Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: Synthesis, characterization and reactivity

Article abstract of DOI:10.1039/b106511d

Treatment of the Schiff base 2-ClC₆H₄C(H)=NCH₂CH₂SMe, 1, with palladium(II) acetate in dry toluene gave the mononuclear cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe} (O₂CMe)], 2. Reaction of 2 with aqueous sodium chloride gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe} (Cl)], 3, after a metathesis reaction. The X-ray crystal structure of 3 was determined and shows that the palladium atom is bonded to four different donor atoms: C, N, S and Cl. Treatment of 3 with triphenylphosphine in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}(Cl) (PPh₃)] with cleavage of the Pd-S bond. However, treatment of 3 with silver triflate and triphenylphosphine gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}(PPh ₃)][CF₃SO₃], 10, in which the Pd-S bond is retained. Reaction of 3 with the diphosphines dppm, dppb or dppf in a 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe] (Cl)}₂{μ-Ph₂P(CH₂)nPPh₂}], (n = 1, 5; n = 4, 6), and [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe] (Cl)}₂(μ-Ph₂PC₅H₄FeC ₅H₄PPh₂)], 7. Treatment of 3 with dppb in a 2:1 molar ratio and AgCF₃SO₃ gave the dinuclear cyclometallated complex [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe]} ₂{μ-Ph₂P(CH₂)₄PPh ₂}][CF₃SO₃]₂ , 11, which was characterized by X-ray crystal structure analysis. Reaction of 3 with dppe in a 1:1 molar ratio and sodium perchlorate gave the mononuclear complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}{Ph ₂P(CH₂)₂PPh₂-P,P}][ClO ₄], 8. Treatment of 3 with bis(2-diphenylphosphinoethyl)phenylphosphine in a 1:1 molar ratio, followed by treatment with sodium perchlorate gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}{(Ph ₂PCH₂CH₂)₂PPh-P,P,P}][ClO ₄], 9, in which the triphosphine is bonded to the palladium atom through the three phosphorus atoms.

Full text of DOI:10.1039/b106511d

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Cyclopalladated compounds derived from a [C,N,S] terdentate ligand:
synthesis, characterization and reactivity. Crystal and molecular
structures of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)] and
[{Pd[2-ClC6H3C(H)=NCH2CH2SMe]}2{m-Ph2P(CH2)4PPh2}]-
[CF3SO3]2
Alberto Fernandez,*a Digna Vazquez-Garcıa,a Jesus J. Fernandez,a Margarita Lopez-Torres,a
Antonio Suarez,a Samuel Castro-Juiz,a Juan M. Ortigueirab and Jose M. Vila*b
a
Departamento de Quımica Fundamental, Universidad de L a Corun˜a, E-15071 L a Corun˜a,
Spain.E-mail: qiluaafl @udc.es; Fax: þ 49 81 167065
b
Departamento de Quımica Inorganica, Universidad de Santiago de Compostela,
E-15782 Santiago de Compostela, Spain.E-mail: qideport @usc.es; Fax: þ 49 81 595012
Received (in London, UK) 20th July 2001, Accepted 10th October 2001
First published as an Advance Article on the web 8th January 2002
Treatment of the Schiff base 2-ClC6H4C(H)=NCH2CH2SMe, 1, with palladium(II) acetate in dry toluene gave
the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(O2CMe)], 2. Reaction
of 2 with aqueous sodium chloride gave [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)], 3, after a metathesis
reaction. The X-ray crystal structure of 3 was determined and shows that the palladium atom is bonded to four
different donor atoms: C, N, S and Cl. Treatment of 3 with triphenylphosphine in acetone gave the
mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)(PPh3)] with cleavage of the
Pd–S bond. However, treatment of 3 with silver triflate and triphenylphosphine gave [Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(PPh3)][CF3SO3], 10, in which the Pd–S bond is retained. Reaction of 3 with the
diphosphines dppm, dppb or dppf in a 2 : 1 molar ratio gave the dinuclear cyclometallated complexes
[{Pd[2-ClC6H3C(H)=NCH2CH2SMe](Cl)}2{m-Ph2P(CH2)nPPh2}], (n ¼ 1, 5; n ¼ 4, 6), and [{Pd[2-
ClC6H3C(H)=NCH2CH2SMe](Cl)}2(m-Ph2PC5H4FeC5H4PPh2)], 7. Treatment of 3 with dppb in a 2 : 1 molar
ratio and AgCF3SO3 gave the dinuclear cyclometallated complex [{Pd[2-ClC6H3C(H)=NCH2CH2SMe]}2{m-
Ph2P(CH2)4PPh2}][CF3SO3]2 , 11, which was characterized by X-ray crystal structure analysis. Reaction
of 3 with dppe in a 1 : 1 molar ratio and sodium perchlorate gave the mononuclear complex
[Pd{2-ClC6H3C(H)=NCH2CH2SMe}{Ph2P(CH2)2PPh2-P,P}][ClO4], 8. Treatment of 3 with
bis(2-diphenylphosphinoethyl)phenylphosphine in a 1 : 1 molar ratio, followed by treatment with sodium
perchlorate gave [Pd{2-ClC6H3C(H)=NCH2CH2SMe}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4], 9, in which the
triphosphine is bonded to the palladium atom through the three phosphorus atoms.
Introduction
The study of cyclometallated compounds has attracted much
attention over the last three decades.1–5 They have numerous
applications in organic and organometallic synthesis,6 inser-
tion reactions,7 the synthesis of new metal mesogenic com-
pounds8 and biologically active compounds9,10 and as catalytic
materials.11 By far the most widely studied examples of
cyclometallated complexes are five-membered palladacycles
with nitrogen donor atoms. Among these, cyclometallated
complexes derived from potentially terdentate [C,N,N] and
[C,N,S] ligands have been described.12–23 In previous work, we
have shown that potentially terdentate ligands, such as Schiff
bases I,24–27 semicarbazones II28,29 and thiosemicarbazones
III,30,31 undergo facile metallation with palladium(II), palla-
dium(0) and platinum(II) to give compounds with two five-
membered fused rings at the metal centre. The Schiff base and
semicarbazone derivatives are monomeric species but the
complexes derived from thiosemicarbazones present a tetra-
nuclear structure.
