A study of mono- and 1,1′-diphosphaferrocenes as building blocks for π-conjugated systems

Article abstract of DOI:10.1021/om050593s

The synthesis of mono- and 1,1′-diphosphaferrocenes bearing thienyl or phenyl substituents at the PCα carbon is described. Monophosphaferrocenes can be obtained using a one-pot procedure involving the oxidative coupling of phenyl- or thienyl-capped octa-1,7-diynes with zirconocene. This route implies a Cp transfer from a Zr species to the iron centers. These novel compounds have been characterized by X-ray diffraction study, and their optical and electrochemical behaviors have been elucidated. These data revealed that the optical gaps vary with the substitution pattern and the nature of the metallocene (mono vs diphosphaferrocenes), whereas their electrochemistry is mainly controlled by the structure of the metallocene. The lowest gaps are obtained with thienyl-substituted mono- and diphosphaferrocenes. Compared to the corresponding oligomers featuring phosphole units, these phosphaferrocene-based compounds exhibit higher thermal stability and higher HOMO-LUMO separation.

Full text of DOI:10.1021/om050593s

Organometallics 2005, 24, 5369-5376
5369
A Study of Mono- and 1,1′-Diphosphaferrocenes as
Building Blocks for π-Conjugated Systems
Lingzhi Zhang,† Muriel Hissler,† Hang-Beom Bu,‡ Peter Ba¨uerle,*,‡
Christophe Lescop,† and Re´gis Re´au*,†
Institut de Chimie, UMR 6509 CNRS-Universite´ de Rennes 1, Campus de Beaulieu,
35042 Rennes Cedex, France, and Department Organic Chemistry II, University of Ulm,
Albert-Einstein-Allee 11, 89081 Ulm, Germany
Received July 14, 2005
The synthesis of mono- and 1,1′-diphosphaferrocenes bearing thienyl or phenyl substituents
at the PCR carbon is described. Monophosphaferrocenes can be obtained using a “one-pot”
procedure involving the oxidative coupling of phenyl- or thienyl-capped octa-1,7-diynes with
zirconocene. This route implies a Cp transfer from a Zr species to the iron centers. These
novel compounds have been characterized by X-ray diffraction study, and their optical and
electrochemical behaviors have been elucidated. These data revealed that the optical gaps
vary with the substitution pattern and the nature of the metallocene (mono vs diphospha-
ferrocenes), whereas their electrochemistry is mainly controlled by the structure of the
metallocene. The lowest gaps are obtained with thienyl-substituted mono- and diphospha-
ferrocenes. Compared to the corresponding oligomers featuring phosphole units, these
phosphaferrocene-based compounds exhibit higher thermal stability and higher HOMO-
LUMO separation.
Introduction
and pyrrole are aromatic “electron-excessive” heteroare-
nes, whereas siloles combine diene character with high
electron affinity due to a unique σ*-π* interaction.2a,b
Phosphorus heterocycles have been considered only very
recently as possible building blocks with the synthesis
of phosphole-based oligomers A-C and polymers D-F
(Figure 1).3 In contrast to pyrroles or thiophenes, the
sextet of the phosphole ring is weakly delocalized, and
thus phospholes possess a low aromatic character and
a nucleophilic heteroatom.4 Insertion of this P-hetero-
cycle within classical π-conjugated systems results in a
lowering of their HOMO-LUMO gaps3c-e since conju-
gation is enhanced for macromolecules incorporating
units exhibiting low resonance energies.1,2 Moreover, the
phosphole building block is a potential source of further
structural variations by (i) changing the nature of the
P substituent, (ii) chemical modifications of the nucleo-
philic P atom, or (iii) using this P ring as a precursor of
other P heterocycles featuring a π-system such as
phosphametallocenes. The two first possibilities have
π-Conjugated systems have attracted considerable
interest in the past decades due their potential applica-
tions as materials for optoelectronics such as light-
emitting diodes, field effect transistors, photovoltaic
cells, and lasers.1 These materials combine the advan-
tages of being processable with the possibility to have
their optical and electronic properties tuned by exploit-
ing the enormous versatility and scope of organic
chemistry. The development of new advanced organic
materials is directly linked to the ability of chemists to
design and create novel structures and, subsequently,
to establish structure-property relationships. A fruitful
approach for the tailoring of π-conjugated systems
involves the incorporation of heterocyclopentadienes
into their backbones since these building blocks offer a
range of electronic properties (aromaticity, electronic
affinity, ionization potential, etc. ) depending on the
nature of the heteroatoms.1,2 For example, thiophene
* To whom correspondence should be addressed. (R.R.) Fax: +33
(0)223236939. Phone: +33 (0)223235784. E-mail: regis.reau@univ-
rennes1.fr. Fax: +49-731-5022840. (P.B.) Phone: +49-731-5022850.
E-mail: peter.baeuerle@chemie.uni-ulm.de.
(3) (a) Deschamps, E.; Ricard, L.; Mathey, F. Angew. Chem., Int.
Ed. Engl. 1994, 11, 1158. (b) Mao, S. S. H.; Tilley, T. D. Macromolecules
1997, 30, 5566. (c) Hay, C.; Fischmeister, C.; Hissler, M.; Toupet, L.;
Re´au, R. Angew. Chem., Int. Ed. 2000, 10, 1812. (d) Hay, C.; Hissler,
M.; Fischmeister, C.; Rault-Berthelot, J.; Toupet, L.; Nyulaszi, L.; Re´au,
R. Chem. Eur. J. 2001, 7 (19), 4222. (e) Hay, C.; Fave, C.; Hissler, M.;
Rault-Berthelot, J.; Re´au R. Org. Lett. 2003, 19, 3467. (f) Morisaki,
Y.; Aiki, Y.; Chujo, Y. Macromolecules 2003, 36, 2594. (g) Fave, C.;
Cho, T.-Y.; Hissler, M.; Chen, C.-W.; Luh, T.-Y.; Wu, C.-C.; Re´au R. J.
Am. Chem. Soc. 2003, 125, 9254. (h) Baumgartner, T.; Neumann, T.;
Wirges, B. Angew. Chem., Int. Ed. 2004, 43, 6197. (i) Baumgartner,
T.; W. Bergmans, T. Karpati, T. Neumann, M. Nieger, L. Nyulaszi, L.
Eur. J. Chem. 2005, 11, 4687.
† UMR 6509 CNRS-Universite´ de Rennes 1.
‡ University of Ulm.
