Redox-active, multinuclear (ferrocenylethynyl)phosphanes and their palladium and platinum complexes

Article abstract of DOI:10.1021/om0606892

A series of (ferrocenylethynyl)phosphanes with increasing number of ferrocenylethynyl units, including corresponding PdCl₂, PtCl ₂, and PdI₂ complexes were prepared, their spectroscopic data investigated, and the solid-sta

Full text of DOI:10.1021/om0606892

Organometallics 2006, 25, 5657-5664
5657
Redox-Active, Multinuclear (Ferrocenylethynyl)phosphanes and
Their Palladium and Platinum Complexes
Thomas Baumgartner,*,†,‡ Marcel Fiege,‡ Florian Pontzen,‡ and Rocio Arteaga-Mu¨ller‡
Department of Chemistry, UniVersity of Calgary, 2500 UniVersity DriVe NW, Calgary, AB, T2N 1N4,
Canada, and Institute of Inorganic Chemistry, RWTH-Aachen UniVersity,
Landoltweg 1, 52074 Aachen, Germany
ReceiVed July 31, 2006
A series of (ferrocenylethynyl)phosphanes with increasing number of ferrocenylethynyl units, including
corresponding PdCl2, PtCl2, and PdI2 complexes were prepared, their spectroscopic data investigated,
and the solid-state structures of three of the complexes determined. The complexes exhibit increased
steric bulk, affording bent ethynyl moieties in the cis-configured PdCl2 and PtCl2 complex. The PdI2-
based complex shows a favorable trans-configuration with almost linear acetylene units. The thermal
behavior of some of the complexes indicated their utility as potential precursors for magnetic ceramic
nanomaterials. Electrochemical investigations of the ligands and the corresponding complexes revealed
that the structural motif of the ligands does not support multistep redox processes within the materials.
All compounds showed single, reversible redox processes whose potential is influenced by the substitution
pattern of the ligands as well as the respective complex geometries.
highly metallized, molecular materials are thus exciting research
targets.1,9 Main chain metallopolymers with covalent bonds are
now relatively well developed, as nicely illustrated by systems
such as polyferrocenes and polymetallaynes.1,10 The use of
coordinate bonds for the construction of highly metallized
macromolecular and supramolecular materials, however, pro-
vides an attractive alternative approach.11,12 Most work in this
area to date has focused on the use of bidentate, nitrogen-donor
ligands, and building blocks employed as spacers in these
ligands almost exclusively rely on π-conjugated units such as
arylenes, arylene-vinylenes, or nonconjugated oligo(ethylene-
glycol)s.13 The use of value-added, “smart” linkers that incor-
porate additional redox or optical features, on the other hand,
is surprisingly rare; only a few reports in the literature utilize,
for example, ferrocene units as an integral part of the spacer
ligands, despite its highly valuable redox properties, chemical
robustness, and versatility.14 It is also striking that, although
phosphane ligation is ubiquitous in molecular transition metal
Introduction
The incorporation of metal atoms into supramolecular assem-
blies and macromolecules is an intriguing perspective for the
development of new materials with novel, unusual properties.1
Transition metal centers can, for example, permit redox control
of the size and shape of a macroscopic object,2 selective binding
and sensing,3 the generation of liquid crystalline materials4 or
magnetic nanoparticle composites,5,6 and etch resistance to
plasmas,7 as well as several other useful physical and chemical
characteristics.8 With regard to molecular electronics, these
features have become particularly desirable in recent years, and
* Author to whom correspondence should be addressed. E-mail:
thomas.baumgartner@ucalgary.ca.
† Current address: University of Calgary.
‡ RWTH-Aachen University.
(1) (a) Archer, R. D. Inorganic and Organometallic Polymers; John
Wiley & Sons Inc.: New York, 2001. (b) Manners, I. Synthetic Metal
Containing Polymers; Wiley-VCH: Weinheim, 2004. (c) Macromolecules
Containing Metal and Metal-Like Elements; Abd-el-Aziz, A. S., Carraher,
C. E., Jr.; Pittman, C. U., Jr.; Sheats, J. E.; Zeldin, M., Eds.; Wiley: New
York, 2004-2006; Vols. 1-7.
(2) (a) Yoshida, R.; Takahashi, T.; Yamaguchi, T.; Ichijo, H. AdV. Mater.
1997, 9, 175. (b) Arsenault, A. C.; Miguez, H.; Kitaev, V.; Ozin, G. A.;
Manners, I. AdV. Mater. 2003, 15, 503.
(3) (a) McQuade, D. T.; Pullen, A. E.; Swager, T. M. Chem. ReV. 2000,
100, 2537. (b) Stott, T. L.; Wolf, M. O. Coord. Chem. ReV. 2003, 246, 89.
(4) Steffen, W.; Ko¨hler, B.; Altmann, M.; Scherf, U.; Stitzer, K.; zur
Loye, H.-C.; Bunz, U. H. F. Chem. Eur. J. 2001, 7, 117.
(7) (a) Massey, J.; Winnik, M. A.; Manners, I.; Chan, V. C. H.; Spatz,
J. P.; Ostermann, J. M.; Enchelmaier, R.; Mo¨ller, M. J. Am. Chem. Soc.
2001, 123, 3147. (b) Cheng, J. Y.; Ross, C. A.; Chan, Z.-H.; Thomas, E.
L.; Lammertink, R. G. H.; Vancso, G. J. AdV. Mater. 2001, 13, 1174.
(8) (a) Inorganic Materials; Bruce, D. W., O’Hare, D., Eds.; Wiley: New
York, 1992. (b) Extended Linear Chain Compounds, Miller, J. S., Ed.;
Plenum: New York, 1982; Vols. 1-3. (c) Ingham, S. L.; Long, N. J. Angew.
Chem. 1994, 106, 1847; Angew. Chem., Int. Ed. 1994, 33, 1752. (d) Serrano,
J. L. AdV. Mater. 1995, 7, 348.
(5) (a) MacLachlan, M. J.; Ginzburg, M.; Coombs, N.; Coyle, T. W.:
Raju, N. P.; Greedan, J. E.; Ozin, G. A.; Manners, I. Science 2000, 287,
1460. (b) Park, C.; McAlvin, J. E.; Fraser, C. L.; Thomas, E. L. Chem.
Mater. 2002, 14, 1225.
(9) (a) Low, P. J. Dalton Trans. 2005, 2821. (b) Holliday, B. J.; Swager,
T. M. Chem. Commun. 2005, 23. (c) Leoni, P.; Marchetti, L.; Mohapatra,
S. K.; Ruggeri, G.; Ricci, L. Organometallics 2006, 25, 4226.
(10) (a) Manners, I. Chem. Commun. 1999, 857. (b) Kingsborough, R.
