Reactivity of trimethylaluminum with lanthanide aryloxides: Adduct and tetramethylaluminate formation

Article abstract of DOI:10.1021/om020784k

The reaction of various highly substituted lanthanide(III) and -(II) aryloxide complexes with trimethylaluminum (TMA) was investigated. The solvent-free, π-arene-bridged dimers [Ln(OAr^iPr,H)₃]₂, derived from the ortho-iPr₂-substituted aryloxide ligand OC₆H₃ⁱPr₂-2,6, form bis-TMA adduct complexes, Ln(OAr^iPr,H)₃(AlMe₃)₂, for the metal centers yttrium, samarium, and lanthanum. Homoleptic monomeric Ln(OAr)₃, featuring a large La center and sterically bulkier ortho-tBu₂-substituted aryloxide ligands, afford the mono-TMA adducts La(OAr^tBu,R)₃(AlMe₃) (R = H, Me). The hetero-bridged moieties "Ln(μ-OAr)(μ-Me)Al" of these adduct complexes are rigid in solution, while at ambient temperature the exchange of bridging and terminal aluminum methyl groups is fast on the NMR time scale. Monomeric Ln(OAr^tBu,R)₃ (R = H, Me, tBu) of the smaller rare-earth-metal centers yttrium and lutetium react with TMA to give mono(tetramethylaluminate) complexes of the type (Ar^tBu,RO)₂Ln[(μ-Me)₂AlMe₂]. The heteroleptic Cp=supported complex (C₅Me₅)Y(OAr^tBu,H)₂ also produced a tetramethyl-aluminate complex, namely (C₅Me₅)Y(OAr^tBu,H)[(μ-Me)₂ AlMe₂], in the TMA reaction. The solvated aryloxide complexes Ln(OAr)₂(THF)_x (x = 1, 2), featuring the divalent rare-earth-metal centers ytterbium and samarium, yield the bis-TMA adduct complexes Ln[(μ-OAr^tBu,R)-(μ-Me)AlMe₂]₂. However, it was found that the generation of homoleptic hexane-insoluble [Ln(AlMe₄)₂]_n is an important reaction pathway governed by the size (oxophilicity) of the metal center (Yb ? Sm), the amount of TMA, the reaction period, and the substituents of the aryloxide ligand (OAr^iPr,H ? OAr^tBu,H > OAr^tBu,Me ? OAr^tBu,tBu). For the Ln(III) aryloxide complexes, peralkylated complexes Ln(AlMe₄)₃ were detected only in the presence of the least bulky ligand, OAr^iPr,H. Various mechanistic scenarios are depicted on the basis of the rare-earth-metal species identified, including byproducts such as [Me₂Al(μ-OAr)]₂, and of the interactivity of rare-earth alkoxide complexes with trialkylaluminum compounds known from the literature. the complexes Y(OC₆H₃ⁱPr₂-2,6) [(μ-OC₆H₃ⁱPr₂-2,6)(μ-Me) AlMe₂]₂ and Ln(OC₆H₃^tBu₂-2,6)₂[(μ- Me)₂AlMe₂] (Ln = Y, Lu) have been characterized by X-ray diffraction structure determinations.

Full text of DOI:10.1021/om020784k

Organometallics 2003, 22, 499-509
499
Rea ctivity of Tr im eth yla lu m in u m w ith La n th a n id e
Ar yloxid es: Ad d u ct a n d Tetr a m eth yla lu m in a te
F or m a tion
Andreas Fischbach,† Eberhardt Herdtweck,† Reiner Anwander,*,†
Georg Eickerling,‡ and Wolfgang Scherer‡
Anorganisch-chemisches Institut, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching, Germany, and Institut fu¨r Physik, Universita¨t Augsburg,
Universita¨tsstrasse 1, D-86159 Augsburg, Germany
Received September 18, 2002
The reaction of various highly substituted lanthanide(III) and -(II) aryloxide complexes
with trimethylaluminum (TMA) was investigated. The solvent-free, π-arene-bridged dimers
i
[Ln(OAriPr,H)3]2, derived from the ortho-iPr2-substituted aryloxide ligand OC6H3 Pr2-2,6, form
bis-TMA adduct complexes, Ln(OAriPr,H)3(AlMe3)2, for the metal centers yttrium, samarium,
and lanthanum. Homoleptic monomeric Ln(OAr)3, featuring a large La center and sterically
bulkier ortho-tBu2-substituted aryloxide ligands, afford the mono-TMA adducts La(OArtBu,R)3-
(AlMe3) (R ) H, Me). The hetero-bridged moieties “Ln(µ-OAr)(µ-Me)Al” of these adduct
complexes are rigid in solution, while at ambient temperature the exchange of bridging and
terminal aluminum methyl groups is fast on the NMR time scale. Monomeric Ln(OArtBu,R
)
3
(R ) H, Me, tBu) of the smaller rare-earth-metal centers yttrium and lutetium react with
TMA to give mono(tetramethylaluminate) complexes of the type (ArtBu,RO)2Ln[(µ-Me)2AlMe2].
The heteroleptic Cp*-supported complex (C5Me5)Y(OArtBu,H)2 also produced a tetramethyl-
aluminate complex, namely (C5Me5)Y(OArtBu,H)[(µ-Me)2AlMe2], in the TMA reaction. The
solvated aryloxide complexes Ln(OAr)2(THF)x (x ) 1, 2), featuring the divalent rare-earth-
metal centers ytterbium and samarium, yield the bis-TMA adduct complexes Ln[(µ-OArtBu,R)-
(µ-Me)AlMe2]2. However, it was found that the generation of homoleptic hexane-insoluble
[Ln(AlMe4)2]n is an important reaction pathway governed by the size (oxophilicity) of the
metal center (Yb . Sm), the amount of TMA, the reaction period, and the substituents of
the aryloxide ligand (OAriPr,H . OArtBu,H > OArtBu,Me . OArtBu,tBu). For the Ln(III) aryloxide
complexes, peralkylated complexes Ln(AlMe4)3 were detected only in the presence of the
least bulky ligand, OAriPr,H. Various mechanistic scenarios are depicted on the basis of the
rare-earth-metal species identified, including byproducts such as [Me2Al(µ-OAr)]2, and of
the interactivity of rare-earth alkoxide complexes with trialkylaluminum compounds known
i
i
from the literature. The complexes Y(OC6H3 Pr2-2,6)[(µ-OC6H3 Pr2-2,6)(µ-Me)AlMe2]2 and
t
Ln(OC6H3 Bu2-2,6)2[(µ-Me)2AlMe2] (Ln ) Y, Lu) have been characterized by X-ray diffraction
structure determinations.
In tr od u ction
tion of trialkylaluminum reagents with rare-earth-metal
alkoxide and aryloxide complexes. In the course of these
studies various Ln-Al heterobimetallic complexes have
been isolated.2-10 Table 1 summarizes structurally
Multicomponent Ziegler-Natta systems implicating
rare-earth alkoxides and organoaluminum compounds
display efficient polymerization catalysis: e.g., in diene
and styrene polymerization.1 As a consequence, there
has been considerable interest in examining the interac-
(2) Evans, W. J .; Boyle, T. J .; Ziller, J . W. J . Am. Chem. Soc. 1993,
115, 5084.
(3) Biagini, P.; Lugli, G.; Abis, L.; Millini, R. J . Organomet. Chem.
1994, 474, C16.
(4) Evans, W. J .; Boyle, T. J .; Ziller, J . W. J . Organomet. Chem. 1993,
462, 141.
(5) Gordon, J . C.; Giesbrecht, G. R.; Brady, J . T.; Clark, D. L.; Keogh,
D. W.; Scott, B. L.; Watkin, J . G. Organometallics 2001, 21, 127.
(6) Giesbrecht, G. R.; Gordon, J . C.; Brady, J . T.; Clark, D. L.; Keogh,
D. W.; Michalczyk, R.; Scott, B. L.; Watkin, J . G. Eur. J . Inorg. Chem.
2002, 723.
(7) Evans, W. J .; Ansari, M. A.; Ziller, J . W. Inorg. Chem. 1995, 34,
3079.
(8) Evans, W. J .; Ansari, M. A.; Ziller, J . W. Polyhedron 1997, 16,
3429.
(9) Evans, W. J .; Greci, M. A.; Ziller, J . W. Inorg. Chem. 1998, 37,
5221.
(10) (a) Greco, A.; Bertolini, G. J . Organomet. Chem. 1976, 113, 321.
(b) Greco, A.; Bertolini, G.; Cesca, S. Inorg. Chim. Acta 1977, 21, 245.
* To whom correspondence should be addressed. Fax: +49 89 289
13473. E-mail: reiner.anwander@ch.tum.de.
† Technische Universita¨t Mu¨nchen.
‡ Universita¨t Augsburg.
(1) (a) Comprehensive Organometallic Chemistry; Wilkinson, G.,
Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982;
Vol. 3, p 475. (b) Sinn, H.; Kaminsky, W. Adv. Organomet. Chem. 1980,
18, 99. (c) Organometallics of the f-Elements; Marks, T. J ., Fischer, R.
D., Eds.; D. Reidel: Dordrecht, Holland, 1978; Chapter 2. (d) Shen,
Z.; Ouyang, J . In Handbook on the Physics and Chemistry of Rare
Earth; Gschneidner, K. A., J r., Fleming, L., Eds.; Elsevier Science:
Amsterdam, 1987; Chapter 61. (e) Taube, R.; Sylvester, G. In Applied
Homogeneous Catalysis with Organometallic Compounds; Cornils, B.,
Herrmann, W. A., Eds.; VCH: Weinheim, Germany, 1996; Vol. 1, p
280. (f) Yasuda, H.; Ihara, E. Bull. Chem. Soc. J pn. 1997, 70, 1745.
(g) Yasuda, H. J . Polym. Sci., Part A: Polym. Chem. 2001, 39, 1955.
10.1021/om020784k CCC: $25.00 © 2003 American Chemical Society
Publication on Web 01/07/2003

500 Organometallics, Vol. 22, No. 3, 2003
Fischbach et al.
