Dicationic ruthenium(II) complexes containing bridged η1:η6-phosphinoarene ligands for the ring-opening metathesis polymerization

Article abstract of DOI:10.1016/S1381-1169(00)00229-6

Tertiary phosphines with pendant genes R₂PR' (R = Cy, Ph; R' = CH₂CH₂Ph or CH₂CHPh₂) (1-4) were synthesized and converted to the corresponding chelating ruthenium(II) complexes [RuCl₂(η¹:η⁶-R₂PR')] (1a-4a). Halide exchange yielded [RuI₂(η¹:η⁶-R₂PR')] (1b,3b), which were structurally characterized by single crystal X-ray diffraction. The systems (1a,2a,4a) were activated for ROMP of norbomene by addition of a diazo compound (trimethylsilyldiazomethane) and AgBF₄ (A), by a diazo compound alone (B) or by a combination of the sodium salt NaB(Ar(f))₄(Ar(f) = 3,5-(CF₃)₂C₆H₃) and methanol (C). The influence of the thereby created differing number of accessible coordination sites on the polymerization activity and the polymer microstructure (cis/trans ratio) was investigated. The nucleophilicity of the counter ion was found to play a crucial role in terms of catalytic activity. (C) 2000 Elsevier Science B.V.

Full text of DOI:10.1016/S1381-1169(00)00229-6

Ž
.
Journal of Molecular Catalysis A: Chemical 160 2000 23–33
www.elsevier.comrlocatermolcata
1
6
ž /
Dicationic ruthenium II complexes containing bridged h :h -
phosphinoarene ligands for the ring-opening metathesis
polymerization
Alexandra Abele a, Roland Wursche a, Martti Klinga b, Bernhard Rieger a,)
a
Department of Inorganic Chemistry II, Materials and Catalysis, UniÕersity of Ulm, 89069 Ulm, Germany
b
Laboratory of Inorganic Chemistry, UniÕersity of Helsinki, 00014 Helsinki, Finland
Abstract
X
X
Ž
. Ž
.
.
Tertiary phosphines with pendant arenes R2PR RsCy, Ph; R sCH2CH2Ph or CH2CHPh2 1–4 were synthesized
Ž .
w
Ž
X .x Ž
1a–4a . Halide exchange
1
6
and converted to the corresponding chelating ruthenium II complexes RuCl2 h :h -R2PR
yielded RuI2 h :h -R2PR 1b,3b , which were structurally characterized by single crystal X-ray diffraction. The systems
1
6
w
Ž
X .x Ž
.
Ž
.
Ž
.
.
1a,2a,4a were activated for ROMP of norbornene by addition of a diazo compound trimethylsilyldiazomethane and
Ž . Ž . . Ž
Ž
Ž
.
AgBF4 A , by a diazo compound alone B or by a combination of the sodium salt NaB Arf Arf s3,5- CF3 2C6H3 and
4
Ž .
methanol C . The influence of the thereby created differing number of accessible coordination sites on the polymerization
Ž
.
activity and the polymer microstructure cisrtrans ratio was investigated. The nucleophilicity of the counter ion was found
to play a crucial role in terms of catalytic activity. q 2000 Elsevier Science B.V. All rights reserved.
Ž .
Keywords: Phosphine ligands; Ruthenium II complexes; Chelating complexes; Metathesis; Norbornene
1. Introduction
ruthenium-based catalytic systems due to their
w x
tolerance towards functional groups 2 .
Ž .
Over the past decades, olefin metathesis reac-
tions have attracted growing interest from dif-
ferent fields. For instance, ring closing metathe-
Ruthenium II carbene complexes of the type
`
wŽ
.
x
w
Ž
.
-
PCy3 2Cl2Ru5CH CH5CPh2 and PCy3 2
x
Ž
. Ž
Cl2Ru5CHPh Cyscyclohexyl Grubbs’ ca-
Ž
.
Ž
.
.
talyst were used for the RCM of dienes, ROM
sis RCM , acyclic diene metathesis ADMET
or ring-opening metathesis polymerization
w
x
w x
of olefins or for ROMP 3–5 . Furstner et al. 6
introduced cationic allenylidene ruthenium
¨
Ž
.
ROMP have opened a new and elegant ap-
Ž .
w
Ž
.
proach to low molecular weight compounds as
II complexes like Ru5C5C5CR2 PCy3
Ž
.
x
well as to a wide variety of polymer materials
w x
1 . Attention has been particularly focused on
arene PF6 as excellent catalysts for RCM.
Phosphinoarene ruthenium II dichlorides Ru-
Cl2 arene PR3
ready used by Hafner et al. 7,8 and Demon-
ceau et al. 9 for ROMP of strained cyclic
olefins like norbornene or even cyclooctene-type
Ž .
w
Ž
.Ž
.
x
Ž
.
PR3 sphosphine were al-
w
x
w x
)
Corresponding author.
1381-1169r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
Ž
.
PII: S1381-1169 00 00229-6

(
)
24
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
monomers where the double bond is less
2. Experimental
Ž .
strained. In the case of ruthenium II dichlo-
rides, the activation, i.e. the in situ formation of
carbene complexes, is performed by the addi-
tion of diazo compounds like trimethylsilyldia-
2.1. Materials
All reactions were performed under argon
using standard Schlenk or vacuum-line tech-
niques. Solvents were freshly distilled from
standard drying agents and kept under argon.
Norbornene, styrene derivatives , dicyclo-
hexylphosphine, 2-phenylethylbromide were
reagent grade and used without further purifica-
Ž
. w x
zomethane TMSD 9 , by heating or treatment
w
x
with UV light 7,8 .
Apart from the generation of carbene species,
all these procedures involve the decoordination
of either the phosphine ligand or the aromatic
moiety to form flexible complexes with a low
degree of control over the catalytic process.
