Synthesis and Olefin polymerization catalysis of new trivalent samarium and yttrium complexes with bridging bis(cyclopentadienyl) ligands

Article abstract of DOI:10.1021/om000226a

New trivalent samarium and yttrium complexes with bridging bis(cyclopentadienyl) ligands were synthesized, and olefin polymerization catalysis of the complexes having an alkyl group [R = CH(SiMe₃)₂] on the metal was investigated. Three types of the rare earth halides (rac, C₁, and meso) whose structures differed with respect to the bridging group and the positions of substituents on the cyclopentadienyl (Cp) rings were prepared: rac-Sm-Cl, Me₂Si[2,4-(Me₃Si)₂C₅ H₂]₂SmCl₂Li(THF)₂ (1a); C₁-Sm-Cl, Me₂Si[2,4-(Me₃Si)₂ C₅H₂][3,4-(Me₃Si)₂C₅ H₂]-SmCl₂Li(THF)₂ (2a); C₁(Ph₂Si)-Sm-Cl, Ph₂Si[2,4- (Me₃Si)₂C₅H₂][3,4- (Me₃Si)₂C₅H₂]SmCl₂- Li(THF)₂ (3); meso-Sm-Cl, [1,2-(Me₂Si)(Me₂SiOSiMe₂)](4-Me₃ CC₅H₂)₂SmCl₂Li(THF)₂ (4a);rac-Y-Cl, Me₂Si[2,4-(Me₃Si)₂C₅ H₂]₂YCL₂Li(THF)₂ (5a); C₁-Y-Cl, Me₂Si[2,4-(Me₃Si)₂ C₅H₂][3,4-(Me₃Si)₂C₅ H₂]YCl₂Li(THF)₂ (6a); meso-Y-Cl, [1,2-(Me₂Si)(Me₂SiOSiMe₂)](4-Me₃ SiC₅H₂)₂YCl-(THF) (7a). Although the rac and C₁ complexes (1a, 2a and 5a, 6a) were obtained as an isomeric mixture by the reaction of LnCl₃ (Ln = Sm, Y) with a dilithium salt of the ligand Me₂Si[(Me₃Si)₂C₅ H₃]₂, it could be separated into both the pure complexes by utilizing the difference of solubility in hexane in each case. Structural data were obtained on 1a, 2a, 3, and 7a to confirm the structures expected from NMR spectroscopy. The (ring centroid)- metal-(ring centroid) angles in these complexes are ca. 10-20° smaller than those in nonbridging bis(cyclopentadienyl) rare earth complexes. The rare earth halides 1a, 2a, 4a, 5a, 6a, and 7a reacted with LiCH(SiMe₃)₂ to afford rare earth alkyl complexes, rac-Sm-R, Me₂Si[2,4-(Me₃Si)₂C₅ H₂]₂SmCH(SiMe₃)₂ (1b); C₁-Sm-R, Me₂Si[2,4-(Me₃Si)₂ C₅H₂][3,4-(Me₃Si)₂C₅ H₂]SmCH(SiMe₃)₂ (2b); meso-Sm-R, [1,2-(Me₂Si)(Me₂SiOSiMe₂)] (4-Me₃CC₅H₂)₂SmCH (SiMe₃)₂ (4b); rac-Y-R, Me₂Si[2,4-(Me₃Si)₂C₅ H₂]₂YCH(SiMe₃)₂ (5b); C₁-Y-R, Me₂Si[2,4-(Me₃Si)₂ C₅H₂][3,4-(Me₃Si)₂C₅ H₂] YCH(SiMe₃)₂ (6b); meso-Y-R, and [1,2-(Me₂Si)(Me₂SiOSiMe₂)] (4-Me₃SiC₅H₂)₂YCH (SiMe₃)₂ (7b), respectively. Only C₁ type alkyl complexes (2b and 6b) polymerize ethylene, giving high molecular weight polyethylenes, and the precise structure of the active Sm complex 2b was determined by X-ray crystallography.

Full text of DOI:10.1021/om000226a

1752
Organometallics 2001, 20, 1752-1761
Syn th esis a n d Olefin P olym er iza tion Ca ta lysis of New
Tr iva len t Sa m a r iu m a n d Yttr iu m Com p lexes w ith
Br id gin g Bis(cyclop en ta d ien yl) Liga n d s
Eiji Ihara,† Shiro Yoshioka,† Masahito Furo,† Kenji Katsura,† Hajime Yasuda,*,†
Shouhei Mohri,‡ Nobuko Kanehisa,‡ and Yasushi Kai*,‡
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527, J apan, and Department of Applied Chemistry,
Faculty of Engineering, Osaka University, Suita 565-0871, J apan
Received March 14, 2000
New trivalent samarium and yttrium complexes with bridging bis(cyclopentadienyl) ligands
were synthesized, and olefin polymerization catalysis of the complexes having an alkyl group
[R ) CH(SiMe3)2] on the metal was investigated. Three types of the rare earth halides (rac,
C1, and meso) whose structures differed with respect to the bridging group and the positions
of substituents on the cyclopentadienyl (Cp) rings were prepared: rac-Sm-Cl, Me2Si[2,4-
(Me3Si)2C5H2]2SmCl2Li(THF)2 (1a ); C1-Sm-Cl, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]-
SmCl2Li(THF)2 (2a ); C1(Ph2Si)-Sm-Cl, Ph2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]SmCl2-
Li(THF)2 (3); meso-Sm-Cl, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3CC5H2)2SmCl2Li(THF)2 (4a );
rac-Y-Cl, Me2Si[2,4-(Me3Si)2C5H2]2YCl2Li(THF)2 (5a ); C1-Y-Cl, Me2Si[2,4-(Me3Si)2C5H2][3,4-
(Me3Si)2C5H2]YCl2Li(THF)2 (6a ); meso-Y-Cl, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3SiC5H2)2YCl-
(THF) (7a ). Although the rac and C1 complexes (1a , 2a and 5a , 6a ) were obtained as an
isomeric mixture by the reaction of LnCl3 (Ln ) Sm, Y) with a dilithium salt of the ligand
Me2Si[(Me3Si)2C5H3]2, it could be separated into both the pure complexes by utilizing the
difference of solubility in hexane in each case. Structural data were obtained on 1a , 2a , 3,
and 7a to confirm the structures expected from NMR spectroscopy. The (ring centroid)-
metal-(ring centroid) angles in these complexes are ca. 10-20° smaller than those in
nonbridging bis(cyclopentadienyl) rare earth complexes. The rare earth halides 1a , 2a , 4a ,
5a , 6a , and 7a reacted with LiCH(SiMe3)2 to afford rare earth alkyl complexes, rac-Sm-R,
Me2Si[2,4-(Me3Si)2C5H2]2SmCH(SiMe3)2 (1b); C1-Sm-R, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3-
Si)2C5H2]SmCH(SiMe3)2 (2b); meso-Sm-R, [1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3CC5H2)2SmCH-
(SiMe3)2 (4b); rac-Y-R, Me2Si[2,4-(Me3Si)2C5H2]2YCH(SiMe3)2 (5b); C1-Y-R, Me2Si[2,4-
(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]YCH(SiMe3)2 (6b); meso-Y-R, and [1,2-(Me2Si)(Me2SiOSi-
Me2)](4-Me3SiC5H2)2YCH(SiMe3)2 (7b), respectively. Only C1 type alkyl complexes (2b and
6b) polymerize ethylene, giving high molecular weight polyethylenes, and the precise
structure of the active Sm complex 2b was determined by X-ray crystallography.
In tr od u ction
on Cp*2Sm- and [Cp*2Sm(µ-H)]2-initiated olefin poly-
merization using field desorption mass spectrometry
have been reported.2f,g Although the inherent air sen-
Since it was found that the trivalent bis(pentamethyl-
cyclopentadienyl) (bis-Cp*) rare earth metal complexes
Cp*2LnR possessed ethylene polymerization activity in
the early 1980s,1 much attention has been paid to this
class of single-component olefin polymerization cata-
lysts.2 Mechanistic details of the polymerization were
revealed using Cp*2LuR1c,2d and Cp*2ScR.2k,l (Cp*2LaH)2
has been shown to have high ethylene polymerization
activity comparable to those of Kaminsky type catalysts,
although the complex gave low molecular weight oligo-
mers by the reaction with 1-olefins.2n It has been shown
that the divalent bis-Cp* Sm compound (Cp*2SmL) can
also act as an initiator.1a Detailed mechanistic studies
(2) (a) Yasuda, H.; Ihara, E. Adv. Polym. Sci. 1997, 133, 53-101.
(b) Ihara, E.; Nodono, M.; Katsura, K.; Adachi, Y.; Yasuda, H.;
Yamagashira, M.; Hashimoto, H.; Kanehisa, N.; and Kai, Y. Organo-
metallics 1998, 17, 3945-3956. (c) Long, D. P.; Bianconi, P. A. J . Am.
