Systematic formation of mixed-metal high-nuclearity clusters: The synthesis and characterisation of [Os6(CO)17(Au2dppm)] and [Os6(CO)17(Au2dppm){Ru(η5-C 5H5)}2] (dppm = Ph2PCH2PPh2)

Article abstract of DOI:10.1016/S0022-328X(99)00695-6

Reaction of the hexaosmium cluster [Os₆(CO)₁₈] with 1.1 equivalents of Me₃NO, in CH₂Cl₂, in the presence of one equivalent of [Au₂dppm]Cl₂ (dppm = Ph₂PCH₂PPh₂), at room temperature, affords the new mixed-metal cluster [Os₆(CO)₁₇(Au₂dppm)] (1), in high yield. Subsequent reduction of 1 with Na-Hg amalgam, and subsequent treatment with [Ru(η⁵-C₅H₅)(MeCN)₃][PF ₆] (2) afforded two decanuclear clusters [Os₆(CO)₁₇(Au₂dppm){Ru(η⁵-C ₅H₅)}₂] (3) and [Os₆(CO)₁₆(Au₂dppm){Ru(η⁵-C ₅H₅)}₂] (4) in moderate yield. Cluster 3 loses CO under reflux in toluene to produce 4. The new clusters have been fully characterised by IR, ¹H- and ³¹P-NMR spectroscopies, and mass spectrometry. The molecular and crystal structures of 1 and 3 have been established by single-crystal X-ray analyses. In 1, the bicapped tetrahedral osmium core of [Os₆(CO)₁₈] is retained and the two Au atoms of the Au2dppm group cap one Os₃ face in a μ₃-η² bonding mode. In 3 the metal core consists of a capped square-based pyramidal arrangement of Os atoms that is capped over the square face by the Au2dppm group. One Ru atom caps another face of the Os₅ square-based pyramid, and the second Ru atom caps the Ru atom, two Os atoms and an Au atom to form a trigonal bipyramidal arrangement.

Full text of DOI:10.1016/S0022-328X(99)00695-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 596 (2000) 204–211
Systematic formation of mixed-metal high-nuclearity clusters: the
synthesis and characterisation of [Os6(CO)17(Au2dppm)] and
[Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (dppm=Ph2PCH2PPh2)
Zareen Akhter, Andrew J. Edwards, John F. Gallagher 1, Jack Lewis,
Paul R. Raithby *, Gregory P. Shields
Department of Chemistry, Uni6ersity of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
Received 4 October 1999; received in revised form 10 November 1999
Dedicated to Professor F. Albert Cotton in recognition of his seminal contribution to organometallic chemistry
Abstract
Reaction of the hexaosmium cluster [Os6(CO)18] with 1.1 equivalents of Me3NO, in CH2Cl2, in the presence of one equivalent
of [Au2dppm]Cl2 (dppm=Ph2PCH2PPh2), at room temperature, affords the new mixed-metal cluster [Os6(CO)17(Au2dppm)] (1),
in high yield. Subsequent reduction of 1 with Na–Hg amalgam, and subsequent treatment with [Ru(h5-C5H5)(MeCN)3][PF6] (2)
afforded two decanuclear clusters [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3) and [Os6(CO)16(Au2dppm){Ru(h5-C5H5)}2] (4) in
moderate yield. Cluster 3 loses CO under reflux in toluene to produce 4. The new clusters have been fully characterised by IR,
1H- and 31P-NMR spectroscopies, and mass spectrometry. The molecular and crystal structures of 1 and 3 have been established
by single-crystal X-ray analyses. In 1, the bicapped tetrahedral osmium core of [Os6(CO)18] is retained and the two Au atoms of
the Au2dppm group cap one Os3 face in a m3-h2 bonding mode. In 3 the metal core consists of a capped square-based pyramidal
arrangement of Os atoms that is capped over the square face by the Au2dppm group. One Ru atom caps another face of the Os5
square-based pyramid, and the second Ru atom caps the Ru atom, two Os atoms and an Au atom to form a trigonal bipyramidal
arrangement. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Ionic coupling; Osmium; Ruthenium; Gold; X-ray structure; Carbonyl cluster
1. Introduction
product distribution, with no specific clusters being
prepared in high yield [6]. However, during the last
decade a number of research groups have developed a
synthetic methodology that involves the ionic coupling
between a pre-formed cluster anion and a mono- or
dinuclear cationic metal complex. This method leads to
a systematic increase in cluster nuclearity by one or two
metal units [7,8], and since the coupling reactions gener-
ally occur at room temperature it is much easier to
control the product distribution, thereby permitting
specific clusters to be targeted. Using a range of precur-
sor cationic species, it has been possible to prepare a
range of novel high-nuclearity mixed-metal clusters [9].
