Synthesis, structures, and reactivity of the first silylene-linked cyclopentadienyl-phosphido lanthanide complexes

Article abstract of DOI:10.1021/om010469i

Reaction of KPHAr (Ar = C₆H₂^tBu₃-2,4,6) with 1 equiv of Me₂SiCl(C₅Me₄H) in THF afforded Me₂Si(C₅Me₄H)(PHAr) (1) in 92% isolated yield. Metalation

Full text of DOI:10.1021/om010469i

Organometallics 2001, 20, 4565-4573
4565
Syn th esis, Str u ctu r es, a n d Rea ctivity of th e F ir st
Silylen e-Lin k ed Cyclop en ta d ien yl-P h osp h id o La n th a n id e
Com p lexes
Olivier Tardif, Zhaomin Hou,* Masayoshi Nishiura, Take-aki Koizumi, and
Yasuo Wakatsuki*
Organometallic Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical
Research), Hirosawa 2-1, Wako, Saitama 351-0198, J apan
Received J une 4, 2001
t
Reaction of KPHAr (Ar ) C6H2 Bu3-2,4,6) with 1 equiv of Me2SiCl(C5Me4H) in THF afforded
Me2Si(C5Me4H)(PHAr) (1) in 92% isolated yield. Metalation of 1 with 2 equiv of BuLi in
t
THF followed by metathesis reaction with BuOK gave the corresponding potassium complex
[Me2Si(C5Me4)(PAr)K2(thf)4]2 (2) in 88% isolated yield. Reactions of 2 with 2 equiv of LnI2-
(thf)2 in THF afforded the corresponding lanthanide(II) complexes Me2Si(C5Me4)(PAr)Ln(thf)3
(Ln ) Sm (3, 66%), Yb (4, 81%)). Two of the three thf ligands in 3 could be removed under
vacuum to give [Me2Si(C5Me4)(PAr)Sm(thf)] (3′). Treatment of 3 with hexamethylphosphoric
triamide (hmpa) or dimethoxyethane (dme) yielded the corresponding hmpa- or dme-
coordinated complex Me2Si(C5Me4)(PAr)Sm(hmpa)2 (5) or Me2Si(C5Me4)(PAr)Sm(dme)2 (6),
respectively. The reaction of 2 equiv of 3 or 3′ with benzophenone in THF afforded the
corresponding disamarium(III) benzophenone-dianion complex [Me2Si(C5Me4)(PAr)Sm(thf)]2-
(µ-η2-OCPh2) (7). Treatment of 3 or 3′ with ICH2CH2I in toluene easily afforded the cor-
responding samarium(III) iodide complex [Me2Si(C5Me4)(PAr)Sm(µ-I)(thf)]2 (8). The solid
structures of all of these compounds, 1-8, have been determined by X-ray analyses. The
mono(thf)-coordinated Sm(II) complex 3′ was active for the polymerization of ethylene,
ꢀ-caprolactone, and 1,3-butadiene under appropriate conditions.
In tr od u ction
Since the discovery of the Kaminsky metallocene
catalysts in 1980, extensive studies on the design and
application of organometallic complexes as polymeriza-
tion catalysts have been carried out.1 Today, the search
for well-defined metal complexes with new ligand
systems toward the development of more efficient, more
selective catalyst families continues to attract intensive
attention from both academic and industrial research-
ers. In this development, group 3 and 4 metal complexes
bearing the silylene-linked cyclopentadienyl-amido
ligands (type B) have received much current interest
owing to their electronically more unsaturated and
sterically more accessible properties than those of the
metallocene analogues (e.g., type A).2 In contrast,
however, the analogous linked cyclopentadienyl-phos-
phido complexes (type C) have very hardly been ex-
plored, although this type of phosphido complex is of
much interest in comparison with the amido analogues.
It was previously claimed in a patent that the silylene-
linked cyclopentadienyl-phosphido complexes Me2Si(C5-
Me4)(PPh)MCl2 (M ) Ti or Zr) were formed in the
reactions of Li2[Me2Si(C5Me4)(PPh)] with MCl4, but no
spectroscopic or analytical data were given to support
this assumption.3 A more recent report showed that
similar reactions of Li2[Me2Si(C5Me4)(PR)] (R ) cyclo-
hexyl or C6H2Me3-2,4,6) with ZrCl4 did not give the
expected cyclopentadienyl-phosphido complexes, but
instead led to P-Si bond cleavage of the ligands.4 As
far as we are aware, a structurally characterized,
silylene-linked cyclopentadienyl-phosphido complex has
never been reported to date for any metal.5 In this
paper, we report the synthesis, structures, and prelimi-
nary reaction studies of the first linked cyclopentadi-
enyl-phosphido lanthanide complexes. The synthesis
(3) Stevens, J . C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G. F.;
Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. (Dow) Eur. Pat.
Appl. 0 416 815 A2, 1991.
(4) Koch, T.; Blaurock, S.; Somoza, F. B.; Voigt, A.; Kirmse, R.; Hey-
Hawkins, E. Organometallics 2000, 19, 2556.
(1) Recent reviews leading to references: (a) Chem. Rev. 2000, 100,
1167-1645 (a special thematic issue on metal-catalyzed polymeriza-
tion). (b) Togni, A.; Halterman, R. L. Metallocenes; Wiley-VCH:
Weinheim, Germany, 1998; Vols. 1-2.
(2) Reviews: (a) McKnight, A. L.; Waymouth, R. M. Chem. Rev.
1998, 98, 2587. (b) Okuda, J .; Eberle, T. In Metallocenes; Togni, A.,
Halterman, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998; Vol.
1, p 415.
(5) Formation of the dilithium salts of linked cyclopentadienyl-
phosphido ligands was reported.3,4,5a-c Methylene-linked cyclopenta-
dienyl-phosphido titanium and zirconium complexes were also reported
very recently.5d (a) Koch, T.; Hey-Hawkins, E. Polyhedron 1999, 18,
2113. (b) Izod, K. Adv. Inorg. Chem. 2000, 50, 33. (c) Bildmann, U. J .;
Muller, G. Z. Naturforsch. 2000, 55, 895. (d) Kunz, K.; Erker, G.;
Do¨ring, S.; Fro¨hlich, R.; Kehr, G. J . Am. Chem. Soc. 2001, 123, 6181.
10.1021/om010469i CCC: $20.00 © 2001 American Chemical Society
Publication on Web 10/02/2001

4566 Organometallics, Vol. 20, No. 22, 2001
Tardif et al.
and X-ray structures of the ligand and its potassium
salt are also described.
Resu lts a n d Discu ssion
Liga n d Syn th esis a n d P ota ssiu m Com p lex F or -
m a tion . Our initial interest in linked cyclopentadienyl-
phosphido lanthanide complexes stemmed originally
from our studies on lanthanide complexes bearing mixed
(unlinked) C5Me5/ER ligands (ER ) a monodentate
anionic ligand such as an aryloxide, thiolate, amido,
phosphido, or alkyl group).6 In relation to the phosphido
ligand that was used in a previous study,6d we chose
t
C6H2 Bu3-2,4,6 as a substituent on the P atom for our
linked cyclopentadienyl-phosphido ligand. The reaction
of KPHAr7a with 1 equiv of Me2SiCl(C5Me4H) in THF
readily afforded the expected secondary phosphine Me2-
t
Si(C5Me4H)PHAr (1, Ar ) C6H2 Bu3-2,4,6) as colorless
F igu r e 1. ORTEP drawing of 1 with 30% thermal el-
lipsoids. Selected bond lengths (Å) and angles (deg):
P1-H1, 1.24(6); P1-Si1, 2.310(2); P1-C12, 1.856(4); H1-
P1-C12, 102(2); H1-P1-Si1, 96(3); Si1-P1-C12, 100.5(1);
P1-Si1-C1, 107.3(1); C1‚‚‚C29, 3.84; C10‚‚‚C19, 3.46;
C11‚‚‚C12, 3.26; C10‚‚‚C12, 4.46; C11-Si1-P1-C12,
-9.8(2); C10-Si1-P1-C12, 110.8(2).
crystals in 92% yield (eq 1). Metalation of 1 with 2 equiv
of BuLi in THF followed by metathesis reaction with
tBuOK gave the corresponding dipotassium cyclopen-
tadienyl-phosphido complex [Me2Si(C5Me4)(PAr)K2(thf)4]2
(2) in 88% isolated yield (eq 2).
carbon of an ortho-tBu group in the Ar unit is as short
as 3.46 Å. These distances are much shorter than the
sum of the van der Waals radius of a methyl group (2.0
Å),8 and considerable van der Waals repulsion between
the Ar unit and the substituents on the Si atom must
be present. Because of this repulsion, the C(12) atom is
no longer coplanar with the other five carbon atoms
C(13-17) in the phenyl ring of the Ar group (cf. C(12)‚
‚‚(13-17) plane: 0.194(5) Å), and the P(1) atom is
further out of the plane, with the distance of P(1) to the
C(13-17) plane being as long as 0.873(7) Å (cf. Table 1
and Figure 1).
