Mixed triply and doubly bridged dinuclear palladium(II) cyclometalated compounds. Crystal and molecular structures

Article abstract of DOI:10.1021/om0201866

Crystal and molecular structures of cyclometalated compounds were discussed. Nuclear magnetic resonance spectroscopy (NMR) was used. Results showed that flexibility due to methylenes brings metal centers close together to bridge the palladium atoms.

Full text of DOI:10.1021/om0201866

3628
Organometallics 2002, 21, 3628-3636
Mixed Tr ip ly a n d Dou bly Br id ged Din u clea r
P a lla d iu m (II) Cyclom eta la ted Com p ou n d s. Cr ysta l a n d
Molecu la r Str u ctu r es of
[1,3-{P d [2,3,4-(MeO)3C6HC(H)dNCH2](µ-O2CMe)}2C6H4]
a n d [1,4-{P d [2,3,4-
(MeO)3C6HC(H)dNCH2](Cl)}2C6H4(µ-P h 2P (CH2)3P P h 2)]
Margarita Lo´pez-Torres,*,† Pilar J uanatey,† J esu´s J . Ferna´ndez,†
Alberto Ferna´ndez,† Antonio Sua´rez,† Roberto Mosteiro,†
J uan. M. Ortigueira,‡ and J ose´ M. Vila*,‡
Departamento de Quı´mica Fundamental, Universidad de La Corun˜a, E-15071 La Corun˜a,
Spain, and Departamento de Quı´mica Inorga´nica, Universidad de Santiago de Compostela,
E-15782 Santiago de Compostela, Spain
Received March 5, 2002
Reaction of the Schiff base ligand 1,3-[2,3,4-(MeO)3C6H2C(H)dNCH2]2C6H4 (1) with
palladium(II) acetate in toluene gave the doubly cyclometalated complex [1,3-{Pd[2,3,4-
(MeO)3C6HC(H)dNCH2](µ-O2CMe)}2C6H4] (2), in which the two palladium atoms are
intramolecularly bonded by acetato bridging ligands. The crystal structure of 2 is given.
Reaction of the Schiff base ligand 1,4-[2,3,4-(MeO)3C6H2C(H)dNCH2]2C6H4 (6) with palla-
dium(II) acetate under similar reaction conditions yielded the cyclometalated complex [1,4-
{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](µ-O2CMe)}2C6H4]n (7), probably of polymeric nature.
Reaction of 2 and 7 with aqueous sodium chloride gave the chloro-bridged complexes [1,3-
{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](µ-Cl)}2C6H4]2 (3) and [1,4-{Pd[2,3,4-(MeO)3C6HC(H)d
NCH2](µ-Cl)}2C6H4]2 (8), respectively, after a metathesis reaction. Treatment of complex 2
with Ph2P(CH2)3PPh2 (dppp) in a 1:1 molar ratio gave the dinuclear cyclometalated complex
[1,3-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](OAc)}2C6H4(µ-Ph2P(CH2)3PPh2)] (4), in which the
metal atoms are bonded by the diphosphine ligand. Treatment of the chloro-bridged complex
3 with dppp in a 1:2 molar ratio gave the dinuclear cyclometalated complex [1,3-{Pd[2,3,4-
(MeO)3C6HC(H)dNCH2](Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)] (5), with the palladium atoms in-
tramolecularly bridged by the diphosphine. The complex showed a fluxional behavior in
solution, with the cyclometalated moieties adopting a cis/trans arrangement. Reaction of
the chloro-bridged complex 8 with dppp in a 1:2 molar ratio yielded the mixture of complexes
[1,4-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)] (9) and [1,4-{Pd[2,3,4-
(MeO)3C6HC(H)dNCH2](Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)]2 (10), of which only 9 was isolated
pure. Compound 9 showed a structure and solution behavior similar to those of 5; however,
the structure of 10 was not unambiguously established. The crystal structure of 9 is also
reported.
In tr od u ction
been extensively reviewed.5-9 More recently we have
reported their use in promoting new coordination en-
vironments.10,11
In the majority of cases, cyclometalation involves the
coordination of one metal atom per organic ligand;
however, a relatively large number of examples with
Cyclometalated compounds have aroused great inter-
est due to the many applications they present in, for
example, organic and organometallic chemistry1,2 or in
the synthesis of bioactive compounds,3,4 and they have
* To whom correspondence should be addressed. Fax: M.L.-T., +34/
981-167065; J.M.V., +34/981-595012. E-mail: M.L.-T., qimarga@udc.es;
J .M.V., qideport@usc.es.
(5) Omae, I. In Organometallic Intramolecular-Coordination Com-
pounds; Elsevier Science: Amsterdam, New York, 1986.
(6) V. V. Dunina, O. A. Zalevskaya, V. M. Potapov, Russ. Chem. Rev.
(Engl. Transl.) 1984, 571, 250.
† Universidad de La Corun˜a.
‡ Universidad de Santiago de Compostela.
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nometallics 1993, 12, 1386.
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10.1021/om0201866 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 07/25/2002

Doubly and Triply Bridged PdII Compounds
Organometallics, Vol. 21, No. 17, 2002 3629
2
flexible to bring near both metal centers (III),13 hence
promoting intramolecular bridging.
In past years we have been interested in the double
cyclometalation of Schiff base ligands derived from 1,4-
phenylenediamine.35,36 In these complexes, the relative
position of the metal atoms did not allow the formation
of the intramolecular bridge. Therefore, with this in
mind we designed the more flexible ligands 1,3-[2,3,4-
(MeO)3C6H2C(H)dNCH2]2C6H4 (1) and 1,4-[2,3,4-(MeO)3-
C6H2C(H)dNCH2]2C6H4 (6) to achieve intramolecular
coordination of the metal atoms via a second ligand.
Reaction of 1 with palladium(II) acetate gave the doubly
cyclometalated complex 2, in which both palladium
atoms were intramolecularly bonded by the acetato
bridging ligands, which was characterized crystallo-
graphically. However, the reaction of 6 with palladium-
(II) acetate under analogous conditions also gave a
doubly cyclometalated complex, but probably of poly-
meric nature. We also report the reactivity of the
complexes with the tertiary diphosphine Ph2P(CH2)3-
PPh2 (dppp) which revealed the tendency of the com-
plexes to undergo intramolecular coordination. The
X-ray crystal structure of one of these complexes is also
described.
F igu r e 1.
Resu lts a n d Discu ssion
doubly cyclometalated ligands are known.12-33 Much
less common are those compounds in which the two
metal atoms bonded to the organic moiety are also
intramolecularly linked through a second ligand. Since
the first compound of this kind was reported by Trofi-
menko (I; see Figure 1),24 little work has been done on
this subject. With the purpose of promoting formation
of the intramolecular bridge the geometric character-
istics of the cyclometalated ligand must be carefully
selected. Thus, the ligand may be either rigid enough
to hold the metalated atoms close together and induce
intramolecular coordination (I and II)24,34 or sufficiently
For the convenience of the reader the compounds and
reactions are shown in Schemes 1 and 2. The compounds
described in this paper were characterized by elemental
1
analysis (C, H, N), IR spectroscopy, H, 31P{1H}, and
(in part) 13C{1H} NMR spectroscopy, and FAB mass
spectrometry (data are given in the Experimental Sec-
tion).
