Synthesis and electrochemistry of complexes containing the ferrocenyl-phosphine ligand PPh(CH2CH2-η5-C5H 4)2Fe

Article abstract of DOI:10.1016/S0022-328X(98)01032-8

Treatment of the tethered bis(cyclopentadienyl)-phosphine compound bis(2-cyclopentadienylethyl)phenylphosphine (1) produces moderate yields (40-50%) of the ferrocene complex PPh(CH₂CH₂-η⁵-C₅H ₄)₂Fe (2). Reaction of 2 with Me₃NO in tetrahydrofuran gives the phosphine oxide O=PPh(CH₂CH₂-η⁵-C₅H ₄)₂Fe (3) whereas treatment with the metal complexes trans-PdCl₂(PhCN)₂, cis-PtCl₂(PhCN)₂, Fe₂(CO)₉, and Mo(CO)₅(THF) give the corresponding di- or tri-metallic complexes trans-PdCl₂[PPh(CH₂CH₂-η⁵-C ₅H₄)₂Fe]₂ (4), cis-PtCl₂[PPh(CH₂CH₂-η⁵-C ⁵H₄)₂Fe]₂ (5), (OC)₄FePPh(CH₂CH₂-η⁵-C ₅H₄)₂Fe (7), and (OC)₅MoPPh(CH₂CH₂-η⁵-C ₅H₄)₂Fe (8), respectively, in which 2 is acting as a neutral two-electron-donor phosphine ligand. The electrochemistry of complexes 2, 3, 4, 5 and 7 have been investigated and complexes 3, 4 and 7 have been characterised further by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(98)01032-8

Journal of Organometallic Chemistry 577 (1999) 44–57
Synthesis and electrochemistry of complexes containing the
ferrocenyl–phosphine ligand PPh(CH2CH2-p5-C5H4)2Feꢀ
Julian J. Adams a, Owen J. Curnow a,*, Gottfried Huttner b, Samuel J. Smail a,
Mark M. Turnbull a,1
a Department of Chemistry, Uni6ersity of Canterbury, Pri6ate Bag 4800, Christchurch, New Zealand
b Ruprecht-Karls Uni6ersita¨t Heidelberg, Anorganisch-Chemisches Institut, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Received 11 August 1998
Abstract
Treatment of the tethered bis(cyclopentadienyl)-phosphine compound bis(2-cyclopentadienylethyl)phenylphosphine (1) produces
moderate yields (40–50%) of the ferrocene complex PPh(CH2CH2-p5-C5H4)2Fe (2). Reaction of 2 with Me3NO in tetrahydrofuran
gives the phosphine oxide OꢀPPh(CH2CH2-p5-C5H4)2Fe (3) whereas treatment with the metal complexes trans-PdCl2(PhCN)2,
cis-PtCl2(PhCN)2, Fe2(CO)9, and Mo(CO)5(THF) give the corresponding di- or tri-metallic complexes trans-PdCl2[PPh(CH2CH2-
p5-C5H4)2Fe]2 (4), cis-PtCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (5), (OC)4FePPh(CH2CH2-p5-C5H4)2Fe (7), and (OC)5MoPPh(CH2CH2-
p5-C5H4)2Fe (8), respectively, in which 2 is acting as a neutral two-electron-donor phosphine ligand. The electrochemistry of
complexes 2, 3, 4, 5 and 7 have been investigated and complexes 3, 4 and 7 have been characterised further by X-ray
crystallography. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Ferrocene; Phosphine; Heterobimetallics; Cyclopentadienyl; Group 10; Molybdenum
The major reasons for the successful use of these lig-
ands, particularly in the area of homogeneous catalysis,
are their ability to stabilise a range of metal oxidation
states and because it is relatively easy to alter their
steric and electronic properties by changing their
substituents.
There is now a large range of Group 15 function-
alised cyclopentadienyl ligands, particularly with amine
and amide functionalities [3]. The number of phosphine
functionalised cyclopentadienyl ligands is relatively
small, but there are now examples of ligands containing
zero-, one-, two- or three-atom bridges between the
cyclopentadienyl and phosphine moieties [4–7]. Most
work to date has focused on the zero- and two-atom
bridged ligands. The number of functionalised bis-cy-
clopentadienyl ligands, however, is still quite small.
Ligands prepared to date include pyridyl [8–10], amino
[9,11], ether [12], furanyl [13], and arsine [14,15] substi-
tuted bis-cyclopentadienyl ligands. Most of the chem-
1. Introduction
The chemistry of functionalised cyclopentadienyl lig-
ands is a rapidly expanding area of research [1]. Apart
from an enhanced thermodynamic stability that is im-
parted through the chelate effect, changes in the coordi-
nation bite angle may also be used to alter the frontier
orbitals of the metal–ligand fragment and, thus, alter
the reactivity [2]. Alternatively, such ligands may be
used to build hetero- and homo-bimetallic complexes
which may exhibit interesting and useful properties.
Cyclopentadienyl and phosphine ligands are two of the
most important ligands in organometallic chemistry:
ꢀ Dedicated to Professor Warren Roper on the occasion of his 60th
birthday.
* Corresponding author. Tel.: +64-3-3642819; fax: +64-3-
3642110; e-mail: o.curnow@chem.canterbury.ac.nz
1 Present address: Department of Chemistry, Clark University,
Worcester, MA 01610, USA.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01032-8

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
45
vices, Otago University, Dunedin. Cyclic voltam-
mograms of 10−3 M solutions of 3, 4, 5 and 7 were
recorded using a PAR 173 potentiostat coupled to a
home-built waveform generator and a PAR 17S Uni-
versal Programmer and a Graphtech WX1200 X–Y
recorder. The three-electrode cell was comprised of a
platinum-disk working electrode (1 mm diameter), a
istry of these functionalised bis-cyclopentadienyl lig-
ands has focused on the lanthanide coordination
chemistry, particularly with the hard nitrogen- and
oxygen-containing functional groups. Qian has re-
ported recently a lanthanide complex containing an
oxygen atom tethered to two indenyl groups via
ethylene bridges [16]. The only examples of bis-cy-
clopentadienyl-phosphine ligands are RP(C5H4−)2
(R=Cl, alkyl, aryl) [15,17,18] and C6H11P(CHMe-
2-PPh2C5H3−)2 [19]. This paper reports the synthesis
of the bis(cyclopentadienyl)-phosphine ligand precur-
sor, bis(2-cyclopentadienylethyl)phenylphosphine (1),
its conversion to the ferrocenyl complex PhP(CH2-
CH2C5H4)2Fe (2), and some phosphine coordination
chemistry of 2. Some of this work has been reported
in this journal as a communication [20]. Examples of
the ligand [PPh(CH2CH2C5H4)2]2− coordinated to zir-
conium have been reported earlier [21] in which the
phosphine is intramolecularly coordinated to the
metal centre to give a septadentate coordination
mode (counting each cyclopentadienyl group as a tri-
dentate ligand) for the ligand.
platinum-wire auxiliary and
a M
Ag/Ag+ (0.01
AgNO3, 0.1 M [Bu4N]PF6–CH3CN) reference elec-
trode. Cyclic voltammograms of 10−3 M solutions of
2 were recorded using a Princeton applied research
potentiostat 273 equipped with a BBC/Servogor (XY
733) plotter as the recording instrument. The three-
electrode cell was comprised of a platinum-wire auxil-
iary electrode (0.3 mm diameter), a glassy-carbon disk
working electrode (3 mm diameter) and an SCE refer-
ence electrode (0.01 M AgNO3, 0.1 M [Bu4N]PF6–
CH3CN). All potentials are reported versus the
couple ferrocene+/ferrocene (Fc+/Fc) after referenc-
ing to in situ ferrocene or cobaltocenium. Before use,
electrodes were polished with 1 mm diamond paste
and cleaned ultrasonically for 15 s in acetone fol-
lowed by triply distilled water. All electrochemical
measurements were made at 2292°C and a dinitro-
gen atmosphere was maintained in the cell.
2. Experimental
2.1. General considerations
2.2. Preparation of PPh(CH2CH2C5H5)2 (1)
All manipulations and reactions were carried out
under an inert atmosphere by use of standard
Schlenk line techniques. Reagent grade solvents were
dried and distilled prior to use: diethyl ether and te-
A solution of phenylphosphine (2.00 g, 18.2 mmol)
and spiro[2.4]hepta-4,6-diene (4.15 g, 45.0 mmol) in
THF (60 ml) was cooled to −78°C. n-BuLi (13.0 ml,
1.4 M in hexane, 18.2 mmol) was then added and the
solution allowed to warm to ambient temperature.
After stirring for 2 h, the mixture was again cooled
to −78°C and n-BuLi (15.6 ml, 1.4 M in hexane,
21.8 mmol) added. The solution was then allowed to
warm to ambient temperature and stirred overnight.
Excess dinitrogen-saturated water was added. The or-
ganic layer was collected and the aqueous layer was
extracted with 3×50 ml portions of diethyl ether
which were added to the organic fraction. The or-
ganic fraction was dried over Na2SO4 and filtered.
Removal of the volatiles in vacuo gave an orange oil
which, after chromatography down a 5×5 cm silica
column with 1:1 petroleum ether+CH2Cl2, produced
a colourless oil of 1 (5.05 g, 94% yield). 31P-NMR
(CDCl3): l −22.25, −22.40, −22.55 (1:2:1 ratio).
MS (EI), m/z (rel. intensity): 294 (44) [M]+, 215 (24)
[M–CH2C5H5]+, 202 (100) [PhPH(CH2CH2C5H5)]+,
174 (61) [Ph(C5H5)PH]+, 173 (43) [Ph(C5H5)P]+, 109
(53) [PhPH]+, 93 (34) [CH2CH2C5H5]+, 91 (73)
[C7H7]+, 79 (35) [CH2C5H5]+, 77 (58) [C6H5]+.
Anal. calc. for C20H23P: C, 81.60; H, 7.88; P, 10.52.
Found: C, 81.15; H, 8.23; P, 10.17.
trahydrofuran
(THF)
from
Na/benzophenone;
dichloromethane and petroleum ether (50–70°C frac-
tion) from CaH2. Spiro[2.4]hepta-4,6-diene [22] and
phenylphosphine [23] were prepared by published pro-
cedures, and bis(benzonitrile)palladium(II) chloride by
crystallisation of PdCl2 from benzonitrile. All other
1
reagents were purchased from Aldrich Chemical. H-,
13C{1H}- and 31P{1H}-NMR data were collected on a
Varian XL-300 spectrometer operating at 300, 75 and
121 MHz, respectively. Unless otherwise stated, spec-
tra were measured at ambient temperature with
1
residue solvent peaks as internal standard for H- and
13C{1H}-NMR. 31P{1H}-NMR chemical shifts were
reported relative to external 85% H3PO4, positive
shifts representing deshielding. NMR data for all
compounds, except compound 1, are collected to-
gether in Table 1. The 1H- and 13C-NMR assign-
ments for 1 are given in Table 2. EI and FAB mass
spectra were collected on a Kratos MS80RFA mass
spectrometer. IR spectra were obtained on a Shi-
madzu FTIR-8201PC spectrophotometer. Elemental
analyses were done by Campbell Microanalysis Ser-

