Synthesis, characterization, and crystal structures of tris(2-pyridyl) phosphine sulfide and selenide

Article abstract of DOI:10.1080/10426501003636778

We report the synthesis and structural determinations of tris(2-pyridyl)phosphine sulfide and selenide, which were prepared by the reaction of 2-lithiopyridine with phosphorus trichloride at -100°C, and treatment of resulted (2-pyridyl)phosphine with elemental sulfur or selenium in hot toluene. These compounds were characterized by elemental analysis, melting point determination, mass spectroscopy, IR, ¹H, and ³¹P NMR spectroscopies. Furthermore, the molecular structures of tris(2-pyridyl)phosphine sulfide and selenide were determined by single crystal X-ray analysis and compared with the structures of tris(2-pyridyl)phosphine and tris(2-pyridyl)phosphine oxide. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426501003636778

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Synthesis, Characterization, and Crystal
Structures of Tris(2-pyridyl)phosphine
Sulfide and Selenide
Ali Nemati Kharat a , Abolghasem Bakhoda a , Taraneh Hajiashrafi a
& Alireza Abbasi a
a School of Chemistry, University College of Science , University of
Tehran , Tehran , Iran
Published online: 05 Nov 2010.
To cite this article: Ali Nemati Kharat , Abolghasem Bakhoda , Taraneh Hajiashrafi & Alireza Abbasi
(2010) Synthesis, Characterization, and Crystal Structures of Tris(2-pyridyl)phosphine Sulfide
and Selenide, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:11, 2341-2347, DOI:
10.1080/10426501003636778
To link to this article: http://dx.doi.org/10.1080/10426501003636778
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Phosphorus, Sulfur, and Silicon, 185:2341–2347, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003636778
SYNTHESIS, CHARACTERIZATION, AND CRYSTAL
STRUCTURES OF TRIS(2-PYRIDYL)PHOSPHINE SULFIDE
AND SELENIDE
Ali Nemati Kharat, Abolghasem Bakhoda,
Taraneh Hajiashrafi, and Alireza Abbasi
School of Chemistry, University College of Science, University of Tehran,
Tehran, Iran
We report the synthesis and structural determinations of tris(2-pyridyl)phosphine sulfide and
selenide, which were prepared by the reaction of 2-lithiopyridine with phosphorus trichloride
at –100◦C, and treatment of resulted (2-pyridyl)phosphine with elemental sulfur or selenium
in hot toluene. These compounds were characterized by elemental analysis, melting point
1
determination, mass spectroscopy, IR, H, and 31P NMR spectroscopies. Furthermore, the
molecular structures of tris(2-pyridyl)phosphine sulfide and selenide were determined by
single crystal X-ray analysis and compared with the structures of tris(2-pyridyl)phosphine
and tris(2-pyridyl)phosphine oxide.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental
file.
Keywords: 2-Lithiopyridine; oxygen; selenium; single crystal X-ray analysis; sulfur; tris(2-
pyridyl)phosphine
INTRODUCTION
Organophosphorus compounds are an important class of ligands with potential ap-
plications as selective homogenous catalysts.1–3 Among of them, pyridylphosphine ligands
and their chalcogenides derivatives are very interesting for catalytic and structural investiga-
tions.4,5 Pyridyl-substituted phosphines, which were first reported more than 60 years ago,
have been extensively used in metal ion coordination chemistry for their ease of functional-
ization and the electronic properties that they impart to metal complexes used for catalysis
purposes.6,7 According to hard and soft acid base theory (HSAB), these types of ligands are
especially suitable for complexing with noble metals, which are important in catalysis.8–10
The first preparation of pyridylphosphine was presented in 1944 by Davies and Mann as
part of a study on the optical resolution of tertiary phosphines.11 There has been an increas-
ing usage of tris(2-pyridyl)phosphine, P(2-py)3, in inorganic and organometallic chemistry,
Received 7 November 2009; accepted 19 January 2010.
Financial support of the University of Tehran for this research is gratefully acknowledged.
Address correspondence to Ali Nemati Kharat, School of Chemistry, University College of Science, Uni-
versity of Tehran, PO Box 13145-1357, Tehran, Iran. E-mail: alnema@khayam.ut.ac.ir
2341

