Aluminum Complexes Incorporating Bidentate Amido Phosphine Ligands

Article abstract of DOI:10.1021/ic035373q

A series of aluminum complexes supported by o-phenylene-derived amido phosphine ligands, N-(2-diphenylphosphinophenyl)-2,6-dimethylanilide ([Me-NP]^-) and N-(2-diphenylphosphinophenyl)-2,6-diisopropylanilide ([ⁱPr-NP]^-), ha

Full text of DOI:10.1021/ic035373q

Inorg. Chem. 2004, 43, 2166−2174
Aluminum Complexes Incorporating Bidentate Amido Phosphine
Ligands
,†
Lan-Chang Liang,* Mei-Hui Huang,† and Chen-Hsiung Hung‡
Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat-sen
UniVersity, Kaohsiung 80424, Taiwan, and Department of Chemistry, National Changhua
UniVersity of Education, Changhua 50058, Taiwan
Received November 27, 2003
A series of aluminum complexes supported by o-phenylene-derived amido phosphine ligands, N-(2-diphenylphos-
i
phinophenyl)-2,6-dimethylanilide ([Me-NP]-) and N-(2-diphenylphosphinophenyl)-2,6-diisopropylanilide ([Pr-NP]-),
i
have been prepared. The reactions of trialkylaluminum with H[Me-NP] and H[Pr-NP], respectively, in refluxing
i
toluene produced the corresponding dialkyl complexes [Me-NP]AlR and [Pr-NP]AlR (R ) Me, Et). Deprotonation
2
2
of H[Me-NP] with n-BuLi in THF at −35 °C followed by addition of AlCl3 in toluene at −35 °C afforded [Me-NP]-
AlCl2, which was subsequently reacted with 2 equiv of trimethylsilylmethyllithium in toluene to give [Me-NP]Al(CH -
2
SiMe3)2. The aluminum complexes were all characterized by 1H, 13C, 31P, and 27Al NMR spectroscopy. The solid-
i
state structures of monomeric, four-coordinate [Me-NP]AlEt2 and [Pr-NP]AlMe and five-coordinate [Me-NP]AlCl2(THF)
2
1
were determined by X-ray crystallography. The H NMR studies of [Me-NP]AlEt2, [Me-NP]Al(CH SiMe3)2, and
[Pr-NP]AlEt2 indicate diastereotopic R-hydrogen atoms in these molecules. Heteronuclear COSY and NOE
experiments suggest that the phosphorus donor in [Me-NP]Al(CH SiMe3)2 and [Pr-NP]AlEt2 is coupled to only one
2
i
i
2
of the diastereotopic R-hydrogen atoms that is virtually antiperiplanar with respect to the phosphorus atom.
Introduction
[N-S]-.21 Representative examples are depicted in Chart 1.
Aluminum complexes of bidentate [N-P]- ligands are
notably unexplored.22 In an effort to expand the territory of
aluminum chemistry and evaluate the possibility of catalytic
polymerization thereafter, we chose to examine complexes
Organoaluminum complexes supported by monoanionic,
bidentate, four-electron [L-X]- ligands are currently receiv-
ing considerable attention due to their increasing role in
polymerization chemistry.1 Several classes of ligands inves-
tigated thus far include [N-N]-,1-18 [N-O]-,19,20 and
(10) Gibson, V. C.; Redshaw, C.; White, A. J. P.; Williams, D. J. J.
Organomet. Chem. 1998, 550, 453-456.
(11) Kincaid, K.; Gerlach, C. P.; Giesbrecht, G. R.; Hagadorn, J. R.;
Whitener, G. D.; Shafir, A.; Arnold, J. Organometallics 1999, 18,
5360-5366.
(12) Schmidt, J. A. R.; Arnold, J. Organometallics 2002, 21, 2306-2313.
(13) Hao, H.; Bhandari, S.; Ding, Y.; Roesky, H. W.; Magull, J.; Schmidt,
H.-G.; Noltemeyer, M.; Cui, C. Eur. J. Inorg. Chem. 2002, 1060-
1065.
* Corresponding author. Fax: +886-7-5253908. E-mail: lcliang@mail.
nsysu.edu.tw.
† National Sun Yat-sen University.
‡ National Changhua University of Education.
(1) Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1997, 119, 8125-
8126.
(2) Aeilts, S. L.; Coles, M. P.; Swenson, D. G.; Jordan, R. F.; Young, V.
G. Organometallics 1998, 17, 3265-3270.
(3) Coles, M. P.; Swenson, D. C.; Jordan, R. F.; Young, V. G.
Organometallics 1997, 16, 5183-5194.
(14) Huang, J.-H.; Chen, H.-J.; Chang, J.-C.; Zhou, C.-C.; Lee, G.-H.; Peng,
S.-M. Organometallics 2001, 20, 2647-2650.
(15) Liang, L.-C.; Yang, C.-W.; Chiang, M. Y.; Hung, C.-H.; Lee, P.-Y.
J. Organomet. Chem. 2003, 679, 135-142.
(4) Dagorne, S.; Guzei, I. A.; Coles, M. P.; Jordan, R. F. J. Am. Chem.
Soc. 2000, 122, 274-289.
(16) Qian, B. X.; Ward, D. L.; Smith, M. R. Organometallics 1998, 17,
3070-3076.
(5) Ihara, E.; Young, V. G.; Jordan, R. F. J. Am. Chem. Soc. 1998, 120,
8277-8278.
(17) Cosledan, F.; Hitchcock, P. B.; Lappert, M. F. Chem. Commun. 1999,
705-706.
(6) Korolev, A. V.; Guzei, I. A.; Jordan, R. F. J. Am. Chem. Soc. 1999,
121, 11605-11606.
(18) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao, H.;
Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4272-4276.
(19) Cameron, P. A.; Gibson, V. C.; Redshaw, C.; Segal, J. A.; Solan, G.
A.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 2001,
1472-1476.
(7) Korolev, A. V.; Ihara, E.; Guzei, I. A.; Young, V. G.; Jordan, R. F. J.
Am. Chem. Soc. 2001, 123, 8291-8309.
(8) Radzewich, C. E.; Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1998,
120, 9384-9385.
(9) Radzewich, C. E.; Guzei, I. A.; Jordan, R. F. J. Am. Chem. Soc. 1999,
121, 8673-8674.
(20) Dagorne, S.; Lavanant, L.; Welter, R.; Chassenieux, C.; Haquette, P.;
Jaouen, G. Organometallics 2003, 22, 3732-3741.
2166 Inorganic Chemistry, Vol. 43, No. 6, 2004
10.1021/ic035373q CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/20/2004

Amido Phosphine Complexes of Aluminum
Chart 1. Representative Examples of Monoanionic, Bidentate, Four-Electron [L-X]- Ligands
Scheme 1
and elemental analysis. Consistent with the steric size of the
ortho substituents, the isopropyl derivatives require relatively
harsh conditions for both palladium-catalyzed cross-coupling
reaction and nucleophilic phosphanylation for high yield
isolation of the desired products as compared to their methyl
analogues. Solution NMR spectroscopic data indicate that
the o-alkyl groups in these fluorine and phosphine com-
pounds are chemically equivalent. The isopropylmethyl
groups in H[iPr-NP] are diastereotopic as two doublet
of N-arylated amido phosphine ligands that contain the
potentially rigid and robust o-phenylene backbone ([NP]-,
Chart 1). Ligands of this type can be regarded as phosphine-
functionalized biaryl amides. We have recently shown that
coordinatively unsaturated zinc complexes are readily ac-
cessible by the utilization of sterically demanding [NP]-
ligands.23 Recent reports by Jordan and co-workers reveal
that the use of bulky [L-X]- ligands is essential for
generating reactive aluminum cations for polymerization
purposes.4 In this paper, we aim to demonstrate the synthetic
possibility of aluminum complexes incorporating the [NP]-
ligands. Spectroscopic data concerning the steric properties
of the amido phosphine ligands are discussed.