This drawback might be overcome by utilizing
more rigid ligand frameworks, for instance
phosphinoarene chelates, which are bound to
Ž
.
w
Ž
.
x
w x
tion. RuCl2 C6H5COOEt
10 , DPDCyPE
2
w
x
Ž
. Ž
Ž
.
. w x
15 and NaB Arf Arf s3,5- CF3 2C6H3 16
4
were prepared according to literature proce-
dures.
1
6
Ž
.
the metal in a h :h fashion. Complexes of
this type have been recently introduced by Ther-
2.2. Ligands and complexes
w
x
w x
rien et al. 10 and Simal et al. 11 . First
applications include the atom transfer radical
(
)
[ ]
2.2.1. Diphenylphospine, C6 H5 2 PH 17
Ž
. w x
polymerization ATPR 12 of vinyl monomers,
olefin cyclopropanation and olefin metathesis
Ž
.
50 g 0.19 mol triphenylphosphine was dis-
solved in 500 ml dried and degassed THF and
w
x
13 , where the influence of chelating and non-
Ž
.
treated with 2.75 g 0.39 mmol of lithium
shavings. The mixture was stirred at room tem-
perature until the lithium was dissolved. The
deep-red solution was carefully hydrolyzed by
dropwise addition of a stochiometric amount of
w
x
chelating catalyst geometries was discussed 11 .
In order to monitor the effect of increasing
steric interaction between substrate and ligand
sphere on activity and regioselectivity in meta-
thesis reactions, we synthesized a series of
phosphine ligands: 2-phenyl-1-diphenylphos-
Ž
.
degassed water 10 ml . After 1 h of additional
stirring, the solvent was removed and the prod-
Ž . Ž
. w x
phinoethane 1 PDPPE 10 , 2-phenyl-1-di-
uct was isolated by vacuum distillation. Yield
Ž . Ž
. w x
cyclohexylphosphinoethane 2 PDCyPE 14 ,
2,2-diphenyl-1-diphenylphosphinoethane
DPDPPE and 2,2-diphenyl-1-dicyclohexyl-
1
Ž
.
Ž
.
28.4 g 80% . H NMR d CDCl3 : 7.63 ppm
Ž .
3
m, 4H, Ar , 7.42 ppm m, 6H, Ar . 31P NMR d
CDCl3 : y39.5 ppm.
Ž
.
Ž
.
Ž
.
Ž
.
Ž . Ž
. w x
phosphinoethane 4 DPDCyPE 15 , which
were subsequently converted to new chelating
1
6
w
Ž
.
x
Ž
. w
( )
2.2.2. 2-Phenyl-1-diphenylphosphinoethane 1
complexes RuCl2 h :h -1
1a , Ru-
1
6
1
6
Ž
.
x
Ž
.
w
.
Ž
.
x
Ž
.
Ž .
Cl2 h :h -2
2a , RuCl2 h :h -3
3a and
6 ml 34 mmol diphenylphosphine, 3.9 ml
1
6
w
Ž
.
x
Ž
Ž
.
Ž
.
RuCl2 h :h -4 4a to be tested in the ROMP
34 mmol styrene free of inhibitor and 280
X
Ž
.
Ž
.
of norbornene. By applying several activation
techniques we obtained catalytically active
species which differ from the number of avail-
able coordination sites and, thus, the degree of
steric interaction between ligand, growing poly-
mer chain and coordinated monomer. This
paper is focused on synthetic and structural
aspects as well as on a discussion of first poly-
merization results.
mg 1.71 mmol a,a -azobis isobutyronitrile
Ž
.
AIBN were dissolved in 20 ml degassed di-
ethyl ether and irradiated with UV light for 24
h. The volatile materials were removed in vac-
uum, the oily residue was recrystallized from
ethanol to afford colourless crystals. Yield 8.5 g
1
Ž
.
Ž
.
Ž
86% . H NMR d CDCl3 : 7.46 ppm m, 4H,
.
Ž
Ž
.
Ž
Ar , 7.32 ppm m, 6H, Ar , 7.25 ppm m, 2H,
Ar , 7.18 ppm m, 3H, Ar , 2.73 ppm m, 2H,
.
.
Ž

(
)
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
25
CH2 , 2.38 ppm m, 2H, CH2 . 31P NMR d
.
Ž
.
.
x
C6H5COOEt
was added. After stirring at
2
Ž
.
Ž
.
Ž
Ž
CDCl3 : y14.8 ppm. MS EI mrz rel inten-
sity : 290 M , 100 , 262 39 , 186 24 , 121
59 , 108 32 , 91 16 , 77 24 , 51 18 .
room temperature, the solution became clear
.
Ž
w
qx
.
Ž
.
.
and was refluxed until the chelating process was
complete according to 31P NMR of the reaction
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
solution . The addition of n-pentane caused the
2.2.3. 2-Phenyl-1-dicyclohexylphosphinoethane
( )
precipitation of the chelating complexes in
quantitative yield.
2
Ž
.
To a solution of 4 g 20 mmol dicyclo-
hexylphosphine in 20 ml of dry THF, 12.5 ml of
1
6
[
(
(
))]
(
)
2.2.5.1. RuCl2 h :h - PDPPE
1a .
Ž
Ž
.
Ž .
a 1.6 M solution of n-butyllithium in THF 20
450 mg 1.55 mmol PDPPE 1 , orange-col-
1
.
Ž
.
Ž
mmol was added at y208C. The deep-red solu-
tion was stirred at room temperature for 1 h. At
ored solid; H NMR d CDCl3 : 7.87 ppm m,
4H, Ar , 7.50 ppm m, 6H, Ar , 6.24 ppm m,
2H, Ar , 6.04 ppm m, 1H, Ar , 5.00 ppm d,
.
Ž
Ž
.
.
Ž
Ž
.
.
