The syntheses, structures and redox properties of phosphine-gold(I) and triruthenium-carbonyl cluster derivatives of tolans

Article abstract of DOI:10.1016/j.ica.2007.03.032

The syntheses of several ethynyl-gold(I)phosphine substituted tolans (1,2-diaryl acetylenes) of general form [Au(C{triple bond, long}CC₆H₄C{triple bond, long}CC₆H₄X)(PPh₃)] are described [X = Me (2a), OMe (2b), CO₂Me (2c), NO₂ (2d), CN (2e)]. These complexes react readily with [Ru₃(CO)₁₀(μ-dppm)] to give the heterometallic clusters [Ru₃(μ-AuPPh₃)(μ-η¹,η²-C₂C₆H₄C{triple bond, long}CC₆H₄X)(CO)₇(μ-dppm)] (3a-e). The crystallographically determined molecular structures of 2b, 2d, 2e and 3a-e are reported here, that of 2a having been described on a previous occasion. Structural, spectroscopic and electrochemical studies were conducted and have revealed little electronic interaction between the remote substituent and the organometallic end-caps.

Full text of DOI:10.1016/j.ica.2007.03.032

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 1646–1658
www.elsevier.com/locate/ica
The syntheses, structures and redox properties of phosphine-gold(I)
and triruthenium-carbonyl cluster derivatives of tolans
a
a
a
a
´
Wan M. Khairul , David Albesa-Jove , Dmitri S. Yufit , Maha R. Al-Haddad ,
a
b,
a
a
Jonathon C. Collings , Frantisˇek Hartl *, Judith A.K. Howard , Todd B. Marder ,
a,
*
Paul J. Low
a
Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
b
Received 6 January 2007; accepted 19 March 2007
Available online 27 March 2007
Dedicated to Professor Pierro Zanello, on the occasion of his 65th birthday, in recognition of his many contributions to organometallic chemistry.
Abstract
The syntheses of several ethynyl-gold(I)phosphine substituted tolans (1,2-diaryl acetylenes) of general form
[Au(C„CC6H4C„CC6H4X)(PPh3)] are described [X = Me (2a), OMe (2b), CO2Me (2c), NO2 (2d), CN (2e)]. These complexes react
readily with [Ru3(CO)10(l-dppm)] to give the heterometallic clusters [Ru3(l-AuPPh3)(l-g1,g2-C2C6H4C„CC6H4X)(CO)7(l-dppm)]
(3a–e). The crystallographically determined molecular structures of 2b, 2d, 2e and 3a–e are reported here, that of 2a having been
described on a previous occasion. Structural, spectroscopic and electrochemical studies were conducted and have revealed little electronic
interaction between the remote substituent and the organometallic end-caps.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Tolan; Ruthenium cluster; Gold complex; Electrochemistry; Spectroelectrochemistry
1. Introduction
the capacity for p-conjugated ligands to transmit electronic
effects between mono-metallic fragments, we were inter-
ested to discover if the tolan (1,2-diphenylacetylene) frag-
ment was an efficient conduit for the transmission of
electronic effects between a remote substituent and a cluster
core [11]. However, whilst there are numerous examples of
complexes derived from oligomeric phenylene ethynylenes
and their various properties, especially non-linear optical
response and excited state structures have been well
described [12–28], cluster compounds featuring these
‘‘wire-like’’ ligands are particularly scarce [29,30].
Gold(I)phosphine acetylide complexes are efficient
reagents for the transfer of acetylenic fragments to polyme-
tallic clusters, either by addition of the Au–C bond across a
metal–metal bond [31], or via elimination of gold(I)phos-
phine halide complexes upon Pd(0)/Cu(I) catalyzed reac-
tion with halocarbynes [32]. In this work, a series of
Molecular and polymeric compounds featuring
extended p-conjugated electronic structures are of consid-
erable interest from the point of view of developing new
materials for optical and electronic applications [1–5]. In
this context, oligomeric phenylene ethynylenes have been
particularly well studied [6]. The introduction of a metal
centre into the p-conjugated framework offers many possi-
bilities for further tuning of the physical properties, which
are modified by mixing of the metal d and ligand-based p
orbitals [7–10]. Although there are many discussions of
*
Corresponding authors. Tel.: +44 191 334 2114; fax: +44 191 384 4737
(P.J. Low), tel.: +31 20 525 6450; fax: +31 20 525 6456 (F. Hartl).
E-mail addresses: f.hartl@uva.nl (F. Hartl), p.j.low@durham.ac.uk
(P.J. Low).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.03.032

