Synthesis and reactivity towards carbon monoxide of an optically active endo five-membered ortho-cyclopalladated imine: X-ray molecular structure of trans-(μ-Cl)2[Pd(κ2-C,N-(R)-C6H4-CH{double bond, long}N-CHMe-Ph)]2

Article abstract of DOI:10.1016/j.jorganchem.2007.03.035

(R)-1-Phenylethyl-benzylidene-amine (1) reacted with Pd(OAc)₂ in acetic acid at 60 °C under nitrogen affording the acetato-bridged dinuclear endo five-membered ortho-cyclopalladated compound (μ-OAc)₂[Pd(κ²-C,N-(R)-C₆H₄-CH{double bond, long}N-CHMe-Ph)]₂ (2) in 65% yield. Compound 2 was converted by a metathesis reaction with LiCl into the corresponding chloro-bridged dinuclear cyclopalladated compound (μ-Cl)₂[Pd(κ²-C,N-(R)-C₆H₄-CH{double bond, long}N-CHMe-Ph)]₂ (3). ¹H NMR of CDCl₃ solutions of compounds 2 and 3 treated separately with py-d₅, (R)-1-phenylethylamine and racemic 1-phenylethylamine were consistent with the endo cyclopalladated structure and the R absolute configuration of the chiral carbon atoms of compounds 2 and 3. Compounds 2 and 3 reacted with carbon monoxide in methanol affording, as major compounds, methyl 2-formylbenzoate (91% chemical yield) and the epimers of 3-methoxy-2-[(R)-1-phenylethyl]isoindolin-1-one (64% chemical yield) in ca. 20% diastereomeric excess, respectively. The trans isomer of compound 3 crystallized in the P2₁ monoclinic space group with a = 10.430(4) A?, b = 12.082(8) A?, c = 11.168(4) A? and β = 95.20(3)° and presented C-H?Cl intramolecular and C-H?Pd intermolecular non-conventional hydrogen bonds.

Full text of DOI:10.1016/j.jorganchem.2007.03.035

Journal of Organometallic Chemistry 692 (2007) 3070–3080
www.elsevier.com/locate/jorganchem
Synthesis and reactivity towards carbon monoxide of an optically
active endo five-membered ortho-cyclopalladated
imine: X-ray molecular structure of
trans-(l-Cl)2[Pd(j2-C,N-(R)-C6H4-CH@N-CHMe-Ph)]2
a,
a
a
a
*
´
Joan Albert , Lucıa D’Andrea , Jaume Granell , Raquel Tavera ,
b
b
`
Merce Font-Bardia , Xavier Solans
a
` `
´
Departament de Quı´mica Inorganica, Universitat de Barcelona, Martı i Franques, 1-11, 08028 Barcelona, Spain
`
b
`
´
Departament de CristalÆlografia, Mineralogia i Diposits Minerals, Universitat de Barcelona, Martı i Franques s/n, 08028 Barcelona, Spain
Received 14 February 2007; received in revised form 23 March 2007; accepted 23 March 2007
Available online 30 March 2007
Abstract
(R)-1-Phenylethyl-benzylidene-amine (1) reacted with Pd(OAc)2 in acetic acid at 60 ꢀC under nitrogen affording the acetato-bridged
dinuclear endo five-membered ortho-cyclopalladated compound (l-OAc)2[Pd(j2-C,N-(R)-C6H4-CH@N-CHMe-Ph)]2 (2) in 65% yield.
Compound 2 was converted by a metathesis reaction with LiCl into the corresponding chloro-bridged dinuclear cyclopalladated com-
1
pound (l-Cl)2[Pd(j2-C,N-(R)-C6H4-CH@N-CHMe-Ph)]2 (3). H NMR of CDCl3 solutions of compounds 2 and 3 treated separately
with py-d5, (R)-1-phenylethylamine and racemic 1-phenylethylamine were consistent with the endo cyclopalladated structure and the
R absolute configuration of the chiral carbon atoms of compounds 2 and 3. Compounds 2 and 3 reacted with carbon monoxide in meth-
anol affording, as major compounds, methyl 2-formylbenzoate (91% chemical yield) and the epimers of 3-methoxy-2-[(R)-1-phenyl-
ethyl]isoindolin-1-one (64% chemical yield) in ca. 20% diastereomeric excess, respectively. The trans isomer of compound 3
˚
˚
˚
crystallized in the P21 monoclinic space group with a = 10.430(4) A, b = 12.082(8) A, c = 11.168(4) A and b = 95.20(3)ꢀ and presented
C–Hꢀ ꢀ ꢀCl intramolecular and C–Hꢀ ꢀ ꢀPd intermolecular non-conventional hydrogen bonds.
ꢁ 2007 Elsevier B.V. All rights reserved.
Keywords: Cyclometallation; Optically active imine; Palladium; Non-conventional hydrogen bond; Carbonylation
1. Introduction
processes leading to stereoselective synthesis of organic
molecules [12–16].
Interest in the cyclometallation reaction has been
renewed in recent years due to the incorporation of this
reaction in catalytic cycles that transform C–H bonds of
heterosubstituted organic molecules into C–X bonds
(X = B, C, Si, N, O or halogen) [1–11]. In spite of this,
the reactivity of the C–M r bond of cyclometallated com-
pounds has not been extensively studied—especially the
In this paper, we present an extension of the carbonyl-
ation reaction of endo five-membered ortho-cyclopalla-
dated imines in presence of nucleophiles, which produced
racemic 3-nucleophile-2-(aryl or benzyl)isoindolin-1-ones
(Fig. 1), with the aim of obtaining this type of compound
in a diastereoselective form [17–19]. For this purpose, we
prepared the optically active endo five-membered ortho-
cyclopalladated imines 2 and 3 (Scheme 1) and studied
their reactivity towards carbon monoxide in methanol.
It should be noted that the bromo- and chloro-bridged
endo cyclopalladated derivatives of the enantiomer of imine
1 (Scheme 1) have been previously reported, and cationic
*
Corresponding author. Tel.: +34 93 4039131; fax: +34 93 4907725.
E-mail address: joan.albert@qi.ub.es (J. Albert).
0022-328X/$ - see front matter ꢁ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.03.035

J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3071
between a and b, and a and MeA protons were consistent
with an E configuration for imine 1.
Treatment of imine 1 with Pd(OAc)2 in acetic acid in a 1
to 1 molar ratio under nitrogen afforded the dimeric ace-
tato-bridged five-membered ortho-cyclopalladated imine
2, which was easily converted by metathesis reaction with
LiCl into the corresponding chloro-bridged cyclopalla-
dated dimer 3 (Scheme 1). Compounds 2 and 3 were iso-
lated in pure form by chromatography in 65% and 88%
yield, respectively. They were air-stable yellow solids, solu-
ble in chloroform and in acetone, and produced satisfac-
tory elemental analysis, IR, 1H NMR, FAB(+) and
optical rotation.
