Synthetic, spectroscopic and electrochemical characterisation of mixed-metal acetylide complexes

Article abstract of DOI:10.1016/S0022-328X(98)00816-X

Terminal metal acetylide complexes trans-[(dppm)₂(Cl)Os(-CC-R-CC-H)] (dppm=Ph₂PCH₂PPh₂, R=-p-C₆H₄- (1), -p-C₆H₄-C₆H₄-p- (2)) and trans-[(Et₃P)₂(Ph)Pt(CC-p-C₆H₄-CCH)] (3) have been synthesised by the application of established synthetic routes. Acetylide bridged mixed-metal complexes trans-[(dppm)₂(Cl)Os-CC-p-C₆H ₄-CC-Ru(Cl)(dppm)₂] (4), trans-[(Et₃P)₂(Ph)Pt-CC-p-C₆H ₄-CC-Ru(Cl)(dppm)₂] (5), trans-[(Et₃P)₂(Ph)Pt-CC-p-C₆H ₄-CC-Ru(Ph₃P)₂(η⁵-C ₅H₅)] (6) and trans-[(Et₃P)₂(Ph)Pt-CC-p-C₆H ₄-CC-Ru(Ph₃P)₂(η⁵-C ₅H₄-CH₃)] (7) have been formed by the reaction of 1, 2 and 3 with the appropriate metal chlorides. Complex 6 is less soluble in common organic solvents than the other complexes but this insolubility has been overcome by introducing a methylcyclopentadienyl group on the ruthenium centre to form complex 7. Complexes 1, 2, 4, 6 and 7 have shown reversible redox chemistry and in the di-metallic complexes, intramolecular electronic communication has been investigated by cyclic voltammetry. The shift in the lowest energy band in the UV-vis spectra of the mixed-metal complexes 4, 5, 6 and 7 is largely dependent on the various metal fragments.

Full text of DOI:10.1016/S0022-328X(98)00816-X

Journal of Organometallic Chemistry 570 (1998) 55–62
Synthetic, spectroscopic and electrochemical characterisation of
mixed-metal acetylide complexes
Muhammad Younus a,*, Nicholas J. Long a, Paul R. Raithby b, Jack Lewis b
a Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2AY, UK
b Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, UK
Received 16 April 1998
Abstract
Terminal metal acetylide complexes trans-[(dppm)2(Cl)Os(–CꢀC-R-CꢀC–H)] (dppm=Ph2PCH2PPh2, R=-p-C6H4– (1), -p-
C6H4–C6H4-p- (2)) and trans-[(Et3P)2(Ph)Pt(CꢀC-p-C6H4–CꢀCH)] (3) have been synthesised by the application of established
synthetic routes. Acetylide bridged mixed-metal complexes trans-[(dppm)2(Cl)Os–CꢀC-p-C6H4–CꢀC–Ru(Cl)(dppm)2] (4), trans-
[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Cl)(dppm)2] (5), trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Ph3P)2(p5-C5H5)] (6) and
trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Ph3P)2(p5-C5H4–CH3)] (7) have been formed by the reaction of 1, 2 and 3 with the
appropriate metal chlorides. Complex 6 is less soluble in common organic solvents than the other complexes but this insolubility
has been overcome by introducing a methylcyclopentadienyl group on the ruthenium centre to form complex 7. Complexes 1, 2,
4, 6 and 7 have shown reversible redox chemistry and in the di-metallic complexes, intramolecular electronic communication has
been investigated by cyclic voltammetry. The shift in the lowest energy band in the UV–vis spectra of the mixed-metal complexes
4, 5, 6 and 7 is largely dependent on the various metal fragments. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Acetylide; Ruthenium; Osmium; Platinum; Electrochemistry
ties of these metal poly-ynes can be varied by changing
the nature of the spacer groups of an acetylide bridge
1. Introduction
[16,17] and in metal poly-ynes, y-electron delocalisation
can be transferred through the metals utilising their
There is a growing interest in the chemical, physical
and material properties of organometallic dimers,
diffuse d-orbitals [18,19]. The chemical and physical
oligomers and polymers in which a conjugated carbon
properties of carbon-rich organic polymers often can-
framework is spanned by transition metal centres [1–9].
not be exploited due to their poor solubility but this
Transition metal centres possess redox, magnetic, opti-
can be improved by incorporating alkyl substitutents
cal and electronic properties and by changing the ligand
in a complex or polymer, variation in these properties
can be ‘fine-tuned’ and optimised [10–15]. The conju-
on the ligands [20].