The group in Cambridge has concentrated on devel-
oping the chemistry of coupling reactions between clus-
ter anions and cationic species that contain either
metal-arene or metal-cyclopentadienyl fragments such
Since the pioneering work of Cotton [1], Chini et al.
[2], Johnson and Lewis [3] and others [4] in the 1950s
and 1960s, polynuclear organometallic chemistry has
been a major research area in inorganic chemistry.
Now, at the beginning of the 21st century, the subject
continues to grow and develop into new areas [5].
Throughout this period one of the main challenges of
the subject has been to prepare specific high-nuclearity
clusters in good yield. Until recently, the most common
synthetic routes used have involved thermolysis or py-
rolysis techniques, and these methods favour a wide
* Corresponding author. Fax: +44-1223-336-362.
E-mail address: prr1@cam.ac.uk (P.R. Raithby)
1 Present address: School of Chemical Sciences, Dublin City Uni-
versity, Dublin 9, Ireland.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00695-6

Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
205
as ‘[Ru(h6-C6H6)]2+’, ‘[Os(h6-C6H5Me)]2+’, ‘[Rh(h5-
C5H5)]2+’ and ‘[Ru(h5-C5H5)]+’ [10–14]. These groups
either cap triangular faces of the cluster anions or
bridge metal–metal edges of the metal cores. In a
similar manner we have used mono- and digold species
such as [AuPPh3]+ [15], [Au2dppm]2+ and [Au2dppe]2+
[16–19], to build high-nuclearity clusters that display a
range of novel geometries [20]. We now report the
combination of these two reactions leading to the for-
mation of the novel triheterometallic clusters [Os6-
(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3) and [Os6(CO)16-
(Au2dppm){Ru(h5-C5H5)}2] (4) (dppm=Ph2PCH2-
PPh2) by the coupling of the new [Os6(CO)17(Au2-
dppm)]2− dianion with two equivalents of [Ru(h5-
C5H5)(MeCN)3]+.
[Os6(CO)17]2− dianion to form [Os6(CO)17(Au2dppm)]
(1).
The molecular structure of 1 was established and the
crystal structure determined by means of a single-crys-
tal X-ray diffraction experiment. The molecular struc-
ture of 1 is illustrated in Fig. 1, while the Os6Au2P2 core
geometry is presented in Fig. 2. Selected bond parame-
ters are listed in Table 2. In 1 the bicapped tetrahedral
Os6 core of the parent [Os6(CO)18] [22] is retained and
the ‘Au2(dppm)’ fragment m3:h2 caps a triangular face
of the osmium core to form an Os3Au2 square-based
pyramid. This coordination mode has been previously
reported in the structures of [Ru4H4(CO)12(Au2dppm)]
[23] and [Ru4H2(CO)12(Au2(Ph2AsCH2AsPPh2))] [24].
All the carbonyl ligands in the cluster are terminal and
essentially linear [mean OsꢀCꢀO 175°]. Each Os atom is
coordinated to three carbonyls, except Os(3), which is
linked to only two. There are, however, two short
2. Results and discussion
,
Au···C contacts (Au(1)···C(302) 2.68(3)
A
and
,
Au(2)···C(403) 2.58(3) A) between the Au atoms and
the carbonyl ligands. This is a common feature in
mixed osmium and ruthenium clusters that contain
coinage metals [25]. It is not entirely clear whether these
short Au···C contacts represent some degree of long-
range interaction [25] or whether they are the result of
steric effects in the solid state [26].
