Adducts of diethyldithiocarbamate complexes of zinc(II) and copper(II) with piperidine [M(Pip)(Edtc)2] and their solvated forms [M(Pip)(Edtc)2] · L (L = C6H6, C5H5N, C4H9NO): Synthesis, EPR and solid-state (13C, 15N) CP/MAS NMR studies

Article abstract of DOI:10.1023/A:1009590026768

Crystal adducts of diethyldithiocarbamate complexes of zinc(II) and copper(II) with piperidine (Pip) were synthesized, and their solvated forms with the outer-sphere molecules of benzene, pyridine (Py), and morpholine (Mf) were obtained. Adducts with composition [M(Pip)(Edtc)₂] · L (L = Py, Mf) were shown to be able, in principle, to give solvated isomers [M(L)(Edtc)₂] · Pip with the Pip molecule arranged in the outer sphere. The composition, structure, and properties of the obtained adducts were studied by EPR, high-resolution solid-state ¹³C, ¹⁵N NMR spectroscopy. Solvation of all three adducts with Pip, Mf, and Py was found to result in a substantial increase in the contribution of the trigonal-bipyramidal component to the geometry of a copper coordination pentahedron. In addition, for adducts with Mf and Py, a structural unification of two isomeric forms was observed at the molecular level to yield a qualitatively new (rather than intermediate) state. It was shown that in all solvated forms of the copper(II) adducts, the metal polyhedron is mainly a trigonal bipyramid, while the square-pyramidal contribution is insignificant. Results of (¹³C, ¹⁵N) NMR studies revealed a structural inequivalence of the Edtc^- ligands in the zinc adducts under investigation.

Full text of DOI:10.1023/A:1009590026768

Russian Journal of Coordination Chemistry, Vol. 27, No. 3, 2001, pp. 158–166. Translated from Koordinatsionnaya Khimiya, Vol. 27, No. 3, 2001, pp. 174–183.
Original Russian Text Copyright © 2001 by Ivanov, Forsling, Antzutkin, Novikova.
Adducts of Diethyldithiocarbamate Complexes of Zinc(II) and
Copper(II) with Piperidine [M(Pip)(Edtc)2] and Their Solvated
Forms [M(Pip)(Edtc)2] · L (L = C6H6, C5H5N, C4H9NO):
Synthesis, EPR and Solid-State (13C, 15N) CP/MAS NMR Studies
A. V. Ivanov, W. Forsling, O. N. Antzutkin, and E. V. Novikova
Amur Institute of Integrated Research, Far East Division, Russian Academy of Sciences,
Relochnyi per. 1, Blagoveshchensk, 675000 Russia
Luleå University of Technology, S-971 87, Luleå, Sweden
Blagoveshchensk State Pedagogical University, Blagoveshchensk, 675000 Russia
Received June 15, 2000
Abstract—Crystal adducts of diethyldithiocarbamate complexes of zinc(II) and copper(II) with piperidine
(Pip) were synthesized, and their solvated forms with the outer-sphere molecules of benzene, pyridine (Py), and
morpholine (Mf) were obtained. Adducts with composition [M(Pip)(Edtc)2] · L (L = Py, Mf) were shown to be
able, in principle, to give solvated isomers [M(L)(Edtc)2] · Pip with the Pip molecule arranged in the outer
sphere. The composition, structure, and properties of the obtained adducts were studied by EPR, high-resolu-
tion solid-state 13C, 15N NMR spectroscopy. Solvation of all three adducts with Pip, Mf, and Py was found to
result in a substantial increase in the contribution of the trigonal–bipyramidal component to the geometry of a
copper coordination pentahedron. In addition, for adducts with Mf and Py, a structural unification of two iso-
meric forms was observed at the molecular level to yield a qualitatively new (rather than intermediate) state. It
was shown that in all solvated forms of the copper(II) adducts, the metal polyhedron is mainly a trigonal bipyr-
amid, while the square–pyramidal contribution is insignificant. Results of (13C, 15N) NMR studies revealed a
structural inequivalence of the Edtc– ligands in the zinc adducts under investigation.
According to data of three independent investiga- nal–bipyramidal (TB) contribution to the geometry of
tion methods (EPR, high-resolution solid-state (13C,
15N) NMR, and X-ray diffraction) carried out in [1, 2],
it was shown that crystal adducts of dialkyldithiocar-
bamate complexes of zinc(II) and copper(II) with pyri-
dine (Py) and morpholine (Mf) occur as two conforma-
tional isomers that differ in the spatial orientation of
their coordinated heterocycles. Studies of their interac-
tion with organic molecules of different nature (ben-
zene [3], Py [4], methylene chloride and chloroform
[5], dichloroethane [6], and carbon tetrachloride [7, 8])
made it possible to establish that even with an
unchanged state of aggregation, the solvation of the
above crystal adducts results in the formation of
ordered molecular channels in their lattice, the chan-
nels being occupied with the solvated molecules, and
the structure thus being rearranged into a clathrate.