As part of our studies on the synthesis and reactivity
of cyclometallated complexes derived from multidentate
DOI: 10.1039/b106511d
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Scheme 1 (i) Pd(AcO)2 , (toluene); (ii) NaCl (acetone–water); (iii) PPh3 (acetone); (iv) dppm, dppb or dppf (acetone, 2 : 1 molar ratio); (v)
AgCF3SO3 , PPh3 (acetone); (vi) AgCF3SO3 , dppb (acetone, 2 : 1 molar ratio); (vii) AgCF3SO3 (acetone).
ligands, we synthesized the potentially [C,N,S] Schiff base 2-
ClC6H4C(H)=NCH2CH2SMe, 1, where metallation may occur
by activation of a C–H bond or by oxidative addition across
the C–Cl bond, in order to study its reactivity and also the
behavior of the subsequent metal compounds derived from 1.
Therefore, in the present work, we report the reaction of 1 with
the metallating reagents Pd(AcO)2 , [Pd2(dba)3] (dba ¼ di-
benzylideneacetone) and Li2[PdCl4]. In the resulting
complexes, the ligand behaves as [C, N, S] terdentate yielding
the monomeric species 2 and 3, in contrast with the tetrameric
structure observed for the [C, N,S] thiosemicarbazone cyclo-
metallated derivatives. Moreover, the reactivity of 3 with
tertiary phosphines such as triphenylphosphine, bis(diphenyl-
phosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane
(dppe), 1,4-bis(diphenylphosphino)butane (dppb), 1,10-bis(di-
phenylphosphino)ferrocene (dppf) and the triphosphine bis(2-
diphenylphosphinoethyl)phenylphosphine (triphos), may be
regulated to give compounds where the Pd–S bond may be
retained or cleaved, which is achieved by the use of a chloride
removing agent, usually a silver(I) salt, in the reaction media.
Scheme 2 (i) dppe, NaClO4 (acetone–water, 1 : 1 molar ratio); (ii)
triphos, NaClO4 (acetone, 1 : 1 molar ratio).
In the former case, the coordination vacancy is occupied by the
phosphine, and in the latter, opening of the coordination ring
occurs. Such a reactivity pattern differs from that observed for
the related thiosemicarbazones.
31P-{1H} (see Table 1) and, in part, 13C-{1H} NMR spectro-
scopy, and FAB mass spectrometry (see Experimental section).
Treatment of the Schiff base 2-ClC6H4C(H)=N-
CH2CH2SMe, 1, with palladium(II) acetate in dry toluene gave
Results and discussion
For the convenience of the reader, the compounds and reac-
tions are shown in Schemes 1 and 2. The compounds described
in this paper were characterised by elemental analysis (C, H,
N), IR spectroscopy (data in the Experimental section), 1H,
the
mononuclear
cyclometallated
complex
[Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(O2CMe)], 2, in 21% yield,
which was fully characterized. The 1H NMR spectrum shows a
singlet resonance at d 7.93, assigned to the HC=N proton,
106
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Table 1 31P-{1H}a and 1H NMRb–d data
31P
Aromatic
Others
1
7.70 [m, 3H, H3, H4, H5]
8.02[dd, 1H, H6 6.9 f, 2.3e]
8.73 [t, 1H, Hi 1.5e]
3.88 [2H, (CH2)g 13.6h]
2.85 [2H, (CH2)i]
2.16 [s, 3H, Me]
2
3
7.25 [d, 1H, H5 7.8 f ]
8.34 [s, 1H, Hi]
7.15 [t, 1H, H4 7.8 f, 7.8 f ]
7.00 [dd, 1H, H3 7.8 f 1.0e]
3.94 [2H, (CH2)g 12.2h]
2.94 [2H, (CH2)i]
2.64 [s, 3H, Me]
2.11 [s, 3H, OC(Me)O]
8.23 [t, 1H, Hi 1.7e]
4.02 [2H, (CH2)g 12.2h]
3.11 [2H, (CH2)i]
2.57 [s, 3H, Me]
7.64 [dd, 1H, H5 7.8 f, 1.0e]
7.11 [t, 1H, H4 7.8f]
6.96 [dd, 1H, H3 7.8 f, 1.0e]
4
42.3s
30.1s
34.0s
31.1s
6.87 [d, 1H, H3 7.8 f ]
6.49 [t, 1H, H4 7.8 f ]
6.28 [d, 1H, H5 7.8 f ]
8.64 [s, 1H, Hi]
4.19 [2H, (CH2)g 13.2h]
3.10 [2H, (CH2)i]
2.18 [s, 3H, Me]
5i
6
6.79 [d, 1H, H3 7.6 f ]
6.43 [t, 1H, H4 7.6 f ]
5.90 [m, 1H, H5]
8.44 [s, 1H, Hi]
4.05 [2H, (CH2)g]
3.04 [2H, (CH2)i 11.2h]
2.19 [s, 3H, Me]
6.83 [d, 1H, H3 7.8 f]
6.42 [t, 1H, H4 7.8 f]
8.49 [d, 1H, Hi 7.8k]
4.12 [2H, (CH2)g]
3.08 [2H, (CH2)i 12.6h]
2.20 [s, 3H, Me]
6.27 [dd, 1H, H5 7.8 f, 5.4k]
7j
8
6.88 [d, 1H, H3 7.3 f]
6.51 [br, 1H, H4]
6.21 [m, 1H, H5]
8.57 [br, 1H, Hi]
4.16 [2H, (CH2)g]
3.07 [2H, (CH2)i]
2.17 [s, 3H, Me]
62.5 [d, 27.1m]
44.6d
6.99 [d, 1H, H3 7.8 f]
8.69 [d, 1H, Hi 6.8k]
3.51 [2H, (CH2)g]
2.65 [2H, (CH2)i]
1.89 [s, 3H, Me]
6.73 [dt, 1H, H4 7.8 f, 3.0k]
6.55 [q, 1H, H5 7.8 f, 7.8k]
9
90.1 [t, 26.3m]
45.4d
6.86 [d, 1H, H3 7.8 f]
8.35 [s, 1H, Hi]
6.38 [dt, 1H, H4 7.8 f, 2.3k]
6.84 [t, 1H, H5 7.8 f, 7.8k]
3.27 [2H, (CH2)g 13.6h]
2.69 [2H, (CH2)i]
1.85 [s, 3H, Me]
10
11
37.8s
32.5s
6.95 [dd, 1H, H3 7.8 f, 1.0e]
6.63 [t, 1H, H4 7.8 f]
8.76 [s, 1H, Hi]
4.40 [2H, (CH2)g 12.6h]
3.22 [2H, (CH2)i]
1.81 [s, 3H, Me]
6.28 [dd, 1H, H5 7.8 f, 1.0e]
6.95 [d, 1H, H3 7.8 f]
6.74 [t, 1H, H4 7.8 f]
8.49 [d, 1H, Hi 7.8k]
4.24 [2H, (CH2)g 12.6h]
3.23 [2H, (CH2)i]
1.98 [s, 3H, Me]
6.40 [dd, 1H, H5 7.8 f, 5.5k]
a
b
In CDCl3 . Measured at 80.9 MHz (ca. Æ20 ꢀC); chemical shifts (d) in p p mÆ( 0.1) to high frequency of 85% H3PO4 . In CDCl3 . Measured at
c
d
