Ferrocenylalkynes as ligands in transition metal complexes

Article abstract of DOI:10.1039/b008803j

Several ferrocenylalkynes have been prepared and their reaction with dicobalt octacarbonyl led to the formation of [Co₂(CO)₆(μ-η² : η²-ethynylferrocene)] 1, [Co₂(CO)₆(μ-η2 : η²-1,4-bis(ferrocenyl)butadiyne)] 2, [(Co₂(CO)₆)₂-(μ-η² : η²,μ-η² : η²-1,4-bis(ferrocenyl)butadiyne)] 3, [Co₂(CO)₆(μ-η² : η²-1-ferrocenylethynyl-2-hydro-1,2-dihydro[60]fullerene)] 4, [Co₂(CO)₆(μ-η² : η²-1,1'-bis(phenylethynyl)ferrocene)] 5 and [(Co₂(CO)₆)₂(μ-η² : η²,μ-η² : η²-1,1′-bis(phenylethynyl)ferrocene)] 6. The [Mo-Co]-alkyne adducts [MoCo(CO)₅(η⁵-C₅H₅)(μ- η² : η²-ethynylferrocene)] 7 and [MoCo(CO)₅(η⁵-C₅H₅)(μ- η² : η²-1,4-bis(ferrocenyl)butadiyne)] 8 were obtained from complexes 1, 2 and 3. The molecular structures of compounds 2, 3, 6 and 7 were determined by X-ray diffraction, only 6 has the cyclopentadienyl rings of the ferrocene unit eclipsed. The reaction of 1 with bis(diphenylphosphino)methane (dppm) and 1,1′-bis(diphenylphosphino)ferrocene (dppf) resulted in the formation of [Co₂(CO)₄(μ-η¹ : η¹-dppm)(μ-η² : η²-ethynylferrocene)] 9 and [(Co₂(CO)₄)₂(μ-η¹ : η¹-dppf)₂(η¹-μ-η¹ -dppf)(μ-η² : η²-ethynylferrocene)₂] 10, respectively. The reaction of HPPh₂ with 7 gave the monosubstituted product [MoCo(CO)₄(η⁵-C₅H₅)(PHPh ₂)(μ-η²,η²-ethynylferrocene)] 11. The bis(phosphido)-bridged complex [Co₂(CO)₆(μ-PPh₂)₂] undergoes regiospecific insertion with ethynylferrocene to give [Co₂(CO)₄{(μ-η⁴-PPh₂CHCRC (O)}(μ-PPh₂)] (R = ferrocene) 12, which was characterized by X-Ray diffraction and contains a five-membered metallacyclic ring.

Full text of DOI:10.1039/b008803j

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Ferrocenylalkynes as ligands in transition metal complexes
Elise Champeil and Sylvia M. Draper*
Chemistry Department, University of Dublin, Trinity College, Dublin 2, Ireland.
E-mail: suidraper@tcd.ie
Received 1st November 2000, Accepted 7th March 2001
First published as an Advance Article on the web 10th April 2001
Several ferrocenylalkynes have been prepared and their reaction with dicobalt octacarbonyl led to the formation
of [Co2(CO)6(µ-η2 : η2-ethynylferrocene)] 1, [Co2(CO)6(µ-η2 : η2-1,4-bis(ferrocenyl)butadiyne)] 2, [(Co2(CO)6)2-
(µ-η2 : η2,µ-η2 : η2-1,4-bis(ferrocenyl)butadiyne)] 3, [Co2(CO)6(µ-η2 : η2-1-ferrocenylethynyl-2-hydro-1,2-dihydro-
[60]fullerene)] 4, [Co2(CO)6(µ-η2 : η2-1,1’-bis(phenylethynyl)ferrocene)] 5 and [(Co2(CO)6)2(µ-η2 : η2,µ-η2 : η2-1,1Ј-
bis(phenylethynyl)ferrocene)] 6. The [Mo–Co]-alkyne adducts [MoCo(CO)5(η5-C5H5)(µ-η2 : η2-ethynylferrocene)] 7
and [MoCo(CO)5(η5-C5H5)(µ-η2 : η2-1,4-bis(ferrocenyl)butadiyne)] 8 were obtained from complexes 1, 2 and 3. The
molecular structures of compounds 2, 3, 6 and 7 were determined by X-ray diffraction, only 6 has the cyclopenta-
dienyl rings of the ferrocene unit eclipsed. The reaction of 1 with bis(diphenylphosphino)methane (dppm) and
1,1Ј-bis(diphenylphosphino)ferrocene (dppf) resulted in the formation of [Co2(CO)4(µ-η1 : η1-dppm)(µ-η2 : η2-
ethynylferrocene)] 9 and [(Co2(CO)4)2(µ-η1 : η1-dppf)2(η1-µ-η1-dppf)(µ-η2 : η2-ethynylferrocene)2] 10, respectively.
The reaction of HPPh2 with 7 gave the monosubstituted product [MoCo(CO)4(η5-C5H5)(PHPh2)(µ-η2,η2-ethynyl-
ferrocene)] 11. The bis(phosphido)-bridged complex [Co2(CO)6(µ-PPh2)2] undergoes regiospecific insertion with
ethynylferrocene to give [Co2(CO)4{(µ-η4-PPh2CHCRC(O)}(µ-PPh2)] (R = ferrocene) 12, which was characterized
by X-Ray diffraction and contains a five-membered metallacyclic ring.
to link three different metal centres all with their own unique
Introduction
electronic requirements: M1M2[ferrocenylalkyne] (M1 = Mo,
M2 = Co). In the case of asymmetrical alkynes this differenti-
ates the four apices of the metal–alkyne core and the complex
is rendered chiral. Work in this area has shown that the use
of similar diastereomerically pure complexes in the Pauson–
Khand reaction can give rise to organic products with no sign
of the other diastereoisomer in each case.9
Compounds generated from the reaction of alkynes with transi-
tion metal carbonyls have found considerable utility. None more
so, perhaps, than those complexes based on a Co2C2 core. The
resurgence of interest in the cobalt carbonyl catalysed [2 ϩ
2 ϩ 1] cycloaddition of alkyne, alkene and carbon monoxide
(the Pauson–Khand cycloaddition) for the preparation of
cyclopentenones has generated a host of new alkyne co-
ordinated metal carbonyl complexes.1 These have successfully
extended the synthetic versatility of the reaction, which can be
photolytically activated,2 polymer supported3 and/or stereo-
selective.4 As part of our work5 on the metallisation of alkynes
we describe here a systematic study into the modification of
ferrocene substituted M1M2[alkyne] complexes.
