Synthesis, structure and spectroscopic properties of nickel(II) macrocyclic and open-chain complexes resulted from 1-phenyl-butane-1,3-dione mono-S-methylisothiosemicarbazone template self-condensation

Article abstract of DOI:10.1016/S0020-1693(00)00318-2

Self-condensation of 1-phenyl-butane-1,3-dione mono-S-methylisothiosemicarbazone (6) in the presence of nickel(II) acetate in methanol gives rise to a mixture of two complexes: [2,9-bis(methylthio)-5,13-dimethyl-7,14-diphenyl-1,3,4,8,10,11- hexaazacyclotetradeca-2,4,6,9,11,13-hexaenato(2-) N¹,N⁴,N⁸,N¹¹]nickel(II) (7) and [1-amino-1,6-bis(methylthio)-4,9-dimethyl-11-phenyl-2,3,4,7,8- pentaazaundeca-1,3,6,8,10-pentaenato(-)-11-olato(-)N², N⁴,N⁸,O]nickel(II) (8). Both the macrocyclic complex 7 and the open-chain chelate 8 are characterised by X-ray diffraction methods, which reveal their square-planar structure. Electronic, IR, NMR, electron impact mass spectra and cyclic voltammograms of new compounds are also reported.

Full text of DOI:10.1016/S0020-1693(00)00318-2

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Inorganica Chimica Acta 313 (2001) 30–36
Synthesis, structure and spectroscopic properties of nickel(II)
macrocyclic and open-chain complexes resulted from
1-phenyl-butane-1,3-dione mono-S-methylisothiosemicarbazone
template self-condensation
Julieta I. Gradinaru a, Yurii A. Simonov b, Vladimir B. Arion* a,1, Polina N. Bourosh b,
Maria A. Popovici a, Vitalii K. Bel’skii c, Nicolai V. Gerbeleu* a,2
a Institute of Chemistry of the Academy of Sciences of Moldo6a, Str. Academiei, 3, MD-2028 Chishinau, Moldo6a
b Institute of Applied Physics of the Academy of Sciences of Moldo6a, Str. Academiei, 5, MD-2028 Chishinau, Moldo6a
c L.Ya. Karpo6’s Institute of Physical Chemistry, 103064 Moscow, Russia
Received 28 April 2000; accepted 15 September 2000
Abstract
Self-condensation of 1-phenyl-butane-1,3-dione mono-S-methylisothiosemicarbazone (6) in the presence of nickel(II) acetate in
methanol gives rise to a mixture of two complexes: [2,9-bis(methylthio)-5,13-dimethyl-7,14-diphenyl-1,3,4,8,10,11-hexaazacyclote-
tradeca-2,4,6,9,11,13-hexaenato(2-)N1,N4,N8,N11]nickel(II) (7) and [1-amino-1,6-bis(methylthio)-4,9-dimethyl-11-phenyl-2,3,4,7,8-
pentaazaundeca-1,3,6,8,10-pentaenato(-)-11-olato(-)N2,N4,N8,O]nickel(II) (8). Both the macrocyclic complex 7 and the open-chain
chelate 8 are characterised by X-ray diffraction methods, which reveal their square-planar structure. Electronic, IR, NMR,
electron impact mass spectra and cyclic voltammograms of new compounds are also reported. © 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Nickel(II) complexes; Isothiosemicarbazide-based ligands; Crystal structures
1. Introduction
Metal-directed condensation of 1, n-diamines with
aldehydes or ketones produces mainly symmetric
polyazamacrocyclic compounds [1–4]. The use of the
S-alkylisothiosemicarbazide hydroiodide (NH2ꢀNꢁ
C(SR)ꢀNH2HI) as a building block in such reactions is
particularly interesting. This leads to various macro-
cyclic systems containing two different b-dicarbonyl
residues, as well as differently arranged S-alkyliso-
thiosemicarbazide fragments around the metal ion.
