Structural studies of N-2-(6-picolyl)-N′-tolylthioureas

Article abstract of DOI:10.1023/A:1015688104995

Reaction of 2-amino-6-picoline with 2-, 3-, and 4-tolyl isothiocyanates produces the three N-2-(6-picolyl)-N′-tolylthioureas, 6PicTu2T, 6PicTu3T, and 6PicTu4T. 6PicTu2T is monoclinic, space group P2₁/n with a = 8.1700(3) A, b = 25.5840(6) A, c = 12.6840(5) A, β = 98.8750(16)°, and V = 2619.5(2) A³ with Z = 8, for d _calc = 1.305 g/cm³. 6PicTu3T is monoclinic, space group C2/c with a = 23.879(3) A, b = 6.744(3) A, c = 17.116(10) A, β = 99.26(4)°, and V = 2720(3) A³ with Z = 8, for d_calc = 1.257 g/cm³. 6PicTu4T is triclinic, space group P-1 with a = 8.829(6) A, b = 8.8950(15) A, c = 10.495(3) A, α = 68.63(3)°, β = 72.19(4)°, γ = 63.06(4)°, and V = 681.2(5) A³ with Z = 2, for d_calc = 1.255 g/cm³. Intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen and the planarity of the thiourea are affected by the position of substitution on the aryl ring. ¹H NMR studies in CDCl₃ show the NH′ hydrogen resonance considerably downfield from other signals in the spectrum of each thiourea. The enthalpies of fusion of the present thioureas reflect the extent of intermolecular hydrogen bonding and are compared to other heterocyclic thioureas.

Full text of DOI:10.1023/A:1015688104995

C
Journal of Chemical Crystallography, Vol. 32, Nos. 1–2, February 2002 ( 2002)
Structural studies of N-2-(6-picolyl)-N0-tolylthioureas
Anne K. Hermetet,(1) Lily J. Ackerman,(1) John K. Swearingen,(1) Carmina A. Presto,(1)
Diantha R. Kelman,(2) James M. Giesen,(2) Karen I. Goldberg,(2)
Werner Kaminsky,(2) and Douglas X. West(2)
Received June 21, 2001
Reaction of 2-amino-6-picoline with 2-, 3-, and 4-tolyl isothiocyanates produces the three
N-2-(6-picolyl)-N0-tolylthioureas, 6PicTu2T, 6PicTu3T, and 6PicTu4T. 6PicTu2T is mono-
˚
˚
˚
clinic, space group P21/n with a = 8.1700(3) A, b = 25.5840(6) A, c = 12.6840(5) A,
= 98.8750(16) , and V = 2619.5(2)A with Z = 8, fordcalc = 1.305g/cm3. 6PicTu3Tis
3
˚
˚
˚
˚
monoclinic, space group C2/c with a = 23.879(3) A, b = 6.744(3) A, c = 17.116(10) A,
= 99.26(4) , and V = 2720(3) A with Z = 8, for dcalc = 1.257 g/cm3. 6PicTu4T is
3
˚
˚
˚
˚
triclinic, space group P-1 with a = 8.829(6) A, b = 8.8950(15) A, c = 10.495(3) A,
3
˚
= 68.63(3) , = 72.19(4) , = 63.06(4) , and V = 681.2(5) A with Z = 2, for
dcalc = 1.255 g/cm3. Intermolecular hydrogen bonding involving the thione sulfur and the
NH hydrogen and the planarity of the thiourea are affected by the position of substitution
on the aryl ring. 1H NMR studies in CDCl3 show the NH0 hydrogen resonance considerably
downfield from other signals in the spectrum of each thiourea. The enthalpies of fusion of the
present thioureas reflect the extent of intermolecular hydrogen bonding and are compared
to other heterocyclic thioureas.
KEY WORDS: Thiourea; pyridine; hydrogen bonding; planarity; enthalpy of fusion.