Ž
Ž
08C, 2.8 ml 20 mmol 2-phenylethylbromide
was slowly added and the solution became col-
orless. After treatment with a degassed, satu-
rated aqueous solution of ammoniumchloride,
the organic phase was separated and dried over
Na2SO4. The solvent was evaporated. Since
attempts for crystallization failed, the oily
residue was used for complexation without fur-
.
Ž
.
2H, Ar , 2.63 ppm m, 2H, CH2 , 2.63 ppm m,
2H, CH2 . 31P NMR d CDCl3 : 46.8 ppm.
Anal. Calcd. for 1a: C, 51.95; H, 4.11. Found:
C, 51.43; H, 4.13.
.
Ž
.
1
6
[
(
(
))] (
)
2.2.5.2. RuCl2 h :h - PDCYPE
2a .
Ž
.
Ž .
268 mg 1.55 mmol PDCyPE 2 , reddish-
1
Ž
Ž
.
ther purification purity about 75% according to
brown solid; H NMR d CDCl3 : 6.22 ppm
m, 1H, Ar , 5.83 ppm m, 2H, Ar , 5.04 ppm
m, 2H, Ar , 2.93 ppm m, 2H, CH2 , 2.61 ppm
P NMR . Yield: 2.9 g 48% . 1H NMR d
31
.
Ž
.
Ž
Ž
Ž
.
.
Ž
.
.
Ž
.
Ž
.
Ž
Ž
CDCl3 : 7.20 ppm m, 2H, Ar , 7.14 ppm m,
.
Ž
.
Ž
.
Ž
3H, Ar , 2.87 ppm m, 2H, CH2 , 2.68 ppm m,
m, 2H, CH2 , 2.31–1.29 ppm several m, 22H,
Cy . 31P NMR d CDCl3 : 70.4 ppm. Anal.
Calcd for 2a: C, 50.63; H, 6.54. Found: C,
51.07; H, 6.74.
.
Ž
.
Ž
.
2H, CH2 , 1.70–1.16 ppm several m, 22H,
31
.
Ž
.
.
Ž
.
.
Cy . P NMR d CDCl3 : y2.4 ppm. MS EI
Ž
Ž
w
qx
.
Ž
mrz rel intensity : 302 M , 100 , 219 16 ,
Ž
.
Ž .
117 42 , 83 9 .
1
6
[
(
(
))] (
)
2.2.5.3. RuCl2 h :h - DPDPPE
3a .
Ž
.
Ž .
2.2.4. 2,2-Diphenyl-1-diphenylphosphinoethane
567 mg 1.55 mmol DPDPPE 3 , orange, mi-
1
( )
Ž
.
3
crocrystalline solid; H NMR d CDCl3 : 8.02
ppm m, 2H, Ar , 7.58 ppm m, 2H, Ar , 7.47
ppm m, 3H, Ar , 7.36 ppm m, 8H, Ar , 6.23
ppm m, 1H, Ar , 6.15 ppm m, 1H, Ar , 6.00
ppm m, 1H, Ar , 5.39 ppm m, 1H, Ar , 4.94
ppm m, 1H, Ar , 4.00 ppm m, 2H, CH2 , 3.76
ppm m, 1H, CH . P NMR d CDCl3 : 33.5
ppm. Anal. Calcd. for 3a: C, 57.99; H, 4.28.
Found: C, 57.35; H, 4.01.
Ž
.
Ž
.
DPDPPE was synthesized analogously to
Ž .
Ž
.
Ž
.
Ž
.
PDPPE 1 from 4 ml 23 mmol diphenylphos-
X
Ž
.
Ž
.
Ž
.
Ž
Ž
.
phine, 4.1 ml 23 mmol of 1,1 -diphenyl-
ethene and 186 mg 1.1 mmol of AIBN. Re-
Ž
.
Ž
.
.
.
Ž
Ž
.
crystallization from ethanol afforded colourless
needles. Yield: 5.5 g 65% . 1H NMR d
31
Ž
.
Ž
.
Ž
.
Ž
.
Ž
Ž
.
.
Ž
Ž
CDCl3 : 7.37 ppm m, 4H, Ar , 7.21 ppm m,
6H, Ar , 3.93 ppm m, 1H, CH , 2.83 ppm d,
.
31
.
Ž
.
Ž
2H, CH2 . P NMR d CDCl3 :y20.1 ppm.
qx
.
1
6
Ž
.
Ž
.
w
[
(
(
))] (
)
MS EI mrz rel intensity : 366 M , 9 , 262
2.2.5.4. RuCl2 h :h - DPDCYPE
4a .
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
Ž
Ž .
100 , 199 15 , 121 34 , 77 11 .
486 mg 1.55 mmol DPDCyPE 4 , light-orange
1
.
Ž
solid; H NMR d CDCl3 : 7.37 ppm m, 5H,
Ar , 6.25 ppm m, 1H, Ar , 6.12 ppm m, 1H,
Ar , 5.65 ppm m, 1H, Ar , 5.18 ppm m, 2H,
Ar , 3.94 ppm m, 1H, CH , 3.36–3.13 ppm m,
X)] (
)
1
6
[
(
.
Ž
Ž
.
Ž
2.2.5. RuCl2 h :h -PR2 R
1a–4a . To a so-
Ž
.
.
.
.
.
Ž
lution of the phosphine 1–4 1.55 mmol in dry
6
Ž
.
w
Ž
Ž
Ž
chloroform, 500 mg 0.77 mmol RuCl2 h -

(
)
26
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
Ž
.
Fig. 1. Synthesis of phosphine ligands with pendant arene moieties 1–4 .
.
Ž
2H, CH2 , 2.41–1.28 ppm several m, 22H,
2.2.6. Halide exchange
0.043 mmol of 1a or 3a were suspended in
20 ml of degassed acetone. After adding 195
Cy . 31P NMR d CDCl3 : 53.4 ppm. Anal.
