A structural comparison of some amine- and thione-substituted triazoles

Article abstract of DOI:10.1016/S0022-2860(98)00470-0

A series of amine- and thione-substituted triazoles have been synthesized and their structures determined by single-crystal X-ray diffraction methods. The compounds differ in the identity of the amine- and alkyl-substituents on the triazole ting. Crystal data for 4- furfuralideneamino-3-methyl-4,5-dihydro-1H-1,2,4-triazole-5-thione, C₈H₈N₄OS: triclinic, space group P1, Z=2, a=10.490(2) A, b=10.700(2) A, c=4.2185(8) A, α=92.68(2)°, β=90.17(2)°, γ=92.61(1)°, V=472.5(1) A³, R(F)=0.040 for 151 variables and 1056 observations (I > 3σ(I)); 4- furfuralideneamino-3-ethyl-4,5-dihydro-1H-1,2,4triazole-5-thione, C₉H₁₀N₄OS: triclinic, space group P1, Z=2, a=8.366(3) A, b=9.296(2) A, c=7.953(2) A, α=113.72(2)°, β=108.54(3)°, γ=84.94(3)°, V=536.3(3) A3, R(F)=0.037 for 136 variables and 1126 observations (I > 3σ(I)); 4- furfuralideneamino-3-propyl-4,5-dihydro-1 H-1,2,4-triazole-5-thione, C₁₀H₁₂N₄OS: triclinic, space group P1, Z=2, a=9.149(3) A, b=9.177(2) A, c=8.045(4) A, α=110.11(2)°, β=114.52(3)°, γ=86.44(2)°, V=574.5(4) A³, R(F)=0.040 for 145 variables and 1414 observations (I > 3σ(I)); 4-(2- acetylpytidyleneamino)-3-ethyl-4,5-dihydro-1H1,2,4-triazole-5-thione, C₁₁H₁₃N₅S: triclinic, space group P1, Z=2, a=7.736(3) A, b=11.752(4) A, c=7.219(2) A, α=93.68(3)°, β=106.26(3) A, γ=91.04(3)°, V=628.3(4) A³, R(F)=0.043 for 154 variables and 1224 observations (I > 3σ(I)). The molecules show substantial variations in conformation as well as in crystal packing. The differences in molecular structure are discussed in terms of the potential of the molecules to act as bidentate ligands towards metal ions.

Full text of DOI:10.1016/S0022-2860(98)00470-0

MOLSTR 10363
Journal of Molecular Structure 470 (1998) 61–69
A structural comparison of some amine- and thione-substituted
triazoles
Ashok K. Sena, Rajkumar Noren Singha, Ram N. Handaa, Surendra N. Dubeya,
,
Philip J. Squattritob *
aDepartment of Chemistry, Kurukshetra University, Kurukshetra 136119, Haryana, India
bDepartment of Chemistry, Central Michigan University, Mt. Pleasant, MI 48859 USA
Received 3 November 1997; revised 15 December 1997; accepted 5 January 1998
Abstract
A series of amine- and thione-substituted triazoles have been synthesized and their structures determined by single-crystal
X-ray diffraction methods. The compounds differ in the identity of the amine- and alkyl-substituents on the triazole ring.
