Molecular structure and properties of N,N′-disulfinyl-1,2-diaminobenzene

Article abstract of DOI:10.1023/A:1013101604063

According to X-ray diffraction data, N,N′-disulfinyl-1,2-diaminobenzene in crystal exists as a planar Z,Z isomer. On heating or under the action of catalytic amounts of water, as well as in reactions with LiN(SiMe₃)₂ or PCl₅ in 1:1 or 1:2 molar ratios it quantitatively converts into 2,1,3-benzothiadiazole. According to ¹⁵N NMR data, this transformation is accompanied by deshielding of the nitrogen atoms by 18 ppm.

Full text of DOI:10.1023/A:1013101604063

Russian Journal of General Chemistry, Vol. 71, No. 7, 2001, pp. 1050 1054. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 7, 2001,
pp. 1116 1120.
Original Russian Text Copyright
2001 by Bagryanskaya, Gatilov, Makarov, Shakirov, Shuvaev, Zibarev.
Molecular Structure and Properties
of N,N -Disulfinyl-1,2-diaminobenzene
I. Yu. Bagryanskaya, Yu. V. Gatilov, A. Yu. Makarov,
M. M. Shakirov, K. V. Shuvaev, and A. V. Zibarev
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division,
Russian Academy of Sciences, Novosibirsk, Russia
Novosibirsk State University, Novosibirsk, Russia
Received March 9, 2000
Abstract According to X-ray diffraction data, N,N -disulfinyl-1,2-diaminobenzene in crystal exists as a
planar Z,Z isomer. On heating or under the action of catalytic amounts of water, as well as in reactions with
LiN(SiMe3)2 or PCl5 in 1: 1 or 1: 2 molar ratios it quantitatively converts into 2,1,3-benzothiadiazole. Accord-
ing to 15N NMR data, this transformation is accompanied by deshielding of the nitrogen atoms by 18 ppm.
Cyclic arylenazathienes of general formula I at
certain values of the a, b, and c indices form a unique
sequence of alternating every 2 electrons ten-,
twelve-, fourteen-, and more- -electron (hetero)aro-
matic and antiaromatic systems [1]. Studies on such
systems are useful for further development of the
concept of (anti)aromaticity, especially in relation to
nontraditional objects.
having
N=S=N S N=S=N
[12],
S N=S=N
S N=S=N [13], and S N=S=N S N=S=N S [14]
chains, respectively, have been obtained and struc-
turally characterized.
A priori a convenient starting material for prepar-
ing V might be N,N -disulfinyl-1,2-diaminobenzene
VI [15, 16], but the information on this compound is
controversial. Thus, the synthesis of VI from 1,2-di-
aminobenzene and SOCl2 in boiling benzene has been
described [15]. At the same time, the same reaction
in boiling toluene or in the presence of HCl acceptor
(for instance, pyridine) in ether leads to compound
II [17].
Sa (N=S=N S)b
N
Sc N==S
a, c = 0, 1; b = 0, 1, 2, ...
S
S
N
N
S
The aim of this work was to test the procedure for
preparing compound VI, described in [15], to charac-
terize this compound, and study its utility for syn-
thesis of heterocycles like V.
N
S
N
N
S
S
N
II (10 )
III (12 )
IV (14 )
Compound VI can actually be prepared by a slight-
ly modified procedure [15] in a practically quantita-
tive yield.
N
N
N
N=S=O
S
S
S
N
N=S=O
According to X-ray diffraction data, compound VI
in crystal exists as a planar Z,Z isomer (Fig. 1).
Selected bond lengths, , and bond angles, deg, in
compound VI are as follows: C1 N1 1.387(4), N1 S1
1.511(3), S1 O1 1.449(3), C2 N2 1.385(4), N2 S2
1.521(3), S2 O2 1.443(3), C1 C2 1.423(4) ; C1N1S1
V (16 )
VI
At present 10 -electron 2,1,3-benzothiadiazoles II,
[3 6], 12 -electron 1,3,2,4-benzodithiadiazines III
[6 10], and 14 -electron 1,3,5,2,4-benzotrithiadiaze-
pines IV [1, 6, 11] have been synthesized and charac-
terized as possessing a planar geometry and a united
molecular system. Further members of this series,
beginning with 16 -electron V, are still unknown [1].
No prohibition on their existence, in any case in
regard to stability of azathiene chains, evidently exists.
Acyclic analogs of 16, 18, and 20 -electron systems I
133.1(2), N1S1O1 121.52(17), C2N2S2 132.6(2),
N2S2O2 120.74(17), C3C2N2 124.5(3), C1C2N2
116.1(3), C6C1N1 124.8(3), C2C1N1 116.7(3) .
The bond lengths and bond angles in the N=S=O
groups coincide, within the experimental error, with
that in other structurally characterized compounds of
1070-3632/01/7107-1050$25.00 2001 MAIK Nauka/Interperiodica

