Mono- and dinucleating Ni(II), Cu(II), Zn(II) and Fe(III) complexes of symmetric and unsymmetric Schiff bases incorporating salicylimine functions - Synthetic and structural studies

Article abstract of DOI:10.1016/j.poly.2014.03.002

The known Schiff base, 3-(2-aminophenylamino)-1-phenylbut-2-en-1-one (1), formed by 1:1 condensation of o-phenylenediamine and benzoylacetylacetone reacts at its free amine site with salicylaldehyde and 5-tert-butylsalicylaldehyde in the presence of Ni(II) and Cu(II) acetates, or with 5-tert-butylsalicylaldehyde in the presence of Zn(II) acetate, to generate 1:1 (M:L) diimine complexes (2) of the corresponding doubly deprotonated, unsymmetric, O₂N ₂-tetradentate ligands. In contrast, reaction of Zn(II) acetate with 1 and salicylaldehyde led to Schiff base exchange (with loss of benzoylacetylacetone) to yield symmetric [ZnL³] [where L³ is N,N′-o-phenylenebis(salicyliminato)]. Similarly, when Fe(II) chloride was substituted for metal acetate in the reaction of 1 with 5-tert-butyl- salicylaldehyde and the initial product crystallised in the presence of dabco (as base), a related Schiff base exchange reaction occurred along with aerial oxidation of the Fe(II) to produce the neutral dinuclear [Fe ^III(L⁴)₂(μ-O)] species [where L⁴ is N,N′-o-phenylenebis(5-tert-butylsalicyliminato)] in which Fe(III) centres are linked by an oxo group to produce two 5-coordinate Fe(III) centres; pairs of these (oxo-bridged) dinuclear complex units are further linked via elongated intermolecular Fe-O_phenolic contacts (Fe-O, 2.44 A?) to form an unusual tetranuclear supramolecular cluster. This complex was also synthesised directly by the in situ reaction of 5-tert-butyl-salicylaldehyde, o-phenylenediamine and Fe(II) chloride (2:1:1 mol ratio) in air. In an extension of these studies, the in situ reaction of the 1,3-aryl linked bis-β-diketone, 1,1-(1,3-phenylene)-bis-butane-1,3-dione), o-phenylenediamine, salicylaldehyde and Ni(II) acetate in a 1:2:2:2 ratio yielded [Ni₂L⁵], the dinuclear analogue of the unsymmetric mononuclear Ni(II) complex 2, in which each nickel centre has a square planar environment. Reaction of the above 1,3-phenylene linked bis-β-diketone precursor with o-phenylenediamine in a 1:2 M ratio yields 1,3-bis(4-methyl-3H- benzo[b][1,4]diazepin-2-yl)benzene as its monohydrate (3·H₂O) incorporating two 7-membered diaza heterocyclic rings; thus contrasting with the 'open' Schiff base structure observed for 1. X-ray structures of 1, 3·H₂O, [NiL¹]·py, [NiL¹] ·EtOH, [NiL²], [CuL¹]·py, [CuL ¹]·0.5CHCl₃, [(FeL⁴)₂(μ-O) ]₂·1.5THF·0.4EtOH·0.6H₂O and [NiL⁵]·0.25EtOH·0.125py are reported.

Full text of DOI:10.1016/j.poly.2014.03.002

Polyhedron 74 (2014) 113–121
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Mono- and dinucleating Ni(II), Cu(II), Zn(II) and Fe(III) complexes
of symmetric and unsymmetric Schiff bases incorporating salicylimine
functions – Synthetic and structural studies
c
a,
a,
Qinghua Meng a,b, Jack K. Clegg a,c, , Aidan J. Brock , Katrina A. Jolliffe , Leonard F. Lindoy
,
⇑
⇑
⇑
Gang Wei d,
⇑
a School of Chemistry, University of Sydney, NSW 2006, Australia
b School of Chemistry and Chemical Engineering, Shanghai JiaoTong University, Shanghai 200240, PR China
c School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane St Lucia, QLD 4072, Australia
d CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
The known Schiff base, 3-(2-aminophenylamino)-1-phenylbut-2-en-1-one (1), formed by 1:1 condensa-
tion of o-phenylenediamine and benzoylacetylacetone reacts at its free amine site with salicylaldehyde
and 5-tert-butylsalicylaldehyde in the presence of Ni(II) and Cu(II) acetates, or with 5-tert-butylsalicylal-
dehyde in the presence of Zn(II) acetate, to generate 1:1 (M:L) diimine complexes (2) of the corresponding
doubly deprotonated, unsymmetric, O2N2-tetradentate ligands. In contrast, reaction of Zn(II) acetate with
1 and salicylaldehyde led to Schiff base exchange (with loss of benzoylacetylacetone) to yield symmetric
[ZnL3] [where L3 is N,N0-o-phenylenebis(salicyliminato)]. Similarly, when Fe(II) chloride was substituted
for metal acetate in the reaction of 1 with 5-tert-butyl-salicylaldehyde and the initial product crystallised
in the presence of dabco (as base), a related Schiff base exchange reaction occurred along with aerial oxi-
Received 24 April 2012
Accepted 3 March 2014
Available online 12 March 2014
Keywords:
Schiff base
Nickel(II)
Copper(II)
Zinc(II)
dation of the Fe(II) to produce the neutral dinuclear [FeIII(L4)2( -O)] species [where L4 is N,N0-o-phenylene-
l
Iron(III)
bis(5-tert-butylsalicyliminato)] in which Fe(III) centres are linked by an oxo group to produce two 5-
coordinate Fe(III) centres; pairs of these (oxo-bridged) dinuclear complex units are further linked via elon-
gated intermolecular Fe–Ophenolic contacts (Fe–O, 2.44 Å) to form an unusual tetranuclear supramolecular
cluster. This complex was also synthesised directly by the in situ reaction of 5-tert-butyl-salicylaldehyde,
o-phenylenediamine and Fe(II) chloride (2:1:1 mol ratio) in air. In an extension of these studies, the in situ
reaction of the 1,3-aryl linked bis-b-diketone, 1,1-(1,3-phenylene)-bis-butane-1,3-dione), o-phenylenedi-
amine, salicylaldehyde and Ni(II) acetate in a 1:2:2:2 ratio yielded [Ni2L5], the dinuclear analogue of the
unsymmetric mononuclear Ni(II) complex 2, in which each nickel centre has a square planar environment.