Ta ble 1. Selected Br id gin g Bon d Dista n ces (Å) of Str u ctu r a lly Ch a r a cter ized Ln -Al Heter obim eta llic
Alk yl Com p lexes
d(Ln-O)
d(Al-O)
d(Ln-C)
d(Al-C)
Ln(µ-OR)(µ-alkyl)Al(alkyl)2
2
Y[(µ-OtBu)(µ-Me)AlMe2]3
Nd[(µ-OtBu)(µ-Me)AlMe2]3
2.21(1)
2.303(7)
2.280(4)
2.254a
1.86(2)
2.69(3)
2.78(1)
2.562(6)
2.702a
2.626a
2.780a
2.638a
2.10(2)
2.05(2)
2.025(7)
2.052a
2.047a
2.047a
2.061a
3
1.871(7)
1.841(4)
1.841a
4
(C5H4SiMe3)Y[(µ-OtBu)(µ-Me)AlMe2]2
(tBuO)(THF)Y[(µ-OtBu)(µ-Me)AlMe2]2
2
5
(AriPr,HO)Sm[(µ-OAriPr,H)(µ-Me)AlMe2]2
(AriPr,HO)La[(µ-OAriPr,H)(µ-Me)AlMe2]2
2.292a
1.870a
6
2.377a
1.856a
6
(AriPr,HO)Sm[(µ-OAriPr,H)(µ-Et)AlEt2]2
2.294a
1.876a
Ln(µ-OR)2Al(alkyl)2
2.306(8)
(ArMe,HO)2(THF)2Yb[(µ-OArMe,H)2AlMe2]7
(ArMe,HO)2(THF)2Nd[(µ-OArMe,H)2AlEt2]7
1.85(1)
1.810(8)
1.843a
2.447(7)
8
Nd[(µ-OArH,Me)2AlMe2]3
2.356a
Ln(µ-OR)Al(alkyl)3
2.420(8)b
[Me3Al(µ-η2-OCH2CH2OMe)Eu
1.811(5)b
1.771(4)c
9
(µ-η2-OCH2CH2OMe)2AlMe2]2
2.548(7)c
Average value. AlMe3 unit. c AlMe2 unit.
a
b
Ch a r t 1. P h en ols Used in th e Liter a tu r e a n d in
Th is Wor k
ides, anticipating that steric factors and solubility
behavior as well as the variation of the ligand pKa value
and the metal oxidation state might markedly affect the
reaction protocol. Here we report on the reactivity of
trimethylaluminum (TMA) toward variously substituted
Ln(II) and Ln(III) aryloxide complexes.13
Resu lts a n d Discu ssion
Syn t h esis of La n t h a n id e(III) a n d La n t h a n id e-
(II) Ar yloxid es. All of the lanthanide aryloxides were
synthesized according to slightly modified literature
procedures14,15 using bis(trimethylsilyl)amide complexes
Ln[N(SiMe3)2]3 (Ln ) Y, La, Lu)16 and Ln[N(SiMe3)2]2-
(THF)2 (Ln ) Sm, Yb)17 as starting materials (eqs 1 and
2). The silylamine elimination reactions were performed
Ln[N(SiMe3)2]3 + 3HOAr f
Ln(OAr)3 + 3HN(SiMe3)2 (1)
Ln[N(SiMe3)2]2(THF)2 + 2HOAr f
Ln(OAr)2(THF)x + 2HN(SiMe3)2 (2)
characterized derivatives according to the bonding mode
of the organoaluminum moiety: that is, either Ln(µ-
OR)(µ-alkyl)Al(alkyl)2 or Ln(µ-OR)xAl(alkyl)y (x ) 1, 2;
y ) 2, 3; x + y ) 4). Interestingly, the formation of a
“peralkylated” Ln(µ-alkyl)xAl(alkyl)y fragment (x + y )
4) has not yet been fully identified in such alkoxide-
based binary systems. Note that the ternary system
Nd(OiPr)3/AlEt3/AlEt2Cl (1:10:1.5) formed crystals of
molecular composition [Al3Nd6(µ-Cl)6(µ3-Cl)6(µ-C2H5)9-
(C2H5)5(OiPr)]2, featuring a Nd(µ-Et)3AlEt moiety, only
after a period of several months.11 Moreover, the forma-
tion of rare-earth alkyl species has been postulated
for the binary systems Nd(OR)3/MgnBu2 and Nd(OR)3/
MgHex2.12
in toluene at 110 °C (Ln(III)) or n-hexane at ambient
temperature (Ln(II)), and the complexes were isolated
by evaporating the solvent in vacuo. The analytical data
are in agreement with those reported in the literature.
For the divalent lanthanide aryloxides, the amount of
coordinated tetrahydrofuran (x ) 1, 2) was determined
by elemental analysis and, in the case of the ytterbium
1
derivatives, by H NMR spectroscopy.
TMA Ad d u ct F or m a tion of Yttr iu m (III) a n d
La n th a n u m (III) Ar yloxid es. Recently, Gordon et al.
described the synthesis and structural characterization
(13) Fischbach, A.; Perdih, F.; Sirsch, P.; Scherer, W.; Anwander,
R. Organometallics 2002, 21, 4569.
(14) Lappert, M. F.; Singh, A.; Smith, R. G. Inorg. Synth. 1990, 27,
164.
Recently, we started a systematic investigation of the
alkylation capability of organoaluminum compounds
toward rare-earth complexes with O-bonded ligands
such as carboxylates, alkoxides, aryloxides, and silox-
(15) (a) Deacon, G. B.; Hitchcock, P. B.; Holmes, S. A.; Lappert, M.
F.; MacKinnon, P.; Newnham, R. H. J . Chem. Soc., Chem. Commun.
1989, 935. (b) van den Hende, J . R.; Hitchcock, P. B.; Lappert, M. F.
J . Chem. Soc., Chem. Commun. 1994, 1413. (c) Evans, W. J .; Anwan-
der, R.; Ansari, M. A.; Ziller, J . W. Inorg. Chem. 1995, 34, 5.
(16) Bradley, D. C.; Ghotra, J . S.; Hart, F. A. J . Chem. Soc., Dalton
Trans. 1973, 1021.
(17) (a) Evans, W. J .; Drummond, D. K.; Zhang, H.; Atwood, J . L.
Inorg. Chem. 1988, 27, 575. (b) Boncella, J . M.; Andersen, R. A.
Organometallics 1985, 4, 205. (c) Boncella, J . M. Ph.D. Thesis,
University of California, Berkeley, CA, 1982.
(11) Shan, C.; Lin, Y.; Ouyang, J .; Fan, Y.; Yang, G. Makromol.
Chem. 1987, 188, 629.
(12) (a) Gromada, J .; Chenal, T.; Mortreux, A.; Ziller, J . W.; Leising,
F.; Carpentier, J .-F. J . Chem. Soc., Chem. Commun. 2000, 2183. (b)
Gromada, J .; Fouga, C.; Chenal, T.; Mortreux, A.; Carpentier, J .-F.
Macromol. Chem. Phys. 2002, 3, 550. (c) Gromada, J .; Mortreux, A.;
Chenal, T.; Ziller, J . W.; Leising, F.; Carpentier, J .-F. Chem. Eur. J .
2002, 8, 3773.

Reactivity of AlMe3 with Lanthanide Aryloxides
Organometallics, Vol. 22, No. 3, 2003 501
Sch em e 1a
a
The presence of different isopropyl groups in solution as
1
shown by H NMR spectroscopy is indicated by a, b, and c.
of bis(trialkylaluminum) adducts of lanthanide aryloxide
complexes by employing 2,6-diisopropylphenoxide ligands
and the large Ln(III) centers lanthanum and samari-
um.5,6 The complexes Ln(OAriPr,H)3(AlR3)2 (R ) Me, Et)
could be isolated from the reaction of the π-arene-
bridged dimers [Ln(OAriPr,H)3]2 (Ln ) La, Sm) with at
least 4 equiv of AlR3. In the context of our Ziegler-Natta
related work we have also been investigating the
reactivity of TMA toward sterically crowded homoleptic
yttrium and lanthanum aryloxides.
F igu r e 1. Region of the 1H NMR spectrum (d8-toluene,
400 MHz) of complex 1 at various temperatures. The
solvent signal is indicated by an asterisk.
temperature. However, the last fluxional process is
suppressed at lowered temperature. Figure 1 shows that
at -80 °C decoalescence of the TMA methyl resonance
occurred into two separate signals (integral ratio: 2:1)
representing the terminal and bridging methyl groups.
Note that this decoalescence was not observed for the
larger metal centers La and Sm.5,6 The presence of
Ln‚‚‚H-C R-agostic interactions in solution, which have
been discussed for the La and Sm derivatives, is not
suggested by the relevant spectroscopic features of
In accordance with the reactivity of the ortho-iPr2-
substituted aryloxide complexes of the heavier metal
centers lanthanum and samarium, the reaction of
the corresponding yttrium compound [Y(OAriPr,H)2(µ-
OAriPr,H)]2 with 6 equiv of TMA in n-hexane yielded the
bis-TMA adduct Y(OAriPr,H)3(AlMe3)2 (1) in 46% yield
after 16 h at ambient temperature. Complex 1 could be
separated from the reaction mixture by crystallization
at -45 °C. A detailed investigation of the crude reaction
mixture of the above reaction revealed the formation
of three other products (Scheme 1). The homoleptic
(peralkylated) yttrium tetramethylaluminate Y[(µ-Me)2-
1
compound 1. Both the J C-H coupling constant of 108-
109 Hz and νCH stretching vibrations of >2900 cm-1 are
not indicative of any significant agostic bonding in
complex 1.
Recrystallization of TMA adduct 1 from saturated
n-hexane solutions yielded single crystals suitable for
an X-ray structure analysis. Its solid-state structure,
which is structurally related to those previously re-
ported for the samarium and lanthanum derivatives,
is shown in Figure 2. Selected intramolecular bond
distances and angles are presented in Table 2.
The five-coordinate yttrium center adopts a distorted-
trigonal-bipyramidal geometry, the two bridging methyl
groups occupying the apical position C37-Y-C40 angle
(156.58(6)°). The terminal and bridging Y-O bond
lengths of 2.023(1) and 2.230 Å (average), respectively,
lie in the range of yttrium alkoxide complexes such as
Cp*Y(OArtBu,H)2 (average 2.078 Å),19 (C5H4SiMe3)Y[(µ-
OtBu)(µ-Me)AlMe2]2, and Y[(µ-OtBu)(µ-Me)AlMe2]3 (Table
1). Another interesting aspect of the molecular structure
is the coordination chemistry of the bridging five-
coordinate carbon atoms, which display a distorted-
trigonal-bipyramidal geometry with one hydrogen atom
and the yttrium metal in the apical positions ( Y-C-H
) 175(1), 179(2)°). The hydrogen atoms of the bridging
methyl groups were located and refined. The Y-C(µ)
distance of 2.542 Å (average) is similar to the 2.562(6)
Å in formally seven-coordinate (C5H4SiMe3)Y[(µ-OtBu)-
(µ-Me)AlMe2]2 (Table 1).
18
AlMe2)]3 and the corresponding aryloxide mono-
exchange product [Me2Al(µ-OAriPr,H)]2 were unequivo-
cally identified by 1H NMR spectroscopy. The third
compound also contains an aryloxide ligand; however,
its full composition is still unclear.
