Palladium complexes of a phosphorus ylide with two stabilizing groups: Synthesis, structure, and DFT study of the bonding modes

Article abstract of DOI:10.1021/ic060706f

The phosphorus ylide ligand [Ph₃P=C(CO₂Me)C(=NPh) CO₂Me] (L1) has been prepared and fully characterized by spectroscopic, crystallographic, and density functional theory (DFT) methods (B3LYP level). The reactivity of L1 toward several cationic Pd^II and Pt^II precursors, with two vacant coordination sites, has been studied. The reaction of [M(C∧X)(THF)₂]ClO₄ with L1 (1:1 molar ratio) gives [M(C∧X)(L1)]ClO₄ [M = Pd, C∧X = C₆H₄CH₂NMe₂ (1), S-C ₆H₄C(H)MeNMe₂ (2), CH₂-8-C ₉H₆N (3), C₆H₄-2-NC ₅H₄ (4), o-CH₂C₆H ₄P(o-tol)₂ (6), η³-C₃H ₅ (7); M = Pt, C∧X = o-CH₂C₆H ₄P(o-tol)₂ (5); M(C∧X) = Pd(C₆F ₅)(SC₄H₈) (8), PdCl₂ (9)]. In complexes 1-9, the ligand L1 bonds systematically to the metal center through the iminic N and the carbonyl O of the stabilizing CO₂Me group, as is evident from the NMR data and from the X-ray structure of 3. Ligand L1 can also be orthopalladated by reaction with Pd(OAc)₂ and LiCl, giving the dinuclear derivative [Pd(μ-Cl)(C₆H₄-2-PPh ₂=C(CO₂Me)C(CO₂Me)=NPh)]₂ (10). The X-ray crystal structure of 10 is also reported. In none of the prepared complexes 1-10 was the Cα atom found to be bonded to the metal center. DFT calculations and Bader analysis were performed on ylide L1 and complex 9 and its congeners in order to assess the preference of the six-membered N,O metallacycle over the four-membered C,N and five-membered C,O rings. The presence of two stabilizing groups at the ylidic C causes a reduction of its bonding capabilities. The increasing strength of the Pd-C, Pd-O, and Pd-N bonds along with other subtle effects are responsible for the relative stabilities of the different bonding modes.

Full text of DOI:10.1021/ic060706f

Inorg. Chem. 2006, 45, 6803−6815
Palladium Complexes of a Phosphorus Ylide with Two Stabilizing
Groups: Synthesis, Structure, and DFT Study of the Bonding Modes†
Larry R. Falvello,‡ Juan Carlos Gine´s,‡ Jorge J. Carbo´,§ Agust´ı Lledo´s,*,| Rafael Navarro,‡
Tatiana Soler, and Esteban P. Urriolabeitia*,‡
Departamento de Compuestos Organometa´licos, Instituto de Ciencia de Materiales de Arago´n,
UniVersidad de Zaragoza - CSIC, 50009 Zaragoza, Spain, Departament de Qu´ımica-F´ısica i
Inorga´nica, UniVersitat RoVira i Virgili, 43007 Tarragona, Spain, Departament de Qu´ımica,
Edifici Cn, UniVersitat Auto`noma de Barcelona, 08193 Bellaterra, Barcelona, Spain, and SerVicios
Te´cnicos de InVestigacio´n, Facultad de Ciencias Fase II, 03690 San Vicente de Raspeig,
Alicante, Spain
Received April 26, 2006
The phosphorus ylide ligand [Ph3PdC(CO2Me)C(dNPh)CO2Me] (L1) has been prepared and fully characterized
by spectroscopic, crystallographic, and density functional theory (DFT) methods (B3LYP level). The reactivity of L1
toward several cationic PdII and PtII precursors, with two vacant coordination sites, has been studied. The reaction
of [M(C
S-C6H4C(H)MeNMe2 (2), CH2-8-C9H6N (3), C6H4-2-NC5H4 (4), o-CH2C6H4P(o-tol)2 (6),
o-CH2C6H4P(o-tol)2 (5); M(C X) Pd(C6F5)(SC4H8) (8), PdCl2 (9)]. In complexes 1−
∧
X)(THF)2]ClO4 with L1 (1:1 molar ratio) gives [M(C
∧
X)(L1)]ClO4 [M
)
Pd, C
∧
X
)
C6H4CH2NMe2 (1),
3-C3H5 (7); M
Pt, C
9, the ligand L1 bonds
η
)
∧
X
)
∧
)
systematically to the metal center through the iminic N and the carbonyl O of the stabilizing CO2Me group, as is
evident from the NMR data and from the X-ray structure of 3. Ligand L1 can also be orthopalladated by reaction
with Pd(OAc)2 and LiCl, giving the dinuclear derivative [Pd(
µ
-Cl)(C6H4-2-PPh2dC(CO2Me)C(CO2Me)dNPh)]2 (10).
The X-ray crystal structure of 10 is also reported. In none of the prepared complexes 1−10 was the CR atom found
to be bonded to the metal center. DFT calculations and Bader analysis were performed on ylide L1 and complex
9 and its congeners in order to assess the preference of the six-membered N,O metallacycle over the four-
membered C,N and five-membered C,O rings. The presence of two stabilizing groups at the ylidic C causes a
reduction of its bonding capabilities. The increasing strength of the Pd−C, Pd−O, and Pd−N bonds along with
other subtle effects are responsible for the relative stabilities of the different bonding modes.
Introduction
cyano group), or even situations in which the same ylide
shows a combination of bonding modes.1 An interesting fact
is that, despite the presence of several potential donor atoms
on the same ylide, they always behave as ambidentate
ligands.1
We are interested in the bonding properties of polyfunc-
tional phosphorus ylides, and we have now focused our
attention on the doubly stabilized ylides. The presence of
functional groups containing donor atoms expands the
bonding abilities of the ylides. The introduction of an
additional stabilizing functional group can be achieved
through several simple synthetic procedures: acylation,2
reactivity toward alkynes or other unsaturated compounds,3
reactivity of iminophosphoranes with alkynes,4 retro-Wittig
reactions,5 and other less common processes.6 These types
of ylides have been the subject of intensive research from a
The chemistry of metal complexes with ylides is a subject
of present interest.1 The R-stabilized phosphorus ylides
[Ph3PdC(H)R] [R ) CN, C(O)R′; R′ ) Me, Ph, OMe,
NMe2] have proven to be versatile ligands toward transition
metals because of the presence of different functional groups
in their molecular skeleton.1a-s This versatility has allowed
the characterization of coordinated ylides in different bonding
modes: C-coordinated (through the CR atom), O-bonded
(through the carbonyl O), N-bonded (through the N of the
† Dedicated to Professor Victor Riera on the occasion of his 70th birthday.
* To whom correspondence should be addressed. E-mail: agusti@
klingon.uab.es (A.L.), esteban@unizar.es (E.P.U.). Fax: (+34) 976761187.
‡ Universidad de Zaragoza.
§ Universitat Rovira i Virgili.
| Universitat Auto`noma de Barcelona.
Facultad de Ciencias Fase II.
10.1021/ic060706f CCC: $33.50
Published on Web 07/28/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 17, 2006 6803

Falvello et al.
Figure 1. Resonance forms of the ylide L1.
purely organic point of view. However, metal complexes of
doubly stabilized phosphorus ylides are scarcely explored,
and few examples have been characterized crystallographi-
cally.7 The reaction of mercury(II) halides HgX2 (X ) Cl,
Br, I) or uranium(VI) salts with Ph3PdC[C(O)Me][C(O)-
Ph] (ABPPY) gives mono- and dinuclear complexes in which
the ylide bonds to the metal center through the acetyl O.7a,d
The reactivity of the ABPPY ylide toward HgX2 complexes
is different from that observed with the stabilized ylide
Ph3PdC(H)C(O)Ph (BPPY) because the latter coordinates
selectively through the CR atom.8 Meanwhile, the reaction
of PtCl2(NCC6F5)2 with Ph3PdC(H)CO2Me gives, among
other products, the imine-ylide complex [PtCl2{NHd
C(C6F5)C(dPPh3)C(O)Me}2],7b coordinated to the Pt center
through the imine N atom. All of these examples share a
common feature, which is the fact that the ylidic CR atom is
not involved in the coordination to the metals.
Aiming to expand our knowledge of the bonding properties
of doubly stabilized phosphorus ylides, we have studied the
reactivity of the ylide [Ph3PdC(CO2Me)C(dNPh)CO2Me]
(L1)4 toward bis-solvates of PdII and PtII. In this ylide, there
are three functional groups with a total of six donor atoms.
Despite the polydenticity of L1, N,O-chelate complexes were
obtained selectively. CR-bonded complexes were not ob-
served in any of the cases studied. This paper reports the
results of the observed reactivity and aims to explain, on
the basis of density functional theory (DFT) calculations,
why the CR atom is not bonded to the metal center.
(1) (a) Navarro, R.; Urriolabeitia, E. P. J. Chem. Soc., Dalton Trans. 1999,
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I. Phosphorus Ylides, Chemistry and Applications in Organic Synthesis;
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L. Organometallics 2000, 19, 1373. (e) Bertani, R.; Pandolfo, L.;
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Selivanov, S. I.; Kukushkin, V. Y.; Vicente, J.; Haukka, M.; Pombeiro,
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(k) Falvello, L. R.; Margalejo, M. E.; Navarro, R.; Urriolabeitia, E.
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Falco´n, M. M.; Ram´ırez de Arellano, M. C.; Jones, P. G. Organo-
metallics 2003, 22, 4327. (p) Vicente, J.; Chicote, M. T.; Lagunas,
M. C. HelV. Chim. Acta 1999, 82, 1202. (q) Vicente, J.; Singhal, A.
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J. F. J. Org. Chem. 1965, 30, 3312.
Results and Discussion
1. Synthesis and Reactivity of L1. The ylide L1 was
obtained following previously reported procedures4 with
minor modifications (see the Experimental Section). The IR
spectrum of L1 shows three strong absorptions at 1734, 1647,
and 1571 cm-1, assigned to the carbonyl stretch of the
â-remote nonconjugated CO2Me group, to the CdO stretch
in the R-resonance-stabilized CO2Me unit,9 and to the CdN
iminic stretching,10 respectively. The absorptions due to the
resonance-stabilized CdN and CdO bonds appear at lower
energies than expected, in accord with the charge delocal-
ization through the N-C-C(P)-C-O system (Figure 1).
(6) Gru¨tzmacher, H.; Pritzkow, H. Chem. Ber. 1989, 122, 1411.
(7) (a) Laavanya, P.; Venkatasubramanian, U.; Panchanatheswaran, K.;
Krause Bauer, J. A. Chem. Commun. 2001, 1660. (b) Vicente, J.;
Chicote, M. T.; Beswick, M. A.; Ram´ırez-de-Arellano, M. C. Inorg.
Chem. 1996, 35, 6592. (c) Vicente, J.; Chicote, M. T.; Lagunas, M.
C.; Jones, P. G. Inorg. Chem. 1995, 34, 5441. (d) Spencer, E. C.;
Kalyanasundari, B.; Mariyatra, M. B.; Howard, J. A.; Pancha-
natheswaran, K. Inorg. Chim. Acta 2006, 359, 35.
(8) (a) Kalyanasundari, M.; Panchanatheswaran, K.; Robinson, W. T.;
Wen, H. J. Organomet. Chem. 1995, 491, 103. (b) Kalyanasundari,
B.; Panchanatheswaran, K.; Parthasarathi, V.; Robinson, W. T. Bull.
Chem. Soc. Jpn. 1999, 72, 33.
(9) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Pascual, I.; Urriolabeitia,
E. P. J. Chem. Soc., Dalton Trans. 1997, 763.
(10) Pretsch, E.; Bu¨hlmann, P.; Affolter, C.; Herrera, A.; Mart´ınez, R.
Determinacio´n Estructural de Compuestos Orga´nicos, Springer-Verlag
Ibe´rica: Barcelona, Spain, 2001.
