Pyrimidyl-2-selenolates of cadmium and mercury: Synthesis, characterization, structures and their conversion to metal selenide nano-particles

Article abstract of DOI:10.1016/j.ica.2013.11.018

Reactions of [MCl₂(tmeda)] (M = Cd or Hg; tmeda = N,N,N′,N′-tetramethylethylenediamine) with NaSeC₄H(R-4,6) ₂N₂ (R = H or Me) gave selenolate complexes of the general formula [M{SeC₄H(R-4,6)₂N₂} ₂(tmeda)_n] (M/R/n = Cd/H/1 (1); Cd/Me/1 (2); Hg/H/1 (3) and Hg/Me/0 (4)). The chloro complexes of general formula, [MCl{SeC ₄H(Me-4,6)₂N₂}(tmeda)] (M = Cd (6) or Hg (7)) have been synthesized by redistribution reaction of [M{SeC₄H(Me-4,6) ₂N₂}₂] with MCl₂ followed by treatment with tmeda. The complexes have been characterized by elemental analysis, UV-Vis and NMR (¹H, ¹³C, ⁷⁷Se, ¹¹³Cd and ¹⁹⁹Hg) spectroscopy. The molecular structures of [Cd{SeC₄H(Me-4,6)₂N₂}₂(tmeda)] and [Hg{SeC₄H(Me-4,6)₂N₂}₂] were established by single crystal X-ray diffraction. The complex, [Cd{SeC ₄H(Me-4,6)₂N₂}₂(tmeda)] comprises of an octahedral cadmium atom containing chelating, two SeC₄H(4,6-Me) N₂ and one tmeda, ligands. The complex, [Hg{SeC₄H(Me-4,6) ₂N₂}₂] has a linear structure with monodentate selenolate ligand. Thermolysis of [Cd{SeC₄H(Me-4,6)₂N ₂}₂(tmeda)] and [Hg{SeC₄H(Me-4,6) ₂N₂}₂] in various coordinating solvents afforded CdSe and HgSe nanoparticles which were characterized by UV-Vis, XRD, SEM, EDX and TEM.

Full text of DOI:10.1016/j.ica.2013.11.018

Inorganica Chimica Acta 411 (2014) 90–96
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Pyrimidyl-2-selenolates of cadmium and mercury: Synthesis,
characterization, structures and their conversion to metal
selenide nano-particles
Rakesh K. Sharma a, Amey Wadawale a, G. Kedarnath a, B. Vishwanadh b, Vimal K. Jain a,
⇑
a Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Reactions of [MCl2(tmeda)] (M = Cd or Hg; tmeda = N,N,N0,N0-tetramethylethylenediamine) with
NaSeC4H(R-4,6)2N2 (R = H or Me) gave selenolate complexes of the general formula [M{SeC4H(R-4,6)2N2}2
(tmeda)n] (M/R/n = Cd/H/1 (1); Cd/Me/1 (2); Hg/H/1 (3) and Hg/Me/0 (4)). The chloro complexes of general
formula, [MCl{SeC4H(Me-4,6)2N2}(tmeda)] (M = Cd (6) or Hg (7)) have been synthesized by redistribution
reaction of [M{SeC4H(Me-4,6)2N2}2] with MCl2 followed by treatment with tmeda. The complexes have
been characterized by elemental analysis, UV–Vis and NMR (1H, 13C, 77Se, 113Cd and 199Hg) spectroscopy.
The molecular structures of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] and [Hg{SeC4H(Me-4,6)2N2}2] were estab-
lished by single crystal X-ray diffraction. The complex, [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] comprises of an
octahedral cadmium atom containing chelating, two SeC4H(4,6-Me)N2 and one tmeda, ligands. The com-
plex, [Hg{SeC4H(Me-4,6)2N2}2] has a linear structure with monodentate selenolate ligand. Thermolysis
of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] and [Hg{SeC4H(Me-4,6)2N2}2] in various coordinating solvents affor-
ded CdSe and HgSe nanoparticles which were characterized by UV–Vis, XRD, SEM, EDX and TEM.
Ó 2013 Elsevier B.V. All rights reserved.
Article history:
Received 23 August 2013
Received in revised form 17 October 2013
Accepted 16 November 2013
Available online 25 November 2013
Keywords:
Pyrimidyl selenolate
Cadmium
Mercury
NMR
Metal selenide nanoparticle
1. Introduction
source molecular precursors for the preparation of metal selenide
nanoparticles.