We chose ferrocene as a template for two reasons. It has
established synthetic versatility and imparts improved crystal-
linity to its compounds. Here we report the molecular struc-
tures of [Co2(CO)6(µ-η2 : η2-1,4-bis(ferrocenyl)butadiyne)] 2,
[(Co2(CO)6)2(µ-η2 : η2,µ-η2 : η2-1,4-bis(ferrocenyl)butadiyne)]
3, and [(Co2(CO)6)2(µ-η2 : η2,µ-η2 : η2-1,1Ј-bis(phenylethynyl)-
ferrocene)] 6 which enable us to assess the structural changes
imposed on changing the position and substituents on the
ferrocenylalkyne.
Extended alkyne π-systems e.g. to give dendritic macro-
molecules, are of interest because of the possibility of charge
transfer along the conjugated backbone.6 Ferrocene is an
electron donating group, widely used in the construction of
compounds with non-linear optical properties.7 In this work,
we report the synthesis of [Co2(CO)6(µ-η2 : η2-1-ferrocenyl-
ethynyl-2-hydro-1,2-dihydro[60]fullerene)] 4, a compound with
potential non-linear optical properties, where the ferrocenyl
donor group is linked via an electron-rich backbone to a
polyaromatic acceptor moiety.
Another approach to the development of asymmetric vari-
ants of the Pauson–Khand reaction has been to render the
Co–Co core of the dicobalt hexacarbonyl adduct chiral by
replacing carbonyl ligands with chiral substituents. Some recent
examples have used chiral phosphines as ligands in order to
increase the stereocontrol of the reaction.10 Here we report the
synthesis of a number of phosphine substituted metal carbonyl
moieties using 1,1Ј-bis(diphenyldiphosphino)methane and bis-
(diphenylphosphino)ferrocene. The products are phosphine
dependent giving the chelated [Co2(CO)4(µ-η1 : η1-dppm)-
(µ-η2 : η2-ethynylferrocene)] 9 and bridged [(Co2(CO)4)2(µ-η1:
η1-dppf)2(η1-µ-η1-dppf)(µ-η2 : η2-ethynylferrocene)2] 10, cobalt
carbonyl species. Reaction of the mixed Mo–Co complex 7 with
diphenylphosphine generated the monocarbonyl substituted
[MoCo(CO)5(η5-C5H5)(PHPh2)(µ-η2,η2-ethynylferrocene)] 11.
The reaction of the bis(phosphido)-bridged cobalt carbonyl
species resulted in an inserted phosphametallacycle [Co2-
(CO)4{(µ-η4-PPh2CHCRC(O)}(µ-PPh2)] (R = ferrocene) 12.
The later is reminiscent of an intermediate generated from the
Pauson–Khand process.
Results and discussion
(a) Synthesis of dicobalt hexacarbonyl complexes
The treatment of dicobalt octacarbonyl with alkynes proceeds
via loss of two equivalents of CO to yield the corresponding
metallatetrahedranes. In a similar manner the ferrocenylalkynes
used here lead to complexes 1–6 (Scheme 1). The incorporation
of one or two Co2(CO)6 units and a consequent reduction in
In addition, the attachment of adjacent organometallic
moieties via alkyne linkages results in electronic interactions
between metal atoms and the potential for tunable redox
behaviour.8 The inclusion of a ferrocenyl moiety has allowed us
1440
J. Chem. Soc., Dalton Trans., 2001, 1440–1447
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b008803j

View Article Online
Scheme 1
triple bond character is characterised by the downfield shift
in the proton and carbon NMR spectra of the products.
In particular, the deshielding of the C60 methine proton of
1-ferrocenylethynyl-2-hydro-1,2-dihydro[60]fullerene (δH 7.13),
ascribed to the presence of the triple bond, was lost upon com-
plexation and a signal more reminiscent of C60 alkyl or phenyl
derivative (RC60H) is now observed (δH 6.04 for R = Me and
δH 6.81 for R = Ph).11 The synthesis and spectroscopic charac-
terisation (IR, 1H NMR) of complexes 2 and 3 have been
reported previously.12
The IR spectra of 1–6 showed the expected absorptions in
the carbonyl region.7 Compound 4 exhibits the lowest ν1(A1)
stretching frequencies of all the complexes. This would be
expected in a situation where there is an increase in electron
density around the cobalt atoms of 4, and the dicobalt unit is
acting as an electron sink.
In general, in complexes 9–12 where CO ligands are replaced
by poorer π-accepting phosphines, the ν(CO) IR absorption
bands are lower than in the unsubstituted carbonyl complexes.13
For complexes 9, 10 and 11, where structural comparisons
can be made, a trend is observed where the higher the degree
of phosphine substitution, the lower the ν(CO) frequencies.
The ν1(A1) shift of the carbonyl complexes compared to their
phosphine derivatives is 50 cmϪ1 for monosubstitution in 12,
65 cmϪ1 for disubstitution in 9 and 80 cmϪ1 for trisubstitution
in 10.
Fig. 1 ORTEP drawing of the structure of 2 (thermal ellipsoids have
been drawn at the 20% probability level, hydrogen atoms have been
omitted for clarity).
(b) Crystal structures of dicobalt hexacarbonyl complexes 2, 3
and 6
Single crystals of compounds 2, 3 and 6 were obtained from
saturated solutions of the compounds in dichloromethane
(2 and 3) or hexane (6). The molecular structures of 2, 3 and
6 are depicted in Figs. 1, 2 and 3. In all cases the Co–Co
bond lengths are shorter (2.46–2.47 Å) than those observed in
the parent carbonyl (2.52 Å).14 This observation agrees with
previously reported dicobalt systems bridged by perpendicular
alkynes.15 A common feature of all the molecular structures
obtained is the presence of distorted Co2C2 cores. The
asymmetry of the dimetallatetrahedranes is most clearly seen
in the disparity of the (ferrocene)Co–Co bond lengths of 3
(C(11)–Co(1) 1.983(9) Å, C(11)–Co(2) 1.946(9) Å).
Fig. 2 ORTEP drawing of the structure of 3 (thermal ellipsoids have
been drawn at the 20% probability level, hydrogen atoms have been
omitted for clarity).
presence of the second Co2(CO)6 fragment is considered.
Despite this difference, the C–C bond lengths of the Co2C2
tetrahedranes in 2, 3 and 6 vary very little (2: 1.33(2) Å, 3:
1.322(12) Å, 6: 1.335(4) and 1.332(4) Å). The free alkyne unit
in 3 retains its linearity as expected and the relevant bond
length is consistent with the retention of significant triple bond
character (C(13)–C(14) 1.20(2) Å).
