Synthesis and characterization of high-nuclearity iridiumruthenium and -gold mixed-metal carbonyl clusters, [Ir7Ru3(CO)23]

Article abstract of DOI:10.1039/b003100n

The new carbonyl cluster [PPh₄][Ir,Ru₃(CO)₂₃] 1 has been obtained by the high yield reaction of [PPh₄]₂[Ir₆(CO),₅] with [Ru₃(CO)₁₂] in the presence of p-toluenesulfonic acid. The monoanionic decanuclear cluster 1 has an octahedral arrangement of the iridium atoms with three ruthenium atoms and an iridium atom tetrahedrally capping four triangular faces. Two terminal CO ligands are bound to each iridium atom and three to each ruthenium atom. In this synthesisp-toluenesulfonic acid served as a degradation reagent for [Ir₆(CO)₁₅]^2- to generate the capping {Ir(CO)2}+ moiety. Reaction of 1 with [AuCl(PPh₃)] in the presence of AgOSO2CF3 at ambient temperature yielded the undecanuclear neutral cluster [Ir₇Ru₃(CO)1(AuPPh₃)]₂. The {AuPPh₃}⁺ group co-ordinates to the apical iridium atom of the parent metal carbonyl monoanion 1 maintaining the cluster framework as well as the stereogeometry of the CO ligands. Thermal treatment of 1 with [AuCl(PPh₃)] in refluxing 1,2-dichloroethane caused substitution of the capping {Ir(CO)₂}⁺ group in 1 with an isolobal {AuPPh3}+ group, resulting in the formation of decanuclear monoanionic cluster [PPh₄][Ir₆Ru₃(CO)₂1(AuPPh ₃)]₃. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b003100n

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Synthesis and characterization of high-nuclearity iridium–
ruthenium and –gold mixed-metal carbonyl clusters,
[Ir7Ru3(CO)23]؊, [Ir7Ru3(CO)23(AuPPh3)] and [Ir6Ru3(CO)21-
(AuPPh3)]؊, possessing tetrahedrally capped octahedral iridium
cores obtained by capping reactions with [Ru3(CO)12] and
[AuCl(PPh3)]
Teiji Chihara,*a Mayumi Sato,b Hiromi Konomoto,b Satoshi Kamiguchi,a Haruo Ogawab and
Yasuo Wakatsukia
a The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198,
Japan. E-mail: chihara@postman.riken.go.jp
b Department of Chemistry, Tokyo Gakugei University, Koganei-shi, Tokyo 184-8501, Japan
Received 17th April 2000, Accepted 6th June 2000
Published on the Web 30th June 2000
The new carbonyl cluster [PPh4][Ir7Ru3(CO)23] 1 has been obtained by the high yield reaction of [PPh4]2[Ir6(CO)15]
with [Ru3(CO)12] in the presence of p-toluenesulfonic acid. The monoanionic decanuclear cluster 1 has an octahedral
arrangement of the iridium atoms with three ruthenium atoms and an iridium atom tetrahedrally capping four
triangular faces. Two terminal CO ligands are bound to each iridium atom and three to each ruthenium atom.
In this synthesis p-toluenesulfonic acid served as a degradation reagent for [Ir6(CO)15]2Ϫ to generate the capping
{Ir(CO)2}ϩ moiety. Reaction of 1 with [AuCl(PPh3)] in the presence of AgOSO2CF3 at ambient temperature yielded
the undecanuclear neutral cluster [Ir7Ru3(CO)23(AuPPh3)] 2. The {AuPPh3}ϩ group co-ordinates to the apical iridium
atom of the parent metal carbonyl monoanion 1 maintaining the cluster framework as well as the stereogeometry of
the CO ligands. Thermal treatment of 1 with [AuCl(PPh3)] in refluxing 1,2-dichloroethane caused substitution of the
capping {Ir(CO)2}ϩ group in 1 with an isolobal {AuPPh3}ϩ group, resulting in the formation of decanuclear
monoanionic cluster [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3.
way, the decaruthenium nitrido cluster [Ru10N(CO)24]Ϫ has
Introduction
selectively been obtained from [Ru6N(CO)16]Ϫ and [Ru3(CO)12].
