Heterobimetallic Species Containing Trialkylaluminum Fragments
FULL PAPER
temperature for 90 minutes. The solvent was removed under va-
cuum and the sticky residue was washed with a minimum of hex-
ane. Slow evaporation of a saturated hexamethyldisiloxane solution
yielded small orange crystals (340 mg, 80% yield). Selected 13C
NMR spectroscopic data (125 MHz, [D6]benzene): δ ϭ 7.2 (t,
Experimental Section
General Remarks: All manipulations were carried out under an in-
ert atmosphere of oxygen-free UHP grade argon using standard
Schlenk techniques or under oxygen-free helium in a Vacuum At-
mospheres glovebox. AlMe3 (2.0 hexane solution) and AlEt3 (1.9
toluene solution) were purchased from Aldrich and used as re-
ceived. 2,6-diisopropylphenol was purchased from Aldrich, distilled
over sodium and crystallized at Ϫ40 °C prior to use. [Sm(OAr)3]2,[1]
1
1JC-H ϭ 126 Hz, 4C, nonagostic AlCH2), Ϫ5.3 (t, JC-H ϭ 102 Hz,
∆ν1/2 ϭ 150 Hz, 2C, agostic AlCH2). IR (Nujol): ν˜ ϭ 2785 cmϪ1
(w), 2727 (w), 1588 (m), 1424 (s), 1391 (s), 1317 (m), 1243 (m),
1186 (m), 1181 (m), 1088 (m), 1047 (w), 1030 (m), 965 (w), 948
(m), 924 (w), 883 (m), 855 (m), 825 (m), 785 (s), 735 (s), 686 (w),
673 (m), 654 (w). C48H81Al2O3Sm (910.5): calcd. C 63.32, H 8.97;
found C 61.69, H 9.36.
[2]
[28]
[La(OAr)3]2
and [Me2Al(OAr)]2
were prepared according to
literature procedures. Hexane and toluene were deoxygenated by
passage through a column of supported copper redox catalyst (Cu-
0226 S) and dried by passing through a second column of activated
alumina. Hexamethyldisiloxane was distilled over sodium benzo-
phenone and degassed prior to use. [D6]benzene and [D8]toluene
were degassed, dried over Na-K alloy, and trap-to-trap distilled be-
[Et2Al(OAr)]2 (5): AlEt3 (1.00 mL of a 1.9 solution in toluene,
1.90 mmol) was added to a toluene solution of 2,6-diisopropyl-
phenol (340 mg, 1.90 mmol). Gas evolution was apparent immedi-
ately. The reaction mixture was stirred for 1 h, and the solvent re-
moved under vacuum to yield a white, crystalline solid (420 mg,
1
fore use. H NMR spectra were recorded on a Bruker AMX 500
spectrometer at ambient temperature; chemical shifts are given rel-
ative to residual [D5H]benzene (δ ϭ 7.15) or [D7H]toluene (δ ϭ
2.09). 13C NMR chemical shifts are given relative to [D6]benzene
(δ ϭ 128.39) or [D8]toluene (δ ϭ 20.4). Infrared spectra were re-
corded on a Nicolet Avatar 360 FT-IR spectrometer; solid-state
spectra were taken as Nujol mulls between KBr plates, while solu-
tion spectra were recorded as benzene solutions vs. a solvent blank
3
84% yield). 1H NMR (500 MHz, [D6]benzene): δ ϭ 0.41 (q, JH-
3
ϭ 8.2 Hz, 8 H, CH3CH2Al), 1.01 (t, JH-H ϭ 8.2 Hz, 12 H,
H
3
CH3CH2Al), 1.30 (d, JH-H ϭ 6.8 Hz, 24 H, CHMe2), 3.72 (sept,
3JH-H ϭ 6.8 Hz, 4 H, CHMe2), 6.95Ϫ7.04 (overlapping m, 6 H,
m,p-H). 13C{1H} NMR (125 MHz, [D6]benzene):
δ ϭ 0.8
(CH3CH2Al), 10.6 (CH3CH2Al), 25.9 (CHMe2), 27.2 (CHMe2),
125.7 and 125.9 (phenyl CH), 141.0 (o-phenyl), 145.8 (ipso-phenyl).
IR (Nujol): ν˜ ϭ 1445 cmϪ1 (s), 1411 (m), 1383 (m), 1377 (m), 1344
(w), 1320 (w), 1260 (m), 1245 (w), 1189 (m), 1162 (s), 1097 (s), 1054
(m), 1041 (w), 972 (m), 949 (m), 933 (m), 884 (m), 833 (s), 800 (m),
758 (s), 693 (s), 668 (s), 633 (s), 610 (s). C32H54Al2O2 (524.7): calcd.
C 73.25, H 10.37; found C 72.31, H 11.04.
in KBr cells. Elemental analyses were performed on
a
PerkinϪElmer 2400 CHN analyzer. Elemental analysis samples
were prepared and sealed in tin capsules in a glovebox prior to
combustion.
