Synthesis, structural characterization and reactivity of triosmium carbonyl clusters containing oxime ligands

Article abstract of DOI:10.1039/b107628k

Reaction of [Os₃(CO)₁₁(NCMe)] with phenyl 2-pyridyl ketoxime produced the clusters [Os₃(CO)₈{μ-η³-ON=CPh(NC ₅H₄)}₂] 1 and [Os₃H(CO)₁₁{η²-ON=CPh(NC₅H ₄)}] 2 in 4 and 17% yields, respectively. Oxidative addition of the oximes to the clusters with O-H bond cleavage and the loss of labile acetonitrile groups, and in the case of complex 1 decarbonylation, are observed. Cluster 2 possesses an open linear metal skeleton attached to both the pyridine nitrogen and oximato nitrogen on one terminal Os atom. Heating 2 in refluxing toluene gave [Os₃(μ-H)(CO)₉{μ-η³-ON=CPh(NC ₅H₄)}] 3 in 13% yield. Treatment of a CH₂Cl₂ solution of [Os₃(CO)₁₀(NCMe)₂] with phenyl 2-pyridyl ketoxime at ambient conditions afforded the bridging oximato clusters 1 and 3 in moderate yields. Cluster 3 and 1 equiv. of phenyl 2-pyridyl ketoxime in refluxing toluene led to conversion to clusters 1 and [Os₃(CO)₈{μ-η³-ON=CPh(NC₅ H₄)} {μ-η²-N(H)CHPh(NC₅H₄)}] 4 in 12 and 16% yields, respectively. In cluster 4, one of the oximato moieties is deoxygenated with N-O bond cleavage. Treatment of another oxime ligand, benzophenone oxime, with [Os₃(CO)₁₀(NCMe)₂] gave [Os₃(μ-H)(CO)₁₀{μ-η²-ON=CPh ₂}] 5 in moderate yield. On thermolysis of 5 in toluene, [Os₃(μ-H)₂(CO)₉-{μ-η³- ON=CPh(C₆H₄)}] 6 and [Os₃(CO)₁₀(μ-OH){μ-N=CPh₂}] 7 were isolated in 27 and 21% yields, respectively. The oxime ligand in 6 is converted to a tridentate ligand. In addition to the μ-η²-oximato N-O bridge, the phenyl carbon on the ligand coordinates to the cluster core by ortho-metallation. Cluster 5 isomerizes thermally to 7, which is formed by oxidative addition of the oxime with N-O bond cleavage. A μ₄-oxo hexaosmium cluster, [Os₆(CO)₁₆(μ₄-O){μ-η³- N=CPh(C₆H₄)}₂] 8, was isolated in low yield upon refluxing 5 in octane. Vacuum pyrolysis of 5 in 140°C yielded a pentaosmium carbonyl cluster, [Os₅(CO)₁₅{μ-η³-N=CPh(C₆H ₄)}] 9. All these clusters have been fully characterized by both spectroscopic and crystallographic techniques.

Full text of DOI:10.1039/b107628k

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Synthesis, structural characterization and reactivity of
triosmium carbonyl clusters containing oxime ligands
Janet Shuk-Yee Wong and Wing-Tak Wong*
Department of Chemistry, T he University of Hong Kong, Pokfulam Road, Hong Kong,
P. R. China. E-mail:wtwong @hkucc.hku.hk
Received (in Montpellier, France) 13th August 2001, Accepted 8th October 2001
First published as an Advance Article on the web 9th January2002
Reaction of [Os3(CO)11(NCMe)] with phenyl 2-pyridyl ketoxime produced the clusters [Os3(CO)8{m-Z3-
ON=CPh(NC5H4)}2] 1 and [Os3H(CO)11{Z2-ON=CPh(NC5H4)}] 2 in 4 and 17% yields, respectively.
Oxidative addition of the oximes to the clusters with O–H bond cleavage and the loss of labile acetonitrile
groups, and in the case of complex 1 decarbonylation, are observed. Cluster 2 possesses an open linear metal
skeleton attached to both the pyridine nitrogen and oximato nitrogen on one terminal Os atom. Heating 2 in
refluxing toluene gave [Os3(m-H)(CO)9{m-Z3-ON=CPh(NC5H4)}] 3 in 13% yield. Treatment of a CH2Cl2
solution of [Os3(CO)10(NCMe)2] with phenyl 2-pyridyl ketoxime at ambient conditions afforded the bridging
oximato clusters 1 and 3 in moderate yields. Cluster 3 and 1 equiv. of phenyl 2-pyridyl ketoxime in refluxing
toluene led to conversion to clusters 1 and [Os3(CO)8{m-Z3-ON=CPh(NC5H4)} {m-Z2-N(H)CHPh(NC5H4)}] 4
in 12 and 16% yields, respectively. In cluster 4, one of the oximato moieties is deoxygenated with N–O bond
cleavage. Treatment of another oxime ligand, benzophenone oxime, with [Os3(CO)10(NCMe)2] gave
[Os3(m-H)(CO)10{m-Z2-ON=CPh2}] 5 in moderate yield. On thermolysis of 5 in toluene, [Os3(m-H)2(CO)9-
{m-Z3-ON=CPh(C6H4)}] 6 and [Os3(CO)10(m-OH){m-N=CPh2}] 7 were isolated in 27 and 21% yields,
respectively. The oxime ligand in 6 is converted to a tridentate ligand. In addition to the m-Z2-oximato N–O
bridge, the phenyl carbon on the ligand coordinates to the cluster core by ortho-metallation. Cluster 5
isomerizes thermally to 7, which is formed by oxidative addition of the oxime with N–O bond cleavage.
A m4-oxo hexaosmium cluster, [Os6(CO)16(m4-O){m-Z3-N=CPh(C6H4)}2] 8, was isolated in low yield upon
refluxing 5 in octane. Vacuum pyrolysis of 5 in 140 ꢀC yielded a pentaosmium carbonyl cluster,
[Os5(CO)15{m-Z3-N=CPh(C6H4)}] 9. All these clusters have been fully characterized by both spectroscopic
and crystallographic techniques.
The coordination chemistry of oxime (hydroxyimine),
RR0=NOH, has been well documented.1–7 Often oximato
Results and discussion
groups act as bi- or multidentate ligands that are attached to a
Reaction of [Os3(CO)11(NCMe)] with phenyl 2-pyridyl
single metal atom. The oxime group may coordinate to metals
ketoxime
either through a nitrogen or an oxygen atom or both. Reac-
tivity observed for coordinated oxime ligands on transition
Treatment of [Os3(CO)11(NCMe)] with 1 equiv. of phenyl
metals includes (a) oxidative deoximation to a ketone,3 (b)
2-pyridyl ketoxime at room temperature afforded [Os3(CO)8-
reduction to an imine,4,5 (c) dehydroxylation to a ligated
{m-Z3-ON=CPh(NC5H4)}2] 1 and [Os3H(CO)11{Z2-ON=CPh-
(NC5H4)}] 2 in low yields upon TLC separation (Scheme 1).
The spectroscopic data of 1 and 2 (and all other products) are
listed in Table 1. The molecular structure of 1 was established
methyleneamide,4 (d) dehydration to a nitrile,4 (e) oxidation to
a nitrosoalkane6 and (f ) coupling with nitrile to give imino-
acylated species.7 Metal clusters containing bridging oximato
ligands are also known, however, their chemical properties
by X-ray analysis using a red, air stable crystal that was
obtained by diffusion of n-hexane into a CH2Cl2 solution at
have not been well developed. To our knowledge, reports
concerning the cluster chemistry of oximes are rather rare.
