New condensed nitrogen–phosphorus heterocycles

Article abstract of DOI:10.1016/j.poly.2016.12.036

To extend our previous study aimed at the reactions of chlorodithiophosphoric acid pyridiniumbetaine (py·PS₂Cl) with thiosemicarbazide derivatives, we performed the reactions of chlorodithiophosphoric acid pyridiniumbetaine with a new group of polyfunctional nucleophiles – symmetrical and nonsymmetrical derivatives of hydrazine-1,2-bis(thiocarboamide) of general formula R(H)N–C(S)N(H)N(H)C(S)–N(H)R (R?=?methyl, i-propyl, ethyl, t-butyl, phenyl). In analogy to heterocyclic anions obtained with the thiosemicarbazide derivatives, the hydrazine derivatives were expected to form heterobicyclic dianions from the reactions with py·PS₂Cl. All the reactions were carried out in acetonitrile in the presence of pyridine to keep the same reaction conditions as with the previous experiments. Four new compounds were prepared and characterized by³¹P NMR, FTIR, Raman spectroscopy, and single crystal X-ray diffraction. Molecular structures of the products are based on heterobicyclic dianion consisting of two condensed five membered P–N–N–C–N rings, each of them bearing an organic group. Both of the organic groups in heterobicyclic dianion are either identical (Me,ⁱPr) or different (Et/^tBu, Et/Ph). The molecular structure of the heterobicyclic dianion with unusual structural features was further examined by quantum chemistry calculations.

Full text of DOI:10.1016/j.poly.2016.12.036

Accepted Manuscript
New condensed nitrogen-phosphorus heterocycles
Richard Ševč ík, Jiř í Př íhoda, Marek Nečas
PII:
S0277-5387(16)30687-8
DOI:
http://dx.doi.org/10.1016/j.poly.2016.12.036
POLY 12394
Reference:
Polyhedron
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Accepted Date:
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22 December 2016
23 December 2016
Please cite this article as: R. Ševč ík, J. Př íhoda, M. Nečas, New condensed nitrogen-phosphorus heterocycles,
Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.12.036
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New condensed nitrogen-phosphorus heterocycles
Richard Ševčík a, Jiří Příhodaa,∗, Marek Nečasa, b
a Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech
Republic
b CEITEC - Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500 Brno, Czech
Republic
Abstract
To extend our previous study aimed at the reactions of chlorodithiophosphoric acid
pyridiniumbetaine (py.PS2Cl) with thiosemicarbazide derivatives, we performed the reactions
of chlorodithiophosphoric acid pyridiniumbetaine with a new group of polyfunctional
nucleophiles
–
symmetrical and nonsymmetrical derivatives of hydrazine-1,2-
bis(thiocarboamide) of general formula R(H)N-C(S)N(H)N(H)C(S)-N(H)R (R = methyl, i-
propyl, ethyl, t-butyl, phenyl). In analogy to heterocyclic anions obtained with the
thiosemicarbazide derivatives, the hydrazine derivatives were expected to form heterobicyclic
dianions from the reactions with py.PS2Cl. All the reactions were carried out in acetonitrile in
the presence of pyridine to keep the same reaction conditions as with the previous
experiments. Four new compounds were prepared and characterized by 31P NMR, FTIR,
Raman spectroscopy, and single crystal X-ray diffraction. Molecular structures of the
products are based on heterobicyclic dianion consisting of two condensed five membered P-
N-N-C-N rings, each of them bearing an organic group. Both of the organic groups in
heterobicyclic dianion are either identical (Me, iPr) or different (Et/tBu, Et/Ph). The molecular
structure of the heterobicyclic dianion with unusual structural features was further examined
by quantum chemistry calculations.
1
∗ Corresponding author. Address: Department of Chemistry, Faculty of Science, Masaryk University,
Kamenice 5, CZ-625 00 Brno, Czech Republic. Tel.: +420 549 49 6690; fax: +420 549 49 2443.
E-mail address: JiriPrihoda@seznam.cz (J. Příhoda).

