Synthesis and Structural Characterization of Neutral and Cationic Alkylaluminum Complexes Based on Bidentate Aminophenolate Ligands

Article abstract of DOI:10.1021/om0302185

The reaction of the aminophenols 2-(CH₂L)-6-R-C ₆H₃OH (R = Ph, L = NMe₂, 1a; R = ^tBu, L = NMe₂, 1b; R = ^tBu, L = NC ₄H₈) 1c; R = ^tBu, L = NC

Full text of DOI:10.1021/om0302185

3732
Organometallics 2003, 22, 3732-3741
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of Neu tr a l
a n d Ca tion ic Alk yla lu m in u m Com p lexes Ba sed on
Bid en ta te Am in op h en ola te Liga n d s
Samuel Dagorne,*,† Laurent Lavanant,† Richard Welter,‡
Christophe Chassenieux,§ Pierre Haquette,† and Ge´rard J aouen†
Laboratoire de Chimie Organome´tallique, UMR CNRS 7576, Ecole Nationale Supe´rieure
de Chimie de Paris, 11, rue Pierre et Marie Curie, F-75231 Paris Cedex 05, France,
Laboratoire DECMET, Institut Le Bel, Universite´ Louis Pasteur, 4, rue Blaise Pascal,
67000 Strasbourg, France, and Laboratoire de Physico-chimie Macromole´culaire,
UMR CNRS 7615, Ecole Supe´rieure de Physique et de Chimie Industrielles,
10, rue Vauquelin, 75231 Paris Cedex 05, France
Received March 21, 2003
The reaction of the aminophenols 2-(CH2L)-6-R-C6H3OH (R ) Ph, L ) NMe2, 1a ; R ) tBu,
t
t
L ) NMe2, 1b; R ) Bu, L ) NC4H8, 1c; R ) Bu, L ) NC5H10, 1d ) with 1 equiv of AlMe3
affords the corresponding dimethyl Al complexes {2-(CH2L)-6-R-C6H3O}AlMe2 (R ) Ph, L )
t
t
t
NMe2, 2a ; R ) Bu, L ) NMe2, 2b; R ) Bu, L ) NC4H8, 2c; R ) Bu, L ) NC5H10, 2d ) in
high yields. Compounds 2a -d appear to be monomeric, on the basis of X-ray analysis for
2b,d and NMR data for 2a -d , and are stable in the presence of THF. {2-(CH2NMe2)-6-Ph-
C6H3O}AlMe2 (2a ) cleanly reacts with B(C6F5)3 to yield the dinuclear cationic Al species
3a +. X-ray diffraction analysis shows that the cation 3a + can be seen as an adduct of the
three-coordinate cation {2-(CH2NMe2)-6-Ph-C6H3O}AlMe+ and the neutral precursor 2a , in
which the two Al centers are connected via a µ2-O aminophenolate bridge. Similarly, the
reaction of Al dimethyl complexes 2b-d with B(C6F5)3 yields dinuclear cationic Al species
3b-d +/3b′-d ′+ (3b+/3b′+ in a 1/1 ratio; 3c,d +/3c′,d ′+ in a 3/1 ratio, respectively) as
diastereomeric mixtures. Cations 3b-d +/3b′-d ′+ adopt a structure similar to that of cation
3a +, as determined by X-ray crystallography analysis for 3b′+ and 2D NMR studies for 3a +
and 3c,d +/3c′,d ′+. All the formed dinuclear cations are quite stable and robust in solution,
and no fluxional behavior for any of them was observed up to 80 °C in C6D5Br. Cations
3b-d +/3b′-d ′+ react with a Lewis base such as THF to afford the corresponding THF adduct
cation 4b-d + along with 1 equiv of the corresponding neutral precursor 2b-d . In contrast,
3a + reacts with THF to yield unidentified species. 3a + and 3c,d +/3c′,d ′+ are inactive in
ethylene polymerization, but cations 3b-d +/3b′-d ′+ polymerize PO with moderate activity
to yield low-molecular-weight PPO.
In tr od u ction
activity and may allow new applications.4 In particular,
three- and four-coordinate cationic Al alkyls are now
attracting attention, since they have been shown to
polymerize ethylene under mild conditions.1c Such cat-
ionic species can be generated by the reaction of Al
dialkyl precursors bearing a monoanionic bidentate
(LX-) or tridentate (L2X-) ligand with [Ph3C][B(C6F5)4]
or B(C6F5)3, via an alkyl abstraction at the metal
center.1c,d
There has recently been an increased interest in cat-
ionic aluminum complexes for use in olefin,1b-e alkene
oxide,1a,e,2 and (D,L)-lactide3 polymerization catalysis.
These species are interesting, because the enhanced
Lewis acidity of the aluminum center versus that of
their neutral analogues should yield greater catalytic
* To whom correspondence should be addressed. Fax: +33 1 43 26
00 61. E-mail: dagorne@ext.jussieu.fr.
Whereas the ionization chemistry of neutral Al di-
alkyls {L2X}AlR2 usually generates stable four-coordi-
nate cationic Al species,1d,5 that of {LX}AlR2 complexes
may yield more reactive three-coordinate Al alkyl
cations due to the absence of a second L ligand to
stabilize the formed cationic Al center.6 Thorough stud-
ies by J ordan on cationic Al alkyls containing N,N-
† Ecole Nationale Supe´rieure de Chimie de Paris.
‡ Universite´ Louis Pasteur.
§ Ecole Supe´rieure de Physique et de Chimie Industrielles.
(1) For key references, see: (a) Atwood, D. A.; J egier, J . A.;
Rutherford, D. J . Am. Chem. Soc. 1995, 117, 6779. (b) Bochmann, M.;
Dawson, D. M. Angew. Chem., Int. Ed. Engl. 1996, 35, 2226. (c) Coles,
M. P.; J ordan, R. F. J . Am. Chem. Soc. 1997, 119, 8125. (d) Bruce, M.;
Gibson, V. C.; Redshaw, C.; Solan, G. A.; White, A. J . P.; Williams, D.
J . Chem. Commun. 1998, 2523. (e) Kim, K.-C.; Reed, C. A.; Long, G.
S.; Sen, A. J . Am. Chem. Soc. 2002, 124, 7662.
(4) Atwood, D. A. Coord. Chem. Rev. 1998, 176, 407.
(5) (a) Cameron, P.; Gibson, V. C.; Redshaw, C.; Segal, J . A.; Bruce,
M. D.; White, A. J . P.; Williams, D. J . Chem. Commun. 1999, 1883. (b)
Cameron, P.; Gibson, V. C.; Redshaw, C.; Segal, J . A.; Bruce, M. D.;
White, A. J . P.; Williams, D. J . J . Chem. Soc., Dalton Trans. 2002,
415.
(2) (a) J egier, J . A.; Atwood, D. A. Inorg. Chem. 1997, 36, 2034. (b)
Munoz-Hernandez, M.-A.; Sannigrahi, B.; Atwood, D. A. J . Am. Chem.
Soc. 1999, 121, 6747.
(3) Emig, N.; Nguyen, H.; Krautscheid, H.; Re´au, R.; Cazaux, J .-B.;
Bertrand, G. Organometallics 1998, 17, 3599.
10.1021/om0302185 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 08/02/2003

Neutral and Cationic Alkylaluminum Complexes
Organometallics, Vol. 22, No. 18, 2003 3733
Ch a r t 1
F igu r e 1. Molecular structure of complex 2b. The H atoms
are omitted for clarity. Selected bond lengths (Å) and angles
(deg): Al(1)-O(1) ) 1.758(1), Al(1)-N(1) ) 2.036(1),
Al(1)-C(7) ) 1.956(2), Al(1)-C(8) ) 1.954(2); O(1)-Al(1)-
C(8) ) 109.95(7), O(1)-Al(1)-C(7) ) 112.94(6), C(8)-
Al(1)-C(7) ) 118.13(7), O(1)-Al(1)-N(1) ) 97.17(5), C(8)-
Al(1)-N(1) ) 108.67(6), C(7)-Al(1)-N(1) ) 107.81(7).
Selected torsion angles (deg): Al(1)-O(1)-C(1)-C(2) )
39.29(16), O(1)-C(1)-C(2)-C(11) ) 3.13(18), N(1)-C(11)-
O(1)-Al(1) ) 23.21(9).
Sch em e 1
limit association reactions, we focused our studies on
the use of di-ortho-substituted aminophenols. Overall,
the geometrical and electronic differences between F
and A-E may be reflected in the structure and the
reactivity of the obtained cationic Al alkyls. Here we
report the synthesis and structure of neutral and
cationic aluminum complexes incorporating aminophe-
nolate ligands of type F . The newly synthesized cationic
species have also been tested for polymerization activity.
bidentate systems (A-C; Chart 1) showed that the
structure of these species, their stability, and their
reactivity are strongly influenced by the nature of the
ancillary ligand.6,7 In particular, the design of the
chelating N,N-bidentate ligand strongly affects the
catalytic activity of the derived cations.
In contrast to the N,N-ligand systems (A-D; Chart
1),6,7,8 O,N-bidentate cationic Al complexes have re-
ceived much less attention, with the exception of recent
reports on the ionization chemistry of Al dialkyl com-
plexes containing one mono(iminophenolate) ligand (E;
Chart 1), which yielded unstable cations in the absence
of an external Lewis base.5a,8b,9
Our attention focused on the synthesis of stable and
well-defined O,N-bidentate Al alkyl cations, because
such species may be structurally interesting as well as
useful for catalytic purposes. Bidentate O,N-aminophe-
nolate ligands (F ; Chart 1) seemed suitable for our
studies, since they may constitute an excellent chelate
for the oxophilic Al center and may form a stable, while
still flexible, six-membered Al metallacycle. Aluminum
phenolates without sterically demanding ortho substit-
uents are known to readily form aggregates.10 Thus, to
Resu lts
Syn th esis a n d Str u ctu r e of Mon o(a m in op h en o-
la te) Al Dim eth yl Com p lexes. The reaction of ami-
nophenols 1a -d with 1 equiv of AlMe3 in pentane at 0
°C affords the corresponding Al dimethyl complexes {2-
(CH2L)-6-R-C6H3O}AlMe2 (R ) Ph, L ) NMe2, 2a ; R )
t
t
tBu, L ) NMe2, 2b; R ) Bu, L ) NC4H8, 2c; R ) Bu,
L ) NC5H10, 2d ; Scheme 1) as analytically pure colorless
solids in high yields. X-ray-quality crystals of 2b and
2d were obtained from a saturated Et2O solution, and
the molecular structures of both compounds were de-
termined by X-ray crystallographic analysis, establish-
ing their monomeric nature. The molecular structures
of 2b,d and their selected bond distances and angles
are shown respectively in Figures 1 and 2, and crystal-
lographic data are given in Table 1. Compounds 2b,d
exhibit very similar structural features, and thus, we
will discuss only the features for 2d .
(6) (a) Ihara, E.; Young, V. G., J r.; J ordan, R. F. J . Am. Chem. Soc.