The reduction of the hexaosmium cluster [Os6(CO)18]
with 1.1 equivalents of Me3NO, in CH2Cl2, at ambient
temperature, afforded a reddish–brown anionic cluster
[21], which, if immediately treated with one equivalent
of [Au2dppm]Cl2, in CH2Cl2, at room temperature, in
the presence of Tl[PF6] (which acts as a halide abstrac-
tor), gives an 80% yield of [Os6(CO)17(Au2dppm)] (1)
after chromatographic work-up. This cluster was ini-
tially characterised by spectroscopic and mass spectro-
metric techniques (Table 1). The IR spectrum in the
carbonyl region indicated the presence of terminal car-
bonyls, and the band pattern was reminiscent of that
observed for [Os6(CO)18] [22], suggesting that the bi-
capped tetrahedral osmium core framework had been
In terms of electron counting, if each of the Au
atoms in the Au2dppm group donates one electron to
the cluster, then as a whole the cluster is an 84 e−
system, which is consistent with the observed bicapped
tetrahedral osmium core geometry, similar to that ob-
served in [Os6(CO)18] [22]. However, there is some
distortion of the metal core that may reflect the intro-
duction of the heteroatoms. The longest OsꢀOs edge
1
retained. The H-NMR spectrum confirmed the pres-
ence of the dppm ligand. The 31P-NMR spectrum dis-
played only one signal, indicating that the two P nuclei
were in equivalent environments or that a fluxional
process, which made the two nuclei equivalent on
the NMR timescale, was occurring. The mass spec-
trum displayed a molecular ion that was consistent
with the addition of an [Au2dppm]2+ ligand to the
,
(Os(3)ꢀOs(4), 2.9399(13) A) is in the central tetrahedron
and is bridged by the Au(2) atom. The second edge
,
(Os(1)ꢀOs(3), 2.7193(14) A) that is bridged by Au(1) is
the shortest OsꢀOs distance in the structure. The third
,
bridged edge (Os(1)ꢀOs(4), 2.8843(14) A) is intermedi-
ate in length. The OsꢀAu distances also show signifi-
cant asymmetry, with the two longer distances being
Table 1
Spectroscopic data for [Os6(CO)17(Au2dppm)] (1), [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3) and [Os6(CO)16(Au2dppm){Ru(h5-C5H5)}2] (4)
a
Compound
IR w(CO) (cm−1
)
1H-NMR b
(ppm)
l
31P-NMR c l (ppm)
Mass spec-
troscopy m/z
d
1
3
2083(m), 2053(s), 2039(vs), 2015(vs), 1981(vw)
2067(s), 2020(vs), 2006(s), 1961(m, br), 1788(m)
7.30–7.77(m)
7.22–7.67(m),
4.78(s), 5.07(s)
7.25–7.76(m),
5.16(s), 5.42(s)
−86.01(s)
−58.23(d), −67.88(d),
2407 (2406)
2738 (2738)
J
PP=137.7 Hz
−86.51(d), −80.87(d),
PP=65.5 Hz
4
2060(s), 2036(s), 2006(vs), 1984(s, br), 1971(m), 1928(w, br),
1790(m, br)
2710 (2710)
J
a In CH2Cl2.
b In CDCl3.
c Ref. TMP.
d Based on 192Os, calculated values in parentheses.

206
Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
Fig. 1. The molecular structure of [Os6(CO)17(Au2dppm)] (1) showing the atom numbering scheme adopted.
Fig. 2. The core geometry in [Os6(CO)17(Au2dppm)] (1).
,
Au(1)ꢀOs(1) (2.9781(14) A) and Au(2)ꢀOs(3)
amalgam or K–Ph2CO leads to the formation of
mixed-metal anions that are susceptible to attack by
metal-containing cationic species [20]. The reactivity of
1 follows the expected path, and reduction with Na–Hg
amalgam, in tetrahydrofuran (THF), at room tempera-
ture results in the formation of anionic species that
,
,
(2.9415(13) A). The Au···Au separation is 2.7587(14) A,
but this may not be indicative of a direct metal–metal
bond since the distance is a function of the ligand bite.