The C@N stretching of compounds 2 and 3 appeared at
1606 and 1604 cmꢁ1, respectively, as an intense band
shifted to lower wave numbers in relation to 1, according
to the coordination of the iminic nitrogen to the palla-
dium(II) centre [33]. The asymmetric and symmetric
stretchings of the carboxylic functions of compound 2 pro-
duced broad intense bands at 1566 and 1413 cmꢁ1, respec-
tively, according to a bridging coordination mode of the
acetato ligands [34]. The FAB(+) of compounds 2 and 3
afforded intense peaks for the monopositive molecular cat-
ions [M+H+], [Mꢁ(Xꢁ)] and [M/2ꢁ(Xꢁ)], where X is ace-
tato for 2 and chloro for 3, in agreement with their dimeric
structure with acetato and chloro bridges, respectively [35].
Fig. 1. 3-Nucleophile-2-(aryl or benzyl)isoindolin-1-ones prepared by
carbonylation of endo five-membered ortho-cyclopalladated imines in
presence of nucleophiles.
derivatives of these cyclopalladated compounds have been
used as precatalysts in the telomerization of isoprene and
butadiene with methanol [20,21]. Furthermore, endo and
exo five-membered optically active cyclopalladated imines
analogous to compounds 2 and 3 have been used as deri-
vating agents for optical resolution of chiral phosphines
[22,23] or for optical purity determination of optically
active phosphines by NMR [24]. The endo and exo descrip-
tors were initially introduced to differentiate between the
structural isomers of ortho-cyclopalladated benzyl-benzyli-
dene-amine (Fig. 2) [17], but the use of these descriptors
has been extended to refer in general to cyclometallated
imines with the C@N bond inside the metallacycle, endo
cyclometallated imines, and outside the metallacycle, exo
cyclometallated imines [25–30].
1
The H NMR in CDCl3 of compound 2 produced two
sharp sets of signals in ca. 3 to 1 ratio, which indicated that
it consisted of two isomers, hereafter referred to as I (major
isomer) and II (minor isomer). In dimers I and II, their
monomeric units of formula trans-C,O-Pd{j2-C,N-(R)-
C6H4-CH@N-CHMe-Ph}(j1-O-OAc) were equivalent,
e.g. the MeB protons produced only one singlet signal at
2.20 ppm for I and at 2.04 ppm for II, showing that their
{j2-C,N-(R)-C6H4-CH@N-CHMe-Ph} ligands were in a
trans arrangement. Acetato-bridged cyclopalladated
dimers present a folded structure (Fig. 3a), usually named
open book structure, both in the solid state and in chloro-
form solution [36]. Thus, we propose that I and II in CDCl3
solution present a trans folded structure belonging to C2
point group. The unusual upfield chemical shift in relation
to imine 1 of the a proton of I and the MeA protons of II
could be an indication of their trans folded structure (Table
1) [37]. A 1H–1H NOESY experiment at 400 MHz in
CDCl3 showed that I and II were interconverting in CDCl3
solution but we were not able to deduce from cross-peaks
of proximity between protons of I or II either their axial
configuration in relation to the chirality of their carbon
atoms or the conformation of their N–CHMe–Ph molecu-
lar fragments.
2. Results and discussion
Scheme 1 shows the compounds prepared in this work
and the labelling of the protons, and Table 1 presents the
chemical shift of selected protons of compounds 1–9.
2.1. Synthesis and characterization of compounds 1–3
Imine 1 was prepared by an adaptation of the condensa-
tion reaction between benzaldehyde and (R)-1-phenylethyl-
amine previously reported [31] (Scheme 1) and was purified
by distillation at low pressure. 1 was an orange oil which
produced satisfactory elemental analysis, IR, 1H NMR,
FAB(+) and optical rotation. Its 1H NMR presented a sin-
gle set of signals, indicating that it should consist of only
the E geometrical isomer in relation to the carbon nitrogen
1
In the H NMR at 400 MHz in CDCl3 of compound 3
at room temperature all protons presented sharp signals,
except the MeA protons, for which two broad signals at
1.83 and 1.77 ppm in ca. 1.5 to 1 ratio were observed,
showing that compound 3 consisted of two isomers in this
solvent, hereafter referred to as III (major isomer) and IV
(minor isomer). Chloro-bridged cyclopalladated dimers
1
double bond [32]. H–1H COSY and NOESY experiments
at 500 MHz allowed the assignation of almost all protons
of 1, and the cross-peaks in the NOESY experiment

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J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
Scheme 1. (i) Pd(OAc)2, acetic acid, 60 ꢀC, 4 h; (ii) column chromatography; (iii) LiCl, acetone, room temperature, 4 h; (iv) py-d5, (R)-1-phenylethylamine
or ( )-1-phenylethylamine, CDCl3, room temperature; (v) CO, 1.6 bar, methanol, room temperature, 6 h; (vi) CO, 1.6 bar, methanol, room temperature,
24 h.
present a planar structure (Fig. 3b), and in chloroform or
dichloromethane solution their trans and cis isomers can
be interconverting between them through intermediate sol-
vento complexes (Fig. 3c) [38]. Therefore, isomers III and
IV could be the trans and cis isomers of 3, and the broad
signal observed for their MeA protons in CDCl3 solution
at 400 MHz and at room temperature, an indication of a
dynamic equilibrium between them through an intermedi-
ate mononuclear chloroform solvento complex. It should
be noted that in CDCl3 solution at 250 MHz and at
220 K, the MeA protons of III and IV gave place to sharp
doublets at 1.84 and 1.77 ppm, respectively. Note that both
MeA protons are equivalent in the trans and cis dimeric
molecules of 3 because they belong to the C2 point group.
Fig. 2. endo and exo structural isomers of cyclopalladated benzyl-
benzylidene-amine.

J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3073
Table 1
palladated aromatic ring protons was an indication of the
trans disposition of the L ligand in relation to the iminic
nitrogen (Scheme 1) [26,39].
