Influence of phenyl ring substituents in the cyclometallation of Schiff base ligands: Crystal and molecular structures of [Pd-{3,4-(OCH2O)C6H 2C(H)=N(Cy)-C2,N}(μ-O2CMe)]2 and [Pd-{3,4-(OCH2

Article abstract of DOI:10.1016/S0022-328X(99)00680-4

Reaction of Pd(OAc)₂ with the Schiff base ligands 3,4-{O(CH₂)_nO}C₆H₃C(H)=NR (n=1, 2; R=Cy, 3,4-(OCH₂O)C₆H₃CH₂-) leads to dinuclear cyclometallated products

Full text of DOI:10.1016/S0022-328X(99)00680-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 598 (2000) 71–79
Influence of phenyl ring substituents in the cyclometallation of
Schiff base ligands: crystal and molecular structures of
[Pd-{3,4-(OCH2O)C6H2C(H)ꢀN(Cy)-C2,N}(m-O2CMe)]2 and
[Pd-{3,4-(OCH2CH2O)C6H2C(H)ꢀN(Cy)-C6,N}(m-O2CMe)]2
Berta Teijido a, Alberto Ferna´ndez a, Margarita Lo´pez-Torres a, Samuel Castro-Juiz a,
Antonio Sua´rez a, Juan M. Ortigueira b, Jose´ M. Vila b,*, Jesu´s J. Ferna´ndez a
a Departamento de Qu´ımica Fundamental e Industrial, Uni6ersidad de La Corun˜a, E-15071 La Corun˜a, Spain
b Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain
Received 8 April 1999; received in revised form 29 October 1999
Abstract
Reaction of Pd(OAc)2 with the Schiff base ligands 3,4-{O(CH2)nO}C6H3C(H)ꢀNR (n=1, 2; R=Cy, 3,4-(OCH2O)C6H3CH2-)
leads to dinuclear cyclometallated products in which each palladium atom is C,N bonded to a deprotonated organic ligand, and
to two acetate groups which bridge both metal centers. Treatment of 3,4-{O(CH2)2O}C6H3C(H)ꢀNCH2CH2NMe2 with
[PtMe2(COD)] gives mononuclear compounds with the ligand as terdentate through the [C, N, N] atoms. The regioselectivity of
1
the cyclometallation processes is discussed by H-NMR spectroscopy and X-ray diffraction studies. © 2000 Elsevier Science S.A.
All rights reserved.
Keywords: Palladium(II); Platinum(II); Schiff bases; Cyclometallation; Crystal structure
[4], among others. Recently, new cyclopalladated com-
plexes have been described that catalyze the Heck ole-
1. Introduction
fination [5], that exhibit some interesting photochemical
The reaction that gives cyclometallated palladium(II)
and electrochemical properties [6] or which show
complexes — albeit described for the first time more
promising cytotoxic activity [7]. Cyclometallated com-
than 25 years ago [1] — has been studied thoroughly
pounds are usually classified according to the metal, to
since then by numerous research groups in view of the
the donor atom, or to chelate ring size [8]. By far the
enormous potential use of the compounds in organic
most well-studied examples are five-membered pallada-
synthesis [2], design of new metallomesogens [3] or
cycles with nitrogen donor atoms.
characterization of enatiomerically chiral compounds
When there are more than one possible metallation
sites on the ligand the question of regioselectivity arises
as we have been reported previously [9,10]. We have
studied the influence of different substituents adjacent
to the carbon atom where metallation is possible as is
depicted in Fig. 1. Methoxy groups at the C3 and C5
atoms hinder direct metallation by palladium(II) at the
C2 or at the C6 atoms (i); with only one methoxy
group, in the C3 position, the C6 carbon is selectively
metallated (ii); whereas the less sterically demanding
methyl group allows attack of the palladium atom at
the C2 atom in all cases (iii, iv).
Fig. 1. Possible metallation sites.
* Corresponding author. Fax: +34-81-595012.
E-mail address: qideport@usc.es (J. Vila)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00680-4

72
B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
Scheme 1. Condition reactions: Pd(OAc)2, 80°C, AcOH or toluene. *, impurified with 1a and 1c, respectively.
Recently, metallation of a methoxy group has been
2. Results and discussion
achieved to give cyclometallated complexes with a six-
membered metallacycle [11].
2.1. Cyclometallation reaction
Therefore, in view of the influence that methoxy and
methyl substituents bear on the metallated ring, we
sought out to study the influence that change in the
size of the ring attached to the phenyl ring would
exert.