1998, 120, 8277. (b) Radzewich, C. E.; Guzei, I. A.; J ordan, R. F. J .
Am. Chem. Soc. 1999, 121, 8673.
(7) (a) Radzewich, C. E.; Coles, M. P.; J ordan, R. F. J . Am. Chem.
Soc. 1998, 120, 8673. (b) Dagorne, S.; Guzei, I. A.; Coles, M. P.; J ordan,
R. F. J . Am. Chem. Soc. 2000, 122, 274. (c) Korolev, A. V.; Ihara, E.;
Guzei, I. A.; Young, V. G., J r.; J ordan, R. F. J . Am. Chem. Soc. 2001,
122, 274.
Compound 2d crystallizes as a monomer in which the
Al center adopts a slightly distorted tetrahedral geom-
etry. The bite angle of the η2(O,N)-bonded aminophe-
(8) (a) Schmidt, J . A. R.; Arnold, J . Organometallics 2002, 21, 2306.
(b) Pappalardo, D.; Tedesco, C.; Pellecchia, C. Eur. J . Inorg. Chem.
2002, 621.
(9) Cameron, P.; 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.
(10) (a) Pasynkiewicz, S.; Starowieyski, K. B.; Skowronska-Ptasin-
ska, M. J . Organomet. Chem. 1973, 52, 269. (b) Starowieyski, K. B.;
Skowronska-Ptasinska, M. J . Organomet. Chem. 1978, 157, 379. For
a review on sterically crowded aryloxide compounds of aluminum,
see: (c) Healy, M. D.; Power, M. B.; Barron, A. R. Coord. Chem. Rev.
1994, 130, 63.

3734 Organometallics, Vol. 22, No. 18, 2003
Dagorne et al.
Syn th esis a n d Str u ctu r e of Ca tion ic Al Alk yls
Der ived fr om Com p lexes 2a -d . Rea ction of {2-
(CH2NMe2)-6-P h -C6H3O}AlMe2 (2a ) w ith B(C6F 5)3.
The reaction of the Al dimethyl compound {2-(CH2-
NMe2)-6-Ph-C6H3O}AlMe2 (2a ) with 1 equiv of B(C6F5)3
in CD2Cl2 (30 min, room temperature) cleanly affords
the dinuclear cations [{2-(CH2NMe2)-6-Ph-C6H3O}-
AlMe‚{2-(CH2NMe2)-6-Ph-C6H3O}AlMe2]+ (3a +) as
MeB(C6F5)3- salts (100% conversion by 1H NMR; Scheme
2), along with 0.5 equiv of unreacted B(C6F5)3, as
observed by 19F NMR. This reaction generates the
dinuclear species 3a +, which contains two elements of
chirality: i.e., a stereogenic tetrahedral Al center and a
second element of chirality resulting from the configu-
rational stability of the AlMe2 chelate ring.14 Thus, two
diastereomers are a priori expected. In this case, the
reaction is diastereoselective at room temperature
1
F igu r e 2. Molecular structure of complex 2d . The H atoms
are omitted for clarity. Selected bond lengths (Å) and angles
(deg): Al-O ) 1.768(2), Al-N ) 2.019(2), Al-C(1) ) 1.957-
(3), Al-C(2) ) 1.954(3); O-Al-C(1) ) 113.3(1), O-Al-C(2)
) 108.5(1), C(1)-Al-C(2) ) 116.4(1), O-Al-N ) 96.81-
(9), C(2)-Al-N ) 108.5(1), C(1)-Al-N ) 107.2(1). Selected
torsion angles (deg): Al-O-C(4)-C(5) ) 11.9, O(1)-C(1)-
C(2)-C(11) ) 3.13(18), N-C(3)-O-Al ) 35.9, C(4)-C(3)-
O-C(5) ) 2.5.
(>96% by H NMR), since only cation 3a + is observed.
The salt [3a ][MeB(C6F5)3] is stable in CD2Cl2 at room
temperature for several days and was isolated as an
analytically pure colorless solid in 76% yield by genera-
tion in CH2Cl2, removal of volatiles, and pentane wash-
ing. X-ray-quality crystals of [3a ][MeB(C6F5)3] were
grown from a saturated 10/1 CH2Cl2/pentane solvent
mixture at room temperature and its molecular struc-
ture was determined by X-ray crystallography analysis.
Molecu la r Str u ctu r e of [3a ][MeB(C6F 5)3]. [3a ]-
[MeB(C6F5)3] crystallizes as discrete 3a + (Figure 3) and
MeB(C6F5)3- ions with no close cation-anion contacts.
The structure of MeB(C6F5)3- is normal. The molecular
structure of 3a + is shown in Figure 3, crystallographic
data are given in Table 1, and selected bond distances
and angles are summarized in Table 2. It has an overall
C1 symmetry structure and can be seen as an adduct of
the three-coordinate cation {2-(CH2NMe2)-6-Ph-C6H3O}-
AlMe+ and the neutral four-coordinate complex {2-(CH2-
NMe2)-6-Ph-C6H3O}AlMe2, in which the two Al centers
are linked by a µ2-O bridging aminophenolate ligand
through O(2). A related cationic Al dinuclear adduct,
but containing a µ2-amido bridge, was observed in the
ionization chemistry of the amidinate complex {tBuC-
(NiPr)2}AlMe2; this adduct was revealed to be unstable
and could not be fully characterized.7b
nolate (N-Al-O ) 96.81(9)°) is compensated by the
opening of the C(1)-Al-C(2) and O-Al-C bond angles
(average 116.4(1) and 112.9°, respectively). The N-Al-C
bond angles (107.9(7)°) are very close to the ideal
tetrahedral angle (109.49°). The six-membered-ring Al
metallacycle is puckered, with the Me2N-Al moiety well
above the nearly planar O-C(5)-C(4)-C(3) backbone,
as shown by the C(5)-C(4)-C(3)-N and O-Al-N-C(3)
torsion angles (56.0 and 47.6°, respectively). Similar
puckering was also observed in the related boron
analogue {2-(CH2NMe2)C6H4O}BPh2.11 The Al-O and
Al-N bond distances (1.768(2) and 2.019(2) Å, respec-
tively) are in the normal range found for aluminum
phenolates (1.640(5)-1.773(2) Å)10c,12 and for Al-N
dative bonds (1.957(3)-2.238(4) Å),13 respectively.
The NMR data for 2a -d are consistent with the
chelation of one aminophenolate ligand to the Al center
and with the solid-state structure being retained in
solution. These data also show an effective Cs symmetry
for 2a -d on the NMR time scale in C6D6 at room
temperature, which is most likely due to a fast confor-
mation change of the six-membered-ring Al metallacycle
under these conditions, as observed in solution for {2-
(CH2NMe2)C6H4O}BPh2.11 No reaction was observed
between 2a -d and THF (1 equiv) after 2 days at 70 °C
in C6D6. This contrasts with the lack of stability of
{2-(CH2NMe2)C6H4O}AlMe2 in the presence of such a
Lewis base, which undergoes a disproportionation re-
action to yield {2-(CH2NMe2)C6H4O}2AlMe and THF-
AlMe3.12 Such different reactivity may be ascribed to
the more sterically demanding aminophenolate in
2a -d .
The geometrical parameters at the Al centers for 3a +
are nearly unchanged as compared to those of the
neutral precursors. Both Al centers adopt a slightly
distorted tetrahedral structure with N-Al-O bite angles
(N(1)-Al(1)-O(1) ) 99.16° and N(2)-Al(2)-O(2) )
96.07°) similar to those of 2b,d (average 96.9(2)°).
The presence of two aminophenolate ligands in a
different binding mode is clearly manifest through their
geometrical differences. As shown in Figure 2, the six-
membered-ring Al(1) metallacycle is slightly puckered,
with Al(1) and N(1) slightly outside of the rest of the
ring. In contrast, the six-membered-ring Al(2) metalla-
cycle containing the bridging aminophenolate adopts a
boatlike conformation with the O(2) and C(21) well
above the Al(2)-N(2)-C(21)-C(22) backbone, which
(11) Hagen, H.; Reinoso, S.; Albrecht, M.; Boersma, J .; Spek, A. L.;
van Koten, G. J . Organomet. Chem. 2000, 608, 27.
(12) Hogerheide, M. P.; Wesseling, M.; J astrzebski, J . T. B. H.;
Boersma, J .; Kooijman, H.; Spek, A. L.; van Koten, G. Organometallics
1995, 14, 4483.
(13) (a) Hill, J . B.; Eng, S. J .; Pennington, W. T.; Robinson, G. H. J .
Organomet. Chem. 1993, 445, 11. (b) Kumar, R.; Sierra, M. L.; Oliver,
J . P. Organometallics 1994, 13, 4285.
(14) The obtainment in solution of two diastereomers in the 3b-
d +/3b′-d ′+ cationic systems (vide infra) imposes the presence of a
second element of chirality for these cations. This second source of
chirality most likely originates from a configurationally stable (i.e. with
no inversion) AlMe2 chelate ring in all the obtained dinuclear cations.
This feature is proposed on the basis of the solid-state structure studies
of 3a + and 3b′+ and of the lack of dynamic behavior in solution for
3a + and 3b-d +/3b′-d ′+ (vide infra).

Neutral and Cationic Alkylaluminum Complexes
Organometallics, Vol. 22, No. 18, 2003 3735
Ta ble 1. Cr ysta llogr a p h ic Da ta for 2b,d , [3a ][MeB(C6F 5)], a n d [3b′][MeB(C6F 5)]
2b
2d
[3a ][MeB(C6F5)]
[3b′][MeB(C6F5]
formula
fw
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
4(C15H26AlNO)
1053.39
0.13 × 0.10 × 0.08
triclinic
P1h
10.310(5)
12.692(5)
25.691(5)
78.056
80.587(5)
87.421(5)
3245(2)
2
not measd
17223
C18H30AlNO
303.43
0.20 × 0.10 × 0.08
monoclinic
P21/c
9.7860(3)
10.2945(4)
18.1648(7)
90
96.603(5)
90
C52H44Al2BF15N2O2
1078.69
C
48H52Al2BF15N2O2
1038.71
0.10 × 0.08 × 0.06
monoclinic
P21/c
16.8813(2)
11.1788(1)
25.4984(4)
90
90.479
90
4811.7(1)
4
0.11 × 0.09 × 0.06
triclinic
P1h
10.1644(2)
16.1355(2)
16.6117(3)
114.004(5)
91.562(5)
93.640(5)
2479.59(12)
2
1817.8(1)
4
1.11
Z
Dcalcd (g cm-3
)
1.44
1.43
13331
no. of indep rflns
no. of params
R1
4223
649
190
667
631
0.051a
0.045b
0.043b
0.042b
wR2 (all data)
goodness of fit
0.1508
1.050
0.123
1.068
0.227
1.134
1.154
a
b
R1 (I > 2σ(I)). R1 (I > 3σ(I)).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3a +
Al(1)-O(1)
Al(1)-N(1)
Al(2)-O(2)
Al(2)-C(19)
1.729(2)
1.975(2)
1.881(2)
1.948(3)
Al(1)-O(2)
Al(1)-C(1)
Al(2)-N(2)
Al(2)-C(20)
1.846(1)
1.926(3)
2.020(2)
1.936(3)
Al(1)-O(2)-Al(2)
N(1)-Al(1)-O(1)
129.24(8) N(2)-Al(2)-O(2)
96.09
99.16(8)
Al(1)-O(2)-C(23)
N(1)-Al(1)-O(2)
112.4(1)
114.02(7)
112.7(1)
Al(2)-O(2)-C(23) 108.7(1)
O(2)-Al(1)-C(1)
111.39(9) O(2)-Al(2)-C(20)
O(2)-Al(2)-C(19) 110.1(1)
N(2)-Al(2)-C(20) 111.4(1)
C(20)-Al(2)-C(19) 116.2(1)
N(2)-Al(2)-C(19)
O(1)-Al(1)-C(1)
108.6(1)
120.4(1)
N(1)-Al(1)-C(1)
111.9(1)
Ch a r t 2
F igu r e 3. Molecular structure of complex 3a +. The H
atoms are omitted for clarity.