(1) (a) Mu¨llen, K.; Wegner, G. Electronic Materials: The Oligomer
Approach; Wiley-VCH: Weinheim, 1998. (b) Roncali, J. Chem. Rev.
1997, 97, 173. (c) Tour, J. M. Acc. Chem. Res. 2000, 33, 791. (d) Meyer,
E. A.; Castellano, R. K.; Diederich, F. Angew. Chem., Int. Ed. 2003,
42, 1210. (e) Skotheim T. A.; Elsenbaumer R. L.; Reynolds J. R.
Handbook of Conducting Polymers, 2nd ed.; Dekker: New York, 1998.
(f) Nalwa, H. S. Handbook of Conductive Materials and Polymers; John
Wiley and Sons: New York, 1997.
(2) (a) Yamagushi, S.; Tamao. K. Chem. Lett. 2005, 34, 2. (b)
Yamagushi, S.; Tamao, K. J. Chem. Soc., Dalton Trans. 1998, 3693.
(c) Hissler, M.; Dyer, P.; Re´au, R. Coord. Chem. Rev. 2003, 244, 1. (c)
Salzner, U.; Lagowski, J. B.; Pickup, P. G.; Poirier, R. A. Synth. Met.
1998, 96, 177. (d) Ma, J.; Li, S.; Jiang, Y. Macromolecules 2002, 35,
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(4) (a) Phosphorus-Carbon Heterocyclic Chemistry: The Rise of a
New Domain; Mathey, F., Ed.; Elsevier Science Ltd: Oxford, 2001. (b)
Phosphorus: The Carbon Copy; Dillon, K., Mathey, F., Nixon, J. F.,
Eds.; John Wiley and Sons Ltd.: Chichester, 1998. (c) Nyulaszi, L.
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10.1021/om050593s CCC: $30.25 © 2005 American Chemical Society
Publication on Web 09/27/2005

5370 Organometallics, Vol. 24, No. 22, 2005
Zhang et al.
Figure 1. Representative π-conjugated systems incorporating phosphole units.
Scheme 1
been exploited and appeared to be key issues for
optoelectronic applications of phosphole-based π-conju-
gated systems since they allow a fine-tuning of their
physical properties.3c-i Until now, the last possibility
has not been investigated,5 although the chemistry of
phosphametallocenes is well-developed.6 The incorpora-
tion of phosphametallocenes into a π-conjugated system
is of particular interest since they possess properties
that are completely different from those of phospholes.
First, they feature a fully delocalized (aromatic) endocy-
clic π-system and an sp2-hybridized P atom exhibiting
some electrophilic character.6 Second, the LUMO of
phosphametallocenes has an appreciable ligand char-
highly moisture sensitive phospholyl anions 2a,b, char-
acterized by a 31P resonance at low field (31P NMR: 2a,
+91.4: 2b, +78.0), are obtained by reductive cleavage
either of the P-Ph bond of the corresponding 1-phe-
nylphospholes 1a,b3c or of the P-P bond of 1,1′-diphos-
pholes 3a,b7 (Scheme 1). The route using 3a,b is more
convenient since it avoids the formation of phenyl-
containing byproducts. The phospholyl anions 2a,b are
then converted into compounds 4a,b and 5a,b upon
reaction with (p-xylene)cyclopentadienedienyliron(II)
hexafluorophosphate salt and FeCl2, respectively (Scheme
1).8 Mono- and 1,1′-dipdiphosphaferrocenes can be iso-
lated as air-stable derivatives in satisfactory yields
following purification by crystallization (Table 1). Note
that the main byproducts formed along with the mono-
and diphosphaferrocenes are 1,1′-diphospholes 3a,b.
We have recently described that 1,1′-diphospholes
3a,b are accessible according to an expedient one-pot
synthesis involving subsequent reaction of “zirconocene”
and PBr3 with thienyl- or phenyl-capped 1,7-octadiynes
6a,b7 (Scheme 2). This feature prompted us to investi-
gate the direct synthesis of 4a,b and 5a,b via a one-pot
procedure involving five steps starting from these
diynes. Octadiynes 6a,b were thus subsequently treated
with Cp2ZrCl2, n-BuLi, PBr3, lithium, and [(p-xylene)-
FeCp]+PF6 (Scheme 2). The intermediate formations of
1,1′-diphospholes 3a,b and of the phospholyl anions 2a,b
were monitored by 31P NMR spectroscopy of the crude
reaction mixtures after addition of PBr3 and lithium,
acter, whereas the HOMO exhibits an essentially pure
metal character.6e Last, the possibility to prepare mono-
and 1,1′-diphosphametallocenes offers an appealing
route to structural variations. In this paper, we describe
the synthesis, solid-state structures, and optical and
electrochemical properties of mono- and 1,1′-diphospha-
ferrocenes, the oldest class of phosphametallocenes,
bearing either phenyl or thienyl substituents at the PCR
carbon atoms. The properties of these novel P-containing
π-conjugated systems are compared to those of the
corresponding phosphole-based derivatives.
Results and Discussion
Synthesis of Phosphametallocenes 4a,b and 5a,b.
The target mono- and 1,1′-diphosphaferrocenes have
been prepared via a classical two-step sequence.4a,b,6 The
(5) For dipoles with nonlinear optical properties bearing 1,1′-
diphosphaferrocenes, see: (a) Klys, A.; Zakrewski, J.; Nakatani, K.;
Delaire, J. A. Inorg. Chem. Com. 2001, 4, 205. For an approach toward
diphosphaferrocene-containing polymers, see: (b) Scheibitz, M.; Bolte,
M.; Lerner, H.-W.; Wagner, M. Organometallics 2004, 23, 3556.
(6) (a) Carmichael, D.; Mathey, F. Topics in Current Chemistry;
Springer-Verlag: Berlin, 2002. (b) Mathey, F. J. Organomet. Chem.
2002, 646, 15. (c) Nief, F. Eur. J. Inorg. Chem. 2001, 4, 891. (d) Ganter,
C. J. Chem. Soc., Dalton Trans. 2001, 3541. (e) Kostic, N. M.; Fenske,
R. F. Organometallics 1983, 2, 1008. (f) Frison, G.; Mathey, F.; Sevin,
A. J. Phys. Chem. A 2002, 106, 5653. (g) Turcitu, D.; Nief, F.; Ricard,
L. Chem. Eur. J. 2003, 9, 4916. (h) Shintani, R.; Fu, G. C. J. Am. Chem.
Soc. 2003, 125, 10778. (i) Weber, L. Angew. Chem. Int. Ed. 2002, 41,
563. (j) Ogasawara, M.; Nagano, T.; Hatashi, T. Organometallics 2003,
22, 1174. (k) Wang, L.-S.; Hollis, K. Org. Lett. 2003, 14, 2543. (l) Sava,
X.; Melaimi, M.; Ricard, L.; Mathey, F.; Le Floch, P. New J. Chem.
