heteromultimetallic compounds based on polyfunctional … · 2020. 1. 22. · heteromultimetallic...
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Heteromultimetallic compounds based on polyfunctional carboxylate linkers
Khairil A. Jantan,†‡ James A. McArdle,† Lorenzo Mognon,† Valentina Fiorini,+ Luke A.
Wilkinson,† Andrew J. P. White,† Stefano Stagni,+ Nicholas J. Long*,† and James D. E. T.
Wilton-Ely*,†
† Department of Chemistry, Imperial College London, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, UK.
‡ Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Malaysia.
+ Department of Industrial Chemistry “Toso Montanari” – University of Bologna, Viale del
Risorgimento 4, Bologna 40126, Italy.
e-mail: [email protected]
e-mail: [email protected]
In memory of Professor Robin J. H. Clark FRS, CNZM (1935 – 2018)
Abstract
A series of homo- and hetero-nuclear, bi- and trimetallic compounds are accessible using
polyfunctional linkers with carboxylic acid and alkynyl or pyridyl donor combinations. This
versatile approach affords reaction at a specific donor site in each case, to accommodate both
ruthenium(II) or osmium(II) units and also rhenium and gold centres. Due to the orientation of
the nitrogen donors of the bipyridyl moiety in 2,2’-bipyridine-4,4’-dicarboxylic acid, the metal
addition must be performed in a certain sequence due to steric considerations. One example
was investigated crystallographically to add to the spectroscopic and analytical
characterisation performed for all complexes. Photophysical investigations reveal the effect of
incorporating second or third row transition metal centres. This approach was expanded
through the use of a linker bearing both carboxylic acid and alkynyl functionalities, 1,1’-
ethynylferrocene carboxylic acid. This allows initial coordination of the carboxylate donors to
be followed by the formation of either an acetylide or a vinyl bridge to another metal, providing
access to heterotrimetallic (FeRuOs and FeRuAu) compounds as well as a
heteroheptametallic Fe3Ru2Au2 example. Preliminary electrochemical studies were performed
on the latter example.
Keywords: Multimetallic, ruthenium, osmium, vinyl, carboxylate, gold
Introduction
The utility and versatility of transition metals can often be enhanced by bringing multiple
metal centres into the same assembly. This approach has been employed successfully in many
areas, including catalysis,1 sensing2 and imaging.3 Many multimetallic compounds involve
multiple units of the same metal, such as metal-organic frameworks (MOFs)4 and coordination
polymers,6d,e but increasingly heteromultimetallic systems are being exploited due to the
possibilities afforded by the incorporation of multiple metal-based properties within the same
system. However, the rational synthesis of heteromultimetallic compounds has always proved
a greater challenge due to the requirement to link different metals together in a controllable
manner. This can be achieved through the protection and deprotection of donor groups, but an
attractive, more synthetically straightforward option is to tailor bifunctional linkers to the metals
involved. This approach has been employed by us7 and others8 to prepare molecular assemblies
consisting of 2-6 metals, including compounds with six different metals.9
Due to our interest in 1,1’-dithio ligands,10 our previous contributions have mainly
focused on sulfur ligands and these have proved exceptionally useful in the construction of
both molecular and nanoparticle systems. However, the range of metal units based on
carboxylate chelates is wide and encompasses examples of metals in many different oxidation
states. This is borne out by the widespread use of dicarboxylic acids and bipyridines as
bridging ligands in coordination polymers5 and metal-organic frameworks(MOFs).4 In this
contribution, the reactivity of 2,2’-bipyridine-4,4’-dicarboxylic acid (H2dcbpy) is explored. This
dicarboxylic acid has been used extensively in the preparation of ruthenium-based
photosensitizers, such as [Ru(NCS)2(H2dcbpy)2],11 and its commercial availability is likely to
be driven by this application. However, in such compounds, the presence of the carboxylic
acid groups is simply to aid water-solubility, whereas the work described here uses this
commercial compound as a trifunctional linker for multimetallic assemblies based on rhenium
and group 8 metals. The differing reactivity of nitrogen and oxygen donors allows the stepwise
construction of these heteromultimetallic compounds. This difference in reactivity is also
employed in the other linker used in this contribution, 1,1’-ethynylferrocene carboxylic acid, in
which the carboxylic acid and alkynyl groups display contrasting reactivity profiles (Figure 1).
In order to illustrate the potential for wide-ranging application of this approach, a series
of different metal units were employed, which possess widely employed properties, such as
reliable redox behaviour [of the Fe(II/III) and Ru(II/III) couples] and the photophysical attributes
of Re(I)-diimine moieties.
Figure 1. Carboxylate linkers used in this contribution.
Results and Discussion
The species [Ru(CR=CHR’)Cl(CO)(L)2] (L = PiPr3,12 PPh313) and
[Ru(CR=CHR’)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole)14 have been used widely
as versatile entry points to ruthenium vinyl chemistry.15 The latter BTD complexes have since
found application as probes for the chromogenic and fluorogenic sensing of carbon
monoxide.16 Both 5- and 6-coordinate complexes undergo reaction with deprotonated
carboxylic acid ligands to yield the corresponding octahedral carboxylate complexes.6b,6d,6g,17
Such ruthenium complexes also react with bipyridine ligands to yield cationic complexes of
the form [Ru(CR=CHR’)(CO)(bpy)(PPh3)2]+. It was therefore not immediately clear whether
commercially-available 2,2’-bipyridine-4,4’-dicarboxylic acid (H2dcbpy) would react at the
nitrogen or oxygen donors, or both. It is known6b that, unless a base is used, the addition of
carboxylic acids to ruthenium vinyl complexes results in cleavage of the vinyl group. Thus,
H2dcbpy was stirred with excess base (sodium methoxide) before addition of two equivalents
of [Ru(CH=CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2]. After a further 2 hours and subsequent
purification to remove inorganic salts and excess base, [{Ru(CH=CHC6H4Me-
4)(CO)(PPh3)2}2(µ-dcbpy)] (1) was isolated as a brown powder (Scheme 1). 31P{1H} NMR
analysis revealed a singlet at 38.2 ppm confirming clean formation of the new complex as well
as suggesting the mutually trans disposition of the two phosphine ligands at each metal centre.
A carbonyl absorption was noted in the solid-state infrared spectrum at 1928 cm-1, alongside
an absorption assigned to a coordinated carboxylate unit at 1573 cm-1. Both of these features
were found to be at values shifted compared to those in the precursors. The retention of the
vinyl ligands was confirmed by the presence of characteristic resonances in the 1H NMR
spectrum at 5.89 (d, Hβ) and 7.81 (dt, Hα), showing a mutual coupling of 15.2 Hz, while the
lower field resonance also showed 3JHP coupling to the two equivalent phosphorus nuclei. The
presence of the tolyl substituent was also clearly indicated by resonances at 2.23 ppm (s,
CH3), 6.35 and 6.82 ppm, with the latter displaying an AA’BB’ spin system showing a coupling
of 7.8 Hz. The features at 6.92 (dd), 7.66 (m) and 8.46 (d) ppm were assigned to the bipyridyl
unit. In particular, the chemical shift of the 8.46 ppm resonance18 suggests that the bpy unit
remains uncoordinated to the ruthenium centre. The overall composition was confirmed by
mass spectrometry and elemental analysis.
Following a similar strategy, the dark red [{Ru(C(C≡CPh)=CHPh)(CO)(PPh3)2}2(µ-
dcbpy)] (2) was formed from the coordinatively-unsaturated enynyl compound
[Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh3)2] and H2dcbpy in the presence of sodium methoxide
(Scheme 1). In addition to carbonyl (1929 cm-1) and carboxylate (1522 cm-1) absorptions in
the solid-state infrared spectrum, a new band was noted at 2163 cm-1, which was assigned to
an C≡C absorption originating from the enynyl ligand. Other spectroscopic features for 2 were
found to be similar to those observed for 1 apart from a broadened singlet absorption in the
1H NMR spectrum at 5.79 ppm, which was assigned to the Hβ proton of the enynyl ligand.
Scheme 1. Synthetic routes to compounds 1 to 7 (L = PPh3).
