Multimetallic complexes and functionalized nanoparticles based on oxygen- and nitrogen-donor combinations

Article abstract of DOI:10.1021/ic400335y

The versatile precursors [Ru(CH=CHC₆H₄Me-4)Cl(CO) (BTD)(PPh₃)₂] (BTD = 2,1,3-benzothiadiazole) and [Ru(C(Ci - CPh)=CHPh)Cl(CO)(PPh₃)₂] were treated with isonicotinic acid, 4-cyanobenzoic acid, and 4-(4-pyridyl)benzoic acid under basic conditions to yield [Ru(vinyl)(O₂CC₅H ₄N)(CO)(PPh₃)₂], [Ru(vinyl)(O ₂CC₆H₄CN-4)(CO)(PPh₃)₂], and [Ru(vinyl){O₂CC₆H₄(C₅H ₄N)-4}(CO)(PPh₃)₂], respectively. The osmium analogue [Os(CH=CHC₆H₄Me-4)(O₂CC ₅H₄N)(CO)(PPh₃)₂] was also prepared. cis-[RuCl₂(dppm)₂] was used to prepare the cationic compounds [Ru(O₂CC₅H₄N)(dppm)₂] ⁺ and [Ru{O₂CC₆H₄(C ₅H₄N)-4}(dppm)₂]⁺. The treatment of 2 equiv of [Ru(C(Ci - CPh)=CHPh)(O₂CC₅H ₄N)(CO)(PPh₃)₂] and [Ru(O₂CC ₅H₄N)(dppm)₂]⁺ with AgOTf led to the trimetallic compounds [{Ru(C(Ci - CPh)=CHPh)(CO)(PPh₃) ₂(O₂CC₅H₄N)}₂Ag] ⁺ and [{Ru(dppm)₂(O₂CC₅H ₄N)}₂Ag]³⁺. In a similar manner, the reaction of [Ru(O₂CC₅H₄N)(dppm)₂]⁺ with PdCl₂ or K₂PtCl₄ yielded [{Ru(dppm) ₂(O₂CC₅H₄N)}₂MCl ₂]²⁺ (M = Pd, Pt). The reaction of [RuHCl(CO)(BTD) (PPh₃)₂] with HCi - CC₆H₄F-4 provided [Ru(CH=CHC₆H₄F-4)Cl(CO)(BTD)(PPh ₃)₂], which was treated with isonicotinic acid and base to yield [Ru(CH=CHC₆H₄F-4)(O₂CC₅H ₄N)(CO)(PPh₃)₂]. The addition of [Au(C ₆F₅)(tht)] (tht = tetrahydrothiophene) resulted in the formation of [Ru(CH=CHC₆H₄F-4){O₂CC ₅H₄N(AuC₆F₅)}(CO)(PPh ₃)₂]. Similarly, [Ru(vinyl)(O₂CC ₆H₄CN-4)(CO)(PPh₃)₂] reacted with [Au(C₆F₅)(tht)] to provide [Ru(vinyl){O₂CC ₆H₄(CNAuC₆F₅)-4}(CO)(PPh ₃)₂]. The reaction of 4-cyanobenzoic acid with [Au(C ₆F₅)(tht)] yielded [Au(C₆F₅) (NCC₆H₄CO₂H-4)]. This compound was used to prepare [Ru(CH=CHC₆H₄F-4){O₂CC ₆H₄(CNAuC₆F₅)-4}(CO)(PPh ₃)₂], which was also formed on treatment of [Ru(CH=CHC₆H₄F-4)(O₂CC₆H ₄CN-4)(CO)(PPh₃)₂] with [Au(C₆F ₅)(tht)]. The known compound [RhCl₂(NC₅H ₄CO₂)(NC₅H₄CO₂Na) ₃] and the new complex [RhCl₂{NC₅H ₄(C₆H₄CO₂)-4}{NC₅H ₄(C₆H₄CO₂Na)-4}₃] were prepared from RhCl₃·3H₂O and isonicotinic acid or 4-(4-pyridyl)benzoic acid, respectively. The former was treated with [Ru(CH=CHC₆H₄Me-4)Cl(CO)(BTD)(PPh₃) ₂] to yield [RhCl₂{NC₅H₄CO ₂(Ru(CH=CHC₆H₄Me-4)(CO)(PPh₃) ₂}₄]Cl. As an alternative route to pentametallic compounds, the Pd-coordinated porphyrin [(Pd-TPP)(p-CO₂H) ₄] was treated with 4 equiv of [Ru(CH=CHR)Cl(CO)(BTD)(PPh ₃)₂] in the presence of a base to yield [(Pd-TPP){p-CO₂Ru(CH=CHR)(CO)(PPh₃)₂} ₄] (R = C₆H₄Me-4, CPh₂OH). Where R = CPh₂OH, treatment with HBF₄ led to the formation of [(Pd-TPP){p-CO₂Ru(=CHCH=CPh₂)(CO)(PPh₃) ₂}₄](BF₄)₄. [(Pd-TPP){p-CO ₂Ru(dppm)₂}₄](PF₆)₄ was prepared from [(Pd-TPP)(p-CO₂H)₄] and cis-[RuCl ₂(dppm)₂]. The reaction of AgNO₃ with sodium borohydride in the presence of [Ru(O₂CC₅H ₄N)(dppm)₂]⁺ or [RuR{O₂CC ₆H₄(C₅H₄N)-4}(dppm) ₂]⁺ provided silver nanoparticles Ag[NC₅H ₄CO₂Ru(dppm)₂]⁺ and Ag[NC ₅H₄{C₆H₄CO₂Ru(dppm) ₂}-4]⁺.

Full text of DOI:10.1021/ic400335y

Article
pubs.acs.org/IC
Multimetallic Complexes and Functionalized Nanoparticles Based on
Oxygen- and Nitrogen-Donor Combinations†
Saira Naeem,‡ Angela Ribes,‡ Andrew J. P. White,‡ Mohammed N. Haque,§ Katherine B. Holt,§
and James D. E. T. Wilton-Ely*,‡
‡Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
§Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
S
* Supporting Information
ABSTRACT: The versatile precursors [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) and
[Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] were treated with isonicotinic acid, 4-cyanobenzoic acid, and 4-(4-pyridyl)benzoic
acid under basic conditions to yield [Ru(vinyl)(O2CC5H4N)(CO)(PPh3)2], [Ru(vinyl)(O2CC6H4CN-4)(CO)(PPh3)2], and
[Ru(vinyl){O2CC6H4(C5H4N)-4}(CO)(PPh3)2], respectively. The osmium analogue [Os(CHCHC6H4Me-4)(O2CC5H4N)-
(CO)(PPh3)2] was also prepared. cis-[RuCl2(dppm)2] was used to prepare the cationic compounds [Ru(O2CC5H4N)(dppm)2]+
and [Ru{O2CC6H4(C5H4N)-4}(dppm)2]+. The treatment of 2 equiv of [Ru(C(CCPh)CHPh)(O2CC5H4N)(CO)(PPh3)2]
and [Ru(O2CC5H4N)(dppm)2]+ with AgOTf led to the trimetallic compounds [{Ru(C(CCPh)CHPh)(CO)-
(PPh3)2(O2CC5H4N)}2Ag]+ and [{Ru(dppm)2(O2CC5H4N)}2Ag]3+. In a similar manner, the reaction of [Ru(O2CC5H4N)-
(dppm)2]+ with PdCl2 or K2PtCl4 yielded [{Ru(dppm)2(O2CC5H4N)}2MCl2]2+ (M = Pd, Pt). The reaction of
[RuHCl(CO)(BTD)(PPh3)2] with HCCC6H4F-4 provided [Ru(CHCHC6H4F-4)Cl(CO)(BTD)(PPh3)2], which was
treated with isonicotinic acid and base to yield [Ru(CHCHC6H4F-4)(O2CC5H4N)(CO)(PPh3)2]. The addition of
[Au(C6F5)(tht)] (tht = tetrahydrothiophene) resulted in the formation of [Ru(CHCHC6H4F-4){O2CC5H4N(AuC6F5)}-
(CO)(PPh3)2]. Similarly, [Ru(vinyl)(O2CC6H4CN-4)(CO)(PPh3)2] reacted with [Au(C6F5)(tht)] to provide [Ru(vinyl)-
{O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2]. The reaction of 4-cyanobenzoic acid with [Au(C6F5)(tht)] yielded [Au(C6F5)-
(NCC6H4CO2H-4)]. This compound was used to prepare [Ru(CHCHC6H4F-4){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2],
which was also formed on treatment of [Ru(CHCHC6H4F-4)(O2CC6H4CN-4)(CO)(PPh3)2] with [Au(C6F5)(tht)]. The
known compound [RhCl2(NC5H4CO2)(NC5H4CO2Na)3] and the new complex [RhCl2{NC5H4(C6H4CO2)-4}-
{NC5H4(C6H4CO2Na)-4}3] were prepared from RhCl3·3H2O and isonicotinic acid or 4-(4-pyridyl)benzoic acid, respectively.
The former was treated with [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] to yield [RhCl2{NC5H4CO2(Ru(CH
CHC6H4Me-4)(CO)(PPh3)2}4]Cl. As an alternative route to pentametallic compounds, the Pd-coordinated porphyrin [(Pd-
TPP)(p-CO2H)4] was treated with 4 equiv of [Ru(CHCHR)Cl(CO)(BTD)(PPh3)2] in the presence of a base to yield [(Pd-
TPP){p-CO2Ru(CHCHR)(CO)(PPh3)2}4] (R = C6H4Me-4, CPh2OH). Where R = CPh2OH, treatment with HBF4 led to
the formation of [(Pd-TPP){p-CO2Ru(CHCHCPh2)(CO)(PPh3)2}4](BF4)4. [(Pd-TPP){p-CO2Ru(dppm)2}4](PF6)4 was
prepared from [(Pd-TPP)(p-CO2H)4] and cis-[RuCl2(dppm)2]. The reaction of AgNO3 with sodium borohydride in the
presence of [Ru(O2CC5H4N)(dppm)2]+ or [RuR{O2CC6H4(C5H4N)-4}(dppm)2]+ provided silver nanoparticles
Ag@[NC5H4CO2Ru(dppm)2]+ and Ag@[NC5H4{C6H4CO2Ru(dppm)2}-4]+.
Multimetallic networks based on symmetrical linkages, such
as dicarboxylic acids or bipyridines, are well established,
perhaps most impressively in the construction of coordination
polymers1b,c and metal−organic frameworks (MOFs).2 How-
INTRODUCTION
■
The incorporation of more than one metal unit into the same
covalent framework offers many benefits, especially if the
properties of different metals are combined. Accordingly, the
area of multimetallic compounds promises potential in many
areas, such as catalysis, imaging, therapy, and sensing.1a
Received: February 7, 2013
Published: April 2, 2013
© 2013 American Chemical Society
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ever, the joining of two different metal centers has always
proved especially challenging. Either a protection/deprotection
strategy must be employed or the donor combinations of the
linker must be carefully tailored to the metals involved. In
recent work,3 a zwitterion based on piperazine,
H2NC4H8NCS2, was shown to react with metals exclusively
at the dithiocarbamate unit while leaving the ammonium end
intact. Subsequent treatment with a base and carbon disulfide
generated a new dithiocarbamate, which was treated with a
second, different metal unit. This approach has proved both
versatile and successful, allowing heteromultimetallic com-
pounds with 2−6 metal units to be prepared. This methodology
was also extended to the functionalization of nanoparticles with
ruthenium and nickel transition-metal units.4
pharmaceuticals.9 However, the use of dinitriles to bridge metal
centers is less common than that of bipyridines, although some
examples of bisbenzonitrile being employed in this manner
have been reported.10
The properties of dicarboxylate and bipyridine (or dinitrile)
ligands have been mentioned very briefly above; however, the
possibilities that arise from combining them in mixed-donor
ligands have often been overlooked. The linkers chosen for use
in this research (Figure 2) are inexpensive and commercially
available and have been employed in a limited fashion already.
While these investigations based on 1,1-dithio ligands have
been encouraging, it was decided to broaden the scope of these
explorations to include other units that could fulfill the same
role but would exploit the innate affinity of certain donor
combinations for particular metals rather than a protection
strategy.