2003, 27, 1233. (m) de Lauzon, G.; Deschamps B.; Fischer, J.; Mathey,
F.; Mitschler, A. J. Am. Chem. Soc. 1980, 102, 994. (n) Sava, X.; Ricard,
L.; Mathey, F.; Le Floch, P. Organometallics 2000, 19, 4899. (o) Nief,
F.; Tayart De Borms, B.; Ricard, L.; Carmichael, D. Eur. J. Inorg.
Chem. 2005, 4, 637. (p) Carmichael, D.; Klankermayer, J.; Ricard, L.;
Seeboth, N. Chem. Commun. 2004, 9, 1144. (q) Hitchcook, P. B.;
Lawless, G. A.; Marziano, I. J. Organomet. Chem. 1997, 527, 305.
(7) Fave, C.; Hissler, M.; Ka´rpa´ti, T.; Rault-Berthelot, J.; Deborde,
V.; Toupet, L.; Nyula´szi, L.; Re´au, R. J. Am. Chem. Soc. 2004, 136,
6058.
(8) (a) Frisson, G.; Ricard, L.; Mathey, F. Organometallics 2001, 20,
5513S. (b) Deschamps, E.; Ricard, L.; Mathey, F. Organometallics 2001,
20, 1499. (c) Robert, R. M. G.; Well, A. S. Inorg. Chim. Acta 1986, 112,
171.

Mono- and 1,1′-Diphosphaferrocenes
Organometallics, Vol. 24, No. 22, 2005 5371
Table 1. Yields, NMR Data,a Td5,b UV-Vis Data,c and Oxidation Potentialsd for Monophosphaferrocenes
4a,b and Diphosphaferrocenes 5a,b
δ(13C)
yielde (%)
64 (24)
δ(31P)
-65.9
PCR
PCâ
Td5 (°C)
λmax (nm)
ꢀ (mol-1 L cm-1
)
λonset (nm)
E0ox1 (V)
Epaf (V)
4a
4b
5a
5b
87.8 (56.2)
95.7 (4.4)
375
282
445
274
447
305
488
277
492
19 750
1400
570
0.22
1.19
53 (30)
67
-64.2
-53.1
-53.9
96.8 (56.7)
92.6 (54.0)
99.4 (52.7)
95.3 (4.2)
97.4 (3.7)
98.8 (5.1)
380
297
355
17 000
450
550
640
620
0.20
0.13
0.14
37 350
1370
1.18
58
32 350
800
a Measured in CD2Cl2 at 298 K. b Decomposition temperature estimated by thermogravimetric analysis, 5% weight loss. c Measured in
CH2Cl2. d Referenced to the reversible potential of the ferrocene/ferrocenium couple. e Yields using 3a,b (Scheme 1). In brackets, yields
f
obtained with the “one-pot” procedure (Scheme 2). Irreversible process.
Scheme 2
Table 2. Summary of Crystal Data and Structure Refinement for 4a, 4b, 5a, and 5b
4a
4b
5a
5b
molecular formula
C
21H19PS2Fe
C25H23PFe
410.25
C32H28P2S4Fe
658.57
C40H36P2Fe
634.52
molecular weight
a (Å)
422.30
7.125(5)
13.894(5)
18.632(5)
90
9.310(5)
9.256(5)
25.168(5)
17.118(5)
15.236(5)
90
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
10.341(5)
10.440(5)
85.409(5)
84.841(5)
82.864(5)
990.9(9)
10.504(5)
15.503(5)
99.012(5)
106.469(5)
91.192(5)
1424.2(11)
2
90
90
108.563(5)
90
1844.5(15)
4
6223(3)
Z
2
8
Dc (g cm-3
)
1.521
1.375
1.536
1.355
cryst system
space group
orthorhombic
Pc21n
triclinic
triclinic
monoclinic
C2/c
P1h
P1h
temperature (K)
wavelength Mo KR (Å)
cryst size (mm)
293(2)
0.71069
293(2)
293(2)
293(2)
0.71069
0.71069
0.71069
0.14 × 0.08 × 0.06
0.4 × 0.26 × 0.22
0.30 × 0.20 × 0.10
0.25 × 0.12 × 0.1
µ (mm-1
F(000)
)
1.131
0.848
0.958
0.616
872
428
680
2656
θ limit (deg)
2.93-27.48
-9 e h e 9,
-17 e k e 18,
-24 e l e 24
3998
2.70-30.04
-13 e h e 13,
-14 e k e 14,
-14 e l e 14
11 021
2.99-27.57
-12 e h e 12,
-13 e k e 13,
-20 e l e 18
11 371
2.21-27.49
-32 e h e 32,
-22 e k e 22,
-19 e l e 19
14 037
index ranges hkl
no. of reflns collected
no. of indep reflns
no. of reflns [I > 2σ(I)]
no. of data/restraints/params
goodness-of-fit on F2
final R indices
3998
2855
3998/19/209
1.029
R1 ) 0.0541
wR2 ) 0.1307
R1 ) 0.0858
wR2 ) 0.1519
0.612 and -0.593
5782
4292
5782/0/245
1.019
R1 ) 0.0391
wR2 ) 0.0987
R1 ) 0.0607
wR2 ) 0.1105
0.476 and -0.430
6519
4343
6519/0/357
1.024
R1 ) 0.0614
wR2 ) 0.1599
R1 ) 0.1010
wR2 ) 0.1864
0.942 and -0.777
7144
4543
7144/0/389
1.013
R1 ) 0.0483
wR2 ) 0.1196
R1 ) 0.0892
wR2 ) 0.1407
0.515 and -0.423
[I > 2σ(I)]
R indices (all data)
largest diff peak and hole (e Å-3
)
respectively. Although this “one-pot” procedure afforded
monophosphaferrocenes 4a,b in rather modest yields
(Table 1), it is more convenient than that starting from
isolated 1,1′-diphospholes 3a,b since it is much less
time-consuming. Very surprisingly, when this “one-pot”
procedure is conducted with FeCl2(THF)1.5, monophos-
phaferrocenes 4a,b are obtained instead of the expected
diphosphaferrocenes 5a,b (Scheme 2). The only source
of the Cp ligand of monophosphaferrocenes 4a,b is the
zirconium complex used to prepare the 1,1′-diphospholes
3a,b. Hence, the formation of monophosphaferrocenes
4a,b implies the transfer of one Cp ligand from a
zirconium species to the Fe(II) center. This reaction can
involve either a direct zirconium to iron transfer of a
Cp ligand or a reduction of a Cp2Zr fragment by lithium
leading to CpLi, which will be the cyclopentadienyl
ligand source. It is noteworthy that this Cp transfer is
very efficient since the yields are very similar (ca. 30%)
using [CpFe(p-xylene)]PF6 or FeCl2(THF)1.5 as a source
of Fe(II).