200 MHz (ca. Æ20 ꢀC); chemical shifts (d) in p p mÆ(0.01) to high frequency of SiMe4 . Coupling constants in Hz. s, singlet; d, doublet;
dd, doublet of doublets; t, triplet; dt, doublet of triplets; q, quadruplet; m, multiplet; br, broad. 4J(HH). 3J(HH). HC ¼ NCH2 .
e
f
g
h
i
j
k
l
m
N values. CH2SMe. d(PCH2P) ¼ 4.70 t. J(PH). d(CHFerrocene) ¼ 5.06 [br, 2H], 4.50 [br, 2H].
J(PP).
shifted to lower frequency due to coordination of the imine
groupto the palladium atom via the lone pair of the nitrogen
atom.32 Coordination of the palladium atom to the C=N
moiety is confirmed by the shift to lower wavenumbers of the
complex 2. However, the low conductivity shown by the
complex in acetonitrile solution precludes an ionic formula-
tion. Consequently, the signal assignable to [2M þ O2CMe]
can be explained by the dimerization produced in the ioniza-
tion chamber, as has been described for related cyclometal-
lated complexes.27 In order to improve the poor yield of the
metallation reaction of 1 we attempted oxidative addition
reactions with Pd(0) compounds, but with little or no success.
For instance, treatment of 1 with [Pd2(dba)3] in dry toluene
gave a large residue of metallic palladium as a black powder,
and similarly, reaction of 1 with Li2[PdCl4] in methanol did not
yield the expected cyclometallated complex.
Reaction of 2 with aqueous sodium chloride gave [Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(Cl)], 3, as a pure air-stable
solid which was fully characterized (see Table 1 and Experi-
mental section). The 1H NMR spectrum of the complex shows
a singlet resonance at d 2.57 assigned to the SMe protons
(shifted to higher frequency by 0.41 ppm as compared with the
free ligand) and the 13C-{1H} spectrum shows a signal assigned
to the SMe methyl carbon at d 18.4 (also shifted to higher
n(C=N) band in the IR spectrum (1635s, 1, 1613sh s cmÀ 1
,
2).33,34 The C=N–CH2CH2–SMe resonances appear as well-
defined virtual triplets at d 3.94 and 2.94, respectively
(N ¼ 13.6 Hz). A singlet at d 2.64 was assigned to the SMe
protons. This signal is shifted to higher frequency from its
value in the free ligand due to coordination of the sulfur atom.
The 13C-{1H} spectrum shows resonances at d 172.4 (C=N),
161.4 (C6) and 145.6 (C1) shifted to higher frequency from the
free ligand values, thus confirming formation of the cyclome-
tallated ring.24,35 The signal at 18.1, assigned to the SMe
group, is also shifted to higher frequency upon coordination of
the sulfur atom. The FAB mass spectrum of the complex
shows
peaks
assigned
to
[M À O2CMe]þ
and
[2M þ O2CMe]þ , both with chemically reasonable isotopic
patterns. These data suggest the formulation [{Pd[2-
ClC6H3C(H)=NCH2CH2SMe]}2(m-O2CMe)]þ [O2CMe]À for
New J.Chem. , 2002, 26, 105–112
107

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atom, and a doublet signal at d 45.4 was assigned to the two
frequency), showing coordination of the sulfur atom to pal-
ladium. This was confirmed by the determination of the
molecular structure of complex 3 by X-ray single crystal dif-
fraction. Treatment of 3 with triphenylphosphine in acetone
gave the mononuclear cyclometallated complex [Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(Cl)(PPh3)], 4, which was fully
characterized (see Experimental section and Table 1). The low
conductivity value observed for complex 4 precludes the
equivalent mutually trans phosphorus nuclei. The latter signal
appears at lower frequency, in accordance with the high trans
influence of the phosphine ligand.37 The resonance of the
proton in the ortho position to the metallated carbon appears
as a triplet showing coupling to the central 31P atom
[J(PH) ¼ 7.8 Hz]; no coupling was observed to the terminal
phosphorus nuclei. The shift of the n(C=N) stretching vibra-
tion to lower wavenumbers,33,34 as well as the upfield shift of
the HC=N proton resonance in the 1H NMR spectrum,32
indicates the existence of palladium–nitrogen interaction in
solution. In agreement with the results previously obtained by
us for related species in solution and in the solid state,26,38
these data strongly agree with a penta-coordinate palladium(II)
compound in which the metallated ring is nearly perpendicular
to the plane defined by the three phosphorus atoms, and point
towards a square-pyramidal geometry in solution. These
observations were confirmed by selective decoupling experi-
ments (see Scheme 2). Recently, the chemistry of the related
ligand C6H5C(H)=NCH2CH2SEt, bearing no chlorine atom,
has been reported and two compounds similar to 3 and 4 have
been described. It should be noted that direct metallation of
this Schiff base with Na2[PdCl4] and Na(CH3COO) in
methanol gave [Pd{C6H4C(H)=NCH2CH2SEt}(Cl)] in good
yield, as opposed to ligand 1 in the present paper, where
metallation was achieved only by reaction with palladium(II)
acetate.