–
or acyl oxygen.3 10 There is also an intermolecular
Introduction
NH hydrogen bond with a sulfur of a neighboring
1
A H NMR study of 2-pyridyl thioureas1
molecule to form a two-dimensional network in
these thioureas. In addition, structures have been
reported of substituted thioureas with intermolec-
ular N----H S bonding, but without intramolec-
showed intramolecular hydrogen bonding be-
tween the pyridyl nitrogen and N0H, and the struc-
ture of N-2-(pyridyl)-N0-phenylthiourea2 showed
this same interaction in the crystalline state. Stud-
ies of a number of substituted thioureas, including
N-benzoylthioureas, show intramolecular hydro-
gen bonding between N0H and the benzoyl, alkyl,
–
ular hydrogen bonding.11 15
More recent structural studies of substituted
N-(2-pyridyl)-N0-arylthioureas include N-(2-
pyridyl)-N0-tolylthioureas,16 the three N-2-(4,6-
lutidyl)-N0-tolylthioureas,17 N-2-(5-bromopyri-
dyl)-N0-2-(2,5-dimethoxyphenylethyl)thiourea,18
and the N-2-(picolyl)- and N-(4,6-lutidyl)-N0-
phenylthioureas.19 The aforementioned 2-pyridyl
(1) Department of Chemistry, Illinois State University, Normal,
Illinois.
(2) Department of Chemistry, 351700, University of Washington,
Seattle, Washington 98195-1700.
* To whom correspondence should be addressed. E-mail: westdx@
chem.washington.edu.
–
thioureas, like the N-benzoyl-N0-thioureas,3 10
feature both intramolecular and intermolecular
17
C
1074-1542/02/0200-0017/0 2002 Plenum Publishing Corporation

18
Hermetet, Ackerman, Swearingen, Presto, Kelman, Giesen, Goldberg, Kaminsky, and West
186–187 C; and 6PicTu4T, 213–214 C. Their
1H and 13C NMR spectra were recorded in
CDCl3 with a Bruker 300 MHz spectrometer and
the enthalpies of fusion were obtained with ap-
proximately 3 mg samples at a heating rate of
10 /min using a Perkin-Elmer Differential Scan-
ning Calorimeter, DSC7.
Crystals were grown by slow evaporation of
1:1 by volume acetone–anhydrous ethanol mix-
tures at room temperature. The colorless thiourea
crystals were mounted in random orientation on
Fig. 1. Representations of 6PicTu2T, 6PicTu3T, and
6PicTu4T showing expected intramolecular and intermolec-
ular hydrogen bonding.
glass fibers and the structures were solved by
direct methods and missing atoms were found
by difference-Fourier synthesis. The nonhydro-
gen atoms were refined with anisotropic tempera-
ture factors. The hydrogens attached to nitrogens
and ring carbons in 6PicTu3T and 6PicTu4T were
refined isotropically and the aryl hydrogens of
6PicTu2T and the methyl hydrogens of the three
thioureas were allowed to ride on their carbons
and assigned a fixed isotropic temperature factor,
hydrogen bonding, but ring substituents affect the
distances and angles of both types of hydrogen
bonds. Also, there is considerable difference in the
planarity among the 2-pyridyl thioureas. Here
we report the crystal structures, 1H NMR
spectra and enthalpies of fusion of N-2-(6-
picolyl)-N0-2-tolylthiourea, 6PicTu2T, N-2-(6-
picolyl)-N0-3-tolylthiourea, 6PicTu3T, and N-2-
(6-picolyl)-N0-4-tolylthiourea, 6PicTu4T, which
are represented in Fig. 1. A companion paper
is a similar study of N-2-(4-picolyl)-N0-2-
tolylthiourea, 4PicTu2T, N-2-(3-picolyl)-N0-4-
tolylthiourea, 3PicTu4T, and N-2-(4-picolyl)-N0-
4-tolylthiourea, 4PicTu4T.20
2
˚
U = 0.05 A . One of the two unique molecules of
6PicTu2T showed disorder but acquiring data at
130(2) K did not alter the disorder suggesting it to
be static. Scattering factors are from Wassmaire
and Kirfel,21 calculations were done by MaXus,
version 2.0,22 and graphics are PLATON for
Windows.23 Table 1 summarizes the crystal data,
collection information and refinement data for
these thioureas.