Deeming and co-workers reported that the O–H bond cleavage
À20 ꢀC. Fig. 1 shows the perspective view and the numbering
scheme for the resulting molecular configuration. Selected
in the oxidative addition of Me2C=NOH to the osmium
bond parameters are given in Table 2. The cluster consists of
+
cluster [Os3(CO)10(NCMe)2] gives [Os3(m-H)(m-Me2C=NO)-
(CO)10], which thermally isomerizes to the hydroxo isomer
[Os3(m-OH)(m-Me2C=N)(CO)10].8 Lu and co-workers also
reported the first example containing a m2-Z1-O-oximato
coordinating group in [(m-H)Os3(CO)10(m2-Z1-OC9H6N2Cl)].9
The reactivity of oximes towards triosmium clusters is one
of our current interests. In this paper, the synthesis and
spectroscopic studies of triosmium clusters with oxime ligands
are reported.
an open triosmium triangle [Os(1)–Os(2) 2.8472(6) A] with two
+
oximato ligands spanning the open OsÁ Á ÁOs edge (3.60 A) via
the N–O group in a m-Z2 fashion and is similar to the cluster
[Ru3(m3-NPh)2(m-Z2-ONPh)2(CO)7].10 Cluster 1 possesses C2
symmetry with the principal axis passing through Os(2) and
bisecting the open triangular metal framework. The molecule
of 1 contains two oximato ligands that chelate to the metal
core in a m-Z3 manner. The ligand is bound to the cluster by
coordination of the pyridine nitrogen lone pair [Os(1)–N(1)
94
New J. Chem., 2002, 26, 94–104
DOI: 10.1039/b107628k
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2002

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Scheme 1
+
2.165(9)A] and the oximato oxygen and nitrogen atoms
[Os(1*)–O(5) 2.115(7), Os(1)–N(2) 2.146(9) A]. The oximato
oxygen atoms span to the neighbouring metal centre over the
by the oximato ligands. The oximato ligands in 1 act as 5eÀ
donors. Together with the eight terminal carbonyls, cluster 1 is
electron precise with a cluster valence electron (CVE) count of
50, which is expected for a trinuclear cluster with two metal–
metal bonds.
The mass and IR spectra show that 2 is a triosmium com-
pound with terminal carbonyls only. The 1H NMR signal at d
À 10.09 is attributed to a terminal metal hydride. In order to
establish the molecular structure of 2 the compound was
+
+
open metalÁ Á Ámetal edge. The N–O bond distance is 1.35(1) A.
Most of the reported complexes with a m-Z2-coordinated oxi-
mato N–O unit are dimetallic or trimetallic in nature with the
metal–metal bond remaining intact.1,8,9 Opening up of the Ru–
Ru bond by coordination of the m-Z2-nitrosobenzene ligand
has been reported.10 In cluster 1, one Os–Os bond is opened up
Table 1 Spectroscopic data for compounds 1–9
Cluster
IR spectraa n(CO)=cmÀ1
Mass spectrab m=z
H NMR spectrac d, J=Hz
1
2
3
2072m, 1995vs, 1925w,
1189
1077
1021
8.86 (d, J ¼ 6.7, 4H, Py), 7.81 (td, J ¼ 6.7, 1.3, 4H, Py),
7.31 (t, J ¼ 7.0, 6H, Ph), 7.06 (d, J ¼ 7.0, 4H, Ph)
1922w, 1914w (CH2Cl2)
2122w, 2084s, 2064w, 2049m,
2041w, 2028vs, 2018s, 1999s, 1987w
2053s, 2016vs, 2006w, 1993s,
1970s, 1952m
8.73 (dd, J ¼ 6.2, 1.2, 1H, Py), 7.61 (m, 1H, Py), 7.45 (m, 5H, Ph),
7.29 (dd, J ¼ 8.3, 1.0, 1H, Py), 7.04 (m, 1H, Py), À 10.09 (s, 1H, Os–H)
9.02 (dd, J ¼ 6.2, 1.1, 1H, Py), 7.72 (td, J ¼ 6.5, 1.1, 1H, Py),
7.54 (dd, J ¼ 6.5, 1.4, 1H, Py), 7.49 (m, 5H, Ph),
7.25 (td, J ¼ 6.2, 1.4, 1H, Py), À 18.20 (s, 1H, Os–H)
4
2066m, 1989s, 1978sh,
1900w (CH2Cl2)
1175
9.02 (d, J ¼ 6.5, 1H, Py), 8.75 (d, J ¼ 6.0, 1H, Py),
7.88 (t, J ¼ 7.0, 1H, Py), 7.53 (t, J ¼ 6.4, 1H, Py), 7.46 (t, J ¼ 6.5, 1H, Py),
7.35 (m, 4H, Ph), 7.26 (m, 2H, Ph), 7.22 (d, J ¼ 7.0, 1H, Py),
6.96 (t, J ¼ 6.0, 1H, Py), 6.86 (m, 4H, Ph), 6.74 (d, J ¼ 6.4, 1H, Py),
4.38 (d, J ¼ 4.8, 1H, NH), 2.51 (d, J ¼ 4.8, 1H, C–H)
7.49 (m, 3H, Ph), 7.39 (m, 2H, Ph), 7.23 (m, 5H, Ph),
À 11.64 (s, 1H, Os–H)
5
6
2109m, 2072s, 2059s, 2026vs, 2014s,
2003m, 1981m
2128w, 2082s, 2051vs, 2039s, 2028w,
2008w, 1991m, 1974m
1048
1020
7.85 (d, J ¼ 7.4, 1H, Ph), 7.34 (m, 3H, Ph), 7.24 (m, 2H, Ph),
7.06 (t, J ¼ 7.4, 1H, Ph), 6.97 (d, J ¼ 7.9, 1H, Ph), 6.84 (t, J ¼ 7.9, 1H, Ph),
À 13.05 (d, J ¼ 1.7, 1H, Os–H, À 14.38 (d, J ¼ 1.7, 1H, Os–H)
7.45 (m, 8H, Ph), 7.37 (m, 2H, Ph), À 0.10 (s, 1H, OH)
7
8
9
2101w, 2069vs, 2049m, 2014s,
2003s, 1987m, 1976w
2097w, 2078vs, 2064vs, 2049w, 2018vs,
2008m, 1997m, 1993m, 1968w
2099w, 2072s, 2033vs, 2008w, 1997w
1048
1964
1550
7.77 (d, J ¼ 7.1, 2H, Ph), 7.56 (m, 6H, Ph), 7.36 (m, 4H, Ph), 7.18 (m, 4H, Ph),
7.03 (dd, J ¼ 6.1, 2.2, 2H, Ph)
8.05 (d, J ¼ 7.5, 1.4, 1H, Ph), 7.44 (m, 3H, Ph), 7.34 (td, J ¼ 7.5, 1.4, 1H, Ph),
7.02 (m, 3H, Ph), 6.58 (dd, J ¼ 7.7, 1.4, 1H, Ph)
a
b
In n-hexane unless otherwise stated. Parent ion peak; the observed value is the same as that calculated from the molecular formula.