(4) (a) Lwowski, W.; Walker, B. J. J. Chem. Soc., Perkin Trans. 1 1975,
1309. (b) Briggs, E. M.; Brown, G. W.; Dawson, W. T.; Jiricny, J. J.
Chem. Soc., Chem. Commun. 1975, 641. (c) Mak, T. C. W.; Trotter,
J. Acta Crystallogr. 1965, 18, 81. (d) Barluenga, J.; Lo´pez, F.; Palacios,
F. J. Chem. Soc., Chem. Commun. 1985, 1681. (e) Barluenga, J.;
Lo´pez, F.; Palacios, F. J. Chem. Soc., Chem. Commun. 1986, 1574.
(f) Barluenga, J.; Lo´pez, F.; Palacios, F.; Sa´nchez-Ferrando, F.
Tetrahedron Lett. 1988, 29, 381. (g) Barluenga, J.; Lo´pez, F.; Palacios,
F. J. Chem. Soc., Perkin Trans. 1 1989, 2273. (h) Barluenga, J.;
Merino, I.; Palacios, F. Tetrahedron Lett. 1989, 30, 5493. (i) Barluenga,
J.; Merino, I.; Palacios, F. J. Chem. Soc., Perkin Trans. 1 1991, 341.
(5) Ciganek, E. J. Org. Chem. 1970, 35, 1725.
6804 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
Chart 1
The position of the 31P{1H} NMR signal (17.37 ppm) is in
good agreement with the presence of the ylidic PdC bond,9
as well as the doublet peak in the 13C{1H} NMR spectrum
at 59.19 ppm (1JPC ) 119.6 Hz). Signals attributed to the
carbonyl and imine groups are also observed in the 13C{1H}
NMR spectrum at 160.33 (CdN), 166.56 (CdO nonresonant
with the PdC bond), and 168.47 (CdO resonant) ppm. Full
assignment of the 13C NMR signals (in L1 and in all
complexes) was performed with the help of heteronuclear
signal due to the ylidic C atom (PdC) appears, in the
13C{1H} NMR spectra, in a narrow range of frequencies (65-
72 ppm), close to that in the starting compound L1 (59.19
ppm) and, moreover, with a coupling constant (average 1JPC
) 117 Hz) very similar to that observed for L1 (1JPC ) 119.6
Hz). This set of observations allows us to discard those
bonding modes containing a C-bonded ylide (proposals II,
V, and VI in Chart 1) because C coordination produces a
clear deshielding of the 31P signal9 and a shielding of the
signal due to the ylidic CR atom in the 13C NMR spectra,
1
single quantum coherence and multiple-bond H-13C cor-
1
relations.
together with a notable decrease in the value of the JPC
The cationic precursors [M(C∧X)(THF)2]ClO4 (THF )
tetrahydrofuran) were prepared by the reaction of the
corresponding dinuclear derivatives [M(µ-Cl)(C∧X)]2 with
AgClO4 (1:2 molar ratio; C∧X ) ancillary ligands; see eq
1) in THF at room temperature. After elimination of the silver
halide, the freshly prepared solutions of [M(C∧X)(THF)2]-
ClO4 were treated with ylide L1 (1:1 molar ratio), resulting
in the formation of the cationic mononuclear complexes
[M(C∧X)(L1)]ClO4 (1-8). Complex 9 was synthesized by
the reaction of Li2[PdCl4] with L1 in methanol. The
elemental analyses of complexes 1-9 are in good agreement
with the stoichiometries shown in eq 1, and their mass spectra
(positive ion fast atom bombardment, FAB+) show in all
cases the presence of the cationic fragment with the correct
isotopic distribution. Because of the presence of at least four
potential donor atoms (see Chart 1, I), no less than eight
possible bonding modes can be envisaged (Chart 1, II-IX).
The spectroscopic data of 1-9 allow their structure and,
moreover, their stereochemistry to be ascertained.
The NMR spectra of complexes 1-9 show the following
general features: (i) in all cases, only one set of signals is
observed (even at low temperature, CD2Cl2, 183 K), with
this fact suggesting that all products are obtained as single
isomers; (ii) the pattern of resonances for complexes 1 and
3-6 shows that the molecular plane is a plane of symmetry;
(iii) for 1-9, the position of the P signal in the 31P{1H} NMR
spectra is slightly deshielded (range 18-22 ppm) with respect
to the free ligand L1 (17.37 ppm); (iv) also in all cases, the
coupling constant, due to the hybridization change.9 More-
over, C coordination should lead to the obtention of
diastereoisomers in 2 (not observed) and to the loss of the
molecular plane of symmetry in 1, 3, 5, and 6. The structures
III and IV in Chart 1 can also reasonably be discarded
because of the following facts: (i) the stoichiometry of the
complexes shows clearly the presence of only one ligand
per M atom; thus, it seems very likely that the ligand L1
(which has four potential donor atoms) behaves as a chelating
ligand; (ii) moreover, no solvent molecules (which could also
be coordinated to the metal center) are observed in the NMR
spectra; (iii) finally, the IR data show absorptions due to
-
the presence of an ionic, noncoordinated ClO4 as the
counterion.11
The discrimination between structures VII-IX (Chart 1)
can be easily achieved from the IR data. The IR spectra of
1-9 show, for all studied complexes, the presence of a strong
band in the range 1730-1750 cm-1 (mainly in the very
narrow range 1730-1735 cm-1) and another broad band in
the range 1570-1610 cm-1. It is sensible to suppose that
the former is due to the carbonyl stretch of the CO2Me unit
nondelocalized by resonance because of its very close
position with respect to that observed in free L1 (1734 cm-1).
This observation suggests that this carbonyl group is not
involved in coordination to the metal center (otherwise, a
(11) Nakamoto, K. Infrared Spectra of Inorganic and Coordination
Compounds, 2nd ed.; Wiley: New York, 1963; pp 111 and 175-
177.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6805

Falvello et al.
decrease in this carbonyl frequency should be observed) and
that structures VII and IX (Chart 1) can also be discarded.
Only structure VIII, a six-membered chelate ring formed by
coordination of the iminic N atom and the stabilized carbonyl
O, fits with all spectroscopic parameters. It is interesting to
note that achievement of the optimal orientation in this
bonding mode implies the rotation (at least) of the CdN bond
around the CR-Câ bond. An additional argument in favor
of the N,O-chelating coordination comes from the deshield-
ing observed for the 13C NMR signals due to the iminic Nd
C and the stabilized carbonyl CdO carbon atoms (see the
Experimental Section).9,12 In fact, this coordination mode of
the ligand is also in very good agreement with the resonance
forms envisaged in Figure 1. For all of these reasons, we
propose the N,O-coordination mode shown in eq 1 for ligand
L1.
of these data and because of the close similarity of the C,N-
orthopalladated ligands in complexes 1-4, it is sensible to
propose the same arrangement (C-trans-O) for all of them.
This hypothesis was confirmed through the determination
of the X-ray structure of 3 (see below). In the case of
complexes 5 and 6, the key feature is the observation of a
clear nuclear Overhauser enhancement (NOE) effect (in the
1
2D H NOESY spectra) between the Hortho protons of the
NPh group and the methylene protons of the metalated MCH2
units. For complex 8, the 1H NOESY spectrum does not show
NOE correlations between the protons of the SC4H8 ligand
and the protons of the L1 ligand. However, this fact cannot
be considered as a positive argument in favor of a given
structure. Consequently, the 2D 19F-1H NOESY spectrum
of 8 was measured (see the Experimental Section). This
spectrum shows three very clear heteronuclear NOE ef-
fects: a NOE between the Fortho nuclei of the C6F5 ligand
and the SCH2 protons of the tetrahydrothiophene ligand and
NOEs between the Fortho nuclei of the C6F5 ligand and the
Hortho and Hmeta protons of the NPh unit. The structure
depicted in eq 1 (C ) C6F5; X ) SC4H8) for complex 8
matches all of these facts.
Further reactivity of ligand L1 was attempted. The
treatment of L1 with Pd(OAc)2 (OAc ) acetate; 1:1 molar
ratio) in methanol, followed by the addition of an excess of
LiCl, gives the orthometalated dinuclear derivative [Pd(C6H4-
2-PPh2dC(CO2Me)-C(CO2Me)dNPh-κ-C,N)(µ-Cl)]2 (10) in
moderate yield (see eq 2). Complex 10 gives correct
1
elemental analysis for the proposed stoichiometry. The H
NMR spectrum of 10 shows, in the aromatic region, four
well-separated signals (6.57, 6.72, 6.77, and 6.93 ppm)
corresponding to the four protons of the cyclopalladated
phenyl ring. In addition, resonances corresponding to the
other expected groups (PPh2, NPh, and OMe) are also
observed. The presence of the metalated phenyl ring can also
be inferred from the 13C{1H} NMR spectrum because five
different peaks (two partially overlapped) can be observed
in the 120-130 ppm region together with an additional
deshielded signal (153.01 ppm), which is attributed to the
metalated C.13 The 13C{1H} NMR spectrum also shows that
the ylidic carbon atom CR is not bonded to the Pd atom
The asymmetry of ylide L1 should give, a priori, two
possible geometric isomers when N,O-bonded to the metal
atom of precursors 1-6 and 8. However, as has been stated,
only one set of signals is observed in the NMR spectra over
a wide range of temperatures, meaning that each compound
is obtained as a single isomer. The C-trans-O arrangement
proposed in eq 1 is supported by the observation in the 2D
1H NOESY spectrum of complex 3 of a cross-peak between
the Hortho protons of the NPh group (6.94 ppm) and the
methylene protons of the PdCH2 unit of the 8-mq ligand (2.94
ppm). The O bonding of a keto-stabilized ylide trans to C is
a common feature of this type of chemistry.1,9 On the basis
because the assigned signal appears as a doublet (1JPC
)
125.1 Hz) at 61.35 ppm, that is, in a position very similar to
that observed for the free ligand L1 (59.19 ppm) and with
(12) Bravo, J.; Cativiela, C.; Navarro, R.; Urriolabeitia, E. P. J. Organomet.
Chem. 2002, 650, 157.
6806 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
virtually the same coupling (1JPC ) 119.6 Hz). The metal-
lacycle is closed by coordination of the iminic N atom,
forming a seven-membered ring, as can be inferred from the
position of the iminic C resonance (164.56 ppm), deshielded
from its position in the free ylide (160.33 ppm). The 31P{1H}
NMR spectrum of 10 shows a signal at 9.56 ppm, shielded
with respect to its position in free L1 (17.37 ppm). This fact
is an additional proof of the absence of interaction between
the ylidic CR atom and the Pd atom because C bonding
promotes a deshielding of the corresponding signal.13 All of
these facts are in very good agreement with the structure
depicted in eq 2 for 10. This structure has been confirmed
by X-ray diffraction methods.
The cyclopalladation of R-stabilized phosphorus ylides is
not a very unusual reaction, and several examples have
already been described.1,13 However, in all reported cases,
the metallacycle is closed forming a five-membered ring in
which the donor atoms are the arylic C atom, that which
has undergone the C-H bond activation process, and the
ylidic C atom. This is not our case because the reluctance
of the ylidic CR atom to bind to the transition metal results
in the formation of a seven-membered cycle, instead of the,
in principle, more stable five-membered ring. Seven-
membered metallacycles are very scarce, as can be seen from
a search in the Cambridge Structural Database.14 Of the most
common metallacycles (four through seven members), a very
low percentage (1.7%) have seven members (12 entries out
of 691 having Pd with C and N donor atoms). This
percentage increases slightly (2.6%) when considering all
possible transition metals (49 entries out of 1890 with C and
N donor atoms). The reactivity of 10 seems to be similar to
that observed for other classical C,N-cyclopalladated deriva-
tives. For instance, 10 reacts with PPh3 (1:2 molar ratio, room
temperature, CD2Cl2) to give the mononuclear 11, by
cleavage of the halide bridging system (see eq 2). When the
reaction was performed with an excess of PPh3 (1:4 molar
ratio), 11 and unreacted PPh3 were the only species detected
in solution, this fact demostrating a noteworthy stability of
the cycle. No other reactions were attempted.