The most symmetric decanuclear clusters have the shape of a
tetrahedron formed by capping of the central octahedral unit
In both cases a neutral {Ru(CO)3} unit produced by pyrolysis
of [Ru3(CO)12], which is unstable above 120 ЊC in both solu-
with four metal atoms. Non-carbonyl cluster complexes
tion and the solid state, capped the octahedron of the Ru6
[Hg6Rh4(PMe3)12],1 [Hg6Pt4(dipb)4] (dipb = (i-Pr)2P(CH2)4-
cluster framework. The compound [Ru3(CO)12] has a rich
P(i-Pr)2)2 and [Cu6Re4H24(PPh3)8]2ϩ 3 have been reported.
chemistry in homogeneous catalysis due to the active Ru–Ru
[Cu6Fe4(CO)16]2Ϫ 4 is an example of a carbonyl cluster which is
bonds.11
important as a model of CO adsorption on the surface of cubic
close-packed (ccp) metal arrays. Although various clusters have
been reported, the systematic synthesis of high-nuclear mixed
metal carbonyls has proved to be difficult. Most of the reported
clusters are incidental products obtained in very small amounts,
and their determination is restricted to single crystal structure
analysis.
However, the reaction of the interstitial hexaruthenium
species with [Ru3(CO)12] did not prove to be a generally applic-
able route to tetracapped octahedral clusters.9 Various metals
form clusters with an octahedral metal framework.12 The
dianionic iridium complex [Ir6(CO)15]2Ϫ 13 is one example. This
complex was chosen as a starting material for the synthesis of
mixed metal clusters by thermolytic reaction with [Ru3(CO)12]
because of its thermal stability up to 200 ЊC, easy accessibility
and possession of negative charges for redox condensation.
Many examples of Ir–Ru mixed metal clusters have been
reported, however the clusters of the highest nuclearities are
hexanuclear species: [Ir2Ru4B(CO)16]2Ϫ and its triphenylphos-
phine gold derivative [Ir2Ru4B(CO)16(AuPPh3)]Ϫ.14 In this paper
we report the syntheses of novel high-nuclearity IrRu clusters
with capping {Ru(CO)3} groups.
Several decanuclear osmium carbonyl clusters of large tetra-
hedral metal cores, e.g. [Os10H2C(CO)24]5 and [Os10C(CO)24]2Ϫ 6
,
have been synthesized by pyrolysis of [Os3(CO)12] or
[Os3(CO)11(py)]. Pyrolysis of [Os3(CO)10(NCMe)2] at temper-
atures above 260 ЊC under vacuum led to the larger cluster
[Os20(CO)40] of the same Td symmetry.7 This thermolytic
method is also applicable to synthesis of the corresponding
decanuclear ruthenium cluster [Ru10N(CO)24]Ϫ, which had been
obtained directly from [Ru3(CO)12] by reaction with 1/3 equiv-
alent of [N(PPh3)2][N3] under thermolysis in bis(2-methoxy-
ethyl) ether (diglyme).8,9 The improved synthesis of the
decanuclear nitridoruthenium cluster is slightly different from
that of osmium. We previously reported a high-yield repro-
ducible synthesis of the decaruthenium carbido dianion
[Ru10C(CO)24]2Ϫ by redox condensation of the interstitial
carbido dianion [Ru6C(CO)16]2Ϫ with [Ru3(CO)12].10 In the same
Results and discussion
Synthesis of [PPh4][Ir7Ru3(CO)23] 1
A solution of [PPh4]2[Ir6(CO)15] and [Ru3(CO)12] in diglyme was
refluxed (161 ЊC) under argon and after 4 h no starting material,
[PPh4]2[Ir6(CO)15], was observed by IR. When the [N(PPh3)2]ϩ
DOI: 10.1039/b003100n
J. Chem. Soc., Dalton Trans., 2000, 2295–2299
This journal is © The Royal Society of Chemistry 2000
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Table 1 Selected bond lengths (Å) for [N{P(C6H4Me-p)3}2][Ir7Ru3-
(CO)23] 1a
and crystal structure determination. All the carbonyl ligands
are terminally bonded and essentially linear.
