Molecular and crystal structures of tris(3-methylphenyl)phosphine and its chalcogenides

Article abstract of DOI:10.1016/j.molstruc.2019.07.094

The molecular and crystal structures of tris(3-methylphenyl)phosphine, tris(3-methylphenyl)phosphine oxide, tris(3-methylphenyl)phosphine sulfide and tris(3-methylphenyl)phosphine selenide were determined by X-ray diffraction. It was previously indicated

Full text of DOI:10.1016/j.molstruc.2019.07.094

Journal of Molecular Structure 1197 (2019) 681e690
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Molecular and crystal structures of tris(3-methylphenyl)phosphine
and its chalcogenides
I.V. Sterkhova*, V.I. Smirnov, S.F. Malysheva, V.A. Kuimov, N.A. Belogorlova
A. E. Favorskii Irkutsk Institute of Chemistry, Siberian Division of Russian Academy of Sciences, 1 Favorskii Street 664033, Irkutsk, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
The molecular and crystal structures of tris(3-methylphenyl)phosphine, tris(3-methylphenyl)phosphine
oxide, tris(3-methylphenyl)phosphine sulfide and tris(3-methylphenyl)phosphine selenide were deter-
mined by X-ray diffraction. It was previously indicated that phosphine oxide should be isostructural with
phosphine sulfide and phosphine selenide. However, this statement was not confirmed experimentally:
the geometrical structure of the phosphine oxide is closer to the geometry of the phosphine. Tris(3-
methylphenyl)phosphine, tris(3-methylphenyl)phosphine sulfide and tris(3-methylphenyl)phosphine
selenide crystallize in the orthorhombic space group Pbca, while the phosphine oxide molecules in the
crystal are packaged in the space group Pca21 with screw axis.
Received 12 April 2019
Received in revised form
25 June 2019
Accepted 24 July 2019
Available online 26 July 2019
Keywords:
tris(3-methylphenyl)phosphine
tris(3-methylphenyl)phosphine
chalcogenides
© 2019 Published by Elsevier B.V.
Crystal structure
DFT calculations
1. Introduction
tritolyl-substituted phosphines possess anti-bacterial and anti-
cancer activity [25,26].
Phosphines and their derivatives represent an important class of
compounds for life sciences and the chemical industry [1]. In
general, trivalent phosphines are used in numerous classic organic
transformations [2e6], such as the Mitsunobu reaction [7], the
Wittig reaction [8,9], Mukaiyama-Corey lactonization [10], the
Appel reaction [11], Staudinger reaction [12] and so on. Further-
more, in organometallic chemistry they represent prime ligands to
control most transition metal catalyzed reactions due to their
excellent metal ligation properties. Functionalized triar-
ylphosphines are widely used as ligands for transition metal com-
plexes and as synthetic intermediates for the production of new
materials [13].
For example, tolyl-substituted phosphine ligands are part of
various transition metal complexes that catalyze various processes
in industrial synthesis [14e19], are included in the meso-porous
zeolite structures [20], and are used as new polymeric materials
[21]. Copper (I) complexes with m-tolylphosphine ligands are
promising for the production of OLEDs [22,23], Eu (III) clusters
exhibit luminescent properties [24], and palladium complexes of
Tritolylphosphine chalcogenides have been used as ligands for
transition metal catalysts that catalyze the epoxidation reaction
[27], hydroformylation [28], for luminescent materials [24], as well
as nonlinear optics [29], as building blocks, including restoration
[30], C-H amidation [31] and ortho-alkenylation [32]. The Au (I)
complexes of tritolylphosphine sulfide and selenide possess activ-
ity against rheumatoid arthritis [33].
Thus, the determination of the molecular structure of
substituted phosphines and their chalcogenides and the study of
the influence of the nature of substituents on the phosphorus atom
both on the geometry of molecules and on the features of inter-
molecular binding in a crystal is an important task. Such studies are
necessary to explain the physicochemical properties of the com-
pounds under study, including their complexing ability, to evaluate
and predict their reactivity. In this paper we discussed the features
of the preparation, molecular and crystal structures of tris(3-
methylphenyl)phosphine
1
and its chalcogenides: tris(3-
methylphenyl)phosphine oxide 2, tris(3-methylphenyl)phosphine
sulfide 3 and tris(3-methylphenyl)phosphine selenide 4.
* Corresponding author.
