Heterobimetallic ruthenium-cobalt complexes containing the pentamethylcyclopentadienyl or indenyl ligand

Article abstract of DOI:10.1002/ejic.200500785

The salt elimination reaction between NaCo(CO)₄ and the ruthenium complexes LRu(diphos)Cl and [(Ind)Ru(CO)₂Cl] afforded the Ru-Co bimetallic complexes [LRu(μ-CO)₂(μ-diphos)Co(CO) ₂] [L = C₅Me₅ (Cp*), diphos = Ph ₂P(CH₂)_nPPh₂, 3a: n = 1 , or 3b: n = 2; 3. L = C₉H₇ (Ind), diphos = Ph₂PCH ₂PPh₂ ] and [(Ind)Ru(CO)₂Co(CO)₄] (3d), respectively, in high yields. However, the same reaction with the monophosphane analogue, [(Ind)Ru(PPh₃)₂Cl], gave the heterobimetallic complex [(Ind)Ru(PPh₃)(CO)(μ-CO)Co(CO) ₃] (3e) in fair yield, together with redox-initiated derivatives Ru(PPh₃)₂(CO)₃ (4e) and [(Ind)Co(CO)(PPh ₃)] (6e). A similar redox process in the reaction of the dppf analogue, [(Ind) Ru(dppf)Cl] (dppf = 1,1′-diphenylphosphanylferrocene) gave [Ru(dppf)(CO)₃] (4f) and [(Ind)Co(CO)₂] (6f), together with a complex salt [(Ind)Ru(dppf)(CO)][Co(CO₄)] [5f·Co(CO)₄]. Wiley-VCH Verlag GmbH & Co. KGaA, 2006).

Full text of DOI:10.1002/ejic.200500785

FULL PAPER
DOI: 10.1002/ejic.200500785
Heterobimetallic Ruthenium-Cobalt Complexes Containing the
Pentamethylcyclopentadienyl or Indenyl Ligand
Sin Yee Ng,[a] Lai Yoong Goh,*[a] Lip Lin Koh,[a] Weng Kee Leong*[a] Geok Kheng Tan,[a]
Suming Ye,[b] and Yinghuai Zhu[b]
Keywords: Heterometallic complexes / Ruthenium / Cobalt / Phosphanes / Indenyl
The salt elimination reaction between NaCo(CO)4 and the
ruthenium complexes LRu(diphos)Cl and [(Ind)Ru(CO)2Cl]
afforded the Ru–Co bimetallic complexes [LRu(μ-CO)2(μ-di-
phos)Co(CO)2] [L = C5Me5 (Cp*), diphos = Ph2P(CH2)nPPh2,
3a: n = 1 , or 3b: n = 2; 3: L = C9H7 (Ind), diphos =
Ph2PCH2PPh2 ] and [(Ind)Ru(CO)2Co(CO)4] (3d), respec-
tively, in high yields. However, the same reaction with the
monophosphane analogue, [(Ind)Ru(PPh3)2Cl], gave the het-
erobimetallic complex [(Ind)Ru(PPh3)(CO)(μ-CO)Co(CO)3]
(3e) in fair yield, together with redox-initiated derivatives
Ru(PPh3)2(CO)3 (4e) and [(Ind)Co(CO)(PPh3)] (6e). A similar
redox process in the reaction of the dppf analogue, [(Ind)
Ru(dppf)Cl] (dppf = 1,1Ј-diphenylphosphanylferrocene) gave
[Ru(dppf)(CO)3] (4f) and [(Ind)Co(CO)2] (6f), together with a
complex salt [(Ind)Ru(dppf)(CO)][Co(CO4)] [5f·Co(CO)4].
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
gand dissociation. Most of the reported compounds of this
class were isolated in low yields, e.g., [(p-cymene)Ru-
(CO)(μ2-PPh2)Co(CO)3] (30% yield),[3d] [CpRu(CO)2-
Co(CO)4] (10% yield),[3a] [CpRu(PPh3)2Co(CO)4] (28%
yield),[2e] and [CpRuCo(CO)3(R-DAB)] (R = iPr, tBu, DAB
= 1,4-diaza-1,3-butadiene) (10% yield).[3f] However, Matsu-
zaka et al. managed to isolate [Cp*Ru(CO)2(μ2-CO)-
Co(CO)3] in high yield (86%);[3h,7] subsequent substitution
by dppm, tBuNC and alkynes (HCϵCTol, HCϵCCO2Me)
in the presence of Me3NO·2H2O gave very high yields of
the substituted products.
In this paper, we present results from the reactions of
various Cp* and Ind complexes of ruthenium with NaCo-
(CO)4 (1), which gave in addition to the anticipated Ru–
Co metal–metal bonded complexes, derivatives arising from
redox pathways.
Introduction
There has been much research activity on the employ-
ment of heterobimetallic complexes in catalysis.[1] The
prime motivation for this has been the possibility of cooper-
ative reactivity of adjacent heterometallic centres, which
may impart new reactivity patterns significantly different
from those of the homobimetallic complexes. Early reports
of the superb catalytic efficacy of mixtures of cobalt and
ruthenium compounds,[2] and later of ruthenium-cobalt
heterobimetallic complexes,[2e] in methanol homologation,
had spurred a surge in synthetic and reactivity studies of
these complexes.[3,4] When supported on silica, they have
also been found to be effective catalysts in hydrofor-
mylation.[5]
Synthetic routes to metal–metal bonded heterobimetallic
complexes are very well documented;[6] one of the most
commonly employed being the displacement of a halide li-
gand by an anionic metal fragment such as [Co(CO)4]–.