In order to better explore the coordination behaviour of the dcbpy ligand, a different
and more robust precursor was employed. While allowing fewer possibilities to tune the
functionality of the ligands, cis-[RuCl2(dppm)2] offers better resistance to acidic conditions than
the vinyl moieties and is less prone to the loss of the phosphine ligands than the
bis(phosphine) complexes. Following a similar procedure to that used for the synthesis of 1
and 2, cis-[RuCl2(dppm)2] was added to a mixture of H2dcbpy, sodium methoxide and NH4PF6,
to yield the complex [{Ru(dppm)2}2(µ-dcbpy)](PF6)2 (3·2PF6) as a dark brown solid. 31P{1H}
NMR spectroscopy revealed a dramatic change in the chemical shift of the two resonances,
from -27.0 and -0.9 ppm (JPP = 36.1 Hz) in the precursor to -11.9 and 8.7 pm (JPP = 38.8 Hz)
for 3·2PF6. The 1H NMR spectrum was dominated by the multiplets arising from the phenyl
protons in the aromatic region, but a singlet at 8.55 ppm and a doublet at 8.91 ppm could be
discerned for the protons of dcbpy. The protons of the PCH2P methylene bridges of the dppm
ligands were found to resonate at 4.16 and 4.76 ppm. The infrared spectra showed an
absorption at 1521 cm-1, attributed to the coordinated carboxylate moiety. The overall
composition was confirmed by mass spectrometry and elemental analysis.
Despite repeated attempts, experiments to obtain single crystals of 1 – 3 suitable for
X-ray analysis proved unsuccessful. However, the charged nature of 3 allowed a range of
different counterions to be investigated in order to improve the crystallinity of the material. The
use of the more bulky tetraphenylborate anion had the desired effect and allowed yellow
needles of the complex [{Ru(dppm)2}2(µ-dcbpy)](BPh4)2 (3·2BPh4) to be obtained by slow
diffusion of diethyl ether in a dichloromethane solution of the compound (Figure 2). Some of
the structural features of the complex match those determined for mononuclear compounds
reported in the literature, such as [Ru(O2CMe)(dppm)2]BPh4.19 The geometry of the molecule
is determined by both the constraints of the three bidentate ligands, all of which coordinate to
the ruthenium creating a four-membered ring, and on the high steric demand of the dppm
ligands, and especially of the phenyl moieties. The influence of the bidentate nature of the
ligands can be seen in the distorted octahedral geometry around the ruthenium atom, and
especially in its angles: the angle O(3)-Ru(1)-O(1) formed by the carboxylate moiety is
59.79(15)°, while the intraligand angles arising from the dppm coordination, P(13)-Ru(1)-P(11)
and P(43)-Ru(1)-P(41), are 71.70(6)° and 72.45(6)° respectively. In order to accommodate
this deviation from the 90° of a regular octahedron, the cis-interligand angles were found to lie
in the range 90.23(11)˚ and 108.41(1)°. It is noteworthy that the axial Ru-P bonds are longer
(2.3361(16) and 2.3570(16) Å) than those trans to the oxygen atoms (2.2640(16) and
1.916(17) Å), probably due to a weak trans effect. Another interesting feature is the difference
in bond length between the two oxygen atoms and the ruthenium: Ru(1)-O(3) is 2.161(4)Å and
Ru(1)-O(1) is 2.232(4), and this asymmetry is likely to be due the steric hindrance of the dppm
ligand. The rest of the bond distances are unremarkable. The entire
RuO2C(NC5H3C5H3N)CO2Ru unit is almost coplanar with very little rotation observed about
the C(6)-C(6A) bond.
Figure 2. The structure of the Ci-symmetric complex present in the crystal of 3·2BPh4.
Since the report by Schulten in 1939 on the discovery of pentacarbonyl halides by the
action of carbon monoxide on the corresponding hexahalogenorhenates,20 these complexes
have been used as synthons for a vast range of substitution reactions, and especially with
diamine donors, such as bipyridine and phenanthrene derivatives. Thus, compounds 1 - 3
were treated with pentacarbonylchlororhenium(I), with the objective of coordinating the
rhenium to the nitrogen donors of the dcbpy ligand. However, despite forcing conditions being
employed (toluene reflux), no trimetallic product could be obtained. The structure of 3·2BPh4
(Figure 1) shows the typical arrangement for the bipyridine nitrogen donors on opposite sides
of the dcbpy ligand. Thus, bidentate coordination of the Re(I) centre would require rotation
about the C(6)-C(6A) bond. In order to probe whether the bulk of the ruthenium termini is
preventing rotation and hence attachment of the rhenium unit or if the coordination ‘pocket’ is
simply too small to accommodate the metal, a different strategy was therefore devised to
obtain the trimetallic compounds. This involved the synthesis of the known orange complex,
[ReCl(CO)3(µ-H2dcbpy)] (4),21 as the starting point for the addition of the termini. Solutions of
4 were thus treated with sodium methoxide and two equivalents of either [Ru(CH=CHC6H4Me-
4)Cl(CO)(BTD)(PPh3)2] or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh3)2], to give
[{Ru(CH=CHC6H4Me-4)(CO)(PPh3)2}2(µ-dcbpy)ReCl(CO)3] (5)
or[{Ru(C(C≡CPh)=CHPh)(CO)(PPh3)2}2(µ-dcbpy)ReCl(CO)3] (6), respectively. The 31P{1H}
spectra for both complexes failed to show any significant differences compared to their
bimetallic counterparts (1 and 2), suggesting a very similar environment for the termini.
However, solid-state infrared spectra showed the presence of diagnostic peaks for the
tricarbonyl-rhenium unit around 2019 and 1890 cm-1 while the absorption for the carbonyl
ligand coordinated to the ruthenium was shifted to 1918 (5) and 1919 cm-1 (6). Modest
changes were also apparent in the chemical shifts of the bipyridyl features in the 1H NMR
spectrum of Ru2Re complex 5 (7.01, 7.26, 8.68 ppm), compared to the corresponding
resonances in the compound 1 (6.92, 7.66 and 8.46 ppm) without coordination at the bpy unit.
Mass spectral data and elemental analysis confirmed the hypothesised composition. In order
to complete the series of trimetallic complexes, [{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7)
was obtained from the reaction of 4 with two equivalents of cis-[RuCl2(dppm)2]. The conversion
of the mononuclear complex [ReCl(CO)3(µ-H2dcbpy)], (4) into the trimetallic assembly
[{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7) was also monitored by investigating the variation
of the UV-vis absorption and emission properties.
Figure 3. Absorption profiles of [ReCl(CO)3(µ-H2dcbpy)], (4), red dashed trace and
[{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7), blue solid trace, obtained from ca. 10-5 M
acetonitrile solutions.
The absorption profile of the neutral species [ReCl(CO)3(µ-H2dcbpy)] (4), obtained
from the corresponding diluted (ca. 10-5 M) acetonitrile solution, displayed typical features for
this class of d6 metal complexes, with intense ligand centred (LC) –* transitions occurring
in the 250–350 nm region followed by weaker metal to ligand charge transfer (MLCT) bands
above 350 nm. The coordination of two {Ru(dppm)2} fragments through the deprotonated
carboxylic acid termini of complex 4 provided the dicationic, trimetallic complex
[{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7). The addition of the metal units induced a shift to
higher energy for the MLCT absorption band (max = ca. 365 nm, see Figure 3 and Table 1).
However, the broad profile of this band did not permit the Re(I)-centred transitions to be
distinguished from those arising from the Ru(II) metal centres.
Figure 4. Emission profiles of air-equilibrated solutions (10-5 M in CH3CN, 298K) of
[ReCl(CO)3(µ-H2dcbpy)], (4), red dashed trace, and [{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2
(7), blue solid trace.
In good agreement with the data reported in the literature,22 the excitation of the MLCT
features of a dilute (10-5 M) acetonitrile solution of the complex [ReCl(CO)3(µ-H2dcbpy)] (4)
produced a weak emission centred at ca. 720 nm (Figure 4 and Table 1). The broad and
structureless shape of the corresponding emission profile suggested a metal to ligand charge
transfer (MLCT) character of the emissive excited states,23 and this assignment was further
corroborated by the pronounced rigidochromic blue shift of the emission maximum observed
on moving from room temperature to 77 K (Table 1).24 In addition, the slight but observable
increase of the emission intensity and the concomitant elongation of the emission lifetimes
(Table 1 and Figure S3-2 in the Supporting Information) that were detected upon the removal
of dissolved O2 (i.e. by degassing the acetonitrile solution of the complex under argon)
provided an indication of the triplet spin multiplicity of emissive excited states. If compared to
the neutral precursor species, [ReCl(CO)3(µ-H2dcbpy)] (4), under the same experimental
conditions (10-5 M solution in acetonitrile at 298 K), the dicationic, trimetallic complex
[{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7), displayed a significantly blue shifted (max = ca.