Reaction of the above 1,3-phenylene linked bis-b-diketone precursor with o-phenylenediamine in a 1:2 M
ratio yields 1,3-bis(4-methyl-3H-benzo[b][1,4]diazepin-2-yl)benzene as its monohydrate (3ꢀH2O) incor-
porating two 7-membered diaza heterocyclic rings; thus contrasting with the ‘open’ Schiff base structure
observed for 1. X-ray structures of 1, 3ꢀH2O, [NiL1]ꢀpy, [NiL1]ꢀEtOH, [NiL2], [CuL1]ꢀpy, [CuL1]ꢀ0.5CHCl3,
[(FeL4)2(
l
-O)]2ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O and [NiL5]ꢀ0.25EtOHꢀ0.125py are reported.
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
tetradentate ligand types but also some of the most studied
[1–4]. Indeed such species have been known since Alfred Werner’s
time. [1] Ligands of this type typically lose two protons and
coordinate in a square-planar manner to form neutral metal com-
plexes with a number of divalent metal ions. Individual complexes
have been investigated for a number of applications, including as
oxygen carriers [5], as non-linear optical materials [6], as catalysts
(and especially asymmetric catalysts) [2,7], in inorganic biochem-
ical roles [8] and as components of metallosupramolecular systems
[2,9]. In contrast to symmetrical Schiff base systems, unsymmetric
Symmetrical Schiff bases derived from 2:1 condensation of
b-diketone or salicylaldehyde derivatives with 1,2-diamine
moiety represent, not only some of the earliest examples of
a
⇑
Corresponding authors. Address: School of Chemistry, University of Sydney,
NSW 2006, Australia. Tel.: +61 2 93514400; fax: +61 2 9351 3329 (K.A. Jolliffe and
L.F. Lindoy).
E-mail addresses: k.jolliffe@chem.usyd.edu.au (K.A. Jolliffe), lindoy@chem.usyd.
edu.au (L.F. Lindoy), gang.wei@csiro.au (G. Wei).
http://dx.doi.org/10.1016/j.poly.2014.03.002
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

114
Q. Meng et al. / Polyhedron 74 (2014) 113–121
1
systems have received significantly less attention, in part reflecting
that their syntheses are usually [6,10,11] (but not always) [12]
somewhat less facile than for related symmetrical systems.
to B1g transition) was partly obscured by the tail of an intense
MLCT transition that extended from the UV region into the visible.
Unless otherwise stated, all products were dried in air over silica
gel before microanalysis.
Previous studies [11,13,14] have shown that o-phenylenedi-
amine undergoes 1:1 Schiff base condensation with individual
b-diketones; for example, reaction with benzoylacetylacetone
yields 3-(2-aminophenylamino)-1-phenylbut-2-en-1-one (1) that
incorporates a free amine site [11,13]. As an extension of these
prior studies, we now report the metal template syntheses of
new Ni(II), Cu(II) and Zn(II) complexes of type 2 (see Fig. 1). These
incorporate the deprotonated forms of the unsymmetric ligands,
H2L1 (R = H) and H2L2 (R = t-Bu), derived respectively from 1:1 con-
densation of 1 with salicylaldehyde or 5-tert-butylsalicylaldehyde.
Related symmetric Zn(II) and Fe(III) complexes incorporating
respectively N,N0-o-phenylenebis(salicyliminato) (L3) and N,N0-o-
phenylenebis(5-tert-butylsalicyliminato) (L4) (see 3) generated by
Schiff base exchange reactions are also reported. The formation
2.2. Ligand and complex synthesis
3-(2-Aminophenylamino)-1-phenylbut-2-en-1-one (1): This
was prepared by reaction of o-phenylenediamine with benzoylace-
tone using a similar procedure to that reported previously [13].
Yield 75%. 1H NMR (d, ppm /CDCl3): 12.47 (H, br), 7.92 (2H, m),
7.44 (3H, m), 7.06 (2H, m), 6.76 (2H, m), 5.93 (1H, s), 3.87 (2H,
br), 1.99 (3H, s). MS(ESI+): 253.0 (M+H+). An X-ray diffraction study
on a colourless single crystal of this product confirmed its expected
structure.