We have shown that in related systems the OCH2O
group does not impede metallation of the phenyl ring
by palladium(II) at the ortho position of the
methylenedioxo group, i.e. C(2), for reasons given ear-
lier [10]. For example, the bidentate Schiff base ligand,
in 1,4-{3,4-(OCH2O)C6H3C(H)ꢀNꢁ}2C6H4, double pal-
ladation occurred at the carbon atom ortho to the
OCH2O group [12]. Platinum(II) seems to show a simi-
lar behavior towards the metallation of related sys-
tems, as is the case with potentially terdentate ligand
3,4-(OCH2O)C6H3C(H)ꢀNCH2CH2NMe2 where the C2
carbon atom is exclusively platinated [13].
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
analysis (C, H, N) and by IR (data in Section 4) and by
1H-, and 13C-{1H}-NMR spectroscopy (Table 1).
Here we present our results on the synthesis of new
cyclometallated compounds derived from Schiff base
ligands with two potential metallation sites, in an at-
tempt to study the influence of the cyclic substituent
ring size on the potential metallation position of the
phenyl ring.
Scheme 2. Condition reactions: PtMe2(COD), 90°C, toluene.

B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
73
Table 1
1H-NMR a data b,c
Compound
l(Hi)
l(H2)
l(H5)
l(H6)
7.10dd
6.72d
l(O(CH2)nO)
Others
a
8.18s
7.26s
7.23s
8.18s
7.35d
6.80d
5.98s
4J(H2H6)=1.5
3J(H5H6)=8.0
6.47d
1a
2a
b
5.93d
5.88d
5.90d
5.83d
4.27m
J(CH2)=1.1
l(MeCO2)=2.03s
J(CH2)=1.1
3J(H5H6)=7.7
6.52s
6.48s
l(MeCO2)=2.05s
7.27d
6.87d
7.21dd
4J(H2H6)=1.9
6.48s
3J(H5H6)=8.3
6.64s
1b
7.19s
4.20m
l(MeCO2)=2.11s
d
c
8.24t
7.41d
6.83d
4J(HiNCH2)=1.4
4J(H2H6)=1.9
3J(H5H6)=8.3
7.13dd
6.71d
5.99s
5.94s
5.94s
5.88d
1c e
7.05s
6.54d
J(CH2)=1.3
l(MeCO2)=2.09s
3J(H5H6)=7.8
5.78d
g
g
2c f
d h,i
7.02s
8.23t
6.61s
7.33d
6.64s
6.89d
7.26dd
7.21dd
5.94s
4J(HiNCH2)=1.4
6.97t
4J(H2H6)=1.9
6.55s
3J(H5H6)=8.3
6.66s
4.28m
5.95m
4.20m
4.27m
1d h,j
f k
l(MeCO2)=2.16s
l(NMe2)=2.30s
4J(HiNCH2)=1.5
8.17t
7.26d
6.86d
4J(Hia-CH2)=1.4
8.39t
4J(H2H6)=1.9
6.99s
3J(H5H6)=8.3
6.86d
1f l
4.21m
l(NMe2)=2.81s
J(PtNMe2)=20.5
l(PtMe)=0.86s
J(PtMe)=78.6
4J(Hia-CH2)=1.4
N(PtHi)=59.1
J(PtH5)=11.2
a In CDCl3. Measured at 200 MHz (ca. 20°C), chemical shifts (l) in ppm (90.01) to high frequency of SiMe4.
b Coupling constants in Hz.
c s, singlet; d, doublet, dd, doublet of doublets, t, triplet; b, broad; m, multiplet.
d l(NCH2)=4.69d, l(H8,H9,H12)=6.84b, 6.79b.
e l(NCH2)=4.53d, 3.99d, J(CH2)=15.6, l(H8)=6.31d, 4J(H8H12)=1.5, l(H11)=6.73d, 3J(H11H12)=7.8, l(H12)=6.44dd.
f l(NCH2)=4.44d, 3.95d, J(CH2)=15.0, l(H8)=6.25d, 4J(H8H12)=1.5, l(H11), l(H12) occluded.
g l(OCH2O), l(MeCO2) occluded.
h l(OCH2O)\l(OCH2CH2O).
i l(NCH2)=4.69d, l(H8,H9,H12)=6.83b, 6.78b.
j l(NCH2)=4.47dd, 4.12dd, J(NCH2)=16.6, l(H8)=6.19d, 4J(H8H12)=1.4, l(H11)=6.76d, 3J(H11H12)=7.8, l(H12)=6.32dd.
k l(a-CH2)=3.96td, l(b-CH2)=2.62t, J(a,b-CH2)=12.7.
l l(a-CH2)=3.97td, l(b-CH2)=3.11t, J(a,b-CH2)=11.6.