The interaction of the Co2(CO)6 units lengthens the alkyne
᎐
bond consistent with the loss of C᎐C bond character resulting
᎐
from the delocalisation of electron density onto the Co2
unit. The deviation from sp hybridisation on metallisation is
also apparent e.g. in the pivotal angles of C(11) and C(12)
An interesting feature of the molecular structures is the
position of the ferrocenyl units. In 2 they exhibit an orthogonal
relationship whereas in 3 they are related by the crystallo-
graphic centre of symmetry that lies at the centre of the
butadiyne. In both these structures the Cp rings of each
ferrocene unit are staggered (average 9Њ). Compound 6,
however, crystallises in a configuration where the Cp rings of
the linking ferrocene are eclipsed; this appears to reduce any
in
2 (C(10)–C(11)–C(12), 141.5(13)Њ, C(11)–C(12)–C(13),
141.6(12)Њ). These angles, within crystallographic error, are
generally independent of the substituents attached to the
alkyne but in 3 the pivotal angle (C(10)–C(11)–C(12), 136.7(8)Њ)
is the smallest yet reported. This might be expected when the
J. Chem. Soc., Dalton Trans., 2001, 1440–1447
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Fig. 4 ORTEP drawing of the structure of one enantiomer of 7
(thermal ellipsoids have been drawn at the 30% probability level,
hydrogen atoms have been omitted for clarity). There was considerable
rotational disorder of the unbound Cp ring. This was modelled as two
Cp rings with refined occupancies of 55.8 and 44.2% and the carbon
atoms were held isotropic.
Fig. 3 ORTEP drawing of the structure of 6 (thermal ellipsoids have
been drawn at the 20% probability level, hydrogen atoms have been
omitted for clarity).
steric interactions between the phenyl substituents on the
alkyne. Interestingly the Cp rings in unmetallated 1,1Ј-bis-
(phenylethynyl)ferrocene are also eclipsed16 but in this case the
molecule crystallises with a cis arrangement of the phenyl-
ethynyl ligands. Clearly the increased steric requirements on
metallisation lead to the twisting of substituents away from
each other but not to the extent that a 180Њ or trans arrange-
ment is observed.
(e) Phosphine substituted complexes
The facile substitution of carbonyl ligands by phosphines in
dicobalt hexacarbonyl complexes22 prompted us to investigate
the reaction of 1 with dppm and dppf. The small bite angle
of dppm was expected to lead to the formation of a bridged
dicobalt complex. Indeed, the addition of dppm to 1 in a 1 : 1
ratio lead to the formation of dark-red, air-stable 9. The
31P{1H} NMR spectrum of compound 9 exhibits a single
resonance at δ 41.5 consistent with the coordination of both
phosphorus atoms in the same chemical environment. Metal
coordination results in a 62.5 ppm upfield shift of the 31P{1H}
NMR signal compared to the free ligand. Further evidence for
the structure proposed is provided by the solution IR spectrum
which exhibits four terminal stretching frequencies.
(c) Synthesis of heterobimetallic complexes
The chiral heterobimetallic MoCoC2 adducts 7 and 8 were
obtained from complexes 1 and 2 respectively, via replacement
17
of a Co(CO)3 vertex by the isolobal moiety MoCp(CO)2
(Scheme 1). Complex 3 lost an additional Co2(CO)6 in the sub-
stitution resulting in an alternative route to 8. Interestingly,
it has been reported that only one of the CC bonds of
4,4Ј-dipyridylbutadiyne reacts with Cp2Mo2(CO)4, even in the
presence of an excess of the metal complex.18
The ligand dppf has been shown to be flexible in relation
to its coordination to metal carbonyl complexes, it has proven
ability to both bridge and link Co(CO)2 moieties.23 The reaction
of 1 with an excess (1.5 equivalents) of dppf, resulted in the
isolation of a dark brown product 10. Although 10 is highly air-
sensitive and unstable in solution (no elemental analysis could
be obtained), comparison of its spectroscopic data with similar
compounds24 suggests the structure presented in Scheme 2 as
the linked η1-µ-η1 cluster: [(Co2(CO)4)2(µ-η1 : η1-dppf)2(η1-
µ-η1-dppf)(µ-η2 : η2-ethynylferrocene)2]. The 31P{1H} NMR
exhibits two signals in the region expected for metal coordi-
nated phosphorus atoms, a doublet (3J(PP) 97 Hz, 4P) at δ 43.4
and a broad singlet (2P) at δ 34.4. These are shifted 60.4 ppm
upfield for the doublet and 51.4 ppm upfield for the singlet
compared to free dppf. The 31P{1H} NMR spectrum of a
similar compound with the same [(Co2(CO)4)2(µ-η1 : η1-dppf)2-
(η1-µ-η1-dppf)] core also shows two signals in the same region
(a broad singlet (4P) at δ 42.1 and a triplet (3J(PP) 50 Hz,
2P) at δ 32.2).24 In both cases the 31P nuclei attached to the
“outer” Co atoms (labelled Co* in Scheme 2) resonate at lower
field. However, different coupling patterns are observed. In
Robinson’s case each “outer” P atom couples to the two nearest
The 13C{1H} NMR spectra of 7 and 8 exhibit three terminal
carbonyl resonances as seen with other heterobimetallic species
with a MoCoC2 core.19 These consist of two sharp downfield
signals typical of molybdenum-bound carbonyls and one broad
upfield shift typical of cobalt-bound carbonyls (δ 203.0, 226.2,
225.7 for 7 and δ 202.5, 224.5, 224.4 for 8). This implies that the
two carbonyl groups on the molybdenum atom are inequivalent
in solution. Hence, the ligands on the molybdenum are either
non-fluxional at 293 K or, alternatively, a fluxional process can
be invoked involving a series of twists of the three ligands
which maintains the inequivalence.20 The IR spectra of
compounds 7 and 8 show seven stretching frequencies in the
carbonyl region. This high number of bands is probably due to
the presence of isomers in solution.
(d) Crystal structure of 7
Single crystals of 7 were obtained from a saturated dichloro-
methane solution. The molecular structure of 7 is depicted in
Fig. 4. The presence of a cobalt atom and a molybdenum atom
means the cluster is chiral.21 Evidence of the presence of two
enantiomers is given by the fact that crystallisation occurs in a
centrosymmetric space group. Only one of these is shown in
Fig. 4. The replacement of one Co(CO)3 moiety by MoCp-
(CO)2 decreases the symmetry of the metal acetylene linkage
resulting in a more distorted tetrahedron than that observed for
compounds 2, 3 and 6 (C(11)–Mo 2.140(4) Å, C(12)–Mo
2.167(4) Å, C(11)–Co 2.025(4) Å, C(12)–Co 1.951(4) Å). The
CoMoC2 tetrahedrane opens up so as to incorporate the two
different metal centres (C(11)–C(12) 1.342(6) Å, C(11)–Co–
C(12) 47.94(10)Њ, C(11)–Mo–C(12) 45.84(11)Њ). It appears
that the distortion resulting from mixed metal complexation
renders the reaction of both alkynes unfavourable in this case.
3
“inner” ones (t, J(PP) 50 Hz) whereas in 10 no coupling is
observed for the “outer” P atoms but the “inner” P atoms
couple to give a doublet (d, 3J(PP) 97 Hz). The signals in the 1H
NMR spectrum of 10 integrate for an ethynylferrocene : dppf
ratio of 2 : 3 consistent with the structure proposed.
