Synthesis of new bis(acetylide)-substituted fluorene derivatives and their bimetallic and polymeric complexes

Article abstract of DOI:10.1016/S0022-328X(97)00711-0

A new series of bis(acetylide) organic ligands having fluorene or fluorenone moieties in the backbone, 2,7-di(trimethylsilylethynyl)fluorene (1a), 2,7-di(ethynyl)fluorene (1b), 2,7-di(trimethylsilylethynyl)fluoren-9-one (2a) and 2,7-di(ethynyl)fluoren-9-one (2b), has been prepared. Reaction of the diterminal alkynyl fluorene derivatives 1b and 2b with two equivalents of the complex trans-[(Ph)(PEt₃)₂Pt(Cl)] in CH₂Cl₂/ⁱPr₂NH with catalyic CuI readily affords the diplatinum(II) bis(acetylide) complexes trans-[(Ph)(PEt₃)₂Pt-CC-R¹-CC-Pt(PEt ₃)₂(Ph)] (R¹=2,7-fluorenyl 3) and trans-[(Ph)(PEt₃)₂Pt-CC-R²-CC-Pt(PEt ₃) ₂(Ph)] (R²=2,7-fluoren-9-onyl 4) in good yields. Two new rigid-rod organometallic polymers trans-[-Pt(PBuⁿ₃)₂-CC-R¹-CC-]∞ (5) and trans-[-Pt(PBuⁿ₃)₂-CC-R²-CC-]∞ (6) have also been prepared in good yields, in a similar manner to their dinuclear complexes 3 and 4, by the CuI-catalysed dehydrohalogenation reaction of trans-[Pt(PBuⁿ₃)₂Cl₂] with one equivalent of 1b or 2b, in an amine solvent, at ambient temperature. Both poly-yne polymers (colourless 5, deep red 6) exhibit good solubility in common organic solvents and readily cast into thin films. The organometallic terminal alkyne complexes trans-[Cl(dppm)₂M-CC-R²-CCH] (M=Ru 7, Os 8), obtained by treatment of 2b with one equivalent of cis-[M(dppm)₂Cl₂] (M=Ru, Os), based on a NaPF₆/DBU method have been utilised as starting products for access to the homobimetallic trans-[Cl(dppm)₂M-CC-R²-CC-M(dppm)₂Cl] (M=Ru 9, Os 10) and heterobimetallic trans-[Cl(dppm)₂Ru-CC-R²-CC-Os(dppm)₂Cl] (11) systems by reaction with a suitable choice of cis-M(dppm)₂Cl₂ (M=Ru or Os). All the new compounds have been characterised by analytical and spectroscopic methods, and the single-crystal X-ray structure of 1b has been determined.

Full text of DOI:10.1016/S0022-328X(97)00711-0

Journal of Organometallic Chemistry 556 (1998) 219–228
Synthesis of new bis(acetylide)-substituted fluorene derivatives and
their bimetallic and polymeric complexes
Jack Lewis, Paul R. Raithby *, Wai-Yeung Wong
Department of Chemistry, Uni6ersity of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
Received 24 October 1997
Abstract
A new series of bis(acetylide) organic ligands having fluorene or fluorenone moieties in the backbone, 2,7-di(trimethylsi-
lylethynyl)fluorene (1a), 2,7-di(ethynyl)fluorene (1b), 2,7-di(trimethylsilylethynyl)fluoren-9-one (2a) and 2,7-di(ethynyl)fluoren-9-
one (2b), has been prepared. Reaction of the diterminal alkynyl fluorene derivatives 1b and 2b with two equivalents of the complex
trans-[(Ph)(PEt3)2Pt(Cl)] in CH2Cl2/iPr2NH with catalyic CuI readily affords the diplatinum(II) bis(acetylide) complexes trans-
[(Ph)(PEt3)2Pt-CꢀC-R1-CꢀC-Pt(PEt3)2(Ph)] (R1=2,7-fluorenyl 3) and trans-[(Ph)(PEt3)2Pt-CꢀC-R2-CꢀC-Pt(PEt3) (Ph)] (R2=2,7-
2
fluoren-9-onyl 4) in good yields. Two new rigid-rod organometallic polymers trans-[–Pt(PBun3)2-CꢀC-R1-CꢀC–]ꢀ (5) and
trans-[–Pt(PBun3)2-CꢀC-R2-CꢀC–]ꢀ (6) have also been prepared in good yields, in a similar manner to their dinuclear complexes
3 and 4, by the CuI-catalysed dehydrohalogenation reaction of trans-[Pt(PBun3)2Cl2] with one equivalent of 1b or 2b, in an amine
solvent, at ambient temperature. Both poly-yne polymers (colourless 5, deep red 6) exhibit good solubility in common organic
solvents and readily cast into thin films. The organometallic terminal alkyne complexes trans-[Cl(dppm)2M-CꢀC-R2-CꢀCH]
(M=Ru 7, Os 8), obtained by treatment of 2b with one equivalent of cis-[M(dppm)2Cl2] (M=Ru, Os), based on a NaPF6/DBU
method have been utilised as starting products for access to the homobimetallic trans-[Cl(dppm)2M-CꢀC-R2-CꢀC-M(dppm)2Cl]
(M=Ru 9, Os 10) and heterobimetallic trans-[Cl(dppm)2Ru-CꢀC-R2-CꢀC-Os(dppm)2Cl] (11) systems by reaction with a suitable
choice of cis-M(dppm)2Cl2 (M=Ru or Os). All the new compounds have been characterised by analytical and spectroscopic
methods, and the single-crystal X-ray structure of 1b has been determined. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Fluorenyl ligand; Platinum; Ruthenium; Osmium; Acetylide
1. Introduction
investigation of charge transfer complexes [6], in activa-
tion of photoconductivity of organic semiconductors
([6]h), and as electron transport materials [7]. Among
them, 9-oxo-substituted fluorenes (i.e. fluoren-9-ones)
have been most extensively studied [8]. Studies of some
2,7-substituted-9-fluorenyl-ferrocenes as well as the for-
mation of their copolymers with 2,5-diethynyl-1,4-bis(-
decyloxy)benzene have appeared recently [9].
