Iridium-Ruthenium-gold cluster complexes: Structures, and skeletal Rearrangements

Article abstract of DOI:10.1016/j.jorganchem.2012.01.012

Three new IrRuAu trimetallic cluster complexes: IrRu₃(CO) ₁₃AuPPh₃, 1, HIrRu₃(CO)₁₂(AuPPh ₃)₂, 2 and IrRu₃(CO)₁₂(AuPPh ₃)₃, 3 were obtained in low yields from the reaction of HIrRu₃(CO)₁₃ with [(AuPPh₃)₃O] [BF₄]. Compounds 1 and 3 were subsequently obtained in much better yields (82%) and (84%) from the reactions of [AuPPh₃][NO₃] and [(AuPPh₃)₃O][BF₄] with [PPN][IrRu ₃(CO)₁₃], respectively. The molecular structures of all three compounds were established by single crystal x-ray diffraction methods. Compounds 1 and 2 contain an Au(PPh₃) group that bridges one triangular face of a tetrahedral IrRu₃ cluster. Compound 2 contains a second Au(PPh₃) capping group that bridges an Ir-Ru-Au triangle. Compound 3 consists of a pentagonal bipyramidal Au₃IrRu₃ cluster that has three gold atoms and two of the ruthenium atoms in the equatorial plane. There is a bond between the apical Ir and Ru atoms. Compounds 2 and 3 exhibit dynamical activity in the metal skeleton that leads to a rapid averaging of the inequivalent Au(PPh₃) groups on the NMR timescale at room temperature.

Full text of DOI:10.1016/j.jorganchem.2012.01.012

Journal of Organometallic Chemistry 706-707 (2012) 20e25
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
IridiumeRutheniumegold cluster complexes: Structures, and skeletal
Rearrangements
*
Richard D. Adams , Perry J. Pellechia, Mark D. Smith, Qiang Zhang
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new IrRuAu trimetallic cluster complexes: IrRu3(CO)13AuPPh3, 1, HIrRu3(CO)12(AuPPh3)2, 2 and
IrRu3(CO)12(AuPPh3)3, 3 were obtained in low yields from the reaction of HIrRu3(CO)13 with [(AuPPh3)3O]
[BF4]. Compounds 1 and 3 were subsequently obtained in much better yields (82%) and (84%) from the
reactions of [AuPPh3][NO3] and [(AuPPh3)3O][BF4] with [PPN][IrRu3(CO)13], respectively. The molecular
structures of all three compounds were established by single crystal x-ray diffraction methods.
Compounds 1 and 2 contain an Au(PPh3) group that bridges one triangular face of a tetrahedral IrRu3
cluster. Compound 2 contains a second Au(PPh3) capping group that bridges an IreRueAu triangle.
Compound 3 consists of a pentagonal bipyramidal Au3IrRu3 cluster that has three gold atoms and two of
the ruthenium atoms in the equatorial plane. There is a bond between the apical Ir and Ru atoms.
Compounds 2 and 3 exhibit dynamical activity in the metal skeleton that leads to a rapid averaging of the
inequivalent Au(PPh3) groups on the NMR timescale at room temperature.
Received 11 November 2011
Received in revised form
23 December 2011
Accepted 9 January 2012
Keywords:
Cluster
Trimetallic
Gold
Iridium
Ruthenium
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
[BF4]. We have obtained three new iridiumerutheniumegold
carbonyl cluster complexes, have established their molecular
Applications for iridium in catalysis continue to grow [1].
Although most catalytic applications are of a homogeneous type
[1,2], it has been shown that iridium complexes can also serve as
precursors to catalysts that exhibit good activity for the hydroge-
nation of aromatics and olefins when placed on supports [3].
Heterogeneous iridium-iron catalysts derived from bimetallic
cluster complexes have been shown to exhibit good catalytic
activity for the formation of methanol from synthesis gas. [4].
Iridiumeruthenium complexes have been shown to serve as
precursors to catalysts for the carbonylation methanol [5]. Sup-
ported bimetallic iridiumeruthenium catalysts have been shown to
produce C2 oxygenates from syngas [6] and also to exhibit unusu-
ally high catalytic activity for the oxygen evolution reaction in the
electrolysis of water [7]. Recently, gold nanoparticles have been
shown to exhibit significant catalytic activity for the oxidation of CO
and certain olefins [8]. Combining transition metals with gold has
led to interesting new bimetallic oxidation nanocatalysts [9].