Chem. Soc. 1996, 118, 12453-12454. (d) Gilchrist, J . H.; Bercaw, J .
E. J . Am. Chem. Soc. 1996, 118, 12021-12028. (e) Mitchell, J . P.;
Hajela, S.; Brookhart, S. K.; Hardcastle, K. I.; Henling, L. M.; Bercaw,
J . E. J . Am. Chem. Soc. 1996, 118, 1045-1053. (f) Evans, W. J .;
DeCoster, D. M.; Greaves, J . Organometallics 1996, 15, 3210-3221.
(g) Evans, W. J .; DeCoster, D. M.; Greaves, J . Macromolecules 1995,
28, 7929-7936. (h) Shapiro, P. J .; Cotter, W. D.; Schaefer, W. P.;
Labinger, J . A.; Bercaw, J . E. J . Am. Chem. Soc. 1994, 116, 4623-
4640. (i) Schaverien, C. J . Organometallics 1994, 13, 69-82. (j)
Coughlin, E. B. J . Am. Chem. Soc. 1992, 114, 7606-7607. (k) Piers,
W. E.; Bercaw, J . E. J . Am. Chem. Soc. 1990, 112, 9406-9407. (l)
Burger, B. J .; Thompson, M. E., Cotter, W. D.; Bercaw, J . E. J . Am.
Chem. Soc. 1990, 112, 1566-1577. (m) Shapiro, P. J .; Bunel, E.;
Schaefer, W. P. Organometallics 1990, 9, 867-869. (n) J eske, G.;
Lauke, H.; Mauermann, H.; Swepston, P. N.; Schumann, H.; Marks,
T. J . J . Am. Chem. Soc. 1985, 107, 8091-8103. (o) J eske, G.; Schock,
L. E.; Swepston, P. N.; Schumann, H.; Marks, T. J . J . Am. Chem. Soc.
1985, 107, 8103-8110.
† Hiroshima University.
‡ Osaka University.
(1) (a) Watson, P. L.; Herskovitz, T. ACS Symp. Ser. 1983, 212, 459-
479. (b) Watson, P. L.; Parshall, G. W. Acc. Chem. Res. 1985, 18, 51-
56. (c) Watson, P. L.; Roe, D. C. J . Am. Chem. Soc. 1982, 104, 6471-
6473. (d) Watson, P. L. J . Am. Chem. Soc. 1982, 104, 337-339.
10.1021/om000226a CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/04/2001

New Trivalent Samarium and Yttrium Complexes
Organometallics, Vol. 20, No. 9, 2001 1753
Sch em e 1
sitivity would be an obstacle for industrial use of the
rare earth metal complexes, they are still promising
olefin polymerization catalysts considering the advan-
tage of being active without any aid of cocatalysts.
In addition to the fundamental investigations based
on the use of bis-Cp* compounds mentioned above,
modification of the cyclopentadienyl framework aiming
for the improvement of the catalytic performance has
also been carried out. Creating more open space around
the metal center by connecting the two Cp* rings by a
dimethylsilylene bridge has been shown to result in a
higher ethylene polymerization activity.2o More impor-
tantly, iso-specific polymerization of 1-olefins was
achieved by C2 symmetric ansa-yttrocene [rac-Me2Si-
(2-Me3Si-4-tBuC5H2)2YH]2,2j which implies that the
subtle steric factors imposed by substitution on the
bridged Cp rings substantially influence the polymeri-
zation activity of this type of complex. Introduction of a
chiral unit into the bridging group led to the isolation
of a pure enantiomer of this type of complex,2e which
was then used in an elegant study to establish the
stereoselectivity of initial insertion steps in the iso-
specific 1-olefin polymerization.2d
We have been interested in the relationship between
the steric factors imposed by the substituents on the
bridged Cp rings and the polymerization activity.2a,b
Recently, we reported a detailed investigation on the
relationship by using several divalent silylene-bridged
samarium compounds.2b With the use of a variety of
ligands with two connected Cp rings, we have succeeded
in preparing four types of compounds: C2 symmetric
rac, Me2Si(2-Me3Si-4-tBuC5H2)2Sm(THF)2; C1 symmet-
ric, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]Sm(THF)2;
meso with two bridging groups, [1,2-(Me2Si)(Me2SiO-
SiMe2)](4-Me3CC5H2)2Sm(THF)2; Ph2Si-bridged C2v sym-
metric, Ph2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]Sm-
(THF)2. It was found in the study that in the series of
divalent Sm complexes (i) the meso type exhibited the
highest ethylene polymerization activity, (ii) the C1
symmetric type gave the highest molecular weight
polyethylene (Mn > 1 000 000), and (3) only the rac type
was able to polymerize 1-olefins.
the preparation of three types (rac, C1, and meso) of
trivalent Sm and Y complexes and the reactivity of the
complexes bearing a CH(SiMe3)2 group toward olefin
monomers.
Resu lts a n d Discu ssion
Syn th esis of r a c a n d C1 Typ e Ra r e Ea r th Ha lid es
[r a c-Sm -Cl (1a ), C1-Sm -Cl (2a ), C1(P h 2Si)-Sm -
Cl (3), r a c-Y-Cl (5a ), a n d C1-Y-Cl (6a )]. The ligand
Me2Si[(Me3Si)2C5H3], 8, consisting of Me2Si-bridged Cp
rings with two Me3Si groups on each Cp ring, was used
for the synthesis of both rac and C1 type compounds.
The reaction of SmCl3 with a dilithium salt of 8 afforded
a mixture of rac-Sm-Cl (1a ) and C1-Sm-Cl (2a ).
Although the structures of 1a and 2a differ only in the
position of one of the Me3Si groups in one Cp ring, the
difference of their solubility is large enough for us to
separate the two isomers. Hence, extraction with hexane
led to the isolation of rac isomer 1a , and extraction of
the hexane-insoluble residue with ether gave C1 sym-
metric isomer 2a , as shown in Scheme 1.
The 1H NMR spectrum of 1a contains two Me3Si
resonances at 0.01 and -1.73 ppm, one Me2Si resonance
at 2.27 ppm, and two Cp-H resonances at 16.37 and 5.84
ppm, which clearly indicates C2 symmetric character of
1a . The same type of resonance pattern was observed
for the divalent Sm compound rac-Me2Si(2-Me3Si-4-
1
tBuC5H2)2Sm(THF)2.2b On the other hand, the H NMR
spectrum of 2a contains four resonances (1.18, -0.54,
-0.82, and -2.33 ppm) for Me3Si groups, two reso-
nances (2.97 and 1.14 ppm) for the bridging Me2Si
group, and four resonances (17.10, 10.35, 9.73, and 4.01
ppm) for Cp-Hs, which suggests that 2a assumes a C1
symmetric structure. This resonance pattern was ob-
served for the C1 symmetric divalent Sm complex
Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]Sm(THF)2, in
which the two Me3Si groups were located on the 2,4
positions in one Cp ring and the 3,4 positions in the
other Cp ring.2b
The estimations from the 1H NMR spectra were
unambiguously verified by X-ray crystallographic analy-
ses of 1a and 2a (Figures 1, 2, and Tables 1, 2), although
only the connectivity of the atoms can be reliably
We have extended the investigation into trivalent rare
earth metal complexes employing the same strategy
used for the divalent Sm compounds. We report here

1754 Organometallics, Vol. 20, No. 9, 2001
Ta ble 1. Cr ysta l Da ta for 1a , 2a , 2b, 3, a n d 7a
Ihara et al.
1a
2a
2b
3
7a
formula
fw
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
C
32H62Cl2LiO2Si5Sm
C32H62Cl2LiO2Si5Sm
847.52
monoclinic
P21/c
17.483(3)
13.427(3)
19.475(2)
104.47(1)
104.23(1)
83.17(1)
4431(1)
4
1.270
1756
16.08
10 984
11.1
4320
C31H65Si7Sm
784.85
monoclinic
P21/c
17.385(4)
10.03(1)
24.744(4)
C42H66Cl2LiO2Si5Sm
971.66
triclinic
C26H48ClO2Si5Y
657.45
orthorhombic
Pnma
15.950(5)
17.862(5)
12.495(5)
847.52
triclinic
P1
P1
12.611(4)
17.109(3)
12.134(4)
99.74(3)
115.16(2)
90.91(3)
2324(1)
2
1.211
878
15.33
11 176
13.8
14.557(2)
15.145(2)
13.184(2)
91.94(2)
92.99(1)
4311(3)
4
2793.8(7)
2
3559(1)
4
Z
D
calcd/(g cm-3
)
1.209
1644
15.77
9278
8.2
1.155
1006
12.83
13 333
19.4
1.227
1384
19.03
4565
7.6
F(000)
µ(Mo KR)/cm-1
no. of measd rflns
ratio of reflns/params
no. of obsd rflns
(I > 2.0σ(I))
4807
2901
9252
1291
Ra (Rw)b
0.123 (0.148)
0.075 (0.054)
0.097 (0.072)
0.058 (0.071)
0.096 (0.053)
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) (∑w(|Fo| - |Fc|)2/∑w|Fo| )1/2; w ) 1/σ2(Fo).