Experimental
Results and discussion
2-Amino-6-picoline, as well as 2-tolyl-, 3-
tolyl-, and 4-tolyl isothiocyanate, were purchased
from Aldrich and used as received. 2-Amino-6-
picoline was mixed with a tolyl isothiocyanate in
a 1:1 molar ratio (i.e., 2 mmol) in 30 mL of 95%
ethanol, and the mixture stirred with warming for
a minimum of 1 h. On cooling and slowly evap-
orating the reactant mixture (35 C), the thioureas
crystallized from solution. The solids were fil-
tered, washed with cold isopropanol, dried on a
warm plate, and then stored until required for
spectral characterization. The yields are ca. 70%
for each of the thioureas and the melting points
are as follows: 6PicTu2T, 195–196 C; 6PicTu3T,
Structural studies
The ORTEP plot of 6PicTu2T is shown in
Fig. 2, its packing diagram in Fig. 3, and the
ORTEP plots of 6PicTu3T and 6PicTu4T are in
Figs. 4 and 5, respectively. Table 2 is a list of
their fractional atomic coordinates and equivalent
isotropic displacement parameters. 6PicTu3T, like
N-2-(6-picolyl)-N0-phenylthiourea, 6PicTuPh,19
is in the space group C 2/c (#15) with one unique
molecule per unit cell, but 6PicTu2T has two
unique molecules in the asymmetric unit and
6PicTu4T is triclinic, P-1 (#2). Although the data

N-2-(6-picolyl)-N0-tolylthioureas
19
Table 1. Crystallographic Data for 6PicTu2T, 6PicTu3T, and 6PicTu4T
6PicTu2T 6PicTu3T
6PicTu4T
Crystal data
CCDC no.
163120
Colorless, prism
14H15N3S
257.35
130(2)
0.31 0.26 0.24
Monoclinic
P21/n(#14)
8.1700(3)
25.5840(6)
12.6840(5)
90
98.8750(16)
90
2619.5(2)
8
163121
163122
Crystal color, habit
Empirical formula
Formula weight
Temperature, K
Crystal size, mm
Crystal system
Space group
Colorless, prism
C14H15N3S
257.35
Colorless, prism
C14H15N3S
257.35
293(2)
0.32 0.25 0.20
Triclinic
P-1(#2)
8.829(6)
8.8950(15)
10.495(3)
68.63(3)
72.19(4)
63.06(4)
681.2(5)
2
1.255
0.223
Nonius MACH3, ω
2.11–27.41
3307
C
293(2)
0.24 0.20 0.16
Monoclinic
C2/c(#15)
23.879(3)
6.744(3)
17.116(10)
90
99.26(4)
90
2720(3)
8
1.257
0.224
Nonius MACH3, ω
1.72–27.40
5744
˚
a, A
˚
b, A
˚
c, A
,
,
,
3
˚
Volume, A
Z
Density (calcd.), g/cm3
Absorption coefficient, mm
Diffractometer/scan
1.305
0.232
Nonius Kappa CCD,
2.98–29.97
10871
1
range for data collection, deg
Reflections collected
Independent reflections (Rint
Observed reflections
Data/restraints/parameters
Extinction coefficient
Goodness-of-fit
)
6531(0.0435)
6531[I > 2 (I)]
6531/0/408
0
2994(0.0660)
1272[I > 2 (I)]
2994/0/201
0
3104(0.0270 )
2494[I > 2 (I)]
3104/0/201
0
0.966
0.970
1.105
R1, wR2
R1, wR2 (all data)
0.0473, 0.1035
0.0988, 0.1182
0.0644, 0.1463
0.1540, 0.2072
0.0420, 0.1186
0.0544, 0.1364
Fig. 2. ORTEP diagram of 6PicTu2T with atom numbering scheme
and displacement ellipsoids at 50% probability level.

20
Hermetet, Ackerman, Swearingen, Presto, Kelman, Giesen, Goldberg, Kaminsky, and West
Fig. 3. Packing diagram for 6PicTu2T along the 100 axis.
were collected at 130 K, one of the two molecules
in the asymmetric unit of 6PicTu2T has dis-
order of the 2-tolyl ring. The packing diagram,
Fig. 3, shows that adjacent S2 molecules may
sterically crowd each other if the methyl groups
are directed toward each other. Thus, the 2-tolyl
ring appears twice with the two species approx-
imately related to each other by a 2-fold rota-
tion around the N6----C28 bond (i.e., the methyl
groups are in opposite directions), but there is
a distinct tilt off this axis. The site occupancy
was refined to 51.3(5)% for C28----C29(CH3) ----
C30----C31----C32----C33 and 48.7(5)% for the
related residual C75----C76(CH3) ---- C77 ---- C78 ----
C79----C80. Thus, almost with the error limits, the
disorder is complete, that is, 1:1.