Reaction of the Schiff base ligands a or c with
palladium(II) acetate in toluene at 80°C for 2 h gave
yellow solids identified as mixtures of two products
each: one derived from CꢁH activation at the 2-position
(ortho to the OCH2O group), 1a, 1c, and the other one
derived from CꢁH activation at the 6-position (meta to
the OCH2O group) 2a, 2c. The mixtures are in 2:1
(1a/2a) and 20:1 (1c/2c) ratios, as calculated from the
and 1c showed two doublets assigned to the H(5) and
H(6) protons. The signal for the H(2) nucleus was
absent upon metallation at C(2), as expected.
On the other hand, the reaction between ligands b or
d and palladium(II) acetate in toluene or in glacial
acetic acid afforded a single product, i.e. the one
derived from CꢁH activation exclusively at the 6-posi-
tion, 2b and 2d, and no isomer with the metal boned to
the C(2) atom was found. Two singlets assigned to the
1
integrals in the H-NMR spectra. No modification of
1
these ratios was found for shorter reaction times or
even when the mixtures were heated for 24 h. The
metallation process was repeated for ligand a in glacial
acetic acid to give an analogous mixture, but in a 1a/2a
9:1 ratio. Attempts to separate the reaction products by
chromatographic methods failed, and we only obtained
H(2) and H(5) protons were observed in the H-NMR
spectrum for 2b and 2d; the resonance for the H(6)
proton being absent.
In the IR spectra of the complexes the w(CꢀN)
stretching band (see Section 4) appeared at lower fre-
quency than the corresponding one in the free imines in
accordance with nitrogen coordination to metal center
[14]. This was supported by the upfield shift of the
1
in pure form (as shown by H-NMR) isomers 1a and
1c, whereas 2a and 2c were always contaminated with
1
1
1a and 1c, respectively. The H-NMR spectra for 1a
HCꢀN resonance in the H-NMR spectra, ca. 1 ppm

74
B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
[15]. The was(COO) and ws(COO) values were consistent
with bridging acetato groups [16]; the singlet resonance
at ca. 2.00 ppm (6H) in the 1H-NMR spectra was
assigned to the equivalent methyl acetate protons, consis-
tent with a trans geometry of the cyclometallated moieties
[17]. The 13C-{1H}-NMR spectra revealed the election of
the metallated carbon atom, by the strong downfield shift
of the corresponding C2 or C6 carbon resonance to
values greater than 140 ppm (see Section 4).
2.2. Molecular structure of complexes 1a and 2b
Suitable crystals were grown by recrystallization
from chloroform–n-hexane solution of complexes 1a
and 2b. The schemes used for labeling atoms in the
Schiff base complex are shown in Figs. 2 and 3. Crys-
tallographic data and selected bond lengths and angles
are listed in Tables 2 and 3. The crystals consist of
discrete dinuclear molecules separated by normal van
der Waals distances. The species possess C2 symmetry
with the twofold axis perpendicular to the PdꢁPd
vector.
The molecular configuration of these species is a
dimeric form of the anti isomer with the cyclopalla-
dated moieties in an open book arrangement linked by
two acetate bridging ligands between the palladium
atoms, as observed in the related dimers (see Fig. 4)
[18,19].
The next step in the comparison of OCH2O versus
OCH2CH2O was to change the denticity of the ligand
and also the nature of the metal. For potentially terden-
tate ligands such as 3,4-(OCH2O)C6H3C(H)=NCH2-
CH2NMe2 the reaction with [PtMe2(COD)] gave the
complex with platinum(II) bonded to the carbon next
to the OCH2O moiety, as we have reported previous-
ly [13]. However, when the related ligand 3,4-
{O(CH2)2O}C6H3C(H)ꢀNCH2CH2NMe2 (f), was tested
towards metallation by platinum(II), the metal atom
only binds to the C(6) carbon atom. Thus, treatment of
ligand f with [PtMe2(COD)] in toluene gave the
mononuclear compound [Pt(3,4-{O(CH2)2O}C6H3-
C(H)ꢀNCH2CH2NMe2,)] (1f), as an air-stable orange
solid which as fully characterized (see Section 4 and
,
The palladium···palladium distances are 2.8653(3) A
,
in the piperonal derivative (1a) and 2.8485(10) A in the
benzodioxan derivative (2b), which may be regarded as
nonbonding; the covalent radius of square-planar
Pd(II) has been estimated as approximately 1.31 A [20].
