Dialkyllanthanide complexes containing new tridentate monoanionic ligands with nitrogen donors

Article abstract of DOI:10.1021/om7010936

Three new tridentate NNN ligand precursors, CH₃C(2,6-( ⁱPr)₂C₆H₃NH)CHC(CH ₃)(NCH₂CH₂-D) (D = NMe₂, NEt ₂, N((CH₂CH₂)₂CH₂)), were synthesized. Subsequent metalations with in situ generated Ln(CH ₂SiMe₃)₃(THF)_n, (Ln = Nd, Sm, Y, Lu) provided six solvent-free dialkyllanthanide complexes. Five of the lanthanide complexes were characterized by single-crystal X-ray diffraction, which showed that the pendant arm D bonds to the lanthanide ion in the solid state. The NMR spectra of these complexes in C₆D₆ showed that such coordination is retained in solution. These dialkyllanthanide complexes show high activities for the ring-opening polymerization of ε-caprolactone, in which narrow-polydispersity polymers were produced. The size of the pendant arm has a significant effect on the molecular weight of the polymer obtained. In comparison to the Y complex with a - NMe₂ group, the Y complexes with -NEt₂ and - N((CH₂CH₂)₂CH ₂) groups yield much higher molecular weight polymer (60 000 vs 20 000).

Full text of DOI:10.1021/om7010936

758
Organometallics 2008, 27, 758–763
Dialkyllanthanide Complexes Containing New Tridentate
Monoanionic Ligands with Nitrogen Donors
Xin Xu,† Xiaoyan Xu,†,‡ Yaofeng Chen,*,† and Jie Sun†
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese
Academy of Science, 354 Fenglin Road, Shanghai 200032, People’s Republic of China, and School of
Materials Science and Engineering, Tongji UniVersity, 1239 Siping Road,
Shanghai 200092, People’s Republic of China
ReceiVed October 30, 2007
Three new tridentate NNN ligand precursors, CH3C(2,6-(iPr)2C6H3NH)CHC(CH3)(NCH2CH2-D) (D
) NMe2, NEt2, N((CH2CH2)2CH2)), were synthesized. Subsequent metalations with in situ generated
Ln(CH2SiMe3)3(THF)n (Ln ) Nd, Sm, Y, Lu) provided six solvent-free dialkyllanthanide complexes.
Five of the lanthanide complexes were characterized by single-crystal X-ray diffraction, which showed
that the pendant arm D bonds to the lanthanide ion in the solid state. The NMR spectra of these complexes
in C6D6 showed that such coordination is retained in solution. These dialkyllanthanide complexes show
high activities for the ring-opening polymerization of ꢀ-caprolactone, in which narrow-polydispersity
polymers were produced. The size of the pendant arm has a significant effect on the molecular weight
of the polymer obtained. In comparison to the Y complex with a -NMe2 group, the Y complexes with
-NEt2 and -N((CH2CH2)2CH2) groups yield much higher molecular weight polymer (60 000 vs 20 000).
opening polymerization of ꢀ-caprolactone or lactides,7f,8c methyl
Introduction
methacrylate polymerization,7b ethylene polymerization,6c and
copolymerization of cyclohexene oxide and CO2.8e Among
Organolanthanide complexes are useful catalysts in many
polymer1 and organic syntheses.2 The most widely investigated
organolanthanides are those bearing Cp-type ligands. The search
for new-generation organolanthanide catalysts has led to the
exploration of organolanthanide complexes with ancillary
ligands beyond Cp and its derivatives.3 In this connection,
ligands with nitrogen donor atoms have received much attention,
as they form strong N-Ln bonds with the acidic and hard Ln3+
ions and are expected to stabilize the highly electrophilic
organolanthanide complexes. One promising set of nitrogen-
containing ligands is the family of ꢀ-diketiminato ligands.4 The
precursors for these ligands can be readily prepared by
condensation of ꢀ-diketones with anilines. The steric and
electronic properties of these types of ligands can be easily tuned
by an appropriate choice of ꢀ-diketone and aniline starting
materials, and they can coordinate to lanthanide ions in different
bonding modes ranging from purely σ to a combination of σ
and π donation. Therefore, numerous ꢀ-diketiminato lanthanide
complexes have been prepared in the past few years.5–8 Some
of them show good activities in polymer synthesis, such as ring-
ꢀ-diketiminato lanthanide complexes, the dialkyl derivatives are
of the greatest interest, as they provide highly reactive Ln-C
bonds. However, examples of these complexes are few in
number. Piers and co-workers reported several Sc dialkyl
(5) (a) Hitchcock, P. B.; Lappert, M. F.; Tian, S. J. Chem. Soc., Dalton
Trans. 1997, 1945. (b) Eisenstein, O.; Hitchcock, P. B.; Khvostov, A. V.;
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Soc. 2003, 125, 10790. (c) Avent, A. G.; Hitchcock, P. B.; Khvostov, A. V.;
Lappert, M. F.; Protchenko, A. V. Dalton Trans. 2003, 1070. (d) Avent,
A. G.; Caro, C. F.; Hitchcock, P. B.; Lappert, M. F.; Li, Z.; Wei, X. H.
Dalton Trans. 2004, 1567. (e) Avent, A. G.; Hitchcock, P. B.; Khvostov,
A. V.; Lappert, M. F.; Protchenko, A. V. Dalton Trans. 2004, 2272. (f)
Hitchcock, P. B.; Lappert, M. F.; Protchenko, A. V. Chem. Commun. 2005,
951.
(6) (a) Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J.; Clegg, W.;
Parvez, M. Organometallics 1999, 18, 2947. (b) Hayes, P. G.; Piers, W. E.;
Lee, L. W. M.; Knight, L. K.; Parvez, M.; Elsegood, M. R. J.; Clegg, W.
Organometallics 2001, 20, 2533. (c) Hayes, P. G.; Piers, W. E.; McDonald,
R. J. Am. Chem. Soc. 2002, 124, 2132. (d) Hayes, P. G.; Piers, W. E.;
Parvez, M. J. Am. Chem. Soc. 2003, 125, 5622. (e) Knight, L. K.; Piers,
W. E.; Fleurat-Lessard, P.; Parvez, M.; McDonald, R. Organometallics 2004,
23, 2087. (f) Lauterwasser, F.; Hayes, P. G.; Bräse, S.; Piers, W. E.; Schafer,
L. L. Organometallics 2004, 23, 2234. (g) Hayes, P. G.; Piers, W. E.; Parvez,
M. Organometallics 2005, 24, 1173.
(7) (a) Yao, Y. M.; Zhang, Y.; Shen, Q.; Yu, K. B. Organometallics
2002, 21, 819. (b) Yao, Y. M.; Zhang, Y.; Zhang, Z. Q.; Shen, Q.; Yu,
K. B. Organometallics 2003, 22, 2876. (c) Yao, Y. M.; Xue, M. Q.; Luo,
Y. J.; Jiao, R.; Zhang, Z. Q.; Shen, Q.; Wong, W. T.; Yu, K. B.; Sun, J. J.
Organomet. Chem. 2003, 678, 108. (d) Yao, Y. M.; Luo, Y. J.; Jiao, R.;
Shen, Q.; Yu, K. B.; Weng, L. H. Polyhedron 2003, 22, 441. (e) Zhang,
Z. Q.; Yao, Y. M.; Zhang, Y.; Shen, Q.; Wong, W. T. Inorg. Chim. Acta
2004, 357, 3173. (f) Xue, M. Q.; Yao, Y. M.; Shen, Q.; Zhang, Y. J.