Crystal data for 4-furfuralideneamino-3-methyl-4,5-dihydro-1H-1,2,4-triazole-5-thione, C8H8N4OS: triclinic, space group P1,
3
˚
˚
˚
˚
Z = 2, a = 10:490(2) A, b = 10:700(2) A, c = 4:2185(8) A, a = 92:68(2)Њ, b = 90:17(2)Њ, g = 92:61(1)Њ, V = 472:5(1) A ,
R(F) =0:040 for 151 variables and 1056 observations (I Ͼ 3j(I)); 4-furfuralideneamino-3-ethyl-4,5-dihydro-1H-1,2,4-
˚
˚
˚
triazole-5-thione, C9H10N4OS: triclinic, space group P1, Z = 2, a = 8:366(3) A, b = 9:296(2) A, c = 7:953(2) A,
3
˚
a = 113:72(2)Њ, b = 108:54(3)Њ, g = 84:94(3)Њ, V = 536:3(3) A , R(F) =0:037 for 136 variables and 1126 observations
(I Ͼ 3j(I)); 4-furfuralideneamino-3-propyl-4,5-dihydro-1H-1,2,4-triazole-5-thione, C10H12N4OS: triclinic, space group P1,
3
˚
˚
˚
˚
Z = 2, a = 9:149(3) A, b = 9:177(2) A, c = 8:045(4) A, a = 110:11(2)Њ, b = 114:52(3)Њ, g = 86:44(2)Њ, V = 574:5(4) A ,
R(F) =0:040 for 145 variables and 1414 observations (I Ͼ 3j(I)); 4-(2-acetylpyridyleneamino)-3-ethyl-4,5-dihydro-1H-
˚
˚
˚
1,2,4-triazole-5-thione, C11H13N5S: triclinic, space group P1, Z = 2, a = 7:736(3) A, b = 11:752(4) A, c = 7:219(2) A,
3
˚
˚
a = 93:68(3)Њ, b = 106:26(3) A, g = 91:04(3)Њ, V = 628:3(4) A , R(F) =0:043 for 154 variables and 1224 observations
(I Ͼ 3j(I)). The molecules show substantial variations in conformation as well as in crystal packing. The differences in
molecular structure are discussed in terms of the potential of the molecules to act as bidentate ligands towards metal ions.
᭧ 1998 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structure; Triazoles; Amine-substituted triazoles; Thione-substituted triazoles
1. Introduction
[1–4]. Molecules that possess an S–C–N–N linkage
can potentially bind to a metal ion in a bidentate fash-
ion through the S atom and the second N atom. One
such molecule is 4-amino-3-methyl-4,5-dihydro-1H-
1,2,4-triazole-5-thione [5] which has been found to
coordinate to nickel(II) [6] and copper(I) [7] through
the amine and thione substituents on the triazole ring.
In crystals of the free ligand and its metal complexes,
this triazole exists as the thione tautomer with the H
Metal complexes of compounds with S–C–N
linkages display a wide range of biological activity
* Corresponding author. Tel.: 001 517 774 3981; Fax: 001 517 774
3883; E-mail: philip.squattrito@cmich.edu
Dedicated with affection and gratitude to Professor Abraham
Clearfield on the occasion of his 70th birthday
0022-2860/98/$ - see front matter ᭧ 1998 Elsevier Science B.V. All rights reserved.
PII S0022-2860(98)00470-0

62
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
8.0 g of 4-amino-3-methyl-4,5-dihydro-1H-1,2,4-
triazole-5-thione in ethanol. After 2 h of refluxing, a
brown solid began to separate from the solution. The
reaction mixture was cooled and the product isolated
by filtration. The product was recrystallized from
ethanol and light brown crystals of 1 were obtained
with a yield of 75% (m.p., 225ЊC). Analysis (National
Chemical Consulting, Tenafly, NJ): found, C (46.78);
H (3.24); N (28.20); calculated, C (46.14); H (3.87); N
(26.90).
2.2. Synthesis of 3-C2H5-4-(C4H3O)CHN-5-S-C2N3H
(2)
A mixture of 10 g (0.094 mol) of thiocarbohydra-
zide in 60 ml of propionic acid was heated under
reflux for 4 h. Within 1 h of refluxing, a pale yellow
solid began to separate from the clear solution. The
product of this reaction, 4-amino-3-ethyl-4,5-dihydro-
1H-1,2,4-triazole-5-thione, was isolated with a 76%
yield, and was recrystallized from water (m.p.,
148ЊC). The final product, 4-furfuralideneamino-3-
ethyl-4,5-dihydro-1H-1,2,4-triazole-5-thione (2), was
prepared by refluxing an equimolar mixture of
furfuraldehyde and 4-amino-3-ethyl-4,5-dihydro-1H-
1,2,4-triazole-5-thione in ethanol for 3–4 h. The
solution was allowed to stand overnight at room
temperature, during which time pale yellow crystals
of 2 formed. The product was recrystallized from
ethanol (m.p., 190ЊC). Analysis: found, C (48.57); H
(4.05); N (25.24); calculated, C (48.64); H (4.54); N
(25.21).