Orange crystals of 2 suitable for diffraction studies
were obtained from a concentrated THF solution. An
X-ray analysis established that one of the two K atoms,
K(1), is chelated by the Cp′-phosphido ligand, while the
other K atom (K(2)) is bonded to the other side of the
Cp′ unit (Cp′ ) C5Me4) (Figure 2). The whole molecule
adopts a dimeric structure through “intermolecular”
interaction between the chelated K(1) atom and the P
atom, with a crystallographic inversion center being
present at the center of the molecule. As compared with
1, the chelation of the Cp′-phosphido ligand to the
potassium atom in 2 further increased the steric repul-
sion between the methyl groups on the Si atom and the
ortho-tBu groups in the aryl unit (cf. Table 1 and Figure
2). Therefore, the P(1) and C(12) atoms in 2 were further
dragged out of the C(13-17) plane, with the distances
of P(1) and C(12) to the C(13-17) plane being increased
to 1.10(2) and 0.24(1) Å, respectively. The average bond
distance of the chelating K(1)-Cp′ bonds (3.049(8) Å)
is slightly longer than that of the K(2)-Cp′ bonds
(2.987(8) Å). But, both can be compared with that of the
K-Cp* bonds found in [(Cp*K(Py)2]n (Cp* ) C5Me5, Py
) pyridine) (3.030(2) Å).9 The K(1)-P(1) bond distance
(3.324(4) Å) in 2 is significantly shorter than that of the
K(1)-P(1*) bond (3.430(3) Å), but is in the 3.181-3.345
An X-ray analysis has shown that the structure of 1
is highly distorted because of the steric repulsion
between the bulky aryl group and the whole silyl unit
on the P atom (Figure 1 and Table 1). To reduce the
repulsion, the C5Me4H group is oriented away from the
Ar group, while one of the two methyl groups on the Si
atom, C(11), is placed between the two ortho-tBu groups
of the Ar unit and directed almost parallel along the
C(12)-P(1) bond (cf. C(11)-Si(1)-P(1)-C(12) torsion
angle: 9.8(2)°). As a consequence, the C(11) methyl
carbon on the Si atom is as close as 3.26 Å to the ipso-
carbon C(12) of the Ar group, and the distance of the
C(10) methyl carbon on the Si atom to the C(19) methyl
(6) (a) Hou, Z.; Zhang, Y.; Tardif, O.; Wakatsuki, Y. J . Am. Chem.
Soc. 2001, 123, 9216. (b) Hou, Z.; Kaita; S. Wakatsuki, Y. Pure Appl.
Chem. 2001, 73, 291. (c) Hou, Z. J . Synth. Org. Chem. J pn. 2001, 59,
82. (d) Hou, Z.; Zhang, Y.; Tezuka, H.; Xie, P.; Tardif, O.; Koizumi, T.;
Yamazaki, H.; Wakatsuki, Y. J . Am. Chem. Soc. 2000, 122, 10533. (e)
Hou, Z.; Wakatsuki, Y. J . Alloys Compd. 2000, 303-304, 75. (f) Zhang,
Y.; Hou, Z.; Wakatsuki, Y. Macromolecules 1999, 32, 939. (g) Hou, Z.;
Tezuka, H.; Zhang, Y.; Yamazaki, H.; Wakatsuki, Y. Macromolecules
1998, 31, 8650. (h) Zhang, Y.; Hou, Z.; Wakatsuki, Y. Bull. Chem. Soc.
J pn. 1998, 71, 1381. (i) Hou, Z.; Zhang, Y.; Yoshimura, T.; Wakatsuki,
Y. Organometallics 1997, 16, 2963.
(7) (a) Rabe, G.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem. 1997,
36, 1990. (b) Frenzel, C.; J o¨rchel, P.; Hey-Hawkins, E. Chem. Commun.
1998, 1363.
(8) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; pp 260-261.

Silylene-Linked Cyclopentadienyl-Phosphido Complex
Organometallics, Vol. 20, No. 22, 2001 4567
Ta ble 1. Su m m a r y of Selected Dista n ces (Å) a n d An gles (d eg) for th e Silylen e-Lin k ed
Cyclop en ta d ien yl-P h osp h id o Com p lexes of Typ e D (see a lso F igu r es 1-7)
1
2
4
5
6 (two molecules)
7
8
M )
H
K
Yb(II)
2.72(1)
2.43
2.851(4)
2.198(5)
1.87(1)
1.09(4)
0.24(3)
3.46
3.38
3.89
3.83
59(1)
61(1)
96.4
168.7(4)
88.4(2)
102.5(4)
359.6
Sm(II)
2.796(7)
2.525
3.041(2)
2.238(3)
1.869(6)
1.10(1)
0.26(1)
3.79
3.58
3.38
4.41
19.3(5)
98.7(4)
93.0
128.7(2)
85.37(8)
102.3(2)
316.4
Sm(II)
2.858(5), 2.848(6)
2.594, 2.581
2.977(2), 2.973(2)
2.212(2), 2.213(2)
1.864(6), 1.866(6)
1.10(2), 0.85(2)
0.24(1), 0.19(1)
3.53, 3.49
3.42, 3.47
3.59, 4.00
4.05, 4.11
44.7(4), 53.6(4)
72.3(4), 65.4(4)
92.5, 91.6
161.1(2), 160.5(2)
89.51(7), 90.83(7)
101.0(2), 107.4(2)
351.1, 358.7
Sm(III)
2.708(3)
2.426
2.7962(9)
2.211(1)
1.877(3)
1.35(2)
0.27(1)
3.55
3.58
3.93
3.90
60.3(4)
58.9(4)
95.3
164.4(1)
91.37(4)
103.2(1)
359.0
Sm(III)
2.690(7)
2.402
2.720(2)
2.195(3)
1.868(8)
1.08(2)
0.22(1)
3.44
3.64
4.17
3.88
70.2(6)
51.2(5)
96.0
156.0(3)
92.9(1)
107.6(1)
356.5
M-Cp′(av)
M-Cp′(centrd)
M-P
3.049(8)
2.802
1.24(6)
2.310(2)
1.856(4)
0.873(7)
0.194(5)
3.84
3.46
3.26
4.46
9.8(2)
3.324(4)
2.232(3)
1.895(8)
1.10(2)
0.24(1)
3.48
3.62
4.15
3.44
84.4(5)
30.3(5)
86.8
144.8(3)
85.8(1)
99.3(2)
329.9
P-Si
P-C1
P‚‚‚plane(C2-6
)
Cl‚‚‚plane(C2-6
Me1‚‚‚tBu1
Me2‚‚‚tBu2
Me1‚‚‚C1
)
Me2‚‚‚C1
|Me1-Si-P-C1|
|Me2-Si-P-C1|
Cp′(centrd)-M-P
M-P-C1
110.8(2)
102(2)
96(3)
100.5(1)
298.5
M-P-Si
Si-P-C1
∑ of angles around P
easily afforded the corresponding Cp′-phosphido lan-
thanide(II) complexes Me2Si(C5Me4)(PAr)Ln(thf)3 (Ar )
t
C6H2 Bu3-2,4,6; Ln ) Sm (3), Yb (4)) in good yields (eq
3). Two of the three thf ligands in 3 could be removed
F igu r e 2. ORTEP drawing of 2 with 30% thermal el-
lipsoids. Selected bond lengths (Å) and angles (deg):
K1-C1, 2.953(8); K1-C2, 3.016(9); K1-C3, 3.114(8);
K1-C4, 3.126(8); K1-C5, 3.037(7); K2-C1, 2.959(7);
K2-C2, 2.979(7); K2-C3, 3.034(8); K2-C4, 3.02(1);
K2-C5, 2.944(8); K1-P1, 3.324(4); K1-P1*, 3.432(2);
K1-O1, 2.714(8); K2-O2, 2.72(1); K2-O3, 2.72(1); K2-
O4, 2.728(9); P1-Si1, 2.232(3); P1-C12, 1.895(8); Cp′-
(centroid)-K1-P1, 86.7; Cp′(centroid)-K1-1*, 126.7; Cp′-
(centroid)-K1-1, 115.3; P1-K1-P1*, 106.53(7); K1-P1-
K1*, 73.47(7); K1-Cp′(centroid)-K2, 172.9; O2-K2-
Cp′(centroid), 135.0; O3-K2-Cp′(centroid), 117.6; O4-
K2-Cp′(centroid), 121.2; O2-K2-O3, 85.3(4); O2-K2-O4,
96.8(4); O3-K2-O4, 86.6(4); K1-P1-C12, 144.8(3);
K1-P1-Si1, 85.8(1); Si1-P1-C12, 99.3(2). C10‚‚‚C21,
3.48; C11‚‚‚C29, 3.62; C10‚‚‚C12, 4.15; C11‚‚‚C12, 3.44;
C10-Si1-P1-C12, -84.4(5); C11-Si1-P1-C12, 30.3(5).
