Synthesis, structure and reactivity of 4-phosphanylated 1,3-dialkyl-imidazole-2-thiones

Article abstract of DOI:10.1039/c2dt12483a

Selective formation of 4-phosphanylated 1,2-dialkyl imidazole-2-thiones 3a-f has been obtained via a lithiation followed by phosphanylation reaction. The reactivity of 3a-f was examined towards oxidation and complexation reactions. All products were unambiguously characterized by elemental analyses, spectroscopic and spectrometric methods including X-ray analysis (3a, 3b, 4b, 4d, 5b, 6a and 6d).

Full text of DOI:10.1039/c2dt12483a

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PAPER
Synthesis, structure and reactivity of 4-phosphanylated 1,3-dialkyl-imidazole-
2-thiones†
Susanne Sauerbrey,a Paresh Kumar Majhi,a Gregor Schnakenburg,a Anthony J. Arduengo III*b
and Rainer Streubel*a
Received 23rd December 2011, Accepted 13th February 2012
DOI: 10.1039/c2dt12483a
Selective formation of 4-phosphanylated 1,2-dialkyl imidazole-2-thiones 3a–f has been obtained via a
lithiation followed by phosphanylation reaction. The reactivity of 3a–f was examined towards oxidation
and complexation reactions. All products were unambiguously characterized by elemental analyses,
spectroscopic and spectrometric methods including X-ray analysis (3a, 3b, 4b, 4d, 5b, 6a and 6d).
and elemental sulphur in the presence of catalytic amount of
Introduction
potassium tert-butoxide in tetrahydrofuran in good to very good
yields (Scheme 1).22 The obtained yields were increased
Imidazole-2-thiones are a long known class of heterocyclic com-
pounds,1 which are of importance for chemical and pharma-
in comparison to those reported in the literature, where the
ceutical industry. Some of their applications include drugs
treating hyperthyroidism like Methimazol or Carbimazol,2,3 or
catalyst in cross-linking of polymers,4 complexation agents5 and
precursors of halogen-free ionic liquids6 as well as stable N-
heterocyclic carbenes.7 Backbone-substituted imidazole-2-thiones
include ring-anellated compounds,8–10 those with nitrogen-
containing substituents (amino,11 azo,12 imino13), oxygen-
containing substituents (hydroxy,14 methoxy15), and halogen-
substituted compounds.16 However, the access to a large library
of imidazol-2-thione substituted phosphanes has not achieved
considerable attention.
imidazole-2-thiones have been prepared using different
bases19,20,25 or different methodologies.6,26
Commonly used synthetic routes to the phosphorylated hetero-
cycles28,29 in pyridine–triethylamine mixtures proved to be
unsuitable in the case of imidazole-2-thiones. Therefore another
synthetic methodology to the imidazole-2-thione was followed
by reacting 2a–f with n-butyl lithium and then subsequently
with diphenylchlorophosphane to yield the 4-phosphanylated
imidazole-2-thiones 3a–f (Scheme 1).27 The completion of the
reaction was monitored by 31P NMR spectroscopy. After
removal of the formed lithium chloride, the crude product were
purified and isolated via recrystallization from hot toluene or
diethyl ether–n-pentane mixtures as colorless to yellow solids
(3a–f). The final products were unequivocally established by 1H,
13C, and 31P NMR spectroscopy (see Experimental section).
Analysis of the phosphanylated compounds by 31P NMR spec-
troscopy confirms that only a single product is formed, which
resonates in the chemical shift range of −31 ppm to −35 ppm
with a coupling constant (3JP, H ) range of 5 to 9 Hz depending
upon the substituent at the both nitrogen centre of the imidazole-
2-thione. The selective phosphanylation at the 4-position, might
be due to steric reasons in the asymmetric substituted imidazole-
2-thiones 2d and 2f. Only in the case of 2e, a positional isomer,
Results and discussion
In this paper we present the synthesis, structural characterization
and reactivity of a series of 4-phosphanylated imidazole-2-
thiones. Different imidazole-2-thiones, namely 1,3-dimethylimi-
dazole-2-thione (2a),19–23 1,3-diphenylimidazole-2-thione (2b),6
1,3-diisopropylimidazole-2-thione (2c),19 1-isopropyl-3-methyli-
midazole-2-thione (2d),25 1-n-butyl-3-methylimidazole-2-thione
(2e)6 and 1-tert-butyl-3-methylimidazole-2-thione (2f),26 were
used as starting materials. Except for 1,3-diphenylimidazole-2-
thione (2b), which was prepared following a literature protocol,6
all imidazole-2-thiones 2a–f were synthesized via the reaction of
the corresponding imidazolium salts 1a–f19 with sodium hydride
namely
1-n-butyl-3-methyl-5-diphenylphosphino-imidazol-2-
thione 3e′, was observed (ratio 3e : 3e′ 2.3 : 1). In this case, the
steric demand of the n-butyl group was probably not bulky
enough to prevent the lithiation followed by phosphanylation at
C5 position.
X-ray single-crystal structure analysis was performed for the
compounds 3a and 3b. The crystals were obtained from toluene
at low temperature. These two compounds crystallized isostruc-
turally in the monoclinic crystal system, with different space
group P21/c for 3a and P21/n for 3b. The selected bond para-
meters were given in the figure caption of the corresponding
aInstitut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-
Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany.
E-mail: r.streubel@uni-bonn.de; Fax: +49-228-73-9616
bDepartment of Chemistry, The University of Alabama, Tuscaloosa,
AL 35487, USA. E-mail: aj@ajarduengo.net
†Electronic supplementary information (ESI) available: CCDC 859623
(3a), 859624 (3b), 859625 (4b), 859626 (4d), 859627 (5b), 859628
(6d) and 859812 (6a). For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c2dt12483a
5368 | Dalton Trans., 2012, 41, 5368–5376
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Scheme 1 Synthesis of P-functional imidazole-2-thiones.
further as bond lengths and angles are in the common range for
diphenylphosphino substituted heterocycles.31
To study the reactivity of 3a,b,d, various oxidation and com-
plexation reactions were performed as described in Scheme 2.
The reactions of compound 3a,b,d with H2O2–urea adduct,
elemental sulphur and selenium were quantitative according to
31P NMR spectroscopy. However elemental tellurium did not
react with 3a,b,d under the same condition as of 5a,b,d. All
phosphane oxides 4a,b,d were recrystallized from hot toluene
and obtained as white solid. The thio (5a,b,d) and seleno (6a,b,
d) phosphorylated imidazole-2-thione were crystallized out of
the reaction mixtures and thus could easily be obtained in pure
form. The analytical data of phosphane oxides, sulfides and sele-
nides are given in the Experimental section. As expected for PV
derivatives the 31P NMR signal of 4a,b,d–6a,b,d was shifted to
lower field compared to phosphane 3a,b,d, whereby the greatest
shift was observed for the phosphane sulfide 5a,b,d. The same
tendencies were observed before in the series of imidazole phos-
phane chalcogens.30
Fig. 1 Molecular structure of compound 3a. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.360(2), C(1)–N(2) 1.363(2), C(2)–C(3) 1.349(2), C(4)–N(1)
1.452(2), C(1)–S(1) 1.6821(18), P(1)–C(3) 1.8185(18), P(1)–C(6)
1.8368(18), P(1)–C(12) 1.8287(19); C(3)–P(1)–C(6) 102.23(8), C(3)–P
(1)–C(12) 98.22(8), N(1)–C(3)–P(1) 121.81(13), C(6)–P(1)–C(12)
103.40(8).
IR spectra of phosphorylated derivatives are summarized in
the Experimental section. A strong absorption band in the region
1305–1230 cm−1 in 4a,b,d has been ascribed to PvO stretching
vibrations. Another absorption bands in the region 660–
640 cm−1 in derivatives 5a,b,d were assigned for PvS
vibrations.
