Synthesis of cis-dichloride complexes of Group 6 transition metals bearing alkyne and chalcogen-bridged chelating bis(aryloxo) ligands as catalyst precursors for ring-opening metathesis polymerization

Article abstract of DOI:10.1016/S0022-328X(02)01377-3

Dichlorotungsten complexes, W(η²-RC≡CR)(R₂′tbp)Cl₂ (1-C_s: R = Ph, R₂′tbp = 2,2′-thiobis(4-methyl-6-tert-butylphenoxo) (^tBu₂tbp); 2-C_s: R = Et, R₂′tbp = 2,2′-thiobis(4,6-dimethylphenoxo) (Me₂tbp); 3-C₁: R = Et, R₂′tbp = ^tBu₂tbp; 4-C₁: R = SiMe₃, R₂′tbp = ^tBu₂tbp), 2,2′-tellurobis(4-methyl-6-tert-butylphenol). The C_s symmetric complex 1-C_s isomerized to the C₁ isomer 1-C₁ in solution at room temperature. The molecular structures of 1-C₁, 3-C₁, 5-C₁ and 6-C_s were determined to reveal their six coordinated pseudo-octahedral geometry by X-ray crystallography. The M-C(alkyne) bond distances in the C_s complexes 2-C_s and 6-C_s ranging from 2.014(7) to 2.035(6) A? are apparently shorter than those in the corresponding C₁ complexes 1-C₁, 3-C₁ and 5-C₁ ranging from 2.04(1) to 2.09(1) A?. In accordance with the structural data, the resonances of the alkyne carbons of the C_s complexes in ¹³C-NMR spectra appeared at 233.1-244.5 ppm, typical for four electron donating alkynes, and those of the C₁ complexes appeared at 198.6-215.4 ppm, typical for two electron donating alkynes. The substituent effects of the ligands on the catalytic behavior of the complexes for the ring-opening metathesis polymerization of norbornene derivatives were studied in the presence of Mg(CH₂SiMe₃)₂ as a cocatalyst. The catalytic activities of the sulfur-bridged complexes tend to increase with increasing the bulkiness of acetylene ligand. The tellurium-bridged complex 5-C₁ was found to be remarkably more active than the corresponding sulfur-bridged complexes.

Full text of DOI:10.1016/S0022-328X(02)01377-3

Journal of Organometallic Chemistry 654 (2002) 74Á82
/
www.elsevier.com/locate/jorganchem
Synthesis of cis-dichloride complexes of Group 6 transition metals
bearing alkyne and chalcogen-bridged chelating bis(aryloxo) ligands
as catalyst precursors for ring-opening metathesis polymerization
Yoshinori Takashima a, Yuushou Nakayama b, Hajime Yasuda b, Akira Nakamura c,
Akira Harada a,*
a Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
b Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
c OM Research, 7-2-1308, Minami-ohgimachi, Kita-ku, Osaka 530-0052, Japan
Received 15 January 2002; received in revised form 5 February 2002; accepted 5 March 2002
Abstract
Dichlorotungsten complexes, W(h2-RCÅ
/
CR)(R2tbp)Cl2 (1-Cs: Rꢀ
/
Ph, R2tbpꢀ
/
2,2?-thiobis(4-methyl-6-tert-butylphenoxo)
?
?
(tBu2tbp); 2-Cs : Rꢀ
/
Et, R2tbpꢀ
tBu2tbp), W(h2-PhCÅCPh)(tBu2Tebp)Cl2 (3-C1: t Bu2Tebpꢀ
Mo(h2-PhCÅCPh)(tBu2tbp)Cl2 (6-Cs) were prepared by the reaction of W(h2-RCÅ
/
2,2?-thiobis(4,6-dimethylphenoxo) (Me2tbp); 3-C1: Rꢀ
/
Et, R2tbpꢀ
/
tBu2tbp; 4-C1: Rꢀ
SiMe3,
/
?
?
?
R2tbpꢀ
/
/
/
2,2?-tellurobis(4-methyl-6-tert-butylphenoxo) (5-C1) and
/
/
CR)Cl4 (RꢀPh, Et, SiMe3) with 2,2?-
/
thiobis(4-methyl-6-tert-butylphenol), 2,2?-thiobis(4,6-dimethylphenol) or with 2,2?-tellurobis(4-methyl-6-tert-butylphenol). The Cs
symmetric complex 1-Cs isomerized to the C1 isomer 1-C1 in solution at room temperature. The molecular structures of 1-C1, 3-C1,
5-C1 and 6-Cs were determined to reveal their six coordinated pseudo-octahedral geometry by X-ray crystallography. The MÃ
/
˚
C(alkyne) bond distances in the Cs complexes 2-Cs and 6-Cs ranging from 2.014(7) to 2.035(6) A are apparently shorter than those
˚
in the corresponding C1 complexes 1-C1, 3-C1 and 5-C1 ranging from 2.04(1) to 2.09(1) A. In accordance with the structural data, the
resonances of the alkyne carbons of the Cs complexes in 13C-NMR spectra appeared at 233.1Á
/
244.5 ppm, typical for four electron
215.4 ppm, typical for two electron donating alkynes. The
donating alkynes, and those of the C1 complexes appeared at 198.6Á
/
substituent effects of the ligands on the catalytic behavior of the complexes for the ring-opening metathesis polymerization of
norbornene derivatives were studied in the presence of Mg(CH2SiMe3)2 as a cocatalyst. The catalytic activities of the sulfur-bridged
complexes tend to increase with increasing the bulkiness of acetylene ligand. The tellurium-bridged complex 5-C1 was found to be
remarkably more active than the corresponding sulfur-bridged complexes. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Group 6 transition metal complexes; Alkyne ligand; Chalcogen-bridged bis(aryloxo) ligand; Ring-opening metathesis polymerization;
Stereo selectivity
1. Introduction
tungsten complexes [3], and can be regarded as dianionic
p-donors like imido or oxo ligands [4]. Most of the
reported Group 6 alkyne complexes have carbonyl and
cyclopentadienyl (Cp) type ligands [5], and those with-
out carbonyl and Cp ligands are relatively rare [6].
