Synthesis and characterization of some thallium cyclopentadienide fused ring pyridazines

Article abstract of DOI:10.1080/00397911.2012.698356

Thallium cyclopentadiene (Cp) salts are important precursors for the synthesis of a variety of compounds having materials and commercial applications. The synthesis of 5,6-fused ring thallium Cp pyridazines 2a-d from previously reported 5,6-fused ring pyr

Full text of DOI:10.1080/00397911.2012.698356

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Synthesis and Characterization of Some
Thallium Cyclopentadienide Fused Ring
Pyridazines
Jason O. E. Young a , Chad A. Snyder a , Nathan C. Tice b , Seth L.
Sloan a , Adam C. Smith a , Sana A. Shah a , Levi A. Dopierala a ,
Michael S. Crocker a , Yuto Kobayashi a & Michael G. Mazzotta c
a Department of Chemistry , Western Kentucky University , Bowling
Green , Kentucky , USA
b Department of Chemistry , Butler University , Indianapolis ,
Indiana , USA
c Department of Chemistry , Eastern Kentucky University ,
Richmond , Kentucky , USA
Published online: 03 Jun 2013.
To cite this article: Jason O. E. Young , Chad A. Snyder , Nathan C. Tice , Seth L. Sloan , Adam C.
Smith , Sana A. Shah , Levi A. Dopierala , Michael S. Crocker , Yuto Kobayashi & Michael G. Mazzotta
(2013): Synthesis and Characterization of Some Thallium Cyclopentadienide Fused Ring Pyridazines,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 43:18, 2441-2451
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Synthetic Communications1, 43: 2441–2451, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2012.698356
SYNTHESIS AND CHARACTERIZATION OF
SOME THALLIUM CYCLOPENTADIENIDE
FUSED RING PYRIDAZINES
Jason O. E. Young,1 Chad A. Snyder,1 Nathan C. Tice,2
Seth L. Sloan,1 Adam C. Smith,1 Sana A. Shah,1
Levi A. Dopierala,1 Michael S. Crocker,1 Yuto Kobayashi,1
and Michael G. Mazzotta3
1Department of Chemistry, Western Kentucky University, Bowling Green,
Kentucky, USA
2Department of Chemistry, Butler University, Indianapolis, Indiana, USA
3Department of Chemistry, Eastern Kentucky University, Richmond,
Kentucky, USA
GRAPHICAL ABSTRACT
Abstract Thallium cyclopentadiene (Cp) salts are important precursors for the synthesis of
a variety of compounds having materials and commercial applications. The synthesis of
5,6-fused ring thallium Cp pyridazines 2a–d from previously reported 5,6-fused ring pyrida-
zines is described herein. This route was quite general, and features an efficient and
convenient two-step synthesis of a series of TlCp salts in a THF solution of thallium
ethoxide. Full characterization of newly formed TlCp salts 3a–d are reported.
Keywords Cyclopentadiene; 1,2-diacylcyclopentadiene; fulvenes; pyridazines; thallium
INTRODUCTION
Thallium cyclopentadienide salts have long been shown to be convenient trans-
metallating reagents. Compared to their sodium or potassium analogs, they tend to
display greater environmental stability because thallium has a slightly larger ionic
Received May 14, 2012.
Address correspondence to Chad A. Snyder, Department of Chemistry, Western Kentucky
University, 1906 College Heights Blvd., Bowling Green, KY 42101, USA. E-mail: chad.synder@wku.edu
2441

2442
J. O. E. YOUNG ET AL.
radius and possesses d orbitals.[1,2] In addition to their air, moisture, and temperature
stability, thallium salts are well known for their efficient transfer of cyclopentadienyl
(Cp) moieties in solution with various transition-metal atoms such as manganese and
rhenium.[3,4] These thallium intermediates are also often easy to synthesize and isolate
because of their stability and insolubility in nonpolar organic solvents. For instance,
TlCp salts are stable in the presence of air and moisture, which affords synthetic
convenience in comparison to the highly reactive NaCp and KCp salts. These TlCp
salts have proven to be excellent trnasmellating agents in group VII complexation
synthesis.[3,4] In addition, thallium salts have been successfully utilized in a variety
of applications, such as in antibiotics,[5] catalysis,[6] and synthetic photosynthesis.[6]
Our current interests focus upon the potential role of pyridazine complexes in next-
generation electronic devices, which utilize organics as the semiconducting material.
