McMurry reactions of (η5-acetylcyclopentadienyl) cobalt-(η4-tetraphenylcyclobutadiene) with benzophenone: Ketone couplings and a pinacol/pinacolone rearrangement

Article abstract of DOI:10.1016/j.jorganchem.2004.07.015

The reaction of (η⁴-C₄Ph₄) Co[η⁵-C₅H₄-C(O)Me], 5, with benzophenone under McMurry conditions (TiCl₄/Zn/THF) gives the hetero-coupled product (η⁴-C₄Ph₄)Co[η⁵- C₅H₄-C(Me)CPh₂], 7, together with the dicobalt species: trans-(η⁴-C₄Ph₄) Co[(η⁵-C₅H₄-C(Me)C(Me)-η⁵- C₅H_4-)] Co(η⁴-C₄Ph₄), 9, and the pinacolone Me[(η⁴-C₄Ph₄) Co(η⁵-C₅H₄)]₂C-C(O)Me, 10. The latter is apparently formed from the pinacol by migration of an (η⁴-C₄Ph₄)Co[(η⁵-C ₅H₄) group. Preferential migration of the cobalt sandwich moiety rather than a methyl group is rationalized in terms of a favored transition state involving a metal-stabilized cation. The products 7, 9 and 10, and also the ketone (η⁴-C₄Ph₄) Co[η⁵- C₅H₄-C(O)Et], 6, were all characterized by X-ray crystallography.

Full text of DOI:10.1016/j.jorganchem.2004.07.015

Journal of Organometallic Chemistry 689 (2004) 4683–4690
www.elsevier.com/locate/jorganchem
McMurry reactions of (g5-acetylcyclopentadienyl)
cobalt-(g4-tetraphenylcyclobutadiene) with benzophenone:
ketone couplings and a pinacol/pinacolone rearrangement
Yannick Ortin, John Grealis, Conor Scully, Helge Muller-Bunz,
*
¨
Anthony R. Manning , Michael J. McGlinchey
*
Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
Received 1 June 2004; accepted 12 July 2004
Available online 19 August 2004
Abstract
The reaction of (g4-C4Ph4) Co[g5-C5H4–C(@O)Me], 5, with benzophenone under McMurry conditions (TiCl4/Zn/THF) gives the
hetero-coupled product (g4-C4Ph4)Co[g5-C5H4–C(Me)@CPh2], 7, together with the dicobalt species: trans-(g4-C4Ph4)Co[(g5-C5H4–
C(Me)@C(Me)-g5-C5H4À] Co(g4-C4Ph4), 9, and the pinacolone Me[(g4-C4Ph4)Co(g5-C5H4)]2C–C(@O)Me, 10. The latter is appar-
ently formed from the pinacol by migration of an (g4-C4Ph4)Co[(g5-C5H4)] group. Preferential migration of the cobalt sandwich
moiety rather than a methyl group is rationalized in terms of a favored transition state involving a metal-stabilized cation. The prod-
ucts 7, 9 and 10, and also the ketone (g4-C4Ph4)Co[g5-C5H4–C(@O)Et], 6, were all characterized by X-ray crystallography.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Cyclobutadiene–cobalt complexes; McMurry couplings; X-ray crystallography; Pinacol rearrangement
1. Introduction
the mechanisms of cell death (apoptosis or necrosis) and
of cell signaling mediated by the ferrocifens are yet to be
unravelled, their efficacy against tamoxifen-resistant
tumors has been clearly demonstrated [6]. We here re-
port preliminary experiments directed towards the syn-
thesis of an analogous series, the cobaltifens, 3.
The emerging discipline of bio-organometallic chem-
istry has revealed its potential for applications in such
varied areas as receptor assays [1], multi-immuno and
anti-epileptic drug assays [2], agents for tumor imaging
and therapy [3] and, more recently, organometallic sand-
wich compounds with significant anti-cancer activity [4].
Amongst the most promising of these are the ferrocifens,
pioneered by Jaouen and his colleagues [5]. In these a
phenyl substituent in tamoxifen, 1, – the current first-
line treatment for hormone-dependent breast cancer –
has been replaced by a ferrocenyl moiety, as in 2. While
OH
R
Et
Et
O
O
Fe
Me2N-(CH2)n
Me2N-(CH2)2
1a. R = H (tamoxifen)
1b. R = OH (hydroxytamoxifen)
*
2. hydroxyferrocifens
(n = 2,3,4,5,8)
Corresponding authors. Tel.: +353 17162880; fax: +353 17161178.