2.2.1. General procedure for the synthesis of Ni(II), Cu(II) and Zn(II)
complexes of type 2 incorporating unsymmetric L1 and L2
of
a
related dinuclear Ni(II) Schiff base complex([Ni2L5])
incorporating the deprotonated form of the difunctional ligand 4
is described, with the latter derived from the condensation of 1
with the 1,3-phenylene-linked bis-b-diketone derivative,
1,10-(1,4-phenylene)bisbutane-1,3-dione.
The procedure is a modified version of that previously reported
for [NiL1] [11] (which was also synthesised in the present study as
its ethanol solvate). Intermediate 1 (1 mmol) and salicylaldehyde
or 5-tert-butyl-salicylaldehyde (1 mmol) (to produce H2L1 and
H2L2 respectively) were dissolved in hot ethanol (15 mL). The
mixture was heated under reflux for 1 h, and then 1 mmol of Ni(II)
acetate tetrahydrate, Cu(II) acetate monohydrate or Zn(II) acetate
dihydrate in ethanol (5 mL) was added dropwise to the warm solu-
tion. The reaction mixture was heated at reflux for 2 h and then left
overnight at room temperature. In each case the precipitate that
formed was removed by filtration and recrystallised from ethanol.
X
N
N
OH
OH
NH
N
O
O
HN
N
OH
OH
2.2.1.1. [NiL1]ꢀEtOH and [NiL1]ꢀpy. [NiL1]ꢀEtOH: yield 78%, dark red-
brown crystals. 1H NMR (d, ppm/CDCl3): 8.18 (1H, s), 7.87 (2H, d),
7.53 (1H, d), 7.35 (6H, m), 7.05 (3H, m), 6.64 (1H, t), 6.02 (1H, s),
2.52 (3H, s). UV–Vis (pyridine): k ꢁ570 (sh) nm. Anal. Calc. for
X
3
4
H2L3, X = H
H2L5
H2L4, X = t-Bu
C
25H24NiN2O3: C, 65.50; H, 5.24; N, 6.11. Found: C, 65.57; H,
4.71; N, 6.51%. Crystals suitable for X-ray analysis were obtained
by slow evaporation of an ethanol solution of the above product
and one of these was used for an X-ray structure determination.
[NiL1]ꢀpy: A portion of the above product was recrystallised from
pyridine (py) to yield brown crystals of [NiL1]ꢀpy; a crystal from
this batch was used directly for a structure determination.
2. Experimental
2.1. Materials and instrumentation
All reagents and solvents were obtained from commercial
sources and used without further purification. 1H NMR spectra
were recorded on a Bruker Avance DPX200 spectrometer with
(CH3)4Si as the internal reference. Mass spectra (ESI-MS) were ob-
tained on a Finnigan LCQ-8 spectrometer with the sample dis-
solved in methanol. UV–Vis spectra of the Ni(II) complexes were
recorded on a Cary 1E spectrophotometer; in each case the d–d
2.2.1.2. [NiL2]ꢀ0.33H2O. Yield 85%, dark red-brown crystals. 1H NMR
(d, ppm/CDCl3) 8.17 (1H, s), 7.86 (2H, s), 7.64 (1H, d), 7.39 (3H, m),
7.36 (2H, m), 7.22 (1H, m), 7.04 (3H, m), 6.02 (1H, s), 2.52 (3H, s),
1.30 (9H, s). UV–vis (pyridine), k ꢁ570 (sh) nm. Anal. Calc. for C27-
H26.66NiN2O2.33: C, 68.25; H, 5.66; N, 5.90. Found: C, 68.24; H, 5.67;
N, 5.93%. Crystals of [Ni(L2)] suitable for X-ray analysis were ob-
tained by slow evaporation of an ethanol solution of the above
product.
1
transition assigned to square planar coordination (due to the A1g
Ph
O
O
NH2
NH2
M(II)
NH
O
N
N
O
O
Ph
O
OH
M
NH2
1
R
2
R
[ML1], R = H
[ML2], R = t-Bu
Fig. 1. Synthesis of the 1:1 Schiff base intermediate 3-(2-aminophenylamino)-1-phenylbut-2-en-1-one, 1, followed by in situ reaction with salicylaldehyde or 5-tert-
butylsalicylaldehyde in the presence of Ni(II), Cu(II) or Zn(II) acetate to produce complexes of type 2, [ML1] (M = Ni, Cu) or [CuL2], that incorporate the doubly deprotonated
forms of the unsymmetric ligands H2L1 (R = H) and H2L2 (R = t-Bu).

Q. Meng et al. / Polyhedron 74 (2014) 113–121
115
2.2.1.3. [CuL1]ꢀ0.5CHCl3. Yield 89%, dark green crystals. MS(ESI+):
418.20 (M + H)+. Anal. Calc. for C23H18CuN2O2: C, 66.10; H, 4.34;
N, 6.70. Found: C, 65.85; H, 4.35; N, 6.78%. Crystals of composition
of [CuL1]ꢀ0.5CHCl3 suitable for X-ray crystal analysis were obtained
on slow evaporation of a chloroform solution of the above product.
standing, a crystal from this batch was used directly for an X-ray
structure determination without further drying.
This complex was also synthesised by the more direct in situ
reaction of 5-tert-butyl-salicylaldehyde, o-phenylenediamine and
iron(II) chloride (2:1:1 mol ratio) in ethanol (thus circumventing
the Schiff base exchange step in the above synthesis).
