Palladium(II)-allyl complexes containing chiral N-donor ferrocenyl ligands

Article abstract of DOI:10.1016/j.jorganchem.2007.06.016

A study of the reactivity of enantiopure ferrocenylimine (S_C)-[FcCH{double bond, long}N-CH(Me)(Ph)] {Fc = (η⁵-C₅H₅)Fe{(η⁵-C ₅H₄)-} (1a) with palladium(II)-allyl complexes [Pd(η³-1R¹,3R²-C₃H₃ )(μ-Cl)]₂ {R¹ = H and R² = H (2), Ph (3) or R¹ = R² = Ph (4)} is reported. Treatment of 1a with 2 or 3 {in a molar ratio Pd(II):1a = 1} in CH₂Cl₂ at 298 K produced [Pd(η³-3R²-C₃H₄){FcCH{do uble bond, long}N-CH(Me)(Ph)}Cl] {R² = H (5a) or Ph (6a)}. When the reaction was carried out under identical experimental conditions using complex 4 as starting material no evidence for the formation of [Pd(η³-1,3-Ph₂-C₃H₃){FcC H{double bond, long}N-CH(Me)(Ph)}Cl] (7a) was found. Additional studies on the reactivity of (S_C)-[FcCH{double bond, long}N-CH(R³)(CH₂OH)] {R³ = Me (1b) or CHMe₂ (1c)} with complex 4 showed the importance of the bulk of the substituents on the palladium(II) allyl-complex (2-4) or on the ferrocenylimines (1) in this type of reaction. The crystal structure of 5a showed that: (a) the ferrocenylimine adopts an anti-(E) conformation and behaves as an N-donor ligand, (b) the chloride is in acis-arrangement to the nitrogen and (c) the allyl group binds to the palladium(II) in a η³-fashion. Solution NMR studies of 5a and 6a and [Pd(η³-1,3-Ph₂-C₃H₃){FcC H{double bond, long}N-CH(Me)(CH₂OH)}Cl] (7b) revealed the coexistence of several isomers in solution. The stoichiometric reaction between 6a and sodium diethyl 2-methylmalonate reveals that the formation of the achiral linear trans-(E) isomer of Ph-CH{double bond, long}CH-CH₂Nu (8) was preferred over the branched derivative (9). A comparative study of the potential utility of ligand 1a, complex 5a and the amine (S_C)-H₂N-CH(Me)(Ph) (11) as catalysts in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with the nucleophile diethyl 2-methylmalonate (Nu^-) is reported.

Full text of DOI:10.1016/j.jorganchem.2007.06.016

Journal of Organometallic Chemistry 692 (2007) 4215–4226
www.elsevier.com/locate/jorganchem
Palladium(II)–allyl complexes containing chiral N-donor
ferrocenyl ligands
a
a
a,
b
Ana E. Platero-Prats , Sonia Perez , Concepcion Lopez *, Xavier Solans ,
´
´
´
Merce Font-Bardıa , Piet W.N.M. van Leeuwen c,1, Gino P.F. van Strijdonck ,
b
c
`
´
c,1
Zoraida Freixa
a
´
Departament de Qu´ımica Inorganica, Facultat de Quımica, Universitat de Barcelona, Martı i Franques 1-11, 08028-Barcelona, Spain
`
´
`
b
´
`
`
Departament de CristalÆlografia, Mineralogia i Diposits Minerals, Facultat de Geologia, Universitat de Barcelona, Martı i Franques s/n,
08028-Barcelona, Spain
Van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018-WV Amsterdam, The Netherlands
c
Received 20 February 2007; received in revised form 12 June 2007; accepted 12 June 2007
Available online 23 June 2007
Abstract
A study of the reactivity of enantiopure ferrocenylimine (SC)-[FcCH@N–CH(Me)(Ph)] {Fc = (g5-C5H5)Fe{(g5-C5H4)–} (1a) with
palladium(II)–allyl complexes [Pd(g3-1R1,3R2-C3H3)(l-Cl)]2 {R1 = H and R2 = H (2), Ph (3) or R1 = R2 = Ph (4)} is reported. Treat-
ment of 1a with 2 or 3 {in a molar ratio Pd(II):1a = 1} in CH2Cl2 at 298 K produced [Pd(g3-3R2-C3H4){FcCH@N–CH(Me)(Ph)}Cl]
{R2 = H (5a) or Ph (6a)}. When the reaction was carried out under identical experimental conditions using complex 4 as starting material
no evidence for the formation of [Pd(g3-1,3-Ph2-C3H3){FcCH@N–CH(Me)(Ph)}Cl] (7a) was found. Additional studies on the reactivity
of (SC)-[FcCH@N–CH(R3)(CH2OH)] {R3 = Me (1b) or CHMe2 (1c)} with complex 4 showed the importance of the bulk of the substit-
uents on the palladium(II) allyl–complex (2–4) or on the ferrocenylimines (1) in this type of reaction. The crystal structure of 5a showed
that: (a) the ferrocenylimine adopts an anti-(E) conformation and behaves as an N-donor ligand, (b) the chloride is in a cis-arrangement
to the nitrogen and (c) the allyl group binds to the palladium(II) in a g3-fashion. Solution NMR studies of 5a and 6a and [Pd(g3-1,3-Ph2-
C3H3){FcCH@N–CH(Me)(CH2OH)}Cl] (7b) revealed the coexistence of several isomers in solution. The stoichiometric reaction between
6a and sodium diethyl 2-methylmalonate reveals that the formation of the achiral linear trans-(E) isomer of Ph–CH@CH–CH2Nu (8) was
preferred over the branched derivative (9). A comparative study of the potential utility of ligand 1a, complex 5a and the amine (SC)-
H2N–CH(Me)(Ph) (11) as catalysts in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with the nucleophile diethyl
2-methylmalonate (Nuꢀ) is reported.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Palladium(II)–allyl-complexes; Allylic alkylation; Ferrocene derivatives; Chiral palladium(II) compounds
1. Introduction
interest in the last years due to their physical and chemical
properties or their potential applications in a wide variety
of areas [1–7]. Examples of molecular devices and chemical
sensors or receptors containing ferrocenyl units have been
reported [3,4]. Furthermore, the study of the applications
of this type of compounds in homogeneous catalysis has
increased exponentially during the last decade [1,6–9].
One of the most widely studied processes is the catalytic
allylic alkylation [7–9], which constitutes an effective tool
for the formation of C–C and C–heteroatom bonds.
The development of new ferrocene derivatives having
one or more heteroatoms with good donor abilities and
their transition metal complexes has drawn considerable
*
Corresponding author.
´
E-mail address: conchi.lopez@qi.ub.es (C. Lopez).
Present address: Institute of Chemical Research of Catalonia (ICIQ),
1
Avda Pa¨ısos Catalans, 16, 43007 Tarragona, Spain.