Previously, it has been found that [1+2] condensa-
tion of pentane-2,4-dione with S-alkylisothiosemicar-
bazide hydroiodide in the presence of nickel(II) affords
the complex [Ni(H2L)]I, where H3L=pentane-2,4-
dione bis(S-alkylisothiosemicarbazone) [5]. The latter
can successfully be used as a precursor for building up
1 *Corresponding author. Present address: Laboratoire de Chimie
de Coordination du CNRS, 205 route de Narbonne, F-31077 Tou-
louse Cedex 04, France. Tel.: +33-5-6133 3159; fax: +33-6155 3003;
the macrocylic species 1–4 [6–10]. The unexpected
formation of macrocyclic compounds with symmetri-
arion@lcc-toulouse.fr
2 *Corresponding author
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(00)00318-2

J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
31
2. Experimental
cally disposed S-alkylisothiosemicarbazide groups (de-
scribed as trans) around the nickel atom (regarded here
as an inversion centre) from a precursor, in which the
corresponding residues are arranged non-symmetrically
around the same centre (described as cis), needs a series
of successive transformations: (i) hydrolytic breaking of
one CꢁN bond with liberation of the free S-alkyliso-
thiosemicarbazide; (ii) reaction of the latter with Hacac,
providing the formation of the tridentate ligand –
pentane-2,4-dione mono-S-alkylisothiosemicarbazone;
(iii) the self-condensation of the tridentate ligand in the
presence of nickel(II), yielding the trans-macrocyclic
species.
2.1. Chemicals
All chemicals used were analytical reagent grade.
S-Methylisothiosemicarbazide hydroiodide and 1-
phenyl-butane-1,3-dione mono-S-methylisothiosemicar-
bazone were prepared as described elsewhere [12,15].
2.2. Syntheses
2.2.1. Complexes 7 and 8
1-Phenyl-butane-1,3-dione
mono-S-methylisothio-
semicarbazone (0.50 g, 20 mmol) in methanol (10 cm3)
was added to Ni(OAc)2·4H2O (0.25 g, 10 mmol) in
methanol (10 cm3) and the reaction mixture was heated
under reflux for 2 h. The brown rhombic crystals
formed (7) were separated by filtration, washed with
methanol and ether. Yield 0.20 g, 38.5%. Anal. Found:
C, 54.91; H, 4.82; N, 15.73; Ni, 11.05. Calc. for
C24H24N6NiS2 (fw 519.33): C, 55.51; H, 4.66; N, 16.18;
Ni, 11.31. Molecular peak in the electron impact (EI)
The formation of trans-hexaazamacrocylic products
in [2+2] condensation of S-alkylisothiosemicarbazide
with b-dicarbonyl compounds appears to be more
preferable than that of cis-species. This was confirmed
by template reaction of S-alkylisothiosemicarbazide hy-
droiodide with 1,1,3,3-tetraethoxypropane, which pro-
vided the formation of the trans-product 5 [11].
Efforts to explore this chemistry further were di-
rected to extension of the range of b-dicarbonyl build-
ing blocks, which can lead to new macrocyclic systems.
Only a few coordination compounds, e.g. [Fe(HL1)Cl2]
[12], [Ni(HL1)NH3]I [13] and [Ni(HL1)Py] [14], where
H2L1=1-phenyl-butane-1,3-dione mono-S-methyliso-
thiosemicarbazone (6), were synthesised starting from
1-phenyl-butane-1,3-dione.
1
mass spectrum: m/z 518 (see supplementary data). H
and 13C NMR spectra for 7 (see supplementary data):
lH (300 MHz, CDCl3) 7.37–7.29 (m, 10H, Ph), 4.69
(s, 2H, ꢀCHꢁ), 2.17 (s, 6H, SCH3), 2.10 (s, 6H, CH3);
lC (75.5 MHz, CDCl3) 162.5, 158.4, 154.0, 139.3, 129.5,
129.3, 128.4, 109.1, 19.70, 19.69. Electronic spectrum
(CHCl3), u/nm (m/l cm−1 mol−1): 620 (820), 494 (5950),
416 (7370), 347 (26 040), 277 (19 970). The filtrate was
left to stand for 2 days and the orange precipitate
containing 8 that formed was collected and purified by
chromatography on a silica column using as eluent a
2:1 mixture hexane–chloroform. Yield 0.06 g, 13.8%.
Herein we report on the synthesis, structure and
physico-chemical properties of new products (7) and (8)
of nickel(II)-controlled self-condensation of 1-phenyl-
butane-1,3-dione mono-S-methylisothiosemicarbazone
(6) (Scheme 1).
Scheme 1.

