Aldol condensation reactions of [Co(η4-C4Ph 4){η5-C5H4C(O)CH3}]

Article abstract of DOI:10.1016/j.jorganchem.2005.11.057

The aldol condensation reaction between [Co(η⁴-C ₄Ph₄){η⁵-C₅H₄C(O) CH₃}] and a range of aromatic aldehydes [RCHO] and [RCHCH-CHO] gives a series of α,β-unsaturated ketones [Co(η⁴-C ₄Ph₄){η⁵-C₅H₄C(O) CHCH-R}] and [Co(η⁴-C₄Ph₄) {η⁵-C₅H₄C(O)CHCH-CHCH-R}] (3). The reaction is promoted by various bases: NaH proved to be the most effective whilst ⁿBuLi gave [Co(η⁴-C₄Ph₄) {η⁵-C₅H₄C(OH)(ⁿBu)CH ₃}] as the major product. NaOH was ineffective, perhaps indicating that that the methyl protons in [Co(η⁴-C₄Ph ₄){η⁵-C₅H₄C(O)CH₃}] are less acidic than those in [Fe(η⁵-C₅H ₅){η⁵-C₅H₄C(O)CH₃}]. Compounds 3 were characterised spectroscopically. Their ¹H NMR spectra are consistent with a trans configuration about their CC bond, and this was confirmed by X-ray crystallography in five cases, which showed that all have the same basic structure with parallel cyclobutadiene and cyclopentadienyl ligands, but they are not identical. The C₅H₄C(O)(CHCH) _n-R (n = 1 or 2) moieties show little evidence for delocalisation and often deviate from planarity. The UV/Vis spectra of those 3 with smaller aromatic rings (R = C₆H₅, 4-C₆H ₄NMe₂, 2-C₄H₃S and 1-C ₁₀H₇) suggest that these are donor-π-acceptor systems, but as the annellation of R increases (R = 9-C₁₄H₉, 1-C₁₆H₉ and 1-C₂₀H₁₁) the spectra increasingly resemble those of the parent polycyclic aromatic hydrocarbon, RH. Reduction of [Co(η⁴-C₄Ph₄) {η⁵-C₅H₄C(O)CHCH-C₁₀H ₇-1}] with DIBAL gives a mixture of [Co(η⁴-C ₄Ph₄){η⁵-C₅H₄C(O) CH₂CH₂-C₁₀H₇-1}] and [Co(η⁴-C₄Ph₄){η⁵-C ₅H₄CH(OH)CHCH-C₁₀H₇-1}]. A minor product from the preparation of [Co(η⁴-C₄Ph ₄){η⁵-C₅H₄C(O)CH₃}] was shown by X-ray crystallography to be the η⁴-butadiene complex [Co{η⁴-Ph(H)CC(Ph)-C(Ph)C(H)Ph}{η⁵-C ₅H₄C(O)CH₃}].

Full text of DOI:10.1016/j.jorganchem.2005.11.057

Journal of Organometallic Chemistry 691 (2006) 1183–1196
www.elsevier.com/locate/jorganchem
Aldol condensation reactions of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}]
a
a
a,
b
Christoph Behrendt , Sven Dabek , Jurgen Heck *, Donagh Courtney ,
b,
b,
b
b
Anthony R. Manning *, Michael J. McGlinchey *, Helge Mueller-Bunz , Yannick Ortin
a
Institut fu¨r Anorganische und Angewandte Chemie, Universita¨t Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
b
School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
Received 4 October 2005; received in revised form 18 November 2005; accepted 21 November 2005
Available online 4 January 2006
Abstract
The aldol condensation reaction between [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] and a range of aromatic aldehydes [RCHO] and
[RCH@CH–CHO] gives a series of a,b-unsaturated ketones [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–R}] and [Co(g4-C4Ph4){g5-
C5H4C(O)CH@CH–CH@CH–R}] (3). The reaction is promoted by various bases: NaH proved to be the most effective whilst nBuLi gave
[Co(g4-C4Ph4){g5-C5H4C(OH)(nBu)CH3}] as the major product. NaOH was ineffective, perhaps indicating that that the methyl protons
in [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] are less acidic than those in [Fe(g5-C5H5){g5-C5H4C(O)CH3}]. Compounds 3 were characterised
spectroscopically. Their 1H NMR spectra are consistent with a trans configuration about their C@C bond, and this was confirmed by X-
ray crystallography in five cases, which showed that all have the same basic structure with parallel cyclobutadiene and cyclopentadienyl
ligands, but they are not identical. The C5H4C(O)(CH@CH)n–R (n = 1 or 2) moieties show little evidence for delocalisation and often
deviate from planarity. The UV/Vis spectra of those 3 with smaller aromatic rings (R = C6H5, 4-C6H4NMe2, 2-C4H3S and 1-C10H7)
suggest that these are donor–p-acceptor systems, but as the annellation of R increases (R = 9-C14H9, 1-C16H9 and 1-C20H11) the spectra
increasingly resemble those of the parent polycyclic aromatic hydrocarbon, RH. Reduction of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–
C10H7-1}] with DIBAL gives a mixture of [Co(g4-C4Ph4){g5-C5H4C(O)CH2CH2–C10H7-1}] and [Co(g4-C4Ph4){g5-C5H4CH(OH)CH@
CH–C10H7-1}]. A minor product from the preparation of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] was shown by X-ray crystallography to be
the g4-butadiene complex [Co{g4-Ph(H)C@C(Ph)–C(Ph)@C(H)Ph}{g5-C5H4C(O)CH3}].
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Cobalt; Tetraphenylcyclobutadiene; Aldol condensation; Unsaturated ketones
1. Introduction
has also been studied with the intention of preparing allylic
alcohols as precursors to cationic merocyanines such as
[Co(g4-C4Ph4){g5-C5H4CHCHCH–C10H7-1}][BF4].
Acids and bases promote the reversible formation of
aldols from enolisable aldehydes and ketones (Scheme 2,
Step 1). The reaction was discovered independently by
Borodin [1a] and Wurtz [1b] ca. 1870, and since then it
has provided a versatile method for preparing new CAC
bonds [1c]. Furthermore, as both of these carbon atoms
may end up as chiral centres there has been much recent
research into the asymmetric aldol addition reaction [1d].
However, aldols are b-hydroxy-aldehydes or ketones and
are, therefore, susceptible to irreversible dehydration with
the formation of a,b-unsaturated aldehydes or ketones
(Scheme 2, Step 2).
Although the chemistry of ferrocene and its derivatives
has been studied extensively, less effort has been expended
on their isoelectronic counterparts derived from [Co(g4-
C4Ph4)(g5-C5H5)]. Here, we report a series of a,b-unsatu-
rated ketones [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–R}]
(Scheme 1) obtained from the base-promoted aldol
condensation of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] with
various aldehydes RCHO. The reduction of [Co(g4-
C4Ph4){g5-C5H4C(O)CH@CH–C10H7-1}] (3i), with DIBAL
*
Corresponding authors.
E-mail address: Anthony.Manning@ucd.ie (A.R. Manning).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.11.057

