Stilbene analogues incorporating the Co(η4-C 4Ph4)(η5-C5H4-) end group

Article abstract of DOI:10.1016/j.jorganchem.2011.01.017

A number of organometallic stilbenes of the general type [Co(η⁴-C₄Ph₄)(η⁵-C ₅H₄CHCHR] are reported where R is C₆H ₄X-4 (X = H, OMe, Br, NO₂), 1-naphthyl, 9-anthryl, 1-pyrenyl, (η⁵-C₅H₄)Co(η⁴- C₄Ph₄), and (η⁵-C₅H ₄)Fe(η⁵-C₅H₄Y) {Y = CHO, CHC(CN)₂ and CHCHC₅H₄-η⁵) Co(η⁴-C₄Ph₄)}. They were prepared by Wittig or Horner-Wadsworth-Emmons reactions which yield both E and Z or only E products respectively. The isomers were separated and all compounds characterised by standard spectroscopic techniques as well as by X-ray diffraction methods in many cases. The electrochemistry of the stilbene analogues in dichloromethane solution is also reported. In most, the (η⁵-C₅H₄)Co(η⁴-C ₄Ph₄) functional group undergoes a reversible one-electron oxidation. For those molecules that also include (η⁵-C ₅H₄)Fe(η⁵-C₅H₄Y), this is preceded by the reversible oxidation of the ferrocenyl group. Spectroscopic and structural data suggests that for most compounds there is little electronic interaction between Co(η⁴-C₄Ph ₄)(η⁵-C₅H₄) and the R end groups which are effectively independent of one another. The only exceptions to this are Z and E-[Co(η⁴-C₄Ph₄) (η⁵-C₅H₄CHCHC₆H ₄NO₂-4], and [Co(η⁴-C₄Ph ₄)(η⁵-C₅H₄CHCHC ₅H₄-η⁵)Fe{η⁵-C ₅H₄CHC(CN)₂}] where the electronic spectra are respectively consistent with a significant Co(η⁴-C ₄Ph₄)(η⁵-C₅H₄)/ NO₂ donor/acceptor interaction and a less significant Co(η⁴-C₄Ph₄)(η⁵-C ₅H₄)/C(CN)₂ one. However, OTTLE studies show that in the electronic spectra of [Co(η⁴-C₄Ph ₄)(η⁵-C₅H₄CHCHR]⁺ there are low energy absorption bands (950-1800 nm) which are attributed to R → Co(η⁴-C₄Ph₄)(η⁵- C₅H₄)⁺ or, when R is a ferrocenyl-base group, Co(η⁴-C₄Ph₄)(η⁵-C ₅H₄) → (η⁵-C₅H ₄)Fe(η⁵-C₅H₄Y)⁺ charge transfer transitions. The ferrocenyl compounds undergo cis/trans isomerisation on the OTTLE experiment timescale.

Full text of DOI:10.1016/j.jorganchem.2011.01.017

Journal of Organometallic Chemistry 696 (2011) 1510e1527
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Stilbene analogues incorporating the Co(
h
4-C4Ph4)(
h
5-C5H4-) end group
,
a
a
a
Paul O’Donohue a, C. John McAdam b , Donagh Courtney , Yannick Ortin , Helge Müller-Bunz ,
*
Anthony R. Manning a, Michael J. McGlincheya, Jim Simpson b
a School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
b Department of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
a r t i c l e i n f o
a b s t r a c t
A number of organometallic stilbenes of the general type [Co(h h
4-C4Ph4)(
where R is C6H4X-4 (X ¼ H, OMe, Br, NO2), 1-naphthyl, 9-anthryl, 1-pyrenyl, (
5-C5H4CH]CHR] are reported
5-C5H4)Co( 4-C4Ph4), and
h h
5)Co( 4-C4Ph4)}. They were prepared
Article history:
Received 21 November 2010
Received in revised form
21 December 2010
h
h
(
h
5-C5H4)Fe(
h
5-C5H4Y) {Y ¼ CHO, CH]C(CN)2 and CH]CHC5H4-
by Wittig or HornereWadswortheEmmons reactions which yield both E and Z or only E products
respectively. The isomers were separated and all compounds characterised by standard spectroscopic
techniques as well as by X-ray diffraction methods in many cases. The electrochemistry of the stilbene
Accepted 11 January 2011
Keywords:
Cobalt
Tetraphenycyclobutadiene
Stilbene
Ferrocenyl
analogues in dichloromethane solution is also reported. In most, the (
group undergoes a reversible one-electron oxidation. For those molecules that also include (
5-C5H4Y), this is preceded by the reversible oxidation of the ferrocenyl group. Spectroscopic and
structural data suggests that for most compounds there is little electronic interaction between Co(h4
C4Ph4)(
5-C5H4) and the R end groups which are effectively independent of one another. The only
exceptions to this are and E-[Co(
4-C4Ph4)( 5-C5H4CH]CHC6H4NO2-4], and [Co( 4-C4Ph4)(h5
C5H4CH]CHC5H4-
5)Fe{ 5-C5H4CH]C(CN)2}] where the electronic spectra are respectively consistent
with a significant Co(
4-C4Ph4)(
5-C5H4)/C(CN)2 one. However, OTTLE studies show that in the electronic spectra of [Co(h4
h
5-C5H4)Co(
h
4-C4Ph4) functional
5-C5H4)Fe
h
(
h
-
h
Z
h
h
h
-
h
h
h
h
5-C5H4)/NO2 donor/acceptor interaction and a less significant Co(h4
-
-
C4Ph4)(
C4Ph4)(
h
h
5-C5H4CH]CHR]þ there are low energy absorption bands (950e1800 nm) which are attributed
to R / Co(
C5H4)Fe(
5-C5H4Y)þ charge transfer transitions. The ferrocenyl compounds undergo cis/trans isomer-
isation on the OTTLE experiment timescale.
h h h h -
4-C4Ph4)( 5-C5H4)þ or, when R is a ferrocenyl-base group, Co( 4-C4Ph4)( 5-C5H4) / (h5
h
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
groups. We have reported detailed spectroscopic, structural, elec-
trochemical and theoretical studies on [Fe(
5-C5H5)( 5-C5H4CH]
h
h
Stilbenes and stilbenoids are an important class of compounds
based on 1,2-diarylethenes [1e4]. Their photochemical and pho-
tophysical properties have been studied in detail [1], and they have
many uses and roles based on these properties. For example, they
CHR)] derivatives where R is phenyl, 1-naphthyl, 2-naphthyl, 9-
phenanthryl, 9-anthryl,1-pyrenyl and 3-perylenyl) [7,8], and on the
mixed metal stilbenoid [Fe(
4-C4Ph4)] [9]. Herein we describe the preparation, spectra,
structures and electrochemisty of [Co(
4-C4Ph4)( 5-C5H4CH]
CHR)] complexes where R is C6H4X-4 (X ¼ H, OMe, Br, NO2), 1-
h h h
5-C5H5)( 5-C5H4CH]CHC5H4- 5)Co
(h
act as the
p
-spacer in D(onor)-p-A(cceptor) systems such as the
h
h
NLO-active DANS, 4-Me2NC6H4CH]CHC6H4NO2-40 [5]; they form
the basis of many dyes and optical brighteners (e.g. DAS or DAST,
4,40-diaminostilbene-2,20-disulphonic acid) [2,3]; many are present
naturally in plants (e.g. resveratrol or trans-3,5,40-trihydrox-
ystilbene) [4]; and others are synthetic oestrogens (e.g. diethyl-
stilbestrol) [6].
naphthyl, 9-anthryl, 1-pyrenyl, (h h
5-C5H4)Co( 4-C4Ph4), and some
(h
5-C5H4)Fe(
CHC5H4-
5)-Co(
C4Ph4)(
[Co(
4-C4Ph4){
h
5-C5H4X) where X ¼ CHO, CH]C(CN)2 and (CH]
h
h
h -
4-C4Ph4). Previously we have described E-[Co(h4
5-C5H4CMe]CMeC5H4-
h h
5)Co( 4-C4Ph4)] prepared from
h
h
5-C5H4C(O)Me}] by McMurry coupling [10].
Of particular interest to us are those stilbenes where one or both
aryl groups have been replaced by pseudo-aromatic organometallic
2. Experimental
Unless otherwise stated, all reactions were carried out at room
temperature under nitrogen in dried and deoxygenated solvents.
* Corresponding author. Tel.: þ64 3 479 4897; fax: þ64 3 479 7906.
E-mail address: mcadamj@alkali.otago.ac.nz (C.J. McAdam).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.01.017

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1511
Previously reported procedures or closely related ones were used
toprepare [Co(
4-C4Ph4)( 5-C5H4CHO)] (1) [11 and refstherein], [Co
dichloromethane-pentane to give Z-4d (0.092 g, 30%) and E-4d
h
h
(0.122 g, 40%).
(
(
(
h
h
h
4-C4Ph4){
h
5-C5H4CH2P(O)(OEt)2}] (2) [12], [Co(
h
4-C4Ph4)
[Co(h
4-C4Ph4)(
h
5-C5H4CH]CHC10H7-1)] (C10H7 ¼ naphthyl), 4e.
5-C5H4CH2PPh3)]Cl, [3]Cl, [12], [FcCH2PPh3]I, {Fc ¼ ferrocenyl ¼ Fe
From n-BuLi in hexane (0.3 ml, 1.2 mmol), [1-C10H7CH2PPh3]Cl
5-C5H5)(
h
5-C5H4-} [13], 9-anthracenecarboxaldehyde [14],
(0.780 g, 1.6 mmol) and [Co(h h
4-C4Ph4)( 5-C5H4CHO)] (0.300 g,
1-pyrenecarboxaldehyde [15], and [Fe(
h
5-C5H4CHO)2] [16]. Other
0.59 mmol). The isomers were separated by column chromatog-
raphy on silica (cyclohexane-toluene; 9/1) and crystallised from
dichloromethane-pentane to give Z-4e (0.033 g, 9%) and E-4e
(0.109 g, 29%).
reagents were purchased from commercial sources unless other-
wise stated.
IR spectra were recorded on a Perkin Elmer Paragon 1000 FTIR
spectrometer, and NMR spectra on Varian Inova 300, 400 or
500 MHz spectrometers. 1H (300 and 400 MHz), and 13C (75 and
100 MHz) chemical shifts are reported downfield from tetrame-
thylsilane as the internal standard. All coupling constants are given
in Hertz. UV/Visible spectra were recorded on a UNICAM UV2
spectrometer. Elemental analyses were performed in the Micro-
analytical Laboratory, University College Dublin.
2.2. Preparation of [Co(
h
4-C4Ph4)(
h
5-C5H4CH]CHR)], [R ¼ 9-
C14H9 ¼ 9-anthryl, 4f; 1-C16H9 ¼ 1-pyrenyl, 4g; and Co(
h
4-C4Ph4)
(h
5-C5H4-), 5], and [{Co(
h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)}2Fe], 9,
by the HornereWadswortheEmmons reaction
h h
To a cooled solution (ꢁ78 ꢀC) of [Co( 4-C4Ph4){ 5-C5H4CH2P(O)
Cyclic voltammetric experiments were carried out at 20 ꢀC in
CH2Cl2 solutions degassed with nitrogen. A three-electrode cell was
used with Cypress Systems 1 mm diameter Pt or 1.4 mm glassy
carbon working, Ag/AgCl reference and platinum wire auxiliary
electrodes. Solutions were w10ꢁ3 M in electroactive material and
contained 0.1 M [Bu4N][PF6] as the supporting electrolyte. Vol-
tammograms were recorded using a Powerlab/4sp computer-
controlled potentiostat. All potentials are referenced to the
(OEt)2}], 2, (0.320 g, 0.50 mmol) in dry THF (35 ml) was added t-BuLi
in pentane (0.31 ml, 0.40 mmol) and, after 1 h, 9-C14H9CHO (0.100 g,
0.48 mmol). The mixture was stirred for a further hour, allowed to
return to room temperature and stirred overnight. The reaction was
quenched with water and extracted with dichloromethane. The
organic layer was separated, dried over MgSO4, filtered and column
chromatographed on silica (dichloromethane-pentane; 1/2). The
first band gave red-brown crystals which were precipitated from
a dichloromethane-pentane solution and identified as E-4f (0.090 g,
33%). The second band gave an orange powder from a dichloro-
methane-pentane solution which was identified as 5 (0.018 g, 4%).
The same procedure was used to prepare:-
reversible formal potential (taken as Eꢀ ¼ 0.00 V) for the [Fe(h5
-
C5Me5)2]þ/0 process [17] where Eꢀ was calculated from the average
of the oxidation and reduction peak potentials under conditions of
cyclic voltammetry. Under the same conditions, Eꢀ calculated for
[Fe(h
5-C5H5)2]þ/0 was 0.55 V.
[Co(h
4-C4Ph4)(
h
5-C5H4CH]CHC16H9-1)] (C16H9-1 ¼ 1-pyrenyl),
4g. From t-BuLi in pentane (0.24 ml, 0.4 mmol), [Co(h -
4-C4Ph4){h5
C5H4CH2P(O)(OEt)2}] (0.320 g, 0.5 mmol), and 1-C16H9CHO
(0.092 g, 0.4 mmol). The products were separated by column
chromatography on silica (pentane-toluene; 3/2), and crystallised
from dichloromethane-pentane solutions to give red-brown crys-
tals of E-4g (0.055 g, 19%) and orange 5 (0.017 g, 4%).
2.1. Preparation of [Co(
h
4-C4Ph4)(
h
5-C5H4CH]CHC6H4X-4 )], (X ¼ H,
4a; OMe, 4b; Br, 4c; NO2, 4d), and [Co(h h
4-C4Ph4)( 5-C5H4CH]
CHC10H7-1 )] (1-C10H7 ¼ 1-naphthyl), 4e by the Wittig reaction
n-BuLi in hexane (0.87 ml,1.38 mmol) was added to a solution of
[PhCH2PPh3]Br (0.897 g, 2.1 mmol) in dry THF (50 ml) at ꢁ78 ꢀC,
and the mixture stirred at this temperature for 30 min. It was
[Co(
BuLiinpentane (0.22 ml, 0.38 mmol), [Co(
(OEt)2}] (0.260 g, 0.41 mmol) and [Co(
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
h
h
5)Co(
4-C4Ph4){
4-C4Ph4)(
h
4-C4Ph4)], 5. From t-
5-C5H4CH2P(O)
5-C5H4CHO]
h
h
h
allowed to warm to room temperature and solid [Co(h -
4-C4Ph4)(h5
(0.254 g, 0.5 mmol). The product was purified by column chroma-
tography on silica (dichloromethane-pentane; 3/5) and orange crys-
tals of E-5 grown from a chloroform-pentane solution (0.065 g, 16%).
C5H4CHO)], 1, (0.350 g, 0.69 mmol) added. The mixture was
refluxed overnight, quenched with water and extracted with
CH2Cl2. The organic layer was separated, dried over magnesium
sulphate and concentrated. The isomers were separated by column
chromatography on silica (cyclohexane-toluene; 9:1) and crystal-
lised from a dichloromethane-pentane solution to give Z-4a (Yield
0.105 g, 26%) and E-4a (Yield 0.165 g, 41%).
[{Co(
pentane (0.11 ml, 0.18 mmol), [Co(
(OEt)2}] (0.130 g, 0.21 mmol) and [Fe(
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
h
5)}2 Fe], 9. From t-BuLi in
4-C4Ph4){ 5-C5H4CH2P(O)
5-C5H4CHO)2] (0.025 g,
h
h
h
0.1mmol). Two products were separated by chromatography on
silica (dichloromethane-pentane; 3/5) and crystallised from
dichloromethane-pentane solutions to give orange-red E,E-9
(0.025 g, 21%) and orange 5 (0.007 g, 4%).
The same procedure was used to prepare, separate and purify
the following:
[Co(
hexane (0.52 ml, 0.83 mmol), [4-MeOC6H4CH2PPh3]Br (0.519 g,
1.24 mmol) and [Co(
4-C4Ph4)( 5-C5H4CHO)] (0.210 g, 0.41 mmol).
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4OMe-4)], 4b. From n-BuLi in
h
h
2.3. Preparation of [Co(
C5H4CHO)], 7, by the Wittig reaction
h h h -
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe(h5
The isomers were separated by column chromatography on silica
(cyclohexane-toluene; 4/1) and crystallised from dichloromethane-
pentane to give Z-4b (34%) and E-4b (33%).
To
a solution of [Co(h h
4-C4Ph4)( 5-C5H4CH2PPh3)]Cl, [3]Cl,
[Co(
hexane (0.43 ml, 0.71 mmol), [4-BrC6H4CH2PPh3]Br (0.403 g,
0.79 mmol) and [Co(
4-C4Ph4)( 5-C5H4CHO)] (0.200 g, 0.39 mmol).
h
4-C4Ph4)(
h
5-C5H4CH]CHC6H4Br-4)], 4c. From n-BuLi in
(0.40 g 0.51 mmol) in dry THF (15 ml) at ꢁ78 ꢀC was added n-BuLi
in hexane (0.31 ml, 0.45mmol) and, after 2 h, solid [Fe(h5
-
h
h
C5H4CHO)2] (0.120 g 0.51 mmol). After a further 1 h, the mixture
was warmed to room temperature and stirred overnight. It was
quenched with water and extracted with dichloromethane. The
organic layer was separated, dried over magnesium sulphate,
filtered, concentrated and chromatographed on silica (dichloro-
methane). One red band was obtained which was shown to be
a mixture of Z and E isomers of 7 by NMR spectroscopy. Red-orange
crystals of the pure Z isomer precipitated from a dichloromethane-
pentane solution (0.110 g, 34%).
The isomers were separated by column chromatography on silica
(pentane-dichloromethane; 5/1) and crystallised from dichloro-
methane-pentane to give Z-4c (0.093 g, 36%) and E-4c (0.098 g, 38%).
[Co(
hexane (0.63 ml, 1.0 mmol), [4-NO2C6H4CH2PPh3]Br (0.576 g,
1.0 mmol) and [Co(
4-C4Ph4)( 5-C5H4CHO)] (0.200 g, 0.39 mmol)
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4NO2-4)], 4d. From n-BuLi in
h
h
(0.25 g, 0.49 mmol). The isomers were separated by column chro-
matography on silica (pentane-toluene; 1/1) and crystallised from