The cluster is a monoanion so it cannot be formulated as
[Ir6Ru4(CO)23]2Ϫ, which corresponds to the simple addition
product of four {Ru(CO)3} groups to the Ir6 metal core. No
resonance characteristic for an M–H linkage was detected in the
1H NMR spectrum of 1 (δ Ϫ100 to ϩ100) and no reaction was
observed with [OH]Ϫ. Thus 1 is not a protonated product
formulated as [Ir6Ru4H(CO)23]Ϫ with four tetrahedrally capping
ruthenium atoms and 134 valence electrons, which we initially
assumed. Twentyfour carbonyl ligands are necessary for the
assignment of two carbonyl groups to each iridium atom and
three to each ruthenium atom of [Ir6Ru4(CO)23]2Ϫ or [Ir6Ru4-
H(CO)23]Ϫ, provided that there are no bridging carbonyl
groups. All the known anionic and neutral decanuclear
carbonyl clusters of the same metal framework have only
terminally co-ordinated carbonyl ligands and no bridging
carbonyl ligands have been reported.4–6,8–10,15 From the isotope
shift of the Mössbauer spectrum of [N(PPh3)2]2[Ru10C(CO)24]
at 5 K the state of the ruthenium atoms has been revealed to be
essentially neutral,16 which shows that the negative charges are
located not on the ruthenium atoms but on the CO ligands.
Strong electron-withdrawing groups such as bridging or
capping CO ligands are not appropriate for such high-
nuclearity complexes. Consequently, cluster 1 was produced by
incorporation of the capping {Ir(CO)2}ϩ moiety to avoid the
deficiency in the number of terminally bound carbonyl ligands.
The effect of the addition of p-toluenesulfonic acid was
examined. Product 1 was fairly stable, and was quantitatively
recovered after treatment with an equimolar amount of
p-toluenesulfonic acid at reflux temperature in diglyme for 1 h.
One third of [PPh4]2[Ir6(CO)15] was decomposed by heating at
120 ЊC for 1 h in the presence of p-toluenesulfonic acid in
diglyme and practically all was decomposed by heating at
140 ЊC for 30 min, whereas in the absence of the acid no break-
down was detected after refluxing for 4 h in diglyme. Con-
sequently, protonation served to decompose the [Ir6(CO)15]2Ϫ to
produce {Ir(CO)2}ϩ, in accordance with the different reactivity
Ir1–Ir2
Ir1–Ir3
Ir1–Ir4
Ir1–Ir5
Ir1–Ir7
Ir1–Ru1
Ir2–Ir3
Ir2–Ir5
Ir2–Ir6
Ir2–Ir7
Ir2–Ru2
Ir3–Ir4
Ir3–Ir6
Ir3–Ir7
2.761(1)
2.752(1)
2.757(1)
2.766(1)
2.939(1)
2.699(2)
2.735(1)
2.740(1)
2.738(1)
2.721(1)
2.730(2)
2.738(1)
2.736(1)
2.704(1)
Ir3–Ru3
Ir4–Ir5
Ir4–Ir6
Ir4–Ru1
Ir4–Ru3
Ir5–Ir6
Ir5–Ru1
Ir5–Ru2
Ir6–Ru2
Ir6–Ru3
Ir–C (mean)
Ru–C (mean)
IrO–C (mean)
RuO–C (mean)
2.742(2)
2.719(1)
2.736(1)
2.761(2)
2.742(2)
2.727(1)
2.758(2)
2.753(2)
2.767(2)
2.760(2)
1.854(11)
1.878(7)
1.154(6)
1.151(9)
Fig. 1 Anion structure of [N{P(C6H4Me-p)3}2][Ir7Ru3(CO)23] 1a with
labelling of selected atoms; carbon atoms have the same digit as the
oxygen atoms to which they are bonded.
of the counter cations of [Ir6(CO)15]2Ϫ
.
X-Ray studies of compound 1a confirmed that the Ir6 unit
has remained intact in the reaction with [Ru3(CO)12]. As shown
in Table 1, the Ir–Ir bond lengths in the octahedron range from
2.719(1) to 2.766(1) Å (average 2.742(4) Å). The corresponding
bond lengths in the parent molecule [Ir6(CO)15]2Ϫ and in the
neutral cluster [Ir6(CO)16] are in the ranges 2.730(1)–2.822(1)
(mean 2.773(8))13 and 2.743(2)–2.810(2) (mean 2.779 Å),17
respectively. The octahedron shrank slightly upon capping by
{Ru(CO)3} and {Ir(CO)2} groups as was also observed in the
or [N{P(C6H4Me-p)3}2]ϩ salt of [Ir6(CO)15]2Ϫ was employed as
the starting material the reaction time decreased to 2 or 1 h,
respectively, suggesting that the higher acidity of the counter
cation increased the reactivity. IR and X-ray analysis confirmed
that the anionic products of the cluster complexes were identi-
cal. The yields of the cluster anion were consistent with the
relative reactivity series of the counter cation, that is [N{P(C6H4-
Me-p)3}2]ϩ > [N(PPh3)2]ϩ > [PPh4]ϩ. The effect of proton addi-
tion was examined. In the presence of an equimolar amount of
p-toluenesulfonic acid the reaction between [PPh4]2[Ir6(CO)15]
and [Ru3(CO)12] was completed after 1 h heating at 120 ЊC. The
main product was purified by crystallization and analysed by
X-ray diffraction.