80 nm, see Figure 4 and Table 1), brighter, and longer-lived phosphorescence. This is likely
to originate from 3MLCT excited states, as suggested by the sensitivity of the excited state
lifetime τ and quantum yield Φ to the presence of dissolved O2 (Table 1 and Figure S3-4 in
the Supporting Information). Taken together, these data reveal an effective enhancement of
the luminescent behaviour on going from the neutral complex [ReCl(CO)3(µ-H2dcbpy)] (4) to
the dicationic complex [{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7). The increase in the
values of τ and Φ on coordination of two Ru(dppm)2 units could be rationalised by the increase
of the relative energy of the 3MLCT excited state, as predicted by the energy gap law. Even
though it was not possible to selectively excite the MLCT features of the Re(I) or the Ru(II)
centres, it is likely that the phosphorescent emission of [{Ru(dppm)2}2(µ-
dcbpy)ReCl(CO)3](PF6)2 (7) can be traced solely to the fac-[Re(CO)3(µ-dcbpy)] fragment of
the molecule - an assignment that was supported by the non-emissive character of the
Ru(dppm)2 metal fragments.
Table 1. Relevant photophysical data for compounds 4 and 7.
Complex
(in CH3CN)
Absorption
λabs (nm)
(10-4ε)(M-1cm-1)
Emission 298 Ka Emission 77Kb
λ em
(nm)
τ air
(μs)
τ Ar
(μs)
φair+
(%)
φAr+
(%)
λ em
(nm)
τ
(μs)
4 240 (7.11), 309 (4.05), 400 (0.98) 720 0.012 0.015 <1% <1% 584 2.86(34%)
8.86(66%)
7 243 (11.87), 304 (2.03), 366 (0.88) 638 0.054 0.067 <1% 1.22 594 6.75
a Air = air equilibrated solutions, Ar = deoxygenated solutions under argon atmosphere; + [Ru(bpy)3]Cl2 / H2O was
used as reference for quantum yield determinations (Φr = 0.028); b in frozen solvent matrix, CH3OH.
While compounds 5 – 7 demonstrate the possibility of inserting a metal (Re) within the
polyfunctional linker, the peerless synthetic versatility of ferrocene among organometallic
sandwich complexes offers the option to design a carboxylate linker based around the
bis(cyclopentadienyl)iron(II) unit. This has been explored through the use of 1,1’-
ferrocenedicarboxylate as a linker,25 however, this only provides access to symmetrical
multimetallic compounds. The synthesis of 1,1’-ethynylferrocene carboxylic acid was first
reported in 200926 and this bifunctional molecule was chosen to broaden the approach
described here through the particular and selective reactivity of the ethynyl unit. It was
anticipated that reaction would first take place at the carboxylate donors with the ruthenium
compounds used as precursors above.
Reaction of the 5-coordinate enynyl complex, [Ru{C(C≡CPh)=CHPh}Cl(CO)(PPh3)2],
with deprotonated 1,1’-ethynylferrocene carboxylic acid led to the formation of
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CH)(CO)(PPh3)2] (8) in 69% yield (Scheme 2). The
31P{1H} NMR spectrum gave rise to a new resonance at 35.5 ppm – a similar value to that
found for [{Ru(C(C≡CPh)=CHPh)(CO)(PPh3)2}2(µ-dcbpy)] (2). 1H NMR analysis proved
diagnostic with the presence of the new ligand being confirmed by resonances at 3.38, 3.88,
4.01 and 4.12 ppm for the C5H4 rings and the acetylenic proton of the terminal alkyne
appearing as a singlet at 3.23 ppm. The retention of the enynyl ligand was indicated by the
broadened singlet at 5.61 (Hβ) in this spectrum and the presence of the C≡C absorption for
the C≡CPh unit at 2143 cm-1. Alongside this feature was observed a band for the terminal
alkyne at 2100 cm-1, the carbonyl at 1908 cm-1 and the carboxylate unit at 1501 cm-1. The
formulation of 8 was further confirmed by elemental analysis.
Scheme 2. Formation of heteromultimetallic complexes based on a bifunctional ferrocenyl unit;
DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene.
The reaction of alkynes with gold halide precursors under basic conditions is well
known to result in alkynyl gold complexes.27 These compounds have been implicated in many
organic transformations catalysed by gold(I) compounds.28,29 They have also been used in
pioneering work by Lang and co-workers to create heteromultimetallic complexes.30 Reaction
of 8 with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and [AuCl(PPh3)] resulted in the formation
of the acetylide complex [Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CAuPPh3)(CO)(PPh3)2]
(9), as shown in Scheme 2. The successful addition of the gold-phosphine unit was indicated
by a new singlet in the 31P{1H} NMR spectrum at 42.0 ppm, to lower field of the resonance at
35.3 ppm assigned to the ruthenium-bound triphenylphosphine ligands. The absence of the
acetylenic proton in the 1H NMR spectrum also provided indirect evidence for the formation of
this bimetallic complex. The 1,1’-bis(diphenylphosphino)ferrocene compound [dppf(AuCl)2]
provides a versatile starting point for multimetallic complexes, particularly through the
formation of gold thiolates.6g,31 Treatment of [dppf(AuCl)2] with two equivalents of 8 in the
presence of base (DBU) led to the formation of the heteroheptametallic Fe3Ru2Au2 complex,
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡C)(CO)(PPh3)2]2(Au2dppf) (10). The 31P{1H} NMR
spectrum revealed two resonances at 35.7 (RuPPh3) and 36.6 (Au-dppf) ppm, while the 1H
NMR spectrum displayed additional cyclopentadienyl resonances attributed to the dppf unit.
Good agreement between calculated and experimentally determined elemental analysis
values confirmed the overall formulation.
Having exploited the reactivity of the terminal alkynyl group in 8 to form acetylides, the
insertion of the alkyne into metal hydride bonds was next investigated – the same reaction
used to form the vinyl complexes was employed in this work. Compound 8 was found to react
rapidly with the hydride complex [RuHCl(CO)(BTD)(PPh3)2] to form
[Ru{C(C≡CPh)=CHPh}{O2CC5H4FeC5H4CH=CH(RuCl(CO)(BTD)(PPh3)2)}(CO)(PPh3)2] (11)
in a 100% atom efficient reaction (Scheme 2). The new resonance at 26.9 ppm in the 31P{1H}
NMR spectrum, shifted slightly upfield with respect to the resonance of the carboxylate metal
unit (35.4 ppm) was assigned to the new vinyl complex. 1H NMR analysis revealed resonances
for the protons of both the enynyl (5.60 ppm) and the new vinyl units (at 5.41 and 7.82 ppm).
Only one broad infrared absorption was observed for the complex, at 1918 cm-1, due to the
similarity of the carbonyl environments at each metal centre. However, the analogous osmium
complex,
[Ru{C(C≡CPh)=CHPh}{O2CC5H4FeC5H4CH=CH(OsCl(CO)(BTD)(PPh3)2)}(CO)(PPh3)2] (12),
gave rise to an absorption at 1921 cm-1 for the carbonyl on the ruthenium centre with a
shoulder at 1898 cm-1 for the CO ligand bonded to the more electron-rich osmium centre. The
differences in the electronic environments of the two metal centres were also reflected in the
31P{1H} spectrum, in which the phosphorus nuclei of the osmium centre resonated at much
lower chemical shift (-3.1 ppm) than those of the ruthenium centre (35.4 ppm). Complex 12 is
one of only a small number6g,32 of complexes to combine all the metals of group 8 in the
periodic table.