W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
1647
tolan derivatives Me3SiC„CC6H4C„CC6H4X [X = Me
(1a), OMe (1b), CO2Me (1c), NO2 (1d), CN (1e)] have been
prepared, converted to the gold(I) complexes
[Au(C„CC6H4C„CC6H4X)(PPh3)] [2a–e] and subse-
quently reacted with [Ru3(CO)10(l-dppm)] to give the
ventional fashion (K2CO3/MeOH) to afford terminal alky-
nes (1-H). Reaction of either the Me3Si- or H-terminated
ethynyl tolans with [AuCl(PPh3)] in the presence of NaOMe
gave the gold complexes [Au(C„CC6H4C„CC6H4X)-
(PPh3)] [X = Me (2a), OMe (2b), CO2Me (2c), NO2 (2d),
CN (2e)], the yield being comparable from both routes
(70–84%) (Scheme 1). The complexes were characterized
by the usual spectroscopic methods, which included singlet
phosphorus resonances near d 43 ppm and a single
m(C„C) band slightly above 2200 cmꢀ1, and by single crys-
tal X-ray diffraction in the case of 2a, 2b, 2d and 2e (vide
infra).
cluster-substituted
tolans
[Ru3(l-AuPPh3)(l-g1,g2-
C2C6H4C„CC6H4X)(CO)7(l-dppm)] (3a–e) which feature
the desired cluster-tolan-substituent motif. The molecular
structures, electrochemical and spectroscopic properties,
and IR spectroelectrochemical response of these com-
pounds are described herein.
2. Results and discussion
Reaction of the gold complexes 2a–e with [Ru3(CO)10(l-
dppm)] in refluxing THF, gave Ru3(l-AuPPh3)(l-
C2C6H4C„CC6H4X)(CO)7(l-dppm) (3a–e) (Scheme 2).
Similar species have been obtained from reactions of gold
acetylides with triangulo triruthenium clusters, [36] or
through the auration of cluster anions obtained by depro-
tonation of the corresponding hydride clusters [37]. Spec-
troscopic parameters consistent with the proposed
structure were obtained, and the characterization com-
pleted in each case by a single crystal X-ray diffraction
study. The 31P NMR spectrum was particularly informa-
tive, with the three chemically distinct phosphorus centres
giving rise to a characteristic pattern in which the reso-
nance arising from P(2) was split into a doublet of doublets
by coupling to both the gold-bound phosphine P(1) and the
dppm phosphorus centre P(3). The electrospray ionization
2.1. Syntheses
The trimethylsilyl-protected tolan Me3SiC„CC6H4C„
CC6H4Me-4 (1a) was prepared by sequential reaction of lith-
ium tolylacetylide and lithium trimethylsilylacetylide with
benzoquinone and reduction of the mixture of diols thus
formed, as described previously [30,33]. The other protected
tolans, Me3SiC„CC6H4C„CC6H4X [X = OMe (1b),
CO2Me (1c), NO2 (1d), CN (1e)] were prepared via Sono-
gashira Pd/Cu cross-coupling protocols, taking advantage
of the availability of 1-trimethylsilylethynyl-4-ethynylben-
zene (Scheme 1) [34]. Alternative synthetic pathways can also
be employed [35], but we favour the approach described here
for its simplicity. Compounds 1a–e were desilylated in con-
Me3Si
C
C
C
X
C H
NEt3
+
Me3Si
C
C
C
C
X
PdCl2(PPh3)2
CuI
1
Hal
K2CO3 / MeOH
Hal = I, X = OMe
Hal = Br, X = CO2Me, NO2, CN
H
C
C
C
C
X
AuCl(PPh3)
NaOMe
(Ph3P)Au
C
C
C
C
X
2
Scheme 1. The preparation of 1 and 2.
X
C
Ru3(CO)10(dppm)
C
C
C
X
(Ph3P)Au C C
C
C
2
(OC)2Ru
Ru(CO)3
Au(PPh3)
X = Me (a), OMe (b), CO2Me (c), NO2 (d), CN (e)
Ph2P
(OC)2Ru
P
Ph2
3
Scheme 2. The preparation of cluster compounds 3a–e.

1648
W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
mass spectra (ES-MS) of these clusters were characterized
by the observation of the simple protonated species
[M+H]+ or the aggregate ion [M+AuPPh3]+.
the phenylene ethynylene portion of the molecule and the
˚
C(1)–C(2) [1.191(8)–1.204(3) A] and C(9)–C(10) [1.198(3)–
˚
1.207(7) A] acetylide bond lengths are the same within
Interestingly, the electronic environment of the cluster
core, as measured by the characteristic m(CO) band pat-
terns, is almost the same in each member of the series
3a–e, with no apparent systematic shift in frequency that
could be attributed to variation in p-back-bonding from
the ruthenium centres brought about by the electron-
donating or electron-withdrawing properties of the tolan
substituent.
the limits of precision of the structure determination. The
P–Au–C moiety is essentially linear [171.6(2)–176.4(6)ꢁ],
but there is a gentle curvature in the molecular backbone,
particularly pronounced at C(1) [Au–C(1)–C(2) 168.2(5)–
175.3(2)ꢁ], brought about by crystal packing effects.
The complexes 2a–e offer an opportunity to examine
systems in which Auꢁ ꢁ ꢁAu and pꢁ ꢁ ꢁp interactions, together
with other weak interactions such as CHꢁ ꢁ ꢁp, may work to
influence the solid-state structures. In this work, no auro-
philic interactions were found in the extended solid-state
structures, with pꢁ ꢁ ꢁp interactions between the tolan moie-
ties being more prevalent. In each structure the molecules
lie in an anti-parallel arrangement with a number of
CH(from various phenyl rings)ꢁ ꢁ ꢁp(phenyl or acetylene
bond) interactions being evident (Fig. 2). Stacking pꢁ ꢁ ꢁp
interactions between the phenyl rings of the tolan moieties
are observed only in the structures 2d and 2e, which also
carry the most strongly electron-withdrawing terminal sub-
stituents (X = NO2 and CN). Whilst in the case of 2e both
tolan ring systems are stacked, only the more highly polar-
ized terminal phenyl ring in 2d is involved in this motif. Ste-
ric constraints associated with the PPh3 supporting ligand
likely restrict the close approach of the gold centres, and
Auꢁ ꢁ ꢁAu aurophilic interactions are superseded by these
various p-hydrocarbon based interactions [40].
2.2. Molecular structures
The molecular structure of 2a has been reported
recently, and only pertinent data are included here for pur-
poses of comparison [30]. A molecule of 2d, which is repre-
sentative of the series, is illustrated in Fig. 1 to show to the
atom labelling scheme. Selected bond lengths and angles
are summarized in Table 1. Within the series 2a–e, the
˚
Au–C(1) [1.999(2)–2.023(4) A] and Au–P(1) [2.2652(14)–
˚
2.2752(5) A] bond lengths are comparable with those of
related acetylide complexes, such as [Au(C„CPh)(PPh3)]
˚
[Au–C 1.97(2)/2.02(2); Au–P 2.276(5)/2.282(4) A, for two
independent molecules] [38] and [Au(C„CSiMe3)(PPh3)]
˚
[Au–C 2.000(4); Au–P 2.2786(10) A] [39]. There is no evi-
dence for significant cumulene/quinoidal character within
Fig. 1. A plot of a molecule of 2d illustrating the atom numbering scheme.
Table 1
Selected bond lengths (A) and angles (ꢁ) associated with complexes 2a, 2b, 2d and 2e
˚
2a 2b
2d
2e
Au(1)–P(1)
Au(1)–C(1)
C(1)–C(2)
C(2)–C(3)
C(9)–C(10)
2.2752(5)
1.999(2)
1.204(3)
1.441(3)
1.198(3)
2.2652(14)
2.003(6)
1.191(8)
1.447(8)
1.204(8)
2.2889(12)
2.023(4)
1.195(6)
1.439(6)
1.207(7)
2.2764(5)
1.999(2)
1.204(3)
1.438(3)
1.201(3)
P(1)–Au(1)–C(1)
Au(1)–C(1)–C(2)
C(1)–C(2)–C(3)
C(8)–C(9)–C(10)
C(9)–C(10)–C(11)
176.4(6)
170.5(2)
174.6(2)
178.8(2)
177.8(2)
171.6(2)
168.2(5)
177.3(6)
178.4(7)
177.3(6)
176.3(1)
172.8(4)
178.8(5)
178.8(6)
178.2(6)
176.0(6)
175.3(2)
178.0(2)
178.7(3)
179.3(3)