There have been very few structural characterizations of
structures and have investigated their properties in solution. These
results are reported herein.
2. Experimental
General Data. Reagent grade solvents were dried by the standard
procedures and were freshly distilled prior to use. Infrared spectra
were recorded on a Thermo Nicolet Avatar 360 FT-IR spectropho-
tometer. Room temperature 1H NMR and 31P{1H} NMR were
recorded on a Bruker Avance/DRX 400 NMR spectrometer oper-
ating at 400.3 and 162.0 MHz, respectively. Different temperature
31P{1H} NMR for compound 3 were recorded on a Varian Mercury
400 spectrometer operating at 161.9 MHz 31P {1H} NMR spectra
were externally referenced against 85% o-H3PO4. Positive/negative
ion mass spectra were recorded on a Micromass Q-TOF instrument
by using electrospray (ES) ionization. Ru3(CO)12 and Ir4(CO)12 were
obtained from STREM and were used without further purification.
HIrRu3(CO)13 [12], [PPN][IrRu3(CO)13] [12], [AuPPh3][NO3] [13] and
[(AuPPh3)3O][BF4] [14] were prepared according to the previously
reported procedures. Product separations were performed by TLC
in air on Analtech 0.25 silica gel 60 Å F254 glass plates. Dynamic
NMR simulations for compound 3 were performed by using the
SpinWorks program [15]. The exchange rates were determined at
seven different temperatures in the temperature range ꢀ60
to þ20 ꢁC. The activation parameters were determined from a least-
iridiumerutheniumegold carbonyl cluster complexes [10]. In the
ꢀ
course of our studies of the chemistry of [IrRu3(CO)13
]
[11], we
have investigated its reactions with [AuPPh3]NO3 and [(AuPPh3)3O]
* Corresponding author.
E-mail address: Adams@mail.chem.sc.edu (R.D. Adams).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.01.012

R.D. Adams et al. / Journal of Organometallic Chemistry 706-707 (2012) 20e25
21
squares Eyring plot by using the program Microsoft Excel 2007:
[IrRu3(CO)13] dissolved in 30 mL of THF. After 2h at 25 ꢁC, the
solvent was removed in vacuo, and the product was then isolated
by TLC using a 2:1 hexane/methylene chloride solvent mixture.
32.24 mg of 3 (84% yield) was obtained.
6
Hz ¼ 48.8(5) kJ molꢀ1
,
6
Sz ¼ 17.3(5) J molꢀ1 Kꢀ1
.
2.1. Reaction of HIrRu3(CO)13 with [(AuPPh3)3O][BF4]
2.3.1. Crystallographic analyses
A mixture of 18.70 mg (0.01263 mmol) of [(AuPPh3)3O][BF4] and
21.35 mg (0.02481 mmol) of HIrRu3(CO)13 was stirred in 30 mL of THF
for 2 h. The solvent was removed in vacuo, and the product was then
isolated by TLC by using a 4:1 hexane/methylene chloride solvent
mixture to yield in order of elution the following: 5.8 mg (36.8%) of
Ru3(CO)12, 1.2 mg (6.3%) of H2Ru4(CO)13, 2.3 mg (7% yield) of IrRu3(-
CO)13AuPPh3, 1, 3.2 mg (7.3% yield) of HIrRu3(CO)12(AuPPh3)2, 2 and
1.6 mg (2.9% yield) of IrRu3(CO)12(AuPPh3)3, 3, and some uncharac-
terized compounds. Spectral data for 1: IR nCO (cmꢀ1 in CH2Cl2):
2084(m), 2041(s), 2007(m),1990(m),1844(w).1H NMR (CD2Cl2, 25 ꢁC,
Red single crystals of 1, orange single crystals of 2 and black
single crystals of 3 suitable for x-ray diffraction analyses were all
obtained by slow evaporation of solvent from solutions of the pure
compounds in hexane/methylene chloride solvent mixture
at ꢀ25 ꢁC. Each data crystal was glued onto the end of a thin glass
fiber. X-ray intensity data were measured by using a Bruker SMART
APEX CCD-based diffractometer by using Mo
Ka radiation
(l
¼ 0.71073 Å). The raw data frames were integrated with the
SAINT þ program by using a narrow-frame integration algorithm
[16]. Correction for Lorentz and polarization effects were also
applied using SAINTþ. An empirical absorption correction based on
the multiple measurement of equivalent reflections was applied
using the program SADABS. All structures were solved by a combi-
nation of direct methods and difference Fourier syntheses, and
were refined by full-matrix least-squares on F2 by using the
SHELXTL software package [17]. All non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydrogen
atoms were placed in geometrically idealized positions and
included as standard riding atoms during the least-squares
refinements. Crystal data, data collection parameters, and results
of the analyses are listed in Table 1.
