Ligand-induced and thermally-induced orthometalation of the bis(ylide) ligand [Ph3P=C(H)]2CO. Generation of the C,C-chelating group C6H4-2-PPh2C(CH)COCH2PPh 3

Article abstract of DOI:10.1021/om980625u

The dinuclear complex [Pd(μ-Cl){[C(H)PPh₃] ₂CO}]₂(ClO₄)₂ (2c) undergoes thermal rearrangement in refluxing NCMe, giving the dinuclear orthometalated derivative [Pd(μ-Cl)-(C₆H₄-2-

Full text of DOI:10.1021/om980625u

Organometallics 1998, 17, 5887-5900
5887
Liga n d -In d u ced a n d Th er m a lly-In d u ced Or th om eta la tion
of th e Bis(ylid e) Liga n d [P h 3P dC(H)]2CO. Gen er a tion of
th e C,C-Ch ela tin g Gr ou p C6H4-2-P P h 2C((H)COCH2P P h 3
Larry R. Falvello, Susana Ferna´ndez, Rafael Navarro,* Angel Rueda, and
Esteban P. Urriolabeitia
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-Consejo Superior de Investigaciones Cientı´ficas,
E-50009 Zaragoza, Spain
Received J uly 22, 1998
The dinuclear complex [Pd(µ-Cl){[C(H)PPh3]2CO}]2(ClO4)2 (2c) undergoes thermal rear-
rangement in refluxing NCMe, giving the dinuclear orthometalated derivative [Pd(µ-Cl)-
(C6H4-2-PPh2C(H)COCH2PPh3)]2(ClO4)2 (4c) as a mixture of two diastereoisomers (RR/ SS
and RS/ SR). The orthometalation proceeds through an electrophilic substitution pathway,
and the formation of the C,C-chelating ligand (C6H4-2-PPh2C(H)COCH2PPh3) results from
an intramolecular acid-base reaction in which the proton generated in the orthometalation
reaction is captured by an ylide group. A decrease in the cone angle of the phosphonium
group dramatically reduces the conversion of the bis(ylide) ligand into the orthometalated
ligand. The orthometalation reaction can also be induced by ligand addition to the dimer
[Pd(µ-Cl){[C(H)PPh3]2CO}]2(ClO4)2 (2c) under very mild conditions. For instance, complex
2c reacts with PPh3 or PPhMe2 in CH2Cl2 at room temperature to give [PdCl(C6H4-2-
PPh2C(H)COCH2PPh3)(PR3)](ClO4) (PR3 ) PPh3 8, PPhMe2 9). Less sterically hindered
ligands such as pyridine or 3,5-lutidine react with 2c to give in a first step the bis(ylide)
complexes [PdCl{[C(H)PPh3]2CO}(L)](ClO4) (L ) py; 3,5-lut), which are transformed into
the corresponding orthometalated derivatives [PdCl(C6H4-2-PPh2C(H)COCH2PPh3)(L)](ClO4)
(L ) py 6, 3,5-lut 7) by thermal treatment in refluxing NCMe. This different behavior is
explained on the grounds of the different steric requirements of the incoming ligand
(phosphine/pyridine). Similar behavior has been observed for the complex [Pd{[C(H)PPh3]2-
CO}(NCMe)2](ClO4)2 (3c). 3c reacts with py or dppm giving [Pd{[C(H)PPh3]2CO}(L)2](ClO4)2
(L ) py 10, L2 ) dppm 11), which is transformed into [Pd(C6H4-2-PPh2C(H)COCH2PPh3)-
(L2)](ClO4) (L ) py 12, L2 ) dppm 13a + dppm-O 13b) by refluxing in NCMe. However,
complex 3c reacts with PPh3, dppe, or phen in CH2Cl2 at room temperature giving [Pd-
(C6H4-2-PPh2C(H)COCH2PPh3)(L2)](ClO4) (L2 ) PPh3, NCMe 14, dppe 15, phen 16). Complex
3c is not transformed into its corresponding orthometalated derivative [Pd(C6H4-2-
PPh2C(H)COCH2PPh3)(NCMe)2](ClO4)2 (17) by refluxing in NCMe, but 17 can be obtained
by treatment of 4c with TlClO4 in NCMe. The orthometalation reaction of the bis(ylide)
ligand can even occur spontaneously. The acetate-bridged dimer [Pd(µ-OOCCH3){[C(H)PPh3]2-
CO}]2(ClO4)2 (18) transforms spontaneously at room temperature into the mixed orthometa-
lated bis(ylide)complex [(C6H4-2-PPh2C(H)COCH2PPh3)Pd(µ-OOCCH3)2Pd{[C(H)PPh3]2CO}]-
(ClO4)2 (19). The crystal structure of [Pd(C6H4-2-PPh2C(H)COCH2PPh3)(PPh3)(NCMe)](ClO4)2
(14) has been determined and reveals the presence of an orthometalated C6H4-2-PPh2 unit,
a C-linked ylide Pd-C(H), and a phosphonium fragment CH2PPh3. The phosphine group is
coordinated cis to the orthometalated carbon atom.
In tr od u ction
C(H)COR (R ) Me, Ph, OMe, NMe2) and Ph3PdC(H)-
CN.2-7 Throughout these studies, we have observed the
Ylides of phosphorus are now recognized as a class of
extremely powerful ligand systems that form complexes
with both main group and transition metals.1 In recent
papers, we have described a selection of the chemistry
of PdII and PtII with R-stabilized ylides, such as Ph3Pd
(2) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Pascual, I.; Urriola-
beitia, E. P. J . Chem. Soc., Dalton Trans. 1997, 763, and references
therein.
(3) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P.
Inorg. Chem. 1996, 35, 3064, and references therein.
(4) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P.
Inorg. Chem. 1997, 36, 1136, and references therein.
(5) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P.
New. J . Chem. 1997, 21, 909.
(1) (a) J ohnson, A. W.; Kaska, W. C.; Starzewski, K. A. O.; Dixon,
D. A. Ylides and Imines of Phosphorous; J ohn Wiley & Sons: New
York, 1993; Chapter 14, and references therein. (b) Belluco, U.;
Michelin, R. A.; Mozzon, M.; Bertani, R.; Facchin, G.; Zanotto, L.;
Pandolfo, L. J . Organomet. Chem. 1998, 557, 37.
(6) Ferna´ndez, S.; Garc´ıa, M. G.; Navarro, R.; Urriolabeitia, E. P.
J . Organomet Chem. 1998, 561, 67.
10.1021/om980625u CCC: $15.00 © 1998 American Chemical Society
Publication on Web 12/03/1998

5888 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
Ch a r t 1
ability of these ylides to behave as ambidentate ligands
(except for the NMe2 derivative7), and it has been
demonstrated that control can be exerted over the
bonding modes: that given an organometallic substrate
the coordination mode of a given ylide can be predicted
and, conversely, a substrate can be designed to obtain
a given bonding mode.
More recent studies are focused on the reactivity of
palladium complexes with bis(ylides) such as Ph3Pd
C(H)COC(H)dPPh3. In a first communication8 we have
described the synthesis of palladium(II) complexes in
which this bis(ylide) acts as a C,C-chelate through the
two ylidic carbon atoms. Through subsequent study we
have now found an interesting reactivity of these
chelates, namely, the rearrangement of the C,C-
coordinated ligand [C(H)PPh3]2CO to give the ortho-
metalated unit C6H4-2-PPh2C(H)COCH2PPh3, which is
linked to the metal center through an aromatic carbon
atom and through an ylidic carbon atom. This C-H
activation can be induced either thermally (refluxing
NCMe) or by addition of auxiliary ligands under very
mild conditions (CH2Cl2, room temperature). Due to the
intrisic interest of reactions involving C-H activation9
and also due to the fact that the number of C,C-
orthometalated complexes is relatively scarce10-20 com-
pared with other C,X-cyclometalated (X ) heteroatom)
derivatives,9,21 we have performed a systematic study
of this particular C-H activation in bis(ylide) com-
plexes. Even though the orthometalation of ylides has
been known for several years,10-13,15,18 we are not aware
of a mechanistic proposal for this reaction, nor of a study
of the influence of different parameters on this process.
To shed light on these questions, we report here our first
results with this previously unexplored chemistry.
COCH2PPh3)](ClO4)2 (4c) can be isolated in good yield
(see Chart 1 and eq 1). The mass spectrum of 4c
(1)
Resu lts a n d Discu ssion
Th er m a lly-In d u ced Or th om eta la tion s. The pro-
longed reflux in NCMe (8 h) of a suspension of the
yellow dimer [Pd(µ-Cl){[C(H)PPh3]2CO}]2(ClO4)2 (2c)
affords an orange solution from which the orthometa-
lated dinuclear complex [Pd(µ-Cl)(C6H4-2-PPh2C(H)-
confirms its dinuclear nature, through the observation
of a peak of medium intensity at 1541 amu, which
corresponds to the dinuclear dicationic fragment plus
one ClO4- group. The IR spectrum of 4c shows a broad
absorption at 278 cm-1, suggesting the presence of the
Pd(µ-Cl)2Pd unit, and a strong absorption at 1648 cm-1
attributed to the carbonyl group. This latter absorption
is shifted to higher energies with respect to that in the
starting product 2c (1617 cm-1),8 and this shift agrees
with the change in the chemical environment of the
carbonyl group on passing from the bis(ylide) in 2c to
the ylide-phosphonium in 4c.
(7) Barco, I. C.; Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urrio-
labeitia, E. P. J . Chem. Soc., Dalton Trans. 1998, 1699.
(8) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Rueda, A.; Urriola-
beitia, E. P., Inorg. Chem., in press.
(9) Ryabov, A. D. Chem. Rev. 1990, 90, 403, and references therein.
(10) Baldwin, J . C.; Kaska, W. C. Inorg. Chem. 1979, 18, 686.
(11) Illingsworth, M. L.; Teagle, J . A.; Burmeister, J . L.; Fultz, W.
C.; Rheingold, A. L. Organometallics 1983, 2, 1364.
(12) Teagle, J . A.; Burmeister, J . L. Inorg. Chim. Acta 1986, 118,
65.
(13) Vicente, J .; Chicote, M. T.; Ferna´ndez-Baeza, J . J . Organomet.
Chem. 1989, 364, 407.
(14) Liu, C.-H.; Li, C.-S.; Cheng, C.-H. Organometallics 1994, 13,
18.
(15) Vicente, J .; Chicote, M. T.; Lagunas, M. C.; J ones, P. G.;
Bembenek, E. Organometallics 1994, 13, 1243.
(16) Vicente, J .; Chicote, M. T.; Lagunas, M. C.; J ones, P. G. Inorg.
Chem. 1995, 34, 5441.
(17) (a) Avis, M. W.; Vrieze, K.; Ernsting, J . M.; Elsevier: C. J .;
Veldman, N.; Spek, A. L.; Katti, K. V.; Barnes, C. L. Organometallics
1996, 15, 2376. (b) Canty, A. J .; van Koten, G. Acc. Chem. Res. 1995,
28, 406.
(18) Facchin, G.; Zanotto, L.; Bertani, R.; Nardin, G. Inorg. Chim.
Acta 1996, 245, 157.
1
The H NMR spectrum of 4c shows, as expected, two
identical sets of signals (molar ratio 1.77:1) correspond-
ing to the two possible diastereoisomers (RR/ SS and
RS/ SR). Although the reaction is slightly stereoselective
(de ) 27.8%), we have not been able to determine the
absolute configurations in the major isomer. The ob-
served pattern of signals reveals the presence of an ylide
C-bonded to the Pd center and of a phosphonium group.
The resonances attributed to the methine protons
appear as doublet of doublets at 4.58 and 4.52 ppm with
(19) Avis, M. W.; van der Boom, M. E.; Elsevier: C. J .; Smeets, W.
J . J .; Spek, A. L. J . Organomet. Chem. 1997, 527, 263.
(20) Bennet, M. A.; Dirnberger, T.; Hockless, D. C. R.; Wenger, E.;
Willis, A. C. J . Chem. Soc., Dalton Trans. 1998, 271.
(21) Omae, I. Organometallic Intramolecular-Coordination Com-
pounds; Elsevier Science Publishers: Amsterdam, New York, 1986.
2
4
coupling constants J P-H around 4 Hz and J P-H around

