Cyclopalladation of Schiff bases from phenylalanine and 2-phenylglicine

Article abstract of DOI:10.1016/S0022-328X(02)01928-9

The action of palladium acetate on the Schiff bases 4-ClC₆H₄CH=N-CH(R²)COOR¹ (R¹ = Me, Et; R² = Ph, CH₂Ph), in acetic acid for 3 h at 70 °C and subsequent treatment of the reaction residues with LiCl in acetone, affords the corresponding chlorobridged five-membered endo-metallacycles [PdCl(C-N)]₂, 1a, 2a. The action of palladium acetate on the Schiff bases 2,6-Cl₂C₆H₃CH=N-CH (R²)COOR¹ (R¹ = Me, Et; R² = Ph, CH₂Ph), in chloroform at room temperature and subsequent treatment of the reaction residues with LiCl in acetone, affords the corresponding chloro-bridged five- or six-membered exo-metallacycles, by metallation of the amino acid moiety [PdCl(C-N)]₂, 3a-exo, 4a-exo. A small amount of the endo-metallacycles was also obtained, probably by oxidative addition of the ortho C-Cl bond of these imines to Pd(0) formed in situ. Reaction of dimers 1a-4a with PPh₃ affords the mononuclear complexes [PdCl(C-N)(PPh₃)] 1b-4b.

Full text of DOI:10.1016/S0022-328X(02)01928-9

Journal of Organometallic Chemistry 663 (2002) 277ꢂ283
/
www.elsevier.com/locate/jorganchem
Cyclopalladation of Schiff bases from phenylalanine and
2-phenylglicine
Joan Albert a, J. Magali Cadena a, Asensio Gonza´lez b, Jaume Granell a,ꢀ,
Xavier Solans c, Merce` Font-Bardia c
a
´
Departament de Quımica Inorga`nica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain
´
Laboratorio de Quımica Orga`nica, Facultat de Farma`cia, Universitat de Barcelona, Pl. Pius XII, s/n, 08028 Barcelona, Spain
b
c
´
Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals, Universitat de Barcelona, Martı i Franque`s s/n, 08028 Barcelona, Spain
Received 17 July 2002; accepted 18 September 2002
Dedicated to Professor Pascual Royo on the occasion of his 65th birthday
Abstract
The action of palladium acetate on the Schiff bases 4-ClC6H4CHÄ
acid for 3 h at 70 8C and subsequent treatment of the reaction residues with LiCl in acetone, affords the corresponding chloro-
bridged five-membered endo-metallacycles [PdCl(CÃN)]2, 1a, 2a. The action of palladium acetate on the Schiff bases 2,6-
Cl2C6H3CHÄNÃ Ph, CH2Ph), in chloroform at room temperature and subsequent treatment of
CH(R2)COOR1 (R1ꢁMe, Et; R2ꢁ
the reaction residues with LiCl in acetone, affords the corresponding chloro-bridged five- or six-membered exo-metallacycles, by
metallation of the amino acid moiety [PdCl(CÃN)]2, 3a-exo, 4a-exo. A small amount of the endo-metallacycles was also obtained,
probably by oxidative addition of the ortho CÃCl bond of these imines to Pd(0) formed in situ. Reaction of dimers 1aꢂ4a with PPh3
affords the mononuclear complexes [PdCl(CÃN)(PPh3)] 1bꢂ4b.
/
N-CH(R2)COOR1 (R1ꢁ
/
Me, Et; R2ꢁ
Ph, CH2Ph), in acetic
/
/
/
/
/
/
/
/
/
/
/
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Palladium; Imines; Amino acid; Cyclometallation
1. Introduction
amino acid derivatives by palladium. Ryabov et al.
reported the cyclopalladation of the (R)-N,N-dimethyl-
2-phenylglycine methyl ester by palladium acetate [2],
Fuchita et al. described the metallation of the primary
benzylamine derivative (R)-2-phenylglycine methyl ester
[3] and Grigg et al. reported the synthesis of ortho-
palladated imines of a-amino acids [4]. Recently, Beck
and coworkers described the cyclopalladation of several
Schiff bases from a-amino acid and peptide esters [5].
As part of our studies on the cyclometallation of N-
donor ligands, we examined the action of palladium
acetate on imines from phenylalanine and 2-phenylgly-
cine. These ligands were obtained by condensation of
the corresponding benzaldehyde with the a-amino acid
ester.