2342
A. N. KHARAT ET AL.
primarily because of its interesting structural feature that retains both phosphorus and ni-
trogen atoms with versatile coordination possibility. There are four coordination modes
found for complexes containing P(2-py)3, namely, phosphorus monodentate,12,13 η2-P,N-
chelate,14,15 µ-P,N-bridge,16 and η3-N, Nꢁ, Nꢁꢁ-chelate.17 Thus, application of P(2-py)3 lig-
ations affords numerous novel and useful complexes.18–20 Apart from its characteristics
in coordination chemistry, the catalysis aspects of P(2-py)3 for the reactions employing
triphenylphosphine have been recently explored.21 In an effort to progress our knowledge
about the relation between structure and properties, we have reported the synthesis and
structure of tris(2-pyridyl)phosphine sulfide and selenide by single crystal X-ray analysis.
Some structural aspects of these compounds were compared with tris(2-pyridyl)phosphine
and tris(2-pyridyl)phosphine oxide. These compounds were further characterized by ele-
1
mental analysis, melting point determination, mass spectroscopy, IR, H, and 31P NMR
spectroscopies.
RESULTS AND DISCUSSION
Synthesis
P(2-py)3 wassynthesizedbythereactionof2-lithiopyridine, preparedbythetreatment
of butyl lithium on 2-bromopyridine at –100◦C, with phosphorus trichloride at the same
temperature (Scheme 1).22
Scheme 1
The method in the literature23 was used for synthesis of phosphine oxide, by the
reaction of P(2-py)3 with 30% hydrogen peroxide in acetone. The phosphine sulfide and
selenide derivatives were prepared by treatment of appropriate phosphine with elemental
sulfur and red selenium in refluxing toluene (Scheme 2).
X
P
N
N
P
N
Elemental Sulfur or Selenium
N
N
N
(X= S, Se)
Scheme 2

TRIS(2-PYRIDYL)PHOSPHINE SULFIDE AND SELENIDE
2343
Recrystallization of crude solids from hot methanol and a few drops of chloroform
afforded colorless crystals of tris(2-pyridyl)phosphine sulfide and selenide suitable for x-
ray crystallographic analysis. The pyridylphosphine was isolated in moderate to good yield
(65%), but its chalcogenides can be isolated in very good yields (84–94%).
Characterization
All compounds were characterized by CHN elemental analysis, melting point deter-
1
mination, mass spectroscopy, IR, H, and 31P NMR spectroscopies. The crystal structure
of tris(2-pyridyl)phosphine sulfide and selenide were determined by x-ray single crystal
1
analysis. As expected, the resonance in the 31P{ H} NMR spectra of P(2-py)3 and P(2-py)3
oxide appeared at –0.5 and 29.47 ppm, respectively. Furthermore, the resonance in the
1
31P{ H} NMR spectra of P(2-py)3 sulfide and selenide appeared at 34.89 and 29.47 ppm,
respectively (see the Supplemental Materials, available online). Selenium satellites are ob-
served. These chemical shifts are similar to the related phosphine sulfides and selenides that
were previously reported in the literature.24–26 In the mass spectra of P(2-py)3, a cleavage of
the carbon–phosphorus bond is observed. Also, a cleavage of the oxygen, sulfur, and sele-
nium bonds with phosphorus are found in the derivatives of P(2-py)3. Hence, the fragments
of pyridyl rings, sulfur, selenium, and phosphorus are found. The stretching vibration of the
C C and C N bond of pyridyl rings in IR spectroscopy was found between 1420–1464
cm−1 and 1566–1697 cm−1 as strong absorptions. The stretching vibrations of P O, P S,
and P Se bonds were observed at 1175, 621, and 537 cm−1, respectively.
X-Ray Analyses
Crystallographic data and selected bond lengths and angles are listed in Tables I and
II, respectively.
C15H12N3PS (1) crystallizes in the monoclinic space group P21/c (No. 14) with four
molecules in the unit cell (Figure 1). Three pyridine rings, A, B, and C (A: C1/N1/C2 C5,
B: C6/N2/C7 C10, and C: C11/N3/C12 C15) are making dihedral angles of 77.94◦
between A & B, 89.43◦ between A & C, and 83.97◦ between B & C. Ring C is located so
C8
C9
C7
N2
C10
C4
C2
C5
N1
C6
S1
P1
C3
C1
C15
C14
C13
C11
N3
C12
Figure 1 ORTEP drawing of tris(2-pyridyl)phosphine sulfide, with 50% probability thermal ellipsoid.

