Unexpected formation of a sterically protected nitrogen pentasulfide ArNS5 (Ar = 2,6-dimesityl-4-methylphenyl) and the X-ray crystallographic analysis

Article abstract of DOI:10.1039/a805235b

A stable cyclic nitrogen pentasulfide ArNS₅ (Ar = 2,6-dimesityl-4-methylphenyl) was unexpectedly obtained by passing the corresponding N-thiosulfinylaniline through a silica gel column and the chair form of the six-membered ring was revealed by

Full text of DOI:10.1039/a805235b

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Unexpected formation of a sterically protected nitrogen pentasulfide ArNS5
(Ar = 2,6-dimesityl-4-methylphenyl) and the X-ray crystallographic analysis
Shigeru Sasaki, Hiroya Hatsushiba and Masaaki Yoshifuji*
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan.
E-mail: yoshifj@mail.cc.tohoku.ac.jp
A stable cyclic nitrogen pentasulfide ArNS5 (Ar = 2,6-dime-
sityl-4-methylphenyl) was unexpectedly obtained by passing
the corresponding N-thiosulfinylaniline through a silica gel
column and the chair form of the six-membered ring was
revealed by X-ray crystallographic analysis.
similarly to other sterically protected anilines.7 Sulfurization of
2† with S2Cl2 in the presence of triethylamine6,8 gave a reddish
purple oil, which was assigned as N-thiosulfinylaniline 3.
Almost quantitative formation of 3 was confirmed by 1H NMR.
However, 3 decomposed during attempted purification by
column chromatography (SiO2–n-hexane) and cyclic nitrogen
pentasulfide 1 was isolated in 21% as a yellow solid. N,NA-
Bis(2,6-dimesityl-4-methylphenyl)sulfurdiimide 4 (10%) was
another identified product and 61% of aniline 2 was recovered.
Pale yellow prisms suitable for X-ray crystallographic analysis
were obtained after recrystallization from n-hexane.§
Cyclic nitrogen polysulfides NSx other than the eight-mem-
bered ring were not known for many years due to the lack of an
appropriate method of preparation and their instability. Re-
cently, Steudel et al. discovered a route to NSx heterocycles (x
= 5, 6, 8, 9, 11)1 by using titanocene complexes, but most of
them turned out to be unstable materials. On the other hand,
introduction of sterically demanding groups has played an
important role in the isolation of several cyclic polysulfides
such as CSx,2 but such an attempt at kinetic stabilization of
cyclic nitrogen polysulfides has not been reported. Recently,
we3 and Protasiewicz4 have reported the synthesis of group15
element compounds such as diphosphenes and phosphaarsene
possessing sterically protecting groups of the 2,6-diarylphenyl
type, which have been successfully used by Power et al. for the
stabilization of a wide range of compounds from low valent
transition metals to main-group element compounds.5 One of
the noteworthy points of the 2,6-dimesityl-4-methylphenyl
group is the difference of reactivity of the ortho substituents as
compared with the widely used 2,4,6-tri-tert-butylphenyl group,
in spite of the comparable sterically protecting effect.3 During
our systematic study on group 15 compounds possessing the
2,6-dimesityl-4-methylphenyl group, we became interested in
N-thiosulfinylaniline 3, since the 2,4,6-tri-tert-butylphenyl
derivative cyclizes to form a five membered heterocycle despite
the bulkiness of the tert-butyl group.6 However, 3 was not so
stable as expected and we obtained the stable cyclic nitrogen
pentasulfide ArNS5 1 unexpectedly (Scheme 1).
