Synthesis and characterization of new 2-pyrimidyl chalcogen (S, Se, Te) compounds: X-ray crystal structure of bis(4,6-dimethyl-2-pyrimidyl)diselenide and 4,6-dimethyl-2-(phenylselanyl)pyrimidine

Article abstract of DOI:10.1016/j.jorganchem.2013.02.014

New and synthetically important symmetrical bis(4,6-dimethyl-2-pyrimidyl) dichalcogenides have been synthesized by reacting 4,6-dimethyl-2- chloropyrimidine with the corresponding dichalcogenide (E₂ ^2- where E = S, Se, Te) ion. The u

Full text of DOI:10.1016/j.jorganchem.2013.02.014

Journal of Organometallic Chemistry 732 (2013) 137e141
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of new 2-pyrimidyl chalcogen (S, Se, Te)
compounds: X-ray crystal structure of bis(4,6-dimethyl-2-pyrimidyl)diselenide
and 4,6-dimethyl-2-(phenylselanyl)pyrimidine
,
a
a
a
a
a
b
b
K.K. Bhasin a , Ekta Arora , Alka S. Grover , Jyoti , H. Singh , S.K. Mehta , Aman K.K. Bhasin , C. Jacob
*
a Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, U.T., India
b Division of Bio-organic Chemistry, School of Pharmacy, Saarland State University, D-66123 Saarbrücken, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
New and synthetically important symmetrical bis(4,6-dimethyl-2-pyrimidyl)dichalcogenides have been
synthesized by reacting 4,6-dimethyl-2-chloropyrimidine with the corresponding dichalcogenide (E22ꢀ
where E ¼ S, Se, Te) ion. The unsymmetrical 4,6-dimethyl-2-(arylchalcogenyl)pyrimidines have also been
prepared by reacting 4,6-dimethyl-2-chloropyrimidine with the arylselenide ion, ArSeꢀ (Ar ¼ phenyl,
naphthyl, p-tolyl, 4-chloro-2-pyrimidyl). All the newly synthesized compounds have been thoroughly
characterized with the help of various spectroscopic techniques viz., NMR (1H, 13C, 77Se), FT-IR and mass
spectrometry (in representative cases). The crystal structures of bis(4,6-dimethyl-2-pyrimidyl)diselenide
and 4,6-dimethyl-2-(phenylselanyl)pyrimidine have been determined by X-ray crystallography.
Ó 2013 Elsevier B.V. All rights reserved.
Received 25 December 2012
Received in revised form
8 February 2013
Accepted 13 February 2013
Keywords:
Pyrimidine
Chalcogen
Dichalcogenides
Arylselenide ion
1. Introduction
dimethyl-2-pyrimidyl)dichalcogenide and 4,6-dimethyl-2-(arylse-
lanyl)pyrimidine compounds.
Organochalcogen compounds are well documented to play an
indispensable role in synthetic chemistry because of their unique
ability to produce reactive electrophilic [1] and nucleophilic [2]
species. These compounds also find widespread use as conve-
nient intermediates or reagents in organic synthesis [3e5],
biochemistry [6,7], organic superconductors [8,9], and semi-
conducting materials [10,11]. In pursuance of our earlier studies
aimed toward the synthesis of new organochalcogen compounds
[12e18], we have recently reported a facile synthesis of bis(4-
dimethylamino-2-pyrimidyl)dichalcogenide [19] and bis(4-chloro-
2. Experimental section
2.1. Materials and instrumentation
All experiments were carried out in a dioxygen-free nitrogen
atmosphere. IR spectra were recorded between KBr plates on a
PerkineElmer Model 1430 ratio recording spectrophotometer. 1H
NMR and 13C NMR spectra were recorded in CCl4/CDCl3 using tet-
ramethylsilane as an internal standard and 77Se NMR with dimethyl
selenide as an external reference on a Jeol 300 MHz spectrometer.
The mass spectra were obtained on Q-TOF micro mass spectrom-
eter. Carbon, Hydrogen and Nitrogen were estimated micro
analytically on a PerkineElmer 2400 CHN Elemental analyzer.
