Synthesis of terminal and bridging acetonyl complexes of palladium(II). See abstract

Article abstract of DOI:10.1021/om000860o

The reaction of the palladium-hydroxo complex [{(o-C₆H₄CH₂NMe₂)Pd}₂ (μ-OH)₂] with acetone leads to the formation of the bridging O,C-acetonyl complexes [{(o-C₆H₄CH₂NMe₂)Pd}₂ (μ-OH){μ-CH₂C(O)CH₃}] (1) and [{(o-C₆H₄CH₂NMe₂)Pd}₂ {μ-CH₂C(O)CH₃}₂] (2). The reaction (1:2 molar ratio) of [{(AsPh₃)(C₆F₅)Pd}₂ {(μ-Cl)}₂] with 20% aqueous [NBu₄]OH in acetone yields [{(AsPh₃)(C₆F₅)Pd}₂ {μ-CH₂C(O)CH₃}₂] (3). The reaction (1:1 ratio) between 2 or 3 and t-BuNC gives the monomeric complexes [(o-C₆H₄CH₂NMe₂)Pd {CH₂C(O)Me}(t-BuNC)] (4) and [(AsPh₃)(C₆F₅)Pd {CH₂C(O)CH₃}(t-BuNC)] (5). Heating an acetone solution of [NBu₄]₂ [{(C₆F₅)₂Pd}₂(μ-OH)₂] gave the 2,4-dimethyl-1-oxapenta-1,3-dienyl palladium complex [NBu₄][(C₆F₅)₂Pd (η⁵-2,4-Me₂-C₄H₃O)] (6). The reaction of [{(o-C₆H₄CH₂NMe₂)Pd}₂ (μ-OH)₂] with CH₂(CO₂R)₂ (R = Et, Me) leads to [(o-C₆H₄CH₂NMe₂)Pd {O,O′-CH(CO₂R)₂}] (7, R = Me; 8, R = Et). The crystal structures of 3, 5, and 8 have been established by X-ray diffraction studies. The structure of 3 shows the C,O-enolate anion bridging two palladium atoms with a head-to-tail arrangement. In the monomeric complex 5 the C-bound acetonyl is trans to triphenylarsine. In 8 the diethyl malonate ligand and the palladium atom form a six-membered chelate ring.

Full text of DOI:10.1021/om000860o

Organometallics 2001, 20, 1973-1982
1973
Syn th esis of Ter m in a l a n d Br id gin g Aceton yl Com p lexes
of P a lla d iu m (II). Cr ysta l Str u ctu r es of
[{(AsP h 3)(C6F 5)P d }2{µ-CH2C(O)CH3}2],
[(AsP h 3)(C6F 5)P d {CH2C(O)CH3}(t-Bu NC)], a n d
[(o-C6H4CH2NMe2)P d {O,O′-CH(CO2Et)2}]
J ose´ Ruiz, Venancio Rodr´ıguez, Natalia Cutillas, Mercedes Pardo,
J ose´ Pe´rez, and Gregorio Lo´pez*
Departamento de Quı´mica Inorga´nica, Universidad de Murcia, 30071- Murcia, Spain
Penny Chaloner and Peter B. Hitchcock
School of Chemistry, Physics and Environmental Science, University of Sussex,
Brighton BN1 9QJ , U.K.
Received October 10, 2000
The reaction of the palladium-hydroxo complex [{(o-C6H4CH2NMe2)Pd}2(µ-OH)2] with
acetone leads to the formation of the bridging O,C-acetonyl complexes [{(o-C6H4CH2NMe2)-
Pd}2(µ-OH){µ-CH2C(O)CH3}] (1) and [{(o-C6H4CH2NMe2)Pd}2{µ-CH2C(O)CH3}2] (2). The
reaction (1:2 molar ratio) of [{(AsPh3)(C6F5)Pd}2(µ-Cl)}2] with 20% aqueous [NBu4]OH in
acetone yields [{(AsPh3)(C6F5)Pd}2{µ-CH2C(O)CH3}2] (3). The reaction (1:1 ratio) between 2
or 3 and t-BuNC gives the monomeric complexes [(o-C6H4CH2NMe2)Pd{CH2C(O)Me}(t-
BuNC)] (4) and [(AsPh3)(C6F5)Pd{CH2C(O)CH3}(t-BuNC)] (5). Heating an acetone solution
of [NBu4]2[{(C6F5)2Pd}2(µ-OH)2] gave the 2,4-dimethyl-1-oxapenta-1,3-dienyl palladium
complex [NBu4][(C6F5)2Pd(η5-2,4-Me2-C4H3O)] (6). The reaction of [{(o-C6H4CH2NMe2)Pd}2-
(µ-OH)2] with CH2(CO2R)2 (R ) Et, Me) leads to [(o-C6H4CH2NMe2)Pd{O,O′-CH(CO2R)2}]
(7, R ) Me; 8, R ) Et). The crystal structures of 3, 5, and 8 have been established by X-ray
diffraction studies. The structure of 3 shows the C,O-enolate anion bridging two palladium
atoms with a head-to-tail arrangement. In the monomeric complex 5 the C-bound acetonyl
is trans to triphenylarsine. In 8 the diethyl malonate ligand and the palladium atom form
a six-membered chelate ring.
Sch em e 1
In tr od u ction
Transition metal enolates have been proposed as
intermediates in numerous organic transformations.1-8
The term enolate is used as a generic name for the
CR2C(dO)R′ unit that can coordinate to a metal atom
either through the oxygen atom (common for the oxo-
philic early transition metals; A in Scheme 1) or through
the carbon atom (common for the carbophilic late
transition metals; B in Scheme 1). The chemistry
associated with these two metal enolates are very
different. The synthesis of C-bound metal enolates (B)
is normally achieved by an oxidative addition reaction
* Corresponding author. E-mail: gll@um.es.
(1) Seebach, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 1624.
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M., Ed.; Pergamon: New York, 1991; Vol. 3, Chapter 3.3, p 611.
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to a low-valent metal, and they undergo typical reac-
tions of metal alkyls, but the presence of a nucleophilic
site (oxygen) may also make them prone to electrophilic
attack. As expected for a carbophilic metal, enolates
10.1021/om000860o CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/07/2001

1974 Organometallics, Vol. 20, No. 10, 2001
Ruiz et al.
Sch em e 2
prefer to coordinate to palladium in the binding mode
B,9-15 but the chelating η3-oxoallyl (C, Scheme 1)16-19
and bridging C-O (D, Scheme 1)11,20 modes are also
found. The O-bound type A (Scheme 1) has also been
proposed.21 Although palladium has been widely used
for assisting the reactivity of enolate species, the
number of isolated and well-characterized complexes is,
however, rather limited.
The most convenient way of preparation of palladium
enolates is the oxidative addition of haloketones to a
Pd(0) complex (eq 1, Scheme 1).11,15,20,22,23 However, Pd-
acetonyl (methyl enolate) complexes have also been
prepared by reacting acetone with hydroxo complexes
(eq 2, Scheme 1).24-27
Following our systematic study of the reactivity of di-
µ-hydroxo complexes of the group 10 metals toward
weak, protic electrophiles, we have now found that these
dimeric compounds are very convenient starting materi-
als for the preparation of Pd-acetonyl complexes based
on the acid-base reaction between the basic >Pd(µ-
OH)2M< complex and Me2CO. Bridging C,O-bound and
terminal C-bound acetonyl complexes can be prepared
and, under appropriate conditions, acetone undergoes
aldol condensation to give 2,4-dimethyl-1-oxapenta-1,3-
dienyl at a palladium site. We report here the first
crystal structures of a mononuclear and a binuclear
palladium-acetonyl complex.