These types of molecular electronic materials possess many advantages over
traditional inorganic semiconducting materials including lower cost of production,
greater processibility, and the ability to function on flexible substrates (so-called
plastic electronics).[7–9] Molecular electronics offer new materials suitable for a
variety of next-generation applications such as organic light-emitting diodes
(OLEDs) and organic photovoltaic cells (OPVs).[7] Our recent efforts have been
focused on the synthesis of a variety of 5,6-fused ring pyridazines. These fused hetero-
cycles will serve as synthetic models and building blocks for potential organic or orga-
nometallic conducting polymers. One synthetic pathway toward these pyridazine
complexes focuses upon an off-metal ring closure of a 1,2-diacylcyclopentadiene
(fulvene) to form the corresponding pyridazine, followed by complexation. A key
intermediate in this proposed route is the thallium fused-ring pyridazine salt. Herein,
we present the synthesis and characterization of some novel 1,2-disubstituted
5,6-fused-ring pyridazine thallium salts.
RESULTS AND DISCUSSION
The compounds presented herein were constructed from 1,2-diacylcyclopenta-
dienes (fulvenes). Fulvenes 1,2-C5H3(COR)(COHR) 1a–d were successfully synthe-
sized using a modified procedure of Linn and Sharkey (Scheme 1).[10] For all fulvene
synthesis, 3 molar equivalents of freshly cracked cyclopentadiene were added to a
n
solution of 2 molar equivalents of BuLi in dry ethyl ether in an ice bath. The sus-
pension was stirred for 10–15 min followed by dropwise addition of the appropriate
acid chloride. A distinct color change was observed with addition of each acid chlor-
ide. For example, 1,2-C5H3(CO-(5-BrC4H2O)(COH-(5-BrC4H2O)) (1a), prepared
using 5-bromo-2-furoyl chloride, gave an immediate red suspension. All reaction
mixtures were allowed to warm to room temperature and stirred for 45–60 min.
The reactions were then hydrolyzed with dilute acetic acid, extracted with ethyl
ether or methylene chloride, dried over MgSO4, filtered, and reduced to an oil or
semisolid. Crude fulvenes 1b–d were filtered through a silica plug (50:50 dichloro-
methane–hexane), and the solvent was reduced in vacuo. Any semisolids were tritu-
rated using cold hexane to afford solid fulvenes 1a–d. Fulvene 1a was recrystallized
from a solvent mixture of methylene chloride and pentane to give 46.0% product.
Yields for the fulvenes in some cases were modest but reasonable (23–86%).[11–13]
Lower than expected yields were observed for 1a, yet are typical for furyl

THALLIUM CP SALTS
2443
Scheme 1. Synthetic route to thallium salts 3a–d.
substituted fulvenes.[14] We are currently optimizing the isolation and purification
methods for fulvene 1a.
The structure of fulvene 1a was confirmed by 1H NMR, 13C NMR, and infrared
(IR) spectroscopy. The cyclopentadiene (Cp) ring protons are observed as an
unresolved triplet for CHCHCH and a doublet (CHCHCH) having chemical shifts
of 6.65 and 6.84 ppm, respectively. These chemical shift ranges match closely with
previously reported fulvenes.[11–13] The furoyl protons are also observed as unre-
solved doublets at 7.47 ppm and 8.08 ppm, respectively. The Cp ring carbons for ful-
vene 1a, CHCHCH and CHCHCH, are observed in their typical range of 115.1 and
122.4 ppm, respectively. IR analysis confirmed the presence of the carbonyl functional
group, with a distinct stretching frequency at 1567 cmꢀ1. These stretches display
a shift to lower energies as a result of the fulvene’s enolized, delocalized structure
when in solution, which matches with the corresponding values for previously
reported fulvenes.[11–13] Analysis of 1a by mass spectrometry (DART-LTQ) also
confirmed the structure of the 5-bromofuroyl fulvene 1a (Mþ þ H ¼ 412.99).
The 5,6-fused-ring pyridazines 2a–d were successfully synthesized using a
modified procedure of Snyder and Tice (Scheme 1).[11,14] New pyridazines 2a and
b are reported here. Treating fulvenes 1,2-C5H3(COR)(COHR) 1a–d to a solution
of excess hydrazine hydrate in methanol or tetrahydrofuran (THF) at room tempera-
ture yielded the corresponding pyridazines 2a–d (Scheme 1). Reaction times varied
from 24–48 h, followed by a water quench and then either an ethyl ether or methyl-
ene chloride extraction. Pyridazines 2a and b were purified via hexane trituration.
