Dialkyl rare earth complexes supported by potentially tridentate amidinate ligands: Synthesis, structures, and catalytic activity in isoprene polymerization

Article abstract of DOI:10.1002/ejic.201101440

Two new amidines that contain a pendant Lewis base in the side arm, 2-MeOC₆H₄NC(tBu)NH(2,6-R₂C₆H ₃) (R = Me, iPr), were synthesized and successfully employed as tridentate ligands for the preparation

Full text of DOI:10.1002/ejic.201101440

FULL PAPER
DOI: 10.1002/ejic.201101440
Dialkyl Rare Earth Complexes Supported by Potentially Tridentate Amidinate
Ligands: Synthesis, Structures, and Catalytic Activity in Isoprene
Polymerization
Vassily Yu. Rad’kov,[a] Grigorii G. Skvortsov,[a] Dmitry M. Lyubov,[a] Anton V. Cherkasov,[a]
Georgy K. Fukin,[a] Andrei S. Shavyrin,[a] Dongmei Cui,[b] and Alexander A. Trifonov*[a]
Keywords: Lanthanides / Ligand design / Polymerization
Two new amidines that contain a pendant Lewis base in the
side arm, 2-MeOC6H4NC(tBu)NH(2,6-R2C6H3) (R = Me, iPr),
were synthesized and successfully employed as tridentate li-
gands for the preparation of the dialkyl rare earth complexes
[2-MeOC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2SiMe3)2(L)n {Ln
= Y, Lu; R = Me, iPr; L = thf (n = 2), dme (n = 1)}. These
ligands provided enhanced stability for the complexes. The
X-ray structure determinations revealed that intramolecular
2,6-diisopropylaniline in hexane at –70 °C, regardless of the
ratio of the reagent, afforded the six-coordinate diamido
compound [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NHC6H3-
2,6-iPr2)2(thf), for which intramolecular coordination of the
oxygen atom of the side chain was detected by an X-ray
study. Complex [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y-
(CH2SiMe3)2(thf) was evaluated as a precatalyst for isoprene
polymerization. The ternary system [2-MeOC6H4NC(tBu)-
coordination of the 2-MeOC6H4 group is realized if a thf mo- N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf)/[Ph3C][B(C6F5)4]/AliBu3
lecule is coordinated to the metal center (Ln = Y, Lu), which
results in the coordination number of six. The treatment of
provided isoprene polymerization with moderate activity but
without control of the regioselectivity (3,4-regularity was
slightly predominant at 52%). Nevertheless, high 1,4-trans-
selectivity was found (96%) for the 1,4-polyisoprenes. The
obtained polyisoprene has a Mn of 13.0ϫ104 and moderate
polydispersity (2.12).
complex
[2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2Si-
Me3)2(thf) with dme afforded a six-coordinate dme adduct in
which the methoxy group of the amidinate ligand has drifted
out from the metal coordination sphere. The reaction of [2-
MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) with
ter. This emphasizes the role of ligand design as a useful
means of modification and control of the reactivity. “Tailor-
ing” of new ligand systems that are suitable for coordina-
tion to rare earth metals and allow for the synthesis of iso-
lable alkyl species, and investigation of the structure–reac-
tivity relationships are some of the main trends in organo-
rare-earth chemistry.[4] The four-electron chelating
monoanionic amidinate fragment [RC(NRЈ)2]– is widely
used as a platform for development of new versatile ligands
due to easy modification of its steric and electronic proper-
ties through variation of the organic substituents on the
nitrogen and carbon atoms. The combination of flexibility
and variety of the coordination modes of the amidinate li-
gands with donor properties provides their compatibility
with a wide number of metal ions across the periodic table
of elements.[5] The amidinate fragment presents high poten-
tial interest as a supporting ligand framework that allows
control over the metal atom coordination sphere and metal-
mediated chemical processes. Amidinate ligands have been
successfully employed in organo-rare earth chemistry and
they have allowed for the synthesis and characterization of
a new series of isolable highly reactive species.[6,7] Mono-
alkyl, dialkyl, cationic alkyl, and hydrido rare earth com-
plexes that are supported by amidinate ligands have been
Introduction
Enormous progress was made in the chemistry of σ-
bonded rare earth metal alkyls, which proved to be highly
active species that exhibit unique reactivity.[1] Extensive re-
search over the past decades on the monoalkyl complexes
demonstrated their potential in the catalysis of a wide range
of conversions of unsaturated substrates.[2] Dialkyl rare
earth complexes, which until recently remained virtually un-
explored, are currently in the focus of interest as potential
precursors to cationic monoalkyl species that were found
to be efficient catalysts of homo- and copolymerization of
olefins.[3] Both the stability and reactivity of organic deriva-
tives of rare earth metals are known to be highly dependent
on the coordination and steric saturation of the metal cen-
[a] G. A. Razuvaev Institute of Organometallic Chemistry of
Russian Academy of Sciences,
Tropinina 49, 603950 Nizhny Novgorod, GSP-445, Russia
Fax: +007-831-4627497
E-mail: trif@iomc.ras.ru
[b] State Key Laboratory of Polymer Physics and Chemistry,
Changchun Institute of Applied Chemistry, Chinese Academy
of Sciences,
Changchun 130022, China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201101440.
Eur. J. Inorg. Chem. 2012, 2289–2297
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. A. Trifonov, et al.
FULL PAPER
[15]
described and some of them have performed catalytic ac- Ln(CH2SiMe3)3(thf)2
(Ln = Y, Lu) with the amidines 1
tivity in transformation reactions of unsaturated substrates and 2 were carried out in C6D6 under 1H NMR spec-
(olefin polymerization,[7d,7e,7g] isoprene polymerization,[8] troscopy control and showed clear formation of the dialkyl
acetylene dimerization,[7c] olefin hydroboration,[9] hydro- complexes [2-MeOC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2-
silylation,[10] and hydroamination[11]).
SiMe3)2(thf) {R = Me, Ln = Y (3); R = Me, Ln = Lu (4);
Hemilabile ligands,[12] which bear, in addition to an inert R = iPr, Ln = Y (5); R = iPr, Ln = Lu (6)} in quantitative
fragment, weakly coordinating groups that are strongly yield and with the liberation of one equivalent of TMS
bonded to the metal, attract substantial interest from the (Scheme 2).
point of view of possible catalytic applications. They are
capable of temporarily occupying coordination sites at reac-
tive metal centers in the absence of a substrate and thus
saturating its coordination sphere. However, in the presence
of the substrate the coordination bond between the weakly
coordinating group and the metal ion can dissociate, which
liberates the coordination site for a substrate, while the inert
part of the ligand remains anchored to the metal center.