Reaction of the Schiff base ligand 1,3-[2,3,4-(MeO)3C6-
H2C(H)dNCH2]2C6H4 (1) with palladium(II) acetate in
toluene gave the doubly cyclometalated complex [1,3-
{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](µ-O2CMe)}2C6H4] (2),
which was fully characterized. The IR spectrum of 2
showed the ν(CdN) stretch at 1600 cm-1, shifted to
lower wavenumbers (as compared to the free ligand) due
to N-coordination of the imine.37,38 The IR spectrum also
showed strong bands assigned to the symmetric and
asymmetric ν(COO) vibrations, in agreement with those
expected for bridging acetate ligands39 (see Experimen-
tal Section). The resonance corresponding to the
(12) Selvakumar, K.; Vancheesan, S. Polyhedron 1995, 14, 2091.
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1
HCdN proton in the H NMR spectrum was shifted to
lower frequency consequent upon coordination of the
imine group to the palladium atom via the lone pair of
the nitrogen atom.40 The assignment of the aromatic
proton resonances unequivocally showed that metala-
tion had taken place at the C6 carbon atoms. The
presence of only one set of signals for the HCdN and
aromatic protons was indicative of the symmetric nature
(26) Chakladar, S.; Paul, P.; Mukherjee, A. K.; Dutta, S. K.; Nanda,
K. K.; Podder, D.; Nag, K. J . Chem. Soc., Dalton Trans. 1992, 3119.
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3630 Organometallics, Vol. 21, No. 17, 2002
Lo´pez-Torres et al.
Sch em e 1a
a
Legend: (i) Pd(AcO)2 (toluene); (ii) NaCl (acetone/water); (iii) dppp (chloroform).
of the complex, showing that double metalation had
taken place. A noticeable feature of the 1H NMR
spectrum was the low-field shift of the H8 resonance
(as compared to the free ligand 1) by 1.1 ppm. We
believe this is due to approximation of the deshielding
zone of the HCdN groups to the H8 proton compelled
resonances as proof of a syn geometry,27 imposed by
linkage of the C6H4(CH2)2 group to both nitrogen imine
atoms. The 13C{1H} NMR spectrum of 2 showed the
high-frequency shift of the resonances corresponding to
the HCdN, C6, and C1 carbons, confirming that meta-
lation had occurred.47
1
by the bridging acetate ligands. The H NMR of ligand
The reaction of the Schiff base ligand 1,4-[2,3,4-
(MeO)3C6H2C(H)dNCH2]2C6H4 (6) with palladium(II)
acetate under similar reaction conditions yielded the
complex [1,4-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](µ-O2-
CMe)}2C6H4]n (7). The IR spectrum showed features
similar to those described for complex 2. Likewise, the
1H NMR spectrum showed the low-frequency shift of the
singlet resonance corresponding to the HCdN protons
and the absence of the H6 signal, indicating double
metalation had occurred. This was confirmed by the
shift toward higher frequency of the HCdN, C6, and
C1 resonances in the 13C{1H} NMR spectrum. However,
two broad signals at δ 4.39 and 3.65 were assigned to
the CH2 protons, and the 1H NMR spectrum showed
only one resonance for the MeCOO protons, δ 2.08; the
13C{1H} NMR spectrum showed two signals for the
MeCOO and MeCOO carbons, δ 24.3 and 181.0, respec-
tively, as expected for an anti conformation. These data
preclude a dinuclear formulation analogous to the one
described for complex 2, which would require a syn
arrangement. A tetranuclear formulation, similar to
those reported for other doubly cyclometalated com-
1 showed a singlet resonance for the four CH2 protons.
However, two doublet signals (δ 5.05, 4.55; J (HH) ) 15.6
Hz) were assigned to the diastereotopic CH2 protons in
1
the H NMR spectrum of 2. This was due to the lower
symmetry of 2. The acetato-bridged complexes showed
the characteristic open-book geometry,41-46 for which
two different dispositions are possible, syn and anti
(Figure 2), with equivalent (anti) and nonequivalent
(syn) MeCOO groups, that give rise to one and two
1
MeCOO signals in the H NMR spectrum, respectively.
1
The H NMR spectrum of 2 showed two singlets at δ
2.23 and 1.26 assigned to the nonequivalent MeCOO
(41) Teijido, B.; Ferna´ndez, A.; Lo´pez-Torres, M.; Castro-J uiz, S.;
Sua´rez, A.; Ortigueira, J . M.; Vila, J . M.; Ferna´ndez. J . J . J . Organomet.
Chem. 2000, 598, 71.
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T.; Gayoso, M. Acta Crystallogr., Sect. C 1986, 42, 1136.
(43) Gayoso, M.; Alonso, M.; Vila, J . M.; Rivero, E. B.; Hiller, W.;
Strahle, J . Acta Crystallogr., Sect. C 1988, 44, 929.
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Mossmer, C.; Strahle, J . Z. Naturforsch., B 1993, 48, 906.
(45) Mosteiro, R.; Perille, E.; Ferna´ndez, A.; Lo´pez-Torres, M.; Vila,
J . M.; Sua´rez, A.; Ortigueira, J . M.; Pereira, M. T.; Ferna´ndez, J . J .
Appl. Organomet. Chem. 2000, 14, 634.
(46) Lousame, M.; Ferna´ndez, A.; Lo´pez-Torres, M.; Va´zquez-Garc´ıa,
D.; Vila, J . M.; Sua´rez, A.; Ortigueira, J . M.; Ferna´ndez, J . J . Eur. J .
Inorg. Chem. 2000, 2055.
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1997, 532, 171.

Doubly and Triply Bridged PdII Compounds
Organometallics, Vol. 21, No. 17, 2002 3631
2
Sch em e 2a
a
Legend: (i) Pd(AcO)2 (toluene); (ii) NaCl (acetone/water); (iii) dppp (chloroform).
and angles with estimated standard deviations are
shown in Table 2.
The crystal structure consists of discrete molecules
separated by van der Waals distances. The asymmetric
unit comprises two molecules with similar structures,
of which only one will be discussed.
The molecular structure consists of the doubly cyclo-
metalated Schiff base ligand 1 with the two metal
centers bridged by two acetato ligands and with the two
metalated phenyl rings in an open-book disposition.