F igu r e 1. Structure of rac-Sm-Cl 1a .
described for 1a because of the poor quality of the data.
F igu r e 2. Structure of C1-Sm-Cl 2a .
The structure of 1a is similar to that of the previ-
ously reported yttrium complex rac-Me2Si(2-Me3Si-4-
tBuC5H2)2YCl2Li(THF)2.2j Although it is not clear which
factors determine the positions of Me3Si groups on the
two Cp rings, it is interesting to note that two bulky
substitutents such as Me3Si groups are located on
adjoining carbons on the same Cp ring in 2a , which
seems to be highly sterically demanding. It is also
noteworthy that the substantial difference of solubility
between 1a and 2a arises from the difference of the
position of just one Me3Si group, as mentioned above.
In 2a , the (ring centroid)-metal-(ring centroid) angle
is 116.3°, which is similar to the angles of Me2Si-
bridged divalent Sm complexes [rac-Me2Si(2-Me3Si-4-
tBuC5H2)2Sm(THF)2, 115.8°; (Me2Si)(Me2SiOSiMe2)](4-
Me3CC5H2)2Sm(THF)2, 116.5°]2b and is about 20° smaller
than that of the trivalent nonbridging Sm complex
(C5Me5)2SmI(THF) (136(1)°, 137(1)°).3A Ph2Si-bridged
compound 9 was used for the complexation with SmCl3.
This ligand was designed in order to disfavor the
location of bulky substituents on the 2,4 positions owing
to steric repulsion with the Ph2Si group. In the case of
divalent Sm complexes, 9 afforded C2v symmetric com-
plex Ph2Si[3,4-(Me3Si)2C5H2]2Sm(THF)2, which had all
four Me3Si groups on the 3 and 4 positions as expected.2b,4
In contrast to the divalent Sm complex, the reaction of
a dilithium salt of 9 with SmCl3 led to the C1 symmetric
complex 3 according to Scheme 2. Because of the steric
repulsion with the Ph2Si group, the formation of the rac-
type complex did not occur in this case. In addition, the
formation of a C2v type complex was also not observed.
Thus, the use of the ligand 9 allows us to obtain the C1
symmetric complex exclusively in this case. The 1H
NMR spectrum of 3 shows the typical resonance pattern
of C1 type complexes, and the precise structure was
revealed by X-ray crystallography (Figure 3, Tables 1,
2). As summarized in Table 2, the important bond
(4) Because of the highly fluxional character of the Si-C(Cp) bonds,
movement of Me3Si groups on Cp rings occurred during the transfor-
mation from 9 to 3 so as to form the thermodynamically stable complex.
For the fluxionality of silyl groups on the Cp ring, see: J utzi, P. Chem.
Rev. 1986, 86, 983-996.
(3) Evans, W. J .; Grate, J . W.; Levan, K. R.; Bloom, I.; Peterson, T.
T.; Doedens, R. J .; Zhang, H.; Atwood, J . L. Inorg. Chem. 1986, 25,
3614-3619.

New Trivalent Samarium and Yttrium Complexes
Organometallics, Vol. 20, No. 9, 2001 1755
Sch em e 2
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1a , 2a , 2b, a n d 3a
1a
2a
2b
3
Bond Lengthsb
C(11)-C(12)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(11)
C(21)-C(22)
C(22)-C(23)
C(23)-C(24)
C(24)-C(25)
C(25)-C(21)
C(13)-Si(13)
C(14)-Si(14)
C(15)-Si(15)
C(22)-Si(22)
C(24)-Si(24)
Si(1)-C(11)
Si(1)-C(21)
Si(1)-C(1)
1.40(4)
1.48(4)
1.44(4)
1.39(4)
1.52(4)
1.46(4)
1.47(4)
1.48(4)
1.38(4)
1.42(3)
1.83(3)
1.88(1)
1.81(3)
1.88(3)
1.85(2)
1.87(3)
1.86(3)
1.92(3)
1.92(4)
1.43(2)
1.46(4)
1.45(4)
1.50(4)
1.42(4)
1.42(4)
1.47(4)
1.48(3)
1.36(3)
1.39(3)
1.49(4)
1.88(3)
1.889(8)
1.416(9)
1.41(1)
1.428(9)
1.404(10)
1.413(9)
1.46(1)
1.41(1)
1.416(10)
1.41(1)
1.42(2)
1.41(2)
1.43(2)
1.41(2)
1.43(2)
1.42(2)
1.41(2)
1.41(2)
1.42(2)
1.89(1)
1.88(3)
1.421(9)
1.882(7)
1.88(1)
1.86(1)
1.85(2)
1.84(1)
1.86(2)
1.84(1)
1.87(3)
1.93(2)
1.83(3)
1.80(3)
1.84(2)
1.83(3)
1.877(7)
1.858(7)
1.872(7)
1.869(8)
1.872(8)
1.877(7)
2.678(2)
2.668(2)
2.445
F igu r e 3. Structure of C1(Ph2Si)-Sm-Cl 3.
Si(1)-C(2)
Syn th esis of m eso Typ e Ra r e Ea r th Ha lid es
[m eso-Sm -Cl (4a ) a n d m eso-Y-Cl (7a )]. We have
already found that the Cs symmetric meso type divalent
Sm complex, in which two Cp rings are connected by
two different bridging groups, Me2Si and Me2SiOSiMe2,
can be obtained from the ligand 10.2b The syntheses of
trivalent meso type Sm and Y complexes were attempted
by using this type of ligand. The reaction of SmCl3 with
the dilithium salt of 10 afforded meso type Sm halide
Sm-Cl(1)
2.708(8) 2.698(4)
2.705(7) 2.694(4)
2.45
2.45
2.74
2.74
Sm-Cl(2)
Sm-Cp(1)
2.44
2.44
2.72
2.73
2.57
2.42
2.81
2.71
2.47(2)
2.84(3)b
1.85(3)
1.83(2)
Sm-Cp(2)
2.447
2.724
2.729
C[Cp(1)]-Sm(av)
C[Cp(2)]-Sm(av)
Sm-C(3)
Sm-C(7)b
C(3)-Si(2)
C(3)-Si(3)
1
4a according to Scheme 3. In the H NMR spectrum of
Bond Angles
[Cp(1) centroid]-Sm- 119.7
[Cp(2) centroid]
116.3
117.1
118.9
4a , the presence of three resonances for the bridging
MeSi groups in 2:2:1 integral ratio, together with one
and two resonances for t-Bu and Cp-H respectively,
indicated the Cs symmetric structure of the complex.
The same resonance pattern was observed in the 1H
NMR spectrum of meso type divalent Sm complex [1,2-
(Me2Si)(Me2SiOSiMe2)](4-Me3CC5H2)2Sm(THF)2, which
was further characterized by X-ray diffraction.2b
C(11)-Si(1)-C(21)
C(1)-Si(1)-C(2)
Cl(1)-Sm-Cl(2)
Sm-C(3)-Si(2)
Sm-C(3)-Si(3)
Si(2)-C(3)-Si(3)
C(3)-Si(3)-C(7)
C(3)-Si(3)-C(8)
C(3)-Si(3)-C(9)
a
99(1)
108(1)
84.8(2)
98.1(7)
101.0(3)
106.6(3)
83.88(6)
106.1(7) 107(1)
83.4(1)
137(1)
98(1)
115(1)
106(1)
115(1)
114(1)
In a similar manner, meso type yttrium halide 7a was
obtained from YCl3 and a dilithium salt of Me3Si-
substituted doubly bridged compound 11, as shown in
Cp(1) and Cp(2) are the Cp rings consisting of C(11), C(12),
C(13), C(14), C(15) and C(21), C(22), C(23), C(24), C(25), respec-
b
tively. Sm-C(7) an intramolecular interaction.
1
Scheme 4. The H NMR spectrum of 7a contains two
lengths and angles in 3 are similar to those in C1-Sm-
Cl (2a ), which means that the change of the bridging
group from Me2Si to Ph2Si does not affect the structure
of the complexes, at least in the solid state.
sets of resonances characteristic of meso type structure
in an almost 1:1 ratio, although the structural difference
of the two species in solution is not clear. Compared to
Sm analogue 4a , the integral ratio of coordinated THF
molecules indicated that the molar ratio of THF to the
ligand moiety was 1:1 in the spectrum. The structure
of 7a in the solid state was revealed by a single-crystal
X-ray diffraction study, and the ORTEP drawing is
shown in Figure 4 and selected bond lengths and angles
are listed in Table 3. As expected from the 1H NMR
spectrum, only one THF molecule is coordinated to the
Y center along with the coordination of a Cl anion. It is
clearly shown that 7a has a Cs symmetric meso type
structure in which a mirror plane including Y, Cl, O(3),
Si(1), O(1), C(1), and C(2) bisects the whole molecule.