1512
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
Table 1a
Crystal data for E-4a, E-4b, E-4c, E-4d, and E-4e.
Compound
E-4a
E-4b
E-4c
E-4d
E-4e
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
Unit cell dimensions (Å), (ꢀ) a ¼ 11.3993(15)
b ¼ 15.383(2)
C41H31Co
582.59
293(2) K
0.71073 Å
Monoclinic
P21/c
C42H33OCo
612.61
293(2) K
0.71073 Å
Triclinic
Pe1
C41H30CoBr
661.49
100(2) K
0.71073 Å
Monoclinic
P21/c
C41H30NO2Co
627.59
100(2) K
0.71073 Å
Triclinic
Pe1
C45H33Co
632.64
293(2) K
0.71073 Å
Triclinic
Pe1
a ¼ 10.3708(15)
b ¼ 11.4773(17)
c ¼ 14.889(2)
a ¼ 8.7371(7)
b ¼ 57.863(5)
c ¼ 17.7746(15)
a ¼ 16.4543(9)
b ¼ 17.3347(10)
c ¼ 19.1133(11)
a ¼ 11.5130(14)
b ¼ 12.1254(15)
c ¼ 12.2446(15)
c ¼ 16.962(2)
a
b
g
¼ 90
a
b
g
¼ 79.517(2)
¼ 70.378(2)
¼ 69.945(2)
a
b
g
¼ 90
a
b
g
¼ 68.677(2)
¼ 64.746(2)
¼ 71.731(2)
a
b
g
¼ 84.916(2)
¼ 82.227(2)
¼ 71.843(2)
¼ 98.457(2)
¼ 90
¼ 90.581(2)
¼ 90
Volume (Å3)
Z
2942.0(7)
4
1563.6(4)
2
8985.6(13)
12
4511.3(4)
6
1607.3(3)
2
Density calculated (Mg/m3) 1.315
1.301
1.467
1.386
1.307
Absorption coefficient
(mmꢁ1
F(000)
Crystal size (mm)
0.612 mmꢁ1
0.582 mmꢁ1
1.936 mmꢁ1
0.610 mmꢁ1
0.566 mmꢁ1
)
1216
1.00 ꢂ 0.10 ꢂ 0.01
640
4056
1956
660
0.60 ꢂ 0.40 ꢂ 0.20
1.89e28.49ꢀ.
ꢁ13<¼h<¼13,
ꢁ14<¼k<¼15,
ꢁ19<¼l<¼19
26597
0.50 ꢂ 0.20 ꢂ 0.03
1.20e20.84ꢀ.
ꢁ8<¼h<¼8,
ꢁ57<¼k<¼57,
ꢁ16<¼l<¼17
32919
0.60 ꢂ 0.60 ꢂ 0.20
0.40 ꢂ 0.30 ꢂ 0.30
1.68e28.32ꢀ.
ꢁ15<¼h<¼14,
ꢁ16<¼k<¼16,
ꢁ16<¼l<¼16
13851
q
range for data collection 1.80e24.00ꢀ.
1.28e39.35ꢀ.
Index ranges
ꢁ13<¼h<¼13,
ꢁ17<¼k<¼17,
ꢁ19<¼l<¼19
18777
ꢁ29<¼h<¼29,
ꢁ30<¼k<¼30,
ꢁ33<¼l<¼33
183650
Reflections collected
Independent reflections
4607 [R(int) ¼ 0.0509]
7317 [R(int) ¼ 0.0266]
9409 [R(int) ¼ 0.0449]
51066 [R(int) ¼ 0.0224]
7233 [R(int) ¼ 0.0166]
Completeness to
q
¼ 24.0ꢀ 100.0%
92.5%
99.7%
95.1%
90.4%
Absorption correction
Semieempirical from
equivalents
Numerical
Semieempirical from
equivalents
Semieempirical from
equivalents
Numerical
Max. and min. transmission 0.9939 and 0.7215
Refinement method
0.8926 and 0.7217
0.9442 and 0.7129
0.8878 and 0.7484
0.8486 and 0.8053
Fullematrix least-squares Fullematrix least-squares Fullematrix least-squares Fullematrix least-squares Fullematrix least-squares
on F2
Data/restraints/parameters 4607/0/379
Goodnesseofefit on F2
1.006
on F2
7317/0/529
1.052
on F2
9409/534/1162
1.220
on F2
51066/0/1576
1.035
on F2
7233/0/547
1.069
Final R indices [I > 2sigma R1 ¼ 0.0452, wR2 ¼ 0.0958 R1 ¼ 0.0409,
R1 ¼ 0.0644, wR2 ¼ 0.1287 R1 ¼ 0.0451, wR2 ¼ 0.1218 R1 ¼ 0.0472,
(I)]
wR2 ¼ 0.1073
R1 ¼ 0.0744, wR2 ¼ 0.1055 R1 ¼ 0.0485,
wR2 ¼ 0.1133
wR2 ¼ 0.1112
R1 ¼ 0.0769, wR2 ¼ 0.1330 R1 ¼ 0.0600, wR2 ¼ 0.1317 R1 ¼ 0.0568,
wR2 ¼ 0.1176
R indices (all data)
Largest diff. peak and hole 0.359 and ꢁ0.190
0.661 and ꢁ0.201
1.249 and ꢁ0.592
1.851 and ꢁ0.500
0.456 and ꢁ0.159
(e.Åꢁ3
)
2.4. Preparation of [Co(
C5H4CH]C(CN)2}], 8
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
h
5)Fe{h5
-
2.5.2. E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC6H5)], E-4a
m.p. 229e231 ꢀC (Found: C 84.43, H 5.41, Co 9.96; C41H31Co
requires C 84.51, H 5.37, Co 10.11%). IR
y
/cmꢁ1
:
y
(C]C) 1598, 1499
A drop of triethylamine was added to a solution of Z-[Co(h4
C4Ph4)(
5-C5H4CH]CHC5H4- 5)Fe( 5-C5H4CHO)], Z-7, (0.030 g,
-
(CH2Cl2); y d 7.32e7.10 (m,
(C]C) 1595, 1497 (KBr). 1H NMR (CDCl3):
h
h
h
25H, Ph, C6H5); 6.31 and 6.13 [2 ꢂ (d, 3JH,H 16 Hz, 1H, CH]CH)]; 4.66
0.042 mmol) and malononitrile (0.003 g, 0.045 mmol) in
dichloromethane (10 ml), and the mixture was stirred overnight.
It was filtered through a small pad of Celite and the filtrate
chromatographed on silica (pentane-dichloromethane; 2/1). The
product was eluted as a red band and dark red crystals of 8 were
obtained from a pentane-dichloromethane solution (0.026 g,
81%).
and 4.58 [2 ꢂ (m, 2H, C5H4)]. 13C NMR (CDCl3):
d 136.6 (Ci, C6H5),
135.0, 127.7, 126.9 and 125.1 (C4Ph4); 127.8 and 122.6 (CH]CH);
127.3, 124.9 and 126.8 (CH, C6H5); 95.6 (Cipso, C5H4), 84.8 and 81.1
(CH, C5H4); 75.6 (C4Ph4). lmax/nm (
(CH2Cl2): 248 (43); 274 (47); 309 (sh, 31), 340 (sh, 27), 402 (sh, 7.7);
(CH3CN): 248 (38), 272 (42), 289 (30), 337 (sh, 24), 399 (sh, 7.0).
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1
)
2.5.3. Z-[Co(
m.p. 140e143 ꢀC (Found: C 81.99, H 5.35, Co 9.38; C42H33OCo
requires C 82.33, H 5.44, Co 9.62%). IR (C]C) 1602, 1596,
/cmꢁ1
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4OMe-4)], Z-4b
y
: y
2.5. Characterisation
1508,1498 (KBr). 1H NMR (CDCl3):
d 7.51e7.13 (m, 20H, Ph); 7.10 and
6.74 [2 ꢂ (d, 3JH,H 9 Hz, 2H, C6H4OMe)]; 6.19 and 5.55 [2 ꢂ (d, 3JH,H
2.5.1. Z-[Co(
m.p. 157e159 ꢀC (Found: C 84.13, H 5.32, Co 10.50; C41H31Co
h h
4-C4Ph4)( 5-C5H4CH]CHC6H5)], Z-4a
12 Hz, 1H, CH]CH)]; 4.54 (m, 4H, C5H4). 13C NMR (CDCl3):
d 158.4
requires C 84.51, H 5.37, Co 10.11%). IR y : y(C]C) 1597, 1498
/cmꢁ1
(Cp, C6H4OMe); 136.2, 128.9, 128.0, 126.2 (C4Ph4); 130.5 (Ci,
C6H4OMe); 130.0 and 113.5 (Co/m, C6H4OMe); 129.0 and 123.3 (CH]
CH); 93.7 (Cipso, C5H4); 84.3 and 83.0 (CH, C5H4); 75.2 (C4Ph4); 55.3
(CH2Cl2);
y
(C]C) 1597, 1498 (KBr). 1H NMR (CDCl3):
d
7.40e7.10
3
(m, 25H, Ph, C6H5); 6.24 and 5.64 [2 ꢂ (d, JH,H 12 Hz, 1H, CH]
(CH3). lmax/nm (
(30), 398 (sh, 5.6); (CH3CN): 255 (39), 305 (30), 388 (sh, 6.8).
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 252 (41), 309
CH)]; 4.53 (s, 4H, C5H4). 13C NMR (CDCl3):
d 138.1 (Ci, C6H5); 136.2,
128.9, 128.0 and 126.2 (C4Ph4); 129.3, 128.8 and 128.1 (CH, C6H5);
126.8 and 124.7 (CH]CH); 93.3 (Cipso, C5H4), 84.4 and 83.1 (CH,
C5H4); 75.3 (C4Ph4). lmax/nm (
241 (33), 267 (30), 310 (27), 398 (4.1); (CH3CN): 272 (30), 298 (30),
390 (6.4).
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
2.5.4. E-[Co(
m.p. 168e170 ꢀC (Found: C 82.39, H 5.47, Co 9.55; C42H33OCo
requires C 82.33, H 5.44, Co 9.62%). IR (C]C) 1596, 1512,
/cmꢁ1
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4OMe-4)], E-4b
e
y
: y