It has been established that reduction of high-nucle-
arity osmium–gold neutral clusters with either Na–Hg

Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
207
[Os7C(CO)19(Au2dppm)] [19]. The mass spectra of the
two clusters gave molecular ion peaks that are consis-
tent with the proposed formulae for 3 and 4.
were not isolated. The immediate in situ reaction of the
anion with an excess of [Ru(h5-C5H5)(MeCN)3][PF6]
(2), acting as the source of ‘[Ru(h5-C5H5)]+’, affords
two neutral deca-metal clusters [Os6(CO)17(Au2dppm)-
{Ru(h5-C5H5)}2] (3) and [Os6(CO)16(Au2dppm){Ru(h5-
C5H5)}2] (4) after purification by thin-layer chro-
matography (TLC).
From the spectroscopic data, cluster 4 can be viewed
as derived from 3 by the loss of a carbonyl group. This
has been proven experimentally, since 4 is generated
from 3 if the latter cluster is heated in toluene, under
reflux, for 8 h. This is consistent with a reduction in the
formal electron count of two electrons, from 110 e− in
3 (if the Au2dppm ligand is considered to be a 2 e−
donor ligand) to 108 e− in 4. A loss of electrons is often
accompanied by a metal framework rearrangement [20],
and this may be the case here since the symmetry of the
two molecules from the IR spectral data is different.
The decarbonylation reaction is irreversible.
In order to establish the molecular structures of the
two clusters, attempts were made to grow single crystals
suitable for X-ray analyses. Unfortunately only suitable
crystals could be obtained for 3. These were obtained
by slow diffusion of hexane into a dichloromethane
solution of the compound, and a full structure determi-
nation was carried out on this cluster. The molecular
structure of [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3)
is shown in Fig. 3, while a diagram of the metal core
arrangement is presented in Fig. 4. Selected bond
lengths and angles are presented in Table 3.
The crystal structure of [Os6(CO)17(Au2dppm)-
{Ru(h5-C5H5)}2] (3) consists of discrete molecular units
with the shortest intermolecular contacts involving car-
bonyl oxygens on adjacent molecules. The osmium
metal core within the molecular structure of 3 may be
described as a capped square-pyramid, where the trian-
gular face opposite the Os cap is capped by a ruthe-
nium atom {Ru(1)}, and this Ru atom and the two
adjacent Os atoms {Os(1) and Os(2)} are capped by the
second ruthenium atom {Ru(2)}. This generates a trigo-
nal bipyramid defined by Ru(1), Ru(2), Os(1), Os(2)
and Os(3) (Fig. 4), which is further fused with the
capped square-pyramidal osmium core. The two Au
atoms of the Au2dppm ligand asymmetrically bridge
opposite edges of the square base of the osmium
square-based pyramid, with Au(1) also coordinating to
Ru(2), thus adopting a m3-bonding mode. The arrange-
ment of a digold chelating ligand spanning a square
face of the cluster has been previously observed in
several high-nuclearity clusters of osmium and ruthe-
Clusters 3 and 4 were initially characterised by IR,
1H- and 31P-NMR spectroscopies and also by mass
spectrometry (Table 1). Both clusters showed medium-
intensity IR bands around 1790 cm−1, suggesting the
presence of capping carbonyl groups, in addition to a
number of bands in the region 2070–1920 cm−1 that
are readily assigned to terminal carbonyl ligands. Simi-
lar signals are observed for the m3-carbonyl groups in
[Os5Ru2(CO)9(m3-CO)2(h5-C5H5)2] [27]. Two sharp sin-
1