NMe2)Pd}2{µ-κ2-C,O-CH2C(O)CH3}2] (2). These reactions
imply proton abstraction from acetone by the hydroxo
complex with the concomitant release of water. The
formation of 1 or 2 depends on the reaction conditions
used (30 min reflux or 4 h reflux, respectively), and both
complexes may be obtained as pure samples. On pro-
tonation of the hydroxo complex, it is likely that an
intermediate aqua complex is formed, but we have not
been able to detect this species. The presence of the
hydroxo ligand in complex 1 is manifested by the
observation of the characteristic IR absorption at 3560
cm-1 (OH str) and a high-field proton resonance at δ
-2.01.28-30 The ν(CO) absorptions are observed in the
vicinity of 1560 cm-1. The analysis of the 1H NMR
spectrum gave more structural information on 1. Thus,
Resu lts a n d Discu ssion
µ-Aceton yl P a lla d iu m Com p lexes [{(o-C6H4CH2-
NMe2)P d }2(µ-OH ){µ-K2-C,O-CH 2C(O)CH 3}]
a n d
[{(o-C6H4CH 2NMe2)P d }2(µ-K2-C,O-CH 2 C(O)CH 3)2].
The reaction of the hydroxo palladium complex28 [{(o-
C6H4CH2NMe2)Pd(µ-OH)}2] with acetone under reflux
leads (Scheme 2) to the formation of the bridging O,C-
bound acetonyl complexes [{(o-C6H4CH2NMe2)Pd}2(µ-
OH){µ-κ2-C,O-CH2C(O)CH3}] (1) and [{(o-C6H4CH2-
(9) Vicente, J .; Abad, J . A.; Chicote, M. T.; Abrisqueta, M. D.; Lorca,
J . A.; Ram´ırez de Arellano, M. C. Organometallics 1998, 17, 1564.
(10) Burkhardt, E. R.; Bergman, R. G.; Heathcock, C. H. Organo-
metallics 1990, 9, 30.
1
the singlet signals observed in the H NMR spectrum
at δ 3.22 and 2.24 are assignable to the methylene and
methyl protons of the acetonyl ligand, respectively, and
in addition to the low-field resonances of the C6H4
groups, two singlet resonances for the N-Me groups (at
δ 2.74 and 2.67) and two singlet resonances for the CH2
protons (at δ 3.81 and 3.22) of bonded C6H4CH2NMe2
are observed, which indicate the presence of two in-
equivalent chelating C-N ligands. The 13C{1H} NMR
spectrum shows signals at δ 41.6 and 28.7 which are
assignable to the methylene and methyl carbons of the
acetonyl ligand, but the CO resonance could not be
observed. All these NMR data indicate that only one of
the four possible geometrical isomers (Scheme 3) is
present in solution. Moreover, the strong NOE observed
between the CH2CO protons and the aromatic H reso-
nances of the bidentate C6H4CH2NMe2 ligand indicates
the proximity of the interacting nuclei. This would not
be possible for the isomers a and b in Scheme 3. The
selective irradiation at δ -2.01 produced a clear NOE
(11) Veya, P.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organome-
tallics 1993, 12, 4899.
(12) Suzuki, K.; Yamamoto, H. Inorg. Chim. Acta 1993, 208, 225.
(13) Byers, P. K.; Canty, A. J .; Skelton, B. W.; Traill, P. R.; Watson,
A. A.; White, A. H. Organometallis 1992, 11, 3085.
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1984, 269, C-15.
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Am. Chem. Soc. 1979, 101, 494.
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391.
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Chem. 1973, 52, C-58.
(20) Albe´niz, A. C.; Catalina, N. M.; Espinet, P.; Redo´n, R. Orga-
nometallis 1999, 18, 5571.
(21) Fujii, A.; Hagiwara, E.; Sodeoka, M. J . Am. Chem. Soc. 1999,
121, 5450.
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E.; Miravitlles, C. Inorg. Chem. 1991, 30, 2605.
(28) Ruiz, J .; Cutillas, N.; Rodr´ıguez, V.; Sampedro, J .; Lo´pez, G.;
Chaloner, P. A.; Hitchcock, P. J . Chem. Soc., Dalton Trans. 1999, 2939.
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Mart´ınez-Ripoll, M. J . Organomet. Chem. 1996, 526, 67.

Terminal and Bridging Acetonyl Complexes of Pd(II)
Organometallics, Vol. 20, No. 10, 2001 1975
Sch em e 3
Sch em e 5
Sch em e 4
to that of similar dinuclear acetonyl complex 3 described
below, which has a chair-type conformation of the eight-
membered ring composed of Pd centers and bridging
acetonyl ligands. For the acetonyl ligands a resonance
at δ 2.24 for the methyl protons, which allows the
discard of the syn-arrangments a and d shown in
Scheme 4, and two resonances at δ 3.53 and 2.73 for
the methylene protons are observed. The assignment
of the CH2CO resonances is confirmed by selective
irradiation at δ 2.73, which produces a NOE enhance-
ment of the signal at δ 3.53. Moreover, for complex 2
there is a strong NOE interaction from aromatic protons
of the bidentate C6H4CH2NMe2 ligand to the CH2CO
resonances, indicating that the O-trans-to-NMe2 geom-
etry such as in d (Scheme 4) should be excluded. We
suggest the anti-arrangement (c) for this binuclear
complex where a CH2-trans-to-NMe2 ligand geometry
is present.
enhancement of the aromatic signal at δ 6.9, which
excludes isomer d. Therefore analysis of the NMR
spectra including proton NOE difference spectra sug-
gests that an anti-arrangement (c) is the most probable
structure for this binuclear complex 1. We found a
similar anti-arrangement in the previously reported
[Pd2(PPh3)2Ph2(µ-OH)(µ-NHC6H4OMe-p)].31
The IR spectrum of complex 2 shows a ν(CO) absorp-
1
tion at 1566 cm-1. The H NMR spectrum is tempera-
µ-Aceton yl P a lla d iu m Com p lex [{(AsP h 3)(C6F 5)-
P d }2{µ-K2-C,O-CH 2C(O)CH 3}2]. The reaction of
[{(AsPh3)(C6F5)Pd}2(µ-Cl)2] with 20% aqueous [NBu4]-
OH (1:2 ratio) at room temperature, in acetone, yields
[{(AsPh3)(C6F5)Pd}2{µ-CH2C(O)CH3}2] (3) (Scheme 5).
Although the formation of the acetonyl derivative 3
could be thought to occur through the intermediacy of
the hydroxo complex [{(AsPh3)(C6F5)Pd}2(µ-OH)2], we
have proved that this is not the case. In fact [{(AsPh3)-
(C6F5)Pd}2(µ-OH)2]32 was recovered unchanged after
heating it under reflux in acetone for 2 h. We assume
that in this case the acetonyl ligandssgenerated in situ
on deprotonation of the ketone by free OH-sreplace
both chloro ligands from the starting complex with
formation of 3 along with [NBu4]Cl.
ture dependent, showing broad resonances at room
temperature. At -20 °C sharp resonances are observed,
indicating that only one of the four possible geometrical
isomers (a-d, Scheme 4) with a head-to-tail arrange-
ment is present in solution at low temperature. The
detailed NMR analysis including proton NOE difference
spectra suggests that an anti-arrangement (c) is the
most probable structure for this binuclear complex at
low temperature. Two singlet resonances for the N-Me
groups and an AB quartet (J AB ) 13.8 Hz) for the CH2
protons of bonded C6H4CH2NMe2 are observed. This
NMR pattern, which has been found in other related
complexes such as [{(o-C6H4CH2NMe2)Pd}2(µ-RC(O)-
NH)2],28 can be rationalized by assuming a frozen
conformation of the Pd-N-C-C-C chelate ring or
much slower interconversion of the conformations than
the NMR time scale. The structure of 2 may be related
The IR spectrum of complex 3 shows the character-
istic absorptions of the C6F5 group33 at 1630, 1490, 1450,
1050, 950 and a single band at ca. 800 cm-1, which is
derived from the so-called X-sensitive mode34 in C6F5-
halogen molecules and behaves like a ν(M-C) band. The
(31) Ruiz, J .; Rodr´ıguez, V.; Lo´pez, G.; Chaloner, P. A.; Hitchcock,
P. B. J . Chem. Soc., Dalton Trans. 1997, 4271.

1976 Organometallics, Vol. 20, No. 10, 2001
Ruiz et al.
