Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

Article abstract of DOI:10.1016/j.jorganchem.2008.04.005

The new ferrocenyl substituted ditertiary phosphine {FcCH₂N(CH₂PPh₂)CH₂}₂ [Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH₂N(H)CH₂}₂ with 2 equiv. of Ph₂PCH₂OH in CH₃OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo⁰, Ru^II, Rh^I, Pd^II, Pt^II and Au^I to afford the heterometallic complexes {RuCl₂(p-cym)}₂(1) (2), (AuCl)₂(1) (3), cis-PtCl₂(1) (4), cis-PdCl₂(1) (5), cis-Mo(CO)₄(1) (6), trans,trans-{Pd(CH₃)Cl(1)}₂ (7) and trans,trans-{Rh(CO)Cl(1)}₂ (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4-6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 · 2CH₂Cl₂, 3 · CH₂Cl₂, 4 · CH₂Cl₂, 6 · 0.5CHCl₃ and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.

Full text of DOI:10.1016/j.jorganchem.2008.04.005

Journal of Organometallic Chemistry 693 (2008) 2317–2326
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, coordination studies and redox properties of a novel ditertiary
phosphine bearing two ferrocenyl groups
*
Mark R.J. Elsegood, Andrew J. Lake, Roger J. Mortimer, Martin B. Smith , George W. Weaver
Department of Chemistry, Loughborough University, Loughborough, Leics LE11 3TU, UK
a r t i c l e i n f o
a b s t r a c t
The new ferrocenyl substituted ditertiary phosphine {FcCH2N(CH2PPh2)CH2}2 [Fc = (g5-C5H4)Fe(g5-C5H5)]
(1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine
{FcCH2N(H)CH2}2 with 2 equiv. of Ph2PCH2OH in CH3OH. Phosphine 1 readily coordinates to various tran-
sition-metal centres including Mo0, RuII, RhI, PdII, PtII and AuI to afford the heterometallic complexes
{RuCl2(p-cym)}2(1) (2), (AuCl)2(1) (3), cis-PtCl2(1) (4), cis-PdCl2(1) (5), cis-Mo(CO)4(1) (6), trans,trans-
{Pd(CH3)Cl(1)}2 (7) and trans,trans-{Rh(CO)Cl(1)}2 (8). In complexes 2, 3, 7 and 8 ligand 1 displays a
P,P0-bridging mode whilst for 4–6 a P,P0-chelating mode is observed. All new compounds have been fully
characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 ꢀ 2CH2Cl2,
3 ꢀ CH2Cl2, 4 ꢀ CH2Cl2, 6 ꢀ 0.5CHCl3 and 8 have been elucidated by single crystal X-ray crystallography.
Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both non-
complexed ligand 1 and representative compounds containing this new ditertiary phosphine.
Ó 2008 Elsevier B.V. All rights reserved.
Article history:
Received 6 March 2008
Received in revised form 28 March 2008
Accepted 3 April 2008
Available online 7 April 2008
Keywords:
Phosphine ligands
Ferrocenyl compounds
Organometallic complexes
X-ray crystallography
Electrochemical studies
1. Introduction
gand and selected compounds is reported along with six single
crystal X-ray structure determinations.
The ferrocenyl (Fc) group continues to play a fundamental role
in the design of new mono- and polyphosphorus containing
ligands and some of their transition metal complexes have been
studied as homogenous catalysts [1–5]. The versatility of the Fc
group in synthesis can be illustrated by some of the diverse com-
pounds (Chart 1) previously documented in the literature. The Fc
group can be employed either as a substituent bonded to phospho-
rus [6] or a metal centre [7] through an ethynyl linker or alterna-
2. Experimental
2.1. Materials
Standard Schlenk techniques were used for the synthesis of 1
whilst all other reactions were carried out in air using previously
distilled solvents unless otherwise stated. Diphenylphosphino-
methanol has been reported elsewhere [28] and the metal precur-
sors {RuCl2(p-cym)}2 (p-cym = p-cymene) [29], AuCl(tht)
(tht = tetrahydrothiophene) [30], MCl2(cod) (M = Pd, Pt, cod =
cycloocta-1,5-diene) [31], Pd(CH3)Cl(cod) [32] and Mo(CO)4 (nbd)
(nbd = norbornadiene) [33] prepared according to known proce-
dures. The secondary amine {FcCH2N(H)CH2}2 was prepared fol-
lowing slight modification of a known method [34b] whilst all
other chemicals were obtained from commercial sources and used
directly without further purification.
tively as
a backbone for accessing primary and secondary
phosphines [8], di- and polyphosphines [9,10], nonsymmetric
ligands [11–14] and chiral systems [15–18]. To date,
1,10-bis(diphenylphosphino)ferrocene (dppf) possibly remains the
most iconic example of a phosphorus(III) based ligand containing
the Fc moiety [4,19–23]. Furthermore the ferrocenyl group contin-
ues to attract much attention because of the redox active metal
centre present, thereby allowing studies of electronic communica-
tion for the development of new electronic materials and devices
[24–26]. Recently Tucker and co-workers have shown how ferroce-
nyl modified ureas can be used as enantioselective electrochemical
sensors for chiral carboxylates [27].
2.2. Instrumentation
We report here the synthesis of a new ditertiary phosphine
bearing two pendant ferrocenyl groups and a brief survey of its
coordination chemistry to Mo0, RuII, RhI, PdII, PtII and AuI metal
centres. The electrochemical properties of the non complexed li-
Infrared spectra were recorded as KBr pellets in the range
4000–200 cmꢁ1 on a Perkin–Elmer System 2000 Fourier-transform
spectrometer, 1H NMR spectra (400 MHz) on a Bruker DPX-400 FT
spectrometer with chemical shifts (d) in ppm to high frequency of
Si(CH3)4 and coupling constants (J) in Hz, 31P{1H} NMR spectra
* Corresponding author. Tel.: +44 (0)1509 222553; fax: +44 (0)1509 223925.