The same synthetic procedure can be applied for the
synthesis of rac and C1 type yttrium halides (5a and
6a ) as shown in Scheme 1. The yttrium compounds show
the similar difference of solubility, which enables us to
separate them into pure isomers. The structures of 5a
and 6a were confirmed from their 1H NMR spectra,
whose resonance patterns were analogous to those of
1a and 2a , respectively, although the chemical shift of
the resonances were in a reasonable range shifted,
reflecting the diamagnetic character of the yttrium
element.

1756 Organometallics, Vol. 20, No. 9, 2001
Ihara et al.
Sch em e 3
Sch em e 4
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 7a a
Bond Lengths
C(11)-C(12)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(11)
C(14)-Si(141)
C(11)-Si(1)
C(12)-Si(121)
Si(121)-O(1)
Si(1)-C(1)
Si(1)-C(2)
Y-Cl
1.43(2)
1.42(2)
1.44(2)
1.41(2)
1.39(2)
1.87(1)
1.89(1)
1.83(1)
1.634(5)
1.86(2)
1.80(2)
2.541(8)
2.35(2)
2.38
Y-O(3)
Y-Cp(1)
Bond Angles
[Cp(1) centroid]-Y-[Cp(1*) centroid]
C(11)-Si(1)-C(11*)
C(1)-Si(1)-C(2)
120.8
96.1(6)
107.2(10)
89.7(5)
110.4(6)
145.3(8)
Cl-Y-O(3)
C(12)-Si(121)-O(1)
Si(121)-O(1)-Si(121*)
a
Cp(1) and Cp(1*) are the Cp rings consisting of C(11), C(12),
C(13), C(14), C(15) and C(11*), C(12*), C(13*), C(14*), C(15*),
respectively.
F igu r e 4. Structure of meso-Y-Cl 7a .
the anionic group to the highly electrophilic metal
center. In addition, â-alkyl elimination, which has been
frequently observed as a decomposition pathway of
electrophilic early transition metal complexes, can be
hampered because the high-energy SidC bond should
be formed by the elimination.2n Hence, we conducted
transformation of the rare earth halides prepared above
(1a , 2a , 3, 4a , 5a , 6a , 7a ) to the alkyl complexes by the
reaction with LiCH(SiMe3)2.
In the similar manner reported for bis-Cp type
complexes,2n,4,5 the reaction of the halides (1a , 2a , 4a ,
5a , 6a , 7a ) with an ether solution of LiCH(SiMe3)2 in
toluene at 23 °C proceeded smoothly to give alkyl
complexes (1b, 2b, 4b, 5b, 6b, 7b) after recrystallization
from hexane according to Scheme 5. However, for the
Ph2Si-bridged halide 3, the alkyl complex was obtained
only as a crude powder, and we have not succeeded in
isolating the complex in a pure form. In the NMR
spectra of the rac and meso type complexes, two Cp rings
became nonequivalent by the introduction of the alkyl
group, which was the reported phenomenon for other
symmetric bis-Cp type rare earth complexes.2n,4,5 In the
The (ring centroid)-Y-(ring centroid) angle in 7a is
120.8°, which is ca. 11-14° smaller than those of
nonbridging bis-Cp Y complexes, Cp*2YCH(SiMe3)2
(134.4(4)°) and Cp*2YN(SiMe3)2 (132.2(2)°, 132.4(2)°).5
Syn th esis of Ra r e Ea r th Meta l Alk yl Com p lexes
w ith Br id gin g Bis-Cp Liga n d s. It has been reported
that bis-Cp type rare earth halides can be effectively
converted to the neutral alkyl derivatives by the reac-
tion with MCH(SiMe3)2 (M ) Li, K).2n,o,5,6 The steric
bulkiness of the CH(SiMe3)2 moiety prevents the coor-
dination of Lewis basic compounds such as THF or ether
and the formation of ate compounds by the attack of
(5) Haan, K. H.; Boer, J . L.; Teuben, J . H.; Spek, A. L.; Kojic-Prodic,
B.; Hays, G. R.; Huis, R. Organometallics 1986, 5, 1726-1733.
(6) (a) Schumann, H.; Rosenthal, E. C. E.; Kocio-Ko¨hn, Molander,
G. A.; Winterfeld, J . J . Organomet. Chem. 1995, 496, 233-240. (b)
Giardello, M. A.; Conticello, V. P.; Brard, L.; Sabat, M.; Rheingold, A.
L.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1994, 116, 10212-
10240. (c) Schumann, H.; Esser, L.; Loebel, J .; Dietrich, A.; Helm, D.;
J i, X. Organometallics 1991, 10, 2585-2592. (d) Heeres, H. J .;
Renkema, J .; Booij, M.; Meetsma, A.; Teuben, J . H. Organometallics
1988, 7, 2495-2502.

New Trivalent Samarium and Yttrium Complexes
Organometallics, Vol. 20, No. 9, 2001 1757
Sch em e 5
13C NMR spectra of yttrium alkyl complexes 5b and 7b,
a clear 1J coupling was observed between 89Y and the
R-carbon of the alkyl group. The coupling constants for
5b (31.9 Hz) and 7b (32.8 Hz) are similar to the reported
values for Cp*2YCH(SiMe3)2 (36.6 Hz)4 and (C5Me4-
Et)2YCH(SiMe3)2 (35 Hz).5a
Str u ctu r e of Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2-
C5H2]Sm CH(SiMe3)2 (2b). The structure of rac-Sm-R
(2b) was precisely determined by a single-crystal X-ray
diffraction study (Figure 5 and Tables 1, 2). The four
Me3Si groups on the ligand are located at the 3,4 and
2,4 positions on the Cp rings in the same manner as
the starting halide 2a , which indicates that the trans-
formation with LiCH(SiMe3)2 did not affect the ligand
framework with respect to the positions of the substit-
uents on the Cp rings. The Sm-C(3) bond distance,
2.47(2) Å, is unexceptional compared to the distances
of analogous complexes (R)-Me2Si(C5Me4)[(-)-menthyl-
Cp]SmCH(SiMe3)2] (12) (2.504(7), 2.487(7) Å)5b and
(C5Me4Et)2SmCH(SiMe3)2 (13) (2.502(3) Å).5a
As has always been observed in other rare earth alkyl
complexes with the CH(SiMe3)2 group, one of the two
Me3Si groups approaches the Sm center at an acute Ln-
CR-Siâ angle in the solid state.4,5 The Sm-C(3)-Si(3)
angle is 98(1)°, which is 39° smaller than the other
angle, Sm-C(3)-Si(2) 137(1)°. This phenomenon has
been ascribed to the interaction between the metal
center and the electron density of the Siâ-Cγ bond in
order to compensate the high electron deficiency of the
metal center.5b In accord with the presence of the
interaction, the location of one of the Me groups on Si(3)
is close to the Sm center [Sm-C(7), 2.84(3) Å], forming
a pseudo-metalacyclobutane conformation [cf. Sm-C(6),
4.62(3) Å]. The distance is also comparable to the
F igu r e 5. Structure of C1-Sm-R 2b.
corresponding bond lengths in 12 (2.865(7), 2.998(6) Å)5b
and 13 (2.953 Å).5a In addition, the CR-Siâ-Cγ angle
with the γ-carbon interacting with Sm [C(3)-Si(3)-C(7),
106(1)°] is significantly smaller than the other two
angles [C(3)-Si(3)-C(8), 115(1)°; C(3)-Si(3)-C(9),
114(1)°]. It is also interesting to note that the Sm-Cγ
interaction exists in the more sterically crowded side
on the equatorial girdle with two Me3Si groups on the
4 position on both Cp rings. As a result, the more
sterically demanding side of the CH(SiMe3)2 group is
oriented toward the less sterically crowded side in the
equatorial girdle, as is clearly seen from the top view
of 2b (Figure 5, bottom). The same kind of orientation
of the CH(SiMe3)2 group has been observed in 12 and
related complexes.5b
Another structural point of interest in 2b is the
difference of the average C(Cp)-Sm distances for the
two Cp rings. There is a significant difference between
the distance on Cp with Me3Si on the 3,4 positions (2.81
Å) and that with Me3Si on the 2,4 positions (2.71 Å).
The longer C(Cp)-Sm distance on the former Cp ring
suggests that high steric crowding exists around the Cp

1758 Organometallics, Vol. 20, No. 9, 2001
Ihara et al.
