Synthesis, characterization and reactivity of palladium(II) compounds containing terdentate [Csp2, N, S]- or [Csp3, N, S]- ligands

Article abstract of DOI:10.1016/S0022-328X(02)01252-4

The study of the reactivity of R-CH=N-(C₆H₄-2-SMe)with R = C₆H₅ or 2,4,6-Me₃-C₆H₂ with palladium(II) salts is reported. These studies have allowed us to prepare and characterize

Full text of DOI:10.1016/S0022-328X(02)01252-4

Journal of Organometallic Chemistry 650 (2002) 258ꢃ267
/
www.elsevier.com/locate/jorganchem
Synthesis, characterization and reactivity of palladium(II)
compounds containing terdentate [Csp2, N, S]ꢀ or [Csp3, N, S]ꢀ
ligands
Concepcio´n Lo´pez a,*, Sonia Pe´rez a, Xavier Solans b, Merce` Font-Bardia b
a Departament de Qu´ımica Inorga`nica, Facultat de Qu´ımica, Universitat de Barcelona, Mart´ı i Franque`s 1-11, E-08028 Barcelona, Spain
b Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals, Facultat de Geologia, Universitat de Barcelona, Marti i Franque`s s/n, E-08028
Barcelona, Spain
Received 29 October 2001; received in revised form 23 January 2002; accepted 23 January 2002
Abstract
The study of the reactivity of Rꢀ
These studies have allowed us to prepare and characterize the coordination complexes: cis-[Pd{Rꢀ
{RꢁC6H5 or 2,4,6-Me3-C6H2} and the cyclopalladated compounds [Pd{C6H4ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl] and [Pd{(2-CH2-4,6-
Me2-C6H2)ꢀ
/
CHꢁ
/
Nꢀ
/
(C6H4-2-SMe) with Rꢁ
/
C6H5 or 2,4,6-Me3-C6H2 with palladium(II) salts is reported.
/
CHꢁNꢀ(C6H4-2-SMe)}Cl2]
/
/
/
/
/
/
/
CHꢁ
/
Nꢀ
/
(C6H4-2-SMe)}Cl]. The X-ray crystal structures of the latter complexes reveal that the thioimines act as a
[Csp2, phenyl,N,S]ꢀ and as a [Csp3, N,S]ꢀ terdentate group, respectively. The study of the reactions of the cyclopalladated
compounds with PPh3 is also reported. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Palladium; Cyclopalladated; Terdentate ligands
1. Introduction
As a part of a project directed towards the syntheses
and characterization of pallada- and platinacycles, some
of us have recently reported the activation of the
The study of cyclopalladated compounds has at-
tracted great interest in last decade due to their
applications in different areas [1]. A wide variety of
s(Csp2, aryl-H) bond of the thioimine: C6H5ꢀ
CH2ꢀCH2ꢀSEt, which has lead to syntheses and
characterization of the mononuclear compounds:
[M{C6H4ꢀCHꢁNꢀCH2ꢀCH2ꢀSEt}Cl] {MꢁPd (4a)
or Pt (4b)} (Fig. 1) [7]. In the view of these facts we
decided to study whether: (a) the replacement of the ꢀ
CH2ꢀCH2ꢀ moiety by a less flexible backbone between
/
CHꢁ
/
Nꢀ
/
/
/
palladacycles containing a s(Pdꢀ
bond and a bidentate [C,X]ꢀ {Xꢁ
terdentate [C,X,Y]ꢀ or [X,C,Y]ꢀ {X, Yꢁ
/
Csp2) or a s(Pdꢀ
N, P, O} ligand or a
N, P, O}
/
Csp3)
/
/
/
/
/
/
/
/
groups have been described so far [2,3]. However, few
articles focus on cyclopalladated compounds with
terdentate [C,N,S]ꢀ ligands [4,6], and in most of these
cases, the palladacycles arise from the activation of
s(Csp2, phenyl-H) bonds of benzylthio- or benzosulfinyl
substituted azobenzenes exclusively (Fig. 1, 1 and 2)
[4,5]. Besides that, cyclopalladated compounds contain-
ing a [Csp3, N,S]ꢀ chelating ligand are even less
common [6]. To our knowledge only one compound of
this kind has been reported (Fig. 1, 3) [6].
/
/
/
the two heteroatoms (N and S) or (b) the incorporation
of alkyl groups in the ortho sites of the aryl ring of the
thioimine could be important in determining the nature
of the final product and/or the ease with which the
activation of the s(Cꢀ
basis, we were prompted to prepare the ligands: Rꢀ
CHꢁNꢀ(C6H4-2-SMe) with RꢁC6H5 (5a) or 2,4,6-
/
H) bond takes place. On this
/
/
/
/
Me3-C6H2 (5b) (Fig. 1) and to study their reactivity
versus palladium(II) salts. In this paper we present a
general procedure to easily achieve the activation of the
s(Csp2ꢀ
/
H) bond (in 5a) or the s(Csp3ꢀ
/H) bond (in 5b)
* Corresponding author. Tel.: ꢂ
725.
E-mail address: conchi.lopez@qi.ub.es (C. Lo´pez).
/
34-93-4021-274; fax: ꢂ34-93-4907-
/
of the thioimines using palladium(II) salts, which has
allowed us to isolate and characterize the first example
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 2 5 2 - 4

C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ
/267
259
(for 5b) solid formed {Scheme 1, steps (a)}. Their
characterization data based on elemental analyses, IR
and NMR spectroscopy (see Section 3) were consistent
with those expected for cis-[Pd{Rꢀ
/
CHꢁ
/
Nꢀ
/
(C6H4-2-
SMe)}Cl2] {RꢁC6H5 (6a) or 2,4,6-Me3-C6H2 (6b)}, in
/
which the ligand acts as a neutral [N,S] bidentate group.
1
In the H-NMR spectra of 6 the signal due to the
imine proton appeared at lower fields than for the free
ligands. This finding suggests, according to the literature
[8], a syn-conformation of the ligands in compounds 6.
Complex 6b has also been characterized structurally. A
perspective view of its molecular structure together with
the atom numbering scheme is shown in Fig. 2.