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.06.016

4216
A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
Consequently, it is of great importance in synthetic
chemistry [10,11]. Usually, in these reactions the catalytic
precursor is a palladium(II) complex containing the (g3-
C3H5) ligand and either one bidentate (L, L0) or two
monodentate (L and L0 or L and X) ligands. Often these
precursors are generated in situ by treatment of the
[Pd(g3-C3H5)(l-Cl)]2 complex and the corresponding
ligand. The mechanism accepted for the catalytic allylic
alkylation process with stabilized nucleophiles proceeds
in four consecutive steps (Scheme 1A–D) and the regio-
as well as the stereoselectivity of the process are dependent
on several factors that include the number and structures of
the different isomeric forms of the intermediate species
formed in step (B), their interconversion rates and the ease
with which they undergo the nucleophilic attack [10,11].
Despite the large amount of ferrocene derivatives pub-
lished so far, most of the reports concerning their applica-
tion in the palladium(II) catalyzed allylic alkylation involve
the presence of potentially bidentate ligands [7,8]. Studies
dealing with enantiopure N-donor ferrocene derivatives
or their palladium(II) complexes are not so common [9]
and most of them focus on the use of ferrocenyl oxazolines
[9c,9d] while related studies on ferrocenylimines are not
known.
In this contribution we present some palladium(II)–allyl
complexes of general formula: [Pd(g3-1R1,3R2-C3H3)-(L)-
Cl] where L represents the enantiopure Schiff bases
(SC)-[FcCH@N–CH(Me)(Ph)] (1a) or (SC)-[FcCH@N–
CH- (R3)(CH2OH)] {R3=Me (1b) or CHMe2 (1c)} together
with a comparative study of the catalytic activity of 1a,
complex (SC)-[Pd(g3-C3H5){FcCH@N–CH(Me)(Ph)}Cl]
(5a) and the amine (SC)-H2N–CH(Me)(Ph) (11) in the
allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl)
acetate with sodium diethyl 2-methylmalonate. Detailed
NMR studies on the allyl complexes indicate that several
isomers coexist in solution. For compound (SC)-[Pd(g3-3-
Ph–C3H4){FcCH@N–CH(Me)(Ph)}Cl] (6a), which is the
key intermediate in the catalytic process, these studies as
well as the results obtained from its reactivity with the
nucleophile have allowed us to rationalize the regioselectiv-
ity of the process.
2. Results and discussion
2.1. Synthesis
The ligand (SC)-[FcCH@N–CH(Me)(Ph)] (1a) was pre-
pared according to the general procedure described for
most ferrocenylaldimines [12]. Proton and 13C{1H} NMR
spectra indicated that only one isomer was present in solu-
tion and the {1H–1H} NOESY revealed that the ligand
adopted the anti-(E) conformation. This result agrees with
those obtained for ferrocenylaldimines and ketimines of
general formula [FcC(R4) = N-R5], (R4 = H, Me or Ph
and R5 = phenyl, benzyl or naphthyl groups) reported so
far [13]. Besides that, it is well known that the reaction
between aldehydes and optically pure amines such as:
H2N–CH(R3)R6 with R3 = Me, CHMe2 and R6 = CH2OH
or naphthyl or R3 = CO2Me and R6 = CH2–CH2-SMe
does not affect the chirality of the stereogenic centre
[14–16]. Thus, the absolute configuration of 1a is expected
to be SC.
Treatment of the ferrocenylimine 1a with the corre-
sponding allyl compound [Pd(g3-1R1,3R2-C3H3)(l-Cl)]2
{R1 = H and R2 = H (2) or Ph (3)} in a molar ratio Pd(II):
1a = 1 in CH2Cl2 at 298 K gave, after concentration to dry-
ness, [Pd(g3-3R2-C3H4){FcCH@N–CH(Me)(Ph)}Cl] {with
R2 = H (5a) or Ph (6a), respectively} (Scheme 2).
In contrast with these results the reaction of 1a with
[Pd(g3-1,3-Ph2-C3H3)(l-Cl)]2 (4) under identical experi-
mental conditions showed no evidence for the formation
of [Pd(g3-1,3-Ph2-C3H3){FcCH@N–CH(Me)(Ph)}Cl] (7a)
and the starting reagents were recovered unreacted. The
addition of NaOH [in molar ratios NaOH:Pd(II) = 1] to
the reaction medium lead to the decomposition of the
reagents, giving metallic palladium and ferrocenecarboxal-
dehyde as the major products. These findings suggested
that the presence of the two bulky phenyl groups in the
allyl ligand inhibits the formation of complex 7a. Molecu-
lar models of 7a reveal that the presence of two phenyl
groups in the (1,3-Ph2-C3H3) unit does not permit a co-pla-
nar arrangement of the imine moiety and the centroids of
the two C–C bonds of ‘‘C3-backbone’’ of the allyl. Addi-
tionally, for a nearly orthogonal arrangement of these
units, one of the phenyl groups will be extremely close to
the hydrogen atoms of the ‘‘(g5-C5H5)Fe(g5-C5H4)’’ unit
and the other will be too close to the aromatic ring on
the stereogenic carbon. Consequently, the formation of
7a is unlikely to occur. In order to elucidate the effect of
the substituents on the viability of the formation of the
palladium(II) allyl complexes, we also studied the reac-
tion between [Pd(g3-1,3-Ph2-C3H3)(l-Cl)]2 (4) and the
imine (SC)-[FcCH@N–CH(R3)(CH2OH)] {R3=Me (1b) in
Scheme 1. Mechanism of the palladium-catalyzed allylic substitution
reactions using stabilized nucleophiles {where S = solvent, L and L0
monodentate ligands or (L, L0) bidentate ligand, LG = leaving group and
Nuꢀ nucleophile.

A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
4217
Scheme 2. i) [Pd(g3-3-R2-C3H4)(l-Cl)]2 in a molar ratio 1a:Pd(II) = 1 in CH2Cl2 at 298K.
Fig. 1. Other ligands used in this study and their palladium(II)–allyl complexes.
Fig. 1} [14b,16], containing a smaller2 [17] and more
flexible substituent on the stereogenic carbon than 1a. This
gave an orange solid, whose characterization data (see
Section 3) agreed with those expected for [Pd(g3-1,3-
Ph2-C3H3){FcCH@N–CH(Me)(CH2OH)}Cl] (7b) (Fig. 1).
However, when the reaction was performed with
(SC)-[FcCH@N–CH(CHMe2)(CH2OH)] (1c in Fig. 1)
[14b,16], which arises from 1b by replacement of the methyl
group by a bulkier –CHMe2 unit3, the starting materials
were recovered and no evidence for the formation of
[Pd(g3-1,3-Ph2-C3H3){FcCH@N–CH(CHMe2)(CH2OH)}-
Cl] (7c) (Fig. 1) was detected. These findings provide addi-
tional proofs for the importance of the bulkiness of the
substituents on the stereogenic carbon on the reactivity of
ligands 1a–1c with [Pd(g3-1,3-Ph2-C3H3)(l-Cl)]2 (4), which
determine the viability of the formation of the palla-
dium(II)–allyl complexes (7a–7c).
may differ in the conformation of the Schiff base {syn-(Z)
or anti-(E)}, the relative arrangements between the methyl
group and the central Cb–Hb bond of the allyl ligand (endo-
or exo-) (Fig. 2). In addition for complexes 6a and 7b other
sources of isomerism should also be considered. In these
products, the phenyl rings could be in a syn- or anti- posi-
tion in relation to the central hydrogen (Hb) of the allyl
unit. For 6a, which contains a non-symmetric allyl group,
the substituted carbon of the allyl group (Cc) may be
located in a cis- or trans- arrangement in relation to the
imine nitrogen. Furthermore, the inhibition of the free
rotation around the Cipso–Cimine bond or the Pd–Nimine
bond may also produce rotameric species. This could be
particularly relevant at low temperatures.