Keywords
chlorodithiophosphoric acid pyridiniumbetaine, polyfunctional nucleophiles, heterocycles,
nitrogen-phosphorus compounds, NMR, FTIR, X-ray, DFT
1. Introduction
Recently, we reported on the reactions of chlorodithiophosphoric acid pyridiniumbetaine
(py.PS2Cl, I) with a variety of polyfunctional nucleophiles [1-5] yielding mostly heterocyclic
compounds featuring a (PS2)- group in their structures. Among them the reactions of py.PS2Cl
with thiosemicarbazide and its monoalkyl- and monoarylderivatives [3,4,5] were studied as
well. It was found that thiosemicarbazide or its derivatives bearing small organic groups in
position 4 (methyl, ethyl, phenyl, 4-nitrophenyl) react with py.PS2Cl to give analogous
products A – E with five-membered P-N-N-C-N heterocyclic anions bearing the organic
groups (Eq. 1).
pyH+
S-
H
S
R
H
N
S
P
N
pyridine
- py.HCl
N+
P
Cl
+
(Eq. 1)
H N
NH2
N
N
H
R
C
S
C
S
S-
A
B
C
D
: R = H; ref. [3]
: R = Me; ref. [4]
: R = Et; ref. [4]
: R = Ph; ref. [5]
: R = 4-NO2Ph; ref. [5]
E
In case of thiosemicarbazide monoalkylderivatives with more bulky substituents (iso-propyl,
tert-butyl), all attempts to prepare analogous P-N-N-C-N heterocyclic rings were not
successful, only presumptive evidences (31P NMR) of their formation were obtained and they

were not isolated in a pure form. During the study of the reactions of I with 4-iso-
propylthiosemicarbazide, a new compound with unexpected molecular structure containing a
heterobicyclic dianion was obtained when formerly prepared 4-iso-propylthiosemicarbazide
was used. The formation of this product may be explained if hydrazine-1,2-bis(thiocarbo-iso-
propylamide) is considered as the reacting polynucleophile instead of 4-iso-
propylthiosemicarbazide (Eq. 2) as it was previously assumed by Janča [3]; yet there was no
evidence for the assumption. The assumed hydrazine derivative possibly arose from two
molecules of 4-iso-propylthiosemicarbazide through condensation reaction which probably
occurred on standing at room temperature or during azeotropic distillation process that was
performed to remove the moisture before use.
S
pyH+
S-
C
2 py.PS2Cl
2 pyridine
iPr
iPr
H
N
H
N
iPr
iPr
H
N
S
P
N
N
-N2H4
(Eq. 2)
H
N
N H
2
H
N
NH2
- 2 py.HCl
N
P
S
N
C
S
C
S
C
S
iPr
C
S
S-
pyH+
To confirm our postulate, we prepared hydrazine-1,2-bis(thiocarbo-iso-propylamide) and used
it as starting nucleophile in the reaction with py.PS2Cl. Subsequently we prepared a series of
symmetrical and nonsymmetrical substituted hydrazine-1,2-bis(thiocarboamide) derivatives
and studied their reactivity towards py.PS2Cl. In this paper we report results of the study and
discuss the molecular and crystal structures of the products.
2. Experimental
2.1. Chemicals and synthetic procedures

All chemicals were used as supplied (Aldrich, Lachema). Solvents were dried by standard
methods and were distilled prior to use [6]. Chlorodithiophosphoric acid pyridiniumbetaine
was prepared according to the known procedure [7]. Hydrazine-1,2-bis(thiocarboamide)
derivatives were prepared according to the literature procedure [8] by two-step reactions of
hydrazine and particular iso-thiocyanate derivatives. In case of symmetrical hydrazine
derivatives syntheses were arranged as one-pot reactions, in other cases intermediary
thiosemicarbazide derivative was isolated before the second reaction step. In the first step iso-
thiocyanate derivative reacts with hydrazine intensively at room temperature, the second
reaction step mostly necessitates higher temperature (reflux). Basic characteristics of the
prepared nucleophiles and syntheses details are given in Table 1.
Table 1. Characteristics of the prepared hydrazine-1,2-bis(thiocarboamide) derivatives
R1N(H)C(S)N(H)N(H)C(S)N(H)R2
reflux time
(min)
yield
(%)
color
melting point
(° C)
R1
Me
i-Pr
Et
R2
Me
i-Pr
t-Bu
Ph
30
60
180
-
60
90
62
85
white
white
white
white
212-213
198-200
165-166
172-173
Et
2.2. Physical measurements
The 31P NMR spectra were measured in acetonitrile using a Bruker AVANCE DRX 300
instrument and were referenced to 85% H3PO4. The IR spectra were recorded in nujol mulls
on a Bruker IFS 28 spectrometer. The Raman spectra of solid samples were collected in
Raman capillaries on a Bruker Equinox X55/S instrument.