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1513
Table 1b
Crystal data for E-4f, E-4g, E-5.CHCl3, Z-7.CH2Cl2, Z-8, and E,E-9.
Compound
E-4f
E-4g
E-5.CHCl3
Z-7.CH2Cl2
Z-8
E,E-9
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C
49H35Co
C51H35Co
706.72
293(2) K
0.71073 Å
Triclinic
Pe1
C69H51Cl3Co2
1104.31
100(2) K
0.71073 Å
Triclinic
Pe1
C47 H37OCl2FeCo
803.45
293(2) K
0.71073 Å
Monoclinic
P21/n
C49H35N2CoFe
766.57
293(2) K
0.71073 Å
Orthorhombic
P212121
C80H60Co2Fe
1194.99
100(2) K
0.71073 Å
Triclinic
Pe1
682.70
100(2) K
0.71073 Å
Monoclinic
P21/c
Unit cell
dimensions
(Å) a ¼ 10.169(2)
b ¼ 28.520(6)
c ¼ 12.667(3)
a ¼ 12.802(2)
b ¼ 17.526(3)
c ¼ 18.123(3)
a ¼ 12.7089(8)
b ¼ 14.2356(9)
c ¼ 14.5400(9)
a ¼ 10.0740(7)
b ¼ 25.3200(17)
c ¼ 14.7185(10)
a ¼ 9.3446(10)
b ¼ 10.6383(12)
c ¼ 37.476(4)
a ¼ 10.4172(10)
b ¼ 13.1619(13)
c ¼ 21.528(2)
(ꢀ)
a
b
g
¼ 90
a
b
g
¼ 103.485(3)
¼ 106.953(3)
¼ 103.971(3)
a
b
g
¼ 91.055(1)
¼ 98.951(1)
¼ 94.319(1)
a
b
g
¼ 90
a
b
g
¼ 90
¼ 90
¼ 90
a
b
g
¼ 92.338(2)
¼ 93.572(2)
¼ 98.429(2)
¼ 108.248(4)
¼ 90
¼ 94.8980(10)
¼ 90
Volume (Å3)
Z
3488.8(12)
4
3566.8(10)
4
2589.9(3)
2
3740.6(4)
4
3725.5(7)
4
2910.5(5)
2
Density calculated 1.300
1.316
1.416
1.427
1.367
1.364
(Mg/m3)
Absorption
coefficient
F(000)
0.527 mmꢁ1
1424
0.518 mmꢁ1
0.840 mmꢁ1
1.011 mmꢁ1
0.872 mmꢁ1
0.857 mmꢁ1
1472
1140
1656
1584
1240
Crystal size (mm) 0.60 ꢂ 0.30 ꢂ 0.01
0.40 ꢂ 0.30 ꢂ 0.05
0.50 ꢂ 0.40 ꢂ 0.20
0.80 ꢂ 0.40 ꢂ 0.30
1.00 ꢂ 0.30 ꢂ 0.02
0.50 ꢂ 0.20 ꢂ 0.02
q
range for data
collection
1.43e24.00ꢀ.
1.46e24.00ꢀ.
1.44e28.58ꢀ.
2.13e26.00ꢀ.
1.99e24.00ꢀ.
1.57e24.00ꢀ.
Index ranges
ꢁ11<¼h<¼11,
ꢁ32<¼k<¼32,
ꢁ14<¼l<¼14
23413
ꢁ14<¼h<¼14,
ꢁ20<¼k<¼20,
ꢁ20<¼l<¼20
47113
ꢁ17<¼h<¼16,
ꢁ18<¼k<¼18,
ꢁ19<¼l<¼19
44661
ꢁ12<¼h<¼12,
ꢁ31<¼k<¼31,
ꢁ18<¼l<¼18
64277
ꢁ10<¼h<¼10,
ꢁ12<¼k<¼11,
ꢁ42<¼l<¼42
24477
ꢁ11<¼h<¼11,
ꢁ15<¼k<¼15,
ꢁ24<¼l<¼24
20786
Reflections
collected
Independent
reflections
5478 [R(int) ¼ 0.0947] 11192 [R(int) ¼ 0.0306] 12151 [R(int) ¼ 0.0255] 7349 [R(int) ¼ 0.0213] 5854 [R(int) ¼ 0.0389] 9073 [R(int) ¼ 0.0479]
Completeness to 99.8%
q
99.9%
91.9%
100.0%
100.0%
99.4%
¼ 24.0ꢀ
Absorption
correction
Multiescan
Semieempirical from
equivalents
Semieempirical from
equivalents
Semieempirical from
equivalents
Semieempirical from
equivalents
Semieempirical from
equivalents
Max. and min.
transmission
Refinement
method
Data/restraints/
parameters
0.9948 and 0.5366
0.9746 and 0.8784
0.8500 and 0.6890
0.7513 and 0.6105
0.9828 and 0.7704
0.9831 and 0.5946
Fullematrix least-
squares on F2
5478/0/451
Fullematrix least-
squares on F2
11192/198/1145
Fullematrix least-
squares on F2
12151/0/871
Fullematrix least-
squares on F2
7349/0/469
Fullematrix least-
squares on F2
5854/0/478
Fullematrix least-
squares on F2
9073/3/701a
Goodnesseofefit 1.012
1.080
1.047
1.042
1.045
0.932
on F2
Final R indices
R1 ¼ 0.0628,
R1 ¼ 0.0452,
R1 ¼ 0.0367,
R1 ¼ 0.0453,
R1 ¼ 0.0357,
R1 ¼ 0.0425,
[I > 2sigma(I)] wR2 ¼ 0.1494
R indices (all data) R1 ¼ 0.0991,
wR2 ¼ 0.1711
wR2 ¼ 0.1050
R1 ¼ 0.0597,
wR2 ¼ 0.0933
R1 ¼ 0.0405,
wR2 ¼ 0.1198
R1 ¼ 0.0489,
wR2 ¼ 0.0736
R1 ¼ 0.0433,
wR2 ¼ 0.0883
R1 ¼ 0.0764,
wR2 ¼ 0.1128
0.394 and ꢁ0.147
wR2 ¼ 0.0958
1.281 and ꢁ1.176
wR2 ¼ 0.1233
1.023 and ꢁ0.895
wR2 ¼ 0.0764
0.322 and ꢁ0.148
wR2 ¼ 0.0985
0.440 and ꢁ0.332
Largest diff. peak 1.215 and ꢁ0.474
and hole (e.Åꢁ3
)
1498 (KBr). 1H NMR (CDCl3):
d
7.51e7.13 (m, 20H, Ph); 6.99 and 6.80
247 (50), 305 (34), 335 (sh, 26), 398 (7.1); (CH3CN): 245 (50), 271
(44), 301 (34), 334 (sh, 25), 400 (7.4).
[2 ꢂ (d, 3JH,H 9 Hz, 2H, CHo/m C6H4OMe)]; 6.36 and 6.07 [2 ꢂ (d, 3JH,H
16 Hz, 1H, CH]CH)]; 4.73 and 4.67 [2 ꢂ (s, 2H, C5H4)]. 13C NMR
(CDCl3):
d
157.7 (Cp, C6H4OMe); 135.1, 127.7, 126.9, 125.1 (C4Ph4);
2.5.6. E-[Co(
m.p. 182e184 ꢀC (Found: C 73.75, H 4.68, Br 12.39, Co 8.58;
C41H30BrCo requires C 74.44, H 4.57, Br 12.08, Co 8.91%). IR : y
/cmꢁ1
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4Br-4)], E-4c
129.6 (Ci, C6H4OMe); 126.4 and 119.2 (CH]CH); 126.1 and 112.7 (Co/
m, C6H4OMe); 96.1 (Cipso, C5H4); 83.4 and 79.7 (CH, C5H4); 75.5
(C4Ph4); 54.2 (CH3). lmax/nm (
278 (47), 306 (sh, 33), 339 (sh, 29), 400 (sh, 8.3); (CH3CN): 275 (45),
305 (sh, 32), 338 (sh, 28), 401 (sh, 8.0).
y
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
(C]C) 1597, 1498, (CH2Cl2); y
(C]C), 1594, 1498, (KBr). 1H NMR
(CDCl3):
d
7.41e7.14 (m, 20H, Ph); 7.35 and 6.88 [2 ꢂ (d, 3JH,H 8 Hz,
2H, C6H4Br]); 6.29 and 6.19 [2 ꢂ (d, 3JH,H 16 Hz, 1H, CH]CH)]; 4.75
and 4.70 [2 ꢂ (m, 2H, C5H4)]. 13C NMR (CDCl3):
d 136.8 (Cp, C6H4Br);
2.5.5. Z-[Co(
m.p. 106e110 ꢀC (Found: C 74.36, H 4.90, Br 12.37, Co 8.61;
C41H30BrCo requires C 74.44, H 4.57, Br 12.08, Co 8.91%). IR
/cmꢁ1
h
4-C4Ph4)(
h
5-C5H4CH]CHC6H4Br-4)], Z-4c
136.2, 129.0, 128.2, 126.5 (C4Ph4); 131.6 and 127.7 (Co/m, C6H4Br);
126.5 and 123.8 (CH]CH); 95.1 (Cipso, C5H4); 85.1 and 81.3 (CH,
y
:
y
C5H4); 75.8 (C4Ph4).). lmax/nm (
247 (47), 277 (57), 305 (sh, 35), 344 (28), 404 (9.6); (CH3CN): 249
(38), 275 (45), 301 (sh, 30), 342 (26), 404 (8.1).
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
(C]C) 1597, 1498, (CH2Cl2);
y
(C]C), 1592, 1495, (KBr). 1H NMR
(CDCl3):
d
7.39e7.19 (m, 20H, Ph); 7.32 and 6.99 [2 ꢂ (d, 3JH,H 8 Hz,
2H, C6H4Br)]; 6.14 and 5.67 [2 ꢂ (d, 3JH,H 12 Hz, 1H, CH]CH)]; 4.55
and 4.51 [2 ꢂ (m, 2H, C5H4)]. 13C NMR (CDCl3):
d
137.2 (Cp, C6H4Br);
2.5.7. Z-[Co(
m.p. 195e197 ꢀC (Found: C 78.32, H 4.85, N 2.22, Co 9.77;
h h
4-C4Ph4)( 5-C5H4CH]CHC6H4NO2-4)], Z-4d
136.2, 129.0, 128.2, 126.5 (C4Ph4); 131.4 and 130.6 (Co/m, C6H4Br);
127.9 and 125.7 (CH]CH); 93.0 (Cipso, C5H4); 84.8 and 83.3 (CH,
C41H30NO2Co requires C 78.46, H 4.82, N 2.23, Co 9.39%). IR
y
/cmꢁ1
:
C5H4); 75.6 (C4Ph4). lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
y
(C]C) 1597, 1497, (NO2) 1517,1342 (CH2Cl2); (C]C) 1595, 1499,
y
y
y