E-mail address: m.b.smith@lboro.ac.uk (M.B. Smith).
were recorded on
a Bruker DPX-400 FT spectrometer with
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.005

2318
M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
PPh2
CH2PH2
PPh2
PPh2
PPh2
OH
Fe
Fe
Fe
Fe
PPh2
Chart 1.
chemical shifts (d) in ppm to high frequency of 85% H3PO4. All NMR
spectra were measured in CDCl3 unless otherwise stated. Elemen-
tal analyses (Perkin–Elmer 2400 CHN or Exeter Analytical, Inc. CE-
440 Elemental Analyzers) were performed by the Loughborough
University Analytical Service within the Department of Chemistry.
tion was stirred for 0.5 h and the solvent concentrated to ca. 2 mL
under reduced pressure. Diethyl ether (25 mL) was added and the
resulting yellow suspension stirred for a further 0.5 h. The yellow
precipitate was filtered and dried under reduced pressure. Yield:
0.085 g, 86%. Selected data for 4: 31P{1H} NMR (CDCl3): 2.60 ppm,
1J(PtP) 3666 Hz. 1H NMR: d 7.60–7.20 (m, 20H, arom. H), 4.11 (m,
3
2.3. Syntheses
4H, C5H4), 4.01 (s, 10H, C5H5), 3.98 (m, 4H, C5H4), 3.76 (s, 4H, JPtH
33.1 Hz, CH2P), 3.09 (s, 4H, CH2NH), 3.02 (s, 4H, CH2C5H4). FT-IR
(KBr): mPtCl 318 and 294 cmꢁ1. FAB-MS: m/z 1118 [M]. Anal. Calc.
for C50H50N2Fe2P2Cl2Pt ꢀ 2.5H2O (1163.64) requires: C, 51.60; H,
4.75; N, 2.40. Found: C, 51.65; H, 4.60; N, 2.30%.
2.3.1. {FcCH2N(CH2PPh2)CH2}2 (1)
Under
a nitrogen atmosphere, an orange suspension of
{FcCH2N(H)CH2}2 (0.496 g, 1.087 mmol) and Ph2PCH2OH (0.495 g,
2.175 mmol) in methanol (HPLC grade, 20 mL) was stirred at room
temperature for 72 h. The yellow suspension was concentrated un-
der reduced pressure to approximately (10 mL) and the solid fil-
tered and dried under reduced pressure. Yield: 0.663 g, 72%.
Selected data for 1: 31P{1H} NMR (CDCl3): ꢁ27.3 ppm. 1H NMR: d
7.35–7.21 (m, 20H, arom. H), 4.01 (m, 4H, C5H4), 4.00 (m, 4H,
2.3.5. PdCl2{FcCH2N(CH2PPh2)CH2}2 (5)
Compound 1 (0.011 g, 0.124 mmol) was added to a stirred solu-
tion of PdCl2(cod) (0.034 g, 0.117 mmol) in CH2Cl2 (20 mL). The
solution was stirred for 0.5 h and the solvent concentrated to ca.
2 mL under reduced pressure. Diethyl ether (25 mL) was added
and the resulting cream suspension stirred for a further 0.5 h.
The cream precipitate was filtered and dried under reduced pres-
sure. Yield: 0.089 g. Attempts to obtain an analytically pure sample
of 5 were hampered by slow decomposition in solution.
2
C5H4), 3.99 (s, 10H, C5H5), 3.54 (s, 4H, CH2NH), 3.11 (d, 4H, JPH
3.6 Hz, CH2P), 2.58 (s, 4H, CH2C5H4). FAB-MS: m/z 667 [MꢁPPh2].
Anal. Calc. for
69.35; H, 6.00; N, 3.25. Found: C, 69.25; H, 5.95; N, 3.35%.
C
50H50N2Fe2P2 ꢀ 0.75H2O (866.11) requires: C,
2.3.2. {RuCl2(p-cym)}2{FcCH2N(CH2PPh2)CH2}2 (2)
2.3.6. cis-Mo(CO)4{FcCH2N(CH2PPh2)CH2}2 (6)
Compound 1 (0.038 g, 0.043 mmol) was added to a stirred solu-
tion of {RuCl(l-Cl)(p-cym)}2 (0.026 g, 0.043 mmol) in CH2Cl2
(20 mL). The resulting solution was stirred for 0.5 h before concen-
trating the solvent under reduced pressure to approximately
(2 mL). Hexane (25 mL) was added and the resulting orange suspen-
sion stirred for a further 0.5 h. The orange precipitate was filtered
and dried under reduced pressure. Yield: 0.054 g, 86%. Selected data
for 2: 31P{1H} NMR (CD2Cl2): 25.2 ppm. 1H NMR: d 7.94–7.46 (m, 20
H, arom. H), 5.37 (s, 4H, CH2NH), 5.20 (d, 4H, 3JHH 5.2 Hz, CH), 5.12
Compound 1 (0.096 g, 0.107 mmol) and Mo(CO)4(nbd) (0.032 g,
0.107 mmol) in degassed CH2Cl2 (10 mL) were stirred at ambient
temperature for ca. 10 d under a nitrogen atmosphere. The solvent
was concentrated to approx. 2 mL under reduced pressure. Diethyl
ether (25 mL) was added and the resulting orange suspension stir-
red for a further 0.5 h. The orange precipitate was filtered and dried
under reduced pressure. Yield: 0.065 g, 58%. Selected data for 6:
31P{1H} NMR (CDCl3): 29.0 ppm. 1H NMR: d 7.44–7.32 (m, 20H,
arom. H), 3.99 (m, 4H, C5H4), 3.85 (m, 14H, C5H4 and C5H5), 3.29
(s, 4H, CH2), 2.78 (s, 4H, CH2), 1.97 (s, 4H, CH2). FT-IR (KBr): mCO
2018, 1918, 1898, 1870 cmꢁ1. FAB-MS: m/z 1061 [M]. Anal. Calc.
for C54H50N2O4Fe2P2Mo ꢀ 1.75CH2Cl2 (1209.28) requires: C, 55.37;
H, 4.46; N, 2.32. Found: C, 55.40; H, 4.25; N, 2.45%.
