Synthesis and characterisation of saturated and unsaturated triruthenium clusters containing electronically symmetrical and asymmetrical alkynes

Article abstract of DOI:10.1016/j.jorganchem.2003.09.038

The synthesis and characterisation of μ₃-η²- alkynyl triruthenium clusters, [Ru₃(μ₃-η ²-R¹-4-C₆H₄CCR²) (μ-dppm)(μ-CO)(CO)₇] (1, saturated), [Ru₃(μ₃-η²-R¹-4- C₆H₄CCR²)(μ-dppm)(CO)₇] (2, unsaturated) and [Ru₃(μ₃-η ²-R¹-4-C₆H₄CCR²) (μ-dppm)(PPh₃)(CO)₇] (3, saturated) containing symmetrical and asymmetrical alkynes in which R¹ and R² are electron donor or electron withdrawing groups in the para position of the aromatic ring(s]) or R² is ferrocenyl, are reported. Clusters 1 were obtained from the reactions of [PPN][Ru₃(μ-Cl)(CO)₁₀] with R¹-4-C₆H₄CCR² and dppm. Clusters 1 were successfully decarbonylated to give unsturated clusters 2, with the exception of the FcCCC₆H₄-4- NO₂ containing cluster, which is stable. Novel adducts 3 were obtained in high yields by addition of PPh₃ to unsaturated clusters 2. Clusters 1-3 were characterised by analytical and spectroscopic data, and structures were proposed on the basis of systematic ³¹P NMR studies and correlations with X-ray structural data of related compounds available in the literature. Saturated compounds 1 contain a CO and a dppm ligands bridging the same edge, which is also parallel to the μ₃-η²-alkyne, as opposed to the structure previously proposed for the PhCCPh and other derivatives, and established by X-ray crystallography for the PhC≡;CCCPh cluster derivative, in which the dppm ligand bridges a different edge. Unsaturated compounds 2 exhibit the same structure established for the PhCCPh derivative in the solid state, with the alkyne bonded in the μ₃-η²-mode perpendicular to the Ru₂ edge supported by the dppm ligand. Because the dppm phosphorus chemical shifts were sensitive to the alkyne electronic asymmetry, it was possible to show that clusters containing electronically asymmetrical alkynes exist in two inseparable isomeric forms, which differ with respect to the alkyne orientation. Similarly to their osmium analogues, saturated compounds 3 exist as inseparable mixtures of isomers that differ with respect to the position of the bridging CO and dppm ligands, and in the cases of asymmetrical alkyne derivatives, also with respect to the orientation of the alkyne. This work has established, therefore, that μ-CO and dppm ligand positions respective to the μ₃-η²-alkyne in saturated clusters 1 and 3 are sensitive both to the nature of the coordinated alkyne and to the presence of a PPh₃ in place of a CO ligand on the metal frame. 2003 Elsevier B.V. All rights reserved.

Full text of DOI:10.1016/j.jorganchem.2003.09.038

Journal of Organometallic Chemistry 689 (2004) 111–121
www.elsevier.com/locate/jorganchem
Synthesis and characterisation of saturated and unsaturated
triruthenium clusters containing electronically symmetrical
and asymmetrical alkynes
*
Renato Rosseto, Maria D. Vargas
Instituto de Quꢀımica, Universidade Estadual de Campinas, C.P. 6154, Campinas 13083-970, Brazil
Received 31 July 2003; accepted 26 September 2003
Abstract
The synthesis and characterisation of l3-g2-alkynyl triruthenium clusters, [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(l-CO)(CO)7]
(1, saturated), [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(CO)7] (2, unsaturated) and [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(PPh3)
(CO)7] (3, saturated) containing symmetrical and asymmetrical alkynes in which R1 and R2 are electron donor or electron with-
drawing groups in the para position of the aromatic ring(s) or R2 is ferrocenyl, are reported. Clusters 1 were obtained from the
reactions of [PPN][Ru3(l-Cl)(CO)10] with R1-4-C6H4CCR2 and dppm. Clusters 1 were successfully decarbonylated to give uns-
turated clusters 2, with the exception of the FcCCC6H4-4-NO2 containing cluster, which is stable. Novel adducts 3 were obtained in
high yields by addition of PPh3 to unsaturated clusters 2. Clusters 1–3 were characterised by analytical and spectroscopic data, and
structures were proposed on the basis of systematic 31P NMR studies and correlations with X-ray structural data of related
compounds available in the literature. Saturated compounds 1 contain a CO and a dppm ligands bridging the same edge, which is
also parallel to the l3-g2-alkyne, as opposed to the structure previously proposed for the PhCCPh and other derivatives, and es-
tablished by X-ray crystallography for the PhCBCCCPh cluster derivative, in which the dppm ligand bridges a different edge.
Unsaturated compounds 2 exhibit the same structure established for the PhCCPh derivative in the solid state, with the alkyne
bonded in the l3-g2-mode perpendicular to the Ru2 edge supported by the dppm ligand. Because the dppm phosphorus chemical
shifts were sensitive to the alkyne electronic asymmetry, it was possible to show that clusters containing electronically asymmetrical
alkynes exist in two inseparable isomeric forms, which differ with respect to the alkyne orientation. Similarly to their osmium
analogues, saturated compounds 3 exist as inseparable mixtures of isomers that differ with respect to the position of the bridging CO
and dppm ligands, and in the cases of asymmetrical alkyne derivatives, also with respect to the orientation of the alkyne. This work
has established, therefore, that l-CO and dppm ligand positions respective to the l3-g2-alkyne in saturated clusters 1 and 3 are
sensitive both to the nature of the coordinated alkyne and to the presence of a PPh3 in place of a CO ligand on the metal frame.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Cluster; Alkynes; Decarbonylation; 31P{1H} NMR
1. Introduction
nated alkynes or poly-ynes with different redox-active
sites [1–3]. These clusters can exhibit electronic delo-
calisation (donor-p-acceptor systems) and show poten-
tial as molecular wires, sensors, electrochemical agents
or non-linear optical materials, among others [4].
In recent years there has been a great deal of interest
in the structural, bonding, chemical and electrochemical
aspects of metal cluster carbonyls containing coordi-
A number of saturated triruthenium-alkynyl clusters
of general formula [Ru3(l3-g2-RCCR0)(CO)10] have
been obtained from the direct reactions of alkynes with
[Ru3(CO)12] [5], or by displacement, by the alkyne, of
the labile ligands in activated precursors, [Ru3(CO)10
(NCMe)2] [6] or [PPN][Ru3(l-Cl)(CO)10] [7,8], in the
*
ꢀ
Corresponding author. Present address: Departamento de Quımica
Inorganica, Instituto de Quımica, Universidade Federal Fluminense,
ꢀ
~
~
Outeiro de Sao Joao Batista s/n, Campus do Valonguinho, Centro,
Niterꢀoi, RJ 24020150, Brazil. Tel.: +55-21-22660167; fax: +55-21-
27178375.