Metal complexes of hemilabile bidentate ligands containing
chalcogen atom and nitrogen donor have been of considerable
interest for the last 15 years or so [1–3]. Such ligands offer possibil-
ities to design metal complexes with new structural motifs [4–7]
and also assist in suppressing polymerization of metal chalcogen-
olate precursors used in chemical vapor deposition (CVD) [3,8].
Metal complexes derived from such ligands have been used as cat-
alyst in C–C coupling reactions [9–13] and have also emerged as
promising single source precursors for the synthesis of mono-dis-
persed metal chalcogenide naoparticles [14–17].
Several different families of hemilabile bidentate chalcogen
ligands, viz. N,N-dimethylalkylchalcogenolate [8,18,19], 2-pyridyl-
chalcogenolate [3], etc., have been extensively investigated.
2-Pyrimidyl chalcogenolate ligands (I) constitute yet another inter-
esting group of hemilabile bidentate chalcogenolate ligands.
Although metal complexes of 2-thiopyrimidine group (I, E = S)
have been investigated during last few years [20–23], the com-
plexes with heavier chalcogen ligands (I, E = Se or Te) have hardly
received any attention [24]. Thus we have studied 2-pyrimidylse-
lenolates of cadmium and mercury and have used them as single
(E = S, Se, Te and R = H or Me)
I
2. Experimental
2.1. Materials and methods
Metal chlorides, N,N,N0,N0-tetramethylethylenediamine (tmeda),
oleylamine (OA), tri-n-octylphosphine oxide (TOPO), tri-n-octyl-
phosphine (TOP) and other solvents were obtained from commer-
cial sources. [Se-C4H3N2]2 (1H NMR (CDCl3) d: 7.03 (t, 4.5 Hz,
CH-5); 8.51 (d, 4.5 Hz, CH-4,6). 13C{1H} NMR (CDCl3) d: 118.3
(CH-5); 157.9 (CH-4,6); 166.4 (C-2). 77Se{1H} NMR (CDCl3) d:
490 ppm) and [Se-C4H(Me-4,6)2N2]2 (1H NMR (CDCl3) d: 2.37 (s,
Me); 6.71 (s, CH-5). 13C{1H} NMR (CDCl3) d: 23.7 (Me); 117.2
(CH-5); 165.7 (C-2); 167.5 (C-4,6). 77Se{1H} NMR (CDCl3) d:
486 ppm) were prepared according to literature method [24].
⇑
Corresponding author. Tel.: +91 22 2559 5095; fax: +91 22 2552 5151.
E-mail address: jainvk@barc.gov.in (V.K. Jain).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.11.018

R.K. Sharma et al. / Inorganica Chimica Acta 411 (2014) 90–96
91
Table 1
Crystallographic and structural determination details for [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) and [Hg{SeC4H(Me-4,6)2N2}2] (4).
[Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2)
18H30CdN6Se2
[Hg{SeC4H(Me-4,6)2N2}2] (4)
Chemical formula
Formula weight
C
C12H14HgN4Se2
572.78
600.80
Crystal size (mm)
Crystal system/space group
0.10 ꢁ 0.02 ꢁ 0.01
0.40 ꢁ 0.30 ꢁ 0.10
monoclinic/P2/m
monoclinic/P21/c
Unit cell dimensions
a (Å)
b (Å)
c (Å)
ß(°)
17.0200(11)
7.7520(5)
17.3313(10)
94.154(5)
2280.7(2)
4
11.346(7)
9.761(4)
14.964(6)
108.31(4)
1573.4(13)
4
V (Å3)
Z
Dcalc (g cmꢀ3
)
1.750
2.418
l
(mmꢀ1)/F(000)
11.431/1184
ꢀ20 6 h 6 20
ꢀ9 6 k 6 9
ꢀ20 6 l 6 20
5.12–67.47
5149/6831
6831/0/254
0.0857, 0.2208
0.1010, 0.2306
1.000
14.400/1048
ꢀ14 6 h 6 13
ꢀ12 6 k 6 0
ꢀ10 6 l 6 19
2.53–27.49
1852/3611
3611/0/176
0.0574, 0.1524
0.1449, 0.1977
1.000
Limiting indices
h Range of data of collection
No. of reflections collected/unique
No. of data/restraints/parameters
Final R1,
R1, R2 (all data)
Goodness-of-fit (GOF) on F2
xR2 indices [I > 2r(I)]
x
Elemental analyses were carried out on a Thermo Scientific
Flash EA1112 elemental analyzer. 1H, 13C{1H}, 77Se{1H}, 113Cd{1H}
and 199Hg{1H} NMR spectra were recorded on a Bruker Avance-
II-300 NMR spectrometer operating at 300, 75.47, 57.24, 66.66
and 53.76 MHz, respectively. Chemical shifts are relative to inter-
nal chloroform peak for 1H and 13C{1H} spectra, external Ph2Se2
(d 463 ppm relative to Me2Se), Cd(OAc)2.2H2O in CH3OD and Ph2Hg
in CDCl3 (d = –745 ppm relative to Me2Hg) for 77Se{1H}, 113Cd{1H}
and 199Hg{1H} NMR spectra. UV–Vis absorption spectra were re-
corded on a JASCO V-630 double beam UV–Vis spectrophotometer.