1184
C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
(1b) [3], and [Fe(g-C5H5)(g5-C5H4CHO)] (2b) [4]. Other
chemicals were purchased and used as received.
Unless otherwise stated, all reactions were carried out at
room temperature under an atmosphere of nitrogen in
dried and deoxygenated solvents. They were monitored
by thin-layer chromatography and NMR spectroscopy.
O
O
H
R
H
Co
H
Fe
H
Ph
Ph
Ph
Ph
Co
Ph
Ph
Ph
Ph
3
3c
2.1. Preparation of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}]
(1a), and [Co{g4-Ph(H)CC(Ph)C(Ph)CHPh}{g5-
C5H4C(O)CH3}] (1c)
(a) (C5H4)Co( 4-C4Ph4)
(b) C5H4Fe( -C5H5)
(c) (C5H4)Co( 4-C4Ph4)*
(d) C6H5
R =
(f) C6H4NMe2-4
(k) C14H9-9 (9-anthryl)
(g) CH=CH-C6H4NMe2-4
(h) C4H3S-2 (2-thienyl)
(i) C10H7-1 (1-naphthyl)
(j) C14H9-9 (9-phenanthryl)
(l) C16H9-1 (1-pyrenyl)
(m) C20H11-1 (1-perylenyl)
This followed the procedure given in Ref. [2]. A solution
of sodium cyclopentadienide from freshly cracked cyclo-
pentadiene (0.5 mL and sodium metal) and methyl acetate
(0.61 mL) in tetrahydrofuran (20 mL) was refluxed for 2 h
and then cooled. To it was added Co(PPh3)3Cl (5 g), tolu-
ene (100 mL) and, after 30 min, C2Ph2 (2.0 g). The red mix-
ture was refluxed overnight, cooled, and filtered through
Celite. The filtrate was evaporated to dryness, and chro-
matographed on alumina using toluene–pentane mixtures
as eluent. The desired product was the third to be eluted.
Concentration of this band at reduced pressure and recrys-
tallization of the residue from dichloromethane–pentane
mixtures gave orange-brown crystals of [Co(g4-C4Ph4)-
{g5-C5H4C(O)CH3}] (1a) (yield 0.98 g, 33%).
(e) CH=CH-C6H5
* 3c is [Fe( 5-C5H5){ 5-C5H4C(O)CH=CH- 5-C5H4}Co( 4-C4Ph4)] (see above).
Scheme 1.
Of particular interest to us is a variant of the aldol con-
densation in which an aromatic or aliphatic methyl ketone
undergoes a base-catalysed condensation with a non-enoli-
sable aromatic aldehyde (Claisen–Schmidt condensation)
[1e,1f]. The presence of the adjacent aromatic substituents
means that the initially formed aldol dehydrates very read-
ily (Scheme 2, Step 2). In this context the ferrocenyl group
is aromatic and the formation of condensation products
[Fe(g5-C5H5){g5-C5H4C(O)CH@CH–R}] from [Fe(g5-
C5H5){g5-C5H4C(O)CH3}] and [RCHO] [1g] or [Fe(g5-
C5H5){g5-C5H4CH@CHC(O)R}] from [RC(O)CH3] and
[Fe(g5-C5H5)(g5-C5H4CHO)] [1h] in base-catalysed reac-
tions has been investigated since the earliest days of ferro-
cene chemistry. Recently, similar aldol condensations
of [Fe(g5-C5H5){g5-C5H4C(O)CH3}] with [4-Et2NC6H4-
CHO] and [4-Me2NC6H4CH@CHCHO] have been used
to prepare [Fe(g5-C5H5){g5-C5H4C(O)CH@CHC6H4-
NEt2-4}] and [Fe(g5-C5H5){g5-C5H4C(O)CH@CH–CH@
CHC6H4NMe2-4}], respectively, which act as calcium ion
detectors [1i]. We describe its reaction with [Co(g4-
C4Ph4)(g5-C5H4CHO)].
Further elution gave a deep red band from which was
isolated (recrystallisation from dichloromethane/pentane)
dark red crystals of [Co{g4-Ph(H)CC(Ph)C(Ph)CHPh}-
{g5-C5H4C(O)CH3}] (1c) (yield 0.03 g, 1%).
2.2. Aldol condensations using LinBu as the deprotonating
agent
In a typical reaction, a solution of [Fe(g5-C5H5){g5-
C5H4C(O)CH3}] (1b), (0.197 g, 1 mmol) in dry tetrahydro-
furan (15 mL) was cooled to ꢀ80 ꢁC and a 2.5 M solution
of LinBu in hexane (0.4 mL) added dropwise. The mixture
was warmed to ꢀ60 ꢁC for 15 min, [Co(g4-C4Ph4)(g5-
C5H4CHO)] (2a), (0.46 g, 1 mmol) added to it and the
whole allowed to warm to room temperature. After the
addition of water (3 drops) the mixture was allowed to
stand for a further hour before the solvent was removed
at reduced pressure leaving a red solid. This was extracted
2. Experimental
Published procedures were used to prepare [Co(g4-
C4Ph4){g5-C5H4C(O)CH3}] (1a) [2], [Co(g4-C4Ph4)(g5-
C5H4CHO)] (2a) [2], [Fe(g-C5H5){g5-C5H4C(O)CH3}]
O
O
O
O
(ii),(iii)
(i)
R'
H
R
R'
O
H
R
+
R'
R
H
Step 1
Step 2
CH3
H
H
H
1
3
2
O
OH
O
H
R'
H
R'
H
R
R'
H
H
R
(iv)
+
H
R
H
H
H
3
4
1
Scheme 2. Conditions: (i) deprotonating agent, (ii) +H+, (iii) –H2O, (iv) DIBAL.

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1185
repeatedly with ether, the ether solution evaporated to dry-
ness, and the residue chromatographed on alumina. Elu-
tion with ether–pentane mixtures gave a red band from
which could be isolated [Fe(g5-C5H5){g5-C5H4C(O)CH@
CH–g5-C5H4}Co(g4-C4Ph4)] (3c). It was recrystallized
from dichloromethane–pentane mixtures as a red solid
(yield 15%).
changed to yellow. Removal of the solvent gave a brown
residue, which was chromatographed on alumina. Elution
with a 25:75 ethylacetate–pentane mixture gave two bands.
From the first was isolated Co(g4-C4Ph4){g5-
C5H4C(O)CH2CH2–1-C10H7} (yield 22%); from the second
Co(g4-C4Ph4){g5-C5H4CH(OH)CH@CH–1-C10H7} (54%).
Both were purified by recrystallisation from dichlorometh-
ane–pentane.
A similar procedure was used for the reaction of [Co(g4-
C4Ph4){g5-C5H4C(O)CH3}] (1a)/LinBu with [Fe(g5-C5H5)-
(g5-C5H4CHO)] (2b). On chromatography of the reaction
mixture (alumina with 20:80 ethylacetate/pentane) the first
compound to be eluted and isolated was [Co(g4-C4Ph4){g5-
C5H4C(O)CH@CH–g5-C5H4}Fe(g5-C5H5)] (3b), as red
crystals from dichloromethane–pentane (yield 15%).
The second was a brown oily solid from dichlorometh-
ane–pentane identified as [Co(g4-C4Ph4){g5-C5H4C(OH)-
(nBu)(CH3)}] (4a) (yield 48%).
2.4.1. [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] (1a)
Yield 0.98 g, 33%. IR (THF): m(CO): 1672 cmꢀ1 1H
.
NMR (300 MHz, CDCl3): d 7.48–6.98 (m, 20H, C6H5),
5.20 (m, 2H, C5H4), 4.77 (m, 2H, C5H4), 1.65 (s, 3H,
CH3). 13C NMR (75.4 MHz, CDCl3): d 197.49 (CO),
135.2 (Cipso, C6H5), 128.8, 128.3 (Cortho and Cmeta, C6H5),
127.0 (Cpara, C6H5), 93.9, 87.7, 83.4 (C5H4), 76.7
(C4Ph4), 27.2 (CH3). UV/Vis: kmax/nm (CH2Cl2): 277,
318 (sh), 412.
2.3. Aldol condensations using sodium hydride as the
deprotonating agent
2.4.2. [Co{g4-Ph(H)CC(Ph)C(Ph)CHPh}
{g5-C5H4C(O)CH3}] (1c)
The procedure adopted was similar to that used for reac-
tions of acetylferrocene but with sodium hydride in place of
potassium hydride [5].
Yield 0.03 g, 1%. Anal. Calc. for C35H29OCo: C, 80.14;
H, 5.57; Co, 11.23. Found: C, 80.30; H, 5.64; Co, 10.75%.
IR (KBr): m(CO) 1662 cmꢀ1. 1H NMR (500 MHz, CDCl3):
d 7.87–6.74 (m, 20H, C6H5), 4.94 (m, 2H, C5H4), 4.21 (m,
2H, C5H4), 2.16 (s, 3H, CH3), 1.61 (s, 2H, CHPh). 13C
NMR (125.7 MHz, CDCl3): d 196.31 (CO), 143.4, 136.9,
129.3, 128.3, 127.2, 125.6 (C6H5), 98.1 (C@CHPh), 94.9,
90.8 and 84.1 (C5H4), 54.8 (CHPh) and 27.7 (COCH3).
2.3.1. Reaction of [Fe(g5-C5H5){g5-C5H4C(O)CH3}]
(1b), with [Co(g4-C4Ph4)(g5-C5H4CHO)] (2a)
Sodium hydride (0.024 g, 1 mmol) was added to a solu-
tion of [Fe(g5-C5H5){g5-C5H4C(O)CH3}] in tetrahydrofu-
ran (15 mL). The mixture was allowed to stand for 4 h
refluxed for 1 h, cooled to room temperature, [Co(g4-
C4Ph4)(g5-C5H4CHO)] (0.509 g, 1 mmol) added to it, and
the whole allowed to stand overnight. Removal of the sol-
vent gave a red residue which was chromatographed on
alumina. Elution with ethyl acetate–pentane (20:80) gave
UV/Vis:
(16442), 411 (638).
k ) (CH2Cl2): 265
max/nm (e/dm3 molꢀ1 cmꢀ1
2.4.3. [Co(g4-C4Ph4){g5-C5H4C(O)CH2CH2–C10H7-1}]
(1d) (1-C10H7 = 1-naphthyl)
Yield 22%. Mp. 83–86 ꢁC. Anal. Calc. for C46H35OCo Æ
H2O: C, 81.2; H, 5.4; Co, 8.7. Found: C, 81.0; H, 5.4; Co,
a
red band from which was isolated red crystals
of [Fe(g5-C5H5){g5-C5H4C(O)CH@CH–g5-C5H4}Co(g4-
C4Ph4)] (3c), in 55% yield.
8.3%. IR m/cmꢀ1: m(CO) 1662 (KBr). H NMR (300 MHz,
1
CDCl3): d 7.0–8.0 [27H, m, C6H5 and 1-C10H7], 5.20 [2H,
Co(g-C5H4)], 4.79 [2H, Co(g-C5H4)], 3.01 [1H, t,
J = 8 Hz, CH2CH2C(O)], 2.48 [1H, t, J = 8 Hz, CH2-
CH2C(O)].
Using the same methodology, [Co(g4-C4Ph4){g5-
C5H4C(O)CH3}] (1a), and various RCHO, 2, gave the
chalcones [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–R}] (3),
where R = (a) (g5-C5H4)Co(g4-C4Ph4), (b) (g5-C5H4)-
Fe(g5-C5H5), (d) C6H5, (e) –CH@CH–C6H5, (f) C6H4-
NMe2-4, (g) –CH@CH–C6H4NMe2-4, (h) 2-C4H3S
(2-thienyl), (i) 1-C10H7 (1-naphthyl), (j) 9-C14H9 (9-phen-
anthryl), (k) 9-C14H9 (9-anthryl), (l) 1-C16H9 (1-pyrenyl),
and (m) 1-C20H11 (1-perylenyl) in fair to good yields.
2.4.4. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–g5-C5H4-
Co(g4-C4Ph4)}] (3a)
Yield 40%. Mp. 171–173 ꢁC. Anal. Calc. for
C69H50OCo2: C, 81.8; H, 5.0. Found: C, 81.3; H, 5.4%.
IR m/cmꢀ1: m(CO) 1652, m(C@C) 1596, 1498 (KBr). 1H
NMR (300 MHz, CDCl3): d 7.14–7.38 [40H, m, C6H5],
6.66 [1H, d, J = 15.4 Hz, CH@CHC(O)], 5.68 [1H, d,
J = 15.4 Hz, CH@CHC(O)], 5.10 [2H, Co(g-C5H4)], 4.78
[2H, Co(g-C5H4)], 4.72 [2H, Co(g-C5H4)], 4.65 [2H,
Co(g-C5H4)]. 13C NMR (75.4 MHz, CDCl3): d 186.5
[CO], 136.8 [CH@CHC(O)], 135.4–126.5 [C6H5], 122.1
[CH@CHC(O)], 95.4, 92.1, 87.6, 86.2, 83.1 and 82.5
2.4. Reduction of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–
C10H7-1}]
On addition of a 1.5 M solution of diisobutylalumini-
umhydride, DIBAL, (1.33 mL, 2 mmol) to a solution of
[Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–1-C10H7}] (0.33 g,
0.5 mmol) in toluene (50 mL), the colour turned from
orange to deep red. When, after 5 h, methanol was added
to the reaction mixture to destroy excess DIBAL, its colour
[Co(g-C5H4)], 76.0 [C4Ph4]. UV/Vis:
kmax/nm (e/
dm3 molꢀ1 cmꢀ1) (CH2Cl2): 278 (77599), 495 (sh), 402
(sh).