3
(d, 4H, JHH 6 Hz, CH), 3.99 (t, 4H, C5H4), 3.88 (s, 10H, C5H5), 3.74
2
(t, 4H, C5H4), 3.64 (d, 4H, JPH 2.8 Hz, CH2P), 2.52 (s, 4H, CH2C5H4),
3
3
2.39 (sept, JHH 7 Hz, 2H, CH), 1.79 (s, 6H, CH3), 0.96 (d, 12H, JHH
6.8 Hz, CH3). FAB-MS: m/z 973 [MꢁRuCl2(p-cym)PPh2]. Anal. Calc.
for C78H78N2Fe2P2Cl4Ru2 ꢀ CH2Cl2 (1550.03) requires: C, 55.00; H,
5.20; N, 1.80. Found: C, 54.95; H, 5.25; N, 2.15%.
2.3.7. Trans,trans-{Pd(CH3)Cl{FcCH2N(CH2PPh2)CH2}2}2 (7)
Compound 1 (0.111 g, 0.121 mmol) was added to a stirred solu-
tion of Pd(CH3)Cl(cod) (0.032 g, 0.121 mmol) in CH2Cl2 (20 mL).
The solution was stirred for 0.5 h and the solvent concentrated to
approx. 2 mL under reduced pressure. Hexane (25 mL) was added
and the resulting cream suspension stirred for a further 0.5 h.
The cream precipitate was filtered and dried under reduced pres-
sure. Yield: 0.074 g, 61%. Selected data for 7: 31P{1H} NMR (CDCl3):
13.0 ppm. 1H NMR: d 7.83–7.33 (m, 20H, arom. H), 4.29 (t, 4H,
C5H4), 4.24 (t, 4H, C5H4), 4.20 (s, 10H, C5H5), 3.81 (s, 4H, CH2),
2.3.3. {AuCl}2{FcCH2N(CH2PPh2)CH2}2 (3)
Compound 1 (0.108 g, 0.118 mmol) was added to a stirred solu-
tion of AuCl(tht) (0.076 g, 0.236 mmol) in CH2Cl2 (20 mL). The
resulting solution was stirred in the dark for 0.5 h and concentrated
under reduced pressure to approx. 2 mL. Hexane (25 mL) was added
and the resulting yellow suspension stirred for a further 0.5 h. The
yellow precipitate was filtered and dried under reduced pressure.
Yield: 0.130 g, 84%. Selected data for 3: 31P{1H} NMR (CDCl3):
19.4 ppm. 1H NMR: d 7.68–7.40 (m, 20H, arom. H), 4.03 (m, 18H,
C5H4 and C5H5), 3.64 (d, 4H, 2JPH 1.2 Hz, CH2P), 3.51 (s, 4H, CH2NH),
2.60 (s, 4H, CH2C5H4). FT-IR (KBr): mAuCl 330 cmꢁ1. FAB-MS: m/z
1317 [M]. Anal. Calc. for C50H50N2Fe2P2Au2Cl2 (1317.47) requires:
C, 45.60; H, 3.85; N, 2.15. Found: C, 45.45; H, 3.85; N, 2.00%.
3
3.67 (s, 4H, CH2), 3.59 (br, 4H, CH2), 0.00 (t, 3H, JPH 12 Hz, CH3).
FT-IR (KBr): mPdCl 262 cmꢁ1. FAB-MS: m/z 973 [MꢁCl]. Anal. Calc.
for C51H53N2Fe2P2ClPd ꢀ 2.5H2O (1054.56) requires: C, 58.10; H,
5.05; N, 2.65. Found: C, 58.05; H, 5.10; N, 2.70%.
2.3.8. Trans,trans-{Rh(CO)Cl{FcCH2N(CH2PPh2)CH2}2}2 (8)
2.3.4. cis-PtCl2{FcCH2N(CH2PPh2)CH2}2 (4)
Compound 1 (0.075 g, 0.088 mmol) was added to a stirred solu-
tion of PtCl2(cod) (0.033 g, 0.087 mmol) in CH2Cl2 (20 mL). The solu-
Compound 1 (0.098 g, 0.112 mmol) was added to a stirred solu-
tion of {Rh(l-Cl)(CO)2}2 (0.023 g, 0.056 mmol) in CH2Cl2 (20 mL).
The solution was stirred for 0.5 h and the solvent concentrated to

M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
2319
Table 1a
ca. 2 mL under reduced pressure. Diethyl ether (25 mL) was added
Crystallographic data for 1, 2 ꢀ 2CH2Cl2 and 3 ꢀ CH2Cl2
and the resulting orange suspension stirred for a further 0.5 h. The
orange precipitate was filtered and dried under reduced pressure.
Yield: 0.033 g, 29%. Selected data for 8: 31P{1H} NMR (CDCl3):
16.6 ppm., 1J(RhP) 130 Hz. 1H NMR: d 7.73–7.29 (m, 20H, arom.
H), 4.19 (t, 4H, C5H4), 4.16 (t, 4H, C5H4), 4.11 (s, 10H, C5H5), 3.94
(s, 4H, CH2), 3.76 (s, 4H, CH2), 3.57 (s, 4H, CH2). FT-IR (KBr): mCO
1969 cmꢁ1. FAB-MS: m/z 983 [MꢁCl]. Anal. Calc. for C51H50N2O-
Fe2P2ClRh ꢀ 1.25H2O (1041.51) requires: C, 58.80; H, 5.10; N, 2.70.
Found: C, 58.40; H, 4.80; N, 3.20%.
