Synthesis of Phosphine Chalcogenides Under Solvent-Free Conditions Using a Rotary Ball Mill

Article abstract of DOI:10.1002/ejic.201701414

The mechanochemical technique of ball milling has been applied to the solventless and eco-friendly synthesis of chalcogenides (sulfide and selenide) of a variety of tertiary and aminophosphines. In most of the cases, the products are obtained in almost quantitative yields with high purity by applying a simple workup procedure without using chromatographic techniques or any other purification methods. The scope of this methodology was explored by using a range of phosphines (mono, di and tetra) to synthesize partial as well as mixed chalcogenides. The use of almost equimolar amounts of starting materials and the absence of any byproducts significantly simplifies the product isolation compared with the standard solution state reactions, thus providing a highly atom economic (100 %) method with an ideal E-factor (E = 0). The solid-state reactions were monitored by ³¹P{¹H} NMR spectroscopy. The structures of some of the products are also confirmed by single-crystal X-ray analyses. Although most of the reactions were carried out on ca. 100-mg scale, the scaling up of the reaction did not affect the course of the reaction.

Full text of DOI:10.1002/ejic.201701414

A Journal of
Accepted Article
Title: Synthesis of Phosphine-chalcogenides under Solvent-free
Conditions using Rotary Ball Mill
Authors: Rajnish Kumar, Saurabh Kumar, Madhusudan K Pandey,
Vitthalrao S Kashid, Latchupatula Radhakrishna, and
Maravanji Shivaramaiah Balakrishna
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201701414
Link to VoR: http://dx.doi.org/10.1002/ejic.201701414

10.1002/ejic.201701414
European Journal of Inorganic Chemistry
Synthesis of Phosphine-chalcogenides under Solvent-free Conditions using
Rotary Ball Mill
Rajnish Kumar, Saurabh Kumar, Madhusudan K. Pandey, Vitthalrao S. Kashid, Latchupatula
Radhakrishna and Maravanji S. Balakrishna*
This paper describes the prepartion of chalcogenides and partially oxidized derivatives of tertiary
phosphines, amino- and a vareity of bisphosphines in almost quantitative yields under solvent free
conditions using rotary ball mill. The scope of this methodology was shown by ployphosphines
and also in scaled up reactions. The short duration, absence of solvents and lower rotation
frequency makes it a environmentaly benign and energy saving method.
1
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
Synthesis of Phosphine-chalcogenides under Solvent-free Conditions using
Rotary Ball Mill
Rajnish Kumar, Saurabh Kumar, Madhusudan K. Pandey, Vitthalrao S. Kashid, Latchupatula
Radhakrishna and Maravanji S. Balakrishna*
Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India.
Abstract: The mechanochemical technique of ball milling has been applied to the solvent-less and
eco-friendly synthesis of chalcogenides (sulfide and selenide) of a variety of tertiary and amino-
phosphines. In most of the cases, the products are obtained in almost quantitative yields with high
purity by applying a simple workup procedure without using chromatographic techniques or any
other purification methods. The scope of this methodology was explored by using a range of
phosphines (mono, di and tetra) to synthesize partial as well as mixed-chalcogenides. The use of
almost equimolar amounts of starting materials and absence of any by-product significantly
simplifies the product isolation compared to the standard solution state reactions, thus providing a
highly atom economic (100%) method with an ideal E-factor (E = 0). The solid state reactions
were monitored by 31P{1H} NMR spectroscopy. The structures of some of the products are also
confirmed by single crystal X-ray analyses. Although most of the reactions were carried out in
~100 mg scale, the scaling up of the reaction did not affect the course of the reaction.
Keywords: Ball Mill; Solid State; Phosphines; Chalcogenides; Oxidation.