E-mail address: irina_sterkhova@irioch.irk.ru (I.V. Sterkhova).
https://doi.org/10.1016/j.molstruc.2019.07.094
0022-2860/© 2019 Published by Elsevier B.V.

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I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
2. Experimental section
3JHH ¼ 8.1 Hz, 4JPH ¼ 2.9 Hz), 7.61 (2,6-H, C6H4, 6H, dd, 3JHH ¼ 8.1 Hz,
3JPH ¼ 13.6 Hz). 13C NMR (100.62 MHz, CDCl3,
d, ppm): 21.37 (Me, d,
1
2.1. Synthesis
5JPC ¼ 1.7 Hz), 128.85 (1-C, C6H4, d, JPC ¼ 79.2 Hz), 129.12 (3,5-C,
C6H4, d, 3JPC ¼ 12.9 Hz), 132.53 (2,6-C, C6H4, d, 2JPC ¼ 11.2 Hz), 141.85
4
2.1.1. Tris(3-methylphenyl)phosphine 1
(4-C, C6H4, d, JPC ¼ 3.2 Hz). 31P NMR (161.98 MHz, CDCl3,
d, ppm):
1
Tris (3-methylphenyl) phosphine 1 was synthesized according
to the procedure given in the literature [34].
34.59 (s þ d satellites: JPSe ¼ 720.0 Hz). 77Se NMR (76.31 MHz,
1
CDCl3,
d
, ppm): ꢁ260.47 (d, JPSe ¼ 720.0 Hz). For C21H21PSe calcd
Colorless crystals, m.p. 134 ꢀC (i-PrOH). FTIR (KBr, cmꢁ1): 3066,
3011, 2970, 2919, 2864, 1915, 1813, 1654, 1595, 1491, 1446, 1392,
1303, 1182, 1088, 1018, 807, 707, 620, 508. 1H NMR (400.13 MHz,
(%): С, 65.80; Н, 5.52; Р, 8.08; Se, 20.60. Found: С, 65.72; Н, 5.51; Р,
7.98; Se, 20.12.
CDCl3,
d, ppm): 2.36 (Me, 9H, s), 7.16 (3,5-H, C6H4, 6H, d,
2.2. X-ray study and refinement
3
3
3JHH ¼ 7.5 Hz), 7.23 (2,6-H, C6H4, 6H, t, JHH ¼ 7.5 Hz, JPH ¼ 7.5 Hz).
13C NMR (100.62 MHz, CDCl3,
d, ppm): 21.22 (Me), 129.21 (3,5-C,
Single crystals of compounds 1, 3 and 4 were obtained by re-
crystallization from isopropanol, compound 2 e from heptane.
Crystal data were collected on a Bruker D8 Venture diffractometer
with MoKa radiation (l ¼ 0.71073) using the 4 and
C6H4, d, 3JPC ¼ 6.9 Hz), 133.60 (2,6-C, C6H4, d, 2JPC ¼ 19.5 Hz), 134.16
(1-C, C6H4, d, JPC ¼ 9.2 Hz), 138.46 (4-C, C6H4). 31P NMR
1
(161.98 MHz, CDCl3,
d
, ppm): ꢁ7.63. For C21H21P calcd (%): С, 82.87;
u scans. The
Н, 6.95; Р, 10.18. Found: С, 82.84; Н, 6.96; Р, 9.98.
structures were solved and refined by direct methods using the
SHELX programs set [35]. Data were corrected for absorption effects
using the multi-scan method (SADABS). Nonhydrogen atoms were
refined anisotropically using SHELX [35] (Sheldrick, 2008). All
hydrogen atoms were found via Fourier difference maps. CCDC
1921474 (1), 1577514 (2), 1577515 (4), 1577516 (3) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
2.1.2. Tri(3-methylphenyl)phosphine oxide 2
Phosphine 1 (0.22 g, 0.723 mmol) dissolved in EtOH (5 ml) and
aq.H2O2 (34%, 0.075 g) was added and resulted mixture was stirred
during 1 h at room temperature. In 1 h MnO2 was added to quench
the traces of H2O2. Then the mixture was filtered through K2CO3
and EtOH was removed in vacuum to give the phosphine oxide 2 as
white powder.
