Bis(cyclopentadienyl)phenylphosphine as ligand precursor for assembling heteropolymetal complexes

Article abstract of DOI:10.1021/om701221p

The dilithium salt of bis(cyclopentadienyl)phenylphosphine has been used as a multidentate ligand to generate unprecedented heteropolymetal arrays via the bimetal precursors [MI(CO)₃]₂[(η⁵-C ₅H₄)P(Ph)(η⁵-C₅H₄)] (9, M = Mo; 10, M = W). The trimetal complexes MI(CO)₃[(η ⁵-C₅H₄)P(Ph)(η⁵-C ₅H₄)](CO)₃-MPd(PPh₃)I (14, M = Mo; 15, M = W), obtained by reaction of 9 and 10 with Pd(PPh₃) ₄, respectively, have been found to lose PPh₃ converting to the hexametal derivatives {MI(CO)₃[(η⁵-C ₅H₄)P(Ph)(η⁵-C₅H ₄)](CO)₃MPd}(μ-I₂){PdM(CO) ₃[(η⁵-C₅H₄)P(Ph) (η⁵-C₅H₄)](CO)₃MI} (18, M = Mo; 19, M = W). Compound 18 also has been prepared by reaction of 9 with a PPh ₃-free zerovalent palladium species such as Pd₂(dba) ₃; treatment of 18 with PPh₃ regenerated the trimetal complex 14. The pentametal complex {MoI(CO)₃[(η⁵- C₅H₄)P(Ph)(η⁵-C₅H ₄)](CO)₃Mo}Pd{Mo(CO)₃[(η⁵-C ₅H₄)P(Ph)(η⁵-C₅H ₄)](CO)₃MoI}(22), containing a linear Mo-Pd-Mo array, has been spectroscopically observed by reacting 18 with 1,2-bis(diphenylphosphino) ethane.

Full text of DOI:10.1021/om701221p

Organometallics 2008, 27, 1617–1625
1617
Bis(cyclopentadienyl)phenylphosphine as Ligand Precursor for
Assembling Heteropolymetal Complexes
Antonella Ricci,*,§ Francesco Angelucci,‡,# Marco Chiarini,§ Claudio Lo Sterzo,§,‡
Dante Masi,† Giuliano Giambastiani,† and Claudio Bianchini†
Dipartimento di Scienze degli Alimenti, Facoltà di Agraria, UniVersità degli Studi di Teramo, Via Carlo R.
Lerici 1, 64023 Mosciano Sant’Angelo (Teramo), Italy, Istituto CNR di Metodologie Chimiche (IMC-CNR),
Sezione Meccanismi di Reazione, Dipartimento di Chimica, Box 34-Roma 62, UniVersità degli Studi di
Roma “Sapienza”, P.le Aldo Moro 5, 00185 Roma, Italy, and Istituto di Chimica dei Composti
Organometallici (ICCOM-CNR), Via Madonna del Piano 10, Sesto Fiorentino, 50019 Firenze, Italy
ReceiVed December 6, 2007
The dilithium salt of bis(cyclopentadienyl)phenylphosphine has been used as a multidentate ligand to
generate unprecedented heteropolymetal arrays via the bimetal precursors [MI(CO)3]2[(η5-C5H4)P(Ph)(η5-
C5H4)] (9, M ) Mo; 10, M ) W). The trimetal complexes MI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3-
MPd(PPh3)I (14, M ) Mo; 15, M ) W), obtained by reaction of 9 and 10 with Pd(PPh3)4, respectively,
have been found to lose PPh3 converting to the hexametal derivatives {MI(CO)3[(η5-C5H4)P(Ph)(η5-
C5H4)](CO)3MPd}(µ-I2){PdM(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MI} (18, M ) Mo; 19, M ) W).
Compound 18 also has been prepared by reaction of 9 with a PPh3-free zerovalent palladium species
such as Pd2(dba)3; treatment of 18 with PPh3 regenerated the trimetal complex 14. The pentametal complex
{MoI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3Mo}Pd{Mo(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoI} (22),
containing a linear Mo-Pd-Mo array, has been spectroscopically observed by reacting 18 with 1,2-
bis(diphenylphosphino)ethane.
Chart 1
Introduction
As part of our studies of Pd-assisted metal–carbon and
metal-metal bond-forming reactions,1,2 we have recently com-
municated the synthesis and characterization of trimetal com-
plexes containing linear M-Pd-M arrays (M ) Mo, W)2d
(Chart 1).
Since early late heteropolymetal complexes have relevance
to catalysis3 as well as to the construction of metal-containing
oligomers and polymers,4 a project has been initiated aimed at
rationalizing the design of heteropolymetal compounds contain-
ing M-Pd and M-Pd-M moieties where M is an early
transition metal. To this purpose, our attention was immediately
attracted by bis(cyclopentadienyl)phenylphosphine (bcp) that,
upon simple lithiation, affords a tridentate ligand (Li2bcp) with
a great potential to assemble homo- and heteropolymetal
structures.5–9 Previous examples of metal complexes stabilized
by bcp2- are shown in Chart 2. These include structures of type
* To whom correspondence should be addressed. E-mail: aricci@unite.it.
§ Università degli Studi di Teramo, Italy.
‡ IMC-CNR, Roma, Italy.
# Present address: Dipartimento di Scienze Biochimiche “A. Rossi
Fanelli”, Università degli Studi di Roma “Sapienza”, P.le Aldo Moro 5,
00185 Roma, Italy.
(5) For different use of cyclopentadienyls and other aromatic units
containg either alkylene or alkenylene spacers and a variety of heteroatom-
centered groups based on B, Ge, Si, Sn, P, As, and S, see also: (a) Lee, I.;
Dahan, F.; Maisonnat, A.; Poilblanc, R. Organometallics 1994, 13, 2743.