Sch em e 2
respectively), but both distances compare to those in
Et2Al(µ-O-2,6-Me2Ph)2AlEt2 (average 1.86(1) Å), which
shows the bridging phenoxide nature of the O(2) group.15
The similar µ-O-Al bond distances in 3a + contrast with
the different values of the Al(1)-O and Al(2)-O bond
distances (1.855(2) and 1.989(2) Å, respectively) in a
related neutral trinuclear complex (G; Chart 2).12 The
more symmetrical phenoxide Al-O-Al bridge in our
case may be ascribed to the electron deficiency of both
Al centers as a result of the cationic charge. The Al-
(1)-N(1) bond distance (1.975(1) Å) is shorter than the
Al(2)-N(2) distance (2.020(2) Å), the latter being identi-
cal with that in 2d (2.019(2) Å), while both remain in
the normal range for Al-N dative bonds (1.957(3)-
2.238(4) Å).12,13 Overall, the shorter Al(1)-N and Al-
(1)-O bond distances as compared to the Al(2)-N and
Al(2)-O bond distances in 3a + may suggest a more
electron-deficient Al(1) vs Al(2).
illustrates the flexibility of this ligand. Such a confor-
mation can be rationalized by the geometrical restraints
imposed on the aminophenolate ligand by both the
coordination of O(2) to Al(1) and the tetrahedral geom-
etry preferred by Al(2).
The coordination of the O(2) to both Al centers leads
to a slightly distorted trigonal planar geometry around
O(2), the sum of the angles amounting to 350.3(4)° (O(2)
is 0.31(1) Å out of the plane defined by Al(1), Al(2), and
C(23)). In comparison to the geometry around the
oxygen in 2b,d , this can be seen as a rehybridization
from sp3 to sp2 caused by the coordination of O(2) to
Al(1). The Al(1)-O(2) bond distance is shorter than the
Al(2)-O(2) bond distance (1.846(1) and 1.881(2) Å,
Solu tion Str u ctu r e a n d Sta bility of [3a ][MeB-
(C6F 5)3]. The solution structure of [3a ][MeB(C6F5)3] was
(15) Giesbrecht, G. R.; Gordon, J . C.; Brady, J . T.; Clark, D. L.;
Webster Keogh, D.; Michalczyk, R.; Scott, B. L.; Watkin, J . G. Eur. J .
Inorg. Chem. 2002, 723.

3736 Organometallics, Vol. 22, No. 18, 2003
Dagorne et al.
Sch em e 3
F igu r e 4. Molecular structure of complex 3b′+. The H
atoms are omitted for clarity.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3b′+
Al(2)-O(2)
Al(2)-N(2)
Al(1)-O(1)
Al(1)-C(2)
1.736(2)
1.983(2)
1.885(2)
1.941(3)
Al(2)-O(1)
Al(2)-C(16)
Al(1)-N(1)
Al(1)-C(1)
1.855(2)
1.934(2)
2.019(2)
1.943(3)
studied by a combination of 1D (1H, 11B, 13C, and 19F
NMR) and 2D (HMQC and HMBC) NMR spectroscopy
techniques, which allowed a complete assignment for
all resonances.
Al(1)-O(1)-Al(2)
N(2)-Al(2)-O(2)
Al(1)-O(1)-C(3)
121.69(8) N(1)-Al(1)-O(1)
95.97(8)
107.7(1)
95.72(7)
125.4(1)
111.77(7)
106.46(9)
119.4(1)
107.7(1)
Al(2)-O(1)-C(3)
N(2)-Al(2)-O(1)
O(1)-Al(1)-C(1)
C(1)-Al(1)-C(2)
N(1)-Al(1)-C(2)
The 1H, 11B, 13C, and 19F NMR data for [3a ][MeB-
(C6F5)3] between -40 and +40 °C in CD2Cl2 are es-
O(1)-Al(2)-C(16) 111.5(1)
-
sentially unchanged, showing that the MeB(C6F5)3
O(1)-Al(1)-C(2)
N(1)-Al(1)-C(1)
112.5(1)
112.6(1)
anion is free in solution and that the cation 3a + is not
fluxional over this range of temperature. Similar NMR
data are obtained for [3a ][MeB(C6F5)3] in C6D5Br be-
tween -10 and +80 °C in C6D5Br. However, cation 3a +
decomposes at 90 °C in C6D5Br (t1/2 ≈ 3h) to unidentified
N(2)-Al(2)-C(16) 110.5(1)
O(2)-Al(2)-C(16) 118.07(9)
100% conversion by 1H NMR; Scheme 3), along with 0.5
equiv of unreacted B(C6F5)3 as observed by 19F NMR.
Thus, the diastereoselectivity of this reaction is signifi-
cantly lower than that with 2a and appears to be highly
influenced by the steric nature of the aminophenolate
ligand. The different diastereomeric ratios of 3a + vs 3b+/
3b′+ and of 3b+/3b′+ vs 3c,d +/3c′,d ′+ show that both
the phenol and the amino groups influence the diaste-
reoselectivity of these reactions.
1
species. In addition, the H NMR spectrum of 3a + also
remains unchanged in the presence of the neutral
precursor 2a (1 equiv) between 25 and 80 °C in C6D5Br
showing that no exchange reaction occurs between the
two species under such conditions.
The 1H and 13C NMR data for 3a + are consistent with
a C1-symmetric structure in solution. For example, the
1H spectrum for 3a + at 35 °C contains 3 AlMe reso-
nances, 4 NMe signals, 4 PhCH2 resonances, and two
sets of aminophenolate resonances in the aromatic
region. In addition, the atomic connectivity for 3a +
established on the basis of HMQC and HMBC NMR
experiments is consistent with the solid-state structure.
Overall, the NMR data for 3a + strongly suggest that
its solid-state structure is retained in solution.
Rea ction of Dim eth yl Al Com p lexes 2b-d w ith
B(C6F 5)3. The ionization chemistry of neutral precur-
sors incorporating bulkier aminophenolates (2b-d ) was
studied in order to probe the influence of the aminophe-
nolate sterics on the structure and the nature of the
formed Al alkyl cations. As described below, the change
from a Ph ortho substituent in 2a to a tBu ortho
substituent in 2b-d does not affect the overall structure
of the formed cations but does affect the diastereose-
lectivity.
[3b-d /3b′-d ′][MeB(C6F5)3] were isolated at room
temperature as diastereomeric mixtures as analytically
pure colorless solids in good yields, using a procedure
similar to that for [3a ][MeB(C6F5)3]. Crystals of [3b′]-
[MeB(C6F5)3] were obtained from a 5/1 pentane/CH2Cl2
saturated solution, and its molecular structure was
determined by X-ray crystallographic analysis. The
molecular structure of 3b′+ is illustrated in Figure 4,
crystallographic data are given in Table 1, and selected
bond distances and angles are shown in Table 3. Cation
3b′+ adopts a structure similar to that of 3a + and is a
formal adduct of {6-tBu-2-(CH2NMe2)C6H3O}AlMe+
and the neutral four-coordinate complex {2-tBu-6-
(CH2NMe2)C6H3O}AlMe2 linked by a µ2-O aminophe-
nolate ligand through O(2). However, the stereogenic
Al center in 3b′+ adopts a configuration opposite to that
in 3a +, whereas the AlMe2 chelate ring adopts the same
configuration as that in 3a +. This key stereochemical
difference between the molecular structures of 3a + and
3b ′+ explains the presence of two diastereomers in
3b-d +/3b′-d ′+. Overall, the structural and geometrical
parameters for 3b′+ are similar to those of 3a +, showing
The compounds {2-(CH2L)-6-tBu-C6H3O}AlMe2 (L )
NMe2, 2b; L ) NC4H8, 2c; L ) NC5H10, 2d ; Scheme 3)
react with B(C6F5)3 to yield the corresponding dinuclear
cations [{2-(CH2L)-6-tBu-C6H3O}AlMe‚{{2-(CH2L)-6-
tBu-C6H3O}AlMe2]+ (3b-d +/3b′-d ′+) as a mixture of
t
that the presence of the more bulky Bu ortho substitu-
-
two diastereomers and as MeB(C6F5)3 salts (3b+/3b′+
ent vs a Ph ortho substituent in 3a + does not provide
in a 1/1 ratio; 3c,d +/3c′,d ′+ in a 3/1 ratio, respectively,
enough steric shielding to prevent association.

Neutral and Cationic Alkylaluminum Complexes
Organometallics, Vol. 22, No. 18, 2003 3737
Solu tion Str u ctu r e of [3b-d+/3b′-d′][MeB(C6F5)3].
The solution structure of [3b-d /3b′-d ′][MeB(C6F5)3]
was studied by a combination of 1D (1H, 11B, 13C, and
19F NMR) and 2D (HMQC and HMBC) NMR tech-
niques, which allowed a complete assignment for all
resonances and connectivity assignments for cations 3b+
and 3c,d +/3c′,d ′+. The combined 1D and 2D NMR data
show the following. (i) The cation and the anion are fully
dissociated in CD2Cl2 solution between -80 and 35 °C
and between room temperature and 70 °C in C6D5Br.
(ii) Each cation remains C1 symmetric with no fluxional
behavior under the studied conditions. (iii) The diaster-
eomeric ratios 3b-d +/3b′-d ′+ are not modified over the
studied range of temperature, which suggests that the
reaction is under kinetic control and shows that the Al
stereogenic center and the AlMe2 chelate ring are
configurationally stable under these conditions.