alternative formulation as
a 1 : 1 electrolyte [Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(PPh3)]Cl, after displacement
of the chloride ligand rather than the thioether from the pal-
ladium coordination sphere. Furthermore, the SMe resonance
in the 1H NMR spectrum appears at d 2.18 (2.16 for 1) and at
15.9 (16 for 1) in the 13C NMR spectrum, suggesting the SMe
groupis not coordinated to the palladium atom as in the
complexes 10 and 11 (vide infra), in which cases d values under
2 (1H NMR) and 16 (13C NMR) would be expected for
complex 4. Also, the IR spectrum of 4 shows a band assigned
to the n(Pd–Cl) stretch, at 306 m cmÀ 1, which was absent in
the IR spectra of compounds 10 and 11. The 31P-{1H} spec-
trum of 4 shows a singlet resonance at d 42.3, in accordance
with coordination of the phosphine ligand trans to the nitrogen
atom.
Reaction of 3 with the diphosphines dppm, dppb and dppf
in a 2 : 1 molar ratio the dinuclear gave the cyclometalla-
ted complexes [{Pd[2-ClC6H3C(H)=NCH2CH2SMe](Cl)}2{m-
Ph2P(CH2)nPPh2}], (n ¼ 1, 5; n ¼ 4, 6) and [{Pd[2-ClC6H3C(H)=
NCH2CH2SMe](Cl)}2(m-Ph2PC5H4FeC5H4PPh2)], 7, respec-
tively (see Experimental section and Table 1). The 1H (and 13C-
{1H} NMR in the case of compound 6) data are in agreement
with Pd–S bond cleavage. The 31P-{1H} NMR spectra show
a singlet resonance, indicating the compounds to be centro-
symmetric. Reaction of 3 with AgCF3SO3 followed by PPh3
(1 : 1 molar ratio) or by Ph2P(CH2)4PPh2 (2 : 1 molar ratio),
gave the mono- and dinuclear species [Pd{2-ClC6H3-
Crystal structure of [Pd{2-ClC6H3C(H)=NCH2-
CH2SMe}(Cl)] (3)
Crystal data are given in Table 2 and selected bond distances
and angles with estimated standard deviations are shown in
Table 3. Suitable crystals of the title compound were grown by
slowly evaporating a chloroform solution. The molecular
structures, which are illustrated in Fig. 1 and 2, consist of
discrete molecules separated by van der Waals distances.
The structure of 3 comprises two molecules of [Pd{2-
ClC6H3C(H)=NCH2CH2SMe}(Cl)(PPh3)] per asymmetric unit
(these are slightly different and will be labelled as 3a and 3b).
In both cases, the palladium atom is bonded in a slightly dis-
torted square-planar geometry to the carbon atom of the
C(H)=NCH2CH2SMe}(PPh3)][CF3SO3],
10,
and
[{Pd[2-
ClC6H3C(H)=NCH2CH2-SMe]}2{m-Ph2P(CH2)4PPh2}][CF3SO3]2 ,
11, respectively, after halide extraction. The IR spectra support
the presence of the [CF3SO3]À anion, showing the character-
istic stretching bands of the free anion,36 ca. 1271, 1228, 1157
and 1028 cmÀ 1. The 1H spectra of the complexes show singlet
signals for the SMe protons at d 1.81 and 1.98, we suggest
these low values are due to shielding of the phosphine phenyl
rings.24 Nevertheless, the resonance at d 22.7 in the 13C-{1H}
NMR spectrum of 11 is in agreement with coordination of the
sulfur atom to palladium. Complexes 10 and 11 can also be
prepared by treatment of 4 and 6, respectively, with silver
triflate.
Table 2 Crystal and structure refinement data for 3 and 11
3
11
Treatment of 3 with dppe in a 1 : 1 molar ratio and sodium
perchlorate gave the mononuclear cyclometallated complex
[Pd{2-ClC6H3C(H)=NCH2CH2SMe}{Ph2P(CH2)2PPh2-,P,P}]
[ClO4], 8 (see Experimental section and Table 1). The 31P-{1H}
NMR spectrum shows two doublets [J(PP) ¼ 27.1 Hz], the
resonance at lower frequency was assigned to the phosphorus
nucleus trans to the phenyl carbon atom in accordance with
the higher trans influence of the latter with respect to the C=N
nitrogen atom.37 The HC=N resonance in the 1H NMR
spectrum is only coupled to the 31P nucleus trans to nitrogen
and the H5 resonance is coupled to both phosphorus nuclei.
The SMe resonance is shifted to lower frequency as a con-
sequence of Pd–S bond cleavage. Reaction of 3 with the
tertiary triphosphine bis(2-diphenylphosphinoethyl)phenyl-
phosphine in a 1 : 1 molar ratio, followed by treatment with
sodium perchlorate gave [Pd{2-ClC6H3C(H)=NCH2CH2-
SMe}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4], 9. The phos-
phorus resonances in the 31P-{1H} NMR spectrum of the
complex are downfield shifted from their values in the free
phosphine, suggesting coordination of the three phosphorus
atoms to the metal centre. A triplet resonance at d 62.5 was
assigned to the central 31P nucleus, trans to the phenyl carbon
Formula
Mr
T=K
l=A
Crystal syst.