(b) Viotte, M.; Gautheron, B.; Kubicki, M.; Mugnier, Y.; Parish, R. V.
Inorg. Chem. 1995, 34, 3465. (c) Curnow, O. J.; Huttner, G.; Smail, S. J.;
Turnbull, M. M. J. Organomet. Chem. 1996, 524, 267. (d) Iretskii, A.;
Jennings, M. C.; Poilblanc, R. Inorg. Chem. 1996, 35, 1266. (e) Schaverien,
C. J.; Ernst, R.; Terlouw, W.; Schut, P.; Sudneijer, O.; Budzelaar, P. H. M.
J. Mol. Catal. A: Chem. 1998, 128, 245. (f) Shin, J. H.; Hascall, T.; Parkin,
G. Organometallics 1999, 18, 6. (g) Shapiro, P. Coord. Chem. ReV. 2002,
231, 67. (h) Zachmanoglou, C. E.; Docrat, A.; Bridgewater, B. M.; Parkin,
G.; Brandow, C. G.; Bercaw, J. E.; Jardine, C. N.; Lyall, M.; Green, J. C.;
Keister, J. B. J. Am. Chem. Soc. 2002, 124, 9525. (i) Erker, G.; Kehr, G.;
Fröhlich, R. J. Organomet. Chem. 2004, 689, 1402.
† ICCOM-CNR, Florence, Italy.
(1) (a) Lo Sterzo, C. Synlett 1999, 1704. (b) Antonelli, E.; Rosi, P.; Lo
Sterzo, C.; Viola, E. J. Organomet. Chem. 1999, 578, 210. (c) Altamura,
P.; Giardina, G.; Lo Sterzo, C.; Russo, M. V. Organometallics 2001, 20,
4360. (d) La Groia, A.; Ricci, A.; Bassetti, M.; Masi, D.; Bianchini, C.; Lo
Sterzo, C. J. Organomet. Chem. 2003, 683, 406.
(2) (a) Tollis, S.; Narducci, V.; Cianfriglia, P.; Lo Sterzo, C.; Viola, E.
Organometallics 1998, 17, 2388. (b) Ricci, A.; Angelucci, F.; Bassetti, M.;
Lo Sterzo, C. J. Am. Chem. Soc. 2002, 124, 1060. (c) Ricci, A.; Lo Sterzo,
C. J. Organomet. Chem. 2002, 653, 177. (d) Angelucci, F.; Ricci, A.; Lo
Sterzo, C.; Masi, D.; Bianchini, C.; Bocelli, G. Organometallics 2002, 21,
3001. (e) Angelucci, F.; Ricci, A.; Masi, D.; Bianchini, C.; Lo Sterzo, C.
Organometallics 2004, 23, 4105.
(6) (a) Köpf, H.; Khal, W. J. Organomet. Chem. 1974, 64, C37. (b)
Köpf, H.; Klouras, N. Monatsh. Chem. 1983, 114, 243.
(3) (a) Bianchini, C.; Meli, A. Acc. Chem. Res. 1998, 31, 109. (b)
Bianchini, C.; Meli, A.; Vizza, F. Eur. J. Inorg. Chem. 2001, 43, 43. (c)
Wheatley, N.; Kalck, P. Chem. ReV. 1999, 99, 3379. (d) Makoto, M.; Shin-
ichi, K.; Norio, K.; Terunori, F. Curr. Trends Polym. Sci. 2001, 6, 85.
(4) (a) Fujimura, T.; Seino, H.; Hidai, M.; Mizobe, Y. J. Organomet.
Chem. 2004, 689, 738 and references cited therein. (b) Zhang, K.; Chen,
Z.; Zou, Y.; Yang, C.; Qin, J.; Cao, Y. Organometallics 2007, 26, 3699.
(7) Troitskaya, L. L.; Ovseenko, S. T.; Krylova, A. I.; Sokolov, V. I.
Russ. Chem. Bull. 2001, 50 (11), 2212.
(8) (a) Mathey, F.; Lampin, J. P. J. Organomet. Chem. 1977, 128, 297.
(b) Herberhold, M.; Biersack, M. J. Organomet. Chem. 1990, 381, 379. (c)
Imamura, Y.; Kubo, K.; Mizuta, T.; Miyoshi, K. Organometallics 2006,
25, 2301.
10.1021/om701221p CCC: $40.75
2008 American Chemical Society
Publication on Web 03/13/2008

1618 Organometallics, Vol. 27, No. 7, 2008
Ricci et al.
previously reported by Lampin.6b,11 The complete conversion
of dichlorophenylphosphine 2 into 3 was achieved by using a
4-fold excess of 112 that was later eliminated from the reaction
mixture by using Et2O as reaction solvent. In this solvent, both
1 and the byproduct TlCl are scarcely soluble, in fact, so that
they could be separated from 3 by simple filtration. After solvent
evaporation, 3 was used in the next reaction step with no need
of further purification. Crude 3 was actually dissolved in THF
to give a solution that, upon treatment with 2 equiv of BuLi at
0 °C, contained exclusively the bis(cyclopentadienyl) dianion
4. To the solution of this dilithium salt was added with stirring
M(CH3CN)3(CO)3 (M ) Mo, 5; M ) W, 6) and the resulting
reaction mixture was first stirred overnight at room temperature,
then refluxed for 2 h. Finally, the addition of stoichiometric
1,2-diiodoethane led to the formation of 9 and 10, likely through
intermediates 7 and 8, respectively. All our attempts to isolate
9 and 10 in the pure form by chromatographic techniques were
unsuccessful due to extensive on-column decomposition.13
However, when the crude mixture containing 9 or 10 was filtered
through a Celite pad and the solvent was evaporated to small
volume, then the simple addition of n-pentane caused the
precipitation of pure 9 and 10 as dark red microcrystals, which
were isolated in 63% and 68% yield, respectively.