P.; Swager, T. M. Prog. Inorg. Chem. 1999, 48, 123. (c) Nguyen, P.; Go´mez-
Elipe, P.; Manners, I. Chem. ReV. 1999, 99, 1515.
(6) (a) Berenbaum, A.; Ginzburg-Margau, M.; Coombs, N.; Lough, A.
J.; Safa-Sefat, A.; Greedan, J. E.; Ozin, G. A.; Manners, I. AdV. Mater.
2003, 15, 51. (b) Clendenning, S. B.; Aouba, S.; Rayat, M. S.; Grozea, D.;
Sorge, J. B.; Brodersen, P. M.; Sodhi, R. N. S.; Lu, Z.-H.; Yip, C. M.;
Freeman, M. R.; Ruda, H. E.; Manners, I. AdV. Mater. 2004, 16, 215. (c)
Clendenning, S. B.; Han, S.; Coombs, N.; Paquet, C.; Rayat, M. S.; Grozea,
D.; Brodersen, P. M.; Sodhi, R. N. S.; Yip, C. M.; Lu, Z.-H.; Manners, I.
AdV. Mater. 2004, 16, 291. (d) Lastella, S.; Jung, Y. J.; Yang, H.; Vajtai,
R.; Ajayan, P. M.; Ryu, C. Y.; Rider, D. A.; Manners, I. J. Mater. Chem.
2004, 14, 1791. (e) Chan, W. Y.; Clendenning, S. B.; Berenbaum, A.; Lough,
A. J.; Aouba, S.; Ruda, H. E.; Manners, I. J. Am. Chem. Soc. 2005, 127,
1765.
(11) (a) Lehn, J.-M. Supramolecular Chemistry. Concept and Perspec-
tiVes; VCH: Weinheim, 1995.
(12) (a) Schubert, U. S.; Heller, M. Chem. Eur. J. 2001, 7, 5252. (b)
Lahn, B.; Rehahn, M. Macromol. Symp. 2001, 163, 157.
(13) See e.g.: (a) Andres, P. R.; Schubert, U. S. AdV. Mater. 2004, 16,
1043. (b) Newkome, G. R.; Cho, T. J.; Moorefield C. N.; Mohapatra, P.
P.; Godinez, L. A. Chem. Eur. J. 2004, 10, 1493. (c) Iyer, P. K.; Beck, J.
B.; Weder, C.; Rowan, S. J. Chem. Commun. 2005, 319. (d) Maeda, H.;
Hasegawa, M.; Hashimoto, T.; Kakimoto, T.; Nishio, S.; Nakanishi, T. J.
Am. Chem. Soc. 2006, 128, 10024.
10.1021/om0606892 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 10/05/2006

5658 Organometallics, Vol. 25, No. 23, 2006
Baumgartner et al.
Scheme 1. Redox-Active, Ferrocenyl-Functionalized
Phosphanes17,18
Scheme 2. Synthesis of (Ferrocenylethynyl)phosphanes
chemistry, the utility of metal-P-donor interactions for the
creation of metallopolymers or supramolecular assemblies is
relatively unexplored and that the use of value-added spacers
is unknown in this context.15,16
As part of our research on organophosphorus and organo-
metallic materials, we have now targeted ferrocenylethynyl-
functionalized phosphanes as new, potentially multiredox
synthons for the generation of highly metallized materials via
metal-P-donor interactions. Yoshifuji and co-workers have
recently reported a related building block, 1, that has been used
for the generation of the redox-active, bidentate, low-coordinate
P-ligand 2 (Scheme 1).17 Electrochemical investigations of the
corresponding complexes 3 have revealed that the three metal
centers within the complexes exhibit strong electronic interac-
tions evident in two reversible {Fe(II) f Fe(III)} and one
irreversible {M(II) f M(IV)} oxidation.17 In 2006, Sasaki and
co-workers were able to show that ferrocene-containing, crowded
triarylphosphanes 4 also allow strong electronic interactions with
multistep reversible redox processes between the attached
ferrocene units (Scheme 1).18 These observations have stimu-
lated us to investigate the (ferrocenylethynyl)phosphane system
and determine its potential for molecular electronics.
Results and Discussion
Synthesis of (Ferrocenylethynyl)phosphane Ligands. To
verify whether electronic communication between several ferro-
cene units through a phosphorus center within the same ligand
was possible, we synthesized a set of three ligands with increas-
ing number of ferrocenylethynyl moieties (1 f 3). These ligands
would provide access to model complexes with two, four, or
six ferrocene functionalities, respectively, next to the central
transition metal (Pd or Pt). The ethynylene spacer groups of
the ligands were anticipated to reduce the steric bulk around
the phosphorus center to some extent, but also to promote elec-
tronic communication throughout the ligands via π-conjugation.
Bearing the design of corresponding bidentate ligands in mind,
this structural motif is furthermore expected to suppress potential
intramolecular interactions with coordinating transition metal
centers due to an unfavorable bite angle in future supramolecular
assemblies.16b
With the ultimate generation of redox-active supramolecular
assemblies and polymers in mind, in the present paper we report
our initial studies in this area and describe the synthesis and
electronic properties of three novel phosphane ligands as well
as corresponding Pd- and Pt-based model complexes to explore
the suitability of this structural motif for prospective materials.
Following a known procedure toward the synthesis of
phosphinoacetylenes,19 the mono- and bis-ferrocenylethynyl-
functionalized phosphanes 6 and 7 were obtained by reaction
of ferrocenylacetylene 5 with n-BuLi at -78 °C in THF and
subsequent treatment with an appropriate chlorophosphane or
dichlorophosphane (Scheme 2). After filtration over neutral
alumina, the products were obtained as orange-brown amor-
phous powders in good isolated yields (6: 73%; 7: 72%). Due
to the shielding nature of the electron-rich acetylene unit, their
31P NMR signals are considerably high-field shifted, with the
bis-ethynyl compound 7 showing a resonance at δ31P ) -59.5
ppm and the mono-ethynyl species 6 at δ31P ) -32.8 ppm.
These values compare to those of phenylethynyl analogues,
(14) (a) Ma, K.; Scheibitz, M.; Scholz, S.; Wagner, M. J. Organomet.
Chem. 2002, 652, 11. (b) Cui, X.; Carapuca, H. M.; Delgado, R.; Drew,
M. G. B.; Felix, V. Dalton Trans. 2004, 1743. (c) Dong, T.-Y.; Chang,
S.-W.; Lin, S.-F.; Lin, M.-C.; Wen, Y.-S.; Lee, L. Organometallics 2006,
25, 2018. (d) Ko¨cher, S.; van Klink, G. P. M.; van Koten, G.; Lang, H. J.
