Indole-based mono- and poly-nuclear acyclic chelating systems: Syntheses and selected transition metal complexes

Article abstract of DOI:10.1039/b101350p

The treatment of 3-(4-chlorophenyl)-4,6-dimethoxyindole with phosphoryl chloride in dimethylformamide generates the regioselective product 3-(4-chlorophenyl)-4,6-dimethoxyindole-7-carbaldehyde. This serves as a valuable ligand precursor and, on reaction w

Full text of DOI:10.1039/b101350p

View Article Online / Journal Homepage / Table of Contents for this issue
Indole-based mono- and poly-nuclear acyclic chelating systems:
syntheses and selected transition metal complexes‡
Paul K. Bowyer,*a† David StC. Black,*a Donald C. Craig,a A. David Raeb and
Anthony C. Willisb
a School of Chemistry, University of New South Wales, Sydney NSW 2052, Australia
b Research School of Chemistry, Australian National University, Canberra,
Australian Capital Territory 0200, Australia
Received 12th February 2001, Accepted 11th May 2001
First published as an Advance Article on the web 11th June 2001
The treatment of 3-(4-chlorophenyl)-4,6-dimethoxyindole with phosphoryl chloride in dimethylformamide generates
the regioselective product 3-(4-chlorophenyl)-4,6-dimethoxyindole-7-carbaldehyde. This serves as a valuable ligand
precursor and, on reaction with selected di- and tri-amines, yields a number of new acyclic ligands. Treatment of
these ligands with selected divalent transition metal acetates in the presence of triethylamine in acetonitrile affords
a range of neutral complexes, encompassing both tetrahedral and square-planar metal geometries, of differing
nuclearities. In addition to the chemical and physical properties of the ligands and complexes reported, single crystal
analyses were employed for geometric analysis in two ligand derivatives: the first, a mononuclear distorted tetrahedral
racemic nickel() complex; the second, a dinickel heterochiral complex.
hydrolysis. Systems of higher denticity can be more laborious
Introduction
to synthesize than tetradentate systems, however they remain
The porphyrin moiety has been known and extensively studied
synthetic targets for this reason alone, coupled with the
for decades, and variations on the basic porphyrin unit are to be
often physically and chemically unprecedented characteristics
found in a large proportion of terrestrial organisms. Some time
discovered.
ago Sessler et al.1 reported notable characteristics of what may
Some years ago a general procedure for the synthesis of
be viewed as a logical progression of the natural base porphyrin
3-arylindoles was developed from a method reported by
system: an “expanded” 22π pentapyrroloporphyrin called
Nordlander et al.5 for the synthesis of indoles via N-trifluoro-
sapphyrin 1. Since its report in 1966,2 numerous derivatives of
acetyl-2-anilino acetals. These new arylindole derivatives are
found to eliminate unwanted reactivity problems, whilst
additionally allowing access to new ligand precursors that
display differing levels of nucleophilicity at the indole 2 and 7
positions.
The generation of acyclic structures requires that, where two
active sites on a precursor exist, activity must be reduced at
one position in order to extend maximum synthetic advantage.
Strategic positioning of electron-donating methoxy groups on
the indole precursor provides nucleophilic activity at the 7
position, whilst modification of the 3-aryl para substituent,
with respect to electron donating or withdrawing ability, affords
a variety of relative levels of nucleophilicity at the indole 2
position. Variation in the geometric arrangements of selected
di- and tri-amines thus permitted the production of a range of
this species have appeared.3 In the light of this work, indole-
new indole-containing Schiff base ligands whose transition
based acyclic and macrocyclic chelating systems were envis-
aged, due to the structural and chemical similarities between
pyrrole and indole. Some of these new ligand systems and
associated complexes are reported here.
Tetradentate indole-containing chelate systems have been
known for some time,4 however this work centred around tem-
plated Schiff base syntheses. While simplifying the synthetic
procedures, such methods usually do not permit studies of the
parent free-base ligand due to the rigours of the metal extrac-
tion process and susceptibility of the acyclic free bases to imine
metal complexes are of differing nuclearities, metal geometries
and ligand configurations.
Results and discussion
Ligand precursors and syntheses
Nucleophilically active species react with the Vilsmeier reagent
to produce formylated products after basic hydrolysis of the
intermediate. For the purposes of the synthesis of acyclic
ligands the 3-(4-halogenophenyl)indole derivatives6 are the
most useful due to the electron-withdrawing nature of the para-
halogeno functionality. The decreased nucleophilic activity at
the 2 position of the indole compared with the highly activated
7 position produces a higher yield of 7-formylindole on reac-
tion with the Vilsmeier reagent. No 2-formylindole is observed
in formylation reactions except in the case of the highly activ-
† Current address: School of Wine and Food Sciences, Charles Sturt
University, Locked Bag 588, Wagga Wagga NSW 2678, Australia.
E-mail pbowyer@csu.edu.au
‡ Electronic supplementary information (ESI) available: rotatable 3-D
crystal structure diagram in CHIME format; analytical and physical
data for 3–10. See http://www.rsc.org/suppdata/dt/b1/b101350p/
1948
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b101350p

View Article Online
ated 4,6-dimethoxy-3-(4-methoxyphenyl)indole, and then only
as a minor product, indicating that in all other instances 2,7
diformylation is preceded by 7 formylation. This hypothesis
gains support through recent studies on the corresponding
2-arylindole isomers, where only 7 formylation was observed.7
Thus, a chilled solution of 3-(4-chlorophenyl)-4,6-dimethoxy-
indole 2 in dimethylformamide reacted with a chilled solution
of the Vilsmeier reagent to afford 3-(4-chlorophenyl)-4,6-
dimethoxyindole-7-carbaldehyde 3 in a yield of 84% (Scheme
1). A 1H NMR investigation of the product indicates the loss of
A standard procedure for the syntheses of the target ligands
(4–10) was developed. The combination of starting materials in
benzene at reflux under an inert atmosphere in the presence of a
trace of p-toluenesulfonic acid promoted a steady reaction rate.
It is believed that the same electron density increase generated
by the methoxy-groups hinders the Schiff base procedure due
to the resultant decreased electrophilic character of the formyl
carbon. Water removal was effected by the placement of activ-
ated, degassed 4A molecular sieves in the catchment arm of
a Dean–Stark apparatus. The methods of product isolation
varied according to the physical characteristics and hydrolytic
susceptibilities of the compounds, and are commented on
individually where necessary.
Mononuclear systems
Complexes of 4. Treatment of 4 with nickel(), cobalt(),
copper() and palladium() acetates afforded the neutral,
highly insoluble square-planar complexes 4a–d respectively
(Scheme 2). The nickel() and palladium() complexes are
characterised by molecular ions in their FAB mass spectra
corresponding to the respective M ϩ 1 Cl35/35 mass units; the
cobalt() complex displays a 90% relative intensity peak. The
FAB mass spectrum of the copper() complex displays only
mass signals for the demetallated complex, a phenomenon
which has been observed in the FAB mass spectra of similar
systems and is commented upon elsewhere.8
Scheme 1 Reagents and conditions: (i) POCl3, DMF, 0 ЊC; (ii) NaOH,
water.
the H7 proton resonance (δ H7 6.45), collapse of the H5 reson-
ance from a doublet in the precursor (4JH5H7 = 1.9 Hz) to a
singlet at δ 6.15 and retention of the H2 resonance as a doublet
(3JH2NH = 2.2 Hz). The aldehyde is characterized by a new signal
at δ 10.35. All additional spectroscopic and analytical data are
in full accord with the proposed structure.
The cobalt, copper and palladium complexes are all brown,
whilst the nickel complex is red. The 1H NMR spectrum of the
nickel() complex mirrors that of the C2 symmetric free-base
ligand with small field shifts (ca. 0.1–0.2 ppm) for all signals. Of
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
1949

View Article Online
because it cannot easily support a square-planar chelation
mode.
Treatment of 5 with nickel() acetate in acetonitrile at reflux
produced an immediate change from the orange of the free-
base ligand to red-brown. Isolation of 5a followed by spectro-
scopic investigation indicated a complex that is structurally
different from those previously discussed. An NH absorption is
visible in the IR spectrum at 3354 cmϪ1, indicative of a non-
coordinating bridging amino group, in contrast to complexes
5b–d. Additionally, the fingerprint region of the spectrum
1
differs notably from those for the previous complexes. The H
NMR spectrum indicates the presence of paramagnetic (and
therefore non-planar) nickel atoms, with a large array of reson-
ances observed.