Chemical shift (in ppm) of selected protons of compounds 1–9
Compound
Proton
1H–1H NOESY and COSY experiments for the solu-
tions containing compounds 4 and 5 made it possible to
establish unambiguously the endo structure of compounds
2 and 3. Thus, a strong NOE between the a and 5 protons
allowed the assignation of the 5 proton and, starting from
a
b
MeA
1
8.38
6.98a
7.63
7.59
7.66
7.65
7.73
7.62
7.73
7.67
7.62
7.73
4.56
4.67
4.61
1.60
1.76
0.85a
1.79
1.78
1.83
1.83
1.89
1.83
1.81
1.88
1.88
2 (Isomer I)
2 (Isomer II)
3
5.34b
5.24b
5.96b
5.37b
5.82b
5.36b
5.36b
5.83b
5.83b
4
1
this proton, the H–1H COSY experiment, permitted the
5
assignation of the 4–2 protons [40]. The 5–2 protons turned
out to be those of the ortho-metallated ring since they pro-
duced a coupling pattern for a 1,2-disubstituted aromatic
ring and were upfield shifted in relation to the non-metal-
lated phenyl protons [26,39].
6
7
8 (Diastereoisomer RR)
8 (Diastereoisomer RS)
9 (Diastereoisomer RR)
9 (Diastereoisomer RS)
1
In addition, the H NMR at 400 MHz of the solutions
Unusual aup- and bdownfield chemical shift in relation to 1.
containing compounds 6–9 confirmed that the chiral carbon
atoms of compounds 2 and 3 were configurationally stable.
1
2.2. endo Structure and configurational stability of the chiral
carbon atoms of compounds 2 and 3
This was unequivocally established because the H NMR
spectra of the solutions containing compounds 6 and 7,
which presented (R)-1-phenylethylamine coordinated to
the palladium(II) centres, produced a single set of signals,
showing that compounds 6 and 7 consisted of only the
RR diastereoisomer, while the 1H NMR spectra of the solu-
tions containing compounds 8 and 9, which presented race-
mic 1-phenylethylamine coordinated to the palladium(II)
centres, produced two sets of signals in a 1 to 1 ratio, indi-
cating that compounds 8 and 9 consisted of a mixture in a 1
to 1 molar ratio of the RR and RS diastereoisomers.
Although it is likely that compounds 2 and 3 present an
endo structure [17,20–30] and that their chiral carbon
atoms are configurationally stable [20–24], we checked
these two items by NMR. For this purpose, CDCl3 solu-
tions of compounds 2 and 3 were treated separately with
py-d5, (R)-1-phenylethylamine and racemic 1-phenylethyl-
amine, and the resulting solutions were studied by NMR.
In all cases, a colour change of the initial orange or pale
yellow solution to a colourless solution indicated the quan-
titative transformation of the dimeric cyclopalladated com-
pounds 2 and 3 in the corresponding mononuclear
cyclopalladated compounds 4–9 (Scheme 1). This was con-
2.3. Non-conventional hydrogen bonds in solution
Notably, the chemical shift of the b proton of com-
pounds 3–9 appeared quite downfield shifted in relation
to imine 1, between 0.68 and 1.40 ppm (Table 1). This
1
firmed by the H NMR at 400 MHz of the final colourless
solutions. In compounds 4–9, the upfield shift of the ortho-
Fig. 3. (a) Folded structure of acetato-bridged cyclopalladated dimers, (b) planar structure of chloro-bridged cyclopalladated dimers and (c) dynamic
equilibrium between trans and cis isomers of chloro-bridged cyclopalladated dimers.

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J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
In order to obtain more information on this kind of
interaction we prepared in CDCl3 solution compound
trans-N,N-[Pd(j2-C,N-C6H4-CH@N-CH2-C6H5)(OAc)(py-
d5)] (compound A in Scheme 1) and registered its 1H NMR
in this solvent. In this case, the CH2 protons of compound A
resonate at 4.86 ppm, very close to the CH2 protons of ben-
zyl-benzylidene-amine, which resonate at 4.74 ppm [40]. In
addition, the chemical shift of the c proton of compounds
6–9 in CDCl3 appeared in the interval between 4.56 and
4.16 ppm, very close to the c proton of (R)-1-phenethyl-
amine, which resonate at 4.57 ppm in CDCl3 solution.
These latter results suggest that a fine-tuning of steric and
electrostatic effects are cooperating in order to establish
the proposed intramolecular C–Hbꢀ ꢀ ꢀX non-conventional
hydrogen bond in compounds 3–9. It should be noted that
compounds 3–9 should present in solution a conformation
in which the b proton is near the coordination plane of the
palladium(II) centre in order to diminish steric repulsions.
Thus, the paramagnetic anisotropy of the palladium(II)
centre should not be the origin of the unusual downfield
chemical shift of the b proton of compounds 3–9 [48].
Fig. 4. Proposed intramolecular C–Hbꢀ ꢀ ꢀX non-conventional hydrogen
bond in CDCl3 solution for compounds 3–9.
could indicate that in CDCl3 solution these compounds
present an intramolecular C–Hbꢀ ꢀ ꢀX non-conventional
hydrogen bond, where X is either the j1-oxygen atom of
the acetato ligand or the chlorine atom of the chloro ligand
(Fig. 4). An analogous intramolecular C–Hꢀ ꢀ ꢀCl non-con-
ventional hydrogen bond has previously been reported
in the solid state for a mononuclear endo cyclopalladated
ferrocenylbenzylimine [41]. It should be noted that (i)
non-conventional hydrogen bonds [42] can explain the con-
formation and association of molecules, both in the solid
state and in solution [43–46], and (ii) the chemical shift of
the hydrogen atom involved in non-conventional hydrogen
bonds is shifted to downfield due to the transfer of part of
its electronic density to the acceptor atomic centres, as in
conventional hydrogen bonds [46,47].
2.4. X-ray molecular structure of the trans isomer of
compound 3
Suitable crystals for an X-ray diffraction study were
obtained from compound 3. The selected crystal was con-
Fig. 5. X-ray molecular structure and atom labelling scheme for the trans isomer of 3. Dashed lines indicate intramolecular C–Hꢀ ꢀ ꢀCl non-conventional
hydrogen bonds.

J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3075
Table 2
stituted by molecules of the trans isomer of 3, pertained to
Non-conventional hydrogen bonds for the trans isomer of 3
the P21 monoclinic space group and produced a satisfac-
tory Flack · parameter of ꢁ0.01(7)—assuming that its
molecules presented an R absolute configuration at the chi-
ral carbon atoms. Figs. 5 and 6 show the X-ray molecular
structure of the trans isomer of 3 and the labelling of the
atoms for the discussion that follows (Fig. 5) and a simpli-
fied view of the crystal down the c-axis (Fig. 6). Tables 2–4
give bonding parameters for intra- and intermolecular non-
conventional hydrogen bonds (Table 2), selected distances
and angles (Table 3) and planes of atoms (Table 4) for
the molecule of the trans isomer of 3.