Complex 10 presents an unusual series of metal units which are typically stable
towards oxidation, with three ferrocenyl units in two different environments and two ruthenium
atoms in the same environment. It was therefore decided to explore briefly the electrochemical
behaviour of the heteroheptametallic complex. For comparison purposes, data were also
collected for precursors [dppf(AuCl)2] and the compound
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CH)(CO)(PPh3)2] (8) (Figure 5). Complex 8 shows
two redox processes at 0.24 and 0.39 V respectively (vs Fc/Fc+). After correcting for
resistance, it was found that the former is electrochemically reversible (ΔE = 62 mV, ipa and ipc
proportional to square root of scan rate) whereas the latter is only quasi-reversible (ΔE = 102
mV, ipa proportional and ipc not proportional to scan rate, Figure S4-2). As the two redox
processes were somewhat broad and close together (ΔE1/2 = 141 mV) it was not possible to
determine ipa/ipc for either process. Comparison with literature data33,34 led us to assign the
lower potential process to the Fe(II/III) couple, while the wave at higher potential is related to
the ruthenium alkenyl moiety.35,6e
-0.2 0.0 0.2 0.4 0.6 0.8 1.0
E / V vs Fc / Fc+
2 A
Figure 5. Cyclic voltammogram for [dppf(AuCl)2] (blue), 8 (red) and 10 (black). Conditions:
0.1 M TBAPF6/DCM, 100 mV/s, glassy carbon electrode.
The cyclic voltammogram of 10 shows multiple redox processes, the origins of which
are difficult to assign with cyclic voltammetry alone. However, based on a comparison with the
CV of 8 and the starting material [dppf(AuCl)2], some tentative assignments can be made. It
is likely that the redox process at 0.64 V corresponds to the [dppf(AuCl)2] moiety; if the scan
exceeds this potential, the CV loses much of its reversibility, which is consistent with the
dissociation of the molecule upon oxidation of the central dppf moiety (Figure S4-5). The redox
process at 0.35 V is possibly related to the ruthenium alkenyl fragment. The redox process at
0.04 V does not appear in any of the component parts, but it is likely that this corresponds the
ethynylferrocenecarboxylate ligand which has become easier to oxidise upon conjugation to
gold. A smaller redox event can be observed between the major processes at 0.35 and 0.04
V. As the oxidative wave is broad and overlaps strongly with the waves either side, it is difficult
to assign a formal potential to this process and it is not clear as to its origins. A possible
explanation may be due to communication between the linked ethynylferrocenecarboxylate
ligands within the framework of 10 although this too is difficult to prove by CV alone. A scan
rate analysis was performed but scanning too slowly (20 and 50 mV/s) resulted in deposition
on the electrodes, while inclusion of the signal at 0.64 V resulted in chemical irreversibility as
evidenced in figure S4-5. Within the limits of the chemistry exhibited, we were able to
demonstrate that the signals at 0.04 and 0.35 V were both quasi-reversible (Figure S4-4).
Further investigations lie beyond the scope of this present contribution.
Conclusions
This contribution illustrates how polyfunctional linkers combining carboxylic acid and alkynyl
or pyridyl donors can be used to generate a series of homo- and heteronuclear, bi- and
trimetallic of Re(I), Ru(II), Os(II) and Au(I) in a controlled, selective and stepwise manner. The
literature compound [ReCl(CO)3(µ-H2dcbpy)] (4) leads to trimetallic complexes, which are not
accessible from the parent H2dcbpy ligand, which only results in bimetallic compounds. A
comparison of the photophysical properties of 4 and [{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2
(7) illustrates the effect of adding Ru(II) termini, which leads to enhanced luminescent
behaviour. The second linker studied, 1,1’-ethynylferrocene carboxylic acid, brings together
oxygen donor and alkynyl functionalities, allowing initial coordination of a ruthenium(II) vinyl
unit to give [Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CH)(CO)(PPh3)2] (8). The pendant
ethynyl unit can be exploited to form either acetylide or vinyl bridges to a further metal unit,
allowing the extension to heterotrimetallic FeRuOs and FeRuAu compounds. The
electrochemical behaviour of the heteroheptametallic Fe3Ru2Au2 complex (10) was explored,
and through a comparison to that of 8 and [dppf(AuCl)2], a reasonable assignment of the
individual metal units could be made. This study illustrates how linkers with carefully selected
donor groups can be employed to generate a wide variety of multimetallic complexes with a
variety of different metals from across the d-block. Once combined in a heterometallic
assembly, the photophysical and electrochemical properties can be interrogated as a function
of the metal units employed.
Acknowledgements
K.A.J. would like to thank the Ministry of Higher Education, Malaysia for a scholarship
on the IPTA Academic Training Scheme and for an Academic Staff Scholarship from
the Universiti Teknologi MARA, Malaysia. L.M. gratefully acknowledges the support of
the Royal Society for a RS-CNR International Fellowship.
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Supporting Information
Heteromultimetallic compounds based on polyfunctional carboxylate linkers
Khairil A. Jantan, James A. McArdle, Lorenzo Mognon, Valentina Fiorini, Luke A. Wilkinson,
Andrew J. P. White, Stefano Stagni, Nicholas J. Long* and James D. E. T. Wilton-Ely*
S1. Experimental page 1
S2. Crystallography page 26
S3. Photophysics page 27
S4. Electrochemistry page 30
S5. References page 32
S1. Experimental
General Comments. Unless otherwise stated, all experiments were carried out in the air, and
the complexes obtained appear stable towards the atmosphere, whether in solution or the
solid-state. Reagents and solvents were used as received from commercial sources.
Petroleum ether is the fraction boiling in the 40–60 °C range. The following complexes were
prepared following literature routes: cis-[RuCl2(dppm)2],S1
[Ru(CH=CHC6H4Me4)Cl(CO)(BTD)(PPh3)2],S2 [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh3)2],S3
[ReCl(CO)3(dcbpy)],S4 (HC≡CC5H4)Fe(C5H4CO2H),S5 [OsHCl(CO)(BTD)(PPh3)2] (M = Ru,S6
OsS7), [AuCl(PPh3)]S8 and [(dppf)AuCl2].S9 Electrospray (ES) and Fast Atom Bombardment
(FAB) mass data were obtained using Micromass LCT Premier and Autospec Q instruments,
respectively. Infrared data were obtained using a Perkin-Elmer Spectrum 100 FT-IR
spectrometer employing an ATR method, and characteristic triphenylphosphine-associated
infrared data are not reported. NMR spectroscopy was performed at 25 °C using Bruker AV400
or AV 500 spectrometers in CDCl3 unless stated otherwise. All coupling constants are in Hertz.
Resonances in the 31P{1H} NMR spectrum due to the hexafluorophosphate counteranion were
observed where the formulation indicates but are not included below. Elemental analysis data
were obtained from London Metropolitan University. Solvates were confirmed by integration
of the 1H NMR spectra. The procedures given provide materials of sufficient purity for synthetic
and spectroscopic purposes.
[{Ru(CH=CHC6H4Me-4)(CO)(PPh3)2}2(µ-dcbpy)] (1)
A solution of 2,2’-bipyridine-4,4’-dicarboxylic acid (10.0 mg, 0.041 mmol) and sodium
methoxide (6.7 mg, 0.123 mmol) in methanol (10 mL) was stirred at room temperature for 30
minutes. A dichloromethane (20 mL) solution of [Ru(CH=CHC6H4Me–4)Cl(CO)(BTD)(PPh3)2]
(77 mg, 0.082 mmol) was added and stirred for another 2 h at room temperature. All the
solvent was removed under vacuum and the crude product was dissolved in dichloromethane
(10 mL) and filtered through Celite to remove NaCl, NaOMe and excess ligand. The solvent
was again removed using rotary evaporator. Diethyl ether (10 mL) was added, and the
resulting mixture triturated in the ultrasonic bath. The dark brown precipitate obtained was
filtered under vacuum, washed with diethyl ether (10 mL) and dried. Yield: 34 mg (47%). The
product can be recrystallised from dichloromethane-diethyl ether mixtures. IR: 1928 (CO),
1573, 1544 (OCO), 1481, 1433, 1185, 1090, 979, 875, 836, 741, 692 cm–1. 1H NMR (CDCl3):
2.23 (s, 6H, CH3), 5.89 (d, 2H, Hβ, JHH = 15.2 Hz), 6.35, 6.82 (AB, 8H, C6H4, JAB = 7.8 Hz),
6.92 (dd, 2H, bpy, JHH = 4.9, 1.4 Hz), 7.30 – 7.43, 7.50 (m x 2, 60H, C6H5), 7.66 (m, 2H, bpy),
7.82 (dt, 2H, Hα, JHH = 15.2 Hz, JHP = 2.7), 8.46 (d, 2H, bpy, JHH = 4.9) ppm. 31P{1H} NMR
(CDCl3): 38.2 (s, PPh3) ppm. MS (ES +ve) m/z (abundance): 1894 (4) [M+4Na+H2O]+, 1543
(3) [M–PPh3+Na]+, 1113 (50) [M–vinyl–CO–2PPh3]+, 991 (100) [M–CO–3PPh3+Na]+. Elem.