There is growing interest in the synthesis, reactivity
and applications of organometallic complexes with
biologically important ligands and the term bioorgano-
metallic chemistry is used to describe this new research
field on the border between biochemistry and organo-
metallic chemistry [1].
a-Amino acids are highly versatile ligands and can
afford two classes of compounds: complexes in which
the amino acid is coordinated to an organometallic
fragment via their donor atoms (amino, carboxylato or
other basic groups) and complexes in which the amino
acid is coordinated to the metal through a carbonꢂ
bond, this last class being comparatively rare [1a]. Some
CÃN chelates have been synthesized by metallation of
/metal
/
Imines can undergo metallation on different carbon
atoms, giving organometallic complexes of different
structures: endo-metallacycles, if the CÄ
/
N bond is
ꢀ Corresponding author. Fax: ꢃ
E-mail address: jgranell@kripto.qui.ub.es (J. Granell).
/
34-93-411-1492
included in the metallacycle, or exo-derivatives. In
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 9 2 8 - 9

278
J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ283
/
addition, imines can exist in E or Z isomers, but in
general, N-substituted aldimines adopt the more stable
E form [6]. endo- or exo-Metallacycles can be obtained
from imines in the E form but the Z isomer can afford
only exo-metallacycles [7].
low yield of the metallation reaction can be explained by
the instability of the imines.
It has been shown that exo-metallacycles can be
obtained by cyclopalladation of imines if the ortho
positions of the benzal ring (which leads to the forma-
tion of endo-metallacycles) are blocked by substituents
such as chlorine atoms [7a]. Following and expanding
this strategy to prepare exo-cyclic imine cyclopalladated
derivatives, the action of palladium acetate on imines 3
and 4, derived from 2,6-dichlorobenzaldehyde, was
studied.
The reaction was performed in chloroform at room
temperature and the reaction residues were treated with
LiCl in acetone. After purification by SiO2 column
chromatography, the corresponding chloro-bridged cy-
clopalladated dimers 3a and 4a were isolated. NMR
data showed that these complexes are the exo-deriva-
2. Results and discussion
The Schiff bases 1 and 2 were treated with palladium
acetate in acetic acid for 3 h at 70 8C. Subsequent
treatment of the reaction residues with LiCl in acetone
afforded, after purification by SiO2 column chromato-
graphy, the corresponding chloro-bridged cyclopalla-
dated dimers 1a and 2a, in a yield of 25 and 40%,
respectively (Scheme 1). Overall NMR data showed that
only the endo-derivative was formed, which is consistent
with reports of the strong tendency of imines to form
endo-metallacycles [8]. These imines might also afford
exo-metallacycles (of five- and six-membered, respec-
tives, with a Caromatic Pd bond, containing the imine in
Ã
/
the Z form. A small amount of the endo-metallacycles
was also obtained, probably by oxidative addition of the
ortho CÃ
/Cl bond of these imines to Pd(0) formed in situ
tively) by activation of a Caromatic
acid moiety but their formation was not observed. The
Ã
/
H bond of the amino
[7a,9].
Scheme 1. (i) Pd(AcO)2, AcOH, 3 h, 70 8C; (ii) LiCl, acetone, room temperature, 30 min; (iii) PPh3, acetone; (iv) Pd(AcO)2/CHCl3, room
temperature, 2 h.

J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ
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279
Reaction of dimers 1aꢂ
mononuclear complexes [PdCl(CÃ
/
4a with PPh3 afforded the
All the free ligands and endo-metallacycles, which
bear a chloro substituent at the C2 position of the aryl
ring, show a downfield shift of the imine resonance
/
N)(PPh3)] 1bꢂ4b. The
/
high-field shift of the aromatic protons of the palladated
ring in these complexes, due to the aromatic rings of the
phosphine, indicates the cis disposition of the phospho-
rus relative to the metallated carbon atom, and the
chemical shift of the phosphorus confirms this arrange-
ment [7]. This arrangement is usual in cyclopalladated
compounds containing phosphines [10].
The structure of 4b-exo was determined by X-ray
diffraction (Fig. 1, Table 1). The crystal structure
consists of discrete molecules separated by van der
Waals distances. The palladium atom is in a square-
planar environment, coordinated to carbon, chlorine,
nitrogen and phosphorus atoms. The coordination plane
shows a tetrahedral distortion, the deviation from the
which is consistent with a NÄ
/
CHÁ Á ÁCl interaction
between the imine proton and the chlorine atom. Similar
shifts have been previously observed for analogous
compounds with chloro or fluoro substituents. This
interaction, which reinforces the planarity of the ArCÄ
/
N fragment, has been confirmed in some cases by X-ray
crystal structure determination [12].