E-mail address: mdvargas@vm.uff.br (M.D. Vargas).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.09.038

112
R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
latter case resulting in selective formation of the desired
products. In these clusters the alkyne is coordinated to
the metal frame in the classic l3-g2 perpendicular mode,
and one of the aims of the above mentioned studies was
the synthesis of the elusive unsaturated derivatives
[Ru3(l3-g2-RCCR0)(CO)9] containing the alkyne coor-
dinated in the l3-g2- perpendicular mode, as in [Fe3(l3-
g2-RCCR)(CO)9] [9]. Trapping of the alkyne in its
unstable perpendicular coordination mode in the triru-
thenium and triosmium derivatives could only be
achieved by incorporation of bis(dipheny1phosph-
ino)methane (dppm) into the ligand shell of [M3(l3-g2-
RCCR0)(CO)10] (M ¼ Ru [10], Os [11]), and stabilization
of the alkyne in this coordination mode in the unsatu-
rated compounds [M3(l3-g2-RCCR0)(CO)9] was asso-
ciated with the increased back-donating ability of the
metal induced by the dppm ligand [12].
In this paper we report the synthesis and solution
characterisation of three series of l3-g2-alkynyl triru-
thenium clusters, [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)
(l-CO)(CO)7] (1, saturated), [Ru3(l3-g2-R1-4-C6H4
CCR2)(l-dppm)(CO)7] (2, unsaturated) and [Ru3(l3-g2-
R1-4-C6H4CCR2)(l-dppm)(PPh3)(CO)7] (3, saturated)
containing symmetrical and asymmetrical alkynes in
which R1 and R2 are electron donating or electron
withdrawing groups in the para position of the aromatic
ring(s), or R2 ¼ ferrocenyl. The interest in this type of
compounds stems from the possibility of tuning the
electronic properties, not only of the coordinated al-
kyne, but also of the metallic frame upon saturation/
unsaturation and/or CO substitution with phosphines
and diphosphines, and thus probing the communication
between the metal frame and the alkyne in the cluster.
Preliminary work on the electrochemistry of compounds
2 has been reported [1a], and work on their non-linear
optical properties is in progress. It was also of interest to
investigate the effect of R1 and R2 on the decarbonyla-
tion process of clusters 1 and stabilization of the un-
saturated clusters 2.
2. Results and discussion
2.1. Synthesis of [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)
(l-CO)(CO)7] (1b–1h)
The alkyne substituted species 1b–1h were prepared
by the Lavigne methodology [10], starting from the
‘‘activated’’ anionic cluster [PPN][Ru3(l-Cl)(CO)10]
(PPN1), generated in situ from [Ru3(CO)12] by treat-
ment with PPNCl in THF. Addition of the respective
alkynes R1-4-C6H4CCR2 (Scheme 1) to burgundy PPN1
at room temperature, under a stream of argon, gener-
ated the dark yellow anionic intermediate clusters
[PPN][Ru3(l-Cl)(CO)9(l3-g2-R1-4-C6H4CCR2)] (PPN
1b–h) in spectroscopically quantitative yields which were
isolated as crystalline powders for the next step of the
preparation of clusters 1b–1h. The speed of these reac-
tions was sensitive to the electronic properties of the
substituent on the alkyne. Good electron withdrawing
groups (–NO2, –CHO and –CN) accelerated the reac-
tions, which were instantaneous, whereas in the case of
the electron donor group –OMe the mixture had to be
stirred for 1 h for reaction completion.
Clusters PPN1b–h were identified by their IR spectra
in the mCO region (see experimental) which were all very
similar to that of PPN1a previously reported [8c]. The
analogous reactions of PPN1 with the nitrogenated al-
kynes R1-4-C6H4CCPh (R1 ¼ NH2 and N ¼ CHC6H4-4-
NO2) did not yield the desired products according to IR
spectroscopy, most probably due to nucleophilic attack
of the nitrogen electron pair at the metal core, which
thus competes with the alkyne, and on the thin-layer
chromatography (TLC) plates the reaction mixtures
R2
C
C
Ru
Clusters 1 were obtained from the reactions of
[PPN][Ru3(l-Cl)(CO)10] with R1-4-C6H4CCR2, and
with the exception of the cluster containing R1 ¼ NO2
and R2 ¼ Fc, which was stable, were successfully de-
carbonylated to give clusters 2, following LavigneÕs
methodologies [8,10]. Novel adducts 3 were obtained in
high yields by addition of PPh3 to unsaturated clusters 2.
The solution structures of clusters 1–3 were proposed on
the basis of systematic 31P NMR studies and correlations
with X-ray structural data of related compounds avail-
able in the literature. The spectroscopic data provided
definite proof for the existence of an isomeric form of
compounds 1, which is different from the one previously
established by X-ray crystallography, thus highlighting
the importance of solution structural investigation even
in the cases where solid state structures are successfully
determined.
PPh2
Ru
Ph2P
Ru
R1
H
R2
R1
NO2
R2
1a
NO2
1f
H
H
H
1b
NO2
1g
H
OMe
CHO 1c
NO2
1h
Fe
1d
CN
H
C
1i
CN-W(CO)5
H
H
1e
NO2
C
Scheme 1. Structures of clusters [Ru3(l3-g2-R1-4-C6H4CCR2)(l-
dppm)(l-CO)(CO)7] (1a–1i).

R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
113
yielded several unidentified species which underwent
decomposition.
under photolytic conditions [15]. Attempts at isolating
cluster PPN1i from the reaction of PPN1 and
{(CO)5W}NC-4-C6H4CCPh also led to the formation of
[Ru3(CO)12], presumably due to the facile dissociation
and decomposition of the ‘‘W(CO)5’’ fragment from the
alkyne in the presence of MeOH, thus generating free
CO, which was scavenged by PPN1 [8].
Products 1b–1h were obtained by slow addition of
dppm in CH2Cl2 to clusters PPN1b–h in CH2Cl2, in the
presence of MeOH, to help displace the Clꢀ ligand, and
under a slight pressure of CO to avoid CO dissociation
(vide infra). Clusters 1b–h were isolated as purple mi-
crocrystalline solids in yields varying from 77 (1h) to
about 50% (1g) (see Table 1), depending on the alkyne,
the CO pressure and the mode of addition of the dppm.