Carboxylates, pyridines, and nitriles are some of the most
common donor types in transition-metal research, and all three
enjoy extremely rich coordination chemistry. Of these donors,
carboxylates display the greatest variety of bonding modes,
having the ability to coordinate to metal centers in
monodentate, bidentate, and bridging modes. Many bimetallic
“paddlewheel” complexes employ bridging carboxylate donors,
allowing multiple bonds to exist between the metal centers in
many cases.5,6 In some examples, the carboxylate chelate can
not only bridge the dimetal unit but also form molecular
squares.5c The most recent, high-profile setting for (di)-
carboxylate linkers is in MOFs, which have become important
candidates for gas storage, separation, and sequestration
because of the huge internal surface area created by the cavities
between the linked metal units.2
Figure 2. Mixed-donor ligands employed in this work.
Isonicotinic acid (pyridine-4-carboxylic acid) is an isomer of
nicotinic acid, also called niacin or vitamin B3. Although
overshadowed by this better-known isomer, isonicotinic acid
and its derivatives have been used in a variety of contexts,11
including as a structural element in MOFs.11d Despite the
potential of this bifunctional ligand for use in the assembly of
multimetallic compounds, only a few examples exist of its use in
this capacity.11e,f
Unlike isonicotinic acid, the nitrile donor group in 4-
cyanobenzoic acid is external to the aromatic system and can be
expected to display subtle differences in its reactivity compared
to isonicotinic acid. Unsurprisingly, a number of complexes of
4-cyanobenzoic acid have been reported,12 although the
potential for ditopic coordination is largely unexplored.
In this report, the mixed-donor ligands isonicotinic acid and
4-cyanobenzoic acid are investigated as linkers for hetero-
nuclear bi-, tri-, and pentametallic systems based on careful
consideration of their donor properties toward various
transition metals (Ru, Rh, Pd, Pt, Ag, and Au). Furthermore,
the potential for this approach to be extended to the
functionalization of nanoparticles with metal units is explored.
Within the same sphere of activity, 4,4′-bipyridine has been
widely employed as an ideal linker for transition-metal centers,
such as the tetrametallic arrangement shown in Figure 1.7 It
RESULTS AND DISCUSSION
■
Bi- and Trimetallic Complexes. The coordinatively
unsaturated vinyl complexes [Ru(CR1CHR2)Cl(CO)-
(PR3)2] (R = Ph,13 iPr14) are formed from the hydro-
ruthenation of alkynes by [RuHCl(CO)(PPh3)3] or [RuHCl-
(CO)(PPri3)2] and have shown themselves to be incredibly
versatile metal units. Transformations can take place at the
vinyl ligand or at the metal center, leading to a wealth of
reactivity15−20 and permitting the exploration of many
associated properties (e.g., electron transfer19g−n). A number
of comprehensive reviews exist, which cover the fascinating area
of ruthenium vinyl chemistry.21 Reaction of [RuHCl(CO)-
(PPh3)3] with alkynes in the presence of the labile 2,1,3-
benzothiadiazole (BTD) ligand yields the equally useful starting
materials [Ru(CR1CHR2)Cl(CO)(BTD)(PPh3)2]. The
competition of BTD with the liberated PPh3 ligand ensures
that the vinyl complexes are formed cleanly without
contamination with tris(phosphine) byproducts. The vinyl
species [Ru(CR1CHR2)Cl(CO)(BTD)(PPh3)2] are partic-
ularly suitable as starting points for the formation of
multimetallic compounds because they possess ligands with
diagnostic spectroscopic properties (1H, 13C, and 31P NMR and
IR analysis). The vinyl ligand, in particular, allows the
Figure 1. Iconic example of a multimetallic compound based on
pyridyl bridging ligands.
provides a rigid connector for the propagation of coordination
networks while its length is suited to the creation of sizable
cavities upon the formation of networks with metal ions.8
Acetonitrile is a common stabilizing donor and is found in
many common starting materials, such as [PdCl2(NCMe)2] or
[Cu(NCMe)4]+, while benzonitriles are important building
blocks of dyes, natural products, herbicides, agrochemicals, and
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Scheme 1. Formation of Heterotrimetallic Complexes from Monometallic Carboxylate Compounds (BTD = 2,1,3-
Benzothiadiazole)
introduction of spectroscopic labels (e.g., 19F NMR active units,
vide infra) to aid in analysis. However, the sensitivity of the
vinyl ligand toward acid and the lability of the phosphines can
sometimes prove a disadvantage. In these situations, the more
robust starting material cis-[RuCl2(dppm)2] is preferred, which
also possesses useful spectroscopic properties (NMR spectros-
copy) associated with the phosphorus nuclei and the protons of
the methylene groups.
confirmed by a νCC absorption at 2159 cm−1 in the solid-state
IR spectrum and a singlet resonance at 5.72 ppm (Hβ) in the
1H NMR spectrum. Single crystals of the compound were
obtained by the slow diffusion of a DCM solution of the
complex into ethanol. An X-ray diffraction study revealed the
structure shown in Figure 3.
The structure of complex 2 is based on a distorted octahedral
arrangement with cis angles at the metal center in the range
86.73(3)−111.43(5)°, excluding the O(1)−Ru−O(3) bite
angle of 58.47(4)°. The Ru−O(1) and Ru−O(3) distances of
2.3050(10) and 2.1804(10) Å, respectively, are not equal and
A slight excess of isonicotinic acid was deprotonated with
sodium methoxide and the mixture added to a dichloromethane
(DCM) solution of [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)-
(PPh3)2]. An immediate color change was observed from red to
yellow. After workup, the yellow product was analyzed by 31P
1
NMR spectroscopy, displaying a new singlet at 38.1 ppm. H
NMR analysis revealed typical resonances for the vinyl ligand at
7.76 (Hα) and 5.36 (Hβ) ppm showing mutual JHH coupling of
15.3 Hz. The lower field resonance also showed coupling
(doublet of triplets) to the phosphorus nuclei of the phosphine
ligands (JHP = 2.6 Hz), suggesting a mutually trans arrangement
for the phosphines. Doublets at 6.83 and 6.88 ppm (JHH = 7.9
Hz) were observed for the tolyl substituent along with a singlet
at 2.24 ppm for the methyl group. A doublet resonance at 8.31
ppm (JHH = 5.6 Hz) was assigned to the protons in positions 2
and 6 of the pyridinecarboxylate ligand, while the remaining
protons of the ligand were observed at 6.33 ppm (JHH = 5.6
Hz). Retention of the carbonyl ligand was supported by an
intense absorption at 1912 cm−1 in the IR spectrum along with
a band at 1515 cm−1 attributed to the coordinated carboxylate
group. A molecular ion was observed in the mass spectrum
(MS) at m/z 893 (fast atom bombardment in positive mode,
FAB+). These data, in conjunction with a good agreement of
elemental analysis with calculated values, confirmed the overall
formulation (Scheme 1) to be [Ru(CHCHC6H4Me-4)-
(O2CC5H4N)(CO)(PPh3)2] (1).
Figure 3. Molecular structure of 2. Selected bond distances (Å) and
angles (deg): Ru−C(26) 1.8144(14), Ru−C(10) 2.0618(14), Ru−
O(3) 2.1804(10), Ru−O(1) 2.3050(10), Ru−P(1) 2.3683(4), Ru−
P(2) 2.3758(4), O(1)−C(2) 1.2620(17), C(2)−O(3) 1.2647(17),
C(10)−C(19) 1.352(2), C(10)−C(11) 1.427(2), C(11)−C(12)
1.205(2), C(26)−O(26) 1.1582(17); O(3)−Ru−O(1) 58.47(4),
C(19)−C(10)−Ru 130.56(11), P(1)−Ru−P(2) 175.240(13),
C(12)−C(11)−C(10) 176.69(16), O(1)−C(2)−O(3) 120.46(13).
A similar reaction ensued between HO2CC5H4N and
[Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] in the presence
of NaOMe to yield [Ru(C(CCPh)CHPh)(O2CC5H4N)-
(CO)(PPh3)2] (2). The presence of the enynyl ligand was
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indicate the superior trans influence of the vinyl ligand, causing
elongation of the Ru−O(1) bond. The precursor to compound
2 is formed by insertion of an alkyne into a Ru−H bond, a
process that typically occurs to yield the E isomer.21 This is
reflected in the observed regiochemistry at the double bond of
the vinyl ligand in the structure of 2. The C(10)−C(19)
distance of 1.352(2) Å is typical for a double bond between
carbon atoms, while the C(11)−C(12) [1.205(2) Å] distance is
within the usual range for triple bonds.22 Otherwise, the
structural data associated with the vinyl ligand are unremark-
able and compare well with those of related complexes such as
[Ru(C(CCPh)CHPh)(O2CFc)(CS)(PPh3)2].16j
decided to explore the construction of heterotrimetallic
complexes based on coordination of the nitrogen donors in 5
to palladium and platinum. The reaction of 2 equiv of 5 with 1
equiv of PdCl2 led to the formation of a dark-yellow solid. This
was formulated as [{Ru(dppm)2(O2CC5H4N)}2PdCl2](PF6)2
(7) on the basis of a molecular ion in the FAB MS spectrum at
m/z 2306 and a good agreement of analytical data with
1
calculated values. Again, H NMR spectroscopy revealed a
small downfield shift for the 2,6-pyridyl resonance at 8.94 ppm
(JHH = 6.5 Hz), compared to the precursor 5. The same feature
was observed in the spectrum of the platinum analogue
(Scheme 1), [{Ru(dppm)2(O2CC5H4N)}2PtCl2](PF6)2 (8),
except that the multiplicity of the resonance was not clearly
resolved because of a small J(Pt,H) coupling.
Having achieved the synthesis of heterotrimetallic examples
of the form RuMRu (M = Ag, Pd, Pt), the focus of the research
then shifted to attempts to introduce a second organometallic
center into the molecule. Gold(I) compounds are known to
coordinate readily to nitrogen donors, especially when
possessing an electron-withdrawing ligand such as the
pentafluorophenyl group. Thus, it was decided to explore the
coordination chemistry of [Au(C6F5)(tht)] (tht = tetrahy-
drothiophene) with vinyl complexes bearing the pyridine-4-
carboxylate ligand.
One of the most attractive aspects of the reactivity displayed
by the compound [RuHCl(CO)(BTD)(PPh3)2] is the
potential for introducing functionality through the facile
reaction with both terminal and internal alkynes. The resulting
complexes, [Ru(CR1CHR2)Cl(CO)(BTD)(PPh3)2], are
known for a wide range of substituents (R1 and R2).20a In
the context of the planned reaction with [Au(C6F5)(tht)], this
approach was exploited in order to introduce a fluorinated “tag”
to the vinyl unit. The commercially available alkyne, 1-ethynyl-
4-fluorobenzene, was used to prepare the new vinyl compound
[Ru(CHCHC6H4F-4)Cl(CO)(BTD)(PPh3)2] (9) in 89%
yield from [RuHCl(CO)(BTD)(PPh3)2] (Scheme 2). The 19F
An osmium analogue of compound 1, [Os(CH
CHC6H4Me-4)(O2CC5H4N)(CO)(PPh3)2] (3), was prepared
in an identical manner. Spectroscopic features were found to be
very similar to those observed for 1 apart from the
characteristically lower frequency shift of the νCO absorption
in the IR spectrum at 1900 cm−1.
Having confirmed that coordination of deprotonated
isonicotinic acid occurred through the carboxylate group, the
generation of heterotrimetallic complexes was explored through
the addition of metals known to favor nitrogen donors. Thus,
the treatment of 2 with 0.5 equiv of AgOTf led to linking of the
pyridyl units to form the trimetallic complex [{Ru(C(C
CPh)CHPh)(CO)(PPh3)2(O2CC5H4N)}2Ag]OTf (4).
Although little change was observed in the 31P NMR spectrum
of 4 compared to the spectrum of the precursor, a small shift in
the resonance of the protons in the 2 and 6 positions of the
1
pyridyl ring was observed in the H NMR spectrum (to 8.44
ppm). In the MS spectrum (FAB), a molecular ion was
observed at m/z 2066, which displayed the correct isotopic
distribution for the presence of a silver ion. The formulation
was further supported by a good agreement of elemental
analysis with calculated values.
The compound cis-[RuCl2(dppm)2] was stirred with
isonicotinic acid in the presence of NaOMe and NH4PF6 to
yield the new compound [Ru(O2CC5H4N)(dppm)2]PF6 (5) in
79% yield. The resonance displayed by this compound in the
1H NMR spectrum at 8.73 ppm (JHH = 5.6 Hz) was attributed
to the pyridylcarboxylate ligand, while the remaining
resonances were obscured by those for the dppm ligands.