Sch em e 6
undergoes dissociation to give two monomers [(AsPh3)-
(C6F5)Pd{η3-CH2C(O)CH3}] can be proposed,35 as shown
1
in Scheme 6. The H NMR spectrum (Figure 1) consists
of four signals for the CH2 group; the singlets at δ 3.70
and 2.70 are assigned to the dimer with a head-to-tail
arrangement of the µ-CH2C(O)CH3 ligands and the two
doublets at δ 3.35 and 2.62 to the η3-CH2C(O)CH3 ligand
of the monomer. The observed NMR pattern is a
consequence of the absence of a molecular symmetry
plane. The dimer:monomer ratio increases as the tem-
perature decreases. The weak signals observed at lower
temperatures (-40 and -60 °C, Figure 1) are probably
due to the presence of other dimeric isomers similar to
those shown in Scheme 3. The 19F NMR spectrum of 3
at 25 °C (Figure 2) is consistent with the above 1H NMR
data. The two triplets of the para-fluorine atoms indi-
cate the presence of two different C6F5 groups, and the
ortho- and meta-fluorine resonances are duplicated
because there is no molecular mirror plane. Variable-
temperature 19F NMR studies for a solution of 20 mg of
3 in 0.7 mL of CDCl3 show a dimer:monomer ratio of
1.6:1 at 233 K. As the temperature is raised, the relative
proportion of monomer increases. The equilibrium con-
stant (Keq) over the range 233-283 K fits a linear plot
of ln Keq versus 1/T, which gives ∆H ) 19.8 kJ mol-1
and ∆S ) 40 J K-1 mol-1. The positive value observed
for ∆S agrees with the presence of a dissociative process
in solution.36
The crystal structure of 3 has been established by
X-ray diffraction. A view of the molecule is given in
Figure 3. There are two independent molecules in the
unit cell. Each of these lies on an inversion center, so
that in the solid state at least the aryl rings are
equivalent in the dimers. Selected bond lengths and
angles are given in Table 1. The complex is a dinuclear
unit where two enolato anions bridge two {Pd(C6F5)-
(AsPh3)} fragments with a head-to-tail arrangement and
an anti-structure. The oxygen atom is trans to the
pentafluorophenyl ligand in each case. Coordination
geometry at palladium is approximately square planar.
The eight-membered ring formed by the bridging eno-
late ligands adopts an approximately chairlike confor-
mation. Although a number of bridging enolato com-
plexes of palladium37,38 and other metals39,40 have been
structurally characterized, in most of these the enolato
ligand is part of a larger, often geometrically constrained
or chelating group. The only comparable species for
which a structure is available is [{Pd(PPh3)2}2(µ-{CH2-
C(Ph)dO-O,C})2][CF3SO3]2.11 This also shows distorted
square planar geometry at palladium, but the eight-
membered ring adopts a distorted boat conformation.
F igu r e 1. Variable-temperature 1H NMR spectra of
complex 3 in the CH2 region.
carbonyl stretching frequency for this palladium com-
1
plex is found at 1554 cm-1. The H NMR spectrum of 3
in CDCl3 is temperature dependent, showing broad
resonances at room temperature. In fact, the variable-
temperature 1H NMR spectra (Figure 1) of a sample
obtained by redissolution in CDCl3 of white crystals of
complex 3 (grown from toluene-hexane) indicate a rapid
temperature-dependent equilibrium between two spe-
cies. A process whereby the dimeric complex [{(AsPh3)-
(C6F5)Pd}2{µ-CH2C(O)CH3}2], in chloroform solution,
(32) The preparation of this complex is similar to that previously
used for the tripheylphosphine analogue: Ruiz, J .; Vicente, C.; Mart´ı,
J . M.; Cutillas, N.; Garc´ıa, G.; Lo´pez, G. J . Organomet. Chem. 1993,
460, 241. To a suspension of [Pd2(C6F5)2(AsPh3)2(µ-Cl)}2] (250 mg; 0.203
mmol) in THF (15 mL) was added 20% aqueous [NBu4]OH (0.532 mL,
0.406 mmol), and the resulting solution was stirred at room temper-
ature for 30 min and then the solvent was partially evaporated under
reduced pressure. On addition of ethanol and a few drops of water, a
pale yellow solid precipitated, which was filtered off and air-dried.
Yield: 89%. Anal. Found: C, 48.5; H, 2.9. Calcd for C32H32F10O2As2-
Pd2: C, 48.3; H, 2.7. IR (Nujol, cm-1): ν(OH), 3602; Pd-C6F5 str, 794.
1H NMR: δ 7.60-7.32 (15 H, AsPh3), δ 1.49 (s, 2 H, OH). 19F NMR:
δ -117.3 (d, Fo, J om ) 22.3 Hz), -160.6 (t, Fp, J pm ) 19.7 Hz), -163.8
(m, Fm).
(35) Slough, A.; Hayashi, R.; Ashbaugh, J . R.; Shamblin, S. L.;
Aukamp, A. M. Organometallics 1994, 13, 890.
(36) Gupta, M.; Cramer, R. E.; Kachum, O.; Pettersen, C.; Mishina,
S.; Belli, J .; J ensen, C. M. Inorg. Chem. 1995, 34, 60.
(33) Long, D. A.; Steel, D. Spectrochim. Acta 1963, 19, 1955.
(34) Maslowski, E. Vibrational Spectra of Organometallic Com-
pounds; Wiley: New York, 1977; p 437.

Terminal and Bridging Acetonyl Complexes of Pd(II)
Organometallics, Vol. 20, No. 10, 2001 1977
F igu r e 2. 19F NMR spectrum at 25 °C of complex 3: (a) ortho-fluorine region; (b) para- and meta-fluorine region.
palladium-oxygen bond lengths in 3 (2.104(7) and
2.092(8) Å) are similar to those in the previously studied
species (2.116(5) and 2.101(5) Å). The lengths of the
carbon-oxygen double bonds in 3 (1.285(12) and 1.248-
(14) Å) are surprisingly dissimilar for no obvious reason
and bracket those for the previously studied {CH2C-
(Ph)dO} derivative (1.261(12) and 1.256(10) Å). There
was also some evidence for the dissociation of the
{CH2C(Ph)dO} complex in solution.
Mon om er ic Acet on yl P a lla d iu m Com p lexes
[(AsP h 3)(C6F 5)P d {CH2C(O)CH3}(t-Bu NC)] a n d [(o-
C6H4CH2NMe2)P d {CH2C(O)Me}(t-Bu NC)]. The reac-
tions of 2 and 3 with t-BuNC (in 1:1 molar ratio) in
benzene or dichloromethane at room temperature yield
the monomeric complexes [(o-C6H4CH2NMe2)Pd{CH2C-
(O)Me}(CNBu-t)] 4 and 5, respectively (Schemes 2 and
5). The insertion of t-BuNC into the Pd-C bond of
[(PPh3)2(Cl)Pd{CH2C(O)Ph}] to yield trans-[(PPh3)2(Cl)-
PdC(NHBu-t)dCH-C(O)Ph] and the reaction of [(o-
C6H4CH2NMe2)PdCl(CNBu-t)] with t-BuNC to give the
iminoacyl complex [{o-C6H4(CdNR)CH2NMe2}PdCl-
(CNBu-t)] have been previously reported.11,41 The IR
spectrum of 4 shows a ν(CN) absorption42 at 2182 (2200
F igu r e 3. ORTEP diagram of 3. Thermal ellipsoids are
at 50% probability.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for Com p lex 3a
bond distances
bond angles
for 5) cm-1 and a ν(CO) band at 1638 (1650 for 5) cm-1
.