These thioureas, like other pyridyl thio-
–
ureas,1,16 20 are found in a conformation resulting
from intramolecular hydrogen bonding of N3H
(N0H) to the pyridine nitrogen, N1, in a manner

N-2-(6-picolyl)-N0-tolylthioureas
21
Table 2. Fractional Atomic Coordinates and Equivalent Isotropic
2
˚
Displacement Parmeters (A )
x
y
z
Ueq
6PicTu2T
C2
0.1300(2)
0.1089(3)
0.1642(3)
0.2382(2)
0.2555(2)
0.0726(2)
0.1878(2)
0.1758(2)
0.2156(2)
0.2686(3)
0.2823(3)
0.2425(2)
0.3317(3)
0.1226(3)
0.2736(2)
0.2469(3)
0.3133(3)
0.4023(2)
0.4218(2)
0.2180(2)
0.3218(9)
0.1920(9)
0.2354(12)
0.3956(16)
0.5219(7)
0.4834(9)
0.5152(3)
0.0144(8)
0.2531(10)
0.0989(11)
0.0815(9)
0.2175(13)
0.376(2)
0.30757(7)
0.32210(8)
0.28830(8)
0.24138(8)
0.23002(7)
0.33653(6)
0.28312(6)
0.23073(7)
0.21792(7)
0.25543(7)
0.30697(7)
0.32091(7)
0.18009(8)
0.18904(7)
0.48424(7)
0.49625(7)
0.46378(8)
0.42025(8)
0.40999(7)
0.51492(6)
0.4571(4)
0.4495(2)
0.4351(2)
0.4282(5)
0.43483(15) 0.9959(3)
0.4495(2)
0.36322(8)
0.4537(3)
0.4576(4)
0.4549(3)
0.43938(18) 0.9802(4)
0.4254(3)
0.4249(5)
0.32967(14) 0.0303(4)
0.22271(15) 0.0440(5)
0.15195(16) 0.0491(6)
0.18791(15) 0.0391(5)
0.29519(15) 0.0333(4)
0.50993(13) 0.0265(4)
0.66784(13) 0.0264(4)
0.69672(14) 0.0302(4)
0.80405(15) 0.0357(5)
0.87965(15) 0.0400(5)
0.84957(15) 0.0411(5)
0.74365(14) 0.0344(4)
0.34005(16) 0.0466(5)
0.61529(16) 0.0474(5)
0.50999(14) 0.0308(4)
0.40235(15) 0.0391(5)
0.33400(16) 0.0447(5)
0.37362(16) 0.0418(5)
0.48123(16) 0.0370(5)
0.68919(14) 0.0305(4)
C3
C4
C5
C6
C7
C8
C9
Fig. 4. ORTEP diagram of 6PicTu3T with atom numbering
scheme and displacement ellipsoids at 50% probability level.
C10
C11
C12
C13
C14
C15
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C75
C76
C77
C78
C79
C80
C81
N1
–
similar to the benzoyl and acyl thioureas3 10
and“cis–cis”like N-phenyl-N0-phenylthiourea.11
The three 2-pyridyl thioureas of this study have
similar bond distances and angles (Table 3). The
one exception is the N3----C8----C13 angle, which
is larger in 6PicTu4T. 6PicTuPh19 and the N-2-
(4,6-lutidyl)-N0-tolylthioureas (i.e., 4,6LutTu2T,
4,6LutTu3T, and 4,6LutTu4T)17 also have similar
bond distances and angles and the N3----C8----C13
angle is similarly significantly larger for
4,6LutTu4T than 4,6LutTu2T and 4,6LutTu3T. A
comparison with thioureas having oxygen invo-
lvedintheintramolecularhydrogenbond6,7 shows
0.8444(9)
0.9001(6)
1.0078(5)
1.0554(6)
0.0312(19)
0.0363(15)
0.0425(17)
0.050(2)
0.0452(14)
0.0362(14)
0.8888(5)
0.52993(18) 0.0466(5)
0.8526(7)
0.8452(9)
0.8794(6)
0.0412(17)
0.0281(18)
0.044(2)
–
that the 2-pyridyl thioureas1,16 19 generally have
a shorter N2----C7 bond, and the S1----C7 bond is
marginally longer for the 2-pyridyl thioureas.