Calcd. for 4a: C, 56.72; H, 6.36. Found: C,
56.14; H, 6.24.
.
Ž
.
Ž
.
mg 1.29 mmol NaI, the mixture was stirred for
Ž
.
Fig. 2. Synthesized chelating complexes a: XsCl; b: XsI .

(
)
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
27
Ž
.
Fig. 3. Molecular structure of complexes 1b and 3b ORTEP plot . 1b represents only one of the two independent species present in the unit
cell. In the case of 3b, the enclosed acetone molecule has been omitted. Thermal ellipsoids are at the 50% probability level.
2 h at room temperature. The solvent was re-
moved and the residue dissolved in CH2Cl2 in
order to remove NaCl and excess NaI by filtra-
tion. CH2Cl2 was evaporated and single crystals
Table 1
Crystal data and structure refinement for 1b
1
6
w
Ž
.x Ž .
RuI2 h :h y1 1b
Ž
.
Empirical formula
Formula weight
C20 H19 I2 PRu
645.19
Crystal size mm
Ž .
0.38=0.20=0.12
2.74–25.00
Q range 8
Ž
.
Ž .
193 2
Temperature K
Index ranges
17DhD-14, 17DkD-17, 11DlD-11
˚
Ž
.
w
x
Wavelength A
Crystal system
Space group
0.71073
triclinic
P-1
Reflections collectedrunique
8071r6566 Rint s0.0212
Refinement method
Full-matrix least-squares on F2
˚
Ž
.
Ž . Ž .
as14.385 4 , as95.67 2
Unit cell dimensions A, 8
Datarrestraintsrparameters
6566r36r433
Goodness-of-fit on F2
1.023
Ž . Ž .
bs14.923 4 , bs99.40 3
Ž . Ž .
w
Ž .x
cs9.513 3 , gs99.36 2
Final R indices I)2s I
R1s0.0370, wR2s0.0874
R1s0.0435, wR2s0.0905
0.950 and y1.971
3
˚
Ž
.
Ž
.
Ž
.
Volume A
1971.3 10
R indices all data
3
Ž
.
Z, calculated density grcm
4, 2.174
Largest diffraction peak and
y3
˚
Ž
.
hole erA
y1
Ž
.
Absorption coefficient mm
4.008
1216
Ž
.
F 000
Ž
.
Data collection, cell refinement and data reduction were performed with TEXSAN Molecular Structure Corporation, 1993 . A psi-scan
w
x
Ž
absorption correction was performed, 0.579-T-0.786 28 . Intensities were corrected for Lorentz and polarization effects. For structure
solution SHELXS-97 and structure refinement SHELXL-97 both Sheldrick, 1997 were used. Molecular Graphics: ORTEP III. Non-hydro-
.
gen atom positions were obtained with direct methods and anisotropically refined. Hydrogen atoms were refined on calculated positions.
Ž
Displacement factors of the H atoms were 1.2= to that of the host atom. There are two independent C20 H19 I2 PRu molecules and their
.
symmetry equivalents in one unit cell, Zs4.

(
)
28
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
1
6
w
Ž
Ž
..
x
Ž
.
Ž .
secondary phosphines and styrene derivatives .
X
of
w
RuI 2 h :h - PD PPE
1b
and
1
6
Ž
Ž
..
x
Ž
.
Ž
w x.
RuI2 h :h - DPDPPE
3b were grown from
The tertiary phosphines PR2R , 1 and 3 15
acetone by slow evaporation of the solvent.
2.3. Polymerization procedure
were formed in a radical reaction upon addition
Table 2
4
Ž
.
Atomic coordinates =10 and equivalent isotropic displacement
parameters A =10 for 1b
2
3
˚
Ž
.
In a typical polymerization experiment, 5.6
X
= 10y mmol of RuCl2 h :h -PR 2 R
2
1
6
w
Ž
.x
1b
X
Y
Z
U
eq
Ž
.
1a,2a,4a was dissolved in dry CH2Cl2.
Sodium salt 133 mg 0.15 mmol NaB Arf
Ž .
1850 1
Ž .
1014 1
Ž .
2604 1
Ž .
4079 1
Ž .
2411 1
Ž .
5469 1
Ž .
30 1
Ž .
32 1
I1
I2
Ž
Ž
.
Ž
. .
4
Ž .
3213 1
Ž .
3700 1
Ž .
7463 1
Ž .
5671 1
Ž .
3396 1
Ž .
602 1
Ž .
37 1
Ž .
40 1
I3
I4
Ž
Ž
.
or silver salt 32.8 mg 0.17 mmol AgBF4 or
Ž
.
.
57.7 mg 0.17 mmol AgSbF6 were added
Ž .
2680 1
Ž .
3570 1
Ž .
5046 1
Ž .
21 1
Ru1
Ru2
P1
Ž
.
Ž .
Ž .
Ž .
Ž .
2155 1
6373 1
1044 1
21 1
methods A,C , the solution was filtered under
Ž .
2250 1
Ž .
2357 1
Ž .
6298 2
Ž .
22 1
Ž
.
argon and 1 g 10.6 mmol norbornene was
introduced. Thereafter, 1 ml of a 0.2 M solution
of TMSD in hexanesrCH2Cl2 0.2 mmol
TMSD methods A,B or 0.5 ml dry methanol
Ž .
Ž .
2793 4
Ž .
Ž .
1343 4
Ž .
Ž .
6013 7
Ž .
Ž .
25 1
P2
C1
2449 1
7384 1
y608 2
19 1
Ž
Ž .
Ž .
3715 5
Ž .
Ž .
448 5
Ž .
Ž .
4726 8
Ž .
Ž .
36 2
C2
C3
3288 5
1213 4
4898 7
29 1
. Ž
.
Ž .
Ž .
3179 5
Ž .
2743 5
Ž .