Organomet. Chem. 2006, 691, 3319.
(15) (a) Sherlock, S. J.; Cowie, M.; Singleton, E.; de V. Steyn, M. M.
Organometallics 1988, 7, 1663. (b) Wright, M. E.; Lawson, L.; Baker, R.
T.; Roe, D. C. Polyhedron 1992, 11, 323. (c) Puddephatt, R. J. Coord.
Chem. ReV. 2001, 216-217, 313. (d) Paulusse, J. M. J.; Sijbesma, R. P.
Chem. Commun. 2003, 1494. (e) Paulusse, J. M. J.; Sijbesma, R. P. Angew.
Chem. 2004, 116, 4560; Angew. Chem., Int. Ed. 2004, 43, 4460.
(16) (a) Xu, D.; Hong, B. Angew. Chem., Int. Ed. 2000, 39, 1826. (b)
Baumgartner, T.; Huynh, K.; Schleidt, S.; Lough, A. J.; Manners, I. Chem.
Eur. J. 2002, 8, 4622. (c) James, S. L. Chem. Soc. ReV. 2003, 32, 276. (d)
Lin, R.; Yip, J. H. K.; Zhang, K.; Koh, L. L.; Wong, K.-Y.; Ho, K. P. J.
Am. Chem. Soc. 2004, 126, 15852. (e) Martin-Redondo, M. P.; Scoles, L.;
Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. J. Am. Chem. Soc. 2005,
127, 5038. (f) Gianneschi, N. C.; Masar, M. S., III; Mirkin, C. A. Acc.
Chem. Res. 2005, 38, 825.
1
which is also true for the corresponding H and 13C NMR
spectroscopic data.19,20 In the case of the tris(ferrocenylethynyl)-
phosphane 8, it should be noted that the synthesis only
(17) Kawasaki, S.; Nakamura, A.; Toyota, K.; Yoshifuji, M. Organo-
metallics 2005, 24, 2983.
(18) Sutoh, K.; Sasaki, S.; Yoshifuji, M. Inorg. Chem. 2006, 45, 992.
(19) Carty, A. J.; Hota, N. K.; Ng, T. W.; Patel, H. A.; O’Connor, T. J.
Can. J. Chem. 1971, 49, 2706.
(20) Hengefeld, A.; Nast, R. Chem. Ber. 1983, 116, 2035.

Redox-ActiVe, Multinuclear (Ferrocenylethynyl)phosphanes
Organometallics, Vol. 25, No. 23, 2006 5659
Scheme 3. Synthesis of (Ferrocenylethynyl)phosphane
Complexes
Figure 1. Molecular structure of 9 in the solid state (50% proba-
bility level; H atoms omitted for clarity). Selected bonds lengths
(Å) and angles (deg): Pd1-P1: 2.2591(16); Pd1-P2: 2.2394-
(17); P1-C1: 1.758(6); P2-C13: 1.742(6); C1-C2: 1.197(8);
C13-C14: 1.206(8); C2-C3: 1.409(9); C14-C15: 1.416(8);
Cl1-Pd1-Cl2: 90.30(6); P1-Pd1-P2: 93.59(6); P1-Pd1-Cl1:
175.15(6); P2-Pd1-Cl2: 174.97(6); Pd1-P1-C1: 117.9(2);
Pd1-P2-C13: 108.9(2); P1-C1-C2: 170.7(6); P2-C13-C14:
157.3(6); C1-C2-C3: 179.5(7); C13-C14-C15: 176.1(7).
proceeded to the desired product (isolated yield 57%) when an
excess of TMEDA was present in the reaction mixture (Scheme
2). Absence of TMEDA led to a mixture of products that could
be identified as mono- and bis(ethynyl) species. This observation
was attributed to the steric bulk of the ferrocenylethynyl group,
reducing the accessibility of the phosphorus center and only
allowing for a trisubstitution with monomeric lithio-acetylenes
that are activated by TMEDA. The presence of the three ethynyl
groups in 8 leads to a strongly high-field shifted resonance in
the 31P NMR spectrum at δ ) -87.9 ppm.20
Synthesis and X-ray Crystal Structure Analyses of Pd and
Pt Complexes Based on (Ferrocenylethynyl)phosphanes. The
synthesis of the PdCl2 as well as PtCl2 complexes of the ligands
6-8 was straightforward by following conditions reported in
the literature for related complexes.16b,21 Complexes 9-12 were
obtained via treatment of 2 equiv of the corresponding ligand
with 1 equiv of the appropriate complex precursor [(cod)PdCl2
or K2PtCl4] in dichloromethane at room temperature (Scheme
3). The dark red solutions were stirred for 4 h (9-11) or 3 days
(12), respectively, to afford the complexes in very good isolated
yields (78-93%). Coordination of the phosphorus centers to
the transition metal causes a low-field shift of the 31P NMR
resonances (∆δ ) 30-38 ppm), now appearing at δ31P ) 5.0
ppm (9), δ31P ) -24.9 ppm (10), δ31P ) -57.8 ppm (11), and
δ31P ) -17.8 ppm (12). The latter signal also exhibited a 1J(P-
195Pt) coupling constant of 3768 Hz, confirming the cis-complex
geometry, as expected.22 The absence of further resonances in
the 31P NMR spectra of 9-12 indicated the formation of only
1
one complex configuration isomer in each case. The H NMR
data of the complexes were comparable to those of the free
ligands, with the exception that the ortho-H atoms of the phenyl
substituents in 9, 10, and 12 showed a significant low-field
shift.16b The formation of complexes with two phosphane ligands
was further corroborated by the respective 13C NMR spectra of
the complexes 9-12, as most of the resonance signals showed
either a double doublet or higher order splitting pattern due to
coupling with the two different phosphorus centers located at
the same and the adjacent ligand. We were also able to obtain
suitable single crystals for X-ray crystallographic analyses of
9 and 12 from concentrated solutions (CH2Cl2/CHCl3, 1:2) at
room temperature that allowed us to confirm the complex
geometries. The crystal structure analyses (Figures 1 and 2)
revealed that both compounds are cis-configured in the solid
state and almost isostructural (space group P21/n). Surprisingly,
the ethynyl units show a significant deviation from their genuine
linear shape with P1-C1-C2 angles of 170.7(6)° for 9, 170.3-
(3)° for 12 and P2-C13-C14 angles of 157.3(6)° for 9, 156.6-
(3)° for 12, which is most likely due to increased steric bulk
within the complexes. Furthermore, the two acetylene units in
9 and 12 do not show a coplanar arrangement with the central
MCl2P2 plane. As observed for related (phenylethynyl)phos-
phane complexes by Carty et al.23 and later also by Manners
and co-workers,16b the two P-CtC units exhibit a cisoid-
arrangement with a torsion angle of 56.7° (9) or 56.2° (12)
between them. However, the torsion angles are significantly
smaller than those of the phenylethynyl species (ca. 69°).16b,23
The other structural parameters (see Figure 1 and 2) are
unexceptional and correspond to those of related compounds.16b
(21) (a) Simpson, R. T.; Carty, A. J. J. Coord. Chem. 1973, 2, 207. (b)
Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc. 1979, 101,
5612. (c) Carty, A. J.; Efraty, A. Can. J. Chem. 1969, 47, 2573. (d) Fornie´s,
J.; Lalinde, E.; Mart´ın, A.; Moreno, M. T.; Welch, A. J. J. Chem. Soc.