In conclusion the results here reported show that
imines derived from amino acids have a strong tendency
to afford endo-metallacycles. Nevertheless the exo-
derivatives can be obtained if the ortho positions of
the benzal ring (which leads to the formation of endo-
metallacycles) are blocked by chloro substituents. There
is no clear explanation of this endo-effect. The aroma-
ticity of the five-membered metallacycle, involving the
mean plane being: ꢄ
/
0.049(1), ꢄ
/
0.064(5), ꢃ0.051(4)
/
˚
and 0.062(5) A for Cl, C1, P and N, respectively. The
distances between palladium and the coordinated atoms
are similar to those reported for analogous compounds
[7,11], the angles between adjacent atoms in the co-
two conjugated bonds CÄ
/
C, CÄ
/
N and the filled d
orbital of the metal of appropriate symmetry has been
proposed to explain the greater stability of endo-cyclic
compounds [13]. Besides this, kinetic studies of the
influence of temperature and pressure on a wide variety
of imines have also been reported. In these studies the
formation of a highly ordered transition state, in which
there is a four centered interaction between the carbon
ordination sphere lie in the range 81.79(16) (C1Ã
to 94.00(12) (C1ÃPdÃP). The phosphorus and nitrogen
atoms adopt a trans arrangement, the metallacycle does
not contain the CÄN bond and the imine is in the Z-
form.
/
PdÃ/N)
/
/
/
and hydrogen bonds of the CÃ
/
H bond to be activated,
All the new organometallic compounds obtained were
1
characterized by elemental analysis, IR spectra, and H
the oxygen atom of the acetate ligand and the palladium
atom, is proposed to explain the endo-effect [8a,8b,14].
and 31P-NMR spectra. In some cases, 2D-NMR experi-
ments and positive FAB-mass spectra were carried out
to complete the characterization. It should be noted that
complete racemization of the Schiff base takes place
during the cyclopalladation reaction.
3. Experimental
1H-NMR spectra at 200 MHz were recorded on a
1
Varian Gemini 200 spectrometer and H-NMR at 500
MHz and 31P{1H} at 101.26 MHz were recorded,
respectively, on a Varian VXR 500 or a Bruker DRX
250 spectrometers. Chemical shifts (in ppm) were
Table 1
˚
Selected bond lengths (A) and angles (8) for 4b-exo
Bond lengths
PdÃC(1)
PdÃN
1.999(4)
2.096(3)
2.2460(10)
2.3863(12)
1.721(6)
1.738(6)
O(1)ÃC(9)
O(2)ÃC(9)
O(2)ÃC(10)
NÃC(12)
NÃC(8)
1.187(7)
1.312(8)
1.454(10)
1.267(6)
1.486(6)
PdÃP
PdÃCl(1)
Cl(2)ÃC(14)
Cl(3)ÃC(18)
Bond angles
C(1)ÃPdÃN
C(1)ÃPdÃP
NÃPdÃP
C(1)ÃPdÃCl(1)
NÃPdÃCl(1)
PÃPdÃCl(1)
81.73(16)
94.00(12)
172.64(10)
172.55(12)
90.84(11)
93.44(4)
C(9)ÃO(2)ÃC(10)
C(12)ÃNÃC(8)
C(12)ÃNÃPd
C(8)ÃNÃPd
NÃC(8)ÃC(9)
NÃC(8)ÃC(7)
119.3(6)
120.1(3)
121.3(3)
117.9(2)
111.6(4)
108.5(3)
Fig. 1. ORTEP plot of the structure of 4b-exo.

280
J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ
/283
1
measured relative to SiMe4 for H and to 85% H3PO4
for 31P. Microanalyses were performed at the Institut de
Qu´ımica Bio-Orga`nica de Barcelona and the Serveis
Cient´ıfico-Te`cnics de la Universitat de Barcelona. Infra-
red spectra were recorded as KBr disks on a Nicolet 520
FT-IR spectrometer. Mass spectra were recorded on a
Fisons VG-Quattro spectrometer. The samples were
introduced in a matrix of 2-nitrobenzylalcohol for
FAB analysis and then bombarded with cesium atoms.
in vacuo, and the solid obtained was dissolved in
acetone (20 ml) and was treated with LiCl (2.44 mmol,
104 mg) for 30 min at room temperature (r.t.). The
solution was concentrated in vacuo and the precipitate
formed was purified by column chromatography over
SiO2 with chloroformꢂacetone (100:4) as eluent to
/
obtain 1a and 2a in a yield of 25 and 40%, respectively.
The cyclometallated complexes 3a and 4a were
similarly prepared by reaction between palladium ace-
tate and the corresponding imine in CHCl3 for 2 h at r.t.
The resulting solution was concentrated in vacuo, and
the solid obtained was dissolved in acetone (20 ml) and
was treated with LiCl (2.44 mmol, 104 mg) for 30 min at
r.t. The solution was concentrated in vacuo and the
precipitate formed was purified by column chromato-
graphy over SiO2 with CHCl3:MeOH (100:1) as eluent.
The compounds were obtained in a yield of 5% for 3a-
endo, 20% for 3a-exo, 8% for 4a-endo, and 25% for 4a-
exo.