The electronic communication (metal–metal interac-
tion) between metal centres of dimetallic complexes and
gated acetylide units in metal poly-yne systems, which
polymers can be investigated by electrochemical studies,
formally have alternate triple and single bonds, have a
where the metal centres are redox active [21,22].
rigid-rod geometry and can act as good potential path-
Acetylide-bridged homo-metallic systems of the type
ways for electronic interaction between metal centres. It
M–CꢀC–R–CꢀC–M (M=Fe and Ru; R=aromatic
or heteroaromatic spacer) and Fc–CꢀC–C6H4-p-CꢀC–
M (Fc=ferrocenyl, M=Ru, Os and Mn) have been
studied extensively by our group and by others [21–25].
has been shown that the electronic and optical proper-
* Corresponding author. Fax: +44 171 5945804; e-mail:
m.younus@ic.ac.uk
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00816-X

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M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
Scheme 1. Synthesis of terminal acetylide complexes. Reagents and conditions: i) cis-[(dppm)2OsCl2], 2NaPF6, CH2Cl2; ii) DBU; iii) trans-
[(Et3P)2Pt(Ph)Cl], Cul, Et2NH.
Compared to homometallic systems however, literature
reports on mixed metal acetylide systems are very rare
[26]. We have considered the possibility of improving
electronic communication in systems where the
acetylide bridge links alternate donor and acceptor
metal centres in a polymeric chain. We therefore, report
herein the design and synthesis of osmium and plat-
inum di-yne precursors and their mixed-metal com-
plexes of ruthenium. Electrochemical studies of these
complexes are performed to elucidate the metal–metal
interactions and the UV–vis spectra of the complexes
show how the metals and ligands influence the lowest
energy band in the mixed-metal complexes.
cal trans orientation of the ligands and the +FAB
mass spectra of the complexes exhibit peaks corre-
sponding to the molecular ion.
The platinum di-yne trans-[(Et3P)2(Ph)Pt(CꢀC-p-
C6H4–CꢀCH)] (3) was prepared by applying the syn-
thetic route of Sonogashira et al. [28]. The reaction of
trans-[(Et3P)2(Ph)PtCl] with two equivalents of HCꢀC-
p-C6H4–CꢀCH, in CH2Cl2/Et2NH in the presence of
CuI, while stirring at room temperature (r.t.) for 4 h,
afforded complex 3 as an off white solid in an 83%
yield (Scheme 1).
The IR spectrum of 3 displays characteristic w(CꢀC)
and w(ꢀC–H) frequencies at 2091 and 3295 cm−1 which
lie in the usual frequency ranges for platinum |-
acetylide complexes [28]. The terminal acetylenic proton
CꢀC–H of the complex appears at 3.08 ppm as a
singlet in the 1H-NMR spectrum and the 31P-{1H}-
NMR spectrum contains a singlet with Pt satellites
2. Results and discussion
2.1. Synthesis of terminal metal acetylide complexes
1
(coupling constant J(Pt–P) of 2679 Hz) which is consis-
The complexes trans-[(dppm)2(Cl)Os(CꢀC-p-C6H4–
CꢀC–H)] (1) and trans-[(dppm)2(Cl)Os(CꢀC-p-C6H4–
C6H4-p-CꢀC–H)] (2) were prepared by a modification
of published procedures [26,27]. The reaction of cis-
[(dppm)2OsCl2] with one equivalent of terminal di-
tent with the trans geometry of the phosphine ligands.
The +FAB mass spectrum displays a signal for the
molecular ion of 3 at 633 a.m.u. and shows the loss of
the acetylide ligand.
acetylenes
H–CꢀC-R-CꢀC–H
(R=p-C6H4,
2.2. Synthesis of mixed-metal acetylide complexes
p-C6H4–C6H4-p-) and two equivalents of NaPF6 gave
vinylidene complexes which were not isolated but in-
stead, deprotonated in situ using one equivalent of
DBU (Scheme 1).
The reaction of cis-[(dppm)2RuCl2] with one equiva-
lent of trans-[(dppm)2(Cl)Os(CꢀC-p-C6H4–CꢀC–H)] 1
and two equivalents of NaPF6, gave a vinylidene com-
plex which upon in situ deprotonation by DBU af-
forded trans-[(dppm)2(Cl)Os(CꢀC-p-C6H4–CꢀC–Ru-
(Cl)(dppm)2] (4) in a 45% yield (Scheme 2).
1
Complexes 1 and 2 were characterised by IR, H-
NMR, 31P-{1H}-NMR and mass spectroscopies. Char-
acteristic w(CꢀC) and w(ꢀC–H) vibrations were
observed in the IR spectrum at 2071 and ca. 3300
cm−1, respectively. Terminal acetylenic protons of the
complexes appeared at ca. 3.05 ppm as a singlet and the
protons of the aromatic spacer groups displayed the
The IR spectrum of the complex contains a charac-
teristic broad peak at 2075 cm−1 corresponding to a
w(CꢀC) stretching frequency. The mono-terminal
acetylides of ruthenium and osmium have a w(CꢀC)
1
expected (AB)2 pattern in the H-NMR spectra of the
stretching frequency in the same region (2070 cm−1
)
complexes. The 31P-{1H}-NMR spectra contain singlets
[29], therefore, the broad peak at 2075 cm−1 is proba-
bly due to both ruthenium and osmium bound acetylide
at −190 ppm which are consistent with the symmetri-

M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
57
Scheme 2. Synthesis of Os–Ru mixed-metal acetylide complexes. Reagents and conditions: i) cis-[(dppm)2RuCl2], 2NaPF6, CH2Cl2, ii) DBU.