Bearing this in mind, a program was initiated to
investigate the possibility of using fluorenyl moieties in
the design of new organometallic dimers, oligomers and
polymers. In view of the fact that acetylides are ideal
moieties for the synthesis of rigid-rod organometallic
species, we believe that the introduction of acetylene-
functionalised fluorene derivatives would impart new
Conjugated organometallic systems represent an in-
teresting and active area of research in the materials
industry [1]. Rigid-rod poly-yne complexes of the type
trans-[–Pt(PBun3)2-CꢀC-R-CꢀC–]ꢀ (R=phenyl [2],
pyridyl [3], oligothienyl [4], alkynyl [5], etc.) have been
prepared and extensively studied by our group. How-
ever, to our knowledge, there is no report on such
systems bearing fluorenyl derivatives in the backbone.
It has been shown that fluorene electron acceptors and
their derivatives are widely used in the preparation and
* Corresponding author. Fax:
prr1@cam.ac.uk
+
44 1223 336352; e-mail:
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00711-0

220
J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–228
Scheme 1. Cross-coupling reactions producing compounds 1a, 2a and 1b, 2b.
properties to these systems. Here, we report the synthe-
sis and characterisation of some 2,7-disubstituted
bis(acetylide) fluorene (I) and fluoren-9-one (II) com-
pounds and their use in the formation of new bimetallic
(both homo- and hetero-bimetallic) di-yne complexes
and polymers. The molecular structure of Me3Si-CꢀC-
R1-CꢀC-SiMe3 (R1=2,7-fluorenyl) has been deter-
mined by X-ray crystallography.
minal ligands H-CꢀC-R1-CꢀC-H (R1=2,7-fluorenyl 1b)
and H-CꢀC-R2-CꢀC-H (R2=2,7-fluoren-9-onyl 2b)
proceed smoothly at room temperature (r.t.) by desily-
lation of 1a and 2a with K2CO3 in MeOH [11] (Scheme
1). All the products were purified by column chro-
matography on silica gel and isolated as white (1a and
1b) and bright yellow (2a and 2b) solids in yields of
69–75%. They were fully characterised by IR, NMR
(1H and 13C), UV/VIS spectroscopy, EI-mass spec-
trometry as well as satisfactory elemental analyses.
These diterminal acetylenes are found to be air- and
light-stable.
The synthesis of the platinum(II) dimers and poly-
mers is outlined in Scheme 2. The complex trans-
[(Ph)(PEt3)2Pt(Cl)] was reacted with half an equivalent
of 1b and 2b in CH2Cl2/iPr2NH, in the presence of CuI,
at r.t., to afford the dimeric platinum(II) complexes
trans-[(Ph)(PEt3)2Pt-CꢀC-R1-CꢀC-Pt(PEt 3)2(Ph)] (3)
and
trans-[(Ph)(PEt3)2Pt-CꢀC-R2-CꢀC-Pt(PEt3)2(Ph)]
(4), respectively, after TLC purification. Subsequent
recrystallisation from a dichloromethane/hexane mix-
ture gave crystals of 3 (colourless) and 4 (red) in good
yields. Moreover, the dehydrohalogenation reaction be-
tween trans-[Pt(Bun3)2Cl2] and the bis(acetylide) reagents
1b or 2b (1:1 equivalent) in diisopropylamine, with a
catalytic amount of CuI, readily provided a colourless
polymer trans-[–Pt(PBun3)2-CꢀC-R1-CꢀC–]ꢀ (5) and a
bright red polymer trans-[–Pt(PBun3)2-CꢀC-R2-CꢀC–]ꢀ
(6), respectively. Purification of these polymers was
accomplished by alumina column chromatography us-
ing dichloromethane as eluent, and they were isolated
in high purity and good yields (57% 5, 65% 6). Both
polymers 5 and 6 are soluble in common organic sol-
vents and cast tough, free-standing films. Gel perme-
ation chromatography (GPC) measurements show that
2. Results and discussion
2.1. Syntheses
2,7-Di(trimethylsilylethynyl)fluorene (1a) and 2,7-
di(trimethylsilylethynyl)fluoren-9-one (2a) were pre-
pared via a PdII/CuI-catalysed cross-coupling reaction
of the respective dibromo fluorenes with trimethylsily-
lacetylene [10] (Scheme 1). Transformation of these
trimethylsilyl (TMS)-substituted acetylides to the diter-

J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–225
221
Scheme 2. Synthesis of platinum(II) dimers and polymers.
the weight-average molecular-weight (Mw) values for 5
and 6 are 38960 (n=1.820) and 76460 (n=1.970),
respectively. This indicates a high degree of polymerisa-
tion. The number-average molecular weight (Mn) values
of 5 and 6 correspond to 26 and 47 repeating units per
chain, respectively. All the spectroscopic and analytical
data of 3–6 are in accord with the proposed structures
and all these metal complexes are air-stable and soluble
in common organic solvents.
the new compounds in this study. The all-trans configu-
ration of the Pt |-acetylide dimers and polymers was
clearly shown by the simple singlet pattern of their wCꢀC
IR and 31P{1H}-NMR spectra. The wCꢀC values for the
diterminal acetylide precursors 1b and 2b (2104–2110
cm−1) are much lower than those for the TMS-substi-
tuted ligands 1a and 2a (2148–2155 cm−1). The fact
that terminal acetylenes (HCꢀCR) have lower wCꢀC fre-
quencies than their RCꢀCR% counterparts (by about 43
cm−1 in this case) is well established [13]. Furthermore,
the platinum complexes 3–6 display smaller wCꢀC values
than those in the corresponding organic ligands, which
is attributed to the metal-to-alkyne ligand charge trans-
fer process [14]. For those ligands and platinum(II)
complexes containing fluoren-9-one moieties, strong ab-
sorption bands due to wCꢀC stretching were detected in
the IR spectra. In all cases, signals arising from the
aromatic protons of the fluorene fragments were also
observed. From the 31P{1H}-NMR spectral data of all
the di-ynes and poly-ynes of platinum, it is clearly seen
New terminal acetylide complexes of ruthenium and
osmium trans-[Cl(dppm)2M-CꢀC-R2-CꢀC-H] (M=Ru
7, Os 8) were made by a modification of the published
procedure through the formation of vinylidene interme-
diates followed by deprotonation ([1]d) [12]. The reac-
tion of cis-[M(dppm)2Cl2] (M=Ru, Os) with one
equivalent of 2b and two equivalents of NaPF6 gener-
ated vinylidene complexes which were not isolated but,
instead, were deprotonated in situ by one equivalent of
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (Scheme 3).