The cluster was formulated as [PPh4][Ir7Ru3(CO)23] 1, but
the single crystals of the [PPh4]ϩ salt were very thin plates
which were difficult fully to characterize. In order to obtain
better single crystals for X-ray analysis the [N(PPh3)2]ϩ and
[N{P(C6H4Me-p)3}2]ϩ salts were prepared. Well grown thick
single crystals of the latter were obtained and successfully char-
acterized by X-ray crystallography. The molecular structure of
the cluster anion of [N{P(C6H4Me-p)3}2][Ir7Ru3(CO)23] 1a is
shown in Fig. 1 and selected bond lengths are given in Table 1.
The cluster is a monoanion with a tetracapped octahedral metal
framework, which represents a rare example of a heteronuclear
IrRu cluster. The overall metal structure is identical to those of
[Ru10C(CO)24]2Ϫ, [Ru10N(CO)24]Ϫ and [Os10C(CO)24]2Ϫ contain-
ing 134 cluster valence electrons. Of the four capping metal
atoms, three are ruthenium and the fourth, quite unexpectedly,
is iridium. The assignment was confirmed by chemical analysis
formation of [Ru10C(CO)24]2Ϫ 10 from [Ru6C(CO)16]2Ϫ 18,19
The
.
capping {Ir(CO)2} group is asymmetric with one long (2.939(1)
Å) and two short bonds (2.721(1) and 2.704(1) Å) to the central
octahedron. Two kinds of triply bridging iridium–carbonyl
groups that are co-ordinated to the octahedral iridium metal
framework have been reported: {Ir(CO)3} in [Ir14(CO)27]Ϫ 20 and
{Ir(CO)2} in [Ir12(CO)24]2Ϫ 21
. The former is a symmetrical cap
with Ir–Ir distances in the range 2.674(1)–2.681(1) Å, and the
latter is an asymmetric cap with a longer Ir–Ir distance of
2.939(1) Å and shorter distances of 2.672(1) and 2.654(1) Å.
Similar to the latter case, the capping atom Ir7 in 1a adopts an
almost square planar co-ordination with respect to its two
terminal carbonyl ligands and iridium atoms (Ir2 and Ir3) and
interacts weakly with the axial Ir1.
There have been no examples of a Ru metal atom capping a
triangular face of iridium. The capping Ru–Ir distances in
compound 1a (mean 2.746(7) Å) are substantially equal to the
corresponding capping Ru–Ru distances in the structurally
similar clusters [Ru10C(CO)24]2Ϫ (mean 2.769(4) Å) but slightly
shorter than those in [Ru10N(CO)24]Ϫ (mean 2.788(3) Å). All the
carbonyls in 1a are terminal: two are connected to each iridium
atom and three to each ruthenium atom with bonding param-
2296
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Table 2 Selected bond lengths (Å) for [Ir7Ru3(CO)23(AuPPh3)] 2
Table 3 Selected bond lengths (Å) for [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3
Au–Ir7
Au–P
2.620(2)
2.269(8)
2.745(1)
2.752(1)
2.741(1)
2.754(2)
2.844(1)
2.701(2)
2.724(1)
2.741(1)
2.741(1)
2.729(2)
2.754(3)
2.738(1)
2.731(2)
Ir3–Ir7
Ir3–Ru3
Ir4–Ir5
Ir4–Ir6
Ir4–Ru1
Ir4–Ru3
Ir5–Ir6
Ir5–Ru1
Ir5–Ru2
Ir6–Ru2
Ir6–Ru3
Ir–C (mean)
Ru–C (mean)
IrO–C (mean)
RuO–C (mean)
2.699(1)
2.757(2)
2.721(1)
2.726(1)
2.765(2)
2.746(2)
2.733(1)
2.755(2)
2.753(2)
