Synthesis and Reactivity of Selones and Dihaloselones: Complexation of Selones with d8- and d10-Metal Ions

Article abstract of DOI:10.1002/ejic.201700218

The reactivities of the monodentate selone LSe (L = 1,3-dibutylbenzimidazol-2-ylidene; 10a), the bidentate pyridine-functionalized selone L′Se (L′ = 1-pyridyl-3-butylimidazol-2-ylidene; 10b) and the multidentate ether-functionalized selone L′′Se {L′′ = 1,3-bis[2-(2-methoxyethoxy)ethyl]benzimidazol-2-ylidene; 10c} with soft transition-metal halides (PdX₂, PtX₂, ZnX₂, CdX₂ and HgX₂; X = Cl, Br, I) are probed. Compounds 10a and 10c react with metal halides to give complexes of the type [Cu₂(μ-X)₂(LSe)₂] (X = Br, I; 11, 12), [MX₂(LSe)₂] (13–22) or [M₂X₂(μ-X)₂(L′′Se)₂] (X = Cl, Br, I; 26–32), whereas 10b and HgX₂ (X = Cl, Br, I) form 1:1 complexes HgX₂(L′Se) (21–23), in which the pyridine moiety coordinates to the metal centre to form a six-membered chelate. The reactivity of 10a was compared with those of triphenylphosphine and triethylamine. The reaction of 10c with molecular iodine yields the diiodoselone L′′SeI₂ (35), which disproportionates to give the selone adduct of the iodonium ion, [(L′′Se)₂I]⁺I₃^– (36). The reactions of LSeX₂ [X = Cl (34a), Br (34b), I (34c)] with organotellurium compounds, namely, tellone LTe (10d) and diphenyl telluride (37), afford the dihalotellones LTeX₂ [X = Cl (38a), Br (38b), I (38c)] and Ph₂TeX₂ [X = Cl (39a), Br (39b), I (39c)], respectively. The oxidizing properties of LSeX₂ (34a–34c) were investigated with rare-earth metals.

Full text of DOI:10.1002/ejic.201700218

A Journal of
Accepted Article
Title: Synthesis and Reactivity of Selones and Dihaloselones:
Complexation of Selones with d8- and d10-Metal Ions
Authors: Harkesh B. Singh, Sangeeta Yadav, and Ray J Butcher
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Link to VoR: http://dx.doi.org/10.1002/ejic.201700218

10.1002/ejic.201700218
European Journal of Inorganic Chemistry
Synthesis and Reactivity of Selones and Dihaloselones: Complexation of
Selones with d8- and d10-Metal Ions
Sangeeta Yadav,[a] Harkesh B. Singh*[a] and Ray J. Butcher[b]
[a]
Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076,
India.
[b]
Department of Chemistry, Howard University, Washington, D. C. 20059, USA.
Keywords
Selone • Metal halide complex of selone • Halogenating agent
Abstract
The reactivity of monodentate selone, LSe (L = 1,3-dibutylbenzimidazol-2-ylidene,
C15H22N2)
(10a), bidentate pyridine-functionalized selone, L'Se (L' = 1-pyridyl-3-
butylimidazol-2-ylidene, C12H15N3) (10b) and multidentate ether-functionalized selone, L”Se
[L" = 1,3-bis{2-(2-methoxyethoxy)ethyl}benzimidazol-2-ylidene, C17H26N2O4] (10c) is
probed with soft transition metal halides (PdX2, PtX2, ZnX2, CdX2 and HgX2; X = Cl, Br, I).
LSe (10a) and L"Se (10c), on treatment with metal halides give complexes of the type,
[Cu2(-X)2(LSe)2] (X = Br, I) (11, 12) or [MX2(LSe)2] (13-22) or [M2X2(-X)2(L”Se)2] (X =
Cl, Br, I) (26-32). Whereas, L'Se 10b and HgX2 (X = Cl, Br, I) form 1:1 complexes,
HgX2(L'Se) (21-23) where pyridine coordinates with metal centres to form a six-membered
chelate rings. The reactivity of LSe (10a) has been compared with triphenylphosphine, PPh3
and triethylamine, NEt3.
The reaction of 10c with molecular iodine yields diiodoselone, L"SeI2 (35), which
ˉ
disproportionates to give the selone adduct of iodonium ion, [(L"Se)2I]+I3 (36). The reactions
1
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of LSeX2 {(X = Cl (34a), X = Br (34b), X = I (34c)} with organotellurium compounds,
namely tellone, LTe (10d) and diphenyl telluride, Ph2Te (37) afford dihalotellones, LTeX2
{(X = Cl (38a), X = Br (38b), X = I (38c)} and diphenyltellurium dihalide, Ph2TeX2 {(X = Cl
(39a), X = Br (39b), X = I (39c)} respectively. The hydrogenating/oxidizing property of
LSeX2 (34a-34c) is further investigated with rare earth metals.
Introduction
Chalcogenones (LE where, L = carbene, E = S, Se, Te), the carbene derivatives of
chalcogens (S, Se, Te), have attracted considerable current interest due to their application in
various fields. For example, selenoneine (1),1 which has been isolated from the blood and
tissues of tuna, has strong antioxidant capacity. It also reacts with methyl mercury halides.2
Brumaghim and coworkers have shown that coordination of thiones and selones inhibits
,
copper mediated oxidative damage and the chalcogenone ligands resemble selenoneine.3 4
Mugesh and coworkers have reported that selones (2a-2d) exhibit inhibitory activity towards
lactoperoxidase catalyzed oxidation and iodination reactions.5 Palmer and Parkin6 have
reported that the reaction of 1-methyl-1,3-dihydro-2H-benzimidazole-2-selone (2e) (Scheme
1), a structural analogue of selenoneine with methylmercury halides, results in cleavage of
the Hg-C bond. This observation provides a mechanism for mercury detoxification. Very
recently, Roy and coworkers7 have shown that suitably substituted thiones and selones (2a,
2f) could be used to detoxify various organomercurials. Williams and coworkers have studied
the selone complexes of zinc chloride as a potential zinc selenide synthon.8
2
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European Journal of Inorganic Chemistry
Scheme 1. Selenoneine (1) and related chalcogenones (2a-2f, 3-5)].
The dihalogen derivatives of chalcogenones (LEX2 where, L = carbene, E = S, Se, Te;
X = Cl, Br, I) find application in synthesis, biology, materials and industrial chemistry.9
Recently, while attempting to prepare dicationic diselenides, [L2Se2]2+ by the reaction of
dihaloselones with elemental tellurium, we observed facile halogenation of tellurium.10 The
monomeric tellurium tetrahalides were isolated as selone adducts. The polymer particles
containing imidazoline-2-selone show color-sensing for halogen and mercury ions.11
Similarly, the iodine adducts of compounds 3 and 4 react with mercury and gold to give
mercury(II) and gold(I) complexes.12 Aragoni et al. have reported that I2 adducts of
structurally related ligand tetraphenyldithioimido-diphosphinic acid (5), react with
mercury(0) to give HgI2 complexes of compound 5.13 Selones are excellent ligands for both
the main group elements and transition metals ions.14 Selone complexes of copper halides
have been well established in the literature, whereas, the solution studies and structural
characterization of the selone complexes of related d8- and other d10-metal halides are
limited.15 Recently, we have observed that selone complexes of metal halides, [MX2(LSe)2]
3
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are excellent precursors for the synthesis of dicationic diselenides, [L2Se2]2+[MX4]2-.
Controlled oxidation of the [MX2(LSe)2] with halogenating agents (SOCl2/Br2/I2) provides
the dicationic diselenides, [L2Se2]2+[MX4]2-.16 We have found this method to be a quite
general for the convenient synthesis of a broad range of dicationic diselenides. As a part of
these studies, it was envisaged to undertake a systematic study on the solution, structural and
reactivity aspects of the selone complexes of the d8- and d10-metal ions.