,
Each palladium atom is in a slightly distorted square-
planar coordination environment. The coordination
sphere around each palladium atom consists of a nitro-
gen atom of the imine group, a ortho carbon of the
phenyl ring, and two oxygen atoms (one from each
of the bridging acetate ligands). The Schiff base ligands
are bonded through the C2 (1a) and C6 (2b) carbon
atoms in the complexes, in accordance with the spectro-
scopic results. Furthermore, the C(2)ꢁC(3)ꢁO(1) angle
of 118.2(7) in 2b is smaller than the C(2)ꢁC(3)ꢁO(1)
angle of 128.2(3) in 1a, which confirms the steric effect
of the OCH2CH2O group which impedes the metal
to come close to the aromatic C2ꢁH bond of ligand
b.
1
Table 1). The H-NMR spectrum contains only one set
of signals in accordance with the presence of only one
isomer in solution, i.e. the one with the platinated C6
carbon atom. The 13C-{1H}-NMR spectrum showed
the strong downfield shift of the C6, CꢀN and C1
resonances, confirming metallation of the ligand at the
C6 carbon atom. Two singlet resonances were assigned
to the H2 and H5 protons, at l 6.99 and 6.86 ppm,
respectively, with the latter showing coupling to plat-
inum, 3J(PtH)=11.2 Hz. The HCꢀN and NMe2 signals
3
also showed coupling to platinum with J(PtH)=59.1
and 78.6 Hz, respectively. The remaining signals were
unequivocally assigned (see Section 4 and Table 1).
Fig. 2. Labeling of atoms in [Pd-{3,4-(OCH2O)C6H2C(H)ꢀN(Cy)-C2,N}(m-O2CMe)]2 (1a).

B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
75
Fig. 3. Labeling of atoms in [Pd-{3,4-(OCH2CH2O)C6H2C(H)ꢀN(Cy)-C6,N}(m-O2CMe)]2 (2b).
deviations are clearly illustrated in Fig. 4. The two
acetate bridges are separated by dihedral angles of
89.3° in the piperonal complex and 83.5° in the benzo-
dioxan complex.
The angles between adjacent atoms in the coor-
dination sphere are close to the expected value of
90°, in the range 81.1–96.5°, with the distortions
more noticeable in the bite angles, which are
C(2)ꢁPd(1)ꢁN(1), 81.51(9)°, in the piperonal complex
and C(6)ꢁPd(1)ꢁN(1), 81.1(2)°, in the benzodioxan
complex.
Table 2
Crystal data and structure refinement
The palladiumꢁnitrogen bond lengths are Pd(1)ꢁN(1)
,
,
=2.018(2) A for 1a and Pd(1)ꢁN(1)=2.015(5) A for
1a
2b·2CHCl3
2b. This is in agreement with the predicted value of
Formula
Mr
C32H38N2O8Pd2
791.44
C36H44Cl6N2O8Pd2
1058.23
,
2.01 A, based on the sum of covalent radii for nitrogen
2
,
(sp ) and palladium, 0.701 and 1.31 A, respectively
Temperature (°C)
293(2)
293(2)
[21].
,
Wavelength (A)
0.71073
0.71073
In contrast with this, the palladiumꢁcarbon bond
lengths are Pd(1)ꢁC(2)=1.974(2) (1a) and Pd(1)ꢁC(6)
Crystal system
Space group
Cell dimensions
Tetragonal
P-4
Tetragonal
I41/a
,
=1.949(6) A (2b), which are substantially shorter than
,
a (A)
13.02633(3)
13.02633(3)
9.6612(2)
1639.36(6)
2
1.603
1.148
800
17.5686(1)
17.5686(1)
29.4984(2)
9104.85(10)
8
1.544
1.189
4256
0.45×0.40×0.25
51.9
,
the predicted value of 2.081 A (based on the sum of
,
b (A)
covalent radii for carbon (sp2) and palladium, 0.771
,
c (A)
3
,
V (A )
Z
,
and 1.31 A, respectively). This suggests some degree of
multiple-bond character in the PdꢁC(aryl) linkage, as
has been observed before [12,22].
Dcalc. (Mg m−3
)
v (mm−1
F(000)
)
The trans-lengthening influence of s-bonded carbon
is illustrated clearly by the lengthening of the palla-
diumꢁoxygen distance trans to carbon, relative to that
trans to nitrogen. Thus, we have Pd(1)ꢁO(4A)=
2.139(2) versus Pd(1)ꢁO(3)=2.037(2) in complex 1a
and Pd(1)ꢁO(4)=2.153(5) versus Pd(1)ꢁO(3)=2.050(4)
Crystal size (mm)
2qmax (°)
Reflections:
collected
0.35×0.25×0.20
56.6
12144
25063
unique
4051 (Rint=0.021) 4004 (Rint=0.12)
Transmissions
No. of parameters
No. of restraints
S
1.00, 0.85
199
0
1.036
0.0207
0.0519
0.001
0.214
0.01(2)
1.00, 0.49
244
3
1.053
0.0632
0.1792
0.001
0.680
,
A in complex 2b.