Chart 2
Chart 3
Compounds 9 and 10 have been unambiguously characterized
by IR, MS, and multinuclear NMR spectroscopy. The solid-
state molecular structure of 9 has been determined by an X-ray
diffraction analysis of a single crystal obtained by liquid
diffusion recrystallization of the crude product with dichlo-
romethane/n-pentane (Figure 1). Crystal and structural refine-
ment data for 9 are listed in Table 1.
In the molecular structure of 9, the two Mo(CO)3I groups
are pseudo-trans to each other, very likely for steric reasons, so
as to give a locked system with no possibility to exchange their
position also in solution (vide infra). For this reason, 9 should
exist as an atropoisomeric mixture of the two isomers 9a and
9b (Figure 1). The crystal studied by X-ray diffraction analysis
was stereoisomer 9a, featured by a torsion angle of 54.3°
between the planes of the two Cp rings. Because of the rigid
transoid configuration of the two Mo(CO)3I units, one Mo(CO)3I
group is facing the phosphorus lone pair in one side of the ligand
plane, while the second Mo(CO)3I fragment is facing the phenyl
unit on the opposite face.
II,6 where both Cp units are bound to the same metal center
such as in “molecular tweezers”, structures of type III,7 where
each Cp unit is part of an independent ferrocenyl fragment,
structures of type IV, where each Cp unit holds in a half-
sandwich fashion two different metal centers,8 or structures of
type V, where bcp2- uses all its donor atoms to form a trimetal
species.9
In this paper, we describe our approach to the design of
unprecedented hexametallic structures of type VI (Chart 3),
where two halo-bridged palladium centers are bonded to an early
transition metal from a half-sandwich metallocene. The molec-
ular structure is completed by two half-metallocenes exhibiting
no bonding interaction with the Pd centers.
(11) Mathey, F.; Lampin, J. P. Tetrahedron 1975, 31, 2685.
(12) The reaction of 1 and 2 in the 2/1 stoichiometric ratio always affords
the monosubstituted derivative Cl-P(Ph)-(C5H4) (Butler, I. R.; Cullen,
W. R.; Rettig, S. J. Organometallics 1987, 6, 872) as the main product.
(13) Although 31P NMR analysis of a sample of crude reaction mixture
clearly indicated the complete and exclusive formation of 9 and 10, the
subsequent chromatographic purification always produced three different
products. The first eluted band (deep red) gave, after solvent evaporation,
a small amount of a dark solid whose characterization is still under
investigation. The second eluted fraction (red) was identified as the expected
product, and the third (purple) fraction after evaporation of the solvent gave
a red-purple solid that was identified by NMR spectroscopy and mass
spectroscopy as the dimeric complex (Shin, J. H.; Parkin, G. Inorg. Chem.
Commun. 1999, 2, 428) represented in the following structure.
Spectroscopic evidence for the formation of polymetal
structures of type VII (Chart 3), containing linear M-Pd-M
arrays with metal-metal bond interactions, is also reported. Due
to the half-sandwich coordination of the early transition metals
and the vacant site at Pd,10 structures of the latter type are
promising building blocks for creating new heteropolymetal
assemblies.
Results and Discussion
Preparation of [MI(CO)3]2[(η5-C5H4)P(Ph)(η5-C5H4)] (M
) Mo, 9; M ) W, 10). The homobimetal complexes 9 and 10
were prepared as described in Scheme 1. While CpTl (1) was
purchased from a commercial supplier, bis(cyclopentadienyl)phe-
nylphosphine 3 was synthesized by modifying a procedure
(9) Anderson, G. K.; Lin, M. Inorg. Chim. Acta 1988, 142, 7.
(10) (a) Braunschweig, H.; Breitling, F. M.; Burschka, C.; Seeler, F. J.
Organomet. Chem. 2006, 691, 702. (b) Morandini, F.; Munari, I.; Panese,
M.; Ravazzolo, A.; Consiglio, G. Inorg. Chim. Acta 2005, 358, 2697.