32
J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
Table 1
Absorption spectra were recorded on a Perkin–Elmer
Lambda 19 spectrophotometer. Cyclic voltammetric
measurements were performed using an EG&G Model
273A potentiostat. The three-electrode cell consisted of
a platinum working electrode, a platinum counter-elec-
trode, and an Ag/AgCl/saturated LiCl (EtOH) reference
electrode. Ferrocene was used as an internal standard.
Deaeration of all solutions was accomplished by passing
a stream of high-purity argon through the solution for
10 min prior to the measurements and then maintaining
a blanketing atmosphere of argon over the solution
during the measurements. Cyclic voltammograms in
CH2Cl2 containing 0.10 M tetra-n-butylammonium hexa-
fluorophosphate as the supporting electrolyte and ꢀ
10−3 M complex were recorded at scan rates ranging
from 100 to 500 mV s−-1.
Crystal data and details of data collection for 7 and 8
7
8
Chemical formula
M (g mol−1
Crystal size (mm)
C24H24NiN6S2
519.33
0.2×0.2×0.2
dark brown,
prism
monoclinic
P21/n (no. 14)
8.915(2)
13.835(3)
10.106(2)
107.26(3)
1190.3(4)
2
293
1.449
Mo Ka
0.71073
10.15
540
0.60
−9/10
−16/0
C
435.21
0.4×0.3×0.3
orange, prism
16H20NiN6OS2
)
Crystal colour, habit
Crystal system
Space group
monoclinic
P21 (no. 4)
14.083(3)
9.535(2)
7.2060(10)
79.84(3)
952.5(3)
2
293
1.518
Mo Ka
0.71073
12.56
,
a (A)
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
T (K)
Dc (g cm−3
Radiation
)
2.3.1. Crystal structure determination of 7 and 8
,
u (A)
X-ray diffraction measurements were performed on
Enraf–Nonius CAD4 (7) and DAR-UMB (8) diffrac-
tometers. Crystal data, data collection, and structure
refinement details are given in Table 1. Lattice parame-
ters were determined by a least-squares procedure from
25 (q range 13.0–20.5°) (7) and 24 (q range 12.8–23.2°)
(8) reflections. The structures were solved by direct
methods and refined by full-matrix least-squares tech-
niques. The non-H atoms were refined with anisotropic
displacement parameters. In both cases, H atoms were
calculated and allowed to ride. A Pentium II computer
and the programs SHELXS-86 (for structure solution) [16]
and SHELXL-93 (for refinement ) [17] were used.
v (cm−1
F(000)
)
452
0.65
−16/18
0/12
0/9
−1
,
(sin q/u)max (A
h range
k range
)
l range
−12/0
1403
1388
No. measured reflections
No. reflections used in
refinement
No. parameters
R1 (obs.)
1824
1824
154
229
0.0281
0.0743
1.085
0.220
0.0416
0.1130
1.071
0.389
wR2 (all data)
S
Final diff. density (e−
A
)
−3
,
Anal. Found: C, 43.91; H, 4.58; N, 19.18; Ni, 13.34.
Calc. for C16H20N6NiOS2 (fw 435.21): C, 44.16; H, 4.63;
N, 19.31; Ni, 13,49. Base peak in the EI mass spectrum:
3. Results and discussion
Self-condensation
of
1-phenyl-butane-1,3-dione
1
m/z 434. H and 13C NMR spectra for 8: lH (300 MHz,
mono-S-methylisothiosemicarbazone (6) in the presence
of nickel(II) acetate results in a mixture of two, easily
separated products: the hexaazamacrocyclic complex 7
and the open-chain species 8. Both are diamagnetic
substances, soluble in chloroform, less soluble in
methanol and ethanol, and insoluble in hexane, diethyl
ether and water.
CDCl3) 7.49–7.46 (m, 2H, Ph), 7.34–7.31 (m, 3H, Ph),
6.2–6.8 (br s, 2H, NH), 5.61 (s, 1H, ꢀCHꢁ), 2.53 (s, 3H,
CH3), 2.30 (s, 3H, CH3), 2.29 (s, 3H, CH3), 2.27 (s, 3H,
CH3); lC (75.5 MHz, CDCl3) 168.9, 166.9, 157.7, 153.3,
152.9, 140.4, 129.1, 128.8, 126.6, 98.0, 19.7, 17.3, 15.9,
13.3.