As a result of Pd(1) and Pd(2) being bridged by two
mutually cis m-acetate ligands the chelating C,N
bonded Schiff bases are forced to lie above one an-
other in the dimeric molecules. This leads to inter-
ligand repulsions on the open side of the molecule and
results in the coordination planes of the palladium
atoms being tilted at an angle of 26.0 and 25.6° to one
another in complexes 1a and 2b, respectively. These
R [F, I\2|(I)]
wR [F2, all data]
max D/|
−3
,
max z (e A
)
Absolute structure
parameter

76
B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
Table 3
3. Conclusions
a
,
Selected bond distances (A) and angles (°) for complexes 1a and 2b
The results presented here are further examples of
Schiff base ligands that possess two potential metalla-
tion sites, in a similar fashion as was found by us earlier
for related ligands with methoxy and methyl groups.
However, whereas in the latter case steric effects were
claimed to be the inducement for the adoption of the
metallation position, in the ligands of the present paper
a ring size effect seems to operate. Whether it is due
solely to electronic or to steric effects, or both operating
together, we believe that further studies are needed in
order to make a final judgement; these will be under-
taken by us. Nevertheless, the experimental results
shown here put forward the fact that careful selection
of the phenyl ring substituents may conduct metallation
towards the carbon atom of our choice.
1a
2b
Bond distances
C(2)ꢁPd(1)
N(1)ꢁPd(1)
O(3)ꢁPd(1)
Pd(1)ꢁO(4)c1
Pd(1)ꢁPd(1)c1
C(3)ꢁO(1)
1.974(2)
2.018(2)
2.0371(18) Pd(1)ꢁO(3)
2.1388(18) Pd(1)ꢁO(4)
2.8653(3)
1.385(3)
1.375(4)
1.416(4)
1.424(5)
1.439(4)
1.286(3)
1.474(3)
Pd(1)ꢁC(6)
Pd(1)ꢁN(1)
1.949(6)
2.015(5)
2.050(4)
2.153(5)
Pd(1)ꢁPd(1)c2 2.8485(10)
O(1)ꢁC(3)
O(2)ꢁC(4)
O(1)ꢁC(14)
O(2)ꢁC(15)
C(1)ꢁC(7)
N(1)ꢁC(7)
N(1)ꢁC(8)
1.373(8)
1.367(8)
1.390(12)
1.367(12)
1.439(9)
1.294(9)
1.474(8)
C(4)ꢁO(2)
C(14)ꢁO(1)
C(14)ꢁO(2)
C(1)ꢁC(7)
C(7)ꢁN(1)
C(8)ꢁN(1)
Bond angles
C(2)ꢁPd(1)ꢁN(1)
C(2)ꢁPd(1)ꢁO(3)
N(1)ꢁPd(1)ꢁO(3)
81.51(9)
94.39(10) C(6)ꢁPd(1)ꢁO(3)
175.90(8)
C(6)ꢁPd(1)ꢁN(1) 81.2(2)
93.8(2)
N(1)ꢁPd(1)ꢁO(3) 174.0(2)
C(6)ꢁPd(1)ꢁO(4) 177.2(2)
N(1)ꢁPd(1)ꢁO(4) 96.5(2)
O(3)ꢁPd(1)ꢁO(4) 88.60(19)
O(1)ꢁC(3)ꢁC(2) 118.2(7)
O(2)ꢁC(4)ꢁC(5) 117.1(6)
C(2)ꢁPd(1)ꢁO(4)c1 175.84(9)
4. Experimental
N(1)ꢁPd(1)ꢁO(4)c1
O(3)ꢁPd(1)ꢁO(4)c1
C(2)ꢁC(3)ꢁO(1)
94.69(8)
89.40(8)
128.2(3)
126.4(3)
4.1. Materials and instrumentation
C(5)ꢁC(4)ꢁO(2)
Solvents were dried according to the standard meth-
ods [23]. Palladium(II) acetate and (1,5-cyclooctadi-
ene)dimethylplatinum(II) were used as supplied from
Johnson Matthey. Elemental analyses were carried out
by the Servicios Generales de la Universidad de La
Corun˜a using a Carlo-Erba elemental analyzer, Model
1108. IR spectra were recorded on a Perkin–Elmer
1330 spectrophotometer. NMR spectra were obtained
as CDCl3 solutions and referenced to SiMe4 ((1H) and
13C-{1H}) or 85% H3PO4 (31P-{1H}) and were recorded
on a Bruker AC 200F spectrometer.
a Symmetry transformations used to generate equivalent atoms:
c1 −x+1, −y, z; c2 −x+1, −y+3/2, z+0.
