Investigations on organo-sulfur-nitrogen rings and the thiocyanogen polymer, (SCN)x

Article abstract of DOI:10.1002/chem.200501528

The synthesis and full characterisation of a series of 1,2,4-thiadiazoles is reported. (SCN)_x has been studied by a variety of techniques and the data compared with 1,2,4-thiadiazole and 1,2,4-dithiazoles. The observed data suggest that the polymer consists of 1,2,4-dithiazole rings linked by nitrogen atoms. For (SCN)_x, the MALDI-TOF mass spectroscopy showed a parent ion at 1149 and a series of peaks with (SCN)₂ repeat units (116 m/z); this result implies that (SCN)₂ may be the monomer unit of the polymer. Its IR spectrum shows a very broad peak with maximum at 1134 cm^-1 consisting of several overlapping peaks in the same region as ring vibrations for 1,2,4-thiadiazole and 1,2,4-dithiazole compounds. Peaks in the Raman spectrum in the range 400-480 cm^-1 support the presence of disulfide units within the polymer. The solid-state ¹³C NMR (99% ¹³C-labelled) spectrum is dominated by two singlets of equal intensity at approximately 187 and 184 ppm with low intensity peaks in the range 152-172 ppm, in approximately the same range as both 1,2,4-thiadiazoles and 1,2,4-dithiazoles. The solid-state ¹⁵N NMR (99% ¹⁵N labelled) spectrum displays two major peaks of similar intensity at 236.9 and 197.2 ppm, which are clearly very different environments to those observed in bis(3-bromo-1,2,4-thiadiazol-5-yl) disulfide, but similar to 1,2,4-dithiazoles. The X-ray structures of seven C-S-N systems are reported. Preliminary studies on (SeCN)_x suggest that literature references to this polymer may be in error with the red solid actually being red selenium.

Full text of DOI:10.1002/chem.200501528

DOI: 10.1002/chem.200501528
Investigations on Organo–Sulfur–Nitrogen Rings andthe Thiocyanogen
Polymer, (SCN)x
W. Russell Bowman,[b] Colin J. Burchell,[a] Petr Kilian,[a] Alexandra M. Z. Slawin,[a]
[a]
Philip Wormald,[a] andJ. Derek Woollins*
Abstract: The synthesis and full charac-
terisation of a series of 1,2,4-thiadi-
1134 cmÀ1 consisting of several overlap-
ping peaks in the same region as ring
vibrations for 1,2,4-thiadiazole and
1,2,4-dithiazole compounds. Peaks in
the Raman spectrum in the range 400–
480 cmÀ1 support the presence of disul-
fide units within the polymer. The
solid-state 13C NMR (99% 13C-label-
led) spectrum is dominated by two sin-
glets of equal intensity at approximate-
ly 187 and 184 ppm with low intensity
peaks in the range 152–172 ppm, in ap-
proximately the same range as both
1,2,4-thiadiazoles and 1,2,4-dithiazoles.
The solid-state 15N NMR (99% 15N la-
belled) spectrum displays two major
peaks of similar intensity at 236.9 and
197.2 ppm, which are clearly very dif-
ferent environments to those observed
in bis(3-bromo-1,2,4-thiadiazol-5-yl) di-
sulfide, but similar to 1,2,4-dithiazoles.
The X-ray structures of seven C-S-N
systems are reported. Preliminary stud-
ies on (SeCN)x suggest that literature
references to this polymer may be in
error with the red solid actually being
red selenium.
A
studied by a variety of techniques and
the data compared with 1,2,4-thiadi-
A
served data suggest that the polymer
consists of 1,2,4-dithiazole rings linked
by nitrogen atoms. For (SCN)x, the
MALDI-TOF
mass
spectroscopy
showed a parent ion at 1149 and a
series of peaks with (SCN)2 repeat
units (116 m/z); this result implies that
(SCN)2 may be the monomer unit of
the polymer. Its IR spectrum shows a
very broad peak with maximum at
Keywords: nitrogen heterocycles ·
polymers · structure elucidation ·
sulfur heterocycles
Introduction
published work on polythiocyanogen reports that the mate-
rial is a semiconductor,[5] though thin films appear to be in-
sulators,[6] that it is photoactive[7] and it has been used in
photocatalytic systems.[8] Several groups have proposed that
the mechanism for polymerisation is a radical process in-
Polythiocyanogen (or parathiocyanogen) with the empirical
formula (SCN)x was first reported in 1919 by Soderback,[1]
who observed that thiocyanogen (SCN)2 was thermally un-
stable and spontaneously polymerised to give an orange/
brick-red solid product. It can also be prepared by chemical
or electrical oxidation of thiocyanates in melts or solution[2,3]
or, in the solid state, by passing chlorine gas over alkali
metal thiocyanates.[4] Though all of these routes probably in-
volve forming (SCN)2 at some stage, it should be noted that
the method in reference [4]may give rise to material conta-
minated with NaCl, since the reported yield is 135%. The
C
volving SCN and that the polymer has a conjugated double-
bond structure. The spectroscopic data published for poly-
thiocyanogen is limited and some of it is of quite poor quali-
ty,[4,9–13] for example, Cataldo has illustrated two completely
different solution-state 13C NMR spectra, the first[11] with a
S/N ratio of approximately 1.6 was assigned with dC =
144 ppm and second[12] has dC =189 ppm and is remarkable
for the absence of any solvent (DMF) resonances, especially
when one considers that (SCN)x is almost completely insolu-
ble. A number of speculative structures have been proposed
in the literature. An early hypothesis was that the structure
could be composed of 1,3,5-triazine rings linked by disulfide
bridges formed by the trimerisation of the nitrile groups in
thiocyanogen (Figure 1).[9,10] An alternative proposal was
that polythiocyanogen has a linear structure analogous to
that of polythiazyl (SN)x (Figure 1b).[4,11] The most recent
structure proposed by Cataldo et al. consists of polyazome-
[a]Dr. C. J. Burchell, Dr. P. Kilian, Prof. A. M. Z. Slawin,
Dr. P. Wormald, Prof. J. D. Woollins
School of Chemistry, University of St. Andrews
St. Andrews, Fife, KY16 9ST (UK)
Fax : (+44)1334-463-384
E-mail: jdw3@st-andrews.ac.uk
[b]Prof. W. R. Bowman
Department of Chemistry, Loughborough University
Loughborough LE11 3TU (UK)
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FULL PAPER
Hordvic confirmed the 3-amino-5-thione-1,2,4-dithiazole
structure by X-ray crystallography, which clearly showed the
presence of two adjacent sulfur atoms in a five membered
ring.[17] Of the two possible tautomers Hordvic proposed
structure I, with the both hydrogen atoms located on the
exocyclic nitrogen (Figure 2). This structure was further sup-
Figure 2. Possible tautomers of isoperthiocyanic acid.
ported by IR data published by Emeleus et al. confirming
that an NH2 group is present.[18] Isoperthiocyanic acid is
readily converted into the barium salt of perthiocyanic acid
by treatment with barium hydroxide.[19] The isomerisation
can be reversed by treatment of the barium salt of perthio-
cyanic acid with hydrochloric acid (Scheme 2).
Figure 1. Proposed structures for polythiocyanogen a) 1,3,5-triazine struc-
ture, b) linear structure and c) polyazomethine chain.
Scheme 2. Reaction of isoperthiocyanic acid with barium hydroxide.[19]
thine chains analogous to those in polycyanogen (CN)x but
cross-linked by disulfide bridges (Figure 1c).[12,13] Cataldo
has also speculated[13] that a cross-linked polycyanogen
structure, with Sz bridges, can be used to rationalise the
structures of a new series of polymers [Sz(CN)2]x (z=1–4),
though this work has to be treated with some skepticism
since 1) the SzCl2 starting materials do not appear to have
been distilled and so are probably a mixture of S2Cl2 and
SCl2 and 2) the new polymers have only been characterised
by their (very broad) IR spectra and no analytical data is in-
cluded in the report.
In preliminary work in collaboration with Knoll Micro-
Check into the biological activity of SCN containing species,
we carried out some studies on polythiocyanogen (SCN)x. In
these studies, UV/VIS, Raman and 14N NMR spectroscopy
suggested to us that the polymer may be based on five-
membered rings. The literature further supports this propos-
al. It was reported in 1821 by Wohler that concentrated sol-
utions of isothiocyanic acid HNCS deposited isoperthiocyan-
ic acid (SCN)2HS2 (Scheme 1).[14–16]
Furthermore Soderback reported that reaction of thiocya-
nogen with HCl in ethereal solution yields two products: a
colourless crystalline compound of formula (SCN)2·2HCl
and a yellow solid with molecular formula (SCN)4Cl2.[19,20]
The reaction of (SCN)2·2HCl with water yields (SCN)2·H2O
(Scheme 3).[21]
Scheme 3. Speculative structures of the species involved in the reaction
of (SCN)2·2HCl with water.[21]
The 1,2,4-dithiazole structure of (SCN)2·H2O was con-
firmed by X-ray crystallography;[22] this result led to struc-
ture III being proposed for (SCN)2·2HCl (Figure 3). The as-
Scheme 1. Synthesis of isoperthiocyanic acid.[14–16]
Figure 3. Proposed structure for (SCN)2·2HCl and (SCN)4Cl2.[18]
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J. D. Woollins et al.
signment of structure III was further supported by compari-
son of the IR spectra of (SCN)2·H2O and (SCN)2·2HCl.[18]
A 1,2,4-thiadiazol-3-yl disulfide structure (IV) has been
suggested for the second product (SCN)4Cl2.[19,20] Some simi-
larities of the IR spectra with perthiocyanic acid and its
barium salt have been observed,[23] but the spectroscopic evi-
dence is not conclusive. Soderback reported that reduction
of (SCN)4Cl2 with mercury gives a compound Hg[(SCN)2Cl]2
N
that can be reconverted to (SCN)4Cl2 by reaction with
iodine (Scheme 4).[19,20] Treatment of the mercury compound
(V) with sodium sulfide was reported to give a highly unsta-
ble sodium salt which was proposed to be of 5-chloro-3-thio-
1,2,4-thiadiazole.[19,20]
It was reported that reaction of this sodium salt (VI) with
sodium hydroxide yields a mixture of polythiocyanogen, the
disodium salt of 5-hydroxy-3-thio-1,2,4-thiadiazole (VII) and
a
by-product with molecular formula C4N4OS4Na2
Figure 4. Our proposed structures of polythiocyanogen based on 1,2,4-
thiadiazole (top) and 1,2,4-dithiazoles (bottom).
