1,2-cyclopentadienyl diimine-group 13 complexes

Full text of DOI:10.1021/ic9903782

Inorg. Chem. 1999, 38, 5189-5191
5189
solvent was removed under vacuum to yield an orange powder.
Recrystallization from benzene afforded orange crystals. Yield: 73%.
1H NMR (C6D6, 25 °C): δ 7.01 (4H, d, |JH-H| ) 6.9 Hz), 6.86 (6H,
m), 6.68 (2H, d, |JH-H| ) 3.9 Hz), 6.18 (1H, t, |JH-H| ) 3.9 Hz), 6.12
(2H, s). 13C{1H} NMR (C6D6, 25 °C): δ 175.1, 144.5, 141.5, 130.98,
129.7, 125.8, 120.9, 120.4. Anal. Calcd for C19H15N2GaCl2: C, 55.26;
H, 3.91. Found: C, 55.03; H, 3.78.
1,2-Cyclopentadienyl Diimine-Group 13
Complexes
Christopher M. Ong and Douglas W. Stephan*
School of Physical Sciences, Chemistry and Biochemistry,
University of Windsor, Windsor, Ontario Canada N9B 3P4
Synthesis of [(1,2-C5H3(C(Ph)NH)2)]AlR2, R ) Me (3), Et (4).
These complexes were prepared in a similar manner employing the
appropriate Al reagent, and thus only a single representative preparation
is described. To a solution of H[1,2-C5H3(C(Ph)NH)2] (0.07 g, 0.26
mmol) in benzene (5 mL) was added 2.0 M Me3Al (0.13 mL, 0.26
mmol). The solution was allowed to stir for 12 h, and the solution was
filtered. The remaining solvent was removed under vacuum to yield a
yellow powder. Recrystallization from benzene afforded dark orange
ReceiVed April 7, 1999
Introduction
The burgeoning academic interest and financial significance
of transition metal based olefin polymerization catalysts has
recently spawned exploration of related Lewis acidic main group
compounds. In this vein, Jordan and co-workers have recently
reported the characterization of aluminum cationic complexes
incorporating aminidinate1,2 and aminotroponiminate ligands.3
In addition, Smith et al.4 have reported related diketiminato
complexes. In our own efforts, we have previously reported the
convenient synthesis of 1,2-cyclopentadienyl diimine anions,
another bidentate, monoanionic ligand that chelates to early
transition metal centers via two nitrogen atoms.5 In this paper,
we expand our efforts to group 13 species, developing synthetic
routes to complexes of 1,2-cyclopentadienyl diimines. These
systems are characterized, and the implications with respect to
applications in catalysis are considered.
1
crystals of 3. Yield: 83%. H NMR (C6D6, 25 °C): δ 7.19 (4H, d,
|JH-H| ) 7.4 Hz), 7.09 (4H, t, |JH-H| ) 7.4 Hz), 6.97 (2H, t, |JH-H| )
7.4 Hz), 6.77 (2H, d, |JH-H| ) 3.8 Hz), 6.41 (1H, t, |JH-H| ) 3.8 Hz),
6.15 (2H, s), -0.32 (6H, s). 13C{1H} NMR (C6D6, 25 °C): δ 176.16,
143.5, 139.5, 130.44, 129.6, 121.6, 118.6, 109.9, 7.32. Anal. Calcd for
C21H21N2Al: C, 76.57; H, 6.73. Found: C, 76.38; H, 6.55. (4) Yield:
1
69%. H NMR (C6D6, 25 °C): δ 7.24 (4H, d, |JH-H| ) 6.9 Hz), 7.08
(4H, m), 6.97 (2H, m), 6.71 (2H, d, |JH-H| ) 3.8 Hz), 6.34 (1H, t,
|JH-H| ) 3.8 Hz), 6.17 (2H, s), 1.30 (4H, q, |JH-H| ) 8.1 Hz), 0.24
(6H, t, |JH-H| ) 8.1 Hz). 13C{1H} NMR (C6D6, 25 °C): δ 177.2, 144.09,
140.3, 131.08, 130.07, 129.04, 121.98, 119.21, 25.82, 10.76.
