Playing with different metalloligands [NiL] and Hg to [NiL] ratios to tune the nuclearity of Ni(II)-Hg(II) complexes: Formation of di-, tri-, hexa- and nona-nuclear Ni-Hg clusters

Article abstract of DOI:10.1016/j.poly.2014.11.025

Five new hetero-metallic nickel(II)-mercury(II) complexes, [(NiL¹)HgCl₂] (1), [(NiL¹)₂HgCl₂] (3), [(NiL¹)₂Hg(N₃)₂] (4), [{(NiL²)₂Hg(N₃)(μ_1,1-N₃)}₂] (5) and [{(NiL²)₂Hg(N₃)(μ_1,1-N₃)HgCl₂}₂{Hg(N₃)(μ_1,1-N₃)}] (6) have been synthesized by reacting metalloligands [NiL¹] or [NiL²] (where H₂L¹ is N,N′-bis(salicylidene)-1,2-ethylenediamine and H₂L² is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX₂ (X^- = Cl^- or N₃^-) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1, the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL¹] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In the trinuclear complexes 3 and 4, the central Hg(II) ion is coordinated by two terminal [NiL¹] units through two phenoxido oxygens from each and two terminal chloride (in 3) or azide (in 4) ions. The centrosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL²)₂Hg(N₃)(μ_1,1-N₃)] units, where the phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one azido ligand adopts a μ_l,1-briding mode between Hg and Ni whereas the other one is terminal. In the nonanuclear complex 6, two tetranuclear [{(NiL²)₂Hg(N₃)(μ_1,1-N₃)}HgCl₂] units are linked to a central Hg(II) positioned on a two fold axis, via chlorido, azido, and phenoxido bridges. The tetranuclear unit is formed by the addition of a HgCl₂ molecule to a trinuclear [(NiL²)₂ Hg(N₃)(μ_1,1-N₃)] unit, similar to that present in 5. Complex 5 shows weak ferromagnetic interactions (J = +2.1 cm^-1) between the two octahedral Ni(II) ions through double phenoxido bridges with a Ni-O-Ni bond angle of 95.87(11)°.

Full text of DOI:10.1016/j.poly.2014.11.025

Polyhedron 87 (2015) 311–320
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Playing with different metalloligands [NiL] and Hg to [NiL] ratios to tune
the nuclearity of Ni(II)–Hg(II) complexes: Formation of di-, tri-, hexa-
and nona-nuclear Ni–Hg clusters
a
b
c
a,
⇑
Lakshmi Kanta Das , Carlos J. Gómez-García , Michael G.B. Drew , Ashutosh Ghosh
a
Department of Chemistry, University College of Science, University of Calcutta, 92, APC Road, Kolkata 700009, India
Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, C/Catedrático José Beltrán 2, 46980 Paterna, Valencia, Spain
School of Chemistry, The University of Reading, P.O. Box 224, Whiteknights, Reading RG6 6AD, UK
b
c
a r t i c l e i n f o
a b s t r a c t
1
1
1
Article history:
Five new hetero-metallic nickel(II)–mercury(II) complexes, [(NiL )HgCl ] (1), [(NiL ) HgCl ] (3), [(NiL )
2
2
2
2-
Received 15 August 2014
Accepted 6 November 2014
Available online 3 December 2014
2
2
Hg(N
3
)
2
] (4), [{(NiL )
2
Hg(N
3
)(
l
1,1-N
3
)}
2
] (5) and [{(NiL )
2
Hg(N
3
)(
l
1,1-N
3
)HgCl
2
}
2
{Hg(N
3
)(
l
1,1-N
3
)}] (6)
is N,N -bis(salicylid-
1
2
1
0
have been synthesized by reacting metalloligands [NiL ] or [NiL ] (where H
2
L
2
0
ꢀ
ꢀ
ene)-1,2-ethylenediamine and H
2
L
is N,N -bis(salicylidene)-1,3-propanediamine) with HgX
) at different molar ratios. All five complexes have been characterised by X-ray single-crystal struc-
tural, elemental and spectroscopic analyses. In complex 1, the Hg(II) ion is coordinated to two phenoxido
oxygen atoms of one [NiL ] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In
the trinuclear complexes 3 and 4, the central Hg(II) ion is coordinated by two terminal [NiL ] units
through two phenoxido oxygens from each and two terminal chloride (in 3) or azide (in 4) ions. The cen-
trosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL )
2
(X = Cl
ꢀ
or N
3
Keywords:
Nickel(II)
Mercury(II)
Hetero-metallic complexes
Crystal structure
Ferromagnetic interaction
1
1
2
2
Hg(N
3
)(l
1,1-N
3
)] units, where the
phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one
azido ligand adopts a l,1-briding mode between Hg and Ni whereas the other one is terminal. In the
nonanuclear complex 6, two tetranuclear [{(NiL )
Hg(II) positioned on a two fold axis, via chlorido, azido, and phenoxido bridges. The tetranuclear unit
l
2
2 3 3 2
Hg(N )(l1,1-N )}HgCl ] units are linked to a central
2
2 2 3 3
is formed by the addition of a HgCl molecule to a trinuclear [(NiL ) Hg(N )(l1,1-N )] unit, similar to that
1
ꢀ
present in 5. Complex 5 shows weak ferromagnetic interactions (J = +2.1 cm ) between the two octahe-
dral Ni(II) ions through double phenoxido bridges with a Ni–O–Ni bond angle of 95.87(11)°.
Ó 2014 Elsevier Ltd. All rights reserved.
1
. Introduction
In recent years, the design and synthesis of high nuclearity
reactant ratios and the counter ions [4]. High coordination num-
bers of M enhance the probability of binding to additional ML
0
units and may open up the possibility of building high nuclearity
hetero-metallic clusters. In this approach, besides the size and type
metal clusters have become a very popular research topic not only
for their unique and attractive structures but also for their diverse
applications such as optical materials, magnetic materials and cat-
alysts for organic reactions [1]. Moreover, the introduction of a het-
0
0
of M , the M :ML ratio may also play an important role in determin-
0
ing the number of ML complexes that coordinate to M and, there-
fore, in the final nuclearity of the hetero-metallic cluster [5]. A
third factor playing a key role is the counter-ion when it has a coor-
dinating and/or bridging capacity since it may further increase the
nuclearity of the final hetero-metallic cluster [6]. Since the stability
of the metalloligand is strongly dependent on the chelating ring
size of the ligand moiety [7], we have performed a systematic
study to determine the influence of metalloligand with different
0
ero-metallic centre (M ) into the cluster may modify the topologies
or may create unusual metal coordination environments that influ-
ence the physical properties of the materials [2]. The complex (ML),
essentially a metalloligand, has been widely used to synthesize
hetero-metallic complexes containing divalent transition metal
ions (M) and different hetero-metals (M ) [3] because their nucle-
arity can be sometimes controlled by changing M , the ML:M
0
0
0
0
chelating ring size in the diamine fragments and the M :ML ratios
on the nuclearity of the hetero-metallic cluster in a Hg:NiL system
containing salen type Schiff base ligands (L). We have selected
metalloligands containing Ni(II) and salen type Schiff bases for
the following reasons: (i) Ni(II) is capable of forming four, five or
⇑
Corresponding author. Fax: +91 33 2351 9755.