Yield 0.229 g (99%). M.p. 148-150 ꢀC (heptane), FTIR (KBr, cmꢁ1):
3024, 2921, 2862, 2819, 1922, 1820, 1656, 1599, 1499, 1444, 1399,
1310, 1175, 1115, 1025, 807, 660, 523, 464; 1H NMR (400.13 MHz,
2.3. NMR spectroscopy
1H, 13C, 31P NMR spectra were recorded on a Bruker DPX
400 MHz (400.13, 100.61, 161.98 and 76.31 MHz, respectively) with
cyclohexane as an internal standard.
CDCl3,
d, ppm): 2.35 (Me, 9H, s), 7.16 (3,5-H, C6H4, 6H, br.d,
3JHH ¼ 7.9 Hz), 7.52 (2,6-H, C6H4, 6H, dd, 3JHH ¼ 7.9 Hz,
3JPH ¼ 11.8 Hz). 13C NMR (100.62 MHz, CDCl3,
d, ppm): 21.55 (Me),
3
129.14 (3,5-C, C6H4, d, JPC ¼ 12.6 Hz), 129.45 (1-C, C6H4, d,
1JPC ¼ 107.5 Hz), 132.10 (2,6-C, C6H4, d, JPC ¼ 10.4 Hz), 142.21 (4-C,
2
2.4. IR spectroscopy
C6H4, d, 4JPC ¼ 2.8 Hz); 31P NMR (161.98 MHz, CDCl3,
d, ppm): 27.49.
For C21H21PO calcd (%): С, 78.73; Н, 6.61; Р, 9.67. Found: С, 78.65; Н,
6.59; Р, 9.47.
The FTIR spectra were taken on a FTIR Spectrometer Varian
3100. For neutral compounds the spectra were recorded in KBr
pellets.
2.1.3. Phosphine sulfide 3 and phosphine selenide 4
Phosphine 1 (0.21 g, 0.69 mmol) was dissolved in Et2O (5 ml)
and elemental sulfur or selenium (0.70 mmol) was added and
resulted mixture stirred during 1 h at room temperature. Then the
mixture was filtered off and Et2O was removed to give the phos-
phine chalcogenide 3 and 4 as powders.
3. Results and discussion
3.1. Synthetic features
Oxidation of phosphines (III) remains the most direct way to
obtain phosphine-chalcogenides. The procedures for oxidation
with elemental sulfur and selenium described in the literature
proceed in benzene (toluene or chloroform) by boiling the reagents
for 4-48 h [36,37].
In order to improve the method of obtaining phosphine-
chalcogenides, we chose tris(3-methylphenyl)phosphine 1 as a
model substrate, which was synthesized using the procedure given
in literature [34]. Oxidation of phosphine 1 with elemental sulfur or
selenium was carried out in diethyl ether, phosphine oxide was
prepared by reacting phosphine 1 with hydrogen peroxide in EtOH.
All experiments were performed at room temperature. It was
established that when mixing of phosphine and oxidizing agents,
the reaction with elemental sulfur or selenium ends in 1 h, and the
reaction in EtOH also ends in 1 h at 40 ꢀC.
2.1.4. Tri(3-methylphenyl)phosphine sulfide 3
Yield 0.229 g (99%). M.p. 189-190 ꢀC (i-PrOH). FTIR (KBr, cmꢁ1):
3018, 2920, 2865, 1921, 1819, 1654, 1595, 1494, 1444, 1396, 1304,
1184, 1100, 1023, 808, 687, 645, 578, 510, 440. 1H Я
МР (400.13 MHz,
CDCl3,
d, ppm): 2.40 (Me, 9H, s), 7.24 (3,5-H, C6H4, 6H, dd,
3JHH ¼ 8.2 Hz, 4JPH ¼ 2.7 Hz), 7.61 (2,6-H, C6H4, 6H, dd, 3JHH ¼ 8.2 Hz,
3JPH ¼ 13.1 Hz). 13C NMR (100.62 MHz, CDCl3,
d, ppm): 21.10 (Me, d,
5JPC ¼ 1.4 Hz), 128.81 (3,5-C, C6H4, d, JPC ¼ 12.9 Hz), 129.74 (1-C,
3
C6H4, d, 1JPC ¼ 87.5 Hz), 131.87 (2,6-C, C6H4, d, 2JPC ¼ 11.1 Hz), 141.48
(4-C, C6H4, d, JPC ¼ 3.1 Hz). 31P NMR (161.98 MHz, CDCl3,
d, ppm):
4
42.53. For C21H21PS calcd (%):С, 74.97; Н, 6.29; Р, 9.21; S, 9.53.
Found: С, 74.86; Н, 6.27; Р, 9.18; S, 9.41.