Percentage yields for compounds 2a and b ranged were 26% and 79%, respectively.
The structures for pyridazines 2a and b were confirmed by 1H NMR, 13C NMR,
and IR spectroscopy and are listed in Table 1. Pyridazine 2a and 2b Cp ring protons
CHCHCH are both observed as doublets at 6.79 ppm (3J ¼ 3.4 Hz) and 7.04 ppm

2444
J. O. E. YOUNG ET AL.
Table 1. Selected 1H and 13C NMR data for 2a–b and 3a–d
Parameter
2a
2b
3a
3b
3c
3d
Ha
Hb
7.41, t,
J ¼ 3.4 Hz
6.79, d,
J ¼ 3.4 Hz
108.0
7.54, t,
J ¼ 3.5 Hz
7.04, d,
J ¼ 3.5 Hz
109.3
7.07, t,
J ¼ 4.0 Hz
7.21, d,
J ¼ 4.0 Hz
110.3
6.79, t,
J ¼ 3.4 Hz
6.44, d,
J ¼ 3.4 Hz
110.0
6.37 br
s
6.84, t,
J ¼ 2.9 Hz
6.41, d,
J ¼ 2.9 Hz
99.2
6.84 br
s
Ca
Cb
Cc
92.0
98.3
148.2
114.1
150.8
120.3
133.5
113.9
158.3
116.5
155.0
121.6
149.3
Note. NMR solvents: 2a, acetone-d6; 2b, CDCl3; 3a–d, DMSO-d6.
(3J ¼ 3.5 Hz), respectively. Triplets are seen at 7.41 ppm (2a) and 7.54 ppm (2b), cor-
responding to the CHCHCH proton, and having coupling constants of 3.4 Hz and
3.5 Hz, respectively. Because of their delocalized nature in solution, the 2a and b
amine protons were observed downfield (10–12 ppm range), closely matching the
previously reported pyridazine N-H chemical shifts, such as 2c and d.[11–15] For
instance, the 2a amine proton was seen at 10.6 ppm. Just as with the previously
reported 2c and d, the 13C NMR spectrum for 2a and b showed the disappearance
of the carbonyl group (167.6–184.3 ppm) as observed in fulvenes 1a and b. Instead,
=
pyridazines 2a and b show the characteristic C N carbon signals at 150.8 and
=
133.5 ppm, respectively. The signal for the C N carbon in pyridazine 2a is found
more downfield at 150.8 ppm, presumably reflecting the greater delocalized nature
=
of its C N bond due to the larger conjugation of the phenyl groups. The Cp ring car-
bons CHCHCH carbons are seen at 114.1 and 120.3 ppm, respectively, whereas the
CHCHCH signals are observed at 108.0 and 109.3 ppm, respectively. IR spectroscopy
for pyridazines 2a and b confirms the loss of the carbonyl stretches and the appear-
ance of C N stretches seen at 1619 and 1591 cmꢀ1, respectively (Table 2). Secondary
=
Table 2. Selected IR data for 1a, 2a, and 3a–d
Parameter
1a
2a
3a
3b
3c
3d
=
C
O–H
O
1567
3435
—
—
—
—
—
—
—
—
—
—
—
—
—
=
N
C
N-H
1619
3215
1591
3156
1516
3113
1526
3105
—

THALLIUM CP SALTS
2445
amine stretches for 2a and b are observed at 3215 and 3200 cmꢀ1, respectively. MS
and HRMS analysis confirmed the structure for 2a, showing a 406 Mþ peak followed
by loss of bromine at 299 (Mþ–Br). HRMS observed the Mþ at 405.8950, matching
closely to the calculated Mþ of 405.8952. Pyridazine 2b also showed the Mþ peak
(428 m=z) with loss of bromine at 349 (Mþ–Br). HRMS for 2b structure was
confirmed with the calculated Mþ at 427.9378, matching closely with the observed
value of 427.9348.