2-pyrimidyl)dichalcogenide
[20]
compounds
from
2,4-
dichloropyrimidine by using strategies involving the use of Na2E2
(E ¼ S, Se, Te) in different solvents resulting in the formation of
structurally dissimilar dichalcogenides. The applications of 5-
(phenylselenenyl)-pyrimidine nucleosides and 6-phenylselenenyl
acyclic pyrimidines have been extensively studied by several
groups as potential antimicrobial and anti HIV-1 agents respec-
tively [21,22]. In view of the importance of the pyrimidine ring with
diverse biological activities [23e25], the present studies are aimed
at synthesizing the hitherto unknown new compounds viz., bis(4,6-
2.2. Synthesis of 4,6-dimethyl-2-hydroxypyrimidine hydrochloride
[26]
Urea (12 g) in 100 ml of boiling ethanol was treated with acetyl
acetone (20 g) and the hot solution was treated with 27 ml of conc.
hydrochloric acid with stirring. The mixture was refluxed for 24 h
and the product was isolated by filtration and subsequent washing
with cold ethanol and diethyl ether.
* Corresponding author. Tel.: þ91 9779924966; fax: þ91 (0)172 2545074.
E-mail addresses: kkbhasin@pu.ac.in (K.K. Bhasin), c.jacob@mx.uni-saarland.de
(C. Jacob).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.02.014

138
K.K. Bhasin et al. / Journal of Organometallic Chemistry 732 (2013) 137e141
2.3. Synthesis of 4,6-dimethyl-2-chloropyrimidine [26]
DMF
4E + N2H4.H2O + 4 NaOH
2Na2E2 + 5 H2O + N2
A mixture of 4,6-dimethyl-2-hydroxypyrimidine hydrochloride
(20.0 g, 0.125 mol) and phosphorous oxychloride (110 ml) was
refluxed for 10 h after which time the residual phosphorous oxy-
chloride was removed in vacuum. The residual oil was poured into
50 g of ice and was neutralized below 10 ꢁC with a concentrated
solution of potassium hydroxide. The resulting mixture with
300 ml diethyl ether was vigorously stirred for 10 h. The organic
extract was evaporated to dryness. The residual crude product was
recrystallized from a minimal amount of petroleum ether (b.pt. 40e
CH3
CH3
CH3
N
N
DMF
N
2-
E2
+
H3C
N
E
E
N
CH3
H3C
N
Cl
Ia-c
E = S, Se, Te
Scheme 1. Scheme for the synthesis of bis(4,6-dimethyl-2-pyrimidyl)dichalcogenides,
Iaec.
70 ꢁC) giving 13.8
chloropyrimidine plates (m.pt. 37e38 ꢁC). 1H NMR (CDCl3/CCl4)
6.89(1H, s), 2.37 (6H, s).
g (77%) of as colorless 4,6-dimethyl-2-
under vacuum. The organic layer was repeatedly washed with
distilled water (3 ꢂ 40 ml), dried over anhydrous sodium sulfate.
Solvent was removed on a rota evaporator and the product was
subjected to purification on a silica column using hexane as eluant.
d
2.4. Synthesis of bis(4,6-dimethyl-2-pyrimidyl)dichalcogenide
(Iaec)
2.5.1. 4,6-Dimethyl-2-(phenylselanyl)pyrimidine (IIa)
To a vigorously stirred mixture of powdered sodium hydroxide
(3.0 g, 75 mmol), elemental chalcogen (S ¼ 1.6 g, 50 mmol,
Se ¼ 4.0 g, 50 mmol or Te ¼ 6.4 g, 50 mmol) and dimethylforma-
mide (30 ml), 100% hydrazine hydrate was added slowly. After
stirring for nearly 6 h at room temperature, a solution of 4,6-
dimethyl-2-chloropyrimidine (100 mmol) dissolved in 15 ml DMF
was added drop wise. The reaction mixture was refluxed for 2e3 h
and continuously monitored by TLC. After the completion of the
reaction, it is diluted with about 250 ml of distilled water and
extracted with dichloromethane (3 ꢂ 50 ml). The organic layer was
separated and solvent removed to get the crude product in solid
form. The product was subjected to purification on a silica column
using hexane as the eluant.
Yield ¼ 75%, white crystalline solid, m.p. ¼ 58e62 ꢁC, Anal. Calc
for C12H12N2Se: Calcd. C, 54.50; H, 4.54, N, 10.60. Found: C, 54.89, H,
4.35, N, 10.86. IR (KBr, cmꢀ1): 2924.0, 1578.0, 1529.0, 1438.0, 1341.0,
783.0, 542.0. 1H NMR:
d
7.63e7.60 (2H, d), 7.26e7.24 (3H, m), 6.58
170.3,166.9,136.9,136.0,129.6,128.2,
(1H, s), 2.28 (6H, s); 13C NMR:
d
117.5, 36.8, 23.8; 77Se NMR:
d
486.8; MS-EI, m/e (R.I. %, assignment):
265 (100, [C12H12N2Se]þ þ 1), 185 (30, [C6H7N2Se]þ ꢀ 2).