E-mail address: ghosh_59@yahoo.com (A. Ghosh).
http://dx.doi.org/10.1016/j.poly.2014.11.025
277-5387/Ó 2014 Elsevier Ltd. All rights reserved.
0

3
12
L.K. Das et al. / Polyhedron 87 (2015) 311–320
1
2
2
.2. Synthesis of Schiff base ligands (H
2
L and H
2
L ) and metalloligands
1
2
[NiL ] and [NiL ]
N
N
N
N
0
Ni
NiL1]
Ni
[NiL2]
The two di-condensed Schiff base ligands, N,N -bis(salicylid-
O
O
O
O
1
0
ene)-1,2-ethylenediamine (H
2
L ) and N,N -bis(salicylidene)-1,3-
L ) were prepared by standard methods.
10 mmol of salicylaldehyde (1.04 mL) in methanol (20 mL) were
mixed with 5 mmol of the required amine 1,2-ethylenediamine
[
2
propanediamine (H
2
1
2
Scheme 1. Metalloligands [NiL ] and [NiL ] used in the syntheses.
(
0.30 mL) or 1,3-propanediamine (0.42 mL) in methanol (20 mL).
six coordinated complexes and (ii) the chelating ring size can be
modified by simply changing the chain length in the amine. We
have chosen Hg(II) as hetero-metal (M ) because it may present dif-
The resulting solutions were refluxed for ca. 2 h and allowed to
1
0
cool. The yellow precipitate of H
methanol and dried in a vacuum desiccator containing anhydrous
CaCl . On the other hand, the yellow coloured methanolic solution
2
L was filtered off, washed with
ferent coordination numbers and geometries given the lack of
energy of stabilization of the crystal field in Hg(II) (d10 ion) com-
2
2
of H
2
L was used directly for complex formation. An aqueous solu-
ꢁ6H O (1.820 g, 5 mmol) and 10 mL
plexes for any geometry with only
included two different counterions (Cl and N
r bonds. Finally, we have also
ꢀ
ꢀ
tion (20 mL) of Ni(ClO
ammonia solution (20%) were added to a methanolic solution of
H
4
)
2
2
3
) to study the influ-
ence of the coordinating/bridging capacity of these ligands into the
nuclearity of the final hetero-metallic clusters.
1
2
2
L or H
2
L (5 mmol, 20 mL) to prepare the respective complexes
1
2
[
NiL ] or [NiL ] as reported earlier [23].
Herein, we report the synthesis and structural characterization of
five hetero-metallic Ni(II)–Hg(II) coordination complexes presenting
different nuclearities, thanks to the use of different ring sizes in L,
1
2
2.3. Synthesis of [(NiL )HgCl ] (1) and [(NiL )HgCl ] (2)
2
2
0
M :ML ratios and counter ions. These clusters include: a dinuclear
1
1
1
complex [(NiL )HgCl
2
] (1), two trinuclear complexes [(NiL )
2
HgCl
Hg(N
2
]
)
)
The previously prepared [NiL ] complex (0.325 g, 1 mmol) was
dissolved in methanol (50 mL) and then an aqueous solution
(1 mL) of HgCl2 (0.242 g, 1 mmol) was added to the methanolic
solution. The solution was stirred for 1 h at room temperature
and filtered off. The filtrate was allowed to stand overnight result-
ing in the formation of prismatic red X-ray quality single crystals of
1. Red prismatic-shaped single crystals of complex 2 were obtained
in the same manner as for 1, except that [NiL ] (0.339 g, 1 mmol)
was used in the synthesis instead of [NiL ]. The crystals were
washed with a methanol–water mixture (1:1) and dried in a desic-
1
2
(
3) and [(NiL )
2
Hg(N
3
)
2
] (4), a hexanuclear complex [{(NiL )
2
3
2
(l
1,1-N
3
)}
{Hg(N
) with two metalloligands [NiL ] and [NiL ] with different ring
2
] (5) and a nonanuclear complex [{(NiL )
2 3 3
Hg(N )(l1,1-N
HgCl }
2 2
3
)( )}] (6), prepared by reacting HgX
l1,1-N
3
2
(X = Cl or
1
2
N
3
1
sizes (Scheme 1) and at different molar ratios (Scheme 2) (H
N,N -bis(salicylidene)-1,2-ethylenediamine and H
2
L
is
0
2
0
2
L is N,N -bis(sali-
2
cylidene)-1,3-propanediamine). A careful search in the CCDC data-
base (updated November 2013) shows that among the several
1
0
thousands of complexes prepared with N,N -bis(salicylidene)-
diamine-type Schiff bases, only 25 contain Hg as hetero-metal: three
chain complexes (two alternating Cu–Hg [8,9] and one Mn–Hg [10]),
cator containing anhydrous CaCl , and then characterised by ele-
mental analysis, spectroscopic methods and X-ray diffraction.
2
three tetranuclear (two Hg
trinuclear (four HgCu [9,11,14] and one HgMn
dinuclear (six HgNi, [13,15,16] six HgCu [11,13,17–20] and one HgZn
21]) and one mononuclear [22]. Therefore, complexes 5 and 6 are the
2
Cu
2
[11,12] and one Hg
3
Cu [13]), five
Complex 1: Yield: 0.534 g (89%). Anal. Calc. for C16H14Cl HgN2
2
2
2
[10]), thirteen
NiO : C, 32.22; H, 2.37; N, 4.70. Found: C, 32.49; H, 2.31; N,
2
4.88%. UV–Vis: kmax (solid, reflectance) = 554 and 413 nm. IR
ꢀ1
[
(KBr): m(C@N) 1619 cm .
only known examples presenting nuclearities of six and nine, respec-
tively, in these kind of complexes.
Complex 2: Yield: 0.557 g (91%). Anal. Calc. for C17H16Cl HgN2
2
NiO : C, 33.44; H, 2.64; N, 4.59. Found: C, 33.41; H, 2.55; N,
2
4
.71%. UV–Vis: kmax (solid, reflectance) = 598, 490 and 392 nm. IR
ꢀ1
(
KBr):
m(C@N) 1618 cm .
2
. Experimental
1
2.1. Starting materials
2.4. Synthesis of [(NiL )
2
HgCl
2
] (3)
Salicylaldehyde, 1,2-ethylenediamine and 1,3-propanediamine
were purchased from Lancaster and were of reagent grade. They
were used as received.
Complex 3 was prepared by mixing the same components as for
1
1 but doubling the NiL :Hg ratio (2:1 instead of 1:1). The precursor
1
metalloligand [NiL ] (0.325 g, 1 mmol) was dissolved in methanol
Caution! Perchlorate and azide salts of metal complexes with
organic ligands are potentially explosive. Only a small amount of
material should be prepared and it should be handled with care.
