Reactivity of 6-(2-tolyl)- and 6-(2,6-xylyl)-2,2′-bipyridines with palladium(II) derivatives. Selective C(sp3)-H vs. C(sp2)-H activation

Article abstract of DOI:10.1016/S0022-328X(03)00457-1

Two new 6-substituted 2,2′-bipyridines, L, 6-(2-tolyl)bipy, L¹, and 6-(2,6-xylyl)bipy, L², have been synthesized. Their reactions with Na₂[PdCl₄] or {Pd(OAc)₂} afford either 1:1 adducts [Pd(L)X₂] (X=Cl, OAc) or five-membered cyclometallated derivatives [Pd(L¹-H)X] arising from C(sp²)-H activation. From the chloro-alkyl intermediates [Pd(L)(Me)Cl], in the presence of Na[BAr′₄] (Ar′=3,5-(CF₃)₂ C₆H₃), cationic species [Pd(L)(Me)(S)]⁺ (L=L¹, L²; S=CH₃CN) can be obtained. At variance, in less coordinating solvents, e.g. dichloromethane, unexpected activation of a C(sp³)-H bond occurs with loss of methane, to afford 6-membered cyclometallated derivatives. The latter species were isolated as [Pd(L-H)(PPh₃)] [BAr′₄].

Full text of DOI:10.1016/S0022-328X(03)00457-1

Journal of Organometallic Chemistry 679 (2003) 1ꢂ9
/
www.elsevier.com/locate/jorganchem
Reactivity of 6-(2-tolyl)- and 6-(2,6-xylyl)-2,2?-bipyridines with
palladium(II) derivatives. Selective C(sp3)ꢀH vs. C(sp2)ꢀ
H activation
/
/
Sergio Stoccoro *, Barbara Soro, Giovanni Minghetti, Antonio Zucca,
Maria A. Cinellu
Dipartimento di Chimica, Universita` di Sassari, via Vienna 2, I-07100 Sassari, Italy
Received 22 April 2003; received in revised form 15 May 2003; accepted 15 May 2003
Abstract
Two new 6-substituted 2,2?-bipyridines, L, 6-(2-tolyl)bipy, L1, and 6-(2,6-xylyl)bipy, L2, have been synthesized. Their reactions
with Na2[PdCl4] or {Pd(OAc)2} afford either 1:1 adducts [Pd(L)X2] (Xꢀ
[Pd(L1-H)X] arising from C(sp2)ꢀ
(Ar?ꢀ
3,5-(CF3)2C6H3), cationic species [Pd(L)(Me)(S)]ꢁ (Lꢀ
coordinating solvents, e.g. dichloromethane, unexpected activation of a C(sp3)ꢀ
/
Cl, OAc) or five-membered cyclometallated derivatives
?
/
H activation. From the chloro-alkyl intermediates [Pd(L)(Me)Cl], in the presence of Na[BAr4]
/
/
L1, L2; Sꢀ
/CH3CN) can be obtained. At variance, in less
/
H bond occurs with loss of methane, to afford 6-
?
membered cyclometallated derivatives. The latter species were isolated as [Pd(L-H)(PPh3)][BAr4].
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Cyclometallation; 2,2?-Bipyridine; Palladium
1. Introduction
Intramolecular Cꢀ
even subtle differences can play a role in the outcome of
the reaction. As part of an ongoing study into the effects
of ligand variations, we have now synthesized two new
ligands, namely 6-(2-tolyl)-2,2?-bipy and 6-(2,6-xylyl)-
2,2?-bipy, which bear sterically demanding substituents.
Their reactivity was explored at first with Na2[PdCl4]
and {Pd(OAc)2} and afterwards with palladium chloro-
methyl-derivatives. With the latter intermediates in the
?