Figure 2. Thermal ellipsoid plot of L1. Non-H atoms are drawn at the
50% probability level.
Figure 3. Thermal ellipsoid plot of the cationic part of 3. Non-H atoms
are drawn at the 50% probability level.
In conclusion, the ylide L1 coordinates as a neutral ligand
to PdII and PtII solvates through the iminic N atom and
through the resonance-stabilized carbonyl O. The orthometa-
lation of L1 can easily be achieved, with the concomitant
formation of an unusual Caryl,N seven-membered ring.
Despite the presumed nucleophilic properties of the ylidic
carbon CR, this atom does not coordinate to the metal center
in any of the cases studied.
2. Crystal Structures of L1, 3, and 10‚0.5CHCl3.
Molecular drawings are shown in Figures 2 (L1), 3 (3), and
4 and 5 (10). Parameters from the data collection and
structure solution and refinement are given in Table 1, and
Figure 4. Thermal ellipsoid plot of complex 10. Non-H atoms are drawn
at the 50% probability level.
selected bond distances and angles are collected in Tables 2
(L1), 3 and 4 (3), and 5 and 6 (10).
The molecular skeleton of L1 is very similar to that
reported previously for the closely related ylide [Ph3PdC(CO2-
Me)C(dNC6H4-p-Br)CO2Me].4c Key features are the cisoid
arrangement of the PdC and CdN bonds, also observed in
other imine-stabilized ylides,15 and the transoid arrangement
of the PdC and CdO bonds, usually observed in ester-
(13) For some representative examples, see: (a) Teagle, J. A.; Burmeister,
J. L. Inorg. Chim. Acta 1986, 118, 65. (b) Vicente, J.; Chicote, M. T.;
Ferna´ndez-Baeza, J. J. Organomet. Chem. 1989, 364, 407. (c) Falvello,
L. R.; Ferna´ndez, S.; Navarro, R.; Rueda, A.; Urriolabeitia, E. P.
Organometallics 1998, 17, 5887.
(14) (a) Allen, F. H. Acta Crystallogr., Sect. B 2002, 58, 380. (b) Bruno,
I. J.; Cole, J. C.; Edgington, P. R.; Kessler, M.; Macrae, C. F.; McCabe,
P.; Pearson, J.; Taylor, R. Acta Crystallogr., Sect. B 2002, 58, 389.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6807

Falvello et al.
different planes can be clearly differentiated: one containing
the 8-mq ligand and the other containing the PC(CdN)(Cd
O) skeleton of the ylide. In one of the organometallic cations
(molecule A), the Pd atom lies in the best least-squares plane
defined by the atoms N(2), C(32), C(13), P(1), C(11), and
O(1) [and, of course, Pd(1); N(2) shows the major deviation
from the plane, 0.078 Å], while the 8-mq ligand defines
another plane. The dihedral angle between these two planes
is 18.2(3)°. In the other cation (molecule B), the Pd atom is
best located in the best least-squares plane defined by the
8-mq atoms C(42), C(41), C(47), and N(3) [and Pd(2)], and
the angle of this plane with that defined by N(4), C(72),
C(53), P(2), C(51), and O(5) [C(72) shows the major
deviation from the plane, 0.110 Å] is 25.6(3)°. This means
that the planarity of the skeleton of the ylide ligand is
preserved after bonding.
Figure 5. Thermal ellipsoid plot of complex 10. Detail of the environment
of one Pd atom.
In each molecule, the Pd atom is located in a distorted
square-planar environment (bond angles around the Pd atom
different from 90°, in addition to the loss of planarity),
surrounded by the C and N atoms of the metalated 8-mq
ligand and the N (imine) and O (carbonyl) atoms of the ylide.
This confirms our previous analysis based on NMR data and
confirms that the CR atom of the ylide is not bonded to the
Pd atom. The internal structural parameters of the 8-mq
ligand are very similar to those described previously21 and
do not merit further comment. The Pd-N bond distances
[Pd(1)-N(2) ) 2.041(3) Å; Pd(2)-N(4) ) 2.033(3) Å] are
similar to those found in related N-bonded phenylimines,22
while the Pd-O bond distances [Pd(1)-O(1) ) 2.070(2) Å;
Pd(2)-O(5) ) 2.103(2) Å] are shorter than those found in
other O-bonded ylides trans to a C atom.19 Moreover, the
ligand L1 has undergone important structural changes during
the coordination process. The most relevant of them is that
the CdN bond, which initially was cisoid with respect to
the PdC bond in L1, is now in a transoid arrangement
[dihedral angle P(1)-C(13)-C(32)-N(2) ) -170.7(4)°].
This rearrangement and the coordination to the metal should
be reflected in changes in the internal bond distances and
angles, in addition to those reported for the dihedral angles.
However, the changes in bond distances, even between atoms
directly involved in bonding to the metal, are not as
pronounced as expected, as can be inferred from Tables 2-4
and 7, and almost all distances are identical within experi-
mental error. This fact probably means that there is extensive
charge delocalization.
stabilized ylides.2f,16 The atoms P(1), C(4), C(5), O(4), C(3),
and N(1) are almost coplanar {maximum deviation 0.10 Å
[C(3)]}. The P(1)-C(4) bond distance [1.745(4) Å] is shorter
than the P(1)-C(Ph) bond distances, in accord with a partial
double-bond character, but is longer than those usually found
in stabilized ylides with a single keto stabilizing group
[Ph3PdC(H)C(O)R, range 1.704-1.711 Å].2f,17 This signals
a higher charge delocalization in L1, compared with that
found in ylides Ph3PdC(H)C(O)R, probably because of the
simultaneous presence of two delocalizing groups. This high
degree of delocalization is also reflected in the CR-C bond
distances C(4)-C(3) ) 1.442(5) Å and C(4)-C(5) )
1.424(5) Å, which are identical within experimental error.
These values are shorter than the “standard” value for a
C(sp2)-C(sp2) single bond (1.478 Å)18 but are longer than
those found in free2f,17 or O-bonded9,19 ylides (range 1.366-
1.394 Å). The two CdO bond distances are identical, within
experimental error [1.196(4) and 1.212(5) Å], while the
C(3)-N(1) bond distance [1.287(4) Å] also reflects partial
double-bond character.2f,15 Finally, it is worth noting that the
intramolecular distance P(1)-N(1) is 2.841 Å, a value clearly
shorter than the sum of the van der Waals radii (3.40 Å),20
and that the torsion angle P(1)-C(4)-C(3)-N(1) is 14.1°.
Complex 3 (Figure 3) has two independent molecules in
the asymmetric unit, although a comparison of the structural
parameters of these two molecules reveals quite similar
geometric arrangements with minor differences (see Tables
3 and 4). These differences reside mainly in the planarity of
the molecule as a whole because in each molecule two
The molecule of complex 10‚0.5CHCl3 shows a dimeric
structure (Figure 4) in which the two Pd atoms are bridged
by two Cl atoms, and each Pd atom is also bonded to the
palladated [C6H4-2-PPh2dC(CO2Me)C(CO2Me)dNPh] unit.
The two metalated seven-membered boatlike rings are folded
to opposite sides of the molecular plane and have their two
aryl groups in a syn arrangement. As a whole, the molecule
shows pseudo-C2 symmetry. Each Pd atom is located in a
(15) Braunstein, P.; Pietsch, J.; Chauvin, Y.; Mercier, S.; Saussine, L.;
DeCian, A.; Fischer, J. J. Chem. Soc., Dalton Trans. 1996, 3571.
(16) (a) Lledo´s, A.; Carbo´, J. J.; Urriolabeitia, E. P. Inorg. Chem. 2001,
40, 4913 and references cited therein. (b) Lledo´s, A.; Carbo´, J. J.;
Navarro, R.; Urriolabeitia, E. P. Inorg. Chim. Acta 2004, 357, 1444.
(17) (a) Geoffroy, M.; Rao, G.; Tancic, Z.; Bernardinelli, G. J. Am. Chem.
Soc. 1990, 112, 2826. (b) Shao, M.; Jin, X.; Tang, Y.; Huang, Q.;
Huang, Y. Tetrahedron Lett. 1982, 23, 5343. (c) Kalyanasundari, M.;
Panchanatheswaran, K.; Parthasarathi, V.; Robinson, W. T.; Wen, H.
Acta Crystallogr., Sect. C 1994, 50, 1738. (d) Boyle, P. D. Acta
Crystallogr., Sect. C 1996, 52, 2859.
(21) Ara, I.; Fornie´s, J.; Navarro, R.; Sicilia, V.; Urriolabeitia, E. P.
Polyhedron 1997, 16, 1963.
(22) For instance, see: (a) Delis, J. G. P.; Aubel, P. G.; Vrieze, K.; van
Leeuwen, P. W. N. M.; Veldman, N.; Spek, A. Organometallics 1997,
16, 4150. (b) Schmid, M.; Eberhardt, R.; Klinga, M.; Leskela, M.;
Rieger, B. Organometallics 2001, 20, 2321.
(18) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, 685 (S1-S19).
(19) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P. Inorg.
Chem. 1996, 35, 3064.
(20) Bondi, A. J. Chem. Phys. 1964, 68, 441.
