Synthesis and reactivity of novel cyclometallated complexes derived from [C,N,O] terdentate ligands. Crystal structure of [Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H 4]}(PPh3)]

Article abstract of DOI:10.1039/b110197h

Treatment of the Schiff base ligands 2,3,4-(MeO)₃C₆H₂C(H)=N[2-(OH)C₆H ₄], a, and 2,3,4-(MeO)₃C₆H₂-C(H)=N[2-(OH)-4-MeC ₆H₄], b, with palladium(II) acetate in toluene gave the cyclometallated complexes [Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)C₆H ₄]}]_n, 1a, and [Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)-4-MeC₆H ₄]}]_n, 1b, respectively, as air stable solids, with the [C,N,O] ligand terdentate after deprotonation of the -OH group. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species [Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)C₆H ₄]}(PPh₃)], 2a, and [Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)-4-MeC₆H ₄]}-(PPh₃)], 2b, with cleavage of the polynuclear structure. The molecular structure of 2a has been determined by X-ray crystallography. Treatment of 1a and 1b with the diphosphines dppm, dppp, dppb, dpppe and dppf in a 1:2 molar ratio afforded the dinuclear cyclometallated complexes [(Pd{2,3,4-(MeO)₃C₆HC (H)=N[2-(O)C₆H₄]})₂{μ-PPh₂ (CH₂)_nPPh₂}] (3a: n = 1; 4a: n = 3; 5a: n = 4; 6a: n = 5), [(Pd{2,3,4-(MeO)₃ C₆HC(H)=N[2-(O)C₆H₄]})₂(μ-PPh ₂C₅H₄FeC₅H₄PPh ₂)], 7a, [(Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)-4-MeC₆H ₄]})₂{μ-PPh₂(CH₂) _nPPh₂}] (3b: n = 3; 4b: n = 4) and [(Pd{2,3,4-(MeO)₃C₆HC(H)=N[2-(O)-4-MeC₆H ₄]})₂(μ-PPh₂C₅H₄ FeC₅H₄PPh₂)], 5b, as air stable solids. Treatment of 1a and 1b with an excess of mono- or diphosphine did not produce cleavage of the Pd-O_chelating bond.

Full text of DOI:10.1039/b110197h

View Article Online / Journal Homepage / Table of Contents for this issue
Synthesis and reactivity of novel cyclometallated complexes derived
from [C,N,O] terdentate ligands. Crystal structure of
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]}(PPh3)]
a
Alberto Fernandez,* Digna Vazquez-Garcıa, Jesus J. Fernandez, Margarita Lopez-Torres,
a
a
a
´
Antonio Suarez, Samuel Castro-Juiz and Jose M. Vila*
´
´
´
´
´
a
a
b
´
´
a
´
Departamento de Quımica Fundamental, Universidad de La Corun˜a, E-15071 La Corun˜a
Spain. E-mail: qiluaafl@udc.es; Fax: +34 981 167065
b
´
Departamento de Quımica Inorganica, Universidad de Santiago de Compostela,
E-15782 Santiago de Compostela, Spain. E-mail: qideport@usc.es; Fax: +34 981 595012
´
Received (in London, UK ) 9th September 2001, Accepted 2nd January 2002
First published as an Advance Article on the web 12th March 2002
Treatment of the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)=N[2-(OH)C6H4], a, and 2,3,4-(MeO)3C6H2-
C(H)=N[2-(OH)-4-MeC6H4], b, with palladium(II) acetate in toluene gave the cyclometallated complexes
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]}]n , 1a, and [Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H4]}]n , 1b,
respectively, as air stable solids, with the [C,N,O] ligand terdentate after deprotonation of the –OH group.
Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]}(PPh3)], 2a, and [Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H4]}-
(PPh3)], 2b, with cleavage of the polynuclear structure. The molecular structure of 2a has been determined by
X-ray crystallography. Treatment of 1a and 1b with the diphosphines dppm, dppp, dppb, dpppe and dppf
in a 1 : 2 molar ratio afforded the dinuclear cyclometallated complexes [(Pd{2,3,4-(MeO)3C6HC
(H)=N[2-(O)C6H4]})2{m-PPh2(CH2)nPPh2}] (3a: n ¼ 1; 4a: n ¼ 3; 5a: n ¼ 4; 6a: n ¼ 5), [(Pd{2,3,4-(MeO)3
C6HC(H)=N[2-(O)C6H4]})2(m-PPh2C5H4FeC5H4PPh2)], 7a, [(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-
MeC6H4]})2{m-PPh2(CH2)nPPh2}] (3b: n ¼ 3; 4b: n ¼ 4) and [(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-
MeC6H4]})2(m-PPh2C5H4FeC5H4PPh2)], 5b, as air stable solids. Treatment of 1a and 1b with an excess of
mono- or diphosphine did not produce cleavage of the Pd–Ochelating bond.
(Fig. 1);29 whereas deprotonation was not observed in the
semicarbazone complexes.