Thermogravimetric analyses (TGA) were carried out on a Nitz-
sch STA 409 PC-Luxx TG-DTA instrument, which was calibrated
with CaC2O4.H2O. The TG curves were recorded at a heating rate
of 10 °C min–1 under a flow of argon. X-ray powder diffraction pat-
terns were obtained on a Philips PW-1820 powder diffractometer
washed thoroughly with diethyl ether and extracted with dichloro-
methane and filtered. The filtrate was concentrated under reduced
pressure and the residue was recrystallized from dichlorometh-
ane–hexane mixture to yield yellow crystals (170 mg, 80%), m.p.
124 °C. Anal. Calc. for
C14H22CdN6Se2: C, 30.87; H, 4.07; N,
15.42%. Found: C, 30.7; H, 3.78; N, 15.3%. UV–Vis kmax (CH2Cl2):
287 nm. 1H NMR (CDCl3) d: 2.41 (s, NMe2); 2.61 (s, NCH2ꢀ); 6.87
(t, 5 Hz, CH-5); 8.22 (d, 5 Hz, CH-4,6) (ring protons). 13C{1H} NMR
(CDCl3) d: 45.5 (NMe2); 56.9 (NCH2); 114.7 (CH-5); 155.7 (CH-
4,6); (C-2 not detected) (ring carbons). 77Se{1H} NMR (CDCl3) d:
214. 113Cd{1H} NMR (CDCl3) d: 352.
2.2.2. Preparation of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2)
Prepared in a similar fashion to 1 and the complex was recrys-
tallized from dichloromethane in 73% yield as pale yellow crystals,
m.p. 184 °C. Anal. Calc. for C18H30CdN6Se2: C, 35.98; H, 5.03; N,
13.98%. Found: C, 35.49; H, 4.83; N, 13.76%. UV–Vis kmax (CH2Cl2):
287 nm. 1H NMR (CDCl3) d: 2.34 (s, Me); 2.41(s, NMe2); 2.62 (s,
NCH2ꢀ); 6.57 (s, ring proton). 13C{1H} NMR (CDCl3) d: 23.6 (Me);
46.8 (NMe2); 56.7 (NCH2); 114.7 (CH-5); 166.1 (C-4,6); 176.3 (C-
2) (ring carbons). 77Se{1H} NMR (CDCl3) d: 331. 113Cd{1H} NMR
(CDCl3) d: 213.
using Cu K
a radiation. SEM and EDX measurements were carried
out on ULTRA 55 FESEM of Zeiss and Oxford Inca instruments,
respectively. A JEOL-2000FX transmission electron microscope
operating at accelerating voltages up to 200 kV was used for TEM
studies. The samples for TEM and SAED were prepared by placing
a drop of sample dispersed in acetone on a carbon coated copper
grid.