6808 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
Table 1. Crystal Data and Structure Refinement for L1, 3, and 10‚0.5CHCl3
L1
3
10‚0.5CHCl3
empirical formula
fw
C30H26NO4P
495.49
C40H34ClN2O8PPd
843.51
C60.5H50Cl3.5N2O8P2Pd2
1331.84
temp (K)
radiation (λ, Å)
cryst syst
space group
a (Å)
294(2)
123(1)
100(2)
Mo KR (0.710 73)
monoclinic
P21/n
11.194(5)
13.585(6)
17.625(8)
90.583(9)
2680(2)
Mo KR (0.710 73)
monoclinic
P21/c
24.3083(5)
14.5144(2)
23.1589(4)
115.874(3)
7351.8(2)
8
Mo KR (0.710 73)
monoclinic
P21/c
11.8913(11)
32.154(3)
15.7008(15)
90.432(2)
6003.1(10)
4
b (Å)
c (Å)
â (deg)
V (Å3)
Z
D
4
calcd (Mg/m3)
1.228
0.137
0.966
1.524
0.678
1.006
1.474
0.862
0.991
µ (mm-1
)
GOF on F 2
final R indices [I > 2σ(I)]
R1 ) 0.0656
wR2 ) 0.1166
R1 ) 0.1666
wR2 ) 0.1506
0.196, -0.206
R1 ) 0.0376
wR2 ) 0.0699
R1 ) 0.1076
wR2 ) 0.1005
0.881, -0.426
R1 ) 0.0575
wR2 ) 0.1367
R1 ) 0.0850
wR2 ) 0.1454
1.696, -0.628
R indices (all data)
largest diff peak, hole (e Å-3
)
Table 2. Selected Bond Lengths (Å) and Angles (deg) for L1
Table 4. Selected Bond Angles (deg) for 3
P(1)-C(4)
P(1)-C(19)
N(1)-C(3)
O(1)-C(2)
C(3)-C(4)
C(4)-C(5)
1.745(4)
1.806(4)
1.287(4)
1.196(4)
1.442(5)
1.424(5)
P(1)-C(13)
P(1)-C(25)
N(1)-C(7)
C(2)-C(3)
O(4)-C(5)
1.805(4)
1.807(4)
1.426(5)
1.516(5)
1.212(5)
molecule A
molecule B
N(1)-Pd(1)-C(1)
C(1)-Pd(1)-N(2)
N(1)-Pd(1)-O(1)
N(2)-Pd(1)-O(1)
C(11)-O(1)-Pd(1)
O(1)-C(11)-C(13)
82.64(13) N(3)-Pd(2)-C(41)
83.34(12)
96.83(12)
92.71(10)
87.26(10)
124.6(2)
99.49(13) C(41)-Pd(2)-N(4)
89.32(10) N(3)-Pd(2)-O(5)
88.38(10) N(4)-Pd(2)-O(5)
127.5(2)
128.1(3)
C(51)-O(5)-Pd(2)
O(5)-C(51)-C(53)
C(72)-C(53)-C(51) 119.7(3)
C(72)-C(53)-P(2)
C(51)-C(53)-P(2)
N(4)-C(72)-C(53)
C(72)-N(4)-Pd(2)
C(3)-N(1)-C(7)
O(2)-C(2)-C(3)
C(5)-O(3)-C(6)
N(1)-C(3)-C(2)
C(5)-C(4)-C(3)
C(3)-C(4)-P(1)
O(4)-C(5)-C(4)
122.0(4)
123.7(4)
117.9(4)
121.5(4)
119.2(4)
113.6(3)
126.0(4)
O(2)-C(2)-O(1)
O(1)-C(2)-C(3)
N(1)-C(3)-C(4)
C(4)-C(3)-C(2)
C(5)-C(4)-P(1)
O(4)-C(5)-O(3)
O(3)-C(5)-C(4)
124.9(4)
111.2(4)
119.8(4)
118.7(4)
127.2(3)
119.4(4)
114.6(4)
127.3(3)
C(32)-C(13)-C(11) 120.5(3)
C(32)-C(13)-P(1)
C(11)-C(13)-P(1)
N(2)-C(32)-C(13)
C(32)-N(2)-Pd(1)
126.2(3)
112.4(3)
128.0(3)
125.8(2)
124.0(3)
115.3(2)
125.9(3)
124.7(2)
Table 5. Selected Bond Lengths (Å) for 10‚0.5CHCl3
Table 3. Selected Bond Lengths (Å) for 3
Pd(1)-C(1)
Pd(1)-Cl(2)
Pd(2)-C(31)
Pd(2)-Cl(2)
P(1)-C(19)
P(1)-C(13)
P(2)-C(49)
P(2)-C(32)
O(1)-C(20)
O(5)-C(50)
N(1)-C(22)
N(2)-C(52)
C(1)-C(2)
1.960(6)
2.3314(17)
1.937(7)
2.3377(15)
1.757(7)
1.807(6)
1.753(6)
1.798(7)
1.201(8)
1.211(8)
1.307(8)
1.301(8)
1.377(9)
1.395(9)
1.406(10)
1.430(9)
1.518(10)
1.418(9)
1.365(10)
1.373(10)
1.441(9)
Pd(1)-N(1)
Pd(1)-Cl(1)
Pd(2)-N(2)
Pd(2)-Cl(1)
P(1)-C(7)
2.035(5)
2.4437(15)
2.017(5)
2.4590(17)
1.806(7)
1.822(6)
1.791(7)
1.798(6)
1.196(8)
1.192(9)
1.433(9)
1.443(8)
1.379(9)
1.373(10)
1.359(10)
1.431(10)
1.406(9)
1.400(10)
1.372(10)
1.423(9)
1.536(9)
molecule A
molecule B
Pd(1)-N(1)
Pd(1)-C(1)
Pd(1)-N(2)
Pd(1)-O(1)
O(1)-C(11)
C(11)-C(13)
C(13)-C(32)
C(13)-P(1)
C(32)-N(2)
C(32)-C(33)
C(33)-O(3)
C(33)-O(4)
O(4)-C(34)
N(2)-C(35)
2.006(3)
2.028(3)
2.041(3)
2.070(2)
1.217(4)
1.443(5)
1.413(5)
1.772(4)
1.306(4)
1.528(5)
1.198(4)
1.322(5)
1.436(4)
1.445(4)
Pd(2)-N(3)
2.002(3)
2.006(3)
2.033(3)
2.103(2)
1.237(4)
1.448(5)
1.431(4)
1.767(4)
1.327(4)
1.527(5)
1.181(4)
1.326(5)
1.438(4)
1.450(4)
Pd(2)-C(41)
Pd(2)-N(4)
Pd(2)-O(5)
O(5)-C(51)
C(51)-C(53)
C(53)-C(72)
C(53)-P(2)
C(72)-N(4)
C(72)-C(73)
C(73)-O(7)
C(73)-O(8)
O(8)-C(74)
N(4)-C(75)
P(1)-C(2)
P(2)-C(43)
P(2)-C(37)
O(3)-C(23)
O(7)-C(53)
N(1)-C(25)
N(2)-C(55)
C(1)-C(6)
C(2)-C(3)
C(3)-C(4)
C(5)-C(6)
C(4)-C(5)
C(19)-C(20)
C(22)-C(23)
C(31)-C(36)
C(33)-C(34)
C(35)-C(36)
C(49)-C(50)
C(19)-C(22)
C(31)-C(32)
C(32)-C(33)
C(34)-C(35)
C(49)-C(52)
C(52)-C(53)
distorted square-planar environment, surrounded by the
metalated aryl C atom and the N atom of the [C6H4-2-
PPh2dC(CO2Me)C(CO2Me)dNPh] ligand and the two bridg-
ing Cl atoms (Figure 5). The Pd-Cl bond distances fall in
the usual range of distances found for this type of bond,23
and the observed differences [for instance, Pd(1)-Cl(1) )
2.4437(15) Å; Pd(1)-Cl(2) ) 2.3314(17) Å] can be related
to their positions trans to atoms with very different trans
influences [Cl(1) trans to C(1) and Cl(2) trans to N(1)]. The
Pd(1)-C(1) bond distance [1.960(6) Å] is typical for
orthopalladated aryl groups of ylide ligands,13c and the Pd-
(1)-N(1) bond distance [2.035(5) Å] is also typical for this
type of bond.12 Within the seven-membered metallacycle,
the most relevant facts are as follows: (i) the P(1)-C(19)
bond distance [1.757(7) Å] is shorter than the other P-C
distances and is identical (within experimental error) to that
found in L1 [1.745(4) Å]; (ii) the C(19)-C(20) [1.430(9)
Å] and C(19)-C(22) [1.431(10) Å] bond distances are
identical with each other (within experimental error) and to
the respective distances in L1 [1.442(5) and 1.424(5) Å];
(iii) the C(22)-C(23) bond distance [1.518(10) Å] indicates
clear single-bond character; (iv) the C(22)-N(1) bond
(23) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D.
G. J. Chem. Soc., Dalton Trans. 1989, S1.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6809

Falvello et al.
stabilized phosphorus ylides.16 We used the topological
analysis of the electron density (Bader’s atoms in molecules
theory)27 in order to determine and characterize the possible
1,4-P‚‚‚N contact. Despite many efforts, we were not able
to find a bond critical point (cp) between the P and N atoms,
which would have confirmed the existence of the P‚‚‚N
interaction. Furthermore, the topological analysis of the
Laplacian of the charge density [L(r)] provides information
about the spatial localization of the electronic charge,
showing a remarkable correspondence with the valance-shell
electron pair repulsion (VSEPR) model. The local maxima
or (3, -3) cp’s, whose presence denotes a charge concentra-
tion, can be used to locate the lone pairs of the atoms. For
the L1 structure, the (3, -3) cp corresponding to the N lone
pair was localized. The angle formed between the N atom,
its lone pair, and the P atom is 119.4°. This value is
significantly smaller than that found for the O-cp-P angle
(162.3°) on H3PdC(H)C(O)C(H)dPH3 ylide, for which a
1,4-P‚‚‚O interaction could be characterized.16 Thus, in the
case of the imide-stabilized ylides, the orientation of the N
lone pair is not suitable for establishing an electrostatic
interaction with the positively charged P atom. This empha-
sizes the relevance of the spatial arrangement of the charge
density in the determination of these nonbonded intramo-
lecular interactions. Thus, the preference of the conformation
with a cisoid arrangement of CdP and CdN bonds cannot
be attributed to the 1,4-P‚‚‚N intramolecular contact.
We have computed the energy value for the cisoid (L1)
and transoid (L1rot) arrangements of the CdP and CdN
bonds, with the latter conformation being the one found in
the X-ray structure of complex 3. In agreement with the
experimental findings for the free ligand, the cisoid confor-
mation gives a slightly lower value of the energy than the
transoid one, ∆E(L1rot-L1) ) 30 kJ mol-1. If one analyzes
the geometry of the rotated structure L1rot (vide infra),
important structural changes can be observed. The PdCs
CdN skeleton loses its planarity [dihedral angle P(1)-C(4)-
C(3)-N(1) ) 144.7°], which is probably a consequence of
the electrostatic repulsion between the N of the imide moiety
and the carbonyl O of the ester-stabilizing moiety (see
Scheme 1). Another relevant observation is that the possible
1,5-P‚‚‚O interaction between the phosphorus ylide and one
of the O atoms of the ester group bound to the Câ can be
precluded. The P-O distances (P-O ) 3.498 and 4.243 Å
for carbonylic and methoxy O atoms, respectively) are
significantly longer than those previously characterized for
1,4-P‚‚‚O interaction described in keto-stabilized bis-ylide
H3PdC(H)C(O)C(H)dPH3 (P-O ) 2.288 Å).16 These
features are responsible for the higher stability of the
conformation with a cisoid arrangement of the PdC and Cd
N bonds. However, the absence of 1,4-P‚‚‚N intramolecular
interactions explains the modest energy difference between
the two conformers, favoring that the cisoid arrangement is
not transferred to the metallic fragment, as it was transferred
in the case of keto-stabilized phosphorus ylides.16b
Table 6. Selected Bond Angles (deg) for 10‚0.5CHCl3
C(1)-Pd(1)-N(1)
N(1)-Pd(1)-Cl(1)
C(31)-Pd(2)-N(2)
N(2)-Pd(2)-Cl(1)
Pd(1)-Cl(2)-Pd(2)
C(22)-N(1)-Pd(1)
C(2)-C(1)-C(6)
C(6)-C(1)-Pd(1)
85.9(2)
92.81(15) Cl(2)-Pd(1)-Cl(1)
86.3(2) C(31)-Pd(2)-Cl(2)
93.36(15) Cl(2)-Pd(2)-Cl(1)
C(1)-Pd(1)-Cl(2)
92.71(19)
88.73(6)
92.33(19)
88.23(5)
88.56(5)
129.8(4)
119.4(5)
122.8(5)
113.3(5)
112.9(6)
120.9(6)
94.29(5)
122.0(5)
118.7(6)
121.8(5)
Pd(1)-Cl(1)-Pd(2)
C(52)-N(2)-Pd(2)
C(2)-C(1)-Pd(1)
C(22)-C(19)-P(1)
C(20)-C(19)-P(1)
O(2)-C(20)-C(19)
N(1)-C(22)-C(23)
C(20)-C(19)-C(22) 123.4(6)
O(1)-C(20)-C(19)
N(1)-C(22)-C(19)
C(19)-C(22)-C(23) 115.8(5)
C(32)-C(31)-Pd(2) 119.4(5)
124.7(6)
123.3(6)
C(32)-C(31)-C(36) 117.6(6)
C(36)-C(31)-Pd(2) 122.9(5)
C(52)-C(49)-P(2)
O(5)-C(50)-O(6)
O(6)-C(50)-C(49)
N(2)-C(52)-C(53)
122.1(5)
121.5(6)
111.1(5)
116.5(5)
C(50)-C(49)-P(2)
O(5)-C(50)-C(49)
N(2)-C(52)-C(49)
120.3(5)
127.3(6)
124.9(5)
C(49)-C(52)-C(53) 118.5(6)
distance [1.307(8) Å] shows that this bond still preserves
double-bond character, although it is slightly longer than its
analogue in L1 [1.287(4) Å] because of N coordination to
the PdII atom. All of these facts mean that there is still
delocalization of the charge density in the P(1)-C(19)[-
C(20)]-C(22)-N(1) chain. Similar results hold for the
environment of Pd(2) because the halves of the molecule
are identical within experimental error.