The presence of the carboxylate unit was confirmed by an
absorption at 1513 cm−1 in the IR spectrum and a resonance at
180.3 ppm in the 13C NMR spectrum. Further features in the
same spectrum at 150.6, 139.5, and 121.9 ppm were assigned to
the pyridinecarboxylate ligand. Compound 5 provided an
alternative starting point for subsequent transformations,
allowing more forcing conditions to be employed in the
presence of the robust dppm ligands.
Scheme 2. Formation of a Heterobimetallic Compound
Bearing Fluorinated Ligands (BTD = 2,1,3-
Benzothiadiazole)
Reaction of 5 with silver triflate led to isolation of the
complex [{Ru(dppm)2(O2CC5H4N)}2Ag](PF6)2(OTf) (6) in
75% yield. Again, little change was evident in the 31P NMR
spectrum. However, the resonances of the protons adjacent to
the pyridine nitrogen atom were shifted slightly from 8.73 ppm
in the precursor (5) to 8.87 ppm (JHH = 6.0 Hz) in 6. In the
absence of a molecular ion in the MS (FAB+) spectrum, the
formulation rested partly on the presence of a fragmentation for
[Ru(dppm)2(O2CC5H4N)Ag]+ at m/z 1100 showing the
correct isotopic distribution. The good agreement of elemental
analysis with calculated values further supported the structure
shown in Scheme 1.
NMR spectrum displayed a singlet resonance at −120.1 ppm,
while the remaining spectroscopic data were found to be
unremarkable. The same procedure employed to prepare 1 was
used to convert 9 into the pyridyl-4-carboxylate compound
[Ru(CHCHC6H4F-4)(O2CC5H4N)(CO)(PPh3)2] (10). In
addition to spectroscopic data similar to those seen for 1, the
19F NMR remained essentially unshifted, at −121.4 ppm. The
treatment of equimolar quantities of 10 and [Au(C6F5)(tht)]
led to formation of the brown compound [Ru(CH
CHC6H4F-4){O2CC5H4N(AuC6F5)}(CO)(PPh3)2] (11). As
anticipated, the most diagnostic data came from the 19F
Some of the most prominent group 10 metal compounds
bear nitrogen-based ligands, such as cis-platin.23 It was therefore
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Scheme 3. Two Routes to the Same Heterobimetallic Compounds (L = PPh3; R3 = C6H4F-4; BTD = 2,1,3-Benzothiadiazole)
NMR spectrum, which displayed resonances at −163.1, −159.3,
and −116.5 ppm for the m-, p-, and o-F nuclei of the C6F5
ligand, respectively, along with a peak at −121.2 ppm for the
vinyl substituent. The integration of these resonances was
found to be 2:1:2:1, confirming formation of the hetero-
bimetallic complex bearing both fluorinated vinyl and aryl
ligands (Scheme 2).
shifted resonances in the 1H NMR spectrum for the N-
coordinated isonicotinic acid ligand. No change in the νOCO
absorption was observed in the IR spectrum compared to the
features displayed by the free ligand. On the basis of these data
and the FAB MS spectrum, which displayed a molecular ion at
m/z 513, the product was formulated as [Au(C6F5)-
(NCC6H4CO2H-4)] (18). This compound was then deproto-
nated with NaOMe and used to convert 9 into [Ru(CH
CHC6H4F-4){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2] (17).
This alternative route to 17 provides an illustration of the
flexibility of the approach, in which the coordinated donor is
selective for the first metal introduced (Scheme 3).
In order to broaden the scope of this approach, the reactivity
of the related 4-cyanobenzoic acid ligand was also investigated.
While structurally similar to isonicotinic acid, the nitrogen
donor of the nitrile group is external to the aromatic system,
leading to subtle differences in the effects on the reactivity
observed. The compounds [Ru(CR1CHR2)(O2CC6H4CN-
4)(CO)(PPh3)2] (R1 = H, R2 = C6H4Me-4, 12; R1 = CCPh,
R2 = Ph, 13; R1 = H, R2 = C6H4F-4, 14) were prepared from
the appropriate vinyl precursors, [Ru(CR1CHR2)Cl(CO)-
(BTD)(PPh3)2] or [Ru(C(CCPh)CHPh)Cl(CO)-
(PPh3)2], in a procedure similar to that employed in the
Pentametallic Complexes. A recent report24 described a
new variation on the standard reaction of pyridine with
rhodium chloride, in which RhCl3·3H2O reacts with
isonicotinic acid to give [RhCl2(NC5H4CO2H)4]Cl. Upon
reaction with a saturated sodium hydroxide solution, this is
converted to [RhCl2(NC5H4CO2)(NC5H4CO2Na)3], which
boasts four carboxylate units. This was identified as a versatile
starting point from which to prepare pentametallic compounds
using the approach already demonstrated. The preference
displayed by rhodium for the pyridine nitrogen over oxygen
donors left substantial potential for further functionalization.
The treatment of a methanol solution of this compound with 4
equiv of [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2]
yielded [RhCl2{NC5H4CO2Ru(CHCHC6H4Me-4)(CO)-
(PPh3)2}4]Cl (19; Scheme 4). Evidence for the presence of
the ruthenium vinyl units was provided by a diagnostic doublet
of triplets (shifted relative to the precursor) at 7.77 ppm for the
Hα proton, while the C5H4N unit gave rise to doublet
resonances at 6.42 and 8.32 ppm. These chemical shift values
are very close to those observed for complex 1, which are
identical with the termini formed in the reaction to yield 19.
Good agreement of elemental analysis with calculated values
indicated successful coordination of all four ruthenium units,
although no clear molecular ion was observed in the MS
spectrum in either FAB or MALDI modes, probably because of
the high molecular mass.
1
preparation of 1, 2, and 10. In the H NMR spectrum of
compound 12, the coordinated 4-cyanobenzoate ligand gave
rise to doublets at 6.42 and 6.79 ppm, showing a mutual
coupling of 8.0 Hz. Similar features were observed in 13 and
14.
The treatment of 12−14 with [Au(C6F5)(tht)] led to the
formation of [Ru(CR1CHR2){O2CC6H4(CNAuC6F5)-4}-
(CO)(PPh3)2] (R1 = H, R2 = C6H4Me-4, 15; R1 = CCPh,
R2 = Ph, 16; R1 = H, R2 = C6H4F-4, 17). Initial experiments
were carried out to form 15 and 16. Apart from a shift in the
resonance attributed to the aromatic protons closest to the
nitrile group, little spectroscopic change was observed.
However, elemental analysis data and the observation of
diagnostic fragments in the MS spectra supported the proposed
formulations. Again, the fluorine “tag” allowed the reaction to
be confirmed spectroscopically for compound 17. The expected
ratio of resonances was seen in the 19F NMR spectrum at
chemical shifts very similar to those found for 11. While the
methodology described is useful, it becomes more powerful
when it can be employed from either end of the molecule,
allowing flexibility in the design of such multimetallic systems.
Thus, the reaction of 4-cyanobenzoic acid and [Au(C6F5)(tht)]
was investigated. A colorless solid was obtained that displayed
Although the reaction to form 19 proved successful, the
product was prone to loss of triphenylphosphine (observed as
the oxide in the 31P NMR spectrum), probably due to steric
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recent reports, with the carboxylate termini playing a key role in
creating porous materials with dirhodium paddlewheel units29a
and those based on nodes of cobalt29b and zinc29b,c ions.
However, despite this activity in the area, no examples exist
with ruthenium units or nonhomoleptic termini (i.e., with
coligands).
Scheme 4. Formation of a Pentametallic Compound Based
on a Rhodium Core (R = CHCHC6H4Me-4; L = PPh3)
Thus, [(Pd-TPP)(p-CO2H)4] (Scheme 6)28 was employed
as the basis of pentametallic systems. The reaction of cis-
[RuCl2(dppm)2] with the metalloporphyrin, in the presence of
NaOMe and NH4PF6, provided [(Pd-TPP){p-CO2Ru-
(dppm)2}4](PF6)4 (23) in 74% yield. The orange product
was characterized initially based on the distinctive resonances in
1
the H NMR spectrum. Three resonances were observed for
the porphyrin at 8.97 (singlet), 8.32 (doublet, JHH = 7.8 Hz),
and 8.17 (multiplet, coincident with a C6H5 resonance) ppm.
The first of these was attributed to the pyrrole protons, and the
last pair of resonances was assigned to the AB system for the
carboxyphenyl substituents. These features integrated correctly
with the characteristic peaks for the methylene protons of the
dppm ligands (4.07 and 4.74 ppm). In the solid-state IR
spectrum, an intense νOCO absorption was observed at 1519
cm−1.
congestion. Therefore, a different unit of greater length was
prepared from the reaction of rhodium trichloride and 4-(4-
pyridyl)benzoic acid under the same conditions as those used
to generate [RhCl2(NC5H4CO2)(NC5H4CO2Na)3]. The com-
pounds [RhCl2{NC5H4(C6H4CO2H)-4}4]Cl (20) and
[RhCl2{NC5H4(C6H4CO2)-4}{NC5H4(C6H4CO2Na)-4}3]
(21), shown in Scheme 5, were isolated and characterized. The
4-(4-pyridyl)benzoate ligand in 21 gave rise to four resonances
Further functionality was introduced into the system through
the reaction of [(Pd-TPP)(p-CO2H)4] with 4 equiv of
[Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] in the pres-
ence of excess base. The product [(Pd-TPP){p-CO2Ru(CH
CHC6H4Me-4)(CO)(PPh3)2}4] (24), shown in Scheme 6,
gave rise to distinctive resonances in the 1H NMR spectrum for
the tolylvinyl ligand at 2.27 (Me), 6.67 (Hβ), 6.97, 7.10 (both
C6H4), and 8.57 (Hα) ppm. The lowest-field resonance of
these was observed as a doublet of triplets (JHH = 15.3 Hz; JHP
= 2.7 Hz) assigned to the Hα protons, with the fine structure
indicating the retention of mutually trans-phosphine ligands on
the metal units. Intense absorptions were observed at 1919
cm−1 (νCO) and 1508 cm−1 (νOCO) in the solid-state IR
spectrum. The overall formulation was confirmed by a good
agreement of elemental analysis with calculated values. The γ-
hydroxyvinyl compound [(Pd-TPP){p-CO2Ru(CH
CHCPh2OH)(CO)(PPh3)2}4] (25) was prepared in a similar
fashion. Dehydration of this pentametallic complex with HBF4
led to formation of the vinylcarbene compound [(Pd-TPP){p-
CO2Ru(CHCHCPh2)(CO)(PPh3)2}4](BF4)4 (26). A
1
between 7.75 and 8.65 ppm in the H NMR spectrum. The
reaction of 21 with cis-[RuCl2(dppm)2] in the presence of
excess NH4PF6 led to the formation of [RhCl2{NC5H4(C6H4-
CO2Ru(dppm)2)-4}4](PF6)5 (22), as shown in Scheme 5.
In addition to typical resonances for the O2CC6H4C5H4N
1
ligand in the H NMR spectrum of 22, characteristic features
were observed for the methylene protons of the dppm ligands
at 4.03 and 4.75 ppm. The presence of all four Ru(dppm)2
units was confirmed by analytical data.
Following the success of this approach to pentametallic
complexes, attention turned to other metallic “cores” with
terminal carboxylic acid groups. In addition to their applications
in fields as diverse as catalysis25 and photodynamic therapy,26
metalloporphyrins have also been employed as versatile
building blocks for more complex systems. Their use as motifs
in MOF design has been explored in a number of reports,27
which have illustrated the potential of using peripheral
functional groups to build complexity into the system in a
controlled manner. The palladium-centered tetraphenylpor-
phyrin, [(Pd-TPP)(p-CO2H)4],28 has featured in a number of
1
broad resonance in the H NMR spectrum at 14.94 ppm was
assigned to the carbenic proton, based on similar complexes
bearing the same ligand,3d while the Hβ proton was obscured
by the features of the C6H5 units. The remaining peaks were
similar to those found for compounds 23−25. This result
illustrates that not only can such metalloporphyrins be used as a
scaffold for additional metal units but further functionalization
Figure 5. TEM images of NP1 (left), NP2 (center), and NP1 in higher resolution (right).