Amidinate ligands that contain an additional donor
group[13] in the side chain enabled the synthesis of dialkyl
rare earth species. In order to provide control of the geome-
Scheme 2. Synthesis of complexes 3–6.
try of the metal coordination sphere and control of the re-
activity of the metal complexes, we focused on elaboration
of new bulky amidinate ligands that bear a Lewis donor
group o-C6H4OMe, which is capable of coordinating to a
metal ion, in the side chain. Herein we report on the synthe-
sis of the new amidines 2-MeOC6H4NC(tBu)NH(2,6-
R2C6H3) (R = Me, iPr) and the synthesis, structure, and
reactivity of the dialkyl rare earth complexes [2-Me-
OC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2SiMe3)2 (Ln) {Ln =
Y, Lu; R = Me, iPr; L = thf (n = 2), dme (n = 1)} that are
supported by these ligands.
The preparative scale syntheses of complexes 5 and 6
were carried out in n-hexane at 0 °C. Prolonged cooling of
the reaction mixtures at –20 °C afforded these complexes
as colorless crystals in 57 and 50% yield, respectively. This
decrease in the isolated yields of complexes 5 and 6 com-
pared to those in the NMR tube scale experiment is appar-
ently caused by the high solubility of these compounds in
aliphatic and aromatic hydrocarbons.
All of the attempts to obtain complexes 3 and 4 derived
from the Me-substituted amidinate ligand in the crystalline
state failed and afforded viscous oils that were difficult to
characterize. The treatment of tetrahydrofuranate 4 with
dme followed by recrystallization from hexane at –20 °C en-
abled the isolation of the complex coordinated by one dme
molecule, [2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2-
SiMe3)2(dme) (7), in 63% yield (Scheme 3).
Results and Discussion
o-Anisidine was used as a platform for the synthesis of
amidines that contain a pendant Lewis base in the side arm.
The general procedure was based on previously reported
methods[14] and used pivaloyl chloride to give a tertiary-
butyl group on the amidine C-functionality. The synthetic
route is shown in Scheme 1. Amidines 1 and 2 were ob-
tained in 63 and 70% yield, respectively.
Scheme 3. Synthesis of complex 7.
The colorless crystalline compounds 5 to 7 are moisture
and air-sensitive. The complexes are fairly soluble in com-
monly used organic solvents (thf, toluene, hexane). Under
inert atmosphere, complexes 5 to 7 can be stored in the
crystalline state at 0 °C without decomposition for several
months. These compounds turned out to be surprisingly
stable even in solution. At 70 °C in C6D6 no decomposition
Scheme 1. Synthesis of amidines 1 and 2. (i) tBuC(O)Cl, Et3N,
CH2Cl2, 40 °C, 24 h; (ii) PCl5, C6H5Cl, 60 °C, 72 h; (iii)
R2C6H3NH2 (R = Me, iPr), toluene, 80 °C, 72 h.
An alkane elimination reaction was used as a synthetic of the compounds was observed over 2 h.
1
approach to the synthesis of the dialkyl species supported
In the H NMR spectra of 3 to 6 the amidinate ligands
by the potentially tridentate amidinate ligands. The NMR appear as the expected sets of signals. The methylene pro-
tube scale reactions of the tris(alkyl) derivatives tons of the alkyl groups attached to the metal atoms appear
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Dialkyl Rare Earth Complexes
as a sharp doublet (2JY,H = 2.9 Hz) at –0.62 ppm for yt- Table 1. Complexes 5 and 6 crystallize in the triclinic space
¯
trium complex 3 or as a singlet at –0.78 ppm for lutetium group P1 with two molecules in the unit cell. Complex 7
complex 4. The methylene carbons of the alkyl groups give crystallizes in the monoclinic space group P21/c with four
rise to a doublet at 31.4 ppm (1JY,C = 38 Hz) in the 13C{1H} molecules in the unit cell. The X-ray diffraction study re-
NMR spectrum of 3, while in the spectrum of 4 they appear vealed that complexes 5 and 6 are isostructural. In both
1
as a singlet at 39.3 ppm. In the H NMR spectra of com- monomeric compounds intramolecular coordination of the
plexes 5 and 6, which contain the 2,6-diisopropylphenyl- o-C6H4OMe group oxygen atoms of the amidinate ligands
substituted amidinate ligand, the broaden singlets at –0.64
and –0.66 ppm, respectively, are attributed to the CH2 pro-
tons of the alkyl ligands. Spin-spin coupling constants of
the methylene protons with the yttrium atom were not ob-
served in the spectrum of 5 at room temperature. The corre-
sponding methylene carbon atom that is covalently bonded
to the Y-center appears in the 13C{1H} NMR spectrum as
a doublet at 31.7 ppm (1JY,C = 42 Hz). The methylene car-
bons of the lutetium analogue 6 give a singlet at 41.5 ppm
in the 13C{1H} NMR spectrum. The dme-containing deriv-
1
ative 7 also presents the expected set of signals in the H
and 13C{1H} NMR spectra due to the amidinate ligand.
The signals of the methylene protons and carbons of the
alkyl ligands appear as singlets at –0.73 and 37.9 ppm,
respectively. The 1H and 13C NMR spectroscopy investi-
gations of complexes 3 to 7 at various temperatures (T =
–80 to 60 °C, [D8]toluene) did not give clear evidence for
Figure 2. Molecular structure of complex [2-MeOC6H4NC(tBu)-
N(2,6-iPr2C6H3)]Lu(CH2SiMe3)2(thf) (6). Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms and C atoms
of thf are omitted for clarity. Selected distances [Å] and angles [°]:
Lu(1)–N(1) 2.284(2), Lu(1)–N(2) 2.367(2), Lu(1)–C(25) 2.385(2),
Lu(1)–C(29) 2.387(2), Lu(1)–O(1) 2.377(2), Lu(1)–O(1S) 2.384(2),
N(1)–C(1) 1.362(3), N(2)–C(1) 1.334(3), O(1)–C(7) 1.392(3), N(1)–
Lu(1)–N(2) 56.25(6), N(1)–C(1)–N(2) 108.9(2), C(25)–Lu(1)–C(29)
119.76(8).
dynamic behavior, in particular, for intramolecular coordi-
nation–decoordination of the methoxy group to the metal
center.