In CD2Cl2 .
c
New J. Chem., 2002, 26, 94–104
95

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Fig. 2 Molecular structure of [Os3H(CO)11{Z2-ON=CPh(NC5H4)}] 2
and the atom numbering scheme.
CHCl3 solution at À 20 ꢀC. The molecular structure of 3 is
depicted in Fig. 3, and selected bond parameters are given in
Table 4. Cluster 3 consists of a triangular metal core [Os(1)–
Fig. 1 Molecular structure of [Os3(CO)8{m-Z3-ON=CPh(NC5H4)}2] 1
and the atom numbering scheme.
Os(2) 2.8800(5), Os(2)–Os(3) 2.8470(5), Os(1)–Os(3) 2.8473(5)
A] in which the Os(1) and the Os(3) atoms are edge-bridged by
+
characterized by X-ray crystallographic analysis (Fig. 2).
Selected bond parameters are presented in Table 3. This
molecule contains an open linear Os3(CO)11 cluster [Os(1)–
Os(2)–Os(3) 175.79(2)ꢀ] attached to both the pyridine nitrogen
a hydride and an oximato ligand. The molecule of 3 contains
one oximato ligand that chelates to the metal frameworkin a
similar manner, m-Z3, as in 1 [Os(1)–N(1) 2.092(8), Os(3)–O(10)
2.166(6), Os(1)–N(2) 2.039(7) A]. The pyridyl nitrogen N(1)
+
and oximato nitrogen atoms on the terminal Os atom [Os(1)–
N(1) 2.11(1), Os(1)–N(2) 2.10(1) A]. The metal core of 2 is
and the oximato nitrogen N(2) chelate to Os(1) and form a five-
membered metallacyclic ring [Os(1), N(1), C(14), C(15), N(2)]
with a mean deviation of 0.048 A from the least-squares plane.
+
+
similar to [Os3(CO)11(m3-FcC4Fc)] in which the bond angle of
Os(1)–Os(2)–Os(3) is 162.65(4)ꢀ.11 The oxime moiety acts as a
bidentate ligand that coordinates to the Os(1) at the axial and
equatorial positions via the pyridine nitrogen and oximato
nitrogen atoms, respectively, to form a five-memebered che-
lated ring, while the oximato oxygen atom remains non-
coordinating. The ligand groups on Os(1), Os(2) and Os(3) are
staggered with respect to the ligands on the adjacent metal so
as to minimize steric crowding. A similar effect is observed in
The metallacyclic ring is fused to the four-membered ring
containing Os(1), Os(3), N(2) and O(10) and pyridyl ring con-
taining N(1), C(10), C(11), C(12), C(13) and C(14) with dihe-
dral angles of 23.46ꢀ and 174.78ꢀ, respectively. The presence of
the bridging hydride on the metal core is supported by the
signal at d À 18.20 in the 1H NMR spectrum. The bond lengths
+
of N(2)–O(10) and N(2)–C(15) are 1.348(10) and 1.30(1) A,
respectively, which indicates their partial double-bond char-
acter. The sp2 hybridization associated with the N(2) and C(15)
centers was confirmed by the sum of the bond angles at N(2)
(359.9ꢀ) and at C(15) (360.0ꢀ). This type of oximato bridge
has been observed before in the clusters [Os3(m-H)(m2-Me2-
C=NO)(CO)10] and [(m-H)Os3(CO)10{m2-Z2-ON-C9H6NCl)].8,9
The conversion of cluster 2 to cluster 3 may involve the loss of
CO under high temperature, which is followed by the coordi-
nation of the oximato oxygen to another terminal Os atom and
the formation of an Os–Os bond. Therefore, cluster 2 should be
an intermediate in the formation of cluster 3.
other linear clusters.12–14 The N–O bond distance of the oxi-
+
mato group is 1.28(1) A, which is within the range found in
most metal complexes with N-bonded nitroso group15–17 but is
comparably shorter than the corresponding value observed in
complex 1, since both N and O are coordinated in 1 but not in
2. The oxime ligand in 2 acts as a 3eÀ donor rather than a 5eÀ
donor as in the case for 1. Together with the eleven terminal
carbonyls, cluster 2 retains a CVE count of 50.
Thermolysis of 2 in toluene
Heating 2 in refluxing toluene for 3 h gave [Os3(m-H)(CO)9
{m-Z3-ON=CPh(NC5H4)}] 3 in low yield along with decom-
position of the starting material. Crystals of 3 suitable for X-ray
analysis were obtained by slow evaporation from an n-hexane–
Reaction of [Os3(CO)10(NCMe)2] with phenyl 2-pyridyl
ketoxime
Treatment of a CH2Cl2 solution of [Os3(CO)10(NCMe)2] with
1 equiv. of phenyl 2-pyridyl ketoxime at ambient conditions
+
Table 2 Selected bond distances (A) and angles (ꢀ) for cluster 1
+
Table 3 Selected bond distances (A) and angles (ꢀ) for cluster 2
Os(1)–Os(2)
Os(1)–N(1)
Os(1)–N(2)
Os(1)–O(5*)
N(2)–O(5)
2.8472(6)
2.165(9)
2.146(9)
2.115(7)
1.35(1)
N(1)–C(5)
N(1)–C(9)
N(2)–C(10)
C(9)–C(10)
1.36(1)
1.35(1)
1.29(1)
1.46(1)
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–N(1)
Os(1)–N(2)
N(1)–C(12)
2.9038(7)
2.9160(7)
2.11(1)
2.10(1)
1.37(2)
N(1)–C(16)
N(2)–O(12)
N(2)–C(17)
C(16)–C(17)
1.35(2)
1.28(1)
1.34(2)
1.45(2)
Os(1)–Os(2)–Os(1*)
Os(2)–Os(1)–N(2)
Os(2)–Os(1)–O(5*)
Os(1)–N(1)–C(5)
Os(1)–N(1)–C(9)
Os(1)–N(2)–O(5)
Os(1)–N(2)–C(10)
78.52(2)
92.9(2)
89.0(2)
126.6(9)
114.9(7)
124.2(6)
118.2(7)
Os(1)–O(5*)–N(2*)
N(1)–Os(1)–N(2)
N(1)–C(9)–C(10)
N(2)–C(10)–C(9)
N(2)–C(10)–C(11)
O(5)–N(2)–C(10)
113.0(6)
73.9(3)
115.5(10)
115.2(10)
121.3(10)
117.6(9)
Os(1)–Os(2)–Os(3)
Os(1)–N(1)–C(12)
Os(1)–N(1)–C(16)
Os(1)–N(2)–O(12)
Os(1)–N(2)–C(17)
175.79(2)
N(1)–C(16)–C(17)
N(2)–C(17)–C(16)
N(2)–C(17)–C(18)
O(12)–N(2)–C(17)
C(16)–C(17)–C(18)
115(1)
125.0(10)
115.6(8)
121.1(8)
117.2(8)
114(1)
122(1)
121(1)
122(1)
96
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4 (Scheme 1). Cluster 4 was characterized by various spectro-
scopic methods (Table 1). The IR spectrum shows the presence
of terminal carbonyl ligands and the mass spectrum exhibits
molecular ion envelopes that agree with the formula of the
compound, with ion peaks corresponding to CO losses also
being present. The 1H NMR spectrum of 4 is complicated and
consists of proton signals ranging from d 2.5 to 9.0; no metal
hydride could be detected. The proton resonance between d 6.7
and 9.0 are due to the aromatic ring system, while the two
doublets centred at d 4.38 and 2.51, which are coupled to each
other, are attributable to the N–H and C–H protrons,
respectively.