Compound
1
2 ꢀ 2CH2Cl2
3 ꢀ CH2Cl2
Empirical
formula
C50H50Fe2N2P2
C70H78Cl4Fe2N2P2Ru2
2CH2Cl2
ꢀ
C50H50Au2Cl2-
Fe2N2P2 ꢀ CH2Cl2
1402.32
Formula weight 852.56
1634.78
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Triclinic
P1
Triclinic
P1
Triclinic
ꢀ
ꢀ
ꢀ
P1
7.6347(4)
11.3939(5)
12.7421(6)
95.6966(5)
103.7690(5)
102.5657(5)
1037.36(9)
1
10.4845(4)
12.6125(5)
15.1788(7)
96.720(2)
105.962(2)
106.968(2)
1802.81(13)
1
11.9161(2)
12.7979(2)
17.2109(3)
72.111(2)
81.279(2)
80.243(2)
2447.75(7)
2
a (°)
b (°)
c (°)
2.4. X-ray crystallography
Volume (Å3)
Z
Crystals of 1 and 6 were obtained by slow diffusion of CH3OH
into a CH2Cl2 solution. Suitable crystals of 2 and 3 were grown
by vapour diffusion of hexane onto CH2Cl2 solutions. X-ray quality
crystals of compounds 4 and 8 were obtained by slow evaporation
of a CH2Cl2/Et2O solution.
Details of the crystal data for 1, 2 ꢀ 2CH2Cl2, 3 ꢀ CH2Cl2,
4 ꢀ CH2Cl2, 6 ꢀ 0.5CHCl3 and 8 along with a summary of data collec-
tion parameters are given in Table 1. Measurements for 2 ꢀ 2CH2Cl2
and 4 ꢀ CH2Cl2 were made on a Bruker Apex 2 CCD diffractometer
using graphite monochromated radiation from a sealed tube Mo
Ka source. For 1 and 8 silicon 111 monochromated synchrotron
radiation at Daresbury Laboratory SRS station 9.8 on a Bruker Apex
k
0.6710
150(2)
1.365
0.814
0.71073
150(2)
1.506
0.71073
120(2)
1.903
T (K)
Dcalc (Mg/ m3)
Absorption
coefficient
1.188
6.877
(mmꢁ1
)
Crystal habit and Lath; orange
colour
Block; orange
Tablet; yellow
Crystal size
0.19 ꢂ 0.04 ꢂ 0.03 0.40 ꢂ 0.28 ꢂ .11
0.18 ꢂ 0.08 ꢂ 0.04
(mm3)
h Range (°)
Reflections
collected
1.75–31.02
13143
1.99–30.56
21443
3.00–27.54
52848
Independent
reflections
6964 [0.0326]
10789 [0.0187]
11242 [0.0406]
2
CCD diffractometer. Diffraction data for 3 ꢀ CH2Cl2 and
6 ꢀ 0.5CHCl3 was collected using a rotating anode source and a Bru-
ker–Nonious 95 mm or Roper CCD camera. Narrow frame x-scans
were employed for 1, 2 ꢀ 2CH2Cl2, 4 ꢀ CH2Cl2 and 8, ø and x-scans
were used for 3 ꢀ CH2Cl2 and 6 ꢀ 0.5CHCl3. Intensities were cor-
rected semi-empirically for absorption, based on symmetry-equiv-
alent and repeated reflections. The structures were solved by direct
methods (Patterson synthesis for 2 ꢀ 2CH2Cl2 and 3 ꢀ CH2Cl2) and
refined on F2 values for all unique data by full-matrix least squares.
All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were constrained in a riding model with Ueq set to 1.2Ueq
of the carrier atom (1.5Ueq for methyl hydrogen). In 3 ꢀ CH2Cl2
and 4 ꢀ CH2Cl2 the CH2Cl2 molecule was modelled with the carbon
and one chlorine disordered over two sets of positions; major occu-
pancy = 59.2(9)% for 4 ꢀ CH2Cl2 and 70.9(5)% for 3 ꢀ CH2Cl2. Pro-
grams used were COLLECT [35] or Bruker AXS APEX2 [36] for
diffractometer control and DENZO or SAINT for frame integration
[37,38], Bruker SHELXTL [39] for structure solution, refinement, and
molecular graphics and local programs. Disordered molecules of
CH2Cl2 (for 2 ꢀ 2CH2Cl2) or CHCl3 (for 6 ꢀ 0.5CHCl3) were modelled
by the Platon Sqeeze procedure [40].
[Rint
]
Completeness
(%)
Number of
parameters
Final Ra, Rwb
97.4
253
99.4
99.3
373
588
0.036, 0.099
0.028, 0.072
0.028, 0.064
P
P
a
R ¼ kFoj ꢁ jFck= jFoj.
P
P
2
2 1=2
wR2 ¼ ½ ½wðF2o ꢁ Fc2Þ ꢃ= ½wðF2oÞ ꢃꢃ
.
b
3. Results and discussion
3.1. Ligand synthesis
Ferrocenyl derived phosphines have been accessed through a
number of established methods previously [1a,2,6,8,12,14]. In our
work we have found that phosphorus based Mannich condensation
reactions are extremely flexible procedures for preparing highly
functionalised phosphines [41] and even nonsymmetric diphos-
phines [42] by employing two consecutive elimination steps. The
new ditertiary phosphine 1 was synthesised in 72% yield by double
condensation of the known bis secondary amine precursor
{FcCH2N(H)CH2}2 [34] with 2 equiv. of Ph2PCH2OH in CH3OH at
ambient temperature (Eq. (1)). The 31P{1H} NMR spectrum showed
one new phosphorus resonance at d(P) ꢁ27.3 ppm, some 20 ppm
upfield from that observed for the starting compound Ph2PCH2OH.
Compound 1 showed no evidence for oxidation when CDCl3 solu-
tions were left to stand for ca. 6 d. The 1H NMR spectrum showed
all the characteristic resonances expected for 1 and, furthermore,
the absence of a mNH stretch in the FT-IR spectrum confirmed the
ternary nature of both nitrogen atoms.
2.5. Electrochemistry
Cyclic voltammetric measurements were carried out on a EG&G
Model PAR 263A potentiostat/galvanostat using a standard cell,
consisting of a Pt disc working electrode (d = 1.6 mm), Ag/AgCl ref-
erence electrode in a 3 M NaCl solution and a Pt gauze counter elec-
trode, at a scan rate of 50 mV/s. All measurements were performed
at ambient temperature (22 1 °C) in dry, degassed CH2Cl2 solu-
tions containing analyte (0.001 M) and [NBu4][BF4] (0.1 M) as the
supporting electrolyte. Ferrocene was used as an internal standard.