The preparation of ligand e and complex 1e were
described in an earlier paper [13]. The synthesis of the
Schiff base ligands a, b, c, d and f were performed by
heating a chloroform solution of the appropriate quan-
tities of piperonal or 1,4-benzodioxan-6-carboxalde-
hyde and the corresponding amine in a Dean–Stark
apparatus under reflux.
3,4-{OCH2O}C6H3C(H)ꢀN(C6H11) (a). Yield: 88.8%.
Anal. Found: C, 72.6; H, 7.5; N, 6.1. Anal. Calc.: C,
72.7; H, 7.4; N, 6.1. IR: w(CꢀN)=1639s cm−1 13C-
.
Fig. 4. The piperonal derivative, showing the non parallel nature of
the cyclometallated moieties. The benzodioxan derivative is closely
similar.
{1H}-NMR: l157.7 (CꢀN); l 149.5, 148.1 (C3, C4); l
131.5 (C1); l 124.0 (C5); l 107.9, 106.7 (C2, C6); l
101.3 (OCH2O); C6H11 group: l 69.7 (C7), l 34.4 (C8,
C12), l 25.6 (C10), l 24.8 (C9, C11).
Except for the cyclohexyl and methyl groups, the
Schiff base ligand is almost planar. The deviations from
the least-squares mean plane at the coordination sphere
of palladium (plane 1), the metallacycle (plane 2) and
the phenyl ring (plane 3) are in the range 0.018–0.0358
3,4-{OCH2CH2O}C6H3C(H)ꢀN(C6H11) (b). Yield:
87.0%. Anal. Found: C, 73.4; H, 7.6; N, 5.6. Anal.
Calc.: C, 73.4; H, 7.8; N, 5.7. IR: w(CꢀN)=1630s
cm−1 13C-{1H}-NMR: l 157.7 (CꢀN); l 145.5, 143.6
.
(C3, C4); l 130.5 (C1); l 121.6 (C5); l 117.3, 116.7 (C2,
C6); l 64.5, 64.2 (OCH2CH2O); C6H11 group: l 69.8
(C7), l 34.4 (C8, C12), l 25.6 (C10), l 24.8 (C9, C11).
3,4 - {OCH2O}C6H3C(H)ꢀNCH2(3,4-{OCH2O}C6H3)
(c). Yield: 85.0%. Anal. Found: C, 68.0; H, 4.5; N, 5.0.
,
A. The angles between planes are as follows: plane
1/plane 2: 3.4°, plane 1/plane 3: 6.8°, plane 2/plane 3:
3.9° (1a), and: plane 1/plane 2: 1.7°, plane 1/plane 3:
2.7°, plane 2/plane 3: 1.0° (2b).

B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
77
C11). 13C-{1H}-NMR (2a): l 181.0 (O2CMe); l 166.2
(CꢀN); l 148.0, 146.6, l 144.2 (C3, C4, C6); l 138.5
(C1); l 112.1, 106.3 (C2, C5); l 100.5 (OCH2O); l 23.4
(O2CMe); C6H11 group: l 64.0 (C7), l 34.6 (C8, C12),
l 25.9 (C10), l 25.6 (C9, C11).
Synthesis of [Pd-{3,4-(OCH2CH2O)C6H2C(H)ꢀN-
(C6H11)-C6,N}(m-O2CMe)]2 (2b). 3,4-{OCH2CH2O}-
C6H3C(H)ꢀN(C6H11) (0.585 g, 2.384 mmol) and palla-
dium(II) acetate (0.500 g, 2.227 mmol) were added to
25 cm3 of dry toluene to give a yellow solution which
was heated at 80°C for 3 h under argon. After cooling
to room temperature the solution was filtered to elimi-
nate the small amount of black palladium formed. The
solvent was removed under vacuum and the product
recrystallized from chloroform–n-hexane to give the
desired complex as yellow microcrystals.
Anal. Calc.: C, 67.8; H, 4.6; N, 4.9. IR: w(CꢀN)=1635s
cm−1 13C-{1H}-NMR: l 160.8 (CꢀN); l 149.9, 148.3
(C3, C4); l 147.7, 146.5 (C9, C10); l 133.4 (C7); l
131.0 (C1); l 124.5 (C5); l 121.0 (C11); l 108.6, 108.2
(C8, C12); l 108.0, 106.7 (C2, C6); l 104.4, 100.9
(OCH2O); l 64.5 (NCH2).