2344
A. N. KHARAT ET AL.
Table I Crystallographic data of compounds 1 and 2
Compound
1
2
Chem. formula
C15H12N3PS
297.32
Pale yellow
Monoclinic
P21/c
9.5990(11)
9.3105(8)
16.0933(18)
90.00
96.381(9)
90.00
1429.4(3)
4
1.382
0.330
0.0524
C15H12N3PSe
344.21
Colorless
Trigonal
R3c
13.2300(19)
13.2300(19)
14.355(3)
90.00
Formula wt. [gmol−1
]
Color
Cryst. system
Space group
a [Å]
b [Å]
c [Å]
α [◦]
β [◦]
90.00
γ [◦]
120.00
2176.0(6)
6
1.576
2.691
0.0452
1032
0.0257
0.0487
0.983
V [Å3]
Z
ρ calcd. [gcm−3
]
µ [mm−1
Rint
]
F (000)
R1(R [F2 > 2σ (F2)])
wR2 (F2)
616
0.0427
0.0899
1.067
GooF
CCDC #
720506
720507
that N3 is pointing to the same direction as the sulfur atom, while the remaining nitrogen
atoms (N1 & N2) point in the opposite direction (see Figure 1). This type of arrangement
has been previously seen in the structure of tris(2-pyridyl)phophine oxide.27 The P-S bond
distance, 1.9428(8) Å, shows double bond character, as we expect from coordination of
phosphorus. All bond lengths and angles are comparable with similar structures found in
the literature.27
. . .
Crystal structure packing dominates by C H π interactions between neighboring
i
. . .
molecules (C3 H3 Cg1 = 2.893 Å, Cg1 being the ring C11/N3/C12 C15, with i =
1−x, 0.5+y, 0.5−z, see Figure S1, Supplemental Materials). C15H12N3PSe (2) crystallizes
in the trigonal space group R3c (No. 161) with six molecules in the unit cell (Figure 2).
The structure 2 is analogous to the 1 and tris(2-pyridyl)phosphine oxide,27 with distorted
tetrahedral configuration around the phosphorous atom. Due to the symmetry, three pyridine
rings are symmetrically related and are making dihedral angles of 69.16◦ between rings.
The dihedral angles between pyridine rings in 2 are much smaller than in 1. Moreover,
Table II Selected bond lengths (Å) and angles (◦) in 1 and 2
Compound
P
X [Å]
P
C [Å]
C
P
C [◦]
C P
X [◦]
1.
1.9428(8)
1.826(2)
1.828(2)
1.837(2)
1.832(3)
1.832(3)
1.832(3)
104.84(10)
105.59(9)
106.36(9)
104.76(13)
104.76(13)
104.76(13)
113.37(7)
113.45(7)
112.51(8)
113.85(11)
113.85(11)
113.85(11)
2.
2.1050(15)

TRIS(2-PYRIDYL)PHOSPHINE SULFIDE AND SELENIDE
2345
C4
C3
C2
C5
C5
C2
N1
C1
C3
C1
N1
C4
Se1
P1
C1
C5
C4
N1
C2
C3
Figure 2 ORTEP drawing of tris(2-pyridyl)phosphine selenide, with 50% probability thermal ellipsoid.
all nitrogen atoms in 2 are pointing in the same direction as the Se atom, while only one
nitrogen atom points to the same side as the S atom in 1, which can be related to the greater
polarizability of Se than the S atom in the structures 2 compared to 1.
Each pyridine ring is connected to four neighboring molecules through relatively
weak hydrogen bonds, stabilizing the three-dimensional crystal system (Supplemental
Materials).
EXPERIMENTAL
All manipulations were carried out under air- and moisture-free conditions under
nitrogen using standard Schlenk or drybox techniques. Diethyl ether was dried over lithium
aluminium hydride (LiAlH4) and was freshly distilled prior to use. n-Butyllithium (15%
solution in n-hexane), 2-bromopyridine, phosphorus trichloride, sulfur, and selenium were
purchased from Merck and were purified before use according to the standard methods.
Melting points were obtained with an Electrothermal 9200 melting point apparatus. Infrared
spectrum from 400 to 4000 cm−1 was recorded on a Shimadzu 470 FT-IR instrument, using
1
KBr pellets. H and 31P NMR spectra were recorded at room temperature in CDCl3 on
a Bruker Avance 300 MHz. The NMR spectra are referenced to Me4Si (1H) or H3PO4
85% (31P) as external standards. The mass spectroscopy was performed on a Varian MAT
44 instrument (electron impact, 20 eV). The calculated isotopic distribution for each ion
was in agreement with experimental values. CHN analysis was performed using a Heraeus
CHN–O Rapid Analyzer.
X-Ray Structure Determination
X-ray diffraction data were collected at room temperature on small crystals enclosed
in thin walled glass capillaries by means of a Stoe imaging plane. The X-Area program was
used for indexing and integrating the single crystal reflections. The structures (1 and 2) were
solved by direct methods using SHELXS-97, and were refined by full matrix least squares
on F2, SHELXL-97.28 Minimum and maximum final electron densities were –0.205 to