2 equiv.
Ph2PCH2OH
N
N
N
N
H
H
Fe
Fe
Fe
Fe
CH3OH
ð1Þ
PPh2
PPh2
1

2320
M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
3.2. Coordination studies
(CH2OH)2 (R, R0 = Ph, Cy) [44]. With 4 this transformation is very
slow as would be expected for the different reactivity between
Pd(II) and Pt(II) square-planar metal centres. The octahedral
cis-tetracarbonylmolybdenum(0) complex 6 was prepared from
Mo(CO)4(nbd) and one equiv. of 1 in dichloromethane. Further
characterising details for compounds 2–6 are given in the Experi-
mental Section.
Complexation of the metalloligand 1 to various transition metal
centres was explored in order to understand the ligating modes of
this new ferrocenyl ditertiary phosphine. The diphosphine dppf is
known to preferentially act either in a g2-chelating fashion or
P,P0-bridging mode [3]. Treatment of {RuCl(l-Cl)(p-cym)}2 (1
equiv.) or AuCl(tht) (2 equiv.) with 1 in dichloromethane at
ambient temperature gave the tetrametallic complexes {RuCl2-
(p-cym)}2{FcCH2N(CH2PPh2)CH2}2 (2) and {AuCl}2{FcCH2N-
(CH2PPh2)CH2}2 (3), respectively (Scheme 1). In both complexes
diphosphine 1 bridges either {RuCl2(p-cym)} or AuCl metal frag-
ments. Displacement of cod from PtCl2(cod) with 1 equiv. of 1 in
dichloromethane gave the new square-planar trimetallic com-
plexes cis-PtCl2(1) (4). In contrast, reaction of 1 with either
PdCl2(cod) or PdCl2(PhCN)2 gave an impure sample of cis-PdCl2(1)
(5) which, by 31P{1H} NMR spectroscopy in solution, revealed the
presence of several phosphorus containing species [d(P) 20.8
ppm, 11.1 ppm], the major being assigned to either cis- or trans-
isomers of PdCl2(1) (possibly monomeric or dimeric). Careful mon-
itoring of CDCl3, CD2Cl2 or C6D6 solutions over a period of four days
revealed the gradual disappearance of these signals and two new
doublets at significant downfield shifts [d(P) 159.9 ppm,
Reaction of 1 with Pd(CH3)Cl(cod) in dichloromethane gave
trans,trans-{Pd(CH3)Cl(1)}2 (7). In 7, we believe the diphosphine 1
functions as a bridging ligand on the basis of the spectroscopic data
obtained. A further example of this ligand behaviour is seen in the
analogous chlorocarbonylrhodium(I) complex 8 prepared from
{Rh(l–Cl)(CO)2}2 and 2 equiv. of 1. A trans disposition of –PPh2
groups was inferred by a sharp doublet at d(P) 16.6 ppm (1JRhP
130 Hz) in the 31P{1H} NMR spectrum and the geometry account-
able on the basis of the large spacer separation between both
phosphorus(III) groups. However a dimeric species with a trans,
trans-{Rh(CO)Cl} fragment disposition has been proposed [45] for
[{RhCl(CO){Ph2P(CH2)nPPh2}]2 (n = 1, 3 or 4) and, on the basis of
FT-IR data for 8 [mCO 1969 cmꢁ1], this geometry would be antici-
pated for 8 and similarly for the dipalladium(II) complex 7. The
X-ray structure (vide infra) for 8 has been determined and confirms
the dimeric nature. In contrast FAB-MS data on the bulk sample
showed only a significant monomeric [MꢁCl] ion at m/z 983
whereas MALDI analysis gave unreliable results.
2
79.1 ppm, JPP 17 Hz]. This in conjunction with the observation of
a new doublet at d(H) 3.06 ppm (2JHP 39 Hz) in the 1H NMR spec-
trum led us to speculate that 5 undergoes slow decomposition to
give the five-membered chelate complex [PdCl2(Ph2PCH2OPPh)2]
with elimination of some hitherto unidentified ferrocenylamine
byproducts. Support for the nonsymmetric nature of this coordi-
nated bidentate phosphorus(III) ligand comes from previous
studies with Ph2PCH2OPPh2 [43] and, more recently, RR0POCH2P-
3.3. Single crystal X-ray studies
The single crystal X-ray structures of the free ligand 1 and
five illustrative complexes 2 ꢀ 2CH2Cl2, 3 ꢀ CH2Cl2, 4 ꢀ CH2Cl2,
6 ꢀ 0.5CHCl3 and 8 have each been determined with selected bond
N
N
Fe
Fe
PPh2 Ph2P
MLn
LnM
MLn = RuCl2(p-cym)
MLn = AuCl
2
3
N
N
Fe
Fe
PPh2
M
(i)
X
PPh2
M
Cl
(iii)
1
Cl
Ph2P
X
PPh2
(ii)
N
N
Fe
Fe
N
N
Fe
Fe
Y
M
Y
M = Pd, X = CH3
M = Rh, X = CO
7
8
Ph2P
X
PPh2
X
M = Pt, X = Cl, Y = nothing
M = Pd, X = Cl, Y = nothing
M = Mo, X = Y = CO
4
5
6
Scheme 1. (i) {RuCl(l-Cl)(p-cym)}2 or AuCl(tht), CH2Cl2; (ii) MCl2(cod), CH2Cl2 or Mo(CO)4(nbd), CH2Cl2; (iii) Pd(CH3)Cl(cod) or {Rh(l–Cl)(CO)2}2, CH2Cl2.

