Organoaluminates with three terminal phenylethynyl groups and their interactions with alkali metal cations

Article abstract of DOI:10.1021/om010690v

The synthesis of [K⁺·THF(2,6-iPr₂C₆H₃N-(SiMe ₃)Al(C≡CPh)₃)^-]₂ (1), [Na⁺·THF (2,6-iPr₂C₆H₃N-(SiMe₃)Al(C≡CPh )₃)^-]₂ (2), and [Li⁺·dioxane (2,6-iPr₂-C₆H₃N(SiMe₃)Al(C≡CPh )₃)^-]₂·2dioxane (3) respectively by the reaction of [2,6-iPr₂C₆H₃N(SiMe₃)AlCl₂ ]₂ (4) with the corresponding phenylethynyl alkali metal salt is reported. In compound 1 the potassium (2, sodium) interacts with the C≡C bonds of four phenylethynyl groups. A further coordination site of the potassium (sodium) is occupied by a THF molecule. Thus, the cation therein acts as a bridging moiety to form the dimer. In compound 3 each of the lithium cations is 2-fold coordinated by phenylethynyl ligands and two dioxane molecules. One of the dioxane molecules in 3 functions as a bridge forming the dimer. The herein described compounds are the first structurally characterized species having three terminal phenylethynyl groups bound to the aluminum atom.

Full text of DOI:10.1021/om010690v

1300
Organometallics 2002, 21, 1300-1303
Or ga n oa lu m in a tes w ith Th r ee Ter m in a l P h en yleth yn yl
Gr ou p s a n d Th eir In ter a ction s w ith Alk a li Meta l
Ca tion s†
Marcus Schiefer, Hagen Hatop, Herbert W. Roesky,* Hans-Georg Schmidt, and
Mathias Noltemeyer
Institut fu¨r Anorganische Chemie, Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received August 1, 2001
Summary: The synthesis of [K+‚THF(2,6-iPr2C6H3N-
(SiMe3)Al(CtCPh)3)-]2 (1), [Na+‚THF (2,6-iPr2C6H3N-
(SiMe3)Al(CtCPh)3)-]2 (2), and [Li+‚dioxane (2,6-iPr2-
C6H3N(SiMe3)Al(CtCPh)3)-]2‚2dioxane (3) respectively
by the reaction of [2,6-iPr2C6H3N(SiMe3)AlCl2]2 (4) with
the corresponding phenylethynyl alkali metal salt is
reported. In compound 1 the potassium (2, sodium)
interacts with the CtC bonds of four phenylethynyl
groups. A further coordination site of the potassium
(sodium) is occupied by a THF molecule. Thus, the cation
therein acts as a bridging moiety to form the dimer. In
compound 3 each of the lithium cations is 2-fold coor-
dinated by phenylethynyl ligands and two dioxane
molecules. One of the dioxane molecules in 3 functions
as a bridge forming the dimer. The herein described
compounds are the first structurally characterized spe-
cies having three terminal phenylethynyl groups bound
to the aluminum atom.
F igu r e 1. Molecular structure of 4. For clarity, the hydro-
gen atoms have been omitted. Non-hydrogen atoms are
represented by thermal ellipsoids drawn at the 50% prob-
ability level. Selected bond lengths (Å) and angles (deg) for
4: Al(1′)-Cl(1′) 2.0667(12), Al(1′)-Cl(2′) 2.2813(11), Al(1′)-
Cl(2) 2.2855(11), Cl(1′)-Al(1′)-Cl(2) 106.58(5), Cl(2′)-Al-
(1′)-Cl(2) 89.38(4), Al(1)-Cl(2′)-Al(1′) 90.41(4).