Introduction
Cyclometallated compounds have been extensively surveyed1–5
and they exhibit a good number of applications which extend
from organic and organometallic compounds, to metal meso-
genic species and catalytic materials,6–14 as well as promoting
unusual coordination environments.15
Therefore, in view of these results, we reasoned that using
phenol
the
derivatives
2,3,4-(MeO)3C6H2C(H)=N[2-
In the past, we have been interested in palladium(II) and pla-
tinum(II) cyclometallated complexes derived from [C,N,X]
(X ¼ N, O, S) terdentate ligands.16–21 Those derived from
semicarbazones reacted readily with palladium(II) salts to give
cyclometallated complexes with the [C,N,O] ligand terdentate,
yielding mononuclear species.16,17 Also, reactions of o-hydroxy-
azobenzenes with palladium(II) salts to give mononuclear
[C,N,O]22 or dinuclear [C,N]23 cyclometallated complexes have
been reported. In the case of the terdentate [C,N,S] thiosemi-
carbazones, I (Fig. 1), the corresponding palladium(II) and pla-
tinum(II) derivatives show tetranuclear structures, with an
eight membered Pd4S4 core,24,25 as opposed to the mononuc-
lear semicarbazone analogues. Similar tetranuclear complexes
have also been reported by Navarro-Ranninger et al.;26 and
Kawamoto et al. have reported the synthesis of tetranuclear
cluster complexes derived from benzothiazolines II (Fig.
1).27,28 In order to attain neutrality, the ligand is usually depro-
tonated in the complex at the hydrazinic or the benzothiazoline
nitrogen atom. Even in cases where there is no metal–carbon
bond formation, the tetranuclear structure is reached only
after deprotonation, as has been reported for a coordination
compound derived from an [N,N,S] terdentate ligand, III
Fig. 1 Complexes of Pd(II) and Pt(II) derived from thiosemicarba-
zones (I) and benzothiazolines (II), and a Pd(II) complex derived from
an [N,N,S] terdentate ligand (III).
398
New J. Chem., 2002, 26, 398–404
DOI: 10.1039/b110197h
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2002

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(OH)C6H4]
and
2,3,4-(MeO)3C6H2C(H)=N[2-(OH)-4-
nuclear composition for 1a and 1b until additional data, such
as X-ray diffraction analysis, is possible. Nevertheless, the
reactivity of complexes 1a and 1b towards tertiary phosphines
suggests that the P–Ochelating bond is unexpectedly strong, in
contrast to earlier results with semicarbazones. The X-ray dif-
fraction structure of one of these complexes is also presented.
MeC6H4] we would be able to synthesize tetranuclear cyclo-
metallated palladium(II) compounds with [C,N,O] terdentate
ligands, hitherto unknown, with deprotonation of the –OH
group. Consequently, we prepared the Schiff base ligands a
and b by reaction of 2,3,4-trimethoxybenzaldehyde and 2-
aminophenol or 2-amino-3-methylphenol, respectively, and
treated them with palladium(II) acetate, upon which we
obtained cyclometallated compounds with [C,N,O] terdentate
ligands, 1a and 1b, and the results are reported herein. How-
ever, although the spectroscopic and FAB mass data point
to a tetranuclear structure, we tentatively propose a poly-
Results and discussion
For the convenience of the reader, the compounds and reac-
tions are shown in Scheme 1. The compounds described in this
Scheme 1 (i) Pd(AcO)2 (toluene); (ii) PPh3 (acetone); (iii) diphosphine (acetone).
New J. Chem., 2002, 26, 398–404
399

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paper were characterized by elemental analysis (C, H, N) and
by IR spectroscopy (data in the Experimental section) and by
1H, 31P-{1H} (see Table 1) and, in part, 13C-{1H} NMR spec-
troscopy and FAB mass spectrometry (Experimental section).
Reaction of the Schiff base ligands a and b with palladium(II)
acetate in toluene at 60 ꢀC gave the complexes [Pd{2,3,4-
(MeO)3C6HC(H)=N[2-(O)C6H4]}]n , 1a and [{Pd[2,3,4-
(MeO)3C6HC(H)=N[2-(O)-4-MeC6H3]}]n, 1b, respectively, as
air stable solids which were fully characterized. The IR spectra
showed a shift of the n(C=N) stretch toward lower wavenum-
bers as compared to the free ligand, due to N-coordination of
the imine,30,31 and the absence of the n(O–H) band [present in
the spectra of the free ligands at 3428 (a) and 3450 cmꢁ1 (b)], in
accordance with loss of the –OH proton. The absence of
n(COO) bands in the IR spectra precludes the formulation of
compounds 1a and 1b as typical dinuclear species with brid-
ging acetate ligands, as obtained previously when using palla-
dium(II) acetate as the metal salt.32
bond cleavage. Whereas in the synthesis of compound 2a a
1 : 4 complex : phosphine molar ratio was used, the pre-
paration of 2b required excess triphenylphosphine and the final
product was isolated by column chromatography. In both
cases, the Pd–Ochelating bond remained, as shown by the spec-
troscopic data (see Experimental and Table 1). The strength
of the Pd–Ochelating bond was tested by treating 1a and 1b with
a large excess of phosphine, which only yielded complexes 2a
and 2b, as well as unreacted phosphine. This behaviour con-
trasts with the facile breakage of the palladium–oxygen bond
observed by us in semicarbazone compounds.16, 17
1
The H NMR spectra of 2a and 2b showed resonances due
to the H5 and HC=Nprotons coupled to the 31P nucleus of
the phosphine ligand (ca. 4 and 10 Hz, respectively), and in
the 31P-{1H} spectra the phosphorus resonances were singlets
at d ca. 34; these findings are in agreement with a phosphorus
trans to nitrogen arrangement.33–36 The HC=Nproton reso-
nances at d 8.17 (2a) and 8.12 (2b) showed smaller low-field
shifts than in compounds 1a and 1b, in agreement with the
opening of the polynuclear structure. However, the H5 reso-
nances at d 5.51 (2a) and 5.50 (2b) showed greater shifts than
in 1a and 1b due to shielding by the phosphine phenyl rings, as
we have observed before in related complexes;24,25 this shield-
ing also affects the C4-MeO proton signals, which are also
moved to lower frequency upon phosphine coordination to
the metal. The FAB mass spectrum of 2a showed the cluster
of peaks at 653 amu characteristic of the [M]+ fragment.