The IR spectrum of 7 shows no absorption in the
3100–3400 cm−1 region or at 1700 cm−1, indicating the
absence of any unreacted NH2 or CꢁO groups. Intense
and very intense bands that can be attributed to charge-
transfer and intraligand transitions dominate the elec-
tronic spectrum of 7 in chloroform. A broad band with
a maximum at ꢀ625 nm can be attributed to the d–d
transition. The EI mass spectrum of 7 is rather simple
and provides a direct confirmation of the macrocycle
formation (see supplementary data). The most intense
peak is that of the molecular ion [M]+·, the further
fragmentation of which under EI is insignificant. The
presence of the doubly-charged ion [M]2+, which is the
second most abundant ion in the spectrum (9% relative
2.3. Analyses and physical measurements
Nickel was determined gravimetrically as Ni(DMG)2,
where H2DMG=dimethylglyoxime. C, H, N contents
were determined by standard micromethods. IR spectra
were recorded on a Perkin–Elmer 2000FT-IR spec-
trophotometer using KBr disks (4000–400 cm−1).
Mass-spectrometric analysis was performed with a
Finningan MAT 95 (Finningan GmbH, Bremen, Ger-
many) doubly focusing (BE) mass spectrometer using EI
ionisation (70 eV) and standard resolution conditions,
1
m/Dm=2300. Solution H and 13C NMR spectra were
recorded on Bruker AC 270 and AM 300 spectrometers.

J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
33
The number of signals indicates the presence of the
inversion centre in the macrocyclic molecule. The H
intensity), indicates the high stability of the molecular
ion. Its further fragmentation under EI is almost negli-
gible. The fragment ions mainly arise by losses from the
side groups and could easily be related to the structure
of the complex (see supplementary data). Their relative
1
NMR data for two closely related trans-macrocyclic
complexes 4 and 5 are available as supplementary data.
All these data, in addition to the previous results [6–
11], suggest the building up the trans-hexaazamacro-
cyclic complex 7 through the nickel(II)-controlled
self-condensation of 6.
1
intensities do not exceed 6%. The H NMR spectrum
offers further evidence for the formation of the trans-
macrocycle. Four distinct absorption regions were ob-
served at 7.37–7.29 (m), 4.69 (s), 2.17 (s), and 2.10 ppm
(s). The relative intensities were in accordance with the
expected ratio of 5:1:3:3 between the resonance signals
of phenyl, methine, thiomethyl and methyl protons.
Inspection of the results for 8 showed its considerable
difference from 7. In particular, the IR spectrum of 8
contains a band at 3130–3370 cm−1 attributable to wNH
1
stretching vibrations. The number of signals in the H
and 13C NMR spectra indicates the absence of an
inversion centre in the molecule. The deuterochloro-
1
form H NMR spectrum of 8 consists of seven signals
at 7.49–7.31 (m), 6.2–6.8 (br s), 5.61 (s), 2.53 (s), 2.30
(s), 2.29 (s), and 2.27 ppm (s), assigned to Ph, NH2,
ꢁCH−, two SCH3 and two CH3 groups respectively.
The proton-decoupled 13C NMR spectrum showed the
presence of 16 carbon atoms in the molecule. These
data are in agreement with the non-symmetric structure
of 8. The EI mass spectrum of the latter reveals its
reasonable stability under these conditions. The most
abundant ion is that of [M]+·, the further fragmenta-
tion of which is more extensive than for 7, with in-
creased relative amounts of the fragment ions formed
(see supplementary data). Note also the presence of the
doubly-charged molecular ion [M]2+ in the spectrum.
But the peak of the latter is overlapped with the peak
due to the [Ni(C6H5COCHC(CH3)N]+ ion. From the
above observations we concluded that 8 has an open-
chain square-planar structure.
Fig. 1. ORTEP representation of the complex 7, showing 50% proba-
bility thermal ellipsoids.