We recently reported a series of new tungsten dialkyl
The importance of coordinatively unsaturated alkyne
complexes of molybdenum and tungsten has been
known since 1963 reported for the zerovalent tris(alk-
yne) complex [W(CO)(h2-hex-3-yne)3] [1] and has been
highlighted by the extensive review on Mo(II) and W(II)
alkyne complexes by Templeton [2]. The alkyne ligands
can act as variable electron donors from two to four
electron donors in mononuclear molybdenum and
complexes bearing diphenylacetylene and OÃ
dentate chelating diaryloxo ligands, W(h2-PhCÅ
CPh)(tBu2tbp)R2 (tBu2tbpꢀ
2,2?-thiobis(4-methyl-6-
tert-butylphenoxo); RꢀCH2SiMe3, CH2Ph, CH3),
/
SÃ
/
O tri-
/
/
/
which initiate the ROMP of norbornene to give
poly(norbornene) with high molecular weight and high
cis-content [7]. On the other hand, we also studied the
* Corresponding author. Fax: ꢁ81-6-6850-5445.
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 3 7 7 - 3

Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á
/82
75
synthesis and reactivity of titanium complexes having a
tellurium bridged chelating diaryloxo ligand, {2,2?-Te(4-
Me-6-tBuC6H2O)2} TiX2 (XꢀCl, OiPr) [8]. These
/
complexes catalyzed lower activity in polymerization
of ethylene [8] and better living nature in polymerization
of o-caprolactone and
L-lactide in comparison with the
corresponding sulfur-bridged complexes [9]. This en-
couraged us to investigate the effect of the bridging
atom of the chelating diaryloxo ligand on the ROMP of
norbornene by tungsten complexes as well as the alkyl
substituent effects of the ligands. Here we report the
synthesis and structures of cis-dichloride complexes of
Group 6 transition metal complexes bearing alkyne and
chalcogen-bridged chelating bis(aryloxo) ligands, and
their catalytic behavior for the ROMP of norbornene.
2. Results and discussion
Fig. 1. ORTEP drawing of C1-W(h2-PhCÅ
with a numbering scheme.
/
CPh)(t Bu2tbp)Cl2 (1-C1)
2.1. Synthesis and structures of dichlorotungsten
complexes 1-Cs Á6-Cs
/
1
The H-NMR spectra of the complexes 1-Cs, 2-Cs
and 6-Cs showed one singlet for the protons of the two
tert-butyl or methyl substituents at 6-position and one
singlet for the protons of the two methyl substituents at
4-position, while the aromatic protons at 3- and 5-
positions appeared as two doublets. In 13C-NMR
spectra of 1-Cs, 2-Cs and 6-Cs, the alkyne carbon
resonances appeared as a single peak at 236.5, 244.5
and 233.1 ppm, respectively. The complexes 3-C1, 4-C1
and 5-C1 showed two singlets for the protons of the two
tert-butyl at 6-position and two singlets for the protons
of the two methyl substituents at 4-position, while the
aromatic protons at 3- and 5-positions appeared as four
The reaction of W(h2-RCÅ
SiMe3) with 2,2?-E(4-Me-6-R?C6H2OH)2 (R?ꢀt
Me; EꢀS, Te) gave dichlorotungsten complexes,
W(h2-RCÅ
/
CR)Cl4 (Rꢀ
/
Ph, Et,
Bu,
/
/
?
/
CR)(R2tbp)Cl2
tBu2tbp; 2-Cs [7], Rꢀ
bis(4,6-dimethyl-phenoxo) (Me2tbp); 3-C1, Rꢀ
(1-Cs
[7],
Rꢀ
2,2?-thio-
Et;
tBu2tbp)
CPh)(tBu2Tebp)Cl2 (5-C1, tBu2-
2,2?-tellurobis(4-methyl-6-tert-butylphenoxo))
as shown in Eqs. (1) and (2). A molybdenum analogue,
Mo(h2-PhCÅCPh)(tBu2tbp)Cl2 (6-Cs), was also pre-
pared according to the literature (Eq. (1)) [7].
/Ph,
?
?
R2tbpꢀ
/
/
Et; R2tbpꢀ
/
/
R2tbpꢀ
and W(h2-PhCÅ
Tebpꢀ
/
tBu2tbp; 4-C1, Rꢀ
/
SiMe3; R2tbpꢀ
/
?
?
/
/
/

76
Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á82
/
doublets. In the 13C-NMR spectrum, the alkyne carbon
resonances were observed as two peaks at 208.5 and
198.6 ppm for 3-C1, 202.2 and 190.1 ppm for 4-C1, and
at 215.4 and 201.8 ppm for 5-C1. These data together
with the HÁ1
1
/
H-NOESY, HMQC and HMBC spectra
of 1Á6 suggested that 1-Cs, 2-Cs and 6-Cs had Cs
/
symmetric structure and that 3-C1, 4-C1 and 5-C1 had
C1 symmetric structure, which were also supported by
X-ray crystallography of 2-Cs, 3-C1, 5-C1 and 6-Cs (vide
1
infra). The variable temperature H-NMR spectra of 3-
C1 in toluene-d8 showed the coalescence point for the
four methylene alkyne proton resonances at about ꢂ
20 8C, and an approximate value of DG%ꢀ
13.2 kcal
molꢂ1 for the alkyne rotation could be estimated.