*Corresponding author: M. S. Balarkishna, E-mail: krishna@chem.iitb.ac.in or
msb_krishna@iitb.ac.in
2
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Introduction
In recent years, synthetic chemists have given much attention towards developing the
methodologies which are inexpensive, eco-friendly and recyclable, mainly due to the growing
environmental concerns. A reaction under solvent free condition or solid support provides many
advantages over the conventional solution phase synthesis[1] in terms of product yield, reaction
time, benign condition, ease of purification, and recyclability of the support,[2] minimizing the
generation of toxic and nontoxic waste and disposal of the solvents. Another emerging field of
research in this respect is the employment of techniques such as mixing, grinding, or ball milling,
to carry out chemical reactions in the absence of a solvent,[3] which considerably decreases the E-
factor[4] of the reactions. Exploring the low cost eco-friendly methods for the ease and simple
preparation of compounds by ball milling, also known as mechanochemistry,[5] is a challenging
task especially to reduce the reaction time, the temperature and simplifying the workup procedures.
Mechanochemistry has been exploited for the derivatization of biological molecules, for example,
synthesis of amino acids,[6] amino esters,[7] peptides,[8] functionalization of nucleosides or
carbohydrates.[9] Reactions such as anhydride opening,[10] oxidative 2-naphthol dimerizations,[11]
Heck-type cross-couplings,[12] the protection of diamines,[13] the preparation of phosphorus
ylides,[14] cyclodiphosphazane derivatives,[15] the metal free reductive benzylization of
malononitrile,[16] the functionalization of fullerenes[17] and catalysis[18] have also been carried out
using ball milling method which involves lesser reaction time, high yield and simplified workup
procedures compared to the conventional solution phase reactions. Synthesis of chalcogenides, in
particular sulfides and selenides of phosphines and bisphosphines, is carried out often at high
temperature, using high boiling solvents such as benzene, toluene or xylene which are considered
as hazardous.[19] In addition, reaction time also varies between 3 to 18 hours depending on the
3
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
substrate. Further, isolation and purification in the case of partially oxidized bisphosphines is a
tedious task owing to the formation of bischalcogenides and the presence of unreacted
bisphosphines in the reaction product. In view of this, we sought to develop a more convenient
and environmentally benign method for the synthesis of chalcogenides. Ball milling has been
proven to be an excellent alternative for the green synthesis of many organic compounds[20] but
never employed in the synthesis of phosphorus-chalcogenides despite their utility in coordination
chemistry. Herein, we report the solid state synthesis of phosphorus-chalcogenides using rotary
ball mill, which does not require any solvent for the synthesis, and the products formed also do not
need any further purification as the yields were almost quantitative in most of the cases. The
absence of by-products in the reaction makes it a highly atom economic (100%) method with an
ideal E-factor of zero and can be termed as a green chemical method.
Results and discussion
Synthesis of the chalcogenides
The syntheses of chalcogenides of phosphorus compounds were carried out using a rotary ball mill
without using any solvent. The solid phosphines were mixed with stoichiometric amounts of
elemental sulfur or selenium in a jar and rotated in the rotary ball mill containing a set of different
sized ceramic balls (1 x 15 mm, 2 x 12 mm, 7 x 10 mm, 12 x 8 mm and 40 x 5 mm) for 4 h at a
frequency of 450 rpm. Use of different sized balls will ensure effective grinding and hence better
yields. To begin with, the reactions of triphenylphosphine were carried out with elemental sulfur
and selenium for 4 h and the reaction mixtures were characterized by 31P{1H}NMR spectra which
showed single resonances at 43.3 and 35.3 ppm (1JPSe = 728 Hz), respectively, for Ph3P=S (1a)
and Ph3P=Se (1b), indicating the quantitative conversions. In another attempt, the same reaction
4
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
under identical conditions yielded the chalcogenides 1a and 1b within 2 h. However, the reaction
of PPh3 with elemental tellurium did not give Ph3P=Te even after 6 h, instead yielded a small
quantity of Ph3P=O (P = 29.9 ppm) as confirmed from its 31P{1H} NMR data. These results
prompted us to explore the oxidation of a variety of phosphines with sulfur and selenium using
rotary ball mill and the details are given in Table 1.