46
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
Table 1
1H-, 13C- and 31P-NMR data for compounds 2, 3, 4, 5, 7 and 8
2
3
4
5
7
8
1H-NMR
Ph
7.39 (2H)
7.29 (2H)
7.21 (1H)
4.06 (2H)
4.02 (2H)
4.01 (2H)
4.01 (2H)
2.5–2.3 (4H)
2.20 (2H)
2.05 (2H)
7.46 (2H)
7.38 (2H)
7.28 (1H)
4.14 (2H)
4.10 (2H)
4.06 (2H)
4.01 (2H)
2.58 (2H)
2.53 (2H)
2.34 (2H)
2.19 (2H)
7.73 (4H)
7.44 (6H)
7.50 (4H)
7.47 (6H)
7.5 (5H)
7.48 (5H)
Cp
4.12 (4H)
4.09 (4H)
4.06 (4H)
3.97 (4H)
2.9–2.4 (16H) 2.65–2.4 (12H)
2.15–1.95 (4H)
4.11 (4H)
4.07 (4H)
4.02 (4H)
3.83 (4H)
4.13 (2H)
4.13 (2H)
4.09 (2H)
3.94 (2H)
2.8–2.5 (8H)
4.11 (2H)
4.11 (2H)
4.09 (2H)
3.95 (2H)
2.7–2.4 (8H)
PCH2CH2
13C-NMR
ipso-Ph l/1JPC (Hz)
o- and m-Ph l/JPC (Hz)
140.7/16.4
130.6/15.7
128.0/5.2
127.2/0
90.4/2.2
67.9/3.7
66.8
133.9/94.9
130.9/8.4
128.8/10.4
131.8/3.0
90.0/2.0
67.9
not observed
131.6/5.3
128.7/4.2
131.1/0
91.0/2.0*
67.7
not observed
131.8/8.4
128.8/9.4
131.4/0
90.8/0
67.4 (4C)
67.0 (4C)
134.5/45.9
129.3/7.3
128.6/9.4
129.9/2.1
89.4/3.0
137.2/32.3
129.0/9.4
128.3/8.4
128.7/0
89.8/3.0
66.6
p-Ph l/4JPC (Hz)
ipso-Cp l/3JPC (Hz)
Cp l/4JPC (Hz)
67.0
66.9
67.5
67.2
66.6
66.5
67.1
67.1
66.6
66.5
66.1
22.9/10.5
21.4/18.8
66.7
26.0/65.7
18.9/2.0
67.0
66.5
66.4
PCH2 l/1JPC (Hz)
CH2Cp l/2JPC (Hz)
CO l/2JPC (Hz)
17.6/13.1a
22.4/0a
20.0/m
21.6/0
24.7/25.0 (at 80°C)
21.9/3.1 (at 80°C)
213.5/18.8
22.9/20.3 (at 80°C)
22.4/0 (at 80°C)
210.1/21.9 (trans)
205.9/9.2 (cis)
31P-NMR (ppm)
−16.8
41.6
22.1
4.1
66.7
32.6
(1JPtP=3542 Hz)
(2JPP=6 Hz)
a n
n
n+2
J
values for compound 4 are actually ꢀ JPC
+
J
ꢀ values.
PC
PC
2.3. Preparation of PPh(CH2CH2-p5-C5H4)2Fe (2)
2.4. Preparation of OPPh(CH2CH2-p5-C5H4)2Fe (3)
After cooling a solution of 1 (2.40 g, 8.16 mmol) in
THF (40 ml) to −78°C, a solution of n-BuLi (11.7 ml,
1.4 M in hexane, 16.3 mmol) was added. The solution
was then allowed to warm to ambient temperature and
was then stirred for 2 h. A slurry of anhydrous FeCl2
(1.08 g, 8.50 mmol) in THF (250 ml) was added and the
solution stirred overnight. Filtration through celite to
remove insoluble polymeric material followed by re-
moval of the volatiles in vacuo left an orange oil.
Chromatography down a 5×15 cm silica column with
1:1 petroleum ether+CH2Cl2 eluted an orange
product. Recrystallisation from 10:1 petroleum ether+
CH2Cl2 yielded orange needles (0.97 g, 34% yield),
m.p. 123–125°C. MS (EI), m/z (rel. intensity): 348
(100) [M]+, 347 (62) [M–H]+, 346 (19) [M–2H]+, 320
(42) [M–C2H4]+, 270 (15) [M–CH2C5H4]+, 256 (28)
[M–CH2CH2C5H4]+. Anal. calc. for C20H21PFe: C,
68.99; H, 6.08; P, 8.89. Found: C, 68.79; H, 6.17; P,
8.73.
A solution of 2 (0.20 g, 0.57 mmol) in THF (30 ml)
was added to a solution of trimethylamine N-oxide
(0.13 g, 1.70 mmol) in THF (50 ml). The mixture was
heated to reflux and the reaction monitored by 31P-
NMR spectroscopy. After completion of the reaction,
the volatiles were removed in vacuo. Chromatography
down a 2×5 cm silica column with CHCl3 eluted a
yellow product. Recrystallisation from 1:1 petroleum
ether+CH2Cl2 gave dark orange needles (0.15 g, 72%
yield). IR (CDCl3): wPO 1265 cm−1. MS (EI), m/z (rel.
intensity): 364 (100) [M]+, 348 (10) [M–O]+. Anal.
calc. for C20H21FePO: C, 65.95; H, 5.82. Found: C,
66.22; H, 6.18.
2.5. Preparation of
trans-PdCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (4)
A solution of 2 (0.25 g, 0.72 mmol) in THF (25 ml)
was added to a solution of bis(benzonitrile)palla-