/
H activation promoted by palla-
dium derivatives has been a topic of interest for many
years [1]. A number of N donors have been studied, as
supporting ligands, including potentially bidentate het-
erocyclic molecules such as 2,2?-bipyridines and 1,10-
phenanthrolines [1d,2]. Previously, we investigated the
behaviour of several 6-substituted-2,2?-bipyridines with
palladium(II) salts and isolated both adducts and
cyclometallated derivatives with an NfflNfflC sequence
of donor atoms [3]. The substituents were aryl, benzyl
presence of Na[BAr4] (Ar?ꢀ3,5-(CF3)2C6H3), in poorly
/
coordinating solvents such as dichloromethane, metalla-
tion involving an unactivated methyl group vs. cleavage
of an aromatic Cꢀ/H bond was achieved.
and alkyl groups and activation of both C(sp2)ꢀ
/H and
Today the influence of the nature of the substituents
on diimine ligands is of great interest particularly for d8
complexes (Ni, Pd, Pt): species of this type are exten-
sively investigated owing to their potential as catalytic
precursors in processes of paramount importance such
as polymerization of olefines (Ni, Pd) [4], copolymeriza-
C(sp3)ꢀ
/H bonds was achieved. The nature of the
substituent was shown to be crucial in driving the
reactivity of the ligand, often in unpredictable ways:
tion of CO/olefines (Pd) [5] and Cꢀ
/
H intermolecular
* Corresponding author.
E-mail address: stoccoro@uniss.it (S. Stoccoro).
activation (Pt) [6].
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00457-1

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S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ9
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Table 1
Proton and 31P-NMR dataa
Compound
CH3
CH2
H(6?)
Other aromatics
31P
2-(2-tolyl)pya
2.35 [s, 3H]
2.04 [s, 6H]
2.48 [s, 3H]
2.12 [s, 6H]
2.63 [s, 3H]
2.66 [s, 3H]
2.70 [s, 3H]
2.17 [s, 3H]
2.61 [s, 3H]
8.67 [d, 1H]
8.72 [d, 1H]
8.68 [d, 1H]
8.70 [d, 1H]
8.89 [d, 1H]
9.31 [d, 1H]
7.16ꢂ
7.25ꢂ
7.08ꢂ
7.13ꢂ
6.89ꢂ
6.86ꢂ
6.49ꢂ
6.91ꢂ
/
7.71 [m, 7H]
8.49 [m, 6H]
7.78 [m, 10H]
8.42 [m, 9H]
8.06 [m, 9H]
8.33 [m, 9H]
8.25 [m, 25H]
8.04 [m, 9H]
2-(2,6-xylyl)pya
/
6-(2-tolyl)-2,2?-bipy (L1)a
6-(2,6-xylyl)-2,2?-bipy (L2)a
[Pd(L1-H)Cl] (1b)b
[Pd(L1-H)I] (1c)b
[Pd(L1-H)(PPh3)][BF4] (1d)b
[Pd(L1-H)(OAc)] (1e)b
/
/
/
/
/
40.21
8.61 [d, 1H]
/
[Pd(L1)(OAc)2] (1f)b
1.32 [s, 3H]
2.01 [s, 3H]
2.68 [s, 3H]
7.29ꢂ/8.73 [m, 11H]
[Pd(L1)(Me)Cl] (1g)a
0.02 [s, 3H]
1.12 [s, 3H]
2.53 [s, 6H]
9.21 [d, 1H]
8.64 [d, 1H]
7.26ꢂ/8.11 [m, 20H]
1
[Pd(L )(Me)(MeCN)][BAr4] (1h)
a
?
1.00 [s, 3H]
1.78 [s, 3H]c
2.40 [s, 3H]
8.45 [d, 1H]
7.35ꢂ/7.99 [m, 22H]
1
a
3.07 [s, 2H] {5.6}e
6.59ꢂ
7.12ꢂ
7.14ꢂ
/
8.01 [m, 38H]
8.18 [m, 9H]
8.34 [m, 9H]
37.63
?
[Pd(*L -H)(PPh3)][BAr4] (1j)
[Pd(L2)Cl2] (2a)b
2.34 [s, 6H]
1.32 [s, 3H]
1.98 [s, 3H]
2.35 [s, 6H]
9.39 [d, 1H]
8.36 [d, 1H]
/
[Pd(L2)(OAc)2] (2f)b
/
[Pd(L2)(Me)Cl] (2g)a
0.05 [s, 3H]
1.12 [s, 3H]
2.21 [s, 6H]
2.27 [s, 6H]
9.28 [d, 1H]
8.65 [d, 1H]
7.11ꢂ/8.16 [m, 18H]
2
[Pd(L )(Me)(MeCN)][BAr4] (2h)
a
?