In a similar manner, homometallic di-yne complexes
trans-[Cl(dppm)2M-CꢀC-R2-CꢀC-M(dppm)2Cl] (M=
Ru 9, Os 10) and a mixed metal di-yne complex of
ruthenium and osmium trans-[Cl(dppm)2Ru-CꢀC-R2-
CꢀC-Os(dppm)2Cl] (11) have been prepared via the
NaPF6/DBU method involving cis-[Ru(dppm)2Cl2] and
8 in a 1:1 molar ratio (Scheme 3). All these newly
synthesised compounds were isolated as bright to dark
green solids with yields ranging from 49 to 72% and
display good solubility in dichloromethane. The identi-
1
that the JPt–P coupling constants for the dimers (3 and
4) are larger than those for the polymers (5 and 6) by
almost 300 Hz. Also, we note that the J values associ-
ated with the electron deficient fluorenone spacer are
slightly lower than those observed in the corresponding
polymers.
For 7 and 8, characteristic wCꢀC and wC–H IR vibra-
tions were observed at 2063–2068 and 1717 cm−1
,
respectively. The acetylenic moieties in all these homo-
and hetero-bimetallic ruthenium and osmium com-
plexes (9–11) were characterised by IR spectroscopy in
the range 2064–2069 cm−1, with the wCꢀC value of 11
lying in the middle of 9 and 10. The fluorenone unit in
all these metal complexes were also evident from the
wCꢁO stretching modes. The terminal protons of both
1
ties of these complexes were based on their IR, H- and
31P{1H}-NMR spectra and positive FAB-mass spectra.
2.2. Solution spectroscopy
Table 1 summarises basic spectroscopic data for all

222
J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–228
Scheme 3. Generation of the vinylidene complexes 7–11, demonstrating deprotonation in situ by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).
complexes 7 and 8 show a singlet resonance at about
3.13 ppm whereas the dppm ligands give a strong signal
at −147.81 and −190.25 ppm, respectively. In the
31P{1H}-NMR spectra of 9 and 10, each shows only a
singlet for the eight equivalent 31P nuclei, in accord
with a trans-chloroalkynylruthenium or osmium com-
pound. A singlet in the 31P{1H}-NMR spectra of 9 and
10 was observed, characteristic of a –M(dppm)2– unit
in a trans geometry. The mixed metal bis(acetylide)
complex 11 displays two signals at −147.69 and
−190.20 ppm due to the ruthenium and osmium-bound
P atoms, respectively.
fluorene-containing complexes 3 and 5, only intense
intraligand y“y* bands were observed in the near UV
region. Apart from the ligand-based y“y* band at 374
(4) and 382 nm (6), complexes 4 and 6 also exhibit a
broader, intense low-energy absorption feature in the
visible region (494 nm 4, 506 nm 6), which is tentatively
assigned to a metal-to-ligand charge transfer (MLCT)
transition. The MLCT nature of this transition was
partly supported by solvatochromatic studies. The red
shift of 18 nm from hexane (u 487 nm) to acetone (u
505 nm) for 4 indicates a change in the dipole moment
of the excited state with respect to that of the ground
state and is consistent with a dipolar excited state
([9]a)[15]. Due to these MLCT absorptions, the solu-
tions of 4 and 6 have an intense red colour in CH2Cl2.
It is noteworthy that this lowest MLCT energy band is
red-shifted from dimer to polymer and this suggests a
higher degree of y-conjugation through the platinum
centre in the latter.
2.3. Electronic absorption spectra
The data for the electronic absorption spectra in the
range 300–700 nm for compounds 3–11, at r.t., in
CH2Cl2, are presented in Table 1, together with data
for the corresponding bis(acetylide) fluorene ligands.
The UV/VIS absorption spectra of 1a and 1b display
similar structured intense bands in the UV range (ca.
304–335 nm) which arise from fluorene-localised y“
y* transitions of these ligands. Similarly, the spectra of
2a and 2b essentially consist of y“y* ligand transi-
tions in the near UV (ca. 308–340 nm) and in the
visible region at 431 and 421 nm, respectively. For the
The ruthenium and osmium complexes 7–11 are
intensely coloured compounds and their absorption
spectra are characterised by a strong featureless absorp-
tion band around 400 nm and a low-energy band
beyond 400 nm. These bands are ascribed to the ligand-
based y“y* and the MLCT transitions, respectively.
We observe that both transitions appear at longer

J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–225
223
Table 1
Some spectroscopic data for the ligand precursors and their metal complexes
Compounds
IR in CH2Cl2 (cm−1
)
31P{1H}-NMR (ppm)a
lmax in CH2Cl2 (nm)b
wCꢀC
wCꢁO
wC–H
1a
1b
2a
2b
3
4
5
6
7
8
9
10
11
2148
2104
2155
2110
2090
2088
2094
2093
2068
2063
2069
2064
2065
304 (1.9), 314 (1.8), 327 (1.6), 335 (1.8)
314 (1.2), 319 (1.1), 324 (1.1), 327 (1.2)
313 (0.9), 326 (1.5), 340 (1.7), 431 (0.1)
308 (1.7), 321 (2.3), 334 (1.6), 421 (0.2)
374 (5.2)
3299
3298
1720
1738, 1720
−131.18 (2645)c
−131.07 (2637)c
−138.03 (2363)c
−137.87 (2340)c
−147.81
−190.25
−147.70
−190.23
−147.69, −190.20
1715
374 (3.4), 494 (0.3)
394 (5.9)d
1715
1716
1718
1711
1712
1713
382 (5.1), 506 (0.4)d
3297
3299
400 (3.1), 563 (0.5)
415 (2.2), 601 (0.3)
404 (6.1), 579 (0.6)
412 (4.3), 603 (0.6)
409 (2.6), 590 (0.4)
c 1
a Referenced to P(OMe)3. b Extinction coefficient (in 104 cm−1
d Molarity is based on the repeating unit of the polymer.
M
−1) is given in parentheses.
J
value (in Hz) is given in parentheses.
Pt–P
wavelengths for the osmium complexes than those in
the ruthenium counterparts.