Anal. Calcd. for C104H84N2O6P4Ru2·2.5CH2Cl2 (MW = 1996.16): C 64.1, H 4.5, N 1.4%. Found:
C 63.7, H 4.2, N 1.8%
Figure S1-1. 31P{1H} NMR spectrum of compound 1 in CDCl3.
Figure S1-2. 1H NMR spectrum of compound 1 in CDCl3.
Figure S1-3. Solid-state infrared spectrum of compound 1.
[{Ru(C(C≡CPh)=CHPh)(CO)(PPh3)2}2(µ-dcbpy)] (2)
A methanolic solution (10 ml) of 2,2’-bipyridine-4,4’-dicarboxylic acid (20 mg, 0.082 mmol) and
sodium methoxide (13.3 mg, 0.246 mmol) was stirred for 30 minutes at room temperature and
treated with a dichloromethane solution (10 mL) of [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh3)2]
(146.3 mg, 0.164 mmol). The reaction was stirred for 2h at room temperature. The solvent
was removed under vacuum (rotary evaporator) and the resulting red product was dissolved
in the minimum amount of dichloromethane. This was filtered through Celite and the solvent
removed by rotary evaporation. Diethyl ether (10 mL) was added, and subsequent ultrasonic
titruration provided a dark red precipitate, which was filtered, washed with diethyl ether (10
mL) and dried. Yield: 80 mg (50%). The product is slightly soluble in diethyl ether. IR: 2163
(C≡C), 1929 (CO), 1522 (OCO), 1482, 1432, 1186, 1094, 877, 743, 691 cm–1. 1H NMR (CDCl3):
6.01 (s(br), 2H, Hβ), 6.92 (dd, 2H, bpy, JHH = 6.2), 7.00 (m, 6H, C6H5), 7.09 (t, 6H, CC6H5,
JHH = 7.5 Hz), 7.20 - 7.22 (m, 34H, PC6H5), 7.35 (m, 4H, CC6H5), 7.42 (t, 4H, CC6H5, JHH = 7.5
Hz), 7.54 - 7.59 (m, 26H, PC6H5), 7.78 (m, 2H, bpy), 8.46 (dd, 2H, bpy) ppm. 31P{1H} NMR
(CDCl3): 38.2 (s, PPh3) ppm. MS (ES +ve) m/z (abundance): 1980 (10) [M+H+Na]+, 897
(100) [M–4PPh3–CO+H2O]+. Elem. Anal. Calcd. for C118H88N2O6P4Ru2 (MW = 1956.01): C
72.4, H 4.5, N 1.4%. Found: C 72.3, H 4.3, N 1.6%.
Figure S1-4. 31P{1H} NMR spectrum of compound 2 in CDCl3.
Figure S1-5. 1H NMR spectrum of compound 2 in CDCl3.
Figure S1-6. Solid-state infrared spectrum of compound 2.
[{Ru(dppm)2}2(µ-dcbpy)](PF6)2 (3·2PF6)
A solution of 2,2’-bipyridine-4,4’-dicarboxylic acid (10.0 mg, 0.041 mmol) and sodium
methoxide (8.9 mg, 0.164 mmol) in methanol (10 mL) was stirred for 30 minutes at room
temperature. A solution of cis-[RuCl2(dppm)2] (77 mg, 0.082 mmol) in dichloromethane (20
mL) was then added along with ammonium hexafluorophosphate (22.6 mg, 0.123 mmol). The
reaction mixture was stirred for 2 h at room temperature. All the solvent was then removed
using a rotary evaporator and the crude product was re-dissolved in dichloromethane (10 mL)
and filtered through Celite. Ethanol (20 mL) was added and the solvent volume slowly reduced
on a rotary evaporator until the formation of a brown solid. The precipitate was filtered, washed
with petroleum ether (10 mL) and dried under vacuum. The product is partially soluble in
ethanol, contributing to a reduced yield. Yield: 48 mg (51%). IR: 1593, 1521 (OCO), 1482,
1426, 1186, 1093, 835 (PF) cm–1. 1H NMR (CDCl3): 4.16, 4.76 (m x 2, 2 x 4H, PCH2P), 6.26
(m, 8H, C6H5), 6.99 − 7.54 (m, 56H + 2H, C6H5 + bpy), 7.65, 7.80 (m x 2, 2 x 8H, C6H5), 8.55
(s, 2H, bpy), 8.91 (d, 2H, bpy, JHH = 4.3 Hz) ppm. 31P{1H} NMR (CDCl3): −11.9, 8.7
(pseudotriplet x 2, dppm, JPP = 38.8 Hz) ppm. MS (MALDI +ve) m/z (abundance): 2128 (12)
[M+H+PF6]+, 1981 (11) [M+H]+. Elem. Anal. Calcd. for C112H94F12N2O4P10Ru2·CH2Cl2 (MW =
2356.75): C 57.6, H 4.1, N 1.2%. Found: C 57.3, H 4.2, N 1.0%. [{Ru(dppm)2}2(µ-
dcbpy)](PF6)2 (3·2BPh4) was prepared in an identical manner, using sodium
tetraphenylborate. Spectroscopic data for the cation were found to be identical to those for
3·2PF6.
Figure S1-7. 31P{1H} NMR spectrum of compound 3·2PF6 in CDCl3.
Figure S1-8. 1H NMR spectrum of compound 3·2PF6 in CDCl3.
Figure S1-9. Solid-date IR spectrum of compound 3·2PF6.
[ReCl(CO)3(µ-H2dcbpy)] (4)
Re(CO)5Cl (193 mg, 0.53 mmol) was dissolved in an hot toluene (50 mL) and methanol (20
mL). 4,4’-dicarboxyl-2,2’-bipyridine (130 mg, 0.53 mmol) was added to the solution, and the
reaction mixture was stirred under reflux for 1h. During this time, the colour of the solution
changed from colourless to orange. The solution was kept at –20 degrees for 1h to precipitate
the unreacted starting material which was then filtered. The resulting orange solution was
evaporated to dryness to yield the product. Yield: 233 mg (80 %). IR: 2030 (CO), 1902 (CO),
1875 (CO), 1734, 1511 (OCO), 1426, 1214, 1095, 832, 772, 731, 691, 663 cm–1. 1H NMR (d6-
DMSO): 8.14 (dd, 2H, bpy, JHH = 5.7, 1.7 Hz), 9.15 (dd, 2H, bpy, JHH = 1.7, 0.8 Hz), 9.22
(dd, 2H, bpy, JHH = 5.7, 0.8 Hz), 14.39 (s(br), 2H, CO2H) ppm. The data obtained were found
to be in good agreement with those reported in the literature.S4
Figure S1-10. 1H NMR spectrum of compound 4 in DMSO (solvent peaks removed).
Figure S1-11. Solid-state IR spectrum of compound 4.