links. The 31P-{1H}-NMR spectrum of the complex
contains two signals at −147.5 and −190.2 ppm
corresponding to the ruthenium and osmium bound
phosphorus atoms, respectively and multiplets at 4.90
[(Et3P)2(Ph)Pt – CꢀC-p-C6H4 – CꢀC – Ru(Ph3P)2(p5-C5-
H5)] (6). The synthetic route applied here is analogous
to that previously reported for the preparation of ruthe-
nium bis-acetylides [30]. Complex 6 was obtained by
refluxing a suspension of [(p5-C5H5)(Ph3P)2RuCl] and
1
and 5.44 ppm in the H-NMR spectrum correspond to
the PCH2P protons of the dppm ligands at ruthenium
and osmium centres, respectively. The +FAB mass
spectrum displays a signal at 2022 corresponding to the
molecular ion of the complex 4.
trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀCH)]
(3),
in
methanol for 0.5 h, followed by treatment with a
10-fold excess of sodium in the reaction mixture after
cooling. The product was obtained as a pale yellow
powder in a 49% yield (Scheme 3) but is less soluble in
common organic solvents than the other complexes and
also decomposes gradually in chlorinated solvents. To
overcome the solubility problems, a similar methyl-sub-
stituted cyclopentadienyl complex trans-[(Et3P)2(Ph)Pt–
CꢀC-p-C6H4–CꢀC–Ru(Ph3P)2(p5-C5H4–CH3)] (7) was
synthesised, using the same procedure. Complex 7, with
the solubilising methylcyclopentadienyl group is signifi-
cantly more soluble and fairly stable in chlorinated
solvents.
The complex trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–
CꢀC–Ru(Cl)(dppm)2] (5) was synthesised and purified
following the method discussed for 4 and obtained in
an 85% yield (Scheme 3). All the spectroscopic data are
in accord with the formulation of the new complex. The
IR spectrum shows two w(CꢀC) frequencies at 2075 and
2091 cm−1 which are consistent with the frequencies of
ruthenium and platinum bound |-acetylides, respec-
tively [27]. The 31P-{1H}-NMR spectrum of 5 contains
a singlet at −147.5 ppm corresponding to the trans
geometry of the ligands which is a common feature of
ruthenium mono-chloro-acetylides [27,29] and a signal
at −131.4 ppm with Pt satellites (1J(Pt–P)=2688) corre-
sponding to PEt3 coordinated to the platinum centre.
The +FAB mass spectrum of complex 5 shows a
molecular ion signal at 1537 a.m.u. The 31P-{1H}-NMR
and mass spectra also show the formation of trace
amounts of the trinuclear platinum and ruthenium
The IR spectra of 6 exhibited two w(CꢀC) stretching
frequencies at 2070 and 2090 cm−1 for the |-bonded
ruthenium and platinum acetylides, respectively. The
five protons of the p5-bound C5H5 group appeared at
1
4.47 ppm as a singlet in the H-NMR spectrum of the
complex and the 31P-{1H}-NMR spectrum of the com-
plex displayed a singlet at −89.9 ppm which was
assigned to the PPh3 bonded to ruthenium and another
singlet at −130.1 with Pt satellites (1J(Pt–P)=2695 Hz)
was assigned to PEt3 bonded to platinum. The mass
spectrum contained a signal at 1325 a.m.u. correspond-
ing to the molecular ion peak of complex 6. Complex 7
was also characterised similarly (spectroscopic data in
Section 4.2.6).
complex
trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–
Ru(dppm)2–CꢀC-p-C6H4–CꢀC–Pt(Ph)(PEt3)2] which
was formed by the substitution of two chlorides of
[Ru(dppm)2Cl2] (subsequent efforts to form this trinu-
clear complex have been unsuccessful to date). To
alleviate the formation of mixures, the ruthenium-
mono-chloride precursor [(p5-C5H5)(Ph3P)2RuCl] was
used in the synthesis of the mixed metal di-yne trans-
Table 1 shows the lowest absorption bands of all the
mono- and di-nuclear complexes. Molecular orbital cal-
Scheme 3. Synthesis of Pt–Ru mixed metal acetylide complexes. Reagents and conditions: i) cis-[(dppm)2RuCl2], 2NaPF6, CH2Cl2, ii) DBU; iii)
[Ru(C5H5) (PPh3)2Cl], Na, CH3OH.