2
(50 mL) and then an aqueous solution (1 mL) of HgCl (0.121 g,
0.5 mmol) was added. The solution was stirred for 1 h at room
temperature and filtered off. Brown rhombic shaped X-ray quality
Dinuclear
Dinuclear
1
[
(NiL )HgCl ] (
1)
2
2
[(NiL )HgCl ] (
2)
2
1
2
[
NiL ]:HgCl
2
[NiL ]:HgCl
(1:1)
2
(
1:1)
1
[NiL1]
2
[NiL2] [NiL ]:HgCl :NaN
2
[
NiL ]:HgCl :NaN
1
[NiL ]:HgCl :NaN
2
3
[NiL ]:HgCl2
2:1)
2
3
2
3
(
2:1:2)
(2:1:2)
(1:2:1)
(
Trinuclear
Trinuclear
Hexanuclear
Nonanuclear
1
1
2
2
[
(NiL ) Hg(N ) ] (
4)
[(NiL ) HgCl ] (
3)
[{(NiL ) Hg(N )
[{(NiL )
Hg(N
)(µ1,1-N
)
2
3 2
2
2
2
3
2
3
3
(
µ1,1-N )} ] (
5)
HgCl } {Hg(N )(µ1,1-N )}] (6)
2 2 3 3
3
2
Scheme 2. Synthesis of the complexes 1–6.

L.K. Das et al. / Polyhedron 87 (2015) 311–320
313
single crystals of 3 were obtained by slow evaporation of the fil-
trate. The crystals were washed with diethyl ether and dried in a
dia
the salt as deduced by using Pascal’s constant tables (v =
ꢀ839 ꢂ10 cm mol ) [24].
ꢀ6
3
ꢀ1
desiccator containing anhydrous CaCl
Complex 3: Yield: 0.394 g, (85%). Anal. Calc. for C32
: C, 41.71; H, 3.06; N, 6.08. Found: C, 41.69; H, 3.18; N,
.02%. UV–Vis: kmax (solid, reflectance) = 551 and 414 nm. IR
2
.
H
2 4
28Cl HgN
2.8. Crystallographic data collection and refinement
2 4
Ni O
6
4
966 and 10884 independent reflection data for 1 and 6 were
ꢀ
1
(
KBr):
m
(C@N) 1620 cm .
collected with Cu K and Mo K radiation, respectively at 150 K
a
a
using the Oxford Diffraction X-Calibur CCD System. The crystals
were positioned at 50 mm from the CCD. For 1, 1450 and for 6,
321 frames were measured with counting times of 1 and 10 s,
respectively. Data analyses were carried out with the CRYSALIS
program [25]. 3093, 5189, 5904 reflections for 3, 4 and 5 were
1
2
2
.5. Synthesis of [(NiL )
2
Hg(N
3
)
2
] (4) and [{(NiL )
2
Hg(N
3
)(
l
1,1-N
3
)}
2
]
(5)
1
The precursor metalloligand [NiL ] (0.325 g, 1 mmol) was dis-
solved in methanol (50 mL) and then an aqueous solution
0.5 mL) of HgCl (0.121 g, 0.5 mmol) followed by an aqueous solu-
tion (0.5 mL) of sodium azide (0.065 g, 1 mmol) were added to this
solution. The mixture was stirred for 1 h at room temperature and
filtered off. The filtrate was allowed to stand overnight at open
atmosphere resulting in the formation of red prismatic shaped
X-ray quality single crystals of 4. Brown prismatic-shaped single
crystals of complex 5 were obtained in the same manner as 4,
except that [NiL ] (0.339 g, 1 mmol) was used in the synthesis
instead of [NiL ]. The crystals were washed with a methanol–water
mixture (1:1) and dried in a desiccator containing anhydrous CaCl
Complex 4: Yield: 0.353 g, (76%) Anal. Calc. for C32 28HgN10Ni
: C, 41.12; H, 3.02; N, 14.99. Found: C, 41.21; H, 3.02; N, 15.11%.
UV–Vis: kmax (solid, reflectance) = 552 and 409 nm. IR (KBr):
collected using Mo Ka radiation at 293 K using the Bruker-AXS
(
2
SMART APEX II diffractometer. The crystals were positioned at
60 mm from the CCD. 360 frames were measured with a counting
time of 5 s. All five structures were solved using direct methods
with the SHELXS97 program [26]. The non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydrogen atoms
bound to carbon were included in geometric positions and given
thermal parameters equivalent to 1.2 times those of the atom to
which they were attached. Absorption corrections were carried
out using the ABSPACK program [27] for 1 and 6 and SADABS program
[28] for 3, 4 and 5. Data collection, structure refinement parame-
ters and crystallographic data for the five complexes are given in
Table 1.
2
1
2
.
H
2
O
4
ꢀ1
m
(C@N) 1615 and
Complex 5: Yield: 0.331 g, (69%) Anal. Calc. for C68
: C, 42.42; H, 3.35; N, 14.55. Found: C, 42.68; H, 3.51; N,
3
m(N ) 2044 cm .
3
. Results and discussion
.1. Synthesis of the complexes
The Schiff base ligands H
H
2 20
64Hg N
Ni
1
4 8
O
3
4.69%. kmax (solid, reflectance) = 1028, 568, 410 and 358 nm. IR
ꢀ1
(
KBr):
m
(C@N) 1616 and
m
(N
3
) 2047 and 2075 cm
.
L1 and H
L2 and their corresponding
2
2
1
2
Ni(II) complexes [NiL ] and [NiL ] were synthesized using the
reported procedure [23]. The [NiL ] metalloligand on reaction
2
2
.6. Synthesis of [{(NiL )
2
Hg(N
3
)( )HgCl {Hg(N
l1,1-N
3
2
}
2
3
)(
l
1,1-N
3
)}]
1
(6)
with HgCl
2
, in a 1:1 molar ratio, resulted in a hetero-metallic
1
discrete dinuclear complex, [(NiL )HgCl
2
] (1) (Scheme 2). Complex
2
(NiL )HgCl ] (2) was synthesized by following a similar procedure
Complex 6 was also prepared by mixing the same components
as for 5 but with a greater proportion of HgCl . The precursor met-
alloligand [NiL ] (0.339 g, 1 mmol) was dissolved in methanol
50 mL) and then an aqueous solution (0.5 mL) of HgCl (0.484 g,
mmol) followed by an aqueous solution (0.5 mL) of sodium azide
0.065 g, 1 mmol) were added to this solution. The solution was
stirred for 1 h at room temperature and filtered off. Evaporation
at room temperature of the filtrate yielded red needle shaped
X-ray quality single crystals of 6. The crystals were washed with
a methanol–water mixture (1:1) and dried in a desiccator contain-
2
[
2
2
1
to that of 1, by using [NiL ] instead of [NiL ]. The structure of 2 has
been reported previously by others [15,16], although the influence
of the synthetic conditions on the nuclearity of the obtained
complex was not studied. Therefore, we include complex 2 in the
present study only to establish a relationship between synthetic
conditions and the nuclearities and structures of the obtained com-
2
(
2
(
2
plexes, but we will not describe the structure in detail. The CIF file
1
obtained by us is given as ESI. Interestingly, when the [NiL ]:HgCl
2
ratio was increased from 1:1 to 2:1, the trinuclear complex
ing anhydrous CaCl
Complex 6: Yield: 0.266 g, (38%, calculated based on [NiL ]).
Anal. Calc. for C68 Hg : C, 29.67; H, 2.34; N, 13.23.
Found: C, 29.77; H, 2.31; N, 13.31%. UV–Vis: kmax (solid, reflec-
tance) = 1026, 570, 412 and 360 nm. IR (KBr): (C@N) 1617 and
2
.