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C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
2.4.5. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–g5-
C5H4}Fe(g5-C5H5)] (3b)
Yield 15%. Mp. 104–105 ꢁC. Anal. Calc. for
C46H35OCoFe Æ CH3CO2C2H5: C, 74.5; H, 5.34; Co, 7.32;
Fe, 6.95. Found: C, 73.92; H, 4.92; Co, 7.52; Fe, 7.39%.
IR m/cmꢀ1: m(CO) 1647, m(C@C) 1589 (KBr). 1H NMR
and 15 Hz, CH@CHCH@CHC(O)], 6.07 [1H, d,
J = 15 Hz, CH@CHCH@CHC(O)], 5.29 [2H, Co(g-
C5H4)], 4.83 [2H, Co(g-C5H4)]. 13C NMR (75.4 MHz,
CDCl3): d 188.0 (CO), 141.0, 140.2, 127.0 and 125.4
[CH@CH–CH@CH], 136.6, 135.1, 128.8, 128.3, 128.2,
127.5, 127.0 and 126.8 [C6H5], 94.9, 88.2 and 83.2
(300 MHz, CDCl3):
d
7.1–7.5 [21H, m, C6H5,
[Co(g-C5H4)], 76.9 [C4Ph4]. UV/Vis
kmax/nm (e/
CH@CHC(O)], 6.27 [1H, d, J = 15 Hz, CH@CHC(O)],
5.27 [2H, Co(g-C5H4)], 4.83 [2H, Co(g-C5H4)], 4.39 [2H,
Fe(g-C5H4)], 4.31 [2H, Fe(g-C5H4)], 4.09 [5H, s, Fe(g-
C5H5)]; 13C NMR (75.4 MHz, CDCl3): d 187.2 [CO],
142.7 [CH@CHC(O)], 135.2, 128.8, 128.1 and 126.8
[C6H5], 120.4 [CH@CHC(O)], 95.2, 87.9 and 83.2 [Co(g-
C5H4)], 79.7, 70.8 and 68.8 [Fe(g-C5H4)], 76.7 [C4Ph4],
dm3 molꢀ1 cmꢀ1) (CH2Cl2): 284 (48100), 344 (38100),
407 (sh).
2.4.9. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C6H4N-
(CH3)2-4}] (3f)
Yield 35%. Mp. 180–182 ꢁC. Anal. Calc. for C46H38ON-
Co Æ CH3CO2C2H5: C, 77.7; H, 6.0; Co, 7.9; N, 1.9. Found:
C, 78.2; H, 6.2; Co, 7.4; N, 1.8%. IR m/cmꢀ1: m(CO) 1641,
m(C@C) 1602, 1576 (KBr). 1H NMR (300 MHz, CD2Cl2): d
7.0–7.6 [25H, m, C6H5], ca. 7.20 [C6H4], ca. 7.20
[CH@CHC(O)], 6.64 [1H, d, J = 9 Hz, C6H4], 6.44 [1H,
d, J = 15 Hz, CH@CHC(O)], 5.31 [2H, Co(g-C5H4)], 4.82
69.6 [Fe(g-C5H5)]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1
(CH2Cl2): 277 (40840), 390 (sh), 491 (620).
)
2.4.6. [Fe(g5-C5H5){g5-C5H4C(O)CH@CH–g5-
C5H4}Co(g4-C4Ph4)] (3c)
Yield 55%. Mp. 199–199.5 ꢁC. Anal. Calc. for
C46H35OCOFe: C, 76.9; H, 4.91; Co, 8.20; Fe, 7.77. Found:
C, 76.82; H, 5.05; Co, 7.89; Fe, 7.63%. IR m/cmꢀ1: m(CO)
1650 (KBr). 1H NMR (300 MHz, CDCl3): d 7.4–7.2
[20H, m, C6H5], 7.17 [1H, d, J = 16 Hz, CH@CHCO],
6.34 [1H, d, J = 16 Hz, CH@CHCO), 4.93 [2H, Co(g-
C5H4)], 4.79 [2H, Co(g-C5H4)], 4.67 [2H, Fe(g-C5H4)],
4.49 [2H, Fe(g-C5H4)], 4.10 [5H, s, Fe(g-C5H5)]. 13C
[2H, Co(g-C5H4)]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1
)
(CH2Cl2): 263 (63600), 281 (sh), 418 (34000).
2.4.10. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–CH@CH–
C6H4N(CH3)2-4}] (3g)
Yield 63%. Mp. 190–191 ꢁC. Anal. Calc. for
C46H38ONCo: C, 81.3; H, 5.6; Co, 8.7; N, 2.1. Found: C,
80.5; H, 5.8; Co, 7.9; N, 1.79%. IR m/cmꢀ1: m(CO) 1642,
1
NMR (75.4 MHz, CDCl3):
[RHC@CHCO], 135.4 [Cipso, C6H5], 128.8 and 128.2 [Cortho
and Cmeta C6H5], 126.7 (Cpara C6H5]), 121.9
d
192.1 [CO], 137.3
m(C@C) 1602, 1565 (KBr). H NMR (300 MHz, CDCl3):
d 7.1–7.6 [25H, m, C6H5], 7.36 [1H, d, J = 9 Hz, C6H4],
7.09 [1H, dd, J = 11, 15 Hz, CH@CHCH@CHC(O)], 6.74
[1H, d, J = 15 Hz, CH@CHCH@CHC(O)], 6.70 [1H, d,
J = 8 Hz, C6H4], 6.34 [1H, dd, J = 11, 15.3 Hz,
CH@CHCH@CHC(O)], 5.98 [1H, d, J = 15 Hz, CH@
CHCH@CHC(O)], 5.27 [2H, Co(g-C5H4)], 4.80 [2H,
Co(g-C5H4)], 3.02 [6H, s, N(CH3)2]. 13C NMR (75.4
MHz, CDCl3): d 187.5 (CO), 142.4, 141.2, 124.2 and
123.2 [CH@CH–CH@CH], 150.2, 135.2, 128.8, 128.5,
128.1, 126.7 and 124.8 [C6H5, C6H4], 95.6, 87.8 and 83.1
[Co(g-C5H4)], 76.7 [C4Ph4], 40.3 [N(CH3)2]. UV/Vis:
,
,
[COCH@CHR], 92.5, 86.7 and 82.6 [Co(g-C5H4)], 80.9,
72.2 and 69.7 [Fe(g-C5H4)], 76.4 [Co(g-C4Ph4)], 69.9
[Fe(g-C5H5)]. UV/Vis (CH2Cl2):
k
max/nm (e/dm3
molꢀ1 cmꢀ1) 359 (5512), 389 (4492), 473 (1837).
2.4.7. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C6H5}]
(3d)
Yield 65%. Mp. 173–174 ꢁC. Anal. Calc. for
C42H31OCo: C, 82.48; H, 5.11; Co, 9.64. Found: C,
81.75; H, 5.19; Co, 8.96%. IR m/cmꢀ1: m(CO) 1654,
k
max/nm (e/dm3 molꢀ1 cmꢀ1) (CH2Cl2): 281 (49100), 431
1
m(C@C) 1596 (KBr). H NMR (300 MHz, CDCl3): d 7.1–
(39900).
7.9 (26H, m, C6H5]), 7.29 [d, J = 16 Hz, CH@CHC(O)],
6.69 [1H, d, J = 16 Hz, CH@CHC(O)], 5.34 [2H, Co(g-
C5H4)], 4.86 [2H, Co(g-C5H4)]. 13C NMR (75.4 MHz,
CDCl3): d 187.5 [CO], 141.2 [CH@CHC(O)], 135.2, 128.8,
128.2 and 126.8 [C6H5], 123.0 [CH@CHC(O)], 95.2, 88.1
and 83.4 [Co(g-C5H4)], 76.9 [C4Ph4]. UV/Vis: kmax/nm
(e/dm3 molꢀ1 cmꢀ1) (CH2Cl2): 283 (20314), 310 (sh), 405
(2200).
2.4.11. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C4H3S-
2}] (3h)
Yield 26%. Mp. 183–184 ꢁC. Anal. Calc. for
C40H29OSCo: C, 77.91; H, 4.74; Co, 9.56; S, 5.19. Found:
C, 77.65; H, 4.85; Co, 9.52; S, 5.23%. IR m/cmꢀ1: m(CO)
1
1647, m(C@C) 1586 (KBr). H NMR (300 MHz, CDCl3):
d
7.0–7.6 [23H, m, C6H5, and C4H3S], ca. 7.4
[CH@CHC(O)], 6.53 [1H, d, J = 15 Hz, CH@CHC(O)],
5.41 [2H, t, Co(g-C5H4)], 4.95 [2H, t, Co(g-C5H4)].
13C NMR (75.4 MHz, CDCl3): d 187.2 [CO], 140.9 [CH@
CHC(O)], 135.0, 128.8, 128.2 and 126.8 [C6H5], 133.8,
131.1, 128.3, [C4H3S] 121.9 [CH@CHC(O)], 95.2, 88.1
and 83.4 [Co(g-C5H4)], 76.9 [C4Ph4]. UV/Vis: kmax/nm
(e/dm3 molꢀ1 cmꢀ1) (CH2Cl2): 278 (79000), 341 (17000),
408 (sh).
2.4.8. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–CH@CH–
C6H5}] (3e)
Yield 80%. Mp. 188–9 ꢁC. IR m/cmꢀ1: m(CO) 1645,
m(C@C) 1595(sh), 1582 (KBr). 1H NMR (300 MHz,
CDCl3): d 7.1–7.6 [25H, m, C6H5], 7.06 [1H, dd, J = 11
and 15 Hz,CH@CHCH@CHC(O)], 6.79 [1H, d,
J = 15 Hz, CH@CHCH@CHC(O)], 6.51 [1H, dd, J = 11