Although a large number of crystal structures of di-
nuclear acetato-bridged cyclometalated complexes have
been reported, examples of a syn disposition remained
unknown. Each palladium atom is bonded, in a slightly
distorted square planar geometry, to one carbon atom
of the phenyl ring and one imine nitrogen atom of the
Schiff base ligand and to two oxygen atoms of the
bridging acetato ligands. The Pd(1)-Pd(2) bond distance
of 3.0748(5) Å is slightly longer than values reported
for related complexes41 and can be regarded as non-
bonding. The sum of angles around the palladium atoms
is approximately 360°. The angles between adjacent
atoms in the coordination sphere are close to the
F igu r e 2.
plexes,27 may also be rejected, because it would require
a relative syn disposition. Furthermore, the FAB mass
spectrum of 7 did not show peaks assignable to a
dinuclear or tetranuclear formulation; therefore, we
suggest the anti disposition should be formulated as a
polymeric or oligomeric species.
Cr ysta l Str u ctu r e of [1,3-{P d [2,3,4-(MeO)3C6HC-
(H)dNCH2](µ-O2CMe)}2C6H4] (2). Suitable crystals of
complex 2 were grown by slowly evaporating a n-
hexane/dichloromethane solution at room temperature.
The molecular structure is shown in Figure 3. Crystal
data are given in Table 1, and selected bond distances

3632 Organometallics, Vol. 21, No. 17, 2002
Lo´pez-Torres et al.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2
Pd(1)-C(1)
Pd(1)-N(1)
Pd(1)-O(7)
Pd(1)-O(8)
C(1)-C(6)
C(6)-C(10)
C(10)-N(1)
N(1)-C(11)
C(11)-C(12)
1.983(5)
2.031(4)
2.150(3)
2.048(3)
1.403(7)
1.448(7)
1.305(6)
1.467(6)
1.506(7)
Pd(2)-C(25)
Pd(2)-N(2)
Pd(2)-O(9)
Pd(2)-O(10)
C(25)-C(20)
C(20)-C(19)
C(19)-N(2)
N(2)-C(18)
C(18)-C(14)
1.967(4)
2.027(4)
2.160(3)
2.034(3)
1.399(6)
1.440(6)
1.295(6)
1.471(6)
1.490(7)
C(1)-Pd(1)-N(1)
C(1)-Pd(1)-O(8)
N(1)-Pd(1)-O(8)
C(1)-Pd(1)-O(7)
N(1)-Pd(1)-O(7)
O(8)-Pd(1)-O(7)
C(1)-C(6)-C(10)
C(6)-C(10)-N(1)
81.4(2) C(25)-Pd(2)-N(2)
91.9(2) C(25)-Pd(2)-O(10)
169.7(1) N(2)-Pd(2)-O(10)
175.1(2) C(25)-Pd(2)-O(9)
94.9(2) N(2)-Pd(2)-O(9)
91.3(1) O(10)-Pd(2)-O(9)
81.6(2)
91.6(2)
167.2(1)
177.7(2)
96.2(1)
90.7(1)
114.0(4) C(25)-C(20)-C(19) 114.1(4)
117.1(5) C(20)-C(19)-N(2)
C(10)-N(1)-C(11) 119.6(4) C(19)-N(2)-C(18)
N(1)-C(11)-C(12) 114.7(4) N(2)-C(18)-C(14)
117.4(4)
120.2(4)
111.5(4)
previously reported.41,45 The differing Pd(1)-O(8) and
Pd(1)-O(7) (2.048(3) and 2.150(3) Å, respectively) and
Pd(2)-O(10) and Pd(2)-O(9) (2.034(4) and 2.160(3) Å,
respectively) bond distances reflect the higher trans
influence of the aryl carbon as compared to the imine
nitrogen atom. The geometry about the palladium atoms
is planar (plane 1, Pd(1),C(1),N(1),O(7),O(8); plane 2,
Pd(2),C(25),N(2),O(9),O(10); rms ) 0.0478 and 0.0937
Å, respectively) and coplanar with the cyclometalated
rings (plane 3, Pd(1),C(1),C(6),C(10),N(1); plane 4, Pd-
(2),C(25),C(20),C(19),N(2); rms ) 0.0046 and 0.0139 Å,
respectively) (angles: plane 1/3 ) 3.8°; 2/4 ) 5.5°). The
angle between the coordination planes is 42.1°, consid-
erably larger than the values reported for acetato-
bridged complexes with anti geometry.41,45 This is
probably due to the geometrical constraint imposed by
the coordination of the palladium atoms to the same
Schiff base ligand.
The reactions of 2 and 7 with aqueous sodium chloride
gave the chloro-bridged complexes [1,3-{Pd[2,3,4-
(MeO)3C6HC(H)dNCH2](µ-Cl)}2C6H4]2 (3) and [1,4-{Pd-
[2,3,4-(MeO)3C6HC(H)dNCH2](µ-Cl)}2C6H4]2 (8), respec-
tively. The IR spectra of the complexes showed the
absence of the ν(COO) bands. The 1H NMR spectra
showed only one set of resonances for the imine and
phenyl protons, indicating double metalation of the
ligand. The CH2 resonances appeared as two broad
signals at δ 4.98, 4.67 and δ 4.96, 4.70 for complexes 3
and 8, respectively. The FAB mass spectra of both
complexes showed peaks at 1548 and 1513 amu whose
isotopic patterns were in agreement with the [M]+ and
[M - Cl]+ fragments, based on a tetranuclear formula-
tion, although the [M]+ peaks were of relatively low
intensity. Therefore, the data fit with the proposed
tetranuclear formulation, similar to that reported by us
for related doubly cyclometalated complexes.35
F igu r e 3. Molecular structure of [1,3-{Pd[2,3,4-(MeO)3-
C6H1C(H)dNCH2](µ-O2CMe)}2C6H4] (2), with the labeling
scheme. Only one of the two independent molecules is
shown. Hydrogen atoms have been omitted for clarity.
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p lexes 2
a n d 9
2
9
empirical formula
C
32H36N2O10Pd2
C
58H62N2O6Cl8P2Pd2
fw
T (K)
λ (Å)
cryst syst
space group
a (Å)
821.43
293(2)
1441.44
173(2)
0.710 73
orthorhombic
Pbcn
22.731(1)
22.896(1)
24.918(1)
12968(1)
16
0.710 73
orthorhombic
P212121
14.389(1)
18.384(1)
23.815(1)
6300(1)
4
b (Å)
c (Å)
V (Å3)
Z
µ (mm-1
)
1.169
0.80, 0.65
1.010
0.82, 0.72
max, min
transmissn
Fcalcd (g cm-3
)
1.683
1.26-28.49
68 271
1.520
2.40-28.30
44 226
θ range (deg)
no. of rflns
collected
no. of indep rflns
16 086 (Rint ) 0.074) 15 617 (Rint ) 0.039)
R1a
0.0494
0.1041
0.0366
wR2b
0.0776
abs structure
param
-0.02(2)
R1 ) ∑||Fo| - |Fc||/∑|Fo| (F > 4σ(F)). wR2 ) [∑[w(Fo2 - Fc2)2/
a
b
∑w(Fo2)2]1/2 (all data).