Organomet. Chem. 2005, 690, 4685. (g) Yao, Y. M.; Zhang, Z. Q.; Peng,
H. M.; Zhang, Y.; Shen, Q.; Lin, J. Inorg. Chem. 2006, 45, 2175.
(8) (a) Basuli, F.; Tomaszewski, J.; Huffman, J. C.; Mindiola, D. J.
Organometallics 2003, 22, 4705. (b) Cui, C. M.; Shafir, A.; Schmidt,
J. A. R.; Oliver, A. G.; Arnold, J. Dalton Trans. 2005, 1387. (c) Sánchez-
Barba, L. F.; Hughes, D. L.; Humphrey, S. M.; Bochmann, M. Organo-
metallics 2005, 24, 3792. (d) Vitanova, D. V.; Hampel, F.; Hultzsch, K. C.
Dalton Trans. 2005, 1565. (e) Vitanova, D. V.; Hampel, F.; Hultzsch, K. C.
J. Organomet. Chem. 2005, 690, 5182.
* To whom correspondence should be addressed. Fax: 0085-21-
64166128. E-mail: yaofchen@mail.sioc.ac.cn.
† Shanghai Institute of Organic Chemistry.
‡ Tongji University.
(1) (a) Yasuda, H. J. Organomet. Chem. 2002, 647, 128. (b) Arndt, S.;
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10.1021/om7010936 CCC: $40.75
2008 American Chemical Society
Publication on Web 01/19/2008

Dialkyllanthanide Complexes
Chart 1
Organometallics, Vol. 27, No. 4, 2008 759
tion occurred, and the target Y complex was formed nearly
quantitatively in 10 min. A C6D6 solution of the Y complex
formed is quite stable and showed no sign of decomposition
over 1 day. Accordingly, the alkane elimination method was
applied for the synthesis of dialkyl complexes 4-9. Reactions
between in situ generated Ln trialkyl complexes (Ln ) Y, Lu,
Sm) and the ligand precursors HL1-HL3 in hexane at 0 °C
provided dialkyl complexes 4-6, 8, and 9 in 38–73% isolated
yields. Attempts to prepare the L1NdR2 complex 7 by the same
procedure failed, probably due to the instability of the in situ
generated Nd trialkyl complex in hexane.14 Therefore, the Nd
trialkyl complex was prepared and reacted with HL1 in THF.
The THF was evaporated under vacuum after the reaction was
complete. Recrystallization of the residue from hexane provided
the desired Nd complex as greenish blue crystals in 33% yield.
Single crystals of the complexes 4-7 and 9 were grown from
hexane solutions and characterized by X-ray diffraction. ORTEP
diagrams are shown in Figures 1 and 2,15 and selected bond
lengths and angles are given in Table 1. One interesting feature
of these complexes is that they are all solvent-free, five-
coordinate monomers, even those of large lanthanide ions, such
as Nd3+ and Sm3+. In the complexes, ligand L1 or L3 serves
as a tridentate ligand and the five-coordinate center is completed
by a pair of -CH2SiMe3 substitutents. The geometry at the metal
centers is best described as distorted square pyramidal with one
of the -CH2SiMe3 substitutents taking the apical station. The
backbone of the ligands is bonded to the metal ions at Ln-N
separations from 2.28 to 2.42 Å, which fall in the range of
2.04-2.49 Å observed for Ln-N bonds in other reported
ꢀ-diketiminato lanthanide complexes,5–7 and those values are
closely dependent on the central metal ions and increase as the
lanthanide ion size becomes larger. As expected, the Ln-N bond
lengths of the pendant arms (2.50–2.66 Å) are longer than those
of the backbone, because the pendant arm acts as a neutral donor
while the backbone is an anionic donor. The C-N and C-C
bond lengths of the ꢀ-diketiminato backbone are intermediate
between those of typical single and double bonds, and N1, C2,
C3, C4, and N2 atoms are coplanar, indicating a delocalized
electronic structure. The metal ions sit above the C3N2 ligand
plane from 1.17 to 1.37 Å, and the deviation values are larger
than that in [(CH(C(Me)NCH2CH2NEt2)2)Tb(CH2SiMe3)2] (0.81
Å),10b less than that in [(CH(C(Ph)NSiMe3)2)Ce(CH(SiMe3)2)2]
(1.84 Å),5a and close to those in [(CH(C(R)N(2,6-(iPr)2Ph)2)-
ScR/2] (1.11–1.26 Å).6b Although the lanthanide ions are situated
out of the ligand plane significantly, distances from metal ions
to the ligand backbone carbon atoms C2, C3 and C4 are too
long for effective interaction (>3.15 Å). Thus, the bonding mode
of the ligands is best described as 2-σ-electron donors. The size
of the metal ion is considered to be a potential contributing
factor to out-of-plane bonding. The characterization of the solid-
state structures of complexes 4-7, which differ only in the metal
ions, provides direct crystallographic information of the metal
size’s effect on the out-of-plane bonding. It was found that the
degrees of the metal’s deviation from the ligand plane in these
complexes are almost the same if the difference in Ln3+ radii
complexes stabilized by the bulky ꢀ-diketiminato ligand derived
from A6b (Chart 1), and Lappert’s group synthesized a Ce
complex, [(CH(C(Ph)NSiMe3)2)Ce(CH(SiMe3)2)2], having the
bulky and less reactive -CH(SiMe3)2 substituent.5a Generally,
ꢀ-diketiminato lanthanide dialkyl complexes are difficult to
synthesize, due to their tendency to undergo ligand redistribu-
tion, dimerization, and elimination reactions.8c
Usually, introducing neutral pendant arms is a useful strategy
for stabilizing the organolanthanide complexes.9 Roesky and
co-workers developed the ꢀ-diketiminato derivative B, which
contains two dangling arms with nitrogen donors incorporated.