.
3,4 - {OCH2CH2O}C6H3C(H)ꢀNCH2(3,4 - {OCH2O}-
C6H3) (d). Yield: 85.0%. Anal. Found: C, 68.4; H, 5.0;
N, 4.9. Anal. Calc.: C, 68.7; H, 5.1; N, 4.7. IR:
w(CꢀN)=1630s cm−1 13C-{1H}-NMR: l160.9 (CꢀN);
.
l 147.7, 146.5 (C9, C10); l 145.9, 143.7 (C3, C4); l
133.4 (C7); l 130.4 (C1); l 121.9, 121.0 (C5, C11); l
117.3, 116.9 (C2, C6); l 108.6, 108.2 (C8, C12); l 100.9
(OCH2O); l 64.6, 64.5, 64.1 (OCH2CH2O, NCH2).
3,4-{OCH2CH2O}C6H3C(H)ꢀNCH2CH2NMe2
(f).
Yield: 83.9%. Anal. Found: C, 66.9; H, 7.6; N, 11.9.
Anal. Calc.: C, 66.6; H, 7.7; N, 12.0. IR: w(CꢀN)=
Yield: 83.1%. Anal. Found: C, 49.5; H, 5.0; N, 3.3.
Anal. Calc.: C, 49.8; H, 5.2; N, 3.4. IR: w(CꢀN)=1605
1635s cm−1 13C-{1H}-NMR: l 160.9 (CꢀN); l 145.8,
.
s, was(COO)=1585 m; ws(COO)=1420 m, sh cm−1
.
143.6 (C3, C4); l 130.1 (C1); l 121.7 (C5); l 117.2,
116.8 (C2, C6); l 64.5, 64.2 (OCH2CH2O); l 60.2, 59.7
(NCH2CH2N), l 45.8 (NMe2).
13C-{1H}-NMR: l 180.6 (O2CMe); l 166.3 (CꢀN); l
146.9, 143.4, 140.1, 139.7, (C1, C3, C4, C6); l
120.2(C5); l 115.0 (C2); l 64.6, 64.3 (OCH2CH2O); l
25.2 (O2CMe); C6H11 group: l 64.0 (C7), l 34.6 (C8,
C12), l 25.9 (C10), l 25.7 (C9, C11).
4.2. Synthesis of complexes
A similar procedure may be used to synthesize com-
pound 1a, which was obtained as a mixture of 1a/2a in
2:1 molar ratio and purified as described before.
Synthesis of [Pd-{3,4-(OCH2O)C6H2C(H)ꢀNCH2(3,4-
{OCH2O}C6H3)-C2,N}(m-O2CMe)]2 (1c). Using a simi-
lar procedure as for compound 2b a mixture of 1c and
2c in a 20:1 molar ratio was obtained.
Synthesis of [Pd{3,4-(OCH2O)C6H2C(H)ꢀN(C6H11)-
C2,N}(m-O2CMe)]2 (1a). 3,4-(OCH2O)C6H3C(H)ꢀN-
(C6H11) (0.550 g, 2.377 mmol) and palladium(II) acetate
(0.500 g, 2.227 mmol) were added to 50 cm3 of glacial
acetic acid to give a yellow solution. After heating at
80°C for 3 h under argon the solution was cooled and
the acetic acid removed in vacuo. The residue was
diluted with water and extracted with dichloromethane.
The combined extract was dried with anhydrous
sodium sulfate, filtered and then concentrated in vacuo
to give a yellow solid, which was column chro-
matographed on silica gel, eluting starting Schiff base
with dichloromethane. Elution with dichloromethane–
ethanol 1% gave a mixture of 1a and 2a in a 9:1 molar
ratio. Compound 1a could be obtained from the mix-
ture in pure form by fractional recrystallization. The
mixture was dissolved in 25 ml of warm chloroform,
filtered, n-hexane carefully added and the resultant
solution kept at −15°C for 48 h. Yellow crystals of 1a
were formed. The chloroform–n-hexane solution was
evaporated to dryness giving a mixture of 1a/2a in 2:1
ratio.
Overall yield: 79.5%. Anal. Found: C, 48.3; H, 3.5;
N, 3.2. Anal. Calc.: C, 48.2; H, 3.4; N, 3.1. IR:
w(CꢀN)=1607 s, was(COO)=1580 m; ws(COO)=1425
m, sh cm−1 13C-{1H}-NMR (1c): l 182.2 (O2CMe); l
.