However, we believe that the deep structural rearrange-
ment of the adducts observed simultaneously at the
molecular level [3–8] is much more essential. This rear-
rangement involves structural unification of two con-
formers of initial nonsolvated adducts and transition
into a qualitatively new (not intermediate) structural
state. This state is distinguished by (a) changing M–N
distance, (b) spatial reorientation of the coordinated
the metal coordination polyhedron.
Previously [9], we synthesized and characterized by
EPR and thermographic methods isotope-substituted
(63Cu, 65Cu) samples of bis(diethyldithiocarbam-
ato)piperidinecopper(II) [63/65Cu(Pip)(Edtc)2] magneti-
cally diluted with zinc.We established that unlike the
respective adducts with Py [1], Mf [2], and trimeth-
ylphosphine [10], which at the molecular level occur in
the form of two or even three isomers, an adduct with
piperidine exists in one molecular form.
The aim of this work was to synthesize adducts of
diethyldithiocarbamate complexes of zinc(II) and cop-
per(II) with piperidine and their solvated forms, includ-
ing outer-sphere cyclic molecules of the donor bases
with different chemical nature (Py and Mf) and ben-
zene, and to study their composition, structure, and
spectra by using EPR and high-resolution solid-state
(13C, 15N) NMR (with a natural abundance of isotopes).
EXPERIMENTAL
Bis(diethyldithiocarbamato)piperidinezinc(II) [Zn-
(Pip)(Edtc)2] (I) was synthesized using the following
heterocycle, and (c) a significant increase in the trigo- two methodological procedures:
1070-3284/01/2703-0158$25.00 © 2001 åÄIä “Nauka /Interperiodica”

ADDUCTS OF DIETHYLDITHIOCARBAMATE COMPLEXES
159
(1) by dissolving dimeric diethyldithiocarbama- mental spectra, we varied the g-factors, HSF constants,
tozinc(II) complex [Zn2(Edtc)4] in toluene containing resonance line widths, and percentage of the Lorentz
piperidine in an amount exceeding the stoichiometric and Gauss contribution to the line shape.
amount by ~10% and through further crystallization of
Zinc compounds I–IV were studied using high-res-
the adduct at room temperature (by analogy with pro-
olution solid-state 13C (I = 1/2, µ = 0.7021) and 15N (I =
cedures described in [11–13]);
(2) by quantitative absorption of piperidine vapors
from the gas phase with powdered [Zn2(Edtc)4].
1/2, µ = –0.2831) pulse NMR spectroscopy with a nat-
ural abundance of isotopes. 13C and 15N NMR spectra
were registered at room temperature on a CMX-360
radiospectrometer (Chemagnetics Infinity, USA) with
working frequencies of 90.52 and 36.48 MHz, respec-
tively, and a superconducting magnet (B0 = 8.46 T) and
Solvates having composition [Zn(Pip)(Edtc)2] · L
with L = C6H6, Py, Mf (complexes II, III, and IV,
respectively) were obtained via careful wetting of the
crystal adduct I with the respective solvents without
changing its state of aggregation. The degree of conver-
sion of I into the solvated forms and stoichiometric
ratios Zn : Pip : L were determined by jointly using data
of 13C NMR and gravimetry.
Compound II was also produced by crystallization
from a solution, as in the case of I. However, this time,
benzene was used instead of toluene. Crystals of I and
II were separated from the mother liquor, washed with
a small amount of the respective solvent, and dried in
air until they became loose. The soichiometric ratios of
M : Pip and M : Pip : C6H6 were determined in them
from the loss of sample mass after the full desorption of
piperidine and benzene (upon careful heating). To
improve the accuracy of determination, we used sam-
ples with masses less than 1 g. Data of 13C, 15N NMR
reveal the spectral identity of samples I and II obtained
by different methods.
In order to increase the amount of information on
EPR spectra, bis(diethyldithiocarbamato)piperidi-
necopper(II) [Cu(Pip)(Edtc)2] (V) and its solvated
forms with ë6ç6, Py, and Mf (complexes VI, VII, and
VIII, respectively) were obtained as isotope-substi-
tuted compounds magnetically diluted with zinc (Cu :
Zn = 1 : 1000) by analogy with I–IV. Copper (II) salts
with a concentration of 63Cu 99.3(1) at. % and of 65Cu
99.2(1) at. % were used. The ratios of Cu : Pip : L were
determined in the same way as was done for zinc com-
plexes, the only difference being that the degree of
transformation of crystals V into solvated forms was
estimated from EPR spectra.
Fourier transformation. 13C spectra were obtained using
1
the proton cross-polarization effect [14], the H–13C
interaction time being 2 ms. Dipole–dipole 13C–1H
interactions were suppressed by applying the proton
decoupling effect with an rf field corresponding to the
proton resonance frequency and ωH1 /2π = 54.2 kHz
[14]. The duration of the π/2 proton pulses was 5.0 µs.