W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
1649
Fig. 2. Representative molecular packing diagrams for (a) 2d and (b) 2e.
There are few, if any, differences of note within the
structures of 3a–e. The common cluster core geometry is
illustrated schematically in Fig. 3, with a molecule of 3d
shown in Fig. 4 as a representative example of the series.
Selected bond lengths and angles are summarized in Table
2. The clusters 3a–e feature a triangular Ru3 metal frame-
work, with the Au(PPh3) moiety bridging the RuB–RuC
bond, and the RuA–RuB bond supported by the bridging
dppm ligand. The gold supported metal–metal bond is
the shortest of the three Ru–Ru bonds in the cluster, with
the unsupported RuA–RuC bond generally being the lon-
gest. The C(1)–C(2) acetylide ligand caps the triangular
face in the expected l3-g1,g2,g2 mode. As a consequence
of the interaction with the metal centres, this bond is elon-
gated in comparison to typical acetylenic C„C bond
Planar tolan structures are thought to be more conduct-
ing than conformers in which the phenyl ring systems are
twisted with respect to one another [41]. Thus, whilst the
barrier to rotation about the aryl–ethynyl single bond is
small in the gas phase and in solution [42], much of the
interest in the solid-state structures of tolan and related
oligo(phenylene ethynylene) compounds lies in the analysis
of the inter-ring torsion angles. In the case of the clusters
3a–e, the dihedral angles between the planes of the tolan
phenyl rings range from 33.2ꢁ to 42.8ꢁ.
In much the same way as observed in the structures of
the parent compounds 2, the packing of the molecules
3a–e in the crystalline state is also determined by a number
of relatively weak C–Hꢁ ꢁ ꢁX (X = O, Cl, p) interactions.
However, the presence of carbonyl ligands and solvent
molecules in the structures 3 results in a much more com-
plicated 3D-network of these interactions than was
observed in the structures of compounds 2. We note that
there are no obvious stacking pꢁ ꢁ ꢁp interactions between
tolan ligand fragments in the case of the cluster structures.
˚
lengths [1.318(6)–1.324(5) A]. The tolan C(9)„C(10)
˚
alkyne bond is in the normal range [1.191(5)–1.201(6) A].
C3
C2
C1
2.3. UV–Vis spectroscopy
RuC
RuA
P
PPh2
RuB
The electronic absorption spectra of the ligand precur-
sors 1a–e, the mononuclear gold complexes 2a–e and the
heterometallic clusters 3a–e were recorded as dilute (1–
10 lmol dmꢀ3) solutions in CH2Cl2 (Table 3). The spectra
(Ph3P)Au
Ph2
Fig. 3. A schematic representation of the cluster core in 3a–e.

1650
W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
Fig. 4. A plot of a molecule of 3d, which is representative of the compounds in the series.
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for 3a–e
3a
3b
3c
3d
3e
RuA–RuB
RuA–RuC
RuB–RuC
RuA–C(1)
C(1)–C(2)
C(2)–C(3)
RuB–C(1)
RuC–C(1)
RuB–C(2)
RuC–C(2)
2.8345(5)
2.8330(5)
2.7994(4)
1.939(4)
1.322(6)
1.458(5)
2.198(4)
2.021(4)
2.217(4)
2.273(4)
2.8271(4)
2.8394(4)
2.7861(4)
1.9747(3)
1.324(5)
1.460(5)
2.193(3)
2.210(3)
2.231(3)
2.243(3)
2.8248(6)
2.8451(7)
2.7933(6)
1.944(4)
1.318(6)
1.460(6)
2.191(4)
2.213(4)
2.238(4)
2.229(4)
2.8140(6)
2.8321(6)
2.7987(5)
1.952(4)
1.318(6)
1.459(6)
2.186(4)
2.223(4)
2.229(4)
2.242(4)
2.8175(3)
2.8353(3)
2.7987(3)
1.951(3)
1.322(4)
1.470(4)
2.192(3)
2.218(2)
2.231(3)
2.229(3)
RuA–RuB–RuC
RuA–RuC–RuB
RuB–RuA–RuC
RuB–Au–RuC
RuA–C(1)–C(2)
C(1)–C(2)–C(3)
60.37(1)
60.43(1)
59.20(1)
60.79(1)
154.8(3)
139.4(4)
60.77(1)
60.33(1)
58.90(1)
59.97(1)
154.0(3)
140.7(3)
60.85(2)
60.12(2)
59.03(1)
60.11(1)
154.0(3)
142.2(4)
60.61(2)
59.96(2)
59.43(1)
60.48(1)
153.1(3)
141.6(4)
60.64(1)
60.00(1)
59.35(1)
60.34(1)
152.8(2)
141.8(3)
of 1a–c and 1e are characteristic of the tolan (1,2-diphenyl-
acetylene) moiety, exhibiting three relatively intense transi-
tions between ca. 280 and 350 nm [30,43]. The spectrum of
nitro-substituted derivative 1d contains a broad absorption
band from the nitrobenzene moiety centred near 340 nm.
Substitution of the SiMe3 group for Au(PPh3) resulted in
little change to these spectroscopic profiles. As noted previ-
ously, the UV–Vis absorption spectra of the cluster deriva-
tives 3a–e exhibit several new features that were not present
in the spectra of the precursors 1a–e and 2a–e. The clusters
all exhibit an absorption band of low intensity near
450 nm, which is associated with charge transfer transitions
from the cluster to the unoccupied orbitals of the tolan
moiety. This assignment is supported by the cyclic voltam-
metric investigations presented below. Two bands between
300 and 400 nm, which were not resolved in all cases (Table
3) and a higher energy absorption band near 280 nm were
also observed. Given their similar energetic positions and
intensities as observed for 1a–e, these absorption bands
likely contain contributions from tolan-centred transitions.
2.4. Electrochemical properties
Transition metal clusters typically offer closely spaced
frontier orbitals with a significant metal character. This
can lead to a rich electrochemical response in these systems,
and has led to the description of cluster compounds as
‘‘electron sinks’’ [44]. This potential for redox activity, cou-
pled with the ready spectroscopic probes offered by both
the carbonyl ligands and several of the remote substituents
(e.g., the ester and nitro groups) prompted us to examine
the heterometallic (Ru3–Au) clusters 3a–d and their mono-
nuclear (phosphine)Au-tolan precursors 2a–d using cyclic
voltammetry and, in selected examples, IR spectroelectro-
chemical methods. Compounds 3e and 2e were not
included in the spectroelectrochemical studies.