2.1.5. Tri(3-methylphenyl)phosphine selenide 4
Yield 0.262 g (99%). M.p. 199-200 ꢀC (i-PrOH). RTIR (KBr, cmꢁ1):
3043, 3026, 2920, 2859, 1914, 1645, 1595, 1494, 1444, 1394, 1305,
1184, 1097, 1021, 805, 704, 644, 625, 505, 438. 1H NMR (400.13 MHz,
In all experiments, yields of the obtained phosphine chalco-
genides are about 99%. A comparison of our optimized real-time
oxidation reaction conditions with those already described
CDCl3,
d, ppm): 2.40 (Me, 9H, s), 7.23 (3,5-H, C6H4, 6H, dd,

I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
683
[36,37] shows that our system under the conditions of “mixing and
stirring”, as described above, is the fastest method and allows to
obtain selectively pure tris(3-methylphenyl)phosphine chalcogen-
ides. The proposed system does not contain additives and only a
small stoichiometric excess of oxidant (sulfur, selenium or
hydrogen peroxide) is used, the oxidation is completed faster than
boiling in benzene or toluene.
two in the opposite direction (Fig. 2c and d). The geometric char-
acteristics of the molecular and crystalline structure of compounds
1, 3, and 4 are close to those established earlier [39].
The CeC bond lengths in compounds 1-4 are close to the
average, in the phenyl fragments they range from 1.375 to 1.405 Å,
in C-Me they are 1.502e1.512 Å. The average values of the angles
CePeC are 101.7, 106.4, 106.6, and 106.6ꢀ in compounds 1-4,
respectively, which is 3e8ꢀ less than the ideal pyramidal angle
(109.5ꢀ). The average values of the CePeX angles (where X ¼ O, S
and Se) in compounds 2-4 are close to 112.52, 112.55, and 112.20ꢀ,
respectively, which is slightly greater than the ideal pyramidal
angle.
The average value of P-C interatomic distance in phosphine 1 is
1.834 Å, the C-P-C angles are 101.72ꢀ, which is close to the values of
these parameters in triphenylphosphine [43] (1.831 Å and 102.8ꢀ),
tris(pyrenyl)phosphine [44] (1.838 Å and 102.38ꢀ) and tris(1-
naphtalenyl)phosphine [45] (1.837 Å and 102.43ꢀ). In phosphine
oxide 2, the mean value of the PeC bond lengths is 1.806 Å, the P]
O bond length is 1.492 Å, which is slightly different from the values
in tris(pyrenyl)phosphine oxide [41] (1.826 (P-C) and 1.481 Å (P-
O)), but very close to the values of the bonds Р-С and Р ¼ О in tri-
phenylphosphine oxide [46] (1.802 and 1.487 Å). In phosphine
sulfide 3 and phosphine selenide 4, the mean values of Р-С bond
lengths are very close and equal to 1.814 and 1.816 Å, respectively.
The bond length of P]S in compound 3 is 1.957 Å, which is close to
the values of this bond in such compounds as triphenylphosphine
sulfide (1.950 Å) [47] and bis(2-(dimethylaminomethyl)phenyl)
phenylphosphine sulfide (1.955 Å) [48]. The P]Se bond length in
compound 4 is 2.105 Å, which is close to the values of this bond in
3.2. Structural analysis
The molecular structures of phosphine 1 and its chalcogenides
2-4 are depicted in Fig. 1. Crystal data, data collection and structure
refinement details are summarized in Table 1. Principal bond dis-
tances, bond angles and torsion angles are presented in Table 2.
The literature contains data on the molecular structure of tris(2-
methylphenyl)substituted phosphine and its chalcogenides [38],
tris(3-methylphenyl)substituted phosphine, its sulfide and selenide
[39], and tris(4-methylphenyl)substituted phosphine selenide in
the solid state [40]. However, the structures of these phosphines are
mainly considered from the point of view of their participation as
ligands in complexes with metals.