0.0598(18)
0.059(3)
0.058(3)
1.0479(5)
1.0162(6)
The N3----H3
tions (Table 4) have similar N3
N1 intramolecular interac-
N1 distances
0.3932(9)
0.5597(9)
0.20220(18) 0.26318(5)
0.0700(2) 0.34109(6)
0.44091(19) 0.9131(5)
0.4408(3) 0.8752(8)
0.0458(16)
0.078(3)
0.36585(11) 0.0304(4)
0.40209(12) 0.0298(4)
0.55680(12) 0.0281(3)
0.54974(12) 0.0324(4)
0.58124(12) 0.0309(4)
0.73501(12) 0.0364(4)
N2
N3
N4
0.15488(19) 0.29524(5)
0.35833(18) 0.44196(6)
N5
N6
S1
S2
0.2113(2)
0.2772(2)
0.02882(6)
0.15624(7)
0.51801(6)
0.47046(6)
0.381404(17) 0.57194(4) 0.03010(13)
0.566893(18) 0.75486(4) 0.03966(15)
6PicTu3T
C2
C3
C4
C5
C6
C7
C8
0.00839(12) 0.2486(5)
0.06765(13) 0.2410(5)
0.09163(14) 0.2382(6)
0.05749(16) 0.2466(6)
0.00026(14) 0.2539(5)
0.07353(12) 0.2463(5)
0.17114(12) 0.2268(5)
0.55101(17) 0.0336(6)
0.5334(2)
0.4551(2)
0.3965(2)
0.0432(7)
0.0478(8)
0.0505(8)
0.41841(18) 0.0407(7)
0.66303(17) 0.0358(6)
0.63098(18) 0.0406(8)
Fig. 5. ORTEP diagram of 6PicTu4T with atom numbering
scheme and displacement ellipsoids at 50% probability level.
(Continued)

22
Hermetet, Ackerman, Swearingen, Presto, Kelman, Giesen, Goldberg, Kaminsky, and West
neighboring molecule. To date 4,6LutTu2T17 has
Table 2. (Continued)
the shortest nonbonding N S distance among
x
y
z
Ueq
2-pyridyl thioureas, suggesting the strongest
interaction, and 3PicTuPh19 has the longest
nonbonding distance. The thioureas of this study
are at the lower end of the range indicating strong
N ---- H S hydrogen bonding. The H2 S1
C9
0.20335(15)
0.26212(14)
0.28750(16)
0.25586(16)
0.19744(15)
0.04037(16)
0.29555(18)
0.02484(10)
0.01735(10)
0.11103(10)
0.09137(4)
0.3579(6)
0.3462(7)
0.1974(7)
0.0639(7)
0.0790(6)
0.2600(6)
0.4980(8)
0.2540(4)
0.2499(4)
0.2417(4)
0.5955(2)
0.6072(2)
0.6559(3)
0.6902(2)
0.6784(2)
0.3594(2)
0.5689(3)
0.49474(15) 0.0353(6)
0.63006(15) 0.0370(6)
0.61219(16) 0.0379(6)
0.0464(8)
0.0554(10)
0.0653(13)
0.0633(11)
0.0521(9)
0.0568(10)
0.0820(15)
C10
C11
C12
C13
C14
C15
N1
N2
N3
S1
˚
distances, which average ca. 2.6 A for the
2-pyridyl thioureas of this study, are longer than
˚
found for PyTu2T, 2.45(2) A, but much shorter
20
˚
compared to 3.07(7) A for 3PicTu4T. C3H
0.25076(18) 0.76203(5) 0.0587(4)
is positioned to also interact with the same S1
of a neighboring molecule because the pyridyl
ring and thiourea moiety are approximately
coplanar (vide infra). The comparatively long
distance found for 2-pyridyl thioureas with a
3-substituent, 3PicTuPh19 and 3PicTu4T,20 is
indicative of the steric effect of the methyl group
in this position, as well as the of absence of the
“assisting H3.”