They were used directly for
a structure determination. On
prolonged drying in air, this product lost chloroform to give the
non-solvated product. Anal. Calc. for C23H18CuN2O2: C, 66.10; H,
4.34; N, 6.70. Found: C, 65.85; H, 4.35; N, 6.78%.
o-Phenylenediamine (1 mmol) and 5-tert-butyl-salicylaldehyde
(2 mmol) were dissolved in hot ethanol (15 mL). The mixture was
heated under reflux for 1 h, then iron(II) chloride tetrahydrate
(1 mmol) in ethanol (5 mL) was added dropwise to the warm solu-
tion. The reaction mixture was heated at reflux for 2 h and then left
overnight at room temperature. The dark brown precipitate that
formed was then collected, dissolved in a 1:1 mixture of tetrahy-
drofuran and ethanol containing one equivalent of dabco as base
(note: attempts to isolate the same product without the addition
of dabco failed to produce crystalline materials). The resulting dark
brown solution was allowed to stand for several days over which
time dark red crystals of product formed. These were isolated
and allowed to dry in air over several days. Yield 0.233 g (65%).
UV–Vis (Nujol): k 415 nm. MS(ESI+): 1003.3 [(FeL4)2O + Na]+. Anal.
Calc. for C112H120Fe4N8O10ꢀ3.5H2O: C, 66.44; H, 6.32; N, 5.53.
Found: C, 66.35; H, 6.19; N, 5.56%.
2.2.1.4. [CuL1]ꢀpy. Green crystals of composition [CuL1]ꢀpy, suitable
for X-ray crystal analysis, were obtained on slow evaporation
of a pyridine solution of the above product. Anal. Calc. for
C28H23CuN3O2: C, 67.66; H, 4.66; N, 8.45. Found: C, 67.62; H,
4.65; N, 8.55%.
2.2.1.5. [CuL2]ꢀ0.5H2O. Yield 82%, dark green crystals. MS(ESI+):
474.1 (M + H)+. Anal. Calc. for C27H27CuN2O2.5: C, 67.13; H, 5.63;
N, 5.80. Found: C, 67.17; H, 5.37; N, 5.70%.
2.2.1.6. [ZnL2]ꢀ1.5H2O. Yield 53%, yellow crystals. 1H NMR (d, ppm/
CDCl3) 8.31 (1H, s), 7.72 (2H, d), 7.29 (3H, m), 7.11 (2H, m), 6.90
(2H, m), 5.39 (1H, s), 2.16 (3H, s), 1.24 (9H, s).
MS(ESI+): 475.27(M+H)+. Anal. Calc. for C27H29N2O3.5Zn: C,
64.48; H, 5.81; N, 5.57. Found: C, 64.42; H, 5.97; N, 5.50%.
2.3. Crystallography
2.3.1. Data collection and structure solution
X-ray structural data were collected on either a Bruker-Nonius
APEX2-X8-FR591 diffractometer employing graphite-monochro-
2.2.1.7. [Ni2L5]ꢀ0.25EtOHꢀ0.125py. 1,10-(1,3-Phenylene)-bis-butane-
1,3-dione [15], (1 mmol), o-phenylenediamine (2 mmol) and sali-
cylaldehyde (2 mmol) were dissolved in hot ethanol (25 mL). The
reaction mixture was refluxed for 1 h and then Ni(II) acetate tetra-
hydrate (2 mmol) in ethanol (5 mL) was added dropwise to the
warm solution. The reaction mixture was refluxed for a further
2 h, and then left overnight at room temperature. The product
formed as red-brown crystals. Yield 80%. UV–vis (pyridine), k
ꢁ570 (sh) nm. 1H NMR (d, ppm/CDCl3) 8.28 (1H, s), 8.20 (2H, s),
7.99 (2H, m), 7.66 (2H, m), 7.36 (5H, m), 7.15 (4H, m), 6.98 (4H,
m), 6.66 (2H, m), 6.12 (2H, s), 2.56 (6H, s). MS(ESI+): 768.87
(M+Na)+. Slow evaporation of a pyridine solution of this product
yielded crystals suitable for X-ray analysis and a crystal from this
batch was used directly for the structure determination.
mated Mo
(0.71073 Å) with
SMART 1000 diffractometer employing graphite-monochromated
Mo K radiation generated from a sealed tube (0.71073 Å). Data
K
a
radiation generated from
a rotating anode
x
and scans [16] or with scans using a Bruker
w
a
were collected at 150 K to approximately 56° 2h. Data integration
and reduction were undertaken with SAINT and XPREP [17,18]
and subsequent computations were carried out using the
WinGX-32 graphical user interface [19]. The structures were
solved by direct methods using SIR97 [20]. Multi-scan empirical
absorption corrections were applied to the data set using the pro-
gram SADABS [21]. Data were refined and extended with SHELXL-97
[22]. In general, non-hydrogen atoms with occupancies greater
than or equal to 0.5 were refined anisotropically. Carbon and alco-
hol O-bound hydrogen atoms were included in idealised positions
and refined using a riding model. Water hydrogen atoms were first
located in the difference Fourier map before refinement with bond
length and angle restraints as required to facilitate realistic model-
ling, where they could not be located they were not modelled. X-
ray data are summarised in Table 1 and specific refinement details
(where required) are given below.
