Synthesis, Molecular, and Crystal Structure of Tris(2-carbamoylmethoxyphenyl)phosphine Oxide

Article abstract of DOI:10.1134/S1070363220100059

Abstract: New tripodal ligand, tris(2-carbamoylmethoxyphenyl)phosphine oxide, has been synthesized via the alkylation of tris(2-hydroxyphenyl)phosphine oxide with chloroacetamide. The ligand structure has been studied by means of IR and NMR (¹H

Full text of DOI:10.1134/S1070363220100059

ISSN 1070-3632, Russian Journal of General Chemistry, 2020, Vol. 90, No. 10, pp. 1840–1844. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Obshchei Khimii, 2020, Vol. 90, No. 10, pp. 1506–1511.
Synthesis, Molecular, and Crystal Structure
of Tris(2-carbamoylmethoxyphenyl)phosphine Oxide
a
a,
b
c
T. V. Baulina , I. Yu. Kudryavtsev *, A. V. Artem’ev , I. Yu. Bagryanskaya ,
a
a
M. P. Pasechnik , and V. K. Brel
a
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russia
b
c
Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090 Russia
Vorozhtsov Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090 Russia
*
e-mail: zaq@ineos.ac.ru
Received June 17, 2020; revised June 17, 2020; accepted June 30, 2020
Abstract—New tripodal ligand, tris(2-carbamoylmethoxyphenyl)phosphine oxide, has been synthesized via the
alkylation of tris(2-hydroxyphenyl)phosphine oxide with chloroacetamide. The ligand structure has been studied
1
31
by means of IR and NMR ( H, P) spectroscopy as well as X-ray diffraction.
Keywords: tripodal ligand, tris(2-carbamoylmethoxyphenyl)phosphine oxide, crystal and molecular structure
DOI: 10.1134/S1070363220100059
Tripodal ligands form a promising group of organic
with the guest ions and molecules with minor change of
the ligand conformation [15–17].
complex-forming agents, versatile structure of which
affords the compounds capable of binding the substrates
of different classes. The ligands containing carbamoyl
groups can form strong complexes with the salts of d-
and f-elements and can be used as extracting agents for
recovery and separation of valuable metals as well as
for reprocessing of spent nuclear fuel [1–5]. Tripodal
ligands bearing functional proton-donor groups can form
complexes with anions [6–9]. Tuning of the tripodal
ligands structure has allowed ionophores for ion-selective
electrodes and optical sensors for metal ions [10–12].
Tripodal ligands can bind neutral organic molecules, for
example carboxylic acids [13] and carbohydrates [14] and
act as sensors, receptors, and artificial enzymes.
In contrast to the extracting agents used in hydro-
metallurgy, which should exhibit significant lipophilicity
and low solubility in water, sometimes it is desirable to
obtain water-soluble ligands and complexes, for example,
in industries utilizing water as the cheapest and the most
available solvent. Solubility in water is a prerequisite for
the ligands and their complexes suitable for application
in physiological media (drugs, components of diagnostics
systems, contrasting agents, etc.). Moreover, it is desirable
that the ligands and complexes applied in biomedicine are
neutral and do not significantly affect the solutions pH.
Herein we discuss the synthesis of a novel promising
water-soluble tripodal ligand for the binding of cations,
anions, and organic molecules in aqueous solutions and
biological fluids {tris[2-(carbamoylmethoxy)phenyl]-
phosphine oxide (NH COCH OC H ) PO 1} as well
The so-called propeller ligands based on pyramidal
organic compounds with three aryl substituents and
functional groups in the side chain form a special type of
tripodal ionophores. These ligands include the derivatives
of triarylmethane, triarylamine, triarylphosphine, and
triarylphosphine oxide. The most stable conformation of
such molecules corresponds to the geometry of asymmetric
propeller with the ortho-substituents in the benzene rings
being oriented to the same direction (Scheme 1). Such
geometry allows the preparation of ionophores with the
coordinating moieties in the side chains being spatially
close and hence prone to the formation of multiple bonds
2
2
6
4 3
Scheme 1.
1
840