In contrast to the lanthanum congener (two septets
in a 2:1 ratio)5,6 the ambient-temperature 1H NMR
spectrum of complex 1 shows three different septets at
3.44, 3.57, and 3.64 ppm for the isopropyl methine
protons (integral ratio 2:2:2) and six doublets for the
diastereotopic isopropyl methyl groups (integral ratio
6:6:6:6:6:6; Figure 1). On the other hand, the coordi-
nated TMA molecules show only a single proton reso-
nance at -0.29 ppm. This NMR scenario can be ascribed
to a rather rigid structure of 1 in solution. First, the
separate signal for the terminal aryloxide ligand ex-
cludes any TMA migration. Second, the two separate
signals for the bridging aryloxide ligands indicate
enhanced steric crowding at the yttrium center, which
counteracts rotation about the O-Cipso axis. Finally and
not surprisingly, the smaller bridging methyl groups
rapidly exchange with the terminal ones at ambient
(19) Schaverien, C. J .; Frijns, J . H. G.; Heeres, H. J .; van den Hende,
J . R.; Teuben, J . H.; Spek, A. L. J . Chem. Soc., Chem. Commun. 1991,
642.
(18) Evans, W. J .; Anwander, R.; Ziller, J . W. Organometallics 1995,
14, 1107.

502 Organometallics, Vol. 22, No. 3, 2003
Fischbach et al.
Sch em e 2a
a
The presence of different tert-butyl groups in solution as
1
shown by H NMR spectroscopy is indicated by a and b.
workers.5,6 For complex 2a , lowering of the temperature
to -90 °C gave a better separation of the aryloxide
signals, while an additional decoalescence of the coor-
dinated TMA into bridging and terminal methyl groups
did not occur. Proton-coupled 13C NMR spectra of
complexes 2 showed at all temperatures (+20 to -90
°C) quadruplet signals for the aluminum-bound methyl
F igu r e 2. PLATON50 drawing of the complex Y(OC6H3-
i
iPr2-2,6)[(µ-OC6H3 Pr2-2,6)(µ-Me)AlMe2]2 (1). Atoms are
represented by atomic displacement ellipsoids at the 50%
level.
1
groups with J C-H coupling constants of about 110 Hz,
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
which are similar to those reported for (AriPr,HO)La[(µ-
OAriPr,H)(µ-Me)AlMe2]2.6 Such marginally decreased
coupling constants have been associated with the pres-
ence of La‚‚‚H-C R-agostic interactions.6 However, for
complexes 2, their infrared spectra recorded as Nujol
mulls did not show any definite evidence for the pres-
ence of such agostic interactions in the solid state.
Ar yloxid e-Tetr a m eth yla lu m in a te In ter ch a n ge
in Yttr iu m (III) a n d Lu tetiu m (III) Ar yloxid es. Sur-
prisingly, the corresponding yttrium and lutetium aryl-
oxide complexes displayed quite a different reaction
behavior with TMA. Under identical reaction condi-
tionss6 equiv of TMA, 16 h, ambient temperatures
mono(tetramethylaluminate) complexes of the type
(ArtBu,RO)2Y[(µ-Me)2AlMe2] (3a , R ) H; 3b, R ) Me; 3c,
R ) tBu) and (ArtBu,RO)2Lu[(µ-Me)2AlMe2] (4a , R ) H;
4b, R ) Me) formed along with [Me2Al(µ-OArtBu,R)]2 and
MeAl(OArtBu,R)2 (Scheme 3).20,21 It is worth noting that
addition of 1 equiv of TMA did not produce a mono-TMA
adduct, in analogy to the formation of La(OArtBu,R)3-
(AlMe3) (2); instead, unreacted starting materials and
complexes 3 and 4 were identified. In the >2 equiv
reactions higher alkylated byproducts such as (ArtBu,RO)-
Ln[(µ-Me)2AlMe2]2 and even homoleptic “peralkylated”
tetramethylaluminates Ln(AlMe4)3 (5)18 could not be
detected independent of the amount of TMA (e.g., 12
equiv) and the reaction period (<4 days).
(d eg) for (Ar O)Y[(µ-OAr )(µ-Me)AlMe2]2 (1)
Y-Al1
Y-Al2
Y-O1
3.1924(5)
3.1871(6)
2.023(1)
2.231(1)
2.229(1)
2.544(2)
2.541(2)
1.409(2)
1.406(2)
O1-C1
1.368(2)
1.861(1)
1.873(1)
2.069(2)
1.954(2)
1.962(2)
2.070(2)
1.962(2)
1.955(2)
O2-Al1
O3-Al2
Al1-C37
Al1-C38
Al1-C39
Al2-C40
Al2-C41
Al2-C42
Y-O2
Y-O3
Y-C37
Y-C40
O2-C13
O3-C25
O1-Y-O2
O1-Y-O3
O2-Y-O3
O1-Y-C37
O1-Y-C40
O2-Y-C37
O2-Y-C40
O3-Y-C37
117.68(4)
118.51(4)
123.80(4)
102.07(6)
101.34(6)
74.85(5)
94.90(6)
92.63(5)
O3-Y-C40
C37-Y-C40
Y-O1-C1
Y-O2-C13
Y-O3-C25
Y-O2-Al1
Y-O3-Al2
Y-C37-H371
Y-C40-H402
75.40(6)
156.58(6)
174.3(1)
125.33(9)
129.0(1)
102.17(5)
101.64(5)
175(1)
179(2)
A similar reactivity was observed for the bulkier 2,6-
di-tert-butylphenoxide ligand OArtBu,H and its 4-methyl-
substituted derivative OArtBu,Me. However, use of an
excess of TMA (>4 equiv) in n-hexane yielded the mono-
TMA adducts La(OArtBu,R)3(AlMe3) (2) exclusively
(Scheme 2). It appears plausible that the enhanced
steric bulk of the tBu vs the iPr groups ensures the
coordination of only one TMA molecule.
Complexes 2 were isolated via crystallization from
saturated n-hexane solutions as colorless amorphous
solids in good yields (2a , 83%; 2b, 87%), which can be
redissolved in aliphatic and aromatic solvents. Elemen-
tal analysis and 1H and 13C{1H} NMR spectroscopy
confirmed the overall composition shown in Scheme 2.
Two separated sets of ArtBu,RO resonances with an
integral ratio of 2:1 were observed, although the mobil-
ity of the coordinated TMA at ambient temperature
causes a distinct broadening of the signals. This obser-
vation is in good agreement with the integrity of the
aluminum-oxygen bonds reported by Gordon and co-
The aluminate complexes 3a ,b and 4 were isolated
in moderate to good yields (55-70%) by repeated
crystallization from n-hexane solutions at -45 °C. Due
to its high solubility in aliphatic solvents, it was only
compound 3c which could not be separated from the
byproducts (characterization by NMR only). Microana-
lytical and NMR spectroscopic data are in agreement
(20) Skowron´ska-Ptasin´ska, M.; Starowieyski, K. B.; Pasynkiewicz,
S.; Carewska, M. J . Organomet. Chem. 1978, 160, 403.
(21) (a) Mehrotra, R. C.; Rai, A. K. Polyhedron 1991, 10, 1967. (b)
Healy, M. D.; Power, M. B.; Barron, A. R. Coord. Chem. Rev. 1994,
130, 63.

Reactivity of AlMe3 with Lanthanide Aryloxides
Organometallics, Vol. 22, No. 3, 2003 503
Sch em e 3
with the molecular composition of complexes 3 and 4
given in Scheme 3. The proton NMR spectra of the
yttrium complexes showed characteristic doublets (2J Y-H
) 3.7 Hz) for the AlMe4 moieties at 0.02 (3a ), 0.04 (3b),
and 0.03 ppm (3c), respectively. A variable-temperature
NMR study revealed that a further separation of these
signals into bridging and terminal methyl groups did
not occur for complex 3a , even at -90 °C. However, for
the lutetium complex 4a , the sharp singlet of the AlMe4
moiety at 0.30 ppm broadens into the baseline at -90
°C, indicating reduced exchange of the bridging and
terminal methyl groups at the smaller metal center
(enhanced steric crowding!). The low-temperature NMR
experiments also exclude the presence of the monomer-
dimer equilibrium 2(ArO)2Ln[(µ-Me)2AlMe2] a (ArO)2-
Ln[(µ-Me)AlMe2(µ-Me)]2Ln(OAr)2. Such dimerization
reactions are a common feature of structurally related
lanthanidocene aluminate complexes of the type Cp*2Ln-
(AlMe4).22-24 The formation of a Ln-bonded tetramethyl-
aluminate moiety in the solid state could be unequivo-
cally proven by the X-ray structure analyses of com-
plexes 3a and 4a . Single crystals were obtained by
slowly cooling warm n-hexane solutions. The solid-state
structure of 4a is shown in Figure 3, and relevant
intramolecular bond lengths and angles are presented
in Table 3. Both tetramethylaluminates are isotypes and
crystallize in the orthorhombic space group Pbca. The
metal center is four-coordinated by two aryloxide oxygen
atoms and one η2-coordinating tetramethylaluminate
ligand, resulting in a distorted-tetrahedral geometry.
The molecular structure of the approximate C2-sym-
metric complexes 3a and 4a resembles those of struc-
turally characterized lanthanidocene complexes of the
type Cp2Ln(µ-Me)2AlMe2, featuring a different ancillary
ligand set.25
F igu r e 3. PLATON50 drawing of the complex Lu(OC6H3-
tBu2-2,6)2[(µ-Me)2AlMe2] (4a ). Heavy atoms are represented
by atomic displacement ellipsoids at the 50% level.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (Ar tBu ,HO)2Y[(µ-Me)2AlMe2] (3a ) a n d
(Ar tBu ,HO)2Lu [(µ-Me)2AlMe2] (4a )
3a (Ln ) Y)
4a (Ln ) Lu)
Ln-Al
Ln-O1
Ln-O2
Ln-C3
Ln-C4
Al-C3
Al-C4
Al-C1
Al-C2
3.067(1)
2.023(2)
2.032(2)
2.500(4)
2.494(3)
2.101(3)
2.086(4)
1.964(4)
1.964(4)
3.000(1)
2.006(3)
1.999(3)
2.435(4)
2.425(4)
2.105(4)
2.101(4)
1.966(6)
1.965(5)
Ln-O1-C5
Ln-O2-C19
O1-Ln-O2
C3-Ln-C4
C3-Al-C4
C1-Al-C2
176.1(2)
178.2(2)
114.55(8)
85.3(1)
107.8(1)
117.0(2)
178.6(2)
177.4(2)
114.4(1)
88.03(1)
106.8(2)
116.9(2)
the five-coordinate complexes Lu(OAriPr,H)3(THF)2 and
Lu[calix[4]arene(OBenz)2][N(SiHMe2)2] feature Lu-O-
(aryloxide) bond lengths of 2.043 and 2.011 Å (average),
respectively.27,28 The bond distances of the symmetric
(µ-Me)2AlMe2 unit in 3a are comparable to those of other
hetero- and homoleptic tetramethylaluminates. The
Y-C(µ) distance of 2.497 Å (average) is similar to those
in eight-coordinate Cp2Y(µ-Me)2AlMe2 (2.58(4) Å)29 and
six-coordinate Y[(µ-Me)2AlMe2]3 (2.505(7)-2.514(8) Å).18
For comparison, the Lu-C(µ) bond lengths in homome-
tallic asymmetrically bridged Cp*2Lu(µ-Me)LuCp*2Me
featuring seven- or eight-coordinate lutetium centers are
2.440(9) and 2.756(9) Å, respectively.30 The slightly
longer Y-Al distance of 3.067(1) Å (3a ) in comparison
to the 3.000(1) Å in 4a reflects the larger size of the
yttrium center. As reported earlier for the homoleptic
The Ln-O bond distances of 2.023(2) and 2.032(2) Å
(3a ) and 1.999(3) and 2.006(3) Å (4a ) are slightly longer
than those reported for the homoleptic aryloxide Y(O-
ArtBu,H)3 (average 2.00 Å),26 which is in accord with their
formally higher coordination number. For comparison,
(22) den Haan, K. H.; Wielstra, Y.; Eshuis, J . J . W.; Teuben, J . H.