Nevertheless, ruthenium-cobalt heterobimetallic complexes
containing a half-sandwich ruthenium moiety have been rel-
atively less studied. Ligands such as cyclopentadienyl (Cp)
or Cp* often confer stability on the complexes, and when
derivatised can effect changes in properties at the metal cen-
tre. The indenyl ligand is of much interest on account of its
“indenyl effect”, which is primarily a reflection of the li-
gand’s ability to undergo η5 ↔ η3 ring slippage, thereby
creating a vacant site on the metal centre without any li-
Results and Discussion
Salt elimination reactions between NaCo(CO)4 (1), and
the ruthenium complexes LRu(diphos)Cl (2) [L = Cp*, di-
phos = Ph2P(CH2)nPPh2, 2a: n = 1 , or 2b: n = 2; 2c: L =
Ind, diphos = Ph2PCH2PPh2], at room temperature af-
forded Ru–Co bimetallic complexes [LRu(μ-CO)2(μ-diphos)-
Co(CO)2] (3), in 78–85% yields (Scheme 1). The displace-
ment of the halide ligand by the anionic metal fragment
[Co(CO)4]– is accompanied by the bridging of the diphos-
phane and two carbonyl ligands across the Ru–Co bond.
We note that while [(Ind)Ru(CO)2Cl] (2d) reacted with 1 to
give the metal–metal bonded complex 3d, Cp*Ru(CO)2Cl
[a] Department of Chemistry, National University of Singapore,
3 Science Drive 3, Singapore 117543
[b] Institute of Chemical and Engineering Sciences,
1 Pesek Road, Jurong Island, Singapore 627833
Eur. J. Inorg. Chem. 2006, 663–670
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
663

S. Y. Ng, L. Y Goh, L. L. Koh, W. K. Leong, G. K. Tan, S. Ye, Y. Zhu
FULL PAPER
(2dЈ) gave a monocarbonyl-bridged complex 3eЈ (the prime spectra indicated the presence of both terminal and bridg-
refers to previously reported complexes), which could be ing carbonyls. Complex 3c has also been characterized by a
decarbonylated to produce 3a (Scheme 2).[3h]
single-crystal X-ray structural study (Figure 1); that for 3a
has already been reported.[3h] Their molecular structures
are very similar in that both comprise a bimetallic complex
in which the ruthenium and cobalt atoms are connected by
a metal–metal bond, two bridging CO ligands and a bridg-
ing diphos ligand. The Ru–Co bond length in 3c is shorter
than that in 3a [2.6474(4) and 2.677(2) Å, respectively] and
probably reflects the weaker indenyl-ruthenium compared
to the Cp*–ruthenium interaction; stronger interaction in
the latter would be expected to lengthen the metal–metal
bond via a trans influence. The metal–phosphane bond
lengths in both 3a and 3c are shorter to cobalt than to
ruthenium [Ru(1)–P(3) = 2.3048(6) Å and Co(2)–P(4) =
2.2199(7) Å for 3c]; these are comparable to the Co–P bond
length of 2.175(1) Å in Co2(CO)6(PMe3)2,[8] and the Ru–P
bond length of 2.385 Å in {Ru2(CO)4(PMe3)2(μ-
O2CCH2CO2)}2,[9] and suggest that the difference is due to
the different formal oxidation states [Co(0) vs. RuI] since
ruthenium and cobalt have the same covalent radii (1.26 Å).
However, the reverse situation seems to be the case with
regard to the bridging carbonyls.
Scheme 1.
Figure 1. ORTEP diagram (50% probability thermal ellipsoids, hy-
drogen atoms omitted) and selected bond lengths [Å] and angles
[°] of 3c. Ru(1)–Co(2) = 2.6474(4); Ru(1)–P(3) = 2.3048(6); Co(2)–
P(4) = 2.2199(7); Ru(1)–C(11) = 1.947(3); Ru(1)–C(12) = 1.962(3);
Co(2)–C(22) = 1.772(3); Co(2)–C(21) = 1.776(3); Co(2)–C(12) =
2.002(3); Co(2)–C(11) = 2.021(3); O(11)–C(11) = 1.170(3); O(12)–
C(12) = 1.182(3); O(21)–C(21) = 1.144(4); O(22)–C(22) = 1.130(4);
P(3)–Ru(1)–Co(2) = 92.116(18); P(4)–Co(2)–Ru(1) = 99.16(2);
Ru(1)–C(11)–Co(2) = 83.69(10); Ru(1)–C(12)–Co(2) = 83.80(10).
The IR spectrum of [(Ind)Ru(CO)2Co(CO)4] (3d) showed
clearly the absence of any bridging carbonyl ligand, in con-
trast to that for the Cp* analogue 3eЈ. This may be attrib-
Scheme 2.
The complexes 3a–c exhibited the expected resonances uted to the greater electron donating ability of Cp* com-
for the diphosphanes and Cp* or indenyl ligands in their pared to Ind,[3h] and hence the tendency for the carbonyl
1H NMR spectra. Their 31P{1H} NMR spectra all showed ligands to bridge. This tendency is further enhanced by
a sharp doublet and a broad doublet at lower field; the phosphane substitution at the metal centres, as observed in
latter due to quadrupolar coupling to the cobalt. The IR 3a–3c.
664
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 663–670

Heterobimetallic Ruthenium-Cobalt Complexes
FULL PAPER
The analogous reaction of the monophosphane-substi-
tuted derivative [(Ind)Ru(PPh3)2Cl] (2e), however, was more
complex (Scheme 3). In addition to the expected heterobi-
metallic product [(Ind)Ru(PPh3)(CO)(μ2-CO)Co(CO)3]
(3e), there were the mononuclear complexes Ru(PPh3)2-
(CO)3 (4e), and [(Ind)Co(CO)(PPh3)] (6e). These three com-
pounds have been characterized completely, including by
single-crystal X-ray crystallographic studies which con-
firmed that exchange of CO and PPh3 ligands had occurred
between the metal centres. The structure of 4e determined
here in the form of its CH2Cl2 solvate is essentially similar
to that of its THF solvate reported previously.[10] The mo-
lecular structures of 3e and 6e are shown in Figure 2 and
Figure 3, respectively.