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5889
2.5 Hz, this fact also showing the inequivalence of the
phosphorus atoms. On the other hand, the resonances
assigned to the CH2PPh3 protons appear as AB spin
systems coupled with the adjacent P nucleus. The 13C-
{1H} NMR spectrum of 4c also shows two sets of signals.
The carbonyl group appears in both isomers as a triplet.
Two doublet resonances at 157.58 (major isomer) and
157.49 (minor isomer) ppm signal the existence of the
Pd-Corthometalated bond, since this region (155-164 ppm)
is characteristic of this kind of bond.14,17a,20 The ylidic
carbon atom of the major isomer appears at 31.35 ppm
as a doublet of doublets with characteristic coupling
constants for a C-bonded ylide2-7 (1J P-C ) 66.8 Hz, 3J P-C
) 8.8 Hz). The 31P{1H} NMR spectrum shows two AB
spin sytems, as expected for two diastereoisomers with
two chemically inequivalent P atoms each.
The presence of only two sets of signals in the NMR
spectra also reveals that only one geometrical isomer
(anti or syn) is present. Although with the current data
it is not possible to deduce which geometrical isomer
has been obtained, further reactivity of this complex22
has shown that 4c is actually obtained as the anti
isomer.
a polar solvent with high coordinating strength and an
intermediate boiling point (80 °C) such as NCMe does
the orthometalation reaction proceed. These results are
similar to those described by Vicente et al.13
As has been pointed out,9,17,21,23-26a the orthometala-
tion reaction of a given ligand requires the concurrence
of several factors such as the presence of bulky groups
in the donor atom or the existence of some degree of
flexibility in the ligand to be orthometalated. In addi-
tion, the existence of ring strain in four-membered
metallocycles could also be responsible for the ortho-
metalation and transformation of these sterically hin-
dered rings into the more stable five-membered cycles.
We think that this last factor especially applies to our
case. The bulky phenyl groups on both P atoms of the
C,C-chelated bis(ylide) ligand and the fact that both
PPh3 fragments lie on the same side of the molecular
plane8 promote the orthometalation. In addition, in the
crystal structure of the dinuclear derivative [Pd(µ-Cl)-
{[C(H)PPh3]2CO}]2(ClO4)2 (2c),8 one ortho H atom of one
phenyl group is in close proximity to the palladium(II)
center and is most likely to orthometalate; however, we
must note that even if this proximity is a prerequisite,
this “nonbonding” interaction is not the true intermedi-
ate stage in the C-H bond activation process.26b Thus,
we think that the driving force for orthometalation in
our complexes is the simultaneous presence of a four-
membered cycle (ring strain) and one bulky PPh3 group
supported at each donor ylidic carbon atom (steric
hindrance).
To elucidate the nature of this orthometalation reac-
tion, we have studied the influence of several param-
eters on the global process. The influence of the phos-
phonium group, the solvent, the temperature, the net
charge of the starting complex, and the addition of
halide ligands have been examined.
Two new phosphonium salts have been obtained,
[PhEt2PCH2COCH2PPhEt2]Cl2 and [Ph2EtPCH2COCH2-
PPh2Et]Cl2, by reaction of the corresponding phosphine
and 1,3-dichloroacetone (2:1 molar ratio) in CHCl3 (see
Experimental Section). Following the same experimen-
tal method described for the synthesis of 1c and 2c8 (see
Experimental Section), we have synthesized the neutral
derivatives Cl2Pd{[CH(PR3)]2CO]} (PR3 ) PPhEt2 1a ,
PPh2Et 1b) and the dinuclear [Pd(µ-Cl){[CH(PR3)]2-
CO]}]2(ClO4)2 (PR3 ) PPhEt2 2a , PPh2Et 2b) (see Chart
1). Complexes 2a and 2b were subjected to the same
experimental conditions which produced the orthometa-
lation of 2c to give 4c (NCMe, reflux, 8 h). After the
reaction and usual workup, complex 2a did not show
evidence of transformation and was recovered in almost
quantitative yields. However, the refluxing of complex
2b afforded a mixture in which were identified the
starting product 2b together with some of the possible
isomers of the resulting product 4b (now there are four
chiral centers in the molecule). The approximate con-
version was 50% based on the integrals of the 31P
resonances (see Experimental Section).
The importance of the solvent in the development of
the reaction is not negligible. Other solvents were tried
instead of NCMe, with negative results. The use of
coordinating solvents but with lower boiling points such
as MeOH or acetone resulted in the recovery of the
starting product 2c. On the other hand, the use of high
boiling point solvents without coordinating ability such
as toluene resulted in the decomposition of the starting
product 2c and formation of black palladium. Only with
The reactivity of complexes 2a and 2b provides
additional proof, since a decrease in the cone angle of
the PR3 group at the ylidic carbon atom results in a
gradual quench of the orthometalation reaction. Com-
plex 2a , which possesses the phosphine with the small-
est cone angle (PPhEt2, 136°),27 does not show ortho-
metalation at all, while complex 2b (PPh2Et, 140°)27
shows only partial conversion, both under the same
conditions in which 2c (PPh3, 145°)27 orthometalates in
100% spectroscopic yield. The importance of steric
effects in the orthometalation reaction will be proved
definitively in the next section (see Ligand-Induced
Orthometalations).
We have also compared the reactivity of complexes
1c (neutral), 2c (dinuclear, dicationic), and 3c (mono-
nuclear, dicationic) under the same conditions (NCMe,
reflux, 8 h) aiming to determine the influence of the net
charge of the starting compound on the orthometalation
reaction. The reactions were followed by 1H and 31P-
{1H} NMR spectroscopy (see Experimental Section).
Similar conversions were obtained for complexes 1c and
2c, and these results can be rationalized taking into
account the following observations: (a) the dinuclear
complex 2c in NCCD3 is fully dissociated into the
monomer [PdCl{[C(H)PPh3]2CO}(NCCD3)]+, character-
ized by its NMR spectra (see Experimental Section); (b)
the neutral complex 1c, when dissolved in NCCD3,
(23) Dehand, J .; Pfeffer, M. Coord. Chem. Rev. 1976, 18, 344.
(24) Shaw, B. L. J . Organomet. Chem. 1980, 200, 311.
(25) Omae, I. Coord. Chem. Rev. 1988, 83, 137.
(26) (a) Evans, D. W.; Baker, G. R.; Newkome, G. R. Coord. Chem.
Rev. 1989, 93, 155. (b) Dupont, J .; Beydoun, N.; Pfeffer, M. J . Chem.
Soc., Dalton Trans. 1989, 1715.
(27) McAuliffe, C. A. In Comprehensive Coordination Chemistry;
Wilkinson, G., Gillard, R. D., McCleverty, J . A., Eds.; Pergamon
Press: Oxford, 1987: Vol. 2, p 1012ff, and references therein.
(22) Complex 4c reacts with Hg(OOCCH3)2 to give the trinuclear
derivative [Pd2(µ-Cl)2(C6H4-2-PPh2C(H)COC(H)PPh3)2(µ-Hg)](ClO4)2,
and the X-ray crystal structure of this complex reveals the anti
disposition of the cyclometalated rings. Falvello, L. R.; Ferna´ndez, S.;
Navarro, R.; Urriolabeitia, E. P. Manuscript submitted to Inorg. Chem.

5890 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
Sch em e 1
exists as an equilibrium mixture between the neutral
form 1c and the cationic form [PdCl{[C(H)PPh3]2CO}-
(NCCD3)]+; (c) the existence of a true equilibrium
between these two forms was established by measure-
ment of the NMR spectra of 1c at different temperatures
and by addition of LiCl to an NCCD3 solution of 2c. All
these facts are compiled in Scheme 1. Thus, the “active
species” in the orthometalation reaction of 1c and 2c is
the monocationic complex [PdCl{[C(H)PPh3]2CO}-
(NCCD3)]+ (named A in Scheme 1), which orthometa-
lates to give the monocationic solvate B. This solvate B
can dimerize to give 4c by addition of a precipitating
agent (Et2O) or, through reaction with Cl-, can give 5.
It is worth noting that the reaction of 3c in refluxing
NCMe does not afford the corresponding orthometalated
[Pd(C6H4-2-PPh2C(H)COCH2PPh3)(NCMe)2]2+ (17) (which
can easily be obtained by reaction of 4c with TlClO4 in
NCMe; see Scheme 5) and that the starting product is
recovered at the end of the reaction. We are unaware
of the reasons for this behavior, but it seems that the
Cl- ligands are not simple spectators in this reaction.
There are two generally accepted mechanisms for
C-H bond activation by palladium(II): oxidative addi-
tion resulting from nucleophilic attack by the metal on
the phenyl ring and electrophilic substitution in the
aromatic ring. Although there are known examples in
which the Pd(II) center behaves as a nucleophile,9 most
reports of cyclopalladation describe this reaction as an
electrophilic substitution. In some cases, alteration of
the electron density at the aromatic ring or the metal
center provides evidence for this mechanism. In our
case, the results obtained with complexes 2a , 2b, and
2c can be related with an electrophilic substitution
mechanism, since a decrease in the basicity of the
phosphine (PPhEt2 in 2a > PPh2Et in 2b > PPh3 in 2c)
would result in a decrease in the electron-donating
capacity of the ylidic carbon in the respective complexes
and, consequently, in a more favorable setting for
electrophilic attack by the metal center following the
sequence 2c > 2b > 2a . However, this argument is not
a definitive proof for this mechanism, since the decrease
in the electron density at the metal center follows the
same order as the increase of the cone angle of the
phosphine, as already described (see above).
by coordinated or free bases.17 In our case, we have an
internal base in the form of two ylidic C atoms of the
C,C-chelate bis(ylide) ligand, which can capture the
proton resulting from the C-H bond activation. With
these data we propose the mechanism shown in Scheme
2 for the orthometalation of complex 2c. The reaction
begins with the cleavage of the halide bridging system
and formation of the “active species” A, in which the
electrophilic attack by the metal on the phenyl group
takes place. The proton resulting from the C-H bond
activation is captured by one of the basic ylidic frag-
ments, giving the species B, which contains a phospho-
nium group. Dimerization of B results in the formation
of 4c.
The generation of the phosphonium group in the final
product can be rationalized in two different ways. One
of these is that shown in Scheme 2 involving an
intramolecular acid-base reaction and is similar to that
described in the orthometalation of bis(N-arylimino-
phosphoranyl)alkanides of Pd(II) and Pt(II).17a The other
route would involve the presence of HCl, which proto-
nates the metal center; transfer of this proton to one
ylidic group would be followed by elimination of a
phosphonium fragment, oxidative addition of the phen-
ylic C-H bond, and reductive elimination of HCl, as has
been described for the formation of the anionic18 complex
{PtCl2[C(H)COMe(PPh2-o-C6H4)]}- (that is, the C-H
activation takes place after the formation of the phos-
phonium group). However, although this second alter-
native could explain the role of the Cl- ligands (see
above), we propose the first pathway due to the follow-
ing facts: (a) the orthometalation reaction performed
in the presence of K2CO3 did not show an appreciable
decrease in yield; (b) the orthometalation of the ylide-
phosphonium salt [Ph3PdC(H)COCH2PPh3]ClO4 was
attempted with a variety of Pd(II) precursors, but it was
always unsuccessful even in the presence of external
bases (thus, the reaction is intramolecularly base-
assisted); (c) if HCl were formed during the reaction,
its elimination under the reaction conditions used
(reflux/air) would be especially favorable.
In conclusion, the thermal orthometalation of the C,C-
chelating bis(ylide) ligand [C(H)PPh3]2CO generates the
C,C-chelating [C6H4-2-PPh2C(H)COCH2PPh3] ligand
through an electrophilic substitution at the phenyl ring
and an intramolecular acid-base reaction. The driving
Another argument in favor of electrophilic substitu-
tion is the fact that these reactions are often assisted