A FAB mass spectral analysis gave an ion at m/z 1701 and
a smaller peak at m/z 851, corresponding to Ni2L2 and NiL
respectively. Modelling studies with tetrahedral metal centres
suggest that the dimer is unlikely to adopt a pseudo-linear
“meso” structure, where the two ligands are parallel and
approximately linear, even though examples of such com-
plexes appear in the literature.9 In the absence of a solid-
state analysis we thus tentatively suggest that the Ni2L2
complex adopts a less sterically demanding helical structure
(Scheme 4).
Scheme 2 Reagents and conditions: (i) M(OAc)2ؒnH2O, CH3CN,
Et3N, ∆.
note is the slight upfield shift from δ 9.15 to 8.91 observed for
the imine proton resonance on chelation, presumably due to the
proximity of the shielding metal orbitals. The downfield shift of
0.36 ppm of the H2 proton resonance is indicative of a net loss
of electron density in the indole moiety due to the presence of
the metal and formation of covalent N–M bonds. The absence
of evidence for axial ligands, particularly in the NMR (4a and
4d) and IR spectra, strongly suggests that all complexes are
square-planar neutral species.
Complexes of 5. Reaction of ligand 5 with cobalt(),
copper(), and zinc() acetates affords complexes 5b–d respec-
tively that are all mononuclear and, based on physical
and spectroscopic data, their collective metal geometries are
postulated as distorted tetrahedral, with possible supporting
chelation from the bridging amino lone pair (Scheme 3). The
Scheme 3 Reagents and conditions: as in Scheme 2.
cobalt() complex yields a weak molecular ion under mass
spectral analysis. In the case of the copper() complex only
demetallation fragments are observed, as for 4c, whilst the
zinc() complex gave a strong molecular ion. A demetallation
peak was also observed for all complexes excepting that of
cobalt().
No absorption from the bridging NH was observed in the IR
spectra of any of the complexes, possibly due to its low inten-
sity, or as a result of weak dative interaction with the metal
centre: the proximity of the amino lone pair to the metal centre
would suggest the latter to be likely. The zinc() complex dis-
plays a 1H NMR spectrum that closely parallels that of the free-
base ligand, as anticipated, with the obvious omission of the
indole NH resonance.
The complexes decomposed on attempted recrystallization.
This thermal instability is suggestive of an imperfect coordin-
ation sphere with respect to the requirements of the metal
centre. Ligand 5 failed to coordinate palladium(), presumably
Scheme 4 Reagents and conditions: (i) Ni(OAc)2ؒ4H2O, CH3CN,
Et3N, ∆.
A MALDI (matrix-assisted laser-desorption ionization)-
TOF analysis of 5a gave peaks of 45 and 25% relative inten-
sities corresponding to Ni2L2 and NiL2 respectively, and peaks
of 100 and 90% relative intensities corresponding to NiL and L
respectively. It is unclear whether fragmentation of a dinuclear
complex is being seen, or whether a mixture of mononuclear
and dinuclear complexes is present. The large number of reson-
ances observed in the 1H NMR spectrum of the complex
1950
J. Chem. Soc., Dalton Trans., 2001, 1948–1958

View Article Online
Table 1 Selected bond lengths (Å), angles and torsional angles (Њ) for
compound 6aؒCHCl3
suggests the latter to be correct, although it is uncertain if these
species retain structural integrity in solution.
Ni–N1
Ni–N2
Ni–N3
Ni–N4
N1–C1
N1–C8
N2–C17
N2–C18
1.930(5)
N1–Ni–N2
N1–Ni–N3
N1–Ni–N4
N2–Ni–N3
N2–Ni–N4
N3–Ni–N4
Ni–N1–C1
Ni–N1–C8
C17–N2–C18
C18–C23–C46–C41
93.6(2)
109.6(2)
140.6(2)
127.5(2)
98.8(2)
Complexes of 6. Extended heating of 6 in acetonitrile was
required to effect metal complexation, affording complexes 6a-d
(Scheme 5). The spectral data are in accord with the proposed
1.984(6)
1.922(5)
1.994(5)
1.376(8)
1.361(8)
1.324(8)
1.435(8)
91.9(2)
129.7(4)
124.9(5)
115.0(6)
Ϫ64.8(9)
Scheme 5 Reagents and conditions: as in Scheme 2.
structures. The zinc() complex 6d gave a molecular ion under
MALDI conditions yet showed demetallation under FAB
ionization.
The 1H NMR spectrum of the zinc complex is unremarkable
whilst that of the nickel complex shows resonances over a field
of some 100 ppm (signals are observed from δ Ϫ10 to 90) and is
indicative of a paramagnetic complex. Interestingly, the reson-
ance linewidths were found not to be excessively large, as is the
case with many paramagnetic NMR spectra.9 The observed
massive field shifts and loss of polarization due to the presence
of the paramagnetic metal centre meant that few routine proton
assignments could be made. The integral ratios in combination
Fig. 1 Thermal ellipsoid diagram of 6aؒCHCl3. Ellipsoids indicate
10% probability levels.
1
with a H–1H correlation permitted peak assignments to be
Dinuclear systems
made with some degree of accuracy. The extreme downfield
broad singlet at δ 90.00 is tentatively assigned as the resonance
of the imine proton with H2, being spatially closest to the metal
centre, unobserved.
The vast solubility difference between the free-base ligand
and its complexes is noteworthy. The 2,2Ј-biphenyl linkage
necessarily enforces great torsional deformation in the chelate
ring about the annular linkage. The free-base ligand is able to
alleviate these steric interactions by adopting a more linear con-
formation, which presumably reduces solubility. The stepwise
coordination of metal ions would then produce a more com-
pact and easily solvated structure, resulting in the observed
greater solubility of the complex.
The crystal and molecular structures of 6a were determined
(Tables 1 and 3). The complex crystallises in the monoclinic
space group P21/c. The nickel atom lies in a distorted tetra-
hedral environment with bond angles of 98.8, 91.9, 109.6 and
93.6Њ. Coordination of a tetrahedral metal centre by an
unsymmetrical bis-bidentate ligand affords a chiral complex;
the ∆ enantiomer is depicted in Fig. 1. The nickel–indole nitro-
gen bond distances are Ni–N1 1.930(5) Å and Ni–N3 1.922(5)
Å, whilst the Ni–imine nitrogen bond distances are Ni–N2
1.984(6) Å and Ni–N4 1.994(5) Å, illustrating the stronger
bonds to the electron-rich indole unit. The structure also shows
that the Ni–imine hydrogen distance is approximately 3.9 Å and
the Ni–indole H2 distance is 3.2 Å, reinforcing the proton
NMR assignment.
The synthesis of dinuclear complexes requires certain basic
conditions to be met. The ligands must possess at least two
coordinating domains, and the linkage between these domains
must display some degree of flexibility so as to facilitate the
coordination of two metal atoms by one ligand. Additionally,
the ligand should not be linear or capable of forming mono-
nuclear complexes. Two commercially available diamines were
seen to fulfil these requirements in choosing a ligand pre-
cursor: 4,4Ј-methylenedianiline and 4,4Ј-ethylenedianiline. One
important feature that led to the selection of these two particu-
lar diamines is that the nature of the molecular fulcrum in each
case is based on a tetrahedron, which should favour formation
of a “bent” conformation. Additionally, the complexes of the
more flexible ethane-linked ligand would provide valuable
comparisons with those obtained from the methylene-linked
complexes, given the difference in ligand bite angle produced in
each case.
Complexes of 7. In each case it was decided to treat the ligand
with nickel() acetate, because of the information provided by
1
the H NMR spectra of the complexes, even in the case of a
paramagnetic complex. Additionally, in the case of 7, cobalt()
was included for examination due to its larger ionic radius when
compared with nickel(), and the lack of electronic preference
for square-planar coordination that the d8 metal ion possesses.