Intensity data for [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) and
[Hg{SeC4H(Me-4,6)2N2}2] (4) were measured as on a Rigaku AFC7S
2.2.3. Preparation of [Hg(SeC4H3N2)2(tmeda)] (3)
diffractometer fitted with Mo Ka radiation so that hmax = 27.5°. The
Prepared in the same way as 1 by employing HgCl2.tmeda and
NaSeC4H3N2 and the complex was recrystallized from dichloro-
methane-hexane mixture as colorless crystals (yield 160 mg,
65%), m.p. 110 °C (dec.). Anal. Calc. for C14H22HgN6Se2: C, 26.57;
H, 3.50; N, 13.28%. Found: C, 26.28; H, 3.32; N, 13.89%. UV–Vis kmax
(CH2Cl2): 270, 306 (sh) nm. 1H NMR (CDCl3) d: 2.30 (s, NMe2); 2.48
(s, NCH2ꢀ); 6.98 (t, 4.8 Hz, CH-5); 8.31 (d, 4.8 Hz, CH-4,6) (ring
protons). 13C{1H} NMR (CDCl3) d: 45.6 (NMe2); 57.1 (NCH2);
116.0 (CH-5); 156.0 (CH-4,6); 162.3 (C-2) (ring carbons). 77Se{1H}
NMR (CDCl3) d: 254.
unit cell parameters (Table 1) were determined from 25 reflections
measured by a random search routine. The intensity data were cor-
rected for Lorentz, polarization and absorption effects with an
empirical procedure [25]. The structures were solved by direct
methods using SHELX-97 [26] and refined by full-matrix least
squares methods [27]. The non-hydrogen atoms were refined
anisotropically. The hydrogen atoms were fixed in their calculated
positions. Molecular structures were drawn using ORTEP [28].
2.2. Syntheses of complexes
2.2.4. Preparation of [Hg{SeC4H(Me-4,6)2N2}2] (4)
2.2.1. Preparation of [Cd(SeC4H3N2)2(tmeda)] (1)
The reaction of either HgCl2.tmeda or HgCl2 with NaSeC4H(Me-
4,6)2N2 invariably yielded the title complex (4) which was recrys-
tallized from dichloromethane–hexane as colorless crystals (yield
360 mg, 78%), m.p. 154 °C (decomp.). Anal. Calc. for C12H14HgN4-
Se2: C, 25.16; H, 2.46; N, 9.78%. Found: C, 25.33; H, 2.49; N,
10.17%. UV–Vis kmax (CH2Cl2): 266, 302 (sh) nm. 1H NMR (CDCl3,)
To a freshly prepared NaSe–C4H3N2 [from toluene–methanol
solution of (SeC4H3N2)2 (123 mg, 0.39 mmol) and NaBH4 (33 mg,
0.87 mmol) in methanol], CdCl2.tmeda (116 mg, 0.39 mmol) was
added with stirring which continued for 3 h at room temperature.
The solvents were evaporated under vacuum. The residue was

92
R.K. Sharma et al. / Inorganica Chimica Acta 411 (2014) 90–96
d: 2.28 (s, Me); 6.76 (s, ring proton). 13C{1H} NMR (CDCl3,) d: 23.6
(Me); 116.6 (CH-5); 166.8 (C-4,6); 171.6 (C-2) (ring carbons).
77Se{1H} NMR (CDCl3) d: 342. 199Hg{1H} NMR (CDCl3,) d: ꢀ1521.
in situ by reduction of Se–Se bond in [{SeC4H(R-4,6)2N2}2] in tolu-
ene–methanol by a methanolic solution of NaBH4 under an argon
atmosphere) gave selenolate complexes, [Cd{SeC4H(4,6-R)2N2}2
(tmeda)] (Eq. (1)). Similar reaction with HgCl2.tmeda gave
[Hg(SeC4H3N2)2(tmeda)] and [Hg{SeC4H(Me-4,6)2N2}2] depending
on the substituent in the pyrimidyl ring. The latter and its cad-
mium analog can be prepared readily by the reaction between
MCl2 (M = Cd or Hg) and NaSe-C4H(Me-4,6)N2 (Eq. (2)). Redistribu-
tion reaction between [M{Se-C4H(Me-4,6)N2}2] and MCl2 followed
by treatment with tmeda afforded heteroleptic complexes,
[MCl{SeC4H(Me-4,6)2N2}(tmeda)] (Eq. (3)).
2.2.5. Preparation of [Cd{SeC4H(Me-4,6)2N2}2] (5)
To a freshly prepared NaSeC4H(Me-4,6)2N2 [from toluene–
methanol solution of [{SeC4H3(Me-4,6)2N2}2] (300 mg, 0.81 mmol)
and NaBH4 (66 mg, 1.74 mmol) in methanol], CdCl2 (145 mg,
0.79 mmol) was added with stirring which continued for 2 h at
room temperature. The solvents were evaporated under vacuum.