X-ray single-crystal structure analysis was performed for com-
pounds 4b, 4d, 5b, 6a and 6d. The selected bond parameters are
given in the figure caption of the corresponding compounds
(Fig. 3–7, respectively). For crystallographic data see Tables S1
and S2 (ESI†). Despite the structure, these are the first report of
a diphenyl(thio, seleno)phosphoryl substituted imidazole-2-
thione derivatives, structural parameters shall not be discussed
further as bond lengths and angles are in the common range for
PV chalcogenide derivatives.32–34
Fig. 2 Molecular structure of compound 3b. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.373(2), C(1)–N(2) 1.3773(19), C(2)–C(3) 1.352(2), C(4)–N
(1) 1.4419(19), C(1)–S(1) 1.6683(16), P(1)–C(3) 1.8190(5), P(1)–C(6)
1.8318(16), P(1)–C(22) 1.8337(17); C(3)–P(1)–C(16) 102.53(7), C(3)–P
(1)–C(22) 99.42(7), N(1)–C(3)–P(1) 122.42(11), C(16)–P(1)–C(22)
102.26(7).
As an extension of this work, we also examined the reactivity
of phosphanylated 1,2-dialkylimidazole-2-thiones towards
borane. For this 3a,b were reacted with the BH3–THF complex
at room temperature. The completion of the reaction was moni-
tored by 31P{1H}-NMR spectroscopy. After the removal of
solvent, colorless solid was obtained; this was then washed with
n-pentane and then dried. The product 7a,b were characterized
compounds. For crystallographic data see Table S1 (ESI†). The
structure and numbering scheme for 3a and 3b are shown in
Fig. 1 and 2 respectively. Despite that, the structure of 3a and 3b
are the first report of a diphenylphosphino substituted imidazole-
2-thione derivative, structural parameters shall not be discussed
1
by 31P, 11B, H and 13C-NMR spectroscopy. The 31P{1H}-NMR
spectra of 7a,b showed a downfield shift around 9 ppm as of
corresponding phosphanes. The 11B{1H}-NMR spectra of 7a,b
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Scheme 2 Reactions of P-functional imidazole-2-thiones.
Fig. 4 Molecular structure of compound 4d. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.363(2), C(1)–N(2) 1.362(2), C(2)–C(3) 1.348(2), C(4)–N(1)
1.477(2), C(1)–S 1.6831(19), P–O 1.4858(13), P–C(3) 1.7857(18), P–C
(8) 1.798(2), P–C(14) 1.7966(18); C(3)–P–C(8) 102.82(8), C(3)–P–C
(14) 106.96(8), N(2)–C(3)–P 126.48(13), C(8)–P–C(14) 106.21(8), C
(3)–P–O 115.02(8), C(8)–P–O 113.14(8), C(14)–P–O 111.90(8).
Fig. 3 Molecular crystal structure of compound 4b. Hydrogen atoms
have been omitted for clarity. Selected bond distances (Å) and angles
(°): C(1)–N(1) 1.370(3), C(1)–N(2) 1.375(3), C(2)–C(3) 1.349(3), C(4)–
N(1) 1.446(3), C(1)–S1 1.670(3), P–O 1.4875(17), P–C(2) 1.785(3), P–
C(16) 1.796(3), P–C(22) 1.799(3); C(2)–P–C(16) 102.23(8), C(2)–P–C
(22) 102.83(12), N(1)–C(2)–P 124.96(18), C(16)–P–C(22) 108.45(12),
C(2)–P–O 113.79(11), C(16)–P–O 112.32(12), C(22)–P–O 112.70(22).
Conclusions
resonates in the chemical shift range of −40 ppm to −42 ppm.
Electron-impact mass spectrometry was a useful tool in proving
the structure of phosphane boranes 7a,b. In these cases, intense
loss of BH3 could be seen. To the best of our knowledge, no
examples of phosphane borane complexes of phosphorus substi-
tuted imidazole-2-thione derivatives are known so far.
A synthetic methodology has been developed to synthesize a
series of phosphanyl substituted 1,3-dialkyl imidazole-2-thione.
The oxidation of phosphanyl substituted 1,3-dialkyl imidazole-
2-thione occurred selectively to yield the corresponding PV–E
products (E = O, S, Se) 4a,b,d–6a,b,d, firmly established by
5370 | Dalton Trans., 2012, 41, 5368–5376
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Fig. 5 Molecular structure of compound 5b. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.368(3), C(1)–N(2) 1.379(3), C(2)–C(3) 1.352(3), C(4)–N(1)
1.444(3), C(1)–S(1) 1.666(2), P(1)–S(2) 1.9526(8), P(1)–C(3) 1.801(2),
P(1)–C(16) 1.822(2), P(1)–C(22) 1.820(2); C(3)–P(1)–C(16) 106.42
(10), C(3)–P(1)–C(22) 103.22(10), N(1)–C(3)–P(1) 124.78(16), C(16)–
P(1)–C(22) 107.50(10), C(3)–P(1)–S(2) 114.17(8), C(16)–P(1)–S(2)
112.32(8), C(22)–P(1)–S(2) 112.54(8).
Fig. 7 Molecular structure of compound 6d. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.372(3), C(1)–N(2) 1.364(3), C(2)–C(3) 1.355(3), C(4)–N(1)
1.485(3), C(1)–S(1) 1.680(2), P(1)–Se(1) 2.1083(6), P(1)–C(2) 1.791
(2), P(1)–C(8) 1.815(2), P(1)–C(14) 1.812(3); C(2)–P(1)–C(8) 104.04
(10), C(2)–P(1)–C(14) 103.90(11), N(2)–C(2)–P(1) 124.04(18), C(8)–P
(1)–C(14) 107.05(11), C(2)–P(1)–Se(1) 113.56(8), C(8)–P(1)–Se(1)
113.42(8), C(14)–P(1)–Se(1) 113.92(8).
Diphenylchlorophosphane was distilled prior to use and stored
under an argon atmosphere. All other chemicals were used as
received. 1,3-Dimethylimidazolium iodide (1a),19 1,3-diisopro-
pylimidazolium chloride (1c),20 1-isopropyl-3-methylimidazo-
lium bromide (1d),16 1-n-butyl-3-methylimidazolium iodide
(1e),17 1-tert-butyl-3-methylimidazolium iodide (1f)18 and 1,3-
diphenylimidazole-2-thione (2b)6 were synthesized following lit-
erature protocols. All NMR spectra were recorded on a Bruker
1
AX-300 spectrometer, with a frequency of 300.1 MHz for H.
1
The H and 13C spectra were referenced to the residual protons
Fig. 6 Molecular structure of compound 6a. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å) and angles (°): C
(1)–N(1) 1.360(3), C(1)–N(2) 1.357(5), C(2)–C(3) 1.356(4), C(4)–N(1)
1.461(4), C(1)–S(1) 1.679(3), P(1)–Se(1) 2.1008(9), P(1)–C(3) 1.782
(3), P(1)–C(6) 1.811(3), P(1)–C(12) 1.811(3); C(3)–P(1)–C(6) 105.17
(14), C(3)–P(1)–C(12) 101.78(14), N(2)–C(3)–P(1) 125.3(2), C(6)–P
(1)–C(12) 107.83(13), C(3)–P(1)–Se(1) 113.91(10), C(6)–P(1)–Se(1)
113.16(10), C(12)–P(1)–Se(1) 114.00(10).
and the 13C signals of the deuterated solvents, the 11B to
BF3*OEt2 and 31P to 85% H3PO4 as external standard, respect-
ively. Melting points were determined in one-side melted off
capillaries using a Büchi Type S or a Carl Roth Type MPM-2
apparatus, they are uncorrected. Elemental analyses were carried
out on a Vario EL gas chromatograph. Mass spectrometric data
were collected on a Kratos MS 50 spectrometer using EI, 70 eV.
The infrared spectra were recorded on a Nicolet 80 FT-IR spec-
trometer using KBr plates or Nujol. The UV/Vis spectra were
recorded in solution on a Shimadzu UV-1950 PC spectrometer.