2.757(2)
2.770(2)
1.899(11)
1.896(10)
1.131(9)
1.124(16)
Au–Ir1
Au–Ir2
Au–Ir3
Au–P1
Ir1–Ir2
Ir1–Ir3
Ir1–Ir4
Ir1–Ir5
Ir1–Ru1
Ir2–Ir3
Ir2–Ir5
Ir2–Ir6
Ir2–Ru2
Ir3–Ir4
Ir3–Ir6
2.826(3)
2.812(2)
2.857(2)
2.22(1)
Ir3–Ru3
Ir4–Ir5
Ir4–Ir6
Ir4–Ru1
Ir4–Ru3
Ir5–Ir6
Ir5–Ru1
Ir5–Ru2
Ir6–Ru2
Ir6–Ru3
Ir–C (mean)
Ru–C (mean)
IrO–C (mean)
RuO–C (mean)
2.702(4)
2.730(3)
2.718(3)
2.755(6)
2.747(6)
2.724(4)
2.755(5)
2.771(5)
2.762(4)
2.759(4)
1.83(3)
Ir1–Ir2
Ir1–Ir3
Ir1–Ir4
Ir1–Ir5
Ir1–Ir7
Ir1–Ru1
Ir2–Ir3
Ir2–Ir5
Ir2–Ir6
Ir2–Ir7
Ir2–Ru2
Ir3–Ir4
Ir3–Ir6
2.771(3)
2.773(4)
2.753(2)
2.767(2)
2.696(5)
2.750(3)
2.766(3)
2.773(2)
2.680(4)
2.763(3)
2.762(2)
1.87(3)
1.19(3)
1.17(3)
Fig. 2 Structure of [Ir7Ru3(CO)23(AuPPh3)] 2. Details as in Fig. 1.
eters corresponding to those of normal iridium or ruthenium
carbonyl cluster complexes, respectively.
Fig. 3 Anion structure of [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3. Details as
in Fig. 1.
Synthesis of [Ir7Ru3(CO)23(AuPPh3)] 2
(Tables 1 and 2). On the other hand, the metal–carbon distances
of the terminal carbonyl ligands in 2 (mean 1.898(8) Å) are
longer than in 1a (mean 1.863(7) Å), and the C–O distances in
2 (mean 1.128(8) Å) are shorter than the corresponding dis-
tances in 1a (mean 1.153(4) Å). Neutralization of the negative
charge in 1a by addition of {AuPPh3}ϩ caused the decrease of
metal–carbonyl back bonding interactions.
Cluster 1 was allowed to react with [AuCl(PPh3)] in the
presence of AgOSO2CF3 at room temperature. The reaction
proceeded immediately to produce a neutral cluster. The IR
spectrum of the product exhibits bands similar to those of 1,
but shifted ca. 13 cmϪ1 to higher wavenumber, consistent with
the normal addition of the electrophilic gold fragment
{AuPPh3}ϩ to a parent cluster. The structure of the product
[Ir7Ru3(CO)23(AuPPh3)] 2 is shown in Fig. 2 and selected bond
lengths are presented in Table 2. The metal skeleton as well as
the terminal carbonyl group stereochemistry in 2 is practically
identical with that of 1a. Formally, addition of {AuPPh3}ϩ to
the less hindered apical iridium atom of 1 yielded 2. One of the
common metal–gold bond linkages is linear, as in Ir–Au
dinuclear complexes. However, there are no precedents of gold
ligands terminally co-ordinating to an iridium atom in cluster
complexes. The Ir–Au bond (2.620(2) Å) is markedly shorter
than the corresponding bonds (2.6569(6) to 3.007(3) Å) in
complexes where the gold atoms serve as bridging or face-
capping ligands: [Ir4(CO)10(PPh2)(µ-AuPPh3)],22 [Ir4(CO)11-
Synthesis of [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3
A solution of compound 1 and [AuCl(PPh3)] in 1,2-dichloro-
ethane was refluxed for 3 h until the ν(C᎐O) bands character-
᎐
istic for 1 disappeared. After chromatographic purification
followed by crystallization the main product was isolated. The
pattern of the ν(C᎐O) absorption bands is similar to that of 1.