Several groups have explored the reaction of diphenyl-
phosphine with metallic complexes containing an [M1M2C2]
core (where M1 = Co and M2 = Mo or Co). The formation of
phosphido-bridged complexes via P–H cleavage has literature
precedence.25 However, in the reaction of 7 with diphenylphos-
phine no cleavage of the P–H bond was observed irrespective
of temperature or reaction time. Instead, diphenylphosphine
coordinated to the cobalt moiety to give 11. The 31P NMR
proton coupled spectrum of 11 exhibits only one signal that is
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J. Chem. Soc., Dalton Trans., 2001, 1440–1447

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Scheme 2
shifted 74 ppm upfield compared to free diphenylphosphine.
3
This signal is a doublet of doublets (1J(PH) 348 Hz, J(PH)
27.1 Hz) assigned to the HPPh2 and HCCHPPh2 interactions
respectively. The 13C NMR spectrum of compound 11 exhibits
four terminal carbonyl resonances. Two at higher chemical
shift are assigned to Mo-bound carbonyls and two at a lower
chemical shift are assigned to cobalt-bound carbonyls. These
data imply that none of the CO ligands are equivalent. The
appearance of six carbonyl stretches in the IR spectra of 11
can be explained in a similar manner as that for 7 and 8.
An alternative synthetic strategy is to react bis(phosphido)–
bridged complexes such as [Co2(CO)6(µ-PPh2)2] with alkynes.
Here we report the first reaction of [Co2(CO)6(µ-PPh2)2] with
ethynylferrocene which affords 12 in 72% yield. As expected,
ethynylferrocene reacted regiospecifically i.e. for steric reasons,
only the product isomer with the more bulky alkyne substituent
(ferrocene) attached to the carbon atom remote from the PPh2
group was formed.26
Fig. 5 ORTEP drawing of the structure of one enantiomer of 12
(thermal ellipsoids have been drawn at the 20% probability level, hydro-
gen atoms have been omitted for clarity); 12 crystallised with one
molecule of CH2Cl2 per asymmetric unit. This has been omitted from
the drawing.
In the 31P{1H} NMR spectrum, the broad resonance at δ 43.6
was assigned to P(1) (for atom numbering see crystal struc-
ture below), the phosphido bridging ligand, while the broad
resonance at δ 160.4 was assigned to P(2), the phosphorus atom
involved in the five-membered phosphametallocycle. Both
phosphorus signals are shifted upfield (157.1 ppm for P(1)
and 273.9 ppm for P(2)) with respect to the 31P signal in
[Co2(CO)6(µ-PPh2)2]. In the 13C NMR spectrum, the most
downfield signal (δ 212.8) was assigned to the inserted CO;
C(11) and C(12) appear as doublets with 2J(CP) 36 and 1J(CP)
43 Hz, respectively.
The IR spectrum shows the presence of four terminal
CO groups (four bands below 1850 cmϪ1) and one bridging
carbonyl (ν(CO) at 1657 cmϪ1) consistent with the solid state
structure.
(f) Crystal structure of 12
Dark brown crystals of 12 were obtained from a saturated
dichloromethane solution. The molecular structure of 12 is
shown in Fig. 5. Compound 12 crystallised with one dichloro-
1
In the H NMR spectrum, the signal at δ 5.63 due to the
acetylenic H appears as a triplet (2J(HP) 4 Hz). It is deshielded
compared to the analogous H atom in 1 due to the enhanced
double bond character of C(12)–C(11).
¯
methane molecule in space group P1. C(11) has four different
substituents attached to it. Therefore the molecule is chiral
J. Chem. Soc., Dalton Trans., 2001, 1440–1447
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Table 1 Crystallographic data for compounds 2, 3, 6, 7 and 12
2
3
6
7
12
Empirical formula
Mw
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
C30H18Co2Fe2O6
704.00
Orthorhombic
P212121
10.6378(7)
11.5265(7)
22.328(2)
90
90
90
2737.8(4)
4
2.272
C36H18Co4Fe2O12
989.92
C38H18Co4FeO12
958.09
C22H15CoFeMoO5
570.06
C42H32C12Co2FeO5P2
923.23
Triclinic
Triclinic
Triclinic
Triclinic
¯
¯
¯
¯
P1
P1
P1
P1
9.064(9)
9.311(4)
11.82(2)
81.84(12)
88.1(2)
65.13(7)
896(2)
2
10.914(3)
12.113(2)
14.919(2)
93.710(11)
107.05(2)
96.54(2)
1863.3(6)
2
8.2046(8)
8.7356(7)
14.869(2)
78.365(7)
87.176(8)
78.197(7)
1021.7(2)
2
10.597(9)
11.004(5)
18.059(8)
74.86(4)
88.66(5)
71.27(5)
1921(2)
2
β/Њ
γ/Њ
V/Å3
Z
µ/cmϪ1
2.661
2.186
2.139
1.494
2θmax/Њ
49.93
2176
2176
361
0.0467
0.1292
49.8
3289
3081
244
0.987
0.223
51.6
6494
6148
496
0.0297
0.065
49.94
3738
3482
275
0.0318
0.0658
49.94
6438
6206
494
0.0373
0.0974
No. of data
Unique data
No. of parameters
R1a
wR2b
¹
2
2
2
2 2
a R1 = F0| Ϫ Fc /ΣF0|. b wR2 = {Σ[w(F0 Ϫ Fc ) ]/Σ[w(F0 ) ]} .

²
and as crystallisation occurs in a centrosymmetric space
group, a racemic mixture of both enantiomers is present in the
crystal.
Experimental
General comments
The two Co atoms are bridged by a diphenylphosphido
ligand while Co(1) is incorporated in a five-membered metal-
Unless otherwise stated, all reactions were carried out under
argon atmosphere using standard Schlenk techniques. Solvents
were distilled under nitrogen from appropriate drying agents
and degassed prior to use. Chromatographic separations were
undertaken in air except for compound 6 where dry and
degassed solvents were used under a nitrogen atmosphere were
used. CHCl3-d and acetone-d6 were distilled from molecular
sieves. IR spectra were recorded on a Perkin-Elmer Paragon
spectrophotometer. NMR spectra were recorded on DPX 400
spectrometer operating at 400.13 MHz for 1H, 100.61 MHz for
lacyclic ring consisting of P(2)C(12)᎐C(11)C(13)Co(1).