Sch em e 6
Ta ble 4. Eth ylen e P olym er iza tion by Tr iva len t
Ra r e Ea r th Alk yl Com p lexesa
ring owing to the presence of the two adjoining Me3Si
groups on the Cp ring. Because of the steric crowding,
two of the Sm-C(Cp) distances [Sm-C(13), 2.88(3) Å,
Sm-C(14), 2.92(3) Å] are even longer than the Sm-
C(7) distance of the agostic interaction (2.84(3) Å). The
steric effect will be related with the reactivity of the
complexes with olefins in the next section.
react
period,
min
activity, 10-4
g
of PE/(mol h)
initiator
10-4Mn Mw/Mn
rac-Sm-R 1b
C1-Sm-R 2b
no polymerization
2.92
3.08
2.43
3
5
10
7.46
9.96
15.2
2.07
1.84
2.01
Olefin P olym er ization by Rar e Ear th Alkyl Com -
p lexes. It is generally considered that the CH(SiMe3)2
group on rare earth metal complexes is more useful as
a precursor to generate hydride derivatives than as an
initiating group for olefin polymerization.2n,o Although
the steric bulkiness is essential to prevent the undesir-
able coordination of Lewis basic compounds, it may also
prevent the approach and coordination of olefin mol-
ecules to the metal center, which should precede the
initiation and propagation of the polymerization. Ac-
cordingly, in contrast to the very high ethylene poly-
merization activity of (Cp*2LnH)2 (Ln ) La, Nd),
Cp*2LnCH(SiMe3)2 was reported to be completely inac-
tive for the polymerization.2n However, owing to the
intrinsic high reactivity, rare earth hydride derivatives
are more difficult to handle than alkyl derivatives. For
example, we have observed that (Cp*2SmH)2 decom-
poses slowly at 23 °C in toluene under a complete argon
atmosphere. On the other hand, stabilized by the Ln-
Cγ interaction, rare earth alkyl compounds bearing
CH(SiMe3)2 groups in this study did not show any
decomposition for several months in benzene-d6 solution
at 23 °C. Thus, to explore the possibility of using the
stable alkyl complexes as initiators for olefin polymer-
ization, we examined the reactivity of alkyl derivatives
1b, 2b, 4b, 5b, 6b, and 7b toward olefin monomers.
As summarized in Table 4, it was found that C1
symmetric alkyl derivatives 2b and 6b polymerized
ethylene at 23 °C in toluene with ethylene pressure of
1 atm. In contrast, no evidence of ethylene polymeriza-
tion was observed for C2 and Cs symmetric complexes
(1b, 4b, 5b, and 7b) in the same condition. The activity
for yttrium complex 6b is higher than samarium
complex 2b, reaching 186 000 gPE/mol‚h‚atm. The
molecular weight of the polyethylene obtained by 6b,
which is more than 300 000, is also higher than that
meso-Sm-R 4b
rac-Y-R 5b
C1-Y-R 6b
no polymerization
no polymerization
18.6
1
3
33.1
31.9
1.65
2.31
7.4
meso-Y-R 7b
no polymerization
a
Reaction conditions: temperature, 23 °C; initiator concentra-
tion, 1.0 mM; solvent, toluene; ethylene pressure, 1 atm.
obtained by 2b. The molecular weight distributions of
the polyethylenes are relatively narrow (Mw/Mn ) 1.6-
2.3).
It is interesting to note that the ethylene polymeri-
zation activity was observed only on C1 symmetric
complexes (2b, 6b), which had the most sterically
crowded environment around the metal center because
of the presence of three Me3Si groups on the 3,4
positions on the Cp rings. Recently, it was reported that
the unusually high reactivity of Cp*3Sm can be ascribed
to the high steric crowding around the metal center by
comparison of the reactivities and crystal structures of
Cp*3Sm and Me2Si(C5Me4)2SmCp*.6 The less crowded
nature of the latter complex was confirmed by the
normal Sm-C(Cp*) bond distances, whereas the bond
distances on Cp*3Sm have been found to be extremely
long.7 It was concluded that because of the steric
crowding, one of the Cp* could not form a stable bond
with the metal center and ethylene could insert into the
unstable Sm-C(Cp*) bond. We believe that the same
theory can be applied in the case of our C1 type rare
earth alkyl complexes 2b and 6b. The aforementioned
difference of Sm-C(Cp) distances in 2b indicates that
high steric crowding exists around the metal center in
these C1 symmetric complexes. Although the Sm-
(7) Evans, W. J .; Cano, D. A.; Greci, M. A.; Ziller, J . W. Organo-
metallics 1999, 18, 1381-1388.

New Trivalent Samarium and Yttrium Complexes
Organometallics, Vol. 20, No. 9, 2001 1759
Ta ble 5. 1-Olefin P olym er iza tion by C1-Y-R (6b)a
of poly(1-pentene) and poly(1-hexene) were determined by gel
permeation chromatography (GPC) on a Tosoh SC-8010 using
TSKgel G2000, G3000, G4000, and G5000 columns in chloro-
form at 40 °C. Mw and Mw/Mn values of polyethylene were
react
temp, °C
react
period, h
monomer
10-4Mn
Mw/Mn
1-pentene
1-hexane
23
23
23
0
3
3
6
3
1.60
2.54
3.11
6.45
1.42
1.63
1.82
1.20
determined by GPC on
a Waters 150C using a Shodex
AT806MS column in 1,2,4-trichlorobenzene at 140 °C. Mw and
Mw/Mn were calibrated from standard polystyrene.
Str u ctu r e Solu tion a n d Refin em en t for Com p lexes 1a ,
2a , 2b, 3, a n d 7a . All diffraction measurements was performed
on a Rigaku AFC-5R diffractometer with graphite-monochro-
mated Mo KR radiation. Since the complexes were highly air-
sensitive, crystals were sealed in a thin-walled glass capillary
tube under an argon atmosphere. The X-ray data were
collected at room temperature using the ω-2θ scan technique
to a maximum 2θ value of 55.0° for 1a , 2a , 3, and 7a , and
52.0° for 2b. The intensity data were corrected for conventional
Lorentz and polarization effects and absorption based on a
series of azimuthal scans.
The non-hydrogen atoms were refined anisotropically by
full-matrix least-squares methods except for the carbon atoms
of THF ligands in 1a , which were refined isotropically. The
hydrogen atoms were fixed at their standard geometries and
were not refined. The carbon atoms of THF ligands in all the
complexes seem to be disordered. However, since the attempts
to locate these carbon atoms into two separate positions were
unsuccessful, the THF ligands are described as having planar
conformation consisting of the carbon atoms with large ther-
mal vibrational parameters. All calculations were performed
by the use of the teXsan crystallographic software package
(teXsan: Crystal Structure Analysis Package, Molecular Struc-
ture Corp. [1985 and 1999]).
P r ep a r a tion of r a c-Me2Si[2,4-(Me3Si)2C5H2]2Sm Cl2Li-
(THF)2 (1a )a n d Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]-
Sm Cl2Li(THF )2 (2a ). A solution of the ligand 8 (2.00 g, 4.19
mmol) in THF (25 mL) was cooled to 0 °C. nBuLi (1.60 M
solution in hexane, 5.3 mL, 8.5 mmol) was added to the
solution dropwise, and the mixture was stirred and warmed
to 23 °C gradually over 6 h. The resulting solution of the
lithium dianion of 8 was added to a suspension of SmCl3 (1.15
g, 4.48 mmol) in THF (20 mL), and the mixture was refluxed
for 11 h. After the solvent was removed by evaporation, the
residual solid was dried under vacuum. Hexane (80 mL) was
added to the solid, and the resulting suspension was stirred
for 15 h at 23 °C. The suspension was separated into a yellow
supernatant and a hexane-insoluble solid by centrifugation.
After a part of the hexane was removed from the supernatant
under reduced pressure, by cooling the resulting concentrated
solution at -20 °C, 1a was obtained as yellow crystals (0.88
g, 1.0 mmol, 25%). Ether (20 mL) was added to the hexane-
insoluble solid mentioned above, and the suspension was
stirred at 23 °C for 2 days. A yellow ether solution was
obtained by centrifugation, and recrystallization of the solution
at -20 °C afforded 2a as yellow crystals (0.78 g, 0.92 mmol,
22%).
r a c-Me2Si[2,4-(Me3Si)2C5H 2]2Sm Cl2Li(TH F )2 (1a ). 1H
NMR (400.14 MHz, C6D6): δ 16.37 (s, 2H, Cp-H), 5.84 (s, 2H,
Cp-H), 4.76 (s, 8H, THF-R), 2.27 (s, 6H, Me2Si), 2.01 (s, 8H,
THF-â), 0.01 (s, 18H, Me3Si), -1.73 (s, 18H, Me3Si). Anal.
Calcd for C32H62Cl2LiO2Si5Sm: Sm, 17.74. Found: Sm, 17.94.