177(2)° for the Si–CꢀC units in the two independent
˚
molecules. The CꢀC bond distance [av. 1.18(2) A] in the
trimethylsilylacetylide moiety is typical of terminal
acetylides [16].
2.4. Crystal structure of Me3Si-CꢀC-R1-CꢀC-SiMe3
(R1=2,7-fluorenyl)
For 3, a preliminary X-ray diffraction analysis shows
that it consists of discrete diplatinum(II) molecules,
with no apparent intermolecular stacking interaction
between individual molecules [17]. There are one and a
half molecules in the asymmetric unit. Because of poor
refinement caused by the disorder of the solvent
molecules and the ethyl groups, the detailed molecular
dimensions for 3 will not be reported in this article.
Structurally, the molecule itself is similar to the dimeric
complexes reported recently with oligothienyl spacer
groups [4].
Single crystals of 1a suitable for X-ray diffraction
studies were grown by slow evaporation of its solution
in hexane/CH2Cl2 at r.t. Fig. 1 shows a perspective view
of the molecule together with the atom-numbering
scheme and some selected bond parameters are pre-
sented in Table 2. Due to the poorly diffracting nature
of the crystal sample of 1a, the bond parameters should
be considered approximate only. There are two inde-
pendent molecules per asymmetric unit in 1a and no
intermolecular stacking interactions between individual
fluorene units in the lattice is observed. In the solid
state, each molecule of 1a consists of two trimethylsily-
lacetylenic groups appended to a fluorene unit at the
2,7-disubstituted positions. Basically, the molecule has
a coplanar conformation and no deviation of the
fluorene ring from planarity is apparent (mean devia-
3. Conclusion
Our present work has demonstrated the versatility of
preparing bis(acetylide)-functionalised fluorene deriva-
tives at the 2,7-positions and that complexation of these
organic acetylides with transition metals can occur with
good yields at r.t. to afford fluorenyl-bridged conju-
gated bimetallic and polymeric species. The results have
shown that electronic absorption spectral features of
these complexes extend over a wide range and can be
easily tuned by switching from a fluorene to a fluoren-
9-one moiety. Work is currently in progress to further
investigate the extent of electron delocalisation and
other photophysical properties in these systems. Prelim-
inary work also indicates that the polymers are pho-
toresponsive and their photovoltaic behaviour will be
the subject of a future article.
˚
tion 0.05 A). The two fragments C(4)–C(14)–C(15)–
Si(1) and C(11)–C(16)–C(17)–Si(2) are essentially
linear, as evident from the mean angles of 175(2) and
Fig. 1. Molecular structure of Me3Si-CꢀC-R1-CꢀC-SiMe3 (R1=2,7-
fluorenyl 1a).

224
J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–228
Table 2
˚
Selected bond lengths (A) and angles (°) for 1a
Molecule 1
Si(1)–C(15)
Si(2)–C(17)
1.83(2)
1.83(2)
C(14)–C(15)
C(16)–C(17)
1.18(2)
1.17(2)
C(4)–C(14)
C(11)–C(16)
1.46(2)
1.44(2)
C(4)–C(14)–C(15)
C(11)–C(16)–C(17)
C(2)–C(1)–C(13)
178(2)
179(2)
101(1)
C(14)–C(15)–Si(1) 175(1)
C(16)–C(17)–Si(2) 180(2)
Molecule 2
Si(3)–C(38)
Si(4)–C(40)
C(27)–C(37)–C(38)
C(34)–C(39)–C(40)
C(25)–C(24)–C(36)
1.81(2)
1.82(2)
175(2)
175(2)
104(1)
C(37)–C(38)
C(39)–C(40)
1.19(2)
1.20(2)
C(27)–C(37)
C(34)–C(39)
1.50(2)
1.44(2)
C(37)–C(38)–Si(3) 175(2)
C(39)–C(40)–Si(4) 174(1)
4. Experimental
for 20 h. The completion of the reaction was deter-
mined by IR and silica TLC. The solution was allowed
to cool down to r.t., Et2O (100 cm3) was added and the
precipitate was filtered off. The pale yellow filtrate was
evaporated to dryness. The residue was redissolved in
Et2O (100 cm3) and washed sequentially with 10% HCl
(3×100 cm3), H2O (3×100 cm3), NaHCO3 (3×100
cm3) and H2O (3×100 cm3). The resulting organic
solution was then dried (MgSO4), the solvent removed,
and the yellow residue chromatographed over a silica
gel column by eluting with a 90:10 v/v mixture of
hexane and CH2Cl2. The product eluted as an off-white
band and the pure fraction was evaporated to dryness
and recrystallised from hexane/CH2Cl2 to give 1a as an
off-white solid in 75% yield (3.23 g). IR (CH2Cl2): w
4.1. General procedures
Solvents were predried and distilled from appropriate
drying agents [18]. All chemicals, except where stated,
were from commercial sources and used as received.
The compounds trans-[(Ph)(PEt3)2Pt(Cl)] [19] and
trans-[Pt(PBun3)2Cl2] [20] were prepared via literature
procedures. NMR spectra were recorded on a Bruker
WM-250 or AM-400 spectrometer in appropriate sol-
vents. 31P{1H}-NMR spectra were referenced to exter-
nal trimethylphosphite, and the 1H- and 13C{1H}-NMR
spectra were referenced to solvent resonances. Infrared
spectra were recorded as CH2Cl2 solutions, in a NaCl
cell, on a Perkin-Elmer 1710 Fourier Transform IR
spectrometer and mass spectra on a Kratos MS890
spectrometer by either the electron impact or fast atom
bombardment technique. Microanalyses were per-
formed in the Department of Chemistry, University of
Cambridge. Electronic absorption spectra were ob-
tained with a Perkin-Elmer Lambda UV/NIR spec-
trometer. Preparative TLC was carried out on
commercial Merck plates with a 0.25 mm layer of silica,
or on 1 mm silica plates prepared at the University
Chemical Laboratory, Cambridge. Column chromatog-
raphy was performed either on Kieselgel 60 (230–400
mesh) silica gel or alumina (Brockman Grade II–III).