An automatic search for p–p stacking interactions and
non-conventional hydrogen bonds in the crystal structure
did not find p–p stacking interactions, but it revealed the
presence of the intra- and intermolecular non-conventional
hydrogen bonds given in Table 2 [51]. The intramolecular
hydrogen bonds C2–H2ꢀ ꢀ ꢀCl2 and C17–H17ꢀ ꢀ ꢀCl1 were
forced by the trans planar configuration of the molecule
(Fig. 5). In spite of this, the intramolecular hydrogen bonds
C9–H9Bꢀ ꢀ ꢀCl1 and C23–H23ꢀ ꢀ ꢀCl2 were not imposed by
geometrical constraints and, it seems likely, that they deter-
mined the molecular conformation in the crystal. It is
worth highlighting that the intramolecular hydrogen bond
C9–H9Bꢀ ꢀ ꢀCl1 forced a Pd1–N1–C8–H8 torsion angle of
173ꢀ that prepared the H8 atom for the intermolecular
interaction C8–H8ꢀ ꢀ ꢀPd2 which, in its turn, generated
chains of molecules along the b axis of the crystal (Fig. 6).
Non-conventional
hydrogen bonds
D–Hc
Hꢀ ꢀ ꢀAd,e
Dꢀ ꢀ ꢀA
D–Hꢀ ꢀ ꢀA
C2–H2ꢀ ꢀ ꢀCl2a
C9–H9Bꢀ ꢀ ꢀCl1a
C17–H17ꢀ ꢀ ꢀCl1a
C23–H23ꢀ ꢀ ꢀCl2a
C8–H8ꢀ ꢀ ꢀPd2b
0.93
0.96
0.93
0.98
0.98
2.67
2.69
2.76
2.75
2.71
3.235(16)
3.504(15)
3.271(15)
3.357(15)
3.638
120
143
116
120
159
˚
Distances in A, angles in ꢀ, D = donor, A = acceptor.
a
Intramolecular.
Intermolecular.
Calculated.
b
c
d
˚
Interval for an Hꢀ ꢀ ꢀCl non-conventional hydrogen bond: 2.40–2.90 A
[49].
e
Interval for an Hꢀ ꢀ ꢀPd non-conventional hydrogen bond: 2.30–2.90
[50].
Table 3
˚
Selected bond distances (A) and angles (ꢀ) for the trans isomer of 3
Pd1–Cl1
Pd1–Cl2
Pd1–N1
Pd1–C1
N1–C7
C6–C7
C1–C6
N1–C8
C8–C9
2.488(4)
2.324(4)
2.079(11)
1.937(14)
1.226(19)
1.46(2)
1.44(2)
1.464(19)
1.517(19)
Pd2–Cl1
Pd2–Cl2
Pd2–N2
Pd2–C16
N2–C22
C21–C22
C16 –C21
N2–C23
C23–C24
2.313(4)
2.456(4)
1.968(13)
1.958(13)
1.30(2)
1.41(3)
1.43(2)
1.41(2)
1.54(2)
Pd1–Cl2–Pd2
Cl1–Pd1–Cl2
Cl2–Pd1–C1
C1–Pd1–N1
N1–Pd1–Cl1
C1–Pd1–Cl1
N1–Pd1–Cl2
N1–C8–C9
95.01(13)
84.63(12)
92.1(4)
Pd1–Cl1–Pd2
Cl1–Pd2–Cl2
Cl1–Pd2–C16
C16–Pd2–N2
N2–Pd2–Cl2
C16–Pd2–Cl2
N2–Pd2–Cl1
N2–C23–C24
94.44(13)
85.58(12)
93.4(4)
84.0(6)
96.8(4)
173.5(4)
177.1(4)
118.1(13)
83.0(5)
100.4(3)
171.5(4)
174.9(3)
109.3(11)
Table 4
Selected planes of atoms for the trans isomer of 3
Plane 1
Atoms
Pd1
Cl1
Cl2
N1
Deviation 0.010(1)
0.000(3)
ꢁ0.004(3) ꢁ0.005(11)
Equation
7.822(19)x ꢁ 7.92(2)y + 0.238(17)z = 1.38(3)
Plane 2
Atoms
Pd2
Cl1
Cl2
N2
Deviations 0.020(1)
ꢁ0.009(3) 0.000(3)
ꢁ0.011(13)
Equation
7.22(3)x ꢁ 8.61(3)y + 0.596(17)z = 0.78(3)
Plane 3
Atoms
Pd1
Pd2
Cl1
Cl2
Deviations 0.047(1)
0.047(1)
ꢁ0.047(3) ꢁ0.047(3)
Equation
7.505(4)x ꢁ 8.297(6)y + 0.420(15)z = 1.095(15)
Plane 4
Atoms
Pd1
N1
C1
C6
C7
Deviations ꢁ0.008(1) 0.010(11) 0.009(15) ꢁ0.004(16) ꢁ0.007(15)
Equation
8.04(3)x ꢁ 7.68(4)y ꢁ 1.27(7)z = 0.64(6)
Plane 5
Atoms
Fig. 6. View of the crystal structure of the trans isomer of 3 down the
c-axis. Dashed lines indicate intermolecular C–Hꢀ ꢀ ꢀPd non-conventional
hydrogen bonds. For simplicity, only the molecular fragments H8–C8–
N1–Pd1–Cl1–Pd2 involved in the formation of intermolecular C–Hꢀ ꢀ ꢀPd
non-conventional hydrogen bonds are represented.
Pd2 N2 C16 C21
C22
ꢁ0.055(16)
Deviations ꢁ0.027(1) 0.052(13) 0.009(13) 0.021(16)
Equation
7.96(3)x ꢁ 7.80(5)y ꢁ 0.45(7)z = 1.38(8)
˚
Deviations in A. Equations in fractional coordinates.

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J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
We also notice that the intramolecular hydrogen bond
C23–H23ꢀ ꢀ ꢀCl2 is of the same type than that we have pro-
posed for compounds 3–9 in CDCl3 solution. This rein-
forces the idea that the downfield shift of the b proton of
compounds 3–9 in CDCl3 solution is a consequence of an
intramolecular C–Hbꢀ ꢀ ꢀX non-conventional hydrogen
bond, where X is either the j1-oxygen atom of the acetato
ligand or the chlorine atom of the chloro ligand of com-
pounds 3–9 (Fig. 4). Note also that H23 is not very dis-
placed from the coordination plane of Pd2 since the
dihedral angle H23–Cl2–Pd2–Cl1 is 171ꢀ.
Distances and angles for the molecule of the trans iso-
mer of 3 (Table 3) were between the normal intervals for
analogous chloro-bridged cyclopalladated dimers [52–54].