J . Organomet. Chem. 1987, 323, 181.
(23) Busch, M. A.; Harlow, R.; Watson, P. L. Inorg. Chim. Acta 1987,
140, 15.
(24) Evans, W. J .; Chamberlain, L. R.; Ulibarri, T. A.; Ziller, J . W.
J . Am. Chem. Soc. 1987, 109, 7209.
(25) For example, see: Holton, J .; Lappert, M. F.; Ballard, D. G.
H.; Pearce, R.; Atwood, J . L.; Hunter, W. E. J . Chem. Soc., Dalton
Trans. 1979, 45.
(27) Barnhart, D. M.; Clark, D. L.; Gordon, J . C.; Huffman, J . C.;
Vincent, R. L.; Watkin, J . G.; Zwick, B. D. Inorg. Chem. 1994, 33, 3487.
(28) Estler, F.; Herdtweck, E.; Anwander, R. J . Chem. Soc., Dalton
Trans. 2002, 3088.
(26) Hitchcock, P. B.; Lappert, M. F.; Smith, R. G. Inorg. Chim. Acta
1987, 139, 183.
(29) Scollary, G. R. Aust. J . Chem. 1978, 31, 411.
(30) Watson, P. L.; Parshall, G. W. Acc. Chem. Res. 1985, 18, 51.

504 Organometallics, Vol. 22, No. 3, 2003
Fischbach et al.
Sch em e 4. F or m a tion of TMA Ad d u cts (1 a n d 2) a n d Tetr a m eth yla lu m in a tes (3-5) fr om La n th a n id e(III)
Ar yloxid esa
a
Fully characterized complexes are shown in boxes (I1: a-c indicate different reaction pathways).
aryloxides,26 the Ln-O-Cipso angles of 176.1(2)/178.2(2)°
(3a ) and 177.4(2)/178.6(2)° (4a ) are almost linear.
The formation of tetramethylaluminate units using
homoleptic lanthanide aryloxides as starting materials
has not been observed so far. In the case of the even
less bulky 2,6-dimethylphenoxides Ln(OArMe,H)3(THF)x
(Ln ) Y, Yb), Evans et al. have been able to isolate bis-
(aryloxide)-bridged systems of the type (ArMe,HO)2(THF)2-
Ln[(µ-OArMe,H)2AlR2].7 Although the formation of fur-
ther alkylated products was theorized, none could be
isolated or characterized by spectroscopic methods.
Labile alkylation products were also discussed by Gor-
don et al., resulting from the system Ln(OAriPr,H)3(AlR3)2
(R ) Me, Et) via elimination of [R2Al(µ-OAriPr,H)]2.6
From the several products obtained from these TMA
addition reactions, it appears that once the sterically
crowded lanthanide(III) aryloxides start to react, several
pathways are possible. Factors such as the size of the
metal center, the steric bulk of the aryloxide ligand, and,
hence, complex agglomeration govern the mechanistic
scenario proposed in Scheme 4. Initial attack of TMA,
which is a dimer in hexane solution, onto the tris-
(aryloxide) complexes Ln(OAr)3 appears to be the rate-
determining step. Although coordination of additional
donor molecules to formally three-coordinated homo-
leptic aryloxide complexes carrying the bulkiest aryl-
oxide ligands has been structurally evidenced in, e.g.,
Sm(OArtBu,Me)3(THF),31 Yb(OArtBu,tBu)3(THF),32 and Ce-
(OArtBu,H)3(CNtBu)2,33 formation of intermediate I1 should
be impeded for steric reasons. For ortho-tBu2-substi-
tuted aryloxide ligands and large Ln metal centers such
as lanthanum, elimination of “AlMe3” from I1 (route a
in Scheme 4) yields the stable mono-TMA adduct 2
featuring truly bridging alkyl and aryloxide ligands
(Table 2). Alternatively, complex 2 may be obtained by
attack of monomeric “AlMe3” onto Ln(OAr)3. Note that
TMA adducts are not produced from homoleptic Ln-
[N(SiMe3)2]3 for steric reasons.34 In the presence of the
less bulky ortho-iPr2-substituted aryloxide ligands, a
bis-TMA adduct (1) is preferentially formed. This can
occur via either intramolecular ligand reorientation in
I1 (route b in Scheme 4) or addition of another “AlMe3”
monomer to a mono-TMA adduct I2.
The formation of mono(tetramethylaluminate) com-
plexes 3 and 4 via aryloxide-alkyl interchange is the
predominant pathway for smaller Ln metal centers
carrying ortho-tBu2-substituted aryloxide ligands. A
possible associative mechanism requires the formation
of intermediate I1 followed by cleavage of Me2AlOAr
(route c in Scheme 4). The aluminum monoaryloxide
6,35,36
may either dimerize to [Me2Al(µ-OAr)]2
or dispro-
(32) Deacon, G. B.; Feng, T.; Nickel, S.; Ogden, M. I.; White, A. H.
Aust. J . Chem. 1992, 45, 671.
(33) Stecher, H.; Sen, A.; Rheingold, A. L. Inorg. Chem. 1988, 27,
1130.
(34) Anwander, R.; Runte, O.; Eppinger, J .; Gerstberger, G.;
Herdtweck, E.; Spiegler, M. J . Chem. Soc., Dalton Trans. 1998, 847.
(35) Firth, A. V.; Stewart, J . C.; Hoskin, A. J .; Stephan, D. W. J .
Organomet. Chem. 1999, 591, 185.
(31) Qi, G.; Lin, Y.; Hu, J .; Shen, Q. Polyhedron 1995, 14, 413.

Reactivity of AlMe3 with Lanthanide Aryloxides
Organometallics, Vol. 22, No. 3, 2003 505
Sch em e 5
There is a distinct analogy to the reaction of (C5Me5)Y-
(OArtBu,H)2 with 1 equiv of methyllithium, previously
reported by Schaverien.41 The methyl-bridged hetero-
leptic aryloxide [Y(C5Me5)(OArtBu,H)(µ-Me)]2, which was
produced in the methyllithium reaction, could be cleaved
by addition of tetrahydrofuran to yield the monomeric
complex (C5Me5)(ArtBu,HO)YMe(THF)2 (7), featuring a
terminal methyl group (1H NMR δ -0.33 ppm (d, 2J Y-H
1
) 2.3 Hz); 13C NMR δ 22.8 ppm (d, J Y-C ) 60 Hz)).
Complex 7 was also formed via a donor-induced cleavage
of complex 6, as shown by the NMR spectrum of 6
recorded in d8-THF. The importance of the type of OR
ligand for the outcome of the TMA-mediated alkylation
is evident from the reaction of [Cp′Y(OR)2]2 (Cp′ ) C5H4-
SiMe3, R ) tBu) with TMA.4 In this reaction, the bis-
TMA adduct Cp′Y[(µ-OR)(µ-Me)AlMe2]2 was isolated in
hexane solution after 8 h in high yield (90%).
Rea ction of TMA w ith Ytter biu m (II) a n d Sa -
m a r iu m (II) Ar yloxid es. Although the reactivity of
TMA toward various divalent ytterbium and samarium
compounds has been examined,42 aryloxide derivatives
apparently escaped that attention. For example, YbCp*2-
(THF)2 simply forms the organoaluminum adduct com-
plex Cp*2Yb(µ-Et)AlEt2(THF),43 while samarocene(II)
complexes reduce AlR3 compounds to yield samarocene-
(III) tetraalkylaluminate complexes.24,44 Depending on
the amount of AlR3 reagent, silylamide complexes of
Yb(II) and Sm(II) form bis-AlR3 adducts or bis(tetra-
portionate to TMA and monomeric MeAl(OAr)2,37 coun-
teracting reassociation with I1. However, not only for
steric reasons do we favor a dissociative mechanism
involving a mono-TMA adduct I2 as an intermediate.
For smaller rare-earth-metal centers, I2 still displays
steric oversaturation forcing Me2AlOAr dissociation and
generation of I3. This is in accord with the decreased
oxophilicity of the smaller rare-earth-metal centers
(disruption energy of metal monooxides, D0(MO): La >
Y > Lu . Al).38 Finally, sterically unsaturated I3 is
converted to heteroleptic tetramethylaluminates 3 and
4. This may also proceed via the methyl-bridged inter-
mediate I4. Such a sterically induced tetramethylalu-
minate formation is corroborated by (i) the kinetic
lability of Ln-O(alkoxide/aryloxide) bonds,39,40 (ii) the
isolation of I2 as the lanthanum derivative 2, and (iii)
the exclusive generation of mono(tetramethylaluminate)
adduct and starting material from an equimolar reac-
tion with Ln(OAr)3:TMA ) 1:1. The kinetic control of
this alkylation reaction is also evident from the forma-
tion of peralkylated species Ln[(µ-Me)2AlMe2]3 (5) in the
presence of sterically less encumbered aryloxide ligands
OAriPr,H as well as from the reaction behavior of Ln(II)
aryloxides discussed in the following. The formation of
homoleptic 5 probably proceeds via a series of other
intermediates starting with I5.
alkylaluminate) complexes of composition Ln[N(SiMe3)2]2-
17b
(AlMe3)2
and [Ln(AlR4)2]n,45 respectively.