Red crystals of 4 suitable for diffraction studies were grown
from a saturated solution of n-hexane and CHCl3 at À 20 ꢀC.
The molecular structure of 4 has also been established by X-
ray crystallography. There are two independent molecules in
each asymmetric unit, which are essentially the same. One of
the molecules is depicted in Fig. 4 and selected bond lengths
and angles are given in Table 5. One and a half molecules of
CHCl3 , as a solvent of crystallization, are found in the crystal
lattice. Cluster 4 retains the open triangular metal arrangement
of 1 with the two Os–Os bonds being almost equi-distance
[2.8531(8) vs. 2.8170(8) A], while the Os(1)Á Á ÁOs(3) edge is
+
Fig. 3 Molecular structure of [Os3(m-H)(CO)9{m-Z3-ON=CPh-
(NC5H4)}] 3 and the atom numbering scheme.
+
non-bonded with a separation of 3.31 A. The molecule con-
tains one oximato ligand and one deoxygenated oximato
ligand. The oximato ligand adopts the same coordination
mode to the metal centres as those in clusters 1 and 3
[Os(1)–N(1) 2.156(10), Os(3)–O(9) 2.136(9) and Os(1)–
N(2) 2.12(1) A] and the N–O bond distance in 4 is 1.34(1) A,
which is comparable to those in 1 and 3. The deoxygenated
oximato ligand is believed to undergo N–O bond cleavage of
the oximato moiety and coordinate to Os(1) and Os(3) through
gave clusters 1 and 3 in moderate yields upon TLC separation
(Scheme 1). The reaction of [Os3(CO)10(NCMe)2] with phenyl
2-pyridyl ketoxime proceeds much faster than that of
[Os3(CO)11(NCMe)] with the same ligand. Cluster 2, cannot be
obtained in the former reaction. This is probably because
[Os3(CO)10(NCMe)2] contains two labile acetonitrile groups,
which favour capping by the pyridine nitrogen and the oxi-
mato oxygen and nitrogen atoms of the oxime ligand.
The cluster [Os3(CO)10(NCMe)2] is a ready source of
Os3(CO)10 fragments in reactions leading to oxidative addition
of HX to give compounds of the type [Os3(m-H)(m-X)(CO)10].
For example, alcohols react to give [Os3(m-H)(m-OR)(CO)10].18
Pyridine undergoes ortho-metallation to afford [Os3(m-H)(m-
C5H4N)(CO)10].19 Therefore, in principle, oximes R2C=NOH
could give [Os3(m-H)(m-R2C=NO)(CO)10] or [Os3(m-H)(m-
RC=NOH)(CO)10] if the R group trans to OH in the oxime
is an H atom.8 According to our results, the primary products
from the reaction of phenyl 2-pyridyl ketoxime with
[Os3(CO)10(NCMe)2] are all derived in the same way from
oxidative addition with O–H bond cleavage.
+
+
the oximato nitrogen and pyridine nitrogen [Os(1)–N(4)
2.164(10) Os(3)–N(4) 2.155(9) and Os(3)–N(3) 2.138(10) A],
+
which is similar to the reported ruthenium cluster [Ru3(m-H)(m-
HNCHPh2)(CO)10].20 The C(26)–N(4) in the deoxygenated
+
ligand has a length of 1.53(1) A thus is a single C–N bond. The
deoxygenated oximato ligand should be a 5eÀ donor with the
bridging nitrogen and the pyridine nitrogen atoms contribut-
ing three and two electrons to the cluster framework, respec-
tively; together with the oximato ligand and eight terminal
Thermolysis of 3with phenyl 2-pyridyl ketoxime in toluene
A solution of cluster 3 and 1 equiv. of phenyl 2-pyridyl
ketoxime in refluxing toluene led to conversion to 1 and
[Os3(CO)8{m-Z3-ON=CPh(NC5H4)}{m-Z2-N(H)CHPh(NC5H4)}]
+
Table 4 Selected bond distances (A) and angles (ꢀ) for cluster 3
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–Os(3)
Os(1)–N(2)
Os(1)–N(1)
Os(3)–O(10)
2.8800(5)
2.8470(5)
2.8473(5)
2.039(7)
2.092(8)
2.166(6)
N(1)–C(10)
N(1)–C(14)
N(2)–O(10)
N(2)–C(15)
C(14)–C(15)
1.34(1)
1.37(1)
1.348(10)
1.30(1)
1.45(1)
Os(1)–Os(2)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–Os(1)–O(3)
Os(1)–Os(3)–O(10)
Os(2)–Os(3)–O(10)
Os(2)–Os(1)–N(2)
Os(3)–Os(1)–N(2)
Os(1)–N(1)–C(10)
Os(1)–N(1)–C(14)
59.62(1)
60.76(1)
59.61(1)
69.4(2)
90.8(2)
84.1(2)
68.0(2)
126.5(7)
114.6(6)
Os(1)–N(2)–O(10)
Os(1)–N(2)–C(15)
Os(3)–O(10)–N(2)
N(1)–Os(1)–N(2)
N(1)–C(14)–C(15)
N(2)–C(15)–C(14)
N(2)–C(15)–C(16)
O(10)–N(2)–C(15)
C(10)–N(1)–C(14)
116.8(6)
120.3(6)
103.9(5)
76.0(3)
114.9(8)
113.2(8)
113.9(8)
122.8(8)
118.9(8)
Fig. 4 Molecular structure of [Os3(CO)8{m-Z3-ON=CPh(NC5H4)}-
{m-Z2-N(H)CHPh(NC5H4)}] 4 and the atom numbering scheme.
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+
Table 5 Selected bond distances (A) and angles (ꢀ) for cluster 4
Attempted thermolysis and hydrogenation of 1
Molecule 1
Molecule 2
Heating complex 1 in refluxing toluene for 2 days results in
no observable change in the IR spectrum and spot TLC
monitoring. Cluster 1 is thermally stable up to the boiling
point of toluene without any molecular rearrangement or bond
cleavage.
Hydrogenation of complex 1 was attempted in refluxing
CHCl3 , monitored by IR and TLC. However, no reaction was
observed after 5 h. Thermolysis and hydrogenation of 1 failed
to give complex 4. Therefore, complexes 1 and 4 may be
formed via different pathways.