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European Journal of Inorganic Chemistry
Table 1. Synthesis of sulfide and selenide of phosphines using ball milling
% Conversionb
(Isolated yield)
Details of conventional
synthesis
S. No.
1
Phosphine
Chalcogenide
31P{1H}a NMR Shift
43.3 (s)
Reaction in benzene under
N2 at r.t. for 7 days, yield
not mentioned (ref 18c, d)
100(95)
Reflux in CDCl3 (60-70
C) for 3-16 h, yield not
mentioned (ref 18g, h)
2
3
35.3 (s, JP-Se = 728)
100(97)
55.4 (s)
100(93)
NR
6
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European Journal of Inorganic Chemistry
4
55.3 (s, JP-Se = 778)
100(94)
NR
Reflux in benzene under
N2 for 30-60 min, 65%
yield (ref 18b)
5
6
35.3 (s)
100(96)
100(94)
Reflux in deoxygenated
toluene under N2 for
overnight, 82% yield (ref
18a)
25.1 (s, JP-Se = 724)
7
8
9
32.3 (s)
22.4 (s, JP-Se = 750)
32.5 (s)
100(96)
100(92)
100(92)
NR
NR
NR
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10
22.0 (s, JP-Se = 750)
100(90)
NR
11
12
40.8 (s)
100(92)
100(90)
NR
NR
32.7 (s, JP-Se = 736)
Reflux in toluene for 24 h,
87% yield (ref 25b)
13
14
41.9 (s)
100(92)
100
34.1 (s, JP-Se = 732)
NR
15
26.0 (s)
40
NR
8
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European Journal of Inorganic Chemistry
16
17.5 (s, JP-Se = 770)
92
NR
17
18
40.5 (s)
100(94)
53
NR
NR
32.0 (s, JP-Se = 740)
Reflux in THF for 2 h,
86% yield (ref 18f)
19
20
21.6 (s)
100(93)
100(97)
Reaction in benzene at 20
C for 12 h, yield not
reported (ref 18e)
7.6 (s, JP-Se = 772)
Reflux in THF for 6 h,
57% yield (ref 25d)
21
69.6 (s)
100
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European Journal of Inorganic Chemistry
Reflux in THF for 6 h,
55% yield (ref 25d)
22
68.8 (s, JP-Se = 800)
100
(4 equiv. of E)
aδ in ppm and J in Hz, b Based on 31P{1H} NMR. NR = Not Reported
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After the completion of the reaction, in each case, the product was isolated by dissolving the
reaction mixture in ethyl acetate (5-10 mL) followed by solvent removal under reduced pressure.
The product formation was analyzed by 31P{1H} NMR spectrum of the reaction mixture, which
showed the formation of the corresponding sulfides and selenides in almost quantitative yield.
Only in the case of 8a, 8b and 9b the respective yields were 40%, 92% and 53% (Table 1, entry
15, 16 and 18). The reaction of bis(diphenylphosphino)methane (3) with two equivalents of
elemental sulfur or selenium yielded bischalcogenides (3a′ and 3b′) (Table 1, entry 5 and 6). These
reaction conditions are also suitable for amino phosphines (secondary phosphines) where the
corresponding chalcogenides were obtained in quantitative yields (Table 1, entry 3, 4, 21 and 22).
The reaction of Ph2PH under identical conditions resulted in Ph2P(S)H and Ph2P(Se)H in 75% and
71%, respectively and the formation of Ph2P(O)H was observed in both the cases due to the
oxidation by the moisture present in the system. However, quantitative formation of both the
chalcogenides can be observed if the reaction is carried out in an inert atmosphere. These results
suggest that ball milling is a very useful and efficient method for the synthesis of chalcogenides
of most of the phosphines.
Partial oxidation of bisphosphines with O, S, Se or N3R (Staudinger reaction) to form
bisphosphine-monochalcogenides is an important method for generating the heterodifunctional
ligands which find application in homogeneous catalysis.[21] Due to the presence of both hard- and
soft-donor atoms, these ligands when bound to low-valent soft platinum metals via chelation, can
readily cleave metal–hetero donor atom bond during oxidative addition to form 14 or 16 e− species,
an important step in homogeneous catalysis. In view of this, there is a scope to generate
heterodifunctional ligands using a simple strategy such as controlled oxidation of bisphosphines.