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
47
dium(II) chloride (0.13 g, 0.35 mmol) in THF (25 ml).
After heating to reflux for 12 h, the solution was
allowed to cool to ambient temperature whereupon an
orange crystalline product precipitated. The solvent was
then filtered off and the solid dried in vacuo to give
orange crystals of 4 (0.13 g, 43% yield), m.p. 199–
205°C. MS (FAB), m/z (rel. intensity): 874 (5) [M]+,
837 (4) [M–Cl]+, 802 (2) [M–2Cl]+, 491 (7) [ClPdP-
(CH2CH2C5H4)2Fe]+, 454 (9) [PdPPh(CH2CH2-
C5H4)2Fe]+, 348 (100) [PPh(CH2CH2C5H4)2Fe]+.
Anal. calc. for C40H42P2Cl2Fe2Pd.2THF: C, 56.64; H,
5.74. Found: C, 55.45; H, 5.50. This result is consistent
with the loss of 0.4THF prior to analysis.
mixture was stirred overnight and then heated to reflux
for 5 h. The volatiles were removed in vacuo and the
residue was redissolved in 1:1 petroleum ether+
CH2Cl2. Chromatography down a 3×12 cm silica
column eluted a yellow product. Recrystallisation from
petroleum ether yielded orange needles (0.11 g, 27%
yield). M.p. 125–127°C. IR (CHCl3): wCO 2046 (m),
1969 (w), 1932 (s) cm−1. MS (FAB), m/z (rel. inten-
sity): 516 (18) [M]+, 460 (7) [M–2CO]+, 432 (100)
[M–3CO]+, 404 (39) [M–4CO]+, 348 (24) [M–
Fe(CO)4]+. Anal. calc. for C24H21O4PFe2: C, 55.85; H,
4.11. Found: C, 56.02; H, 4.14.
2.8. Preparation of
2.6. Preparation of
(CO)5MoPPh(CH2CH2-p5-C5H4)2Fe (8)
cis-PtCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (5)
A solution of 2 (0.25 g, 0.72 mmol) in THF (20 ml)
was added to a slurry of Mo(CO)6 in THF (30 ml). The
mixture was heated to reflux for 20 h. The volatiles
were removed in vacuo and the residue redissolved in
2:1 petroleum ether+CH2Cl2. Chromatography down
a 2×20 cm silica column eluted an orange product.
Recrystallisation from 2:1 petroleum ether+CH2Cl2
yielded orange needles (0.16 g, 38% yield). M.p. 159–
162°C. IR (CHCl3): wCO 2070 (mw), 1987 (w), 1942 (vs)
cm−1. MS (FAB), m/z (rel. intensity): 586 (53) [M]+,
530 (25) [M–2CO]+, 446 (36) [M–5CO]+, 348 (100)
[M–Mo(CO)5]+. Anal. calc. for C25H21FeMoO5P: C,
51.40; H, 3.63. Found: C, 50.77; H, 4.42.
A solution of 2 (0.20 g, 0.57 mmol) in THF (30 ml)
was added to a slurry of cis-bis(benzonitrile)plati-
num(II) chloride (0.14 g, 0.29 mmol) in THF (30 ml).
The mixture was heated to reflux for 12 h and cooled at
−20 °C for several days. The solvent was decanted off
and the precipitate was dried in vacuo to give a gold
solid. Recrystallisation from THF gave gold needles
(0.17 g, 30% yield). M.p. 214°C (dec.). MS (FAB), m/z
(rel. intensity): 962 (5) [M]+, 926 (10) [M–Cl]+, 890
(30) [M–2Cl]+, 540 (28) [PtPPh(CH2CH2C5H4)2Fe]+,
348 (100) [PPh(CH2CH2C5H4)2Fe]+. Anal. calc. for
C40H42P2Cl2Fe2Pt: C, 49.91; H, 4.41. Found: C, 49.65;
H, 4.45.
2.7. Preparation of (CO)4FePPh(CH2CH2-p5-C5H4)2Fe
(7)
3. X-ray crystallography
A solution of 2 (0.27 g, 0.78 mmol) in THF (20 ml)
was added to a slurry of Fe2(CO)9 in THF (30 ml). The
3.1. X-ray structure of OPPh(CH2CH2-p5-C5H4)2Fe
(3)
Table 2
1H- and 13C-NMR assignments for compound 1
Single crystals of 3 were obtained by cooling a
petroleum ether+CH2Cl2 solution to −20°C. A dark
orange rod was mounted on a glass capillary. The unit
cell parameters were obtained by least-squares refine-
ment of the setting angles of 18 reflections with 3.57°5
q512.46° from a Siemens P4 diffractometer. Data
were refined on F2 using the full-matrix least-squares
method [24] after being corrected for absorption by
using the „-scan method. The intensities of three stan-
dard reflections, measured every 97 reflections through-
out the data collection, showed only 14.21% decay. The
structure was solved by the heavy atom Patterson
method [25]. Hydrogen atoms were fixed in idealised
positions with isotropic thermal parameters 1.2 times
that of the attached atom. All non-hydrogen atoms
were refined with anisotropic atomic displacement
parameters. Neutral scattering factors and anomalous
dispersion corrections for non-hydrogen atoms were
taken from Ibers and Hamilton [26]. Crystal data, data
13C (ppm)
JPC (Hz)
1H (ppm)
Assignment
149.8
147.3
138.3
134.4
133.9
132.4
132.3
130.7
128.8
128.4
126.4
125.8
43.1
3JPC=12.2
3JPC=11.0
1JPC=10.0
Ipso-Cp
Ipso-Cp
Ipso-Ph
Cp ring A
Cp ring A
Ortho-Ph
Cp ring B
Cp ring B
Para-Ph
Meta-Ph
Cp ring B
Cp ring A
Ring B CH2
Ring A CH2
PCH2 ring B
PCH2 ring A
CpCH2CH2 ring B
CpCH2CH2 ring A
6.40
6.39
7.55
6.39
6.23
7.34
7.36
6.15
6.00
2.85
2.93
1.94
1.96
2.47
2.42
2JPC=18.3
4JPC=3.0
3JPC=7.0
41.2
28.2
27.3
27.0
1JPC=12.4
1JPC=11.7
2JPC=16.0
2JPC=15.7
26.2

48
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
Table 3
Crystal data, data collection and refinement parameters for OPPh(CH2CH2C5H4)2Fe (3), trans-PdCl2[PPh(CH2CH2C5H4)2Fe]2·2THF (4·2THF)
and Fe(CO)4[PPh(CH2CH2C5H4)2Fe] (7)
Parameter
3
4
7
Crystal data
Empirical formula
Formula weight
Crystal dimensions (mm)
Crystal system
Space group
C20H21FeOP
364.19
0.70×0.15×0.15
Monoclinic
P21/c
C48H58Cl2Fe2O2P2Pd
1017.88
0.75×0.40×0.20
Monoclinic
P21/c
C24H21Fe2O4P
516.08
0.65×0.23×0.20
Orthorhombic
Pna21
Z
a (A)
b (A)
c (A)
h (°)
i (°)
k (°)
4
2
8
˚
˚
˚
6.015(5)
18.219(8)
14.594(7)
90
99.11(6)
90
1579(2)
760
1.532
16.908(2)
7.8432(11)
16.686(2)
90
96.303(9)
90
2199.4(5)
1048
1.537
24.060(3)
8.490(2)
21.093(6)
90
90
90
4309(2)
2112
1.591
3
˚
V (A )
F(000)
Dcalc. (Mg m−3
)
v (Mo–Kh) (mm−1
)
1.058
1.288
1.450
Transmission
0.1657–0.3123
0.3360–0.4225
0.240–0.258
Data collection
Radiation type
Monochromator
T (K)
˚
˚
˚
Mo–Kh (u=0.71073 A)
Graphite
158(2)
Mo–Kh (u=0.71073 A)
Graphite
158(2)
Mo–Kh (u=0.71073 A)
Graphite
169(2)
q scan range (°)
Range of h, k, l
2.24–22.50
−65h50
05k519
2.42–25.00
−195h520
−95k50
2.54–22.50
−255h50
−15k59
−155l515
2219
−195l50
3957
05l522
2910
Reflections collected
Independent reflections
2067 (Rint=0.0495)
2067/0/208
0.759
3876 (Rint=0.0153)
3876/0/259
0.936
2903 (Rint=0.2518)
2903/1/559
0.846
Solution and refinement data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|\(I)]
R1=0.0600,
wR2=0.1308
R1=0.1139,
wR2=0.1425
0.859 to −0.365
R1=0.0278,
wR2=0.0660
R1=0.0363,
wR2=0.0679
0.530 to −0.336
R1=0.0395,
wR2=0.1004
R1=0.0576,
wR2=0.1163
0.473 to −0.348
R indices (all data)
−3
˚
Residual electron density (e A
)
collection and refinement parameters are given in Table
3, atomic coordinates and isotropic displacement
parameters are given in Table 4, bond distances are
given in Table 5 and selected bond angles are given in
Table 6. Fig. 1 shows an isotropic displacement plot
with the atomic labelling scheme.
being corrected for absorption by using the „-scan
method. The intensities of three standard reflections,
measured every 97 reflections throughout the data col-
lection, showed only 4.64% decay. The structure was
solved by direct methods [25]. Hydrogen atoms were
fixed in idealised positions with isotropic thermal
parameters 1.2 times that of the attached atom. All
non-hydrogen atoms were refined with anisotropic
atomic displacement parameters. Neutral scattering fac-
tors and anomalous dispersion corrections for non-hy-
drogen atoms were taken from Ibers and Hamilton [26].
Crystal data, data collection and refinement parameters
are given in Table 3, atomic coordinates and isotropic
displacement parameters are given in Table 7, bond
distances are given in Table 5 and selected bond angles
are given in Table 6. Fig. 2 shows an isotropic displace-
ment plot with the atomic labelling scheme.
3.2. X-ray structure of
trans-PdCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (4)
Single crystals of 4·2THF were obtained by cooling a
saturated THF solution to −20°C. An orange plate
was mounted on a glass capillary. The unit cell parame-
ters were obtained by least-squares refinement of the
setting angles of 20 reflections with 4.84°5q512.51°
from a Siemens P4 diffractometer. Data were refined on
F2 using the full-matrix least-squares method [24] after

