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K2[Al12iBu12] a Compound with Al12 Icosahedra.

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Experimental
Typical procedure (Table 1, entry 2): 5a (403 mg, 1.0mmol) was added to a
from diisopropylamine
cooled solution (-78 "C) of LDA-prepared
(0.184mL, 1.3 mmol) and nBuLi (1.58M hexane solution, 0.76mL,
1.2 mmol)-in TH F (5 mL), and the solution was stirred for 2 h at -78 "C.
nBuLi (1.58mL, 2.5 mmol) was added by syringe. The reaction mixture was
allowed to warm to 0 "C and stirred for 30 min. Thereafter it was cooled again
to -78 C , and I-bromopentane (453 mg, 3.0mmol) was added. The mixture
was allowed to warm to - 20°C and stirred for 1 h. Dilution with ether followed by washing with water, drying (MgSO,), concentration, and flash chromatography (SiO,, 10% ether in pentane) gave 7 (130 mg,71 %).
structure was essentially based on only a deuterolysis experiment in which the amount of liberated D, was measured;
isolation of the pure compound has not yet been achieved.
The only compound with an AI-AI bond so far characterized
spectroscopically and by crystal structure analysis is tetra-
kis[bis(trimethylsilyl)methyl]dialuminum(,4/-A~(l).l3I
(Me3Sil$H,
,CH(SiMe$2
(MqSi12CH' AI-AI, CHISiMe312
1
Received: August 28,1990 [Z 4197 IE]
German version: Angew. Chem. 103 (1990) 178
CAS Registry numbers:
3a, 131435-69-3;3b, 131435-70-6;3c, 131435-71-7;3d, 131435-72-8;5a,
97782-58-6;
Sb, 129266-32-6;
SC, 131435-61-5;Sd,97782-59-7;
6a,131435-626; 6b, 131435-64-8;6c, 131435-67-1;6d, 131435-68-2;7, 61759-36-2;8,
131435-63-7;9,131435-65-9;10,131435-66-0;C,H,,Br, 110-53-2;(CH,),C=
CHCH,Br, 870-63-3.
[I] a) D. P. G. Hamon, R. W. Sinclair, 1 Chem. SOC.Chem. Commun. 1968,
890; b) C . S . Shiner, A. H. Berks, A.M. Fisher, J. Am. Chem. SOC.110
(1988)957.
[2] Reviews: a) D. Seebach, Angew. Chem. 91 (1979)259; Angew. Chem. I n / .
Ed. Engl. 18 (1979)239; b) N.H. Werstiuk, Tetrahedron 39 (1983)205;c)
J. C.Stowell, Chem. Rev. 84 (1984) 409; d) D.Hoppe, Angew,. Chem. 96
(1984)930;Angew. Chem. Inr. Ed. Engl. 23 (1984)932;e) T. A. Hase (Ed.):
Umpoled Synrhons, Wiley, New York 1987.
[3] For z,D-dianions of ketones bearing the anion-stabilizing substituents
(RO),P(O)- [a], aryl [b, c], PhS- [d], vinyl [e, f], or divinyl [g] see: a) R.
Goswami, J. Am. Chem. Soc. 102(1980) 5973; b) C.-L. Mao, C . R. Hauser,
M. L. Miles, ibid. 89 (1967) 5303; c) B. M. Trost, L. H. Latimer, 1 Org.
Chem.42(1977)3212;d)K. Ramig,M. Bhupathy,T.Cohen,ibid.54(1989)
4404; e) D.Seebach, M. Pohmakotr, Tetrahedron 37 (1981) 4047; f) D.
Seebach, M. Pohmakotr, C. Schregenberger, B. Weidmann, R. S . Mail, S .
Pohmakotr. Helv. Chim. Acta 65 (1982)419;g) I. T. Badejo, R. Karaman,
N. W. 1. Lee, E. C. Lutz, M. T. Mamanta, J. L. Fry, J. Chem. Soc. Chem.
Commun. 1989. 566.