In tr od u ction
The cation π-interaction is of importance within the
numerous known noncovalent interactions and is the
subject of several publications.1 There are only three
known potassium compounds of this type of bonding
that are structurally characterized,2 but nevertheless
1 is the first example of a compound in which potassium
is coordinated exclusively to alkynyl groups and a THF
molecule.
alkali metal ion. The centrosymmetric compounds [K+‚
THF(2,6-iPr2C6H3N(SiMe3)Al(CtCPh)3)-]2 (1), [Na+‚
THF(2,6-iPr2C6H3N(SiMe3)Al(CtCPh)3)-]2 (2), and [Li+‚
dioxane(2,6-iPr2C6H3N(SiMe3)Al(CtCPh)3)-]2‚2diox-
ane (3) are unique. Only a few aluminum alkynyl com-
plexes have been structurally characterized, and com-
pounds 1, 2, and 3 are the first in which an aluminum
center is bonded to three alkynyl groups.5
In the case of sodium there are three known alkynyl
compounds with such π-interactions that have been
structurally characterized.3 Furthermore, lithium alky-
nyl π-interactions have been observed in compounds of
transition metals and main group elements.4 To the best
of our knowledge there is no known aluminum alkynyl
compound in which the alkynyl group interacts with an
In a previous report5d it was shown that aluminum
alkynyl compounds are not very soluble in organic
solvents or give oily products. Therefore we used an
aluminum compound with a sterically demanding ligand
(2,6-iPr2C6H3N(SiMe3)). The resulting products usually
give well-formed single crystals. The reaction of [2,6-
iPr2C6H3N(SiMe3)AlMe2]2 with Me3SnCl yielded [2,6-
iPr2C6H3N(SiMe3)AlCl2]2 (4) with elimination of Me4Sn.
The single-crystal X-ray structural analysis of 4 shows
a dimeric compound containing a four-membered Al2-
Cl2 ring (Figure 1). The Al-Cl bond lengths (2.0667-
2.2855 Å) correspond to those of known Al-Cl com-
* To whom correspondence should be addressed. E-mail: hroesky@
gwdg.de. Fax: (+49)551-393373.
† Dedicated to Professor Walter Siebert on the occasion of his 65th
birthday.
(1) (a) Ma, J . C.; Dougherty, D. A. Chem. Rev. 1997, 97, 1303. (b)
Gokel, G. W.; De Wall, S. L.; Meadows, E. S. Eur. J . Org. Chem. 2000,
2967. (c) Bonomo, L.; Solari, E.; Scopelliti, R.; Floriani, C. Chem. Eur.
J . 2001, 7, 1322. (d) Smith, J . D. Adv. Organomet. Chem. 1998, 43,
267. (e) Lambert, C.; Schleyer, P. v. R. Angew. Chem. 1994, 106, 1187;
Angew. Chem., Int. Ed. Engl. 1994, 33, 1129.
(2) (a) Evans, W. J .; Keyer, R. A.; Ziller, J . W. Organometallics 1993,
12, 2618. (b) Varga, V.; Hiller, J .; Pola´sˇek, M.; Thewalt, U.; Mach, K.
J . Organomet. Chem. 1996, 515, 57. (c) Varga, V.; Hiller, J .; Thewalt,
U.; Pola´sˇek, M.; Mach, K. J . Organomet. Chem. 1998, 553, 15.
(3) (a) Geissler, M.; Kopf, J .; Weiss, E. Chem. Ber. 1989, 122, 1395.
(b) Hiller, J .; Varga, V.; Thewalt, U.; Mach, K. Collect. Czech. Chem.
Commun. 1997, 62, 1446. (c) Karl, M.; Seybert, G.; Massa, W.; Harms,
K.; Agarwal, S.; Maleika, R.; Stelter, W.; Greiner, A.; Heitz, W.;
Neumu¨ller, B.; Dehnicke, K. Z. Anorg. Allg. Chem. 1999, 625, 1301.
(4) (a) Varga, V.; Mach, K.; Hiller, J .; Thewalt, U. J . Organomet.
Chem. 1996, 506, 109. (b) J ohn, K. D.; Geib, S. J .; Hopkins, M. D.
Organometallics 1996, 15, 4357. (c) Veith, M.; Koban, A.; Huch, V. Helv.