Pd(1)-As(1)
2.4182(14)
2.106(10)
2.012(11)
2.104(7)
C(4)-Pd(1)-O(1)′
176.2(4)
92.7(3)
89.9(4)
92.7(3)
85.2(2)
174.7(3)
176.3(5)
90.8(5)
89.4(4)
94.1(4)
85.8(2)
175.1(3)
These last values are similar to those found in the
related monomeric â-carbonylmethyl palladium com-
plexes9-11,43-45 and are indicative of the absence of
interaction between the carbonyl group and the pal-
ladium atom. The singlet signals observed in the 1H
NMR spectrum of 4 at δ 2.60 (2.81 for 5) and 2.14 (2.06
for 5) are assignable to the methylene and methyl
protons of the acetonyl ligand, respectively. Further, a
unique singlet resonance for the N-Me groups and a
singlet resonance for the CH2 protons of bonded C6H4-
CH2NMe2 are observed. In accord with the structure of
the starting dimer 3, a MeCOCH2-trans-to-NMe2 ligand
geometry for monomer 4 is proposed. Proton NOE
difference spectra confirmed this suggestion.
Pd(1)-C(1)
Pd(1)-C(4)
Pd(1)-O(1)′
Pd(2)-As(2)
Pd(2)-C(28)
Pd(2)-C(31)
Pd(2)-O(2)′′
C(4)-Pd(1)-C(1)
O(1)′-Pd(1)-C(1)
C(4)-Pd(1)-As(1)
O(1)′-Pd(1)-As(1)
C(1)-Pd(1)-As(1)
C(31)-Pd(2)-O(2)′′
C(31)-Pd(2)-C(28)
O(2)′′-Pd(2)-C(28)
C(31)-Pd(2)-As(2)
O(2)′′-Pd(2)-As(2)
C(28)-Pd(2)-As(2)
2.421(2)
2.129(11)
2.009(12)
2.092(8)
a
Symmetry transformations used to generate equivalent at-
oms: ′ -x, -y+2, -z; ′′ -x, -y, -z+1.
The palladium-carbon bond lengths in this complex
(2.162(10) and 2.137(10) Å) are just slightly longer than
those noted for 3 (2.106(10) and 2.130(11) Å). The
(40) Fornie´s, J .; Navarro, R.; Toma´s, M.; Urriolabeitia, E. P.
Organometallics 1993, 12, 940.
(37) Suzuki, H.; Moro-Oka, Y.; Ikawa, T.; Miyajima, T.; Tanaka, I.;
Ashida, T. Chem. Lett. 1982, 1369.
(38) Garc´ıa-Ruano, J. L.; Gonza´lez, A. M.; Lo´pez-Solera, I.; Masaguer,
J . R.; Navarro-Ranninger, C.; Raithby, P. R.; Rodr´ıguez, J . H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 1351.
(39) Yamaguchi, T.; Sasaki, Y.; Ito, T. J . Am. Chem. Soc. 1990, 112,
4038.
(41) Yamamoto, Y.; Yamazaki, H. Inorg. Chim. Acta 1980, 41, 229.
(42) Ruiz, J .; M. T. Mart´ınez; Vicente, C.; Garc´ıa, G.; Lo´pez, G.;
Chaloner, P. A.; Hitchcock, P. B. Organometallics 1993, 12, 1594.
(43) Fuchita, Y.; Harada, Y. Inorg. Chim. Acta 1993, 208, 43.
(44) Suzuki, K.; Yamamoto, H. Inorg. Chim. Acta 1993, 208, 225.
(45) Allan, D. R.; Clark, S. J .; Ibberson, R. M.; Parsons, S.; Pulham,
C. R.; Sawyer, L. Chem. Commun. 1999, 751-752.

1978 Organometallics, Vol. 20, No. 10, 2001
Ruiz et al.
Sch em e 7
F igu r e 4. ORTEP diagram of 5. Thermal ellipsoids are
at 50% probability.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for Com p lex 5
bond distances
bond angles
Pd-C(10)
1.971(4)
2.035(4)
2.111(4)
2.4393(5)
1.230(5)
1.435(5)
1.493(6)
C(10)-Pd-C(1)
178.8(2)
91.9(2)
86.8(2)
91.39(11)
89.84(10)
176.59(11)
Pd-C(1)
Pd-C(7)
Pd-As
C(10)-Pd-C(7)
C(1)-Pd-C(7)
C(10)-Pd-As
C(1)-Pd-As
C(7)-Pd-As
O-C(8)
C(7)-C(8)
C(8)-C(9)
The crystal structure of 5 has been established by
X-ray diffraction. A view of complex 5 is given in Figure
4, and Table 2 lists some selected bond lengths and bond
angles. The geometry around the metal atom is es-
sentially square planar; the deviation of Pd from the
best plane through the atoms defining the coordination
plane is 0.008(2) Å. The distances Pd-As and Pd-C (7)
are similar to that found in the µ-acetonyl complex 3.
The length of the carbon-oxygen double bond (1.230-
(5) Å) is shorter than that found in the bridged complex
3 but longer than that of the solid acetone.46 The
distances C-CH2 and C-CH3 are shortened and en-
larged respectively with regard to those of the solid
acetone.46 The enolate ligand is nearly perpendicular
to the mean coordination plane (dihedral angle 79.4-
(3)°); this conformation is found in [Pt(CH2COCH3)Cl-
(bipy)]47 or in [Pd(CH2COPh)Cl(PPh3)2].11 The Pd-C10
distance, 1.971(4) Å, is inside the range of distances
found for isocyanide complexes of palladium.48
Sch em e 8
2,4-Dim et h yl-1-oxa p en t a -1,3-d ien ylp a lla d iu m
Com plex [NBu 4][(C6F5)2P d(µ5-2,4-Me2-C4H3O)]. When
a solution of the di-µ-hydroxo palladium complex [NBu4]2-
[(C6F5)2Pd(µ-OH)2Pd(C6F5)2] in acetone was heated un-
der reflux for 6 h, the 1-oxapenta-1,3-dienylpalladium
complex 6 was obtained (Scheme 7). A metal-catalyzed
aldol condensation is perhaps involved in the formation
of the oxodienyl ligand. Alternatively, complex 6 can also
be prepared from mesityl oxide (Scheme 7). The related
ruthenium complex [Cp*Ru(η5-2,4-Me2-C4H3O)] (I,
Scheme 8) has been previously reported using [Cp*RuCl]4
and mesityl oxide [CH3C(Me)dCHCOCH3] in the pres-
ence of the mild base K2CO3 in hot THF.49 The reaction
of coordinated acetone solvent species with acetone to
(46) Falvello, L. R.; Garde, R.; Miqueleiz, E. M.; Toma´s, M.;
Urriolabeitia, E. P.; Inorg. Chim. Acta 1997, 264, 297-303.
(47) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S1.
(48) Suzuki, K.; J indo, A.; Hanaki, K. Inorg. Chim. Acta 1993, 210,
57.
(49) Trakarnpruk, W.; Ariff, A. M.; Ernst, R. D. Organometallics
1992, 11, 1686.