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1187
2.4.12. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C10H7-1}]
(3i) (1-C10H7 = 1-naphthyl)
2.4.16. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C20H11-
1}] (3m) (1-C20H11 = 1-perylenyl)
Yield 75%. Mp. 209–210 ꢁC. Anal. Calc. for
C46H33OCo Æ H2O: C, 81.4; H, 5.2; Co, 8.7. Found: C,
81.0; H, 5.4; Co, 8.3%. IR m/cmꢀ1: m(CO) 1647, m(C@C)
1595 (KBr). 1H NMR (300 MHz, CDCl3): d 7.0–8.1
[27H, m, C6H5 and 1-C10H7] 8.19 [1H, d, J = 15 Hz,
CH@CHC(O)], 6.80 [1H, d, J = 15 Hz, CH@CHC(O)],
5.38 [2H, Co(g-C5H4)], 4.86 [2H, Co(g-C5H4)]. 13C
Yield 65%. Mp. 243–245 ꢁC. Anal. Calc. for
C56H37OCo Æ 1/2CH2Cl2: C, 82.1; H, 4.6. Found: C, 82.3;
H, 5.9%. IR m/cmꢀ1: m(CO) 1644, m(C@C) 1587, 1498
(KBr). 1H NMR (300 MHz, CDCl3): d 8.13 [1H, d,
J = 15 Hz, CH@CHC(O)], 7.39–8.29 [11H, m, 3-C20H11],
7.17–7.26 [20H, m, C6H5], 6.73 [1H, d, J = 15 Hz,
CH@CHC(O)], 5.40 [2H, Co(g-C5H4)], 4.90 [2H, Co(g-
C5H4)]. 13C NMR (75.4 MHz, CDCl3): d 187.5 [CO],
137.5 [CH@CHC(O)], 135.2–119.8 [C6H5 and C20H11],
124.0 [CH@CHC(O)], 88.2 and 83.5 [Co(g-C5H4)], 77.0
[C4Ph4]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1) (CH2Cl2):
258 (65026), 288 (44205), 470 (30667).
NMR (75.4 MHz, CDCl3):
d
187.4 [CO], 138.0
[CH@CHC(O)], 135.1–124.8 [C6H5 and C10H7], 123.9
[CH@CHC(O)], 95.2, 88.3 and 83.5 [Co(g-C5H4)], 77.0
[C4Ph4]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1) (CH2Cl2):
257 (47400), 278 (44400), 347 (20800), 421(sh).
2.4.13. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C14H9-9}]
(3j) (9-C14H9 = 9-phenanthryl)
2.4.17. [Co(g4-C4Ph4){g5-C5H4C(OH)(C4H9)CH3}]
(4a)
Yield 35%. Mp. 244–246 ꢁC. Anal. Calc. for
C50H34OCo Æ CH3CO2C2H5: C, 81.2; H, 5.3; Co, 7.4.
Found: C, 81.4; H, 5.2; Co, 7.6%. IR m/cmꢀ1: m(CO)
1651, m(C@C) 1598, 1498 (KBr). 1H NMR (300 MHz,
CDCl3): d 8.19 [1H, d, J = 15 Hz, CH@CHC(O)], 7.64–
8.75 [9H, m, 9-C14H9], 7.15–7.47 [20H, m, C6H5], 6.77
[1H, d, J = 15 Hz, CH@CHC(O)], 5.42 [2H, Co(g-
C5H4)], 4.90 [2H, Co(g-C5H4)]. 13C NMR (75.4 MHz,
CDCl3): d 187.5 [CO], 138.5 [CH@CHC(O)], 135.2–122.5
[C6H5 and C20H11], 124.8 [CH@CHC(O)], 95.0, 88.2 and
83.5 [Co(g-C5H4)], 76.9 [C4Ph4]. UV/Vis: kmax/nm (e/
dm3 molꢀ1 cmꢀ1) (CH2Cl2): 256 (96716), 274 (85636),
350 (24541).
Yield 50%. Red-brown oil. Anal. Calc. for
C39H27OCo Æ CH2Cl2: C, 73.3; H, 4.43; Co, 9.0. Found:
C, 73.06; H, 5.90; Co, 8.93%. IR m/cmꢀ1: m(OH) 3550
(CH2Cl2). 1H NMR (500 MHz, CDCl3):
d 7.6–7.0
[20H, m, C6H5], 4.96 [1H, m, Co(g-C5H4)], 4.82 [1H,
Co(g-C5H4)], 4.51 [1H, Co(g-C5H4)], 4.43 [1H, m,
Co(g-C5H4)], 1.4 [2H, m, CH2CH2CH2CH3], 1.1 [1H, s,
OH], 1.08–1.02 [4H, m, CH2CH2CH2CH3], 1.13 [3H, s,
CH3], 0.77 [3H, t, J = 6.8 Hz, CH2CH2CH2CH3]. 13C
NMR (125.7 MHz, CDCl3): d 136.8, 129.1, 128.5 and
126.6 [C6H5], 111.1, 83.3, 83.1, 81.1 and 80.2 [Co(g-
C5H4)], 75.2 [C4Ph4], 71.8 [C(OH)], 44.3, 27.8, 26.5, 23.2
14.3 [C(OH)(CH3)CH2CH2CH2CH3].
2.4.14. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C14H9-9}]
(3k) (9-C14H9 = 9-anthryl)
2.4.18. [Co(g4-C4Ph4){g5-C5H4CH(OH)CH@CH–C10H7-
1}] (4b) (1-C10H6 = 1-naphthyl)
Yield 50%. Mp. 209–210 ꢁC. Anal. Calc. for
C50H35OCo: C, 84.5; H, 4.9; Co, 8.3. Found: C, 82.05;
H, 5.22; Co, 8.34%. IR m/cmꢀ1: m(CO) 1651, m(C@C)
1592 (KBr). 1H NMR (300 MHz, CDCl3): d 7.0–8.1
[27H, m, C6H5 and 1-C14H9], 8.44 [1H, s, C14H9], 8.41
[1H, d, J = 16 Hz, CH@CHC(O)], 6.64 [1H, d,
J = 16 Hz, CH@CHC(O)], 5.31 [2H, Co(g-C5H4)], 4.89
Yield 55%. Mp. 87–90 ꢁC. Anal. Calc. for
C46H35OCo Æ 1/2CH2Cl2: C, 77.8; H, 5.4; Co, 7.8. Found:
C, 79.0; H, 5.1; Co, 7.75%. IR m/cmꢀ1: m(OH) 3436 (KBr).
1H NMR (300 MHz, CDCl3): d 7.1–8.0 [27H, m, C6H5
and 1-C10H7], 7.08 [1H, d, J = 16 Hz, CH@CHC(OH)],
6.10 [1H, dd, J = 6, 16 Hz, CH@CHC(O)], 4.92 [2H,
Co(g-C5H4) and CH(OH)], 4.74 [1H, Co(g-C5H4)], 4.64
[1H, Co(g-C5H4)], 4.59 [1H, Co(g-C5H4)], 1.6 [1H, OH].
[2H, Co(g-C5H4)]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1
)
(CH2Cl2): 254 (120000), 280 (sh), 410 (16400, br).
UV/Vis: k ) (CH2Cl2): 263
max/nm (e/dm3 molꢀ1 cmꢀ1
(41900), 296 (44800), 408 (1900).
2.4.15. [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C16H9-1}]
(3l) (1-C16H9 = 1-pyrenyl)
2.5. Crystal structure determination
Yield 55%. Mp. 187–188 ꢁC. Anal. Calc. for
C52H35OCo Æ 1/2CH2Cl2: C, 81.1; H, 4.6; Co, 7.6. Found:
C, 81.9; H, 5.07; Co, 7.43%. IR m/cmꢀ1: m(CO) 1646,
Crystals of 1c, 3e, 3g, 3i and 3k were grown from dichlo-
romethane–pentane mixtures and of 3d and 3h from tolu-
ene–hexane mixtures. Data were collected on a Bruker
SMART Apex CCD diffractometer controlled by SMART
[6], processed using SAINT [7] and semi-empirical absorption
corrections based on redundant reflections applied using
SADABS [8] The structure was solved using SHELXS-97 [9]
and refined by full-matrix least-squares on F2 using
SHELXL-97 [10]. All non-hydrogen atoms were assigned
anisotropic temperature factors. The hydrogen atoms of
3d, 3e, 3g and 3i were refined as were the terminal H atoms,
1
m(C@C) 1596, 1578 (KBr). H NMR (300 MHz, CDCl3): d
8.46 [1H, d, J = 15 Hz, CH@CHC(O)], 7.8–8.45 [9H, m, 1-
C16H9], 7.0–7.6 [20H, m, C6H5], 6.90 [1H, d, J = 15 Hz,
CH@CHC(O)], 5.44 [2H, Co(g-C5H4)], 4.91 [2H, Co(g-
C5H4)]. 13C NMR (75.4 MHz, CDCl3): d 187.4 [CO], 137.8
[CH@CHC(O)], 135.1–124.3 [C6H5 and C16H9], 123.1
[CH@CHC(O)], 95.4, 88.2 and 83.5 [Co(g-C5H4)], 77.0
[C4Ph4]. UV/Vis: kmax/nm (e/dm3 molꢀ1 cmꢀ1) (CH2Cl2):
266 (44700), 287 (44900), 389 (25800), 419 (26100).