ꢃ
2.5.2. 4,6-Dimethyl-2-(naphthalen-2-ylselanyl)pyrimidine (IIb)
Yield ¼ 67%, yellow crystalline solid, m.p. ¼ 95e97 ꢁC, Calcd.
Anal. Calc for C16H14N2Se: C, 61.14 H, 4.45, N, 8.91. Found: C, 61.01, H,
4.22, N, 8.65. IR (KBr, cmꢀ1): 2925.1, 1541.5, 1399.1, 1324.1, 791.0,
669.4. 1H NMR:
d
7.80e7.78 (1H, d), 7.44e7.35 (3H, d), 7.18e7.11 (2H,
t), 6.86 (1H, s), 6.60 (1H, d), 2.41 (6H, s); 13C NMR:
d
175.1, 160.6,
2.4.1. Bis(4,6-dimethyl-2-pyrimidyl)disulfide (Ia)
157.2, 137.4, 134.6, 134.5, 131.8, 128.9, 128.1, 127.6, 124.3, 118.7, 23.8.
Yield ¼ 60%, white crystalline solid, m.p. ¼ 115e116 ꢁC, Anal.
Calc for C12H14N4S2: Calcd. C, 51.79, H, 5.03, N, 20.14. Found: C, 51.57,
H, 5.23, N, 20.40. IR (KBr, cmꢀ1): 2919.0, 1659.9, 1376.5, 1455.0,
2.5.3. 2-(p-tolylselanyl)-4,6-dimethylpyrimidine (IIc)
Yield ¼ 78%, light yellow crystalline solid, m.p. ¼ 67e69 ꢁC, Anal.
Calc for C13H14N2Se: Calcd. C, 56.11, H, 5.03, N, 10.07. Found: C,
55.99, H, 5.23, N, 10.23. IR (KBr, cmꢀ1): 2926.4, 1570.0, 1524.0,
881.5, 842.4, 766.2, 722.2. 1H NMR:
d C
6.64 (1H, s), 2.36 (6 H, s); 13
NMR: d 169.4, 167.2,116.8, 23.9; MS-EI, m/e (R.I. %, assignment): 279
(100, [C12H14N4S2þ1]þꢃ), 245 (10, [C12H14N4S ꢀ 1]þꢃ), 140 (5,
1421.0, 783.0, 542.0. 1H NMR:
d
7.58e7.52 (2H, d), 6.86e6.81 (2H, d),
[C6H7N2S þ 1]þꢃ).
6.63 (1H, s), 3.81 (3H, s), 2.29 (6H, s); 13C NMR:
d
170.5, 166.9, 159.9,
137.7, 118.5, 117.4, 116.6, 115.6, 114.5, 113.6, 55.7, 23.8; MS-EI, m/e
2.4.2. Bis(4,6-dimethyl-2-pyrimidyl)diselenide (Ib)
(R.I. %, assignment): 278 (100, [C13H14N2Se]þꢃ).
Yield ¼ 58%, red crystalline solid, m.p. ¼ 142e145 ꢁC, Anal. Calc
for C12H14N4Se2: Calcd. C, 38.50, H, 3.94, N, 14.97.Found: C, 38.17, H,
3.72, N, 14.71. IR (KBr, cmꢀ1): 2923.3, 2852.5, 1580.0, 1384.0, 785.9.
2.5.4. 2-(4-Chloropyrimidin-2-ylselanyl)-4,6-dimethylpyrimidine
(IId)
1H NMR:
d d 168.9, 167.3, 116.9,
6.60 (1H, s), 2.30 (6H, s); 13C NMR:
Yield ¼ 54%, white crystalline solid, m.p. ¼148e149 ꢁC, Anal. Calc
for C10H9N4SeCl: Calcd. C, 39.93, H, 2.99, N,18.63. Found: C, 40.20, H,
3.13, N, 18.37. IR (KBr, cmꢀ1): 2925.4, 1581.7, 1543.2, 1398.5, 1328.9,
23.8; 77Se NMR:
d
486.2; MS-EI, m/e (R.I. %, assignment): 371 (þ32,
[C12H14N4Se2]þ ꢀ 3), 213(95, [C12H14N4]þ ꢀ 1) 107(96, [C6H7N2] ꢃ).