1
[
(NiL )
2 2
HgCl ] (3), with a Ni:Hg ratio of 2:1, was obtained. How-
2
2
ever, for the metalloligand [NiL ], no product other than complex
could be isolated when the proportion of [NiL ] is increased from
:1 to 2:1 or even to 4:1. As expected, the use of N
H
64Cl
4
5
N
26Ni
4
O
8
2
2
1
ꢀ
3
as co-ligand
m
has led to the preparation of additional complexes with larger
ꢀ1
m
(N
3
) 2050 and 2078 cm
.
1
nuclearities. Thus, the trinuclear complex [(NiL )
2 3 2
Hg(N ) ] (4)
1
was synthesized by mixing [NiL ], HgCl
2
and NaN
3
in a 2:1:2 molar
2
1
2
.7. Physical measurements
ratio. Interestingly, when using [NiL ] instead of [NiL ], the hexa-
2
nuclear complex [{(NiL )
2 3 3 2
Hg(N )(l1,1-N )} ] (5) was obtained by
Elemental analyses (C, H and N) were performed using a Perkin-
Elmer 2400 series II CHN analyzer. IR spectra in KBr pellets
following a similar procedure to that of 4. Furthermore, when the
2
same components i.e., [NiL ], HgCl
2
and NaN
3
were mixed in a 1:2:1
, then the nona-
{Hg(N )( )}]
ꢀ1
(
4000–500 cm ) were recorded using a Perkin-Elmer RXI FT-IR
molar ratio i.e., increasing the proportion of HgCl
2
2
spectrophotometer. Electronic spectra in solid state were recorded
in a Hitachi U-3501 spectrophotometer. The magnetic susceptibil-
ity measurements were carried out in the temperature range 2–
nuclear complex [{(NiL )
2 3
Hg(N )(
3
l1,1-N )HgCl
}
2 2
3 3
l1,1-N
1
(6) was obtained. It may also be noted that for the [NiL ] metallo-
ligand, complex 4 was the only product even when the molar ratio
3
00 K with an applied magnetic field of 0.1 T on a polycrystalline
of HgCl
2
was increased. Thus a complex equivalent to nona-nuclear
1
sample of complex 5 (with a mass of 31.17 mg) with a Quantum
Design MPMS-XL-5 SQUID susceptometer. The susceptibility data
were corrected for the sample holder previously measured using
the same conditions and for the diamagnetic contribution of
species 6 was not formed with L . Thus, it can be concluded that
the reaction of the [NiL ] metalloligand with HgCl
ar (1) and trinuclear (3) complexes by simply increasing the
proportion of [NiL ]. However, for the [NiL ] metalloligand this
1
2
, yields dinucle-
1
2

3
14
L.K. Das et al. / Polyhedron 87 (2015) 311–320
Table 1
Crystal data and structure refinement of complexes 1 and 3–6.
Complexes
1
3
4
5
6
Formula
M
Crystal system
Space group
a (Å)
C
16
H
14Cl2.25Hg1.13
N
2
NiO
2
C
32
H
28Cl
2
HgN
Ni
4 2
O
4
C
32
H
28HgN10Ni
2
O
4
C
68
H
64Hg
2
N
20Ni
4
O
8
C
68 4 5 4 8
H64Cl Hg N26Ni O
630.43
triclinic
P1ꢀ
921.45
triclinic
P1ꢀ
8.573(5)
9.632(5)
10.677(5)
74.338(5)
78.861(5)
67.585(5)
780.7(7)Å
1
1.960
6.314
450
934.65
monoclinic
Cc
1925.33
triclinic
P1ꢀ
2753.04
monoclinic
C2/c
40.627(5)
9.9391(7)
24.408(2)
90
125.518(16)
90
8022.0(13)
2
2.280
10.650
5192
9.2950(6)
10.0541(7)
10.1801(6)
72.156(6)
77.803(5)
86.275(6)
885.15(10)
2
16.354(5)
10.684(5)
19.377(5)
90
105.887(5)
90
3256(2)
4
1.906
10.329(5)
10.828(5)
15.940(5)
104.847(5)
99.058(5)
94.813(5)
1687.3(12)
1
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
calc (g cmꢀ3)
(mm
2.365
21.771
593
1.895
5.699
948
ꢀ
1
)
5.903
1832
F (000)
R
int
0.084
8126
2486
2269
0.0549
0.1410
150
0.023
9368
3093
2847
0.0245
0.0653
293
0.025
11117
5189
0.024
19378
5904
0.096
17256
8775
Total reflections
Unique reflections
I > 2
r
(I)
4571
5354
4906
a
R
1
(I > 2
r
(I))
0.0277
0.0553
293
0.0260
0.0666
293
0.0684
0.1313
150
b
wR
2
(all data)
Temperature (K)
Goodness-of-fit (GOF)c
1.06
1.08
0.95
1.09
0.93
P
P
a
R
1
=
||F
o
| ꢀ|F
c
||/ |F
o
|.
2
P
P
b
c
2
2
o
2
4
]½
wR
2
(F
o
) = [w(F
ꢀF
c
) / wF
o
.
P
2
2
) /(Nobs ꢀNparams)]½
2
GOF = [w(F
o
ꢀF
c
.
increase has no influence on the final obtained complex and we
could isolate only dinuclear complex 2. On the other hand, the
1.0
0.8
0.6
0.4
1
[
NiL ]
2
ꢀ
[NiL ]
use of N
[
3
inverts this tendency and thus, the metalloligand
2
1
3
4
5
6
NiL ] gives rise to high nuclearity (six and nine) complexes by
2
ꢀ
3
increasing the proportion of HgCl
ratio. In contrast, the reaction of the metalloligand [NiL ] with
HgCl and NaN only gives rise to the trinuclear complex 4 even
with high molar ratio of HgCl
2
without changing the [NiL ]:N
1
2
3
2
.
0.2
3.2. IR spectra and UV–Vis spectra of the complexes
0.0
400
600
800
1000
1200
Wave length (nm)
Besides the elemental analysis, all six complexes were initially
characterised by IR spectroscopy (Figs. S1–S6). A strong and sharp
band due to the azomethine (C@N) group of the Schiff base
Fig. 1. Electronic spectra of the metalloligands and complexes in the solid state.
m
ꢀ1
appears at 1619, 1618, 1620, 1615, 1616 and 1617 cm for com-
plexes 1–6, respectively. In addition, the presence of azido ligands
in complexes 4–6 is confirmed by the detection of a sharp and
expected to exhibit absorption bands near 610 (
1
m ) and 500 nm
l
l
(
m
2
) corresponding to the spin allowed d–d transitions Blg
A , respectively [29]. Here, the m2 band cannot be
g
located presumably because it overlaps with charge transfer bands.
On the other hand, the spectra of complexes 5 and 6, containing the
H L ligand, are different from their mononuclear precursor [NiL ].
A
g
l
l
ꢀ
ꢀ
1
1
and B3g
strong characteristic stretching band in the 2080–2040 cm
region. In case of 4, a single strong and sharp peak at 2044 cm
appeared while there were strong and sharp peaks at 2075 and
2
2
ꢀ1
ꢀ1
2
2
078 cm along with shoulders at 2047 and 2050 cm in the
2
The [NiL ] shows band maxima (
1
m ) at 623 nm along with a less
spectra of 5 and 6. The splitting of the band is indicative of the
presence of two different coordinated azide ions in both 5 and 6,
in agreement with their crystal structures.
