Dipole moments and structure of ortho-diphenyl(diethyl)phosphinoyl- substituted benzyl alcohols, phenols, and their derivatives

Article abstract of DOI:10.1134/S1070363208090041

The method of dipole moments and DFT B3LYP/6-31G*quantum-chemical calculations were used to study the structures of ortho-substituted aryl-and arylmethyldiphenyl(diethyl)phosphine oxides. It was established that methyl ethers of phosphorus-containing benz

Full text of DOI:10.1134/S1070363208090041

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 9, pp. 1662–1667. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © E.A. Ishmaeva, A.A. Gazizova, Ya.A. Vereshcjhagina, N.A. Bondarenko, 2008, published in Zhurnal Obshchei Khimii, 2008,
Vol. 78, No. 9, pp. 1429–1434.
Dipole Moments and Structure
of ortho-Diphenyl(diethyl)phosphinoyl-substituted
Benzyl Alcohols, Phenols, and Their Derivatives
E. A. Ishmaevaa, A. A. Gazizovab, Ya. A. Vereshcjhaginaa,b, and N. A. Bondarenkoc
a Kazan State University,
ul. Kremlevskaya 18, Kazan, 420008 Russia
e-mail: Eleonora.Ishmaeva@ksu.ru
b Kazan State Technological University, Kazan, Russia
c Scientific Research Institute of Chemical Reagents and Ultrapure Chemical Substances (FGUP IREA), Moscow, Russia
Received April 11, 2008
Abstract―The method of dipole moments and DFT B3LYP/6-31G* quantum-chemical calculations were used
to study the structures of ortho-substituted aryl- and arylmethyldiphenyl(diethyl)phosphine oxides. It was
established that methyl ethers of phosphorus-containing benzyl alcohols and phenols exist as equilibrium
mixtures of several conformers with prevalence of forms with the weakest steric interactions. Preferred
conformers of о-[(diethylphosphinoyl)methyl]benzyl alcohol and о-[(diphenylphosphinoyl)methyl]phenol
contain an intramolecular hydrogen bond between the hydroxyl hydrogen atom and phosphinoyl oxygen atom.
DOI: 10.1134/S1070363208090041
ortho-Substituted aryl- and arylmethyldiphenyl(dieth-
yl)phosphine oxides are precursors of phosphorus-contain-
ing podands, acyclic analogs of crown ethers. Elucida-
tion of the structure of such compounds is significant for
studying complex formation with phosphorus-contain-
ing reagents. We measured the dipole moments of phos-
phine I and phosphine oxides II–IX in benzene (Table 1).
of compounds I–IX. The calculated data are presented
for those conformers whose relative energies are no
higher than 3 kcal mol−1.
Below we depict the possible conformers of о-
(methoxymethyl)diphenylphosphine (I) and о-(me-
thoxymethyl)diphenylphosphine oxide (II).
R1
Table 1. Coefficients of calculational equations, orienta-
tional polarizations, and experimental dipole moments of
compounds I–IX
R2
α
γ
Po, cm3
μexp, D
Comp. no.
R1 = CH2OMe, R2 = PPh2 (I); R1 = CH2OMe, R2 =P(O)Ph2
(II); R1 = CH2OMe, R2 = CH2P(O)Ph2 (III); R1 = = OMe,
R2 = CH2P(O)Et2 (IV); R1 = OMe, R2 = CH2P(O)Ph2 (V);
R1 = CH2OMe, R2 = CH2P(O)Et2 (VI); R1 = CH2Br, R2 =
CH2P(O)Et2 (VII); R1 = CH2OH, R2 = CH2P(O)Et2 (VIII);
R1 = OH, R2 = CH2P(O)Ph2 (IX).
1.269
5.671
0.315
0.319
0.264
0.175
0.264
0.115
0.175
0.143
0.221
54.987
324.691
373.803
505.700
478.743
385.670
365.509
744.970
666.449
1.63
3.96
4.25
4.95
4.81
4.32
4.21
6.00
5.68
I
II
6.162
III
IV
V
12.045
8.160
The dipole moments of these compounds fit the
range of the dipole moments of tri- and tetracoordinate
phosphorus compounds, listed in the handbook [1].
8.629
VI
VII
VIII
IX
6.895
17.605
13.369
To interpret the experimental results, we performed
DFT B3LYP/6-31G* quantum-chemical calculations
1662