Result and discussion
Compounds 8a and 8c were prepared in ~80% yield by N-alkylation of benzimidazole (6)
with n-butylbromide (7a) and 1-bromo-2-(2’-methoxyethoxy) ethane (7c) respectively in
30% NaOH in the presence of phase-transfer catalyst (tetrabutylammonium bromide, TBAB)
(Scheme 2)7 Compounds 8a and 8c were purified by column chromatography (petroleum
ether: ethyl acetate, 3:1) and were characterized by NMR spectroscopic techniques.
Compound 8b was prepared by following the reported procedure.17 Compounds 8a-8c were
refluxed with alkyl bromides (7a-7c) in dry 1,4-dioxane for 12 h under nitrogen atmosphere
to produce white precipitates of 1,3-dialkylbenzimidazolium salts, 9a-9c in ~90% yield
(Scheme 2).7,16 Compounds 9a-9c were filtered and the precipitates were washed with ethyl
acetate to give the pure products. The reactions of precursors, 9a-9c, with in situ generated
Na2Se2 in presence of potassium tert-butoxide at room temperature, produced the selone
ligands (10a-10c) in ~80% yield (Scheme 2). Compounds 10a-10c were characterized by
NMR spectroscopic and mass spectrometric studies. The molecular structure of compound
10c was further confirmed by X-ray crystallographic studies (vide infra).
4
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European Journal of Inorganic Chemistry
Scheme 2 Synthesis and reactivity of monodentate, bidentate and multidentate selone ligands
(10a-10c).
Synthesis of selone complexes of metal halides:
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Monodentate selone (10a) was treated with one equivalent of transition metal halides (CuBr,
CuI, ZnCl2, ZnBr2, ZnI2, CdCl2, CdI2, HgCl2, HgBr2, HgI2, PdCl2 and PtCl2) in diethyl ether
to afford the precipitates of selone complexes (11-22) of metal halides (Scheme 2). The
precipitates were filtered and washed with diethyl ether to remove the impurities of the
starting materials. The precipitates were recrystallized from dichloromethane to give pure
complexes. Compounds 12, 13, 14, 20 and 21 have been characterized by X-ray
crystallographic studies (vide infra).
Similarly, when the bidentate selone (10b) was treated with mercuric halides (HgX2, X = Cl,
Br, I) in diethyl ether solvent at room temperature, after 6 hours of stirring, off-white
precipitates of selone complexes of mercuric halides (23-25) were obtained. Compounds 23-
25 were recrystallized from dichloromethane and were characterized by using various
spectroscopic techniques. Compound 25 was further characterized by X-ray crystallographic
studies. In the molecular structure of compound 25, it was observed that nitrogen of pyridyl
group also coordinates to mercury along with selenium to form a six membered chelate ring
(vide infra).
Subsequently, the reactions of the multidentate selone ligand (10c) were explored with
transition metal halides, CuI and MX2 (M = Zn, Cd, Hg; X = Cl, Br, I). Selone, 10c when
treated with one equivalent of CuI and MX2 to produced selone complexes (26-33) (Scheme
2). Complexes 30-33 were recrystallized from dichloromethane in 60-80% yields, whereas,
complexes 26-29 were semisolid in nature, therefore could not be recrystallized. The
structures of complexes 30-33 were further confirmed by X-ray crystallographic studies (vide
infra).
6
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Dihaloselones as halogenating agents:
Selone (10a) was halogenated by treating with one mole of molecular halogens (Cl2, Br2, I2)
to give dihaloselones 34a-34c. Selone, 10c was reacted with one equivalent I2 in dry THF at
o
0-5 C temperature to form diiodoselone 35. Compound 35 was characterized by various
NMR spectroscopic methods. During the process of crystallization, 35 disproportionates to
the give the selone complex of iodonium ion (36) (Scheme 2). Molecular structure of
compound 36 was confirmed by X-ray crystallographic studies (vide infra).
Dihaloselones on treating with tellurium(0) gave selone adducts of tellurium(IV)
tetrahalides.7 In view of the facile oxidation of Te(0) to Te(IV), it was planned to explore the
oxidative properties of dihaloselones (34a-34c) with organotellurium compounds, viz.
tellurone (10d) and diphenyltellurium (37). Dihaloselones (34a-34c), on treatment with 10d
and 37 in dry diethyl ether, gave oxidized compounds 38a-38c7 and 39a-39c18 respectively
(Scheme 3). Dihaloselones (34a-34c) oxidise tellurium centres of 10d and 37 from +2 to +4.
In these cases, the formation of the selone adducts of tellurium(IV) halides was not observed.
It is probably due to the higher stability of the C-Te bonds in 38a-38c and 39a-39c. The
dihalotellones (38a-38c) show different stability under ambient conditions. Dichlorotellone
(38a) and dibromotellone (38b) are sensitive towards light and temperature, whereas,
diiodotellone (38c) is stable under atmospheric conditions. Compounds 39a-39c are also
stable under atmospheric conditions. Compounds 39a and 39b can be stored in dark at low
temperature for long time. When tellone (10d) was halogenated with molecular halogen, the
reactions proceeded differently. Halogenation of tellone (10d) with I2 gave the same product
i. e. diiodotellone (38c), whereas with Br2 and Cl2, C=Te bond of tellone got cleaved.
Therefore, it can be stated that the halogenation of 10d using dihaloselones (34a-34c) is a
clean method to produce dihalotellones (38a-38c). Compounds 38a-38c and 39a-39c were
characterised by NMR spectroscopy and mass spectrometry. DFT calculations were
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performed to support the oxidizing and halogenating properties of dihaloselones. The overall
energy was calculated for the reaction of 10d with 34a to produce compound 38a. Here the
energy of products is 121.3 kcal/mol lower than the reactants. Similarly, the energy was
calculated for the reaction of 34a with 37 to produce compound 39a. Here the energy of
products is 67.7 kcal/mol lower than the reactants. Therefore, DFT calculations support the
oxidizing and halogenating nature of dihaloselones.
Reaction of diiodoselone (34c, 35) with lanthanides It has been discussed that
dihaloselones (34a-34c) have the tendency to oxidize transition metals as well as main group
elements.7,14 During the course of exploring the oxidizing nature of dihaloselones towards
rare earth metals, diiodoselone (34c) was treated with lanthanide metal powder (La and Sm)
in diethyl ether under inert conditions (Scheme 3). The reaction mixture turned colourless
from dark brown. The colourless reaction mixture was filtered and the filtrate was
characterized to be selone (10a). This observation indicated that, though, diiodoselone has
been reduced to selone, the desired coordination complexes of lanthanides and selone could
not be isolated and characterused. Presumably, because of the hard nature of lanthanides, soft
selone ligands do not coordinate to it. The resulting metal products were not further
characterized. To bring the selenium and lanthanide metal centres in close proximity, suitably
designed ligand containing several oxygen donors, 35 was reacted with La and Sm powder.
However, the reactions afforded similar results.
8
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Scheme 3. Dihaloselones as halogenating/oxidizing agents.
Comparison of the reactivity of selones with triphenylphosphine and triethylamine
After exploring the reactivity of dihaloselones (10a-10c) with organotellurium
compounds, lanthanide powders (La, Sm) and transition metal halides, it was planned to
compare the reactivity of selone 10a with triphenylphosphine and triethylamine. The metal
halide complexes of triphenylphosphine (40a-40f),19 selone (13, 16, 18-21) and triethylamine
(41a-41j)20 were prepared by treating metal halides with PPh3, selone and NEt3 respectively
in diethyl ether solvent (Scheme 4). For the reactivity comparison, the following experiments
were performed; (i) selone complexes (13, 16, 18-21) of metal halides were treated with
triphenylphosphine. After 15 min, the selone ligand was completely substituted by PPh3 to
produce triphenylphosphine complexes of metal halides (40a-40f, Scheme 4). (ii) Complexes
40a-40f were stirred with selone (10a) at room temperature in diethyl ether solvent. No
change in the reaction mixture was observed even after 24 h and the starting materials were
recovered. (iii) The selone complexes of metal halides (13, 16, 18-21) were treated with
triethylamine in diethyl ether at room temperature. After 24 h, the starting materials were
recovered without any change in the reaction mixture. (iv) Compounds 41a-41j were reacted
with selone. After 15 min, precipitates of the selone complexes of metal halides (13, 16, 18-
21) were obtained. From these experiments it can be concluded that, selone (10a) is more
reactive than triethylamine and is less reactive than triphenylphosphine. At the same time
selone ligand is more labile than triphenylphosphine. Selone complexes of metal halides are
very stable under ambient conditions, therefore, these adducts (13, 16, 18-21) can be used as
effective metal halide transferring reagents.