MOLECULAR STRUCTURE AND PROPERTIES OF N,N -DISULFINYL-1,2-DIAMINOBENZENE
1051
O2
the general formula Ar N S=O {they all have Z con-
figuration, both planar (Ar = 4-BrC6H4 [8]) or non-
planar (Ar = 2,6-F2C6H3 [19] or 2,4,6-(t-Bu)3C6H2
[20]} and close to mean values [21]. The C1 C2 bond
in VI [1.423(4) ] is considerably longer than in 1,2-
diaminobenzene (1.406 [22]). In the PM3-optimized
geometry of VI, which well reproduces experimental
data, this bond length is 1.427 . According to the
calculations, the elongation of the C1 C2 bond in
going from 1,2-diaminobenzene to compound VI is
connected with decrease in its order (1.32 and 1.26,
respectively). The contribution of mutual repulsion of
the N=S=O groups in compound VI in this effect is
evidently negligible, because the C C N, C N=S, and
N=S=O angles in VI and 4-BrC6H4NSO coincide.
Moreover, in the closest analog with bulky substitu-
ents on nitrogen, N,N -bis(5-chloro-o-phenylenedi-
S2
C3
C2
N2
C4
C5
C1
N1
C6
oxy)-1,2-diaminobenzene [23], the C1 C2 distance is
S1
as small as 1.402
.
In the crystal of compound VI intermolecular inter-
O1
Fig. 1. Crystal structure of compound VI.
actions lead to formation of layers with shortened
(C5 )H5 S1 [2.85(4)
contacts (Fig. 2)
] and O1 S2 (3.265
)
Fig. 2. Crystal packing of compound VI (projection along the a axis).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 7 2001

