Supramolecular Tetrahedral M4L6 Cluster
J. Am. Chem. Soc., Vol. 121, No. 17, 1999 4205
University of California, Berkeley. Unless otherwise noted, all chemicals
and starting materials were obtained commercially and used without
further purification. Organic solvents and mineral acids were of reagent
grade and were used as supplied. Tetrahydrofuran (THF) was distilled
from sodium benzophenone prior to use. Water was deionized and
further purified by a Millipore cartridge system (resistivity 18 MΩ cm).
Metal complex syntheses were performed under a nitrogen atmosphere
using Schlenk techniques.
Table 1
empirical formula
formula weight
crystal color, habit
crystal dimens (mm)
crystal system
space group
C186H234Ga4N30O42
3840.91
colorless, prism
0.10 × 0.10 × 0.05
tetragonal
I41/a (no. 88)
8
a ) b ) 24.0738(2) Å
c ) 68.5828(5) Å
V ) 39747.0(5) Å3
1.284
Z
lattice params
Isophthaloyl Dichloride. Isophthalic acid (4.00 g, 24.1 mmol) was
heated with 5 mL of SOCl2 and a drop of DMF until gas evolution
ceased. Excess SOCl2 was then removed under reduced pressure. The
liquid residue crystallized upon cooling to room temperature to yield
Dcalcd (g/cm3)
F000
16160
6.18
1
a white crystalline product. Yield: 4.8 g (98%). H NMR (300 MHz,
µ(Mo KR) (mm-1
diffractometer
radiation
)
CDCl3): δ 8.80 (t, 1H, J ) 1.8 Hz), 8.39 dd, 2H, J ) 7.9 Hz, 1.8 Hz),
7.74 (t, 1H, J ) 7.9 Hz).
Siemens SMART
Mo KR (λ ) 0.71069 Å)
graphite monochromated
60
N-(4-Methylphenyl)hydroxylamine. 4-Nitrotoluene (12.0 g, 87.5
mmol) was dissolved in a mixture of 5.0 g (94 mmol) of NH4Cl, 100
mL of H2O, and 100 mL of ethanol. Zinc powder (17 g, 260 mmol)
was added to the mixture in small portions while the temperature was
kept below 10 °C by cooling with an ice bath. After the addition of
zinc was complete the mixture was stirred for 2 h and filtered. The
precipitate was washed with ethanol, and the combined solvents were
reduced by rotary evaporation. The resulting yellow solids were
dissolved in diethyl ether, dried with MgSO4, and filtered. The ether
was removed by rotary evaporation. The resulting yellow residue was
washed with hexanes to yield a white, flaky product. Yield :7.3 g, 67%.
1H NMR (300 MHz, CDCl3): δ 7.09 (d, 2H, J ) 6 Hz), 6.92 (d, 2H,
J ) 6 Hz), 5.47 (bs, 2.5 H), 2.31 (s, 3H). Anal. Calcd (Found) for
C7H9NO: C, 68.26 (69.20); H, 7.37 (7.24); N, 11.37 (11.56).
Isophthal-di-N-(4-methylphenyl)hydroxamic Acid (H2E). To a
solution of 6.1 g (50 mmol) of N-(4-methylphenyl)hydroxylamine in
40 mL of dioxane was added 4.0 mL (50 mmol) of pyridine. To the
resulting mixture was added a solution of 5.0 g (25 mmol) of
isophthaloyldichloride dropwise, while the temperature of the mixture
was maintained below 15 °C. The mixture was stirred for 3 h. The
solvents were removed by rotary evaporation, and the solid residue
was treated with 100 mL of concentrated aqueous NH3. After being
stirred for 1 h, a white precipitate had formed and the mixture was
filtered. The solid was stirred with 0.1 M HCl, washed with H2O, and
dried under vacuum to yield 4.2 g (44%). 1H NMR (300 MHz,
CDCl3): δ 7.63 (s, 1 H), 7.35 (d, 2 H, J ) 7.5 Hz), 7.12 (t, 1 H, J )
7.5 Hz), 7.10 (d, 4 H, J ) 8.3 Hz), 7.02 (d, 4 H, J ) 8.3 Hz), 2.33 (s,
6 H). Anal. Calcd (Found) for C22H20N2O4‚1/2(H2O): C, 68.56 (68.30);
H, 5.49 (5.10); N, 7.27 (7.40).
Fe4(E)6. To a solution of 200 mg (0.53 mmol) of H2E and 2 drops
of triethylamine in 30 mL of acetone was added a solution of 125 mg
of Fe(acac)3 (acac ) acetylacetonate) (0.35 mmol) in 10 mL of acetone.