Ligand 7 was treated with nickel() acetate tetrahydrate to
1
In contrast to the red planar complex 4a the tetrahedral
complex 6a is almost black, reflecting the significant geometric-
ally enforced chromophoric differences and the qualitative
manner in which the geometry of the metal centre in these
neutral indole complexes can be deduced.
yield 7a. The H NMR spectrum of the complex (Fig. 2) indi-
cates the presence of tetrahedral nickel, in that the resonances
are observed over a field range of some 50 ppm. Only ten
resonances are observed, indicating that the complex possesses
C2 or higher symmetry. As with 6a a single upfield resonance is
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
1951

View Article Online
Fig. 2 1H NMR spectrum (299.95 MHz; [2H]chloroform) of 7a, illustrating the presence of a symmetrical dimer with paramagnetic tetrahedral
nickel metal centres.
observed near δ Ϫ10. No IR absorption is observed in the range
of 3600–3200 cmϪ1, indicating coordination saturation. A
MALDI-TOF mass spectral analysis displays a 15% relative
intensity peak at m/z 1701, corresponding to the target Ni2L2
mass unit.
The mass ion at m/z 1701 clearly indicates the presence of a
2 : 2 complex. Modelling studies suggest that a linear dinuclear
complex is disfavoured in preference for a double helix (Scheme
6). The formation of helical species with such a ligand is not
suggested that the preferred conformation of these complexes is
that of a double helix.
Reaction of 3 with 1,3-diaminobenzene. The synthesis of 9
was expected to produce a ligand whose coordination field was
too large to form mononuclear complexes with the first-row
transition metals employed in this study, thus forcing the ligand
to form di- or poly-nuclear species. 1,3-Diaminobenzene was
treated with 3 but product formation was slow and incomplete.
Unchanged 3 was removed by the addition of small amounts of
2,2Ј-diaminobiphenyl (ca. 10 mg) to the reaction mixture, pro-
ducing highly insoluble 6. After the solvent was removed under
reduced pressure, the solid residue was boiled in chloroform
and filtered hot to separate the two ligands (Scheme 7). Spectro-
Scheme 6 Reagents and conditions: as in Scheme 2.
Scheme 7 Reagents and conditions: (i) 1,3-diaminobenzene, C6H6,
∆, N2; (ii) 2,2Ј-diaminobiphenyl, CHCl3, ∆.
without precedent given that a similar ligand, using the same
coordinating domain spacer, forms a dinuclear triple helicate
in the presence of nickel():10 presumably 7 does not form a
species of identical stoichiometry as the literature example due
to the bis-anionic coordination domains.
Peaks corresponding to the Co2L2 mass unit were also
obtained for the complex 7b.
scopic and physical data for 9 are in full accord with the
proposed structure.
Complexes of 9. Complexes 9a–c were produced according to
the standard procedure (Scheme 8). A palladium() complex
Complexes of 8. Complex 8a (Scheme 6) shows no NH-
assignable absorption in the IR spectrum. Mass spectral
demetallation was observed as in the case of 4c and 6a, again
indicating possible weak coordination of the metal. The para-
1
magnetic H NMR spectrum of 8a indicates tetrahedral nickel
atoms. Only ten resonances are observed, suggesting C2 or
higher symmetry, which strongly implies a dimer.
Zinc complex 8b also displayed no NH absorptions in its IR
spectrum and gave a Zn2L2 peak at m/z 1741. The breakdown
pattern of 8b is similar to that observed for the complexes of 7,
indicating that the tertiary structures of the two groups of
complexes are potentially quite similar. Unfortunately, 8b was
found to be too insoluble for 1H NMR characterization.
Since the formation of a dinuclear meso species is strongly
disfavoured and in consideration of the literature precedent
for helicate formation in ligands employing this spacer,10 it is
Scheme 8 Reagents and conditions: as in Scheme 2.
could not be formed, indicating the preference of 9 for
tetrahedral chelation. MALDI-TOF mass spectral analyses
curiously indicated the formation of mononuclear complexes,
1952
J. Chem. Soc., Dalton Trans., 2001, 1948–1958

View Article Online
Table 2 Selected bond lengths (Å) and angles (Њ) for compound
9aؒ7DMF
Ni1–N1
Ni1–N2
Ni1–N3
Ni1–N4
N1–C1
N1–C4
N2–C9
1.910(5)
1.998(5)
1.922(5)
1.996(5)
1.376(6)
1.367(6)
1.320(6)
1.422(6)
7.211(4)
N1–Ni1–N2
N1–Ni1–N3
N1–Ni1–N4
N2–Ni1–N3
N2–Ni1–N4
N3–Ni1–N4
Ni1–N2–C9
Ni1–N2–C35
Ni1–N3–C18
Ni1–N3–C21
92.5(2)
118.0(2)
127.1(2)
121.7(2)
107.6(2)
92.3(2)
126.5(4)
115.8(3)
129.1(4)
125.3(4)
N2–C35
Ni ؒ ؒ ؒ Ni
Fig. 5 Partial molecular structure of 9aؒ7DMF, showing the meso-like
disposition of the ligands about the Ni–Ni axis. Peripheral atoms and
solvent molecules have been omitted for clarity.
regarded as 1 : 1 disordered. There are 7 solvent molecules per
unit cell, one of them disordered about 1/2,0,0 and all have
large thermal motion, explaining the lack of crystal stability
on removal from the mother liquor. Refinement used the
constrained refinement program RAELS 9611 so as to allow
anisotropic thermal parameters to be defined by rigid body
parameterizations. This allowed just 270 independent variables
adequately to refine the structure down to R(F) = 0.074 for the
4299 reflections with I > 3σ(I) used in the refinement. The Ni
was refined as an isolated anisotropic atom but the remaining
atoms were described using local coordinates defined relative to
orthonormal axial systems.12
Fig. 3 Thermal ellipsoid diagram of 9aؒ7DMF with labelling of
selected atoms. Asterisks indicate atoms that have been generated by the
crystallographic symmetry operation (Ϫx, 1 Ϫ y, 1 Ϫ z). Both locations
of each disordered atom are shown. Ellipsoids indicate 30% probability
levels. Hydrogen atoms and solvent molecules have been omitted for
clarity.
The dimer has inherent 2/m symmetry with the inversion
centre being exact: the distances hold this symmetry relation-
ship well. The nickel coordination is distorted tetrahedral, with
bond angles of 92.5, 92.3, 118.0 and 107.6Њ, with the last two
angles showing the only significant departure from the inherent
symmetry relationships between angles in the dimer.
The adoption of tetrahedral geometry by the metal is
believed to be a means of reducing the aryl H2–metal inter-
action, to such an extent that the electronic preference of
nickel() for square-planar geometry is overcome. It appears
that, on coordination of the metal ion, the interaction between
the aryl H2 and the metal atom (in addition to the large size of
the coordination sphere) is sufficient to discourage planar
coordination but does not preclude the formation of a dimeric
complex with two tetrahedral metal centres. Since the ligand is
achiral the resulting complex is a meso species and is therefore
also achiral, with metal centres of opposing chirality.
It is particularly noteworthy that the system does not adopt
the more common helical coordination mode observed for
ligands of this type.13 In such cases the ligands are seen to wrap
themselves about the metal–metal axis,9,13 however 9a forms a
complex whereby each ligand remains essentially on one side
only of the metal–metal axis (Fig. 5). The exception to this is the
central region where π-stacking necessitates the proximity of
the aryl spacers.
Fig. 4 Thermal ellipsoid diagram of 9aؒ7DMF. Both locations of
each disordered atom are shown. Ellipsoids indicate 30% probability
levels. Hydrogen atoms and solvent molecules have been omitted for
clarity.
with demetallation peaks observed for 9b and 9c. Complex
9a is black, again indicative of a tetrahedral metal geometry.
Complexes 9a–c were crystallised from dimethylformamide
as rectangular blocks. Removal of these crystals from the
mother liquor induced immediate decomposition. In order for a
structural analysis to be undertaken, a suitable crystal of 9a was
drawn into a glass capillary onto glass fibres so that the crystal
remained in contact with the mother liquor. The sealed
assembly was used for data collection.
On the basis of these observations it is presumed that the
cobalt and copper complexes 9b and 9c are also dinuclear, given
the similarities in physical data with those of 9a.
The complex 9a (Figs. 3 and 4) exists in the solid state as a
dimer, with a centre of inversion coincident with a crystallo-
graphic inversion centre of P1; bond lengths and angles are
given in Table 2 and crystallographic data appear in Table 3.
Nickel-to-indole and -imine bond lengths compare favourably
with those of the mononuclear species 6a; the Ni ؒ ؒ ؒ Ni dis-
tance is 7.211(4) Å. One half of the dimer shows distinctly more
thermal motion than the other and the C atoms of the four
methoxy groups of the crystallographic asymmetric unit were
Complexes of 10. Ligand 10 was treated with nickel() acetate
tetrahydrate (Scheme 9). A yield calculation of 99% was based
on a hypothetical monomeric complex 10a.