ꢃ
ꢃ
844.3, and 540.5. 1H NMR:
d 8.39e8.36 (1H, d), 8.36e8.33 (1H, d),
2.4.3. Bis(4,6-dimethyl-2-pyrimidyl)ditelluride (Ic)
6.79 (1H, s), 2.39 (6H, s); 13C NMR:
d 167.7, 157.3, 122.1, 118.2, 23.8.
Yield ¼ 50%, blue crystalline solid, m.p. ¼ 121e124 ꢁC, Anal. Calc
for C12H14N4Te2: Calcd. C, 30.63, H, 2.97, N, 11.91. Found: C, 30.50, H,
2.88, N,11.55. IR (KBr, cmꢀ1): 2929.8, 2838.5,1600.0,1369.0, 706.3.1H
2.6. X-ray crystallographic studies
NMR: d d 169.0,165.0,117.4, 23.81.
6.51 (1H, s), 2.25 (6H, s); 13C NMR:
Diffraction quality colorless single crystals of Ib and IIa were ob-
tainedby the slow evaporation of dichloromethaneehexane solution
2.5. Synthesis of 4,6-dimethyl-2-(arylselanyl)pyrimidine
compounds (IIaed)
CH3
NaBH4/C2H5OH-DMF,0-50C
N
Ar-Se-Se-Ar
To a solution of diaryldiselenide, Ar2Se2 (Ar ¼ phenyl, naphthyl,
tolyl, 4-chloro-2-pyrimidyl) in 50 ml of C2H5OH-DMF (3:2) was
added 0.456 g (12 mmol) of sodium borohydride in parts with
continuous stirring at 0e5 ꢁC. To the resulting solution, 10 mmol of
4,6-dimethyl-2-chloropyrimidine diluted with an equal volume of
DMF was added drop wise. Reaction was complete within 1e2 h.
Extraction was done in dichloromethane after removing ethanol
CH3
H3C
N
Se Ar
II a-d
Ar = C6H5, C10H7, p-CH3C6H5, , C4N2H2Cl.
Scheme 2. Scheme for the synthesis of 4,6-dimethyl-2-(arylselanyl)pyrimidines, IIaed.
r.t
N
,
N
H3C
Cl

K.K. Bhasin et al. / Journal of Organometallic Chemistry 732 (2013) 137e141
139
Fig. 1. X-ray structure showing (a) the conformation and atom numbering scheme drawn with 50% ellipsoidal probability and (b) packing diagram for bis(4,6-dimethyl-2-pyrimidyl)
diselenide, Ib.
of the corresponding compound. Suitable crystals were chosen from
a crop of crystals, mounted on glass fibers and data collected on
Bruker Smart Apex diffractometer using graphite monochromated
Mo K/a radiation (0.71073 A), for the cell determination and intensity
data collection. Crystal structure was solved by direct methods
preparation of unsymmetrical selenides and tellurides [33,34].
Sodium borohydride generates ArSeꢀ anions effectively from diaryl
diselenides in ethanol-dimethylformamide system that acts as a
good nucleophile in case of 2-halopyrimidine and generate com-
pounds IIaed (Scheme 2) in good yields.
ꢀ
(SHELX-97) [27] and refined by full matrix least squares method.
Compounds (Iaec) and (IIaed) thus prepared are stable and
have been purified by column chromatography (silica gel using
hexaneeethyl acetate). All the compounds are soluble in conven-
tional organic solvents and have a shelf life of several months
without any sign of decomposition even at room temperature un-
der di-nitrogen atmosphere.
3. Results and discussion
The pyridyl or substituted pyridyl organoselenium compounds
have emerged as important synthons in heterocyclic chemistry,
biochemistry and coordination chemistry [28,29]. An encouraging
report on anti-human immunodeficiency-virus-type-1 (HIV-1) ac-
tivity of 6-phenylselenenyl acyclic pyrimidines [30] further adds
new dimensions to chalcogen chemistry acknowledging the pres-
ence of two nitrogen atoms in the pyrimidyl ring on the properties
of organochalcogen compounds.