Compounds 5a, 6a and 7b were characterized by ele-
mental analyses, mass spectroscopy, IR and one and two-
dimensional NMR spectroscopy. Elemental analyses (see
Section 3) are consistent with the proposed formulae and
their mass spectra showed peaks at m/z = 501 (for 5a),
575 (for 6a) 570 (for 7b). The former two peaks are consis-
tent with those expected for the cations [Pd(g3-3-R2-
C3H4){FcCH@N–CH(Me)(Ph)}Cl]+ with R2 = H (5a) or
Ph (6a), while the latter agrees with that of the ion
{[M]ꢀCl}+ of 7b.
2.2. Characterization
The new palladium(II)–allyl complexes can adopt a wide
variety of isomeric forms. In particular for 5a, the isomers
2
The Charton’s steric parameters (Es-CH) of the substituents Ph and
In the IR spectra of 5a, 6a and 7b, the band due to the
stretching of the ˜C@N– group appeared at lower energy
than for the corresponding free ligand {1641 cmꢀ1 (1a)
CH2OH are 3.00 and 2.00, respectively [17].
3
The Es-CH parameters of Me and CHMe2 are 1.00 and 3.00,
respectively [17].

4218
A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
Fig. 3. ORTEP plot of [Pd(g3-C3H5){FcCH@N–CH(Me)(Ph)}Cl] (5a).
Hydrogen atoms have been omitted for clarity. Selected bond lengths (in
˚
A) and angles (in ꢁ): Pd–N, 2.123(4); Pd–Cl, 2.224(8); Pd–C(20), 2.058(5);
Pd–C(21), 2.224(8); Pd–C(22), 2.086(6); C(10)–C(11), 1.457(6); C(11)–N,
1.255(6); N–C(12), 1.495(5); C(12)–C(13), 1.570(8); C(12)–C(14), 1.574(8);
C(14)–C(15), 1.434(10); C(15)–C(16), 1.420(10); C(16)–C(17), 1.215(10);
C(17)–C(18), 1.347(10); C(18)–C(19), 1.346(11); C(20)–C(21), 1.407(5);
C(21)–C(22), 1.446(13); Cl–Pd–N, 96.14(10); N–Pd–C(22), 99.7(2); C(20)–
Pd–Cl, 93.8(2); C(20)–Pd–C(22), 70.3(3); C(10)–C(11)–N, 127.0(4); N–
C(12)–C(13), 197.5(4); N–C(12)–C(14), 106.7(4) and C(20)–C(21)–C(22),
113.5(7).
Fig. 2. Simplified view of the isomeric forms expected for 5a. In two of
them (a,b) the imine has the anti-(E) conformation, while in the pair (c, d)
it adopts the syn-(Z) form. The main difference between a and b (or c and
d) is the conformation of the allyl group {exo- (in a and c) and endo- (in b
and d)}.
plane defined by the atoms C(20)–C(22) forms an angle
of 62ꢁ with that of the imine group. The variations detected
in the Cl–Pd–C(20) and N–Pd–C(22) bond angles [93.8(2)ꢁ
and 99.7(2)ꢁ] suggest that the presence of the bulky substit-
uents on the imine nitrogen may introduce steric hindrance
between this ligand and the substituents on the C(22) car-
bon atom. Additionally, for the arrangement of the groups
depicted in Fig. 3, the distance between the palladium and
the hydrogen on the ortho site of the C5H4 ring, H(6), is
or 1638 cmꢀ1 (1b) [14b,16]}. This suggests, according to the
literature [18], that the imine nitrogen coordinated to the
palladium(II).
The crystal structure of 5a4 consists of molecules of
[Pd(g3-C3H5){FcCH@N–CH(Me)(Ph)}Cl] separated by
van der Waals distances. In each one of these heterodime-
tallic units (Fig. 3) the palladium(II) is bound to the imine
nitrogen, a chloride and the C3H5 ligand in a g3-fashion.
The value of the N–Pd–Cl bond angle [95.14(10)ꢁ] indicates
a cis-arrangement of the chloride and the imine nitrogen.
˚
rather small (2.061 A) and suggests a weak Pdꢁ ꢁ ꢁH interac-
tion. Similar features have also been described for other
palladium(II) complexes containing one or two N-donor
ligands [21].
˚
The Pd–N bond length [2.123(4) A] is in good agreement
Furthermore, the hydrogen bound to the C(22) atom
with those reported for other palladium(II) complexes con-
taining ferrocenyl Schiff bases [12–14c,19]. The Pd–C(20)
˚
and located on the anti-position is only 2.60 A away from
the H(3) hydrogen of the ferrocenyl unit. This suggests that
the surroundings of the C(22) atom are rather crowded. In
addition, the hydrogen atoms H(19) (on the ortho site of
˚
bond length [2.058(5) A] is shorter than the Pd–C(22) bond
˚
distance [2.086(6) A]. This could be due to the different
influence of the donor atoms in a trans-position [20]. In
˚
the phenyl ring) and H(4) are only 2.71 A apart.
˚
addition the C(20)–C(21) bond [1.407(5) A] is shorter than
˚
The ˜C@N– bond length [1.255(6) A] is consistent with
˚
the C(21)–C(22) bond [1.446(13) A]. The C(21) carbon
those reported for related palladium(II) complexes contain-
ing ferrocenylimines [12–14c,19] and the value of the tor-
sion angle C(10)–C(11)–N–C(12) (174.1ꢁ) indicates that
the imine adopts the anti-(E) conformation.
atom and the iron(II) centre are located on opposite sides
of the coordination plane of the palladium(II) and the
The two pentagonal rings of the ferrocenyl unit are pla-
nar and nearly parallel (tilt angle = 2.54ꢁ) and they deviate
by ca. 2.1(1)ꢁ from the ideal eclipsed conformation. Bond
lengths and angles of this moiety are similar to those
reported for other monosubstituted ferrocene derivatives
[19].
4
Crystal data: C22H24ClFeNPd, FW = 500.12, T = 293(3)K, ortho-
˚
˚
˚
rhombic, a = 9.496(1) A, b = 10.520(1) A, c = 20.709(1) A, a = 90.0ꢁ,
b = 90.01ꢁ, c = 89.85ꢁ, V = 2068.3(3) A , Z = 4, Dcalc = 1.606 g cmꢀ3
,
3
˚
l = 1.704 mmꢀ1
, F(0 0 0) = 1008, final R indices: R1 = 0.0465,
wR2 = 0.1233 {for I > 2r(I)} and R1 = 0.0465 and wR2 = 0.1508 (for all
data).