1514
[RCH2PPh3]+
RCH2P(O)(OEt)2
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
R'CHO
y
(C]C) 1629, 1591, 1498,
y
(NO2) 1514, 1339 (CH2Cl2);
y
(C]C) 1629,
base
base
(1)
RCHPPh3
RCH=CHR'
R'CHO
1588, 1498 y d 8.15 and 7.13
(NO2) 1508, 1335 (KBr). 1H NMR (CDCl3):
[2 ꢂ (d, 3JHH 9 Hz, 2H, C6H4NO2)]; 7.44e7.18 (m, 20H, Ph); 6.43 and
[RCHP(O)(OEt)2]-
RCH=CHR (2)
3
6.38 [2 ꢂ (d, JHH 16 Hz, 1H, CH]CH)]; 4.86 and 4.82 [2 ꢂ (s, 2H,
C5H4)]. 13C NMR (CDCl3):
d 146.2 (Cp, C6H4NO2); 144.5 (Ci,
Scheme 1.
C6H4NO2); 135.9, 129.0, 128.3, 126.6 (C4Ph4); 128.6 and 125.0 (CH]
CH); 126.3 and 124.2 (Co/m, C6H4NO2), 94.1 (Cipso, C5H4); 85.9 and
(NO2) 1514,1340 (KBr). 1H NMR (CDCl3):
d
8.06 and 7.30 [2 ꢂ (d, 3JH,H
81.8 (CH, C5H4); 76.1 (C4Ph4). lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1
)
8 Hz, 2H, C6H4NO2)]; 7.40e7.17 (m, 20H, Ph); 6.22 and 5.85 [2 ꢂ (d,
3JH,H 12 Hz, 1H, CH]CH)]; 4.64 and 4.55 [2 ꢂ (m, 2H, C5H4)]. 13C
(CH2Cl2): 243 (41), 260 (42), 307 (sh, 33), 429 (17); (CH3CN): 243
(40), 269 (40), 304 (sh, 30), 421 (16).
NMR (CDCl3):
d 146.4 (Cp, C6H4NO2); 145.4 (Ci, C6H4NO2); 136.0,
129.0, 128.3, 126.7 (C4Ph4); 129.7 and 123.8 (Co/m, C6H4NO2); 128.8
and 126.6 (CH]CH); 92.2 (Cipso, C5H4); 85.5 and 83.3 (CH, C5H4);
2.5.9. Z-[Co(
m.p. 163e165 ꢀC (Found: C 85.76, H 5.77, Co 6.53; C45H33Co
requires C 85.42, H 5.27, Co 9.31%). IR (C]C) 1596, 1498
/cmꢁ1
(CH2Cl2); 8.27e7.09 (m,
(C]C) 1596,1498 (KBr). 1H NMR (CDCl3):
h h
4-C4Ph4)( 5-C5H4CH]CHC10H7-1)], Z-4e
75.8 (C4Ph4). lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 242
(43), 260 (44), 305 (sh, 34), 414 (9.9); (CH3CN): 244 (39), 261 (41),
301 (sh, 31), 408 (9.2).
y
: y
y
d
27H, Ph & C10H7); 6.62 and 5.95 [2 ꢂ (d, JH,H 12 Hz, 1H, CH]CH)];
2.5.8. E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC6H4NO2-4)], E-4d
4.45 and 4.37 [2 ꢂ (t, JH,H 2 Hz, 2H, C5H4)]. 13C NMR (CDCl3):
d
135.0,
m.p. 203e205 ꢀC (Found: C 76.82, H 4.74, N 2.45, Co 9.01;
128.0, 127.0, 125.3 (C4Ph4); 134.4, (Ci, C10H7), 132.6 and 130.6 (Cq,
C10H7); 128.2, 127.8, 127.4, 125.1, 124.6, 124.4 and 123.1 (CH, C10H7);
C41H30NO2Co requires C 78.46, H 4.82, N 2.23, Co 9.39%). IR
y
/cmꢁ1
:
EtO
Ph
P
OEt
O
Ph
Ph
P
CHO
Co
Cl
Co
Co
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
1
[3]Cl
2
(iv)
R
H
H
[Co]
(i)
H
H
Co
Fe
Ph
Ph
Ph
Ph
(ii)
C
H
Z-4(a-e), Z-6
O
(iii)
E-7
H
+
[Co]
H
R
H
Co
H
Ph
Ph
Ph
Ph
Fe
C
H
E-4(a-g), E-5, E-6
H
O
[Co]
Z-7
H
H
Fe
[Co]
(v)
H
[Co]
H
E,E'-9
[Co]
Co
H
H
=
CN
CN
Fe
Ph
Ph
Ph
Ph
Z-8
Me
Ph
H
[Co]
Ph
Fc
Me
Me
H
Co
Co
Co
Ph
Ph
Ph
Ph
Et
Et
Ph
Ph
Ph
Ph
Et
Et
E-10
11
E-12
Scheme 2. (i) [RCH2PPh3]X/n-BuLi; 4 {R ¼ (a) C6H5, (b) C6H4OMe-4, (c) C6H4Br-4, (d) C6H4NO2-4, (e) 1-naphthyl} and 6 {R ¼ Fe(
h
5-C5H5)(
h
5-C5H4-)}. (ii) t-BuLi then RCHO; 4 {R ¼ (f)
9-anthryl, (g) 1-pyrenyl}, 5 {R ¼ Co(
h
4-C4Ph4)( 5-C5H4-)}. (iii) t-BuLi then 0.5 [Fe( 5-C5H4CHO)2]. (iv) n-BuLi then 1 [Fe(
h
h
h
5-C5H4CHO)2]. (v) CH2(CN)2/Et3N.

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1515
C31
C32
C33
C37
C34
C38
C39
C35
C21
C36
C41
C30
C29
C16
C40
Co
C22
C14
C15
C12
C17
C11
C20
C2
C19
C13
C18
C23
C24
C4
C1
C10
C9
C8
C25
C5
C6
C28
C27
C26
C7
Fig. 1. Molecular structure and atom labelling of E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC6H5)], E-4a; thermal ellipsoids are drawn at the 25% probability level. Selected bond lengths (Å)
Co-C4Ph4(cent) 1.694(1); Co-C5H4(cent) 1.671(1); C(33)-C(34) 1.465(4); C(34)-C(35) 1.317(4); C(35)-C(36) 1.458(4). Selected bond angles (ꢀ) C(32)-C(33)-C(34) 127.6(3); C(29)-C(33)-
C(34) 125.4(3); C(33)-C(34)-C(35) 126.1(3); C(34)-C(35)-C(36) 127.0(3); C5H4(cent)-Co-C4Ph4(cent) 178.12(2).
126.5 and 126.0 (CH]CH); 92.9 (Cipso, C5H4); 83.7 and 83.3 (CH,
2.5.13. Eꢁ[Co(
m.p. 286e290 ꢀC (Found:
C68H50Co2.CHCl3 requires C 78.75, H 4.87, Co 11.28%). IR
(C]C) 1602, 1498 (CH2Cl2);
(C]C) 1596, 1498 (KBr). 1H NMR
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
78.49,
h
5)Co(
5.02, Co 11.32;
/cmꢁ1
h
4-C4Ph4)], E-5
C5H4); 75.1 (C4Ph4). lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
C
H
311 (39), 335 (sh, 35); (CH3CN): 309 (24), 332 sh (23).
y
: y
y
2.5.10. Eꢁ[Co(
m.p. 176e178 ꢀC (Found: C 83.98, H 5.49, Co 8.43; C45H33Co
requires C 85.42, H 5.27, Co 9.31%). IR (C]C) 1598, 1499
/cmꢁ1
(CH2Cl2);
(C]C) 1596, 1572, 1498, 1443 (KBr). 1H NMR (CDCl3):
h
4-C4Ph4)(
h
5-C5H4CH]CHC10H7-1)], E-4e
(CDCl3): d 7.36e7.12 (m, 40H, Ph); 5.46 (s, 2H, CH]CH); 4.59 and
4.43 [2 ꢂ (m, 4H, C5H4)]. 13C NMR (CDCl3):
d 136.4, 128.9, 128.0 and
126.2 (C4Ph4); 121.8 (CH]CH); 96.3 (Cipso, C5H4); 84.0 and 80.7 (CH,
y
:
y
y
C5H4); 75.3 (C4Ph4). lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2):
d
7.95e6.98 (m, 27H, Ph & C10H7); 7.31 and 6.34 [2 ꢂ (d, JH,H 16 Hz, 1H,
247 (63), 265 (67), 305 (sh, 41), 350 (32), 412 (15); (CH3CN):
insoluble.
CH]CH)]; 4.87 and 4.73 [2 ꢂ (m, 2H, C5H4)].13C NMR (CDCl3):
d 135.5,
128.4, 127.6 and 125.8 (C4Ph4); 134.5, (Ci, C10H7); 133.1 and 130.5 (Cq,
C10H7); 128.0, 126.9, 125.4, 125.3, 125.2, 123.5 and 122.8 (CH, C10H7),
125.4 and 124.1 (CH]CH); 95.8 (Cipso, C5H4); 85.3 and 81.3 (CH, C5H4),
75.9 (C4Ph4). lmax/nm (
301 (sh, 27), 347 (20); (CH3CN): 297 (sh, 26), 346 (20).
2.5.14. Z-[Co(h h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe( 5-C5H4CHO)],
Z-7
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 228 (52),
m.p. 168e171 ꢀC (Found: C 70.19, H 4.68, Co 7.22; C46H35OFe-
/cmꢁ1
(C]O) 1679, 1663,
(C]C) 1594, 1498 (KBr). 1H NMR (CDCl3):
y d 9.82 (s, 1H, CHO),
Co.CH2Cl2 requires C 70.26, H 4.64, Co 7.33, Fe 6.95%). IR
(C]O) 1681, 1664, (C]C) 1598, 1499 (CH2Cl2);
y
: y
y
y
2.5.11. Eꢁ[Co(
m.p. 178e182 ꢀC (Found: C 85.26, H, 5.21, Co 8.16; C49H35Co
requires C 86.20, H 5.17, Co 8.63%). IR (C]C) 1602
/cmꢁ1
(CH2Cl2); 8.35e7.10 (m,
(C]C) 1594, 1499 (KBr). 1H NMR (CDCl3):
h
4-C4Ph4)(
h
5-C5H4CH]CHC14H9-9)], E-4f
7.38e7.16 (m, 20H, Ph); 5.85 and 5.52 [2 ꢂ (d, 3JH,H 12 Hz, 1H, CH]
y
: y
y
d
29H, Ph & C14H9); 7.42 and 6.32 [2 ꢂ (d, JH,H 16 Hz, 1H, CH]CH)];
5.03 and 4.76 [2 ꢂ (s, 2H, C5H4)]. 13C NMR (CDCl3):
d 136.0, 128.8,
C42
C36
C35
128.0 and 126.4 (C4Ph4); 132.9 (Ci, C14H9); 131.7, 128.5, 126.0, 125.4,
125.0 (CH, C14H9), 131.5, 129.3 (Cq, C14H9); 125.9 and 123.8 (CH]
C33
C29
C30
C39
O
C32
C31
C34
CH); 96.0 (Cipso, C5H4); 85.3 and 80.5 (CH, C5H4); 75.5 (C4Ph4). lmax
/
nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 258 (110), 408 (15);
(CH3CN): 255 (98), 407 (13).
Co
C4
C23
C5
C1
2.5.12. Eꢁ[Co(
m.p. 199e201 ꢀC (Found: C 86.73, H 4.80, Co 8.34; C51H35Co
requires C 86.67, H 4.99, Co 8.34%). IR (C]C) 1602, 1499
/cmꢁ1
(CH2Cl2); 8.22e7.14 (m, 29H Ph &
(C]C) (KBr). 1H NMR (CDCl3):
h h
4-C4Ph4)( 5-C5H4CH]CHC16H9-1)], E-4g
C17
C3
C2
C11
y
: y
y
d
C
16H9); 7.55 and 6.54 [2 ꢂ (d, JH,H 16 Hz,1H, CH]CH)]; 4.95 and 4.77
[2 ꢂ (s, 2H, C5H4)]. 13C NMR (CDCl3):
d 135.5, 128.4, 127.6 and 125.9
(C4Ph4); 131.7 (Ci, C16H9); 131.2, 130.6, 129.9, 127.2 and 124.7 (Cq,
C16H9); 127.1, 126.8, 126.5, 125.5, 124.7, 124.4, 123.0 and 122.9 (CH,
C16H9); 125.6 and 124.0 (CH]CH); 96.0 (Cipso, C5H4); 85.4 and 81.4
(CH, C5H4); 76.1 (C4Ph4). lmax/nm (
(CH2Cl2): 243 (57), 280 (45), 380 (27), 405 (sh, 25); (CH3CN): 231
(46), 279 (36), 376 (23).
Fig. 2. Molecular structure and atom labelling of E-[Co(
h
4-C4Ph4)( 5-C5H4CH]
h
CHC6H4OMe-4)], E-4b; thermal ellipsoids are drawn at the 25% probability level.
Selected bond lengths (Å) Co-C4Ph4(cent) 1.692(1); Co-C5H4(cent) 1.678(1); C(29)-C
(34) 1.457(3); C(34)-C(35) 1.328(3); C(35)-C(36); 1.466(3). Selected bond angles (ꢀ) C
(33)-C(29)-C(34) 125.52(17); C(30)-C(29)-C(34) 127.96(17); C(29)-C(34)-C(35) 125.51
(19); C(34)-C(35)-C(36) 126.5(2); C5H4(cent)-Co-C4Ph4(cent) 178.15(2).
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1
)