C10H11NCl2SPd2
354.56
293(2)
0.71073
Monoclinic
P21=n
8.241(1)
15.229(1)
13.367(1)
C50H50N2O6F6Cl2P2S4Pd2
1362.80
173(2)
0.71073
Triclinic
ꢀ
P1
10.350(1)
11.126(1)
12.780(2)
74.691(3)
82.642(3)
82.434(3)
1400.7(4)
1
+
Space group
+
a=A
+
b=A
+
c=A
a=ꢀ
b=ꢀ
90.207(1)
g=ꢀ
+
U=A3
2430.6(1)
4
2.103
56.6
16 370
5963 (Rint ¼ 0.04)
0.0372
0.0856
0.946
Z
m=mmÀꢀ 1
1.012
56.6
2ymax
=
Collected refl.
Unique refl.
Ra
9629
6726 (Rint ¼ 0.04)
0.0515
0.1513
0.832
wRb
+
max r=eA3
a
b
2
R1 ¼ SkFoj À jFck=SjFoj, [F > 4s(F)]. wR2 ¼ [S[w(Fo À Fc2)2=Sw
(Fo2)2]1=2, all data.
108
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+
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Table 3 Selected bond lengths [A] and angles [ꢀ] for 3
of 80.78(14) and 81.45(14)ꢀ for 3a and 3b, respectively. The
sum of the angles about palladium is approximately 360ꢀ in
both cases. The Pd–N bond distances [1.989(3), 3a, and
3a
3b
+
1.985(3) A, 3b], as well as the Pd–Cl bond distances [2.314(1)
A, 3a, 3b] are in accordance with previously reported
+
Pd(1)–C(1)
Pd(1)–N(1)
Pd(1)–S(1)
Pd(1)–Cl(1)
C(1)–C(6)
C(6)–C(7)
C(7)–N(1)
Cl(2)–C(5)
C(1)–Pd(1)–N(1)
C(1)–Pd(1)–Cl(1)
C(1)–Pd(1)–S(1)
N(1)–Pd(1)–Cl(1)
N(1)–Pd(1)–S(1)
Cl(1)–Pd(1)–S(1)
Pd(1)–C(1)–C(6)
1.999(4)
1.989(3)
2.413(1)
2.314(1)
1.420(5)
1.447(5)
1.276(5)
1.750(4)
80.78(14)
96.66(11)
165.10(11)
176.92(10)
84.46(10)
98.03(4)
112.1(3)
Pd(2)–C(11)
Pd(2)–N(2)
Pd(2)–S(2)
Pd(2)–Cl(3)
C(11)–C(16)
C(16)–C(17)
C(17)–N(2)
Cl(4)–C(15)
C(11)–Pd(2)–N(2)
C(11)–Pd(2)–Cl(3)
C(11)–Pd(2)–S(2)
N(2)–Pd(2)–Cl(3)
N(2)–Pd(2)–S(2)
Cl(3)–Pd(2)–S(2)
Pd(2)–C(11)–C(16)
2.005(4)
1.985(3)
2.422(1)
2.314(1)
1.423(5)
1.450(5)
1.279(4)
1.747(4)
81.45(14)
96.69(11)
165.94(11)
179.09(9)
84.49(9)
97.34(4)
111.0(3)
values.24,25,27,30 The Pd–C bond distances of 1.999(4), 3a, and
2.005(4) A, 3b, are somewhat shorter than predicted from
+
their covalent radii39 but similar to values found earlier.24,25,27
The Pd–S bond lengths of 2.413(1), 3a, and 2.422(1) A, 3b,
reflect the strong trans-influence of the metallated carbon
+
atom.13–16,30
The geometry around the palladium atom [Pd, C, N, S, Cl] is
+
planar (r.m.s. ¼ 0.0122 and 0.0371 A for 3a and 3b, respec-
tively; planes 1 and 2). The metallated rings [Pd(1), C(1), C(6),
C(7), N(1) and Pd(2), C(11), C(16), C(17), N(2)] are also pla-
+
nar (r.m.s. ¼ 0.0156 and 0.0256 A for 3a and 3b, respectively;
planes 3 and 4). Angles between planes are as follows: plane
1=plane 3 ¼ 0.3 ꢀ; plane 2=plane 4 ¼ 4.6 ꢀ. The two molecules of
the asymmetric unit are nearly parallel (plane 1=plane 2 ¼ 3.2 ꢀ;
plane 3=plane 4 ¼ 5.3 ꢀ). As expected, the coordination rings
[Pd(1), N(1), C(8), C(9), S(1) and Pd(2), N(2), C(18), C(19),
S(2)] show large deviations from planarity with C(8) [C(19) for
3b] lying above the least square plane and C(9) [C(18) for 3b]
below. Recently, a structure similar to 3 has been reported40
where the asymmetric unit consists of three molecules, in
contrast to the two found in the structure of compound 3. The
bond distances and bond angles show values very close to
those observed in the present case.
Crystal structure of [{Pd[2-ClC6H3C(H)=NCH2CH2SMe]}2-
(l-Ph2P(CH2)4PPh2)][CF3SO3]2 (11)
Crystal data are given in Table 2 and selected bond distances
and angles with estimated standard deviations are shown in
Table 4. The molecular structure is illustrated in Fig. 3. Sui-
table crystals of the title compound were grown by slowly
evaporating a dichloromethane solution.
The crystal structure comprises a centrosymmetric dinuclear
cation (half the cation per asymmetric unit) and two triflate
anions. Each four-coordinate palladium is bonded to the ter-
dentate Schiff base ligand through the aryl C(1) carbon, the
imine N(1) nitrogen and the sulfur atom, and to the phos-
phorus atom of the 1,4-bis(diphenylphosphine)butane, which
bridges the two metal atoms.