The X-ray analyses were performed on a Nonius Kappa CCD or
a Bruker X8-KappaApex TT type diffractometer at 123(2) or
100(2) K, respectively. The structures were solved by direct
methods refined by full-matrix least-squares technique in aniso-
tropic approximation for non-hydrogen atoms using SHELXS97
and SHELXL9735 program packages. Hydrogen atoms were
located from Fourier synthesis and refined isotropically.
their X-ray crystal structures; derivatives 4b, 4d, 5b, 6a and 6d
represent the first examples within the series of P-substituted
imidazole-2-thione derivatives. New examples of phosphane
borane complexes of phosphorus substituted imidazole-2-thione
derivatives were reported. This synthetic route is amenable to the
preparation of multigram quantities of product in a linear
fashion. Current studies aim at the synthesis of new backbone
functionalized N-heterocyclic carbenes (NHCs) starting from
phosphanyl and phosphoryl substituted imidazol-2-thiones
described herein.
General protocol for the synthesis of imidazole-2-thiones 2a–f
Experimental section
The imidazolium salts (0.1 mol) were suspended in 125 mL of
tetrahydrofuran in a Schlenk flask. Sublimed elemental sulphur
(3.21 g, 0.1 mol) was added and the mixture was stirred for 2 h
at ambient temperature. Upon addition of potassium tert-butoxide
(112 mg, 0.001 mol) the reaction mixture turned reddish brown.
The flask was cooled in a water bath. Sodium hydride (60–80%
in oil, 0.1 mol) was added in small portions. After each portion
it was waited for the end of gas evolution before the next portion
General
The synthesis of the imidazole-2-thiones and the lithiation reac-
tions were performed under an argon atmosphere, using common
Schlenk techniques and dry solvents. Tetrahydrofuran was
dried over sodium wire–benzophenone, dichloromethane over
calcium hydride and further purified by subsequent distillation.
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of sodium hydride was added. During the reaction, the color
changed from reddish brown to light orange. After complete
addition the reaction mixture was stirred overnight. The whole
work-up should be done under a well-ventilated fume hood, due
to the formation of smelly by-products. The imidazole-2-thiones
themselves are odourless. It was filtrated from the precipitated
sodium salts using a g3-frit equipped with a celite pad. The
light-yellow colored filtrate was collected and concentrated
in vacuo (8 × 10−3 mbar). The obtained residue was washed
multiple times with n-pentane to remove traces of the oil and
then recrystallized from hot water. The obtained crystal needles
were collected, washed with cold water and dried. 1-n-Butyl-3-
methylimidazole-2-thione (2e) was purified using column
chromatography with silica gel as stationary phase and petrol
ether–diethyl ether mixtures as eluents. The yellow product
fraction was collected and concentrated in vacuo (8 × 10−3
mbar) to give a very viscous yellow liquid. The analytical data
of 1,3-dimethylimidazole-2-thione (2a),19–23 1,3-diphenylimida-
zole-2-thione (2b),6,24 1,3-diisopropylimidazole-2-thione (2c),19
1-isopropyl-3-methylimidazole-2-thione (2d),25 1-n-butyl-3-
methylimidazole-2-thione (2e)6 and 1-tert-butyl-3-methylimida-
zole-2-thione (2f)26 were consistent with those reported in the
literature.
1389 (s, ν(CvN)), 1190 (s, ν(CvS)), 755, 743 and 700 (s,
δ(C6H5)). UV/Vis (Et2O): λmax: 209 nm. EA: calc. C 65.37, H
5.49, N 8.97, S 10.27, found: C 65.32, H 5.51, N 8.95, S 10.32.
1,3-Diphenyl-4-diphenylphosphino-imidazol-2-thione (3b)
1
Yield: (3.58 g, 82%), light yellow solid, mp. 213 °C. H NMR
(300 MHz, CDCl3): δ = 6.32 (s br, 1H, C5–H), 7.12 (dd, 3JH,H
=
4
7.7 Hz, JH,H = 1.5 Hz, 2H, N–C6H5–H), 7.22–7.33 (m, 12H,
3
C6H5–H), 7.39 (t br, JH,H = 7.7 Hz, 4H, P–C6H5–H), 7.53 (dd,
3JH,H = 7.8 Hz, 4JH,H = 1.5 Hz, 4H, P–C6H5–H). 13C{1H} NMR
(75.0 MHz, CDCl3): δ = 124.5 (s br, C5), 128.5 (s, N–C6H5),
128.8 (d, JP, C = 7.2 Hz, P–C6H5), 128.9 (d, JP, C = 2.4 Hz, P–
1
C6H5), 129.1 (s, N–C6H5), 129.6 (d, JP, C = 12.8 Hz, C4), 129.8
1
(s, N–C6H5), 133.1 (d, JP, C = 8.0 Hz, P–ipso-C6H5), 133.7
(d, JP, C = 20.8 Hz, P–C6H5), 136.3 (s, N–ipso-C6H5), 138.1
(s, N–ipso-C6H5), 167.3 (s, CvS). 31P NMR (121.5 MHz,
3
CDCl3): δ = −31.7 (quint br, JP, H = 9.2 Hz). MS (EI, 70 eV):
+
+
+
˙
˙
˙
m/z = 436 (M , 100%), 403 (M − S, 24%), 359 (M − C6H5,
+
28%), 328 (M+−C6H5–S, 4%), 183 (P(C6H5)2 , 10%), 77
˙
+
(C6H5 , 14%). Exact mass: found: 436.1165, calc.: 436.1163. IR
(KBr, cm−1): ν˜ 3064 and 3011 (w, ν(C–H)), 1593 (m, ν(CvC)),
1496 (vs, ν(P–CvC)), 1434 (s, ν(P–C6H5)), 1380 (s, ν (CvN)),
1152 (m, ν (CvS)), 771, 764 and 699 (s, δ(C6H5)). UV/Vis
(Et2O): λmax: 209 nm. EA: calc. C 74.29, H 4.85, N 6.42, found:
C 73.97, H 4.83, N 6.32.
Typical lithiation and phosphanylation protocol for the synthesis
of 3a–f
In a Schlenk flask, the imidazole-2-thiones 2a–f (10 mmol) were
dissolved in 100 mL of tetrahydrofuran and cooled to −80 °C.
n-Butyllithium (1.6 M in n-hexane, 17 mL, 11 mmol) was added
and the reaction mixture was slowly warmed up to −40 °C. It
was stirred for 2 h at this temperature. The reaction mixture was
cooled again to −80 °C. The diorganochlorophosphane (Ph2PCl)
(11 mmol) was added and the reaction mixture was stirred over-
night and warmed up to ambient temperature. It was concen-
trated in vacuo (8 × 10−3 mbar) and the residue was taken up
in dichloromethane and filtered to remove the formed lithium
chloride. The filtrate was collected and the solvent was removed
in vacuo (8 × 10−3 mbar). The crude product was purified via
recrystallization from hot toluene or a n-pentane–diethyl ether
mixture (3a–f, 7a–d). Colorless to light yellow crystals were
obtained.
1,3-Diisopropyl-4-diphenylphosphino-imidazole-2-thione (3c)
1
Yield: (53 mg, 1.43%), colorless solid, mp. 186 °C. H NMR
3
(300 MHz, CDCl3): δ = 1.29 (d, JH,H = 6.8 Hz, 6H, C3H7–
3
CH3), 5.09 (hept, JH,H = 6.8 Hz, 1H, C3H7–CH), 6.03 (s, 1H,
C5–H), 7.02–7.75 (m, 10H, C6H5–H). 13C{1H} NMR
(75.0 MHz, CDCl3): δ = 20.9 (s, C3H7–CH3), 47.4 (s, C3H7–
2
CH), 127.2 (d, JP, C = 7.1 Hz, C5), 127.8 (d, JP, C = 7.8 Hz,
1
C6H5), 128.5 (s, C6H5), 129.7 (d, JP, C = 12.8 Hz, C4), 131.6
1
(d, JP, C = 2.7 Hz, ipso-C6H5), 132.3 (d, JP, C = 20.7 Hz, C6H5),
164.4 (s br, CvS). 31P NMR (121.5 MHz, CDCl3): δ = −31.2
3
+
˙
(quint, JP, H = 5.1 Hz). MS (EI, 70 eV): m/z = 368 (M , 100%),
+
+
+
˙
˙
˙
335 (M − S, 30%), 326 (M − C3H6, 68%), 291 (M − C6H5,
+
+
˙
23%), 284 (M − 2C3H6, 34%), 183 (P(C6H5)2 , 26%), 77
+
+
(C6H5 , 8%), 43 (C3H6 , 4%). Exact mass: found: 368.1481,
calc.: 368.1476. IR (KBr, cm−1): ν˜ 3143 and 3079 (w, ν(C–H)),
1433 (s, ν(P–C6H5)), 1410 (s, ν(CvN)), 1171 (m, ν(CvS)),
752 and 691 (s, δ(C6H5)). UV/Vis (Et2O): λmax: 268 nm.