Chim. Acta 1998, 81, 1640.
(5) (a) Stucky, G. D.; McPherson, A. M.; Rhine, W. E.; Eisch, J . J .;
Considine, J . L. J . Am. Chem. Soc. 1974, 96, 1941. (b) Erker, G.;
Albrecht, M.; Kru¨ger, C.; Nolte, M.; Werner, S. Organometallics 1993,
12, 4979. (c) Erker, G.; Albrecht, M.; Kru¨ger, C.; Werner, S. Organo-
metallics 1991, 10, 3791. (d) Zheng, W.; Mo¨sch-Zanetti, N. C.; Roesky,
H. W.; Hewitt, M.; Cimpoesu, F.; Schneider, T. R.; Stasch, A.; Prust,
J . Angew. Chem. 2000, 112, 3229; Angew. Chem., Int. Ed. 2000, 39,
3099.
10.1021/om010690v CCC: $22.00 © 2002 American Chemical Society
Publication on Web 02/19/2002

Notes
Organometallics, Vol. 21, No. 6, 2002 1301
Sch em e 1
F igu r e 3. Molecular structure of 3. For clarity, the
hydrogen atoms have been omitted. Non-hydrogen atoms
are represented by thermal ellipsoids drawn at the 50%
probability level. One additional dioxane is not shown.
F igu r e 2. Stick and ball model of isomorphous compounds
1 and 2 (M ) K+ (1); Na+ (2)).
pounds.6 The reaction of 4 with 6 equiv of potassium or
sodium phenylacetylide in THF at 50 °C yielded the
aluminum phenylethynyl complex 1 or 2 (Scheme 1,
Figure 2), while the reaction of lithium phenylacetylide
with 4 gave an oily product. However, a colorless
crystalline compound 3 was obtained when the latter
was treated with dioxane (Figure 3).
The bond distances between the alkylnyl carbon atom
and the potassium ion in 1 and the sodium ion in 2 are
in the range from 2.969 to 3.473 Å (1) and 2.651 to 3.358
Å (2), respectively, which are slightly longer than the
reported values (K-Calkynyl 2.868-3.197 Å; Na-Calkynyl
2.533-2.891 Å).2,3 It is quite obvious that the difference
of the latter bond distances in 2 (0.707 Å) is more
distinct than the corresponding one in 1 (0.504 Å).
However, there is a lack of comparable data due to the
fact that 1 and 2 are the first potassium and sodium
aluminum alkynyl compounds (other examples are
Mg,3a Ti,3b Sm2b,3c ). The C-M-C angles are in the
range 20.23-22.68° (1) and 20.6-24.76° (2), respec-
tively, and are comparable with those of other alkali
metal alkynyl compounds.2a,3
In contrast to compounds 1 and 2, the lithium ion in
3 is bound to two phenylethynyl groups and two solvent
molecules, whereas the alkali metal ions in 1 and 2 are
coordinated to four phenylethynyl ligands. Thus the
alkali metal ion in compound 3 is not a bridging unit.
Moreover, the [Li+‚dioxane(2,6-iPr2C6H3N(SiMe3)Al(Ct
CPh)3)-] cores in 3 are connected by a dioxane molecule.
The Al-C bond lengths (1.943-1.998 Å) and the Al-
CtC angles (166.6-175.6°) are similar to those of
compounds 1 and 2. One additional dioxane molecule
in the lattice is not shown in Figure 3.
The single-crystal X-ray structural analysis of 1 and
2 revealed that the potassium and sodium ions, respec-
tively, are π-coordinated by four phenylethynyl groups.
