Distinct reaction pathways of peraikylated LnIIAlIII heterobimetallic complexes with substituted phenols

Article abstract of DOI:10.1021/ic702517s

The protonolysis reaction of heterobimetallic peralkylaled complexes [Ln(AlR₄)₂]_n (Ln = Sm, Yb; R = Me, Et) with 2 equiv of HOC₆H₂tBu₂-2,6-Me-4 affords the bis(trialkylaluminum) adducts Ln[(μ-OAr^tBu,Me)(μ-R)AlR ₂]₂ in good yields. Analogous reactions with the less sterically demanding iPr-substituted phenol result in ligand redistributions and formation of X-ray structurally evidenced Ln[(μ-OAr^iPr,H) ₂AlR₂]₂ (Ln = Yb, R = Me; Ln = Sm, R = Et), Yb[(μ-OAr^iPr,H)(μ-Et)AlEt₂]₂(THF), and [Et₂Al(μ-OAr^iPr,H)₂Yb(μ-Et) ₂AlEt₂]₂. The solid-state structures of serendipitous alumoxane complex Sm[(μ-OAr^tBu,Me)AlEt ₂OAlEt₂(μ-OAr^tBu,Me)](toluene) and dimeric AlMe₃-adduct complex [(AlMe₃)(μ-OAr^tBu,Me) Sm(μ-OAr^tBu,Me)₂Sm(μ-OAr^tBu,Me)(AlMe ₃)] were also determined by X-ray crystallography. While the former can be discussed as a typical hydrolysis product of Sm[(μ-OAr ^tBu,Me)(μ-Et)AlEt₂]₂, the latter was isolated from the 1:1 reaction of [Sm(AlEt₄)₂]_n with HOAr^tBu,Me.

Full text of DOI:10.1021/ic702517s

Inorg. Chem. 2008, 47, 4696-4705
Distinct Reaction Pathways of Peralkylated LnIIAlIII Heterobimetallic
Complexes with Substituted Phenols†
Hanne-Marthe Sommerfeldt, Christian Meermann, Karl W. Törnroos, and Reiner Anwander*
Department of Chemistry, UniVersity of Bergen, Allégaten 41, N-5007 Bergen, Norway
Received December 31, 2007
The protonolysis reaction of heterobimetallic peralkylated complexes [Ln(AlR4)2]n (Ln ) Sm, Yb; R ) Me, Et) with
2 equiv of HOC6H2tBu2-2,6-Me-4 affords the bis(trialkylaluminum) adducts Ln[(µ-OArtBu,Me)(µ-R)AlR2]2 in good yields.
Analogous reactions with the less sterically demanding iPr-substituted phenol result in ligand redistributions and
formation of X-ray structurally evidenced Ln[(µ-OAri Pr,H)2AlR2]2 (Ln ) Yb, R ) Me; Ln ) Sm, R ) Et), Yb[(µ-
OAri Pr,H)(µ-Et)AlEt2]2(THF), and [Et2Al(µ-OAri Pr,H)2Yb(µ-Et)2AlEt2]2. The solid-state structures of serendipitous
alumoxane complex Sm[(µ-OArtBu,Me)AlEt2OAlEt2(µ-OArtBu,Me)](toluene) and dimeric AlMe3-adduct complex [(AlMe3)(µ-
OArt Bu,Me)Sm(µ-OArt Bu,Me)2Sm(µ-OArt Bu,Me)(AlMe3)] were also determined by X-ray crystallography. While the former
can be discussed as a typical hydrolysis product of Sm[(µ-OArt Bu,Me)(µ-Et)AlEt2]2, the latter was isolated from the
1:1 reaction of [Sm(AlEt4)2]n with HOArt Bu,Me
.
Introduction
protocols aiming at metal alkylation.13,14 Accordingly, the
alkylation receptivity of homoleptic complexes Ln(OArR)3
in the presence of organoaluminum compounds, in particular
[AlMe3] (TMA) and [AlEt3] (TEA), has been studied in
detail.14 It was found that product formation in reaction
mixtures Ln(OArR)3/[AlR3] is mainly governed by the size
of the rare-earth metal center and the substitution pattern of
the aryloxide ligand. X-ray crystallographically authenticated
alkylated LnIII-AlIII heterobimetallic complexes are depicted
in Chart 1, showing organoaluminum adduct formation
(A),15–19 [phenolate] f [alkyl] interchange (B),17 and ligand
redistribution (C, D)20,21 as the predominant reaction pathways.
Because the reaction outcome is decisively affected by
the LnIII cation size, different product spectra could be
anticipated for similar transformations involving the larger
Aryloxide (phenolate) moieties [OArR] provide versatile
ancillary ligand sets for the highly oxophilic rare-earth metal
centers and have been widely used as monovalent [O]– and
chelating divalent [O(Do)nO]2– derivatives (Do ) neutral
donor functionalitiy, n ) 0, 1, 2).1,2 While the latter received
considerable attention as stabilizing ligands in organolan-
thanide catalysis (e.g., linked bis(phenolates) or SALEN-
type ligands),3–12 the former promote valuable synthesis
* To whom correspondence should be addressed. Fax: (+47) 5558-9490.
Phone: (+47) 5558-9491. E-mail: reiner.anwander@kj.uib.no.
† Dedicated to Prof. Jon Songstad on the occasion of his 70th birthday.
(1) Anwander, R. Top. Curr. Chem. 1996, 179, 149.
(2) Bradley, D. C.; Mehrota, R. C.; Rothwell, I. P.; Singh, A. Alkoxo and
Aryloxo DeriVatiVes of Metals; Academic Press: San Diego, CA, 2001;
p 704.
(13) Anwander, R. Top. Organomet. Chem. 1999, 2, 1.
(14) Fischbach, A.; Anwander, R. AdV. Polym. Sci. 2006, 204, 155.
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D. W.; Scott, B. L.; Watkin, J. G. Organometallics 2002, 21, 127.
(16) 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.
(3) Piers, W. E.; Emslie, D. J. H. Coord. Chem. ReV. 2002, 233–234,
131.
(4) Hou, Z.; Wakatsuki, Y. Coord. Chem. ReV. 2002, 231, 1.
(5) Cozzi, P. G. Chem. Soc. ReV. 2004, 33, 410.
(6) Aspinall, H. C. Chem. ReV. 2002, 102, 1807.
(7) Hultzsch, K. C. AdV. Synth. Catal. 2005, 347, 367.
(8) Hultzsch, K. C.; Gribkov, D. V.; Hampel, F. J. Organomet. Chem.
2005, 690, 4441.
(17) Fischbach, A.; Herdtweck, E.; Anwander, R.; Eickerling, G.; Scherer,
W. Organometallics 2003, 22, 499.
(9) Larrow, J. F.; Jacobsen, E. N. Top. Organomet. Chem. 2004, 6, 123.
(10) Katsuki, T. Chem. Soc. ReV. 2004, 33, 437.
(11) Jacobsen, E. N. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
VCH: New York, 1993.
(18) Fischbach, A.; Meermann, C.; Eickerling, G.; Scherer, W.; Anwander,
R. Macromolecules 2006, 39, 6811.
(19) Fischbach, A. PhD Thesis, Technische Universität München: München,
Germany, 2003.
(12) Jacobsen, E. N. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Hegedus, L. S., Eds.; Pergamon:
Oxford, U.K., 1995; Vol. 12.
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4696 Inorganic Chemistry, Vol. 47, No. 11, 2008
10.1021/ic702517s CCC: $40.75  2008 American Chemical Society
Published on Web 04/29/2008

Peralkylated LnIIAlIII Heterobimetallic Complexes
Chart 1. X-ray Crystallographically Characterized Alkylated LnIII-AlIII
(in toluene) and 2 (in hexane) with bulky 2,6-di-tert-butyl-4-
methylphenol (HOArtBu,Me) and 2,6-di-isopropylphenol (HOAr-
iPr,H) at ambient temperature (Scheme 2).