Dalton Trans. 1995, 1333.
(22) (a) Power, W. P.; Wasylishen, R. E. Inorg. Chem. 1992, 31, 2176.
(b) Lindner, E.; Fawzi, R.; Mayer, H. A.; Eichele, K.; Hiller, W.
Organometallics 1992, 11, 1033.
(23) (a) Carty, A. J.; Taylor, N. J.; Johnson, D. K. J. Am. Chem. Soc.
1979, 101, 5422. (b) Johnson, D. K.; Rukachaisirikul, T.; Sun, Y.; Taylor,
N. J.; Canty, A. J.; Carty, A. J. Inorg. Chem. 1993, 32, 5544.

5660 Organometallics, Vol. 25, No. 23, 2006
Baumgartner et al.
Figure 3. Molecular structure of 13 in the solid state (50%
probability level). Selected bonds lengths (Å) and angles (deg):
Pd1-P1: 2.314(3); P1-C1: 1.736(12); C1-C2: 1.199(18); C2-
C31: 1.420(17); I1-Pd1-I1.A: 180.00(4); P1-Pd1-P1A: 180.0;
P1-Pd1-I1: 87.67(8); P1A-Pd1-I1: 92.33(8); Pd1-P1-C1:
114.6(5); P1-C1-C2: 172.4(12); C1-C2-C31: 177.1(13).
We also attempted to synthesize corresponding PtCl2 com-
plexes based on the bis(ferrocenylethynyl) and tris(ferrocenyl-
ethynyl) ligands 7 and 8. However, the investigation indicated
that the steric bulk with the increasing number of ferrocenyl-
ethynyl groups is too large to accommodate cis-configured com-
plexes. In contrast to their Pd congeners, Pt complexes always
adopt this geometry, irrespective of the nature of the ligand of
the halogen.16b,21,23 Therefore, the ligand 7 was only partially
consumed (ca. 50%) to afford the corresponding Pt complex
[(FcCC)2PPh]2PtCl2 (δ31P ) -40.8 ppm,1J(P-195Pt) ) 3926
Hz), even after prolonged reaction times (4 days). Ligand 8 on
the other hand did not react at all with the added K2PtCl4 and
could be recovered completely after 4 days.
Thermal Behavior of the Multi-ferrocene Complexes 10
and 11. The elemental analyses of the complexes 10 and 11,
respectively, always resulted in drastically low carbon values
(-7% for 10; -8% for 11), indicating the formation of carbides
during the combustion process. These observations led us to
perform preliminary investigations toward the formation of
nanoscale ceramics by means of thermogravimetric analysis
(TGA). The results from these studies (Figure 4) further indi-
cated that the two complexes 10 and 11 do form nanocomposites
in relatively high yields. Complex 10 gives about 68% ceramic
yield, and the major portion of the weight loss can be observed
between 300 and 700 °C. The thermal stability of hexaferrocene
complex 11, on the other hand, is significantly greater than that
of complex 10, which can be attributed to the higher metal
concentration in 11 compared to 10. A significant weight loss
can be observed only above 550 °C before leveling off at around
950 °C, providing a ceramic yield of ca. 60%. It should be
mentioned that both samples recovered after the pyrolysis were
also attracted to a bar magnet, which is highly intriguing for
potential application in molecular electronics.6
Figure 2. Molecular structure of 12 in the solid state (40%
probability level, H atoms omitted for clarity). Selected bonds
lengths (Å) and angles (deg): Pt1-P1: 2.2500(9); Pt1-P2: 2.2241-
(10); P1-C1: 1.755(4); P2-C13: 1.758(4); C1-C2: 1.200(5);
C13-C14: 1.200(5); C2-C3: 1.429(5); C14-C15: 1.436(5);
Cl1-Pt1-Cl2: 88.05(4); P1-Pt1-P2: 94.30(3); P1-Pt1-Cl1:
174.04(4); P2-Pt1-Cl2: 176.15(3); Pt1-P1-C1: 117.08(12);
Pt1-P2-C13: 109.63(14); P1-C1-C2: 170.3(3); P2-C13-
C14: 156.6(3); C1-C2-C3: 178.5(4); C13-C14-C15: 176.8(4).
Carty et al. also established for (phenylethynyl)phosphanes that
palladium chloride complexes generally tend to adopt cis-
configurations, whereas the corresponding palladium iodide
complexes are trans-configured.21,23 To be able to compare
potential differences in the electronic properties of the complexes
arising from different configurations, we have transformed the
PdCl2 complex 9 into the corresponding PdI2 species 13 in
quantitative yield by treatment of an acetone solution of 9 with
potassium iodide at room temperature (Scheme 3, bottom).21a
The significantly high-field shifted 31P NMR resonance signal
of 13 (δ ) -11.2 ppm), compared to that of 9 (cf. δ31P ) 5.0
ppm), supported the change of the complex geometry.16b The
1H and 13C NMR spectroscopic data of 13, on the other hand,
were not affected very much by the transformation and relate
to those of 9. The trans-geometry was, however, confirmed by
an X-ray crystal structure analysis (see Figure 3). Suitable single
crystals24 were obtained from a CHCl3 solution of 13 by slow
evaporation of the solvent. The molecular structure of 5 in the
solid state exhibits an inversion center about the central Pd atom,
leading to a coplanar transoid-arrangement of the two P-Ct
C units. The fact that the trans-configuration of 13 is more
favorable than the cis-configuration becomes evident in an
almost linear acetylene moiety (angle P1-C1-C2: 172.4(12)°),
contrasting with the solid-state structures of 9 and 12. However,
the ligands do not show a coplanar arrangement with the central
MI2P2 plane, as already observed for 9 and 12; for the palladium
iodide species 13 the torsion angle amounts to 46.5° (cf. ca.