Table 2
,
Selected interatomic bond distances (A) and angles (°) for 7
Distances
NiꢀN1
NiꢀN3
SꢀC1
SꢀC12
N1ꢀC4*
N1ꢀN2
N2ꢀC1
N3ꢀC2
N3ꢀC1
C2ꢀC3
1.821(2)
1.861(2)
1.764(3)
1.800(3)
1.318(4)
1.400(3)
1.287(4)
1.376(3)
1.397(4)
1.372(4)
C3ꢀC4
C4ꢀC5
C2ꢀC6
C6ꢀC7
C6ꢀC11
C7ꢀC8
C8ꢀC9
C9ꢀC10
C10ꢀC11
1.410(4)
1.501(4)
1.491(4)
1.383(4)
1.393(4)
1.385(5)
1.375(6)
1.372(5)
1.380(4)
3.1. X-ray diffraction structures of 7 and 8
Fig. 1 reveals the structure of the centrosymmetric
complex 7. Selected bond lengths and angles are given
in Table 2. As in 4 and 5, a trans-arrangement of the
ꢀSCH3 groups has been found in 7. In the coordination
of the macrocycle with the nickel atom there are four
chelate rings formed: two six-membered NiN2C3 and
two five-membered NiN3C in the sequence 5, 6, 5, 6.
The square-planar coordination of the ligand to nick-
Angles
N1ꢀNiꢀN3
N1*ꢀNiꢀN3
C1ꢀSꢀC12
C4*ꢀN1ꢀN2
C4*ꢀN1ꢀNi
N2ꢀN1ꢀNi
C1ꢀN2ꢀN1
C2ꢀN3ꢀC1
C2ꢀN3ꢀNi
C1ꢀN3ꢀNi
N2ꢀC1ꢀN3
N2ꢀC1ꢀS
84.09(10)
95.91(10)
99.6(2)
N1*ꢀC4ꢀC5
C3ꢀC4ꢀC5
C2ꢀC3ꢀC4
C3ꢀC2ꢀN3
C3ꢀC2ꢀC6
N3ꢀC2ꢀC6
C7ꢀC6ꢀC11
C7ꢀC6ꢀC2
C11ꢀC6ꢀC2
C6ꢀC7ꢀC8
C7ꢀC8ꢀC9
C8ꢀC9ꢀC10
C9ꢀC10ꢀC11
C10ꢀC11ꢀC6
119.9(3)
119.6(3)
127.8(3)
121.4(3)
116.9(2)
121.6(2)
118.6(3)
120.9(3)
120.3(3)
120.7(3)
119.6(4)
120.6(3)
119.9(4)
120.5(3)
,
el(II) occurs through four nitrogen atoms at 1.821(2) A
,
(NiꢀN1) and 1.861(2) A (NiꢀN3). The corresponding
115.4(2)
128.8(2)
115.8(2)
110.4(2)
125.4(2)
124.9(2)
109.7(2)
119.5(3)
116.2(2)
124.0(2)
120.5(3)
,
distances in 4 are at 1.835(2) and 1.882(4) A [7],
whereas they are at 1.827(19), 1.829(19) and 1.818(18),
,
1.826(19) A in two independent molecules of 5 [11]. The
non-significant differences in the NiꢀN distances can be
explained by the influence of the substituent R on the
electron density distribution over the macrocyclic
ligand.
N3ꢀC1ꢀS
N1*ꢀC4ꢀC3
The 14-membered skeleton of the macrocycle in 7 is
practically planar. The dihedral angle between the five-
and six-membered chelate rings is 4.8°. The phenyl ring
at C2 forms an angle of 111.6° with the plane through
* Symmetry transformations used to generate equivalent atoms:
−x, −y+1, −z

34
J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
,
contact at 3.180(2) A [19] was found in bis(dimethylgly-
oximato)nickel(II). In 7 the phenyl ring at C2 impedes
the stacking of the molecules. Instead, a short C10···Ni
,
contact at 3.957 A with the corresponding H···Ni sepa-
,
ration at 3.07 A has been found. Such contacts have
also been mentioned for NiL1Py (L1=dianion of the
1-phenyl-butane-1,3-dione mono-S-methylisothiosemi-
carbazone), where the carbon atom of the adjacent
,
pyridine molecule is shown to be at 3.421(3) A from the
nickel(II) atom [14]. All other intermolecular contacts
can be regarded as van der Waals interactions.