Balakrishna et al. reported the formation of monosulfide and monoselenide derivatives of
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aminobisphosphines by refluxing the bisphosphine and elemental sulfur or selenium in hexanes as
solvent, in which both bisphosphine and their monochalcogenides are insoluble, in almost
quantitative yield.[22] These reactions, which appear to proceed via solid-surface interactions,
prompted us to employ a ball mill strategy for the generation of sulfide and selenide derivatives of
various bi-, tri- or polyphosphines. Reaction of bis(diphenylphosphino)methane (3) with one
equivalent of elemental sulfur or selenium resulted in the formation of monosulfide (3a) and
monoselenide (3b) in 55% and 90% yields, respectively (Table 2, entry 1 and 2). A similar trend
was observed in the case of bisphosphines 5 and 10, wherein monochalcogenides 5a, 5b, 10a and
10b were major products and dichalcogenides obtained as minor products (Table 2, entry 3-6).
Scaled up reactions in the case of 5 (1.5 g) with sulfur and selenium did not affect the yields
Interestingly, in some of the cases, the yields of monosulfides were less than the corresponding
monoselenide derivatives indicating the influence of atomic size of reactants on the product
formation.[23] In the case of bisphosphines, wherever a mixture of both mono- and
bischalcogenides were formed, the products were separated by column chromatography, which is
in contrast to the solution state reactions, where isolation and purification, especially in the case
of partially oxidized bisphosphines is a tedious task owing to the formation of bischalcogenides
31
and due to the presence of unreacted bisphosphines in the reaction mixture. The P{1H} NMR
spectral data of isolated products are listed in Table 2. The formation of chalcogenides was also
supported by various spectroscopic data (see ESI Figures S39 – S53).
An alternative method for the preparation of monochalcogenides is through redistribution method
which involves the interaction of equimolar quantities of bisphosphines and the corresponding
bischalcogenides through chalcogen exchange mechanism.[24] In order to examine this method,
bisphosphine 10 was treated with bischalcogenides 10a′ and 10b′, which resulted in the formation
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of monosulfide (10a) and monoselenide (10b) derivatives in 14% and 74% yield, respectively
(Table 2). To check the reproducibility, the reactions of bisphosphine 10 and disulfide 10a′ were
repeated and exactly the same results were obtained. These results suggest that the selenide
derivatives react faster compared to the sulfide derivatives.[23]
Table 2. Synthesis of monosulfide and monoselenide of bisphosphines using ball milling
%
Conversionc
(Isolated
yield)
S. No.
Phosphine
Chalcogenide
31P{1H} NMR Shifta
40.2 (d, 2JPP = 76) &
55(52)
+
−28.0 (d, 2JPP = 76)
1
+
35.3 (s)
45(40)
30.7 (d, 2JPP = 83, JP-Se
= 728) & −26.9 (d, 2JPP
= 83)
90(85)
+
2
+
10(7)
25.1 (s, JP-Se = 726)
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32.2 (s) & −21.9 (s)
60(56)
+
3
32.5 (s)
40(33)
22.3 (s, JP-Se = 748) &
−22.4 (s)
54
+
4
+
28
22.0 (s, JP-Se = 750)
20.0 (s) & −33.2 (s)
43 (14)b
+
+
5
6
21.6 (s)
38
5.8 (d, 3JPP = 40, JP-Se
=
772 ) & −33.1 (d, 3JPP =
77 (74)b
40 )
+
+
16
7.6 (s, JP-Se = 772 )
aδ in ppm and J in Hz. bYield of the reaction between the bisphosphine and its bischalcogenide. c
conversion based on 31P{1H} NMR.
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Table 3. Synthesis of mixed chalcogenide of bisphosphines using ball milling
Isolated
yield (% )
S. No.
Bischalcogenides
Mixed Chalcogenide 31P{1H} NMR Shifta
35.3 (s)
+
1
93
25.1 (s, JP-Se = 726)
32.5 (s)
+
2
95
21.9 (s, JP-Se = 750)
21.6 (s)
+
3
92
7.6 (s, JP-Se = 772)
aδ in ppm and J in Hz.