Ž .
Ž .
6832 8
Ž .
6979 7
Ž .
Ž .
39 2
Ž .
31 2
C4
C5
C6
3668 5
y185 5
5690 8
39 2
Ž
.
method C was added and the mixture was
Ž .
y57 5
stirred at room temperature. The polymer was
precipitated into methanol, washed thoroughly
with methanol and dried under vacuum at room
temperature.
Ž .
700 5
Ž .
1026 4
Ž .
426 6
Ž .
Ž .
1435 7
Ž .
6360 7
Ž .
5123 9
Ž .
26 1
Ž .
63 3
C7
C8
1847 4
Ž .
y509 6
Ž .
Ž .
1004 6
Ž
.
Ž .
73 3
C9
1036 8
5124 10
Ž .
y840 5
Ž .
Ž .
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
6385 9
45 2
Ž .
Ž .
Ž .
7631 9
Ž .
40 2
y255 5
1387 5
Ž .
Ž .
1816 5
Ž .
Ž .
678 5
7636 8
34 2
2.4. Physical measurements
Ž .
2802 5
Ž .
Ž .
8133 7
Ž .
30 1
2861 5
Ž .
Ž .
3330 5
Ž .
Ž .
3840 5
8111 8
37 2
1H and 31P NMR spectra were recorded on a
Bruker AMX 500 spectrometer; H chemical
Ž .
3869 4
Ž .
Ž .
6834 7
Ž .
31 2
3869 5
1
Ž .
Ž .
4654 5
Ž .
Ž .
3451 5
6722 8
35 2
Ž .
3376 5
Ž .
Ž .
5433 8
Ž .
37 2
5059 5
shifts are given in ppm relative to internal stan-
dard TMS, 31P chemical shifts were referenced
to external 85% H3PO4. Mass Spectra were
recorded on a Varian GCrMS 2000. Elemental
analyses were performed in the Microanalytical
Section of the University of Ulm. X-ray struc-
ture determination was carried out on a Rigaku
AFC7S diffractometer. The measurements uti-
Ž .
Ž .
4668 5
Ž .
Ž .
3672 5
4223 9
42 2
Ž .
4073 5
Ž .
Ž .
4320 8
Ž .
38 2
3868 5
Ž .
Ž .
3489 5
Ž .
Ž .
4221 5
5606 8
37 2
Ž .
2000 4
Ž .
Ž .
y394 6
Ž .
21 1
8454 4
Ž .
Ž .
8634 4
Ž .
Ž .
1225 4
y1342 7
26 1
Ž .
892 5
Ž .
Ž .
Ž .
31 1
9453 5
y1150 7
Ž .
Ž .
10109 5
Ž .
Ž .
1324 5
y14 8
35 2
Ž .
2107 5
Ž .
Ž .
Ž .
33 2
9941 5
946 8
Ž .
Ž .
9123 4
Ž .
758 7
Ž .
2434 5
29 1
Ž .
3630 4
Ž .
Ž .
Ž .
24 1
7745 4
y1015 7
Ž
.
Ž
lized Mo Ka radiation wavelength 0.71073
Ž .
Ž .
8153 5
Ž .
Ž .
4389 5
87 7
34 2
Ž .
5296 5
Ž .
Ž .
Ž .
42 2
8442 6
y189 8
˚
.
A; fine-focused sealed tube with a graphite
monochromator.
Ž .
Ž .
8334 6
Ž .
Ž .
5463 5
y1569 9
43 2
Ž .
4715 5
Ž .
Ž .
Ž .
38 2
7944 5
y2683 8
Ž .
Ž .
7651 4
Ž .
Ž .
3804 5
y2404 7
29 1
Ž .
1735 4
Ž .
Ž .
Ž .
25 1
6731 4
y2274 7
Ž .
Ž .
6266 5
Ž .
y1981 7
Ž .
743 4
28 1
3. Results and discussion
Ž .
840 4
Ž .
Ž .
Ž .
27 1
5959 4
y527 7
Ž .
Ž .
5169 4
Ž .
Ž .
1234 4
y242 8
32 2
Ž .
1425 5
Ž .
Ž .
1188 10
Ž .
45 2
3.1. Ligand and complex synthesis
4957 5
Ž .
Ž .
5526 6
Ž .
Ž .
1258 5
2335 9
46 2
Ž .
883 5
Ž .
644 4
Ž .
Ž .
2078 8
Ž .
655 7
Ž .
40 2
Ž .
31 2
6336 6
Phosphine ligands with pendant arene groups
PR2R were prepared Fig. 1 starting from
Ž .
6520 5
X
Ž
.
Ž
.

(
)
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
29
Table 3
Crystal data and structure refinement for 3bPacetone
1
6
w
Ž
.x
RuI2 h :h y3 Pacetone
Ž
.
Empirical formula
Formula weight
C29 H29 I2OPRu
779.36
Crystal size mm
Ž .
0.25=0.24=0.12
2.71–25.00
Q range 8
Ž
.
Ž .
193 2
Temperature K
Index ranges
15DhD0, 17DkD0, 17DlD-18
˚
Ž
.
w
x
Wavelength A
Crystal system
Space group
0.71073
monoclinic
P 21rc
Reflections collectedrunique
4758r4549 Rint s0.0401
Refinement method
Full-matrix least-squares on F2
˚
Ž
.
Ž .
Ž .
Unit cell dimensions A, 8
as12.799 5 , as90
Datarrestraintsrparameters
4758r27r307
bs15.032 6 , bs110.56 2 Goodness-of-fit on F2
1.043
Ž .
Ž .
w
Ž .x
cs15.547 4 , gs90
Final R indices I)2s I
R1s0.0452, wR2s0.1012
R1s0.0576, wR2s0.1066
0.741 and y0.792
3
˚
Ž
.
Ž
.
Ž
.