Synthesis of [(1,2-C5H3(C(Ph)NH)2)]MR2, M ) Al, R ) CH2Ph
(5), Ph (6), M ) Ga, R ) Me (7), Et (8), CH2Ph (9), Ph (10). These
complexes were prepared in a similar manner employing the appropriate
Grignard reagent metal halide precursor, and thus only a single
representative preparation is described. To a solution of 1 (0.053 g,
0.14 mmol) in benzene (5 mL) was added 1.0 M PhCH2MgCl (0.30
mL, 0.29 mmol). The solution was allowed to stir for 12 h, and the
solution was filtered. The remaining solvent was removed under vacuum
Experimental Section
General Data. All preparations were done under an atmosphere of
dry, O2-free N2 employing both Schlenk line techniques and Innovative
Technologies and Vacuum Atmospheres inert atmosphere gloveboxes.
Solvents were purified employing a Grubb’s type column system
manufactured by Innovative Technology. All organic reagents were
purified by conventional methods. 1H and 13C{1H} NMR spectra were
recorded on Bruker Avance-300 and -500 spectrometers operating at
300 and 500 MHz, respectively. Trace amounts of protonated solvents
were used as references, and chemical shifts are reported relative to
SiMe4. Guelph Chemical Laboratories Ltd. Guelph, Ontario, performed
combustion analyses. The compound H[(1,2-C5H3(C(Ph)NH)2)] was
prepared via literature methods.5 AlMeCl2, AlMe2Cl, and AlMe3 were
purchased from the Aldrich Chemical Co.
1
to yield an orange powder. (5) Yield: 75%. H NMR (C6D6, 25 °C):
δ 7.26 (6H, m), 7.23 (4H, m), 7.16 (4H, m), 7.06 (6H, m), 6.89 (2H,
d, |JH-H| ) 3.86 Hz), 6.53 (1H, t, |JH-H| ) 3.8 Hz), 6.15 (2H, s), 2.02
(4H, s). 13C{1H} NMR (C6D6, 25 °C): δ 176.28. 146.97, 143.00,
140.20, 130.92, 129.79, 128.97, 128.38, 127.27, 122.08, 121.54, 119.21,
19.68. (6) Yield: 82%. 1H NMR (C6D6, 25 °C): δ 7.99 (4H, m), 7.40
(4H, m), 7.33 (4H, m), 7.13 (2H, m), 7.04 (2H, m), 6.91 (4H, m), 6.79
(2H, d, |JH-H| ) 3.9 Hz), 6.42 (2H, s), 6.36 (1H, t, |JH-H| ) 3.9 Hz).
13C{1H} NMR (C6D6, 25 °C): δ 176.73, 142.93, 141.08, 139.79, 138.31,
129.38, 128.52, 128.29, 121.36, 119.19. (7) Yield: 64%. 1H NMR
(C6D6, 25 °C): δ 7.22 (4H, m), 7.09 (2H, m), 6.97 (4H, m), 6.73 (2H,
d, |JH-H| ) 3.82 Hz), 6.43 (1H, t, |JH-H| ) 3.82 Hz), 6.16 (2H, s),
-0.02 (6H, s). 13C{1H} NMR (C6D6, 25 °C): δ 176.15, 144.06, 138.37,
130.22, 129.65, 129.06, 117.56, 9.39. (8) Yield: 71%. 1H NMR (C6D6,
25 °C): δ 7.30 (4H, m), 7.09 (2H, m), 6.99 (4H, m), 6.72 (2H, d,
|JH-H| ) 3.8 Hz), 6.41 (1H, t, |JH-H| ) 3.8 Hz), 6.22 (2H, s), 2.16
(4H, q, |JH-H| ) 7.22 Hz), 0.66 (6H, t, |JH-H| ) 7.24 Hz). 13C{1H}
NMR (C6D6, 25 °C): δ 176.80, 144.19, 138.71, 130.25, 129.52, 128.51,
120.98, 117.65, 47.66, 9.43. (9) Yield: 68%. 1H NMR (C6D6, 25 °C):
δ 7.18 (4H, m), 7.11 (6H, d, |JH-H| ) 7.5 Hz), 6.98 (10H, m), 6.74
(2H, d, |JH-H| ) 3.8 Hz), 6.44 (1H, t, |JH-H| ) 3.8 Hz), 6.06 (2H,s),
2.17 (4H, s). 13C{1H} NMR (C6D6, 25 °C): δ 176.29, 145.64, 143.53,
139.12, 130.70, 129.77, 128.82, 128.18, 127.64, 122.58, 121.03, 118.07,
Synthesis of [1,2-C5H3(C(Ph)NH)2]AlCl2, 1. To a solution of