TMS)
d
¼ 7.29e7.55 (m, 15H, Ph). 31P{1H} NMR (CD2Cl2, 25 ꢁC),
d
¼ 73.85 (s,1P, PeAu). Mass Spec: ES-/MS m/z ¼ 1365 (M þ CO2Hꢀ).
Spectraldatafor2:IRnCO (cmꢀ1 inCH2Cl2):2070(s), 2046(s), 2009(vs),
1961(m),1809(w).1HNMR(CD2Cl2, 25ꢁC, TMS)
d
¼ 7.08e7.52(m, 30H,
Ph),
d
¼ ꢀ17.43 (s,1H, hydride). 31P{1H} NMR (CD2Cl2, 25 ꢁC)
¼ 70.20
d
(s, 2P); at ꢀ80 ꢁC in CD2Cl2:
¼ 70.23 (s,1P), 67.67 (s, 1P). Mass Spec:
d
ESþ/MS, m/z ¼ 1752 Mþ. Spectral data for 3: IR nCO (cmꢀ1 in CH2Cl2):
2051(vs), 2010(vs), 1986(s), 1955(m), 1914(w), 1784(br). 1H NMR
(CD2Cl2, 25 ꢁC, TMS)
d
¼ 7.12e7.33 (m, 45H, Ph). 31P{1H} NMR (CD2Cl2,
25 ꢁC)
d
¼ 65.59 (s, 3P, PeAu); at ꢀ80 ꢁC
¼ 68.47 (2P) and 58.00 (1P).
d
Mass Spec: ESþ/MS, m/z ¼ 2210.
Compound 1 crystallized in the monoclinic crystal system. The
space group P21/n was indicated by the unique pattern of system-
atic absences observed in the data and was confirmed by the
successful solution and refinement of the structure. Compounds 2
and 3 both crystallized in the triclinic crystal system. The space
2.2. Improved synthesis of IrRu3(CO)13AuPPh3, 1
11.2 mg (0.0215 mmol) of [AuPPh3][NO3] was added to a 100 mL
three neck flask with a solution of 30.0 mg (0.0215 mmol) [PPN]
[IrRu3(CO)13] in 30 mL THF. The solvent was removed in vacuo after
15 min at room temperature, and the product was then isolated by
TLC using a 4:1 hexane/methylene chloride solvent mixture:
23.3 mg of 1 (82% yield) was obtained.
‾
group P1 was assumed in both cases and was confirmed by the
successful solutions and refinements of the structures. For the
structure of 2, there were two independent molecules of the
complex and two hexane molecules from the crystallization solvent
present in the asymmetric unit. The hydride ligand was located
along one of the RueRu bonds in each molecule. The hydride ligand
in both molecules was refined with fixed RueH bond distances
(1.75Å). The iridium atom Ir(1) and the ruthenium atom Ru(3) in
2.3. Improved synthesis of 3
To a 100 mL three neck flask, 25.8 mg (0.0174 mmol) of [(AuP-
Ph3)3O][BF4] was added to 24.37 mg (0.0174 mmol) of [PPN]
Table 1
Crystallographic data for compounds 1e3.