[{Ru(CH=CHC6H4Me-4)(CO)(PPh3)2}2(µ-dcbpy)ReCl(CO)3] (5)
A solution of 4 (30 mg, 0.055 mmol) and sodium methoxide (11.9 mg, 0.22 mmol) in methanol
(10 mL) was stirred for 30 minutes at room temperature. A solution of [Ru(CH=CHC6H4Me–
4)Cl(CO)(BTD)(PPh3)2] (102.7 mg, 0.109 mmol) in dichloromethane (10 mL) was added and
stirred for another 2h. Ethanol (10 mL) was added and the solvent volume slowly reduced on
a rotary evaporator until the formation of a brown solid was complete. The precipitate was
filtered, washed with ethanol (10 mL) and dried under vacuum. Yield: 79 mg (69 %). IR: 2019
(CO), 1918 (CO), 1890 (CO), 1531 (OCO), 1481, 1433, 1391, 1184, 1090, 979, 827, 743, 692
cm–1. 1H NMR (CDCl3): 2.23 (s, 6H, CH3), 5.94 (d, 2H, Hβ, JHH = 15.0 Hz), 6.38, 6.82 (AB,
8H, C6H4, JAB = 7.7 Hz), 7.01 (dd, 2H, bpy, JHH = 5.6, 1.4 Hz), 7.26 (m, 2H, bpy), 7.36, 7.52 (m
x 2, 60H, C6H5), 7.84 (dt, 2H, Hα, JHH = 15.0 Hz, JHP = 2.8 Hz), 8.68 (d, 2H, bpy, JHH = 5.6 Hz)
ppm. 13C{1H} NMR (CD2Cl2): 206.4 (t, RuCO, JPC = 15.0 Hz), 197.8 (s, 2 x ReCO), 197.6 (s,
ReCO), 172.8 (s, CO2), 155.1, 152.6 (s x 2, 2 x bpy), 151.0 (t, C, JPC = 11.5 Hz), 142.4 (s,
bpy), 138.0 (s, ipso/p-C6H4), 134.7 (tv, o/m-C6H5, JPC = 5.4 Hz), 133.7 (s, C), 132.2 (s, ipso/p-
C6H4), 131.1 (tv, ipso-C6H5, JPC = 22.0 Hz), 130.7 (s, p-C6H5), 128.7 (tv, o/m-C6H5, JPC = 5.5
Hz), 128.4 (s, o/m-C6H4), 125 (s, bpy), 124.6 (s, o/m-C6H4), 121.5 (s, bpy), 21.0 (s, p-C6H4)
ppm. 31P{1H} NMR (CDCl3): 38.1 (s, PPh3) ppm. MS (ES +ve) m/z (abundance): 1244 (12)
[M–3PPh3–3CO+H+Na]+, 1303 (4) [M–3PPh3]+. Elem. Anal. Calcd. for C107H84N2O9P4ReRu2
(MW = 2089.51): C 61.5, H 4.1, N 1.3%. Found: C 61.4, H 3.9, N 1.4%.
Figure S1-12. 31P{1H} NMR spectrum of compound 5 in CDCl3.
Figure S1-13. 13C{1H} NMR spectrum of compound 5 in CDCl3.
Figure S1-14. 1H NMR spectrum of compound 5 in CDCl3.
Figure S1-15. Solid-state IR spectrum of compound 5.
[{Ru(C(C≡CPh)=CHPh)(CO)(PPh3)2}2(µ-dcbpy)ReCl(CO)3] (6)
A solution of 4 (30 mg, 0.055 mmol) and sodium methoxide (11.9 mg, 0.22 mmol) in methanol
(10 ml) was stirred for 30 minutes at room temperature. A brown solution of
[Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh3)2] (97.3 mg, 0.109 mmol) in dichloromethane (10 mL)
was added and stirred for another 2h. Ethanol (10 mL) was added and the solvent volume
slowly reduced on a rotary evaporator until the formation of a brown solid was complete. The
precipitate was filtered, washed with ethanol (10 mL) and dried under vacuum. Yield: 82 mg
(66 %). IR: 2019 (CO), 1917 (CO), 1890 (CO), 1531 (OCO), 1481, 1433, 1185, 1094, 826, 743,
691 cm–1. 1H NMR (CDCl3): 6.12 (s(br), 2H, Hβ), 6.89 (d, 2H, bpy, JHH = 5.6 Hz), 7.04 (m,
6H, CC6H5), 7.12 (t, 6H, CC6H5, JHH = 7.4 Hz), 7.21 - 7.35 (m, 36H, PC6H5), 7.39 -7.46 (m, 8H,
CC6H5), 7.59 (m, 24H + 2H, PC6H5 + bpy), 8.66 (d, 2H, bpy, JHH = 5.6 Hz) ppm. 31P{1H} NMR
(CDCl3): 37.9 (s, PPh3) ppm. MS (ES +ve) m/z (abundance): 1245 (4) [M–3PPh3–CO–
enynyl]+, 898 (100) [(M–PPh3–enynyl)/2]+. Elem. Anal. Calcd. for C121H88ClN2O9P4ReRu2 (MW
= 2261.70): C 64.3, H 3.9, N 1.2%. Found: C 64.1, H 3.8, N 1.2%.
Figure S1-16. 31P{1H} NMR spectrum of compound 6 in CDCl3.
Figure S1-17. 1H NMR spectrum of compound 6 in CDCl3.
Figure S1-18. Solid-state IR spectrum of compound 6.
[{Ru(dppm)2}2(µ-dcbpy)ReCl(CO)3](PF6)2 (7)
An orange solution of 4 (30 mg, 0.055 mmol) and sodium methoxide (11.9 mg, 0.22 mmol) in
methanol (10 mL) was stirred for 30 minutes at room temperature. A yellow solution of cis-
[RuCl2(dppm)2] (102.5 mg, 0.11 mmol) in dichloromethane (10 mL) was added to the mixture
leading to an immediate colour change to orange. Potassium hexafluorophosphate (40.5 mg,
0.22 mmol) was added and the reaction mixture was stirred for another 1 h at room
temperature. All the solvent was removed under vacuum and the crude product was dissolved
in dichloromethane (10 mL) and filtered through Celite to remove NaCl, NaOMe and excess
ligand. Ethanol (10 mL) was added and the solvent volume was slowly reduced on a rotary
evaporator until the formation of an orange solid. The precipitate was filtered, washed with
ethanol (10 mL) and dried under vacuum. Yield: 85 mg (60%). IR: 2020 (CO), 1919 (CO), 1892
(CO), 1515 (C-O), 1482, 1434, 1092, 839, 741, 692 cm–1. 1H NMR (CD2Cl2): 4.25, 4.80 (m x
2, 2 x 4H, PCH2P), 6.28 (m, 8H, C6H5), 7.03 − 7.93 (m, 72H + 2H, C6H5 + bpy), 7.92 (d, 2H,
bpy, JHH = 8.9 Hz), 9.18 (dd, 2H, bpy, JHH = 11.2, 5.2 Hz) ppm. 31P{1H} NMR (CD2Cl2): −11.5,
9.3 (pseudotriplet x 2, dppm, JPP = 38.9 Hz) ppm. MS (ES +ve) m/z (abundance): 1144 (100)
[M/2]+. Elem. Anal. Calcd. for C115H94ClF12N2O7P10ReRu2·2CH2Cl2 (MW = 2747.37): C 51.1, H
3.6, N 1.0%. Found: C 50.9, H 3.3, N 1.3%.
Figure S1-19. 31P{1H} NMR spectrum of compound 7 in CD2Cl2.
Figure S1-20. 1H NMR spectrum of compound 7 in CD2Cl2.
Figure S1-21. Solid-state IR spectrum of compound 7.
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CH)(CO)(PPh3)2] (8)
1,1’-Ethynylferrocene carboxylic acid (132 mg, 0.520 mmol) was suspended in
dichloromethane (100 mL) and triethylamine (0.3 mL, 2.15 mmol) added. The reaction was
stirred until complete dissolution had occurred (30-45 minutes).
[RuCl{C(C≡CPh)CHPh}(CO)(BTD)(PPh3)2] (489 mg, 0.420 mmol) was added and the mixture
stirred for a further three hours. All solvent was removed under reduced pressure and the
resultant crude product dissolved in a minimum volume of dichloromethane and filtered
through Celite. Ethanol (100 mL) was added and the solvent volume was reduced (rotary
evaporation) to form a bright orange product. This was washed with cold ethanol (20 mL) and
n-hexane (20 mL) and dried under vacuum. Yield: 330 mg (69%). IR: 3298, 2143 (C≡C), 2100
(C≡C), 1908 (CO), 1501 (OCO), 1433, 1187, 1093 cm-1. 1H NMR (d6-acetone): 3.23 (s, 1H,
C≡CH); 3.38, 3.88, 4.01, 4.12 (s(br) x 4, 4 x 2H, C5H4), 5.61 (s(br), 1H, H), 6.94 - 7.80 (m,
30H + 10H, PC6H5 + CC6H5) ppm. 13C{1H} NMR (CD2Cl2): 207 (t, CO, JPC = 16.5 Hz), 181.3
(s, CO2), 144.2 (t, C, JPC unresolved), 140.2 (s, C), 135.1 (tv, o/m-PC6H5, JPC = 5.6 Hz),
131.9 (s, C6H5), 131.5 (tv, ipso-C6H5, JPC = 21.5 Hz), 130.4 (s, C6H5), 130.2 (s, p-C6H5), 130.1
(s, C6H5), 128.5 (s, C6H5), 128.2 (tv, o/m-C6H5, JPC = 4.8 Hz), 127.3 (s, C6H5), 126.7 (s, C≡CPh),
124.9 (s, C6H5), 109.9 (s, C≡CPh), 82.2 (s, C≡CH), 77.2 (s, C≡CH), 74.0 (s, C1-C5H4), 72.3,
72.2, 70.5, 70.0 (s x 4, C2-4-C5H4), 64.4 (s, C1-C5H4) ppm. 31P{1H} NMR (d6-acetone): 35.5
(s, PPh3) ppm. MS (ES +ve) m/z (abundance) = 1149 (6) [M+K]+. Anal. Calcd. for
C66H50FeO3P2Ru (MW = 1109.96): C 71.4, H 4.5%. Found: C 71.3, H 4.4%.