1,3-Dimethyl-4-diphenylphosphino-imidazole-2-thione (3a)
Yield: (2.47 g, 79%), colorless solid, mp. 187 °C. 1H NMR
(300 MHz, CDCl3): δ = 3.43 (s br, 3H, N3–CH3), 3.48 (s br, 3H,
N1–CH3), 6.02 (s br, 1H, C5–H), 7.24–7.35 (m, 10H, C6H5–H).
1-Isopropyl-3-methyl-4-diphenylphosphino-imidazole-2-
thione (3d)
3
13C{1H} NMR (75.0 MHz, CDCl3): δ = 33.4 (d, JP, C = 9.5 Hz,
N3–CH3), 35.9 (s, N1–CH3), 124.0 (d, 2JP, C = 4.8 Hz, C5), 126.1
Yield: (2.89 g, 85%), colorless solid, mp. 132 °C. 1H NMR
(d, 1JP, C = 10.7 Hz, C4), 128.6 (d, JP, C = 7.3 Hz, C6H5), 129.4 (s,
(300 MHz, CDCl3): δ = 1.28 (d, JH,H = 6.8 Hz, 6H, C3H7–
3
1
3
C6H5), 132.6 (d, JP, C = 7.2 Hz, ipso-C6H5), 133.0 (d, JP, C
=
CH3), 3.50 (s, 3H, N3–CH3), 5.09 (hept, JH,H = 6.8 Hz, 1H,
20.3 Hz, C6H5), 165.1 (s, CvS). 31P NMR (121.5 MHz,
C3H7–CH), 6.19 (s, 1H, C5–H), 7.30–7.42 (m, 10H, C6H5–H).
13C{1H} NMR (75.0 MHz, CDCl3): δ = 21.8 (s, C3H7–CH3),
3
CDCl3): δ = −31.5 (quint, JP, H = 6.4 Hz). MS (EI, 70 eV): m/z
+
+
+
3
= 312 (M , 100%), 235 (M − C6H5, 5%), 221 (M − C6H5–
33.4 (d, JP, H = 9.3 Hz, N3–CH3), 49.1 (s, C3H7–CH), 119.8
˙
˙
˙
+
2
1
CH3, 44%), 183 (P(C6H5)2 , 8%). Exact mass: found: 312.0846,
(d, JP, C = 7.3 Hz, C5), 126.7 (d, JP, C = 12.0 Hz, C4), 129.0
calc.: 312.0850. IR (KBr, cm−1): ν˜ 3155 and 3042 (w, ν(C–H)),
1570 (m, ν(CvC)), 1476 (m, ν(P–CvC)), 1435 (s, ν(P–C6H5)),
(d, JP, C = 7.4 Hz, C6H5), 129.7 (s, C6H5), 133.1 (d, JP, C = 7.3
1
Hz, ipso-C6H5), 133.2 (d, JP, C = 20.1 Hz, C6H5), 164.4 (s br,
5372 | Dalton Trans., 2012, 41, 5368–5376
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3
3
CvS). 31P NMR (121.5 MHz, CDCl3): δ = −31.6 (quint, JP, H
32.4 (d, JP, H = 9.1 Hz, N3–CH3), 58.4 (s, C4H9–C), 120.5
= 8.1 Hz). MS (EI, 70 eV): m/z = 340 (M , 100%), 298 (M −
(d, JP, C = 8.4 Hz, C5), 123.9 (d, JP, C = 11.6 Hz, C4), 127.9
(d, JP, C = 7.8 Hz, C6H5), 128.6 (s, C6H5), 132.2 (d, JP, C = 7.1
.+
+
2
1
˙
+
+
1
˙
˙
C3H6, 20%), 249 (M − C6H5–CH3, 9%), 221 (M − C3H6–
+
+
˙
˙
C6H5, 6%), 215 (M − C6H5–CH3–S, 24%), 207 (M − C3H6–
Hz, ipso-C6H5), 132.2 (d, JP, C = 20.0 Hz, C6H5), 163.1 (s br,
+
+
C6H5–CH3, 41%), 183 (P(C6H5)2 , 20%), 44 (C3H7 , 16%).
Exact mass: found: 340.1160, calc.: 340.1163. IR (KBr, cm−1):
ν˜ 3143, 3051 and 2974 (w, ν(C–H)), 1584 (w, ν(CvC)), 1436
(s, ν(P–C6H5)), 1404 (s, ν(CvN)), 1179 (vs, ν(CvS)), 751, 745
and 698 (s, δ(C6H5)). UV/Vis (Et2O): λmax: 208 nm. EA: calc. C
67.04, H 6.22, N 8.23, found: C 67.60, H 5.91, N 6.59.
CvS). 31P NMR (121.5 MHz, CDCl3): δ = −30.3 (quint br,
3
+
˙
JP, H = 8.9 Hz). MS (EI, 70 eV): m/z = 354 (M , 48%), 298
+
+
˙
˙
(M − C4H8, 100%), 207 (M − C4H9–C6H5–CH3, 66%), 183
+
+
˙
(P(C6H5)2 , 16%), 170 (M − 2C6H5–P, 65%). Exact mass:
found: 354.1323, calc.: 354.1320. IR (KBr, cm−1): ν˜ 3178,
3066, 2984 and 2966 (w, ν(C–H)), 1549 (w, ν(CvC)), 1475
(m, ν(P–CvC)), 1434 (s, ν(P–C6H5)), 1397 (s, ν(CvN)), 1362
(vs, ν(C–C)), 1173 (vs, ν(CvS)), 756, 741 and 698
(s, δ(C6H5)). UV/Vis (Et2O): λmax: 209 nm. EA: calc. C 67.77,
H 6.54, N 7.90, found: C 67.57, H 6.39, N 7.97.
1-n-Butyl-3-methyl-4-diphenylphosphino-imidazole-2-thione (3e)
Yield: (2.98 g, 84%), colorless solid, mp. 45 °C. 1H NMR
(300 MHz, CDCl3): δ = 0.82 (t, JH,H = 7.4 Hz, 3H, C4H9–
3
3
3
CH3), 1.21 (q, JH,H = 7.6 Hz, 2H, C4H9–CH2), 1.60 (q, JH,H
=
Typical procedure for the generation of phosphane oxides
7.7 Hz, 2H, C4H9–CH2), 3.50 (s, 3H, N3–CH3), 3.92 (m, 2H,
C4H9–CH2), 6.03 (s, 1H, C5–H), 7.22–7.30 (m, 10H, C6H5–H).
The phosphanes 3a,b,d (3 mmol), 10 mL of chloroform and
H2O2–urea adduct (3 mmol) was stirred for 24 h. The reaction
mixture was then filtered off to remove unreacted urea. Then the
solvent was removed in vacuo (8 × 10−3 mbar). The product was
recrystallized from hot toluene followed by washing with
n-pentane and then dried in vacuo (8 × 10−3 mbar) to form
white solid.