2.2.2. Schiff base exchange reactions
2.2.2.1. [ZnL3]ꢀH2O. This complex was obtained from Zn(II) acetate
using the general procedure outlined above. The procedure led to
Schiff base condensation coupled with imine exchange (with loss
of benzoylacetylacetone) to yield the symmetric mononuclear
complex [ZnL3]ꢀH2O (L3 is the doubly deprotonated form of
N,N0-o-phenylenebis(salicylimine). Yield 48%, yellow crystals. 1H
NMR (d, ppm/DMSO-d6): 9.04 (2H, s), 7.93 (2H, m), 7.43 (4H, m),
7.24 (2H, t), 6.73 (2H, d), 6.54 (2H, t). MS(ESI+): 379.20 (M+H)+.
Anal. Calc. for C20H16N2O3Zn: C, 60.40; H, 4.05; N, 7.04. Found: C,
60.92; H, 4.20; N, 7.05%.
2.3.2. Specific refinement details
2.3.2.1. [NiL1]ꢀEtOH. Each of the ethanol solvent molecules are
disordered and modelled over two positions.
2.2.2.2. [(FeL4)2(
l
-O)]2ꢀ3.5H2O (where L4 is the doubly deprotonated
form of N,N’-o-phenylenebis(5-tert-butylsalicylimine). This complex
was synthesised by the general procedure outlined in Section
2.2.1 employing intermediate 1, 5-tert-butyl-salicylaldehyde and
an ethanol/chloroform (1:1) solvent mixture but with Fe(II) chlo-
ride (1 mmol) substituted for the metal acetate. Once again Schiff
base condensation coupled with imine exchange (with loss of
benzoylacetylacetone) was observed to occur. The initial non-
crystalline product obtained was dissolved in a 1:1 mixture of
tetrahydrofuran and ethanol containing one equivalent of the
difunctional base dabco. Dark red crystals formed on slow evapora-
tion of this solution over several days. Yield, 70%. These were
removed from solution and since they tended to lose solvent on
2.3.2.2. [(FeL4)2(
l
-O)]2ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O. One of the THF mol-
ecules and the water molecules are disordered and each was mod-
elled over two positions. The water hydrogens could not be located
in the difference Fourier map and were not modelled. A number of
bond length and angle restraints were required in the modelling of
the disordered THF and the ethanol molecule.
2.3.2.3. [Ni2L5]ꢀ0.25EtOHꢀ0.125py. The ethanol and pyridine solvate
molecules are disordered across a special position and a number
of bond length and angle restraints were required to facilitate
realistic modelling.

Table 1
Crystal and structure refinement data.
Compound
1
[Ni(L1)]ꢀpy
[Ni(L1)]ꢀEtOH
[Ni(L2)]
[Cu(L1)]ꢀpy
[Cu(L1)]ꢀ0.5CHCl3 [Fe(L4)2(l2
-
3ꢀH2O
[Ni2(L5)]ꢀ0.25EtOHꢀ0.125py
O)]2ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O
Formula of refinement C16H16N2O
model
C28H23N3NiO2
C25H24N2NiO3
C27H26N2NiO2
C28H23CuN3O2
C47H37Cl3Cu2N4O4 C62.80H75.60Fe3N4O7.50
C26H24N4O
C41.625H32.625N4.125Ni2O4.25
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
252.31
492.20
1501.01
monoclinic
Cc(#9)
20.063(3)
19.879(3)
22.246(3)
469.21
497.03
955.24
1118.17
triclinic
408.49
776.01
monoclinic
C2/c(#15)
15.5020(10)
16.3660(10)
11.6720(7)
orthorhombic
Pbca(#61)
16.209(2)
11.9420(15)
23.643(3)
monoclinic
P21/c(#14)
12.4950(10)
16.2690(13)
11.7310(10)
monoclinic
P21/n(#14)
13.200(3)
9.639(2)
monoclinic
P21/n(#14)
18.425(9)
10.912(5)
22.707(14)
orthorhombic
Pbcn(#60)
13.452(3)
16.994(3)
9.221(2)
monoclinic
P21/c(#14)
11.6715(6)
22.0514(12)
13.4293(7)
ꢀ
P1(#2)
12.083(5)
14.335(6)
18.401(8)
72.461(8)
86.676(9)
82.305(7)
3011(2)
1.233
17.734(4)
a
(°)
b (°)
111.136(3)
102.714(2)
113.7480(10)
93.023(3)
113.821(6)
100.232(2)
c
(°)
V (Å3)
2762.0(3)
1.214
8
4576.5(10)
1.429
8
8655(2)
1.410
16
2182.8(3)
1.428
4
508.5(3)
1.465
4
4176(4)
1.519
4
2108.0(7)
1.287
4
3401.4(3)
1.515
4
Dc (g cmꢂ1
)
Z
2
Crystal size (mm)
Crystal colour
Crystal habit
T (K)
0.30 ꢃ 0.25 ꢃ 0.10 0.40 ꢃ 0.35 ꢃ 0.30 0.40 ꢃ 0.35 ꢃ 0.32 0.40 ꢃ 0.35 ꢃ 0.30 0.40 ꢃ 0.30 ꢃ 0.25 0.30 ꢃ 0.20 ꢃ 0.05 0.40 ꢃ 0.30 ꢃ 0.05