DIPOLE MOMENTS AND STRUCTURE
1663
Me
O
H
H
O
H
Me
O
C
O
Me
2
2
2
2
2
Me
Me
H
Ph3
H
Ph3
H
Ph3
1
Ph
1
Ph
1
Ph
1
Ph
1
Ph
Ph3
Ph3
P
P
P
P
P
а
c
d
e
b
The relative energies of conformers of compounds I
and II and their theoretical, vector-additive, and
experimental dipole moments are listed in Table 2.
Comparison of the experimental, vector-additive, and
theoretical dipole moments of compounds I and II
leads to a conclusion that in both cases we deal with a
conformational equilibrium of several forms, but
energetically preferable are conformers Ia and IIa with
minimum steric interactions. Note that the difference
in the dipole moments of the conformers is controlled
by the steric arrangement of the МеОСН2 group in the
ortho position of the second benzene ring, since the
dipole moment is insensitive to rotational isomerism at
the P–Csp2Ph bond [2].
energy 0 kcal mol−1 has only one phenyl ring arranged
gauche to the P=О group (Table 2), while the other
phenyl fragments are turned by 23°–25° from a
position in which they are eclipsing the Ph and P=O
groups.
We calculated possible conformers of о-[diphenyl-
phosphinoyl)methyl]benzyl alcohol (III) and о-[di-
ethylphosphinoyl)methyl]benzyl alcohol (VI). These
calculations showed (Table 3) that compounds III and
VI exist as equilibrium mixtures of conformers a–c,
most contributed by conformers IIIa and VIa,
respectively. In g+g+ conformer VIa, the ethyl groups
are not eclipsing the P=O bond.
The data in Table 4 show that о-[(diethyl-
phosphinoyl)methyl]anisole (IV) and о-[(diphenyl-
phosphinoyl)methyl]anisole (V), too, are equilibrium
mixtures of a series of conformers; therewith, the
fractions of energetically (ΔЕ = 0 kcal mol−1) preferred
As follows from the data in Table 2, the
energetically preferable conformer of phosphine Ia has
all the three phenyl rings synclinal to the lone electron
pair of PIII. The picture for phosphine oxide II is
somewhat different. The conformer IIa with the
forms are IV 67.5 (IV) and 70% (V).
Me
Me
O
O
O
O
O
P
R
P
R
P
H
R
H
R
H
H
R
H
R
P
P
R
R
R
O
R
O
H
H
H
H
H
O
O
O
Me
Me
Me
а
d
b
c
e
Table 2. Relative energies, dipole moments (theoretical μtheor., vector-additive μcalc., and experimental μexp.), and B3LYP/6-
31G* dihedral angles C1Ph–C2Ph–P–Y (Y is the lone electron pair (I) or О atom (II)] for compounds I and II
Dihedral angle, deg
Conformer
ΔЕ, kcal mol–1
μtheor, D
μcalc, D
μexp, D
C1Ph
1
−C2Ph
1
−P−Y
C1Ph
2
−C2Ph
2
−P−Y
C1Ph
3
−C2Ph
−P−Y
3
0
1.48
1.63
0.56
1.32
1.93
3.20
3.71
2.78
1.56
1.51
0.73
1.59
2.31
3.82
4.27
3.19
1.63
–34.3
–32.7
–37.4
–27.1
–24.9
–23.4
–19.8
–26.4
–44.4
–48.4
–49.4
–28.8
–30.3
–44.7
–53.7
–37.2
–36.1
–35.2
–27.9
–60.2
–62.2
–25.4
–24.5
–30.4
Ia
0.10
0.43
1.85
2.23
0
Ib
Ic
Id
Ie
3.96
IIa
IIb
IIc
0.54
0.60
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1664
ISHMAEVA et al.
The results of quantum-chemical calculations for
compounds I–VII are nicely consistent with the
experimental dipole-moment data.
Table 3. Relative energies and theoretical, vector-additive,
and experimental. dipole moments of compounds III and VI
Conformer
IIIa
ΔЕ, kcal mol–1
μtheor, D
3.54
μcalc, D μexp, D
H
H
Br
Br
H
0
4.21
4.64
4.77
4.32
4.74
4.93
4.25
C
C
C
C
H
H
O
0.59
0.70
0
3.37
IIIb
R
3.65
IIIc
R
P
R
P
H
H
O
3.58
4.32
VIа
H
R
1.88
0.92
3.42
VIb
VIIа
VIIb
3.62
VIc
Previously Bondarenko [3] considered the IR
spectra of phosphorus-containing ortho derivatives of
benzyl alcohol VIII and phenol IX in CCl4 and CHCl3
solutions of varied concentration. The absence in the
spectra of the free OH absorption band and the
concentration independence of the intensity of the
associated OH absorption band show that the only
conformers of phosphine oxides VIII and IX, existing
in the solutions, are those containing intramolecular
hydrogen bonds between the OH and P=O groups,
which close seven- and eight-membered rings (forms
VIIIb and IXb).
Table 4. Relative energies and theoretical, vector-additive,
and experimental. dipole moments of compounds IV and V
Conformer
IVa
IVb
IVc
IVd
IVe
Va
ΔЕ, kcal mol–1
μtheor, D
4.85
5.29
2.67
2.27
2.31
4.75
4.66
2.85
2.30
2.30
μcalc, D μexp, D
0
4.74
5.36
4.49
4.37
4.49
4.64
5.18
4.23
4.28
4.23
4.95
0.56
1.25
1.33
2.21
0
HO
4.81
CH2
O
P
2.16
1.54
1.47
1.49
Vb
O
H
O
Vc
PEt2
Vd
Et
Et
Ve
VIIIа
VIIIb
H
O
O
Table 5 Relative energies and theoretical, vector-additive,
and experimental. dipole moments of the conformers of
compound VII
H
O
O
PPh2
2
Ph
P
1
Conformer
VIIа
ΔЕ, kcal mol–1
0.00
μtheor, D
4.43
μcalc, D
4.41
μexp, D
Ph
IXа
4.27
IXb
1.58
2.76
4.52
VIIb
The presence of two ethyl groups at the phosphorus
atom in о-(hydroxymethyl)phenyl-substituted phos-
phine oxide VIII complicates the conformational pic-
ture. Below are presented the Newman projections of
the possible rotational isomers of compound VIII, R =
CH2C6H4CH2OH.
The energetically preferable conformer of o-
[(diethylphosphinoyl)methyl)]benzyl bromide (VII)
has the two bulky substituents at the neighboring
carbon atoms of the benzene ring trans to each other
(Table 5).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