13C{1H} NMR (75.0 MHz, CDCl3): δ = 13.3 (s, C4H9–CH3),
3
19.4 (s, C4H9–CH2), 30.5 (s, C4H9–CH2), 33.4 (d, JP, H
=
9.5 Hz, N3–CH3), 47.4 (s, C4H9–CH2), 123.1 (d, 2JP, C = 6.0 Hz,
C5), 126.0 (d, JP, C = 11.3 Hz, C4), 128.6 (d, JP, C = 7.2 Hz,
1
1
C6H5), 129.4 (s, C6H5), 132.7 (d, JP, C = 7.2 Hz, ipso-C6H5),
132.9 (d, JP, C = 20.3 Hz, C6H5), 164.4 (s br, CvS). 31P NMR
3
(121.5 MHz, CDCl3): δ = −31.6 (quint br, JP, H = 6.4 Hz). MS
+
+
+
˙
˙
˙
(EI, 70 eV): m/z = 354 (M , 39%), 321 (M − S, 22%), 298 (M
+
+
1,3-Dimethyl-4-diphenylphosphoryl-imidazole-2-thione (4a)
˙
− C4H8, 8%), 203 (M − 2C6H5, 100%), 183 (P(C6H5)2 , 14%),
+
+
˙
˙
1
170 (M − 2C6H5–P, 65%), 137 (M − 2C6H5–P–S, 36%), 114
Yield: (309 mg, 94%), colorless solid, mp. 156 °C. H NMR
+
+
˙
˙
(300 MHz, CDCl3): δ = 3.50 (s, 3H, N3–CH3), 3.52 (s, 3H, N1–
(M − 2C6H5 − P − C4H8, 36%), 84 (M − 2C6H5 − P − C4H8
+
CH3), 6.34 (d, JP, H = 2.8 Hz, 1H, C5–H), 7.25–7.58 (m, 6H,
3
− S, 17%), 57 (C4H9 , 9%). Exact mass: found: 354.1320, calc.:
354.1320. IR (Nujol, cm−1): ν˜ 3158 and 3050 (w, ν(C–H)), 1552
(m, ν(CvC)), 1439 (vs, ν(P–C6H5)), 1408 (s, ν(CvN)), 1179
(m, ν(CvS)), 751 and 695 (s, δ(C6H5)). UV/Vis (CH2Cl2):
λmax: 271 nm. EA: calc. C 67.77, H 6.54, N 7.90, found: C
67.76, H 6.30, N 7.29.
3
3
4
C6H5–H), 7.64 (ddd, JP, H = 12.8 Hz, JH,H = 7.0 Hz, JH,H
=
1.3 Hz, ortho-C6H5–H). 13C{1H} NMR (75.0 MHz, CDCl3): δ =
34.5 (s, N3–CH3), 35.5 (s, N1–CH3), 122.4 (d, JP, C = 124.2 Hz,
1
C4), 127.7 (d, JP, C = 19.2 Hz, C5), 129.0 (d, JP, C = 12.8 Hz,
2
1
C6H5), 130.0 (d, JP, C = 112.9 Hz, ipso-C6H5), 131.8 (d, JP, C
=
10.4 Hz, C6H5), 133.0 (d, JP, C = 3.2 Hz, C6H5), 167.6 (d, 3+4JP, C
= 4.8 Hz, CvS). 31P NMR (121.5 MHz, CDCl3): δ = 15.8
1-n-Butyl-3-methyl-5-diphenylphosphino-imidazole-2-
thione (3e′)
3
+
˙
(quint br, JP, H = 12.8 Hz). MS (EI, 70 eV): m/z = 328 (M ,
+
+
+
˙
˙
˙
8%), 312 (M − O, 100%), 279 (M − O − S, 3%), 235 (M −
1
+
˙
Colorless dense liquid. H NMR (300 MHz, CDCl3): δ = 0.72
O − C6H5, 6%), 221 (M − O − C6H5 − CH3, 49%), 183
(t, JH,H = 7.4 Hz, 3H, C4H9–CH3), 3.43 (s, 3H, N3–CH3), 6.02
(P(C6H5)2 , 5%). HR-ESI-MS: found: 351.0692, calc.:
3
+
(s, 1H, C5–H). The other signals were masked by the major
isomer 3e. 13C{1H} NMR (75.0 MHz, CDCl3): δ = 13.3
351.0691, as C17H17N2OPSNa+. IR (KBr, cm−1): ν˜ 3129 and
3075 (w, ν(C–H)), 1589 (w, ν(CvC)), 1479 (s, ν(P–CvC)),
1439 (s, ν(P–C6H5)), 1398 (s, ν(CvN)), 1304 (m, ν(PvO)),
1189 (vs, ν(CvS)), 751, 723 and 695 (s, δ(C6H5)). UV/Vis
(n-pentane): λmax: 272 nm. EA: calc. C 62.18, H 5.22, N 8.53, S
9.76, found: C 62.37, H 5.27, N 8.56, S 9.87.
4
(s, C4H9–CH3), 19.5 (s, C4H9–CH2), 30.1 (d, JP, C = 3.0 Hz,
C4H9–CH2), 34.7 (s, N3–CH3), 46.5 (d, JP, C = 8.4 Hz, C4H9–
3
CH2), 124.3 (d, JP, C = 7.2 Hz, C4), 125.9 (d, JP, C = 10.7 Hz,
2
1
C5), 128.5 (d, JP, C = 7.8 Hz, C6H5), 129.3 (s, C6H5), 133.1
1
(d, JP, C = 20.9 Hz, C6H5), 134.8 (d, JP, C = 7.2 Hz, ipso-C6H5),
164.4 (s br, CvS). 31P NMR (121.5 MHz, CDCl3): δ = −35.3
1,3-Diphenyl-4-diphenylphosphoryl-imidazole-2-thione (4b)
(s br).
1
Yield: (421 mg, 93%), light yellow solid, mp. 266 °C. H NMR
(300 MHz, CDCl3): δ = 6.84 (d, JP, H = 3.8 Hz, 1H, C5–H),
3
1-tert-Butyl-3-methyl-4-diphenylphosphino-imidazole-2-thione
(3f)
7.07–7.73 (m, 20H, C6H5–H). 13C{1H} NMR (75.0 MHz,
1
CDCl3): δ = 121.1 (d, JP, C = 119.6 Hz, C4), 124.9 (s, N–C6H5),
1
2
Yield: (2.09 g, 59%), light yellow solid, mp. 163 °C. H NMR
125.2 (s, N–C6H5), 125.3 (d, JP, C = 3.3 Hz, C5), 125.4 (s, N–
1
(300 MHz, CDCl3): δ = 1.65 (s br, 9H, C4H9), 3.39 (s br, 3H,
N3–CH3), 6.21 (s, 1H, C5–H), 7.18–7.32 (m, 10H, C6H5–H).
13C{1H} NMR (75.0 MHz, CDCl3): δ = 27.0 (s, C4H9–CH3),
C6H5), 125.8 (d, JP, C = 20.0 Hz, P–C6H5), 126.9 (d, JP, C
=
112.5 Hz, P–ipso-C6H5), 128.2 (d, JP, C = 9.7 Hz, P–C6H5),
129.1 (d, JP, C = 2.6 Hz, P–C6H5), 133.1 (s, N–C6H5), 134.3
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3+4
(s, N–C6H5), 165.2 (d,
J
P, C
= 3.9 Hz, CvS). 31P NMR
(121.5 MHz, CDCl3): δ = 27.2 (qqd, 3JP, H = 14.0 Hz, 3JP, H = 3.8
3
3
+
˙
(121.5 MHz, CDCl3): δ = 9.0 (quint, JP, H = 12.7 Hz, 3.8 Hz).
MS (EI, 70 eV): m/z = 452 (M , 100%), 375 (M − C6H5,
10%), 183 (P(C6H5)2 , 3%). HR-ESI-MS: found: 475.1008,
Hz, JP, H = 2.5 Hz). MS (EI, 70 eV): m/z = 344 (M , 10%), 312
+
+
+
+
+
˙
˙
˙
˙
˙
(M − S, 2%), 279 (M − S − CH3, 3%), 256 (M − 88,
+
+ +
˙
˙
100%), 224 (M − 88 − S, 8%), 192 (M − 88 − 2S, 38%),
calc.: 475.1004, as C27H21N2OPSNa+. IR (KBr, cm−1): ν˜ 3061
(w, ν(C–H)), 1594 (w, ν(CvC)), 1498 (s, ν(P–CvC)), 1437 (s,
ν(P–C6H5)), 1386 (s, ν(CvN)), 1234 (m, ν(PvO)), 1196 (vs,
ν(CvS)), 760, 726 and 693 (s, δ(C6H5)). UV/Vis (n-pentane):
λmax: 272 nm. EA: calc. C 71.66, H 4.68, N 6.19, found: C
69.64, H 4.76, N 5.72.