᎐
However, each band is shifted by ca. 14 cmϪ1 to lower energy,
which indicates that the electron density on the metals has
increased. The structure of the product was confirmed by X-ray
single-crystal analysis. The molecular structure of the cluster
anion is shown in Fig. 3 and the selected bond lengths are listed
in Table 3. The product cluster [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3
was formed by replacement of the capping {Ir(CO)2}ϩ group in
1 with {AuPPh3}ϩ. In the reported reaction of [Pt6(µ-CO)6-
(µ-dppm)3] (dppm = Ph2PCH2PPh2) with [Ir(CO)4]Ϫ that gives
[Pt6(µ-CO)6(µ-dppm)3{µ3-Ir(CO)2}], the reagent acted as a
(PhPPPh)Ir4(CO)9(µ3-AuPEt3)(µ4-AuPEt3)],23
[Ir6(CO)15-
(µ3-AuPPh3)]Ϫ 24 and [Ir6(CO)15(µ-AuPPh3)(µ4-AuPPh3)].25
There are no significant differences between the Ir–Ir and
Ir–Ru bond lengths in the metal cores of compounds 1a and 2
J. Chem. Soc., Dalton Trans., 2000, 2295–2299
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Table 4 Crystallographic data for compounds 1a, 2 and 3
[N{P(C6H4Me-p)3}2][Ir7Ru3(CO)23]
[Ir7Ru3(CO)23(AuPPh3)]ؒ2CH2Cl2
[PPh4][Ir6Ru3(CO)21(AuPPh3)]
Chemical formula
Formula weight
Crystal system
Space group (no.)
a/Å
b/Å
c/Å
α/Њ
C42H42NP2ؒC23Ir7O23Ru3
2915.74
C41H15AuIr7O23PRu3ؒC2H4Cl4
2922.11
Monoclinic
P21/n (no. 14)
17.271(2)
17.957(4)
C24H20PؒC39H15AuIr6O21PRu3
2843.40
Triclinic
Triclinic
¯
¯
P1 (no. 2)
P1 (no. 2)
15.898(2)
22.118(2)
11.950(1)
94.89(2)
96.11(1)
105.50(2)
3997.7(9)
21
16.819(9)
17.188(4)
16.321(3)
110.74(2)
112.47(3)
64.29(4)
3827(3)
21
21.029(3)
β/Њ
111.525(10)
γ/Њ
U/Å3
6067(2)
21
T/ЊC
Z
2
4
2
µ/cmϪ1 (Mo-Kα)
Measured reflections
Unique observed
reflections
Final R (RЈ)
122.89
15446
8020
187.43
12874
8028
130.12
12393
5688
0.042 (0.048)
0.051 (0.054)
0.064 (0.069)
source of {Ir(CO)2}Ϫ, which serves as a 2-electron ligand.
Comparison of [Pt6(µ-CO)6(µ-dppm)3(µ3-AuPPh3)2] with [Pt6-
(µ-CO)6(µ-dppm)3{µ3-Ir(CO)2}(µ3-AuPPh3)] suggests that the
{Ir(CO)2}ϩ group is isolobal with {AuPPh3}ϩ even though the
latter complex has not fully been characterized.26 In this study
comparison of 1a and 3 clearly shows that the {Ir(CO2)}ϩ
group, originating from decomposition of [Ir6(CO)15]2Ϫ by pro-
tonation, is isolobal with the {AuPPh3}ϩ group. Note that the
electron count used is for the Ir6Ru3 unit only, counting either
the {Ir(CO)2}ϩ or {AuPPh3}ϩ units as a 0-electron ligand. This
treatment is appropriate since the similarity in structures of the
Ir6Ru3 cores in 1a and 3 is then emphasized, but it is also
possible to consider the adducts as decanuclear clusters and
then 1a and 3 are not strictly isoelectronic.
The monoanion 3 exhibits an approximate C3 symmetry.
There is little asymmetry in the capping mode of AuPPh3 as
indicated by the 2.812(2)–2.857(2) Å Ir–Au distances in 3,
which are in the expected range for Ir–Au single bonds as men-
tioned above. There are no significant differences between Ir–Ir
and Ir–Ru bond lengths in complexes 1a and 3.