Me 2Si[2,4-(Me 3Si)2C5H 2][3,4-(Me 3Si)2C5H 2]Sm Cl2Li-
(THF )2 (2a ). 1H NMR (400.14 MHz, C6D6): δ 17.10 (s, 1H,
Cp-H), 10.35 (s, 1H, Cp-H), 9.73 (s, 1H, Cp-H), 4.43 (s, 8H,
THF-R), 4.01 (s, 1H, Cp-H), 2.97 (s, 3H, Me2Si), 1.85 (s, 8H,
THF-â), 1.18 (s, 9H, Me3Si), 1.14 (s, 3H, Me2Si), -0.54 (s, 9H,
Me3Si), -0.82 (s, 9H, Me3Si), -2.33 (s, 9H, Me3Si). Anal. Calcd
for C32H62Cl2LiO2Si5Sm: Sm, 17.74. Found: Sm, 17.90.
r a c-Me2Si[2,4-(Me3Si)2C5H2]2Sm CH(SiMe3)2 (1b). A solu-
tion of 1a (0.80 g, 0.94 mmol) in toluene (50 mL) was placed
in a Schlenk tube and cooled to 0 °C. (Me3Si)2CHLi (0.54 M
solution in ether, 2.6 mL, 1.4 mmol) was added to the solution
dropwise, and the mixture was stirred and warmed to 23 °C
a
Reaction conditions: neat; initiator concentration, 0.2 mol %.
C[CH(SiMe3)]2 distance is normal, the Sm-C bond
should be perturbed in solution by free rotations of
C(Cp)-Si bonds on the 3,4 positions on the Cp rings.
The free rotation in solution is confirmed by the sharp
1
singlet resonances for the Me3Si groups in the H NMR
of 2b and 6b. In such a manner, the Sm-C[CH(SiMe3)]2
bond could be lengthened or possesses ionic character,
which would result in a high activity for ethylene
insertion.In addition to ethylene, 1-olefins such as
1-pentene and 1-hexane were polymerized by a C1
symmetric alkyl complex of yttrium, 6b (Table 5).
Although the reactivity was very low and polymers were
obtained in a trace yield, GPC analysis indicated the
poly(1-hexane) obtained by the reaction at 0 °C had a
high molecular weight (Mn ) 64 500) and a narrow
molecular weight distribution (Mw/Mn ) 1.20).
In conclusion, we have demonstrated that a series of
bridging bis(cyclopentadienyl) ligands employed in this
study are very useful to prepare a variety of rare earth
metal metallocene complexes with different steric en-
vironments around the metal center. The steric factors
strongly influence the reactivity of the Ln-C bond of
the alkyl derivatives, resulting in the high ethylene
insertion activity in the C1 type complex.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All operations were performed
under argon by using standard Schlenk techniques. Tetrahy-
drofuran (THF), hexane, and diethyl ether (ether) were dried
over Na/K alloy and distilled before use. Toluene was dried
over Na and distilled before use. Toluene used for polymeri-
zation was dried over Na/K alloy and thoroughly degassed by
trap-to-trap distillation. Ethylene (Nakamura Oxygen Co.) was
used without further purification. 1-Pentene and 1-hexene
were dried over Na/K alloy and distilled before use. ClMe2-
OSiOMe2Cl (ShinEtsu Silicon Chemicals) was dried over NaH
and used without further purification. The preparation of all
the ligands used in this study except for 10 was already
reported.2b SmCl3 and YCl3 were prepared by the reactions of
Ln2O3 (Shiga Rare Metals & Chemicals Co.) and excess NH4Cl
in concentrated HCl at 100 °C followed by removal of excess
1
NH4Cl by sublimation at 360 °C/0.1 mmHg. H NMR spectra
were recorded on a Bruker AMX 400wb spectrometer (400.14
MHz) or J EOL J NM-LA 400 (395.75 MHz) spectrometer in
sealed tubes at ambient probe temperature. 13C NMR spectra
were recorded on a J EOL J NM-LA 400 (99.45 MHz) spectrom-
eter in sealed tubes at ambient probe temperature. 1H and
13C chemical shifts are reported versus SiMe4 and were
determined by reference to the residual 1H and 13C solvent
peaks. Complexometric metal analyses were conducted by the
method reported by Atwood and Evans.8 (The analyses did not
give satisfactory results in two cases, probably because of the
high air sensitivity of the complexes.) Mw and Mw/Mn values
(8) Evans, W. J .; Gonzales, S. L.; Ziller, J . W. J . Am. Chem. Soc.
1991, 113, 7423.
(9) Atwood, J . L.; Hunter, W. E.; Wayda, A. L.; Evans, W. J . Inorg.
Chem. 1981, 20, 4115-4119.

1760 Organometallics, Vol. 20, No. 9, 2001
Ihara et al.
gradually over 12 h. After the solvent was removed by
evaporation, the residual solid was dried under vacuum.
Hexane (40 mL) was added to the solid, and the resulting
suspension was stirred at 23 °C for 12 h. The hexane-insoluble
solid was removed by centrifugation. After a part of the hexane
was removed from the supernatant under reduced pressure,
by cooling the resulting concentrated solution at -20 °C, 1b
was obtained as red crystals (0.20 g, 0.25 mmol, 27%). 1H NMR
(400.14 MHz, C6D6): δ 17.65 (s, 1H, Cp-H or SmCH(SiMe3)2),
16.66 (s, 1H, Cp-H or SmCH(SiMe3)2), 16.49 (s, 1H, Cp-H or
SmCH(SiMe3)2), 10.34 (s, 1H, Cp-H or SmCH(SiMe3)2), 3.76
(s, 3H, Me2Si), 1.74 (s, 3H, Me2Si), 0.25 (s, 9H × 2, Me3Si),
0.10 (s, 9H, Me3Si), -0.29 (s, 9H, Me3Si), -1.77 (s, 9H, Me3Si),
-3.10 (s, 9H, Me3Si). One of the Cp-H or SmCH(SiMe3)2 signals
Recrystallization from hexane yielded 0.87 g (1.18 mmol,
54.0%) of 4b as a red microcrystalline solid. H NMR (395.75
1
MHz, C6D6): δ 20.38 (s, 1H, Cp-H or SmCH(SiMe3)2), 13.09
(s, 1H, Cp-H or SmCH(SiMe3)2), 12.66 (s, 1H, Cp-H or
SmCH(SiMe3)2), 4.06 (s, 1H, Cp-H or SmCH(SiMe3)2), 3.89 (s,
3H, Me2Si), 3.24 (s, 1H, Cp-H or SmCH(SiMe3)2), 2.83 (s, 9H,
Me3C), 2.59 (s, 9H, Me3C), 1.30 (s, 3H, Me2Si), 1.26 (s, 3H,
Me2Si), -0.57 (s, 3H, Me2Si), -2.25 (s, 9H, Me3Si), -4.36 (s,
3H, Me2Si), -4.80 (s, 3H, Me2Si), -6.30 (s, 9H, Me3Si). 13C
NMR (99.45 MHz, C6D6): δ 151.8 (Cp), 149.9 (Cp), 129.0 (Cp),
128.5 (Cp), 127.9 (Cp), 127.6 (Cp), 117.0 (Cp), 116.8 (Cp), 116.1
(Cp), 114.3 (Cp), 41.4, 31.4, 29.9, 8.4, 3.3, 3.1, 1.4, -0.7, -2.6,
-3.4, -3.7, -6.6. Anal. Calcd for C31H59OSi5Sm: Sm, 20.35.
Found: Sm, 19.92.
was obscured by the other resonances. Anal. Calcd for C31H65
Si7Sm: Sm, 19.16. Found: Sm, 18.90.
-
r a c-Me2Si[2,4-(Me3Si)2C5H2]2YCl2Li(THF )2 (5a ). A solu-
tion of the ligand 8 (3.0 g, 6.3 mmol) in THF (25 mL) was cooled
to 0 °C. nBuLi (1.60 M solution in hexane, 8.2 mL, 13.1 mmol)
was added to the solution dropwise, and the mixture was
stirred and warmed to 23 °C gradually over 6 h. The resulting
solution of the lithium dianion of 8 was added to a suspension
of YCl3 (1.82 g, 9.32 mmol) in THF (30 mL), and the mixture
was refluxed for 6 h. After the solvent was removed by
evaporation, the residual solid was dried under vacuum.
Hexane (80 mL) was added to the solid, and the resulting
suspension was stirred for 15 h at 23 °C. The insoluble solid
was removed by centrifugation. The solvent was removed by
evaporation, and the residual solid was dried under vacuum.
Recrystallization of the solid from toluene afforded 5a as
Me 2Si[2,4-(Me 3Si)2C5H 2][3,4-(Me 3Si)2C5H 2]Sm CH (Si-
Me3)2 (2b). 2a was prepared by using the procedure reported
above for 1b with 2a (1.44 g, 1.70 mmol), (Me3Si)2CHLi (0.83
M solution in ether, 2.5 mL, 2.1 mmol), and toluene (50 mL).