0.20 ꢃ 0.10 ꢃ 0.05 03 ꢃ 0.2 ꢃ 0.05
colourless
plate
brown
brown
brown
green
green
red
colourless
plate
brown
block
block
block
prism
plate
plate
plate
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
150(2)
k(Mo K
a
a
) (Å)
0.71073
0.077
0.71073
0.879
0.71073
0.926
0.71073
0.916
0.71073
1.001
0.71073
1.261
0.71073
0.536
0.71073
0.081
0.71073
1.159
l(Mo K
) (mm–1
)
T(SADABS)min,max
2hmax (°)
0.5140, 0.7461
60.88
0.6581, 0.7457
56.64
0.6323, 0.7457
56.64
0.6232, 0.7457
56.62
0.6471, 0.7457
56.74
0.5191, 0.7457
52.74
0.6587, 0.7457
54.26
0.6246, 0.7457
56.50
0.6454, 0.7457
56.70
hkl range
ꢂ22 17, ꢂ23 20,
ꢂ20 21, ꢂ15 15,
ꢂ26 26, ꢂ26 25,
ꢂ16 16, ꢂ21 21,
ꢂ17 17, ꢂ12 12,
ꢂ21 23, ꢂ13 13,
ꢂ15 15, ꢂ18 18, ꢂ23 23
ꢂ17 17, ꢂ22 22,
ꢂ15 15, ꢂ28 29, ꢂ17 17
ꢂ16 16
ꢂ31 31
ꢂ29 29
ꢂ15 15
ꢂ23 23
ꢂ27 28
ꢂ12 12
N
20528
43098
42827
21636
21684
29543
27429
12699
67496
Nind (Rmerge
)
4183 (0.0584)
3362
5638 (0.0673)
3895
20032 (0.0339)
17227
5288 (0.0201)
4870
5445 (0.0500)
3824
8489 (0.0948)
5568
13058 (0.0648)
6933
2581 (0.1295)
947
8355 (0.0431)
6914
Nobs (I > 2r(I))
Nvar
183
0.0438
0.1318
0.0699, 1.2169
1.032
308
0.0379
0.0854
0.0354, 2.1618
0.990
1150
0.0415
0.1001
0.0536, 2.1420
1.013
293
0.0290
0.0827
0.0488, 1.1140
1.004
308
0.0391
0.0975
0.0490,0.4488
1.010
543
0.0982
0.2634
0.0677, 84.4600
1.049
722
0.0634
0.2029
0.1099, 0.0000
0.969
146
0.0689
0.1630
0.0589, 0.0687
0.980
481
0.0711
0.1572
0.0000, 21.23520
1.243
a
R1 (F) (I > 2
r(I))
wR2a (F2) (all)
Aa, Ba
Goodness-of-fit
D
qmin,max (e– Å–3
)
ꢂ0.291, 0.450
ꢂ0.258, 0.536
ꢂ0.361, 1.620
ꢂ0.248, 0.504
ꢂ0.447, 0.462
ꢂ1.270, 1.819
ꢂ0.935, 0.829
ꢂ0.364, 0.258
ꢂ0.888, 1.442
P
P
P
a
R1
=
||Fo| ꢂ |Fc||/ |Fo| for Fo > 2
r
(Fo) and wR2 = (
R
w(Fo2 ꢂ Fc2)2/ (wFc2)2)1/2 where w = 1/[
r
2(Fo2) + (AP)2 + BP], P = (Fo2 + 2Fc2)/3 and A and B are listed in the crystal data su.

Q. Meng et al. / Polyhedron 74 (2014) 113–121
117
structures, that also show related Ni–
metal-
p
system contacts [24]. These
3. Results and discussion
p
contacts are reminiscent of those observed previously in a
number of Cu(II) complex species [25].
Reaction of o-phenylenediamine and benzoylacetone in reflux-
ing ethanol yielded the 1:1 Schiff base condensation product 1
whose X-ray structure (Fig. 2) confirmed the previously assigned
‘open’ single imine structure [11,13] (rather than a 7-membered
diaza ring structure of the type obtained previously from the 1:1
condensation of acetylacetone and ethylenediamine) [23].
Reaction of 1 with salicylaldehyde or 5-tert-butyl-salicylaldehyde
in situ in the presence of Ni(II), Cu(II), or Zn(II) acetate resulted in
metal template syntheses of the corresponding asymmetric Schiff
base complexes of type 2: [NiL1]ꢀpy, [NiL1]ꢀEtOH, [NiL2]ꢀ0.33H2O,
[CuL1]ꢀ0.5CHCl3, [CuL1]ꢀpy, [CuL2]ꢀ0.5H2O and [ZnL2]ꢀ1.5H2O.
The X-ray structures of [NiL1]ꢀpy and [NiL1]ꢀEtOH (Fig. 3a and b)
are similar and confirm that the Ni(II) ion has a square planar
coordination geometry in each case with the benzene ring from
the o-phenylenediamine moiety rotated between 14 and 18 de-
grees with respect to the coordination plane in the respective
structures. In both structures, two adjacent molecules pack closely
together in a dimeric arrangement (Fig. 3b). There is a moderately
In [NiL1]ꢀpy there are also a number of weak
p-p interactions
between adjacent dimers and pyridine solvate molecules leading
to an overall three dimensional network arrangement. In [NiL1]-
ꢀEtOH the disordered solvent is hydrogen bonded to the coordi-
nated oxygens and weak
p–p interactions occur between dimers,
resulting in a two-dimensional array that extends throughout the
lattice.