Table 1
Crystal data for [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–R}] complexes
R
C6H5 (3d)
CH@CH–C6H5 (3e)
CH@CH–C6H4NMe2-4 (3g) 2-C4H3S (3h)
1-C10H7 (3i)
9-C14H9 (3k)
1ca
Empirical formula
Formula weight
T (K)
C42H31OCo
610.60
100(2)
C44H33OCo
636.63
100(2)
C46H38NOCo
679.70
100(2)
C40H29OSCo
616.62
293(2)
C46H33OCo
660.65
100(2)
C50H35OCo
710.71
100(2)
C35H29OCo
524.51
100(2)
˚
k (A)
0.71073
0.71073
0.71073
0.71073
0.71073
0.71073
0.71073
Crystal system
Space group
Orthorhombic
Pna21 (#33)
Monoclinic
P21/c (#14)
Monoclinic
P21/c (#14)
Orthorhombic
Pna21 (#33)
Monoclinic
P21/c (#14)
Monoclinic
P21/n (#14)
Orthorhombic
Aba2 (#41)
Unit cell dimensions
˚
a (A)
17.4395(16)
12.4667(12)
27.938(3)
90
90
90
6074.0(10)
8
1.335
0.599
2544
1.00 · 1.00 · 0.50
1.46–28.30
ꢀ23 6 h 6 23,
ꢀ16 6 k 6 16,
ꢀ37 6 l 6 36
97767
16.4586(14)
12.3073(10)
16.8219(14)
90
112.200(1)
90
3154.9(5)
4
1.340
24.549(5)
9.8275(19)
14.089(3)
90
90.789(3)
90
3398.6(11)
4
1.328
17.6869(18)
12.5070(13)
27.912(3)
90
90
90
10.770(2)
17.396(3)
17.358(3)
90
96.960(3)
90
3228.2(11)
4
1.359
16.186(2)
9.1822(12)
24.669(3)
90
106.750(2)
90
13.4856(16)
21.449(3)
18.287(2)
90
90
90
5289.4(11)
8
1.317
0.675
2192
1.00 · 0.60 · 0.50
1.90–28.28
ꢀ17 6 h 6 17,
ꢀ26 6 k 6 27,
ꢀ23 6 l 6 23
21934
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
6174.3(11)
8
3510.9(8)
4
Z
Dcalc (Mg/m3)
1.327
1.345
Absorption coefficient (mmꢀ1
F(000)
)
0.579
1328
0.543
1424
0.655 mmꢀ1
2560
0.569
1376
0.529 mmꢀ1
1480
Crystal size (mm3)
0.30 · 0.20 · 0.20
2.11–27.00
ꢀ20 6 h 6 20,
ꢀ15 6 k 6 15,
ꢀ21 6 l 6 21
25659
0.40 · 0.40 · 0.05
1.66–26.00
ꢀ30 6 h 6 30,
ꢀ12 6 k 6 12,
ꢀ17 6 l 6 17
50459
0.50 · 0.50 · 0.50
1.78–26.00
ꢀ20 6 h 6 21,
ꢀ15 6 k 6 15,
ꢀ24 6 l 6 34
31710
0.40 · 0.30 · 0.20
1.66–27.00
ꢀ13 6 h 6 13,
ꢀ22 6 k 6 22,
ꢀ22 6 l 6 22
53083
0.40 · 0.30 · 0.10
1.35–24.00
ꢀ18 6 h 6 18,
ꢀ10 6 k 6 10,
ꢀ28 6 l 6 28
43112
h Range for data collection (ꢁ)
Index ranges
Reflections collected
Independent reflections (Rint
Completeness to h = 26.00ꢁ (%) 98.0
)
14519 (0.0401)
6879 (0.0361)
99.9
6687 (0.0356)
100.0
10517 (0.0325)
99.9
7039 (0.0293)
100.0
5520 (0.0828)
100.0
6180 (0.0169)
97.0
Absorption correction
Semi-empirical from Semi-empirical from
Numerical
Semi-empirical
from equivalents
0.8947 and 0.7384
Semi-empirical
from equivalents
0.9490 and 0.5525
Semi-empirical
from equivalents
0.7289 and 0.5602
equivalents
equivalents
Maximum and
minimum transmission
Refinement method
0.7540 and 0.5859
Full-matrix
0.8929 and 0.7052
0.9734 and 0.7568
0.7355 and 0.7355
Full-matrix
Full-matrix
Full-matrix
least-squares on F2
6687/0/594
Full-matrix
Full-matrix
Full-matrix
least-squares on F2 least-squares on F2
least-squares on F2 least-squares on F2 least-squares on F2 least-squares on F2
Data/restraints/parameters
Goodness-of-fit on F2
14519/1/1042
1.035
6879/0/547
1.024
10517/1/777
1.043
7039/0/565
1.051
5520/0/469
1.285
6180/1/343
1.024
1.084
Final R indices [I > 2r(I)]
R1 = 0.0364,
wR2 = 0.0884
R1 = 0.0407,
wR2 = 0.0908
0.079(7)
R1 = 0.0398,
wR2 = 0.0914
R1 = 0.0542,
wR2 = 0.0988
R1 = 0.0395,
wR2 = 0.0990
R1 = 0.0449,
wR2 = 0.1026
R1 = 0.0445,
wR2 = 0.1119
R1 = 0.0504,
wR2 = 0.1170
0.117(13)
R1 = 0.0385,
wR2 = 0.0961
R1 = 0.0417,
wR2 = 0.0986
R1 = 0.0742,
wR2 = 0.1510
R1 = 0.0824,
wR2 = 0.1544
R1 = 0.0287,
wR2 = 0.0736
R1 = 0.0296,
wR2 = 0.0743
ꢀ0.004(8)
R indices (all data)
Absolute structure parameter
Largest difference in
1.394 and ꢀ0.223
0.623 and ꢀ0.219
0.697 and ꢀ0.274
1.015 and ꢀ0.204
0.558 and ꢀ0.167
0.823 and ꢀ0.759
0.386 and ꢀ0.196
ꢀ3
˚
peak and hole (e A
)
a
[Co(g4-C4Ph4H2){g-C5H4C(O)Me}].