/
/
The Cs complex 1-Cs gradually isomerized to C1
complex 1-C1 in solution at room temperature (Eq. (3)),
which showed two singlets for the protons of the two
tert-butyl groups at 6-position and two singlets for those
of the two methyl substituents at 4-position, and it was
also supported by X-ray crystallography of 1-C1 (vide
infra). We have already reported a similar isomerization
of the corresponding bis(trimethylsilylmethyl) complex,
Fig. 2. ORTEP drawing of C1-W(h2-EtCÅ
a numbering scheme.
/
CEt)(t Bu2tbp)Cl2 (3-C1) with
oxygen atom of the chelating diaryloxo ligands. The
complex 6-Cs was revealed to have Cs structure in which
the alkyne ligands were at trans position to the sulfur
atom of the tBu2tbp ligand, like the geometry of
W(h2-PhCÅ
/
CPh)(tBu2tbp)(CH2SiMe3)2, from Cs sym-
metric structure to C1 symmetric structure [7]. The least
and most sterically crowded complexes, 2-Cs and 6-Cs,
did not isomerize to C1 structure under the same
conditions. We speculate that the Cs structure of 2
would thermodynamically more stable than C1 struc-
ture, while the Cs structure of 6 might be kinetically
stabilized.
complex 2-Cs. The WÃ
symmetric 3-hexyne complex 3-C1 (2.549(2) A) is
significantly shorter than that of the Cs 3-hexyne
/
S bond distance of the C1
˚
˚
complex 2-Cs (2.638(2) A) due to the weaker trans
influence of the chloride ligand than that of the 3-hexyne
ligand, and is also shorter than that of the C1
˚
diphenylacetylene complex 1-C1 (2.604(2) A). The WÃ
/
˚
Te bond distance (2.828(5) A) of 5-C1 is considerably
shorter than the TiÃ
/
Te distances in [Ti(tBu2Tebp)Cl2]2
t
(2.933(1) A) [8] and [Ti( Bu2Tebp)(O Pr)2]2 (3.021(1) A)
i
˚
˚
ð3Þ
2.2. Molecular structures of dichlorotungsten complexes
1-C1, 3-C1, 5-C1 and 6-Cs by X-ray analysis
Figs. 1Á4 show the molecular structures of 1-C1, 3-C1,
/
5-C1 and 6-Cs determined by X-ray crystallography,
respectively. Selected bond distances and angles of these
complexes are summarized in Table 1, which also
includes those of the already reported 2-Cs for compar-
ison [7]. Regarding the alkyne ligands as monodentate
ligands, the coordination geometry around the metal
center of these complexes can be described as pseudo-
octahedral. The tBu2tbp and Me2tbp ligands coordinate
to tungsten in a facial fashion. The complexes 1-C1, 3-C1
and 5-C1 were revealed to have C1 structure in which the
alkyne ligands were at trans position to one of the
Fig. 3. ORTEP drawing of C1-W(h2-PhCÅ
with a numbering scheme.
/
CPh)(t Bu2Tebp)Cl2 (5-C1)

Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á
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77
the bridging tellurium atom coordinate to tungsten more
strongly than the bridging sulfur atom, as observed in
the titanium analogues [8]. This should make the trans
ligand to tellurium more labile in comparison with those
trans to sulfur in the sulfur-bridged complexes. The
distortion of Cl1Ã
/
WÃ
/
Cl2 angle from the octahedral
geometry in 3-C1 (101.4(1)8) is significantly larger than
that in 1-C1 (97.56(10)8), 2-Cs (86.65(7)8) and 5-C1
(91.8(1)8), while the O1Ã
/
WÃO2 angle in 5-C1 (86.5(3)8)
/
is more deviated from the octahedral geometry than that
in 1-C1 (88.2(3)8), 2-Cs (89.4(2)8) and 3-C1 (88.7(2)8).
The bond distances of the molybdenum complex 6-Cs
are similar to those of the corresponding tungsten
complexes, while the OÃ
considerably wider than the OÃ
tungsten complexes.
/
MoÃ
/
O angle of 6-Cs is
/
WÃO angles of the
/
The most notable difference between Cs and C1
complexes is in the bonding mode of the alkyne ligands.
The WÃ
/
C(alkyne) bond distances in the Cs complex 2-
˚
Cs (2.014(7) A) are apparently shorter than those in the
corresponding C1 complexes 1-C1, 3-C1 and 5-C1 ran-
Fig. 4. ORTEP drawing of Cs -Mo(h2-PhCÅ
with a numbering scheme.