3. DFT Studies. The reluctance of L1 to coordinate to
the MII center (M ) Pd, Pt) using the ylidic CR atom, in
either its neutral (1-9) or anionic (10 and 11) forms, is quite
noteworthy. Two different bonding modes have been char-
acterized (N,O and Caryl,N bonding) without the participation
of the ylidic CR. Also relevant is the presence in 10 of a
seven-membered ring, which should not be energetically
favorable when compared with the, in principle, more stable
five-membered ring, which would be formed after hypotheti-
cal CR-Pd bonding. The X-ray structures of L1, 3, and 10
show a high delocalization of the charge density, greater than
that observed in the ylides [R3PdC(H)C(O)R′], but we think
that this isolated fact does not itself seem to offer a reasonable
explanation for the lack of reactivity of this atom. In addition
to this, as stated in the Introduction, other examples of metal
complexes with doubly stabilized ylides are known.7,24,25
To shed some light about these questions, the bonding
modes of the ylide ligand L1 to a MII metal fragment have
been studied by means of DFT calculations (B3LYP
functional)26 on the ligand L1 and the metal fragment PdCl2
(complex 9) (see the Supporting Information for figures of
the optimized complexes and other tabular material). The
computed geometry for ligand L1 is in generally good
agreement with that experimentally determined for L1. A
relevant fact in the structure L1 is the cisoid arrangement of
the PdC and CdN bonds. This may suggest that an
intramolecular interaction between the positively charged
phosphonium P atom and the negatively charged N atom is
responsible for this conformation, and this interaction could
be similar to the 1,4-P‚‚‚O interaction described in keto-
(24) Pohlhaus, P. D.; Bowman, R. K.; Johnson, J. S. J. Am. Chem. Soc.
2004, 126, 2294.
(25) Bowman, R. K.; Johnson, J. S. J. Org. Chem. 2004, 69, 8537.
(26) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. ReV. B 1988, 37, 785.
(27) (a) Bader, R. F. W. Atoms in Molecules: A Quantum Theory;
Clarendon Press: Oxford, U.K., 1990. (b) Bader, R. F. W. Chem.
ReV. 1992, 92, 893.
6810 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
Scheme 1
Table 7. Relative Energies (kJ mol-1) of the Different Isomers of L1
and Energy Decomposition for the Ylide Bonding to PdCl2, Calculated
Following Scheme 1
dination modes. The analysis of the bonding energy and its
different components has shed some light on this aspect.
We can consider the formation of Cl2Pd(L1) (9, 9cn, and
9co) from the PdCl2 and L1 fragments, at their optimized
geometries when infinitely apart (see Scheme 1). The ∆E
of this reaction is the bonding energy of the ylide to the
PdCl2 fragment (∆Ebonding). This ∆E can be decomposed into
two terms: one accounting for the distortions of the L1 and
PdCl2 fragments from their isolated optimized geometries
to the final geometries in the complex (∆Edist) and the other
one for the interaction energy of the distorted fragments to
give the complex (∆Einteraction). The distortion energies can
be further divided into the distortion of the PdCl2 group and
that of the L1 ylide ligand. In the case of the formation of
complex 9, the distortion of L1 can be decomposed into two
additional terms: the optimized rotation of L1 to give L1rot
and the distortion of L1rot to give L1dist. The structures
of L1, L1rot, PdCl2, and PdCl2(L1) for each of the possible
cycles (six, five, and four members) have been optimized,
while the fragments L1dist and PdCl2dist were calculated
as single points, using the geometrical parameters of the
optimized 9, 9cn, or 9co.
The data presented in Table 7 reveal that the energies of
distortion of the PdCl2 unit are similar (ranging from 10.3
to 13.0 kJ mol-1), as are those of the distortion of the ligands
(ranging from 50.6 to 59.8 kJ mol-1), despite the very
different distortions undergone by L1 to achieve the final
arrangements shown in 9, 9co, or 9cn. The changes from
L1 to L1dist in complexes 9co or 9cn do not seem to imply
large distortions because the cisoid conformations of the Pd
C and CdO or CdN bonds are retained, and the distortion
energies amount to 50.6 kJ mol-1 (9cn) or 59.8 kJ mol-1
N,O-chelate
six-membered
ring 9
C,N-chelate
four-membered
ring 9cn
C,O-chelate
five-membered
ring 9co
Erel(complex)
Erel(PdCl2dist)
Erel(L1dist)
0.0
0.0
0.0
+12.4
+2.1
-3.3
+37.9
-0.6
+5.9
∆Erot(L1)
∆Edist(L1)
∆Erot+dist(L1)
∆Edist(Pd)
∆Einteraction
∆Ebonding
+30.0
+23.9
+53.9
+10.9
-299.7
-234.9
+50.6
+59.8
+13.0
-286.1
-222.5
+10.3
-267.1
-197.0
The coordination of the ylide L1 to the PdCl2 fragment
gives complex 9, if the bonding is produced through the N
and O atoms, but it could also give other isomeric complexes,
namely, all possible chelating modes shown in Chart 1
(structures V-IX). To study the bonding of CR to the PdII
atom, we have selected, from all of these structures, those
in which the CR atom is coordinated; thus, we have discarded
structures VII-IX, and from the two possible structures V,
we have only optimized the five-membered ring shown in
Chart 1 (see the Supporting Information for figures). As can
be seen from Table 7, the most stable structure is that
corresponding to the six-membered ring (9), with energy
differences of +12.4 kJ mol-1 (9cn) and +37.9 kJ mol-1
(9co) with respect to 9. While the lowest energy of isomer
9 is in keeping with experimental facts, the small energy
difference between 9cn and 9 is remarkable, as is the fact
that the four-membered ring 9cn is notably more stable than
the five-membered ring 9co. Thus, subtle effects may be
responsible of the relative stabilities of the different coor-
Inorganic Chemistry, Vol. 45, No. 17, 2006 6811

Falvello et al.
(9co). On the other hand, the change from L1 to L1dist in
complex 9 through L1rot implies a complete rotation around
the CR-C(N) bond, from the cisoid to the transoid form.
We have stated that the rotation process from L1 to L1rot
has an energy cost of about 30 kJ mol-1. However, this
additional energy is compensated for with the lower distortion
energy required in the six-membered-ring coordination of
the rotated ligand L1rot than in the five- and four-membered-
ring coordinations of the nonrotated ligand. The computed
energy for the distortion from L1rot to L1dist in 9 is 23.9
kJ mol-1. It is interesting to point out that, because of the
absence of stabilizing 1,4-P‚‚‚N intramolecular interactions,
the ligand distortion energy in N,O-bonding remains rela-
tively low, favoring the formation of the complex with a
transoid arrangement of the PdC and CdO bonds. Finally,
we have similar distortion energies, although the nature,
magnitude, and types of bonds implied in the distortions are
different.
When the relative energies of the distorted fragments are
considered, small differences were found (see Table 7), and
in any case, these differences can justify the relative
stabilization of the metallic complexes. On the other hand,
there is a clear correlation between the relative energy of
the complexes (0.0, +12.4, and +37.9 kJ mol-1 for 9, 9cn,
and 9co, respectively) and their corresponding relative
interaction energies (0.0, +13.6, and +32.6 kJ mol-1 for 9,
9cn, and 9co, respectively). This should be directly related
to the nature of the formed bonds Pd-C, Pd-N, and Pd-
O. Unfortunately, the estimation of the interaction energy
of one arm of a bindentate ligand on a given environment is
a difficult task, and only indirect evidences can be handled.
On going from 9cn to 9, the Pd-Cl distance trans to the N
atom remains virtually the same (2.333 and 2.339 Å,
respectively). This suggests that the Pd-C interaction is more
or less similar in the two N-bonded complexes and that the
energy gap of 13.6 kJ mol-1 between 9cn and 9 comes from
the stabilization produced by the change from the ylidic C
donor to a better donor, the carbonyl O. The low affinity of
the Pd atom for the carbonyl O of a stabilized ylide is well
documented.1,19 However, in this case the presence of two
stabilizing substituents at the ylidic C seems to weaken its
donor capability, making it a worse donor than the carbonyl
O. The final evidence is the very long Pd-C bond distance
found in 9co (2.278 Å) and 9cn (2.219 Å), compared with
those calculated and reported for similar structural environ-
ments (range 2.100-2.151 Å for the C-trans-Cl arrange-
ment),16b Thus, the concomitant presence of two weak donors
at the PdII center (C and O) in 9co gives the less stable
complex. The substitution of one of the weak donors by a
better donor (the N atom) results in a notable stabilization
of the resulting complex (9cn or 9) and, in this delicate
balance, the N,O bonding gives the most stable arrangement.
Thus, the formation of the Pd-C bond seems to be the less
favored process, compared with the Pd-O and Pd-N bonds.
This particular weakness of the Pd-C bond (in this case)
could be related to the low value of the natural population
analysis (NPA) charge of the CR atom (-0.69), while that
of the P atom is +0.86 (see the Supporting Information).
The values in the closely related stabilized ylide CMPPY
[H3PdC(H)CO2Me]16 are -0.98 and +0.86. While the
charges at the P atom are identical in L1 and CMPPY, there
is a notable decrease (0.29e) in the NPA charge at the CR
atom going from CMPPY to L1, reflecting the higher
delocalization of the charge density in the latter. It is then
sensible to assume that this decrease of the charge density
at CR is responsible for the lack of reactivity observed. Even
in the case of the CMPPY ylide [q(CR) ) -0.98; q(O) )
-0.62], its behavior toward PdII has been reported as
“ambidentate”; that is, it can competitively coordinate
through the O or CR atoms. A decrease in the charge of the
CR atom breaks this competitive situation, making the ylidic
CR atom unavailable for bonding to the PdII atom. This fact
could be the clue for the understanding of the observed
reactivity.
Conclusions. The ylide L1, which contains two stabilizing
groups at the ylidic CR atom, coordinates to organometallic
PdII and PtII moieties through the iminic N atom and through
the resonance-stabilized carbonyl O. The X-ray structures
of L1 and complex 3 have been determined, showing
extensive delocalization of the ylidic charge density. The
orthometalation of L1 can easily be achieved, with the
formation of an unusual Caryl,N seven-membered ring.
Despite the presumed nucleophilic properties of the ylidic
carbon CR, this atom does not coordinate to the metal center
in any of the cases studied. The DFT studies performed on
ligand L1 and complex 9 show that the N,O bonding of ylide
L1 forming a six-membered metallacycle is the most stable
situation. These studies also show a notable decrease in the
charge density at the CR atom, compared with the situation
found in singly stabilized keto ylides, which seems to be
responsible for the lack of reactivity of the CR.
Experimental Section
Safety Note. Caution! Perchlorate salts of metal complexes with
organic ligands are potentially explosiVe. Only small amounts of
these materials should be prepared, and they should be handled
with great caution. See: J. Chem. Educ. 1973, 50, A335-A337.
General Methods. Solvents were dried and distilled under Ar
using standard procedures before use. Elemental analyses were
carried out on a Perkin-Elmer 2400-B microanalyzer. IR spectra
(4000-200 cm-1) were recorded on a Perkin-Elmer 883 IR
spectrophotometer from Nujol mulls between polyethylene sheets.
1H (300.13 or 400.13 MHz), 19F (282.41 MHz), 13C{1H} (75.47
MHz), and 31P{1H} (121.49 MHz) NMR spectra were recorded in
CDCl3, CD2Cl2, or DMSO-d6 solutions at room temperature (other
temperatures were specified) on Bruker ARX-300 or Avance-400
spectrometers (δ in ppm and J in Hz); 1H and 13C{1H} NMR were
referenced using the solvent signal as the internal standard, while
19F and 31P{1H} NMR were externally referenced to CFCl3 and
1
H3PO4 (85%), respectively. The H SELNO-1D and SELRO-1D
NMR experiments were performed with optimized mixing times
(D8), depending on the irradiated signal. The 19F-1H HOESY
experiment on complex 8 was carried out on a Bruker Avance-400
spectrometer equipped with a QNP probe. A mixing time (D8) of
600 ms was used. The T1 values for 19F were calculated using
Bruker XwinNMR software, and D1 was set to 5T1 accordingly.