under vacuum to give the monosolvated Sm(II) complex
[Me2Si(C5Me4)(PAr)Sm(thf)] (3′). Treatment of 3 with
hexamethylphosphoric triamide (hmpa) or dimethoxy-
ethane (dme) yielded the corresponding hmpa- or dme-
coordinated complex, 5 or 6, respectively (Scheme 1).
Sch em e 1
Å range reported for the K-P bonds in the polymeric
t
potassium phosphido compounds [KPH(C6H2 Bu3-
2,4,6)]n and [K3(thf)2{PH(C6H2Me3-2,4,6)}3]n.7b
7a
La n th a n id e(II) Com p lexes. Despite the intense
distortion in the ligand, metathetical reactions of the
potassium complex 2 with 2 equiv of LnI2(thf)2 in THF
The three thf ligands in the Yb(II) complex 4 could be
easily removed by dissolving 4 in toluene followed by
(9) Rabe, G.; Roesky, H. W.; Stalke, D.; Pauer, F.; Sheldrick, G. M.
J . Organomet. Chem. 1991, 403, 11.

4568 Organometallics, Vol. 20, No. 22, 2001
Tardif et al.
F igu r e 4. ORTEP drawing of 5 with 30% thermal el-
lipsoids. Selected bond lengths (Å) and angles (deg):
Sm1-P1, 3.041(2); Sm1-C1, 2.740(6); Sm1-C2, 2.741(6);
Sm1-C3, 2.810(7); Sm1-C4, 2.879(8); Sm1-C5, 2.812(8);
Sm1-O1, 2.456(5); Sm1-O2, 2.476(5); P1-Si1; 2.238(3);
P1-C12, 1.869(6); Cp′(centroid)-Sm1-P1, 93.04; Cp′-
(centroid)-Sm1-O1, 113.0; Cp′(centroid)-Sm1-O2, 116.9;
Sm1-P1-C12, 128.7(2); Sm1-P1-Si1, 85.37(8); Si1-P1-
C12, 102.3(2); P1-Sm1-O1, 101.2; P1-Sm1-O2, 135.7(1);
O1-Sm1-O2, 96.2(2); C10‚‚‚C28, 3.79; C11‚‚‚C19, 3.58;
C10‚‚‚C12, 3.38; C11‚‚‚C12, 4.41; C10-Si1-P1-C12,
-19.3(5); C11-Si1-P1-C12, 98.7(4).
F igu r e 3. ORTEP drawing of 4 with 30% thermal el-
lipsoids. Selected bond lengths (Å) and angles (deg):
Yb1-P1, 2.851(4); Yb1-C1, 2.64(1); Yb1-C2, 2.70(1); Yb1-
C3, 2.77(1); Yb1-C4, 2.80(2); Yb1-C5, 2.71(1); Yb1-O1,
2.535(9); Yb1-O2, 2.425(9); Yb1-O3, 2.469(9); P1-Si1;
2.198(5); P1-C12, 1.87(1); Cp′(centroid)-Yb1-P1, 96.4;
Cp′(centroid)-Yb1-O1, 107.2; Cp′(centroid)-Yb1-O2, 122.0;
Cp′(centroid)-Yb1-O3, 125.0; P1-Yb1-O1, 156.3(2);
P1-Yb1-O2, 92.4(3); P1-Yb1-O3, 92.7(3); O1-Yb1-O2,
76.73(3); O1-Yb1-O3, 72.6(3), O2-Yb1-O3, 111.6(4);
Yb1-P1-C12, 168.7(4); Yb1-P1-Si1, 88.4(2); Si1-P1-
C12, 102.5(4); C11‚‚‚C28, 3.46; C10‚‚‚C19, 3.38; C11‚‚‚C12,
3.89; C10‚‚‚C12, 3.83; C11-Si1-P1-C12, -59(1); C10-
Si1-P1-C12, 61(1).
evaporation of the solvent under vacuum, which yielded
the unsolvated complex [Me2Si(C5Me4)(PAr)Yb] (4′).
Orange needlelike single crystals of 4 were obtained
from a saturated THF solution. An X-ray analysis
showed that 4 adopts a monomeric structure, in which
the Yb(II) center is bonded to one chelating Cp′-
phosphido ligand and three thf terminal ligands (Figure
3). The average Yb-C(Cp′) bond distance in 4 (2.72 Å)
is significantly longer than that found in the analogous
Cp′-anilido ytterbium(II) complex Me2Si(C5Me4)(NPh)-
Yb(thf)3 (2.65 Å),10 while the Yb-P bond distance in 4
(2.851(4) Å) is much shorter than those reported for the
bis(phosphido) ytterbium(II) complexes such as Yb-
F igu r e 5. ORTEP drawing of 6 with 30% thermal el-
lipsoids. Only one of the two independent molecules is
shown. Selected bond lengths (Å) and angles (deg):
Sm1-P1, 2.977(2); Sm1-C1, 2.778(5); Sm1-C2, 2.848(5);
Sm1-C3, 2.934(5); Sm1-C4, 2.917(5); Sm1-C5, 2.816(5);
Sm1-O1, 2.740(5); Sm1-O2, 2.575(5); Sm1-O3, 2.601(6);
Sm1-O4, 2.645(6); P1-Si1; 2.212(2); P1-C12, 1.864(6);
Cp′(centroid)-Sm1-P1, 92.5; Cp′(centroid)-Sm1-O1, 177.3;
Cp′(centroid)-Sm1-O2, 116.9; Cp′(centroid)-Sm1-O4,
103.5; Sm1-P1-C12, 161.1(2); Sm1-P1-Si1, 89.51(7);
Si1-P1-C12, 101.0(2), P1-Sm1-O1, 85.1(1); P1-Sm1-
O2, 110.5(2); P1-Sm1-O3, 99.8(2); P1-Sm1-O4, 159.1(2);
C11‚‚‚C29, 3.53; C10‚‚‚C20, 3.42; C11‚‚‚C12, 3.59;
C10‚‚‚C12, 4.05; C11-Si1-P1-C12, -44.7(4); C10-Si1-
P1-C12, 72.3(4).