1516
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
C35
C34
C31
C32
C33
C37
C19
C18
C30
C38
C39
C26
C36
C20
C21
C29
C24
C41
C25
C27
C40
Co1
C17
C28
C22
C23
Br1
C4
C1
C3
C2
C5
C12
C13
C10
C11
C9
C6
C16
C15
C7
C14
C8
Fig. 3. Molecular structure and atom labelling of Molecule 1 of E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC6H4Br-4)], E-4c; thermal ellipsoids are drawn at the 50% probability level. Bond
length and angle data for the three unique molecules. Selected bond lengths (Å) Co-C4Ph4(cent) 1.694(1), 1.690(1), 1.702(1); Co-C5H4(cent) 1.673(1), 1.674(1), 1.686(1); C(29)-C(34)
1.447(10), 1.457(11), 1.475(11); C(34)-C(35) 1.341(10), 1.324(10), 1.301(11); C(35)-C(36) 1.471(11), 1.455(11), 1.504(11). Selected bond angles (ꢀ)C(29)-C(33)-C(34) 125.1(7), 126.3(7),
122.9(7); C(32)-C(33)-C(34) 127.6(7), 127.4(7), 129.9(7); C(33)-C(34)-C(35) 127.3(7), 126.5(8), 126.5(8); C(34)-C(35)-C(36) 127.9(7), 127.5(8), 124.8(8); C5H4(cent)-Co-C4Ph4(cent)
178.28(7), 177.06(7), 177.49(6).
CH)]; 4.64 and 4.45 [2 ꢂ (t, 3JH,H 2 Hz, 2H, C5H4CHO)]; 4.60 and 4.57
[2 ꢂ (t, 3JH,H 2 Hz, 2H, C5H4Co)]; 4.30 and 4.22 [2 ꢂ (t, 3JH,H 2 Hz, 2H,
2.6. Crystal structure determinations
C5H4Fe)]. 13C NMR (CDCl3):
d
193.5 (CHO); 136.1, 128.8, 127.9, 126.2
The structures of E-4a, E-4b, E-4c, E-4d, Z-4e, E-4f, E-4g, E-5, Z-7,
Z-8 and E,E-9 were determined by X-ray diffraction methods in the
X-raylaboratory of University College Dublin. The structures of E and
Z-6 have been reported previously [9] but various features are dis-
cussed for comparison purposes. The data were collected using
a Bruker SMARTAPEXCCD area detector diffractometerand an X-ray
(C4Ph4); 124.8 and 123.9 (CH]CH); 93.5 (Cipso, C5H4Co); 84.9 (Cipso
,
C5H4Fe); 84.4 and 82.9 (CH, C5H4Co); 79.8 (Cipso, C5H4CHO); 75.2
(C4Ph4); 74.4 and 70.6 (CH, C5H4CHO); 70.6 and 69.7 (CH, C5H4Fe).
lmax/nm (
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 238 (24), 262 (23),
300 (17), 404 (3.5); (CH3CN): 238 (40), 262 (39), 299 (29), 411 (4.7).
tube utilising graphite-monochromated Mo
K
a
radiation
2.5.15. Z-[Co(h h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe{ 5-C5H4CHC
(CN)2}], Z-8
m.p. 214e216 ꢀC (Found: C 71.71, H 4.16, N 2.72; C49H35N2Co-
C41
C35
Fe.CH2Cl2 requires C 70.50, H 4.38, N 3.29%). IR (C^N)
y
/cmꢁ1
:
y
2225, (C]C) 1598, 1575, 1499 (CH2Cl2); (C^N) 2219, y(C]C)
y
y
C39
C40
O2
N1
1594, 1574, 1498 (KBr). 1H NMR (CDCl3):
d 7.42 (s, 1H, CH]C(CN)2);
C31
C30
C36
C37
C34
C29
7.39e7.19 (m, 20H, Ph); 5.71 and 5.64 [2 ꢂ (d, 3JH,H 12 Hz, 1 H, CH]
C38
3
CH)]; 4.81, 4.68, 4.66, 4.62, 4.36 and 4.24 [6 ꢂ (t, JH,H 2 Hz, 2H,
C32
C33
O1
C5H4)]. 13C NMR (CDCl3):
d 162.7 (CH]C(CN)2); 136.1, 129.0, 128.2,
Co1
126.5 (C4Ph4); 125.4 and 123.9 (CH]CH); 115.4 and 114.5 (C^N);
93.3 (Cipso, C5H4Co); 86.5 (Cipso, C5H4Fe); 84.8 and 83.1 (CH,
C5H4Co); 76.5 (C4Ph4); 75.2 and 72.7 (CH, C5H4Fe-CH]C(CN)2); 75.1
(Cipso, C5H4CH]C(CN)2); 71.9 and 71.2 (CH, C5H4Fe). lmax/nm
C12
C11
C2
C3
C24
C18
C17
C6
C5
C1
(e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1) (CH2Cl2): 243 (42), 262 (44), 307 (37),
C4
405 (9.1), 536 (3.0); (CH3CN): 239 (47), 260 (47), 303 sh (38), 392
(14), 528 (3.9).
C23
2.5.16. E,Eꢁ[{Co(
h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5}2Fe], E,E-9
m.p. 225e228 ꢀC (Found: C 80.01, H 5.18, Co 9.39, Fe 4.51;
C80H60Co2Fe requires C 80.41, H 5.06, Co 9.86, Fe 4.67%). IR y/
cmꢁ1
:
y
(C]C) 1597, 1499 (CH2Cl2). 1H NMR (CDCl3):
d
7.43e7.18
Fig. 4. Molecular structure and atom labelling of Molecule 1 of E-[Co(h -
4-C4Ph4)(h5
3
(m, 40H, Ph); 6.07 and 5.82 [2 ꢂ (d, JH,H 16 Hz, 2H, CH]CH)];
C5H4CH]CHC6H4NO2-4)], E-4d; thermal ellipsoids are drawn at the 50% probability
level. Bond length and angle data for the three unique molecules. Selected bond
lengths (Å) Co-C4Ph4(cent) 1.696(1), 1.694(1), 1.696(1); Co-C5H4(cent) 1.680(1), 1.675
(1), 1.679(1); C(29)-C(34) 1.4615(14), 1.4527(13), 1.4483(13); C(34)-C(35) 1.3412(15),
1.3444(13), 1.3442(14); C(35)-C(36) 1.4653(15), 1.4589(13), 1.3442(14). Selected bond
angles (ꢀ) C(33)-C(29)-C(34) 123.18(10), 123.95(9), 123.87(9); C(30)-C(29)-C(34)
129.27(10), 128.76(8), 128.75(9); C(29)-C(34)-C(35) 123.66(10), 124.07(9), 125.89(9); C
(34)-C(35)-C(36) 125.75(10), 125.24(9), 124.62(9); C5H4(cent)-Co-C4Ph4(cent) 177.27
(1), 176.76 (1), 179.03(1).
3
4.64 and 4.61 [2 ꢂ (m, 4H, C5H4Co)]; 4.04 and 3.99 [2 ꢂ (t, JH,H
2 Hz, 4H C5H4Fe)]. 13C NMR (CDCl3):
d 136.2, 128.8, 127.9, and
126.1 (C4Ph4); 126.0 and 120.1 (CH]CH); 96.6 (Cipso, C5H4Co);
84.4 (Cipso, C5H4Fe); 84.1 and 80.3 (CH, C5H4Co); 75.2 (C4Ph4);
69.8 and 67.3 (CH, C5H4Fe). lmax/nm (
(CH2Cl2): 245 (87), 261 (85), 306 (59), 404 (18); (CH3CN):
insoluble.
e
ꢂ 10ꢁ3/dm3molꢁ1cmꢁ1
)

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1517
(l
¼ 0.71073 Å). A full sphere of the reciprocal space was scanned by
phi-omega scans. Pseudo-empirical absorption correction based on
redundant reflections was performed by the program SADABS [18].
The structures were solved by direct methods using SHELXS-97 [19]
and refined by full matrix least-squares on F2 for all data using
SHELXL-97 [19]. For compounds E-4a, E-4c, E-4f, E-4g, E-5, Z-7, Z-8
and E,E-9 all hydrogen atoms were added at calculated positions and
refined using a riding model. Their isotropic temperature factors
were fixed to 1.2 times (1.5 times for methyl groups) the equivalent
isotropic displacement parameters of the carbon/nitrogen atom the
H atom is attached to. For compounds E-4b, E-4d and Z-4e all
hydrogen atoms were located in the difference Fourier map and
allowed to refine freely with isotropic temperature factors. Aniso-
tropic temperature factors were used for all non-hydrogen atoms.
Some calculations were carried out using ORTEX [20] and Mercury
[21].
C38
C39
C44
C37
C31
C30
C29
C40
C41
C36
C33
C32
C34
C45
C43
C35
Co
C42
C3
C17
C11
C2
C5
C4
C1
C23
Crystal structure data are given in Tables 1a and 1b.
3. Results and discussion
Fig. 5. Molecular structure and atom labelling of Z-[Co(h h
4-C4Ph4)( 5-C5H4CH]
Organic stilbenes may be prepared in many ways, but we have
found that their ferrocenyl analogues are most conveniently
obtained by routes based on the Wittig reaction [22,23] or its Hor-
nereWadswortheEmmons (HWE) [24,25] modification (Scheme 1.
Eqs. (1) and (2) respectively). In general, the Wittig reagent gives
a mixture of Z and E alkenes. The HornereWadswortheEmmons
reagent is more reactive, but gives the E alkene only. Herein we
CHC10H7-1)], Z-4e; thermal ellipsoids are drawn at the 50% probability level. Selected
bond lengths (Å) Co-C4Ph4(cent) 1.695(2); Co-C5H4(cent) 1.679(2); C(29)-C(34) 1.454
(3); C(34)-C(35) 1.326(3); C(35)-C(36) 1.484(3). Selected bond angles (ꢀ) C(33)-C(29)-C
(34) 124.1(2); C(30)-C(29)-C(34) 129.0(2); C(29)-C(34)-C(35) 128.1(2); C(34)-C(35)-C
(36) 125.5(2); C5H4(cent)-Co-C4Ph4(cent) 178.21(2).
(
h
4-C4Ph4)(
CHO)2]/[Co(
h
h
5-C5H4CHO]/[RCH2PPh3]þ, and 7 from [Fe(
h
5-C5H4
extend this methodology to stilbenes containing the Co(
5-C5H4-) end group starting from either [Co( 4-C4Ph4)(h5
C5H4CHO)], 1, or [Co(
4-C4Ph4)( 5-C5H4PPh3)][Cl], [3]Cl/[Co(h4
C4Ph4)(
5-C5H4P(O)(OEt)2], 2, depending on circumstances.
h
4-C4Ph4)
4-C4Ph4)( 5-C5H4CH2PPh3]þ (1:1) using n-BuLi as
h
(h
h
-
-
a base. It always gave mixtures of Z and E isomers which were
separated in most cases. However it failed to give 4f, 4g and 5
h
h
h
where
R
¼
9-anthryl, 1-pyrenyl and Co(h h
4-C4Ph4)( 5-C5H4-)
The reactions carried out in the course of this work are shown in
Scheme 2. The Wittig reaction (Scheme 1, Eq. (1)) was used to
prepare 4a, 4b, 4c, 4d, 4e and the previously reported 6 from [Co
respectively. These and 9 were prepared by the HWE route (Scheme
1, Eq. (2)) from [Co(
h
4-C4Ph4)( 5-C5H4CH2P(O)(OEt)2], 2, and the
h
C40
C41
C39
C38
C42
C29
C33
C37
C36
C43
C44
C35
C30
C7
C34
C27
C6
C49
C8
C32
C26
C5
C9
C10
C28
Co
C45
C46
C25
C48
C24
C1
C23
C4
C3
C47
C12
C13
C2
C17
C11
C16
C14
C18
C22
C21
C15
C19
C20
Fig. 6. Molecular structure and atom labelling of E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC14H9-9)], E-4f; thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths
(Å) Co-C4Ph4(cent) 1.678(1); Co-C5H4(cent) 1.665(1); C(33)-C(34) 1.447(6); C(34)-C(35) 1.323(6); C(35)-C(36) 1.481(6). Selected bond angles (ꢀ) C(32)-C(33)-C(34) 128.1(4); C(29)-C
(33)-C(34) 124.6(4); C(33)-C(34)-C(35) 125.1(4); C(34)-C(35)-C(36) 124.4(4); C5H4(cent)-Co-C4Ph4(cent) 177.27(4).

1518
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
C44A
C45A
C46A
C47A
C42A
C48A
C43A
C29A
C30A
C51A
C35A
C36A
C33A
C34A
C5
C50A
C49A
C41A
C31A
C40A
C39A
C37A
C32A
Co1
C1
C38A
C11
C17
C2
C3
C4
C23
Fig. 7. Molecular structure and atom labelling of E-[Co(h h
4-C4Ph4)( 5-C5H4CH]CHC16H9-1)], E-4g; thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths
(Å) Co2-C4Ph4(cent) 1.689(2); Co2-C5H4(cent) 1.677(2); C(84)-C(85) 1.495(4); C(85)-C(86) 1.331(4); C(86)-C(87) 1.463(4). Selected bond angles (ꢀ) C(83)-C(84)-C(85) 126.1(3); C(80)-
C(84)-C(85) 127.7(3); C(84)-C(85)-C(86) 126.0(3); C(85)eC(86)eC(87); 126.3(3); C5H4(cent)-Co2-C4Ph4(cent) 178.10(3).
appropriate RCHO using t-BuLi as the base, but only their E isomers
were formed. However, the symmetrical E-[Co(
4-C4Ph4)(h5
C5H4CH]CHC5H4-
5)Co( 4-C4Ph4)], 5, was always a by-product of
ferrocene at 2220 cmꢁ1 [32]. These
y(C^N) vibrations have lower
h
-
frequencies than that observed for malononitrile, 2274 cmꢁ1 [12].
h
h
The 1H NMR spectra of 4e9 show strong multiplets between
these reactions, and we have found that many RCH2P(O)(OEt)2/t-
BuLi reagents give homodimers RCH ¼ CHR in good yields when
worked up in the absence of an aldehyde [26]. A similar reaction
takes place with [RCH2PPh3]þ, t-BuOK and acetophenone in polar
aprotic solvents such as acetonitrile (R ¼ aryl) [27].
d
7.40 and
the substituted cyclopentadienyl ligand give rise to a pair of triplets
or a pair of broad resonances between 5.00 and 4.43. The
d 7.10 due to the protons of the h
4-C4Ph4 ligands whilst
d
d
protons of the CH]CH linker give rise to a singlet in the spectrum
of 5 where the two end groups are identical, but all other
compounds described have different end groups, the magnetic
inequivalence generating two doublet signals. The observed
coupling constants distinguish between the E (JHH ¼ 16 Hz) and Z
(JHH ¼ 12 Hz) isomers of the stilbenes, and in all instances, coupling
constant and X-ray data are consistent. In 4a, 4e, 4f and 4g reso-
nances due to the aromatic end groups R either cannot be distin-
guished from those due to the C4Ph4 ligand or are weak,
complicated multiplets. However, those due to the C6H4X-4 protons
of 4b, 4c and 4d are readily identified as two characteristic doublets
in each case with JHH ¼ 8e9 Hz whose chemical shifts depend on X
The compounds 4e9 are air-stable crystalline solids soluble in
many organic solvents though E-5 and E,E-9 are insoluble in
acetonitrile. 4aec, Z-4d, 4eeg and 5 are orange or orange brown, E-
4d is red-brown, and 6, 9, 7 and 8 are red though the colour
deepens markedly along that series.
3.1. Spectra
The IR spectra of 4e9 are dominated by the absorption bands
due to the
h
4-C4Ph4 ligand, particularly those at ca. 1500 and
1600 cmꢁ1 due to the
y
(C]C) vibrations. There is little difference
and move downfield for OMe < Br < NO2. Where R ¼ Fe(
5-C5H4-) in 6 the C5H5 protons give rise to a singlet and the h5
C5H4 to two triplets or broad resonances. In 7, 8 and 9 the Fe(h5
C5H4-)(
bands. It is normally straight-forward to distinguish between Co
5-C5H4-) and Fe( 5-C5H4-) signals as those due to the latter tend
to lie upfield of those due to the former except in Fe(
5-C5H4-)(h5
h
5-C5H5)
between them unless R contains an IR-active group. Thus the
(h
-
-
spectra of 4d show absorption bands at ca. 1510 and 1340 cmꢁ1 due
to their
of 1526 and 1347 cmꢁ1 [27]. The aldehyde 7 shows two strong
absorption bands in the
(CO) region at 1679 and 1663 cmꢁ1 whose
y(NO2) vibrations; for nitrobenzene these have frequencies
h
5-C5H4-) moiety gives rise two pairs of triplets or broad
y
(h
h
frequencies are essentially identical with those found for its fer-
h
-
rocenyl aꢁn1alogue 1-formyl-10-(ferrocenylethenyl)-ferrocene, 1679,
C5H4X) complexes 7 and 8 where X is an electron-withdrawing
CHO or CHC(CN)2 substituent. These substituents themselves give
1663 cm
in NaCl [28], and for 1,10-diformyl-ferrocene, 1684,
1664 cmꢁ1 in KBr [29], but predictably are different from that
reported for monosubstituted [Fe(
5-C5H5)( 5-C5H4CHO)],
1690 cmꢁ1 [30]. The dicyanovinyl 8 has a strong absorption band in
the
(CN) region at 2225 cmꢁ1. At first glance this is significantly
higher in energy than dicyanovinylferrocene (2185, 2170 cmꢁ1) [31]
and bears a closer resemblance to the 2225 cmꢁ1 band for [Co(h4
C4Ph4){
5-C5H4CH]C(CN)2}] [12]. However, as with 7, the presence
of a 10- conjugating group on the ferrocene lowers the stretching
frequency of the 1- ring substituent, and thus the (C^N) vibration
for 8 compares favourably with that of 1,10-bis(dicyanovinyl)-
rise to downfield singlets at d 9.82, CHO, and d 7.42, CHC(CN)2.
h
h
It is also relatively straight-forward, by using homonuclear and
correlation spectroscopy NMR techniques, comparisons with
related compounds [7,12] and internal consistency, to assign peaks
in the 13C NMR spectra of E and Z isomers of 4e9 to the C4 ring and
its attached Ph rings (1 and 4 resonance respectively), the C5H4Co
ring (3 res), the CH]CH alkene carbons (2 res, but 1 in 5), the
terminal p-C6H4X (4 res) groups (4b-4d), and many of those of the
y
-
h
y
polyaromatic end-groups of 4ee4g. Rotation about the h5
C5H4dCH(]), (])CHdC6H4X and (])CHdanthryl bonds is fast on
-