In the asymmetric units of compounds 1-4 there are one
molecule, the disordering of methyl group (C19) is observed for 1
(Fig. 1). For the molecular structures of tri(3-methylphenyl)phos-
phine 1 and its halcogenides 2-4, the characteristic propeller
conformation type (Fig. 2) [41,42], in which two of the three re-
pellent substituents are deployed symmetrically about the Cg-P
axis for phosphine 1 and the Cg-P-(O, S, Se) axis for phosphine
chalcogenides 2-4. The torsion angles Cg1P1C1C2, Cg1P1C7C12 and
Cg1P1C13C18 in phosphine 1 are ꢁ131.80, 129.31 and ꢁ142.85ꢀ, in
phosphine oxide 2 -154.61, ꢁ57.57 and ꢁ22.94ꢀ, in phosphine
sulfide 3 166.17, ꢁ57.60 and ꢁ24.97ꢀ and in phosphine selenide 4
165.47, ꢁ59.53 and ꢁ25.06ꢀ (Fig. 2aed). This arrangement corre-
sponds to cis, cis, trans- orientation of tolyl fragments with respect
to the P ¼ X bond (X ¼ LP, O, S, Se) in compounds 1e4. In phosphine
1, the distance from the P atom to the centroid of the base of the
C1C7C13 (Cg1) pyramid (Fig. 2a) is 0.815 Å; in compounds 2-4,
these distances are 0.692 Å, 0.690 Å and 0.686 Å, respectively
(Fig. 2bed). Thus, the height of the pyramid depends on the pres-
ence and nature of the substituent X at the phosphorus atom and
decreases in the series: X ¼ LP > O > S > Se. (LP ¼ lone pair).
Geometrically, the crystal structure of the phosphine oxide
molecule 2 is closer to the molecular structure of phosphine 1,
which contradicts the previously published data, which talked
about the isostructural character of all chalcogen-substituted
tris(3-methylphenyl)phosphine [39]. In compounds 1 and 2, the
two methyl groups of the tolyl substituents are turned towards LP
of the phosphorus atom in phosphine 1, and towards the oxygen
atom in phosphine oxide 2, one methyl group is turned in the
opposite direction (Fig. 2a and b). In contrast, in the phosphine
sulfide 3 and phosphine selenide 4 molecules, the methyl groups
are different: one is turned in the direction of the heteroatom, and
other
similar
structures,
for
example,
in
tris(3-
trifluoromethylphenyl)phosphine selenide (2.093 Å) [49] and in
tris(4-fluorophenyl)phosphine selenide (2.110 Å) [50].
Thus, it can be seen from the above data that the length of the
PeC bond in structures 1-4 is affected by the presence (or lack) of
an heteroatom at the phosphorus atom, and the higher the elec-
tronegativity of this heteroatom, the shorter the PeC distance.
Therefore, the PeC bond length decreases in row 1 > 4 > 3 > 2:
LP > Se > S > O.
Compounds 1, 3 and 4 crystallize in the orthorhombic space
group Pbca, 3 and 4 are isomorphic, their crystal lattice parameters
are close to those described in Ref. [39], whereas crystal of 1 has
completely different unit cell parameters. The molecules of com-
pound 2 in the crystal are packed in the space group Pca21. Frag-
ments of the crystal structures of compounds 1-4 are shown in
Fig. 3(aed).
The crystal structure of phosphines 1-4 is formed due to weak
non-covalent interactions (Fig. 4aed). In the crystal of compound 1,
the length of the short contacts C/H between the carbon atoms of
the benzene ring and the hydrogens of the methyl groups of
adjacent molecules is 2.869 Å (Fig. 4a). The shortest intermolecular
contacts are observed between the oxygen atoms of phosphine
oxide 2 and the hydrogen atoms of the methyl groups of the

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I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
Fig. 1. Molecular structures of phosphine 1, phosphine oxide 2, phosphine sulphide 3 and phosphine selenide 4 (50% probability ellipsoids).

I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
685
Table 1
Crystal data, details of measurements and structure refinement for compounds 1e4.