Fig. 1 shows the molecular structure of 1. The NS5 ring takes
11
a chair form like CS5,9 S6,10 and TiS5 heterocycles and the
torsion angles within the six-membered ring range from
67.42(5) to 74.88(8)°, which deviate markedly from values of
ca. 100° of the stable eight-membered rings such as HNS712 and
S8.13 On the other hand, the bond lengths and angles do not
differ greatly from those for HNS7.12 The nitrogen atom takes
almost planar geometry with the sum of the bond angles around
N(1) as 359.57°, and the dihedral angle between the plane
2,6-Dimesityl-4-methylaniline (2) was prepared by LiAlH4
reduction of the corresponding phenyl azide in 96%, which was
synthesized from the corresponding iodobenzene by lithiation
followed by quenching with p-toluenesulfonyl azide in 95%.
Oxidation of 2 with MCPBA afforded the corresponding
nitrosobenzene‡ as a stable pale green solid in 72% yield
I
NH2
NSS
Mes
Mes
i, ii, iii
Mes
Mes
Mes
Mes
iv
CH3
CH3
CH3
2
3
S
N
S
S
S
Fig. 1 Molecular structure of 1 in the crystal. ORTEP drawing with 50%
probability ellipsoids. Selected bond lengths (Å), bond angles (°), and
torsion angles (°): S(1)–N(1) 1.699(1), S(1)–S(2) 2.0612(7), S(2)–S(3)
2.0803(6), S(3)–S(4) 2.0718(6), S(4)–S(5) 2.0704(7), S(5)–N(1) 1.700(1),
N(1)–C(1) 1.442(2), S(2)–S(1)–N(1) 104.40(5), S(1)–S(2)–S(3) 100.89(3),
S(2)–S(3)–S(4) 99.14(2), S(3)–S(4)–S(5) 102.12(2), S(4)–S(5)–N(1)
104.01(5), S(1)–N(1)–S(5) 116.01(8), S(1)–N(1)–C(1) 121.61(10),
S(5)–N(1)–C(1) 121.95(10), S(1)–S(2)–S(3)–S(4) –70.01(3), S(1)–N(1)–
S(5)–S(4) 73.29(8), S(2)–S(1)–N(1)–S(5) –74.88(8), S(2)–S(3)–S(4)–S(5)
69.64(3), S(3)–S(2)–S(1)–N(1) 69.20(5), S(3)–S(4)–S(5)–N(1) 69.20(5).
S
Mes
NSN
Mes Mes
Mes
Mes
Mes
v
H3C
CH3
+
CH3
1
4
Scheme 1 Reagents and conditions: i, n-BuLi, THF; ii, TsN3; iii, LiAlH4,
diethyl ether; iv, S2Cl2, Et3N, diethyl ether; v, SiO2
Chem. Commun., 1998
2221

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15), a = 28.445(7), b = 12.653(2), c = 17.078(2) Å, b = 125.79(1)°, U =
4985(1) Å3, Z = 8, Dc = 1.337 g cm23, m = 0.479 mm21, T = 112(1) K,
F(000) = 2112.00. Rigaku RAXIS-IV imaging plate area detector with
defined by N(1), S(1), S(5), and C(1) and the central benzene
ring is 55.07°. The NS5 ring aligns in the direction of the b axis
with the short contact less than the sum of van der Waals radii
between S(2) and S(5*), S(1) and S(4*) of the neighboring
molecules (marked with*), being 3.4102(6) and 3.6219(6) Å,
respectively. Although the mechanism of the formation of 1 is
not clear at present, oligomerization (stoichiometrically trimer-
ization) of N-thiosulfinylaniline 3 followed by elimination of a
stable sulfurdiimide 4 might afford 1, since the electrophilicity
of 3 might be enhanced by an acid on the silica gel surface. The
ring size could depend on the steric demand or the cavity size
made by the two mesityl groups.