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1519
C29
C30
C34
C31
C34
C8
C33
C4
C32
C9
C7
C13
Co1
C10
C12
C11
C6
C14
C15
C5
C2
C1
C16
C23
C28
C27
C3
C24
C18
C19
C17
C26
C22
C20
C21
Fig. 8. Molecular structure and atom labelling of Molecule 1 of E-[Co(
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
h
5)Co(
h
4-C4Ph4)], E-5; thermal ellipsoids are drawn at the 50% probability
level. Labelled atoms are related to unlabelled atoms by the symmetry operation 1-x, 1-y, 2-z. Bond length and angle data for both unique molecules. Selected bond lengths (Å) Co-
C4Ph4(cent) 1.687(1), 1.691 (1); Co-C5H4(cent) 1.672(1), 1.673(1); C(33)eC(34) 1.458(2), 1.464(2); C(34)eC(34)#1 1.339(3), 1.330(4); C(33)eC(34) 1.458(2), 1.464(2). Selected bond
angles (ꢀ) C(32)eC(33)eC(34) 124.72(16), 124.23(17); C(29)eC(33)eC(34) 128.25(16), 128.70(17); C(34)#1-C(34)eC(33) 124.3(2), 124.7(2); C(34)#1-C(34)eC(33) 124.3(2), 124.7(2);
C5H4(cent)-Co-C4Ph4(cent) 177.44(1), 177.59(1).
the NMR timescale. The resonances due to the Fe(
h
5-C5H5)(h5
-
interactions between Co(
(acceptor) groups. Similar low energy MLCT bands are observed in
the spectra of the NLO-active Z and E-[Fe(
5-C5H5)( 5-C5H4CH]
CHCHC6H4NO2-4)] (
¼ 480 and 496 nm respectively) [34,35]. Of the
remaining compounds, 5e9, only Z-8, Z-[Co(
4-C4Ph4)(h5
C5H4CH]CHC5H4-
5)Fe{ 5-C5H4CHC(CN)2}], shows a weak, low
energy absorption band in its electronic spectrum at
¼ 536 nm
(CH2Cl2 solution). Similar bands are observed at 536 nm for [Co(h4
C4Ph4){
5-C5H4CH]C(CN)2}] (CH2Cl2 solution) [12] and 521 nm for
[Fe(
5-C5H5){ 5-C5H4CH]C(CN)2}] (EtOH solution) [32].
h h
4-C4Ph4)( 5-C5H4) (donor) and NO2
C5H4-) (4) or Fe(
h
5-C5H4-)( 5-C5H4-) (3 or 6) groups of 6 e 9 tend to
h
lie upfield of those due to C5H4Co but move downfield when the
electron-withdrawing CHO/CHC(CN)2 are present.
h
h
l
The electronic spectra (300e900 nm) of 4a e 4c are similar to
h
-
that of [Co(
h
4-C4Ph4)(
h
5-C5H5)] with a weak absorption band at ca.
h
h
400 nmwith a long tail [33]. Those of 4e e 4g also contain absorption
bands which clearly arise from transitions within the naphthyl,
anthryl or pyrenyl groups [7]. The spectra of Z and E isomers are very
similar and are not greatly affected by the solvent. There appears to
l
-
h
h
h
be limited or no electronic interactions between the Co(
5-C5H4-) and R groups. Similar behaviour has been observed and
discussed for related [Fe(
5-C5H5)( 5-C5H4CH]CHR)] compounds
[7]. However, the spectra of 4d are different as they show a relatively
strong absorption band at 408e429 nm. Its wavelength ( ) and
intensity ( ) depends on the isomer and the former is solvent
dependent i.e. for Z-4d ¼ 9200; 9800
¼ 414; 408 nm and
h
4-C4Ph4)
(h
3.2. Crystal and molecular structures
h
h
The structures of all 1e9 have been determined by X-ray
diffraction techniques. Those of 1 - 3 have been reported previously
[11,12] and will not be discussed further; those of Z-6 and E-6 have
also been reported previously [9] but are included here for
comparison with the closely related structures 7e9. Crystal data are
listed in Tables 1b and 1b, and molecular structures together with
atom labelling are illustrated in Figs. 1e13.
l
e
l
e
dm3molꢁ1cmꢁ1 in CH2Cl2; CH3CN solutions, whilst for E-4d
l
¼ 429;
421 nm and
e
¼ 16,600; 16,400 dm3molꢁ1cmꢁ1 (CH2Cl2; CH3CN).
It appears that for these compounds there are some electronic

1520
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
C5
C23
C1
C4
C3
C11
C2
C17
Co
C34
C35
C29
C33
C37
C30
C32
C36
C40
C38
C45
C44
C41
Fe
C42
C43
Fig. 9. Molecular structure and atom labelling of Z-[Co(
h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe( 5-C5H5)], Z-6; thermal ellipsoids are drawn at the 50% probability level. Selected
h h h
bond lengths (Å) Co-C4Ph4(cent) 1.691(1); Co-C5H4(cent) 1.674(1); Fe-C5H5(cent) 1.651(1); Fe-C5H4(cent) 1.644(1); C(29)-C(34) 1.464(2); C(34)-C(35) 1.338(2); C(35)-C(36) 1.470(2).
Selected bond angles (ꢀ) C5H4(cent)-Fe-C5H5(cent) 179.18(2); C5H4(cent)-Co-C4Ph4(cent) 179.07(1). Taken from Ref [9].
In the cases of E-4c and E-4d, and E-5 and E,E-9 there are
respectivelythree andtwounique moleculesin the asymmetricunit.
Both molecules of 5 and 9 lie on special positions. In both molecules
of 5 the centre of the C]C alkene double bond lies on an inversion
centre, in 9, it is the central ferrocenyl iron atoms that sit on inver-
sion centres. In molecule 2 of 9 the central di(cyclopentadienyl)
ethene is disordered over two positions with refined occupancies of
0.600(6) and 0.400(6).
a CH]CH alkene linker which is, in turn, s-bonded to R (CCo-C(H)]
C(H)-CR constitutes Plane 3) where R is a ca. planar aromatic or
polyaromatic (C6H4X-4, 1-naphthyl, 9-anthryl or 1-pyrenyl) or the
cyclopentadienyl of a ferrocenyl group or second Co(h -
4-C4Ph4)(h5
C5H4) moiety (Plane 4). Plane 5 is the plane through the para-
phenyl -OCH3 and -NO2 substituent of 4b and 4d. Plane 6 is that of
the second ring of these sandwich groups, (
C5H4Y). The angles between these planes are listed in Table 2
together with the configurations of the Co(
4-C4Ph4)( 5-C5H4)
h -
4-C4Ph4) or (h5
The structures of the [Co(
h
4-C4Ph4)(
h
5-C5H4CH]CHR)]
h
h
complexes 4e9 are broadly similar and conform to expectations.
Their carbon frameworks contain a number of planes or quasi-
planes which help describe them. The Co atom is sandwiched
and ferrocenyl groups. The C5 and C4 ligands on Co or the two C5
ligands on Fe are effectively parallel with interplanar angles (1e2 or
3e6) of 0e4.9ꢀ. The dihedral between the 5-C5H4(Co) and alkene
h
between two ca. planar
h
4-C4Ph4 (the C4 ring is Plane 1) and h5
-
[CCo-C(H)]C(H)-CR] planes lie between 8.9 and 25.8ꢀ except for
molecule 2 of E-5 (1.9ꢀ) and for Z-8 (46.6ꢀ). Progressing through the
C5H4- (Plane 2) ligands. The cyclopentadienyl ligand is s-bonded to
C31
C30
C11
C4
C32
Co
C33
C29
C34
C17
C42
C43
C1
C41
C45
C3
C2
C5
C37
C35
C36
Fe
C38
C44
C23
C40
C39
Fig. 10. Molecular structure and atom labelling of E-[Co(h h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe( 5-C5H5)], E-6; thermal ellipsoids are drawn at the 50% probability level. Selected
bond lengths (Å) Co-C4Ph4(cent) 1.688(1); Co-C5H4(cent) 1.674(1); C(29)eC(34) 1.469(4); C(34)eC(35) 1.303(4); C(35)eC(36) 1.471(4); Fe-C5H5(cent) 1.648(1); Fe-C5H4(cent) 1.641
(1). Selected bond angles (ꢀ) C5H4(cent)-Fe-C5H5(cent) 178.20(2); C5H4(cent)-Co-C4Ph4(cent) 179.10(2). Taken from Ref [9].

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1521
O
C46
Fe
C44
C45
C43
C41
C39
C40
C31
C32
C42
C30
C38
C36
C29
C34
C35
C33
C37
C11
Co
C3
C4
C2
C17
C23
C1
C5
Fig. 11. Molecular structure and atom labelling of Z-[Co(h h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe( 5-C5H4CHO)], Z-7; thermal ellipsoids are drawn at the 25% probability level.
Selected bond lengths (Å) Co-C4Ph4(cent) 1.691(1); Co-C5H4(cent) 1.674(1); C(33)eC(34) 1.464(4); C(34)eC(35) 1.336(5); C(35)-C(36) 1.468(4); Fe-C5H4-CHO(cent) 1.638(1);
FeeC5H4eC]C (cent) 1.646(1). Selected bond angles (ꢀ) C5H4(cent)-Fe-C5H4(cent) 177.89(3); C5H4(cent)-Co-C4Ph4(cent) 176.68(2).
C38
C19
C39
Fe
C20
C43
C45
C31
C37
C36
C18
C44
C21
C22
C32
C40
C42
C30
C17
C33
C29
C35
C3
C34
C16
C41
Co
C11
C2
C28
C46
C48
C4
C1
C14
C27
C26
C12
C13
C47
C49
C23
C24
C25
C5
C10
C9
N49
C6
C7
C8
Fig. 12. Molecular structure and atom labelling of Z-[Co(h h h h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5)Fe{ 5-C5H4CH]C(CN)2}], Z-8; thermal ellipsoids are drawn at the 25% probability level.
Selected bond lengths (Å) Co-C4Ph4(cent) 1.691(1); Co-C5H4(cent) 1.673(1); C(33)eC(34) 1.466(5); C(34)eC(35) 1.332(4); C(35)eC(36) 1.457(5); FeeC5H4eCH]C(CN)2(cent) 1.651
(1); FeeC5H4eC]C (cent) 1.651(1). Selected bond angles (ꢀ) C5H4(cent)-Fe-C5H4(cent) 175.61(3); C5H4(cent)-Co-C4Ph4(cent) 178.80(3), 175.61(3).