Volume A
2800.6 17
R indices all data
3
y3
˚
Ž
.
Ž
.
Z, calculated density grcm
4, 1.848
2.841
Largest diff. peak and hole erA
y1
Ž
.
Absorption coefficient mm
Ž
.
F 000
1504
Ž
.
Data collection, cell refinement and data reduction were performed with TEXSAN Molecular Structure, 1993 . A psi-scan absorption
w
x
correction was performed, 0.700-T-0.997 28 . Intensities were corrected for Lorentz and polarization effects. For structure solution
Ž
.
SHELXS-97 and structure refinement SHELXL-97 both Sheldrick, 1997 were used. Molecular Graphics: ORTEP III. Non-hydrogen atom
positions were obtained with direct methods and anisotropically refined. Hydrogen atoms were refined on calculated positions. Displacement
factors of the H atoms were 1.2= to that of the host atom. The acetone molecule present within the unit cell is more or less disordered as
can be seen from the values of the anisotropic displacement parameters.
.
phosphines : addition of tertiary phosphines to a
of AIBN and treatment with either UV light or
w
x
Ž .
suspension of the dimeric arene ruthenium II
by heating up 10 . A second possibility is to
Ž
w
Ž
.x
use metal phosphides metalssodium, potas-
complexes RuCl2 arene cleaves the chlorine
2
sium or lithium, phosphidessdiphenylphos-
phide or dicyclohexylphosphide and add either
2-phenylethylbromide 2 or a styrene deriva-
bridges to afford orange to red, air-stable phos-
.
Ž .
phinoarene ruthenium II dichloride complexes
Ž .
x
Ž
w
Ž
.
x w
x
Ž
.
RuCl2 arene PR3 9,21 Fig. 2 .
Even in the case of electron-rich ligands, the
. Ž . Ž
.
w
tive
4
Fig. 1 14,15 .
This variety of reaction pathways allows ac-
cess to phosphine ligands with different substi-
tution patterns at the pendant arene moiety or in
the bridge.1
chelating effect was insufficient for the desired
displacement of the coordinated arene, which is
necessary in order to create the corresponding
X
1
6
w
Ž
.x
chelating complexes RuCl2 h :h -PR2 R
Ž .
w
Ž
.
w
x
Arene ruthenium II complexes RuCl2-
1a–4a 10,18a,18b . Examples for the prob-
Ž
.x Ž
arene arenesC6H6, PhMe, p-C6H4Me2,
2
lems with arene displacement reactions at ruthe-
.
Ž .
w x
1,3,5,-C6H3Me3 or p-MeC6H4CHMe2 are
accessible by dehydrogenation of the corre-
sponding cyclohexadienes with an ethanolic so-
nium II are known from the literature 20 . A
strategy to facilitate arene exchange has been
w
x
proposed by Therrien et al. 10 who suggested
Ž
.
w
x
Ž .
lution of ruthenium III trichloride 19,20 .
These complexes are used as precursor for the
the use of labile ruthenium II arene dimers
comprising of electron-poor arenes like
C6H5COOEt, which were expected to be more
easily replaced by the pendant arene group
Ž .
synthesis of phosphinoarene ruthenium II
w
Ž
.
x Ž
dichlorides RuCl2 arene PR3 PR3 stertiary
Ž
.
Fig. 2 . Accordingly, we obtained the phosphi-
Ž .
noarene ruthenium II dichloride complexes
1 These included R2 PCH2CH2 Ar RsPh, Cy; Ars2,5-
X
6
Ž
w
Ž
Ž
.Ž
.
x
RuCl2 h -C6H5COOEt PR2R
by reacting
X
Ž
.
C6 H3Me2 , 2,4,6-C6 H2 Me3 or 4-C6 H4C CH3 or R2 PCHR-
CH2 Ar RsPh, Cy; R sMe, Ph; ArsPh ; see also Refs.
3
w . Ž
RuCl2 arene
2
x
.
X
arenesC6H5COOEt and the
Ž
.
w
x
desired phosphines 1–4 in chloroform at room
18a,18b .

(
)
30
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
Table 4
w
x
temperature 10 . After refluxing these solu-
4
Ž
.
Atomic coordinates =10 and equivalent isotropic displacement
parameters A =10 for 3b
1
6
w
Ž
tions, the chelating complexes RuCl2 h :h -
2
3
˚
Ž
.
X
.
x
Ž
.
PR2R
1a–4a precipitated by the addition of
n-pentane to yield red microcrystalline solids
Fig. 2 . All phosphines were observed to act as
h :h -chelates, and no substitution pattern at
the arene or in the bridge hindered the exchange
process. Single crystals of 1b and 3b were
grown after halide exchange by slow evapora-
tion of an acetone solution. The structure of
3bPAcetone
X
Y
Z
U
eq
Ž .
3073 1
3316 1
Ž .
4310 1
3001 2
Ž .
1349 1
Ž .
Ž .
1027 1
Ž .
4568 1
6273 1
Ž .
6361 1
6873 1
8157 10 182 5
6601 5 34 2
5992 5 39 2
5749 6 45 2
6136 6 55 2
6746 6 54 2
6978 5 42 2
6704 6
7403 11 111 5
7234 14 145 7
6389 12
5718 10 134 7
5874 8
Ž .
8131 4
8371 4
Ž .
7643 4
6947 5
Ž .
6203 5
6182 5
Ž .
6893 5
7615 4
Ž .
9331 5
9620 5
Ž .
10491 6
11080 6
Ž .
10811 5
9937 5
9395 13 251 15
Ž .
37 1
41 1
Ž .
26 1
30 1
I1
I2
Ru
P
O
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
Ž
Ž
.
.
Ž .
Ž .
Ž .
y589 1
1
6
Ž .
Ž
Ž .
Ž .
Ž
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž
Ž
Ž
Ž
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
1671 1
.
Ž
.