W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
1651
Table 3
-600
The principal UV–Vis absorption bands observed from CH2Cl2 solutions
R2
of 1a–e, 2a–e, 3a–e
-400
-200
0
Compound
k, nm (e, Mꢀ1 cmꢀ1
)
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
3a
3b
3c
3d
3e
a
290 (53200)
306 (62300)
313 (62700)
314 (59300)
300sh (41200)
315 (47300)
315 (69400)
320 (65900)
327 (44900)
299 (37100)
328 (55500)
324 (41200)
329 (22100)
336 (43000) 376 (32000)
390 (24500)
326 (59500)
332 (58300)
335 (50800)
342 (42900)
336 (45900)
337 (68300)
341 (62500)
348 (39900)
358 (30300)
349 (51400)
450 (5500)
450 (3000)
451 (8000)
463 (9000)
440 (5800)
a
rO1
rO2/3
285 (84200)
280 (64900)
287 (30000)
297 (41700)
b
I (nA)
rR2
200
400
600
800
O1
310 (33500)
284 (42200)
310 (39500)c
O2
O3
275 (46600)
283 (102000)
283 (65900)
285 (84200)
1
0
-1
E (V) vs Fc/Fc+
-2
-3
331 (34700) 376 (25600)
Fig. 5. Cyclic voltammogram of heterometallic cluster 3c (Scheme 2;
X = OMe). The asterisks denote two small cathodic peaks observed in
addition to rO1 during the reverse cathodic scan triggered beyond O1.
Experimental conditions: carefully polished Pt disk microelectrode,
dichloromethane containing 10ꢀ1 M Bu4NPF6, v = 100 mV sꢀ1 at 293 K.
Several unresolved bands were also observed between 250 and 300 nm
(ca. 43000 Mꢀ1 cmꢀ1).
b
Several unresolved bands were also observed between 260 and 300 nm
(ca. 28000–48000 Mꢀ1 cmꢀ1).
c
Several unresolved bands were also observed between 260 and 300 nm
(ca. 24000–34000 Mꢀ1 cmꢀ1).
2a–d (Table 4, Fig. 5). The similarity of these electrochem-
ical events point to their localization at the terminal 1,2-
diphenylacetylene moiety, indicating that the tolan chain
is not significantly affected by coordination to the triruthe-
nium cluster core through the acetylide moiety. The anodic
waves O2 partly overlap with higher-lying irreversible
waves O3, which are not observed for 2a–d. The chemically
irreversible nature of R2 is further illustrated by the pres-
ence of a new anodic wave rR2 arising in the course of
the reverse potential scan initiated beyond R2 (Fig. 5). This
wave is shifted some 1.7–1.8 V positively relative to R2,
and arises from oxidation of an unassigned secondary
reduction product.
2.5. Cyclic voltammetry
The cyclic voltammograms of the mononuclear gold
complexes 2a–d in dichloromethane show totally irrevers-
ible anodic [O2, between 0.85 and 1.15 V versus Fc/Fc+]
and cathodic [R2 < ꢀ2.20 V versus Fc/Fc+] waves close
to, or beyond, the limits of the solvent potential window
(Table 4). Indeed, for 2a and 2b which feature electron-
donating tolan substituents X = Me and OMe, respec-
tively, the cathodic waves are shifted beyond the limit of
the electrochemical window. These irreversible redox pro-
cesses were not studied in detail. Complex 2d shows an
additional cathodic wave R1 at ꢀ1.49 V, which is fully
reversible and apparently belongs to the reduction of the
remote X = NO2 substituent.
The nitro group in 3d is reduced at essentially the same
cathodic potential R1 as that in 2d (Table 4). At room tem-
perature, the peak-to-peak separation (DEp = Ep,c ꢀ Ep,a
)
The cyclic voltammograms of the heterometallic clusters
3a–d exhibit irreversible redox processes at very similar
electrode potentials to those observed in the precursors
for this redox couple (100 mV) is only slightly larger than
the value of 80 mV determined for the Fc/Fc+ internal
Table 4
Electrochemical properties of the Au-tolan complexes 2a–d and corresponding heterometallic cluster compounds 3a–da
Compound
Ep,c (R2, tolan)
E1/2 (R1, NO2)
Ep,a (O1, Ru3-core)
Ep,a (O2/O3, tolan)
2a
2b
2c
2d
3a
3b
3c
3db
a
not observed
not observed
ꢀ2.37
0.94
0.88
1.14
1.13
0.93/1.02
0.88/0.95
1.04/1.16
1.02/1.15
ꢀ2.23
ꢀ1.49
ꢀ1.47
ꢀ2.49
0.19
0.18
0.25
0.29
ꢀ2.48
ꢀ2.35
ꢀ2.16
Redox potentials (V vs. Fc/Fc+) were determined from cyclic voltammetric scans. Experimental conditions: Pt disk working microelectrode,
v = 100 mV sꢀ1, T = 293 K. Ep denotes peak potential of a chemically irreversible step.
b
See Fig. 5.