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Chalcogen exchange reactions can also be used to synthesize mixed chalcogenides by reacting
disulfides and diselenides in 1:1 molar ratios. Reactions between disulfides (3a′, 5a′ and 10a′) and
diselenides (3b′, 5b′ and 10b′) under ball mill conditions resulted in the formation of the
corresponding monosulfide-monoselenide derivatives (3c, 5c and 10c) in quantitative yields
(Table 3). Although the 31P{1H} NMR spectra did not show any appreciable change in the
chemical shifts due to the sulfide- and selenide-P moieties in the mixed chalcogen derivatives
compared to the corresponding dichalcogenides, the formation of the product was confirmed by
the HRMS analysis where peaks at 503.0203 (calcd. 503.0238, M+Li), 714.0521 (calcd. 714.0522,
M+Na), and 513.0805 (calcd. 513.0086, M+Li) were observed for 3c, 5c and 10c, respectively
(see ESI).
The reactions of PPh3 and bisphosphine 5 with elemental sulfur or selenium were scaled up to 3 g
and 1.5 g scale, respectively, and it did not affect the course of the reaction and in both the cases
the corresponding products 1a, 1b and 5a, 5b were obtained in quantitative yield. However, in the
case of 5 the reaction time was extended by an hour to ensure the completion of the reaction
although it was not necessary.
Structural characterization of the chalcogenides
a
b
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Figure 1. Molecular structure of (a) 2a and (b) 2b with 50% ellipsoid probability. Most of the H-
atoms and co-crystallized water molecule for 2b are omitted for clarity. Selected bond distances
(Å) and bond angles (deg): for 2a: N1‒C1 1.446(5), N1‒P1 1.684(3), P1‒S1 1.936(16), P1‒C34
1.811(5), P1‒C40 1.820(4), C1‒N1‒P1 123.1(3), N1‒P1‒S1 111.98(13), C34‒P1‒S1 114.10(15),
C40‒P1‒S1 113.53(14); for 2b: N1‒C1 1.444(6), N1‒P1 1.674(4), P1‒Se1 2.0906(14), P1‒C34
1.813(6), P1‒C40 1.825(5), C1‒N1‒P1 125.9(3), N1‒P1‒Se1 113.65(16), C34‒P1‒Se1
114.59(19), C40‒P1‒Se1 112.93(18).
The molecular structures of 2a-b and 4b are presented in Figure 1 and Figure 2 and the
crystallographic details are listed in Table 4. Compound 2a crystallizes in the orthorhombic system
with Pbca space group while compounds 2b and 4b crystallize in the monoclinic system with Cc
and I2/a space groups, respectively. Their asymmetric unit consists of one molecule and that of 2b
additionally contains one molecule of water as the solvent of crystallization. As expected, the
geometry around phosphorus in 2a-b is distorted tetrahedral where the P‒S and P‒Se distances are
1.936(16) and 2.0906(14) Å, respectively, which lies in the reported range of P‒S (1.919(1)‒
1.9505(10) Å) and P‒Se (2.0563(14)‒2.1115(7) Å) distances.[25] The P‒Se bond length in 4b is
2.1179(13) Å which is slightly longer than that found in 2b and [{(Se)P(μ-NtBu)}2{1,3-(O)2-
C6H4}]2 (2.0670(4) Å) but is similar to that observed for {tBuHN(tBuNP(Se))2-OCH2}2 (2.1115(7)
Å).[25]
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Figure 2. Molecular structure of 4b with 50% ellipsoid probability. H-atoms are omitted for clarity.
Selected bond distances (Å) and bond angles (deg): C8‒P1 1.825(5), P1‒Se1 2.117(13), P1‒C9
1.812(5), P1‒C15 1.836(5), C8‒P1‒Se1 112.96(16), C9‒P1‒Se1 114.88(16), C15‒P1‒Se1
111.12(17).
Figure 3. Molecular structure of 6a with 50% ellipsoid probability and its dimeric form showing
intermolecular H-bonding. Most of the H-atoms are omitted for clarity. Selected bond distances
(Å) and bond angles (deg): N1‒C13 1.4474(18), N1‒C14 1.3627(19), C13‒P1 1.8384(15), P1‒S1
18
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1.9539(6), P1‒C6 1.845(15), P1‒C12 1.8109(15), N1···N3 2.995, N1‒C13‒P1 109.29(10), C13‒
P1‒S1 112.36(5), C6‒P1‒S1 113.35(5), C12‒P1‒S1 112.17(5), N1‒H1···N3 164.28.