Reaction of the cyclometallated tetramers with the dipho-
sphines dppm, dppp, dppb, dpppe and dppf in a 1 : 2 molar
ratio gave the dinuclear cyclometallated complexes
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]})2{m-PPh2(CH2)n-
PPh2}] (3a: n ¼ 1; 4a: n ¼ 3; 5a: n ¼ 4; 6a: n ¼ 5), [(Pd{2,3,4-
(MeO)3C6HC(H)=N[2-(O)C6H4]})2(m-PPh2C5H4FeC5H4PPh2)],
1
In the H NMR spectra, all the resonances were high-field
shifted as compared to the uncoordinated ligand (see Table
1) and they were in agreement with metallation of the ligand
with coordination of the palladium atom via the imine nitrogen
5
atom. The most noticeable shifts concern the HC=Nand H
resonances, ca. 1.5 and 1.1 ppm, respectively (Table 1), which
are usually in the range 0.5–1.0 ppm; the low d values in these
cases are due to the structure of the complexes (a fragment is
5
depicted in Fig. 2) which puts the HC=Nand H protons in
the proximity of the shielding area of the phenyl rings of a
neighbouring metallated ligand (a similar situation has been
reported by us in the structurally related thiosemicarbazone
derivatives, where a tetranuclear structure was confirmed by
X-ray diffraction analysis24,25).
Deprotonation of the –OH group was confirmed by the
1
absence of OH resonances in the H NMR spectra. Likewise,
7a,
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H4]})2{m-
no signals could be assigned to the acetate methyl groups,
showing these ligands were not present in the coordination
sphere of palladium.
PPh2(CH2)nPPh2}] (3b: n ¼ 3; 4b: n ¼ 4) and [(Pd{2,3,4-
(MeO)3C6HC(H)=N[2-(O)-4-MeC6H4]})2(m-PPh2C5H4FeC5-
H4PPh2)], 5b, as air stable solids, which were fully character-
The 13C-{1H} spectra of the complexes showed signals
assigned to the C6, C=N, and C1 carbons, shifted to higher fre-
quency, confirming that metallation had occurred.24,25 How-
ever, the shift of the C=Ncarbon resonance was less than
the expected, ca. 15 ppm. The resonance assigned to the C–
O carbon was shifted to higher frequency by ca. 15 ppm upon
Pd–O bond formation.
ized (see Experimental section and Table 1). The IR and H
1
NMR spectra of the complexes showed similar features for
the cyclometallated moiety as those of the parent mononuclear
compounds (see Table 1). Only one singlet for the two equiva-
lent nuclei was observed in each 31P-{1H} NMR spectrum, in
accordance with the centrosymmetric nature of the dinuclear
complexes. The FAB mass spectra of the dinuclear complexes
showed sets of peaks corresponding to the [M]+ or [MH]+
ions.
The strength of the Pd–Ochelating bond was confirmed by the
reaction of 1a and 1b with a large excess of diphosphine. As
we16,17 and others37 have shown before, in complexes with
Pd–O bonds, the use of tertiary diphosphines in the appropri-
ate molar ratio yields species with the phosphine chelated to
the metal center through both phosphorus atoms, with clea-
vage of the Pd–O bond; the stability of the compound being
enhanced by the chelate effect of the bidentate phosphine.
However, in the present case, even the use of strong chelating
phosphines such as dppm did not split the Pd–O bond, and the
oxygen atom was coordinated to the metal in all cases.
The FAB mass spectra of 1a and 1b showed clusters of
peaks, centred at 1566 and 1623 amu, which correspond to
[M]+ and [MH]+, respectively. Although the isotopic pattern
is in good agreement with a tetramer, it could also be due to
a tetranuclear fragment of a larger polynuclear species.
Reactivity of the complexes
Treatment of the cyclometallated complexes with triphenyl-
phosphine gave the mononuclear species [Pd{2,3,4-
(MeO)3C6HC(H)=N[2-(O)C6H4]}(PPh3)], 2a, and [Pd{2,3,4-
(MeO)3C6HC(H)=N[2-(O)-4-MeC6H3]}(PPh3)], 2b, in which
the polynuclear structure has been opened due to P–Obridging
Crystal structure of [Pd{2,3,4-(MeO)3C6HC(H)=N[2-
(O)C6H4}(PPh3)], 2a
Suitable crystals of the title compound were grown by slowly
evaporating a chloroform solution. The molecular structure
is illustrated in Fig. 3.
The crystal structure comprises one molecule of 2a per
asymmetric unit. The palladium(II) atom is bonded to the aryl
carbon C(1), the imine nitrogen N(1) and the oxygen O(1) of
the Schiff base ligand and to a phosphorus atom of the triphe-
nylphosphine ligand, P(1).
Fig. 2 The tetranuclear core of 1a and 1b. The phenyl substituents
have been omitted for clarity.