With the tetradentate ligand derived from B, they prepared a
series of salt- and solvent-free lanthanide complexes, such as
LLnX2 (X ) Cl, Br, I) and LLn(BH4)2.10 However, the
preparation of the corresponding dialkyl complxes is very
difficult, and only LTb(CH2SiMe3)2 has been obtained.10b After
considering both steric and electronic features of the ligand,
which are crucial to the stabilization of organolanthanide
complexes, we designed a new type of tridentate NNN ligands
derived from C. The ligand precursors C can be conveniently
prepared from 2-((2,6-diisopropylphenyl)imido)-2-penten-4-one
and the appropriate diamine, and these precursors have proved
to be ideal for ancillary ligands for the organolanthanide dialkyl
complexes, including those of larger metal ions, such as Nd3+
and Sm3+. Herein we report the preparation of these ligand
precursors, the preparation and structures of organolanthanide
dialkyl complexes containing these ligands, and their application
in the ring-opening polymerization of ꢀ-caprolactone.
Results and Discussion
Synthesis and Characterization. 2-((2,6-Diisopropylphe-
nyl)imido)-2-penten-4-one was prepared by condensation of
acetylacetone with 2,6-diisopropylaniline.11 Subsequent treat-
ment of this product with an appropriate diamine in benzene or
toluene using a catalytic amount of p-toluenesulfonic acid
provided the desired tridentate ligand precursors HL1-HL3
in 56–67% yield (Scheme 1). These were characterized by NMR
and mass spectroscopy and by elemental analysis.
The dialkyllanthanide complexes usually were prepared via
salt5a,6b,10b,12 or alkane elimination.13 The addition of 1 equiv
of Y(CH2SiMe3)3(THF)2 to the ligand precursor HL1 was
monitored by 1H NMR spectroscopy in C6D6. Alkane elimina-
(9) (a) Schumann, H.; Meese-Marktscheffel, J. A.; Esser, L. Chem. ReV.
1995, 95, 865. (b) Wang, B.; Deng, D. L.; Qian, C. T. New J. Chem. 1995,
19, 515.
(10) (a) Neculai, D.; Roesky, H. W.; Neculai, A. M.; Magull, J.; Schmidt,
H. G.; Noltemeyer, M. J. Organomet. Chem. 2002, 643, 47. (b) Neculai,
D.; Roesky, H. W.; Neculai, A. M.; Magull, J.; Herbst-Irmer, R.; Walfort,
B.; Stalke, D. Organometallics 2003, 22, 2279. (c) Nikiforov, G. B.; Roesky,
H. W.; Labahn, T.; Vidovic, D.; Neculai, D. Eur. J. Inorg. Chem. 2003,
433. (d) Neculai, A. M.; Neculai, D.; Roesky, H. W.; Magull, J.; Baldus,
M.; Andronesi, O.; Jansen, M. Organometallics 2002, 21, 2590. (e) Neculai,
A. M.; Neculai, D.; Roesky, H. W.; Magull, J. Polyhedron 2004, 23, 183.
(11) He, X. H.; Yao, Y. Z.; Luo, X.; Zhang, J.; Liu, Y.; Zhang, L.; Wu,
Q. Organometallics 2003, 22, 4952.
(13) (a) Hultzsch, K. C.; Spaniol, T. P.; Okuda, J. Angew. Chem., Int.
Ed. 1999, 38, 227. (b) Li, X. F.; Baldamus, J.; Hou, Z. M. Angew. Chem.,
Int. Ed. 2005, 44, 962. (c) Marinescu, S. C.; Agapie, T.; Day, M. W.;
Bercaw, J. E. Organometallics 2007, 26, 1178. (d) Liu, X. L.; Shang, X. M.;
Tang, T.; Hu, N. H.; Pei, F. K.; Cui, D. M.; Chen, X. S.; Jing, X. B.
Organometallics 2007, 26, 2747.
(14) Schumann, H.; Freckmann, D. M. M.; Dechert, S. Z. Anorg. Allg.
Chem. 2002, 628, 2422.
(12) (a) Jeske, G.; Schock, L. E.; Swepston, P. N.; Schumann, H.; Marks,
T. J. J. Am. Chem. Soc. 1985, 107, 8103. (b) Qian, C. T.; Zou, G.; Chen,
Y. F.; Sun, J. Organometallics 2001, 20, 3106.
(15) Since the structures of 4–7 are very similar, only the ORTEP figure
of 7 is shown in the main text; others are given in the Supporting
Information.

760 Organometallics, Vol. 27, No. 4, 2008
Xu et al.
Scheme 1
is counted; this phenomenon reveals that the metal size hardly
plays a role in the complexes’ adoption of the out-of-plane
bonding mode. The size of the pendant arm affects the
alkyl-Ln-alkyl angle, and the complex 9, with bulkier N
substituents, displays a larger alkyl-Ln-alkyl angle (117.22(19)°)
compared to those in complexes 4-7 (average 111.4°).
The 1H NMR spectrum of complexes 4, 5, 8, and 9 in C6D6
shows an AB system for the Y-CH2 methylene protons,
indicating a Cs-symmetric structure in solution, and in all Y
complexes, the signals for M-CH2 are further split into doublets
with a coupling constant of 3 Hz due to the Y-H coupling.
For the ligand precursor HL2, the methylene units of
-N(CH2CH3)2 display one peak at 2.30 ppm. In the Y complex
8, however, an AB pattern was observed for those -CH2- units:
one signal at 2.83 ppm and the other at 2.47 ppm, the latter
being partly overlapped with the signal of -NCH2CH2N- (2.44
ppm). However, the former clearly shows a sextet. This is
consistent with a coordination interaction between Y and the
pendant group, and two hydrogen atoms on the -CH2- unit
become diastereotopic as the rotation around the N-C bond is
hindered after the pendant arm bonds to the metal. The -CH2-
signal is split into a doublet with a J value of 14 Hz due to the
H-H coupling between two diastereotopic hydrogen atoms, and
each of these two doublets is further split into a quartet with
3JH-H ) 7 Hz; two quartets partially overlap to form the sextet
observed. A similar change was observed in the 1H NMR
spectrum of Y complex 9 as compared to that of HL3. The 1H
NMR spectrum of HL3 features one broad signal at 2.19 ppm
for N(-CH2-)2 in the N((-CH2CH2)2CH2) group, while for
the Y complex 9, the N(-CH2-)2 group displays two broad
signals at 2.10 and 3.16 ppm, respectively.
Polymerization of E-Caprolactone. The complexes 4-9
were used for the ring-opening polymerization of ꢀ-caprolactone
(ꢀ-CL), and the results are summarized in Table 2. All of these
complexes are highly active initiators for the ꢀ-caprolactone ring-
opening polymerization in toluene. Over 85% yields were
achieved at room temperature in 20 min using a very small
mount of initiator (ꢀ-CL/initiator molar ratio 2000), and activities
of the initiators range up to 570–670 kg of PCL/((mol of Ln)
h). The Mw values of the polymers obtained are between 20 000
and 70 000, and the polydispersities are narrow (<1.4).