The structure consists of discrete molecules of
[Pd{(2,4,6-Me3-C6H2)ꢀ
(6b) separated by van der Waals distances. In each
molecule the palladium is in a slightly distorted squareꢃ
/
CHꢁ
/
Nꢀ
/
(C6H4-2-SMe)}Cl2]
/
planar environment [9], bound to two chlorines in a cis-
arrangement and to the two heteroatoms (N and S) of
the thioimine forming a five-membered chelate ring with
an envelope-like conformation in which the palladiu-
m(II) deviates from the plane defined by the remaining
˚
atoms [10] by ca. 0.622 A towards the C(17) atom. The
bond length is similar to those reported in the
literature for related Schiff bases and their palladium(II)
ꢂCꢁ
/
Nꢀ
/
compounds [11]. In 6b, the ligand adopts the syn-
conformation {the torsion angle: C(9)ꢀ
/
C(8)ꢀ
/
Nꢀ/C(7)
Fig. 1. Schematic view of the cyclopalladated compounds containing
terdentate (C,N,S)ꢀ ligands described so far together with that of the
is 4.088}.
The two aryl rings are planar, and none of them is
coplanar with the functional group since they form
angles of 59.56 and 36.358 with the imine moiety.
In compound 6b, the distance between the Cl(2) and
˚
the imine hydrogen, H(8), is [2.7411 A] smaller than the
sum of the van der Waals radii of these two atoms (Cl:
thioimines under study of general formula: Rꢀ
/
CHꢁ
/
Nꢀ(C6H4-2-SMe)
/
with RꢁC6H5 (5a) or 2,4,6-Me3-C6H2 (5b).
/
of a mononuclear cyclopalladated complex containing a
[Csp3,N,S]ꢀ terdentate ligand. Besides that, the com-
parison of the reactivity of 4a and those of the
cyclopalladated complexes obtained from ligands 5a
and 5b, has allowed us to establish the factors affecting
˚
˚
1.75 A and H: 1.20 A) [12], thus suggesting a weak
Clꢀ ꢀ ꢀH interaction. A similar type of interaction has also
been found in related palladium(II) compounds [7,13].
The crystal contains a (1:1) mixture of the two
enantiomers. This result is consistent with the absence
of any additional factor of chiral induction during the
synthesis of this material.
the lability of the Pdꢀ
/
S and Pdꢀ
/
N bond in palladacycles
with [C,N,S]ꢀ terdentate ligands.
2. Results and discussion
In order to explore whether the procedure described
previously for the cyclometallation of C6H5ꢀ
/
CHꢁ
/
Nꢀ
/
2.1. The ligands and the palladium(II) compounds
CH2ꢀCH2ꢀSEt could be also extended to compounds
/
/
6, they were treated with sodium acetate in refluxing
methanol for 12 h. This produced the dissolution of the
starting materials giving a deep orange (for 6a) or brown
(for 6b) solution. For 6a, concentration to dryness on a
rotary evaporator followed by the work up of an SiO2
column chromatography produced the release of a
yellow band, which was collected. Slow evaporation of
the solution at ca. 20 8C produced golden monocrys-
tals. Their characterization data (see below) agreed with
those expected for the cyclopalladated compound:
Compounds: Rꢀ
/
CHꢁ
/
Nꢀ
/
(C6H4-2-SMe) with Rꢁ
/
C6H5 (5a) or 2,4,6-Me3-C6H2 (5b), were prepared by
condensation between equimolar amounts of 2-mercap-
toaniline and the corresponding aldehyde in refluxing
ethanol, and they were characterized by IR, and NMR
spectroscopy (see Section 3). According to NMR data,
only one isomer (anti-form) of compounds 5 was
present in solution.
When the thioimines 5a or 5b were treated with the
stoichiometric amount of Na2[PdCl4] in methanol at
room temperature a pale yellow (for 5a) or an orange
[Pd{C6H4ꢀ
/
CHꢁ
/
Nꢀ/(C6H4-2-SMe)}Cl] (7a) with
a
s(Pdꢀ
/
Csp2, phenyl) bond.

260
C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ267
/
Scheme 1. (a) Na2[PdCl4] in methanol at room temperature. (b) Na(CH3COO) in refluxing methanol (see text), followed by SiO2-column
chromatography. (c) PPPh3 in CH2Cl2 at room temperature.
18 h (yieldꢁ62%). Compound 7b is a monomeric
/
complex with a six-membered palladacycle in which
the thioimine behaves as a [Csp3,N,S]ꢀ terdentate
group; this type of compounds are really rare in the
literature [6].
Compounds 7 have been also characterized by 1H and
13C{1H}-NMR spectroscopy (see Section 3) and the
assignment of the signals has been carried out unam-
biguously with the aid of two-dimensional NMR
experiments (HSQC and HMBC) which provided con-
clusive evidence for (a) the binding of the two heteroa-
toms to the palladium and (b) the formation of the
s(Pdꢀ/C) bonds. The X-ray crystal structures of 7a and
7b (described below) also confirmed this finding. The
comparison of 13C{1H}-NMR data revealed that the
resonance due to the metalated carbon of 7a has low
intensity and it is low-field shifted when compared with
the free thioimine 5a and complex 6a. A similar trend is
also found for the resonance of carbon of the metallated
Fig. 2. Molecular structure and atom numbering scheme for com-
pound cis-[Pd{(2,4,6-Me3-C6H2)ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl2] (6b).
N, 2.043(2); PdꢀS, 2.2477(8); Pdꢀ
Cl(2), 2.2971(8); SꢀC(1), 1.807(3); SꢀC(2),
C(7), 1.423(3) and NꢀC(8), 1.267(3). Selected bond angles
S, 85.50(7); SꢀPdꢀCl(1), 87.66(3); NꢀPdꢀCl(2), 93.66(7);
Cl(2), 93.19(3); PdꢀSꢀC(1), 109.31(11); PdꢀSꢀC(2),
97.39(10); NꢀC(8)ꢀC(9): 130.5(3); NꢀC(7)ꢀC(2), 117.1(2) and C(7)ꢀ
NꢀC(8), 122.4(2).