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New J. Chem., 2002, 26, 398–404

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Dean–Stark apparatus for 4 h. After cooling to room tempera-
ture, the chloroform was removed to give a brown solid. Yield
89%. IR (cmꢁ1): n(O–H) 3428s; n(C=N) 1612sh, m.13C-{1H}
NMR (50.28 MHz, CDCl3): d 152.8 (C=N); 122.6 (C1);
156.8, 154.7, 141.8 (C2, C3, C4); 107.9 (C5); 122.5 (C6);
136.4 (C7); 116.0 (C8); 120.0 (C9); 128.3 (C10); 114.7 (C11);
152.1 (C12); 62.1, 60.9, 56.1 (OCH3).
2,3,4-(MeO)3C6H2C(H)=N[2-(OH)-4-MeC6H3] (b). Schiff
base b was prepared similarly and obtained as a brown solid.
Yield 97%. IR (cmꢁ1): n(O–H), 3450s cmꢁ1; n(C=N), 1612sh,
m cmꢁ1 13C-{1H} NMR (50.28 MHz, CDCl3): d 152.5
.
(C=N); 122.7 (C1); 156.7, 154.7, 141.8 (C2, C3, C4); 107.9
(C5);122.5 (C6); 136.1 (C7); 116.5 (C8); 129.2 (C9); 128.8
(C10); 114.4 (C11); 149.9 (C12); 62.1, 60.9, 56.1 (OCH3).
Fig. 3 Molecular structure of [Pd{2,3,4-(MeO)3C6HC(H)=N[2-
(O)C6H4]}(PPh3)], 2a. Ellipsoids drawn at 40%. Selected bond dis-
Preparation
C6H4)]}]n (1a).
of
A
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-
pressure tube containing 2,3,4-
ꢀ
˚
tances (A) and angles ( ): Pd(1)–N(1) 2.012(2), Pd(1)–C(1) 2.021(3),
Pd(1)–O(4) 2.098(2), Pd(1)–P(1) 2.2624(8), C(1)–C(6) 1.426(4), C(6)–
C(7) 1.446(5), N(1)–C(7) 1.278(4), N(1)–C(8) 1.414(4), C(8)–C(13)
1.415(4), O(4)–C(13) 1.321(4); N(1)–Pd(1)–C(1) 81.75(11), N(1)–
Pd(1)–O(4) 80.90(9), C(1)–Pd(1)–O(4) 162.65(10), N(1)–Pd(1)–P(1)
177.35(7), C(1)–Pd(1)–P(1) 99.44(9), O(4)–Pd(1)–P(1) 97.91(6).
(MeO)3C6H2C(H)=NC6H4OH (0.652 g, 2.26 mmol), palla-
dium acetate (0.510 g, 22.7 mmol) and 20 cm3 of dry toluene
was sealed under argon. The resulting mixture was heated at
60 ꢀC for 24 h. After cooling to room temperature, the solution
was filtered through Celite to remove the small amount of
black palladium formed. The solvent was removed under
vacuum to give a red oil, which was chromatographed on a
column packed with silica gel. Elution with dichloro-
methane–ethanol (0.4%) afforded a red oil after solvent
removal, which was recrystallized from dichloromethane–hex-
ane to give the desired product as a red solid. Yield 83%. Anal.
found: C, 48.5; H, 3.8; N, 3.4; C64H60N4O16Pd4 (based on a
tetranuclear fragment) requires C, 49.1; H, 3.8; N, 3.6%. IR
(cmꢁ1): n(C=N), 1589sh, m. 13C-{1H} NMR (50.28 MHz,
CDCl3): d 155.0 (C=N);137.1, 136.8, 134.9 (C1, C3, C7);
155.3, 152.6, 151.0 (C2, C4, C6); 111.2 (C5); 116.9 (C8);
123.5 (C9); 128.9 (C10); 114.4 (C11); 167.3 (C12); 61.7, 60.6,
55.8 (OCH3). FAB-MS: m/z 1566 [M]+; 391 [M/4]+.
˚
The Pd–N(1) bond distance of 2.012(2) A is within the value
expected based on the sum of the covalent radii38 for palla-
2
dium (1.31 A) and sp nitrogen (0.7 A) and similar to other dis-
˚
˚
tances reported previously.16,17,39 The Pd–C(1) [2.021(3) A]
˚
˚
and Pd(1)–P(1) [2.2624(8) A] bond distances, somewhat
shorter than the predicted values,38 are within the range found
earlier for related complexes.16,17 The Pd–O(1) bond distance
˚
˚
[2.098(2) A] is longer than the predicted value of 1.97 A, but
analogous to Pd–O bond distances reported in the litera-
tue,40–42 and reflects the trans influence of the aryl carbon
atom. The sum of the angles about the palladium atom is ca.
360ꢀ (359.99ꢀ), with the only noteworthy deviations being the
somewhat reduced N(1)–Pd(1)–C(1) and N(1)–Pd(1)–O(1)
bond angles of 81.75(11) and 80.90(9)ꢀ, respectively, as a con-
sequence of chelation.
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H3)]}]n
(1b).