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–N(1)
Os(1)–N(2)
Os(1)–N(4)
Os(3)–N(3)
Os(3)–N(4)
Os(3)–O(9)
N(1)–C(13)
N(2)–O(9)
2.8531(8)
2.8170(8)
2.156(10)
2.12(1)
2.164(10)
2.138(10)
2.155(9)
2.136(9)
1.38(1)
1.34(1)
1.32(1)
1.35(2)
1.33(1)
2.8624(8)
2.8166(8)
2.13(1)
2.093(10)
2.16(1)
2.12(1)
2.14(1)
2.099(8)
1.34(1)
1.35(1)
1.32(1)
1.36(2)
1.35(2)
1.51(2)
1.46(2)
1.52(2)
N(2)–C(14)
N(3)–C(21)
N(3)–C(25)
N(4)–C(26)
C(13)–C(14)
C(25)–C(26)
1.53(1)
1.44(2)
1.52(2)
Reaction of [Os3(CO)10(NCMe)2] with benzophenone oxime
To explore the change in the reactivity of the oxime with
different substitutents, we investigated the reaction of
[Os3(CO)10(NCMe)2] with benzophenone oxime, in addition to
phenyl 2-pyridyl ketoxime. Treatment of 1 equiv. benzo-
phenone oxime with [Os3(CO)10(NCMe)2] in CH2Cl2 at room
temperature over a period of 5 h afforded [Os3(m-H)(CO)10{m-
Z2-ON=CPh2}] 5 in 27% yield (Scheme 2). The preparation
and the spectroscopic data of cluster 5 have been reported and
a structure for 5 proposed by comparing the spectroscopic
data with those of the compound [Os3(m-H)(m2-Me2C=NO)-
(CO)10].8 We determined the structure of cluster 5 by both
spectroscopic techniques (Table 1) and X-ray diffraction ana-
lysis in this work. There are two independent molecules of 5
in each asymmetric unit, which are essentially the same; one of
the molecules is depicited in Fig. 5 and relevant bond para-
meters are in Table 6. The molecule contains a triangular metal
Os(1)–Os(2)–Os(3)
Os(2)–Os(1)–N(1)
Os(2)–Os(1)–N(2)
Os(2)–Os(1)–N(4)
Os(2)–Os(3)–N(3)
Os(2)–Os(3)–N(4)
Os(2)–Os(3)–O(9)
Os(1)–N(1)–C(13)
Os(1)–N(2)–O(9)
Os(1)–N(2)–C(14)
Os(1)–N(4)–Os(3)
Os(1)–N(4)–C(26)
Os(3)–N(3)–C(21)
Os(3)–N(3)–C(25)
Os(3)–N(4)–C(26)
Os(3)–O(9)–N(2)
N(1)–C(13)–C(14)
N(2)–C(14)–C(13)
N(3)–C(25)–C(26)
N(4)–C(26)–C(25)
O(9)–N(2)–C(14)
71.45(2)
170.2(3)
95.8(3)
71.83(2)
166.6(3)
93.2(3)
82.6(3)
160.9(3)
84.0(3)
89.3(2)
114.5(8)
120.7(7)
118(1)
101.4(4)
115.0(8)
125.9(10)
117.0(8)
115.0(8)
112.0(6)
116(1)
82.4(2)
160.5(3)
83.5(2)
91.5(2)
113.9(8)
120.0(8)
118.2(9)
100.1(4)
118.6(7)
124.8(8)
117.0(8)
114.8(7)
111.5(7)
115(1)
115(1)
120(1)
109.1(10)
120(1)
112(1)
119(1)
109(1)
118(1)
core [Os(1)–Os(2) 2.8736(8), Os(2)–Os(3) 2.8740(9), Os(1)–
Os(3) 2.8471(8) A]. The oximato ligand chelates to the metal
+
framework via the N–O unit [Os(1)–N(1) 2.155(10), Os(3)–
O(11) 2.091(9) A], in the same way as in the reported cluster
+
carbonyls a CVE count of 50 is obtained, which is electron
precise for a triosmium cluster containing two metal–metal
bonds in accordance with the effective atomic number
(EAN) rule.
[Os3(m-H)(m-Me2C=NO)(CO)10],8 by oxidative addition with
O–H cleavage. The N–O bond distance is found to be
1.35(1) A, which is comparable with those in previously
+
Scheme 2
98
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Yellow crystals of 6 and 7 suitable for diffraction analysis
were obtained by slow evaporation of these compounds in
n-hexane–CH2Cl2 at À 20 ꢀC. Perspective views of the mole-
cular structures of 6 and 7 are shown in Fig. 6 and 7, respec-
tively, and relevant bond parameters in Tables 7 and 8,
respectively. Complex 6 retains the same cluster core as 5. On
thermolysis, the oxime was converted into a tridentate ligand
by ortho-metallation. In addition to the m-Z2-oximato N–O
bridge, the phenyl a-carbon on the ligand coordinates to Os(1)
[Os(1)–C(22) 2.11(1) A] and leads to the formation of a five-
+
membered ring [Os(1), C(22), C(17), C(10), N(1)] with a mean
deviation of 0.044 A from the least-squares plane. The
+
metallacyclic five-membered ring is fused to the four-mem-
bered ring containing Os(1), Os(3), N(1) and O(10) and the
phenyl ring containing C(17), C(18), C(19), C(20), C(21) and
C(22) with dihedral angles of 14.19ꢀ and 5.61ꢀ, respectively.
The coordination mode of the ligand in 6 resembles that in 3 in
Fig. 5 Molecular structure of [Os3(m-H)(CO)10{m-Z2-ON=CPh2}] 5
and the atom numbering scheme.
mentioned complexes.1,8 In contrast to 3, the oxime ligand in 5
acts as a bidentate ligand and chelates to the metal core in a
m-Z2-manner while the oxime in 3 binds to the cluster in a
m-Z3-fashion, with one more coordination via the pyridine
nitrogen atom.
Thermolysis of 5 in toluene
Cluster 5 was heated in refluxing toluene until complete con-
sumption was observed by TLC monitoring. Two products,
identified as [Os3(m-H)2(CO)9{m-Z3-OH=CPh(C6H4)}] 6 and
[Os3(CO)10(m-OH){m-N=CPh2}] 7, were isolated in 27 and 21%
1
yields, respectively (Scheme 2). The H NMR signals due to
the organic moieties of the two complexes are fully consistent
with their structures. The signals of the two hydrides in 6 are
observed at d À 14.38 and À 13.05, while a signal at d À 0.10 in
7 is assigned to the bridging hydroxy proton. The mass spectra
exhibit molecular ion envelopes that agree with the formulae of
the compounds (Table 1).
Fig. 6 Molecular structure of [Os3(m-H)2(CO)9{m-Z3-ON=CPh-
(C6H4)}] 6 and the atom numbering scheme.
+
Table 6 Selected bond lengths (A) and angles (ꢀ) for cluster 5
Molecule 1
Molecule 2
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–Os(3)
Os(1)–N(1)
Os(3)–O(11)
N(1)–O(11)
N(1)–C(11)
C(11)–C(12)
C(11)–C(18)
2.8736(8)
2.8740(9)
2.8471(8)
2.155(10)
2.091(9)
1.35(1)
1.31(2)
1.50(7)
1.49(2)
2.8594(9)
2.8605(9)
2.8747(8)
2.170(10)
2.077(9)
1.35(1)
1.32(2)
1.48(2)
1.48(2)
Os(1)–Os(2)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–O(11)
Os(2)–Os(1)–N(1)
Os(2)–Os(3)–O(11)
Os(3)–Os(1)–N(1)
Os(1)–N(1)–O(11)
Os(1)–N(1)–C(11)
Os(3)–O(11)–N(1)
O(11)–N(1)–C(11)
N(1)–C(11)–C(12)
N(1)–C(11)–C(18)
C(12)–C(11)–C(18)
59.39(2)
60.30(2)
60.31(2)
69.7(2)
86.4(3)
89.9(3)
68.9(3)
108.7(7)
132.8(9)
112.1(7)
117(1)
60.34(2)
59.81(2)
59.85(2)
69.4(2)
87.4(3)
90.1(3)
68.4(3)
108.4(7)
132.1(9)
113.5(7)
119(1)
124(1)
117(1)
117(1)
125(1)
118(1)
116(1)
Fig. 7 Molecular structure of [Os3(CO)10(m-OH){m-N=CPh2}] 7 and
the atom numbering scheme.