Best yields were obtained from the reactions of PPN1b,
PPN1f and PPN1h containing alkynes bearing the
electron withdrawing –NO2 group, which suggests that
the metal frames of these clusters were most electron
deficient and prone to nucleophilic attack of the dppm.
When the solution was saturated with CO, formation of
the starting material [Ru3(CO)12] was noted, whereas
fast addition of the dppm to solutions of PPN1a–h led
to the formation of [Ru3(CO)10(dppm)] [13] and
[Ru3(R1-4-C6H4CCR2)(dppm)2(CO)6] [10a] which were
identified by their IR spectra.
Cluster 1j, previously obtained from the reaction of
[Ru3(CO)10(dppm)] with PhCBCCBCPh in the presence
of Me3NO in 36% yield [14], was also prepared by the
Lavigne methodology and obtained in 60% yield (see
Table 1).
The cluster adduct [Ru3(l3-g2-{(CO)5W}NC-4-
C6H4CCPh)(l-dppm)(l-CO)(CO)7] (1i) could only be
synthesised from [Ru3(l3-g2-NC-4-C6H4CCPh)(l-
dppm)(l-CO)(CO)7] (1d) by reaction with [W(CO)5
THF], formed in situ from the hexacarbonyl, in THF,
2.2. Characterisation of [Ru3(l3-g2-R1-4-C6H4CCR2)
(l-dppm)(l-CO)(CO)7] (1b–1i)
Clusters 1b–1i were formulated on the basis of ana-
lytical and spectroscopic data (see Tables 1 and 2) and
by comparison with the data reported for 1a and other
analogous clusters [10]. They are all relatively stable in
air in the solid state, and only 1g undergoes decompo-
sition when manipulated in the presence of air and light.
The IR spectra of 1b–1h are very similar to that of 1a,
with respect to both band frequencies and intensities,
which were mostly insensitive to the substituents on the
alkyne; all exhibit a bridging CO band besides bands
due to the terminal CO ligands. The 1H NMR spectra of
all compounds exhibit multiplets in the d 6.5 and 7.9
region due to the phenyl protons and two multiplets in
the d 3–4 region attributed to the dppm methylene hy-
drogens as previously observed for 1a and other anal-
ogous systems [14,16,17]. The 1H NMR spectra of
clusters 1c, 1g, and 1h also exhibit the expected peaks
due to the –CHO, –OMe and ferrocenyl hydrogens, re-
spectively (see Table 2).
Table 1
Analytical and spectroscopic data for the [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(l-CO)(CO)7] (1a–1j) derivatives
Cluster (% yield)
Elemental analyses
Found (Calc.) %
IRa (mCO)/cmꢀ1
R1 ¼ H, R2 ¼ Ph (1a) (50%)
R1 ¼ NO2, R2 ¼ Ph (1b) (65%)
C47H32O8P2Ru3
C: 51.79(51.65); H: 2.96(2.95).
C47H31NO10P2Ru3
2052s, 2001vs, 1972m, 1830w
2059s, 2005vs, 1974w, 1834w
C: 49.74(49.61); H: 2.87(2.75);
N: 1.17(1.23)
C48H32O9P2Ru3
R1 ¼ CHO, R2 ¼ Ph (1c) (58%)
R1 ¼ CN, R2 ¼ Ph (1d) (56%)
2057s, 2004vs, 1976sh, 1940wbr
C: 51.57(51.43); H: 2.75(2.88)
C48H31NO8P2Ru3
2225w (CN), 2057s, 2003vs, 1976m,
1835wbr
2056s, 2002vs, 1974m, 1833w
C: 51.71(51.57); H: 2.74(2.80); N: 1.22(1.25)
C55H37NO10P2Ru3
R1 ¼ CHCHC6H4–4–NO2, R2 ¼ Ph (1e)
(52%)
R1 ¼ NO2, R2 ¼ C6H4–4–NO2 (1f) (68%)
C: 53.40(53.27); H: 2.93(3.01); N: 1.06(1.13)
C47H30N2O12P2Ru3
2058s, 2000vs, 1974m, 1835w
2053s, 2001vs, 1973m, 1830vw
2055s, 2000vs, 1973m, 1826vw
C: 47.84(47.72); H: 2.48(2.56); N: 2.31(2.37)
C48H34O9P2Ru3
R1 ¼ OCH3, R2 ¼ Ph (1g) (51%)
R1 ¼ NO2, R2 ¼ Fc (1h) (77%)
R1 ¼ CNWCO5, R2 ¼ Ph (1i) (56%)
R1 ¼ CCPh R2 ¼ Ph (1j) (60%)
C: 51.43(51.34); H: 2.92(3.05)
C51H35NO10P2Ru3Fe
C: 49.29(49.16); H: 2.84(2.83); N: 1.27(1.12)
C53H31NO13P2Ru3W
2073w, 2058s, 2005vs, 1977sh, 1939vs,
1900m
C: 43.91(44.24); H: 2.11(2.17); N: 1.01(0.97)
C49H32O8P2Ru3
C: 52.60(52.83); H: 2.84(2.90)
2107vw, 2061s, 2013m, 2001vs, 1972sh,
1839w
a Measured in CH2Cl2.