The synthesis of the thallium cyclopentadienide salts 3a–d was successfully
performed using a modified procedure of Snyder and Tice (Scheme 1).[14] New
thallium compounds 3a–d are reported here. Treating pyridazines 1,2-C5H3(COR)
(COHR) 2a–d to a solution of thallium(I) ethoxide in tetrahydrofuran (THF) at
room temperature yielded the corresponding thallium cyclopentadienide salts 3a–d
(Scheme 1). The thallium compounds were allowed to react for 24 h, isolated via
filtration, and then washed with cold hexane. The thallium cyclopentadienide salts
3a–d were dried and characterized with no further purification. Percentage yields
for compounds 3a–d ranged from 70 to 100%.
1
Thallium Cp salts 3a–d were confirmed by H NMR, 13C NMR, and IR spec-
troscopy (Tables 1 and 2). The Cp ring protons are observed as a triplet (CHCHCH)
and doublet (CHCHCH) having chemical shifts of 6.37–7.07 ppm and 6.41–7.21 ppm,
respectively. The coupling constants for the Cp CHCHCH and CHCHCH chemical
shifts ranged from 2.9 to 4.0 Hz for the Cp protons. The furyl protons for 3a are
observed as broad singlets at 6.88 and 7.60 ppm. The Cp ring carbons for thallium
Cp salts 3a–d, CHCHCH and CHCHCH, are observed between of 92.0–110.3 ppm
and 98.3–121.6 ppm, respectively, which corresponds well with previously reported
thallium Cp salts.[12–15] IR analysis confirmed the presence of the C N bond, with
=
a distinct stretching frequency range found between 1516 and 1600 cmꢀ1 (Table 3).
These stretches are typical of previously reported pyridazines.[12–14] Analysis of
3a–d by MS also confirmed the structures for each of the thallium Cp salts, with either
the Mþ and=or Mþ–Tl observed for each case. For example, thallium Cp salt 3a
displayed the Mþ–Tl signal at 408 m=z.
The structure of 1,2-C5H3(CC6H4BrNH)(CC6H4BrN) (2b) was determined by
x-ray crystallographic methods. The crystals for which data were collected had been
grown by slow evaporation from acetone at room temperature. These crystals were
mounted on glass fibers with Paratone N oil. Data were collected at 90 K on a Nonius
KappaCCD diffractometer. The main programs used were DENZO-SMN to obtain
cell parameters and for data reduction, SCALEPACK for absorption correction,
SHELXS-86 for structure solution, and SHELXL-93 for refinement.[16] Hydrogen
atoms were placed in geometrically calculated positions. Crystal data and a summary
of experimental details are given in Table 3.
Recrystallization of 2b from acetone and hexane affords the pyridazine as
orange block crystals (Fig. 1). Pyridazine 2b crystallizes in a triclinic P-1 space group,
with four molecules in the unit cell. Compound 2b actually exists as two unique
molecules (which have been labeled A and B). Although molecules A and B do display
face-to-face orientation, there are no closest contacts (a distance less than the sum of
the van der Waals radii) between the two. Thus, it is likely the actual amount of
p-stacking present between A and B is quite weak. There are hydrogen bonds present
between adjacent molecules of A (N1A-H1A . . . N2A) and B (N1B-H1B . . . N2B),

2446
J. O. E. YOUNG ET AL.
Table 3. Crystal data and structure refinement for pyridazine 2b
Parameter
Value
Empirical formula
Formula weight
Temperature
C19H12Br2N2
428.13
90.0(2) K
˚
0.71073 A
Triclinic, P-1
Wavelength
Crystal system, space group
Unit cell dimensions
a ¼ 112.7426(5)ꢁ
b ¼ 97.6426(5)ꢁ
c ¼ 91.8075(5)ꢁ
˚
a ¼ 8.4507(1) A
˚
b ¼ 13.8248(1) A
˚
c ¼ 15.1280(1) A
3
˚
Volume
Z
1608.82(2) A
4
Calculated density
Absorption coefficient
F(000)
1.768 Mg=m3
5.038 mmꢀ1
840
Crystal size
h range for data collection
Limiting indices
0.18 ꢂ 0.14 ꢂ 0.12 mm
1.48 to 27.46ꢁ
ꢀ10 < ¼ h< ¼ 10, ꢀ17 < ¼ k< ¼ 17, ꢀ19 < ¼ l< ¼ 19
40102=7337 [R(int) ¼ 0.0380]
100.0%
Reflections collected = unique
Completeness to h ¼ 27.46
Absorption correction
Max. and min. transmission
Refinement method
Data=restraints=parameters
Goodness of fit on F2
Final R indices [I > 2 r(I)]
R indices (all data)
Largest diff. peak and hole
Semi-empirical from equivalents
0.583 and 0.514
Full-matrix least-squares on F2
7337=0=415
1.040
R1 ¼ 0.0255, wR2 ¼ 0.0534
R1 ¼ 0.0375, wR2 ¼ 0.0567
ꢀ3
˚
0.483 and ꢀ0.451 e A
˚
with bond lengths at 2.14 and 2.16 A, respectively. The average Cp carbon–carbon
˚
bond lengths for molecules A and B are 1.4157(3) A and 1.414(7) A, respectively.