2.3. X-Ray measurements
Diffraction data were collected on a KUMA KM-4 κ-axis CCD diffractometer with graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å). The temperature during data collection
was 120(2) K. The intensity data were corrected for Lorentz and polarization effects. All the
structures were solved by direct methods and refined by full-matrix least-squares methods
using anisotropic thermal parameters for the non-hydrogen atoms. Crystal data and structure
refinement parameters are listed in Table 3. The software packages used were Xcalibur CCD
system [9] for the data collection/reduction, and SHELXTL [10] for the structure solution,
refinement, and drawing preparation (thermal ellipsoids are drawn at the 50% probability
level).
2.4. Quantum chemistry calculations
DFT using ADF® 2014 molecular modeling suite [11, 12] was used for computation of
optimized structures and properties; the OPBE exchange-correlation functional [13], Slater
type basis set TZ2P [14] with small frozen core were used. Analytical normal mode
frequencies were calculated. Bonding energies are given w. r. t. spherical spin-restricted
neutral atoms used in ADF-package.
2.5. Reactions of py.PS2Cl with hydrazine-1,2-bis(thiocarboamide) derivatives
All reactions of py.PS2Cl with hydrazine-1,2-bis(thiocarboamide) derivatives were performed
under dry nitrogen atmosphere in anhydrous solvents using conventional Schlenk techniques.

First, a solution of py.PS2Cl and pyridine in acetonitrile was prepared. Then a suspension of
dry hydrazine-1,2-bis(thiocarboamide) derivative in acetonitrile was added into the reaction
mixture which was subsequently stirred for specified time at room temperature. At the end of
the reaction, precipitated white solids insoluble in acetonitrile were filtered off and dried
under vacuum. In case of ethyl/tert-butyl derivative, main fraction of the product (soluble in
acetonitrile) was obtained from the concentrated solution upon standing at -25 °C overnight.
Reaction details and yields are presented in Table 2.
Table 2. Experimental details and reaction yields
hydrazine-1,2-bis(thiocarboamide)
py.PS2Cl
pyridine
CH3CN time yield
derivative
(mmol)
2.24
product
R1
Me
i-Pr
Et
R2
(g)
(mmol)
(g)
(mmol) (ml)
(ml)
46
(h)
48
48
72
72
(%)
92
II
III
IV
V
Me
0.400
0.300
0.460
0.460
4.49
2.56
3.93
3.62
0.941
0.537
0.823
0.758
4.49
2.56
3.93
3.62
0.37
0.21
0.32
0.30
i-Pr
t-Bu
Ph
1.28
1.96
1.81
28
90
40
85
Et
36
88
2.6. Bis(pyridinium) salt of 2,6-dimethyl-3,7-dithioxotetrahydro-1H,5H-
[1,2,4,3]triazaphospholo[2,1-a][1,2,4,3]triazaphosphole-1,5-bis(thiolate)-1,5-disulfide
(II)
White powder, yield: 92 % (with respect to I). 31P NMR (dimethylformamide): δ = 89.7 ppm,
singlet. IR: 3205 vw, 3145 vw, 3127 vw, 3095 vw, 3062 vw, 1635 vw, 1603 w, 1527 w, 1483
m, 1457 w, 1425 w, 1336 vs, 1323 vs (sh), 1256 vw, 1237 vw, 1192 w, 1156 vw, 1115 w,
1057 vw, 1045 vw, 1025 vw, 1006 vw, 988 vw, 865 w, 768 s, 744 w, 697 s, 671 w, 661 w,
608 vw, 566 s, 499 vw. RA: 3089 w, 3053 vw, 3035 vw, 2926 vw, 1634 vw, 1601 vw, 1481

vw, 1311 vw, 1257 sh, 1231 vw, 1192 w, 1155 vw, 1056 vw, 1026 w, 1008 vs, 943 vw, 757
vw, 636 vw, 602 w, 446 w, 397 s, 352 vw, 319 w, 248 vw, 193 w, 166 w, 130 vs, 83 s.
2.7. Bis(pyridinium) salt of 2,6-diisopropyl-3,7-dithioxotetrahydro-1H,5H-
[1,2,4,3]triazaphospholo[2,1-a][1,2,4,3]triazaphosphole-1,5-bis(thiolate)-1,5-disulfide
(III)
White powder, yield: 90 % (with respect to I). 31P NMR (dimethylformamide): δ = 87.8 ppm,
singlet. IR: 3221 vw, 3146 vw, 3134 vw, 3061 w, 1633 vw, 1607 vw, 1534 w, 1527 w, 1483
w, 1467 w, 1423 m, 1352 w, 1308 vs, 1293 vs, 1187 w, 1131 w, 1083 w, 1054 vw, 1024 vw,
1006 vw, 982 vw, 894 vw, 852 w, 768 m, 741 w, 694 m, 672 w, 608 vw, 569 s, 483 vw, 462
vw, 437 vw. RA: 3086 w, 2989 vw, 2970 vw, 2938 vw, 2921 vw, 2870 vw, 1631 vw, 1606
vw, 1426 vw, 1277 vw, 1224 vw, 1187 vw, 1160 vw, 1137 vw, 1110 vw, 1064 vw, 1054 vw,
1027 w, 1008 vs, 945 vw, 933 vw, 873 vw, 857 w, 775 vw, 693 vw, 636 vw, 610 sh, 604 w,
484 vw, 441 vw, 398 s, 370 w, 312 vw, 298 m, 240 vw, 205 vw, 178 sh, 161 sh, 127 m, 103
m, 83 m.
2.8. Bis(pyridinium) salt of 2-tert-butyl,6-ethyl-3,7-dithioxotetrahydro-1H,5H-
[1,2,4,3]triazaphospholo[2,1-a][1,2,4,3]triazaphosphole-1,5-bis(thiolate)-1,5-disulfide
(IV)
White powder, yield: 85 % (with respect to I). 31P NMR (dimethylformamide): δ = 88.6 ppm
(triplet 1:2:1, 3J[P-H]= 12 Hz; doublet, 3J[P-P] = 4.6 Hz), δ = 86,9 ppm (doublet, 3J[P-P] =
4.6 Hz). IR: 3206 m, 3139 m, 3127 m, 3081m, 3063 s, 1635 w, 1613 w, 1603 w, 1527 m,
1482 m, 1397w, 1367 m, 1340 s, 1314 vs, 1290 vs, 1224 w, 1206 w, 1190 m, 1158 w, 1104
w, 1081 vw, 1066 vw, 1057 vw, 1046 vw, 980 vw, 858 vw, 799 w, 750 s, 693 s, 636 w, 608
w, 558 s, 516 vw, 505 vw. RA: 3092 vw, 3076 sh, 2956 vw, 2931 vw, 1632 vw, 1602 vw,