Scheme 1.
atom on the ring N atom adjacent to the thione. As a
continuation of this study, we have synthesized and
structurally characterized a series of amine- and
thione-substituted triazoles, shown above in
Scheme 1, that differ in the identity of the alkyl R
group on the triazole ring and the RЈ group on the
amine substituent. These molecules represent poten-
tial ligands for metal complexes that may also be
biologically active. In this paper we report the crystal
and molecular structures of this set of related com-
pounds and examine the likelihood of their chelating
metal ions given their observed conformations.
2. Experimental
2.1. Synthesis of 3-CH3-4-(C4H3O)CHN-5-S-C2N3H
2.3. Synthesis of 3-C3H7-4-(C4H3O)CHN-5-S-C2N3H
(1)
(3)
A mixture of 10 g (0.094 mol) of thiocarbohydra-
zide in 60 ml of glacial acetic acid was heated under
reflux for 4 h. Within 1 h of refluxing, a pale yellow
solid started separating from the clear solution. The
reaction mixture was allowed to stand overnight at
room temperature, and the product of this reaction,
4-amino-3-methyl-4,5-dihydro-1H-1,2,4-triazole-5-
thione, was isolated with a yield of 80%, and recrys-
tallized from ethanol (m.p., 204ЊC). The final product,
4-furfuralideneamino-3-methyl-4,5-dihydro-1H-1,2,-
4-triazole-5-thione (1), was prepared by refluxing an
equimolar mixture of 5.1 ml of furfuraldehyde and
A mixture of 10 g (0.094 mol) thiocarbohydrazide
in 30 ml of butanoic acid was heated under reflux for
5–6 h. Within 1 h of refluxing, a cream-colored solid
started separating from the solution. After the reflux,
the excess butanoic acid was distilled off and the
remaining liquid was allowed to stand overnight at
room temperature. The solid that had crystallized
was filtered, washed with ether and recrystallized
from an equimolar solution of dioxane and water.
Cream-colored crystals of 4-amino-3-propyl-4,5-
dihydro-1H-1,2,4-triazole-5-thione were isolated
with a 74% yield (m.p., 104ЊC). The final product,

63
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
4-furfuralideneamino-3-propyl-4,5-dihydro-1H-1,2,-
4-triazole-5-thione (3), was prepared by refluxing an
equimolar mixture of furfuraldehyde and 4-amino-
3-propyl-4,5-dihydro-1H-1,2,4-triazole-5-thione in
ethanol for 2–3 h. The solution was concentrated
and allowed to stand overnight at room temperature
during which time cream-colored crystals of 3
formed. The product was recrystallized from ethanol
(m.p., 155ЊC). Analysis: found, C (49.60); H (4.65);
N, (23.24); calculated, C (50.83); H (5.12); N (23.71).
dispersion terms [11] were from standard sources.
Data were corrected for Lorentz and polarization
effects. An absorption correction based on w scans
[12] of three reflections was applied to the data of 2.
The space group was assigned in each case as P1
based on intensity statistics and the overall likelihood
of the centrosymmetric space group. Successful
refinements confirmed the space group selection.
The S atoms were located on E-maps generated by
the direct methods program MITHRIL [13], while
the lighter non-hydrogen (O, N and C) atom positions
were obtained by difference Fourier methods (DIR-
DIF [14]). The hydrogen atoms were located on dif-
ference electron density maps following least-squares
refinement. The H atom positions of 1 were refined
while those of the other compounds were kept fixed.
The Biso value of each H atom was set at 1.2 times the
Beq value of the attached atom at the time of its inclu-
sion. Final refinements included anisotropic displace-
ment parameters for all non-hydrogen atoms and were
performed on those data having I Ͼ 3j(I). There were
no unusual variations in Fo − Fc as a function of
(sin v)/l, Miller indices, or Fo. Crystallographic data
for the four compounds are summarized in Table 1.
Final positional and equivalent isotropic displacement
parameters are listed in Table 2.
2.4. Synthesis of 3-C2H5-4-(C5H4N)C(CH3)N-5-S-
C2N3H (4)
An equimolar mixture of 4-amino-3-ethyl-4,5-
dihydro-1H-1,2,4-triazole-5-thione and 2-acetylpyri-
dine in dry methanol was refluxed for 6 h. The solu-
tion was cooled and kept undisturbed for 5–6 days in
the refluxing flask. During this time, large colorless
block-shaped crystals of 4 were obtained with a 75%
yield (m.p., 190ЊC). Analysis: found, C (54.53); H
(5.05); N 29.04; calculated, C (53.42); H (5.30); N
(28.32).