Spectroscopic and Solid-State Characteriza-
tions of Phosphametallocenes 4a,b and 5a,b. The

5372 Organometallics, Vol. 24, No. 22, 2005
Zhang et al.
Figure 2. Molecular structure of 4a (thermal ellipsoids
50% probability). Hydrogen atoms have been omitted for
clarity.
Figure 4. Molecular structure of 5a (thermal ellipsoids
50% probability). Hydrogen atoms have been omitted for
clarity.
Figure 3. Molecular structure of 4b (thermal ellipsoids
50% probability). Hydrogen atoms have been omitted for
clarity.
novel mono- and diphosphaferrocenes 4a,b and 5a,b
were characterized by NMR techniques, high-resolution
mass spectrometry, and elemental analysis. Their multi-
nuclear NMR data are comparable to those of related
compounds bearing alkyl substituents.6 The 13C NMR
spectrum showed two signals for the PCR and PCâ
carbon atoms with typical large J1 and small J2
coupling constants, respectively (Table 1). It is note-
worthy that the 13C chemical shifts of the PCR carbon
atoms vary with the nature of the aromatic substituent;
they are downfield shifted by ca. 6 ppm in the thienyl
series (Table 1). Of particular importance for potential
applications in the field of material science, mono- and
1,1′-diphosphaferrocenes are much more thermally stable
than the corresponding phospholes 1a,b. Derivatives
4a,b and 5a,b decompose above 300 °C, as estimated
by thermal gravimetric analysis performed in air (Table
1), whereas the corresponding phospholes 1a and 1b
decompose at 210 and 199 °C, respectively.3d
These new phosphametallocenes have been subjected
to X-ray diffraction studies (Table 2). The phospholyl
and cyclopentadienyl ligands of 4a,b are eclipsed, and
their two planes are almost parallel (Figures 2 and 3).
The two diphosphaferrocenes 5a and 5b exhibit differ-
ent conformations. Tetrathienyl derivative 5a adopts a
C2h conformation with the two P atoms pointing in
opposite directions (R ) 180°, Figure 4). Phenyl-capped
derivative 5b possesses a C1 conformation in which the
P atoms of the phospholyl units superpose with the Câ
of the other P ligand (R ) 127°, Figure 5). This
conformation is not maintained in solution since NMR
spectra show that both P atoms and phenyl substituents
Figure 5. Molecular structure of 5b (thermal ellipsoids
50% probability). Hydrogen atoms have been omitted for
clarity.
are magnetically equivalent. These data suggest a very
weak rotation barrier as supported by calculations on
the parent compound FeC8H8P2, showing that the
energy difference between the two C2h and C1 conform-
ers is low (ca. 6 kcal mol-1),6e and the observation of
different conformers in the cell unit of octaethyl-
diphosphaferrocene.6n The planarity of the diarylphos-
pholyl moieties, a key structural factor influencing the
delocalization of the π-system,1b depends on the struc-
ture of the phosphametallocenes. Monophosphafe-
rocenes 4a and 4b both exhibit considerable rotational
disorder in the solid state (Figures 2 and 3). The twist
angles between the phospholyl ligand and the aromatic
substituents are slightly higher for thienyl-capped 4a
(54.9° and 57.6°) than for phenyl-capped 4b (43.4° and
49.1°) derivatives. In the diphosphaferrocene series, the
reverse trend is observed. The two di(2-thienyl)phos-
pholyl moieties of compound 5a are almost planar (twist
angles: 0.5-12.9°), while for phenyl-substituted deriva-
tive 5b, the twist angles range from 17.2° to 46.8°
(Figures 3 and 4). The large rotational disorder observed
for derivatives 4a,b and 5b prevents an efficient delo-
calization of the π-system over the three cycles in the
solid state since the orbital overlap varies approximately
with the cosine of the twist angle.1b Only diphospha-
ferrocene 5a possesses planar π-conjugated systems as
PC
PC

Mono- and 1,1′-Diphosphaferrocenes
Organometallics, Vol. 24, No. 22, 2005 5373
Figure 6. UV/vis spectra (250-700 nm) of monophosphaferrocenes 4a,b and diphosphaferrocenes 5a,b in CH2Cl2.
Figure 7. Visible spectra (400-700 nm) of monophosphaferrocenes 4a,b and diphosphaferrocenes 5a,b in CH2Cl2.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Monophosphaferrocenes 4a,b and
Diphosphaferrocenes 5a,b
4a
4b
5a
5b
5a
5b
P1-C1
1.775(8)
1.414(9)
1.410(6)
1.426(9)
1.796(7)
1.461(12)
1.505(12)
1.788(2)
1.427(2)
1.428(2)
1.427(2)
1.789(2)
1.486(2)
1.783(4)
1.438(6)
1.424(6)
1.425(6)
1.781(4)
1.469(6)
1.463(6)
1.788(3)
1.434(4)
1.424(4)
1.423(4)
1.775(3)
1.483(4)
P2-C31
1.782(4)
1.435(6)
1.431(7)
1.427(6)
1.785(5)
1.460(6)
1.787(3)
1.428(4)
1.431(4)
1.417(4)
1.777(3)
C1-C2
C31-C32
C32-C37
C37-C38
C38-P2
C2-C7
C7-C8
C8-P1
C8-C9
C31-C43
C32-C45
C38-C39
C31-P2-C38
C1-C13
C1-C15
C1-P1-C8
1.488(4)
1.483(4)
90.07(13)
1.488(2)
89.45(8)
1.493(4)
1.460(7)
90.1(2)
88.77(17)
90.2(2)
observed for the corresponding 2,5-dithienylphosphole
1a (twist angles: 12.5° and 16.2°).3d Note that the bond
distances for 5a and 5b are similar, excepted the inter-
ring distances, which are slightly smaller for the planar
di(2-thienyl)phospholyl moieties of 5a than for the
rotationally disordered diphenylphospholyl unit of 5b
(Table 3).
