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M. Dakovic´ et al. / Polyhedron 27 (2008) 210–222
211
CHNS-microanalyses were performed by the Chemical
added. After several hours colourless crystals of mercury(II)
thiocyanate were obtained. The crystals were filtered off,
washed with water and dried. Total yield 85% (0.54 g;
1.7 mmol). Hg(SCN)2 was then dissolved in ethanol
(0.32 g; 1 mmol in 100 mL) by gentle heating and the etha-
nol solution (30 mL) of picolinamide (0.24 g; 2 mmol) was
added in it. The resulting mixture was refluxed for 1 h.
The clear solution thus formed was allowed to stand for a
few days to yield colourless crystals of compound 3 suitable
for X-ray investigations. Total yield corresponds to 82%
(0.36 g; 0.82 mmol) based on Hg. Anal. Calc. for
C16H12Hg2N8O2S4 (3): C, 21.89; H, 1.38; N, 12.77; S,
14.61. Found: C, 21.95; H, 1.40; N, 12.82; S, 14.73%.
Selected IR data (cmꢀ1, KBr pellets): 3409s, 3292s, 2130vs,
1691vs, 1616m-s, 1583s, 1568m, 1142w, 1095m, 1044w,
999m, 749s, 676m-w, 636m-w, 617m-s, 559m-s, 496m, 462m.
-
´
Analytical Service of the Ruder Bosˇkovic Institut, Zagreb.
Infrared spectra were obtained from KBr pellets within
the range 4000–400 cmꢀ1 with a Perkin–Elmer FTIR spec-
trometer 1600 Series.
1
The one-dimensional H and 13C NMR spectra were
recorded with a Bruker AV 600 spectrometer, operating
at 600.133 MHz and 150.971 MHz for the 1H and 13C
nuclei, respectively. Samples were measured in DMSO-d6
solution and chemical shifts (ppm) are referred to TMS.
The thermal measurements were performed using a
simultaneous TGA–DTA analyzer (TA Instruments, SDT
Model 2960). The TGA and DTA curves were obtained
by placing samples of about 6 mg in mass, in small open
platinum pans, with a heating rate of 10 ꢁC/min and nitro-
gen (purity above 99.996%) pouring at a flow rate of 50 mL/
min. All samples were heated from room temperature up to
700 ꢁC. The SDT was calibrated with indium and silver.
2.3. X-ray structural analysis
2.2. Preparation of the complexes
The general and crystal data, and summary of intensity
data collection and structure refinement for compounds
1–3 are given in Table 1.
2.2.1. Preparation of [Zn(NCS)2(pia)2] (1a and 1b)
A warm solution (50 mL) of picolinamide (0.24 g;
0.2 mmol) in water was slowly added to an aqueous solu-
tion (10 mL) of zinc nitrate hexahydrate (0.30 g; 0.1 mmol).
Into the resulting solution was then added an aqueous solu-
tion (10 mL) of potassium thiocyanate (0.18 g; 0.2 mmol).
After keeping the mother liquid for few days, white crystals
suitable for further X-ray diffraction experiments were
obtained. Total yield corresponds to 88% (0.37 g;
0.88 mmol) based on Zn. Anal. Calc. for C14H12ZnN6O2S2
(1): C, 39.49; H, 2.84; N, 19.74; S, 15.06. Found: C, 39.61;
H, 2.98; N, 19.95; S, 15.16%. Selected IR data (cmꢀ1, KBr
pellets): 3330s, 3184s, 2096vs, 1688s, 1666vs, 1624m,
1612m, 1593s, 1585s, 1569s, 1423s, 1184w, 1160w, 1124w,
1109m-w, 1074w, 1056w, 1024m, 798w, 780w, 755m,
744m, 724m-w, 528w. From the reaction mixture, in which
an excess of a picolinamide was present, 1a together with a
few crystals of another polymorph 1b were obtained.
Data for structure 1a were collected at 200 K on a Non-
ius KappaCCD diffractometer with a crystal-detector dis-
tance of 30 mm. The extraction and correction of the
intensity data, absorption correction and the refinement
of the unit cell parameters were performed with the pro-
gram package DENZO-SMN [9].
Data for structures 1b, 2 and 3 were collected at 293 K
on an Oxford Diffraction Xcalibur four-circle kappa geom-
etry single-crystal diffractometer with a Sapphire 3 CCD
detector, by applying the CrysAlis software system [10].
The crystal-detector distance was 60 mm. Data reduction,
including absorption correction, was done by the CrysAlis
RED application of the CrysAlis software system [10].
The structures were solved by direct methods using the
SHELXS97 program [11]. The coordinates and the aniso-
tropic thermal parameters for all non-hydrogen atoms were
refined by the least-squares methods based on F2 using the
SHELXL97 program [12]. The hydrogen atoms were gener-
ated geometrically using the riding model with the isotropic
factor set at 1.2Ueq of the parent atom. Hydrogen atoms on
the amide nitrogen atom, as well as on the oxygen atom of
the H2O molecule were located in the difference Fourier
map at the final stage of the refinement and were refined
freely. Graphical work has been performed by the program
ORTEP-3 for Windows [13] and Mercury 1.4.1 [14]. The
thermal ellipsoides are drawn at the 50% probability level.
2.2.2. Preparation of [Cd(SCN)2(pia)]n (2)
Compound 2 was prepared in an analogous way to 1,
only using cadmium nitrate tetrahydrate (0.31 g; 0.1 mmol)
as the starting metal salt. Total yield corresponds to 77%
(0.28 g; 0.77 mmol) based on Cd. Anal. Calc. for
C8H6CdN4OS2 (2): C, 27.40; H, 1.72; N, 15.98; S, 18.29.
Found: C, 27.48; H, 1.81; N, 16.03; S, 18.32%. Selected
IR data (cmꢀ1, KBr pellets): 3408s, 3343m, 3284m,
3203s, 2119vs, 2094vs, 1669vs, 1610m-s, 1584s, 1571s,
1419s, 1181w, 1161w, 1117m, 1092w, 1054w, 1016s,
782w, 747s, 659s, 638m-w, 541m.
3. Results and discussion
3.1. Preparation of the complexes
2.2.3. Preparation of [Hg(SCN)2(pia)]2 (3)
Into an aqueous solution (100 mL) of mercury(II) nitrate
monohydrate (0.68 g; 2 mmol) with a few drops of diluted
nitric acid (20% by weight), an aqueous solution (10 mL)
of potassium thiocyanate (0.36 g; 4 mmol) was slowly
The zinc and cadmium thiocyanato complexes 1 (1a and
1b) and 2 were prepared in situ from aqueous solutions.
The mercury complex 3 could not be obtained in the same
way due to very low solubility of mercuric thiocyanate in