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
49
Table 5
˚
3.3. X-ray structure of
Bond lengths (A) for compounds 3, 4 and 7
(OC)4FePPh(CH2CH2-p5-C5H4)2Fe (7)
Bond lengths
(A)
3
4
7
7%
˚
Single crystals of 7 were obtained by cooling a satu-
rated petroleum ether solution to −20°C. An orange
needle was mounted on a glass capillary. The unit cell
parameters were obtained by least-squares refinement
of the setting angles of 22 reflections with 5.19°5q5
10.97° from a Siemens P4 diffractometer. Data were
refined on F2 using the full-matrix least-squares method
[24] after being corrected for absorption by using the
„-scan method. The intensities of three standard reflec-
tions, measured every 97 reflections throughout the
data collection, showed no variation within experimen-
tal error. The structure was solved by direct methods
[25]. Hydrogen atoms were fixed in idealised positions
with isotropic thermal parameters 1.2 times that of the
attached atom. All non-hydrogen atoms were refined
with anisotropic atomic displacement parameters. Neu-
tral scattering factors and anomalous dispersion correc-
tions for non-hydrogen atoms were taken from Ibers
and Hamilton [26]. Crystal data, data collection and
refinement parameters are given in Table 3, atomic
coordinates and isotropic displacement parameters are
given in Table 8, bond distances are given in Table 5
and selected bond angles are given in Table 6. Fig. 3
shows a thermal ellipsoid plot with the atomic labelling
scheme.
Fe1–CNT(2)
Fe1–CNT(3)
Fe1–C23
Fe1–C24
Fe1–C25
Fe1–C26
Fe1–C27
Fe1–C33
Fe1–C34
Fe1–C35
Fe1–C36
Fe1–C37
P–C11
1.65(1)
1.65(1)
1.662(3)
1.657(3)
2.082(3)
2.062(3)
2.044(3)
2.040(3)
2.058(3)
2.074(3)
2.059(3)
2.043(3)
2.041(3)
2.044(3)
1.819(3)
1.824(3)
1.820(3)
1.385(4)
1.396(4)
1.397(4)
1.369(5)
1.380(5)
1.397(4)
1.551(4)
1.498(4)
1.434(4)
1.427(4)
1.417(4)
1.423(4)
1.424(4)
1.543(4)
1.505(4)
1.434(4)
1.424(4)
1.417(4)
1.419(5)
1.424(4)
2.3208(7)
2.2993(7)
1.65(1)
1.63(1)
1.64(1)
1.66(1)
2.058(8)
2.025(9)
2.024(9)
2.027(9)
2.028(9)
2.043(9)
2.012(10)
2.029(9)
2.024(9)
2.023(8)
1.829(9)
1.771(9)
1.811(9)
1.390(12)
1.372(11)
1.383(12)
1.364(13)
1.376(13)
1.384(12)
1.549(11)
1.490(12)
1.428(12)
1.409(12)
1.397(12)
1.403(12)
1.377(12)
1.553(11)
1.503(12)
1.404(12)
1.409(12)
1.387(12)
1.393(12)
1.411(11)
1.468(7)
2.041(11)
2.043(12)
2.055(12)
2.053(13)
2.030(12)
2.018(11)
2.019(12)
2.021(11)
2.039(11)
2.044(11)
1.833(12)
1.833(11)
1.824(11)
1.39(2)
1.39(2)
1.38(2)
1.37(2)
1.35(2)
1.39(2)
1.50(2)
1.52(2)
1.44(2)
1.43(2)
1.42(2)
1.41(2)
1.38(2)
1.533(14)
1.53(2)
1.39(2)
1.42(2)
1.41(2)
2.082(11)
2.036(11)
2.009(12)
2.031(11)
2.070(11)
2.061(9)
2.041(11)
2.017(11)
2.070(10)
2.038(9)
1.830(11)
1.832(11)
1.816(11)
1.388(14)
1.39(2)
1.39(2)
1.37(2)
1.41(2)
1.38(2)
1.54(2)
1.51(2)
1.43(2)
1.41(2)
P–C21
P–C31
C11–C16
C11–C12
C12–C13
C13–C14
C14–C15
C15–C16
C21–C22
C22–C23
C23–C24
C23–C27
C24–C25
C25–C26
C26–C27
C31–C32
C32–C33
C33–C34
C33–C37
C34–C35
C35–C36
C36–C37
P–Ea
1.40(2)
1.41(2)
1.42(2)
1.532(14)
1.501(14)
1.43(2)
1.42(2)
1.40(2)
Table 4
Atomic coordinates (×104) and isotropic displacement parameters
2
3
˚
1.44(2)
1.43(2)
2.254(3)
1.43(2)
1.40(2)
2.226(3)
(A ×10 ) for OPPh(CH2CH2C5H4)2Fe (3)
x
y
z
Ueq
Pd–Cl
Fe2–C1
Fe2–C2
Fe2–C3
Fe2–C4
C1–O1
C2–O2
C3–O3
C4–O4
1.782(13)
1.812(14)
1.776(12)
1.793(13)
1.150(14)
1.135(14)
1.144(14)
1.153(14)
1.813(13)
1.780(13)
1.785(12)
1.793(14)
1.124(14)
1.134(14)
1.163(13)
1.15(2)
Fe
P
O
9231(2)
7651(1)
5961(1)
5966(4)
5358(5)
5266(5)
4811(5)
4453(5)
4553(5)
5010(5)
6855(5)
7508(5)
7948(5)
8308(5)
8730(5)
8618(5)
8129(5)
5647(5)
5990(5)
6559(5)
7013(5)
7396(5)
7204(5)
6697(5)
804(1)
28(1)
29(1)
48(2)
27(2)
39(3)
43(3)
37(3)
44(3)
31(2)
33(2)
31(2)
33(2)
30(2)
35(3)
30(2)
29(2)
34(2)
26(2)
29(2)
33(2)
36(2)
32(2)
29(2)
5404(4)
3038(11)
5814(16)
4015(17)
4219(18)
6195(18)
8014(19)
7853(16)
6354(15)
5351(13)
7034(17)
6547(16)
8396(16)
10097(14)
9263(15)
7348(16)
7120(15)
8828(16)
8682(16)
10707(15)
12128(16)
10985(14)
−1163(2)
−1026(4)
−2124(6)
−2820(6)
−3560(7)
−3595(7)
−2906(7)
−2162(6)
−1482(6)
−999(6)
−351(6)
444(6)
809(6)
278(6)
−445(6)
−203(6)
749(5)
C11
C12
C13
C14
C15
C16
C31
C32
C33
C34
C35
C36
C37
C21
C22
C23
C24
C25
C26
C27
a E=O for 3, Pd for 4 and Fe2 for 7.
4. Results and discussion
4.1. Synthesis and characterisation of
bis(2-cyclopentadienylethyl)phenylphosphine (1)
1097(6)
1883(6)
2109(6)
1472(6)
The most useful synthetic route to prepare a tethered
cyclopentadienyl-phosphine ligand depends upon the
spacer between the two groups [27]. Whereas reaction
of cyclopentadienide with a chlorophosphine will give
the zero-atom bridged ligand, the methylene-bridged
875(6)