Figure 3. ORTEP diagram (50% probability thermal ellipsoids, hy-
drogen atoms omitted) and selected bond lengths [Å] and angles
[°] of 6e. Co(1)–C(1) = 1.711(3); Co(1)–P(1) = 2.1459(7); O(1)–C(1)
=
1.156(3); C(1)–Co(1)–P(1)
= 95.39(9); O(1)–C(1)–Co(1) =
176.3(3).
atomic numbering scheme and selected bond parameters
are collected in Table 1. The overall structural features of
the three compounds are the same, comprising of a single
carbonyl bridging the Ru–Co bond, a terminal carbonyl on
the ruthenium, and three on the cobalt. As in the case of
3c, the Ru–Co bond length for 3e is significantly shorter
than in either of the Cp* analogues [2.677(2) vs. 2.7445(6)
and 2.735(4) Å in 3e, 3eЈ and 3fЈ, respectively]. The bridging
carbonyl is obviously skewed towards the cobalt in all three
compounds, as in the case of 3c. Although there appears to
be only one bridging carbonyl in these three compounds, in
contrast to two for 3a and 3c, the carbonyl which should
have made up the second bridging carbonyl [CO(11)] is ac-
tually semi-bridging [ЄRu–C(11)–O(11) Ϸ 167–169°, com-
pared with ЄCo–C–O Ϸ 173–179°].[11] This can be attrib-
uted to the presence of an electron-donating phosphorus on
cobalt in the case of 3a and 3c, which increased electron
density on the cobalt and hence the propensity towards
bridging carbonyl.[12]
Scheme 3.
The molecular structure of 6e is similar to those of
known cyclopentadienyl analogues such as [CpCo(CO)2],[13]
and [Cp*Co(CO)2],[14] and substituted indenyl analogues
such as [(η5-C9H3Me4)Rh(CO)2],[15] and [(η5-C9H6CHPh2)-
Rh(CO)(PiPr3)].[16] The indenyl ligand is coordinated un-
symmetrically to the Co centre, as indicated by the longer
bond lengths (by Ϸ 0.1 Å) from the metal to the bridgehead
carbons than to the other three carbons of the five-mem-
bered ring. The values of the slip-fold parameters: slip dis-
tortion, Δ = 0.12(3) Å; hinge angle, HA = 5.6°; and fold
angle, FA = 5.3°, are in agreement with η5 coordination of
the indenyl.[15,17]
Figure 2. ORTEP diagram of 3e (50% probability thermal ellip-
soids, hydrogen atoms omitted).
The presence of the complexes 4e and 6e indicated that
There is no known Cp or Cp* analogue to 3e. However, ligand exchange and redox reaction between the ruthenium
it is interesting to compare its structure with those of the and cobalt precursors had occurred. While the oxidation
previously reported Cp* parent carbonyl [Cp*Ru(CO)2(μ- state of Ru has been reduced from +2 to 0 in 4e, that for
CO)Co(CO)3] (3eЈ) and its isocyanide derivative Co has been increased from –1 to +1 in 6e; the ruthenium
[Cp*Ru(CNBut)(CO)(μ-CO)Co(CO)3] (3fЈ);[3h] a common complex has also lost its indenyl and phosphane ligands in
Eur. J. Inorg. Chem. 2006, 663–670
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
665

S. Y. Ng, L. Y Goh, L. L. Koh, W. K. Leong, G. K. Tan, S. Ye, Y. Zhu
Table 1. Common atomic numbering scheme and selected bond parameters for 3e, 3eЈ and 3fЈ.
FULL PAPER
Bond lengths [Å] or angles [°]
3e
3eЈ
3fЈ
Ru–Co
2.677(2)
2.319(4)
2.7445(6)
1.890(4)
1.899(4)
2.206(3)
1.817(4)
1.136(4)
1.174(4)
103.7(1)
168.6(3)
126.0(3)
148.5(3)
2.735(4)
1.94(3)
1.92(3)
2.10(3)
1.83(3)
1.11(3)
1.20(3)
101.7(8)
168(2)
Ru–L[a]
Ru–C(11)
Ru–C(12)
Co–C(12)
C(11)–O(11)
C(12)–O(12)
Co–Ru–L[a]
Ru–C(11)–O(11)
Ru–C(12)–O(12)
Co–C(12)–O(12)
1.929(14)
2.030(12)
1.877(14)
1.105(16)
1.186(16)
115.12(11)
167.2(15)
135.5(11)
138.0(11)
127(2)
145(3)
[a] Refers to centroid of the five-membered ring.
exchange for three carbonyls. This result was in sharp con-
trast with the reported chemistry of the Cp analogue, for
which the heterobimetallic complex, viz., [CpRu(PPh3)2-
Co(CO)4] was isolated in low yield from the reaction of
[CpRu(PPh3)2Cl] with TlCo(CO)4, but on switching from
the Tl+ to the Na+ salt, the complex salt [CpRu(PPh3)2(CO)]-
[Co(CO)4] was isolated instead.[3e] Neither the displacement
of PPh3 by CO, nor the redox products that we have ob-
served, were reported in these reactions.
Similar redox chemistry was also observed in the case of
[(Ind)Ru(dppf)Cl] (2f). However, the heterobimetallic com-
plex was not isolated and instead the complex salt [(Ind)-
Ru(dppf)(CO)][Co(CO4)] (5f·[Co(CO)4]) was obtained, to-
gether with the Ru0 complex [Ru(dppf)(CO)3] (4f) and the
known CoI complex [(Ind)Co(CO)2] (6f) (Scheme 4).[18] The
IR spectrum of 4f exhibited three CO stretching bands
(2007, 1924 and 1896 cm–1), as opposed to one (1896 cm–1)
for 4e. This indicated that they have different symmetries,
as was confirmed by an X-ray crystallographic study on 4f
(Figure 4). Complex 4f adopts a distorted trigonal bipyram-
Scheme 4.