(PHC6H2 Bu3-2,4,6)2(thf)4 (3.025(2) Å),11a Yb(PPh2)2(thf)4
t
(2.991(2) Å),11b Yb{P(C6H3OMe-2-Me-3)CH(SiMe3)2}2-
(thf)2 (2.969(3) Å),11c and Yb{P(C6H2Me3-2,4,6)2}2(thf)4
(2.925(2) Å).11d The P-Yb-Cp′(centroid) angle in 4
(96.4°) is comparable with the N-Yb-Cp′(centroid)
angle in Me2Si(C5Me4)(NPh)Yb(thf)3 (95°).10
Although the X-ray structure of the thf-coordinated
Sm(II) complex 3 could not be satisfactorily refined
owing to poor quality of the crystal, the connectivity of
the molecule, which is similar to that of the Yb(II)
analogue 4, was unambiguously determined.12 The
structures of the hmpa-coordinated Sm(II) complex 5
(Figure 4) and its dme analogue 6 (Figure 5) could be
well refined. In the case of 6, two independent molecules
were found in the unit cell. The average Sm-C(Cp′)
bond distance in 5 (2.796(7) Å) is shorter than those in
6 (2.858(5), 2.848(6) Å) and those of the Sm-C(Cp*)
bonds found in the unlinked half-metallocene Sm(II)
complexes such as Cp*Sm(N(SiMe3)2)(hmpa)2 (2.86(2)
t
Å)6d and Cp*Sm(OC6H2 Bu2-2,6-Me-4)(hmpa)2 (2.860(7)
Å, Cp* ) C5Me5).6i The Sm-P bond distance in 5
(3.041(2) Å) is, however, longer than those in 6 (2.977(2),
2.973(2) Å). The PAr unit in 5 adopts a “bent” structure
( Sm-P-Ar: 128.7(2)°), which is in contrast with the
“linear” ones in 6 ( Sm-P-Ar: 161.1(2)°, 160.5(2)°) and
4 ( Yb-P-Ar: 168.7(4)°) (cf. Table 1). Moreover, the
sum of the bond angles around the P atom in 5 (316.4°)
is much less than 360°, showing that the P atom and
the atoms around it are arranged in a pyramidal form.
In contrast, the analogous angle sum in 4 (359.6°) or 6
(351.1°, 358.7°) is close to 360°, which indicates that the
P atom and the atoms around it in 4 and 6 are almost
coplanar. These results suggest that the donation of the
lone electron pair on the P atom to the central metal
ion in 5 is not as sufficient as that in 4 and 6, probably
(10) Hou, Z.; Koizumi, T.; Nishiura, M.; Wakatsuki, Y. Organome-
tallics 2001, 20, 3323.
(11) (a) Rabe, G. W.; Guzei, I. A.; Rheingold, A. L. Inorg. Chem. 1997,
36, 4914. (b) Rabe, G. W.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem.
1995, 34, 4521. (c) Clegg, W.; Izod, K.; Liddle, S. T.; O’Shaughnessy,
P.; Sheffield, J . M. Organometallics 2000, 19, 2090. (d) Atlan, S.; Nief,
F.; Ricard, L. Bull. Chim. Soc. Fr. 1995, 132, 649.
(12) Crystal data for 3: monoclinic, space group C2/m, a ) 25.414-
(7) Å, b ) 14.461(6) Å, c ) 13.977(3) Å, â ) 94.101(2)°, V ) 5123(3) Å3,
Z ) 4.

Silylene-Linked Cyclopentadienyl-Phosphido Complex
Organometallics, Vol. 20, No. 22, 2001 4569
owing to the influence of the strongly electron-donating
hmpa ligands in 5.13 The extent of distortion in the Cp′-
phosphido ligands of 4-6 is comparable with each other
and also with that in 2, in terms of the distances
between the P atom or the methyl groups on the Si atom
and the aryl unit (cf. Table 1).
On e-Electr on -Tr a n sfer Rea ction s of th e Sm (II)
Com p lex 3. Despite the great distortion in the struc-
tures of 2-6, these complexes were quite stable in solid
state at room temperature under an inert atmosphere.
However, the lanthanide(II) complexes 3-6 gradually
decomposed into yet unidentified products in a THF
solution during a period of 1-3 days. Nevertheless, the
reduction chemistry of such a lanthanide(II) complex
(e.g., 3) could be examined in THF or toluene. The
reaction of 2 equiv of 3 or 3′ with benzophenone in THF
afforded the corresponding disamarium(III) benzophe-
none-dianion complex 7 in 64% isolated yield (eq 4).
F igu r e 6. ORTEP drawing of 7 with 30% thermal el-
lipsoids. The lattice THF molecules are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Sm1-P1,
2.7962(9); Sm1-C8, 2.665(3); Sm1-C9, 2.658(3); Sm1-
C10, 2.711(3); Sm1-C11, 2.764(3); Sm1-C12, 2.740(3);
Sm1-C1, 2.584(2); Sm1-O1, 2.2932(3); Sm1-O2, 2.470(2);
P1-Si1; 2.211(1); P1-C19, 1.877(3); C(1)-O(1), 1.426(4);
Cp′(centroid)-Sm1-P1, 95.3; Cp′(centroid)-Sm1-O1, 109.7;
Cp′(centroid)-Sm1-C1, 134.2; Cp′(centroid)-Sm1-O2,
106.3; P1-Sm1-O1, 119.54(3); P1-Sm1-O2, 106.81(6);
P1-Sm1-C1, 124.154(19); Sm1-P1-C19, 164.4(1); Sm1-
P1-Si1, 91.37(1); Si1-P1-C19, 107.6(1), O2-Sm1-O1,
116.54(8); O1-Sm1-C1, 33.34(9); O2-Sm1-C1, 85.39(9);
Sm1-O1-Sm1*, 169.15(12); Sm1-C1-Sm1*, 124.17(15);
C2-C1-O1, 116.2(2); C2-C1-C2*, 127.7(4); C17‚‚‚C34,
3.55; C18‚‚‚C27, 3.58; C17‚‚‚C19, 3.93; C18‚‚‚C19, 3.90;
C17-Si1-P1-C19, -60.3(4); C18-Si1-P1-C19, 58.9(4).
found in the Sm(II) complexes 5 and 6, owing to the
smaller size of Sm(III) than that of Sm(II) (Table 1).16
Complex 7 has a crystallographic 2-fold axis passing
through the C(1)-O(1) bond of the benzophenone unit
(Figure 6). The two Sm atoms are symmetrically bridged
by the CO group of the benzophenone unit in a η2-
fashion. The C(1)-O(1) bond distance in 7 (1.426(4) Å)
is comparable with those reported for the benzophe-
none-dianion units in [Li2(OCPh2)(thf)(tmeda)]2 (1.406
Å) (tmeda ) tetramethylethylenediamine)14d and [Yb-
(µ-η1:η2-OCPh2)(hmpa)2]2 (1.39(6) Å)14b,c and signifi-
cantly longer than that of the C-O double bond found
in free benzophenone (1.23 Å).17 The distance of the
bridging Sm(1)-C(1) bond in 7 (2.584(2) Å) is much
longer than that reported for the terminal Sm-methyl
bond in (C5Me5)2SmMe(thf) (2.48(1) Å).18 Similarly, the
distance of the bridging Sm(1)-O(1) bond in 7 (2.2932(3)
Å) is significantly longer than those of the terminal Sm-
O(diphenylmethoxy) bonds found in Sm(OCHPh2)2-
The use of 1 equiv of 3 in this reaction also gave 7 as
the only isolable product, albeit in a lower yield, which
suggests that the formation of a benzophenone-dianion
species is easier than that of a ketyl species in the
present reaction.14,15 These results are in contrast with
those previously reported for the analogous reactions
of lanthanide(II) complexes bearing other ligand sys-
tems such as (C5Me5)2Sm(thf)2,15c Sm(OC6H2 Bu2-2,6-
t
Me-4)2(thf)2,15c,g and Me2Si(C5Me4)(NPh)Yb(thf)3.10 Treat-
ment of 3 or 3′ with ICH2CH2I in toluene easily afforded
the corresponding samarium(III) iodide complex 8 in
78% isolated yield (eq 5). The Sm(III) complexes 7 and
8 seemed to be much more stable than the lanthanide-
(II) complexes 3-6 in THF solution.