114
R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
Table 2
1H and 31P{1H} NMR data for clusters 1a–1j, 2a–2f and 3a–3f
Cluster
d1H (ppm)a;b
d
31P {1H}, JP–P (Hz)a;b
1a
1b
1c
6.80–7.42(m, 30H, C6H5), 3.64(m, 1H, CH2), 3.10(m br, 1H, CH2)
7.20–8.18(m, 29 H, C6H5 and C6H4), 3.84(m br, 1H, CH2), 3.36(m br, 1H, CH2)
10.0(s, 1H, CHO), 7.20–7.82(m, 29H, C6H5 and C6H4), 3.84(m, 1H, CH2), 3.36(m br,
1H, CH2)
35.5 (s)
36.15 (d, 135), 35.42 (d)
36.47 (d, 130), 36.06 (d)
1d
1e
1f
6.90–7.50(m, 29H, C6H5 and C6H4), 3.62(m, 1H, CH2), 3.10(m, 1H, CH2)
7.00–8.20(m, 35H, C6H5, C6H4 and CH@CH), 3.62(m, 1H, CH2), 3.12(m, 1H, CH2)
6.82–7.46(m, 28H, C6H4), 3.69(m, 1H, CH2), 3.22(m br, 1H, CH2)
6.60–7.50(m, 29H, C6H5 and C6H4), 3.80(s, 3H, OCH3), 3.65(m, 1H, CH2), 3.12(m, 1H,
CH2)
35.85 (d, 132), 35.35 (d)
35.5 (s)
36.0 (s)
1g
35.5 (s)
1h
7.10–8.40(m, 24H, C6H5 and C6H4), 4.30(s, 5H, Cp), 4.20–4.27(m, 4H, C5H4), 3.75(m,
1H, CH2), 3.07(m, 1H, CH2)
35.47 (d, 136), 33.91 (d)
1i
1j
6.80–7.40(m, 29H, C6H5 and C6H4), 3.10(m, 1H, CH2), 3.55–3.65(m, 1H, CH2)
7.10–7.70(m, 30H, C6H5), 5.97(m, 1H, CH2), 4.65(m, 1H, CH2)
36.06 (d, 134), 35.19 (d)
33.5 (d, 40), 12.6 (d), 12.3 (s) [2:2:3]c
2a
2b
2c
6.83–7.51(m, 30H, C6H5), 3.71(m, 1H, CH2), 3.12(m, 1H, CH2)
7.25–8.21(m, 29 H, C6H5 and C6H4), 3.84(m, 1H, CH2), 3.46(m, 1H, CH2)
10.02(s, 1H, CHO), 9.90(s, 1H, CHO), 6.8–7.6(m, 58H, C6H5 and C6H4), 3.95(m, 2H,
CH2), 3.25(m, 2H, CH2)
40.6 (s)
43.1 (s), 41.3 (s) [1:3]c
42.5 (s), 41.3 (s) [1:3]c
2d
2e
2f
6.70–7.80(m, 29H, C6H5 and C6H4), 4.00(m, 1H, CH2), 3.20(m, 1H, CH2)
6.80–8.40(m, 35H, C6H5, C6H4 and CH@CH), 4.20(m, 1H, CH2), 3.30(m, 1H, CH2)
6.80–8.00(m, 28H, C6H4), 3.90(m, 1H, CH2), 3.25(m, 1H, CH2)
42.4 (s), 41.3 (s) [1:3]c
41.2 (s), 41.1 (s) [1:1]c
42.2 (s)
3a
3b
3c
6.72–8.32(m, 45H, C6H5), 4.82(m, 1H, CH2), 3.43(m, 1H, CH2)
6.80–7.70(m, 44H, C6H5 and C6H4), 3.82(m br, 1H, CH2), 3.40(m, 1H, CH2)
9.82(s, 1H, CHO), 6.80–7.60(m, 44H, C6H5 and C6H4), 4.40(m, 1H, CH2), 3.80(m, 1H,
CH2)
42.5 (br s), 15.0 (br s)
42.5 (br s), 13 (br s)
41.0 (br s), 12.0 (br s)
3d
3e
3f
6.66–8.12(m, 44H, C6H5 and C6H4),4.00 (m, 1H, CH2), 3.21(m, 1H, CH2)
7,04–8.12(m, 50H, C6H5, C6H4, CH@CH), 4.21(m,1H, CH2), 3.33(m, 1H, CH2)
7.20–7.60(m, 43H, C6H5 and C6H4), 3.90(m, CH2), 3.35(m, CH2)
42.0 (br s), 12.5 (br s)
42.5 (br s), 15.5 (br s)
42.5 (br s), 12.5 (br s)
a In CDCl3.
b Room temperature.
c Relative intensities.
In the 31P{1H} NMR spectra of clusters 1a–1i, the
phosphorus nuclei of the dppm ligand appear around d
35 as a singlet or two second-order AB type doublets,
depending on the nature of the alkyne ligand. In the
second case, the spectra were simulated to determine the
exact chemical shifts of the P nuclei [18].
The 31P{1H} NMR spectra of clusters 1a and 1f,
which contain symmetrical alkynes PhCCPh and NO2-
4-C6H4CCC6H4-4-NO2, exhibit a broad singlet at d 35.5
[10] and 36.0, respectively, which sharpens upon lower-
ing the temperature down to )90 °C (in CD2Cl2/CS2),
thus indicating that the two phosphorus atoms are
equivalent.
In the 31P{1H} NMR spectra of the asymmetrical
derivatives 1b–1d and 1h–1i, however, the phosphorus
nuclei appear as two second order AB type doublets
(JP–P ꢁ 130Hz) whose chemical shift difference (dD ¼
dP1 ꢀ dP2/Hz) decreases with the electronic asymmetry
of the coordinated alkyne [1h (NO2/Fc, 190) > 1i (H/–
CN–W(CO)5, 106) > 1b (H/–NO2, 90) > 1d (H/–CN,
60) ꢂ 1c (H/–CHO, 50)] (see Table 2). The spectrum of
cluster 1b stays unchanged upon lowering the tempera-
ture down to )90 °C.
(R1 ¼ CHCHC6H4-4-NO2 and OMe), respectively, the
two phosphorus nuclei appear as a singlet (see Table 2),
which shows that R1 does not alter significantly the
electronic density on the ruthenium atom bonded to the
carbon bearing the R1-4-C6H4– group, as in compounds
1b–1d and 1h–1i, either because the electron withdraw-
ing group (R1 ¼ –NO2) is situated too far away from the
metal on the organic chain (cluster 1e), or because R1 is
an electron donating group (–OMe) that does not con-
tribute significantly with electron density to the cluster
(1g). Similar behaviour has been reported for the acet-
ylide compounds [RuCp(PPh3)2(CBCC6H4-4-R)] (R ¼
H, –CHCHC6H4-4-NO2 and –NCHC6H4-4-NO2),
whose phosphorus chemical shift (a singlet) is not af-
fected by the nature of the R group either [19].
All these data suggest that compounds 1b–1e, 1g–1h
and 1i are isostructural with the symmetrical derivatives
1a and 1f whose dppm phosphorus atoms are equivalent
and whose structure is proposed herein to contain a CO
and a dppm ligands bridging the same edge which is also
parallel to the l3-g2-alkyne (see Scheme 2(A)). An al-
ternative structure containing the bridging dppm ligand
bonded to a different metal edge had been assumed
previously for 1a, in spite of the fact that the dppm
phosphorus nuclei had been found to be equivalent in
In contrast, in the spectra of the asymmetric deriva-
tives 1e and 1g, which contain alkynes R1-4-C6H4CCPh

R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
115
seems to exhibit in solution same structure as in the solid
state. The 31P{1H} NMR spectrum of this cluster (which
has not been reported previously) is rather different
from those of the other clusters of the series (see Table 2)
and exhibits two doublets at d 33.5 and 12.6 (JP–P ¼ 40
Hz), which we attribute tentatively to the dppm phos-
phorus nuclei bonded to the metal atoms that interact
with the alkyne in a r- and p-fashions, respectively, by
comparison with the chemical shifts observed for clus-
ters 1a–1i. The characterisation of 1j was ambiguous,
because this compound exhibits a different 31P{1H}
NMR spectrum after each purification by TLC. We also
observed that its IR spectrum (Table 1) is slightly dif-
ferent from those of clusters 1a–1i.