/
/
/
˚
Selected bond lengths (in A): Pdꢀ
Cl(1), 2.2808(8); Pdꢀ
1.767(3); Nꢀ
(8): NꢀPdꢀ
Cl(1)ꢀPdꢀ
/
/
/
/
/
/
/
/
ꢀ
/
CH2ꢀ
/
unit in 7b, when compared with that of the
/
/
/
/
/
/
methyl group in the ortho sites of 5b or 6b. These
observations are consistent with previous NMR-studies
of related palladacycles [14].
/
/
/
/
/
/
/
/
/
/
/
/
When 6b was used as starting material, the work up of
the column yielded unreacted 6b (ca. 40%) and a new
compound 7b. Its analytical data, mono- and two-
dimensional (HSQC and HMBC) NMR data were
consistent with those expected for [Pd{(2-CH2-4,6-
2.2. Description of the crystal structures of [Pd{C6H4ꢀ
CHꢁNꢀ(C6H4-2-SMe)}Cl] (7a) and [Pd{(2-CH2-4,6-
Me2)ꢀC6H2ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl] (7b)
/
/
/
/
/
/
/
The molecular structures of 7a and 7b and their atom
labeling schemes are depicted in Figs. 3 and 4. A
selection of bond lengths and bond angles for the two
structures are presented in Tables 1 and 2, respectively.
Me2-C6H2)ꢀ
1, steps (b)}. The yield of 7b improved considerably
increasing the reaction period from 12 h (yieldꢁ27%) to
/
CHꢁ
/
Nꢀ/(C6H4-2-SMe)}Cl] (7b) {Scheme
/

C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ
/267
261
Table 1
˚
Bond lengths (A) and selected bond angles (8) for [Pd{C6H4ꢀ
/
CHꢁ
/
Nꢀ
/
(C6H4-2-SMe)}Cl] (7a)
Bond lengths
Pdꢀ
Pdꢀ
Sꢀ
Nꢀ
C(1)ꢀ
C(2)ꢀ
C(4)ꢀ
C(7)ꢀ
C(8)ꢀ
C(10)ꢀ
C(12)ꢀ
/
C(13)
1.987(3)
2.3006(17)
1.779(4)
1.293(4)
1.398(5)
1.371(7)
1.389(6)
1.441(5)
1.401(5)
1.371(6)
1.393(5)
Pdꢀ
Pdꢀ
Sꢀ
Nꢀ
C(1)ꢀ
C(3)ꢀ
C(5)ꢀ
C(8)ꢀ
C(9)ꢀ
C(11)ꢀ
/
N
2.008(3)
/Cl
/
S
2.3863(13)
1.804(5)
1.425(4)
1.402(5)
1.375(7)
1.385(5)
1.400(5)
1.370(5)
1.392(6)
/
C(1)
/
C(14)
C(6)
/
C(7)
/
/
C(6)
C(3)
C(5)
C(8)
C(13)
/
C(2)
C(4)
C(6)
C(9)
C(10)
/
/
/
/
/
/
/
/
/C(11)
/
C(12)
/C(13)
Selected bond angles
C(13)ꢀPdꢀ
NꢀPdꢀ
C(1)ꢀSꢀ
C(2)ꢀC(1)ꢀ
C(5)ꢀC(6)ꢀ
/
/
N
81.94(12)
84.83(9)
96.17(12)
119.5(3)
123.1(3)
C(13)ꢀ
ClꢀPdꢀ
C(6)ꢀC(1)ꢀ
NꢀC(7)ꢀC(8)
C(1)ꢀC(6)ꢀ
/
Pdꢀ
/
Cl
96.46(10)
96.90(5)
121.0(3)
116.6(3)
117.1(3)
/
/
S
/
/
S
Fig. 3. Molecular structure and atom labeling scheme for [Pd{C6H4ꢀ
CHꢁNꢀ(C6H4-2-SMe)}Cl] (7a).
/
/
/
Pd
/
/
S
/
/
/
/S
/
/
/
/N
/
/
N
The labeling of the atoms refers to Fig. 3. S.D. parameters are given
in parenthesis.
Table 2
˚
Bond lengths (A) and selected bond angles (8) for [Pd{(2-CH2-4,6-Me2-
C6H2)ꢀ
/
CHꢁ
/
Nꢀ(C6H4-2-SMe)}Cl] (7b)
/
Bond lengths
Pdꢀ
Pdꢀ
Sꢀ
Nꢀ
C(2)ꢀ
C(3)ꢀ
C(5)ꢀ
C(8)ꢀ
C(9)ꢀ
C(10)ꢀ
C(12)ꢀ
C(13)ꢀ
/
C(17)
2.041(4)
2.313(3)
1.786(4)
1.296(4)
1.370(5)
1.382(5)
1.390(5)
1.460(5)
1.425(5)
1.508(5)
1.381(5)
1.405(5)
Pdꢀ
Pdꢀ
Sꢀ
Nꢀ
C(2)ꢀ
C(4)ꢀ
C(6)ꢀ
C(9)ꢀ
C(10)ꢀ
C(11)ꢀ
C(12)ꢀ
C(14)ꢀ
/
N
2.026(4)
2.409(3)
1.764(4)
1.445(4)
1.402(5)
1.382(6)
1.404(5)
1.400(5)
1.394(5)
1.373(5)
1.516(5)
1.468(5)
/Cl(1)
/
S
/
C(1)
/
C(2)
C(7)
/
C(8)
/
/
C(7)
C(4)
C(6)
C(9)
C(14)
/
C(3)
C(5)
C(7)
C(10)
/
/
/
/
/
/
Fig. 4. Molecular structure and atom labeling scheme for [Pd{(2-CH2-
4,6-Me2-C6H2)ꢀCHꢁNꢀ(C6H4-2-SMe)Cl] (7b).