2.5. Crystallographic studies
All the single-crystal X-ray diffraction measure-
ments were performed at room temperature on a
Rigaku AFC6S four-circle diffractometer (graphite-
monochromated 2.0 kW Mo Ka X-ray source;
3. Results
˚
l = 0:71069 A) operated by MSC-AFC diffractometer
3.1. 3-CH3-4-(C4H3O)CHN-5-S-C2N3H
control software [8]. All crystals were cut from larger
fragments and were mounted on glass fibers with sili-
cone cement. Unit cell parameters were obtained by
indexing 25 reflections found during a search of reci-
procal space and were refined by a least-squares
analysis of the setting angles of 20–24 high-angle
reflections (19Њ Ͻ 2v(Mo Ka) Ͻ 42Њ). Intensity data
in the range 3–50Њ2v were collected with q scans of
4Њ min−1 (1 and 4) or 8Њ min−1 (2 and 3). Reflections
were measured at a constant scan rate with up to four
scans for weaker data (those with I Ͻ 10j(I)). The
intensities of three standard reflections measured
after every 150 data showed no significant variations
in any of the experiments. All crystallographic calcu-
lations were performed on a VAXStation 3100/76
computer with the TEXSAN [9] series of programs.
Atomic scattering factors [10] and anomalous
The molecular structure of 1 is shown in Fig. 1 and
a packing diagram with the unit cell outline is pro-
vided in Fig. 2. Selected bond distances and angles for
all four compounds are presented in Table 3. The
molecule exists in the thione tautomeric form with
˚
an S–C distance of 1.681(4) A which indicates
substantial double bond character [5]. All the bond
distances and angles of the triazole moiety are
within four estimated standard deviations of those
reported for 4-amino-3-methyl-4,5-dihydro-1H-
1,2,4-triazole-5-thione [5], except the angles involv-
ing the amine substituent. The angles in 1 are approxi-
mately 5Њ larger (C1–N1–N4 = 133:7(3)Њ) and smaller
(C2–N1–N4 = 118:7(3)Њ) than those in the parent
triazole. This distortion may be the result of non-
bonded interactions between the S atom and H2, the

64
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
Table 1
Crystallographic data for new amine- and thione-substituted triazoles
Parameter
(1)
(2)
(3)
(4)
Empirical formula
Formula weight
Crystal system
C8H8N4OS
208.24
Triclinic
10.490(2)
10.700(2)
4.2185(8)
92.68(2)
90.17(2)
92.61(1)
472.5(1)
P1 (no. 2)
2
C9H10N4OS
222.26
C10H12N4OS
236.29
Triclinic
9.149(3)
9.177(2)
8.045(4)
110.11(2)
114.52(3)
86.44(2)
574.5(4)
P1 (no. 2)
2
C11H13N5S
247.32
Triclinic
7.736(3)
11.752(4)
7.219(2)
93.69(3)
106.27(3)
91.05(3)
628.3(4)
P1 (no. 2)
2
Triclinic
8.366(3)
9.296(2)
7.953(2)
113.72(2)
108.54(3)
84.94(3)
536.3(3)
P1 (no. 2)
2
˚
a (A)
˚
b (A)
˚
c (A)
a (Њ)
b (Њ)
g (Њ)
3
˚
V (A )
Space group
Z value
Dcalc (g cm−3
F(000)
)
1.464
216
2.99
1.376
232
2.68
1.366
248
2.54
1.307
260
2.32
m (cm−1
)
Transmission factors
2v range for data (Њ)
Data collected
None
3–50
+ h, Ϯ k, Ϯ l
1738
0.93–1.00
3–50
+ h, Ϯ k, Ϯ l
2012
None
3–50
+ h, Ϯ k, Ϯ l
2151
None
3–50
+ h, Ϯ k, Ϯ l
2386
Total data
Number of unique data
Rint
1640
0.034
1874
0.014
2012
0.012
2206
0.030
Number of data I Ͼ 3j(I)
Number of variables
RꢀF†; RwꢀF† (I Ͼ 3jꢀI†)
Goodness of fit
1056
151
0.040; 0.039
2.05
0.27, − 0.19
1126
136
0.037; 0.036
2.00
0.17, − 0.16
1414
145
0.040; 0.039
2.43
0.20, − 0.25
1224
154
0.043; 0.040
2.10
0.18, − 0.25
−
−3
˚
Peaks in final DF (e A
)
latter of which is not present in the parent. Overall, the
molecule is fairly flat, with a dihedral angle of 14.3Њ
between the essentially planar triazole and furfurali-
dene rings. The torsion angle C1–N1–N4–C3 is 11.2Њ
so that the furfuralidene group is rotated towards the
viewer relative to the triazole ring. The packing diagram
Fig. 1. ORTEP diagram of the molecular structure of 1 showing the
atom labelling scheme. In this and subsequent figures, the displace-
ment ellipsoids are shown at the 50% probability level except for
those of the hydrogen atoms, which are shown as spheres of arbi-
trary size.