Mass spectra (FAB+) were recorded from CH2Cl2 solutions on a
VG Autospec spectrometer. The starting compounds L1,4 [Pd(µ-
6812 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
Cl)(C6H4CH2NMe2-C2,N)]2,28 [Pd(µ-Cl)(S-C6H4C(H)MeNMe2-
C2,N)]2,28 [Pd(µ-Cl)(NC13H8-C10,N)]2,29 [Pd(µ-Cl)(CH2NC9H6-
C8,N)]2,30 [Pd(µ-Cl)(C6H4-2-NC5H4-C2,N)],31 [M(µ-Cl)(o-CH2C6H4)
P(o-tol)2]2 (M ) Pd,32 Pt33), [Pd(µ-Cl)(η3-C3H5)]2,34 [Pd(µ-Cl)-
(C6F5)(tht)]2,35 and the ylide Ph3PdC(H)CO2Me36 were prepared
according to reported methods. Other reagents such as Ph3PdNPh
and DMAD (MeO2CsCtCsCO2Me) were purchased from com-
mercial sources (Aldrich) and were used without further purification.
Synthesis of Ph3PdC(CO2Me)C(dNPh)CO2Me (L1). To a
solution of Ph3PdNPh (1.00 g, 0.283 mmol) in dry CH2Cl2 (20
mL) under an Ar atmosphere was added DMAD (0.35 mL, 0.285
mmol). The yellow solution was stirred at 25 °C for 24 h, and then
the solvent was evaporated to dryness. Treatment of the oily residue
with Et2O (20 mL) gave L1 as a pale-yellow solid. Obtained: 1.20
g (85.6% yield). IR (ν, cm-1): 1571 (νCN), 1647 (νCO conjug), 1734
PdC, 1JPC ) 117.3), 74.30 (CH2N), 124.23 (d, Cipso, PPh3, 1JPC
)
92.9), 124.47, 127.03, 127.11, 136.05, 144.59, 151.31 (C6H4),
126.37 (Cmeta), 128.82 (Cpara), 130.50 (Cortho), 149.65 (Cipso, NPh),
131.48 (d, Cortho, 2JPC ) 12.7), 135.27 (d, Cmeta, 3JPC ) 11.3), 135.80
2
(Cpara, PPh3), 165.43 (CO nonconjug), 167.07 (d, CdN, JPC
16.4), 174.47 (d, CO conjug, JPC ) 9.4).
)
2
Synthesis of 2. Complex 2 was obtained following the same
synthetic method as that described for 1. [Pd(µ-Cl)(S-C6H4CH(Me)-
NMe2-C2,N)]2 (0.116 g, 0.20 mmol) was reacted with AgClO4
(0.083 g, 0.40 mmol) and ylide L1 (0.198 g, 0.40 mmol) in dry
THF at room temperature to give 2 as an orange solid. The yield
was quantitative. Anal. Calcd for C40H40ClN2O8PPd: C, 56.55; H,
4.74; N, 3.30. Found: C, 56.53; H, 4.48; N, 3.22. MS (FAB+, m/z,
%): 749 [(M - ClO4)+, 100%]. IR (ν, cm-1): 1590 (br, νCN
+
1
νCO conjug), 1731 (νCO nonconjug). H NMR (CD2Cl2, δ): 1.59
1
3
(νCO nonconjug). H NMR (CD2Cl2, δ): 3.22 (s, 3H, OMe), 3.54
(d, 3H, Me, JHH ) 6.6), 2.53 (s, 3H, NMe2), 2.65 (s, 3H, OMe),
3
4
(s, 3H, OMe), 6.24 (dd, 2H, Ho, NPh, JHH ) 7.5, JHH ) 1.2),
6.81 (tt, 1H, Hp, NPh), 6.99 (t, 2H, Hm, NPh), 7.61-7.46 (m, 9H,
PPh3), 7.85-7.77 (m, 6H, PPh3). 31P{1H} NMR (CD2Cl2, δ): 17.37.
13C{1H} NMR (CDCl3, δ): 49.83 (OMe), 51.38 (OMe), 59.19 (d,
2.79 (s, 3H, NMe2), 3.28 (s, 3H, OMe), 4.05 (q, 1H, CH), 6.92-
7.18 (m, 9H, NPh + C6H4), 7.62-7.68 (m, 6H, Hm, PPh3), 7.74-
7.80 (m, 3H, Hp, PPh3), 7.90-7.97 (m, 6H, Ho, PPh3). 31P{1H}
NMR (CD2Cl2, δ): 19.62. 13C{1H} NMR (CDCl3, δ): 17.91 (Me),
45.41 (NMe2), 50.78 (NMe2), 52.62 (OMe), 53.18 (OMe), 70.92
1
PdC, JPC ) 119.6), 120.28 (Cmeta, NPh), 122.30 (Cpara, NPh),
1
(d, PdC, 1JPC ) 117.2), 74.57 (CH), 122.23 (d, Cipso, PPh3, 1JPC
)
125.93 (d, Cipso, PPh3, JPC ) 94.1), 127.97 (Cortho, NPh), 128.41
2
(d, Cortho, PPh3, JPC ) 12.6), 131.87 (s, Cpara, PPh3), 133.77 (d,
93), 122.76, 125.17, 125.32, 134.08, 143.04, 152.81 (C6H4), 124.34
(Cmeta), 126.85 (Cpara), 128.70 (Cortho), 149.42 (Cipso) (NPh), 129.67
C
meta, PPh3, 3JPC ) 9.8), 150.47 (Cipso, NPh), 160.33 (d, CdN, 2JPC
3
(d, Cortho, 2JPC ) 12.7), 133.77 (d, Cmeta, 3JPC ) 10.0), 134.04 (Cpara
,
) 6.8), 166.56 (d, CO nonconjug, JPC ) 12.7), 168.47 (d, CO
conjug, JPC ) 15.1).
2
2
PPh3), 163.90 (CO nonconjug), 164.79 (d, CdN, JPC ) 16.5),
2
Synthesis of 1. To a suspension of [Pd(µ-Cl)(C6H4CH2NMe2-
C2,N)]2 (0.182 g, 0.33 mmol) in dry THF (20 mL) under an Ar
atmosphere was added AgClO4 (0.137 g, 0.66 mmol). The resulting
suspension was stirred for 20 min at room temperature with
exclusion of light and then filtered over a Celite pad in order to
remove AgCl. To the freshly prepared solution of the solvate
derivative was added the ylide L1 (0.327 g, 0.66 mmol). The
resulting solution was stirred for 1 h at room temperature and then
the solvent evaporated to dryness. Treatment of the residue with
Et2O (25 mL) and vigorous stirring gave 1 as a yellow solid, which
was filtered, washed with Et2O (10 mL), and air-dried. Obtained:
0.4474 g (81.0% yield). Anal. Calcd for C39H38ClN2O8PPd: C,
56.06; H, 4.58; N, 3.35. Found: C, 55.86; H, 4.39; N, 3.44. MS
(FAB+, m/z, %): 735 [(M - ClO4)+, 80%]. IR (ν, cm-1): 1590
(br, νCN + νCO conjug), 1731 (νCO nonconjug). 1H NMR (CD2Cl2,
δ): 2.64 (s, 3H, OMe), 2.73 (s, 6H, NMe2), 3.28 (s, 3H, OMe),
4.00 (s, 2H, CH2N), 6.93-7.19 (m, 9H, NPh + C6H4), 7.62-7.69
(m, 6H, Hm, PPh3), 7.73-7.79 (m, 3H, Hp, PPh3), 7.89-7.97 (m,
6H, Ho, PPh3). 31P{1H} NMR (CD2Cl2, δ): 19.60. 13C{1H} NMR
(CD2Cl2, δ): 52.96 (NMe2), 54.38 (OMe), 54.77 (OMe), 72.30 (d,
172.52 (d, CO conjug, JPC ) 9.4).
Synthesis of 3. Complex 3 was obtained following the same
synthetic method as that reported for 1, except that 3 precipitated
in THF. [Pd(µ-Cl)(CH2NC9H6-C8,N)]2 (0.114 g, 0.20 mmol) was
reacted with AgClO4 (0.083 g, 0.40 mmol) and ylide L1 (0.198 g,
0.40 mmol) in dry THF to give 3 as a white solid. Obtained: 0.150
g (44.3% yield). Anal. Calcd for C40H34ClN2O8PPd: C, 56.95; H,
4.06; N, 3.32. Found: C, 56.71; H, 3.81; N, 3.53. MS (FAB+, m/z,
%): 743 [(M - ClO4)+, 100%]. IR (ν, cm-1): 1616 (br, νCN
+
1
νCO conjug), 1734 (νCO nonconjug). H NMR (CD2Cl2, δ): 2.31
(s, 3H, OMe), 2.94 (s, 2H, PdCH2), 3.39 (s, 3H, OMe), 6.94 (dd,
2H, Ho, NPh, 3JHH ) 7.2, 4JHH ) 1.2), 7.13 (tt, 1H, Hp, NPh, 3JHH
) 7.5), 7.31 (pseudot, 2H, Hm, NPh), 7.40 (dd, 1H, H7, NC9H6,
3JHH ) 7.2, 4JHH ) 1.2), 7.48 (t, 1H, H6, NC9H6, 3JHH ) 7.5), 7.55
3
3
(dd, 1H, H3, NC9H6, JHH ) 8.4, JHH ) 5.1), 7.59-7.69 (m, 7H,
PPh3 + H5), 7.70-7.76 (m, 3H, PPh3), 7.78-7.85 (m, 6H, PPh3),
3
4
8.38 (dd, 1H, H4, NC9H6, JHH ) 8.4, JHH ) 1.5), 8.76 (dd, 1H,
H2, NC9H6, JHH ) 5.1, JHH ) 1.5). 31P{1H} NMR (CD2Cl2, δ):
21.74. 13C{1H} NMR (CDCl3, δ): 31.38 (PdCH2), 52.03 (OMe),
53.02 (OMe), 65.58 (d, PdC, 1JPC ) 116.6), 122.28, 123.88, 128.20,
128.37, 128.99, 138.46, 146.89, 148.31, 152.69 (NC9H6), 122.72
3
4
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1
(d, Cipso, PPh3, JPC ) 93), 124.21 (Cmeta), 125.87 (Cpara), 128.00
(Cortho), 149.45 (Cipso, NPh), 129.58 (d, Cortho, 2JPC ) 12.9), 133.80
(Cpara), 133.87 (d, Cmeta, 3JPC ) 10.2, PPh3), 163.06 (CO nonconjug),
165.15 (d, CdN, 2JPC ) 18.3), 169.67 (d, CO conjug, 2JPC ) 8.4).
Synthesis of 4. Complex 4 was obtained following the same
synthetic method as that reported for 1, except that 4 precipitated
in THF. [Pd(µ-Cl)(C6H4-2-NC5H4-C2,N)]2 (0.118 g, 0.20 mmol) was
reacted with AgClO4 (0.083 g, 0.40 mmol) and L1 (0.198 g, 0.40
mmol) in dry THF to give 4 as a yellow solid. Obtained: 0.193 g
(56.4% yield). Anal. Calcd for C41H34ClN2O8PPd: C, 57.56; H,
4.00; N, 3.27. Found: C, 57.67; H, 3.85; N, 3.50. MS (FAB+, m/z,
%): 755 [(M - ClO4)+, 85%]. IR (ν, cm-1): 1575, 1593 (νCN
+
1
νCO conjug), 1733 (νCO nonconjug). H NMR (CD2Cl2, δ): 2.74
(s, 3H, OMe), 3.39 (s, 3H, OMe), 6.80 (dd, 1H, H6′, C6H4-phpy,
3JHH ) 7.8, 4JHH ) 0.9), 6.97 (td, 1H, H5′, C6H4-phpy, 3JHH ) 7.8,
4JHH ) 1.5), 7.13 (td, 1H, H4′, C6H4-phpy, 3JHH ) 7.5, 4JHH ) 0.9),
(36) Isler, O.; Gutmann, H.; Montavon, M.; Ruegg, R.; Ryser, G.; Zeller,
P. HelV. Chim. Acta 1957, 40, 1242.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6813

Falvello et al.