1445 vw, 1366 vw, 1344 vw, 1288 vw, 1220 vw, 1189 w, 1154 vw, 1056 vw, 1026 w, 1007
vs, 924 vw, 896 vw, 811 vw, 720 vw, 637 w, 608 vw, 601 sh, 503 vw, 397 m, 379 sh, 308 vw,
286 vw, 251 vw, 221 vw, 166 w, 135 s, 112 s, 97 s, 84 vs.
2.9. Bis(pyridinium) salt of 2-ethyl,6-phenyl-3,7-dithioxotetrahydro-1H,5H-
[1,2,4,3]triazaphospholo[2,1-a][1,2,4,3]triazaphosphole-1,5-bis(thiolate)-1,5-disulfide
(V)
White powder, yield: 88 % (with respect to I). 31P NMR (dimethylformamide): δ = 88.5 ppm
(triplet 1:2:1, 3J[P-H]= 12 Hz; doublet, 3J[P-P] = 7.8 Hz), δ = 87,9 ppm (doublet, 3J[P-P] =
7.8 Hz). IR: 3203 vw, 3143 w, 3127 w, 3093 w, 3063 m, 1634 vw, 1601 w, 1527 m, 1482 m,
1456 w, 1439 w, 1376 s, 1368 s, 1342 vs, 1315 vs, 1274 w, 1257 m, 1188 s, 1160 vw, 1148
vw, 1079 vw, 1054 vw, 1045 vw, 1016 vw, 970 w, 927 vw, 873 vw, 808 vw, 774 m, 744 m,
704 s, 674 w, 604 vw, 584 w, 560 s, 506 vw, 424 vw. RA: 3090 vw, 3079 vw, 3066 vw, 3054
vw, 3040 vw, 2963 vw, 2936 vw, 2927 vw, 2866 vw, 1631 vw, 1611 sh, 1601 vw, 1439 vw,
1366 vw, 1324 sh, 1306 vw, 1276 vw, 1254 vw, 1235 vw, 1191 vw, 1159 vw, 1080 vw, 1057
vw, 1026 w, 1007 vs, 931 vw, 897 vw, 728 vw, 636 vw, 604 w, 559 vw, 508 vw, 492 vw, 427
vw, 400 s, 316 w, 287 vw, 267 vw, 238 vw, 191 w, 168 w, 127 s, 104 s, 83 s.
3. Results and discussion
3.1. Products and reaction mechanism
A series of reactions of I with hydrazine-1,2-bis(thiocarboamide) derivatives were carried out
to yield new compounds with heterobicyclic dianions (Eq. 3). Obtained results confirmed that