E-mail address: michael.mcglinchey@ucd.ie (M.J. McGlinchey).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.07.015

4684
Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
OH
C9
C8
O
C7
Et
C5
C10
C6
Co1
C2
C11
C12
O
Co
C3
R
R
Me2N-(CH2)n
R
R
C4
C1
3. hydroxycobaltifen
Co
C
H
O
Fig. 1. X-ray crystal structure of (g4-C4Ph4)Co[g5-C5H4C(@O)Et], 6.
Selected bond lengths (A) and angles (ꢁ): Co–Cp(ctrd), 1.681(1); Co–
Cb(ctrd), 1.694(1); C5–C10, 1.475(3); C10–C11, 1.504(3); C10–O, 1.224;
2. Results and discussion
˚
The most efficient route [5] to the ferrocifens in-
volves a McMurry coupling between propionylferro-
cene, 4, and an appropriately functionalized
benzophenone, as depicted in Scheme 1. In the ferroce-
nyl system, Friedel-Crafts acylation provides a conven-
ient, high-yield route to the ketone 4. In contrast, for
compounds of the type (g5-C5H5)Co(g4-C4R4), where
R = H or Ph, it is the cyclobutadiene ring (or an at-
tached phenyl substituent) that is the favored site for
acylation [7].
Consequently, it is necessary to functionalize the five-
membered ring before attachment of the organo–cobalt
fragment. Early routes [8] to these cobalt sandwich com-
plexes involved the reaction, and subsequent coupling,
of two alkynes with CpCo(CO)2; however, more recent
Cp(ctrd)–Co–Cb(ctrd), 178.52(11); C5–C10–C11, 117.94(16), C5–C10
O, 120.22(17); C6–C5–C10–C11, 2.0(3); C9–C5–C10–O, 2.8(3).
–
work by Stevens and Richards [9] has demonstrated that
higher yields are achievable by use of chlorotris(triphe-
nylphosphine)cobalt(I), as shown in Scheme 2.
Typically, (g5-acetylcyclopentadienyl)cobalt(g4-tetra-
phenylcyclobutadiene), 5, and its propionyl homologue,
6, have been prepared in yields of 26% and 11%, respec-
tively. The X-ray crystal structure of 6 appears as Fig. 1
and closely resembles that previously reported [10] for
the acetyl complex 5. The cobalt atom in 6 is almost
equidistant from both rings (CoÁ Á ÁCp-centroid =
˚
˚
1.681(1) A, CoÁ Á ÁCb-centroid = 1.694(1) A), the propio-
Et
Et
Ar
Ar
O
Et-CO-Cl
AlCl3
TiCl4, Zn, THF
Ar2C=O
Fe
Fe
Fe
4
Scheme 1. Synthetic route to the ferrocifens.
R
O
R
O
R
O
+2 C2R'2
-2 PPh3
O
(Ph3P)3CoCl
-
C2H5OC-R
-
Co
Co
R'
R'
Na+
Na+
Ph3P
PPh3
R'
R'
5. R = Me, R' = Ph
6. R = Et, R' = Ph
Scheme 2. Synthesis of cobalt sandwich complexes.

Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
4685
Me
[Co]
Me
Ph2C=CPh2
+
+
O
8
[Co]
Me
9
+
TiCl4, Zn, THF
Ph2C=O
+
[Co] =
Co
[Co]
Ph
Me
Ph
Ph
Ph
O
Co
5
Ph
Ph
Ph
Ph
Ph
Ph
Me
[Co]
[Co]
Me
7
10
Scheme 3. McMurry coupled products from (C4Ph4)Co[C5H4C(@O)Me] and Ph2C@O.
C31
C32
C37
C30
C39
C33
C29
C40
C36
C38
C34
C35
Co1
C2
C3
C4
C44
C43
C32
C33
Co2
C46
C36
C29
C42
C41
C34
C31
C45
C1
C30
Co
C35
C4
C1
C3
C2
Fig. 3. X-ray crystal structure of trans-(Me)[Co]–C@C(Me)[Co], 9.