7.17-7.38 (m, 6H, NPh + H5), 7.47 (dd, 1H, H3′, C6H4-phpy, 3JHH
) 7.5, 4JHH ) 1.5), 7.59-7.65 (m, 6H, PPh3), 7.71-7.78 (m, 4H,
PPh3 + H3), 7.81-7.88 (m, 6H, PPh3), 7.98 (td, 1H, H4, NC5H4-
phpy, 3JHH ) 8.1, 4JHH ) 1.5), 8.43 (dd, 1H, H6, NC5H4-phpy, 3JHH
ClNO8PPd: C, 53.38; H, 4.21; N, 1.89. Found: C, 52.72; H, 4.03;
N, 1.90. MS (FAB+, m/z, %): 642 [(M - ClO4)+, 40%]. IR (ν,
1
cm-1): 1607 (br, νCN + νCO conjug), 1751 (νCO nonconjug). H
NMR (CDCl3, δ): 2.23 (s, 3H, OMe), 3.04 (d, 2H, C3H5 anti, 3JHH
) 12), 3.16 (s, 3H, OMe), 3.57 (s, br, 2H, C3H5 syn), 5.77 (tt, 1H,
Hc, C3H5, 3JHH ) 6.9), 6.90 (d, 2H, Ho, NPh, 3JHH ) 7.5), 6.98 (t,
4
) 5.7, JHH ) 1.5). 31P{1H} NMR (CD2Cl2, δ): 19.20. 13C{1H}
NMR (CDCl3, δ): 52.59 (OMe), 53.64 (OMe), 67.15 (d, PdC,
1JPC ) 116.6), 119.16, 123.41, 123.82, 125.62, 129.22, 133.93,
140.33, 145.64, 148.29, 148.58, 163.34 (C6H4-2-NC5H4), 122.72
3
1H, Hp, NPh, JHH ) 7.5), 7.18 (t, 2H, Hm, NPh), 7.57-7.67 (m,
9H, PPh3), 7.77-7.85 (m, 6H, Ho, PPh3). 31P{1H} NMR (CDCl3,
δ): 21.76. 13C{1H} NMR (CDCl3, δ): 51.89 (OMe), 52.56 (OMe),
1
(d, Cipso, PPh3, JPC ) 93), 124.85 (Cmeta), 127.33 (Cpara), 128.64
(Cortho), 148.59 (Cipso, NPh), 129.65 (d, Cortho, 2JPC ) 12.9), 133.61
62.50 (CH2, C3H5), 65.49 (d, PdC, JPC ) 118.2), 117.03 (CH,
1
3
4
(d, Cmeta, JPC ) 10.1), 133.95 (d, Cpara, JPC )2.6, PPh3), 164.53
C3H5), 122.36 (Cmeta), 125.37 (Cpara), 128.38 (Cortho), 153.14 (Cipso,
2
1
(CO nonconjug), 165.78 (d, CdN, JPC ) 16.1), 172.31 (d, CO
conjug, JPC ) 9.1).
NPh), 122.49 (d, Cipso, PPh3, JPC ) 93), 129.40 (d, Cortho, PPh3,
2
4
2JPC ) 12.7), 133.56 (d, Cpara, PPh3, JPC ) 2.5), 133.99 (d, Cmeta
,
PPh3, 3JPC ) 10.0), 163.20 (d, CdN, 2JPC ) 17.7), 163.66 (d, CO
Synthesis of 5. Complex 5 was obtained following the same
synthetic method as that reported for 1. [Pt(µ-Cl)(o-CH2C6H4P(o-
tol)2)]2 (0.195 g, 0.18 mmol) was reacted with AgClO4 (0.076 g,
0.36 mmol) and ylide L1 (0.181 g, 0.36 mmol) in dry THF to give
5 as a white solid. Obtained: 0.361 g (91.0% yield). Anal. Calcd
for C51H46ClNO8P2Pt: C, 56.02; H, 4.24; N, 1.28. Found: C, 55.63;
H, 4.57; N, 1.25. MS (FAB+, m/z, %): 993 [(M - ClO4)+, 65%].
IR (ν, cm-1): 1591 (br, νCN + νCO conjug), 1732 (νCO nonconjug).
1H NMR (CD2Cl2, δ): 2.38 (s, 3H, OMe), 2.62 (s, 3H, OMe), 2.69
(s, br, 6H, Me-tol), 2.89 (s, br, 2H, PtCH2), 6.95-7.42 (m, 17H,
NPh + C6H4-tol), 7.61-7.81 (m, 15H, PPh3). 31P{1H} NMR (CD2-
Cl2, δ): 16.46 (s, Pt-P, 1JPtP ) 4212), 20.85 (PdC). 13C{1H} NMR
2
nonconjug, JPC ) 2.0), 170.24 (d, CO conjug, JPC ) 8.6).
Synthesis of 8. Complex 8 was obtained following the same
synthetic method as that reported for 1. [Pd(µ-Cl)(C6F5)(tht)]2 (0.159
g, 0.20 mmol) was reacted with AgClO4 (0.083 g, 0.40 mmol) and
ylide L1 (0.198 g, 0.40 mmol) in dry THF to give 8 as a white
solid. Obtained: 0.208 g (54.0% yield). Anal. Calcd for C40H34-
ClF5NO8PPdS: C, 50.22; H, 3.58; N, 1.46; S, 3.35. Found: C,
50.51; H, 3.39; N, 1.32; S, 3.33. MS (FAB+, m/z, %): 856 [(M -
ClO4)+, 85%]. IR (ν, cm-1): 798, 959, 1502 (C6F5), 1603 (br, νCN
+ νCO conjug), 1732 (νCO nonconjug). 1H NMR (CDCl3, δ): 2.07
(s, br, 4H, Hâ, SC4H8), 2.17 (s, 3H, OMe), 2.96 (s, br, 4H, HR,
SC4H8), 3.32 (s, 3H, OMe), 6.52 (m, 2H, Ho), 6.82-6.87 (m, 3H,
Hp + Hm, NPh), 7.61-7.77 (m, 15H, PPh3). 19F NMR (CDCl3, δ):
1
(CDCl3, δ): 11.26 (s, PtCH2, JPtC ) 835), 22.42 (Me-tol), 22.58
(Me-tol), 52.25 (OMe), 52.42 (OMe), 66.24 (d, PdC, 1JPC ) 116.6),
1
3
3
121.83 (d, Cipso, PPh3, JPC ) 93), 124.84 (Cmeta), 126.40 (Cpara),
-121.33 (pseudod, 2Fo, JFF ) 23), -158.91 (t, 1F, Fp, JFF )
127.88 (Cortho), 147.32 (Cipso, NPh), 125.82 (d, C6H4-tol, JPC ) 8.8),
20), -162.07 (pseudot, 2F, Fm). 31P{1H} NMR (CDCl3, δ): 21.45.
13C{1H} NMR (CDCl3, δ): 30.02 (Câ, SC4H8), 36.49 (SCR, SC4H8),
52.08 (OMe), 53.75 (OMe), 67.12 (d, PdC, 1JPC ) 115.6), 110.45
126.21 (d, C6H4-tol, JPC ) 9), 128.10 (C6H4-tol), 129.64 (d, Cortho
,
2
PPh3, JPC ) 12.9), 131.29-131.91 (several m, C6H4-tol), 132.91
(d, C6H4-tol, JPC ) 6.7), 132.99 (d, C6H4-tol, JPC ) 8), 133.85 (d,
1
(tm, Cipso, C6F5, JCF ) 39.7), 121.84 (d, Cipso, PPh3, JPC ) 93),
C
meta, PPh3, 3JPC ) 10), 134.11 (d, Cpara, PPh3, 4JPC ) 2.4), 142.08
123.82 (Cmeta), 125.97 (Cpara), 127.17 (Cortho), 148.94 (Cipso) (NPh),
(d, C6H4-tol, JPC ) 11.4), 158.42 (d, C6H4-tol, JPC ) 27), 163.01
129.70 (d, Cortho, PPh3, 2JPC ) 12.9), 133.89 (d, Cmeta, PPh3, 3JPC
)
)
2
(d, CdN, JPC ) 17.1), 163.31 (d, CO nonconjug, JP′C ) 2.1),
10.1), 134.08 (d, Cpara, PPh3, 4JPC ) 2.6), 137.40 (dm, C6F5, JCF
2
169.04 (d, CO conjug, JPC ) 8.3).
241), 138.38 (dm, C6F5, JCF ) 247), 146.54 (dm, C6F5, JCF ) 230),
2
162.08 (d, CO nonconjug, JPC ) 2.2), 164.72 (d, CdN, JPC
17.6), 169.87 (d, CO conjug, JPC ) 8.3).
)
Synthesis of 6. Complex 6 was obtained following the same
synthetic method as that reported for 1. [Pd(µ-Cl)(o-CH2C6H4P(o-
tol)2)]2 (0.178 g, 0.20 mmol) was reacted with AgClO4 (0.083 g,
0.40 mmol) and ylide L1 (0.198 g, 0.40 mmol) in dry THF to give
6 as a white solid. Obtained: 0.312 g (77.7% yield). Anal. Calcd
for C51H46ClNO8P2Pd: C, 60.96; H, 4.61; N, 1.39. Found: C, 60.93;
H, 4.88; N, 1.45. MS (FAB+, m/z, %): 904 [(M - ClO4)+, 100%].
IR (ν, cm-1): 1598 (br, νCN + νCO conjug), 1731 (νCO nonconjug).
1H NMR (CDCl3, δ): 2.34 (s, 3H, OMe), 2.54 (s, 3H, OMe), 2.65
(s, br, 6H, Me-tol), 2.80 (s, br, 2H, PdCH2), 6.87-7.41 (m, 17H,
NPh + C6H4-tol), 7.58-7.76 (m, 15H, PPh3). 31P{1H} NMR
(CDCl3, δ): 20.86 (PdC), 35.42 (s, Pd-P). 13C{1H} NMR (CDCl3,
δ): 22.82 (Me-tol), 22.87 (Me-tol), 32.08 (s, PdCH2), 51.55 (OMe),
52.08 (OMe), 64.76 (d, PdC, 1JPC ) 117.1), 122.16 (d, Cipso, PPh3,
1JPC ) 92), 123.85 (Cmeta), 125.75 (Cpara), 128.09 (Cortho), 148.32
(Cipso, NPh), 126.25 (d, C6H4-tol, JPC ) 8.3), 126.31 (s, br, C6H4-
tol), 128.20 (d, C6H4-tol, JPC ) 10.8), 129.52 (d, Cortho, PPh3, 2JPC
2
Synthesis of 9. PdCl2 (0.071 g, 0.40 mmol) and LiCl (0.034 g,
0.80 mmol) were refluxed in 15 mL of methanol until complete
dissolution of the palladium salt (30 min). After cooling, the deep-
red solution was filtered over Celite to remove insoluble impurities
(mainly Pd0). To this methanolic solution of Li2[PdCl4] (0.40 mmol)
was added ligand L1 (0.198 g, 0.40 mmol). A deep-red solid (9)
precipitated almost instantaneously. The solid was filtered, washed
with additional methanol (10 mL) and ethanol (30 mL), and dried
by suction. Obtained: 0.111 g (41.2% yield). Anal. Calcd for
C30H26Cl2NO4PPd: C, 53.55; H, 3.89; N, 2.08. Found: C, 53.81;
H, 3.95; N, 2.01. MS (FAB+, m/z, %): 600 [(M - 2Cl - H)+,
25%]. IR (ν, cm-1): 1569, 1581 (br, νCN + νCO conjug), 1739 (νCO
nonconjug). 1H NMR (CDCl3, δ): 2.20 (s, 3H, OMe), 2.89 (s, 3H,
OMe), 7.05 (m, 3H, Hp + Hm, NPh), 7.33 (d, 2H, Ho, NPh, 3JHH
)
7.8), 7.74 (m, 3H, Hp, PPh3), 8.00 (m, 6H, Hm, PPh3), 8.26 (m,
) 12.8), 131.51-132.48 (m, C6H4-tol), 132.88 (d, C6H4-tol, JPC
)
6H, Ho, PPh3). 31P{1H} NMR (CDCl3, δ): 20.27. 13C{1H} NMR
6.4), 133.89 (Cpara, PPh3), 133.90 (d, Cmeta, PPh3, 3JPC ) 9.8), 141.90
(d, C6H4-tol, JPC ) 10.2), 156.56 (d, C6H4-tol, JPC ) 31), 163.37
(CD2Cl2, δ): 52.59 (OMe), 55.38 (OMe), 70.46 (d, PdC, JPC
)
1
1
117.3), 121.62 (d, Cipso, PPh3, JPC ) 92), 127.40 (Cmeta), 128.29
2
(d, CO nonconjug, JP′C ) 1.6), 164.23 (d, CdN, JPC ) 17.7),
(Cortho), 130.20 (Cpara), 145.27 (Cipso, NPh), 130.39 (d, Cortho, PPh3,
2
3
169.95 (d, CO conjug, JPC ) 8.7).