9
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European Journal of Inorganic Chemistry
Scheme 4 Reactivity comparison of selone (10a) with triphenylphosphine and triethylamine.
Spectroscopic studies
1
Compounds 9a-9c exhibit their characteristic carbene precursor CH signals in H NMR
13
spectra at ~10.5 ppm, which disappear in compounds 10a-10c. The signal for NCN in C
NMR spectra of compounds 9a-9c at ~143 ppm is shifted downfield in selones (10a-10c),
because of the deshielding caused by the donation of electron density from carbene to
selenium. The selone complexes of metal halides showed upfield 77Se NMR signals as
compared with the selones. Compounds 13, 14 and 15 showed signals in 77Se NMR spectra at
-60 ppm, -29 ppm and 8 ppm respectively. This upfield shift may be interpreted in terms of
the π-accepter nature of the selones. Ganter and coworkers,21 have used the variation in the
77Se NMR chemical shifts of selones to determine the π-acceptor properties of N-heterocyclic
carbenes.
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This is corroborated from the changes observed in the C-Se bond lengths of the metal
complex (Table 2) (vide infra). The C-Se bond lengths are longer in the complexes than the
corresponding selone, while the C-N bond lengths are shorter in complexes than selone. It is
probably due to the back donation from metal to selone. As a result of this, the double bond
character in the neighbouring C-N bond increases and the C-N bond length decreases (vide
infra). This has been further supported by NBO analysis (Table S5). It is observed that for
77
compounds 13, 14 and 15, the signals in Se NMR shift more upfield from iodo- to bromo-
to chloro. For palladium and platinum complexes (21, 22), the chemical shifts are downfield
77
than the selone. In Se NMR spectrum, the signal obtained at 57 ppm for compound 10b
shifted upfield in compound 23 (7 ppm) and 24 (18 ppm) due to the shielding because of the
back donation from mercury to selenium. While in compound 25 (67 ppm), there is a small
upfield shift in Se signal that is because of the decreased extent of back donation than
77
compounds 23 and 24. Similarly, in Se NMR spectrum, the signal was obtained at 58 ppm
for compound 10c, which shifted upfield in the selone complexes of metal halides (24-30) as
compared to 10c. The pattern of change in chemical shifts is similar to the metal halide
complexes of 10a. 125Te NMR spectra showed a large downfield shift from tellone (10d) to
dichlorotellone (35a), dibromotellone (35b) and diiodotellone (35c), i. e. -165 ppm, 909 ppm,
698 ppm and 332 ppm respectively. From compound 35a to 35c there is upfield shift in 125Te
NMR signal due to the electronegativity change from Cl to I. Signals in 125Te NMR spectra
for compounds 39a, 39b and 39c are observed at 918, 883 and 826 ppm respectively, which
are comparatively downfield than diphenyltelluride (34) i. e. 688 ppm. There is an upfield
shift in 125Te NMR signal from compound 39a to 39c.
Table 1. 13C and 77Se NMR chemical shifts for compounds 10a-10c, 11-33 and 35-36.
Compound
No.
C=Se signal
in 13C NMR
Selenium
signal in 77Se
Compound
No.
Carbene
carbon signal signal in 77Se
Selenium
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(ppm)
NMR (ppm)
in 13C NMR
(ppm)
NMR (ppm)
165.15
155.24
165.62
154.37
-
53
57
59
-21
37
-60
-29
8
154.52
149.26
149.38
149.09
159.65
160.59
-
121
7
10a
10b
10c
11
22
23
24
25
26
27
28
29
30
31
32
33
35
36
19
67
1
12
-
17
-13
32
-28
-16
9
13
153.93
156.88
158.54
156.76
154.83
155.75
157.73
157.26
14
163.15
155.35
150.29
151.83
155.11
147.60
147.31
15
-24
-29
-9
16
17
18
8
50
141
158
19
34
152
20
21
X-ray crystallographic studies
Molecular Structure of 10c: The molecular structure of 10c is shown in Figure 1a. The C1-
Se bond length is 1.838(1) Å, which is similar to the reported C-Se bond length in selones.22
The bond angles between N2-C1-Se is 126.36(10)o. There is no intramolecular interaction
between ether groups and Se.
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(a)
(b)
(c)
(d)
Figure1. Molecular structures of complexes: (a) 10c, (b) 12, (c) 13 and (d) 14. Hydrogen
atoms are omitted for clarity.
Molecular structure of 12: The molecular structure of compound 12 is shown in Figure 1b.
The complex crystallizes as a dimer. The central (SeCuI)2 unit is planar. Cu-Se bond length
is 2.331(1) Å which is similar to the Cu-Se bond length (2.335(1) Å) for the selone
]
complexes of cuprous iodide reported in literature.[23 In this molecule, both the Cu-I
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distances differ from each other, i. e. 2.537(1) Å and 2.640(1) Å. The bond angles I-Cu-I and
Cu-Se-C1 are 119.795(21)o and 111.50(11)o respectively.
Molecular structures of 13, 14: The molecular structures of complexes 13 and 14 are shown
in Figure 1c and 1d. The geometry around zinc is tetrahedral in both the complexes. In
complex 13, the Zn-Se bond lengths are 2.468(2) Å and 2.472(2) Å. The Zn-Cl bond lengths
are 2.256(2) Å and 2.250(2) Å. The bond angles around Zn, viz. Se(1)-Zn-Se(2), Se(1)-Zn-
Cl(1) and Cl(1)-Zn-Cl(2) are 120.19(10)o, 109.58(10)o, 117.51(10)o respectively. In
compound 14, the Zn-Se bond lengths are 2.465(1) Å and 2.482(1) Å. Zn-Br bond lengths are
2.402(1) Å and 2.396(1) Å. Bond angles around Zn, viz. Se(1)-Zn-Se(2), Se(1)-Zn- Br(1) and
Br(1)-Zn-Br(2) are 120.00(03)o, 108.121(03)o and 118.81(04)o respectively.
Table 2. Selected bond lengths and bond angles for compound 10a, 12, 13, 14, 20 and 21.
10a7
12
13
14
20
21
Se-M (Å)
Se-C (Å)
-
2.331(1)
1.872(3)
1.353(5)
2.537(1)
2.640(1)
-
2.468(2)
1.897(7)
1.335(1)
2.256(2)
2.250(2)
2.465(8)
1.877(5)
1.357(6)
2.4021(8)
2.3958(7)
2.692(1)
1.837(1)
1.348(1)
2.750(1)
2.766(1)
2.431(2)
1.893(19)
1.33(2)
2.315(4)
2.315(4)
180.00
1.831
C-N (Å)
1.364
M-X1 (Å)
M-X2 (Å)
Se-M-Se (o)
M-Se-C (o)
Se-C-N (o)
-
-
-
-
120.19(04) 120.00(03) 107.28(05)
111.50(11) 107.00(20) 103.42(15) 93.90(30) 102.10(60)
128.40(30) 125.40(50) 125.00(40) 128.00(80) 126.50(14)
Molecular structure of 25: The molecular structure of compound 25 is shown in Figure 2a.
The geometry around Hg is tetrahedral. Nitrogen from pyridine is bonded with Hg along with
the Se to form a six-membered non-planer chelate ring. Hg-N1, Hg-Se1 and Se1-C6 bond
lengths are 2.617(4), 2.583(1) and 1.881(5) Å respectively. C6-Se1-Hg and Se1-Hg-N1 bond
angles are 90.14(16) and 81.86(10) o respectively.