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5891
Sch em e 2
Sch em e 3
force for this reaction seems to be related to the steric
repulsions between the two PPh3 fragments in the
chelating bis(ylide) group and to the transformation of
a four-membered ring into a five-membered ring. More-
over, the orthometalation can be promoted under very
mild conditions by the addition of ligands. As will be
described in the following section, we have also studied
the reactivity of complexes 2c and 3c toward a variety
of neutral mono- and bidentate ligands.
Liga n d -In d u ced Or th om eta la tion s. In a previous
paper8 we described the reactivity of the dinuclear
complex 2c toward different neutral monodentate ligands
L (1:2 molar ratio, CH2Cl2, room temperature) such as
pyridine, lutidine, and phosphorus ylides. These reac-
tions resulted in the cleavage of the halide bridging
system and formation of the mononuclear derivatives
[PdCl{[C(H)PPh3]2CO}L]ClO4 (see Scheme 3, path a1).
The reactivity of 2c with other neutral monodentate
ligands such as phosphines shows a very different
behavior.
with the proposed structure in Scheme 3. The IR spectra
show the carbonyl absorption at about 1630 cm-1
,
shifted to higher energies with respect to that in C,C-
bis(ylide) complexes.8 On the other hand, the Pd-Cl
stretch appears in the 270 cm-1 region, suggesting that
the Cl ligand is trans to the orthometalated carbon
1
atom.28 The H NMR spectra show the presence of the
CH2P group as an AB spin system coupled to the P atom
of the phosphonium group and also show the CH ylidic
proton as a triplet of doublets. The shape of the latter
signal means that this proton is coupled with the
adjacent P atom in the ring, with the phosphonium atom
and with the P atom of the PR3 ligand. The magnitudes
of the coupling constants strongly suggest that the PR3
ligand is trans to the ylidic carbon atom. Additional
evidence for this stereochemistry can be found in the
13C{1H} NMR spectrum of 8. There, the orthometalated
carbon atom (C1) appears at 163.86 ppm as a doublet
(2J P-C ) 20 Hz) by coupling with the P atom in the ring,
while a coupling with a trans phosphine should give a
coupling constant of about 110-130 Hz.17a Moreover,
the 31P{1H} NMR spectra of 8 and 9 show the same
pattern of resonances (with the expected difference in
The reaction of 2c with 2 equiv of phosphines PR3
(PPh3, PPhMe2) in CH2Cl2 at room temperature results
in the formation of the cationic orthometalated deriva-
tives [PdCl(C6H4-2-PPh2C(H)COCH2PPh3)L]ClO4 (L )
PPh3 8, PPhMe2 9) in very good yields (see Scheme 3,
path b). The spectroscopic data of 8 and 9 are in keeping
(28) Crociani, B.; Boschi, T.; Pietropaolo, R.; Belluco, U. J . Chem.
Soc. (A) 1970, 531.

5892 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
the chemical shift of the PR3 ligand), in which the P
atom in the ring appears as a doublet of doublets by
coupling with the trans-PR3 ligand and with the phos-
mixture shows the presence of three resonances at 31.45
(Pd-PPh3), 26.75, and 23.67 ppm (bis(ylide)), which are
consistent with the proposed intermediate. On warming
this solution to room temperature, these resonances
disappear and only the resonances attributed to 8 are
observed. Thus, the reaction begins with the cleavage
of the halide bridging system, giving the intermediate
[PdCl{[C(H)PPh3]2CO}(PPh3)]ClO4, which is very un-
stable and undergoes internal metalation to give 8, and
it is sensible to assume that this metalation occurs
through a mechanism similar to that described for 2c.
We reported in the first section that complex 3c does
not undergo thermal orthometalation. Prompted by the
results obtained in the synthesis of 8 and 9, we have
explored the reactivity of this complex toward different
neutral monodentate and bidentate ligands. The reac-
tion of 3c with 2 equiv of pyridine results in the
formation of the bis(ylide) derivative [Pd{[C(H)PPh3]2-
CO}(py)2](ClO4)2 (10), which was characterized by its
analytical and spectroscopic data (see Experimental
Section). In accord with the foregoing discussion of the
complexes [PdCl{[C(H)PPh3]2CO}(py)]ClO4 (see preced-
ing paragraphs), complex 10 is stable toward ortho-
metalation since the steric repulsion between the pyri-
dine ligands and the ylidic C(H)PPh3 fragments is not
severe. More interesting is the reaction between 3c and
dppm (Ph2PCH2PPh2) in 1:1 molar ratio (CH2Cl2, room
temperature), which results in the formation of [Pd-
{[C(H)PPh3]2CO}(dppm)](ClO4)2 (11) (see Scheme 4,
path a1). The 31P{1H} NMR spectrum of 11 shows only
two resonance triplets at 22.40 and -25.54 ppm. This
spectrum shows that the molecule has high symmetry
since the two P atoms of the dppm ligand (-25.54 ppm)
are equivalent, as are the two P atoms of the bis(ylide)
ligand (22.40 ppm). The location of the dppm resonances
at high field shows that this ligand is coordinated as a
P,P-chelate30 and, thus, that the bis(ylide) ligand acts
as a C,C-chelate. The triplet shape of each signal results
from virtual coupling between the P atoms of the spin
system. The 1H NMR spectrum of 11 confirms the
proposed structure (see Scheme 4) and shows the
presence of three resonances of relative intensity 2:1:1.
The resonance at lowest field (5.16 ppm) is attributed
to the ylidic CH protons and appears as a false quin-
tuplet due to virtual coupling with the four P atoms
present in the molecule. The other two resonances at
higher field (4.83 and 4.02 ppm) are attributed to the
CH2 protons of the dppm, and each signal appears as a
doublet of triplets (an AB spin system coupled to two
equivalent P atoms).
1
phonium group. Finally, the H-1H NOESY spectrum
of complex 9 shows a strong NOE interaction between
the Me resonances of the PPhMe2 ligand (1.57 and 1.37
ppm) and the H6 proton of the orthometalated C6H4
group (6.82 ppm), indicating their proximity and hence
their relative cis disposition. All of these data support
the structure shown in Scheme 3 for 8 and 9 in which
the PR3 ligand is trans to the ylidic C atom, in line with
the transphobia of the phosphine ligands to coordinate
trans to an orthometalated carbon atom.29
The different behavior observed in the reaction of 2c
with pyridines and with phosphines can be related to
steric effects. Ligands such as pyridine, which can be
accommodated in a plane perpendicular to the molecular
plane, do not exert a considerable influence upon the
ylidic C(H)PPh3 group located in the cis position, and
the molecule remains stable toward orthometalation.8
However, the volume occupied by ligands such as
phosphines is considerably larger and such ligands could
crowd the two cis ylidic C(H)PPh3 fragments. As a
result, the molecule evolves to give a less hindered
situation via orthometalation. Differences in the nature
of the donor atom (N versus P) do not seem to play an
important role here since, as we will see later, we have
been able to obtain complexes with P donor ligands and
the C,C-chelating bis(ylide) (complex 11) and ortho-
metalated complexes with N donor ligands (complex 16),
and these differences can be explained taking into
account only steric factors. We have not tried reactions
with smaller phosphines (PMe3), and the reactions with
larger amines (NEt3) are more complicated since they
involve deprotonation of the CH2PPh3 group generated.
The synthesis of the complexes [PdCl(C6H4-2-PPh2C-
(H)COCH2PPh3)L]ClO4 (L ) py 6, 3,5-lutidine 7) can
be accomplished in three ways: (a) by reaction of 4c
with the appropriate amount of ligand; (b) by refluxing
complex 2c in NCMe in the presence of an excess of
ligand; and (c) by refluxing the corresponding C,C-
chelating bis(ylide) complexes [PdCl{[C(H)PPh3]2CO}L]-
ClO4 in NCMe. In our experience, the best results have
been obtained using method (c), and this method is
described in the Experimental Section (see also Scheme
3, path a2).
The reaction of 2c with PPh3 has been followed by
NMR spectroscopy. A solution of 2c in CD2Cl2 was
mixed with PPh3 (1:2 molar ratio), and the 1H NMR
spectrum of the mixture was measured at 183 K 5 min
after mixing (the time needed for locking and shim-
From these data it is clear that the nature of the
donor atom is not determinative for the orthometalation,
since with both trans P- and N-donor atoms the result-
ing bis(ylide) complexes 10 and 11 are stable toward
orthometalation. An explanation for the stability of 10
has been given in the preceding paragraphs, and we
think that the stability of complex 11 can be explained
by taking into account that both ligands (the bis(ylide)
and the dppm) are chelates and that both chelates are
four-membered rings; hence they show small bite angles
(for instance, for complex 2c8 the value of the bite angle
is about 68° and for dppm-chelating complexes a typical
1
ming). This H NMR spectrum shows, in addition to the
resonances for 8, two new resonances of very weak
intensity: a doublet of doublets at 3.72 ppm (2J P-H
)
4
6.2 Hz, J P-H ) 3.4 Hz) and a doublet of doublets of
doublets at 2.64 ppm (3J P-H ) 11.4 Hz, 2J P-H ) 5.0 Hz,
4J P-H ) 2.3 Hz). These two resonances could indicate
the presence of the intermediate complex [PdCl{[C(H)-
PPh3]2CO}(PPh3)]ClO4, since the first resonance would
correspond to the ylidic proton cis to the PPh3 ligand
and the second to the ylidic proton trans to the PPh3
group. Moreover, the 31P{1H} NMR spectrum of this
(29) Vicente, J .; Arcas, A.; Bautista, D.; J ones, P. G. Organometallics
1997, 16, 2127, and references therein.
(30) Falvello, L. R.; Fornie´s, J .; Navarro, R.; Rueda, A.; Urriolabeitia,
E. P. Organometallics 1996, 15, 309, and references therein.

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5893
Sch em e 4
value of this angle30 is about 74°). Thus, the interactions
between the Ph groups of the dppm ligand and the ylidic
fragments C(H)PPh3 are not strong enough to promote
the orthometalation.
The reaction of 3c with other monodentate or biden-
tate ligands follows different trends. The reaction of 3c
with PPh3 (1:1 molar ratio) in CH2Cl2 at room temper-
ature results in the formation of [Pd(C6H4-2-PPh2C(H)-
COCH2PPh3)(PPh3)(NCMe)](ClO4)2 (14), even if the
reaction is performed in the presence of an excess of
PPh3. On the other hand, the reaction of 3c with dppe
or phen (1:1 molar ratio) in CH2Cl2 at room temperature
affords the dicationic derivatives [Pd(C6H4-2-PPh2C(H)-
COCH2PPh3)(L2)](ClO4)2 (L2 ) dppe 15, phen 16) in very
good yields (see Scheme 4, path b). The analytical and
spectroscopic data of complexes 14-16 are in good
agreement with the proposed structures in Scheme 4
As has been described for the syntheses of complexes
6 and 7, the synthesis of the orthometalated complexes
derived from 10 and 11 can be carried out by refluxing
these complexes (10 and 11) in NCMe (see Scheme 4,
path a2). The refluxing of 10 in NCMe gives [Pd(C6H4-
2-PPh2C(H)COCH2PPh3)(py)2](ClO4)2 (12), which is char-
acterized on the basis of its analytical and spectroscopic
data (see Experimental Section). However, prolonged
reflux of 11 in NCMe does not afford a single product
but a mixture of two products as can be inferred from
the 31P{1H} NMR spectrum of the crude reaction
mixture, which gives two sets of resonances. One set of
resonances appears at 23.55 (ddd), 21.49 (d), -14.43
(dd), and -29.19 (dd) and is attributed to the ortho-
metalated [Pd(C6H4-2-PPh2C(H)COCH2PPh3)(dppm)]-
(ClO4)2 (13a ), since the two high-field resonances signal
the presence of the P,P-chelating dppm ligand30 and the
signals at 23.55 and 21.49 ppm are characteristic of the
orthometalated group. The second set of signals appears
at 59.14 (d), 25.41 (dd), 21.36 (d), and 17.15 (dd). The
absence of resonances at high field and the presence of
a peak at 59.14 ppm show that one of the P atoms of
the dppm ligand has been oxidized and the four-
memebered ring has been transformed into a five-
membered ring, giving [Pd(C6H4-2-PPh2C(H)COCH2-
PPh3)(dppm-O)](ClO4)2 (13b). Similar aerobic oxidations
of the dppm ligand have been described29 for C,N-
orthometalated complexes of Pd(II) such as [Pd(C6H4Nd
NPh-2)(η2-dppmO)]SbF6. In the latter, oxidation has
occurred at the P atom trans to the aryl group. By
analogy to this compound, we propose the same struc-
ture for 13b; that is, the oxygen atom is trans to the
arylic carbon atom. In addition, this arrangement of
ligands matches that expected from consideration of the
antisymbiotic effect;31 that is, the hardest donor atom
of the dppmO ligand (the oxygen) is trans to the softer
donor atom of the orthometalated group (the arylic
carbon).
1
(complete assignment of the resonances in the H NMR
spectrum of 16 was carried out with the help of the 1H-
1H NOESY spectrum), and further characterization is
provided by the determination of the crystal structure
of complex 14‚2CHCl3.
Crystals suitable for X-ray analysis were obtained by
slow diffusion of n-hexane into a solution of 14 in CHCl3.
A drawing of the organometallic cation is shown in
Figure 1, relevant crystallographic parameters are given
in Table 1, and selected bond distances and angles are
collected in Table 2. The complex crystallizes in the
triclinic space group P1h with Z ) 2. Thus, although only
one enantiomer is shown in Figure 1, the crystal as a
whole is racemic. The palladium atom is located in a
distorted square-planar environment, surrounded by the
P atom of the PPh3 ligand, the N atom of the NCMe
ligand, and the two carbon atoms of the orthometalated
ligand, one arylic [C(38)] and one ylidic [C(57)]. As was
expected on the basis of the transphobic effect, the PPh3
ligand is coordinated trans to the ylidic carbon. The Pd-
C(aryl) bond distance [Pd - C(38) ) 1.999(8) Å] is
similar to those reported in the literature for this kind
of bond,29 as are the Pd-C(ylide) bond distance [Pd -
C(57) ) 2.161(8) Å],2,5,7 the Pd-P bond distance [2.315-
(2) Å],29 and the Pd-N bond distance [2.091(7) Å].29
Other internal structural parameters of the orthometa-
lated ligand, the PPh3 group, and the NCMe ligand are
unremarkable.
The synthesis of complex 14 can be rationalized in
the same way as was done for complexes 8 and 9; that
(31) Pearson, R. G. Inorg. Chem. 1973, 12, 712.