3.1. Materials and synthesis
All solvents were dried and degassed by standard
methods. All chemicals were of commercial grade and
used as received. Crystals of 4b-exo for X-ray structure
determination were obtained from a Et2O solution. The
proton NMR spectra of cyclopalladated compounds
1aꢂ
drops of pyridine-d5 to obtain the corresponding mono-
nuclear complexes [PdCl(CÃN)py].
/
4a were performed in CDCl3 the presence of a few
/
1a: Characterization data: Anal. Calc. (found) for
C32H26Cl4N2O4Pd2: C, 44.84 (44.7); H, 3.06 (2.9); N,
3.1.1. Synthesis of imines 1ꢂ
/
4
3.27 (3.3)%. 1H-NMR (200 MHz, CDCl3): 1aꢃ
/
pyridine-
3.83 (s, 3H, Me); 6.05 (s, 1H, HCCOOMe); 6.75
(s, 1H, H1); 7.01 (d, 1H, JHH 8.0 Hz, H2), 7.15 (d, 1H,
JHH
8.0 Hz, H3); 7.45 (m, 5H, aromatic); 7.86 (s, 1H,
HCÄN).
A mixture of 1.7 mmol of amino acid ester (pheny-
lalanine ethyl ester and phenylglycine methyl ester) and
1.7 mmol of the corresponding aldehyde and MgSO4
d5, dꢁ
/
ꢁ
/
ꢁ
/
was stirred in CH2Cl2 for 20 h to obtain the ligands 1ꢂ
/
4.
/
The solution was filtered and concentrated in vacuo and
2a: Characterization data: Anal. Calc. (found) for
1
the oil obtained was characterized by H-NMR and IR
spectra and was used without further purification.
C36H34Cl4N2O4Pd2: C, 47.35 (47.6); H, 3.75 (3.6); N,
3.07 (3.0)%. MS-positive FAB: 912 (Mꢃ), 877 {(Mꢄ
/
1: 1H-NMR (200 MHz, CDCl3) dꢁ
/
3.73 (s, 3H, Me);
7.30 (m, 7H, aromatic);
8.4 Hz); 8.28 (s, 1H, HCÄ
Cl)ꢃ}. H-NMR (200 MHz, CDCl3): dꢁ
JHH 7.2 Hz, CH3CH2O); 3.40 (br m, 1H, CH2CHN);
3.60 (m, 1H, CH2N); 4.24 (q, 2H, JHH 6.6 Hz,
CH2CH3); 4.60 (br m, 1H, HCCOOEt); 7.03 (s, 1H,
H1); 7.20ꢂ
7.40 (m, 7H, aromatic); 7.64 (s, 1H, HCÄN).
1H-NMR (200 MHz, CDCl3) 2aꢃ
pyridine-d5, dꢁ1.20
(t, 3H, JHH 7.0 Hz, CH3CH2O); 3.30 (dd, 1H, JHH
6.6 Hz, CH2CHN); 3.60 (dd, 1H, JHH
5.8 Hz, CH2CHN); 4.17 (q, 2H, JHH
/
1.28 (t, 3H,
1
5.19 (s, 1H, HCCOOMe); 7.50ꢂ
/
ꢁ
/
7.75 (d, 2H, aromatic, JHH
N).
ꢁ
/
/
ꢁ
/
2: 1H-NMR (200 MHz, CDCl3) dꢁ
/
1.24 (t, 3H,
7.2 Hz); 3.15 (dd, 1H, JHH 13.4
9 Hz, CH2N); 3.40 (dd, 1H, dd, 1H, JHH
13.4 Hz, JHH 5.2 Hz, CH2N); 4.18 (m, 3H,
HCCOOEt, CH2O); 7.20ꢂ7.15 (m, 5H, aromatic); 7.33
(d, 2H, JHH 8.8 Hz, aromatic); 7.62 (d, 2H, JHH 8.8
Hz, aromatic); 7.85 (s, 1H, HCÄN).
3: 1H-NMR (200 MHz, CDCl3) dꢁ
5.32 (s, 1H, HCCOOMe); 7.50ꢂ7.30 (m, 6H, aromatic);
7.2 Hz); 8.53 (s, 1H, HCÄ
/
/
CH3CH2O, JHH
ꢁ
/
ꢁ
/
/
/
Hz, JHH
ꢁ
/
ꢁ
/
ꢁ
ꢁ
ꢁ
/
ꢁ
/
ꢁ
/
12.8 Hz, JHH
12.8 Hz, JHH
/
ꢁ
/
/
/
ꢁ
/
ꢁ
/
ꢁ
/
7.0 Hz, CH2CH3); 5.60 (br m, 1H, HCCOOEt); 6.10 (s,
1H, H1); 7.0ꢂ
7.40 (m, 7H, aromatic); 7.81 (s, 1H, HCÄ
N).