glets at l 4.78 and l 5.07 in the H-NMR spectrum of
3 can be assigned to two h5-coordinated cyclopentadi-
enyl ligands in different chemical environments. The
chemical shifts are comparable to those observed for
the two non-equivalent cyclopentadienyl groups in
[Os5Ru2(CO)9(m3-CO)2(h5-C5H5)2] [27]. Similar chemi-
cal shift values are also observed in the 1H-NMR
spectrum of 4, for which two singlets at l 5.16 and l
5.42 are observed, and again, these are assigned to
non-equivalent h5-cyclopentadienyl rings. The 31P-
NMR spectrum of 3 displays two doublets at −67.88
and −58.2 ppm, with a large coupling constant of
137.7 Hz, and these signals are assigned to two non-
equivalent phosphorus nuclei bonded to two chemically
different gold atoms of the Au2dppm ligand. Again, in
4, a similar pattern of signals is observed, with two
doublets at −86.51 and −80.87 ppm with a coupling
constant of 65.5 Hz, and similar assignments can be
made. The observed coupling constant in 4 is similar to
the value of 68.6 Hz observed in [Os7(CO)20(Au2dppm)]
and lower than the value of 83.3 Hz reported for
Table 2
,
Selected bond lengths (A) and angles (°) for [Os6(CO)17(Au2dppm)]
(1)
Bond lengths
Os(1)ꢀOs(3)
Os(1)ꢀOs(6)
Os(1)ꢀAu(2)
Os(2)ꢀOs(4)
Os(2)ꢀOs(6)
Os(3)ꢀOs(4)
Os(3)ꢀOs(6)
Os(4)ꢀAu(2)
Os(5)ꢀOs(6)
Au(1)ꢀP(1)
P(1)ꢀC(1)
2.7193(14)
2.9352(14)
3.2801(14)
2.8041(13)
2.8428(14)
2.9399(13)
2.7896(13)
2.7247(13)
2.8590(13)
2.264(6)
Os(1)ꢀOs(4)
Os(1)ꢀAu(1)
Os(2)ꢀOs(3)
Os(2)ꢀOs(5)
Os(3)ꢀAu(1)
Os(3)ꢀOs(5)
Os(3)ꢀAu(2)
Os(4)ꢀOs(6)
Au(1)ꢀAu(2)
Au(2)ꢀP(2)
P(2)ꢀC(1)
2.8843(14)
2.9781(14)
2.7465(13)
2.7697(14)
2.7118(13)
2.7294(13)
2.9415(13)
2.8127(13)
2.7587(14)
2.300(6)
,
nium [20]. The Au···Au separation of 2.874(2) A in 3 is
,
significantly longer than the value of 2.811(1) A found
in the closely related [Os6(CO)18(Au2dppm)], but in
neither case is there thought to be significant direct
AuꢀAu bonding, the distance being a function of the
ligand bite [28]. The shortest AuꢀOs contact is 2.715(2)
1.86(2)
1.85(2)
,
A between Au(2) and Os(5) and the longest is 2.846(2)
Bond angles
,
A between Au(1) and Os(1). These values compare with
C(1)ꢀP(1)ꢀAu(1) 108.0(8)
P(1)ꢀC(1)ꢀP(2) 114.4(12)
C(1)ꢀP(2)ꢀAu(2)
113.0(8)
,
the average AuꢀOs distance in the cluster of 2.825 A.
,
The single AuꢀRu contact of 2.877(3) A is significantly

208
Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
Fig. 3. The molecular structure of [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3) showing the atom numbering scheme adopted.
Fig. 4. The metal core geometry in [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3).

Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
209
The structure of 3 may be rationalised successfully in
terms of the Mingos Condensed Polyhedral counting
scheme [29], as a 110 e− cluster, as the condensation of
an Os6 capped square-based pyramid (86 e−) with an
Os3Ru2 trigonal bipyramid (72 e−) less 48 e− for the
common triangular face; the (Au2dppm) fragment is
taken to be a 2 e− donor in this scheme. A consequence
of the reasoning put forward in these last two para-
graphs is that the metal framework structure of
[Os6(CO)16(Au2dppm){Ru(h5-C5H5)}2] (4) must have a
higher level of condensation (more metal–metal con-
tacts) than 3 since it has two electrons fewer.
longer. The OsꢀOs contacts within the core lie in the
,
range 2.734(2)–2.953(2) A as has been found previously
in other high-nuclearity osmium cluster systems [8,9].