᎐
The C(11)᎐C(12) bond is η2-coordinated to the second Co(2)
᎐
atom. The overall structure is very similar to that already
reported for [Co2(CO)4{(µ-η4-PPh2CHCPhC(O)}(µ-PPh2)].27
The P(2)C(12)᎐C(11)C(13) system is folded so as to make the
᎐
Co–Co and the C(11)–C(12) axes almost perpendicular. The
C(11)–C(12) bond length at 1.424(4) Å is shorter than in the
analogous literature system. The asymmetry of the Co(1)-
P(1)Co(2) bridge, however, is comparable to that reported,
with the Co(2)–P(1) distance being shorter (2.169(1) Å)
than the Co(1)–P(1) distance (2.194(1) Å). Ferrocene sub-
stitution in comparison to phenyl substitution causes a
marginal reduction in the steric strain of the five-membered
metallocycle. This is illustrated by the relevant bond angles
(C(11)–C(12)–P(2) 112.0(3)Њ, C(12)–C(11)–C(13) 115.0(3)Њ,
Co(1)–C(13)–C(11) 110.3(2)Њ, Co(1)–P(2)–C(12) 95.2(1)Њ).
The carbons of the Cp rings are staggered as seen before in 2
and 3 by ca. 9Њ.
1
13C and 161.97 MHz for 31P nuclei, respectively. H and 13C
NMR were referenced relative to SiMe4, 31P NMR chemical
shifts are given relative to 85% orthophosphoric acid with
downfield shifts reported as positive. Analyses were performed
by the analytical service at University College Dublin. The fer-
rocenylalkynes were prepared following reported literature pro-
cedures.16,28 The C60 ethynyl ligand was synthesised using a
modified literature procedure (THF was used as the solvent
system).29
X-Ray crystallographic data collection and refinement of the
structures
Conclusion
This work illustrates the coordination of several ferro-
cenylalkynes to [Co–Co] and [Co–Mo] moieties. The various
acetylenic ligands synthesised react readily with Co2(CO)8
NaMoCp(CO)3 and Co2(CO)6(PPh2)2. However, the coordi-
nation of two [Co–Mo] units to two adjacent triple bonds
proved too sterically demanding. In the solid state, the
ferrocenyl fragments of the complexes synthesised show high
flexibility and adopt a configuration which minimises steric
interactions. Further work will examine a way to modify the
electronic properties of such compounds in order to investigate
their redox and NLO behaviour. This work has shown that
phosphine substitution on the cobalt atom of such complexes
proceeds easily. For instance, the electronic environment of
the metal atoms could be modified via replacement of some
carbonyls by suitable chiral phosphine ligands. An alternative
method would be to modify the sphere of coordination by
incorporating M(L)n building blocks (M = Ni, Fe; L = Cp, CO)
to form alkyne bridged clusters of higher nuclearity and dif-
fering electronic properties.
Single crystals of 2, 3, 6, 7 and 12 were mounted in glass
capillaries. Data were collected on an Enraf-Nonius CAD-4
diffractometer (Mo-Kα, λ = 0.71073 Å radiation, graphite
monochromator, ω-2θ scan mode) at 20 ЊC. Unit cell dimen-
sions were refined with 25 reflections. The final cell parameters
were determined using the Celdim routine. An empirical
absorption correction based on azimuthal scans of 6–8 reflec-
tions was applied to the data collected for 6 and 7. The crystal
data and experimental parameters for 2, 3, 6, 7 and 12 are
summarised in Table 1.
The data were processed using the WINGX software
packages. The structures were solved by automatic direct
methods using SHELXS-8630 and were refined by full-matrix
least-squares analysis on F2 with SHELXL93.31 All structures
were readily solved and refined by direct methods. All non-
hydrogen atoms were refined anisotropically except the carbon
atoms of the unbound Cp ring in 12. In this case the rotational
disorder was modelled as two Cp rings with refined occupancies
of 55.8 and 44.2% and the carbon atoms were held isotropic.
1444
J. Chem. Soc., Dalton Trans., 2001, 1440–1447

View Article Online
The relatively high R1 value for 3 was a result of the data collec-
tion (tube fading) and not poor crystal quality.
Crystals of 12 contain one molecule of dichloromethane per
asymmetric unit. This dichloromethane solvent molecule was
found to be well defined and the chlorine and carbon atoms
were refined anisotropically.
The hydrogen atoms bound to C(12) in 7 and 12 were located
from difference Fourier maps and refined isotropically.
All other CH hydrogen atoms were placed at calculated
positions and refined as riding atoms with isotropic displace-
ment parameters. Diagrams of the structures were drawn using
ORTEX.32
(2 H, s, HCp), 4.54 (5 H, s, HCp) and 4.26 (2 H, s, HCp);
δC(CDCl3–CS2) 198.93 (6 C, br, CO), 154.55, 152.57, 147.44,
147.16, 146.35, 146.31, 146.27, 146.21, 146.10, 146.07, 145.08,
145.52, 145.40, 145.32, 145.26, 144.62, 144.39, 144.10, 142.58,
142.54, 142.23, 142.02, 141.94, 141.83, 141.60, 140.33, 139.99,
136.00, 135.06 (C60 core), 92.41 (1 C, (C–C)[Co–Co]), 84.77
(1 C, (C–C)[Co–Co]), 71.6 (1 C, Cquat/Cp), 70.66 (2 C, CCp), 70.15
(5 C, CCp), 70.04 (2 C, CCp), 67.64 (1 C, quaternary sp3–C in
the C60 core) and 63.02 (1 C, CH in the C60 core); λmax/nm
(cyclohexane) 203, 245, 253, 316 and 373.
Synthesis of [Co2(CO)6(ꢀ-ꢁ2 : ꢁ2-1,1Ј-bis(phenylethynyl)-
ferrocene)] 5
CCDC reference numbers 151896–151900.
See http://www.rsc.org/suppdata/dt/b0/b008803j/ for crystal-
lographic data in CIF or other electronic format.
1,1Ј-Bis(phenylethynyl)ferrocene (0.046 g, 0.12 mmol) was dis-
solved in 50 ml of dichloromethane. One equivalent of
Co2(CO)8 (0.041 g, 0.12 mmol) was added and the reaction
mixture was allowed to stir overnight at room temperature.
TLC analysis revealed two spots attributed to compound 5
(Rf = 0.5) and 6 (Rf = 0.3). Products were separated by flash
chromatography (SiO2, hexane–dichloromethane 4 : 1). Dark
purple crystals of 5 were obtained from a saturated solution of
hexane–dichloromethane 1 : 1 at 195 K (0.058 g, 72%) (Found:
C, 57.63; H, 3.08. C32H18O6FeCo2 requires C, 57.18; H, 2.70%);
νmax/cmϪ1 (CO) 2085s, 2050vs, 2025vs, 2020s, 2007w and
1980w (hexane); δH(CDCl3) 7.93–7.91 (2 H, m, Hphenyl), 7.53–
7.34 (8 H, m, Hphenyl), 4.57 (2 H, t, J(HH) 1.76 Hz, HCp), 4.53
(2 H, t, J(HH) 2.04 Hz, HCp) and 4.25 (2 H, t, J(HH) 1.76 Hz,
HCp); δC(CDCl3) 199.3 (6 C, br, CO), 138.4 (1 C, Cquat/phenyl),
131.4, 129.7, 128.9, 128.3, 127.9 (10 C, Cphenyl), 123.6 (1 C,
Cquat/phenyl), 91.6 (1 C, (C–C)[Co–Co]), 91.0 (1 C, (C–C)-
[Co–Co]), 87.4 (1 C, Cquat/Cp), 86.6 (1 C, Cacetylenic), 86.3 (1 C,
Cacetylenic), 72.6 (2 C, CCp), 72.2 (2 C, CCp), 71.5 (2 C, CCp), 70.8
(2 C, CCp) and 66.4 (1 C, Cquat/Cp).