H[(1,2-C5H3(C(Ph)NH)2)] (0.092 g, 0.34 mmol) in benzene (5 mL) was
added 1.0 M MeAlCl2 (0.34 mL, 0.34 mmol). The solution was allowed
to stir for 12 h, and the solution was filtered. The remaining solvent
was removed under vacuum to yield an orange solid. Recrystallization
1
from benzene afforded orange crystals. Yield: 79%. H NMR (C6D6,
25 °C): δ 7.04 (2H, m), 6.97 (4H, m), 6.88 (4H, m), 6.76 (2H, d,
|JH-H| ) 4.0 Hz), 6.26 (1H, t, |JH-H| ) 4.0 Hz), 6.12 (2H, s). 13C{1H}
NMR (C6D6, 25 °C): δ 175.57, 143.64, 142.32, 141.21, 130.61, 129.52,
121.19, 119.49. Anal. Calcd for C19H15N2AlCl2: C, 61.64; H, 4.36.
Found: C, 61.48; H, 4.21.
Synthesis of [1,2-C5H3(C(Ph)NH)2]GaCl2, 2. To a solution of
H[1,2-C5H3(C(Ph)NH)2] (0.087 g, 0.32 mmol) in benzene (5 mL) was
added GaCl3 (0.056 g, 0.32 mmol) and NEt3 (1.00 mmol). The solution
was allowed to stir for 12 h, and the solution was filtered. The remaining
1
48.42. (10) Yield: 74%. H NMR (C6D6, 25 °C): δ 7.85 (4H, m),
7.35 (4H, m), 7.29 (4H, m), 7.18 (2H, m), 7.04 (2H, m), 6.92(4H, m),
6.73 (2H, d, |JH-H| ) 3.9 Hz), 6.42 (2H, s), 6.36 (1H, t, |JH-H| ) 3.9
Hz). 13C{1H} NMR (C6D6, 25 °C): δ 176.95, 145.10, 143.58, 140.17,
137.44, 130.37, 129.61, 128.68, 128.51, 127.89, 121.04, 118.31.
(1) Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1997, 119, 8125.
(2) Coles, M. P.; Swenson, D. C.; Jordan, R. F.; Young, J. V. G.
Organometallics 1997, 16, 5183.
(3) Ihara, E.; Young, V. G.; Jordan, R. F. J. Am. Chem. Soc. 1998, 120,
X-ray Data Collection and Reduction. X-ray-quality crystals of
1, 2, and 3 were obtained directly from the preparation as described
above. The crystals were manipulated and mounted in capillaries in a
glovebox, thus maintaining a dry, O2-free environment for each crystal.
Diffraction experiments were performed on a Siemens SMART System
8277.
(4) Qian, B.; Ward, D. L.; Smith, M. R., III Organometallics 1998, 17,
3070.
(5) Etkin, N.; Ong, C. M.; Stephan, D. W. Organometallics 1998, 17,
3656.
10.1021/ic9903782 CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/08/1999

5190 Inorganic Chemistry, Vol. 38, No. 22, 1999
Notes
Table 1. X-ray Crystallographic Dataa
1
2
3
empirical formula
fw
temp (k)
C22H18AlCl2N2
408.26
293(2)
C22H18Cl2GaN2
451.00
293(2)
C24H24AlN2
367.43
293(2)
wavelength (Å)
space group
a (Å)
b (Å)
c (Å)
0.710 73 (Mo KR)
P2(1)/n (no. 14)
9.859(9)
15.699(16)
13.755(9)
0.710 73 (Mo KR)
P2(1)/n (no. 14)
9.838(2)
15.702(3)
13.755(2)
0.710 73 (Mo KR)
P1h (no. 2)
7.685(2)
10.5330(15)
13.120(5)
R (deg)
91.94(3)
105.14(2)
95.39(2)
2051.1(7), 4
1.461
â (deg)
105.00(6)
91.86(3)
γ (deg)
vol (Å3), Z
density(calcd) (g/cm3)
2056(3), 4
1.319
0.367
R1 ) 0.0996, wR2 ) 0.1959
R1 ) 0.3534,
wR2 ) 0.2836
0.774
1056.0(5), 2
1.156
0.106
µ (mm-1
)
1.611
R indices [I > 2σ(I)]
R1 ) 0.0481, wR2 ) 0.1372
R1 ) 0.0575,
wR2 ) 0.1496
1.006
R1 ) 0.0436, wR2 ) 0.1440
R indices (all data)
R1 ) 0.0527,
wR2 ) 0.1521
1.189
GOF
2
a R ) ∑||Fo| - |Fc||/∑|Fo|, Rw ) [∑(|Fo| - |Fc|)2|/∑|Fo| ]0.5
.