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1189
O1
C11
C17
C18
C10
C12
C13
C14
C5
C9
C6
C16
C15
C7
C8
C35
C28
C36
C34
C33
C27
Co1
C26
C31
C29
C32
C30
C25
C3
C4
C2
C1
C38
C19
C39
C37
C42
C24
C21
C20
C40
C23
C41
C22
Fig. 1. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C6H5}] (3d); thermal ellipsoids are drawn at the 50% probability level.
C33
C30
C32
C38
O
C39
C29
C31
C34
C36
C35
C37
C40
Co
C11
C4
C6
C5
C1
C17
C3
C2
C18
C12
C23
C24
Fig. 2. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–CH@CH–C6H5}] (3e); thermal ellipsoids are drawn at the 50% probability level.
C33
C32
C31
O
C29
C30
C35
C34
C23
C37
C36
C43
C38
Co
C44
C42
C39
C40
C41
C5
C1
N
C46
C2
C11
C4
C3
C45
C17
Fig. 3. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–CH@CH–C6H4NMe2}] (3g); thermal ellipsoids are drawn at the 50% probability level.
on C(1) and C(4), of 1c. The H atoms of 3h, 3i and the
remainder of those of 1c were included in calculated posi-
tions and refined using a riding model.
Crystal data are summarised in Table 1, and molecu-
lar structures and atom labelling are illustrated in Figs.
1–7.

1190
C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
O1
C6
C7
C5
C11
C10
C14
C13
S1
C12
C9
Co1
C24
C8
C26
C25
C15
C27
C16
C22
C17
C21
C20
C28
C1
C23
C2
C34
C4
C19
C18
C33
C3
C32
C29
C40
C30
C35
C36
C37
C39
C38
C31
Fig. 4. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C4H3S}] (3h) (molecule 1); thermal ellipsoids are drawn at the 25% probability level.
C40
C39
C41
C38
C36
C37
C42
C35
C46
C45
C43
C34
C29
C33
Co
C31
C32
O
C30
C44
C12
C6
C5
C11
C2
C1
C4
C3
C17
C23
C24
C18
Fig. 5. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C10H7-1}] (3i); thermal ellipsoids are drawn at the 50% probability level.
C33
O
C32
C29
C35
C34
C45
C31
C30
Co
C36
C37
C46
C39
C6
C40
C38
C5
C23
C1
C4
C3
C12
C2
C11
C17
C18
C24
Fig. 6. The structure of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–C14H9-9}] (3k); thermal ellipsoids are drawn at the 50% probability level.

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1191
ous aromatic aldehydes, and although LinBu deprotonated
both [Fe(g5-C5H5){g5-C5H4C(O)CH3}] and [Co(g4-
C4Ph4){g5-C5H4C(O)CH3}] to their respective enolate
anions, it proved to be unsatisfactory. Yields of the desired
products from aldol condensation reactions were low due,
in part at least, to the competing reaction involving nucle-
ophilic attack by a butyl anion on the acetyl carbonyl
group to give tertiary alcohol 4a (Scheme 4).
Consequently, we used an alkali metal hydride as the
deprotonating agent as described by Floriani et al. [5]. They
showed that KH promoted the aldol condensation between
[Fe(g5-C5H5){g5-C5H4C(O)CH3}] and [RCHO], and we
found that NaH promoted similar condensations of both
[Fe(g5-C5H5){g5-C5H4C(O)CH3}] and [Co(g4-C4Ph4){g5-
C5H4C(O)CH3}] with a range of aldehydes to give a,b-
unsaturated ketones, normally in good yields and without
side-products. We assume that the hydride anion deproto-
nates the acetylcyclopentadienyl complexes to their enolate
anions which are the active species (Scheme 5).
C34
C29
C35
O
C33
C8
C9
C32 C31
C10
C5
C30
C6
C7
Co
C23
C27
C25
C28
C1
C26
C4
C3
C24
C2
C11
C12
C13
C17
C18
C19
C20
C16
C14
C22
C21
C15
Fig. 7. The structure of [Co(g4-C4Ph4H2){g5-C5H4C(O)CH3}] (1c); ther-
mal ellipsoids are drawn at the 50% probability level.
3. Results and discussion
3.1. Spectra
The reactions investigated in the course of this work are
summarised in Scheme 1. They are the base-promoted reac-
tion of methyl ketones 1 with aldehydes 2 (the Claisen–
Schmidt variant of the aldol condensation reaction). The
initially formed aldols undergo facile dehydration to a,b-
unsaturated ketones 3 (e.g., Scheme 2). Compounds 3 are
reduced to a mixture of saturated ketones 1 and allylic
alcohols 4.
The IR spectra of [Co(g4-C4Ph4)(g5-C5H4CHO)],
[Co(g4-C4Ph4){g5-C5H4C(O)CH3}] and [(g4-C4Ph4)Co-
(g5-C5H4)C(O)CH2CH2(C10H7-1)] (1d), the saturated
counterpart of 3i, between 1500 and 1700 cmꢀ1 each show
a strong absorption band together with a number of weak
bands. The strong bands are found at 1683, 1672 and
1662 cmꢀ1, respectively, and are assigned to m(CO) vibra-
tions. They are normal for aromatic aldehydes and ketones
(cf. 1684 cmꢀ1 for C6H5CHO). In the corresponding
regions of the spectra of 3a–d, 3f and 3g–m there are nor-
mally two bands of comparable intensities at 1646–1654
and 1579–1596 cmꢀ1 which are attributed to the m(CO)
and m(C@C) modes of the C(@O)CH@CH– moieties. There
are other weak bands in the same region that are probably
due to the internal vibrations of the various end-groups.
We wished to use [Co(g4-C4Ph4){g5-C5H4C(O)CH3}]
(1a) as the ketone but, unlike ferrocene, [Co(g4-
C4Ph4)(g5-C5H5)] does not readily undergo a Friedel–
Crafts acylation on the five-membered ring to give
[Co(g4-C4Ph4){g5-C5H4C(O)CH3}] [11]. However, there
is a well-established route to this compound [2] using pre-
formed sodium acetylcyclopentadienide as outlined in
Scheme 3 and described in Section 2.
In our hands this not only gave [Co(g4-C4Ph4){g5-
C5H4C(O)CH3}] (1a), in modest yield, but it also gave a
second g5-C5H4C(O)CH3 complex in very low yields
of ca. 1% which X-ray diffraction showed to be [Co-
{g4-Ph(H)CC(Ph)C(Ph)C(H)Ph}{g5-C5H4C(O)CH3}] (1c),
with an g4-cis-1,2,3,4-tetraphenylbuta-1,3-diene ligand. It
is further discussed below.
O
OH
n
Bu
CH3
CH3
(i)
Co
Co
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
(ii)
1a
4a
NaOH in aqueous ethanol failed to bring about the
reaction of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] with vari-
Scheme 4. Conditions: (i) nBuLi; (ii) H2O.
O
O
O
CH3
CH3
(ii)
(i)
(iii)
Co
Co
Ph
Ph
Ph
Ph
CH3
Ph3P
PPh3
1a
Scheme 3. Conditions: (i) [MeCO2Me]; (ii) [Co(PPh3)3Cl]; (iii) [C2Ph2], D.

1192
C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
O
O
O
H
R
CH2
CH3
(ii)
(i)
Co
Co
Co
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
(iii)
3
1a
Scheme 5. Conditions: (i) NaH; (ii) RCHO; (iii) +H+, –H2O.
The spectra of the two pentadiene-1-one derivatives 3e and
3g show three strong absorption bands in this region which
are attributed to the m(CO)/m(C@C) vibrations of the
C(O)CH@CHACH@CH– group. In the case of 3e with
its C6H5 end-group, these three bands have wavenumbers
(relative intensities) of 1645 (10), 1595 (10), 1583 (15.5),
but for 3g where Ar = 4-Me2NC6H4 they are 1642 (10),
1602 (8.5), 1565 (23.6). These low frequencies and the high
intensity of the 1565 cmꢀ1 band of 3g are probably a conse-
quence of the presence of the donor Me2N group and a
strong Me2N–p-C(O) donor–acceptor interaction with its
consequent lessening of the bond-order alternation along
the p chain. A similar effect is observed when the IR spectra
of C6H5CHO (1684 cmꢀ1) and [4-Me2NC6H4CHO] {1661
(10), 1601 (13.5) cmꢀ1} are compared. The m(CO) vibration
of 3d (1654 cmꢀ1) has a much lower energy than that of
[C6H5–CH@CH–CHO] (1676 cmꢀ1) which suggests that
there is an electronic interaction between the C@O and
Co(g4-C4Ph4){g5-C5H4–} groups and that resonance forms
such as C contribute to an overall description of the elec-
tronic structures of 3 (Fig. 8).
3JHH coupling constants @CH–CH@ in 3e and 3g at ca.
11 Hz are normal but high, and the coupling constants
CH@CH across the double bonds (ca. 15 Hz) indicates
their trans configurations [12]. This is consistent with the
structures found in the solid state for 3d, 3e, 3g, 3h, 3i
and 3k, and suggests that these are retained in solution.
The attribution of the more deshielded of the ethylenic
proton resonances, generally found at d 7.2–8.5, to
–CH@CH–C(O) is consistent with the assignment of the
1H NMR spectrum of [Fe(g-C5H5)(g5-C5H4CH@CH–
CHO)] which is rendered unambiguous by the @CH–
CHO coupling. It has been confirmed for 3d by correlation
(HMBC) of C(O) with the d 6.69 resonance but not with
that at d 7.39, and by correlation (NOESY) of the d 6.69
resonance with the cyclopentadienyl resonance at d 5.34
(but not that at d 4.86) whilst the d 7.39 resonance corre-
lates with neither cyclopentadienyl resonance. This also is
consistent with the structures found in the solid state with
their cis-C@C–C@O moiety. These observations also aid
the assignment of the CH@CH–CH@CH resonances in
the spectra of 3e and 3g, and suggest that resonance forms
such as B and C (Fig. 8) also contribute to an overall
description of the electronic structures of 3.
The chemical shifts for the RCH@CHC(O) and
RCH@CHC(O) both decrease along the series R = Fe(g-
C5H5)(g5-C5H4–) < C6H5 < 1-C10H7 < 9-C14H9 < 1-C16H9
with a very marked increase in the deshielding of RCH in
going from R = Fe(g-C5H5)(g5-C5H4–), C6H5 and C4H3S
(d ca. 7.2) to the more highly annelated R = C10H7,
C14H9 and C16H9 (d 8.19–8.46). When R = Co(g4-
C4Ph4){g5-C5H4–} and C6H4NMe2-4, the RCH@CHC(O)
protons are less deshielded than those for other 3. When
the spectra of 3f and 3g are compared with those of
the related [Fe(g-C5H5){g5-C5H4–C(O)–CH@CH–C6H4-
NEt2-4}] and [Fe(g-C5H5){g5-C5H4–C(O)–(CH@CH)2–
C6H4NMe2-4}], respectively, the chemical shifts of the
indicated protons of the ferrocenyl complexes are always
The IR spectra of the alcohols 4a and [Co(g4-
C4Ph4){g5-C5H4CH2OH}] which possess neither C@O
nor C@C show only very weak bands between 1500 and
1700 cmꢀ1 as does the allylic alcohol [(g4-C4Ph4)Co{g5-
C5H4CH(OH)CH@CH–C10H7-1}] (4b).
The NMR spectra of 3 are consistent with their struc-
1
tures. All except 3c contain two multiplet H resonances
at ca. d 5.27–5.44 and 4.80–4.95 characteristic of the
Co{g4-C5H4C(O)–} group. The NOESY correlation for
3d confirms that the former are due to CaH. The most
intense resonances in all spectra are assignable to the phe-
1
nyl groups of the g4-C4Ph4 ligand which often obscure H
resonances of the CH@CH and R groups. However, the
former can be detected and sometimes identified by using
2-D techniques. The most useful resonances are those due
to the CH@CH and CH@CH–CH@CH protons. The
O
O
O
O
H
R
H
R
H
R
H
R
Co
Co
Co
Co
H
H
H
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
D
A
B
C
Fig. 8. Resonance forms of 3.