The metal core of compound 3 may be viewed as being
derived by addition of a capping {AuPPh3}ϩ group to the
Ir6Ru3 metal framework in [Ir6Ru3(CO)21]2Ϫ, which is assumed
to have 122 valence electrons. On the other hand, the corre-
sponding osmium cluster complex [Os9H(CO)24]Ϫ with a tri-
capped octahedral metal core has been reported.27 The three Ru
atoms in 3 lie below the plane defined by Ir1, Ir2 and Ir3 with
an average deviation of 0.089 Å. For [Os9H(CO)24]Ϫ there is an
average deviation of 0.30 Å from the corresponding plane. This
feature is not observed in 1a and 2, where the corresponding
values are Ϫ0.037 and Ϫ0.021 Å, respectively.
and NMR spectra were measured with a Perkin-Elmer FT1600
spectrophotometer and a JEOL RX-270 spectrometer, respec-
tively, FAB-MS spectra with a JEOL JMS-HX 110A double-
focusing spectrometer using m-nitrobenzyl alcohol as a liquid
matrix.
Syntheses
[PPh4][Ir7Ru3(CO)23] 1. An ethanol solution of p-toluene-
sulfonic acid monohydrate (42 mg, 0.22 mmol in 0.22 cm3
ethanol) was added to a flask containing [PPh4]2[Ir6(CO)15]
(0.500 g, 0.222 mmol) and [Ru3(CO)12] (0.185 mg, 0.289 mmol)
and evaporated to dryness. After addition of diglyme (15 cm3)
the suspension was heated in an oil-bath at 120 ЊC for 1 h dur-
ing which time the solid disappeared and the solution changed
from brown to deep green. After reduction of the solvent in
vacuo followed by the addition of CH2Cl2 (10 cm3), the solution
was filtered to remove insoluble materials. Hexane (2 cm3) was
slowly added and partial reduction of the solvent gave a deep
green crystalline product (0.459 mg, 90% yield based on
[PPh4]2[Ir6(CO)15]), νmax/cmϪ1 (CO) 2089w, 2051vs, 2035s and
2021m (CH2Cl2).
[N{P(C6H4Me-p)3}2][Ir7Ru3(CO)23] 1a was obtained in the
same way from [N{P(C6H4Me-p)3}2]2[Ir6(CO)15] (Found: C,
27.31; H, 1.84; Ir, 45.25; N, 0.47; Ru, 10.68. C65H42Ir7NO23-
P2Ru3 requires C, 26.78; H, 1.45; Ir, 46.15; N, 0.48; Ru, 10.40%);
νmax/cmϪ1 (CO) 2089w, 2051vs, 2035s and 2021m (CH2Cl2).
Clusters 1 and 1a can be purified by cellulose column chrom-
atography when necessary.
[Ir7Ru3(CO)23(AuPPh3)] 2. CH2Cl2 (6 cm3) was added to
a flask containing [AuCl(PPh3)] (72 mg, 0.146 mmol) and
AgOSO2CF3 (27 mg, 0.105 mmol). Then the fine white precipi-
tate was removed by filtration. [PPh4][Ir7Ru3(CO)23] (251 mg,
0.095 mmol) was added to the filtrate with stirring and immedi-
ately the deep green solution turned green. The solution was
evaporated to dryness under vacuum and the product purified
by column chromatography on silica gel (10% water, 2.5 cm
i.d. × 20 cm). A green band eluted with hexane–CH2Cl2 (9:1)
was collected and the solvent evaporated to dryness. Recrystal-
lization of the residue from CH2Cl2–hexane yielded deep green
crystals (93 mg, 36%) (Found: C, 18.31; H, 0.67. C41H15AuIr7-
O23PRu3 requires C, 17.89; H, 0.55%); νmax/cmϪ1 (CO) 2097w,
2065vs, 2047s and 2034m (CH2Cl2).
Experimental
General procedures
The compounds [N{P(C6H4Me-p)3}2]Cl,28 [PPh4]2[Ir6(CO)15]29
and [AuCl(PPh3)]30 were prepared according to the published
procedures. The complexes [N{P(C6H4Me-p)3}2]2 [Ir6(CO)15]
and [N(PPh3)]2[Ir6(CO)15] were prepared using [N{P(C6H4-
Me-p)3}2]Cl and [N(PPh3)2]Cl instead of [PPh4]Br. The
solvents used for the reactions, CH2Cl2, CH2ClCH2Cl and
bis(2-methoxyethyl) ether, were distilled over phosphorus
pentaoxide or sodium under argon. Solvents used for purifi-
cation were used as received. All the reactions and crystalliz-
ation procedures were carried out under an atmosphere of
purified argon. Other procedures were promptly performed
under the ambient atmosphere because the products were
moderately air-stable in solution as well as in the solid state. IR
[PPh4][Ir6Ru3(CO)21(AuPPh3)] 3. A solution of [PPh4][Ir7-
Ru3(CO)23] (204 mg, 0.077 mmol) and [AuCl(PPh3)] (109 mg,
0.22 mmol) in CH2ClCH2Cl (12 cm3) was refluxed for 3 h. The
deep green solution turned dark. Concentration of the solution
2298
J. Chem. Soc., Dalton Trans., 2000, 2295–2299