Heterobimetallic Aryloxides
Protonolysis reactions occurred instantly as indicated by
gas evolution and color change. The reaction mixtures were
stirred overnight, filtered to remove possible insoluble starting
materials, and the solvent evaporated. The obtained residues
were examined by NMR spectroscopy either directly or after
crystallization. The LnII-AlIII heterobimetallic aryloxide
complexes 3-10 could be isolated as dark-red (Sm) or
yellow crystalline solids (Yb). Generally, the reactions gave
complicated product mixtures containing up to three alkyl-
ation products. As a rule, fractionate crystallization was the
only proper means to unequivocally characterize the reaction
products. Single-crystal X-ray diffraction analyses were
performed on complexes 4a, 5, 6, 7b, 8a, 9, and 10 after
recrystallization from toluene or hexane at -35 °C. The fully
characterized reaction products are shown in Scheme 2.
[Ln(AlMe4)2]n-HOArtBu,Me Reactions. Treatment of a
suspension of [Ln(AlMe4)2]n in toluene with HOArtBu,Me gave
reddish brown (Ln ) Sm, 3a) or yellow (Ln ) Yb, 3b)
compounds which could be crystallized from toluene in
Scheme 1. TMA Adduct Formation versus Peralkylation of
Lanthanide(II) Aryloxides with Excess of Trimethylaluminum17
1
moderate yields. The H NMR spectra of compounds 3
proved the formation of bis(TMA) adducts of the composi-
tion Ln[(µ-OArtBu,Me)(µ-Me)AlMe2]2, in agreement with our
previous findings using LnII aryloxides and excess [AlMe3]
(Scheme 1).17 Hence, the bis(TMA) adducts can be obtained
by at least two different synthesis approaches. Unfortunately,
single-crystals of 3b from this alternative synthesis protocol
provided only nonconclusive crystallographic data. In an
attempt to access putative mono(TMA) adduct-tetramethyl-
aluminate intermediates Sm[(µ-OArtBu,Me)(µ-Me)AlMe2]-
(AlMe4), we reacted [Sm(AlMe4)2]n (1a) with only 1 equiv
of HOArtBu,Me. However, unreacted 1a, which was separated
from the reaction mixture after 16 h of stirring at ambient
temperature, pointed to a more complex protonolysis reac-
tion. The toluene-soluble part of the reaction mixture was
stored at -35 °C, and few single-crystals could be harvested
after several months. X-ray diffraction analysis revealed the
formation of complex [AlMe3(µ-OArtBu,Me)]Sm(µ-O-
ArtBu,Me)2Sm[(µ-OArtBu,Me)AlMe3] (5, Figure 1, Table 1).
Complex 5 is in accordance with the initial occurrence of an
LnII metal centers. Herein we describe the synthesis and
structural characterization of such alkylated LnII–AlIII het-
erobimetallic aryloxide complexes.
Results and Discussion
We have previously reported that TMA adduct formation
and [phenolate] f [alkyl] interchange are the predominant
reaction pathways when LnII(OArR)2(THF)x are treated with
TMA. As shown for a series of 2,6-di-tert-butyl- and
diphenyl-substituted phenolate complexes of the divalent
lanthanide metal centers samarium and ytterbium, homoleptic
bis(trialkylaluminum) adducts Ln[(µ-OArR)(µ-R)AlR2]2 could
be generated in good yields (Scheme 1).17 Depending on
the type of phenolate substituent in the 4-position (H vs Me
vs tBu) varying amounts of permethylated [Ln(AlMe4)2]x
were obtained as byproducts. The sterically less crowded 2,6-
iPr2-substituted phenolates afforded homoleptic tetramethy-
laluminates in quantitative yields.17 Unfortunately, such
binary Ln(OArR)2(THF)x/[AlR3] mixtures did not afford
single-crystalline mixed alkyl/aryloxide complexes.
extensive protonolysis reaction, with full [AlMe4]/[µ-OArtBu,Me
]
ligand exchange. One can speculate about that the “relatively
small” amount of TMA released by this one equivalent reaction
might not be sufficient to completely disrupt the dimeric/
tBu,Me
oligomeric arrangement of [Sm(OAr
) ] . Such a scenario
2 n
would make mono(TMA) adduct complex 5 a plausible
intermediate in binary Ln(OArtBu,H)2(THF)x/exc AlR3 mixtures
leading to the bis(TMA) adducts (Scheme 1). Alternatively,
The aim of the present study was therefore to apply a different
reaction protocol. Peralkylated [Ln(AlR4)2]n (R ) Me (1), Et
(2); Ln ) Sm (a), Yb (b)) are readily available LnII-AlIII
heterobimetallic complexes which were found to engage in
protonolysis reactions with HC5Me5.22 Aiming at bis(aryloxide)
complexes LnII[(OArR)x(AlRy)z] of the A- and B-type (Chart
1), we examined the two equivalent reactions of complexes 1
(22) Sommerfeldt, H. M.; Meermann, C.; Schrems, M. G.; Törnroos, K. W.;
Frøystein, N. Å.; Miller, R. J.; Scheidt, E.-W.; Scherer, W.; Anwander,
R. 2008, 1899.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4697

Sommerfeldt et al.
a
Scheme 2. Reactivity of [Ln(AlR4)2]n (R ) Me (1), Et (2); Ln ) Sm (a), Yb (b)) toward bulky phenols HOAriPr,H and HOArtBu,Me
a All reactions were performed in toluene (for 1) or hexane (for 2) with 2 equiv of HOArR. Isolated complexes are shown only, and X-ray crystallographically
authenticated complexes are denoted by asterisks. (i) Reaction performed in toluene with 1 equiv HOArtBu,Me. (ii) Degradation product, most likely the result
of the presence of traces of H2O. (iii) 7b was also obtained with 4 equiv of HOAriPr,H. (iv) Coordinated THF possibly originates from Yb(AlEt4)2(THF)2
present as a minor impurity. (v) Main product, but slower crystallization.
Table 1. Selected Interatomic Distances (Å) and Angles (deg) for 5
bond distances
Sm1· · ·Sm1′
Sm1-O1
Sm1′-O1
Sm1-O2
Sm1-C10′
Sm1-C13′
Sm1· · ·C16
4.0036(2)
2.4017(12)
2.4748(13)
2.5953(12)
3.142
Al1-O2
O1-C1
O2-C16
Al1-C31
Al1-C32
Al1-C33
1.8682(13)
1.365(2)
1.369(2)
1.992(2)
1.990(2)
1.993(2)
3.133
2.8412(17)
bond distances
Sm1-O1-Sm1′
Sm1-O1-C1
Sm1′-O1–C1
Sm1-O2-C16
Sm1-O2-Al1
110.36(5)
Al1-O2-C16
O1-Sm1-O1′
O1-Sm1-O2
O2-Sm1-O1′
140.41(11)
69.64(5)
141.17(4)
147.33(4)
140.33(11)
109.07(10)
85.66(9)
133.93(6)
oxygen atoms of the terminal aryloxide each feature one
coordinated TMA molecule. Such single mono[aryl(alk)ox-
ide] bridges were previously observed in the only other
reported LnII–AlIII heterobimetallic alkoxide complex, [AlMe3-
(µ-OCH2CH2OMe)]Eu[(µ-OCH2CH2OMe)2AlMe2]2Eu[(µ-
OCH2CH2OMe)AlMe3] (formula E, Chart 2).24,25
Another interesting structural feature of 5 is a rather acute
Sm1-O2-C16 angle (85.66(9)°) and concomitant short
contact of 2.8412(17) Å between the metal center and the
ipso-carbon of the aromatic ring. This Sm1 · · · C16 distance
lies in the range of ordinary SmII-C bond lengths as reported
for [Sm{C(SiMe3)2(SiMe2OMe)}2(THF)] (2.787(5) and
2.845(5) Å)26 and Sm(AlEt4)2(THF)2 (2.774 Å).27 Similar
Ln-heteroatom-Cipso bonding patterns were observed in
[{[(Me3Si)2CH](C6H4-2-CH2NMe2)P}2Sm(THF)] (Sm · · ·C )
Figure 1. Molecular structure of 5 with atomic displacement parameters
set at the 50% probability level. Hydrogen atoms are omitted for clarity.
extensive ligand redistribution could lead to the formation of
compound 5.