1
resonances are observed at room temperature in H NMR
spectroscopy. A variable temperature 1H NMR study (50 mM
in toluene-d8) revealed that the two doublet resonances tend
to broaden at temperatures higher than 110 °C, consistent
with restricted rotation about the N-aryl bond.24 The NH
proton appears as one doublet resonance (JHP ) ca. 8 Hz
for both H[Me-NP] and H[iPr-NP]) in 1H NMR spectroscopy.
The solid-state structure of H[Me-NP] (Table 1, Figure 1)
was determined to investigate the relative orientation of the
substituents at both donor atoms. The 2,6-dimethylphenyl
ring is nearly perpendicular to the o-phenylene backbone.
The N-C bond distance is slightly longer for the 2,6-
dimethylphenyl group than for the o-phenylene backbone.
The two phenyl rings at the phosphorus donor are oriented
such that they are virtually orthogonal to each other. All bond
distances and angles obtained are well within their expected
values and comparable to those of the closely related bis-
(2-diphenylphosphinophenyl)amine.25
Results and Discussion
Preparation of H[Me-NP] and H[iPr-NP]. The synthesis
of N-(2-diphenylphosphinophenyl)-2,6-diisopropylaniline (H-
[iPr-NP]) has been communicated lately.23 Following the
same synthetic protocol (Scheme 1), N-(2-diphenylphosphi-
nophenyl)-2,6-dimethylaniline (H[Me-NP]) is readily acces-
sible. The phosphine compounds and their fluorine precursors
were all characterized by multinuclear NMR spectroscopy
Syntheses and NMR Studies of Aluminum Derivatives.
Alkane elimination reactions of H[Me-NP] with trialkyl-
aluminum in toluene at 110 °C produced [Me-NP]AlR2 (R
) Me, Et) quantitatively (Scheme 2, eq 2). High yields of
(21) Coles, M. P.; Swenson, D. C.; Jordan, R. F.; Young, V. G.
Organometallics 1998, 17, 4042-4048.
(22) Examples of tridentate and tetradentate ligands are known; see refs
36 and 37, respectively.
(24) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics 1996,
15, 5085-5089.
(23) Liang, L.-C.; Lee, W.-Y.; Hung, C.-H. Inorg. Chem. 2003, 42, 5471-
(25) Liang, L.-C.; Lin, J.-M.; Hung, C.-H. Organometallics 2003, 22,
3007-3009.
5473.
Inorganic Chemistry, Vol. 43, No. 6, 2004 2167

Liang et al.
Scheme 2
Table 1. Crystallographic Data for H[Me-NP]
formula
fw
C52H48N2P2
762.86
crystal system
space group
a (Å)
monoclinic
P21/c
14.7253(9)
b (Å)
16.8991(11)
c (Å)
16.5500(11)
â (deg)
V (Å3)
Z
95.384(2)
4100.2(5)
4
D
calcd (g cm-3
)
1.236
2θmax (deg)
T (K)
55.08
293(2)
diffractometer
SMART CCD
radiation, λ (Å)
total reflections
Mo KR, 0.710 73
25 775
independent reflections
absorption coefficient (mm-1
data/restraints/parameters
Rint
9367
0.145
9367/0/517
0.0655
)
goodness of fit
0.724
final R indices [I > 2σ(I)]
R indices (all data)
R1 ) 0.0433, wR2 ) 0.0848
R1 ) 0.1206, wR2 ) 0.1200
Table 2. Selected NMR Spectroscopic Data for Four-Coordinate
Aluminum Complexesa
compound
δ
HR (3JPH
)
δ
CR (2JPC
)
δP (∆V1/2
)
δ
Al (∆V1/2
)
[Me-NP]AlCl2
[Me-NP]AlMe2 -0.24 (4)
[Me-NP]AlEt2
-36.1 (137) 94 (293)
-8.7 (22) -24.1 (6)
0.9 (18) -24.0 (4)
-0.30 (0), -0.39 (7) -2.2 (16) -24.2 (5)
158 (10 289)
158 (12 763)
159 (13 712)
0.43 (NA)b
[Me-NP]Al-
(CH2SiMe3)2
[iPr-NP]AlCl2
-34.4 (180) 99 (295)
[iPr-NP]AlMe2 -0.23 (4)
-9.1 (20) -21.6 (7)
0.2 (20) -21.4 (4)
151 (10 023)
152 (12 565)
[iPr-NP]AlEt2
0.48 (0), 0.37 (7)
a All spectra were recorded in C6D6 at room temperature, chemical shifts
are in ppm, coupling constants are in Hz, peak widths at half-height are in
Hz. b Not available.
by multinuclear NMR spectroscopy. Selected data are
summarized in Table 2.
Figure 1. Molecular structure of H[Me-NP] with thermal ellipsoids drawn
at the 35% probability level. The asymmetric unit cell contains two
independent molecules; only one is shown. Selected bond distances (Å)
and angles (deg): C(8)-N(1) 1.438(3), C(9)-N(1) 1.384(3), C(14)-P(1)
1.836(3), C(15)-P(1) 1.832(3), C(21)-P(1) 1.830(3), C(9)-N(1)-C(8)
122.9(2), C(21)-P(1)-C(15) 102.05(12), C(21)-P(1)-C(14) 101.33(11),
C(15)-P(1)-C(14) 103.50(12).
The 1H and 13C NMR spectra of the aluminum derivatives
are all consistent with a tetrahedral structure having a mirror-
plane symmetry passing through the aluminum center and
two donor atoms of the amido phosphine ligand. The
aluminum-bound alkyl groups are chemically equivalent in
all cases, as are the o-alkyl groups. The isopropylmethyl
groups in the [iPr-NP]- derivatives are diastereotopic, again
implying restricted N-Ar bond rotation in these molecules
due to significant steric demand.24 The CR atoms in all dialkyl
complexes appear as a doublet resonance in 13C{1H} NMR
spectroscopy, indicating coordination of the phosphorus
[iPr-NP]AlMe2 and [iPr-NP]AlEt2 were obtained in a similar
manner. Typically, evaporation of the reaction mixture
affords the desired products that can be readily recrystallized
from a concentrated THF/Et2O solution. Alternatively, the
aluminum derivatives are accessible by a metathetical method
(Scheme 2, eq 3). The reactions of AlCl3 with 1 equiv of
lithium amides (either generated in situ or isolated) in toluene
at -35 °C cleanly produced the dichloride compounds.
Subsequent alkylation of [Me-NP]AlCl2 with 2 equiv of
trimethylsilylmethyllithium in toluene at room temperature
generated [Me-NP]Al(CH2SiMe3)2 in 90% isolated yield,
whereas that of [iPr-NP]AlCl2 with trimethylsilylmethyl-
lithium (either 1 or 2 equiv) did not proceed at all under
similar conditions,26 suggesting significant steric repulsion
between [iPr-NP]- and trimethylsilylmethyl ligands. These
aluminum complexes are extremely sensitive to air and
moisture but are stable, even at elevated temperatures, under
an inert atmosphere for a prolonged period of time. The
solution structures of these compounds were all determined
1
donor. The H NMR spectra of [Me-NP]AlMe2 and [iPr-
NP]AlMe2 reveal a doublet resonance for the Al-Me groups
(Figure 2), whereas those of the others are indicative of
diastereotopic R-hydrogen atoms for the Al-CH2R frag-
ments. Chart 2 depicts possible Newman projections for the
dialkyl complexes in which the backbone and substituents
of the amido phosphine ligand are omitted for clarity. The
chemical nonequivalence of the HR atoms in Al-CH2R
(26) No reaction was found at room temperature for more than a week;
however, after 2 weeks at 110 °C, the reaction partially proceeded to
produce a mixture of products, presumably [iPr-NP]Al(CH2SiMe3)2
1
and [iPr-NP]Al(CH2SiMe3)Cl on the basis of H and 31P{1H} NMR
spectroscopy, regardless of the stoichiometry employed. The signals
similar to those found for the R-hydrogen atoms in [Me-NP]Al(CH2-
1
SiMe3)2 are observed at ca. -0.3 ppm in the H NMR spectroscopy.