Crystals of complexes 5 to 7 that were suitable for X-ray
diffraction studies were obtained by cooling the concen-
trated hexane solutions to –20 °C. The molecular structures
of complexes 5 to 7 are shown in Figures 1, 2, and 3, respec-
tively, and the structure refinement data are listed in
Figure 1. Molecular structure of complex [2-MeOC6H4NC(tBu)-
N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) (5). Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms and C atoms
of thf are omitted for clarity. Selected distances [Å] and angles [°]:
Y(1)–N(1) 2.332(2), Y(1)–N(2) 2.407(2), Y(1)–C(25) 2.430(2),
Figure 3. Molecular structure of complex [2-MeOC6H4NC(tBu)-
N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(dme) (7). Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms are omitted
for clarity. Selected distances [Å] and angles [°]: Lu(1)–N(1)
2.262(2), Lu(1)–N(2) 2.428(2), Lu(1)–C(25) 2.360(3), Lu(1)–C(29)
Y(1)–C(29) 2.433(2), Y(1)–O(1) 2.401(2), Y(1)–O(1S) 2.419(2), 2.380(3), Lu(1)–O(1) 4.031(2), Lu(1)–O(1S) 2.435(2), Lu(1)–O(2S)
N(1)–C(1) 1.366(3), N(2)–C(1) 1.336(3), O(1)–C(7) 1.393(3), N(1)– 2.385(2), N(1)–C(1) 1.349(1), N(2)–C(1) 1.324(4), O(1)–C(7)
Y(1)–N(2) 55.30(6), N(1)–C(1)–N(2) 109.0(2), C(25)–Y(1)–C(29)
118.79(9).
1.377(4), N(1)–Lu(1)–N(2) 56.05(8), N(1)–C(1)–N(2) 111.4(3),
C(25)–Lu(1)–C(29) 96.5(1).
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Table 1. Crystallographic data and structure refinement details for 5 to 8.
5
6
7
8
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C36H63N2O2Si2Y
700.97
C36H63N2O2Si2Lu
787.03
C32H57N2O3Si2Lu
748.95
monoclinic
P21/c
13.3927(8)
15.638(1)
18.3003(11)
90
106.718(1)
90
C52H77N4O2Y
879.09
orthorhombic
Pbca
13.0667(3)
22.4027(6)
33.4130(8)
90
90
90
9781.0(4)
8
1.194
triclinic
triclinic
¯
¯
P1
P1
10.6114(12)
14.0012(16)
14.1226(16)
84.610(2)
83.286(2)
68.310(2)
1933.4(4)
2
10.6154(3)
14.0070(4)
14.1194(4)
84.651(1)
83.133(1)
68.205(1)
1932.64(10)
2
α [°]
β [°]
γ [°]
Volume [Å3]
Z
3670.7(4)
4
1.355
ρcalcd [mg/m3]
1.204
1.601
1.352
2.647
μ [mm–1]
2.785
1.234
F(000)
Crystal size [mm]
Θ range [°]
752
816
1544
3776
0.15ϫ0.10ϫ0.08
2.08–26.00
Ϯ13, Ϯ17, Ϯ17
16468
7544
0.0479
0.15ϫ0.13ϫ0.10
2.07–26.00
Ϯ13, Ϯ17, Ϯ17
16912
7581
0.0168
0.30ϫ0.16ϫ0.12
2.05–26.00
Ϯ16, Ϯ19, Ϯ22
30404
7186
0.0302
0.23ϫ0.07ϫ0.04
1.90–27.00
(–11/16), Ϯ28, Ϯ42
61197
10655
0.0931
Index ranges (h, k, l)
Reflections collected
Independent reflections
Rint
Goodness-of-fit on F2
R1/wR2 [IϾ2σ(I)]
R1/wR2 (all data)
Largest diff. peak/hole [Å3]
1.006
1.093
0.992
1.015
0.0483/0.1070
0.0787/0.1151
1.086 and –0.841
0.0207/0.0503
0.0227/0.0510
1.710 and –0.576
0.0281/0.0674
0.0435/0.0715
2.139 and –0.669
0.0435/0.0833
0.0959/0.0936
0.715 and –0.328
to the metal centers takes place. The coordination sphere alkyl groups, two nitrogen atoms of the bidentate amidinate
of the rare earth ions consists of two carbon atoms of alkyl ligand, and two oxygen atoms of a dme molecule. The for-
groups, two nitrogen atoms of the chelating amidinate li- mal coordination number of the metal center in 7 is six,
gand, one oxygen atom of the pendant Lewis base group, which is similar to that of 5 and 6. A clear distinction in
and one oxygen atom of a thf molecule, which results in the the geometry of 7 compared with that of complexes 5 and
formal coordination number of six. It is noteworthy that 6 is the mutual orientation of the amidinate NCN fragment
the nitrogen and oxygen atoms are situated in the equatorial and the plane of the o-C6H4OMe ring. In complexes 5 and
plane (maximum deviation of N and O atoms from the 6 the 2,6-iPr2C6H3 rings adopt nearly orthogonal orienta-
plane in 5 and 6 is 0.012 Å) while two carbons occupy the tion with respect to the NCN fragment (the dihedral angles
apical positions. The mutual orientation of the amidinate are 83.03 and 82.34° for 5 and 6, respectively) while the
ligand and alkyl groups in complexes 5 and 6 is similar to planes of the o-C6H4OMe rings and amidinate fragments
that in the related six-coordinate amidinate yttrium deriva- are nearly coplanar (the dihedral angles are 9.18 and 8.63°
tive, [PhC(NC6H3iPr2-2,6)2]Y(CH2SiMe3)2(thf)2.[7d] Thus, for 5 and 6, respectively). In 7 both of the substituted Ph
in 5 and [PhC(NC6H3iPr2-2,6)2]Y(CH2SiMe3)2(thf)2 the rings are nearly orthogonal to the NCN plane. The dihedral
NYN and CYC planes are close to adopting an orthogonal angles between Me2C6H3, the o-C6H4OMe rings, and the
orientation (88.68 and 88.60°,[7d] respectively). The Ln–C amidinate fragments are 77.95(8) and 76.81(8)°, respec-
bond lengths in complexes 5 [2.430(3) and 2.433(3) Å] and tively. This difference in the coordination environments of
6 [2.385(2) and 2.387(2) Å] have similar values if the differ- the metal atoms strongly effects the values of the C–Ln–C
ence in the ionic radii[16] is taken into consideration and are bond angles. Thus, in 6 this angle has a value of 119.76(8)°
comparable to the related distances in six-coordinate dialkyl while in 7 it is noticeably smaller [96.54(10)°]. The Lu–C
complexes (for comparison see Y[7d,17] and Lu[18]). The Y– bond lengths in 7 [2.360(3) and 2.380(3) Å] fall into the re-
N [2.332(2) and 2.407(2) Å] and Lu–N [2.284(2) and gion normally observed for six-coordinate dialkyllutetium
2.367(2) Å] distances differ only slightly from each other. species.[18,19]
The coordination bonds between the metal ions and the
The terminal imido rare earth complexes that contain a
oxygen atoms of a thf molecule and a pendant Lewis base double Ln=N bond remain very scarce and challenging
in both complexes have values that are close to one another compounds.[20] Dialkyl rare earth derivatives can serve as
[5: 2.400(2) and 2.419(2) Å; 6: 2.377(2) and 2.384(2) Å].