1
(cm−1) 2148 (CꢀC). H-NMR (250 MHz, CDCl3): l
0.26 (s, 18H, SiMe3), 3.84 (s, 2H, CH2) and 7.47–7.69
(m, 6H, aromatic H). 13C{1H}-NMR (100.6 MHz,
CDCl3): l 0.03 (SiMe3), 36.44 (CH2), 94.45 (CꢀC),
105.67 (CꢀC), 119.97 (fluorenyl CH), 121.59 (fluorenyl
quat. C), 128.55 (fluorenyl CH), 131.00 (fluorenyl CH),
141.32 (fluorenyl quat. C) and 143.38 (fluorenyl quat.
C). EI-mass spectrum: m/z 358 (M+). Calc. for
C23H26Si2: C, 77.06; H, 7.32. Found: C, 76.79; H,
7.29%.
4.2.2. 2,7-Di(ethynyl)fluorene (1b)
A mixture of 1a (0.50 g, 1.4 mmol) and K2CO3 (0.19
g, 1.4 mmol) in MeOH (50 cm3) was stirred at r.t. for
20 h. IR spectroscopy showed that all the starting
material had been consumed. Solvent was removed
under reduced pressure to leave a pale yellow residue.
This residue was dissolved in the minimum amount of
CH2Cl2 and subjected to column chromatography on
silica using hexane/CH2Cl2 (60:40 v/v) as eluent to
afford a major off-white product identified as 1b (0.22
g, 73%). IR (CH2Cl2): w (cm−1) 2104 (CꢀC), 3299
4.2. Ligand syntheses
4.2.1. 2,7-Di(trimethylsilylethynyl)fluorene (1a)
To an ice-cooled mixture of 2,7-dibromofluorene
(3.89 g, 12 mmol) in 70 cm3 of freshly distilled diiso-
propylamine under nitrogen were added CuI (30 mg,
0.16 mmol), Pd(OAc)2 (30 mg, 0.13 mmol) and PPh3
(90 mg, 0.34 mmol). The solution was stirred for 20
min. Me3SiCꢀCH (2.95 g, 30.0 mmol) was then added
and the suspension was stirred for another 30 min in an
ice bath before being warmed to r.t. After reacting for
30 min at r.t., the reaction mixture was heated to 75°C
1
(CꢀCH). H-NMR (250 MHz, CDCl3): l 3.12 (s, 2H,
CꢀCH), 3.88 (s, 2H, CH2) and 7.51–7.72 (m, 6H,
aromatic H). 13C{1H}-NMR (100.6 MHz, CDCl3): l
36.52 (CH2), 77.43 (CꢀC), 84.18 (CꢀC), 120.14

J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–225
225
(fluorenyl CH), 120.69 (fluorenyl quat. C), 128.78
4.3. Complex and polymer preparations
(fluorenyl CH), 131.20 (fluorenyl CH), 141.55 (fluorenyl
CH) and 143.48 (fluorenyl quat. C). EI-mass spectrum:
m/z 214 (M+). Calc. for C17H10: C, 95.29; H, 4.71.
Found: C, 95.23; H, 4.96%.
4.3.1. Trans-[(Ph)(PEt3)2Pt-CꢀC-R1-CꢀC-
Pt(PEt3)2(Ph)] (R1=2,7-fluorenyl, 3)
Treatment of the diterminal alkyne 1b (43 mg, 0.2
mmol) with two equivalents of trans-[(Ph)(PEt3)2Pt(Cl)]
(0.22 g, 0.4 mmol) for 15 h at r.t., in the presence of
CuI (3 mg), in CH2Cl2/iPr2NH (50 cm3, 1:1 v/v) gave
the title complex as a colourless solid in 65% yield (0.16
g) after purification on silica TLC plates using hexane/
CH2Cl2 (40:60, v/v) eluent. IR (CH2Cl2): w (cm−1) 2090
4.2.3. 2,7-Di(trimethylsilylethynyl)fluoren-9-one (2a)
2,7-Dibromofluoren-9-one (4.06 g, 12.0 mmol),
i
Me3SiCꢀCH (2.95 g, 30.0 mmol) and Pr2NH (100 cm3)
1
(CꢀC). H-NMR (250 MHz, CDCl3): l 1.10 (m, 36H,
were mixed as in 1a with catalytic amounts of CuI (30
mg), Pd(OAc)2 (30 mg) and PPh3 (90 mg). The crude
product was worked-up, as before, to yield a yellow
residue which was then applied to a silica column,
eluting with hexane/CH2Cl2 (1:1, v/v). The desired com-
pound 2a was isolated as a bright yellow solid (3.10 g,
69%). IR (CH2Cl2): w (cm−1) 2155 (CꢀC), 1720 (CꢁO).
1H-NMR (250 MHz, CDCl3): l 0.24 (s, 18H, SiMe3)
and 7.43–7.72 (m, 6H, aromatic H). 13C-NMR (100.6
MHz, CDCl3): l −0.40 (SiMe3), 96.73 (CꢀC), 103.91
(CꢀC), 120.49 (fluoren-9-onyl CH), 124.39 (fluoren-9-
onyl quat. C), 128.46 (fluoren-9-onyl CH), 134.31
(fluoren-9-onyl quat. C), 138.19 (fluoren-9-onyl CH),
143.36 (fluoren-9-onyl quat. C), 143.36 (fluoren-9-onyl
quat. C) and 192.11 (CꢁO). EI-mass spectrum: m/z 372
(M+). Calc. for C23H24OSi2: C, 74.17; H, 6.50. Found:
C, 74.24; H, 6.49%.
CH3), 1.77 (m, 24H, CH2), 3.77 (s, 2H, fluorenyl CH2),
6.79 (t, 2H, Hpara of Ph), 6.96 (t, 4H, Hmeta of Ph), 7.26
(m, 2H, fluorenyl CH), 7.32 (br, 4H, Hortho of Ph), 7.41
3
(s, 2H, fluorenyl CH) and 7.53 (d, 2H, JHH=7.9 Hz,
fluorenyl CH). 31P{1H}-NMR (101.3 MHz, CDCl3): l
1
−131.18, JPt–P=2645 Hz. FAB-mass spectrum: m/z
1229 (M+). Calc. for C53H78P4Pt2: C, 51.79; H, 6.40.
Found: C, 52.32; H, 6.58%.