Synthesis of [Co2(CO)6(ꢀ, ꢁ2 : ꢁ2-ethynylferrocene)] 1
Dicobalt octacarbonyl (1.32 g, 4 mmol) was added to a solution
of ethynylferrocene (0.84 g, 4 mmol) in hexane (100 ml). The
reaction was allowed to proceed for 12 h at room temperature.
After removal of the solvent, compound 1 was purified by flash
chromatography (SiO2, hexane) followed by crystallisation from
hexane (1.785 g, 90%) (Found: C, 43.31; H, 1.98; Fe, 11.04;
Co, 24.02. C18H10O6FeCo2 requires C, 43.59; H, 2.03; Fe, 11.26;
Co, 23.76%); νmax/cmϪ1 (CO) 2092s, 2066w, 2051s, 2021s, 2010m
and 1983w (hexane); δH(CDCl3) 6.3 (1 H, s, Hacetylenic), 4.37 (2 H,
s, HCp), 4.34 (2 H, s, HCp) and 4.18 (5 H, s, HCp); δC(CDCl3)
203 (6 C, br, CO), 84.3 (1 C, (C–C)[Co–Co]), 79.9 (1 C, (C–C)-
[Co–Co]), 73.8 (1 C, Cquat/Cp), 70.2 (2 C, CCp), 69.7 (5 C, CCp
)
and 69 (2C, CCp).
Synthesis of [Co2(CO)6(ꢀ-ꢁ2 : ꢁ2-1,4-bis(ferrocenyl)butadiyne)] 2
Dark purple crystals of 2 were from a saturated solution of
dichloromethane at 195 K (0.985 g, 70%) (Found: C, 50.75; H,
2.18; Fe, 16.04; Co, 17.06. Calc. for C30H18O6Fe2Co2: C, 51.18;
H, 2.58; Fe, 15.87; Co, 16.74%); νmax/cmϪ1 (CO) 2090m, 2078w,
2055vs, 2032vs, 2024s and 1981w (hexane); δH(CDCl3) 4.51
(2 H, t, J(HH) 2 Hz, HCp), 4.41 (2 H, t, J(HH) 2 Hz, HCp), 4.39
(5 H, s , HCp), 4.16 (2 H, t, J(HH) 2 Hz, HCp), 4.34 (2 H, t,
J(HH) 2 Hz, HCp) and 4.30 (5H, s, HCp); δC(CDCl3) 198.3 (6 C,
br, CO), 99.2 (1 C, (C–C)[Co–Co]), 93.8 (1 C, (C–C)[Co–Co]),
84.8 (1 C, Cacetylenic), 83.3 (1 C, Cacetylenic), 71.2 (2 C, CCp), 70.6
(1 C, Cquat/Cp), 69.5 (5 C, CCp), 69.4 (2 C, CCp), 69.3 (5 C, CCp),
69.1 (1 C, Cquat/Cp), 69.0 (2 C, CCp) and 68.8 (2 C, CCp).
Synthesis of [(Co2(CO)6)2(ꢀ-ꢁ2 : ꢁ2,ꢀ-ꢁ2 : ꢁ2-1,1Ј-bis(phenyl-
ethynyl)ferrocene)] 6
1,1Ј-Bis(phenylethynyl)ferrocene (0.046 g, 0.12 mmol) was
dissolved in 50 ml of dichloromethane. Two equivalents of
Co2(CO)8 (0.082 g, 0.24 mmol) were added and the reaction
mixture was allowed to stir overnight at room temperature.
TLC analysis revealed the formation of 6 (Rf = 0.3). The
product was purified by flash chromatography (SiO2, hexane–
dichloromethane 4 : 1). Green crystals of 6 were obtained from
a saturated solution of hexane at 195 K (0.094 g, 82%) (Found:
C, 47.26; H, 1.79; Co, 24.41; Fe, 5.66. C38H18O12Co4Fe requires
C, 47.64; H, 1.89; Co, 24.6; Fe, 5.83%); νmax/cmϪ1 (CO) 2084m,
2050vs, 2026s, 2019s, 2004w and 1983w (hexane); δH(CDCl3)
7.85–7.83 (4 H, m, Hphenyl), 7.50–7.39 (6H, m, Hphenyl), 4.55 (4 H,
t, J(HH) 2.02 Hz, HCp) and 4.34 (4 H, t, J(HH) 2.02 Hz, HCp);
δC(CDCl3) 198.5 (12 C, br, CO), 138.4 (2 C, Cquat/phenyl), 129.6,
128.9, 128.0 (10 C, Cphenyl), 91.8 (2 C, (C–C)[Co–Co]), 91.0
(2 C, (C–C)[Co–Co]), 86.0 (2 C, Cquat/Cp), 72.2 (4 C, CCp) and
70.6 (4 C, CCp).
Synthesis of [(Co2(CO)6)2(ꢀ-ꢁ2 : ꢁ2,ꢀ-ꢁ2 : ꢁ2-1,4-bis(ferrocenyl)-
butadiyne)] 3
Dark green crystals of 3 were obtained from a saturated solu-
tion of dichloromethane at 195 K (1.742 g, 88%) (Found: C,
43.42; H, 2.35; Fe, 10.89; Co, 23.57. Calc. for C36H18O12Fe2Co4:
C, 43.68; H, 1.83; Fe, 11.28; Co, 23.81%); νmax/cmϪ1 (CO) 2096w,
2077m, 2056vs, 2033m, 2022s and 1975w (hexane); δH(CDCl3)
Synthesis of [MoCo(CO)5(ꢁ5-C5H5)(ꢀ-ꢁ2 : ꢁ2-ethynylferrocene)]
7
4.45 (4 H, t, J(HH) 2 Hz, HCp), 4.35 (4 H, t, J(HH) 2 Hz, HCp
)
and 4.27 (10 H, s, HCp); δC(CDCl3) 198.7 (12 C, br, CO), 100.5
(2 C, (C–C)[Co–Co]), 96.4 (2 C, (C–C)[Co–Co]), 87.8 (2 C,
Cquat/Cp), 70.6 (4 C, CCp), 69.1 (10 C, CCp) and 68.2 (4 C, CCp).