The fifth coordination site is occupied by a THF mol-
ecule. Compounds 1 and 2 have an inversion center. The
(2,6-iPr2C6H3N(SiMe3)Al(CtCPh)3)- cores are con-
nected by two alkali metal ions. Moreover, the three
phenylethynyl groups and one 2,6-iPr2C6H3N(SiMe3)
group are situated in a slightly distorted tetrahedral
environment about the aluminum center. The Al-C
bond lengths (Al-Calkynyl 1.960-1.988 Å) are compa-
rable to those found in the literature.5a,d The angle
between the aluminum and the two alkynyl carbon
atoms (Al-C-C) ranges from 164.2° to 176.7°. This
strong deviation from linearity of the Al-CtC unit,
coordinated by two potassium or two sodium atoms,
respectively (Al(1)-C(2)-C(20) 165.7° (1); 164.2°(2)), is
a rare example in main group chemistry.3a,5d The reason
for this bending might be the small energy difference
between a linear and a nonlinear Al-CtC unit.
The results of the structural analysis of compounds
1, 2, and 3 are surprising. The hard metal cations
coordinate as well to the hard oxygen of the THF and
dioxane molecule, respectively, as to the four softer
coordination sites of the alkynyl groups. Obviously, the
(6) (a) Wehmschulte, R. J .; Grigsby, W. J .; Schiemenz, B.; Bartlett,
R. A.; Power, P. P. Inorg. Chem. 1996, 35, 6694. (b) Uhl, W.; Vester,
A.; Hiller, W. Z. Anorg. Allg. Chem. 1990, 589, 175. (c) Allegra, G.;
Perego, G.; Immirzi, A. Makromol. Chem. 1963, 61, 69.

1302 Organometallics, Vol. 21, No. 6, 2002
Ta ble 1. Su m m a r y of Cr ysta l Da ta for Com p lexes 1, 2, 3, a n d 4
Notes
1
2
3
4
formula
fw
C
86H98Al2K2N2O2Si2
C86H98Al2N2Na2O2Si2
1347.78
C94H114Al2Li2N2O8Si2
1523.89
C15H26AlCl2NSi
346.34
1380.00
temp, K
cryst syst
space group
a, Å
b, Å
c, Å
a, deg
â, deg
γ, deg
V, Å3
200(2)
monoclinic
P21/ n
12.3241(16)
19.54.8(3)
17.333(3)
90
92.084(15)
90
200(2)
monoclinic
P21/n
12.403(3)
19.036(4)
17.193(3)
90
91.24(3)
90
4058.4(14)
2
1.103
203(2)
triclinic
P1h
12.216(14)
13.039(18)
15.551(14)
106.92(12)
106.731(18)
95.89(3)
2221
1
1.139
0.114
200(2)
monoclinic
P21/n
13.7686(16)
18.803(3)
15.258(3)
90
98.075(14)
90
4172.9(12)
2
1.098
3911.0(10)
8
1.176
Z
F
calcd, g cm-3
abs coeff, mm-1
0.208
0.121
0.430
no. of reflns collected
no. of indep reflns
data /restraints/params
GOF/F2
8317
7175
8051
9844
7363 (Rint ) 0.1240)
7363/0/440
1.042
7175 (Rint ) 0.0000)
7175/4/441
1.034
7596 (Rint ) 0.1647)
7596/0/503
1.023
6877 (Rint ) 0.0292)
6877/0/375
1.026
R indices [I>2σ(I)]
R1 ) 0.0518
wR2 ) 0.1224
R1 ) 0.0728
wR2 ) 0.1405
0.302/-0.310
R1 ) 0.0720
wR2 ) 0.1704
R1 ) 0.1087
wR2 ) 0.2000
0.822/-0.480
R1 ) 0.0603
wR2 ) 0.1614
R1 ) 0.0736
wR2 ) 0.1800
0.589/-0.439
R1 ) 0.0471
wR2 ) 0.1181
R1 ) 0.0659
wR2 ) 0.1310
0.380/-0.536
R indices (all data)
largest diff peak/ hole, e Å-3
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d s 1, 2, a n d 3 (M ) K+ (1);
Na + (2); Li+ (3))
potassium and the sodium ions prefer to coordinate to
the alkynyl groups even in the presence of an excess of
THF. The products formed by the alkynyl groups seem
to be energetically more favorable in comparison to
completely solvated cations such as [K(THF)6]+.