0.99 [s, 3H]
1.87 [s, 3H]c
2.13 [s, 6H]
8.45 [d, 1H]
7.14ꢂ/8.05 [m, 21H]
2
[Pd(*L -H)(PPh3)][BAr4] (2j)
a
3.52 [br, 1H]d
2.45 [br, 1H]d
6.37ꢂ/8.05 [m, 37H]
35.50
?
2.43 [s, 3H]
Spectra recorded at room temperature in CDCl3 (a) or CD2Cl2 (b); chemical shifts in ppm from internal TMS (1H) and external 85% H3PO4 (31P);
coupling constants are given in Hertz: J(PꢀH) in curly brackets; sꢀsinglet, dꢀdoublet, mꢀmultiplet; (c) CH3CN; (d) at ꢃ30 8C ABX system:
Xꢀ31P; dA 3.44, 3JPꢀH ca. 2 Hz; dB 2.36, 3JPꢀH ca. 8 Hz; (e) 13C{1H}-NMR in CDCl3: d 30.44 (2JCꢀP 3.0 Hz). *Ln -H: Pdꢀ
not resolved, JAB
CH2 bonded.
/
/
/
/
/
/
ꢀ/
ꢀ/
ꢀ/
ꢀ/
/
2. Results and discussion
The two new ligands, 6-(2-tolyl)-bipy, L1, and 6-(2,6-
xylyl)-bipy, L2, were prepared through a multistep
reaction scheme according to literature procedures [7].
The intermediate pyridine 2-(2-tolyl)py was obtained
in good yields, ca. 80%, whereas for 2-(2,6-xylyl)py the
yield was low (ca. 25%). The 1H-NMR data of L1 and L2
as well as of the corresponding pyridines are reported in
Table 1.
With the aim of promoting metallation, the reaction
of Na2[PdCl4] with L1 and L2 was carried out in water in
presence of HCl, heating the solution in a steam bath as
previously described for similar 6-substituted-bipy [2a].
Under these conditions, the cyclometallated species 1b
and the adduct 2a were obtained in good yields,
according to reaction 1and 2:
ð1Þ
ð2Þ

S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ
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3
We were unable to isolate the adduct [Pd(L1)Cl2] (1a),
in pure form; however when the reaction is carried out
at room temperature, the crude product is a mixture (ca.
1:1) of 1a and 1b. Their separation is hampered by the
poor solubility of both species. Evidence for the
refluxing acetic acid (ca. 55%). In methanol solution, in
the presence of LiCl, the acetate 1e is converted to 1b,
but yields are unsatisfactory, 20ꢂ25%.
/
Isolation of the adduct [Pd(L2)(OAc)2] (2f), can be
achieved directly from {Pd(OAc)2} in mild conditions,
i.e. at room temperature in methanol, acetone or acetic
acid. Addition of a few drops of acetic acid to the
acetone solution of {Pd(OAc)2} to prevent the forma-
tion of dimers, improves the yields [9]. The latter
expedient allowed us to isolate also the analogous
adduct with L1, [Pd(L1)(OAc)2] (1f), in reasonable
yields, ca. 65%.
1
presence of 1a in the mixture is provided by the H-
NMR spectra: by comparison with similar species the
two resonances at low field, d 8.89 and 9.28 can be
assigned to the H(6?) protons of 1b and 1a, respectively
[3].
Complex 1b belongs to a well known series of
NfflNfflC(sp2) cyclometallated derivatives 2a,b,c,8, and
can easily be converted into other neutral, e.g. 1c, or
cationic, 1d, complexes:
1
It is worth noting that the H-NMR spectra of the
adducts 2a and 2f, at room temperature, show one
(3)
(4)
Under comparable conditions, substitution of CO for
the chloride ligand does not occur.
As expected the cyclometallation is easier and occurs
under mild conditions if palladium acetate is used in
place of the rather weak palladation agent Na2[PdCl4]
[1g].
The cyclometallated species 1e
is obtained by reaction of {Pd(OAc)2} with L1 in
methanol at room temperature (yield ca. 75%) or in
resonance for the ortho-methyl protons, indicating
either free rotation of the substituent or a xylyl group
perpendicular to the coordination plane.
