Preparation of amorphous water-soluble complexes of biometals with (1-hydroxyethylidene)diphosphonic acid, 2-aminoethanol, and 2-amino-2-(hydroxymethyl)propane-1,3-diol

Article abstract of DOI:10.1134/S1070363215050199

Multifold enhancement of solubility in water of Fe(III) and Mn(II) complexes with (1-hydroxyethylidene) diphosphonic acid has been achieved by their transformation into the corresponding salts via interaction of aqueous suspensions of the poorly soluble complexes with 2-aminoethanol and 2-amino-2-(hydroxymethyl)propane-1,3-diol. Molecular structure of tris(2-hydroxyethanaminium)(1-hydroxyethylidene)-diphosphonate has been determined. Potential agricultural efficiency of the prepared iron and manganese derivatives as well as zinc and copper complexes with (1-hydroxyethylidene)diphosphonic acid as a microfertilizer has been estimated.

Full text of DOI:10.1134/S1070363215050199

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 5, pp. 1116–1124. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © V.V. Semenov, N.V. Zolotareva, B.I. Petrov, E.V. Baranov, V.I. Titova, L.D. Varlamova, E.Yu. Geiger, I.D. Korolenko,
E.V. Dabakhova, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 5, pp. 822–830.
Preparation of Amorphous Water-Soluble Complexes
of Biometals with (1-Hydroxyethylidene)diphosphonic Acid,
2-Aminoethanol, and 2-Amino-2-(hydroxymethyl)propane-1,3-diol
V. V. Semenova, N. V. Zolotarevaa, B. I. Petrova, E. V. Baranova, V. I. Titovab,
L. D. Varlamovab, E. Yu. Geigerb, I. D. Korolenkob, and E. V. Dabakhovab
a G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
ul. Tropinina 49, Nizhni Novgorod, 603950 Russia
e-mail: vvsemenov@iomc.ras.ru
b Nizhni Novgorod State Agricultural Academy, pr. Gagarina 97, Nizhni Novgorod, 603107 Russia
Received December 8, 2014
Abstract—Multifold enhancement of solubility in water of Fe(III) and Mn(II) complexes with (1-hydroxy-
ethylidene)diphosphonic acid has been achieved by their transformation into the corresponding salts via
interaction of aqueous suspensions of the poorly soluble complexes with 2-aminoethanol and 2-amino-2-
(hydroxymethyl)propane-1,3-diol. Molecular structure of tris(2-hydroxyethanaminium)(1-hydroxyethylidene)-
diphosphonate has been determined. Potential agricultural efficiency of the prepared iron and manganese
derivatives as well as zinc and copper complexes with (1-hydroxyethylidene)diphosphonic acid as a
microfertilizer has been estimated.
Keywords: (1-hydroxyethylidene)diphosphonic acid, iron, manganese, 2-aminoethanol, microfertilizer, agri-
cultural efficiency
DOI: 10.1134/S1070363215050199
High solubility of metal complexes in water is a
key factor of their efficient application as micro-
fertilizer. Long-term storage of concentrated aqueous
solutions (commercial form of many microfertilizers)
under conditions of alternating temperature often
results in precipitation of crystalline coordination
compounds that are dissolved extremely slowly. We
have earlier suggested a method to enhance the
solubility of iron and manganese salts of (1-hydroxy-
ethylidene)diphosphonic acid H4L via the controlled
treatment with potassium and ammonium hydroxides
[1]. The so formed mixed salts are transformed into
colored gels upon water removal, and their further
drying yields transparent glass, easily grinded into a
powder. Long-term storage of concentrated solutions
of the mixed salts over winter and spring does not
result in precipitation, probably due to the amorphous
structure of the coordination compounds.
methyl)propane-1,3-diol II. The so prepared com-
pounds as well as zinc and copper derivatives with (1-
hydroxyethylidene)diphosphonic acid, readily soluble
in water, were tested as microfertilizers.
Amines [2] and aqueous ammonia [3] formed
poorly soluble mixed salts with (1-hydroxyethylidene)-
diphosphonic acid bound to transition or rare-earth
metals. The crystalline compounds were isolated from
the hot aqueous solutions under conditions of hydro-
thermal synthesis. On the contrary, the presence of one
or three hydroxyl group(s) favored formation of amor-
phous compounds, readily soluble in water.