A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
4219
2.3. Solution studies
in the NMR spectra of 6aI and 6aII affect the position
of the signals due to: (a) the substituents (H and Me)
on the stereogenic centre and (b) those of the allylic pro-
tons. In particular, for 6aII the resonance of the methyl
protons (at 1.61 ppm) appeared at higher fields than that
of 6aI (at 1.98 ppm) and the signals due to the proton of
the ˜CH(Me) moiety exhibited the opposite trend
(d = 4.57 and 4.82 ppm for 6aI and 6aII, respectively).
These variations, which were not observed for the major
isomers of 5a {5aI and 5aII}, suggested that the H and
Me sub- stituents of 6aI and 6aII were affected by the ring
current of the phenyl group of the allyl ligand. The exis-
tence of NOE peaks between the signal at 1.61 ppm and
the resonance of an aromatic proton at 7.92 ppm con-
firmed the proximity between the phenyl and the methyl
groups in 6aII.
For all the three isomers, the signals due to the allylic
protons appeared as a multiplet {in the range of
5.0–6.0 ppm assigned to the central proton (Hb)} and three
additional doublets in the area 2.6–4.0 ppm. The two-
dimensional [{1H–13C} HSQC and {1H–1H} NOESY]
NMR experiments gave evidence for the signals due to
Haanti; Hasyn and Hcanti protons of the (g3-3-Ph–C3H4) ligand.
Additionally, the existence of a NOE peak between the sig-
nal of the Haanti proton of 6aII and that of the protons of the
C5H5 ring indicates that in 6aII these groups are close. All
these results suggest that in 6aI and 6aII: (a) the substituted
carbon of the allyl ligand is close to the stereogenic centre
and (b) the two isomers differ in the relative arrangement of
the central Cb–Hb bond in relation to the methyl group
(endo- or exo-).
NMR studies of 7b suggested the coexistence of four iso-
meric forms (7bI–7bIV, in a 10.0:6.6:0.9:0.8 ratio, respec-
tively) in CDCl3 at 298 K. The {1H–1H} NOESY
spectrum (Fig. 4) showed cross-peaks between the signals
due to the imine proton and those of the H5 and ˜CH– pro-
tons of 7bI and 7bII. This means that in both cases the
ligand adopts the anti-(E) conformation. The values of
the coupling constants between the allylic protons (see Sec-
tion 3) were larger than 10 Hz and strong NOE cross-peaks
between the signals due to Ha and Hc were also observed
for 7bI and 7bII. According to the bibliography [8] these
two findings are consistent with a syn-, syn- arrangement
of the two phenyl groups of the (g3-1,3-Ph2-C3H3) ligand.
In view of this observation, we assumed that the main dif-
ference between 7bI and 7bII arises from the arrangement
between the central Cb–Hb bond of the allyl ligand and
the methyl group on the stereogenic carbon (endo- or
exo-).
As mentioned above the new palladium(II)–allyl com-
plexes may exhibit different isomeric forms. NMR studies
of 5a, 6a and 7b have been very useful to determine the
number of isomers and the differences between the major
isomeric forms present in solution.
The 1H NMR spectrum of 5a in CD2Cl2 at 298 K
showed three sets of superimposed signals of relative inten-
sities (10.0:7.6:0.3). This could be indicative of the presence
of three isomeric forms of 5a (5aI, 5aII, 5aIII, respectively).
At 273 K 5aI–5aIII coexisted in molar ratios of 10.0:5.4:0.3.
For 5aI and 5aII, the {1H–1H} NOESY spectrum
showed the existence of NOE interactions between the sig-
nals due to imine protons and that on the stereogenic car-
bon of (5aI and 5aII). This is only possible if the ligand
adopts the anti-(E) conformation in the two isomers.
The resonances due to the allylic protons on the termi-
nal carbon nuclei of 5aI appeared as two doublets {at
d = 3.03 (J = 12.0 Hz) [for Haanti and Hcanti] and 4.17 ppm
(J = 7.0 Hz) [for Hsayn and Hscynꢂ}; while for 5aII four dou-
blets {at d = 2.60 (J = 12.0 Hz), 2.73 (J = 12.0 Hz), 3.20
(J = 7.0 Hz) and 2.71 (J = 7.0 Hz)} were detected. Since
the values of the J(Hanti–Hb) are greater than J(Hsyn–Hb)
[22] we assigned the signals at 3.03 (in 5aI) and the pair
of resonances at 2.60 and 2.73 ppm of 5aII to the protons
in the anti-positions. The analyses of the cross-peaks
detected in the {1H–13C} HSQC spectrum as well as the
NOE peaks observed in the {1H–1H} spectrum allowed
to identify unambiguously the signals due to the different
types of protons and 13C-nuclei of the allyl group of 5aI
and 5aII. An interesting result obtained from the
{1H–1H} NOESY spectrum is the presence of a NOE
cross-peak between the resonance of the allylic proton
Hcanti and one proton of the phenyl group of 5bII, thus
suggesting that these two moieties are proximal. This is
only possible if the aromatic ring and the Hcanti proton are
on the same side of the coordination plane in 5bII (Fig. 2,
type a). For 5aI the existence of a NOE contact between
the pair of protons H2 and Hsayn suggests that in this case
the orientation of the allyl group is that presented in
Fig. 2 (type b).
Due to the low abundance of 5aIII, we were neither able
to establish the conformation of the imine (syn- or anti-)
nor the conformation of the allyl group (endo- or exo-).
The proton-NMR spectrum of 6a at 298 K showed four
sets of superimposed broad signals. At 273 K the signals
became narrower and the analyses of the resonances sug-
gested the presence of four isomeric forms of 6a
(6aI–6aIV) in
respectively.
a
relative abundance 10.0:5.1:0.4:0.1,
The 1H NMR spectrum of 7b showed that the signal due
to the methyl protons of 7bII (d = 0.41 ppm) was shifted to
upfield compared to 7bI (d = 1.18 ppm). This suggested
that in 7bII the Me unit could be affected by the ring current
produced by the phenyl group of the allylic ligand. The
{1H–1H} NOESY spectrum confirmed this by the presence
of three NOE contacts (cross-peaks c–e, in Fig. 4) between
the protons of one of the two Ph groups of the allyl unit
The {1H–1H} NOESY spectrum at 273 K indicated
that for 6aI and 6aII the imine adopts the anti-(E) confor-
mation. Besides that, the existence of NOE peaks between
the signals due to the Hb and the aromatic protons of the
allyl unit suggested that in both cases the phenyl is in the
syn-position. The most relevant differences detected

4220
A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
Fig. 4. {1H–1H} NOESY spectrum of 7b in CDCl3 at 298 K showing the most relevant NOE peaks (a–e) detected for the major isomers 7bI and 7bII
(labels in italics correspond to isomer 7bII). For 7bI, the cross-peaks a–b indicate NOE interactions between: the methyl protons and Hc(a), and the H2
nuclei of the C5H4 ring and an aromatic proton of the allyl ligand (b); while the peaks (c–e) detected for 7bII, are due to NOE contacts between: the methyl
and an aromatic proton of one of the C6H5 rings of the g3-1,3-Ph2-C3H3 group (c), the phenyl protons of the other ring of the allyl ligand and those of the
non-substituted ring of the ferrocenyl unit (d) and the Haanti of the allyl group and the H2 proton of the C5H4 moiety (e).
and those of the Me substituents, the H2 proton of the ferr-
ocenyl moiety and the Haanti proton and the resonances of
the C5H5 ring and that of an aromatic ring of the ‘‘1,3-
Ph2-C3H3’’ unit. These findings are consistent with an
endo-conformation of the 1,3-Ph2-C3H3 group and conse-
quently 7bII corresponds to the (endo-, syn-, syn-) (W-type)
isomer (Fig. 5).
of resonances due to Hc and Me, and H2 (of the ferrocenyl
unit) and one aromatic proton.