2168 Inorganic Chemistry, Vol. 43, No. 6, 2004

Amido Phosphine Complexes of Aluminum
Figure 2. Multiplet resonance(s) observed for the HR atoms in (a) [Me-NP]AlMe2, (b) [Me-NP]AlEt2, (c) [Me-NP]Al(CH2SiMe3)2, (d) [iPr-NP]AlMe2, and
(e) [iPr-NP]AlEt2 recorded in C6D6 at room temperature.
Chart 2. Possible Newman Projections of a Dialkyl Complex (R ) H,
Me, SiMe3) along One of the Al-CR Bonds
phenomenon (vide infra). Though sterically demanding, the
phosphorus donor of [Me-NP]AlEt2, [Me-NP]Al(CH2-
SiMe3)2, and [iPr-NP]AlEt2 does not dissociate readily even
at high temperatures, as internuclear HR-P coupling is
observed for these molecules at temperatures as high as 100
°C (in toluene-d8).
It has been well documented that the coordination number
of neutral aluminum complexes correlates well with the
chemical shifts of 27Al NMR spectroscopy.29 The 27Al
chemical shifts of 151-159 ppm observed for the dialkyl
complexes and 94-99 ppm for the dichloride derivatives
are within the expected region for a four-coordinate alumi-
num species, indicating the coordination of both donor atoms
of the amido phosphine ligands. Similar chemical shifts are
found for four-coordinate Al2Me6 (156 ppm),30 AlEt3-
fragments is ascribable to the lack of symmetry of these
molecules with respect to internal rotation involving the
R-methylene groups.27 In the case of dimethyl complexes
(R ) H in Chart 2), the HR atoms are in principle chemically
nonequivalent as well, as no symmetry operation exchanges
these hydrogen atoms. Rapid rotation of the methyl groups
about the Al-C bonds should be responsible for the
observation of the doublet resonance. Notably, two well-
resolved resonances are observed for the diastereotopic HR
atoms in both [Me-NP]Al(CH2SiMe3)2 and [iPr-NP]AlEt2
with the more upfield one having more fine-coupling. The
steric demand of the amido phosphine ligands diminishes
i
(thiophene) (154 ppm),31 (iPr2-ATI)AlMe2 (154 ppm, Pr2-
ATI ) N,N′-diisopropylaminotroponiminate),7 Al2Cl6 (98
ppm),32 AlCl3(PMe3) (108 ppm),33 and (iPr2-ATI)AlCl2 (109
ppm).7 The 27Al resonances are all much broader for dialkyl
than for dichoride (Table 2), a phenomenon that has been
noted previously and ascribed to the differences in the ionic
character of Al-N versus Al-Cl or Al-C bonds.7 It is
interesting to note that all dialkyl complexes are not
associated with coordinating solvents such as THF and
diethyl ether, while the dichloride derivatives adopt THF
readily, providing five-coordinate THF adducts as suggested
by 27Al NMR spectroscopy29 (74 and 69 ppm for [Me-NP]-
AlCl2(THF) and [iPr-NP]AlCl2(THF), respectively) and X-ray
crystallography (vide infra). This result is in good agreement
with a more electrophilic aluminum center of the four-
coordinate dichloride complexes than that of their dialkyl
counterparts (electronegativity: Cl 3.16, C 2.55).34
An upfield change in the 31P chemical shift is observed
for both dichloride and dialkyl complexes as compared to
the corresponding ligand precursors. The phosphorus donor
of the dichloride complexes appears as a broad singlet
resonance (∆V1/2 ) 137-180 Hz), consistent with the fast
relaxation of quadrupolar aluminum atom (27Al, I ) 5/2,
100% natural abundance).29,35 Interestingly, the dialkyl
complexes exhibit a relatively sharp singlet resonance (∆V1/2
1
or precludes the population of rotamer II. The H-31P
correlation spectra of [Me-NP]Al(CH2SiMe3)2 and [iPr-NP]-
AlEt2 reveal that the phosphorus donor in these molecules
is coupled to only one of the diastereotopic R-hydrogen
atoms that is shifted more upfield (see Supporting Informa-
tion), thus eliminating the possibility of a structure similar
to rotamer III. A 1H NMR NOE experiment of [iPr-NP]AlEt2
revealed NOE contacts of the isopropylmethine groups with
both diastereotopic R-hydrogen atoms (+1.09% and +1.22%,
respectively), consistent with a structure similar to rotamer
I instead of II or III. An enhancement (+1.84%) was also
observed for [iPr-NP]AlEt2 between the o-hydrogen atoms
of the PPh2 moiety (7.39 ppm) and the R-hydrogen atom
that is not coupled to the phosphorus donor (0.48 ppm),
indicating this R-hydrogen’s proximity to the phosphorus
donor. Therefore, we conclude that the observed 3JPH in both
[Me-NP]Al(CH2SiMe3)2 and [iPr-NP]AlEt2 is the conse-
quence of pseudo-antiperiplanar orientation of the phosphorus
donor and HB rather than HA in rotamer I. A similar
phenomenon is also reported for the methylene hydrogen
atoms in methyl 2,3-dibromo-2-methylpropionate.28 In con-
trast, signals observed for the diastereotopic R-hydrogen
atoms in [Me-NP]AlEt2 are not resolved. The solid-state
structure of [Me-NP]AlEt2 was thus pursued to elucidate this
(29) Delpuech, J. J. NMR of Newly Accessible Nuclei; Laszlo, P., Ed.;
Academic Press: New York, 1983; Vol. 2, pp 153-195.
(30) O’Reilly, D. E. J. Chem. Phys. 1960, 32, 1007.
(31) Swift, H. E.; Poole, C. P.; Itzel, J. F. J. Phys. Chem. 1964, 68, 2509.
(32) Noth, H.; Rurlander, R.; Wolfgardt, P. Z. Naturforsch. 1982, 37B,
29.
(33) Vriezen, W. H. N.; Jellinek, F. Chem. Phys. Lett. 1967, 1, 284.
(34) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; p 93.
(27) Waugh, J. S.; Cotton, F. A. J. Phys. Chem. 1961, 65, 562-563.
(28) Tormena, C. F.; Freitas, M. P.; Rittner, R.; Abraham, R. J. Magn.
Reson. Chem. 2002, 40, 279-283.
(35) Akitt, J. W. Prog. NMR Spectrosc. 1989, 21, 1.
Inorganic Chemistry, Vol. 43, No. 6, 2004 2169

Liang et al.