Polycrystalline samples of the complexes under study
weighing ~350 mg were pressed into standard rotors
made from zirconium dioxide with a diameter of
7.5 mm. Due to the low natural abundance of the 13C
isotope (1.108 at. %), a signal acquisition procedure
was used with the number of scans ranging from 1024
to 2048 and a scan time of 2 s. In order to average the
anisotropy of chemical shift δ for investigated nuclei in
the course of signal acquisition, the rotors with the
samples were rotated by a stream of dry air at a magic
angle (α = 54.75°) to the magnetic field direction. The
spinning frequencies were 4400, 5200, and 5500 (2) rps,
respectively. The 13C isotropic chemical shifts were
measured relative to a low-field component of an exter-
nal standard, i.e., crystal adamantane (δ = 38.56 ppm
relative to tetramethylsilane [15]). The chemical shifts
were corrected for drift of the magnetic field intensity
during the experiments, the frequency equivalent of the
drift for the 13C nuclei being 0.051 Hz/h.
15N NMR spectra were registered using proton
1
cross-polarization with an H–15N interaction time
equal to 1.2 ms. Proton frequency ωH1 /2π = 58.3 kHz
was used for the purpose of suppression of the 15N–1H
dipole–dipole interactions in decoupling. The duration
of the π/2 pulses was 5.0 µs. The natural abundance of
the 15N isotope amounts to 0.365 at. %; therefore, 2500
to 18500 scans were used in the spectra acquisition, the
scan time being 2 s. The spinning rate was 4400, 5500,
and 6000(2) rps. The 15N isotropic chemical shifts were
measured relative to the crystal NH4Cl used as an exter-
nal standard (0 ppm, –341 ppm in an absolute scale [16,
17]). Drift of the magnetic field intensity for the 15N
nuclei in the frequency equivalent was 0.016 Hz/h.
All of the obtained compounds were kept in sealed
tubes. The reagents used in the synthesis were made by
NaEdtc · 3H2O (Fluka), piperidine (BDH Chemicals
Ltd), morpholine, and pyridine (Aldrich).
EPR spectra of magnetically diluted compounds V–
VIII were recorded at room temperature on a 70-02
XD/1 (MP “SZ”, Minsk) radiospectrometer at a work-
ing frequency of ~9.5 GHz. Frequency measurement
was performed using a ChZ-46 frequency meter. g-Fac-
tors were calculated relative to DPPH. The accuracy of
determination of the g-factor was ±0.002%, while that
of the hiperfine structure (HFS) constants was ±2%.
EPR spectra were simulated within the framework of a
second approximation of the perturbation theory using
WIN-EPR SimFonia software, version 1.2 (Bruker). In
RESULTS AND DISCUSSION
EPR Spectra. Experimental EPR spectra of com-
the course of approximating model spectra to experi- pounds V–VIII exhibit a number of common features
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27 No. 3
2001

160
IVANOV et al.
DPPH
DPPH
H
114 Oe
H
114 Oe
‡
b
a
b
Fig. 2. EPR spectra of solvate isomers of
63
63
(a) [ Cu(Pip)(Edtc) ] · Mf and (b) [ Cu(Mf)(Edtc) ] · Pip
2
2
magnetically diluted with zinc(II).
c
assumption of the third orientation in the high-field
region. However, of the four HFS components with the
orientation being discussed, only one component can
be observed in reality, the remaining three components
having been overlapped by AA peaks and HFS compo-
nents with intermediate orientation. Therefore, EPR
parameters of this orientation were refined on the basis
of the results of a computer simulation in two stages.
First, model EPR spectra were properly constructed
(Fig. 1b). Then, a double differentiation of the experi-
mental spectra was made to result in a basic reduction
of the HFS components and thus in an increase in the
resolution level. At the second stage, the third deriva-
tives of the model spectra (Fig. 1d) were approximated
as closely as possible to the experimental spectra
(Fig. 1c). The EPR parameters produced from the
results of the best approximation are listed in Table 1.
It is evident that the solvated adducts
[Cu(Pip)(Edtc)2] · B (B = Py, Mf) containing two mole-
cules of the donor bases with different chemical natures
(Pip–Mf and Pip–Py) can have isomeric forms. These
forms will differ in the manner of distribution of Pip
and B (Mf, Py) molecules in the inner and outer coor-
dination sphere and, hence, can be regarded as solvate
isomers.
d
Fig. 1. (a, c) Experimental and (b, d) theoretical EPR spec-
tra of solvated adduct [ Cu(Pip)(Edtc) ] · Py magnetically
diluted with zinc in the form of (a, b) the first and (c, d) the
third derivatives (T = 295 K).