suitable precursors for the synthesis of terminal imido com-
The X-ray diffraction study of complex 7 revealed that, plexes by reacting them with primary amines. In order to
unlike in compounds 5 and 6, the oxygen atom of a pendant prepare imido complexes that are supported by a bulky tri-
donor function is not coordinated to the lutetium ion [the dentate amidinate ligand, we attempted the reaction of 5
Lu(1)···O(1) distance is 4.031(2) Å]. No intermolecular co- with an equimolar amount of 2,6-diisopropylaniline in hex-
ordination of this group was detected. The coordination ane at –70 °C. Concentration and cooling of the reaction
sphere of the lutetium ion is set up by two carbon atoms of mixture at –20 °C over one week afforded the dianilido
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Dialkyl Rare Earth Complexes
complex 8 (Scheme 4), which was isolated in 41% yield. The
formation of 8 instead of the expected imido or alkyl-anil-
ido species[21] can be rationalized by the ligand redistri-
bution reaction as described previously for a Sc com-
pound.[21b] On the other hand, the ligand redistribution re-
action of the alkyl-anilido complex should afford 5. Never-
1
theless, H NMR spectroscopy analysis of the crude prod-
uct that was obtained after in vacuo removal of the volatiles
from the mother liquor did not give evidence for the pres-
ence of complex 5. The NMR tube reaction of 5 with 2,6-
diisopropylaniline (C6D6, 20 °C) gave unambiguous evi-
dence for the formation of the alkyl-anilido complex and
one equivalent of TMS (see Exp. Section). However, after
ca. 0.5 h a growing singlet at 4.54 ppm, which corresponds
to the NH protons of 8, appeared in the 1H NMR spectrum
of the reaction mixture. At the same time a progressive in-
crease in the TMS signal indicates decomposition of the
YCH2SiMe3 species. After ca. 3 days the alkyl-anylido com-
plex disappeared completely, while the set of signals that
are characteristic for 8 was present. Taking into account the
enhanced stability of 5, one can conclude that the formation
of 8 is the result of a more complex process than the ligand
redistribution reaction.
Figure 4. Molecular structure of complex [2-MeOC6H4NC(tBu)-
N(2,6-Me2C6H3)]Y(NHC6H3-2,6-iPr2)2(thf) (8). Thermal ellipsoids
are drawn at the 30% probability level. Hydrogen atoms and C
atoms of thf are omitted for clarity. Selected distances [Å] and
angles [°]: Y(1)–N(1) 2.396(2), Y(1)–N(2) 2.325(1), Y(1)–N(3)
2.240(2), Y(1)–N(4) 2.259(2), Y(1)–O(1) 2.385(1), Y(1)–O(1S)
2.435(1), N(1)–C(1) 1.328(2), N(2)–C(1) 1.359(2), O(1)–C(7)
1.394(2), N(1)–Y(1)–N(2) 55.49(5), N(1)–C(1)–N(2) 109.9(2),
N(3)–Y(1)–N(4) 123.55(6).
Cationic alkyl rare earth complexes proved to be highly
active catalysts for olefin and diene polymerizations.[3] In
order to synthesize these reactive species, the reactions of
complexes 3 to 7 with [Et3NH][BPh4], [PhNMe2H][B-
(C6F5)4], and BPh3 were attempted (thf, C6H5Br) and af-
forded intractable viscous oils. The reactions of 3 to 7 with
[Et3NH][BPh4] and [PhNMe2H][B(C6F5)4] afforded TMS as
a result of protonation of the MCH2SiMe3 bonds. Unfortu-
nately all of our efforts to isolate cationic alkyl complexes
failed.
Complexes 3 to 7, as well as the combinations of com-
plex/MAO (1:100 molar ratio) and complex/[Et3NH][BPh4]/
MAO (1:1:100 molar ratio), were found to be inactive as
precatalysts for ethylene polymerization (toluene, 20 °C,
1 bar).
Scheme 4. Reaction of complex 5 with 2,6-iPr2C6H3NH2 (1:1 molar
ratio).
Clear colorless crystals of 8 that were suitable for X-ray
diffraction study were obtained by prolonged cooling of the
concentrated hexane solution at –20 °C. Complex 8 crys-
tallizes in orthorhombic, Pbca space group with eight mole-
cules in the unit cell. The molecular structure of complex 8
is shown in Figure 4 and the structure refinement data are
listed in Table 1. The X-ray diffraction study of 8 revealed
that the compound is monomeric with intramolecular coor-
dination of the pendant methoxy group of the tridentate
ligand to the yttrium atom. The yttrium atom in 8 is coordi-
nated by two nitrogen atoms of the chelating amidinate li-
gand, two nitrogen atoms of the two anilido ligands, and
two oxygen atoms from the pendant Lewis group and the
thf molecule. The formal coordination number of yttrium
Catalysis of Isoprene Polymerization
Dialkyl rare earth metal complexes are suitable precur-
in 8 is six. The distances between the yttrium and nitrogen sors for catalytic systems performing controlled diene poly-
atoms of the monoanionic chelating amidinate ligand are merization with high activities and selectivities. Most of
different [Y(1)–N(1) 2.3959(14) Å; Y(1)–N(2) 2.3253(14) Å] these catalytic systems are efficient for the production of
and are noticeably longer than the distances between yt- 1,4-polyisoprene[22] while the catalysts for the synthesis of
trium and the amido nitrogens [Y(1)–N(3) 2.2399(15) Å, 3,4-polyisoprene have been also reported.[23] Isoprene poly-
Y(1)–N(4) 2.2591(15) Å]. The intramolecular coordination merization that is initiated by complex 5 was explored with
Y–O bond [Y(1)–O(1) 2.3846(12) Å] is considerably shorter the aim to clarify the possibility of control of the selectivity
than the bond between yttrium and the oxygen atom of the of diene polymerization by the use of hemilabile amidinate
thf molecule [Y(1)–O(1S) 2.4350(12) Å].