5894 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 14‚2CHCl3
Pd-C(38)
1.999(8)
2.161(8)
1.766(8)
1.795(8)
1.764(7)
1.801(8)
1.405(11)
1.129(10)
1.456(11)
1.533(10)
Pd-N(1)
2.091(7)
2.315(2)
1.784(8)
1.801(7)
1.778(7)
1.808(8)
1.390(10)
1.456(12)
1.212(9)
Pd-C(57)
Pd-P(1)
P(2)-C(31)
P(2)-C(25)
P(3)-C(57)
P(3)-C(37)
C(37)-C(38)
N(1)-C(55)
C(57)-C(58)
C(58)-C(59)
P(2)-C(19)
P(2)-C(59)
P(3)-C(43)
P(3)-C(49)
C(38)-C(39)
C(55)-C(56)
C(58)-O(9)
C(38)-Pd-N(1)
N(1)-Pd-C(57)
N(1)-Pd-P(1)
173.3(3)
88.4(3)
90.59(19) C(57)-Pd-P(1)
C(38)-Pd-C(57)
C(38)-Pd-P(1)
86.7(3)
93.8(2)
174.2(2)
118.7(6)
124.9(7)
N(1)-C(55)-C(56) 177.5(9)
C(58)-C(57)-P(3)
O(9)-C(58)-C(57)
C(57)-C(58)-C(59) 115.6(7)
C(58)-C(57)-Pd
O(9)-C(58)-C(59) 119.5(7)
C(58)-C(59)-P(2) 113.4(5)
107.2(5)
The fact that either an N-donor ligand or a P-donor
ligand can promote the same reaction means that the
nature of the donor atom does not have a decisive
influence on the overall process. However, the fact that
the dppm ligand does not promote orthometalation at
room temperature (synthesis of 11), while dppe does
under the same conditions (synthesis of 15), means that
the ring size is critical. Thus, the phenyl groups on the
P atoms and the ylidic units are “far apart” in 11 and
the molecule is “stable” toward orthometalation, while
in the case of dppe the increase in the bite angle of the
ligand (average value 86°)32,33 leaves the two groups in
close proximity (similar to the case of PPh3), and the
orthometalation can easily be induced, giving 15. The
same reasoning applies to the synthesis of 16, although
in this case the interaction must be between the ylidic
groups and the C2-HR groups adjacent to the nitrogen
of the phen ligand.
F igu r e 1. Thermal ellipsoid plot of the organometallic [Pd-
(C6H4-2-PPh2C(H)COCH2PPh3)(PPh3)(NCMe)]2+ cation. At-
oms are drawn at the 50% probability level.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 14‚2CHCl3
empirical formula
fw
C61H52Cl8NO9P3Pd
1425.95
temp
150(1) K
wavelength
cryst system
space group
unit cell dimens
0.710 73 Å
triclinic
P1h
a ) 9.6940(10) Å R ) 79.150(10)°
b ) 13.299(2) Å â ) 86.530(10)°
c ) 25.154(3) Å γ ) 73.900(10)°
volume
3059.9(7) Å3
Z
2
density (calcd)
abs coeff
1.548 Mg/m3
0.788 mm-1
F(000)
1448
cryst size
θ range for data collection
index ranges
0.26 × 0.12 × 0.09 mm
2.09-22.50°
It should be noted that the presence of large substit-
uents on the donor atom of the incoming ligand is also
important (for instance, two phenyl groups on the P
atoms of dppe), since the absence of substituents on the
donor atoms, even if they give a sufficient ring size to
promote the orthometalation, could result in no ortho-
metalation. We have a clear example of this in the
reaction of 2c with Tlacac,8 which results in the forma-
tion of [Pd{[C(H)PPh3]2CO}(acac-O,O′)]ClO4 without
contamination by other products. Thus, the combination
of an appropriate ring size and large substituents on
the donor atom are mandatory requirements for the
induction of the orthometalation.
0 e h e 10, -13 e k e 14,
-27 e l e 27
8619
8008 (Rint ) 0.0574)
ψ-scan
reflns collected
ind reflns
abs correction
max. and min. transmission 0.932 and 0.821
refinement method
full-matrix least-squares on F2
no. of data/restrains/params 8008/0/748
goodness-of-fit on F2a
R indices [I > 2σ(I)]b
largest diff peak and hole
1.025
R1 ) 0.0617, wR2 ) 0.1279
0.990 and -1.819 eÅ-3
Goodness-of-fit ) [∑w(Fo - Fc2)2/(Nobs - Nparam)]1/2
.
R1)
a
2
b
∑(|Fo| - |Fc|)/∑|Fo|. wR2 ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2
.
2
is, coordination of PPh3 to the starting complex 3c leaves
the phenyl groups of the phosphine in close proximity
to the ylidic fragments C(H)PPh3 and promotes the
orthometalation in order to minimize steric repulsions.
Regardless of where the phosphine attacks 3c, only one
isomer is obtained in the final product 14, which is, as
predicted by the transphobic effect, that containing PPh3
trans to the ylidic carbon and cis to the arylic carbon
(see the crystal structure of 14). The synthesis of 15 and
16 under mild conditions provides strong evidence in
favor of the importance of steric repulsions in the
promotion of the orthometalation reaction. Both com-
plexes are obtained by reaction of 3c with chelating
ligands which contain substituents on the donor atom
and which, once coordinated, form five-membered rings.
We have already mentioned that complex 3c does not
undergo internal metalation by refluxing in NCMe, but
the corresponding orthometalated complex 17 can be
obtained by treating 4c with TlClO4 (1:2 molar ratio)
in NCMe, as indicated in Scheme 5.
The orthometalation can also be produced spontane-
ously, without thermal induction or addition of ligands.
The dinuclear complex [Pd(µ-OOCMe){[C(H)PPh3]2-
CO}]2(ClO4)2 (18)8 evolves spontaneously in CH2Cl2 at
room temperature, resulting in the formation of [(C6H4-
(32) Oberhauser, W.; Bachmann, C.; Stampfl, T.; Haid, R.; Bru¨ggeller,
P. Polyhedron 1997, 16, 2827.
(33) Wu, B.; Zhang, W.; Huang, X.; Wu, X.; Yu, S. Polyhedron 1997,
16, 801.

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5895
Sch em e 5
obtained from the 1H-1H NOESY spectrum of 19. In
this spectrum, a strong NOE interaction is observed
between the resonance at 2.99 ppm and that at 4.70
ppm, showing the proximity of one ylidic proton of the
chelating bis(ylide) and the ylidic proton in the ring of
the orthometalated ligand. This proximity suggests that
the stereochemistry of 19 is that shown in eq 2. The
acetate ligands adopt an “open-book” structure, bridging
the two palladium atoms, and there is a bis(ylide) ligand
chelating one palladium and an orthometalated ligand
chelating the other palladium. In additon, the hydrogen
atoms of the bis(ylide) ligand should be directed to the
inner side of the complex and the bulky PPh3 groups to
the outer side. In the orthometalated ligand, the ylidic
proton is also directed inward and the bulky COCH2-
PPh3 group outward, resulting in minimization of the
steric repulsions between the bulky substituents. The
NOESY spectrum also shows a NOE interaction be-
tween the highest-field acetate resonance (0.60 ppm)
and the phenyl groups, confirming the suggestion of the
anisotropic shielding mentioned earlier.
2-PPh2C(H)COCH2PPh3)Pd(µ-OOCMe)2Pd{[C(H)PPh3]2-
CO}](ClO4)2 (19) in quantitative yield (see eq 2). The
(2)
The transformation of 18 to 19 has two striking
characteristics.The first is the spontaneity of the reac-
tion, since in this case neither incoming ligands nor
heating is required to promote the orthometalation. The
steric crowding in 18, which can be considered as the
kinetic isomer in the reaction of Pd(OAc)2 with
[Ph3PdC(H)COCH2PPh3]ClO4,8 appears to be the sole
driving force for the orthometalation. The second note-
worthy feature is that the thermodynamic isomer 19
contains only one orthometalated group. We have at-
tempted the orthometalation of the remaining bis(ylide)
ligand in 19 by refluxing in THF or NCMe, but in all
cases the dimer 19 was recovered. Thus, 19 is remark-
ably stable and does not show any tendency to further
transform.
Other reactions were attempted for the synthesis of
the expected acetate-bridging orthometalated com-
pound. The most obvious of them is the replacement of
the chloride-bridging ligands in 4c by acetate ligands
through the reaction of 4c with Ag(OOCCH3) in a
noncoordinating solvent such as CH2Cl2. Surprisingly,
the reaction product contains complex 19 exclusively;
thus at some point in the reaction one of the orthometa-
lated ligands has reverted to the bis(ylide); that is, we
have induced the reversibility of the cyclometalation.
characterization of this compound has been carried out
on the basis of its analytical and spectroscopic data. The
1H NMR spectrum of 19 shows characteristic resonances
for the CH2PPh3 group (5.74 ppm, ddd; 5.50, dd) and
for the ylidic C(H) proton in the ring (4.70, pseudo
triplet). In addition, two doublets at 2.99 and 2.85 ppm
reveal the presence of the bis(ylide) ligand. The reso-
nances attributed to the acetate ligands appear at 1.45
and 0.60 ppm, at unusually high fields, probably due
to the anisotropic shielding of the methyl moieties by
the phenyl groups. The 31P{1H} NMR spectrum shows
the presence of two AB spin systems, one of them (25.74
and 25.54 ppm) assigned to the bis(ylide) group and the
other one (30.14 and 22.23 ppm) to the orthometalated
ligand. These assignments were confirmed by measure-
1
ment of the H{31P} spectra and selective irradiation of
all P resonances. More structural information can be