[4] For unfunctionalized %a- and ad-dianions of ketones, see: a) C . J. Kowalski. M. L. O'Dowd, M. C. Burke, K. W. Fields, 1 Am. Chem. Soc. f 0 2
(1980) 5411; b) C. J. Kowalski, G . S . Lal, ibid. 108 (1986) 5356; c) J. S.
Hubhard, T. M. Harris, ibid. 102 (1980)2110.
[5] An approach to unfunctionalized dianions 3 based on deprotonation of
(I-pheny1)allyloxy anions was first reported by Dimmel et al., but their
system suffered from rapid D-protonation, see: D. R. Dimmel, W. Y Fu,
S . B. Gharpure, J. Org. Chem. 41 (1976)3092. For a recent study involving
deprotonation in potassium allyloxide systems, see: T.Cuvigny, M. Julia, L.
Jullien. C . Roland, Tetrahedron Let/. 28 (1987)2587.
[6] a) H.Nakahira. 1. Ryu, A. Ogawa, N. Kambe. N. Sonoda. Organometallics
9 (1990)277;b) I. Ryu. S . Murai, N. Sonoda, J. Org. Chem. 51 (1986)2389.
171 Reviews: a) J. d'Angelo, Tetrahedron 32 (1976) 2979; b) L. M. Jackman,
B. C. Lange. ibid. 33 (1977)2737;c) R. L. Augustine (Ed.): Carbon-Carbon
Bond Formation. Vol. 2, Marcel Dekker, New York 1979.
The reaction mentioned above, which was carried out in
n-hexane, results in formation of a brown precipitate consisting mostly of potassium chloride. Extraction of this precipitate with toluene, however, gives a low but reproducible yield
of a further product, which crystallizes at - 30 "C as dark
red octahedra. The crystal structure determination showed
that this product was dipotassium closo-dodecaisobutyldodecaaluminate, K,[AI, 2 i B ~ 1 2(2),
] in which All icosahedra are present (Fig. 1). The crystals of 2 contain toluene,
which is completely removed over several hours under vacuum
Torr) at room temperature. However, the crystals
thereby become brittle and break upon even gentle handling.
We obtained single crystals suitable for X-ray diffraction analysis by drying the crystals under vacuum at - 30 "C;
their composition was approximately K,Al,,iBu,, . 1.2
C,H, according to integration of the 'H NMR spectrum.
Whereas, under normal conditions, 2 completely decomposes within 30 min upon exposure to an X-ray beam, the diffraction pattern can be measured at - 65 "C without any
significant change in the intensities of the control reflections.
Fig. 1. Stereoscopic drawing of the AI,, icosahedron (thermal ellipsoids at
30% probability). For clarity, only the A1 and K atoms are shown. Selected
bond lengths [pm] and angles ["I: AI-AI 267.9(5), 268.0(4). 269.6(5), K-AI
400.4(3); AI-AI-AI 59.8(1), 60.0,60.4(2).
K2[AlI2zBul2~,
a Compound with All, Icosahedra **
By Worfgang Hiller, Karl- Wilhelm Klinkhammer,
Werner Uhl,* and Jiirgen Wagner
The reduction of chlorodiisobutylaluminum with potassium to give the corresponding tetraisobutyldialuminum(A1A l ) was first described in 1976.l'- However, the proposed
~
[*I
I**]
Dr. W. Uhl, K.-W. Klinkhammer, J. Wagner
Institut fur Anorganische Chemie der Universitat
Pfaffenwaldring 55, W-7000 Stuttgart 80 (FRG)
Dr. W. Hiller
Institut fur Anorganische Chemie der Universitat Tiibingen
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
Angew. Chem. Int. Ed. Engl. 30 (1991) No. 2
0 VCH
Compound 2 crystallizes in the centrosymmetric cubic
space group Fd3 with eight formula units per unit
There are three slightly different bond lengths between the
aluminum atoms of the icosahedron (267.9(5), 268.0(4), and
269.6(5) pm). Moreover, the bond angles between the triangular sides, which exhibit a maximum deviation of 0.4" from
the ideal value of 60", are consistent with nearly undistorted
icosahedral symmetry. The AI-A1 bonds are only slightly
longer than that in the Al, compound 1 (266.0 ~ m ) . [ ~ l