ligands. The catalytic activity of complex 5 in isoprene poly-
Eur. J. Inorg. Chem. 2012, 2289–2297
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2293

A. A. Trifonov, et al.
FULL PAPER
merization was explored in toluene under different condi-
tions at room temperature. Complex 5 alone showed no ac-
tivity towards isoprene polymerization, neither did the bi-
nary systems formed from complexes 5/AlR3 (R = Et, iBu;
[AlR3]/[Ln] = 10). Activation of 5 with an equimolar
amount of [Ph3C][B(C6F5)4] afforded trace amounts of
polyisoprene. When [Et3NH][BPh4] was used (1:1 molar ra-
tio) no polymerization occurred. The catalytic activities of
the ternary systems 5/borate/AlR3 turned out to be dramat-
ically influenced by the nature of borate. Thus, the systems
that contained [Et3NH][BPh4] showed no activity ([5]/[bor-
ate]/[AliBu3] = 1:1:10), while those with [Ph3C][B(C6F5)4]
under similar conditions initiated isoprene polymerization
with moderate rates. The system 5/[Ph3C][B(C6F5)4]/AliBu3
converts 1000 equiv. of isoprene into polyisoprene with to-
tal conversion in 60 min and with almost no regioselectivity
(3,4-regularity is slightly predominant at 52%). Neverthe-
less, for the 1,4-polyisoprenes high 1,4-trans-selectivity was
found (96%). The GPC curve indicated that the polyiso-
prene sample produced by this ternary catalyst system is
unimodal with a Mn of 13.0ϫ104, albeit with moderate
polydispersity (2.12). When the [IP]/[Ln] ratio was increased
to 5000 in 60 min the conversion reached 70% and afforded
the polyisoprene with a Mn of 20.0ϫ104 and polydispersity
of 2.78. The 3,4-regioselectivity of polyisoprene was slightly
higher (55%) with a content of 1,4-trans units of 92%.
Experimental Section
General: All of the experiments were performed in evacuated tubes
by using standard Schlenk techniques with rigorous exclusion of
all traces of moisture and air. After being dried with KOH, thf was
purified by distillation from sodium/benzophenone ketyl; hexane
and toluene were dried by distillation from sodium/triglyme and
benzophenone ketyl prior to use. C6D6 and [D8]toluene were dried
with sodium and condensed in vacuo into NMR tubes prior to use.
CDCl3 was used without additional purification. 2,6-Diisoprop-
ylaniline, 2,6-dimethylaniline, o-anizidine, and Et3N were pur-
chased from Acros and were dried with CaH2. tBuC(O)Cl was pur-
chased from Acros and was used without additional purification.
CH2Cl2 and C6H5Cl were dried with P2O5. Anhydrous YCl3,
LuCl3,[24] Me3SiCH2Li,[25] (Me3SiCH2)3Ln(thf)2
(Ln = Y, Lu),
[15]
and 2-MeOC6H4[N=C(Cl)tBu][14] were prepared according to lit-
erature procedures. All of the other commercially available chemi-
cals were used after the appropriate purifications. The NMR spec-
tra were recorded with Bruker Avance DRX-400 and DPX-200
spectrometers in CDCl3, C6D6, or [D8]toluene at 25 °C, unless
otherwise stated. The chemical shifts for the 1H and 13C NMR
spectra were referenced internally to the residual solvent resonances
and are reported relative to TMS. The IR spectra were recorded as
Nujol mulls with a Bruker Vertex 70 instrument. The lanthanide
metal analyses were carried out by complexometric titration. The
C, H, N elemental analyses were performed in the microanalytical
laboratory of the G. A. Razuvaev Institute of Organometallic
Chemistry.
2-MeOC6H4NC(tBu)NH(2,6-Me2C6H3) (1): 2,6-Dimethylaniline
(2.27 g, 18.73 mmol) was added to
a solution of 2-Me-
OC6H4[N=C(Cl)tBu] (4.13 g, 18.30 mmol) and Et3N (2.6 mL,
1.89 g, 18.68 mmol) in toluene (50 mL) under rigorous stirring. The
reaction mixture was stirred at 80 °C for 3 d, then the solvent was
removed in vacuo. The resultant off-white solid was dissolved in
diethyl ether (100 mL) and was washed with Na2CO3 solution (1%,
Conclusions
In order to provide stabilization of dialkyl rare earth 3ϫ 100 mL). The organic layer was separated and dried with