Fig. 2. ORTEP packing diagram of 1 showing the outline of the unit
cell. View is approximately along the c axis. The S, O and N atoms
are shown with octant shading.

65
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
Table 2
Table 2 Continued
Fractional atomic coordinates and equivalent isotropic displace-
ment parameters
a
Atom
x
y
z
Beq
a
3-C2H5-4-(C5H4N)C(CH3)N-5-S-C2N3H
Atom
x
y
z
Beq
S
0.7420(2)
0.6070(4)
0.4462(4)
0.3592(4)
0.7294(4)
1.1854(4)
0.5981(5)
0.4580(5)
0.8857(5)
0.4227(5)
0.2510(6)
0.9490(5)
1.0171(5)
0.9636(5)
1.0942(7)
1.2671(6)
1.3083(5)
0.1289(1)
0.1958(3)
0.0654(3)
0.0901(3)
0.2904(3)
0.3381(3)
0.1289(3)
0.1720(3)
0.2639(3)
0.2341(4)
0.1954(4)
0.1478(3)
0.3635(3)
0.4738(4)
0.5627(4)
0.5374(4)
0.4250(4)
0.0544(2)
− 0.3145(4)
− 0.2485(5)
− 0.4341(5)
− 0.2944(5)
− 0.2674(5)
− 0.1682(5)
− 0.4703(6)
− 0.3042(5)
− 0.6471(6)
− 0.7932(7)
− 0.3386(6)
− 0.2730(5)
− 0.2525(6)
− 0.2159(7)
− 0.2051(7)
− 0.2343(7)
4.61(5)
3.4(1)
3.7(1)
3.6(1)
3.8(1)
4.7(2)
3.3(2)
3.5(2)
3.2(2)
4.7(2)
7.0(3)
4.6(2)
3.3(2)
4.6(2)
5.6(2)
5.4(2)
5.6(2)
3-CH3-4-(C4H3O)CHN-5-S-C2N3H
N1
N2
N3
N4
N5
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
S
O
0.6749(1)
0.9771(2)
0.6893(3)
0.5414(3)
0.5309(3)
0.7875(3)
0.6356(3)
0.6225(3)
0.8616(3)
0.9652(3)
1.0636(4)
1.1417(4)
1.0866(4)
0.6559(4)
0.49327(9)
0.8610(2)
0.7540(3)
0.6746(3)
0.8027(3)
0.7871(3)
0.6402(3)
0.8475(3)
0.7046(4)
0.7392(3)
0.6764(4)
0.7612(4)
0.8707(4)
0.9823(4)
0.3475(3)
1.0232(6)
0.3970(7)
0.0957(8)
0.0841(7)
0.6089(7)
0.2794(8)
0.2683(9)
0.6999(9)
0.9101(9)
1.017(1)
4.15(5)
3.9(1)
3.0(1)
3.7(2)
3.6(1)
3.1(1)
3.2(2)
3.3(2)
3.3(2)
3.0(2)
4.4(2)
4.6(2)
4.4(2)
4.0(2)
N1
N2
N3
N4
C1
C2
C3
C4
C5
C6
C7
C8
1.203(1)
1.200(1)
0.334(1)
3-C2H5-4-(C4H3O)CHN-5-S-C2N3H
S
O
0.2998(1)
0.1394(3) − 0.2303(3)
0.2944(1)
0.3265(1)
0.4243(3)
0.6261(3)
0.6812(4)
0.8438(4)
0.5550(4)
0.5436(4)
0.8070(4)
0.4118(5)
0.3337(4)
0.1784(5)
0.1709(5)
0.3199(6)
0.9369(5)
1.1130(5)
5.00(4)
5.0(1)
3.1(1)
4.2(1)
4.1(1)
3.5(1)
3.6(1)
3.4(1)
3.7(1)
3.4(1)
4.6(1)
5.3(2)
5.8(2)
4.3(1)
5.9(2)
aBeq = (4=3)[a2b11 + b2b22 + c2b33 +(2ab cos g)b12 +(2ac cos b) ×
b13 + (2bc cos a)b23
]
N1
N2
N3
N4
C1
C2
C3
C4
C5
C6
C7
C8
C9
0.4081(3)
0.5301(3)
0.6046(3)
0.3207(3)
0.4111(4)
0.5286(4)
0.1866(4)
0.0911(4) − 0.1297(4)
− 0.0467(4) − 0.1909(4)
− 0.0869(5) − 0.3382(4)
0.0261(5) − 0.3564(4)
0.1902(3)
0.4015(3)
0.3705(3)
0.0461(3)
0.2945(4)
0.2407(4)
0.0162(4)
shows that the molecules are arranged in staggered rows