Bis(cyclopentadienyl)phenylphosphine
Organometallics, Vol. 27, No. 7, 2008 1619
Scheme 1
Table 1. Crystal Data and Structure Refinement Details for 9
The rigid transoid disposition of the M(CO)3I moieties (M
) Mo (9), W (10)), with respect to the bis(cyclopentadi-
enyl)phenylphosphine ligand, is likely maintained also in
empirical formula
fw
C22H13I2Mo2O6P5
849.97
temp [K]
wavelenght [Å]
cryst system, space group
a [Å]
293(2)
0.71069
monoclinic
11.859(3)
1
solution as shown by the H and 13C NMR spectra displaying
four distinct resonances for the Cp protons and five distinct
resonances for the Cp carbons, respectively.14
b [Å]
18.165(5)
Selected bond distances and angles are given in Table 2 (see
the Supporting Information for full listings) The Cp1-P-Ph
and Cp2-P-Ph angles measure 98.0° and 104.6°, respectively,
which reflects the distortion of the system caused by the opposite
orientation of the Mo(CO)3I units. In this way, the Cp2 ring
can adopt a spatial conformation that minimizes the contact
between the phenyl and the Mo(CO)3I fragment forcing, on the
other hand, an ortho hydrogen atom of the phenyl group to
c [Å]
12.637(4)
R [deg]
90
111.89(2)
90
2526.0(12)
4, 2.235
3.535
ꢀ [deg]
γ [deg]
V [Å3]
Z, Dc [g cm-3
]
abs coeff [mm-1
F(000)
]
1592
cryst size [mm3]
0.375 × 0.125 × 0.075
2.01–24.98
-14 e h e )13
0 e k e 21
0 e l e 15
4640/4429
Θ range for data collection [deg]
limiting indices
no. of reflns collected/unique
GOF on F2
1.020
no. of data/restraints/parameters
final R indices [I > 2σ(I)]
R indices (all data)
4429/0/287
R1 ) 0.0315, wR2 ) 0.0675
R1 ) 0.0599, wR2 ) 0.0756
0.838 and -0.987
largest diff peak and hole [e Å-3
]
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 9
Mo(1)-I(1)
2.8406(9)
2.8308(9)
1.829(5)
1.840(5)
104.6(2)
98.07(19)
Mo(2)-I(2)
P(1)-C(10)
P(1)-C(15)
C(10)-P(1)-C(17)
C(17)-P(1)-C(15)
assume a position close to that of the C(1) atom of the Cp1 ring
(2.778 Å). Interestingly, one of the coordinated iodine atoms,
as already established in a similar compound,15 lies in close
proximity to the phosphorus atom, with no covalent bonding
interaction as shown by the interatomic distance (4.288 Å),
which exceeds the sum of the van der Waals radii.16
The bis(cyclopentadienyl)phenylphosphine ligand adopts the
1,1′-(η5:η5) binding mode, and the Mo centers have a four-
legged piano stool structure (square pyramidal). In 9, the C-P
(14) Ebels, J.; Pietschnig, R.; Kotila, S.; Dombrowski, A.; Niecke, E.;
Nieger, M.; Schiffner, H. M. Eur. J. Inorg. Chem. 1998, 331.
(15) Brownie, J. H.; Baird, M. C.; Schmider, H. Organometallics 2007,
26, 1433.
Figure 1. Atropoisomers 9a and 9b and ORTEP drawings of
compound 9.
(16) Emsley, J. The Elements, 2nd ed.; Clarendon Press: Oxford, U.K.,
1991.

1620 Organometallics, Vol. 27, No. 7, 2008
Ricci et al.
latter two compounds, even after repeated chromatographic
purifications, led us to consider the occurrence of a transforma-
tion of 14 under chromatographic conditions. This hypothesis
was confirmed by the fact that the addition of an excess of PPh3
to the mixture resulted in the disappearance of the peaks at 37.7
and 37.3 ppm and the selective formation of 14 (Figure 3, trace
b). Apparently, under chromatographic conditions, 14 releases
PPh3 to give a species that regenerates 14 upon PPh3 uptake. It
has been ascertained (vide infra) that this new species is the
µ-(I)2dimer{MoI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoPd}(µ-
I2){PdMo(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoI} (18), which
exists as two diastereoisomers (Scheme 2).
It is noteworthy that the mechanism of formation of 18 as well
as its structure have a close precedent in the conversion of com-
pound 20 into 21, recently reported by some of us (Scheme 3).2b,e
Further conclusive evidence of the formation of the dimer
18 as well as of the reversible release/uptake of PPh3 by 14/
18 was provided by an in situ NMR experiment (Scheme 4).
Complex 9 was dissolved in CDCl3 and a 31P{1H} NMR
spectrum (singlet at -30.1 ppm) was acquired at room
temperature (Figure 4 trace a). To this solution was added 1
equiv of Pd2(dba)3, which caused the immediate and complete
conversion of 9 into 18 (Figure 4, trace b). Finally, the
addition of 1 equiv of PPh3 regenerated the characteristic
AB system of 14 together with the singlet at 13.5 ppm due
to 13.
Figure 2. In situ 31P{1H} NMR study in CDCl3 of the reaction
between 9 and Pd(PPh3)4.
distances P(1)-C(10) and P(1)-C(15), respectively, and the
CdO bond lengths (from (1.118(6) Å to (1.140(7) Å) are within
the expected range.17 The Mo-Cp ring carbon distances range
from 2.270(5) to 2.381(5) Å, consistent with Mo-Cp ring
carbon distances expected for other compounds.15 The Mo-I
distances, Mo(1)-I(1) 2.8406(9) Å and Mo(2)-I(2) 2.8308(9)
Å, also fall in the normal range of distances.17
As previously anticipated, the dimer 18 is actually a mixture
of two diastereomers, rac dl-18a and meso-18b, due to the
stereogenic nature of the two phosphorus atoms (Chart 4), which
accounts for the two singlets observed in the 31P{1H} NMR
spectrum.23
Reactions of 9 and 10 with Pd(PPh3)4 and Pd2(dba)3. The
reactions of 9 and 10 with Pd(PPh3)4 were preliminarily carried
out in NMR tubes and were followed by 31P{1H} NMR
spectroscopy.
In trace a of Figure 2 is reported the spectrum of 9 in CDCl3
(singlet at -30.1 ppm). Upon addition of 2 equiv of Pd(PPh3)4,
all 9 disappeared with formation of three products: free PPh3,
the square-planar trans-complex Pd(I)2(PPh3)218,19 (13) at 13.5
ppm, and a major compound featured by an AB spin system
centered at 21.5 ppm with JPP ) 491 Hz (simulated value),20
hence attributable to the trans phosphorus atoms.21
The same sequence of reactions and products was obtained
with the tungsten precursor 10.
As regards the mechanism of formation of the square-planar
diiodide byproduct 13, invariably obtained in 15–20% yield from
9 or 10,24 no clear-cut explanation can be given at this stage.
The most straightforward interpretation is to think of 13 as a
thermodynamically stable species resulting from a metathesis
reaction between Pd(PPh3)4 and the M-I moieties in 9 or 10.