expected value of 90°; the most noticeable distortion
corresponds to the C(1)-Pd(1)-N(1) and C(25)-Pd(2)-
N(2) angles of 81.6(2) and 81.4(2)°, respectively, conse-
quent upon chelation. The Pd(1)-C(1) and Pd(2)-C(25)
bond distances of 1.983(5) and 1.967(4) Å, respectively,
are somewhat shorter than the values predicted from
their covalent radii48 but similar to values found ear-
lier.41,45 However, the Pd(1)-N(1) and Pd(2)-N(2) bond
lengths of 2.031(4) and 2.027(4) Å, respectively, are in
agreement with the value based on the sum of covalent
radii for nitrogen and palladium48 and similar to values
Reaction of complex 2 with Ph2P(CH2)3PPh2 (dppp)
in a 1:1 molar ratio gave the dinuclear cyclometalated
complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](OAc)}2-
C6H4(µ-Ph2P(CH2)3PPh2)] (4). The IR spectrum of 4
showed two strong bands at 1580 s and 1380 s cm-1
,
assigned to the νas(COO) and νs(COO) vibrations, in
agreement with those expected for monodentate acetate
1
ligands.39 The H NMR spectra showed coupling of the
HCdN and the H5 resonances to the phosphorus
nucleus (δ 8.46 and 5.72, J (HP) ) 7.3 and 5.4 Hz,
(48) Pauling. L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: New York, 1960.

Doubly and Triply Bridged PdII Compounds
Organometallics, Vol. 21, No. 17, 2002 3633
2
respectively), and in the 31P{1H} NMR spectrum, the
phosphorus resonance appeared as a singlet at δ 30.7,
in accordance with the symmetric nature of the complex.
These findings and the low-frequency shift of the
resonance assigned to the C4-OMe group, due to
shielding by a phenyl ring from the phosphine, were in
agreement with a phosphorus trans to nitrogen arrange-
ment.49-51 The resonances corresponding to the diaste-
reotopic CH2 protons (consequent upon the formation
of the intramolecular bridge) appeared at δ 5.08 and
4.46 as a doublet and a doublet of doublets, respectively,
the latter showing coupling to the phosphorus nucleus
(J (HP) ) 5.4 Hz). Only one signal, at δ 1.91, was
assigned to the MeCO2 acetate protons. The FAB mass
spectrum showed a set of peaks at 1173 amu assignable
to the [M - OAc]+ fragment. The conductivity measure-
ments carried out in dry acetonitrile have shown the
compound to be a nonelectrolyte.
Treatment of the chloro-bridged complex [1,3-{Pd-
[2,3,4-(MeO)3C6HC(H)dNCH2](µ-Cl)}2C6H4]2 (3) with
dppp in a 1:2 molar ratio gave the dinuclear cyclometa-
lated complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2]-
F igu r e 4.
the [M]+ and [M - Cl]+ fragments, respectively, whose
isotopic patterns were in agreement with the proposed
dinuclear formulation.
1
(Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)] (5). The IR and H NMR
spectra of the complex showed features similar to those
described for 4 (except for the absence of the acetato
ligands), with the most noticeable difference corre-
sponding to the absence of the CH2 resonances and the
low-field shift of the H8 signal (δ 8.29), which appeared
close to the position observed in the spectrum of the
acetato-bridged compound 2. However, the 1H NMR
spectrum recorded at 50 °C showed a broad resonance
at δ 5.20 assigned to the CH2 protons. Bearing this in
mind, we decided to record the spectra at lower tem-
peratures. This showed the progressive broadening and
splitting of the signals corresponding to the HCdN, H8,
H5, CH2, and C4-OMe resonances, indicating the
existence of two isomers at -50 °C. The HCdN and H5
signals (at δ 8.65, 8.48 and δ 5.87, 5.62, respectively)
showed coupling to the phosphorus nuclei. The CH2
resonances appeared as doublets at δ 6.05 and 5.93 and
at δ 4.30 as a multiplet. This assumption was confirmed
by the presence of two singlet signals at δ 33.2 and 32.6,
in the 31P{1H} NMR spectrum (-50 °C). The spectro-
scopic features of both isomers were similar and,
consequently, their structural features. Therefore, we
propose the equilibrium depicted in Figure 4, in which
the metalated moieties adopt alternatively a cis and
trans disposition. For compound 5 a relative proportion
of isomers of 1:1.5 was observed with a Tc value of 20
°C. The energy difference between both isomers was
Reaction of the chloro-bridged complex [1,4-{Pd[2,3,4-
(MeO)3C6HC(H)dNCH2](µ-Cl)}2C6H4]2 (8) with dppb in
a 1:2 molar ratio yielded the mixture of complexes
[1,4-{Pd[2,3,4-(MeO)3C6HC(H)dNCH2](Cl)}2C6H4(µ-Ph2-
P(CH2)3PPh2)] (9) and [1,4-{Pd[2,3,4-(MeO)3C6HC(H)d
NCH2](Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)]2 (10). Complex 9
was isolated from the mixture by column chromatogra-
phy (elution with dichloromethane/ethanol (1.2%)); how-
ever, we were unable to obtain complex 10 pure. A
mixture enriched in 10 (9:10 ) 0.25:1) was prepared
by column chromatography using dichloromethane/
1
ethanol (0.4%). The IR and H NMR spectra of 9 were
similar to those of 5, with the HCdN band shifted to
lower frequency and the HCdN and H5 resonances
coupled to the phosphorus nuclei. However, the 1H NMR
spectrum showed two broad resonances at δ 5.70, 4.57
assigned to the CH2 protons. NMR low-temperature
experiments were carried out with a chloroform solution
of 9. These suggested a behavior similar to that de-
1
scribed for complex 5. The H NMR spectrum at -50
°C showed the presence of two isomers. This was
confirmed by the 31P{1H} spectrum at the same tem-
perature, which showed the presence of two singlet
resonances at δ 33.4 and 32.9. In view of the similarity
shown by the spectra of 5 and 9, we propose a similar
structure and solution behavior for both complexes. For
compound 9 a relative proportion of isomers of 1:2.5 was
observed with a Tc value of 50 °C. The energy difference
between both isomers was 76.8 kJ mol-1. However, the
74.1 kJ mol-1
.
A similar equilibrium may be proposed for complex
1
4. However, the H NMR spectra did not change upon
1
structure of complex 10 is uncertain. The H NMR of
1
lowering the temperature. Although the H NMR data
10 showed the HCdN and H5 resonances at δ 8.19 and
5.73 (J (HP) ) 7.8 and 5.9 Hz), respectively. The signal
corresponding to the CH2 protons appeared as a some-
what broad singlet, at δ 5.13, due to the change in
symmetry (vide supra). The 31P{1H} NMR spectrum
showed only one singlet. In view of these results we
tentatively propose for complex 10 a tetranuclear struc-
ture similar to that reported by us for other doubly
cyclometalated complexes.10
do not exclude either one of the two possible cis or trans
geometries, we tentatively propose that the bulky
nature of the acetato ligand, as compared to chlorine,
hinders the cis disposition. The FAB mass spectrum of
5 showed peaks at 1186 and 1151 amu assignable to
(49) Bosque, R.; Granell, J .; Sales, J .; Fon-Bardia´, M.; Solans, X. J .