˚
Selected bond lengths (A) and angles (ꢁ): Co(1)–Cp(ctrd), 1.671(6);
Co(1)–Cb(ctrd), 1.688(6); Co(2)–Cp(ctrd), 1.678(5); Co(2)–Cb(ctrd),
Fig. 2. X-ray crystal structure of (g4-C4Ph4)Co[g5-C5H4–
1.676(5);
Cp(ctrd)–Co(1)–Cb(ctrd),
C
29–C34
,
1.44(2); C34–C36
,
1.37(2); C36–C38, 1.51(2);
Cp(ctrd)–Co(2)–Cb(ctrd),
˚
C(Me)@CPh2], 7. Selected bond lengths (A) and angles (ꢁ): Co–
176.7(2);
Cp(ctrd), 1.678(1); Co–Cb(ctrd), 1.694(1); C29–C34, 1.4776(17); C34
C36, 1.3539(18); C34–C35, 1.5129(18); Cp(ctrd)–Co–Cb(ctrd), 177.40(1);
29–C34–C35 115.41(11), C29–C34–C36 122.05(12); C35–C34–C36
122.45(12).
–
176.7(2); C29–C34–C35, 116.3(16), C29–C34–C36, 123.9(17); C35–C34
C36, 119.5(18); C34–C36–C37, 120.1(17), C34–C36–C38, 123.8(17); C37
–
–
C
,
,
,
C36–C38, 115.6(16); C35–C34–C36–C37, 163.9(16); C29–C34–C36–C38,
178.7(14).
nyl group lies almost perfectly coplanar with the cyclo-
pentadienyl ring, and the phenyl substituents on the
cyclobutadiene ring adopt a propeller arrangement with
dihedral angles ranging from 25ꢁ to 60ꢁ.
C37
C36
C11
When a 3:1 mixture of the acetyl derivative 5 and
benzophenone was subjected to the McMurry proce-
dure, chromatographic separation of the products fur-
nished the desired hetero-coupled alkene 7 in 23%
yield and three homo-coupled products 8, 9 and 10
(Scheme 3). As anticipated, the McMurry coupling of
benzophenone gave some tetraphenylethylene, 8, but
the other two products were evidently derived from
the cobalt starting material, 5. The unsymmetrical alk-
ene 7 was identified spectroscopically, and by microanal-
ysis, but was also characterized by X-ray
crystallography (Fig. 2). The metric parameters within
the cobalt sandwich are normal, the new carbon–carbon
C40
O
C39
C30
C31
Co1
C2
C41
C42
C17
C38
C34
C35
C29
C33
C3
C1
Co2
C44
C59
C45
C4
C5
C32
C65
C46
Co
C
C43
C47
C53
C23
O
Fig. 4. X-ray crystal structure of Me[(g4-C4Ph4)Co(g5-C5H4)]2C–
C(@O)Me, 10. Selected bond lengths (A) and angles (ꢁ): Co(1)–
Cp(ctrd), 1.683(2); Co(1)–Cb(ctrd), 1.700(2); Co(2)–Cp(ctrd), 1.700(3);
˚
Co(2)–Cb(ctrd), 1.708(3); C29–C34, 1.528(15); C34–C35, 1.528(14); C34–
C36, 1.553(15); C34–C38, 1.531(14) Cp(ctrd)–Co(1)–Cb(ctrd), 174.2(1);
˚
double bond length is 1.354 A, and the two phenyl rings
derived from benzophenone are oriented almost mutu-
Cp(ctrd)–Co(2)–Cb(ctrd), 173.6(1); C29–C34–C36, 107.9(9), C35–C34
C36, 107.1(8); C38–C34–C36, 110.3(8).
–
ally orthogonally (interplanar angle 83ꢁ).

4686
Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
The dicobalt complex 9 was identified as the trans-
O
O
2,3-disubstituted 2-butene in which the methyl and org-
ano–cobalt moieties have adopted the sterically least
hindered orientation. The presence of the methyl groups
prevents the two cyclopentadienyl rings from displaying
a coplanar arrangement that would presumably have
maximized conjugation between the organometallic
units. As shown in Fig. 3, the molecule exhibits a con-
formation of almost ideal C2 symmetry whereby the
cyclopentadienyl rings are twisted through 42 2ꢁ out
of the plane of the alkene (C@C bond length 1.37(2)
TiCl3/Zn
Fe
2x
Fe
Fe
Scheme 5. Pinacol/pinacolone rearrangement of [3]-ferrocenophan-1-
one.
depicted in Scheme 6, that would lead to the trans
isomer of (g4-C4Ph4)Co(g5-C5H4)–CMe@CMe-(g5-
C5H4)Co(g4-C4Ph4), 9. However, the steric crowding re-
quired to form the cis isomer of 9 may be such as to
favor migration of the organocobalt moiety, leading
ultimately to the pinacolone rearranged product 10.
