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A. Hazari, A. Ghosh / Polyhedron 87 (2015) 403–410
properties of two new hetero-metallic complexes of Hg(II), [(CuL)2-
Hg(N3)2] (1 and 10) and [(CuL)2Hg(NCO)2] (2 and 20) with azide and
cyanate as coligands [where H2L = N,N0-bis(salicylidene)-1,
4-butanediamine]. Both compounds crystallize with Z0 = 1 and
Z0 = 0.5 depending upon the time of crystallization. The rapid crys-
tallization produces crystals with Z0 = 1 (1 and 2) whereas slow
crystallization affords crystals with Z0 = 0.5 (10 and 20). The
C–Hꢁ ꢁ ꢁN and C–Hꢁ ꢁ ꢁO weak-interactions between two independent
molecules seem to be responsible for the stabilization of the
crystals with higher Z0 values.
2.4. Synthesis of the complexes with Z0 = 0.5, complexes
[(CuL)2Hg(N3)2] (10) and [(CuL)2Hg(OCN)2] (20)
For the preparation of these complexes, similar layering of the
solutions as mentioned above was done. However, the crystals at
the junction were not collected after 12 h; instead the tubes were
allowed to stand for several days. It was found that after ca. 60–
70 h very small but crystalline light green products started to
appear in the lower portion of aqueous layer. After about 7–8 days
these crystals grew and found to stick to the glass wall of the tube
in the part containing the aqueous solution. The crystals were nee-
dle shaped light green for 10 and cubic shaped light green for 20. The
deep green crystals of 1 and 2 which appeared initially remained
unaltered during this period. As their morphologies were distinctly
different and they appeared only at the junction of the two liquids,
they were removed manually before collection of the crystals of 10
or 20. The crystals from the aqueous layer were then collected and
used for X-ray diffraction and other physio-chemical studies.
Compound 10: Yield: 0.251 g, 25% (with respect to [CuL]), Anal.
Calc. for C36H36Cu2HgN10O4: C, 43.22; H, 3.63; N, 14.00; O, 6.40.
Found: C, 43.58; H, 3.52; N, 14.11%. UV–Vis: kmax (solid, reflec-
2. Experimental
2.1. Starting materials
The salicylaldehyde, 1,4-butanediamine were purchased from
Lancaster and were of reagent grade. They were used without fur-
ther purification.
Caution! Perchlorate and azide salts of metal complexes with
organic ligands are potentially explosive. Only a small amount of
material should be prepared and it should be handled with care.
Moreover, mercuric chloride is toxic.
tance) = 621 and 376 nm. IR (KBr):
m , m(N3)
(C@N) 1619 cmꢀ1
2043 cmꢀ1
.
Compound 20: Yield, 0.214 g, 21% (with respect to [CuL]), Anal.
Calc. for C38H36Cu2HgN6O6: C, 45.62; H, 3.63; N, 8.40; O, 9.60. Found:
C, 45.58; H, 3.52; N, 8.61%. UV–Vis: kmax (solid, reflectance) = 635
2.2. Synthesis of the Schiff base ligand N,N0-bis(salicylidene)-1,4-
butanediamine (H2L) and the ‘‘metalloligand’’ [CuL]
and 368 nm. IR (KBr): m , m .
(@N) 1618 cmꢀ1 (OCN) 2169 cmꢀ1
The di-Schiff base ligand was synthesized by
a standard
method. 5 mmol of 1,4-butanediamine (0.440 g) was mixed with
10 mmol of the salicylaldehyde (1.04 mL) in methanol. The result-
ing solution was refluxed for ca. 4 h, and allowed to cool in a free-
zer for overnight. The yellow solid mass was collected by filtration
and then washed with cold methanol. 5 mmol (1.47 g) of this yel-
low solid, H2L was dissolved in 10 mL methanol by heating over a
water-bath for 10 min and then added to a methanolic solution
(20 mL) of Cu(ClO4)2ꢁ6H2O (1.852 g, 5 mmol) to prepare the ‘‘met-
alloligand’’ [CuL] [20,21].