(OAr)(hmpa)2 (av 2.145(5) Å) (Ar ) C6H3 Bu2-2,6).19 As
t
far as we are aware, 7 represents the first example of a
structurally characterized lanthanide(III) ketone-di-
anion complex.
Complex 8 possesses a crystallographic inversion
center at the center of the molecule (Figure 7). The
The average bond distances of the Sm-C(Cp′) bond
(2.708(3) Å) and the Sm-P bond (2.7962(9) Å) in 7 are
somewhat longer than those in 8 (Sm-C(Cp′), 2.690(7)
Å; Sm-P, 2.720(2) Å), respectively. However, all of these
bond distances are respectively much shorter than those
(15) For examples of formation and structures of ketyl complexes,
see: (a) Hou, Z.; J ia, X.; Fujita, A.; Tezuka, H.; Yamazaki, H.;
Wakatsuki, Y. Chem. Eur. J . 2000, 6, 2994. (b) Hou, Z.; Fujita, A.;
Koizumi, T.; Yamazaki, H.; Wakatsuki, Y. Organometallics 1999, 18,
1979. (c) Hou, Z.; Fujita, A.; Zhang, Y.; Miyano, T.; Yamazaki, H.;
Wakatsuki, Y. J . Am. Chem. Soc. 1998, 120, 754. (d) Hou, Z.; J ia, X.;
Wakatsuki, Y. Angew. Chem., Int. Ed. Engl. 1997, 36, 1292. (e) Clegg,
W.; Eaborn, C.; Izod, K.; O’Shaughnessy, P.; Smith, J . D. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2815. (f) Takats, J . J . Alloys Compd.
1997, 249, 51. (g) Hou, Z.; Miyano, T.; Yamazaki, H.; Wakatsuki, Y. J .
Am. Chem. Soc. 1995, 117, 4421.
(13) Generally, HMPA is much more electron-donating than THF
or DME. For examples, see: (a) Hou, Z.; Zhang, Y.; Wakatsuki, Y. Bull.
Chem. Soc. J pn. 1997, 70, 149. (b) Hou, Z.; Wakatsuki, Y. J . Chem.
Soc., Chem. Commun. 1994, 1205. (c) Hou, Z.; Kobayashi, K.; Yamaza-
ki, H. Chem. Lett. 1991, 265.
(14) For examples of formation and structures of ketone-dianion
complexes, see: (a) Hou, Z.; Fujita, A.; Yamazaki, H.; Wakatsuki, Y.
Chem. Commun. 1998, 669. (b) Hou, Z.; Yamazaki, H.; Kobayashi, K.;
Fujiwara, Y.; Taniguchi, H. J . Chem. Soc., Chem. Commun. 1992, 722.
(c) Hou, Z.; Yamazaki, H.; Fujiwara, Y.; Taniguchi, H. Organometallics
1992, 11, 2711. (d) Bogdanovic, B.; Kruger, C.; Wermeckes, B. Angew.
Chem., Int. Ed. Engl. 1980, 19, 817.
(16) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751.
(17) Fleischer, E. B.; Sung, N.; Hawkinson, S. J . Phy. Chem. 1968,
72, 4311.
(18) Evans, W. J .; Chamberlian, L. R.; Ulibarri, T. A.; Ziller, J . W.
J . Am. Chem. Soc. 1988, 110, 6423.
(19) Hou, Z.; Yoshimura, T.; Wakatsuki, Y. J . Am. Chem. Soc. 1994,
116, 11169.

4570 Organometallics, Vol. 20, No. 22, 2001
Tardif et al.
(MMAO ) modified methylaluminoxane which contains
isobutylaluminoxane) as a cocatalyst, 3′ showed high
activity and 1,4-cis selectivity for the polymerization of
1,3-butadiene (1,4-cis:1,4-trans:1,2- ) 92.8:4.0:3.2; Mn
) 3.07 × 105, Mw/Mn ) 1.99).23
Con clu sion
We have shown that the silylene-linked cyclopenta-
dienyl phosphido unit [Me2Si(C5Me4)(PC6H2 Bu3-2,4,6)]2-
t
can serve as a useful ancillary ligand system for both
divalent and trivalent lanthanides. The potassium
complex (2) and the lanthanide complexes (3-8) re-
ported in this paper represent the first examples of
structurally characterized, silylene-linked cyclopenta-
dienyl-phosphido complexes. The previous lack of suc-
cess in obtaining an analogous group 4 metal complex4
and the difference in stability among the potassium and
divalent and trivalent lanthanide complexes 2-8 sug-
gest that the stability of a silylene-linked cyclopenta-
dienyl-phosphido complex is very dependent on the
nature of the central metal ion. Preliminary reaction
studies on the Sm(II) complex 3 demonstrate that the
linked cyclopentadienyl-phosphido lanthanide(II) com-
plexes can serve as a new family of reducing agents and
polymerization catalysts. Studies on analogous lan-
thanide complexes bearing other phisphido ligands are
under progress.
F igu r e 7. ORTEP drawing of 8 with 30% thermal el-
lipsoids. Selected bond lengths (Å) and angles (deg): Sm1-
P1, 2.720(2); Sm1-C1, 2.628(7); Sm1-C2, 2.655(8); Sm1-
C3, 2.713(7); Sm1-C4, 2.753(7); Sm1-C12, 2.701(7); Sm1-
O1, 2.446(5); Sm1-I1, 3.1037(7); Sm1-I1*, 3.2299(7); P1-
Si1; 2.195(3); P1-C12, 1.868(8); Cp′(centroid)-Sm1-P1,
96.0; Cp′(centroid)-Sm1-I1, 102.1; Cp′(centroid)-Sm1-
I1*, 171.8; Cp′(centroid)-Sm1-O1, 101.0; P1-Sm1-I1,
114.51(6); P1-Sm1-I1*, 91.70(5); P1-Sm1-O1, 102.74(14);
O1-Sm1-I1, 133.24(12); O1-Sm1-I1*, 74.37(12); I1-
Sm-I1*, 77.18(2); Sm1-I1-Sm1*; 102.82(2); Sm1-P1-
C12, 156.0(3); Sm1-P1-Si1, 92.9(1); Si1-P1-C12,
107.6(1); C10‚‚‚C20, 3.44; C11‚‚‚C27, 3.64; C10‚‚‚C12, 4.17;
C11‚‚‚C12, 3.88; C10-Si1-P1-C12, -70.2(6); C11-Si1-
P1-C12, 51.2(5).
Sm(1)-I(1) bond distance (3.1037(7) Å) is significantly
shorter than that of the Sm(1)-I(1*) bond (3.2299(7) Å),
showing that the iodide bridges are asymmetric. These
bridging Sm-I bond distances are significantly longer
than those of the terminal Sm-I bonds found in
(C5Me5)2SmI(thf) (3.048(2) Å)20 and (ArO)2SmI(thf)2
Exp er im en ta l Section
Gen er a l Meth od s. All reactions were carried out under a
dry and oxygen-free argon atmosphere by using Schlenk
techniques or under a nitrogen atmosphere in an MBraun
glovebox. The argon was purified by being passed through a
Dryclean column (4 Å molecular sieves, Nikka Seiko Co.) and
a Gasclean GC-XR column (Nikka Seiko Co.). The nitrogen in
the glovebox was constantly circulated through a copper/
molecular sieves (4 Å) catalyst unit. The oxygen and moisture
concentrations in the glovebox atmosphere were monitored by
an O2/H2O Combi-Analyzer (MBraun) to ensure both were
always below 1 ppm. Samples for NMR spectroscopic measure-
ments were prepared in the glovebox by use of J . Young valve
NMR tubes (Wilmad 528-J Y). 1H, 13C, and 31P NMR spectra
were recorded on a J NM-EX 270 (FT, 270 MHz) spectrometer.