/
/
C(11)
C(12)
C(16)
C(17)
/
/
/
/
C(15)
C(13)
C(14)
/
/
/
The structures consist of discrete molecules of
[Pd{C6H4ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl] (in 7a) or of
(C6H4-2-SMe)}Cl]
/
/
/
/
/
Selected bond angles
C(17)ꢀPdꢀN(1)
N(1)ꢀPdꢀS(1)
C(3)ꢀC(2)ꢀS(1)
N(1)ꢀC(8)ꢀC(9)
[Pd{(2-CH2-4,6-Me2-C6H2)ꢀ
/
CHꢁ
/
Nꢀ
/
/
/
87.47(15)
84.04(12)
120.1(3)
C(17)ꢀ
Cl(1)ꢀPdꢀ
C(7)ꢀC(2)ꢀ
C(2)ꢀC(7)ꢀ
/
Pdꢀ
/
Cl
92.52(14)
94.44(10)
121.0(3)
(in 7b) separated by van der Waals contacts.
Each molecule contains a tetracyclic system formed
/
/
/
/
S(1)
/
/
/
/
S(1)
/
/
126.5(3)
/
/
N(1)
118.4(3)
by an aryl ring which shares a ꢀ
/
Cꢀ
/
Cꢀ
/
bond {the C(1)ꢀ
/
C(6) bond in 7a or the C(2)ꢀC(7) bond in 7b} with the
/
The labeling of the atoms refers Fig. 4. S.D. parameters are given in
parenthesis.
chelate ring, formed by the coordination of the two
heteroatoms (N and S) to the palladium, a five- (in 7a)
or a six- (in 7b) membered palladacycle and the other
phenyl ring.
The variations observed in the Pdꢀ
/
S bond lengths in 6b
˚
˚
˚
{2.2477(8) A}, 7a {2.386(13) A} and 7b {2.409(3) A}
can be adscribed to the different nature of the atom [16]
in a trans-arrangement: the Cl in 6b, a metallated Csp2
atom in 7a or a Csp3 atom in 7b.
In the two structures the palladium atom is in a
slightly distorted squareꢃplanar environment bound to
/
the chlorine, the sulfur, the imine nitrogen and the C(13)
atom of the phenyl ring in 7a or the C(17) atom in 7b
[15]. This confirmed the mode of binding of the
thioimines to the palladium (II).
The angles between adjacent atoms in the coordina-
96.90(5)8 (for 7a)
tion sphere lie in the ranges: 81.94(12)ꢃ
/
and 84.04(12)ꢃ94.44(10)8 (in 7b) the smallest angles
/
The Pdꢀ
/
C and Pdꢀ
/
N bond distances are consistent
corresponding to the terdentate ligand.
In 7a, the metallacycle, which is formed by the atoms:
Pd, N, C(7), C(8) and C(13), is nearly planar [17] and it
with those reported for a wide variety of palladacycles
holding [C,N]ꢀ, [C,N,N?]ꢀ or [N,C,N]ꢀ ligands [11].

262
C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ267
/
forms angles of 2.04, 3.65, 5.68 and 2.808 with the
attached aryl group, the five-membered chelate ring, the
other phenyl ring and with the coordination plane of the
palladium, respectively. In 7b, the palladacycle, formed
by the atoms: Pd(1), N(1), C(8), C(9), C(14) and C(17),
has a chair-conformation in which the atoms C(9) and
detected by NMR spectroscopy. This suggests that in
compounds 7ꢃ8 the PdꢀN bond exhibits low lability.
These findings are in sharp contrast with those reported
for [Pd{C6H4ꢀCHꢁNꢀCH2ꢀCH2ꢀSMe}Cl] (4a) and
[Pd{C6H4ꢀCHꢁNꢀCH2ꢀCH2ꢀSMe}Cl(PPh3)] (9a),
which react with PPh3 in a (1:2) or (1:1) molar ratio,
respectively, producing the cleavage of the PdꢀN bond
and the formation of [Pd{C6H4ꢀCHꢁNꢀCH2ꢀCH2ꢀ
/
/
/
/
/
/
/
/
/
/
/
/
˚
Pd deviate by ca. 0.258 and 0.858 A from the main plane
/
towards the Me group of the SMe substituent [18].
In the two structures, the ligand adopts the anti-
conformation and the imine group is contained in the
/
/
/
/
/
SMe}Cl(PPh3)2] (10a) [7a]. The results presented here
suggest that compounds 4a and 9a are more prone to
metallacycle (endocyclic). The ꢂCꢁ
/
Nꢀ
/
bond lengths
undergo the cleavage of the Pdꢀ
/
N bond, with the
˚
˚
[1.293(4) A in 7a and 1.296(4) A in 7b)] are similar to
those found for 6b as well as for related palladacycles
derived from Schiff bases [14].
subsequent opening of the palladacycle, than their
partners 7a and 8a. Despite the formal similarity
between the two pairs of compounds (4a and 5a) and
(8a and 9a), they exhibit different reactivity versus
excesses of PPh3.This may be related to the effects
In compound 7a, the distance between the Cl and the
˚
H(12) atom [2.859 A] [12], also suggests a weak
Clꢀ ꢀ ꢀHꢀ ꢀ ꢀC(12) intramolecular interaction.
induced by the replacement of the ‘ꢀ
/
CH2ꢀ
/
CH2ꢀ
/
’
On the other hand, since these compounds crystallize
in the centrosymmetric space group: P21/n, the crystals
contain a (1:1) mixture of the two enantiomers. This
result is consistent with the absence of any additional
factor of chiral induction during the synthesis of these
compounds.
moiety (intercalated between the two heteroatoms N
and S) by a more rigid system such as the 1,2-
disubstituted C6H4 ring.
To sum up, the results presented here provide a neat
and useful procedure for the preparation of pallada-
cycles containing terdentate [Csp2, phenyl,N,S]ꢀ or
[Csp3,N,S]ꢀ ligands derived from thioimines. As far as
we know compounds 7b and 8b are the first examples of
monomeric and cyclopalladated complexes containing a
[Csp3,N,S]ꢀ terdentate ligand. The comparison of the
results obtained in the reactions of compounds 7 and 4a
Besides that, it should be noted that, since the ligand
has the syn-conformation in 6a and 6b and adopts the
anti-form in 7a and 7b, we can conclude that, the
transformation 60
the ligand (syn-0anti-) and (b) the activation of the
s(Csp2, phenyl-H) bond (in 6a) or the s(Csp3ꢀ
H) bond
(in 6b).