/
CPh)(t Bu2tbp)Cl2 (6-Cs )
˚
ging from 2.04(1) to 2.09(1) A, indicating that the alkyne
ligands in the Cs complex coordinate to tungsten more
strongly than those in the C1 complexes. In accordance
with the structural data, the resonances of the alkyne
carbons of the Cs complexes 2-Cs and 6-Cs appeared at
[8] taking into account of similar ionic radii of W6ꢁ(0.74
4ꢁ
˚
A) and Ti (0.745 A) [10] due to the stronger coordina-
˚
233.1Á
244.5 ppm in 13C-NMR spectra, typically for
/
tion of diphenylacetylene ligand. Although the WÃ
/Te
four electron donating alkynes [4]. The 13C-NMR
spectra of the C1 complexes showed signals of the
bond distance of 5-C1 is longer than the WÃS bond
/
˚
distance of 1-C1 (2.604(2) A) and 3-C1 (2.549(2) A), the
˚
W-terminal Cl bond distances trans to tellurium in 5-C1
˚
alkyne carbons at 206.7Á215.4 ppm, which indicated
two electron donating alkynes [4]. Thus, the alkyne
ligands in Cs complexes can be considered as four
/
(2.350(5) A) is slightly longer than those of 1-C1
˚
(2.325(3) A) and 3-C1 (2.337(3) A). This suggests that
˚
Table 1
Selected bond distances (A) and angles (8) of complexes 1-C1, 2-Cs a, 3-C1, 5-C1, and 6-Cs
˚
a
Complex
1-C1
2-Cs
3-C1
5-C1
6-Cs
Bond distances
MÃO
2.029(6) (O1)
1.890(7) (O2)
2.604(2)
1.931(5) (O1)
1.945(5) (O2)
2.638(2)
1.878(5) (O1)
2.008(6) (O2)
2.549(2)
2.030(7) (O1)
1.892(7) (O2)
2.828(5)
1.947(4) (O1)
1.947(4) (O2)
2.613(2)
MÃE (EꢀS, Te)
MÃC
2.071(9) (C47)
2.069(9) (C57)
2.332(3) (Cl1)
2.325(3) (Cl2)
1.301(13)
2.015(8) (C17)
2.014(7) (C18)
2.350(2) (Cl1)
2.394(2) (Cl2)
1.28(1)
2.04(1) (C25)
2.062(9) (C26)
2.338(2) (Cl1)
2.337(3) (Cl2)
1.21(1)
2.06(1) (C23)
2.09(1) (C24)
2.364(3) (Cl1)
2.350(5) (Cl2)
1.31(1)
2.035(6) (C27)
2.011(6) (C28)
2.385(2) (Cl1)
2.378(2) (Cl2)
1.281(8)
MÃCl
CÅC(alkyne)
Bond angles
OÃMÃO
CÃEÃC (EꢀS, Te)
ClÃMÃCl
88.2(3)
100.7(4)
89.4(2)
102.7(3)
86.65(7)
88.7(2)
103.0(4)
101.4(1)
86.5(3)
91.7(4)
91.8(1)
96.2(2)
107.5(3)
88.68(6)
97.56(10)
125.9(6) (O1)
132.1(6) (O2)
85.1(2) (O1)
104.2(2) (O2)
36.6(4)
MÃOÃC
130.3(4) (O1)
127.2(4) (O2)
89.0(1) (O1)
89.0(2) (O2)
37.1(3)
133.4(5) (O1)
126.2(5) (O2)
155.9(1) (O1)
84.9(2) (O2)
34.4(4)
133.1(6) (O1)
138.6(7) (O2)
85.5(2) (O1)
108.6(2) (O2)
36.9(4)
128.3(4) (O1)
126.7(4) (O2)
84.1(1) (O1)
84.6(1) (O2)
36.9(2)
OÃMÃCl
CÃMÃC
OÃMÃE (EꢀS, Te)
75.3(2)
75.9(2)
77.3(2)
78.4(1)
76.5(2)
79.1(2)
77.0(2)
76.6(2)
78.0(1)
78.5(1)
a
Reference [7].

78
Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á82
/
Table 2
ROMP of norbornene by M(h2-RCÅCR){E(4-Me-6-R?C6H2O)2}Cl2
(MꢀW, Mo) activated with Mg(CH2SiMe3)2
The tellurium-bridged complex 5 system showed
remarkably higher activity than those of the correspond-
ing sulfur-bridged complexes, thus the introduction of
a
b
c
cis-Content (%)
Complex Yield (%) Mn/104 b Mw/Mn
WÃ
/
Te coordination bond is quite effective for enhan-
cing the catalytic activity. The molecular weight of the
polymer obtained by 5 is also higher than those obtained
1-Cs
2-Cs
3-C1
4-C1
5-C1
6-Cs
5.9
B1
8.6
34
40
2.1
51
by 1Á4, thus the higher activity of 5 comes from faster
/
31
38
3.0
2.7
1.6
2.0
59
41
24
54
d
propagation rather than higher concentration of active
species. As mentioned above, the tellurium atom co-
ordinates to tungsten more strongly, this should activate
74
79
69
ꢀ200
e
the WÃ
/
C bond trans to the tellurium in matallacyclo-
In toluene, at 60 8C, [Monomer]0/[M]ꢀ100, [Mg]/[M]ꢀ1,
Timeꢀ1 h.
Methanol-insoluble fraction.
butane intermediates resulting in the faster propagation
in the tellurium-bridged system. Moreover, the C1
structure of 5 would be more favorable for generation
of active species than Cs structure. In contrast to the
sulfur-bridged system, the polymer produced by 5 had
trans-rich structure.
a
b
Determined by GPC analysis in THF calibrated with standard
poly(styrene). Theoretical Mn value is less than the experimental one
[17].
c
1
Microstructure of double bonds in polymer as determined by H-
19].
Bimodal.
NMR spectra [17Á
/
d
e
The molybdenum complex (6-Cs) showed apparently
higher activity than those of the corresponding tungsten
complex (1-Cs) to give a poly(norbornene) with high
molecular weight [7]. Since the molecular structure of 6-
Cs is similar to those of the tungsten derivatives (vide
supra), the higher activity of 6-Cs should result from
electronic reasons, possibly higher Lewis acidity of
molybdenum.
Reference [7].
electron donor ligands, while those in C1 complexes can
be regarded as two electron donor ligands. In the C1
isomers, the p-donation from the trans aryloxo oxygen
to the same d-orbital could disturb the donation from
the alkyne ligand.