˚
As expected [55], the Pd1–Cl1 [2.488(4) A] and Pd2–Cl2
˚
[2.456(4) A] distances were larger than those of Pd1–Cl2
˚
˚
[2.324(4) A] and Pd2–Cl1 [2.313(4) A] due to the greater
trans influence of the C1 and C16 coordinated carbon
atoms in relation to the N1 and N2 coordinated nitrogen
atoms. The coordination angles of the palladium atoms
were close to 90ꢀ and 180ꢀ. The chelate bite angles, C1–
Pd1–N1 and C16–Pd2–N2, were 83.05(5)ꢀ and 84.0(6)ꢀ,
respectively (Table 3). Each palladium atom together with
its coordinated nitrogen and chlorine atoms determined a
plane—planes 1 (Pd1, Cl1, Cl2 and N1) and 2 (Pd2, Cl1,
Cl2 and N2) in Table 4. The deviations of the C1 and
C16 metallated carbon atoms from planes 1 and 2 were
˚
0.281(15) and ꢁ0.185(13) A, respectively. The (l-Cl)2Pd2
central core of the molecule and both endo five-membered
metallacycles were planar, planes 3–5 in Table 4, but the
molecule was somewhat folded since the angle between
the planes 1 (Pd1, Cl1, Cl2 and N1) and 2 (Pd2, Cl1, Cl2
and N2) was 4.9(3)ꢀ.
2.5. Carbonylation of compounds 2 and 3
Scheme 2. Mechanism for the carbonylation reaction of endo five-
membered ortho-cyclopalladated imines in methanol, leading to methyl
2-formylbenzoates or 3-methoxy-2-(aryl or benzyl)isoindolin-1-ones.
Scheme 2 shows the mechanism proposed for the
carbonylation reaction of endo five-membered ortho-cyclo-
palladated imines in methanol, leading to methyl 2-form-
ylbenzoates or 3-methoxy-2-(aryl or benzyl)isoindolin-1-
ones, including the compounds prepared in this work by
the carbonylation reaction of compounds 2 and 3 [18].
Compounds 2 and 3 were treated in methanol at room
temperature with carbon monoxide at 1.6 bar in a glass-
ware reactor for 6 and 24 h, respectively (Scheme 1). In
both cases a voluminous precipitate of palladium(0) and
a colourless solution were formed. Removal of the palla-
dium(0) by filtration and subsequent concentration of the
obtained colourless solution afforded an oily material,
which was studied by TLC and subjected to column
chromatography.
were identical to those previously reported for 2-form-
ylbenzoate [56]. The third band contained a small amount
of a sample enriched in the epimers of 3-methoxy-2-[(R)-
1-phenylethyl]isoindolin-1-one in ca. 20% diastereomeric
excess, compound 11 in Schemes 1 and 2. The diastereo-
meric excess of these epimers was determined by the inte-
gration of their methoxy protons, which appeared as
singlet signals, at 2.93 ppm for the major epimer, hereafter
referred to as V, and at 2.47 ppm for the minor epimer,
hereafter referred to as VI. It should be noted that 2-form-
ylbenzoate was formed by hydrolysis of the carbon nitro-
gen double bond of its precursor imine (imine X in
Scheme 2) since this imine was the major compound pres-
ent in the oily material obtained from the carbonylation of
For the oily material obtained from the carbonylation of
compound 2, the second eluted band was the most impor-
tant one. This band, after concentration of the solvents,
afforded methyl 2-formylbenzoate in 91% chemical yield,
compound 10 in Schemes 1 and 2. This was confirmed by
1
2, as it showed its H NMR at 400 MHz.
In the case of the oily material obtained from the car-
bonylation of compound 3, the third eluted band was the
1
the IR and H NMR of the obtained white solid, which

J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3077
major one. This band, after concentration of the solvents,
produced a yellow oil, which was a mixture of the epimers
of 3-methoxy-2-[(R)-1-phenylethyl]isoindolin-1-one, com-
pound 11 in Schemes 1 and 2, and 2-[(R)-1-phenylethyl]iso-
indolin-1-one, compound 12 in Schemes 1 and 2, in ca. 7 to
1 molar ratio. The epimers of 11 were the major compo-
nents of this mixture. This sample is henceforth referred
to as sample A. The mass of sample A and its molar com-
position made it possible to determine that the epimers of
11 were obtained in 64% chemical yield in the carbonyl-
ation of 3. In sample A, the major epimer of 11 was epimer
V, which was present in this sample in ca. 20% diastereo-
meric excess, as was also the case in the sample containing
a small amount of the epimers of 11 obtained from the car-
bonylation of 2.
Finally, it should be noted that the selectivity change in
the carbonylation products of compounds 2 and 3, when
the acetato ligands are replaced by chloro ligands in the
starting endo five-membered ortho-cyclopalladated imine,
is remarkable and reproduces well the results previously
reported [17–19,59].
3. Experimental
3.1. Instruments and reagents
Elemental analyses of C, H and N were performed with
an Eager 1108 microanalyzer. Infrared spectra were
recorded on a Nicolet Impact-400 spectrophotometer using
pressed discs of dispersed samples of compounds 2 and 3 in
KBr, a thin film of 1 between NaCl windows and a CHCl3
A 1H–1H NOESY experiment at 400 MHz in CDCl3 for
sample A did not allow us to carry out the determination of
the relative configuration of the chiral carbon atoms in the
epimers of 11. Nevertheless, since: (i) the NOESY experi-
ment did not present exchange peaks between the epimers
of 11, (ii) the molar ratio between the three components
of sample A remained unchanged after several weeks, an
1
solution of compounds 10–12 in a NaCl cell. H NMR at
500, 400, 250 and 200 MHz were recorded in Varian Inova,
Varian Mercury, Bruker DRX and Varian Gemini instru-
ments, respectively. Chemical shifts are reported in d values
(ppm) relative to SiMe4 and coupling constants in Hz.
FAB(+) mass spectra were obtained with a VG-Quatro
Fisions instrument, using 3-nitrobenzylalcohol as matrix.
The CI mass spectrum was obtained with a ThermoFinni-
gan TRACE DSQ instrument, using NH3 as reactive gas.
The HPLC analysis was carried out in a Waters 717 Plus
autosampler chromatograph with a Waters 996 multidiode
array detector, fitted with a Chiracel OD-H chiral column.
The eluent was a mixture of n-hexane/iPrOH (95/5). Opti-
cal rotations were measured with a polarimeter Perkin
Elmer 241MC at the D line of Na (589 nm) with a cell of
1 mL and an optical path of 10 cm. All chemicals and
solvents were of commercial grade and used as received.