The authors are grateful for financial support in part from The
Japan Securities Scholarship Foundation and Grants-in-Aid for
Scientific Research from the Ministry of Education, Science,
Sports and Culture (Nos. 08454193 and 09239101). Shin-Etsu
Chemical Co. is also gratefully appreciated for donation of
silicon chemicals. The authors also thank Instrumental Analysis
Center for Chemistry, Graduate School of Science, Tohoku
University for the measurement of mass spectra.
graphite monochromated Mo-Ka radiation, l
= 0.71070 Å. No. of
reflections measured 4405. No. of observations [I > 3.00s(I)] 4060. The
structure was solved by direct method (SAPI9114), expanded using Fourier
techniques (DIRDIF9415), and refined by full matrix least squares on F for
389 variable parameters. The non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were refined isotropically. R = 0.031 Rw = 0.054
for observed reflections [I > 3.00s(I)] and R = 0.034, Rw = 0.058 for all.
Goodness of fit S = 1.42. The maximum and minimum peaks on the final
difference Fourier map corresponded to 0.26 and 20.29 e Å23, re-
spectively. Structure solution, refinement, and graphical representation
were carried out using teXsan package.16 CCDC 182/994.
1 For x = 8, 9: K. Bergemann, M. Kustos, P. Krüger and R. Steudel,
Angew. Chem., Int. Ed. Engl., 1995, 34, 1330; for x = 8, 9, 11: R.
Steudel, K. Bergemann, J. Buschmann and P. Luger, Angew. Chem., Int.
Ed. Engl., 1996, 35, 2537; for x = 5, 6: R. Steudel, O. Schmann, J.
Buschmann and P. Luger, Angew. Chem., Int. Ed. Engl., 1998, 37,
492.
2 N. Takeda, N. Tokitoh, T. Imakubo, M. Goto and R. Okazaki, Bull.
Chem. Soc. Jpn., 1995, 68, 2757.
3 K. Tsuji, Y. Fujii, S. Sasaki and M. Yoshifuji, Chem. Lett., 1997,
855.
Notes and References
4 E. Urnezius and J. D. Protasiewicz, Main Group Chemistry, 1996, 1,
369; S. Shah, S. C. Burdette, S. Swavey, F. L. Urbach and J. D.
Protasiewicz, Organometallics, 1997, 16, 3395.
5 X. He, M. M. Olmstead and P. P. Power, J. Am. Chem. Soc., 1992, 114,
9668; J. J. Ellison, K. Ruhlandt-Senge and P. P. Power, Angew. Chem.,
Int. Ed. Engl., 1994, 33, 1178; S. Simons, L. Pu, M. M. Olmstead and
P. P. Power, Organometallics, 1997, 16, 1920.
6 Y. Inagaki, R. Okazaki and N. Inamoto, Bull. Chem. Soc. Jpn., 1979, 52,
1998.
7 R. Okazaki, T. Hosogai, E. Iwadare, M. Hashimoto and N. Inamoto,
Bull. Chem. Soc. Jpn., 1969, 42, 3611.
8 Y. Inagaki, R. Okazaki and N. Inamoto, Bull. Chem. Soc. Jpn., 1979, 52,
1998.
9 F. Von Fehér and J. Lex, Z. Anorg. Allg. Chem., 1976, 423, 103.
10 J. Donohue, A. Caron and E. Goldish, J. Am. Chem. Soc., 1961, 83,
3748.
11 E. F. Epstein, I. Bernal and H. Köpf, J. Organomet. Chem., 1971, 26,
229.
12 H.-J. Von Hecht, R. Reinhardt, R. Steudel and H. Bradaczek, Z. Anorg.
Allg. Chem., 1976, 426, 43.
13 A. S. Cooper, W. L. Bond and S. C. Abrahams, Acta. Crystallogr., 1961,
14, 1008; A. Caron and J. Donohue, ibid., 1965, 18, 562; S. C.
Abrahams, ibid., 1965, 18, 566.
14 H.-F. Fan, 1991, Structure Analysis Programs with Intelligent Control,
Rigaku Corporation, Tokyo, Japan.
15 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman, R. de
Gelder, R. Israel and J. M. M. Smits, 1994, The DIRDIF94 program
system, Technical Report of the Crystallography Laboratory, University
of Nijmegen, The Netherlands.