Interestingly, although the cis analogue of 9 was not
isolable from the McMurry reaction, an molecular model
of this isomer generated by rotating about the central
double bond of the trans compound, 9 (see Fig. 5) reveals
no particular steric problems. This reinforces the idea
that crowding in the intermediate depicted in Scheme
4, whereby two bulky (g4-C4Ph4)Co(g5-C5H4) groups
are eclipsed when bonded to adjacent tetrahedral car-
bons, leads to ring-opening and migration.
˚
A), and the helicity of the two C4Ph4 propellers is the
same in any given molecule.
Turning now to molecule 10, one might have antici-
pated the formation of the cis-analogue of 9, but such
1
is not the case. The H and 13C NMR spectra of 10 ex-
hibit two methyl environments, while its infrared spec-
trum has a peak at 1704 cmÀ1 indicating the presence
of a ketone. These observations were confirmed by X-
ray crystallography and the molecular structure of 10
is shown in Fig. 4. The product is clearly the result of
a pinacol/pinacolone rearrangement whereby a cobalt
sandwich substituent, rather than a methyl group, has
migrated. This is perhaps most readily rationalized in
terms of the enhanced migratory aptitude of the organ-
ometallic moiety such that the positive charge can be
delocalized onto the metal centre in the transition state,
as depicted in Scheme 4.
When the McMurry reaction was carried out with a
5:1 ratio of benzophenone to the cobalt ketone, 5, the
unsymmetrical alkene 7 was obtained in 71% yield and
only traces of the dicobalt complexes 9 and 10 were
observed.
In seeking a precedent for such an observation, we
note the recent report by Ha¨rter [11] in which a ferroce-
nyl group undergoes migration in preference to an alkyl
chain during the rearrangement of a ferrocenophane, as
depicted in Scheme 5.
The mechanism of the McMurry coupling has been
`
extensively investigated, most notably by Bogdanovic
[12], and by Geise [13]. It has been proposed that alkene
To conclude, the McMurry reaction of (g4-
C4Ph4)Co[g5-C5H4–C(@O)Me], 5, with benzophenone
yields not only the desired hetero-coupled alkene (g4-
C4Ph4)Co(g5-C5H4)–C(Me)@CPh2, 7, but also tetraphe-
nylethylene, 8, and two products, 9 and 10, derived from
the homo-coupling of the ketonic cobalt sandwich 5.
Our continuing efforts to synthesize cobaltifens and to
gauge their biological activity will be the subject of fu-
ture reports.
formation proceeds via a dimetallic intermediate, 11, as
Cl
Cl
-
-
O
O
Ti
Cl
Cl
Cl
Cl
O-Ti
O-Ti
O
O
Me
Me
+
Me
C
C
C
C
Me
C
C
[Co]
Me
[Co]
[Co]
[Co]
Me
Ph
Ph
Ph
[Co]
+
Co
Ph
-TiOCl2
[Co]
O
Co
[Co]
=
Ph
Me
[Co]
Ph
Ph
Me
Ph
10
Scheme 4. Proposed transition state for migration of an (g4-C4Ph4)Co(g5-C5H4) group.

Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
4687
ClTiO
OTiCl
Me
[Co]
Me
-2 TiOCl
C
C
C
C
[Co]
Me
[Co]
[Co]
Me
9
11
Co
[Co] =
Ph
Ph
Scheme 6. Proposed mechanism of alkene formation in a McMurry coupling reaction.
Ph
Ph
was added to the reaction mixture and the whole was
stirred at reflux for 4 h. During this time a dark red col-
our developed. After cooling the solution to room tem-
perature, dry toluene (100 mL) was added, followed by
chlorotris(triphenylphosphine)cobalt (I) (5.0 g, 5.7
mmol). The solution was stirred at room temperature
for 30 min after which time diphenylacetylene (2.0 g,
11.2 mmol) was added, and the mixture was heated at
reflux overnight. The mixture was cooled, filtered
through celite, concentrated in vacuo and chromato-
graphed on an alumina column. Four bands were eluted
using hexane/toluene; the product was collected in the
third band as a dark red fraction, which was concen-
trated to yield an orange solid (0.46 g, 0.86 mmol,
11%), m.p. 241 ꢁC. X-ray quality crystals were grown
Fig. 5. Molecular model of cis-(Me)[Co]–C@C(Me)[Co].