The molecular structures of compounds 6a and 6b are shown in Figures 3 and 4 respectively, and
their crystallographic details are listed in Table 5. Both the compounds crystallize in monoclinic
system with P2(1)/c space group. Molecule 6a contains one while 6b contains two molecules in
the asymmetric unit. The presence of H-bond donor and acceptor within the molecule resulted in
their dimerization in the solid state by virtue of intermolecular N‒H···N H‒bonding (Figures 3
and 4). The P‒S distance of 1.9539(6) Å is longer than that found in 2a while the P‒Se distance of
2.1084(6) Å is slightly longer than that found in 2b [2.0906(14) Å] but is marginally shorter than
that in 4b [2.1179(13) Å].
Figure 4. Molecular structure of 6b with 50% ellipsoid probability and its dimeric form showing
intermolecular H-bonding. Most of the H-atoms are omitted for clarity. Selected bond distances
(Å) and bond angles (deg): N3‒C4 1.355(3), N3‒C5 1.440(3), C5‒P1 1.846(2), P1‒Se1 2.1084(6),
P1‒C6 1.817(2), P1‒C12 1.818(2), N1···N6 3.004, N3···N4 2.988, N3‒C5‒P1 112.90(15), C5‒
19
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P1‒Se1 112.67(8), C6‒P1‒Se1 113.27(7), C12‒P1‒Se1 114.27(7), N6‒H6···N1 145.51, N3‒
H3···N4 169.43.
Figure 5. Molecular structure (top view and side view) of 8b with 50% ellipsoid probability. H-
atoms are omitted for clarity. Selected bond distances (Å) and bond angles (deg): C1‒P1 1.817(3),
P1‒Se1 2.1020(8), P1‒C15 1.819(3), P1‒C21 1.810(3), C1‒P1‒Se1 113.39(10), C15‒P1‒Se1
115.52(10), C21‒P1‒Se1 114.01(10).
Figure 5 and Figure 6 show the molecular structures of compounds 8b and 11a, respectively, and
their crystallographic details are listed in Table 5. Both the molecules crystallize in the monoclinic
system with P2(1)/n and P2(1)/c space groups, respectively. The structure of 8b shows that the
phenyl substituents on the triazole ring makes an angle of around 45 (deg.) with the plane of the
triazole core. The asymmetric unit of 11a contains half of the molecule. The sulfur atoms are
pointed in opposite directions to accommodate the substituents on the N atoms. The P1‒S1
(1.9529(9) Å) and P2‒S2 (1.9440(8) Å) bond distances vary slightly and are longer than those
found in 2a but are similar to those of 6a.
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Figure 6. Molecular structure of tetrasulfide 11a with 50% ellipsoid probability. H-atoms are
omitted for clarity. Selected bond distances (Å) and bond angles (deg): N1‒P1 1.7188(19), N1‒P2
1.7060(19), P1‒S1 1.9529(9), P1‒S2 1.9440(8), P1‒C2 1.812(2), P1‒C8 1.818(3), P2‒C14
1.809(3), P2‒C20 1.814(3), P1‒N1‒P2 133.31(12), N1‒P1‒S1 113.97(8), C2‒P1‒S1
112.85(8),C8‒P1‒S1 109.51(8),N1‒P2‒S2 112.13(7), C14‒P2‒S2 109.21(8), C20‒P2‒S2
110.38(8).
21
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Table 4. Crystallographic information for compounds 2a, 2b and 4b
2a
2b
4b
Empirical formula
Formula weight
Wavelength (Å)
Temperature (K)
Crystal system
Space group
a/Å
C45H38NPS
655.79
0.71075
150(2)
C45H40NOPSe
720.74
C20H16N3PSe
408.29
0.71075
150(2)
0.71075
150(2)
orthorhombic
Pbca
Monoclinic
Cc
Monoclinic
I2/a
20.246(7)
15.490(6)
23.316(9)
90
9.703(3)
43.815(14)
9.179(3)
107.724(4)
3717(2)
4
18.860(15)
8.069(5)
24.696(15)
106.90(5)
3596(4)
8
b/Å
c/Å
β/degree
Volume (Å3)
7343.5(9)
8
Z
Dcalcd, g cm-3
µ/mm-1
1.186
1.284
1.508
0.164
1.088
2.184
F(000)
2768
1488
1648
Crystal size/mm
 range (degree)
Total/ unique no. of
reflns.