127 (C5H7N2S+, 42%). HR-ESI-MS: found: 345.0645,
+
calc.: 344.0571, as C17H18N2PS2 . IR (KBr, cm−1): ν˜ 3147
(w, ν(C–H)), 1438 (s, ν(P–C6H5)), 1394 (s, ν(CvN)), 1189 (vs,
ν(CvS)), 717 and 696 (s, δ(C6H5)), 648 (s, ν(PvS)). UV/Vis
(Et2O): λmax: 209 nm. EA: calc. C 59.28, H 4.97, N 8.13, S
18.62, found: C 58.53, H 5.00, N 8.06, S 18.23.
1-Isopropyl-3-methyl-4-diphenylphosphoryl-imidazole-2-thione
(4d)
1,3-Diphenyl-4-diphenylthiophosphoryl-imidazole-2-thione (5b)
1
Yield: (1.307 g, 93%), light yellow solid, mp. 234 °C. H NMR
1
3
(300 MHz, CDCl3): δ = 6.74 (d, JP, H = 3.3 Hz, 1H, C5–H),
Yield: (342 mg, 96%), colorless solid, mp. 157 °C. H NMR
3
3
(300 MHz, CDCl3): δ = 1.21 (d, JH,H = 6.8 Hz, 6H, C3H7–
6.96–7.51 (m, 16H, C6H5–H), 7.69–7.74 (dd, JP, H = 13.7 Hz,
3
CH3), 3.51 (s, 3H, N3–CH3), 4.99 (hept, JH,H = 6.8 Hz, 1H,
3JH,H = 7.6 Hz, 4H, ortho-C6H5–H). 13C{1H} NMR (75.0 MHz,
CDCl3): δ = 124.1 (d, 1JP, C = 102.5 Hz, C4), 124.9 (s, N–C6H5),
3
C3H7–CH), 6.38 (d, JP, H = 2.8 Hz, 1H, C5–H), 7.44–7.56
3
3
2
125.2 (s, N–C6H5), 128.0 (d, JP, C = 17.6 Hz, C5), 128.5 (s, N–
(m, 6H, C6H5–H), 7.64 (ddd, JP, H = 12.8 Hz, JH,H = 7.1 Hz,
4JH,H = 1.3 Hz, 4H, ortho-C6H5–H). 13C{1H} NMR (75.0 MHz,
CDCl3): δ = 21.7 (s, C3H7–CH3), 34.1 (s, N3–CH3), 49.5
1
C6H5), 128.8 (d, JP, C = 12.8 Hz, P–C6H5), 129.9 (d, JP, C = 92.1
Hz, P–ipso-C6H5), 132.2 (d, JP, C = 11.2 Hz, P–C6H5), 132.4
1
2
(s, C3H7–CH), 122.8 (d, JP, C = 124.2 Hz, C4), 123.2 (d, JP, C
=
=
(d, JP, C = 2.4 Hz, P–C6H5), 135.9 (s, N–ipso-C6H5), 137.6
19.2 Hz, C5), 129.0 (d, JP, C = 12.8 Hz, C6H5), 130.1 (d, JP, C
1
3+4
(s, N–ipso-C6H5), 169.9 (d,
J
= 3.2 Hz, CvS). 31P NMR
P, C
3
112.9 Hz, ipso-C6H5), 131.6 (d, JP, C = 10.4 Hz, C6H5), 133.0
(121.5 MHz, CDCl3): δ = 27.5 (quint br, JP, H = 13.7 Hz). MS
3+4
= 4.8 Hz, CvS). 31P
˙
˙
+
+
(d, JP, C = 3.2 Hz, C6H5), 166.5 (d,
J
P, C
NMR (121.5 MHz, CDCl3): δ = 15.9 (quint br, 3JP, H = 12.8 Hz).
(EI, 70 eV): m/z = 468 (M , 15%), 436 (M − S, 3%), 375
+
+
˙
˙
(M − S − C6H5, 5%), 283 (M − 2S − C6H5, 2%), 183
+
+
+
˙
˙
MS (EI, 70 eV): m/z = 356 (M , 100%), 323 (M − S, 4%), 314
(P(C6H5)2 , 3%). HR-EI-MS: found: 468.0889, calc.: 468.0884.
+
+
+
IR (KBr, cm−1): ν˜ 3142 and 3058 (w, ν(C–H)), 1591
(m, ν(CvC)), 1496 (s, ν(P–CvC)), 1438 (s, ν(P–C6H5)), 1383
(s, ν(CvN)), 1168 (vs, ν(CvS)), 763, 720 and 690
(s, δ(C6H5)), 660 (s, ν(PvS)). UV/Vis (CH2Cl2): λmax: 230 nm.
EA: calc. C 69.21, H 4.52, N 5.98, S 13.69, found: C 70.43, H
4.88, N 5.71, S 13.00.
˙
˙
˙
(M − C3H6, 17%), 281 (M − C3H7 − S, 2%), 265 (M
−
+
˙
C6H5 − CH3, 10%), 223 (M − C3H6 − C6H5 − CH3, 6%), 183
+
(P(C6H5)2 , 7%). HR-ESI-MS: found: 357.1187, calc.:
357.1190, as C19H21N2OPSH+. IR (KBr, cm−1): ν˜ 3140, 3077
and 2961 (w, ν(C–H)), 1590 (w, ν(CvC)), 1483 (w, ν(P–
CvC)), 1437 (s, ν(P–C6H5)), 1413 (s, ν(CvN)), 1276
(s, ν(PvO)), 1195 (vs, ν(CvS)), 750, 723 and 699 (s, δ(C6H5)).
UV/Vis (Et2O): λmax: 273 nm. EA: calc. C 64.03, H 5.94, N
7.86, S 9.00, found: C 63.79, H 5.97, N 7.85, S 9.10.
1-Isopropyl-3-methyl-4-diphenylthiophosphoryl-imidazole-2-
thione (5d)
1
Yield: (1.062 g, 95%), colorless solid, mp. 178 °C. H NMR
Typical procedure for the generation of phosphane sulfides and
selenides
3
(300 MHz, CDCl3): δ = 1.44 (d, JH,H = 6.9 Hz, 6H, C3H7–
CH3), 3.93 (s, 3H, N3–CH3), 5.35 (hept, JH,H = 6.9 Hz, 1H,
3
C3H7–CH), 6.60 (d, JP, H = 2.9 Hz, 1H, C5–H), 7.42–7.30 (m,
3
The phosphanes 3a,b,d (3 mmol), 10 mL of toluene and elemen-
tal sulphur or selenium (3 mmol) were heated for 3 h at 110 °C.
The reaction mixture was cooled down to ambient temperature.
The product precipitated in the form of colorless crystals. The
obtained crystals were washed with n-pentane and dried in vacuo
(8 × 10−3 mbar).