63
2
(Figs. 1, 2). Thus, their high-field regions contain two
high-intensity peaks due to additional absorption (AA)
[18]. In this case, the close intensities of the HFS com-
ponents in two quartets of the nonequidistant lines due
to the interaction of an unpaired electron with nuclei of
63Cu or 65Cu (I = 3/2) are evidence of the three-axial
anisotropy of the EPR parameters. In addition, simula-
tion of a high-field AA peak having the shape of the
adsorption line can only be performed under the
In so far as piperidine (pKa = 11.25) is a donor base
1
stronger than Mf (8.33) and Py (5.20) [19], it was
1
The basicity of nondissociating organic bases is characterized by
+
the value of pK (K is a dissociation constant for acid [BH] con-
a
a
jugated with base B).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27 No. 3
2001

ADDUCTS OF DIETHYLDITHIOCARBAMATE COMPLEXES
Table 1. EPR* parameters of compounds V–X
161
A1Cu , Oe
No.
Complex
g1
g2
A2Cu , Oe
g3
A3Cu , Oe
V
[Cu(Pip)(Edtc)2]
2.120
2.117
2.118
2.122
2.121
2.120
2.120
2.121
2.118
2.120
125/134
117/125
123/132
119/128
135/145
133/143
119/127
135/145
137/147
120/128
2.061
2.075
2.064
2.065
2.038
2.038
2.068
2.039
2.039
2.069
52/56
64/68
55/59
54/58
21/23
21/23
59/63
32/34
32/34
61/65
2.016
2.017
2.016
2.015
2.038
2.038
2.015
2.019
2.019
2.015
19/20
21/23
18/19
13/14
21/23
21/23
13/14
5.0/5.5
5.0/5.5
13/14
VI
VII
[Cu(Pip)(Edtc)2] · C6H6
[Cu(Pip)(Edtc)2] · Py
VIII [Cu(Pip)(Edtc)2] · Mf
[Cu(Mf)(Edtc)2]** [2]
X
[Cu(Mf)(Edtc)2] · Pip
[Cu(Py)(Edtc)2]** [1]
IX
[Cu(Py)(Edtc)2] · Pip
63
65
* HFS constants are given for Cu and Cu isotopes.
** Data for two isomeric forms of adducts are given.
interesting to study, in principle, the possibility of syn-
Qualitatively, the predominate transition from the
thesizing solvated adducts [Cu(êÛ)(Edtc)2] · Pip (IX) SP to the TB configuration is accompanied by the
and [Cu(Mf)(Edtc)2] (X). In this case, despite their appearance in the experimental EPR spectra of a third
strong basic nature, Pip molecules will be located in the (high-field) orientation with g3 ≈ 2.00. In this case, a
outer coordination sphere, while the molecules of N-
organic less strong bases will be coordinated to the cen-
tral atom. Solvated forms of the adducts under discus-
sion were obtained by quantitative absorption of Pip
with crystals of [Cu(B)(Edtc)2], which were carefully
wetted with piperidine (taken in stoichiometric ratio)
without changing the state of aggregation. Unfortu-
nately, the attempt to produce adducts IX and X by tra-
ditional methods of crystallization from the solutions
failed.
gradual increase in the TB contribution to the geometry
of the copper coordination polyhedron leads to an anti-
bate change in A1Cu and AC2 u , such that the constants of
the hiperfine structures of low-field orientation
decrease, while those of an intermediate orientation
increase (i.e., they become close in absolute values).
With this point in view, let us consider the possibility of
applying the difference ∆ = AC1 u – A2Cu in practice for
the purpose of estimating the TB contribution to the
geometry of the copper polyhedron with CN = 5.
EPR spectra of solvated forms [Cu(Pip)(Edtc)2] · Mf
(VIII) and [Cu(Mf)(Edtc)2] · Pip (X) can be compared
in Fig. 2. Despite the similar shapes of their spectra and
close values of their EPR parameters, these compounds
are spectrally nonidentical (Table 1). The individual
spectral pattern of compound X (Fig. 2b) does not
reveal any redistribution of the base molecules between
the inner and outer coordination spheres, since not even
a trace of adduct VIII can be detected in the sample
composition.
Experimental EPR spectra qualitatively similar to
those discussed above were previously observed by us
in [3, 4], for example, for magnetically diluted forms of
[Cu(Py)(Edtc)2] solvated with benzene and pyridine
(Table 1). Analysis of X-ray diffraction data for the
above coordination compounds, performed as
described in [20], made it possible to establish the pre-
dominate (above 80%) contribution of the TB compo-
nent to the geometry of the metal coordination polyhe-
dron. In the case of an initial nonsolvated adduct whose
crystals have two isomeric forms (α and β), this contri-
bution only slightly exceeds 50% [1]. It is noteworthy
that the TB contribution for two isomeric forms of
[Cu(Mf)(Edtc)2] calculated in the same manner turned
out to be 7.5% and 22.7% [2]. Solvation of
[Cu(Py)(Edtc)2] with molecules of different chlorohy-
drocarbons, whose sizes are smaller than those of the
cyclic benzene or Py molecules, is also followed by dis-
tortion of the copper polyhedron geometry toward TB,
but to a significantly lesser extent (64–71%) [5–8].