Sch em e 4
Sch em e 5
In addition to 1D and 2D NMR connectivity assign-
ments, a close analysis of the 13C NMR data for
3b-d +/3b′-d ′+ favors the proposed µ2-O bridging struc-
ture of these cations in solution. In particular, for each
of these cations, the C(2) and C(4) phenol carbons
resonances of the µ2-O aminophenolate are significantly
deshielded as compared to the corresponding resonances
of the second aminophenolate ligand. In contrast, the
C(1) phenol resonance of the µ-O-aminophenolate in
3b-d +/3b′-d ′+ is shielded as compared to those of the
other aminophenolate.16 These two observations show
that the µ-O phenol ring is significantly more electron-
deficient than the other phenol ring, as expected for this
type of structure. Overall, the NMR data for cations
3b-d +/3b′-d ′+ suggest that they all adopt a structure
in solution similar to that of 3b′+ in the solid state and
that, like 3a +, cations 3c,d +/3c′,d ′+ are quite robust in
solution.
by heating [3b/3b′][MeB(C6F5)3] in benzene for 18 h
allowed it to be obtained as an analytically pure solid
after recrystallization from pentane. The 1H and 13C
NMR data for 5b are consistent with a C1-symmetric
structure and the 19F NMR data with the presence of
the C6F5 moiety. The NMR data for MeB(C6F5)2 match
those of the literature.19 Similar degradation reactions
between cationic Al alkyl systems incorporating biden-
tate ligands and the MeB(C6F5)3- anion occurring via a
-
C6F5 transfer from the anion to the Al center have
previously been observed.7b,19 However, degradations of
this type usually take place at a temperature lower than
that observed here for 3b+/3b′+, thus illustrating the
excellent stability of the 3b+/3b′+ system.
Rea ction of Al Ca tion s [3a ][MeB(C6F 5)3], [3b-d +/
3b′-d ′][MeB(C6F 5)3] w ith THF . The reactivity of the
obtained dinuclear cations with a Lewis base such as
THF was investigated. The NMR scale reaction of
[3b -d /3b ′-d ′][MeB(C6F5)3] with 1 equiv of THF in
CD2Cl2 at room temperature results in quantitative
conversion to the cationic THF adduct Al alkyl com-
plexes [4b-d ][MeB(C6F5)3] and the neutral precursors
In the case of cations 3c,d +/3c′,d ′+, 2D NMR data,
including NOESY data, remained inconclusive as to the
determination of 3c+ and 3d + as the major diastereo-
1
mers. Rather, the comparison of H NMR AlMe reso-
nances of 3c,d +/3c′,d ′+ to those of 3b/3b′+ provided
insight into this issue.17 The 1H NMR AlMe sets of
resonances for 3b+, 3c+, and 3d + are almost identical
but exhibit chemical shifts quite different from those,
also very similar to one another, for 3b′+, 3c′+, and
3d ′+.18 This key difference allowed NMR assignments
for cations 3c+ and 3d +.
1
2b-d in a 1/1 ratio, as observed by H NMR (Scheme
5). Attempts to isolate [4b-d ][MeB(C6F5)3] by their
generation on a preparative scale remained unsuccessful
due to their oily nature. In contrast to that of [4b-d ]-
[MeB(C6F5)3], the reaction of [3a ][MeB(C6F5)3] with THF
in CD2Cl2 at room temperature yields unidentified
species. When this reaction was performed at -40 °C,
a similar intractable mixture was obtained.
Decom p osition of [3b/3b′][MeB(C6F 5)3] in solu -
t ion . The stability of the 3b+/3b′+ diastereomeric
mixture (1/1 ratio) as MeB(C6F5)3- salts was studied in
C6D5Br on an NMR scale. Complete conversion of
[3b/3b′][MeB(C6F5)3] to a 1/1/1 ratio of the neutral
monomethyl complex {2-(CH2NMe2)-6-tBu-C6H3O}Al-
(Me)(C6F5) (5b), complex 2b, and three-coordinated
borane MeB(C6F5)2 was observed after 5 h at 80 °C in
C6D5Br (Scheme 4). A preparative-scale synthesis of 5b
Compounds [4b-d ][MeB(C6F5)3] are fully dissociated
in CD2Cl2 with no cation-anion interaction at room
1
temperature, as observed by H and 19F NMR spectros-
copy. Key characteristic 1H NMR resonances for
4b-d + include (i) the AlMe+ resonances (δ -0.33,
-0.37, -0.27 for 4b-d +, respectively) are downfield
shifted as compared to those in the neutral precursors
(δ -0.76, -0.77, -0.73 respectively), a result of the
cationic charge on the Al center, and (ii) the THF
resonances (δ (average) 4.44, 2.23) also appear at
significantly lower field than those for free THF (δ 3.67,
1.81), showing effective THF coordination to the cationic
Al center. The 13C NMR data for 4b -d + exhibit a
(16) For the µ-O aminophenolate: δ (average) 126.8 (C′(2)), 127.6
(C′(4)), 146.5 (C′(1)). For the other aminophenolate: δ (average) 120.7
(C(2)), 119.9 (C(4)), 154.7 (C(1)). For more details, see the Experimental
Section.
(17) The NMR data of the single crystals obtained from slow
crystallization of [3b+/3b′][MeB(C6F5)3] (1/1 ratio) from solution contain
signals for only one diastereomer, which were assigned to cation 3b′+
on the basis of X-ray crystallographic results.
(18) 1H NMR AlMe resonances (CD2Cl2): 3b+, δ -0.71, -0.29, -0.09;
3c+, δ -0.69, -0.33, -0.09; 3d +, δ -0.70, -0.25, -0.06; 3b′+, δ -1.00,
-0.79, -0.17; 3c′+, δ -0.97, -0.78, -0.19; 3d ′+, δ -0.87, -0.77, -0.16.
(19) Qian, B.; Ward, D. L.; Smith, M. R., III. Organometallics 1998,
17, 3070.

3738 Organometallics, Vol. 22, No. 18, 2003
Dagorne et al.
similar trend, with the 4b-d + resonances appearing at
lower field than those of 2b-d . In addition, the presence
of only one NMe2 resonance and one PhCH2 resonance
for 4b-d + in CD2Cl2 at room temperature indicates an
effective Cs symmetry, which is most likely due to a fast
face exchange of THF on the NMR time scale.
Ch a r t 3
The obtainment of cations 4b-d + from the reaction
of 3b-d + with THF is consistent with the proposed
adduct structure of these cations and shows that
3b-d + can be considered as a formal source of three-
coordinate {2-(CH2L)-6-tBu-C6H3O}AlMe+ cations sta-
bilized by the corresponding neutral precursors
{2-(CH2L)-6-tBu-C6H3O}AlMe2 acting as Lewis bases.
In contrast, the outcome of the reaction of 3a + with THF
remains perplexing to us, given the apparent structural
similarities in the solid state and in solution of all the
obtained cations.
(iminophenolate) Al dimethyl complexes may be related
to the excellent flexibility of the chelating aminophe-
nolate backbone, as illustrated by the molecular struc-
tures of 3a + and 3b′+, allowing this ligand to adapt to
the steric and electronic requirements of the chelated
metal center. On the other hand, this good stability
associated with the robustness of 3a + and 3b -d +/
3b′-d ′+ probably explains their lack of reactivity with
ethylene.
Further studies will focus on a better understanding
of the reactivity of 3a + and on the design of new O,N
bidentate ligands for the synthesis of more reactive
cationic Al alkyls.
Rea ctivity of 3a + a n d 3b-d +/3b′-d ′+ w ith Eth -
ylen e a n d P r op ylen e Oxid e (P O). Cations 3a + and
3b-d +/3b′-d ′+ are not active in ethylene polymeriza-
tion at 70 °C in toluene under 5 bar of ethylene pressure,
as might be expected by the robustness and the lack of
fluxional behavior of these adduct cations. These species
do, however, initiate the polymerization of propylene
oxide under mild conditions (room temperature, 15 min,
toluene) to yield atactic PPO, as determined by 13C NMR
data (200 equiv of PO; conversion: 3b+/3b′+, 55%; 3c+/
3c′+, 51%; 3d +/3d ′+, 61%). In contrast, 3a + does not
polymerize PO, which further illustrates the clear
difference in reactivity of 3a + vs 3b-d +/3b′-d ′+ toward
Lewis bases. As estimated from SEC data, similar low-
molecular-weight polymers are obtained with all three
active cations (3b+/3b′+, Mn ) 2840, Mw/Mn ) 1.54; 3c+/
3c′+, Mn ) 2560, Mw/Mn ) 1.61; 3d +/3d ′+, Mn ) 3076,
Mw/Mn ) 1.50). The polymerization activity of 3b+/3b′+
was also tested at 0 °C (1 h, toluene), showing a higher
conversion to PPO (70% conversion, Mn ) 9022, Mw/Mn
) 1.73). In this case, the obtained polymer possesses a
much higher molecular weight, comparable to those of
PPOs obtained with porphyrinato-aluminum chloride
complexes.20 The catalytic activity of 3b-d +/3b′-d ′+ at
room temperature for PO polymerization compares with
that of Schiff base-AlEt2Cl initiator systems but is
lower than that of porphyrinato-aluminum chloride
complexes.20,21
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were carried out
under N2 using standard Schlenk techniques or in a Mbraun
Unilab glovebox. Benzene, pentane, and THF were distilled
from Na/benzophenone and stored over activated molecular
sieves (4 Å) in a glovebox prior to use. CH2Cl2 and CD2Cl2,
were distilled from CaH2 and stored over activated molecular
sieves (4 Å) in a glovebox prior to use. C6D6 and C6D5Br were
degassed under a N2 flow and stored over activated molecular
sieves (4 Å) in a glovebox prior to use. The aminophenols 1a -d
were synthesized according to general literature procedures,
and NMR data for 1a ,b matched those in the literature.22
B(C6F5)3 was purchased from Strem Chemicals and was
extracted with dry pentane prior to use. CD2Cl2, C6D6, and
C6D5Br were purchased from Eurisotope. All other chemicals
were purchased from Aldrich and were used as received. All
NMR spectra were obtained on a Bruker AC 200 or 400 MHz
spectrometer, in Teflon-valved J . Young tubes at ambient
temperature, unless otherwise indicated. 1H and 13C chemical
shifts are reported versus SiMe4 and were determined by
reference to the residual 1H and 13C solvent peaks. 11B and
19F chemical shifts are reported respectively versus BF3‚Et2O
in CD2Cl2 and versus neat CFCl3. NMR assignments were
supported by two-dimensional experiments (HMQC and HMBC)
where appropriate. Size exclusion chromatography (SEC)
analyses were carried out using a Waters 150CV instrument
(M590 pump, U6K injector) equipped with a R410 refracto-
meter and a Waters capillary viscometer and five Ultrastyragel
columns (Waters). The SEC columns were eluted with THF
at 40 °C at 1 mL/min. All the results are given in real
molecular weight averages due to a universal calibration
procedure. Elemental analyses were all performed by Mik-
roanalytisches Labor Pascher, Remagen-Bandorf, Germany,
except those for 1c-e, performed by the microanalysis labora-
tory of the Universite´ Pierre et Marie Curie, Paris, France.
For the cationic Al species 3a -d +/3a ′-d ′+, NMR assign-
ments are quoted with reference to the general labeling chart
given in Chart 3.