5896 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
Sch em e 6
carried out on a Perkin-Elmer 240-B microanalyzer. Infrared
spectra (4000-200 cm-1) were recorded on a Perkin-Elmer 883
infrared spectrophotometer from Nujol mulls between poly-
We propose the reaction pathway shown in Scheme
6 to explain the reversibility of the orthometalation. In
a first step, the reaction of 4c with silver acetate in a
noncoordinating solvent would produce the precipitation
of AgCl and the generation of two vacant sites which
could immediately be occupied by the acetate ligand (A).
The proximity of the acetate ligands and the phospho-
nium moiety could result in an interaction between one
oxygen and the H atoms of the CH2P group and
subsequent deprotonation of the latter, giving a free
ylidic fragment and acetic acid. The coordination of the
ylide generated and protonation of the C(aryl)-Pd bond
results in the formation of species B, which can be
recombinated with A to give complex 19.
As a general conclusion, the orthometalation of the
bis(ylide) ligand [C(H)PPh3]2CO can be induced by
addition of bulky ligands under very mild conditions,
this reaction being controlled by steric factors. Moreover,
if the steric crowding in the starting compound is
important, the orthometalation can occur spontane-
ously. Another important conclusion is that the ortho-
metalation can be reversed through an intermediate in
which a second ylide is generated. We have now focused
our efforts on the stabilization of compounds in which
the orthometalated phosphonium ligand is transformed
into a new group in which the orthometalated unit is
preserved and which also contains an ylide fragment.
1
ethylene sheets. H (300.13 MHz), 13C{1H} (75.47 MHz), and
31P{1H} (121.49 MHz) NMR spectra were recorded in CDCl3
or CD2Cl2 solutions at room temperature (unless otherwise
stated) on a Bruker ARX-300 spectrometer; 1H and 13C{1H}
were referenced using the solvent signal as internal standard,
and 31P{1H} was externally referenced to H3PO4 (85%). The
two-dimensional 1H-1H NOESY experiments for complexes
9, 16, and 19 were performed at a measuring frequency of
300.13 MHz. The data were acquired in a phase-sensitive mode
into a 512 × 1024 matrix and then transformed into 1024 ×
1024 points using a sine window in each dimension. The
mixing time was 400 ms. Mass spectra (positive ion FAB) were
recorded on a V. G. Autospec spectrometer from CH2Cl2
solutions. Electrical conductivity measurements were per-
formed in acetone solutions with concentrations of about 5 ×
10-4 M with a Philips PW 9509 conductivity cell.
The starting bis(ylide) complexes cis-PdCl2[{C(H)PPh3}2CO]
(1c), {Pd(µ-Cl)[{C(H)PPh3}2CO]}2(ClO4)2 (2c), {Pd[{C(H)PPh3}2-
CO](NCMe)2}(ClO4)2 (3c), and {Pd(µ-OAc)[{C(H)PPh3}2CO]}2-
(ClO4)2 (18) were prepared according to published methods.8
P r epar ation of P h osph on iu m Salts. [Et2P h P CH2COCH2-
P P h Et2]Cl2. To a solution of ClCH2COCH2Cl (2.000 g, 15.75
mmol) in 35 mL of deoxygenated CHCl3 under nitrogen was
added PPhEt2 (6.86 mL, 39.4 mmol) in one portion. After an
initial period in which the mixture warmed gently, it was
allowed to reach room temperature, then refluxed for 1 h, and
again stirred at room temperature overnight. The resulting
solution was added to 200 mL of an Et2O/CHCl3 mixture (10:
1). An oily material was formed, which was subjected to
vigorous stirring until a white solid was obtained. This solid
was filtered, washed with additional portions of a mixture of
Et2O/CHCl3 (3 × 10 mL), and dried in vacuo. Obtained: 6.115
g (84% yield). The product crystallizes as a monohydrate.
Exp er im en ta l Section
Sa fety 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 ref 34.
Gen er a l P r oced u r es. Solvents were dried and distilled
under nitrogen before use: diethyl ether and tetrahydrofuran
over benzophenone ketyl, dichloromethane and chloroform over
P2O5, acetonitrile over CaH2, methanol over magnesium and
n-hexane and toluene over sodium. Elemental analyses were
Anal. Calcd. for C23H34Cl2OP2‚OH2 (477.39 g/mol): C, 57.86;
H, 7.60. Found: C, 57.42; H, 7.59. IR (ν, cm-1): 1714 (νCO). 1H
NMR (CDCl3): δ 7.90 (m, 2H, Ho, Ph), 7.57 (m, 3H, Hm + Hp,
2
Ph), 5.51 (d, 2H, CH2, J P-H ) 9 Hz), 2.74 (m, 4H, CH2CH3),
3
3
1.19 (dt, 6H, CH2CH3, J P-H ) 20 Hz, J H-H ) 7 Hz). 31P{1H}
(34) Wolsey, W. C. J . Chem. Educ. 1973, 50, A335.
NMR (CDCl3): δ 30.52.

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5897
[EtP h 2P CH2COCH2P P h 2Et]Cl2. To a solution of ClCH2-
COCH2Cl (2.000 g, 15.75 mmol) in 35 mL of deoxygenated
CHCl3 under nitrogen was added PPh2Et (8.11 mL, 39.4 mmol)
in one portion. The resulting mixture was refluxed for 3 h and
stirred overnight at room temperature. The resulting solution
was added to 200 mL of anhydrous Et2O. An oily material was
formed, which was subjected to vigorous stirring until a white
solid was obtained. This solid was filtered, washed with
additional portions of Et2O (3 × 10 mL), and dried in vacuo.
Obtained: 7.285 g (83% yield). The product crystallizes as a
dihydrate.
Anal. Calcd for C62H64Cl4O10P4Pd2 (1447.69 g/mol): C, 51.44;
H, 4.46. Found: C, 50.64; H, 3.84. IR (ν, cm-1): 1621 (νCO). 1H
NMR (CD2Cl2): δ 7.87-7.48 (m, 10H, Ph), 3.92 (d, 1H, CH,
2J P-H ) 3.7 Hz), 2.54 (m, 2H, CH2CH3), 1.08 (br m, 3H,
CH2CH3). 31P{1H} NMR (CD2Cl2): δ 28.81.
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)(µ-Cl)]2(ClO4)2 (4c).
A suspension of complex 2c (0.200 g, 0.122 mmol) in NCMe
(20 mL) was refluxed for 8 h. During this time, the initial
yellow suspension gradually dissolved and gave an orange
solution. Once cooled, this solution was evaporated to small
volume (3 mL). By addition of Et2O (40 mL) and continuous
stirring 4c was obtained as an orange solid, which was filtered,
washed with additional Et2O (20 mL), air-dried, and identified
spectroscopically as a mixture of the diastereomers (RR/ SS)
and (RS/ SR) in molar ratio 1.77:1 (major:minor). Obtained:
0.188 g (94% yield).
Anal. Calcd for C31H34Cl2OP2‚2OH2 (591.47 g/mol): C, 62.95;
H, 6.47. Found: C, 63.35; H, 5.99. IR (ν, cm-1): 1716 (νCO). 1H
NMR (CDCl3): δ 7.85 (m, 4H, Ho, Ph), 7.60 (m, 6H, Hm + Hp,
Ph), 6.02 (s, br, 2H, CH2), 3.17 (m, 2H, CH2CH3), 1.20 (br, 3H,
CH2CH3). 31P{1H} NMR (CDCl3): δ 25.12.
Anal. Calcd for C78H64Cl4O10P4Pd2 (1639.87 g/mol): C, 57.13;
H, 3.93. Found: C, 57.17; H, 3.99. MS [m/z, %]: 1541 [(M2 -
ClO4)+, 25]. IR (ν, cm-1): 1648 (νCO), 278 (νPd-Cl). 1H NMR (CD2-
Cl2): δ 7.78-7.48 (m, Ph), 7.14-7.12 (m, C6H4), 5.30 (dd, CH2P,
maj), 5.21 (dd, CH2P, min), 4.98 (dd, CH2P, min, 2J H-H ) 17.3
Hz, 2J P-H ) 14.1 Hz), 4.78 (pseudo t, CH2P, maj, 2J H-H = 2J P-H
Cl2P d {[C(H)P P h Et2]2CO} (1a ). To a solution of Pd(OAc)2
(0.3000 g, 1.336 mmol) in CH2Cl2 (35 mL) was added [Et2-
PhPCH2COCH2PPhEt2]Cl2 (0.614 g, 1.336 mmol). The initial
orange solution evolved to give a yellow solution, which was
stirred at room temperature for 4 h. The solvent was then
evaporated to dryness and the residue treated with Et2O (30
mL). Continuous stirring gave 1a as a yellow solid, which was
filtered and air-dried. Obtained: 0.637 g (85% yield). Crude
1a was recrystallized from CH2Cl2/Et2O, giving deep yellow
crystals of 1a ‚0.75CH2Cl2, which were used in analytical and
spectroscopic measurements. The amount of CH2Cl2 of crystal-
2
4
) 15 Hz), 4.58 (dd, CH, min, J P-H ) 3.9 Hz, J P-H ) 2.5 Hz),
2
4
4.52 (dd, CH, maj, J P-H ) 4.3 Hz, J P-H ) 2.7 Hz). 31P{1H}
NMR (CD2Cl2): δ 22.84 (d, min, C6H4PPh2, 4J P-P ) 7 Hz), 21.68
4
(d, maj, C6H4PPh2, J P-P ) 9 Hz), 21.21 (d, maj, CH2PPh3),
21.14 (d, min, CH2PPh3). 13C{1H} NMR (CD2Cl2): δ 190.87 (t,
2
2
1
CO, min, J P-C ) 7 Hz), 190.36 (t, CO, maj, J P-C ) 6.4 Hz),
lization was determined by H NMR integration.
157.58 (d, C1, C6H4, maj, 2J P-C ) 18.8 Hz), 157.49 (d, C1, C6H4,
Anal. Calcd for C23H32Cl2OP2Pd‚0.75CH2Cl2 (627.46
g/mol): C, 45.46; H, 5.38. Found: C, 45.49; H, 4.97. MS [m/z,
%]: 529 [(M - Cl)+, 35%]. IR (ν, cm-1): 1599 (νCO); 277, 260
(νPd-Cl). 1H NMR (CDCl3): δ 7.92 (m, 2H, Ho, Ph), 7.60 (m, 3H,
2
min, J P-C ) 18.8 Hz), 137-120 (Ph + C6H4, both isomers),
1
43.76 (br d, CH2, min, J P-C ) 49.2 Hz), 38.85 (dd, CH2, maj,
1J P-C ) 57.5 Hz, J P-C ) 10.5 Hz), 31.35 (dd, CH-ylide, maj,
3
1J P-C ) 66.8 Hz, J P-C ) 8.8 Hz).
3
2
Hm + Hp, Ph), 3.25 (d, 1H, CH, J P-H ) 6 Hz), 2.98 (m, 2H,
Attem p ts a t Or th om eta la tion of Com p lexes 2a a n d 2b.
Complex 2a was refluxed in NCMe under the same conditions
as those described for 2c. At the end of the reaction and after
the usual workup, the NMR spectra of the solid obtained
showed that the starting product 2a had been recovered in
almost quantitative yield. In the same way, complex 2b was
refluxed in NCMe for 8 h. At the end of the reaction a mixture
of 2b and 4b (three diastereoisomers) was identified by 31P-
{1H} NMR spectroscopy. The resonances attributed to 4b are
as follows (CD2Cl2): δ 33.39 (d, 4J P-P ) 6.5 Hz, C6H4-2-PPhEt),
33.15 (d, 4J P-P ) 6 Hz, C6H4-2-PPhEt), 32.07 (d, 4J P-P ) 7 Hz,
C6H4-2-PPhEt), 26.67 (d, CH2PPh3), 26.51 (d, CH2PPh3), 26.23
(d, CH2PPh3).
CH2CH3), 2.76 (m, 1H, CH2CH3), 2.63 (m, 1H, CH2CH3), 1.21
3
3
(dt, 3H, CH2CH3, J P-H ) 19 Hz, J H-H ) 7.6 Hz), 1.14 (dt,
3H, CH2CH3, J P-H ) 19 Hz, J H-H ) 7.6 Hz). 31P{1H} NMR
3
3
(CD2Cl2): δ 33.82.
Cl2P d {[C(H)P P h 2Et]2CO} (1b). Complex 1b was obtained
as a yellow solid similarly to 1a starting from Pd(OAc)2 (0.300
g, 1.336 mmol) and the phosphonium salt [EtPh2PCH2COCH2-
PPh2Et]Cl2 (0.742 g, 1.336 mmol). Obtained: 0.720 g (82%
yield). Crude 1b was recrystallized from CH2Cl2/Et2O giving
deep yellow crystals of 1b‚0.6CH2Cl2, which were used in
analytical and spectroscopic measurements. The amount of
1
CH2Cl2 of crystallization was determined by H NMR integra-
tion.
NMR Exp er im en ts. Ch a r a cter iza tion of th e Equ ilib-
r ia . (a) The NMR spectra of 2c in NCCD3 show resonances
corresponding exclusively to the cationic monomer [PdCl{[C(H)-
Anal. Calcd for C31H32Cl2OP2Pd‚0.6CH2Cl2 (710.81 g/mol):
C, 53.39; H, 4.70. Found: C, 53.33; H, 4.39. MS [m/z, %]: 625
1
[(M - Cl)+, 28]. IR (ν, cm-1): 1604 (νCO); 286, 274 (νPd-Cl). H
PPh3]2CO}(NCCD3)]+ClO4
.
1H: δ 7.76-7.51 (m, 30 H, Ph),
-
NMR (CDCl3): δ 7.95 (m, 2H, Ph), 7.79-7.52 (m, 6H, Ph), 7.40
2
4.16 (d, 1H, CH-ylide, J P-H ) 6 Hz), 4.12 (d, 1H, CH-ylide,
2J P-H ) 3.3 Hz). 31P{1H}: δ 26.30 (d, 1P, 4J P-P ) 10 Hz), 24.90
(d, 1P). (b) The NMR spectra of 1c in NCCD3 show resonances
corresponding to a mixture of 1c and the cationic monomer
2
(m, 2H, Ph), 3.61 (d, 1H, CH, J P-H ) 6.6 Hz), 3.39 (m, 1H,
3
CH2CH3), 2.87 (m, 1H, CH2CH3), 1.11 (dt, 3H, CH2CH3, J P-H
3
) 19 Hz, J H-H ) 7.5 Hz). 31P{1H} NMR (CDCl3): δ 30.11.
[PdCl{[C(H)PPh3]2CO}(NCCD3)]+ClO4 in molar ratio (1c:
[P d (µ-Cl){[C(H)P P h Et2]2CO}]2(ClO4)2 (2a ). To a solution
of 1a (0.300 g, 0.532 mmol) in CH2Cl2 (40 mL) was added
AgClO4 (0.111 g, 0.535 mmol). This suspension was stirred at
room temperature for 4 h and filtered. The resulting orange
solution was evaporated to dryness and the residue treated
with Et2O (30 mL), giving 2a as a yellow solid, which was
filtered and air-dried. Obtained: 0.279 g (83% yield).
-
1
cation) ) 2.6:1. The resonances attributed to 1c are H, δ 3.92
2
(d, 1H, CH-ylide, J P-H ) 7.5 Hz); 31P{1H}, δ 26.31 (s). When
this mixture was heated to 313 K, the molar ratio (1c:cation)
changed to 3.9:1. (c) The addition of LiCl to a solution of 2c in
NCCD3 and subsequent measurement of the NMR spectra
showed the presence of the mixture 1c:cation in molar ratio
(1c:cation) ) 2.6:1.
Anal. Calcd for C46H64Cl4O10P4Pd2 (1255.52 g/mol): C, 44.00;
H, 5.14. Found: C, 43.67; H, 4.88. IR (ν, cm-1): 1614 (νCO);
270, 248 (νPd-Cl). 1H NMR (CDCl3): δ 7.81 (m, 2H, Ho, Ph),
7.61 (m, 1H, Hp, Ph), 7.52 (m, 2H, Hm, Ph), 3.66 (br, 1H, CH),
2.49 (m, 4H, CH2CH3), 1.17 (br m, 6H, CH2CH3). 31P{1H} NMR
(CDCl3): δ 33.24.
[P d (µ-Cl){[C(H)P P h 2Et]2CO}]2(ClO4)2 (2b). Complex 2b
was obtained as a yellow solid similarly to 2a starting from
1b (0.300 g, 0.455 mmol) and AgClO4 (0.095 g, 0.46 mmol).
Obtained: 0.292 g (89% yield).
Or th om eta la tion Rea ction s. The NCCD3 solutions (a)
and (b) described above were heated at a temperature of 80
1
°C for 8 h, and after cooling, the H and 31P{1H} NMR spectra
were measured in the same solvent. Experiment (a) showed a
conversion of 100% of the starting product 2c into the
monomer [Pd(C6H4-2-PPh2C(H)COCH2PPh3)Cl(NCCD3)]+. The
resonances attributed to this compound are 1H, δ 7.73-7.51
(m, 25H, Ph), 7.36-7.17 (m, 4H, C6H4), 6.01 (dd, 1H, CH2PPh3,
2
2J H-H ) 16.5 Hz, J P-H ) 10.2 Hz), 4.62 (pseudo t, 1H, CH2-