S
C
pyH+
S
S-
S
R2
R1
N
H
N
R2
N
H
N
P
N
N
2 pyridine
- 2 py.HCl
N+
P
Cl
H
H
(Eq. 3)
2
+
N
P
S
N
C
S
C
S
R1
S-
C
S
S-
pyH+
R = R = Me (comp.
)
R = Et, R = tBu (comp.
)
IV
II
1
2
1
2
R1 = R2 = iPr (comp. III) R1 = Et, R2 = Ph (comp. V)
hydrazine-1,2-bis(thiocarboamide) derivatives react with I under the formation of compounds
with the heterobicyclic dianion, and a two-step reaction mechanism (Eq. 4) was
experimentally confirmed for dimethylderivative (R1 = R2 = Me). In the first step, I reacts
with hydrazine-1,2-bis(thiocarboamide) derivative under the formation of a heterocyclic
intermediate with a five-membered P-N-N-C-N ring similar to five-membered rings in
compounds A – E. The heterocyclic intermediate with R1 = R2 = Me (compound VI) was
isolated and characterized by single crystal X-ray diffraction. In the next step the heterocyclic
intermediate reacts with the second molecule of I under the formation of a heterobicyclic
dianion. Compound VI should be considered only a reaction intermediate since an attempt to
prepare VI by the reaction of equimolar amounts of I and hydrazine-1,2-
bis(thiocarbomethylamide) was not successful; only compound II was obtained as the main
product, although in low yield and purity, while traces of the intermediate VI were confirmed
only in the reaction mixture by 31P-NMR.

S
R1
H N
H
N
R2
N
H
N
H
N+
P
Cl
+
C
S
C
S
S-
pyridine
- py.HCl
(Eq. 4)
pyH+
S-
S
pyH+
S-
S
C
C
R2
R2
S
P
N
pyridine
- py.HCl
N
S
P
N
N
H
N
P
S
N
N
N
R1
H
R1
C
S
S-
pyH+
C
S
heterocyclic
intermediate
S
heterobicyclic
product
N+
P
Cl
S-
As both the present reaction of I with intentionally prepared hydrazine-1,2-bis(thiocarbo-iso-
propylamide) and the previously studied reaction of I with “4-iso-propylthiosemicarbazide”
yielded the same product III, we can conclude that the same nucleophile hydrazine-1,2-
bis(thiocarbo-iso-propylamide) was employed in both the reactions. The present results thus
confirm at least a part of the proposed reaction route (Eq. 2). Although the first step, i.e.
proposed condensation 4-iso-propylthiosemicarbazide was not studied, it is legitimate to
claim that its transformation to hydrazine-1,2-bis(thiocarbo-iso-propylamide) occurred on
prolonged standing at room temperature or during azeotropic distillation. To avoid the issue
with 4-iso-propylthiosemicarbazide transformation it is necessary to use freshly prepared
derivative which can be dried simply under vacuum.
3.2. Nuclear magnetic resonance

The products are insoluble (II and III) or slightly soluble (IV and V) in acetonitrile and are
easily isolated from the reaction mixtures. All of the compounds are well soluble in
dimethylformamide. In 31P NMR spectra of the compounds II and III, only singlets are
observed. Signal spliting due to P-H or P-N interactions is not observed which is rather
unexpected in case of II as spliting due to P-H interaction is observed in B that contains an
analogous P-N-N-C-N ring with methyl group. 31P NMR spectra of nonsymmetrical
compounds IV and V show two doublets due to inequivalence of phosphorus atoms; one of
them is split further into a triplet by coupling to CH2 hydrogens of ethyl group.
3.3. Molecular spectroscopy
Infrared and Raman spectra of compounds II – V are quite simple but assignment is
complicated because of absorption bands overlaps. Nevertheless, the presence of pyridinium
cations, and of phenyl group in case of V, is clearly seen in the infrared spectra. A band
around 3202 cm-1 is in all cases assigned to N-H bonding vibration in pyridinium cations,
other bands belonging to cations can be found in the region above 3000 cm-1 (aromatic C-H
bonding vibrations) and at 1500-1650 cm-1. Some of the cation bands are still found in the
region of 650-790 cm-1 but they are overlapped by bands of PS2 group. Absorption bands
belonging to C=S bonding vibrations were not identified. Vibrations of pyridinium cations are
observed in Raman spectra as well, they can be found in the same regions as in infrared
spectra, moreover very strong band at ca 1007 cm-1 is assigned to pyridinium cation as well.
The presence of organic substituents in the molecules of II – V is evidenced by the bands at
2850-3000 cm-1 belonging to aliphatic C-H bonding vibrations, with more bands being
observed for the bulkier organic substituents.
3.4. X-ray diffraction analysis