2.3. Polymerization of norbornene by 1-Cs Á
/
6-Cs/
3. Conclusion
Mg(CH2SiMe3)2
A series of dichlorotungsten complexes of Group 6
metals coordinated with various chelating aryloxo
Without cocatalyst, these complexes 1-Cs Á
/
6-Cs
showed no catalytic activity for the polymerization of
ligands and acetylene ligands, M(h2-RCÅ
/
CR)[E(4-Me-
Ph, Et, SiMe3;
S, Te), was synthesized. These
complexes had Cs or C1 structure depending on the
metal, bridging atom, and substituents. The W(h2-PhCÅ
norbornene, while the addition of Mg(CH2SiMe3)2 to 1-
6-R?C6H2O)2]Cl2 (Mꢀ
/
W, Mo; Rꢀ
/
Cs Á
2. In the polymerization of norbornene by the sulfur-
bridged complexes 1-Cs Á4-C1/Mg(CH2SiMe3)2 systems,
the activities of these complexes are in the order of 4ꢀ
3:1ꢁ2. The use of bulkier alkyne ligands tends to
/6-Cs enhanced the activity as summarized in Table
R?ꢀt
/
Bu, Me; Eꢀ
/
/
/
/
CPh){S(4-Me-6-tBuC6H2O)2}Cl2 (1-Cs) isomerized to
the C1 symmetric isomer in solution at ambient tem-
perature. These complexes showed catalytic activity for
the ring-opening metathesis polymerization of norbor-
nene upon activation with Mg(CH2SiMe3)2. In the
polymerization of norbornene by sulfur-containing
tungsten complexes, the use of more bulky ligands
resulted in the higher polymer yield. The corresponding
tellurium-bridged complex (5-C1) showed remarkably
higher catalytic activity than those of the corresponding
sulfur-bridged complexes.
/
/
show higher activity. Because we assumed that the
isomerization from Cs to C1 structure should occur
before a-H elimination to generate active species [7], the
low activity of 2-Cs could be attributed to its stable Cs
structure. The activity of the 1-Cs/Mg(CH2SiMe3)2
system (6% polymer yield in toluene at 60 8C for 1 h)
is considerably lower than that of the corresponding
bis(trimethylsilylmethyl)
complex,
W(h2-PhCÅ
/
CPh)(tBu2tbp)(CH2SiMe3)2 (7, 63% polymer yield un-
der the same conditions), and even lower than those of
the dibenzyl (22%) and dimethyl (8%) complexes [7].
This might come from the slower generation of active
species in the 1-Cs/Mg(CH2SiMe3)2 system. The cis-
selectivity of the 1-Cs/Mg(CH2SiMe3)2 system (51%)
was lower than that of the corresponding dialkyl
complex 7 (83%), probably due to some interactions
between the active species and the magnesium com-
pounds in the 1-Cs/Mg(CH2SiMe3)2 system.
4. Experimental
4.1. General procedures
All manipulations involving air- and moisture-sensi-
tive organometallic compounds were carried out by the
use of standard Schlenk techniques under an argon

Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á
/82
79
atmosphere. Diethyl ether, THF, toluene, and n-pen-
tane were dried and deoxygenated by distillation over
sodium benzophenone ketyl under argon. Benzene-d6
CEt)[S(4-Me-6-tBuC6H2O)2]Cl2 (3-C1) (0.67 g, 88%) as
black crystals, m.p. 185Á
/
187 8C. 1H-NMR (Toluene-d8,
4
ꢂ
/
60 8C, 270 MHz): d 7.17 (d, JHH
ꢀ1.32 Hz, 1H, 3?-
/
4
C6H2O), 7.15 (d, JHH
and toluene-d8 were distilled from NaÃ/K alloy and
ꢀ1.35 Hz, 1H, 5?-C6H2O), 6.82
/
4
(d, JHH
4
thoroughly degassed by trap-to-trap distillation before
use. Norbornene (bicyclo[2,2,1]hept-2-ene) purchased
from Aldrich Chemical Co. was refluxed over sodium
ꢀ
/
1.16 Hz, 1H, 3-C6H2O), 6.64 (d, JHH
ꢀ
/
1.32
9.25 Hz, 1H,
9.41 Hz, 1H, CH2CH3),
9.89 Hz, 1H, CH2CH3), 3.25 (q,
3
Hz, 1H, 5-C6H2O), 4.50 (q, JHH
ꢀ
/
3
CH2CH3), 4.16 (q, JHH
ꢀ
/
and distilled prior to use. Complexes M(h2-RCÅ
/
/
CR)Cl4
W, RꢀSiMe3;
Ph] [11] and 2,2?-tellurois(4-methyl-6-tert-
3
3.72 (q, JHH
3JHH
ꢀ9.73 Hz, 1H, CH2CH3), 2.19 (s, 3H, 4-Me?),
3
ꢀ
/
[Mꢀ
/
W, Rꢀ
/
Ph; Mꢀ
/
W, Rꢀ
/
Et; Mꢀ
/
/
MꢀMo, Rꢀ
/
/
1.78 (s, 9H, 6-tBu), 1.69 (s, 3H, 4-Me), 1.32 (t, JHH
ꢀ
/
butylphenol) [8] were prepared according to the litera-
ture. 2,2?-Thiobis(4-methyl-6-tert-butylphenol) was sup-
3
7.50 Hz, 6H, CH2CH3), 1.13 (t, JHH
ꢀ7.25 Hz, 6H,
/
CH2CH3), 1.09 (s, 9H, 6-tBu). 13C-NMR (Toluene-d8,
plied by CibaÁGeigy AG.