The residue was thoroughly washed with water followed by ace-
tone and dried under vacuum to yield yellow powder (318 mg,
83%), m.p. 200 °C. Anal. Calc. for C12H14CdN4Se2: C, 29.74; H,
2.91%. Found: C, 29.06; H, 2.93%.
½CdCl2ðtmedaÞꢂ þ 2 NaSeC4HðR-4; 6ÞN2
Â
Ã
CdfSeC4HðR-4; 6Þ2N2g2ðtmedaÞ þ 2NaCl
ð1Þ
ð2Þ
ð3Þ
ƒƒƒ!
where R = H, Me
2.2.6. Preparation of [CdCl{SeC4H(Me-4,6)2N2}(tmeda)] (6)
½MCl2=HgCl2ðtmedaÞꢂ þ 2 NaSeC4HðMe-4; 6Þ2N2
To a suspension of 5 (250 mg, 0.52 mmol) in toluene–methanol
mixture, solid CdCl2 (95 mg, 0.52 mmol) was added and after stir-
ring for 3 h at room temperature, tmeda in excess was added in the
solution and stirred for 30 min. The solvent was evaporated in vac-
uum and the residue was extracted from dichloromethane and
recrystallized similar to 1 (357 mg, 77%), m.p. 148 °C. Anal. Calc.
for C12H23CdClN4Se: C, 32.01; H, 5.15%. Found: C, 32.43; H, 4.89%.
UV–Vis kmax (CH2Cl2): 285 nm. 1H NMR (CDCl3) d: 2.35 (s, Me);
2.48 (s, NMe2); 2.63 (s, NCH2ꢀ); 6.63 (ring proton). 13C{1H} NMR
(CDCl3) d: 23.5 (Me); 47.1 (NMe2); 56.6 (NCH2); 114.8 (CH-5);
166.2 (C-4,6); 175.8 (C-2) (ring carbons). 77Se{1H} NMR (CDCl3)
d: 198. 113Cd{1H} NMR (CDCl3) d: 342.
Â
Ã
MfSeC4HðMe-4; 6Þ2N2g2 þ 2NaCl
ƒƒƒ!
where M = Cd, Hg
Â
Ã
MfSeC4HðMe-4; 6Þ2N2g2 þ MCl2 þ tmeda
Â
Ã
2
MClfSeC4HðMe-4; 6Þ2N2gðtmedaÞ
ƒƒƒ!
where M = Cd, Hg
Electronic spectra of these complexes in dichloromethane
showed single absorption band in the region 266–287 nm with a
shoulder at ꢃ304 nm only in mercury derivatives (3, 4). The ob-
served absorption can be assigned to ligand-to-ligand charge
transfer transition in the selenolate ligand.
2.2.7. Preparation of [HgCl{SeC4H(Me-4,6)2N2}(tmeda)] (7)
The 1H and 13C{1H} NMR spectra displayed expected reso-
nances. The CH-5 proton and carbon-13 resonance are shielded
in complexes with respect to the corresponding resonance for
the diselenides. Similarly CH-4,6 proton and carbon NMR reso-
nances of 1 and 3 are shielded. The 77Se NMR spectra exhibited a
single resonance in the region 214–342 ppm as expected for selen-
olate complexes. The resonance for Hg complex appeared at lower
field as compared to the corresponding signals for cadmium deriv-
atives (e.g., 77Se NMR d: 214 (1 Cd) versus 254 (3 Hg) ppm and 331
(2 Cd) versus 342 (4 Hg)). The 77Se NMR resonances for the chloro
complexes (6, 7) showed significant shielding with respect to the
corresponding bis derivatives (2 and 4) due to the presence of
chloro ligand. Both 113Cd{1H} and 199Hg{1H} NMR spectra showed
single resonances indicating the presence of a single molecular
Prepared in a similar fashion to 6 employing [Hg{SeC4H(Me-
4,6)2N2}2] (360 mg, 0.63 mmol), HgCl2 (171 mg, 0.63 mmol) and
tmeda (excess) and the resulting complex was recrystallized from
dichloromethane–hexane as colorless crystals (yield 561 mg, 83%),
m.p. 124 °C. Anal. Calc. for C12H23ClHgN4Se: C, 26.78; H, 4.31%.