The crystal structure of [NiL2] (Fig. 4) shows that the metal is
again square planar being bound to the O2N2 donor set of the
doubly deprotonated form of H2L2; adjacent molecules again pack
closely to yield a dimeric arrangement. However, in contrast to the
structures just discussed, there are no Ni–C distances of less than
3.5 Å (attributable to the steric influence of the bulky tert-butyl
group); while there is a number of offset face-to-face
tions present. Neighbouring dimers stack in a herringbone-like
motif through edge-to-face interactions.
p–p interac-
p–p
In a similar fashion to the nickel complexes just discussed, the
crystal structures of [CuL1]ꢀpy and [CuL1]ꢀ0.5CHCl3 reveal that the
Cu(II) centres adopt square planar geometries (Fig 5). The crystal
packing in [CuL1]ꢀ0.5CHCl3 is quite similar to that occurring for
[NiL1]ꢀpy, with adjacent molecules forming dimeric species via
close contact between the conjugated c-carbon and the adjacent
Ni(II) centres of 3.3 Å in the case of [NiL1]ꢀpy and 3.2 Å in [NiL1]-
ꢀEtOH, which may assist with stabilisation of the close (dimeric)
packing arrangement. Although such a contact does not seem
to have been highlighted in the past, a search of the CSD revealed
Cu–p interactions (3.1 Å) that appear similar to those described
previously by us and others [25]. If these weak interactions are
a
number of other low-spin Ni(II), nominally square planar
Fig. 2. X-ray structure of the Schiff base intermediate, 3-(2-aminophenylamino)-1-phenylbut-2-en-1-one (1), formed by 1:1 condensation of o-phenylenediamine and
benzoylacetone, shown with 50% probability ellipsoids. The dashed line indicates a hydrogen bond.
Fig. 3. (a) X-ray structure of the [NiL1]ꢀpy with 50% probability ellipsoids and (b) schematic representation of the dimeric close packing in [NiL1]ꢀEtOH. Both complexes have
similar square planar coordination geometries and dimeric packing arrangements. Dashed lines indicate intermolecular contacts between nickel centres and the
adjacent bound L1 ligands; solvate molecules not shown.
p-systems of

118
Q. Meng et al. / Polyhedron 74 (2014) 113–121
Ph
O OH
NH
O
Zn(II) +
N
N
O
O
O
O
Zn
+
Ph
NH2
1
[ZnL3]
Fig. 6. Schiff base exchange reaction to form [ZnL3].
driven by the formation of more thermodynamically stable sym-
metrical Schiff base products. Alternatively, the relative solubilities
of the symmetrical versus the non-symmetrical products under the
conditions employed could also be important in determining
which of these products is isolated.
Crystals of the oxo-bridged species, [(FeL4)2O]ꢀ1.5THFꢀ0.4EtOHꢀ
0.6H2O, suitable for X-ray diffraction were obtained on slow evap-
oration of an ethanol/chloroform solution of the initial isolated
complex in the presence of added dabco as base. In forming this iron
complex clearly the Fe(II) employed initially is aerially oxidised to
Fe(III) during the course of the reaction which was carried out in
air; other examples of such Fe(II)/Fe(III) oxidation in air have been
documented [29]. This complex was also synthesised directly by
the in situ reaction of 5-tert-butyl-salicylaldehyde, o-phenylenedi-
amine and Fe(II) chloride (2:1:1 mol ratio) in ethanol in air.
Other related oxo bridged Fe(III) species incorporating Schiff
base ligands derived from salicylaldehyde or its substituted
derivatives have been reported [30-32]. The X-ray structure of
the present complex (Fig. 7) shows that the iron centres in each
[FeIIIL4]+ unit are bridged by an oxo bridge to form dinuclear
[(FeL4)2O] units; pairs of these are then further intermolecularly
linked via phenoxide oxygen to Fe(III) contacts (Fe–Ophenolic dis-
tances of 2.44 Å) to form an unusual supramolecular [(FeL4)2O]2
tetranuclear cluster. The Fe–Ooxo–Fe angle is 153.6°, compared to
Fig. 4. X-ray structure of [NiL2] shown with 50% probability ellipsoids.
included as part of the coordination sphere then the overall
coordination geometry can be considered as pseudo-five coordi-
nate; the chloroform solvate molecule is hydrogen bonded to
adjacent coordinated oxygens. Neighbouring dimers again interact
via
a series of weak p–p interactions to form an infinite
three-dimensional arrangement. This contrasts slightly with the
packing in [CuL1]ꢀpy in which the copper centres interact with
o-phenylenediamine rings, indicated by Cu-C distances of 3.0–
3.3 Å, forming infinite columnar arrays. These p-stack further with
adjacent columns and pyridine solvent molecules to yield an
infinite three-dimensional lattice.
Unexpectedly, attempts to obtain mononuclear complexes of
types [ZnL1] and [FeL2] using a similar procedure to that illustrated
in Fig. 1, resulted instead in Schiff base exchange to yield the
known [26] symmetric Schiff base complex [ZnL3] [where L3 is
N,N’-o-phenylenebis(salicylimineato)] (see Fig. 6) and the new
Fe(III) species [(FeL4)2O]ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O [where L4 is
N,N0-o-phenylenebis(5-tert-salicylimineato)], the crystal structure
of this iron complex was determined (see below). In these products
the benzoylacetonimine moiety in the precursor 1 has been
replaced by a salicylaldiminato or 5-tert-butylsalicyliminato group,
undoubtedly reflecting the inherent solution lability of the imine
functions present in 1 [27], with the exchange reaction represent-
ing an example of ‘‘dynamic covalent chemistry’’ [28], perhaps
176.5° in the related complex, [{Fe(3,5-t-BuSalphen)}2(l-O)]
(where 3,5-t-BuSalphen is the corresponding ligand incorporating
tert-butyl in both the 3- and 5-positions of its salicyl rings) [31].