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1193
more deshielded then those of their Co(g4-C4Ph4){g5-
C5H4–} counterparts [1].
bands of 3 generally have lower energies than those of the
parent arene, but the difference becomes less marked as the
complexity of the aryl group increases.
In the 13C NMR spectra the assignment of the reso-
nances at d 140 and 123 to the CH@CH–C(O) and
CH@CH–C(O) atoms is consistent with the above argu-
ments and are further confirmed by HMBC and HSQC
correlations. These resonances are particularly easy to
identify unambiguously in the spectra of 3a, 3b and 3c
with their Co(g4-C4Ph4){g5-C5H4–} and Fe(g-C5H5){g5-
C5H4–} end-groups, but this is not always the case when
aromatic end-groups are present.
Absorption bands in the UV/Vis spectra of 3d (283,
385 nm), 3e (284, 344 nm) and 3i (257, 278, 347 nm) have
lower energies than those found in the spectra of their
organic counterparts such as [C6H5–CH@CHC(O)Me]
(222, 285 nm), [C6H5–CH@CH–CH@CHC(O)Me] (233,
319 nm) and [1-C10H7–CH@CHC(O)Me] (233, 251,
334 nm) [15]. This is consistent with the proposed
electronic interaction between the C@O and Co(g4-
C4Ph4){g5-C5H4–} groups and the contribution of
resonance forms such as C to an overall description of
the electronic structures of 3 (Fig. 8).
These observations suggest that 3 are typical donor–p-
acceptor chromophores with two donors. Increasing the
annellation of the aryl end-group means that the energy
of its LUMO falls and its HOMO increases so that the
HOMO and LUMO of the whole molecule becomes
increasingly dominated by the aryl end-group.
The NMR spectra of the alcohols 4a and 4b show four
1H and five 13C resonances as a consequence of the chiral
nature of the C(Me)(OH)(Bun) or C(H)(OH)(CH@CH–
C10H7) substituents on the cyclopentadienyl ligands. The
CH@CH coupling constant for 4b confirms that the trans
conformation about the double bond is retained on reduc-
tion of the carbonyl group of 3d.
The UV/Vis spectrum of [Co(g4-C4Ph4)(g5-C5H5)]
shows a very intense absorption band lying below
250 nm, a strong band at 274 nm and a very weak one
at 412 nm. That of [Co(g4-C4Ph4){g5-C5H4–C(O)Me}] is
similar but also has an added prominent shoulder at
318 nm. The spectrum of [Co(g4-C4Ph4){g5-C5H4C(O)-
CH@CH–C6H5}] (3d), is comparable to these in that it
has a very intense absorption band lying below 250 nm,
3.2. Structures of [Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–
R}], [R = (d) C6H5, (e) CH@CH–C6H5, (g) CH@CH–
C6H4N(CH3)2-4, (h) 3-C4H3S, (i) 1-C10H7, and (k)
9-C14H9]
an intense band at 285 (38000) nm (e/dm3 molꢀ1 cmꢀ1
,
X-ray diffraction has been used to determine the crys-
tal and molecular structures of 3d, 3e, 3g, 3h, 3i and 3k.
The structures and atom labelling are shown in Figs. 1–
6. All six molecules contain a Co atom sandwiched
between g4-C4Ph4 and g5-C5H4 ligands with the cyclo-
pentadienyl ligand as part of a C5H4–C(@O)–CH@CH–
R or C5H4–C(@O)–CH@CH–CH@CH–R system which
has an all-trans conformation. The two cyclic ligands
are almost parallel with dihedral angles of 0–3.9ꢁ
between them. They may be oriented such that one car-
bon bond of the cyclobutadiene is parallel to one of the
three different types of C–C bonds of the substituted
cyclopentadienyl ligand, (a)–(c) in Fig. 9, and or so that
one C atom of the cyclobutadiene eclipses a C atom of
the cyclopentadienyl ligand, (d)–(f) in Fig. 9. Compound
3k adopts orientation (a), 3i adopts orientation (b), 3d,
3g and 3h adopt orientation (c), and 3e adopts orienta-
tion (f).
in parentheses) with a marked shoulder at 310 nm and a
much weaker band at 405 nm (2200). When the conju-
gated linker is increased by –CH@CH–, 3e, an extra band
appears at 344 nm (38000). When C6H5 is replaced by 4-
Me2NC6H4 these bands red-shift to 418 nm (34000) for 3f
and to 431 nm (39900 br) for 3g, and become broader as
well as more intense. This behaviour is that expected for a
donor–p-acceptor system in which conjugated chain
length is increased and the donor is replaced by a stronger
one.
When the terminal phenyl group in 3d is replaced by 1-
naphthyl in 3i, the 285 nm band is replaced by two bands at
257 (47400) and 278 nm (44400) and the 310 nm shoulder
by a well-defined band at 347 nm (20800) which is absent
from the spectrum of (g4-C4Ph4)Co{g5-C5H4–CH-
(OH)CH@CH–C10H7-1} (4b). This suggests that the
354 nm band is due to p–p* electronic transitions involving
the molecule as a whole rather than just the aryl end-
groups. On this basis it seems reasonable to suggest that
the 310 nm shoulder of 3d also arises from related p–p*
transitions as does the 410 (16400) nm band in the anth-
racenyl derivative 3k, the pair of absorption bands at 389
(25800) and 419 (26100) nm in the spectrum of the pyrenyl
complex 3l, and the broad absorption band in the spectrum
of the perylenyl derivative 3m at 468 nm with its ill-defined
shoulders at 424 and 452 nm. However, it is clear that as
the annellation of the aryl end-group increases, the UV/
Vis spectra of 3 increasingly resemble those of the parent
polycyclic aromatic hydrocarbons [13], though without
well-defined vibrational fine structure [14]. The absorption
The Co–C(cyclopentadienyl) distances lie in the range
˚
2.0528(18)–2.102(5) A. They are always significantly longer
˚
than Co–C(cyclobutadiene) 1.9634(15)–2.0026(18) A and
show greater variation, but the differences between the
Co–centroid distances are much smaller and in the oppo-
˚
site sense with 1.675–1.687 A to the cyclopentadienyl
˚
ligand and 1.688–1.702 A to the cyclobutadiene. C–C bond
lengths within the cyclopentadienyl ring, 1.400(8)–
˚
1.441(6) A, are shorter than those within the cyclobutadi-
˚
ene, 1.456(3)–1.480(4) A, and the C–C(cyclopentadienyl)
˚
bonds to C*–C(O) are longer, 1.422(6)–1.440(7) A, than
˚
the other three, 1.400(8)–1.425(3) A, but shorter than C*–
˚
C(O), 1.469(2)–1.486(3) A.