58
M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
Table 1
Electrode potentials and lowest energy absorption peaks of mononuclear and mixed-metal acetylide complexes
Complex
E1I (V)
E1II (V)
umax in nm (log m)
2
2
Trans-[(dppm)2(Cl)Os(–CꢀC-p-C6H4–CꢀC–H)] 1
Trans-[(dppm)2(Cl)Os–CꢀC-p-C6H4–C6H4-p-CꢀC–H)] 2
Trans-[(dppm)2(Cl)Ru(–CꢀC-p-C6H4–CꢀC–H)] [27]
Trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–H) 3
−0.16
−0.26
0.0
—
—
—
—
−0.48
—
—
—
—
359 (4.30)
381 (4.11)
386 (4.35)
327 (4.58)
380 (4.11)
360 (4.69)
—
306 (4.60)
360 (4.67)
360 (4.46)
—
Trans-[(dppm)2(Cl)Os–CꢀC-p-C6H4–CꢀC–Ru(Cl)(dppm)2] 4
Trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Cl)(dppm)2] 5
[(p5-C5H5)(Ph3P)2RuCl]
−0.12
0.07b
+0.12
0.0
−0.13
−0.19
[(p5-C5H5)(Ph3P)2Ru(CꢀC–C6H5)] [33]c
Trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Ph3P)2(p5-C5H5)] 6
Trans-[(Et3P)2(Ph)Pt–CꢀC-p-C6H4–CꢀC–Ru(Ph3P)2(p5-C5H4–CH3)] 7
—
a Scan rate 100 mV s−1. All E1 values referenced to ferrocene in the same system. b Irreversible anodic peak. c Fc=0.55 V versus Ag/AgCl.
2
culations on the Group 10 acetylide systems trans-
[L2M(CꢀCR)2] (L=alkyl phosphines; M=Pt, Pd, Ni;
R=H, alkyl, aryl) reveal that the lowest energy
bands arise from the electronic transitions from
y(CꢀCR) to y(CꢀCR)* orbitals. These transitions
possess charge-transfer character as a result of mixing
between the (CꢀCR)* and metal p-orbitals [31]. Our
previously reported molecular orbital calculations on
energy band in the spectra due to the platinum com-
plexes as being a result of ligand to metal charge
transfer (LMCT) and that of ruthenium and osmium
species as being due to the metal to ligand charge
transfer (MLCT) transitions. Indeed, Whittall et al.
assigned the lowest energy band of [(p5-
C5H5)Ru(PPh3)2(CꢀC–R)] (R=Ph, C6H4-p-NO2) as a
MLCT band [33]. The lowest energy band of the din-
uclear ruthenium–osmium complex (4) and ruthe-
nium–platinum complex (5) lies in between their
mononuclear precursors (Fig. 1). No significant shifts
were observed in the lowest energy bands of com-
plexes 6 and 7 compared to 5 when ligand environ-
ments were changed around ruthenium.
Group
8
acetylide systems [L4M(CꢀC-p-C6H4–
CꢀCH)2] (L=phosphine, CO; M=Fe, Ru) shows
that the highest occupied molecular orbitals (HOMO)
are d-like and the lowest unoccupied molecular or-
bitals (LUMO) are CꢀC*-like in character [32]. Based
on these previous studies we can assign the lowest
Fig. 1. UV–vis spectra of platinum and ruthenium mononuclear and mixed metal acetylide complexes.

M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
59
couple is lowered significantly (from −0.16 to −0.48
V). Conversely, the RuII centre undergoes oxidation at
−0.12 V which was unexpected, as the oxidation of the
ruthenium centre should be more difficult after the
oxidation of the osmium centre.
Electrochemical investigations of dimetallic complexes
of the type trans-[(dppm)2(Cl)M–CꢀC-p-C6H4–CꢀC–
M(dppm)2(Cl)] (M=Ru and Os) have shown a similar
trend in that the ruthenium centres oxidised at −0.30
and 0.0 V and the osmium centres oxidised at −0.51
and −0.21 V, respectively [25]. Theoretical studies are
underway to try and rationalise these observations, but
it is likely that this anomalies arise from the formation
of a delocalised allenylidene type structure facilitating
unusual electrochemical behaviour. For 5 an irre-
versible wave was observed at 0.07 V, which may be
due to the oxidation of the ruthenium centre. The
previously reported trinuclear mixed metal complex
trans-[(dppe)2(Cl)Ru–CꢀC-p-C6H4 –CꢀC–(Bu3P)2Pd–
CꢀC-p-C6H4–CꢀC–Ru(Cl)(dppe)2] showed a reversible
wave at 0.33 V versus SCE and an irreversible wave at
1.14 versus SCE which were due to the oxidations of
RuII/RuIII and RuIII/RuIV, respectively [26]. The cyclic
voltammogram of the mixed-metal di-yne trans-
[(Et3P)2(Ph)Pt – CꢀC – C6H4-p-CꢀC – Ru(Ph3P)2(p5-C5-
H5)] (6) showed a quasi-reversible oxidation (DE=86
mV) wave at −0.13 V which is significantly lower than
the oxidation potential of [(Ph3P)2(p5-C5H5)RuCl]
(E1 = +0.12 V) and [(Ph3P)2(p5-C5H5)Ru(CꢀC–C6H5)]
(E21 =0.0 V) [33], thus indicating that the platinum
fragment transfers electron density to the ruthenium
2
Fig. 2. Cyclic voltammograms of (a) trans-[(dppm)2(Cl)Ru–CꢀC-p-
C6H4–CꢀC–Os(Cl)(dppm)2] (b) trans-[(dppm)2(Cl)Ru(–CꢀC-p-
C6H4–CꢀC–H)] (c) trans-[(dppm)2(Cl)Os(–CꢀC-p-C6H4–CꢀC–H)].