Starting substrates diphenyl diselenide, ditolyl diselenide,
dinaphthyl diselenide and dipyrimidyl diselenide were prepared by
using standard literature methods [31,32]. The synthetic strategy to
prepare bis(4,6-dimethyl-2-pyrimidyl)dichalcogenide (Iaec) in-
volves the reduction of elemental chalcogen atom to dichalcoge-
nide anion by hydrazine hydrate in alkaline medium followed by
the nucleophilic substitution reaction of 4,6-dimethyl-2-
chloropyrimidine at C-2 (Scheme 1). Hydrazine hydrate has been
preferred over other reducing agents because of its low cost and its
ability to generate dichalcogenide anions cleanly.
The newly synthesized compounds have been characterized
with the help of various spectroscopic techniques viz. NMR (1H, 13
C
and 77Se), FT-IR and mass spectrometry (in representative cases).
3.1. Spectroscopic studies
1H NMR characterization of bis(4,6-dimethyl-2-pyrimidyl)
dichalcogenides shows an upfield shift of ring protons w.r.t the
protons of 4,6-dimethyl-2-chloropyrimidine due to displacement
of electronegative chlorine with chalcogen atom. The aromatic
proton of the pyrimidyl ring, H-5 resonates at high d value in case of
ditelluride compared to corresponding diselenide as well as di-
sulfide. It can be easily explained on the basis of decreased elec-
tronegativity down the group in chalcogen family. 1H NMR spectra
in case of 4,6-dimethyl-2-(arylselanyl)pyrimidine compounds (IIae
d) show an downfield shift in the chemical shift values for the ar-
omatic proton of 4,6-dimethylpyrimidyl ring from tolyl to phenyl
moiety and further to naphthyl and 4-chloropyrimidyl group. This
Cleavage of seleniumeselenium bond in diorganyl diselenides
using sodium borohydride has been accomplished for the
Fig. 2. (a) ORTEP diagram showing the conformation and atom numbering scheme drawn with 50% ellipsoidal probability and (b) packing diagram showing SeeH intermolecular
interactions for 4,6-dimethyl-2-(phenylselanyl)pyrimidine, IIa.

140
K.K. Bhasin et al. / Journal of Organometallic Chemistry 732 (2013) 137e141
Table 1
3.2. Crystal structure determination of Ib and IIa
Crystal structure data and refinement for Ib and IIa.
To have an understanding of the structural details, single crystal
X-ray diffraction of Ib and IIa was carried out. A perspective view
and atom numbering scheme of Ib and IIa is given in Figs.1a and 2a.
All other relevant details about crystal structure determination and
refinement parameters are given in Table 1. The molecular geom-
etry of the pyrimidine is as expected in terms of the bond length
Parameters
Compound Ib
Compound IIa
Formula
C12H14N4Se2
189.98
200
C12H12N2Se
263.20
293(2) K
Monoclinic
P21/n
8.2903(12)
9.344(3)
15.234(5)
95.526(19)
1174.5(5)
4
3.165
1.488
Formula weight
Temperature/K
Crystal system
Space group
Monoclinic
P21/n (no.14)
8.018(5)
8.716(5)
9.939(5)
95.830(5)
691.0(7)
4
8.464
1.826
358
50.20
ꢀ9 < h < 8;
ꢀ10 < k < 10;
ꢀ11 < l < 11
3153 [Rint ¼ 0.0664]
1223
ꢀ
a/A
ꢀ
ꢀ
and bond angles. The SeeC bond lengths are [Se(1)eC(1) 1.903 A]
b/A
ꢀ
ꢀ
ꢀ
c/A
and [Se(1)eC(7) 1.910(3) A], [Se(1)eC(6) 1.914(2) A] in Ib and IIa
ꢁ
b
/
ꢀ
respectively which are in agreement with the value of 1.930 A as
3
ꢀ
Volume/A
suggested by Pauling [35] a typical value found in other diselenides.
Z
ꢀ
Absorption coefficient/mmꢀ1
Density calc./g/cm3
F(000)
The average CeC bond length of the pyrimidine ring is 1.369 A and
ꢀ
1.379 A in Ib and IIa respectively. The torsion angle, C(002)eSe(2)e
Se(2)eC(002) has been found to be 180ꢁ and the bond angle
C(002)eSe(2)eSe(2) is 92.93ꢁ. Each pyrimidine ring in the mole-
528
2theta/ꢁ
3.29e25.00
ꢀ9 ꢄ h ꢄ 9,
ꢀ11 ꢄ k ꢄ 11,
ꢀ17 ꢄ l ꢄ 18
9997 [Rint ¼ 0.0220]
2057
Index ranges
ꢀ
cule is substituted at C-2 position [SeeC bond length 1.903 A] and at
ꢀ
C-4 as well as C-6 position [CH3eC bond length 1.494 A] in com-
ꢀ
Reflections collected
Reflections unique
Parameters
pound Ib. The SeeSe bond length 2.342 A is in agreement with the
single covalent SeeSe bond length on the Pauling scale [35]
87
1.085
138
1.091
ꢀ
(2.290e2.390 A). Nine molecules of Ib are packed in a unit cell
GOOF
with eight molecules disposed at the corners and one molecule at
the body centre. Significant CeC intermolecular interactions have
been observed as shown in Fig. 1b.