Compound 1b was prepared similarly and obtained as a red
solid. Yield 80%. Anal. found: C, 50.4; H, 4.2; N, 3.3;
C68H68N4O16Pd4 (based on a tetranuclear fragment) requires
C, 50.3; H, 4.2; N, 3.4%. IR (cmꢁ1): n(C=N), 1572s. 13C-
{1H} NMR (50.28 MHz, CDCl3): d 154.3 (C=N); 137.2,
136.4, 135.0 (C1, C3, C7); 155.1, 152.6, 151.9 (C2, C4, C6);
111.1 (C5); 123.1 (C8); 126.0 (C9); 129.8 (C10); 114.6 (C11);
165.3 (C12); 61.6, 60.8, 55.5 (OCH3). FAB-MS: m/z 1623
[MH]+; 406 [(M/4)H]+.
A characteristic of the coordinated ligand is the shortening
of the O(4)–C(13) bond distance as compared to values
reported previously for uncoordinated phenols43 [1.321(4) vs.
˚
1.411(5) A in N-(2-hydroxyphenyl)-2-hydroxyaniline].
Experimental
General procedures
Solvents were purified by standard methods.44 Chemicals were
reagent grade. The phosphines PPh3 , Ph2PCH2PPh2 (dppm),
Preparation of [Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]}-
(PPh3)] (2a). PPh3 (16 mg, 0.061 mmol) was added to a suspen-
sion of 1a (24 mg, 0.015 mmol) in acetone (15 cm3). The
mixture was stirred for 12 h and the solvent removed to give
a violet solid which was recrystallized from acetone–hexane.
Yield 67%. Anal. found: C, 62.1; H, 4.5; N, 2.0;
C34H30NO4PPd requires C, 62.4; H, 4.6; N, 2.1%. IR (cmꢁ1):
n(C=N), 1571s. FAB-MS: m/z 653 [M]+.
Ph2P(CH2)3PPh2
(dppp),
Ph2P(CH2)4PPh2
(dppb),
Ph2P(CH2)5PPh2 (dpppe) and Ph2PC5H4FeC5H4PPh2 (dppf)
were purchased from Aldrich-Chemie. Microanalyses were
carried out using a Carlo Erba Model 1108 elemental analyzer.
IR spectra were recorded from Nujol mulls or KBr discs on
Perkin-Elmer 1330 and Mattson spectrophotometers. NMR
spectra were obtained from CDCl3 solutions and referenced
to SiMe4 (1H, 13C-{1H}) or 85% H3PO4 (31P-{1H}) and were
recorded on a Bruker AC-200F spectrometer. All chemical
shifts are reported downfield from the standards. The FAB
mass spectra were recorded using a Quatro mass spectrometer
with a Cs ion gun; 3-nitrobenzyl alcohol was used as the
matrix.
Compounds 3a–7a were obtained following a similar proce-
dure, but using a 1 : 2 complex 1a : diphosphine molar
ratio, and obtained as red (3a, 5a) or violet (4a, 6a, 7a) solids.
[{Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]}}2(l-PPh2CH2-
PPh2)] (3a). Yield 94%. Anal. found: C, 58.1; H, 4.4; N, 2.3;
C57H52N2O8P2Pd2 requires C, 58.6; H, 4.5; N, 2.4%. IR
(cmꢁ1): n(C=N), 1573s. 13C-{1H} NMR (50.28 MHz, CDCl3):
d 153.3 (d, C=N, JCP ¼ 4.2); 139.4, 137.7, 136.5 (d, C1, C3,
C7, JCP ¼ 2.1); 154.3 (d, JCP ¼ 3.5), 153.7 (d, JCP ¼ 7.8),
152.3 (C2, C4, C6); 117.3 (d, C5, JCP ¼ 8.5); 115.6 (C8);
120.9 (C9); 130.6 (C10); 113.6 (C11); 172.3 (d, C12, JCP ¼ 3.5);
3.5); 61.7, 60.6, 55.2 (OCH3); P-phenyl: 135.4 [d, Co,
Syntheses
Preparation of 2,3,4-(MeO)3C6H2C(H)=N[2-(OH)C6H4] (a).