50
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
Table 6
Table 7
Selected bond angles (°) for compounds 3, 4 and 7
Atomic coordinates (×104) and isotropic displacement parameters
2
3
˚
(A ×10 ) for trans-PdCl2[PPh(CH2CH2C5H4)2Fe]2·2THF (4·2THF)
Bond angle (°)
3
4
7
7%
x
y
z
Ueq
C31–P–C21
C31–P–C11
C21–P–C11
C12–C11–P
C16–C11–P
C22–C21–P
C32–C31–P
C22–C23–Fe1 134.3(6)
C32–C33–Fe1 131.4(6)
C21–C22–C23 115.6(7)
C24–C23–C22 123.4(8)
C27–C23–C22 131.0(8)
C33–C32–C31 115.0(7)
C34–C33–C32 124.2(9)
C37–C33–C32 128.4(8)
107.3(4)
104.8(4)
105.1(4)
117.1(7)
122.1(7)
115.9(6)
114.3(6)
102.59(13)
107.11(12)
105.24(13)
119.8(2)
121.1(2)
114.1(2)
110.2(2)
134.6(2)
131.1(2)
115.1(2)
124.6(3)
127.8(3)
114.3(2)
125.7(3)
126.8(3)
113.82(9)
117.53(9)
109.70(9)
92.01(3)
87.99(3)
107.3(6)
105.7(5)
103.7(5)
118.5(9)
122.1(10)
121.0(8)
119.4(8)
130.8(8)
125.9(7)
116.7(10)
127.8(11)
125.8(11)
113.9(9)
126.7(10)
124.1(9)
113.4(4)
111.3(4)
114.8(4)
103.3(5)
103.7(5)
103.6(5)
121.9(8)
119.9(8)
115.5(8)
114.2(7)
137.5(8)
131.1(7)
117.5(9)
126.8(10)
125.2(11)
114.2(8)
126.6(9)
125.7(9)
113.5(4)
116.1(4)
115.0(4)
Pd
Fe
P
Cl
5000
0
5000
14(1)
21(1)
16(1)
25(1)
21(1)
32(1)
40(1)
42(1)
41(1)
32(1)
20(1)
25(1)
22(1)
26(1)
31(1)
34(1)
29(1)
21(1)
22(1)
24(1)
30(1)
37(1)
33(1)
27(1)
83(1)
73(1)
63(1)
65(1)
72(2)
1560(1)
3864(1)
5529(1)
3940(2)
4239(2)
4356(2)
4177(2)
3877(2)
3762(2)
3632(2)
2906(2)
2197(2)
1386(2)
878(2)
1368(2)
2177(2)
2950(2)
2839(2)
2078(2)
1991(2)
1172(2)
747(2)
3338(1)
1039(1)
2691(1)
730(4)
2036(5)
1768(5)
223(5)
−1076(5)
−828(4)
3293(3)
3914(4)
4435(4)
4129(4)
5025(4)
5902(4)
5537(4)
1(4)
5055(1)
4252(1)
5179(1)
3183(2)
2734(20
1928(2)
1572(2)
2008(2)
2816(2)
4358(2)
3782(2)
4188(2)
3870(2)
4346(2)
4961(2)
4866(2)
4476(2)
5376(2)
5525(2)
6153(2)
6135(2)
5501(2)
5118(2)
7869(2)
7160(3)
7230(3)
7909(2)
8097(2)
C11
C12
C13
C14
C15
C16
C21
C22
C23
C24
C25
C26
C27
C31
C32
C33
C34
C35
C36
C37
O
C31–P–Ea
C21–P–Ea
C11–P–Ea
Cl–Pd–P
ClA–Pd–P
P–Fe2–C1
P–Fe2–C2
P–Fe2–C3
P–Fe2–C4
112.4(4)
115.3(4)
111.1(4)
226(4)
179.7(4)
87.7(4)
88.0(4)
87.7(4)
171.9(4)
88.4(4)
92.3(4)
84.0(4)
1104(4)
2316(4)
2718(4)
1778(4)
797(4)
1636(5)
1195(7)
1745(6)
2997(6)
3209(6)
1306(2)
9590(2)
9139(3)
8316(2)
8376(3)
9253(3)
a E=O for 3, Pd for 4 and Fe2 for 7.
C41
C42
C43
C44
ligand is best prepared by reaction of an appropriate
phosphide with a pentafulvene. The trimethylene-
bridged ligands are best prepared by reaction of cy-
clopentadienide with
a
3-chloropropylphosphine.
Analogous routes are generally unsuitable for ethylene-
bridged ligands due to a range of undesirable side
reactions. One notable exception is the one-pot synthe-
sis of 2-(tetramethylcyclopentadienyl)-1-(diphenylphos-
phino)ethane by Szymoniak and coworkers by
treatment of tetramethylcyclopentadiene with 2-
chloroethyl tosylate followed by lithium diphenylphos-
phide [28]. More generally, the ethylene-bridged ligands
are best prepared by the ring-opening reaction of a
spiro[2.4]hepta-4,6-diene with a phosphide. Thus, the
route taken to prepare bis(2-cyclopentadienylethyl)-
phenylphosphine (1) involves the treatment of two
equivalents
of
spiro[2.4]hepta-4,6-diene
with
phenylphosphine and two equivalents of n-BuLi, fol-
lowed by aqueous hydrolysis (Scheme 1). After chro-
matography, 1 is obtained in high yield as a colourless
or slightly yellow oil.
Compound
1
has been characterised by 1H-,
13C{1H}-, 31P{1H}-NMR, H/13C-HETCOR-, and H-
COSY-NMR spectroscopy, as well as by mass spec-
trometry and microanalysis. 1H- and 13C{1H}-NMR
1
1
Fig. 1. Isotropic displacement plot with the atomic numbering scheme
Fig. 2. Isotropic displacement plot with the atomic numbering scheme
for OPPh(CH2CH2C5H4)2Fe (3).
for trans-PdCl2[PPh(CH2CH2C5H4)2Fe]2 (4).