A view of the molecule of 8, along with the atom
numbering scheme, is shown in Fig. 2. Selected bond
lengths and angles are given in Table 3. A square-pla-
nar coordination of the ligand to the nickel(II) occurs
through three nitrogen and one oxygen atoms with the
corresponding bond distances (NiꢀO1=1.838(4),
Fig. 2. ORTEP representation of the complex 8, showing 50% proba-
bility thermal ellipsoids.
Table 3
,
Selected interatomic bond distances (A) and angles (°) for 8
NiꢀN1=1.825(5),
NiꢀN3=1.834(5),
NiꢀN5=
Distances
,
1.901(5) A) similar to those in some S-alkylisothiosemi-
carbazide-based analogues. The tetradentate ligand
forms three chelate rings, one being six-membered and
the two other five-membered, in the sequence 6, 5, 5.
This is a common feature for a number of complexes
with pentane-2,4-dione bis(S-alkylisothiosemicarba-
zones) [1,5,10,20]. It is worth noting the additional
pseudo metal ring formation in them via the H-bonding
between the terminal NH groups and the I− anion. In
8 the pseudo ring is formed by the N6ꢀH···O1 in-
tramolecular H-bond (Fig. 2). Finally, the complex can
be described as pseudo-macrocyclic with a 6, 5, 5, 6
sequence of chelate cycles. The same alternation of
chelate rings has previously been found in [(1,9-dihy-
droxyimino-5-ethylthio-1,2-di(a-furyl)-8-methyl-3,4,6,7-
tetraazanona - 2,4,7 - trienato(2-)N,N3,N6,N1)]nickel(II)
[21].
NiꢀN1
NiꢀO1
NiꢀN3
NiꢀN5
S1ꢀC1
S1ꢀC12
S2ꢀC15
S2ꢀC16
O1ꢀC5
N1ꢀC2
N1ꢀN2
N2ꢀC1
N3ꢀC1
N3ꢀC13
N4ꢀC13
1.825(5)
1.838(4)
1.834(5)
1.901(5)
1.763(6)
1.800(8)
1.759(4)
1.803(4)
1.305(7)
1.312(9)
1.427(7)
1.307(9)
1.365(8)
1.374(9)
1.303(8)
N4ꢀN5
N5ꢀC15
N6ꢀC15
C2ꢀC4
C2ꢀC3
C4ꢀC5
C5ꢀC6
C6ꢀC7
C6ꢀC11
C7ꢀC8
C8ꢀC9
1.437(7)
1.298(6)
1.349(7)
1.428(9)
1.514(8)
1.358(5)
1.505(9)
1.388(10)
1.399(9)
1.385(10)
1.371(11)
1.367(12)
1.382(9)
1.385(10)
C9ꢀC10
C10ꢀC11
C13ꢀC14
Angles
N1ꢀNiꢀO1
N1ꢀNiꢀN3
O1ꢀNiꢀN3
N1ꢀNiꢀN5
O1ꢀNiꢀN5
N3ꢀNiꢀN5
O1ꢀC5ꢀC6
C5ꢀC4ꢀC2
C4ꢀC2ꢀN1
95.3(2)
84.1(2)
178.6(2)
166.5(2)
98.1(2)
C2ꢀN1ꢀN2
N1ꢀN2ꢀC1
N2ꢀC1ꢀN3
C1ꢀN3ꢀC13
N3ꢀC13ꢀN4
C13ꢀN4ꢀN5
N4ꢀN5ꢀC15
N5ꢀC15ꢀN6
116.1(5)
108.8(5)
119.8(5)
132.9(5)
117.6(6)
111.1(5)
112.1(5)
120.7(4)
Here, the similarity with the other S-alkylisothiosemi-
carbazide-based ligands ends. The two S-methyliso-
thiosemicarbazide residues in the template-assembled
ligand of 8 are arranged ‘tail-to-head’. They adopt two
different conformations: Z for N1N2C1N3 and E for
N4N5C15N6 moieties. Only one of the isothiosemicar-
bazide residues is bound to the metal via two terminal
nitrogen atoms to form a chelate ring. The second
shows unusual monodentate behaviour, being coordi-
nated to the metal through the N5 atom. This is due to
the stereochemical demands of the nickel(II) template
and the ability of the ligand product formed to meet
them. Involvement of the non-terminal hydrazine nitro-
gen in coordination to the metal has been revealed for
(p-anisaldehyde thiosemicarbazonato)dimethylthallium-
(III) by X-ray diffraction methods [22]. The binding
mode of the second S-methylisothiosemicarbazide frag-
ment does not strongly influence the distribution of the
electron density over the whole ligand. The noticeable
changes are only observed in the N5ꢀC15ꢀN6 moiety,
and the reason might be the coordination of N5 to
nickel(II).