Strangely, however, the 31P{1H} NMR spectrum of
the analogous cluster containing the Fc substituted
asymmetrical alkyne, [Ru3(l3-g2-FcCCCBCFc)(l-dppm)
(l-CO)(CO)7], reported recently [22], was described to
consist of two singlets at d 35.85 and 36.17 and the
compound was proposed to exhibit same structure as 1j
(Scheme 2D), although the alternative symmetrical
structure was not ruled out [20]. In our opinion the
spectral data seem to be incomplete, since the spectra of
Ru3 and Os3 clusters of this series, which contain non
equivalent dppm phosphorus nuclei, exhibit JP–P vary-
ing from 30 to above 100 Hz. Considering that the
phosphorus chemical shift values reported for this
compound are very close to those observed for the
asymmetrical clusters 1b–1d, 1h and 1i (see Table 2) it
appears that also in this case, instead of singlets, the
spectrum may consist of two second-order AB type
doublets. Therefore the structure of this asymmetrical
compound is probably similar to those of clusters 1b–1d,
1h and 1i.
Scheme 2. (A) Proposed structure for clusters 1a–1i (see Scheme 1); (B)
and (C) molecular structures of [Ru3{l3-g2-C2(CO2Me)}2(PMe2Ph)2
(l-CO)(CO)7] [20] and [Os3(l3-g2-PhCCPh)(PBu)3(l-CO)(CO)6] [21],
respectively; (D) structure of 1j determined by X-ray diffraction stud-
ies [14].
the 31P NMR spectrum [10]. This was done based on a
supposed structure determined for the C2(CO2Me)2
analogous derivative [16], which to our knowledge, has
1
never been published, although the H NMR data of
this compound described later (no 31P NMR data were
reported) suggested indeed that the structure was
asymmetrical. Nevertheless our proposal is supported in
the first place by the fact that the X-ray molecular
structure of the related compound [Ru3{l3-g2-
C2(CO2Me)2}(PMe2Ph)2(l-CO)(CO)7] (Scheme 2(B))
[20] is symmetrical and similar to that proposed for
clusters 1b–1i, except that the PMe2Ph ligands occupy
equatorial positions in place of the dppm that we believe
occupy axial positions, as a result of the presence of the
bridging CO on the same edge. Furthermore, the ligand
arrangement in one of the isomers of the related osmium
cluster [Os3(l3-g2-PhCCPh)(l-dppm)(PBu3)(l-CO)
(CO)6] whose molecular structure has been determined
by an X-ray study (Scheme 2(C)) [21], is similar to that
proposed for 1b–1i with a dppm and a semi-bridging CO
ligands supporting the same Os2 edge. Further evidence
for axial coordination of the dppm ligand in our com-
pounds comes from the observation that axially coor-
dinated dppm phosphorus chemical shifts usually
appear at relatively high frequencies and that the JP–P
are large (over 110 Hz), which is the case with our
compounds (see Table 2) [21].
2.3. Decarbonylation of 1a–1f : formation of the unsatu-
rated clusters [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)
(CO)7] (2a–2f )
As described previously for cluster 1a, heating purple
compounds (1b–1f) in toluene at 70 °C for about 1 h
under a stream of argon led to the formation of the
unsaturated green compounds (2b–2f), which were ob-
tained in yields varying from 76% to 88% after crystal-
lisation from CH2Cl2/hexane (see Table 3 and Scheme
3). Compounds 1b–1f were regenerated instantaneously
upon bubbling CO through the solutions of the respec-
tive unsaturated species 2b–2f, as previously described
for 2a.
In contrast, it was impossible to obtain the unsatu-
rated products from the decarbonylation of compounds
1g, 1h and 1i. Whereas 1g (PhCCC6H4-4-OMe con-
taining cluster) underwent decomposition above room
temperature, 1h (FcCCC6H4-4-NO2 containing cluster)
was stable at 70 °C, even after heating for 6 h, but
raising the reaction temperature to 90 °C led to the
Secondly, the diyne containing cluster [Ru3(l3-g2-
PhC2CCPh)(l-dppm)(l-CO)(CO)7] (1j), whose molecu-
lar structure, reported recently [14], is as proposed
previously for the C2(CO2Me)2 derivative (Scheme 2(D)),

116
R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
Table 3
Analytical and spectroscopic data for the [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(CO)7] (2a–2f) derivatives
Cluster (% yield)
Elemental analyses Found (Calc.) %
IRa (mCO)/cmꢀ1
R1 ¼ H, R2 ¼ Ph (2a) (82%)
C46H32O7P2Ru3C: 51.62(51.89); H:
3.09(3.03)
2055s, 1987vs, 1925m
R1 ¼ NO2, R2 ¼ Ph (2b) (85%)
C46H31NO9P2Ru3C: 49.12(49.78); H:
2.92(2.82); N: 1.32(1.26)
2062s, 1993vs, 1929m
R1 ¼ CHO, R2 ¼ Ph (2c) (88%)
C47H32O8P2Ru3C: 51.47(51.65); H:
3.02(2.95)
2059s, 1991vs, 1927m
R1 ¼ CN, R2 ¼ Ph (2d) (76%)
C47H31NO7P2Ru3C: 51.72(51.80); H:
2.94(2.87); N: 1.36(1.29)
2225w (CN), 2058s, 1991vs, 1926w
2063s, 1992vs, 1930m
R1 ¼ CHCHC6H4-4-NO2, R2 ¼ Ph (2e) (78%)
R1 ¼ NO2, R2 ¼ C6H4-4-NO2 (2f) (86%)
C54H37NO9P2Ru3C: 53.39(53.51); H:
3.01(3.08); N: 1.22(1.16)
C46H30N2O11P2Ru3C: 47.73(47.84); H:
2.74(2.62); N: 2.51(2.43)
2065s, 1993vs, 1929m
a Measured in CH2Cl2.
dinated FcCCC6H4-4-NO2 seems to be counteracted by
that of the electron donating Fc group at the other end
of the alkyne. Certainly, further investigation still needs
to be carried out on these systems.
R2
R2
C
C
C
C
Ph2
P
Ph2
P
Ru
Ru
2.4. Characterisation of [Ru3(l3-g2-R1-4-C6H4CCR2)
(l-dppm)(CO)7] (2b–2f )
Ph2P
Ru
Ru
Ph2P
Ru
Ru
(A)
(B)
R1
H
R2
R1
R2
The unsaturated clusters 2b–2f were characterised by
analytical and spectroscopic data (see Tables 2 and 3)
and by comparison with the spectroscopic data reported
for compound 2a, whose structure was confirmed by an
X-ray diffraction study [10]. These compounds exhibit
IR spectra in the mCO region, which are very similar to
that of 2a, and 1H NMR spectra, similar to those of the
clusters from which they originated (1b–1f, see Table 2).