CH3
O
P
O
P
HO
HO
OH
OH
C
OH
H4L
The following poorly soluble salts were used as
models to test the solubility enhancement [4]: diiron(III)
tris[(1-hydroxyethylidene)diphosphonate] tetrahydrate
Herein we present a new method to enhance the
solubility of iron and manganese salts via their treat-
ment with 2-aminoethanol I and 2-amino-2-(hydroxy-
1116

PREPARATION OF AMORPHOUS WATER-SOLUBLE COMPLEXES
1117
Table 1. Selected bond lengths (d) and bond angles (ω) in
the molecule of tris(2-hydroxyethanaminium)(1-hydroxy-
ethylidene)diphosphonate IV
Fe2(H2L)3·4H2O (solubility in water of 0.2 g in 100 mL
of the solution) and manganese(II) (1-hydroxy-ethyl-
idene)diphosphonate dihydrate MnH2L·2H2O (0.1 g
per 100 mL) [4].
Bond
d, Å
Angle
ω, deg
С1–C2
С1–O7
С1–P1
С1–P2
P1–O1
P1–O2
P1–O3
P2–O4
P2–O5
P2–O6
1.523(2)
1.452(2)
1.853(2)
1.848(2)
1.522(1)
1.525(1)
1.538(1)
1.509(1)
1.498(1)
1.593(1)
С1P1O1
С1P1O2
С1P1O3
O1P1O2
O2P1O3
O1P1O3
С1P2O4
С1P2O5
С1P2O6
O4P2O5
O5P2O6
O4P2O6
P1C1P2
С2C1O7
С2C1P1
С2C1P2
P1C1O7
O7C1P2
110.05(6)
107.78(6)
103.69(6)
111.44(6)
110.82(6)
112.68(6)
108.02(7)
111.62(7)
103.40(6)
117.12(6)
109.97(6)
105.68(6)
113.39(8)
105.62(12)
111.9(1)
Six free acid groups were present in the Fe2(H2L)3·
4H2O molecule, capable of the salt formation with the
amine. On top of that, neutral 2-aminoethanol ligand,
being more nucleophilic, could replace four water
molecules initially forming coordination bonds with
iron. Hence, one molecule of the iron complex was
expected to bind up to ten molecules of 2-amino-
ethanol I. The interaction of Fe2(H2L)3·4H2O suspen-
sion with a large excess of compound I (1 : 87 mol/mol)
yielded the iron derivative containing nine 2-amino-
ethanol molecules, Fe2(H2L)3·9H2NCH2CH2OH (III).
The product was a light-brown powder, readily soluble
in water and 2-aminoethanol but poorly soluble in
methanol. Evidently, one of the six acid groups re-
mained unbound. The assumption was further sup-
ported by the result of the interaction of (1-hydroxy-
ethylidene)diphosphonic acid with 2-aminoethanol.
The isolated crystalline compound IV was a salt
containing three fragments of the amine, C(CH3)(OH)·
[P(O)O–NH3+CH2CH2OH]3[P(O)(OH)] (Fig. 1), as
evidenced by the data of elemental analysis and X-ray
diffraction analysis (Tables 1 and 2).
110.72(10)
107.23(9)
107.51(9)
their lengths coinciding with those of the cor-
responding bonds in the Zolendronic acid [1.501(1)
and 1.502(2) Å] [6]. Evidently, equality of the P2–О4
and P2–О5 bond lengths was due to delocalization of
the negative charge and conjugation with the P=O
bond in the O4–P2–O5 fragment (1.483–1.503 Å [7]).
The O4P2O5 angle of 117.12(6)° was remarkably
different from the O5P2O6 [109.97(6)°] and O4P2O6
[105.68(6)°] angles. The P1–O1–3 distances in the [P(O)
O22–] fragment were very close [1.522(1)–1.538(1) Å],
somewhat longer than the P2–O4,5 ones. The P1–O1–3
bond lengths were close to the average P–O distance in
the О=P–O22– fragment with two delocalized negative
charges (1.513 Å [7]). The angles between the О1, О2,
and О3 atoms at the P1 atom were close [110.82(6)°–
112.68(6)°].
The available data on the dissociation constants
(рKа1 1.70 and рKа2 2.47) stated that (1-hydroxy-
ethylidene)diphosphonic acid was a strong one [5].
However, the acidic properties were weakened at
further dissociation steps (рKа3 7.28 and рKа4 10.29),
similarly to the polybasic acids; that explained the
absence of coordination of the fourth molecule of 2-
aminoethanol with (1-hydroxyethylidene)diphosphonic
acid.