56° for 9 and 12), which can be attributed to repulsive inter-
actions between the iodide and the ethynyl group. The other
structural parameters are similar to those of 9, 12, and related
phenylethynyl species (see Figure 3).16b,23
Electrochemical Investigations. As mentioned earlier, the
ferrocene-containing, crowded triarylphosphanes 4 (Scheme 1)
allow strong electronic communication between the attached
ferrocene units via the π-conjugated system and the phosphorus
center. The same is true for the ferrocenylphosphanes Fc2PPh
and Fc3P, whose electrochemical behavior was investigated
systematically by Barriere, Kirss, and Geiger.25 Both studies
(24) The single crystals of 13 were twinned non-merohedrally, with 880
out of 4634 reflexes affected; BASF for 2nd individuum is 0.206.
(25) Barriere, F.; Kirss, R. U.; Geiger, W. E. Organometallics 2005, 24,
48.

Redox-ActiVe, Multinuclear (Ferrocenylethynyl)phosphanes
Organometallics, Vol. 25, No. 23, 2006 5661
Figure 4. TGA traces and temperature profile of the analyses of
complexes 10 (a, top) and 11 (b, bottom).
Table 1. CV Data for Compounds 6-13a
compound
E
pc [V]
Epa [V]
6
7
8
0.48
0.50
0.51
0.57
0.55
0.63
0.58
0.54
0.59
0.59
0.60
0.69
0.68
0.72
0.70
0.66
9
10
11
12
13
a vs SCE, in CH2Cl2, with 0.1 M [NBu4][PF6], scan rate 50 mV/s, T )
293 K, E1/2(FcH/FcH+) ) 0.4 V.
have revealed multistep, reversible redox processes for the
respective systems that also involve the oxidation of the phos-
phorus center. In the case of Fc2PPh and Fc3P, the first oxidation
process seems to involve a species with significant radical cation
character at the phosphorus atom. In contrast, oxidation of the
phosphorus atom in 4 occurs only after the oxidation of the
ferrocene units.18 These observations indicate that different
spacer moieties between the ferrocene groups and the central
phosphorus atom could lead to a completely different electro-
chemical behavior. To our surprise, the new ligands 6-8 did
indeed show completely different redox properties from the
systems reported in the literature. The redox potentials of the
ligands 6-8 and the complexes 9-13 are summarized in Table
1. The cyclic voltammograms of 6-8 in CH2Cl2 (0.1 mM,
[NBu4][PF6], 50 mV/s, SCE, 293 K) exhibited only one
reversible redox wave, respectively, despite the presence of
multiple π-conjugated ferrocene units in 7 and 8 (Figure 5).
However, the oxidation processes appeared at significantly
Figure 5. Cyclic voltammograms of 8 (a, top), 10 (b, middle),
and 11 (c, bottom) at 293 K. Conditions: Pt disk (0.2 mm2) as
working electrode; solutions (ca. 0.1 mM) in CH2Cl2 with [NBu4]-
PF6 as supporting electrolyte; scan rate 50 mV/s; potentials are
referred to the SCE where ferricinium/ferrocene potential is 0.4 V
vs SCE.
higher potential than the ferrocene/ferricinium couple (0.4 V
vs SCE) at E1/2 ) 0.54 V (6), E1/2 ) 0.55 V (7), and E1/2
)
0.56 V (8), indicating a potential influence of the substitution
pattern at the phosphorus center on the electronic properties of
the ligands. The phosphinoacetylene units appear to have an
electron-withdrawing effect on the ferrocene moieties, thus
leading to increasingly higher oxidation potentials (6 f 8)
compared to that of native ferrocene. The completely reversible
nature of the redox processes suggests the exclusive oxidation
of the iron centers, particularly in the presence of [NBu4][PF6]
as supporting electrolyte; under the experimental conditions
employed, a radical phosphane species generally would show

5662 Organometallics, Vol. 25, No. 23, 2006
Baumgartner et al.
disk (0.2 mm2) as working electrode and solutions (ca. 0.1 mM) in
CH2Cl2 with [NBu4]PF6 as supporting electrolyte. Potentials are
referred to the SCE where the ferricinium/ferrocene potential is
0.4 V vs SCE.
some irreversible electrochemical behavior.25 An extension of
the observed trend in the redox behavior was found in the
corresponding complexes 9-11. The complexes showed single
reversible oxidation waves at E1/2 ) 0.63 V (9), E1/2 ) 0.62 V
(10), and E1/2 ) 0.68 V (11), also supporting the oxidation of
the iron centers, exclusively (Figure 5). The higher potentials
in this case could be explained with further decreased electron
densities at the ferrocene moieties, caused by the complexation
of the phosphorus centers. Considering different complex
geometries for complexes 9 and 10/11 could explain the non-
linear trend within the observed values. It is very likely that
complexes 10 and 11 adopt a trans-configuration due to the
steric bulk within the ligands. This assumption was further
supported by the oxidation potentials of the cis-configured Pt
complex 12 with E1/2 ) 0.64 V and the trans-configured PdI2
complex 13 at E1/2 ) 0.60 V, indicating that the complex
geometry does have an effect on the electrochemical properties
of the ferrocene units as well. It should also be mentioned in
this context that an oxidation of the transition metal centers in
the complexes 9-13 was not observed, which is in contrast to
the systems 3 investigated by Yoshifuji and co-workers.17
Preparation of Ligand 6. To a solution of ferrocenylacetylene
(0.92 g, 4.36 mol) in THF (50 mL) was added dropwise n-BuLi
(1.74 mL, 4.36 mmol) at -78 °C, and the reaction mixture was
subsequently warmed to room temperature. After 30 min, the solu-
tion was cooled to -78 °C again and Ph2PCl (0.92 g, 4.36 mmol)
was added dropwise. The reaction mixture was allowed to warm,
and after 2 h at room temperature the solvent was removed under
vacuum. The remaining residue was taken up in dichloromethane
and filtered to remove the LiCl. The filtrate was then concentrated
and filtered over neutral alumina using pentane as eluent. Evapora-
tion of the solvent afforded 6 as an orange-brown solid. Yield:
1.26 g (73%). 31P{1H} NMR (162.0 MHz, CDCl3): δ -32.8 ppm.