3
3
4
6H, C6H5–H), 8.12 (ddd, JP, H = 14.6 Hz, JH,H = 7.3 Hz, JH,H
= 1.3 Hz, 4H, ortho-C6H5–H). 13C{1H} NMR (75.0 MHz,
CDCl3): δ = 21.7 (s, C3H7–CH3), 34.3 (s, N3–CH3), 49.8
(s, C3H7–CH), 122.4 (d, JP, C = 107.0 Hz, C4), 122.5 (d, JP, C
=
=
1
2
18.1 Hz, C5), 129.2 (d, JP, C = 12.9 Hz, C6H5), 130.8 (d, JP, C
1
88.6 Hz, ipso-C6H5), 132.2 (d, JP, C = 11.8 Hz, C6H5), 132.8
3+4
(d, JP, C = 3.3 Hz, C6H5), 167.5 (d,
J
= 5.2 Hz, CvS). 31P
P, C
1,3-Dimethyl-4-diphenylthiophosphoryl-imidazole-2-thione (5a)
3
NMR (121.5 MHz, CDCl3): δ = 26.9 (quint, JP, H = 14.6 Hz,
JP, H = 2.9 Hz). MS (EI, 70 eV): m/z = 372 (M , 100%), 340
(M − S, 20%), 326 (M − S − CH3, 8%), 298 (M − C3H7 − S,
1
3
+
˙
Yield: (940 mg, 91%), colorless solid, mp. 227 °C. H NMR
+
+
+
(300 MHz, CDCl3): δ = 3.47 (s, 3H, N3–CH3), 3.53 (s, 3H, N1–
˙
˙
˙
3
+
+
+
CH3), 6.21 (d, JP, H = 2.5 Hz, 1H, C5–H), 7.42–7.56 (m, 6H,
5%), 183 (P(C6H5)2 , 60%), 77 (C6H5 , 5%), 42 (C3H6 , 5%).
HR-EI-MS: found: 352.0878, calc.: 372.0884. IR (KBr, cm−1): ν˜
3054 and 2972 (w, ν(C–H)), 1437 (s, ν(P–C6H5)), 1381
(m, ν(CvN)), 1184 (s, ν(CvS)), 754, 716 and 696 (s, δ(C6H5)),
644 (s, ν(PvS)). UV/Vis (Et2O): λmax: 209 nm. EA: calc. C
61.26, H 5.68, N 7.52, S 17.22, found: C 61.25, H 5.70, N 7.52,
S 16.97.
C6H5–H), 7.70–7.78 (m, JP, H = 14.0 Hz, ortho-C6H5–H). 13C
3
{1H} NMR (75.0 MHz, CDCl3): δ = 34.2 (s, N3–CH3), 35.1 (s,
N1–CH3), 121.3 (d, JP, C = 107.3 Hz, C4), 126.3 (d, JP, C = 17.3
1
2
Hz, C5), 128.7 (d, JP, C = 13.1 Hz, C6H5), 129.6 (d, JP, C = 91.2
1
Hz, ipso-C6H5), 131.6 (d, JP, C = 11.3 Hz, C6H5), 132.3 (d, JP, C
3.0 Hz, C6H5), 167.4 (d,
=
3+4
J
= 5.4 Hz, CvS). 31P NMR
P, C
5374 | Dalton Trans., 2012, 41, 5368–5376
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1
17.5 Hz, C5), 128.8 (d, JP, C = 81.5 Hz, ipso-C6H5), 129.1 (d,
1,3-Dimethyl-4-diphenylselenophosphoryl-imidazole-2-thione
(6a)
JP, C = 12.9 Hz, C6H5), 132.4 (d, JP, C = 11.6 Hz, C6H5), 132.7
(d, JP, C = 3.2 Hz, C6H5), 167.0 (d,
3+4
J
= 4.5 Hz, CvS). 31P
P, C
1
Yield: (1.151 g, 97%), colorless solid, mp. 206 °C. H NMR
1
NMR (121.5 MHz, CDCl3): δ = 16.0 JSe,P = 751.5 Hz (quint,
(300 MHz, CDCl3): δ = 3.48 (s, 3H, N3–CH3), 3.53 (s, 3H, N1–
3JP, H = 14.0 Hz, JP, H = 2.5 Hz). MS (EI, 70 eV): m/z = 420
3
3
CH3), 6.18 (d, JP, H = 2.5 Hz, 1H, C5–H), 7.41–7.56 (m, 6H,
+
+
+
˙
˙
˙
(M , 30%), 372 (M − S − CH3, 8%), 340 (M − Se, 100%),
3
C6H5–H), 7.71–7.79 (m, JP, H = 14.0 Hz, ortho-C6H5–H). 13C
+
+
˙
˙
326 (M − Se − CH3, 5%), 298 (M − C3H7 − S, 20%), 249
{1H} NMR (75.0 MHz, CDCl3): δ = 33.6 (s, N3–CH3), 34.5
+
+
˙
˙
(M − Se − CH3 − C6H5, 9%), 207 (M − Se − CH3 − C6H5 −
1
2
(s, N1–CH3), 118.9 (d, JP, C = 98.9 Hz, C4), 125.6 (d, JP, C
=
+
C3H7, 38%), 183 (P(C6H5)2 , 22%). HR-EI-MS: found:
1
16.8 Hz, C5), 127.6 (d, JP, C = 82.1 Hz, ipso-C6H5), 128.0 (d,
JP, C = 12.9 Hz, C6H5), 131.5 (d, JP, C = 11.6 Hz, C6H5), 131.7
(d, JP, C = 3.2 Hz, C6H5), 167.0 (s, CvS). 31P NMR
416.0348, calc: 420.0328. IR (KBr, cm−1): ν˜ 3154, 3052 and
2970 (w, ν(C–H)), 1571 (m, ν(CvC)), 1435 (vs, ν(P–C6H5)),
1381 (s, ν(CvN)), 1182 (s, ν(CvS)), 753, 714 and 701
(s, δ(C6H5)). UV/Vis (CH2Cl2): λmax: 281 nm. EA: calc. C
54.41, H 5.05, N 6.68, S 7.65, found: C 54.48, H 5.06, N 6.70,
S 7.78.
1
3
(121.5 MHz, CDCl3): δ = 15.3 JSe,P = 754.0 Hz (qqd, JP, H
=
3
3
14.0 Hz, JP, H = 3.8 Hz, JP, H = 2.5 Hz). MS (EI, 70 eV): m/z =
+
+
+
˙
˙
˙
392 (M , 13%), 344 (M − S − CH3, 18%), 312 (M − Se,
+
+
˙
˙
100%), 225 (M − Se − C6H5, 10%), 221 (M − Se − C6H5 −
+
CH3, 36%), 183 (P(C6H5)2 , 42%). HR-ESI-MS: found:
393.0091, calc.: 392.0015, as C17H18N2PSSe+. IR (KBr, cm−1):
ν˜ 3146 (w, ν(C–H)), 1436 (vs, ν(P–C6H5)), 1393 (vs, ν(CvN)),
1198 (s, ν(CvS)), 760, 715 and 691 (s, δ(C6H5)). UV/Vis
(Et2O): λmax: 208 nm. EA: calc. C 52.18, H 4.38, N 7.16, S
8.19, found: C 52.04, H 4.39, N 7.13, S 8.25.
Procedure for the synthesis of phosphane borane complexes
In a Schlenk flask, the phosphanes 3a,b (500 mg, 1.6 to
1.1 mmol) were dissolved in 20 mL of tetrahydrofuran. Borane
tetrahydrofuran complex (1 M solution in tetrahydrofuran,
1 equivalent) was added and the reaction mixture was stirred
for 3 h at ambient temperature. The solvent was removed
in vacuo (8 × 10−3 mbar), and the crude product was washed
with n-pentane and dried in vacuo (8 × 10−3 mbar).