Optical and Redox Properties of Phosphamet-
allocenes 4a,b and 5a,b. The UV/vis and fluorescence
spectra of all new phosphametallocene derivatives were
recorded in CH2Cl2. For each compound, intense bands
are observed between 350 and 450 nm (Figure 6, Table
1) along with a red-shifted broad shoulder (Figure 7).
Although care must be taken in the interpretation of

5374 Organometallics, Vol. 24, No. 22, 2005
Zhang et al.
these data, since the orbitals of the P ligands interact
with the Fe atom,6e some conclusions can be drawn. The
molecular extinction coefficients of the high-energy
absorptions (ꢀ: 17 000-38 000 mol-1 L cm-1, Table 1,
Figure 6) are by far superior to those of the red-shifted
shoulders (ꢀ: 450-1500 mol-1 L cm-1, Table 1, Figure
7). Furthermore, the intensity of the high-energy ab-
sorptions approximately doubles on going from mono-
phosphaferrocene to the corresponding diphosphafer-
rocene (4a vs 5a, 4b vs 5b, Table 1, Figures 6 and 7).
These data strongly suggest that the bands of high
energy are mainly ligand centered, whereas those of
lower energy can be assigned to ligand-metal charge
transfer. This hypothesis is supported by the fact that
ferrocene also displays a weak absorption band at 442
nm. In light of this, two features are particularly
noteworthy. First, for both series, a bathochromic shift
is observed by replacing phenyl by thienyl substituents
(4a vs 4b; 5a vs 5b, Figure 6), this trend being less
pronounced for the λonset (Table 1, Figure 7). A similar
bathochromic shift induced by phenyl/thiophene sub-
stitutions was already observed in the phosphole series
(λmax: 1a, 410 nm; 1b, 354 nm).3d Second, the spectra
of 1,1′-diphosphaferrocenes are red shifted compared to
those of the corresponding monophosphaferrocenes (5a
vs 4a; 5b vs 4b, Figure 6). These data suggest an
interesting decrease of the HOMO-LUMO separation
of the π-ligand on going from mono- to 1,1′-diphospha-
ferocenes. It is noteworthy that the λmax of phosphafer-
rocene-based π-conjugated systems are blue shifted
compared to the corresponding phosphole-based deriva-
tives. This increase of the “optical” HOMO-LUMO gap
of the π-system can be attributed to the fact that
phospholyl ligands exhibit a higher aromatic character
than phospholes. No fluorescence behavior was observed
for mono- and 1,1′-diphosphaferrocenes in degassed
THF or CH2Cl2 solutions. In conclusion, this study
revealed interesting optical properties-relationships.
Both the nature of the 2,5-substituent and the structure
of the metallocene influence the absorption properties
of these novel P-containing π-conjugated systems. π-Con-
jugated systems incorporating phosphametallocene build-
ing blocks are more thermally stable and exhibit higher
gap than the corresponding systems featuring phosphole
units.
the terminal thiophene rings, which are known to
undergo irreversible oxidation in this potential range.1a
The same general trends are observed in the 1,1′-
diphosphaferrocene series. Thienyl- and phenyl-substi-
tuted derivatives 5a and 5b undergo a first reversible
oxidation at similar potentials (ca. 0.13 V, Table 1),
which is assigned to an Fe2+ f Fe3+ process. Only
thienyl-substituted 5a shows a second irreversible
oxidation process at a potential (1.18 V) similar to that
observed for monophosphaferrocene 4a (1.19 V). These
data suggest that, as usually observed for phospha-
ferrocenes,6e the HOMOs of thienyl- or phenyl-substi-
tuted derivatives 4a,b and 5a,b have an essentially pure
metal character. The oxidation of the di(2-thienyl)-
phospholyl moiety of 4a and 5a occurs at more anodic
potential compared to di(2-thienyl)phosphole 1a (E° )
+0.40 V vs Fc/Fc+),3b,c probably due to the preliminary
oxidation of the Fe center. It is noteworthy that no
anodic electropolymerization process was observed with
compounds 4a and 5a.
Conclusion
We have described the synthesis of a novel series of
mixed conjugated oligomers including mono- and diphos-
phaferrocene units and elucidated their optical and
electrochemical properties. These model molecules have
revealed interesting structure-property relationship.
Both the nature of the 2,5-substituent (phenyl vs
thienyl) and the structure of the metallocene (mono- vs
1,1′-di-) influence their optical properties, while their
electrochemical behavior is mainly controlled by the
structure of the metallocene. It is worth noting that the
λmax(π-π*) of 1,1′-diphosphaferrocene-based oligomers
are red shifted compared to those of their monophos-
phaferrocene-containing analogues. As observed for
structurally related phosphole-based oligomers, the
lowest HOMO-LUMO π-gap is obtained with thienyl-
substitued metallocenes. However, the properties of
phosphaferrocene- and phosphole-containing conjugated
systems differ markedly due to the profoundly different
electronic nature of these two P building blocks. These
results nicely illustrate the potential of P building blocks
to create structural diversity and to tune the physical
properties of π-conjugated systems.10
The electrochemical behavior of mono- and diphos-
phaferrocene derivatives was investigated by cyclic
voltammetry (CV). The CV at 100 mV s-1 has been
performed in a three-electrode cell configuration (Pt disk
working electrode, Pt wire counter electrode, Ag/AgCl
secondary reference electrode, internally calibrated vs
the redox couple ferrocene/ferricenium: Fc/Fc+) with
dichloromethane as solvent and tetrabutylammonium
hexafluorophosphate (TBAHFP) (0.1 M) as electrolyte.
A reversible oxidation is observed for 4a (+0.20 V) and
4b (+0.22 V) at potentials that are similar to that of
monophosphaferrocene lacking in aromatic 2,5-substit-
uents (E°1/2 ) +0.18 V vs Fc/Fc+).9 These data strongly
suggest that this first oxidation process is metal cen-
tered (Fe2+ f Fe3+). For the thienyl-capped derivative
4a, a second and irreversible oxidation process occurs
at 1.19 V. This second oxidation very probably involves
Experimental Section
General Remarks. All experiments were performed under
an atmosphere of dry argon using standard Schlenk tech-
niques. Solvents were freshly distilled under argon from
sodium/benzophenone (tetrahydrofuran, diethyl ether, toluene)
or from phosphorus pentoxide (pentane, dichloromethane,
acetonitrile). Triethylamine was freshly distilled under argon
(10) For conjugated systems based on other P moieties, see: (a)
Smith, R. C.; Chen, X.; Protasiewicz, J. D. Inorg. Chem. 2003, 42, 5468.