Compound
1
2
3
Empirical formula
Formula weight
Crystal system
Lattice parameters
a (Å)
C
31H15O13PAuIrRu3
C48H31O12P2Au2IrRu3∙C6H14
1837.18
Triclinic
C66H45O12P3Au3IrRu3
2209.24
Triclinic
1318.78
Monoclinic
16.6814(6)
9.7331(4)
22.0846(8)
90
99.996(1)
90
3531.3(2)
P21/n
4
13.7813(6)
20.8227(9)
20.8318(9)
90.055(1)
100.701(1)
96.540(1)
5834.3(4)
Pꢀ1
13.4662(3)
14.7194(3)
19.1092(4)
107.322(1)
99.010(1)
109.378(1)
3271.04(12)
Pꢀ1
b (Å)
c (Å)
a
b
g
(deg)
(deg)
(deg)
V (Å3)
Space group
Z value
4
2
r
m
calc (g/cm3)
2.481
9.257
2.092
8.150
2.243
9.534
(Mo K
a
) (mm-1)
Temperature (K)
max (ꢁ)
No. Obs. (I > 2
No. Parameters
294(2)
50.04
6239
294(2)
48.22
18532
1161
293(2)
50.04
11556
794
2
Q
s
(I))
451
Goodness of fit (GOF)
1.096
1.026
1.094
Max. shift in cycle
0.001
0.002
0.001
Residualsa: R1; wR2
0.0220; 0.0545
1.000/0.423
2.146
0.0686; 0.1413
1.000/0.689
1.738
0.0321; 0.0734
1.000/0.628
4.287
Absorption Correction Max/min
Largest peak in Final Diff. Map (eꢀ/Å3)
P
P
R ¼ Shkl(rrFobsrꢀrFcalcrr)/ShklrFobsr; Rw ¼ ½ hklwðjFobsj ꢀ jFcalcjÞ2= hklwF2obsꢂ1=2; w ¼ 1/
s
2(Fobs); GOF ¼ [Shklw(rFobsrꢀrFcalcr)2/(ndataꢀnvari)]1/2
.
a

22
R.D. Adams et al. / Journal of Organometallic Chemistry 706-707 (2012) 20e25
compound 3 were disordered in the solid state. The occupancies of
these two atoms were refined by using EXYZ and EADP constraints.
The occupancies in the final cycle of refinement were 0.78/0.22.
triangular faces of an Ir6 octahedron. If the AuPPh3 group is consid-
ered as a one electron donor to the IrRu3 tetrahedron, then the IrRu3
cluster contains a total of 60 valence electrons which means that the
Ir atom and each of the Ru atoms formally have 18 electron
configurations.
3. Results and discussion
An ORTEP diagram of the molecular structure of compound 2 is
shown in Fig. 2. The metal cluster in 2 can be described as an
Au(PPh3) capped trigonal-bipyramidal AuIrRu3 cluster, but this
AuIrRu3 cluster is not the same as that in 1. The Au atom in AuIrRu3
cluster in 2 caps an IrRu2 triangle not the Ru3 triangle as in 1 and the
Au(PPh3) cap on that bridges one of the AuIrRu triangles. The AueAu
bond distance, Au(1)eAu(2) ¼ 2.8563(10) Å, is slightly longer than
the AueAu bond distance in the Au2CoRu3 compound HCoR-
u3(CO)13(AuPPh3)2, 5, 2.787 (1) Å, which contains an Au(PPh3)
capping group on a trigonal-bipyramidal AuCoRu3 cluster that has
a similar structure to 2.10a Compound 2 contains one hydride ligand,
Three new IrRuAu compounds: IrRu3(CO)13(AuPPh3), 1 (7%
yield), HIrRu3(CO)12(AuPPh3)2,
2 (7.3% yield) and IrRu3(CO)12
(AuPPh3)3, 3 (2.9% yield) were obtained from the reaction of
HIrRu3(CO)13 with [(AuPPh3)3O][BF4]. Compounds 1 and 3 were
subsequently obtained in much better yields (82%) and (84%) from
the reactions of [AuPPh3][NO3] and [(AuPPh3)3O][BF4] with [PPN]
[IrRu3(CO)13], respectively, see Scheme 1. Each of the new
complexes was characterized by a combination of IR, 1H NMR, mass
spectral and single crystal X-ray diffraction analyses.
An ORTEP diagram of the molecular structure of compound 1 is
shown in Fig.1. The basic framework of the IrRu3Au metal cluster in 1
is best described as an Au-capped IrRu3 tetrahedron. The Au atom
caps the Ru3 triangle. The RueAu distances in 1 span a considerable
range, Au(1)eRu(1) ¼ 3.0056(4) Å, Au(1)eRu(2) ¼ 2.8063(4) Å,
Au(1)eRu(3) ¼ 2.7486(4) Å, and this may be related to the unsym-
metric distribution of the CO ligands on the Ru atoms, see below.