SYNTHESIS, MOLECULAR, AND CRYSTAL STRUCTURE
1841
as its structure and properties. Owing to the tripodal
structure with concerted orientation of the functional
groups, compound 1 can potentially form complexes
with cations (via the P=O and C=O groups) as well as
with anions and organic molecules (via hydrogen bonding
with the NH moiety)
2
Compound1waspreparedfromtris(2-hydroxyphenyl)-
phosphine oxide 2 and 2-chloroacetamide (Scheme 2).
Compound 2 is readily formed upon the action
of lithium diisopropylamide on triphenyl phosphate
3
2
[18]. The alkylation of the phosphine oxide 2 with
-chloroacetamide afforded the tripodal ligand 1 bearing
amide functional group in the side chains. The reaction
was promoted by KBr. Compound 1 was isolated from
the reaction mixture as a trihydrate (as per the elemental
analysis data). Compound 1 is noticeably soluble in water,
readily soluble in polar organic solvents (EtOH, MeOH,
DMF, and DMSO) and insoluble in nonpolar solvents
Fig. 1. General view of a molecule of tris[2-(carbamoyl-
methoxy)phenyl]phosphine oxide 1 in the crystal.
were –10.768(623)°. The P=O bond (1.502 Å) was
longer than that in the analogous triarylphosphine oxides
(
hexane, ether, CH Cl , CHCl ).
2 2 3
Composition and structure of compound 1 were
confirmed by the data of elemental analysis as well as IR,
H NMR, and P{ H} NMR spectroscopy. The molecular
without hydrogen bonds (1.486 Å in [2-Bu NC(O)·
2
CH OC H ] PO [1]), but approximately equal in length
2
6
4 3
1
31
1
as in the phosphine oxides with the P=O group forming a
hydrogen bond {1.502 Å in Ph P(O)CH CH CH(OH)Me
structure was elucidated by X-ray diffraction analysis.
2
2
2
The structure of tris[2-(carbamoylmethoxy)phenyl]-
phosphine oxide was determined for the trihydrate
[20], 1.503 Å in [2-HO(CH2)2OC6H4]3PO [21], and
1.513 Å in (HOCH2CH2CH2)3PO [22]}.
(
NH COCH OC H ) PO·3H O which was prepared via
2 2 6 4 3 2
The molecules of compound 1 in the crystal were
associated and linked to water molecules via strong N–
H∙∙∙O and O–H∙∙∙O intermolecular hydrogen bonds, so
crystallization from an aqueous solution. The solvate was
crystallized in the R-3 space group with 1/3 molecules
of compound 1 in the asymmetric unit. The molecules of
phosphine oxide 1 adopt the propeller structure (OPCC
that each C(O)NH group formed a pair of intermolecular
2
1
3
N –H∙∙∙O hydrogen bonds with an amide group of the
neighbor molecule, the H∙∙∙O и N ∙∙∙O bond lengths
3
1
3
torsion angles τ = 51.90°), the OCH C(O)NH groups
2
2
1
being turned toward the O atoms of the P=O group
Fig. 1).
Three amide hydrogen atoms formed an intramolecular
in the 8-membered ring being 2.071 and 2.923 Å,
(
respectively. One proton in each group NH formed a
2
1
1
N –H∙∙∙O (P) hydrogen bond, and another proton was
involved in a shorter N –H∙∙∙O (С) bond formation.
1
1
1
3
trifurcate (four-centered) N –H∙∙∙O hydrogen bonds, with
the H∙∙∙O and N ∙∙∙O distances being d = 2.398 and
3
1
1
1
The carbonyl oxygen atom was associated with water
1
1
1
3
.251 Å, respectively, and the N –H∙∙∙O angle being
molecules via strong intermolecular O (W)–H∙∙∙O
2
7
8
1
1
3
equal to 171.54°. The O –C –C –N torsion angles
hydrogen bonds with the O (W)∙∙∙O distances being
Scheme 2.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 90 No. 10 2020