Organomet. Chem. 1994, 453, 147.
(50) Vila, J . M.; Gayoso, M.; Pereira, M. T.; Romar, A.; Ferna´ndez,
J . J .; Thornton-Pett, M. J . Organomet. Chem. 1991, 401, 385.
(51) Bosque, R.; Granell, J .; Sales, J .; Fon-Bardia´, M.; Solans, X.
Organometallics 1995, 14, 1393.
[1,4-{P d [2,3,4-(MeO)3C6HC(H)dNCH2](Cl)}2C6H4-
(µ-P h 2P (CH2)3P P h 2)] (9). Suitable crystals of complex

3634 Organometallics, Vol. 21, No. 17, 2002
Lo´pez-Torres et al.
Pd(2)-N(2) bond lengths of 2.089(3) and 2.095(3) Å,
respectively, show the high trans influence of the
phosphine phosphorus as compared to oxygen (Pd-N
distances of 2.031(4) and 2.027(4) Å for complex 2). The
Pd-P and Pd-Cl bond distances are also within the
expected values.53
The geometry about the palladium atoms is square
planar, slightly twisted toward tetrahedral (plane 1
Pd(1),C(6),N(1),Cl(1),P(1), rms ) 0.125 Å, maximum
deviation from the least-squares plane 0.169 Å for C(6);
plane 2 Pd(2),C(16),N(2),Cl(2),P(2), rms ) 0.144 Å,
maximum deviation from the least-squares plane 0.199
Å for C(16)).
The angle between the coordination planes (plane 1
and plane 2) is 49.7°, similar to that shown by complex
2. The two cyclometalated moieties, the central phenyl
ring (C(23)-C(28)), and the dppp phosphine define a
molecular box (Pd-Pd distance of 6.498(1) Å). However,
none of the dichloromethane solvent molecules were
located inside the cavity.
F igu r e 5. Molecular structure of [1,4-{Pd[2,3,4-(MeO)3C6-
HC(H)dNCH2](Cl)}2C6H4(µ-Ph2P(CH2)3PPh2)] (9), with the
labeling scheme. Hydrogen atoms and solvate molecules
have been omitted for clarity.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 9
Pd(1)-C(6)
Pd(1)-N(1)
Pd(1)-P(1)
Pd(1)-Cl(1)
C(6)-C(1)
2.025(4)
2.089(3)
2.2626(9)
2.369(1)
1.425(5)
1.435(6)
1.281(5)
1.455(5)
1.518(5)
Pd(2)-C(16)
Pd(2)-N(2)
Pd(2)-P(2)
Pd(2)-Cl(2)
C(16)-C(11)
C(11)-C(17)
C(17)-N(2)
N(2)-C(21)
C(21)-C(26)
2.016(3)
2.095(3)
2.2516(9)
2.377(1)
1.413(5)
1.435(5)
1.283(5)
1.450(5)
1.519(5)
Con clu sion s
We have shown that potentially [C,N,C,N] tetraden-
tate Schiff base ligands may be doubly cyclometalated
to render species in which the metalated N-(benz-
ylidene) moieties are linked to the central amine phenyl
ring via -CH2- groups. The flexibility awarded by the
methylenes makes it possible for the metal centers to
be brought close together, allowing bidentate ligands,
such as the acetate ion and tertiary diphosphine ligands,
to bridge the palladium atoms, yielding intramolecular
bridged dinuclear compounds. In the case of the diphos-
phines, cis and trans arrangements are possible, as
shown by variable-temperature NMR spectroscopy. We
are currently in the process of detailing further the
characteristics of this equilibrium system.
C(1)-C(7)
C(7)-N(1)
N(1)-C(22)
C(22)-C(23)
C(6)-Pd(1)-N(1)
C(6)-Pd(1)-P(1)
N(1)-Pd(1)-P(1)
C(6)-Pd(1)-Cl(1)
N(1)-Pd(1)-Cl(1)
P(1)-Pd(1)-Cl(1)
C(6)-C(1)-C(7)
C(1)-C(7)-N(1)
C(7)-N(1)-C(22)
81.2(1)
100.7(1)
175.98(8) N(2)-Pd(2)-P(2)
166.3(1)
91.79(9) N(2)-Pd(2)-Cl(2)
87.11(3) P(2)-Pd(2)-Cl(2)
116.5(3)
118.0(3)
120.5(3)
C(16)-Pd(2)-N(2)
C(16)-Pd(2)-P(2)
80.7(1)
98.1(1)
174.51(8)
C(16)-Pd(2)-Cl(2) 166.1(1)
93.99(9)
88.43(3)
C(16)-C(11)-C(17) 116.1(3)
C(11)-C(17)-N(2)
C(17)-N(2)-C(21)
N(2)-C(21)-C(26)
117.9(3)
121.2(3)
111.8(3)
N(1)-C(22)-C(23) 111.9(3)
Exp er im en ta l Section
9 were grown by slowly evaporating a n-hexane/di-
chloromethane solution at room temperature. The mo-
lecular structure is shown in Figure 5. Crystal data are
given in Table 1, and selected bond distances and angles
with estimated standard deviations are shown in Table
3.
Solvents were purified by standard methods.54 Chemicals
were reagent grade. Microanalyses were carried out using a
Carlo Erba elemental analyzer, Model 1108. IR spectra were
recorded as Nujol mulls or polyethylene disks on a Perkin-
Elmer 1330 instrument and on a Mattson spectrophotometer.
NMR spectra were obtained as CDCl3 or (CD3)2SO 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 were reported downfield from 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. Conductivity measurements were made on a
CRISON GLP 32 conductivimeter using 10-3 mol dm-3 solu-
tions in dry acetonitrile.
The syntheses of the Schiff bases 1,3-[2,3,4-(MeO)3C6H2C-
(H)dNCH2]2C6H4 (1) and 1,4-[2,3,4-(MeO)3C6H2C(H)dNCH2]2-
C6H4 (6) were performed by heating chloroform solutions of
the appropriate quantities of 2,3,4-trimethoxybenzaldehyde
and m-xylylenediamine or p-xylylenediamine, respectively, in
a Dean-Stark apparatus under reflux.
The crystal comprises one molecule of 9 and three
dichloromethane solvate molecules.
The molecular structure consists of the doubly cyclo-
metalated Schiff base ligand 6. Each palladium atom
is bonded, in a slightly distorted square-planar geom-
etry, to one carbon atom of the phenyl ring and to one
imine nitrogen atom of the Schiff base ligand and to one
chloro ligand and a phosphorus atom of the tertiary
phosphine dppp, which bridges the two metallic centers.