(Scheme 4).[19,20] Structure VIII was suggested for Na2-
[C4N4OS4], since this compound can also be prepared by the
reaction of the sodium salt VI with VII.[19,20]
Although some of these 1,2,4-
thiadiazoles have been synthes-
ised before, the spectroscopic
data is very limited[19,24–26] and
only one compound has pub-
lished 13C NMR data.[27] We
also report the synthesis of
model compounds composed of
two
1,2,4-thiadiazole
rings
linked by a sulfur bridge. Se-
lected examples have been
studied by X-ray crystallogra-
phy. The spectroscopic data ob-
tained for polythiocyanogen has
U
also been compared to a series
of known 1,2,4-dithiazole com-
pounds and we conclude that
the structure of (SCN)x is based
Scheme 4. Proposed reactions of (SCN)4Cl2.[19,20]
upon
1,2,4-dithiazole
rings
linked by nitrogen atoms.
Though often unsupported by modern spectroscopic
methods, the literature clearly illustrates the diversity of het-
erocyclic five-membered C-S-N rings. Therefore we thought
it is quite possible that polythiocyanogen could be composed
of such rings. We considered two possible structures for
(SCN)x. Firstly a structure based on 1,2,4-thiadiazole rings
with sulfur bridges and secondly 1,2,4-dithiazole rings linked
by exocyclic nitrogen atoms (Figure 4). In both structures
the SCN topology is retained.
Experimental Section
Unless otherwise stated, all operations were carried out under an
oxygen-free nitrogen atmosphere by using standard Schlenk techniques.
All solvents and reagents were purchased from Aldrich, Alfa Aesar,
BOC, BDH, Fisons and Strem. We are grateful to Johnson Matthey PLC
for the loan of precious metal salts. Diethyl ether and THF were purified
by reflux over sodium/benzophenone and distillation under nitrogen.
Hexane was purified by reflux over sodium and distillation under an at-
mosphere of nitrogen. Dichloromethane was heated to reflux over pow-
dered calcium hydride and distilled under nitrogen. Chloroform (99
atom% d), and CD2Cl2 (99.6+ atom D) were used as received. Labelled
(99%) 15N and 13C KNCS came from Aldrich. Dipotassium cyanodithio-
Clearly, this is a very confused and difficult area with
many different speculative structures for (SCN)x and a pau-
A
N heterocycles. Here we report the synthesis and spectro-
scopic characterisation of polythiocyanogen (including 13C
and 15N labeling experiments). Furthermore, the literature
structures in Schemes 3 and 4 led us to synthesise a series of
1,2,4-thiadiazoles for spectroscopic comparison with (SCN)x.
imidocarbonate was prepared by the reaction of cyanamide with carbon
disulfide and potassium ethoxide.[28] Potassium methyl cyanodithioimido-
carbonate was prepared by reaction of dipotassium cyanodithioimidocar-
bonate with methyl iodide.[29] S-Methylisothiourea hydrochloride and S-
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Sulfur–Nitrogen Heterocycles
FULL PAPER
tert-butylisothiourea hydrochloride were prepared by the reaction of thio-
urea, HCl and methanol or tert-butanyl alchohol, respectively.[30] [PtCl2-
807 (m), 740 (w), 713 (w), 688 (s), 589 (m), 538 (m), 524 (m), 484 (s), 436
(w), 409 (w), 374 (w), 306 cmÀ1 (w); Raman (glass capillary): n˜ =2970 (s),
2927 (vs), 1452 (w), 1347 (s), 1200 (w), 1162 (w), 936 (vw), 911 (vw), 809
(w), 687 (s), 591 (m), 411 (m), 309 cmÀ1 (s).
ACHTREUNG
ACHTREUNG
Synthesis of compound3 : Compound
(BOC) was dried by passing the gas over phosphorus pentoxide. Ammo-
nium hydroxide, bromine, copper(I) chloride, ferric acetylacetonate, lithi-
um triethylborohydride 1m in THF, N-methylpyrrolidone, methylmagne-
sium bromide, potassium thiocyanate, sodium hydroxide, sodium methox-
ide, sodium thiomethoxide, sulfuryl chloride, trichloromethylsulfenyl
chloride were used as received. Silver thiocyanate was prepared by
mixing equimolar quantities of potassium thiocyanate with silver nitrate
in water. Infrared and Raman spectra were recorded (IR spectra as KBr
discs unless otherwise stated) on a Perkin–Elmer System 2000 FT/IR/
1 (1.000 g. 6.00 mmol) was dissolved in
methanol (40 cm3). Sodium thiometh-
oxide (0.421 g, 6.00 mmol) was added
as a solid in one portion. The resultant
solution was heated to 408C for 24 h.
The solvent was removed in vacuo and
dichloromethane (50 cm3) added. The
resultant mixture was filtered through
a celite pad to remove precipitated
1
Raman spectrometer. 31P, 13C and H NMR spectra were recorded using a
NaCl. The solvent was then removed in vacuo to give the product as a
yellow oil. Yield 0.883 g (83%); elemental analysis calcd (%) for
C4H6N2S3: C 26.95, H 3.39, N 15.71; found: C 26.93, H 3.36, N 15.64;
13C{1H} NMR (CD2Cl2): d=189.1 (s C5), 171.5 (s, C3), 16.8 (s, C5SCH3),
15.1 ppm (s, C3SCH3); 1H NMR (CD2Cl2): d=2.59 (s, 3H; C3SCH3),
2.53 ppm (s, 3H; C5CH3); ES+ MS: m/z: 178 [M+H]+; IR (KBr): n˜ =
3000 (w), 2927 (m), 2845 (vw), 2413 (vw), 2282 (vw), 1591 (w), 1526 (m),
1424 (s), 1371 (w), 1348 (m), 1314 (m), 1218 (s), 1091 (w), 1067 (s), 1050
(s), 968 (s), 932 (w), 908 (s), 802 (m), 736 (w), 714 (w), 684 (m), 588 (vw),
546 (w), 508 (vw), 489 (w), 470 (w), 443 (w), 383 (w), 331 cmÀ1 (vw);
Raman (glass capillary): n˜ =3001 (w), 2929 (vs), 1426 (w), 1372 (m), 1350
(s), 1316 (m), 1219 (w), 910 (w), 803 (w), 721 (m), 683 (m), 672 (m), 448
(m), 409 (vw), 384 (w), 335 (w), 302 (w), 261 cmÀ1 (w).
JEOL DELTA GSX 270 FT NMR spectrometer. Microanalysis was per-
formed by the University of St. Andrews service. Mass spectra were re-
corded by both the University of St. Andrews mass spectrometry service
and the Swansea mass spectrometry service. The 13C and 15N solid-state
NMR spectra were recorded using a 500 MHz triple channel Varian In-
finityplus spectrometer operating at 125.76 and 50.68 MHz, respectively.
The samples were packed in a 4 mm ZrO2 rotor with vespel drive tip and
teflon spacers. The direct-polarisation magic angle spinning (DP-MAS)
NMR spectra were recorded with 10 kHz spinning using a 908 pulse dura-
tion of 4 ms and a recycle delay of 500 s. The 13C and 15N spectra were ref-
erenced to adamantane (38.4 ppm) and ammonium nitrate (À5.1 ppm).
Synthesis of compound1 : S-Methyliso-
thiourea
hydrochloride
(20.000 g,
Synthesis of compound4 : Compound 2 (1.000 g, 4.79 mmol) was dis-
solved in dichloromethane (30 cm3) and cooled to 08C. Chlorine gas
(excess) was bubbled slowly through the solution for 20 min. The di-
chloromethane and excess chlorine were removed under reduced pres-
sure. The residue was then dissolved in THF (30 cm3) and copper(I)
0.158 mol) was suspended in dichloro-
methane (200 cm3). A small volume of
water (4 cm3) was added and the mix-
ture cooled to À108C. Trichloro-
A
chloride
(29.364 g,
0.158 mol) in diethyl ether (50 cm3)
and sodium hydroxide (25.273 g,
0.632 mol) in water (50 cm3) were
added dropwise over 1 h, while the mixture was kept at À108C. The mix-
ture was then stirred for a further 2 h at room temperature followed by
the addition of ammonium hydroxide (5 cm3). The organic layer was then
extracted with dichloromethane (2”150 cm3). The solvent was then re-
moved in vacuo. The product was then isolated by distillation in vacuo at
508C by using Kugelrohr apparatus. The product was found to be a pale
yellow oil, which upon cooling became a pale yellow crystalline solid.
Crystals suitable for X-ray diffraction were obtained. Yield 15.830 g
(60%); elemental analysis calcd (%) for C3H3ClN2S2: C 21.62, H 1.81, N
16.81; found: C 21.80, H 1.84, N 16.51; 13C{1H} NMR (CD2Cl2): d=173.1
chloride (0.474 g, 4.79 mmol) was added. The resultant solution was stir-
red in the dark for 2h. Reaction was observed to be complete when the
green copper (I) chloride was converted to brown copper(II) chloride.
The solvent was removed in vacuo and the residue dissolved in dichloro-
methane (30 cm3). The mixture was filtered through celite and the sol-
vent removed in vacuo. The product was isolated by column chromatog-
raphy on silica eluting with a 50:50 mixture of dichloromethane/hexane.
The product was obtained as a cream powder. Yield 0.256 g (35%); ele-
mental analysis calcd (%) for C4Cl2N4S4: C 15.84, N 17.82; found: C
15.68, N 18.27; 13C{1H} NMR (CD2Cl2): d=174.9 (s, C5), 167.5 (s, C3);
ES+ MS: m/z: 325 [M+Na]+, 303 [M+H]+; IR (KBr): n˜ =2764 (w), 1442
(s), 1436 (s), 1379 (w), 1360 (w), 1339 (m), 1213 (s), 1203 (s), 1082 (s),
1072 (s), 1007 (brs), 905 (s), 801 (w), 685 (m), 674 (m), 539 (m), 486 (m),
471 (m), 380 (m), 348 (m), 302 (w), 282 (w), 271 cmÀ1 (w); Raman (glass
capillary): n˜ =1359 (m), 1341 (m), 1211 (w), 907 (w), 805 (w), 693 (vs),
547 (m), 473 (w), 443 (m), 318 (vs), 271 (vw), 241 cmÀ1 (s).