Table 3. Crystallographic Data for [Me-NP]AlCl2(THF),
[Me-NP]AlEt2, and [iPr-NP]AlMe2
{[Me-NP]AlCl2-
(THF)}(THF)
[Me-NP]AlEt2
[iPr-NP]AlMe2
formula
fw
crystal system
space group
a (Å)
C34H39AlCl2NO2P C30H33AlNP
C32H37AlNP
493.611
triclinic
P1h
8.6900(4)
17.6389(9)
19.2049(11)
90.020(2)
90.014(3)
93.799(2)
2937.3(3)
4
622.51
465.557
monoclinic
P21/n
monoclinic
P21/c
9.355(2)
9.997(2)
34.033(7)
9.7187(5)
14.9887(10)
18.5256(11)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90.000(5)
96.725(4)
3182.9(12)
4
2680.1(3)
4
D
calcd (g cm-3
)
1.299
1.154
1.116
2θmax (deg)
T (K)
55.02
150(2)
49.70
298
50.18
298
diffractometer
radiation, λ (Å)
total reflections
independent
reflections
SMART CCD
Mo KR, 0.710 73 Mo KR, 0.710 73 Mo KR, 0.710 73
10 934
6147
Kappa CCD
Kappa CCD
17 196
4505
20 479
9250
Figure 3. Molecular structure of [Me-NP]AlCl2(THF) with thermal
ellipsoids drawn at the 35% probability level. The asymmetric unit cell
contains one unbound THF molecule, which is omitted for clarity. Selected
bond distances (Å) and angles (deg): Al(1)-N(1) 1.870(4), Al(1)-O(1)
1.981(3), Al(1)-Cl(2) 2.163(2), Al(1)-Cl(1) 2.172(2), Al(1)-P(1) 2.5882(19),
N(1)-Al(1)-O(1) 96.09(17), N(1)-Al(1)-Cl(2) 122.54(15), O(1)-Al(1)-
Cl(2) 90.11(12), N(1)-Al(1)-Cl(1) 118.92(15), O(1)-Al(1)-Cl(1) 91.95(12),
Cl(2)-Al(1)-Cl(1) 117.85(9), N(1)-Al(1)-P(1) 81.37(13), O(1)-Al(1)-
P(1) 177.42(13), Cl(2)-Al(1)-P(1) 91.67(7), Cl(1)-Al(1)-P(1) 88.87(7).
absorption
0.314
0.153
0.143
coefficient (mm-1
data/restraints/
parameters
)
6147/0/372
4505/0/298
9250/0/631
Rint
0.0701
0.998
R1 ) 0.0651
0.189
1.131
R1 ) 0.1294
0.138
0.966
R1 ) 0.0873
goodness of fit
final R indices
[I > 2σ(I)]
wR2 ) 0.1368
R1 ) 0.1304
wR2 ) 0.1682
wR2 ) 0.2825
R1 ) 0.3227
wR2 ) 0.3950
wR2 ) 0.1895
R1 ) 0.2484
wR2 ) 0.2729
phino)methyl)phenyl]aluminum (2.729 Å average).38 The
Al-O and Al-Cl distances in [Me-NP]AlCl2(THF) are
almost identical to those found in trans-AlCl3(THF)2,42 while
the Cl-Al-Cl angle is slightly smaller for the former by
3.15° than the latter. The N(1)-Al(1)-P(1) binding angle
of 81.37(13)° is smaller than those found in the closely
related, five-coordinate AlCl2[N(SiMe2CH2PiPr2)2] (86.0°
average).36 The aluminum atom is deviated from the N-phen-
ylene-P plane by 0.3934 Å. As expected, the dimethylphenyl
ring is roughly perpendicular to the N-Al-P plane (dihedral
angle 91.4°).
Solid-State Structures of [Me-NP]AlEt2 and [iPr-NP]-
AlMe2. Single crystals of [Me-NP]AlEt2 and [iPr-NP]AlMe2
suitable for X-ray diffraction studies were grown from
concentrated diethyl ether solutions at -35 °C. Figures 4
and 5 depict the ORTEP diagrams of [Me-NP]AlEt2 and
[iPr-NP]AlMe2, respectively. Crystallographic details are
summarized in Table 3. Consistent with the NMR spectro-
scopic data, both [Me-NP]AlEt2 and [iPr-NP]AlMe2 exist as
monomeric, four-coordinate species with the aluminum atom
being surrounded by two alkyl groups and the nitrogen and
phosphorus donors of the amido phosphine ligand. The Al-
N, Al-P, and Al-C distances are all typical for a tetrahedral
complex of aluminum.3,36,43 The aluminum atom in [Me-NP]-
AlEt2 lies virtually on the N-phenylene-P plane, whereas
that of [iPr-NP]AlMe2 is markedly deviated from the plane
by 0.6969 Å (average for the two independent molecules
found in the asymmetric unit cell). This observation high-
lights the significant steric crowding imposed by the [iPr-
NP]- ligand. A similar result is also observed for the four-
R indices (all data)
) 4-7 Hz) for the phosphorus donor. Similar observations
on the chemical shift change and the distinct peak widths at
half-height for the dichloride and dialkyl derivatives have
also been reported for other phosphine coordinated aluminum
complexes.36-38
Solid-State Structure of [Me-NP]AlCl2(THF). Colorless
crystals suitable for X-ray crystallography were grown from
a concentrated THF solution at -35 °C. Crystallographic
details are summarized in Table 3. As illustrated in Figure
3, this compound is a five-coordinate species, consistent with
27Al NMR spectroscopy. The coordination geometry is best
described as trigonal bipyramidal with the phosphorus donor
and the THF molecule occupying axial positions (O(1)-Al-
(1)-P(1) ) 177.42(13)°). The aluminum center lies on the
equatorial plane as indicated by the sum of the three
equatorial angles of 359.31°. The Al(1)-N(1) distance of
1.870(4) Å is comparable to those of aluminum diarylamide
complexes such as (t-Bu)2Al[N(2,4,6-C6H3Me3)2] (1.823(4)
Å)39 and [Li(THF)4][HAl(NPh2)3] (1.870 Å average).40 The
Al(1)-P(1) distance of 2.5882(19) Å is within the expected
values for five-coordinate aluminum phosphine complexes
such as trans-AlI3(PEt3)2 (2.524 Å average),41 AlCl2[N(SiMe2-
CH2PiPr2)2] (2.5255 Å average),36 and tris[o-((diphenylphos-
(36) Fryzuk, M. D.; Giesbrecht, G. R.; Olovsson, G.; Rettig, S. J.
Organometallics 1996, 15, 4832-4841.
(37) Fryzuk, M. D.; Giesbrecht, G. R.; Rettig, S. J. Inorg. Chem. 1998,
37, 6928-6934.
(38) Muller, G.; Lachmann, J.; Rufinska, A. Organometallics 1992, 11,
2970-2972.
(39) Petrie, M. A.; Ruhlandtsenge, K.; Power, P. P. Inorg. Chem. 1993,
32, 1135-1141.
(42) Cowley, A. H.; Cushner, M. C.; Davis, R. E.; Riley, P. E. Inorg. Chem.
1981, 20, 1179.
(40) Pauls, J.; Neumuller, B. Inorg. Chem. 2001, 40, 121.
(41) Ecker, A.; Schnockel, H. Z. Anorg. Allg. Chem. 1998, 624, 813.
(43) Dias, H. V. R.; Jin, W.; Ratcliff, R. E. Inorg. Chem. 1995, 34, 6100-
6105.
2170 Inorganic Chemistry, Vol. 43, No. 6, 2004

Amido Phosphine Complexes of Aluminum
Figure 6. Two views of the molecular structure of [Me-NP]AlEt2 along
the Al-C(4) (left view) and Al-C(2) (right view) bonds.
Figure 4. Molecular structure of [Me-NP]AlEt2 with thermal ellipsoids
drawn at the 35% probability level. Selected bond distances (Å) and angles
(deg): P(1)-Al(1) 2.456(4), Al(1)-N(1) 1.894(8), Al(1)-C(4) 1.973(12),
Al(1)-C(2) 1.993(13), N(1)-Al(1)-C(4) 111.7(5), N(1)-Al(1)-C(2)
119.2(5), C(4)-Al(1)-C(2) 118.1(5), N(1)-Al(1)-P(1) 84.2(3), C(4)-
Al(1)-P(1) 118.4(4), C(2)-Al(1)-P(1) 100.0(4).