Elemental analyses were performed by the Chemical Analysis
Laboratory of RIKEN. Solvents were distilled from sodium/
benzophenone ketyl, degassed by the freeze-pump-thaw
method (three times), and dried over fresh Na chips in the
glovebox. HMPA was distilled from Na under reduced pres-
sure, degassed by the freeze-thaw method, and dried over
molecular sieves (4 Å). (C5Me4H)SiMe2Cl was purchased from
(3.024(2) Å) (Ar ) OC6H2 Bu2-2,6-Me-4).21
t
P olym er iza tion Rea ction s. The polymerization of
ethylene by the mono(thf)-coordinated Sm(II) complex
3′ at room temperature under 1 atm yielded extremely
high molecular weight polyethylene that was insoluble
in ortho-dichlorobenzene at 135 C° (13.6 kg polymer
(mol Sm)-1 h-1, Mn > 4 × 106). This result is in contrast
with what was observed in the case of the analogous,
less sterically demanding Cp′-anilido Sm(II) complex
Me2Si(C5Me4)(NPh)Sm(thf)x (x ) 0-1) (44.8 kg polymer
(mol Sm)-1 h-1, Mn ) 7.26 × 105, Mw/Mn ) 1.58)10
and the mixed C5Me5/PHAr-ligated Sm(II) complex
t
[(C5Me5)Sm(PHAr)(thf){K(thf)(C5Me5)}]n (Ar ) C6H2 Bu3-
2,4,6) (57.6 kg polymer (mol Sm)-1 h-1, Mn ) 5.0 × 105,
Mw/Mn ) 2.9).6d Complex 3′ seemed to react with styrene
in toluene at room temperature, but no polymer product
was obtained. The less reducing Yb(II) complex 4 or 4′
or the more crowded Sm(II) complexes 3, 5, and 6 did
not show an activity for ethylene polymerization under
the same conditions. Complex 3′ was also very active
for the ring-opening polymerization of ꢀ-caprolactone
(CL), which quantitatively converted 1000 equiv of CL
into poly(CL) (Mn ) 1.06 × 105, Mw/Mn ) 1.54) at room
temperature within 10 min.22 In the presence of MMAO
Aldrich. PH2(C6H2 Bu3-2,4,6),24 KPH(C6H2 Bu3-2,4,6),7a and
t
t
25
LnI2(thf)2 (Ln ) Sm, Yb) were prepared according to litera-
ture methods.
t
Me2Si(C5Me4H)P H(C6H2tBu 3-2,4,6) (1). KPH(C6H2 Bu3-
2,4,6) (4.25 g, 13.43 mmol) in THF (50 mL) was added dropwise
at -78 °C to a THF solution (50 mL) of Me2SiCl(C5Me4H) (2.97
g, 13.83 mmol). The reaction mixture was then warmed to
room temperature and stirred for 14 h. Removal of the THF
under vacuum afforded a white residue, which was then
(20) 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.
(21) Hou, Z.; Fujita, A.; Yoshimura, T.; J esorka, A.; Zhang, Y.;
Yamazaki, H.; Wakatsuki, Y. Inorg. Chem. 1996, 35, 7190.
(22) For examples of the ring-opening polymerization of lactones by
Sm(II) complexes, see: (a) Nishiura, M.; Hou, Z.; Koizumi, T.; Imamoto,
T.; Wakatsuki, Y. Macromolecules 1999, 32, 8245. (b) Evans, W. J .;
Katsumata, H. Macromolecules 1994, 27, 2330.
(23) For stereospecific 1,4-cis, living polymerization of 1,3-butadiene
by samarocene-based catalysts, see: (a) Kaita, S.; Hou, Z.; Wakatsuki,
Y. Macromolecules 1999, 32, 9078. (b) Kaita, S.; Hou, Z.; Wakatsuki,
Y. Macromolecules 2001, 34, 1538.
(24) Cowley, A. H.; Norman, N. C.; Pakulski, M.; Becker, G.; Layh,
M.; Kirchner, E.; Schmidt, M. Inorg. Synth. 1990, 27, 235.
(25) Watson, P. L.; Tulip, T. H.; Williams, I. Organometallics 1990,
9, 1999.

Silylene-Linked Cyclopentadienyl-Phosphido Complex
Organometallics, Vol. 20, No. 22, 2001 4571
extracted with hexane. The volatiles were removed under
reduced pressure to yield 1 as a white crystalline powder (5.63
g, 12.33 mmol, 92% yield). Colorless blocks of 1 suitable for
X-ray analysis were obtained from a concentrated hexane
solution. 1H NMR (C6D6, 22 °C): δ -0.28 (s, 3H, SiMe), -0.09
para-tBu), 2.19 (br s, 6H, C5Me4), 3.64 (q, J ) 3.23 Hz, 4H,
THF), 4.72 (br s, 18H, ortho-tBu), 8.36 (br s, 2H, C6H2). Anal.
Calcd for C41H71O3PSiSm (3): C, 59.95; H, 8.71; for C33H55
-
OPSiSm (3-2THF): C, 58.53; H, 8.19; for C29H47PSiSm (3-
3THF): C, 57.56; H, 7.83. Found: C, 52.84-53.31, H, 7.55-
7.59. The low value of the observed carbon content was
probably due to formation of incombustible carbide species.26
Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Yb(th f)3 (4, n ) 3; 4′, n
) 0). Addition of 2′ (0.772 g, 0.57 mmol) to a THF solution (20
mL) of YbI2(thf)2 (0.651 g, 1.14 mmol) gave immediately a
cloudy orange solution. The solution was stirred for 45 min
and the solvent was removed under vacuum. Addition of
toluene to the orange residue resulted in formation of a bright
green solution with precipitation of KI. After filtration and
evaporation of the solvent under vacuum, a green oily residue
was obtained, which after being washed with hexane and dried
under vacuum yielded 4′ (4-3THF) as a green powder (0.579
g, 0.92 mmol, 81% yield). Orange needlelike crystals of 4 could
be obtained from a saturated THF solution. Leaving 4 under
vacuum for 2 h regenerated 4′. 1H NMR (C5D5N, 22 °C): δ
0.64 (s, 6H, SiMe), 1.42 (s, 9H, para-tBu), 2.08 (s, 6H, C5Me4),
2.13 (br s, 24H, ortho-tBu, C5Me4), 7.50 (s, 2H, C6H2). 1H NMR
(C4D8O, 22 °C): δ 0.05 (s, 6H, SiMe), 1.26 (s, 9H, para-tBu),
1.73 (s, 18H, ortho-tBu), 1.95 (s, 6H, C5Me4), 2.15 (s, 6H, C5-
Me4), 7.03 (s, 2H, C6H2). 31P NMR (C5D5N, 22 °C): δ -113.5
(s with 171Yb satellites, J P-Yb ) 992 Hz). Anal. Calcd for
3
(d, J P-H ) 3.8 Hz, 3H, SiMe), 1.32 (s, 9H, para-tBu), 1.64 (br
s, 18H, ortho-tBu), 1.80 (s, 6H, C5Me4), 1.95 (s, 3H, C5Me4),
1.99 (s, 3H, C5Me4), 3.12 (br s, 1H, C5Me4H), 4.45 (d, J P-H
)
215 Hz, 1H, PH), 7.45 (d, 4J P-H ) 2.2 Hz, 2H, C6H2). 13C NMR
(C6D6, 22 °C): δ -1.84 (s, 1C, SiMe2), -1.71 (s, 1C, SiMe2),
11.33 (s, 1C, C5Me4), 11.39 (s, 1C, C5Me4), 14.89 (s, 2C, C5Me4),
31.58 (s, 3C, CMe3), 33.64 (s, 6C, CMe3), 34.81 (s, 1C, para-
CMe3), 38.27 (s, 2C, ortho-CMe3), 55.75 (s, 1C, ipso-C5Me4),
121.57 (d, 2C, J P-C ) 3.0 Hz, meta-C6H2), 130.21 (d, 1C, J P-C
) 35.0 Hz, ipso-C6H2), 132.97 (d, J P-C ) 19.8 Hz, ortho-C6H2),
136.61 (d, J P-C ) 7.6 Hz, para-C6H2), 147.79 (s, 2C, C5Me4),
154.92 (s, 2C, C5Me4). 31P NMR (C6D6, 22 °C): δ -131.2 (d,
J P-H ) 215 Hz). Anal. Calcd for C29H49PSi: C, 76.26; H, 10.81.