The Mw values of polymers obtained when complexes 4, 6,
and 7 were used are very similar (Table 2, entries 1, 3, and 4)
and are much lower than the predicted values. The lower Mw
values of polymers obtained using complexes 4, 6, and 7 are
mainly due to transesterification reactions during the polymer-
ization process, as observed in other ꢀ-CL polymerization
systems.7g In comparison with the cases for the Nd, Sm, and Y
initiators, the Lu initiator 5 produces a polymer with a higher
Mw value (Table 2, entry 2). The most interesting observation
of the present catalytic system is that the transesterification
reaction can be efficiently suppressed by using a bulkier
substituent on the pendant nitrogen atom (Table 2, entries 5
and 6). The Y complexes 8 and 9 with -NEt2 and
-N((CH2CH2)2CH2) groups provide a polymer with a much
higher Mw value than does the Y complex 1 with -NMe2.
Conclusion
A series of dialkylorganolanthanide complexes containing
tridentate monoanionic ligands with nitrogen donors have been
prepared by alkane elimination from in situ generated
Ln(CH2SiMe3)3(THF)n with the ligand precursors. The addition
Figure 1. Molecular structure of 7 with thermal ellipsoids at the
30% probability level.
Figure 2. Molecular structure of 9 with thermal ellipsoids at the
30% probability level.

Dialkyllanthanide Complexes
Organometallics, Vol. 27, No. 4, 2008 761
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Complexes 4–7 and 9
4 (Ln ) Y)
5 (Ln ) Lu)
6 (Ln ) Sm)
7 (Ln ) Nd)
9 (Ln ) Y)
Ln-N1
2.338(4)
2.340(4)
2.555(4)
2.403(5)
2.406(5)
1.329(6)
1.319(6)
1.394(6)
1.403(7)
1.229(7)
78.07(14)
143.91(15)
69.27(15)
111.11(18)
124.3(5)
128.5(5)
123.8(5)
120.0(3)
119.2(3)
103.4(3)
2.289(4)
2.279(5)
2.499(5)
2.368(5)
2.339(5)
1.322(7)
1.326(8)
1.393(8)
1.389(8)
1.166(7)
79.46(15)
145.97(16)
69.86(16)
111.2(2)
124.5(5)
128.3(6)
123.2(5)
119.9(3)
119.9(4)
102.8(4)
2.381(2)
2.394(3)
2.625(3)
2.451(4)
2.441(3)
1.315(4)
1.313(5)
1.407(5)
1.402(5)
1.320(4)
76.63(9)
140.84(10)
67.75(10)
111.56(12)
124.4(3)
128.6(4)
123.4(3)
119.5(2)
118.5(2)
103.1(2)
2.405(3)
2.421(3)
2.656(3)
2.485(4)
2.471(4)
1.319(5)
1.310(5)
1.409(5)
1.393(5)
1.374(5)
76.17(10)
139.16(11)
66.85(11)
111.95(13)
123.5(3)
129.3(4)
124.4(4)
119.0(2)
116.9(3)
103.8(3)
2.352(4)
2.339(4)
2.543(4)
2.410(5)
2.397(5)
1.361(6)
1.328(7)
1.402(7)
1.395(7)
1.147(6)
77.72(14)
145.84(14)
71.01(15)
117.22(19)
123.6(5)
129.1(5)
123.2(5)
121.9(3)
121.8(3)
99.9(3)
Ln-N2
Ln-N3
Ln-C22
Ln-C26
C2-N1
C4-N2
C2-C3
C3-C4
N2C3 plane-Ln
N1-Ln-N2
N1-Ln-N3
N2-Ln-N3
C22-Ln-C26
N1-C2-C3
C2-C3-C4
C3-C4-N2
Ln-N1-C2
Ln-N2-C4
Ln-N3-C7
Table 2. Polymerization of E-Caprolactone with Complexes 4-9a
c
entry
initiator
yield (%)
activityb
Mw
Mw/Mn
1
2
3
4
5
6
4, Y(Ll)
5, Lu(Ll)
6, Sm(Ll)
7, Nd(Ll)
8, Y(L2)
9, Y(L3)
89
95
85
89
97
98
610
618
575
610
664
671
23 700
46 900
28 700
29 400
62 500
67 800
1.37
1.35
1.35
1.35
1.39
1.34
a Polymerization conditions: 6.8 µmol of initiator, ꢀ-CL/initiator molar ratio 2000, 6 mL of toluene, T ) 26 °C, polymerization time 20 min. b In
units of kg of polymer/((mol of Ln) h). c Determined by GPC relative to polystyrene standards.
on a Waters 1515 apparatus equipped with a set of Waters Styragel
columns (HR3, HR4, and HR5) at 35 °C. THF was used as the
eluent, and the system was calibrated using polystyrene standards.
Elemental analysis was performed by the Analytical Laboratory of
Shanghai Institute of Organic Chemistry. Melting points of the
complexes were determined on an SWG X-4 digital melting point
apparatus in a sealed capillary and are uncorrected.
of a neutral pendant arm to the commonly used ꢀ-diketiminato
ligand has a dramatic effect on the stabilization of the highly
reactive dialkylorganolanthanide complexes. Therefore, those
of larger metal ions, such as Nd3+ and Sm3+, were accessible.
These dialkylorganolanthanide complexes are highly active
initiators for the ꢀ-caprolactone ring-opening polymerization.
It is worth noting that the molecular weight of the polymer
obtained is greatly affected by the substituent on the pendant
nitrogen atom, which could provide a convenient way to control
the molecular weight of the polymer by an appropriate choice
of pendant arm.
HL1. 2-((2,6-Diisopropylphenyl)imido)-2-penten-4-one (8.20 g,
31.6 mmol), N,N-dimethylethylenediamine (2.79 g, 31.6 mmol),
and a catalytic amount of p-toluenesulfonic acid in benzene (30
mL) were combined and heated at reflux overnight. The water
produced during the reaction was removed as a benzene azeotrope
using a water separator. The benzene was removed in vacuo after
the reaction was complete. Distillation of the residue under reduced
pressure (bp 120 °C, 8 Pa) provided HL1 as a light yellow oil
(7.02 g, 67% yield). Anal. Calcd for C21H35N3: C, 76.54; H, 10.71;
N, 12.75. Found: C, 76.65; H, 10.86; N, 12.76. 1H NMR (300 MHz,
C6D6, 25 °C): δ (ppm) 11.04 (br s, 1H, NH), 7.24–7.14 (m, 3H,
Experimental Section
General Procedures. All operations were carried out under an
atmosphere of argon using standard Schlenk techniques or in a
nitrogen-filled glovebox. THF was distilled from Na-benzophenone
ketyl; toluene and hexane were dried over Na/K alloy. CDCl3 was
purchased from Cambridge Isotopes and dried over 4 Å molecular
sieves; C6D6 was purchased from Cambridge Isotopes, dried over
Na/K alloy, distilled under vacuum, and stored in the glovebox.