Molecular structures of compounds II - VI (Fig. 2 – 6) were definitely confirmed by single
crystal X-ray diffraction. The molecules of II – IV possess heterobicyclic moieties substituted
i
by two hydrocarbon groups, either identical (Me – II, Pr – III) or different (Et/tBu – IV,
Et/Ph – V) from each other. While in II the heterobicyclic moiety is perfectly planar as a
result of crystallographically imposed mirror symmetry, in the other compounds the deviation
from planarity is less or more pronounced. The r.m.s. deviation of atoms fitted to the ring
plane is largest for one of the crystallographically independent molecules in III (0.2232 Å).
The ring planarity is reflected in tendency of nitrogen atoms towards sp2 hybridization, as
documented by bond valence angles sums on nitrogen atoms which range from 353.4 to 360.0
°. The P–S bond lengths range from 1.939 to 1.975 Å and are significantly longer than in the
starting py.PS2Cl (1.920 Å) [15]. In agreement with the concept of a charge delocalization in
the (PS2)- moiety [1,2], the respective P–S bond lengths are very similar in the present
compounds, although the differences are more significant in case of unsymmetrically
substituted dianions (compounds IV and V). In the crystal structures of the present
compounds, pyridinium cations are involved in a network of hydrogen bonds between N–H
groups and sulfur atoms, with the exception of III for which N–H…Cl bonds to chloride
anions are preferred.

S(6)
C(2)
S(2)
C(R )
2
S(1) P(1)
N(1)
N(2)
N(4)
N(3)
P(2) S(5)
S(4)
C(R )
1
C(1)
S(3)
Fig. 1 X-ray diffraction analysis – general numbering scheme for heterobicyclic dianions of II
– V used in the text and Tab. 4 (C(R1) and C(R2) represent carbon atoms binding organic
substituents to heterobicyclic skeleton, R1 stands for ethyl group in compounds IV and V).
Intermediate VI keeps the same numbering scheme but contains only one P-N-C-N-N ring
marked with lower numbers.
Fig. 2 The ORTEP drawing of anionic part of compound II.

Fig. 3 The ORTEP drawing of anionic part of compound III.
Fig. 4 The ORTEP drawing of anionic part of compound IV.

Fig. 5 The ORTEP drawing of anionic part of compound V.
Fig. 6 The ORTEP drawing of anionic part of intermediate VI.

3.5. Quantum chemistry calculation
Tendency of nitrogen atoms of heterobicyclic dianions of II – V to possess rather sp2
hybridization was further examined by quantum chemistry calculations. Optimized structure
and properties of the dianion C4H6N4P2S62- (symmetry D2h) of compound II with its perfect
planar geometry was calculated via DFT. Calculated bond lengths (Fig. 7) are mostly in good
agreement with the experimental ones, although with the exception of P(1)-N(1) bond they
are more or less shorter. The largest difference can be found for exocyclic bonds C(1)-
S(3)/C(2)-S(6) (0.027 Å) and N(3)-C(R1)/N(4)-C(R2) (0.033 Å) and especially for endocyclic
N(1)-N(2) bond (0.039 Å) but as we can see in case of two crystallographically independent
molecules of III, lengths of the N(1)-N(2) bond can differ even more (0.049 Å). The
distribution of the electron density - contour map, Hirshfeld charges [16] and Voronoi
deformation density [17] - in the dianion was calculated. The extent of π-conjugation in the
dianion is clearly seen from the Fig. 8 showing two bonding π-orbitals 2Au and 3Bg. Except
for the two phosphorus atoms all atoms in plane are engaged; the role of the phosphorus d-
orbitals in bonding is qualitatively negligible as usual. Bond order analysis in the Nalewajski-
Mrozek approach [18] shows that the C-S and P-S bonds have a biggest share of a partial
double bond. Results of the DFT computation are thus in compliance with experimental data
of the single crystal X-ray diffraction and confirm presumptive π-electron conjugation in the
heterobicyclic dianion.

Fig. 7 Bond lenghts (Å) in anionic part of compound II calculated via DFT.
Fig. 8 Bonding π-orbitals 2Au (left) and 3Bg (right) in anionic part of compound II calculated
via DFT.

Conclusion
We have studied the reactions of py.PS2Cl with disubstituted derivatives of hydrazine-1,2-
bis(thiocarboamide) and prepared four new heterobicyclic compounds with two condensed P-
N-N-C-N rings in high yields. Some details about the mechanism of their formation were
obtained through isolation of an intermediate heterocyclic compound. DFT calculations show
an extensive conjugation of π-electron density leading to preferred planar geometry of the
heterobicyclic dianions, which was fully confirmed by single crystal X-ray diffraction.
Appendix A. Supplementary data
CCDC 1494069 - 1494073 contain the supplementary crystallographic data for compounds II
-
VI.
These
data
can
be
obtained
free
of
charge
via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgements
We would like to thank to Pavel Kubáček for his valuable contribution dealing with DFT
computations.
References
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3. M. Janča, Dissertation, Masaryk University Brno, 2002.