Found: C, 76.31; H, 11.01.
[Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)K2(th f)n ]2 (2, n ) 4; 2′,
n ) 2). BuLi (2.52 M, 14.8 mL, 37.30 mmol) was added to a
THF solution (40 mL) of 1 (7.71 g, 16.88 mmol) at -78 °C.
The resulting mixture was warmed to room temperature and
t
stirred for 2 h. BuOK (4.16 g, 37.07 mmol) was then added.
After the mixture was stirred for 2 days, the solvent was
removed under vacuum. The residue was washed with hexane
t
C
41H71O3PSiYb (4): C, 58.34; H, 8.48; for C29H47PSiYb (4-
to remove BuOLi and dried under vacuum for 1 h to yield
3THF): C, 55.48; H, 7.55. Found: C, 48.01-49.84; H, 7.31-
7.41. The low value of the observed carbon content was
probably due to formation of incombustible carbide species.26
Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Sm (h m p a )2 (5). Addition
of HMPA (52 µL, 0.296 mmol) to 3′ (0.100 g, 0.148 mmol) in
toluene (5 mL) gave a dark green solution. After evaporation
of the solvent under vacuum, the residue was washed with
hexane and dried to yield 5 as pale green powder (0.134 g,
0.139 mmol, 94%). Cubic dark green crystals of 5 were grown
in a saturated toluene solution in a few days. 1H NMR (C5D5N,
22 °C): δ -1.04 (br s, 6H, SiMe), 0.77 (br s, 6H, C5Me4), 2.06
(br s, 9H, para-tBu), 2.21 (br d, J P-H ) 8.70 Hz, 36H, NMe),
2.79 (br s, 6H, C5Me4), 4.76 (br s, 18H, ortho-tBu), 8.27 (br s,
orange powder of 2′ (2-4THF) (10.12 g, 7.47 mmol, 88% yield).
Large orange prisms of 2 could be grown from a concentrated
THF solution. 1H NMR (C5D5N, 22 °C) (2′): δ 0.56 (s, 12H,
SiMe), 1.45 (s, 18H, para-tBu), 1.60 (q, J ) 3.23 Hz, 16H, THF),
2.17 (s, 12H, C5Me4), 2.30 (s, 36H, ortho-tBu), 2.60 (s, 12H,
C5Me4), 3.63 (q, J ) 3.23 Hz, 16H, THF), 7.48 (s, 4H, C6H2).
13C NMR (C5D5N, 22 °C): δ 8.29 (s, 1C, SiMe2), 8.38 (s, 1C,
SiMe2), 11.99 (s, 2C, C5Me4), 15.35 (s, 1C, C5Me4), 15.40 (s, 1C,
C5Me4), 25.84 (s, 2C, THF), 32.27 (s, 3C, CMe3), 34.61 (s, 1C,
para-CMe3), 34.86 (s, 3C, CMe3), 35.01 (s, 3C, CMe3), 39.68 (s,
2C, ortho-CMe3), 67.87 (s, 2C, THF), 111.21 (s, 2C, C5Me4),
116.48 (s, 2C, C5Me4), 117.81 (s, 2C, meta-C6H2), 135.91 (s, 1C,
ipso-C5Me4), 141.20 (s, 1C, para-C6H2), 155.40 (d, 1C, J P-C
)
1
73.3 Hz, ipso-C6H2), 157.31 (s, 2C, ortho-C6H2). 31P NMR
(C5D5N, 22 °C): δ -124.4 (s). Anal. Calcd for C90H158K4O8P2-
Si2 (2): C, 65.80; H, 9.69; for C74H126K4O4P2Si2 (2-4THF): C,
65.63; H, 9.38; for C58H94K4P2Si2 (2-8THF): C, 65.36; H, 8.89.
Found: C, 64.24-64.83, H, 9.58-9.51. The low value of the
observed carbon content was probably due to formation of
incombustible carbide species.26
2H, C6H2). H NMR (C6D6, 22 °C): δ -4.53 (br s, 6H, SiMe),
0.06 (br s, 36H, NMe); 2.67 (br s, 9H, para-tBu), 6.86 (br s,
6H, C5Me4), 8.36 (br s, 18H, ortho-tBu), 9.55 (br s, 2H, C6H2),
14.73 (br s, 6H, C5Me4). Anal. Calcd for C41H83N6O2P3SiSm
(5): C, 51.11; H, 8.68. Found: C, 48.08-50.17; H, 8.47-8.65.
The low value of the observed carbon content was probably
due to formation of incombustible carbide species.26
Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Sm (d m e)2 (6). Dissolving
of 3′ (0.100 mg, 0.148 mmol) in dimethoxyethane (DME) gave
a dark brown solution. After removal of the solvent under
vacuum, the residue was washed with hexane and dried to
yield 6 as a dark brown powder (0.096 g, 0.122 mmol, 83%
yield). Black cubic crystals of 6 were obtained by layering of
Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Sm (th f)n (3, n ) 3; 3′, n
) 1). To a dark blue THF solution (15 mL) of SmI2(thf)2 (0.548
g, 1 mmol) was added 2′ (0.677 g, 0.5 mmol), which resulted
in immediate formation of a cloudy dark brown solution. After
the mixture was stirred for 45 min, toluene (7 mL) was added
and was then stirred for 5 min to fully precipitate KI. After
filtration and evaporation of the solvent, the residue was
dissolved in THF. The THF solution was concentrated under
reduced pressure, and hexane was layered to precipitate dark
crystals of 3, which after being dried under vacuum for 3 h
yielded 3′ (3-2THF) as a brown powder (0.447 g, 0.660 mmol,
66% yield). 1H NMR (C4D8O, 22 °C): δ -1.53 (br s, 6H, SiMe),
1.36 (br s, 6H, C5Me4), 1.94 (br s, 9H, para-tBu), 3.21 (br s,
6H, C5Me4), 4.55 (br s, 18H, ortho-tBu), 7.73 (br s, 2H, C6H2).
1H NMR (C5D5N, 22 °C): δ -0.60 (br s, 6H, SiMe), 0.31 (br s,
6H, C5Me4), 1.60 (q, J ) 3.23 Hz, 4H, THF), 2.11 (br s, 9H,
1
hexane to a concentrated DME solution. H NMR (C5D5N, 22
°C): δ -0.74 (br s, 6H, SiMe), 0.13 (br s, 6H, C5Me4), 2.08 (br
s, 9H, para-tBu), 2.25 (br s, 6H, C5Me4), 3.28 (s, 12H, OMe),
3.47 (s, 8H, OCH2), 4.65 (s, 18H, ortho-tBu), 8.27 (s, 2H, C6H2).
1H NMR (C4D8O, 22 °C): δ -1.65 (br s, 6H, SiMe), 1.15 (br s,
6H, C5Me4), 1.98 (br s, 9H, para-tBu), 2.70 (br s, 6H, C5Me4),
2.83 (s, 8H, OCH2), 4.31 (s, 12H, OMe), 4.73 (br s, 18H, ortho-
tBu), 7.80 (br s, 2H, C6H2). Anal. Calcd for C37H67O4PSiSm
(6): C, 56.59; H, 8.60. Found: C, 53.34-53.54; H, 8.27-8.42.
The low value of the observed carbon content was probably
due to formation of incombustible carbide species.26
[Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Sm (th f)]2(µ:η2-OCP h 2)‚
THF (7‚THF ). To 3′ (0.272 g, 0.402 mmol) was added ben-
zophenone (0.037 g, 0.201 mmol) in THF (10 mL). The
resulting green solution was stirred at room temperature for
1 h. After reduction of the solution volume under reduced
pressure, hexane was layered to give 7‚THF as dark green
crystals, which after being dried, yielded 7 (0.200 g, 0.129
(26) Failure in obtaining satisfactory microanalytical data for some
lanthanide complexes bearing P atom-containing ligands was also
mentioned previously by other groups. For examples, see: (a) Nief,
F.; Ricard, L. J . Organomet. Chem. 1994, 464, 149; 1997, 529, 357. (b)
Rabe, G. W.; Ziller, J . W. Inorg. Chem. 1995, 34, 5378. (c) Gro¨b, T.;
Seybert, G.; Massa, W.; Weller, F.; Palaniswami, R.; Greiner, A.;
Dhnicke, K. Angew. Chem., Int. Ed. 2000, 39, 4373. See also refs 4,
11d.

