homogeneous.['. 21 The Al-O(H) distances (av 1.800 A) are 0.1 8, longer
than the other A1-0 distances in 3 (1.698 8,).
Why are only three of the four ether molecules directly coordinated to the AI,(OH), unit? An exact analysis of the distances
between atoms not directly bonded to one another shows that
there is not enough space for another ether molecule to approach the free OH group. Evidently coordination of the fourth
ether molecule would require distortion of the [ (Ph,Si),O,],Al,(OH), polycycle; hence, two (Ph,Si),O,Al,OH wings would
come closer together and result in considerable steric hindrance.
To confirm this theory, we treated the ether adduct 3 with
triethylamine; this is more sterically demanding and a stronger
base than diethyl ether [Eq. (I)].
[(Ph,Si)203],AI,(OH)4~4Et20+ 2Et,N
influences the annelated Si,O,Al, rings is clearly confirmed.
The best-fit plane for the Si,O,Al, eight-membered rings adjacent to the coordinated OH groups forms an average angle of
120.6' to the central A1,0, ring, whereas the the other two
Si,O,Al, rings form an angle of 138.2'. The access to OH
groups that are not coordinated to amine molecules is threrefore
hindered. The host-guest principle for more than two Et,N
molecules does not work because of the "closing of the Si,O,Al,
rings".
The higher basicity of the nitrogen atom in triethylamine
compared to that of the oxygen atom in diethyl ether, also has
an influence on the bonding in the central Al,(OH), ring.
Hence, the bonds to 0(1) (Al(2)-O(1) 1.829(4), Al(1)-O(1)
1.820(4) 8,) differ from those to O(2) (Al(1)-O(2) 1.733(3),
Al(2)-O(2') 1.724(3)8,). The latter are 0.1 A shorter than a
normal AlO(H)Al bridge, which leads to the conclusion that the
hydrogen atom is in fact bound to Et,N and an A10-A1 bridge
is present instead of an AlO(H)Al bridge. Therefore, 4 is best
described, at least in the crystal, as an ion pair of the form
[(Ph,Si)8Al,0,,(OH),]2- '2HNEt: (a detailed analysis of solution and solid-state NMR spectra of 4 in comparision to that of
Et,NH+Cl- indicates that an ion pair also exists in solution).
The O(2)-N bond length is 2.72 8, and is thus slightly longer
than the 0-0 bond length between the ether molecules and the
OH groups in 3.[81The solid-state IR spectrum of 4 only shows
one broad OH band at 3550 cm-', whereas the N-H stretches
attributed to Et,NH+ are possibly hidden by C-H vibrations.
Received: July 29, 1996 [Z9395IE]
German version: Angen. Chem. 1996, 108, 140-142
+40Et,
(1)
Keywords: aluminum
Regardless of the reaction stoichiometry, only two equivalents of triethylamine react with 3 under complete substitution
or loss of the ether molecules to form the amine adduct 4.[91This
crystallizes from the toluene solution and can be isolated almost
quantitatively.
The crystal structures of 3 and 4 (Figure 3)['' differ in the
number of coordinated donor molecules; the aluminosiloxane
units are basically the same. Molecule 4 has C,point symmetry;
the twofold axis is perpendicular to the central A1,0, eightmembered ring. The hypothesis presented above that coordination of base molecules to the hydrogen atoms of the OH groups
0 VCH
1.820(4), A1(2)-0(1) 1.829(4), Al(l)-0(2) 1.733(3), Al(l)-0(3) 1.727(3), Al(l)-0(6)
1.727(3), A1(2)-0(2') 1.724(3), A1(2)-0(5') 1.722(3), A1(2)-0(7) 1.715(3); Al(1)0(1)-A1(2) 134.6(3), Al(l)-O(Z)-Al(2) 130.5(2); mean values: Si-O,, 1.604(4), S O , ,
1.625(5); Si-0-Si 147 2(3), Si-0-AI 149.8(3).
-*
[{(Ph,Si),0,},AI,0,(OH)2]~ . 2 H N E t l
118
Figure 3. Ball-and-stick representation of 4 in the crystal [S]. The view is orthogonal to that in Figure2. Important bond lengths [A] and angles ["I: Al(l)-0(1)
Verlagsgesellschaft mbH. 0.69451 Weinheim. 1997
- aluminosilicates - polycycles - silicon
[l] M. L. Montero, A . Voigt, M. Teichert, I. Uson, H. W. Roesky, Angew,. Chem.
1995, 107, 2761 ; Angen. Chem. Int. Ed. Engl. 1995, 34, 2504.
[Z] M. L. Montero, I. Uson, H. W. Roesky, Angen. Chem. 1994,106,2198; Angen.
Chem. Int. Ed. Engl. 1994, 33, 2103.
[3] M. Veith, S. Faber, H. Wolfanger, V. Huch, Chem. Ber. 1996, 129, 381.