Acetylacetone, 2,6-diisopropylaniline, N,N-dimethylethylenedi-
amine, N,N-diethylethylenediamine, and N-(2-aminoethyl)piperidine
were purchased from Acros and used without purification. 2-((2,6-
Diisopropylphenyl)imido)-2-penten-4-one was synthesized by fol-
lowing the literature procedure.11 LiCH2SiMe3 was prepared
according to a standard procedure.16 ꢀ-CL (Acros) was dried by
stirring with CaH2 for 48 h and then distilled under reduced pressure
3
ArH), 4.71 (s, 1H, MeC(N)CH), 3.20 (sp, JHH ) 6.9 Hz, 2H,
3
3
ArCHMe2), 2.97 (t, JHH ) 6.3 Hz, 2H, NCH2), 2.18 (t, JHH
)
6.3 Hz, 2H, NCH2), 1.95 (s, 6H, NMe2), 1.69 (s, 3H, MeC(NHAr)),
1.66 (s, 3H, MeC(NCH2CH2NMe2)), 1.27 (t, 3JHH ) 7.8 Hz, 12H,
1
ArCHMe2). H NMR (300 MHz, CDCl3, 25 °C): δ (ppm) 10.83
(br s, 1H, NH), 7.12–7.01 (m, 3H, ArH), 4.65 (s, 1H, MeC(N)CH),
3.33 (q, 2H, NCH2), 2.88 (sp, 3JHH ) 7.2 Hz, 2H, ArCHMe2), 2.39
3
(t, JHH ) 7.2 Hz, 2H, NCH2), 2.21 (s, 6H, NMe2), 2.02 (s, 3H,
3
MeC(NHAr)), 1.62 (s, 3H, MeC(NCH2CH2NMe2)), 1.16 (d, JHH
) 6.9 Hz, 6H, ArCHMe2), 1.12 (d, 3JHH ) 6.6 Hz, 6H, ArCHMe2).
13C NMR (75 MHz, CDCl3, 25 °C): δ (ppm) 165.9 (1C,
MeC(NCH2CH2NMe2)), 155.3 (1C, MeC(NHAr)), 146.9 (1C, Cipso),
137.9 (2C, Cortho), 122.5 (2C, Cmeta), 122.3 (1C, Cpara), 93.1 (1C,
MeC(N)CH), 59.8 (1C, N CH2), 45.7 (2C, NMe2), 41.5 (1C, NCH2),
27.9 (2C, ArCHMe2), 23.8 (2C, ArCHMe2), 22.7 (2C, ArCHMe2),
21.5 (1C, MeC(NHAr)), 19.4 (1C, MeC(NCH2CH2NMe2)). EIMS:
m/z 329 (M+, 1.30), 271 (100), 58 (48.53).
1
and degassed prior to the polymerization experiment. H and 13C
NMR spectra were recorded on a Varian Mercury 300 spectrometer
at room temperature, and the chemical shifts are reported in δ (ppm)
units referenced to the residual solvent resonances of the deuterated
solvents. Gel permeation chromatographic analysis was performed
(16) Tessier-Youngs, C.; Beachley, O. T. Inorg. Synth. 1986, 24, 95.

762 Organometallics, Vol. 27, No. 4, 2008
Xu et al.
HL2. The procedure described for HL1 was used, but with
2-((2,6-diisopropylphenyl)imido)-2-penten-4-one (5.79 g, 22.3 mmol),
N,N-diethylethylenediamine (2.59 g, 22.3 mmol), and a catalytic
amount of p-toluenesulfonic acid in toluene (30 mL). The product
HL2 (4.51 g, 56% yield) was obtained as a yellow oil by distillation
under reduced pressure (bp 140–142 °C, 8 Pa). Anal. Calcd for
C23H39N3: C, 77.26; H, 10.99; N, 11.75. Found: C, 77.45; H, 10.95;
N, 11.64. 1H NMR (300 MHz, C6D6, 25 °C): δ (ppm) 10.95 (br s,
1H, NH), 7.23–7.13 (m, 3H, ArH), 4.72 (s, 1H, MeC(N)CH), 3.21
4 as a pale yellow crystalline solid (448 mg, 40% yield). Mp:
117–120 °C without decomposition. Anal. Calcd for C29H56N3Si2Y:
C, 58.85; H, 9.54; N, 7.10. Found: C, 58.64; H, 9.26; N, 7.05. H
1
NMR (300 MHz, C6D6, 25 °C): δ (ppm) 7.17–7.13 (m, 3H, ArH),
4.88 (s, 1H, MeC(N)CH), 3.25 (sp, 3JHH ) 6.6 Hz, 2H, ArCHMe2),
3
3
2.88 (t, JHH ) 5.8 Hz, 2H, NCH2), 2.21 (t, JHH ) 6.1 Hz, 2H,
NCH2), 2.07 (s, 6H, NMe2), 1.69 (s, 3H, MeC), 1.63 (s, 3H, MeC),
3
3
1.43 (d, JHH ) 6.6 Hz, 6H, ArCHMe2), 1.16 (d, JHH ) 6.9 Hz,
2
6H, ArCHMe2), 0.22 (s, 18H, Y(CH2SiMe3)2), -0.67 (dd, JHH
)
3
2
2
(sp, JHH ) 6.9 Hz, 2H, ArCHMe2), 2.99 (q, 2H, NCH2), 2.38 (t,
12 Hz, JYH ) 3 Hz, 2H, CH2SiMe3), -0.92 (dd, JHH ) 12 Hz,
2JYH ) 3 Hz, 2H, CH2SiMe3). 13C NMR (75 MHz, C6D6, 25 °C):
δ (ppm) 166.4 (1C, imine C), 165.7 (1C, imine C), 144.1 (1C),
142,7 (2C), 126.1 (1C), 124.5 (2C) (ArC), 98.0 (1C, MeC(N)CH),
58.0 (1C, NCH2), 47.3 (1C, NCH2), 44.9 (2C, NMe2), 35.6 (d, 1JYC
) 39.8 Hz, 2C, CH2SiMe3), 28.3 (2C, ArCHMe2), 25.3 (2C,
ArCHMe2), 24.6 (2C, ArCHMe2), 24.1 (1C, MeC), 23.3 (1C, MeC),
4.6 (6C, CH2SiMe3).