MgSO4, the solvent was removed and the solid residue was recrys-
tallized from hexane. Complex 1 was isolated in 63% yield (3.58 g,
11.53 mmol); m.p. 68–72 °C. C20H26N2O (310.43): calcd. C 77.38,
H 8.44, N 9.02; found C 77.15, H 8.56, N 9.08. 1H NMR
(400 MHz, C6D6, 25 °C): δ = 1.26 [s, 9 H, C(CH3)3], 2.17 [s, 6 H,
(CH3)2C6H3], 3.22 [s, 3 H, o-C6H4(OCH3)], 6.33 [d, 3JH,H = 8.0 Hz,
complexes by intramolecular Lewis base coordination, two
new hemilabile amidines that contain a pendant 2-Me-
OC6H4 group in the side chain were synthesized. Dialkyl
rare earth complexes coordinated by these potentially tri-
dentate ligands were obtained by the reaction of the parent
amidines with Ln(CH2SiMe3)3(thf)2 (Ln = Y, Lu) in good
yields and demonstrated enhanced stability. No decomposi-
tion was detected for complexes 3 to 6 at room temperature
in C6D6 over five days. Decomposition of these compounds
1 H, o-C6H4(OCH3)], 6.45 (br. s, 1 H, NH), 6.56 [t, 3JH,H = 7.5 Hz,
3
1 H, (CH3)2C6H3], 6.72 [m, 2 H, o-C6H4(OCH3)], 6.87 [d, JH,H
=
7.5 Hz, 2 H (CH3)2C6H3], 7.31 [br. s, 1 H, o-C6H4(OCH3)] ppm.
13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 18.4 [(CH3)2C6H3],
in solution becomes noticeable above 70 °C. The X-ray 29.3 [C(CH3)3], 39.8 [C(CH3)3], 55.4 [o-C6H4(OCH3)], 109.5, 119.8
[o-C6H4(OCH3)], 120.7 [(CH3)2C6H3], 123.5 [o-C6H4(OCH3)],
126.4, 127.3, 128.7, 147.3 [(CH3)2C6H3], 150.5 [o-C6H4(OCH3)],
structure determinations revealed that in the crystal state
the oxygen atom of the 2-MeOC6H4 group can be intramo-
lecularly coordinated or not depending on the denticity of
other donor ligands bound to the metal atom, whereas no
fluctional behavior was detected in solution. The reaction
of [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2-
(thf) with 2,6-diisopropylaniline in hexane at –70 °C, re-
gardless of the reaction stoichiometry, afforded diamido
complex [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NHC6-
H3-2,6-iPr2)2(thf) for which intramolecular coordination of
the oxygen atom of the side chain was detected by an X-
ray study. Complex 5, activated by [Ph3C][B(C6F5)4] in the
presence of AliBu3, initiates isoprene polymerization with
moderate activity and affords the polymer that contains
52% of 3,4-units and has moderate polydispersity.
156.2 (NCN) ppm. IR (KBr): ν = 3463 (m, NH), 1653 (s, C=N),
˜
1590 (m), 1285 (w), 1261 (w), 1221 (w), 1149 (w), 1088 (w), 1028
(w), 940 (s), 744 (s), 572 (s) cm–1. MS (EI): m/z = 310.43 [M+].
2-MeOC6H4NC(tBu)NH(2,6-iPr2C6H3) (2): The same synthetic
procedure was used. Complex 2 was isolated after recrystallization
from hexane as colorless crystals in 70% yield (3.22 g); m.p. 74 °C.
C24H34N2O (366.54): calcd. C 78.64, H 9.35, N 7.64; found C
78.22, H 9.44, N 7.68. 1H NMR (400 MHz, C6D6, 25 °C): δ = 1.22
3
[d, JH,H = 7.0 Hz, 6 H, (CH3)2CH], 1.29 [m, 15 H, (CH3)2CH,
C(CH3)3], 3.16 [m, 2 H, (CH3)2CH], 3.21 [s, 3 H, o-C6H4(OCH3)],
6.34 [d, 3JH,H = 8.0 Hz, 1 H, o-C6H4(OCH3)], 6.39 (br. s, 1 H, NH),
3
3
6.59 (t, JH,H = 7.5 Hz, 1 H, iPr2C6H3), 6.74 [t, JH,H = 8.0 Hz, 1
3
H, o-C6H4(OCH3)], 6.97 [m, 1 H, o-C6H4(OCH3)], 7.04 (d, JH,H
= 7.0 Hz, 2 H, iPr2C6H3), 7.44 [br. s, 1 H, o-C6H4(OCH3)] ppm.
2294
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Eur. J. Inorg. Chem. 2012, 2289–2297

Dialkyl Rare Earth Complexes
13C{1H} NMR (100 MHz, C6D6, 25 °C): δ = 22.6, 22.9 [(CH3)2- Slow cooling of this solution to –20 °C afforded colorless crystals
CH], 28.5 [C(CH3)3], 29.1 [(CH3)2CH], 39.9 [C(CH3)3], 54.6 [o- of 6 (0.42 g, 50%). C36H63LuN2O2Si2 (787.04): calcd. C 54.94, H
C6H4(OCH3)], 109.3, 120.1 [o-C6H4(OCH3)], 121.7 (iPr2C6H3), 8.07, N 3.56, Lu 22.23; found C 54.64, H 8.18, N 3.64, Lu 22.20.
122.3 [o-C6H4(OCH3)], 123.7, 129.2, 136.1, 145.2 (iPr2C6H3), 150.7 1H NMR (400 MHz, C6D6, 25 °C): δ = –0.66 (s, 4 H, LuCH2), 0.24
[o-C H (OCH )], 154.6 (NCN) ppm. IR (KBr): ν = 3466 (m, NH),
[s, 18 H, CH2Si(CH3)3], 1.10 [s, 9 H, C(CH3)3], 1.13 (m, 4 H, β-
˜
6
4
3
3
3
1651 (s, C=N), 1598 (m), 1456 (m), 1284 (w), 1219 (w), 1145 (m), thf), 1.30 [d, JH,H = 6.8 Hz, 6 H, (CH3)2CH], 1.33 [d, JH,H
=
1043 (m), 1026 (m), 935 (s), 744 (s), 570 (s), 484 (m) cm–1. MS (EI):
6.8 Hz, 6 H, (CH3)2CH], 3.45 (t, JH,H = 6.8 Hz, 4 H, α-thf), 3.53
3
m/z = 366.54 [M+].
[m, 2 H, (CH3)2CH], 3.62 [s, 3 H, o-C6H4(OCH3)], 6.58 [m, 1 H,
o-C6H4(OCH3)], 6.89 [m, 2 H, o-C6H4(OCH3)], 7.01 (m, 3 H,
iPr2C6H3), 7.33 [m, 1 H, o-C6H4(OCH3)] ppm. 13C{1H} NMR
(100 MHz, C6D6, 25 °C): δ = 4.2 [CH2Si(CH3)3], 23.3 [(CH3)2CH],
24.6 (β-thf), 25.5 [CH(CH3)2], 27.9 [CH(CH3)2], 29.8 [C(CH3)3],
41.5 (LuCH2), 43.6 [C(CH3)3], 55.2 [o-C6H4(OCH3)], 69.4 (α-thf),
110.2, 121.0, 122.8, 123.3, 123.9, 125.8, 136.8, 141.3, 144.6, 153.0
[2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Y(CH2SiMe3)2(thf) (3): The
reaction of 1 (0.015 g, 0.048 mmol) with Y(CH2SiMe3)3(thf)2
(0.0237 g, 0.048 mmol) was performed in an NMR tube (C6D6,
1
2
0.6 mL). H NMR (400 MHz, C6D6, 25 °C): δ = –0.62 (d, JY,H
=
2.9 Hz, 4 H, YCH2), 0.18 [s, 18 H, Si(CH3)3], 1.10 [s, 9 H,
C(CH3)3], 1.37 (br. s, 4 H, β-thf), 2.26 {s, 6 H, [C6H3(CH3)2]}, 3.63
(Ar), 179.5 (NCN) ppm. IR (KBr): ν = 1462 (s), 1377 (m), 1286
˜
3
(br. s, 4 H, α-thf), 3.93 (s, 3 H, OCH3), 6.64 [dd, JH,H = 8.1 Hz,
(w), 1232 (m), 1180 (m), 1016 (m), 898 (w), 850 (s), 767 (w), 717
3JH,H = 1.2 Hz, 1 H, C6H4], 6.73–6.88 (m, 5 H, C6H4, C6H3), 7.20
(w), 667 (w) cm–1.