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
51
Table 8 (continued)
Table 8
Atomic coordinates (×104) and isotropic displacement parameters
(A ×10 ) for Fe(CO)4[PPh(CH2CH2C5H4)2Fe] (7)
2
3
˚
x
y
z
Ueq
C34%
C35%
C36%
C37%
2927(4)
2927(5)
3267(5)
3466(4)
5561(14)
4386(13)
3113(13)
3508(13)
2758(5)
2291(5)
2512(5)
3116(6)
23(3)
27(3)
26(3)
21(2)
x
y
z
Ueq
Molecule 1
Fe1
Fe2
P
C1
C2
C3
C4
O1
O2
5007(1)
4166(1)
4863(1)
3613(5)
3695(5)
4329(4)
4504(5)
3258(4)
3394(3)
4413(4)
4716(4)
5562(5)
5788(5)
6304(5)
6599(5)
6379(6)
5863(5)
4821(4)
5213(5)
4993(5)
4439(5)
4409(5)
4935(6)
5288(5)
4873(5)
5399(4)
5301(4)
4817(4)
4892(4)
5453(5)
5705(4)
12900(2)
8559(2)
4372(1)
2043(1)
2652(1)
1565(6)
20(1)
20(1)
18(1)
32(3)
30(3)
23(3)
29(3)
47(3)
32(2)
39(2)
42(2)
25(3)
33(3)
41(3)
41(4)
46(4)
31(3)
23(3)
32(3)
26(3)
29(3)
34(3)
44(4)
33(3)
25(3)
16(2)
20(3)
21(3)
23(3)
29(3)
22(3)
9487(3)
7825(14)
9060(12)
10056(13)
6678(15)
7390(11)
9403(9)
spectroscopy (see Table 2) indicate that there are two
major cyclopentadiene ring isomers, shown below as
ring A and ring B, in approximately equal amounts. No
peaks corresponding to the third possible ring isomer,
C, have been observed. There are six multiplets in the
vinyl proton region (three from ring A and three from
ring B) which are associated with six carbon resonances
in the 13C-NMR spectrum. Two singlets in the
methylene region (2.93 and 2.85 ppm) and their associ-
ated 13C resonances are assigned to the cyclopentadiene
methylene groups. Combinations of the two ring iso-
mers should give three isomers of compound 1 in about
a 1:2:1 ratio. The methylene region is expected to be
complex—with up to four ABCD patterns that could
be observed. The HETCOR (8.456 T) spectrum, how-
ever, distinguishes only four proton environments each
of which is associated with a different carbon atom.
This observation is consistent with each set of A/B and
C/D resonances being approximately degenerate and
the nature of one ring isomer having little or no effect
on the chemical shifts observed for the other cyclopen-
tadienylethyl substituent. That there are indeed three
isomers for 1 was confirmed by 31P{1H}-NMR spec-
troscopy which gives three peaks (−22.55, −22.40
and −22.25 ppm) resulting from the AA, AB and BB
isomers (not necessarily in that order). Although the
26820(7)
1485(6)
2065(6)
1245(5)
3073(4)
1121(4)
2076(5)
2390(6)
1868(6)
1638(6)
1927(7)
2435(8)
2687(6)
3461(5)
3968(6)
4421(6)
4458(6)
4995(6)
5288(6)
4950(6)
2711(6)
2948(5)
3515(5)
3654(6)
4222(5)
4427(6)
3985(5)
O3
O4
11027(10)
5460(10)
8922(13)
9681(14)
9280(18)
8100(16)
7348(17)
7737(14)
8708(14)
9264(13)
10500(12)
11125(14)
12131(15)
12115(15)
11148(13)
11630(13)
12461(12)
13554(13)
14378(12)
15229(12)
14937(12)
13883(12)
C11
C12
C13
C14
C15
C16
C21
C22
C23
C24
C25
C26
C27
C31
C32
C33
C34
C35
C36
C37
Molecule 2
Fe1%
Fe2%
P%
C1%
C2%
C3%
C4%
O1%
O2%
2619(1)
2096(1)
2762(1)
1506(5)
1721(5)
2534(5)
2164(5)
1131(4)
1485(4)
2810(3)
2229(4)
3432(4)
3580(4)
4090(5)
4465(5)
4315(4)
3804(4)
2614(5)
2068(4)
2106(4)
1806(4)
1867(5)
2200(5)
2347(5)
2932(4)
3415(4)
3263(4)
3494(2)
7828(2)
6349(3)
3104(1)
5378(1)
4951(1)
5753(6)
4655(6)
5397(6)
6037(6)
5976(4)
4189(5)
5393(5)
6453(4)
5361(5)
5816(6)
6121(6)
5972(5)
5524(5)
5229(5)
4892(6)
4558(6)
3890(6)
3352(6)
2855(6)
3072(6)
3711(6)
4142(5)
3855(5)
3274(5)
19(1)
24(1)
18(1)
33(3)
36(3)
27(3)
30(3)
46(2)
55(3)
43(2)
46(2)
21(2)
27(3)
34(3)
27(3)
25(3)
17(2)
26(3)
31(3)
23(3)
33(3)
36(3)
32(3)
28(3)
19(2)
14(2)
15(2)
1
nature of one ring does not significantly affect the H
8770(15)
7659(16)
9525(13)
6507(15)
9336(11)
7642(12)
10649(10)
5646(11)
6422(12)
5315(14)
5385(15)
6549(14)
7702(14)
7628(11)
4238(13)
3805(14)
3189(13)
3748(16)
2669(16)
1418(15)
1740(13)
6896(12)
5959(12)
5035(11)
and 13C chemical shifts of either the phenyl atoms or
the other cyclopentadienylethyl substituent atoms, it
does affect the 31P chemical shift. Paolucci and cowork-
ers, based on 1H- and 13C{1H}-NMR spectroscopy,
reported that they observed only the mixed AB isomer
for the related compound 2,6-bis(cyclopentadienyl-
methyl)pyridine [10]. They may not have been able to
detect the presence of the AA and BB isomers.
O3%
O4%
C11%
C12%
C13%
C14%
C15%
C16%
C21%
C22%
C23%
C24%
C25%
C26%
C27%
C31%
C32%
C33%
The P–C coupling constants are consistent with
those found for PhPEt2 and PhPnPr2 [29,30]. The JPC
1
2
coupling constants are smaller than the JPC values: for
the ethylene bridge, 1JPC=12.4 and 11.7 Hz versus 12.5
Hz for PhPEt2 and 12.8 Hz for PhPn-Pr2 whereas
2JPC=16.0 and 15.7 Hz versus 14.7 Hz for PhPEt2 and
1
15.4 Hz for PhPn-Pr2. For the phenyl ring, the JPC

52
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
4.3. Synthesis and characterisation of
OPPh(CH2CH2-p5-C5H4)2Fe (3)
Treatment of 2 with trimethylamine-N-oxide in THF
gives the phosphine oxide complex OꢀPPh(CH2CH2-p5-
C5H4)2Fe (3) (Scheme 2). Air oxidation of solutions of
2 also give this product, however, the reaction is not as
clean. As with 2, NMR spectroscopy indicates Cs sym-
metry with the mirror plane through the phenyl group
and the Fe, P and O atoms: the four ring protons
exhibit an ABCD pattern and there are five ring carbon
atoms in the 13C-NMR spectrum. The 31P resonance
has shifted 58.4 ppm downfield from that found in 2 to
41.6 ppm. This chemical shift difference is typical for
the formation of phosphine oxides.
Fig. 3. Thermal ellipsoid plot with the atomic numbering scheme for
Fe(CO)4[PPh(CH2CH2C5H4)2Fe] (7).
coupling constant of 10.0 Hz appears to be small
2
compared with 17.9 Hz for PhPEt2, however, the JPC
3
(18.3 vs. 18.6 Hz) and JPC (7.0 vs. 6.7 Hz) coupling
constants are similar.
An X-ray crystallographic analysis of 3 was carried
out to determine the ligand conformation. This analysis
showed one unique molecule of 3 per asymmetric unit.
The molecule consists of a fully eclipsed ferrocene unit
(the C33–CNT(3)–CNT(2)–C23 dihedral angle is 9.7°)
with the two cyclopentadienyl rings linked to a phos-
phorus atom by ethylene bridges (Fig. 1). The phospho-
rus atom is approximately tetrahedral and has a phenyl
substituent and oxygen atom attached to it in addition
to the ethylene bridges to the ferrocenyl unit.
4.2. Synthesis and characterisation of
PPh(CH2CH2-p5-C5H4)2Fe (2)
Deprotonation of 1 with two equivalents of n-BuLi
followed by treatment with FeCl2 gives the ferrocene
complex PPh(CH2CH2-p5-C5H4)2Fe (2) in moderate
yields of 40–50%. A significant amount of dark brown
gelatinous material, which is presumably polymeric, is
produced also. We have been unable to isolate any
1
other compounds. The H-NMR spectrum is consistent
The CNT(2)–Fe–CNT(3) angle of 177.5° indicates
that there may be a small amount of ring strain. This is
with an average Cs symmetry with the mirror plane
through the phenyl group and the Fe and P atoms:
There is one ABCD pattern for the cyclopentadienyl
protons and one ABCD pattern for the methylene
protons. The 13C{1H}-NMR spectrum is also consistent
with a Cs structure. 31P{1H}-NMR spectroscopy shows
one peak at −16.8 ppm. This is small upfield shift of
3.6 ppm from the protonated ligand 1 and indicates
that the P atom is not coordinated to an Fe atom.
Scheme 2.
Scheme 1.