/7 requires: (a) the isomerization of
/
/
with PPh3 reveal that the Pdꢀ
/
N is more prone to cleave
in 4a than in 7a or 7b. This can be explained on the basis
of the greater flexibility of the five-membered chelate
ring formed by the coordination of the two heteroatoms
(N and S) in 4a than in 7. Besides that, the cyclopalla-
dated complexes reported here have an additional
interest since it is well known that the insertion of small
molecules (i.e. alkynes, alkenes, isonitriles, oxygen or
2.3. Study of the reactivity of compounds 7 with PPh3
As a first attempt to explore the ease with which the
hapticity of the ligand in compounds 7 could be
modified we proceeded to study their reactivity versus
PPh3. When 7a or 7b were treated separately with
equimolar amounts of PPh3 in CH2Cl2 at room tem-
CO) into the s(Pdꢀ/C) of cyclopalladated derivatives
may lead to novel organic or organometallic compounds
[1a, 1e, 1f, 5]. Further work focused on the reactivity of
compounds 7a and 7b is currently on the way.
perature, compounds: [Pd{C6H4ꢀ
SMe)}Cl(PPh3)] (8a) or [Pd{(2-CH2-4,6-Me2-C6H2)ꢀ
CHꢁNꢀ(C6H4-2-SMe)}Cl(PPh3)] (8b) (Scheme 1) were
obtained. These compounds arise from 7 by the cleavage
of the PdꢀS bond and the incorporation of a PPh3 in the
/
CHꢁ
/
Nꢀ
/
(C6H4-2-
/
/
/
/
3. Experimental
coordination sphere of the palladium. The characteriza-
tion data of compounds 8, presented in the Section 3,
agreed with the proposed formula. Their 31P{1H}-NMR
showed a singlet at 38.00 ppm for 8a and at 34.79 ppm
for 8b. The position and multiplicity of these signals are
consistent with the presence of one PPh3 ligand bound
to the palladium in a trans-arrangement to the nitrogen
[19]. This is the usual result of the reaction between
(C,N)ꢀ cyclopalladated compounds and phosphine
ligands [20] due to the so-called transphobia effect [21].
When compounds 8a or 8b were treated separately
with larger excesses of PPh3 {molar ratio PPh3: 8 up to
3.1. Materials and methods
Elemental analyses (C, H, N and S) were carried out
at the Serveis Cientifico-Te`cnics (Universitat de Barce-
lona). Infrared spectra were recorded with a Nicolet
Impact 400 instrument using NaCl discs for the ligand
and KBr pellets for the remaining compounds. Routine
1H-NMR and 13C{1H}-NMR spectra were obtained
with a Gemini-200 MHz and with a Bruker 250 DXR
instruments. High resolution 1H-NMR and the two
dimensional NMR experiments {heteronuclear single
quantum coherence (HSQC) and heteronuclear multiple
8} no evidences of the cleavage of the Pdꢀ
/
N bond were

C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ
/267
263
bond coherence (HMBC)} were carried out using a
Varian 500 or a Bruker 500 instrument. In all cases, the
solvent used for the NMR experiments was CDCl3
(99.9%) and SiMe4 was used as internal reference. The
31P{1H}-NMR spectra of 8a and 8b were recorded with
a Bruker 250 DXR instrument using CDCl3 as solvent
then a solution formed by Na2[PdCl4] (0.865 g, 2.93ꢄ
/
10ꢀ3 mol) and methanol (15 cm3) was added. During
the addition an orange precipitate formed. The reaction
mixture was stirred at room temperature (r.t.) (ca.
20 8C) for 2 h. The solid formed was collected by
filtration and air-dried [yields: 0.621 g (72.9%) and 0.638
g (68%), for 6a and 6b, respectively].
and P(OMe)3 as reference [d31P{P(OMe)3}ꢁ
140.17
/
ppm]. In all cases the chemical shifts (d) are given in
ppm.
2-Mercaptoaniline was obtained from Aldrich and
used as received. The remaining reagents were obtained
from commercial sources and used as received. Benzal-
dehyde and all the solvents used in this work, except
methanol, were dried and distilled before use. The
methanol used for the preparation of compounds 7
was HPLC grade [22].
3.2.2.1. Characterization data for 6a. Anal. (%), Calc.
for: C14H13Cl2NSPd (found): C, 41.6 (41.5); H, 3.3 (3.2);
N, 3.5 (3.5) and S, 7.91 (7.9)%. IR: 1597 and 1570 cmꢀ1
.
1H-NMR data [23]: 2.81 [s, 3H, -SMe], 8.69 [s, 1H, ꢀ
7.50
/
CH ꢁ
/
N ꢀ
/
], 7.83 [d, 1H, H2], 7.19 [m, 3H, H3], 7.46ꢃ
/
[m, 2H, H4 and H5], 7.60 [d, 1H, H6], 7.41 [H3?], 7.10 [m,
1H, H4?], 7.14 [m, 1H, H5?] and 7.71 [d, 1H, H6?]. For 6b:
Anal. (%) Calc. for: C17H19Cl2NSPd (found) C, 45.75
(45.8); H, 4.29 (4.3); N, 3.14 (3.2) and S, 7.18 (7.0)%. IR:
3.2. Preparation of the compounds
1590 and 1567 cmꢀ1. H-NMR data [23]: 2.99 [s, 3H, -
1
3.2.1. Preparation of: Rꢀ
RꢁC6H5 (5a) or 2,4,6-Me3-C6H2 (5b)
2-Mercaptoaniline (1.000 g, 7.19ꢄ
10ꢀ3 mol) was
dissolved in 10 cm3 of ethanol. Then a solution formed
10ꢀ3 mol of the corresponding aldehyde and 5
/
CHꢁ
/
Nꢀ/(C6H4-2-SMe) with
SMe], 9.68 [s, 1H, ꢀ
/
CHꢁ
/
Nꢀ
/
], 2.30 [s, 3H, Me], 2.17 [s,
3H, Me], 1.90 [s, 3H, Me], 6.88 [s, 1H, H3], 6.81 [s, 1H,
H5], 7.04 [t, 1H, H2?], 7.58 [d, 1H, H3?], 7.31 [t, 1H, H4?]
and 6.72 [d, 1H, H6?]. 13C{1H}-NMR data [23]: 27.3 [-
/
/
SMe], 19.5 and 21.3 [Me], 178.9 [ꢀ
/
CHꢁ
/
Nꢀ
/
], 145.3 [C1],
by 7.19ꢄ
/
cm3 of ethanol was added. The resulting mixture was
refluxed for 2 h. The bright yellow solution was
concentrated to dryness on a rotary evaporator giving
a yellow oil (for 5a) or a yellow solid (for 5b), [yields:
1.50 g (91.6%) and 1.82 g (86%), respectively].