Con clu sion s
This work shows that the mono(aminophenolate) Al
dimethyl complexes 2a -d can be cleanly converted to
robust and stable dinuclear cationic Al alkyls (3a +, 3b-
d +/3b′-d ′+). Solid-state and solution studies as well as
their reactivity with THF are consistent with 3b-d +/
3b′-d ′+ being formal adducts of three-coordinate {2-
(CH2L)-6-tBu-C6H3O}AlMe+ and the corresponding neu-
tral precursors 2a -d via an Al-µ2-O-Al phenoxide
bridge. In the case of 3a +, its apparent structural
similarities with 3b-d +/3b′-d ′+ are in contrast with
its difference of reactivity with Lewis bases such as THF
and PO. In the present case, the higher stability of the
obtained cations versus those derived from mono-
The cationic Al complexes were all obtained as fully dis-
sociated MeB(C6F5)3- salts in solution. The NMR data for the
-
MeB(C6F5)3 anion are listed below for all of the compounds.
(20) Sugimoto, H.; Kawamura, C.; Kuroki, M.; Aida, T.; Inoue, S.
Macromolecules 1994, 27, 2013.
(21) Vincens, V.; Le Borgne, A.; Spassky, N. Makromol. Chem.
Rapid. Commun. 1989, 10, 623.
(22) (a) Pochini, A.; Puglia, G.; Ungaro, R. Synthesis 1983, 11, 906.
(b) Salakhutdinov, N. F.; Krysin, A. P.; Koptyug, V. A. J . Org. Chem.
USSR (Engl. Transl.) 1990, 26, 664.

Neutral and Cationic Alkylaluminum Complexes
Organometallics, Vol. 22, No. 18, 2003 3739
Da ta for MeB(C6F 5)-. 1H NMR (400 MHz, CD2Cl2): δ 0.48
(BMe). 11B{1H} NMR (128 MHz, CD2Cl2): δ -11.9 (br s, BMe).
PhCH2), 6.61 (dd, 3J H,H ) 7.4 Hz, 4J H,H ) 1.6, 1H, H(3)-PhO),
3
3
6.77 (t, J H,H ) 7.4 Hz, 1H, H(4)-PhO), 7.40 (dd, J H,H ) 7.8
1
4
13C{1H} NMR (100 MHz, CD2Cl2): δ 148.6 (d, J CF ) 233 Hz,
Hz, J H,H ) 1.8 Hz, 1H, H(5)-PhO). 13C{1H} NMR (100 MHz,
o-C6F5), 137.9 (d, 1J CF ) 238, p-C6F5), 136.7 (d, 1J CF ) 233 Hz,
m-C6F5), 10.3 (MeB). 19F NMR (376 MHz, CD2Cl2): δ -133.5
C6D6): δ -10.9 (AlMe2), 30.1 (CMe3), 35.3 (CMe3), 44.6 (NMe2),
62.7 (PhCH2), 117.5 (C(4)-PhO), 122.1 (C(2)-PhO), 128.4
(C(3)-PhO), 129.2 (C(5)-PhO), 139.5 (C(6)-PhO), 158.4 (C(1)-
PhO). 1H NMR (400 MHz, CD2Cl2, 25 °C): δ -0.76 (s, 6H,
AlMe2), 1.41 (s, 9H, tBu), 2.41 (s, 6H, NMe2), 3.75 (s, 2H,
PhCH2), 6.63 (t, 3J H,H ) 7.4 Hz, 1H, H(4)-PhO), 6.86 (dd, 3J H,H
3
3
(d, J FF ) 19 Hz, 2F, o-C6F5), -165.7 (t, J FF ) 20 Hz, 1F,
3
p-C6F5), -168.2 (m, J FF ) 19 Hz, 2F, p-C6F5).
2-(CH2NC4H8)-6-tBu -C6H3OH (1c) a n d 2-(CH2NC5H10)-6-
tBu -C6H3OH (1d ). In a 100 mL round-bottom flask, 2-tBu-
C6H4OH (3.00 g, 20.0 mmol), formaldehyde (1.5 equiv, 2 mL
of a 37% weight in water), and 1.3 equiv of the appropriate
cyclic amine were added and dissolved in 50 mL of EtOH. The
mixture was refluxed, and the reaction was monitored by TLC,
revealing that the reaction was complete after 3 h. The mixture
was then warmed to room temperature, and the volatiles were
removed under vacuum. Pure 1c,d were obtained after puri-
fication via a silica gel column chromatography using as an
eluent system a 4/1 pentane/Et2O mixture for 1c (Rf ) 0.25,
65% yield) and a 98/2 pentane/ethyl acetate mixture for 1d
(Rf ) 0.20, 70% yield).
4
3
) 7.4 Hz, J H,H ) 1.6 Hz, 1H, H(3)-PhO), 7.23 (dd, J H,H
)
7.8 Hz, 4J H,H ) 1.8 Hz, 1H, H(5)-PhO). Anal. Calcd for C15H26
-
AlNO: C, 68.41; H, 9.95. Found: C, 68.31; H, 10.19.
Da ta for 2c. 1H NMR (400 MHz, CD2Cl2): δ -0.77 (AlMe2),
t
1.40 (s, 9H, Bu), 1.90-2.05 (m, 4H, H(â)-N), 2.63 (m, 2H,
H(R)-N), 3.12 (m, 2H, H(R)-N), 3.82 (s, 2H, PhCH2), 6.61 (t,
3J H,H ) 7.4 Hz, 1H, H(4)-PhO), 6.87 (dd, 3J H,H ) 7.5 Hz, 4J H,H
3
4
) 1.8 Hz, 1H, H(3)-PhO), 7.23 (dd, J H,H ) 7.5 Hz, J H,H
)
1.8 Hz, 1H, H(5)-PhO). 13C{1H} NMR (400 MHz, CD2Cl2): δ
-11.9 (AlMe2), 22.2 (C(â)-N), 28.9 (CMe3), 34.3 (CMe3), 54.1
(C(R)-N), 59.1 (PhCH2), 115.9 (C(4)-PhO), 122.2 (C(2)-PhO),
126.9 (C(3)-PhO), 127.3 (C(5)-PhO), 138.4 (C(6)-PhO), 158.6
(C(1)-PhO). Anal. Calcd for C17H28AlNO: C, 70.56; H, 9.75.
Found: C, 70.44; H, 9.86.
Da ta for 1c. 1H NMR (200 MHz, CDCl3): δ 1.52 (s, 9H,
tBu), 1.91 (m, 4H, H(â)-N), 2.70 (m, 4H, H(R)-N), 3.89 (s, 2H,
PhCH2), 6.79 (t, 3J H,H ) 7.5 Hz, 1H, H(4)-PhO), 6.94 (dd, 3J H,H
) 7.4 Hz, 3J H,H ) 1.0 Hz, H(3)-PhO), 7.28 (dd, 3J H,H ) 7.4 Hz,
3J H,H ) 1.0 Hz, H(5)-PhO). 13C{1H} NMR (50 MHz, CDCl3):
δ 23.5 (C(â)-N), 29.2 (CMe3), 34.4 (CMe3), 53.0 (C(R)-N), 59.0
(PhCH2), 117.7 (C(4)-PhO), 122.5 (C(2)-PhO), 125.4 (C(3)-
or C(5)-PhO), 125.7 (C(3)- or C(5)-PhO), 136.0 (C(6)-PhO),
156.8 (C(1)-PhO). Anal. Calcd for C15H23NO: C, 77.21; H, 9.93.
Found: C, 77.17; H, 9.83.
Da ta for 2d . 1H NMR (400 MHz, CD2Cl2): δ -0.72 (AlMe2),
t
1.40 (s, 9H, Bu), 1.55 (m, 1H, H(γ)-N), 1.69 (m, 5H, H(γ)-
and H(â)-N), 2.44 (m, 2H, H(R)-N), 3.09 (m, 2H, H(R)-N),
3
3.83 (s, 2H, PhCH2), 6.62 (t, J H,H ) 7.5 Hz, 1H, H(4)-PhO),
3
4
6.90 (dd, J H,H ) 7.5 Hz, J H,H ) 1.8 Hz, 1H, H(3)-PhO), 7.23
(dd, J H,H ) 7.5 Hz, J H,H ) 1.8 Hz, 1H, H(5)-PhO). 13C{1H}
NMR (400 MHz, CD2Cl2): δ -10.6 (AlMe2), 20.9 (C(â)-N), 22.7
(C(γ)-N), 28.7 (CMe3), 34.1 (CMe3), 53.2 (C(R)-N), 59.0
(PhCH2), 116.0 (C(4)-PhO), 120.8 (C(2)-PhO), 126.9 (C(3)-
PhO), 126.8 (C(5)-PhO), 138.0 (C(6)-PhO), 158.5 (C(1)-PhO).
Anal. Calcd for C18H30AlNO: C, 71.25; H, 9.97. Found: C,
71.14; H, 10.10.
3
4
Da ta for 1d . 1H NMR (200 MHz, CDCl3): δ 1.52 (s, 9H,
tBu), 1.58 (broad s, 2H, H(γ)-N), 1.72 (m, 4H, H(â)-N), 2.57
3
(broad s, 4H, H(R)-N), 3.73 (s, 2H, PhCH2), 6.79 (t, J H,H
)
3
3
7.5 Hz, 1H, H(4)-PhO), 6.92 (dd, J H,H ) 7.5 Hz, J H,H ) 1.0
Hz, H(3)-PhO), 7.26 (dd, 3J H,H ) 7.4 Hz, 3J H,H ) 1.0 Hz, H(5)-
PhO). 13C{1H} NMR (50 MHz, CDCl3): δ 24.0 (C(γ)-N), 25.7
(C(â)-N), 29.4 (CMe3), 34.6 (CMe3), 53.5 (C(R)-N), 62.4
(PhCH2), 118.0 (C(4)-PhO), 121.8 (C(2)-PhO), 125.6 (C(3) or
C(5)-PhO), 126.6 (C(3) or C(5)-PhO), 136.3 (C(6)-PhO), 157.1
(C(1)-PhO). Anal. Calcd for C16H25NO: C, 77.68; H, 10.19.
Found: C, 77.57; H, 10.02.
[{2-(C H 2 N Me 2 )-6-P h -C 6 H 3 O }2 Al2 Me 3 ][Me B (C 6 F 5 )3 ]
([3a ][MeB(C6F 5)3]). In a glovebox, equimolar amounts of {6-
(CH2NMe2)-2-Ph-C6H3O}AlMe2 (2a ) (90.0 mg, 0.318 mmol) and
B(C6F5)3 (81.6 mg, 0.159 mmol) were added to a sample vial
and dissolved in 1 mL of CH2Cl2. The resulting colorless
solution was stirred for 1 h at room temperature and then
evaporated to dryness to yield a colorless foam. Trituration
with cold pentane provoked the precipitation of a colorless
solid. The mixture was filtered through a glass frit and the
solid residue dried under vacuum to afford pure [3a ][MeB-
(C6F5)3] as a colorless solid (131 mg, 76% yield). Complete
assignments of the 1H and 13C NMR resonances of 3a + were
possible using a combination of HMQC and HMBC 2D NMR
techniques, and these data are listed below.
