S. Eswari et al.
Polyhedron 206 (2021) 115330
3. Results and discussion
the Cd2+ and CS2 moiety of bridging dithiocarbamate ligands, which
adopts twisted chair confirmation (motif-II, Fig. 1(b)) [1,14].
Dimeric-1 and trimeric-1 structures crystallize in triclinic system
3.1. Synthesis and spectral studies
¯
with space group Pı. But unlike the dimeric structure determined for 1,
The ligand was generated in situ by treatment of a methanol solution
of N,N-di(4-fluorobenzyl)amine with carbon disulfide. Complexes 1 and
2 were prepared in good yields (Scheme-1) by treating one equivalent of
metal salt with two equivalents of ligand. Both complexes are air and
moisture stable. IR, UV–vis and NMR spectra of complexes are displayed
in Figure S1-S8. The IR spectra of both complexes exhibit bands around
1505 cmꢀ 1 and 975 cmꢀ 1 due to vC-N (thioureide) and vC-S frequencies
which are characteristic of dithiocarbamate ligand [43,44]. The 1H and
13C NMR spectra of complexes 1 and 2 show resonance signals charac-
teristic of the ligand functionalities (see ESI).
trimeric-1 is an unusual centrosymmetric trinuclear molecule in which
six N,N-di(4-fluorobenzyl)dithiocarbamate ligands are coordinated to
three Cd2+ ions. The central Cd2+ ion (Cd1) in octahedral environment
which is flanked by another two square pyramidal cadmium centers
(Cd2 and Cd2i). The equatorial position of octahedral Cd2+ are occupied
by S5, S6, S5i, S6i atoms from two
μ
2κ2 – tridentate dithiocarbamate
ligands. The axial positions are occupied by two S atoms (S2 and S2i)
from two bridging dithiocarbamate ligands, one from each square py-
ramidal cadmium dithiocarbamate moiety. These two dithiocarbamate
ligands are primarily linked to Cd2 and Cd2i. The distortion of the
[CdS6] octahedral geometry is due to the bite angles of the dithiocar-
bamate ligands i.e. 67.53(2) to 69.53(3)◦. The coordination environ-
ments of Cd2 and Cd2i are similar. The S1, S2, S3 and S4 atoms occupy
the equatorial positions of square pyramidal Cd2. The axial position is
occupied by a sulfur atom (S5) from the μ2, κ2-tridentate dithiocarba-
mate ligand of central Cd1 octahedral species. The coordination geom-
3.2. Structural analysis
ORTEP of dimeric-1, trimeric-1 and 2 are shown in Fig. 2. Selected
bond lengths and bond angles are given in Table-2. Cadmium atom in
dimeric-1 is coordinated by four sulfur atoms from a symmetrically
chelating S3, S4 (Cd-S3 = 2.5990(5) Å and Cd-S4 = 2.5660(5) Å)
etry around Cd2+ in dimeric-1 (τ5 = 0.33) and Cd2 in trimeric-1 (τ5
=
0.34) is distorted square pyramid as seen in the τ5 value around 0.30
compared to zero and one for ideal square pyramidal and trigonal
bipyramidal geometries, respectively [45].
dithiocarbamate ligand and asymmetrically
μ
2κ2-tridentate S1, S2 (Cd-
S1 = 2.5711(5) Å and Cd-S2 = 2.6120(5) Å) dithiocarbamate ligand. A
fifth position is occupied by S2i (symmetry: i = ꢀ x,ꢀ y,ꢀ z) atom derived
from centrosymmtrically related molecule (Cd-S2i = 2.7904 Å) leading
to the formation of dimeric structure. These distances are similar to
those found in other dimeric Cd(II) dithiocarbamate complexes [6,7].
The molecule consists of an eight membered ring [(CdSCS)2] defined by
Single crystal X-ray structural analysis shows that complex 2 exists as
monomer (Fig. 2(c)). Hg atom is tetracoordinated with four sulfur atoms
from two N,N-di(4-flurobenzyl)dithiocarbamate ligands. The coordina-
tion sphere of mercury is approximated as distorted tetrahedral geom-
etry with two short (2.4031 Å) and two long (2.7880 Å) mercury – sulfur
bonds. The anisobidentate coordination form chelate rings HgS2C. The
two, four membered chetate rings are planar. The distortion index (τ4
and τ′4 values) is 0 and 1 for perfect square planar and tetrahedral,
respectively. For complex 2, the τ4 = 0.53 and τ′4 = 0.65 reveal that the
coordination geometry around mercury is a distorted tetrahedral ge-
ometry [46]. As far as the angles around the mercury are concerned, the
value for the bite angle of dithiocarbamate ligand is 69.44(2)◦ which is
mainly responsible for the distortion from tetrahedral geometry. The
bond parameters and geometry observed in this complex are similar to
those reported for similar monomeric mercury(II) bis(dithiocarbamate)
complexes [14].
(a)
Tiekink and Zukerman-Scheptor described the important role of
…
–
C
H
π
(chelate, MS2C) interaction in metal dithiocarbamates that
allowed formation of 1D, 2D and 3D supramolecular networks [47]. In
the case of dimeric-1, the H24A proton on methylene C24 carbon
bifurcate forming hydrogen bonds between π- chelating (C16, S3, Cd1,
S4) and S4 atom (Fig. S9) which leads to the formation of 1D chain. The
molecular association in the crystal structures of dimeric-1, trimeric-1
…
–
and 2 is stabilized via C H S interactions (Figs. S10-S12) In the case of
…
–
dimeric-1 and 2, these C H S interactions lead to form ladder like
structure and R12(6) topological motif, respectively. In these structures,
the fluorine atoms participate in hydrogen bonds and these interactions
dominate the crystal packing of the compounds [8,48]. Fluorine atoms
are also involved in bifurcated and trifurcated hydrogen bonds (Fig. S13-
(b)
…
–
H
S15). In addition, intermolecular and intramolecular C
π
in-
teractions observed in dimeric-1 and trimeric-1, respectively (Fig. S16
and S17; Tables S1-S3).
Single crystal X-ray structure of bis(N,N-di(4-fluorobenzyl)dithio-
carbamato-S,S′)zinc(II) was reported [42]. This complex is a centro-
symmetric dimer. Complex 1 exists as dimer and trimer. Complex 2 is a
monomer. In same solvent mixture (chloroform-acetonitrile), bis(N,N-di
(4-fluorobenzyl)dithiocarbamato-S,S′)zinc(II), and 2 crystallizes as
dimer and monomer, respectively. Dimeric-1 (chloroform-acetonitrile)
and trimeric-1 (benzene-acetonitrile) were obtained using different
solvents for crystallization. This study indicates that solvent used for
crystallization and the central metal ions affect the solid state structure
of group-12 dithiocarbamate complexes.
(c)
Fig. 2. ORTEP diagrams of (a) dimeric-1, (b) trimeric-1 and (c) 2.
4
Ciattini, Samuele