The molecular structure of 5 is comparable to dimeric
23
[Yb(OArtBu,H)(µ-OArtBu,H)]2 (Table 2) except that the
(23) van den Hende, J. R.; Hitchcock, P. B.; Holmes, S. A.; Lappert, M. F.
J. Chem. Soc., Dalton Trans. 1995, 1435.
4698 Inorganic Chemistry, Vol. 47, No. 11, 2008

Peralkylated LnIIAlIII Heterobimetallic Complexes
Table 2. Ln-O Bond Distances in Homoleptic and Heteroleptic Yb(II) and Sm(II) Aryloxides
compounda
Ln-O (Å)
Ln-(µ-O) (Å)
ref
homoleptic (+ donor)
[Yb(µ-OC6H2tBu2-2,6-Me-4)(OC6H2tBu2-2,6-Me-4)]2
Yb(OC6H2tBu2-2,6-Me-4)2(L)x (L ) HMPA, THF, OEt2)
[Yb(OC6H2tBu3-2,4,6)2(THF)3](THF)n (n ) 0, 0.5)
Yb(OC6H3tBu2-2,6)2(NCMe)4
[Yb(OC6H2tBu2-2,6-OMe-4)2(THF)3](THF)
[Sm(OC6H2tBu2-2,6-OMe-4)2(THF)3](THF)
[Sm(OC6H2tBu2-2,6-Me-4)2(THF)3](L) (L ) THF or MePh)
[Sm(OC6H2tBu3-2,4,6)2(THF)3](THF)
2.08(2), 2.10(2)
2.25(2)-2.37(2)
23, 31
32, 33
34, 35
36
37
37
38–40
41
42
2.126(9)-2.298(7)
2.219(8)-2.232(8)
2.204(12), 2.245(10)
2.229(5), 2.232(5)
2.299(7), 2.305(7)
2.290(9)-2.347(13)
2.325(6), 2.343(6)
2.336(7)
[KSm(OC6H2tBu2-2,6-Me-4)3(THF)]∞
2.362(6), 2.319(9)
2.425(5),2.512(16)
heteroleptic
{Yb(OC6H2tBu2-2,6-Me-4)[(DIPPh)2nacnac](THF)}(THF)
[Sm(OC6H2tBu2-2,6-Me-4)(µ-I)(THF)3]2(THF)2
(C5Me5)Sm(OC6H2tBu2-2,6-Me-4)(HMPA)2
2.179(3)
2.300(10)
2.345(4)
43
38
38
30
[(C5Me5)Sm(µ-OC6H2tBu3-2,4,6)]2
[(C5Me5)Sm(OC6H2tBu2-2,6-R-4)(µ-C5Me5)K(THF)2]∞ (R ) H, Me)
2.29(2), 2.330(6)
30, 44
a [(DIPPh)2nacnac] ) Diisopropylphenyl ꢀ-diketiminate.
3.030(3) Å, Sm-P-C ) 70.89(8)°),28 and [{Me2Al(µ-
Me2)}2Nd(µ3-NPh)(µ-Me)AlMe]2 (Nd · · · C ) 2.723(6) Å,
Nd-N-C ) 87.03(3)°).29 The Sm-Cipso interactions in 5
imply longer Sm-O2 bond distances (2.5953(12) Å) than
those of the asymmetrically homometal-bridging unit
(2.4017(12) and 2.4748(13) Å). The latter Sm-O1/O1′ bond
lengths, however, are similar to the ones reported for
[(C5Me5)Sm(µ-OC6H2tBu3-2,4,6)]2 (see Table 2).30
[Ln(AlEt4)2]n-HOArtBu,Me Reactions. Similar to the
[Ln(AlMe4)2]n-reactions, treatment of the perethylated com-
plexes [Ln(AlEt4)2]n with two equivalents HOArtBu,Me af-
forded reddish brown (Ln ) Sm, 4a) and yellow (Ln ) Yb,
4b) solids. The solution 1H NMR spectra of 4 were consistent
with the formation of bis(TEA) adducts Ln[(µ-OArtBu,Me)(µ-
(24) Evans, W. J.; Greci, M. A.; Ziller, J. W. Inorg. Chem. 1998, 37, 5221.
(25) For similar coordination motifs in alkaline earth metal chemistry, see:
(a) Urko, J.; Szafert, S.; Jerzykiewicz, L. B.; Sobota, P. Inorg. Chem.
2005, 44, 5194. (b) Urko, J.; Ejfler, J.; Szafert, S.; John, L.;
Jerzykiewicz, L. B.; Sobota, P. Inorg. Chem. 2006, 45, 5302.
(26) Clegg, W.; Eaborn, C.; Izod, K.; O’Shaughnessy, P.; Smith, J. D.
Angew. Chem., Int. Ed. 1997, 36, 2815.
Figure 2. Ball and stick structure of 4a.
(27) Schrems, M. G.; Dietrich, H. M.; Törnroos, K. W.; Anwander, R.
Chem. Commun. 2005, 5922.
Et)AlEt2]2. Dark-red single crystals of 4a suitable for an
X-ray structure analysis were grown from a hexane solution.
Although low-quality crystallographic data unambiguously
revealed the connectivity of 4a as a bis(TEA) adduct, a
detailed analysis of the metrical parameters is not warranted
(Figure 2). The samarium atom is surrounded by two [(µ-
Et)(AlEt2)] units and two aryloxide ligands, which are tilted
toward the lanthanide center, resulting in short Sm-Cipso
contacts as observed in complex 5 (vide supra).
Exhaustive recrystallization of compound 4a from toluene
yielded few dark-red single-crystals of plate-like morphology.
The X-ray structure analysis revealed the formation of
complex Sm[(µ-OArtBu,Me)AlEt2OAlEt2(µ-OArtBu,Me)](tolu-
ene) (6) (Figure 3, Table 3), apparently generated by
adventitious hydrolysis of 4a. Thus, release of two ethane
molecules and a concomitant alumoxane linkage accom-
plished a new tridentate bis(aryloxide)alumoxane ligand. The
formation of the latter [OOO]2-–type ligand can also be
rationalized by the templating action of the large SmII center.
Complex 6 in a way provides additional evidence of the
existence of bis(TEA) adducts 4. Similar ethylalumoxane
(28) Izod, K.; O’Shaughnessy, P.; Sheffield, J.; Clegg, W.; Liddle, S. Inorg.
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(29) Evans, W. J.; Ansari, M. A.; Ziller, J. W.; Khan, S. I. Inorg. Chem.
1996, 35, 5435.
(30) Hou, Z.; Zhang, Y.; Yoshimura, T.; Wakatsuki, Y. Organometallics
1997, 16, 2963.
(31) van den Hende, J. R.; Hitchcock, P. B.; Lappert, M. F. J. Chem. Soc.,
Chem. Commun. 1994, 1413.
(32) Hou, Z. M.; Yamazaki, H.; Kobayashi, K.; Fujiwara, Y.; Taniguchi,
H. J. Chem. Soc., Chem. Commun. 1992, 722.
(33) Deacon, G. B.; Hitchcock, P. B.; Holmes, S. A.; Lappert, M. F.;
Mackinnon, P.; Newnham, R. H. J. Chem. Soc., Chem. Commun. 1989,
935.
(34) Trifonov, A. A.; Kirillov, E. N.; Fedorova, E. A.; Makarenko, N. P.;
Bochkarev, M. N.; Schumann, H.; Muehle, S. Russ. Chem. Bull. 1998,
47, 2274.