L1Lu(CH2SiMe3)2 (5). Following the procedure described for
4, reaction of anhydrous LuCl3 (510 mg, 1.8 mmol), LiCH2SiMe3
(503 mg, 5.3 mmol), and HL1 (489 mg, 1.5 mmol) gave 5 as a
pale yellow crystalline solid (732 mg, 73% yield). Mp: 105–109
°C without decomposition. Anal. Calcd for C29H56N3Si2Lu: C,
51.38; H, 8.33; N, 6.20. Found: C, 51.18; H, 8.21; N, 6.14. 1H
NMR (300 MHz, C6D6, 25 °C): δ (ppm) 7.17–7.15 (m, 3H, ArH),
4.86 (s, 1H, MeC(N)CH), 3.28 (sp, 3JHH ) 6.6 Hz, 2H, ArCHMe2),
3JHH ) 6.9 Hz, 2H, NCH2), 2.30 (q, 4H, N(CH2CH3)2), 1.70 (s,
3
6H, MeC(NHAr) and MeC(NCH2CH2NEt2)), 1.28 (d, JHH ) 6.9
Hz, 6H, ArCHMe2), 1.24 (d, 3JHH ) 6.2 Hz, 6H, ArCHMe2), 0.83
(t, 3JHH ) 6.9 Hz, 6H, N(CH2CH3)2). 1H NMR (300 MHz, CDCl3,
25 °C): δ (ppm) 10.76 (br s, 1H, NH), 7.13–7.01 (m, 3H, ArH),
3
4.64 (s, 1H, MeC(N)CH), 3.30 (q, 2H, NCH2), 2.88 (sp, JHH
)
6.6 Hz, 2H, ArCHMe2), 2.52 (ov, m, 6H, NCH2 and N(CH2CH3)2),
2.02 (s, 3H, MeC(NHAr)), 1.61 (s, 3H, MeC(NCH2CH2NEt2)), 1.15
3
3
(d, JHH ) 6.9 Hz, 6H, ArCHMe2), 1.12 (d, JHH ) 6.9 Hz, 6H,
ArCHMe2), 0.95 (t, JHH ) 6.9 Hz, 6H, N(CH2CH3)2). 13C NMR
(75 MHz, CDCl3, 25 °C):
3
δ
(ppm) 165.9 (1C,
MeC(NCH2CH2NEt2)), 155.4 (1C, MeC(NHAr)), 147.1 (1C, Cipso),
137.9 (2C, Cortho), 122.6 (2C, Cmeta), 122.3 (1C, Cpara), 92.9 (1C,
MeC(N)CH), 53.5 (1C, NCH2), 47.3 (2C, N(CH2CH3)2), 41.7 (1C,
NCH2), 27.9 (2C, ArCHMe2), 23.8 (2C, ArCHMe2), 22.8 (2C,
ArCHMe2), 21.6 (1C, MeC(NHAr)), 19.5 (1C, MeC(NCH2-
CH2NEt2)), 11.7 (2C, N(CH2CH3)2). EIMS: m/z 357 (M+, 2.84),
271 (100), 86 (96.57).
3
3
2.88 (t, JHH ) 5.7 Hz, 2H, NCH2), 2.15 (t, JHH ) 6 Hz, 2H,
NCH2), 2.04 (s, 6H, NMe2), 1.66 (s, 3H, MeC), 1.62 (s, 3H, MeC),
3
3
1.43 (d, JHH ) 6.9 Hz, 6H, ArCHMe2), 1.16 (d, JHH ) 6.6 Hz,
HL3. The procedure described for HL1 was used, but with
2-((2,6-diisopropylphenyl)imido)-2-penten-4-one (5.01 g, 19.3 mmol),
N-(2-aminoethyl)piperidine (2.47 g, 19.3 mmol), and a catalytic
amount of p-toluenesulfonic acid in toluene (25 mL). The product
HL3 (4.19 g, 59% yield) was obtained as a yellow oil by distillation
under reduced pressure (bp 130–132 °C, 5 Pa). Anal. Calcd for
C24H39N3: C, 77.99; H, 10.64; N, 11.37. Found: C, 78.01; H, 10.46;
N, 10.93. 1H NMR (300 MHz, C6D6, 25 °C): δ (ppm) 11.01 (br s,
1H, NH), 7.24–7.16 (m, 3H, ArH), 4.71 (s, 1H, MeC(N)CH), 3.20
2
6H, ArCHMe2), 0.21 (s, 18H, Lu(CH2SiMe3)2), -0.88 (d, JHH
)
12 Hz, 2H, CH2SiMe3), -1.08 (d, 2JHH ) 12 Hz, 2H, CH2SiMe3).
13C NMR (75 MHz, C6D6, 25 °C): δ (ppm): 166.8 (1C, imine C),
166.5 (1C, imine C), 145.3 (1C), 142.7 (2C), 126.0 (1C), 124.4
(2C) (ArC), 98.6 (1C, MeC(N)CH), 57.7 (1C, NCH2), 47.4 (1C,
NCH2), 45.0 (2C, NMe2), 43.0 (2C, CH2SiMe3), 28.2 (2C,
ArCHMe2), 25.3 (2C, ArCHMe2), 24.8 (2C, ArCHMe2), 24.5 (1C,
MeC), 23.3 (1C, MeC), 4.8 (6C, CH2SiMe3).
L1Sm(CH2SiMe3)2 (6). Following the procedure described for
4, reaction of SmCl3 (478 mg, 1.9 mmol), LiCH2SiMe3 (517 mg,
5.5 mmol), and HL1 (502 mg, 1.5 mmol) gave 6 as a yellow
crystalline solid (486 mg, 49% yield). Mp: 115–117 °C without
decomposition. Anal. Calcd for C29H56N3Si2Sm: C, 53.32; H, 8.64;
N, 6.43. Found: C, 52.71; H, 8.41; N, 6.66. 6 is paramagnetic. 1H
NMR (300 MHz, C6D6, 25 °C): δ (ppm) 8.49 (s, 1H), 7.13 (br s,
3
3
(sp, JHH ) 6.9 Hz, 2H, ArCHMe2), 3.03 (t, JHH ) 6.9 Hz, 2H,
3
NCH2), 2.27 (t, JHH ) 6.6 Hz, 2H, NCH2), 2.19 (m, 4H,
N(CH2CH2)2CH2), 1.69 (s, 3H, MeC(NHAr)), 1.67 (s, 3H,
MeC(NCH2CH2NC5H10)), 1.39 (m, 4H, N(CH2CH2)2CH2), 1.29 (d,
3
3JHH ) 6.9 Hz, 6H, ArCHMe2), 1.24 (d, JHH ) 6.6 Hz, 6H,
1
ArCHMe2), 1.17 (m, 2H, N(CH2CH2)2CH2). H NMR (300 MHz,
CDCl3, 25 °C): δ(ppm) 10.79(br s, 1H, NH), 7.13–7.01 (m, 3H,
ArH), 4.63 (s, 1H, MeC(N)CH), 3.35 (q, 2H, NCH2), 2.87 (sp, 3JHH
) 6.9 Hz, 2H, ArCHMe2), 2.40 (ov, m, 6H, NCH2 and
N(CH2CH2)2CH2), 2.01 (s, 3H, MeC(NHAr)), 1.61 (s, 3H,
MeC(NCH2CH2NC5H10)), 1.50 (m, 4H, N(CH2CH2)2CH2), 1.37 (m,
3
3
2H), 6.56 (t, JHH ) 7.8 Hz, 1H), 5.96 (d, JHH ) 7.8 Hz, 2H),
4.77 (br s, 2H), 3.22 (s, 3H), 2.41 (s, 3H), 1.24 (s, 18H), 0.47 (d,
3
3JHH ) 6.3 Hz, 6H), -0.58 (br s, 2H), -0.63 (d, JHH ) 6.3 Hz,
6H), -1.46 (s, 6H), -1.55 (br s, 2H), -5.54 (s, 2H). 13C NMR
(75 MHz, C6D6, 25 °C): δ (ppm) 176.1, 171.3, 138.6, 138.5, 124.4,
123.4, 104.3, 47.3, 44.1, 39.9, 25.8, 23.3, 23.0, 21.9, 4.1.