CCD diffractometer collecting a hemisphere of data in 1329 frames
with 10 s exposure times. Crystal data are summarized in Table 1. The
observed extinctions were consistent with the space groups in each
case. The data sets were collected (4.5° < 2θ < 45-50.0°). A measure
of decay was obtained by recollecting the first 50 frames of each data
set. The intensities of reflections within these frames showed no
statistically significant change over the duration of the data collections.
The data were processed using the SAINT and XPREP processing
package. An empirical absorption correction based on redundant data
was applied to each data set. Subsequent solution and refinement was
performed using the SHELXTL solution package operating on a SGI
Challenge mainframe computer with remote X-terminals or a PC
Figure 1. ORTEP drawings of 1; 30% thermal ellipsoids are shown.
Hydrogen atoms have been omitted for clarity. Al(1)-N(1) 1.846(9)
Å, Al(1)-N(2) 1.860(8) Å, Al(1)-Cl(2) 2.109(5) Å, Al(1)-Cl(1)
2.111(5) Å, N(1)-C(6) 1.321(12) Å, N(2)-C(13) 1.314(12) Å, N(1)-
Al(1)-N(2) 104.3(4)°, N(1)-Al(1)-Cl(2) 109.0(3)°, N(2)-Al(1)-Cl-
(2) 110.7(3)°, N(1)-Al(1)-Cl(1) 113.4(3)°, N(2)-Al(1)-Cl(1) 107.3-
(3)°, Cl(2)-Al(1)-Cl(1) 112.0(2)°, C(6)-N(1)-Al(1) 130.9(8)°, C(13)-
N(2)-Al(1) 131.1(8)°.
2
2
employing X-emulation. The reflections with Fo > 3σFo were used
in the refinements.
Structure Solution and Refinement. Non-hydrogen atomic scat-
tering factors were taken from the literature tabulations.6,7 The heavy
atom positions were determined using direct methods employing either
of the SHELXTL direct methods routines. The remaining non-hydrogen
atoms were located from successive difference Fourier map calculations.
The refinements were carried out by using full-matrix least-squares
techniques on F, minimizing the function ω(|Fo| - |Fc|)2 where the
Scheme 1
2
2
weight ω is defined as 4Fo /2σ(Fo ) and Fo and Fc are the observed
and calculated structure factor amplitudes. In the final cycles of each
refinement, all non-hydrogen atoms were assigned anisotropic temper-
ature factors. Carbon bound hydrogen atom positions were calculated
and allowed to ride on the carbon to which they are bonded assuming
a C-H bond length of 0.95 Å. Hydrogen atom temperature factors
were fixed at 1.10 times the isotropic temperature factor of the carbon
atom to which they are bonded. The hydrogen atom contributions were
calculated, but not refined. Each molecule crystallized with 0.5C6H6
in the asymmetric unit. The final values of refinement parameters are
given in Table 1. The locations of the largest peaks in the final
difference Fourier map calculation as well as the magnitude of the
residual electron densities in each case were of no chemical significance.
Positional parameters, hydrogen atom parameters, thermal parameters,
and bond distances and angles have been deposited as Supporting
Information.
via reaction of GaCl3 with the ligand precursor in the presence
of base. In this manner 2 is subsequently isolated in 73% yield.
NMR parameters for 1 and 2 were not unlike those observed
for [(1,2-C5H3(C(Ph)NH)2)]ZrCl3(THF), suggesting a similar
binding mode.5 The precise structures of 1 and 2 were confirmed
via an X-ray structural studies (Figures 1 and 2).