1522
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
C26
C25
C21
Co1
C38
C20
C18
C24
C37
C27
C22
C40
C28
C36
C40
C23
C39
C17
Fe1
C36
C39
C37
C35
C4
C3
C38
C34
C7
C33
C32
Co1
C1
C31
C2
C6
C5
C16
C11
C12
C29
C8
C10
C30
C15
C9
C14
C13
Fig. 13. Molecular structure and atom labelling of Molecule 1 of E,E-[{Co(
h
4-C4Ph4)( 5-C5H4CH]CHC5H4- 5}2Fe], E,E-9; thermal ellipsoids are drawn at the 50% probability level.
h h
Labelled atoms are related to unlabelled atoms by the symmetry operation 2-x, 2-y, 1-z. Bond length and angle data for both unique molecules. Selected bond lengths (Å) Co-
C4Ph4(cent) 1.685(1), 1.688(1); Co-C5H4(cent) 1.669(1), 1.701(2), 1.660(2); C(33)eC(34) 1.450(4), 1.484(6), 1.491(9); C(34)eC(35) 1.328(4), 1.337(8), 1.291(11); C(35)eC(36) 1.451(4),
1.427(6), 1.481(9); Fe-C5H4(cent) 1.664(2), 1.650(1), 1.649(1). Selected bond angles (ꢀ) C5H4(cent)-Fe-C5H4(cent) 180.0(3), 180.0; C5H4(cent)-Co-C4Ph4(cent) 177.64(3), 176.10(3),
173.12(3).
molecule, the angles between alkene (Plane 3) and aryl terminal or
5-C5H4 (Plane 4) range from an approximately coplanar 1.9ꢀ to
The largest dihedrals are observed for Z-4e and E-4f and are clearly
the result of steric crowding. For the E- structures the angles
between Plane 2 and Plane 4 give an indication of the overall
sandwich-aryl or sandwichesandwich planarity (and hence
possible conjugation through the alkene link), and lie between
21.4ꢀ and 44.1ꢀ The exceptions to this are the two molecules of E-5
which lie on special crystallographic position (and thus have an
h
near orthogonal 72.4ꢀ. They are smaller (1.9e18.6ꢀ) for the benzene
compounds E-4ae4d, the pyrene derivative E-4g, and E-5. They
tend to be smaller for E molecules than Z, and in the Z complexes
Plane 3 has a pronounced helical distortion with angles of 3.6(3) e
6.8(6)ꢀ between its two constituent planes, CCoeCeH and C-H-CR.
Table 2
Interplane angles and conformation of the two
p
-ligands coordinated to Co or Fe in [Co(
Interplane angles (ꢀ)a
h h
4-C4Ph4)( 5-C5H4CH]CHR)] complexes.
Conformations
Rb
1e2
2.7
1.8
2.3
3.5
1.8
3.3
2.2
0.8
3.4
4.2
1.9
3.1
3.3
1.8
1.2
3.3
0.5
4.1
2e3
22.2
22.0
13.6
13.3
9.4
17.2
14.5
14.1
20.6
9.2
8.9
10.2
1.9
18.2
13.8
25.8
46.6
19.6
3e4
12.2
16.1
10.9
9.5
4-5 or 4e6
2e4
1 vs 2c
4 vs 6d
C6H5 (E-4a)
C6H4OMe-4 (E-4b)
C6H4Br-4 (E-4c)
34.4
38.1
24.4
22.7
21.5
26.6
29.3
32.9
68.5
44.1
26.8
0
0
51.6
2.9
50.6
51.8
43.3
e/c
e
e
g
f
e
a
f
c
e
f
b
b
e
b
e
e
c
4.16
12.3
9.7
C6H4NO2ꢁ4(E-4d)
10.9
5.3
4.0
14.8
18.8
72.4
53.2
18.1
10.2
1.9
52.2
11.1
44.3
16.8
23.6
1-C10H7 (Z-4e)
1-C14H9 (E-4f)
1-C16H9 (E-4g)
Co(
h
4-C4Ph4)(
h
5-C5H4-) (E-5)
3.1
3.3
0.6
2.6
2.3
4.9
0
e
Fe(
Fe(
Fe(
Fe{
Fe{
h
h
h
5-C5H5)(
5-C5H5)(
h
h
5-C5H4-) (Z-6)
5-C5H4-) (E-6)
ec
ec
ec
st
5-C5H4CHO)(
h
5-C5H4-) (Z-7)
h
h
5-C5H4CH]C(CN)2}(
5-C5H4CH]CH[Co]}(
h
h
5-C5H4-) (Z-8)
5-C5H4-) (E,E-9)
a
For definition of planes see text.
b
c
[Co] h Co(
The relative orientations of C4 and C5 ligands in the Co(
h h
4-C4Ph4)( 5-C5H4-).
h
4-C4Ph4)(
5-C5H4Y)(
Approximately midway between eclipsed and staggered.
h
5-C5H4-) moiety. Nomenclature taken from ref. [33].
d
e
The relative orientations of two C5 ligands in the Fe(
h
h
5-C5H4-) moiety; ec ¼ eclipsed and st ¼ staggered.

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1523
(
h
5-C5H4CH]X) bonding is much greater when X ¼ O or C(CN)2
X
X
than when X ¼ CHR.
Cβ
Cβ
Y
Y
Cα
H
Cα
H
There is a further interesting feature of the structure and
bonding in Z-8 which is not present in Z-7. The two C5 ligands on Fe
are eclipsed in both compounds but the CH]O and CH]CH
substituents in Z-7 are not. However, in Z-8 the CH]C(CN)2 and
CH]CH substituents are eclipsed and the non-bonded C,,,,C
distances decrease C(34),,,,C(47) > C(36),,,,C(41) > C(35),,,,C
(46) at 3.535(5), 3.411(5) and 3.325(5) Å compared with the inter-
plane separation of 3.35 Å in graphite [39]. This suggests there is an
attractive electronic interaction between the relatively electron-
rich CH]CH and electron-poor CH]C(CN)2 ethylenic systems. This
interaction cannot be negligible as it has a further consequence. In
Z-6 and Z-7 the angles between the Planes 2 and 3 are 18.2 and
25.8ꢀ respectively whilst those between Planes 3 and 4 are 52.2 and
44.3ꢀ; in Z-8 they are 46.5 and 16.8ꢀ i.e. the introduction of the CH]
C(CN)2 substituents brings the C5H4(Fe) and CiCH]CHCi groups
closer to co-planarity, but has the opposite effect on the C5H4(Co)
and CiCH]CHCi moieties. The totally eclipsed conformation has
M
M
1
2
Fig. 14. Possible mesomers of M{
Fe(
5-C5H5).
h
5-C5H4CH]C(X)Y} derivatives, M ¼ Co(
h
4-C4Ph4) or
h
inversion centre generated 0ꢀ dihedral) and the ferrocenyl E-6
(2.9ꢀ). The angles involving Plane 3 appear to be controlled by intra
and inter-molecular non-bonding interactions, as they are in E and
Z-stilbene where the angles between the equivalent of Planes 2 and
3 are respectively 1ꢀ/5ꢀ (X-ray diffraction) [36] and 43.2ꢀ (electron
diffraction) [37], and electronic communication (or electron delo-
calization) between Co(
the C]C is probably limited in most instances. Calculations have
shown that this is the case in various [Fe(
5-C5H5)( 5-C5H4CH]
CHR)] derivatives and it is reasonable to assume that the same is
true here [8]. However, it is also probable that the Co(
4-C4Ph4)
fragment has a greater steric influence than Fe(
5-C5H5) and
h h
4-C4Ph4)( 5-C5H4-) and R groups across
h
h
been found in the E ferrocenyl aldehyde [Fe(
C5H4CH]CHFc-E)] which is disordered [28], [Fe(
CHFc-E){
5-C5H4CH]CH-C5H5N/Cr(CO)5-E}] [28] where the non-
bonded C,,,C distances equivalent to those for Z-8 are 3.720(8),
3.344(8) and 3.367(8) Å, [Fe(
5-C5H4CH]CH-C6H5Br-E)2] [40], and
l,l’-bis{(5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene)
methyl}ferrocene, Fe(
5-C5H4CH]CS2C2S2C2H4)2] [41].
h
5-C5H4CHO)(h5
5-C5H4CH]
-
h
h
h
h
consequently steric effects would be expected to be greater for
complexes of the former than the latter even if electronic
communication is anticipated. This is particular well-illustrated by
h
the structures of E-[M(
h
5-C5H4CH]CHC6H4NO2-4)]. When M ¼ Fe
h
(h
5-C5H5) the (
h
5-C5H4CH]CHC6H4NO2-4) portion of the molecule
On the other hand 9 is a E,E molecule. Both centrosymmetric
is close to planar [38], whereas for E-4d the dihedral angle between
molecules in the asymmetric unit adopt a strictly staggered
C5H4 and C6H4NO2 planes averages 29.6ꢀ (Table 2). With the
conformation of the two (h h h
5-C5H4CH]CHC5H4- 5)Co( 4-C4Ph4)
exception of Molecule 1 of E,E-9, the [Co(
h
4-C4Ph4)(
h
5-C5H4CH]
ligands on Fe. This arrangement has also been observed for the
CHC5H4-
h
5)Fe( 5-C5H5)] derivatives tend to have their metal
h
sandwich end groups on opposite sides of the CCoeCH]CHeCR
plane.
Table 3
4-C4Ph4)(
h
5-C5H4CH]CHR)]a,b and related
The structures of the Co(
same as those in related derivatives [9e12,33]. The
h h
4-C4Ph4)(
5-C5H4-) fragments are the
4-C4Ph4
Electrochemical data for [Co(
compounds.
h
h
ligands constitute a four-bladed propeller with the Ph planes
inclined to the C4 planes (interplanar angles ¼ 18ꢀe66.5ꢀ), whilst
the CPh bonds point away from Co. The Co-centroid distances are
1.678(1) e 1.696(1) Å for the cyclobutadiene ligand and 1.665(1) e
1.680(1) Å for the cyclopentadienyl ligand. However, the Co-C
distances are 1.95e2.00 Å and 2.03e2.10 Å respectively, and their
CeC bond lengths are 1.45e1.48 Å and 1.38e1.44 Å respectively as
compared with 1.303(4) e 1.343(4) Å for their ethylenic C]C bond
lengths.
Compound
Oxidations Eo/V
[Co]
Other oxidns
[Co(
C6H5
C6H5
C6H4OMe-4
C6H4OMe-4
C6H4Br-4
h
4-C4Ph4)(
h
5-C5H5)]
0.98
0.94
0.92
Z-4a
E-4a
Z-4b
E-4b
Z-4c
E-4c
Z-4d
E-4d
E-4e
E-4f
E-4g
E-5
Z-6
E-6
Z-7
Z-8
E,E-9
E-10
11
0.89
0.87
1.15 (ipc/ipa 0.7)
1.14 (ipc/ipa 0.7)
0.96
0.93
1.01
0.99
C6H4Br-4
C6H4NO2ꢁ4
C6H4NO2ꢁ4
C10H7ꢁ1
For the Co(
carbon atoms
h
4-C4Ph4)(
[C(34)] and
h
5-C5H4C(34)H]C(35)H-R moiety the
[C(35)] to the cyclopentadienyl ring
0.92
a
b
C14H9ꢁ9
Epa 0.89
0.88
do not lie in its plane. On average C(34) is displaced from it by
0.0047 Å towards Co whilst for C(35) the displacement is ꢁ0.101 Å
i.e. away from Co. However, in these complexes C(34) and C(35) are
C
Co(
16H9ꢁ1
1.10 (ipc/ipa 0.8)
h
4-C4Ph4)(
h
5-C5H4-)
0.76, 0.90
0.96
0.97
Fe(
Fe(
h
h
5-C5H5)(
h
h
5-C5H4-)c
0.53
0.49
0.76
0.81d
5-C5H5)(
5-C5H4-)c
also
b and a respectively to R where similar displacements are
Fe (
h
5-C5H4CHO)(
h
5-C5H54−)
0.89
apparent. Such displacements can be attributed to the contribution
that charge-separated fulvenic mesomers such as 2 make to the
description of the electronic structures of these compounds
(Fig. 14). However, this appears to be small as the displacement of
Ca is generally limited and variable, and is probably subordinate to
steric effects except when substituents X and Y are electron
Fe{
Fe{
h h
5-C5H4CHCH]C(CN)2}( 5-C5H54−) 0.81d
h
5-C5H4CHCH]CH[Co]}(
h
5-C5H4-) 0.88, 1.03 0.42
[Co]-CMe]CMe-[Co]e
0.74, 0.88
0.90
0.55
[Co]-CMe]CPh2)]e
[Co(h
4-C4Me4)(
h
5-C5H5)]f
Z-12
E-12
[Et4Co]-CH]CH-Fcg
[Et4Co]-CH]CH-Fcg
0.72
0.69
0.48
0.46
accepting groups as in Z-7 and Z-8. Both of these compounds are
a
1
ꢂ
10ꢁ3
M
in CH2Cl2/0.1
M
[Bu4N][PF6]/Pt/100mVsꢁ1/internal [Fe(h5
-
derivatives of Z-[Co(
C5H5)], Z-6, but have their second
C5H4CHO and
CH]O and CH]C(CN)2
towards Fe by 0.121 Å and 0.109 Å, whereas for the (
CHC5H4-
5)Co( 4-C4Ph4) ligands on Fe the comparable displace-
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-
h
5)Fe(h5
-
-
C5Me5)2]þ/0 reference, [Fe(
h
5-C5H5)2]þ/0 ¼ 0.55 V [46].
h
5-C5H5 ligand substituted by h5
b
[Co] h [Co(
h
4-C4Ph4)( 5-C5H4-)]; [Et4Co] h [Co( 4-C4Et4)( 5-C5H4-)]; Fc h Fe
h h h
h
5-C5H4CH]C(CN)2 respectively. For these their
(
h
5-C5H5)(
h
5-C5H4-).
c
d
e
Taken from ref. [9].
Two-electron process.
Preparation of E-[Co(
h
Data from ref. [45] (converted from original SCE ref.).
Preparation reported in ref. [43].
C
a
atoms are displaced from the C5 plane
h
5-C5H4CH]
h h h h
4-C4Ph4)( 5-C5H4CMe]CMeC5H4- 5)Co( 4-C4Ph4)] and
h
h
[Co(
4-C4Ph4)( 5-C5H4CMe]CPh2)] reported in ref. [10].
h
f
ments are 0.058 and 0.092 Å, whilst in Z-6 it is ꢁ0.039 Å away from
g
Fe. This suggests that the contribution made by mesomer 2 to Fe/