centre. Similar observations were reported on the
mixed-metal ferrocenylacetylides trans-[(Ph3P)2(Ph)-
Pt(CꢀCFc)] where the redox potential of the ferrocenyl
unit is significantly lowered after introduction of the
platinum fragment (E1 of FcCꢀC-p-C6H4–CH3 is 0.12
V and that of trans-[2(Ph3P)2(Ph)Pt(CꢀCFc)] is −0.13
V) [34]. Complex 7 was quasi-reversibly oxidised (DE=
84 mV) at −0.19 V indicating that the methyl cy-
clopentadienyl unit did not significantly ease the
oxidation of the Ru centre compared to an unsubsti-
tuted cyclopentadienyl ring.
3. Electrochemistry of mixed-metal acetylide complexes
The cyclic voltammogram of the complex trans-
[(dppm)2(Cl)Os – CꢀC-p-C6H4 – CꢀC – Ru(Cl)(dppm)2]
(4) displays two well-separated (DE1 =0.36 V) re-
2
versible waves (DE1=63 eV, DE2=58 eV) at −0.48
In conclusion, we have synthesised some novel
mixed-metal ruthenium–osmium and ruthenium–plat-
inum complexes. Cyclic voltammetry of these com-
plexes shows that metal fragments can act as electron
donors or acceptors and the lowest energy absorption
band in the UV–vis spectra of the complexes can be
optimised by changing the metal centres. The synthesis
and optical spectroscopy of an extended range of
mixed-metal poly-ynes are in progress in our
laboratories.
and −0.12 V which can be considered as two one
electron oxidations at the osmium and ruthenium cen-
tres, respectively (Fig. 2). The reference complexes
trans-[(dppm)2(Cl)Ru(CꢀC-p-C6H4–CꢀC–H)] [27] and
trans-[(dppm)2(Cl)Os(CꢀC-p-C6H4–CꢀC–H)] (1) are
reversibly oxidised at 0.0 and −0.16 V, respectively
(Fig. 2). From the cyclic voltammogram of 4, it may be
concluded that the ruthenium centre releases electron
density to the osmium unit via the CꢀC-p-C6H4–CꢀC
bridge and thus the electrode potential of the OsII/OsIII

60
M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
4. Experimental
4.1. General
methanol and recrystallised from dichloromethane/hex-
ane to give a pale yellow microcrystalline powder in a
71% yield (0.106 g). Anal. calc. for C60H49ClP4Os: C
64.36, H 4.38; Found C 63.93 H 4.76%. IR (CH2Cl2)
1
All reactions were performed under an inert nitrogen
atmosphere using standard Schlenk techniques. Sol-
vents were freshly distilled, dried and degassed before
use by the standard procedures [35]. IR spectra were
recorded as dichloromethane solutions, in an NaCl cell,
on a Perkin-Elmer 1710 Fourier Transform spectrome-
ter. UV–vis spectra were recorded in a Perkin-Elmer
Lambda 11 spectrometer. 1H-NMR and 31P-{1H}-
NMR spectra were recorded on a Bruker WM-250
spectrometer in appropriate solvents. The chemical
shifts were referenced to TMS for 1H-NMR and to
trimethylphosphite for 31P-{1H}-NMR spectra. Mass
spectra were recorded as dichloromethane solutions on
a Kratos MS890 spectrometer. Elemental analyses were
performed at the Department of Chemistry, University
of Cambridge and at the Department of Chemistry,
Imperial College of Science, Technology and Medicine,
London. Electrochemical data were recorded using an
Autolab PGSTAT 20 potentiostat with a standard three
electrode system (platinum as working and auxiliary
electrodes and Ag/AgCl reference electrode). All elec-
trochemical measurements were referenced to the fer-
rocene/ferrocenium redox couple (Fc=0.50 V vs.
Ag/AgCl at 298 K in 0.1 M [Bu4N][BF4] solution in
CH2Cl2).
The commercially available starting materials, PEt3,
Ph2PCH2PPh2 (dppm), Br-p-C6H4–Br, Br-p-C6H4–
C6H4-p-Br, PhLi, CuI, Ph3P, Pd(OOCCH3)2 were ob-
tained from Aldrich and PtCl2, RuCl3 ·3H2O from
Johnson Matthey and used without further purification.
Samples of HCꢀCSi(CH3)3 were obtained from the
preparation laboratory of the Department of Chem-
istry, University of Cambridge. The metal halides,
trans-[(Et3P)2Pt(Ph)(Cl)] [36], cis-[(dppm)2RuCl2] [37],
[(p5-C5H5)(Ph3P)2RuCl] [38], [(p5-C5H4–CH3)(Ph3P)2-
RuCl] [38], cis-[(dppm)2OsCl2] [37] and terminal di-
acetylenes HCꢀC-p-C6H4–CꢀCH and HCꢀC-p-C6H4–
C6H4-p-CꢀCH were prepared by published procedures
[39].
w(CꢀC), 2071 cm−1, w(CꢀCH) 3307 cm−1. H-NMR
(CDCl3, 250 Hz, l ppm) 3.04 (s, 1H, CꢀCH), 5.45 (m,
3
4H, PCH2P), 5.91 (d, J −H )=8 Hz, 2H, aromatic
2
3
spacer protons), other ar(oHmatic spacer protons overlap
with diphos. aromatics, 6.83–7.66 (m, 42H, Ph). 31P-
{1H}-NMR (CDCl3, 250 Hz, l ppm) −190.0. FAB
MS: 1120 (calc. M+ 1118).