5898 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
2
2
2
3
4
2
PPh3, J H-H = J P-H ) 16 Hz), 4.56 (d, 1H, CH-ylide, J P-H
)
) J P-H ) 8.2 Hz, J P-H ) 1.6 Hz), 4.80 (dd, CH2P, 1H, J P-H
) 13.3 Hz). 31P{1H} NMR (CD2Cl2): δ 31.60 (d, Pd-PPh3, 3J P-P
4.2 Hz); 31P{1H} NMR, δ 25.29 (d, J P-P ) 6.2 Hz), 22.33 (d).
Experiment (b) also showed a 100% conversion of the starting
product 1c into a compound with the same pattern of reso-
nances as has the monomer [Pd(C6H4-2-PPh2C(H)COCH2-
PPh3)Cl(NCCD3)]+ but slightly shifted, probably due to the
presence of a fast equilibrium with 5.
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)Cl2] (5). To a solution
of 4c (0.553 g, 0.337 mmol) in acetone (20 mL) was added an
excess of LiCl (0.200 g, 4.72 mmol), and the resulting solution
was stirred at room temperature for 12 h. During this time
complex 5 precipitated as a yellow solid, which was filtered,
washed with small portions of acetone (5 mL), and air-dried.
Obtained: 0.220 g (43% yield). The washings were evaporated
to dryness and treated with MeOH (10 mL), giving a second
crop of 5. Obtained: 0.088 g (net yield 61%).
4
4
) 13.8 Hz), 21.00 (d, CH2PPh3, J P-P ) 7.8 Hz), 17.02 (dd,
C6H4-2- PPh2). 13C{1H} NMR (CDCl3) (the carbonyl and ylidic
2
carbons were not observed): δ 163.86 (d, C1, C6H4, J P-C ) 20
Hz), 138.87, 131.12, 129.62, 129.14, 124.17 (C6H4), 134-127
1
(Ph), 125.23 (d, Cipso, Ph, J P-C ) 90 Hz), 118.66 (d, Cipso, Ph,
1J P-C ) 89 Hz), 37.93 (dd, CH2, 1J P-C ) 56 Hz, 3J P-C ) 14 Hz).
[P d (C6H 4-2-P P h 2C(H )COCH 2P P h 3)Cl(P P h Me2)](ClO4)
(9). Complex 9 was obtained similarly to 8 starting from 2c
(0.442 g, 0.269 mmol) and PPhMe2 (76 µL, 0.54 mmol).
Obtained: 0.372 g (72% yield).
Anal. Calcd for C47H43Cl2O5P3Pd (958.08 g/mol): C, 58.92;
H, 4.52. Found: C, 58.85; H, 4.46. MS [m/z, %]: 857 [M+, 100].
IR (ν, cm-1): 1627 (νCO), 257 (νPd-Cl). 1H NMR (CD2Cl2): δ
7.83-7.33 (m, 30 H, Ph), 7.14-6.96 (m, 3H, C6H4), 6.82 (m,
2
2
Anal. Calcd for C39H32Cl2OP2Pd (755.94 g/mol): C, 61.97;
1H, C6H4), 5.79 (dd, 1H, CH2P, J H-H ) 17.1 Hz, J P-H ) 11.1
2 3 4
H, 4.27. Found: C, 61.94; H, 4.17. IR (ν, cm-1): 1636 (νCO),
Hz), 4.76 (td, 1H, CH-ylide, J P-H ) J P-H ) 8.7 Hz, J P-H )
2
1
277 (νPd-Cl). H NMR (CD2Cl2): δ 8.00-7.43 (m, 26H, C6H4
+
2.3 Hz), 4.63 (dd, CH2P, 1H, J P-H ) 13.8 Hz), 1.57 (d, CH3,
2 2
Ph), 7.02 (m, 3H, C6H4), 6.49 (br t, 1H, CH2P), 4.64 (br s, 1H,
3H, J P-H ) 10.5 Hz), 1.37 (d, CH3, 3H, J P-H ) 10.1 Hz). 31P-
CH-ylide), 4.37 (pseudo t, 1H, CH2P, 2J H-H = 2J P-H ) 15.3 Hz).
{1H} NMR (CD2Cl2): δ 21.22 (d, CH2PPh3, J P-P ) 7.5 Hz),
4
31P{1H} NMR (CD2Cl2): δ 23.35 (d), 20.75 (d, J P-P ) 7.3 Hz).
15.13 (dd, C6H4-2- PPh2), 0.95 (d, Pd-PPhMe2, J P-P ) 13.7
Hz).
4
3
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)Cl(p y)](ClO4) (6). A
solution of [PdCl{[C(H)PPh3]2CO}(py)]ClO4 (0.243 g, 0.270
mmol) in NCMe (20 mL) was refluxed for 8 h. After cooling,
this solution was evaporated to small volume (3 mL). By
addition of Et2O (40 mL) and continuous stirring 6 was
obtained as a white solid, which was filtered, washed with
additional Et2O (20 mL), and air-dried. Obtained: 0.160 g (67%
yield).
[P d {[CH(P P h 3)]2CO}(p y)2](ClO4)2 (10). To a solution of
complex 3c (0.151 g, 0.156 mmol) in CH2Cl2 (20 mL) was added
pyridine (51 µL, 0.63 mmol), and the resulting solution was
stirred for 1 h at room temperature. The solvent was evapo-
rated to dryness and the residue treated with Et2O (10 mL),
giving 10 as a white solid, which was filtered, washed with
Et2O (20 mL), and air-dried. Obtained: 0.110 g (68% yield).
Anal. Calcd for C49H42Cl2N2O9P2Pd‚0.25CH2Cl2 (1063.37
g/mol): C, 55.63; H, 4.02; N, 2.63. Found: C, 55.37; H, 3.81;
N, 2.79. MS [m/z, %]: 783 [(M - 2py-ClO4)+, 60]. IR (ν, cm-1):
1614, 1607 (νCO). 1H NMR (CDCl3): δ 8.76 (d, 2H, Ho, py,
3J H-H ) 5.1 Hz), 7.97-7.21 (m, 16 H, Ph + Hp(py)), 6.87 (t,
Anal. Calcd for C44H37Cl2NO5P2Pd (899.04 g/mol): C, 58.78;
H, 4.15; N, 1.56. Found: C, 58.31; H, 4.19; N, 1.30. MS [m/z,
%]: 798 [M+, 15]. IR (ν, cm-1): 1645 (νCO), 278 (νPd-Cl). 1H NMR
3
(CDCl3): δ 8.04 (d, 2H, H2 + H6, py, J H-H ) 5.1 Hz), 7.83-
7.43 (m, 26H, Ph + H4 (py)), 7.23 (m, 2H, H3 + H5, py), 7.15-
3
3
2
6.96 (m, 3H, C6H4), 6.23 (d, 1H, H6, C6H4, J H-H ) 7.2 Hz),
2H, Hm, py, J H-H = 6 Hz), 4.99 (d, 1H, CH ylide, J P-H ) 3.9
2
2
6.12 (dd, 1H, CH2P, J H-H ) 15.3 Hz, J P-H ) 10.5 Hz), 4.71
Hz). 31P{1H} NMR (CDCl3): δ 24.83.
2
2
(pseudo t, CH2P, 1H, J H-H = J P-H ) 16 Hz), 4.58 (dd, 1H,
[P d {[CH(P P h 3)]2CO}(d p p m )](ClO4)2 (11). To a solution
of complex 3c (0.200 g, 0.207 mmol) in CH2Cl2 (20 mL) was
added dppm (0.079 g, 0.21 mmol), and the resulting solution
was stirred for 1 h at room temperature. The solvent was
evaporated to dryness and the residue treated with Et2O (10
mL), giving 11 as a white solid, which was filtered, washed
with Et2O (15 mL), and air-dried. Obtained: 0.240 g (92%
yield).
Anal. Calcd for C64H54Cl2O9P4Pd (1268.33 g/mol): C, 60.61;
H, 4.29. Found: C, 60.47; H, 4.22. MS [m/z, %]: 1169 [(M -
ClO4)+, 20], 1067 [(M - 2ClO4 + H)+, 100]. IR (ν, cm-1): 1589
(νCO). 1H NMR (CD2Cl2): δ 7.80-6.87 (m, 50H, Ph), 5.16
(virtual q, 2H, CH-ylide, J P-H ) 1.8 Hz), 4.83 (dt, 1H, CH2-
CH-ylide, J P-H ) 6 Hz, J P-H ) 2.7 Hz). 31P{1H} NMR
2
4
4
(CDCl3): δ 23.17 (d, J P-P ) 6.2 Hz), 21.42 (d).
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)Cl(3,5-lu tid in e)](Cl-
O4) (7). Complex 7 was obtained similarly to 6 starting from
[PdCl{[C(H)PPh3]2CO}(3,5-lutidine)]ClO4 (0.339 g, 0.365 mmol).
Obtained: 0.270 g (82% yield).
Anal. Calcd for C46H41Cl2NO5P2Pd (927.09 g/mol): C, 59.59;
H, 4.46; N, 1.51. Found: C, 59.45; H, 4.14; N, 1.75. MS [m/z,
%]: 826 [M+, 20]. IR (ν, cm-1): 1647 (νCO), 263 (νPd-Cl). 1H NMR
(CD2Cl2): δ 7.93-7.39 (m, 28 H, Ph + NC5H3), 7.18-7.04 (m,
3
3H, C6H4), 6.33 (d, 1H, H6, C6H4, J H-H ) 7.5 Hz), 6.09 (dd,
1H, CH2P, 2J H-H ) 16 Hz, 2J P-H ) 10.5 Hz), 4.51 (dd, 1H, CH-
2
4
2
2
ylide, J P-H ) 6.6 Hz, J P-H ) 2.4 Hz), 4.44 (dd, CH2P, 1H,
dppm, J H-H ) 15.3 Hz, J P-H ) 10.8 Hz), 4.02 (dt, 1H, CH2-
2 2
2J P-H ) 14 Hz), 2.18 (s, 6H, Me). 31P{1H} NMR (CD2Cl2): δ
dppm, J H-H ) 15.3 Hz, J P-H ) 9.6 Hz). 31P{1H} NMR
(CD2Cl2): δ 22.40 (virtual t, bis(ylide), 3J P-P ) 4.4 Hz), -25.54
(virtual t, dppm).
4
22.76 (d, J P-P ) 6.2 Hz), 21.19 (d).
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)Cl(P P h 3)](ClO4) (8).
To a solution of complex 2c (0.186 g, 0.113 mmol) in CH2Cl2
(20 mL) was added PPh3 (0.059 g, 0.23 mmol), and the
resulting solution was stirred for 6 h at room temperature.
The solvent was evaporated to dryness and the residue treated
with MeOH (10 mL), giving 8 as a white solid, which was
filtered, washed with additional MeOH (5 mL), and Et2O (20
mL), and air-dried. Obtained: 0.140 g (56% yield). Recrystal-
lization of 8 from CH2Cl2/Et2O gave colorless crystals of
8‚0.5CH2Cl2, which were used for analytical and spectroscopic
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)(p y)2](ClO4)2 (12). A
solution of complex 10 (0.197 g, 0.189 mmol) in NCMe (15 mL)
was refluxed for 8 h. After cooling, this solution was evaporated
to dryness. By addition of Et2O (30 mL) and continuous stirring
12 was obtained as a white solid, which was filtered, washed
with additional Et2O (20 mL), and air-dried. Obtained: 0.144
g (73% yield). Recrystallization of 12 from CH2Cl2/n-hexane
gave colorless crystals of 12‚0.25CH2Cl2, which were used for
analytical and spectroscopic measurements. The amount of
1
1
measurements. The amount of CH2Cl2 was determined by H
CH2Cl2 was determined by H NMR integration.
NMR integration.
Anal. Calcd for
Anal. Calcd for C49H42Cl2N2O9P2Pd‚0.25CH2Cl2 (1063.37
C
57H47Cl2O5P3Pd‚0.5CH2Cl2 (1124.69
g/mol): C, 55.63; H, 4.02; N, 2.63. Found: C, 55.46; H, 3.70;
g/mol): C, 61.40; H, 4.30. Found: C, 61.33; H, 4.20. MS [m/z,
%]: 981 [M+, 100]. IR (ν, cm-1): 1628 (νCO), 270 (νPd-Cl). 1H
NMR (CD2Cl2): δ 7.79-7.15 (m, 40H, Ph), 7.03 (m, 1H, C6H4),
6.85 (m, 1H, C6H4), 6.55 (m, 2H, C6H4), 5.86 (dd, 1H, CH2P,
2J H-H ) 17.1 Hz, 2J P-H ) 11.4 Hz), 5.00 (td, 1H, CH-ylide, 2J P-H
N, 2.78. MS [m/z, %]: 864 [(M - py-ClO4)+, 10]. IR (ν, cm-1):
3
1652 (νCO). 1H NMR (CDCl3): δ 8.71 (d, 2H, Ho, py, J H-H
)
5.1 Hz), 8.31 (d, 2H, Ho, py, 3J H-H ) 4.8 Hz), 7.91-7.18 (m, 31
H, Ph + Hm + Hp(py)), 7.01 (m, 2H, C6H4), 6.78 (m, 1H, C6H4),
6.57 (d, 1H, C6H4, J H-H ) 7.2 Hz), 5.43 (dd, 1H, CH2P, J H-H
3
2