Carbon monoxide was CON47 Alphagaz, which contained
less than 1 ppm of hydrogen. Compound (l-OAc)2[Pd(j2-C,
N-C6H4-CH@N-CH2-Ph)]2 was prepared as previously
reported [40].
1
occurrence which was checked by H NMR and (iii) an
HPLC analysis of sample A with a chiral column afforded
three well-separated signals for its three components, we
concluded that the epimers of 11 were configurationally
stable, which was consistent with precedents in the litera-
ture [57].
The fourth eluted band during the chromatography of
the oily material obtained in the carbonylation of 3 pro-
duced a small amount of another sample, hereafter referred
to as sample B, which was enriched in compound 12. Thus,
from samples A and B, it was possible to assign the charac-
teristic NMR proton resonances and IR absorptions for
compounds 11 and 12 (see Section 3). Furthermore, the
FAB(+) mass spectrum of sample A produced the most
abundant peaks at 268 and 236, which corresponded to
the molecular monopositive cations [M11+H+] and
[M11+H+-MeOH], and the CI mass spectrum of sample
B displayed the most abundant peak at 268, which corre-
sponded to the molecular monopositive cation [M12+H+],
where M11 and M12 were the masses of the most abundant
isotopomer of 11 and 12, respectively.
It seems likely that (i) compound 12 could be formed by
methanolysis of the Pd–C r bond of the intermediate a-
aminoalkylpalladium complex (Z in Scheme 2) or else by
reductive elimination of palladium(0) in a hydridepalla-
dium complex formed by b elimination of a methyl hydro-
gen of the methanol ligand of intermediate Z, and that (ii)
the induction of the diastereoselection observed in the syn-
thesis of compound 11 takes place during the transforma-
tion of the intermediate acylpalladium complex (Y in
Scheme 2) into the intermediate a-aminoalkylpalladium
complex (Z in Scheme 2). We notice that this latter trans-
formation corresponds to an intramolecular insertion of
the carbon nitrogen double bond of the acylpalladium
complex Y into its Pd–C r bond [58].
3.2. Preparation of 1
1.433 g (13.50 mmol) of benzaldehyde and 1.651 g
(13.62 mmol) of R-(+)-1-phenylethylamine were treated at
reflux of ethanol (20 mL) for 4 h. The resulting solution
was concentrated in vacuum and the oil obtained was puri-
fied by distillation in a Buchi oven for distillation. The Schiff
¨
base 1 was obtained as an orange oil in 84% yield (2.376 g).
Characterization data: Anal. Calc. for C15H15N: C, 86.08,
H, 7.22; N, 6.69. Found: C, 84.02; H, 7.2; N, 6.7%. IR
(NaCl, cmꢁ1): 1653 (C@N st). FAB(+) (most intense peaks):
[M+H+] = 210,
(500 MHz, CDCl3, 298 K): 8.38 (s, Ha), 7.81–7.79 (m, H1
[M+H+ꢁCH4] = 194.
1H
NMR
3
and H5), 7.46 (dd, H6 and H10, JHH = 8.3 Hz,
4JHH = 1.1 Hz), 7.43–7.40 (m, H2, H4 and H3), 7.36 (t, H7
3
3
and H9, JHH = 7.7 Hz), 7.26 (tt, H8, JHH = 7.3 Hz,
4JHH = 1.5 Hz), 4.56 (q, Hb, 3JHH = 6.6 Hz), 1.60 (d, MeA,
27
3JHH = 6.7 Hz). ½aꢂ589 (c = 0.36 g/100 mL, CHCl3) (litera-
ture [31], c = 1.0 g/100 ml) = ꢁ64.4ꢀ (ꢁ64.7ꢀ).

3078
J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3.3. Preparation of 2
ourless solution indicated the quantitative formation of the
corresponding monomeric cyclopalladated compound, as
showed the 1H NMR of the final colourless solution. Char-
acterization data: 1H NMR (CDCl3, 298 K) (selected data):
A suspension formed by 2.22 mol (0.500 g) of Pd(OAc)2,
2.22 mmol (0.465 g) of 1 and 20 mL of acetic acid was stir-
red under nitrogen at 60 ꢀC for 4 h. The resulting red solu-
tion was concentrated in vacuum and the residue was
eluted through a silica gel column chromatography with
a solution of methanol in chloroform in a 2 to 100 volume
ratio. The orange bands were collected and concentrated
under vacuum. Addition of diethylether (5 mL) to the res-
idue produced the precipitation of 2 as a yellow powder,
which was filtered and dried under vacuum. Yield: 65%
(0.539 g). Characterization data: Anal. Calc. for
C34H34O4N2Pd2: C, 54.63; H, 4.58; N, 3.75%. Found: C,
54.0; H, 4.5; N, 3.8%. IR (KBr, cmꢁ1): 1606 (C@N st),
1595 st as (carboxylato), 1420 st s (carboxylato). FAB(+)
(most intense peaks): [M+H+] = 749, [Mꢁ(OAcꢁ)] = 690,
[(M/2)-(OAcꢁ)] = 315. 1H NMR (400 MHz, CDCl3,
298 K) (selected data) (I and II isomers in 3 to 1 molar
4
Compound 4 (400 MHz): 7.66 (d, Ha, JHH = 1.0 Hz),
3
4
7.14 (dd, H5, JHH = 7.4 Hz, JHH = 1.4 Hz), 6.97 (td, H4,
3JHH = 7.4 Hz, 4JHH = 1.0 Hz), 6.88 (td, H3, 3JHH = 7.5 Hz,
3
4
4JHH = 1.5 Hz), 6.18 (dd, H2, JHH = 7.6 Hz, JHH
=
0.7 Hz), 5.24 (q, Hb, 3JHH = 6.9 Hz), 1.90 (s, MeB), 1.78 (d,
3
MeA, JHH = 6.9 Hz). Compound 5 (400 MHz): 7.65 (s,
Ha), 7.15 (d, H5, 3JHH = 7.0 Hz), 7.00 (t, H4, 3JHH = 7.3 Hz),
6.91 (t, H3, 3JHH = 7.5 Hz), 6.14 (d, H2, 3JHH = 7.6 Hz), 5.96
(q, Hb, 3JHH = 6.9 Hz), 1.83 (d, MeA, 3JHH = 6.9 Hz). Com-
pound 6 (RR diastereoisomer) (400 MHz): 7.73 (d, Ha,
3
4
4JHH = 1.1 Hz,), 7.09 (td, H4, JHH = 7.4 Hz, JHH
=
3
4
1.7 Hz), 7.04 (td, H3, JHH = 7.4 Hz, JHH = 1.2 Hz), 6.86
3
4
(dd, H2, JHH = 7.4 Hz, JHH = 0.9 Hz), 5.37 (q, Hb,
3JHH = 6.8 Hz), 4.26–4.16 (m, Hc), 3.64 (d, 1H, NH2,
2JHH = 8.7 Hz), 1.98 (s, MeB), 1.83 (d, MeC, 3JHH = 6.8 Hz),
1.75 (d, MeA, 3JHH = 6.9 Hz). Compound 7 (RR diastereo-
isomer) (400 MHz): 7.62 (d, Ha, JHH = 0.7 Hz), 7.17 (dd,
H5, JHH = 7.2 Hz, JHH = 1.6 Hz), 7.11 (td, H4, JHH =
4
ratio): 7.63 (d, Ha, JHH = 1.2 Hz, II), 6.98 (d, Ha,
3
4
4JHH = 1.2 Hz, I), 4.67 (q, Hb, JHH = 6.8 Hz, II), 4.61
3
3
4
3
(q, Hb, JHH = 6.8 Hz, I), 2.20 (s, MeB, I), 2.04 (s, MeB,
3
4
3
II), 1.76 (d, MeA, JHH = 6.8 Hz, I), 0.85 (d, MeA,
7.5 Hz, JHH = 1.6 Hz), 7.06 (td, H3, JHH = 7.2 Hz,
23:5
3JHH = 7.2 Hz, II). ½aꢂ589 (c = 0.29 g/100 mL, CHCl3) =
4JHH = 0.8 Hz), 6.85 (d, H2, JHH = 7.5 Hz), 5.82 (q, Hb,
3
+179.9ꢀ.