The failure to form the heterobimetallic complex at all in
idal geometry at the ruthenium atom. The two phosphorus this case was intriguing. We have found that the halide li-
atoms of the diphos occupy an axial [P(1)] and an equato- gand in 2f could not be substituted by CO in a direct reac-
rial position [P(2)].
tion to form [(Ind)Ru(dppf)(CO)]Cl (5f·Cl); a mixture of
However, the 31P NMR spectrum of 4f showed only a products which were not characterized was obtained in-
singlet at δ = 40.8 ppm, implying fluxionality, as may be stead. However, stirring 2f under 1 atm of CO and in the
expected for
a
five-coordinate complex. Complex presence of NaPF6 afforded 5f·PF6 in high yield; the same
5f·[Co(CO)4] was characterized spectroscopically and ana- product could also be obtained from the reaction of the
lytically. Its IR spectrum showed two carbonyl stretches at solvated complex [(Ind)Ru(dppf)(NCCH3)]PF6 (7) with
1972 and 1889 cm–1; very similar to the values for 1 atm of CO (Scheme 5). We therefore believe that in the
[CpRu(PPh3)2(CO)][Co(CO)4]
(ν
=
1978
and reaction between 2f and 1, the Cl– ligand was abstracted
˜
CO
1872 cm–1).[3e] The cation showed up as a molecular ion in and this was replaced by the coordination of CO originating
the positive mode of the FAB-MS at m/z 799, together with from the decomposition of [Co(CO)4]–. It is this coordina-
fragments corresponding to subsequent loss of a CO and tion of CO to the Ru centre which inhibits formation of a
an indenyl ligand, while the anion appeared in the negative Ru–Co bond, presumably because of the reduced electro-
mode at m/z 171.
philicity.
666
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 663–670

Heterobimetallic Ruthenium-Cobalt Complexes
FULL PAPER
Experimental Section
General Procedures: All reactions were performed under dry nitro-
gen using Schlenk techniques or under argon in a Braun Labmaster
130 glovebox. Chromatographic separations were performed inside
the glovebox. 1H, 31P{1H} and 13C{1H} NMR spectra were re-
corded with a Bruker ACF300 NMR spectrometer, with chemical
shifts referenced to residual non-deuterio solvent and external
H3PO4, respectively. IR spectra were obtained as either KBr pellets
or as a solution with a Shimadzu Prestige-21 FTIR-8400S spec-
trometer. Mass spectra were obtained with either a Finnigan
MAT95XL-T (FAB) or a Finnigan MAT LCQ (ESI) spectrometer.
All elemental analyses were performed by the Microanalytical Lab-
oratory in NUS. The complexes 1[19] and 2a–f,[20] were prepared
according to published methods. All other reagents are commer-
cially available and used without further purification. All solvents
were distilled from standard drying agents before use.
Reaction of NaCo(CO)4 with [Cp*Ru{Ph2P(CH2)nPPh2}Cl] (n = 1,
2): To a THF (10 mL) solution of [Cp*Ru(Ph2PCH2PPh2)Cl] (2a)
(100 mg, 0.15 mmol) was added a solution of NaCo(CO)4 (1) in
THF (1 equiv. in 5 mL) by cannula transfer, and the solution was
refluxed for 40 h. The solvent was then removed in vacuo and the
resulting residue extracted with CH2Cl2. Removal of the solvent
gave an orange-red solid which was recrystallized from THF/hex-
ane to afford [Cp*Ru(μ-CO)2(μ-Ph2PCH2PPh2)Co(CO)2] (3a) as
Figure 4. ORTEP diagram (50% probability thermal ellipsoids, hy-
drogen atoms omitted) and selected bond lengths [Å] and angles
[°] of 4f. Ru(1)–C(3) = 1.899(4); Ru(1)–C(1) = 1.902(4); Ru(1)–C(2)
= 1.912(4); Ru(1)–P(1) = 2.3737(9); Ru(1)–P(2) = 2.3957(9); O(1)–
C(1) = 1.150(4); O(2)–C(2) = 1.148(4); O(3)–C(3) = 1.133(4); C(3)–
Ru(1)–C(1) = 88.53(16); C(3)–Ru(1)–C(2) = 87.62(16); C(1)–Ru(1)–
C(2) = 135.35(16); C(3)–Ru(1)–P(1) = 168.31(12); C(1)–Ru(1)–P(1)
= 86.86(12); C(2)–Ru(1)–P(1) = 88.12(11); C(3)–Ru(1)–P(2) =
red crystals. Yield 102 mg (85%). IR (KBr, cm–1): ν
= 1973 s,
˜
CO
1913 s, 1784 w, 1721 s (lit. values:[3h] (THF) ν = 1985 s, 1923 s,
˜
CO
1728 m). 1H NMR (300 MHz, CDCl3): δ = 1.60 (s, 15 H, Cp*), 2.14
(t, 2 H, PCH2P), 7.20–7.37 (m, 20 H, Ph) ppm. 31P{1H } NMR: δ
= 55.8 (d, 2JPP = 103 Hz, Ru–P), 43.5 (br. s, Co–P) ppm. MS (ESI):
m/z (%) = 791 [M]+, 677 [M – Co(CO)2]+. C39H37CoO4P2Ru: C
59.2, H 4.7; formula mass 791.67; found C 59.2, H 5.2. The residue
from a similar reaction between 1 and [Cp*Ru{Ph2P(CH2)2-
PPh2}Cl] (2b) was dissolved in a minimum volume of THF for
chromatographic separation on silica gel. The main fraction (elu-
ent: hexane/THF, 5.5:1, v/v) gave [Cp*Ru(μ-CO)2{μ-Ph2P(CH2)2-
PPh2}Co(CO)2] (3b) as an orange-red solid. Yield 94 mg (78%). IR
94.04(12); C(1)–Ru(1)–P(2)
= 110.63(12); C(2)–Ru(1)–P(2) =
114.01(12); P(1)–Ru(1)–P(2) = 97.63(3).
(KBr, cm–1): ν
= 1978 s, 1920 s, 1771 w, 1722 s. 1H NMR
˜
CO
(300 MHz, CDCl3): δ = 1.60 (s, 15 H, Cp*), 2.04, 1.84 (m, 4 H,
PCH2CH2P), 7.19–7.68 (m, 20 H, Ph) ppm. 31P{1H } NMR: δ =
45 (s, Ru–P), 34.6 (br. s, Co–P) ppm. MS (ESI): m/z (%) = 806
[M]+, 778 [M – CO], 691 [M – Co(CO)2]+. C40H39CoO4P2Ru: calcd.
C 59.6, H 4.9; formula mass 805.70; found C 59.9, H 5.2.