4572 Organometallics, Vol. 20, No. 22, 2001
Tardif et al.
mmol, 64% yield). 1H NMR (C5D5N, 22 °C): δ -1.06 (s, 3H,
SiMe), -0.50 (s, 3H, SiMe), 1.39 (s, 9H, tBu), 1.47 (s, 9H, tBu),
t
1.50 (s, 9H, Bu), 1.52 (s, 3H, C5Me4), 1.61 (q, J ) 3.08 Hz,
4H, THF), 1.83 (s, 3H, C5Me4), 1.98 (s, 3H, C5Me4), 2.24 (s,
3H, C5Me4), 3.64 (q, J ) 3.08 Hz, 4H, THF), 7.38 (s, 1H, C6H2),
7.53 (s, 1H, C6H2), 7.63 (t, J ) 7.5 Hz, 1H, Ph), 7.75 (t, J ) 7.5
Hz, 2H, Ph), 9.48 (d, J ) 7.5 Hz, 2H, Ph). Anal. Calcd for
C
79H120O3P2Si2Sm2 (7): C, 61.75; H, 7.87. Found: C, 57.42-
59.30; H, 7.77-7.88. The low value of the observed carbon
content was probably due to formation of incombustible carbide
species.26
[Me2Si(C5Me4)(P C6H2tBu 3-2,4,6)Sm (µ-I)(th f)]2 (8). A tolu-
ene solution (30 mL) of ICH2CH2I (0.200 g, 0.709 mmol) was
slowly added to 3′ (0.904 g, 1.335 mmol). The resulting dark
orange solution was stirred at room temperature for 4 h.
Removal of the solvent under vacuum afforded a pale orange
residue, which was washed with hexane and dried under
vacuum to give 8 as an orange powder (0.840, 0.522 mmol,
78% yield). Orange crystals of 8 were obtained from benzene/
hexane. 1H NMR (C5D5N, 22 °C): δ 0.42 (s, 6H, SiMe), 1.27
(s, 9H, para-tBu), 1.36 (s, 18H, ortho-tBu), 1.60 (m, 4H, THF),
1.64 (s, 6H, C5Me4), 1.77 (s, 6H, C5Me4), 3.64 (m, 4H, THF),
1
7.08 (s, 2H, C6H2). H NMR (C6D6, 22 °C): δ -1.60 (br s, 6H,
SiMe), -0.39 (br s, 18H, ortho-tBu), 0.33 (br s, 6H, C5Me4),
1.23 (m, 4H, THF), 1.38 (s, 9H, para-tBu), 1.61 (s, 6H, C5Me4),
2.00 (m, 4H, THF), 7.27 (s, 2H, C6H2). Anal. Calcd for
C
66H110O2P2Si2I2Sm2: C, 49.29; H, 6.89. Found: C, 48.66-
48.75; H, 6.85-6.89. The low value of the observed carbon
content was probably due to formation of incombustible carbide
species.26
X-r a y Cr ysta llogr a ph ic Stu d ies. Crystals for X-ray analy-
ses were obtained as described in the preparations. The
crystals were manipulated in the glovebox under a microscope
mounted on the glovebox window and were sealed in thin-
walled glass capillaries. Data collections for 1, 2, 5, and 6 were
performed at 20 °C on a Rigaku RAXIS CS imaging plate
diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.71070 Å). The structures of 1, 2, 5, and 6 were solved
by using the teXsan software package. Data collections for 4,
7, and 8 were performed at 20 °C on a Bruker SMART APEX
diffractometer with a CCD area detector, using graphite-
monochromated Mo KR radiation (λ ) 0.71069 Å). The deter-
mination of crystal class and unit cell parameters was carried
out by the SMART program package. The raw frame data were
processed using SAINT and SADABS to yield the reflection
data file. The structures of 4, 7, and 8 were solved by using
the SHELXTL program. Refinements were performed on F for
1, 2, 5, and 6 and on F2 for 4, 7, and 8 anisotropically for all
non-hydrogen atoms by the full-matrix least-squares method.
The hydrogen atom on the P atom in 1 was located from the
difference Fourier map and was refined isotropically. Other
hydrogen atoms were placed at the calculated positions and
were included in the structure calculation without further
refinement of the parameters. The residual electron densities
were of no chemical significance. Crystal data and processing
parameters are summarized in Table 2.
P olym er iza tion of Eth ylen e. In the glovebox, 3′ (34 mg,
0.05 mmol), a magnetic stir bar, and toluene (15 mL) were
placed in a 100 mL three-neck flask. The flask was taken
outside, set in a water bath (25 °C), and then connected to a
Schlenk line, a well-purged ethylene line, and a mercury-
sealed stopper. Introduction of ethylene resulted in immediate
formation (precipitation) of polyethylene. The mixture was
stirred for 15 min, during which a slightly positive ethylene
pressure was maintained by the stopper. MeOH (20 mL) was
added. The resultant mixture was poured into 300 mL of
MeOH in a 1 L beaker and then stirred to further precipitate
the polymer product. After filtration, the polymer product was
dried under vacuum in an oven (80 °C) overnight, yielding 170
mg of polyethylene. Characterization of this polymer was

Silylene-Linked Cyclopentadienyl-Phosphido Complex
Organometallics, Vol. 20, No. 22, 2001 4573
difficult because of its low solubility (insoluble in ortho-
dichlorobenzene even at 135 °C).
The reactor was cooled to -78 °C, and butadiene (2.2 mL, 1.35
g, 25 mmol) was then introduced. The resulting pale yellow
solution was warmed to 50 °C and stirred vigorously for 80
min. The polymerization was terminated by pouring the
mixture into a large quantity of methanol containing a small
amount of hydrochloric acid (ca. 0.5 M) and butylhydroxytolu-
ene (BHT) as a stabilizer agent. The polymer was isolated by
decantation and dried under reduced pressure at 60 °C
overnight (0.877 g, 65% yield). The microstructure of the
polymer was measured by 1H NMR and 13C NMR spectroscopy
in CDCl3. The molecular weight and molecular weight distri-
P olym er iza tion of E-Ca p r ola cton e (CL). In the glovebox,
3′ (14 mg, 0.02 mmol) was dissolved in 20 mL of toluene in a
two-neck flask which was equipped with a magnetic stir bar
and a dropping funnel containing 2.28 g of CL (20 mmol). The
flask was taken outside and connected to a Schlenk line. CL
was added through the funnel with vigorous stirring. The color
of the mixture changed immediately from brown to pale yellow,
and the resulting pale yellow solution quickly became viscous.
The magnetic stirring was ceased within a minute owing to
the viscosity. After 10 min, methanol was added to precipitate
poly(CL), which after filtration was dried at 60 °C overnight
and weighted (2.28 g, 100% yield). The molecular weight and
molecular weight distribution of the polymer were determined
at 40 °C against polystyrene standard by gel permeation
chromatography (GPC) on a Shodex GPC System-11 apparatus
with two KF 805L columns. THF was used as an eluent.
P olym er iza tion of 1,3-Bu ta d ien e. In the glovebox, 3′ (7
mg, 0.01 mmol) and toluene (6.7 mL) were placed in a glass
pressure-reactor. The reactor was taken out from the glovebox,
and MMAO (2.09 mmol, 1.1 mL × 1.9 M in toluene obtained
from Tosoh Finechem Co.) was added. The mixture was stirred
for 5 min at room temperature to give a wine-red solution.
bution were determined at 40 °C against
a polystyrene
standard by GPC on a Shodex GPC System-11 apparatus.
Ack n ow led gm en t. This work was partly supported
by a grant-in-aid from the Ministry of Education,
Culture, Sports, Science and Technology, J apan.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, thermal parameters, and bond distances and
angles for 1, 2, and 4-8. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM010469I