/
ꢂ
/
60 8C, 67.5 MHz): 208.5 (C?Et), 198.6 (CEt), 165.7
1
The H- (500, 400 and 270 MHz), and 13C- (125, 100
and 67.5 MHz) NMR spectra in benzene-d6 and toluene-
d8 were measured on JEOL JNM-LA500, JEOL JNM-
GSX400 and JEOL JNM-EX270 spectrometers. Assign-
(1?-C6H2O), 161.3 (1-C6H2O), 142.6 (6?-C6H2O), 139.0
(6-C6H2O), 133.9 (4?-C6H2O), 130.5 (5?-C6H2O), 130.1
(4-C6H2O), 129.2 (5-C6H2O), 128.4 (3?-C6H2O), 127.6
(3-C6H2O), 124.6 (2?-C6H2O), 120.0 (2-C6H2O), 36.8
(CH2CH3), 36.0 (6-C?Me3), 35.0 (6-CMe3), 29.8 (6-
1
ments of H- and 13C-NMR peaks for some complexes
1
1
were aided by 2D HÁ1
/
H-NOESY, 2D HÁ1
H-COSY,
/
?
CMe3), 29.2 (6-CMe3), 21.2 (4-Me?), 20.50(4-Me), 16.4
2D HMQC and 2D HMBC spectra. Elemental analyses
were performed at Elemental Analysis Center, Faculty
of Science, Osaka University. All melting points (m.p.)
of the complexes were measured in sealed tubes under an
argon atmosphere. ESIMS measurements were per-
(CH2C?H3), 16.3 (CH2CH3). Anal. Calc. for
C28H38Cl2O2SW: C, 48.50; H, 5.52. Found: C, 48.80;
H, 5.49%.
formed on a PerkinÁ
meter. W(h2-PhCÅCPh)[S(4-Me-6-tBuC6H2O)2]Cl2 (1-
Cs), W(h2-EtCÅ
CEt)[S(4,6-Me2C6H2O)2]Cl2 (2-Cs) and
Mo(h2-PhCÅCPh)[S(4-Me-6-tBuC6H2O)2]Cl2
(6-Cs)
were prepared according to the literature [7].
/
Elmer/Sciex API III plus spectro-
/
4.4. Preparation of W(h2-Me3SiCÅ
6-tBuC6H2O)2]Cl2 (4-C1)
/
CSiMe3)[S(4-Me-
/
/
A toluene solution of 2,2?-S(4-Me-6-tBuC6H2OH)2
(0.26 g, 0.72 mmol) was added to a solution of W(h2-
4.2. Isomerization of 1 from Cs complex to C1 complex
Me3SiCÅ
/
CSiMe3)Cl4 (0.36 g, 0.72 mmol) in a mixture of
toluene (35 ml) and Et2O (5 ml) at ꢂ
/
78 8C. The
Complex 1-Cs was dissolved in C6D6 (0.6 ml) in a 5
mm NMR tube, which was sealed under argon and kept
at room temperature (r.t.). The color changed from red
to pale orange, and the 1H-NMR spectrum of the
solution was measured. The conversion was 42% after
reaction mixture was stirred for 10 min and then allowed
to warm to ambient temperature. The color of the
solution changed from red to dark red. After refluxing
the solution for 2 h, all volatiles were removed under
reduced pressure. Recrystallization from a mixture of
1
4 days. H-NMR (C6D6, 30 8C, 270 MHz): d 8.20 (d,
toluene
and
n-pentane
gave
W(h2-Me3SiCÅ
/
4JHH
7.30Á
ꢀ1.35 Hz, 2H, o-PhC), 7.55 (s, 2H, o-PhC?),
/
CSiMe3)[S(4-Me-6-tBuC6H2O)2]Cl2 (4-C1) (0.29 g,
44%) as black crystals. 1H-NMR (C6D6, 30 8C, 500
/6.79 (m, 10H, PhC and 3, 5-C6H2O), 2.21 (s, 3H,
4-Me), 1.82(s, 9H, 6-tBu), 1.77 (s, 3H, 4?-Me), 1.27 (s,
MHz): d 7.30 (s, 4JHH
ꢀ1.51 Hz, 1H, 3?-C6H2O), 7.20 (s,
/
9H, 6?-tBu).
4
1H, 5?-C6H2O), 7.04 (s, JHH
ꢀ1.10 Hz, 1H, 3-C6H2O),
/
4
6.71 (s, JHH
4.3. Preparation of W(h2-EtCÅ
6-tBuC6H2O)2]Cl2 (3-C1)
/CEt)[S(4-Me-
ꢀ1.53 Hz, 1H, 5-C6H2O), 2.21 (s, 3H, 4?-
/
Me), 1.80 (s, 3H, 4-Me), 1.75 (s, 9H, 6?-tBu), 1.03 (s,
t
9H, 6- Bu), 0.75 (s, 9H, SiMe3), 0.43 (s, 9H, SiMe3). 13C-
?
A toluene solution of 2,2?-S(4-Me-6-tBuC6H2OH)2
(0.40 g, 1.11 mmol) was added to a solution of W(h2-
NMR (C6D6, 30 8C, 125 MHz): 202.2 (MeSiC), 190.1
(MeSiC?), 165.7 (1?-C6H2O), 161.4 (1-C6H2O), 143.0 (6?-
C6H2O), 139.7 (6-C6H2O), 130.9 (5?-C6H2O), 130.2 (5-
C6H2O), 134.5 (4?-C6H2O), 131.6 (4-C6H2O), 128.6 (3?-
C6H2O), 127.8 (3-C6H2O), 35.7 (6?-CMe3), 34.4 (6-
CMe3), 29.9 (6?-CMe3), 29.3 (6-CMe3), 20.8 (4?-Me),
EtCÅ
/
CEt)Cl4 (0.45 g, 1.11 mmol) in a mixture of
toluene (35 ml) and Et2O (5 ml) at ꢂ
/
78 8C. The
reaction mixture was stirred for 10 min and then allowed
to warm to ambient temperature. The color of the
solution changed from red to dark red. After refluxing
the solution for 2.5 h, all volatiles were removed under
reduced pressure to give microcrystals. Recrystallization
?