1
from toluene/hexane. H NMR (300 MHz, CDCl3): d
3. Experimental
7.52–7.27 (m, Ph); 5.31 and 4.85 (m, Cp); 2.09 (q,
CH2); 0.78 (t, CH3). 13C–{1H} NMR (75.4 MHz,
CDCl3): d 199.9 (CO); 135.2 (Cipso, Ph); 128.8 and
128.2 (Cortho and Cmeta, Ph); 126.9 (Cpara, Ph); 94.0,
87.2, 83.1 (Cp); 32.8 (CH2); 7.5 (CH3). IR (THF, mCO):
1672 cmÀ1. MS (ES+) m/z 537.1 [(M + H)]+, 559.1
[(M + Na)]+. Calc. for C36H29OCo: C, 80.59; H, 5.45;
Co, 10.98. Found: C, 79.14; H, 5.46; Co, 11.23%.
3.1. General methods
All reactions were carried out under an atmosphere
of dry nitrogen. Alumina 90 standardized (Merck) was
used for flash chromatography. NMR spectra were re-
corded on Varian Inova 300 or 500 MHz spectrometers.
Electrospray mass spectrometry was performed on a
Micromass Quattro micro instrument. Infrared spectra
were recorded on a Perkin–Elmer paragon 1000 FT-IR
instrument and were calibrated with polystyrene. Melt-
ing points were determined on an Electrothermal
ENG. instrument and are uncorrected. Elemental anal-
yses were carried out by the Microanalytical Laboratory
at University College Dublin.
3.3. McMurry reaction of (C4Ph4)Co(C5 H4COMe) (5)
and benzophenone in a 3:1 ratio
Zn (0.6 g, 15.3 mmol), which had been previously
activated with dilute HCl (5.0 mL), washed several times
with distilled water and dried, was added to dry THF
(30 mL) and the mixture was cooled to 0 ꢁC. TiCl4
(9.0 mL, 1M solution in CH2Cl2) was added, the solu-
tion was stirred for 10 min during which time the colour
changed from clear to yellow to light green. The solution
was allowed to warm to room temperature and was then
heated at reflux for 2 h to yield a dark blue/black solu-
tion. (C4Ph4)Co(C5H4COMe) (1.5 g, 2.9 mmol), pre-
pared as previously described [10], and benzophenone
(0.17 g, 0.9 mmol) were added together and the mixture
heated at reflux for a further 12 h, resulting in the for-
mation of a dark blue precipitate. The reaction was
3.2. Preparation of (g5-propionylcyclopentadienyl) (g4-
tetraphenylcyclobutadiene)cobalt (6)
In a 3-necked flask equipped with a condenser, so-
dium metal in excess was added to a solution of freshly
distilled cyclopentadiene (0.50 mL, 7.6 mmol) in dry
THF (25 mL) and the mixture stirred until all the reac-
tion had ceased (ca. 30 min). After removal of the excess
sodium metal, methyl propionate (0.75 mL, 7.8 mmol)

4688
Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
quenched with of saturated sodium carbonate solution
(80 mL), transferred to a separatory funnel and the
product extracted with ether until the organic layer
was no longer yellow. After removal of solvent and dis-
solution in a minimum quantity of ether, the product
was chromatographed on alumina. Initially, the eluent
was pentane, but this was gradually changed in 1%
increments to ether/pentane 25/75, and yielded five
fractions.
Fraction 1: Tetraphenylethene (8) (0.10 g, 33%), m.p.
210–222 ꢁC (dec.) was eluted by using a mixture of ether/
pentane (6/94), and was isolated as a white solid that
was characterized by comparison of its melting point,
NMR and mass spectra with literature data [14]. 1H
NMR (300 MHz, CDCl3): d 7.09 (m, CH ortho and
meta, Ph), 7.03 (m, CH para, Ph). 13C–{1H} NMR
(125.7 MHz, CDCl3): d 143.8 (Cq, Ph), 141.0 (@CPh2),
131.4, 127.7(CH ortho and meta, Ph), 126.5 (CH para,
Ph).