View Article Online
10 T. Chihara, R. Komoto, K. Kobayashi, H. Yamazaki and Y.
followed by separation by column chromatography on 15%
water-containing silica gel (hexane–CH2Cl2, 1:3) gave the green
band of the product. Slow evaporation of the solvent yielded
deep green crystals (72 mg, 32%) ([N{P(C6H4Me-p)3}2] salt,
Found: C, 27.38; H, 1.72. C67H43AuIr6O21P2Ru3 requires C,
27.75; H, 1.49%); νmax/cmϪ1 (CO) 2076w, 2038vs, 2020s, and
2006m (sh) (CH2Cl2); m/z 2504 ([Ir6Ru3(CO)21AuPPh3]ϩ).
Matsuura, Inorg. Chem., 1989, 28, 964.
11 G. Lavigne and B. Bonneval, in Catalysis by Di- and Polynuclear
Metal Cluster Complexes, eds. R. D. Adams and F. A. Cotton,
Wiley-VCH, New York, 1998, ch. 2, pp. 39–93; W. L. Gladfelter and
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12 D. M. P. Mingos and A. S. May, in The Chemistry of Metal Cluster
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New York, 1990, ch. 2, pp. 11–119; Early Transition Metal Cluster
with Π-Donor Ligands, ed. M. H. Chisholm, VCH, New York,
1995.
13 F. Demartin, M. Manassero, M. Sansoni, L. Garlaschelli,
S. Martinengo and F. Canziani, J. Chem. Soc., Chem. Commun.,
1980, 903.
14 J. R. Galsworthy, A. D. Hattersley, C. E. Housecroft, A. L.
Rheingold and A. Waller, J. Chem. Soc., Dalton Trans., 1995,
549.
15 A. Bashall, L. H. Gade, J. Lewis, B. F. G. Johnson, G. J. McIntyre
and M. McPartlin, Angew. Chem., Int. Ed. Engl., 1991, 30,
1164.
16 Y. Kobayashi, M. Katada, H. Sano, T. Chihara, H. Yamazaki,
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Structure determinations
Black single crystals of compound 1a were grown by diffusion
of hexane into a CH2Cl2 solution in a glass tube (internal diam-
eter 8 mm) at ambient temperature. Deep green single crystals
of 2 and 3 were obtained by slow evaporation of the solvent
from CH2Cl2–hexane solutions. Crystals were fixed on the tip of
a glass fibre with cyanoacrylate adhesive. Intensity data were
collected on a Rigaku RAXIS CS Imaging Plate diffractometer
with graphite monochromated Mo-Kα radiation. Crystallo-
graphic data are given in Table 4. As refinement proceeded the
tolyl groups of 1a and phenyl groups of 3 in the counter cation
were treated as rigid groups. Cluster 2 crystallized with two
molecules of CH2Cl2 in the asymmetric crystal unit. In 1a and
2 treatment of all four capping metals as ruthenium led to
marginally higher residuals and abnormally low thermal
parameters for one of the atoms, while treatment of the atom as
iridium led to appropriate final data.
18 G. B. Ansell and J. S. Bradley, Acta Crystallogr., Sect. B, 1980, 36,
726.
CCDC reference number 186/2022.
See http://www.rsc.org/suppdata/dt/b0/b003100n/ for crystal-
lographic files in .cif format.
19 B. F. G. Johnson, J. Lewis, S. W. Sankey, K. Wong, M. McPartlin
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20 R. D. Pergola, L. Garlaschelli, M. Manassero, N. Masciocchi and
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22 F. S. Livotto, M. D. Vargas, D. Braga and F. Grepionic, J. Chem.
Soc., Dalton Trans., 1992, 577.
23 J. N. Nicholls, P. R. Raithby and M. D. Vargas, J. Chem. Soc., Chem.
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