1652
W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
standard. At 206 K, however, the DEp value of the nitro
reduction increases to 600 mV while that of the internal
Fc/Fc+ standard does not change. The electrochemically
quasireversible to irreversible nature of the cathodic step
R1 in 3d may reflect some hindered access of the remote
NO2 group to the electrode surface, and in turn sluggish
electron transfer kinetics.
A
The dominant new feature in the cyclic voltammograms
of clusters 3a–d is the irreversible two-electron anodic wave
O1 (Table 4, Fig. 5) that corresponds to oxidation of the
triruthenium cluster core. The reverse cathodic scan at
room temperature reveals the presence of three small
cathodic peaks due to reduction of secondary oxidation
products, which are shifted significantly more negatively
from O1, for example in the case of 3a by 0.63, 1.13 and
1.81 V, respectively. The minor dependence of the anodic
potentials O1 on the nature of the electron-donating or
electron-withdrawing substituents X (Scheme 2) reflects a
rather limited degree of electronic communication between
the cluster core and the substituted tolan moiety, in agree-
ment with the conclusions drawn from the IR spectra of the
3a–e series (see above).
*
2200
2100
2000
1900
1800
Wavenumber (cm-1)
Fig. 6. IR spectral changes in the C„C and C„O stretching region
observed during the irreversible oxidation of complex 3d at the anodic
wave O1 (Table 2) in CH2Cl2 at 293 K, using an OTTLE cell. The asterisk
denotes a product of a slow thermal reaction of the oxidized complex.
1 cmꢀ1, respectively, to higher frequencies when the triru-
thenium cluster core in 3d was oxidized at the anodic
potential O1 (Table 4). In addition, the oxidation at poten-
tial O1 was accompanied by a m(C„C) shift to 2217 cmꢀ1
(Fig. 6), which is a significantly smaller absolute shift
2.6. IR spectroelectrochemistry
The triruthenium clusters 3a (X = Me), 3c
(X = CO2Me) and 3d (X = NO2) were selected for IR spec-
troelectrochemical investigations aimed at obtaining more
information about the electronic communication between
the cluster core and the remote substituent X on the conju-
gated tolan chain. These experiments were carried out in
dichloromethane solutions containing 10ꢀ1 M NBu4PF6
as supporting electrolyte. For reference purposes, the car-
bonyl stretching frequencies of the parent compounds in
dichloromethane are listed in Section 4.
(3 cmꢀ1
) than that induced by the NO2 reduction
(27 cmꢀ1). Perhaps surprisingly, the irreversible oxidation
of the cluster core largely preserved the m(C„O) band pat-
tern, with the oxidation product exhibiting m(CO) bands at
2100m, 2051s, 2014s, 1997sh, 1977mw, 1962sh and 1947w
cmꢀ1 (Fig. 6). The shift of the m(C„O) bands to higher
wavenumbers by 40–70 cmꢀ1, the greatest shift being asso-
ciated with the fully symmetric all-CO-stretching mode, is
consistent with the two-electron nature of the oxidation
wave O1. Whilst it is beyond the scope of this work to
determine the structure of the oxidation product, we can,
however, state firmly that the irreversible two-electron oxi-
dation of 3d does not induce a rapid CO dissociation reac-
tion and that the geometry of the triruthenium-carbonyl
moiety remains largely preserved after this initial oxidation
event. The initially observed oxidation product is, however,
thermally unstable and slowly converts to another carbonyl
cluster species, as judged from a new absorption at
2081 cmꢀ1 (Fig. 6).
One-electron reduction of the nitro group in compound
3d at the electrode potential R1 (Table 4) led to the
expected disappearance of the absorption bands at 1519
and 1344 cmꢀ1, which can be attributed to the mas(NO2)
and ms(NO2) modes, respectively [45]. A new band arose
at 1367 cmꢀ1, assigned to masðNO ÅꢀÞ [46]. In addition, an
2
absorption band at 1589 cmꢀ1 was replaced by a new one
at 1568 cmꢀ1 that may be due to a nitrobenzene ring
m(C@C) mode. This NO2-localized reduction also results
in a low-frequency shift of the m(C„C) band from 2213
to 2186 cmꢀ1. The m(C„O) band pattern of the carbonyl-
triruthenium fragment was almost unchanged by the reduc-
tion, with wavenumbers of individual bands decreasing by
only 1–2 cmꢀ1, in agreement with the weak influence of the
nitro group on the electronic properties of the metal centres
and hence hardly affecting the ruthenium-to-CO p-back-
bonding interactions. Apparently, the NO2 substituent is
relatively strongly conjugated with the uncoordinated acet-
ylene moiety of the cluster-anchored tolan ligand, while
interactions with the cluster core are more limited.
The oxidation products derived from 3a and 3c were sig-
nificantly more chemically reactive, with rapid in situ elec-
trochemical oxidation of either species resulting directly in
a product with a m(C„O) band pattern (2083m, 2074sh,
2049m, 2035s, 2024m, 2008s, 1995m-s, 1983m, 1960m-w,
1946sh and 1917w cmꢀ1) quite different from the parent
clusters being observed in each case. In line with the very
limited electronic communication between the X group
and the cluster core, the m(C@O) band of the ester moiety
in 3c was almost unchanged, shifting from 1720 cmꢀ1 in
The first oxidation event is clearly cluster centred (Table
4). The mas(NO2) and ms(NO2) bands shifted by 2 and