(35) Deacon, G. B.; Feng, T.; Mackinnon, P.; Newnham, R. H.; Nickel,
S.; Skelton, B. W.; White, A. H. Aust. J. Chem. 1993, 46, 387.
(36) Carretas, J.; Branco, J.; Marcalo, J.; Domingos, A.; Pires de Matos,
A. Polyhedron 2003, 22, 1425.
(37) Deacon, G. B.; Fallon, G. D.; Forsyth, C. M.; Harris, S. C.; Junk,
P. C.; Skelton, B. W.; White, A. H. Dalton Trans. 2006, 802.
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H.; Wakatsuki, Y. Inorg. Chem. 1996, 35, 7190.
(39) Qi, G. Z.; Shen, Q.; Lin, Y. H. Acta Crystallogr., Sect. C 1994, 50,
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Inorganic Chemistry, Vol. 47, No. 11, 2008 4699

Sommerfeldt et al.
Coordination of the tridentate bis(aryloxide)alumoxane
ligand renders the SmII center in complex 6 sterically
unsaturated. The Sm-O-Cipso angles of 101.84(13)° and
105.68(16)° are considerably less acute than in complex 5
(85.66(9)°); however, additional Sm · · · Cipso contacts of av
3.170 Å seem to increase the coordination number. More-
over, a toluene molecule was found in close proximity to
the SmII center, apparently residing in a coordination pocket
formed by equidirectional tilting of the phenyl rings (cf.,
metal calix[n]arene complexes).46,47 Significant π-coordina-
tion is indeed indicated by an average Sm-C(toluene)
distance of 3.24 Å (Sm-Cnt ) 2.935(7) Å). For comparison,
the formally nine-coordinated (η6-arene)SmIII(AlCl4)3 com-
pounds show Sm-C(arene) bond distances in the range of
2.89 – 2.91 Å.48 The Sm-O(aryloxide) bond lengths of av
2.552 Å are in the same range as found for 5. The
Sm-O(alumoxane) bond distance of 2.346(2) Å is the
shortest Sm-[OOO] contact in 6 and is comparable to
terminal Sm-O(aryloxide) bonds (Table 2).
Figure 3. Molecular structure of 6 with atomic displacement parameters
set at the 50% probability level. Hydrogen atoms and a second noncoor-
dinating toluene molecule are omitted for clarity.
[Ln(AlMe4)2]n–HOAriPr,H Reactions. In contrast to the
aforementioned HOArtBu,Me reactions, the less bulky phenol
HOAriPr,H led to extensive ligand rearrangement at the large
LnII metal centers (Scheme 2). Formation of large quantities
of [R2Al(µ-OAriPr,H)]2,49 which reassociate with the LnII metal
centers to form bidentate ligands [R2Al(µ-OAriPr,H)2] is
proposed. Such ligand rearrangement reactions are also
common for LnIII metal centers; however, in the presence
of the smaller aryl(alk)oxide ligands [OiPr],50 [OtBu],51
[OArMe,H] (C),20 and [OArH,Me] (D).21,52 Complexes showing
LnIII[R2Al(µ-OAriPr,H)2] moieties, have not yet been reported.
Note that EuII complex E (Chart 2) features bridging [R2Al(µ-
OR)2] ligands derived from the donor-functionalized ligand
[OCH2CH2OMe].24
Instant reaction of [Ln(AlMe4)2]n (1) with 2 equiv of
HOAriPr,H was indicated by gas evolution and color change
of the reaction mixture. For ytterbium (1b), the pale yellow
suspension turned into a red solution. The rearrangement
product Yb[(µ-OAriPr,H)2AlMe2]2 (7b) was obtained in form
of yellow crystals (45% yield). Surprisingly, unreacted or
ligand-reassembled, toluene-insoluble starting material
[Yb(AlMe4)2]n was not observed. At this place, one might
have speculated about the formation of toluene-soluble
π-coordinated coproducts Yb(AlMe4)2(C6H5Me), formed via
protonolytic degradation of the polymeric network of 1b and
subsequent ligand rearrangement. For comparison, tetra-
Table 3. Selected Interatomic Distances (Å) and Angles (deg) for 6
bond distances
Sm· · ·Al1
Sm· · ·Al2
Sm-O1
3.3320(7)
3.3314(8)
2.5525(17)
2.5522(18)
2.3485(17)
3.134(2)
3.205(2)
2.935(7)
1.8518(18)
Al2-O2
Al1-O3
Al2-O3
Al1-C16
Al1-C18
Al2-C20
Al2-C22
O1-C1
1.857(2)
1.7571(2)
1.7638(2)
1.987(3)
1.988(4)
1.990(4)
1.980(3)
1.369(3)
1.368(3)
Sm-O2
Sm-O3
Sm· · ·C1
Sm· · ·C24
Sm· · ·Cnta
Al1-O1
O2-C24
bond angles
O1-Sm-O2
Sm-O1-C1
Sm-O2-C24
127.46(6)
101.84(13)
105.68(16)
Sm-O1-Al1
Sm-O2-Al2
Al1-O3-Al2
97.04(7)
96.89(7)
144.73(11)
a Cnt ) ring centroid of the coordinated toluene molecule.
Chart 2. Unusual Al-O Interactions in Ln-AlIII Heterobimetallic
Complexes
(44) Hou, Z.; Zhang, Y.; Tezuka, H.; Xie, P.; Tardif, O.; Koizumi, T. A.;
Yamazaki, H.; Wakatsuki, Y. J. Am. Chem. Soc. 2000, 122, 10533.
(45) Evans, W. J.; Champagne, T. M.; Ziller, J. W. Organometallics 2005,
24, 4882.
(46) Gutsche, C. D. Calixarenes; Royal Society of Chemistry: Cambridge,
U.K., 1989.
units have been found recently in a samarocene(III) complex
F (Chart 2), obtained by treatment of carboxylate complex
[(C5Me5)2Sm(µ-O2CPh)]2 with TEA.45
(47) Asfari, Z.; Böhmer, V.; Harrowfield, J.; Vicens, J. Calixarenes 2001;
Kluwer Academic: New York, 2001.
(48) Deacon, G. B.; Shen, Q. J. Organomet. Chem. 1996, 506, 1.
(49) Firth, A. V.; Stewart, J. C.; Hoskin, A. J.; Stephan, D. W. J.
Organomet. Chem. 1999, 591, 185.
(41) Yuan, F. G.; Zhu, X. H.; Weng, L. H. Chinese J. Struct. Chem. 2005,
(50) Giesbrecht, G. R.; Gordon, J. C.; Clark, D. L.; Scott, B. L.; Watkin,
J. G.; Young, K. J. Inorg. Chem. 2002, 41, 6372.
(51) Evans, W. J.; Boyle, T. J.; Ziller, J. W. J. Am. Chem. Soc. 1993, 115,
5084.
24, 1152.
(42) Evans, W. J.; Anwander, R.; Ansari, M. A.; Ziller, J. W. Inorg. Chem.
1995, 34, 5.
(43) Yao, Y.; Zhang, Y.; Zhang, Z.; Shen, Q.; Yu, K. Organometallics
2003, 22, 2876.
(52) Fischbach, A.; Perdih, F.; Herdtweck, E.; Anwander, R. Organome-
tallics 2006, 25, 1626.