running parallel to the a axis with the molecules in
adjacent rows in opposite orientations. The main inter-
molecular interaction is a hydrogen bond between H1
…
˚
and S (N2–H1 S, 0.97(3); 2.37(3) A; 173(3)Њ) on each
side of the center of inversion.
0.5598(4)
0.7105(5)
0.1562(4)
0.2228(5)
3.2. 3-C2H5-4-(C4H3O)CHN-5-S-C2N3H
The molecular structure of 2 is depicted in Fig. 3,
while a packing diagram and unit cell outline are
shown in Fig. 4. The bond distances and angles in
the triazole moiety (Table 3) are not substantially dif-
ferent from those in 1; however the conformation of
the molecule is different. The dihedral angle of 13.3Њ
between the triazole and furfuralidene rings is similar
to that in 1, indicating that 2 is also approximately
planar; however, the furfuralidene ring is rotated
in the opposite direction to 1, away from the
viewer relative to the triazole (torsion angle
C1–N1–N4–C3 = −22:3Њ). The molecules also pack
differently. As in 1, there are staggered rows of
molecules, in this case running parallel to the c axis,
with adjacent rows related by the center of inversion.
The molecules in 2 are standing upright in their rows
3-C3H7-4-(C4H3O)CHN-5-S-C2N3H
S
0.7201(1)
1.2500(2)
0.8120(3)
0.5981(3)
0.6224(3)
0.9624(3)
0.7101(3)
0.7545(3)
0.9837(3)
1.1335(3)
1.1842(4)
1.3415(4)
1.3759(4)
0.8349(4)
0.7573(4)
0.7876(4)
0.1879(1)
0.3453(3)
0.0898(2)
− 0.0318(3)
− 0.0981(3)
0.1738(3)
0.0822(3)
− 0.0229(3)
0.3096(3)
0.4045(3)
0.5500(3)
0.5849(4)
0.4610(4)
− 0.0431(3)
− 0.1787(4)
− 0.3345(4)
0.6819(1)
4.32(3)
5.24(9)
2.98(8)
3.66(9)
3.9(1)
3.30(9)
3.1(1)
3.3(1)
3.4(1)
3.2(1)
4.6(1)
4.9(1)
6.2(2)
4.3(1)
4.7(1)
5.7(1)
O
0.5985(3)
0.3744(3)
0.3194(3)
0.1520(3)
0.4510(3)
0.4589(4)
0.1897(4)
0.5761(4)
0.6581(4)
0.7898(4)
0.8136(5)
0.6976(6)
0.0567(4)
− 0.1373(4)
− 0.1163(5)
N1
N2
N3
N4
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10

66
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
Fig. 3. ORTEP diagram of the molecular structure of 2 showing the
atom labelling scheme.
Fig. 4. ORTEP packing diagram of 2 showing the outline of the unit
cell. View is approximately along the a axis. The S, O and N atoms
are shown with octant shading.
while those in 1 are lying on their sides. Despite the
…
consistent with those in 1 and 2, although a small
but significant lengthening of the N1–N4 bond and
contraction of the N1–N4–C3 angle are evident in
Table 3. As was the case with 1 and 2, the most sub-
stantial change is in the conformation of the molecule.