In this respect, it is likely that the size and steric properties of
PPh3 may play a crucial role in determining both the transoid
structure of 14 and 15 as well as the formation of the trans
complex 13. Indeed, as shown by the reaction of 18 with 1,2-
diphenylphosphinoethane (dppe) (vide infra), a trimetal linear
array actually can be achieved with the bcp2- ligand.2d
Formation of Trimetal Linear M-Pd-M Arrays (M )
Mo, W). Compound 9 and Pd2(dba)3 were reacted in a Schlenck
flask containing degassed THF. After all 9 was converted to 18
(NMR evidence) (Scheme 5), the solvent was removed under
reduce pressure and the residue was redissolved in distilled
CH2Cl2. Addition of degassed n-pentane led to the immediate
Of the two possible structures that one may propose for the
product featured by the AB pattern (Scheme 2), the structure
containing a trimetallic Mo-Pd-Mo array (11) was initially
taken as the more likely just in view of the formation of
byproduct 13.22 This interpretation was later discarded on the
basis of experimental evidence pointing to MoI(CO)3[(η5-
C5H4)P(Ph)(η5-C5H4)](CO)3MoPd(PPh3)I (14) as the product
with the trans-P atoms (vide infra).
All our attempts to isolate 14 in the pure form from the
reaction mixture by chromatographic techniques were unsuc-
cessful, a unique fraction containing 14, 13, and a third complex
featured by two singlets at 37.7 and 37.3 ppm being invariably
obtained (Figure 3, trace a). The persistent appearance of the
(22) While observation of 13 was retained perfectly coherent with
formation of 11 (Scheme 2), its occurrence seemed to rule out formation
of 14. To force formation of 11 we used a twofold excess of Pd(PPh3)4.
One equivalent of Pd would be necessary to form the trimetallic array
Mo-Pd-Mo of 11, while the second equivalent was expected to extract
the two iodine groups from 9 with formation of 13. Moreover, it is worthy
of note to underline variations of oxidation numbers of metal centers taking
place in the transformations outlined in Scheme 2. Upon formation of 11
and 12 the molybdenum and tungsten atoms of 9 and 10 are reduced from
the initial oxidation numbers +2 into +1. Conversely, while the zerovalent
palladium entering into 9 and 10 to form 11 and 12 maintains its zero
oxidation number, the palladium forming trans-(PPh3)2PdI2 is oxidized from
Pd(0) to Pd(+2).
(17) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, 12, S1–S83.
(18) Amatore, C.; Jutand, A.; Mottier, L. Eur. J. Inorg. Chem. 1999,
1081.
(19) Formation of trans-(PPh3)2PdI2 (13) as side product in the oxidative
addition of zerovalent palladium has been reported: Weigelt, M.; Becher,
D.; Poetsch, E.; Bruhn, C.; Steinborn, D. Z. Anorg. Allg. Chem. 1999, 625,
1542.
(20) The coupling constant for compound 14 was obtained from 1H{31P}
spectra with the aid of computer simulation, using the gNMR program. See:
Budzelaar, P. H. M. gNMR, V4.0; Cherwell Scientific Publishing, Copyright
Iviry soft, 1995–1997.
(21) (a) Casey, C. P.; Bullock, R. M.; Nief, F. J. Am. Chem. Soc. 1983,
105, 7574. (b) Bianchini, C.; Masi, D.; Meli, A.; Peruzzini, M.; Zanobini,
F. J. Am. Chem. Soc. 1988, 110, 6411.
(23) Haltermann, R. L. Chem. ReV. 1992, 92, 965.
(24) Formation of compound 13 was also observed upon treatment of
dimer 18 with PPh3 in a 1:2 stoichiometric ratio.

Bis(cyclopentadienyl)phenylphosphine
Organometallics, Vol. 27, No. 7, 2008 1621
Scheme 2
Scheme 3
formation of a dark red precipitate that was isolated by filtration
and repeatedly washed with n-pentane to eliminate the dba
residue. Finally, a chromatographic purification of the crude
material over silica gel gave pure 18 as a diastereoisomer
mixture (18a-18b, Chart 4).
Taking into account our recent results obtained for compounds
having a dihalide bridged core identical with that shown by 18,2d
we focused our attention on the reactivity of the latter compound
in the presence of a chelating diphosphine. The reaction of 18
with a stoichiometric amount of dppe (Scheme 5) was monitored
by 31P{1H} NMR spectroscopy and showed the complete
disappearance of 18 and the simultaneous appearance of two
new signals at 18.7 and 17.7 ppm, respectively, attributed to
the pentametallic compound 22, flanked by a signal at 62.7 ppm
due to the square-planar complex cis-(dppe)PdI2 (23)25 (Scheme
5). The signals at 18.7 and 17.7 ppm respectively have been
attributed to the formation of the complex 22 according to
similar results previously observed by some of us.2d This
transformation is in line with the observed ability of triph-
enylphosphine to abstract PdI2 moiety from bcp2- complexes
(see Scheme 4).
Conclusions
Herein we have shown that the dilithium salt of bis(cyclo-
pentadienyl)phenylphosphine is a versatile µ3[(η5-Cp):(η5-Cp′):
(κ-P)] ligand capable of forming polymetal complexes with a
variety of structures and stereochemical conformations contain-
ing bimetal M-Pd and trimetal M-Pd-M arrays (M ) Mo,
W). The presence of chemically labile CO-ligands and
Figure 3. Trace a: 31P{1H} NMR spectrum in CDCl3 of the fraction
obtained by chromatographic purification of complex 14. Trace b:
31P{1H} NMR spectrum recorded after addition of an excess of
PPh3 to the above solution.