R1/wR2 [I > 2
R1/wR2 (all data)
Largest res. Peak/e A
s
(I)]
0.0524/0.1156
0.0733/0.1336
0.949
0.0285/0.0786
0.0397/0.0808
0.443 and ꢀ0.467
ꢀꢀ3
ꢀ
The average CeC bond length in phenyl ring is 1.368 A and the
bond angle N(1)eC(6)eSe(1) 120.33ꢁ almost equivalent to regular
trigonal planar angle of 120ꢁ in compound IIa. The unit cell con-
tains four molecules interacting intermolecularly through SeeH
study is in accord with the greater deshielding influence of the 4-
chloropyrimidyl ring over the naphthyl, phenyl and the tolyl ring
successively. 13C NMR of 4,6-dimethyl-2-(arylselanyl)pyrimidine
compounds (IIaed) displays signals from both the pyrimidine ring
as well as the aryl group in agreement with the literature values.
EI-MS of the compound bis(4,6-dimethyl-2-pyrimidyl)disulfide
(Ia) shows the base peak corresponding to [M þ 1]þꢃ at m/z value of
279. Other observed peaks correspond to the ions formed by the
loss of sulfur atom and due to cleavage of SeS bond at m/z value 245
and 140 respectively. However, in case of bis(4,6-dimethyl-2-
pyrimidyl)diselenide (Ib), no molecular ion peak is observed and
the prominent peak correspond to the 4,6-dimethylpyrimidyl ring
at m/z value of 107. The mass spectrum in case of 4,6-dimethyl-2-
(phenylselanyl)pyrimidine (IIa) displays the base peak for the
ꢀ
(3.092 A) interactions. All other important bond parameters have
been tabulated in Table 2.
4. Conclusions
The present work reports a simple protocol for the synthesis of
synthetically important bis(4,6-dimethyl-2-pyrimidyl)dichalcoge-
nides (E ¼ S, Se, Te) and 4,6-dimethyl-2-(arylselanyl)pyrimidines in
good yields. These compounds are anticipated to act as suitable
candidates in coordination chemistry.
Acknowledgments
[M þ 1]þ ion at m/z value 265 whereas 2-(p-tolylselanyl)-4,6-
ꢃ
KKB is thankful to DST, New Delhi for research grant (SR/S1/IC-
37/2009). We are thankful to Prof. P. Mathur, Director, Indian
Institute of Technology, Indore for providing facilities for X-ray
crystallographic studies.
dimethylpyrimidine (IIc) shows the base peak corresponding to
the molecular ion [M]þꢃ at m/z value 278. The compound (IIa) also
displays the peak at m/z value 185 corresponding to the fragment
arising from the cleavage of C(phenyl)eSe bond. The fragments
containing selenium show a highly characteristic and well define
pattern of signal intensities depending on the natural abundance of
various isotopes of selenium.
Appendix A. Supplementary material
Crystallographic data for the structural analyses have been
deposited with the Cambridge Crystallographic Data Centre, CCDC
No. 902877 (Ib) and 902876 (IIa). Copies of this information may be
obtained free of charge from: The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK [fax: (int. code) þ44 1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk].
Table 2
Selected bond parameters of Ib and IIa.
Bond length (A)
Bond angle (ꢁ)
ꢀ
Compound Ib
Se2 C002
Se2 Se2
N2 C008
C8 C7
C008 C20
Compound IIa
Se(1)eC(7)
Se(1)eC(6)
N(2)eC(6)
C(7)eC(8)
C(4)eC(5)
References
1.903(7)
2.342(16)
1.350(8)
1.367(10)
1.489(10)
C002 Se2 Se2
N1 C002 N2
N2 C002 Se2
N1 C8 C10
92.9(2)
128.7(6)
111.9(5)
116.4(6)
116.7(6)
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