The two ruthenium atoms are separated by a relatively
,
short metal–metal distance of 2.730(3) A, but which is
,
longer than the related RuꢀRu distance of 2.691(3) A in
[Os5Ru2(CO)9(m3-CO)2(h5-C5H5)2] [27]. As in the
Os5Ru2 cluster, each Ru in 3 is bonded to a h5-termi-
nally bonded cyclopentadienyl ligand and to two m3-
carbonyls; these two carbonyls cap the Ru(1), Ru(2),
Os(1) and Ru(1), Ru(2), Os(2) faces. The presence of
the capping carbonyls is consistent with the view that
the ‘Ru(h5-C5H5)’ centres are electron rich, and that the
capping carbonyls help to distribute the ‘excess’ elec-
tron density over the cluster framework. In terms of
metal connectivity, each ruthenium atom is coordinated
to four other metals. All the other carbonyls in the
cluster are terminally coordinated, three to each Os
atom except Os(3) which is bonded to only two termi-
nal carbonyl groups.
3. Experimental
All reactions were performed under an atmosphere of
purified dinitrogen using standard Schlenk and vacuum
line techniques [30]. Subsequent work-up of products
was carried out without precautions to exclude air.
Solvents used were distilled from appropriate drying
agents under dinitrogen. Routine separations of prod-
ucts were performed by thin-layer chromatography
using commercially prepared glass plates, precoated to
0.25 mm thickness with E. Merck Kieselgel 60 PF254, or
using laboratory prepared glass plates coated to 1 mm
In the structure of 3 there has been a change in metal
framework geometry compared with that in the parent
pre-reduced cluster [Os6(CO)17(Au2dppm)] (1) where
the osmium framework adopts the bicapped tetrahedral
core, but it is similar to the capped square-based pyra-
midal arrangement found in [Os6(CO)18(Au2dppm)]
[28]. Thus the addition of a ‘{Ru2(h5-C5H5)2}’ fragment
is equivalent, from the structural viewpoint, to adding a
carbonyl ligand, so that simplistically, the ‘{Ru2(h5-
C5H5)2}’ fragment can be considered as a 2 e− donor.
thickness with E. Merck Kieselgel 60 PF254
.
IR spectra were recorded as dichloromethane solu-
tions on a Perkin–Elmer 1710 Fourier Transform spec-
1
trometer. H- and 31P{1H}-NMR spectra were recorded
on a Bruker AM-400 spectrometer and were referenced
to external tetramethylsilane and trimethylphosphite,
respectively. Mass spectral data were obtained by nega-
tive ion FAB mass spectrometry on a Kratos MS902
mass spectrometer.
Table 3
,
Selected bond lengths (A) and angles (°) for [Os6(CO)17(Au2dppm)-
{Ru(h5-C5H5)}2] (3)
Bond lengths
The compounds [Ru(h5-C5H5)(MeCN)3][PF6] [31]
and [Au2(dppm)]Cl2 [32] were prepared by literature
methods. All other chemicals were used as purchased
without further purification.
Os(1)ꢀOs(3)
Os(1)ꢀRu(2)
Os(1)ꢀAu(1)
Os(2)ꢀOs(3)
Os(2)ꢀAu(1)
Os(2)ꢀOs(5)
Os(3)ꢀOs(6)
Os(3)ꢀOs(4)
Os(4)ꢀOs(6)
Os(5)ꢀAu(2)
Ru(1)ꢀRu(2)
Au(1)ꢀP(1)
Au(2)ꢀP(2)
P(2)ꢀC(0)
2.737(2)
2.785(3)
2.845(2)
2.734(2)
2.800(2)
2.943(2)
2.744(2)
2.784(2)
2.857(2)
2.715(2)
2.730(3)
2.316(8)
2.302(8)
1.89(3)
Os(1)ꢀRu(1)
Os(1)ꢀOs(2)
Os(1)ꢀOs(4)
Os(2)ꢀRu(1)
Os(2)ꢀRu(2)
Os(3)ꢀRu(1)
Os(3)ꢀOs(5)
Os(4)ꢀAu(2)
Os(4)ꢀOs(5)
Os(5)ꢀOs(6)
Ru(2)ꢀAu(1)
Au(1)ꢀAu(2)
P(1)ꢀC(0)
2.750(3)
2.828(2)
2.897(2)
2.768(3)
2.835(3)
2.736(3)
2.774(2)
2.828(2)
2.953(2)
2.873(2)
2.877(3)
2.874(2)
1.78(3)
3.1. Preparation of [Os6(CO)17(Au2dppm)] (1)
To a solution of [Os6(CO)18] (50 mg, 3.04×10−5
mol) in CH2Cl2 were added 1.1 equivalents Me3NO
(2.28 mg) and the reaction mixture was stirred for 3
min under an atmosphere of N2 at room temperature
(r.t.). The reaction mixture was passed through Celite
to remove the excess amine oxide and then reacted with
one equivalent of [Au2dppm]Cl2 (25.8 mg) and an ex-
cess of Tl[PF6] (26.5 mg). After stirring for 30 min the
solvent was removed in vacuo and the residue was
dissolved in a small quantity of CH2Cl2 and purified by
TLC using 60:40 CH2Cl2–hexane as eluent. The red-
dish–brown product was isolated as the main product
in 70–80% yield. Anal. Calc. for Os6Au2P2O17C42H22
(1): C, 21.05; H, 0.93. Found: C, 21.18; H, 0.92%.