3
3
(dd, JH,H = 8.0 Hz, JH,H = 1.4 Hz, 1 H, C6H3) ppm. 13C{1H}
[2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(dme) (7):
A solution of 1 (0.38 g, 1.22 mmol) in hexane (30 mL) was added
to a solution of Lu(CH2SiMe3)3(thf)2 (0.71 g, 1.22 mmol) in hexane
(30 mL) at 0 °C and the reaction mixture was stirred for 30 min.
The volatiles were removed in vacuo, the solid residue was treated
with dme (0.5 mL, 0.43 g, 4.77 mmol), dried in vacuo at ambient
temperature, and redissolved in hexane (5 mL). Cooling the solu-
tion at –20 °C afforded colorless crystals of 7 (0.58 g, 63%).
C32H57LuN2O3Si2 (748.94): calcd. C 51.32, H 7.67, N 3.74, Lu
23.36; found C 51.12, H 7.74, N 3.83, Lu 23.37. 1H NMR
(400 MHz, C6D6, 25 °C): δ = –0.73 (s, 4 H, LuCH2), 0.34 [s, 18 H,
CH2Si(CH3)3], 1.15 [s, 9 H, C(CH3)3], 2.37 {s, 6 H, [(CH3)2C6H3]},
2.76 (s, 6 H, dme), 3.14 (s, 4 H, dme), 3.42 [s, 3 H, o-C6H4(OCH3)],
NMR (100 MHz, C6D6, 25 °C):
[C6H3(CH3)2], 25.4 (CH2, β-thf), 29.6 [C(CH3)3], 31.4 (d, JY,C
38 Hz, YCH2), 41.4 [C(CH3)3], 57.8 (OCH3), 68.9 (CH2, α-thf),
110.5, 120.6, 122.2, 122.9, 123.1, 131.1, 137.3, 148.2, 151.7
(C6H4, C6H3), 178.2 (NCN) ppm.
δ = 4.7 [Si(CH3)3], 20.5
1
=
[2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(thf)2 (4):
The reaction of 1 (0.020 g, 0.064 mmol) with Lu(CH2SiMe3)3-
(thf)2 (0.0370 g, 0.064 mmol) was performed in an NMR tube
(C6D6, 0.6 mL). 1H NMR (400 MHz, C6D6, 25 °C): δ = –0.78 (s, 4
H, LuCH2), 0.19 [s, 18 H, Si(CH3)3], 1.06 [s, 9 H, C(CH3)3], 1.29
(br. s, 4 H, β-thf), 2.31 {s, 6 H, [C6H3(CH3)2]}, 3.74 (br. s, 4 H, α-
3
thf), 3.76 (s, 3 H, OCH3), 6.58 (d, JH,H = 7.9 Hz, 1 H, C6H4),
6.73–6.91 (m, 5 H, C6H4, C6H3), 7.19 (d, JH,H = 7.6 Hz, 1 H,
3
3
6.53 [d, JH,H = 7.8 Hz, 1 H, o-C6H4(OCH3)], 6.90 [m, 5 H, o-
C6H3) ppm. 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ = 4.4
[Si(CH3)3], 20.0 [C6H3(CH3)2], 24.9 (CH2, β-thf), 29.1 [C(CH3)3],
39.3 (CH2), 42.0 [C(CH3)3], 56.4 (OCH3), 69.5 (CH2, α-thf), 110.1,
121.2, 121.4, 122.8, 124.1, 131.2, 137.1, 147.4, 152.2 (C6H4, C6H3),
178.7 (NCN) ppm.
C6H4(OCH3), (CH3)2C6H3], 7.33 [m, 1 H, o-C6H4(OCH3)] ppm.
13C{1H} NMR (100 MHz, C6D6, 25 °C): δ = 4.7 [CH2Si(CH3)3],
19.8 [C6H3(CH3)2], 29.3 [C(CH3)3], 37.9 (LuCH2), 42.7 [C(CH3)3],
54.2 [o-C6H4(OCH3)], 59.8, 71.0 (dme), 110.0, 120.7, 121.3, 121.9,
122.5, 122.9, 130.9, 138.4, 148.1, 153.0 (Ar), 178.9 (NCN) ppm. IR
(KBr): ν = 1666 (m), 1591 (m), 1454 (m), 1446 (m), 1377 (w), 1247
˜
[2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) (5):
A
(w), 1128 (w), 1047 (w), 860 (m), 740 (m) cm–1.
solution of 2 (0.37 g, 1.01 mmol) in hexane (40 mL) was added to
a solution of Y(CH2SiMe3)3(thf)2 (0.49 g, 1.00 mmol) in hexane
(30 mL) at 0 °C and the reaction mixture was stirred at room tem-
perature for 20 min. Slow cooling of this solution to –20 °C af-
forded colorless crystals of 5 (0.40 g, 57%). C36H63N2O2Si2Y
(700.97): calcd. C 61.68, H 9.06, N 4.00, Y 12.68; found C 61.40,
H 9.13, N 4.08, Y 12.72. 1H NMR (400 MHz, C6D6, 25 °C): δ =
[2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NH-2,6-iPr2C6H3)2(thf)
(8): A solution of 2,6-diisopropylaniline (0.063 g, 0.36 mmol) in
hexane (15 mL) was added to a solution of 5 (0.25 g, 0.36 mmol)
in hexane (30 mL) at –70 °C. The reaction mixture was slowly
warmed up to ambient temperature and was stirred for 10 min. The
volatiles were removed in vacuo and the solid residue was redis-
solved in pentane. Concentration of the solution and cooling at
2
–0.64 (d, JY,H = 2.8 Hz, 4 H, YCH2), 0.20 [s, 18 H, CH2Si-
(CH3)3], 1.16 [br. m, 13 H, C(CH3)3, β-thf], 1.30 [br. m, 12 H,
–20 °C afforded colorless crystals of
8
(0.132 g, 41%).