Orthometalation of [Ph3PdC(H)]2CO
Organometallics, Vol. 17, No. 26, 1998 5899
2
=
2J P-H ) 16.8 Hz), 4.60 (d, 1H, CH-ylide, J P-H ) 3.9 Hz),
) 60 Hz, 2J P-C ) 11 Hz), 37.73 (dd, CH2, dppe, 1J P-C ) 53 Hz,
4.17 (dd, CH2P, 1H, J P-H ) 10.2 Hz). 31P{1H} NMR (CDCl3):
2J P-C ) 17 Hz), 28.02 (dt, CH2PPh3, J P-C ) 36 Hz, J P-C
=
2
1
3
4
δ 22.80 (d, J P-P ) 10.7 Hz), 20.97 (d).
4J P-C ) 11 Hz).
Attem p ted Or th om eta la tion of [P d {[CH(P P h 3)]2CO}-
(d p p m )](ClO4)2 (11). A solution of complex 11 (0.262 g, 0.207
mmol) in NCMe (15 mL) was refluxed for 8 h. After cooling,
this solution was evaporated to dryness. By addition of Et2O
(30 mL) and continuous stirring a white solid was obtained,
which was filtered, washed with additional Et2O (20 mL), air-
dried, and identified spectroscopically as a mixture of [Pd-
(C6H4-2-PPh2C(H)COCH2PPh3)(Ph2PCH2PPh2-P,P′)](ClO4)2 (13a)
and[Pd(C6H4-2-PPh2C(H)COCH2PPh3)(Ph2PCH2P(O)Ph2-P,O)]-
(ClO4)2 (13b). Obtained: 0.168 g.
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)(p h en )](ClO4)2 (16).
Complex 16 was obtained in a way similar to that described
for 14, starting from 3c (0.130 g, 0.134 mmol) and 1,10-phen
(0.024 g, 0.13 mmol). Obtained: 0.100 g (70% yield).
Anal. Calcd for C51H40Cl2N2O9P2Pd (1064.14 g/mol): C,
57.56; H, 3.79; N, 2.63. Found: C, 57.58; H, 3.43; N, 2.83. IR
1
(ν, cm-1): 1620 (νCO). H NMR (CD2Cl2): δ 9.77 (dd, 1H, HR,
phen, 3J Râ ) 5 Hz, 4J Rγ ) 1.1 Hz), 9.00 (dd, 1H, HR′, phen, 3J R′â′
4
3
) 4.5 Hz, J R′γ′ ) 1 Hz), 8.62 (dd, 1H, Hγ′, phen, J γ′â′ ) 8.2
3
Hz), 8.51 (dd, 1H, Hγ, phen, J γâ ) 8.2 Hz), 8.09 (dd, 1H, Hâ,
3
1H NMR (CD2Cl2): (13a ) δ 5.57-5.51 (m, 1H, CH-ylide),
4.91-4.70 (m, 2H, CH2PPh3 + dppm), 4.29 (dd, 1H, CH2PPh3,
phen), 8.01-7.96 (AB spin system, 2H, Hδ + Hδ′, phen, J H-H
) 8.9 Hz), 7.96 (dd, 1H, Hâ′, phen), 7.91-7.84 (m, 2H, Ph),
2
2J H-H ) 18 Hz, J P-H ) 13.5 Hz), 4.15-3.98 (m, 1H, dppm);
7.71 (d, 1H, H6, C6H4, 3J H-H ) 7.7 Hz), 7.63-7.26 (m, 26H, Ph
2
2
2
2
(13b) δ 5.37 (dd, 1H, CH2PPh3, J H-H ) 17.7 Hz, J P-H ) 13.8
+ C6H4), 5.38 (dd, 1H, CH2P, J H-H ) 17.8 Hz, J P-H ) 12.1
2
2
2
Hz), 5.12 (dd, 1H, CH2PPh3, J H-H ) 17.7 Hz, J P-H ) 11.1
Hz), 5.35 (pseudo t, 1H, CH-ylide, J P-H =
4J P-H ) 1.6 Hz),
2
Hz), 4.33 (d, 1H, CH-ylide, J P-H ) 13.5 Hz), 3.75 (dt, CH2-
5.16 (dd, 1H, CH2P, 2J P-H ) 12.3 Hz). 31P{1H} NMR (CD2Cl2):
2
2
4
dppm, J H-H ) 15 Hz, J P-H ) 10 Hz), 3.53 (dt, CH2-dppm,
δ 21.43 (d, J P-P ) 10.3 Hz), 20.32 (d). This complex was
2J H-H ) 15 Hz, J P-H ) 11 Hz).
insufficiently soluble for 13C NMR measurements.
2
31P{1H} NMR (CD2Cl2): (13a ) δ 23.55 (ddd, 1P, C6H4-2-PPh2,
[P d(C6H4-2-P P h 2C(H)COCH2P P h 3)(NCMe)2](ClO4)2 (17).
To a solution of 4c (0.300 g, 0.182 mmol) in NCMe (20 mL)
was added TlClO4 (0.110 g, 0.365 mmol). The resulting
suspension was stirred for 12 h at room temperature and
filtered through Celite. The clear solution was evaporated to
small volume (2 mL), and Et2O (30 mL) was added. By
continuous stirring, complex 17 was obtained as a white solid,
which was filtered, washed with Et2O (10 mL), and air-dried.
Obtained: 0.307 g (87% yield).
3J P-P ) 33.9 Hz, J P-P ) 16.1 Hz, J P-P ) 8.9 Hz), 21.49 (d,
1P, CH2PPh3, 4J P-P ) 8.9 Hz), -14.43 (dd, 1P PPh2 cis-to-CH-
ylide, 2J P-P ) 59.4 Hz, 3J P-P ) 16.1 Hz), -29.19 (dd, 1P, PPh2
3
4
2
3
trans-to-CH-ylide, J P-P ) 59.4 Hz, J P-P ) 33.9 Hz); (13b) δ
2
59.14 (d, 1P, PdO, J P-P ) 24.8 Hz), 25.41 (dd, 1P, Pd-PPh2,
3J P-P ) 17.7 Hz), 21.36 (d, CH2PPh3, J P-P ) 8.9 Hz), 17.15
4
(dd, 1P, C6H4-2-PPh2).
[P d (C6H 4-2-P P h 2C (H )C O C H 2P P h 3)(N C Me )(P P h 3)]-
(ClO4)2 (14). To a solution of 3c (0.150 g, 0.155 mmol) in CH2-
Cl2 (20 mL) was added PPh3 (0.040 g, 0.16 mmol), and the
resulting solution was stirred for 24 h at room temperature.
This clear solution was evaporated to small volume (2 mL),
and Et2O (30 mL) was added. By continuous stirring, 14 was
obtained as a white solid, which was filtered, washed with
Et2O (10 mL), and air-dried. Obtained: 0.135 g (73% yield).
Recrystallization of 14 from CH2Cl2/n-hexane gave colorless
crystals of 14‚0.75CH2Cl2, which were used for analytical and
spectroscopic measurements. The amount of CH2Cl2 was
Anal. Calcd for C43H38Cl2N2O9P2Pd (966.04 g/mol): C, 53.46;
H, 3.96; N, 2.90. Found: C, 52.95; H, 3.62; N, 2.89. MS [m/z,
%]: 783 [(M - 2NCMe-ClO4)+, 55]. IR (ν, cm-1): 2319, 2291
(νCN), 1653 (νCO). 1H NMR (CDCl3/213 K): δ 7.78-7.09 (m, 29H,
Ph + C6H4), 5.08 (br m, 1H, CH-ylide), 5.02, 4.98 (br AB spin
2
system, CH2P, J H-H ) 13 Hz), 2.41 (s, 3H, NCMe), 2.28 (s,
3H, NCMe). 31P{1H} NMR (CDCl3/213 K): δ 23.82 (br s), 21.81
(br s).
[(C6H 4-2-P P h 2C(H )COCH 2P P h 3)P d (µ-Ac)2P d {[C(H )-
P P h 3]2CO}](ClO4)2 (19). A solution of complex 18 in CH2Cl2
(20 mL) was stirred at room temperature for 48 h. At the end
of the reaction the solvent was evaporated to dryness, and the
orange 19 was collected with Et2O (25 mL), filtered, and air-
dried. The yield is quantitative. Recrystallization of 19 from
CH2Cl2/n-hexane gave colorless crystals of 19‚0.5CH2Cl2, which
were used for analytical and spectroscopic measurements. The
1
determined by H NMR integration.
Anal. Calcd for
C59H50Cl2NO9P3Pd‚0.75CH2Cl2 (1250.97
g/mol): C, 57.36; H, 4.15; N, 1.11. Found: C, 57.12; H, 4.17;
N, 1.09. MS [m/z, %]: 1045 [(M - NCMe-ClO4)+, 20]. IR (ν,
cm-1): 2319, 2291 (νCN), 1640 (νCO). 1H NMR (CDCl3): δ 8.01-
7.95 (m, 2H, Ph), 7.69-7.28 (m, 38H, Ph), 7.05 (m, 1H, C6H4),
1
6.94 (m, 1H, C6H4), 6.67 (m, 2H, C6H4), 5.54 (br m, 1H, CH-
amount of CH2Cl2 was determined by H NMR integration.
2
ylide), 5.37 (pseudo t, 1H, CH2P, J H-H
=
2J P-H ) 16.8 Hz),
Anal. Calcd for
C82H70Cl2O14P4Pd2‚0.5CH2Cl2 (1729.52
4.96 (dd, 1H, CH2P, 2J P-H ) 10.8 Hz), 1.86 (s, 3H, NCMe). 31P-
g/mol): C, 57.29; H, 4.13. Found: C, 56.94; H, 4.09. MS [m/z,
%]: 1587 [(M2 - ClO4)+, 10]. IR (ν, cm-1): 1640-1565 (broad
absorption,νCO, ylide and acetate). 1H NMR (CD2Cl2): δ 7.85-
{1H} NMR (CDCl3): δ 30.84 (d, Pd-PPh3, J P-P ) 15.2 Hz),
3
4
22.73 (d, CH2PPh3, J P-P ) 8 Hz), 17.45 (dd, C6H4-2-PPh2).
3
[P d (C6H4-2-P P h 2C(H)COCH2P P h 3)(d p p e)](ClO4)2 (15).
Complex 15 was obtained in a similar way to that described
for 14 starting from 3c (0.200 g, 0.207 mmol) and dppe (0.081
g, 0.21 mmol). Obtained: 0.238 g (90% yield).
7.28 (m, 58H, Ph + C6H4), 6.81 (td, 1H, C6H4, J H-H ) 7.8 Hz,
2
2
5J P-H ) 2.9 Hz), 5.74 (ddd, 1H, CH2P, J H-H ) 17.8 Hz, J P-H
4
2
) 9.5 Hz, J P-H ) 1.2 Hz), 5.50 (dd, 1H, CH2P, J P-H ) 15
2
4
Hz), 4.70 (pseudo t, 1H, CH-ylide (orthom), J P-H = J P-H
)
2
3.1 Hz), 2.99 (d, 1H, CH-bis(ylide), J P-H ) 5.1 Hz), 2.85 (dd,
Anal. Calcd for C65H56Cl2O9P4Pd (1282.36 g/mol): C, 60.88;
H, 4.40. Found: C, 60.52; H, 4.34. MS [m/z, %]: 1181 [(M -
ClO4)+, 12]. IR (ν, cm-1): 1642 (νCO). 1H NMR (CDCl3): δ 7.91-
2
4
1H, CH-bis(ylide), J P-H ) 5.6 Hz, J P-H ) 0.8 Hz), 1.45 (s,
3H, Me), 0.60 (s, 3H, Me). 31P{1H} NMR (CDCl3): δ 30.14 (d,
4J P-P ) 8.8 Hz, P in orthom ring), 25.74, 25.54 (AB spin system,
3
6.87 (m, 46H, Ph + C6H4), 6.76 (t, 1H, C6H4, J H-H ) 7.8 Hz),
bis(ylide), J P-P ) 8.5 Hz), 22.23 (d, CH2PPh3). 13C{1H} NMR
4
3
3
6.68 (d, 1H, C6H4, J H-H ) 7.2 Hz), 6.64 (d, 1H, C6H4, J H-H
)
2
2
3
(CD2Cl2): δ 195.88 (t, COCH2, J P-C ) 4 Hz), 192.50 (dd, CO-
7.8 Hz), 5.10 (dd, 1H, CH-ylide, J P-H ) 10.2 Hz, J P-H ) 6.3
bisylide, 2J P-C ) 7 Hz, 2J P′-C ) 4 Hz), 181.08 (s, COO-), 180.62
2
2
Hz), 4.02 (dd, 1H, CH2P, J H-H ) 18 Hz, J P-H ) 13.8 Hz),
(s, COO-), 155.36 (d, C1, C6H4, 2J P-C ) 22 Hz), 136.61-119.79
2
3.52 (dd, 1H, CH2P, J P-H ) 10.2 Hz), 3.16, 2.71, 2.52, 2.31
1
(4m, 4H, CH2-dppe). 31P{1H} NMR (CDCl3): δ 55.03 (dd, 1P,
P-dppe-cis-to-C-ylide, 3J P-P ) 16.8 Hz, 3J P-P (dppe) ) 23.4 Hz),
(m, Ph + C6H4), 52.41 (dd, Pd-CH in ring, J P-C ) 54 Hz,
3J P-C ) 14 Hz), 41.03 (dd, Pd-CH bis(ylide), J P-C ) 58 Hz,
1
3J P-C ) 10 Hz), 39.74 (dd, CH2P, J P-C ) 60 Hz, J P-C ) 12
1
3
3
3
43.67 (dd, 1P, P-dppe-trans-to-C-ylide, J P-P ) 31.8 Hz, J P-P
1
3
4
Hz), 39.45 (dd, Pd-CH bis(ylide), J P-C ) 58 Hz, J P-C ) 10
Hz), 24.48 (s, CH3), 23.13 (s, CH3).
(dppe) ) 23.4 Hz), 24.13 (ddd, C6H4-2-PPh2, J P-P ) 9 Hz),
22.23 (d, CH2PPh3). 13C{1H} NMR (CDCl3): δ 193.46 (t, CO,
2J P-C ) 5 Hz), 169.25 (ddd, C1, C6H4, 2J Ptrans-C ) 125 Hz, 2J Pcis-C
Cr ysta llogr a p h y. Da ta Collection . Crystals suitable for
X-ray measurements were grown by slow diffusion of a CHCl3
solution of 14 into n-hexane at room temperature. A pale
2
) 29 Hz, J P-C ) 6 Hz), 138-117 (Ph + C6H4), 47.12 (t, CH-
ylide, J P-C = J Ptrans-C ) 55 Hz), 39.11 (dd, CH2, dppe, J P-C
1
2
1