.
8388 10
Ž .
1823 10
Ž .
2647 6
2849 5
Ž .
Ž .
3026 6
Ž .
2693 7
1993 8
3311 5
Ž .
4186 5
Ž .
Ž .
Ž .
4595 5
1
6
1
6
w
Ž
.
x
Ž
.
w
Ž
.
x
Ž
.
RuI2 h :h -1 1b and RuI2 h :h -3 3b
was determined by X-ray crystallography and is
Ž .
1636 8
Ž .
4156 6
Ž .
1958 6
Ž .
3275 5
Ž .
1202 5
Ž .
Ž .
Ž .
Ž
.
1634 7
44 2
presented as ORTEP plot Fig. 3 . The unit cell
of 1b encloses two independent molecules and
their symmetry equivalents . In the case of 3b,
an acetone molecule is present in the unit cell
that is more or less disordered — as can be seen
from the values of the anisotropic displacement
parameters. Crystallographic data and structure
refinement for 1b and 3b are given in Tables 1
Ž
Ž
Ž
Ž
Ž
Ž .
.
.
.
.
.
Ž
.
.
.
.
.
.
1351 10
258 12
894 10
Ž
Ž
578 11
Ž .
.
Ž .
98 5
y494 11
550 9
Ž
.
.
Ž .
Ž .
y214 11
862 13
Ž
862 10
1178 11
Ž .
108 5
Ž .
33 2
32 2
Ž .
28 2
34 2
Ž .
34 2
35 2
Ž .
34 2
30 2
Ž .
35 2
52 2
Ž .
63 3
61 3
Ž .
51 2
44 2
3735 6
Ž .
4953 6
5404 6
Ž .
5499 6
5733 6
Ž .
5984 6
5939 6
Ž .
5631 6
5684 7
Ž .
6829 7
7533 9
Ž .
7123 9
6025 9
Ž .
5303 8
10040 2
9248 10
1627 5
Ž .
Ž .
Ž .
1919 4
Ž .
Ž .
1563 4
Ž .
Ž .
Ž .
2127 5
Ž .
Ž .
1747 5
Ž
.
Ž
.
and 2 1b and Tables 3 and 4 3b .
Ž .
Ž .
Ž .
837 5
Ž .
Ž .
288 5
Ž .
Ž .
Ž .
638 4
Ž .
3.2. Polymerization
Ž .
1632 5
Ž .
Ž .
Ž .
1832 6
In order to be active for ROMP, established
ruthenium catalysts, e.g. ruthenium II arene
dimers or phosphinoarene ruthenium II dichlo-
rides, require an activation step 7–9 . That
means, initial carbene species must either be
generated in situ by adding diazo compounds
Ž .
Ž .
1584 7
Ž .
Ž .
Ž .
Ž .
1143 6
Ž .
Ž .
945 5
Ž .
Ž .
Ž .
Ž
Ž
Ž .
Ž .
Ž .
1191 5
w
x
Ž .
Ž
Ž
Ž
.
.
.
.
1843 14
Ž .
.
.
2202 8
8539 10 110 5
Ž .
8162 12 164 8
Ž
Ž .
9574 15
3028 11
w
x
9,22,23 or be formed in a reaction between
precatalyst and monomer under UV irradiation
w
x
or by heating 24,25 . Alternatively, catalysts
may be utilized in which the required carbene
fragment has been preformed by reacting a suit-
able complex precursor with certain reagents to
generate stable carbene complexes, which can
be isolated and stored over longer periods of
labile coordination sphere lacks rigid elements
that are necessary to control the catalytic pro-
cess.
With respect to the ROMP of norbornene as
model system for metathesis reactions, three
activation patterns for the structurally related
w x
time without significant decomposition 2 .
X
1
6
w
Ž
.x
All these pathways lead to active species in
which only monodentate ligands are present.
Additionally, dissociation of phosphines or arene
RuCl2 h :h -PR2R were pursued in order to
vary the number of available coordination sites
and therefore, the steric bulk at the catalytic
w x
Ž
.
moieties from the metal center occurs 5 . The
center Fig. 4 . The species A, B, C depicted
represent structural principles, not real
molecules. In solution, such fragments would be
stabilized either by coordinating solvent
resulting free coordination sites are occupied by
solvent or monomer molecules, which may dis-
place each other in equilibrium processes. This

(
)
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
31
Fig. 5. Hypothetical pathway for the formation of carbene species
Ž
.
1
6
in the presence of methanol method C; Dsphosphine .
Ž
.
Fig. 4. Activation methods for h :h -phosphinoarene
Ž .
Ž
.
ruthenium II dichloride complexes Lscarbene and correlated
ruthenium fragments.
results occurred if the ruthenium dichlorides
Ž
.
were exposed to TMSD Fig. 4, method B . If
methanol was introduced after the chlorine ab-
straction step, we also observed the formation
of polynorbornene — what implies the genera-
molecules or monomer, which would prevent a
coordinative unsaturation.
Abstraction of the chlorine moieties by reac-
Ž .
Ž
.
tion with silver I salts AgX XsBF4,SbF6 or
Ž
.
tion of a carbene species Fig. 4, method C .
Here, carbenes can be speculated to be pro-
duced by oxidative addition of methanol to
ruthenium II species, alkene insertion into the
Ru H bond, H elimination to the carbene
species, followed by reductive elimination of
methanol Fig. 5 27 . This procedure would
yield carbene complexes with coordinated arene
moiety and one coordination site left 26 . In
contrast, method A produces four and method B
w
Ž
.
sodium - tetrakis - 3,5-bis - trifluoromethyl phe-
x
Ž
Ž
.
Ž
Ž
.
nyl borate
NaB Arf
Arf s 3,5 - CF3 2
-
4
..
C6H3 cleanly produced the dicationic com-
Ž .