1842
BAULINA et al.
Fig. 2. Intermolecular hydrogen bonds between the molecules of compound 1 and H O.
2
–
1
2.780 Å.As a result, a three-dimensional supramolecular
1090 cm in the IR spectrum of (2-HOC H ) PO [18]}.
6 4 3
network was formed. Figure 2 displays the intermolecular
hydrogen bonds between the molecules of compound 1
The position of the ν(СО) and ν(NH) bands practically
was not changed. It could be suggested that the competing
interactions between both proton-accepting groups and
and H O.
2
the NH moieties occurred in the solution, the possible
2
IR spectrum of solid compound 1 showed the ν(РО)
–
1
forms being in equilibrium.
band at 1117 cm , i. e. the wavenumber of the Р=О
1H NMR spectrum of a solution of compound 1 in
bond vibration was noticeably lower than in the tri-
–1
DMSO-d showed a singlet signal of the methylene
arylphosphine oxides without hydrogen bonds (1180 cm
in the spectrum of [2-Bu NC(O)CH OC H ] PO [1]) but
6
protons at 4.45 ppm. The region typical of the aromatic
2
2
6
4 3
4
protons displayed a triplet of doublets at 7.12 ppm (H )
somewhat higher than in the spectrum of tris[2(tetrazol-
6
3
–
1
and a triplet at 7.66 ppm (H ). The signals of the H and
5
-ylmethoxy)phenyl]phosphine oxide (1098 cm ) with
5
H protons were overlapping and appeared as a complex
a bifurcate hydrogen bond with two protons of the NH
multiplet at 7.16–7.29 ppm. The signals of the NH group
2
groups [5]. Broad bands of the ν(NH) vibrations showed
protons were two strongly separated singlets at 7.31 and
–
1
the maxima at 3343 and 3172 cm , which could be
assigned to the vibrations of the NH groups associated
with phosphoryl and carbonyl groups, respectively.
7
.85 ppm, likely, due to the hindered rotation of the NH2
group about the C–N bond [19]. Such difference in the
positions of the signals of the NH group protons could be
–
1
2
The ν(СО) band appeared at 1685 cm . Hence, the IR
spectrum of the compound agrees well with its suggested
structure.
due to the formation of different hydrogen bonds with the
31
1
РО and СО groups. The P{ H} NMR spectrum showed
a singlet at 30.5 ppm corresponding to the chemical
shift of triarylphosphine oxide with a phosphoryl groups
Dissolution in DMSO usually leads to the disruption
of the intermolecular hydrogen bonds, while the
intramolecular hydrogen bonds are preserved. However,
disruption of the intermolecular С=О∙∙∙HN groups
in compound 1 could lead to the formation of the
intramolecular hydrogen groups involving the liberated
groups, i. e. rearrangements of the hydrogen bonds
system. Comparison of the IR spectrum of the solution
involved in strong hydrogen bonding, for example, δ 35.9
P
3
1
1
ppm in the P{ H} NMR spectrum of (2-HOC H ) PO
6
4 3
(DMSO) [18].
The synthesized novel tripodal ligand, tris[2-(car-
bamoylmethoxy)phenyl]phosphine oxide, can be used
in the preparation of various complexes with d- and
f-elements as well as with different organic molecules
bearing polar groups. The obtained structural data are
applicable in molecular docking of the related compounds.
of phosphine oxide 1 in DMSO-d with that of the solid
6
sample revealed the absence of the ν(РО) band at 1117
–
1
cm as well as a band in the region characteristic of
the free Р=О group. We could not reliably identify the
position of the ν(РО) band, possibly due to its overlap
with the solvent absorption, which would mean the
shift to the low-frequency region {for example, ν(РО)
EXPERIMENTAL
Organic solvents (reagent grade) were dried and
purified via conventional methods [23]. The deuterated
solvent DMSO-d (Aldrich) was used as received.
6
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 90 No. 10 2020

SYNTHESIS, MOLECULAR, AND CRYSTAL STRUCTURE
1843
IR spectra were recorded using a FTIR Tensor 37
Bruker spectrometer. The spectrum of the crystalline
sample (KBr pellets) was recorded over 4000–400 cm ,
at 296(2) K: a = 13.9869(17), b = 13.9869(17), c =
23.896(3) Å, α = 90.00, β = 90.00, γ = 120.00°, V =
–
1
3
3
4048.6(11) Å , Z = 6, d = 1.357 g/cm , μ(MoK ) =
calc α
0.161 mm ; 21932 reflections were measured at 2θ up to
–1
and the spectrum of the solution in DMSO-d was
6
–
1
1
31
1
obtained over 4000–1090 cm . H and P{ H} NMR
50.8°, 1654 of them being independent (R = 0.097) and
int
spectra of compound 1 were recorded using a Bruker
1034 being observed; R (obs) = 0.062, wR (all) = 0.177,
GOF = 1.058. The crystallographic data were deposited
at the Cambridge Crystallographic Data Centre (CCDC
1
2
1
AV-300 instrument operating at 300.13 ( H) and 121.49
3
1
1
(
P{ H}) MHz with residual signals of the deuterated
1
solvent as internal reference for the H NMR spectra
and 85% H PO as external reference for Р{ H} NMR
1
937005).
3
1
1
3
4
FUNDING
spectra.
This study was financially supported by the Russian
Tris(2-hydroxyphenyl)phosphine oxide 2 was
Science Foundation (project no. 20-13-00329). Spectral
experiments were performed using the equipment of the Center
for Molecular Structure Studies, Nesmeyanov Institute of
Organoelement Compounds, Russian Academy of Sciences.
Elemental analysis was performed in the Laboratory of
Microanalysis, Nesmeyanov Institute of Organoelement
Compounds, Russian Academy of Sciences.
prepared as described elsewhere [18].
Tris[2-(carbamoylmethoxy)phenyl]phosphine
oxide (1).Amixture of 0.98 g (0.003 mol) of compound 2,
2
1
0 mLof DMF, 2.50 g (0.18 mol) of potassium carbonate,
.68 g (0.18 mol) of chloroacetic acid amide, and 0.25 g
(0.002 mol) of KBr was stirred during 26 h at 90°C. The
solvent was removed under vacuum and 50 mL of water
and 50 mL of chloroform were added to the residue. The
formed clotted precipitate was filtered off, washed with
water and with ether, and triturated in a mixture of ether
with methanol (20 : 1). The obtained powder was dried
in air. Yield of compound 1 trihydrate 1.51 g (91.2%),
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
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