In isotropic liquids, due to the coordination unsatur-
ation, copper dithiocarbamate complexes form adducts
having a square-pyramidal (SP) structure (C4v symme-
try) with N-donor organic bases. In these adducts, mol-
ecules B have an axial coordination and the copper(II)
unpaired electron is mainly localized on 3dx2
AO. In
– y2
our case, the manifestation of rhombic nature in exper-
imental EPR spectra of solvated and nonsolvated forms
of crystal adducts suggests that the copper coordination
polyhedron is significantly distorted toward trigonal
bipyramid (D3h symmetry) [1–9] when the ground state
of the copper unpaired electron is considered to be the
Data in Table 2 indicate that for eight solvated and
nonsolvated molecular forms of magnetically diluted
adduct [Cu(Py)(Edtc)2], with a gradual increase in TB
result of a combination of 3dx2
and 3dz2 -Äé.
– y2
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27
No. 3
2001

162
IVANOV et al.
Table 2. Trigonal–bipyramidal contribution to the geometry
of Cu(II) coordination polyhedron in adduct [Cu(Py)(Edtc)2]
and its solvated forms [Cu(Py)(Edtc)2] · L
and VIII is ~80%, and that for the remaining adducts
(IX, X, and VI) significantly exceeds 85%.
Thus, data of EPR spectroscopy make it possible to
state that, in a general case, solvation of all three crystal
adducts with Pip, Mf, and Py results in an increase in
the TB contribution to the copper pentahedron geome-
try. However, solvation of [Cu(Mf)(Edtc)2] and
[Cu(Py)(Edtc)2] is characterized by one more essential
feature: in the cases under consideration, structural uni-
fication of two isomeric forms of the adducts is
observed at the molecular level, as well as a transition
to a qualitatively new (but not intermediate) structural
state.
High-resolution solid-state 13C and 15N NMR
spectra. The patterns of experimental EPR spectra of
copper(II) adducts depend both on the composition and
structure of the nearest environment of the central
atom. Therefore, it was reasonable to study the respec-
tive nonparamagnetic zinc mixed-ligand compounds
using solid-state multinuclear NMR spectroscopy,
since in this case, the structural state of the ligands can
be characterized as a whole.
Complex
TB, %
∆, Oe
[β-Cu(Py)(Edtc)2]
55.0
55.6
64.0
67.0
67.8
71.0
82.1
84.6
105
103
86
[α-Cu(Py)(Edtc)2]
[Cu(Py)(Edtc)2] · 2CCl4
[Cu(Py)(Edtc)2] · CHCl3
[Cu(Py)(Edtc)2] · C2H4Cl2
[Cu(Py)(Edtc)2] · CH2Cl2
[Cu(Py)(Edtc)2] · C6H6
[Cu(Py)(Edtc)2] · Py
84
83
80
62
64
contribution to the geometry of the copper coordination
pentahedron, parameter ∆ shows a tendency to decrease
monotonically.
The adducts of copper(II) obtained in this work can
be arranged in the following order of increasing TB
contribution: [Cu(Pip)(Edtc)2] (V), [Cu(Pip)(Edtc)2] ·
13C NMR spectra of zinc adducts I–IV (Fig. 3)
exhibit three groups of signals due to diethyldithiocar-
bamate ligands, coordinated Pip molecules, and to
outer-sphere solvate molecules of benzene, Py, and Mf
(Table 3). The authors of [21, 24] assigned the reso-
nances of the 13C atoms of the Edtc– ligands to the
methyl, methylene, and dithiocarbamate groups. The
Py
(VII),
[Cu(Pip)(Edtc)2]
·
Mf
(VIII),
[Cu(Mf)(Edtc)2] · Pip (X), [Cu(Py)(Edtc)2] · Pip (IX),
[Cu(Pip)(Edtc)2] · C6H6 (VI). In this series, parameter
∆ has the following values: 73, 68, 65, 60, 55, and 53 Oe,
respectively. This allows us to suggest that the TB con-
tribution for compound V equals ~75%, that for VII NC(S)S– groups produce singlet (compounds III, IV)
Table 3. Chemical shifts (ppm) of 13C and 15N NMR signals for adducts [Zn(Pip)(Edtc)2] · L (relative to TMS and NH4Cl)
Pip,
Py
Edtc
Edtc
Pip, Py
Mf
Mf C6H6
Compound
=NCS2–
205.9
204.4(37)* 48.6
–CH2– –CH3 =N–
o-
m-
p- –N= =N–CH2– –O–CH2– –N= =CH–
[Zn(Pip)(Edtc)2]
49.7
13.3 133.7 47.3 28.8 25.2
12.7 129.1
7.0
[Zn(Pip)(Edtc)2] · C6H6 203.4 (46)* 49.3
202.6
12.5 135.8 46.9 28.2 25.2
12.0 132.6
7.5
128.7
11.0