Unfortunately, the low abundance of 7bIII and 7bIV pro-
hibits the determination of the conformation of the imine
{anti-(E) or syn-(Z)}, the arrangement between the methyl
and the Cb–Hb bond of the allyl ligand (endo- or exo-) or
the positions of the phenyl rings (anti- or syn-) on the allyl
ligand. The {1H–1H} NOESY spectrum of 7b, (Fig. 4) also
showed that the isomeric forms 7bI and 7bII interchanged
in solution.
The assignment of the major component 7bI as the exo-,
syn-, syn- (M-type) isomer (Fig. 5) was based on the pres-
ence of two NOE peaks (Fig. 4a and b) between the pairs

A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
4221
systems formed by 1a and [Pd(g3-C3H5)(l-Cl)]2 in this
process.
More interesting were the results obtained when 5a was
used as precursor (Table 1, entry III). The reaction was fas-
ter than in the previous experiments (Table 1, entries I and
II) and there was no evidence for the presence of 10.
For comparison purposes a parallel study with the
amine (SC)-H2N–CH(Me)(Ph) (11) was also performed
(Table 1, entry IV). In this case the formation of 8 and 9
was observed, but the conversion was lower than that
obtained for 5a. Furthermore, gas chromatography analy-
ses and 1H NMR spectra of the samples obtained after 20 h
indicated the presence of unreacted cinnamyl acetate and
product 10.
To sum up, entries I–IV indicate that the best catalytic
results were achieved with 5a for which the reaction is fas-
ter and no evidences of the formation of undesired prod-
ucts, such as 10, were detected. The comparison of the
data obtained for 5a with those previously reported for
[Pd(g3-C3H5){FcCH@N–(C6H4-2SMe)}] [PF6] (12) {with
a (N,S) bidentate ligand} [23] and the allyl complex 13
depicted in Fig. 6 [24] (containing a neutral bidentate
(N,O) ferrocenyl ligand) indicates that for 5a the reaction
is slower than when 12 was used and the regioselectivity
towards the linear product also decreases. However, com-
pound 5a is more effective than 13. The regioselectivities
of the processes catalyzed by 5a and 13 are similar
{92.1:7.9 (after 20 h) and 93:7 (after 24 h), respectively}
(Table 1, entries III and V), but the experimental condi-
tions required for 5a are milder than those reported for
13.5
Fig. 5. Schematic view of two of the isomeric forms of [Pd(g3-1,3-Ph2-
C3H3){FcCH@N–CH(Me)(CH2OH)}Cl] (7b) (7bI and 7bII, respectively).
In both cases the ferrocenyl ligand has the anti-(E) conformation, the
phenyl rings of the allyl group occupy a syn- position in relation to
the central Hb atom. The main difference between 7bI and 7bII arises from
the conformation of the allyl group. In 7bII the central Cb–Hb bond of the
allyl unit and the methyl are on the same side of the coordination plane of
the palladium(II) (endo-) {W-type orientation of the (g3-1,3-Ph2-C3H3)
ligand}; while in 7bI these two groups are on opposite sides (M-type
conformation allyl unit).
2.4. Allylic alkylation reactions
In order to check the reactivity of the coordinated allyl
group of 6a in front of nucleophiles, 6a was treated with an
excess of sodium diethyl 2-methylmalonate in THF at
298 K (stoichiometric reaction, Scheme 3). Upon the addi-
tion of the nucleophile the colour of the mixture changed
(from deep-red to orange) indicating that the reaction
was instantaneous and the final product obtained after
work-up consisted of a mixture of the linear trans-(E)
derivative (8) and the branched product (9) in a molar ratio
of 8:9 = 97.8:2.2.
2.5. Conclusions
The NMR studies of 6a indicated that in the major iso-
meric forms present in solution (6aI and 6aII) the phenyl
group of the allyl group is close to the substituents on
the stereogenic centre {the hydrogen (in 6aI) and the
methyl group (in 6aII)}. Consequently, the preferential for-
mation of the linear trans-(E) product (8) can be explained
assuming that the attack of the nucleophile takes place at
the carbon at the other end of the allyl unit (Ca).
In view of these results and in order to evaluate the
potential utility of ligand 1a or complex 5a we also studied
the alkylation of cinnamyl acetate with sodium diethyl
2-methylmalonate using catalytic amounts of (a) mixtures
of the free ligand 1a and [Pd(g3-C3H5)(l-Cl)]2 (in a 2:1
molar ratio) or (b) complex 5a.
Data presented in Table 1 (entries I and II) show that 1a
is active in the catalytic alkylation of cinnamyl acetate
under mild experimental conditions (room temperature
and short reaction periods) giving a mixture of 8, 9 (in
molar ratios of 92.8:7.2 and 91.1:8.9, respectively) and a
side-product 10. Compound 10 was identified as 1-cinn-
amyl-3-ethyl-2-methylmalonate and it also forms when
cinnamyl acetate is treated with the nucleophile in THF
at room temperature in the absence of any catalyst. The
formation of 10 reduces the effectiveness of the catalytic
The work presented here has allowed the isolation and
characterization of three novel chiral palladium(II)–allyl
complexes (5a, 6a and 7b). The comparative study of the
reactivity of the three imines (1) with compounds [Pd(g3-
1R1,3R2-C3H3)(l-Cl)]2 {R1 = H and R2 = H (2), Ph (3)
or R1 = R2 = Ph (4)} has shown that the presence of bulky
substituents on the stereogenic centre of the imines or on
the allyl complexes is so important as to determine the via-
bility of the formation of compound 7 that contain a (g3-
1,3-Ph2-C3H3) ligand.
Furthermore, the catalytic studies summarized here
have shown that 1a, 5a and the amine 11 (which is used
for the preparation of 1a) are active in the allylic alkylation
of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with sodium
diethyl 2-methylmalonate (Nu). Among the catalytic sys-
tems tested, for 5a the reaction was faster and did not pro-
duce the undesired product 10.
NMR studies of the palladium–allyl complexes have
shown that several isomeric species coexist in solution.
5
For 13, the catalytic study was performed at 343 K and the yield was
93%.

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A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
Scheme 3. Reaction of [Pd(g3-3-R2-C3H4){FcCH@N–CH(Me)(Ph)}Cl] (6a) with sodium diethyl 2-methylmalonate.