2JPC ) 12.9), 134.38 (Cpara, PPh3), 134.99 (d, Cmeta, PPh3, JPC
)
2
10.3), 161.62 (CO nonconjug), 164.33 (d, CdN, JPC ) 17.9),
Synthesis of 7. Complex 7 was obtained following the same
synthetic method as that reported for 1. [Pd(µ-Br)(η3-C3H5)]2 (0.091
g, 0.20 mmol) was reacted with AgClO4 (0.083 g, 0.40 mmol) and
ylide L1 (0.198 g, 0.40 mmol) in dry THF to give 7 as an orange
solid. Obtained: 0.261 g (87.8% yield). Anal. Calcd for C33H31-
2
171.29 (d, CO conjug, JPC ) 8.1).
Synthesis of 10. A suspension of Pd(OAc)2 (0.200 g, 0.891
mmol) and ylide L1 (0.442 g, 0.891 mmol) in methanol (15 mL)
was refluxed for 30 min. At this point, some decomposition is
6814 Inorganic Chemistry, Vol. 45, No. 17, 2006

Palladium Complexes of a Phosphorus Ylide
evident. After cooling, Pd0 was eliminated by filtration over Celite,
and to the resulting clear yellow solution was added LiCl (0.151
g, 3.56 mmol). After 18 h of stirring (25 °C), 10 precipitated as a
pale-yellow solid, which was filtered, washed with methanol (2
mL) and ethanol (25 mL), and air-dried. Obtained: 0.241 g (42.5%
yield). Anal. Calcd for C60H50Cl2N2O8P2Pd2: C, 56.62; H, 3.96;
N, 2.20. Found: C, 56.39; H, 3.85; N, 2.00. IR (ν, cm-1): 1534
(νCN), 1647 (νCO conjug), 1734 (νCO nonconjug). 1H NMR (CDCl3,
δ): 3.09 (s, 3H, OMe), 3.38 (s, 3H, OMe), 6.57 (ddd, 1H, H3,
formational searches were performed at the ONIOM (B3LYP:UFF)
level. Then, the most stable conformers were used as starting points
for full quantum mechanics calculations. The topological properties
of the electron density and Laplacian maps were investigated using
the XAIM 1.0 program,40 whereas the topology of the negative of
the Laplacian of the charge density [L(r)] was analyzed by means
of the AIMPAC series of programs.41
Crystal Structure Determination of Ligand L1 and Com-
plexes 3 and 10‚0.5CHCl3. Crystals of adequate quality for X-ray
measurements were grown by slow vapor diffusion of ethanol into
a CH2Cl2 (L1 and 3) or CHCl3 (10) solution of the corresponding
crude compound. A single crystal (dimensions specified in Sup-
porting Information) was mounted at the end of a quartz fiber in a
random orientation and covered with epoxy.
Data Collection. Data collection was performed at room
temperature (L1) or at 100 K (3 and 10) on Bruker Smart CCD or
Oxford Diffraction Xcalibur2 diffractometers using graphite-
monocromated Mo KR radiation (λ ) 0.710 73 Å). In all cases, a
hemisphere of data was collected based on three ω-scan or φ-scan
runs. The diffraction frames were integrated using the programs
SAINT42 or CrysAlis RED,43 and the integrated intensities were
corrected for absorption with SADABS.44
3
3
4
C6H4, JPH ) 12.3, JHH ) 7.8, JHH ) 1.5), 6.72 (ddd, 1H, H6,
C6H4, 3JHH ) 7.8, 4JPH ) 2.4, 4JHH ) 1.2), 6.77 (ddd, 1H, H4, C6H4,
3JHH ) 7.5, 4JPH ) 3.9, 4JHH ) 1.2), 6.84 (d, 2H, Ho, NPh, 3JHH
)
3
4
5
6.6), 6.93 (tt, 1H, H5, JHH ) 7.5, JHH ) JPH ) 1.2), 7.19-7.42
(m, 9H, Hm + Hp, PPh2 + NPh), 7.48-7.56 (m, 2H, Ho, PPh2),
7.83-7.90 (m, 2H, Ho, PPh2). 31P{1H} NMR (CDCl3, δ): 9.56.
13C{1H} NMR (CDCl3, δ): 50.00 (OMe), 51.88 (OMe), 61.35 (d,
PdC, 1JPC ) 125.1), 123.45 (d, C3, C6H4, JPC ) 13.0), 125.19 (Cmeta
,
1
NPh), 125.84 (Cortho, NPh), 126.65 (d, C2, C6H4, JPC ) 23.5),
127.82-128.10 (br, Cpara (NPh) + C4, C5 (C6H4)), 128.90 (d, Cmeta
,
3
3
PPh2, JPC ) 12.1), 129.26 (d, Cmeta, PPh2, JPC ) 13.6), 130.30
1
(d, C6, C6H4, JPC ) 3.1), 130.56 (d, Cipso, PPh2, JPC ) 103.6),
131.95 (Cpara, PPh2), 132.32 (d, Cpara, PPh2, 4JPC ) 2.3), 132.53 (d,
2
2
C
ortho, PPh2, JPC ) 14.1), 135.00 (d, Cortho, PPh2, JPC ) 12.9),
Structure Solution and Refinement. The structures were solved
by direct or Patterson methods.45 All non-H atoms were refined
with anisotropic displacement parameters. The H atoms were placed
at idealized positions and treated as riding atoms. Each H atom
was assigend an isotropic displacement parameter equal to 1.2 times
the equivalent isotropic displacement parameter of its parent atom.
148.70 (Cipso, NPh), 153.01 (d, C1, C6H4, 2JPC ) 10.8), 164.56 (d,
CdN, 2JPC ) 10.1), 167.52 (d, CO nonconjug, 3JPC ) 4.9), 168.16
2
(d, CO conjug, JPC ) 11.2).
Reactivity of 10 with PPh3. A suspension of 10 (25 mg, 0.019
mmol) in CD2Cl2 (0.5 mL) was treated with PPh3 (10.3 mg, 0.039
mmol). A clear yellow solution of 11 was obtained instantaneously.
The NMR spectra were recorded immediately and showed 100%
2
The structures were refined to Fo , and all reflections were used in
the least-squares calculations.46
1
spectroscopic yield of 11 as a single isomer. H NMR (CD2Cl2,
Acknowledgment. Funding by the Direccio´n General de
Investigacio´n Cient´ıfica y Te´cnica (Spain; Projects CTQ2005-
01037, CTQ2005-09000-C02-01, CTQ2005-03141, and
CTQ2005-06909-C02-01) is gratefully acknowledged. The
authors thank Dr. Teodor Parella (Servei RMN, Universitat
Auto`noma de Barcelona) for his invaluable support in
HOESY experiments. T.S. thanks the MECD (Spain) for a
postdoctoral fellowship.
δ): 3.20 (s, 3H, OMe), 3.39 (s, 3H, OMe), 6.22 (m, 1H, C6H4),
6.41 (m, 1H, C6H4), 6.65-6.75 (m, 2H, C6H4), 7.01-7.93 (m, 30H,
PPh3 + PPh2 + NPh). 31P{1H} NMR (CD2Cl2, δ): 13.79 (s, 1P,
PPh2), 28.13 (s, 1P, Pd-PPh3).
Computational Details. Calculations were performed using the
Gaussian98 series of programs.37 The DFT was used, with the
B3LYP functional.26 Effective core potentials and their associate
double-ú LANL2DZ basis set were used for the Pd atom.37,38 The
N, O, P, and Cl atoms, as well as the ylide CR and iminic and
carbonyl C atoms, were represented by means of the 6-31G(d) basis
set. The H and C atoms of the methyl and phenyl substituents were
represented by means of the 6-31G basis set.39 All geometry
optimizations were full with no restrictions. For the six-membered-
ring structure optimization in 9, the conformation of the X-ray
structure of 3 was used as a starting point for geometry optimization.
For the four- and five-membered-ring structures, systematic con-
Supporting Information Available: Tables giving data col-
lection parameters, atomic coordinates, complete bond distances
and angles, and thermal parameters for the X-ray crystal structure
determination of L1, 3, and 10‚0.5CHCl3; tables giving calculated
Cartesian geometries and energies of L1 and 9, 9co, and 9cn, with
their corresponding figures (6-9); and tables of comparisons of
structural parameters and NPA atomic charges. This material is
available free of charge via the Internet at http://pubs.acs.org.
(37) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R.
L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara,
A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Andres, J. L.; Gonzalez, C.; Head-Gordon, M.;
Replogle, E. S.; Pople, J. A. Gaussian98, revision A.6; Gaussian,
Inc.: Pittsburgh, PA, 1998.
(38) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.
(39) (a) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Phys. Chem. 1972, 56,
2257. (b) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28,
213. (c) Francl, M. M.; Pietro, W. J.; Hehre, W. J.; Binkley, J. S.;
Gordon, M. S.; DeFrees, D. J.; Pople, J. A. J. Chem. Phys. 1982, 77,
3654.
IC060706F
(40) This program was developed by Jose´ Carlos Ortiz and Carles Bo,
Universitat Rovira i Virgili, Tarragona, Spain.
(41) (a) Biegler-Ko¨nig, F. W.; Bader, R. F. W.; Tang, Y. H. J. Comput.
Chem. 1982, 3, 317. (b) Bader, R. F. W.; Tang, Y. H.; Tal, Y.; Biegler-
Ko¨nig, F. W. J. Am. Chem. Soc. 1984, 104, 946.
(42) SAINT, version 5.0; Bruker Analytical X-ray Systems: Madison, WI.
(43) CrysAlis RED, version 1.171.27p8; Oxford Diffraction Ltd., Oxford,
U.K., 2005.
(44) Sheldrick, G. M. SADABS: Empirical absorption correction program;
Go¨ttingen Universitat: Go¨ttingen, Germany, 1996.
(45) Sheldrick, G. M. SHELXS-86. Acta Crystallogr., Sect. A 1990, 46,
467.
(46) Sheldrick, G. M. SHELXL-97: FORTRAN program for the refinement
of crystal structures from diffraction data; Go¨ttingen Universitat:
Go¨ttingen, Germany, 1997. Molecular graphics were done using the
commercial package: SHELXTL-PLUS, release 5.05/V; Siemens
Analytical X-ray Instruments, Inc.: Madison, WI, 1996.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6815