Figure S1-22. 31P{1H} NMR spectrum of compound 8 in d6-acetone.
Figure S1-23. 1H NMR spectrum of compound 8 in d6-acetone.
Figure S1-24. 13C{1H} NMR spectrum of compound 8 in CD2Cl2.
Figure S1-25. Solid-state IR spectrum of compound 8.
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CAuPPh3)(CO)(PPh3)2] (9)
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡CH)(CO)(PPh3)2] (50 mg, 0.045 mmol) was
dissolved in dichloromethane (20 mL) and [AuCl(PPh3)] (22 mg, 0.045 mmol) and a few drops
of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were added. The mixture was stirred in the dark
for 18 hours after which time ethanol (20 mL) was added and the product obtained as a pale
yellow solid by rotary evaporation. This was washed with cold ethanol (10 mL) and n-hexane
(10 mL) and dried under vacuum. Yield: 37 mg (52%). The product is partially soluble in
ethanol and a second crop could be obtained on further evaporation of solvent. IR: 2182 (C≡C),
1920 (CO), 1593, 1500 (OCO), 1435, 1095, 1027, 813 cm-1. 1H NMR (d6-acetone): 3.26,
3.76, 3.94, 4.1 (s x 4, 4 x 2H, C5H4), 5.63 (s(br), 1H, H), 6.92 (t, 1H, p-CC6H5, JHH = 7.3 Hz),
7.06 (m, 4H, CC6H5), 7.28 - 7.26 (m, 18H, PC6H5), 7.51 (m, 3H, CC6H5), 7.55 - 7.67 (m, 28H,
PC6H5), 7.81 (m, 2H, CC6H5) ppm. 31P{1H} NMR (d6-acetone): 35.3 (s, RuPPh3), 42.0 (s,
AuPPh3) ppm. MS (MALDI +ve) m/z (abundance) = 1306 (11) [M–PPh3]+. Anal. Calcd. for
C84H64AuFeO3P3Ru (MW = 1568.21): C 64.3, H 4.1%. Found: C 64.4, H 4.0%.
Figure S1-26. 31P{1H} NMR spectrum of compound 9 in d6-acetone.
Figure S1-27. 1H NMR spectrum of compound 9 in d6-acetone.
Figure S1-28. Solid-state IR spectrum of compound 9.
[Ru{C(C≡CPh)=CHPh}(O2CC5H4FeC5H4C≡C)(CO)(PPh3)2]2(Au2dppf) (10)
Compound 8 (50 mg, 0.045 mmol) and [dppf(AuCl)2] (23 mg, 0.023 mmol) were dissolved in
dichloromethane (20 mL). To this was added a few drops of 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU) and the reaction was stirred in the dark at room temperature for 18 hours. Ethanol
(20 mL) was then added and the solvent volume reduced to provide a pale yellow solid. This
was washed with cold ethanol (10 mL) and n-hexane (10 mL) and dried under vacuum. Yield:
40 mg (56%). IR (solid state): 2160 (C≡C), 1921 (CO), 1594, 1500 (OCO), 1482, 1435, 1094
cm-1. 1H NMR (CD2Cl2): 3.22 (s, 4H, C5H4), 3.87, 3.98, 4.15 (t x 3, 3 x 4H, C5H4, JHH = 1.7
Hz), 4.32, 4.80 (s x 2, 2 x 4H, C5H4), 5.58 (s(br), 1H H), 6.97 (m, 6H, CC6H5), 7.08 (m, 4H,
CC6H5), 7.26 - 7.38 (m, 40H, PC6H5), 7.46 – 7.67 (m, 50H, PC6H5 + CC6H5) ppm. 31P{1H} NMR
(CD2Cl2): 35.7 (s, RuPPh3), 36.6 (s, Au-dppf) ppm. MS (MALDI +ve) m/z (abundance) =
2642 (8) [M–2PPh3]+, 2462 (15) [M–enynyl–PPh3+Na]+. Anal. Calcd. for
C166H126Au2Fe3O6P6Ru2 (MW = 3166.22): C 63.0, H 4.0%. Found: C 63.0, H 3.9%.
Figure S1-29. 31P{1H} NMR spectrum of compound 10 in CD2Cl2.
Figure S1-30. 1H NMR spectrum of compound 10 in CD2Cl2.
Figure S1-31. Solid-state IR spectrum of compound 10.
[Ru{C(C≡CPh)=CHPh}{O2CC5H4FeC5H4CH=CH(RuCl(CO)(BTD)(PPh3)2)}(CO)(PPh3)2]
(11)
[Ru{C(C≡CPh)CHPh}(O2CFcC≡CH)(CO)(PPh3)2] (62 mg, 0.056 mmol) was dissolved in
dichloromethane (25 mL) and [RuHCl(CO)(BTD)(PPh3)2] (40 mg, 0.057 mmol) added. The
mixture was stirred for 30 minutes after which time ethanol (25 mL) was added and the product
obtained as a dark red solid by rotary evaporation. This was washed with cold methanol (5
mL), cold ethanol (5 mL) and petroleum ether (10 mL) and dried under vacuum. Yield: 57 mg
(56%). IR (solid state): 2162 (C≡C), 1918 (CO), 1593, 1572, 1500 (OCO), 1481, 1433, 1092
cm-1. 1H NMR (CD2Cl2): 3.08, 3.32, 3.52, 3.86 (s(br) x 4, 4 x 2H, C5H4), 5.41 (d, 1H,
RuCH=CH, JHH = 14.5 Hz), 5.55 (s(br), 1H, RuC(C≡CPh)=CHPh), 6.99 (m, 3H, CC6H5), 7.09
(m, 2H, CC6H5), 7.24 - 7.52 (m, 50H, PC6H5 + PC6H5), 7.55 (m, 2H, BTD), 7.64 (m, 15H, PC6H5
+ PC6H5), 7.85 (d, 1H, RuCH=CH, JHH = 14.5 Hz), 7.96 (s(br), 2H, BTD) ppm. 31P{1H} NMR
(CD2Cl2): 26.9 (s, vinyl-RuPPh3), 35.4 (s, enynyl-RuPPh3) ppm. MS (MALDI +ve) m/z
(abundance) = 1801 (7) [M–BTD+H]+, 1538 (11) [M–BTD–PPh3]+. Anal. Calcd. for
C109H85ClFeN2O4P4Ru2S (MW = 1936.25): C 67.6, H 4.4, N 1.5%. Found: C 67.7, H 4.6, N
1.6%.
Figure S1-32. 31P{1H} NMR spectrum of compound 11 in CD2Cl2.
Figure S1-33. 1H NMR spectrum of compound 11 in CD2Cl2.
Figure S1-34. Solid-state IR spectrum of compound 11.
[Ru{C(C≡CPh)=CHPh}{O2CC5H4FeC5H4CH=CH(OsCl(CO)(BTD)(PPh3)2)}(CO)(PPh3)2]
(12)
[Ru{C(C≡CPh)CHPh}(O2CFcC≡CH)(CO)(PPh3)2] (61 mg, 0.055 mmol) was dissolved in
dichloromethane (25 mL) and [OsHCl(CO)(BTD)(PPh3)2] (48 mg, 0.052 mmol) was added.