Table 1
Results of the catalytic allylic alkylation of cinnamyl acetate with sodium diethyl 2-methylmalonatea
Me
CO2Et
CO2Et
EtO2C
Ph
Me
+
9
CO2Et
8
Ph
linear product
trans- (E)
branched product
[Pd]
THF
CO2Et
Me
EtO2C
Na
+
Ph
AcO
O
Me
10
Ph
O
CO2Et
Entry
[Pd]
t (h)
Conversion
(%)
Molar ratiob
8:9:10
I
1a and [Pd(g3-
C3H5)(l-Cl)]2
1a and [Pd(g3-
C3H5)(l-Cl)]2
5a
11 and [Pd(g3-
C3H5)(l-Cl)]2
13
20
44
72.1
25.6:2.0:72.4
21.4:2.1:76.5
II
86.9
III
IV
20
20
100.0
83.7
92.1:7.9:0
33.5:2.9:63.6
Vc
24
93:7:0e
d
Experimental conditions: mixtures containing 2.5 · 10ꢀ3 mmol of [Pd(g3-C3H5)(l-Cl)]2 and 5.0 · 10ꢀ3 mmol of 1a (entries I and II) (or 11 in entry IV)
or 5.0 · 10ꢀ3 mmol of 5a (entry III), 0.5 mmol of the allylic substrate, 1 mmol of sodium diethyl 2-methylmalonate, THF (5 mL) and decane (0.258 mmol)
at 298 K.
a
b
Determined by GC.
Data from Ref. [24].
Data not given.
The reaction was performed at 343 K.
c
d
e
In the two major isomers (6aI and 6aII) present in solution
the ligand adopts the anti-(E) conformation and the substi-
tuted carbon of the allyl group (Cc) is in a cis-arrangement
to the Clꢀ ligand and they only differ in the conformation
of the allyl group (endo- or exo-). The preferential forma-
tion of the trans-(E) isomer (8) of the linear product in
the catalytic process and in the stoichiometric reaction
should arise from the attack of the nucleophile to the
non-substituted carbon atom (Ca).
Fig. 6. Chemical formula of the palladium(II)–allyl complex (13).
Finally, it should be noted that the presence of a
stereogenic centre in the backbones of ligands 1 and in
complex 5a is especially interesting in view of their poten-
tial utility as catalysts in asymmetric allylic alkylation
processes.
The results obtained for 6a, which is the key intermediate
of the catalytic process under study, are particularly rele-
vant in order to explain the regioselectivity of the reaction.

A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
4223
3. Experimental
4.11(s, 5H, C5H5), 4.70(s, 1H, H2), 4.34(s, 2H, H3 and
H4), 4.63(s, 1H, H5), 1.56(d, 3H, J = 6.0, Me), 4.41(m,
0
0
0
3.1. Materials and methods
1H, ˜CH–), 7.38(d, 2H, H2 and H6 Þ, 7.32(m, 2H, H3
0
0
and H5 Þ and 7.22(d, 1H, H4 Þ. 13C{1H} NMR data [29]:
Ferrocenecarboxaldehyde and (SC)-H2N–CH(Me)(Ph)
(11) were obtained from Aldrich and used as received.
Ligands (SC)-[FcCH@N–CH(R3)(CH2OH)] {R3 = Me
(1b) or CHMe2 (1c)} and complexes [Pd(g3-1R1,3R2-
C3H3)(l-Cl)]2 {R1 = H and R2 = H (2), Ph (3) or
R1 = R2 = Ph (4)} were prepared as described previously
[14b,16,25–27]. Sodium diethyl 2-methylmalonate (0.5 M
in THF) was prepared from diethyl 2-methylmalonate
and NaH in THF at 273 K. The solvents used in this work
were dried and distilled before use, except benzene [28].
Some of the preparations described below require the use
of benzene, which should be handled with CAUTION!
Elemental analyses were carried out at the Serveis Cien-
d
= 159.9(–CH@N–), 69.1(C5H5), 80.8(C1), 68.3(C2),
70.5(C3), 69.8(C4), 68.8(C5), 24.3(Me), 0 69.5(˜CH–),
0
0
0
0
126.7(C2 and C6 Þ, 126.7(C4 Þ, 128.5(C3 and C5 Þ,
0
145.9(C1 Þ.
3.2.2. [Pd(g3-C3H5){FcCH@N–CH(Me)(Ph)}Cl] (5a)
A mixture containing ligand 1a (0.197 g, 6.2 · 10ꢀ4
mol), [Pd(g3-C3H5)(l-Cl)]2 (0.114 g, 3.11 · 10ꢀ4 mol) and
15 mL of CH2Cl2 was protected from the light with alumin-
ium foil and stirred at ca. 298 K for 1 h. After this period
the orange solution was filtered out, the undissolved mate-
rials were removed by filtration. The filtrate was concen-
trated to dryness on a rotary evaporator. The gummy
residue was dissolved in the minimum amount of CH2Cl2
and the solution was treated with anhydrous Na2SO4 and
then filtered. Addition of hexane to the filtrate followed
by slow evaporation produced the formation of orange
prisms of 5a, which were collected and dried (yield:
0.153 g, 49%). Anal. Calc. for C22H24NClFePd: C, 52.83;
H, 4.89; N, 2.80. Found: C, 52.8; H, 4.7; N, 2.7%.
`
tifico-Tecnics (Univ. Barcelona) and Servei de Recursos
`
Cientifics i Tecnics (Univ. Rovira i Virgili, Tarragona).
Infrared spectra were obtained with a Nicolet Impact
400-instrument using KBr discs. Proton and the two-
dimensional NMR experiments [{1H–1H}-(COSY) and
(NOESY) and the {1H–13C} (HSQC) and (HMBC)] were
run at 500 MHz with either a Varian VRX-500 or a Bruker
Avance 500DMX instruments. This latter equipment was
also used for the variable temperature NMR studies.The
solvents used for the H NMR experiments were CDCl3
(99.9%) or CD2Cl2 (99.9%) with SiMe4 as the internal
reference.
In all cases the chemical shifts (d) are given in ppm and
the coupling constants (J) in Hz. The optical rotation of a
solution of 1a in CH2Cl2 was determined at 293 K using a
Perkin–Elmer 241 MC polarimeter. Mass spectra (FAB+or
ESI+) were obtained with a VG-Quattro Fisions instru-
ment using 3-nitrobenzylalcohol (NBA) as matrix (for
FAB+) and a Waters Micromass instrument (for ESI+).
MS(FAB+): m/z = 501 [M]+. IR: m(˜C@N–) = 1622 cmꢀ1
.