Fig. 1 Molecular structure of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)]
(3a), with labelling scheme. Hydrogen atoms have been omitted for clarity.
The geometry around each metal atom is similar to that
shown by complex 3, with each palladium atom coordinated in
a slightly distorted square-planar environment [mean deviation
from the Pd(1), C(1), N(1), S(1), P(1) least square plane of
0.014 A]. The most noticeable distortions being the C(1)–
Pd(1)–N(1) and N(1)–Pd(1)–S(1) angles of 81.1(2) and
+
81.95(13) ꢀ, respectively.
The Pd(1)–C(1) bond length [2.030(6) A] is shorter than the
+
expected value of 2.081.24,25,27 The Pd(1)–N(1) bond distance
[2.044(4) A] is longer than the values found for complex 3
[1.989(3), 3a, and 1.985(3) A, 3b], reflecting the trans influence
+
+
of the P(1) phosphorus donor ligand.41 The Pd(1)–S(1) bond
distance [2.399(2) A] and the Pd(1)–P(1) length [2.279(1) A]
+
+
+
Table 4 Selected bond lengths [A] and angles [ꢀ] for 11
Fig. 2 Molecular structure of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)]
(3b), with labelling scheme. Hydrogen atoms have been omitted for clarity.
Pd(1)–C(1)
Pd(1)–S(1)
C(1)–C(6)
C(7)–N(1)
C(1)–Pd(1)–N(1)
C(1)–Pd(1)–S(1)
N(1)–Pd(1)–S(1)
Pd(1)–C(1)–C(6)
C(7)–N(1)–Pd(1)
2.030(6)
2.399(2)
1.424(7)
1.283(7)
81.1(2)
162.90(16)
81.95(13)
110.3(4)
115.7(4)
Pd(1)–N(1)
Pd(1)–P(1)
C(6)–C(7)
Cl(1)–C(5)
C(1)–Pd(1)–P(1)
N(1)–Pd(1)–P(1)
P(1)–Pd(1)–S(1)
C(1)–C(6)–C(7)
2.044(4)
2.279(1)
1.456(8)
1.745(6)
97.17(16)
177.17(13)
99.73(5)
116.6(5)
phenyl ring, the imine nitrogen atom, the sulfur atom and to a
chlorine atom. The angles between adjacent atoms in the
coordination sphere of palladium are close to the expected
value of 90ꢀ, with the most noticeable distortions corre-
sponding to the C(1)–Pd(1)–N(1) and C(11)–Pd(2)–N(2) angles
New J.Chem. , 2002, 26, 105–112
109

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The resulting mixture was heated at 60 ꢀC for 12 h. After cooling
to r. t., the solution was filtered through Celite to remove the
black palladium formed. The solvent was removed under vacuum
to give a brown oil, which was chromatographed on a column
packed with silica gel. Elution with dichloromethane–ethanol
(7%) afforded an orange oil after solvent removal, which was
recrystallized from dichloromethane–hexane to give the desired
product as an orange solid. Yield 21%. Anal. found: C, 38.5; H,
3.4; N, 3.6; C12H14NO2SClPd requires C, 38.1; H, 3.7; N, 3.7%.
IR: n(C=N) 1613sh s; nas(COO) 1571s; ns(COO), 1328m cmÀ 1
.
13C-{1H} NMR (50.28 MHz, CDCl3): d 178.4 [OC(CH3)O];
172.4 (C=N); 161.4 (C6); 145.6 (C1); 131.0 (C2), 132.3, 130.0,
125.5 (C3–C5); 56.5 (N–CH2), 37.3 (CH2–S); 23.4 (OC(CH3)O);
18.1 (SMe). FAB-MS: m=z¼ 320 [M À AcO]þ , 697 [2M þ
AcO]þ
.
Fig. 3 Molecular structure of [{Pd[2-ClC6H3C(H)=NCH2CH2-
SMe]}2{m-Ph2P(CH2)4PPh2}][CF3SO3]2 (11), with labelling scheme.
Hydrogen atoms have been omitted for clarity.
Preparation of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)]
(3). An aqueous solution of NaCl (ca. 10À 2 M) was added
dropwise to a solution of 2 (218 mg, 0.29 mmol) in 15
cm3 of acetone. The resulting mixture was stirred for 24 h.
The yellow precipitate formed was filtered off, washed with
water, dried under vacuum and recrystallized from
dichloromethane–hexane to give complex 3 as a yellow
crystalline solid. Yield 98%. Anal. found: C, 38.7; H, 3.1;
N, 4.0; C10H11NSCl2Pd requires C, 38.9; H, 3.1; N, 3.9%)
are within the expected range and similar to values reported
for related complexes.25,28,41 Thus, as for compound 3, the
palladium atom in 11 is bonded to four different donor atoms:
C, N, S and P.
The palladium coordination plane [Pd(1), C(1), N(1), S(1),
P(1)] and the metallated ring [C(1), C(6), C(7), N(1), Pd(1)] are
coplanar (angle between planes 5.3 ꢀ).
IR: n(C=N), 1612s cmÀ 1 13C-{1H} NMR (50.28 MHz,
.
CDCl3): d 172.4 (C=N); 162.1 (C6); 146.3 (C1); 131.1
(C2), 132.6, 132.5, 125.4 (C3–C5); 56.8 (N–CH2), 38.6
(CH2–S); 18.4 (SMe). FAB-MS: m=z ¼ 355 [M]þ
; 320
[M À Cl]þ
.