/
/
/
/
3.76 (s, 3H, Me);
/
3a-endo: Characterization data: Anal. Calc. (found)
for C32H26Cl4N2O4Pd2: C, 44.84 (45.1); H, 3.06 (3.0); N,
7.52 (d, 2H, aromatic, JHH
ꢁ
/
/
N).
3.27 (3.2). MS-positive FAB: 857 (Mꢃ), 820 {(Mꢄ
/
4: 1H-NMR (200 MHz, CDCl3) dꢁ
/
1.27 (t, 3H,
7.4 Hz); 3.10 (dd, 1H, JHH 13.4
9 Hz, CH2Ph); 3.45 (dd, 1H, dd, 1H, JHH
13.4 Hz, JHH 5.2 Hz, CH2Ph); 4.18 (m, 2H,
HCCOOEt, CH2CH3); 7.20ꢂ7.15 (m, 8H, aromatic);
8.19 (s, 1H, HCÄN).
Cl)ꢃ}. H-NMR (200 MHz, CDCl3): dꢁ
Me); 6.02 (s, 1H, HCCOOMe); 6.96 (m, 2H, aromatic);
/
3.84 (s, 3H,
1
CH3CH2O, JHH
ꢁ
/
ꢁ
/
1
Hz, JHH
ꢁ
/
ꢁ
/
7.35ꢂ
NMR (200 MHz, CDCl3), 3a-endoꢃ
3.81 (s, 3H, Me); 6.02 (br, 1H, H1); 6.75 (s, 1H,
HCCOOMe); 6.85ꢂ6.91 (m, 2H, aromatic); 7.36ꢂ7.45
N).
/
7.49 (m, 6H, aromatic); 8.07 (s, 1H, HCÄ
/N). H-
ꢁ
/
/
pyridine-d5: dꢁ
/
/
/
/
/
(m, 5H, aromatic); 8.24 (s, 1H, HCÄ
/
3.1.2. Synthesis of compounds 1aꢂ
A stirred suspension of palladium acetate (2.22 mmol,
500 mg) in AcOH (30 ml) was treated with the
/
4a
3a-exo: Characterization data: Anal. Calc. (found) for
C32H24Cl6N2O4Pd2: C, 41.50 (41.5); H, 2.61 (2.5); N,
3.02 (2.9). MS-positive FAB: 926 (Mꢃ), 890{(Mꢄ
/
1
corresponding ligand 1ꢂ
/
2 (2.22 mmol) for 3 h at 70 8C
Cl)ꢃ}. H-NMR (200 MHz, CDCl3) dꢁ
/3.67 (s, 3H,
under nitrogen. The resulting solution was concentrated
Me); 5.49 (s, 1H, HCCOOMe); 6.90ꢂ7.05 (m, 3H,
/

J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ
/283
281
aromatic); 7.35ꢂ
/
7.40 (m, 4H, aromatic); 9.05 (s, 1H,
N). H-NMR (200 MHz, CDCl3), 3a-exoꢃpyri-
dine-d5, dꢁ3.65 (s, 3H, Me); 5.62 (s, 1H, HCCOOMe);
6.18 (br, 1H, aromatic); 6.95 (t, 1H, JHH
8.0, H2);
7.03ꢂ 7.49 (m, 3H, aro-
7.18 (m, 2H, H3, H4); 7.31ꢂ
N).
JHH
ꢁ
/
2.0 Hz, H1), 6.80 (dd, 1H, JHH
8.2 Hz, H3), 7.20ꢂ
N).
ꢁ
/
8.2 Hz, JHH
ꢁ
/
1
HCÄ
/
/
2.0 Hz, H2), 7.11 (d, 1H, JHH
ꢁ
/
/7.70
/
(m, 20 H, aromatic); 8.05 (s, 1H, HCÄ
/
ꢁ
/
3b-endo Characterization data: Anal. Calc. (found)
for C34H28Cl2NO2PPd: C, 59.11 (59.3); H, 4.09 (4.1); N,
/
/
matic); 9.75 (br, 1H, HCÄ
/
2.03 (1.9)%. 31P{1H}-NMR: dꢁ41.86, s. 1H-NMR (200
/
4a-endo: Characterization data: Anal. Calc. (found)
for C36H34Cl4N2O4Pd2: C, 47.35 (47.4); H, 3.75 (3.6); N,
3.07 (3.0); Cl, 15.56 (15.9)%. MS-positive FAB: 913
MHz, CDCl3): dꢁ
6.0 Hz, JHP
13 Hz; H1); 6,45 (t, 1H, JHH
H2); 6.80 (d, 1H, JHH 8.2, H3); 6.94 (br, 1H,
HCCOOMe); 7.33ꢂ7.81 (m, 20H, aromatic); 8.56 (s,
1H, JHP N).