Compound
1
2
3
4
Empirical formula
Mr, g$molꢁ1
Crystal system
Space group
a/Å
C21H21
304.35
orthorhombic
P b c a
15.945(2)
10.367(1)
20.031(1)
90, 90, 90
3311.2(3)
8
1.221
0.161
4.80e60.14
0.30 ꢂ 0.40 ꢂ 0.42
colorless prism
1296
P
C21H21PO
320.35
orthorhombic
P c a 21
10.003(1)
15.144(2)
11.334(1)
90, 90, 90
1716.9(3)
4
1.239
0.162
4.88e60.09
0.13 ꢂ 0.30 ꢂ 0.50
colorless plate
680
C21H21PS
336.41
orthorhombic
P b c a
10.234(1)
12.010(1)
29.064(2)
90, 90, 90
3572.3(4)
8
1.251
0.268
4.86e60.16
0.10 ꢂ 0.10 ꢂ 0.40
colorless prism
1424
C21H21PSe
383.31
orthorhombic
P b c a
10.272(1)
12.276(1)
29.151(1)
90, 90, 90
3675.9(2)
8
1.385
2.127
5.35e60.14
0.10 ꢂ 0.13 ꢂ 0.43
colorless prism
1568
b/Å
c/Å
a, b, g,ꢀ
Volume/Å3
Z
Densitycalc/g$cmꢁ3
Abs. coeff., mmꢁ1
2
Q
range/ꢀ
Crystal size/mm
Crystal habit
F(000)
Index ranges
ꢁ22 ꢃ h ꢃ 22,
ꢁ13 ꢃ k ꢃ 14,
ꢁ28 ꢃ l ꢃ 21
40607
ꢁ14 ꢃ h ꢃ 14,
ꢁ21 ꢃ k ꢃ 21,
ꢁ15 ꢃ l ꢃ 15
80128
ꢁ14 ꢃ h ꢃ 14,
ꢁ16 ꢃ k ꢃ 16,
ꢁ40 ꢃ l ꢃ 40
175774
ꢁ14 ꢃ h ꢃ 14,
ꢁ17 ꢃ k ꢃ 17,
ꢁ41 ꢃ l ꢃ 41
132794
Refl. collected
Indep. reflections
Max./min. transm.
Num. ref. param.
4858
0.7460/0.6690
215
5017
0.8400/0.7600
211
5250
0.7460/0.7076
211
5396
0.7460/0.6222
211
R1/wR2 [I > 2
R1/wR2 (all data)
Goodness-of-fit
s
(I)]
0.0433/0.0959
0.0675/0.1057
1.033
0.0349/0.0773
0.0475/0.0827
1.065
0.0346/0.0818
0.0472/0.0885
1.051
0.0345/0.0727
0.0463/0.0766
1.125
Larg. diff. peak/hole, e$Åꢁ3
Weight scheme,
P¼(F2oþ2F2c)/3
0.408/ꢁ0.289
0.279/ꢁ0.200
0.342/ꢁ0.306
0.419/ꢁ0.384
w ¼ 1/[
s
2(F2o)þ
w ¼ 1/[
s
2(F2o)þ
w ¼ 1/[
s
2(F2o)þ
w ¼ 1/[
s
2(F2o)þ
(0.0445 P)2þ
(0.0352 P)2þ
(0.0343 P)2þ
(0.0259 P)2þ
1.6469 P]
0.4738 P]
2.5537 P]
3.4923 P]
Table 2
Selected bond lengths, bond and torsion angles in compounds 1e4.
Bond
l, Å
Angle
4,ꢀ
Torsion angle
q,ꢀ
Compound 1
P1-C1
P1-C7
P1-C13
C1-C2
C2-C3
C3-C4
C4-C5
Compound 2
O1-P1
P1-C1
P1-C7
P1-C13
C1-C2
C2-C3
C3-C4
Compound 3
S1-P1
P1-C1
P1-C7
P1-C13
C1-C2
1.836(1)
1.835(1)
1.832(1)
1.405(2)
1.397(2)
1.390(2)
1.384(2)
C1-P1-C7
C1-P1-C13
C7-P1-C13
C1-C2-C3
C2-C3-C4
C2-C1-P1
C12-C7-P1
101.9(1)
101.7(1)
101.7(1)
121.7(1)
118.3(1)
117.1(1)
123.7(1)
C1-C2-C3-C4
C3-C2-C1-P1
C13-P1-C7-C12
C1-P1-C7-C12
C3-C2-C1-C6
P1-C1-C6-C5
C2-C3-C4-C5
1.3(2)
ꢁ179.1(1)
0.3(1)
105.1(1)
ꢁ0.6(2)
178.0(1)
ꢁ0.9(2)
1.492(2)
1.806(2)
1.804(2)
1.807(2)
1.400(3)
1.393(3)
1.393(3)
O1-P1-C1
O1-P1-C7
O1-P1-C13
C1-P1-C7
C1-P1-C13
C7-P1-C13
C1-C2-C3
111.9(1)
113.7(1)
112.0(1)
105.8(1)
106.7(1)
106.3(1)
121.7(1)
C1-C2-C3-C4
C3-C2-C1-P1
O1-P1-C1-C2
O1-P1-C1-C6
C7-P1-C1-C6
C13-P1-C1-C6
C2-C3-C4-C5
ꢁ0.4(3)
ꢁ179.9(2)
ꢁ26.1(2)
154.0(2)
ꢁ81.7(2)
31.2(2)
ꢁ0.6(3)
1.957(1)
1.817(1)
1.811(1)
1.814(1)
1.394(2)
1.395(2)
1.392(2)
S1-P1-C1
S1-P1-C7
S1-P1-C13
C1-P1-C7
C1-P1-C13
C7-P1-C13
C1-C2-C3
112.5(1)
112.0(1)
112.5(1)
107.2(1)
106.0(1)
106.1(1)
121.4(1)
C1-C2-C3-C4
C3-C2-C1-P1
S1-P1-C1-C2
S1-P1-C1-C6
C7-P1-C1-C6
C13-P1-C1-C6
C2-C3-C4-C5
ꢁ0.8(2)
179.5(1)
ꢁ14.3(1)
164.6(1)