Figure 6 depicts two views of molecular structure of [Me-
NP]AlEt2 along the Al-C bonds. The left view is a
reminiscent of the rotamer I in Chart 2, featuring one of the
two diastereotopic R-hydrogen atoms on C(4) being nearly
antiperiplanar with respect to the phosphorus donor. The right
view, however, corresponds to a mirror image of the rotamer
III, in which internuclear coupling between the phosphorus
donor and the two diastereotopic hydrogen atoms at C(2)
becomes possible. This result is consistent with the relatively
small sizes of the ligands in [Me-NP]AlEt2 as compared to
those in [Me-NP]Al(CH2SiMe3)2 and [iPr-NP]AlEt2, thus
exhibiting the unresolved multiplet resonances for the
diastereotopic R-hydrogen atoms of the former in 1H NMR
spectroscopy.
Conclusions
We have prepared and characterized a series of aluminum
dichloride and dialkyl complexes supported by o-phenylene-
derived amido phosphine ligands. Solution NMR and X-ray
crystallographic studies reveal monomeric, four-coordinate
species for these molecules. Five-coordinate dichloride
complexes as a THF adduct may also be obtained. Hetero-
nuclear COSY and NOE experiments elucidate the confor-
mation of the R-methylene moieties in [Me-NP]Al(CH2-
SiMe3)2 and [iPr-NP]AlEt2. Conformations other than that
found in [Me-NP]Al(CH2SiMe3)2 and [iPr-NP]AlEt2 are
accessible with sterically less demanding amido phosphine
and/or alkyl ligands. Studies involving the reactivity chem-
istry of these new molecules will be the subjects of further
reports.
Figure 5. Molecular structure of [iPr-NP]AlMe2 with thermal ellipsoids
drawn at the 35% probability level. The asymmetric unit cell contains two
independent molecules; only one is shown. Selected bond distances (Å)
and angles (deg): P(1)-Al(1) 2.477(3), Al(1)-N(1) 1.894(6), Al(1)-C(31)
1.944(8), Al(1)-C(32) 1.965(9), N(1)-Al(1)-C(31) 114.5(4), N(1)-
Al(1)-C(32) 119.0(3), C(31)-Al(1)-C(32) 116.6(4), N(1)-Al(1)-P(1)
82.1(2), C(31)-Al(1)-P(1) 113.2(3), C(32)-Al(1)-P(1) 105.6(3).
coordinate [iPr-NP]2Zn, where the zinc atom is displaced by
0.6851 Å (average).23 The binding angles of the amido
phosphine ligands are 84.2(3)° and 82.1(2)° for [Me-NP]-
AlEt2 and [iPr-NP]AlMe2, respectively. These angles are
comparable to those of the four-coordinate complexes that
feature five-membered metallacycles such as [iPr-NP]2Zn
(83.695° average)23 and (iPr2-ATI)AlMe2 (83.3(1)°),43 but are
significantly more acute than the ideal tetrahedral angle of
109.47°. As a result, the C-Al-C angles of 118.1(5)° and
116.6(4)° in [Me-NP]AlEt2 and [iPr-NP]AlMe2, respectively,
are notably wider. In both molecules, the dialkylphenyl ring
is approximately perpendicular to the o-phenylene backbone.
In contrast to that found in H[Me-NP], the phosphorus atom
in both [Me-NP]AlEt2 and [iPr-NP]AlMe2 adopts a distorted
tetrahedral geometry where the two phenyl substituents are
roughly displaced evenly with respect to the phenylene
backbone.
Experimental Section
General Procedures. Unless otherwise specified, all experiments
were performed under nitrogen using standard Schlenk or glovebox
techniques. All solvents were reagent grade or better and purified
by standard methods. The NMR spectra were recorded on Varian
instruments. Chemical shifts (δ) are listed as parts per million
downfield from tetramethylsilane, and coupling constants (J) and
1
peak widths at half-height (∆V1/2) are in hertz. H NMR spectra
are referenced using the residual solvent peak at δ 7.16 for C6D6,
δ 7.27 for CDCl3, and δ 2.09 for toluene-d8 (the most upfield
resonance). 13C NMR spectra are referenced using the residual
solvent peak at δ 128.39 for C6D6 and δ 77.23 for CDCl3. The
Inorganic Chemistry, Vol. 43, No. 6, 2004 2171

Liang et al.
assignment of the carbon atoms for all new compounds is based
on DEPT 13C NMR spectroscopy. 19F, 31P, and 27Al NMR spectra
are referenced externally using CFCl3 in CHCl3 at δ 0, 85% H3-
PO4 at δ 0, and AlCl3 in D2O at δ 0, respectively. Routine coupling
constants are not listed. All NMR spectra were recorded at room
temperature in specified solvents unless otherwise noted. The 1H-
31P correlation experiments were carried out on a Varian Inova 500
MHz instrument using HMBC sequence. The NOE data were
obtained with a 1H NMR NOEDIF experimental apparatus.
Elemental analysis was performed on a Heraeus CHN-O Rapid
analyzer. For some aluminum complexes, we were not able to obtain
satisfactory analysis due to extreme air and moisture sensitivity of
these compounds.
condenser was flashed with nitrogen thoroughly. To this flask was
added KPPh2 (110 mL, 0.5 M in THF solution, Aldrich, 55.0 mmol).
THF was removed in vacuo, and a solution of N-(2-fluorophenyl)-
2,6-dimethylaniline (10.6 g, 49.26 mmol) in DME (50 mL) was
added with a syringe. The transparent, ruby reaction solution was
heated to reflux for 2 days, during which time the reaction condition
was monitored by 31P{1H} NMR spectroscopy. All volatiles were
removed from the resulting orange solution under reduced pressure,
and degassed deionized water (140 mL) was added. The product
was extracted with deoxygenated dichloromethane (100 mL). The
dichloromethane solution was separated from the aqueous layer,
from which the product was further extracted with dichloromethane
(20 mL × 2). The combined organic solution was dried over MgSO4
and filtered. All volatiles were removed in vacuo to yield a yellow
solid. The yellow solid was purified by washing it with boiling
MeOH (40 mL × 3) until it became a white powder; yield 15.98
g (85%). 1H NMR (CDCl3, 200 MHz) δ 7.41-7.60 (m, 10, PC6H5),
7.07-7.14 (m, 4, Ar), 6.89 (t, 1, Ar), 6.71 (t, 1, Ar), 6.20 (m, 1,
Ar), 5.90 (d, 1, NH), 2.03 (s, 6, CH3). 1H NMR (C6D6, 500 MHz)
δ 7.47 (m, 4, Ar), 7.11 (td, 1, Ar), 7.06 (m, 6, Ar), 6.94 (m, 4, Ar),
6.61 (t, 1, Ar), 6.31 (m, 1, Ar), 6.04 (d, 1, JHP ) 7, NH), 1.98 (s,
6, CH3). 31P{1H} NMR (C6D6, 202 MHz) δ -19.3. 31P{1H} NMR
(Et2O, 121.5 MHz) δ -18.9. 31P{1H} NMR (CDCl3, 121.5 MHz)
δ -19.1. 13C{1H} NMR (CDCl3, 75.3 MHz) δ 148.6 (JCP ) 17.0),
138.2, 135.8, 135.2, 135.1, 134.1, 133.8, 130.3, 128.8 (JCP ) 18.8),
128.5 (JCP ) 13.5), 125.6, 119.9 (JCP ) 9.1), 118.2, 111.8, 18.2
(CH3). Anal. Calcd for C26H24NP: C, 81.87; H, 6.34; N, 3.67.
Found: C, 81.45; H, 6.42; N, 3.61.