2346
A. N. KHARAT ET AL.
0.320 eÅ−3 and –0.309 to 0.204 eÅ−3 for the structures 1 and 2, respectively. Absorp-
tion corrections were performed with the programs X-RED29 and X-Shape.30 Symmetry
equivalent reflections were used to optimize crystal shape and size. All non-hydrogen
atoms were refined anisotropically. Aromatic H atoms were placed in calculated positions
(C H = 0.93 Å) and were treated as riding on the respective carrier atom, with Uiso(H)
= 1.2 (C). Plots were produced with the Diamond and Mercury programs, and PLA-
TON31 software was used to prepare materials for publication. Crystallographic data for
tris(2-pyridyl)phosphine sulfide and selenide have been deposited at the Cambridge Crys-
tal Structure Database (CCDC), with CCDC numbers 720506 and 720507, respectively.
Copies of available materials can be obtained free of charge upon application to the Di-
rector, CCDC 12 Union Road, Cambridge CB2IEZ, UK (fax: (44)01223336033); E-mail:
deposit@ccdc.ac.uk).
P(2-py)3
Tris(2-pyridyl)phosphine (2-py)3 was synthesized by the method in the literature in
65% yield, mp 113◦C.22
P(O)(2-py)3
Tris(2-pyridyl)phosphine oxide was synthesized by the method in the literature in
94% yield, mp 210–212◦C.23
P(S)(2-py)3
Elemental sulfur (5 mmol) and PPy3 (4 mmol) were refluxed with deoxygenated
toluene (50 mL) under an atmosphere of dry argon overnight. The cooled solution was
filtered through Celite to remove excess sulfur. The filtrate was evaporated, and, after
recrystallization of crude product from chloroform, pale yellow crystals were obtained
in 91% yield, mp 160–161◦C. IR (cm−1): 3037(w), 3014(w), 1566(s), 1448(s), 1418(s),
1277(w), 1152(m), 1132(sh), 1085(m), 1042(m), 980(s), 777(s), 738(s), 657(s), 621(m),
518(s), 473(sh), 440(m). 1H NMR (CDCl3, 300 MHz, 25◦C): δ = 7.35–7.39 (m), 7.79–7.86
3 15
2 1
(m), 8.28–8.33 (t, J N-1H, 6.8 Hz), 8.74–8.75 (d, J H-1H, 4.5 Hz). 31P NMR (CDCl3,
27◦C,121.49 MHz): δ = 34.89 ppm. MS (EI+, 20 eV); m/z (%): 297 (62) [M]+, 265 (67)
[M-S]+, 187 (100) [M-SPy]+, 109(21) [M-Spy2]+, 78 (47) [Py]+. C15H12N3PS (297.32):
calc: N 14.13%, C 60.59%, H 4.03%; found: N 14.04%, C 60.41%, H 3.99%.
P(Se)(2-py)3
This compound can be prepared by the reaction of PPy3 (4 mmol) with red selenium
(5 mmol) as described above for the sulfur derivative. After recrystallization of crude
product from ethanol, colorless crystals were obtained, mp 176–178◦C. The yield of product
was 84%. IR (cm−1): 3065(w), 3034(w), 2998(w), 1673(w), 1569(s), 1450(s), 1423(s),
1285(w), 1244(w), 1165(w), 1126(m), 1083(w), 1051(w), 988(s), 902(w), 771(s), 738(s),
715(sh), 622(w), 561(s), 537(s),505(s), 451(m). 1H NMR (CDCl3, 300 MHz, 25◦C): δ =
7.41–7.47(m), 7.83–7.92(m), 8.14–8.18 (t, 3J15N-1H, 6.8 Hz), 8.61–8.66 (d, 2J1H-1H, 16.6
1
Hz). 31P NMR (CDCl3, 27◦C, 121.49 MHz): δ = 29.47 ppm. J P-Se is 741 Hz. MS

TRIS(2-PYRIDYL)PHOSPHINE SULFIDE AND SELENIDE
2347
(EI+, 20 eV); m/z (%): 345 (53) [M]+, 265 (39) [M-Se]+, 187 (100) [M-SePy]+, 109 (10)
[M-SePy2]+, 78 (32) [Py]+. C15H12N3PSe (344.21): calc: N 12.20%, C 52.34%, H 3.49%;
found: N 12.09%, C 52.13%, H 3.45%.
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