The sum of angles about the palladium atoms is
approximately 360°, with the most noteworthy distor-
tions corresponding to the C(6)-Pd(1)-N(1) and C(6)-
Pd(1)-N(1) angles of 81.2(1) and 80.7(1)°, consequent
upon chelation. The Pd(1)-C(6) and Pd(2)-C(16) bond
distances of 2.0.25(4) and 2.016(3) Å, respectively, are
similar to values found earlier.52,53 The Pd(1)-N(1) and
Schiff base 1: yield 90%. Anal. Found: C, 67.9; H, 6.6;
N, 5.5. Calcd for C28H32N2O6: C, 68.3; H, 6.6; N, 5.7. IR:
ν(CdN), 1635 m cm-1. 1H NMR (200 MHz, CDCl3, δ in ppm, J
in Hz): 8.66 (s, 2H, Hi), 7,73 (d, 2H, H6, J (H5H6) ) 8.8), 7.26
(m, 4H, H8, H9, H10), 6.65 (d, 2H, H5), 4.80 (s, 4H, CH2), 3.90
(52) Ferna´ndez, A.; Lo´pez-Torres, M.; Sua´rez, A.; Ortigueira, J . M.;
Pereira, T.; Ferna´ndez, J . J .; Vila, J . M.; Adams. H. J . Organomet.
Chem. 2000, 598, 1.
(53) Vila, J . M.; Gayoso, M.; Pereira, M. T.; Lo´pez-Torres, M.; Alonso,
G.; Ferna´ndez, J . J . J . Organomet. Chem. 1993, 445, 287.
(54) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: London, 1996.

Doubly and Triply Bridged PdII Compounds
Organometallics, Vol. 21, No. 17, 2002 3635
2
(s, 6H, MeO), 3.86 (s, 6H, MeO), 3.84 (s, 6H, MeO). 13C{1H}
NMR (50.28 MHz, CDCl3, δ in ppm): 157.4 (CdN); 155.9, 153.9
(C2, C4); 141.7, 139.8 (C3, C7); 128.5, 127.5, 126.5 (C8, C9,
C10); 122.7 (C1); 122.4 (C6); 107.7 (C5); 65.4 (CH2); 61.9, 60.9,
56.0 (MeO). FAB-MS: m/z 493 [M]+.
at Co 134.6 d, J (PC) ) 11.4 Hz; Cm 128.5 d, J (PC) ) 10.6 Hz;
PCH2CH2CH2P, 30.5 m; PCH2CH2CH2P, 22.0. FAB-MS: m/z
1173 [M - OAc]+, 763 [M - phosphine - OAc]+, 597 [M -
phosphine - 2OAc - Pd]+.
Syn th esis of [1,3-{P d [2,3,4-(MeO)3C6HC(H)dNCH2]-
(Cl)}2C6H4(µ-P h 2P (CH2)3P P h 2)] (5). To a suspension of 2
(200 mg, 0.13 mmol) in chloroform (ca. 15 cm3) was added
Ph2P(CH2)3PPh2 (106 mg, 0.26 mmol). The mixture was stirred
for 12 h at room temperature. The resulting solution was
chromatographed on silica gel. Elution with dichloromethane/
ethanol (0.8%) afforded the desired complex, which was
recrystallized from dichloromethane/n-hexane to give a yellow
solid. Yield: 0.15 g, 50%. Anal. Found: C, 56.0; H, 4.6; N, 2.4.
Calcd for C55H56N2Pd2O6Cl2P2: C, 55.7; H, 4.8; N, 2.4. IR:
Schiff base 6: yield 90%. Anal. Found: C, 68.0; H, 6.3;
N, 5.5. Calcd for C28H32N2O6: C, 68.3; H, 6.6; N, 5.7. IR:
1
ν(CdN), 1635 s cm-1. H NMR (200 MHz, CDCl3, δ in ppm, J
in Hz): 8.66 (s, 2H, Hi), 7,74 (d, 2H, H6, J (H5H6) ) 8.8), 7.31
(s, 4H, H8), 6.71 (d, 2H, H5), 4.80 (s, 4H, CH2), 3.94 (s, 6H,
MeO), 3.90 (s, 6H, MeO), 3.89 (s, 6H, MeO). 13C{1H} NMR
(50.28 MHz, CDCl3, δ in ppm): 157.4 (CdN); 155.9, 153.9 (C2,
C4); 141.7 (C7); 138.3 (C3); 128.1 (C8); 122.7 (C1); 122.4 (C6);
107.7 (C5); 65.2 (CH2); 61.9, 60.9, 56.0 (MeO). FAB-MS: m/z
493 [M]+.
1
ν(CdN), 1605 s cm-1. H NMR (200 MHz, CDCl3, δ in ppm, J
in Hz, room temperature): 8.51 (d, 2H, Hi, J (HiP) ) 8.3), 8.29
(s, 1H, H8), 5.81 (d, 2H, H5, J (H5P) ) 5.9), 5.20 (br, 4H, CH2
(50 °C)), 3.92 (s, 6H, MeO), 3.72 (s, 6H, MeO), 2.87 (s, 6H,
C(4)-MeO).31P{1H} NMR (80.96 MHz, CDCl3, δ in ppm): 32.9
s. 13C{1H} NMR (50.28 MHz, CDCl3, δ in ppm): 172.2 (d,
CdN, J (CP) ) 4.2); 154.7, 152.2 (C2, C6); 154.5 (d, C4, J (CP)
) 6.4); 139.1, 137.4 (C3, C7); 136.7 (C1); 131.5, 128.5, 127.5
(C8, C9, C10); 117.2 (C5, J (C5P) ) 12.0); 59.9 (CH2); 61.9, 60.7,
54.9 (MeO); P-phenyl, Co 133.7 d, J (PC) ) 12.8 Hz; Cm 128.4
d, J (PC) ) 10.6 Hz; Cp 130.6 d; PCH2CH2CH2P, 31.6 (dd, J (PC)
) 34.0, 5.6); PCH2CH2CH2P, 20.8. 1H NMR (200 MHz, CDCl3,
δ in ppm, J in Hz, 223 K): 8.65 d, 8.48 d (d, 4H, Hi, J (HiP) )
7.8), 8.49, 8.08 (s, 2H, H8), 5.87, 5.62 (d, 2H, H5, J (H5P) )
6.3, 5.3), 6.05 (d, 2H, CH(a)2, J (H(a)H(b)) ) 11.2), 5.93 (d, 2H,
CH(a)2, J (H(a)H(b)) ) 11.2), 4.30 (m, 4H, CH(b)2), 3.92 (s, 12H,
MeO), 3.73 (s, 12H, MeO), 2.87, 2.70 (s, 12H, C(4)-MeO). 31P-
{1H} NMR (80.96 MHz, CDCl3, δ in ppm): 33.2, 32.6 s. FAB-
MS: m/z 1186 [M] +, 1151 [M - Cl]+, 739 [M - phosphine -
Cl]+, 663 [M - phosphine - Cl - Pd]+, 597 [M - phosphine -
2Cl - Pd]+.
