5930 Organometallics, Vol. 29, No. 22, 2010
Kingsley et al.
1.65 (m, 4H, CH), 0.73 (d, 3JHH = 6.6 Hz, 12H, CH3), 0.59 (d,
3JHH = 6.6 Hz, 12H, CH3), 0.52-0.43 (m, 8H, CH2). 13C{1H}
NMR (C6D6, 150.8 MHz): δ 145.64 (s, C3a), 135.53 (s, C7a),
133.01 (s, C2), 123.52 (s, C6), 123.32 (s, C5), 122.42 (s, C3),
119.60 (s, C4), 119.37 (s, C7), 27.61 (s, CH3), 27.57 (s, CH3),
25.92 (s, CH), 23.74 (br s, AlCH2), 9.47 (s, indole CH3). Anal.
Calcd for C34H52N2Al2: C, 75.24; H, 9.66; N, 5.16. Found: C,
73.24; H, 8.64; N, 5.06.
C, 73.26; H, 7.99; N, 6.41; Al, 12.34. Found: C, 72.05; H, 8.34; N,
6.41; Al, 12.80.
Preparation of [{Tri(N-3-methylindolyl)methane}(HAl3 Bu5)] (6).
i
A toluene solution of triisobutylaluminum (3.0 mL, 1.0 M, 3.0
mmol) was added via syringe to a warm (50 °C) solution of tri-
(3-methylindolyl)methane (0.403 g, 1.00 mmol) in 50 mL of
toluene. The resulting yellow solution was stirred at 50 °C for
48 h. Solvent was removed from the reaction solution in vacuo
to yield a yellow oil. The oil was dissolved in 10 mL of hexanes,
and the solution was cooled to -30 °C for 12 h. The resulting
yellow crystalline solid was isolated by filtration. Yield: 0.61 g,
Preparation of [{Di(N-3-methylindolyl)phenylmethane}(AlMe2)2]
(4). A toluene solution of trimethylaluminum (1.0 mL, 2.0 M,
2.0 mmol) was added via syringe to a solution of di(3-methyl-
indolyl)phenylmethane (0.350 g, 1.00 mmol) in 25 mL of
toluene. Gas evolution proceeded immediately, and the solution
slowly turned dark green over 12 h. Solvent was removed in
vacuo, and the remaining green oil was dissolved in 15 mL of
hexanes. The solution was stored at -30 °C for 12 h to yield a green
solid, which was isolated by filtration. Yield: 0.418 g, 0.905 mmol,
90%. Attempts to obtain 4 as a pure sample, free of excess Me3Al,
were not successful. The presence of residual Me3Al in most
samples thwarted satisfactory elemental analyses. A crystalline
sample of 4 suitable for X-ray analysis was obtained by crystal-
lization from toluene. 1H NMR (-40.0 °C, CDCl3, 400 MHz): δ
7.79 (m, 2H, H7), 7.61 (m, 2H, H4), 7.46-7.35 (m, 11H, H2, H5,
H6, aryls), 5.97 (s, 1H, CH), 2.02 (s, 6H, indole CH3), 0.03 (s,
3H, AlCH3), -0.18 (s, 3H, AlCH3), -1.33 (s, 3H, AlCH3),
-1.58 (s, 3H, AlCH3). 13C{1H} NMR (-40.0 °C, CDCl3,
100.6 MHz): δ 142.14 (s, C3a), 141.07 (s, C2), 138.31 (Ph-ipso),
135.95 (s, C7a), 129.29, (s, Ph-para), 128.60 (s, Ph-ortho), 127.12
(s, Ph-meta), 123.80 (s, C5), 123.13 (s, C6), 121.38 (s, C3), 119.05
(s, C4), 116.11, (s, C7), 42.89 (s, CH), 10.07 (s, CH3), -5.27 (br s,
AlCH3), -6.39 (br s, AlCH3), -8.8 (br s, AlCH3).