1
The H NMR spectrum of the complex corresponds to that
of a paramagnetic sample with many resonances, indicating the
presence of at least one tetrahedral nickel atom. The low ratio
of NH-(normally a medium-strong absorption)-to-fingerprint
IR absorptions indicates that either the sample is contaminated
with unchanged ligand, or that only a relatively small amount
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
1953

View Article Online
Table 3 Crystallographic data for complexes 6aؒCHCl3 and 9aؒ7DMF
6aؒCHCl3
9aؒ7DMF
Formula
M
Crystal system
Space group
C46H34Cl2N4NiO4ؒCHCl3
955.8
Monoclinic
P21/c
C80H60Cl4N8Ni2O8ؒ7C3H7NO
2032.28
Triclinic
¯
P1
a/Å
b/Å
c/Å
α/Њ
13.342(3)
20.470(5)
20.763(5)
—
128.417(8)
—
4443(2)
4
7.88
12.952(12)
14.602(12)
15.286(13)
70.36(6)
71.35(6)
85.15(7)
2579(4)
1
β/Њ
γ/Њ
u/Å3
Z
µ(Mo-Kα)/cmϪ1
T/K
5.37
273.2
294
No. of reflections
(total)
(unique)
Rint
5784
3641
0.021
9135
4299
0.028
R, Rw
0.066, 0.101
0.074, 0.101
der Waals forces or hydrogen-bonding interactions. Complex
10b exhibits an amorphous structure and neither 10a nor 10b
gave a diffraction pattern under an X-ray beam, indicating the
absence of crystalline material.
Conclusion
A range of new indole-containing acyclic ligands has been
produced and their coordinating abilities probed by employing
first-row transition metals of varying ionic size and electronic
geometrical preferences. The metal geometries were established
qualitatively, by consideration of the extremely characteristic
1
colours of the nickel() complexes and H NMR data, and
quantitatively in two cases via crystallographic analyses. In each
of the solid state analyses the metal was found to possess a
distorted tetrahedral disposition. The complex 9a was found
to exist as a heterochiral dimer in the solid state. MALDI-TOF
mass spectral analyses proved particularly useful for accumu-
lating evidence for the formation of dinuclear species in the
absence of structural characterizations.
Experimental
Melting points are uncorrected. Microanalyses were performed
Scheme 9 Reagents and conditions: as in Scheme 2.
1
by Dr H. P. Pham of the University of New South Wales. H
of uncoordinated indole remains corresponding to the
uncoordinated terminal indoles of a polymer. A MALDI-TOF
mass spectral analysis of the sample afforded only demetallated
complex peaks. These data and the lack of discrete chelate
masses in the mass spectrum suggest that 10a is polymeric.
Cobalt analogue 10b displays two imine absorptions at 1598
and 1539 cmϪ1, corresponding to uncoordinated and coordin-
ated stretching modes respectively. The fingerprint region of
the spectrum strongly resembled that of the nickel complex,
but was vastly different from that of the free-base ligand.
A MALDI-TOF mass spectral analysis produced only peaks
corresponding to a demetallated complex, as in the case of 10a,
however laser desorption of the sample with no matrix afforded
peaks at m/z 2256 and 1506, which correspond approximately
to the Co2L3 and Co2L2 structures respectively. It is therefore
considered that 10b is also polymeric.
No reaction occurred between 10 and palladium acetate,
suggesting that the metal geometries in 10a and 10b are
tetrahedral.
The products 10a and 10b were studied by transmission elec-
tron microscopy. The images obtained from the nickel complex
10a illustrate that it exists as rod-like structures. In addition,
these rods appear to congregate in clusters, perhaps due to van
and 13C NMR spectra were obtained in the designated solvents
on a Bruker AC300F (300 MHz) spectrometer, variable tem-
1
perature H NMR spectra using a Bruker AM500 (500 MHz)
spectrometer. Data are given as the chemical shift measured in
parts per million (ppm), proton count, multiplicity, observed
coupling constant (J) in Hertz (Hz). Multiplicities are reported
as singlet (s), broad singlet (br s), doublet (d), triplet (t), quartet
(q) and multiplet (m). 13C NMR chemical shifts are reported in
ppm downfield from TMS (δ); the carbon count and identifiable
carbons are given. Transmission electron microscopy was
performed by Ms Vera Piegerova on a JEOC STEM 2000FX.
Infrared spectra were recorded as KBr discs on a Mattson
Sirius 100 FTIR spectrometer. Nujol mulls were recorded on
a Perkin-Elmer 298 or 580B spectrometer. Ultraviolet-visible
spectra were obtained in acetonitrile on a Hitachi UV-3200
spectrophotometer. CI mass spectra were recorded on a Kratos
MS902 or MS840 instrument, EI mass spectra on an AEI MS
12 mass spectrometer at 70 eV ionizing potential and 8000 V
accelerating voltage with an ion source temperature of 210 ЊC,
FAB mass spectra on a VG Biotech Quattro triple quadrupole
spectrometer or a VG Autospec (Mark 1) spectrometer in
EBE configuration, using p-nitrobenzoic acid–dichloromethane
50 : 50 as a matrix and MALDI-TOF mass spectra on a
1954
J. Chem. Soc., Dalton Trans., 2001, 1948–1958

View Article Online
Finnigan MAT Lasermat 2000. The m/z values of the prin-
cipal ion peaks are reported together with their percentage
intensities relative to the base peak (where possible). Flash
chromatography was carried out using Merck silica gel 7730
1,2-diaminobenzene (0.100 g, 0.942 mmol) were treated accord-
ing to the general procedure. After 72 h of heating at reflux a
precipitate was observed and the mixture was cooled, filtered
and the residue recrystallized from CH2Cl2 to afford the ligand
as orange-yellow needles (0.298 g, 45%). δH(299.95 MHz;
solvent [2H]chloroform; standard SiMe4) 3.87 and 3.91 (12 H, s,
OCH3), 6.22 (2 H, s, H5), 6.51 (2 H, s, H2), 7.23 and 7.4 (8 H, d,
J 9.0 Hz, chlorophenyl), 7.26 and 7.30 (4 H, m, aryl), 9.15 (2 H,
60GF254
.
Anhydrous tetrahydrofuran (THF) was distilled from potas-
sium and benzophenone; dimethylformamide (DMF) was
dried over calcium hydride then distilled under reduced pres-
sure onto activated 4A molecular sieves; chloroform (CHCl3)
was distilled from phosphorus pentaoxide, diethyl ether from
sodium and benzophenone. 3-(4-Chlorophenyl)-4,6-dimethoxy-
indole 2 was prepared according to the literature procedure.6
1,2-, 1,3-, 1,4-Diaminobenzene, 4,4Ј-methylenedianiline and
4,4Ј-ethylenedianiline were obtained commercially and purified
before use. 2,2Ј-Diaminobiphenyl was prepared from the
corresponding commercially available dinitro species according
to the literature procedure.14 2,2Ј-Diaminodiphenylamine was
prepared according to the literature procedure.14
s, CH᎐N), 11.61 (2 H, br s, NH); too insoluble for δ ; m/z (FAB)
᎐
C
707 (M ϩ 1, Cl37/37, 20%), 706 (Mϩ, Cl37/37, 35), 705 (M ϩ 1,
Cl35/37, 75), 704 (Mϩ, Cl35/37, 60), 703 (M ϩ 1, Cl35/35, 100), 702
(Mϩ, Cl35/35, 25).