3
CH(CH3)2], 3.41 [sept, JH,H = 6.8 Hz, 2 H, CH(CH3)2], 3.49 (br.
C52H77N4O2Y (879.10): calcd. C 71.05, H 8.83, N 6.37, Y 10.11;
found C 70.67, H 8.94, N 6.42, Y 10.18. 1H NMR (400 MHz,
C6D6, 25 °C): δ = 1.13–1.24 [compl. m, 34 H, CH(CH3)2, β-thf],
3
m, 4 H, α-thf), 3.84 [s, 3 H, o-C6H4(OCH3)], 6.64 [d, JH,H
=
7.8 Hz, 1 H, o-C6H4(OCH3)], 6.80 [br. s, 1 H, o-C6H4(OCH3)], 6.89
3
(t, JH,H = 7.5 Hz, 1 H, iPr2C6H3), 6.70 [m, 3 H, iPr2C6H3, o-
1.27–1.31 [compl. m, 15 H, CH(CH3)2, C(CH3)3], 3.15 [m, 4 H,
C6H4(OCH3)], 7.27 [br. s, 1 H, o-C6H4(OCH3)] ppm. 13C{1H}
NMR (100 MHz, C6D6, 25 °C): δ = 4.2 [CH2Si(CH3)3], 23.3
[CH(CH3)2], 24.7 (β-thf), 25.4 [CH(CH3)2], 28.0 [CH(CH3)2], 30.0
3
CH(CH3)2], 3.25 [s, 3 H, o-C6H4(OCH3)], 3.41 [sept, JH,H
=
6.8 Hz, 2 H, CH(CH3)2], 3.62 (m, 4 H, α-thf), 4.54 (s, 2 H, NH),
6.24 (d, 3JH,H = 8.3 Hz, 1 H, Ar), 6.64 (t, 3JH,H = 7.7 Hz, 1 H, Ar),
1
3
[C(CH3)3], 31.7 (d, JY,C = 38 Hz, YCH2), 42.1 [C(CH3)3], 56.9 [o-
6.83 (t, JH,H = 7.5 Hz, 2 H, Ar), 6.88 (m, 1 H, Ar), 6.95–7.12
3
C6H4(OCH3)], 69.4 (α-thf), 110.2, 121.7, 121.2, 123.5, 124.1, 140.9,
(compl. m, 7 H, Ar), 7.32 (d, JH,H = 7.3 Hz, 1 H, Ar) ppm.
13C{1H} NMR (100 MHz, C6D6, 25 °C): δ = 23.3 [CH(CH3)2], 23.7
[CH(CH3)2], 24.9 [CH(CH3)2], 25.2 (β-thf), 28.0 [CH(CH3)2], 29.4
[CH(CH3)2], 29.6 [C(CH3)3], 41.3 [C(CH3)3], 56.3 [o-C6H4(OCH3)],
69.0 (α-thf), 111.1, 115.1, 120.2, 121.8, 122.0, 122.4, 122.8, 123.7
(CH Ar), 123.4, 128.9, 131.9, 133.3, 141.2, 152.0 (C Ar), 178.4
(NCN) ppm.
152.0 (Ar), 178.3 (NCN) ppm. IR (KBr): ν = 1666 (m), 1651 (s),
˜
1600 (m), 1587 (m), 1531 (s), 1454 (m), 1446 (m), 1377 (m), 1219
(m), 1176 (w), 1145 (w), 1109 (w), 1033 (w), 935 (w), 860 (s), 742
(s) cm–1.
[2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Lu(CH2SiMe3)2(thf) (6): A
solution of 2 (0.40 g, 1.09 mmol) in hexane (40 mL) was added to
a solution of Lu(CH2SiMe3)3(thf)2 (0.62 g, 1.07 mmol) in hexane
(30 mL) at 0 °C and the reaction mixture was stirred for 20 min.
NMR Tube Reaction of 5 with 2,6-Diisopropylaniline: Complex 5
(0.0397 g, 0.057 mmol) was dissolved in C6D6 (0.5 mL) and a solu-
Eur. J. Inorg. Chem. 2012, 2289–2297
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2295

A. A. Trifonov, et al.
FULL PAPER
complexes (Eds.: G. Giambastiani, J. Cámpora), Springer, Hei-
delberg, Germany, 2011, vol. 35, pp. 119–152; c) S. Arndt, J.
Okuda, Adv. Synth. Catal. 2005, 347, 339–354; d) Z. Hou, Y.
Luo, X. Li, J. Organomet. Chem. 2006, 691, 3114–3121; e) P. M.
Zeimentz, S. Arndt, B. R. Elvidge, J. Okuda, Chem. Rev. 2006,
106, 2404–2433.
a) F. T. Edelmann, D. M. M. Freckmann, H. Schumann,
Chem. Rev. 2002, 102, 1851–1896; b) W. E. Piers, D. J. H. Em-
slie, Coord. Chem. Rev. 2002, 233–234, 131–155; c) A. A. Tri-
fonov, Russ. Chem. Rev. 2007, 76, 1051–1072.
tion of 2,6-diisopropylaniline (0.0089 g, 0.051 mmol) in C6D6
(0.2 mL) was added at room temperature. 1H NMR (200 MHz,
C6D6, 25 °C): δ = –0.54 (d, 2JY,H = 2.7 Hz, 2 H, YCH2SiMe3), 0.29
[s, 9 H, Si(CH3)3], 1.17–1.47 [compl. m, 37 H, CH(CH3)2, β-thf,
C(CH3)3], 3.21–3.37 [compl. m, 5 H, CH(CH3)2, OCH3], 3.52 [sept
3
d, JH,H = 6.8 Hz, 2 H, CH(CH3)2], 3.67 (m, 4 H, α-thf), 4.51 (s, 1
[4]
3
H, NH), 6.32 (d, JH,H = 7.8 Hz, 1 H, Ar), 6.75 (t, 3JH,H = 7.8 Hz,
3
1 H, Ar), 6.94–7.12 (compl. m, 7 H, Ar), 7.40 (d, JH,H = 7.8 Hz,
1 H, Ar).
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X-ray Crystallography: The data of 5 to 8 were collected with a
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CCDC-847654 (for 5), -847655 (for 6), -847656 (for 7), and -847657
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this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
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Supporting Information (see footnote on the first page of this arti-
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Received: December 26, 2011
Published Online: March 14, 2012
Eur. J. Inorg. Chem. 2012, 2289–2297
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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