1
0.79 mmol, 79%. IR (KBr, νAl-H, cm-1): 1866 (s). H NMR
(C6D6, 600 MHz): δ 8.15 (d, 3JHH = 7.8 Hz, 1H, H7), 8.07 (d,
3JHH =7.8 Hz, 2H, H7), 7.30 (d, 3JHH =7.8 Hz, 1H, H4), 7.27
(d, 3JHH=7.8 Hz, 2H, H4), 7.21-7.10 (m, 6H, H5, H6), 6.06 (s,
1H, CH), 5.41 (br s, w1/2 ≈ 48 Hz, ≈1H, Al-H), 2.51 (m, 2H,
CH), 2.22 (s, 3H, indole CH3), 2.16 (s, 6H, indole CH3), 1.72 (dd,
2JHH =14.4 Hz, 3JHH =6.6 Hz, 2H, AlCH2), 1.52 (dd, 2JHH
=
14.4 Hz, 3JHH=6.6 Hz, 2H, AlCH2), 1.42 (d, 3JHH=6.6 Hz, 6H,
CH3), 1.31 (d, 3JHH=6.6 Hz, 6H, CH3), 0.71 (m, 3H, CH), 0.40
(d, 3JHH=6.6 Hz, 6H, CH3), 0.19 (d, 3JHH=6.6 Hz, 6H, CH3),
0.13 (d, 3JHH=6.6 Hz, 6H, CH3), -1.55 (d, 3JHH=6.6 Hz, 4H,
AlCH2), -1.92 (d, 3JHH =6.6 Hz, 2H, AlCH2). 13C{1H} NMR
(C6D6, 150.8 MHz): δ 143.95 (s, C3a), 143.49 (s, C3a), 140.34 (s,
C2), 140.32 (s, C2), 137.94 (s, C7a), 137.59 (s, C7a), 125.21 (s,
C5), 125.17 (s, C5), 125.04 (s, C6), 124.99 (s, C6), 122.13 (s, C3),
121.18 (s, C3), 120.11 (s, C4), 120.01 (s, C4), 117.48 (s, C7), 117.37
(s, C7), 33.51(s, CH), 29.15(s, CH3), 28.45 (s, CH3), 27.65 (s, CH3),
27.44 (s, CH3), 27.11 (s, CH3), 26.86 (s, CH), 24.98 (s, CH), 24.67
(br s, AlCH2), 24.44 (s, CH), 14.19 (br s, AlCH2), 11.41 (br s,
AlCH2), 8.66 (s, indole CH3), 8.58 (s, indole CH3). Anal. Calcd
for C48H68N3Al3: C, 75.07; H, 8.92; N, 5.47; Al, 10.54. Found:
C, 72.33; H, 9.07; N, 5.43; Al, 10.74.
Preparation of [{Tri(N-3-methylindolyl)methane}(AlMe2)3] (5a).
A toluene solution of trimethylaluminum (1.0 mL, 2.0 M, 2.0 mmol)
was added via syringe to a warm (50 °C) solution of tri(3-methyl-
indolyl)methane (0.269 g, 0.667 mmol) in 30 mL of toluene. The
reaction solution turned bright yellow and darkened as the
solution was cooled to 25 °C and stirred for 12 h. The solvent
was then removed in vacuo to yield a yellow solid, which was
subsequently dissolved in a mixture of 10 mL of toluene and
5 mL of hexanes followed by cooling to -30 °C for 48 h. The
resulting white crystalline material was isolated by filtration.
Yield: 0.34 g, 0.59 mmol, 88%. 1H NMR (C6D6, 600 MHz): δ
X-ray Crystallography for 3a, 4, and 5a. Crystals of 3a and 5a
were grown at -30 °C from concentrated chloroform and
toluene solutions, respectively. Crystals of 4 were obtained from
a highly concentrated, viscous toluene solution after storage in a
Schlenk flask in the glovebox at room temperature for three
weeks. X-ray diffraction data were collected on a Siemens three-
circle platform diffractometer equipped with a SMART 6000
CCD detector. The frame data were acquired with the SMART
5.625 software29 using Mo KR radiation (λ =0.710 73 A). Cell
˚
3
3
constants were determined from the complete data set and
frames were integrated using SAINT PLUS 6.22.30 Absorption
and decay correction were performed using the SADABS
program.31 The structures were solved by direct methods and
refined by least-squares methods on F2 using the SHELXTL
program suite.32 All ordered and some of the disordered non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were calculated on idealized positions
and included in the refinement with their isotropic displacement
parameters fixed to the equivalent displacement factor of the
bonded atom.