{1,2-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}nickel(II) 4a. This compound was
prepared according to the general method using ligand 4 (0.100
g, 0.142 mmol) dissolved in the minimum amount of
acetonitrile at reflux and nickel() acetate tetrahydrate (0.037 g,
0.15 mmol), prompting an immediate change from yellow-
orange to a vivid red-brown, The mixture was heated at reflux
for 1 h, then allowed to cool to room temperature, chilled and
filtered. The product was washed with acetonitrile followed by
anhydrous diethyl ether, affording the complex as red-brown
microcrystals (0.102 g, 95%). δH(299.95 MHz; solvent [2H]-
chloroform; standard SiMe4) 3.96 and 4.04 (12 H, s, OCH3),
6.16 (2 H, s, H5), 6.87 (2 H, s, H2), 7.17 (6 H, m, chloro-
phenyl ϩ 2 H aryl), 7.47 (4 H, d, J 8.5, chlorophenyl), 7.70 (2 H,
Preparations
General method for Schiff bases. The stoichiometric amounts
of the appropriate aldehyde and amine were placed in a suitably
sized multi-necked round bottom flask. A Dean–Stark appar-
atus was affixed between flask and condenser, the catchment
arm of which contained activated, degassed 4A molecular
sieves. The solutions were heated at reflux under a dinitrogen
atmosphere and the reaction was monitored by TLC. On com-
pletion of the reaction, the products were filtered off where
solids were obtained, or the solvent was removed and the
product obtained by chromatographic purification where
possible.
dd, J 6.0, 3.0 Hz, aryl), 8.91 (2 H, s, CH᎐N); too insoluble for
᎐
δC; m/z (FAB) 763 (M, Cl37/37, 20%), 762 (M ϩ 1, Cl35/37, 55), 761
(Mϩ, Cl35/37, 75), 760 (M ϩ 1, Cl35/35,100), 759 (Mϩ, Cl35/35,70),
758 (M Ϫ 1, Cl35/35, 75), 746 (50), 726 (40), 721 (20), 705 (20).
{1,2-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}cobalt(II) 4b. This compound was
prepared according to the general method using ligand 4 (0.100
g, 0.142 mmol) and cobalt() acetate tetrahydrate (0.037 g, 0.15
mmol) and obtained as red-brown microcrystals (0.101 g,
94%). m/z (FAB) 764 (Mϩ, Cl37/37, 10%), 763 (M ϩ 1, Cl35/37, 30),
General method for complexes. The ligand was suspended or
dissolved in acetonitrile near reflux and anhydrous triethyl-
amine (3 drops) followed by the metal acetate was added. Heat-
ing of the mixture at reflux was continued for the specified
duration, after which the mixture was filtered and the solid
washed with acetonitrile then anhydrous diethyl ether, air dried
and collected.
762 (Mϩ, Cl35/37, 60), 761 (M ϩ 1, Cl35/35, 90), 760 (Mϩ, Cl35/35
85), 759 (M Ϫ 1, Cl35/35, 100), 746 (15), 726 (5), 703 (15).
,
3-(4-Chlorophenyl)-4,6-dimethoxyindole-7-carbaldehyde 3. To
a stirred solution of 3-(4-chlorophenyl)-4,6-dimethoxyindole 2
(5.00 g, 17.4 mmol) in anhydrous dimethylformamide at Ϫ15 ЊC
was added dropwise an ice cold solution of phosphoryl chloride
(4.00 g, 26.1 mmol) in dimethylformamide (3 mL). The mixture
was stirred at this temperature for 1 h, then allowed to come to
room temperature. Ice–water (10 mL) was added and the mix-
ture stirred vigorously for 1 h, then made alkaline (pH 9) with
10% sodium hydroxide solution and stirred vigorously for 4 h.
The mixture was then neutralized with 2 M HCl solution and
extracted with dichloromethane (3 × 100 mL), the organic layer
collected, dried (MgSO4) and the solvent removed under
reduced pressure. The resulting solid was purified by column
chromatography (CH2Cl2–n-hexane 50 : 50 eluent) and the
uppermost band collected and crystallized from dichloro-
methane–n-hexane to afford compound 3 as yellow crystals
(4.6 g, 84%). δH(299.95 MHz; solvent [2H]chloroform; standard
SiMe4) 3.89 and 3.96 (6 H, s, OCH3), 6.15 (1 H, s, H5), 7.04
(1 H, d, JH2NH 2.2, H2), 7.29 and 7.45 (4 H, d, J 8.5 Hz,
chlorophenyl), 10.35 (1 H, s, CHO), 10.49 (1 H, br s, NH);
δC(299.95 MHz; solvent and standard [2H]chloroform) 55.44
and 56.43 (2 C, OCH3), 86.88, 121.85, 127.70 and 130.66 (6 C,
aryl CH), 104.52, 110.03, 117.73, 131.90, 133.94 and 137.77 (8
C, aryl C), 188.37 (1 C, CHO); m/z (EI) 316 (M ϩ 1, 20%), 315
(Mϩ, 100), 300 (20), 265 (50), 229 (10), 78 (40), 43 (60), 32 (100),
28(100).
{1,2-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}copper(II) 4c. This compound was
prepared according to the general method using ligand 4 (0.100
g, 0.142 mmol) and copper() acetate monohydrate (0.0297 g,
0.149 mmol) under a dinitrogen atmosphere and obtained as
brown microcrystals (0.071 g, 65%). m/z (FAB) 706 (demetal-
lated complex, L ϩ 1, 55%).
{1,2-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}palladium(II) 4d. This compound
was prepared according to the general method using ligand 4
(0.100 g, 0.142 mmol) and palladium() acetate (0.034 g, 0.15
mmol) and obtained as brown microcrystals (0.098 g, 86%).
m/z (FAB) 812 (M ϩ 1, Cl37/37, 30%), 811 (Mϩ, Cl37/37, 45), 810
(M ϩ 1, Cl35/37, 70), 809 (Mϩ, Cl35/37, 75), 808 (M ϩ 1, Cl35/35
,
100), 807 (Mϩ, Cl35/35, 80), 806 (M Ϫ 1, Cl35/35, 85), 805 (50), 804
(20), 793 (8).
2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylamine 5. A mixture of 3 (1.23 g, 3.88
mmol) and 2,2Ј-diaminodiphenylamine (0.368 g, 1.85 mmol)
was heated according to the standard procedure. The crude
solid was collected by filtration, purified by thin-layer chrom-
atography (CH2Cl2–n-hexane 70 : 30 eluent) and recrystallized
from dichloromethane–n-hexane to afford compound 5 as
orange-yellow crystals (1.25 g, 85%). δH(299.95 MHz; solvent
[2H]chloroform; standard SiMe4) 3.78 and 3.81 (12 H, s,
OCH3), 6.03 (2 H, s, H5), 6.38 (2 H, d, JNHH2 2.3, H2), 6.96
(2 H, t, J 7.4, aryl), 7.17 (3 H, m, aryl), 7.25 and 7.33 (4 H, d,
1,2-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzene 4. The aldehyde 3 (0.610 g, 1.93 mmol) and
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
1955

View Article Online
J 8.6, chlorophenyl), 7.47 (1 H, t, J 7.4, aryl), 7.61 (2 H, t, J 7.4
ing to the general procedure. After 1 h a yellow precipitate was
Hz, aryl), 7.63 (1 H, br s, NH), 9.07 (2 H, s, CH᎐N), 10.92 (2 H,
observed to form. After 48 h the mixture was allowed to cool to
room temperature then filtered and washed with anhydrous
diethyl ether, affording yellow microcrystals (0.808 g, 95%).
Sample too insoluble for δH or δC; m/z (FAB) 783 (M ϩ 1,
Cl37/37, 25%), 782 (Mϩ, Cl37/37, 50), 781 (M ϩ 1, Cl35/37, 95), 780
(Mϩ, Cl35/37, 70), 779 (M ϩ 1, Cl35/35, 100), 778 (Mϩ, Cl35/35, 20).
᎐
br s, NH); δC(299.95 MHz; solvent and standard [2H]chloro-
form) 55.12 and 56.58 (4 C, OCH3), 87.67, 114.98, 118.51,
120.56, 121.72, 126.18, 127.44 and 130.48 (20 C, aryl CH),
102.62, 109.92, 116.90, 131.22, 134.40, 136.67, 137.17, 141.83,
158.29 and 159.43 (10 C, aryl C), 156.20 (2 C, CH᎐N); m/z (EI)
᎐
799 (M ϩ 1, Cl37/37, 1%), 798 (Mϩ, Cl37/37, 2), 797 (M ϩ 1,
Cl35/37, 3), 796 (Mϩ, Cl35/37, 4), 795 (M ϩ 1, Cl35/35, 5), 794 (Mϩ,
Cl35/35, 4), 779 (3), 613 (1), 586 (1), 507 (1), 494 (2), 460 (3), 413
(1), 391 (3), 361 (1), 349 (3), 329 (5), 307 (100), 289 (60), 273 (5),
220 (5).
