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solutions and the formation of heteropolynuclear gold(III)–cad-
mium(II) complexes, ([Au{S2CN(iso-C4H9)2}2]2[CdCl4])n [8,9] and
([NH2(C4H9)2][Au{S2CN(C4H9)2}2][CdCl4])n [10] as the fixation modes
of gold(III).
2.3. Physical measurements
2.3.1. Elemental analysis
Elemental analysis of adduct 1 for cadmium was carried out by
high resolution inductively coupled plasma – mass spectrometry
(performed in medium resolution mode,
ICP-MS (ELEMENT, Finnigan MAT, Bremen, Germany).
The present work describes the preparation, multinuclear 13C,
15N, 113Cd CP/MAS NMR, single-crystal X-ray diffraction studies
and thermal behaviour of the pyridine adduct of bis(N,N-di-
iso-butyldithiocarbamato-S,S0)cadmium(II), [Cd(C5H5N){S2CN(iso-
C4H9)2}2]. 113Cd CP/MAS NMR spectra of the prepared cadmium(II)
adduct 1 reveal extensive spinning sideband manifolds at moder-
ate spinning frequencies (5.0 and 5.5 kHz). The intensities of spin-
ning sidebands in 113Cd MAS NMR spectra were used in
calculations of 113Cd chemical shift anisotropy (CSA) parameters,
which were correlated with structures of this and other cadmium
compounds. The thermal behaviour of adduct 1 was studied using
the STA method, as a combination of TG and DSC techniques, under
an argon atmosphere.
D
m/m ꢃ 4500) – HR-
2.3.2. 13C, 15N and 113Cd NMR spectroscopy
Solid state 13C, 15N and 113Cd magic-angle-spinning (MAS) NMR
spectra were recorded on a Varian/Chemagnetics InfinityPlus CMX-
360 (B0 = 8.46 T) spectrometer operating in the pulsed Fourier
transform mode, using cross-polarisation (CP) from the protons to-
gether with phase-modulated proton decoupling [15]. The
13C/15N/113Cd operating frequencies were 90.52/36.48/79.86 MHz,
respectively. The proton
CP mixing time was 2.0/1.25/10.0 ms and the nutation frequency
of protons during decoupling was nut/2 = 56/56/56 kHz. For
p/2 pulse durations were 4.5/5.0/5.0 ls,
x
p
the studied sample, 13 800/15 200/1248–7500 transients, spaced
by relaxation delays of 3/2.5/7 s, were accumulated. The polycrys-
talline sample (ca. 350 mg) was packed in zirconium dioxide stan-
dard double-bearing 7.5-mm rotors. The spinning frequencies
ranged from 4000 to 5000/4000 to 5000/5000 to 5500 Hz and were
2. Experimental
2.1. Materials
stabilised to 2 Hz using a built-in stabilisation device. All 13C, 15
N
Sodium N,N-di-iso-butyldithiocarbamate was prepared by
reacting di-iso-butylamine, (iso-C4H9)2NH (Aldrich), with carbon
disulphide, CS2 (Merck), in alkaline media [11]. Thermal analysis
data showed the presence of the initial crystalline sodium salt in
the trihydrated form, Na{S2CN(iso-C4H9)2}ꢁ3H2O [11]. The binu-
clear N,N-di-iso-butyldithiocarbamate cadmium(II) complex,
[Cd2{S2CN(iso-C4H9)2}4], was obtained by mixing aqueous solu-
tions of Cd(ClO4)2ꢁ6H2O (Merck) with an excess (ꢂ10%) of Na{S2C-
N(iso-C4H9)2}ꢁ3H2O [6]. The resulting white precipitate was
collected, filtered off, washed with water and dried naturally. Both
the original sodium salt and the dithiocarbamate cadmium(II)
complex were additionally characterised by solid state 13C CP/
MAS NMR (d, ppm):
Na{S2CN(iso-C4H9)2}ꢁ3H2O (1:2:2:4): 208.2 (–S2CN@); 66.7
(@NCH2–); 28.0, 27.1 (1:1, @CH–); 23.0, 22.4, 20.8 (1:1:2, –CH3).
[Cd2{S2CN(iso-C4H9)2}4] (1:2:2:4): 207.4, 207.2, 203.0, 201.7
(1:1:1:1, –S2CN@); 65.9, 65.1, 62.8 (4:2:10, @NCH2–); 28.7, 28.0,
27.8, 27.5, 27.2, 26.9 (2:3:3:3:2:3, @CH–); 23.1, 22.7, 22.2, 21.9,
21.5, 20.9, 20.7, 20.0 (2:4:2:2:2:1:1:2, –CH3) (single-crystal X-ray
diffraction data [12,13] revealed that the original cadmium(II)
compound simultaneously forms two centrosymmetric isomeric
binuclear molecules).
and 113Cd NMR spectra were recorded at room temperature (ca.