1H NMR (500 MHz, CDCl3): δ 7.65 (m, 4H, o-Ph), 7.36 (m, 6H,
p-Ph, m-Ph), 4.53 (pt, 2/4J(H,H) ) 1.9 Hz, 2H, C5H4), 4.25 (pt,
2/4J(H,H) ) 1.9 Hz, 2H, C5H4), 4.22 (s, 5H, Cp) ppm. 13C{1H}
NMR (125.0 MHz, CDCl3): δ 136.8 (d,1J(C,P) ) 7.5 Hz, ipso-
Ph), 132.4 (d,2J(C,P) ) 21.5 Hz, o-Ph), 128.8 (s, p-Ph), 128.5
(d,3J(C,P) ) 8.6 Hz, m-Ph), 107.6 (d, J(C,P) ) 4.8 Hz, CtC),
81.6 (d, J(C,P) ) 3.2 Hz, CtC), 72.0 (s, Cp2/5), 70.0 (s, Cp), 69.2
(s, Cp3/4), 64.2 (s, Cp1). Anal. Calcd for C29H19FeP: C 73.12; H
4.86. Found: C 73.40; H 5.14. CV: Epc ) 0.48 V; Epa) 0.59 V.
Conclusion
In conclusion, (ferrocenylethynyl)phosphanes can be synthe-
sized by simple chemical procedures and can easily be trans-
formed into the corresponding Pd or Pt complexes with different
complex geometries. The directed syntheses afford highly metal-
lized complexes with up to seven transition metal centers within
one molecule. Electrochemical investigations have revealed that
the ferrocene moieties do not seem to communicate with each
other in either the free ligands or the respective complexes.
However, as the redox processes observed are reversible by
nature, they can be assigned to exclusively originate from the
ferrocene units. The results further indicate that it is possible
to generate highly charged, stable materials (up to hexacationic
species) that could be suitable for molecular electronics, e.g.,
as molecular switches. A very intriguing feature with respect
to the processability of the materials is the tendency of 10 and
11 to form magnetic ceramics in high yields. A systematic
investigation of the new complexes toward materials applications
is therefore currently under detailed investigation as well as the
synthesis of (ferrocenylethynyl)phosphane-based bidentate ligands
to access corresponding supramolecular assemblies.
Preparation of Ligand 7. To a solution of ferrocenylacetylene
(0.92 g, 4.39 mol) in THF (50 mL) was added dropwise n-BuLi
(1.76 mL, 4.39 mmol) at -78 °C, and the reaction mixture was
subsequently warmed to room temperature. After 30 min, the
solution was cooled to -78 °C again, and PhPCl2 (0.39 g, 2.20
mmol) was added dropwise. The reaction mixture was allowed to
warm, and after 2 h at room temperature the solvent was removed
under vacuum. The remaining residue was taken up in dichloro-
methane and filtered to remove the LiCl. The filtrate was then
concentrated and filtered over neutral alumina using pentane as
eluent. Evaporation of the solvent afforded 7 as a light brown solid.
Yield: 0.83 g (72%). 31P{1H} NMR (162.0 MHz, CDCl3): δ -59.5
1
ppm. H NMR (500 MHz, CDCl3): δ 7.77 (m, 2H, o-Ph), 7.34
(m, 3H, p-Ph, m-Ph), 4.45 (pt, 2/4J(H,H) ) 1.9 Hz, 4H, C5H4), 4.16
(pt, 2/4J(H,H) ) 1.9 Hz, 4H, C5H4), 4.16 (s, 10H, Cp) ppm. 13C-
{1H} NMR (125.0 MHz, CDCl3): δ 134.4 (br., ipso-Ph), 131.5
(d,2J(C,P) ) 21.4 Hz, o-Ph), 129.1 (s, p-Ph), 128.7 (d,3J(C,P) )
7.5 Hz, m-Ph), 106.2 (d, J(C,P) ) 7.6 Hz, CtC), 79.4 (br, CtC),
72.2 (s, Cp2), 72.1 (s, Cp5), 70.3 (s, Cp), 69.5 (s, Cp3/4), 63.9 (s,
Cp1). Anal. Calcd for C30H23Fe2P: C 68.48; H 4.41. Found: C
68.50; H 4.47. CV: Epc ) 0.50 V; Epa) 0.59 V.
Preparation of Ligand 8. To a solution of ferrocenylacetylene
(1.01 g, 4.81 mol) in THF (50 mL) and TMEDA (2.18 mL, 14.42
mL) was added dropwise n-BuLi (1.94 mL, 4.81 mmol) at -78 °C,
and the reaction mixture was subsequently warmed to room
temperature. After 30 min, the solution was cooled to -78 °C again,
and PCl3 (0.22 g, 1.60 mmol) was added dropwise. The reaction
mixture was allowed to warm, and after 3 h at room temperature
the solvent was removed under vacuum. The remaining residue
was taken up in dichloromethane and filtered to remove the LiCl.
The filtrate was subsequently filtered over neutral alumina using
dichloromethane as eluent. Evaporation of the solvent afforded 8
as an orange-brown solid. Yield: 0.60 g (57%). 31P{1H} NMR
Experimental Section
General Procedures. All manipulations were carried out under
a dry argon atmosphere employing standard Schlenk techniques.
Solvents were dried using standard procedures. N-BuLi (2.5 M in
hexane), K2PtCl4, and KI were used as received. Ph2PCl, PhPCl2,
PCl3, and TMEDA were freshly distilled prior to use. Ferrocenyl-
acetylene (5)26 and (cod)PdCl2 were prepared as published. 31P-
27
{1H} NMR, 1H NMR, and 13C{H} NMR were recorded on a Bruker
DRX 400, Varian Mercury 200, or Unity 500 MHz spectrometer.
Chemical shifts were referenced to external 85% H3PO4 (31P) or
TMS (13C, 1H). Elemental analyses were performed by the Micro-
analytical Laboratory of the RWTH-Aachen University. Thermo-
gravimetric analyses (TGA) were performed using a Setaram
Setasys 16/18 instrument under a stream of nitrogen with a heating
rate of 2 °C/min. Cyclic voltammetry measurements were performed
on a CH-Instruments 630A electrochemical workstation with a Pt
1
(162.0 MHz, CDCl3): δ -87.9 ppm. H NMR (400 MHz, CD2-
Cl2): δ 4.48 (pt, 2/4J(H,H) ) 1.9 Hz, 6H, C5H4), 4.21 (pt, 2/4J(H,H)
) 1.9 Hz, 6H, C5H4), 4.20 (s, 15H, Cp) ppm. 13C{1H} NMR (100.0
MHz, CD2Cl2): δ 105.8 (d, J(C,P) ) 12.1 Hz, CtC), 76.7 (d,
J(C,P) ) 8.7 Hz, CtC), 72.5 (s, Cp2), 72.4 (s, Cp5), 70.6 (s, Cp),
70.0 (s, Cp3/4), 63.5 (s, Cp1). Anal. Calcd for C36H27Fe3P: C 65.70;
H 4.14. Found: C 65.34; H 4.22. CV: Epc ) 0.51 V; Epa) 0.60 V.