2a was obtained as red crystals (0.926 g, 1.18 mmol, 69.4%).
1H NMR (400.14 MHz, C6D6): δ 17.83 (s, 1H, Cp-H or
SmCH(SiMe3)2), 17.35 (s, 1H, Cp-H or SmCH(SiMe3)2), 13.15
(s, 1H, Cp-H or SmCH(SiMe3)2), 12.27 (s, 1H, Cp-H or
SmCH(SiMe3)2), 3.80 (s, 3H, Me2Si), 0.83 (s, 3H, Me2Si), 0.75
(s, 9H, Me3Si), -0.22 (s, 9H, Me3Si), -0.53 (s, 9H, Me3Si),
-0.55 (s, 9H, Me3Si), -3.05 (s, 9H, Me3Si), -7.29 (s, 9H,
Me3Si). One of the Cp-H or SmCH(SiMe3)2 signals was
obscured by the other resonances. Anal. Calcd for C31H65Si7-
Sm: Sm, 19.16. Found: Sm, 18.95.
1
colorless crystals (0.72 g, 0.92 mmol, 15%). H NMR (400.14
MHz, C6D6): δ 7.27 (s, 2H, Cp-H), 6.98 (s, 2H, Cp-H), 3.55 (s,
8H, THF-R), 1.39 (s, 8H, THF-â), 1.13 (s, 6H, Me2Si), 0.64 (s,
9H, Me3Si), 0.50 (s, 9H, Me3Si). Anal. Calcd for C32H62Cl2LiO2-
Si5Y: Y, 11.31. Found: Y, 11.05.
P h 2Si[2,4-(Me 3Si)2C5H 2][3,4-(Me 3Si)2C5H 2]Sm Cl2Li-
(THF )2 (3). A solution of the ligand 9 (12.10 g, 20.13 mmol)
in THF (60 mL) was cooled to 0 °C. nBuLi (1.63 M solution in
hexane, 24.6 mL, 40.1 mmol) was added to the solution
dropwise, and the mixture was stirred and warmed to 23 °C
gradually over 6 h. The resulting solution of the lithium
dianion of 9 was added to a suspension of SmCl3 (5.15 g, 20.1
mmol) in THF (60 mL), and the mixture was refluxed for 12
h. After the solvent was removed by evaporation, the residual
solid was dried under vacuum. Hexane (80 mL) was added to
the solid, and the resulting suspension was stirred for 15 h at
23 °C. A hexane-insoluble solid was removed by centrifugation.
After a part of the hexane was removed from the supernatant
under reduced pressure, and cooling the resulting concentrated
solution at -20 °C, 3 was obtained as yellow crystals (4.95 g,
r a c-Me2Si[2,4-(Me3Si)2C5H2]2YCl2Li(OEt2)3. This com-
pound was obtained as colorless crystals by recrystallization
1
of 5a from ether. H NMR (395.75 MHz, C6D6): δ 7.29 (s, 2H,
3
Cp-H), 6.93 (s, 2H, Cp-H), 3.55 (q, J HH ) 7.0 Hz, 12H, Et2O-
3
R), 1.09 (s, 6H, Me2Si), 1.03 (t, J HH ) 7.0 Hz, 18H, Et2O-â),
0.59 (s, 9H, Me3Si), 0.47 (s, 9H, Me3Si). 13C NMR (99.45 MHz,
C6D6): δ 138.0 (Cp), 130.4 (Cp), 129.4 (Cp), 128.4 (Cp), 125.9
(Cp), 66.0 (Et2O-R), 25.3 (Me2Si), 14.9 (Et2O-â), 2.4 (Me3Si),
0.4 (Me3Si). Anal. Calcd for C36H76Cl2LiO3Si5Y: Y, 10.29.
Found: Y, 11.05.
r a c-Me2Si[2,4-(Me3Si)2C5H2]2YCH(SiMe3)2 (5b). The afore-
mentioned procedure for 1b was carried out with 5a (0.63 g,
0.80 mmol) and (Me3Si)2CHLi (0.54 M solution in ether, 1.9
mL, 1.03 mmol) in 40 mL of toluene. Recrystallization from
hexane yielded 0.16 g (0.22 mmol, 28%) of 5b as colorless
1
5.09 mmol, 25.3%). H NMR (395.75 MHz, C6D6): δ 16.52 (s,
1H, Cp-H), 10.47 (s, 1H × 2, Cp-H), 10.43 (d, 2H, Ph-H [ortho]),
8.97 (d, 2H, Ph-H [ortho]), 7.88 (t, 2H, Ph-H [meta]), 7.55 (t,
1H, Ph-H [para]), 7.10 (t, 2H, Ph-H [meta]), 6.93 (t, 1H, Ph-H
[para]), 4.74 (s, 8H, THF-R), 4.62 (s, 1H, Cp-H), 2.03 (s, 8H,
THF-â), 1.33 (s, 9H, Me3Si), -0.65 (s, 9H, Me3Si), -0.79 (s,
9H, Me3Si), -2.44 (s, 9H, Me3Si). Anal. Calcd for C42H66Cl2-
LiO2Si5Sm: Sm, 15.48. Found: Sm, 15.37.
[1,2-(Me 2Si)(Me 2SiOSiMe 2)](4-Me 3CC5H 2)2Sm Cl2Li2-
(THF )2 (4a ). The aforementioned procedure for 3 was carried
out with 10 (2.75 g, 6.38 mmol), nBuLi (1.54 M solution in
hexane, 9.0 mL, 13.9 mmol), and SmCl3 (1.55 g, 6.04 mmol)
in 70 mL of THF. Recrystallization from hexane yielded 1.76
g (2.20 mmol, 34.4%) of 4a as yellow crystals. 1H NMR (395.75
MHz, C6D6): δ 12.92 (s, 2H, Cp-H), 5.92 (s, 2H, Cp-H), 4.51
(s, 8H, THF-R), 3.14 (s, 3H, Me2Si), 2.86 (s, 3H, Me2Si), 2.37
(s, 18H, Me3C), 1.91 (s, 8H, THF-â), 0.73 (s, 6H, Me2SiOSiMe2),
-3.75 (s, 6H, Me2SiOSiMe2). 13C NMR (99.45 MHz, C6D6): δ
146.4 (Cp), 128.6 (Cp), 125.6 (Cp), 116.9 (Cp), 115.7 (Cp), 69.3
(THF-R), 39.6 (Me3C), 29.9 (Me3C), 26.0 (THF-â), 23.0 (MeSi),
1
crystals. H NMR (395.75 MHz, C6D6): δ 7.70 (s, 1H, Cp-H),
6.99 (s, 1H, Cp-H), 6.81 (s, 1H, Cp-H), 6.65 (s, 1H, Cp-H), 0.98
(s, 3H, Me2Si), 0.96 (s, 3H, Me2Si), 0.46 (s, 9H, Me3Si), 0.39 (s,
9H, Me3Si), 0.37 (s, 9H, Me3Si), 0.33 (s, 9H, Me3Si), 0.27 (s,
9H, Me3Si), 0.20 (s, 9H, Me3Si). The YCH(SiMe3)2 signal was
obscured by the other resonances. 13C NMR (99.45 MHz,
C6D6): δ 137.1 (Cp), 136.8 (Cp), 133.4 (Cp), 131.8 (Cp), 131.5
(Cp), 131.0 (Cp), 129.9 (Cp), 129.6 (Cp), 129.5 (Cp), 129.0 (Cp),
1
26.6 (d, J Y-C ) 31.9 Hz, Y-CH(SiMe3)2), 5.9 (Me3Si), 2.7
(Me3Si), 2.6 (Me3Si), 2.1 (Me3Si), 0.8 (Me3Si), 0.7 (Me3Si), 0.5
(Me2Si), 0.1 (Me2Si). Anal. Calcd for C31H65Si7Y: Y, 12.29.
Found: Y, 11.54.
Me 2 S i[2,4-(Me 3 S i)2 C 5 H 2 ][3,4-(Me 3 S i)2 C 5 H 2 ]YC l2 L i-
(THF )2 (6a ). A solution of the ligand 8 (7.0 g, 14.7 mmol) in
THF (40 mL) was cooled to 0 °C. nBuLi (1.60 M solution in
hexane, 19.5 mL, 31.2 mmol) was added to the solution
dropwise, and the mixture was stirred and warmed to 23 °C
gradually over 6 h. The resulting solution of the lithium
dianion of 8 was added to a suspension of YCl3 (2.33 g, 11.9
mmol) in THF (40 mL), and the mixture was refluxed for 6 h.