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Molecular structures of 30, 31 and 32: The molecular structures of compounds 30, 31 and
32 are shown in Figure 2b-2d respectively. The geometry around Cd and Hg atoms is
tetrahedral. The C-Se bond lengths are 1.871(8), 1.879(8) Å and 1.905(22) for compounds
30, 31 and 32 respectively, which are considerably longer than C-Se {1.838(1) Å} in selone
(10c). For compounds 30 and 31, Cd1A-Se1A, Hg1-Se1 and Hg1A-Se1A bond lengths are
2.632(1), 2.528(1) and 2.556(2) Å respectively. The M-Se bond distance in cadmium
complex (30) {2.632(1) Å} is comparatively longer than the mercury complex (33) {2.600(3)
Å} (ESI) which indicates a better overlap of orbitals between Hg and Se than Cd and Se due
to "soft"-"soft" interactions. Similar observations have been reported in the selenolato
complexes of metal halides.24 In these molecules all three M-X (X = Cl, I) distances differ
with each other. These compounds are dimeric in nature where one Cl/I is acting as a
bridging ligand. At the same time, no interaction was observed between oxygen and
cadmium/mercury (Figure 2b-2d). These results have been supported by DFT calculations.
The geometry of compound 30 and the expected compound 30a, where ether group is
coordinating with the metal centre (Scheme S1), was optimized in gas phase by using
MPW1PW91 method and TZVP basis set for Cd, Lanl2dz ECP basis set for I and 6-311g(d)
basis set for rest of the atoms. The optimized geometry of 30 was well in agreement with
crystal structure (Table S6). The ground state energy of compound 30 is 19.25 kcal/mol lower
than the energy of 2 moles of compound 30a. This energy difference does not support the
coordination between oxygen of the side chain and cadmium metal centre.
15
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European Journal of Inorganic Chemistry
(a)
(b)
(c)
(d)
Figure 2. Molecular structures of compounds: (a) 25, (b) 30, (c) 31 and (d) 32.
Table 3 Bond lengths (Å) and bond angles (o) of compounds 25 and 30-33.
25
1.881(5)
2.583(1)
2.691(1)
2.732(1)
2.617(4)
90.14(16)
-
30
31
32
33
C-Se
Se-M
1.871(8)
2.632(1)
2.882(1)
2.702(1)
-
1.878(8)
2.528 (1)
2.388(2)
2.728 (1)
-
1.905(22)
2.556(2)
2.532(2)
2.742(3)
-
1.884(19)
2.600(3)
2.691(2)
2.915(2)
-
M-X1
M-X2
Hg-N1
C-Se-M
Se-M-X1
Se-M-X2
95.12(22)
106.32(03)
116.99(03)
95.36(01)
130.47(10)
112.45 (04)
96.12(58)
124.24(10)
106.27(10)
95.41(62)
111.33(10)
120.11(10)
-
16
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Se1-Hg-N1
81.86(10)
-
-
-
-
Molecular structure of compound 35: The molecular structure of compound 35 is shown in
Figure 3a. The geometry around I is linear. The C1B-Se2 bond length is 1.871(2) Å, which is
considerably longer than C-Se {1.838(1) Å} in selone (10c), whereas, it is equal to the C-Se
bond length {2.877(5) Å} in selone adduct of iodonium ion.25 I1-Se2 and I2-Se1 bond
lengths are 2.767(1) and 2.795(1) Å respectively which are comparable with the reported Se-I
{2.804(7) Å}.19 I21-I22 {2.928(1) Å} is also close to the reported I1–I2 {2.909(5) Å}. C1A-
o
o
Se1-I1 {99.59(06) } is equal to the reported C1-Se-I {99.28(2) }, Se1-I1-Se2 bond angle
o
o
{178.61(01) } is as little distorted than the reported Se-I-Se {180.00 }.19 I22-I21-I22 bond
angle is 180.00(01)o.
Molecular structure of compound 38b: The molecular structure of compound 38b is shown
in Figure 3b. The geometry around Te is T-shaped. C1A-Te1A, Br1A-Te1A and Br2A-Te1A
bond lengths are 2.099(6) Å, 2.677(1) Å and 2.757(1) Å respectively. The bond angles
between Br1A-Te2A-Br2A, Br1A-Te2A-C1A and Br2A-Te2A-C1A are 165.34(3)o,
85.15(17)o and 82.36(17)o respectively.
Molecular structure of compound 39a: The molecular structure of compound 39a is shown
in Figure 3c. This compound crystallizes in orthorhombic crystal system. The molecular
structure is monomeric unlike the reported structure of (4-MeC6H5)2TeCl2.17a The geometry
around Te is seesaw. Cl1-Te1, Cl2-Te1, C1-Te1 and C1A-Te1 bond lengths are 2.534(1),
2.484(1), 2.115(2), and 2.112(2) Å respectively which are comparable with the reported for
(4-MeC6H5)2TeCl2 i. e. 2.538(2), 2.492(2), 2.129(3) and 2.103(3) Å respectively. The bond
angles between Cl1-Te1-Cl2, Cl1-Te1-C1 and C1-Te1-C1A are 174.97(2), 88.27(5) and
o
99.10(7) respectively which is close to the reported i. e. 174.85(3), 87.66(8) and 98.71(11)
respectively.
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(a)
(b)
(c)
Figure 3. Molecular structures of compounds (a) 35, (b) 38b and (c) 39a.
Conclusions
Selones (10a-10c) form complexes on treating with d8, d10 transition metal halides. Pyridine
of pyridine-functionalized bidentate selone (10b) coordinates with Hg metal centre and forms
six membered chelate ring. Whereas, there is no coordination observed between the ether
groups of ether-functionalized multidentate selone (10c) and metal centre. It was observed
From DFT calculations that the energy of the selone complex with coordination between
ether group and cadmium (30a) is 19.25 Kcal/mol higher in energy than the complex without
coordination between ether group and cadmium (30), which causes the destabilization of
compound 30a. To study the halogenating properties, dihaloselones (34a-34c) have been
reacted with tellone (10d) and diphenyl telluride (37) and expected halogenated compounds
(38a-38c and 39a-39c respectively) were formed. DFT calculations have supported the
halogenating nature of dihaloselones. The oxidizing property of dihaloselones was further
explored with lanthanides. In course of this, diiodoselone (34c) was reacted with La/Sm
powder. Diiodoselone (34c) oxidized La/Sm and itself got reduced to selone (10a), However,
selone did not coordinate with lanthanum to produce selone complex of lanthanum halide.
Diiodoselone 35 on reacting with La/Sm powder gave similar results as 34c with lanthanides
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10.1002/ejic.201700218
European Journal of Inorganic Chemistry
and again there was no coordination observed between selone and lanthanides. The reactivity
of selones has been compared with PPh3 and NEt3. Selone can substitute triethylamine from
the metal halide complexes, whereas it cannot substitute triphenylphosphine. The trend of
substitution of ligands may also be due to preferential stability of the metal complexes.
Selone complexes of metal halides exhibit high stability towards air and moisture, therefore,
these selone complexes of metal halides can be used as effective metal halide transferring
reagents.
Computational Details
]
All the structures were optimized with Gaussian 09[26 program by using MPW1PW91
method and TZVP basis set for Zn and Cd, Lanl2dz ECP basis set for I, 3-21g(d) basis set for
Te and 6-311g(d) basis set for rest of the atoms. Frequency calculations were used to confirm
that the reported structures are minima on the respective potential energy surfaces.
Experimental Section
All the manipulations were carried out under nitrogen or argon atmosphere using standard
Schlenk techniques unless otherwise noted. Solvents were purified and dried by standard
procedures and were distilled prior to use. Melting points were recorded on a Veego VMP-I
1
melting point apparatus in capillary tubes and were uncorrected. H (400 MHz) and 13C
(100.56 MHz) nuclear magnetic resonance spectra were recorded on Varian VXR 400S and
Bruker AV 400 spectrometers at 25 oC. The 77Se (76.3 MHz) and 125Te (157.97 MHz) spectra
were recorded on a Varian VXR 300S and Bruker AV 400 spectrometers. Chemical shifts are
13
cited with respect to Me4Si as internal standard (1H and C) and Me2Se (77Se) and Me2Te
(125Te) as external standards. Elemental analyses were performed on a Carlo Erba Model
1106 elemental analyser. The ESI mass spectra recorded on a Q-Tof micro (YA-105) mass
spectrometer.