All the complexes are sparingly soluble in organic solvents like
methanol, acetonitrile etc. Therefore, the UV–Vis spectra of the
complexes are recorded in the solid state and their solid state dif-
intense shoulder ( ) at 500 nm, assigned to d–d transitions of
Ni(II) ions with a square planar environment. However, both 5
and 6 exhibit a distinct band at 568 and 570 nm, respectively,
which can be assigned to the spin-allowed d–d transition
2g. In addition, they show a well-separated broad band at
028 and 1026 nm, respectively, due to the transition
for octahedral Ni(II) geometry [30], in agreement with the
structural data (see below). Moreover, complexes 5 and 6 show a
sharp single absorption band near 358 and 360 nm, respectively,
attributed to ligand-to-metal charge transfer transitions.
m
2
3
T
1g
3
(
1
F)
A
3
3
T
2g
A
2g
fuse reflectance spectra are shown in Fig. 1. The electronic spectra
1
of complexes 1, 3 and 4 containing H
2
L
ligand are very similar,
showing a broad absorption band centred at 413, 414 and
09 nm, respectively, attributed to ligand-to-metal charge transfer
transitions. Besides this band, a broad absorption band ( ) is
4
m
1
observed in the visible region at 554, 551 and 552 nm for 1, 3
and 4, respectively (compared to 555 nm in the non-coordinated
metalloligand [NiL ]). This band is typical of d–d transitions of
Ni(II) ions with a square planar environment. The electronic spec-
tra of nickel(II) complexes with square planar geometry are
3.3. Description of the structures of the complexes
1
All six structures contain either L1 or L , the latter having an
2
1
extra methylene moiety. The dinuclear structure of [(NiL )HgCl
2
]

L.K. Das et al. / Polyhedron 87 (2015) 311–320
315
In the structure, there is an inter-molecular
p
–p
stacking
between the two phenyl rings (symmetry: 1 ꢀx, 1 ꢀy, 1 ꢀz) with
a centroid CgꢁꢁꢁCg distance of 3.665(8) Å. Additionally, there is a
weak C20–H20BꢁꢁꢁO30 hydrogen bonding interaction between
the phenoxido oxygen atom, O30 and the methylene hydrogen
atom (H20B) of an adjacent molecule (1 ꢀx, 2 ꢀy, 1 ꢀz) with dis-
tance of O30ꢁꢁꢁC20 3.292(18) Å and C20–H20BꢁꢁꢁO30 angle of 144°.
These interactions generate polymeric chains as depicted in Fig. 3.
1
1
Complexes [(NiL )
2
HgCl
2
] (3) and [(NiL )
2
Hg(N
3
)
2
] (4), both con-
1
taining L are trinuclear and very similar. The main differences are
that 3 contains an crystallographic inversion centre while 4 does
not, although its structure is closely centrosymmetric, and 3 con-
tains chloride ions and 4 azide ions. In both structures the Hg atom
presents an octahedral geometry with two axial short bonds to two
ꢀ
ꢀ
3
mutually trans anions (Cl or N ) and four long equatorial bonds
1
from the four oxygen atoms from the two [NiL ] metalloligands.
The structures of 3 and 4 are shown in Fig. 4 together with the atomic
numbering schemes. Bond lengths and angles in the metal coordina-
tion spheres are given in Tables 3 and 4, respectively.
In 3, the axial Hg(1)–Cl(1) distance is 2.303(2) Å and the weak
equatorial bonds to the oxygen atoms O(11) and O(30) are
2
.827(3) and 2.834(3) Å. These oxygen atoms bridge the Hg and
Ni metals. The nickel atom has the expected four-coordinate
square planar structure with Ni–O bond lengths of 1.844(3) and
Fig. 2. The structure of 1 with ellipsoids at 30% probability. An additional [HgCl]
moiety with 25% occupancy is not shown. The structure of 2 with an additional
methylene moiety is similar.
1
.847(3) Å and Ni–N bond lengths of 1.847(3) and 1.856(3) Å.
The r.m.s deviation for the four donor atoms is 0.006 Å, with the
Ni(1) atom 0.001(2) Å away from the plane.
2
The structure of 4 shows a similar Ni Hg trinuclear unit. The Hg
also presents a compressed octahedral geometry with two short
bonds to the two trans-azide anions with Hg(1)–N(1) 2.067(10) Å
and Hg(1)–N(4) 2.054(9) Å and four longer bonds to the oxygen
atoms of two [NiL ] metalloligands with Hg–O bond lengths in
the range 2.736(5)–2.842(5) Å. These four oxygen are almost
coplanar, with a r.m.s. deviation of 0.036 Å, being the Hg atom
Table 2
Bond distances (Å) and angles (°) for complex 1.
1
Hg(1)–Cl(1)
Hg(1)–Cl(2)
Hg(1)–O(11)
Hg(1)–O(30)
Cl(1)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–O(30)
Cl(2)–Hg(1)–O(30)
Cl(1)–Hg(1)–O(11)
Cl(2)–Hg(1)–O(11)
O(11)–Hg(1)–O(30)
2.320(3)
2.325(3)
2.523(7)
2.488(7)
158.16(12)
99.9(2)
101.3(2)
101.2(2)
94.1(2)
Ni(1)–O(11)
Ni(1)–O(30)
Ni(1)–N(19)
Ni(1)–N(22)
O(11)–Ni(1)–O(30)
O(11)–Ni(1)–N(22)
O(11)–Ni(1)–N(19)
O(30)–Ni(1)–N(22)
O(30)–Ni(1)–N(19)
N(22)–Ni(1)–N(19)
1.862(8)
1.858(7)
1.848(9)
1.837(9)
83.3(3)
178.6(4)
94.1(4)
95.3(4)
0
.030(3) Å away from the plane. These oxygen atoms bridge the
Hg atom to a nickel atom. The nickel atoms are four coordinate
square planar being bound to the four donor atoms of the ligands
with r.m.s. deviations of the four donor atoms of 0.060 and
177.4(4)
87.3(4)
0
.045 Å, being Ni(2) and Ni(3) 0.009(3) and 0.008(3) Å away from
their respective planes, which form a dihedral angle of 6.1(4)°.
The H-bonding and C–Hꢁꢁꢁ interactions in complexes 3 and 4
59.1(2)
p
give rise to a 2D supramolecular network (Fig. 5 for 3 and Fig. S7
for 4). In both complexes, H-bonding interactions are formed
between the phenoxido oxygen atoms and the methylene hydrogen
atom of an adjacent molecule (2 ꢀx, 1 ꢀy, ꢀz for 3 and x, 1 + y, z for
4) with dimensions OꢁꢁꢁC 3.272(6) and 3.452(9) Å and C–HꢁꢁꢁO
angles of 143° and 161°, respectively. Moreover, a trinuclear unit
of complex 4 interacts with other trinuclear unit via two additional
H-bonding between nitrogen atoms of azido ligands and iminic
hydrogen atoms with dimensions NꢁꢁꢁC 3.466(12) and 3.447(13) Å
and C–HꢁꢁꢁN angles of 151° and 176°. Besides these H-bonding inter-
(
1) is shown in Fig. 2 together with the atomic numbering scheme
in the coordination spheres. Bond lengths and angles in the metal
coordination sphere are given in Table 2. The structure of 2 with an
additional methylene moiety is equivalent.