129.3 [C3 and C5], 157.9 [C1?], 132.3 [C2?], 120.3 [C3?],
130.2 [C4?], 130.3 [C5?] and 133.3 [C6?].
3.2.3. Preparation of [Pd{C6H4ꢀ
SMe)}Cl] (7a)
Compound 6a (0.500 g, 1.23ꢄ
pended in 25 cm3 of methanol [22], then sodium acetate
(0.101 g, 1.23ꢄ
10ꢀ3 mol) was added. The resulting
/
CHꢁ
/
Nꢀ/(C6H4-2-
3.2.1.1. Characterization data for 5a. Anal. (%) Calc.
for: C14H13NS (found): C, 73.90 (73.8); H, 5.76 (5.6); N,
/
10ꢀ3 mol) was sus-
1
6.16 (6.2) and S, 14.10 (14.0)%. IR: 1637 cmꢀ1. H-
/
NMR data [23]: 2.46 [s, 3H, Sꢀ
/
Me], 8.41 [s, 1H, ꢀ
/
CHꢁ
/
], 7.98 [d, 1H, H2], 6.95 [m, 1H, H3], 7.46ꢃ
/
7.52 [m,
2H, H4 and H5], 7.94 [d, 1H, H6], 7.16 [d, 1H, H3?], 7.14
[m, 1H, H4?], 7.16 [m, 1H, H5?] and 7.94 [d, 1H, H6?].
reaction mixture was then refluxed for 12 h and allowed
to cool to r.t. (ca. 20 8C). Then the undissolved
materials removed by filtration and discarded and the
filtrate was concentrated to dryness on a rotary eva-
porator. The residue was treated with CH2Cl2 (ca. 20
cm3), filtered out and passed through a SiO2-column
chromatography using CH2Cl2 as eluant. The band
released was collected and slow evaporation of the
solution produced yellowish crystals which were col-
lected and air-dried. (Yield: 0.305 g, 67.5%).
Nꢀ
/
13C{1H}-NMR data [23]: 14.8 [SMe], 159.0 [ꢀ
/
CHꢁ
/
Nꢀ/],
136.1 [C1], 129.7 [C2 and C6], 131.4 [C4], 128.9 [C3, C5],
150.0 [C1?], 133.3 [C2?], 117.39 [C3?], 126.3 [C4?], 125.1
[C5?], 126.3 [C6?]. For 5b: Anal. (%) Calc. for: C17H19NS
(found): C, 75.79 (75.8); H, 7.11 (7.1); N, 5.20 (5.2) and
S, 11.9 (11.9)%. IR: 1606 and 1616 cmꢀ1
data [23]: 2.45 [s, 3H, SꢀMe], 2.61 [s, 6H, Me], 2.31 [s,
], 6.96 [s, 2H, H3 and
.
1H-NMR
/
3H, Me], 8.79 [s, 1H, ꢀ
/
CHꢁ
/
Nꢀ
/
H5], 7.19 [d, 1H, H3?], 7.14 [m, 1H, H4?], 7.16 [m, 1H,
H5?] and 7.32 [d, 2H, H6?]. 13C{1H}-NMR data [23]: 14.7
3.2.3.1. Characterization data. Anal. (%) Calc. for:
C14H12ClNSPd (found): C, 45.63 (45.3); H, 3.25 (3.2);
[SMe], 21. 7 and 21.3 [Me], 160.43 [ꢀ
/
CHꢁ
/
Nꢀ
/
], 140.1
[C1], 139.3 [C2], 129.9 [C3], 140.1 [C4], 129.9 [C5], 139.3
[C6], 150.2 [C1?], 133.7 [C2?], 117.3 [C3?], 126.0 [C4?], 125.1
[C5?] and 124.0 [C6?].
N, 3.80 (3.7) and S, 8.69 (8.5)%. IR: n (ꢂCꢁ
/
Nꢀ
/
)ꢁ1590
/
cmꢀ1. H-NMR data [23]: 2.80 [s, 3H, -SMe], 8.66 [s,
1
1H, ꢀ
/
CHꢁ
/
Nꢀ
/
], 7.80 [d, 1H, H6], 7.60 [d, 1H, H2?], 7.43
[m, 3H, H3, H4 and H5], 7.75 [d, 2H, H4? and H5?], 7.18
[t, 1H, H6?] and 7.02 [t, 1H, H3?]. 13C{1H}-NMR data
3.2.2. Preparation of cis-[Pd{Rꢀ
SMe)}Cl2] {RꢁC6H5 (6a) or 2,4,6-Me3-C6H2 (6b)}
A 2.91ꢄ
10ꢀ3 mol amount of the corresponding
ligand (5a or 5b) was dissolved in 10 cm3 of methanol,
/
CHꢁ
/
Nꢀ/(C6H4-2-
/
[23]: 24.5 [SMe], 167.4 [ꢀ
/
CHꢁ
/
Nꢀ
/
], 148.2 [C1], 147.2
/
[C2], 129.4 [C3], 125.2 [C4], 135.6 [C5], 149.4 [C1?], 125.2
[C2?], 118.2 [C3?], 131.2 [C4?], 129.4 [C5?] and 134.2 [C6?].