To a solution of 1 ( 0.42 g, 2 mmol) in 60 ml of THF was added
a solution of NaCpMo(CO)3 prepared as follows: 0.54 g
(1.11 mmol) of Cp2Mo2(CO)6 in 20 ml of THF was added to an
amalgam (0.1 g of sodium with 5 g of mercury). The reaction
was complete after 1 h at reflux. After removal of the solvent,
the red residue was chromatographed (SiO2, hexane–dichloro-
methane 3 : 1). Further crystallisation from dichloromethane
afforded pure 7 (0.638 g, 56%) (Found: C, 45.8; H, 3.17; Fe,
9.31. C22H15O5FeCoMo requires C, 46.35; H, 2.65; Fe, 9.79%);
νmax/cmϪ1 (CO) 2067w, 2050m, 2027s, 2014s, 2000vs, 1982s and
1944m (hexane); δH(CDCl3) 6.01 (1 H, s, Hacety;enic), 5.39 (5 H, s,
HMoCp), 4.21 (2 H, s, HFeCp), 4.20 (1 H, s, HFeCp), 4.17 (5 H,
s, HFeCp) and 4.14 (1 H, s, HFeCp); δC(CDCl3) 226.2 (1 C, s,
Synthesis of [Co2(CO)6(ꢀ-ꢁ2 : ꢁ2-1-ferrocenylethynyl-2-hydro-
1,2-dihydro[60]fullerene)] 4
1-Ferrocenylethynyl-2-hydro-1,2-dihydro[60]fullerene (0.072 g,
0.077 mmol) was stirred with one equivalent (0.026 g, 0.077
mmol) of dicobalt octacarbonyl in 100 ml of toluene at room
temperature for 12 h, the solvent was removed and 4 was puri-
fied by flash chromatography (SiO2, CS2-hexane 1 : 1) (0.079 g,
85%) (Found: C, 76.45; H, 1.24. C78H10O6FeCo2 requires C,
77.00; H, 0.83%); νmax/cmϪ1 (CO) 2080w, 2061vs, 2053vs, 2038w,
2028w and 1982w (hexane); δH(CDCl3) 7.13 (1 H, s, C60H), 4.83
J. Chem. Soc., Dalton Trans., 2001, 1440–1447
1445

View Article Online
MoCO), 225.7 (1 C, s, MoCO), 203 (3 C, br, CoCO), 91.1 (5 C,
CMoCp), 82.8 (1 C, br, (C–C)[Mo–Co]), 79.8 (1 C, (C–C)[Mo–
Co]), 70 (1 C, CFeCp), 69.3 (6 C, CFeCp), 68.6 (1 C, Cquat/FeCp), 68.1
(1 C, CFeCp) and 67.9 (1 C, CFeCp).
(14 : 15) and purified by column chromatography under nitro-
gen (SiO2, hexane–dichloromethane 14 : 15) (0.167 g, 82%)
(Found: C, 55.00; H, 3.94. C33H26O4PFeCoMo requires C,
54.43; H, 3.60%); νmax/cmϪ1 (CO) 2017s, 2005m, 1970vs, 1946s,
1932vs and 1866m (hexane); δH(acetone-d6) 7.63–7.40 (10 H, m,
Synthesis of [MoCo(CO)5(ꢁ5-C5H5)(ꢀ-ꢁ2 : ꢁ2-1,4-bis(ferrocenyl)-
butadiyne)] 8
Hphenyl), 6.05 (1 H, t, J(HP) 9.2 Hz, Hacetylenic), 5.79 (1 H, d,
3
1J(HP) 348 Hz, HPPH2), 5.62 (5 H, s, HMoCp), 4.47 (1 H, m,
HFeCp), 4.25 (1 H, m, HFeCp), 4.14 (1 H, m, HFeCp), 4.09 (1 H, m,
HFeCp) and 4.04 (5 H, s, HFeCp); δC(acetone-d6) 237.1 (1 C, s,
MoCO), 233.7 (1 C, s, MoCO), 227.5 (1 C, CoCO), 227.4 (1 C,
0.1 g (0.14 mmol) of 2 were added to a solution of NaMoCp-
(CO)3 prepared as above but using 0.069 g (0.14 mmol) of
Cp2Mo2(CO)6 The mixture was allowed to stir for 0.5 h in
refluxing THF. After removal of the solvent, the red residue
was chromatographed (SiO2, hexane–dichloromethane 3 : 1)
(0.065 g, 60%), (Found: C, 52.14; H, 3.53; Fe, 14.17. C34H23O5-
Fe2CoMo requires C, 52.48; H, 2.98; Fe, 14.35%); νmax/cmϪ1
(CO) 2064w, 2051m, 2006vs, 1990s, 1983s, 1967w and 1950m
(hexane); δH(CDCl3) 5.39 (5 H, s, HMoCp), 4.56 (1 H, t, J(HH)
1,6 Hz, HFeCp), 4.48 (1 H, t, J(HH) 1.6 Hz, HFeCp), 4.39 (4 H, t,
J(HH) 1.6 Hz, HFeCp), 4.38 (5 H, s, HFeCp) and 4.28 (10 H, s,
HFeCp); δC(CDCl3) 224.5 (1 C, s, MoCO), 224.4 (1 C, s, MoCO),
202.5 (3 C, br, CoCO), 95.1 (1 C, Cacetylenic), 91.2 (5 C, CMoCp),
87.2 (1 C, br, (C–C)[Mo–Co]),), 85.7 (1 C, Cacetylenic), 75.1 (1 C,
br, (C–C)[Mo–Co]),), 71.2, 71.1, 69.1, 68.4, 67.8, 67.5 (8 C,
CFeCp), 69.5 (5 C, CFeCp), 68.9 (5 C, CFeCp), 68.4 (1 C, Cquat/Cp) and
65.8 (1 C, Cquat/Cp).
1
CoCO), 133.9 (1 C, d, J(CP) 12 Hz, Cquat/phenyl), 133.8 (1 C, d,
2
1J(CP) 12 Hz, Cquat/phenyl), 133.2 (2 C, d, J(CP) 10 Hz, Cphenyl),
2
132.6 (2 C, d, J(CP) 10 Hz, Cphenyl), 130.6 (1 C, Cphenyl), 130.4
(1 C, Cphenyl), 129.3 (2 C, d, 3J(CP) 3 Hz, Cphenyl), 129.2 (2 C, d,
3J(CP) 3 Hz, Cphenyl), 92.4 (5 C, CMoCp), 83.9 (1 C, (C–C)[Mo–
Co]), 82.08 (1 C, br, (C–C)[Mo–Co]), 70.88 (1 C, Cquat/FeCp),
70.82 (1 C, CFeCp), 69.6 (1 C, CFeCp), 66.9 (1 C, CFeCp), 69.7 (5 C,
CFeCp) and 70.3 (1 C, CFeCp); δP(proton coupled, acetone-d6) 35.2
(1 P, dd, 1,3J(PH) 348, 27.1 Hz).