4. R. Ševčík, J. Příhoda, M. Nečas, Polyhedron 24 (2005), 1855.
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Oxford, 1988.
7. M. Meisel, H. Grunze, Z. Anorg. Allg. Chem. 360 (1968) 277.
8. M. Busch, H. Lotz, J. Prakt. Chem., (2) 90 (1914) 260.
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1.168. Oxford, England, 2001.
10. G. M. Sheldrick, Acta Cryst. A64 (2008) 112.
11. C. Fonseca Guerra, J. G. Snijders, G. te Velde, E. J. Baerends, Towards an order-N DFT
method, Theor. Chim. Acta (1998), 99, 391.
12. G. te Velde, F. M. Bickelhaupt, E. J. Baerends, C. Fonseca Guerra, S. J. A. van
Gisbergen, J. G. Snijders, T. Ziegler, Chemistry with ADF, J. Comput. Chem. (2001), 22,
931.
13. M. Swart, A. W. Ehlers, L. Koop, Performance of the OPBE exchange-correlation
functional, Mol. Phys. (2004), 102, 2467.
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118, J. Comput. Chem. (2003) 24, 1142.
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17. C. Fonseca Guerra, J.-W. Handgraaf, E. J. Baerends and F. M. Bickelhaupt, Voronoi
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one-determinantal difference approach, Can. J. Chem. (1996) 74, 1121.

Table 3. Crystal data and details of the structure determination.
II
C14H18N6P2S6
524.64
III
IV
C18H26N6P2S6
580.75
V
C22.5H25Cl0.5N6.5P2S6
658.52
VI
C14H20ClN6PS4
467.02
Empirical formula
C33H44Cl3N9P2S6
927.42
Formula weight
Crystal system
Monoclinic
C2/m
Triclinic
Triclinic
Monoclinic
C2/c
Orthorhombic
Pca21
Space group
P-1
P-1
a (Å)
17.335(4)
7.0873(14)
9.3398(19)
90
9.7991(3)
9.9585(3)
26.9346(8)
100.410(2)
90.300(2)
118.5930(10)
2257.01(12)
2
9.3401(19)
10.441(2)
15.566(3)
106.85(3)
91.28(3)
28.5583(4)
15.4755(2)
14.3913(2)
90
25.969(2)
9.4719(8)
8.8065(9)
90
b (Å)
c (Å)
α (°)
β (°)
97.97(3)
90
110.326(2)
90
90
γ (°)
Volume (Å3)
113.48(3)
1316.0(5)
2
90
1136.4(4)
2
5964.24(14)
8
2166.2(3)
4
Z
Calculated density (Mg/m3)
µ (mm-1)
1.533
1.365
1.466
1.467
1.432
0.757
0.587
0.662
0.637
0.648
Measured / unique reflections
Data / restraints / parameters
4340 / 1126
1126 / 0 / 83
0.0856 / 0.2229
0.0952 / 0.2486
1.099
23011 / 7911
7911 / 96 / 478
0.0561 / 0.1360
0.1190 / 0.1433
1.023
9963 / 4782
4782 / 0 / 293
0.0343 / 0.0749
0.0523 / 0.0797
0.937
34354 / 5244
5244 / 0 / 339
0.0323 / 0.0837
0.0486 / 0.0921
1.110
21814 / 3196
3196 / 1 / 235
0.0336 / 0.0782
0.0382 / 0.0803
1.061
Final R indices [I>2σ(I)]
Final R indices [all data]
GooF
∆ρmax / ∆ρmin (e.A-3)
2.071 / -0.711
0.724 / -0.440
0.630 / -0.282
0.582 / -0.266
0.357 / -0.379