4700 Inorganic Chemistry, Vol. 47, No. 11, 2008

Peralkylated LnIIAlIII Heterobimetallic Complexes
[Ln(AlEt4)2]n-HOAriPr,H Reactions. Similar to the
[Yb(AlMe4)2]n-HOAriPr,H reaction, treatment of hexane-
soluble [Sm(AlEt4)2]n (2a) with 2 equiv of HOAriPr,H gave
predominantly ligand redistribution yielding dark-red Sm[(µ-
OAriPr,H)2(AlEt2)]2 (8a) as the main product. Complex 8a
exhibits a coordination environment and geometry similar
to that found in 7b (Figure 5, Table 4). As discussed for 7b,
a close contact between the metal center and one of the iPr-
groups (Sm · · · C16 ) 3.186 Å) suggests steric saturation by
agostic interactions also in 8a. The average Sm-O bond
distance of 2.484 Å agrees with those in [(C5Me5)Sm(µ-
OC6H2tBu3-2,4,6)]2 (Table 2).30
The analogous reaction between [Yb(AlEt4)2]n (2b) and
HOAriPr,H (2 equiv, 16 h, ambient temperature) resulted in a
product mixture, which after crystallization from hexane at
-35 °C yielded at least two crystalline compounds as
indicated by their different crystal morphologies. Fractionate
crystallization and X-ray diffraction studies revealed the
formation of an ytterbium dimer of the composition [Et2Al(µ-
OAriPr,H)2Yb(µ-Et)2AlEt(µ-Et)]2 (9) and monomeric bis-
(TEA)mono(THF) adduct Yb[(µ-OAriPr,H)(µ-Et)AlEt2]2(THF)
(10) (Figures 6 and 7, Tables 5 and 6). While compound 9
was identified as the main product by NMR spectroscopy,
adventitious amounts of THF facilitated the crystallization
of complex 10 as a minor coproduct. Complex 9 once more
proves that [R2Al(µ-OAriPr,H)]-promoted ligand rearrange-
ment is a favorable reaction pathway at large LnII centers.
Moreover, complex 9 features the only isolated complex in
this study with intact tetraalkylaluminate ligands (coordina-
tion mode ) µ2-η2:η1).55
The ytterbium centers in 9 feature a distorted square
pyramidal coordination geometry with two aryloxide oxygen
atoms of the rearranged bidentate ligand [Et2Al(µ-OAriPr,H)2]
ligand and two methylene carbon atoms of the η2-coordinated
tetraethylaluminate ligand in the basal positions. The apical
position is occupied by the methylene carbon atom of the
second η1-coordinated tetraethylaluminate ligand. In complex
10, the ligands also adopt a square pyramidal geometry, with
one THF molecule in the apical position and two [(µ-
OAriPr,H)(µ-Et)AlEt2] units forming the basal plane. The
Yb-C bond distances average 2.678 Å (9) and 2.678 Å (10)
and are comparable to those in Yb(AlEt4)2(THF)2 (av 2.663
Å)26 and [Yb(AlEt4)2]n (2b, av 2.675 Å).56 These bridging
Yb-C bond distances, however, are markedly longer than
the Yb-C σ-bonds in Yb[C(SiMe3)2(SiMe2CHdCH2)]-
I(OEt2) (2.50(2) Å),57 and Yb(C6H3Ph2-2,6)I(THF)3 (2.529(4)
Å).58 The average Yb-O bond distances in 9 (2.337 Å) and
10 (2.318 Å) lie in the range of Yb-(µ-OAr) distances (Table
2); however, they are shorter than in 7b (2.383 Å).
Figure 4. Molecular structure of 7b. Atomic displacement parameters are
set at the 50% probability level and hydrogen atoms are omitted for clarity,
except for agostically interacting H36B and H13A.
chloro-aluminate complexes [Yb(AlCl4)2] form soluble π-co-
ordinated benzene and mesitylene derivatives.53 However,
the formation of π-coordinated coproducts Yb(AlMe4)2-
(C6H5Me) can be ruled out on the basis of the NMR spectra,
and unfortunately, we could not identify any other YbII
reaction product. Complex 7b was obtained in high yields
by reaction of 1b with 4 equiv of the phenol. In contrast,
such rearrangement products were not observed when
Yb(OAriPr,H)2(THF)2 was treated with 6 equiv of TMA (cf.,
Scheme 1).17 According to the 1H NMR spectrum the
corresponding samarium-reaction did also form one major
product that we assign to Sm[(µ-OAriPr,H)2AlMe2]2 (7a).
The molecular structure and metrical parameters of 7b are
shown in Figure 4 and Table 4, respectively. The ytterbium
metal center adopts a distorted tetrahedral geometry. The
average Yb-O distance of 2.384 Å lies somewhat above
the expected range (cf., Table 2).
All the hydrogen atoms on the carbon atoms C13 and C36
were located in the difference Fourier maps and refined
isotropically, indicating that the coordination sphere of the
ytterbium center is additionally saturated by agostic interac-
tions with two of the iPr groups, resulting in short Yb · · · C
and Yb · · ·H distances (Yb · · ·C13 ) 3.055(4) Å, Yb · · ·H13A
) 2.56(3) Å, Yb · · · C36 ) 3.067(4) Å, Yb · · · H36B )
2.52(3) Å). The average Al-O bond distance (1.839 Å),
O-Yb-O bond angle (66.1°), and O-Al-O bond angle
(89.9°) in 7b compare to [(ArMe,HO)2(THF)2YbIII(µ-
OArMe,H)2AlMe2] (1.846(10) Å/65.6(9)°/85.1(6)°).54 The
Yb-O-Cipso angles (av 131.6°) lie in the range of those
found for the bridging aryloxide ligands in YIII(OAriPr,H)[(µ-
OAriPr,H)(µ-Me)AlMe2]2 (125.33(9)° and 129.0(1)°)17 and
SmIII(OAriPr,H)[(µ-OAriPr,H)(µ-Me)AlMe2]2 (125.9(3)° and
135.2(2)°).15
An interesting aspect of the molecular structures of 9 and
10 is the coordination mode of the bridging ethyl groups.
All the relevant hydrogen atoms were located in the
difference Fourier maps and refined isotropically. Because
(55) Dietrich, H. M.; Schuster, O.; Törnroos, K. W.; Anwander, R. Angew.
Chem., Int. Ed. 2006, 45, 4858.
(56) Klimpel, M. G.; Anwander, R.; Tafipolsky, M.; Scherer, W. Orga-
nometallics 2001, 20, 3983.
(53) Troyanov, S. I. Russ. J. Coord. Chem. 1998, 24, 351.
(54) Evans, W. J.; Ansari, M. A.; Ziller, J. W. Inorg. Chem. 1995, 34,
3079.
(57) Eaborn, C.; Hitchcock, P. B.; Izod, K.; Lu, Z. R.; Smith, J. D.
Organometallics 1996, 15, 4783.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4701

Sommerfeldt et al.
Table 4. Selected Bond Distances (Å) and Angles (deg) for Complexes 7b and 8a
bond distances
Ln· · ·Al1
Ln· · ·Al2
Ln-O1
7b
8a
bond distances
O2-C15b
O3-C29c
O4-C41d
Al1-C1
7b
8a
3.2916(10)
3.3056(9)
2.364(2)
2.407(2)
2.365(2)
2.399(2)
1.849(2)
1.829(2)
1.840(2)
1.839(2)
1.390(4)
3.4162(14)
3.3381(14)
2.457(3)
2.517(2)
2.451(3)
2.531(3)
1.842(4)
1.838(3)
1.824(4)
1.839(4)
1.372(5)
1.386(3)
1.389(3)
1.387(3)
1.958(4)
1.950(4)
1.966(4)
1.964(3)
3.055(4)
3.067(4)
2.56(3)
1.384(5)
1.383(5)
1.389(6)
1.968(6)
1.946(5)
1.952(7)
1.967(6)
3.186(7)
Ln-O2
Ln-O3
Ln-O4
Al1-O1
Al1-O2
Al2-O3
Al2-O4
O1-C3a
Al1-C2e
Al2-C27f
Al2-C28g
Ln · · ·C13h
Ln · · ·C36
Ln · · ·H13Ah
Ln · · ·H36B
2.62
2.52(3)
bond angles
O1-Ln-O2
O3-Ln-O4
O1-Al1-O2
O3-Al2-O4
7b
8a
bond angles
Ln-O1-C3a
Ln-O2-C15b
Ln-O3-C29c
Ln-O4-C41d
7b
8a
66.36(7)
65.84(7)
90.46(10)
89.47(10)
62.90(10)
61.67(10)
89.72(14)
88.43(15)
133.84(2)
132.82(17)
129.22(18)
130.67(16)
127.5(2)
130.3(3)
137.2(3)
134.8(3)
a C5. b C17. c C33. d C45. e C3. f C29. g C31. h C16 in complex 8a.