20.7 (4-Me), 2.79 (SiMe3), 1.8 (SiMe3). Anal. Calc. for
C30H48Cl2O2S1Si2W1×0.5C5H12: C, 47.74; H, 6.41.
Found: C, 47.62; H, 6.39%. ESIMS for m/z: 835 [M]ꢂ.
/
from a mixture of THF and n-pentane gave W(h2-EtCÅ
/

80
Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á82
/
4.5. Preparation of W(h2-PhCÅ
6-tBuC6H2O)2]Cl2 (5-C1)
/CPh)[Te(4-Me-
4.7. GPC analysis of the polymers
GPC analyses were carried out using Tosoh TSKgel
HXL-H and -L columns connected to a Tosoh RI-8012
A toluene solution of 2,2?-Te(4-Me-6-tBuC6H2OH)2
(0.39 g, 0.87 mmol) was added to a solution of W(h2-
detector. Samples were prepared in THF (0.1Á0.3% (w/
/
v)) and were filtered through an Advantec DISMIC-
25JP filter in order to remove particulate before injec-
tion. GPC columns were calibrated versus commercially
available polystyrene standards (Polymer Laboratories
Ltd.) whose molecular weight ranged from 500 to
PhCÅ/CPh)Cl4 (0.43 g, 0.87 mmol) in a mixture of
toluene (35 ml) and Et2O (5 ml) at ꢂ
/
78 8C. The
reaction mixture was stirred for 10 min and then allowed
to warm to ambient temperature. The color of the
solution changed from red to dark red. After refluxing
the solution for 2 h, all volatilies were removed under
reduced pressure. Recrystallization from a mixture of
2.15ꢃ
106.
/
toluene and n-pentane gave W(h2-PhCÅ
/
CPh)[Te(4-Me-
4.8. Crystallographic data collections and structure
determination of 1-C1, 3-C1, 5-C1 and 6-Cs
6-tBuC6H2O)2]Cl2 (5) (0.58 g, 76%) as black crystals.
1H-NMR (C6D6, 30 8C, 500 MHz): d 8.15 (d, 2H, o-
PhC), 7.51 (d, 2H, o-Ph?C), 7.29 (t, 2H, m-PhC), 7.20
A crystal of 1-C1 suitable for X-ray diffraction studies
was mounted on a cryoloop. The measurement of 1-C1
was made on a Rigaku R-AXIS-RAPID imaging plate
4
4
(s, JHH
ꢀ
/
2.1 Hz, 1H, 3?-C6H2O), 7.19 (s, JHH
ꢀ2.1
/
Hz, 1H, 5?-C6H2O), 7.14 (t, 2H, m-Ph?C), 6.79 (s,
4
1.37 Hz, 1H, 3-C6H2O), 6.74 (s, JHH
4JHH
ꢀ
/
ꢀ1.83
/
diffractometer with graphite monochromated MoÁ
/
Ka
radiation (lꢀ0.71069). Relevant crystal and data
/
Hz, 1H, 5-C6H2O), 7.08 (d, 1H, p-PhC), 6.94 (d, 1H, p-
Ph?C), 3.62 (m, 2H, THF), 2.16 (s, 3H, 4?-Me), 1.78 (s,
9H, 6?-tBu), 1.72 (s, 3H, 4-Me), 1.46 (m, 2H, THF), 1.23
(s, 9H, 6-tBu). 13C-NMR (C6D6, 30 8C, 125 MHz):
215.4 (PhC), 201.8 (PhC?), 170.9 (1?-C6H2O), 166.2 (1-
C6H2O), 147.5 (1?-PhC), 143.9 (6?-C6H2O), 140.7 (6-
C6H2O), 138.7 (1-PhC), 134.5 (5-C6H2O), 134.3 (4?-
C6H2O), 133.9 (2-PhC), 133.5 (5?-C6H2O), 131.1 (4-
PhC), 131.1 (4-C6H2O), 130.9 (3?-C6H2O), 130.3 (4?-
PhC), 130.0 (3-C6H2O), 129.1 (3?-PhC), 128.9 (3-PhC),
128.8 (2?-PhC), 116.3 (2-C6H2O), 111.9 (2-C6H2O), 67.8
(THF), 35.9 (6?-CMe3), 35.3 (6-CMe3), 30.0 (6?-CMe3),
29.8 (6-CMe3), 25.8 (THF), 20.7 (4?-Me), 20.5 (4-Me).
statistiCs are summarized in Table 3. Indexing was
performed from one oscillations, which were exposed
for 5.0 min. The camera radius was 127.40 mm. Read-
out was performed in the 0.100 mm pixel mode. A
symmetry-related absorption correction using the pro-
gram ABSCOR was applied [12]. The data was corrected
for Lorentz and polarization effects. The structures of
complex 1-C1 was solved by direct methods (SIR-92)
[13], expanded using Fourier techniques (DIRDIF 94)
[14], and refined by full-matrix least-squares refinement
(
SHELXL-97) [15]. In the subsequent refinement the
jFcj)2 was minimized, where jFoj
function av(jFojꢂ
/
and jFcj are the observed and calculated structure
factors amplitudes, respectively. The agreement indices
Anal. Calc. for C36H38Cl2O2TeW×
/
0.5C4H8O: C, 49.55;
H, 4.60. Found: C, 49.79; H, 4.58%. ESIMS for m/z:
884 [M]ꢂ.