1
(s, C5), 171.8 (s, C3), 14.8 ppm (s, CH3); H NMR (CD2Cl2): d=2.58 ppm
(s, 3H; SCH3); ES+ MS: m/z: 167 [M+H]+; IR (KBr): n˜ =3002 (w), 2928
(m), 2783 (w), 2511 (vw), 1606 (w), 1452 (s), 1347 (m), 1334 (w), 1316
(m), 1216 (s), 1065 (s), 977 (m), 907 (s), 807 (w), 722 (w), 538 (w), 508
(w), 489 (m), 442 (w), 344 cmÀ1 (w).
Synthesis of compound2 : This compound was prepared in the same fash-
ion as compound 1 by using S-tert-bu-
tylisothiourea hydrochloride (20.000 g,
0.119 mol),
chloride (22.039 g, 0.119 mol) and
sodium hydroxide (18.968 g,
trichloromethylsulfanyl
Synthesis of compound5 : Compound 4 (0.046 g, 0.151 mmol) was dis-
solved in THF (10 cm3). The solution was cooled to À408C and a solution
of LiBEt3H (1.0m; 0.032 g, 0.30 mmol) in THF was added dropwise. The
0.474 mol). The product was then iso-
lated by distillation in vacuo at 708C
by using Kugelrohr apparatus. This
gave the product as a yellow oil. Yield
18.743 g (76%); elemental analysis
calcd (%) for C6H9ClN2S2: C 34.52, H 4.35, N 13.42; found: C 34.07, H
4.59, N 13.01; 13C{1H} NMR (CD2Cl2): d=171.8 (s, C5), 171.2 (s, C3), 48.1
(s, C
9H; C
A
N
A
(s), 2964 (s), 2925 (s), 2865 (s), 2777 (m), 2745 (w), 2717 (w), 2507 (w),
1602 (m), 1476 (s), 1448 (s), 1393 (s), 1365 (s), 1344 (s), 1321 (s), 1222 (s),
1197 (s), 1156 (s), 1063 (s), 1037 (m), 1027 (m), 957 (w), 934 (m), 908 (s),
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J. D. Woollins et al.
clear solution was observed to change to pale yellow on addition of
LiBEt3H. The reaction mixture was then stirred for a further hour at
resultant red solution. This caused the colour to change to brown. After
10 min when the colour had changed to dark purple, the reaction mixture
was diluted with diethyl ether (40 cm3) and quenched by the addition of
hydrochloric acid (1.0m, 2 cm3). After extraction of the organic phase the
product was isolated by column chromatography on silica eluting with a
50:50 mixture of dichloromethane/hexane. This gave the product as a
pale yellow oil. Yield 0.632 g (70%). elemental analysis calcd (%) for
C7H12N2S2: C 44.65, H 6.42, N 14.88; found: C 44.42, H 6.11, N 14.31;
À408C then [PtCl
A
one portion with a further portion of THF (10 cm3). The solution was al-
lowed to warm to room temperature and stirred for 24 h. The solvent
was then removed under reduced pressure and the residue dissolved in
dichloromethane (30 cm3). The resultant mixture was filtered through a
celite pad (to removed precipitated LiCl) and the solvent removed in
vacuo to give the product as a pale yellow powder. Crystals suitable for
X-ray diffraction were obtained by vapour diffusion from chloroform/
hexane. Yield 0.098 g (73%); elemental analysis calcd (%) for
C30H24Cl2P2PtN4S4: C 39.18, H 2.63, N 6.09; found: C 38.93, H 2.36, N
5.70; 31P{1H} NMR (CDCl3): d=46.3 ppm (1J(195Pt,31P)=3045 Hz);
1H NMR (CDCl3): d7.83–7.27 (m, 20H; aromatic), 2.61–2.21 ppm (m,
4H; PCH2CH2P); EI+ MS: m/z: 919 [M+Na]+; IR (KBr): n˜ =3050 (w),
2920 (w), 2851 (w), 2179 (w), 1478 (m), 1445 (s), 1436 (s), 1308 (wm)
1183 (m), 1164 (m), 1105 (m), 1051 (m), 1027 (w), 999 (w), 897 (w), 882
(w), 817 (w), 749 (w), 705 (m), 690 (m), 534 (m), 487 (w), 282 cmÀ1 (w).
13C{1H} NMR (CD2Cl2): d=185.6 (s C5), 170.1 (s, C3), 47.5 (s, C
30.3 (s, C
(CH3)3), 16.6 ppm (s, C5CH3); 1H NMR (CD2Cl2): d=2.68 (s,
3H; C5CH3), 1.54 ppm (s, 9H; C
(CH3)3); ES+ MS: m/z: 211 [M+Na]+;
A
AHCTREUNG
AHCTREUNG
IR (KBr): n˜ =2993 (m), 2962 (s), 2923 (s), 2865 (s), 2715 (w), 1611 (w),
1488 (s), 1448 (s), 1393 (m), 1377 (s), 1364 (s), 1343 (m), 1234 (s), 1207
(s), 1159 (s), 1065 (m), 1035 (w), 1025 (w), 993 (w), 935 (m), 909 (w), 852
(w), 810 (m), 695 (m), 675 (w), 587 (m), 533 (w), 493 (w), 424 (w),
378 cmÀ1 (w); Raman (glass capillary): n˜ =2967 (m), 2928 (s), 1454 (w),
1395 (w), 1380 (m), 1346 (w), 1216 (w), 1163 (w), 933 (w), 813 (m), 677
(m), 596 (m), 496 (w), 425 (w), 378 (vw), 338 (w), 307 (vw), 279 cmÀ1
(vw).
Synthesis of compound6 : This com-
pound was prepared in the same fash-
ion as compound 3 but with compound
Synthesis of compound9 : Compound 6 (1.000 g, 4.54 mmol) was dis-
solved in dichloromethane (30 cm3) and cooled to 08C. Chlorine gas
(excess) was bubbled slowly through the solution for 20 min. The di-
2
(2.000 g, 9.58 mmol) and sodium
thiomethoxide (0.672 g, 9.59 mmol) to
AHCTREUNG
give the product as a yellow oil. Yield
1.475 g (70%); elemental analysis
calcd (%) for C7H12N2S3: C 38.15, H
5.49, N 12.71; found: C 38.56, H 5.48,
N 12.89; 13C{1H} NMR (CDCl3): d=
187.6 (s C5), 170.5 (s, C3), 47.9 (s, C
(s, C5SCH3); 1H NMR (CDCl3): d=2.62 (s, 3H; C5SCH3), 1.50 (s, 9H; C-
(CH3)3); ES+ MS: m/z: 243 [M+Na]+; IR (KBr): n˜ =2992 (m), 2963 (s),
A
(CH3)3), 16.6 ppm
ACHTREUNG
chloromethane and excess chlorine were removed under reduced pres-
sure to yield a yellow oil. The product was isolated by column chroma-
tography on silica eluting with a 50:50 mixture of dichloromethane/
hexane. The product was obtained as an off white solid. Yield 0.191 g
(13%); elemental analysis calcd (%) for C6H6N4S6: C 22.07, H 1.85, N
17.16; found: C 21.74, H 1.81, N 16.89; 13C{1H} NMR (CD2Cl2): d=190.0
2923 (s), 2864 (m), 2715 (vw), 1587 (w), 1526 (m), 1475 (m), 1456 (m),
1427 (brs), 1391 (m), 1364 (s), 1347 (m), 1313 (m), 1230 (s), 1199 (brs),
1157 (s), 1063 (s), 1050 (s), 969 (m), 934 (m), 910 (s), 800 (m), 738 (m),
706 (w), 686 (m), 590 (w), 547 (w), 521 (w), 485 (w), 466 (w), 411 (w),
376 cmÀ1 (w); Raman (glass capillary): 2996 (w), 2967 (m), 2922 (vs),
1454 (w), 1374 (w), 1349 (s), 1316 (w), 1201 (w), 1160 (vw), 912 (w), 808
(w), 711 (w), 685 (m), 675 (m), 593 (m), 489 (w), 414 (w), 353 (w), 312
(m), 226 cmÀ1 (w).
1
(s C5), 167.7 (s, C3), 16.8 ppm (s, C5CH3); H NMR (CD2Cl2): d=2.67 (s,
3H; C5CH3); ES+ MS: m/z: 349 [M+Na]+; IR (KBr): n˜ =3000 (vw),
2926 (w), 2913 (w), 2853 (w), 1595 (w), 1518 (w), 1433 (m), 1415 (s), 1357
(w), 1337 (m), 1317 (w), 1211 (s), 1151 (w), 1089 (w), 1067 (m), 1020 (s),
974 (m), 966 (w), 910 (m), 801 (m), 715 (w), 682 (w), 671 (w), 543 (w),
461 (w), 385 (w), 278 (w), 258 cmÀ1 (w).
Synthesis of compound7 : This com-
pound was prepared in the same fash-
ion as compound 3, but by using com-
pound
sodium
2
(0.500 g, 2.39 mmol) and
methoxide (0.129 g,
Synthesis of compound10 : Compound
9 (0.100 g, 0.31 mmol) was dissolved in
THF (20 cm3). The solution was
4.05 mmol). The solution was heated
under reflux for 24 h. This gave the
product as yellow oil. Yield 0.412 g
(84%); elemental analysis calcd (%)
for C7H12N2OS2: C 41.15, H 5.92, N
cooled to À408C and a solution of
LiBEt3H (1.0m; 0.065 g, 0.61 mmol) in
THF was added dropwise. The clear
solution was observed to change to
pale yellow on addition of LiBEt3H.
The reaction mixture was then allowed
13.71; found: C 40.88, H 5.80, N 14.10;
13C{1H} NMR (CD2Cl2): d=190.3 (s C5), 166.7 (s, C3), 60.4 (s, OCH3),
47.6 (s, C
3H; OCH3), 1.55 ppm (s, 9H; C
G
G
to warm to room temperature and stir-
N
red for a further hour. The solvent was evaporated in vacuo to yield the
product as a yellow powder. Yield 0.064 g (63%); elemental analysis
calcd (%) for C3H3N2S3Li: C 21.17, H 1.77, N 16.45; found: C 20.91, H
1.46, N 16.32; ESÀMS: m/z: 163 [M]À, 131 [MÀS]À; IR (KBr): n˜ =3038
(w), 2970 (w), 2928 (w), 2902 (s), 2182 (w), 1509 (w), 1399 (s), 1316 (w),
1306 (m), 1179 (s), 1167 (s), 1097 (w), 1078 (m), 980 (w), 957 (w), 923
(w), 805 (w), 728 (w), 697 (m), 668 (w), 495 (w), 438 (w), 381 (w),
323 cmÀ1 (w).