Table 4. Selected bond lengths (Å) and angles (°).
IV
(R1 = Et,
R2 = tBu)
V
(R1 = Et,
R2 = Ph)
II
(R1 = R2 = Me)
III
VI
(R1 = R2 = iPr)
P(1)-S(1)
P(1)-S(2)
P(2)-S(4)
P(2)-S(5)
P(1)-N(1)
P(2)-N(2)
P(1)-N(3)
P(2)-N(4)
N(2)-C(1)
N(1)-C(2)
N(3)-C(1)
N(4)-C(2)
C(1)-S(3)
C(2)-S(6)
N(3)-C(R1)
N(4)-C(R2)
N(1)-N(2)
1.9750 (12)
1.9750 (12)
1.9750 (12)
1.9750 (12)
1.755 (6)
1.755 (6)
1.750 (5)
1.750 (5)
1.362 (8)
1.362 (8)
1.368 (8)
1.368 (8)
1.698 (5)
1.698 (5)
1.468 (8)
1.468 (8)
1.430 (10)
1.944 (2); 1.9509 (19)
1.950 (2); 1.9564 (19)
1.950 (2); 1.9564 (19)
1.944 (2); 1.9509 (19)
1.738 (4); 1.752 (4)
1.738 (4); 1.752 (4)
1.749 (4); 1.732 (4)
1.749 (4); 1.732 (4)
1.372 (6); 1.358 (6)
1.372 (6); 1.358 (6)
1.377 (6); 1.372 (6)
1.377 (6); 1.372 (6)
1.649 (6); 1.675 (6)
1.649 (6); 1.675 (6)
1.495 (6); 1.496 (6)
1.495 (6); 1.496 (6)
1.450 (8); 1.401 (7)
1.9551 (10)
1.9513 (10)
1.9650 (10)
1.9389 (10)
1.739 (2)
1.737 (2)
1.726 (2)
1.758 (2)
1.354 (3)
1.367 (3)
1.361 (3)
1.371 (3)
1.673 (2)
1.670 (2)
1.479 (3)
1.532 (3)
1.403 (3)
1.9561 (8)
1.9403 (8)
1.9506 (8)
1.9406 (8)
1.7626 (18)
1.7497 (18)
1.733 (2)
1.7426 (19)
1.364 (3)
1.362 (3)
1.351 (3)
1.360 (3)
1.670 (2)
1.669 (2)
1.479 (3)
1.445 (3)
1.424 (3)
1.9382 (14)
1.9476 (14)
1.727 (2)
1.719 (3)
1.342 (4)
1.360 (4)
1.347 (4)
1.328 (4)
1.671 (3)
1.675 (3)
1.458 (4)
1.445 (5)
1.422 (3)
S(1)-P(1)-S(2)
S(4)-P(2)-S(5)
N(1)-P(1)-N(3)
N(2)-P(2)-N(4)
C(1)-N(3)-C(R1)
C(2)-N(4)-C(R2)
C(1)-N(3)-P(1)
C(2)-N(4)-P(2)
N(2)-N(1)-P(1)
N(1)-N(2)-P(2)
C(1)-N(2)-N(1)
C(2)-N(1)-N(2)
N(3)-C(1)-N(2)
N(4)-C(2)-N(1)
N(3)-C(1)-S(3)
N(4)-C(2)-S(6)
N(2)-C(1)-S(3)
N(1)-C(2)-S(6)
120.29 (9)
120.29 (9)
86.1 (2)
120.65 (10); 120.33 (9)
120.65 (10); 120.33 (9)
87.0 (2); 86.60 (19)
87.0 (2); 86.60 (19)
119.9 (5); 119.5 (4)
119.9 (5); 119.5 (4)
116.5 (3); 116.2 (3)
116.5 (3); 116.2 (3)
111.3 (4); 111.6 (4)
111.3 (4); 111.6 (4)
112.3 (5); 113.3 (5)
112.3 (5); 113.3 (5)
109.8 (5); 110.0 (4)
109.8 (5); 110.0 (4)
127.6 (4); 127.2 (4)
127.6 (4); 127.2 (4)
122.6 (4); 122.8 (4)
122.6 (4); 122.8 (4)
118.59 (5)
119.95 (5)
86.31 (10)
87.07 (10)
122.01 (19)
121.94 (19)
117.45 (16)
115.27 (16)
113.13 (15)
112.85 (15)
113.24 (19)
113.52 (19)
109.8 (2)
120.95 (4)
119.73 (4)
85.76 (9)
119.35 (5)
87.35 (12)
86.1 (2)
85.79 (9)
122.8 (5)
122.8 (5)
117.6 (4)
117.6 (4)
113.0 (5)
113.0 (5)
113.1 (6)
113.1 (6)
110.2 (5)
110.2 (5)
126.1 (4)
126.1 (4)
123.8 (5)
123.8 (5)
122.47 (19)
121.43 (19)
117.57 (15)
117.56 (15)
112.36 (13)
112.97 (13)
112.33 (17)
112.82 (17)
110.51 (19)
109.84 (19)
126.07 (17)
127.19 (17)
123.39 (16)
122.94 (16)
123.9 (3)
122.8 (3)
116.3 (2)
112.13 (18)
112.4 (2)
119.3 (2)
111.2 (3)
115.8 (3)
126.2 (3)
124.3 (3)
122.6 (2)
119.9 (2)
110.5 (2)
126.46 (18)
131.07 (18)
123.73 (19)
118.41 (19)
Symmetry codes (II): (i) −x, −y, −z+2; (ii) x, −y, z.
Symmetry codes (III): (i) −x, −y, −z+1; (ii) −x+2, −y+2, −z.

Synopsis
Reactions of chlorodithiophosphoric acid pyridiniumbetaine with symmetrical and
nonsymmetrical derivatives of hydrazine-1,2-bis(thiocarboamide) of general formula R(H)N-
C(S)N(H)N(H)C(S)-N(H)R (R = methyl, i-propyl, ethyl, t-butyl, phenyl) were studied.
Syntheses were carried out in acetonitrile in the presence of pyridine and four new
compounds with heterobicyclic dianions were prepared and characterized.