In the present study, we found that excess TMA (6
equiv) reacts (16 h, ambient temperature) with aryl-
oxides Ln(OArtBu,R)2(THF)x (x ) 1, 2) to afford the
bis-TMA adducts Ln[(µ-OArtBu,R)(µ-Me)AlMe2]2 in good
yields (Scheme 6). Complexes 8-10 are quite soluble
in aromatic solvents and can be crystallized from
n-hexane/toluene mixtures as yellow to orange (Yb) and
brown to grayish (Sm) solids. Depending on the type of
aryloxide substituent at the 4-position (H vs Me vs tBu),
varying amounts of the peralkylated Yb(II) aluminate
[Yb(AlMe4)2]n (11a )45 could be separated off and identi-
fied in the synthesis of 8a (23%) and 8b (2%) as the only
lanthanide-containing byproduct. To investigate the
correlation between excess TMA, (prolonged) reaction
time, and Yb(II) aluminate formation, the reaction of
Yb(OArtBu,H)2(THF)2 with TMA was examined in greater
detail. By using a 6-fold excess of TMA, 40% of insoluble
Yb(II) aluminate 11a was obtained after 96 h at ambient
temperature via 8a , while a 24 equiv reaction produced
53% of 11a within 16 h. For the most soluble complex
8c and the corresponding Sm(II) compounds peralkyl-
ation did not occur within 16 h at ambient temperature.
Interestingly, treatment of the least soluble precursor
system, Yb(OArPh,H)2(THF), with TMA also affords the
bis-TMA adducts 10 exclusively.
Alk yla tion of Cp *-Su p p or ted Heter olep tic Yttr i-
u m (III) Ar yloxid es. Aryloxide-tetramethylaluminate
interchange is not restricted to homoleptic aryloxides.
The reaction of TMA with (C5Me5)Y(OArtBu,H)2, which
was obtained via a salt metathesis reaction from
Y(OArtBu,H)3 and NaCp*, yielded (C5Me5)Y(OArtBu,H)[(µ-
Me)2AlMe2] (6). According to Scheme 5, again a single
aryloxide ligand was eliminated as Me2Al(OArtBu,H).
Alkylated byproducts Cp*Y(AlMe4)2 and Y(AlMe4)3 were
not observed. Although crystals suitable for an X-ray
structure determination were not obtained, microana-
lytical and NMR spectroscopic data are consistent with
the molecular structure proposed in Scheme 5. At
ambient temperature the tetramethylaluminate moiety
in 6 exhibits a characteristic doublet at -0.15 ppm (1H
2
NMR, J Y-H ) 2.9 Hz).
(41) (a) Schaverien, C. J . J . Chem. Soc., Chem. Commun. 1992, 11.
(b) Schaverien, C. J . Organometallics 1994, 13, 69.
(36) Cetinkaya, B.; Hitchcock, P. B.; J asim, H. A.; Lappert, M. F.;
Williams, H. D. Polyhedron 1990, 9, 239.
(37) Shreve, A. P.; Mulhaupt, R.; Fultz, W.; Calabrese, J .; Robbins,
W.; Ittel, S. D. Organometallics 1988, 7, 409.
(42) Nakamura, H.; Nakayama, Y.; Yasuda, H.; Maruo, T.; Kane-
hisa, N.; Kai, Y. Organometallics 2000, 19, 5392.
(43) Yamamoto, H.; Yasuda, H.; Yokota, K.; Nakamura, A.; Kai, Y.;
Kasai, N. Chem. Lett. 1988, 1963.
(38) Murad, E.; Hildenbrand, D. L. J . Chem. Phys. 1980, 73, 4005.
(39) (a) Hubert-Pfalzgraf, L. G. New J . Chem. 1987, 11, 663. (b)
Bradley, D. C. Chem. Rev. 1989, 89, 1317. (c) Bradley, D. C. Polyhedron
1994, 13, 1111. (d) Hubert-Pfalzgraf, L. G. New J . Chem. 1995, 19,
727. (e) Mehrotra, R. C.; Singh, A. Chem. Soc. Rev. 1996, 1.
(40) Anwander, R. Top. Curr. Chem. 1996, 179, 149.
(44) (a) Evans, W. J .; Chamberlain, L. R.; Ulibarri, T. A.; Ziller, J .
W. J . Am. Chem. Soc. 1988, 110, 6423. (b) Evans, W. J .; Leman, J . T.;
Clark, R. D.; Ziller, J . W. Main Group Chem. 2000, 23, 163.
(45) (a) Klimpel, M. G.; Anwander, R.; Tafipolsky, M.; Scherer, W.
Organometallics 2001, 20, 3983. (b) Nagl, I. S. Ph.D. Thesis, Technische
Universita¨t Mu¨nchen, 2002.

506 Organometallics, Vol. 22, No. 3, 2003
Fischbach et al.
Sch em e 6
Sch em e 7. F or m a tion of Bis-TMA Ad d u cts (8-10)
a n d Hom olep tic Tetr a m eth yla lu m in a tes (11) fr om
La n th a n id e(II) Ar yloxid esa
a
Fully characterized complexes are shown in boxes.
of the lanthanide(II) precursors in hexane led to dis-
placement of the coordinated THF molecules, which
preferentially coordinate to the harder Lewis acid center
Al(III) in Me3Al(THF). The next steps principally re-
semble the scenario which has been discussed for the
Ln(III) derivatives in Scheme 4. Stable bis-TMA adducts
8-10 formed in the presence of another 2 equiv of TMA.
Subsequent association with TMA to give intermediates
such as I6 could be a prevalent route for the relatively
larger Ln(II) centers (compared to Ln(III)). Further-
more, a less pronounced Ln-O(Ar) interaction and
hence dissociation of Me2Al(OAr) from I6 (route a in
Scheme 7) to yield I7 should be favored for the smaller
less oxophilic Yb center. Another TMA addition/Me2Al-
(OAr) dissociation sequence produces homoleptic tet-
ramethylaluminate derivatives 11, the insolubility of
which drives the reaction to completion (enhanced
kinetic control).
Elemental analysis and NMR spectroscopic data
confirmed the formation of bis-TMA adducts 8-10.
Complexes 8 and 10a exhibit a single 1H NMR reso-
nance for the aluminum methyl groups (8, δ -0.10 to
-0.13 ppm; 10a , δ -0.76 ppm) in the temperature range
+20 to -90 °C. The ambient-temperature 13C{1H} NMR
signal of their aluminum methyl groups (δ -0.6 to -4.5
1
ppm) appears as a quartet with J C-H coupling con-
1
stants of about 110 Hz. The H NMR AlMe resonances
of the paramagnetic samarium(II) derivatives 9 and 10b
showed a considerable shift to higher field and were
found in the narrow range of -20.6 to -20.9 ppm and
at -23.0 ppm, respectively.
The enhanced steric unsaturation of the larger diva-
lent metal centers compared to the La(III) system
ensures the coordination of two TMA molecules. The
formation of similar bis-TMA adduct complexes has
been previously observed in Yb(II) and Sm(II) bis-
(trimethylsilyl)amides, Ln[N(SiMe3)2]2(AlMe3)2.17b An
additional experiment was performed to investigate the
reaction behavior of the sterically less crowded divalent
lanthanide aryloxides [Ln(OAriPr,H)2(THF)2]x (Ln ) Yb,
Sm). According to eq 3, use of excess TMA afforded the
Con clu sion s
Aryloxide ligands provide a rigid and variable ancil-
lary ligand set for studying the multifunctional reac-
tivity of trimethylaluminum, TMA, toward Ln-OR
moieties. The conversion of divalent and trivalent
rare-earth-metal aryloxides either to TMA-adduct
complexes Ln(OAr)x(AlMe3)y (x ) 2, 3; y ) 1, 2) or to
tetramethylaluminate derivatives of types (ArtBu,RO)2-
Ln[(µ-Me)2AlMe2] and [Ln(AlMe4)x]n (x ) 2, 3) by reac-
tion with TMA once more demonstrates the importance
of steric and, concomitantly, electronic factors in rare-
earth-metal chemistry. This intrinsic alkylation capabil-
ity of TMA, which has to be rationalized on the basis of
the unique stereoelectronic situation implied by aryl-
oxide ligation, is certainly not directly transferable
and applicable to catalytically more relevant alkoxide-
based systems. However, since the outcome of the
TMA reactions seems to be predominantly under kinetic
control, one can easily predict that factors such as
Ln(OAr)x/AlR3 molar ratios and contact time of the
different components are crucial for the uniform forma-
[Ln(OAriPr,H)2(THF)2]x + AlMe3 (excess) f
+ Me2Al(OAriPr,H) +
[Ln(AlMe4)2]n
11
MeAl(OAriPr,H)2 + Me3Al(THF) (3)
homoleptic peralkylated aluminates [Ln(AlMe4)2]n (11)
in quantitative yield after 16 h. Note that under
identical reaction conditions the bulkier 2,6-di-tert-
butylphenoxide ligand gave only 23% of Yb(II) alumi-
nate 11a and the putative Sm(II) aluminate 11b did not
form.
Finally, possible pathways for the formation of the
bis-TMA adducts and peralkylated Ln(II) species are
summarized in Scheme 7. Addition of TMA to mixtures

Reactivity of AlMe3 with Lanthanide Aryloxides
Organometallics, Vol. 22, No. 3, 2003 507
colorless solid (0.208 g, 0.25 mmol, 84%). IR: 1588 w, 1405 s,
1348 m, 1263 m, 1236 s, 1218 s, 1190 s, 1123 m, 1099 w, 882
w, 856 s, 818 m, 745 s, 720 m, 701 m, 688 m, 652 m, 544 w,
tion of the catalytically active (alkylated) species in rare-
earth-metal-based “Ziegler Mischkatalysatoren”. In light
of these findings it is certainly worthwhile to examine
alkoxide-based alkylation reactions in more detail; that
is, the reactivity of TMA toward homoleptic alkoxide
complexes of the type Ln(OR)x (x ) 2, 3; R ) iPr, tBu,
neopentyl, etc.). Not unexpectedly, preliminary studies
on the system Yb(OCtBu3)2/AlMe3 reveal peralkylation,
that is, exclusive generation of [Yb(AlMe4)2]n, in the
presence of excess of TMA, while alkylation of [Ln-
(OiPr)3] with TMA was found to come to a halt at the
stage of the tris-TMA adduct Ln(OtBu)3(AlMe3)3 (Ln )
Y, Nd).2,3
1
503 w cm-1. H NMR: δ 7.20 (m, br, 6 H, Ar Hmeta), 6.80 (m,
br, 3 H, Ar Hpara), 1.48 (s, 18 H, TMAC(CH3)3), 1.44 (s, 36 H,
C(CH3)3), 0.14 (s, br, 9 H, (µ-CH3)Al(CH3)2). 13C NMR: δ 162.0
TMA
1
(s, Cipso), 153.9 (s,
C
), 140.8 (s), 136.9 (s), 127.8 (d, J C,H
ipso
1
1
) 155 Hz), 125.6 (d, J C,H ) 154 Hz), 122.5 (d, J C,H ) 159
Hz), 118.8 (d, J C,H ) 159 Hz), 35.9 (s, TMAC(CH3)3), 34.9 (s,
1
C(CH3)3), 32.7 (q, 1J C,H ) 125 Hz, TMAC(CH3)3), 32.5 (q, 1J C,H
)
125 Hz, C(CH3)3), 1.9 (q, J C,H ) 109 Hz, (µ-Me)AlMe2). 1H
1
3
NMR (d8-toluene, -90 °C): δ 7.15 (d, J H,H ) 8.2 Hz, 4 H, Ar
3
3
H
meta), 7.04 (d, J H,H ) 7.5 Hz, 2 H, TMAAr Hmeta), 6.75 (t, J H,H
) 8.2 Hz, 2 H, Ar Hpara), 6.66 (t, J H,H ) 7.5 Hz, 1 H, TMAAr
3
H
para), 1.36 (s, 36 H, C(CH3)3), 1.33 (s, 18 H, TMAC(CH3)3), 0.20
(s, 9 H, (µ-CH3)Al(CH3)2). Anal. Calcd for C45H72AlLaO3: C,
65.36; H, 8.78. Found: C, 65.38; H, 8.76.