4.3.2. Trans-[(Ph)(PEt3)2Pt-CꢀC-R2-CꢀC-
Pt(PEt3)2(Ph)] (R2=2,7-fluoren-9-onyl, 4)
To a mixture of 2b (46 mg, 0.2 mmol) and two
equivalents of trans-[(Ph)(PEt3)2Pt(Cl)] (0.22 g, 0.4
mmol) in CH2Cl2/iPr2NH (60 cm3, 1:1 v/v) was added
CuI (3 mg). The solution was stirred at r.t. over a
period of 15 h, after which all volatile components were
removed under reduced pressure. The product was
purified on preparative TLC plates with hexane/CH2Cl2
(30:70, v/v) as eluent, giving compound 4 as a red solid
in an isolated yield of 68% (0.17 g). IR (CH2Cl2): 2088
(CꢀC), 1715 (CꢁO). 1H-NMR (250 MHz, CDCl3): l
1.09 (m, 36H, CH3), 1.75 (m, 24H, CH2), 6.80 (t, 2H,
Hpara of Ph), 6.93 (t, 4H, Hmeta of Ph), 7.26 (m, 4H,
fluoren-9-onyl CH), 7.32 (br, 4H, Hortho of Ph) and 7.49
(m, 2H, fluoren-9-onyl CH). 31P{1H}-NMR (101.3
MHz, CDCl3): l −131.07, 1JPt–P=2637 Hz. FAB-
mass spectrum: m/z 1243 (M+). Calc. for
C53H76OP4Pt2: C, 51.20; H, 6.16. Found: C, 51.27; H,
6.13%.
4.2.4. 2,7-Di(ethynyl)fluoren-9-one (2b)
The TMS-derivative 2a (1.00 g, 2.7 mmol) was desily-
lated using K2CO3 (0.37 g, 2.7 mmol) in 50 cm3 MeOH
and the mixture was stirred overnight. The solvent was
then removed under reduced pressure to afford a bright
yellow residue which was dissolved in CH2Cl2 rather
than Et2O, due to its limited solubility in Et2O. Subse-
quent washing with H2O (3×100 cm3) on a separatory
funnel left the crude product 2b in CH2Cl2 layer as a
yellow solution. The organic layer was dried over
MgSO4 and filtered. The filtrate was concentrated and
applied to a silica column. The desired yellow band was
collected with the aid of pure CH2Cl2 to afford 2b (0.45
g, 73%) as a leathery yellow solid. IR (CH2Cl2): w
(cm−1) 2110 (CꢀC), 3298 (CꢀCH), 1738, 1720 (CꢁO).
1H-NMR (250 MHz, CDCl3): l 3.18 (s, 2H, CꢀCH)
and 7.48–7.77 (m, 6H, aromatic H). 13C{1H}-NMR
(100.6 MHz, CDCl3): l 79.24 (CꢀC), 82.57 (CꢀC),
120.65 (fluoren-9-onyl CH), 123.48 (fluoren-9-onyl
quat. C), 128.02 (fluoren-9-onyl CH), 134.34 (fluoren-9-
onyl quat. C), 138.50 (fluoren-9-onyl CH), 143.64
(fluoren-9-onyl quat. C) and 191.91 (CꢁO). EI-mass
spectrum: m/z 228 (M+). Calc. for C17H8O: C, 89.46;
H, 3.53. Found: C, 89.51; H, 3.65%.
4.3.3. Trans-[–Pt(PBun3)2-CꢀC-R1-CꢀC–]ꢀ (5)
To a mixture of trans-[Pt(PBun3)2Cl2] (0.10 g, 0.15
mmol) and one equivalent of H-CꢀC-R1-CꢀC-H (1b, 32
mg, 0.15 mmol) in CH2Cl2/iPr2NH (50 cm3, 1:1 v/v)
was added CuI (3 mg). The solution mixture was stirred
at r.t. over a period of 15 h, after which all volatile
components were removed under reduced pressure. The
residue was redissolved in dichloromethane and filtered
through a short alumina column. After removal of
solvent by rotary evaporator, an almost colourless film
was obtained readily, and it was then washed with
methanol to give the polymer 5 in 57% yield (0.07 g).
Further purification can be accomplished by precipitat-
ing the polymer solution in toluene from methanol. IR

226
J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–228
1
(CH2Cl2): w (cm−1) 2094 (CꢀC). H-NMR (250 MHz,
CD2Cl2): l 0.96 (t, 18H, CH3), 1.42–1.67 [m, 24H,
(CH2)2], 2.05–2.21 (m, 12H, PCH2), 3.79 (s, 2H,
4.3.6. Trans-[Cl(dppm)2M-CꢀC-R2-CꢀC-M(dppm)2Cl]
(M=Ru 9, Os 10)
To a solution of cis-[M(dppm)2Cl2] (M=Ru, Os;
0.03 mmol) in 40 cm3 of CH2Cl2, trans-[Cl(dppm)2M-
CꢀC-R2-CꢀC-H] (7 for M=Ru, 8 for Os; 0.03 mmol)
and NaPF6 (10 mg, 0.06 mmol) were added. The re-
action mixture was allowed to react for 8 h at ambi-
ent temperature. The dark solution was then filtered
and subsequently treated with one equivalent of DBU
for 3 h. Filtration and evaporation of all volatile
components under reduced pressure permitted the iso-
lation of the required product as a green solid in
each case. Purification was achieved by washing the
solid with methanol/hexane and both products were
found to be pure (yield 51% 9, 55% 10). (9): IR
(CH2Cl2): w (cm−1) 2069 (CꢀC), 1711 (CꢁO). 1H-
NMR (250 MHz, CDCl3): l 4.92 (virtual t, 8H,
PCH2P), 5.93 (dd, 2H, JHH=1.4, 7.7, H3,6), 6.33 (d,
2H, J =1.4, H1,8), 6.81 (d, 2H, J=7.7 Hz, H4,5) and
7.05–7.58 (m, 80H, Ph). 31P{1H}-NMR (101.3 MHz,
CDCl3): l −147.70. FAB-mass spectrum: m/z 2037
(M+). Calc. for C117H94Cl2OP8Ru2: C, 68.99; H, 4.65.