0.21x0.11x0.09 0.18x0.07x0.04 0.21x0.16x0.08
4.8 to 48.99
3.01 to 24.99
3.08 to 25.00
32846/6442
22530/6330
17665/3164
Rint
GOF (F2)
0.1924
1.049
0.0517
1.026
0.1054
1.127
R1, wR2
0.0801, 0.1836 0.0482, 0.1264 0.0939, 0.2305
22
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
Table 5. Crystallographic information for compounds 6a, 6b, 8b and 11a
6a
C17H16N3PS
325.36
6b
C17H16N3PSe
372.26
8b
C26H20N3PSe
484.38
11a
C50H44N2P4S4
924.99
Empirical formula
Formula weight
Wavelength (Å)
Temperature (K)
Crystal system
Space group
a/Å
0.71075
150(2)
0.71075
150(2)
0.71075
150(2)
0.71075
150(2)
Monoclinic
P2(1)/c
15.790(3)
10.787(19)
9.819(18)
102.512(13)
1632.8(5)
4
Monoclinic
P2(1)/c
Monoclinic
P2(1)/n
13.5392(9)
8.0627(5)
20.6916(16)
97.374(7)
2240.1(3)
4
Monoclinic
P2(1)/c
17.848(3)
9.6365(16)
19.572(4)
99.183(2)
3323.1(10)
8
12.8507(7)
10.3146(5)
17.7617(9)
109.162(6)
2223.9(2)
2
b/Å
c/Å
β/degree
Volume (Å3)
Z
Dcalcd, g cm-3
µ/mm-1
1.324
1.488
1.436
1.381
0.296
2.355
1.766
0.397
F(000)
680
1504
984
964
Crystal size/mm
 range (degree)
Total/ unique no. of
reflns.
0.23x0.20x0.19 0.26x0.24x0.06 0.18x0.14x0.06
0.19x0.07x0.05
2.30 to 24.99
3.25 to 25.00
3.08 to 25.00
1.99 to 24.99
13966/2869
16312/5825
11568/3945
14539/3916
Rint
GOF (F2)
0.0265
1.056
0.0341
1.039
0.0705
1.054
0.0580
1.047
R1, wR2
0.0306, 0.0777 0.0324, 0.0751 0.0494, 0.1164
0.0411, 0.0898
23
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
Conclusions
A fast, efficient and green route for the syntheses of sulfides and selenides of tertiary phosphines,
aminophosphines and a variety of bisphosphines using a rotary ball mill has been successfully
developed. The method is highly attractive due to the solvent-free nature, short reaction time and
quantitative product formation, which makes this green chemistry protocol a real alternative to the
conventional method. The scope of application was shown by using mono-, bis- and
tetraphosphines and also in scale up reactions. Further, the short reaction time and lower rotation
frequency results in energy saving. We are currently exploring this method in making sulfur
derivatives of organic molecules and also in thiolation reactions.
Experimental Section
Unless otherwise specified, all reagents were purchased from commercial suppliers and used
without further purification. Sulphur powder (S8) (99.5 %) was purchased from Merck Chemicals
and black selenium powder (Se8) (99.5 %) was obtained from Loba chemicals and used as such
without further purification. The phosphines were synthesized according to the literature
procedures.[26] The ball-milling experiments were performed using a Vertical Planetary Ball Mill
model “XQM-0.4A” with four 45-mL grinding bowls and 5-15 mm diameter grinding balls made
of zirconium oxide. The NMR spectra were recorded at 500 MHz (1H) and 202 MHz (31P{1H}) or
400 MHz (1H) and 162 MHz (31P{1H}) ( in ppm) using Bruker AV 500/400 spectrometer. The
spectra were recorded in CDCl3 solution with CDCl3 as an internal lock; TMS and 85% H3PO4
1
were used as external standards for H and 31P{1H} NMR, respectively. Positive shifts lie
downfield to the standard in all of the cases. Mass spectra were recorded using a Bruker Maxis
Impact LC-q-TOF Mass Spectrometer.