W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
1653
3c to 1722 cmꢀ1 in the oxidized species. Interestingly, oxi-
dation of 3a and 3c caused the m(C„C) band to completely
disappear. This observation is in sharp contrast with the
in situ electrochemical oxidation of cluster 3d, where the
m(C„C) band is initially preserved (Fig. 6). We assume
that the ethynylene moiety in 3a and 3c features in fast
chemical reactions that follow the initial two-electron oxi-
dation. In contrast, the conjugation of the acetylene moiety
to the nitro-phenyl-acetylene unit in 3d appears to stabilize
the initial oxidation product to such an extent that it can be
observed by IR spectroelectrochemical methods at room
temperature.
mulls suspended between NaCl plates. NMR spectra were
obtained with Bruker Avance (1H 400.13 MHz, 13C
100.61 MHz, 31P 161.98 MHz) or Varian Mercury (31P
161.91 MHz) spectrometers from CDCl3 solutions and ref-
erenced against solvent resonances (1H, 13C) or external
H3PO4 (31P). Mass spectra were recorded using Thermo
Quest Finnigan Trace MS-Trace GC or Thermo Electron
Finnigan LTQ FT mass spectrometers or Matrix-Assisted
Laser Desorption/Ionization-Time-of-Flight (Mass Spec-
trometry) (MALDI-TOF MS) ABI Voyager STR.
Cyclic voltammograms were recorded at v = 100 mV sꢀ1
from solutions of approximately 10ꢀ4 M in analyte in
dichloromethane containing 10ꢀ1 M Bu4NPF6, using a gas-
tight single-compartment three-electrode cell equipped
with platinum disk working (apparent surface area of
0.42 mm2), coiled platinum wire auxiliary, and silver wire
pseudo-reference electrodes. The working electrode surface
was polished between scans with a diamond paste contain-
ing 0.25 lm grains (Oberfla¨chentechnologien Ziesmer,
Kempen, Germany). The cell was placed in a Faraday cage
and connected to a computer-controlled PAR Model 283
potentiostat. All redox potentials are reported against the
standard ferrocene/ferrocenium (Fc/Fc+) redox couple
used as an internal reference system [50]. Cyclic voltammet-
ric measurements at ca. 210 K were performed with the
electrochemical cell immersed into a bath of acetone/dry
ice.
IR spectroelectrochemical experiments at room temper-
ature were performed with an air-tight optically transpar-
ent thin-layer electrochemical (OTTLE) cell equipped
with a Pt minigrid working electrode (32 wires cmꢀ1) and
CaF2 windows [51]. The cell was positioned in the sample
compartment of a Bruker Vertex 70 FTIR spectrometer
(1 cmꢀ1 spectral resolution, 16 scans). The controlled-
potential electrolyses were carried out with a PA4 potentio-
3. Conclusion
A series of gold(I)-phosphine complexes of ethynyl
tolans has been prepared and structurally characterized.
The solid-state packing of these compounds exhibits vari-
ous intramolecular contacts between the tolan ligands,
but not aurophilic interactions, which are presumably lim-
ited by the steric bulk of the triphenyl phosphine support-
ing ligand. The gold complexes are convenient reagents for
use in the preparation of tolans bearing heterometallic clus-
ter end-caps. The cluster carbonyl bands are insensitive to
the electronic nature of the tolan substituent, including
NO2-centred reduction in the case of 3d. Oxidation is cen-
tred on the cluster core, and in the case of the most stable
system, 3d, IR spectroelectrochemistry reveals the oxida-
tion product to retain the same carbonyl arrangement as
the starting material. The tolan group does not act as a par-
ticularly efficient conduit for passage of the electronic effect
of electron-donating or electron-withdrawing groups to the
cluster core.
4. Experimental
´
stat (EKOM, Polna, Czech Republic).
All reactions were carried out under an atmosphere of
nitrogen using standard Schlenk techniques. Reaction sol-
vents were purified and dried using an Innovative Technol-
ogy SPS-400, and degassed before use. No special
precautions were taken to exclude air or moisture during
work-up. Preparative TLC was performed on 20 · 20 cm
glass plates coated with silica gel (0.5 mm thick, Merck
GF-254). The compounds [Ru3(CO)10(l-dppm)] [47],
[AuCl(PPh3)] [48], [PdCl2(PPh3)2] [49], 1-trimethylsilylethy-
nyl-4-ethynylbenzene [34b], 1a, its analogous terminal
alkyne and 3b [30] were prepared by literature methods.
Other reagents were purchased and used as received.
Dichloromethane (Acros Chemicals) for the spectroelectro-
chemical experiments was freshly distilled from P2O5 under
an atmosphere of dry nitrogen. Bu4NPF6 electrolyte
(TBAH; Aldrich) was recrystallized twice from absolute
ethanol and dried overnight under vacuum at 80 ꢁC before
use.
Diffraction data were collected at 120K on a Bruker
SMART 6000 (2a,e, 3b,e), SMART 1K (2d) and Bruker PROT-
EUM-M (3c,d) three-circle diffractometers, using graphite-
monochromated Mo Ka radiation. The structures were
solved by direct-methods and refined by full matrix least-
squares against F2 of all data using SHELXTL software [52].
All non-hydrogen atoms where refined in anisotropic
approximation except the disordered ones, H atoms were
placed into the calculated positions and refined in ‘‘riding’’
mode. The crystallographic data and parameters of the
refinements are listed in Table 5.
4.1. Preparation of 1b
4.1.1. General procedure
A nitrogen purged, 500 ml Schlenk flask was charged
with 1-iodo-4-methoxybenzene (2.34 g, 10 mmol), 1-trim-
ethylsilylethynyl-4-ethynylbenzene
(2.18 g,
11 mmol),
IR spectra of the synthesized complexes were recorded
using a Nicolet Avatar spectrometer from cyclohexane
solutions in a cell fitted with CaF2 windows, or from Nujol
[PdCl2(PPh3)2] (0.70 g, 0.1 mmol) and CuI (0.19 g,
0.1 mmol). Triethylamine (ca. 250 ml) was transferred to
the reaction flask via cannula and the reaction mixture

Table 5
Crystal data and parameters of refinement of the structures 2b,d,e and 3b–ea
2b
2d
2e
3b
3c
3d
3e
Formula
C
35H26AuOP
C35H25AuCl2NO2P
790.40
triclinic
C35H23AuNP
685.48
triclinic
C67H48AuO8P3Ru3
1574.14
monoclinic
P21/n
11.004(1)
27.520(3)
20.590(2)
90
90.54(3)
90
6235(1)
4
C69H48AuCl3O9P3Ru3
1720.51
monoclinic
P21/c
11.095(2)
27.417(5)
23.226(4)
90
115.83(7)
90
6359(2)
4
C67H46AuCl3NO9P3Ru3
1708.48
monoclinic
P21/c
11.145(2)
27.492(4)
23.130(3)
90
118.25(1)
90
6242(1)
4
C68H46AuCl3NO7P3Ru3
1688.49
monoclinic
P21/n
11.0569(3)
27.3570(7)
20.6694(5)
90
91.71(1)
90
6249.4(3)
4
Formula weight
Crystal system
Space group
690.49
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
˚
a (A)
9.762(1)
17.617(3)
18.133(3)
110.01(1)
100.21(1)
101.30(1)
2770.4(7)
4
11.750(4)
11.792(4)
13.058(4)
64.42(3)
76.49(3)
68.08(3)
1508.2(9)
2
8.7340(8)
9.8435(9)
16.4629(15)
86.948(2)
88.443(2)
82.302(2)
1400.3(2)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg/m3)
1.656
5.394
1352
1.740
5.141
772
1.626
5.334
668
1.677
3.189
3080
1.797
3.258
3364
1.818
3.319
3336
1.795
3.312
3296
Absorption coefficient (mmꢀ1
F(000)
)
Reflections collected
26767
14640
19102
84736
71159
63851
65628
Independent reflections (Rint
Number of parameters
Absorption correction
Goodness-of-fit
)
10880(0.0423)
652
7531(0.0213)
383
8473(0.023)
343
19038(0.038)
578
17700(0.052)
738
15492(0.0532)
784
19840(0.0434)
655
numerical
1.055
b
SADABS
SADABS
SADABS
SADABS
SADABS
SADABS
0.980
1.046
1.040
1.106
1.006
1.067
Final R1 [I > 2r]
Final wR2 (all data)
a
0.0331
0.0797
0.0236
0.0552
0.0206
0.0489
0.0350
0.0925
0.0416
0.0991
0.0423
0.0865
0.0298
0.0714
The structures 3b–e are, in fact, isostructural – the P21/n setting is transformed into the standard P21/c one by usual (1,0,0,0,1,0,ꢀ1,0,1) operation.
b
The disordered solvent (CHCl3) has been taken into account by applying SQUEEZE procedure (PLATON).