In conclusion, with both Na2[PdCl4] and {Pd(OAc)2},
metallation is achieved only in the case of L1, and
involves activation of a C(sp2)ꢀ
No Cꢀ
of the heterocyclic ring is observed. On the whole, the
/
H bond of the aryl ring.
/
H cleavage of an alkyl group or a C(sp2)ꢀ
/H bond
behaviour of L1 and L2 is fully consistent with the
(5)

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S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ9
/
assumption that aromatic Cꢀ
/
H activation is more facile
exchange processes, are often reported as EXSY spectra.
In our case the positive strong cross peaks between the
Pdꢀ
Me of 1gt and the PdꢀMe of 1gc, as well as between
than aliphatic Cꢀ
/
H activation and five- vs. 6-membered
rings are favoured [1].
/
/
Besides Na2[PdCl4] and {Pd(OAc)2}, we studied the
behaviour of the two ligands L1 and L2 with the chloro-
methyl intermediate [Pd(COD)(Me)Cl].
According to reaction (6)
the H(6?) protons of both species, provide evidence for
an equilibrium between the two isomers. It is worth
recalling that two isomers were observed also for
analogous platinum adducts when the 6-substituent
was the phenyl group [11].
[Pd(COD)(Me)Cl]ꢁL
With the aim of promoting metallation, the ability of
ꢃ
?
a non-coordinating anion such as [BAr4] [Ar?ꢀ
/3,5-
C6H6
0 [Pd(L)(Me)Cl]ꢁCOD
(CF3)2C6H3] to displace the coordinated chloride in
complexes 1g and 2g was tested at first in presence of
MeCN. Indeed, reaction (7) affords the cationic adducts
r:t:
(6)
LꢀL11g; LꢀL22g
1h (Lꢀ
/
L1) and 2h (LꢀL2).
/
the adducts 1g and 2g are obtained in good yields by
displacement of the coordinated 1,5-cyclooctadiene.
Complexes 1g and 2g were fully characterized by
elemental analyses and 1H-NMR spectroscopy. The 1H-
NMR spectra provide evidence for the presence in
solution of two stereoisomers arising from the unsym-
metrical nature of the ligands:
[Pd(L)(Me)Cl]ꢁNa[BA4?]
CH2Cl2
0 [Pd(L)(Me)(MeCN)][BA?]ꢁNaCl
(7)
4
MeCN
ð7Þ
The reaction is likely to be driven to completeness by
the insolubility of NaCl in CH2Cl2. Complexes 1h and
2h were isolated and characterized: according to 1H-
NMR spectra, one isomer only is formed. The high-field
resonance of the coordinated MeCN e.g. d 1.78, 1h,
suggests an aryl ring in close proximity. Comparison of
the H(6?) resonances with those of compounds 1g and 2g
supports the isomers 1ht and 2ht.
ð6Þ
There are two methyl signals PdꢀMe, and two H(6?)
/
resonances for both 1g and 2g. The upfield methyl
signals, d 0.02 and 0.05 can be assigned to 1gc and 2gc,
respectively, taking into account the anisotropic shield-
ing effect of the aryl substituent. The more deshielded
H(6?) resonances, d 9.21, 1gc and d 9.28, 2gc, are related
to the same isomers as previously observed for species
having a chlorine in proximity of H(6?) [10]. To achieve
In the absence of MeCN, the reaction was monitored
?
in an NMR tube. On addition of Na[BAr4] to the
1
further information a H NOESY experiment on com-
plex 1g was carried out. The spectrum shows a selective
NOE between the PdꢀMe signal at d 1.12 and the H(6?)
resonance at d 8.64 allowing their assignment to isomer
1gt. Phase sensitive NOESY spectra, having cross peaks
with the same phase as the diagonal, indicative of
suspension of the chloro-methyl derivative 1g in
CH2Cl2, evolution of gas is observed. The 1H-NMR
spectrum, besides a resonance at d 0.20 probably due to
dissolved methane, shows in the aliphatic region a
resonance at d 3.73 due to the CH2 protons of a
benzylic group. A broad resonance at d ca. 2.2 shifts to
/
(8)

S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ
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5
lower field by exchange with D2O. These data suggest
that, under these conditions, metallation occurs through
(2JCꢀP
ꢀ3.0 Hz), relative to a CH2 group: the assign-
/
ment was confirmed by a 13C apt (attached proton test)
1
activation of a C(sp3)ꢀ
be envisaged as the cationic sixꢂ
/
H bond. The resulting species can
membered cyclometal-
experiment. The H, 13C and 31P{1H}-NMR data are
/
fully consistent with the values previously reported for
lated species 1i, where an adventitious water takes up
the fourth coordination site around the palladium ion.