ꢁ71.8(1)
41.2(1)
C2-C3
C3-C4
0.2(2)
Compound 4
Se1-P1
P1-C1
P1-C7
P1-C13
C1-C2
2.105(1)
1.821(2)
1.810(2)
1.816(2)
1.392(2)
1.392(3)
1.394(3)
Se1-P1-C1
Se1-P1-C7
Se1-P1-C13
C1-P1-C7
C1-P1-C13
C7-P1-C13
C1-C2-C3
112.6(1)
111.7(1)
112.3(1)
106.8(1)
106.6(1)
106.5(1)
121.4(2)
C1-C2-C3-C4
C3-C2-C1-P1
Se1-P1-C1-C2
Se1-P1-C1-C6
C7-P1-C1-C6
C13-P1-C1-C6
C2-C3-C4-C5
ꢁ1.0(3)
ꢁ179.7(1)
ꢁ14.4(1)
165.2(1)
ꢁ71.8(2)
41.7(2)
C2-C3
C3-C4
0.5(3)

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I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
Fig. 2. Comparison of molecular geometry of 1e4 (aed) (50% probability ellipsoids, H atoms are omitted for clarity).
neighboring molecules P]O/HeC, 2.5 Å in length (Fig. 4b).
In phosphine sulfide 3, each molecule is associated with two
adjacent molecules with short contacts formed by the sulfur atom
with hydrogen atoms of the methyl and phenyl groups (2.814 and
2.910 Å) (Fig. 4c). Like phosphine sulfide, each molecule of phos-
phine selenide 4 is associated with two neighboring molecules by
short contacts P]Se$$$HC (2.806 and 2.960 Å) (Fig. 4d).
and evaluated the stability of tris(3-methylphenyl)phosphine
complexes with Cu(I) [22]. The spatial structure of tris(3-
methylphenyl)phosphine and its chalcogenides has been studied
by the methods of dipole moments and quantum chemistry [52].
In order to study the effect of intramolecular electron in-
teractions on bond lengths in compounds 1-4, we performed
quantum chemical calculations of their structures by the DFT
method in the B3LYP/6-311 þ G* basis using the Gaussian 09 suite
of programs [53], NBO and MO analysis. The molecular orbital
analysis is widely used to describe the electronic structure and
chemical behavior of the different heteroatom compounds
[54e56], including substituted phosphines [41]. Total optimization
energies (-E), dipole moments, delocalization energy of electron
density E(2), associated with charge transfer from lone pairs (LP) of
3.3. DFT calculations
Theoretical studies of the spatial structure of phosphine and its
chalcogenides with sterically bulky tolyl substituents at the phos-
phorus atom are also limited. For example, by the semi-empirical
method PM3, the preferred conformers of tris(2-methylphenyl)
phosphine and its chalcogenides were found [51], DFT calculated
complexes of triphenylphosphine derivatives with zeolite Y [20]
phosphorus and chalcogen atoms to anti-binding
s*- orbitals,
borderline energy values molecular orbitals HOMO, LUMO and the

I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
687
Fig. 3. Fragments of crystal packing of compounds 1-4: a, d) view along a0 axies; b, c) view along 0с axies (ORTEP, H atoms are omitted for clarity).

688
I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
Fig. 4. Short contacts between molecules of compounds 1-4 in the crystal (ORTEP, 50% probability ellipsoids).