The 31P{1H} NMR spectrum of cluster 2f containing
the symmetrical alkyne O2N-4-C6H4CCC6H4-4-NO2
exhibits a singlet at d 42.2, indicating that the two dppm
phosphorus nuclei are equivalent and therefore that its
structure is similar to that of cluster 2a, which contains
the alkyne bonded in a l2-g2-mode perpendicular to the
Ru2 edge supported by the dppm ligand on pseudo-
equatorial coordination sites.
The 31P{1H} NMR spectra of compounds 2b–2e,
which contain asymmetrical alkynes indicated the pres-
ence of two isomers (A and B) in solution (see Table 2),
as they exhibited two singlets, whose relative intensities
and chemical shifts were sensitive to the nature of the
substituent R1 on the R1-4-C6H4CCPh coordinated al-
kyne. In the cases of compounds 2b–2d (A:B ¼ 1:3) only
the highest frequency peak due to the least abundant
isomer was sensitive to the electron withdrawing effect of
R1 [(dD ¼ dPA ꢀ dPB/Hz, 2b (–NO2, 219) > 2c (–CHO,
146) > 2d (–CN, 134)]. For cluster 2e, the influence of R1
[–C6H4CHCHC6H4-4-NO2, dD ¼ 12 Hz)] was minute
and the isomer ratio A:B ¼ 1:1 confirmed the electronic
nature (rather than steric) of the effect. The structures of
these two isomers, illustrated in Scheme 3, are thus
proposed to differ with respect to the orientation of the
2d
H
H
H
CN
2a
H
C
2b
2c
NO2
H
2e
C
NO2
H
CHO
NO2
NO2
2f
Scheme 3. Structures proposed for the two isomers of unsaturated
clusters 2b–2e (R1 ¼ –NO2 (2b), –CHO (2c), –CN (2d), –C6H4CHC
HC6H4-4-NO2 (2e)).
formation of several unidentified species in minute
amounts according to TLC. Thermolysis of 1i
(PhCCC6H4-4-CNW(CO)5 containing cluster) only led
to the unsaturated compound 2d as a result of the dis-
sociation of ‘‘W(CO)5’’ possibly via scavenging of the
free CO.
It is interesting to speculate about the relative sta-
bility of cluster 1h with respect to CO loss. Formation of
unsaturated Ru3(l3-g2-alkyne) clusters containing the
alkyne bonded in the perpendicular mode has been
shown to be rather sensitive to the electronic density on
the metal frame available for back donation to the al-
kyne in the unsaturated derivative. Thus, of the satu-
rated compounds [Ru3(l3-g2-PhCCPh)(CO)10], [Ru3
(l3-g2-PhCCPh)(PPh3)(CO)9] and [Ru3(l3-g2-PhCCPh)
(dppm)(CO)8], only the latter loses CO to give the un-
saturated derivative [10b]. Therefore, formation and
stabilisation of clusters 2b and 2f might be favoured by
the electron withdrawing ability of one and two –NO2
groups, respectively, on the alkyne (Scheme 3). In cluster
1h, however, the effect of the –NO2 group in the coor-

R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
117
coordinated alkyne. Intuitively the structure of the ma-
jor isomer (B) would be expected to contain the C6H4-4-
NO2 group directed towards the parallel Ru2(dppm)
edge, i.e. bonded to the least electron poor alkyne car-
bon, which is involved only in a p-interaction with the
metal frame. Minor isomer A would contain the elec-
tron-withdrawing group bonded to the alkyne carbon,
which also donates electron density to the cluster via a
r-interaction. The –NO2 group could be expected to
communicate better with the dppm phosphorus in iso-
mer A than in B, due to their transoid orientation and
this is indeed observed.
mental analyses (see Table 4) confirmed that these
compounds resulted from the addition of a single PPh3
molecule to 2a–2f, and their IR spectra in the mCO re-
gion, although shifted to lower frequencies with respect
to those of the saturated analogous compounds 1a–1f,
also exhibited a weak band in the bridging CO region.
As in the case of the precursors 1a–1f, only very small
mCO shifts were observed in the spectra of 3a–3f as the
result of changing the substituent on the alkyne.
The reactions of clusters 2a and 2b with one equiva-
lent of PPh2-2-py and PCy3 proceeded similarly to those
with PPh3, and gave after about 10 min at room tem-
perature, analogous adducts, identified in situ by IR
spectroscopy. However, these adducts reacted further if
left in solution for longer periods of time to give several
unidentifiable products according to the TLC.
2.5. Synthesis and characterisation of [Ru3(l3-g2-R1-4-
C6H4CCR2)(l-dppm)(PPh3)(CO)7] (3a–3f )
The unsaturated compound 2a has been shown pre-
viously to react rapidly with PhCCH and dppm to yield
[Ru3{l-HCC(Ph)C(O)(Ph)CCPh}(l-dppm)(CO)6] and
[Ru3(l3-g2-PhCCPh)(l-dppm)2(CO)6], respectively,
which have been fully characterised [10a].
The reactions of the unsaturated green clusters 2a–2f
with a series of nucleophiles were investigated in an at-
tempt to tune both the electron density in the metal
frame and the electronic communication between the
metal frame and the substituent on the coordinated al-
kynein the addition products.
Clusters 2a and 2b did not react with the nitrogenated
Lewis bases pyridine, 2,20-bipyridil and benzonitrile, at
room temperature in CH2Cl2 or toluene, after 10h, even
in the presence of an excess of the nucleophile, and upon
heating at 50 °C, only decomposition products were
detected on the TLC plates. In contrast, these clusters
reacted rapidly with phenylisocyanide, to give a number
of products, which could not be characterised. Best re-
sults were obtained from the reactions with PPh3, PCy3
and PPh2-2-py.
The room temperature 31P{1H} NMR spectra of
clusters 3a–3f revealed two broad peaks around d 15 and
42. Upon lowering the temperature to )90 °C, the
spectrum of the PhCCPh containing cluster, 3a, (in
CD2Cl2) showed two sharp singlets at d 47.6 and 41.9
(approximate intensities ratio ¼ 3:1), due to the coordi-
nated PPh3, and two broad peaks at d 17.2 and 16.8 due
to two dppm ligands, thus indicating the presence of two
isomers in solution that still undergo some fluxional
process involving the dppm ligand. In contrast, the
variable temperature spectra of cluster 3b, which con-
tains the asymmetrical alkyne PhCCC6H4-4-NO2, indi-
cated clearly that this compound exists in solution as a
mixture of three isomers (of approximate ratio
A:B:C ¼ 5:5:1), as the two broad singlets due to the
dppm and PPh3 ligands in the room temperature spec-
trum separated into six well defined doublets and three
singlets, respectively, at )90 °C (in CD2Cl2/CS2) (see
Fig. 1).