DIPOLE MOMENTS AND STRUCTURE
R
1665
R
P
R
P
Me
Me
Me
CH2
CH2
CH2
CH2
CH2
P
CH2
CH2
CH2
Me
Me
g+g+
Me
g−g+
g+g−
R
R
R
Me
CH2
CH2
Me
CH2
CH2
Me
P
P
P
Me
CH2
Me
Me
g+t
g−t
tg−
R
R
R
Me
Me
CH2
Me
CH2
Me
CH2
Me
P
P
P
CH2
CH2
Me
g−g−
tg+
tt
Table 6 lists the relative energies and experimental,
theoretical, and vector-additive dipole moments of
possible conformers of о-(phosphinoylmethyl)-
substituted benzyl alcohol VIII. As seen from these
data, the energy minimum corresponds to g+g+-
conformer VIIIb with the eight-membered ring closed
by an intramolecular H bond. The theoretical and
vector-additive dipole moments the experimentally
measured polarity of this compound (6.00 D). A
similar situation, when intramolecular hydrogen
bonding stabilizes specifically the same conformation,
by quantum-chemical calculations that the preferable
conformations of о-hydroxy-substituted aryldiphenyl-
and aryldiethylphosphine oxides are those involving
intramolecular hydrogen bonding the OH hydrogen
and P=O oxygen atoms, forming a seven- or an eight-
membered ring.
Table 6. Relative energies and theoretical, vector-additive,
and experimental dipole moments of the conformers of
compound VIII
we
observe
earlier
with
2-phosphinoyl-3-
Conformer ΔЕ, kcal mol–1 μtheor, D
μcalc, D
5.33
6.14
6.17
6.02
6.04
6.11
6.14
5.98
6.16
6.10
μexp, D
hydroxyacrylonitriles [4].
VIIIа (g–g+)
VIIIb (g+g–)
VIIIb (g+g+)
VIIIb (g–g+)
VIIIb (g–g–)
VIIIb (g+t)
VIIIb (tg–)
VIIIb (g–t)
VIIIb (tg+)
VIIIb (tt)
5.70
0.73
0
4.44
5.77
5.81
5.69
5.68
6.05
6.03
5.95
6.01
6.22
6.00
о-[(Diphenylphosphinoyl)methyl]phenol IX, too,
exists as conformer IXb with an intramolecular H
bond forming a seven-membered ring (Table 7). This
conformer corresponds to an energy minimum, and the
theoretical and vector-additive dipole moments fit the
experimental dipole moment of this compound (5.68
D). According to the geometric parameters calculated
by the DFT B3LYP/6-31G* method (Table 7), the
phenyl rings at the phosphorus atom in IXb are almost
eclipsing the P=О bond. Obviously, of key importance
here are steric interactions, and preferred are the least
sterically hindered conformations.
0.75
0.64
0.60
0.64
1.44
0.80
2.75
Thus, it was established by an analysis of the
results obtained by the method of dipole moments and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 9 2008