The combined solutions were heated overnight, and a red microcrys-
talline precipitate formed. The solid was collected by filtration, washed
with a small amount of acetone, and dried. Yield: 130 mg (68%). Anal.
Calcd (Found) for C132H108N12Fe4O24(H2O)4: C, 62.37 (62.12); H, 4.60
(4.98); N, 6.61 (6.21). FAB(+): MH+ 2470.
Ga4(E)6. To a solution of 200 mg (0.53 mmol) of H2E and 2 drops
of triethylamine in 30 mL of acetone was added a solution of 125 mg
of Ga(acac)3 (0.35 mmol) in 10 mL of acetone. The combined solutions
were heated overnight and gave a colorless microcrystalline precipitate.
This was collected by filtration, washed with a small amount of acetone,
and dried. Yield: 130 mg (68%). 1H NMR (300 MHz, CDCl3): δ 8.89
(1 H, s), 7.21 (4 H, d, J ) 8.2 Hz), 7.06 (4 H, d, J ) 8.2 Hz), 6.81 (2
H, d, J ) 7.4 Hz), 6.61 (1 H, t, J ) 7.4 Hz), 2.29 (6H, s). FAB(+):
MH+ 2524.
crystal-to-detector
distance (mm)
temp (°C)
scan type
scan rate (s/frame)
no. of reflns measd
-103
ω (0.3° per frame)
30
total: 63804
unique: 7710 (Rint ) 11.3%)
Lorentz-polarization
absorption: (Tmax ) 0.894, Tmin ) 0.774)
direct methods SHELXTL
full-matrix least-squares
∑w(|Fo| - |Fc|)2
corrections
structure solution
refinement
function minimized
least-squares weights
p-factor
anomalous dispersion
no. of observns
(I > 3.00σ(I))
no. of variables
refln/param ratio
residuals: R; R2w; Rall
goodness-of-fit indicator 1.085
max shift/error in final
cycle
maximum peak in final
diff map (e-/Å3)
minimum peak in final
diff map (e-/Å3)
w ) 1/σ2(Fo ) ) 4Fo /σ2(Fo )
2
2
2
0.030
all non-hydrogen atoms
7710
576
13.4
0.089, 0.22, 0.12
0.061
0.58
-0.53
corresponding to an arbitrary hemisphere of data were collected using
ω scans of 0.3° and a total measuring time of 30 s each. Data were
integrated using SAINT33 with box parameters of 1.3 × 1.3 × 0.4° to
a maximum 2θ value of 46.5°. The data reprocessing and subsequent
refinement led to a significantly more accurate structure than reported
in the preliminary communication.15 An empirical absorption correction
based on the measurement of redundant and equivalent reflections and
an ellipsoidal model for the absorption surface was applied using
XPREP.34 Initially solved by direct methods using the teXsan software
package,35 the final structure solution and refinement were performed
using the SHELXTL software package.36 The Laue group is 4/m but
twinned toward 4/mmm. The twinning was modeled using the method
of Pratt, Coyle, and Ibers.37 The fractional contributions of the two
twin components (related by hkl-khl) were refined to 25.2 and 74.8%.
Four solvent molecules were found in the asymmetric unit, and the
others are severely disordered. The solvent to cluster stoichiometry was
1
derived from a H NMR spectrum of crystals dissolved in acetone.
Final cell parameters are in Table 1, while atom coordinates and
isotropic thermal parameters are as CIF files (Supporting Information).
Large crystals of Ga4E6‚DMF formed after adding the metal solution
to a solution of the ligand and triethylamine in DMF and keeping the
mixture at ambient temperature for a few days.
X-ray Crystal Structure of Ga4E6. The compound Ga4E6‚18 DMF
crystallizes in the tetragonal space group I41/a, with Z ) 8 (Table 1).
All measurements were made on a Siemens SMART diffractometer32
with graphite monochromated Mo KR radiation. Area detector frames
(33) SAINT: SAX Area-Detector Integration Program, V4.024; Siemens
Industrial Automation, Inc., Madison, WI, 1995.
(34) XPREP, 5.03; Siemens Industrial Automation, Inc., Madison, WI,
1995.
(35) teXan: Crystal Structure Analysis Package; Molecular Structure
Corp., 1992.
(36) SHELXTL Crystal Structure Analysis Package; Siemens Industrial
Automation, Inc., Madison, WI, 1995.
(32) SMART Area-Dectector Software Package; Siemens Industrial
Automation, Inc., Madison, WI, 1995.
(37) Pratt, C. S.; Coyle, B. A.; Ibers, J. A. J. Chem. Soc. (A) 1971, 2146.