Compound 1 is similar to the CoRu3Au compound CoRu3(CO)13
AuPPh3, 4, but in 4 the Au atom caps one of the CoRu2 triangles of the
CoRu3 tetrahedron[18]. Forcomparison, the AueRudistancesin 4 are
2.776(1) Å and 2.774(1) Å. Two of the three RueRu bonds in 1 contain
bridging CO ligands and the associated RueRu bond distances,
Ru(1)eRu(2) ¼ 2.8266(5) Å, Ru(1)eRu(3) ¼ 2.7918(5) Å, are signifi-
cantly shorter than the third RueRu bond distance, Ru(2)e
Ru(3) ¼ 3.0064(5) Å, which has no bridging CO ligand. The IreRu
bond distances, Ir(1)eRu(1) ¼ 2.7586(4) Å, Ir(1)eRu(2) ¼ 2.7336(4)
Å, and Ir(1)eRu(3) ¼ 2.7643(4) Å, are similar to the IreRu bond
distances, 2.680(4) Åe2.771(5) Å in the compound [PPh4][Ir6Ru3
(CO)21(AuPPh3)]10a which contains Ru(CO)3 capping groups on three
d
¼ ꢀ17.43 in the H NMR spectrum, which was found to bridge the
Ru(1)eRu(2) bond. As a result, the associated Ru(1)eRu(2) bond
distance is elongated, 2.992(2) Å, due to the presence of this ligand
[19]. Otherwise, the IreRu and RueRu distances in 2 are similar to
those observed in 1. Compound 2 exhibits only one phosphorus
resonance at
ture, but it shows two resonances as expected at
d
¼ 70.20 in its 31P NMR spectrum at room tempera-
d
¼ 70.23 and 67.67
at ꢀ80 ꢁC. This temperature dependence can be explained by
a dynamical exchange process that leads to an interchange of the
environments of the two inequivalent Au(PPh3) groups in 2 on the
NMR timescale at room temperature. A possible mechanism is
illustrated by shifts of the Au2 group to each of the IrRu2 triangles by
using the Ir atom as a pivot point such as shown in Scheme 2.
A number of examples of similarly structured metal cluster
complexes containing Au(PPh3) groups have been reported to
exhibit similar molecular dynamics [20]. As in 1, if each of the
AuPPh3 group is considered as a one electron donor to the IrRu3
tetrahedron, then the IrRu3 cluster contains a total of 60 valence
PPh3
Au
Ir
+[AuPPh3][NO3]
82% yield
Ru
Ru
Ru
Ru
Ru
Ir
Ru
1
-
[IrRu3(CO)13
]
PPh3
Au
PPh3
Au
+[(AuPPh3)3O][BF4]
HIrRu3(CO)13
Ru
Ru
Ir
H
2
Ru
PPh3
Au
Ir
PPh3
Ph3P
+[(AuPPh 3)3O][BF4]
84% yield
Ru
Au
Au
Ru
Ir
Ru
Ru
Ru
Ru
-
[IrRu3(CO)13
]
3
Scheme 1. IrRu3Aun complexes obtained from reaction of IrRu3 complexes with Au cations.

R.D. Adams et al. / Journal of Organometallic Chemistry 706-707 (2012) 20e25
23
Scheme 2. A proposed mechanism for the dynamical averaging of the Au(PPh3)
groups in compound 2.
electrons and the Ir atom and each of the Ru atoms formally have 18
electron configurations.