IR (KBr): n˜ =2994 (m), 2963 (s), 2923 (s), 2866 (m), 2757 (w), 1528 (s),
1476 (m), 1434 (brs), 1401 (s), 1389 (s), 1364 (s), 1230 (brs), 1181 (s),
1158 (s), 1065 (w), 1031 (m), 975 (m), 935 (m), 792 (m), 779 (m), 738 (w),
689 (m), 591 (m), 492 (w), 407 (m), 377 cmÀ1 (m); Raman (glass capilla-
ry): 2964 (s), 2925 (vs), 1528 (w), 1456 (m), 1436 (m), 1403 (w), 1224 (w),
1157 (w), 935 (w), 810 (m), 782 (m), 690 (w), 591 (s), 494 (w), 427 (w),
409 (m), 376 (w), 307 cmÀ1 (w).
Synthesis of compound8 : Compound
2 (1.00 g, 4.791 mmol) was dissolved in
THF (35 cm3) with N-methylpyrroli-
done (3.5 cm3) and a catalytic amount
Synthesis of compound11 : This compound was prepared in the same
fashion as 5 by using 9 (0.049 g, 0.15 mmol), a solution of LiBEt3H (1.0m;
0.032 g, 0.30 mmol) in THF and [PtCl2(dppe)](0.100 g, 0.15 mmol) to
A
give the product as a pale yellow powder. Yield 0.107 g (78%); elemental
analysis calcd (%) for C32H30P2PtN4S6: C 41.78, H 3.29, N 6.09; found: C
41.42, H 2.89, N 6.23; 31P{1H} NMR (CDCl3): d=46.2 ppm (1J(195Pt,31P)=
047 Hz); 1H NMR (CDCl3): d=7.81–7.23 (m, 20H; aromatic), 2.70–
2.16 ppm (m, 4H; PCH2CH2P); EI+ MS: m/z: 942 [M+Na]+; IR (KBr):
of [Fe(acac)3](0.077 g, 0.24 mmol). A
A
solution of methyl magnesium bro-
mide (3.0m in diethyl ether, 1.76 cm3,
5.27 mmol) was added dropwise to the
6370
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Chem. Eur. J. 2006, 12, 6366 – 6381

Sulfur–Nitrogen Heterocycles
FULL PAPER
3.15, N 16.42; 13C{1H} NMR (CD2Cl2): d=191.8 (s, C5), 179.4 (s, C5’),
169.4 (s, C3’), 163.6 (s, C3), 47.9 (s, C
(s, C5SCH3); 1H NMR (CD2Cl2): d=2.80 (s, 3H; C5SCH3), 1.59 ppm (s,
9H; C
(CH3)3); ES+ MS: m/z: 359 [M+Na]+; IR (KBr): n˜ =2959 (w),
A
G
AHCTREUNG
2920 (w), 2858 (w), 1475 (w), 1459 (w), 1436 (s), 1427 (s), 1362 (m), 1342
(w), 1244 (m), 1221 (m), 1208 (m), 1159 (m), 1074 (m), 1061, 971 (w), 917
(w), 797 (w), 675 (w), 501 (w), 475 (w), 402 (w), 278 cmÀ1 (w); Raman
(glass capillary): n˜ =2999 (w), 2965 (m), 2915 (s), 1458 (w), 1435 (w),
1362 (w), 1339 (s), 1323 (w), 1222 (w), 1212 (vw), 1166 (vw), 932 (vw),
919 (w), 812 (w), 801 (w), 714 (w), 676 (s), 598 (m), 490 (w), 478 (m), 443
(w), 383 (w), 368 (w), 319 cmÀ1 (m).
n˜ =3050 (w), 2961 (w), 2920 (w), 2866 (w), 1483 (w), 1435 (m), 1412 (s),
1309 (m), 1262 (m), 1175 (s), 1103 (s), 1042 (m), 1027 (m), 997 (m), 966
(w), 898 (w), 879 (w), 817 (m), 802 (m), 748 (m), 714 (m), 704 (m), 690
(s), 660 (w), 532 (s), 485 (m), 397 cmÀ1 (w).
Synthesis of compound14 : A slurry of
potassium methyl cyanodithioimido-
carbonate (1.257 g, 7.38 mmol) in di-
chloromethane (30 cm3) was stirred at
Synthesis of compound12 : Compound 9 (0.100 g, 0.306 mmol) was dis-
solved in THF (20 cm3). The solution was cooled to À408C and a solution
08C, while sulfuryl chloride (1.267 g,
9.39 mmol) was added dropwise. The
resultant mixture was stirred for a fur-
ther 24 h at room temperature. The
mixture was filtered to remove pre-
cipitated KCl then the solvent was then removed in vacuo to give the
product as a pale yellow crystalline solid. Yield 1.048 g (85%); elemental
analysis calcd (%) for C3H3N2S2Cl: C 21.62, H 1.81, N 16.81; found: C
21.74, H 1.42, N 16.99; 13C{1H} NMR (CD2Cl2): d=191.9 (s, C5), 156.1 (s,
1
C3), 16.5 ppm (s, CH3); H NMR (CD2Cl2): d=2.70 (s, 3H; C5CH3); ES+
MS: m/z: 167 [M+H]+; IR (KBr): n˜ =2990 (w), 2959 (vw), 2922 (w),
2854 (w), 1433 (s), 1425 (s), 1363 (w), 1345 (m), 1330 (w), 1229 (s), 1174
(w), 1073 (s), 1050 (m), 977 (m), 969 (m), 919 (m), 897 (w), 804 (m), 711
(w), 678 (m), 550 (w), 535 (w), 482 (w), 376 cmÀ1 (w); Raman (glass capil-
lary): n˜ =3006 (w), 2995 (m), 2921 (s), 1365 (w), 1347 (vs), 1327 (w), 1233
(w), 918 (w), 806 (w), 715 (w), 680 (vs), 421 (vs), 380 (w), 258 cmÀ1 (w).
of LiBEt3H (1.0m; 0.065 g, 0.61 mmol) in THF was added dropwise. The
clear solution was observed to change to pale yellow on addition of
LiBEt3H. The reaction mixture was then stirred for a further hour. Com-
pound 1 (0.102 g, 0.61 mmol) was then added as a solid in one portion.
The resulting solution was stirred for 24 h. The solvent was evaporated in
vacuo and the remaining solid was extracted with dichloromethane
(20 cm3). The mixture was filtered through a celite pad to remove pre-
cipitated LiCl and washed through with additional dichloromethane
(30 cm3). The filtrate was evaporated to dryness in vacuo to give a cream
powder. Crystals suitable for X-ray diffraction were obtained by vapour
diffusion from chloroform/hexane. Yield 0.120 g (67%); elemental analy-
sis calcd (%) for C6H6N4S5: C 24.47, H 2.05, N ;19.03 found: C 24.72, H
1.64, N 18.63; 13C{1H} NMR (CD2Cl2): d=191.9 (s, C5), 180.8 (s, C5’),
170.5 (s, C3’), 163.4 (s, C3), 17.0 (s, C5SCH3), 14.7 ppm (s, C3’SCH3);
1H NMR (CD2Cl2): d=2.80 (s, 3H; C5SCH3), 2.65 ppm (s, 3H;
C3’SCH3); ES+ MS: m/z .317 [M+Na]+; IR (KBr): n˜ =2996 (w), 2966
(w), 2924 (w), 1443 (m), 1416 (s), 1367 (w), 1343 (w), 1331 (m), 1308 (m),
1249 (s), 1217 (s), 1094 (w), 1066 (m), 1058 (m), 977 (w), 966 (w), 916
(w), 906 (w), 801 (m), 681 (m), 482 (w), 420 (w), 387 (w), 285 cmÀ1 (w);
Raman (glass capillary): n˜ =3004 (w), 2928 (s), 1421 (w), 1370 (w), 1346
(s), 1334 (m), 1310 (w), 1252 (m), 1227 (w), 919 (w), 808 (m), 724 (m),
694 (s), 524 (m) 422 (w), 313 (w), 268 cmÀ1 (w).
Synthesis of compound15 : This com-
pound was prepared in the same fash-
ion as compound 14 using potassium
methyl
cyanodithioimidocarbonate
(4.330 g, 0.025 mol) and bromine
(4.063 g, 0.025 mol) to give the product
as a pale yellow crystalline solid. Yield
5.043 g (95%); elemental analysis
calcd (%) for C3H3BrN2S2: C 17.36, H
1.43, N 13.27; found: C 17.07, H 1.01, N 13.45; 13C{1H} NMR (CDCl3):
d=191.6 (s, C5), 144.3 (s, C3), 16.6 ppm (s, CH3); 1H NMR (CDCl3): d=
2.73 ppm (s, 3H; C5CH3); ES+ MS: m/z: 213 [M+H]+; IR (KBr): n˜ =
2989 (w), 2918 (w), 1561 (w), 1491 (w), 1415 (s), 1354 (m), 1332 (m),
1324 (m), 1208 (brs), 1192 (s), 1096 (w), 1071 (s), 1048 (m), 974 (m), 968
(m), 894 (s), 786 (m), 712 (w), 667 (m), 547 (w), 456 (m), 378 (w), 305
(w), 250 cmÀ1 (w); Raman (glass capillary): n˜ =3004 (w), 2993 (w), 2920
(s), 1423 (vw), 1354 (m), 1347 (m), 1322 (s), 1210 (w), 891 (m), 714 (m),
673 (s), 381 (m), 307 (s), 228 cmÀ1 (w).