171.4 (CꢀN); l 151.5, 148.5, 147.9, 147.4, 141.7 (C2,
C3, C4, C9, C10); l 128.5 (C7); l 128.0 (C1); l 123.4,
123.2 (C5, C11); l 109.9, 108.4 (C8, C12); l 104.3 (C6);
l 101.1, 100.3 (OCH2O); l 60.4 (NCH2); l 23.4
(O2CMe). 13C-{1H}-NMR (2c): l 181.8 (O2CMe); l
170.2 (CꢀN); l 151.3, 147.2, 144.7 (C3, C4, C6, C9,
C10); l 137.8 (C1); l 128.7 (C7); l 123.1 (C11); l 112.3,
106.8 (C2, C5); l 100.7 (OCH2O); l 60.5 (NCH2); l
23.3 (O2CMe).
Synthesis
of
[Pd-{3,4-(OCH2CH2O)C6H2C(H)ꢀ
(2d).
NCH2(3,4-{OCH2O}C6H3)-C6,N}(m-O2CMe)]2
Compound 2d was obtained following a similar proce-
dure to compound 2b.
Overall yield: 90.7% (ca. 60% relative to 1a). Anal.
Found: C, 48.8; H, 4.4; N, 3.6. Anal. Calc.: C, 48.5; H,
4.8; N, 3.5. IR: w(CꢀN)=1610m, was(COO)=1588m,
Yield: 78.1%. Anal. Found: C, 49.7; H, 3.8; N, 3.2.
Anal. Calc.: C, 49.4; H, 3.7; N, 3.0. IR: w(CꢀN)=1607
sh; ws(COO)=1425m, sh cm−1 13C-{1H}-NMR (1a): l
.
s, was(COO)=1590 m; ws(COO)=1427 m cm−1 13C-
.
181.9 (O2CMe); l 167.7 (CꢀN); l 151.4, 147.9, 142.5
(C2, C3, C4); l 128.1 (C1); l 122.6 (C5); l 103.9 (C6);
l 100.2 (OCH2O); l 23.2 (O2CMe); C6H11 group: l
64.1 (C7), l 34.7 (C8, C12), l 26.0 (C10), l 25.7 (C9,
{1H}-NMR: l 181.1 (O2CMe); l 170.1 (CꢀN); l 147.9,
146.5 (C9, C10); l 147.5, 144.0, 140.6, 139.0 (C1, C3,
C4, C6); l 128.1 (C7); l 123.6 (C5); l 120.3 (C11);

78
B. Teijido et al. / Journal of Organometallic Chemistry 598 (2000) 71–79
115.8 (C2); l 110.2, 108.4 (C8, C12); l 101.1 (OCH2O);
l 64.7, 64.0 (OCH2CH2O); l 60.3 (NCH2), l 24.4
(O2CMe).
parameters for the crystal structures of complexes 1a
and 2b available on request from author. The crystallo-
graphic data have been deposited with the Cambridge
Crystallographic Data Centre in CIF format. CCDC
no. 117 008 for compound 1a and no. 117 009 for
compound 2b.
Synthesis of [Pt-{3,4-(OCH2CH2O)C6H2C(H)ꢀN-
CH2CH2NMe2-C6,N,N}(Me)] (1f). {3,4-(OCH2CH2O)-
C6H3C(H)ꢀNCH2CH2NMe2 (0.077 g, 0.329 mmol)
and (1,5-cyclooctadiene)dimethylplatinum(II) (0.100 g,
0.298 mmol) were added to 20 cm3 of dry toluene to
give a pale yellow solution which was heated at 90°C
for 24 h under argon. After cooling at room tempera-
ture the solution was filtered to eliminate the small
amount of black platinum formed. The solvent was
concentrated until an orange crystalline precipitate ap-
peared, the solid filtered off and washed with cold
ethanol and n-hexane.
Acknowledgements
We thank the Xunta de Galicia (Proyecto
XUGA20913B96) and the Universidad de la Corun˜a
for financial support.
Yield: 60.0%. Anal. Found: C, 38.1; H, 4.5; N, 6.1.
Anal. Calc.: C, 37.9; H, 4.5; N, 6.3. IR: w(CꢀN)=1619
m. 13C-{1H}-NMR: l 166.2 (CꢀN), J(CPt) 93.6; l
146.0 (C6), J(C6Pt) 1036.0; l 143.7 (C1), J(C1Pt) 37.6;
l 138.8 (C3); l 134.8 (C4), J(C4Pt) 31.2; l 121.7 (C5),
J(C5Pt) 105.7; l 117.1 (C2), J(C2Pt) 49.7; l 68.0
(aCH2); l 64.6, 64.1 (OCH2CH2O); l 51.7 (bCH2),
J(CH2Pt) 29.1; l 48.5(NMe2); l 9.5 (PtMe).
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.