1
2
3
Al(1)-C(2)
Al(1)-C(3)
Al(1)-C(4)
M(1)-C(2)
M(1)-C(20)
M(1)-C(2A)
M(1)-C(20A)
M(1)-C(3A)
M(1)-C(30A)
M(1)-C(4)
M(1)-C(40)
C(2)-C(20)
C(3)-C(30)
C(4)-C(40)
1.984(3)
1.963(3)
1.962(3)
3.097(2)
3.473(3)
3.063(2)
3.399(3)
3.035(2)
3.089(2)
2.969(2)
3.191(3)
1.212(3)
1.205(3)
1.207(3)
1.988(4)
1.965(4)
1.960(4)
2.876(4)
3.358(4)
2.772(4)
3.221(4)
2.707(4)
2.888(4)
2.651(4)
2.968(4)
1.211(5)
1.213(5)
1.203(5)
1.943(3)
1.998(3)
1.992(3)
Exp er im en ta l Section
All experiments were carried out using standard Schlenk
techniques under a dry nitrogen atmosphere due to the
sensitivity of the reactants and products toward air and
moisture. A Braun MB 150-GI box was used to store the
compounds and to prepare the samples for spectroscopic
characterization. All solvents were distilled from sodium/
benzophenone and degassed prior to use. [2,6-iPr2C6H3N-
(SiMe3)AlMe2]2 was prepared as described in the literature.7
NMR spectra were recorded on a Bruker Avance 200 or Bruker
AC 250 and were referenced to Me4Si and LiCl, respectively.
FT-IR spectra were measured on a Bio-Rad FTS-7 instrument
as Nujol mulls in the range 4000-400 cm-1. Mass spectra were
obtained on a Finnigan MAT 95. Melting points were mea-
sured in sealed glass tubes on a Bu¨chi 540 instrument.
Crystal structure solutions and refinements for compounds
1, 2, 3, and 4 are shown in Table 1. Data for all compounds
were collected on a Stoe four-circle diffractometer. Mo KR
radiation (λ ) 0.71073 Å) was used in all cases. All structures
were solved by direct methods and refined anisotropically with
SHELXTL.8
2.350(5)a
2.594(6)
2.287(5)
2.464(6)
1.209(4)
1.209(4)
1.210(4)
C(3)-Al-C(2)
104.7(1)
110.5(1)
107.3(1)
20.23(6)
22.68(6)
22.22(6)
165.7(2)
175.0(2)
173.6(2)
103.7(1)
110.9(1)
106.1(1)
20.6(1)
24.8(1)
23.9(1)
164.2(3)
176.7(3)
172.2(3)
113.0(1)
97.1(1)
106.6(1)
C(3)-Al-C(4)
C(4)-Al-C(2)
C(2)-M(1)-C(20)
C(3A)-M(1)-C(30A)
C(4)-M(1)-C(40)
Al(1)-C(2)-C(20)
Al(1)-C(3)-C(30)
Al(1)-C(4)-C(40)
27.8(1)a
29.2(1)
175.6(2)
166.6(2)
173.8(2)
a
[C(3A)dC(3); C(30A)dC(30)].
the hexane into the THF solution, the single crystals are
formed after 18 days. 1H NMR (200 MHz, THF-d8): δ 7.3-6.6
(m, 18 H), 4.12 (qq, 2 H, J HH ) 7.0 Hz), 3.6 (m, 4 H), 1.8 (m,
4 H), 1.29 (d, 6 H, J HH ) 7.0 Hz), 1.18 (d, 6 H, J HH ) 7.0 Hz),
0.18 (s, 9 H). 29Si NMR (99 MHz, THF-d8): δ -2.2. 13C NMR
(125 MHz, THF-d8): δ 149.38 (q), 147.71 (q), 132.17, 128.51,
127.73 (q), 127.01, 122.85, 121.58 (s, arom. C), 113.5 (br, Al-
C), 106.11 (s, C-Ph), 68.24 (s, THF), 28.20 (s, THF), 28.11 (s,
CH), 26.46 (s, CH3), 3.37 (SiMe3). IR: ν˜ 2118, 2099, 1654, 1315,
1263, 1240, 1183, 1158, 1053, 927, 798, 759, 691, 576, 539
cm-1. MS(FAB): m/z (%) 578 (1/2[M+ - 2THF - K+], 100),
1195 ([M+ - 2THF - K+], 10). Anal. Calcd for C86H98Al2K2N2-
Si2O2 (1380.07): C, 74.85; H, 7.16; N, 2.03. Found: C, 74.08;
H, 7.33; N, 1.87.