Experimental
General
Preparation of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(Cl)(PPh3)]
(4). PPh3 (7.7 mg, 0.029 mmol) was added to a suspension of 3
(11 mg, 0.030 mmol) in acetone (15 cm3). The mixture was
stirred for 12 h and the solvent removed to give a white solid
which was recrystallized from dichloromethane–hexane. Yield
46%. Anal. found: C, 54.0; H, 3.9; N, 2.0; C28H26NPSCl2Pd
requires C, 54.5; H, 4.2; N, 2.3%. IR: n(C=N) 1617s, n(Pd–Cl),
Caution! Perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only small amounts of
these materials should be prepared and handled with great
caution.
Solvents were purified by standard methods.42 Chemicals
were reagent grade. The phosphines PPh3 , Ph2PCH2PPh2
(dppm), Ph2P(CH2)4PPh2 (dppb), Ph2PC5H4FeC5H4PPh2
(dppf) and (Ph2PCH2CH2)2PPh (triphos), were purchased
from Aldrich-Chemie. Microanalyses were carried out using a
Carlo Erba Model 1108 elemental analyser. IR spectra were
recorded from Nujol mulls or polythene discs on a Perkin-
Elmer 1330 and a Mattson spectrophotometer. NMR spectra
were obtained from CDCl3 solutions, referenced to SiMe4 (1H,
13C-{1H}) or 85% H3PO4 (31P-{1H}) and were recorded on a
Bruker AC-2005 spectrometer. All chemical shifts are reported
downfield from the standards. The FAB mass spectra were
recorded using a VG Quatro mass spectrometer with a Cs ion
gun; 3-nitrobenzyl alcohol was used as the matrix.
306m cmÀ 1 13C-{1H} NMR (50.28 MHz, CDCl3): d 174.6
.
(C=N); 160.3 (C6); 145.0 (C1); 132.2 (C2), 136.6, 131.5, 125.1
(C3–C5); 59.0 (N–CH2), 35.3 (CH2–S); 16.0 (SMe);
P–phenyl; 130.5 [d, Ci , J(PC) ¼ 46.1 Hz], 135.3 [d, Co ,
J(PC) ¼ 12.0 Hz], 128.2 [d, Cm , J(PC) ¼ 11.3 Hz], 131.0 [d, Cp ,
J(PC) ¼ 2.2 Hz]. FAB-MS: m=z ¼ 582 [M À Cl]þ
.
Compounds 5–7 were obtained following a similar proce-
dure as white (5, 6) or orange (7) solids, but using a 2 : 1
complex 3 to diphosphine molar ratio.
[{Pd[2-ClC6H3C(H)=NCH2CH2SMe](Cl)}2(l-Ph2PCH2PPh2)]
(5). Yield 65%. Anal. found: C, 47.3; H, 3.7; N, 2.3;
C45H44N2P2S2Cl4Pd2 ꢁ CH2Cl2 requires C, 46.9; H, 3.9; N, 2.4%.
IR: n(C=N) 1616s cmÀ 1. FAB-MS: m=z¼ 1058 [M À Cl]þ ; 1021
[M À 2Cl]þ ; 704 [(1À H)Pd(dppm)]þ
.
Syntheses
Preparation of 2-ClC6H4C(H)=NCH2CH2SMe (1). 2-
chlorobenzaldehyde (1.166 g, 8.29 mmol) was added to a
solution of 2-(methylthio)ethylamine (0.716 g, 7.85 mmol) in
50 cm3 of dry chloroform. The solution was heated under
reflux in a Dean–Stark apparatus for 4 h. After cooling to
room temperature (r.t.), the chloroform was removed to give a
[{Pd[2-ClC6H3C(H)=NCH2CH2SMe](Cl)}2{l-Ph2P(CH2)4PPh2}]
(6). Yield 76%. Anal. found: C, 50.7; H, 4.4; N, 2.3;
C48H50N2P2S2Cl4Pd2 requires C, 50.8; H, 4.4; N, 2.5%. IR:
n(C=N), 1615s, n(Pd–Cl), 308m cmÀ 1 13C-{1H} NMR (50.28
.
MHz, CDCl3): d 174.0 (C=N); 160.0 (C6); 144.5 (C1); 132.1
(C2), 132.9, 131.5, 125.0 (C3–C5); 58.7 (N–CH2), 34.9 (CH2–
S); 16.0 (SMe); P–phenyl: 129.9 [d,Ci , J(PC) ¼ 46.1 Hz], 133.9
[d,Co , J(PC) ¼ 12.0 Hz], 128.6 [d, Cm , J(PC) ¼ 10.6 Hz],
yellow oil. Yield 95%. IR: n(C=N) 1635s cmÀ 1 13C-{1H}
.
NMR (50.28 MHz, CDCl3): d 158.6 (C=N); 135.0, 133.0 (C1,
C2); 131.5, 129.7, 128.3, 126.9 (C3–C6); 61.1 (N–CH2), 34.9
(CH2–S); 15.9 (SMe).
130.9(Cp) FAB-MS: m=z ¼ 1101 [M À Cl]þ ; 1064 [M À 2Cl]þ
;
746 [(1 À H)Pd(dppb)]þ
.
Preparation of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}(O2CMe)]
(2). A pressure tube containing 2-ClC6H4C(H)=NCH2CH2SMe
(305 mg, 1.42 mmol), palladium(II) acetate (316 mg, 1.41
mmol) and 20 cm3 of dry toluene was sealed under argon.
[{Pd[2-ClC6H3C(H)=NCH2CH2SMe](Cl)}2(l-Ph2PC5H4Fe-
C5H4PPh2)] (7). Yield 97%. Anal. found: C, 51.2; H, 4.4; N,
2.3; C54H50N2P2S2Cl4FePd2 requires C, 51.3; H, 4.0; N, 2.2%.
110
New J.Chem. , 2002, 26, 105–112

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IR: n(C=N) 1622s cmÀ 1. FAB-MS: m=z ¼ 1192 [M À 2Cl]þ
;
Acknowledgements
874 [(1 À H)Pd(dppf)]þ
.
We thank the Ministerio de Educacion y Cultura (Proyecto
PB98-0638-C02-01=02), the Xunta de Galicia (Proyecto
PGIDT99PXI20907B) and the Universidad de Coruna for
financial support.