There is a much larger deviation from coplanarity
between the rings (dihedral angle, 30.5Њ) and the
furfuralidene moiety is rotated further away from
different orientations, the N2–H1 S hydrogen bond-
˚
ing interaction is preserved in 2 (1.02; 2.30 A; 172Њ).
3.3. 3-C3H7-4-(C4H3O)CHN-5-S-C2N3H
The molecular structure of 3 appears in Fig. 5, and a
packing diagram with unit cell outline is present in
Fig. 6. The bond distances and angles are mostly
Table 3
˚
Selected bond distances (A), bond angles (Њ), and torsion angles (Њ)
(1) (2)
(3)
(4)
S–C1
N1–C1
N1–N4
N1–C2
N3–C2
N2–N3
N2–C1
N4–C3
1.681(4)
1.387(4)
1.385(3)
1.379(4)
1.295(4)
1.383(4)
1.330(4)
1.273(4)
1.681(3)
1.377(4)
1.396(3)
1.388(4)
1.296(4)
1.378(3)
1.335(4)
1.274(4)
1.687(3)
1.379(3)
1.403(3)
1.385(3)
1.297(3)
1.379(3)
1.332(3)
1.268(3)
1.679(4)
1.372(4)
1.420(4)
1.376(4)
1.303(4)
1.373(4)
1.343(4)
1.274(4)
S–C1–N1
S–C1–N2
N3–N2–C1
N2–N3–C2
N1–C2–N3
C1–N1–C2
N4–N1–C2
N4–N1–C1
N1–C1–N2
N1–N4–C3
C1–N1–N4–C3
C2–N1–N4–C3
130.1(3)
127.0(3)
114.6(3)
103.1(3)
111.9(3)
107.6(3)
118.7(3)
133.7(3)
102.8(3)
120.2(3)
11.2(5)
131.1(2)
126.6(2)
114.4(2)
104.1(2)
110.3(3)
108.8(2)
118.7(2)
132.2(3)
102.4(3)
118.3(3)
− 22.3(5)
164.6(3)
129.9(2)
127.4(2)
114.3(2)
104.1(2)
110.5(2)
108.5(2)
119.4(2)
131.6(2)
102.7(2)
117.0(2)
− 36.5(4)
153.0(3)
128.0(3)
129.6(3)
113.8(3)
104.5(3)
109.9(3)
109.3(3)
124.6(3)
124.9(3)
102.4(3)
114.4(3)
82.3(5)
− 170.8(3)
− 111.5(4)

67
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
Fig. 5. ORTEP diagram of the molecular structure of 3 showing the
atom labelling scheme.
the
viewer
than
in
2
(torsion
angle
C1–N1–N4–C3 = −36:5Њ). The positioning of the
propyl group results in a further deviation from over-
all planarity for 3 compared to 1 and 2. The molecules
of 3 pack in a manner similar to 1, with adjacent rows
of molecules on their sides (running parallel to the b
axis) related by the center of inversion. The same
intermolecular hydrogen bonding interaction is pre-
Fig. 6. ORTEP packing diagram of 3 showing the outline of the unit
cell. The view is approximately onto the [101] plane. The S, O and
N atoms are shown with octant shading.
…
˚
sent in 3 (N2–H1 S, 1.00; 2.34 A; 165Њ).
approximately perpendicular to one another. The non-
planarity of the molecule and the presence of the
pyridine ring affect the crystal packing as well. As
in 1–3 there are rows of molecules, in this case
3.4. 3-C2H5-4-(C5H4N)C(CH3)N-5-S-C2N3H
The molecular structure of 4 is shown in Fig. 7,
while a packing diagram and unit cell outline appears
in Fig. 8. This molecule carries an ethyl group on the
triazole ring as does 2, but differs from the other
molecules in having the 2-acetylpyridylene group on
the amine in place of the furfuralidene group. This
molecule shows some significant structural differ-
ences from the other members of the series, most
notably a longer N1–N4 bond, nearly equal C2–
N1–N4 and C1–N1–N4 bond angles, and a smaller
N1–N4–C3 bond angle. Presumably these differences
arise from the presence of the methyl group on C3
instead of a hydrogen atom. The torsion angle C1–
N1–N4–N3 is 82.3Њ and the dihedral angle between
the rings is 107.4Њ indicating that in order to avoid
steric interactions between the methyl group of the
2-acetylpyridylene and either the S atom or the ethyl
group of the triazole, the two parts of the molecule are
Fig. 7. ORTEP diagram of the molecular structure of 4 showing the
atom labelling scheme.