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Scheme 5. Pentametallic Compound Based on an Extended Rhodium Core
Scheme 6. Formation of a Pentametallic Compound Based on a Palladium Porphyrin Core (R = CHCHC6H4Me-4, CH
CHCPh2OH)
can be performed subsequently. In all PdRu4 examples (23−
26), absorptions were observed in the UV/vis region at 420
and 525 nm, in positions similar to those found in the [(Pd-
TPP)(p-CO2H)4] precursor.30 The increased intensity of the
absorptions at 420 nm was attributed to features associated
with the ruthenium units.
Electrochemistry. Complexes 24−26 each contain both
palladium and ruthenium centers within a largely conjugated
system. Inspired by investigations of tetraruthenium assemblies
such as those based on the tetrakis(4-styryl)ethane ligand,19m
the electrochemistry of one representative example (24) was
explored briefly. It was found to give rise to a cyclic
voltammogram (Figure 4) showing a reversible redox couple
centered at E = 0.21 V (vs Fc/Fc+) followed by irreversible
oxidation at E = 0.77 V (vs Fc/Fc+). The behavior at lower
Figure 4. Cyclic voltammogram for 24. Conditions: 0.25 mM in 0.1 M
TBAPF6/DCM, 100 mV/s, glassy carbon electrode.
potential is very similar to that observed for the dinuclear
ruthenium complex [{Ru(CHCHC6H4Me-4)(CO)-
(PPh3)2}2(S2COCH2C6H4CH2OCS2)]3g and shows that the
ruthenium centers are not perturbed by the presence of the
palladium porphyrin unit. The highly reversible redox couple at
lower voltage is well-behaved over a range of scan rates,
indicating that the complex is very stable toward electron
transfer. This feature would normally be assigned to RuII/RuIII
electron transfer; however, studies on closely related mono-
and dinuclear systems by Winter and co-workers19l have
established that such alkenyl complexes behave as metal-
stabilized organic radicals. This “non-innocent” behavior of the
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Scheme 7. Functionalization of Silver Nanoparticles
alkenyl ligands, in which they actively participate in the redox
process, leads to considerable ambiguity regarding the metal
oxidation state.31 The irreversible peak at ca. 0.8 V can also be
attributed to further oxidation of the ruthenium alkenyl units
because this peak was also observed for the dinuclear complex
referenced above;3g however, the monometallic starting ma-
terial [(Pd-TPP)(p-CO2H)4] (in tetrahydrofuran) also under-
goes a reversible one-electron oxidation at 0.81 V (vs Fc/Fc+).
Thus, the rather ill-defined peak at 0.8 V in Figure 4 is likely a
superposition of this secondary irreversible oxidation of the
ruthenium alkenyl units and oxidation of the palladium moiety.
In principle, the peak currents for the ruthenium alkenyl units
should be larger than that for the palladium center by a factor
consistent with four-electron transfer for the four ruthenium
alkenyl units to one electron for the palladium center. However,
the superposition of the palladium oxidation with further
oxidation of the ruthenium centers does not allow such a ratio
to be determined for this system. Consistent with observations
for the dinuclear ruthenium complex, we see no evidence from
voltammetry for electronic communication between the
ruthenium centers and electron transfer appears to take place
at the four ruthenium alkenyl units simultaneously.
approach for the surface functionalization of nanoparticles
(Scheme 7).
Because of the robust nature of the dppm ligands (e.g., in the
presence of borohydride), 5 was chosen as the principal surface
unit, while the analogous pyridylbenzoate compound [Ru-
{O2CC6H4(C5H4N)-4}(dppm)2]PF6 (27) was also prepared.
The reaction of AgNO3 with sodium borohydride in the
presence of 5 or 27 gave the silver nanoparticles
Ag@[NC5H4CO2Ru(dppm)2]PF6 (NP1) and Ag@[NC5H4-
{C6H4CO2Ru(dppm)2}-4]PF6 (NP2) as black solids after
centrifuging and extensive washing to remove excess borohy-
dride (water) and unbound surface units (acetone).
Both NP1 and NP2 proved insoluble in common deuterated
laboratory solvents so NMR analysis could not be performed.
However, solid-state IR spectra showed the presence of
characteristic bands for the ruthenium phosphine surface
units. Transmission electron microscopy (TEM) was used to
determine the average size of the nanoparticles (Figure 5), and
this revealed the diameter of NP1 to be 19.0 ( 4.1) nm and
that of NP2 to be 12.8 ( 3.3) nm.
Closer investigation of the images (Figure 5, right), revealed
a surface layer that was analyzed by energy-dispersive X-ray
spectroscopy (EDX) to contain both ruthenium and
phosphorus (in addition to silver), confirming the presence
of the ruthenium phosphine surface units.
While the use of (poly)pyridine units to attach metal units to
the surface of nanoparticles is not a new concept, the use of
simple, cheap linkers could allow more widespread adoption of
these materials in photophysical applications, such as surface-
enhanced Raman scattering.36 Surface coverage in these
materials is not complete, and so access to the nanoparticle
surface (e.g., by analytes) could allow the properties of both the
surface and transition-metal units to be combined.
Functionalized Silver Nanoparticles. While the attach-
ment of molecular metal units to the surface of gold
nanoparticles is now an established area of research,32 less
attention has been focused on the analogous use of silver
nanoparticles. While sulfur-based tethers are typically used in
gold nanoparticle systems, nitrogen groups such as (poly)-
pyridines are frequently used to stabilize silver colloids.33
A
number of publications have employed this approach for the
immobilization of ruthenium phenanthroline units on the
surface of silver nanoparticles.34 In these materials, the
electrochemical and luminescence behaviors are influenced by
the nanoparticle and can be tuned by modifying the distance
between the two metals. In work on 2,2-bipyridine-ligated
ruthenium centers and silver nanoparticles, an enhancement of
the luminescence by the silver nanoparticle is reported,35 while
the same property is quenched when gold nanoparticles are
employed under analogous conditions.35d
CONCLUSION
■
Previously we have described how different metal units can be
joined together through the use of the piperazine-based
zwitterionic dithiocarbamate, H2NC4H8NCS2.3a−d A key
advantage of this route was the inexpensive and accessible
nature of the bridging units. The diverse array of species in this
report extend this potential for the construction of complex
multimetallic assemblies to systems based on simple,
commercially available linkers bearing oxygen and nitrogen
With the utility of the aforementioned nitrogen−oxygen
mixed-donor ligands in the formation of multimetallic
compounds now clear, it was decided to explore the same
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[Os(CHCHC6H4Me-4)(O2CC5H4N)(CO)(PPh3)2] (3). A solution
of [Os(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (100 mg, 0.097
mmol) in DCM (40 mL) was treated with a methanolic solution (20
mL) of isonicotinic acid (13 mg, 0.110 mmol) and sodium methoxide
(10 mg, 0.194 mmol). The reaction mixture was stirred for 3 h at
room temperature. All solvent was removed under vacuum and the red
product triturated ultrasonically in water (10 mL). This was filtered,
washed with hexane (10 mL), and dried under vacuum. Yield: 86 mg
(91%). IR (solid state): 1900 (CO), 1547 (OCO), 1508, 1482, 1245,
1187, 1030, 874, 616 cm−1. 31P NMR (acetone-d6): δ 19.1 (s, PPh3).
1H NMR (acetone-d6): δ 2.16 (s, 3 H, CCH3), 5.81 (d, JHH = 15.7 Hz,
1 H, Hβ), 6.40, 6.76 (AB, JAB = 7.9 Hz, 4 H, C6H4), 6.89 (d, JHH = 5.9
Hz, 2 H, CHCN), 7.39−7.54 (m, 30 H, C6H5), 8.12 (dt, JHH = 15.8
Hz, JHP = 2.1 Hz, 1 H, Hα), 8.37 (d, JHH = 5.9 Hz, 2 H, CHN). MS
(ES+): m/z 984 (100%) [M+], 862 (5%) [M+ − O2CC5H4N]. Elem
anal. Calcd for C52H43NO3OsP2·CH2Cl2 (Mw = 1067.01): C, 59.7; H,
4.3; N, 1.3. Found: C, 59.3; H, 4.0; N, 1.0.
donors. By careful consideration of the coordination prefer-
ences of the transition metals employed, bi-, tri-, and
pentametallic compounds and functionalized silver nano-
particles can be prepared. The introduction of metal units
can often be achieved from either end of the linker, providing a
flexibility of approach that may prove synthetically helpful in
more complex designs. The methodology provides the template
for the stepwise synthesis of functional materials that could be
employed in roles as diverse as catalysis, sensing, and medicine.
EXPERIMENTAL SECTION
■
General Comments. All experiments were carried out under
aerobic conditions, and the products obtained appear indefinitely
stable toward the atmosphere, whether in solution or in the solid state.
Solvents were used as received from commercial sources. The
complexes [RuHCl(CO)(BTD)(PPh3)2]37 and [Ru(CHCHR)Cl-
(CO)(BTD)(PPh3)2] (R = C6H4Me-4, CPh2OH) were prepared by
literature procedures,20a only using commercially available BTD in
place of 2,1,3-benzoselenadiazole (BSD). The compounds [Ru(C-
(CCPh)CHPh)Cl(CO)(PPh3)2],38 cis-[RuCl2(dppm)2],39 [Au-
(C6F5)(tht)],40 [(Pd-TPP)(p-CO2H)4],28 [RhCl2(NC5H4CO2)-
(NC5H4CO2H)3]Cl,24 and [RhCl2(NC5H4CO2)(NC5H4CO2Na)3]24
were prepared as described elsewhere. Petroleum ether refers to the
fraction boiling in the range 40−60 °C. Electrospray (ES) and FAB
MS data were obtained using Micromass LCT Premier and Autospec
Q instruments, respectively. IR data were obtained using a Perkin-
Elmer Spectrum 100 FT-IR spectrometer. Characteristic phosphine-
associated IR data are not reported. UV/vis spectra were obtained
using a Perkin-Elmer Lambda 25 instrument. Unless otherwise
indicated, NMR spectroscopy was performed in CDCl3 at 25 °C
using Varian Mercury 300 and (where stated) Bruker AV400
spectrometers. All couplings are in hertz. Elemental analyses were
provided by London Metropolitan University. Solvates were confirmed
[{Ru(C(CCPh)CHPh)(CO)(PPh3)2(O2CC5H4N)}2Ag]OTf (4).
A DCM solution (40 mL) of 2 (50 mg, 0.051 mmol) and silver
triflate (7 mg, 0.026 mmol) was stirred for 2 h at room temperature.
All solvent was removed under vacuum and the product triturated
ultrasonically in petroleum ether (10 mL). The dark-yellow solid was
filtered and dried under vacuum. Yield: 33 mg (58%). IR (solid state):
2178 (CC), 1925 (CO), 1523 (OCO), 1483, 1289, 1230, 1157,
1
869, 635 cm−1. 31P NMR (acetone-d6): δ 38.5 (s, PPh3). H NMR
(acetone-d6): δ 6.10 (s(br), 2 H, Hβ), 6.95−7.62 (m, 60 H + 20 H + 4
H, PC6H5 + C6H5 + CHCN), 8.44 (d, JHH = 5.8 Hz, 4 H, CHN). MS
(FAB+): m/z 2066 (5%) [M+]. Elem anal. Calcd for
C119H90AgF3N2O9P4Ru2S·3CH2Cl2 (Mw = 2469.76): C, 59.3; H, 3.9;
N, 1.1. Found: C, 59.3; H, 4.0; N, 0.9.
[Ru(O2CC5H4N)(dppm)2]PF6 (5).
A solution of cis-
[RuCl2(dppm)2] (331 mg, 0.352 mmol) in DCM (50 mL) was
treated with a solution of isonicotinic acid (48 mg, 0.387 mmol),
sodium methoxide (38 mg, 0.708 mmol), and ammonium
hexafluorophosphate (114 mg, 0.704 mmol) in methanol (25 mL).
The reaction mixture was stirred for 1 h at room temperature. All
solvent was removed under vacuum and the crude product dissolved in
DCM (10 mL) and filtered through diatomaceous earth (Celite) to
remove NaCl, NaOMe, and excess ligand. Ethanol (20 mL) was then
added, and the solvent volume was slowly reduced on a rotary
evaporator, resulting in the precipitation of a yellow solid. This was
filtered, washed with petroleum ether (10 mL), and dried under
vacuum. Yield: 314 mg (79%). IR (solid state): 1513 (OCO), 1484,
1096, 833 (PF), 734 cm−1. 31P NMR: δ −11.8, 8.8 (t × 2, JPP = 39.1
1
by integration of the H NMR spectra. TEM images and EDX data
were obtained using a JEOL 2010 high-resolution transmission
electron microscope (80−200 kV) equipped with an Oxford
Instruments INCA EDS 80 mm X-Max detector system.