The crystal of compound IV contained anions of
triply deprotonated (1-hydroxyethylidene)diphos-
phonic acid C(CH3)(OH)[P(O)O22–][P(OH)(О)О–] and
the ammonium cations HOCH2CH2NH3+. The central
С1 atom of the anionic part of the molecule revealed
tetrahedral coordination. The bond angles at С1 atom
ranged from 105.62(12)° to 113.39(8)° (Table 1). The
P2–O6 bond length of 1.593(1) Å was comparable to
that of the similar P–OH in the structure of the triply
deprotonated (imid-CH2)C(OH)[P(O)O22–][P(OH)(О)О–]
Zolendronic acid (imid standing for imidazole
fragment) [1.574(1) Å] [6]. The P2–О4 and P2–О5 bonds
in the [P(OH)(О)О–] fragment were noticeable
shortened [1.509(1) and 1.498(1) Å, respectively],
The interaction of Fe2(H2L)3·4H2O with excess of
2-aminoethanol occurred at slight heating and was
complete within 40 min. That was observed as
complete dissolution of the complex suspension and
formation of the transparent red-brown solution;
compound III was isolated from it as light-brown
powder, poorly soluble in ethanol, DMSO, and
acetonitrile. The attempts to re-precipitate the product
by addition of large volume of methanol or ethanol to
the concentrated aqueous solution were not successful.
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1118
SEMENOV et al.
Table 2. Basic crystallographic and structure refinement
parameters of compound IV
The electronic absorption spectrum of compound III
(Fig. 2) contained a weak band assigned to the d–d
transition in the Fe3+ cation at 430 nm, and a set of
poorly resolved stronger bands in UV region, assigned
to the ligand and the metal–ligand transitions [8].
Parameter
Value
Gross formula
C8H29N3O10P2
Molecular mass
389.28
Monoclinic
Interaction of Fe2(H2L)3·4H2O with 2-aminoethanol
in aqueous medium was performed at the reactants
ratios of 1 : 7 and 1 : 4. In the first case, the iron
complex was completely dissolved after 2 h stirring at
20°С, whereas in the latter case the solution remained
turbid due to the lack of 2-aminoethanol. Filtration,
water removal, and drying in vacuum gave compounds
of the same composition, Fe2(H2L)3·5H2NCH2CH2OH·
4H2O (V). The solvent evaporation led to formation of
yellow-orange glassy layer that could be easily ground
in the orange powder, readily and completely soluble
in water. Electronic absorption spectra of the products
were identical to that shown in Fig. 2.
Crystal system
Space group
а, Å
b, Å
с, Å
Р2(1)/n
10.6190(5)
8.7304(4)
18.4489(9)
90.8920(10)
1710.16(14)
4
β, deg
V, Å3
Z
d
calc, g/cm3
1.512
0.307
832
μ, mm–1
F(000)
2θmax, deg
52
Hence, two types of compounds could be prepared
from the poorly soluble Fe2(H2L)3·4H2O iron complex
and 2-aminoethanol. In anhydrous medium and in the
excess of compound I, five of six free Р(О)ОН acid
groups reacted with H2NCH2CH2OH to form the
ammonium salt. Simultaneously, all the four water
molecules were replaced from the coordination sphere
of iron, and the product III was of the Fe2(H2L)3·
9H2NCH2CH2OH composition. The reaction in an
aqueous medium yielded the hydrated complex V,
Fe2(H2L)3·5H2NCH2CH2OH·4H2O.
Number of measured reflections
Number of independent reflections
Rint
14075
3342
0.0351
1.026
0.0339
0.0904
0.0376
0.0930
Goodness of fit
R1 [for reflections with I > 2σ(I)]
wR2 [for reflections with I > 2σ(I)]
R1 (for all reflections)
wR2 (for all reflections)
Residual peaks of electronic density, 0.391/–0.377
max/min, e, Å3
Fig. 1. General view of molecule IV in the crystal. Ellipsoids are given with probability of 30%; some hydrogen atoms are not
shown for the sake of simplicity.
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PREPARATION OF AMORPHOUS WATER-SOLUBLE COMPLEXES
1119
A
A
λ, nm
λ, nm
Fig. 3. Electronic absorption spectra of aqueous solution of
the manganese complex VII.
Fig. 2. Electronic absorption spectra of aqueous solution of
compound III at (1) 2.74 × 10–3 and (2) 1.60 × 10–4 mol/L.
The prepared complex salts were infinitely soluble
pound VIII (Fig. 3) contained a weak band corres-
4
in water and did not form solid precipitate upon
cooling of the concentrated solutions. The Fe2(H2L)3·
4H2O complex did not react with excess of the primary
amine containing no hydroxyl groups. For example,
vigorous stirring of suspension of 1.8 g of the iron
complex in 20 mL of (3-aminopropyl)triethoxysilane
(EtO)3Si(CH2)3NH2 at heating to 100°C did not result
in the complex dissolution. Similarly, 2.0 g of the iron
complex was not dissolved in a large excess (20 mL)
of iminodiethanol; however, addition of 4 mL of water
at heating to 50°С resulted in complete dissolution of
the suspension to form transparent red-brown solution.
ponding to Mn2+ cation at 450 nm (21740 cm–1, T2g)
[8] and a stronger absorption band at 230–370 nm
assigned to the presence of the ligand.