A most interesting difference among the 2-
pyridyl thioureas is the angles between mean
planes; the angle between the pyridyl and aryl
mean planes is a convenient measure of the pla-
narity for these thioureas. Among the 2-pyridyl
thioureas studied to date PyTu3T has the largest
angle, an average more than 79 ,19 and 3PicTu4T,
4.25(21) , the smallest.20 The angle between these
mean planes in the present 2-pyridyl thioureas is
6PicTu4T
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
N1
N2
N3
S1
0.11103(19)
0.0090(2)
0.0221(3)
0.1333(3)
0.2310(2)
0.1804(2)
0.38887(19)
0.3736(3)
0.4830(3)
0.6066(2)
0.6188(2)
0.5112(2)
0.3545(3)
0.7262(3)
0.21913(17)
0.09984(18)
0.28754(17)
0.13679(7)
0.14691(19) 0.88942(16) 0.0506(3)
0.2310(2)
0.1363(3)
0.0348(3)
0.1098(2)
0.78559(19) 0.0627(4)
0.7031(2)
0.7223(2)
0.0696(5)
0.0688(5)
0.82705(18) 0.0596(4)
0.18656(19) 1.08816(16) 0.0514(3)
0.08306(18) 1.22477(15) 0.0493(3)
0.0429(2)
0.1596(3)
0.3164(2)
0.3560(2)
0.2420(2)
0.2952(3)
0.4402(3)
1.34443(19) 0.0711(5)
1.4394(2) 0.0754(5)
1.41940(18) 0.0622(4)
1.3006(2) 0.0650(4)
1.20424(18) 0.0573(4)
0.8580(3)
1.5230(2)
0.0839(6)
0.0867(7)
0.01833(17) 0.90918(13) 0.0534(3)
0.23923(18) 0.97715(14) 0.0552(3)
0.02041(17) 1.11867(14) 0.0529(3)
0.33445(6) 1.17115(5) 0.0774(2)
indicating that the position or extent of sub-
stitution on the pyridyl and aryl rings does
not significantly affect the strength of this in-
teraction. Among the 2-pyridyl thioureas with
methyl groups on one or both rings,1,16,17,19,20
one of the crystallographically unique molecules
of N-2-(5-picolyl)-N0-phenylthiourea, 5PicTuPh,
in the order 6PicTu3T > 6PicTu2T
6PicTu4T
(Table 5). Among the 2-pyridyl thioureas
studied to date the angle between the pyridine
ring and the thiourea moiety mean planes is less
than 15 .1,16,17,19,20
has the shortest N3 N1 nonbonding dis-
Thermal studies
17
tance, 2.596(2) A and N-(2-pyridyl)-N0-3-
˚
16
˚
tolylthiourea, PyTu3T, the longest, 2.697(2) A.