[Ru(CHCHC6H4Me-4)(O2CC5H4N)(CO)(PPh3)2] (1). A solution
of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (200 mg, 0.212
mmol) in DCM (40 mL) was treated with a methanolic solution (30
mL) of isonicotinic acid (29 mg, 0.234 mmol) and sodium methoxide
(23 mg, 0.424 mmol). The reaction mixture was stirred for 1 h at
room temperature. The solvent volume was slowly reduced on a rotary
evaporator, resulting in precipitation of a yellow-orange solid. This was
filtered, washed with petroleum ether (10 mL), and dried under
vacuum. Yield: 156 mg (82%). IR (solid state): 1912 (CO), 1515
1
Hz, dppm). H NMR: δ 4.15, 4.80 (m × 2, 2 × 2 H, PCH2P), 6.25,
7.01, 7.29, 7.49, 7.60, 7.75 (m × 6, 40 H, C6H5), 7.41 (d, JHH = 5.9 Hz,
2 H, CHCN), 8.73 (d, JHH = 5.6 Hz, 2 H, CHN). 13C NMR (CD2Cl2,
400 MHz): δ 180.3 (s, CO2), 150.6 (s, NCH), 139.5 (s, CCO2), 133.7,
132.5 (m × 2, C6H5), 132.2, 131.8 (s × 2, C6H5), 131.2, 130.8 (m × 2,
C6H5), 130.6 (s, C6H5), 130.3 (tv, ipso-PC6H5, JCP = 19.3 Hz), 129.7,
129.5, 129.1, 128.9 (m × 4, C6H5), 121.9 (s, CCN), 43.4 (t, JCP = 13.1
Hz, PCH2P). MS (ES+): m/z 992 (100%) [M+]. Elem anal. Calcd for
C56H48F6NO2P5Ru (Mw = 1136.92): C, 59.1; H, 4.3; N, 1.2. Found: C,
59.2; H, 4.2; N, 1.2.
1
(OCO), 1480, 1185, 865, 745 cm−1. 31P NMR: δ 38.1 (s, PPh3). H
NMR: δ 2.24 (s, 3 H, CCH3), 5.36 (d, JHH = 15.3 Hz, 1 H, Hβ), 6.33
(d, JHH = 5.6 Hz, 2 H, CH2CH2N), 6.83, 6.88 (AB, JAB = 7.9 Hz, 4 H,
C6H4), 7.28−7.48 (m, 30 H, C6H5), 7.76 (dt, JHH = 15.3, JHP = 2.6 Hz,
1 H, Hα), 8.31 (d, JHH = 5.6 Hz, 2 H, CH2CH2N). MS (FAB+): m/z
893 (9%) [M+]. Elem anal. Calcd for C52H43NO3P2Ru (Mw = 892.92):
C, 69.9; H, 4.9; N, 1.6. Found: C, 70.0; H, 4.8; N, 1.5.
[{Ru(dppm)2(O2CC5H4N)}2Ag](PF6)2(OTf) (6). A DCM solution
(40 mL) of [Ru(dppm)2(O2CC5H4N)]PF6 (5; 50 mg, 0.044 mmol)
and silver triflate (6 mg, 0.022 mmol) was stirred for 2 h at room
temperature. All solvent was removed under vacuum and the product
triturated ultrasonically in diethyl ether (10 mL). The dark-yellow
crystalline solid was filtered and dried under vacuum. Yield: 42 mg
(75%). IR (solid state): 1511 (OCO), 1484, 1158, 1096, 1028, 833
[Ru(C(CCPh)CHPh)(O2CC5H4N)(CO)(PPh3)2] (2). A solution
of [Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] (100 mg, 0.112
mmol) in DCM (10 mL) was treated with a solution of isonicotinic
acid (15 mg, 0.123 mmol) and sodium methoxide (7 mg, 0.123 mmol)
in methanol (20 mL). The reaction mixture was stirred for 1 h at room
temperature. The solvent volume was slowly reduced on a rotary
evaporator, resulting in the precipitation of a yellow solid. This was
filtered, washed with petroleum ether (10 mL), and dried under
vacuum. Yield: 71 mg (65%). IR (solid state): 2159 (CC), 1914
(CO), 1740, 1516 (OCO), 1480, 1370, 1311, 1218, 1094, 867, 610
cm−1. 31P NMR: δ 38.1 (s, PPh3). 1H NMR: δ 5.72 (s(br), 1 H, Hβ),
6.87−7.56 (m, 30 H + 10 H + 2 H, PC6H5 + CC6H5 + CHCN), 8.31
(d, JHH = 5.6 Hz, 2 H, CHN). MS (ES+): m/z 980 (2%) [M+], 857
(6%) [M+ − O2CC5H4N]. Elem anal. Calcd for C59H45NO3P2Ru (Mw
= 979.01): C, 72.4; H, 4.6; N, 1.4. Found: C, 72.4; H, 4.7; N, 1.4.
(PF), 731, 636 cm−1. 31P NMR (acetone-d6): δ −12.3, 9.3 (t × 2, JPP
=
39.3 Hz, dppm). 1H NMR (acetone-d6): δ 4.29, 5.14 (m × 2, 2 × 4 H,
PCH2P), 6.40, 7.09, 7.23, 7.33, 7.67, 7.57, 7.79, 8.00 (m × 8, 80 H,
C6H5), 7.71 (d, JHH = 6.0 Hz, 4 H, CHCN), 8.87 (d, JHH = 6.0 Hz, 4
H, CHN). MS (FAB+): m/z 1100 (26%) [Ru(dppm)2(O2CC5H4N)-
Ag+]. Elem anal. Calcd for C113H96AgF15N2O7P10Ru2S (Mw
=
2530.77): C, 53.7; H, 3.8; N, 1.1. Found: C, 53.7; H, 3.9; N, 1.1.
[{Ru(dppm)2(O2CC5H4N)}2PdCl2](PF6)2 (7). A mixed chloroform
(10 mL) and methanol (10 mL) solution of 5 (50 mg, 0.043 mmol)
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and PdCl2 (4 mg, 0.022 mmol) was stirred at reflux for 3 h. All solvent
was removed and the yellow solid triturated with diethyl ether (10
mL) and filtered. Yield: 53 mg (98%). IR (solid state): 1517 (OCO),
1484, 1313, 833 (PF), 773, 730, 713 cm−1. 31P NMR: δ −11.6, 9.1 (t ×
C6H4F), −116.5 (m, 2 F, o-C6F5). MS (FAB+): m/z 1094 (2%) [M+ −
C6F5]. Elem anal. Calcd for C57H40AuF6NO3P2Ru (Mw = 1260.91): C,
54.3; H, 3.2; N, 1.1. Found: C, 54.2; H, 3.3; N, 1.1.
[Ru(CHCHC6H4Me-4)(O2CC6H4CN-4)(CO)(PPh3)2] (12). A
solution of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (100
mg, 0.106 mmol) in DCM (30 mL) was treated with a methanolic
solution (15 mL) of 4-cyanobenzoic acid (17 mg, 0.117 mmol) and
sodium methoxide (11 mg, 0.212 mmol). The reaction mixture was
stirred for 1.5 h at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of a
yellow solid. This was filtered and then washed with petroleum ether
(10 mL). Yield: 77 mg (79%). IR (solid state): 2229 (CN), 1916
(CO), 1579, 1518 (OCO), 1482, 1184, 964, 863, 606 cm−1. 31P NMR
(acetone-d6): δ 37.8 (s, PPh3). 1H NMR (acetone-d6): δ 2.17 (s, 3 H,
CH3), 5.99 (d, JHH = 15.3 Hz, 1 H, Hβ), 6.42, 6.79 (AB, JAB = 8.0 Hz,
4 H, C6H4), 7.27 (d, JHH = 8.4 Hz, 2 H, HCCCO2), 7.37−7.60 (m, 30
H + 2 H, C6H5 + HCCCN), 7.85 (dt, JHH = 15.3 Hz, JHP = 2.7 Hz, 1
H, Hα). MS (ES+): m/z 890 (3%) [M+ − CO], 771 (2%) [M+ −
O2CC6H4CN]. Elem anal. Calcd for C54H43NO3P2Ru (Mw = 916.94):
C, 70.7; H, 4.7; N, 1.5. Found: C, 70.9; H, 4.8; N, 1.5.
[Ru(C(CCPh)CHPh)(O2CC6H4CN-4)(CO)(PPh3)2] (13). A
solution of [Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] (100 mg,
0.112 mmol) in DCM (30 mL) was treated with a solution of 4-
cyanobenzoic acid (18 mg, 0.123 mmol) and sodium methoxide (7
mg, 0.123 mmol) in methanol (15 mL). The reaction mixture was
stirred for 1 h at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of a
yellow solid. This was filtered and then washed with petroleum ether
(10 mL). Yield: 66 mg (59%). IR (solid state): 2227 (CN), 1917
(CO), 1579, 1522 (OCO), 1483, 1186, 1028, 913, 864, 774, 750, 608
cm−1. 31P NMR (acetone-d6): δ 37.8 (s, PPh3). 1H NMR (acetone-d6):
δ 6.13 (s(br), 1 H, Hβ), 6.92−7.73 (m, 30 H + 10 H + 4 H, PC6H5 +
CC6H5 + C6H4CN). MS (ES+): m/z 1004 (12%) [M+]. Elem anal.
Calcd for C61H45NO3P2Ru (Mw = 1003.03): C, 73.0; H, 4.5; N, 1.4.
Found: C, 73.2; H, 4.4; N, 1.3.
1
2, JPP = 38.9 Hz, dppm). H NMR: δ 4.23, 4.77 (m × 2, 2 × 4 H,
PCH2P), 6.27, 7.03, 7.38, 7.56, 7.74 (m × 5, 80 H, C6H5), 7.36 (d, JHH
= 6.5 Hz, 4 H, CHCN), 8.94 (d, JHH = 6.5 Hz, 4 H, CHN). MS
(FAB+): m/z 2306 (8%) [M+]. Elem anal. Calcd for
C112H96Cl2F12N2O4P10PdRu2 (Mw = 2451.16): C, 54.9; H, 4.0; N,
1.1. Found: C, 54.5; H, 3.6; N, 1.0.
[{Ru(dppm)2(O2CC5H4N)}2PtCl2](PF6)2 (8). A mixed chloroform
(10 mL) and ethanol (20 mL) solution of 5 (50 mg, 0.044 mmol) and
K2PtCl4 (9 mg, 0.022 mmol) was heated at reflux for 3 h and then
stirred overnight at room temperature. All solvent was removed and
DCM (10 mL), ethanol (20 mL) was added, and the solvent volume
was slowly reduced on a rotary evaporator, resulting in the
precipitation of an orange solid. This was filtered and dried under
vacuum. Yield: 31 mg (55%). IR (solid state): 1511 (OCO), 1484,
1313, 836 (PF), 774, 732 cm−1. 31P NMR: δ −11.7, 8.8 (t × 2, JPP
=
1
39.2 Hz, dppm). H NMR: δ 4.15, 4.76 (m × 2, 2 × 4 H, PCH2P),
6.25, 7.01, 7.34, 7.60, 7.75 (m × 5, 80 H + 4 H, C6H5 + CHCN), 8.73
(m, 4 H, CHN). MS (FAB+): m/z 2248 (4%) [M+]. Elem anal. Calcd
for C112H96Cl2F12N2O4P10PtRu2 (Mw = 2539.81): C, 52.9; H, 3.8; N,
1.1. Found: C, 53.1; H, 3.7; N, 1.0.
[Ru(CHCHC6H4F-4)Cl(CO)(BTD)(PPh3)2] (9). A solution of
[RuHCl(BTD)(CO)(PPh3)2] (437 mg, 0.528 mmol) in DCM (30
mL) was treated with a methanolic solution (15 mL) of 1-ethynyl-4-
fluorobenzene (0.09 mL, 0.792 mmol). The reaction mixture was
stirred for 0.5 h at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of an
orange solid. This was filtered, washed with ethanol (10 mL) and
petroleum ether (10 mL), and dried under vacuum. Yield: 443 mg
(89%). IR (solid state): 1914 (CO), 1502, 1480, 1220, 1184, 924, 874,
841 cm−1. 31P NMR (CD2Cl2): δ 26.5 (s, PPh3). 1H NMR (CD2Cl2):
δ 5.80 (d, JHH = 16.2 Hz, 1 H, Hβ), 6.85 (m, 4 H, C6H4F), 7.55, 7.95
(m × 2, 2 × 2 H, BTD), 8.59 (dt, JHH = 16.2 Hz, JHP = 3.0 Hz, 1 H,
Hα). 19F NMR (CD2Cl2): δ −120.1 (s, 1 F, CF). MS (ES+): m/z 810
(10%) [M+ − BTD]. Elem anal. Calcd for C51H40ClFN2OP2RuS (Mw
= 946.41): C, 64.7; H, 4.3; N, 3.0. Found: C, 64.8; H, 4.2; N, 2.6.