Os(1)ꢀC(12)
Ru(2)ꢀC(12)
Ru(1)ꢀC(23)
2.22(4)
2.14(4)
2.38(4)
Ru(1)ꢀC(12)
Os(2)ꢀC(23)
Ru(2)ꢀC(23)
2.16(4)
2.03(3)
1.98(3)
Bond angles
C(0)ꢀP(1)ꢀAu(1)
P(1)ꢀC(0)ꢀP(2)
Ru(2)ꢀC(12)ꢀOs(1)
Ru(2)ꢀC(23)ꢀOs(2)
Os(2)ꢀC(23)ꢀRu(1)
110.1(11) C(0)ꢀP(2)ꢀAu(2)
114(2) Ru(2)ꢀC(12)ꢀRu(1)
79.2(13) Ru(1)ꢀC(12)ꢀOs(1)
90.1(14) Ru(2)ꢀC(23)ꢀRu(1)
77.2(11)
110.4(10)
78.7(13)
77.7(12)
76.9(12)

210
Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
C5H5)}2] (3) and [Os6(CO)16(Au2dppm){Ru(h5-C5H5)}2]
(4), were obtained in 30 and 10% yield, respectively.
Anal. Calc. for 3, Os6Au2Ru2P2O17C52H32: C, 23.50; H,
1.43; P, 2.24. Found: C, 23.21; H, 1.60; P, 1.96%.
Table 4
Crystal data and refinement parameters for [Os6(CO)17(Au2dppm)]
(1) and [Os6(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3)
1
3
Empirical formula
C42H22Au2O17Os6 C52H32Au2O17Os6P2
3.3. Crystal-structure determinations of
[Os6(CO)17(Au2dppm)] (1) and
P2
Ru2
Formula weight
Temperature (K)
2395.67
293(2)
2727.99
293(2)
[Os6(CO)17(Au2dppm){Ru(p5-C5H5)}2] (3)
,
Wavelength (A)
0.71073
Orthorhombic
Pbca
0.71073
Orthorhombic
Pna21
Crystal system
Space group
Red crystals of [Os6(CO)17(Au2dppm)] (1) and [Os6-
(CO)17(Au2dppm){Ru(h5-C5H5)}2] (3) were obtained by
recrystallisation from dichloromethane–hexane at
−20°C. Suitable crystals were mounted on glass fibres
with epoxy resin and transferred to a Rigaku AFC7R
diffractometer. Intensity data were recorded using
graphite monochromated MoꢀKa radiation and an ꢀ–
2q technique in the range 552q545°. Absorption
corrections were applied using a semi-empirical method
based on c scans. Crystal data, data collection parame-
ters, and details of structure solution and refinement for
the two structures are listed in Table 4. The structures
were solved by direct methods (SHELXTL-PLUS [33]) and
Unit cell dimensions
,
a (A)
20.124(4)
18.264(4)
26.629(5)
9787(3)
8
25.573(7)
12.184(4)
17.993(5)
5606(3)
4
,
b (A)
,
c (A)
Volume (A )
Z
3
,
Dcalc (Mg m−3
Absorption coefficient
(mm−1
F(000)
Crystal size (mm)
q Range for data collec-
tion (°)
)
3.252
21.617
3.232
19.398
)
8432
4848
0.35×0.35×0.29 0.22×0.21×0.10
2.54–22.50
2.57–22.50
Limiting indices
−215h50,
05k519,
05l528
−275h527,
−135k51,
05l519
refined by full-matrix least-squares on F2
(SHELXL-97
[34]). The Os, Au and P atoms for 1 and the Os, Au,
Ru and P atoms for 3 were assigned anisotropic dis-
placement parameters, while the remaining non-hydro-
gen atoms in each structure were refined with isotropic
displacement parameters. For 3, weak restraints were
placed on the phenyl rings that required them to be flat.