Exp er im en ta l Section
La(OC6H2tBu 2-2,6-Me-4)2[(µ-OC6H2tBu 2-2,6-Me-4)(µ-Me)-
AlMe2] (2b). Following the procedure described above, La-
(OArtBu,Me)3 (0.239 g, 0.30 mmol) and TMA (0.087 g, 1.20 mmol)
yielded 2b as a colorless solid (0.225 g, 0.26 mmol, 86%). IR:
1600 w, 1415 vs, 1362 m, 1350 m, 1263 s, 1225 vs, 1212 vs,
1190 s, 1118 m, 1022 w, 950 w, 920 w, 887 m, 862 m, 830 s,
Gen er a l Con sid er a tion s. All operations were performed
with rigorous exclusion of air and water, using high-vacuum
and glovebox techniques (MB Braun MB150B-G-II; <1 ppm
O2, <1 ppm H2O). Solvents were predried and distilled from
Na/K alloy (benzophenone ketyl) under argon. Deuterated
solvents were obtained from Deutero GmbH and degassed and
dried over Na/K alloy. All phenolic ligands were purchased
from Aldrich and distilled or sublimed before use. Trimethyl-
aluminum, TMA, was purchased from Aldrich and used
822 vs, 803 s, 776 m, 696 s, 601 m, 575 w, 527 s cm-1 1H
.
NMR: δ 7.08 (s, 2 H, TMAAr Hmeta), 7.06 (s, 4H, Ar Hmeta), 2.22
(s, 6 H, CH3), 2.12 (s, 3H, TMACH3), 1.48 (s, br, 54 H, C(CH3)3,
TMAC(CH3)3), 0.18 (s, br, 9 H, (µ-CH3)Al(CH3)2). 13C{1H} NMR:
δ 160.0 (Cipso), 151.2 (TMACipso), 141.0, 136.7, 131.1, 129.7, 126.6,
126.2, 36.0 (TMAC(CH3)3), 34.9 (C(CH3)3), 32.7 (TMAC(CH3)3), 32.6
(C(CH3)3), 21.3 (CH3), 21.1 (TMACH3), 2.0 (br, (µ-Me)AlMe2). 1H
NMR (d8-toluene, -90 °C): δ 7.04 (s, 4 H, Ar Hmeta), 7.00 (s, 2
H, Ar H′meta), 2.22 (s, 6 H, CH3), 2.05 (s, 3 H, CH3), 1.40 (s, 36
H, C(CH3)3), 1.37 (s, 18 H, C(CH3)3), 0.24 (s, 9 H, (µ-CH3)Al-
without further purification. The lanthanide aryloxides Ln-
19
(OAr)3,14 Ln(OAr)2(THF)x,15 and (C5Me5)Y(OArtBu,H
)
2
were
synthesized according to slightly modified literature proce-
dures. NMR spectra were recorded on a Bruker DPX-400 (FT,
400 MHz 1H; 100 MHz 13C) spectrometer in C6D6 at 25 °C
unless otherwise noted. 1H and 13C shifts are referenced to
internal solvent resonances and reported relative to TMS. IR
spectra were recorded on a Perkin-Elmer 1650-FTIR spec-
trometer as Nujol mulls. Elemental analyses were performed
in the microanalytical laboratory of the institute.
Y(OC6H3iP r 2-2,6)[(µ-OC6H3iP r 2-2,6)(µ-Me)AlMe2]2 (1).
To a suspension of [Y(OAriPr,H)3]2 (0.397 g, 0.64 mmol) in
n-hexane was slowly added a n-hexane solution of 6 equiv of
TMA (0.277 g, 3.84 mmol), and the mixture was stirred at
ambient temperature overnight. Then, the solvent and the
excess TMA were removed in vacuo. The remaining solid was
dissolved in n-hexane and crystallized at -45 °C to yield the
TMA adduct as colorless crystals (0.226 g, 0.30 mmol, 46%).
IR: 1588 w, 1439 s, 1363 m, 1321 s, 1260 s, 1245 m, 1204 m,
1168 s, 1098 m, 1054 w, 1042 m, 934 w, 891 m, 870 w, 835 s,
(CH3)2)). 13C NMR (d8-toluene, -90 °C): δ 160.1 (s, Cipso), 151.3
TMA
(s,
C
), 141.5 (s), 136.3 (s), 131.8 (s), 130.0 (s), 127.8 (d,
ipso
1J C,H ) 154 Hz), 125.7 (d, 1J C,H ) 154 Hz), 36.0 (s, TMAC(CH3)3),
1
35.0 (s, C(CH3)3), 32.3 (q, J C,H ) 126 Hz, C(CH3)3), 31.8 (q,
1J C,H ) 125 Hz, TMAC(CH3)3), 21.5 (q, CH3), 21.2 (q, TMACH3),
1
2.7 (q, J C,H ) 110 Hz, (µ-Me)AlMe2). Anal. Calcd for C48H78
AlLaO3: C, 66.34; H, 9.05. Found: C, 66.50; H, 9.13.
-
Gen er a l P r oced u r e for th e Alk yla tion of Yttr iu m (III)
a n d Lu tetiu m (III) Ar yloxid es. Ln(OAr)3 was suspended in
n-hexane. Then, a n-hexane solution of 6 equiv of TMA was
slowly added at ambient temperature. After the mixture was
stirred for 16 h, the solvent and excess TMA were removed in
vacuo. The remaining solid was dissolved in n-hexane and
crystallized at -45 °C to give the aluminate complexes as
colorless solids in moderate yields.
798 m, 755 s, 707 s, 697 s, 603 m, 570 w, 475 w, 470 w cm-1
.
3
3
1H NMR: δ 7.11 (d, J H,H ) 7.7 Hz, 2 H, Ar H), 7.03 (d, J H,H
Y(OC6H3tBu 2-2,6)2[(µ-Me)2AlMe2] (3a ). Following the pro-
cedure described above, Y(OArtBu,H)3 (0.317 g, 0.45 mmol) and
TMA (0.195 g, 2.70 mmol) yielded 3a (0.164 g, 0.28 mmol, 62%)
as colorless crystals. IR: 1582 w, 1412 s, 1350 m, 1263 s, 1241
s, 1215 m, 1193 m, 1125 w, 1100 w, 874 s, 820 m, 796 w, 750
) 6.6 Hz, 2 H, Ar H), 6.97-6.90 (m, 5 H, Ar H), 3.64 (septet,
3
3J H,H ) 7.0 Hz, 2 H, CH(CH3)2), 3.57 (septet, J H,H ) 7.0 Hz, 2
3
H, CH(CH3)2), 3.44 (septet, J H,H ) 6.6 Hz, 2 H, CH(CH3)2),
3
3
1.41 (d, J H,H ) 6.6 Hz, 6 H, CHH(CH3)2), 1.36 (d, J H,H ) 6.6
Hz, 6 H, CHH(CH3)2), 1.31 (d, 3J H,H ) 6.3 Hz, 6 H, CHH(CH3)2),
1
s, 720 s, 695 m, 666 m, 578 m, 550 m, 454 m cm-1. H NMR:
3
3
1.20 (d, J H,H ) 7.0 Hz, 6 H, CHH(CH3)2), 1.18 (d, J H,H ) 7.7
Hz, 6 H, CHH(CH3)2), 0.94 (d, 3J H,H ) 6.6 Hz, 6 H, CHH(CH3)2),
-0.29 (s, 18 H, (µ-CH3)Al(CH3)2). 13C{1H} NMR: δ 156.8 (d,
2J Y,C ) 6.2 Hz, Cipso), 148.4, 139.2, 136.7, 125.6, 125.2, 125.1,
123.6, 120.6, 27.4, 27.3, 26.6, 26.4, 26.2, 25.6, 25.1, 24.2, 23.7,
-2.8 ((µ-CH3)Al(CH3)2). Anal. Calcd for C42H69Al2O3Y: C,
65.95; H, 9.09; Al, 7.06. Found: C, 65.89; H, 9.04; Al, 6.3.
Gen er a l P r oced u r e for th e F or m a tion of Mon o-TMA
Ad d u cts of La n th a n u m (III) Ar yloxid es. To a suspension
3
3
δ 7.21 (d, J H,H ) 7.7 Hz, 4 H, Ar Hmeta), 6.83 (t, J H,H ) 7.7
2
Hz, 2 H, Ar Hpara), 1.40 (s, 36 H, C(CH3)3), 0.02 (d, J Y,H ) 3.7
Hz, 12 H, (µ-CH3)2Al(CH3)2). 13C{1H} NMR: δ 160.5 (d, J Y,C
2
) 5.2 Hz, Cipso), 137.2, 125.5, 119.1, 34.7 (C(CH3)3), 31.7
(C(CH3)3), 2.7 (br, (µ-CH3)2Al(CH3)2). Anal. Calcd for C32H54
-
AlO2Y: C, 65.51; H, 9.28, Al, 4.60. Found: C, 65.37; H, 9.13;
Al, 4.5.
Y(OC6H 2tBu 2-2,6-Me-4)2[(µ-Me)2AlMe2] (3b). Following
of La(OArtBu,R
) in n-hexane was slowly added a n-hexane
3
the procedure described above, Y(OArtBu,Me
) (0.298 g, 0.40
3
solution of 4 equiv of TMA, and the mixture was stirred at
ambient temperature overnight. Then, the solvent and excess
TMA were removed in vacuo. The remaining solid was dis-
solved in n-hexane and crystallized at -45 °C to give the TMA
adducts as amorphous solids in good yields.