[Zn(Pip)(Edtc)2] · Py
202.8 (44)* 48.8
13.1 135.0 46.8 27.1 25.8 –3.7
12.6 132.1 150.3 124.3 136.8 271.5
12.0
10.5
[Zn(Pip)(Edtc)2] · Mf 203.4
49.0
12.6 135.4 47.3 28.6 26.3 –4.9 49.0
68.8 –1.0
67.6
12.2 131.0
11.6
11.0
NaEdtc · 3H2O [21]
C6H6, Pip [22]
206.5 (51)* 48.6 (71)* 13.2 139.1
47.9 27.8 25.9
128.5
Py [24], Mf [23]
149.8 123.6 135.7 258.0 46.7
68.1
13 14
* Asymmetric C– N doublets (Hz).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27 No. 3
2001

ADDUCTS OF DIETHYLDITHIOCARBAMATE COMPLEXES
163
**
*
** *
a
*
*
*
*
b
*
* *
*
*** * *
**
*
c
*
*
*
d
200
150
100
δ, ppm
50
0
13
Fig. 3. C NMR spectra (T = 295 K) of (a) adduct [Zn(Pip)(Edtc) ] and its solvated forms: (b) [Zn(Pip)(Edtc) ] · C H ,
2
2
6
6
13
(c) [Zn(Pip)(Edtc) ] · Py, and (d) [Zn(Pip)(Edtc) ] · Mf. Components that are formed as a result of incomplete averaging of
C
2
2
chemical shift anisotropy are marked with an asterisk. Number of scans/spinning frequency of samples (rps): (a) 2048/5500;
(b) 2048/5200; (c) 1024/4400; (d) 1024/5500.
or doublet (1 : 1) signals (compounds I, II) in the spec- four structural positions (Fig. 3, Table 3). The observed
tra. The doublet nature of the signals reflects some additional asymmetric splitting of the signals of the
structural inequivalence of the Edtc– ligands in com- Edtc– group is due to incomplete suppression of the 13C
pounds I and II. In addition, the terminal methylene dipole–dipole interaction with the quadrupole 14N
groups also turn out to be inequivalent, which can be nucleus (I = 1) under the conditions of the MAS exper-
explained by their distribution over two, three, or even iment [25, 26].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27
No. 3
2001

164
IVANOV et al.
a
*
b
c
125
100
75
50
25
0
δ, ppm
15
Fig. 4. N NMR spectra (T = 295 K) of (a) [Zn(Pip)(Edtc) ], (b) [Cu(Pip)(Edtc) ] · C H , and (c) [Zn(Pip)(Edtc) ] · Mf. Compo-
2
2
6
6
2
15
nents that are formed as a result of incomplete averaging of N chemical shift anisotropy are marked with an asterisk. Number of
scans/spinning frequency of samples (rps): (a) 6000/6000; (b) 2500/4400; (c) 18500/5500.
Comparison of the 13C chemical shifts listed in bonds in the solvated forms. From this point of view,
Table 3 for group NC(S)S– contained in NaEdtc · 3H2O
in nonsolvated (I) and solvated forms of adducts (II–
IV) allows one to note that the ionic form of the ligand
corresponds to the maximum value δ13ë. Covalent
binding of the ligands in adduct I results in a chemical
shift decrease. Further lowering of δ after adduct solva-
the doublet nature of the dithiocarbamate group signals
in the 13C spectra of compounds I and II suggests that
the two Edtc– ligands in these complexes have different
strengths of binding.
Chemical shifts in Table 3 and data in [22] make it
possible to assign a triplet signal in a high-field region
tion can be explained by the strengthening of Zn–S of the 13C spectra to CH2 groups in the o-, m-, and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27 No. 3
2001

ADDUCTS OF DIETHYLDITHIOCARBAMATE COMPLEXES
165
*
*
*
*
250
200
150
100
50
0
δ, ppm
15
Fig. 5. N NMR spectrum (T = 295 K) of [Zn(Pip)(Edtc) ] · Py (11000 scans, sample spinning frequency is 4400 rps). Components
2
15
that are formed as a result of incomplete averaging of N chemical shift anisotropy are marked with an asterisk.Vertical arrow indi-
cates the signal from the Py solvate molecule. The sample contains an admixture of a nonsolvated form of the adduct (~3%).
p-positions of coordinated Pip molecules. The main from the chemical shifts of coordinated Py molecules
difference in the patterns of the 13C NMR spectra of (δ = 140.2–144.0 and 125.5–127.2 ppm) [1, 3–8].
compounds II–IV and I consists in the availability of These data fully agree with the assumption on the outer-
signals due to different solvate molecules (benzene, Py, sphere location of the Py molecule in compound III.