As expected, the coordinated water is rather labile
and can be substituted by PPh3:
complexes having an Arꢀ
/
CH2ꢀ
/
Pd bond cis to a Ph3P
ligand in a six-membered cycle [12].
The selective metallation of L1 to give 1i and 1j
implies a six- vs. a five-membered C,N ring and
(9)
Complex 1j can be obtained in good yields (ca. 80%)
from [Pd(L1)(Me)Cl] in a one-pot reaction:
activation of a C(sp3)ꢀ
/
H vs. a C(sp2)ꢀ
/H bond. The
result is quite unexpected: however, as previously
observed [2], in palladium chemistry the behaviour of
the 6-substituted 2,2?-bipy ligands is somewhat erratic
and often hardly predictable.
[Pd(L1)(Me)Cl]ꢁNa[BAr?]ꢁPPh3
CH2Cl2
4
0
[Pd(L1-H)(PPh3)][BAr?]ꢁNaClꢁCH4 (9)
4
1j
In the case of Pd(II), metallation mostly entails an
The 1H-NMR spectrum of complex 1j shows a
resonance at d 3.07 due to the CH2 group bonded to
electrophilic attack of the metal to the Cꢀ
In our case, however, the selective activation of a
C(sp3)ꢀH vs. a C(sp2)ꢀ
H bond makes a straightforward
electrophilic mechanism most unlikely. Abstraction of
the chloride and substitution by a solvent such as H2O
(or CH2Cl2,), i.e. a very labile ligand, favours the
/
H bond [1h].
palladium: the value of 3JPꢀH, ca. 6 Hz, fits a cis Pꢀ
/
Pdꢀ
/
/
/
CH2 arrangement. The 31P{1H}-NMR spectrum pro-
vides evidence for one species only in solution. The
13C{1H} spectrum shows a resonance at d 30.44
(10)

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S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ9
/
formation of a 14-electron intermediate. A plausible
pathway for the metallation can be envisaged consider-
ing that rotation of the 6-substituent allows the localiza-
variance with ligands where no competition with aryl
Cꢀ
H activation is possible, with the ligand L1 both an
arylic and an alkylic CꢀH bond can in principle be
activated: it is remarkable that C(sp3)ꢀ
H cleavage
occurs selectively, considering that this also implies a
six- vs. a five-membered ring. Such a behaviour is still
very rare: assuming in the present case the 14 electron
species as the actual intermediate, the selectivity of the
activation must be mainly dictated by the more or less
/
/
tion of an aryl Cꢀ
/
H bond or a methyl group in the
H activation can
/
palladium coordination plane. The Cꢀ
/
occur through a four-centre ring, assisted by the methyl
bonded to palladium acting as a base [1h].
Comparison of the two possible intermediates, A and
B, shows thatthe first one, A, which implies a methyl
close approach of the Cꢀ
The role of this factor in driving the cyclopalladation
toward C(sp3)ꢀ
H activation has been previously pointed
/H bond to the metal centre.
pointing toward the metal and a C(sp2)ꢀ
/
H bond toward
H
the H(5) atom of the substituted pyridine allows a Cꢀ
/
/
out [14]: in our case it is noteworthy that the approach
of the methyl to the metal centre in the coordination
plane is not required by the geometry of the ligand as in
the case e.g. of 8-methylquinoline [13a] and 7,8-benzo-
quinoline [15]. Steric repulsion does not hamper metal-
lation of the 2,6-xylyl substituted ligand L2 but
bond to be quite close to the metal. In addition, steric
repulsion between the aryl 6-substituent and the H(5)
atom should be lower than in B. Taken together, these
factors are likely to be responsible for the activation of
the aliphatic rather than the aromatic Cꢀ
/
H bond.
Under the same conditions, the ligand L2 gives the
(11)
same kind of Cꢀ/H activation:
considerably affects the rate of reaction.