Found: C, 68.67; H, 4.59%. (10): IR (CH2Cl2): w
(cm−1) 2064 (CꢀC), 1712 (CꢁO). 1H-NMR (250
MHz, CDCl3): l 5.43 (m, 8H, PCH2P), 5.91 (dd, 2H,
3
fluorenyl CH2), 7.25 (d, 2H, JHH=7.7, fluorenyl CH),
3
7.41 (s, 2H, fluorenyl CH) and 7.57 (d, 2H, JHH=7.9
Hz, fluorenyl CH]. 31P{1H}-NMR (101.3 MHz,
CDCl3): l −138.03, 1JPt–P=2363 Hz. Calc. for
[C41H62P2Pt]n: C, 60.65; H, 7.70. Found: C, 60.20; H,
7.73%. Mw=38960, Mn=21410 (n=1.820).
4.3.4. Trans-[–Pt(PBun3)2-CꢀC-R2-CꢀC–]ꢀ (6)
Similar procedures as in 5 were adopted using H-
CꢀC-R2-CꢀC-H (2b, 34 mg, 0.15 mmol) to produce a
deep red polymer 6 in 65% yield (0.08 g). IR (CH2Cl2):
w (cm−1) 2093 (CꢀC), 1715 (CꢁO). 1H-NMR (250
MHz, CDCl3): l 0.92 (t, 18H, CH3), 1.37–1.70 [m,
24H, (CH2)2], 1.96–2.26 (m, 12H, PCH2), 7.29 (m, 4H,
fluoren-9-onyl CH) and 7.48 (m, 2H, fluoren-9-onyl
CH). 31P{1H}-NMR (101.3 MHz, CDCl3): l −137.87,
1JPt–P=2340 Hz. Calc. for [C41H60OP2Pt]n: C, 59.62;
H, 7.32. Found: C, 58.82; H, 7.40%. Mw=76460, Mn=
38820 (n=1.970).
4.3.5. Trans-[Cl(dppm)2M-CꢀC-R2-CꢀC-H] (M=Ru
7, Os 8)
J
HH=1.4, 7.7, H3,6), 6.27 (d, 2H, J =1.4, H1,8), 6.80
A mixture of cis-[M(dppm)2Cl2] (M=Ru, 4.9 mg;
Os, 54 mg; 0.05 mmol), H-CꢀC-R2-CꢀC-H (2b, 12 mg,
0.05 mmol) and NaPF6 (17 mg, 0.10 mmol) in CH2Cl2
(50 cm3) were stirred for 10 h (20 h in the case of Os)
at r.t. The resulting dark red solution was filtered
through a pad of Celite to remove any excess NaPF6
and NaCl by-product, and DBU (one equivalent) was
added. The solution turned dark green immediately.
After 3 h stirring, the solvent was filtered and then
removed in vacuo. The green product was purified by
washing with a small volume of dry methanol and
hexane to afford a dark green (7) to deep green (8)
powder (yield 40 mg, 71% 7; 44 mg, 72% 8). (7): IR
(CH2Cl2): w (cm−1) 3297 (ꢀC–H), 2068 (CꢀC), 1716
(CꢁO). 1H-NMR (250 MHz, CDCl3): l 3.13 (s, 1H,
ꢀC–H), 4.91 (virtual t, 4H, PCH2P), 6.05 (dd, 1H,
(d, 2H, J=7.7 Hz, H4,5) and 7.07–7.40 (m, 80H, Ph).
31P{1H}-NMR (101.3 MHz, CDCl3): l −190.23.
FAB-mass spectrum: m/z 2217 (M+). Calc. for
C117H94Cl2OP8Os2 ·CH2Cl2: C, 61.62; H, 4.21. Found:
C, 60.87; H, 4.30%.
4.3.7. Trans-[Cl(dppm)2Ru-CꢀC-R2-CꢀC-Os(dppm)2Cl]
(11)
Cis-[Ru(dppm)2Cl2] (28 mg, 0.03 mmol) was re-
acted with trans-[Cl(dppm)2Os-CꢀC-R2-CꢀC-H] (8, 37
mg, 0.03 mmol) and NaPF6 (10 mg, 0.06 mmol) in
CH2Cl2 (40 cm3) for 4 h. The dark brown vinylidene
solution was filtered and DBU (one equivalent) was
added to produce a deep green solution at once. Stir-
ring was continued for 3 h and the solution was
filtered and removed. Analytically pure fine powder of
11 (31 mg, 49%) was obtained after washing with
JHH=1.4, 7.7, H3), 6.26 (d, 1H, JHH =1.4, H1), 7.00
(d, 1H, JHH=7.7 Hz, H4) and 7.06–7.76 (m, 43H,
Ph+H5,6,8). 31P{1H}-NMR (101.3 MHz, CDCl3): l
−147.81. FAB-mass spectrum: m/z 1132 (M+). Calc.
for C67H51ClOP4Ru·MeOH: C, 70.13; H, 4.76. Found:
C, 69.28; H, 4.61%. (8): IR (CH2Cl2): w (cm−1) 3299
(ꢀC–H), 2063 (CꢀC), 1718 (CꢁO). 1H-NMR (250 MHz,
CDCl3): l 3.12 (s, 1H, ꢀC–H), 5.45 (m, 4H, PCH2P),
6.04 (dd, 1H, JHH=1.4, 7.8, H3), 6.21 (d, 1H, JHH
=1.4, H1), 6.99 (d, 1H, JHH=7.8 Hz, H4) and 7.06–
7.77 (m, 43H, Ph+H5,6,8). 31P{1H}-NMR (101.3 MHz,
CDCl3): l −190.25. FAB-mass spectrum: m/z 1222
(M+). Calc. for C67H51ClOP4Os: C, 65.87; H, 4.21.
Found: C, 66.14; H, 4.12%.
methanol followed by hexane. IR (CH2Cl2): w (cm−1
)
2065 (CꢀC), 1713 (CꢁO). 1H-NMR (250 MHz,
CDCl3): l 4.91 [virtual t, 4H, Ru(PCH2P)], 5.44 [m,
4H, Os(PCH2P)], 5.92 (dd, 2H, JHH=1.4, 7.7, H3,6),
6.27 (d, 1H, JHH =1.4, H1 or H8), 6.32 (d, 1H,
J
HH=1.4 Hz, H1 or H8), 6.82 (m, 2H, H4,5) and
7.07–7.76 (m, 80H, Ph). 31P{1H}-NMR (101.3 MHz,
CDCl3): l −147.69, −190.20. FAB-mass spectrum:
m/z 2127 (M+). Calc. for C117H94Cl2OP8RuOs·
CH2Cl2: C, 64.10; H, 4.38. Found: C, 64.16; H,
4.58%.