Attempts at growing crystals of species 3a–3f were
frustrated, as only needle-like crystals were formed in a
variety of solvent systems, and therefore the structures
proposed below for the isomers of 3a and 3b are only
speculative, although they were based on the structures
of the isomers of the analogous osmium clusters [Os3(l3-
Clusters 2a–2f reacted rapidly with PPh3 (one
equivalent or a 2-fold excess) in CH2Cl2 or in toluene, at
room temperature, to give the purple addition products
3a–3f in yields above 90% after crystallisation. Ele-
Table 4
Analytical and spectroscopic data for the [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)(PPh3)(CO)7] (3a–3f) derivatives
Cluster (% yield)
Elemental analyses Found (Calc.) %
IRa (mCO)/cmꢀ1
R1 ¼ H, R2 ¼ Ph (3a) (94%)
C64H47O7P3Ru3C: 57.72(57.92); H: 3.62(3.57)
C64H46NO9P3Ru3C: 55.97(56.02); H: 3.34(3.38); N:
1.08(1.02)
2021w, 1999vs, 1957vs, 1812w
2026m, 2004vs, 1963vs, 1912w, 1817w
R1 ¼ NO2, R2 ¼ Ph (3b) (95%)
R1 ¼ CHO, R2 ¼ Ph (3c) (92%)
R1 ¼ CN, R2 ¼ Ph (3d) (89%)
C65H47O8P3Ru3C: 57.32(57.61); H: 3.50(3.50)
C65H46NO7P3Ru3C: 57.32(57.74); H: 3.37(3.43); N:
1.08(1.04)
2024m, 2001vs, 1960vs, 1910w, 1816w
2226w (CN), 2024m, 1999vs, 1960vs,
1909w, 1815w
R1 ¼ CHCHC6H4-4-NO2, R2 ¼ Ph
C72H52NO9P3Ru3C: 58.78(58.66); H: 3.56(3.56); N:
1.01(0.95)
2025m, 2002vs, 1962vs, 1910w, 1817w
(3e) (98%)
R1 ¼ NO2, R2 ¼ C6H4-4-NO2 (3f)
(96%)
C64H45N2O11P3Ru3C: 53.99(54.24); H: 3.21(3.20); N:
1.99(1.98)
2028m, 2005vs, 1963vs, 1910w, 1820w
a Measured in CH2Cl2.

118
R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
Fig. 1. 31P{1H} NMR spectrum of cluster 3b at )90 °C, showing the presence of three isomers A, B and C, and cluster 1b present as an impurity.
g2-PhCCPh)(l-dppm)(L)(l-CO)(CO)6] (L ¼ PBu3, PPh3,
PMe2Ph and P(OMe)3) [21], which were established by a
combination of X-ray diffraction and 31P NMR spec-
troscopy studies. These compounds exist as a mixture of
three inseparable isomers, whose structures are illus-
trated in Scheme 4. In isomer a, the dppm ligand is
bonded axially to the same Os2 edge that contains a
semi-bridging CO, and the PR3 ligand is coordinated to
an Os atom that is also bonded to one of the dppm
phosphorus atoms. The difference between this isomer
and isomer b is that in the latter the PR3 ligand is co-
ordinated to the Os atom that is not bonded to the
dppm. Isomer c exhibits the alternative ligand arrange-
ment that had been proposed for 1a, with the CO and
dppm bridging different Os edges, and with all phos-
phorus ligands occupying equatorial coordination sites
on different Os atoms.
A similar outcome is possible for the reactions of
clusters 2a and 2b with PPh3, which were investigated
under the same conditions as described above for the
osmium system. We therefore propose that the two iso-
mers of cluster 3a exhibit structures similar to those of
isomers b (symmetrical) and c (asymmetrical) of the os-
mium analogue shown in Scheme 4, with a PPh3 in place
of PBu3 and L, respectively. Because the fluxional process
involving the dppm ligand in cluster 3a could not be
frozen at )90 °C, the JP–P between the phosphorus nuclei
of this ligand could not be measured and it was therefore
impossible to assign the chemical shifts observed to one
or another structure. In any case, it is interesting that CO
substitution for a PPh3 in cluster 1a, which exhibits a
symmetrical structure, results in the stabilisation of both
the ‘‘symmetrical’’ (b) and the ‘‘asymmetrical’’ (c) struc-
tures, thus suggesting that the energy differences between
the two structures is small.
It was found that only isomers b and c were obtained
from the reactions of the unsaturated precursor [Os3(l3-
g2-PhCCPh)(l-dppm)(CO)7] with PPh3 or P(OMe)3 in
polar solvents, such as CH2Cl2, at room temperature,
i.e. nucleophilic attack at the osmium centres bonded to
the dppm ligand was disfavoured under these conditions
[21].
Also in the case of cluster 3b, we suggest that the
three isomers exhibit one of the two structures, b or c,
for the same reason discussed above. As illustrated in
Scheme 5, the two different orientations of the asym-
metrical alkyne in structure b lead to identical struc-
tures, providing that the PPh3 ligand occupies in the
Ph
Ph
Ph
C
C
C
C
C
C
L
Os
Os
Os
Bu3P
Os
Os
Os
Ph2P
Os
Os
PPh2
Os
Ph2P
PPh2
PPh2
PBu3
Ph2P
Scheme 4. Structures of the isomers of [Os3(l3-g2-PhCCPh)(l-dppm)(L)(l-CO)(CO)6] [L ¼ PBu3, PPh3, PMe2Ph and P(OMe)3]. The molecular
structures of isomers a and b of the PBu3 derivative were determined by X-ray diffraction studies and the structure of isomer c was proposed on the
basis of its reactivity and 31P NMR studies [21].

R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
119
ing, as references, 85% H3PO4 (external) for the former
1
NO2
and SiMe4 for H. Elemental analyses were carried out
ꢀ
at the Instituto de Quimica, UNICAMP.