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Synthesis of compound 8c: The starting material benzimidazole (6) (3.22 g, 27.30 mmol)
was dissolved in 30% aq. NaOH (20 mL) and TBAB (0.03 g, 0.06 mmol) was added to it
where further in that colourless solution 1-bromo-2-(2’-methoxyethoxy) ethane (7c) (5 g,
27.30 mmol) was added at room temperature via syringe. The reaction mixture was stirred
continuously for 6 hrs then was poured into 10 mL water and extracted with toluene solvent
(20 mL × 3). The organic layer was washed with water and dried over Na2SO4 and solvent
1
was evaporated. Yield : 5.04 g, (84%). H NMR (400 MHz, CDCl3): (ppm) 8.01 (s, 1H),
7.82-7.80 (m, 1H), 7.43-7.40 (m, 1H), 7.32-7.25 (m, 2H), 4.37 (t, J = 5.24 Hz, 2H), 3.84 (t, J
13
= 5.24 Hz, 2H), 3.56 (t, J = 3.85 Hz, 2H), 3.47 (t, J = 3.85 Hz, 2H), 3.33 (s, 3H). C NMR
(100 MHz, CDCl3) : 143.87 (NCN), 122.93, 122.17, 120.47, 109.65, 72.00, 70.87, 69.58,
59.23, 45.09. ESI-MS (positive mode): [M+H]+ m/z = 221.1280 (observed), 221.1285
(calculated).
Synthesis of compound 9c: A solution of (7c) (1.98 g, 10.16 mmol) and N-alkylated
benzimidazole (8c) (2.39 g, 10.16 mmol) in 1,4-dioxane was refluxed under nitrogen
atmosphere for 24 hrs. Then the solvent was removed and the solid residue was washed with
ethyl acetate followed by the washing with diethyl ether. The white solid obtained was dried
1
under vacuum. Yield : 3.73 g, (95%). H NMR (400 MHz, CDCl3): (ppm) 10.72 (s, 1H),
7.96-7.91 (m, 2H), 7.64-7.61 (m, 2H), 4.87 (t, J = 4.92 Hz, 4H), 4.08 (t, J = 4.92 Hz, 4H),
13
3.69 (t, J = 4.52 Hz, 4H), 3.49 (t, J = 4.52 Hz, 4H), 3.29 (s, 6H); C NMR (100 MHz,
CDCl3): (ppm) 142.71 (NCN), 131.70, 126.84, 113.84, 77.64, 70.38, 68.67, 58.87, 47.76;
ESI-MS (positive mode): [M-Br]+ m/z = 323.1967 (observed), 323.1965 (calculated).
Synthesis of compound 10b: Compound 9b (1.00 g, 3.55 mmol), was added into the brown
solution of in situ generated Na2Se2 (0.36 g, 1.77 mmol) in THF (30 mL) under nitrogen
atmosphere and stirred for 6-8 hrs. at room temperature. Then potassium tert-butoxide (0.40
g, 3.55 mmol) was added to the reaction mixture and stirred for further 5-7 hrs. The reaction
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10.1002/ejic.201700218
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mixture was quenched by adding water (20 mL) and compound was extracted with diethyl
ether, dried over sodium sulphate and the solvent was evaporated to get yellow oil. Yield:
1
0.87 g, (87%). H NMR (500 MHz, CDCl3): (ppm) 8.94-8.92 (m, 1H), 8.49-8.48 (m, 1H),
7.87-7.84 (m, 1H), 7.64 (d, J = 2.45 Hz, 1H), 7.31-7.29 (m, 1H), 7.83 (d, J = 2.45 Hz, 1H),
13
4.21 (t, J = 7.55 Hz, 2H), 1.83 (m, 2H), 1.42 (m, 2H), 0.98 (t, J = 7.40 Hz, 3H); C NMR
(126 MHz, CDCl3): (ppm) 155.24 (NCN), 150.61, 148.57, 137.78, 123.24, 119.92, 119.38,
119.00, 49.72, 31.01, 19.96, 13.85; 77Se NMR (95 MHz, CDCl3): (ppm) 56.69. ESI-MS
(positive mode): [M+H]+ m/z = 282.0488 (observed), 282.0504 (calculated).
Synthesis of compound 10c: Compound (9c) (3.73 g, 9.27 mmol), was added into the brown
solution of in situ generated Na2Se2 (0.53 g, 23.16 mmol) in THF (30 mL) under nitrogen
atmosphere and stirred for 6-8 hrs. at room temperature. Then potassium tert-butoxide (1.04
g, 9.27 mmol) was added to the reaction mixture and stirred for further 5-7 hrs. The reaction
mixture was quenched by adding water (20 mL) and compound was extracted with diethyl
ether, dried over sodium sulphate and the solvent was evaporated. The residue was
o
recrystallized with dichloromethane and hexane solvent at -25 C as pure crystalline solid.
Yield: 2.34 g, (70%). Melting point 51oC. 1H NMR (400 MHz, CDCl3): (ppm) 7.46 (m, 2H),
7.26 (m, 2H), 4.66 (t, J = 5.60 Hz, 4H), 3.93 (t, J = 5.60 Hz, 4H), 3.59 (t, J = 4.80 Hz, 4H),
13
3.47 (t, J = 4.80 Hz, 4H), 3.31 (s, 6H); C NMR (100 MHz, CDCl3): (ppm) 165.62 (NCN),
133.73, 123.16, 110.66, 71.84, 70.63, 68.96, 59.07, 46.88; 77Se NMR (76 MHz, CDCl3):
(ppm) 58.47; ESI-MS (positive mode): [M+Na]+ m/z = 425.0944 (observed), 425.0951
(calculated).
General procedure for the synthesis of compounds 11-33: Selone (10a/10b/10c) was
dissolved in dry diethyl ether and was added to the respective metal halide CuX (X = Br,
I)/MX2 (M = Zn, Cd, Hg, Pd, Pt; X = Cl, Br, I). The reaction mixture was stirred for 3 h at
room temperature. Compounds 11-25, were obtained as white precipitates from the reaction
21
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10.1002/ejic.201700218
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mixture which was further washed with diethyl ether (10 X 2 mL) to remove the unreacted
starting material. Whereas, complexes 26-33 were soluble in diethyl ether, therefore the
evapouration odiethyl ether from reaction mixture gave complexes 26-33. The complexes 11-
25 and 30-33 were recrystalized from dichloromethane to give pure products in 60-80%
yield. Compounds 26-29 were semisolid in nature therefore could not be recrystallized.
Synthesis of compound 11: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
cuprous bromide (0.14 g, 0.97 mmol) in dry diethyl ether. After 48 h the grey precipitate was
separated. Yield: 0.19 g (43%). UV-Vis (CH3CN, 0.1 mmol dm-1): λmax = 262, 313, 322 nm.
1H NMR (400 MHz, CDCl3):  (ppm) 7.42-7.39 (m, 8H), 4.65 (t, 8H), 1.84 (m, 8H), 1.43 (m,
13
8H), 0.96 (t, 12H); C NMR (100 MHz, CDCl3):  (ppm) 154.37, 132.73, 124.84, 111.48,
48.02, 30.99, 20.28, 14.00; 77Se NMR (76 MHz, CDCl3):  (ppm) -21.01. Elemental analysis
calcd (%) for C30H44Cu2Br2N4Se2: C 39.79, H 4.90, N 6.19; found: C 40.08, H 5.06, N 5.20;
ESI-MS (positive mode): [M-CuBr2]+ m/z = 683.1187 (observed), 683.1191 (calculated).