Fraction 2: 1,1-Diphenyl-2-[(g5-cyclopentadienyl)(g4-
tetraphenylcyclobutadiene)cobalt]propene (7) (0.14 g,
23%) was eluted by using a mixture of ether/pentane
(8/92), and was isolated as an yellow-orange solid,
m.p. 207 ꢁC. X-ray quality crystals were grown from
ether/pentane. 1H NMR (500 MHz, CDCl3): d 7.80–
6.80 (m, C4Ph4); 4.37, 4.32 (CH, Cp); 1.50 (s, CH3).
13C–{1H} NMR (125.7 MHz, CDCl3): d 144.8, 144.4
(Cpara, CPh2); 139.6 (@CPh2); 136.7 (Cipso, C4Ph4);
132.7, 130.3 (Cipso, CPh2); 130.4, 129.9, 128.5, 128.1
(Cortho and Cmeta CPh2); 129.1, 128.3 (Cortho and Cmeta
,
C4Ph4); 128.6 (Cipso, @CCH3); 126.5 (Cpara, C4Ph4);
100.3 (Cq, Cp); 84.1, 82.7 (CH, Cp); 75.3 (C4Ph4); 20.5
(CH3). Calc. for C48H37Co: C, 85.70; H, 5.54; Co,
8.76. Found: C, 84.84; H, 5.67; Co, 8.37%.
Table 1
Crystallographic collection and refinement parameters for 6, 7, 9 and 10
Identification code
6
7
9
10
Empirical formula
Formula weight
Temperature (K)
C
36H29Co O
C48H37Co
672.71
100(2)
C70 H54Co2
1012.99
293(2)
(C70 H54Co2O)2ÆCH2Cl2
2142.9
100(2)
536.52
293(2)
˚
Wavelength (A)
0.71073
Monoclinic
P21
Crystal system
Space group
Unit cell dimensions
Orthorhombic
P212121
Triclinic
ꢀ
Triclinic
ꢀ
P1
P1
˚
a (A)
9.0263(10)
10.0028(11)
29.782(3)
90
10.6350(6)
10.8827(6)
15.1610(8)
91.5590(10)
96.5830(10)
102.9290(10)
1696.40(16)
2
12.229(4)
15.238(5)
14.638(5)
90
10.845(3)
16.201(4)
16.409(4)
104.517(4)
108.514(4)
98.377(4)
2565.7(11)
1
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
101.703(6)
90
3
˚
Volume (A )
2689.0(5)
4
1.325
2671.0(16)
2
1.260
Z
Density (calculated)
(Mg/m3)
Absorption coefficient
(mmÀ1
1.317
1.387
0.666
0.541
0.663
0.746
)
F(000)
1120
0.80 · 0.59 · 0.58
2.15–28.27
704
0.50 · 0.20 · 0.20
2.26–29.46
1056
0.20 · 0.05 · 0.05
1.70–19.00
1114
0.20 · 0.20 · 0.10
1.59–23.37
Crystal size (mm3)
Theta range for data
collection (ꢁ)
Index ranges
À116 h 611;
À136 k 613;
À376 l 638;
23 017
À146 h 614;
À146 k 614;
À206 l 620
27 299
À116 h 611;
À136 k 613;
À136 l 613
10 201
À126 h 612;
À186 k 617;
À186 l 618
12 625
Reflections collected
Independent reflections
Completeness to theta (%)
Absorption correction
Max. and min. transmission
Refinement method
6266 [R(int) = 0.0167]
96.8
Semi-empirical from equivalents
8656 [R(int) = 0.0156]
91.9
4281 [R(int) = 0.0883]
99.9
6996 [R(int) = 0.0433]
93.8
0.6988 and 0.6180
0.8996 and 0.7738
0.9676 and 0.8788
0.9291 and 0.8651
Full-matrix least-squares on F2
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
6266/0/459
1.065
8656/0/590
1.054
4281/1/197
0.976
6996/0/682
1.093
R1 = 0.0288,
wR2 = 0.0714
R1 = 0.0300,
wR2 = 0.0719
0.000(8)
R1 = 0.0349,
wR2 = 0.0894
R1 = 0.0373,
wR2 = 0.0913
R1 = 0.1153,
wR2 = 0.2653
R1 = 0.1544,
wR2 = 0.2864
0.02(6)
R1 = 0.0879,
wR2 = 0.2931
R1 = 0.1218,
wR2 = 0.3150
R indices (all data)
Absolute structure parameter
Largest diff. peak and hole (e A
À3
˚
)
0.353 and À0.208
0.514 and À0.241
3.034 and À0.374
1.165 and À1.233

Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
4689
Fraction 3: Trans-2,3-bis[(g5-cyclopentadienyl)(g4-
tetraphenylcyclobutadiene)cobalt]-2-butene (9) (0.24 g,
21%) was eluted by using a mixture of ether/pentane
(8/92), and was isolated as a yellow solid, m.p. 135 ꢁC.