The reaction was stirred for one hour after which time ethanol (20 mL) was added and a dark
purple solid was obtained on reduction of the solvent volume (rotary evaporation). This was
washed with cold ethanol (10 mL) and petroleum ether (10 mL) and dried under vacuum. Yield:
60 mg (54%). IR: 1921 (RuC≡O), 1898 (sh, OsC≡O), 1594, 1573, 1503 (OCO), 1482, 1434, 1395,
1093 cm-1. 1H NMR (CD2Cl2): 3.08, 3.28, 3.63, 3.88 (s x 4, 4 x 2H, C5H4), 5.55 (s, 1H,
RuC=CH), 5.61 (d, 1H, OsC=CH, JHH = 16.8 Hz), 6.99 - 7.66 (m, 70H + 2H, C6H5 + BTD), 8.08
(m, 2H, BTD), 8.48 (d, 1H, OsCH, JHH = 16.8 Hz) ppm. 31P{1H} NMR (CD2Cl2): -3.1 (s,
OsPPh3), 35.4 (s, RuPPh3) ppm. MS (MALDI +ve) m/z (abundance): 1890 (5) [M–BTD]+, 1524
(8) [M–2PPh3+Na]+. Anal. Calcd. for C109H85ClFeN2O4OsP4RuS (MW = 2025.41): C 64.6, H
4.2, N 1.4%. Found: C 64.7, H 4.4, N 1.5%.
Figure S1-35. 31P{1H} NMR spectrum of compound 12 in CD2Cl2.
Figure S1-36. 1H NMR spectrum of compound 12 in CD2Cl2.
Figure S1-37. Solid-state IR spectrum of compound 12.
S2. Crystallography
The X-ray crystal structure of 3·2BPh4
Crystal data for 3·2BPh4: [C112H94N2O4P8Ru2](C24H20B)2·5CHCl2, M = 3044.83, monoclinic,
P21/c (no. 14), a = 11.3803(4), b = 21.7537(9), c = 30.4002(14) Å, β = 92.572(4)°, V =
7518.4(5) Å3, Z = 2 [Ci symmetry], Dc = 1.345 g cm–3, μ(Mo-Kα) = 0.519 mm–1, T = 173 K,
yellow blocky needles, Agilent Xcalibur 3 E diffractometer; 15010 independent measured
reflections (Rint = 0.0412), F2 refinement,S10,S11 R1(obs) = 0.1000, wR2(all) = 0.1925, 10657
independent observed absorption-corrected reflections [|Fo| > 4σ(|Fo|), completeness to
θfull(25.2°) = 98.8%], 886 parameters. CCDC 1840500.
The di-ruthenium complex in the structure of 3·2BPh4 sits across a centre of symmetry at
the middle of the C6–C6A bond linking the two pyridyl rings. The asymmetric unit was found
to contain three distinct sites occupied by dichloromethane solvent molecules, but inspection
of their thermal parameters showed the sites to be only partially occupied, something that was
unsurprising given that the crystal was seen to partially desolvate on the slide before mounting.
When refined freely the occupancies of the C100-, C110-, and C120-based dichloromethane
molecules settled to ca. 0.85, 0.88 and 0.77 respectively, and so for simplicity the combined
occupancy was subsequently set to total exactly 2.5 molecules per asymmetric unit (i.e. 5 per
metal complex). All of the non-hydrogen atoms across all three molecules were refined
anisotropically.
Figure S2-1. The structure of the Ci-symmetric complex present in the crystal of 3·2BPh4
(50% probability ellipsoids).
S3. Photophysics
Absorption spectra were recorded at room temperature using a Perkin Elmer Lambda
35 UV-vis spectrometer. Uncorrected steady-state emission and excitation spectra were
recorded on an Edinburgh FLSP920 spectrometer equipped with a 450 W xenon arc lamp,
double excitation and single emission monochromators, and a Peltier-cooled Hamamatsu
R928P photomultiplier tube (185−850 nm). Emission and excitation spectra were acquired
with a cut-off filter (395 nm) and corrected for source intensity (lamp and grating) and emission
spectral response (detector and grating) by a calibration curve supplied with the instrument.
The wavelengths for the emission and excitation spectra were determined using the
absorption maxima of the MLCT transition bands (emission spectra) and at the maxima of the
emission bands (excitation spectra). Quantum yields (Φ) were determined using the optically
dilute method by Crosby and DemasS12 at an excitation wavelength obtained from absorption
spectra on a wavelength scale [nm] and compared to the reference emitter by the following
equation:S13
where A is the absorbance at the excitation wavelength (λ), I is the intensity of the excitation
light at the excitation wavelength (λ), n is the refractive index of the solvent, D is the integrated
intensity of the luminescence, and Φ is the quantum yield. The subscripts r and s refer to the
reference and the sample, respectively. A stock solution with an absorbance > 0.1 was
prepared, then two dilutions were obtained with dilution factors of 20 and 10, resulting in
absorbances of about 0.02 and 0.08 respectively. The Beer-Lambert law was assumed to
remain linear at the concentrations of the solutions. The degassed measurements were
obtained after passing a stream of argon through the solutions for 10 minutes using a septa-
sealed quartz cell. An air-equilibrated [Ru(bpy)3]Cl2/H2O solution (Φ = 0.028)S14 was used as
the reference. The quantum yield determinations were performed at identical excitation
wavelengths for the sample and the reference, therefore deleting the I(λr)/I(λs) term in the
equation. Emission lifetimes (τ) were determined with the single photon counting technique
(TCSPC) with the same Edinburgh FLSP920 spectrometer using pulsed picosecond LED
(EPLED 360, FWHM < 800ps) as the excitation source, with repetition rates between 1 kHz
and 1 MHz, and the above-mentioned R928P PMT as detector. The goodness of fit was
assessed by minimizing the reduced χ2 function and by visual inspection of the weighted
residuals. To record the 77 K luminescence spectra, the samples were put in quartz tubes (2
mm diameter) and inserted in a special quartz Dewar filled with liquid nitrogen. The solvent
used in the preparation of the solutions for the photophysical investigations was of
spectrometric grade. Experimental uncertainties are estimated to be ±8% for lifetime
determinations, ±20% for quantum yields, and ±2 nm and ±5 nm for absorption and emission
peaks, respectively.
Figure S3-1. Excitation profile of compound 4 in an oxygenated solution of CH3CN (10-5M).
Figure S3-2. Emission profile of compound 4 in an oxygenated solution (red trace) and
deoxygenated solution (blue trace) of CH3CN (10-5 M).
Figure S3-3. Excitation profile of compound 7 in an oxygenated solution of CH3CN (10-5 M).
Figure S3-4. Emission profile of compound 7 in an oxygenated solution (red trace) and
deoxygenated solution (blue trace) of CH3CN (10-5 M).
S4. Electrochemistry
Electrochemical measurements were obtained on a Gamry Reference 600TM (Gamry
Instruments, Warminter, PA, USA) using a standard three-electrode cell with a glassy carbon
disk working electrode (3 mm diameter), Pt wire counter electrode and a Pt wire
pseudoreference electrode. The analyte was dissolved in a 0.1 M solution of NBu4PF6 in
CH2Cl2 and purged with argon prior to, and between scans. At the end of each experiment,
ferrocene was added as an internal standard. The values reported herein are relative to the
Fc/Fc+ couple and corrected for solution resistance (Rs) using Rs values obtained from ac
impedance spectroscopy. NBu4PF6 was obtained from Fluorochem and ferrocene was
obtained from Tokyo Chemical Industry. Both were used as received.
Figure S4-1: The scan rate dependent cyclic voltammogram of 8
Figure S4-2: Plots of ipa (top, blue) and ipc (bottom, orange) vs the square root of the scan
rate for the two redox processes of 8 in figure S4-1.
Figure S4-3: The scan-rate dependent voltammogram of 10
Figure S4-4: Plots of ipa (top, blue) and ipc (bottom, orange) vs the square root of the scan
rate for the two redox processes of 10 in figure S4-3.
Figure S4-5: The CV of 10 showing decomposition of the material after scanning to higher
potentials. The second cycle of the scan (orange) shows a loss of the signal at around 0.2 V
(blue) and a shift in the signal at around 0.6 V (blue) to around 0.8 V.
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