A potassium atom lies on a threefold axis above each of
four faces of the icosahedron and is coordinated by three a-C
atoms of isobutyl groups. As shown in Figure 2, each potas-
VerlagsgesellschaJi mbH, W-6940 Weinheim, 1991
0570-0833/91/0202-0179 $3.50+ ,2510
179
sium atom bridges two icosahedra, so that its coordination
number is six with respect to carbon (CI), resulting in formation of a trigonal antiprism. Thus, the solid-state structure
consists of a three-dimensional network in which the icosahedral centers are surrounded tetrahedrally by potassium
atoms and the cations are coordinated by the All, clusters in
a linear fashion in analogy to a part structure of CU,O.~'~
The K-C distance (323 pm) is consistent with the standard
Two values can be distinvalue reported in the
K,[B,,H,,] crystallizes in the cubic space group Fm5, but
displays a different arrangement of anions and cations with
a potassium ion coordinated by 24 hydrogen atorns.["1
Experimental Procedure
All operations were carried out under purified argon in dry solvents. Chlorodiisobutylaluminum (8.5 g, 48 mmol) was dissolved in 40 mL of n-hexane and
treated with potassium (1.9 g. 48 mmol). The resulting reaction mixture was
stirred for three days at 0 "C and for one day at room temperature. It was then
filtered and the residue was treated with 40 mL of toluene. Concentration of the
solution thereby obtained to roughly one-third of its initial volume and cooling
to - 30°C resulted in formation of dark red crystals of 2, which were dried
under
Torrat room temperature. Yield: 62 mg (1.5% based on Al). Dec.
(under argon) at 150'C. 'H NMR (60 MHz, C,D,): 6 = 2.35 (m; CH), 1.40 (d,
J (H,H) = 6.2 Hz; CHJ, 0.60 (d, J (H,H) = 6.4 Hz; CH,). I3C('H} NMR
(62.896 MHz, C,D,): 6 = 30.9 (CH), 28.8 (CH,), 17.1 (CH,). IR (Nujol; CsBr
disc) [cm-'1: i = 1330 (s). 1315 (s, FCH,), 1250 (w), 1210 (m), 1165 (s, br.,
QCH,), 1070 (w). 1045 (w). 1020 (s v(as)CC), 950 (m), 920 (m). 840 (m). 820 (s,
br.), 780 (sh, v(s)CC). 730 (s). 700 (s), 670 (s, br.), 610 (s, br. vAIC),560 (w), 490
(w). 470 (m),440 (m),400 (m), 375 (m dCC, dAlC (vAIAI?)).A Raman spectrum
could not be recorded.
Received: September 10, 1990 [Z 4173 IE]
German version: Angew. Chem. 103 (1991) 182
CAS Registry numbers:
2, 131513-79-6;CIAl(iBu),, 1779-25-5
Fig. 2. Stereoscopic drawing of the environment of the potassium ions (thermal ellipsoids at 30% probability). For clarity, the methyl groups (C21 and
C22) and the hydrogen atom H21 on C2 are omitted. Important distances [pm]
and angles K-CI 322.6(9), AI-C1 199.9(9), C1-C2 153(1); C1-K-Cl 180.0,
86.8(2) (2 x ) , 93.2(2) (2 x), AI-Cl-K 97.3(3), AI-CI-C2 117.5(7).
guished in crystalline methylpotassium: ['I short contacts
with a mean value of 298.5 pm, where the lone pair of the
carbanion is directed toward the cations, and longer contacts
of 337 pm through C-H c bonds, which correspond more
closely to the bonding in 2. Shorter distances between potassium and carbon than those in 2 are also observed from the
powder data for the structure of potassium tetramethylaluminate (31 5, 348 pm) and -gallate (294, 352 pm)."] The hydrogen atoms on the bridging C3 are 272 and 296 pm from
the potassium atom. A comparable interaction between
potassium and C-H (J bonds was recently found in potassium(dichlorobis[bis(trimethylsilyl)methyl]al~minate}.~~~
The
Al-C bond length (199.9 pm) is considerably shorter than
that usually found for bridged systems and lies in the widespread region of AI-C single bonds. In agreement with the
K-C-AI bridge discussed here, the IR spectrum exhibits
broad bands for the Al-C and C-C stretching modes.
