9100 J. Am. Chem. Soc., Vol. 123, No. 37, 2001
Klemp et al.
are mechanically unstable, sensitive to air or moisture, and powder in
vacuo. Suitable single crystals for X-ray structure analysis as well as
for NMR and XPS investigations were obtained from several similar
experiments.
surfaces were produced by crushing single crystals in the ultrahigh-
-
10
vacuum recipient (basic pressure <10
mbar). All samples were
measured at 78 K in order to reduce the risk of sample decomposition,
which occurred even at that temperature during several hours (cf.
Supporting Information).
X-ray Crystallography. The single crystals decomposed in dry
perfluorpolyether oil within a few minutes. Therefore, they were
mounted quickly after adding them together with the concentrated AlCl
solution to the perfluorpolyether oil which was cooled to -20 °C. X-ray
diffraction data were collected on a STOE IPDS diffractometer with
graphite-monochromatized Mo KR radiation (λ ) 0.710 73 Å) at 190
K. The structures were solved by direct methods (Shelxs 97). A total
of 534 and 611 parameters for 2 and 3, respectively, were refined by
Quantum Chemical Calculations. The structures for the model
systems Al12[AlCl
2THF (C ) (2b), [AlCl
(C ) were optimized at the density functional theory (DFT) level
employing the Becke-Perdew (BP86) functional together with an
2
‚H
2
2
O]10 (S
5
symmetry) (2a), Al12[AlCl
2
‚THF]10
‚
i
‚H O] (D2h), AlCl
2
2
3
‚H O (C ), and AlCl
2
1
3
‚2H O
2
1
3
i
14
1
5
auxiliary basis approximation for the Coulomb energy (RI-DFT).
A
polarized split-valence basis (SV(P))16 was used, where the parentheses
indicate that polarization functions were only considered for non-
hydrogen atoms.
2
full-matrix least squares against F (Shelxl 97) with anisotropic thermal
parameters for all non-hydrogen atoms. H atoms were refined on
calculated positions according to the riding model. 2 and 3 contain
four slightly disordered toluene molecules per Al22 unit. Furthermore,
some of the C atoms of the donor molecules and two Cl atoms are
The 27Al NMR chemical shifts for 2b were computed by employing
the gauge-including atomic orbital (GIAO) Hartree-Fock self-consistent-
field (HF-SCF) method1 using a double-ú polarization (DZP) basis
7,18
16
9
16
slightly disordered.
for Al and Cl and the SV(P) basis for the THF ligands. Relative shifts
-
27
Mass Spectrometry. Mass spectrometric investigations were carried
out on Varian MAT 711 and Finnigan MAT MS8223 spectrometers,
EI ) 70 eV; DI ) 50-150 °C. The observed masses and isotopic
patterns were in good agreement with the calculated values.
NMR Investigations. MAS and MQMAS experiments were carried
out at 9.4-T using a Bruker DSX400 NMR spectrometer, equipped with
a 2.5-mm MAS probe, employing MAS frequencies of 30 kHz and rf
amplitudes of 170 kHz. Chemical shifts were referenced relative to 1
were obtained with AlH
4
as internal reference and a δ Al value for
-
-
AlH
4
of 101 ppm (the absolute shielding calculated for AlH
GIAO-HF-SCF/DZP level is 517.1 ppm).
4
at the
19
Nuclear quadrupole coupling tensors were obtained for 2b using the
following expressions20
ø ) eQq /h
ab
ab
where e is the elementary charge, Q is the nuclear quadrupole moment,
h is Planck’s constant, and qab is the electric field gradient at the
corresponding nuclear positions. The latter were obtained from HF-
SCF calculations using a polarized triple-ú (TZP) basis16 for Al and Cl
and SV(P) for the remainder of the molecule. The value for nuclear
quadrupole moment of 27Al was taken from ref 21. As usual, the
quadrupole coupling constant CQ and the asymmetry factor η are
reported.
3 3
M aqueous Al(NO ) . A non-rotor-synchronized, z-filtered 3QMAS
pulse sequence was used for the Al MQMAS experiment.
XPS Investigations. The XPS data were acquired using an Escalab
1
0
27
5
multimethod spectrometer (Vacuum Generators, East Grinstead, U.K.)
with a nonmonochromatized Mg KR X-ray source (1253.6 eV)
2
operating at 200 W. The sample area was ∼50 mm . The kinetic
energies of the photoelectrons were measured with a hemispheric 150°
sector field analyzer in CAE mode (constant analyzer energy) with a
pass energy of 20 eV for narrow scans. The binding energy (BE) scale
was calibrated with the known photoelectron energies of Au, Ag, and
Cu (fwhm ) 1.2 eV for Au 4f7/2 ) 84.0 eV).
CQ ) øZZ
η ) (øXX - ø )/ø
ZZ
Spectrometer controlling and data collecting were conducted with
the software package VGX-900 (VG Microtech); data analysis was
performed by peak fitting, employing the program UNIFIT F U¨ R
YY
where øZZ, øYY, and øXX are the diagonal elements of the quadrupole
coupling tensor in the principal axis system. The latter are by convention
ordered as |øZZ| g |øYY| g |øXX|.
1
1
WINDOWS (University of Leipzig). The BE reference was set to
85.0 eV for C 1s of alkyl carbon. Due to differential charging,12a the
accuracy of the determined BE is at least 0.3 eV with a fwhm between
.0 and 2.5 eV. We found a BE for Al 2p of 72.5 eV for a freshly
sputtered Al foil. The Al 2p doublet was not separated. Shirley
2
22
For all calculations, the TURBOMOLE program package was used.