The reaction however is much slower than for ligand
L1, probably owing to the enhanced repulsion between
the 6-substituent and the pyridil ring.
The NMR spectra (1H and 31P, CD2Cl2 solution)
show that complex 2j is similar to 1j. A difference in the
1H spectrum is given by the CH2 signal: at room
temperature two broad signals (d 3.52 and 2.45) are
3. Experimental
3.1. General procedures
The bipyridines L were prepared according to litera-
ture methods [7]. Na2[PdCl4] (29.15% Pd) and
[Pd(OAc)2] (47.4% Pd) were obtained from Enghelard.
All the solvents were purified before use according to
standard methods. Elemental analyses were performed
shown for complex 2j, whereas a sharp doublet (CDCl3,
3
d 3.07, d, JPꢀH
ꢀ5.6 Hz) was detected for complex 1j.
/
On lowering the temperature the signals sharpen and at
30 8C an ABX system can be resolved (Xꢀ31
P: dA
not resolved;
ca. 8 Hz): the spectra indicate dynamic behaviour
ꢃ
/
/
3
3
3.44, JPꢀH
ꢀ
/
ca. 2 Hz; dB 2.36, JPꢀH
ꢀ
/
with a PerkinꢂElmer elemental analyser 240B by Mr A.
/
JAB
ꢀ
/
Canu (Dipartimento di Chimica, Universita` di Sassari).
Conductivities were measured with a Philips PW 9505
of the six-membered metallacycle which, in the case of
2j, is relatively slow even at room temperature owing to
hindrance of the methyl group.
conductimeter. Infrared spectra were recorded with a
1
Perkinꢂ
/
Elmer 983 using Nujol mulls. H, 13C{1H}, and
31P{1H}-NMR spectra were measured with a Varian
VWR 300 spectrometer operating at 299.9, 75.4 and
121.4 MHz, respectively. Chemical shifts are given in
parts per million relative to internal Me4Si (1H, 13C) and
external 85% H3PO4 (31P). The 2D experiments were
performed by means of standard pulse sequences. The
In the chemistry of heterocyclic imine nitrogen
donors, examples of intramolecular Cꢀ/H bond activa-
tion of methyl groups promoted by palladium deriva-
tives, are known [13]. Mostly they involve tert-butyl or
neopentyl substituents as in the case of 6-substituted-2-
2?-bipyridines previously reported by us [3,13d]. At

S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ
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7
mass spectrometric measurements were performed on a
VG7070EQ instrument, equipped with a PDP 11-250J
data system and operating under positive ion fast atom
bombardment (FAB) conditions with 3-nitrobenzyl
alcohol as supporting matrix.
ture for 3 days, then evaporated to small volume. The
precipitate formed, after addition of diethyl ether, was
filtered off, washed with diethyl ether, and recrystallized
from CH2Cl2/Et2O to give the analytical sample as a
yellow solid. Yield: 160.1 mg, 75%. M.p.: 243 8C. Anal.
Found: C, 53.01; H, 4.21;
C19H16N2O2Pd×H2O: C, 53.17; H, 4.21; N, 6.53%.
FAB mass spectrum, m/z: 410 [Mꢁ], 351 [Mꢂ
CH3COO]. Complex 1e can also be obtained from
[Pd(OAc)2] in AcOH (105.3 mg, 57%) or in (Me)2CO/
AcOH (5:1) at room temperature (55.1 mg, 61%).
N 6.75%. Calc. for
3.2. Preparations
/
/
3.2.1. Synthesis [Pd(L1-H)Cl] (1b)
(a) To a solution of Na2[PdCl4]×
/
3H2O (380.5 mg, 1.04
mmol) in water (40 cm3) were added 1.04 mmol of
L1(258.6 mg) and 2 cm3 of 2 M HCl. The mixture was
heated in a water bath under stirring until the solution
was colorless. The yellow precipitate formed was filtered
off, washed with water, ethanol and diethyl ether to give
the analytical sample as a yellow solid. Yield: 379.7 mg,
94%. M.p.: stable up to 290 8C. Anal. Found: C, 52.48;
H, 3.41; N 7.35%. Calc. for C17H13ClN2Pd: C, 52.68; H,
3.36; N, 7.23%. FAB mass spectrum, m/z: 386 [Mꢁ],
3.2.5. [Pd(L1)(OAc)2] (1f)
[Pd(OAc)2] (112.6 mg, 0.50 mmol) was dissolved at
room temperature in acetone (10 cm3). After 30 min the
solution was filtered over fine paper and a few drops of
glacial acetic acid were added to prevent formation of
dimers. L1 (147.7 mg, 0.60 mmol) was added as a solid
to the red solution. In a few minutes a yellow product
began to precipitate. After 30 min the precipitate was
filtered off, washed with cold acetone and vacuum dried.