Synthesis of compound 12: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
cuprous iodide (0.18 g, 0.97 mmol) in dry diethyl ether. After 48 h a grey precipitate was
o
separated. Yield: 0.31 g (62%); m.p. 150-152 C. UV-Vis (CH3CN, 0.1 mmol dm-1): λmax
=
1
264, 314 nm. H NMR (400 MHz, CDCl3):  (ppm) 7.61-7.58 (m, 4H), 7.45-7.41 (m, 4H),
13
4.50 (t, J = 7.52 Hz, 8H), 1.87 (m, 8H), 1.42 (m, 8H), 0.96 (t, J = 7.52 Hz, 12H); C NMR
77
(100 MHz, CDCl3):  (ppm) 133.72, 125.90, 112.66, 48.36, 31.29, 20.79, 14.12; Se NMR
(76 MHz, CDCl3):  (ppm) 36.88; ESI-MS (positive mode): [M-CuI2]+ m/z = 683.1202
(observed), 683.1191 (calculated); elemental analysis calcd (%) for C30H44Cu2I2N4Se2: C
36.05, H 4.44, N 5.61; found: C 35.99, H 4.04, N 5.21.
Synthesis of compound 13: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
ZnCl2 (0.07 g, 0.48 mmol) in dry diethyl ether. Yield: 0.28 g (75%); UV-Vis (CH3CN, 0.1
22
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1
mmol dm-1): λmax = 263, 313, 321 nm. H NMR (400 MHz, CDCl3):  (ppm) 7.30-7.34 (m,
13
8H), 4.54 (t, J = 7.64 Hz, 8H), 1.86 (m, 8H), 1.45 (m, 8H), 0.98 (t, J = 7.40 Hz, 12H); C
77
NMR (100 MHz, CDCl3):  (ppm) 133.10, 123.92, 110.63, 47.22, 30.62, 20.35, 14.00; Se
NMR (76 MHz, CDCl3):  (ppm) -59.96; ESI-MS (positive mode): [M-Cl]+ m/z = 719.0895
(observed), 719.0865 (calculated); elemental analysis calcd (%) for C30H44Cl2N4Se2Zn: C
47.73, H 5.87, N, 7.42; found: C 47.20, H 5.64, N 7.43.
Synthesis of compound 14: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
ZnBr2 (0.11 g, 0.48 mmol) in dry diethyl ether. Yield: 0.26 g (63%); UV-Vis (CH3CN, 0.1
1
mmol dm-1): λmax = 262, 312, 323 nm. H NMR (400 MHz, CDCl3):  (ppm) 7.46-7.34 (m,
13
4H), 4.54 (t, J = 7.60 Hz, 4H), 1.86 (m, 4H), 1.45 (m, 4H), 0.97 (t, J = 7.36 Hz, 6H); C
NMR (100 MHz, CDCl3):  (ppm) 153.93 (NCN) 132.80, 125.17, 111.96, 48.18, 30.98,
77
20.21, 13.90; Se NMR (76 MHz, CDCl3):  (ppm) -29.29; ESI-MS (positive mode): [M-
Br]+ m/z = 763.0261 (observed), 763.0360 (calculated); elemental analysis calcd (%) for
C30H44Br2N4Se2Zn: C 42.70, H 5.26, N 6.64; found: C 42.25, H 4.84, N 6.98.
Synthesis of compound 15: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
ZnI2 (0.16 g, 0.48 mmol) in dry diethyl ether. Yield: 0.32 g (69%); m.p. 166-168 oC. UV-Vis
1
(CH3CN, 0.1 mmol dm-1): λmax = 263, 313, 321 nm. H NMR (400 MHz, CDCl3):  (ppm)
7.45-7.37 (m, 8H), 4.57 (t, J = 7.64 Hz, 8H), 1.88 (m, 8H), 1.46 (m, 8H), 0.99 (t, J = 7.40 Hz,
13
12H); C NMR (100 MHz, CDCl3):  (ppm) 156.88 (NCN) 132.97, 124.86, 111.59, 48.12,
77
30.96, 20.35, 13.97; Se NMR (76 MHz, CDCl3):  (ppm) 8.20; ESI-MS (positive mode):
[M-I]+ m/z = 811.0258 (observed), 811.0225 (calculated); elemental analysis calcd (%) for
C30H44I2N4Se2Zn: C 38.42, H 4.73, N 5.97; found: C 38.37, H 4.64, N 6.48.
Synthesis of compound 16: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
o
CdCl2 (0.09 g, 0.48 mmol) in dry diethyl ether. Yield: 0.31 g (80%); m.p. 202-204 C; UV-
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European Journal of Inorganic Chemistry
1
Vis (CH3CN, 0.1 mmol dm-1): λmax = 262, 313, 324 nm. H NMR (400 MHz, CDCl3): 
(ppm) 7.41-7.31 (m, 8H), 4.50 (t, J = 7.64 Hz, 8H), 1.85 (m, 8H), 1.44 (m, 8H), 0.98 (t, J =
7.40 Hz, 12H); 13C NMR (100 MHz, CDCl3):  (ppm) 158.54 (NCN), 132.94, 124.30,
77
110.99, 47.51, 30.67, 20.28, 13.94; Se NMR (76 MHz, CDCl3):  (ppm) -24.09; ESI-MS
(positive mode): [M-Cl]+ m/z = 767.0612 (observed), 767.0623 (calculated); elemental
analysis calcd (%) for C30H44Cl2N4Se2Cd: C 44.93, H 5.53, N 6.99; found: C 44.69, H 5.16,
N 8.79.
Synthesis of compound 17: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
CdI2 (0.18 g, 0.48 mmol) in dry diethyl ether. Yield: 0.37 g (77%); m.p. 137-139 oC; UV-Vis
1
(CH3CN, 0.1 mmol dm-1): λmax = 263, 313, 323 nm. H NMR (400 MHz, CDCl3):  (ppm)
7.40-7.44 (m, 8H), 4.56 (t, J = 7.48 Hz, 8H), 1.86 (m, 8H), 1.45 (m, 8H), 0.98 (t, J = 7.01 Hz,
13
12H); C NMR (100 MHz, CDCl3):  (ppm) 156.76 (NCN), 132.89, 124.78, 111.39, 48.02,
30.84, 20.28, 13.91; 77Se NMR (76 MHz, CDCl3):  (ppm) -28.79; ESI-MS (positive mode):
[M+Na]+ m/z = 1008.8933 (observed), 1008.8927 (calculated); elemental analysis calcd (%)
for C30H44I2N4Se2Cd: C 36.59, H 4.50, N 5.69; found: C 36.27, H 4.15, N 5.77.
Synthesis of compound 18: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
o
HgCl2 (0.13 g, 0.48 mmol) in dry diethyl ether. Yield: 0.35 g (81%); m.p. 220-222 C; UV-
1
Vis (CH3CN, 0.1 mmol dm-1): λmax = 264, 311, 324 nm. H NMR (400 MHz, CDCl3): 
(ppm) 7.38-7.44 (m, 8H), 4.56 (t, J = 6.56 Hz, 8H), 1.86 (m, 8H), 1.44 (m, 8H), 0.98 (t, J =
6.87 Hz, 12H); 13C NMR (100 MHz, CDCl3):  (ppm) 154.83 (NCN), 132.76, 124.95,
77
111.69, 47.99, 30.98, 20.29, 13.97; Se NMR (76 MHz, CDCl3):  (ppm) -9.00; ESI-MS
(positive mode): [M-Cl]+ m/z = 855.1251 (observed), 855.1291 (calculated); elemental
analysis calcd (%) for C30H44Cl2N4Se2Hg: C 40.48, H 4.98, N 6.29; found: C 40.05, H 4.57,
N 5.54.