Results and Discussion
The solid-state structures of 1 and 2 are isostructural. The
diimine anion binds to the Al or Ga center via the nitrogen atoms
while the two chloride atoms complete the pseudotetrahedral
coordination sphere of the main group metals. The Al-N
distances average 1.853(9) Å while the corresponding Ga-N
distances average 1.889(4) Å. These distances are significantly
longer that those found in the iminoaluminum dimer [CpAl(µ-
Naryl)]2 (1.796(2) and 1.811(3) Å)8 but in the range of those
found in the diketiminato derivatives described by Smith et al.4
The 1,2-cyclopentadienyl diimine H[1,2-C5H3(C(Ph)NH)2]
undergoes facile reaction with MeAlCl2 to give the orange
complex [1,2-C5H3(C(Ph)NH)2]AlCl2, 1, in 79% yield (Scheme
1). 1H and 13C NMR data and elemental analyses are consistent
with loss of methane via protonolysis. The analogous gallium
compound [1,2-C5H3(C(Ph)NH)2]GaCl2, 2, is readily prepared
(6) Cromer, D. T.; Mann, J. B. Acta Crystallogr., Sect. A 1968, A24, 324.
(7) Cromer, D. T.; Mann, J. B. Acta Crystallogr., Sect. A 1968, A24, 390.

Notes
Inorganic Chemistry, Vol. 38, No. 22, 1999 5191
Figure 3. ORTEP drawings of 3; 30% thermal ellipsoids are shown.
Hydrogen atoms have been omitted for clarity. Al(1)-N(1) 1.8986-
(17) Å, Al(1)-N(2) 1.9023(15) Å, Al(1)-C(20) 1.951(2) Å, Al(1)-
C(21) 1.955(3) Å, N(1)-Al(1)-N(2) 99.72(7)°, N(1)-Al(1)-C(20)
106.36(9)°, N(2)-Al(1)-C(20) 108.17(9)°, N(1)-Al(1)-C(21) 111.33-
(11)°, N(2)-Al(1)-C(21) 109.09(10)°, C(20)-Al(1)-C(21) 120.19-
(12)°, C(6)-N(1)-Al(1) 132.06(13)°, C(13)-N(2)-Al(1) 130.61(12)°.
Figure 2. ORTEP drawings of 2; 30% thermal ellipsoids are shown.
Hydrogen atoms have been omitted for clarity. Ga(1)-N(2) 1.884(3)
Å, Ga(1)-N(1) 1.895(3) Å, Ga(1)-Cl(2) 2.1564(11) Å, Ga(1)-Cl(1)
2.1595(13) Å, N(1)-C(6) 1.325(4) Å, N(2)-C(7) 1.331(4) Å, N(2)-
Ga(1)-N(1) 105.06(13)°, N(2)-Ga(1)-Cl(2) 112.61(10)°, N(1)-Ga-
(1)-Cl(2) 106.76(9)°, N(2)-Ga(1)-Cl(1) 109.13(11)°, N(1)-Ga(1)-
Cl(1) 111.36(10)°, Cl(2)-Ga(1)-Cl(1) 111.72(5)°, C(6)-N(1)-Ga(1)
129.5(3)°, C(7)-N(2)-Ga(1) 128.1(2)°.
Chart 1
The corresponding M-Cl distances are 2.110(5) and
2.1579(13) Å for Al and Ga, respectively. These distances are
9
typical of the Al-Cl distances in [Cp*AlCl(µ-Cl)]2 and
[Cp*AlMe(µ-Cl)]210 but significantly shorter than those seen
in adducts of the form (Ph3PNSiMe3)AlMe2Cl (2.2150(12) Å).11
The N-M-N bite angles for the diimine anion are 104.3(4)°
and 105.06(13)° in 1 and 2, respectively. The Cl-M-Cl angles
are similar in the two compounds, both being close to 112°.
The phenyl rings on the imino carbons are oriented such that
the planes are approximately orthogonal to that of the cyclo-
pentadienyl ring in the chelate backbone.
with MO calculations previously described for the related Zr
complexes that showed a localization of charge on the cyclo-
pentadienyl ring.5 Such charge separation infers an increase in
the electrophilic character of the corresponding metal centers,
a feature that might be expected to enhance the suitablity for
applications in olefin polymerization chemistry.