X-ray quality crystals were grown from ether/pentane.
1H NMR (500 MHz, CDCl3): d 7.90–6.80 (m, C4Ph4);
4.48, 4.47 (m, Cp); 1.26 (s, CH3). 13C–{1H} NMR
(125.7 MHz, CDCl3): d 136.8 (Cipso, C4Ph4); 129.1,
128.1 (Cortho and Cmeta, C4Ph4); 127.4 (@CCH3);
126.25 (Cpara, C4Ph4); 103.5 (Cq, Cp); 83.3, 82.8 (CH,
Cp); 75.2 (C4Ph4); 20.8 (CH3). Calc. for C70H54Co2: C,
82.99; H, 5.38; Co, 11.63. Found: C, 82.36; H, 5.51;
Co, 10.20%.
tively poor quality of the available crystals of 9, the
R-factors are higher than we would normally report.
Thus, in 9 all five- and 6-membered rings were con-
strained to be regular and all carbon atoms could only
be refined with isotropic temperature factors. All other
non-hydrogen atoms were refined using anisotropic
thermal parameters. Hydrogen atoms in 9 and 10 were
added as fixed contributors at calculated positions,
with isotropic thermal parameters based on the carbon
atom to which they are bonded. All other hydrogen
atoms were located in the difference Fourier map and
allowed to refine freely with isotropic temperature
factors.
Fraction 4: 3,3-Bis[(g5-cyclopentadienyl)(g4-tetra-
phenylcyclobutadiene)cobalt]butan-2-one (10) (0.18 g,
15%) was eluted by using a mixture of ether/pentane
(15/85), and was isolated as a yellow solid. X-ray
quality crystals were grown from ether/pentane. 1H
NMR (500 MHz, CDCl3): d 7.5–7.18 (m, C4Ph4);
5.04 (1H), 4.44 (1H), 4.19 (2H) (m, Cp); 1.51 (s,
COCH3); 1.11 (s, CCH3). 13C–{1H} NMR (125.7
MHz, CDCl3): d 206.7 (CO); 136.7 (Cipso, C4Ph4);
4. Supplementary material
Crystallographic data for the structural analyses have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC Nos. 231150 (6), 231151 (9), 231152 (7)
and 231153 (10). Copies of this information may be ob-
tained free of charge from The Director, CCDC, 12 Un-
ion Road, Cambridge CB2 1EZ (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.
cam.ac.uk).
129.3, 128.2 (Cortho and Cmeta, C4Ph4); 126.5 (Cpara
,
C4Ph4); 105.7 (Cq, Cp); 83.5, 83.1, 82.9, 81.9 (CH,
Cp); 75.1 (C4Ph4); 51.5 (CCH3); 26.6 (COCH3); 15.5
(CCH3). IR (CDCl3, mCO): 1704 cmÀ1. Calc. for
C70H54Co2O: C, 81.73; H, 5.25; Co, 11.46. Found:
C, 81.71; H, 5.74; Co, 9.79%.
Acknowledgement
Fraction 5: Starting material (5) (0.32 g, 21% recov-
ered) was eluted by using a mixture of ether/pentane
(25/75), and was isolated as an orange solid.
Financial support from University College Dublin is
gratefully acknowledged.
3.4. McMurry reaction of (C4Ph4)Co(C5 H4COMe) (5)
and benzophenone in a 1:5 ratio
References
`
[1] S. Top, H. El Hafa, A. Vessieres, J. Quivy, J. Vaissermann, D.W.
Hughes, M.J. Mc Glinchey, J.-P. Mornon, E. Thoreau, G.
Jaouen, J. Am. Chem. Soc. 117 (1995) 8372.
Following the procedure described above, the hetero-
coupled product (7) was isolated in 71% yield, and only
traces of the cobalt complexes 9 and 10 were detected.