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]biphenylato(2؊)}nickel(II) 6a. This compound was
prepared according to the general method using ligand 6 (0.100
g, 0.128 mmol) and nickel() acetate tetrahydrate (0.032 g, 0.13
mmol). After 10 min the yellow suspension was observed to
take on a brown colouration. The mixture was heated at reflux
for 1.5 h, after which little solid remained. The solution was
allowed to come to room temperature then chilled and the
resulting suspension filtered. The crude product was recrystal-
lized from ethyl acetate (100 mL) to afford the complex as
brown crystals (0.080 g, 75%). δH(299.95 MHz; solvent [2H]-
chloroform; standard SiMe4) Ϫ9.25 (2 H, s, H5), Ϫ6.21 and
19.89 (4 H, s, aryl), Ϫ5.57 (2 H, br s, aryl), 1.28 and 3.69 (12 H,
s, OCH3), 2.84 (4 H, d, J 7.3, chlorophenyl), 11.69 (4 H, d, J 7.6,
chlorophenyl), 17.01 (2 H, d, J 5.6 Hz, aryl), 90.00 (2 H, br s,
{Bis[2,2Ј-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]diphenylaminato(2؊)]}dinickel(II) 5a. This com-
pound was prepared according to the general method using
ligand 5 (0.0300 g, 0.0378 mmol) dissolved in the minimum
amount of acetonitrile at reflux (20 mL) and nickel() acetate
tetrahydrate (0.0141 g, 0.0566 mmol). The complex was
obtained as deep red crystals (0.016 g, 50%). δH(299.95 MHz;
solvent [2H]chloroform; standard SiMe4) paramagnetic and
unassignable; m/z (FAB) 1707 (Mϩ, Cl35/37/37/37, 10%), 1706
(M ϩ 1, Cl35/35/37/37, 30), 1705 (Mϩ, Cl35/35/37/37, 40), 1704 (M ϩ 1,
Cl35/35/35/37, 50), 1703 (Mϩ, Cl35/35/35/37, 40), 1702 (M ϩ 1,
Cl35/35/35/35, 90), 1701 (Mϩ, Cl35/35/35/35, 100), 856 (M ϩ 1, NiL,
Cl37/37, 5%), 855 (Mϩ, Cl37/37, 10), 854 (M ϩ 1, Cl35/37, 12), 853
(Mϩ, Cl35/37, 25), 852 (M ϩ 1, Cl35/35, 30), 851 (Mϩ, Cl35/35, 50),
550 (20), 507 (15). m/z (MALDI-TOF) 1699 (Ni2L2, 50%), 1642
(NiL2, 30), 851 (NiL, 100), 795 (L, 90).
CH᎐N), H2 unobserved; m/z (FAB) (demetallation fragments
᎐
observed only) 783 (M ϩ 1, Cl37/37, 20%), 782 (Mϩ, Cl37/37, 40),
781 (M ϩ 1, Cl35/37, 80), 780 (Mϩ, Cl35/37, 65), 779 (M ϩ 1,
Cl35/35, 100), 778 (Mϩ, Cl35/35, 20).
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]biphenylato(2؊)}cobalt(II) 6b. This compound was
prepared according to the general method using ligand 6 (0.100
g, 0.128 mmol) and cobalt() acetate tetrahydrate (0.034 g, 0.14
mmol), and obtained as orange-brown crystals (0.092 g, 86%).
m/z (FAB) 840 (M ϩ 1, Cl37/37, 1%), 839 (Mϩ, Cl37/37, 2), 838
(M ϩ 1, Cl35/37, 3), 837 (Mϩ, Cl35/37, 5), 836 (M ϩ 1, Cl35/35, 4),
835 (Mϩ, Cl35/35, 5).
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylaminato(2؊)}cobalt(II) 5b. This com-
pound was prepared according to the general method using
ligand 5 (0.0300 g, 0.0378 mmol) dissolved in the minimum
amount of acetonitrile at reflux (20 mL) and cobalt() acetate
tetrahydrate (0.0095 g, 0.038 mmol) and obtained as deep
brown crystals (0.010 g, 31%). m/z (EI, 300 ЊC) 855 (Mϩ, Cl37/37
,
1%), 854 (M ϩ 1, Cl35/37, 2), 853 (Mϩ, Cl35/37, 3), 852 (M ϩ 1,
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]biphenylato(2؊)}copper(II) 6c. This compound was
prepared according to the general method using the ligand 6
(0.100 g, 0.128 mmol) and copper() acetate monohydrate
(0.027 g, 0.14 mmol), and obtained as orange-brown crystals
(0.086 g, 80%). m/z (FAB) 845 (M ϩ 1, Cl37/37, 15%), 844 (Mϩ,
Cl37/37, 35), 843 (M ϩ 1, Cl35/37, 60), 842 (Mϩ, Cl35/37, 80), 841
(M ϩ 1, Cl35/35, 100), 840 (Mϩ, Cl35/35, 70).
Cl35/35, 5), 851 (Mϩ, Cl35/35, 5), 567 (20), 553 (30).
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylaminato(2؊)}copper(II) 5c. This compound
was prepared according to the general method using ligand 5
(0.0300 g, 0.0378 mmol) dissolved in the minimum amount of
acetonitrile at reflux (20 mL) and copper() acetate mono-
hydrate (0.0150 g, 0.0566 mmol), and obtained as deep red-
brown crystals (0.015 g, 46%). m/z (FAB) (decomplexation
fragments observed only) 798 (Mϩ, Cl37/37, 1%), 797 (M ϩ 1,
Cl35/37, 2), 796 (Mϩ, Cl35/37, 2), 795 (M ϩ 1, Cl35/35, 3), 794 (Mϩ,
Cl35/35, 3), 557 (3), 513 (4), 469 (3), 453 (4), 437 (2), 409 (3), 393
(5), 375 (3), 349 (4), 331 (7), 313 (4), 287 (6), 271 (30), 245 (80),
227 (100), 209 (80).
{2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]biphenylato(2؊)}zinc(II) 6d. This compound was
prepared according to the general method using ligand 6 (0.050
g, 0.064 mmol) and zinc() acetate dihydrate (0.014 g, 0.067
mmol), with the mixture heated at reflux for 12 h. The yellow
solution was filtered hot through a bed of Celite under vacuum
then all solvent was removed. The solid was boiled in methanol
to afford a yellow suspension, which was filtered and dried to
afford compound 6d as yellow microcrystals (0.047 g, 87%).
δH(299.95 MHz; solvent [2H]chloroform; standard SiMe4) 3.906
and 3.910 (12 H, s, OCH3), 6.11 (2 H, s, H5), 7.11 (3 H, s, aryl),
7.13 (2 H, s, H2), 7.23 and 7.34 (9 H, m, aryl), 7.47 (4 H, d, J 8.5
2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylaminato(2؊)}zinc(II) 5d. This compound
was prepared according to the general method using ligand 5
(0.0700 g, 0.0881 mmol) dissolved in the minimum amount of
acetonitrile at reflux (20 mL) and zinc() acetate monohydrate
(0.0213 g, 0.0969 mmol) and was obtained as bright orange
microcrystals (0.057 g, 75%). δH(299.95 MHz; solvent [2H]-
chloroform; standard SiMe4) 3.78 and 3.88 (12 H, s, OCH3),
5.79 (1 H, s, NH bridging), 6.64 (2 H, s, H5), 6.75 and 6.88 (6 H,
m, aryl), 6.91 (2 H, s, H2), 7.15 (8 H, s, chlorophenyl), 7.20
Hz, chlorophenyl), 8.92 (2 H, s, CH᎐N); δ (299.95 MHz;
᎐
C
solvent and standard [2H]chloroform) 55.29 and 56.47 (4 C,
OCH3), 85.54 (2 C, C5), 122.46, 126.44, 127.54, 129.46, 130.31,
131.71 and 134.63 (16 C, aryl CH), 101.79, 111.98, 117.18,
130.40, 134.28, 135.63, 144.94, 149.82, 161.64 and 161.89 (20 C,
(2 H, s, aryl), 8.64 (2 H, s, CH᎐N); too insoluble for δ ; m/z
(MALDI-TOF) 859 (M ϩ 2, 85%), 795 (demetallated complex,
aryl C), 162.92 (2 C, CH᎐N); m/z (MALDI-TOF) 858 (M ϩ 1,
᎐
᎐
C
Cl35/35, 20%).
55).