2,3,4-(MeO)3C6H2C(=O)H (0.683 g, 3.48 mmol) was added to
a solution of 2-aminophenol (0.380 g, 3.48 mmol) in 50 cm3 of
dry chloroform. The solution was heated under reflux in a
New J. Chem., 2002, 26, 398–404
401

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Table 1 31Pa and 1Hb -NMR data for all the compounds
31P
Aromatic
Others
a
7.90 [d, 1H, H6, 8.8c ]
8.98 [s, 1H, Hd ]
6.78 [d, 1H, H5, 8.8c ]
8.76 [s, 1H, –OHe ]
4.00 [s, 3H, OMe]
3.93 [s, 3H, OMe]
3.91 [s, 3H, OMe]
7.30 [dd, 1H, H8, 7.8c , 1.5f ]
6.91 [dt, 1H, H9, 7.8c , 1.5f ]
7.18 [dt, 1H, H10, 7.8c , 1.5f ]
7.01 [dd, 1H, H11, 7.8c , 1.5f ]
5.67 [s, 1H, H5]
6.62 [dd, 1H, H8, 7.6c , 1.5f ]
6.37 [dt, 1H, H9, 7.5c , 1.5f ]
6.91 [dt, 1H, H10, 7.5c , 1.5f ]
7.44 [d, 1H, H11, 7.6c , 1.5f ]
5.51 [d, 1H, H5, 3.9g ]
7.11 [dd, 1H, H8, 7.6c , 1.5f ]
6.37 [t, 1H, H9, 7.3c ]
6.91 [td, 1H, H10, 7.8c , 1.5d ]
6.52 [dd 1H, H11, 7.6c , 0.9f ]
5.39 [d, 1H, H5, 3.9g ]
7.10 [dd, 1H, H8, 7.6c , 1.5d ]
6.41 [t, 1H, H9, 7.6c ]
6.98 [td, 1H, H10, 7.8c , 1.5f ]
6.52 [dd 1H, H11, 7.6c , 1.5f ]
5.45 [d, 1H, H5, 3.9g ]
7.13 [dd, 1H, H8, 7.6c , 1.5f ]
6.41 [t, 1H, H9, 7.6c ]
1a
7.57 [s, 1H, Hd ]
4.02 [s, 3H, OMe]
3.82 [s, 3H, OMe]
3.51 [s, 3H, OMe]
2a
34.3
26.1
27.7
8.17 [d, 1H, Hd , 10.2g ]
3.96 [s, 3H, OMe]
3.73 [s, 3H, OMe]
2.92 [s, 3H, OMe]
3ad
8.11 [d, 1H, Hd , 10.2g ]
3.93 [s, 3H, OMe]
3.69 [s, 3H, OMe]
2.90 [s, 3H, OMeh ]
4a
8.12 [d, 1H, Hd , 10.7g ]
3.93 [s, 3H, OMe]
3.64 [s, 3H, OMe]
2.96 [s, 3H, OMeh ]
6.95 [td, 1H, H10, 7.8c , 1.5f ]
6.55 [dd 1H, H11, 7.6c , 0.9f ]
5.51 [d, 1H, H5, 3.9g ]
7.09 [d, 1H, H8, 7.6c ]
6.86 [t, 1H, H10, 7.8c ]
5a
6a
29.9
29.8
8.11 [d, 1H, Hd , 10.7g ]
3.92 [s, 3H, OMe]
3.70 [s, 3H, OMe]
2.98 [s, 3H, OMeh ]
8.12 [d, 1H, Hd , 10.3g ]
3.93 [s, 3H, OMe]
3.69 [s, 3H, OMe]
2.98 [s, 3H, OMeh ]
6.34 [m, 2H, H9, H11
]
5.49 [d, 1H, H5, 3.9g ]
7.10 [dd, 1H, H8, 7.8c , 1.5f ]
6.36 [t, 1H, H9, 7.6c ]
6.88 [td, 1H, H10, 7.6c , 1.5f ]
6.44 [dd 1H, H11, 7.6c , 1.2f ]
5.44 [d, 1H, H5, 4.4g ]
7.14 [dd, 1H, H8, 7.6c , 1.5f ]
6.36 [t, 1H, H9, 7.6c ]
6.95 [td, 1H, H10, 7.6c , 1.5f ]
6.57 [dd 1H, H11, 7.6c ]
7.90 [d, 1H, H5, 8.8c ]
6.79 [d, 1H, H6, 8.8c ]
7.10 [s, 1H, H8]
7.00 [dd, 1H, H10, 8.3c , 1.5f ]
6.89 [d, 1H, H11, 8.3c ]
7ai
24.5
8.16 [d, 1H, Hd , 10.8g ]
3.96 [s, 3H, OMe]
3.73 [s, 3H, OMe]
2.88 [s, 3H, OMeh ]
b
8.95 [s, 1H, Hf ]
8.65 [s, 1H, –OHe ]
4.02 [s, 3H, OMe]
3.94 [s, 3H, OMe]
3.92 [s, 3H, OMe]
2.33 [s, 3H, Me]
1b
2b
3b
4b
5.67 [s, 1H, H5]
7.49 [s, 1H, Hd ]
6.41 [d, 1H, H8, 1.5f ]
6.72 [dd, 1H, H10, 8.3c , 1.5f ]
7.34 [d, 1H, H11, 8.3c ]
4.00 [s, 3H, OMe]
3.83 [s, 3H, OMe]
3.48 [s, 3H, OMe]
2.11 [s, 3H, Me]
8.12 [d, 1H, Hd , 10.7g ]
3.96 [s, 3H, OMe]
3.72 [s, 3H, OMe]
2.92 [s, 3H, OMeh ]
2.17 [s, 3H, Me]
8.07 [d, 1H, Hd , 10.7g ]
3.93 [s, 3H, OMe]
3.64 [s, 3H, OMe]
2.96 [s, 3H, OMeh ]
2.21 [s, 3H, Me]
8.07 [d, 1H, Hd , 10.7g ]
3.93 [s, 3H, OMe]
3.70 [s, 3H, OMe]
2.98 [s, 3H, OMeh ]
2.18 [s, 3H, Me]
34.1
27.6
29.8
5.50 [d, 1H, H5, 3.9g ]
6.89 [s, 1H, H8]
6.72 [dd, 1H, H10, 8.3c , 2.2f ]
6.42 [d, 1H, H11, 8.3c ]
5.94 [s, 1H, H5, 4g ]
6.91 [s, 1H, H8,]
6.78 [d, 1H, H10, 7.8c ]
6.46 [d, 1H, H11, 7.8c ]
5.50 [s, 1H, H5, 4g ]
6.88 [s, 1H, H8,]
6.69 [dd, 1H, H10, 8.3c , 1.5f ]
6.27 [d, 1H, H11, 8.3c ]
402
New J. Chem., 2002, 26, 398–404

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Table 1 (continued)
31P
Aromatic
Others
5bi
24.4
5.44 [s, 1H, H5, 4.0g ]
6.93 [s, 1H, H8]
6.77 [dd, 1H, H10, 8.3c , 2.0f ]
6.48 [d, 1H, H11, 8.3c ]
8.11 [d, 1H, Hd , 11.2g ]
3.96 [s, 3H, OMe]
3.73 [s, 3H, OMe]
2.88 [s, 3H, OMeh ]
2.19 [s, 3H, Me]
a
In CDCl3 , unless otherwise stated. Measured at 80.9 MHz (ca. ꢂ20 ꢀC); chemical shifts (d) in ppm (ꢂ0.1) to high frequency of 85% H3PO4 . b In
CDCl3 . Measured at 200 MHz (ca. ꢂ20 ꢀC); chemical shifts (d) in ppm (ꢂ0.01) to high frequency of SiMe4 . Coupling constants in Hz. s, singlet; d,
doublet; dd, doublet of doublets; t, triplet; dt, doublet of triplets; m, multiplet; br, broad. c JHH/Hz. d PCH2P dH 4.1. e Resonance taken from a
3
spectrum recorded in DMSO-d6. f JHH/Hz. g JPH/Hz. h C4-(OMe). i CHFerrocene : dH 5.26 [br, 2H], 4.25 [br, 2H] for compound 7a; dH 5.43 [br,
2H], 4.24 [br, 2H] for compound 5b.