Reaction of 1 with [(Ind)Ru(Ph2PCH2PPh2)Cl]: To a THF (10 mL)
solution of [(Ind)Ru(Ph2PCH2PPh2)Cl] (2c) (100 mg, 0.13 mmol)
was added 1 (1 equiv.) and the solution was stirred at room temp.
for 24 h. The solvent was removed under reduced pressure, and the
residue was first washed with hexane, followed by extraction with
toluene. The toluene extract was concentrated and loaded onto a
silica gel column prepared in n-hexane. Elution with toluene gave
a reddish brown band as the major eluate which afforded [(Ind)
Scheme 5.
Concluding Remarks
The results above clearly show that the salt elimination
reaction between NaCo(CO)4 and Cp* or indenyl ruthe-
nium chloride complexes do not always lead simply to a
heterobimetallic species. The nature of the products de-
pends on the nature of the ligands on ruthenium; in some
cases, there are redox processes involved. Unfortunately, no
clear trend is discernible yet as to when redox processes can
become important although it would appear that a suitable
diphosphane that can bridge across the heterometallic me-
tal–metal bond is important for stabilization of the hetero-
bimetallic product.
Ru(μ-CO)2(μ-Ph2PCH2PPh2)Co(CO)2] (3c). Yield 97 mg (80%). IR
1
(CH Cl , cm–1): ν = 1997 s, 1944 s, 1739 s. H NMR (300 MHz,
˜
2
2
CO
C6D6): δ = 2.03 [t, J = 9.06 Hz, 2 H, CH2(PPh2)2], 5.18–5.20 (m, 3
H, η5-C9H7), 6.64–6.67, 6.89–7.01, 7.10–7.14, 7.30–7.36 [m, 24 H,
CH2(PPh2)2 and η5-C9H7] ppm. 31P{1H} NMR: δ = 44.4 (br. d,
2
2JPP = 109 Hz, Co–P), 59.3 (d, JPP = 109 Hz, Ru–P) ppm. MS
(FAB+): m/z (%) = 716 [M – 2CO]+, 657 [M – 2CO – Co]+, 629
[M – 3CO – Co]+, 601 [M – 4CO – Co]+. C38H29CoO4P2Ru: calcd.
C 59.2, H 3.8; formula mass 771.60; found C 59.6, H 3.4.
For the reaction with [(Ind)Ru(CO)2Cl] (2d) (30 mg, 0.098 mmol),
the hexane extract was concentrated and cooled to –30 °C for 1 day
Eur. J. Inorg. Chem. 2006, 663–670
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
667

S. Y. Ng, L. Y Goh, L. L. Koh, W. K. Leong, G. K. Tan, S. Ye, Y. Zhu
FULL PAPER
to give [(Ind)Ru(CO)2Co(CO)4] (3d) (30 mg, 69%) as dark red crys-
PPh3), 7.87–7.93 (m, 12 H, PPh3) ppm. 31P{1H}NMR: δ = 55.9 (s,
tals.
PPh3) ppm.
For 3d: IR (hexane, cm–1): νCO = 2067 m, 2022 s, 1986 m, br., 1963 For 6e: IR (KBr, cm–1): ν = 1922 s. 1H NMR (300 MHz, C6D6):
˜
˜
CO
1
3
3
w, br., 1955 w, br. H NMR (300 MHz, C6D6): δ = 4.60 (t, JHH
=
δ = 4.61 (s, 2 H, η5-C9H7), 5.67 (t, JHH = 3.3 Hz, 1 H, η5-C9H7),
3.3 Hz, 1 H, η5-C9H7), 4.81 (d, 2 H, η5-C9H7), 6.79 (s, 4 H, η5- 6.74–6.78 (4-lines m, 2 H, η5-C9H7), 6.94–6.97, 6.98–7.01, 7.41–
C9H7) ppm. 13C NMR (75 MHz, C6D6): δ = 76.5 (s, C1,3), 91.5 (s,
C2), 111.1 (s, C8,9), 124.2 and 129.8 (s, C4–7), 204.3 (CO) ppm.
MS (FAB+): m/z (%) = 444 [M]+, 388 [M – 2CO]+, 360 [M –
3CO]+, 332 [M – 4CO]+. C15H7CoO6Ru: calcd. C 40.7, H 1.6; for-
mula mass 443.22; found C 40.8, H 1.5.
7.48 (each m, total 17 H, PPh3 and η5-C9H7) ppm. 31P NMR: δ =
65.6 (br. s, PPh3) ppm. ESI+-MS: 667 [2M – PPh3]+, 405 [2M –
2PPh3]+. C28H22CoOP·1⁄8CH2Cl2: calcd. C 71.0, H 4.7; formula
mass 475.00; found C 70.5, H 4.5. The presence of dichloromethane
1
solvent has been confirmed by H NMR spectroscopy.
For the reaction with [(Ind)Ru(PPh3)2Cl] (2e), the toluene extract
was concentrated and chromatographed on a silica gel column.
Elution gave four fractions: (i) A yellow eluate with hexane/toluene
(4:1, v/v) yielded [(Ind)Co(CO)(PPh3)] (6e) (8 mg, 13%) as air-sen-
sitive dark red crystals after recrystallization from CH2Cl2/hexane;
(ii) an orange-yellow eluate (severe tailing) with hexane/toluene
(3:1, v/v) gave [Ru(PPh3)2(CO)3] (4e) after several recrystallizations
from toluene/hexane (1:4, v/v) (26 mg, 28%); (iii) a reddish brown
eluate with hexane/toluene (1:1, v/v) yielded [(Ind)-
Ru(PPh3)(CO)(μ2-CO)Co(CO)3] (3e) (23 mg, 26%); and (iv) a red
eluate with toluene/THF (1:1, v/v) afforded unreacted 2e (20 mg,
20%).