2.5. Physical measurements and crystallographic data collection and
refinement
Elemental analyses (C, H and N) were performed using a Perkin-
Elmer 2400 series II CHN analyzer. IR spectra in KBr pellets (4000–
400 cmꢀ1) were recorded using a Perkin-Elmer RXI FT-IR spectro-
photometer. Electronic spectra in solid state (800–300 nm) were
recorded in a Hitachi U-3501 spectrophotometer.
Suitable single crystals of each complexes were mounted on a
Bruker-AXS SMART APEX II diffractometer equipped with a graph-
ite monochromator and Mo Ka (k = 0.71073 Å) radiation. The crys-
2.3. Synthesis of the complexes with Z0 = 1, complexes 1
[(CuL)2Hg(N3)2] and 2 [(CuL)2Hg(OCN)2]
tals were positioned at 60 mm from the CCD. Frames (360) were
measured with a counting time of 5 s. The structures were solved
using Patterson method by using the SHELXS 97. Subsequent differ-
ence Fourier synthesis and least-square refinement revealed the
positions of the remaining non-hydrogen atoms. Non-hydrogen
atoms were refined with independent anisotropic displacement
parameters. Hydrogen atoms were placed in idealized positions
and their displacement parameters were fixed to be 1.2 times lar-
ger than those of the attached non-hydrogen atom. Successful con-
vergence was indicated by the maximum shift/error of 0.001 for
the last cycle of the least squares refinement. The structures of 1
and 2 have disorder in the positions of C10B and these disorders
have been refined isotropically in both structures. Absorption cor-
rections were carried out using the SADABS program [22]. All calcu-
lations were carried out using SHELXS 97 [23], SHELXL 97 [24], PLATON
99 [25], ORTEP-32 [26] and WINGX system ver-1.64 [27]. Data collec-
tion and structure refinement parameters and crystallographic
data for the two complexes are given in Table 1. The selected bond
lengths and bond angles are summarized in Tables 2 and 3.
The precursor ‘‘metalloligand’’ [CuL] (0.714 g, 2 mmol) was dis-
solved in methanol (10 mL) and it was slowly poured above a
water solution (5 mL) of HgCl2 (0.271 g, 1 mmol) and sodium azide
(0.130 g, 2 mmol) or sodium cyanate (0.130 g, 2 mmol) in two sep-
arate layer tubes for complexes 1 and 2, respectively (Scheme 1). A
solid powder-like product appeared immediately near the junction
of the two liquids. The powder compounds united together to a
rhombic shaped deep green (1) and a square shaped deep green
(2) X-ray quality single crystals within 6 h at the junction of the
two solutions in the layer tubes. The crystals were collected after
12 h. A few of them were picked for single crystal X-ray diffraction
and the rest were washed with a methanol–water mixture and
dried in a desiccators containing anhydrous CaCl2 and then charac-
terized by elemental analyses and spectroscopic methods.
Compound 1: Yield: 0.089 g, (9%) (With respect to [CuL]), Anal.
Calc. for C36H36Cu2HgN10O4: C, 43.22; H, 3.63; N, 14.00; O, 6.40.
Found: C, 43.58; H, 3.52; N, 14.08%. UV–Vis: kmax (solid, reflec-
tance) = 626 and 375 nm. IR (KBr):
m , m(N3)
(C@N) 1622 cmꢀ1
2044 cmꢀ1
.
3. Results and discussion
Compound 2: Yield: 0.054 g (5%) (With respect to [CuL]), Anal.
Calc. for C38H36Cu2HgN6O6: C, 45.62; H, 3.63; N, 8.40; O, 9.60.
Found: C, 45.58; H, 3.52; N, 8.61%. UV–Vis: kmax (solid, reflec-
3.1. Syntheses of the complexes
tance) = 636 and 365 nm. IR (KBr):
m
(C@N) 1621 cmꢀ1
,
m
(OCN)
The Schiff-base ligand (H2L), and it’s Cu(II) complex, [CuL] were
synthesized using the reported procedures [20,21]. When a
2170 cmꢀ1
.