76.6°),61 [Yb(AlEt4)2]n (2b, Yb· · ·CCH ) 3.056(9)-3.364(6) Å,
3
Yb-C-C ) 85.3(4)-97.3(3)°),56 and [Sm(AlEt4)2]n (2a, av
Sm · · ·CCH ) 3.215 Å, Sm-C-C ) 82.7(6)-93.0(5)°).22
3
Conclusions
Peralkylated complexes [Ln(AlR4)2]n readily undergo
protonolysis/alkane elimination reactions with bulky phenolic
substrates HOArtBu,Me and HOAriPr,H. Two prevalent second-
ary reaction pathways have been unambiguously identified,
TMA(TEA) adduct formation and ligand rearrangement
under formation of the new bidentate ligands [(µ-
OAriPr,H)2AlMe2] and [(µ-OAriPr,H)2AlEt2]. These are known
reaction patterns from trivalent organo-rare-earth metal
chemistry involving binary mixtures Ln(OAr)3(THF)x/AlR3
with smaller methyl-substituted phenol ligands (see Chart
1, C and D). Although, the larger LnII metal centers can
template the formation of [(µ-OAriPr,H)2AlEt2] moieties, the
tert-butyl-substituted aryloxides seem to be too bulky to
engage in such a ligand rearrangement. Because of the
absence of donor solvent molecules the new homo- and
heteroleptic aryloxide complexes are stereoelectronically
unsaturated and, hence, feature distinct secondary intramo-
lecular interactions comprising close Ln-Cipso(aryloxide)
and Ln-πarene(solvent) contacts, as well as LnII · · ·(H-C) R-
and ꢀ-agostic interactions with bridging methyl/ethyl ligands
and the iPr groups of [OAriPr,H].
Figure 5. Molecular structure of 8a. Atomic displacement parameters are
set at the 50% probability level, and hydrogen atoms and iPr-methyl groups
are omitted for clarity.
of the steric unsaturation of the metal center in 9, both of
the hydrogen atoms in the bridging CH2 groups, and
additionally one hydrogen atom of the CH3 group in the µ,η1-
coordinated [AlEt4]– moiety are directed toward the Yb atom
(Yb· · ·C6 ) 2.9694(17) Å, Figure 6B). In complex 10, both
hydrogen atoms on C13, together with H31A and H32B, are
positioned near the Yb center, suggesting one Yb· · · H-C
ꢀ-agostic and three Yb · · · H-C R-agostic interactions. A
similar structural motif was detected in the SmIII bis(TEA)
adduct complex Sm(OAriPr,H)[(µ-OAriPr,H)(µ-Et)AlEt2]2.16
While the Ln-CCH -CCH bond angles in the latter complex
Experimental Section
General Considerations. All manipulations were performed under
an argon atmosphere with rigorous exclusion of oxygen and water,
using standard Schlenk, high-vacuum, and glovebox techniques
(MBraun MB150B-G-II; <1 ppm O2, <1 ppm H2O). Hexane, toluene,
and THF were purified using Grubbs columns (MBraun SPS, solvent
purification system). C6D6 was obtained from Aldrich, dried over Na
for 24 h, filtered, and stored in the glovebox. Trimethyl-, and
triethylaluminum, and 2,6-di-isopropylphenol were purchased from
Aldrich and used as received. 2,6-Di-tert-butyl-4-methylphenol (Al-
drich) was sublimed prior to use. Complexes [Ln(AlR4)2]n (R ) Me
2
3
are almost linear (av 166.3(5)°),16 the C5-C6 (9) and
C31-C32 (10) ethyl groups approach the Yb center side-on
forming short Yb · · ·CCH interactions (2.9694(17) and 3.020(3)
3
Å for 9 and 10, respectively). As a consequence, the
Yb-CCH -CCH angles are 82.11(9)° (9) and 88.02(18)° (10),
2
3
corroborating agostic deformations.56,59,60 Similar side-on
bondings of ethyl groups were previously found in (C5Me5)2Yb(µ-
Et)(AlEt2)(THF) (Yb · · ·CCH ) 2.939(21) Å, Yb-C-C )
3
(60) Haaland, A.; Scherer, W.; Ruud, K.; McGrady, G. S.; Downs, A. J.;
Swang, O. J. Am. Chem. Soc. 1998, 120, 3762.
(58) Heckmann, G.; Niemeyer, M. J. Am. Chem. Soc. 2000, 122, 4227.
(59) Burger, B. J.; Thompson, M. E.; Cotter, W. D.; Bercaw, J. E. J. Am.
Chem. Soc. 1990, 112, 1566.
(61) Yamamoto, H.; Yasuda, H.; Yokota, K.; Nakamura, A.; Kai, Y.; Kasai,
N. Chem. Lett. 1988, 1963.
4702 Inorganic Chemistry, Vol. 47, No. 11, 2008

Peralkylated LnIIAlIII Heterobimetallic Complexes
Figure 6. (A) Molecular structure of 9 with atomic displacement parameters set at the 50% probability level; hydrogen atoms are omitted for clarity. (B)
YbII coordination environment in 9 emphasizing the agostically interacting hydrogen atoms (atomic displacement parameters set at the 50% probability
level).
Table 5. Selected Bond Distances (Å) and Angles (deg) for Complex 9
bond distances
Yb· · ·Al1
Yb· · ·Al2
Yb-O1
Yb-O2
Yb-C1
Yb-C3
Yb-C5
Yb· · ·C6
Al1-O1
Al2-O2
Al1-C1
Al1-C3
Al1-C5
3.1408(4)
3.2339(4)
Al1-C7
1.9785(17)
1.9666(16)
1.9798(17)
1.3875(17)
1.3944(17)
2.494(2)
2.42(2)
2.44(2)
2.42(2)
2.54(2)
2.52(2)
Al2-C9
2.3268(10)
2.3473(10)
2.6511(15)
2.6202(16)
2.7626(16)
2.9694(17)
1.8323(11)
1.8463(11)
2.0392(16)
2.0634(17)
2.0321(16)
Al2-C11
O1-C13
O2-C25
Yb · · ·H1A
Yb · · ·H1B
Yb · · ·H3A
Yb · · ·H3B
Yb · · ·H5A
Yb · · ·H5B
Yb · · ·H6A
2.42(2)
bond angles
O1-Yb-O2
C1-Yb-C3
O1-Yb-C3
O2-Yb-C1
Yb-O1-C13
66.30(3)
79.10(5)
140.47(4)
149.90(4)
126.90(8)
Yb-O2-C25
Yb-C1-C2
Yb-C3-C4
Yb-C5-C6
131.49(8)
168.52(13)
169.32(12)
82.11(9)
410 FTIR spectrometer as Nujol mulls sandwiched between CsI plates.
Elemental analyses were performed on an Elementar Vario EL III.
Crystallographic data for complexes 5, 6, 7b, 8a, 9, and 10 are
compiled in Table 7.
General Procedure for the Synthesis of Ln[(µ-OArtBu,Me)-
(µ-Me)AlMe2]2 (3). To a suspension of [Ln(AlMe4)2]n (1) in
toluene, a solution of HOArtBu,Me diluted in toluene was slowly
added. Gas formation and color changes were observed (Ln ) Sm,
dark purple to reddish brown; Ln ) Yb, pale yellow to bright
Figure 7. Molecular structure of 10 with atomic displacement parameters
set at the 50% probability level. Hydrogen atoms are omitted for clarity,
except for agostically interacting H13A/B, H31A, and H32B.
(1), Et (2)) were synthesized according to literature procedures.22,56
NMR spectra were recorded at 298 K on a Bruker-AV600 (5 mm
cryo probe, 1H 600.13 MHz; 13C 150.91 MHz). 1H and 13C shifts are
referenced to internal solvent resonances and reported in parts per
million relative to TMS. IR spectra were recorded on a Nicolet-Impact
Inorganic Chemistry, Vol. 47, No. 11, 2008 4703

Sommerfeldt et al.