16 Crystal Structure Analysis Package, Molecular Structure Corporation,
1985 and 1992.
† To a solution of 2 (300 mg, 0.873 mmol) in a mixture of triethylamine (0.3
ml, 2.15 mmol) and diethyl ether (15 ml), a solution of disulfur dichloride
(0.09 ml, 1.13 mmol) in diethyl ether (10 ml) was added dropwise at 0 °C
to give a red mixture. After being stirred for 1 h at 0 °C, the reaction mixture
was poured into ice-water, extracted with diethyl ether, dried over MgSO4,
and concentrated to give crude 3 as a red oil almost quantitatively. The oil
was submitted to silica-gel column chromatography (gradient elution with
n-hexane and chloroform) to give 1 (21%) and 4 (10%), together with
recovery of 2 (61%). Further recrystallization of 1 from n-hexane afforded
pure 1 as yellow prisms. 3: reddish brown oil; 1H NMR (200 MHz, CDCl3)
d 7.05 (2H, s, arom.), 6.87 (4H, s, Mes-arom.), 2.43 (3H, s, CH3), 2.28 (6H,
s, Mes-p-CH3), 2.10 (12H, s, Mes-o-CH3); LRMS (EI, 70 eV) m/z 405 (M+,
8), 341 (M+ 2 2S, 62), 326 (M+ 2 2S 2 CH3, 100), 311 (M+ 2 2S 2 2CH3,
25); UV–VIS (CH2Cl2) lmax 465 nm. 1: yellow prisms; mp 133.0–134.0 °C;
1H NMR (200 MHz, CDCl3) d 7.04 (4H, s, Mes-arom.), 6.84 (2H, s, arom.),
2.37 (6H, s, Mes-p-CH3), 2.34 (3H, s, CH3), 2.10 (12H, s, Mes-o-CH3); 13
C
NMR (50 MHz, CDCl3) d 145.3, 137.6, 137.5, 137.5, 136.4 , 130.7, 128.7,
21.3, 21.2, 20.9 (one quarternary carbon peak was missing at 295 and 323
K, probably due to dynamic behavior); IR (KBr) 3016, 2947, 2916, 2854,
1612, 1452, 1444, 1423, 1375, 1205, 1182, 1039, 1030, 870, 849, 758 cm21
;
UV–VIS (hexanes) lmax(e) 246.4 (17900) nm ; LRMS (EI, 70 eV) m/z 501
(M+, 0.4), 405 (M+ 2 3S, 6), 373 (M+ 2 4S, 5), 341 (M+ 2 5S, 58), 326 (M+
2 5S 2 CH3, 100), 311 (M+ 2 5S 2 2CH3, 24), 296 (M+ 2 5S 2 3CH3,
11); HRMS (EI, 70 eV) Found: m/z 501.0757, calc. for C25H27NS5: M
501.0748.
‡ 2,6-Dimesityl-4-methylphenylnitrosobenzene: light green crystals; mp
1
195.0–196.0 °C; H NMR (200 MHz, CDCl3) d 7.03 (2H, s, arom.), 6.93
(4H, s, Mes-arom.), 2.44 (3H, s, CH3), 2.34 (6H, s, Mes-p-CH3), 1.87 (12H,
s, Mes-o-CH3); 13C NMR (50 MHz, CDCl3) d 162.6, 146.0 , 136.6, 135.6,
135.5, 133.8, 131.0, 128.7, 21.7, 21.1, 20.6; LRMS (EI, 70 eV) m/z 357 (M+,
100), 340 (M+ 2 CH3, 87); UV–VIS (CH2Cl2) lmax 810 nm.
§ Crystal data for 1: C25H27NS5, M = 501.79, pale yellow prisms, crystal
dimensions 0.60 3 0.50 3 0.40 mm3, monoclinic, space group C2/c (no.
Received in Cambridge, UK, 7th July 1998; 8/05235B
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Chem. Commun., 1998