[1,4-{P d [2,3,4-(Me O)3C6H C(H )dNCH 2](µ-O2CMe )}2-
C6H4]n (7). Complex 7 was synthesized as a orange solid using
a procedure similar to that described for complex 2. Yield:
80%. Anal. Found: C, 46.5; H, 3.9; N, 3.5. Calcd for [C32H36N2-
Pd2O10]n: C, 46.8; H, 4.4; N, 3.4. IR: νas(COO), 1570 s;
νs(COO),1415 s; ν(CdN), 1600 m sh cm-1. 1H NMR (200 MHz,
CDCl3, δ in ppm, J in Hz): 7.42 (s, 2H, Hi), 7.15, 7.12 (s, 4H,
H8), 6.40 (s, 2H, H5), 4.39, 3.65 (br, 4H, CH2), 3.85 (s, 6H,
MeO), 3.78 (s, 12H, MeO), 2.08 (s, 6H, MeCO2). 13C{1H} NMR
(50.28 MHz, CDCl3, δ in ppm): 181.0 (MeCO2); 169.1 (CdN);
154.5, 151.7, 151.4 (C2, C4, C6); 137.8, 135.9 (C3, C7); 131.0
(C1); 129.2 (C8); 110.3 (C5); 61.3 (CH2); 61.8, 61.0, 56.0 (MeO);
24.3 (MeCO2). FAB-MS: m/z 763 [M - OAc]+ (M ) C32H36N2-
Pd2O10).
Syn th esis of [1,3-{P d [2,3,4-(MeO)3C6HC(H)dNCH2](µ-
O2CMe)}2C6H4] (2). 1,3-[2,3,4-(MeO)3C6H2C(H)dNCH2]2C6H4
(1; 33 mg, 0.67 mmol) and palladium(II) acetate (30 mg, 0.45
mmol) were added to 50 cm3 of toluene to give a dark red
solution. After it was heated at 60 °C for 4 h under argon, the
solution was cooled and filtered through Celite to remove the
small amount of black palladium formed. The solvent was then
removed under vacuum and the required product recrystallized
from dichloromethane/n-hexane.Yield: 0.49 g, 80%. Anal.
Found: C, 46.4; H, 4.3; N, 3.2. Calcd for C32H36N2Pd2O10: C,
46.8; H, 4.4; N, 3.4. IR: νas(COO), 1570 s; νs(COO), 1415 s;
ν(CdN), 1600 m sh cm-1. 1H NMR (200 MHz, CDCl3, δ in ppm,
J in Hz): 8.10 (s, 2H, Hi), 8.35 (s, 1H, H8), 7.22 (t, 1H, H10,
J (H9H10) ) 6.8), 7.03 (d, 2H, H9), 6.13 (s, 2H, H5), 5.05 (d,
2H, CH(a)2, J (H(a)H(b)) ) 15.6), 4.55 (d, 2H, CH(b)2), 3.92 (s,
6H, MeO), 3.79 (s, 6H, MeO), 3.69 (s, 6H, MeO), 2.23 (s, 3H,
MeCO2), 1.26 (s, 3H, MeCO2). 13C{1H} NMR (50.28 MHz,
CDCl3, δ in ppm): 181.5, 179.6 (MeCO2); 172.2 (CdN); 154.5,
151.1, 151.0 (C2, C4, C6); 138.0, 137.7 (C3, C7); 135.6 (C8);
130.5 (C1); 127.6, 123.8 (C9, C10); 111.1 (C5); 62.0 (CH2); 61.6,
60.8, 55.8 (MeO); 24.1, 23.3 (MeCO2). FAB-MS: m/z 822 [M]+,
763 [M - OAc]+, 597 [(1-H)Pd]+.
Syn th esis of [1,3-{P d [2,3,4-(MeO)3C6HC(H)dNCH2](µ-
Cl)}2C6H4]2 (3). An aqueous solution of NaCl (ca. 10-2 M) was
added dropwise to 2 (40 mg, 0.49 mmol) in acetone (ca. 25 cm3).
A yellow solid immediately formed. After the mixture was
stirred for 5 h, the solid was filtered off, washed with water
and cold acetone, and dried in vacuo. Yield: 0.32 g, 86%. Anal.
Found: C, 43.3; H, 4.0; N, 3.6. Calcd for C56H60N4Pd4O12Cl4:
C, 43.4; H, 3.9; N, 3.6. IR: ν(CdN), 1600 s cm-1. 1H NMR (200
MHz, d6-DMSO, δ in ppm, J in Hz): 8.29 (br, 2H, Hi), 7.40
(m, 4H, H8, H9, H10), 6.93 (br, 2H, H5), 4.98, 4.67 (br, 4H,
CH2), 3.80 (s, 6H, MeO), 3.74 (s, 6H, MeO), 3.65 (s, 6H, MeO).
FAB-MS: m/z 1548 [M]+, 1513 [M - Cl]+, 1371 [M - 2Cl -
Pd]+, 739 [(1-H)2Pd(X)]+.
Syn th esis of [1,4-{P d [2,3,4-(MeO)3C6HC(H)dNCH2](µ-
Cl)}2C6H4]2 (8). Complex 8 was synthesized as a yellow solid
using a procedure similar to that described for complex 3.
Yield: 92%. Anal. Found: C, 43.9; H, 4.0; N, 3.8. Calcd for
Syn th esis of [1,3-{P d [2,3,4-(MeO)3C6HC(H)dNCH2]-
(OAc)}2C6H4(µ-P h 2P (CH2)3P P h 2)] (4). To a suspension of 2
(200 mg, 0.24 mmol) in chloroform (ca. 15 cm3) was added
Ph2P(CH2)3PPh2 (100 mg, 0.243 mmol). The mixture was
stirred for 12 h at room temperature. The resulting solution
was chromatographed on silica gel. Elution with dichlo-
romethane/ethanol (0.4%) afforded the desired complex, which
was recrystallized from dichloromethane/n-hexane to give a
yellow solid. Yield: 0.15 g, 50%. Anal. Found: C, 57.0; H, 4.8;
N, 2.3. Calcd for C59H62N2Pd2O10P2: C, 57.4; H, 5.1; N, 2.3.
C
56H60N4Pd4O12Cl4: C, 43.4; H, 3.9; N, 3.6. IR: ν(CdN), 1600
s cm-1. 1H NMR (200 MHz, d6-DMSO, δ in ppm, J in Hz): 8.05
(s, 2H, Hi), 7.54 (s, 4H, H8), 6.60 (s, 2H, H5), 4.96, 4.67 (br,
4H, CH2), 3.95 (s, 6H, MeO), 3.88 (s, 6H, MeO), 3.76 (s, 6H,
MeO). 13C{1H} NMR (50.28 MHz, CDCl3, δ in ppm): 172.2
(CdN); 154.8, 151.5, 150.5 (C2, C4, C6); 138.1, 137.0 (C3, C7);
131.3 (C1); 129.1 (C8); 112.0 (C5); 61.7 (CH2); 61.8, 60.9, 56.2
(MeO). FAB-MS: m/z 1548 [M] +, 1513 [M - Cl]+.
IR: νas(COO), 1580 s; νs(COO), 1380 s; ν(CdN), 1605 s cm-1
.