M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
2321
Table 1b
Crystallographic data for 4 ꢀ CH2Cl2, 6 ꢀ 0.5CHCl3 and 8
Compound
4 ꢀ CH2Cl2
6 ꢀ 0.5CHCl3
8
Empirical formula
Formula weight
C
50H50Cl2Fe2N2P2Pt ꢀ CH2Cl2
C54H50Fe2N2O4P2Mo ꢀ 0.5CHCl3
C102H100Cl2Fe4N4O2P4Rh2
2037.86
1203.48
1120.22
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/n
a (Å)
b (Å)
c (Å)
17.6469(17)
12.6761(12)
21.866(2)
18.1242(3)
12.7301(2)
22.9350(3)
13.0780(10)
20.4797(16)
17.3102(13)
a (°)
b (°)
104.448(2)
109.4910(8)
105.1038(11)
c (°)
Volume (Å3)
Z
4736.6(8)
4
4988.39(13)
4
4476.1(6)
2
k
T/K
0.71073
150(2)
1.688
0.71073
120(2)
1.492
1.014
Tablet; orange
0.26 ꢂ 0.09 ꢂ 0.05
2.91–27.48
53164
0.6884
150(2)
1.512
1.176
Plate; yellow
0.07 ꢂ 0.04 ꢂ 0.02
1.52–29.50
51962
Dcalc [Mg/m3]
Absorption coefficient (mmꢁ1
Crystal habit and colour
Crystal size (mm3)
h Range (°)
)
3.882
Block; yellow
0.29 ꢂ 0.18 ꢂ 0.11
1.71–28.34
47747
Reflections collected
Independent reflections [Rint
Completeness (%)
]
11782 [0.0867]
99.9
11463 [0.0500]
99.8
13698 [0.0895]
99.9
Number of parameters
Final Ra, Rwb
578
0.049, 0.119
587
0.043, 0.121
541
0.049, 0.117
P
P
a
R ¼ kFoj ꢁ jFck= jFoj.
P
P
2
2 1=2
wR2 ¼ ½ ½wðF2o ꢁ Fc2Þ ꢃ= ½wðF2oÞ ꢃꢃ
.
b
lengths and angles given in Tables 2 and 3. The molecular structure
of 1 (Fig. 1) confirms that the phosphorus atoms are in a pyramidal
geometry as indicated by the relevant C–P–C angles. Both phos-
phorus atoms lie in an anti conformation with respect to each
Table 2
Selected bond distances (Å) and angles (°) for compounds 1, 2 ꢀ 2CH2Cl2, 3 ꢀ CH2Cl2, 4 ꢀ CH2Cl2 and 8
1
2 ꢀ 2CH2Cl2(M = Ru)
3 ꢀ CH2Cl2(M = Au)
4 ꢀ CH2Cl2(M = Pt)
8(M = Rh)
Fe(1)–Cpcent
Fe(2)–Cpcent
P(1)–C(13)
C(13)–N(1)
N(1)–C(14)
N(1)–C(25)
C(25)–C(250)
C(25)–C(26)
C(26)–N(2)
N(2)–C(27)
N(2)–C(38)
C(38)–P(2)
Ru–Cymcent
M(1)–Cl(1)
M(1)–Cl(2)
M(1)–P(1)
1.6426(6)
1.6455(6)
1.8922(12)
1.4573(15)
1.4721(15)
1.4653(15)
1.522(2)
1.6423(8)
1.6417(9)
1.8575(15)
1.4560(19)
1.473(2)
1.644(2), 1.655(2)
1.653(2), 1.652(2)
1.851(4)
1.469(5)
1.486(5)
1.654(3)
1.649(3)
1.871(6)
1.456(7)
1.472(7)
1.484(7)
1.6426(17), 1.6415(19)
1.6456(16), 1.6495(18)
1.845(3)
1.458(4)
1.470(4)
1.460(2)
1.521(3)
1.470(5)
1.476(4)
1.524(5)
1.475(5)
1.477(5)
1.467(5)
1.848(4)
1.509(8)
1.485(7)
1.492(7)
1.468(7)
1.853(6)
1.516(4)
1.475(4)
1.470(4)
1.451(4)
1.859(3)
1.6929(7)
2.4088(4)
2.4173(4)
2.3448(4)
2.2836(10)
2.2277(9)
2.3535(14)
2.3558(15)
2.2551(15)
2.2401(14)
2.49
2.3739(9)
2.3063(9)
2.3130(9)
M(1)–P(2)
Pt(1)–H(26A)
Rh(1)–C(51)
C(51)–O(1)
1.809(4)
1.148(4)
P(1)–C(13)–N(1)
C(13)–N(1)–C(14)
C(13)–N(1)–C(25)
N(1)–C(25)–C(250)
N(1)–C(25)–C(26)
C(25)–C(26)–N(2)
C(26)–N(2)–C(27)
C(26)–N(2)–C(38)
C(27)–N(2)–C(38)
N(2)–C(38)–P(2)
Cl(1)–M(1)–P(1)
Cl(2)–M(1)–P(1)
Cl(1)–M(1)–Cl(2)
Cl(1)–M(1)–P(2)
Cl(2)–M(1)–P(2)
P(1)–M(1)–P(2)
115.74(8)
110.69(9)
112.97(9)
110.95(12)
114.40(10)
111.07(12)
112.15(13)
111.29(17)
109.5(3)
112.5(3)
111.0(3)
113.3(4)
110.3(4)
113.3(4)
115.6(2)
112.9(2)
113.1(3)
113.6(3)
109.8(3)
113.9(3)
113.7(3)
109.8(3)
109.3(3)
178.53(4)
114.1(5)
113.5(4)
109.6(4)
112.7(4)
109.5(4)
112.8(4)
84.71(5)
170.42(5)
87.00(5)
166.34(5)
84.71(5)
103.05(5)
114.2(3)
108.8(3)
113.7(3)
114.7(2)
113.9(3)
106.4(2)
90.13(3)
85.276(14)
83.435(14)
88.397(14)
85.31(3)
161.97(3)
90.17(11)
93.82(11)
178.02(12)
C(51)–M(1)–P(1)
C(51)–M(1)–P(2)
C(51)–M(1)–Cl(1)

2322
M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
Table 3
Selected bond distances (Å) and angles (°) for compound 6 ꢀ 0.5CHCl3
6 ꢀ 0.5CHCl3
Fe(1)–Cpcent
Fe(2)–Cpcent
P(1)–C(13)
C(13)–N(1)
N(1)–C(14)
N(1)–C(25)
C(25)–C(26)
C(26)–N(2)
N(2)–C(27)
N(2)–C(38)
C(38)–P(2)
Mo(1)–C(51)
Mo(1)–C(52)
Mo(1)–C(53)
Mo(1)–C(54)
Mo(1)–P(1)
Mo(1)–P(2)
1.6516(15)
1.6537(16)
1.861(3)
1.465(3)
1.478(4)
1.469(3)
1.519(4)
1.461(3)
1.474(3)
1.457(4)
1.867(3)
1.980(3)
1.995(3)
2.022(3)