or Mf). The benzene molecule is represented in the 13C
15N NMR spectra of compounds I–IV (Figs. 4, 5)
NMR spectrum (Fig. 3b) by a singlet signal in order to
contain a singlet signal due to the Pip coordinated mol-
indicate that all six carbon atoms are structurally equiv-
ecule and a symmetric doublet signal (1 : 1) due to the
alent. The observed broadening of the signal resulting
Edtc– ligands. The latter fact reflects the structural
inequivalence of the ligands incorporated in the adducts
from the chemical shift dispersion can be explained by
molecular dynamics or (within the framework of a
under study. It should be noted that in some cases (com-
steady-state model) by the random disordering of car-
pounds III, IV), the 15N NMR doublet signal from the
bon atoms in the crystal lattice of compound II over
NC(S)S– groups corresponds to a singlet signal from
several close structural positions. The chemical shift of
the 13C nuclei of these groups (Figs. 3c, 3d). Thus, the
benzene incorporated in II coincides with a character-
structural equivalence of the carbon atoms directly
interacting with the central atom through a low-size
istic of individual C6H6 [22] to prove its solvate nature.
four-membered metal cycle (trans-annular effect) can
13C NMR spectra of solvated adduct IV are peculiar
be combined with the inequivalence of more distant
in that they exhibit signals assigned in accordance with
nitrogen atoms in the periphery part of the ligand.
data of [23] to OCH2 and NCH2 groups of solvated Mf
Another explanation can be the higher sensitivity of the
molecules. In a spectrum of compound III (Fig. 3c), the
15N chemical shift (as compared to 13C) to small struc-
Py molecule produces a triplet (2 : 1 : 2) signal due to
tural perturbations.
the CH groups in the o-, p-, and m-positions. The ratio
of the component intensities in the triplet suggests that
In addition, 15N NMR spectra of solvated forms III
the frequently observed molecular dynamics of the and IV contain signals from the outer-sphere Py
coordinated Py, as well as the structural disordering of (Fig. 5) and Mf molecules (Fig. 4c). According to data
the carbon atoms, are lacking in this case. According to of [1, 3–8], the 15N chemical shifts of coordinated Py
data of [1, 4], the most sensitive to the structural state molecules lie within the range of 225.2–231.5 ppm,
of the Py molecule are the signals of the carbon atoms whereas for solvate Py molecules, δ15N = 279.4 ppm.
in the p- and m-positions. (Although, one should note Thus, the 15N chemical shift is characterized by high
that the sensitivity of the latter is lower.) On the one sensitivity to the structural functions of the Py molecule
hand, the respective values of δ13ë for the Py molecule contained in the adducts under study, which makes it
in compound III (136.8 and 124.3 ppm) are close to the possible to unambiguously interpret the 15N NMR data.
characteristics of the solvated Py molecule in adduct In the case of compound III, the signal from the Py
[Zn(Py)(Edtc)2] · Py [4] (δ = 135.3 and 123.9 ppm) and molecule has δ15N = 275.1 ppm, which indicates that
also to the characteristics of Py as an individual sub- pyridine is in the outer sphere. This conclusion com-
stance [24] (Table 3), but on the other hand, they differ plies with 13C NMR data.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27
No. 3
2001

166
IVANOV et al.
3. Ivanov, A.V., Kritikos, M., Lund, A., et al., Zh. Neorg.
Khim., 1998, vol. 43, no. 9, p. 1482.
4. Ivanov, A.V., Kritikos, M., Antsutkin, O.N., et al.,
Koord. Khim., 1998, vol. 24, no. 9, p. 689.
5. Ivanov, A.V., Kritikos, M., Antsutkin, O.N., et al.,
Koord. Khim., 1999, vol. 25, no. 8, p. 583.
One should also note that with a long (above one
15
day) period of N NMR spectra acquisition for com-
pound III, in addition to the main group of signals, sig-
nals of relatively low intensity appear due to solvate Py
molecules (272.1 ppm), Edtc– ligands (135.0 and
131.1 ppm), and coordinated Pip molecules (2.5 ppm).
This can be explained by the appearance of one more
impurity form of solvated adduct. The values of δ15N
for the Edtc– ligands and Pip molecules of this impurity
form are intermediate between the corresponding char-
acteristics for [Zn(Pip)(Edtc)2] and [Zn(Pip)(Edtc)2] · Py.
This is evidently due to the fact that the impurity form
of the adduct contains less Py. Slight desorption of Py
from compound III in the course of a long period of
spectra acquisition also favors this assumption.
6. Ivanov, A.V., Kritikos, M., Antsutkin, O.N., and Lund, A.,
Zh. Neorg. Khim., 1999, vol. 44, no. 10, p. 1689.
7. Ivanov, A.V., Forshling, V., Antsutkin, O.N., et al., Dokl.
Akad. Nauk, 1999, vol. 366, no. 5, p. 643.
8. Ivanov, A.V., Forshling, V., Kritikos, M., and Antsut-
kin, O.N., Koord. Khim., 2000, vol. 26, no. 1, p. 56.