Terminal and Bridging Acetonyl Complexes of Pd(II)
Organometallics, Vol. 20, No. 10, 2001 1979
Sch em e 9
proton NOE difference spectra show that irradiation of
the CH signal at δ 4.45 produces an enhancement of
the methyl signals at 1.82 and 1.74. The same effect
has been found in the related complex [NBu4][(C6F5)2-
Pd(acetylacetonate)].29 The 13C NMR signal observed at
δ 197.1, assigned to the CO resonance, is in the region
of the corresponding resonance for the related acetyl-
acetonate complex cited above (δ 185.8). Unfortunately
no suitable single crystals for X-ray diffraction were
obtained. The reaction of 6 with the weak acid pyrazole
(Hpz) yields (Scheme 7) the previously reported pyra-
zole-pyrazolate complex [NBu4]2[(C6F5)2Pd(pz)(Hpz)]
together with 4-methyl-4-penten-2-one;54 no mesityl
oxide was detected by 1H NMR, although the acid-
catalyzed double-bond migration in the former ketone
toward the latter has been previously described.30,55
F igu r e 5. 1H-13C COSY of 6.
give the analogous iridium cation [Cp*Ir(η5-2,4-Me2-
C4H3O)]+ (II, Scheme 8) has also been previously
reported by Maitlis et al.50 The crystal structures of the
ruthenium complexes [Ru(η5-2,4-Me2-C4H3O)2] (III,
Scheme 8) and [Cp*Ru(η5-3,5-Me2-C4H3O)] have been
reported.49,51 On the other hand, the deprotonation of
mesityl oxide to form the η3-allylpalladium complex
[C6H9O‚PdCl]2 (IV, Scheme 8) is well established,52 and
its characterization was based mainly on the observa-
tion of ν(CO) at 1690 cm-1, suggesting that the carbonyl
oxygen was not coordinated and, therefore, the mode of
bonding was η3. However, the IR spectrum of the bis-
(pentafluorophenyl) complex 6 shows a strong, broad
absorption at 1635 cm-1 assigned to coordinated car-
bonyl, indicating that the η3-allyl mode of bonding
should be discarded. It also shows the characteristic
absorptions of the C6F5 group33 and a split band at ca.
800 cm-1 assigned to the cis-Pd(C6F5)2 moiety.34,53 The
19F NMR spectrum of 6 reveals the presence of two
different types of C6F5 groups, one trans to C and one
trans to O. Each freely rotating pentafluorophenyl ring
gives three resonances (in the ratio 2:2:1) for the ortho-,
meta-, and para-fluorine atoms, respectively. The as-
signment of signals (see Experimental Section) and the
Dia lk ylm a lon a te P a lla d iu m
Com p lex [(o-
C6H4CH2NMe2)P d {O,O′-CH(CO2R)2}]. The reaction
(1:2) of [{(o-C6H4CH2NMe2)Pd}2(µ-OH)2] with CH2-
(CO2R)2 (R ) Me, Et) leads (Scheme 9) to the dialkyl
malonate palladium complexes [(o-C6H4CH2NMe2)Pd-
{O,O′-CH(CO2R)2}] (7, R ) Me; 8, R ) Et). Dialkyl
malonates are very versatile ligands, exhibiting either
C- or O-bonding modes due to their small degree of
enolization and depending, in part, on the particular
metal ion.56,57 The IR spectra of complexes 7 and 8 show
a strong ν(CO) absorption at ca. 1620 cm-1 which
excludes the presence of the C-bonding mode.57,58 The
unique singlet resonances observed in the1H NMR
spectra for the CH2N and NMe2 protons show that the
molecular plane of complexes 7 and 8 is a symmetry
plane. Moreover, the two different sets of resonances
observed for the R substituents of the CH(CO2R)2 ligand
(R ) Me or Et) are in agreement with the O,O′-bonding
mode proposed.59,60
structure was performed using a H and 13C NMR study,
1
which comprised heteronuclear (1H-13C) COSY experi-
ments and proton NOE differential spectra. Thus COSY
experiments show (see Figure 5 and Scheme 7 for
The molecular structure of 8 (crystals obtained by
slow diffusion of n-hexane into a CH2Cl2 solution of 8
1
numbering) that the H signals at 3.98 (s, Hd) and 3.65
(s, He) are correlated with the 13C signal at 65.7 ppm
(C(5)), and the 1H resonance at 4.45 (s, Hb) is correlated
with the 13C signal at 71.1 ppm. On the other hand,
(54) Lo´pez, G.; Ruiz, J .; Vicente, C.; Mart´ı, J . M.; Garc´ıa, G.;
Chaloner, P. A.; Hitchcock, P. B.; Harrison, R. M. Organometallics
1992, 11, 4091.
(55) Noyce, D. S.; Evett, M. J . Org. Chem. 1972, 37, 397.
(56) Newkome, G. R.; Gupta, V. K. Inorg. Chim. Acta 1982, 65, L165.
(57) Newkome, G. R.; Gupta, V. K.; Taylor, H. C. R., Fronczek, F.
R. Organometallics 1984, 3, 1549.
(50) White, C.; Thompson, J .; Maitlis, P. M. J . Organomet. Chem.
1977, 134, 319.
(51) Schmidt, T.; Goddard, R. J . Chem. Soc., Chem. Commun. 1991,
1427.
(52) Parshall, G. W.; Wilkinson, G. Inorg. Chem. 1962, 1, 896.
(53) Alonso, E.; Fornie´s, J .; Fortun˜o, C.; Toma´s, M. J . Chem. Soc.,
Dalton Trans. 1995, 3777.
(58) Ito, T.; Yamamoto, A. J . Organomet. Chem. 1979, 174, 237.
(59) Chung, P. J .; Suzuki, H.; Moro-oka, Y.; Ikawa, T. Chem. Lett.
1980, 63.
(60) Sugimoto, R.; Eikawa H.; Suzuki, H.; Moro-oka, Y.; Ikawa, T.
Bull. Chem. Soc. J pn. 1981, 54, 2849.

1980 Organometallics, Vol. 20, No. 10, 2001
Ruiz et al.
ring adopts an envelope conformation with the CH2
group significantly out of the plane.65,66 The differences
in the Pd-O distances (Pd-O(1) 2.030(2) Å, Pd-O(3)
2.102(2) Å) are in accord with the lower trans-influence
of the NMe2 group. Relatively few malonate complexes
have been characterized crystallographically, and there
are no palladium complexes among them. In 8 the
chelating ring of the malonate ligand is close to planar,
with a bite angle of 90.35(8)° at palladium. The carbon-
carbon bond lengths in the ring (1.388(4) and 1.398(4)
Å) show significant double-bond character and indicate
almost total delocalization. They are comparable with
the related bond lengths in [Ni(R-Np)(PPh3){CH-
(COOEt)2}] (1.396(14) and 1.381(13) Å)75 or [Mo(H)-
(dppe)2{CH(COOEt)2}] (1.3865(5) Å).76 By contrast,
complexes of nondeprotonated malonate esters such as
[TiCl4{CH(COOEt)2}]77 and [VOCl2{CH(COOEt)2}4]78
have shorter C-O bond lengths and longer C-C bond
lengths in the chelate ring, and the chelate rings are
not planar.
F igu r e 6. ORTEP diagram of 8. Thermal ellipsoids are
at 50% probability.
Con clu sion s
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for Com p lex 8
The work described herein shows that the hydroxo
complexes of the type [(X)(Y)Pd(µ-OH)2Pd(X)(Y)] are
convenient starting reagents for the preparation of
bridging C,O-enolato complexes via the acid-base reac-
tion >Pd(µ-OH)2Pd< + 2 CH3COCH3 f >Pd{µ-
CH2C(O)CH3}2Pd< + 2H2O, the outcome being depend-
ent on the identity of the ancillary ligands (X, Y). With
the (AsPh3)(C6F5)Pd moiety no reaction takes place,
although the bis(µ-enolato) complex is obtained by
reacting the corresponding bis(µ-chloro) complex with
enolate generated in situ. With the (C-N)Pd moiety
both the (µ-OH)(µ-enolato) and bis(µ-enolato) complexes
are obtained by reaction between the bis(µ-hydroxo)
complex and acetone. However the ligand resulting from
aldol condensation is obtained when Pd(C6F5)2 is used.
There is a correlation between the reactivity and the
basic character of the bis(µ-hydroxo) complex which
increases in the order [(AsPh3)(C6F5)Pd(µ-OH)2Pd-
(AsPh3)(C6F5)] < [(C-N)Pd(µ-OH)2Pd(C-N)] < [(C6F5)2-
Pd(µ-OH)2Pd(C6F5)2]2-, which is in agreement with the
order followed by the high-field proton resonance of the
µ-OH in the above hydroxo complexes (δ -1.49, -2.40,
and -2.84, respectively).79
Bond Distances
Bond Angles
Pd-C(3)
1.961(3)
2.030(2)
2.047(2)
2.102(2)
C(3)-Pd-O(1)
93.31(10)
82.47(11)
174.83(8)
175.83(10)
90.35(8)
Pd-O(1)
Pd-N
C(3)-Pd-N
O(1)-Pd-N
C(3)-Pd-O(3)
O(1)-Pd-O(3)
N-Pd-O(3)
Pd-O(3)
93.97(9)
at room temperature) provides further characterization.