are defined as Rꢀ
/
ajjFojꢂ
/
jFcjj/ajFoj and Rwꢀ
/
[av(F2oꢂ
/
Fc2)2/av(Fo2)2]1/2. The positions of all non-
hydrogen atoms for the complexes were found from a
difference Fourier electron density maps and refined
4.6. Polymerization of norbornene
anisotoropically. All hydrogen atoms were placed in
˚
calculated positions (CÃ
/
Hꢀ0.95 A) and kept fixed.
/
A solution of Mg(CH2SiMe3)2 (0.01 mmol) in toluene
The X-ray diffraction studies were carried out in
sealed glass capillaries under an argon atmosphere. The
crystals of complexes 3-C1, 5-C1 and 6-Cs were mounted
on Rigaku AFC-7R or AFC-5R four-circle diffract-
(50 ml) was added to a solution of W(h2-PhCÅ
/
CPh)[S(4-
Me-6-tBuC6H2O)2]Cl2 (1-Cs) (0.01 mmol) in toluene
(0.75 ml) at ꢂ78 8C. The reaction mixture was stirred
for 10 min and then allowed to be stirred at ambient
temperature for 15 min, followed by cooling to ꢂ78 8C.
To this solution of 1-Cs ÁMg(CH2SiMe3)2 in toluene
was added a solution of norbornene (100 equivalents, 1
mmol) in toluene (0.2 ml) at ꢂ78 8C. The reaction
/
ometers for data collection using MoÁ
/
Ka (graphite
/
monochromated, lꢀ0.71069) radiation. Relevant crys-
/
/
tal and data statistics are summarized in Table 3. The
unit cell parameters and the orientation matrix at 23 8C
were determined by a least-squares fit to 2u values of 25
strong higher reflections for these complexes. Three
standard reflections were chosen and monitored every
150 reflections. Empirical absorption correction was
carried out on the basis of an azimuthal scan. Com-
plexes 3-C1, 5-C1 and 6-Cs showed no significant
intensity decay during the data collection. The structures
of the complexes 3-C1, 5-C1 and 6-Cs were solved by
/
mixture was stirred for 5 min and then allowed to be
stirred at 60 8C for 1 h. A large excess of MeOH was
added to the resulting reddish viscous solution to
precipitate a white polymer. The polymer was washed
with MeOH and then dried in vacuo. 1H-NMR (CDCl3,
30 8C, 270 MHz): d 5.39(br), 2.95(br), 2.09(br),
1.92(br), 1.49(br), 1.21 (q(br)).

Y. Takashima et al. / Journal of Organometallic Chemistry 654 (2002) 74Á
/82
81
Table 3
Crystal data and collection parameters for 1-C1, 3-C1, 5-C1 and 6-Cs
Complex
1-C1
3-C1
5-C1
6-Cs
Formula
C36H38Cl2O2SW
789.47
C28H38Cl2O2SW
693.42
C38H42Cl2O2WTe
921.10
C43H46Cl2O2SMo
793.74
Formula weight
Crystal system
Space group
Monoclinic
P21/n (#14)
10.2438(5)
17.1335(8)
19.3165(13)
Monoclinic
P21/a (#14)
16.090(4)
Monoclinic
P21/a (#14)
17.54(3)
Monoclinic
P21/c (#14)
20.014(5)
˚
a (A)
˚
b (A)
11.113(5)
17.029(3)
18.706(9)
12.09(2)
11.021(8)
20.518(6)
˚
c (A)
a (8)
b (8)
96.031(2)
97.79(2)
104.5(1)
115.37(2)
g (8)
3
V (A )
˚
3371.5(3)
4
1.555
3016(1)
4
1.527
3841(9)
4
1.592
4089(3)
4
1.289
Z
Dcalc (g cmꢂ3
F(000)
)
1576.00
36.77
193 (1)
1384.00
41.01
1800.00
39.24
1648.00
5.35
m [MoÁ
Temperature (K)
Scan speed (8 minꢂ1
Scan width (8)
2umax (8)
/
Ka] (cmꢂ1
)
296 (1)
16.0
296 (1)
16.0
296 (1)
16.0
)
1.42ꢁ0.35tan u
55.0
1.00ꢁ0.3tan u
54.9
1.68ꢁ0.35tan u
55.0
Unique data (Rint
)
Number of observations
7512 (0.0809)
5708
387
6936 (0.047)
3447
307
8793 (0.038)
3488
403
9403 (0.105)
4449
442
Number of variables
R
0.0778
0.1654 (all data)
1.409
0.040
0.044
1.23
0.052
0.057
1.20
0.047
0.050
1.66
Rw
Goodness-of-fit
direct methods (SHELXS-86) [16], expanded using Four-
ier techniques (DIRDIF 94) [14], and refined by the full-
matrix least-square method. Measured non-equivalent
the Director, CCDC, 12 Union Road Cambridge CB2
1EZ, UK (Fax: 44-1223-336033; e-mail: depos-
it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
ꢁ
/
reflections with I ꢀ
/
2.0s(I) were used for the structure
determination for 3-C1 and 5-C1. For 6-Cs measured
non-equivalent reflections with I ꢀ3.0s(I) were used. In
/
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/
jFcj)2
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/
ajFoj and Rwꢀ
/
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