[Ru(CHCHC6H4F-4)(O2CC5H4N)(CO)(PPh3)2] (10). A solution
of [Ru(CHCHC6H4F-4)Cl(BTD)(CO)(PPh3)2] (9; 100 mg, 0.106
mmol) in DCM (30 mL) was treated with a methanolic solution (15
mL) of isonicotinic acid (14 mg, 0.116 mmol) and sodium methoxide
(6 mg, 0.116 mmol). The reaction mixture was stirred for 0.5 h at
room temperature. The solvent volume was slowly reduced on a rotary
evaporator, resulting in the precipitation of a yellow solid. This was
filtered, washed with petroleum ether (10 mL), and dried under
vacuum. Yield: 59 mg (62%). IR (solid state): 1916 (CO), 1571, 1520
(OCO), 1502, 1481, 1218, 1183, 1028, 952, 840, 767, 604 cm−1. 31P
NMR (CD2Cl2): δ 38.1 (s, PPh3). 1H NMR (CD2Cl2): δ 5.86 (d, JHH
= 15.6 Hz, 1 H, Hβ), 6.43, 6.72 (m × 2, 2 × 2 H, C6H4F), 6.89 (d, JHH
[Ru(CHCHC6H4F-4)(O2CC6H4CN-4)(CO)(PPh3)2] (14). A sol-
ution of 9 (100 mg, 0.106 mmol) in DCM (30 mL) was treated with a
methanolic solution (15 mL) of cyanobenzoic acid (17 mg, 0.117
mmol) and sodium methoxide (11 mg, 0.211 mmol). The reaction
mixture was stirred for 0.5 h at room temperature. The solvent volume
was slowly reduced on a rotary evaporator, resulting in the
precipitation of a yellow solid. This was filtered and then washed
with petroleum ether (10 mL). Yield: 80 mg (82%). IR (solid state):
2230 (CN), 1914 (CO), 1740, 1520 (OCO), 1502, 1481, 1222, 1184,
948, 865, 838, 774, 608 cm−1. 31P NMR (acetone-d6): δ 38.0 (s, PPh3).
1H NMR (acetone-d6): δ 5.97 (d, JHH = 15.4 Hz, 1 H, Hβ), 6.49, 6.73
(m × 2, 2 × 2 H, C6H4F), 7.27 (d, JHH = 8.4 Hz, 2 H, HCCCO2),
7.37−7.60 (m, 30 H + 2 H, C6H5, HCCCN), 7.86 (d, JHH = 15.4 Hz,
JHP = 2.5 Hz, 1 H, Hα). 19F NMR (acetone-d6): δ −121.8 (s, CF). MS
(ES+): m/z 921 (6%) [M+]. Elem anal. Calcd for C53H40FNO3P2Ru
(Mw = 920.91): C, 69.1; H, 4.4; N, 1.5. Found: C, 69.0; H, 4.5; N, 1.5.
[Ru(CHCHC6H4Me-4){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2]
(15). A solution of 12 (60 mg, 0.065 mmol) in DCM (15 mL) was
treated with [Au(C6F5)(tht)] (27 mg, 0.059 mmol) dissolved in DCM
(10 mL). The reaction mixture was stirred for 1 h at room
temperature. Ethanol (10 mL) was added, and the solvent volume
was slowly reduced on a rotary evaporator to ca. 5 mL, resulting in the
precipitation of a brown/orange solid. This was filtered and washed
with petroleum ether (10 mL). Further product could be obtained by
evaporation of the filtrate. Yield: 38 mg (60%). IR (solid state): 1924
(CO), 1598, 1550 (OCO), 1498, 1449, 1187, 1051, 951, 863, 778
cm−1. 31P NMR (acetone-d6): δ 37.8 (s, PPh3). 1H NMR (acetone-d6):
δ 2.17 (s, 3 H, CCH3), 5.98 (d, JHH = 15.3 Hz, 1 H, Hβ), 6.42, 6.79
(AB, JAB = 8.0 Hz, 4 H, C6H4), 7.27 (d, JHH = 8.4 Hz, 2 H, HCCCO2),
7.35−7.87 (m, 30 H + 2 H, C6H5, HCCCN), 7.85 (dt, JHH = 15.3 Hz,
JHP = 2.7 Hz, 1 H, Hα). 19F NMR (acetone-d6): δ −165.4 (t, JFF = 20.6
Hz, 2 F, m-C6F5), −164.6 (t, JFF = 20.5 Hz, 1 F, p-C6F5), −115.8 (d,
= 5.8 Hz, 2 H, CHCN), 7.04−7.69 (m, 30 H, C6H5), 7.81 (dt, JHH
=
15.3 Hz, JHP = 2.6 Hz, 1 H, Hα), 8.31 (d, JHH = 5.8 Hz, 2 H, CHN).
19F NMR (CD2Cl2): δ −121.4 (s, 1 F, CF). MS (ES+): m/z 636 (3%)
[M+ − PPh3]. Elem anal. Calcd for C51H40FNO3P2Ru (Mw = 896.88):
C, 68.3; H, 4.5; N, 1.6. Found: C, 68.2; H, 4.4; N, 1.5.
[Ru(CHCHC6H4F-4){O2CC5H4N(AuC6F5)}(CO)(PPh3)2] (11). A
solution of 10 (60 mg, 0.067 mmol) in DCM (25 mL) was treated
with [Au(C6F5)(tht)] (28 mg, 0.061 mmol) dissolved in DCM (10
mL). The reaction mixture was stirred for 1 h at room temperature.
The solvent volume was slowly reduced on a rotary evaporator,
resulting in the precipitation of a brown solid. This was filtered, then
washed with petroleum ether (10 mL), and dried. Yield: 40 mg (70%).
IR (solid state): 1925 (CO), 1743, 1501 (OCO), 1482, 1451, 1221,
1
1057, 952, 869, 841 cm−1. 31P NMR (CD2Cl2): δ 38.0 (s, PPh3). H
NMR (CD2Cl2): δ 5.87 (d, JHH = 15.4 Hz, 1 H, Hβ), 6.43, 6.72 (m ×
2, 2 × 2 H, C6H4F), 6.89 (d, JHH = 5.8 Hz, 2 H, CHCN), 6.96−7.68
(m, 30 H, C6H5), 7.83 (dt, JHH = 4.31 Hz, JHP = 2.6 Hz, 1 H, Hα), 8.31
(d, JHH = 5.8 Hz, 2 H, CHN). 19F NMR (CD2Cl2): δ −163.1 (m, 2 F,
m-C6F5), −159.3 (t, JFF = 20.0 Hz, 1 F, p-C6F5), −121.2 (s, 1 F,
JFF = 22.9 Hz, 2 F, o-C6F5). MS (FAB+): m/z 1164 (2%) [M+
−
alkenyl], 917 (8%) [M+ − AuC6F5]. Elem anal. Calcd for
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C60H43AuF5NO3P2Ru (Mw = 1280.97): C, 56.3; H, 3.4; N, 1.1. Found:
C, 56.4; H, 3.1; N, 1.1.
under vacuum. Yield: 32 mg (71%). IR (solid state): 1916 (CO), 1576,
1519 (OCO), 1481, 1185, 999, 867, 604 cm−1. 31P NMR: δ 38.1 (s,
PPh3). 1H NMR: δ 2.25 (s(br), 12 H, CCH3), 5.90 (d, JHH = 15.6 Hz,
4 H, Hβ), 6.42, 6.85 (d × 2, JHH = 7.5 Hz, 2 × 8 H, C6H4), 6.90 (d,
JHH unresolved, 8 H, CHCN), 7.27−7.52 (m, 120 H, C6H5), 7.77 (dt,
JHH = 15.1 Hz, JHP unresolved, 4 H, Hα), 8.32 (s(br), 8 H, CHN). MS
FAB+ and MALDI+ not diagnostic. Elem anal. Calcd for
C208H172Cl3N4O12P8RhRu4 (Mw = 3780.95): C, 66.1; H, 4.6; N, 1.5.
Found: C, 66.2; H, 4.4; N, 1.4.
[Ru(C(CCPh)CHPh){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2]
(16). A solution of 13 (60 mg, 0.059 mmol) in DCM (15 mL) was
treated with [Au(C6F5)(tht)] (26.5 mg, 0.059 mmol) dissolved in
DCM (10 mL). The reaction mixture was stirred for 1 h at room
temperature. Ethanol (10 mL) was added, and the solvent volume was
slowly reduced on a rotary evaporator to 5 mL, resulting in the
precipitation of a yellow solid. This was filtered and then washed with
petroleum ether (10 mL). Yield: 46 mg (62%). Further product could
be obtained by evaporation of the filtrate. IR (solid state): 2249 (CN),
1975, 1923 (CO), 1596 (OCO), 1494, 1450, 1188, 1053, 951, 864,
778 cm−1. 31P NMR (acetone-d6): δ 37.8 (s, PPh3). 1H NMR
(acetone-d6): δ 6.13 (s(br), 1 H, Hβ), 6.93−7.75 (m, 30 H + 10 H + 4
H, PC6H5, CC6H5, C6H4CN). 19F NMR (acetone-d6): δ −165.4 (t, JFF
= 19.5 Hz, 2 F, m-C6F5), −164.6 (t, JFF = 20.6 Hz, 1 F, p-C6F5),
−115.7 (d, JFF = 20.6 Hz, 2 F, o-C6F5). MS (FAB+): m/z 1367 (2%)
[M+]. Elem anal. Calcd for C67H45AuF5NO3P2Ru (Mw = 1367.06): C,
58.9; H, 3.3; N, 1.0. Found: C, 59.1; H, 3.1; N, 1.0.
[RhCl2{NC5H4(C6H4CO2H)-4}4]Cl (20). An ethanolic suspension
(10 mL) of 4-(4-pyridyl)benzoic acid (200 mg, 1.004 mmol) was
added to a solution of RhCl3·3H2O (64 mg, 0.243 mmol) in 0.25 M
hydrochloric acid (10 mL). The mixture was heated to boiling with
vigorous stirring. After the ligand had dissolved, the red solution
rapidly turned yellow and a fine precipitate formed. Reflux was
continued for a further 5 min, after which the mixture was cooled to
ambient temperature. A sodium hydroxide solution (0.1 M) was added
until the solution reached pH 4.5, increasing the yield of the product.
The pale-yellow-pink solid was collected and washed with hot water (5
mL) and acetone (5 mL). Yield: 207 mg (84%). IR (solid state): 1917,
1691, 1605, 1522 (OCO), 1405, 1115, 1068, 1004, 826, 767, 656
[Ru(CHCHC6H4F-4){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2]
(17). (a) A solution of 14 (60 mg, 0.065 mmol) in DCM (25 mL) was
treated with [Au(C6F5)(tht)] (29.5 mg, 0.065 mmol) dissolved in
DCM (10 mL). The reaction mixture was stirred for 1 h at room
temperature. The solvent volume was slowly reduced on a rotary
evaporator, resulting in the precipitation of a pale-yellow product. This
was filtered and then washed with petroleum ether (10 mL). Yield: 42
mg (50%). (b) A solution of 18 (30 mg, 0.058 mmol) in DCM (25
mL) was treated with sodium methoxide (6 mg, 0.106 mmol) and a
methanolic solution of 9 (51 mg, 0.053 mmol). The reaction mixture
was stirred for 1 h at room temperature. The solvent volume was
slowly reduced on a rotary evaporator, resulting in the precipitation of
a pale-yellow solid. This was filtered and then washed with petroleum
ether (10 mL). Yield: 60 mg (88%). IR (solid state): 2250 (CN),
1967, 1922 (CO), 1596, 1557, 1500 (OCO), 1482, 1450, 1220, 1187,
1094, 1051, 951, 864, 775 cm−1. 31P NMR (acetone-d6): δ 38.0 (s,
1
cm−1. H NMR (CD2Cl2): δ 7.60 (dd, JHH = 4.7 Hz, JRhH = 1.8 Hz, 8
H, CHCN), 7.81, 8.21 (d × 2, JHH = 8.3 Hz, 2 × 8 H, C6H4), 8.72 (dd,
JHH = 4.7 Hz, JRhH = 1.9 Hz, 8 H, CHN), 11.12 (s(br), 4 H, OH). MS
(FAB+): m/z 970 (2%) [M+]. Elem anal. Calcd for C48H36Cl3N4O8Rh
(Mw = 1006.09): C, 57.3; H, 3.6; N, 5.6. Found: C, 57.3; H, 3.7; N,
5.5.