1H NMR (200 MHz, CDCl3, δ in ppm, J in Hz): 8.46 (d, 2H,
Hi, J (HiP) ) 7.3), 5.72 (d, 2H, H5, J (H5P) ) 5.4), 5.08 (d, 2H,
CH(a)2, J (H(a)H(b)) ) 12.7), 4.46 (dd, 2H, CH2(b), J (H(b)P) )
5.4), 3.91 (s, 6H, MeO), 3.68 (s, 6H, MeO), 2.97 (s, 6H, C(4)-
MeO), 1.91 (s, 6H, MeCO2).31P{1H} NMR (80.96 MHz, CDCl3,
δ in ppm): 30.7 s. 13C{1H} NMR (50.28 MHz, CDCl3, δ in ppm,
J in Hz): 176.7 (MeCO2); 172.2 (d, CdN, J (CP) ) 4.3); 154.8,
152.5, 151.8 (C2, C4, C6); 138.5, 137.6 (C3, C7); 133.8 (C1);
131.5, 127.7 (C8, C9, C10); 116.9 (d, C5, J (C5P) ) 11.4); 60.8
(CH2); 61.8, 60.7, 55.2 (MeO); 23.3 (MeCO2); P-phenyl appear
Syn th esis of [1,4-{P d [2,3,4-(MeO)3C6HC(H)dNCH2]-
(Cl)}2C6H 4(µ-P h 2P (CH 2)3P P h 2)] (9) a n d [1,4-{P d [2,3,4-
(MeO)3C6HC(H)dNCH 2](Cl)}2C6H4(µ-P h 2P (CH2)3P P h 2)]2
(10). To a suspension of 8 (200 mg, 0.129 mmol) in chloroform
(ca. 15 cm3) was added Ph2P(CH2)3PPh2 (106 mg, 0.258 mmol).
The mixture was stirred for 12 h at room temperature. The
resulting solution was chromatographed on silica gel. Elution
with dichloromethane/ethanol (1.2%) afforded complex 9,
which was recrystallized from dichloromethane/n-hexane to
give a yellow solid. Elution with dichloromethane/ethanol

3636 Organometallics, Vol. 21, No. 17, 2002
Lo´pez-Torres et al.
(0.4%) afforded a mixture of complexes 9 and 10 (molar ratio
0.25:1, calculated from NMR data), which was recrystallized
from dichloromethane/n-hexane to give a yellow solid.
Complex 9: Yield: 25%. Anal. Found: C, 55.52; H, 4.71; N,
2.41. Calcd for C55H56N2Pd2O6Cl2P2: C, 55.7; H, 4.8; N, 2.4.
IR: ν(CdN) 1610 s cm-1. 1H NMR (200 MHz, CDCl3, δ in ppm,
J in Hz): 8.47 (d, 2H, Hi, J (HiP) ) 7.8), 7.55 (s, 4H, H8), 5.73
(d, 2H, H5, J (H5P) ) 5.8), 5.70, 4.57 (br, 4H, CH2), 3.98 (s,
6H, MeO), 3.74 (s, 6H, MeO), 2.84 (s, 6H, C(4)-MeO). 31P-
{1H} NMR (80.96 MHz, CDCl3, δ in ppm) 32.9 s. 13C{1H} NMR
(50.28 MHz, CDCl3, δ in ppm): 170.9 (CdN); 155.1, 154.6,
152.2 (C2, C4, C6); 137.5, 136.5 (C3, C7); 129.2 (C8); 117.2
(C5); 62.5 (CH2); 61.9, 60.7, 54.9 (MeO); P-phenyl Co 133.7 d,
J (PC) ) 12.8 Hz; Cm 128.4 d, J (PC) ) 10.2 Hz; Cp 131.4 d;
PCH2CH2CH2P, 29.6 m; PCH2CH2CH2P, 18.9. 1H NMR (200
MHz, CDCl3, δ in ppm, J in Hz, 223 K): 8.47 (d, 2H, Hi, J (HiP)
) 7.8), 7.60, 7.51 (s, 4H, H8), 5.70 (m, 4H, H5, CH(a)2), 4.57
(m, 2H, CH(b)2), 3.98, 3.96 (s, 6H, MeO), 3.98, 3.76, 3.96, 3.73
(s, 6H, MeO), 2.78, 2.73 (s, 6H, C(4)-MeO). 31P{1H} NMR (80.96
MHz, CDCl3, δ in ppm) 33.4, 32.9 s.
ω scan method using graphite-monochromated Mo KR radia-
tion. All the measured reflections were corrected for Lorentz
and polarization effects and for absorption by semiempirical
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. Refinement converged
at a final R1 ) 0.0494 and 0.0366 (for complexes 2 and 9,
respectively, observed data, F) and wR2 ) 0.1041 and 0.0776
(for complexes 2 and 9, respectively, unique data, F2), with
allowance for thermal anisotropy of all non-hydrogen atoms.
The structure solution and refinement were carried out using
the program package SHELX-97.55
Ack n ow led gm en t. We thank the Ministerio de
Educacio´n y Cultura (Proyecto PB98-0638-C02-01/02),
the Xunta de Galicia (Proyecto PGIDT99PXI20907B),
and the Universidad de la Corun˜a for financial support.
R.M. acknowledges a fellowship from the Ministerio de
Ciencia y Tecnolog´ıa of Spain.
Complex 10: Yield: 30%. IR: ν(CdN) 1610 s cm-1. 1H NMR
(200 MHz, CDCl3, δ in ppm, J in Hz): 8.19 (d, 2H, Hi, J (HiP)
) 7.8), 7.46 (s, 4H, H8), 5.73 (d, 2H, H5, J (H5P) ) 5.9), 5.13
(s, 4H, CH2), 3.79 (s, 6H, MeO), 3.62 (s, 6H, MeO), 2.87 (s, 6H,
C(4)-MeO). 31P{1H} NMR (80.96 MHz, CDCl3, δ in ppm): 33.4
s. 13C{1H} NMR (50.28 MHz, CDCl3, δ in ppm): 171.8 (CdN);
154.6, 153.8, 152.0 (C2, C4, C6); 137.4, 137.2 (C3, C7); 129.6
(C8); 117.1 (C5); 60.1 (CH2); 61.8, 60.6, 55.2 (MeO); P-phenyl
Co 133.9 d, J (PC) ) 12.8 Hz; Cm 128.6d, J (PC) ) 10.1 Hz; Cp
130.8 d; PCH2CH2CH2P 30.1 m; PCH2CH2CH2P 20.8.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data (excluding structure factors) for structures 2 and 9
reported in this paper. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM0201866
(55) Sheldrick, G. M. SHELX-97, An Integrated System for Solving
and Refining Crystal Structures from Diffraction Data; University of
Go¨ttingen, Go¨ttingen, Germany, 1997.
X-r a y Cr ysta llogr a p h y. Three-dimensional X-ray data
were collected on a Siemens Smart CCD diffractometer by the