8.2 Hz, HCÄ
3b-exo Characterization data: Anal. Calc. (found) for
C34H27Cl3NO2PPd: C, 56.30 (56.5); H, 3.75 (3.9); N,
1.93 (1.8)%. 31P{1H}-NMR: dꢁ41.15, s. 1H-NMR (200
MHz, CDCl3): dꢁ
HCCOOMe); 6.44 (m, 2H, H1, H2); 6.87 (br t, 1H, H3);
7.10 (d, 1H, JHH 7.4 Hz, aromatic) 7.34ꢂ7.85 (m, 18H,
4.8 Hz, HCÄ
aromatic); 9.61 (br d, 1H, JHP N).
/3.78 (s, 3H, Me); 6.26 (t, 1H, JHH
ꢁ
/
ꢁ
/
ꢁ
/
7.6 Hz,
ꢁ
/
(Mꢃ), 877 {(Mꢄ
/
Cl)ꢃ}. H-NMR (200 MHz, CDCl3):
/
1
dꢁ
2H, CH2CHN); 4.24 (q, 2H, JHH
4.60 (br, 1H, HCCOOEt); 6.98 (m, 2H, aromatic); 7.25ꢂ
/1.30 (t, 3H, JHH
ꢁ
/
7.2 Hz, CH3CH2O); 3.4ꢂ/3.7 (m,
ꢁ
/
/
ꢁ/7.2 Hz, CH3CH2O);
/
1
7.31 (m, 6H, aromatic); 7.94 (s, 1H, HCÄ
(200 MHz, CDCl3), 4a-endoꢃpyridine-d5: dꢁ
3H, JHH 7.0 Hz, CH3CH2O); 3.50 (dd, 2H,
CH2CHN); 4.19 (q, 2H, JHH 7.0 Hz, CH2CH3); 5.60
(br, 1H, HCCOOEt); 6.0 (d, 1H, JHH
6.0 Hz, H1);
6.98 (m, 2H, H2, H3); 7.24ꢂ
7.38 (m, 5H, aromatic); 8.2
N).
/
N). H-NMR
/
/
/1.21 (t,
/
3.76 (s, 3H, Me); 5.48 (br s, 1H,
ꢁ
/
ꢁ
/
ꢁ
/
/
ꢁ
/
ꢁ
/
/
/
4b-endo Characterization data: Anal. Calc. (found)
for C36H32Cl2NO2PPd: C, 60.14 (60.1); H, 4.49 (4.6); N,
1.95 (1.9)%. MS-positive FAB: 718.8 [M]ꢃ), 684{[Mꢄ
(s, 1H, HCÄ
/
4a-exo: Characterization data: Anal. Calc. (found) for
C36H32Cl6N2O4Pd2: C, 44.02 (44.0); H, 3.28 (3.2); N,
/
Cl]ꢃ}. 31P{1H}-NMR: dꢁ
MHz, CDCl3): dꢁ1.13 (t, 3H, JHH
CH3CH2O); 3.18 (dd, 1H, JHH 13.6 Hz, JHH
8.4Hz, CH2CHN); 3.69 (dd, 1H, JHH 13.2 Hz,
JHH 5.6 Hz, CH2CHN); 4.12 (q, 2H, JHH 7.1 Hz,
CH3CH2O); 5.81 (br, 1H, HCCOOEt); 6.26 (t, 1H,
JHH JHP
6.2 Hz, H1); 6.45 (t, 1H, JHH 8.2 Hz, H2);
6.82 (d, 1H, JHH 7.78 (m, 20H,
8.0 Hz, H3); 7.19ꢂ
aromatic); 8,66 (d, 1H, JHP N).
8.0 Hz, HCÄ
/
41.89, s. 1H-NMR (250
2.85 (2.9)%. 1H-NMR (250 MHz, CDCl3), 4a-exoꢃ
/
/
ꢁ/7.0 Hz,
pyridine-d5, dꢁ
5H, CH2Ph, CHCOO, CH3CH2); 6.48 (d, 1H, H1), 6.7
(br,1H, H2); 6.90 (d, 2H, aromatic) 7.22ꢂ
7.40 (m, 3H,
aromatic); 9.71 (s, 1H, HCÄN).
/
0.97 (t, 3H, CH3CH2); 3.07ꢂ
/3.85 (m,
ꢁ
/
ꢁ
/
ꢁ
/
/
ꢁ
/
ꢁ
/
/
ꢁ
/
ꢁ
/
ꢁ
/
3.1.3. Synthesis of compounds 1bꢂ
/
4b
ꢁ
/
/
A suspension formed by 0.11 mmol (100 mg) of
compound 1a in 20 ml of acetone was treated with 0.22
mmol (57 mg) of PPh3, the mixture of reaction was
stirred for 30 min at r.t. and then concentrated in vacuo.