Hydrogen atoms in both structures were placed in
idealised positions and allowed to ride on the relevant
carbon atom. In the final cycles of refinement for 1
a weighting scheme of the form w=1/[|2(Fo2)+
(0.0991P)2+128.00P] where P=(Fo2 +2Fc2)/3 was in-
troduced. The final converged R factors for 327 refined
parameters were R1=0.056 (for 5071 reflections with
I\2|(I)]) and wR2=0.163 (for all data), Goodness-of-
fit=1.061. In the final cycles of refinement for 3 a
weighting scheme of the form w=1/[|2(Fo2)+
(0.0255P)2+32.00P] where P=(Fo2 +2F2c)/3 was intro-
duced. The final converged R factors for 384 refined
parameters were R1=0.041 (for 3041 reflections with
I\2|(I)]) and wR2=0.082 (for all data), Goodness-of-
fit=1.074. The function minimised was Sw(F2o−Fc2)2.
Max and min transmis-
sion
Reflections collected
Independent reflections
1.000, 0.270
1.000, 0.625
6384
6384
8206
3802 (Rint=0.147)
3799/190/384
1.074
R1=0.0409,
wR2=0.0721
R1=0.0745,
wR2=0.0824
−0.005(14)
Data/restraints/parameters 6384/0/327
Goodness-of-fit on F2
1.061
Final R indices [I\2|(I)] R1=0.0562,
wR2=0.1508
R indices (all data)
R1=0.0740,
wR2=0.1628
–
Absolute structure
parameter
Largest difference peak
3.575 and
−2.626
1.518 and
−1.570
−3
,
and hole (e A
)
3.2. Preparation of [Os6(CO)17(Au2dppm)-
{Ru(p5-C5H5)}2] (3) and [Os6(CO)16(Au2dppm)-
{Ru(p5-C5H5)}2] (4)
[Os6(CO)17(Au2dppm)] (1) (50 mg, 2.08×10−5 mol)
was reduced by Na–Hg amalgam by dissolving the
cluster in 20 cm3 of dry deoxygenated THF and trans-
ferring the resulting solution to a flask containing
freshly prepared amalgam, with the help of a cannula.
The reaction mixture was stirred for a few minutes. The
stirring was stopped when the reduction had occurred,
as monitored by IR spectroscopy. The solution was
passed through a Celite pad using the cannula–septum
technique to remove the amalgam. The resulting solu-
tion was treated with an excess of [Ru(h5-
C5H5)(MeCN)3][PF6] (27 mg, 6.24×10−5 mol). After
removal of solvent, the solid residue was chro-
matographed by TLC using 60:40 CH2Cl2–hexane as
eluent. Two products, [Os6(CO)17(Au2dppm){Ru(h5-
4. Supplementary material
Crystallographic data for compounds 1 and 3 have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 136781 and 135276, respec-
tively. Copies of this information may be obtained free
of charge from, The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).

Z. Akhter et al. / Journal of Organometallic Chemistry 596 (2000) 204–211
211
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Acknowledgements
We gratefully acknowledge the Cambridge Common-
wealth Trust and the UK Committee of Vice Chancel-
lors and Principals (Z.A.), the European Union
(J.F.G.), the Engineering and Physical Sciences Re-
search Council (A.J.E.) and the Cambridge Crystallo-
graphic Data Centre (G.P.S.) for financial support. We
also thank the EPSRC for funding the purchase of
X-ray equipment and Johnson–Matthey for the gener-
ous loan of heavy metal salts.
[21] B.F.G. Johnson, J. Lewis, M.A. Pearsall, L.G. Scott, J.
Organomet. Chem. 402 (1991) C27.
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