Found: C, 27.01; H, 4.72%. UV–Vis kmax (CH2Cl2): 266 nm. 1H NMR
(CDCl3) d: 2.30 (s, Me); 2.44 (s, NMe2); 2.61 (s, NCH2–); 6.70 (ring
proton). 13C{1H} NMR (CDCl3) d: 23.6 (Me); 46.5 (NMe2); 56.8
(NCH2); 116.0 (CH-5); 166.5 (C-4,6); 171.2 (C-2) (ring carbons).
77Se{1H} NMR (CDCl3) d: 247. 199Hg{1H} NMR (CDCl3) d: ꢀ1218.
2.3. Preparation of metal selenide nanoparticles
To a pre-heated (250 °C) TOPO (3 g) in a three necked flask,
a
solution of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) (100 mg,
Table 2
0.17 mmol) in OA (3 ml) was injected rapidly with vigorous stirring
under flowing argon (experiment 1). The temperature was dropped
to 220 °C, was raised to and maintained at 230 °C for 30 min. The
hot solution was cooled down rapidly to 70 °C and methanol
(20 ml) was added to get a reddish precipitate, which was washed
thoroughly with methanol, followed by centrifuging and drying
under vacuum. Red CdSe was extracted in toluene and evaporated
under vacuum. Similar experiment was also performed in OA
(experiment 2).
Similarly, [Hg{SeC4H(Me-4,6)2N2}2] (4) (90 mg, 0.16 mmol) was
pyrolysed in OA (3 ml)/OA (3 ml) (experiment 3) at 100 °C for
30 min and black precipitate was washed with methanol, followed
by centrifuging and drying under vacuum to give a black powder.
Selected bond lengths (Å) and angles (°) for [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2).
Molecule a
Molecule b
Cd1–Se1
Cd1–N1
Cd1–N2
Se1–C4
2.6247(10)
2.428(7)
2.651(8)
1.907(9)
Cd2–Se2
Cd2–N4
Cd2–N5
Se2–C13
2.6123(10)
2.426(9)
2.672(9)
1.895(9)
Se1–Cd1–Se1i
Se1–Cd1–N1
Se1–Cd1–N1i
Se1–Cd1–N2
Se1–Cd1–N2i
Se1i–Cd1–N1
Se1i–Cd1–N1i
Se1i–Cd1–N2
Se1i–Cd1–N2i
N2–Cd1–N1
N2–Cd1–N1i
N2–Cd1–N2i
N1–Cd1–N2i
N2i –Cd1–N1i
N1–Cd1–N1i
140.15(6)
105.37(18)
105.88(19)
62.92(19)
95.99(18)
105.88(19)
105.37(18)
95.99(18)
62.92(18)
85.0(3)
Se2–Cd2–Se2ii
Se2–Cd2–N4
Se2–Cd2–N4ii
Se2–Cd2–N5
Se2–Cd2–N5ii
Se2ii–Cd2–N4
Se2ii–Cd2–N4ii
Se2ii–Cd2–N5
Se2ii–Cd2–N5ii
N5–Cd2–N4
139.81(6)
106.62(19)
104.9(2)
62.48(19)
96.27(19)
104.9(2)
106.62(19)
96.27(19)
62.49(19)
85.3(3)
3. Results and discussion
154.3(3)
118.0(4)
154.3(3)
85.0(3)
N5–Cd2–N4ii
N5ii–Cd2–N5
N4–Cd2–N5ii
N5ii–Cd2–N4ii
N4ii–Cd2–N4
153.2(3)
118.2(4)
153.2(3)
85.3(3)
3.1. Synthesis and spectroscopy
Treatment of [CdCl2(tmeda)] with two equivalents of sodium
salts of 2-pyrimidyl selenolate, NaSeC4H(R-4,6)2N2 (prepared
75.5(4)
75.6(4)

R.K. Sharma et al. / Inorganica Chimica Acta 411 (2014) 90–96
93
Molecule b
Molecule a
(a)
(b)
(c)
Fig. 1. (a) ORTEP drawing of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) with atomic number scheme. Ellipsoids are drawn with 25% probability and hydrogen atoms are omitted for
clarity. (b) and (c) packing along b and c axis.
(a)
(b)
Fig. 2. (a) ORTEP drawing of [Hg{SeC4H(Me-4,6)2N2}2] (4) with atomic number scheme. Ellipsoids are drawn with 50% probability and hydrogen atoms are omitted for clarity.