4.2.2. Trans-[(dppm)2Os(Cl)(CꢀC-p-C6H4–C6H4-p-
CꢀC–H)] (2)
The complex was obtained as for 1 as a pale yellow
powder in an 87% yield. Anal. calc. for
C66H53ClP4Os·1/2CH2Cl2: C 64.50, H 4.36; Found C
64.45 H 4.56%. IR (CH2Cl2) w(CꢀC) 2071 cm−1
,
w(CꢀCH) 3297 cm−1 1H-NMR (CDCl3, 250 Hz, l
.
ppm) 3.10 (s, 1H, CꢀCH), 5.43 (m, 4H, PCH2P), 6.11
3
(l, J(H −H )=8 Hz, 4H, aromatic spacer protons),
2
3
other aromatic spacer protons overlap with diphos.
aromatics, 6.80–7.54 (m, 44H, Ph). 31P-{1H}-NMR
(CDCl3, 250 Hz, l ppm) −190.09. FAB MS: 1196
(Calc. M+ 1196).
4.2.3. Trans-[(PEt3)2Pt(Ph)(CꢀC-p-C6H4–CꢀC–H)]
(3)
A solution of trans-[(PEt3)2Pt(Ph)(Cl)] (0.350 g, 0.64
mmol) in a 1:1 mixture of dichloromethane and diethy-
lamine (20 ml) was treated with H–CꢀC-p-C6H4–
CꢀC–H (0.161 g, 1.28 mmol) and CuI (3 mg). The
reaction mixture was stirred for 4 h at r.t. The solvent
was then removed and the crude product was subjected
to column chromatography on silica first using hexane
(to remove any excess ligand), followed by
dichloromethane-hexane (1:1) as eluants. After evapo-
ration of solvents in vacuo the complex was obtained as
an off-white solid in an 83% yield (0.340 g). Anal. calc.
for C28H40P2Pt: C 53.08, H 6.31; Found C 52.74 H
5.92%. IR (CH2Cl2) w(CꢀC) 2091 cm−1, w(CꢀCH) 3296
cm−1. 1H-NMR (CDCl3, 250 Hz, l ppm) 1.08 (m, 18H,
CH3), 1.80 (m, 12H, CH2), 3.08 (s, CꢀCH), aromatic
spacer protons overlap with phenyl aromatics, 6.7–7.4
(m, 9H, Ph). 31P-{1H}-NMR (CDCl3, 250 Hz, l ppm)
4.2. Syntheses
1
−131.20, J(Pt–P) 2679 Hz. FAB MS: 633 (Calc. M+
4.2.1. Trans-[(dppm)2Os(Cl)(CꢀC-p-C6H4–CꢀC–H)]
(1)
633).
To a solution of cis-[Os(dppm)2Cl2] (0.136 g, 0.13
mmol) in dichloromethane (40 ml), H–CꢀC-p-C6H4–
CꢀC–H (0.018 g, 0.14 mmol) and sodium hex-
afluorophosphate (0.043 g, 0.26 mmol) were added. The
mixture was stirred for 20 h at r.t. The solution was
filtered and treated with one equivalent of DBU for 3 h
and the solvent was then removed in vacuo. The
product was purified by washing with a few ml of dry
4.2.4. Trans-[(dppm)2(Cl)Os–CꢀC-p-C6H4–CꢀC–
Ru(Cl)(dppm)2] (4)
To a solution of cis-[RuCl2(dppm)2] (0.071 g, 0.07
mmol) in dichloromethane (40 ml), freshly prepared
trans-[(dppm)2Os(Cl)(–CꢀC–p-C6H4–CꢀC–H)] (0.085
g, 0.07 mmol) and sodium hexafluorophosphate (0.023
g, 0.14 mmol) were added. The mixture was stirred for
4 h at r.t. The solution was filtered under N2 and

M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
61
treated with one equivalent of DBU for 3 h. The
4.2.7. Trans-[(Et3P)2(Ph)Pt–CꢀC–C6H4-p-CꢀC–
Ru(Ph3P)2(p5-C5H4–CH3)] (7)
solvent was then removed in vacuo. The product was
purified by washing with a few ml of dry methanol to
afford a reddish–yellow powder in a 45% yield (0.07 g).
The complex was found to be air sensitive and this
precluded accurate microanalysis. IR (CH2Cl2) w(CꢀC),
This was obtained as an analogous fashion to 6 as a
yellow power, yield: 66%. Anal. calc. for
C70H76P4RuPt: C 62.87, H 5.68; Found C 62.36 H
5.41%. IR (CH2Cl2) w(CꢀC), 2069, 2090 cm−1 1H-
.