82.4(2)
115.0(5)
125.7(6)
120.2(6)
the NiN4 core. Sulfur and carbon atoms of thiomethyl
,
groups deviate out from the mean plane of 7 by 0.564 A
,
and 1.048 A respectively. In the macrocycle the inter-
atomic distances are very close to those found in its
nearest analogues 4 and 5 [7,11]. Note that the N2ꢀC1
,
distance of 1.287(4) A is shorter than N3ꢀC1 at
,
1.397(4) A; both five- and six-membered metallocycles
are characterised by p-electron delocalisation.
A number of low-spin square-planar nickel(II) com-
plexes pack in stacks with intermolecular Ni···Ni or
Ni···N contacts. According to the Ref. [18], the metal–
,
metal interactions are possible at distances up to 5.0 A.
In 4 the molecules also form stacks via Ni···Ni interac-
,
tion at 4.915 A. The shortest intermolecular Ni···Ni

J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
35
One of the possible routes to 8 is supposed to be the
intermolecular nucleophilic addition of 6 at the CꢁN
bond of the second molecule of 6 with subsequent
elimination of phenyl-methyl-ketone (Scheme 2). The
metal ion presumably exerts a degree of control over
the reaction. The essential driving force of the reaction
is supposedly the match between the steric and elec-
tronic requirements of the matrix and the ability of the
final ligand product to meet them.
Note that the E-conformation has been documented
for the S-methylisothiosemicarbazidium nitrate [23] and
some metal-free tetradentate isothiosemicarbazide-
based ligand products [24,25].
The skeleton of the molecule of 8 is almost planar,
the dihedral angle between the five-membered rings
being at only 0.9°. The corresponding angle between
the six- and five-membered rings is 2.5°. The phenyl
ring forms an angle of 22.5° with the mean plane of the
six-membered ring NiN2C3.
3.2. Electrochemical beha6iour
The above-mentioned intramolecular H-bond is char-
acterised by the following parameters: N6···O1=
The electrochemical behaviour of the trans-com-
plexes 4, 7 and the open-chain product 8 were studied
by cyclic voltammetry. The cyclic voltammogram of 4
displays two reversible one-electron oxidation transfer
waves at 0.217 and 0.821 V versus the ferrocenium/fer-
rocene couple (Fc+/Fc). The cyclic voltammogram of 7
is shown in Fig. 3. This displays three quasi-reversible
one-electron transfer waves at 0.746, 1.332 and
−1.539 V, and one irreversible cathodic peak at
−1.974 V versus Ag+/Ag. Complex 8 shows one quasi-
reversible, one irreversible anodic, and one irreversible
cathodic peak at 0.814, 1.367 and −1.932 V versus
Ag+/Ag. Conversions from the Ag+/Ag scale to Fc+/
Fc can easily be performed by adding +0.454 V and
+0.493 V respectively to the values given above for 7
and 8. We conclude that the two consecutive one-elec-
tron oxidation steps for 4, 7 and 8 are metal-centred,
and can be represented as shown in Eq. (1):
,
2.751(7), H···O1=1.96 A, the angle at the H atom
being 146°. The second hydrogen of the ꢀNH2 group
joins the symmetry-related molecule (2−x, 0.5+y,
1−z) by weak H-bonding. The corresponding parame-
ters are as follows: N6···N4*=3.163(8), N4*···H=
,
2.47 A, the angle at H being 135°. We also mention the
intermolecular contact Ni···S1 (x, y, −1+z)=
3.982(2) A. All other contacts correspond to van der
,
Waals interactions.
Ni2+ −e−=Ni3+
Ni3+ −e−=Ni4+
(1)
The peak at −1.539 V for 7 we conclude is a one-elec-
tron metal-centred reduction, as shown in Eq. (2):
Ni2+ +e−=Ni+
(2)
The corresponding irreversible cathodic peaks at
−1.974 and −1.932 V for 7 and 8 are supposed to be
ligand-centred. The higher electrochemical flexibility of
7 compared with 8 is due to the macrocyclic nature of
the ligand in 7.