3JHH = 6.8 Hz), 4.56–4.46 (m, Hc), 3.58 (t, 1H, NH2,
2JHH = 10.7 Hz), 3.28 (d, 1H, NH2, JHH = 9.4 Hz), 1.89
2
3
3
3.4. Preparation of 3
(d, MeA, JHH = 6.9 Hz), 1.81 (d, MeC, JHH = 6.9 Hz).
Compound 8 (RR and RS diastereoisomers in 1 to 1 molar
ratio) (400 MHz): 7.73 (d, Ha, 4JHH = 1.1 Hz, RR), 7.67 (d,
A suspension formed by 0.180 g (4.20 mmol) of LiCl,
0.801 g (1.07 mmol) of 2 and 30 mL of acetone was stirred
at room temperature for 4 h. The resulting suspension was
concentrated under vacuum and the residue was eluted
through a silica gel column chromatography with a solu-
tion of methanol in chloroform in a 2 to 100 volume ratio.
The coloured band was collected and concentrated under
vacuum. Addition of diethylether (5 mL) to the residue
produced the precipitation of 3 as a yellow powder, which
was filtered and dried under vacuum. Yield: 88% (0.663 g).
Characterization data: Anal. Calc. for C30H28N2Cl2Pd2: C,
51.45; H, 4.03; N, 4.00. Found: C, 51.0; H, 4.2; N, 3.8%. IR
(KBr, cmꢁ1): 1604 (C@N st). FAB(+) (m/z):
[M+H+] = 701, [Mꢁ(Clꢁ)] = 665, [(M/2)ꢁ(Clꢁ)] = 315.
1H NMR (400 MHz, CDCl3, 298 K) (III and IV isomers
in 1.5 to 1 molar ratio): 7.59 (s, Ha, III and IV), 7.40 (m,
4
3
Ha, JHH = 1.1 Hz, RS), 6.86 (dd, H2, JHH = 7.4 Hz,
4JHH = 0.8 Hz, RR), 6.85 (dd, H2, JHH = 7.3 Hz, JHH
=
3
4
3
0.7 Hz, RS), 5.36 (q, Hb, JHH = 6.8 Hz, RR and RS),
4.24–4.16 (m, Hc, RR and RS), 3.63 (t, 1H, NH2,
2JHH = 8.6 Hz, RR and RS), 1.98 (s, MeB, RR and RS),
3
3
1.83 (d, MeC, JHH = 6.9 Hz, RR), 1.81 (d, MeC, JHH
=
3
6.9 Hz, RS), 1.75 (d, MeA, JHH = 6.9 Hz, RR), 1.73 (d,
MeA, 3JHH = 6.9 Hz, RS). Compound 9 (RR and RS diaste-
reoisomers in 1 to 1 molar ratio) (400 MHz): 7.73 (s, Ha, RS),
3
7.62 (s, Ha,RR), 7.17 (d, H5, JHH = 7.1 Hz, RR and RS),
3
7.11 (td, H4, JHH = 7.2 Hz, RR and RS), 7.05 (td, H3,
3JHH = 7.3 Hz, RR and RS), 6.85 (d, H2, JHH = 7.4 Hz,
3
3
RR and RS), 5.83 (q, Hb, JHH = 6.7 Hz, RR and RS),
4.55–4.47 (m, Hc, RR and RS), 3.58 (t, 1H, NH2,
2
2JHH = 11.2 Hz, RR), 3.52 (t, 1H, NH2, JHH = 11.0 Hz,
3
2
4 H, Har, III and IV, JHH = 6.0 Hz), 7.36–7.32 (m, 2H,
RS), 3.31 (d, 1H, NH2, JHH = 11.2 Hz, RS), 3.27 (d, 1H,
2
3
Har, III and IV), 7.10–7.08 (m, 1H, Har, III and IV),
7.04–6.99 (m, 2H, Har, III and IV), 5.34 (q, Hb, III and
NH2, JHH = 11.2 Hz, RR), 1.88 (t, MeA, JHH = 7.6 Hz,
3
RR and RS), 1.81 (d, MeC, JHH = 6.9 Hz, RR), 1.78 (d,
3
3
IV, JHH = 6.7 Hz), 1.82 (br signal, MeA, III) 1.77 (br sig-
MeC, JHH = 6.9 Hz, RS). Compound A (200 MHz): 7.70
23:5
3
3
nal, MeA, IV). Optical rotation: ½aꢂ589 (c = 0.28 g/100 mL,
(s, Ha), 7.16 (d, H5, JHH = 7.0 Hz), 6.97 (t, H4, JHH
7.0 Hz), 6.88 (t, H3, JHH = 7.0 Hz), 6.03 (d, H2, JHH
=
=
3
3
CHCl3) = + 255.7ꢀ.