Structure solution for 3a showed whole molecule disorder.
The structure was modeled with two orientations of overlapping
anti isomers as well as two orientations of overlapping syn
isomers. A model containing concurrently syn and anti isomers
has been considered. Refinement of the occupancies of the carbon
and N-methylindolide atoms with fixed thermal parameters ruled
out the exclusive presence of the anti isomer and suggests two
orientations of the syn isomer having 56% and 44% occupancy
in the crystal lattice. The anisotropy in the N-Al-CH3 bond angles
of a potential anti isomer (e.g., 118.9/103.8° and 118.3/105.5°
7.87 (d, JHH = 7.8 Hz, 3H, H7), 7.28 (d, JHH = 7.8 Hz, 3H,
H4), 7.13 (t, 3JHH=7.8 Hz, 3H, H5), 7.10 (t, 3JHH=7.8 Hz, 3H,
H6), 6.08 (s, 1H, CH), 2.12 (s, 9H, indolyl CH3), 0.45 (s, 9H,
AlCH3), -2.27 (s, 9H, AlCH3). 13C{1H} NMR (C6D6, 150.8 MHz):
δ 143.23 (s, C3a), 140.03 (s, C2), 137.35 (s, C7a), 125.20 (s, C5),
124.82 (s, C6), 121.66 (s, C3), 120.09 (s, C4), 117.16, (s, C7),
33.58 (s, CH), 8.50 (s, CH3), -6.65 (br s, AlCH3), -19.34 (br s,
AlCH3). Anal. Calcd for C34H40N3Al3: C, 71.44; H, 7.05; N,
7.35; Al, 14.16. Found: C, 71.09; H, 7.56; N, 7.32; Al, 14.87.
Preparation of [{Tri(N-3-methylindolyl)methane}(AlEt2)3] (5b).
A solution of triethylaluminum (0.375 g, 3.27 mmol) in 10 mL of
toluene was added via syringe to a warm (50 °C) solution of tri(3-
methylindolyl)methane (0.442 g, 1.09 mmol) in 50 mL of
toluene. The resulting solution turned slightly yellow and slowly
darkened as the solution was cooled to 25 °C and stirred for 24 h.
Solvent was removed in vacuo to yield a yellow oil, which was
subsequently dissolved in 15 mL of hexanes and stored at -30 °C
for 24 h. The resulting yellow crystalline solid was isolated by filt-
ration. Yield: 0.72 g, 0.86 mmol, 79%. 1H NMR (C6D6, 600 MHz):
δ 7.97 (d, 3H, H7), 7.22 (d, 3H, H4), 7.09-7.06 (m, 6H, H5, H6),
6.00 (s, 1H, CH), 2.08 (s, 9H, indole CH3), 1.44 (t, 3JHH=9.0 Hz,
3
9H, CH2CH3), 1.31 (q, JHH = 9.0 Hz, 6H, CH2CH3), -0.13
(t, 3JHH =9.0 Hz, 9H, CH2CH3), -1.57 (q, 3JHH =9.0 Hz, 6H,
CH2CH3). 13C{1H} NMR (C6D6, 150.8 MHz): δ 143.57 (s, C3a),
140.15 (s, C2), 137.56 (s, C7a), 125.00 (s, C5), 124.98 (s, C6),
121.30 (s, C3), 119.93 (s, C4), 117.54, (s, C7), 33.59 (s, CH), 10.34
(s, CH2CH3), 8.63(s, CH3), 8.20(s, AlCH2CH3), 3.54(brs, AlCH2-
CH3), -7.88 (br s, AlCH2CH3). Anal. Calcd for C40H52N3Al3:
(29) SMART 5.625, Software for the CCD Detector System; Bruker AXS
Inc.: Madison, WI, USA, 1997.
(30) SAINT 6.22, Software for the CCD Detector System; Bruker AXS
Inc.: Madison, WI, USA, 2001.
(31) Sheldrick, G. M. SADABS, Absorption Correction Program; University
€
€
of Gottingen: Gottingen, Germany, 1996.
(32) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.