[K+‚THF (2,6-iP r 2C6H3N(SiMe3)Al(CtCP h )3)-]2 (1). To a
solution of 4 in THF (200 mL) (1.73 g, 2.5 mmol) were added
6 equiv of potassium phenylacetylide (2.10 g, 15 mmol) and
the mixture stirred overnight at 50 °C. After cooling to room
temperature the solvent was removed in vacuum. To the
slightly soluble residue was added hexane (35 mL). The
suspension was stirred for 5 min and then was filtered. The
residue was extracted with THF (250 mL) to yield 1.48 g (2.15
mmol, 43%) of 1 after removing the THF. Single crystals of 1
were obtained by dissolving the crude product in THF. The
latter solution, in a small flask, was placed in a larger vessel
containing 10 mL of n-hexane. Due to the slow diffusion of
[Na +‚THF (2,6-iP r 2C6H3N(SiMe3)Al(CtCP h )3)-]2 (2). To
a solution of 4 in THF (200 mL) (1.73 g, 2.5 mmol) were added
6 equiv of sodium phenylacetylide (1.86 g, 15 mmol), and the
resulting mixture was stirred overnight at 50 °C. After cooling
(7) Waezsada, S. D.; Liu, F.-Q.; Murphy, E. F.; Roesky, H. W.;
Teichert, M.; Uso´n, I.; Schmidt, H.-G.; Albers, T.; Parisini, E.; Nolte-
meyer, M. Organometallics 1997, 16, 1260.
(8) Sheldrick, G. M. SHELX-97, Program for Crystal Structure
Refinement; Universita¨t Go¨ttingen, 1997.

Notes
Organometallics, Vol. 21, No. 6, 2002 1303
to room temperature, the solvent was removed in vacuum. To
the slightly soluble product was added toluene (35 mL). The
mixture was stirred for 5 min and then was filtered. A slightly
yellow residue (3.39 g) containing NaCl and product 2 was
obtained. Due to its low solubility in organic solvents, com-
pound 2 cannot be separated completely from the NaCl. Single
crystals were obtained by adding THF to the crude product,
and the resulting supernatant phase was decanted in a small
flask. This flask was placed in a larger vessel containing 10
mL of n-hexane. A few single crystals of 2, suitable for X-ray
structure analysis, were obtained after 20 days by slow
diffusion of n-hexane into the THF solution of 2. 1H NMR (200
MHz, C6D6): δ 7.5-6.7 (m, 18 H), 4.45 (qq, 2 H, J HH ) 6.9
Hz), 3.27 (m, 4 H), 1.57 (d, 6 H, J HH ) 6.9 Hz), 1.55 (d, 6 H,
J HH ) 6.9 Hz), 1.06 (m, 4 H), 0.67 (s, 9 H). 13C NMR (125 MHz,
THF-d8): δ 149.69 (q), 147.75 (q), 132.22, 128.50, 128.34 (q),
128.26, 122.76, 121.38 (s, arom. C), 112.5 (br, Al-C), 105.40
(s, C-Ph), 68.20 (s, THF), 28.08 (s, THF), 28.04 (s, CH), 26.36
(s, CH3), 3.38 (SiMe3). 29Si NMR (99 MHz, C6D6): δ 0.6. IR: ν˜
2120, 2098, 1597, 1572, 1240, 1184, 1156, 1049, 925, 759, 691,
576, 539 cm-1. The amount of pure 2 was not sufficient enough
for elemental analysis.