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
53
also indicated by the angles between the Cp–CH2 vec-
tor and the cyclopentadienyl ring plane which averages
6.5°. The conformer adopted has an approximate mir-
ror plane through the Fe, O, P and C11 atoms (O–P–
Fe–CNT(3)=77.6° and C11–P–Fe–CNT(2)=85.1°).
The phenyl ring is twisted out of this plane. This
conformation results in the less bulky oxygen atom
being oriented towards the ferrocenyl unit (Fe–P–O=
108.2°) while the bulkier phenyl group is oriented away
from the ferrocenyl unit (Fe–P–C11=140.4°).
by consideration of the angle between the cyclopentadi-
enyl planes (which are tilted away from the heterocyclic
ring) of 6.1°, the CNT(2)–Fe–CNT(3) angle of 175.7°,
and the angles between each cyclopentadienyl plane
and its associated Cp–CH2 bond vector which are 7.6°
(ring C23–C26) and 4.4° (ring C33–C36). Conse-
quently, the angle between the two Cp–CH2 bond
vectors is 19.6° (the C22–C23–C33–C32 dihedral angle
of 6.8° contributes only 1.5° to this value). This is in
contrast to the apparently ring-strain-free ferrocene
complex Me2Si(OSiMe2C5H4)2Fe (6) that was reported
by Manners and coworkers [18]. In 6, the angle between
the cyclopentadienyl rings is less than 2° while the
average angle between each cyclopentadienyl plane and
its ipso-Cp–Si bond vector is only 1.6°. It is most likely
that any ring-strain in 6 is relieved by the wide angles at
the oxygen atoms (average Si–O–Si=159.7°). By com-
parison, all of the ring angles at the sp3 hybridised
atoms in 4 are less than 116°. Both 4 and 6 exhibit an
eclipsed geometry for the cyclopentadienyl rings (the
cyclopentadienyl rings are 5.1° from a perfectly eclipsed
geometry in 4 and 0.9° from a perfectly eclipsed geome-
try in 6). The C–Si bonds in 6, however, are rotated
72.9° from the fully eclipsed geometry.
The conformer adopted for the ring backbone of 4 is
one that places the PdCl2P and phenyl groups in ap-
proximately equivalent environments (Pd–P–Fe–
CNT(3)=49.0° and C11–P–Fe–CNT(2)=53.0° while
Fe–P–Pd=130.9° and Fe–P–C11=119.3°) and as far
away from the ferrocene unit as possible when allowing
for reasonable bond angles and bond distances for the
ring atoms. The nature of this conformer can be ratio-
nalised by considering the similar steric properties of
the phenyl and PdCl2P groups which both have flat
structures. As a result of this steric similarity, there is a
pseudo C2 axis through the P and Fe atoms. The
conformer adopted by 6, however, is dominated by
steric interactions between the SiMe2 groups attached
to the cyclopentadienyl rings.
4.4. Synthesis and characterisation of the trinuclear
complexes trans-PdCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (4)
and cis-PtCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (5)
Trinuclear heterobimetallic complexes were prepared
by treating trans-PdCl2(PhCN)2 and cis-PtCl2(PhCN)2
with two equivalents of
2
to give trans-
(4) and cis-
PdCl2[PPh(CH2CH2-p5-C5H4)2Fe]2
PtCl2[PPh(CH2CH2-p5-C5H4)2Fe]2 (5), respectively
(Scheme 2). As with 2, both of these complexes exhibit
ABCD patterns for the cyclopentadienyl and methylene
1
protons in the H-NMR spectrum. The 31P chemical
shift of 22.1 ppm for 4 is 38.9 ppm upfield of that
observed for 2 whereas a chemical shift of 4.1 ppm is
observed for 5—an upfield shift of 20.9 ppm from that
of 2. These upfield shifts are consistent with coordina-
tion of the phosphine to the metal centre. Similar
upfield shift changes are observed for analogous Pd–
PPhMe2 (42.3 ppm) [31] and Pt–PEt3 (29.1 ppm) [32]
systems. A one bond 195Pt–31P coupling constant of
3542 Hz for complex 5 is consistent with a cis geometry
for this complex [33].
To assist in the characterisation of 4, and to investi-
gate the conformation adopted by the ligand, an X-ray
crystal structure determination was carried out. The
crystal structure shows that one independent molecule
of 4 lies with the palladium atom on a crystallographic
inversion center while one independent molecule of
THF does not. This gives two molecules of THF for
each molecule of 4. Fig. 2 shows an isotropic plot of
one molecule of 4 with the adopted numbering scheme.
4.5. Synthesis and characterisation of the dinuclear
complexes (OC)4FePPh(CH2CH2-p5-C5H4)2Fe (7) and
(OC)5MoPPh(CH2CH2-p5-C5H4)2Fe (8)
Molecule
4 consists of a square-planar trans-
dichlorodiphosphine-palladium centre and, as is usually
observed with such complexes [34], the Pd–P bond
Dinuclear complexes were prepared by treating either
Fe2(CO)9 or Mo(CO)5(THF) with one equivalent of 1
to give (CO)4FePPh(CH2CH2-p5-C5H4)2Fe (7) or
(CO)5MoPPh(CH2CH2-p5-C5H4)2Fe (8), respectively
(Scheme 2). The infrared spectra of 7 and 8 both show
the expected three wCO stretches (2A1 and E) for
Fe(CO)4L and Mo(CO)5L complexes with approximate
C36 and C46 symmetry, respectively. Again, the 1H-
NMR spectra exhibit a single ABCD pattern for the
cyclopentadienyl ring protons while the 13C-NMR spec-
tra show five environments for the cyclopentadienyl
ring carbon atoms. The methylene carbons of both
˚
distances (2.3208(7) A) are longer than the Pd–Cl bond
˚
distances (2.2993(7) A). Each phosphine has one phenyl
substituent and one ferrocenyl substituent which is
linked to the phosphorus atom by two ethylene
bridges—one from each cyclopentadienyl group. The
tetrahedral geometry of the phosphorus atom is dis-
torted by ring strain such that the angle between the
two methylene carbon atoms is reduced to 102.59(13)°.
By comparison, the angles between the phenyl and the
methylene carbon atoms are 105.24(13) and
107.11(12)°. Further evidence of ring-strain is provided

54
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
tween each cyclopentadienyl plane and its associated
Cp–CH2 bond vector are only 4.9° (ring C23–C26) and
0.1° (ring C33–C36). Consequently, the angle between
the two Cp–CH2 bond vectors is significantly less at
14.9° (vs. 19.1, 19.6 and 21.3° for molecules 3, 4, and
the unprimed molecule of 7, respectively). The
CNT(2)–Fe–CNT(3) angle of 175.7° is similar to that
of the other structures.
4.6. 13C-NMR spectra of complexes 2, 3, 4, 5, 7 and 8
Fig. 4. Illustration of the conformational differences between com-
plexes 3, 4, 6 and 7.
The 13C spectrum of 2 is similar to that of 1, but with
a number of resonances shifted upfield. The ipso-cy-
clopentadienyl ring carbon appears at 90.4 ppm with
the other ring resonances at 66.1–67.9 ppm. These are
typical of ferrocene complexes. The ethylene-bridge car-
bons are shifted upfield by ca. 5 ppm with a small
complexes show a number of resonances at room tem-
perature due to the slow interconversion of conformers.
At elevated temperatures, only two resonances are ob-
served as conformational interconversion becomes
rapid. The carbonyl ligands for 7 appear as one doublet
(2JPC=18.8 Hz), as is expected for an Fe(CO)4L com-
plex undergoing rapid Berry pseudorotation. Complex
8, on the other hand, shows two carbonyl environ-
ments. Large downfield shifts relative to 2 for the
31P-NMR resonances (66.7 ppm for 7, D=83.5 ppm,
and 32.6 ppm for 8, D=49.4 ppm) are consistent with
coordination of phosphorus to these metal carbonyls.
An X-ray crystal structure analysis of 7 revealed the
presence of two independent molecules in the asymmet-
ric unit with differing backbone conformations. Fig. 3
shows a thermal ellipsoid plot of the two molecules and
Fig. 4 illustrates the essential differences between the
conformers adopted by 3, 4, 6 and the two molecules of
7. The unprimed molecule has a conformation similar
to that found for the solid-state structure of 3: the Fe1,
Fe2, P and C11 atoms are approximately coplanar with
an approximate mirror plane through them. In this
case, however, the phenyl group is oriented towards the
ferrocene unit (Fe1–P–C11=109.6°) and the bulkier
Fe(CO)4 group is directed away from the ferrocene unit
(Fe1–P–Fe2=135.4°). Like compounds 3 and 4, evi-
dence of ring-strain is provided by the angle between
the cyclopentadienyl planes (which are tilted away from
the heterocyclic ring) of 7.1°, the CNT(2)–Fe–CNT(3)
angle of 176.1°, and the angles between each cyclopen-
tadienyl plane and its associated Cp–CH2 bond vector
which are 10.1° (ring C23–C26) and 4.1° (ring C33–
C36). Consequently, the angle between the two Cp–
CH2 bond vectors is 21.3°. The primed molecule
exhibits a conformation similar to that of 4: there is a
pseudo C2 axis through the Fe1% and P% atoms and the
Fe(CO)4 and phenyl groups are in approximately equiv-
alent environments (C11%–P%–Fe1%–CNT(3)%=50.2°
and Fe2%–P%–Fe1%–CNT(2)%=54.8°). There appears to
be less strain in this conformation: The angle between
the cyclopentadienyl planes (which are tilted away from
the heterocyclic ring) is only 3.2° and the angles be-
1
decrease in the JPC coupling constant and a small
2
increase in the JPC coupling constant. Similarly, the
phenyl resonances exhibit minor variations with the
1
exception of JPC which has increased from 10.0 to 16.4
Hz. This is much more like PhPEt2 (17.9 Hz).
Coordination of 2 to oxygen or a metal complex
gives the largest chemical shift change to the ipso-
phenyl carbon and the methylene-carbon atoms. The
ipso-carbon atoms all move upfield from 140.7 ppm to
between 133.9 and 137.2 ppm. For the methylene-car-
bon atoms, the i-carbon atoms all exhibit upfield shifts
whereas the h-carbon atoms are shifted downfield for
complexes 3, 7 and 8, but upfield for the palladium and
platinum complexes 4 and 5. The behaviour shown by
complexes 3, 7 and 8 is the same as that of PhPEt2
when coordinated to a Ni(CO)3 fragment [30].
The one-bond P–C coupling constants increase by
variable amounts upon coordination of 2. The largest
increase is observed for the phosphine oxide 3 (16.4 to
94.9 Hz for the ipso-phenyl carbon and 10.5 to 65.7 Hz
for the h-methylene carbon atoms). There is a strong
correlation between the coupling constants of the ipso-
carbon atom and the h-methylene carbon atoms (R2=
0.97). The two-bond P–C coupling constants, however,
all decrease upon coordination of 2: from 15.7 Hz to
less than 10 Hz for the ortho-phenyl carbon atoms and
from 10.5 Hz to less than 4 Hz for the i-methylene
carbon atoms.
4.7. Electrochemistry of complexes 2, 3, 4, 5 and 7
The electrochemistry of complexes 2, 3, 4, 5 and 7
was investigated by cyclic voltammetry. The results are
summarised in Table 9. Fig. 5 shows a typical cyclic
voltammogrametric response in acetonitrile for complex
2: an irreversible oxidation occurs at Ep= −0.34 V
versus Fc+/Fc followed by a reversible oxidation at
E
1/2=0.10 V versus Fc+/Fc. This is similar to that
observed by Butler and coworkers for the ferrocene