Scheme 2.
4. Conclusions
Nickel(II)-controlled self-condensation of 6 affords
two different products, the macrocyclic complex 7 and
the open-chain species 8. Complex 7 is presumably
formed by bimolecular nickel(II)-assisted self-condensa-
tion of 6, whereas 8 by intermolecular nucleophilic
addition of 6 at the CꢁN bond of the second molecule
of 6 with subsequent elimination of phenyl-methyl-
ketone.
Fig. 3. Cyclic voltammogram of
7
in CH2Cl2 (0.10 M
[N(C4H9)4][PF6]; platinum working electrode; scan rate 100 mV s−1).

36
J.I. Gradinaru et al. / Inorganica Chimica Acta 313 (2001) 30–36
[7] Yu.A. Simonov, P.N. Bourosh, V.B. Arion, M.D. Mazus, N.V.
5. Supplementary material
Gerbeleu, Kristallografiya 33 (1988) 1535.
[8] N.V. Gerbeleu, J.I. Gradinaru, V.B. Arion, K.M. Indrichan, Zh.
Neorg. Khim. 36 (1991) 100.
[9] A.A. Dvorkin, P.N. Bourosh, Yu.A. Simonov, V.B. Arion, J.I.
Gradinaru, N.V. Gerbeleu, Polyhedron 14 (1995) 571.
[10] V.B.Arion, Ph.D. Thesis, Institute of Physical Chemistry of the
Academy of Sciences of Ukraine, Kiev, 1985.
[11] N.V. Gerbeleu, Yu.A. Simonov, V.B. Arion, J.I. Gradinaru,
V.E. Zavodnik, K.M. Indrichan, T.I. Malinovskii, Zh. Neorg.
Khim. 36 (1991) 96; Russ. J. Inorg. Chem. 36 (1991) 52.
[12] V.M. Leovac, L.S. Jovanovic, V.J. Cesljevic, L.J. Bjelica, V.B.
Arion, N.V. Gerbeleu, Polyhedron 13 (1994) 3005.
[13] N. Galesic, V.M. Leovac, Acta Crystallogr., Sect. C 45 (1989)
745.
[14] G.A. Bogdanovici, A. Spasojevici-de-Bire, V.M. Leovac, V.I.
Cesljevic, Acta Crystallogr., Sect. C 55 (1999) 1656.
[15] M. Freund, Th. Paradies, Ber. Dtsch. Chem. Ges. 34 (1901)
3110.
Complete tables of atomic coordinates, anisotropic
thermal parameters, bond lengths and angles may be
obtained from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1 EZ, UK, on
quoting the depository numbers CCDC 143057 (for 7),
143058 (for 8), the names of the authors and the
journal citation. Structure factors of 7 and 8, Table S1
showing the relative intensities of the identified ions in
the EI mass spectra of 7 and 8, and Table S2 with the
1H NMR data of trans-hexaazamacrocyclic complexes
4, 5 and 7 are available from the authors on request.
Acknowledgements
[16] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[17] G.M. Sheldrick, SHELXL-93, University Go¨ttingen, Germany,
1993.
[18] B.M. Hoffman, J. Martinsen, L.J. Pace, L.A. Ibers, in: J.S.
Miller (Ed.), Extended Linear Chain Compounds, vol. 3,
Plenum, New York, 1983, p. 561.
Mr. Janssen (MPI fu¨r Kohlenforschung, Mu¨lheim an
der Ruhr, Germany) is thanked for carrying out the
cyclic voltammetry measurements.
[19] L.E. Godycki, R.E. Rundle, Acta Crystallogr. 6 (1953) 487.
[20] Yu.A. Simonov, J.I. Gradinaru, A.A. Dvorkin, P.N. Bourosh,
N.V. Gerbeleu, Koord. Khim. 21 (1995) 214.
[21] Yu.A. Simonov, N.V. Gerbeleu, L.A. Nemchinova, S.G. Baka,
A.N. Sobolev, T.I. Malinovskii, Zh. Neorg. Khim. 36 (1991)
2520; Russ. J. Inorg. Chem. 36 (1991) 1416.
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