The structure of 8 is shown in Figure 6. Selected bond
distances and bond angles are given in Table 3. Coor-
dination at palladium is approximately square planar,
although the angles around palladium deviate from 90°
due to the bite of the cyclometalated ligand. The C(3)-
Pd-N angle of 82.47(11)° is within the normal range
for such complexes.61-64 The palladium-carbon bond
length is at the low end of the range of those reported
for the carbon trans to oxygen, and the palladium-
nitrogen distance is also shorter than most of those
reported for comparable species.61-74 The five-membered
(61) Matt, D.; Guillemin, J .-C.; Ziesel, R.; Balegroune, F.; Grandjean,
D. Acta Crystallogr., Sect. C 1994, 50, 193.
(62) Fallon, G. D.; Gatehouse, B. M. J . Chem. Soc., Dalton Trans.
1974, 1632.
(63) Narayan, S.; J ain, V. K.; Butcher, R. J . J . Organomet. Chem.
1997, 549, 73.
(64) Barr, N.; Dyke, S. F.; Smith, G.; Kennard, C. H. L.; McKee, V.
J . Organomet. Chem. 1985, 288, 109.
(65) Andrieu, J .; Braunstein, P.; Drillon, M.; Dusausoy, Y.; Ingold,
F.; Rabu, P.; Tiripicchio, A.; Ugozzoli, F. Inorg. Chem. 1996, 35, 5986.
(66) Andrieu, J .; Braunstein, P.; Dusausoy, Y.; Ghermani, N. E.
Inorg. Chem. 1996, 35, 7174.
(67) Bouaoud, S. E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel,
D. J . Chem. Soc., Chem. Commun. 1987, 488.
The protonation of the binuclear hydroxo complex by
acetone should give an aqua complex intermediate,
which we have not been able to detect. However, we
have recently reported80 the formation of the diaqua
complex [(AsPh3)(C6F5)Pd(OH2)2](CF3SO3) when the
corresponding di-µ-hydroxo complex is protonated by
triflic acid. The noncoordinating triflate anion facilitates
the formation of the aqua complex.
The more basic [(C6F5)2Pd(µ-OH)2Pd(C6F5)2]2- gener-
ates enough enolate for the aldol condensation to
(68) Russell, D. R.; Tucker, P. A. J . Chem. Soc., Dalton Trans. 1975,
1743.
(69) Bhattacharyya, P.; Slawin, A. M. Z. Smith, M. B. J . Chem. Soc.,
Dalton Trans. 1998, 2467.
(70) Ruiz, J .; Cutillas, N.; Sanpedro, J .; Lo´pez, G.; Hermoso, J . A.;
Mart´ınez-Ripoll, M. J . Organomet. Chem. 1996, 526, 67.
(71) Alsters, P.; Teunissen, H. T.; Boersma, J .; Soek, A. L.; Van
Koten, G. Organometallics 1993, 12, 4691.
(75) Agne`s, G.; Bart, J . C. J .; Calcaterra, M.; Cavigioto, W.; Santini,
C. Transition Met. Chem. 1986, 11, 246.
(76) Minato, M.; Kurishima, M.; Nagai, K.; Yamasaki, M.; Ito, T.
Chem. Lett. 1994, 2339.
(77) Sobota, P.; Szafert, S.; Lis, T. J . Organomet. Chem. 1993, 443,
85.
(72) Braunstein, P.; Matt, D.; Nobel, D.; Bouaoud, S.-E.; Grandjean,
D. J . Organomet. Chem. 1986, 301, 401.
(73) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J .; Mitschler,
A.; Ricard, L. J . Am. Chem. Soc. 1981, 103, 5115.
(74) Zhou, Y.; Wagner, B.; Polborn, K.; Su¨nkel, K.; Beck, W. Z.
Naturforsch. 1994, 49b, 1193.
(78) Sobota, P.; Ejfler, J .; Szafert, S.; Glowiak, T.; Fritzky, I. O.;
Szczegot, K. J . Chem. Soc., Dalton Trans. 1995, 1727.
(79) Lo´pez, G.; Garc´ıa, G.; Ruiz, J .; Sa´nchez, G.; Garc´ıa, J .; Vicente,
C. J . Chem. Soc., Chem. Commun. 1989, 1045.
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C.; Lo´pez, G. Inorg. Chem. Commun. 2000, 3, 73.

Terminal and Bridging Acetonyl Complexes of Pd(II)
Organometallics, Vol. 20, No. 10, 2001 1981
P r ep a r a tion of Com p lex [{(AsP h 3)(C6F 5)P d }2{µ-CH2C-
(O)CH3}2] (3). To a suspension of [{Pd(C6F5)(AsPh3(µ-Cl)}2]
(290 mg; 0.236 mmol) in acetone (15 mL) was added 20%
[NBu4]OH(aq) (0.618 mL, 0.472 mmol), and the resulting
solution was stirred at room temperature for 30 min and then
solvent was partially evaporated under reduced pressure. On
addition of methanol and a few drops of water, a pale yellow
solid precipitated, which was filtered off and air-dried. The
solid was redissolved in CH2Cl2 and then filtered through a
small column packed with Florisil. The filtrate was concen-
trated to dryness. Addition of ether/hexane to the residue
followed by vigorous stirring rendered a pale yellow suspen-
sion, from which a pale yellow solid was collected by filtration
and air-dried. Complex 3 was recrystallized from dry toluene/
hexane. Yield: 83%. Anal. Calcd for C54H40As2F10O2Pd2: C,
50.9; H, 3.2. Found: C, 50.3; H, 3.1. Mp: 166 °C dec. IR (Nujol,
cm-1): ν(CO), 1538 Pd-C6F5 str, 784. 1H NMR at 25 °C
(CDCl3): δ 7.30 (m, AsPh3), 3.67 (br, CH2CO), 3.31 (br, CH2-
CO), 2.69 (br, CH2CO), 2.56 (br, CH2CO), 1.87 (br, CH3CO),
0.99 (br, CH3CO). 1H NMR at -20 °C (CDCl3): δ 7.30(m,
AsPh3), 3.70 (s, CH2CO), 3.35 (d, CH2CO, J ) 3.2 Hz), 2.70 (s,
CH2CO), 2.62 (d, CH2CO, J ) 3.2 Hz), 1.91 (s, CH3CO), 1.02
(s, CH3CO). 19F NMR at 25 °C: δ -115.8 (m, Fo), -116.8 (d,
Fo, J om ) 22.6 Hz), -117.8 (d, Fo, J om ) 22.6 Hz), -161.7 (t,
Fp, J pm ) 20.3 Hz), -162.5 (t, Fp, J pm ) 20.3 Hz), -163.3 (m,
Fm), -163.7 (m, Fm), -164.1 (m, Fm).
proceed, and the resulting â-hydroxy ketone is dehy-
drated during the course of the reaction, yielding
complex 6. This reaction resembles the [(C6F5)2Pd(µ-
OH)2Pd(C6F5)2]2--catalyzed cyclotrimerization of mal-
ononitrile very closely, in which the R-carbon of one
malonitrilate anion adds to the CN carbon of malono-
nitrile. In this case, a bridging C,N-bound malonitrilate
complex was isolated.81
Exp er im en ta l Section
In str u m en ta l Mea su r em en ts. C, H, and N analyses were
performed with a Carlo Erba model EA 1108 microanalyzer.