Synthesis of [Co2(CO)4{(ꢀ-ꢁ4-PPh2CHCRC(O)}(ꢀ-PPh2)]
(R ؍ ferrocene) 12
A 500 ml Berghol autoclave was charged with toluene (50 ml)
and Co2(CO)8 (0.8 g, 2.3 mmol). HPPh2 (0.8 ml, 4.3 mmol) was
then added to it. The autoclave was sealed, purged with CO,
pressured to 80 atm, and heated to 383 K for 24 h. When the
sample was required, the CO pressure was released and the
toluene solution of [Co2(CO)6(µ-PPh2)2] decanted. Ethynyl-
ferrocene (0.48 g, 2.3 mmol) was then dissolved in 50 ml of
toluene to which the previous solution of [Co2(CO)6(µ-PPh2)2]
was added. The resulting mixture was allowed to stir 15 h at 293
K. After removal of the solvent in vacuo, 12 was isolated by
chromatography (SiO2, hexane–dichloromethane 1 : 1). Crys-
tallisation from dichloromethane afforded pure 12 (1.38 g, 72%)
(Found: C, 55.76; H, 4.20; P, 6.82; Fe, 6.14; Co, 12.06.
Synthesis of [Co2(CO)4(ꢀ-ꢁ1 : ꢁ1-dppm)(ꢀ-ꢁ2 : ꢁ2-ethynyl-
ferrocene)] 9
Ligand dppm (0.12 g, 0.302 mmol) and 1 (0.15 g, 0.302 mmol)
were stirred in 75 ml of dichloromethane at room tem-
perature for 4 h. The resulting red product was isolated by flash
chromatography (SiO2, hexane–ethyl acetate 3 : 1) and purified
by crystallisation from acetone (0.179 g, 72%) (Found: C, 59.40;
H, 3.94; Fe, 6.54; Co, 14.08. C41H33O4P2FeCo2 requires C,
59.66; H, 4.03; Fe, 6.76; Co, 14.28%); νmax/cmϪ1 (CO) 2019m,
1989s, 1962s and 1943 (sh) (hexane); δH(acetone-d6) 7.52 (8 H,
m, Hphenyl), 7.30 (12 H, m, Hphenyl), 6.09 (1 H, t, 3J(HP) 6.8 Hz,
Hacetylenic), 4.39 (2 H, t, J(HH) 1.6 Hz, HCp), 4.26 (2 H, t, J(HH)
2 Hz, HCp), 4.19 (5 H, s, HCp), 4.05 (1 H, dt, J 10.8, 6 Hz, CH2)
and 3.47 (1 H, dt, J 10.8, 6 Hz, CH2); δC(acetone-d6) 209.6 (4 C,
.
C41H30O5P2FeCo2 CH2Cl2 requires C, 54.64; H, 3.49; P, 7.71; Fe,
6.05; Co, 12.77%); νmax/cmϪ1 (CO) 2045m, 2016vs, 2006m,
1975m and 1657w (hexane); δH(acetone-d6) 8.35–7.29 (20 H, m,
Hphenyls), 5.63 (1 H, t, 2J(HP) 4 Hz, Hacetylenic), 4.28 (1 H, s, HCp),
4.03 (1 H, s, HCp), 4.01 (2 H, s, HCp) and 3.55 (5 H, s, HCp);
δC(acetone-d6) 212.8 (1 C, s, [PPh2CHCRC(O)]), 208.5 (2 C, s,
CoCO), 201.7 (2 C, s, CoCO), 147.5–127.2 (20 C, Cphenyls), 70.06
(1 C, Cquat/Cp), 68.2 (5 C, CCp), 68 (1 C, CCp), 67.3 (2 C, CCp), 66.5
(1 C, CCp), 85.45 (1 C, dd, 1,2J(CP) 43, 36 Hz, (C–C)[Co–Co])
and 42.5 (1 C, dd, 1,2J(CP) 43, 36 Hz, CPPh2); δP(acetone-d6)
160.4 (1 P, br, CPPh2) and 43.6 (1 P, br, CoPPh2Co).
1
br, CO), 137.5 (2 C, t, J(CP) 20 Hz, Cquat/phenyl), 137.4 (2 C, t,
2
1J(CP) 20 Hz, Cquat/phenyl), 132.6 (4 C, t, J(CP) 6 Hz, Cphenyl),
2
132.3 (4 C, t, J(CP) 6 Hz, Cphenyl), 130.1 (1 C, Cphenyl), 130 (1
3
C, Cphenyl), 128.7 (4 C, t, J(CP) 5 Hz, Cphenyl), 127.8 (4 C, t,
3J(CP) 005 Hz, Cphenyl), 90.8 (1 C, (C–C)[Co–Co]), 76.4 (1 C, br,
(C–C)[Co–Co]), 70.4 (2 C, CCp), 69.9 (5 C, CCp), 68.4 (2 C, CCp),
67.7 (1 C, Cquat/Cp) and 40.3 (1 C, t, 1J(CP) 22 Hz, CH2);
δP(acetone-d6) 41.5 (1 P, s).
Acknowledgements
Synthesis of [(Co2(CO)4)2(ꢀ-ꢁ1 : ꢁ1-dppf)2(ꢁ1-ꢀ-ꢁ1-dppf)-
(ꢀ-ꢁ2 : ꢁ2-ethynylferrocene)2] 10
The authors thank ENTERPRISE (Ireland) for financial
support (grant SC/98/420) and the Trinity Trust for a Post-
graduate Scholarship for E. C. They are grateful to Dr B.
Twamley for his expert help in representing the molecular
structures.
Ligand dppf (0.3 g, 0.54 mmol) was added to a solution of 1
(0.18 g 0.36 mmol) in 150 ml of dichloromethane. The solution
was stirred overnight at room temperature. Compound 10
was purified by column chromatography (SiO2, hexane–ethyl
acetate 3 : 1) (0.199 g, 45%), νmax/cmϪ1 (CO) 2003vs, 1977vs,
1962 (sh) and 1920 (sh) (hexane); δH(acetone-d6) 7.12–7.05 (60
H, m, Hphenyl), 6.07 (2 H, t, 3J(HP) 14 Hz, Hacetylenic), 4.53 (4 H, s,
HCp), 4.45 (4 H, s, HCp), 4.39 (8 H, s, HCp), 4.25 (4 H, s, HCp),
4.11 (4 H, s, HCp), 4.04 (10 H, s, HCp), 3.72 (4 H, s, HCp) and 3.95
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3
(4 H, s, HCp); δP(acetone-d6) 43.4 (4 P, d, J(PP) 97 Hz, PCo)
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Synthesis of [MoCo(CO)4(ꢁ5-C5H5)(PHPh2)(ꢀ-ꢁ2,ꢁ2-ethynyl-
ferrocene)] 11
HPPh2 (0.10 g, 0.56 mmol) was added to compound 7 (0.15 g,
0.28 mmol) in 50 ml of toluene. The solution was heated at 338
K for 48 h. After removal of the solvent under vacuum, the
residue was dissolved in degassed hexane–dichloromethane
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