(b) Smith, R. C.; Protasiewcz, J. D. Eur. J. Inorg. Chem. 2004, 998. (c)
Smith, R. C.; Protasiewcz, J. D. J. Am. Chem. Soc. 2004, 126, 998. (d)
Gates, D. P. New Aspects in Phosphorus Chemistry, Topics in Current
Chemistry; Spinger-Verlag: Berlin, 2004; p 107. (e) Wright, V. A.; Gates
D. P. Angew. Chem., Int. Ed. 2002, 268, 66. (f) Jin, Z.; Lucht, B. L. J.
Organomet. Chem. 2002, 65, 167. (g) Jin, Z.; Lucht, B. L. J. Am. Chem.
Soc. 2005, 127, 5586. (h) Lucht, B. L.; St Onge, N. O. Chem. Commun.
2000, 2097. (i) Ito, S.; Sugiyama, H.; Yoshifuji, M. Angew. Chem., Int.
Ed. 2000, 39, 2781. (j) Ito, S.; Miyake, H.; Sugiyama, H.; Yoshifuji, M.
Tetrahedron Lett. 2004, 45, 7019. (k) Nakamura, A.; Toyota, K.;
Yoshifuji, M. Tetrahedron 2005, 61, 5223. (l) Ito, S.; Sekigushi, S.;
Yoshifuji, M. J. Org. Chem. 2004, 69, 4181. (m) Cantat, T.; Me´zailles,
N.; Maigrot, N.; Richard, L.; LeFloch, P. Chem. Commun. 2004, 1274.
(9) Bartsch, R.; Datsenko, S.; Ignatiev, N. V.; Mu¨ller, C.; Nixon, J.
F.; Pickett, C. J. J. Organomet. Chem. 1997, 529, 375.

Mono- and 1,1′-Diphosphaferrocenes
Organometallics, Vol. 24, No. 22, 2005 5375
from potassium hydroxide, and PBr3 was also freshly distilled
under argon. Cp2ZrCl2, Li, Na, and n-BuLi were obtained from
Aldrich Chemical Co. and were used as received without
further purification. 1,8-Di(2-thienyl)octa-1,7-diyne,3d 1,8-di-
(1-phenyl)octa-1,7-diyne,3d 2,5-di(2-thienyl)-1-phenylphosphole,4d
2,5-di(phenyl)-1-phenylphosphole,4d 1,1′-di[2,5-di(2-thienyl)-
(c) From Dyine 6a. A solution of n-BuLi in hexane (1.6
M, 1.3 mL, 2.1 mmol) was added at -78 °C to a THF solution
(25 mL) of 1,8-di(2-thienyl)octa-1,7-diyne (6a; 270 mg, 1.0
mmol) and [Cp2ZrCl2] (293 mg, 1.0 mmol). The reaction was
warmed to room temperature and stirred for 15 h. Freshly
distilled PBr3 (271 mg, 0.1 mL, 1 mmol) was added to this
solution at -78 °C. The solution was allowed to warm to room
temperature and stirred for 4 h. Li metal in excess was added
to this solution at room temperature, and the formation of
phospholyl anion 2a was monitored by 31P NMR spectroscopy.
The solution was stirred for 5 h, and the excess of Li was
phosphole],7 1,1′-di[2,5-di(phenyl)phosphole],7 and [(p-xylene)-
- 11
FeCp]+PF6
were prepared as described in the literature.
FeCl2(THF)1.5 was prepared through a reduction of FeCl3 with
aluminum in THF at -40 °C. Preparative separations were
performed by gravity column chromatography on basic alu-
mina (Aldrich, Type 5016A, 150 mesh, 58 Å) in 3.5-20 cm
columns. 1H, 13C, and 31P NMR spectra were recorded on
Bruker AM300, DPX200. 1H and 13C NMR chemical shifts were
reported in parts per million (ppm) relative to Me4Si as
external standard. 31P NMR downfield chemical shifts were
expressed with a positive sign, in ppm, relative to external
85% H3PO4. Assignment of carbon atoms is based on HMBC
and HMQC experiments. High-resolution mass spectra were
obtained on a Varian MAT 311 or ZabSpec TOF Micromass
instrument at CRMPO, University of Rennes. Elemental
analyses were performed by the CRMPO, University of Rennes.
UV/vis spectra were recorded at room temperature on a
UVIKON 942 spectrophotometer. Cyclic voltammetry experi-
ments were performed with a computer-controlled EG&G PAR
273 potentiostat in a three-electrode single-compartment cell
(5 mL). The platinum working electrode consisted of a plati-
num wire sealed in a soft glass tube with a surface of A )
0.785 mm2, which was polished down to 0.5 µm with Buehler
polishing paste prior to use in order to obtain reproducible
surfaces. The counter electrode consisted of a platinum wire,
and the reference electrode was an Ag/AgCl secondary elec-
trode. All potentials were internally referenced to the fer-
rocene/ferrocenium couple.12 For the measurements concen-
trations of 10-3 M of the electroactive species were used in
freshly distilled and degassed dichloromethane (Lichrosolv,
Merck) and 0.1 M tetrabutylammonium hexafluorophosphate
(TBAHFP, Fluka), which was twice recrystallized from ethanol
and dried under vacum prior to use.
2,5-Di(2-thienyl)-1-monophosphaferrocene, 4a. (a) From
2,5-Di(2-thienyl)-1-phenylphosphole, 1a. Li metal in excess
was added, at room temperature, to a THF solution (10 mL)
of 2,5-di(2-thienyl)-1-phenylphosphole 1a (120 mg, 0.32 mmol).
The mixture was stirred vigorously at room temperature, and
the formation of phospholyl anion 2a was monitored by 31P
NMR spectroscopy. After 12 h, the excess of lithium was
removed and 2-chloro-2-methylpropane (27 mg, 0.32 mmol)
was added. The reaction mixture was stirred for 3 h, and neat
[p-(xylene)CpFe]+PF6- (120 mg, 0.32 mmol) was added to the
green solution. The reaction was monitored by 31P NMR
spectroscopy and, after 4 h, the volatile materials were
removed in a vacuum. Compound 4a was extracted with
pentane (15 mL) and ether (15 mL). 4a was obtained as air-
stable red crystals from a saturated pentane solution at room
temperature (yield: 13 mg, 0.032 mmol, 10%).