Decomposition temperatures were determined with a Mettler
TG-50 thermobalance at a heating rate of 5 °C min-1 with the
solid samples under nitrogen flow (100 mL min-1). Molar
conductivities were measured in acetone solution (c ≈ 5 × 10-4
mol L-1) with a Crison 525 conductimeter. The NMR spectra
were recorded on a Bruker AC 200E or Varian Unity 300
spectrometer, using SiMe4 and CFCl3 as the standard, respec-
tively. Infrared spectra were recorded on a Perkin-Elmer 1430
spectrophotometer using Nujol mulls between polyethylene
sheets. Mass spectra (positive-ion FAB) were recorded on a
V.G. AutoSpecE spectrometer and measured using 3-nitroben-
zyl alcohol as the dispersing matrix.
P r ep a r a tion of Com p lex [(o-C6H4CH2NMe2)P d {CH2C-
(O)Me}(t-Bu NC)] (4). To a suspension of complex 2 (80 mg,
0.134 mmol) in benzene (2 mL) was added t-BuNC (30 µL,
0.268 mmol). The resulting solution was stirred at room
temperature for 5 min, and the solvent was then removed
under vacuum. The residue was treated with hexane, and an
orange solid was collected by filtration and air-dried. The solid
was kept in a refrigerator at 5 °C. Yield: 55%. Anal. Calcd for
C17H26N2O1Pd1: C, 53.6; H, 6.8; N, 7.4. Found: C, 53.5; H,
6.9; N, 7.3. Mp: 103 °C dec. IR (Nujol, cm-1): ν(CN), 2182;
ν(CO), 1638. 1H NMR (CDCl3): δ 7.1-6.9 (m, 4 H, aromatics),
3.85 (s, 2 H, NCH2), 2.72 (s, 6 H, NMe2), 2.60 (s, 2 H, CH2CO),
2.14 (s, 3 H, CH3CO). Positive-ion FAB mass spectrum: m/z
381 (M + 1)+, 324 (M + 1 - CH2COCH3)+.
Ma ter ia ls. The starting complexes [{(o-C6H4CH2NMe2)Pd-
(µ-OH)}2] (C,N ) o-C6H4CH2NMe2)],28 [{(AsPh3)(C6F5)Pd(µ-
Cl)}2],82 and [NBu4]2[(C6F5)2Pd(µ-OH)2Pd(C6F5)2]29 were pre-
pared by procedures described elsewhere. Solvents were dried
by the usual methods.
P r ep a r a tion of Com p lex [{(o-C6H4CH2NMe2)P d }2(µ-
OH){µ-CH2C(O)CH3}] (1). A suspension of [{(o-C6H4CH2-
NMe2)Pd(µ-OH)}2] (60 mg, 0.116 mmol) in acetone (9 mL) was
boiled under reflux for 30 min until the starting product was
completely dissolved. The resulting solution was then concen-
trated under vacuum. The addition of hexane caused the
precipitation of a white solid, which was collected by filtration
and air-dried. Yield: 35%. Anal. Calcd for C21H30N2O2Pd2: C,
45.4; H, 5.5; N, 5.0. Found: C, 45.7; H, 5.6; N, 4.9. Mp: 147
P r ep a r a tion of Com p lex [(AsP h 3)(C6F 5)P d {CH2C(O)-
CH3}(t-Bu NC)] (5). To a solution of complex 3 (90 mg, 0.07
mmol) in CH2Cl2 (6 mL) was added t-BuNC (15.8 µL, 0.14
mmol). The resulting solution was stirred at room temperature
for 15 min and concentrated under vacuum. The addition of
hexane caused the precipitation of a white solid, which was
collected by filtration, washed with hexane, and air-dried.
Yield: 70%. Anal. Found: C, 53.2; H, 4.0; N, 1.9. Calcd for
C32H29F5NOAsPd: C, 53.4; H, 4.0; N, 2.0. IR (Nujol, cm-1):
ν(CN), 2204; ν(CO), 1650; Pd-C6F5 str, 784. 1H NMR: δ 7.60-
7.34 (15 H, AsPh3), 2.81 (s, 2 H, CH2), 2.06 (s, 3 H, CH3CO),
1
°C dec. IR (Nujol, cm-1): ν(OH), 3560; v(CO), 1564, 1556. H
NMR (CDCl3): δ 7.3-6.9 (m, 8 H, aromatics), 3.84 (s, 2 H,
NCH2), 3.81 (s, 2 H, NCH2), 3.22 (s, 2 H, CH2CO), 2.74 (s, 6
H, NMe2 ), 2.67 (s, 6 H, NMe2), 2.24 (s, 3 H, CH3CO), -2.01 (s,
1 H, OH). 13C{1H} NMR (CDCl3): δ 148.5, 147.6, 147.5, 144.2
(aromatics C), 135.2, 130.7, 125.3, 124.6, 124.0, 123.0, 122.0,
121.4 (aromatics CH), 72.8 (CH2NMe2), 71.5 (CH2NMe2), 51.7
(NMe2), 50.1 (NMe2), 41.6 (CH2 CO), 28.7 (CH3CO). Positive-
ion FAB mass spectrum: m/z 556 (M - O)+.
P r ep a r a t ion of Com p lex [{(o-C6H 4CH 2NMe2)P d }2{µ
-CH2C(O)CH3}2] (2). A suspension of [{(o-C6H4CH2NMe2)Pd-
(µ-OH)}2] (60 mg, mmol) in acetone (4 mL) was boiled under
reflux for 4 h. The resulting precipitate was collected by
filtration, washed with hexane, and air-dried. Yield: 74%.
Anal. Calcd for C24H34N2O2Pd2: C, 48.4; H, 5.8; N, 4.7.
Found: C, 48.4; H, 5.7; N, 4.6. Mp: 186 °C dec. IR (Nujol,
cm-1): ν(CO), 1566. 1H NMR at 25 °C (CDCl3): δ 6.9 (br, 8 H,
aromatics) 4.1 (br, 2 H, NCH2), 3.6-3.5 (br, 4 H, NCH2 + CH2-
CO), 2.6 (br, 20 H, CH2CO + CH3CO + NMe2). 1H NMR at
-20 °C (CDCl3): δ 6.8 (m, 8 H, aromatics) 4.13 (d, 2 H, NCH2,
J 13.8), 3.60 (d, 2 H, NCH2, J 13.8), 3.53 (s, 2 H, CH2CO),
2.73 (s, 2 H, CH2CO), 2.65 (s, 6 H, NMe2), 2.63 (s, 6 H, CH3-
CO), 2.17 (s, 6 H, NMe2). 13C{1H} NMR at -20 °C (CDCl3): δ
148.9, 145.5 (aromatics C), 134.0, 125.3, 123.5, 122.4 (aromat-
ics CH), 71.2 (CH2 NMe2), 51.0 (NMe2), 50.4 (NMe2), 33.4 (CH2
CO), 31.4 (CH3CO).
1.20 (s, 9 H, CH3, t-BuNC). 19F NMR: δ -116.2 (d, Fo, J om
22.6 Hz), -162.5 (t, Fp, J pm ) 20.3 Hz), -163.8 (m, Fm).
)
P r ep a r a tion of Com p lex [NBu 4][(C6F 5)2P d (η5-2,4-Me2-
C4H3O)] (6). A solution of [NBu4]2[(C6F5)2Pd(µ-OH)2Pd(C6F5)2]
in acetone (15 mL) was heated under reflux with stirring for
6 h, and the solvent was then removed in vacuo. The residue
was treated with hexane to remove any traces of solvent and
then evaporated to dryness. This was repeated several times
until a white solid was filtered off and air-dried. Yield: 78%.
Alternatively, mesityl oxide [CH3C(Me)dCHCOCH3] (0.488
mmol) was added to a solution of [NBu4]2[(C6F5)2Pd(µ-OH)2Pd-
(C6F5)2] (0.1 g, 0.0714 mmol) in toluene (8 cm3); the solution
was heated under reflux with stirring for 6 h, and the solvent
was then removed in vacuo. The residue was treated with
hexane to remove any traces of mesityl oxide and then
evaporated to dryness. This was repeated several times.