1,3-Diphenyl-4-diphenylselenophosphoryl-imidazole-2-
thione (6b)
1
Yield: (1.515 g, 98%), light yellow solid, mp. 244 °C. H NMR
1,3-Dimethyl-4-diphenylphosphino-κP-borane-imidazole-2-
thione (7a)
3
(300 MHz, CDCl3): δ = 6.74 (d, JP, H = 3.5 Hz, 1H, C5–H),
3
6.94–7.51 (m, 16H, C6H5–H), 7.68–7.74 (ddd, JP, H = 13.7 Hz,
4
3JH,H = 7.1 Hz, JH,H = 1.3 Hz, 4H, ortho-C6H5–H). 13C{1H}
1
Yield: (470 mg, 90%), colorless solid, mp. 184 °C. H NMR
1
NMR (75.0 MHz, CDCl3): δ = 122.0 (d, JP, C = 92.9 Hz, C4),
2
(300 MHz, CDCl3): δ = 1.17 (d vbr, JP, H = 15.7 Hz, 3H, BH3),
2
3.37 (s, 3H, N3–CH3), 3.51 (s, 3H, N1–CH3), 6.47 (d, 3JP, H = 2.6
Hz, 1H, C5–H), 7.40–7.60 (m, 10H, C6H5–H). 13C{1H} NMR
(75.0 MHz, CDCl3): δ = 35.1 (s, N3–CH3), 35.6 (s, N1–CH3),
124.9 (s, N–C6H5), 125.2 (s, N–C6H5), 128.4 (d, JP, C = 16.8
Hz, C5), 128.5 (s, N–C6H5), 128.6 (d, JP, C = 12.8 Hz, P–C6H5),
132.7 (d, 1JP, C = 82.4 Hz, P–ipso-C6H5), 132.4 (d, JP, C = 3.2 Hz,
1
1
118.3 (d, JP, C = 70.5 Hz, C4), 126.2 (d, JP, C = 60.1 Hz, ipso-
P–C6H5), 132.7 (d, JP, C = 12.0 Hz, P–C6H5), 135.8 (s, N–ipso-
3+4
C6H5), 128.2 (d, JP, C = 14.2 Hz, C5),129.4 (d, JP, C = 10.3 Hz,
2
C6H5), 137.5 (s, N–ipso-C6H5), 170.1 (d,
J
= 3.2 Hz,
P, C
CvS). 31P NMR (121.5 MHz, CDCl3): δ = 16.9 JSe,P = 764.5
Hz (quint, JP, H = 13.7 Hz, JP, H = 3.1 Hz). MS (EI, 70 eV): m/z
1
C6H5), 132.4 (d, JP, C = 2.6 Hz, C6H5), 132.8 (d, JP, C = 10.3 Hz,
3
3
3+4
C6H5), 167.9 (d,
J
=
3.2 Hz, CvS). 31P NMR
P, C
(121.5 MHz, CDCl3): δ = 8.3 (s vbr). 11B{1H} NMR
(96.3 MHz, CDCl3): δ = −41.2 (s br). MS (EI, 70 eV): m/z =
+
+
+
˙
˙
˙
= 516 (M , 10%), 436 (M − Se, 48%), 403 (M − Se − S,
+
+
˙
˙
14%), 359 (M − Se − C6H5, 18%), 218 (M − Se − 2S −
+
+
+
+
2C6H5, 6%), 183 (P(C6H5)2 , 8%). HR-EI-MS: found:
˙
˙
˙
326 (M , 3%), 312 (M − BH3, 92%), 279 (M − BH3 − S,
512.0350, calc.: 516.0328. IR (KBr, cm−1): ν˜ 3052 (w, ν(C–H)),
1592 (m, ν(CvC)), 1495 (s, ν(P–CvC)), 1439 (s, ν(P–C6H5)),
1380 (s, ν(CvN)), 1168 (m, ν(CvS)), 750, 731 and 693
(s, δ(C6H5)). UV/Vis (CH2Cl2): λmax: 209 nm. EA: calc. C
62.91, H 4.11, N 5.43, S 6.22, found: C 62.79, H 4.15, N 5.34,
S 6.19.
+
˙
3%), 221 (M − BH3 − S − C6H5 − CH3, 49%), 199
+
(C12H13BP+, 6%), 183 (P(C6H5)2 , 8%). HR-ESI-MS: found:
349.1073, calc.: 349.1070, as C17H20BN2PSNa+. IR (KBr,
cm−1): ν˜ 3150 (w, ν(C–H)), 2389 (vs, ν(B–H), E), 2347
(s, ν(B–H), A′), 1437 (vs, ν(P–C6H5)), 1393 (vs, ν(CvN)),
1154 (vs, ν(CvS)), 694 (s, δ(C6H5)). UV/Vis (Et2O): λmax
:
209 nm.
1-Isopropyl-3-methyl-4-diphenylselenophosphoryl-imidazole-2-
thione (6d)
1,3-Diphenyl-4-diphenylphosphino-κP-borane-imidazole-2-
thione (7b)
Yield: (1.22 g, 97%), colorless solid, mp. 199 °C. 1H NMR
3
1
(300 MHz, CDCl3): δ = 1.20 (d, JH,H = 6.9 Hz, 6H, C3H7–
Yield: (466 mg, 94%), colorless solid, mp. 186 °C. H NMR
3
3
CH3), 3.53 (s, 3H, N3–CH3), 5.00 (hept, JH,H = 6.9 Hz, 1H,
(300 MHz, CDCl3): δ = 1.10 (s vbr, 3H, BH3), 6.92 (d, JP, H =
C3H7–CH), 6.21 (d, JP, H = 2.5 Hz, 1H, C5–H), 7.41–7.55
7.9 Hz, 1H, C5–H), 7.15–7.68 (m, 20H, C6H5–H). 13C{1H}
3
3
3
1
(m, 6H, C6H5–H), 7.73 (ddd, JP, H = 14.0 Hz, JH,H = 6.8 Hz,
4JH,H = 1.5 Hz, 4H, ortho-C6H5–H). 13C{1H} NMR (75.0 MHz,
CDCl3): δ = 21.7 (s, C3H7–CH3), 34.3 (s, N3–CH3), 49.6
NMR (75.0 MHz, CDCl3): δ = 120.2 (d, JP, C = 63.4 Hz, C4),
1
125.2 (s, N–C6H5), 126.0 (d, JP, C = 61.4 Hz, P–ipso-C6H5),
2
128.4 (d, JP, C = 16.8 Hz, C5), 128.9 (s, N–C6H5), 129.0 (d, JP, C
1
2
(s, C3H7–CH), 120.2 (d, JP, C = 98.9 Hz, C4), 122.4 (d, JP, C
=
= 7.1 Hz, P–C6H5), 129.5 (s, N–C6H5), 132.0 (d, JP, C = 2.6 Hz,
Dalton Trans., 2012, 41, 5368–5376 | 5375
This journal is © The Royal Society of Chemistry 2012

View Article Online
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P–C6H5), 133.0 (d, JP, C = 10.3 Hz, P–C6H5), 136.0 (s, N–ipso-
C6H5), 137.6 (s, N–ipso-C6H5), 170.0 (s, CvS). 31P NMR
(121.5 MHz, CDCl3): δ = 8.7 (s vbr). 11B{1H} NMR
(96.3 MHz, CDCl3): δ = −40.5 (s br). MS (EI, 70 eV): m/z =
+
+
+
˙
˙
˙
450 (M , 10%), 436 (M − BH3, 100%), 403 (M − BH3 − S,
+
+
˙
˙
34%), 359 (M − BH3 − C6H5, 30%), 327 (M − BH3 − C6H5
− S, 2%), 281 (M − BH3 − 2C6H5, 2%), 251 (C15H11N2S+,
+
˙
20%), 199 (C12H13BP+, 10%), 183 (P(C6H5)2 , 20%).
+
HR-ESI-MS: found: 473.1391, calc.: 473.1383, as
C27H24N2PSNa+. IR (KBr, cm−1): ν˜ 3058 (w, ν(C–H)), 2363
(vs, ν(B–H), E), 2341 (vs, ν(B–H), A′), 1438 (vs, ν(P–C6H5)),
1381 (s, ν(CvN)), 1167 (m, ν(CvS)), 755 and 694
(s, δ(C6H5)). UV/Vis (Et2O): λmax: 209 nm. EA: calc. C 72.01,
H 5.37, N 6.22, S 7.12, found: C 71.04, H 5.39, N 6.06, S 7.04.
Acknowledgements
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RS gratefully acknowledges the University of Bonn and the
COST action cm0802 “PhoSciNet” and AJA the National
Science Foundation (CHE-0413521 and CHE-0115760) for pro-
viding the funding for this study. AJA gratefully acknowledges
the Saxon Endowment of the University of Alabama.
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5376 | Dalton Trans., 2012, 41, 5368–5376
This journal is © The Royal Society of Chemistry 2012