9. Ivanov, A.V., Mitrofanova, V.I., Rodina, T.A., and
Mel’nikova, M.A., Koord. Khim., 1997, vol. 23, no. 11,
p. 838.
10. Zeng, D., Hampden-Smith, M.J., and Alam, T.M., Poly-
hedron, 1994, vol. 13, no. 19, p. 2715.
Attempts to apply the NMR method to study the
zinc adduct with composition [Zn(B)(Edtc)2] · Pip con-
taining outer-sphere Pip molecules proved unsuccess- 11. Higgins, G.M.C. and Saville, B., J. Chem. Soc., 1963,
p. 2812.
ful. Under high-frequency conditions of the MAS
experiment and the considerable pressures being devel-
oped, redistribution of the base molecules between the
inner and outer coordination spheres occurs very
quickly.
12. Coates, E., Rigg, B., Saville, B., and Skelton, D.,
J. Chem. Soc., 1965, p. 5613.
13. Gupta, S.K. and Srivastava, T.S., J. Inorg. Nucl. Chem.,
1970, vol. 32, no. 5, p. 1611.
Thus, data of EPR, high-resolution solid-state (13C,
15N) NMR spectroscopy, and of a stoichiometric study
reveal that crystal adducts of diethyldithiocarbamate
complexes of zinc(II) and copper(II) with Pip are liable
to produce solvated forms with outer-sphere molecules
of benzene, Py, and Mf. In this case, solvate isomers
were obtained for forms solvated with Py and Mf. It
was shown that solvation of crystal adducts of Cu(II)
with Pip, Mf, and Py leads to a substantial increase in
the TB contribution to the geometry of the Cu(II) coor-
dination polyhedron. Adducts with Mf and Py were
found to exhibit polyhedron distortion together with
structural unification of two isomeric forms at a molec-
ular level with transition to a qualitatively new state.
The structural inequivalence of the Edtc– ligands in the
zinc adducts under study was established on the basis
of 13C, 15N NMR data.
14. Pines, A., Gibby, M.G., and Waugh, J.S., J. Chem. Phys.,
1972, vol. 56, no. 4, p. 1776.
15. Earl, W.L. and VanderHart, D.L., J. Magn. Reson., 1982,
vol. 48, no. 1, p. 35.
16. Ratcliffe, C.I., Ripmeester, J.A., and Tse, J.S., Chem.
Phys. Lett., 1983, vol. 99, no. 2, p. 177.
17. Mason, J., Encyclopedia of Nuclear Magnetic Reso-
nance, Grant, D.M. and Harris, R.K.V., Eds., New York:
Wiley, 1996, p. 3222.
18. Rieger, Ph.H., Electron Spin Resonance (Senior
Reporter Symons M.C.R.), Newcastle upon Tyne: Athe-
naeum, 1993, vol. 13B, p. 178.
19. Khimicheskaya entsiklopediya (Chemical Encyclope-
dia), Zefirov, N.S., Ed., Moscow: Bol’shaya Rossiiskaya
Entsiklopediya, 1992.
20. Holmes, R.R., Prog. Inorg. Chem., 1984, vol. 32, no. 1,
p. 119.
21. Ivanov, A.V., Rodyna, T.A., and Antzutkin, O.N., Poly-
hedron, 1998, vol. 17, no. 18, p. 3101.
22. Levy, G.C., Lichter, R.L., and Nelson, G.L., Carbon-13
Nuclear Magnetic Resonance Spectroscopy, New York:
Wiley, 1980, p. 72.
23. Eliel, E.L. and Pietrusiewicz, K.M., Topics in Carbon-13
NMR Spectroscopy, Levy, G.C., Ed., New York: Wiley,
1980, vol. 3, p. 218.
24. Johnson, L.-R.F. and Jankowski, W.C., Carbon-13
NMR-Spectra. A Collection of Assigned, Coded and
Indexed Spectra, New York: Wiley, 1972.
ACKNOWLEDGMENTS
We are grateful to the Bruker company for the free
use of the WIN-EPR SimFonia software. One of the
authors (A. V. Ivanov) expresses his thanks to the Luleå
University of Technology and to the Wenner-Gren
Foundation (Sweden) for their financial support.
REFERENCES
25. Hexem, J.G., Frey, M.H., and Opella, S.J., J. Chem.
Phys., 1982, vol. 77, no. 7, p. 3847.
1. Ivanov, A.V., Mitrofanova, V.I., Kritikos, M., and Ant-
zutkin, O.N., Polyhedron, 1999, vol. 18, no. 15, p. 2069.
2. Ivanov, A.V., Forshling, V., Kritikos, M., et al., Dokl. 26. Harris, R.K., Jonsen, P., and Packer, K.J., Magn. Reson.
Akad. Nauk, 1999, vol. 369, no. 1, p. 64.
Chem., 1985, vol. 23, p. 565.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 27 No. 3
2001