4
JCP ¼ 14.2]; 128.2 [d, Cm, JCP ¼ 10.6]; 131.0 (Cp); 129.4 [d, Ci ,
JCP ¼ 46.1 Hz]. FAB-MS: m/z 1168 [MH]+; 882 [M ꢁ L]+,
776 [M ꢁ L ꢁ Pd]+.
60.0; H, 4.7; N, 2.1; C61H60N2O8P2Pd2 requires C, 59.9; H,
4.9; N, 2.3%. IR (cmꢁ1): n(C=N), 1572s. FAB-MS: m/z 1225
[M]+; 813 [MH ꢁ L ꢁ Pd]+; 638 [M ꢁ L ꢁ Pd ꢁ
P(C6H5)2]+ ; 406 [MH ꢁ L ꢁ Pd ꢁ dppp]+.
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]})2(l-PPh2(CH2)3-
PPh2)] (4a). Yield 92%. Anal. found: C, 59.5; H, 4.6; N, 2.1;
C59H56N2O8P2Pd2 requires C, 59.3; H, 4.7; N, 2.3%. IR
(cmꢁ1): n(C=N), 1572s. FAB-MS: m/z 1197 [MH]+; 776
[M ꢁ L ꢁ Pd]+; 391 [M ꢁ L ꢁ Pd ꢁ dppp]+.
Preparation of [(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-
MeC6H3]})2(l-PPh2(CH2)4PPh2)] (4b). PPh2(CH2)4PPh2 (9
mg, 0.021 mmol) was added to a suspension of 1b (17.2 mg,
0.042 mmol) in dichloromethane (15 cm3). The mixture was
stirred for 12 h and the solvent removed to give a violet solid
which was recrystallized from dichloromethane–hexane. Yield
34%. Anal. found: C, 59.8; H, 4.9; N, 2.2; C62H62N2O8P2Pd2
requires C, 60.1; H, 5.0; N, 2.3%. IR (cmꢁ1): n(C=N), 1572s.
FAB-MS: m/z 1238 [M]+; 832 [MH ꢁ L ꢁ Pd]+; 647 [M ꢁ
L ꢁ Pd ꢁ P(C6H5)2]+.
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]})2(l-PPh2(CH2)4-
PPh2)] (5a). Yield 68%. Anal. found: C, 59.6; H, 4.8; N, 2.2;
C60H58N2O8P2Pd2 requires C, 59.6; H, 4.8; N, 2.3%. IR
(cmꢁ1): n(C=N), 1573s. 13C-{1H} NMR (50.28 MHz, CDCl3):
d 153.4 (d, C=N, JCP ¼ 4.2); 139.7, 137.8, 135.9 (d, C1, C3,
C7, JCP ¼ 2.1); 154.4 (d, JCP ¼ 3.5), 153.2 (d, JCP ¼ 8.5),
152.5 (C2, C4, C6); 117.3 (d, C5, JCP ¼ 9.2); 115.5 (C8);
121.1 (C9); 130.6 (C10); 113.5 (C11); 173.3 (d, C12, JCP ¼ 3.5);
3.5); 61.7, 60.6, 55.2 (OCH3); P-phenyl: 134.0 (d, Co,
JCP ¼ 12.1); 128.6 (d, Cm , JCP ¼ 10.6); 130.9 (d, Cp ,
JCP ¼ 2.1); 130.2 (d, Ci , JCP ¼ 44.7); P(CH2)4P: 27.1 (d,
PCH2CH2–, JCP ¼ 28.4); 26.0 (d, PCH2CH2–, JCP ¼ 14.9
Hz). FAB-MS: m/z 1210 [M]+.
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H3]})2(l-PPh2-
C5H4FeC5H4PPh2)] (5b). Compound 5b was prepared simi-
larly and obtained as a violet solid. Yield 14%. Anal. found:
C, 59.0; H, 4.4; N, 2.1; C68H62N2O8P2FePd2 requires C,
59.3; H, 4.4; N, 2.1%. IR (cmꢁ1): n(C=N), 1571s. FAB-MS:
m/z 1366 [M]+; 944 [MH ꢁ L ꢁ Pd]+; 710 [M ꢁ L ꢁ Pd ꢁ
P(C6H5)2 ꢁ C5H4]+; 654 [M ꢁ L ꢁ Pd ꢁ P(C6H5)2 ꢁ C5H4
ꢁ Fe]+.