-
removed. Solid [p-(xylene)FeCp]+PF6 (387 mg, 1.0 mmol) or
solid FeCl2(THF)1.5 (235 mg, 0.1 mmol) was added at room
temperature to the solution, which was then stirred overnight.
The solution was filtered through basic alumina, and the
solvent was removed in vacuo. The residue was extracted with
pentane, and 4a was obtained as red crystals by crystallization
from a pentane solution at room temperature [yield: 101 mg,
0.24 mmol, 24%, using [p-(xylene)FeCp]+PF6; 127 mg, 0.3
mmol, 30% using FeCl2(THF)1.5]. 1H NMR (300 MHz, CD2-
Cl2): δ 1.93 (m, 2H, dCCH2CH2), 2.21 (m, 2H, dCCH2CH2),
2.79 (m, 2H, dCCH2), 3.06 (m, 2H, dCCH2), 4.23 (s, 5H, CpH),
3
3
6.92 (dd, JHH ) 3.7 and 5.1 Hz, 2H, H4 Thio); 6.99 (dd, JHH
4
3
) 3.7 Hz, JHH ) 1.0 Hz, 2H, H3 Thio), 7.22 (dd, JHH ) 5.1
Hz, JHH ) 1.0 Hz, 2H, H5 Thio). 13C{1H} NMR (75.46 MHz,
4
CD2Cl2): δ 23.2 (s, dCCH2CH2), 27.9 (s, dCCH2), 75.4 (s, Cp),
87.8 (d, JCP ) 56.2 Hz, PCR), 95.7 (d, JCP ) 4.4 Hz, PCdCâ),
124.2 (d, JCP ) 2.1 Hz, C5 Thio), 125.7 (d, JCP ) 7.3 Hz, C3
Thio), 126.9 (s, C4 Thio), 143.3 (d, JCP ) 20.8 Hz, C2 Thio).
31P{1H} NMR (121.49 MHz, CD2Cl2): δ -65.9 (s). HR-MS
(EI): m/z 422.0011 [M+•]; calcd for C21H19PS2Fe 422.0015. Anal.
Calcd for C21H19S2PFe: C, 59.72; H, 4.53. Found: C, 59.91;
H, 4.59.
2,5-Di(phenyl)-1-monophosphaferrocene, 4b. Following
procedure b described for the compound 4a, the reaction of
1,1′-di[2,5-di(phenyl)phosphole] (3b; 40 mg, 0.07 mmol), so-
dium, and [p-(xylene)FeCp]+PF6- (150 mg, 0.40 mmol) afforded
4b as an air-stable red solid (yield: 30 mg, 0.07 mmol, 53%).
Following procedure c described for compound 4a, reaction of
n-BuLi in hexane (1.6 M, 1.3 mL, 2.1 mmol), 1,8-di(phenyl)-
octa-1,7-diyne (6b; 258 mg, 1.0 mmol), [Cp2ZrCl2] (293 mg, 1.0
mmol), PBr3 (271 mg, 0.1 mL, 1.0 mmol), lithium, and solid
[(p-xylene)FeCp]PF6 (387 mg, 1.0 mmol) or solid FeCl2(THF)1.5
(240 mg, 1 mmol) afforded 4b as an air-stable red solid [yield:
123 mg, 0.30 mmol, 30%, using [(p-xylene)FeCp]PF6; 110 mg,
0.27 mmol, 28%, using FeCl2(THF)1.5]. 1H NMR (200 MHz, CD2-
Cl2): δ 1.89 (m, 2H, dCCH2CH2), 2.16 (m, 2H, dCCH2CH2),
2.72 (m, 2H, dCCH2), 3.00 (m, 2H, dCCH2), 4.21 (s, 5H, CpH),
7.24 (m, 6 H, p-Ph and m-Ph), 7.42 (m, 4H, o-Ph). 13C{1H}
NMR (75.46 MHz, CD2Cl2): δ 23.4 (s, dCCH2CH2), 28.0 (s,
dCCH2), 74.8 (s, Cp), 95.3 (d, JCP ) 4.2 Hz, PCdCâ), 96.8 (d,
JC-P ) 56.7 Hz, PCR), 126.0 (s, p-Ph), 127.8 (s, m-Ph), 129.9
(d, JC-P ) 7.1 Hz, o-Ph), 140.0 (d, JC-P ) 17.4 Hz, ipso-Ph).
31P{1H} NMR (81.02 MHz, CDCl3): δ -64.2 (s). HR-MS (ES,
CH2Cl2): m/z 410.0888 [M+•]; calcd for C25H23PFe 410.0887.
Anal. Calcd for C25H23FeP: C, 73.19; H, 5.65. Found: C, 73.09;
H, 5.52.
1,1′-Di[2,5-di(2-thienyl)diphosphaferrocene], 5a. (a)
From 2,5-Di(2-thienyl)-1-phenylphosphole, 1a. Li metal
in excess was added, at room temperature, to a THF solution
(10 mL) of 2,5-di(2-thienyl)-1-phenylphosphole (1a; 100 mg,
0.26 mmol). The mixture was stirred vigorously at room
temperature, and the formation of phospholyl anion 2a was
monitored by 31P NMR spectroscopy. After 12 h, the excess
lithium was removed and 2-chloro-2-methylpropane (25 mg,
0.26 mmol) was added. The reaction mixture was stirred for 3
h, and solid FeCl2(THF)1.5 (30 mg, 0.13 mmol) was added to
the green solution. The reaction was monitored by 31P NMR
spectroscopy, and after 6 h, the volatile materials were
removed in a vacuum. Compound 4a was extracted with
pentane (15 mL) and ether (15 mL). 4a was obtained as air-
(b) From 1,1′-Diphosphole 3a. Li metal in excess was
added, at room temperature, to a THF solution (25 mL) of 1,1′-
di[2,5-di(2-thienyl)phosphole], 3a (90 mg, 0.15 mmol). The
mixture was stirred vigorously at room temperature, and the
formation of phospholyl anion 2a was monitored by 31P NMR
spectroscopy. After 4 h, neat [p-(xylene)CpFe]+PF6 (350 mg,
-
0.90 mmol) was added at room temperature to the red-green
solution. The reaction was monitored by 31P NMR spectroscopy,
and after 3 h, the solution was filtered through basic alumina
and the solvent was removed in vacuo. 4a was obtained as
air-stable red crystals from a saturated pentane solution at
room temperature (yield: 81 mg, 0.19 mmol, 64%).