264
C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ267
/
3.2.4. Preparation of [Pd{(2-CH2-4,6-Me2)ꢀ
/
C6H2ꢀ
/
PPh3 ligand]. 13C{1H}-NMR (selected data) [23]: 24.0
[SMe], 37.2 [CꢀPd], 20.4 and 21.9 [Me], 161.1 [ꢀCHꢁ
Nꢀ
], 144.9 [C1], 143.8 [C2], 129.5 [C3], 147.7 [C4], 128.7
CHꢁNꢀ(C6H4-2-SMe)}Cl] (7b)
/
/
/
/
/
This complex was prepared according to the proce-
dure described above for 7a, but using complex 6b as
starting material and the stoichiometric amount of
sodium acetate. In this case the reaction mixture was
refluxed for 18 h and allowed to cool to r.t. (ca. 20 8C).
Then the solution was filtered out, the undissolved
materials were discarded and the filtrate was concen-
trated to dryness on a rotary evaporator. The residue
was treated with CH2Cl2 (20 cm3), filtered out and
passed through a SiO2-column chromatography. Slow
evaporation of the solution obtained from the first band
produced orange crystals which were collected and air-
dried. (Yield: 0.313 g, 62%). The concentration to
dryness of the second band yielded small amounts of
unreacted complex 6b (ca. 11%).
/
[C5], 151.9 [C1?], 131.2 [C2?], 120.3 [C3?], 131.7 [C4?], 127.3
[C6?] and four additional doublets centered at ca. 133.9,
131.9 and 131.2 and 129.1. The signals due to the [C5?]
and [C6] carbon atoms are partially masked by these
doublets. 31P{1H}-NMR data (in ppm): 34.79.
3.3. Crystallography
A prismatic crystal of 6b, 7a or 7b was selected and
mounted on a MAR345 diffractometer with image plate
detector (for 6b) or on a ENRAF-CAD4 four-circle
diffractometer (for 7a and 7b). Unit cell parameters
were determined from automatic centring of 25 reflec-
tions in the range 12B
squares method. Intensities were collected with a
graphite monochromatized MoꢃKa radiation, using
v ꢃ2u scan-technique. For 6b, 9934 reflections were
measured in the range: 3.085u 528.848, of which 3994
were non-equivalent by symmetry {Rint (on I)ꢁ0.069},
1987 reflections were assumed as observed applying the
condition I ꢀ2s(I). For 7a, 4167 reflections were
measured in the range 2.475u 529.978, of which
3963 were non-equivalent by symmetry {Rint (on I)ꢁ
0.020}. For 7b, 4738 reflections were measured in the
range 2.325u 529.948, of which 2226 were assumed as
/
u B
/
218 and refined by least-
3.2.4.1. Characterization data. Anal. (%) Calc. for
C17H18ClNSPd (found): C, 49.70 (49.6); H, 4.42 (4.4);
N, 3.41 (3.5) and S, 7.81 (7.8)%. IR: 1565 and 1568
/
/
/
/
1
cmꢀ1. H-NMR data [23]: 2.44 [s, 3H,-SMe], 2.29 [s,
/
3H, Me], 2.43 [s, 3H, Me], 3.69 [m, 2H, ꢀ
1H, H3], 7.18 [s, 1H, H5], 8.39 [s, 1H, ꢀ
[d, 1H, d, 2H, H3?], and 7.40ꢃ7.50 [m, 3 H, H4?, H5? and
H6?]. 13C{1H}-NMR data [23]: 23.1 [SMe], 27.3 [Cꢀ
Pd],
], 140.1 [C1], 128.2
/
CH2ꢀ
/], 6.81 [s,
/
CHꢁNꢀ
/
/], 7.65
/
/
/
/
/
/
19.6 and 21.7 [Me], 176.4 [ꢀ
/
CHꢁ
/
Nꢀ
/
[C2], 148.1 [C4], 126.9 [C5], 157.8 [C1?], 130.3 [C2?], 117.9
[C3?], 130.3 [C4?], 126.9 [C5?], 133.3 [C6?].
/
/
observed. In the three cases, Lorentz polarization
corrections were made but absorption corrections were
not performed. The structures were solved by direct
methods using SHELXS computer program [24] and
refined by full-matrix least-squares method with
SHELX97 computer program [25], using 3963 reflections
for 7a (very negative intensities were not assumed). The
3.2.5. Preparation of compounds 8
Triphenylphosphine (50 mg, 1.91ꢄ
added to a CH2Cl2 solution (50 cm3) containing the
equimolar amount (1.91ꢄ
10ꢀ4 mol) of the correspond-
/
10ꢀ4 mol) was
/
ing cyclopalladated complex 7a or 7b. The reaction
mixture was stirred at r.t. (ca. 20 8C) for ca. 20 min and
filtered out. The filtrate was concentrated on a rotary
evaporator to ca. 5 ml. The yellow (for 7a) or orange
(for 7b) solid formed was collected and dried under
vacuum for 2 days. Yields: 0.106 g (88.3%) for 8a and
0.107 g (83.4%) for 8b.