24
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Synthesis of compound 19: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
o
HgBr2 (0.18 g, 0.48 mmol) in dry diethyl ether. Yield: 0.36 g (76%); m.p. 205-207 C; UV-
1
Vis (CH3CN, 0.1 mmol dm-1): λmax = 266, 313, 322 nm. H NMR (400 MHz, CDCl3): 
(ppm) 7.37-7.46 (m, 8H), 4.55 (t, J = 7.52 Hz, 8H), 1.86 (m, 8H), 1.44 (m, 8H), 0.98 (t, J =
7.34 Hz, 12H); 13C NMR (100 MHz, CDCl3):  (ppm) 155.75 (NCN), 132.74, 124.89,
77
111.56, 47.93, 30.90, 20.27, 13.92; Se NMR (76 MHz, CDCl3):  (ppm) 7.47; ESI-MS
(positive mode): [M-Br]+ m/z = 899.0766 (observed), 899.0783 (calculated); elemental
analysis calcd (%) for C30H44Br2N4Se2Hg: C 36.80, H 4.53, N 5.72; found: C 36.55, H 4.07,
N 5.22.
Synthesis of compound 20: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
HgI2 (0.22 g, 0.48 mmol). Yield: 0.42 g (79%); m.p. 130-132 oC; UV-Vis (CH3CN, 0.1 mmol
1
dm-1): λmax = 265, 310, 324 nm. H NMR (400 MHz, CDCl3):  (ppm) 7.37-7.46 (m, 8H),
13
4.53 (t, J = 7.57 Hz, 8H), 1.86 (m, 8H), 1.44 (m, 8H), 0.98 (t, J = 7.32 Hz, 12H); C NMR
(100 MHz, CDCl3):  (ppm) 157.73 (NCN), 132.75, 124.68, 111.24, 47.72, 30.77, 20.23,
77
13.87; Se NMR (76 MHz, CDCl3):  (ppm) 33.68. ESI-MS (positive mode): [M-I]+ m/z =
947.0647 (observed), 947.0654 (calculated); elemental analysis calcd (%) for
C30H44I2N4Se2Hg: C 33.58, H 4.13, N 5.22; found: C 33.08, H 3.71, N 4.37.
Synthesis of compound 21: The reagents used were selone (10a) (0.30 g, 0.97 mmol) and
o
PdCl2 (0.09 g, 0.48 mmol) in dry diethyl ether. Yield: 0.23 g (60%); m.p. 234-236 C; UV-
1
Vis (CH3CN, 0.1 mmol dm-1): λmax = 259, 314, 386 nm. H NMR (400 MHz, CDCl3): 
(ppm) 7.51-7.45 (m, 8H), 4.64 (t, J = 7.72 Hz, 8H), 1.96 (m, 8H), 1.49 (m, 8H), 1.00 (t, J =
7.32 Hz, 12H); 13C NMR (100 MHz, CDCl3):  (ppm) 157.26 (NCN) 132.72, 124.71, 111.56,
77
47.86, 30.96, 20.29, 13.98; Se NMR (76 MHz, CDCl3):  (ppm) 151.86; ESI-MS (positive
25
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10.1002/ejic.201700218
European Journal of Inorganic Chemistry
mode): [M-Cl]+ m/z = 761.0622 (observed), 761.0629 (calculated); elemental analysis calcd
(%) for C30H44Cl2N4Se2Pd: C 45.27, H 5.57, N 7.04; found: C 44.96, H 5.56, N 9.09.
Synthesis of compound 22: The reagents used were selone (10a) (0.12 g, 0.38 mmol) and
PtCl2 (0.05 g, 0.19 mmol) in dry diethyl ether. Yield: 0.11 g (63%); m.p. 210-204 oC; UV-Vis
1
(CH3CN, 0.1 mmol dm-1): λmax = 284, 326 nm. H NMR (400 MHz, CDCl3):  (ppm) 7.45-
7.42 (m, 4H), 7.38-7.35 (m, 4H), 4.64 (t, J = 7.72 Hz, 8H), 1.99 (m, 8H), 1.47 (m, 8H), 1.01
(t, J = 7.32 Hz, 12H); 13C NMR (100 MHz, CDCl3):  (ppm) 154.52 (NCN) 132.68, 124.76,
77
111.65, 47.61, 30.96, 20.31, 13.99; Se NMR (76 MHz, CDCl3):  (ppm) 120.90; ESI-MS
(positive mode): [M]+ m/z = 884.0912 (observed), 884.0921 (calculated); elemental analysis
calcd (%) for C30H44Cl2N4Se2Pt: C 40.73, H 5.01, N 6.33; found: C 40.69, H 5.39, N 8.21.
Synthesis of compound 23: The reagents used were selone (10b) (0.20 g, 0.71 mmol) and
mercuric chloride (0.19 g, 0.71 mmol). Yield: 0.29 g, (72%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 279, 308 nm. H NMR (500 MHz, CDCl3): (ppm) 8.62-8.60 (m, 1H), 8.17-8.15 (m,
1H), 8.02-7.99 (m, 1H), 7.59 (d, J = 2.15 Hz, 1H), 7.50-7.48 (m, 1H), 7.42 (d, J = 2.15 Hz,
13
1H), 4.56 (t, J = 7.45 Hz, 2H), 1.86 (m, 2H), 1.43 (m, 2H), 0.98 (t, J = 7.35 Hz, 3H); C
NMR (126 MHz, CDCl3): (ppm) 149.26 (NCN), 149.15, 140.30, 139.72, 125.46, 123.23,
122.99, 122.31, 51.91, 31.97, 19.88, 13.83; 77Se NMR (95 MHz, CDCl3): (ppm) 6.96.
Elemental analysis calcd (%) for C12H15Cl2N3Se2Hg: C 26.12, H 2.74, N 7.62; found: C
26.49, H 2.55, N 5.91; ESI-MS (positive mode): for the fragment [M-Cl]+ m/z = 517. 9813
(observed), 517.9806 (calculated).
Synthesis of compound 24: The reagents used were selone (10b) (0.20 g, 0.71 mmol) and
mercuric bromide (0.26 g, 0.71 mmol). Yield: 0.35 g, (75%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 274 nm. H NMR (500 MHz, CDCl3): (ppm) 8.53-8.52 (m, 1H), 8.41-8.39 (m,
1H), 7.95-7.91 (m, 1H), 7.55 (d, J = 2.10 Hz, 1H), 7.42-7.39 (m, 1H), 7.26 (d, J = 2.10 Hz,
26
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10.1002/ejic.201700218
European Journal of Inorganic Chemistry
13
1H), 4.36 (t, J = 7.50 Hz, 2H), 1.85 (m, 2H), 1.41 (m, 2H), 0.95 (t, J = 7.35 Hz, 3H); C
NMR (126 MHz, CDCl3): (ppm) 149.38 (NCN), 148.92, 145.27, 139.16, 124.90, 122.49,
121.93, 121.71, 51.13, 31.46, 19.88, 13.82; 77Se NMR (95 MHz, CDCl3): (ppm) 18.77.
Elemental analysis calcd (%) for C12H15Br2N3Se2Hg: C 22.50, H 2.36, N 6.56; found: C
22.58, H 1.96, N 5.31; ESI-MS (positive mode): for the fragment [M-Br]+ m/z = 561.9304
(observed), 561.9302 (calculated).
Synthesis of compound 25: The reagents used were selone (10b) (0.20 g, 0.71 mmol) and
mercuric iodide (0.32 g, 0.71 mmol). Yield: 0.35 g, (67%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 271, 326 nm. H NMR (500 MHz, CDCl3): (ppm) 8.62-8.60 (m, 1H), 8.17-8.15 (m,
1H), 8.02-7.99 (m, 1H), 7.59 (d, J = 2.25 Hz, 1H), 7.50-7.48 (m, 1H), 7.42 (d, J = 2.25 Hz,
13
1H), 4.56 (t, J = 7.51 Hz, 2H), 1.86 (m, 2H), 1.43 (t, 2H), 0.98 (m, J = 7.36 Hz, 3H); C
NMR (126 MHz, CDCl3): (ppm) 149.39 (NCN), 149.09, 146.91, 139.91, 125.34, 122.61,
122.26, 121.28, 51.32, 31.64, 20/02, 13.85; 77Se NMR (95 MHz, CDCl3): (ppm) 67.41.