The quantum chemical calculations on solid aluminum (assuming
crystal structures of the cubic close packing (fcc) and R-rhombohedral
boron) were performed using the full-potential linearized augmented
2
1
2b
background correction was applied.
2
3
plane wave (FLAPW) method of the WIEN program package. Well-
converged plane wave basis sets with a cutoff parameter Rmt )
A 10-mg sample of single crystals was washed with dry pentane
and transferred with the help of an argon glovebox. Clean sample
K
max
8
.0 and 816 (fcc) and 44 (R-B) K points in the irreducible wedges of
(
9) Crystallographic data for 2: C90H144Al22Cl20O12, 2720.61 g‚mol-1,
the corresponding Brillouin zones were used. The LDA exchange
correlation potential was parametrized according to Perdew and Wang.
-
3
24
pale yellow plate 0.3 × 0.2 × 0.1 mm , triclinic p, space group P-1 (No.
2
)
), a ) 15.806(3) Å, b ) 16.530(3) Å, c ) 16.669(3) Å, R ) 69.95(3)°, â
3
61.88(3)°, γ ) 84.97(3)°, V ) 3594.0(12) Å , and Z ) 1, Fber.) 1.257
(13) See, for example: Parr, R. G.; Yang, W. Density-Functional Theory
of Atoms and Molecules; Oxford University Press: New York, 1989.
(14) Becke, A. D. Phys. Ref. A 1998, 38, 3098. Perdew, J. P. Phys. ReV.
B 1996, 33, 8822.
(15) Eichkorn, K.; Treutler, O.; O¨ hm, H.; H a¨ ser, M.; Ahlrichs, R. Chem
Phys. Lett. 1995, 240, 283.
(16) Sch a¨ fer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97, 2571.
(17) Wolinski, K.; Hinton, J. F.; Pulay, P. J. Am. Chem. Soc. 1990, 112,
8251.
(18) H a¨ ser, M.; Ahlrichs, R.; Baron, H. P.; Weis, P.; Horn, H. Theor.
Chim. Acta 1992, 83, 455.
(19) N o¨ th, H. Z. Naturforsch. B 1980, 35, 119 and references therein.
(20) See, for example: Abragam, A. Principles of Nuclear Magnetism;
Oxford University Press: Oxford, U.K., 1961.
(21) Mills, I.; Cvitas, T.; Homann, K.; Kallay, N.; Kuchitsu K. Quantities,
Units and Symbols in Physical Chemistry; Blackwell Science: Oxford, U.K.,
1993.
-
3
-1
Mg‚m , µMo ) 0.56 mm , θmin ) 0.7415°, θmax ) 0.8501°; reflections,
7 844 measured, 12 949 unique (Rint ) 0.1062), 6065 F > 4σ(F), numerical
absorption correction (min/max transmission: 0.7415/0.8501), gof ) 0.922,
34 parameters, R1(>4σ) ) 0.0968, wR2 ) 0.2891; remaining electron
2
5
-
3
-3
density, max 0.686 e‚Å , min -0.549 e‚Å . Crystallographic data for 3:
-
1
C102H120Al22Cl20O12, 2840.54 g‚mol , pale yellow plate 0.3 × 0.1 × 0.05
-
3
mm , triclinic p, space group P-1 (No. 2), a ) 15.060(3) Å, b ) 15.768-
3) Å, c ) 18.190(4) Å, R ) 96.78(3)°, â ) 105.91(3)°, γ ) 111.38(3) °,
(
3
-3
-1
V ) 3751.4(13) Å , and Z ) 1, Fbor. 1.257 Mg‚m , µMo) 0.539 mm
θmin ) 0.6553°, θmax ) 0.7511°; reflections, 21 687 measured, 11 149 unique
Rint ) 0.1046), 4104 F > 4σ(F), numerical absorption correction (min/
,
(
max transmission, 0.6553/0.7511), gof ) 0.798, 611 parameters, R1(>4σ)
-
3
)
0.0721, wR2 ) 0.1929; remaining electron density, max 0.549 e‚Å ,
-3
min -0.342 e‚Å
.
(
10) Amoureux, J.-P.; Fernandez, C.; Steuernagel, S. J. Magn. Reson.
1
996, 123, 116.
11) Hesse, R. Research Report UNIFIT 2.1, University of Leipzig,
Germany, 1998.
12) (a) Gross, Th.; Lippitz, A.; Unger, W. E. S.; Lehnert, A.; Schmid,
(
(22) Ahlrichs, R.; B a¨ r, M.; H a¨ ser, M.; Horn, H.; K o¨ lmel, C. Chem. Phys.
Lett. 1989, 162, 165.
(23) Blaha, P.; Schwarz, K.; Luitz, J. Program WIEN97: A Full Potential
Linearized Augmented Plane WaVe Package for Calculating Crystal
Properties; Schwarz, K.; Techn. Universit a¨ t Wien, Austria, 1999.
(24) Perdew, J. P.; Wang, Y. Phys. ReV B 1992, 45, 13244.
(
G. Appl. Surf. Sci. 1994, 345. (b) Briggs, D., Seah, M. P., Ed. Practical
Surface Analysis by Auger and X-ray Photoelectron Spectroscopy, 2nd ed.;
Wiley & Sons: Chichester, U.K., 1990.