Yield: 153.2 mg, 65%. M.p.: 144 8C. Anal. Found: C,
351 [MꢂCl].
/
(b) To a solution of [Pd(OAc)2] (117.3 mg, 0.52 mmol)
in methanol (50 cm3) 127.0 mg of L1 (0.52 mmol) were
added. After stirring at room temperature (r.t.) for 2
days an excess of LiCl was added. The yellow precipitate
was filtered off, washed with diethyl ether and recrys-
tallized from CH2Cl2/Et2O to give the analytical sample,
as a solid yellow. Yield: 150.2 mg, 75%. M.p.: stable up
to 290 8C.
51.93; H, 4.18; N 6.00%. Calc. for C21H20N2O4Pd×
C, 51.55; H, 4.50; N, 5.73%. FAB mass spectrum, m/z:
411 [MꢂCH3COO], 352 [Mꢂ2CH3COO].
/
H2O:
/
/
3.2.6. [Pd(L2)Cl2] (2a)
Complex 2a can be obtained according to the
procedure (a) described for 1b. Yield: 193.9 mg, 85%.
M.p.: stable up to 290 8C. Anal. Found: C, 49.63; H,
3.74; N 6.32%, Calc. for C18H16Cl2N2Pd requires C,
49.40; H, 3.68; N, 6.39%. FAB mass spectrum, m/z: 435
3.2.2. [Pd(L1-H)I] (1c)
To a suspension of 1b (47.3 mg, 0.12 mmol) in acetone
(15 cm3) were added under stirring 40.8 mg of KI, (0.25
mmol). The mixture was stirred for 24 h at room
temperature, then evaporated to dryness. The crude
product obtained was crystallized from CH2Cl2/pentane
to give 1c. Yield: 35.3 mg, 61%. M.p.: stable up to
290 8C. Anal. Found: C, 42.79; H, 2.42; N 5.66%. Calc.
for C17H13IN2Pd: C, 42.62; H, 2.72; N, 5.85%.
[Mꢂ
2Me].
/
H], 366 [Mꢂ
/
2Cl], 351 [Mꢂ
/
2Clꢀ
/
Me], 336 [Mꢂ
/
2Clꢀ
/
3.2.7. [Pd(L2)(OAc)2] (2f)
To a solution of [Pd(OAc)2] (113.7 mg, 0.51 mmol) in
methanol (50 cm3) was added 131.7 mg of L2 (0.51
mmol). The red solution was stirred at room tempera-
ture for 3 h, then evaporated to small volume. The
precipitate formed by addition of diethyl ether was
filtered off, washed with diethyl ether, and recrystallized
from CH2Cl2/Et2O to give the analytical sample as a
yellow solid. Yield: 162.6 mg, 65%. M.p.: 165 8C.
{Compound 2f can also be obtained from [Pd(OAc)2]
in CH3COCH3 (188.6 mg, 75%)}. Anal. Found: C,
3.2.3. [Pd(L1-H)(PPh3)][BF4] (1d)
To a suspension of 1b (50.8 mg, 0.13 mmol) in acetone
(25 cm3) were added under stirring 34.6 mg of PPh3
(0.13 mmol) and 71.6 mg of Na[BF4] (5:1 excess). The
mixture was stirred for 1 h at room temperature, then
evaporated to dryness. The crude material obtained was
crystallized from CH2Cl2/Et2O to give 1d. Yield: 88.4
mg, 88%. M.p.: 267 8C. Anal. Found: C, 59.40; H, 3.71;
N 4.36%. Calc. for C35H28BF4N2PPd: C, 59.93; H, 3.99;
52.11; H, 4.65; N 5.73%. Calc. for C22H22N2O4Pd×
C, 52.50; H, 4.77; N, 5.57%. IR (Nujol) nmax(cmꢃ1):
1642s, 1373s. FAB mass spectrum, m/z: 425 [Mꢂ
CH3COO], 366 [Mꢂ2CH3COO].