(b) Packing diagram showing inter molecular interaction. Selected interatomic parameters : Hg1- Se1, 2.463(2) Å; Hg1– Se2, 2.454(2) Å; Se1– C1, 1.933(13) Å; Se2– C7,
1.918(14) Å. Se1– Hg1– Se2, 169.22(6)o; C1– Se1– Hg1, 91.3(4)o; C7– Se2– Hg1, 91.9(5)o.

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R.K. Sharma et al. / Inorganica Chimica Acta 411 (2014) 90–96
120
80
40
0
400
300
200
100
0
(111)
(002)
(101)
(220)
(311)
(100)
(110)
(112)
(103)
(200)
(331)
(400)
10
20
30
40 50
60
70
10
20 30
40
2θ
50 60
70
2
θ
Fig. 5. XRD patten of HgSe NPs obtained by pyrolysis [Hg{SeC4H(Me-4,6)2N2}2] (4)
in OA at 100 °C for 30 min.
Fig. 3. XRD pattern of CdSe nanoparticles obtained by pyrolysis [Cd{SeC4H(Me
4,6)2N2}2(tmeda)] (2) in OA/TOPO at 230 °C for 30 min.
species in solution. The resonance for chloro complexes are signif-
icantly deshielded than the corresponding bis derivatives (e.g.,
113Cd{1H} NMR d: 213 (for 2) and 352 (for 6); 199Hg{1H} NMR d:
ꢀ1521 (for 4) and –1218 (for 7) ppm) owing to the strong – I effect
of the chloro ligand. The observed 113Cd{1H} and 199Hg{1H} NMR
chemical shifts are within the expected region of metal chalcogen-
olates [17,29,30].
of one molecule and the nitrogen atoms of pyrimidine rings of
neighboring molecule (Fig. 1b) molecule leading to the formation
of infinite stack (Fig. 1c). The stacks are mutually perpendicular.
The molecular structure of [Hg{SeC4H(Me-4,6)2N2}2] (4)
(Fig. 2a) is similar to [Hg{SeC5H3(Me-3)N}2] [17] but shows devia-
tion from linearity. The Se–Hg–Se angle is 169.22° while in the lat-
ter this angle is 180°. There are short contacts between N2 of one of
the pyrimidine rings of one molecule and Hg (N2–Hg = 2.914 Å) of
another molecule, whereas other pyrimidine ring is aligned with
3.2. Molecular structures
one of the pyrimidine rings of another molecule through
p–p
stacking (inter planar distance 3.528 Å). The deviation of the Se–
Hg–Se angle from linearity may be due to the repulsions between
The crystal and molecular structures of [Cd{SeC4H(Me-4,6)2N2-
}2(tmeda)] (2) and [Hg{SeC4H(Me-4,6)2N2}2] (4) were determined
by single crystal X-ray diffraction analyses. Selected bond lengths
and angles are given in Table 2, while ORTEP drawings with
crystallographic numbering scheme are shown in Figs. 1 and 2.
All C–C, C–N, and C–Se distances are similar to those reported in
literature [31].
the
p cloud of pyrimidine ring on one side and lone pairs of Se1 and
Se2 on other side. The Hg–Se bond length (2.4585 Å) are smaller
than that reported in [Hg(SeC5H4N)2(tmeda)] (2.4955 Å) [17] and
[Hg{SeC5H3(Me-3)N}2] (2.4629 Å) [17].
3.3. Thermal studies
There are two independent molecules of [Cd{SeC4H(Me-4,6)2
N2}2(tmeda)] (2) (Fig. 1a) in the crystal lattice each of them have
a similar configuration, but differ slightly in various interatomic
parameters. It acquires a distorted octahedral configuration in
which cadmium atom is surrounded by three chelating ligands,
viz. two SeC4H(Me-4,6)2N2 through N, Se and ‘‘tmeda’’. The overall
configuration is similar to analogus 2-selenopyridine complex,
[Cd(SeC5H4N)2(tmeda)] [17]. The Cd–Se bond lengths (2.6247 Å
and 2.6123 Å) are shorter than reported in [Cd(SeC5H4N)2(tmeda)]
(2.73 Å) [17] and slightly longer than that reported in [Cd(Se
COPh)2(tmeda)] (2.5859(6) Å) [32] and [Cd(SeOx)2] (Ox = 2-(4, 4-
dimethyl-2-oxazolinyl)benzene) (ꢃ2.55 Å) [33]. The Cd–N (pyrim-
idyl) bond length (av 2.66 Å) is longer than Cd–N(tmeda) (2.427 Å)
which may due to strain in four-membered ring in the former as
compared to the five membered ring in the later. The packing dia-
gram shows short contacts/interactions (N2–H1A-C1 = 2.744 Å and
N5—H10A-C10 = 2.786 Å) between the methylene goup of tmeda
The TG analysis (supplementary information) of [Cd{SeC4H(Me-
4,6)2N2}2(tmeda)] (2) under flowing argon showed that the com-
plex underwent a two-step decomposition. The first step corre-
sponds to loss of tmeda (weight loss found: 17.3%, calcd. for
tmeda: 19.3%) and the second step shows formation of CdSe
(weight loss found: 48.8%, calcd. for the formation of CdSe: 43%).