J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
55
Table 9
Electrochemical data for compounds 2, 3, 4, 5 and 7 (V vs. Fc+/Fc)
Compound
(solvent)
Scan rate
Ep
E1/2
Ep
(mV s−1
)
2 (CH3CN)
3 (CH2Cl2)
4 (CH2Cl2)
5 (CH2Cl2)
7 (CH3CN)
7 (CH2Cl2)
200
200
100
100
100
50
−0.34
0.10
−0.01
−0.005
0.08
0.05
0.05
0.02
0.35a
a Associated with a reduction peak at Ep=−0.36 V.
complex Fe(C5H4PPhBu)(C5H4-2,2%-bipyridyl) [35] and
by Kagan and coworkers for Fe(C5H5)(C5H3(CHO)-
PPh2) [36]. For the latter complex, the irreversible
oxidation was ascribed to oxidation of the phosphorus
atom to a phosphonium radical cation (after electron
transfer to an Fe(III) centre) with subsequent oxidation
to the phosphine oxide by traces of water. Similarly,
Podlaha and coworkers observed two oxidations for
Fe(C5H4PPh2)(C5H4COOR) (R=H, Me) for which
they proposed, for the first oxidation, a mechanism
similar to that given by Kagan and coworkers. For the
second oxidation process, they observed almost identi-
cal potentials to those of the isolated phosphine oxide
complexes, and thus attributed the second process to
oxidation of the Fe(II) centre of the phosphine oxide
complex [37]. For Fe(C5H4PPh2)2 (dppf), which exhibits
a single oxidation process, Pilloni proposed the cation
radical–substrate coupling mechanism in which, after
oxidation at the iron centre and intramolecular transfer
of an electron from phosphorus to iron, there is a rapid
dimerisation or reaction with substrate to give a P–P
bonded dinuclear dication or cation, respectively [38].
This P–P bonded species then undergoes irreversible
reaction with water to give phosphine oxide and phos-
phonium species. We tentatively propose here a similar
process for the electrochemistry of complex 2 (Scheme
Scheme 3.
3): oxidation at the iron centre is followed by transfer
of an electron to iron from phosphorus which is driven
by a fast reaction with starting substrate to give the
P–P bonded cation 9, the second oxidation is proposed
to occur at an iron centre of 9. The CV of the phos-
phine oxide 3 shows a simple reversible oxidation at
E
1/2= −0.01 V (compared with 0.10 V for the second
oxidation process of 2) which indicates that the second
oxidation process of 2 cannot be due to a phosphine
oxide complex. Attempts to isolate 9 have so far been
unsuccessful.
The cyclic voltammograms of the tetracarbonyl iron
adduct 7 in acetonitrile and dichloromethane are quite
different. In acetonitrile, an irreversible oxidation at
Ep=0.02 V appears very close to a reversible oxidation
at E1/2=0.05 V (Fig. 6). In addition, there is a broad
reduction peak at Ep= −0.65 V. In dichloromethane,
the reversible process still appears at E1/2=0.05 V (Fig.
7(a)), but now the irreversible process occurs at Ep=
0.35 V and is associated with adsorption at the elec-
trode, hence the large reduction peak for the reversible
process (Fig. 7(b)), as well as a small reduction peak at
Ep= −0.36 V. The reversible process is attributed to
oxidation of the ferrocene centre and the irreversible
process is assigned to oxidation of the tetracarbonyl-
Fig. 5. Cyclic voltammogram of PPh(CH2CH2C5H4)2Fe (2) in ace-
Fig. 6. Cyclic voltammogram of Fe(CO)4[PPh(CH2CH2C5H4)2Fe] (7)
tonitrile (200 mV s−1).
in acetonitrile (100 mV s−1).

56
J.J. Adams et al. / Journal of Organometallic Chemistry 577 (1999) 44–57
stituents and one phosphine group. The ferrocene
complex contains an uncoordinated phosphine group
which is then able to coordinate to other metal centres
such as Fe(CO)4 and PdCl2. The crystal structures of 3,
4 and 7 reported here, as well as the zirconocene
complexes [21] reported previously, indicate that the
ligand is highly flexible and is able to adopt a range of
conformations.
6. Supplementary information available
Tables of crystal data, structure refinement details,
atomic coordinates, bond lengths and angles, an-
isotropic displacement parameters, and hydrogen coor-
dinates are available from the authors or from the
Cambridge Crystallographic Data Centre, Lensfield
Road, Cambridge, CB2 1EW, UK.
Acknowledgements
O.J. Curnow wishes to thank the Alexander von
Humboldt Foundation for their generous support. The
New Zealand Lotteries Science Grants Board is to be
thanked for a grant to purchase precious metals. Dr
Alison Downard (University of Canterbury) is thanked
for her assistance with the cyclic voltammetry experi-
ments and for useful discussions regarding those results.
Fig. 7. Cyclic voltammograms of Fe(CO)4[PPh(CH2CH2C5H4)2Fe]
(7) in dichloromethane (50 mV s−1).
phosphine–iron fragment. Apparently, the more polar
and coordinating acetonitrile solvent is able to keep the
product of this oxidation in solution and is probably
taking part in the oxidation process by coordination to
the oxidised iron centre via formation of an
[Fe(CO)4(CH3CN)(PR3)]+ intermediate, hence the
lower oxidation potential. Bond and coworkers ob-
served irreversible oxidations at 1.2 V versus Ag/AgCl
for monophosphino–tetracarbonyl-iron complexes in
acetone [39].
The cyclic voltammograms of the trinuclear com-
plexes 4 and 5 were recorded to determine if there is
any electronic communication between the ferrocene
centres—there are two cross-linked chains, each of
seven non-conjugated atoms, between the ferrocene
centres. A single two-electron reversible redox process
(E1/2= −0.005 V for 4 and 0.08 V for 5, versus Fc+/
Fc) was observed for both complexes indicating that
there is no significant communication.
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