For the reaction with [(Ind)Ru(dppf)Cl] (2f), extraction with tolu-
ene was followed by extraction with CH3CN. The toluene extract
was concentrated and chromatographed on a silica gel column. Elu-
tion with hexane/toluene (2:1, v/v) gave a yellow eluate of [(Ind)-
Co(CO) ] (6f). Yield 4 mg (5%). IR (CH Cl ): ν = 2027 and
˜
CO
2
2
2
1970 cm–1; lit. values (CH2Cl2):[18] 2030, 1970. Further elution with
hexane/toluene (4:3, v/v) afforded an orange-yellow eluate which
gave [Ru(dppf)(CO)3] 4f after several recrystallizations from tolu-
ene/hexane (1:4, v/v). Yield 37 mg (40%). The CH3CN extract gave
[(Ind)Ru(dppf)(CO)][Co(CO4)] (5f·[Co(CO)4]) as a dark brown oil.
Yield 36 mg (30%).
For 4f: IR (CH Cl , cm–1): νCO = 2007 s, 1924 m, 1896 s. 1H NMR
˜
2
2
For 3e: IR (CH Cl , cm–1): νCO = 1975 s, 1920 s, 1744 m. 1H NMR (300 MHz, C6D6): 4.27 (s, 4 H, C5H4), 4.28 (s, 4 H, C5H4), 7.02–
˜
2
2
(300 MHz, C6D6): δ = 4.98 (s, 3 H, η5-C9H7), 6.57–6.93 (m, 4 H,
7.88 (m, 20 H, Ph) ppm. 31P{1H} NMR: δ = 40.8 (s, dppf) ppm.
MS (FAB+): m/z (%) = 740 [M]+, 712 [M – CO]+, 684 [M –
η5-C9H7), 7.03–7.72 (m, 15 H, PPh3) ppm. 31P{1H} NMR: δ = 48.6
(s, PPh3) ppm. MS (FAB+): m/z (%) = 566 [M – 4CO]+, 535 [M – 2CO]+, 655 [M – 3CO]+. C37H28FeO3P2Ru: calcd. C 59.9, H 3.8;
Co – 3CO]+, 479 [M – Co – 5CO]+. C32H22CoFeO5P·2C6H5CH3:
formula mass 739.49; found C 60.1, H 3.8.
calcd. C 64.4, H 4.0; formula mass 816.56; found C 64.1, H 4.2.
The presence of toluene solvent has been confirmed by H NMR
spectroscopy.
For 5f·[Co(CO) ]: IR (CH Cl ): ν
= 1972 m, 1889 s cm–1. 1H
˜
CO
4
2
2
1
NMR (300 MHz, CD3CN): δ = 4.37 (s, 2 H, C5H4), 4.46 (s, 2 H,
C5H4), 4.57 (s, 2 H, C5H4), 4.61 (s, 2 H, C5H4), 5.25 (s, 3 H, η5-
C9H7), 6.77–7.06 (m, 4 H, η5-C9H7), 7.18–7.71 (m, 20 H, Ph) ppm.
31P{1H}: δ = 54.8 (s, dppf) ppm. FAB+-MS: m/z 799 [M]+, 771 [M –
For 4e: IR (CH Cl , cm–1): νCO = 1896 s (lit. values:[10b] (THF) ν
˜
˜
CO
2
2
= 1900 s). 1H NMR (300 MHz, C6D6): δ = 6.96–7.05 (m, 18 H,
Table 2. Crystal and refinement data for 3c, 3e, 4e, 4f and 6e.
Compound
3c
3e
4e
4f
6e
Empirical formula
Formula weight
C38H29CoO4P2Ru·CH2Cl2 C32H22CoO5PRu
C39H30O3P2Ru·CH2Cl2 C37H28FeO3P2Ru
C28H22CoOP
464.36
856.48
677.47
794.57
739.45
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
γ [°]
Volume [Å3]
Z
monoclinic
P21/c
10.5588(5)
16.9898(8)
20.1273(9)
90
94.3280(10)
90
3600.4(3)
4
orthorhombic
P212121
11.898(2)
15.098(3)
15.376(3)
90
90
90
2762.2(9)
4
triclinic
¯
P1
monoclinic
P21/c
9.7242(6)
16.2461(10)
19.9335(12)
90
95.082(2)
90
3136.7(3)
4
monoclinic
P21/c
9.1150(5)
25.7691(15)
10.4250(6)
90
115.9190(10)
90
2202.4(2)
4
9.9667(6)
13.6718(8)
15.4090(9)
63.7400(10)
87.6650(10)
74.4430(10)
1806.60(18)
2
Density (calculated) [Mg/m3]
Absorption coefficient [mm–1
F(000)
1.580
1.158
1728
1.629
1.246
1360
1.461
0.708
808
1.566
1.083
1496
1.400
0.870
960
]
Crystal size [mm]
θ range for data collection [°]
Reflections collected
0.36×0.32×0.20
2.28 to 30.01
33154
0.25×0.08×0.07
2.18 to 26.37
20635
0.20×0.16×0.14
2.34 to 27.50
23823
0.30×0.12×0.09
1.62 to 27.50
18602
0.30×0.10×0.08
1.58 to 27.50
15374
Independent reflections
Max. and min. transmission
Data / restraints / parameters
Goodness-of-fit on F2
10167 [R(int) = 0.0303]
0.8014 and 0.6806
10167 / 7 / 451
1.070
3171 [R(int) = 0.1020] 8273 [R(int) = 0.0430]
7202 [R(int) = 0.0443] 5057 [R(int) = 0.0375]
0.9178 and 0.7458
3171 / 30 / 361
1.333
0.9074 and 0.8714
8273 / 6 / 455
1.101
0.9088 and 0.7371
7202 / 0 / 397
1.037
0.9337 and 0.7804
5057 / 0 / 280
1.114
Final R indices [I Ͼ 2σ(I)]
R1 = 0.0392,
wR2 = 0.1029
R1 = 0.0498,
wR2 = 0.1154
0.942 / –0.492
R1 = 0.0889,
wR2 = 0.1779
R1 = 0.0964,
wR2 = 0.1807
1.958 / –1.437
R1 = 0.0534,
wR2 = 0.1258
R1 = 0.0636,
wR2 = 0.1311
1.158 / –0.813
R1 = 0.0468,
wR2 = 0.1018
R1 = 0.0646,
wR2 = 0.1087
0.682 / –0.337
R1 = 0.0521,
wR2 = 0.1088
R1 = 0.0694,
wR2 = 0.1152
0.654 / –0.236
R indices (all data)
Largest diff. peak / hole [e·Å–3
]
668
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 663–670

Heterobimetallic Ruthenium-Cobalt Complexes
FULL PAPER
CO]+, 655 [M – CO – Ind]+. MS (FAB–): m/z (%) = 171
[Co(CO)4]–. MS (HR-FAB+): m/z (%) = 799.0562 (found), 799.0562
(calcd.).