˚
˚
Both molecules, A and B, have the same N1–N2 bond length of 1.359(2) A, and
Figure 1. Molecular structure for pyridazine 2b. (Figure is provided in color online.)

THALLIUM CP SALTS
2447
the average aromatic ring carbon–carbon bond lengths for molecules A and B are
˚
1.389(6) A and 1.388(3) A, respectively. The carbon–bromine bond lengths for the
˚
˚
para-bromo substitutents for molecule A are 1.9003(19) A and 1.9023(19) A, while
˚
˚
˚
those of molecule B are 1.8982(19) A and 1.9015(19) A. X-ray analysis shows the phe-
nyl rings for molecule A are twisted out of the plane of the central pyridazine, with the
[C19A–C14A–C7A–N2A] and [C13–C8–C1–N1] torsion angles at ꢀ43.1(8) and
34.7(3)ꢁ respectively. Molecule B also displays nonplanarity for its phenyl rings, in
regards to the central ring, with the [C19B–C14B–C7B–N2B] and [C13B–C8B–
C1B–N1B] torsion angles at ꢀ39.9(2) and 43.7(3)ꢁ, respectively.
EXPERIMENTAL
All reactions were carried out using standard Schlenk techniques under a
nitrogen atmosphere unless otherwise noted. NMR solvents CDCl3, acetone-d6,
and dimethylsulfoxide (DMSO-d6) (Aldrich) were used without further purification.
5-Bromo-2-furoic acid, dicyclopentadiene, tetrahydrofuran (THF), hydrazine
hydrate (Aldrich), thallium(I) ethoxide (Strem), and thionyl chloride (Acros) were
used without further purification. Fulvenes 1,2-C5H3(COC6H4Br)(COHC6H4Br)
(1b), 1,2-C5H3(COC6H4Cl)(COHC6H4Cl) (1c), and 1,2-C5H3(COC6H4OCH3)
(COHC6H4OCH3) (1d) were prepared according to the literature methods.[10–15]
5-Bromo-2-furoyl chloride was synthesized from a modified procedure from Petasis
and Teets.[17] Ethyl ether and THF were dried over sodium benzophenone ketyl.
1H and 13C NMR spectra were recorded on a JEOL 500-MHz NMR spec-
trometer at ca. 22 ꢁC and were referenced to residual solvent peaks. All 13C NMR
spectra were listed as decoupled. Infrared (IR) spectra were recorded on Spectrum
One Fourier transform (FT–IR) Spectrometer. Electron ionization (EI) mass spectra
were recorded at 70 eV on a Varian 500-MS Series LC=MS ion trap at Western
Kentucky University’s Advanced Materials Institute as well as on a DART SVP
MS Thermo Scientific LTQ-XL instrument at Eastern Kentucky University’s
Department of Chemistry. Melting points were taken on a standard Mel-Temp
apparatus. X-ray diffraction data were collected at 90 K on a Nonius Kappa CCD
diffractometer at the University of Kentucky. Elemental analysis were performed
at Western Kentucky University’s Advanced Materials Institute and Atlantic Micro-
labs, Inc., in Norcross, Georgia. Elemental analysis of the thallium salts 3a–d
afforded carbon and hydrogen values further outside the acceptable range than those
theoretically calculated. However, we attribute this observation to the presence of
thallium impurities commonly present in these types of salts.[18] These trace
inorganic by-products did not affect the reactivity of compounds 3a–d and further
purification was not attempted.
Synthesis of 1,2-C5H3(CO-(5-BrC4H2O)(COH-(5-BrC4H2O)) (1a)
In a 250-mL, three-necked, round-bottomed flask, n-butyl lithium in hexanes
(2.5 M, 13 mL, 0.0325 mol) was added to 50 mL of anhydrous diethyl ether at 0 ꢁC.