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+
Table 7 Selected bond lengths (A) and angles (ꢀ) for cluster 6
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–Os(3)
Os(1)–N(1)
Os(1)–C(22)
Os(3)–O(10)
3.0327(6)
2.8862(6)
2.9522(6)
2.073(7)
2.11(1)
N(1)–O(10)
N(1)–C(10)
C(10)–C(11)
C(10)–C(17)
C(17)–C(22)
1.346(9)
1.31(1)
1.51(1)
1.46(1)
1.40(1)
2.151(7)
Os(1)–Os(2)–Os(3)
Os(1)–Os(3)–Os(2)
Os(2)–Os(1)–Os(3)
Os(1)–Os(3)–O(10)
Os(2)–Os(1)–N(1)
Os(2)–Os(3)–O(10)
Os(3)–Os(1)–N(1)
Os(1)–N(1)–O(10)
Os(1)–N(1)–C(10)
59.78(1)
62.58(1)
57.65(1)
68.5(2)
84.4(2)
91.2(2)
66.3(2)
117.6(6)
120.2(6)
Os(1)–C(22)–C(17)
Os(1)–C(22)–C(21)
Os(3)–O(10)–N(1)
O(10)–N(1)–C(10)
N(1)–C(10)–C(11)
N(1)–C(10)–C(17)
C(10)–C(17)–C(22)
C(11)–C(10)–C(17)
112.6(7)
129.4(9)
106.7(5)
122.2(7)
123.9(9)
112.5(8)
117.2(9)
123.5(9)
Fig. 8 Molecular structure of [Os6(CO)16(m4-O){m-Z3-N=CPh
(C6H4)}2] 8 and the atom numbering scheme.
+
Table 8 Selected bond lengths (A) and angles (ꢀ) for cluster 7
Os(1)–Os(2)
Os(2)–Os(3)
Os(1)–N(1)
Os(1)–O(11)
Os(3)–N(1)
2.8639(5)
2.8587(6)
2.116(7)
2.149(7)
2.112(7)
Os(3)–O(11)
N(1)–C(11)
C(11)–C(12)
C(11)–C(18)
2.134(6)
1.27(1)
1.51(1)
1.51(1)
structural parameters are listed in Table 9. Complex 8 contains
six metal atoms grouped into a central cluster of four, Os(1)–
Os(2)–Os(3)–Os(4), which is arranged in the form of a ‘‘but-
terfly tetrahedron’’ containing five metal–metal bonds. The
dihedral angle between the Os(1), Os(2), Os(4) and Os(2),
Os(3), Os(4) planes is 27.9ꢀ. The two remaining metal atoms
are linked to this 4-atom cluster at the ‘‘hinge’’ atoms, one to
Os(1)–Os(2)–Os(3)
Os(2)–Os(1)–O(11)
Os(2)–Os(1)–N(1)
Os(2)–Os(3)–N(1)
Os(2)–Os(3)–O(11)
Os(1)–N(1)–Os(3)
Os(1)–O(11)–Os(3)
65.87(1)
82.3(2)
81.8(2)
82.0(2)
82.7(2)
94.8(3)
93.2(2)
Os(1)–N(1)–C(11)
Os(3)–N(1)–C(11)
N(1)–Os(1)–O(11)
N(1)–Os(3)–O(11)
N(1)–C(11)–C(12)
N(1)–C(11)–C(18)
C(12)–C(11)–C(18)
132.8(6)
132.4(6)
74.6(3)
75.0(3)
123.4(8)
123.1(8)
113.4(8)
each, via a metal–metal bond [Os(2)–Os(5) 2.862(1), Os(4)–
Os(6) 2.914(1) A]. The bond between the ‘‘hinge’’ atoms,
Os(2) and Os(4), is quite short, 2.713(1) A, which is relatively
+
+
common in high nuclearity clusters for metals with high
coordination numbers.22,23 In 8, Os(2) and Os(4) have sig-
nificantly higher coordination numbers than the other Os
atoms. The Os–Os bonds from the Os(2) and Os(4) hinge
which the pyridyl nitrogen atom in 3 is replaced by a phenyl
carbon in 6. The bond lengths of N(1)–O(10) and N(1)–C(10)
are 1.346(9) and 1.31(1) A, respectively, which indicates their
+
atoms to the Os(1) and Os(3) ‘‘wing-tips’’ can be grouped into
+
pairs of long [Os(1)–Os(2) 2.891(1), Os(3)–Os(4) 2.885(1) A]
+
partial double-bond character. The sp2 hybridization asso-
ciated with the N(1) and C(10) centres was confirmed by the
sum of the bond angles at N(1) (360.0ꢀ) and at C(10) (359.9ꢀ).
The N–O bond distance of 6 is comparable to those in the
previously mentioned complexes.
and short [Os(1)–Os(4) 2.842(1), Os(2)–Os(3) 2.825(1) A]
bonds. The hexanuclear metal frameworkis related to
those observed in [Os6(m4-S)(m-HC=NC6H5)2(CO)15] and
[Os3(CO)8(m3-S)2]2 .22,23 A novel structural feature of cluster 8
is that a m4-oxo atom is embraced in the semi-open environ-
Apart from 6, complex 7 was also obtained upon thermo-
1
lysis of 5. The H NMR signals due to protons of the phenyl
ment described by Os(2), Os(4), Os(5) and Os(6) [average
+
Os–O 2.11(1) A]. The capping modes of m3-oxo24,25 or m4-oxo26
rings are observed in the range d 7.33–7.48 and the resonance
for the bridging hydroxy proton occurs at d À 0.10. The
in osmium cluster systems have been reported. Another
interesting feature of 8 is the formation of the ortho-metallated
phenyl ring of the N=CPh2 units that arises from C–H fission.
Complex 8 contains two m3 bridging N=CPh2 groups, which
molecule consists of an open triangular array of three osmium
atoms [Os(1)–Os(2) 2.8639(5), Os(2)–Os(3) 2.8587(6) A] with
+
OH and Ph2C=N bridges on the open OsÁ Á ÁOs edge [Os(1)–
O(11) 2.149(7), Os(3)–O(11) 2.134(6), Os(1)–N(1) 2.116(7),
Os(3)–N(1) 2.112(7) A]. Compound 5 isomerizes thermally
+
to 7, which is formed by oxidative addition of the oxime with
N–O bond cleavage. The geometry of 7 is similar to [Os3(m-
OH){m-Me2C=N)(CO)10], which is the product of thermolysis
of [Os3(m-H){m-Me2C=NO)(CO)10]. The mechanism of this
conversion has not been studied but a possible route with
[Os3(m-Me2C=NOH)(CO)10] as an intermediate has been sug-
gested before.8 A reported triruthenium cluster, [Ru3(m-H)-
(m-N=CPh2)(CO)10], also contains an edge bridging N=CPh2
unit that is derived from benzophenone imine.21 The m-OH
and m-N=CPh2 units would be three-electron donors. Together
with ten terminal carbonyls, cluster 7 is electron precise for a
triosmium cluster with two Os–Os bonds.