{2-(CH2NMe2)-6-R-C6H3O}AlMe2 (2a , R ) P h ; 2b, R )
tBu ), {2-(CH 2NC4H 8)-6-tBu -C6H 3O}AlMe2 (2c), a n d {2-
(CH2NC5H10)-6-tBu -C6H3O}AlMe2 (2d ). In a glovebox, a
pentane solution (5 mL) of the appropriate aminophenol ligand
1a -d (4.40 mmol) precooled to - 40 °C was slowly added via
a pipet to a 20 mL vial containing a pentane solution (5 mL)
of AlMe3 (317 mg, 4.40 mmol), also precooled to - 40 °C. With
a loosely capped vial to allow methane escape, the reaction
mixture was warmed to room temperature and stirred for 2
h. The obtained white suspension was then evaporated to yield
a colorless solid as a crude product. Recrystallization of this
solid from a 10/1 pentane/Et2O mixture at -40 °C afforded in
all cases pure aluminum dimethyl complexes 2a -d as colorless
solids (2a , 87% yield; 2b, 75% yield; 2c, 70% yield; 2d , 81%
yield).
Da ta for 3a +. 1H NMR (400 MHz, CD2Cl2, 35 °C):23 δ -1.06
(s, 3H, AlMe), -0.89 (s, 3H, AlMe′), -0.83 (s, 3H, AlMe′), 1.43
(s, 3H, NMe′), 1.58 (s, 3H, NMe′), 2.18 (s, 3H, NMe), 2.21 (s,
2
2
3H, NMe), 3.21 (d, J HH ) 13 Hz, 1H, PhCH2), 3.44 (d, J HH
)
2
14 Hz, 1H, PhCH′2), 4.05 (d, J HH ) 13 Hz, 1H, PhCH2), 4.10
(d, J HH ) 14.1 Hz, 1H, PhCH′2), 6.92 (t, J HH ) 8.1 Hz, 1H,
2
3
2
2
H(4)-PhO), 7.00 (dd, J HH ) 7.9 Hz, J HH ) 2 Hz, 1H,
H(3)-PhO), 7.31-7.36 (m, 3H, H′(3)-PhO and H(2)- and
H(6)-Ph), 7.39-7.44 (m, 3H, H′(4)-PhO and H′(2)- and
H′(6)-Ph), 7.48-7.57 (m, 8H, Ph and PhO). 13C{1H} NMR (100
MHz, CD2Cl2): δ -10.6 (AlMe), -10.3 (AlMe′), -9.8 (AlMe′),
43.0 (NMe′), 45.4 (NMe), 46.5 (NMe′), 46.7 (NMe), 60.8
(PhC′H2), 63.4 (PhCH2), 119.3 (C(2)-PhO), 120.0 (C(4)-PhO),
125.7 (C′(2)-PhO), 127.1 (C(2)- and C(6)-Ph), 127.5 (C′(4)-
PhO), 128.2 (C′(2)- and C′(6)-Ph), 129.2 (C(6)-PhO), 129.4
(C(3)- and C(5)-Ph), 129 5 (C′(3)- and C′(5)-Ph), 129.6
Da ta for 2a . 1H NMR (400 MHz, C6D6): δ -0.59 (s, 6H,
AlMe2), 1.56 (s, 6H, NMe2), 3.03 (s, 2H, PhCH2), 6.64 (dd, 3J H,H
4
3
) 7.0 Hz, J H,H ) 1.7 Hz, 1H, H(3)-PhO), 6.79 (t, J H,H ) 7.0
3
Hz, 1H, H(4)-PhO), 7.15 (t, J H,H ) 8.0 Hz, 1H, H(4)-Ph),
7.31(t, 3J H,H ) 7.9 Hz, 2H, H(2)- and H(6)-Ph), 7.47 (dd, 3J H,H
3
3
) 7.2 Hz, J H,H ) 1.6 Hz, 1H, H(5)-PhO), 7.91 (dd, J H,H ) 8
Hz, 4J H,H ) 2 Hz, 2H, H(3)- and H(5)-Ph). 13C{1H} NMR (100
MHz, C6D6): δ -11.2 (AlMe2), 44.5 (NMe2), 62.5 (PhCH2), 117.5
(C(4)-PhO), 121.8 (C(2)-PhO), 126.7 (C(6)-PhO), 129.0 (C(3)-
PhO), 129.9 (C(4)- and C(6)-Ph), 131.9 (C(5)-PhO), 132.0
(C(3)- and C(5)-Ph), 140.2 (C(1)-Ph), 157.4 (C(1)-PhO).
Anal. Calcd for C17H12AlNO: C, 72.06; H, 7.83. Found: C,
71.83;H, 8.09.
(23) The 1H NMR spectrum of 3a + at room temperature is almost
identical with that at 35 °C, except that it contains two AlMe signals
in a 2/1 ratio versus three AlMe resonances in a 1/1/1 ratio at 35 °C,
as expected for the C1-symmetric 3a +. We assumed that two AlMe
resonances for 3a + have coincidentally the same chemical shift at room
temperature.
Da ta for 2b. 1H NMR (400 MHz, C6D6): δ -0.50 (s, 6H,
AlMe2), 1.54 (s, 6H, NMe2), 1.65 (s, 9H, tBu), 3.02 (s, 2H,

3740 Organometallics, Vol. 22, No. 18, 2003
Dagorne et al.
2
(C′(4)-Ph), 131.2 (C(3)-PhO), 131.3 (C(5)-PhO), 132.4
(C′(3)-PhO), 134.8 (C′(5)-PhO), 135.5 (C′(6)-PhO), 137.2
(C(1)-Ph), 138.6 (C′(1)-Ph), 146.9 (C′(1)-PhO), 153.4 (C(1)-
PhO). Anal. Calcd for C52H44Al2BF15N2O2: C, 57.89; H, 4.12.
Found: C, 57.51;H, 4.02.
3.20 (m, 6H, H(R)-N and H′(R)-N), 3.12 (d, J HH ) 14 Hz,
1H, PhCH2), 3.34 (d, 2J HH ) 14 Hz, 1H, PhCH′2), 3.41 (d, 2J HH
2
) 14, 1H, PhCH2), 3.50 (m, 1H, H(R)-N), 4.93 (d, J HH ) 14
Hz, 1H, PhCH′2), 6.78 (broad d, 2H, H(3) and H(4)-PhO), 7.16
3
4
(dd, J HH ) 8 Hz, J HH ) 2, H′(3)-PhO), 7.34 (m, 1H, H′(4)-
3
[{2-(CH2NMe2)-6-tBu -C6H3O}2Al2Me3][MeB(C6F 5)3] ([3b/
3b′][MeB(C6F5)3]). In a glovebox, {6-(CH2NMe2)-2-tBu-C6H3O}-
AlMe2 (2b; 150.0 mg, 0.570 mmol) and B(C6F5)3 (81.6 mg, 0.285
mmol) were added to a sample vial and dissolved in 1 mL of
CH2Cl2. The resulting colorless solution was stirred for 15 min
at room temperature and was evaporated to dryness to yield
a colorless foam. Trituration with cold pentane followed by
filtration through a glass frit of the precipitated solid afforded,
after drying under vacuum, a pure 1/1 mixture of [3b][MeB-
(C6F5)3] and [3b′][MeB(C6F5)3] as a colorless solid (190 mg, 81%
yield). Anal. Calcd for C48H52Al2BF15N2O2: C, 55.50; H, 4.82.
PhO), 7.39 (m, 2H, H′(3)- and H(5)-PhO), 7.74 (dd, J HH ) 8
Hz, J HH ) 2 Hz, 1H, H′(5)-Ph). 13C{1H} NMR (100 MHz,
4
CD2Cl2): δ -11.5 (AlMe), -9.72 (AlMe′), -9.71 (AlMe′), 20.2
(C(â)-N), 21.0 (C(â)-N), 21.1 (C′(â)-N), 22.0 (C′(â)-N), 29.3
(C(CH3)3), 32.9 (C(C′H3)3), 34.4 (C(CH3)3), 36.6 (C′(CH3)3), 52.0
(C(R)-N), 55.0 (C′(R)-N), 55.8 (C′(R)-N), 56.8 (C(â)-N), 57.2
(PhC′H2), 58.1 (PhCH2), 119.5 (C(4)-PhO), 120.7 (C(2)-PhO),
127.5 (C′(2)-PhO), 128.1 (C′(4)-PhO), 128.3 (C(3)-PhO),
128.7 (C(5)-PhO), 130.2 (C′(3)-PhO), 134.2 (C′(5)-PhO),
139.5 (C(6)-PhO), 142.3 (C′(6)-PhO), 146.1 (C′(1)-PhO),
154.2 (C(1)-PhO).
1
Da ta for 3c′+ (Min or Isom er , 25%). H NMR (400 MHz,
CD2Cl2): δ -0.97 (s, 3H, AlMe), -0.78 (s, 3H, AlMe′), -0.19
1
Found: C, 55.77; H, 5.07. Complete assignments of the H and
13C NMR resonances of 3b+ and 3b′+ were possible using a
combination of HMQC and HMBC 2D NMR techniques, and
these data are listed below.
t
t
(s, 3H, AlMe′), 1.38 (s, 9H, Bu), 1.47 (s, 9H, Bu′), 1.70-2.20
(m, 7H, H(â)-N and H′(â)-N), 2.25 (m, 1H, H′(â)-N), 2.55-
3.20 (m, 6H, H(R)-N and H′(R)-N), 3.45-3.55 (m, 4H,
Da ta for 3b+. 1H NMR (400 MHz, CD2Cl2): δ -0.71 (s, 3H,
AlMe′), -0.29 (s, 3H, AlMe), -0.09 (s, 3H, AlMe′), 1.45 (s, 9H,
2
2H(R)-N and 1PhCH2), 3.56 (d, J HH ) 14 Hz, 1H, 1PhCH′2),
4.36 (d, 2J HH ) 14 Hz, 1H, PhCH2), 5.53 (d, 2J HH ) 14 Hz, 1H,
t
tBu), 1.52 (s, 9H, Bu′), 2.18 (s, 3H, NMe), 2.19 (s, 3H, NMe′),
PhCH′2), 6.77 (m, 1H, H(4)-PhO), 6.84 (dd, 3J HH ) 8 Hz, 4J HH
2
2.30 (s, 3H, NMe), 2.76 (s, 3H, NMe′), 3.05 (d, J HH ) 14 Hz,
3
4
2
2
) 2 Hz, 1H, H(3)-PhO), 6.98 (dd, J HH ) 8 Hz, J HH ) 2 Hz,
1H, PhCH2), 3.28 (d, J HH )14 Hz, 1H, PhCH′2), 3.64 (d, J HH
3
4
2
1H, H′(3)-PhO), 7.24 (dd, 1H, J HH ) 8 Hz, J HH ) 2 Hz,
) 14, 1H, PhCH2), 4.84 (d, J HH ) 14 Hz, 1H, PhCH′2), 6.82
3
3
H(5)-PhO), 7.39 (m, 1H, H′(4)-PhO), 7.68 (dd, J HH ) 8 Hz,
(broad d, 2H, H(3)- and H(4)-PhO), 7.21 (dd, J HH ) 8 Hz,
4J HH ) 2 Hz, 1H, H′(5)-Ph). 13C{1H} NMR (100 MHz, CD2-
Cl2): δ -12.1 (AlMe), -10.4 (AlMe′), -8.6 (AlMe′), 20.9 (C(â)-
N), 21.1 (C(â)-N), 21.8 (C′(â)-N), 22.6 (C′(â)-N), 29.0 (C(CH3)3),
32.93 (C(C′H3)3), 34.2 (C(CH3)3), 36.5 (C′(CH3)3), 54.6 (C(R)-
N), 55.7 (C′(R)-N), 56.2 (C′(R)-N), 57.4 (C(â)-N), 57.9 (PhC′H2),
59.6 (PhCH2), 119.9 (C(4)-PhO), 121.9 (C(2)-PhO), 126.9
(C′(2)-PhO), 127.6 (C′(4)-PhO), 128.3 (C(3)-PhO), 129.0
(C(5)-PhO), 130.0 (C′(3)-PhO), 134.1 (C′(5)-PhO), 139.4
(C(6)-PhO), 141.7 (C′(6)-PhO), 146.7 (C′(1)-PhO), 155.3
(C(1)-PhO).