2.063(3)
2.5416(7)
2.5547(8)
P(1)–C(13)–N(1)
112.55(18)
110.3(2)
111.2(2)
113.2(2)
113.8(2)
113.5(2)
112.3(2)
114.5(2)
111.43(18)
84.46(13)
87.94(13)
92.23(13)
90.09(13)
91.42(13)
178.49(12)
85.07(9)
172.82(9)
169.51(9)
88.61(9)
88.86(9)
90.21(9)
89.66(8)
89.81(8)
101.83(2)
C(13)–N(1)–C(14)
C(13)–N(1)–C(25)
N(1)–C(25)–C(26)
C(25)–C(26)–N(2)
C(26)–N(2)–C(27)
C(26)–N(2)–C(38)
C(27)–N(2)–C(38)
N(2)–C(38)–P(2)
C(51)–Mo(1)–C(52)
C(51)–Mo(1)–C(53)
C(51)–Mo(1)–C(54)
C(52)–Mo(1)–C(53)
C(52)–Mo(1)–C(54)
C(53)–Mo(1)–C(54)
C(51)–Mo(1)–P(1)
C(51)–Mo(1)–P(2)
C(52)–Mo(1)–P(1)
C(52)–Mo(1)–P(2)
C(53)–Mo(1)–P(1)
C(53)–Mo(1)–P(2)
C(54)–Mo(1)–P(1)
C(54)–Mo(1)–P(2)
P(1)–Mo(1)–P(2)
Fig. 1. X-ray structure of 1. All hydrogens have been removed for clarity. Symmetry
0
operator: = ꢁx + 1, ꢁy + 1, ꢁz + 1.
other (symmetry imposed) and the Feꢀ ꢀ ꢀFe separation is 11.181 Å.
This separation could be important in promoting interactions be-
tween iron centres when investigating their electrochemical prop-
erties (vide infra). The two cyclopentadienyl rings of ferrocene are
eclipsed and essentially coplanar (torsional twist about the
Cpcentꢀ ꢀ ꢀFeꢀ ꢀ ꢀCpcent is 3.4°). Upon complexation to afford the tetra-
metallic complexes 2 ꢀ 2CH2Cl2 (Fig. 2) and 3 ꢀ CH2Cl2 (Fig. 3), there
are minimal bond length or bond angle changes in the P–C–N–C–
C–N–C–P saturated backbone (Table 2). In the piano-stool complex
2 ꢀ 2CH2Cl2, the Ru–Cl, Ru–P and Ru–Ccent distances are as expected
[41b] and this trend is similarly observed for the linear gold(I)
complex 3 ꢀ CH2Cl2 which shows typical metric parameters (Table
2) [46]. The Feꢀ ꢀ ꢀFe separation in 2 ꢀ 2CH2Cl2 is 10.187 Å which is
significantly greater than that found in 3 ꢀ CH2Cl2 (6.794 Å) but
slightly shorter than in non complexed 1 (11.181 Å). In 3 ꢀ CH2Cl2
there are no short intramolecular or intermolecular Auꢀ ꢀ ꢀAu sepa-
rations often encountered in many examples of two-coordinate
gold(I) phosphine complexes [41d]. However molecules of
3 ꢀ CH2Cl2 do associate (Fig. 4), via head-to-tail Auꢀ ꢀ ꢀCl contacts
[Cl(2)ꢀ ꢀ ꢀAu(20) 3.950 Å] [47]. For 2 ꢀ 2CH2Cl2 the cyclopentadienyl
rings of ferrocene are eclipsed and essentially coplanar [torsional
twist about the Cpcentꢀ ꢀ ꢀFeꢀ ꢀ ꢀCpcent is 1.1° at Fe(1)] whilst for
2 ꢀ 2CH2Cl2 the torsion angles are larger [4.0° at Fe(1) and 21.9°
at Fe(2)].
Fig. 2. X-ray structure of 2. All hydrogens and solvent molecules have been rem-
oved for clarity. Symmetry operator: = ꢁx + 1, ꢁy + 1, ꢁz + 1.
0
num(II) centre forming a nine-membered chelate ring. Upon
inspection of the structural variations in the P–C–N–C–C–N–C–P
backbone minimal changes are observed when 1 adopts a chelating
mode of coordination. The Feꢀ ꢀ ꢀFe separation in 4 ꢀ CH2Cl2 is
6.510 Å which is shorter than that found in 2 ꢀ 2CH2Cl2, 3 ꢀ CH2Cl2
and noncomplexed 1. A feature in 4 ꢀ CH2Cl2 that has been ob-
served in other medium ring sized palladium(II) and platinum(II)
complexes [48] is the close contact between H(26A) of coordinated
1 and the Pt centre [C(26)ꢀ ꢀ ꢀPt(1) 3.365 Å, H(26A)ꢀ ꢀ ꢀPt(1) 2.4871 Å,
Pt(1)ꢀ ꢀ ꢀH(26A)–C(26) 148°]. This axial interaction between the
Csp3 -H bond of the ligand backbone and the platinum(II) centre is
not significantly mirrored in the 1H NMR spectrum of 4 in which
there is only a small downfield shift (ca. Dd 0.6 ppm). The two
cyclopentadienyl rings of both ferrocenes are eclipsed and essen-
tially coplanar [torsional twist about the Cpcentꢀ ꢀ ꢀFeꢀ ꢀ ꢀCpcent is
1.6° at Fe(1) and 8.5° at Fe(2)]. The molecular structure of mono-
In the dichloroplatinum(II) compound 4 ꢀ CH2Cl2 (Fig. 5) the li-
gand 1 adopts a cis disposition around the square-planar plati-

M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
2323
Fig. 3. X-ray structure of 3. All hydrogens and solvent molecule have been removed
for clarity.