W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
1655
heated to reflux for 2 h. The solvent was removed in vacuo
and the residue passed through a silica pad with hexane
and CH2Cl2. The solvent was removed in vacuo to give a
yellow solid of the title product (1b) which was recrystal-
lized from hexane and CH2Cl2 (1.90 g, 62%). IR (Nujol):
m(C„C) 2215, 2158 cmꢀ1. 1H NMR: d 0.25 (s, 9H; SiMe3),
3.83 (s, 3H; OMe), 6.88 (pseudo-d, JHH = 8.6 Hz, 2H;
C6H4), 7.43 (s, 4H; C6H4), 7.46 (pseudo-d, JHH = 8.6 Hz,
2H; C6H4). 13C NMR: d 0.13 (s, SiMe3), 55.3 (OCH3),
85.7, 91.4, 96.0, 04.76 (4 · s, C„C), 114.04, 115.09,
122.49, 123.70, 131.20, 131.80, 133.08, 159.81 (8 · s, Ar).
EI-MS: m/z 304, M+; 274, [MꢀOMe]+; 201,
[MꢀOMeꢀSiMe3]+. C20H20OSi requires: C, 78.90; H,
7.11. Found: C, 78.24; H, 6.58%.
requires: C, 89.87; H, 3.96; N 6.17. Found: C, 89.43; H,
3.98; N, 5.74%.
4.3. Preparation of 2b
4.3.1. General procedure
A suspension of 1b (135 mg, 0.44 mmol) and NaOH
(162 mg, 4.05 mmol) in MeOH (25 ml) was allowed to stir
for 30 min, to give a clear solution, which was treated with
[AuCl(PPh3)] (200 mg, 0.40 mmol) and allowed to stir for a
further 3 h. The resulting cloudy solution was filtered, the
precipitate washed with MeOH (6 ml), diethylether (6 ml)
and pentane (6 ml) and dried in vacuo to afford 2b
1
(180 mg, 65%). IR (Nujol): m(C„C) 2204, 2113 cmꢀ1. H
Compounds 1c–e were prepared in an entirely analogous
fashion, full details of which will be published elsewhere.
Compound 1c (crystallized from hot toluene, yield 49%).
NMR: d 3.82 (s, 3H, OMe); 6.88 (pseudo-d, JHH = 8.8 Hz,
2H, C6H4); 7.38–7.58 (m, 21H, Ar). 13C NMR: d 55.6 (s,
OCH3); 88.5, 90.8 (2 · s, 2 · C„C); 104.3 (d, = 27 Hz,
Au–C„C), 129.7 (d, JCP = 56 Hz, Au–C„C); 114.2,
115.7, 122.0, 124.7, 131.3, 132.5, 133.5, 135.1 (8 · s, Ar);
129.4 (d, JCP = 11 Hz), 131.9 (d, JCP = 3 Hz), 134.6 (d,
JCP = 14 Hz), 159.8 (s) (P–Ar). 31P NMR: d 43.4. ES-
MS: m/z 721, [Au(PPh3)2]+; 713, [M+Na]+. C35H26NO-
PAu requires: C, 60.87; H, 3.77. Found: C, 60.43; H,
3.73%.
IR (Nujol): m(C„C) 2211, 2155 cmꢀ1
;
m(C@O)
1715 cmꢀ1. C21H20O2Si requires: C, 75.86; H, 6.05. Found:
C, 75.85; H 5.95%. Compound 1d (purified by column
chromatography, silica, hexane–CH2Cl2 70/30, yield
84%). IR (Nujol): m(C„C) 2209, 2149 cmꢀ1. C19H17NO2Si
requires: C, 71.47; H, 5.33; N, 4.39. Found C, 71.44; H,
4.62; N, 4.94%. Compound 1e (purified by column chroma-
tography, Silica, hexane–CH2Cl2 60/40, yield 91%). IR
Compounds 2c–e were prepared in a similar fashion. 2c
(yield 78%). IR (Nujol): m(C„C) 2210, 2111 cmꢀ1; m(C@O)
(Nujol): m(C„N) 2224 cmꢀ1; m(C„C) 2209, 2149 cmꢀ1
.
1
C20H17NSi requires: C, 80.22; H, 5.72; N, 4.68. Found:
C, 79.90; H, 5.63; N, 4.23%.
1776 cmꢀ1. H NMR: d 3.92 (s, 3H, OMe); 7.28–7.58 (m,
21H, Ar); 8.02 (pseudo-d, JHH = 8.8 Hz, 2H, C6H4). 13C
NMR: d 52.5 (s, OCH3); 90.00, 92.9 (2 · s, 2 · C„C);
104.2 (d, = 27 Hz, Au–C„C), 130.1 (d, JCP = 56 Hz,
Au–C„C); 121.0, 125.7, 128.3, 129.8, 130.1, 131.6, 132.6,
135.0 (8 · s, Ar); 129.5 (d, JCP = 11 Hz), 131.9 (d,
JCP = 2 Hz), 134.6 (d, JCP = 14 Hz), 136.0 (s) (P–Ar);
166.8(s, C@OCH3). 31P NMR: d 43.3. ES-MS: m/z 1635,
[M+(AuPPh3)2]+; 1177, [M+AuPPh3]+; 721, [Au(PPh3)2]+.
C36H26O2PAu requires: C, 60.17; H, 3.62. Found: C, 60.31;
H, 3.66%. Compound 2d (yield 69%). IR (Nujol): m(C„C)
2214, 2109 cmꢀ1. 1H NMR: d 7.43–7.58 (m, 19H, Ar); 7.65
(pseudo-d, JHH = 8.8 Hz, 2H, C6H4); 8.22 (pseudo-d,
JHH = 9.2 Hz, 2H, C6H4). 13C NMR: d 88.9, 95.3 (2 · s,
2 · C„C); 130.1 (d, JCP = 56 Hz, Au–C„C); 120.3,
123.9, 126.3, 130.6, 131.8, 132.4, 132.7 (7 · s, Ar); 129.5
(d, JCP = 11 Hz), 131.9 (d, JCP = 2 Hz), 134.6 (d,
JCP = 14 Hz); 147.1 (s) (P–Ar). 31P NMR: d 43.3. ES-
MS: m/z 1625, [M+(AuPPh3)2]+; 1164, [M+AuPPh3]+;
721, [Au(PPh3)2]+. C34H23NO2PAu requires: C, 57.87; H,
3.26; N 1.99. Found: C, 57.46; H, 3.23; N, 1.80%. Com-
4.2. Desilylation of 1b
4.2.1. General procedure
A solution of 1b (150 mg, 0.49 mmol) and potassium
carbonate (273 mg, 1.97 mmol) in MeOH (30 ml) was stir-
red under nitrogen at room temperature overnight (ca.
12 h). The reaction mixture was partitioned between dieth-
ylether (50 ml) and water (50 ml), the organic layer col-
lected, dried over MgSO4, and finally dried in vacuo to
afford HC„CC6H4C„CC6H4OMe-4 (1b-H) as a yellow
solid (102 mg, 89%). IR (Nujol): m(C„C) 2214,
2103 cmꢀ1 1H NMR: d 3.16 (s, 1H, C„CH); 3.83 (s,
.
OMe); 6.90 (pseudo-d, JHH = 8.8 Hz, 2H, C6H4); 7.48
(pseudo-d, JHH = 9.6 Hz, 6H, C6H4). 13C NMR: d 55.3
(s, OCH3); 78.7, 83.3, 87.6, 91.5 (4 · s, 4 · C„C); 114.1,
115.1, 121.5, 124.2, 131.3, 132.0, 133.1, 159.9 (8 · s, Ar).
EI-MS: m/z 232, M+; 217, [MꢀMe]+. C17H12O requires:
C, 87.93; H, 5.17. Found: C, 87.24; H, 5.05%.
pound 2e (yield 71%). IR (Nujol): m(C„N) 2217 cmꢀ1
;
1
Compounds 1c–e were desilylated in a similar fashion,
full details of which will be reported elsewhere. Compound
m(C„C) 2169, 2113 cmꢀ1. H NMR: d 7.41–7.63(m, 19H,
Ar). 13C NMR: d 89.1, 94.3 (2 · s, 2 · C„C); 104.0 (d, =
22 Hz, Au–C„C), 130.0 (d, JCP = 55 Hz, Au–C„C);
111.5, 118.8, 126.1, 126.8, 128.5, 131.6, 131.7, 132.6
(8 · s, Ar); 129.5 (d, JCP = 12 Hz), 131.9 (d, JCP = 2 Hz),
134.6 (d, JCP = 14 Hz), 168.4 (s) (P–Ar). 31P NMR: d
43.3. ES-MS: m/z 1144, [M+AuPPh3]+; 721, [Au(PPh3)2]+.
C35H23NPAu requires: C, 61.31; H, 3.36; N 2.04. Found:
C, 61.61; H, 3.33; N, 1.93%.
1c-H (yield 85%). IR (Nujol): m(C„C) 2211, 2101 cmꢀ1
;
m(C@O) 1707 cmꢀ1. C18H12O2 requires: C, 83.08; H, 4.62.
Found: C, 81.37; H, 4.59%. Compound 1d-H (yield 89%).
IR (Nujol): m(C„C) 2210, 2101 cmꢀ1. C16H9NO2 requires:
C, 77.73; H, 3.64; N 5.67. Found: C, 77.72; H, 3.89; N,
5.31%. Compound 1e-H (yield 51%). IR (Nujol):
m(C„N) 2227 cmꢀ1; m(C„C) 2209, 2100 cmꢀ1. C17H9N