4J HH ) 2, H′(3)-PhO), 7.36-7.42 (m, 2H, H(5) and H′(4)-PhO),
7.76 (dd, J HH ) 8 Hz, J HH ) 2 Hz, 1H, H′(5)-Ph). 13C{1H}
NMR (100 MHz, CD2Cl2): δ -12.1 (AlMe), -9.8 (AlMe′), -9.5
(AlMe′), 29.4 (C(CH3)3), 32.9 (C(C′H3)3), 34.4 (C(CH3)3), 36.6
(C′(CH3)3), 44.8 (NMe), 46.8 (NMe′), 47.3 (NMe), 48.1 (NMe′),
62.1 (PhC′H2), 63.1 (PhCH2), 119.8 (C(4)-PhO), 120.33
(C(2)-PhO), 127.3 (C′(2)-PhO), 127.5 (C′(4)-PhO), 128.2
(C(3)-PhO), 129.2 (C(5)-PhO), 131.0 (C′(3)-PhO), 134.5
(C′(5)-PhO), 139.1 (C(6)-PhO), 142.4 (C′(6)-PhO), 146.0
(C′(1)-PhO), 154.0 (C(1)-PhO).
3
4
Da ta for 3b′+. 1H NMR (400 MHz, CD2Cl2): δ -1.00 (s,
3H, AlMe), -0.79 (s, 3H, AlMe′), -0.17 (s, 3H, AlMe′), 1.35 (s,
9H, Bu), 1.51 (s, 9H, Bu′), 2.33 (s, 3H, NMe′), 2.48 (s, 3H,
Da t a for 3d + (Ma jor Isom er , 75%). 1H NMR (400
MHz, CD2Cl2): δ -0.70 (s, 3H, AlMe′), -0.25 (s, 3H, AlMe),
-0.06 (s, 3H, AlMe′), 1.22-1.96 (m, 12H, H(â)-N, H′(â)-N,
t
t
2
t
t
NMe), 2.80 (s, 3H, NMe′), 2.97 (s, 3H, NMe), 3.34 (d, J HH
)
H(γ)-N, and H′(γ)-N), 1.44 (s, 9H, Bu), 1.50 (s, 9H, Bu′),
2.15-2.33 (m, 2H, H(R)-N), 2.45 (broad d, 1H, H′(R)-N),
2
14 Hz, 1H, PhCH2), 3.42 (d, J HH ) 14 Hz, 1H, PhCH′2), 4.68
2
2
2
(d, J HH ) 14 Hz, 1H, PhCH2), 5.53 (d, J HH ) 14 Hz, 1H,
2.61-2.77 (m, 3H, H(R)-N and H′(R)-N), 3.12 (dt, 1H, J HH
3
2
PhCH′2), 6.90 (t, 1H, J HH ) 8 Hz, H(4)-PhO), 7.04 (dd, 1H,
) 13 Hz, J HH ) 4 Hz, H′(R)-N), 3.28 (d, J HH ) 14 Hz, 1H,
3J HH ) 7 Hz, J HH ) 2 Hz, H(3)-PhO), 7.28 (dd, J HH ) 8 Hz,
4
3
2
PhCH2), 3.44 (d, J HH ) 14 Hz, 1H, PhCH′2), 3.56 (broad m,
4J HH ) 2 Hz, 1H, H′(3)-PhO), 7.36-7.42 (m, 2H, H(5)- and
2
2
1H, J HH ) 13 Hz, H′(R)-N), 3.92 (d, J HH ) 14 Hz, 1H,
3
4
2
3
H′(4)-PhO), 7.76 (dd, J HH ) 8 Hz, J HH ) 2 Hz, 1H, H′(5)-
Ph). 13C{1H} NMR (100 MHz, CD2Cl2): δ -13.1 (AlMe), -10.2
(AlMe′), -7.7 (AlMe′), 29.2 (C(CH3)3), 33.0 (C(C′H3)3), 34.2
(C(CH3)3), 36.5 (C′(CH3)3), 46.1 (NMe′), 46.9 (NMe), 48.2 (NMe),
48.4 (NMe′), 61.5 (PhC′H2), 65.0 (PhCH2), 120.32 (C(4)-PhO),
121.6 (C(2)-PhO), 126.8 (C′(2)-PhO), 127.7 (C′(4)-PhO),
128.5 (C(3)-PhO), 128.9 (C(5)-PhO), 130.8 (C′(3)-PhO), 134.2
(C′(5)-PhO), 139.4 (C(6)-PhO), 141.9 (C′(6)-PhO), 146.9
(C′(1)-PhO), 154.7 (C(1)-PhO). Anal. Calcd for C48H52Al2-
BF15N2O2: C, 55.50; H, 4.82. Found: C, 54.77; H, 5.07.
[{2-(CH2NC4H8)-6-tBu -C6H3O}2Al2Me3][MeB(C6F 5)3] ([3c/
3c′][MeB(C6F 5)3]) a n d [{2-(CH2NC5H 10)-6-tBu -C6H 3O}2-
Al2Me3][MeB(C6F 5)3] ([3d /3d ′][MeB(C6F 5)3]). Compounds
[3c/3c′][MeB(C6F5)3] and [3d /3d ′][MeB(C6F5)3] were obtained
by following the same procedure and using the same quantities
as those for [3b/3b′][MeB(C6F5)3] and were obtained in a 3/1
ratio, respectively, in 81% and 75% overall yields. Complete
assignments of the 1H and 13C NMR resonances of 3c+/3c′+
and 3d +/3d ′+ were also possible using a combination of HMQC
and HMBC 2D-NMR techniques, and these data are listed
below.
PhCH2), 4.61 (d, J HH ) 14 Hz, 1H, PhCH′2), 6.82 (t, 1H, J HH
3
) 8 Hz, H(4)-PhO), 6.88 (m, 1H, H(3)-PhO), 7.17 (dd, J HH
4
3
) 8 Hz, J HH ) 2 Hz, H′(3)-PhO), 7.32 (t, 1H, J HH ) 8 Hz,
3
4
H′(4)-PhO), 7.39 (dd, 1H, J HH ) 8 Hz, J HH ) 2 Hz,
3
4
H(5)-PhO), 7.70 (dd, J HH ) 8 Hz, J HH ) 2 Hz, 1H, H′(5)-
Ph). 13C{1H} NMR (100 MHz, CD2Cl2): δ -11.0 (AlMe), -8.7
(AlMe′), -8.51 (AlMe′), 16.7 (C(γ)-N), 16.9 (C′(γ)-N), 21.7
(C′(â)-N), 21.8 (C(â)-N), 21.9 (C′(â)-N), 22.1 (C(â)-N), 29.4
(C(CH3)3), 32.9 (C(C′H3)3), 34.4 (C(CH3)3), 36.5 (C′(CH3)3), 49.9
(C(R)-N), 51.6 (C′(R)-N), 51.7 (C′(R)-N), 53.0 (C(R)-N), 55.2
(PhC′H2), 56.9 (PhCH2), 119.3 (C(2)-PhO), 119.7 (C(4)-PhO),
126.3 (C′(2)-PhO), 127.4 (C′(4)-PhO), 128.3 (C(3)-PhO),
128.9 (C(5)-PhO), 131.0 (C′(3)-PhO), 134.5 (C′(5)-PhO),
139.1 (C(6)-PhO), 142.1 (C′(6)-PhO), 146.5 (C′(1)-PhO),
154.7 (C(1)-PhO).
Da ta for 3d ′+ (Min or Isom er , 25%). H NMR (400 MHz,
CD2Cl2): δ -0.87 (s, 3H, AlMe), -0.77 (s, 3H, AlMe′), -0.16
(s, 3H, AlMe′), 1.22-1.96 (m, 12H, H(â)-N, H′(â)-N,
1
t
t
H(γ)-N, and H′(γ)-N), 1.35 (s, 9H, Bu), 1.37 (s, 9H, Bu′),
2.07-2.48 (m, 3H, H(R)-N and H′(R)-N), 2.55-2.77 (m, 1H,
H(R)-N), 2.80 (m, 1H, H′(R)-N), 2.90 (m, 1H, H(R)-N), 3.06
Da ta for 3c+ (Ma jor Isom er , 75%). 1H NMR (400 MHz,
CD2Cl2): δ -0.69 (s, 3H, AlMe′), -0.33 (s, 3H, AlMe), -0.09
(m, 1H, H′(R)-N), 3.34 (m, 1H, H′(R)-N), 3.77 (d, J HH ) 14
2
2
Hz, 1H, PhCH′2), 4.21 (d, J HH ) 14 Hz, 1H, PhCH2), 4.33 (d,
t
t
(s, 3H, AlMe′), 1.47 (s, 9H, Bu), 1.51 (s, 9H, Bu′), 1.70-2.20
(m, 8H, H(â)-N and H′(â)-N), 2.45 (m, 1H, H′(R)-N), 2.55-
2J HH ) 14 Hz, 1H, PhCH2), 5.30 (d, 2J HH ) 14 Hz, 1H, PhCH′2),
6.87 (t, 1H, 3J HH ) 8 Hz, H(4)-PhO), 6.88 (m, 1H, H(3)-PhO),

Neutral and Cationic Alkylaluminum Complexes
Organometallics, Vol. 22, No. 18, 2003 3741
7.05 (dd, 3J HH ) 8 Hz, 4J HH ) 2 Hz, 1H, H′(3)-PhO), 7.25 (dd,
complete conversion of [3b/3b′][MeB(C6F5)3] to a 1/1/1 mixture
3
4
1
1H, J HH ) 8 Hz, J HH ) 2 Hz, H(5)-PhO), 7.37 (m, 1H,
of 5b, 2b, and MeB(C6F5)2 after 5 h at 75 °C in C6D6. The H,
3
4
H′(4)-PhO), 7.67 (dd, J HH ) 8 Hz, J HH ) 2 Hz, 1H, H′(5)-
Ph). 13C{1H} NMR (100 MHz, CD2Cl2): δ -11.3 (AlMe), -9.0
(AlMe′), -8.2 (AlMe′), 17.0 (C(γ)-N), 17.6 (C′(γ)-N), 21.9
(C(â)-N), 22.1 (C(â)-N), 22.5 (C′(â)-N), 22.6 (C′(â)-N), 29.2
(C(CH3)3), 33.0 (C(C′H3)3), 34.2 (C(CH3)3), 36.6 (C′(CH3)3), 50.2
(C(R)-N), 52.2 (C′(R)-N), 52.5 (C′(R)-N), 53.2 (C(R)-N), 53.5
(PhC′H2), 59.6 (PhCH2), 120.0 (C(4)-PhO), 120.5 (C(2)-PhO),
126.32 (C′(2)-PhO), 127.2 (C′(4)-PhO), 128.4 (C(3)-PhO),
128.8 (C(5)-PhO), 130.8 (C′(3)-PhO), 134.2 (C′(5)-PhO),
139.3 (C(6)-PhO), 141.9 (C′(6)-PhO), 147.1 (C′(1)-PhO),
155.2 (C(1)-PhO).