In the framework made up of potassium atoms and Al,,
icosahedra, channels extending parallel to the face diagonals
are formed and incorporate crystal toluene. However, the
toluene molecules are so strongly disordered that their positions cannot be completely determined. For a maximum residual electron density of 0.5 eA-3, only the position of a
six-membered ring fragment could be determined and then
refined by restriction of the bond lengths. Its influence on the
R value and standard deviation is small, however. We are
currently attempting to obtain a derivative of 2 that allows
us to circumvent this disorder.
Compound 2 is surprisingly stable in air; it remains crystalline for about 2 h without noticeable change, but then a
colorless substance, presumably AI(OH), ,begins to grow on
the crystal. Under inert atmosphere, 2 is thermally stable to
about 150 "C, above which rapid decomposition occurs with
deposition of aluminum.
Compound 2 corresponds to [Bl,Hl,]2e in its cluster
structure and number of valence electrons and, like that
compound, obeys the Wade rules for a doso structure.
180
0 VCH Verlagsgesellschafi mbH,
W-6940 Weinheim. f991
[l] H. Hoberg, S. Krause. Angew. Chem. 88(1976)760; Angew. Chem. Int. Ed.
Engl. I S (1976) 694.
[2] M. A. Miller, E. P. Schram, Organometallics 4 (1985) 1362.
[3] W. Uhl. Z. Narurforsch. B 43 (1988) 1113.
[4] Crystal structure analysis: CAD4 diffractometer, Mo,. radiation; graphite monochromator, T = - 65°C; VAXSDP and SHELXTL programs;
Z = 8;
cubic, space group FA; a = 2639.3(7) pm; V = 18 385
j t = 2.4 x lo2 m - '; crystal dimensions 0.6 x 0.5 x 0.5 mm; 8-28 scan; 591
unique reflections > 4a(F); 74 refined parameters; H atoms relined as
rigid groups with ideal distances and angles and common U values; other
atoms refined anisotropically ; high-angle refinement; disordered toluene:
C atoms refined with bond-length restrictions based on an ideal model and
with constant (I values; R , = 0.083; R = 0.089. Further details of the
crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe. Gesellschaft fur wissenschaftlich-technischeInformation mbH, W-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting
the depository number CSD-54909, the names of the authors, and the
journal citation.
[5] B. G. Hyde, S. Anderson: Inorganic Crystal Structures. Wiley. New York
1990, p. 12.
[6] C. Schade, P. von R. Schleyer. Adv. Organomet. Chem. 27 (1987) 169.
[7] E. Weiss, T. Lambertsen. B. Schubert, J. K. Cockroft, J. Organomet. Chem.
358 (1988) 1.
[8] R. Wolfrum, G. Sauermann, E. Weiss, J. Organomet. Chem. 18 (1969) 27;
see also: G. Hencken, E. Weiss, ibid. 73 (1974) 35.
[9] W. Uhl, Z . Narurforsch. B 45 (1990) 1349.
[lo] J. A. Wunderlich, W. N. Lipscomb, J. Am. Chem. SOF.82 (1960) 4427.
Double Stereodifferentiation in Carbohydrate
Coupling Reactions: The Mismatched Interaction
of Donor and Acceptor as an Unprecedented Factor
Governing the u/o Ratio of Glycoside Formation **
By Nynke M . Spijker and Constant A . A . van Boeckel*
One century after the first glycoside syntheses of
Michael['] and Fischer,t21the stereochemical outcome (a/$
ratio) of carbohydrate coupling reactions is still difficult to
control. The best-established method for stereoselective car[*] Dr. C. A. A. van Boeckel. Drs. N. Spijker
Akzo Pharma Division,
Organon Scientific Development Group
P.O.Box 20, NL-5340 BH Oss (The Netherlands)
[**I We wish to thank Mr. G. N. Wugenuurs for recording the NMR spectra
0570-0833/91/0202-0iSO$3.50+.25/0
Angew. Chem. Inf. Ed. Engl. 30 (1991) No. 2
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