4,4Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylmethane 7. The 7-formylindole 3 (0.637 g,
2.02 mmol) and 4,4Ј-methylenedianiline (0.200 g, 1.01 mmol)
were treated according to the standard procedure. A yellow
2,2Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]biphenyl 6. The aldehyde 3 (0.688 g, 2.18 mmol) and
2,2Ј-diaminobiphenyl (0.200 g, 1.09 mmol) were treated accord-
1956
J. Chem. Soc., Dalton Trans., 2001, 1948–1958

View Article Online
precipitate was observed after 24 h. Reflux was continued for 4
days, then the mixture was cooled and filtered. The product was
found to undergo hydrolysis on silica, so treatment with char-
coal in chloroform followed by recrystallization from dichloro-
methane–n-hexane afforded the ligand as yellow crystals (0.521
g, 65%). δH(299.95 MHz; solvent [2H]chloroform; standard
SiMe4) 3.91 and 3.98 (1 2H, s, OCH3), 4.06 (2 H, s, CH2), 6.28
(2 H, s, H5), 7.14 (2 H, s, H2), 7.24 (8 H, d, J 1.8, aryl), 7.34 and
reflux for 3 h. The complex was obtained as brown micro-
crystals (0.067 g, 78%). δH(299.95 MHz; solvent [2H]chloro-
form; standard SiMe4) (paramagnetic compound, total
assignment not possible) Ϫ12.35 (4 H, s), 0.94 (8 H, s), 1.87 and
1.94 (24 H, s), 2.98 (8 H, s), 3.75 (4 H, s), 12.58 (8 H, s), 15.3 and
18.3 (8 H, d, J 9.2 Hz, chlorophenyl), 23.45 (8 H, s); m/z
(MALDI-TOF) 808 (demetallated complex, 100%).
Bis{4,4-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]diphenylethanato(2؊)}dizinc(II) 8b. This compound
was prepared according to the general method using ligand 8
(0.080 g, 0.099 mmol) and zinc() acetate monohydrate (0.0239
g, 0.0109 mmol), and obtained as orange microcrystals (0.071
g, 82%), too insoluble for δH and δC; m/z (MALDI-TOF) 1741
(Zn2L2, 10%), 1678 (ZnL2, 8), 809 (demetallated complex, 100).
7.56 (8 H, dt, J 8.5, 2.0 Hz, chlorophenyl), 9.09 (2 H, s, CH᎐N),
᎐
11.40 (2 H, br s, NH); δC(299.95 MHz; solvent and standard
[2H]chloroform) 41.04 (1 C, CH2), 55.29 and 56.77 (4 C, OCH3),
87.69, 121.30, 121.72, 127.76, 129.68 and 130.72 (20 C, aryl
CH), 102.44, 110.25, 117.49, 131.61, 134.53, 137.60, 138.37,
150.96, 158.33 and 159.38 (20 C, aryl C), 155.89 (2 C, CH᎐N);
᎐
m/z (FAB) 798 (M ϩ 1, Cl37/37, 10%), 797 (Mϩ, Cl37/37, 25), 796
(M ϩ 1, Cl35/37, 45), 795 (Mϩ, Cl35/37, 80), 794 (M ϩ 1, Cl35/35
,
1,3-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzene 9. 1,3-Diaminobenzene (0.171 g, 1.58
mmol) and 3 (1.00 g, 3.17 mmol) were treated according to the
general procedure. The reaction was monitored by TLC and
observed not to go to completion. A small aliquot was taken,
the solvent removed and the crude solid examined by 1H NMR,
indicating contamination by 3 and the diamine. Small amounts
of 2,2Ј-diaminobiphenyl (ca. 10 mg) were added and the reac-
tion was continued and monitored by TLC until all 3 was
observed to have reacted. The mixture was cooled and the
solvent removed under reduced pressure. The residue was
boiled in chloroform and the suspension filtered hot. The solid
material was collected and shown to be identical to a genuine
sample of 6. The filtrate was collected and the solvent removed.
The crude solid was crystallized form dichloromethane–n-
hexane to afford compound 9 as orange needles (0.256 g, 23%).
δH(299.95 MHz; solvent [2H]chloroform; standard SiMe4) 3.93
and 4.00 (12 H, s, OCH3), 6.29 (2 H, s, H5), 7.13 (2 H, dd, J 7.9,
2.0, aryl H4,6), 7.17 (2 H, s, H2), 7.19 (1 H, d, J 2.0, aryl H2),
7.34 and 7.55 (8 H, dt, J 8.5, 1.8, chlorophenyl), 7.42 (1 H, t,
75), 793 (Mϩ, Cl35/35, 100), 792 (M Ϫ 1, Cl35/35, 30), 781 (15), 766
(10), 746 (25), 726 (20), 697 (8), 663 (7), 629 (50), 613 (60).
Bis{4,4Ј-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]diphenylmethanato(2؊)}dinickel(II) 7a. This com-
pound was prepared according to the general method using
ligand 7 (0.150 g, 0.189 mmol) and nickel() acetate tetra-
hydrate (0.0470 g, 0.189 mmol), resulting in an immediate
change from yellow to brown, and the mixture was heated at
reflux for 8 h. The mixture was filtered warm and the solid
washed with acetonitrile then anhydrous diethyl ether and dried
to afford compound 7a as brown microcrystals (0.137 g, 85%).
δH(299.95 MHz; solvent [2H]chloroform; standard SiMe4)
(paramagnetic compound, total assignment not possible)
Ϫ12.74 (4 H, s, H2 or H5), 0.93 and 3.67 (24 H, s, OCH3), 2.00
(4 H, s, CH2), 2.26 (16 H, br s, aryl), 13.03 and 24.44 (16 H, s,
chlorophenyl), 33.81 (4 H, s, H2 or H5); m/z (MALDI-TOF)
1701 (Ni2L2, 15%), 1641 (NiL2, 10), 794 (L, 55).
Bis{4,4Ј-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]diphenylmethanato(2؊)}dicobalt(II) 7b. This com-
pound was prepared according to the general method using
ligand 7 (0.150 g, 0.189 mmol) and cobalt() acetate tetra-
hydrate (0.0490 g, 0.198 mmol) and obtained as red-brown
microcrystals (0.129 g, 80%). m/z (MALDI-TOF) 1703 (Co2L2,
60%), 1645 (CoL2, 35), 795 (L ϩ 1, 70).
J 8.0 Hz, aryl H5), 9.16 (2H, s, CH᎐N), 11.41 (2 H, br s, NH);
᎐
δC(299.95 MHz; solvent and standard [2H]chloroform) 55.30
and 56.76 (4 C, OCH3), 87.65 (2 C, C5), 127.77 and 130.72 (8 C,
chlorophenyl CH), 110.25, 113.98, 118.08 and 121.73 (6 C, aryl
CH), 102.38, 117.54, 129.69, 131.62, 134.48 and 137.62 (12 C,
aryl C), 153.81 (2 C, CN᎐CH), 156.41 (2 C, CH᎐N), 158.51 and
᎐
᎐
159.55 (4 C, COCH3); m/z (MALDI-TOF) 704 (M ϩ 1, Cl35/35
,
100%).
4,4Ј-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]diphenylethane 8. The 7-formylindole 3 (0.595 g,
1.88 mmol) and 4,4Ј-ethylenedianiline (0.200 g, 9.42 mmol)
were treated according to the standard procedure. The resulting
yellow solid was purified by charcoal treatment in chloroform
(due to its observed hydrolysis on silica) followed by recrystal-
lization from chloroform to afford the ligand as yellow crystals
(1.14 g, 75%). δH(299.95 MHz; solvent [2H]chloroform; stand-
ard SiMe4) 2.98 (4 H, s, CH2), 3.92 and 3.99 (12 H, s, OCH3),
6.29 (2 H, s, H5), 7.16 (2 H, s, H2), 7.23 (8 H, s, aryl), 7.34 and
Bis{1,3-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]benzenato(2؊)}dinickel(II) 9a. This compound was
prepared according to the general method using ligand 9 (0.050
g, 0.071 mmol) and nickel() acetate tetrahydrate (0.0195 g,
0.0782 mmol), resulting in an immediate change from yellow to
brown. The mixture was heated at reflux for 2 h, filtered warm
and the solid washed with acetonitrile followed by anhydrous
diethyl ether and dried to afford compound 9a as brown micro-
crystals (0.041 g, 76%). δH(299.95 MHz; solvent [2H]dimethyl-
formamide; standard SiMe4) multiple unassignable resonances;
δC(299.95 MHz; solvent and standard [2H]dimethylformamide)
multiple unassignable resonances; m/z (MALDI-TOF) 781
(M ϩ Na, 55%).