11B, 13C, and 19F NMR data for MeB(C6F5)2 matched those of
the literature.17
P r ep a r a tive-Sca le Gen er a tion of 5b. The salt compound
[3b/3b′][MeB(C6F5)3] (231.6 mg, 0.285 mmol) was charged in
a small Schlenk tube, and 10 mL of benzene was added to yield
a two-phase mixture which was heated at 70 °C for 18 h. The
volatiles were then removed under vacuum to afford crude 5b
as a yellowish powder. Recrystallization from pentane at -40
°C afforded pure 5b as a colorless powder (40 mg, 34% yield).
5
1H NMR (200 MHz, C6D6): δ -0.37 (t, J HF ) 1.4 Hz, 3H,
AlMe), 1.51 (s, 3H, NMe), 1.56 (s, 9H, CMe3), 1.59 (s, 3H, NMe),
Gen er a tion of [{2-(CH2L)-6-tBu -C6H3O}Al(Me)(THF )]-
[MeB(C6F 5)3] ([4b-d ][MeB(C6F 5)3]: 4b+, L ) NMe2; 4c+, L
) NC4H8; 4d +, L ) NC5H10). In a sample vial, [3b-d /3b′-
d ′][MeB(C6F5)3] (0.08 mmol) were dissolved in 0.75 mL of
CD2Cl2 and 1 equiv of THF (6.5 µL, 0.08 mmol) was added via
a syringe at room temperature. The vial was vigorously shaken
at room temperature, and a 1H NMR spectrum was recorded
after 10 min, showing the quantitative conversion of [3b-d /
3b′-d ′][MeB(C6F5)3] to 2b-d and [4b/4d ][MeB(C6F5)3]in a 1/1
ratio. The resulting mixture was also characterized by 13C and
19F NMR.
2.67 (d, 2J HH ) 14 Hz, 1H, PhCH2), 3.34 (d, 2J HH ) 14 Hz, 1H,
3
4
PhCH2), 6.60 (dd, J H,H ) 7.4 Hz, J H,H ) 1.6 Hz, 1H, H(3)-
3
3
PhO), 6.78 (t, J H,H ) 7.4 Hz, 1H, H(4)-PhO), 7.37 (dd, J H,H
) 7.8 Hz, J H,H ) 1.8 Hz, 1H, H(5)-PhO). 13C{1H} NMR (100
4
MHz, C6D6): δ -11.0 (AlMe), 29.7 (CMe3), 35.2 (CMe3), 43.6
(NMe2), 44.8 (NMe2), 63.0 (PhCH2), 117.9 (C(4)-PhO), 121.4
(C(2)-PhO), 128.4 (C(3)-PhO), 128.8 (C(5)-PhO), 139.5 (C(6)-
PhO), 157.9 (C(1)-PhO). 19F NMR (376 MHz, C6D6): δ -120.4
3
4
3
(dd, J FF ) 23 Hz, J FF ) 10 Hz, 2F, o-C6F5), -154.1 (t, J FF
23 Hz, 1F, p-C6F5), -162.1 (m, 2F, m-C6F5). Anal. Calcd for
20H23AlF5NO: C, 57.83; H, 5.58. Found: C, 57.50; H, 5.42.
P r op ylen e Oxid e P olym er iza tion P r oced u r e. In
)
C
Da ta for 4b+. 1H NMR (200 MHz, CD2Cl2): δ -0.33 (AlMe),
0.50 (br, 3H, MeB), 1.41 (s, 9H, tBu), 2.21 (m, 4H, H(â)-THF),
2.59 (s, 6H, NMe2), 3.89 (s, 2H, PhCH2), 4.33 (m, 4H, H(â)-
a
glovebox, the catalyst (0.38 mmol) was weighed into a Schlenk
tube equipped with a magnetic stirring bar and 2 mL of
toluene was added. The tube was taken out of the glovebox,
immersed in a temperature-controlled bath, and connected to
a N2 vacuum line. Propylene oxide (2.66 mL, 200 equiv) was
then added by syringe. The mixture was then stirred for 15
min at room temperature (or for 1 h when performed at 0 °C)
and quenched with methanol (15 mL). The resulting precipi-
tate was filtered through a glass frit and the solvent removed
under vacuum to yield an almost colorless viscous liquid, which
was analyzed by 13C NMR spectroscopy and by SEC. 13C
NMR (200 MHz, CDCl3): δ 75.8-75.0 (CH-O), 73.6-72.7
(CH2-O), 17.3-17.0 (CH3).
3
3
THF), 6.88 (t, J H,H ) 7.5 Hz, 1H, H(4)-PhO), 6.99 (dd, J H,H
4
3
) 7.4 Hz, J H,H ) 1.6, 1H, H(3)-PhO), 7.41 (dd, J H,H ) 7.8
Hz, J H,H ) 1.8 Hz, 1H, H(5)-PhO). 13C{1H} NMR (100 MHz,
4
CD2Cl2, 25 °C): δ -17.7 (AlMe), 25.1 (H(â)-THF), 28.9 (CMe3),
34.4 (CMe3), 44.1 (NMe2), 63.0 (PhCH2), 74.1 (H(R)-THF),
119.3 (C(2)-PhO), 119.9 (C(4)-PhO), 128.0 (C(3)-PhO), 128.8
(C(5)-PhO), 139.3 (C(6)-PhO), 154.5 (C(1)-PhO).
Da ta for 4c+. 1H NMR (200 MHz, CD2Cl2): δ -0.37 (AlMe),
0.50 (br, 3H, MeB), 1.41 (s, 9H, tBu), 1.80-2.10 (m, 2H, H(â)-
N), 2.18 (m, 2H, H(â)-N), 2.29 (m, 4H, H(â)-THF), 3.03 (m,
4H, H(R)-N), 3.89 (s, 2H, PhCH2), 4.46 (m, 4H, H(â)-THF),
3
3
6.85 (t, J H,H ) 7.5 Hz, 1H, H(4)-PhO), 6.95 (dd, J H,H ) 7.4
Hz, 4J H,H ) 1.6, 1H, H(3)-PhO), 7.38 (dd, 3J H,H ) 7.8 Hz, 4J H,H
) 1.8 Hz, 1H, H(5)-PhO). 13C{1H} NMR (100 MHz, CD2Cl2,
25 °C): δ -17.4 (AlMe), 21.6 (C(â)-N), 25.1 (C(â)-THF), 28.9
(CMe3), 34.4 (CMe3), 53.4 (C(R)-N), 58.5 (PhCH2), 75.5 (C(R)-
THF), 119.7 (C(4)-PhO), 120.0 (C(2)-PhO), 127.9 (C(3)-PhO),
128.7 (C(5)-PhO), 139.3 (C(6)-PhO), 154.8 (C(1)-PhO).
Da ta for 4d +. 1H NMR (200 MHz, CD2Cl2): δ -0.27 (AlMe),
0.50 (br, 3H, MeB), 1.40 (s, 9H, tBu), 1.50-1.80 (m, 4H, H(â)-
and H(γ)-N), 1.94 (br, 2H, H(â)-N), 2.30 (m, 4H, H(â)-THF),
2.73 (br, 2H, H(R)-N), 3.12 (br, 2H, H(R)-N), 4.01 (s, 2H,
X-r a y Cr ysta llogr a p h ic Stu d y. The structure determina-
tions of 2b,d , [3a ][MeB(C6F5)3], and [3b′][MeB(C6F5)3] were
carried out on a Nonius Kappa-CCD area detector diffracto-
meter using graphite-monochromated Mo KR radiation (λ )
0.710 73 Å). The cell parameters were determined from reflec-
tions taken from one set of 10 frames (1.0° steps in ψ angle),
each at 20 s exposure. The structures were solved using direct
methods (SIR97) and refined against F2 using the SHELXL97
software. The absorption was not corrected. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
generated according to the stereochemistry and refined using
a riding model in SHELXL97. All hydrogen atoms were placed
from Fourier difference maps and refined isotropically.
3
PhCH2), 4.49 (m, 4H, H(R)-THF), 6.86 (t, J H,H ) 7.5 Hz, 1H,
3
4
H(4)-PhO), 7.00 (dd, J H,H ) 7.4 Hz, J H,H ) 1.6, 1H, H(3)-
PhO), 7.38 (dd, 3J H,H ) 7.8 Hz, 4J H,H ) 1.8 Hz, 1H, H(5)-PhO).
13C{1H} NMR (100 MHz, CD2Cl2, 25 °C): δ -14.8 (AlMe), 19.8
(C(γ)-N), 21.8 (C(â)-THF), 25.1 (C(â)-THF), 29.0 (CMe3), 34.4
(CMe3), 53.3 (C(R)-N), 57.8 (PhCH2), 76.0 (C(R)-THF), 118.6
(C(2)-PhO), 119.8 (C(4)-PhO), 128.0 (C(3)-PhO), 128.7 (C(5)-
PhO), 139.0 (C(6)-PhO), 154.8 (C(1)-PhO).
Ack n ow led gm en t. We thank the Centre National
de la Recherche Scientifique (CNRS) for financial sup-
port, A. Decian (University of Strasbourg, France) for
X-ray crystallography analysis of 2d , and M.-N. Rager
(ENSCP, Paris, France) for 2D NMR assistance.
Gen er a tion of {2-(CH2NMe2)-6-tBu -4-Me-C6H2O}Al(Me)-
(C6F 5) (5b ) via Decom p osit ion of (3b /3b′)(MeB(C6F 5)3).
The salt compound [3b/3b′][MeB(C6F5)3] (83.0 mg, 0.08 mmol)
was charged in a J . Young tube, and 0.75 mL of C6D6 was
added. The NMR tube was vigorously shaken to yield a two-
phase mixture that was immersed in an oil bath at 75 °C. The
reaction was monitored by 1H NMR, which revealed the
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
crystallographic data for 2b,d , [3a ][MeB(C6F5)3], and [3b′]-
[MeB(C6F5)3]. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0302185