The DSC plots of these thioureas show a
sharp peak due to melting followed immedi-
ately by a broader peak representing decompo-
sition. The onset temperatures for fusion and
enthalpies of fusion are as follows: 6PicTu2T,
The present 2-pyridyl thioureas are approximately
in the center of this range and other parameters for
this interaction are similar.1,16,17,19,20
As was found for N-benzoyl-N0-(4-
methoxyphenyl)thiourea,7 H2 is involved in inter-
molecular hydrogen bonding with a sulfur from a
1
195.5 , 44.1 kJ mol ; 6PicTu3T, 187.5 , 33.2 kJ
1
1
mol ; and 6PicTu4T, 214 , 47.2 kJ mol . These

N-2-(6-picolyl)-N0-tolylthioureas
23
˚
Table 3. Selected Bond Distances (A) and Bond Angles ( ) for 6PicTu2T, 6PicTu3T, and 6PicTu4T
6PicTu2Ta
6PicTu3T
6PicTu4T
˚
Bond distances (A)
S1----C7
N1----C2
N1----C6
N2----C2
N2----C7
N3----C7
N3----C8
1.6806(17), 1.6872(18)
1.329(2), 1.340(2)
1.354(2), 1.353(2)
1.400(2), 1.401(2)
1.370(2), 1.364(2)
1.680(3)
1.343(4)
1.343(4)
1.393(4)
1.369(4)
1.346(4)
1.423(4)
1.6875(15)
1.331(2)
1.346(2)
1.404(2)
1.374(2)
1.336(2)
1.416(2)
1.341(2), 1.334(2)
1.427(2), 1.421(11), 1.478(10)
Bond angles ( )
C2----N2----C7
C7----N3----C8
N1----C2----N2
N2----C2----C3
S1----C7----N2
S1----C7----N3
N2----C7----N3
N3----C8----C9
N3----C8----C13
130.55(16), 130.48(16)
127.91(15), 130.7(4)
130.5(2)
127.4(3)
118.5(3)
118.8(3)
119.2(2)
124.4(2)
116.3(3)
118.0(3)
122.3(3)
130.65(13)
132.72(14)
118.18(13)
119.18(15)
118.02(12)
126.59(12)
115.39(14)
118.78(15)
126.52(14)
118.62(16), 118.22(16)
118.23(17), 118.81(17)
118.44(13), 118.76(13)
125.47(13), 124.96(14)
116.07(15), 116.27(16)
117.22(15), 115.7(6), 115.9(6)
121.61(15), 121.5(6), 124.3(7)
aThe second numbers listed are the analogous bond distances and angles for the second molecule; the
third number refers to the second aryl ring of the second molecule.
1Hfus values are comparable to related 2-pyridyl
fusion for 6PicTu3T is surprising due to the simi-
larity of intermolecular hydrogen bonding param-
eters among these thioureas.
1
thioureas; for example, 1Hfus = 43.5 kJ mol
for 6PicTuPh.The low value for the enthalpy of
˚
Table 4. Intramolecular and Intermolecular Hydrogen Bond Distances (A) and Hydrogen Bond Angles ( )
for 6PicTu2T, 6PicTu3T, and 6PicTu4T
6
Compound
D
A
D----H
H
A
D ---- H
A
( D ---- H
A)
Intramolecular
6PicTu2T
N3
N6
N3
N3
N1
0.91(2)
0.99(3)
0.87(3)
0.83(2)
2.87(2)
1.79(3)
1.86(3)
1.89(2)
2.642(2)
2.641(2)
2.637(4)
2.623(2)
141.1(17)
142(2)
147(3)
N4
N1
N1
6PicTu3T
6PicTu4T
146.9(19)
Intermolecular
6PicTu2Ta
N2
S2#1
S2#1
S1#1
S1#1
N6#2
S1#3
S1#1
S1#1
S1#1
S1#1
0.858(19)
0.95
0.84(2)
0.95
0.95
0.98
1.00(6)
1.02(4)
0.80(2)
0.92(2)
2.59(8)
2.79
2.60(2)
2.81
2.93
2.73
2.50(6)
2.70(4)
2.66(2)
2.88(2)
3.4330(17)
3.610(2)
3.4245(17)
3.641(2)
3.839(2)
3.711(2)
3.420(3)
3.637(4)
3.443(2)
3.673(2)
166.2(17)
145.3
169.5(18)
146.8
160.5
174.2
152(4)
153(2)
166.8(17)
145.2(18)
C3b
N5
C23
C13
C34
N2
C3
N2
6PicTu3Tc
6PicTu4Td
C3
a#1: x, 1 y, 1 z; #2: x, y, z; #3: 1 + x, y, z.
bC ---- H S and C----H
c#1: x, y, 1.5 z.
d #1: x, 1 y, 2 z.
N interactions are listed if the H
˚
X distance is <3.0 A.