7.56 (8 H, dt, J 8.4, 1.8 Hz, chlorophenyl), 9.10 (2 H, s, CH᎐N),
᎐
11.42 (2 H, br s, NH); δC(299.95 MHz; solvent and standard
[2H]chloroform) 37.62 (2 C, CH2), 55.31 and 56.81 (4 C, OCH3),
87.70, 121.12, 121.70, 127.75, 129.25 and 130.70 (20 C, aryl
CH), 102.48, 110.26, 117.49, 131.62, 134.55, 137.62, 138.85,
150.75, 158.30 and 159.35 (20 C, aryl C), 155.73 (2 C, CH᎐N);
᎐
Bis{1,3-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]benzenato(2؊)}dicobalt(II) 9b. This compound was
prepared according to the general method using ligand 9 (0.050
g, 0.071 mmol) and cobalt acetate tetrahydrate (0.0195 g,
0.0782 mmol), and obtained as red-brown microcrystals
(0.046 g, 85%). m/z (MALDI-TOF) 782 (M ϩ Na, 100%), 705
(M Ϫ Co, 80).
m/z (FAB) 812 (M ϩ 1, Cl37/37, 10%), 811 (Mϩ, Cl37/37, 25), 810
(M ϩ 1, Cl35/37, 45), 809 (Mϩ, Cl35/37, 80), 808 (M ϩ 1, Cl35/35
,
75), 807 (Mϩ, Cl35/35, 100), 806 (M Ϫ 1, 30), 793 (15), 781 (10),
746 (15), 721 (10), 705 (7), 643 (45), 629 (7), 613 (30).
Bis{4,4Ј-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]diphenylethanato(2؊)}dinickel(II) 8a. This com-
pound was prepared according to the general method using
ligand 8 (0.0800 g, 0.0990 mmol) and nickel() acetate tetra-
hydrate (0.0271 g, 0.0109 mmol), resulting in an immediate
change from yellow to brown, and the mixture was heated at
Bis{1,3-bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmeth-
yleneamino]benzenato(2؊)}dicopper(II) 9c. This compound was
prepared according to the general method using ligand 9
(0.050 g, 0.071 mmol) and copper() acetate monohydrate
J. Chem. Soc., Dalton Trans., 2001, 1948–1958
1957

View Article Online
(0.0209 g, 0.0853 mmol), and obtained as brown microcrystals
(0.044 g, 82%). m/z (MALDI-TOF) 766 (M ϩ 1, 40%), 705
(M Ϫ Cu, 100).
Crystallography
The data were collected on Nonius CAD-4 (6aؒCHCl3) or
Philips PW1100/20 (9aؒ7DMF) instruments. Crystallographic
data are summarized in Table 3.
1,4-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzene 10. The aldehyde 3 (0.600 g, 1.90 mmol)
and 1,4-diaminobenzene (0.100 g, 0.942 mmol) were treated
according to the standard procedure with the use of anhydrous
toluene as solvent. After 20 h a yellow precipitate was observed,
and after further heating for 96 h the mixture was cooled,
filtered and the solid washed with diethyl ether. Charcoal
treatment of a chloroform solution (2 L) of the crude product
followed by solvent removal, filtration and washing with
dichloromethane afforded compound 10 as yellow micro-
crystals (0.411 g, 62%). δH(299.95 MHz; solvent [2H]chloro-
form; standard SiMe4) 3.93 and 4.01 (12 H, s, OCH3), 6.30 (2 H,
s, H5), 6.91 (2 H, s, H2), 7.15–7.35 (12 H, m, aryl H), 9.14 (2 H,
CCDC reference numbers 159043 and 159044.
See http://www.rsc.org/suppdata/dt/b1/b101350p/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We are grateful to the Australian Research Council for financial
support including an Australian Postgraduate Award to P. K. B.
References
1 J. L. Sessler, M. J. Cyr, V. Lynch, E. McGhee and J. A. Ibers,
J. Am. Chem. Soc., 1990, 112, 2810.
2 R. Grigg, The Porphyrins, Volume 1 - Synthesis and Structure, Part
B, ed. D. Dolphin, Academic Press, New York, 1978, p. 31.
3 M. J. Broadhurst, R. Grigg and A. W. Johnson, J. Chem. Soc. C,
1971, 3681; M. J. Broadhurst, R. Grigg and A. W. Johnson, J. Chem.
Soc., Perkin Trans. 1, 1972, 2111.
4 D. StC. Black, A. J. Hartshorn, M. Horner and S. Hunig, Aust. J.
Chem., 1977, 30, 2553; D. StC. Black, A. J. Hartshorn, M. Horner
and S. Hunig, Aust. J. Chem., 1977, 30, 2493; D. StC. Black, D. C.
Craig, N. Kumar and L. C. H. Wong, J. Chem. Soc., Chem.
Commun., 1985, 1172; D. StC. Black, D. J. Brockway and G. I.
Moss, Aust. J. Chem., 1986, 39, 1231.
s, CH᎐N), indole NH unobserved; too insoluble for δ ; m/z
᎐
C
(FAB) 707 (M ϩ 1, Cl37/37, 20%), 706 (M, Cl37/37, 35), 705
(M ϩ 1, Cl35/37, 75), 704 (M, Cl35/37, 60), 703 (M ϩ 1, Cl35/35
,
100), 702 (M, Cl35/35, 25).
{1,4-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}nickel(II) polymer 10a. This com-
pound was prepared according to the general method using
ligand 10 (0.100 g, 0.142 mmol) and nickel() acetate tetra-
hydrate (0.0354 g, 0.142 mmol), resulting in an immediate
change from yellow to brown, and the mixture was heated at
reflux for 8 h. It was filtered warm and the product washed with
acetonitrile then anhydrous diethyl ether and dried to afford
a brown solid (0.108 g, 100%). δH(299.95 MHz; solvent [2H]-
chloroform; standard SiMe4) (paramagnetic compound)
Ϫ10.97 (s), 0.9–4.5 (m), 12.5–13 (m), 18.8–20.1 (br s), 121.0 (br
s); m/z (MALDI-TOF) 720 (30%), 704 (demetallated complex,
40).
5 J. E. Nordlander, D. B. Catalane, K. D. Kotian, R. M. Stevens and
J. E. Haky, J. Org. Chem., 1981, 46, 778.
6 D. StC. Black, M. C. Bowyer, P. K. Bowyer, A. J. Ivory, M. Kim,
N. Kumar, D. B. McConnell and M. Popiolek, Aust. J. Chem., 1994,
47, 1741.
7 N. Shakibaee, Honours Thesis, UNSW, 1995.
8 S. Naylor, J. H. Lamb, C. A Hunter, J. A. Cowan and K. M.
Sanders, Anal. Chim. Acta, 1990, 241, 281.
9 E. C. Constable, Tetrahedron, 1992, 48, 10020.
10 M. Hannon, C. L. Painting, A. Jackson, J. Hamblin and W.
Errington, Chem. Commun., 1997, 1807.
11 RAELS 96, A. D. Rae, Australian National University, Canberra,
1996.
{1,4-Bis[3-(4-chlorophenyl)-4,6-dimethoxyindol-7-ylmethyl-
eneamino]benzenato(2؊)}cobalt(II) polymer 10b. This com-
pound was prepared according to the general method using
ligand 10 (0.100 g, 0.142 mmol) and cobalt() acetate tetra-
hydrate (0.0354 g, 0.142 mmol), and afforded a red-brown solid
(0.103 g, 96%). m/z (MALDI-TOF) 735 (25%), 718 (45), 704
(demetallated complex, 95); m/z (MALDI-TOF) no matrix
2256 (20%), 1506 (40), 719 (55), 705 (55).
12 A. D. Rae, Acta Crystallogr., Sect. A, 1975, 31, 560; A. D. Rae,
Acta Crystallogr., Sect. A, 1975, 31, 570.
13 C. Piguet, G. Bernardinelli and G. Hopfgartner, Chem. Rev., 1997,
97, 2005.
14 D. StC. Black and N. E. Rothnie, Aust. J. Chem., 1983, 36,
1141.
1958
J. Chem. Soc., Dalton Trans., 2001, 1948–1958