An ORTEP diagram of the molecular structure of compound 3 is
shown in Fig. 3. Compound 3 contains three Au(PPh3) groups
combined with the IrRu3 cluster of the original reagents HIr-
Ru3(CO)13 or anion [IrRu3(CO)13]ꢀ. The metal cluster in 3 can be
described in different ways. It could be described as an IrRu3
tetrahedron with three bridging three Au(PPh3) groups. Alterna-
tively, the cluster could be described as a seven atom pentagonal
bipyramidal Au3IrRu3 cluster with an additional bond between the
apical atoms Ir(1) and Ru(3), Ir(1) - Ru(3), 2.8770(5) Å. The other
IreRu bond distances are Ir(1)eRu(1) ¼ 2.8406(6) Å and Ir(1)e
Ru(2) ¼ 2.9387(6) Å. There are two bridging CO ligands that
bridge the Ir(1)eRu(1) and Ru(2)eRu(3) bonds. The Au(PPh3)
groups are mutually bonded, but the AueAu bond distances,
Au(1)eAu(2) ¼ 2.9781(4) Å, Au(1)eAu(3) ¼ 2.9726(4) Å, are
significantly longer than that in 2, but are still within the normal
bonding range. For comparison, the AueAu bond distances in the
octahedral hexagold complex[Au6{P-p-tolyl3}][BPh4]2 range from
2.932(2) Åe3.091(2) Å [21]. If one considers compound 3 as a IrRu3
Fig. 1. AnORTEPdiagramofthemolecularstructureofIrRu3(CO)13(AuPPh3),1showing20%
thermal ellipsoidprobabilities. Selected interatomic bonddistances (Å)and angles(o)are as
follows: Au(1)eRu(1) ¼ 3.0056(4), Au(1)eRu(2) ¼ 2.8063(4), Au(1)eRu(3) ¼ 2.7486(4),
Ir(1)eRu(1) ¼ 2.7586(4), Ir(1)eRu(2)
¼ 2.7336(4), Ir(1)eRu(3) ¼ 2.7643(4), Ru(1)e
Ru(2) ¼ 2.8266(5), Ru(1)eRu(3) ¼ 2.7918(5), Ru(2)eRu(3) ¼ 3.0064(5); Au(1)eRu(1)e
Ir(1) ¼ 102.433(12), Au(1)eRu(2)eIr(1) ¼ 108.489(13), Au(1)eRu(2)eIr(1) ¼ 109.278(13).
Fig. 3. An ORTEP diagram of the molecular structure of IrRu3(CO)12(AuPPh3)3,
3
showing 20% thermal ellipsoid probabilities. Selected interatomic bond distances (Å)
and angles (o) are as follows: Au(1)eAu(2) ¼ 2.9781(4), Au(1)eAu(3) ¼ 2.9726(4),
Au(1)eIr(1) ¼ 2.8243(4), Au(1)eRu(3) ¼ 2.8692(5), Au(2)eIr(1) ¼ 2.8829(4), Au(2)e
Fig. 2. An ORTEP diagram of the molecular structure of HIrRu3(CO)12(AuPPh3)2, 2
showing 20% thermal ellipsoid probabilities. Selected interatomic bond distances (Å) and
angles (o) are as follows: Au(1)eAu(2) ¼ 2.8563(10), Au(1)eIr(1) ¼ 2.7769(10), Au(1)e
Ru(1)
Ru(2)
Ru(2)
Ru(3)
¼
¼
¼
¼
2.8878(6), Au(2)eRu(3)
2.9674(6), Au(3)eRu(3)
2.9387(6), Ir(1)eRu(3)
3.0959(7), Ru(2)eRu(3)
¼
¼
2.7596(5), Au(3)eIr(1)
2.8206(5), Ir(1)eRu(1)
2.8770(5), Ru(1)eRu(2)
¼
2.8107(4), Au(3)e
2.8406(6), Ir(1)e
2.8334(8), Ru(1)e
Ru(2)
Ru(3)
Ru(3)
¼
¼
¼
3.0746(16), Au(1)eRu(3)
2.8555(16), Ir(1)eRu(1)
¼
¼
2.8049(15), Au(2)eIr(1)
2.7597(17), Ir(1)eRu(2)
¼
2.7908(10), Au(2)e
2.7915(16), Ir(1)e
¼
¼
¼
¼
2.9606(16), Ru(1)eRu(2)
¼
2.992(2), Ru(1)eRu(3)
¼
2.749(2), Ru(2)e
¼
2.8895(7); Au(1)eIr(1)eRu(1)
¼
116.201(16),
Ru(3) ¼ 2.9621(19); Au(1)eIr(1)eRu(1) ¼ 111.91(4), Au(1)eRu(2)eRu(1) ¼ 98.25(5),
Au(1)eIr(1)eRu(2) ¼ 112.975(16), Au(1)eAu(2)eRu(1) ¼ 110.138(14), Au(1)eAu(3)e
Au(1)eRu(3)eRu(1)
¼
111.38(6), Au(1)eAu(2)eRu(3)
¼
58.82(3), Au(1)eAu(2)e
Ru(2)
Ru(3)
¼
¼
107.993(14),
60.698(11),
Au(2)eAu(1)eAu(3)
Au(2)eIr(1)eAu(3)
¼
103.828(10), Ir(1)eAu(1)e
110.692(13), Au(2)eRu(3)e
Ir(1) ¼ 58.90(3), Au(2)eAu(1)eRu(2) ¼ 105.67(4), Au(2)eIr(1)eRu(1) ¼ 101.18(4), Au(2)e
Ir(1)eRu(2)¼ 115.77(4), Au(2)eRu(3)eRu(1)¼99.84(6),Au(2)eRu(3)eRu(2) ¼108.72(5).