Complexes, Wiley-VCH, Weinheim, 1998; c) P. Braunstein, I.
Rose in Chemical Bonds: Better Ways to Make Them and Break
Them (Ed.: I. Bernal), Elsevier, Amsterdam, 1989, p. 89; d) G.
Süss-Fink, G. Meister, Adv. Organomet. Chem. 1993, 35, 41.
a) W. R. Pretzer, T. P. Kobylinski, J. E. Bozik (Gulf Research
and Development Company), U. S. Patents 4133966, 1979 and
4239924, 1980; b) R. Fiato (Union Carbide Corporation), U. S.
Patent 4253987, 1980; c) British Petroleum, Ltd, British Patent
2036739, 1980; d) G. Doyle (Exxon Research & Engineering
Company), U. S. Patent 4348541, 1982; e) G. Doyle, J. Mol.
Catal. 1983, 18, 251; f) M. Hidai, M. Orisaku, M. Ue, Y. Koy-
asu, T. Kodoma, Y. Uchida, Organometallics 1983, 2, 292; g)
K. Watanabe, K. Kudo, N. Sugita, Bull. Chem. Soc. Jpn. 1985,
58, 2029; h) E. Santacesaria, M. Di Serio, J. Mol. Catal. 1990,
58, 43; i) K. Tominaga, Y. Sasaki, T. Watanabe, M. Saito, Stud.
Surf. Sci. Catal. 1998, 114, 495.
a) A. R. Manning, J. Chem. Soc. (A) 1971, 2321; b) R. Regra-
gui, P. H. Dixneuf, J. Organomet. Chem. 1982, 239, C12; c)
H. C. Foley, W. C. Finch, C. G. Plerpont, G. L. Geoffroy, Orga-
nometallics 1982, 1, 1379; d) R. Regragui, P. H. Dixneuf, N. J.
Taylor, A. J. Carty, Organometallics 1984, 3, 1020; e) G. Doyle,
D. V. Engen, J. Organomet. Chem. 1985, 280, 253; f) R. Zoet,
G. van Koten, A. L. J. van der Panne, P. Versloot, C. H. Stam,
K. Vrieze, Inorg. Chim. Acta 1988, 149, 177; g) M. R. Gagné,
J. Takats, Organometallics 1988, 7, 561; h) H. Matsuzaka, K.
Ichikawa, T. Ishioka, H. Sato, T. Okubo, T. Ishii, M. Yamash-
ita, S. Kondo, M. Kitagawa, J. Organomet. Chem. 2000, 596,
121.
a) R. Regragui, P. H. Dixneuf, N. J. Taylor, A. J. Carty, Organo-
metallics 1984, 3, 814; b) R. Regragui, P. H. Dixneuf, N. J. Tay-
lor, A. J. Carty, Organometallics 1986, 5, 1; c) S. Guesmi, P. H.
Dixneuf, G. Süss-Fink, N. J. Taylor, A. J. Carty, Organometal-
lics 1989, 8, 307; d) J. N. L. Dennett, J. Jacke, G. Nilsson, A.
Rosborough, M. J. Ferguson, M. Wang, R. McDonald, J. Tak-
ats, Organometallics 2004, 23, 4478.
a) L. Tang, M. Huang, Y. Jiang, Reactive Polymers 1994, 23,
119; b) S. Guan, M. Huang, Y. Jiang, Chinese J. Polymer Sci.
1993, 11, 103; c) H. Zong, W. Tang, Z. Chen, Y. Jiang, Chinese
J. Polymer Sci. 1991, 9, 171; d) Q. Tang, H. Zong, Z. Chen, Y.
Jiang, Chinese J. Polymer Sci. 1991, 9, 39; e) S. Cao, M. Huang,
Y. Jiang, Polym. Bull. 1988, 19, 353.
a) D. W. Stephan, Coord. Chem. Rev. 1989, 95, 41; b) N. Wheat-
ley, P. Kalck, Chem. Rev. 1999, 99, 3379; c) E. W. Adams in
Comprehensive Organometallic Chemistry II (Eds.: R. D. Abel,
F. G. A. Stone, G. Wilkinson), Elsevier, Oxford, 1995, vol. 10,
p. 1; d) E. W. Chetcuti in Comprehensive Organometallic Chem-
istry II (Eds.: M. J. Abel, F. G. A. Stone, G. Wilkinson), Elsev-
ier, Oxford, 1995, vol. 10, p. 24.
H. Matsuzaka, K. Ichikawa, T. Ishii, M. Kondo, S. Kitagawa,
Chem. Lett. 1998, 1175.
R. A. Jones, M. H. Seeberger, A. L. Stuart, B. R. Whittlesey,
T. C. Wright, Acta Crystallogr. Sect. C: Cryst. Struct. Commun.
1986, 42, 399.
K.-B. Shiu, H.-C. Lee, G.-H. Lee, Y. Wang, Organometallics
2002, 21, 4013.
a) F. Dahan, S. Sabo, B. Chaudret, Acta Crystallogr. C: Cryst.
Struct. Commun. 1984, 40, 786; b) E. M. Gordon, R. Eisen-
berg, J. Mol. Catal. 1988, 45, 57.
Synthesis of [(Ind)Ru(dppf)(CO)]PF6
[2]
[3]
[4]
Method A: NaPF6 (5 mg, 0.03 mmol) was added to a solution of
2f (20 mg, 0.02 mmol) in THF (10 mL). The mixture was subjected
to three freeze-pump-thaw cycles, then CO (1 atm) was bubbled
through the solution for about 10 min. The reaction mixture was
stirred at room temp. for 24 h, during which the colour of the solu-
tion changed from red to yellow. The mixture was filtered and con-
centrated to ca. 2 mL. Addition of ether (5 mL) followed by cooling
at –30 °C for 1 d gave [(Ind)Ru(dppf)(CO)]PF6 (5f·PF6). Yield
20 mg (85%).