C
C
C
Ph2
P
C
Ph2
P
3.1. Synthesis of precursors [PPN][Ru3(CO)9(l-Cl)
(RC CR)] (PPN 1a–1h)
Ru
Ru
Ph2P
Ph2P
PPh3
Ru
Ru
Ru
Ru
Precursors PPN1a–1h were prepared as described in
the literature [8c]. Spectroscopic data for PPN1a (co-
ordinated alkyne: PhCCPh): IR (mCO(THF)/cmꢀ1): 2056
m, 2035 vs, 1985 vs, 1952m e 1920w. The spectra of
PPN1b (PhCCC6H4-4-NO2), PPN1c (PhCCC6H4-4-
CHO), PPN1d (PhCCC6H4-4-CN), PPN1e (PhCCC6
H4-CH@CHC6H4-4-NO2), PPN1f (O2N–C6H4CCC6
H4-4-NO2), PPN1g (PhCCC6H4-4-OCH3), and PPN1h
(Fc-CCC6H4-4-NO2) are all very similar, with bands
shifted by a maximum of ꢄ6 cmꢀ1 from those of
PPN1a.
PPh3
γ 2
1
γ
NO2
O2N
C
C
C
C
Ru
Ru
Ru
Ph2P
Ru
Ru
Ph2P
Ru
PPh3
PPh3
PPh2
3.2. Preparation of clusters [Ru3(l3-g2-R1-4-C6H4C
CR2) (l-dppm)(l-CO)(CO)7] (1b–1h)
PPh2
Scheme 5. Structures proposed for the isomers of 3b.
Clusters 1b–1h were prepared by slight modification
of a literature method [10] and obtained in yields vary-
ing from 50% to 77%, after crystallisation (Table 1).
Cluster 1i [R1 ¼ –H and R2 ¼ C6H4-4-CN–W(CO)5]
was obtained by slow addition of a THF solution of
freshly prepared [W(CO)5THF] (from W(CO)6, 14 mg,
0.04 mmol) to cluster 1d (45 mg, 0.04 mmol) in THF
(15 ml) [15]. The mixture was left under stirring for
further 20 min. The solvent was then evaporated under
vacuum and the product, purified by TLC (CH2Cl2/
hexane, 1:1) to give compounds 1d (11 mg, 25%) and 1i
(23 mg, 56%). Clusters 1a–1i were characterised by el-
emental analyses, IR (Table 1), 1H and 31P NMR
spectroscopy (Table 2).
two structures, either an axial site, or an equatorial site
transoid to the phenyl group bearing the same 4-sub-
stituent X ¼ H or –NO2. In the case of structure c
though, the two different orientations of the asymmet-
rical alkyne lead to two different structures c1 and c2,
as shown in Scheme 5. In the absence of further struc-
tural information, we do not feel comfortable to attri-
bute the chemical shifts observed to the three structures
proposed.
3. Experimental
All preparations, and manipulations were carried out
under an atmosphere of argon. Starting materials were
purchased from Aldrich and/or Strem and used without
further purification. The alkynes were prepared as de-
scribed in the literature [23,24]. Solvents were dried and
distilled by standard procedures. Preparative TLC was
carried out on glass plates (20 ꢃ 20 cm) coated with
silica gel (Merck 60 GF254, 0.5 mm thickness). The
progress of the reactions was monitored by analytical
TLC (precoated plates, silica gel F254, 0.25 mm thick;
Merck) and IR spectroscopy. All Ru3-clusters were
stored under inert atmosphere to avoid some decom-
position observed in some compounds stored for long
time in the solid state.
3.3. Decarbonylation of (1b–1f ): formation of the
unsaturated clusters [Ru3(l3-g2-R1-4-C6H4CCR2)(l-dppm)
(CO)7] (2b–2f )
Clusters 2b–2f were obtained according to a literature
method [10] in yields varying from 76% to 86%, after
crystallisation (Table 2).
The following procedure described for the synthesis
of cluster 2b was carried out for the syntheses of 2c–2f
(Table 3). A wine coloured toluene solution (20 ml) of 1b
(20 mg, 0.02 mmol) was stirred at 80 °C for 90 min (until
the colour had changed to green). The reaction was also
monitored by TLC and IR spectroscopy in the mCO re-
gion. The product was purified by TLC (CH2Cl2/hex-
ane, 2:3), recrystallised from the same solvent system
and obtained in 85% yield. Clusters 2b–2f were charac-
Infrared spectra were recorded on a Bomen (FT-IR
Michelson) spectrophotometer between 2200 and 1600
1
1
cmꢀ1 (mCO), 31P{1H} and H NMR spectra on a Bruker
AC 300P and/or Varian Gemini 300 spectrometers us-
terised by elemental analyses, IR (Table 2), H and 31P
NMR spectroscopy (Table 2).

120
R. Rosseto, M.D. Vargas / Journal of Organometallic Chemistry 689 (2004) 111–121
3.4. Attempts at decarbonylating 1g–1i
latter containing the dppm ligand on a different edge to
that bridged by the CO ligand. The fact that the dppm
phosphorus chemical shifts are sensitive to the alkyne
electronic asymmetry made it possible to show that
both symmetrical and asymmetrical clusters contain-
ing electronically asymmetrical alkynes exist in two
isomeric forms, which differ with respect to the alkyne
orientation. Furthermore, all clusters 2 exhibit a sym-
metrical structure in which the dppm and the alkyne,
bonded in the perpendicular mode, bridge the same Ru2
edge, however, the derivatives which contain asymmet-
rical alkynes also exist in solution as a mixture of two
isomers which differ with respect to the orientation of
the alkyne.
Treatment of cluster 1g under the conditions de-
scribed above only led to its decomposition, into various
products in very small amounts, according to the TLC.
Heating 1i under the conditions described for the syn-
theses of 2b–2f led to the formation of cluster 2d which
was obtained in 82% yield. Burgundy cluster 1h was
stable when heated under the same conditions, even
after 6 h. Upon increasing the temperature to 90 °C, it
underwent decomposition, after 10 h, into several un-
identified species according to the TLC (CH2Cl2:hexane,
1:3).
3.5. Preparation of clusters [Ru3(l3-g2-R1-4-C6H4
CCR2) (l-dppm)(PPh3)(CO)7] (3a–3f ): general pro-
cedure
Acknowledgements
PPh3 (0.025 mmol) was added as a solid to solutions
of clusters 2a–2f (0.025 mmol) in CH2Cl2 (10 ml). The
colour of the solutions changed immediately from dark
green to burgundy. After 15 min stirring, the volume of
the solutions was reduced to about 1 ml and the prod-
ucts were purified by TLC, using CH2Cl2/hexane, 2:1 as
eluent. Compounds 3a–3f were recrystallised from the
same solvent system and obtained in yields varying from
89% to 98% (Table 4). Clusters 3b–3f were characterised
The authors thank CAPES and FAPESP and CNPq
(Brazil) for financial support.
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