128.60, 128.05 (s, arom. C), 109.0 (br, Al-C), 108.82 (s, C-Ph),
67.17 (s, dioxane), 28.11 (s, CH), 26.49 (s, CH3), 3.36 (SiMe3).
7Li NMR (97.2 MHz, C6D6): δ 0.2. IR: ν˜ 2123, 2111, 1597,
1572, 1486, 1272, 1239, 1181, 1122, 1109, 1079, 925, 872, 796,
759, 693, 445 cm-1. MS(FAB): m/z (%): 592 (1/2[M+ - 4
dioxane], 100), 585 (1/2[M+ - 4 dioxane - Li+], 25). Anal. Calcd
for C94H114Al2Li2N2O8Si2 (1523.89): C, 74.09; H, 7.54; N, 1.84.
Found: C, 73.86; H, 7.85; N, 1.88.
[2,6-iP r 2C6H3N(SiMe3)AlCl2]2 (4). [2,6-iPr2C6H3N(SiMe3)-
AlMe2]2 (30.6 g, 50 mmol) was treated under stirring with
trimethyltin chloride (39.9 g, 200 mmol) in toluene (200 mL)
at -78 °C. The reaction mixture was warmed slowly to room
temperature and stirred overnight. All volatiles were removed
in vacuum. The crude product was washed with pentane (40
mL). After filtration 24.2 g of 4 (35 mmol, 70%) were obtained
1
as a colorless solid. H NMR (200 MHz, C6D6): δ 7.1-6.8 (m,
3 H), 3.56 (qq, 2 H), 1.35 (d, 6 H, J HH ) 7.5 Hz), 1.26 (d, 6 H,
J HH ) 7.5 Hz), 0.29 (s, 9 H). IR (Nujol): ν˜ 2120, 2097, 1597,
1572, 1241, 1181, 925, 759, 723, 691, 576, 539 cm-1. MS(EI):
m/z (%) 345 (1/2[M+], 50), 249 (1/2[M+ - AlCl2], 100). Anal.
Calcd for C30H52Al2Cl4N2Si2 (692.70): N, 4.04. Found: N, 3.36.
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Centre,
CCDC nos. 172242 (1), 163134 (2), 166025 (3), and 163133 (4).
Copies of this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB21EZ, UK
[fax: +44-1223-336-033 or e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.ac-ac.uk].
[Li+‚d ioxa n e (2,6-iP r 2C6H3N(SiMe3)Al(CtCP h )3)-]2‚2d i-
oxa n e (3). To a solution of phenylethyne (3.06 g, 30 mmol) in
ether (100 mL) was added at -78 °C a solution of n-BuLi in
hexane (30 mmol). The reaction mixture was stirred at room
temperature overnight. Compound 4 (3.46 g, 5 mmol) was
added to this solution at -78 °C. Subsequently, the solution
was stirred and warmed slowly to room temperature. After
filtration the filtrate was evaporated in vacuum. To the
resulting oily crude residue was added dioxane (50 mL) and
the resulting mixture stirred for 4 h. Finally the dioxane was
removed in vacuum and the remaining solid was washed with
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement parameters, bond lengths and angles, and
positional and thermal parameters for 1, 2, 3, and 4 are
available free of charge via the Internet at http://pubs.acs.org.
1
hexane (35 mL) to yield 4.31 g (3 mmol, 60%) of 3. H NMR
(200 MHz, C6D6): δ 7.4-6.8 (m, 18 H), 4.40 (qq, 2 H, J HH
)
6.8 Hz), 3.38 (s, 18 H), 1.61 (d, 6 H, J HH ) 6.8 Hz), 1.51 (d, 6
H, J HH ) 6.8 Hz), 0.66 (s, 9 H). 29Si NMR (99 MHz, C6D6): δ
0.2. 13C NMR (125 MHz, C6D6): δ 147.41 (q), 147.30 (q), 131.78,
OM010690V