La(OC6H3tBu 2-2,6)2[(µ-OC6H3tBu 2-2,6)(µ-Me)AlMe2] (2a).
Following the procedure described above, La(OArtBu,H)3 (0.226
g, 0.30 mmol) and TMA (0.087 g, 1.20 mmol) yielded 2a as a
mmol) and TMA (0.173 g, 2.40 mmol) yielded 3b (0.135 g, 0.22
mmol, 55%) as colorless crystals. IR: 1600 w, 1416 s, 1354 m,
1251 s, br, 1226 s, 1213 s, 1182 s, 1117 m, 1106 m, 1034 w,
1021 w, 949 w, 888 w, 865 m, 844 s, 828 s, 806 m, 775 m, 722
m, 699 s, 674 s, 642 w, 608 w, 574 w, 544 m, 534 s, 478 w
cm-1 1H NMR: δ 7.07 (s, 4 H, Ar Hmeta), 2.26 (s, 6 H, CH3),
.
1.44 (s, 36 H, C(CH3)3), 0.04 (d, 2J Y,H ) 3.7 Hz, 12 H, (µ-CH3)2-
2
Al(CH3)2). 13C{1H} NMR: δ 158.5 (d, J Y,C ) 7.6 Hz, Cipso),

508 Organometallics, Vol. 22, No. 3, 2003
Fischbach et al.
Ta ble 4. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s of Com p lexes 1, 3a , a n d 4a
1
3a
4a
chem formula
fw
C
42H69Al2O3Y
C32H54AlO2Y
586.64
C32H54AlO2Lu
672.70
764.84
color/shape
cryst size (mm)
cryst syst
space group
a (Å)
colorless/fragment
0.94 × 0.64 × 0.20
orthorhombic
P212121 (No. 19)
11.7263(1)
18.1264(1)
20.7998(1)
4421.11(5)
4
colorless/fragment
0.51 × 0.30 × 0.20
orthorhombic
Pbca (No. 61)
19.6670(1)
14.4580(2)
23.3750(3)
6646.58(13)
8
colorless/fragment
0.71 × 0.25 × 0.13
orthorhombic
Pbca (No. 61)
19.6660(1)
14.4500(2)
23.2530(2)
6607.89(11)
8
b (Å)
c (Å)
V (Å3)
Z
T (K)
123
1.149
1.392
1640
183
1.173
1.805
2512
183
1.352
3.038
2768
Fcalcd (g cm-3
)
µ (mm-1
F000
)
θ range (deg)
2.07-25.34
(14, (21, (25
102 626
7990/0.053
7757
2.47-26.37
(24, (17, (29
77 434
6669/0.036
4981
1.75-27.48
(25, (18, (30
51 909
7578/0.041
6138
data collected (h,k,l)
no. of rflns collected
no. of indep rflns/Rint
no. of obsd rflns (I > 2σ(I))
no. of params refined
R1 (obsd/all)
710
325
325
0.0197/0.0212
0.0466/0.0471
1.048/1.048
+0.22/-0.21
0.0497/0.0837
0.0966/0.1124
1.096/1.096
+0.86/-0.33
0.0320/0.0495
0.0870/0.1080
1.192/1.192
+0.86/-1.81
wR2 (obsd/all)
GOF (obsd/all)
max/min ∆F (e Å-3
)
136.9, 127.1, 126.0, 34.7 (C(CH3)3), 31.7 (C(CH3)3), 21.5 (CH3),
2.6 (br, (µ-CH3)2Al(CH3)2). Anal. Calcd for C34H58AlO2Y: C,
66.43; H, 9.51. Found: C, 66.20; H, 9.43.
121.8, 118.2 (C5(CH3)5), 34.9 (C(CH3)3), 31.7 (C(CH3)3), 11.5 (C5-
(CH3)5), 1.4 (br, (µ-CH3)2Al(CH3)2). Anal. Calcd for C28H48
-
AlOY: C, 65.10; H, 9.37. Found: C, 65.50; H, 9.52.
Y(OC6H2tBu 3-2,4,6)2[(µ-Me)2AlMe2] (3c). Following the
Gen er a l P r oced u r e for th e Syn th esis of Bis-TMA
Ad d u cts of Ytter biu m (II) a n d Sa m a r iu m (II) Ar yloxid es.
Ln(OAr)2(THF)x was dissolved in n-hexane and a n-hexane
solution of 6 equiv of TMA slowly added. The mixture was
stirred at ambient temperature overnight. Then, the solvent
and excess TMA were removed in vacuo. The remaining solid
was dissolved in toluene and the solution centrifuged, filtered
through a Celite pad to separate insoluble parts, and finally
crystallized from n-hexane or n-hexane/toluene mixtures at
-45 °C to give the TMA adducts as yellow (Yb) or reddish
brown (Sm) solids in good yields.
procedure described above, Y(OArtBu,tBu)3 (0.350 g, 0.40 mmol)
1
and TMA (0.173 g, 2.40 mmol) yielded a yellow oil. H NMR:
δ 7.37 (s, 4 H, Ar Hmeta), 1.45 (s, 36 H, o-C(CH3)3), 1.36 (s, 18
H, p-C(CH3)3), 0.03 (d, 2J Y,H ) 3.7 Hz, 12 H, (µ-CH3)2Al(CH3)2).
2
13C{1H} NMR: δ 158.3 (d, J Y,C ) 5.4 Hz, Cipso), 140.2, 136.3,
122.1, 35.2 (o-C(CH3)3), 35.1 (p-C(CH3)3), 32.0 (o-C(CH3)3), 31.8
(p-C(CH3)3), 2.6 (br, (µ-CH3)2Al(CH3)2).
Lu (OC6H3tBu 2-2,6)2[(µ-Me)2AlMe2] (4a ). Following the
procedure described above, Lu(OArtBu,H)3 (0.356 g, 0.45 mmol)
and TMA (0.195 g, 2.70 mmol) yielded 4a (0.211 g, 0.31 mmol,
70%) as colorless crystals. IR: 1583 w, 1414 vs, 1351 m, 1264
s, 1242 vs, 1219 m, 1195 m, 1125 w, 1099 w, 878 vs, 821 m,
Yb[(µ-OC6H3tBu 2-2,6)(µ-Me)AlMe2]2 (8a ). Following the
procedure described above, Yb(OArtBu,H)2(THF)2 (0.255 g, 0.35
mmol) and TMA (0.151 g, 2.10 mmol) yielded 8a as an orange
solid (0.06 g, 0.08 mmol, 23%). 1H NMR: δ 7.11 (d, 3J H,H ) 7.9
796 w, 750 vs, 720 s, 700 m, 666 s, 579 m, 551 m, 453 m cm-1
.
1H NMR: δ 7.23 (d, J H,H ) 7.7 Hz, 4 H, Ar Hmeta), 6.83 (t,
3J H,H ) 7.7 Hz, 2 H, Ar Hpara), 1.42 (s, 36 H, C(CH3)3), 0.30 (s,
12 H, (µ-CH3)2Al(CH3)2). 13C{1H} NMR: δ 161.1 (Cipso), 137.5,
125.5, 119.1, 34.8 (C(CH3)3), 31.8 (C(CH3)3), 4.9 (br, (µ-CH3)2-
Al(CH3)2). Anal. Calcd for C32H54AlLuO2: C, 57.13; H, 8.09;
Al, 4.01. Found: C, 57.18; H, 8.14; Al, 4.1.
3
3
Hz, 4 H, Ar Hmeta), 6.75 (t, J H,H ) 7.9 Hz, 2 H, Ar Hpara), 1.30
(s, 36 H, C(CH3)3), -0.13 (s, 18 H, (µ-CH3)Al(CH3)2). 13C{1H}
NMR: δ 154.2 (Cipso), 140.1, 127.4, 121.6, 35.6 (C(CH3)3), 32.8
(C(CH3)3), -0.6 ((µ-CH3)Al(CH3)2).
Yb[(µ-OC6H2tBu 2-2,6-Me-4)(µ-Me)AlMe2]2 (8b). Following
the procedure described above, Yb(OArtBu,Me)2(THF)2 (0.219 g,
0.29 mmol) and TMA (0.125 g, 1.74 mmol) yielded 8b as yellow
crystals (0.162 g, 0.21 mmol, 74%). IR: 1411 m, 1265 w, 1255
w, 1229 m, 1204 m, 1189 m, 1117 w, 863 w, 830 w, 818 w, 804
Lu (OC6H2tBu 2-2,6-Me-4)2[(µ-Me)2AlMe2] (4b). Following
the procedure described above, Lu(OArtBu,Me
) (0.342 g, 0.41
3
mmol) and TMA (0.177 g, 2.46 mmol) yielded 4b (0.166 g, 0.24
mmol, 58%) as colorless crystals. IR: 1423 s, 1352 m, 1292 w,
1250 s, br, 1216 m, 1194 m, 1120 m, 1022 w, 950 w, 920 w,
889 w, 860 s, 850 s, 806 w, 776 m, 723 s, 702 s, 632 w, 579 m,
1
w, 774 w, 721 m, 965 m, br, 601 w, 525 w cm-1. H NMR: δ
7.00 (s, 4 H, Ar Hmeta), 2.10 (s, 6 H, CH3), 1.32 (s, 36 H,
C(CH3)3), -0.10 (s, 18 H, (µ-CH3)Al(CH3)2). 13C{1H} NMR: δ
151.7 (Cipso), 140.0, 130.0, 127.6, 35.6 (C(CH3)3), 32.5 (C(CH3)3),
21.0 (CH3), -0.6 ((µ-CH3)Al(CH3)2). Anal. Calcd for C36H64-
Al2O2Yb: C, 57.20; H, 8.53. Found: C, 57.29; H, 8.58.
1
565 m, 548 s, 460 w, 443 m cm-1. H NMR: δ 7.09 (s, 4 H, Ar
H
meta), 2.26 (s, 6 H, CH3), 1.45 (s, 36 H, C(CH3)3), 0.31 (s, 12
H, (µ-CH3)2Al(CH3)2). 13C{1H} NMR: δ 159.0 (Cipso), 137.2,
127.0, 126.0, 34.8 (C(CH3)3), 31.9 (C(CH3)3), 21.4 (CH3), 4.8 (br,
(µ-CH3)2Al(CH3)2). Anal. Calcd for C34H58AlLuO2: C, 58.27; H,
8.34; Al, 3.85. Found: C, 58.18; H, 8.24; Al, 4.0.