The nickel atom has a four coordinate square planar environ-
ment formed by the four donor atoms of the tetradentate Schiff
1
base ligand (L ). Bond lengths from nickel are 1.837(9),
1
.848(9) Å to nitrogen and 1.858(7), 1.862(8) Å to oxygen. The four
donor atoms are planar with a root mean squared (r.m.s.) deviation
of 0.008 Å, the nickel being 0.001(5) Å away from the equatorial
plane. The two oxygen atoms also coordinate the mercury atom
which completes its highly distorted tetrahedral coordination with
two chlorine atoms. The distortions from the regular tetrahedral
geometry are clearly shown by the small O–Hg–O bond angle of
actions two adjacent trinuclear units establish C–Hꢁꢁꢁ
p interactions
between the methylene hydrogen atoms of one trinuclear unit and
the centroid of a phenyl ring of other trinuclear units (symmetry
1 ꢀx,1 ꢀy, ꢀz for 3 and ꢀ1/2 + x, 1/2 + y, z for 4) with distances of
2.59 (3) Å for 3 and 2.52(1) Å for 4.
2
5
9.1(2)°, the large Cl–Hg–Cl angle of 158.16(12)° and by the
Complex [{(NiL ) Hg(N ) } ] (5) is a centrosymmetric hexanu-
2
3 2 2
shorter Hg–Cl bond lengths of 2.320(3) and 2.325(3) Å compared
to Hg–O of 2.488(7) and 2.523(7) Å (Table 2).
clear cluster formed by two symmetry related Ni Hg units. Fig. 6
shows the structure of complex 5 together with the atomic num-
2
Apart from the complex, the structure contains two residual
peaks of high electron density. These were refined as Hg(2) in a
centrosymmetric position and Cl(3) in a general position, with
population parameters of 0.25. The resulting geometry around
Hg(2) is approximately square planar, the metal being bound
weakly to Cl(2) at 2.787(4) Å which bridges to Hg(1) and strongly
to Cl(3) at 2.242(11) Å.
bering scheme. Selected bond lengths and angles are summarized
in Table 4. As in 4, the Hg atoms present a compressed octahedral
geometry with two strongly bound trans-azide ligands Hg–N(1)
and Hg–N(4) at 2.063(4) and 2.093(4) Å, respectively. The equato-
rial plane is formed by four oxygen atoms with longer bond
lengths: Hg–O(61) 2.548 (3) Å, Hg–O(11) 2.719(3) Å, Hg–O(31)
2.733(3) Å and Hg–O(41) 2.964(3) Å. The four oxygen atoms are

3
16
L.K. Das et al. / Polyhedron 87 (2015) 311–320
Fig. 3. The 1D chain formed in 1 through H-bonds and intermolecular
pꢁꢁꢁp interactions. Other H-atoms have been removed for clarity. Distances in Å.
Fig. 4. Left: The centrosymmetric structure of 3 with ellipsoids at 50% probability. Right: The structure of 4 with ellipsoids at 30% probability. The weak HgꢁꢁꢁO interactions
are shown as open bonds in both cases.
Table 3
bond angle of 84.13(11)°). The r.m.s. deviation of the four equato-
rial atoms is 0.088 Å, with the Ni(3) atom 0.061(2) Å away from the
Bond distances (Å) and angles (°) for complex 3.
Hg(1)–Cl(1)
Hg(1)–O(11)
Hg(1)–O(30)
Cl(1)–Hg(1)–O(11)
Cl(1)–Hg(1)–O(30)
O(11)–Hg(1)–O(30)
2.303(2)
2.827(3)
2.834(3)
86.82(6)
86.79(7)
52.32(8)
Ni(1)–O(11)
Ni(1)–N(19)
Ni(1)–N(22)
Ni(1)–O(30)
O(11)–Ni(1)–O(30)
O(11)–Ni(1)–N(22)
O(11)–Ni(1)–N(19)
O(30)–Ni(1)–N(22)
O(30)–Ni(1)–N(19)
N(22)–Ni(1)–N(19)
1.844(3)
1.847(3)
1.856(3)
1.847(3)
85.09(11)
179.44(13)
94.60(13)
94.43(13)
179.46(14)
85.89(15)
plane. The bond lengths are Ni(3)–O 2.052(3) and 1.999(3) Å and
Ni(3)–N = 2.027(3) and 2.054(4) Å, all longer than those observed
for the square planar Ni(2) atom, as a consequence of the extra
coordination of the two axial ligands in Ni(3). The two equatorial
planes around Ni(2) and Ni(3) form a dihedral angle of 46.0(1)°.
In the structure, there is an intra-molecular
p–p stacking
between the two phenyl rings (symmetry: ꢀx, ꢀy, 2 ꢀz) with a cen-
troid CgꢁꢁꢁCg distance of 3.784(3) Å. The non classical hydrogen
bonding interactions [C26–H26ꢁꢁꢁN3 (ꢀ1 ꢀx, ꢀ1 ꢀy, 1 ꢀz) and
C56–H56ꢁꢁꢁN3 (1 + x, y, z) with dimensions NꢁꢁꢁC 3.292(18) and
3
.421(8) Å, respectively] are also present.
almost planar with a r.m.s. deviation of 0.001 Å, with the Hg(1)
atom 0.310(2) Å from the plane directed towards N(1) from the
more strongly bound azide.
The molecular structure of complex 6 contains a nonanuclear
2
unit [{(NiL )
2
Hg(N
3
)(l
1,1-N
3
)HgCl
2
2
} {Hg(N
3
)(
3
l1,1-N )}] with
C
2
symmetry formed by two tetrameric Ni
2
Hg
2
units connected
Ni(2) has a square planar geometry formed by the four donor
atoms of the L ligand showing a r.m.s. deviation of 0.034 Å, being
the Ni(2) atom 0.001(2) Å away from the plane. Bond lengths are
Ni(2)–O = 1.852(3) and 1.869(3) Å and Ni(2)–N = 1.894(4) and
through a Hg(3) atom located on the C
2
axis. The structure of 6 is
2
shown in Fig. 7 together with the atomic numbering scheme.
Dimensions in the metal coordination sphere are given in Table 5.
The central mercury atom Hg(3) occupies a 2-fold axis and presents
a highly distorted octahedral geometry formed by two short mutu-
ally trans azide ligands with dimensions Hg(3)–N(4) 2.042(11) Å,
N(4)–Hg(3)–N(4) 159.6(7)° two mutually cis-O atoms Hg(3)–O(61)
2.679(9) Å, O(61)–Hg(3)–O(61) 142.6(3)°) and two mutually cis-Cl
atoms Hg(3)–Cl(2) 3.081(4) Å, Cl(2)–Hg(3)–Cl(2) 74.8(1)°). Hg(2)
also presents a very distorted octahedral geometry formed by two
trans-azide ligands with dimensions Hg(2)–N(1) 2.101(13) Å,
1
.917(4) Å. In contrast, Ni(3) presents an octahedral geometry
2
formed by four donor atoms from one L ligand in the equatorial
ꢀ
2
plane with a
l1,1-N ligand and an oxygen atom from another L
3
ligand in the axial positions with Ni(3)–N(4) 2.291(4) Å and
Ni(3)–O(41) 2.132(3) Å. Each of these axial atoms connects Ni(3)
to a Hg(1) atom whereas the two O(41) atoms form a double oxido
bridge connecting both Ni(3) atoms (with a Ni(3)–O(41)–Ni(3)

L.K. Das et al. / Polyhedron 87 (2015) 311–320
317
Table 4
Bond distances (Å) and angles (°) for complexes 4 and 5.