24
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
Representative procedure for the solid state synthesis of chalcogenides
Triphenylphosphine (0.525 g, 2.000 mmol) and elemental sulfur (0.064, 2.000 mmol) were both
taken in a jar and one set of ceramic balls (1 x 15 mm, 2 x 12 mm, 7 x 10 mm, 12 x 8 mm and 40
x 5 mm) were added to it. The jar was then fixed in the rotary ball mill and was rotated at a
frequency of 450 rpm for 4 h. Extraction of compound by ethyl acetate (10 mL) and subsequent
removal of the solvent yielded Ph3P=S, 1a as a white crystalline solid. Yield: (0.560 g, 95 %).
31P{1H}NMR (202 MHz, CDCl3, 25 °C, ppm):  43.3 (s).
Chalcogenides of all other phosphines were synthesized using the exact same procedure and the
results are listed in tables 1-3.
Representative procedure for the preparation of mono chalcogenides
Bis(diphenylphosphino)methane (0.20 g, 0.520 mmol) and elemental sulfur (0.017 g, 0.520 mmol)
were both taken in a jar and one set of ceramic balls (1 x 15 mm, 2 x 12 mm, 7 x 10 mm, 12 x 8
mm and 40 x 5 mm) were added to it. The jar was then fixed in the rotary ball mill and was rotated
at a frequency of 450 rpm for 4 h. Extraction of compound by ethyl acetate (5 mL) and subsequent
removal of the solvent yielded mixture of mono as well as dichalcogenide products, which was
separated by column chromatography using petroleum ether/ethyl acetate (1:9) ratio as eluent.
31
Yield: dppmS (3a) 0.113 g (52 %) and dppmS2 (3a′) 0.087 g (40 %). P{1H}NMR (162 MHz,
CDCl3, 25 °C, ppm):  dppmS (3a) 40.4 and 27.88 (d, 1JPP = 76.1 Hz) and dppmS2 35.31 (s).
X-ray crystallography
Suitable single crystals of 2a-b, 4b, 6a-b, 8b and 11a for X-ray diffraction studies were obtained
by slow evaporation of their solution in dichloromethane/petroleum ether (v/v 2/1). A crystal of
25
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
each of these compounds suitable for single crystal X-ray diffraction was mounted in a cryoloop
with a drop of paratone oil and placed in the cold nitrogen stream of the kryoflex attachment of
the Rigaku Saturn 724+ (4×4 bin mode) diffractometer. Data were collected at 150 K using
graphite-monochromated MoKα radiation (λ = 0.71073 Å) with the ω-scan technique. The data
were reduced by using CrysalisPro Red 171.38.43 software. The structures were solved by
ShelXT[27] using OLEX2[28] by direct methods and refined by least-squares against F2 utilizing the
software package ShelXL-97[29]. All non-hydrogen atoms were refined anisotropically and all
hydrogen atoms were refined isotropically on calculated positions using riding models.
Crystallographic refinement data are given in Table 4 and Table 5. Crystallographic data for the
structures reported in this paper have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC 1563578 (2a), 1563579 (2b), 1563580 (4b),
1563581 (6a), 1563582 (6b), 1563583 (8b), and 1563584 (11a).
Acknowledgements
We are grateful to the Science & Engineering Research Board, New Delhi, India, for financial
support of this work through grant No.SB/S1/IC-08/2014. SK, VSK, MKP and LR thank CSIR
and UGC New Delhi, for Senior Research Fellowships (SRF). RK thanks Indian Institute of
Technology Bombay, Mumbai for postdoctoral fellowship. We also thank the Department of
Chemistry for instrumentation facilities.
Supplementary information
Electronic supplementary information (ESI) available. CCDC 1563578‒1563584. For ESI and
crystallographic data in CIF or other electronic format see DOI:10.1039/x0xx00000x.
26
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10.1002/ejic.201701414
European Journal of Inorganic Chemistry
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