+
Table 9 Selected bond lengths (A) and angles (ꢀ) for cluster 8
Os(1)–Os(2)
Os(1)–Os(4)
Os(2)–Os(3)
Os(2)–Os(4)
Os(2)–Os(5)
Os(3)–Os(4)
Os(4)–Os(6)
Os(1)–N(1)
Os(2)–O(17)
Os(3)–N(2)
Os(4)–O(17)
Os(5)–N(1)
2.891(1)
2.842(1)
2.825(1)
2.713(1)
2.862(1)
2.885(1)
2.914(1)
2.10(1)
2.11(1)
2.11(1)
2.13(1)
2.07(1)
Os(5)–O(17)
Os(5)–C(29)
Os(6)–N(2)
Os(6)–O(17)
Os(6)–C(42)
N(1)–C(17)
N(2)–C(30)
C(17)–C(18)
C(17)–C(24)
C(30)–C(31)
C(30)–C(37)
2.07(1)
2.06(2)
2.09(1)
2.13(1)
2.03(2)
1.30(2)
1.29(2)
1.51(2)
1.49(2)
1.49(2)
1.50(3)
Os(2)–O(17)–Os(4)
Os(2)–O(17)–Os(5)
Os(2)–O(17)–Os(6)
Os(4)–O(17)–Os(5)
Os(4)–O(17)–Os(6)
Os(5)–O(17)–Os(6)
Os(1)–N(1)–Os(5)
Os(3)–N(2)–Os(6)
Os(1)–N(1)–C(17)
79.7(4)
86.6(5)
133.8(5)
134.4(6)
86.3(4)
131.2(6)
113.3(6)
113.8(7)
132(1)
Os(5)–N(1)–C(17)
Os(3)–N(2)–C(30)
Os(6)–N(2)–C(30)
N(1)–C(17)–C(18)
N(1)–C(17)–C(24)
N(2)–C(30)–C(31)
N(2)–C(30)–C(37)
C(18)–C(17)–C(24)
C(31)–C(30)–C(37)
114(1)
131(1)
114(1)
122(1)
118(1)
125(1)
117(1)
118(1)
116(1)
Thermolysis of 5 in octane
Heating 5 in refluxing n-octane for 1 h afforded [Os6(CO)16-
(m4-O){m-Z3-N=CPh(C6H4)}2] 8 in low yield (Scheme 2). Dark
green crystals of 8 suitable for diffraction studies were grown
from a saturated solution of n-hexane–n-octane at À 20 ꢀC.
The molecular structure of 8 is depicted in Fig. 8 and relevant
100
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+
Table 10 Selected bond lengths (A) and angles (ꢀ) for cluster 9
are derived from the N–O cleavage of the oximato ligands.
Each N=CPh2 units bridges to one hinge and one wing-tip
Os(1)–Os(2)
Os(1)–Os(3)
Os(1)–Os(4)
Os(2)–Os(3)
Os(2)–Os(4)
Os(2)–Os(5)
Os(3)–Os(4)
2.7528(9)
2.7762(9)
2.9180(9)
2.7703(9)
2.8398(9)
2.8560(9)
2.8453(9)
Os(3)–Os(5)
Os(4)–N(1)
Os(4)–C(18)
Os(5)–N(1)
N(1)–C(16)
C(16)–C(17)
C(16)–C(23)
2.8645(9)
2.13(1)
2.11(2)
2.12(1)
1.30(2)
1.47(3)
1.48(2)
osmium via the m2-oximato nitrogen and the phenyl a-carbon
[average Os–N 2.09(1), Os–C 2.05(2) A]. The coordination
+
geometry of the bridging alkylideneimido units in
8
is similar to that in [Ru3(m-H)2(m3-N=CPhC6H4)(PPh3)2-
(CO)7].27 Assuming that the m4-O and oxime groups behave as
six- and four-electron donors, respectively, then cluster 8 is a
94-electron species, which is consistent with the seven metal–
metal bonds observed in the structure according to the EAN
rule.
Os(4)–N(1)–Os(5)
Os(4)–N(1)–C(16)
Os(5)–N(1)–C(16)
110.5(6)
116(1)
133(1)
N(1)–C(16)–C(17)
N(1)–C(16)–C(23)
C(17)–C(16)–C(23)
117(1)
121(1)
121(1)
Vacuum pyrolysis of 5
purified by standard procedures prior to use.29 Commercial
chemicals such as phenyl 2-pyridyl ketoxime and benzophe-
none oxime were used directly as received. The compounds
[Os3(CO)10(NCMe)2] and [Os3(CO)11(NCMe)] were prepared
by the literature methods.30,31 Infrared spectra were recorded
on a Bio-Rad FTS-135 IR spectrometer, using 0.5 mm calcium
fluoride solutions cells. 1H NMR spectra were recorded on
a Bruker DPX 300 NMR spectrometer using CD2Cl2 with
reference to SiMe4 . Mass spectra were obtained on a Finnigan
MAT 95 mass spectrometer by fast atom bombardment tech-
niques, using m-nitrobenzyl alcohol as the matrix solvent.
Routine purification of products was carried out in air by thin
layer chromatography (TLC) on plates coated with Merck
Kiesegel 60 GF254 . Elemental analyses were conducted by
Butterworth Laboratories, UK.
Solid state pyrolysis of the triosmium cluster 5 at 140 ꢀC
for 1.5 h yielded the pentanuclear cluster [Os5(CO)15{m-Z2-
N=CPh(C6H4)}] 9 in 15% yield (Scheme 2). The molecular
structure of 9 is shown in Fig. 9 together with the atom-
numbering scheme adopted. Bond lengths and interbond
angles are listed in Table 10. The metal frameworkof 9 can be
described as an edge-bridged tetrahedron, similar to that
observed in [Os5H3(CO)14(C5H4N)].28 The m-Z2-alkylidene-
imido ligand is bridged through the nitrogen atom to the
bridging Os atom and the apex of the tetrahedron while
the a-carbon of the phenyl ring is bonded to the same apex.
The angle between the planes formed by Os(1), Os(2), Os(3)
and Os(2), Os(3), Os(5) is 162.4ꢀ, with Os(5) displaced towards
the apical Os(4) atom. The bond lengths between the m-Z2-
alkylideneimido ligand and the metal atoms, Os(4)–C(18),
Os(4)–N(1), and Os(5)–N(1), are not significantly different
from those observed in 8. Complex 9 has an electron count of
74, consistent with the cluster having the observed edge-
bridged tetrahedral geometry. We have been able to obtain
four new clusters upon thermolysis of 5 in refluxing toluene or
octane and vacuum pyrolysis. Upon the use of high tempera-
ture, C–H activation, N–O cleavage of the oxime ligands and
cluster build-up have been observed.
Reactions of triosmium clusters
Reaction of [Os3(CO)11(NCMe)] with phenyl 2-pyridyl
ketoxime. A solution of [Os3(CO)11(NCMe)] (100 mg, 0.109
mmol) in CH2Cl2 was stirred with 1 equiv. of phenyl 2-pyridyl
ketoxime (21.6 mg, 0.109 mmol) at room temperature. The
reaction mixture gradually changed colour from yellow to
deep yellow. The reaction was complete after stirring for 5 h,
as monitored by TLC and IR. The reaction solution was
concentrated in vacuo and separated by TLC using n-hexane–
CH2Cl2 (1 : 6 v=v) as the eluent to afford a pale orange com-
plex 1 (Rf ꢁ 0.50, 5 mg, 0.004 mmol, 4%) and yellow complex
2 (Rf ꢁ 0.20, 20 mg, 0.019 mmol, 17%). Anal. found for 1: C,
32.2; H, 1.5; N, 4.5; calc. for C32H18N4O10Os3: C, 32.3; H, 1.5;
1.5; N, 4.7%. Anal. found for 2: C, 25.5; H, 0.9; N, 2.6; calc.
for C23H10N2O12Os3: C, 25.7; H, 0.9; N, 2.6%.