(26) Doisneau, G.; Balavoine, G.; Fillebeen-Khan, T. J. Organomet.
Chem. 1992, 425, 113.
General Procedure for the Synthesis of the PdCl2 Complexes
(27) Drew, D.; Doyle, J. R. Inorg. Synth. 1972, 13, 52.
9-11. Two equivalents of the corresponding ligand (2 mmol; 6:

Redox-ActiVe, Multinuclear (Ferrocenylethynyl)phosphanes
Organometallics, Vol. 25, No. 23, 2006 5663
Table 2. Crystallographic Data for 9, 12, and 13
9
12
13
formula
Mr
C48H38Cl2Fe2P2Pd
965.72
C48H38Cl2Fe2P2Pt
1054.41
C48H38Fe2I2P2Pd
1148.62
T/K
120(2)
200(2)
228(2)
cryst syst
space group
a/Å
b/Å
monoclinic
P21/n (no. 14)
10.8183(8)
21.3720(15)
17.4369(13)
90
93.297(3)
90
4024.9(5)
4, 1.594
monoclinic
P21/n (no. 14)
10.895(2)
21.539(4)
17.514(3)
90
93.625(3)
90
triclinic
P1h (no. 2)
7.601(3)
12.040(2)
c/Å
13.0166(17)
107.208(13)
101.176(19)
102.58(2)
1067.0(5)
1, 1.787
R/deg
â/deg
γ/deg
V/Å3
4101.6(14)
4, 1.708
2080
Z, Dc/Mg cm-3
F(000)
1952
560
µ(Mo KR)/mm-1
θ range for data collection
no. of reflns collected/unique (Rint
no. of data/restraints/params
final R indices [I > 2σ(I)]
R indices (all data)
GOF on F2
1.400
4.343
2.642
1.51 to 26.10
47 441/7984 (0.1251)
7984/0/496
R1 ) 0.0704, wR2 ) 0.1216
R1 ) 0.0952, wR2 ) 0.1302
1.164
1.50 to 30.04
42 887/11 399 (0.0515)
11 399/0/496
R1 ) 0.0302, wR2 ) 0.0641
R1 ) 0.0521, wR2 ) 0.0743
1.092
2.03 to 26.96
9272/4636 (0.0386)
4636/0/250
R1 ) 0.0845, wR2 ) 0.2790
R1 ) 0.0931, wR2 ) 0.2841
1.109
)
largest diff peak and hole/e Å3
0.624 and -0.869
1.046 and -1.000
5.969 and -1.571
0.79 g; 7: 1.04 g; 8: 1.31 g) were dissolved in dichloromethane
(30 mL), and 1 equiv of (cod)PdCl2 (0.28 g, 1 mmol) was added
at room temperature. The dark red-brown suspensions were stirred
for 4 h at room temperature, and the solvent was subsequently
removed under vacuum. The resulting solids were treated with
pentane to remove residual cyclooctadiene and recrystallized from
dichloromethane/chloroform (1:2) to afford complexes 9-11 as air-
stable, dark red crystals (9) or glassy solids (10, 11). Yields: 93%,
0.90 g (9); 80%, 0.98 g (10); 78%, 1.16 g (11).
brown suspension was stirred for 3 days at room temperature and
filtered subsequently to remove the generated KCl. The solvent
was then removed under vacuum and the residue washed a couple
of times with cold chloroform to afford 12 as an air-stable, bright
red solid. Yield: 0.90 g (85%). Single crystals, suitable for X-ray
crystallography were obtained from a concentrated solution (CH2-
Cl2/CHCl3, 1:2) at room temperature. 31P{1H} NMR (162.0 MHz,
CD2Cl2): δ -11.2 (1J(P,Pt) ) 3768 Hz) ppm. 1H NMR (400 MHz,
CD2Cl2): δ 7.86 (ddm,3J(H,P) ) 13.4 Hz,3J(H,H) ) 8.2 Hz, 8H,
o-Ph), 7.54 (t m, 3J(H,H) ) 7.5 Hz, 4H, p-Ph), 7.45 (t m, 3J(H,H)
) 7.4 Hz, 8H, m-Ph), 4.25 (pt, 2/4J(H,H) ) 2.0 Hz, 4H, C5H4),
4.18 (pt, 2/4J(H,H) ) 2.0 Hz, 4H, C5H4), 4.05 (s, 10H, Cp) ppm.
13C{1H} NMR (100.0 MHz, CDCl3): δ 134.0 (pt, J(C,P) ) 6.9
Hz, o-Ph), 131.7 (s, p-Ph), 129.8 (dd,1J(C,P) ) 78.5 Hz,3J(C,P) )
2.2 Hz, ipso-Ph), 128.8 (pt, J(C,P) ) 6.5 Hz, m-Ph), 113.6 (m,
J(C,P) ) 10.0 Hz, CtC), 75.3 (dd, J(C,P) ) 127.5 Hz, J(C,P) )
4.8 Hz, CtC), 72.6 (s, Cp2/5), 70.5 (s, Cp3/4), 70.4 (s, Cp), 61.3 (s,
Cp1). Anal. Calcd for C48H38Cl2Fe2P2Pt: C 54.68; H 3.63. Found:
C 54.06; H 3.67. CV: Epc ) 0.58 V; Epa) 0.70 V.
Complex 9. 31P{1H} NMR (80.9 MHz, CDCl3): δ 5.0 ppm. 1H
NMR (400 MHz, CD2Cl2): δ 7.89 (dd,3J(H,P) ) 13.4 Hz,3J(H,H)
) 7.4 Hz, 8H, o-Ph), 7.54 (t br.,3J(H,H) ) 7.4 Hz, 4H, p-Ph), 7.45
(t br.,3J(H,H) ) 7.7 Hz, 8H, m-Ph), 4.27 (pt, 2/4J(H,H) ) 2.0 Hz,
4H, C5H4), 4.20 (pt, 2/4J(H,H) ) 2.0 Hz, 4H, C5H4), 4.06 (s, 10H,
Cp) ppm. 13C{1H} NMR (100.0 MHz, CD2Cl2): δ 134.0 (pt, J(C,P)