1
2075 cm−1. H-NMR (CDCl3, 250 Hz, l ppm) 4.90
NMR (CDCl3, 250 Hz, l ppm) 1.07 (m, 18H, CH3),
1.76 (m, 12H, CH2), 2.02 (s, 3H, CH3), 3.93 (s, 2H,
C5H4), 3.79(s, 2H, C5H4), aromatic spacer protons
overlap with phos. aromatics, 7.03–7.50 (m, 39H, Ph).
31P-{1H}-NMR (CDCl3, 250 Hz, l ppm) −131.29,
(1J(Pt–P) 2647 Hz, Pt(PEt3)), −89.67 (Ru(PPh3)). FAB
MS: 1337 (Calc. M+ 1336.5).
(m, 4H, Ru(PCH2P)), 5.44 (m, 4H, Os(PCH2P)), 5.95
3
(d, J(H −H )=8 Hz, 4H, aromatic spacer protons),
2
3
3
7.65 (d, J(H −H )=8 Hz, 4H, aromatic spacer pro-
2
3
tons), 6.79–7.75 (m, 80H, Ph). 31P-{1H} NMR (CDCl3,
250 Hz, ppm) −147.7 (Ru(Ph2PCH2PPh2)),
d
−190.20 (Os(Ph2PCH2PPh2)). FAB MS: 2022 (Calc.
M+ 2021).
Acknowledgements
4.2.5. Trans-[(dppm)2(Cl)Ru–CꢀC-p-C6H4–CꢀC–
Pt(Et3P)2(Ph)] (5)
We thank the Cambridge Commonwealth Trust and
the Overseas Research Scheme for support (M.
Younus) of this work, and Johnson-Matthey plc for the
generous loan of precious metals.
The complex was obtained, as for 4 (except that
trans-[(PEt3)2Pt(Ph)(CꢀC-p-C6H4–CꢀC–H) was used),
as a pale yellow powder in an 85% yield. The crude
powder was redissolved in of 1:4 dichloromethane/hex-
ane (40 ml) and the solvent was evaporated slowly at
r.t. on a rotary evaporator until a reddish oil appeared
in the flask. The supernant liquid was decanted and this
process was repeated once or twice, to leave, after
evaporation of solvents in vacuo, a bright yellow solid.
Anal. calc. for C78H83ClP6RuPt: C 60.91, H 5.40;
Found C 60.64 H 5.34%. IR (CH2Cl2) w(CꢀC), 2075,
2091 cm−1. 1H-NMR (CDCl3, 250 Hz, l ppm) 1.08 (m,
18H, CH3), 1.72 (m, 12H, CH2), 4.91 (m, 4H, PCH2P),
aromatic spacer protons overlap with diphos. aromat-
ics, 6.7–7.4 (m, 49H, Ph). 31P-{1H}-NMR (CDCl3, 250
Hz, l ppm) −131.38 (1J(Pt–P) 2688 Hz, Pt(PEt3)),
−147.48 (Ru(Ph2PCH2PPh2)). FAB MS: 1537 (Calc.
M+ 1536).
References
[1] H.B. Fyfe, M. Mlekuz, D. Zargarian, N.J. Taylor, T.B. Marder,
J. Chem. Soc. Chem. Commun. (1991) 188.
[2] B.F.G. Johnson, A.K. Kakkar, M.S. Khan, et al., J. Mater.
Chem. 1 (1991) 485.
[3] M.S. Khan, S.J. Davies, A.K. Kakkar, et al., J. Organomet.
Chem. 424 (1992) 87.
[4] R. Crescenzi, C.L. Sterzo, Organometallics 11 (1992) 4301.
[5] W. Beck, B. Niemer, M. Wieser, Angew. Chem. Int. Ed. Engl. 32
(1993) 923.
[6] E. Viola, C.L. Sterzo, R. Crescenzi, G. Frachey, J. Organomet.
Chem. 493 (1995) 9.
[7] O. Lavastre, M. Even, P.H. Dixneuf, A. Pacreau, J. Vairon,
Organometallics 15 (1996) 1530.
[8] C.J. Adam, S.L. James, P.R. Raithby, J. Chem. Soc. Chem.
Commun. (1997) 2155.
[9] N. Chawdhury, R.H. Friend, A. Ko¨hler, et al., J. Chem. Phys.
(in press).
[10] J. Manna, K.D. John, M.D. Hopkins, Adv. Organomet. Chem.
38 (1995) 79.
4.2.6. Trans-[(p5-C5H5)(PPh3)2Ru–CꢀC-p-C6H4–
CꢀC–Pt(Et3P)2(Ph)] (6)
A
refluxing solution of [(p5-C5H5)(PPh3)2RuCl]
(0.100 g, 0.137 mmol) in dry methanol (15 ml) was
treated with trans-[(PEt3)2Pt(Ph)(CꢀC-p-C6H4–CꢀC–
H)] (0.094 g, 0.15 mmol) and refluxed for 10 min. It was
then allowed to cool down to r.t. and sodium (10-fold
excess) was added. On stirring a yellow precipitate
appeared which was filtered through a sintered funnel
to afford a analytically pure yellow powder in a 49%
yield (0.115 g). Anal. calc. for C69H74P4RuPt: C 62.62,
H 5.64; Found C 62.35 H 5.27%. IR (CH2Cl2) w(CꢀC),
[11] I. Manners, Adv. Organomet. Chem. 37 (1995) 131.