(ArO)La[(µ-OAr)(µ-Me)AlMe2]2 (1): AlMe3 (0.75 mL of a 2.0
solution in hexane, 1.50 mmol) was added to a toluene solution of
[La(OAr)3]2 (500 mg, 0.37 mmol). The mixture was stirred at room
temperature for 30 minutes and then filtered through a Celite pad.
The solvent was removed under vacuum and the sticky residue was
washed with a minimum of hexane. Slow evaporation of a saturated
toluene solution yielded waxy, colorless crystals (420 mg, 68%
yield). 1H NMR (500 MHz, [D8]toluene): δ ϭ Ϫ0.31 (s, 18 H,
AlMe3), 1.21 and 1.29 (2:1 d, 3JH-H ϭ 6.6 Hz, 36 H, CHMe2), 3.36
and 3.49 (1:2 sept, 3JH-H ϭ 6.6 Hz, 6 H, CHMe2), 6.70Ϫ7.20 (over-
lapping m, 9 H, m,p-H). 13C{1H} NMR (125 MHz, [D8]toluene):
δ ϭ Ϫ0.6 (AlMe3), 24.5, 24.8 and 24.9 (isopropyl methyl), 27.6 and
28.2 (isopropyl methine), 121.2, 123.0, 123.8 and 124.2 (phenyl
CH), 136.7, 139.8, 147.0 and 159.1 (tertiary phenyl). Selected 13C
NMR spectroscopic data (125 MHz, [D8]toluene): δ ϭ Ϫ0.6 (q,
1JC-H ϭ 110 Hz, AlMe3). IR (Nujol): ν˜ ϭ 2783 cmϪ1 (m), 2725
(m), 1588 (m), 1364 (s), 1322 (s), 1252 (s), 1197 (s), 1097 (s), 1054
(m), 1041 (s), 933 (s), 886 (s), 835 (s), 797 (s), 758 (s), 703 (s), 628
(s). C42H69Al2LaO3 (814.9): calcd. C 61.91, H 8.53; found C 60.97,
H 8.24.
X-ray Crystallographic Studies: Crystals of 1, 4, and 5 were
mounted on a thin glass fiber using a small dot of silicone grease.
The crystals were then immediately placed on a Bruker P4/CCD/
PC diffractometer, and cooled to 203 K using a Bruker LT-2 tem-
perature device. The data were collected using a sealed, graphite
monochromatized Mo-Kα X-ray source. A hemisphere of data was
collected using a combination of and ω scans, with 30-second
frame exposures and 0.3° frame widths. Data collection and initial
indexing and cell refinement was handled using SMART[31] soft-
ware. Frame integration and final cell parameter calculations were
carried out using SAINT[32] software. The data were corrected for
absorption using the SADABS[33] program. Decay of reflection in-
tensity was not observed.
The structures were solved using Direct methods and difference
Fourier techniques. The initial solution revealed all non-hydrogen
atom positions. The methyl hydrogen atom positions for C37 and
C40 (1) were found on the difference map and refined with their
2
˚
isotropic temperature factors set to 0.08 A . The methylene hydro-
gen atom positions for C41 and C43 (4) were also found and re-
fined as described above. All other hydrogen atoms positions were
(ArO)La[(µ-OAr)(µ-Et)AlEt2]2 (3): AlEt3 (0.75 mL of a 1.9 solu-
tion in toluene, 1.50 mmol) was added to a toluene solution of
[La(OAr)3]2 (500 mg, 0.37 mmol). The mixture was stirred at room
temperature for 90 minutes. The solvent was removed under va-
cuum and the residue was washed with a minimum of hexane to
yield a colorless oil. Over a period of several days, the residue
changed into a mixture of a dark red oil and large colorless crystals.
X-ray crystallography indicated that the crystals consisted of
[Et2Al(OAr)]2 (5). No discrete lanthanum-containing species were
identified.
˚
˚
˚
idealized, CϪH ϭ 0.93 A (aromatic), 0.96 A (methyl), 0.98 A (me-
˚
thine) and 0.97 A (methylene). The hydrogen atoms were refined
using a riding model, with isotropic temperature factors fixed at
1.5 (methyl) or 1.2 (all others) times the equivalent isotropic U
of the atom they are bonded to. The final refinement[34] included
anisotropic temperature factors on all atoms. Structure solution,
refinement, graphics, and creation of publication materials were
performed using SHELXTL NT.[35] Additional details of data col-
lection and structure refinement are listed in Table 4. Crystallo-
graphic data (excluding structure factors) for the structures re-
ported in this paper have been deposited with the Cambridge Crys-
(ArO)Sm[(µ-OAr)(µ-Et)AlEt2]2 (4): AlEt3 (0.47 mL of a 1.9 solu-
tion in toluene, 0.91 mmol) was added to a toluene solution of
[Sm(OAr)3]2 (310 mg, 0.23 mmol), causing an immediate color tallographic Data Centre as supplementary publication nos.
change from yellow to orange. The mixture was stirred at room
CCDC-171086 (1), CCDC-171087 (4) and CCDC-171088 (5). Cop-
Eur. J. Inorg. Chem. 2002, 723Ϫ731
729
Giesbrecht, Garth R.