(25) (a) Ito, T.; Tsuchiya, H.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1977,
50 (5), 1319. (b) Oberhauser, W.; Bachmann, C.; Stampfl, T.; Haid, R.;
Brüggeller, P. Polyhedron 1997, 16, 2827.

1622 Organometallics, Vol. 27, No. 7, 2008
Ricci et al.
Scheme 4
before use. Chromatographic separations were performed with
70–230 mesh silica gel (Merck). All manipulations were carried
out with Schlenk-type equipment under an argon atmosphere on a
dual manifold/argon-vacuum system. Liquids have been transferred
by either syringe or cannula. THF and Et2O were distilled from
sodium-potassium alloy. Mo(CH3CN)3(CO)3 and W(CH3CN)3-
(CO)3 were prepared according to published procedures.26 (C5H5)Tl,
Cl2PPh, BuLi, ICH2CH2I, Pd2(dba)3, and PPh3 were purchased from
Aldrich and used as received. Otherwise stated, reagents and
solvents have been used as received from the commercial suppliers.
metal-iodide groups at the external Mo or W centers makes
the complexes described in this paper potential building blocks
to generate more elaborate structures such as multinuclear and/
or polymeric inorganic/organometallic materials.1
Experimental Section
General Considerations. Elemental analyses were performed
with a Carlo Erba Model 1106 elemental analyzer with an accepted
tolerance of (0.4 units on carbon (C), hydrogen (H), and nitrogen
(N). FT-IR spectra were recorded on a Nicolet 510 instrument in
the solvent subtraction mode, using a 0.1 mm CaF2 cell. 1H,
13C{1H}, and 31P{1H} NMR spectra were recorded on either a
Bruker AC300P spectrometer at 300, 75, and 121 MHz, respec-
tively, or Bruker Avance DRX-400 (400.13 and 100.62 MHz,
respectively) spectrometers equipped with variable-temperature
control units accurate to (0.1 °C. Chemical shifts are reported in
ppm (δ) relative to TMS or referenced to the chemical shifts of
residual solvent resonances (1H and 13C). The 31P{1H} NMR
chemical shifts are relative to 85% H3PO4. Mass spectra were
obtained on a Fisons Instruments VG-Platform Benchtop LC-MS
(positive ion electrospray, ESP+) spectrometer. Solvents, including
those used for NMR and chromatography, were thoroughly degassed
The following shows the legend for 13C NMR assignments:
[MoI(CO)3]2[(η5-C5H4)P(Ph)(η5-C5H4)] (9). A 250 mL Schlenk
flask was charged with 3.57 g (0.013 mol) of thallium cyclopen-
tadienide. After three cycles of vacuum/argon, 50 mL of Et2O was
added to the flask and the solution was treated with 0.6 mL (0.0043
mol) of dichlorophenylphosphine. The reaction mixture was stirred
for 1 h at room temperature. During this time, thallium chloride
precipitated as a white powder. The resulting suspension was
filtered, and the solid residue was washed three times with 20 mL
portions of Et2O. After removal of the solvent, the resulting pale
yellow oil was dissolved in 50 mL of THF. To this solution, cooled
to 0 °C in an ice bath, was added dropwise nBuLi (1.6 M solution
in hexanes) (5.6 mL, 0.009 mol). Afterward, 2.75 g (0.009 mol) of
Mo(CH3CN)3(CO)3 was added in one portion, causing an immediate
color change from yellow to deep green. After being stirred
overnight at room temperature, the reaction was completed by
refluxing for 2 h. The reaction mixture was allowed to cool to room
temperature and then was treated with 2.54 g (0.009 mol) of solid
1,2-diiodoethane. The resulting deep red solution was stirred for
1 h at room temperature then Celite (8 g) was added and the solvent
was removed under vacuum. The residue was filtered over a silica
gel pad with 1:1 n-hexane/dichloromethane as eluting solution. After
concentration to a small volume, a red solid was obtained by adding
n-pentane, which was filtered on a sintered-glass frit, washed with
n-pentane, and then dried under vacuum to give 2.31 g (63%) of
pure 9.
The recrystallization from CH2Cl2/n-pentane (by liquid diffusion)
at room temperature gave dark red brick crystals, suitable for single-
crystal X-ray diffraction.
1H NMR (CDCl3, ppm): δ 7.60–7.44 (m, 5H, Ph), 5.83 (m, 2H),
5.72 (m, 2H), 5.68 (m, 2H), 5.34 (m, 2H) (Cp). 31P NMR (CDCl3,
ppm): δ -30.1 (s). 13C NMR (CDCl3, ppm): δ 234.5, 219.2, 218.7
Figure 4. Trace a: 31P{1H} NMR spectrum of 9 in CDCl3, Trace
b: 31P{1H} NMR spectrum recorded after addition of 1 equiv
of Pd2(dba)3 to the above solution. Trace c: 31P{1H} NMR
spectrum recorded after subsequent addition of an equivalent
amount of PPh3.
(26) Tate, D. P.; Knipple, W. R.; Augl, J. M. Inorg. Chem. 1962, 1,
433.

Bis(cyclopentadienyl)phenylphosphine
Organometallics, Vol. 27, No. 7, 2008 1623
Chart 4
(CO), 134.2, 133.8, 133.6, 131.2, 129.4, 129.2 (Ph), 105.4 (d, J )
21.4 Hz, C1), 100.6 (d, J ) 15.9 Hz, C2 or C5), 98.9 (s, C3 or C4),
96.4 (d, J ) 2.4 Hz, C3 or C4), 96.1 (d, J ) 10.4 Hz, C2 or C5). IR
(CH2Cl2, cm-1): 2044 (s), 1971 (s) (νCO). MS (15V, ESP+) ) 766
(M + H - 3CO)+, 696 (M - I - CO)+. Anal. Calcd for
C22H13I2Mo2O6P (850.00): C, 31.09; H, 1.54. Found: C, 31.11; H,
1.60.
mixture was stirred for 15 min at room temperature. After the
solvent was removed under reduced pressure, the residue was
redissolved in dichloromethane and precipitated with n-pentane.