Experimental
Methods and materials
All reactions were carried out under an inert atmosphere of
argon using standard Sclencktechniques. Solvents were freshly
Reaction of [Os3(CO)10(NCMe)2] with phenyl 2-pyridyl
ketoxime. A solution of [Os3(CO)10(NCMe)2] (100 mg, 0.107
mmol) in CH2Cl2 was stirred with 1 equiv. of phenyl 2-pyridyl
ketoxime (21.3 mg, 0.107 mmol) at room temperature. An
immediate colour change from yellow to darkred was
observed. After stirring for 15 min, the solution was con-
centrated to 5 cm3 in vacuo. Purification was accomplished by
TLC using n-hexane–CH2Cl2 (2 : 3 v=v) as eluent to afford two
bands with Rf ꢁ 0.75 and 0.33, which were extracted from
silica to yield complex 1 (11 mg, 0.009 mmol, 8%) and complex
3 (38 mg, 0.037 mmol, 35%), respectively.
Reaction of [Os3(CO)10(NCMe)2] with benzophenone
oxime. The cluster [Os3(CO)10(NCMe)2] (100 mg, 0.107 mmol)
and benzophenone oxime (21.1 mg, 0.107 mmol) were allowed
to react in CH2Cl2 (30 ml) at room temperature for 5 h to give
a deep yellow solution. Evaporation to dryness and separation
of the residue by TLC using n-hexane–CH2Cl2 (3 : 1 v=v) gave
the yellow complex 5 (Rf ꢁ 0.50, 30 mg, 0.029 mmol, 27%).
Anal. found: C, 26.4; H, 1.1; N, 1.3; calc. for C23H11NO11Os3 :
C, 26.4; H, 1.1; N, 1.3%.
Fig. 9 Molecular structure of [Os5(CO)15(m-Z2-N=CPh(C6H4)}] 9
and the atom numbering scheme.
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Transformations of oxime containing osmium clusters
Crystallography
Crystals suitable for X-ray analyses were glued on glass fibres
with epoxy resin or sealed in a 0.3 mm glass capillary. Intensity
data were collected at ambient temperature on either a Bruker
AXS SMART CCD diffractometer (complexes 1, 3–9) or a
Rigaku AFC7R diffractometer (complex 2) equipped with
graphite-monochromated Mo-Ka radiation. Details of the
intensity data collection and crystal data are given in Table 11.
The diffracted intensities were corrected for Lorentz-polariza-
tion effects. Absorption corrections were applied by SADABS
for 1 and 3–9,32 while the C-scan method was employed for
semi-empirical absorption corrections in the case of 2.33 All
structures except complex 3 (by heavy-atom Patterson meth-
ods, SAPI9134) were solved by direct methods (SHELXS 8635
for 1, 6; SIR 9236 for 2, 4, 5, 7–9) and expanded by Fourier
difference techniques.37 Atomic coordinates and thermal para-
meters were refined by full-matrix least-squares analysis on F,
with the osmium atoms and non-hydrogen atoms being refined
anisotropically. However, attempts to refine all the atoms
anisotropically were made in structures 4, 8 and 9, but led to
negative anisotropic displacement parameters. Therefore some
non-hydrogen atoms were refined isotropically. Hydrogen
atoms were generated in their ideal positions and included in
the structure factor calculations but not refined. Calculations
were performed on a Silicon Graphics computer using the
teXsan38 crystallographic software package.
Attempted thermolysis and hydrogenation of complex
1. Complex 1 (50 mg, 0.042 mmol) was dissolved in toluene
(30 ml). The orange solution was heated at 125 ꢀC. Using IR and
spot TLC monitoring, novisible change was observed after 2 days.
Complex 1 (50 mg, 0.042 mmol) was dissolved in CHCl3
(20 ml). Hydrogenation of the pale orange solution at atmo-
spheric pressure was then attempted under reflux at 65 ꢀC for
5 h. The reaction was monitored by IR spectroscopy and spot
TLC. However, no change was observed. About 90% of the
starting material was recovered upon separation on pre-
parative silica plates.
Thermolysis of complex 2. Complex 2 (50 mg, 0.046 mmol)
was refluxed in toluene under an inert atmosphere. The reac-
tion was monitored by TLC and IR and completed after 3 h.
The solvent was then removed in vacuo and redissolved in
CH2Cl2 (3 cm3). TLC purification with n-hexane–CH2Cl2 (1 : l
v=v) gave an orange complex 3 (Rf ꢁ 0.70, 6 mg, 0.006 mmol,
13%) and unreacted starting material 2 (Rf ꢁ 0.10, 3 mg, 0.003
mmol, 7%). Anal. found for 3: C, 24.5; H, 1.0; N, 2.6; calc. for
C21H10N2O10Os3 : C, 24.7; H, 1.0; N, 2.7%.
Thermolysis of complex 3with phenyl 2-pyridyl ketox-
ime. Complex 3 (50 mg, 0.049 mmol) and phenyl 2-pyridyl
ketoxime (10 mg, 0.049 mmol) were stirred at reflux in toluene
(30 ml) for 1.5 h. The colour gradually turned from orange to
darkred. The reaction mixture was evaporated to dryness.
The residue was finally redissolved in CH2Cl2 (ca. 2 cm3) and
separated by preparative TLC with an eluent of n-hexane–
CH2Cl2 (1 : 2 v=v) to give complex 1 (Rf ꢁ 0.80, 7 mg, 0.006
mmol, 12%) and pale red complex 4 (Rf ꢁ 0.60, 9 mg, 0.008
mmol, 16%). Anal. found for 4: C, 32.8; H, 1.7; N, 4.9; calc. for
C32H20N4O9Os3 : C, 32.7; H, 1.7; N, 4.7%.
CCDC reference numbers 174851–174859. See http:==
www.rsc.org=suppdata=nj=b1=b107628k= for crystallographic
data in CIF or other electronic format.
Acknowledgements
We gratefully acknowledge financial support from the Hong
Kong Research Grants Council and the University of Hong
Kong. J. S.-Y. W. acknowledges the receipt of a postgraduate
studentship, administered by the University of Hong Kong.
Thermolysis of complex 5 in toluene. Complex 5 (50 mg,
0.048 mmol) was dissolved in toluene and the yellow solution
was allowed to heat under reflux for 6 h. The reaction mixture
changed colour to deep yellow gradually. The solvent was
removed under reduced pressure. The residue was redissolved
in CH2Cl2 (3 cm3) and separated by preparative TLC with
n-hexane–CH2Cl2 (3 : 1 v=v) to yield yellow complex 6
(Rf ꢁ 0.38, 13 mg, 0.013 mmol, 27%) and yellow complex 7
(Rf ꢁ 0.15, 10 mg, 0.010 mmol, 21%). Anal. found for 6: C,
26.3; H, 1.0; N, 1.3; calc. for C23H11NO11Os3: C, 26.4; H, 1.1;
N, 1.3%. Anal. found for 7: C, 25.7; H, 1.1; N, 1.31; calc. for
C22H11NO10Os3 : C, 25.9; H, 1.1; N, 1.4%.
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