1052
BAGRYANSKAYA et al.
Compound VI is thermally unstable, and on short
converts to N-sulfinyl-1,2-diaminobenzene (VII) [16]
and then to compound II in quantitative yield.
boiling in o-xylene it quantitatively cyclizes to give
compound II. Compound VI is extremely sensitive to
water, and already on contact with moist air it quickly
Attempted conversion of compound VI to the
possible precursors of the target heterocycle V [com-
pounds VIII and IX, with subsequent ring closure
under the action of SCl2 or (Me3Si)2N S N(SiMe3)2,
respectively] via standard 1:2 reactions with LiN
(SiMe3)2 [10] or PCl5 [24], too, gave nothing more
than compound II. Analogous result was obtained
with the corresponding 1:1 reactions. Apparently, the
modification of one NSO group in compound VI
under the action of one or another reagent is accom-
panied by fast intramolecular condensation of the
modified fragment with the second NSO group, thus
leading to II.
N
S
SO2
N
N=S=O
N=S=O
II
N=S=O
NH2
H2O
H2O
SO2
VII
N=S=NSiMe3
N=S=NSiMe3
LiN(SiMe3)2
LiOSiMe3
N=S=O
VIII
N=S=NSiMe3
Me3SiNSO
VI
II
N=S=O
N=SCl2
PCl5
SOCl2
POCl3
N=SCl2
N=SCl2
IX
The
and
values in the 15N and 17O NMR
O
Clearly, the facility of transformation to II consi-
derably restricts the utility of compound VI in hetero-
cyclic synthesis. At the same time, this compound,
being now thoroughly characterized, is an interesting
ligand for the coordination chemistry of the
Ar N=S=O group [31, 32].
N
spectra of compound VI (311.9 and 416 ppm, respec-
tively) are characteristic of the Ar N=S=O group
[25 28]. They practically coincide with those in
N-sulfinyl-2-fluoroaniline [25, 26]. In going from
compound VI to compound II ( 329.9 ppm), the
nitrogen atom is deshielded by 18 Nppm. As the trans-
formation of N=S=O to N=S=N (for example, in
going from Ph N=S=O to Ph N=S=N Ph) results in
enhanced (by 20 ppm [29]) shielding of the nitrogen
atom, it can be proposed that the effect observed in
EXPERIMENTAL
The 1H, 13C, 15N, and 17O NMR spectra were
measured for CDCl3 solutions on a Bruker DRX-500
spectrometer at 500.13, 125.76, 50.68, and
67.80 MHz, respectively, against TMS, liquid NH3,
and D2O. The mass spectra were obtained on a
the case of the VI
nature, with prevalence of deshielding due to hetero-
II transformation is integral in
aromatic ring closure. These data are in agreement Finnigan MAT MS-8200 spectrometer (electron
with the fact that the signal of compound II in the 15N
NMR spectra is shifted downfield by 32 ppm from
that of Ph N=S=N Ph [29, 30].
impact, 70 eV). The UV spectra were taken on a
Specord UV-Vis spectrophotometer for heptane
solutions.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 7 2001