4
5
4
5
x = 0, y = 2
x = 1, y = 3
x = 0, y = 2
x = 1, y = 3
Hg(1)–N(1)
Hg(1)–N(4)
Hg(1)–O(11)
Hg(1)–O(3x)
Hg(1)–O(41)
Hg(1)–O(6x)
2.067(10)
2.054(9)
2.768(5)
2.842(5)
2.841(5)
2.736(5)
177.4(5)
92.7(2)
87.6(3)
89.1(3)
88.4(3)
88.5(2)
91.3(2)
89.8(3)
92.8(3)
53.37(15)
176.13(14)
53.47(13)
177.06(17)
123.71(14)
129.46(13)
2.063(4)
2.093(4)
2.719(3)
2.733(3)
2.964(3)
2.548(3)
Ni(2)–N(19)
Ni(2)–N(2y)
Ni(2)–O(11)
Ni(2)–O(3x)
N(19)–Ni(2)–N(2y)
N(19)–Ni(2)–O(11)
N(19)–Ni(2)–O(3x)
N(2y)–Ni(2)–O(11)
N(2y)–Ni(2)–O(3x)
O(11)–Ni(2)–O(3x)
Ni(3)–N(5y)
1.824(6)
1.819(9)
1.851(5)
1.853(5)
85.1(4)
1.917(4)
1.894(4)
1.852(3)
1.869(3)
96.15(18)
91.67(16)
170.63(16)
171.88(16)
92.99(16)
79.23(13)
2.054(4)
95.0(3)
N(1)–Hg(1)–N(4)
N(1)–Hg(1)–O(6x)
N(1)–Hg(1)–O(11)
N(1)–Hg(1)–O(41)
N(1)–Hg(1)–O(3x)
N(4)–Hg(1)–O(6x)
N(4)–Hg(1)–O(11)
N(4)–Hg(1)–O(41)
N(4)–Hg(1)–O(3x)
O(11)–Hg(1)–O(3x)
O(3x)–Hg(1)–O(41)
O(41)–Hg(1)–O(6x)
O(6x)–Hg(1)–O(11)
O(3x)–Hg(1)–O(6x)
O(11)–Hg(1)–O(41)
167.10(16)
100.15(16)
93.06(16)
99.14(14)
93.53(14)
73.73(13)
95.76(13)
67.96(11)
99.32(12)
51.63(9)
166.20(9)
58.90(8)
161.08(10)
113.54(9)
132.34(8)
176.8(3)
175.7(3)
94.4(3)
85.7(2)
1.844(5)
1.850(7)
1.845(4)
1.855(4)
Ni(3)–N(49)
Ni(3)–O(41)
Ni(3)–O(6x)
2.027(3)
2.052(3)
1.999(3)
2.291(4)
Ni(3)–N(4)
Ni(3)–O(41)
a
2.132(3)
N(49)–Ni(3)–N(5y)
N(49)–Ni(3)–O(41)
N(49)–Ni(3)–O(6x)
N(5y)–Ni(3)–O(41)
N(5y)–Ni(3)–O(6x)
O(41)–Ni(3)–O(6x)
O(61)–Ni(3)–N(4)
N(49)–Ni(3)–N(4)
O(41)–Ni(3)–N(4)
N(53)–Ni(3)–N(4)
86.9(3)
94.2(2)
176.7(3)
177.5(2)
93.6(2)
85.5(2)
97.10(14)
91.19(12)
169.11(13)
174.39(12)
89.85(13)
84.88(11)
96.62(11)
89.39(14)
84.20(12)
96.94(14)
168.30(12)
96.62(11)
91.19(12)
84.13(11)
94.59(12)
a
O(41) –Ni(3)–N(4)
a
O(41) –Ni(3)–O(61)
a
O(41) –Ni(3)–N(49)
a
O(41) –Ni(3)–O(41)
a
O(41) –Ni(3)–N(53)
a
=
symmetry element ꢀx, ꢀy, 2 ꢀz.
Fig. 5. The 2D supramolecular network of 3 formed by the H-bonds and intermolecular C–Hꢁꢁꢁ
p interactions. Other H-atoms have been removed for clarity. Distance in Å.
Hg(2)–N(7) 2.088(13) Å and N(1)–Hg(2)–N(7) = 165.8(5)°, three O
atoms Hg(2)–O(11) 2.601(9) Å, Hg(2)–O(31) 2.488(8) Å and
Hg(2)–O(41) 2.855(9) Å with O–Hg(2)–O bond angles in the range
bond angles, ranging from O(41)–Hg(1)–O(61) = 68.9(2)° to Cl(1)–
Hg(1)–Cl(2) = 154.7(1)°. In contrast, the Hg(1)–Cl bond lengths at
2.332(4), 2.339(5) Å are quite similar to Hg(1)–O bond lengths at
2.390(7), 2.418(10) Å.
5
7.9(2)–148.8(2)° and one Cl atom Hg(2)–Cl(1) 3.212(9) Å). Hg(1)
presents a distorted tetrahedral geometry, similar to that observed
in 1. The distortions in the tetrahedron are clearly observed in the
The two nickel atoms, Ni(4) and Ni(5) are both bound to the
four donor atoms of a L ligand although Ni(4) is square planar
2

3
18
L.K. Das et al. / Polyhedron 87 (2015) 311–320
Fig. 6. The centrosymmetric structure of 5 with ellipsoids at 20% probability. Weak interactions to Hg(1) are shown as open bonds.
Fig. 7. The structure of 6 with ellipsoids at 30% probability. Weak interactions from Hg(2) and Hg(3) to oxygen are shown as open bonds. Hg(3) occupies a centre of
symmetry.
whereas Ni(5) presents a regular octahedral environment with two
show any magnetic coupling. A priori, the only complex that may
present a magnetic coupling between paramagnetic Ni(II) centres
is complex 5 since it presents two octahedral Ni(II) ions with a
double oxido bridge (inset in Fig. 8). Accordingly, we have only
ꢀ
additional axial trans-N
3
ligands with bond lengths of 2.125(12)
and 2.186(14) Å). As a consequence, the equatorial bond lengths
around Ni(4) (in the range 1.851(8)–1.869(10) Å) are significantly
shorter than those around Ni(5) (in the range Ni–N = 2.020(10)–
measured the magnetic properties of complex 5. The
m
v T product
2
5
.045(12) Å). The two equatorial planes form a dihedral angle of
0.5(3)°. The r.m.s. deviations of the four donor atoms are 0.189
for complex 5 ( = molar magnetic susceptibility per Ni
plex) shows a room temperature value of ca. 2.35 cm K mol
(Fig. 8), which is the expected value for two isolated S = 1 Ni(II)
v
m
4
Hg
2
com-
3
ꢀ1
and 0.109 Å, with the Ni(4) and Ni(5) atoms 0.002(6) and
0
.011(6) Å away from their respective planes.
m
ions. When the sample is cooled down, v T smoothly increases,
reaching a maximum of ca. 3.30 cm K mol at ca. 9 K (inset in
3
ꢀ1
Fig. 8). Below ca. 9 K T sharply decreases and reaches a value
of ca. 1.4 cm K mol at 2 K. This behaviour suggests the presence
v
m
3.4. Magnetic properties
3
ꢀ1
of ferromagnetic interactions between the two octahedral Ni(II)
Complexes 1–4 contain only diamagnetic Hg(II) cations and
square planar Ni(II) ions, whereas complex 6 only contains two iso-
lated octahedral Ni(II) ions and, therefore, it is not expected to
ions that account for the increase in
m
v T as T decreases. The sharp
decrease at very low temperatures has to be attributed to the

L.K. Das et al. / Polyhedron 87 (2015) 311–320
319
1
Table 5
4
. Conclusions
Bond distances (Å) and angles (°) for complex 6.