The solid formed was washed with Et2O and the yellow
solid was obtained in a yield of 80%.
Compounds 2b, 3b-endo, 3b-exo, 4b-endo, 4b-exo
were prepared in similar ways, in yields of 75, 74, 80, 85
and 80%, respectively.
ꢁ
/
/
4b-exo Characterization data: Anal. Calc. (found) for
C36H31Cl3NO2PPd: C, 57.39 (57.2); H, 4.15 (4.0); N,
1.86 (1.7)%. 31P{1H}-NMR: dꢁ33.78, s. 1H-NMR (250
MHz, CDCl3): dꢁ
HCHPh); 3.87ꢂ4.20 (br, 4H, HCHPh, CHCOO,
CH3CH2); 6.31 (t, 1H, JHH
7.0 Hz, H2), 6.60 (m,
2H, H1, H3); 6.75 (d, 1H, JHH 8.0 Hz, H4) 7.25ꢂ
7.43
(m, 12H, aromatic); 7.58ꢂ7.71 (m, 6H, aromatic), 9.26
(br, 1H, HCÄN).
/
/1.20 (t, 3H, CH3CH2); 3.43 (br, 1H,
/
ꢁ
/
ꢁ
/
/
/
1b Characterization data: Anal. Calc. (found) for
C34H28Cl2NO2PPd: C, 59.11 (59.1); H, 4.09 (3.9); N,
/
2.03 (2.0)%. MS-positive FAB: 689 (Mꢃ), 654{(Mꢄ
/
Cl)ꢃ}. 31P{1H}-NMR: dꢁ
MHz): dꢁ3.77 (s, 3H, Me); 6.23 (dd, 1H, JHP
Hz, JHH 8.0 Hz,
1.6 Hz, H1), 6.84 (dd, 1H, JHH
JHH
1.4 Hz, H2), 6.89 (s, 1H, HCCOOMe); 7.11 (d,
1H, JHH 7.78 (m, 20 H, aromatic);
8.2 Hz, H3); 7.35ꢂ
8.01 (d, 1H, JHP N).
7.6 Hz, HCÄ
/
40,88, s. 1H-NMR (200
3.2. Crystal structure determination
/
ꢁ
/
6.0
ꢁ
/
ꢁ
/
A summary of crystallographic data and some details
of the refinement are given in Table 2. A prismatic
crystal was selected and mounted on a MAR345
diffractometer with a image plate detector. Unit-cell
parameters were determined from automatic centering
ꢁ
/
ꢁ
/
/
ꢁ
/
/
2b Characterization data: Anal. Calc. (found) for
C36H32Cl2NO2PPd: C, 60.14 (60.5); H, 4.49 (4.5); N,
of 25 reflections (3B
squares method. Intensities were collected with graphite
monochromatized MoꢂKa radiation. 14 156 reflections
were measured in the range 1.67Bu B31.60, 5527 of
which were non-equivalent by symmetry [Rint(on I)ꢁ
0.027]. 4602 reflections were assumed as observed
applying the condition I ꢀ2s(I). Lorentz-polarization
but no absorption corrections were made.
/
u B
/
318) and refined by least-
1.95 (1.9)%. MS-positive FAB: 719 (Mꢃ), 684 {(Mꢄ
/
Cl)ꢃ}. 31P{1H}-NMR: dꢁ
MHz, CDCl3): dꢁ1.12 (t, 3H, JHH
CH3CH2O); 3.16 (dd, 1H, JHH 13.2Hz, JHH
Hz, CH2CHN); 3.65 (dd, 1H, JHH 13.2 Hz, JHH
5.6Hz, CH2CHN); 4.10 (q, 2H, JHH 7.0 Hz,
CH2CH3); 5.80 (br m, 1H, HCCOOEt); 6.25 (d, 1H,
/
40,92, s. 1H-NMR (200
7.0 Hz,
8.0
/
/
ꢁ
/
/
/
ꢁ
/
ꢁ
/
/
ꢁ
/
ꢁ
/
ꢁ
/
/

282
J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ283
/
Table 2
Crystal data and structure refinement for 4b-exo
Comissionat per a Universitats i Recerca (project:
2001SGR-00054).