Freshly cracked cyclopentadiene (2.40 mL, 0.0364 mol) diluted with diethyl ether
(10 mL) was then added dropwise to the reaction. A white suspension immediately
formed. After stirring for approximately 15 min, 1a (5.19 g, 0.0248 mol) was dissolved

2448
J. O. E. YOUNG ET AL.
into 10 mL of diethyl ether and the solution was added dropwise to the reaction flask,
causing a brick red suspension to form. The suspension was allowed to warm to room
temperature and was stirred for 1 h. The reaction mixture was hydrolyzed with dilute
acetic acid (5%) and extracted three times with methylene chloride. The organic layers
were collected, dried over MgSO4, and filtered, and the volatiles were removed in
vacuo to yield a red-orange semisolid. Recrystallization using methylene chloride
1
and pentane afforded 1a (2.32 g, 46.0%) as a red-orange solid. Mp: 111–121 ꢁC. H
NMR (500 MHz, acetone-d6, ppm): d 6.65 (br s, 1H, CHCHCH), 6.84 (br s, 2H,
CHCHCH), 7.47 (br s, 2H, CHCHBr), 8.08 (br s, 2H, CHCHBr). 13C NMR
(125 MHz, acetone-d6, ppm): d 115.1 (CHCHCH), 122.4 (CHCHCH), 123.1 (ipso
Cp), 124.9, 128.4, 139.5, 153.1 (Ar), 167.6 (C¼O). IR (KBr, cmꢀ1): 1567 (C O),
=
3146 (CH), 3435 (OH). MS (DART-LTQ): m=z 412.99 (Mþ þ H). Analysis calc.
for C15H8O4Br2: C, 43.7; H, 1.9. Found: C, 46.1; H, 2.1.
Synthesis of 1,2-C5H3(COC4H2BrNH)(COC4H2BrN) (2a)
1,2-C5H3(COC4H2OBr)(COHC4H2OBr) (1a, 518 mg, 1.26 mmol) was
dissolved in methanol (200 mL) in a 500-mL, round-bottomed flask. An excess of
hydrazine hydrate (3.00 mL, 3.09 g, 61.8 mmol) was added to this solution. The
mixture was allowed to stir at reflux for 24 h. Water (20 mL) was added to the
reaction, and a purple precipitate formed immediately. The aqueous suspension
was washed with dichloromethane (3 ꢂ 20 mL) and ethyl ether (3 ꢂ 20 mL), and
the organic layers were collected, dried (MgSO4), and filtered. The volatiles were
removed in vacuo and the crude product was triturated with cold hexane to give
1,2-C5H3(COC4H2BrNH)(COC4H2BrN) (2a, 131 mg, 0.322 mmol, 25.6%) as a
1
purple solid. Mp: 100–108 ꢁC. H NMR (500 MHz, acetone-d6, ppm): d 6.79 (d,
3
3
3
2H, J ¼ 3.4 Hz, CHCHCH), 7.21 (d, 1H, J ¼ 3.5 Hz, Ar), 7.41 (t, 1H, J ¼ 3.4 Hz,
CHCHCH), 7.44 (d, 1H, J ¼ 3.5 Hz, Ar), 10.6 (s, 1H, NH). 13C NMR (125 MHz,
3
acetone-d6, ppm): d 108.0 (CHCHCH), 114.1 (CHCHCH), 124.3 (CCN), 133.0,
133.1, 135.3 (Ph), 150.8 (CN). IR (KBr, cmꢀ1): 1619 (CN), 3047 (C–H), 3215
(N–H). MS: m=z 406 (Mþ), 329 (Mþ–Br), 299 (Mþ–BrCHO). HRMS: (Mþ) calcd.
405.8952, obsd 405.8950. Anal. calcd. for C15H8N2O2Br2: C, 44.2; H, 2.0. Found: C,
44.7; H, 2.9.