[RhCl2{NC5H4(C6H4CO2)-4}{NC5H4(C6H4CO2Na)-4}3] (21). A sa-
turated solution of NaOH was added to 20 (170 mg, 0.169 mmol)
until complete dissolution of the solid phase (molar ratio Rh:NaOH =
1:3) had taken place. The resulting yellow solution was evaporated
until all solvent was removed, and the product was triturated
ultrasonically in acetone (10 mL). The yellow-brown solid was
filtered, washed with ice-cold water (5 mL) and acetone (5 mL), and
dried under vacuum. Yield: 99 mg (57%). IR (solid state): 1593, 1550
1
PPh3). H NMR (acetone-d6): δ 5.97 (d, JHH = 15.3 Hz, 1 H, Hβ),
1
(OCO), 1378, 1222, 1186, 1070, 1005, 833, 777, 736, 700 cm−1. H
NMR (DMSO-d6): δ 7.75 (dd, JHH = 5.7 Hz, JRhH = 1.5 Hz, 8 H,
CHCN), 7.79, 8.02 (d × 2, JHH = 8.1 Hz, 2 × 8 H, C6H4), 8.65 (d(br),
JHH = 5.7 Hz, JRhH unresolved, 8 H, CHN). MS (FAB−): m/z 765
(2%) [M+ − 2Cl − NC5H4(C6H4CO2)]. Elem anal. Calcd for
C48H32Cl2N4Na3O8Rh (Mw = 1035.57): C, 55.7; H, 3.1; N, 5.4.
Found: C, 56.1; H, 3.3; N, 5.3.
6.49, 6.73 (m × 2, 2 × 2 H, C6H4F), 7.27 (d, JHH = 8.3 Hz, 2 H,
HCCCO2), 7.37−7.80 (m, 30 H, C6H5), 7.86 (d, JHH = 15.3 Hz, JHP
=
2.6 Hz, 1 H, Hα), 8.08 (m, 2 H, HCCCN). 19F NMR (acetone-d6): δ
−165.4 (t, JFF = 19.5 Hz, 2 F, m-C6F5), −164.6 (t, JFF = 19.4 Hz, 1 F,
p-C6F5), −121.8 (s, 1 F, C6H4F), −115.8 (d, JFF = 22.9 Hz, 2 F, o-
C6F5). MS (FAB+): m/z 1285 (4%) [M+]. Elem anal. Calcd for
C59H40AuF6NO3P2Ru (Mw = 1284.93): C, 55.2; H, 3.1; N, 1.1. Found:
C, 55.1; H, 3.5; N, 1.0.
[RhCl2{NC5H4(C6H4CO2Ru(dppm)2)-4}4](PF6)5 (22). A solution
of cis-[RuCl2(dppm)2] (100 mg, 0.106 mmol) in chloroform (30 mL)
was treated with a solution of 21 (28 mg, 0.027 mmol) in water (5
mL) and then with a solution of sodium methoxide (6 mg, 0.106
mmol) in ethanol (10 mL). Ammonium hexafluorophosphate (104
mg, 0.638 mmol) was added, and the reaction mixture was heated at
reflux for 15 min. All solvent was removed and the crude product
dissolved in DCM (10 mL) and filtered through diatomaceous earth
(Celite) to remove NaCl. All solvent was again removed and the
residue dissolved in ethanol (10 mL) and filtered through diatoma-
ceous earth (Celite) to remove other impurities. A crystalline black
product was obtained after recrystallization from a DCM/petroleum
ether solution. Yield: 123 mg (88%). IR (solid state): 1604, 1557
(OCO), 1483, 1362, 1187, 867 (PF), 831, 778, 731, 616 cm−1. 31P
NMR (CD2Cl2): δ −11.8, 9.1 (t × 2, JPP = 39.2 Hz, dppm). 1H NMR
(CD2Cl2): δ 4.03, 4.75 (m × 2, 2 × 8 H, PCH2P), 6.52−7.92 (m, 160
H + 16 H + 8 H, C6H5 + C6H4 + CHCN), 8.25 (m, 8 H, CHN). MS
(MALDI+ ): not diagnostic. Elem anal. Calcd for
C248H208Cl2F30N4O8P21RhRu4 (Mw = 5170.82): C, 57.6; H, 4.1; N,
1.1. Found: C, 57.7; H, 4.2; N, 1.1.
[Au(C6F5)(NCC6H4CO2H-4)] (18). A solution of [Au(C6F5)(tht)]
(50 mg, 0.111 mmol) in DCM (25 mL) was treated with a methanolic
solution (15 mL) of 4-cyanobenzoic acid (16 mg, 0.111 mmol). The
reaction mixture was stirred for 1 h at room temperature, and the
solvent volume was slowly reduced on a rotary evaporator, resulting in
the precipitation of an off-white solid. This was filtered and washed
with petroleum ether (10 mL). Yield: 32 mg (57%). IR (solid state):
2278, 2236 (CN), 1698, 1615, 1555, 1504 (OCO), 1461, 1398, 1288,
1
1064, 1017, 957, 863, 807, 771, 644 cm−1. H NMR (acetone-d6): δ
7.93 (d, JHH = 8.1 Hz, 2 H, HCCCO2), 8.23 (d, JHH = 8.1 Hz, 2 H,
HCCCN). 19F NMR (acetone-d6): δ −165.6 (t, JFF = 19.6 Hz, 2 F, m-
C6F5), −164.1 (t, JFF = 19.5 Hz, 1 F, p-C6F5), −115.8 (d, JFF = 21.7
Hz, 2 F, o-C6F5). MS (FAB+): m/z 513 (3%) [M+]. Elem anal. Calcd
for C14H5AuF5NO2 (Mw = 511.15): C, 32.9; H, 1.0; N, 2.7. Found: C,
32.9; H, 0.9; N, 2.8.
[RhCl2{NC5H4CO2Ru(CHCHC6H4Me-4)(CO)(PPh3)2}4]Cl (19).
A solution of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (46
mg, 0.049 mmol) in DCM (10 mL) and acetone (10 mL) was treated
with a solution of [RhCl2(NC5H4CO2)(NC5H4CO2Na)3] (9 mg,
0.012 mmol) in water (5 mL) and acetone (15 mL). The reaction
mixture was stirred for 1 h at room temperature. All solvent was
removed and the crude product dissolved in DCM (10 mL) and
filtered through diatomaceous earth (Celite) to remove NaCl. Ethanol
(20 mL) was added, and the solvent volume was slowly reduced on a
rotary evaporator, resulting in the precipitation of a fine yellow solid.
This was filtered, washed with petroleum ether (10 mL), and dried
[(Pd-TPP){p-CO2Ru(dppm)2}4](PF6)4 (23). A solution of cis-
[RuCl2(dppm)2] (100 mg, 0.106 mmol) in DCM (50 mL) was
treated with a solution of [(Pd-TPP)(p-CO2H)4] (24 mg, 0.027
mmol), sodium methoxide (9 mg, 0.160 mmol), and ammonium
hexafluorophosphate (22 mg, 0.133 mmol) in methanol (30 mL). The
reaction mixture was stirred for 48 h at room temperature. All solvent
was removed and the crude product dissolved in DCM (10 mL) and
filtered through diatomaceous earth (Celite) to remove NaCl and
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NaOMe. Methanol (20 mL) was then added, and the solvent volume
was slowly reduced on a rotary evaporator, resulting in the
precipitation of a bright-red solid. This was filtered, washed with
methanol (10 mL) and petroleum ether (10 mL), and dried under
vacuum. Yield: 98 mg (74%). IR (solid state): 1607, 1584, 1519
(OCO), 1484, 1430, 1095, 1012, 836 (PF), 774, 732, 694, 616 cm−1.
hexafluorophosphate (35 mg, 0.213 mmol) in methanol (20 mL).
The reaction mixture was stirred for 1 h at room temperature. All
solvent was removed and the crude product dissolved in DCM (10
mL) and filtered through diatomaceous earth (Celite) to remove
NaCl, NaOMe, and excess ligand. Ethanol (20 mL) was then added,
and the solvent volume was slowly reduced on a rotary evaporator,
resulting in the precipitation of a yellow solid. This was filtered,
washed with petroleum ether (10 mL), and dried under vacuum. Yield:
51 mg (40%). A further crop could be obtained from slow evaporation
of the filtrate. IR (solid state): 1594, 1500 (OCO), 1484, 1188, 1096,
832 (PF), 778, 755, 732, 617 cm−1. 31P NMR (CD2Cl2): δ −11.9, 9.0
(2t, JPP = 39.2 Hz, dppm). 1H NMR (CD2Cl2): δ 3.99, 4.68 (m × 2, 2
× 2 H, PCH2P), 7.01−7.85 (m, 40 H + 2 H + 4 H, C6H5 + CHCN +
C6H4), 8.75 (d, JHH = 5.6 Hz, 2 H, CHN). MS (FAB+): m/z 1068
1
31P NMR (CD2Cl2): δ −11.6, 9.0 (t × 2, JPP = 39.0 Hz, dppm). H
NMR (CD2Cl2): δ 4.07, 4.74 (m × 2, 2 × 8 H, PCH2P), 6.27, 7.06,
7.21, 7.32, 7.43, 7.54, 7.79, 7.90 (m × 8, 160 H, C6H5), 8.17 (m, 8 H,
C6H4), 8.32 (d, JHH = 7.8 Hz, 8 H, C6H4), 8.97 (s, 8 H, NC4H2). UV/
vis [CH2Cl2; λmax, nm (ε, mol−1 dm3)]: 420 (63270), 525 (5300). MS
(MALDI+ ): not diagnostic. Elem anal. Calcd for
C248H200F24N4O8P20PdRu4 (Mw = 4950.40): C, 60.2; H, 4.1; N, 1.1.
Found: C, 60.1; H, 3.9; N, 1.2.
[(Pd-TPP){p-CO2Ru(CHCHC6H4Me-4)(CO)(PPh3)2}4] (24). A
solution of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (100
mg, 0.106 mmol) in DCM (40 mL) was treated with a methanolic
solution (20 mL) of [(Pd-TPP)(p-CO2H)4] (24 mg, 0.027 mmol) and
sodium methoxide (9 mg, 0.159 mmol). The reaction mixture was
stirred for 18 h at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of a red
solid. This was filtered, washed with methanol (10 mL) and petroleum
ether (10 mL), and dried under vacuum. Yield: 69 mg (64%). IR (solid
state): 1919 (CO), 1508 (OCO), 1481, 1352, 1314, 1181, 1012, 796
cm−1. 31P NMR (C6D6): δ 39.1 (s, PPh3). 1H NMR (C6D6): δ 2.27 (s,
12 H, CH3), 6.67 (d, JHH = 15.2 Hz, 4 H, Hβ), 6.97, 7.10 (d, JAB = 8.1
(12%) [M+]. Elem anal. Calcd for C62H52F6NO2P5Ru (Mw
=
1213.01): C, 61.4; H, 4.3; N, 1.2. Found: C, 61.4; H, 4.3; N, 1.1.