[4] 2 and 3: AIH,OtBu (0.802 g, 4.9 mmol) 131 in diethyl ether (28 mL) was added
dropwise to two molar equivalents of Ph,Si(OH) in diethyl ether (32 mL) at
60 "C (for 2) or Ph,Si(OH), in diethyl ether ( 5 mL) at room temperature (for 3).
The solutions were stirred for 2 h and then allowed to stand for 6 h, which led
to the formation ofcrystals. Yield 2: 90%, 3: 58%. Correct elemental analysis.
NMR (200MHz. [DJbenzene, 296K. TMS): 2: 'H N MR : 6 =1.10 (s, YH,
CMe,). 7.02 -7.21 (m, 18H, C,H,, m, p ) , 7.67-7.71 (m, 12H, C,H,, 0);
"C-NMR: 6 = 31.5 (s, CMe,), 78.3 (s. CMe,), 127.8-138.0 (arom. C);
0570-0833/97/3601-0118 $15.00+ 2510
Angen, Chem. Inf Ed. Engl 1997, 36, No 112
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"SiNMR- & = - 21 9 (s, SiPh,). 3 ' H N M R : 6 = 0 89 (t, 24H, CH,CH2),
The overall process comprises the reaction of an iodoarene, a
3.02(q,16H,CH,CH2),6.17(s,4H,AIOH),7.09-7.16(m,48H,C,H,,m,p),
strained olefin such as norbornene, an aliphatic iodide, and a
7 78-7.90(m. 32H. C,H,, 0);29SiNMR:6 = - 44.1 (s, SiPh,).
terminal olefin as shown in Scheme 1. The catalyst can be intro[5] Crystal structure data for 2: C,,H,,AI,O,Si,,
M , = 1301.79gmol-I, triclinic,
duced in the form of any of the palladium intermediates (or their
space group Pi, a = 978.3(2), b = 1378.1(3), c =1536.6(3) pm, a = 64.34(3),
=
/$=76.92(3). 7=76.43(3)", V=1796.7(6)x106pm3. Z=1, pCAlod
precursors) shown in Scheme 2. The strained olefin is essential
1,199Mgm '. F(000) = 684, Stoe-AED2 four-circle diffractometer, T =
for the reaction to occur, although it is expelled towards the end
293 K. 3 '%20<45', 4699 symmetry-independent reflections, 4699 data, no reof the catalytic process, like a sort of scaffold to be removed
straints. 41 5 parameters, solution with direct methods (SHELXS86), refinement
(SHELXL93) with anisotropic temperature factors for all non-hydrogen atoms,
hydrogen atom5 geometrically fixed, R , = 0.059,wR2 = 0.139.Crystal structure data for 3. C,,H,~AI,O,,Si,-(C,H,,O)~, M , = 2122.75 gmol-', triclinic,
space group Pi,a =1528.7(3), 6 =1607.4(3), c = 2811.9(6)pm, x =105.51(3),
p = 92.20(3). 7 = 116 14(3)", V = 5879(2) x 10, pm3, Z = 2, pcalrd
=
1.199Mgm- '. F(OO0) = 2240. Stoe IPDS Image Plate System, T = 293 K,
4' % 2 0 % 5 0 . 47567 reflections of which 17555 are symmetry-independent
(R,,, = 0.076). 17552 data, 3 restraints, 1213 parameters, solution and refinement as for 2. R , = 0.074,wR2 = 0.233,the C,H, group of one ether molecule
was geometrically fixed. Crystal structure data for 4.C,H8: [C,,H,,Al,0,,Si,]2 -2C,H,,N+.C,H,, M , = 2120.79 gmol-I, orthorhomblc, space
group, Prrn. (I = 1962.0(4), b = 2191.5(4), c = 2839.7(6) pm, V = 12210(4) x
10' pm3. Z = 4. pCslid
=1.154 Mgm-', F(OO0) = 4472, Stoe IPDS Image Plate
System, T = 293 K,4 1 2 6 1 50", 66624 reflections of which 9327 are symmetry-independent (R,,, = 0.1075),9318 data, no restraints, 626 parameters, solution and refinement as for 2, R , = 0.077,wR2 = 0.208. One disordered toluene
molecule per formula unit IS present in a larger cavitiy of the lattice. This means
that, to a certain extent, higher temperature factors are determined, in particular
for the periphery carbon atoms in the cavity. Further details of the crystal
structure investigation can be obtained from the Fachinformationszentrum
Karlsruhe. D-76344 Eggenstein-Leopoldshafen upon quoting the following
numbers- CSD-405887,CSD-405888.and CSD-405889.
[6] A. R. Barron. K . D. Dobbs, M. F. Francl, J. Am. Chem. Soc. 1991, 113,39.
[7] N. N . Korneev. G 1. Shcherbakova, V. S. Kolesov, G. B. Sakharroskaya, E I.
Shevchenko. J Gen. Chem. USSR (Engl. Transl.) 1987,57, 282.
[8] J. E Huheey. E.A. Keiter. R. L. Keiter, Anorganische Chentie, Walter de Gruyter. Berlin, 1995.p. 341.