1524
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
2.5
I / μA
2
1.5
1
Fc*
0.5
-0.2
0.2
0.4
0.6
0.8
1
1.2
E / V
-0.5
-1
-1.5
-2
Fig. 15. Cyclic voltammogram of E-[Co]-CH]CH-[Co], 5 with internal [Fe(
h
5-C5Me5)2] (¼ Fc*) chemical reference (100 mVsꢁ1, Pt, 0.1 M Bu4NPF6 in CH2Cl2, [FcH]0/þ ¼ 0.55 V).
dipyridinyl [Fe(
h
5-C5H4CH]CH-C5H5N-E)2], but in supramolecular
It has been reported previously that various [Co(
C5H4R)] [9,44], and [Co(
5-C5H4R)( 4-C4Me4)] complexes [45]
undergo a chemically reversible one-electron oxidation. For [Co
h -
4-C4Ph4)(h5
aggregates with binaphthol it can adopt other conformations [42].
h
h
(h h -
4-C4Ph4)( 5-C5H5)] (][Co]-H), this occurs at 0.98 V (vs [Fe(h5
3.3. Electrochemistry
C5Me5)2]þ/0 ¼ 0.00 V) and is followed by a second irreversible
oxidation process at higher anodic potential [44]. Similar behav-
Electrochemical data for 4e9 in dichloromethane solution are
summarised in Table 3 together with those for four compounds
whose preparation, spectra and structure have been described
iour is observed for [Co(
oxidation occurring at 0.55 V [45]. All 4e12 display the couple
associated with oxidation of the Co(
4-C4Ph4)( 5-C5H4-)/Co(h4
C4Et4)(
5-C5H4-) moiety which appears to be chemically revers-
h h
4-C4Me4)( 5-C5H5)] with the initial
4-C4Ph4)(
h
5-C5H4CMe]CMeC5H4-
5-C5H4CMe]CPh2], 11 [10]; Z-
5)Fe( 5-C5H5)], Z-12 [43]; and
5)Fe( 5-C5H5)], E-12 [43].
h -
5)Co(h4
h
h
-
elsewhere;
C4Ph4)], E-10 [10]; [Co(
[Co(
4-C4Et4)( 5-C5H4CH]CHC5H4-
E-[Co(
4-C4Et4)( 5-C5H4CH]CHC5H4-
E-[Co(
h
4-C4Ph4)(
h
h
h
ible with ipc/ipa y 1 except for the anthryl stilbene E-4f (see
below).
h
h
h
h
h
h
h
h
2
1.5
1
I / μA
Fc*
0.5
-0.2
0.2
0.4
0.6
0.8
1
1.2
1.4
E / V
-0.5
-1
-1.5
Fig. 16. Cyclic voltammogram of E,E’-[{Co(
CH2Cl2, [FcH]0/þ ¼ 0.55 V).
h
4-C4Ph4)(
h
5-C5H4CH]CHC5H4-h5
}
2 Fe], E,E-9, with internal [Fe(
h
5-C5Me5)2] (¼ Fc*) chemical reference (100 mVsꢁ1, Pt, 0.1 M Bu4NPF6 in

P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
1525
Table 4
resemble those of E-6. The corresponding tetraethylcyclobutadie-
nylcobalt complexes Z and E-12 [43] show similar behaviour, with
the cobalt based oxidation predictably shifted cathodically by
w300 mV as a consequence of the superior electron donor ability of
Spectroelectrochemical data for [Co(
compounds.
h
4-C4Ph4)(
h
5-C5H4CH]CHR)]a and related
Compound
lmax (nm)
the
h h
4-C4Et4 ligand compared with 4-C4Ph4.
Monocation
Dication
E,E0-9 undergoes three reversible oxidations (Fig. 16). The first,
[Co(h
4-C4Ph4)(
h
5-C5H5)]
653
at 0.42 V, is associated with the ferrocenyl centre whilst the other
two (0.88, 1.03 V) are due to the cobalt centres. These clearly
communicate effectively through the extended ethenyl-ferroce-
nium-ethenyl linker, or perhaps more accurately, oxidation of the
first cobalt centre affects the potential at which the second cobalt
E-4a
E-4e
E-4g
E-5
C6H5
C10H7ꢁ1
C16H9ꢁ1
555, 955
628, 1109
655, 700, 1410
651, 1860
531, 1290
Co(
Fe(
Fe{
h
4-C4Ph4)(
h
h
5-C5H4-)
5-C5H4-)b
600
593
E-6
h
5-C5H5)(
E,E-9
E-10
11
h
5-C5H4CHCH]CH[Co]}(
h
5-C5H4-) 541, 1290
649, 1800
[Co]-CMe]CMe-[Co]c
[Co]-CMe]CPh2)]c
[Et4Co]-CH]CH-Fcd
centre is oxidised. DE is 150 mV as compared with 140 mV for E-5
with its shorter single C]C link.
570, 605, 1010
591, 1580
E-12
a
[Co] h [Co(
h
4-C4Ph4)(
h
5-C5H4-)]; [Et4Co] h [Co(
h
4-C4Et4)( 5-C5H4-)]; Fc h Fe
h
(
h
5-C5H5)(
h
5-C5H4-).
3.4. Spectroelectrochemistry
b
Taken from ref. [9].
c
Preparation of E-[Co(h h h h
4-C4Ph4)( 5-C5H4CMe]CMeC5H4- 5)Co( 4-C4Ph4)] and
[Co(h h
4-C4Ph4)( 5-C5H4CMe]CPh2)] reported in ref. [10].
Kudinov et al. have reported oxidation studies on various [Co
(h h
4-C4Me4)( 5-cyclopentadienyl) complexes and the results of DFT
d
Preparation reported in ref. [43].
calculations for [Co(h h
4-C4H4)( 5-C5H5) [45]. One-electron oxida-
tion in some instances gives rise to a relatively unstable mono-
cation and the generation of cobaltocenium cation from
consecutive elimination and disproportionation reactions [44,45].
Stable cations give rise to a new ferrocenium type metal-centred
transition in the visible spectrum 576e680 nm [45]. Our results of
preliminary spectroelectrochemical studies on a selection of the
tetraphenylcyclobutadiene cobalt compounds are presented in
Cyclic voltammetry performed on E-[Co(h -
4-C4Ph4)(h5
C5H4CH]CHC6H5)], E-4a, shows an oxidation couple at 0.92 V. For
Z-4a this appears at 0.94 V, and the anodic sweep of both isomers
also shows an irreversible process at ca. 1.5 V. For other [Co(h4
-
C4Ph4)(h
5-C5H4CH]CHC6H4X-4)], there is also a ca. 0.2 V difference
in Eo between E and Z isomers, but when X is the electron-donating
OMe group there is a cathodic shift of the redox couple to 0.87 V (E-
4b) and 0.89 V (Z-4b) and a quasi-reversible oxidation of the
methoxyphenyl group is observed at 1.14 V. On the other hand,
when X is the electron-withdrawing NO2 group there is a predict-
able anodic shift of the [Co]þ/0 redox couple to 0.99 V for E-4d and
1.01 V for Z-4d. The electrochemistry of the 1-naphthyl complex E-
4e is very similar to that of E-4a; this is to be expected by
Table 4. Oxidation in an OTTLE cell of the parent [Co(h -
4-C4Ph4)(h5
C5H5) generates a new band at 653 nm (
e
¼ 1300 dm3molꢁ1cmꢁ1).
The simple phenyl, naphthyl and pyrenyl [Co(h -
4-C4Ph4)(h5
C5H4CH]CHR)] derivatives E-4a, E-4e and E-4g all show a similar
relatively weak band 555e655 nm. Additionally a new band arises
in the near infrared region of its spectrum associated with a ligand-
to-metal charge transfer (LMCT) from the aryl group to the oxidised
cobalt centre. Their wavelengths, 955, 1110 and 1410 nm respec-
tively, compare with 900, 956 and 1110 nm we reported for
comparisons with the electrochemistry of [Fe(
h -
5-C5H5)(h5
C5H4CH]CHR)] [7] and [Ni(
h
5-C5H5)ChC-R] [47] where R is an aryl
h h
5-C5H5)( 5-C5H4-CH]CH-R)]þ species
group. The pyrenyl analogue E-4g exhibits both the reversible
[Co]þ/0 and a quasi-reversible pyrenyl redox couple at 0.88 V and
1.10 V respectively. Uniquely, the anthracene derivative E-4f shows
only an irreversible oxidation at 0.89 V; a companion cathodic
feature occurs on the reverse sweep at 0.21 V. These may be
associated with the anthryl group.
the analogous E-[Fe(
(R ¼ phenyl, naphthy, pyrenyl) [7]. A similar band at 1010 nm is
present in the spectrum of [Co(h h
4-C4Ph4)( 5-C5H4CMe]CPh2]þ,
[11]þ. The reversibility of the OTTLE spectra attest to the stability of
these cations.
We have previously described the spectroelectrochemistry of
the mixed ferrocene cobalt complex 6. For E-6 a one-electron
oxidation in the OTTLE cell gives rise to a new charge transfer band
The closely related E-5 and E-10 with two redox centres display
the classical Class II profile of two separate reversible one-electron
¼ 2000 dm3molꢁ1cmꢁ1) [7]. The same experiment
oxidations (
4-C4Ph4)(
0.90 V (Fig. 15), whilst for its dimethylated analogue E-[Co(h4
C4Ph4)(
5-C5H4CMe]CMeC5H4- 5)Co( 4-C4Ph4)], E-10, they are
D
h
E ¼ 140 mV) suggesting interaction between the Co
at 1290 nm (
e
(h
5-C5H4-) moieties. For E-5 these occur at 0.76 and
performed on Z-6 shows conclusively that a slow isomerisation to
the sterically preferred E isomer takes place upon the first (ferro-
cenyl) oxidation. No isomerisation occurred when Z-4a was oxi-
dised at Eꢀ[Co]þ/0. The isomerisation of Z-[6]þ may proceed via an
-
h
h
h
found at 0.74, 0.88 V. The 20 mV shift is in the predicted cathodic
direction.
Fe-centred fulvene intermediate and rotation about the Ca-Cb bond
The electrochemistry of Z− and E-6 has been described previ-
ously [9] but is included for comparison purposes. The E- isomer
displays two reversible oxidations at 0.49 and 0.97 V associated
with the ferrocenyl and [Co] groups respectively. However in the
case of the Z- isomer, following the second oxidation, a rapid cis-
trans isomerisation occurs and subsequent potential sweeps
(Scheme 3). OTTLE oxidation of the tetraethylcyclobutadiene
complex 12, results in a CT transition of much longer wavelength
(lower energy), 1580 nm, but the same Z to E isomerisation of the
oxidised species. The near-IR absorption bands of both E-[6]þ and
E-[12]þ disappeared upon their oxidation to [6]2þ or [12]2þ
,
providing additional support for their assignment to CT transitions.
+e-
-e-
[Co]
H
[Co]
H
[Co]
H
H
H
Fe
Fe
Fe
Fe
Fe
[Co]
[Co]
E-6
Z-6
Scheme 3.

1526
P. O’Donohue et al. / Journal of Organometallic Chemistry 696 (2011) 1510e1527
.2
1st and 2nd oxidations
649
.15
593
1800
.1
.05
0
600
800
1000
1200
Nanometers
1400
1600
1800
2000
Fig. 17. UVevis OTTLE spectra of E-[Co(
h
4-C4Ph4)(
h
5-C5H4CMe]CMeC5H4-
h
5)Co( 4-C4Ph4)], E-10.
h
Oxidation of the E-[Co(
h
4-C4Ph4)(
h
5-C5H4CR]CRC5H4-
h
5)Co
Acknowledgements
(h
4-C4Ph4)] complexes E-5 (R ¼ H) and E-10 (R ¼ Me) at 0.75 V
generates E-[Co(
h
4-C4Ph4)(
h
5-C5H4CR]CRC5H4-
h
5)Co(
h
4-C4Ph4)]þ
We thank the New Economy Research Fund (grant No.UOO-
X0808) for support of this work (CJM).
species with one [Co]þ acceptor and one neutral [Co] donor. This
gives rise to a ferrocenium type transition at 650 nm and a broad,
low energy intervalence charge transfer (IVCT) band at ca.1800 nm/
Appendix A. Supplementary material
5550 cmꢁ1
(
e
¼ ca. 1400 dm3molꢁ1cmꢁ1) (Fig. 17). The IVCT inter-
action can be quantified from the electrochemical and OTTLE
results by calculation of the Hush coupling term VAB [48]. For E-5
and 10, VAB ¼ 0.07 eV. These values compare well with those for the
CCDC 801442e801452 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
IVCT band of E-[Fe(
h
5-C5H5)(
¼ 1750 nm (
h h -
5-C5H4CH]CHC5H4- 5)Fe(h5
C5H5)]þ where
l
e
¼ 1200 dm3molꢁ1cmꢁ1) and
VAB ¼ 0.061 eV [49,50]. Upon oxidation of the second [Co] centre at
0.85 V the 1800 nm CT band is bleached and the [Co]þ transition
shifts to shorter wavelength (Fig. 17).
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