3.4. Metal selenide nanomaterials
Thermolysis of [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) in OA/
TOPO or OA were carried out at 230 °C under an argon atmosphere
afforded a red precipitate which was characterized as hexagonal
phase of CdSe from XRD pattern [JCPDS File No. 08-0459] (Fig. 3)
and EDX analysis [Se/Cd atom ratios are 1.05 and 1.07 in OA/TOPO
and OA, respectively]. The diffraction peaks at 23.9, 25.3, 27.1, 42.0,
b
a
(110)
(112)
(205)
20 nm
Fig. 4. (a) TEM image and (b) SAED pattern of CdSe nanoparticles obtained by pyrolysis [Cd{SeC4H(Me-4,6)2N2}2(tmeda)] (2) in OA/TOPO at 230 °C for 30 min.

R.K. Sharma et al. / Inorganica Chimica Acta 411 (2014) 90–96
95
a
(311)
b
(511)
(220)
100 nm
Fig. 6. (a) TEM image and (b) SAED patten of HgSe NPs obtained by pyrolysis [Hg{SeC4H(Me-4,6)2N2}2] (4) in OA at 100 °C for 30 min.
45.8 and 49.7 can be assigned to the (100), (002), (101), (110),
(103) and (112) planes of bulk hexagonal phase of CdSe. The
broadening of the diffraction peaks indicates that the sample is
nanosized. The average diameters estimated by Scherrer formula1
for the CdSe particles prepared in OA/TOPO and OA are 15 and
20 nm, respectively. The TEM image (Fig. 4a) of cadmium selenide
obtained from OA/TOPO revealed irregular size with a diameter of
8–20 nm while in OA a mixture of spherical and elliptical shaped
morphologies with minor axis of 15 nm and major axis of 20–
30 nm is formed (supplementry information). The SAED pattern
(Fig. 4b) revealed that NPs are polycrystalline in nature. SAED pat-
terns showed set of lattice planes, (205), (112), (110) correspond-
ing to hexagonal phase which are consistent with the phases
determined by XRD. The absorption spectra of OA/TOPO and OA/
OA capped NPs obtained by pyrolysis of 2 at 230 °C displayed broad
peak at 650 and 665 nm, respectively which are blue shifted with re-
spect to the bulk CdSe (kmax = 713 nm).
The thermolysis of [Hg{SeC4H(Me-4,6)2N2}2] (4) in OA at 100 °C
yields a black residue, XRD pattern (Fig. 5) of which displayed
broad peaks corresponding to cubic phase of HgSe (JCPDS File
No. 73-1668, EDX analysis: Se/Hg atom ratio: 0.98). The average
particle size estimated from Scherrer formula is 15 nm. The TEM
image (Fig. 6a) of HgSe nanoparticles revealed agglomerated
chunks composed of rod like morphology with an average diame-
ter of 22 nm and a length of 20–40 nm. The lattice planes (511),
(311) and (220) observed in SAED pattern (Fig. 6b) are in confor-
mity with the cubic phase of HgSe as inferred from XRD pattern.
Analytical Chemistry Division and (Mrs.) N. Raje for providing ther-
mogravimetric analyses data.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2013.11.018.
CCDC 949678 and 949677 for [Cd{SeC4H(Me-4,6)2N2}2(tmeda)]
(2) and [Hg{SeC4H(Me-4,6)2N2}2] (4), respectively contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK [Fax: +44 1223/336 033;
deposit@ccdc.cam.ac.uk].
E mail:
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