meric 6 (Fig. 6, Table 3) comprises a cis-chelating 1 and four termi-
nal CO ligands [vide infra for comparison with a related molybde-
num(0) complex of dpph (dpph = 1,6-bis(diphenylphosphino)
hexane) reported by Ueng and Hwang]. The Mo–P and Mo–C bond
lengths are broadly as anticipated [49] and the P(1)–Mo(1)–P(2)
angle similar to that found for 4. In keeping with the structures
of 1–4 discussed previously, the torsion twist angles about the
Cpcentꢀ ꢀ ꢀFeꢀ ꢀ ꢀCpcent in 6 ꢀ 0.5CHCl3 are 11.8 ° and 13.2° while the
Feꢀ ꢀ ꢀFe separation is 7.040 Å.
Fig. 5. X-ray structure of 4. All hydrogens and solvent molecule have been removed
for clarity.
ised metallacycle containing an Rh2Fe4 arrangement of metal cen-
tres. In comparison with the analogous ligand dpph, containing a
C6 carbon backbone, this bridging motif has been observed in sev-
eral complexes with different metal fragments. Hence it has been
shown that two dpph ligands can bridge a range of three- {Cu(O-
ClO3)} [51], four- (trans-PdCl2 [52], tetrahedral CoCl2 [53]) and
six- (trans-Mo(CO)4} [54] coordinate metal centres.
The X-ray structure of 8 (Figs. 7 and 8, Table 2) shows that 1
bridges two trans-RhCl(CO) fragments with formation of a large
18-membered metallomacrocycle. There is
a crystallographic
inversion centre lying at the centroid of the 18-membered ring.
The P(1)–Rh(1)–P(2) angle deviates some 18° from the idealised
angle for a trans disposition of groups. The torsion twist angles
about the Cpcentꢀ ꢀ ꢀFeꢀ ꢀ ꢀCpcent in 8 are 13.0° and 3.4° while the
Feꢀ ꢀ ꢀFe separations are 6.987 Å [Fe(1)ꢀ ꢀ ꢀFe(2)], 13.511 Å
3.4. Electrochemical properties
The electrochemical behaviour of 1 and its related mononuclear
and dinuclear complexes has been investigated by cyclic voltam-
metry and their half-wave redox potentials summarised in Table
4. All of the compounds studied were found to display a single
reversible ferrocene/ferrocenium redox (Fc/Fc+) couple similar to
that of ferrocene. For 1, the half-wave potential of the Fc groups
was found to be at E1/2 +0.055 V whereas for complexes 2, 4, 6
[Fe(1)ꢀ ꢀ ꢀFe(1a)],
14.232 Å
[Fe(1)ꢀ ꢀ ꢀFe(2a)]
and
17.893 Å
[Fe(2)ꢀ ꢀ ꢀFe(2a)]. Between adjacent trans-RhCl(CO) fragments the
Rhꢀ ꢀ ꢀRh separation is 6.199 Å and is considerably shorter than
found in a related dimeric rhodium(I) complex containing a
diphosphine ligand based on bisphenol [9.0005(11) Å] [50]. The
structure of 8 represents the first crystallographically character-
0
Fig. 4. X-ray structure of 3 showing the Auꢀ ꢀ ꢀCl contacts between adjacent molecules. Symmetry operator: = ꢁx + 1, ꢁy, ꢁz + 1

2324
M.R.J. Elsegood et al. / Journal of Organometallic Chemistry 693 (2008) 2317–2326
Fig. 8. X-ray structure of
8
showing the core arrangement of the
metallomacrocycle.
Table 4
Electrochemical dataa for 1 and its mononuclear and dinuclear complexes 2–4, 6 and
7
E1/2 (V)b, FeII/III
1
2
3
4
6
7
+0.055
ꢁ0.018
+0.012
+0.075
+0.135
+0.021
Fig. 6. X-ray structure of 6. All hydrogens and solvent molecule have been removed
for clarity.
a
All experiments were performed in a 0.1M [NBu4][BF4]/dry CH2Cl2 solution at a
scan rate of 50 mV sꢁ1
.
and 7 the half potentials were observed in the range E1/2 ꢁ0.018 to
+0.135 V. The observation of a single Fc/Fc+ wave for 1, 2, 6 and 7
indicates no direct or indirect electronic communication between
the two ferrocene groups, i.e. no electronic interaction via (satu-
rated) covalent bonds or any significant coulombic interaction
through space, as the two ferrocene centres are spatially too far
apart from each other. As a result both ferrocene centres are con-
sidered electrochemically equivalent and apparently undergo
simultaneous oxidation. In contrast, the platinum(II) complex 4
displays a broad cyclic voltammogram suggesting that the two fer-
rocene/ferrocenium redox couples are marginally different.
b
E1/2 = (Epc + Epa)/2 reported relative to the ferrocene/ferrocenium couple.
0.215 V (Fig. 9). These potentials are tentatively assigned to the
irreversible oxidation of both tertiary phosphine centres in 1,
whilst the appearance at two potentials, one more cathodic than
the other, suggests sequential electrochemical oxidation of 1. In
addition to the Fc/Fc+ couple, the dinuclear ruthenium(II) complex
3 was found to exhibit a more complex cyclic voltammogram. This
may tentatively result from two consecutive irreversible single-
electron (per ruthenium atom) RuII ? RuIII oxidations [55,56]. Sim-
ilarly complex 6 showed further irreversible oxidation potentials
The cyclic voltammogram of 1 is more complex showing two
further irreversible oxidation potentials at E1/2 ꢁ0.015 and
Fig. 7. X-ray structure of 8. All hydrogens have been removed for clarity.

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