Synthesis of compound16 : A slurry of dipotassium cyanodithioimidocar-
bonate (7.535 g, 0.04 mol) in dichloromethane (40 cm3) was stirred at
Synthesis of compound13 : This compound was prepared in the same
way as compound 12 by using 9 (0.050 g, 0.15 mmol), LiBEt3H (0.065 g,
0.306 mmol) and compound 2 (0.032 g, 0.31 mmol) to give a cream
powder. Crystals suitable for X-ray diffraction were obtained by vapour
diffusion from chloroform/hexane. Yield 0.053 g (51%); elemental analy-
sis calcd (%) for C9H12N4S5: C 32.11, H 3.59, N 16.65; found: C 31.88, H
À408C, while chlorine (5.498 g, 0.08 mol) in dichloromethane (50 cm3)
was slowly added. The reaction mixture was stirred for 1 h at 08C then
suction filtered. The dichloromethane was then removed in vacuo to give
the product as a yellow crystalline solid. Yield 4.748 g (81%); elemental
analysis calcd (%) for C4N4Cl2S4: C 15.84, N 18.48; found: C 15.99, N
18.45; 13C{1H} NMR (CDCl3): d=188.5 (s, C5), 158.0 ppm (s, C3); EI+
MS: m/z: 302 [M]+; IR (KBr): n˜ =2757 (w), 2423 (w), 1606 (w), 1435 (s),
1362 (m), 1342 (s), 1216 (brs), 1096 (w), 1061 (s), 951 (w), 806 (s), 677
Chem. Eur. J. 2006, 12, 6366 – 6381
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6371

J. D. Woollins et al.
(m), 555 (w), 542 (w), 481 (m), 418 (w), 410 (w), 373 (m), 357 cmÀ1 (w);
Raman (glass capillary): n˜ =1436 (w), 1365 (m), 1342 (vs), 1223 (w), 915
(m), 809 (m), 681 (m), 560 (w), 538 (w), 471 (w), 419 (m), 376 (w),
360 cmÀ1 (w).
tensity spinning side bands); MALDI-TOF MS: m/z: 1149 [S20C20N19]+,
1030 [S18C18N17]+, 914 [S16C16N15]+, 798 [S14C14N13]+, 682 [S12C12N11]+, 566
[S10C10N9]+, 450 [S8C8N7]+, 334 [S6C6N5]+, 218 [S4C4N3]+, 102 [S2C2N]+;
Selected IR data (KBr): n˜ =1206 cmÀ1 (vbrs); Raman (glass capillary):
n˜ =1508 (m), 1207v (brs), 1155(shs), 994 (w), 652 (vbrm), 473 (s), 453
C
Synthesis of compound17 : A slurry of dipotassium cyanodithioimidocar-
bonate (2.00 g, 0.01 mol) in dichloromethane (20 cm3) was stirred at
À408C, while bromine (3.289 g, 0.02 mol) in dichloromethane (10 cm3)
Method B: Potassium thiocyanate (0.500 g, 5.145 mmol) was ground to a
very fine powder and added to a flask. Chlorine gas (excess) was then
passed through the powder for 30 s. The mixture was then heated using a
heat gun for approximately 1 min. Reaction was observed to have occur-
red by the mixture turning a brick red colour. Once cool the mixture was
ground to a fine powder and the process of chlorination followed by
heating then grinding was repeated 5 times to ensure complete reaction.
The resulting mixture was washed with water (30 cm3) and filtered to
remove KCl and any residual KNCS. The red powder collected was
washed with methanol (20 cm3) followed by diethyl ether (20 cm3) then
dried in vacuo. Yield 0.202 g (68%). The analytical and spectroscopic
data for (SCN)x 19 synthesised by this method were identical to those
found in material produced by method A. 13C and 15N-labelled samples
of (SCN)x were prepared by this method using 99% 13C and 99% 15N la-
belled KNCS respectively.
was added dropwise. The mixture was stirred for a further 2 h at 108C.
The solvent and excess bromine was removed in vacuo. The product was
dissolved in dichloromethane (40 cm3) and the solution was filtered. The
solvent was removed in vacuo and the product recrystallised from di-
chloromethane/ether to give a cream crystalline solid. Yield 1.530 g
(76%); elemental analysis calcd (%) for C4N4S4Br2: C 12.25, N 14.29;
X-ray crystallography: Table 1 gives the details of the data collections
and refinements. Intensities were corrected for Lorentz polarisation and
for absorption. Data for 1, 14 and 16 were collected at 93 K by using
MoKa radiation from a high brilliance Rigaku MM007 generator and a
Rigaku Mercury ccd detector; for 5 and 12 at 93 K by using MoKa radia-
tion from a high brilliance Rigaku MM007 generator and a Rigaku
Saturn70 ccd detector; for 13 at 173 K by using CuKa radiation from a
high brilliance Rigaku MM007 generator and a Rigaku Saturn92 ccd de-
tector; and for 17 at 125 K by using MoKa radiation and a Bruker
SMART ccd. The structures were solved by the heavy atom method or
by direct methods. The positions of the hydrogen atoms were idealised.
Refinements were done by full-matrix least squares based on F2 using
SHELXTL.[37] CCDC 290200–290206 (1,5,12,13,14,16, and 17, respective-
ly) contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallograph-
ic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
found:
C 12.56, N
14.18; 13C{1H} NMR (CDCl3): d=188.5 (s, C5),
145.9 ppm (s, C3); 14N NMR (CDCl3): d=310.6 (s, N2), 278.4 ppm (s,
N4); IR (KBr): n˜ =1586 (w), 1561 (w), 1424 (s), 1348 (m), 1325 (m), 1193
(brs), 1082 (w), 1059 (m), 942 (w), 891 (s), 796 (m), 784 (m), 679 (w), 665
(m), 547 (m), 535 (m), 338 (m), 438 cmÀ1 (m); Raman (glass capillary):
n˜ =1426 (w), 1350 (s), 1326 (m), 1194 (w), 1065 (w), 895 (m), 798 (m),
782 (w), 674 (s), 534 (m), 440 (w), 403 (w), 359 (w), 301 cmÀ1 (s).
Synthesis of compound18 : Compound
16 (1.000 g, 3.30 mmol) was dissolved
in dichloromethane and cooled to 08C.
Chorine gas (excess) was bubbled
through the solution. The solution was
then stirred for a further hour at room
temperature then the solvent was re-
moved in vacuo to give the product as
a yellow solid. Yield 1.041 g (84%);
13C-{1H} NMR (CDCl3): d(C) 180.2 (s, C5), 155.9 ppm (s, C3).
Synthesis of compound(SCN) x 19
Results andDiscussion
Method A: Thiocyanogen was allowed to warm to room temperature re-
sulting in spontaneous polymerisation to give polythiocyanogen as a
brick red solid. Yield 0.672 g (58%). elemental analysis calcd (%) for
(SCN)x: C 20.68, N 4.12; found: C 20.44, N 23.89 (2); 13C DP-MAS NMR
(75.4 MHz): d=186.8 ppm (broad slightly asymmetric signal with low in-
As mentioned above there was a need to clarify the data for
a range of C-S-N heterocycles in order to understand both
heterocyclic and polymer chemistry in this area.
Table 1. Details of X-ray data collections and refinements.
1
5
12
13
14
16
17
formula
C3H3ClN2S2
C30H24Cl2N4P2PtS4
0.1”0.03”0.01
C6H6N4S5
0.1”0.03”0.01
orthorhombic
P212121
C9H12N4S5
0.18”0.1”0.01
monoclinic
P21/m
3.9264(3)
9.6948(9)
C3H3ClN2S2
0.2”0.05”0.05
monoclinic
P21
11.3849(13)
8.1655(10)
11.7320(14)
C4Cl2N4S4
0.2”0.1”0.05
monoclinic
P21/n
5.8977(11)
7.1476(13)
25.310(5)
C4Br2N4S4
0.1”0.1”0.01
monoclinic
P21/c
crystal dimensions [mm]0.2”0.2”0.05
crystal system
space group
a [Š]7.615(2)
b [Š]9.474(4)
c [Š]8.961(4)
a [8]90
monoclinic
P21/c
29.675(2)
8.5789(7)
25.351(2)
monoclinic
C2/c
3.9232(11)
8.451(3)
9.5487(8)
6.9794(5)
33.094(11)
10.8821(18)
8.2410(6)
90
90
90
90
90
90
b [8]106.938(10)
g [8]90
94.429(4)
90
6434.5(9)
4
90
90
91.592(3)
90
724.95(14)
4
101.8476(10)
90
307.02(4)
2
111.840(9)
90
1012.4(2)
2
95.044(3)
90
1062.8(3)
4
V [Š3]618.4(4)
Z
1097.2(6)
8
4
Mr
166.64
1.851
4.916
3097
896.70
294.45
1.542
7.272
6257
336.53
1.803
1.184
166.64
303.22
2.451
8.375
4752
392.14
1calcd [gcmÀ3]1.790
m [mmÀ1]1.176
measured reflns
1.782
1.025
20800
5626(0.0445)
0.0451/0.0867
1.989
1.426
1632
9453
4388
independent reflns (Rint
final R1/wR2 [I>2s(I)]0.0240/0.0557
)
1017
A
A
1807
A
1311
A
937
A
1694
A
1513
A
0.0322/0.0643
0.0364/0.0984
0.0228/0.0491
0.0936/0.2082
0.0293/0.0686
6372
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Chem. Eur. J. 2006, 12, 6366 – 6381

Sulfur–Nitrogen Heterocycles
FULL PAPER
1,2,4-Thiadiazoles: Using
(Scheme 5) we attempted to prepare 1,2,4-thiadiazole mono-
mer units that could be linked together by nucleophilic sub-
a
retrosynthetic approach
reported[31] the ring stretching bands for 3-alkylsulfanyl-
1,2,4-thiadiazoles in the ranges 1435–1445 and 1220–
1255 cmÀ1). In the 13C{1H} NMR spectrum of 1 the shifts for
the ring carbons were observed at d=173.1 and 171.8 ppm
and these are assigned as C5 and C3, respectively (c.f. Morel
et al.[27] d=173.2 (C5) and 172 ppm (C3)). Our assignment
was confirmed by H-C HMBC and H-C HSQC experiments.
For compound 2 signals assigned to C5 and C3 were noted
at d=171.8 and 171.2 ppm, respectively. A single-crystal X-
ray diffraction study confirmed the structure of 1 (Figure 5,
Table 2). The X-ray structures of the various heterocycles
will be considered together (vide infra).
Scheme 5. Retrosynthetic approach for the preparation of 1,2,4-thiadia-
zole model compounds.
stitution at C5 to form dimers and higher oligomers. The 3-
alkylsulfanyl-5-chloro-1,2,4-thiadiazoles 1 and 2 were pre-
pared by the reaction of the appropriate S-alkylisothiourea
hydrochloride with trichloromethylsulfanyl chloride and po-
tassium hydroxide in a mixture of dichloromethane and
water [Eq. (1)].