Method B: A solution of 7 (20 mg, 0.02 mmol) in THF (10 mL)
was degassed by three freeze-pump-thaw cycles, and then saturated
with CO (1 atm; bubbling for ca. 10 min). The reaction mixture
was stirred at room temp. for 24 h, filtered and then concentrated
to ca. 2 mL. Addition of ether (5 mL) followed by cooling at –
30 °C for 1 day gave 5f·PF6. Yield 17 mg (86%). IR (THF, cm–1):
ν
= 1973 s. 1H NMR (300 MHz, CD3CN): δ = 4.37 (s, 2 H,
˜
CO
C5H4), 4.46 (s, 2 H, C5H4), 4.57 (s, 2 H, C5H4), 4.61 (s, 2 H, C5H4),
5.24 (s, 3 H, η5-C9H7), 6.76–7.06 (m, 4 H, η5-C9H7), 7.18–7.71 (m,
20 H, Ph) ppm. 31P{1H} NMR: δ = 54.8 (s, dppf), –142.9 (sept,
PF6) ppm. MS (FAB+): m/z (%) = 799 [M]+, 771 [M – CO]+, 655
[M – CO – Ind]+. MS (FAB–): m/z (%) = 145 [PF6]–. C44H35F6FeO-
P3Ru: calcd. C 56.0, H 3.7; formula mass 943.59; found C 56.0, H
3.7.
Crystal Structure Determinations: Crystals were grown from dichlo-
romethane/hexane solutions and mounted on quartz fibres. X-ray
data were collected with a Bruker AXS APEX system, using Mo-
Kα radiation, with the SMART suite of programs.[21] Data were
processed and corrected for Lorentz and polarisation effects with
SAINT,[22] and for absorption effects with SADABS.[23] Structural
solution and refinement were carried out with the SHELXTL suite
of programs.[24] Crystal and refinement data are summarised in
Table 2. The structures were solved by direct methods or Patterson
maps to locate the heavy atoms, followed by difference maps for the
light, non-hydrogen atoms. All non-hydrogen atoms were generally
given anisotropic displacement parameters in the final model (ex-
cept for the carbon atoms of the disordered solvate in 4e). Clusters
3c and 4e had one CH2Cl2 solvate molecule each, which exhibited
disorder over two sites. For 3c, the site occupancies were 0.75 and
0.25; for 4e, these were 0.9 and 0.1. Appropriate restraints were
placed on the atomic anisotropic parameters and bond and in-
teratomic distances.
[5]
[6]
[7]
[8]
CCDC 283009–283013 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
[9]
[10]
[11]
[12]
R. H. Crabtree, M. Lavin, Inorg. Chem. 1986, 25, 805.
P. J. Dyson, J. S. McIndoe, Transition Metal Carbonyl Cluster
Chemistry, Gordon and Breach, Amsterdam, 2000.
M. Y. Antipin, Y. T. Struchkov, A. N. Chernega, M. F. Meid-
ine, J. F. Nixon, J. Organomet. Chem. 1992, 436, 79.
L. R. Byers, L. F. Dahl, Inorg. Chem. 1980, 19, 277.
A. K. Kakkar, N. J. Taylor, T. B. Marder, J. K. She, N. Halli-
nan, F. Basolo, Inorg. Chim. Acta 1992, 198–200, 219.
E. Bleuel, O. Gevert, M. Laubender, H. Werner, Organometal-
lics 2000, 19, 3109.
Acknowledgments
This work was supported by an A*STAR grant (Research Grant
No. 012 101 0035) and one of us (S. Y. N.) thanks the University
for a Research Scholarship. Contribution from Dr. J. Zhang in the
earlier part of this work is also acknowledged.
[13]
[14]
[15]
[16]
[17]
[1] a) P. Braunstein, E. W. Rose in Comprehensive Organometallic
Chemistry II (Eds.: J. Abel, F. G. A. Stone, G. Wilkinson), El-
sevier, Oxford, 1995, vol. 10, p. 351; b) R. D. Adams, F. A.
Cotton (Eds.), Catalysis by Di and Polynuclear Metal Cluster
M. J. Calhorda, L. F. Veiros, Coord. Chem. Rev. 1999, 185–186,
37 and references cited therein.
Eur. J. Inorg. Chem. 2006, 663–670
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
669

S. Y. Ng, L. Y Goh, L. L. Koh, W. K. Leong, G. K. Tan, S. Ye, Y. Zhu
FULL PAPER
[18] A. Salzer, C. Täschler, J. Organomet. Chem. 1985, 294, 261.
[19] W. F. Edgell, J. Lyford, Inorg. Chem. 1970, 9, 1932.
[21] SMART version 5.628, Bruker AXS Inc., Madison, Wisconsin,
USA, 2001.
[22] SAINT+ version 6.22a, Bruker AXS Inc., Madison, Wiscon-
sin, USA, 2001.
[23] G. W. Sheldrick, SADABS, University of Göttingen, 1996.
[24] G. W. Sheldrick, SHELXTL, Bruker Analytical Instruments,
Madison, Version 5.1, 1997.
[20] a) M. I. Bruce, B. G. Ellis, P. J. Low, B. W. Skelton, A. H.
White, Organometallics 2003, 22, 3184; b) L. A. Oro, M. A. Ci-
riano, M. Campo, C. Foces-Foces, F. H. Cano, J. Organomet.
Chem. 1985, 289, 117; c) M. P. Gamasa, J. Gimeno, C. Gon-
zelz-Bernardo, B. M. Martí-Vaca, D. Monti, M. Bassetti, Orga-
nometallics 1996, 15, 302; d) S. Y. Ng, Y. Zhu, W. K. Leong,
R. Webster, L. Y. Goh, manuscript in preparation.
Received: September 6, 2005
Published Online: December 13, 2005
670
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 663–670