Other aspects of the two structures are also quite similar, including
the displacement of the five-coordinate iron centres from their
respective mean basal planes (0.56 Å in the present structure
compared to 0.54 and 0.55 Å in [{Fe(3,5-t-BuSalphen)}2(l-O)]).
However, the present structure differs by the presence of the
bridging phenolic oxygens. Each of the resulting tetranuclear
Fig. 5. X-ray structures of (a) [CuL1]ꢀpy and (b) [CuL1]ꢀ0.5CHCl3 with 50% probability ellipsoids; the pyridine solvate is not shown.

Q. Meng et al. / Polyhedron 74 (2014) 113–121
119
In an extension of the above investigation (that also extends our
past studies involving difunctional b-diketone ligands) [33] we
have probed the use of the 1,3-phenylene-linked, bis-b-diketone
derivative, 1,1-(1,3-phenylene)-bis-butane-1,3-dione [22], in place
of benzoylacetylacetone, for undertaking related studies to those
just described. In an initial attempt to obtain a phenylene-bridged
bis-Schiff base analogue of 1 (see Fig. 1) incorporating terminal
anilino groups by 1:2 reaction of the above bis-b-diketone deriva-
tive with o-phenylenediamine in hot ethanol resulted instead in
the formation of 5, 1,3-bis(4-(methyl)-3H-benzo[b][1,4]diazepin-
2-yl)benzene, as colourless crystals.
N
N
N
N
5
The X-ray stucture of this product (Fig. 8), which crystallises as its
monohydrate, confirmed that two partially conjugated, 7-mem-
bered, diaza-heterocyclic rings had been generated. This arrange-
ment thus contrasts markedly with that obtained (Fig. 2) for the
mono-Schiff base 1 discussed earlier, formed by 1:1 condensation
of o-phenylenediamine and benzoylacetone (see Fig. 1).
The solvent water molecules in the crystal lattice of 3ꢀH2O are
involved in hydrogen bonding interactions with the ‘outermost’
nitrogen atoms of the 7-membered rings (O(1 W)Hꢀ ꢀ ꢀN(1)
1.99(4) Å) forming an undulating hydrogen bonded polymeric
chain that extends along the crystallographic a-axis (Fig. 9).
Despite the above result, it was found that an in situ (presum-
ably template) reaction in which an ethanol solution of Ni(II) ace-
tate was heated with 1,1-(1,3-phenylene)-bis-butane-1,3-dione),
o-phenylenediamine and salicylaldehyde in a 1:2.2 ratio resulted
in isolation of the target dinuclear Schiff base nickel complex of
type [Ni2L5] (6) whose X-ray structure (Fig. 10) indicated an overall
composition of [Ni2L5]ꢀ0.25EtOHꢀ0.125py.
Fig. 7. X-ray structure of the tetrameric complex, [(FeL4)2(
ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O; the lattice solvate molecules are not shown.
l-O)]2-
The two Ni(II) centres adopt, in a similar fashion to [NiL1], a
low-spin square planar coordination geometry. The entire mole-
cule is close to planar with only small deviations from planarity
occurring for the methyl groups and o-phenylenediamine rings.
Presumably reflecting steric effects, the coordinating moieties are
arranged in a syn fashion so that the ‘‘salicylimine’’ aryl rings have
maximum separation and lie closest to the 4 and 6 positions on
the central 1,3-subsituted phenylene (rather than on the opposite
side). This configuration is further stabilised by weak Hphenylene–O
interactions. Interestingly, the syn arrangement contrasts with that
adopted by the precursor bis-b-diketone ligand upon coordination,
but parallels the arrangement adopted by the corresponding free
ligand in the solid state [22].
Fig. 8. X-ray structure of 3ꢀH2O with 50% probability ellipsoids; the water solvate is
not shown.
clusters interacts further with two neighbouring molecules via p–p
As observed in each of the structures reported above, the crystal
interactions (indicated by carbon–carbon distances of 3.2–3.4 Å);
this results in the formation of an infinite one-dimensional poly-
mer that propagates along the crystallographic b-axis.
packing is again dominated by
p–p stacking. Adjacent molecules
once more form a dimeric arrangement with close Ni–O contacts
Fig. 9. Part of the infinite hydrogen bonded chain in the X-ray structure of 3ꢀH2O.

120
Q. Meng et al. / Polyhedron 74 (2014) 113–121
Appendix A. Supplementary data
CCDC 849402–849410 contain the supplementary crystallo-
N
N
O
O
O
O
N
N
graphi data for 1, 3ꢀH2O, [NiL1]ꢀpy, [NiL1]ꢀEtOH, [NiL2], [CuL1]ꢀpy,
Ni
Ni
[CuL1]ꢀ0.5CHCl3,
[(FeL4)2(
l-O)]2ꢀ1.5THFꢀ0.4EtOHꢀ0.6H2O
and
[NiL5]ꢀ0.25EtOHꢀ0.125py. These data can be obtained free of charge
via https://www.ccdc.cam.ac.uk/services/structure_deposit or
from The Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336 033, or e-mail:
deposit@ccdc.cam.ac.uk.
4
6
; [Ni2(L )]
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