Figure 5. X-ray crystal structure of 1.
Reaction of 1 with sodium thiomethoxide in methanol
[Eq. (2)]gives 3,5-bis-methylsulfanyl-1,2,4-thiadiazole 3 in
excellent yield and the disulfide 4 was prepared from 2 ac-
cording to [Eq. (3)].
After dichloromethane extraction of the organic phase
followed by removal of the solvent 1 or 2 was isolated by
distillation in vacuo by using a Kugelrohr apparatus at 508C
or 708C, respectively, which was
Compound
2 was dissolved in dichloromethane and
excess chlorine gas was passed through the solution at 08C
a small modification to the liter-
Table 2. Selected bond lengths [Š]and angles [ 8]for 1, 5, 12 and 13.
ature preparation of 1 and 2 in
water followed by steam distilla-
tion,[31] though only melting
point and IR spectroscopy were
mentioned in this report. More
recently the 13C NMR of 1 was
reported by Morel et al.[27] Com-
pound 1 is a pale yellow oil
which upon cooling slightly
became a pale yellow crystalline
solid. Compound 2 is a yellow
oil. Microanalysis and mass
spectroscopy gave the expected
results for both species and the
1
5
12
13
À
S(1) N(2)
1.6629(13)
–
1.7074(14)
–
1.3160(18)
–
1.383(2)
–
1.657(8)
1.653(8)
1.712(11)
1.719(9)
1.312(12)
1.349(10)
1.425(11)
1.382(10)
1.275(12)
1.284(10)
1.667(3)
1.666(3)
1.735(3)
1.721(3)
1.312(4)
1.305(4)
1.367(4)
1.384(4)
1.319(4)
1.316(4)
1.650(3)
1.657(2)
1.723(3)
1.719(3)
1.314(4)
1.309(4)
1.356(4)
1.383(4)
1.320(4)
1.312(4)
À
S(11) N(12)
À
S(1) C(5)
À
S(11) C(15)
À
N(2) C(3)
À
N(12) C(13)
À
C(3) N(4)
À
C(13) N(14)
À
N(4) C(5)
1.2999(18)
–
À
N(14) C(15)
N(2)-S(1)-C(5)
N(12)-S(11)-C(15)
C(3)-N(2)-S(1)
C(13)-N(12)-S(11)
N(2)-C(3)-N(4)
N(12)-C(13)-N(14)
C(5)-N(4)-C(3)
C(15)-N(14)-C(13)
N(4)-C(5)-S(1)
91.80(7)
–
107.10(10)
–
120.36(13)
–
106.53(12)
–
91.2(4)
91.8(4)
92.55(15)
91.97(15)
106.7(2)
107.8(2)
121.2(3)
120.0(3)
108.1(3)
107.5(3)
111.5(3)
115.5(2)
92.41(15)
91.66(13)
107.2(2)
108.8(2)
120.7(3)
118.8(3)
107.8(3)
108.0(2)
111.8(2)
112.7(7)
109.6(7)
107.6(6)
116.4(8)
118.4(7)
108.2(8)
108.1(7)
114.3(7)
114.1(6)
À
C H stretching bands were
noted in the region 2865–
3002 cmÀ1. The ring vibrations
were observed at 1452 and
1216 cmÀ1 in 1 and 1447 and
1222 cmÀ1 in 2 (Goerdeler et al.
114.22(12)
–
N(14)-C(15)-S(11)
Chem. Eur. J. 2006, 12, 6366 – 6381
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6373

J. D. Woollins et al.
was added. This resulted in the formation of
[Pt(C2N2S2Cl2)2(dppe)]( 5) [Eq. (4)].
A
The microanalysis and mass spectral data for 5 were ac-
ceptable. The ring stretches were observed at 1436 and
1183 cmÀ1 in the IR spectrum.
The 31P{1H} NMR spectrum of
5 consists of a sharp singlet at
46.3 ppm with platinum satel-
lites
(1J(195Pt,31P)=3045 Hz).
The X-ray structure confirms
the connectivity of the com-
pound (Figure 6). Due to the
reactivity of the 1,2,4-thiadi-
to give a mixture of products including the desired sulfenyl
chloride. The 13C{1H} NMR spectrum of the mixture showed
signals assigned to C5 and C3 of the sulfenyl chloride at d=
175.2 and 166.9 ppm, respectively. Due to the air sensitive
nature of the sulfenyl chloride no attempt was made to iso-
late this species. Instead the reaction mixture was used as
obtained for the next stage. Compound 4 was obtained pure
À
after column chromatography, the n(S S) vibration in 4 is
A
assigned as the peak at 471 cmÀ1.
In an attempt to reductively cleave the disulfide bridge
and lead to spontaneous polymerisation, LiBEt3H was
added to the disulfide 4 in THF at À408C, whereupon the
solution turned yellow. After stirring for an hour the yellow
solution was allowed to slowly warm to room temperature
and as the solution warmed a pale yellow solid precipitated.
This solid was insoluble in all common solvents and water.
Solid-state 13C NMR did not yield any useful data. We spec-
ulate that at À408C the lithium salt is formed, but at higher
temperatures it reacts with itself to give an oligomeric/poly-
meric material (Scheme 6) though the colour difference be-
Scheme 6. Proposed polymerisation of the lithium salt of 5-chloro-1,2,4-
thiadiazole-3-thiol.
Figure 6. X-ray crystal structure of 5.
tween this and (SCN)x indicates that this is not the
“normal” polymer. We believe that this reaction yields a
new isomer of (SCN)x and are currently making efforts to
optimise the reaction and isolate enough material for de-
tailed study.
A
Me in 6, 7 and 8, respectively (Scheme 7) enabling us to
obtain a stable lithium salt.
To confirm that the lithium salt was formed at low tem-
perature we trapped the anion as a platinum complex.
LiBEt3H was added to the disulfide 4 in THF at À408C and
Compound 6 was dissolved in dichloromethane and
chlorinated at 08C. Further reaction with copper(I) chloride
did not successfully convert the sulfenyl chloride to the di-
sulfide. However, we found that if the reaction mixture was
the solution was maintained at À408C whilst [PtCl
A
6374
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Chem. Eur. J. 2006, 12, 6366 – 6381

Sulfur–Nitrogen Heterocycles
FULL PAPER
Complex 11 gave rise to a sharp singlet at d=46.2 ppm
with a 1J(195Pt,31P) coupling constant of 3047 Hz in its
31P{1H} NMR spectrum. As expected the values noted were
1
almost identical to those for 5 (d=46.3 ppm, J(195Pt,31P)=
3045 Hz). The ring stretches were observed at 1412 and
1175 cmÀ1 in the IR spectrum. Microanalysis and mass spec-
troscopy gave the expected results.
Having successfully synthesised our monomer units [the
3-alkylsulfanyl-5-chloro-1,2,4-thiadiazoles (1 and 2) and the
lithium salt of 5-methylsulfanyl-1,2,4-thiadiazole-3-thiol
(10)]the next step was to combine the two species by nucle-
ophilic substitution at C5 to form a model compound
[Eq. (8)].
Scheme 7. Synthesis of 6, 7 and 8.
exposed to the atmosphere after chlorination then it was
possible to obtain the disulfide 9 in modest yield [Eq. (5)].
The lithium salt 10 was prepared in situ in THF, a stoi-
chiometric amount of the appropriate 3-alkylsulfanyl-5-
chloro-1,2,4-thiadiazole was added and the resulting solution
stirred overnight to give after workup both 12 and 13 as
cream powders in good yield. In both compounds the micro-
analysis confirmed the purity of the compounds, mass spec-
troscopy showed the [M+Na]+ species and the ring vibra-
tions are observed at approximately 1430 and 1230 cmÀ1.
À1
À
In 9 the n
(S S) vibration was observed at 461 cm . Anal-
ogous reactions to that shown in Equation (5) were attempt-
ed using 7 and 8, but no disulfides were obtained from these
compounds. The lithium salt 10 was synthesised from 9
[Eq. (6)].
1
The methyl protons were observed in the H NMR spectrum
at d=2.80 (C5SCH3) and 2.65 ppm (C3’SCH3) In the
13C{1H} NMR spectrum of 12 the methyl carbons were ob-
served at d=17.0 (C5SCH3)
and 14.7 ppm (C3’SCH3). The
signals of the ring carbons were
observed at d=191.9, 180.8,
170.5, and 163.4 ppm. The
peaks
at
d=191.9
and
170.5 ppm are indisputably as-
signed as C5 and C3’, respec-
Unfortunately the lithium salt 10 was too insoluble to
record 13C NMR data. Therefore platinum complex 11 was
prepared in the same way as 5 to confirm the lithium salt
had been formed [Eq. (7)].
tively, by H-C HMBC and H-C HSQC experiments. The
peaks at d=180.8 and 163.4 ppm were assigned to C5’ and
C3, respectively, by comparison with the shifts recorded in
the other 1,2,4-thiadiazole compounds. In compound 13 the
expected signals were observed in the correct ratio in the
1H NMR spectrum. In the 13C{1H} NMR spectrum the peaks
were noted at d=191.8, 179.4, 169.4 and 163.6 ppm and
were assigned as C5, C5’, C3’ and C3, respectively. H-C
HMBC and H-C HSQC experiments confirmed the assign-
ment of C5. The X-ray structures confirm that the mono-
meric units have been linked together (Figure 7).
The 3-halo-1,2,4-thiadiazoles 14 and 15 were prepared for
spectral comparison according to Equation (9).
Chem. Eur. J. 2006, 12, 6366 – 6381
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6375

J. D. Woollins et al.
The structure of 14 was confirmed by a single crystal X-ray
diffraction study (Figure 8, Table 3).
Figure 8. X-ray crystal structure of 14.
Table 3. Selected bond lengths [Š]and angles [ 8]for 14, 16 and 17.