[Ru(CHCHC6H4Me-4)(O2CC6H4C5H4N)(CO)(PPh3)2] (28). A
solution of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] (100
mg, 0.106 mmol) in DCM (30 mL) was treated with a solution of 4-
pyridylbenzoic acid (23 mg, 0.117 mmol) and sodium methoxide (12
mg, 0.213 mmol) in methanol (20 mL). The reaction mixture was
stirred for 1 h at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of a pale-
yellow solid. This was filtered, washed with petroleum ether (10 mL),
and dried under vacuum. Yield: 100 mg (88%). IR (solid state): 1917
(CO), 1592, 1545, 1507 (OCO), 1482, 1184, 864, 823, 775, 747, 606
1
cm−1. 31P NMR (CD2Cl2): δ 37.7 (s, PPh3). H NMR (CD2Cl2): δ
Hz, 16 H, C6H4Me), 7.28, 8.04 (m × 2, 120 H, C6H5), 7.94 (d, JHH
8.1 Hz, 8 H, C6H4), 8.05 (m, 8 H, o-C6H4), 8.57 (dt, JHH = 15.3 Hz,
JHP = 2.7 Hz, 4 H, Hα), 8.90 (s, 8 H, NC4H2). UV/vis [CH2Cl2; λmax
=
2.24 (s, 3 H, CH3), 5.89 (d, JHH = 15.4 Hz, 1 H, Hβ), 6.42, 6.84 (d ×
2, JAB = 7.2 Hz, 2 × 2 H, CC6H4Me), 7.23 (d, JHH = 6.8 Hz, 2 H,
,
nm (ε, mol−1 dm3)]: 420 (27520), 525 (3180). MS (MALDI+): not
diagnostic. Elem anal. Calcd for C232H180N4O12P8PdRu4·6CH2Cl2 (Mw
= 4484.01): C, 63.8; H, 4.3; N, 1.3. Found: C, 64.1; H, 3.9; N, 1.4.
[(Pd-TPP){p-CO2Ru(CHCHCPh2OH)(CO)(PPh3)2}4] (25). A
solution of [Ru(CHCHCPh2OH)Cl(BTD)(CO)(PPh3)2] (100
mg, 0.097 mmol) in DCM (100 mL) was treated with a solution of
[(Pd-TPP)(p-CO2H)4] (22 mg, 0.024 mmol) and sodium methoxide
(8 mg, 0.145 mmol) in methanol (20 mL). The reaction mixture was
stirred overnight at room temperature. The solvent volume was slowly
reduced on a rotary evaporator, resulting in the precipitation of a
brick-red solid. This was filtered, washed with methanol (10 mL) and
petroleum ether (10 mL), and dried under vacuum. Yield: 42 mg
(40%). IR (solid state): 1919 (CO), 1587, 1512 (OCO), 1482, 1391,
1352, 1312, 1181, 1013, 796, 773 cm−1. 31P NMR (CD2Cl2): δ 38.7 (s,
CHCN), 7.36−7.52 (m, 30 H + 4 H, C6H5 + C6H4), 7.87 (d, JHH
=
15.1 Hz, 1 H, Hα), 8.64 (d(br), JHH unresolved, 2 H, CHN). 13C
NMR (CD2Cl2, 400 MHz): δ 206.9 (t, JCP = 15.4 Hz, CO), 171.1 (s,
CO2), 152.9 (t, JCP = 11.7 Hz, Cα), 150.6 (s, CN), 147.8 (s,
quaternary C), 140.4 (s, quaternary C), 138.5 (s, C1-tolyl), 134.8 (tv,
JCP = 5.6 Hz, o/m-C6H5), 134.3 (s, C4-tolyl), 133.9 (t(br), JCP
unresolved, Cβ), 133.4 (s, quaternary C), 131.7 (tv, JCP = 21.5 Hz,
ipso-C6H5), 130.2 (s, p-C6H5), 129.0 (s, C2,6-tolyl), 128.7 (s, C3,5-
tolyl), 128.4 (tv, JCP = 4.4 Hz, o/m-C6H5), 125.9 (s, benzoate/py-CH),
124.5 (s, benzoate/py-CH), 121.8 (s, CCCO2), 21.0 (s, CH3). MS
(FAB+): m/z 969 (18%) [M+]. Elem anal. Calcd for C58H47NO3P2Ru
(Mw = 969.02): C, 71.9; H, 4.9; N, 1.5. Found: C, 71.7; H, 5.0; N, 1.4.
Ag@[NC5H4CO2Ru(dppm)2]PF6 (NP1). An acetonitrile solution
(15 mL) of AgNO3 (5 mg, 0.030 mmol) was treated with 5 (45 mg,
0.040 mmol) in acetonitrile (5 mL). An aqueous solution of sodium
borohydride (80 μL, 4M) was then added dropwise over 10 min,
causing a darkening of the color. The resulting suspension was stirred
for 1 h at room temperature and then left to stand. The supernatant
was decanted and the solid washed with acetonitrile (2 × 10 mL) to
remove excess ruthenium complex and then with water (2 × 10 mL)
to remove any remaining sodium borohydride. The black solid was
dried under vacuum. IR (solid state): 1590, 1550 (OCO), 1330, 1223,
1134, 1076, 990, 934, 821 (PF), 766, 709, 681 cm−1. TEM: analysis of
100 nanoparticles gave a size of 19.0 4.1 nm. EDX: the presence of
phosphorus, ruthenium, and silver is indicated.
1
PPh3). H NMR (CD2Cl2): δ 1.03 (s, 4 H, OH), 5.99 (d, JHH = 15.3
Hz, 4 H, Hβ), 6.84 (m, 16 H, CC6H5), 7.08 (d, JHH = 15.3 Hz, 4 H,
Hα), 7.18 (m, CC6H5, 24 H), 7.42−7.58 (m, 120 H + 8 H, PC6H5 +
C6H4), 7.74 (d, JHH = 8.0 Hz, 8 H, C6H4), 8.61 (s, 8 H, NC4H2). UV/
vis [CH2Cl2; λmax, nm (ε, mol−1 dm3)]:420 (108520), 525 (10900).
MS (MALDI+): not diagnostic. Elem anal. Calcd for
C256H196N4O16P8PdRu4 (Mw = 4342.80): C, 70.8; H, 4.6; N, 1.3.
Found: C, 71.1; H, 4.5; N, 1.5.
[(Pd-TPP){p-CO2Ru(CHCHCPh2)(CO)(PPh3)2}4](BF4)4 (26).
A suspension of 25 (18 mg, 0.004 mmol) in diethyl ether (5 mL)
was treated with 5 drops of HBF4·OEt2 and stirred for 5 min at room
temperature. The orange solid was filtered and dried under vacuum.
Yield: 17 mg (89%). IR (solid state): 1968 (CO), 1692, 1606, 1497
(OCO), 1481, 1227, 1093 (BF), 1012, 871, 860, 772, 745, 708 cm−1.
31P NMR (CD2Cl2): δ 34.2 (s, PPh3). 1H NMR (CD2Cl2): δ 6.33 (d,
JHH = 7.8 Hz, 8 H, CC6H5), 7.31 (d, JHH = 7.8 Hz, 8 H, CC6H4), 7.43
(t, JHH = 7.7 Hz, 8 H, CC6H5), 7.52−7.66 (m, 120 H + 16 H + 4 H,
PC6H5 + CC6H5 + Hβ), 7.72 (m, 8 H, CC6H5), 7.91 (d, JHH = 8.1 Hz,
8 H, CC6H4), 8.66 (s, 8 H, NC4H2), 14.94 (s(br), 4 H, Hα). UV/vis
[CH2Cl2; λmax, nm (ε, mol−1 dm3)]: 424 (30490), 520 (4530). MS
(MALDI+ ): not diagnostic. Elem anal. Calcd for
C256H192B4F16N4O12P8PdRu4 (Mw = 4621.99): C, 66.5; H, 4.2; N,
1.2. Found: C, 66.7; H, 4.2; N, 1.2.
Ag@[NC5H4{C6H4CO2Ru(dppm)2}-4]PF6 (NP2). An acetonitrile
solution (15 mL) of AgNO3 (3 mg, 0.020 mmol) was treated with 27
(30 mg, 0.030 mmol) in acetonitrile (5 mL). An aqueous solution of
sodium borohydride (50 μL, 4M) was then added dropwise over 10
min, causing a darkening of the color. The resulting suspension was
stirred for 1 h at room temperature and then left to stand. The
supernatant was decanted and the solid washed with acetonitrile (2 ×
10 mL) to remove excess ruthenium complex and then with water (2
× 10 mL) to remove any remaining sodium borohydride. The black
solid was dried under vacuum. IR (solid state): 1555 (OCO), 1361,
1260, 1021, 815 (PF) cm−1. TEM: analysis of 100 nanoparticles gave a
size of 12.8 3.3 nm. EDX: the presence of phosphorus, ruthenium,
and silver is indicated.
[Ru{O2CC6H4(C5H4N)-4}(dppm)2]PF6 (27). A solution of cis-
[RuCl2(dppm)2] (100 mg, 0.106 mmol) in DCM (30 mL) was
treated with a solution of 4-pyridylbenzoic acid (23 mg, 0.117 mmol),
sodium methoxide (12 mg, 0.213 mmol), and ammonium
Crystallography. Crystal data for 2: C59H45NO3P2Ru, M =
978.97, monoclinic, P21/n (No. 14), a = 18.67558(18) Å, b =
13.24963(15) Å, c = 19.20324(19) Å, β = 95.2130(9)°, V =
4711
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4732.08(8) Å3, Z = 4, Dc = 1.374 g cm−3, μ(Mo Kα) = 0.447 mm−1, T
= 173 K, yellow prisms, Oxford Diffraction Xcalibur 3 diffractometer;41
16065 independent measured reflections (Rint = 0.0337), F2
refinement, R1(obs) = 0.0342, wR2(all) = 0.0870, 12963 independent
(11) (a) Huang, D.; Wang, W.; Zhang, X.; Chen, C.; Chen, F.; Liu,
Q.; Liao, D.; Li, L.; Sun, L. Eur. J. Inorg. Chem. 2004, 1454−1464.
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Bol. Soc. Chil. Quim. 1998, 43, 97−102.
observed absorption-corrected reflections [|Fo| > 4σ(|Fo|), 2θmax
66°], 595 parameters. CCDC 859598.
=
ASSOCIATED CONTENT
* Supporting Information
■
(12) (a) Li, Y.; Li, G.-Q.; Zheng, F.-K.; Zou, J.-P.; Zou, W.-Q.; Guo,
G.-C.; Lu, C.-Z.; Huang, J.-S. J. Mol. Struct. 2007, 842, 38−45.
(b) Keys, A.; Bott, S. G.; Barron, A. R. Polyhedron 1998, 17, 3121−
3130. (c) Ma, B. Q.; Gao, S.; Wang, Z. M.; Yi, T.; Yan, C. H.; Xu, G. X.
Acta Crystallogr. 1999, C55, 1420−1422. (d) Yuan, R. X.; Xiong, R. G.;
Chen, Z. F.; You, X. Z.; Peng, S. M.; Lee, G. H. Inorg. Chem. Commun.
2001, 4, 430−433. (e) Barral, M. C.; Gallo, T.; Herrero, S.; Jimenez-
Aparicio, R.; Torres, R. M.; Urbanos, F. A. Inorg. Chem. 2006, 45,
3639−3647.
S
CIF file with crystallographic data and the molecular structure
for 2. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: j.wilton-ely@imperial.ac.uk.
■
(13) Torres, M. R.; Vegas, A.; Santos, A.; Ros, J. J. Organomet. Chem.
1986, 309, 169−177.
Notes
The authors declare no competing financial interest.
(14) Werner, H.; Esteruelas, M. A.; Otto, H. Organometallics 1986, 5,
2295−2299.
ACKNOWLEDGMENTS
We thank Johnson Matthey Ltd. for a generous loan of
ruthenium, rhodium, and gold salts.
(15) (a) Torres, M. R.; Vegas, A.; Santos, A.; Ros, J. J. Organomet.
Chem. 1987, 326, 421. (b) Torres, M. R.; Santos, A.; Ros, J.; Solans, X.
■
Organometallics 1987, 6, 1091−1095. (c) Castano, A. M.; Echavarren,
̃
A. M.; Lop
́
ez, J.; Santos, A. J. Organomet. Chem. 1989, 379, 171−175.
(d) Lopez, J.; Romero, A.; Santos, A.; Vegas, A.; Echavarren, A. M.;
́
DEDICATION
■
Noheda, P. J. Organomet. Chem. 1989, 373, 249−258. (e) Montoya, J.;
Santos, A.; Echavarren, A. M.; Ros, J. J. Organomet. Chem. 1990, 390,
C57−C60. (f) Loumrhari, H.; Ros, J.; Torres, M. R.; Santos, A.;
Echavarren, A. M. J. Organomet. Chem. 1991, 411, 255−261.
†Dedicated to the memory of Dr. Thulani Kunene.
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