1666
ISHMAEVA et al.
Table 7. Relative energies and theoretical, vector-additive, and experimental, dipole moments, and dihedral angles (B3LYP/6-
31G*) C1Ph −C2Ph −P=О, C1Ph −C2Ph
−P=О of the conformers of compound IX
1
1
2
2
Dihedral angle, deg
C1Ph −C2Ph
−P=О
Conformer
ΔЕ, kcal mol–1
μtheor, D
μcalc, D
μexp, D
C1Ph
1
−C2Ph
1
−P=О
2
2
8.09
0.00
2.48
5.65
3.98
5.76
5.68
–5.7
–15.3
–18.3
IXа
–16.3
IXb
product IV, bp 163–165°С (2 mm Hg). Repeated
distillation gave 1.9 g (66%) of the product, bp 152–
153°C (1 mm Hg), nD20 1.5446, d420 1.0964. Found, %:
С 63.8, Н 8.5, P 13.4. С12Н19О2P. Calculated, %: С
63.7, Н 8.5, P 13.7.
EXPERIMENTAL
The dipole moments of phosphine I and phosphine
oxides II–IX were measured in benzene at 25°С by the
procedure in [5].
For calculation of the dipole moments of phosphine
I and phosphine oxides VIII, IX the following bond
and group moments were used, D: m(H–Csp3) = 0.28
[6]; m(H–Csp2) = 0.70 [6]; m(Csp2–P) = 0.39 [1]; m(Csp3–
P) = 0.83 [1]; m(P=O) = 3.40 [1]; m(Me–O) = 1.10
calculated from the μexp of dimethyl ether [7]; m(Csp3–
О) = 1.02 calculated from the μexp of MeOH [7]; m
(Csp3–Csp2) = 0.75 calculated from the μexp of toluene
[7]; m(H–О) = 1.52 calculated from the μexp of water
[7]; m(Csp2Ar–O) = 0.37 calculated from the μexp of
phenol [7]; m(Csp3–Br) = 1.51 calculated from the μexp
of CH3Br [7]. In addition, the geometric parameters
(Table 8) obtained by DTF B3LYP/6-31G* quantum-
chemical calculations were used.
All quantum-chemical calculations were performed
in the Supercomputer Center for Collective Use, Kazan
Research Center, Russian Academy of Sciences (http://
wt.knc.ru).
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A
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DIPOLE MOMENTS AND STRUCTURE
1667
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