14
16
17
À
S(1) N(2)
1.661(2)
–
1.730(3)
–
1.310(4)
–
1.350(4)
–
1.661(7)
1.662(7)
1.716(5)
1.723(8)
1.310(10)
1.307(10)
1.355(9)
1.352(10)
1.317(10)
1.314(10)
1.659(4)
1.658(4)
1.719(5)
1.702(5)
1.313(6)
1.320(6)
1.358(6)
1.378(6)
1.321(6)
1.312(6)
À
S(11) N(12)
À
S(1) C(5)
À
S(11) C(15)
À
N(2) C(3)
À
N(12) C(13)
À
C(3) N(4)
À
C(13) N(14)
À
N(4) C(5)
1.319(3)
–
À
N(14) C(15)
N(2)-S(1)-C(5)
N(12)-S(11)-C(15)
C(3)-N(2)-S(1)
C(13)-N(12)-S(11)
N(2)-C(3)-N(4)
N(12)-C(13)-N(14)
C(5)-N(4)-C(3)
C(15)-N(14)-C(13)
N(4)-C(5)-S(1)
92.29(12)
–
106.22(18)
–
122.3(4)
–
107.2(2)
–
91.4(4)
91.4(4)
91.7(2)
92.1(2)
106.7(5)
107.2(5)
122.3(4)
121.6(7)
105.7(6)
106.9(6)
113.9(6)
113.0(6)
107.1(3)
107.2(3)
121.5(4)
120.2(4)
106.5(4)
106.5(4)
113.2(4)
113.9(4)
111.9(2)
–
N(14)-C(15)-S(11)
Bis(3-halo-1,2,4-thiadiazol-5-yl) disulfides 16 and 17 were
prepared by the reaction of potassium cyanodithioimidocar-
bonate and the appropriate halogen [Eq. (10)].
Figure 7. X-ray crystal structures of 12 (top) and 13 (bottom).
Both 14 and 15 gave satisfactory microanalysis and
showed the anticipated [M]+ in their mass spectra. The ab-
sence of a nitrile band in the region 2000–2200 cmÀ1 con-
firmed no starting material remained in the samples. Witten-
brook et al. have reported that 3-halo-1,2,4-thiadiazole sul-
fides have two strong bands in the ranges 1381–1441 and
1175–1232 cmÀ1 assigned as ring vibrations.[29] They noted
that different substituents attached to the exocyclic sulfur at
C5 do not affect the ring stretches, but different halogen
atoms at C3 produce a detectable shift in both bands. They
report values for the ring stretches of 1425 and 1228 cmÀ1
for 14 and 1404 and 1202 cmÀ1 for 15. The change in ring vi-
brations between 14 and 15 is attributed to chlorine being
replaced by bromine. We observe the ring stretching bands
Both species were prepared in excellent yields. Com-
pounds 16 and 17 have previously been reported in the liter-
ature, but only melting point and IR spectroscopy data were
recorded.[28] Compounds 16 and 17 showed the anticipated
[M]+ ions in their mass spectra with the expected isotopo-
A
at 1425 and 1229 cmÀ1 in 14 and 1415 and 1208 cmÀ1 in 15
specified limits. In the IR spectra the S S stretch is observed
À
À1
with n
ACHTREUNG
at 481 and 448 cmÀ1 in 16 and 17, respectively. The ring vi-
À
6376
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Chem. Eur. J. 2006, 12, 6366 – 6381

Sulfur–Nitrogen Heterocycles
FULL PAPER
brations are noted at 1435 and 1216 cmÀ1 (lit.:[28] 1435,
1215 cmÀ1) in 16 and at 1415 and 1208 cmÀ1 (lit.:[28] 1427,
1192 cmÀ1) for 17. In the 13C{1H} NMR spectrum of 16, C5
and C3 were observed at d=188.5 and 158.0 ppm respec-
tively. Similarly in 17, C5 and C3 were noted at d=188.5
and 145.9 ppm. The 14N NMR spectrum of 17 revealed two
broad singlets centred at d=310.6 and 278.4 ppm assigned
as N2 and N4, respectively. X-ray crystal structures have
been determined (Figure 9).
Table 4. 13C{1H} NMR shifts for ring carbon atoms in 1,2,4-thiadiazoles.
d [ppm]
C5 [C5’]C3 [C3
’]
1
2
3
4
6
7
8
9
173.1
171.8
189.1
174.9
187.6
190.8
185.6
190.0
171.8
171.2
171.5
167.5
170.5
166.7
170.1
167.7
12
13
14
15
16
17
18
191.9 [180.5]163.4 [170.5]
191.8 [179.4]163.6 [169.4]
191.6
191.6
188.5
188.5
180.2
156.1
144.3
158.0
145.9
155.9
thiocyanate, followed by heating. We found that chlorinating
G
for approximately 30 s and heating for 1 min then repeating
the procedure a further five times optimised the yield of
(SCN)x. Using this method we also prepared 13C- and 15N-la-
belled samples of (SCN)x from 13C- and 15N-labelled potassi-
um thiocyanate, respectively. Polythiocyanogen obtained by
both methods gave identical analytical and spectral data. It
is an air stable, brick red, amorphous solid. We made several
attempts under variety of conditions and using different
samples, but were unable to obtain any powder diffraction
whatsoever from (SCN)x; this result is in contrast to Cata-
ldo[12] who observed a broad reflection at about 27o and
more in keeping with the observations of Bowmaker et al.[6]
The broadness of the one reflection in Cataldoꢁs diffracto-
gram precludes any structural conclusions and may be a
background artifact. Conductivity measurements revealed
that samples of (SCN)x prepared in this work were insula-
tors; occasional samples which showed modest conductivity
were always found to be contaminated with KCl and we
speculate that some literature conductivities may be errone-
ous because of the presence of ionic impurities. Polythiocya-
nogen is insoluble in water and all organic solvents, with the
exception of dimethyl formamide and dimethyl sulfoxide in
which it is very sparingly soluble. Microanalysis of (SCN)x
confirmed the composition of the polymer. MALDI-TOF
mass spectra with [3-(4-tert-butylphenyl)-2-methyl-2-prope-
nylidene]malonitrile (DCTB) as the matrix were recorded
several times with the addition of various metal salts (NaI,
Figure 9. X-ray crystal structure of 17, the structure of 16 is very similar
and is not illustrated.
Compound 16 was readily converted into the sulfenyl
chloride 18 by chlorinating with excess Cl2 [Eq. (11)].[28]
Compound 18 is air sensitive; therefore it was stored
under nitrogen and no mass spectroscopy, microanalytical or
IR data were collected. In the 13C{1H} NMR spectrum C5
and C3 were noted at d=180.2 and 155.9 ppm respectively.
In summary, all of the 1,2,4-thiadiazole compounds 1–17
were found to be pure by microanalysis and the expected
ions were observed in the mass spectra. X-ray crystallogra-
phy has been used to establish the connectivity in selected
examples. In the IR and Raman spectra, the ring vibrations
are observed at approximately 1400 and 1200 cmÀ1. The
13C NMR shifts for the ring carbon atoms C5 and C3 are
compiled in Table 4; the data reveal that C5 lies in the
range d=180–192 ppm when bonded to alkyl, alkoxy and
thioalkoxy groups and the peak corresponding to C3 is ob-
served at approximately d=171 ppm when bonded to thioal-
koxy groups.
LiCl, Cu
LiCl did not yield any useful information; however, the
spectra with addition of NaI, Cu(NO2)2 and Ag(NO2)
showed identical results. As an example the spectrum with
Cu(NO2)2 added is illustrated (Figure 10). It contains the
A
G
A
ACHTREUNG
AHCTREUNG
Parathiocyanogen: We synthesised polythiocyanogen by two
different methods. Firstly by allowing thiocyanogen S2(CN)2,
prepared by the reaction of silver thiocyanate with bromine,
to slowly warm to room temperature resulting in spontane-
ous polymerisation to give 19. The second method involved
passing excess chlorine gas through powdered potassium
series at m/z 1149 [S20C20N19]+ (most intense peak m/z value
cited), 1030 [S18C18N17]+, 914 [S16C16N15]+, 798 [S14C14N13]+,
682 [S12C12N11]+, 566 [S10C10N9]+, 450 [S8C8N7]+, 334
[S6C6N5]+, 218 [S4C4N3]+, 102 [S2C2N]+. The isotope pattern
for each set of peaks in the series matches the predicted pat-
terns exactly.
Chem. Eur. J. 2006, 12, 6366 – 6381
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6377

J. D. Woollins et al.
Figure 10. MALDI TOF mass spectrum of polythiocyanogen 19.
The repeat unit of 116 m/z corresponds to (SCN)2, which
suggests that this may be the monomeric unit. The (SCN)2
repeat unit fits very well with our proposed structures of
linked heterocyclic five-membered rings. The absence of any
series with a 58 m/z (SCN) repeat unit is strong evidence
against (SCN)x polymer being composed of linear chains of
linked SCN units as proposed in the literature.[4,11]
The IR spectrum of (SCN)x we obtained is dominated by
a very broad peak with a maximum at 1134 cmÀ1 (Figure 11)
consisting of several overlapping peaks and is comparable
with IR spectra reported in the literature.[4,11–13] The Raman
spectrum (Figure 11) was more informative, but there is still
considerable broadness caused by overlapping peaks. In the
Raman spectra there are no peaks in the range 1600–
3500 cmÀ1; the absence of any bands in the region 2000–
2200 cmÀ1 strongly suggests that there are no nitrile groups
present in (SCN)x. In the range 800–1600 cmÀ1 there is a
small peak at 1508 cmÀ1, a very broad, intense peak at
1207 cmÀ1 with an evident shoulder, a strong peak at
1155 cmÀ1 and a low intensity peak at 994 cmÀ1. In the range
200–800 cmÀ1 there are several overlapping peaks at approx-
imately 650 cmÀ1, several overlapping peaks in the range
400–480 cmÀ1 and two further peaks at 289 and 229 cmÀ1.
À
Figure 11. IR spectrum (top) and Raman spectrum (bottom) of (SCN)x
19.
spectrum is enlightening, since the spectrum illustrated by
Cataldo contains no solvent resonance. This seems remark-
A
tra are actually solid state not solution data or due to impur-
ities such as thiourea. We recorded 13C and 15N NMR spec-
tra of normal and labelled (SCN)x in the solid state. In the
13C{1H} DP-MAS NMR of natural abundance and 99% 13C-
labelled polythiocyanogen we observed a major resonance
at d=186.8 ppm. The signal is broad and slightly asymmetric
with low intensity spinning side bands (Figure 12). As ex-
pected the signal-to-noise ratio was substantially improved
in the 13C-labelled sample.
In the spectrum there is a broad peak centred at d=
186.6 ppm with a visible shoulder. Deconvolution yielded
two singlets at d=187.1 (integral intensity 0.88) and d=
183.8 ppm (integral intensity 1). Additionally there is a mul-
tiplet at d=152–172 ppm with significantly lower intensity.