24
Hermetet, Ackerman, Swearingen, Presto, Kelman, Giesen, Goldberg, Kaminsky, and West
Table 5. Mean Plane Data and Angles Between Planes for 6PicTu2T, 6PicTu3T, and 6PicTu4T
Atom with
Compound
6PicTu2T
Plane
No. Mean plane
greatest deviation
Plane
Angle
N1----C2----C3----C4----C5----C6
N2----C7----S1----N3
C8----C9----C10----C11----C12----C13
N4----C22----C23----C24----C25----C26
N5----C27----N6----S2
C28----C29----C30----C31----C32----C33
C75----C76----C77----C78----C79----C80
N1----C2----C3----C4----C5----C6
N2----C7----S1----N3
C8----C9----C10----C11----C12----C13
N1----C2----C3----C4----C5----C6
N2----C7----S1----N3
1 0.0035
2 0.0043
3 0.0054
4 0.0052
5 0.0043
6 0.0079
7 0.0155
1 0.0046
2 0.0024
3 0.0059
1 0.0015
2 0.0011
3 0.0054
C2, 0.0054(15)
C7, 0.0054(14)
C8, 0.0086(12)
C22, 0.0067(12)
C27, 0.0075(15)
C28, 0.0125(62)
C75, 0.0247(58)
C4, 0.0073(27)
C7, 0.0041(26)
C11, 0.0089(31)
C3, 0.0024(13)
C7, 0.0020(13)
C8, 0.0092(12)
1/2
2/3
3/1
4/5
5/6
6/4
7/6
1/2
2/3
3/1
1/2
2/3
3/1
7.02(9)
46.47(4)
39.64(5)
10.83(8)
66.02(15)
55.42(15)
51.69(19)
3.79(5)
53.97(12)
52.38(14)
2.34(13)
15.41(11)
15.22(12)
6PicTu3T
6PicTu4T
C9----C10----C11----C12----C13----C14
Spectral studies
6PicTu4T, and 6PicTuPh) provides shielding
to the N3H resonance due to the diamagnetic
anisotropic effect of the C6----CH3 bond. A shift to
lowerfrequencyoflargermagnitudeoccursforthe
resonance assigned to N2H with methyl groups on
the pyridyl ring due to their small inductive effect.
There is no difference in the 13C resonance of the
thione carbon, ca. 178 ppm, for the thioureas listed
in Table 6.
1
Selected H and 13C NMR spectral assign-
ments for the three thioureas of this study and
related thioureas are shown in Table 6. The N3H
resonance is affected by the position of the methyl
group on the aryl ring. The thioureas (i.e., PyTu4T
and 6PicTu4T) with a 4-tolyl group have N3H
at higher frequency compared to their 2- and
3-tolyl analogues (Table 6), but at lower frequency
from the thiourea without a methyl substituent on
the aromatic ring (i.e., PyTuPh and 6PicTuPh).
The presence of methyl groups in the 6-position
on the pyridyl ring (i.e., 6PicTu2T, 6PicTu3T,
Conclusion
Considerable difference exists in the pla-
narity of these molecules, which affects some of
the intermolecular hydrogen bonding parameters.
The distances of the intermolecular N2H2 S1
interaction are similar, but 6PicTu3T has a smaller
N ---- H S angle. The 1Hfus for 6PicTu3T is also
substantially lower and both NHs are found fur-
ther upfield in the NMR spectrum.
Table 6. Selected 1H and 13C NMR Assignments for 6PicTu2T,
6PicTu3T, and 6PicTu4T and Related 2-Pyridyl Thioureas
N3H(N0H) N2H(NH) C7
S
Ref.
==
Compound
PyTuPh
PyTu2T
PyTu3T
PyTu4T
6PicTuPh
6PicTu2T
6PicTu3T
6PicTu4T
4,6MTuPh
4,6MTuoT
4,6MTumT
4,6MTupT
13.865
13.494
13.644
13.771
14.103
13.541
13.498
13.919
14.119
13.689
14.052
14.067
10.903
10.013
9.401
10.031
9.205
9.288
8.901
9.042
8.311
9.318
8.731
9.159
178.7
179.3
178.7
178.8
178.5
179.5 This work
178.4 This work
178.5 This work
178.1
179.3
178.4
178.4
19
16
16
16
19
Acknowledgments
Acknowledgment is made to the Camille and
Henry Dreyfus Foundation and the donors of the Petro-
leum Research Fund, administered by the American
Chemical Society, for the partial support of this
research.
19
17
17
17

N-2-(6-picolyl)-N0-tolylthioureas
25
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