Synthesis of 1,2-C5H3(CC6H4BrNH)(CC6H4BrN) (2b)
1,2-C5H3(COC6H4Br)(COHC6H4Br) (1b, 421 mg, 0.970 mmol) was dissolved in
methanol (20 mL) in a 25-mL, round-bottom flask. An excess of hydrazine hydrate
(2.00 mL, 2.06 g, 41.2 mmol) was added to the solution. The solution was stirred
24 h. Water (10 mL) was added to the reaction, and an orange precipitate formed
immediately. The aqueous suspension was washed with dichloromethane (3 ꢂ 5 mL)
and the organic layers were collected, dried (MgSO4), and filtered. The volatiles were
removed in vacuo, and the crude product was triturated with cold hexane to give
1,2-C5H3(CC6H4BrNH)(CC6H4BrN) (2b, 326 mg, 0.762 mmol, 78.6%) as an orange
powder. Mp: 182–187 ꢁC. 1H NMR (500 MHz, CDCl3, ppm): d 7.04 (d, 2H,
3
3
3J¼ 3.5 Hz, CHCHCH), 7.54 (t, 1H, J¼ 3.5 Hz, CHCHCH), 7.67 (d, 1H, J¼ 8.6 Hz,
CHCHCBr), 7.79 (d, 1H, J ¼ 8.6 Hz, CHCHCBr). 13C NMR (125 MHz, CDCl3,
3

THALLIUM CP SALTS
2449
ppm): d 109.3 (CHCHCH), 120.3 (CHCHCH), 124.8 (CCHCH), 130.1, 132.4 (Ph),
133.5 (CN). IR (KBr, cmꢀ1): 1591 (CN), 3075 (C–H), 3200 (N–H). MS: m=z 428
(Mþ), 349 (Mþ – Br). HRMS: (Mþ) calcd. 427.9348, obsd. 427.9348. Anal. calcd.
for C19H12N2Br2: C, 53.3; H, 2.83; N, 6.54. Found: C, 53.1; H, 2.88.; N, 6.71.
Synthesis of [Tlf1,2-C5H3(COC4H2BrNH)(COC4H2BrN)g] (3a)
Thallium(I) ethoxide was added to a solution of 1,2-C5H3(COC6H4Br)
(COHC6H4Br) (2a, 266 mg, 0.650 mmol) in THF (30 mL). A red-orange precipitate
formed after 5 min. The solution was stirred for 24 h at 22 ꢁC. The precipitate was
filtered and washed with cold hexane (3 ꢂ 10 mL), providing [Tlf1,2-C5H3(COC4H2
BrNH)(COC4H2BrN)g] (3a, 69.5%, 276 mg, 0.0.450 mmol) as a red-brown solid.
1
3
Mp: 122–142 ꢁC (dec). H NMR (500 MHz, DMSO-d6, ppm): d 6.88 (d, 1H, J ¼
3
3
3.5 Hz, CHCHCBr), 7.07 (t, 1H, J ¼ 4.0 Hz, CHCHCH), 7.21 (d, 1H, J ¼ 4.0 Hz,
CHCHCH), 7.60 (d, 1H, J ¼ 3.5 Hz, CHCHCBr). 13C NMR (125 MHz, DMSO-
3
d6, ppm): d 110.3 (CHCHCH), 113.9 (CHCHCH), 112.1 (CCHCH), 120.9, 125.2,
126.3, 131.3 (Ph), 158.3 (CN). IR (KBr, cmꢀ1): 1600 (CN), 3110 (CH). MS (EI-pos):
m=z 408 (Mþ – Tl). Anal. calcd. for C15H9N2Br2O2Tl: C, 29.4; H, 1.48; N, 4.57.
Found: C, 20.6; H, 1.31.; N, 2.93.
Synthesis of [Tlf1,2-C5H3(CC6H4BrNH)(CC6H4BrN)] (3b)
Thallium(I) ethoxide was added to a solution of 1,2-C5H3(COC6H4Br)
(COHC6H4Br) (2b, 269 mg, 0.628 mmol) in THF (30 mL). An orange precipitate
formed after 5 min. The solution was stirred for 24 h at 22 ꢁC. The precipitate was
filtered and washed with cold hexane (3 ꢂ 10 mL), providing [Tlf1,2-C5H3(CC6H4
BrNH)(CC6H4BrN)] (3b, quantitative yield, 399 mg, 0.627 mmol) as a yellow solid.
1
3
Mp: 178–195 ꢁC (dec). H NMR (500 MHz, DMSO-d6, ppm): d 6.44 (d, 1H, J ¼
3
3
3.4 Hz, CHCHCH), 6.79 (t, 1H, J ¼ 3.4 Hz, CHCHCH), 7.66 (d, 1H, J ¼ 8.6 Hz,
CHCHCBr), 7.99 (d, 1H, J ¼ 8.6 Hz, CHCHCBr). 13C NMR (125 MHz, DMSO-
3
d6, ppm): d 110.0 (CHCHCH), 116.5 (CHCHCH), 127.0 (CCHCH), 131.0, 131.6
(Ph), 155.0 (CN). IR (KBr, cmꢀ1): 1591 (CN), 3100 (CH). MS (EI-pos): m=z 632
(Mþ), 428 (Mþ – Tl. Anal. calcd. for C19H13N2Br2Tl: C, 36.0; H, 2.07; N, 4.42.