¼
Au(3) ¼ 114.137(16), Au(2)eRu(1)eRu(2) ¼ 107.14(2), Au(3)eRu(2)eRu(1) ¼ 108.75(2).

24
R.D. Adams et al. / Journal of Organometallic Chemistry 706-707 (2012) 20e25
Fig. 4. 31P {H} NMR spectra for compound 3 in CD2Cl2 solvent at various temperatures.
tetrahedron with three one electron Au(PPh3) donors, then the
cluster contains a total of 60 electrons and the Ir and each of the Ru
atoms will formally have 18 electron configurations. Two related
M4(AuPPh3)3 complexes have been reported. These are
H2Ru4(CO)12(AuPPh3)3, 5 [22,23] and CoRu3(CO)12(AuPPh3)3, 6 [18].
The structures of the clusters of these two compounds both contain
(AuPPh3)3 groups in which the central Au atom forms a m3-bridge
across a triangle of the M4 cluster, A, but in 3 the central Au atom
bridges the IreRu edge of the transition metal M4 cluster, B.
uncharged. It is believed that the oxonium oxygen atom of the
cation [(AuPPh3)3O]þ combines with CO to oxidize it to CO2. As
a result, two electrons are formally released from the oxonium
oxygen atom for use in cluster bonding. Thus, the overall reaction
that leads to the formation of 3 can be written as shown in eq. (1).
[IrRu3(CO)13]- þ [(AuPPh3)3O]þ / IrRu3(CO)12(AuPPh3)3 þ CO2 (1)
A similar transformation was proposed for the formation of
compound 6 from the reaction of [(AuPPh3)3O][BF4] with [PPN]
[CoRu3(CO)13] [18].
As with 2, the 31P NMR spectrum of 3 exhibits only one phos-
phorus resonance at room temperature at
d
¼ 65.59, but shows two
resonances in a 2/1 ratio resonances as expected at
d
¼ 68.47 (2P)
and 58.00 (1P) at ꢀ80 ꢁC. As the temperature is raised, the two
resonances broaden and coalesce in
a process indicative of
a dynamical averaging. These spectra are shown in Fig. 4. The
broadened spectra were simulated in order to obtain exchange
rates and activation parameters for the exchange process. The
simulated spectra are shown in Figure S1 in the Supporting Infor-
mation. From these data the activation parameters were deter-
mined
6
Hz
¼
48.8(5) kJ.molꢀ1
,
6
Sz
¼
17.3(5) J.molꢀ1Kꢀ1
.
Dynamical activity in polynuclear metal complexes containing
Au(PPh3) groups has been observed previously [22,24,26]. Note: the
addition of free PPh3 to our NMR samples of 3 did not affect the
exchange broadened spectra, so a mechanism that involves simple
The stoichiometry of the reaction of [(AuPPh3)3O][BF4] with
[PPN][IrRu3(CO)13
] is an unusual, in that the monoanion
ꢀ
[IrRu3(CO)13
]
cannot add three [Au(PPh3)]þ groups and remain
Scheme 3. A proposed mechanism for the dynamical averaging of the Au(PPh3) groups in compound 3.

R.D. Adams et al. / Journal of Organometallic Chemistry 706-707 (2012) 20e25
25
dissociation of PPh3 from the gold atoms is ruled out. Therefore,
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