Materials. Compounds N-(2-fluorophenyl)-2,6-diisopropyla-
niline, N-(2-diphenylphosphinophenyl)-2,6-diisopropylaniline (H[iPr-
NP]), and [iPr-NP]Li(THF)2 were prepared according to the
procedures reported previously.23 All other chemicals were obtained
from commercial vendors and used as received.
X-ray Crystallography. Tables 1 and 3 summarize the crystal-
lographic data for all structurally characterized compounds. Data
for compounds H[Me-NP] and [Me-NP]AlCl2(THF) were collected
on a Bruker SMART 1000 CCD diffractometer with graphite
monochromated Mo KR radiation (λ ) 0.7107 Å). Structures were
solved by direct methods and refined by full-matrix least-squares
procedures against F2 using SHELXTL. All full-weight non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
placed in calculated positions. Data for compounds [Me-NP]AlEt2
and [iPr-NP]AlMe2 were collected on a Bruker-Nonius Kappa CCD
diffractometer with graphite monochromated Mo KR radiation (λ
) 0.7107 Å). Structures were solved by direct methods and refined
by full-matrix least-squares procedures against F2 using maXus.
All full-weight non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were placed in calculated positions. The crystals
of [Me-NP]AlEt2 were of poor quality but sufficient to establish
the identity of this molecule. The data set contains too many weak
reflections, resulting in relatively high R-values.
General Procedures for the Synthesis of [Me-NP]AlR2 and
[iPr-NP]AlR2 (R ) Me, Et). A Teflon-sealed reaction vessel was
charged with a toluene solution containing an appropriate ligand
precursor and 1 equiv of AlMe3 (Aldrich, 2.0 M in toluene) or
AlEt3 (TCI, 15% in toluene). The colorless solution was heated to
110 °C for 2 days. Evaporation of the resulting yellow solution to
dryness under reduced pressure afforded the product as pale-yellow
microcrystals, which were recrystallized from 1:1 THF/Et2O to give
pale-yellow crystals.
Synthesis of N-(2-Fluorophenyl)-2,6-dimethylaniline. A 100-
mL Schlenk flask was charged with 1-bromo-2-fluorobenzene
(15.584 g, 89.05 mmol), 2,6-dimethylaniline (13.034 g, 107.56
mmol, 1.2 equiv), Pd(OAc)2 (0.100 g, 0.445 mmol, 0.5% equiv),
bis[2-(diphenylphosphino)phenyl] ether (DPEphos, 0.36 g, 0.668
mmol, 0.75% equiv), NaOtBu (12.0 g, 125 mmol, 1.4 equiv), and
toluene (30 mL) under nitrogen. The reaction mixture was heated
to reflux for 1 day. Toluene was removed in vacuo, and the reaction
was quenched with deionized water (150 mL). The product was
extracted with CH2Cl2 (200 mL), and the organic portion was
separated from the aqueous layer, which was further extracted with
CH2Cl2 (15 mL × 2). The combined organic solution was dried
over MgSO4 and filtered. All volatiles were removed in vacuo to
yield orange viscous oil, which was subjected to flash column
chromatography on silica gel (9:1 hexanes/Et2O). The first band
(pale yellow) was collected. Solvents were removed in vacuo to
give a yellowish orange solid; yield 12.23 g (64%). 1H NMR
(CDCl3, 200 MHz) δ 7.07-7.13 (m, 4, Ar), 6.87 (t, 1, Ar), 6.65
Synthesis of [Me-NP]AlMe2. Yield 93%. 1H NMR (C6D6, 500
MHz) δ 7.40 (m, 4, Ar), 6.97-7.20 (m, 11, Ar), 6.42 (t, 1, Ar),
3
6.23 (t, 1, Ar), 2.22 (s, 6, C6H3Me2), -0.24 (d, 6, AlCH3, JHP
)
4). 13C{1H} NMR (C6D6, 125.70 MHz) δ 160.8 (d, JCP ) 20.1, C),
144.5 (d, JCP ) 4.5, C), 137.5 (C), 135.2 (CH), 134.9 (CH), 134.0
(d, JCP ) 12.8, CH), 131.1 (d, JCP ) 1.8, CH), 129.7 (CH), 129.6
(d, JCP ) 9.9, CH), 125.7 (CH), 116.1 (d, JCP ) 5.5, CH), 114.7
(d, JCP ) 6.4, CH), 110.9 (C), 110.6 (C), 19.3 (ArCH3), -8.7 (d,
2JCP ) 22, AlCH3). 31P{1H} NMR (C6D6, 202.31 MHz) δ -24.1
(∆V1/2 ) 6 Hz). 27Al NMR (C6D6, 130.22 MHz) δ 158 (∆V1/2
)
10 289 Hz). LRMS (EI) Calcd for C28H29AlNP m/z 437, found m/z
437. Anal. Calcd for C28H29AlNP: C, 76.87; H, 6.68; N, 3.20.
Found: C, 73.95; H, 6.53; N, 3.22.
1
Synthesis of [iPr-NP]AlMe2. Yield 96%. H NMR (C6D6, 500
MHz) δ 7.38 (m, 4, Ar), 7.22 (m, 3, Ar), 7.01 (m, 7, Ar), 6.90 (t,
1, Ar), 6.40 (t, 1, Ar), 6.23 (t, 1, Ar), 3.35 (septet, 2, CHMe2),
3
1.12 (d, 6, CHMe2), 1.04 (d, 6,CHMe2), -0.23 (d, 6, AlCH3, JHP
(m, 1, Ar), 6.22 (t, 1, Ar), 5.35 (br s, 1, NH), 2.22 (s, 6, CH3). 19
F
) 4). 13C{1H} NMR (C6D6, 125.70 MHz) δ 162.2 (d, JCP ) 19.1,
C), 148.0 (C), 141.9 (d, JCP ) 4.5, C), 134.8 (CH), 134.7 (CH),
134.1 (CH), 131.1 (d, JCP ) 1.8, CH), 129.5 (d, JCP ) 10.0, CH),
NMR (CDCl3, 470.5 MHz) δ -138.42. 13C NMR (CDCl3, 125.5
MHz) δ 151.5 (JCF ) 237.4, CF), 137.2, 136.3, 134.7 (JCF ) 10.9,
FCCN), 128.6 (CH), 126.3 (CH), 124.4 (JCF ) 2.8, CH), 117.4
(JCF ) 7.3, CH), 114.7 (JCF ) 18.1, CH), 113.1 (JCF ) 3.6, CH),
18.2 (CH3). Anal. Calcd for C14H14FN: C, 78.11; H, 6.56; N, 6.51.
Found: C, 77.88; H, 6.61; N, 6.48.
12.7 (CH), 125.0 (CH), 117.1 (d, JCP ) 6.4, CH), 116.6 (d, JCP
)
6.4, CH), 112.0 (C), 111.6 (C), 28.4 (CHMe2), 25.6 (CHMe2), 25.2
(CHMe2), -9.1 (d, 2JCP ) 20, AlCH3). 31P{1H} NMR (C6D6, 202.31
MHz) δ -21.6 (∆V1/2 ) 7 Hz). 27Al NMR (C6D6, 130.22 MHz) δ
151 (∆V1/2 ) 10 023 Hz). Anal. Calcd for C32H37AlNP: C, 77.87;
H, 7.56; N, 2.84. Found: C, 77.19; H, 7.53; N, 2.88.