Table 3
MO and NBO analysis data for compounds 1e4.
Characteristics
Compound
1
2
3
4
-Е, a.u.
1154.4485534
1.50
4.58 ÷ 4.87
1229.7249312
4.13
0.53 ÷ 1.00
12.24 ÷ 16.72
1552.6929795
5.44
0.67 ÷ 0.86
11.69 ÷ 14.42
3556.0281408
5.60
0.69 ÷ 0.92
10.51 ÷ 11.01
m
, D
NР
/
s
*
C-С, Е(2), kcal/mol
s*
Р-С, Е(2), kcal/mol,
NХ
/
Х ¼ О (2), S (3), Se (4)
ELUMO, eV
ꢁ0.84
ꢁ5.88
5.04
ꢁ1.06
ꢁ6.86
5.80
ꢁ1.14
ꢁ5.90
4.76
ꢁ1.18
ꢁ5.51
4.33
E
HOMO, eV
E, eV
D
Table 4
Calculated (calc.) and experimental (exp.) bond lengths for compounds 1e4.
of sulfur and selenium atoms, respectively, is 2e4 kcal/mol lower.
In compound 1 the energy of interaction of the LP of the phos-
phorus atom with
s*- orbitals of CeC bonds is approximately
Compound/Bond
1
2
3
4
4.7 kcal/mol, in phosphine chalcogenides 2-4 the energies of this
interaction decreases significantly and consist about 0.5e1.0 kcal/
mol (Table 4). Thus, the calculated PeC bond lengths in compounds
1e4 increase in the series: 2 < 3 < 4 < 1. Although the values of
bond lengths for the gas phase are slightly overestimated (by
0.01e0.04 Å) compared to the experimental ones. From Table 4 it
can be seen that calculated bond lengths are on 0.01e0.04 Å over-
rated in comparison with experimental.
P-X calc.
P-X exp.
P-C calc. (average)
P-C exp. (average)
e
1.502(1)
1.492(2)
1.833(1)
1.806(2)
1.979(1)
1.957(4)
1.842(1)
1.814(1)
2.142(1)
2.105(1)
1.844(1)
1.816(1)
e
1.854(1)
1.837(2)
corresponding energy gap DE, are given in Table 3.
According to the NBO analysis data, in compounds 2-4, the
maximum energy E(2) is observed for the intramolecular interaction
As a rule, rather high values (>5 eV) of the energy difference
between the main bound and unbound states of the molecule
indicate a good chemical stability of the compounds under study.
of the LP of the oxygen atom with the
compound 2, while for the phosphine chalcogenides 3 and 4 the LP
s*- orbitals of the Р-С bond in

I.V. Sterkhova et al. / Journal of Molecular Structure 1197 (2019) 681e690
689
oxygen atom in phosphine oxide 2. In addition, in phosphine 1 it is
evenly distributed on phenyl fragments. In contrast, in the phos-
phine chalcogenides 3 and 4, electron density is mainly distributed
on the LP of the S and Se atoms. Probably, the presence of such
volumetric substituents as S and Se in compounds 3 and 4, and the
localization of the electron density of HOMO on them, determines
their geometry, namely the rotation of the methyl group of the
substituent in the opposite direction from the heteroatom. Unlike
HOMO, LUMO are smaller and delocalized mainly on the phenyl
rings of 1e4 molecules.
4. Conclusion
An optimized method for preparing tris(3-methylphenyl)phos-
phine chalcogenides was described. For the first time monocrystals
of clear tris(3-methylphenyl)phosphine oxide (not co-crystals)
were obtained and it's molecular structure was studied by X-ray
analysis. The work shows the decisive influence of the nature of the
substituent at the phosphorus atom in studied compounds on their
molecular structure. The influence of O, S, and Se atoms on the
change in the P e C bond length has been proved by X-ray
diffraction and quantum chemical calculations. The calculated data
indicate a decrease in the energy of intramolecular interaction of
the phosphorus atom with tolyl substituents in phosphine chalco-
genides compared with unsubstituted phosphine, which affects the
lengths of Р-С bonds in the structures under study. It is also shown
that the crystal structures of 1e4 form by weak hydrogen bonds of
the type CH$$$C, CH$$O, CH$$$S and CH$$$Se.
Acknowledgement
The work was carried out using equipment of the Baikal
Analytical Centre of SB RAS.
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