Table 6. Selected Bond Distances (Å) and Angles (deg) for 10
3.49 (s, 36H, CMe3), 2.77 (s, 6H, ArMe), –20.99 (s, 18H,
(µ-Me)AlMe2). 13C NMR (C6D6, 25 °C): δ 132.0, 129.7, 125.2
(ArC), 49.3 (CMe3), 42.3 (CMe3), 21.8 (ArMe), –13.6 ((µ-
Me)AlMe2). Anal. Calcd for C36H64Al2O2Sm (733.2 g mol-1): C
58.97, H 8.80. Found: C 57.68, H 8.35.
bond distances
Yb· · ·Al1
Yb· · ·Al2
Yb-O1
Yb-O2
Yb-O3
Yb-C13
Yb-C31
Al1-O1
Al2-O2
O1-C1
3.3142(7)
3.2032(8)
2.3303(17)
2.3057(17)
2.3873(19)
2.700(2)
Al1-C13
Al1-C15
Al1-C17
Al2-C31
Al2-C33
Al2-C35
Yb · · ·H13A
Yb · · ·H13B
Yb · · ·H31A
Yb · · ·C32
Yb · · ·H32B
2.035(3)
1.987(3)
1.981(3)
2.049(3)
1.969(4)
1.980(3)
2.41(3)
2.45(3)
2.38(4)
3.020(3)
2.48(4)
Yb[(µ-OArtBu,Me)(µ-Me)AlMe2]2 (3b). Following the procedure
described above, [Yb(AlMe4)2]n (1b, 0.047 g, 0.14 mmol) and
HOArtBu,Me (0.061 g, 0.28 mmol) yielded 3b as a yellow solid (0.070
g, 0.09 mmol, 68%). IR (Nujol, cm-1): 1412 m, 1266 w, 1255 w,
1230 m, 1216 w, 1205 m, 1191 m, 1171 w, 863 w, 830 w, 818 w,
2.656(3)
1.8603(18)
1.8524(2)
1.388(3)
1
O2-C19
1.381(3)
805 w, 774 w, 695 m, 600 m, 529 w. H NMR (C6D6, 25 °C): δ
7.00 (s, 4H, ArH), 2.11 (s, 6H, ArMe), 1.32 (s, 36H, CMe3), –0.10
(s, 18H, (µ-Me)AlMe2). 13C NMR (C6D6, 25 °C): δ 151.5 (Cipso),
139.7, 129.8, 125.4 (ArC), 35.3 (CMe3), 32.3 (CMe3), 20.9 (ArMe),
–0.8 ((µ-Me)AlMe2). Anal. Calcd for C36H64Al2O2Yb (755.9 g
mol-1): C 57.20, H 8.53. Found: C 57.63, H 8.66.
bond angles
O1-Yb-O2
C13-Yb-C31
O1-Yb-C13
O2-Yb-C31
128.87(6)
Yb-O1-C1
126.16(14)
130.17(14)
161.5(2)
164.63(9)
69.94(7)
74.21(8)
Yb-O2-C19
Yb-C13-C14
Yb-C31-C32
88.02(18)
Table 7. Crystallographic Data for Complexes 5, 6, 7b, 8a, 9, and 10
7b
chemical formula C73H118Al2O4Sm2 C52H82Al2O3Sm C52H80Al2O4Y
General Procedure for the Synthesis of Ln[(µ-OArtBu,Me)-
(µ-Et)AlEt2]2 (4). To a solution of [Ln(AlEt4)2]n (2) in hexane, a
solution of HOArtBu,Me diluted in hexane was slowly added. Gas
formation and color change were observed (Ln ) Sm, dark purple
to reddish brown; Ln ) Yb, pale yellow to bright yellow). After it
had been stirred overnight, the solution was filtered, and the volume
was reduced. Crystallization was performed in hexane at -35 °C.
Sm[(µ-OArtBu,Me)(µ-Et)AlEt2]2 (4a). Following the procedure
described above, [Sm(AlEt4)2]n (2a, 0.047 g, 0.11 mmol) and
HOArtBu,Me (0.048 g, 0.22 mmol) yielded 4a as a brown solid (0.079
g, 0.14 mmol, 89%). 1H NMR (C6D6, 25 °C): δ 7.08 (s, 4H, ArH),
3.68 (s, 36H, CMe3), 1.97 (s, 6H, ArMe), –0.73 (s, 18H, (µ-
CH2CH3)Al(CH2CH3)2), –16.95 (s, 12H, (µ-CH2CH3)Al(CH2CH3)2).
13C NMR (C6D6, 25 °C): δ 132.0 (ArC), 129.7 (ArC), 125.2 (ArC),
121.5 (ArC), 49.3 (CMe3), 42.3 (CMe3), 21.8 (ArMe), –13.7 ([µ-
Et]AlEt2). Anal. Calcd for C42H76Al2O2Sm (817.4 g mol-1): C
61.72, H 9.37. Found: C 60.13, H 8.7.
5
6
Mr
1414.33
P1
959.49
996.16
P31c
20.9364(3)
20.9364(3)
43.7686(13)
90
j
j
j
space group
a (Å)
b (Å)
P1
12.9908(4)
13.9942(4)
20(8444(7)
78.114(1)
76.426(1)
77.902(1)
3552.43(19)
2
11.7050(4)
13.5958(5)
18.0156(7)
72.128(1)
80.171(1)
67.093(1)
2509.15(16)
2
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
90
120
16614.9(6)
12
6240
123(2)
1.195
F(000)
T (K)
1476
123(2)
1.322
1.706
1012
123(2)
1.270
Fcalcd (g cm-3
)
µ (mm-1
)
1.244
1.758
R1a (obsd), wR2b 0.0252, 0.0579
(all)
0.0365, 0.0965 0.0458, 0.0867
Sc
1.044
1.075 1.221
8a
9
10
Yb[(µ-OArtBu,Me)(µ-Et)AlEt2]2 (4b). Following the procedure
described above, [Yb(AlEt4)2]n (2b, 0.057 g, 0.12 mmol) and
HOArtBu,Me (0.055 g, 0.25 mmol) yielded 4b as a yellow solid (0.097
g, 0.12 mmol, 94%). IR (Nujol, cm-1): 1294 w, 1262 s, 1205 w,
1120 w, 1093 m, 1052 m, 918 w, 890 m, 860 m, 843 w, 805 w,
chemical formula C56H88Al2O4Sm C36H64Al2O2Yb C40H72Al2O3Yb
Mr
1029.57
P212121
16.2302(6)
18.4725(7)
18.7583(7)
90
755.87
Pbca
827.98
P21/c
18.3390(6)
12.8562(4)
19.6956(6)
90
114.234(1)
90
4234.4(2)
4
space group
a (Å)
b (Å)
18.7310(7)
20.1036(7)
20.4087(7)
90
1
774 w, 722 m, 640 s, 540 w. H NMR (C6D6, 25 °C): δ 7.01 (s,
c (Å)
3
4H, ArH), 2.10 (s, 6H, ArMe), 1.38 (t, JH,H ) 7.9 Hz, 18H, (µ-
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
CH2CH3)Al(CH2CH3)2), 1.34 (s, 36H, CMe3), 0.38 (q, 3JH,H ) 7.8
Hz, 12H, ((µ-CH2CH3)Al(CH2CH3)2). 13C NMR (C6D6, 25 °C): δ
152.3 (Cipso), 139.4 (Corto), 129.7 (Cpara), 125.7 (Cmeta), 35.6 (CMe3),
32.5 (CMe3), 20.8 (ArMe), 10.9 ((µ-CH2CH3)Al(CH2CH3)2), 7.2
((µ-CH2CH3)Al(CH2CH3)2). Anal. Calcd for C42H76Al2O2Yb (840.1
g mol-1): C 60.05, H 9.12. Found: C 60.83, H 9.27.