Synthesis of N-(2-Diphenylphosphinophenyl)-2,6-dimethyl-
aniline, H[Me-NP]. A 100-mL Schlenk flask equipped with a
2172 Inorganic Chemistry, Vol. 43, No. 6, 2004

Amido Phosphine Complexes of Aluminum
1
Synthesis of [Me-NP]AlEt2. Yield 98%. H NMR (C6D6, 500
MHz) δ 7.46 (m, 4, Ar), 7.10 (m, 2, Ar), 7.06 (m, 1, Ar), 6.97-
7.04 (m, 7, Ar), 6.94 (m, 1, Ar), 6.42 (t, 1, Ar), 6.23 (t, 1, Ar),
2.23 (s, 6, C6H3Me2), 1.20 (t, 6, AlCH2CH3), 0.43 (m, 4, AlCH2).
1H NMR (C7D8, 500 MHz) δ 7.35 (m, 4, Ar), 6.91 (m, 10, Ar),
6.80 (t, 1, Ar), 6.30 (t, 1, Ar), 6.07 (t, 1, Ar), 2.09 (s, 6, C6H3Me2),
1.05 (t, 6, AlCH2CH3), 0.28 (m, 4, AlCH2). 13C{1H} NMR (C6D6,
125.70 MHz) δ 161.1 (d, JCP ) 20.8, C), 144.8 (d, JCP ) 4.5, C),
137.3 (C), 135.1 (CH), 134.8 (CH), 133.9 (d, JCP ) 12.7, CH),
131.1 (d, JCP ) 2.8, CH), 129.6 (CH), 129.5 (CH), 126.7 (CH),
116.2 (d, JCP ) 6.4, CH), 114.8 (d, JCP ) 6.4, CH), 110.7 (C),
AlCl2(THF) as colorless crystals suitable for X-ray crystallography.
The recrystallization yield is typically 70%. H NMR (C6D6, 500
MHz) δ 7.76 (m, 4, Ar), 7.14 (m, 1, Ar), 7.04 (m, 6, Ar), 6.97 (m,
2, Ar), 6.92 (m, 2, Ar), 6.50 (t, 1, Ar), 6.18 (t, 1, Ar), 3.58 (m, 4,
OCH2CH2), 2.30 (s, 6, CH3), 1.12 (m, 4, OCH2CH2). 13C{1H} NMR
1
(C6D6, 125.5 MHz) δ 159.2 (d, JCP ) 20.3, C), 146.2 (d, JCP
)
6.4, C), 138.5 (C), 135.9 (CH), 134.6 (d, JCP ) 11.3, CH), 134.1
(CH), 130.8 (C), 130.5 (CH), 129.5 (CH), 129.1 (d, JCP ) 9.5,
CH), 126.0 (CH), 118.0 (d, JCP ) 5.0, CH), 115.1 (d, JCP ) 5.9,
CH), 113.3 (d, JCP ) 35.3, C), 71.1 (OCH2CH2), 25.3 (OCH2CH2),
19.3 (Me). 31P{1H} NMR (C6D6, 121.5 MHz) δ -34.8 (∆V1/2
)
3
110.4 (C), 19.2 (ArCH3), 9.8 (d, JCP ) 1.9, AlCH2CH3), 0.9 (d,
54 Hz). 27Al NMR (C6D6, 130.22 MHz) δ 74 (∆V1/2 ) 351 Hz).
2JCP ) 18, AlCH2). 31P{1H} NMR (C6D6, 202.31 MHz) δ -24.0
Synthesis of [iPr-NP]AlCl2. Solid AlCl3 (250 mg, 1.8749 mmol)
was added in portions to a solution of [iPr-NP]Li(THF)2 (1.0658
g, 1.8157 mmol) in toluene (15 mL) at -35 °C. The reaction
mixture was stirred at room temperature for 4 days and filtered
through a pad of Celite. Concentration of the filtrate under reduced
pressure afforded [iPr-NP]AlCl2 as colorless crystals which were
isolated by filtration and dried in vacuo; yield 951 mg (98.1%). 1H
NMR (C6D6, 500 MHz) δ 7.38 (m, 4, Ar), 7.13 (m, 3, Ar), 6.95
(m, 2, Ar), 6.89 (m, 4, Ar), 6.79 (m, 2, Ar), 6.34 (t, 1, Ar), 6.22 (t,
1, Ar), 3.38 (septet, 2, CHMe2), 1.18 (d, 6, CHMe2), 0.95 (d, 6,
(∆V1/2 ) 4 Hz). 27Al NMR (C6D6, 130.22 MHz) δ 158 (∆V1/2
)
12 763 Hz).
1
Synthesis of [iPr-NP]AlEt2. Yield 92%. H NMR (C6D6, 500
MHz) δ 7.39 (m, 4, Ar), 7.16 (m, 3, Ar), 6.95-7.00 (m, 7, Ar),
6.84 (m, 1, Ar), 6.36 (t, 1, Ar), 6.18 (t, 1, Ar), 3.28 (septet, 2,
CHMe2), 1.18 (t, 6, AlCH2CH3), 1.10 (d, 6, CHMe2), 0.98 (d, 6,
CHMe2), 0.48 (m, 2, AlCHAHB, 2JHH ) 15), 0.37 (m, 2, AlCHAHB,
3JHP ) 7, JHH ) 15). H NMR (C7D8, 500 MHz) δ 7.44 (m, 4,
Ar), 7.21 (m, 3, Ar), 7.02 (m, 7, Ar), 6.89 (t, 1, Ar), 6.41 (t, 1, Ar),
6.24 (t, 1, Ar), 3.32 (septet, 2, CHMe2), 1.22(t, 6, AlCH2CH3), 1.15
(d, 6, CHMe2), 1.03 (d, 6, CHMe2), 0.53 (m, 2, AlCHAHB), 0.42
(m, 2, AlCHAHB). 13C{1H} NMR (C6D6, 125.70 MHz) δ 162.5 (d,
JCP ) 20.0, C), 147.7 (C), 142.4 (d, JCP ) 4.5, C), 134.7 (CH),
2
1
CHMe2). 13C{1H} NMR (C6D6, 125.70 MHz) δ 160.5 (d, JCP
)
14.6, C), 148.2 (C), 139.0 (d, JCP ) 3.6, C), 135.1 (CH), 134.5
(CH), 134.5 (CH), 132.2 (d, JCP ) 2.8, CH), 129.8 (d, JCP ) 10.8,
CH), 127.7 (CH), 125.3 (CH), 124.4 (d, JCP ) 51.8, C), 118.7 (d,
JCP ) 6.3, CH), 117.6 (d, JCP ) 5.4, CH), 109.9 (d, JCP ) 51.0,
C), 28.7 (CHMe2), 25.5 (CHMe2), 25.3 (CHMe2). 31P{1H} NMR
(C6D6, 202.31 MHz) δ -34.4 (∆V1/2 ) 180 Hz). 27Al NMR (C6D6,
130.22 MHz) δ 99 (∆V1/2 ) 295 Hz). Recrystallization of [iPr-NP]-
AlCl2 from THF at -35 °C afforded [iPr-NP]AlCl2(THF) as
134.7 (CH), 134.0 (CH), 131.1 (d, JCP ) 1.8, CH), 129.5 (d, JCP
10.0, CH), 129.5 (CH), 126.6 (CH), 125.0 (CH), 117.3 (d, JCP
5.4, CH), 116.6 (d, JCP ) 5.4, CH), 111.8 (C), 111.5 (C), 28.4
)
)
3
(CHMe2), 25.8 (CHMe2), 24.9 (CHMe2), 9.8 (d, JCP ) 1.8,
AlCH2CH3), 0.2 (d, JCP ) 20, AlCH2). 31P{1H} NMR (C6D6,
2
202.31 MHz) δ -21.4 (∆V1/2 ) 4 Hz). 27Al NMR (C6D6, 130.22
colorless crystals. H NMR (C6D6, 500 MHz) δ 7.55 (m, 4, Ar),
1
2
MHz) δ 151.8 (∆V1/2 ) 12 565 Hz). The coupling constants JHH
7.16 (m, 5, Ar), 7.02 (m, 5, Ar), 6.93 (t, 1, Ar), 6.42 (t, 1, Ar),
6.19 (t, 1, Ar), 3.88 (m, 4, OCH2CH2) 3.44 (septet, 2, CHMe2),
1.19 (m, 4, OCH2CH2), 1.14 (d, 6, CHMe2), 0.97 (d, 6, CHMe2).