1H NMR data (in CD2Cl2) at 273 K three sets of superim-
posed signals of relative intensities (10.0:5.4:0.3) were
detected and suggested the presence of three isomeric forms
of 5 (hereafter referred to as 5aI, 5aII and 5aIII, respectively)
in solution. For 5aI [29,30]: d = 8.34(s, 1H, –CH@N–),
4.27(s, 5H, C5H5), 4.72(s, 1H, H2), 4.49(br s, 2H, H3 and
H4), 4.91(s, 1H, H5), 1.81(d, 3H, J = 6.5, Me), 4.80(m, 1H,
˜CH–), 3.03(d, 2H, J = 12.0, Haanti and Hacnti), 5.42(m, 1H,
J = 12.0 and 6.5, Hb), 4.17(d, J = 6.5, Hasyn and Hscyn). For
5aII [29,30]: d = 8.26(s, 1H, –CH@N–), 4.26(s, 5H, C5H5),
5.40(br s, 2H, H2 and H5), 4.55(s, 2H, H3 and H4), 1.98(d,
3H, J = 6.5, Me), 4.65(m, 1H, ˜CH–), 2.60(d, 1H, J = 12,
HaantiÞ, 3.20(d, 1H, J = 7.0, Hsayn), 4.71(m, 1H, J = 12.0 and
J = 7.0, Hb), 2.73(d, 1H, J = 12.0, Hacnti) and 2.71(d, 1H,
J = 7.0, Hcsyn). 13C{1H} NMR data for 5aI [29,30]:
d = 69.7(C5H5), 71.9(C1), 71.5(C2), 72.3(C3 and C4),
71.8(C5), 21.0(Me), 53.8(˜CH-), 64.6(Ca and Cc),
111.0(Cb) and 165.4(–CH@N–). For 5aII [29,30]: d =
69.9(C5H5), 21.8(Me), 54.2(˜CH–), 62.1(Ca), 111.7(Cb),
58.3(Cc) and 165.2(–CH@N–).
1
3.2. Preparation of the compounds
3.2.1. (SC)-[FcCH@N–CH(Me)(Ph)] (1a)
Ferrocenecarboxaldehyde (2.729 g, 12.7 · 10ꢀ3 mol) was
dissolved in 50 mL of benzene, stirred at 293 K for 30 min
and filtered out. Then, a stoichiometric amount of (SC)-
H2N–CH(Me)(Ph) (11) (1.64 mL, 12.7 · 10ꢀ3 mol) was
added to the filtrate. The reaction flask was connected to
a Dean–Stark apparatus and refluxed until ca. 15 mL of
the azeotrope (benzene/water) was condensed on the
Dean–Stark. The hot reaction mixture was filtered out with
caution and the filtrate was concentrated to dryness using a
rotary evaporator. Next, the residue was treated with
n-hexane (ca. 30 mL) and stirred at 298 K for ca. 30 min.
The orange solid formed was collected by filtration and
air-dried (yield: 3.542 g, 88%). Anal. Calc. for C19H19NFe:
C, 71.94; H, 6.06; N, 4.42. Found: C, 72.0; H, 5.9; N,
4.42%. MS(FAB+): m/z = 317 [M]+. IR: m(˜C@N–) =
1641 cmꢀ1. [a]D (293 K) (c = 0.1 g/100 mL, CH2Cl2) =
+112. 1H NMR data [29]: d = 8.21(s, 1H, –CH@N–),
3.2.3. [Pd(g3-3-Ph–C3H4){FcCH@N–CH(Me)(Ph)}Cl]
(6a)
This compound was prepared using the same procedure
as described above for 5a but using 0.162 g (3.14 ·
10ꢀ4 mol) of [Pd(g3-3-Ph–C3H4)(l-Cl)]2. In this case con-
centration of the reaction mixture gave an orange solid
which was collected and recrystallized in a 1:1 mixture of
CH2Cl2 and n-hexane (yield: 0.326 g, 86%). Anal. Calc.
for C28H28NClFePd: C, 58.36; H, 4.90; N, 2.43. Found:
C, 58.3; H, 4.78; N, 2.5%. MS(ESI): m/z = 575 [M]+ and
540.0 [MꢀCl]+. IR: m(˜C@N–) = 1619 cmꢀ1
.
1H NMR

4224
A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
data (in CD2Cl2): at 273 K four sets of superimposed sig-
nals of relative intensities (10.0:5.1:0.4:0.1) were detected
and suggested the presence of four isomeric forms of 6a
(hereafter referred to as 6aI–6aIV, respectively) in solution.
For 6aI [29,30]: 7.71(s, 1H, –CH@N–), 4.20(s, 5H, C5H5),
4.37(s, 1H, H2), 4.12(s, 1H, H3), 4.03(s, 1H, H4), 4.54(s,
1H, H5), 1.98(d, 3H, J = 6.6, Me), 4.57(q, 1H, J = 12 and
7, ˜CH–), 2.66(d, 1H, J = 12, Haanti), 3.27(d, 1H, J = 7,
Hasyn), 5.50(m, 1H, Hb) and 2.92(s, 1H, J = 12, Haanti); for
6aII [29,30]: 7.65(s, 1H, –CH@N–), 4.16(s, 5H, C5H5),
4.48(s, 1H, H2), 4.28(s, 1H, H3), 4.33(s, 1H, H4), 4.62(s,
1H, H5), 1.61(d, 3H, J = 6.6, Me), 4.82(q, 1H, J = 6.6,
˜CH–), 3.05(s, 1H, J = 12, Haanti), 3.92(d, 1H, J = 7, Hsayn),
5.67(m, 1H, Hb) and 2.96(d, 1H, J = 12, Hcanti); for 6aIII
[29,30]: 7.62(s, 1H, –CH@N–), 4.08(s, 5H, C5H5), 4.33(s,
1H, H2 partially overlapped by the resonance due to the
H4 of isomer 6aII), 4.26(s, 1H, H3), 4.27(s, 1H, H4),
4.35(s, 1H, H5), 1.68(d, 3H, J = 6.6, Me), 4.90(q, 1H,
J = 6.6, ˜CH–), 2:80ðd; 1H; J ¼ 12; HaantiÞ, 3.87(d, 1H,
70.1(C5H5), 78.0(C1), 68.0(C2), 72.2(C3), 72.0(C4),
73.8(C5), 72.4(˜CH–), 18.3(Me), 65.6(–CH2–), 76.8(Ca),
104.9(Cb), 75.7(Cc), 138.3 and 137.7 (Cipso of the two phe-
nyl rings) and for 7bII: 166.4(–CH@N–), 70.4(C5H5),
78.4(C1),
68.2(C2),
72.8(C3),
72.3(C4),
73.6(C5),
72.6(˜CH–), 17.5(Me), 65.1(–CH2–), 78.0(Ca), 100.2(Cb),
74.1 (Cc), 138.4 and 137.3 (Cipso of the two phenyl
rings).
3.3. Alkylation reactions
All these studies were performed under nitrogen. The
stoichiometric reaction of 6a with sodium diethyl 2-methyl-
malonate was carried out at 298 K by adding an excess of
the nucleophile (0.7 mL of a 0.5 M solution in THF) to a
solution containing 70 mg (1.21 · 10ꢀ4 mol) of 6a. The
reaction was instantaneous and after 10 min H2O was
added. The reaction mixture was filtered over Celite and
the filtrate was treated with Et2O (ca. 15 mL). The organic
layer was washed three times with water, the ether layer
was dried over MgSO4 and the resulting filtrate was con-
centrated to dryness on a rotary evaporator. The residue
was then dissolved in a minimum amount of Et2O and
passed over a short SiO2 column (4.0 cm · 0.6 cm). The
band released was collected, concentrated to dryness giving
J = 7, Hasyn), 5.61(m, 1H, Hb) and 2.93(s, 1H, J = 12, Hcanti
,
partially overlapped by the resonance due to the Hcanti of
6aII). 13C{1H} NMR data for 6aI [29,30]: 69.1(C5H5),
25.2(Me), 57.4(Ca), 107.4(Cb), 78.1(Cc) and 164.4-
(–CH@N–); for 6aII [29,30]: 69.6(C5H5), 23.2(Me),
56.2(Ca), 104.8(Cb), 78.1(Cc) and 165.0(–CH@N–).