3
2H, N(CH2CH2)2CH2), 1.15 (d, JHH ) 6.6 Hz, 6H, ArCHMe2),
1.11 (d, 3JHH ) 6.6 Hz, 6H, ArCHMe2). 13C NMR (75 MHz, CDCl3,
25 °C): δ (ppm) 165.9 (1C, MeC(NCH2CH2NC5H10)), 155.4 (1C,
MeC(NHAr)), 147.0 (1C, Cipso), 138.0 (2C, Cortho), 122.6 (2C, Cmeta),
122.3 (1C, Cpara), 93.0 (1C, MeC(N)CH), 60.0 (1C, NCH2), 54.9
(2C, N(CH2CH2)2CH2), 40.9 (1C, N CH2), 28.0 (2C, ArCHMe2),
25.8 (2C, N(CH2CH2)2CH2), 24.2 (1C, N(CH2CH2)2CH2), 23.8 (2C,
ArCHMe2), 22.8 (2C, ArCHMe2), 21.6 (1C, MeC(NHAr)), 19.5 (1C,
MeC(NCH2CH2NC5H10)). EIMS: m/z 369 (M+, 1.37), 271 (100),
98 (87.3).
L1Nd(CH2SiMe3)2 (7). Anhydrous NdCl3 (537 mg, 2.1 mmol)
was suspended in 10 mL of THF and the suspension stirred
overnight. A solution of LiCH2SiMe3 (595 mg, 6.3 mmol in 10
mL of THF) was added to the above suspension at ambient
temperature, and a bright blue solution formed in 10 min. The
reaction mixture was stirred for 2 h and then cooled to 0 °C. HL1
(578 mg, 1.8 mmol) in 5 mL of THF then was added. The reaction
solution was stirred for 2 h at 0 °C. The volatiles were removed
under vacuum, and the residue was extracted with 30 mL of hexane.
Concentration of the extract solution in vacuo to approximately 5
mL and cooling to -10 °C afforded 7 as greenish blue crystals
(374 mg, 33% yield). Mp: 110–112 °C without decomposition.
Anal. Calcd for C29H56N3Si2Nd: C, 53.82; H, 8.72; N, 6.49. Found:
C, 52.98; H, 7.94; N, 6.36. 7 is paramagnetic. 1H NMR (300 MHz,
C6D6, 25 °C): δ (ppm) 20.77 (s), 17.36 (br s), 13.48 (s), 11.76 (s),
L1Y(CH2SiMe3)2 (4). A suspension of anhydrous YCl3 (450 mg,
2.3 mmol) in 5 mL of THF was stirred overnight. The THF solvent
was removed in vacuo, and 5 mL of hexane was added. To the
above suspension was added a solution of LiCH2SiMe3 (640 mg,
6.8 mmol in 15 mL of hexane) at ambient temperature. After 2 h,
the precipitate was separated by centrifugation, and the resulting
clear solution was added to an HL1 solution (622 mg, 1.9 mmol
in 5 mL of hexane) at 0 °C. After 1 h, the reaction solution was
concentrated to approximately 5 mL and cooled to -10 °C to give
3
6.45 (s), 4.59 (s), 3.06 (br s), 1.38 (d, JHH ) 6.9 Hz), -0.18 (s),
-4.27 (s), -8.97 (s), -20.16 (s), -24.58 (br s), -26.85 (s). 13C

Dialkyllanthanide Complexes
Organometallics, Vol. 27, No. 4, 2008 763
Table 3. Crystallographic Data and Refinement for Complexes 4–7 and 9
4 (Ln ) Y)
5 (Ln ) Lu)
6 (Ln ) Sm)
7 (Ln ) Nd)
9 (Ln ) Y)
formula
fw
C29H56N3Si2Y
591.86
C29H56N3Si2Lu
677.92
C29H56N3Si2Sm
653.30
C29H56N3Si2Nd
647.19
C32H60N3Si2Y
631.92
color
cryst syst
space group
a, Å
b, Å
pale yellow
triclinic
P1
pale yellow
triclinic
P1
yellow
greenish blue
triclinic
P1
pale yellow
triclinic
P1
triclinic
j
j
j
j
j
P1
9.6359(18)
11.092(2)
17.373(3)
87.918(3)
75.102(3)
81.202(3)
1773.3(6)
2
9.613(3)
10.999(3)
17.249(5)
87.576(4)
74.846(4)
80.946(5)
1738.6(8)
2
9.5972(7)
11.0827(7)
17.2952(12)
88.2900(10)
75.1190(10)
81.2510(10)
1757.1(2)
2
9.6033(8)
11.1048(9)
17.3163(14)
88.3720(10)
75.2940(10)
81.2820(10)
1765.4(2)
2
10.989(5)
11.935(6)
14.662(8)
89.934(9)
84.979(10)
82.763(11)
1900.3(16)
2
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
Dcalcd, g/cm3
F(000)
1.108
636
1.295
700
1.235
682
1.217
678
1.104
680
θ range, deg
no. of rflns collected
no. of unique rflns
no. of obsd rflns (I > 2σ(I))
no. of params
goodness of fit
final R, Rw (I > 2σ(I))
∆Fmax, ∆Fmin, e Å-3
2.21–26.00
9458
6797
3757
330
0.861
0.0607, 0.1301
1.053, -0.877
1.87–27.00
10 187
7349
6370
330
0.976
0.0433, 0.1055
2.910, -1.359
2.21–26.50
9993
7103
6355
339
0.992
0.0335, 0.0790
1.232, -0.801
1.22–26.00
9556
6804
5830
330
1.009
0.0342, 0.0741
1.222, -0.469
1.72–26.00
10 460
7331
3644
355
0.820
0.0646, 0.1501
0.828, -0.928
NMR (75 MHz, C6D6, 25 °C): δ (ppm) 154.2, 131.8, 125.1, 111.0,
37.1, 17.5, 12.8, 5.9.