1656
W.M. Khairul et al. / Inorganica Chimica Acta 361 (2008) 1646–1658
4.4. Preparation of 3b
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
4.4.1. General procedure
A solution of Ru3(CO)10 (l-dppm) (100 mg, 0.10 mmol)
and 2b (71 mg, 0.10 mmol) in THF (15 ml) was heated at
reflux, with the progress of the reaction being monitored
by TLC and IR spectroscopy. When adjudged complete
(ca. 3 h), the solvent was removed and the residue purified
by preparative TLC (hexane–CH2Cl2 60:40) and the yellow
band collected, and recrystallized (CHCl3/hexane) to afford
orange crystals of 3b (67 mg, 41%) suitable for X-ray crys-
tallography. IR (cyclohexane): m(CO) 2038s, 1993s, 1972s,
Acknowledgements
W.M.K. gratefully acknowledges funding from the Hu-
man Resources Development in Science and Technology
Programme, Ministry of Science, Technology and Innova-
tion Malaysia. M.R.A.H. thanks the Saudi Arabia Cultural
Attache (London) for a postgraduate scholarship. A Royal
Society Joint Project Grant (P.J.L., F.H.) is gratefully
acknowledged, as is funding from ONE NorthEast through
the UIC Nanotechnology programme (P.J.L., T.B.M.,
J.A.K.H.).
1956m, 1939m, 1909w cmꢀ1 1H NMR: d 2.36 (s, 3H,
.
OMe), 3.35, 4.26 (2 · dt, JHP = 12 Hz, JHH = 11 Hz, 2H,
dppm), 6.39–7.94 (m, 43H, Ar). 31P NMR: d 38.5 (d,
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[Au(PPh3)2]+. C67H48O8P3Ru3Au requires: C, 51.12; H,
3.07. Found: C, 51.33; H, 3.10%.
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CCDC 632295, 632296, 632297, 632298, 632299, 632300
and 632301 contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.

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