[12] I. Manners, Chemistry in Britain (1996) 46.
[13] N.D. Jones, M.O. Wolf, Organometallics 16 (1997) 1352.
[14] M.C.B. Colbert, J. Lewis, N.J. Long, P.R. Raithby, A.J.P.
White, D.J. Williams, J. Chem. Soc. Dalton Trans. (1997) 99.
[15] I.R. Whittall, M.G. Humphrey, S. Houbrechts, et al., J.
Organomet. Chem. 544 (1997) 277.
[16] J. Lewis, N.J. Long, P.R. Raithby, G.P. Shields, W.-Y. Wong,
M. Younus, J. Chem. Soc. Dalton Trans. (1997) 4283.
[17] N. Chawdhury, A. Ko¨hler, M. Younus, N.J. Long, P.R.
Raithby, J. Lewis, Macromolecules 31 (1998) 722.
[18] G. Frapper, M. Kartesz, Inorg. Chem. 32 (1993) 732.
[19] M. Springborg, R.C. Albers, Phys. Rev. B 53 (1996) 10626.
[20] N. Hagihara, K. Sonogashira, S. Takahashi, Adv. Polym. Sci. 41
(1980) 149.
1
2070, 2092 cm−1. H-NMR (CDCl3, 250 Hz, l ppm)
0.95 (m, 18H, CH3), 1.73 (m, 12H, CH2), 4.47 (s, 5H,
C5H5), aromatic spacer protons overlap with phos.
aromatics, 6.85–7.80 (m, 39H, Ph). 31P-{1H}-NMR
(CDCl3, 250 Hz, l ppm) −131.41, (1J(Pt–P) 2695 Hz,
Pt(PEt3)), −89.94 (Ru(PPh3)). FAB MS: 1325 (Calc.
M+ 1324).
[21] N.L. Narvor, L. Toupet, C. Lapinte, J. Am. Chem. Soc. 117
(1995) 7129.
[22] N.L. Narvor, C. Lapinte, Organometallics 14 (1995) 634.

62
M. Younus et al. / Journal of Organometallic Chemistry 570 (1998) 55–62
[23] L.D. Field, A.V. George, F. Laschi, E.Y. Malouf, P. Zanello, J.
Organomet. Chem. 435 (1992) 347.
[24] M.C.B. Colbert, S.L. Ingham, J. Lewis, N.J. Long, P.R.
Raithby, J. Chem. Soc. Dalton Trans. (1994) 2215.
[25] M.C.B. Colbert, J. Lewis, N.J. Long, et al., Organometallics 17
(1998) 3034.
White, J. Chem. Soc. Dalton Trans. (1996) 2011.
[31] H. Masai, K. Sonogashira, N. Hagihara, Bull. Chem. Soc. Jpn.
44 (1971) 2226.
[32] M.S. Khan, A.K. Kakkar, S.L. Ingham, et al., J. Organomet.
Chem. 472 (1994) 247.
[33] I.R. Whittall, M.G. Humphrey, D.C.R. Hockless, B.W. Skelton,
A.H. White, Organometallics 14 (1995) 3970.
[26] O. Lavastre, J. Plass, P. Bachmann, S. Guesmi, C. Moinet, P.H.
Dixneuf, Organometallics 16 (1997) 184.
[34] M. Sato, E. Mogi, M. Katada, Organometallics 14 (1995) 4837.
[35] D.D. Perrin, W.L.F. Amarego, D.R. Perrin, Purification of
Laboratory Chemicals, Pergamon, New York, 1980.
[36] J. Chatt, B.L. Shaw, J. Chem. Soc. (1960) 4020.
[37] J. Chatt, R.G. Hayter, J. Chem. Soc. Dalton Trans. (1961) 896.
[38] M.I. Bruce, N.J. Windsor, Aust. J. Chem. 30 (1977) 1601.
[39] S. Takahashi, Y. Kuroyama, K. Sonogashira, N. Hagihara,
Synthesis (1980) 627.
[27] C.W. Faulkner, S.L. Ingham, M.S. Khan, J. Lewis, N.J. Long,
P.R. Raithby, J. Organomet. Chem. 482 (1994) 139.
[28] K. Sonogashira, Y. Fujikura, T. Yatake, N. Toyoshima, S.
Takahashi, N. Hagihara, J. Organomet. Chem. 145 (1978) 101.
[29] A.J. Hodge, S.L. Ingham, A.K. Kakkar, et al., J. Organomet.
Chem. 488 (1995) 205.
[30] L.D. Field, A.V. George, D.C.R. Hockless, G.R. Purches, A.H.
.