Empirical formula
Formula weight
Temperature (K)
C36H31Cl3NO2PPd
753.34
References
293(2)
0.71069
Monoclinic, P21/c
˚
Wavelength (A)
Crystal system, space group
Unit cell dimensions
[1] (a) K. Severin, R. Bergs, W. Beck, Angew. Chem. Int. Ed. 37
(1998) 1634;
˚
a (A)
11.5890(10)
24.4350(10)
13.2510(10)
90.0000(10)
114.3590(10)
90.0000(10)
3418.3(4)
4
(b) G. Jaouen, A. Vessiers, I.S. Butler, Acc. Chem. Res. 26 (1993)
361;
˚
b (A)
˚
c (A)
(c) H. Chen, S. Ogo, R.H. Fish, J. Am. Chem. Soc. 118 (1996)
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a (8)
b (8)
g (8)
V (A )
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˚
[3] Y. Fuchita, K. Yoshinaga, Y. Ikeda, J. Kinoshita-Kawashima, J.
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Dcalc (Mg mꢄ3
)
1.464
0.857
Absorption coefficient (mmꢄ1
F(000)
Crystal size (mm)
)
1528
0.1ꢅ0.1ꢅ0.2
[5] (a) A. Bohm, B. Schreiner, N. Steiner, R. Urban, K. Sunkel, K.
¨
Polborn, W. Beck, Z. Naturforsch. 53b (1998) 191;
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/
31.60
(b) A. Bohm, K. Polborn, K. Sunkel, W. Beck, Z. Naturforsch.
¨
53b (1998) 448;
Index ranges
05h 513, 05k 535,
ꢄ145l 516
(c) A. Bohm, K. Polborn, W. Beck, Z. Naturforsch. 54b (1999)
300.
Reflections collected/unique
Refinement method
14 156/5527 [Rintꢁ0.0276]
Full-matrix least-squares on F2
5527/0/400
[6] C.G. McCarthy, in: S. Patai (Ed.), The Chemistry of the Carbonꢂ
Nitrogen Double Bond, Wiley, Chichester, 1970, pp. 364ꢂ372,
405ꢂ408.
/
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I ꢀ2s(I)]
R indices (all data)
/
1.131
R1ꢁ0.0458, wR2ꢁ0.1346
R1ꢁ0.0633, wR2ꢁ0.1578
/
[7] (a) J. Albert, M. Go´mez, J. Granell, J. Sales, X. Solans,
Organometallics 9 (1990) 1405;
Largest difference peak and hole 0.755 and ꢄ0.820
(e A )
(b) J. Albert, J. Granell, J. Sales, M. Font-Bardia, X. Solans,
Organometallics 14 (1995) 1393.
2
˚
[8] (a) M. Go´mez, J. Granell, M. Martinez, J. Chem. Soc. Dalton
Trans. (1998) 37;
The structure was solved by Direct methods, using
SHELXS computer program and refined by full-matrix
least-squares method with SHELX97 computer program
(b) M. Go´mez, J. Granell, M. Martinez, Organometallics 16
(1997) 2539;
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(1995) 155;
[15]. The function minimized was aw[[Fo]2ꢄ
/
[Fc]2]2,
4.1415P]ꢄ1, and Pꢁ
2[Fc]2)/3, f, f? and f?? were taken from Interna-
where wꢁ
/
[s2(I)ꢃ
/
(0.0902P)2ꢃ
/
/
(d) R. Bosque, C. Lo´pez, M. Font-Bardia, X. Solans, J. Chem.
Soc. Dalton Trans. (1995) 4053;
([Fo]2ꢃ
/
(e) R. Bosque, C. Lo´pez, J. Sales, J. Organomet. Chem. 498 (1995)
147;
tional Tables of X-ray Crystallography [16]. All H
atoms were computed and refined, using a riding model,
with an isotropic temperature factor equal to 1.2 times
the equivalent temperature factor of the atoms which
are linked.
(f) R. Bosque, C. Lo´pez, J. Sales, J. Chem. Soc. Dalton Trans.
(1995) 2445.
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115.
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Hartley, Chem. Rev. 81 (1981) 79; (b) R.G. Pearson, Inorg.
Chem. 12 (1973) 712; (c) R. Navarro, E.P. Urriolabeitia, J. Chem.
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J. Vicente, J.A. Abad, A.D. Frankland, M.C. Ram´ırez de
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J.M. Castineiras, D. Lata, J.J. Ferna´ndez, A. Ferna´ndez, J.
Organomet. Chem. 556 (1998) 31.
4. Supplementary material
Crystallographic data (excluding structure factors) for
4b-exo have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC no. 189590. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ (fax: ꢃ44-1223-336033; e-mail: deposit@ccdc.ca-
/
m.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
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Soc. Jpn. 64 (1991) 801;
This work was supported by the Ministerio de Ciencia
y Tecnolog´ıa (projects: BQU2000-0652) and by the

J. Albert et al. / Journal of Organometallic Chemistry 663 (2002) 277ꢂ
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/