Addition of 2-propanol/hexane afforded a white solid, which
was filtered off and air-dried. Yield: 80%. Mp: 211 °C dec.
ΛM ) 108 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CO), 1635; Pd-
C6F5 str, 780, 765. Anal. Calcd for C34H45NF10OPd: C, 52.35;
(81) Ruiz, J .; Rodr´ıguez, V.; Lo´pez, G.; Casabo´, J .; Molins, E.;
Miravitlles, C. Organometallics 1999, 18, 1177.
(82) Uso´n, R.; Fornie´s, J .; Navarro, R.; Garc´ıa, M. P. Inorg. Chim.
Acta 1979, 33, 69.

1982 Organometallics, Vol. 20, No. 10, 2001
Ta ble 4. Cr ysta l Str u ctu r e Deter m in a tion Deta ils
Ruiz et al.
3
5
8
formula
fw
C
54H40As2F10O2Pd2
C32H29AsF5NOPd
719.88
C16H23NO4Pd
399.7
1273.5
temperature (K)
cryst syst
space group
cell dimens
a (Å)
293(2)
triclinic
P1h (no. 2)
298(2)
monoclinic
P21/n (no. 14)
293(2)
monoclinic
P21/c (no. 14)
12.486(3)
14.119(3)
17.022(4)
69.19(2)
70.35(2)
80.13(2)
2637.1(10)
2
11.3502(9)
10.5017(7)
26.568(2)
6.524(2)
13.570(3)
19.502(3)
b (Å)
c (Å)
R (deg)
â (deg)
95.973(7)
91.10(2)
γ (deg)
cell vol (Å3)
Z
3149.7(4)
4
1.518
1440
1726.2(6)
4
1.54
D
calc (g cm-3
)
1.60
1256
F(000)
816
monochromated Mo KR
0.71069
0.71069
0.71073
radiation, λ (Å)
µ (mm-1
)
2.00
1.686
1.09
cryst size (mm)
0.30 × 0.25 × 0.10
0.30 × 0.15 × 0.10
0.4 × 0.4 × 0.3
θ range for data collection (deg)
index ranges
2 to 25
3.02 to 24.99
2 to 25
0 e h e 14, -16 e k e 16,
-18 e l e 20
9254
0 e h e 13, -12 e k e 12,
-31 e l e 31
11 358
5553 [R(int) ) 0.0435]
SHELXTL-5.0
full-matrix-block
least-squares on F2
SHELXTL-5.0
5553/36/398
1.007
0 e h e 7, 0 e k e 16,
-23 e l e 23
3302
3029 [R(int) ) 0.0224]
SHELXS-86
no. of reflns collected
ind reflns
structure solution
refinement method
9254
SHELXS-86
full-matrix
full-matrix
least-squares on F2
SHELXL-97
9254/0/631
least-squares on F2
SHELXL-97
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
3029/0/200
1.027
R1 ) 0.026, wR2 ) 0.071
R1 ) 0.033, wR2 ) 0.076
0.42 and -0.64
1.059
R1 ) 0.075, wR2 ) 0.190
R1 ) 0.140, wR2 ) 0.231
1.79 and -1.07
R1 ) 0.0372, wR2 ) 0.0614
R1 ) 0.0732, wR2 ) 0.0709
0.260 and -0.335
largest diff peak
and hole (e Å-3
)
1
H, 5.81; N, 1.80. Found: C, 52.12; H, 5.71; N, 1.83. H NMR
(CDCl3): δ 4.45 (s, Hb), 3.98 (s, Hd), 3.65 (s, He), 1.82, 1.74 (ss,
Mea, Mec) and additional peaks from [NBu4]+. 13C{1H} NMR
(CDCl3): δ 197.1 (C(2)), 127.4 (C(4)), 71.1 (C(3)), 65.7 (C(5)),
30.4, 25.3 (Mea and Mec) and additional peaks from [NBu4]+.
19F NMR (CDCl3): δ -110.8 (d, 2 Fo, J om 30.5 Hz), -111.5 (d,
2 Fo, J om 29.1 Hz), -164.0 (t, 1 Fp, J mp 19.8 Hz), -164.3 (t, 1
Fp, J mp 19.8 Hz), -165.2 (m, 4 Fm).
6.8 (m, 4 H, aromatics), 4.20 (s, 1 H, CH(CO2Me)2), 3.66 (s, 3
H, CH3O), 3.54 (s, 3 H, CH3O), 3.88 (s, 2 H, NCH2), 2.81 (s, 6
H, NMe2). Positive-ion FAB mass spectrum: m/z 371 (M+).
Com p lex 8. Yield: 75%. Anal. Calcd for C16H23N1O4Pd1: C,
48.1; H, 5.8; N, 3.5. Found: C, 48.2; H, 5.8; N, 3.5. Mp: 161
°C dec. IR (Nujol, cm-1): ν(CO), 1620. 1H NMR (CDCl3): δ 7.1-
6.9 (m, 4 H, aromatics), 4.24 (s, 1 H, CH(CO2Et)2), 4.19 (q, 2
H, CH2O, J 7.1), 4.09 (q, 2 H, CH2O, J 7.1), 3.84 (s, 2 H, NCH2),
2.86 (s, 6 H, NMe2), 1.28 (t, 6 H, CH2CH3, J 7.1), 1.25 (t, 6 H,
CH2CH3, J 7.1). Positive-ion FAB mass spectrum: m/z 399
(M+).
X-r a y Str u ctu r e Deter m in a tion of 3, 5, a n d 8. Crystals
suitable for a diffraction study were grown from toluene/
hexane (complexes 3 and 5) or dichloromethane/hexane (com-
plex 8) Details of data collection and refinement are given in
Table 4.
Rea ction of Com p lex 6 w ih P yr a zole. To a solution of
complex 6 (60 mg, 0.0769 mmol) in CDCl3 (0.6 mL) was added
pyrazole (Hpz) (10.47 mg, 0.1538 mmol). The resulting solution
was stirred at room temperature for 30 min, during which time
the previously known46 pyrazole-pyrazolate complex [NBu4]2-
[(C6F5)2Pd(pz)(Hpz)] precipitated spontaneously, which was
filtered off and air-dried. (1H NMR in Me2CO-d6: 7.60 (d, 2
H, 5-H ), 6.65 (d, 2 H, 3-H), 6.05 (pseudo-t, 2 H, 4-H)). The
filtrate was directly studied by 1H NMR and identified47 as
4-methyl-4-penten-2-one. (1H NMR (CDCl3): δ 4.91 (br, 1 H),
4.79 (br, 1 H), 3.08 (s, 2 H), 2.12 (s, 3 H), 1.71 (s, 3H)).
Syn t h esis of Com p lexes 7 a n d 8. To a suspension of
[{(o-C6H4CH2NMe2)Pd(µ-OH)}2] (80 mg, 0.155 mmol) in dichlo-
romethane (5 mL) was added the corresponding dialkyl mal-
onate CH2(CO2R)2 (R ) Me, Et) (1.55 mmol). The resulting
solution was stirred at room temperature for 1 h, and the
solvent was then removed under vacuum. The residue was
treated with hexane (R ) Me) or hexane/ether (R ) Et), and
the solid was collected by filtration and air-dried.
Ack n ow led gm en t. Financial support of this work
by the DGES (project PB97-1036), Spain, is acknowl-
edged. V.R. thanks CajaMurcia, Spain, for a research
grant.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinements details, atomic coordinates and equiva-
lent isotropic displacement parameters, complete bond dis-
tances and angles, and ORTEP views for compounds 3, 5, and
8. This material is available free of charge via the Internet at
http://pubs.acs.org.
Com p lex 7. Yield: 80%. Anal. Calcd for C14H19N1O4Pd1: C,
45.2; H, 5.2; N, 3.8. Found: C, 45.4; H, 5.3; N, 3.7. Mp: 166
°C dec. IR (Nujol, cm-1): ν(CO), 1620. 1H NMR (CDCl3): δ 7.1-
OM000860O