Hg(1)–Cl(1)
Hg(1)–Cl(2)
Hg(1)–O(41)
Hg(1)–O(61)
Cl(1)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–O(41)
Cl(2)–Hg(1)–O(41)
Cl(1)–Hg(1)–O(61)
Cl(2)–Hg(1)–O(61)
O(41)–Hg(1)–O(61)
Hg(2)–N(1)
Hg(2)–N(7)
Hg(2)–O(31)
Hg(2)–O(11)
N(1)–Hg(2)–N(7)
N(1)–Hg(2)–O(31)
N(7)–Hg(2)–O(11)
N(7)–Hg(2)–O(31)
N(1)–Hg(2)–O(11)
O(11)–Hg(2)–O(31)
2.332(5)
2.339(5)
2.390(7)
2.418(10)
154.69(13)
93.7(3)
109.7(3)
105.6(2)
92.2(2)
O(11)–Ni(4)–O(31)
O(11)–Ni(4)–N(19)
O(11)–Ni(4)–N(23)
O(31)–Ni(4)–N(19)
O(31)–Ni(4)–N(23)
N(19)–Ni(4)–N(23)
Ni(5)–O(41)
83.3(4)
94.6(4)
167.0(5)
168.2(5)
92.2(4)
92.2(5)
2.020(10)
2.028(8)
2.039(9)
2.045(12)
2.125(12)
2.186(14)
84.4(3)
90.1(4)
170.9(4)
170.7(3)
88.7(4)
97.6(4)
84.4(4)
92.6(4)
94.0(5)
In the present paper, using two related metalloligands [NiL ]
2
1
0
and [NiL ] (where H
2
L
is N,N -bis(salicylidene)-1,2-ethylenedia-
is N,N -bis(salicylidene)-1,3-propanediamine) we
have shown that it is possible to synthesise up to six different
Ni(II)–Hg(II) hetero-metallic complexes of nuclearities from two
to nine, by simply changing the reactant ratios and the counter
2
0
mine and H
2
L
Ni(5)–O(61)
Ni(5)–N(49)
Ni(5)–N(53)
Ni(5)–N(1)
1
2
anions. Both metalloligands [NiL ] and [NiL ] react with HgCl
2
to
produce dinuclear complexes namely 1 and 2. However, when
is decreased only [NiL ] yields a trinuclear
complex, namely 3. On the other hand, when Cl ion is replaced by
, only trinuclear complexes are formed for both ligands; for
NiL ] it remains as a discrete molecule (4) but for [NiL ], terminal
nickel atoms of two trinuclear units join together via phenoxido
bridges to form a hexanuclear species (5). On increasing the pro-
68.8(3)
1
the proportion of HgCl
2
2.101(13)
2.088(13)
2.488(9)
2.602(9)
165.8(5)
92.1(4)
101.1(4)
102.0(4)
86.9(4)
ꢀ
Ni(5)–N(4)
ꢀ
O(41)–Ni(5)–O(61)
O(41)–Ni(5)–N(49)
O(61)–Ni(5)–N(49)
O(41)–Ni(5)–N(53)
O(61)–Ni(5)–N(53)
N(49)–Ni(5)–N(53)
O(41)–Ni(5)–N(1)
O(61)–Ni(5)–N(1)
N(49)–Ni(5)–N(1)
N(53)–Ni(5)–N(1)
O(41)–Ni(5)–N(4)
O(61)–Ni(5)–N(4)
N(49)–Ni(5)–N(4)
N(53)–Ni(5)–N(4)
N(1)–Ni(5)–N(4)
N
[
3
1
2
2
portion of HgCl
2
, [NiL ] even yields an unprecedented nonanuclear
complex (6). Complexes 5 and 6 are the only known examples of
nuclearities higher than four in discrete hetero-metallic clusters
containing Hg(II). The double phenoxido bridged Ni(II) dimer in
complex 5 is ferromagnetically coupled as expected from the Ni–
O–Ni bond angle. All these results demonstrate the possibility to
create novel complexes with different nuclearities by playing not
only with the metal to ligand ratio and/or the presence of different
terminal or bridging co-ligands but also with the size of the chelat-
ing ring in the precursor complexes used as ligands. This strategy is
now being used to combine other magnetic metal atoms, mainly
lanthanides, in order to prepare novel polynuclear complexes with
interesting magnetic properties including single molecules
magnets.
57.8(3)
Hg(3)–N(4)
2.042(11)
159.6(7)
1.851(8)
1.852(9)
1.862(12)
1.869(10)
N(4)–Hg(3)–N(4)a
89.8(5)
89.6(5)
83.3(4)
89.5(4)
95.7(5)
173.0(5)
Ni(4)–O(11)
Ni(4)–O(31)
Ni(4)–N(19)
Ni(4)–N(23)
a
Symmetry element 1 ꢀx, y, 1.5 ꢀz.
Acknowledgments
L.K.D. is thankful to CSIR, India for awarding Senior Research
Fellowship [Sanction No. 09/028(0805)/2010-EMR-I]. Crystallogra-
phy was performed at the DST-FIST, India funded Single Crystal
Diffractometer Facility at the Department of Chemistry, University
of Calcutta. We thank EPSRC and the University of Reading for
funds for the X-Calibur system. We also thank the European Union
(
ERC Advanced Grant SPINMOL), the Spanish MINECO (Project
CTQ-2011-26507) and the Generalitat Valenciana (Prometeo and
ISIC-NANO Programs) for financial support. The authors also thank
the Department of Science and Technology (DST), New Delhi, India,
for financial support (SR/S1/IC/0034/2012).
Fig. 8. Thermal variation of
m 4 2
v T per Ni Hg unit in complex 5. Solid line represents
the best fit to the model (see text).
Appendix A. Supplementary data
presence of a zero field splitting (ZFS) in the resulting S = 2 ground
state of the dimer. Accordingly, we have fitted the magnetic prop-
erties of complex 5 with a simple S = 1 dimer model including ZFS
CCDC 1005578–1005583 contain the supplementary crystallo-
graphic data in CIF format for 1–6, respectively. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
[
31]. This model reproduces very satisfactorily the magnetic prop-
ꢀ1
ꢀ1
erties of 5 with g = 2.132, J = +2.1 cm
and |D| = 8.5 cm
(the
Hamiltonian is written as ꢀJS
1 2
S ). Note that the sign of D cannot
be determined from powder magnetic measurements and also that
this high D value could include an antiferromagnetic inter-dimer
3
36-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.poly.2014.11.025.
coupling through a quite short inter-dimer p–p stacking observed
in complex 5 along the [101] direction.
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