The red powder obtained was found to contain 14 together with
15–20% of trans-(PPh3)2PdI2 (13).27
1H NMR (CDCl3, ppm): δ 8.15 (m, 2H, o-Ph), 7.68–7.43 (m,
18H, Ph), 6.33 (m, 1H), 6.02 (m, 1H), 5.78 (m, 2H), 5.52 (m, 1H),
5.43 (m, 1H), 5.24 (m, 1H), 4.06 (m, 1H) (Cp). 31P NMR (CDCl3,
ppm): AB spin system centered at δ 21.5 (JPP ) 491 Hz). IR
(CH2Cl2, cm-1): 2048 (m), 1972 (s), 1898 (m), 1879 (m) (νCO).
MS (15V, ESP+): 1092 (M - I)+.
[WI(CO)3]2[(η5-C5H4)P(Ph)(η5-C5H4)] (10). Complex 10 was
prepared by employing a procedure analogous to that described
above for 9, except for using 2.53
g (0.0065 mol) of
W(CH3CN)3(CO)3, 3.18 g (0.011 mol) of CpTl, 0.4 mL (0.0029
mol) of dichlorophenylphosphine, 3.9 mL (0.0062 mol) of nBuLi
(1.6 M solution in hexanes), and 1.83 g (0.0065 mol) of 1,2-
diiodoethane. The crude mixture was adsorbed on Celite (5 g) and
filtered over a silica gel pad with a 1:1 n-hexane/dichloromethane
eluting solution. After concentration to a small volume, the addition
of n-pentane caused the precipitation of a dark red solid. The
precipitate was filtered on a sintered-glass frit, washed with
n-pentane, and dried under vacuum to give 2.08 g (68%) of pure
10.
Contamination of compound 14 by complex 13 prevented an
accurate elemental analysis (see trace c in Figure 4).
WI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3WPd(PPh3)I (15). A
100 mL Schlenk flask was charged with 0.50 g (0.49 mmol) of 10
and 0.57 g (0.49 mmol) of Pd(PPh3)4. After three cycles of vacuum/
argon, 30 mL of THF was added to the flask and the resulting dark
solution was stirred for 30 min at room temperature. The crude
mixture was adsorbed on Celite and purified by chromatography
on a silica column (50 × 5 cm). The last fraction eluted with
dichloromethane gave, after removal of the solvent, 15 as a
crystalline red solid, contaminated by a small amount (<1%) of
trans-(PPh3)2PdI2 (13).27
1H NMR (CDCl3, ppm): δ 7.58–7.45 (m, 5H, Ph), 5.97 (m, 2H),
5.85 (m, 2H), 5.73 (m, 2H), 5.41 (m, 2H) (Cp); 31P NMR (CDCl3,
ppm): δ -25.9 (s). 13C NMR (CDCl3, ppm): δ 222.2, 208.0, 207.4
(CO), 134.0 (d, J 23.3 Hz, o-Ph), 133.5 (d, J 9.0 Hz, ipso-Ph),
131.5 (s, p-Ph), 129.5 (d, J ) 9.0 Hz, m-Ph), 102.7 (d, J ) 19.8
Hz, C1), 98.9 (d, J ) 14.4 Hz, C2 or C5), 98.2 (s, C3 or C4), 95.3
(s, C3 or C4), 94.1 (d, J ) 10.8 Hz, C2 or C5). IR (CH2Cl2, cm-1):
2038 (s), 1957 (s) (νCO). MS (15V, ESP+): 939 (M - I + K)+.
Anal. Calcd for C22H13I2O6PW2 (1025.82): C, 25.76; H, 1.28.
Found: C, 25.73; H, 1.31.
1H NMR (CDCl3, ppm): δ 8.15 (m, 2H, o-Ph), 7.72–7.36 (m,
18H, Ph), 6.27 (m, 1H), 5.96 (m, 1H), 5.91 (m, 2H), 5.52 (m, 1H),
5.40 (m, 2H), 4.16 (m, 1H) (Cp). 31P NMR (CDCl3, ppm): AB
(27) Isolation of analytically pure 14 was impaired by two factors: (i)
under chromatographic conditions 14 loses PPh3 generating 18, and (ii)
even by operating under a strict 1/1 stoichiometric ratio of PPh3 and 18,
the contamination by complex 13 is unavoidable. On the other hand,
detachment of PPh3 from the W analogue is more difficult, thus chromato-
graphic purification affording pure 15 is possible.
MoI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoPd(PPh3)I (14). A
100 mL Schlenk flask was charged with 0.50 g (0.26 mmol) of 18,
0.136 g (0.52 mmol) of PPh3, and 40 mL of THF. The reaction

1624 Organometallics, Vol. 27, No. 7, 2008
Ricci et al.
Scheme 5
spin system centered at δ 17.6 (JPP ) 487 Hz). 13C NMR (CDCl3,
ppm): δ 223.9, 220.5, 214.0, 212.6, 207.6, 207.2 (CO), 136.3–127.5
(Ph), 105.0, 102.7, 102.6 (d, J ) 19.7 Hz), 102.2 (d, J ) 19.7 Hz),
98.9, 92.3–90.0, 58.9 (d, J ) 28.7 Hz), 58.8 (d, J ) 28.7 Hz) (Cp).