Found: C, 29.6; H, 1.74; N, 2.96.
Synthesis of [Tlf1,2-C5H3(CC6H4ClNH)(CC6H4ClN)] (3c)
Thallium(I) ethoxide was added to a solution of 1,2-C5H3(COC6H4ClN)
(COHC6H4ClN) (2a, 490mg, 1.44mmol) in THF (30 mL). An orange precipitate
formed after 5 min. The solution was stirred for 24 h at 22 ꢁC. The precipitate was fil-
tered and washed with cold hexane (3ꢂ 10mL), providing [Tlf1,2-C5H3(CC6H4ClNH)
(CC6H4ClN)] (3a, quanitative yield, 869.1 mg, 1.60 mmol) as a yellow solid. Mp:
160–165 ꢁC (dec) 1H NMR (500MHz, DMSO-d6, ppm): d 6.37 (br s, 1H, CHCHCH),
6.84 (br s, 2H, CHCHCH), 7.50 (d, 1H, 3J ¼ 8.0 Hz, CHCHCBr), 8.08 (d, 1H,
3J ¼ 8.0 Hz, CHCHCBr). 13C NMR (125MHz, DMSO-d6, ppm): d 92.0 (CHCHCH),
98.3 (CHCHCH), 121.5 (CCHCH), 128.5, 130.5, 132.1, 140.4 (Ph), 148.2 (CN). IR

2450
J. O. E. YOUNG ET AL.
(KBr, cmꢀ1): 1516 (CN), 3059 (CH). MS (EI-pos): m=z 339 (Mþ – Tl). Anal. calcd. for
C19H13N2Cl2Tl: C, 41.9; H, 2.41; N, 5.14. Found: C, 33.7; H, 1.98; N, 4.21.
Synthesis of [Tlf1,2-C5H3(CC6H4CH3NH)(CC6H4CH3N)g] (3d)
Thallium(I) ethoxide was added to a solution of 1,2-C5H3(CC6H4CH3NH)
(CC6H4CH3N) (2a, 202 mg, 0.676 mmol) in THF (30 mL). An orange precipitate
formed after 5 min. The solution was stirred for 24 h at 22 ꢁC. The precipitate was
filtered and washed with cold hexane (3 ꢂ 10 mL), providing [Tlf1,2-C5H3(CC6H4
CH3NH)(CC6H4CH3N)] (3a, 89.6%, 304 mg, 0.606 mmol) as a yellow solid. Mp:
1
115–120 ꢁC (dec). H NMR (500 MHz, DMSO-d6, ppm): d 2.36 (s, 1H, CHCHC
3
3
CH3), 6.41 (d, 2H, J ¼ 2.9 Hz, CHCHCH), 6.84 (t, 1H, J ¼ 2.9 Hz, CHCHCH),
3
3
7.26 (d, 2H, J ¼ 7.5 Hz, CHCHCCH3), 7.95 (d, 2H, J ¼ 7.5 Hz, CHCHCCH3).
13C NMR (125 MHz, DMSO-d6, ppm): d 21.5 (CH3), 99.2 (CHCHCH), 121.6
(CHCHCH), 125.3 (CCHCH), 128.9, 129.2 (Ph), 149.3 (CN). IR (KBr, cmꢀ1):
1526 (CN), 3013 (CH). MS (EI-pos): m=z 501.2 (Mþ). Anal. calcd. for C21H19N2Tl:
C, 50.1; H, 3.80; N, 5.56. Found: C, 56.6; H, 3.37; N, 5.09.
SUPPLEMENTARY DATA
CCDC 881666 contain the supplementary crystallographic data for 2b. This
data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
ACKNOWLEDGMENTS
We acknowledge our sources of financial support, including Western Kentucky
University’s Chemistry Department, their Office of Sponsored Programs, their
Research and Creative Activities Program (RCAP) scholarship, and the WKU
Advanced Materials Institute. In addition, other sources of support include Eastern
Kentucky University’s Department of Chemistry and the Center for Renewable and
Alternative Fuel Technologies.
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