90
90
90
90
5624.0(4)
4
7685.1(5)
8
F(000)
T (K)
2176
123(2)
1.216
3136
1728
123(2)
1.299
123(2)
1.307
2.506
Fcalcd (g cm-3
)
µ (mm-1
)
1.116
2.282
R1a (obsd), wR2b 0.0370, 0.0994 0.0192, 0.0446 0.0309, 0.0781
(all)
General Procedure for the Synthesis of Ln[(µ-OAriPr,H)2-
AlMe2]2 (7). [Ln(AlMe4)2]n (1) was suspended in toluene, and a
solution of HOAriPr,H diluted in toluene was slowly added. Gas
evolution and color change were observed (Ln ) Sm, dark purple
to dark red; Ln ) Yb, pale yellow to red). The mixture was stirred
for 16 h at ambient temperature, filtered to remove insoluble parts,
dried in vacuo, and finally crystallized from hexane at -35 °C.
[Sm(µ-OAriPr,H)xAlMey] (7a). Following the procedure described
above, [Sm(AlMe4)2]n (1a, 0.044 g, 0.14 mmol) and HOAriPr,H
(0.051 g, 0.29 mmol) yielded a reddish brown solid (0.041 g, 0.04
mmol, 58%). Possible product Sm[(µ-OAriPr,H)2AlMe2]2 (7a). IR
(Nujol, cm-1): 1590 m, 1339 m, 1325 m, 1259 m, 1200 m, 1173 m,
1099 m, 1055 w, 1042 m, 934 w, 920 w, 888 m, 865 w, 834 s,
799 m, 756 s, 722 m, 691 s, 677 m, 620 w, 573 w. 1H NMR (C6D6,
25 °C): δ 5.34, 5.09, 1.44–0.86, –9.55. 13C NMR (C6D6, 25 °C): δ
Sc
1.088
1.078
1.119
a R1 ) ∑(|Fo| - |Fc|)/∑|Fo|. b wR2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2
.
2
2
c S ) [∑w(Fo - Fc )2/(no - np)]1/2
.
2
2
yellow). After it had been stirred overnight, the suspension was
centrifuged and filtered, and the volume was reduced. Crystallization
was performed in toluene at –35 °C.
Sm[(µ-OArtBu,Me)(µ-Me)AlMe2]2 (3a). Following the procedure
described above, [Sm(AlMe4)2]n (1a, 0.053 g, 0.16 mmol) and
HOArtBu,Me (0.058 g, 0.32 mmol) yielded 3a as a reddish brown
solid (0.103 g, 0.14 mmol, 45%). IR (Nujol, cm-1): 1600 w, 1422 s,
1365 s, 1296 w, 1261 m, 1237 m, 1227 m, 1201 s, 1154 w, 1124 w,
1019 m, 953 w, 889 m, 860 m, 833 m, 806 w, 774 m, 721 s, 699 s,
674 w, 576 w, 539 w. 1H NMR (C6D6, 25 °C): δ 7.97 (s, 4H, ArH),
4704 Inorganic Chemistry, Vol. 47, No. 11, 2008

Peralkylated LnIIAlIII Heterobimetallic Complexes
165.7, 120.1, 119.1, 118.0, 55.6, 30.0, –24.8. Anal. Calcd for
C52H80Al2O4Sm (973.5 g mol-1): C 64.15, H 8.28. Found: C 63.42,
H 7.80.
[Et2Al(µ-OAriPr,H)2Yb(µ-Et)2AlEt(µ-Et)]2 (9). To a stirred
solution of [Yb(AlEt4)2]n (2b, 0.091 g, 0.20 mmol) in hexane a
solution of HOAriPr,H (0.071 g, 0.40 mmol) diluted in hexane was
slowly added. Gas formation and color change of the reaction
mixture from yellow to orange were observed. After it had been
stirred overnight, the solution was filtered, and the volume was
reduced. Fractionate crystallization at -35 °C yielded 9 and 10 as
yellow crystals. Because there are several products in the reaction
mixture, the NMR spectra could not be unambiguously assigned
and satisfactory microanalytical data could not be obtained.
Tentatively, the following assignment is made for 9. 1H NMR
(C6D6, 25 °C): δ ) 6.98 (s, 4H ArH), 6.95–6.90 (m, 8H ArH),
Yb[(µ-OAriPr,H)2AlMe2]2 (7b). Following the procedure de-
scribed above, [Yb(AlMe4)2]n (1b, 0.044 g, 0.13 mmol) and
HOAriPr,H (0.048 g, 0.27 mmol) yielded 7b as yellow crystals (0.058
g, 0.06 mmol, 86%). IR (Nujol, cm-1): 1590 m, 1339 s, 1260 s,
1244 m, 1200 m, 1174 s, 1160 m, 1100 m, 1056 w, 1043 m, 934 m,
920 w, 889 w, 833 s, 799 m, 756 s, 722 m, 691 s, 670 m, 617 m,
1
578 m. H NMR (C6D6, 25 °C): δ 7.01–6.91 (m, 12H ArH), 3.60
(sept, 8H, CHMe2), 1.09 (d, 48H, CHMe2), –0.62 (s, 12H,
Al(CH3)2). 13C NMR (C6D6, 25 °C): δ 149.2 (Cipso), 138.3 (Cortho),
124.4 (Cmeta), 123.0 (Cpara), 26.6 (CHMe2), 24.6 (CHMe2), –8.2
(AlMe2). Anal. Calcd for C52H80Al2O4Yb (996.2 g mol-1): C 62.69,
H 8.09. Found: C 63.81, H 8.06.
3
3.65 (sept, 8H, CHMe2), 1.22 (s, br, 48H, CHMe2), 1.16 (t, JH,H
3
) 7.8 Hz, 24H, Al(CH2CH3)4), 1.06 (t, JH,H ) 8.4 Hz, 12H,
3
Al(CH2CH3)2), 0.20 (q, JH,H ) 8.4 Hz, 8H, Al(CH2CH3)2), 0.18
Sm[(µ-OAriPr,H)2AlEt2]2 (8a). To
a stirred solution of
3
(q, JH,H ) 7.8 Hz, 16H, Al(CH2CH3)4).
[Sm(AlEt4)2]n (2a, 0.170 g, 0.39 mmol) in hexane a solution of
HOAriPr,H (0.142 g, 0.80 mmol) diluted in hexane was slowly added.
Gas formation and a color change of the reaction mixture from
dark purple to reddish brown were observed. After it had been
stirred overnight, the solution was filtered, and the volume reduced.
Dark-red crystals of 8a (0.128 g, 0.12 mmol, 62%) were grown
from hexane at -35 °C. IR (Nujol, cm-1): 1590 m 1341 s, 1260 s,
1203 m, 1172 m, 1100 m, 1044 m, 935 w, 920 w, 888 m, 861w,
833 s, 798 m, 756 s, 723 s, 690 m, 641 m. 1H NMR (C6D6, 25 °C):
δ 5.37, 5.12, –5.19, –8.68. 13C NMR (C6D6, 25 °C): δ 163.8 (Cipso),
137.0, 120.1, 117.9 (ArC), 55.1, 23.7, –16.2. Anal. Calcd for
C56H88Al2O4Sm (1029.6 g mol-1): C 65.33, H 8.61. Satisfactory
microanalytical data could not be obtained.
Acknowledgment. We are grateful to the Norwegian
Research Council (Project No. 182547/I30) and the program
Nanoscience@UiB for generous financial support.
Supporting Information Available: 1H NMR spectrum of
[Yb(AlEt4)2]n (2b) contaminated with Yb(AlEt4)2(THF)2 and full
crystallographic data for complexes 5, 6, 7b, 8a, 9, and 10. This
material is available free of charge Via the Internet at http://pubs.
acs.org.
IC702517S
Inorganic Chemistry, Vol. 47, No. 11, 2008 4705