/
H2O:
N, 3.99%. FAB mass spectrum, m/z: 613 [Mꢁ], 351 [Mꢂ
PPh3]; LM (5ꢄ
10ꢃ4 M, acetone): 104.5 Vꢃ1 cm2
molꢃ1
/
/
/
/
.
3.2.8. [Pd(L)(Me)Cl] [Lꢀ
/
L1 1g, LꢀL2 2g]
/
3.2.4. [Pd(L1-H)(OAc)] (1e)
To a solution of [Pd(OAc)2] (116.1 mg, 0.52 mmol) in
methanol (50 cm3) were added 127.8 mg of L1 (0.52
mmol). The red solution was stirred at room tempera-
To a solution of [Pd(COD)(Me)Cl] (103.6 mg, 0.39
mmol) in benzene (3 cm3) was added, under stirring, at
room temperature 0.43 mmol of L (105.9, and 111.9 mg
for L1 and L2, respectively) in 4 cm3 of diethyl ether. In a

8
S. Stoccoro et al. / Journal of Organometallic Chemistry 679 (2003) 1ꢂ9
/
few minutes a yellow solid began to precipitate: after 1 h
it was filtered off, washed with Et2O, dried in vacuo, to
give the analytical sample as a yellow solid. The product
was obtained as a mixture of two isomers (1gt/1gc ca.
0.76/1; 2gt/2gc ca. 1/1, NMR criterion).
3.2.15. 1j
Yield: 239.7 mg, 81%. M.p.: 148ꢂ
Found: C, 54.91; H, 2.36; 1.87%. Calc. for
C67H40BF24N2PPd: C, 54.47; H, 2.71; N, 1.89%. FAB
10ꢃ4 M,
/
150 8C. Anal.
N
mass spectrum, m/z: 613 [Mꢁ]. LM (5ꢄ
/
acetone): 44.1 Vꢃ1 cm2 molꢃ1
.
3.2.9. 1g
3.2.16. 2j
Yield: 138.3 mg, 88%. M.p. (dec.): 175 8C. Anal.
Yield: 195.7 mg, 66%. M.p.: 130ꢂ
Found: C, 54.85; H, 2.64; 1.92%. Calc. for
C68H42BF24N2PPd: C, 54.76; H, 2.82; N, 1.87%. FAB
/
132 8C. Anal.
Found: C, 53.92; H, 4.40;
C18H17ClN2Pd: C, 53.57; H, 4.22; N, 6.94%. FAB
mass spectrum, m/z: 401 [Mꢂ ClꢀCH3].
Hꢁ], 351 [Mꢂ
N 6.73%. Calc. for
N
/
/
/
mass spectrum, m/z: 627 [Mꢁ]. LM (5ꢄ
/
10ꢃ4 M,
acetone): 46.1 Vꢃ1 cm2 molꢃ1
.
3.2.10. 2g
Yield: 141.6 mg, 87%. M.p. (dec.): 187 8C . Anal.
Found: C, 54.71; H, 4.45; 6.58%. Calc. for
C19H19ClN2Pd: C, 54.64; H, 4.55; N, 6.71%. FAB
N
Acknowledgements
mass spectrum, m/z: 365 [Mꢂ
/
Clꢀ
/
CH4].
Financial support from the University of Sassari is
gratefully acknowledged.
3.2.11. [Pd(L)(Me)(MeCN)][BAr4] [Lꢀ
/
L1 1h, Lꢀ
/
?
L2 2h]
?
To a solution of Na[BAr4] (113.9 mg, 0.13 mmol) in
0.25 cm3 of MeCN, were added under stirring at room
temperature 0.13 mmol of [Pd(L)(Me)Cl] (52.4, and 53.4
mg for L1 and L2, respectively) in 20 cm3 of CH2Cl2. The
yellow color of the solution immediately fades and a
NaCl precipitate is formed. After stirring for 1h, the
solution was filtered and evaporated to dryness. The
analytical samples of compounds 1h and 2h were
obtained by crystallization from CH2Cl2/pentane.
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?
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