7.0 Hz), 4.86 (s, CH2), 1.91 (s, OAc).
3.5. NMR tube reactions
3.6. Preparation of 10
An orange or pale yellow solution formed by 10 mg of the
corresponding dimeric cyclopalladated compound in 0.7 mL
of CDCl3 was treated with a drop of the corresponding L
ligand and shaken for a few seconds. The formation of a col-
A 250 mL cylindrical glassware reactor was charged in a
ventilated fume hood with 0.151 g (0.20 mmol) of com-
pound 2, 25 mL of MeOH and carbon monoxide at

J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
3079
Table 5
1.6 bar. The resulting suspension was stirred at room tem-
Crystallographic data for the trans isomer of compound 3
perature for 6 h. After this time, a voluminous precipitate
of palladium(0) was formed and the reactor was opened to
release the excess of carbon monoxide. The palladium(0)
was filtered and the solvent of the resulting solution was
concentrated under vacuum. The residue of the solution
was eluted through a short silica gel column chromatogra-
phy (ca. 10 cm), initially with chloroform and thereafter
with solutions of methanol in chloroform, increasing gradu-
ally the volume ratio between methanol and chloroform
from 0.5 to 100 to 2 to 100. Compound 10 was isolated as
a white solid in 91% yield after concentration under vacuum
of the solvent of the second eluted band. Characterization
data: IR (CHCl3 solution, cmꢁ1): 1723 (C@O st, ester),
1700 (C@O st, aldehyde), 1284 (CO–O st a), 1257 (CO–O
Empirical formula
Formula weight
Temperature
C30H28Cl2N2Pd2
700.24
293(2) K
˚
Wavelength
0.71073 A
Crystal system
Space group
Unit cell dimensions
Monoclinic
P21
˚
a (A)
10.430(4)
12.082(8)
11.168(4)
95.20(3)
˚
b (A)
˚
c (A)
b (ꢀ)
3
˚
Volume
1401.5(12) A
Z
2
Dcalc(Mg/m3)
1.659
1.495
696
Absorption coefficient (mmꢁ1
F(000)
)
1
st s). H NMR (400 MHz, CDCl3, 298 K): 10.62 (s, Ha),
7.99–7.94 (m, 2H, Har), 7.67–7.64 (m, 2H, Har), 3.98 (s, Me).
Crystal size (mm)
h Range for data collection (ꢀ)
0.2 · 0.1 · 0.1
2.49–29.97
ꢁ14 6 h 6 14
0 6 k 6 16
0 6 l 6 15
4749/4253 [0.040]
98.8
Limiting indices
3.7. Preparation of samples A and B
Reflections collected/unique [Rint
Completeness to theta = 29.97ꢀ (%)
Absorption correction
]
A 250 mL cylindrical glassware reactor was charged in a
ventilated fume hood with 0.155 g (0.22 mmol) of compound
3, 25 mL of MeOH and carbon monoxide at 1.6 bar. The
resulting suspension was stirred at room temperature for
24 h. After this time, a voluminous precipitate of palla-
dium(0) was formed and the reactor was opened to release
the excess of carbon monoxide. The palladium(0) was fil-
tered and the solvent of the resulting solution was concen-
trated under vacuum. The residue of the solution was
eluted through a silica gel column chromatography with
chloroform. Four bands were eluted, the most important
being the last two bands. Concentration of the solvent of
the third eluted band afforded 0.085 g of a yellow oil (sample
A), which was a mixture of compounds 11 and 12 in ca. 7 to 1
molar ratio. Concentration of the solvent of the fourth eluted
band afforded 0.011 g of an oil (sample B), which was a mix-
ture of compounds 12 and 11 in ca. 4 to 1 molar ratio. Char-
acterization data: Compound 11 (V and VI epimers in 1.5 to
1 molar ratio): IR (CHCl3 solution, cmꢁ1): 1693 (C@O st).
FAB(+) (m/z) (most intense peaks): [M+H]+ = 268,
[M+H+ꢁMeOH] = 236. 1H NMR (400 MHz, CDCl3,
298 K) (selected data): 6.02 (s, Ha,VI), 5.68 (q, Hb,
3JHH = 7.3 Hz, V), 5.60 (s, Ha, V), 5.39 (q, Hb,
3JHH = 7.4 Hz, VI), 2.92 (s, MeO, V), 2.47 (s, MeO, VI),
1.88 (d, Me, 3JHH = 7.3 Hz, VI), 1.80 (d, Me, 3JHH = 7.3 Hz,
V). HPLC (tR) = 22.5 min (V), 24.4 min (VI). Compound
12: IR (CHCl3 solution, cmꢁ1): 1676 (C@O st). CI-MS/
None
Refinement method
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Flack · parameter
Largest difference in peak and hole (e A ) 0.405 and ꢁ0.520
4253/4/325
0.753
R1 = 0.0364 wR2 = 0.0478
R1 = 0.2676 wR2 = 0.0760
ꢁ0.01(7)
3
˚
in ethyl acetate/dichloromethane (1/1). A prismatic crystal
was selected and mounted on an Enraf-Nonius CAD4
four-circle diffractometer. Intensities were collected with
graphite-monochromatized Mo Ka radiation. The struc-
ture was solved by direct methods using the SHELXS [60]
computer program and refined by the full-matrix least-
squares method, with the SHELXL97 [61] computer program.
A summary of crystallographic data and some details of
the refinement are given in Table 5.
4. Supplementary material
CCDC 633319 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
1
NH3 (m/z) (most intense peak): [M+H+] = 238. H NMR
(400 MHz, CDCl3, 298 K) (selected data): 7.88 (d, 1H, Har,
3
3JHH = 7.0 Hz), 5.82 (q, Hb, JHH = 7.1 Hz), 4.34 (d, 1H,
CH2, 2JHH = 17.0 Hz), 4.00 (d, 1H, CH2, 2JHH = 17.0 Hz),
1.70 (d, Me, 3JHH = 7.1 Hz). HPLC (tR) = 39.4 min.
Acknowledgements
3.8. Crystal structure
We are grateful to the Ministerio de Ciencia y Tec-
´
nologıa for financial support (Grant CTQ2006-02007/
Crystals for the X-ray molecular structure determina-
BQU) and L.D. to the University of Barcelona for a
`
BRD grant. We are also grateful to the group of Catalisi
tion of 3 were obtained by cooling at 4 ꢀC a solution of 3

3080
J. Albert et al. / Journal of Organometallic Chemistry 692 (2007) 3070–3080
[35] M.A. Cinellu, G. Minghetti, G. Banditelli, A.L. Bandini, B. Peli, P.
Traldi, Inorg. Chim. Acta 161 (1989) 57.
[36] P.G. Evans, N.A. Brown, G.J. Clarkson, C.P. Newman, J.P. Rourke,
J. Organomet. Chem. 691 (2006) 1251.
`
Homogenia of the University of Barcelona for the HPLC
experiment.
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