2
2 2
function minimized was awjjFoj ꢀ
{s2(I)ꢂ(0.0163 P)2}ꢀ1 for 6b; wꢁ
P)2ꢂ(0.2477 P)}ꢀ1, for 7a and wꢁ
P)2}ꢀ1 for 7b, and Pꢁ
/
jFcj j , where wꢁ
/
/
/
{s2(I)ꢂ
{s2(I)ꢂ
2
/
(0.0396
/
/
/(0.0094
2
/
{jFoj ꢀ2jFcj }/3; f, f? and fƒ
/
were taken from the literature [26]. For compound 6b,
nine-hydrogen atoms were located from a difference
synthesis and refined with an overall isotropic tempera-
ture factor and the remaining ten hydrogen atoms were
computed and refined with an overall isotropic tem-
perature factor equals to 1.2 times the equivalent
isotropic temperature factor of the attached atom, using
a riding model. For 7a, all hydrogen atoms were located
from a difference synthesis and refined with an overall
isotropic temperature factor. For 7b, all hydrogen atoms
were computed and refined with an overall isotropic
temperature factor equals to 1.2 times the equivalent
isotropic temperature factor of the attached atom, using
a riding model. The final R(on F) factor were: 0.026 (for
3.2.5.1. Characterization data for 8a. Anal. (%) Calc.
for: C32H27NClFeNPPdS (found): C, 60.96 (60.8); H,
4.32 (4.3); N, 2.22 (2.2) and S, 5.09 (5.0)%. IR: 1597
1
cmꢀ1. H-NMR data [23]: 2.80 [s, 3H, -SMe], 8.66 [s,
1H, ꢀ
/
CHꢁ
/
Nꢀ
/
], 7.80 [d, 1H, H6], 7.60 [d, 1H, H2], 7.43
[m, 3H, H3, H4 and H5], 7.75 [d, 2H, H4? and H5?], 7.18
[t, 1H, H6?] and 7.02 [t, 1H, H3?]. 31P{1H}-NMR data:
38.09. For 8b: Anal. (%) Calc. for: C35H33ClNPPdS
(found): C, 62.51 (62.3); H, 4.95 (5.0); N, 2.00 (2.1) and
S, 4.77 (4.7)%. IR: 1580 and 1592 cmꢀ1. 1H-NMR data
[23]: 2.62 [s, 3H,-SMe], 1.96 [s, 3H, Me], 2.19 [s, 3H,
Me], 3.33 [m, 2H, ꢀ
H5], 8.02 [d, 1H, H3?], 8.55 [s, 1H, ꢀ
7.50 [m, 18H, H4?, H5?, H6? and aromatic protons of the
/
CH2ꢀ
/
], 6.04 [s, 1H, H3], 6.98 [s, 1H,
CHꢁNꢀ] and 7.40ꢃ
6b) and 0.035 (for 7a) and 0.029 (for 7b), wR(on Fo)ꢁ
/
/
/
/
/
0.040 (for 6b) and 0.074 (for 7a) and 0.045 (for 7b) and
the goodness-of-fit were 0.792 (for 6b), 1.031 (for 7a)

C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ
/267
265
Table 3
Crystal data and details of the refinement of the crystal structures of compounds: cis-[Pd{(2,4,6-Me3-C6H2)ꢀ
[Pd{C6H4ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl] (7a) and [Pd{(2-CH2-4,6-Me2-C6H2)ꢀCHꢁNꢀ(C6H4-2-SMe)}Cl] (7b)
/
CHꢁ
/
Nꢀ/(C6H4-2-SMe)}Cl2] (6b),
/
/
/
/
/
/
6b
7a
7b
Empirical formula
Formula weight
C
17H19Cl2NPdS
C14H12ClNPdS
368.16
293(2)
C17H18ClPdS
410.23
293(2)
446.69
293(2)
0.71069
Monoclinic
P21/c
Temperature (K)
˚
l (Moꢃ/Ka) (A)
0.71069
Monoclinic
P21/n
0.71069
Monoclinic
P21/n
Crystal system
Space group
˚
a (A)
13.432(1)
8.112(1)
16.660(1)
90.0
9.985(9)
12.367(5)
11.100(3)
90.0
10.376(8)
11.056(15)
14.487(15)
90.0
˚
b (A)
˚
c (A)
aꢁ/g (8)
b (8)
101.956(1)
1775.9(3)
4
96.21(4)
1362.6(14)
4
91.60(7)
1661(3)
4
3
V (A )
˚
Z
Dcalc. (mg mꢀ3
)
1.671
1.458
896
1.795
1.690
728
1.640
1.396
824
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm3)
0.1ꢄ
From 3.08 to 28.84
165h 512, 05k 5
05l 522
9934
/0.1ꢄ
/
0.2
0.1ꢄ
From 1.47 to 29.97
145h 512, ꢀ65
15l 515
4167
/0.1ꢄ
/
0.1
0.1ꢄ
From 2.32 to 29.94
145h 514, 05k 5
05l 520
4738
/0.1ꢄ
/
0.2
u Range for data collection (8)
Index ranges
ꢀ/
/
/
/
/10,
ꢀ/
/
/
/
/
k 5/17,
ꢀ/
/
/
/
/15,
/
/
ꢀ/
/
/
/
/
Number of reflections collected
Number of unique reflections
3994 [Rint
75.3%
ꢁ
/0.0692]
3963 [Rint
95.7%
ꢁ
/
0.0209]
4738 [Rint
93.5%
Full-matrix least-squares on F2
ꢁ0.0000]
/
Completeness to 2uꢁ
Refinement method
Number of data
/29.978
Full-matrix least-squares on F2
Full-matrix least-squares on F2
3994
235
3963
212
4738
199
Number of parameters
Goodness-of-fit on F2
0.792
1.031
0.810
Final R indices [I ꢀ
/
2s(I)]
R1ꢁ/0.0264 wR2ꢁ/0.0407
R1ꢁ/0.0356, wR2ꢁ/0.0748
R1ꢁ/0.0291, wR2ꢁ/0.0454
R indices (all data)
Extinction coefficient
R1ꢁ/0.1034, wR2ꢁ/0.0463
R1ꢁ
0.0040(4)
/
0.0749, wR2ꢁ
/0.0855
R1ꢁ/0.1256, wR2ꢁ/0.0603
Largest difference peak and hole
(e Aꢀ3
0.528 and ꢀ
/
0.791
0.756 and 0.474
0.479 and ꢀ0.930
/
)
and 0.810 (for 7b) for all the observed reflections. The
values of the R indices and further details concerning
the resolution and refinement of this crystal structure
are presented in Table 3.
financial support (projects: BQU2000-0652 and 1999-
SGR-0044).
References
4. Supplementary material
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Acknowledgements
We are grateful to the Ministerio de Ciencia y
Tecnolog´ıa and to the Generalitat de Catalunya for

266
C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ267
/
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˚
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/
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from the plane are: S(1): ꢀ0.103; Cl(1), 0.096; N(1), 0.1207 and
C(17), ꢀ0.1219.
/
(ꢀ
/
0.5409)YOꢂ
/
/
/
ꢀ
/
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/
(ꢀ
/
0.5566)YOꢂ
/
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/
ꢀ/
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/
/
/
/
/
˚
(b) K.D. Kamaraj, D. Bandyopadhyay, Organometallics 18
ꢀ/

C. Lo´pez et al. / Journal of Organometallic Chemistry 650 (2002) 258ꢃ
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/