68
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
contacts between the H atoms on C3 (or C6 in 4)
and those on the R group attached to C2. Other
S–C–N–N–RЈ compounds have been observed to
bind to metal ions in either a monodentate fashion
through S [16] or in the desired chelating S, N
arrangement [17], [18]. In the former case, the RЈ
group is positioned as in 1–4, while in the latter
cases, 2-acetylpyridine [17] and 2-formylpyridine
[18] thiosemicarbazones, the pyridine N atom also
coordinates to the metal making the ligand tridentate.
These molecules adopt conformations as free ligands
which have the coordinating amine N atom and thione
S atom trans to one another across the C–N bond.
Whether a similar coordination mode is possible for
4 remains to be determined. The ability of the mole-
cules in this study to adopt conformations more favor-
able to metal chelation depends in part on the ease of
rotation about the N1–N4 bond. This bond is longer
Fig. 8. ORTEP packing diagram of 4 showing the outline of the unit
cell. View is approximately along the c axis. The S and N atoms are
shown with octant shading.
running parallel to the a axis, with adjacent rows
inverted. In 4 the rows are interleaved so as to afford
a face-to-face contact between the pyridine rings
about the center of inversion. This type of interaction
is not observed in the furfuralidene derivatives. The
˚
(1.385(3)–1.420(4) A) than the correspoding bond in
the heterocyclic thiosemicarbazones (1.375(2) and
˚
1.370(2) A) [18]. Alternatively, replacing the R
…
triazole moieties are arranged so that the N2–H1
S
group with H, or choosing R and RЈ groups capable
of forming intramolecular hydrogen bonds might
result in greater stability for the conformation which
places the lone pair of the amine N atom adjacent to
the S atom, thus leading to greater likelihood of
chelation. Experiments to test these ideas using reac-
tion conditions, such as acidic media [19], which have
been successful in related systems, are underway.
˚
hydrogen bonds are preserved (1.10; 2.20 A; 166Њ).
4. Discussion
Previously we [6], [15] and others [7] have found
that 4-amine-3-methyl-4,5-dihydro-1H-1,2,4-triazole-
5-thione forms bidentate complexes with the divalent
first row transition metals Mn–Zn, coordinating to the
metal ion via the thione and amine substituents on the
triazole ring. It is of interest to examine the coordina-
tion chemistry of larger triazole derivatives, such as
the four molecules in this study, that have organic
functional groups on the amine N atom. Initial efforts
to obtain crystals of the metal complexes suitable for
structural studies have not been successful. One
reason may be that in each case the conformation
adopted by the free ligand in the solid state places
the organic group attached to N4 on the same side
of the N1–N4 bond as the S atom. Thus the C3
atom is blocking N4 from chelating a metal ion
together with the S atom. If this is also the dominant
conformation of these molecules in solution, it would
help to explain the apparent tendency not to bind
strongly to form metal chelates. This conformation
presumably occurs, in part, to avoid non-bonded
5. Supplementary material
Hydrogen atom positions and complete tables of
bond distances and angles have been deposited with
the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK. Additional
crystallographic data can be obtained from the authors
(P.J.S.).
Acknowledgements
The support of the Herbert H. and Grace A. Dow
Foundation, the Dow Chemical Company Foundation
and Central Michigan University in the establishment
of the CMU X-ray Crystallography Laboratory is
gratefully acknowledged.

69
A.K. Sen et al./Journal of Molecular Structure 470 (1998) 61–69
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Vol. IV, Kynoch Press, Birmingham, UK, 1974, Table 2.3.1.
[12] A.C.T. North, D.C. Phillips, F.S. Mathews, Acta Crystallogr.,
Sect. A 24 (1968) 351–359.
[13] C. Gilmore, MITHRIL: A Computer Program for the Auto-
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[14] P. Beurskens, DIRDIF: Direct methods for difference struc-
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