52.3 (1C, N(CH2CH2)2CH2), 52.0 (1C, NCH2), 46.2 (1C, NCH2),
36.5 (d, JYC ) 40.5 Hz, 2C, CH2SiMe3), 28.2 (2C, ArCHMe2),
1
L2Y(CH2SiMe3)2 (8). Complex 8 was prepared according to the
same procedure as that for 4 by reaction of anhydrous YCl3 (286
mg, 1.5 mmol), LiCH2SiMe3 (406 mg, 4.3 mmol), and HL2 (428
mg, 1.3 mmol) as a pale yellow crystalline solid (319 mg, 43%
yield). Mp: 108–111 °C without decomposition. Anal. Calcd for
C31H60N3Si2Y: C, 60.06; H, 9.76; N, 6.78. Found: C, 59.17; H,
9.53; N, 7.01. 1H NMR (300 MHz, C6D6, 25 °C): δ (ppm) 7.17–7.14
(m, 3H, ArH), 4.90 (s, 1H, MeC(N)CH), 3.29 (sp, 3JHH ) 6.9 Hz,
25.4 (2C, ArCHMe2), 24.7 (2C, ArCHMe2), 24.2 (1C, MeC), 23.9
(1C, MeC), 22.7 (2C, N(CH2CH2)2CH2), 21.8 (2C, N(CH2-
CH2)2CH2), 4.5 (6C, CH2SiMe3).
Polymerization of E-Caprolactone. In a glovebox, 6.8 µmol of
initiator in 0.5 mL of toluene was added to a toluene solution of
ꢀ-caprolactone (13.6 mmol in 5.5 mL of toluene). After 20 min,
the reaction vessel was taken out of the glovebox and the
polymerization was quenched with 2 mL of acidic methanol. The
reaction mixture was poured into 20 mL of methanol to precipitate
the polymer. The resulting polymer was isolated, washed with
methanol, and dried under vacuum for 1 day.
X-ray Crystallography. Suitable single crystals of 4-7 and 9
were sealed in thin-walled glass capillaries, and data collection was
performed at 20 °C on a Bruker SMART diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å). The
SMART program package was used to determine the unit-cell
parameters. The absorption correction was applied using SADABS.
The structures were solved by direct methods and refined on F2 by
full-matrix least-squares techniques with anisotropic thermal pa-
rameters for non-hydrogen atoms. Hydrogen atoms were placed at
calculated positions and were included in the structure calculation
without further refinement of the parameters. All calculations were
carried out using the SHELXS-97 program. Crystallographic data
and refinement details are given in Table 3.
3
2H, ArCHMe2), 2.93 (t, JHH ) 5.7 Hz, 2H, NCH2), 2.83 (sextet,
2H, N(CH2CH3)2), 2.51–2.42 (overlapped, m, 4H, N(CH2CH3)2 and
NCH2), 1.69 (s, 3H, MeC), 1.64 (s, 3H, MeC), 1.44 (d, 3JHH ) 6.9
Hz, 6H, ArCHMe2), 1.16 (d, 3JHH ) 6.9 Hz, 6H, ArCHMe2), 0.78
(t, 3JHH ) 7.1 Hz, 6H, N(CH2CH3)2), 0.19 (s, 18H, Y(CH2SiMe3)2),
2
2
-0.62 (dd, JHH ) 12 Hz, JYH ) 3 Hz, 2H, CH2SiMe3), -0.84
2
2
(dd, JHH ) 12 Hz, JYH ) 3 Hz, 2H, CH2SiMe3). 13C NMR (75
MHz, C6D6, 25 °C): δ(ppm) 165.9 (1C, imine C), 165.8 (1C, imine
C), 145.1 (1C), 142.7 (2C), 126.0 (1C), 124.4 (2C) (ArC), 98.0
(1C, MeC(N)CH), 49.9 (1C, NCH2), 46.7 (1C, NCH2), 44.3 (2C,
N(CH2CH3)2), 36.0 (d, 1JYC ) 38.3 Hz, 2C, CH2SiMe3), 28.2 (2C,
ArCHMe2), 25.4 (2C, ArCHMe2), 24.8 (2C, ArCHMe2), 24.3 (1C,
MeC), 22.9 (1C, MeC), 8.4 (2C, N(CH2CH3)2), 4.5 (6C, CH2SiMe3).
L3Y(CH2SiMe3)2 (9). Complex 9 was prepared according to the
same procedure as that for 4 by reaction of anhydrous YCl3 (230
mg, 1.2 mmol), LiCH2SiMe3 (327 mg, 3.5 mmol), and HL3 (369
mg, 1.0 mmol) as a pale yellow crystalline solid (240 mg, 38%
yield). Mp: 119–121 °C without decomposition. Anal. Calcd for
C32H60N3Si2Y: C, 60.82; H, 9.57; N, 6.65. Found: C, 61.79; H,
9.82; N, 6.66. 1H NMR (300 MHz, C6D6, 25 °C): δ (ppm) 7.18–7.14
Acknowledgment. This work was supported by the
National Natural Science Foundation of China, Chinese
Academy of Science, and Shanghai Municipal Committee
of Science and Technology (No. 07JC14063). We thank Prof.
Changtao Qian (Shanghai Institute of Organic Chemistry)
for helpful discussions.
(m, 3H, ArH), 4.91 (s, 1H, MeC(N)CH), 3.29 (sp, 3JHH ) 6.9 Hz,
3
2H, ArCHMe2), 3.16 (m, 2H, N(CH2CH2)2CH2), 2.94 (t, JHH
)
3
5.8 Hz, 2H, NCH2), 2.49 (t, JHH ) 5.6 Hz, 2H, NCH2), 2.10 (m,
2H, -N(CH2CH2)2CH2), 1.69 (s, 3H, MeC), 1.65 (s, 3H, MeC),
3
1.44 (d, JHH ) 7.2 Hz, 6H, ArCHMe2), 1.25 (m, 6H,
3
N(CH2CH2)2CH2 and N(CH2CH2)2CH2), 1.17 (d, JHH ) 6.9 Hz,
Supporting Information Available: ORTEP diagrams of the
molecular structures of 4–6 and CIF files giving X-ray crystal-
lographic data for 4–7 and 9. This material is available free of
charge via the Internet at http://pubs.acs.org.
2
6H, ArCHMe2), 0.20 (s, 18H, Y(CH2SiMe3)2), -0.55 (dd, JHH
)
2
2
12 Hz, JYH ) 3 Hz, 2H, CH2SiMe3), -0.81 (dd, JHH ) 12 Hz,
2JYH ) 3 Hz, 2H, CH2SiMe3). 13C NMR (75 MHz, C6D6, 25 °C):
δ (ppm) 165.9 (1C, imine C), 165.6 (1C, imine C), 145.0 (1C),
142.6 (2C), 126.0 (1C), 124.4 (2C) (ArC), 98.1 (1C, MeC(N)CH),
OM7010936