1194
C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
a
b
c
d
e
f
Fig. 9. Relative orientations of cyclopentadienyl and cyclobutadiene ligands in 3.
The phenyl rings of the C4Ph4 ligands of [Co(g4-
C4Ph4){g5-C5H4-R}] where R = CHO, C(O)Me, CH(OH)
(But) [2] are all tilted with respect to the plane of the cyclo-
butadiene ligand and in the same sense so that these C4Ph4
constitute a four-bladed propeller. A similar arrangement
is observed in 3d and 3h with dihedral angles between
cyclobutadiene and phenyl rings of 28.9–36.6ꢁ and 29.0–
36.2ꢁ, respectively, and in 3k where the dihedral angles
are all different at 42.1ꢁ to C(5), 25.5ꢁ to C(11), 30.4ꢁ to
C(17) and 54.5ꢁ to C(23), as they are in 3g at 19.0ꢁ to
C(5), 57.5ꢁ to C(11), 47.1ꢁ to C(17) and 34.1ꢁ to C(23).
In 3e, on the other hand, the phenyl group which is almost
eclipsed by the cyclopentadienyl substituents, C(5)–C(10)
and its trans partner are almost coplanar with the C4 ring
(dihedral angles of 10.2ꢁ and 6.3ꢁ, respectively), whilst
the other two show dihedral angles of 51.3ꢁ and 67.6ꢁ with
respect to it and are tilted in opposite senses, i.e., they are
close to coplanar. These differing conformations of the
phenyl groups in the C4Ph4 ligand are probably the conse-
quence of the presence of the C(@O)–(CH@CH)n–R substi-
tuent on the cyclopentadienyl ligand which, together with
crystal packing forces, perturb the Ph–Ph steric
interactions.
whereas in 3e it is C(35)–C@C–C@C–C6H5 which consti-
tute a plane with no atom more 0.06 A from it with angles
˚
between this plane, and C(35)–C(@O)–C(29) and C5H4 of
17.4ꢁ and 16.1ꢁ, respectively. In the closely related 3g with
its strong donor end-group the angle between the
C6H4NMe2, C(29)–C(O)–CH@CH–CH@CH–C(39) and
C5H4 planes are, respectively, 17.1ꢁ and 10ꢁ. In 3d and 3h
the angles between the C5H4, C(5)–C(@O)–C(11), C(10)–
C@C–C(13) and phenyl/thiophenyl fragments are 8.4ꢁ,
10ꢁ, 7.6ꢁ and 7.5ꢁ, 8.2ꢁ, 13.1ꢁ, respectively. However, it is
in 3k that distortions from complete planarity are most
marked. C(29)(@O)–C@C is planar but the anthracenyl
C(37) lies below that plane and the dihedral angles between
it and the planar cyclopentadienyl and anthracenyl groups
are 14.8ꢁ and 51.1ꢁ, respectively. Although the non-planar-
ity in the case of 3d, 3e, 3h and 3i may be a consequence of
crystal packing forces, it seems reasonable to assume that
for 3k the distortions are due to intramolecular steric inter-
actions between the anthracenyl group and the C(36)
hydrogen atom on one hand, and the phenyl groups of
the C4Ph4 ligand on the other. In a related complex
Fe(g5-C5H5)(g5-C5H4–CH@CH-9-anthracenyl)
similar
anthracene–alkene steric interactions are relieved by rota-
tion about the C–C bond joining them so that there is an
angle of 62.58(14)ꢁ between alkene and anthracene planes
[17]. The presence of the phenyl groups of the tetraphenyl-
butadiene ligand prevents this in 3k.
The C(Cp)–C(@O)–CH@C*H–R and C(Cp)–C(@O)–
CH@CH–CH@C*H–R systems have trans configurations
about their C@C bonds. The C–C–C bond angles at the
carbonyl carbon C(34) are close to 118ꢁ whilst those at
C* are close to 126ꢁ. The remaining angles in the
–C(O)(CH@CH)n– lie between these two extremes. The
C–C and C@C bond lengths lie in the ranges 1.459(2)–
3.3. [Co{g4-Ph(H)C(Ph)C(Ph)C(H)Ph}{g5-
C5H4C(O)CH3}] (1c)
˚
˚
1.486(7) A and 1.330(2)–1.339(2) A, respectively. These
are comparable with the bond lengths found for [(g5-
C5H5)Fe{g5-C5H4–C(O)–(CH@CH)n–C6H4NEt2-4}] (n =
1, 2) and related systems [1,16]. The presence of the strong
donor group NMe2 in 3g does not greatly affect the bond
alternation in the C4H4 fragment as compared with 3g.
However, it does affect the phenyl ring which in 3e has
Compound 1c is formed during the preparation and
purification of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}] (1a),
and isolated in yields of ca. 1%. A related complex,
[Co{g4-Ph(H)CC(Ph)C(Ph)C(H)Ph}(g5-C5H5)], has been
reported and characterised previously. It was obtained on
the electrochemical reduction of [Co(g4-C4Ph4)(g5-C5H5)]
[18]. Consequently, it seems reasonable to assume that, in
our case, the tetraphenylbutadiene ligand was formed by
the reductive ring-opening of the g4-tetraphenylcyclobut-
adiene of 1a. TLC monitoring of the reaction that formed
1a suggested that 1c was not present in the reaction mixture
prior to chromatography but we cannot be completely cer-
tain of this because it is formed in such low yields. However,
acids have been shown to open the tetramethylcyclobutadi-
ene ligand of [Co(g4-C4Me4)(g5-C5H5)] to give the tetra-
methylbutenyl cation [Co{g3-C4Me4H}(g5-C5H5)]+ which
˚
C–C distances which vary randomly between 1.383(3) A
˚
and 1.402(3) A, whilst in 3g there is a quinonoid distortion
˚
˚
{1.405(3)–1.424(3) A versus 1.376(3), 1.377(3) A} and a
planar NMe2 group with a short C–NMe2 bond. This is
convincing evidence for charge separation along the conju-
gate chain (mesomer C in Fig. 8) with a positively charged
N atom.
The g5-C5H4–C(@O)–(CH@CH)nR moieties are not
planar. In 3i, C5H4–C(@O)–CH@CH and naphthyl frag-
ments are planar with an angle of 31ꢁ between them,

C. Behrendt et al. / Journal of Organometallic Chemistry 691 (2006) 1183–1196
1195
can be reduced by hydride sources to the tetramethylbuta-
1,3-diene complex [Co{g4-Me(H)CC(Me)C(Me)C(H)-
Me}(g5-C5H5)] [19]. Consequently, it is possible that 1c
was formed from 1a in a similar way during work-up of
the reaction mixture, perhaps with the acid coming from
the dichloromethane used in chromatography.
are less acidic than those in [Fe(g5-C5H5){g5-
C5H4C(O)CH3}] or [C6H5C(O)CH3] and can only be
removed by a stronger base such as NaH. This promotes
the condensation of [Co(g4-C4Ph4){g5-C5H4C(O)CH3}]
with aromatic aldehydes, [RCHO] (2a–m), to give
[Co(g4-C4Ph4){g5-C5H4C(O)CH@CH–R}] and [Co(g4-
C4Ph4){g5-C5H4C(O)CH@CH–CH@CH–R}] (3), all of
which have a trans configuration about their C@C dou-
ble bonds. These compounds are very similar to their
ferrocenyl counterparts, [Fe(g5-C5H5){g5-C5H4C(O)CH-
@CH–R}] and [Fe(g5-C5H5){g5-C5H4C(O)CH@CH–
CH@CH–R}], respectively. Although their spectroscopic
properties suggest that 3 are donor–acceptor–donor sys-
tems in which the Co(g4-C4Ph4){g5-C5H4–} and aryl
groups act as donors to the carbonyl groups, the elec-
tronic interactions appear to be relatively limited and
do not result in planar molecules or single bond–double
bond equalisation.
The IR and NMR spectra of 1c are consistent with its
structure but do not define it. The m(CO) vibration of the
acetyl group gives rise to an IR absorption band at
1662 cmꢀ1 compared with 1672 cmꢀ1 for 1a and
1
1684 cmꢀ1 for benzaldehyde. Both the H and 13C NMR
spectra show the expected resonances due to the acetylcy-
clopentadienyl ligand, two types of phenyl groups and
the CH@C–C@CH part of the g4-butadiene ligand (cf.
Ref. [20]).
The molecular structure of 1c is similar to that
of [Co{g4-Ph(H)CC(Ph)C(Ph)C(H)Ph}(g5-C5H5)] [20,21].
It, together with its atom labelling, is shown in Fig. 7.
The Co atom is sandwiched between a g5–acetylcyclopen-
tadienyl and
a
g4-1,3-tetraphenylbutadiene ligand.
5. Supplementary material
Although the C(1)–C(4) and C(29)–C(33) moieties of the
cyclopentadienyl and butadiene ligands are planar, they
are not parallel, and there is a dihedral angle of 14.7ꢁ
between them. The terminal Ph-C–H moieties of the buta-
diene ligand are not coplanar with the C(1)–C(4) plane
but make dihedral angles of 33.7ꢁ and 35.4ꢁ with it so
that both Ph groups adopt the exo configuration and
are tilted towards the cyclopentadienyl ligand. In contrast,
the ipso C atoms of the central Ph groups lie close to the
C(1)–C(4) plane though the rings are tilted with respect to
it by 64.0ꢁ for C(11) and 77.3ꢁ for C(17). The Co–C(buta-
Crystallographic data for the structural analyses have
been deposited at the Cambridge Crystallographic Data
Centre and allocated the deposition numbers: CCDC
285138 (1c), 285136 (3d), 285139 (3e), 285142 (3g),
285137 (3h), 285141 (3i), and 285140 (3k).
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