[9]4: [(Ph2Si),AI0,H],.4Et,0 (3)(0.845 g, 0.398mmol) in toluene (10 mL) was
treated with Et,N (8 mmol) and stirred at room temperature. Crystals formed
upon concentration of the solution. Yield: 85 %. Correct elemental analysis.
'HNMR: d = 0.39(s, br.. CH,CH,N), 2.0 (s, br., CH,CH,N), 6.99-7.10 (m,
br., C,H,. m. p ) , 7.91-8.04 (m, br., C,H,, 0); I3C-NMR: 6 = 8.1 (s, br.,
CH,CH,N). 44.1 (s, br., CH,CH,N), 125.6-140.3(br., arom. C);'9SiNMR:
6 = - 45.9 ( 5 , SiPh,); solid state - "CCP/MASNMR (50.3MHz, TMS):
6 = 7.7(N(CH,CH3),), 44.4(N(CH,CH,),), 124 4- 141.9((C6HJZSi);29SiCP/
MASNMR (39.7MHz, TMS): d = - 47 (three of four overlapping signals).
A Complex Catalytic Cycle Leading
to a Regioselective Synthesis of
o,o'-Disubstituted Vinylarenes**
Marta Catellani,* Franco Frignani, and
Armando Rangoni
The ability to catalyze multistep processes is one of the most
interesting features of transition metal reactivity. In particular
palladium-catalyzed sequential reactions have been the object of
much work.") The present synthesis, consisting of the regioselective functIonalization of aromatic compounds at the 1,2, and
3 positions, is based on the different reactivity of palladium(o),
(II), and (IV) species formed along a catalytic sequence.
[*I Prof. M. Catellani, Dr.F. Frignani, A. Rangoni
Dipartimento di Chimica Organica e Industriale dell'universita
Wale delle Scienze, 1-43100Parma (Italy)
Fax: Int. code +(521)90-5472
e-mail: catell(uipruniv.cce.unipr.it
[**I
This work was supported by the Minister0 dell'universita e della Ricerca
Scientifica e Tecnologica (MURST, Roma), and the Consiglio Nazionale delle
Ricerche (CNR. Roma). Mass and NMR facilities were provided by Centro
Interfacolti dell'universiti di Parma.
AnKen.. Chem. I n t . Ed. Engl. 1997, 36, No. 1/2
after the building of the molecule is complete. It thus behaves as
a catalyst, although an excess is necessary to push the reaction
toward the desired species. To stress this behavior norbornene
has been placed in both terms of the equation reported in
Scheme 1. In a typical example iodobenzene, norbornene,
I
R
o I +&
+
2R'I
+
H&=CHY
Pd cat
.-.
KpCO,, DMA
20 "C, 30 h
Scheme 1. Palladium-catalyzed synthesis of o,o'-dialkylvinylarenes.
n-butyl iodide, and methyl acrylate underwent reaction in
dimethylacetamide (DMA) at 20°C for 30 h with cis,exo-2phenylnorbornylpalladium chloride (PNP) dimerI2] as precursor of the monomeric catalyst (2.5 x
M). A 10: 1 molar ratio
of both iodobenzene and norbornene to palladium was used,
and a 50 % molar excess of methyl acrylate and a large excess of
n-butyl iodide (100%) and of K,CO, were used. After conventional treatment an unexpectedly high yield of methyl (E)-2,6di-n-butylcinnamate (93 Yo based on the arene) was obtained;
the excess starting aliphatic halide was recovered mostly as such
and in part as dialkyl carbonate. The catalyst efficiency is unchanged for about ten cycles and has not been optimized. The
temperature was raised to 50 "C without large variations in
yields and conversions. Beyond 50°C the selectivity began to
decrease remarkably as expected in view of the competition
among the reactants. Other catalysts such as Pdo complexes and
palladium acetate (which is reduced to Pdo under the reaction
conditions) can also be used provided that the molar ratios of
the reagents are properly adjusted. So far, however, the best
results have been obtained with the above mentioned PNP
dimer.
The reaction has general character: substituted aromatic
iodides, primary aliphatic iodides and terminal olefins bearing
either electron-withdrawing or electron-releasing groups can be
used. The examples reported in Table 1 show the potential of the
present reaction. The building blocks of the final product, the
iodoarenes, iodoalkanes, and olefins can be widely varied,
which makes the method extremely versatile for the preparation
of 1,2,3-trisubstituted arenes not easily accessible by conventional methods with complete regioselectivity. As can be seen in
Table 1 selectivities are very high, while conversions vary depending on the type of terminal olefin used.
All new compounds reported in Table 1 were fully characterized by 'H, I3C, 'H-'H and 13C-'H correlation NMR spectroscopy, IR spectroscopy, and mass spectrometry (Table 2). In
the 'HNMR spectra of compounds 1 (R = H ) the aromatic
protons form an AB, system as expected for a 1,2,3-trisubstituted structure, while a singlet is observed for compounds Id
and le.
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