In attempts to explore that potential, attempts to generate Al-
based zwitterions or cations were undertaken. In the case of
the reaction of 3 with B(C6F5)3, monitoring the reaction by NMR
revealed the formation of multiple products. The nature of these
species remains unclear. Similarly, reaction with Ph3C[B(C6F5)4]
in the presence or absence of donors also resulted in several
products which could be neither isolated nor identified. These
observations infer that these reactions follow several competitive
pathways. While abstraction of methyl from aluminum was
anticipated, abstraction of proton from nitrogen and/or associa-
tion of the Lewis acid with the electron rich cyclopentadienyl
ring are also possible avenues for reactivity. Moreover, this
behavior is in direct contrast to that of the aluminum complexes
of aminidinate1,2 and aminotroponiminate3 ligands.
The present results clearly demonstrate that group 13
complexes of the monoanionic, bidentate, 1,2-cyclopentadienyl
diimine ligands are readily available. The relatively short Al-C
and Al-Cl distances suggest a charge separation and thus
electrophilic metal centers. The incorporation of several reactive
sites in these systems apparently precludes the use of the present
systems as precursors to reactive cationic species. While this
might be rectified by suitable ligand modification, it is the
reactivity of these and other electrophilic group 13 species that
is the subject of ongoing study.
Reaction of H[(1,2-C5H3(C(Ph)NH)2)] with either AlMe3 or
AlEt3 affords the dimethyl and diethyl derivatives of 1, [(1,2-
C5H3(C(Ph)NH)2)]AlR2, R ) Me (3), Et (4) (Scheme 1). The
rust orange compounds 3 and 4 were isolated in 83% and 69%
1
yields, respectively. The NMR spectrum of 3 reveals a H
resonance attributable to the methyl group at -0.32 ppm, while
the corresponding 13C NMR resonance appears at 7.32 ppm. In
the case of 4, the ethyl groups give rise to signals in the 1H and
13C NMR at 1.30 and 0.24 ppm and 25.82 and 10.76 ppm,
respectively. The related compounds [(1,2-C5H3(C(Ph)NH)2)]-
MR2, M ) Al, R ) CH2Ph (5), Ph (6) (Scheme 1), M ) Ga, R
) Me (7), Et (8), CH2Ph (9), and Ph (10), were prepared from
reaction of 1 or 2 and the appropriate Grignard reagent. In the
case of 3, the structure was also confirmed crystallographically
(Figure 3). The Al-N distances in 3 of 1.8986(17) and
1.9023(15) Å are slightly longer than those seen in 1. This is
consistent with the presence of the electron-donating methyl
groups in 3. The Al-C distances average 1.953(3) Å, which is
slightly shorter than those seen in (Ph3PNSiMe3)AlMe2Cl
(1.993(2) and 1.982(3)) Å).11 It is also noteworthy that despite
the fact that the N2C2Cp fragment is expected to be fully
conjugated, the chelate ring and cyclopentadienyl group of 1-3
are not coplanar (Chart 1). The dihedral angles between the N2C2
plane and that of the cyclopentadienyl ring are 28.4°, 33.5°,
and 30.5° for 1-3, respectively. This is in direct contrast to
the planarity of aminidinate,1,2 aminotroponiminate,3 and diket-
iminato4 ligands. This disruption of conjugation is consistent
(8) Fisher, J. D.; Shapiro, P.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem.
1996, 35, 271.
(9) Schonberg, P. R.; Paine, R. T.; Campana, C. F. J. Am. Chem. Soc.
1979, 101, 7726.
(10) Koch, H. J.; Schulz, S.; Roesky, H. W.; Noltmeyer, M.; Schmidt, H.
G.; Heine, A.; Herst-Irmer, R.; Stalke, D.; Scheldrick, G. Chem. Ber.
1992, 125, 1107.
(11) Ong, C. M.; McKarns, P.; Stephan, D. W. Organometallics, submitted
for publication.
Acknowledgment. Financial support from NSERC of Canada
is gratefully acknowledged.
Supporting Information Available: Tables listing crystallographic
data. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC9903782