Elemental analysis calcd (%) for C12H15I2N3Se2Hg: C 19.62, H 2.06, N 5.72; found: C 20.01,
H 1.92, N 5.14; ESI-MS (positive mode): for the fragment [M-I]+ m/z = 607. 9164
(observed), 607.9170 (calculated).
Synthesis of compound 26: The reagents used were selone (10c) (0.10 g, 0.25 mmol) and
cuprous iodide (0.05 g, 0.25 mmol). Yield: 0.17 g, (56%). UV-Vis (CH3CN, 0.1 mmol dm-1):
1
λmax = 262, 311, 320 nm. H NMR (400 MHz, CDCl3): (ppm) 7.56-7.51 (m, 4H), 7.32-7.26
(m, 4H), 4.75 (t, J = 5.34 Hz, 8H), 3.97 (t, J = 5.34 Hz, 8H), 3.58 (t, J = 4.32 Hz, 8H), 3.41 (t,
J = 4.32 Hz, 8H), 3.29 (s, 12H); 13C NMR (100 MHz, CDCl3): (ppm) 159.65 (NCN), 133.65,
77
123.92, 111.80, 71.85, 70.62, 69.36, 59.04, 47.86; Se NMR (76 MHz, CDCl3): (ppm) 0.80;
ESI-MS (positive mode): for the fragment [M-CuI2]+ m/z = 867. 1410 (observed), 867.1412
(calculated).
27
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10.1002/ejic.201700218
European Journal of Inorganic Chemistry
Synthesis of compound 27: The reagents used were selone (10c) (0.15 g, 0.37 mmol) and
zinc chloride (0.05 g, 0.37 mmol). Yield: 0.21 g, (68%). UV-Vis (CH3CN, 0.1 mmol dm-1):
1
λmax = 263, 311, 321 nm. H NMR (400 MHz, CDCl3): (ppm) 7.54 (d, 4H), 7.31 (d, 4H),
4.71 (t, J = 5.40 Hz, 8H), 3.95 (t, J = 5.37 Hz, 8H), 3.58 (t, J = 4.76 Hz, 8H), 3.42 (t, J = 4.73
Hz, 8H), 3.28 (s, 12H); 13C NMR (100 MHz, CDCl3): (ppm) 160.59 (NCN), 133.71, 124.01,
77
111.70, 71.93, 70.67, 69.19, 59.12, 47.65; Se NMR (76 MHz, CDCl3): (ppm) 16.69; ESI-
MS (positive mode): [M+Na]+ m/z = 1098.9312 (observed), 1098.9294 (calculated).
Synthesis of compound 28: The reagents used were selone (10c) (0.10 g, 0.25 mmol) and
zinc iodide (0.079 g, 0.25 mmol). Yield: 0.21 g, (76%). UV-Vis (CH3CN, 0.1 mmol dm-1):
1
λmax = 264, 311, 320 nm. H NMR (400 MHz, CDCl3): (ppm) 7.75 (m, 4H), 7.73 (m, 4H),
13
4.86 (t, 8H), 4.13 (t, 8H), 3.98 (t, 8H), 3.81 (t, 8H), 3.49 (t, 12H); C NMR (100 MHz,
CDCl3): (ppm) 155.41 (NCN), 133.66, 125.24, 112.78, 71.94, 70.70, 69.38, 59.22, 48.72;
77Se NMR (76 MHz, CDCl3): (ppm) -13.33; ESI-MS (positive mode): [M+Na]+ m/z =
1464.6865 (observed), 1464.6748 (calculated).
Synthesis of compound 29: The reagents used selone (10c) (0.10 g, 0.25 mmol) and
cadmium chloride (0.04 g, 0.25 mmol) Yield: 0.13 g, (56%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 262, 312, 322 nm. H NMR (400 MHz, CDCl3): (ppm) 7.45 (m, 4H), 7.29 (m, 4H),
4.67 (t, J = 5.52 Hz, 8H), 3.94 (t, J = 5.52 Hz, 8H), 3.59 (t, J = 4.36 Hz, 8H), 3.44 (t, J = 4.36
Hz, 8H), 3.29 (s, 12H); 13C NMR (100 MHz, CDCl3): (ppm) 163.15 (NCN), 133.61, 123.45,
77
111.01, 71.77, 70.54, 68.92, 58.99, 47.13; Se NMR (76 MHz, CDCl3): (ppm) 32.23; ESI-
MS (positive mode): [M+Na]+ m/z = 1192.8838 (observed), 1192.8825 (calculated).
Synthesis of compound 30: The reagents used were selone (10c) (0.10 g, 0.25 mmol) and
cadmium iodide (0.06 g, 0.25 mmol). Yield: 0.13 g, (56%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 263, 312, 321 nm. H NMR (400 MHz, CDCl3): (ppm) 7.67 (m, 4H), 7.43 (m, 4H),
28
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10.1002/ejic.201700218
European Journal of Inorganic Chemistry
4.80 (t, J = 4.98 Hz, 8H), 3.99 (t, J = 4.98 Hz, 8H), 3.62 (t, J = 4.77 Hz, 8H), 3.45 (t, J = 4.77
Hz, 8H), 3.34 (s, 12H); 13C NMR (100 MHz, CDCl3): (ppm) 155.35 (NCN), 133.47, 125.07,
77
112.62, 71.76, 70.51, 69.25, 59.08, 48.53; Se NMR (76 MHz, CDCl3): (ppm) -28.23; ESI-
MS (positive mode): [M-I]+ m/z = 1408.7321(observed), 1408.7335 (calculated); elemental
analysis calcd (%) for C34H52I4N4O8Se2Cd2 (%): C, 26.60; H, 3.41; N, 3.65. Found: C, 26.38;
H, 3.24; N, 4.05.
Synthesis of compound 31: The reagents used were selone (10c) (0.10 g, 0.25 mmol) and
mercuric chloride (0.07 g, 0.25 mmol). Yield: 0.14 g, (52%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 269, 293, 310, 322 nm. H NMR (400 MHz, CDCl3): (ppm) 7.69 (broad, 4H), 7.43
(broad, 4H), 4.87 (broad, 8H), 3.95 (broad, 8H), 3.58 (broad, 8H), 3.41 (broad, 8H), 3.26
13
(broad, 12H); C NMR (100 MHz, CDCl3): (ppm) 150.29 (NCN), 133.48, 125.65, 113.43,
72.01, 70.68, 69.25, 59.16, 49.04; 77Se NMR (76 MHz, CDCl3): (ppm) -16.45; ESI-MS
(positive mode): [M-HgCl3]+ m/z = 639.0441 (observed), 639.0441 (calculated); elemental
analysis calcd (%) for C34H52Cl4N4O8Se2Hg2 (%): C, 30.35; H, 3.89; N, 4.16. Found: C,
30.17; H, 3.65; N, 5.04.
Synthesis of compound 32: The reagents used were selone (10c) (0.10 g, 0.25 mmol) and
mercuric bromide (0.09 g, 0.25 mmol). Yield: 0.15 g, (52%). UV-Vis (CH3CN, 0.1 mmol dm-
1
1): λmax = 272, 313 nm. H NMR (400 MHz, CDCl3): (ppm) 7.69 (m, 4H), 7.43 (m, 4H), 4.87
(t, J = 4.92 Hz, 8H), 3.95 (t, J = 4.92 Hz, 8H), 3.58 (t, J = 3.64 Hz, 8H), 3.41 (t, J = 3.64 Hz,
13
8H), 3.26 (s, 12H); C NMR (100 MHz, CDCl3): (ppm) 151.83 (NCN), 133.43, 125.55,
113.28, 71.94, 70.65, 69.24, 59.11, 48.95; 77Se NMR (76 MHz, CDCl3): (ppm) 9.07; ESI-MS
(positive mode): for the fragment [M-HgBr3]+ m/z = 682.9887 (observed), 682.9947
(calculated); elemental analysis calcd (%) for C34H52Br4N4O8Se2Hg2 (%): C, 26.80; H, 3.44;
N, 3.68. Found: C, 26.67; H, 3.06; N, 4.86.
29
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