(11) Hamon, J.-R.; Astruc, D.; Michaud, P. J. Am. Chem. Soc. 1981,
103, 758.
(12) Pommerehne, H.; Vestweber, W.; Guss, R.; Mahrt, F.; Ba¨ssler,
H.; Porsch, M.; Daub, J. Adv. Mater. 1995, 7, 551.

5376 Organometallics, Vol. 24, No. 22, 2005
Zhang et al.
stable red crystals from a saturated pentane solution at room
temperature (yield: 13 mg, 0.02 mmol, 15%).
(Center de Diffractome´trie, Universite´ de Rennes 1, France),
with Mo KR radiation (λ ) 0.71073 Å). Reflections were
indexed, Lorentz-polarization corrected, and integrated by the
DENZO program of the KappaCCD software package. The
data merging process was performed using the SCALEPACK
program.13 Structure determinations were performed by direct
methods with the solving program SIR97,14 which revealed all
the non-hydrogen atoms. The SHELXL program15 was used
to refine the structures by full-matrix least-squares based on
F2. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms were included in
idealized positions and refined with isotropic displacement
parameters. For compound 4a, the thienyl moieties are
disordered and were modeled with a equidistribution of the
sulfur atoms and the C3H3 atoms of the thienyl moieties over
positions 1 and 3 of the thienyl ring. For compound 5a, half of
the thienyl moieties were found disordered and were modeled
as for compound 4a. Atomic scattering factors for all atoms
were taken from International Tables for X-ray Crystal-
lography.16 Details of crystal data and structural refinements
are given in Table 2. CCDC reference numbers 277996-
277999 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retreving.html or from the Cam-
bridge Crystallographic Data Center, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (internat.) + 44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk.
(b) From 1,1′-Diphosphole, 3a. Li metal in excess was
added, at room temperature, to a THF solution (25 mL) of 1,1′-
di[2,5-di(2-thienyl)phosphole], 3a (85 mg, 0.14 mmol). The
mixture was stirred vigorously at room temperature, and the
formation of phospholyl anion 2a was monitored by 31P NMR
spectroscopy. After for 4 h, solid FeCl2(THF)1.5 (110 mg, 0.47
mmol) was added to the solution. The reaction was monitored
by 31P NMR, and after 3 h the solution was filtered through
basic alumina. The solvent was removed in vacuo, and 5a was
obtained as air-stable red crystals by crystallization from a
pentane solution at room temperature (yield: 62 mg, 0.09
mmol, 67%). 1H NMR (300 MHz, CDCl3): δ 1.61 (m, 4H, d
CCH2CH2), 1.86 (m, 4H, dCCH2CH2), 2.40 (m, 4H, dCCH2),
3
2.63 (m, 4H, dCCH2), 6.66 (d, JHH ) 4.0 Hz, 4H, H3 Thio),
6.72 (dd, 3JHH ) 4.0 and 5.1 Hz, 4H, H4 Thio), 7.02 (d, 3JHH
)
5.1 Hz, 4H, H5 Thio). 13C{1H} NMR (75.47 MHz, CDCl3): δ
22.7 (s, dCCH2CH2), 26.8 (s, dCCH2), 92.6 (d, JCP ) 54.0 Hz,
PCR), 97.4 (d, JCP ) 3.7 Hz, PCdCâ), 124.1 (d, JCP ) 7.0 Hz, C5
Thio), 125.9 (d, JCP ) 11.9 Hz, C3 Thio), 127.3 (s, C4 Thio),
139.5 (d, JCP ) 22.1 Hz, C2 Thio). 31P{1H} NMR (121.49 MHz,
CDCl3): δ -53.1 (s). HR-MS (ES, CH2Cl2): (m/z) 657.9908
[M+•]; calcd for C32H28FeP2S4 657.9899. Anal. Calcd for
C32H28P2S4Fe: C, 58.36; H, 4.29. Found: C, 58.26; H, 4.65.
1,1′-Di[2,5-di(phenyl)diphosphaferrocene], 5b. Follow-
ing procedure b described for compound 5a, reaction of 1,1′-
di[2,5-di(phenyl)phosphole] (3b; 30 mg, 0.05 mmol), sodium,
and solid FeCl2(THF)1.5 (145 mg, 0.62 mmol) afforded 5b as
an air-stable red solid (yield: 20 mg, 0.03 mmol, 58%). 1H NMR
(200 MHz, CD2Cl2): δ 1.50 (m, 4H, dCCH2CH2), 1.69 (m, 4H,
dCCH2CH2), 2.34 (m, 4H, dCCH2), 2.88 (m, 4H, dCCH2), 7.10
(m, 12H, p-Ph and m-Ph), 7.22 (m, 8H, o-Ph). 13C NMR{1H}
(75.46 MHz, CD2Cl2): δ 22.7 (s, dCCH2CH2), 27.0 (s, dCCH2),
98.8 (d, JCP ) 5.1 Hz, PCdCâ), 99.4 (d, JCP ) 52.7 Hz, PCR),
126.2 (s, p-Ph), 127.7 (s, m-Ph), 130.2 (d, JCP ) 12.1 Hz, o-Ph),
136.4 (d, JCP ) 17.2 Hz, ipso-Ph). 31P{1H} NMR (81.02 MHz,
CD2Cl2): δ - 53.9 (s). HR-MS (ES, CH2Cl2): (m/z) 634.1647
[M+•]; calcd for C40H36FeP2 634.1642. Anal. Calcd for C40H36P2-
Fe: C, 75.72; H, 5.72. Found: C, 75.48; H, 5.99.
Acknowledgment. We thank the Ministe`re de
l’Education Nationale, de la Recherche et de la Tech-
nologie, the Institut Universitaire de France, the Centre
National de la Recherche Scientifique, and the Deutsche
Forschungsgemeinschaft for financial support (CNRS-
DFG program).
OM050593S
(13) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol.
276, p 307.
(14) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R.
J. Appl. Crystallogr. 1999, 32, 115.
(15) Sheldrick G. M. SHELX97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Germany, 1997.
(16) International Tables for X-ray Crystallography, Vol C; Klu-
wer: Dordrecht, 1992.
X-ray Crystallographic Study. Single crystals suitable
for X-ray crystal analysis were obtained by slow evaporation
of 80:20 CH2Cl2/Et2O solutions of 4a, 4b, 5a, and 5b at room
temperature. Single-crystal data collection was performed at
room temperature with a Nonius Kappa CCD diffractometer