J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–225
227
Table 3
micron mixed C columns at 30°C running in THF at
1 cm3 min-1 with a Roth Mocel 200 high precision
pump. A DAWN DSP (Wyatt Technology) Multi-
Angle Laser Light Scattering (MALLS) apparatus
with 18 detectors and auxiliary Viscotek model 200
differential refractometer/viscometer detectors was
used to calculate the absolute molecular weights (re-
ferred to GPC LS).
Atomic coordinates (×104) and equivalent isotropic displacement
2
3
˚
parameters (A ×10 ) for 1a
Atom
x
y
z
U(eq)a
Si(1)
Si(2)
Si(3)
Si(4)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
8718(2)
3294(2)
8546(3)
3418(2)
6085(6)
6252(7)
6833(7)
6900(7)
6372(7)
5799(7)
5740(6)
5219(6)
4614(6)
4231(7)
4431(6)
5039(7)
5425(7)
7503(8)
7998(8)
4052(7)
3757(7)
9238(8)
9214(8)
8369(8)
2626(6)
2914(8)
3888(7)
6443(7)
6486(7)
7036(7)
6945(7)
6335(8)
5805(8)
5889(7)
5423(8)
4744(8)
4417(8)
4719(8)
5371(7)
5470(7)
7493(8)
7933(9)
4323(8)
3976(7)
9039(6)
9110(8)
8074(8)
3967(7)
2968(8)
2798(8)
−1299(3)
3216(2)
−1235(3)
3389(2)
1348(6)
613(7)
9655(2)
4665(2)
7268(2)
2058(2)
7454(5)
7637(5)
8086(6)
8177(6)
7803(5)
7348(6)
7263(5)
6820(5)
6337(5)
5944(6)
6017(5)
6524(6)
6919(6)
8652(7)
9038(7)
5580(6)
5224(6)
10175(8)
9337(7)
10105(6)
4020(5)
5031(6)
4389(7)
4450(6)
4992(5)
5396(6)
5871(6)
5950(7)
5552(7)
5082(6)
4585(6)
4473(7)
3965(7)
3582(7)
3699(5)
4205(6)
6312(7)
6694(7)
3052(7)
2636(6)
6905(6)
7882(7)
7583(6)
1794(6)
2432(7)
1420(6)
101(2)
88(2)
114(12
94(2)
81(4)
65(4)
78(4)
77(4)
76(4)
77(4)
51(4)
54(4)
67(4)
74(4)
63(4)
84(4)
66(4)
90(5)
89(5)
81(5)
85(5)
163(8)
185(9)
139(7)
111(5)
132(6)
132(6)
91(50
66(4)
84(5)
80(4)
114(6)
117(6)
75(4)
91(5)
119(6)
113(6)
94(5)
75(4)
75(4)
91(5)
110(6)
97(5)
88(5)
125(6)
143(7)
132(6)
129(6)
150(7)
137(7)
4.5. Crystallography
339(7)
−371(8)
−790(7)
−519(7)
172(7)
604(7)
433(6)
Geometric and intensity data for 1b were collected
using graphite-monochromated Mo-Kh radiation (u=
˚
0.71069 A) on the MAR Research image plate scan-
ner and 65×3° frames with an exposure time of 5
min per frame were used. The intensity data were
corrected for Lorentz and polarisation effects and in-
terframe scaling was applied. The structure was
solved by direct methods (SHELXTL PLUS) [21] and
subsequent Fourier-difference syntheses, and refined
by full-matrix least squares on F2 (SHELXL 93) [22].
Crystal data: C23H26Si2, M 358.62, crystal size 0.22×
0.18×0.17 mm, monoclinic, space group C2/c, a=
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
935(7)
1624(7)
1787(7)
1270(7)
−673(8)
−901(7)
2137(8)
2558(8)
−616(8)
−1837(10)
−1854(8)
2783(7)
3826(7)
3657(8)
1179(7)
764(6)
˚
21.369(2),
b=19.516(2),
c=23.791(2)
A,
3
˚
i=113.09(2)°, U=9127(2) A , Z=16, F(000)=
3072, Dc=1.044 g cm−3, v=0.158 mm−1 T=293(2)
K, 2q=2.9–43.0°, measured reflections 2870, inde-
pendent reflections 2870 (Rint=0), observed reflec-
tions [I\2|(I)] 2863, hydrogen atoms were included
using a riding model, refined parameters 281, weight
371(6)
50(7)
106(8)
491(8)
w
−1=[|2(F2o)+(0.1513P)2] where P=(Fo2 +2F2c)/3,
GOF on F2=0.962, final R1=0.0863, wR2=0.2172
[I\2|(I)]. Because of the very weak diffracting ca-
pacity of 1a, only the silicon and carbon atoms in the
methyl groups were assigned with anisotropic dis-
placement parameters to maintain a reasonable data-
to-parameter ratio of ten. A final Fourier-difference
electron density synthesis revealed maximum and min-
imum residual electron-density peaks of 0.31 and −
814(7)
1247(7)
1424(8)
1832(8)
2048(8)
1860(6)
1447(7)
−389(8)
−703(8)
2448(8)
2809(7)
−1708(8)
−662(7)
−1826(7)
3929(7)
3897(8)
2879(8)
0.29 eA−3. Atomic coordinates are given in Table 3.
˚
Additional material is available from the Cam-
bridge Crystallographic Data Centre (CCDC), com-
prising hydrogen atom coordinates, thermal para-
meters and full tables of bond lengths and angles.
Acknowledgements
a
Equivalent isotropic U(eq) is defined as one third of the trace of the
orthogonalized Uij tensor.
We acknowledge the Croucher Foundation for a
Fellowship (to W.-Y.W.) and the Department of
Chemistry, The University of Hong Kong for the X-
ray data collection of structure 1a during the leave of
absence of W.-Y.W. in Hong Kong. We also thank S.
Mang of the Melville Laboratory for Polymer Synthe-
sis for assistance in GPC measurements.
4.4. Molecular weight measurements
Molar masses were determined by gel permeation
chromatography (GPC) using two PL Gel 30 cm, 5

228
J. Lewis et al. / Journal of Organometallic Chemistry 556 (1998) 219–228
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