1
an oily residue that, according to H NMR(500 Hz) and
3.2.4. [Pd(g3-1,3-Ph2-C3H3){FcCH@N–CH(Me)-
(CH2OH)}Cl] (7b)
GC contained a mixture of compounds 8 and 9 in a molar
ratio 8:9 = 97.8:2.2.
Ligand 1b (0.082 g, 3.01 · 10ꢀ4 mol) was dissolved in 15
mL of CH2Cl2, then [Pd(g3-1,3-Ph2-C3H3)(l-Cl)]2 (0.101 g,
1.51 · 10ꢀ4 mol) was added. The resulting reaction mixture
was stirred at room temperature for 1 h and then filtered
over Celite. The filtrate was concentrated to dryness on a
rotary evaporator giving an orange solid that was collected
and air-dried (yield: 0.168 g, 91.8%). Anal. Calc. for
C29H30NClFeOPd: C, 57.45; H, 4.99; N, 2.31. Found: C,
57.8; H, 5.0; N, 2.4%. MS(ESI): m/z = 570 [MꢀCl]+. IR:
The catalytic reactions were performed at 298 K in THF
(5 mL) using 5.0 · 10ꢀ3 mmol of 5a or mixtures containing
2.5 · 10ꢀ3 mmol of [Pd(g3-C3H5)(l-Cl)]2 and 5.0 · 10ꢀ3
mmol of 1a or 11, 0.5 mmol of cinnamyl acetate and
1.0 mmol of sodium diethyl 2-methylmalonate. The reac-
tion was monitored by taking samples from the reaction.
Each aliquote was diluted in Et2O, washed with H2O, dried
over MgSO4 and then analysed by GC using decane
(0.258 mmol) as internal standard.
m(˜C@N–) = 1627 cmꢀ1 and m(˜O–H) = 3377 cmꢀ1
.
1H
NMR data (in CDCl3 at 298 K): Four superimposed sets
of signals of relative intensities 10.0:6.6:0.9:0.8 were
detected, this suggested the coexistence of four isomeric
forms of 7b (7bI–7bIV) in solution. Due to the low abun-
dance of 7bIII and 7bIV, only the resonances due to 7bI
and 7bII could be assigned. For 7bI (major component)
[30,31]: d = 7.82(s, 1H, –CH = N–), 4.22(s, 5H, C5H5),
6.29(s, 1H, H2), 4.70(s, 1H, H3), 4.49(s, 1H, H4), 4.23(s,
1H, H5), 3.38(m, 1H, ˜CH–), 1.18(d, J = 6, 3H, Me),
3.52 and 4.30(br m, 2H, –CH2–), 4.21(br s, 1H, –OH),
4.71(d, J = 11.5, Ha), 6.02(d, J = 11.5, Hb), 4.38(d, 1H,
J = 11.5, Hc) and 6.90–7.70 (m, 10H, aromatic protons).
For 7bII [30,31]: d = 8.12(s, 1H, –CH@N–), 4.35(s, 5H,
C5H5), 6.73(s, 1H, H2), 4.74(s, 1H, H3), 4.59(s, 1H, H4),
4.57(s, 1H, H5), 3.23(m, 1H, ˜CH–), 0.41(d, J = 6, 3H,
Me), 3.27 and 3.86(br m, 2H, –CH2–), 4.00(br s, 1H,
–OH), 4.66(br, 2H, Ha and Hc), 6.27(d, 1H, J = 11.5, Hb)
and 6.90–7.70(m, 10H, aromatic protons).13C{1H} NMR
data (in CDCl3 at 298K) for 7bI [30,31]: 166.2(–CH@N–),
3.4. Crystallography
A prismatic crystal (0.1 mm · 0.1 mm · 0.2 mm) of 5a
was selected and mounted on a MAR345 diffractometer
with a image plate detector. Unit-cell parameters were
determined from 18515 reflections (3ꢁ < h < 31ꢁ) and
refined by least-squares method. Intensities were collected
with graphite monochromatized Mo Ka radiation. Reflec-
tions (16,625) were measured (in the range 2.36ꢁ 6
h 6 31.66ꢁ), of which 5717 were non-equivalent by sym-
metry {Rint(on I) = 0.037} and 5152 reflections were
assumed as observed applying the condition I > 2r(I).
Lorentz-polarization but no absorption corrections were
made.
The structure was solved by Patterson synthesis, using
SHELXS computer program [32] and refined by full-matrix
least-squares method with SHELX97 computer program [33]
using 5717 reflections (very negative intensities were not
2
2 2
assumed). The function minimized was RwiFoj ꢀ jFcj j ,

A.E. Platero-Prats et al. / Journal of Organometallic Chemistry 692 (2007) 4215–4226
4225
2
2
where w = [r2(I) + (0.1066P)2]ꢀ1 and P = (jFoj + 2jFcj )/3,
f, f 0 and f 00 were taken from the literature [34]. All H atoms
were computed and refined using a riding model, with an iso-
tropic temperature factor equal to 1.2 times the equivalent
temperature factor of the atom which are linked. The final
(f) A. Bertogg, F. Camponovo, A. Togni, Eur. J. Inorg. Chem. (2005)
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[7] (a) For recent applications of palladium(II) complexes containing
bidentate ferrocenyl ligands see for instance: F.L. Lam, T.T.L. Au-
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2
R(on F) factor was 0.041, wR (onjFj ) = 0.012 and goodness
of fit = 1.114 for all observed reflections and the Flack coef-
ficient [35] was 0.14(3). The number of refined parameters
was 235. Max. shift/esd = 0.00, Mean shift/esd = 0.00.
Max. and min. peaks in final difference synthesis was 0.827
´
(b) S. Cabrera, R. Gomez Arrayas, I. Alonso, J.C. Carretero, J. Am.
Chem. Soc. 127 (2005) 17938;
(c) V.C. Gibson, C.M. Halliwell, N.J. Long, P.J. Oxford, A.M.
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Chem. 4 (2002) 103;
and ꢀ0.517 eAꢀ3, respectively.
˚
(e) M. Wildhalm, U. Nettekoven, H. Kalchhauser, K. Mereiter, M.J.
Calhorda, V. Felix, Organometallics 21 (2002) 315;
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Acknowledgements
This work was supported by the Ministerio de Educacio´n
y Ciencia of Spain. A.P. is grateful to the same institution
for a fellowship.
[8] (a) O. Garc´ıa Mancheno, J. Priego, S. Cabrera, R. Go´mez Arraya´s,
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T. Llamas, J.C. Carretero, J. Org. Chem. 68 (2003) 3679;
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Appendix A. Supplementary material
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CCDC 635695 contains the supplementary crystallo-
graphic data for 5a. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
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(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2007.06.016.
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