`
[2] (a) A. Vessieres, K. Kowalski, J. Zakrzewski, A. Stepien,
M. Grabowski, G. Jaouen, Bioconjugate Chem. 10 (1999)
379;
(b) P. Brossier, G. Jaouen, B. Limoges, M. Salmain, A.
3.5. X-ray crystal structure determinations
`
Vessieres, J.-P. Yvert, Ann. Biol. Clin. 59 (2001) 677.
[3] (a) F. Le Bideau, M. Salmain, S. Top, G. Jaouen, Chem. Eur. J. 7
(2001) 2289;
X-ray crystallographic data (see Table 1) for 6, 7, 9
and 10 were each collected from a suitable sample
mounted with grease on the end of a thin glass fiber.
Data were collected on a D8 Bruker diffractometer
equipped with a Bruker SMART APEX CCD area
detector (employing the program SMART) [15] and
an X-ray tube utilizing graphite-monochromated Mo
`
(b) G. Jaouen, S. Top, A. Vessieres, R. Alberto, J. Organomet.
Chem. 600 (2000) 23.
[4] S. Top, E.B. Kaloun, A. Vessie
`res, G. Leclercq, I. Laıos, M.
¨
Ourevitch, C. Deuschel, M.J. McGlinchey, G. Jaouen, Chem.
Bio. Chem. 4 (2003) 754.
`
[5] (a) G. Jaouen, S. Top, A. Vessieres, G. Leclercq, J. Quivy, L. Jin,
A. Croisy, C. R. Acad. Sci., Ser. IIc: Chim. 3 (2000) 89;
˚
Ka radiation (k = 0.71073 A). Data processing was car-
ried out by use of the program SAINT [16], while the
program SADABS [17] was utilized for the scaling of dif-
fraction data and an empirical absorption correction
based on redundant reflections. Structures were solved
by using the direct-methods procedure in the Bruker
SHELXL [18] program library and refined by full-matrix
least-squares methods on F2. As a result of the rela-
`
(b) S. Top, A. Vessieres, C. Cabestaing, I. La¨ıos, G. Leclercq,
C. Provot, G. Jaouen, J. Organomet. Chem. 637-639 (2001)
500;
(c) S. Top, E.B. Kaloun, S. Toppi, A. Herrbach, M.J.
McGlinchey, G. Jaouen, Organometallics 20 (2001) 4554.
`
[6] G. Jaouen, S. Top, A. Vessieres, P. Pigeon, G. Leclercq, I. La¨ıos,
Chem. Commun. (2001) 383.
[7] M.D. Rausch, R.A. Genetti, J. Org. Chem. 35 (1970) 3888.

4690
Y. Ortin et al. / Journal of Organometallic Chemistry 689 (2004) 4683–4690
[8] W.P. Hart, D.W. Macomber, M.D. Rausch, J. Am. Chem. Soc.
102 (1980) 1196.
[14] R. Huisgen, I. Kalvinish, X. Li, G. Mloston, Eur. J. Org. Chem.
(2000) 1685.
[9] A.M. Stevens, C.J. Richards, Organometallics 18 (1999) 1346.
[10] Y. Ortin, K. Ahrenstorf, P. OꢀDonohue, D. Foede, H. Mu¨ller-
Bunz, P. McArdle, A.R. Manning, M.J. McGlinchey, J. Organ-
omet. Chem. 689 (2004) 1657.
[15] G.M. Sheldrick, SMART, Release 5.625, Bruker AXS Inc.,
Madison, WI 53711, 2001.
[16] G.M. Sheldrick, SAINT, Release 6.22, Bruker AXS Inc., Madison,
WI 53711, 2001.
[11] P. Ha¨rter, K. Latzel, M. Spiegler, E. Herdtweck, Polyhedron 17
(1998) 1141.
[17] G.M. Sheldrick, SADABS, Version 2.03, (Siemens Area Detector
Absorption Corrections), Bruker AXS Inc., Madison, WI 53711,
2000.
[12] B. Bogdanoviæ, A. Bolte, J. Organomet. Chem. 502 (1995) 109.
[13] R. Dams, M. Malinowski, I. Westdorp, H. Geise, J. Org. Chem.
47 (1982) 248.
[18] G.M. Sheldrick, SHELXTL
Madison, WI 53711, 2000.
, Version 6.1, Bruker AXS Inc.,