MOLECULAR STRUCTURE AND PROPERTIES OF N,N -DISULFINYL-1,2-DIAMINOBENZENE
1053
X-ray diffraction experiment was performed
with a crystal of compound VI (0.52 0.36 0.12 mm)
on a Bruker P4 diffractometer at 50 C (MoK radia-
tion, graphite monochromator, 2 / -scanning in the
range 2 < 50 C). The crystal is triclinic, a 7.420(3) ,
Atomic coordinates ( 104) and equivalent isotropic
2
parameters (
Atom
,
103) for non-hydrogen atoms in VI
x/a
y/b
z/c
Ueq
b 7.830(2) , c 8.246(2)
,
109.57(2) , 114.90 ,
S1
S2
1176(1) 1867(1)
5682(1)
774(1)
6929(4)
2136(4)
3989(4)
965(4)
3252(4)
1615(4)
801(6)
1587(6)
3162(6)
3979(5)
51(1)
43(1)
79(1)
56(1)
39(1)
35(1)
33(1)
33(1)
44(1)
55(1)
54(1)
47(1)
93.17(3) , V 398.5 3, space group P-1, Z 2, C6H4
2021(1)
3100(4)
1380(4)
919(4)
8591(1)
499(4)
9699(3)
3584(3)
6840(3)
N2O2S2, dcalc 1.669 g/cm3, 0.622 mm . Intensities
O1
O2
N1
N2
C1
C2
C3
C4
C5
C6
1
of 1195 unique reflections were measured. Absorption
correction was determined empirically from the
azimuthal scanning curves for 7 reflections (transmis-
sion 0.41 0.77). The structure was solved by the
direct method using the SHELXS-86 program (posi-
tions of hydrogen atoms were calculated geometrically)
and refined by the least-squares method in the full-
matrix anisotropic isotropic (for H atoms) approxima-
tion using the SHELXL-97 program. The structure
was refined on all F2 to wR2 0.160 and S 1.102; 126
parameters were refined (R 0.0534 for 1062 F > 4 ).
Coordinates and thermal parameters for non-hydrogen
atoms are given in the table.
574(4)
2230(4) 4245(4)
1423(4) 5980(4)
2653(6) 6708(5)
4642(6) 5759(6)
5423(5) 4059(6)
4247(5) 3318(5)
compound II (purified by vacuun sublimation), yield
0.65 g (95%).
The syntheses described below were carried out in
absolute solvents under argon.
c. To a stirred solution of 6.68 g of LiN(SiMe3) in
50 ml of hexane, a solution of 4.00 g or 8.00 g of
compound VI in 100 ml of hexane was added drop-
wise with stirring at 70 C. The mixture was heated
to room temperature within 2 h and then 5 ml of
Me3SiCl was added. The precipitate was filtered off,
the solvent was removed at reduced pressure, and the
residue was crystallized from hexane and sublimed in
a vacuum to obtain 2.05 g (75%) or 4.46 g (82%) of
compound II at 2:1 and 1:1 reagent molar ratios,
respectively.
N,N -Disulfinyl-1,2-diaminobenzene (VI). A solu-
tion of 25 ml of SOCl2 in 15 ml of CCl4 was added
dropwise at 0 C to a solution of 7.56 g of 1,2-diami-
nobenzene in 60 ml of CCl4. The reaction mixture
was refluxed for 2 h, the resulting orange-red solution
was evaporated under reduced pressure, and the re-
sidue was crystallized from a 3:1 hexane CCl4 mix-
ture containing a little SOCl2 to obtain 13.73 g (98%)
of compound VI as bright golden yellow crystals, mp
56 57 C (agrees with [15]). Mass spectrum, M+ (m/z),
measured 199.9739, calculated for C6H4N2S2
d. A mixture of 1.00 g of compound VI, 20 ml of
CCl4, and 2.08 g or 1.04 g of PCl5 was stirred at 40 C
until real solution had formed ( 30 min). The solvent
was removed at reduced pressure, and the residue was
sublimed in a vacuum and crystallized from hexane to
obtain 0.54 g (80%) or 0.58 g (85%) of compound II
at 2:1 and 1:1 reagent molar ratios, respectively.
1
199.9714. H NMR spectrum, , ppm: 8.08 (H3,6),
7.37 (H4, H5) (agrees with [16]. 13C NMR spectrum,
C, ppm; 135.3 (C1, C2) 129.8 (C4, C5), 126.5 (C3,
C6). 15N NMR spectrum: N, ppm: 311.9 t (J 1.0 Hz).
17O NMR spectrum:
416 ppm (
170 Hz). UV
O
spectrum, max, nm (log ): 335 (3.951s/2h), 314 (4.03),
240 (3.77).
Compound II was identified by the melting point,
1H NMR spectrum, UV spectrum, and low-resolution
mass spectrum, which were in agreement with pub-
lished data. 15N NMR spectrum, N, ppm: 329.9 t (J
0.5 Hz). For the 15N NMR spectra of the other com-
pounds I, see [1, 10, 34].
2,1,3-Benzothiadiazole (II). a. A solution of
1.00 g of compound VI in 10 ml of o-xylene was
refluxed (144 C) until decoloration and then distilled
in a vacuum to obtain 0.63 g (92%) of compound II
as a colorless oil, bp 63 64 C (1.5 mm), that crystal-
lized on handling, mp 43 44 C.
b. Compound VI, 1.00 g, without protection from
ACKNOWLEDGMENTS
air moisture quickly converted to a red oil (com-
1
pound VII [16]). Mass spectrum, m/z: 154 (M+). H
The work was financially supported by the Russian
Foundation for Basic Research (project nos. 99-03-
33115 and 96-07-89187).
NMR spectrum agrees with that described in [16].
This compound solidified to colorless crystals of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 7 2001

1054
BAGRYANSKAYA et al.
17. Pesin, V.G., Usp. Khim., 1970, vol. 39, no. 11,
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