Deconvolution of the multiplet yielded three singlets at d=
156.6 ppm (integral intensity 0.24), d=163.2 (integral inten-
sity 0.35) and 168.1 ppm (integral intensity 0.16). Thus, the
13C NMR spectrum of (SCN)x is dominated by two carbon
We propose that the peak at 650 cmÀ1 is due to n
(C S) vi-
brations and we speculate that the peaks in the range 400–
U
480 cmÀ1 may correspond to n
A
À
Raman spectral data for (SCN)x is, as expected, very differ-
ent to the linear small molecules Sn(CN)2 (n=1, 2, 3) which
show virtually no peaks in the range 800–1600 cmÀ1. Inter-
estingly the 1,2,4-thiadiazole compounds that we have pre-
pared and 1,2,4-dithiazole compounds[14,15,18,23] show strong
ring vibrations in the same region as the large central peak
in the IR spectrum of (SCN)x.
We attempted to record the 13C NMR spectrum of (SCN)x
in dimethylformamide, which was reported twice in the liter-
ature by Cataldo.[11,12] We found only a trace amount of the
polymer dissolved resulting in a faint yellow colour of the
solution and no signal was observed (except for dimethylfor-
mamide) even with a 99% 13C-labelled sample of (SCN)x
after 29000 scans. Examination of the published literature
6378
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Chem. Eur. J. 2006, 12, 6366 – 6381

Sulfur–Nitrogen Heterocycles
FULL PAPER
obtained almost identical 13C NMR data with the peaks at
d=208.2 and 183.1 ppm corresponding to C5 and C3, re-
spectively. The C3 atom is bonded to two nitrogen atoms
and one sulfur atom and is comparable to the carbon envi-
ronments in our proposed 1,2,4-dithiazole structure. The
value for C3 at d=183.1 ppm is very similar to the main
peaks observed in (SCN)x (d=183.9 and 187.1 ppm).
Furthermore, Graubaum et al. have prepared several
1,2,4-dithiazole compounds[34,35] in which both carbon atoms
in the ring are in environments comparable to the carbon
environments in our proposed 1,2,4-dithiazole structure for
(SCN)x. The 13C NMR shifts reported are very similar to
those which we have recorded for polythiocyanogen and are
shown in Table 5.
Figure 12. 13
(SCN)x.
C
DP-MAS solid-state NMR spectrum of 13C-labelled
Table 5. 13C NMR data for 3-amino-5-thione-1,2,4-dithiazole and 1,2,4-di-
thiazoles reported by Graubaum et al.[34,35]
shifts at d=183.8 and 187.1 ppm of approximately equal in-
tensity. We attribute these two peaks to the polymer chain
and the lower intensity peaks may be due to terminal
groups or impurities; the intensities of these latter peaks are
in accord with end groups for a “polymer” with a molecular
weight of approximately 1000 as determined from mass
spectrometry. The carbon environments in the polymer 19
are clearly different to that of KSCN (d=133.8 ppm),
S2(CN)2 (d=108.3 ppm) and S(CN)2 (d=100.1 ppm). The
13C shifts recorded for polythiocyanogen are in the same
range as the 1,2,4-thiadiazoles (Table 4) and 1,2,4-dithia-
zoles.[14,15] In polythiocyanogen the close proximity of the
two peaks at d=183.8 and 187.1 ppm indicates that the two
carbon environments in the polymer are very similar. In the
proposed 1,2,4-thiadiazole structure, C5 is bonded to one ni-
trogen atom and two sulfur atoms, whereas C3 is bonded to
two nitrogen atoms and one sulfur atom. We note from
Table 4 that typically the C5 signal is observed in the range
180–192 ppm, whereas C3 atom resonates in the range 163–
172 ppm. If (SCN)x had a 1,2,4-thiadiazole structure, the C3
environment in the polymer would be comparable to that of
C3 in 12 and 13, which are observed at approximately
163.5 ppm. In the 1,2,4-thiadiazole model compounds the
most downfield shift observed for C3 is 172 ppm. This is
strong evidence against a 1,2,4-thiadiazole structure for
d [ppm]
C5
C3
A
187.1
183.8
208.2
184.5
183.1
180.1
185.6
180.7
178.9
174.9
193.3
192.6
180.8
183.0
polythiocyanogen. Furthermore, we note the outcome of the
A
reaction of the lithium salt of bis(5-chloro-1,2,4-thiadiazol-3-
yl) disulfide with itself. If the polymer was made of 1,2,4-
thiadiazole rings this reaction should result in the formation
of polythiocyanogen. Instead it gave a yellow solid which
may be, as indicated earlier, an isomeric form of (SCN)x.
Our alternative hypothesis, described above, was that the
polymer is based on five-membered rings linked by nitrogen
atoms and the 13C NMR data for polythiocyanogen is com-
patible with a structure composed of 1,2,4-dithiazole rings
linked by exocyclic nitrogen atoms; both carbon atoms are
in very similar environments bonded to two nitrogen atoms
and one sulfur atom. Butler and Glidewell reported that the
13C NMR spectrum of isoperthiocyanic acid (3-amino-5-
thione-1,2,4-dithiazole)[32] consists of two peaks at d=208
and 183 ppm. We resynthesised isoperthiocyanic acid[33] and
Even more compelling evidence for the nitrogen-linked
structure came from the solid-state 15N NMR spectrum of
(SCN)x, which we recorded using a 99% 15N-labelled sample
(Figure 13). Two peaks of equal intensity are noted at d=
236.9 and 197.2 ppm. A lower intensity peak is observed at
d=170.2 ppm.
These 15N NMR resonances differ considerably from the
14N NMR shifts for the small molecules Sn(CN)2 (n=1, 2),
which are observed at approximately d=290 ppm indicating
the difference between the nitrogen environments in the
polymer and the linear small molecules. Furthermore, thia-
zoles have 15N NMR shifts at approx d=300 ppm[36] and the
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J. D. Woollins et al.
reconciled with mixtures of (SCN)x and sulfur impurities.
We have repeated the polymerisations as described by Cata-
ldo and the product is invariably contaminated with sulfur
(as determined by HPLC analysis) and we do not consider
the existence of [Sz(CN)2]x to be firmly established.
Polyselenocyanogen: Finally, we note that (SeCN)x has been
recently described[38] by Cataldo, who reported that seleno-
cyanogen (Se2(CN)2) when treated with certain organic sol-
vents (acetone, dimethyl formamide, methanol and triethyl-
amine) spontaneously polymerises to give polyselenocyano-
gen (SeCN)x. In the same work it was reported that polyse-
lenocyanogen could alternatively be prepared from seleno-
cyanogen by heating in high boiling solvents such as xylenes
and decalin. We have examined a number of selenium-con-
taining systems[39–44] and it is reasonable to anticipate that C-
Se-N analogues of the C-S-N described here could exist and
thus we conducted some preliminary experiments on
(SeCN)x and it is appropriate to include our preliminary ob-
servations here.
Figure 13. DP-MAS solid-state 15N NMR spectrum of (SCN)x.
14N NMR spectra for bis(3-bromo-1,2,4-thiadiazol-5-yl) di-
sulfide (17) displays two shifts at d=310.6 and 278.4 ppm as-
signed as N2 and N4 respectively. Thus the nitrogen NMR
data do not support a 1,2,4-thiadiazole structure for (SCN)x.
Butler and Glidewell reported that the 15N NMR spectrum
of isoperthiocyanic acid (3-amino-5-thione-1,2,4-dithia-
zole)[32] consists of two peaks; we repeated this experiment
and observed two broad peaks at d=221 and 106 ppm in
the 14N NMR spectrum of isoperthiocyanic acid. The peak
at d=221 ppm is assigned as N4 and the peak at d=
106 ppm corresponds to the exocyclic NH2. Interestingly 15N
NMR shifts for imino groups are observed in the range 170–
200 ppm.[36] Our observed solid-state 15N data fit very well
with an (SCN)x structure based on repeating 1,2,4-dithiazole
We added selenocyanogen to acetone and a red solid pre-
cipitated as reported.[38] The solid was isolated by suction fil-
tration and dried in vacuo. Analysis of the insoluble red
solid showed it was red selenium rather than (SeCN)x. Mi-
croanalysis showed 2.25% C and 0.42% N compared to the
expected 11.44% C and 13.35% N for (SeCN)x. Positive ion
electron impact mass spectroscopy displayed the [M]+ at
m/z=632 corresponding to Se8. Ions at m/z=553 (Se7),
m/z=474 (Se6), m/z=395 (Se5), m/z=316 (Se4), m/z=238
(Se3), m/z=158 (Se2) and m/z=79 (Se) were all observed
with the expected isotopomer distributions. Raman spectros-
copy showed only one vibration at 253 cmÀ1 corresponding
À
À
rings linked by =N imino nitrogen atoms. The structure
to n(Se Se). Similar results were obtained from reaction
A
proposed in Scheme 8 does not rationalise the [Sz(CN)2]x
polymers claimed by Cataldo;[13] however, as mentioned
above, these polymers have only been characterised by IR
spectroscopy. The spectra in reference [13]can be readily
with methanol and by heating in high boiling solvents. Bow-
maker et al. have prepared thin films of polythiocyanogen
by oxidation of potassium thiocyanate in methanol.[6] When
they carried out oxidation of potassium selenocyanate the
results were far less conclusive. They obtained a patchy
orange red film that exhibited bands due to grey selenium
in the Raman spectrum. Within a day the film had decom-
posed to give grey selenium. On the basis of our evidence
and the observations of Bowmaker et al. we have no reason
to believe that (SeCN)x exists.
Conclusion
This work describes a systematic investigation and full char-
acterisation of a series of 1,2,4-thiadiazoles. Furthermore,
the data we have collected and the propensity of HNCS and
(SCN)2 to form 1,2,4-dithiazole rings leads us to propose
that polythiocyanogen has a structure composed of 1,2,4-di-
thiazole rings linked by nitrogen bridges (Scheme 8). We be-
lieve our analysis, based on good quality spectroscopic data,
provides a reasonable proposal for the structure of (SCN)x
and we do not believe that compelling evidence for the exis-
tence of [Sz(CN)2]or (SeCN) x has been presented to date.
Scheme 8. Proposed mechanism for polymerisation of S2(CN)2.
6380
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Received: December 7, 2005
Published online: June 8, 2006
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