Yb[(µ-OC6H2tBu 3-2,4,6)(µ-Me)AlMe2]2 (8c). Following the
procedure described above, Yb(OArtBu,tBu)2(THF)2 (0.302 g, 0.36
mmol) and TMA (0.156 g, 2.16 mmol) yielded 8c (0.181 g, 0.21
mmol, 60%) as a light yellow solid. IR: 1601 w, 1420 s, 1362
s, 1292 w, 1273 m, 1227 s, 1196 s, 1152 w, 1116 m, 882 wm,
(C5Me5)Y(OC6H3tBu 2-2,6)[(µ-Me)2AlMe2] (6). Following
the procedure described above, Cp*Y(OArtBu,H)2 (0.222 g, 0.35
mmol) and TMA (0.101 g, 1.40 mmol) yielded 6 (0.091 g, 0.18
mmol, 51%) as an amorphous solid. IR: 1582 w, 1410 m, 1303
w, 1245 s, 1210 w, 1193 w, 1169 w, 1153 w, 1127 w, 1102 w,
836 m, 820 w, 776 m, 750 m, 720 s, 691 s, 596 w, 542 w cm-1
.
1H NMR: δ 7.33 (s, 4 H, Ar Hmeta), 1.37 (s, 36 H, o-C(CH3)3),
1.27 (s, 18 H, p-C(CH3)3), -0.13 (s, 18 H, (µ-CH3)Al(CH3)2).
13C{1H} NMR: δ 151.9 (Cipso), 142.9, 139.3, 124.1, 35.9 (o-
C(CH3)3), 34.5 (p-C(CH3)3), 32.6 (o-C(CH3)3), 31.6 (p-C(CH3)3),
-0.7 (µ-CH3)Al(CH3)2). Anal. Calcd for C42H76Al2O2Yb: C,
60.05; H, 9.12. Found: C, 60.42; H, 9.31.
1
1021 w, 871 m, 748 m, 697 m, 663 m, 582 w, 459 w cm-1. H
3
3
NMR: δ 7.25 (d, J H,H ) 7.7 Hz, 2 H, Ar Hmeta), 6.85 (t, J H,H
) 7.7 Hz, 1 H, Ar Hpara), 1.80 (s, 15 H, C5(CH3)5), 1.36 (s, 18
H, C(CH3)3), -0.15 (d, 2J Y,H ) 2.9 Hz, 12 H, (µ-CH3)2Al(CH3)2).
13C{1H} NMR: δ 161.1 (d, J Y,C ) 5.4 Hz, Cipso), 137.4, 125.2,
2

Reactivity of AlMe3 with Lanthanide Aryloxides
Organometallics, Vol. 22, No. 3, 2003 509
Sm [(µ-OC6H3tBu 2-2,6)(µ-Me)AlMe2]2 (9a ). Following the
procedure described above, Sm(OArtBu,H)2(THF)2 (0.303 g, 0.43
mmol) and TMA (0.186 g, 2.58 mmol) yielded 9a as a reddish
brown solid (0.150 g, 0.21 mmol, 50%). IR: 1581 w, 1402 s,
1365 s, 1348 m, 1308 w, 1253 m, 1238 s, 1225 s, 1190 s, 1126
m, 1098 w, 877 w, 864 m, 818 m, 797 w, 754 m, 718 m, 696 s,
for C42H44Al2O2Sm: C, 64.25; H, 5.65; Al, 6.87. Found: C,
63.88; H, 5.64; Al, 6.6.
X-r a y Cr ysta llogr a p h y. Gen er a l P r oced u r e. Crystals
suitable for diffraction experiments were selected in
a
glovebox, coated with perfluorinated ether, and fixed in a
capillary. Preliminary examination of the crystal quality and
data collection were carried out on a Nonius KappaCCD
diffractometer in combination with a rotating-anode X-ray
generator and graphite-monochromated Mo KR radiation
(λ ) 0.710 73 Å) employing the COLLECT software package.46
Cr ysta l Str u ctu r e Deter m in a tion of 1, 3a , a n d 4a . A
total of 1032 (311, 380) collected images were processed using
Denzo.47 Data for compounds 3a and 4a , respectively, are
specified in parentheses. Absorption and/or decay effects
were corrected during the scaling procedure.47 The structures
were solved by direct methods48 and refined with standard
difference Fourier techniques.49 All non-hydrogen atoms of the
asymmetric unit were refined with anisotropic thermal dis-
placement parameters. All hydrogen atoms were placed in
calculated positions and included in the structure factor
calculation but not refined for 3a and 4a . In 1 all hydrogen
atoms were found in the difference Fourier maps and
refined freely with individual isotropic thermal displace-
ment. Full-matrix least-squares refinements were carried out
br, 657 w, 636 w, 596 m, 494 m cm-1
.
1H NMR: δ 7.73 (d,
3J H,H ) 7.3 Hz, 4 H, Ar Hmeta), 7.47 (t, J H,H ) 7.3 Hz, 2 H, Ar
3
H
para), 3.45 (s, 36 H, C(CH3)3), -20.93 (s, 18 H, (µ-CH3)Al-
(CH3)2). Anal. Calcd for C34H60Al2O2Sm: C, 57.91; H, 8.58.
Found: C, 57.17; H, 8.41.
Sm [(µ-OC6H2tBu 2-2,6-Me-4)(µ-Me)AlMe2]2 (9b). Follow-
ing the procedure described above, Sm(OArtBu,Me)2(THF)2 (0.257
g, 0.35 mmol) and TMA (0.151 g, 2.10 mmol) yielded 9b as a
reddish brown solid (0.225 g, 0.31 mmol, 88%). IR: 1601 w,
1409 s, 1366 s, 1347 m, 1266 m, 1251 m, 1234 s 1210 s, 1185
s, 1118 m, 884 w, 864 m, 832 m, 821 m, 805 m, 772 m, 720 s,
1
696 s, br, 632 w, 598 m, 526 w, 491 w cm-1. H NMR: δ 7.87
(s, 4 H, Ar Hmeta), 3.39 (s, 36 H, C(CH3)3), 2.72 (s, 6 H, CH3),
-20.88 (s, 18 H, (µ-CH3)Al(CH3)2). Anal. Calcd for C36H64Al2O2-
Sm: C, 58.97; H, 8.80; Al, 7.36. Found: C, 58.59; H, 8.67; Al,
7.5.
Sm [(µ-OC6H2tBu 3-2,4,6)(µ-Me)AlMe2]2 (9c). Following the
procedure described above, Sm(OArtBu,tBu)2(THF)2 (0.335 g, 0.41
mmol) and TMA (0.177 g, 2.46 mmol) yielded 9c as a reddish
brown solid (0.147 g, 0.18 mmol, 44%). IR: 1600 w, 1418 s,
1363 s, 1344 m, 1292 w, 1273 m, 1235 s, 1203 s, 1189 s, 1152
w, 1118 s, 917 w, 884 m, 841 s, 819 w, 772 w, 751 m, 691 vs,
br, 645 w, 598 m, 536 w, 504 w cm-1. 1H NMR: δ 8.18 (s, 4 H,
Ar Hmeta), 6.38 (s, 36 H, o-C(CH3)3), 1.94 (s, 18 H, p-C(CH3)3),
-20.61 (s, 18 H, (µ-CH3)Al(CH3)2). Anal. Calcd for C42H76Al2O2-
Sm: C, 61.72; H, 9.37; Al, 6.60. Found: C, 62.21; H, 9.26; Al,
6.8.
2
2 2
by minimizing ∑w(Fo - Fc
) employing the SHELXL-97
weighting scheme and stopped at a maximum shift/error of
<0.002 (0.001, 0.001). As demonstrated by the Flack parameter
ꢀ ) 0.156(2), the crystal of compound 1 is partly twinned. In
the final model, including twin refinement for 1, 710 (325, 325)
parameters were refined to wR2 ) 0.0471 (0.1124, 0.1080)
based on all 7990 (6669, 7578) data. For details see Table 4.
Ack n ow led gm en t. We thank the Deutsche For-
schungsgemeinschaft, the Fonds der Chemischen In-
dustrie, and Prof. Wolfgang A. Herrmann for generous
support.
Yb[(µ-OC6H3P h 2-2,6)(µ-Me)AlMe2]2 (10a ). Following the
procedure described above, Yb(OArPh)2(THF) (0.213 g, 0.29
mmol) and TMA (0.125 g, 1.74 mmol) yielded 10a as a yellow
solid (0.223 g, 0.28 mmol, 95%). IR: 1591 w, 1560 w, 1454 vs,
1419 m, 1313 w, 1277 w, 1237 m, 1181 w, 1085 w, 1070 w,
1028 w, 934 w, 856 m, 800 mw, 776 m, 764 s, 755 s, 705 s, br,
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, atomic displacement parameters, and bond dis-
tances and angles for complexes 1, 3a and 4a . This material
is available free of charge via the Internet at http://pubs.acs.org.
1
610 w, 598 w, 576 w, 522 w, 507 w cm-1. H NMR: δ 7.39 (d,
3J H,H ) 7.0 Hz, 8 H, Ar H), 7.08-6.97 (m, 16 H, Ar H), 6.83 (t,
3J H,H ) 7.4 Hz, 2 H, Ar Hpara), -0.76 (s, 18 H, (µ-CH3)Al(CH3)2).
13C{1H} NMR: δ 153.3 (Cipso), 140.2, 133.0, 131.5, 130.5, 129.8,
128.7, 121.3, -4.5 ((µ-CH3)Al(CH3)2). Anal. Calcd for C42H44
Al2O2Yb: C, 62.45; H, 5.49; Al, 6.68. Found: C, 61.57; H, 5.40;
Al, 6.0.
-
OM020784K
(46) Hooft, R. COLLECT, Data Collection Software for Nonius
KappaCCD Devices; Nonius BV, Delft, The Netherlands, 2001.
(47) Otwinowski, Z.; Minor, W. In Processing of X-ray Diffraction
Data Collected in Oscillation Mode; Carter, C. W., J r., Sweet, R. M.,
Eds.; Academic Press: New York, 1997; Vol. 276, pp 307-326.
(48) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435-441.
Sm [(µ-OC6H3P h 2-2,6)(µ-Me)AlMe2]2 (10b). Following the
procedure described above, Sm(OArPh)2(THF) (0.257 g, 0.36
mmol) and TMA (0.156 g, 2.16 mmol) yielded 10b as a grayish
brown solid (0.249 g, 0.32 mmol, 88%). IR: 1592 w, 1582 w,
1565 w, 1490 m, 1419 s, 1314 m, 1276 m, 1236 s, 1201 m, 1176
s, 1084 w, 1070 w, 1028 w, 861 s, 854 s, 800 w, 771 m, 764 s,
754 s, 705 vs, 691 vs, 680 sh, 630 w, 610 m, 596 m, 576 w, 522
(49) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1998.
1
w, 506 w, 497 w cm-1. H NMR: δ 13.56 (s), 12.69 (s), 10.93
(50) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University, Utrecht, The Netherlands, 2001.
(s), 6.06 (m), -23.01 (s, 18 H, (µ-CH3)Al(CH3)2). Anal. Calcd