IR (CH2Cl2, cm-1): 2040 (s), 1965 (s), 1890 (sh), 1869 (s). MS
(15V, ESP+): 1268 (M - I)+.
(Cp). 31P NMR (CDCl3, ppm): 37.7 (s), 37.3 (s). 13C NMR (CDCl3,
ppm): δ 231.7, 231.0, 218.5, 218.2, 217.6, 217.4 (CO), 148.9, 148.7,
142.2–141.8, 136.3–128.4 (Ph), 105.7, 105.1, 102.7, 102.6, 94.7–91.5,
68.0, 47.0 (d, J ) 16.2 Hz), 43.3 (d, J ) 14.4 Hz) (Cp). IR (CH2Cl2,
cm-1): 2050 (s), 1981 (s), 1903 (s) (νCO). MS (15V, ESP+): 883
(M - 4CO + K)+. Anal. Calcd for C44H26I2Mo4O12P2Pd (1552.62):
C, 34.04; H, 1.69. Found: C, 34.10; H, 1.76.
This preparation also gave complex 13 (ca. 1%) thus preventing
an accurate elemental analisys of 15 (31P{1H} NMR spectrum in
the Supporting Information shows contamination of 15 by 13).
It is worth noting that the first fractions eluted contained a
mixture of 15 together with the halobridged dimer 19. The latter
complex was not isolated, but the Mo analogue was isolated
and unambiguously identified (see below).
X-ray Data Collection and Refinement of [MoI(CO)3]2[(η5-
C5H4)P(Ph)(η5-C5H4)] (9). A parallelepiped crystal with dimension
0.375 × 0.125 × 0.075 mm3 was used for the data collection.
Experimental data were recorded at room temperature (20 °C) on
an Enraf-Nonius CAD4. A set of 25 carefully centered reflections
in the range 8.25° e θ g 10.45° was used for determining the
lattice constants. As a general procedure, the intensity of three
standard reflections was measured periodically every 200 reflections
for orientation and intensity control. This procedure did not reveal
decay of intensities. The data were corrected for Lorentz and
polarization effects. Atomic scattering factors were taken from AJC
Wilson28 with anomalous dispersion corrections taken from ref 29.
An empirical absorptions correction was applied via Ψ scan with
correction factors in the range 0.7669-0.5524. The computational
work was carried out by using the program SHELX97.30 Final
atomic coordinates of all atoms and structure factors are available
on request from the authors and are provided as Supporting
Information. The structure was solved by direct methods by using
the SIR97 program.31 The refinement was done by full-matrix least-
squares calculations, initially with isotropic thermal parameters then
with anisotropic thermal parameters for all the atoms. Hydrogen
31P NMR (CDCl3, ppm): δ 27.0 (s), 26.6 (s) (19), AB spin system
centered at δ 17.6 (JPP ) 487 Hz) (15).
{MoI(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoPd}(µ-
I2){PdMo(CO)3[(η5-C5H4)P(Ph)(η5-C5H4)](CO)3MoI} (18). A
100 mL Schlenk flask was charged with 0.70 g (0.82 mmol) of 9
and 0.38 g (0.41 mmol) of Pd2(dba)3. After three cycles of vacuum/
argon, 20 mL of THF was added to the flask and the resulting dark
solution was stirred for 15 min at room temperature. After the
solvent was removed under reduced pressure, the residue was
redissolved in a small amount of dichloromethane. Upon addition
of n-pentane a red-brown powder precipitated, which was collected
by filtration on a sintered-glass frit, washed repeatedly with
n-pentane to eliminate the residual dba ligand, and then chromato-
graphed on silica column (30 × 5 cm). Elution with a 3:7 mixture
of n-hexane/dichloromethane produced a little red band, which was
discarded. The elution was continued with dichloromethane to
obtain a dark red band, which was collected to give 0.43 g (55%)
of pure 18 as red-brown fine powder.
(28) Wilson. A. J.C. International Tables for X-Ray Crystallography;
Kluver Academic: Dordrecht, The Netherlands, The Netherlands, 1992; Vol.
C, p 500.
(29) Wilson. A. J. C. International Tables for X-Ray Crystallography;
Kluver Academic: Dordrecht, The Netherlands, 1992; Vol. C, p 219.
(30) Sheldrick, G. M. SHELX-97. Program for Structure Refinement,
Release 97-2; University of Göttingen: Göttingen, Germany, 1997.
1H NMR (CDCl3, ppm): δ 8.26 (m, 4H, o-Ph), 7.59–7.46 (m,
6H, m,p-Ph), 6.19 (m, 1H), 6.12 (m, 1H), 5.96 (m, 2H), 5.78 (m,
1H), 5.75 (m, 1H), 5.70 (m, 1H), 5.67 (m, 1H), 5.54 (m, 2H), 5.46
(m, 2H), 5.21 (m, 1H), 5.06 (m, 1H), 4.20 (m, 1H), 4.16 (m, 1H)

Bis(cyclopentadienyl)phenylphosphine
Organometallics, Vol. 27, No. 7, 2008 1625
were introduced at calculated positions. The phenyl ring was treated
as a rigid body with D6h symmetry, and the hydrogen atoms were
allowed to ride on the attached carbon atoms.
contamination of 15 by 13. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM701221P
Supporting Information Available: Full tables of crystal data,
atomic coordinates, thermal parameters, bond lengths and angles,
and a CIF file for 9 and 31P{1H} NMR spectrum showing
(31) (A) Altomare, M. C.; Burla, M.; Camalli, G.; Cascarano, C.;
Giacovazzo, A.; Guagliardi, G.; Polidori, R.; Spagna, J. Appl. Cryst. 1999,
32, 115–119.