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]})2(l-PPh2(CH2)5-
PPh2)] (6a). Yield 57%. Anal. found: C, 60.2; H, 4.8; N, 2.1;
C61H60N2O8P2Pd2 requires C, 59.9; H, 4.9; N, 2.3%. IR
(cmꢁ1): n(C=N), 1571s. FAB-MS: m/z 1225 [MH]+; 391
[M ꢁ L ꢁ Pd ꢁ dppp]+.
Single-crystal X-ray diffraction analysis
Three-dimensional, room temperature X-ray data were col-
lected in the range 3.0 < 2y < 56.6ꢀ on a Siemens SMART
CCD diffractometer by the omega scan method. Reflections
were measured from a hemisphere of data collected of frames
each covering 0.3ꢀ in o. Of the 20437 reflections measured, all
of which were corrected for Lorentz and polarisation effects
and for absorption using a semi-empirical correction based
on symmetry-equivalent and repeated reflections (max, min
transmissions 0.87, 0.71), 4859 independent reflections
exceeded the significance level |F|/s(|F|) > 4.0 The structure
was 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 0.0401 (wR2 ¼ 0.0922 for all 7230 unique data),
with allowance for the thermal anisotropy of all non-hydrogen
atoms. Minimum and maximum final electron density ꢁ0.688
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)C6H4]})2(l-PPh2C5H4-
FeC5H4PPh2)] (7a). Yield 34%. Anal. found: C, 59.6; H, 4.3;
N, 2.1; C66H58N2O8P2FePd2 requires C, 59.2; H, 4.4; N,
2.1%. IR (cmꢁ1): n(C=N), 1573s. FAB-MS: m/z 1332 [M]+;
944 [M ꢁ L ꢁ Pd]+; 696 [M ꢁ L ꢁ Pd ꢁ P(C6H5)2 ꢁ C5H4)]+.
Preparation
of
[Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-
MeC6H3]}(PPh3)] (2b). A large excess of PPh3 (25 mg, 0.095
mmol) was added to a suspension of 1b (19 mg, 0.012 mmol)
in dichloromethane (15 cm3). The mixture was stirred for 24
h. The solvent was removed under vacuum to give a violet
oil, which was chromatographed on a column packed with
silica gel. Elution with dichloromethane afforded a violet oil
after solvent removal, which was recrystallized from dichloro-
methane–hexane to give the desired product as a violet solid.
Yield 80%. Anal. found: C, 62.7; H, 4.8; N, 2.0;
C35H32NO4PPd requires C, 62.9; H, 4.8; N, 2.1%. IR (cmꢁ1):
n(C=N), 1572s.
and 0.439 e Aꢁ3. The structure solution and refinement were
˚
carried out using the program package SHELX-97.45
Crystal data: C34H30NO4Pd, M ¼ 653.96, monoclinic,
˚
A,
a ¼ 27.408(1),
b ¼ 12.013(1)
c ¼ 18.325(1)
3
ꢀ
˚
b ¼ 103.171(8) , U ¼ 5875.0(5) A , Z ¼ 8, Dc ¼ 1.479 g
cmꢁ3, space group C2/c (no. 15), m(Mo-Ka) ¼ 0.726 mmꢁ1
,
[(Pd{2,3,4-(MeO)3C6HC(H)=N[2-(O)-4-MeC6H3]})2(l-PPh2-
(CH2)3PPh2)] (3b). Compound 3b was obtained following a
similar procedure as violet solid, but using a 1 : 2 complex
T ¼ 273 K.
CCDC reference number 177246. See http://www.rsc.org/
suppdata/nj/b1/b110197h/ for crystallographic data in CIF
or other electronic format.
1b
: diphosphine molar ratio. Yield 36%. Anal. found: C,
New J. Chem., 2002, 26, 398–404
403

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´
21 A. Fernandez, P. Urıa, J. J. Fernandez, M. Lopez-Torres, A.
Suarez, D. Vazquez-Garcıa, M. T. Pereira and J. M. Vila, J. Orga-
´
´
´
Acknowledgements
´
´
´
nomet. Chem., 2001, 620, 8.
22 E. Steiner and F. A. L. L’Eplattenier, Helv. Chim. Acta, 1978, 61,
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23 A. K. Mahapatra, D. Bandyopadhyay, P. Bandyopadhyay and A.
Chakravorty, Inorg. Chem., 1986, 25, 2214.
´
We thank the Ministerio de Educacion y Cultura (proyecto
PB98–0638-C02–01/02), the Xunta de Galicia (proyecto
PGIDT99PXI20907B) and the Universidad de la Corun˜a for
financial support.
´
24 J. M. Vila, M. T. Pereira, J. M. Ortigueira, M. Lopez-Torres, D.
Lata, M. Gran˜a, A. Suarez, J. J. Fernandez and A. Fernandez, J.
´
´
´
Chem. Soc., Dalton Trans., 1999, 4193.
25 D. Va´zquez-Garc´ıa, A. Ferna´ndez, J. J. Ferna´ndez, M. Lo´pez-
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