) 6.2 Hz, o-Ph), 131.7 (s, p-Ph), 130.3 (dd,1J(C,P) ) 66.8
Hz,3J(C,P) ) 2.6 Hz, ipso-Ph), 128.8 (pt, J(C,P) ) 5.9 Hz, m-Ph),
113.6 (m, J(C,P) ) 9.2 Hz, CtC), 76.2 (dd, J(C,P) ) 111.9 Hz,
J(C,P) ) 8.1 Hz, CtC), 72.6 (s, Cp2/5), 70.6 (s, Cp3/4), 70.5 (s,
Cp), 61.3 (s, Cp1). Anal. Calcd for C48H38Cl2Fe2P2Pd: C 59.69; H
3.97. Found: C 59.85; H 4.06. CV: Epc ) 0.57 V; Epa) 0.69 V.
Complex 10. 31P{1H} NMR (162.0 MHz, CD2Cl2): δ -24.9
Preparation of Complex 13. To a solution of complex 9 (0.49
g, 0.5 mmol) in acetone (20 mL) was added KI (0.17 g, 1 mmol)
at room temperature. The reaction mixture was then stirred for 30
min and the solvent removed under vacuum subsequently. The
residue was taken up in dichloromethane and filtered, and the filtrate
was evaporated to dryness. Recrystallization from chloroform
afforded 13 as air-stable dark orange-red single crystals. Yield: 1.02
1
ppm. H NMR (400 MHz, CD2Cl2): δ 8.21 (dd,3J(H,P) ) 15.9
Hz,3J(H,H) ) 8.0 Hz, 4H, o-Ph), 7.57 (m, 6H, p,m-Ph), 4.27 (d pt,
J(H,P) ) 2.5 Hz, 2/4J(H,H) ) 1.8 Hz, 8H, C5H4), 4.31 (pt, 2/4J(H,H)
) 1.8 Hz, 8H, C5H4), 4.22 (s, 20H, Cp) ppm. 13C{1H} NMR (100.0
MHz, CD2Cl2): δ 133.2 (pt, J(C,P) ) 7.8 Hz, o-Ph), 132.1 (s, p-Ph),
130.0 (dd,1J(C,P) ) 80.6 Hz,3J(C,P) ) 2.4 Hz, ipso-Ph), 129.1
(pt, J(C,P) ) 7.4 Hz, m-Ph), 111.6 (m, J(C,P) ) 11.7 Hz, CtC),
74.4 (dd, J(C,P) ) 133.5 Hz, J(C,P) ) 3.8 Hz, CtC), 72.8 (d,
J(C,P) ) 4.3 Hz, Cp2/5), 70.8 (s, Cp), 70.8 (d, J(C,P) ) 3.0 Hz,
Cp3/4), 61.4 (pt, 3/5J(C,P) ) 1.3 Hz, Cp1). Anal. Calcd for C60H64-
Cl2Fe4P2Pd: C 58.60; H 3.77. Found: C 51.69; H 3.57. CV: Epc
) 0.55 V; Epa) 0.68 V.
1
g (89%). 31P{1H} NMR (80.9 MHz, CDCl3): δ -17.8 ppm. H
NMR (400 MHz, CDCl3): δ 7.73 (m, 8H, o-Ph), 7.39 (m br, 4H,
p-Ph), 7.35 (m br, 8H, m-Ph), 4.55 (pt, 2/4J(H,H) ) 1.8 Hz, 4H,
C5H4), 4.21 (s, 12H, C5H4/Cp) ppm. 13C{1H} NMR (100.0 MHz,
CDCl3): δ 133.5 (pt, J(C,P) ) 6.2 Hz, o-Ph), 129.6 (s, p-Ph), 127.5
(pt, J(C,P) ) 6.6 Hz, ipso-Ph), 127.0 (pt, J(C,P) ) 5.8 Hz, m-Ph),
112.1 (pt, J(C,P) ) 8.7 Hz, CtC), 79.1 (pt, J(C,P) ) 54.2 Hz,
CtC), 71.4 (s, Cp2/5), 69.3 (s, Cp), 68.7 (s, Cp3/4), 61.4 (s, Cp1).
Anal. Calcd for C48H38I2Fe2P2Pd: C 50.19; H 3.33. Found: C 49.94;
H 3.37. CV: Epc ) 0.54 V; Epa) 0.66 V.
X-ray Structure Determination. For complexes 9 and 12, data
were collected on a Bruker SMART D8 goniometer with an APEX
CCD detector at 120 K (9) or 200 K (12), respectively, and for
complex 13 on an Enraf-Nonius CAD4 at 228 K, using Mo KR
radiation (λ ) 0.71073 Å, graphite monochromator). The SAD-
ABS28 method of absorption correction was applied in all cases.
Complex 11. 31P{1H} NMR (162.0 MHz, CDCl3): δ -57.8 ppm.
1H NMR (400 MHz, CD2Cl2): δ 4.55 (pt, 2/4J(H,H) ) 1.6 Hz,
12H, C5H4), 4.23 (br, 42H, C5H4/Cp) ppm. 13C{1H} NMR (100.0
MHz, CD2Cl2): δ 109.1 (m, J(C,P) ) 15.6 Hz, CtC), 72.4 (dd,
J(C,P) ) 154.8 Hz, J(C,P) ) 2.6 Hz, CtC), 72.6 (s, Cp2/5), 70.7
(s, Cp), 70.2 (s, Cp3/4), 61.1 (pt, 3/5J(C,P) ) 1.7 Hz, Cp1). Anal.
Calcd for C72H54Cl2Fe6P2Pd: C 57.90; H 3.64. Found: C 49.46;
H 3.51. CV: Epc ) 0.63 V; Epa) 0.72 V.
Preparation of 12. Two equivalents of ligand 6 (0.79 g, 2 mmol)
were dissolved in dichloromethane (30 mL), and 1 equiv of K2-
PtCl4 (0.42 g, 1 mmol) was added at room temperature. The red-
(28) Sheldrick, G. M. SADABS, Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Germany, 1996.

5664 Organometallics, Vol. 25, No. 23, 2006
Baumgartner et al.
The structures were solved by direct methods (SHELXTL)29 and
refined on F2 by full-matrix least-squares techniques. All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
placed geometrically and refined using a riding model. Crystal data
and details of data collection and structure refinements are given
in Table 2.
Forschungsgemeinschaft (DFG) is gratefully acknowledged. We
thank Prof. Dr. U. Englert for the X-ray data collection and
helpful discussions, Prof. Dr. U. Ko¨lle for his assistance with
the cyclic voltammetry, and D. Mu¨ller and Y. Dienes for their
assistance with the TGA measurements. T.B. thanks the
University of Calgary for start-up funding.
Acknowledgment. The authors thank Prof. Dr. Jun Okuda
for his generous support of this work. Financial support of the
Fonds der Chemischen Industrie (FCI), BMBF, and the Deutsche
Supporting Information Available: Complete tables of crystal
data collections and unit-cell parameters, positional parameters, and
bond distances and angles for 9, 12, and 13. This material is
available free of charge via the Internet at http://pubs.acs.org.
(29) Sheldrick, G. M. SHELXTL, Version 5.1; Bruker AXS Inc.:
Madison, WI, 1998.
OM0606892