X
plexes Ru h :h -PR2R q, as was confirmed
1
6
2
w
Ž
.x
`
1
31
by H and P NMR.2 The subsequent addition
Ž
.
of TMSD Fig. 4, method A to form initial
carbene species led to polymerization active
complexes,3 but in these cases, a decoordination
of the arene moiety was observed.4 Analogous
Ž
. w x
w
x
Table 5
2
1
6
To a solution of 6.3=10y2 mmol RuCl2 h :h - PDCyPE
w
Ž
Ž
..x
Polymerization results of complexes 1a, 2a, 4a
Complex Method of % transa Activity
2a in 1 ml CDCl3 19.0=10y2 mmol AgBF4 were added under
Ž
.
tp
argon and stirred for 10 min. After the removal of AgCl by
3
filtration, a 1H and 31 P NMR spectrum were recorded. Selected
w
Activation
10 gpolymer
r
mol2
spectroscopic data: 1H NMR d CDCl3 : 6.54 ppm m, 2H, Ar ,
x
h
Ž
.
Ž
.
6.12 ppm m, 1H, Ar , 5.54 ppm m, 2H, Ar . 31 P NMR d
Ž
.
Ž
.
1a
1a
1a
2a
2a
2a
4a
4a
4a
A
B
C
A
B
C
A
B
C
59
61
80
61
74
87
55
61
85
909
163
3
9690
4381
65
1558
2
33
14 h
14 h
14 h
8 min
10 min
10 h
20 min
10 min
14 h
Ž
.
CDCl3 : 78.7 ppm. Absorptions in the region of 5.0–6.8 ppm are
especially typical for coordinated arene moieties 20 . The com-
plete abstraction of chlorine is obvious from the appearance of a
single resonance in the P NMR spectrum at 78.7 ppm dichloro
w
x
31
Ž
.
complex: 70.4 ppm .
3 The formation of carbene species upon the addition of TMSD
was concluded from the obvious polymerization activity of the
Ž
w x.
ruthenium complexes after this treatment, see also Ref. 5 .
NMR investigations to ascertain this assumption need to be done.
4 In some cases, the release of the arene moiety plays a crucial
role for generating the catalytic species.
aAccording to the integrated 1H NMR spectra of the formed
Ž
.
poly norbornene s.

(
)
32
A. Abele et al.rJournal of Molecular Catalysis A: Chemical 160 2000 23–33
Further effort, though, will be required to decide
if these findings can be developed into a princi-
ple for the control of the regioselectivity of
olefin metathesis reactions by the design of the
ligand sphere.
References
w x
1
K.J. Ivin, J.C. Mol, Olefin Metathesis and Metathesis
Polymerization, Academic Press, Toronto, 1997.
w x
2
R.H. Grubbs, J. Macromol. Sci., Pure Appl. Chem. A 31
Ž
. Ž
.
11 1994 1829.
w x
3
P. Schwab, R.H. Grubbs, J.W. Ziller, J. Am. Chem. Soc.
Ž
.
118 1996 100.
Fig. 6. Influence of the counter ion on the polymerization activity.
w x
4
Z. Wu, S.T. Nguyen, R.H. Grubbs, J.W. Ziller, J. Am.
Ž
.
Chem. Soc. 117 1995 5503.
w x
5
E.L. Dias, S.T. Nguyen, R.H. Grubbs, J. Am. Chem. Soc.
119 1997 3887.
Ž
.
two unoccupied sites ready for monomer coor-
w x
6
A. Furstner, M. Picquet, C. Bruneau, P.H. Dixneuf, Chem.
¨
Ž
.
dination Fig. 4 .
Ž
.
Commun. 1998 1315.
A comparison of the polymerization activities
obtained within a set of active species suggests
that a high number of available coordination
sites is connected to an increased rate of
w x
7
A. Hafner, P.A. van der Schaaf, A. Muhlebach, WO
¨
96r16100.
w x
8
A. Hafner, P.A. van der Schaaf, A. Muhlebach, WO
¨
96r20235.
w x
9
A. Demonceau, A.W. Stumpf, E. Saive, A.F. Noels,
Ž
.
Ž
.
Macromolecules 30 1997 3127.
monomer conversion Table 5 .
w
w
x
10 B. Therrien, T.R. Ward, M. Pilkington, C. Hoffmann, F.
Additionally, polymerization activity seems
to be governed by the nucleophilicity of the
Ž
.
Gilardoni, J. Weber, Organometallics 17 1998 330.
x
11 F. Simal, D. Jan, A. Demonceau, A. Noels, Tetrahedron
Ž
.
Ž .
Lett. 40 1999 1653.
counter ion Fig. 6 . Weakly coordinating
w
w
x
12 A. Demonceau, personal communication.
Ž
.
counter ions, for instance B Arf 4, show a re-
duced tendency to interact with the metal center
and, hence, do not prevent monomer coordina-
tion as strongly as BF4. The influence of counter
anion on the activity and the selectivity of
ruthenium metathesis catalysts was recently de-
x
13 D. Ian, L. Delaude, A.F. Noels, 13th International Sympo-
sium on Olefin Metathesis and Related Chemistry, Rolduc,
11–15 July, 1999, poster No. 23.
w
x
14 E. Lindner, S. Meyer, P. Wegner, B. Karlen, A. Sickinger,
Ž
.
J. Organomet. Chem. 335 1987 59–70.
w
w
x
Ž
.
15 K. Issleib, K. Jasche, Chem. Ber. 100 1967 412–420.
x
16 M. Brookhart, B. Grant, A.F. Volpe Jr., Organometallics
Ž
.
w
x
11 1992 3920–3922.
scribed by Picquet et al. 26 who performed
metathesis experiments with ruthenium allenyli-
dene complexes.
w
x
Ž
.
17 V.D. Bianco, S. Doronzo, Inorg. Synth. 16 1974 155.
w
w
x
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