After the solvent was removed by evaporation, the residual
solid was dried under vacuum. Ether (40 mL) was added to
the solid, and the resulting suspension was stirred for 15 h at
14.3 (MeSi), 3.0 (MeSi), -3.4 (MeSi). Anal. Calcd for C32H56
Cl2LiO3Si3Sm: Sm, 18.77. Found: Sm, 18.32.
-
[1,2-(Me 2Si)(Me 2SiOSiMe 2)](4-Me 3CC5H 2)Sm CH (Si-
Me3)2 (4b). The aforementioned procedure for 1b was carried
out with 4a (1.75 g, 2.18 mmol) and (Me3Si)2CHLi (0.61 M
solution in ether, 4.5 mL, 2.75 mmol) in 60 mL of toluene.

New Trivalent Samarium and Yttrium Complexes
Organometallics, Vol. 20, No. 9, 2001 1761
23 °C. The insoluble solid was removed by centrifugation. After
a part of the solvent was removed by evaporation, the resulting
concentrated solution was cooled to -20 °C. 6a was obtained
as colorless crystals (1.72 g, 2.19 mmol, 18.4%). 1H NMR
(400.14 MHz, C6D6): δ 6.97 (s, 1H, Cp-H), 6.93 (s, 1H, Cp-H),
6.83 (s, 1H, Cp-H), 6.77 (s, 1H, Cp-H), 3.55 (s, 8H, THF-R),
1.39 (s, 8H, THF-â), 1.00 (s, 3H, Me2Si), 0.99 (s, 3H, Me2Si),
0.61 (s, 9H, Me3Si), 0.58 (s, 9H, Me3Si), 0.56 (s, 9H, Me3Si),
0.46 (s, 9H, Me3Si). Anal. Calcd for C32H62Cl2LiO2Si5Y: Y,
11.31. Found: Y, 11.22.
Me2Si), 0.55 (s, 6H, Me2SiOSiMe2), 0.51 (s, 18H, Me3Si), 0.49
(s, 18H, Me3Si), 0.34 (s, 3H, Me2Si), 0.30 (s, 6H, Me2SiOSiMe2).
Anal. Calcd for C26H48ClO2Si5Y: Y, 13.52. Found: Y, 13.36.
[1,2-(Me 2S i)(Me 2S iO S iMe 2)](4-Me 3S iC 5H 2)YC H (S i-
Me3)2 (7b). The aforementioned procedure for 1b was carried
out with 7a (3.60 g, 5.48 mmol) and (Me3Si)2CHLi (0.75 M
solution in ether, 9.0 mL, 6.8 mmol) in 60 mL of toluene.
Recrystallization from hexane yielded 1.74 g (2.46 mmol,
44.9%) of 7b as colorless crystals. 1H NMR (395.75 MHz,
C6D6): δ 7.53 (s, 1H, Cp-H), 7.33 (s, 1H, Cp-H), 6.33 (s, 1H,
Cp-H), 6.31 (s, 1H, Cp-H), 1.09 (s, 3H, MeSi), 0.67 (s, 3H,
Me 2S i[2,4-(Me 3S i)2C 5H 2][3,4-(Me 3S i)2C 5H 2]YC H (S i-
Me3)2 (6b). The aforementioned procedure for 1b was carried
out with 6a (1.67 g, 2.12 mmol) and (Me3Si)2CHLi (0.86 M
solution in ether, 3.0 mL, 2.58 mmol) in 80 mL of toluene.
Recrystallization from hexane yielded 0.80 g (1.11 mmol,
52.3%) of 6b as colorless crystals. 1H NMR (400.14 MHz,
C6D6): δ 7.66 (s, 1H, Cp-H), 6.61 (s, 1H, Cp-H), 6.56 (s, 1H,
Cp-H), 6.50 (s, 1H, Cp-H), 0.86 (s, 3H, Me2Si), 0.81 (s, 3H,
Me2Si), 0.47 (s, 9H × 2, Me3Si), 0.41 (s, 9H, Me3Si), 0.34 (s,
9H, Me3Si), 0.23 (s, 9H × 2, Me3Si). The YCH(SiMe3)2 signal
2
MeSi), 0.66 (d, 1H, J Y-H ) 2.53 Hz, Y-CH(SiMe3)2), 0.59 (s,
3H, MeSi), 0.56 (s, 3H, MeSi), 0.42 (s, 3H, MeSi), 0.40 (s, 3H,
MeSi), 0.38 (s, 9H, Me3Si), 0.30 (s, 9H × 2, Me3Si), 0.23 (s,
9H, Me3Si). 13C NMR (99.45 MHz, C6D6): δ 138.2 (Cp), 136.7
(Cp), 132.9 (Cp), 132.0 (Cp), 130.9 (Cp), 129.8 (Cp), 129.5 (Cp),
1
129.0 (Cp), 128.8 (Cp), 128.6 (Cp), 29.1 (d, J Y-C ) 32.8 Hz,
Y-CH(SiMe3)2), 5.8 (MeSi), 4.1 (MeSi), 4.0 (MeSi), 2.0 (MeSi),
1.6 (MeSi), 1.3 (MeSi), 0.8 (MeSi), 0.5 (MeSi), 0.4 (MeSi), -3.9
(MeSi). Anal. Calcd for C29H59OSi7Y: Y, 12.53. Found: Y,
12.48.
was obscured by the other resonances. Anal. Calcd for C31H65
Si7Y: Y, 12.29. Found: Y, 12.04.
-
Typ ica l P r oced u r e for Eth ylen e P olym er iza tion . A
solution of an initiator (0.02 mmol) in 20 mL of toluene was
exposed to 1 atm of ethylene. The reaction mixture was stirred
for fixed times defined in Table 4 at 23 °C. The polymerization
was stopped by the addition of methanol. The resulting
polyethylene was washed with methanol twice and dried in
vacuo.
Typ ica l P r oced u r e for 1-Olefin P olym er iza tion . To a
toluene solution (3 mL) of an initiator (0.02 mmol) was added
2 mL of a monomer at 23 °C. The reaction mixture was stirred
for each period defined in Table 5 at 23 °C. The polymerization
was stopped by the addition of methanol. The resulting
polyethylene was washed with methanol twice and dried in
vacuo.
(Me2Si)(Me2SiOSiMe2)(Me3SiC5H3)2 (11). A solution of
(Me3SiC5H4)2SiMe2 (22.7 g, 68.5 mmol) in THF (300 mL) was
placed in a round-bottomed flask equipped with a condenser
and was cooled to 0 °C. nBuLi (1.52 M, 95.0 mL, 144 mmol)
was added dropwise to the solution, and the mixture was
stirred and warmed to 23 °C over 3 h. ClMe2SiOSiMe2Cl (15.0
mL, 76.7 mmol) was added, and the mixture was refluxed for
24 h. The complete disappearance of (Me3C5H4)2SiMe2 was
confirmed by GC analysis. The mixture was poured into 300
mL of NaHCO3 saturated aqueous solution. After extractive
workup with hexane and water, bulb-to-bulb distillation of the
resulting liquid (200 °C/0.1 mmHg) afforded 11 in 89.9% yield
1
(28.5 g, 61.6 mmol) as a yellow oil. The H NMR spectrum of
11 suggested that the compound was a mixture of isomers with
respect to the positions of double bonds and substituents on
the Cp rings.
Ack n ow led gm en t. This work was supported by a
Grant-in-aid for Scientific Research on Priority Areas
(No. 283, “Innovative Synthetic Reactions”) from the
Ministry of Education, Science, and Culture J apan.
[1,2-(Me2Si)(Me2SiOSiMe2)](4-Me3SiC5H2)YCl(THF) (7a).
The aforementioned procedure for 1b was carried out with 11
(4.3 g, 9.3 mmol), nBuLi (1.62 M solution in hexane, 12.0 mL,
19.4 mmol), and YCl3 (2.40 g, 12.3 mmol) in 50 mL of THF.
Recrystallization from hexane yielded 1.38 g (2.10 mmol,
22.6%) of 7a as colorless crystals. The 1H NMR spectrum of
this compound indicated the presence of two kinds of isomers
in almost equal amounts in the C6D6 solution at 23 °C. 1H
NMR (395.75 MHz, C6D6): δ 7.25 (s, 2H, Cp-H), 6.76 (s, 2H,
Cp-H), 6.70 (s, 2H × 2, Cp-H), 3.53 (s, 8H, THF-R), 1.37 (s,
8H, THF-â), 1.25 (s, 6H, Me2SiOSiMe2), 1.15 (s, 3H, Me2Si),
0.93 (s, 3H, Me2Si), 0.85 (s, 6H, Me2SiOSiMe2), 0.77 (s, 3H,
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data and data collection parameters, atom coordi-
nates, anisotropic displacement parameters, equivalent iso-
tropic displacement parameters, bond distances, bond angles,
and hydrogen coordinates for complexes 1a , 2a , 2b, 3, and 7a .
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM000226A