Preparation of [Pd{2-ClC6H3C(H)=NCH2CH2SMe}{Ph2P-
(CH2)2PPh2-P,P}][ClO4] (8). PPh2(CH)2PPh2 (4.9 mg, 0.012
mmol) was added to a suspension of 3 (4.3 mg, 0.012 mmol)
in acetone (20 cm3). The mixture was stirred for 1 h, after
which an excess of sodium perchlorate was added. The
complex was the precipitated out by addition of water,
filtered off and dried in vacuo. Recrystallization from
dichloromethane–hexane gave the final compound as a yellow
solid. Yield 94%. Anal. found: C, 51.3; H, 4.4; N, 1.5;
C36H35NO4P2SCl2Pd ꢁ 0.5CH2Cl2 requires C, 51.0; H, 4.2; N,
References
1
2
3
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1.6%. IR: n(C=N), 1607s cmÀ 1
.
FAB-MS: m=z ¼ 718
[M À ClO4]þ
.
[Pd{2-ClC6H3C(H)=NCH2CH2SMe}{(Ph2PCH2CH2)2PPh-
P,P,P}][ClO4] (9). Yield 72%. Anal. found: C, 52.3; H, 4.4; N,
1.5; C44H44NO4P3SCl2Pd ꢁ CH2Cl2 requires C, 52.0; H, 4.5; N,
4
5
6
1.3%. IR: n(C=N) 1615s cmÀ 1
.
FAB-MS: m=z ¼ 854
[M À ClO4]þ
.
7
8
9
Preparation
of
[Pd{2-ClC6H3C(H)=NCH2CH2SMe}-
(PPh3)][CF3SO3] (10). A solution of 3 (10.4 mg, 0.029 mmol)
in acetone (15 cm3) was treated with silver trifluoro-
methanesulfonate (7.4 mg, 0.029 mmol) and stirred for 2 h.
The resulting solution was filtered through Celite to remove
the AgCl precipitate. PPh3 (7.0 mg, 0.028 mmol) was added to
the filtrate, the solution stirred for another 4 h and the solvent
removed to give a yellow solid which was recrystallized from
dichloromethane–hexane. Yield 89%. Anal. found: C, 48.5; H,
3.7; N, 1.7; C29H26NO3F3PS2ClPd requires C, 47.7; H, 3.6; N,
10 C. Navarro-Ranninger, I. Lopez-Solera, V. M. Gonzalez,
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Ortigueira, A. Fernandez, M. Lopez-Torres and C. Rodrıguez,
Trends Organomet. Chem., 1999, 3, 71.
1.9%. IR: n(C=N), 1628s cmÀ 1
.
13 B. Schreiner, R. Urban, A. Zografidis, K. Sunkel, K. Polborn and
W. Beck, Z. Naturforsch., Teil B, 1999, 54, 970.
14 S. Chattopadhyay, C. Sinha, P. Basu and A. Chakravorty,
Organometallics, 1991, 10, 1135.
Compound 11 was obtained following a similar procedure
as a white solid but using a 2 : 1 complex 3 to diphosphine
molar ratio.
15 C. K. Pal, S. Chattopadhyay, C. Sinha and A. Chakravorty, J.
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21 S. Chattopadhyay, C. Sinha, S. B. Choudhury and A.
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22 S. Chattopadhyay, C. Sinha, P. Basu and A. Chakravorty,
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[{Pd[2-ClC6H3C(H)=NCH2CH2SMe]}2{l-Ph2P(CH2)4PPh2}]-
[CF3SO3]2 (11). Yield 50%. Anal. found: C, 44.2; H, 3.7; N,
1.9; C50H50N2O6F6P2S4Cl2Pd2 requires C, 44.1; H, 3.7; N,
2.1%. IR: n(C=N) 1626s cmÀ 1 13C-{1H} NMR (50.28 MHz,
.
CDCl3): d 172.3 (C=N); 157.6 (C6); 145.6 (C1); 132.4 (C2),
135.5, 129.3, 125.5 (C3–C5); 58.1 (N–CH2), 36.1 (CH2–S); 22.7
(SMe). P-phenyl: 129.8 [d, Ci , J(PC) ¼ 46.8 Hz], 133.7
[d, Co , J(PC) ¼ 10.6 Hz], 128.8 [d, Cm , J(PC) ¼ 9.2 Hz],
131.2(Cp) FAB-MS: m=z ¼ 1213 [M À CF3SO3]þ
;
746
[(1 À H)Pd(dppb)]þ
.
X-Ray crystallographic study
23 X. Riera, A. Caubet, C. Lopez, V. Moreno, X. Solans and M.
Font-Bardıa, Organometallics, 2000, 19, 1384.
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J. Chem. Soc., Dalton Trans., 1999, 4193.
Three-dimensional, room temperature X-ray data were col-
lected on a Siemens Smart CCD diffractometer by the o scan
method using graphite-monochromated Mo-Ka radiation.
All the measured reflections were corrected for Lorentz and
polarisation effects and for absorption by semi-empirical
methods based on symmetry-equivalent and repeated reflec-
tions. The structures were solved by direct methods and
refined by full matrix least squares on F2. Hydrogen atoms
were included in calculated positions and refined in riding
mode. Refinement converged at a final R ¼ 0.0372 and 0.515
(for complexes 3 and 11, respectively, observed data, F) and
wR2 ¼ 0.0856 and 0.1513 (for complexes 3 and 11, respec-
tively, unique data, F2), with allowance for thermal aniso-
tropy of all non-hydrogen atoms. The structure solution and
refinement were carried out using the program package
SHELX-97.43
CCDC reference numbers 157897 and 157898. See
http:==www.rsc.org=suppdata=nj=b1=b106511d= for crystal-
lographic data in CIF or other electronic format.
New J.Chem. , 2002, 26, 105–112
111

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