295 K).
13C isotropic chemical shifts (in the deshielding, d-scale) were
externally referenced to the least shielded resonance of solid ada-
mantine [16] at 38.48 ppm [17] relative to tetramethylsilane.
Chemical shifts and integrated intensity ratios for overlapping sig-
nals in the 13C NMR spectra were additionally refined by fragment-
by-fragment simulation with consideration of line positions and
line widths, as well as of the Lorentzian and Gaussian contributions
to the line shapes. 15N isotropic chemical shift values are given
with respect to the polycrystalline NH4Cl (here 0 ppm; ꢀ341
ppm on the absolute scale [18], externally referenced). 113Cd chem-
ical shifts were externally referenced to the polycrystalline
Cd(NO3)2ꢁ4H2O (ꢀ100 ppm with respect to a 0.1 M Cd(ClO4)2 aque-
ous solution with an ionic strength of 4.5; here, 0 ppm [19]). Drifts
in the 13C/15N/113Cd frequencies (B0-drift) were 0.051/0.018/
0.045 Hz hꢀ1, respectively. The homogeneity of the magnetic field
was monitored by measuring the width of the least shielded refer-
ence signal of polycrystalline adamantane at d(13C) = 38.48 ppm
(lw = 2.8 Hz).
The anisotropy, daniso = dzz ꢀ diso, and the asymmetry parameter
of the 113Cd chemical shift tensor (CST),
g
= (dyy ꢀ dxx)/(dzz ꢀ diso
)
were estimated using v2 statistics in the Mathematica front end
[20], taking into account integrated sideband intensities in the
NMR spectra recorded at two different spinning frequencies and
noise variance [21].
2.2. Synthesis of polycrystalline adduct 1
The original binuclear N,N-di-iso-butyldithiocarbamate cad-
mium(II) complex, [Cd2{S2CN(iso-C4H9)2}4], was dissolved in a
minute volume of toluene under mild heat. Excess (ꢂ10%) pyridine
was added to the prepared solution of cadmium compound (de-
scribed above). For X-ray diffraction studies, suitable single crystals
of bis(N,N-di-iso-butyldithiocarbamato-S,S0)(pyridine)cadmium(II),
[Cd(C5H5N){S2CN(iso-C4H9)2}2] (1) were isolated by means of slow
evaporation of toluene at room temperature. Adduct 1 was isolated
as transparent prismatic crystals. The yield was 87%. Anal. Found:
Cd, 18.68 (on 110Cd, 18.91; 111Cd, 18.74; 112Cd, 18.44, 114Cd,
18.62). Calc. for C23H41N3S4Cd (Mr = 600.23): Cd, 18.73%. Solid state
13C CP/MAS NMR data (d, ppm) for compound 1 are given below:
[Cd(C5H5N){S2CN(iso-C4H9)2}2]: 207.0, 204.8 (1:1, –S2CN@);
66.5, 66.1, 64.4 (2:1:1, @NCH2–); 30.2, 28.5, 27.5 (@CH–); 23.3,
22.8, 22.4, 21.3, 21.0, 20.1 (–CH3); 149.9, 126.2, 142.0 (py: ortho-,
meta- and para- @CH–). Cf. data for liquid pyridine: 149.8, 123.6,
135.7 [14].
The 113Cd and 207Pb chemical shifts [22–25] display dependence
on the spinning frequency, which is caused by heating of the rotor.
Therefore, temperatures in the 7.5-mm rotor were externally cali-
brated by lead(II) nitrate [23]. The spinning frequencies of 5000
and 5500 Hz correspond to temperatures of 312 and 316 K, respec-
tively, inside the rotor. 207Pb NMR measurements were performed
at a carrier frequency of 75.25 MHz.
2.3.3. Crystal structure determination
A suitable single crystal of adduct 1, [Cd(C5H5N){S2CN(iso-
C4H9)2}2], was selected and mounted on a glass capillary with
epoxy glue. Experimental intensity data were collected at
T = 173(1) K on a BRUKER SMART 1000 CCD diffractometer with
graphite monochromated Mo K
range of a semi-sphere [26] (crystal-detector distance 45 mm).
Data were collected in series of 906 frames at = 0°, 90° and
a radiation (k = 0.71073 Å) in the
u