13C{1H} NMR (C6D6, 125.70 MHz) δ 159.8 (d, JCP ) 17.2, C),
147.8 (C), 140.2 (d, JCP ) 4.5, C), 134.2 (CH), 134.0 (CH), 133.9
(CH), 130.8 (d, JCP ) 2.6, CH), 128.8 (d, JCP ) 10.0, CH), 126.8
(CH), 124.6 (CH), 117.8 (d, JCP ) 6.4, CH), 117.0 (d, JCP ) 5.5,
CH), 110.9 (C), 110.5 (C), 71.1 (OCH2CH2), 27.9 (CHMe2), 25.1
(CHMe2), 24.8 (OCH2CH2), 24.2 (CHMe2). 31P{1H} NMR (C6D6,
202.31 MHz) δ -33.7 (∆V1/2 ) 85 Hz). 27Al NMR (C6D6, 130.22
MHz) δ 69 (∆V1/2 ) 387 Hz). Anal. Calcd for C30H31AlCl2NP: C,
67.42; H, 5.85; N, 2.62. Found: C, 66.99; H, 7.07; N, 2.47.
and 3JHP were determined by 1H NMR spectroscopy with selective
decoupling of â-hydrogen atoms. LRMS (EI) Calcd for C34H41-
AlNP m/z 521, found m/z 521.
Synthesis of [Me-NP]AlCl2. To a solution of H[Me-NP] (2.0
g, 5.24 mmol) in THF (15 mL) at -35 °C was added n-BuLi (3.3
mL, 5.24 mmol, 1 equiv). The reaction mixture was naturally
warmed to room temperature and stirred for 3 h. All volatiles were
removed in vacuo. The red viscous residue was triturated with
pentane (15 mL) to yield a yellow solid. The yellow solid was
isolated from the orange solution, washed with pentane (5 mL ×
3), and dried in vacuo to give [Me-NP]Li(THF)2 as indicated by
1
1H NMR spectroscopy; yield 2.67 g (99%). H NMR (C6D6, 500
Synthesis of [Me-NP]Al(CH2SiMe3)2. A pentane solution of
LiCH2SiMe3 (1.1 mL, 1 M in pentane, Aldrich, 1.10 mmol, 2 equiv)
was added dropwise to a solution of [Me-NP]AlCl2 (300 mg, 0.55
mmol) in toluene (10 mL) at -35 °C. The reaction mixture was
stirred at room temperature for 2 days. The insoluble materials thus
produced were removed by filtration with a short column of Celite.
Solvent was stripped and the product was obtained as a pale yellow
solid; yield 286 mg (90%). Recrystallization from diethyl ether
afforded colorless crystals. 1H NMR (C6D6, 500 MHz) δ 7.46 (m,
4, Ar), 7.09 (m, 2, Ar), 7.02 (m, 8, Ar), 6.94 (m, 1, Ar), 6.43 (t, 1,
Ar), 6.18 (t, 1, Ar), 2.21 (s, 6, C6H3Me2), 0.028 (s, 18, SiMe3),
-0.30 (d, 2, AlCHAHB, 2JHH ) 13), -0.39 (dd, 2, AlCHAHB, 3JHP
MHz) δ 7.58 (m, 4, Ar), 7.23 (d, 2, Ar), 7.07-7.16 (m, 8, Ar),
6.97 (m, 1, Ar), 6.38 (m, 1, Ar), 6.33 (m, 1, Ar), 3.23 (m, 8, OCH2-
CH2), 2.26 (s, 6, CH3), 1.19 (m, 8, OCH2CH2). Solid AlCl3 (2.600
g, 1.950 mmol) was added in portions to a solution of [Me-NP]-
Li(THF)2 (1.00 g, 1.881 mmol) in toluene (15 mL) at -35 °C. The
reaction mixture was stirred at room temperature for 4 days and
filtered through a pad of Celite. Solvent was stripped from the
filtrate to afford an off-white solid; yield 905 mg (100%). 1H NMR
(C6D6, 500 MHz) δ 7.53 (m, 4, Ar), 6.94-7.04 (m, 10, Ar), 6.89
(t, 1, Ar), 6.44 (t, 1, Ar), 6.22 (t, 1, Ar), 2.32 (s, 6, CH3). 13C{1H}
NMR (C6D6, 125.5 MHz) δ 159.2 (d, JCP ) 16.4, C), 143.0 (d, JCP
) 5.4, C), 138.0 (C), 135.2 (CH), 134.4 (CH), 134.4 (CH), 131.7
(d, JCP ) 2.8, CH), 129.8 (CH), 129.7 (d, JCP ) 3.6, CH), 126.6
(CH), 126.2 (C), 118.2 (d, JCP ) 6.3, CH), 115.2 (d, JCP ) 5.4,
CH), 110.4 (d, JCP ) 46.3, C), 19.4 (Me). 31P{1H} NMR (C6D6,
121.5 MHz) δ -36.1 (∆V1/2 ) 137 Hz). 27Al NMR (C6D6, 130.22
MHz) δ 94 (∆V1/2 ) 293 Hz). Recrystallization of [Me-NP]AlCl2
from THF at -35 °C produced the solvated compound [Me-NP]-
2
) 7, JHH ) 13). 13C{1H} NMR (C6D6, 125.70 MHz) δ 161.5 (d,
JCP ) 20.0, C), 145.0 (d, JCP ) 5.5, C), 137.8 (C), 135.5 (CH),
134.9 (CH), 133.9 (d, JCP ) 11.8, CH), 131.2 (d, JCP ) 1.9, CH),
129.9 (CH), 129.6 (d, JCP ) 10.0, CH), 126.0 (CH), 116.3 (d, JCP
) 5.4, CH), 115.0 (d, JCP ) 6.4, CH), 111.1 (C), 110.7 (C), 19.7
2
(ArCH3), 3.4 (SiMe), -2.2 (d, JCP ) 16, AlCH2). 31P{1H} NMR
(C6D6, 202.31 MHz) δ -24.2 (∆V1/2 ) 5 Hz). 27Al NMR (C6D6,
Inorganic Chemistry, Vol. 43, No. 6, 2004 2173

Liang et al.
crystallographic assistance on [Me-NP]AlEt2 and [iPr-NP]-
AlMe2.
130.22 MHz) δ 159 (∆V1/2 ) 13 712 Hz). Anal. Calcd for C34H45-
AlNPSi2: C, 70.18; H, 7.80; N, 2.41. Found: C, 67.64; H, 6.99;
N, 2.59.
Supporting Information Available: 1H-31P correlation spectra
of [iPr-NP]AlEt2 and [Me-NP]Al(CH2SiMe3)2, and X-ray crystal-
lographic data in CIF format for H[Me-NP], [Me-NP]AlCl2(THF),
[Me-NP]AlEt2, and [iPr-NP]AlMe2. This material is available free
of charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank the National Science Coun-
cil (NSC 92-2113-M-110-015) of Taiwan for financial
support of this work, Mr. Wei-Ying Lee for preparation of
H[iPr-NP], Ms. Chao-Lien Ho for technical assistance with
NMR experiments, and Mr. Ting-Shen Kuo at the Instru-
mentation Center of National Taiwan Normal University for
IC035373Q
2174 Inorganic Chemistry, Vol. 43, No. 6, 2004