5900 Organometallics, Vol. 17, No. 26, 1998
Falvello et al.
yellow crystal of 14‚2CHCl3 was mounted on a quartz fiber
and covered with epoxy. Normal procedures were used for the
determination of the unit cell constants and for the measure-
ment of intensity data. After preliminary indexing and trans-
formation of the cell to a conventional setting, axial photo-
graphs were taken of the a-, b-, and c-axes to verify the Laue
symmetry and lattice dimensions. Accurate unit cell dimen-
sions were determined from 25 centered reflections in the
range 21.9° e 2θ e 31.9°. For intensity data collection, pure
ω scans were used with ∆ω ) 1.25 + 0.35 tan θ. Three monitor
reflections were measured after every 3 h of beam time, and
the orientation of the crystal was checked after every 500
intensity measurements. Absorption corrections35 were based
on azimuthal scans of 13 reflections, 9 of which had the
Eulerian angle ø near 90°. The other four reflections used for
this purpose had their bisecting-position ø values distributed
in the range 16-60°.
Str u ctu r e Solu tion a n d Refin em en t. The structure was
solved and developed by Patterson and Fourier methods.36 All
non-hydrogen atoms were assigned anisotropic displacement
parameters. The hydrogen atoms of the aromatic groups and
of the CH2 and CH moieties were constrained to idealized
geometries, and the isotropic displacement parameter of each
of these hydrogen atoms was set to a value of 1.2 times the
equivalent isotropic displacement parameter of its parent
carbon atom. The hydrogen atoms of the CH3 group were also
constrained to idealized geometries, and the isotropic displace-
ment parameter of each of these hydrogen atoms was set to a
value of 1.5 times the equivalent isotropic displacement
parameter of its parent carbon atom (C56). The parameters
for the two interstitial CHCl3 molecules did not show signs of
either static or dynamic disorder; the hydrogens atoms of these
groups were omitted from the model. The data-to-parameter
ratio in the final refinement was 10.7. The structure was
refined to Fo2, and all reflections were used in the least-squares
calculation.37 The residuals and other pertinent parameters
are summarized in Table 1. Crystallographic calculations were
done on a Local Area VAXCluster (VAX/VMS V5.5-2). Data
reduction was done by the program XCAD4B.38
Ack n ow led gm en t. We thank the Direccio´n General
de Ensen˜anza Superior (Spain) for financial support
(Projects PB95-0003-C02 and PB95-0792) and Prof. J .
Fornie´s for invaluable logistical support.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement details, atomic coordinates,
bond distances and angles, and anisotropic displacement
parameters for compound 14‚2CHCl3 (9 pages). Ordering
information is given on any current masthead page.
OM980625U
(35) Absorption corrections and molecular graphics were done using
the commercial package SHELXTL-PLUS, Release 4.21/V; Siemens
Analytical X-ray Instruments, Inc.: Madison, WI, 1990.
(37) Sheldrick, G. M. SHELXL-93: FORTRAN program for the
refinement of crystal structures from diffraction data; Go¨ttingen
University, 1993.
(36) Sheldrick, G. M. SHELXS-86. Acta Crystallogr. 1990, A46, 467.
(38) Harms, K. Private communication, 1995.