2-Amino-2-(hydroxymethyl)propane-1,3-diol II was
less reactive towards iron and manganese complexes
as compared to 2-aminoethanol I. Dissolution of the
Fe2(H2L)3·4H2O complex in the aqueous phase in the
presence of compound I occurred at room temperature,
whereas in the case of compound II the dissolution
was possible only upon heating to 80–90°С. After
water removal, transparent strong green-yellow glass
was obtained; it could be ground into powder only
after prolonged (14 h) annealing in air at 110–115°С.
The subsequent heat treatment at 200°С in vacuum
resulted in mass loss of about 16%, due to drying and
elimination of small amount of the starting compound
II. According to the elemental analysis data, the
obtained water-soluble complex VIII contained six
molecules of 2-amino-2-(hydroxymethyl)-propane-1,3-
diol and four water molecules: Fe2(H2L)3·6H2NC(CH2OH)3·
4H2O.
Whereas compound III was readily soluble in 2-amino-
ethanol, vigorous stirring of a light-pink suspension of
MnH2L·2H2O in 2-aminoethanol yielded a finely
dispersed dark-grey insoluble MnH2L·xH2NCH2CH2OH·
yH2O salt VI that strongly densified the reaction
mixture and complicated isolation of the pure reaction
product. Addition of water (10 mL per 1 g of the
starting MnH2L·2H2O) resulted in dissolution of the
formed salt VI in the mixed 2-aminoethanol–Н2О
solvent. In view of that, preparation of manganese
complex with 2-aminoethanol was performed only in
aqueous medium. White aqueous suspension of the
manganese complex became transparent and turned red
15 min after addition of excess of 2-aminoethanol; the
color was changed to dark-cherry after 12 h. The
solvent evaporation and heating in vacuum yielded the
manganese salt dihydrate MnH2L·2H2NCH2CH2OH·
2H2О (VII), brown powder, readily soluble in water
and poorly soluble in methanol. Precipitate was not
formed during the long-term storage of concentrated
solution of complex VII at alternating temperatures as
well as upon addition of a large volume of methanol.
Electronic absorption spectrum of solution of com-
White suspension of the MnH2L·2H2O manganese
complex was dissolved in water in the presence of
compound II faster (within 20 min) and at lower
temperature (50°С) as compared to the Fe2(H2L)3·
4H2O iron complex. Each of the acid groups bound a
single molecule of the amine, and two water molecules
were incorporated into the metal coordination sphere
in the so formed MnH2L·2H2NC(CH2OH)3·2H2O
complex IX. In contrast to the corresponding iron
compound, the manganese complex IX was easily
ground into the fine-dispersed light-grey powder after
water evaporation and drying at 110°С.
A special feature of (1-hydroxyethylidene)diphos-
phonic acid and 2-amino-2-(hydroxymethyl)propane-
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1120
SEMENOV et al.
1,3-diol derivatives was formation of glassy and resin-
like substances. Interaction of those reactants at the
molar ratio of 1 : 4 or 1 : 3 in various organic solvents
(methanol, ethanol, acetone, toluene, or dimethyl-
sulfoxide) resulted in fast formation of white
suspension of the salt that was transformed into a
colorless viscous resin precipitating at the flask bottom
under the reaction conditions. In the case of high-
boiling DMSO as solvent, the reaction product isolated
after separation the solvent off and heating at 70–80°С
remained resin-like. In the cases of other solvents,
solidified melts were so obtained; they could hardly be
peeled off the flask and were softened upon heating to
100–120°С. Their heating at 200°С in vacuum resulted
in the melting and expansion; however, no solid or
liquid products were condensed at the cold walls of the
reactor.
Polymeric structure and the strong hydrogen
bonding of the salt X caused its poor solubility in the
organic solvents and good solubility in water.
According to X-ray diffraction analysis data, the
coordination compounds of iron and manganese (III,
V, and VII–IX) were X-ray amorphous (Fig. 4). The
diffraction patterns were identical and contained peaks
of amorphous halo at the reflection angles of 5–8, 17–
20, and 30°–33°. The peaks of the manganese com-
pounds were somewhat shifted towards lower 2θ
values. The middle amorphous halo was absent in the
diffraction pattern of compound V.
The suspensions of somewhat better water-soluble
solid complexes of iron Fe(H3L)3·4H2O and manga-
nese Mn(H3L)2·4H2O readily passed into the aqueous
solution upon addition of 2-aminoethanol. Synthesis,
isolation, and drying (see Experimental section)
yielded the hydrated compounds of iron and manganese
containing six [Fe(H3L)3·6H2NCH2CH2OH·2H2O, XI]
or three [Mn(H3L)2·3H2NCH2CH2OH·4H2O, XII]
molecules of 2-aminoethanol. Of all the prepared com-
plexes, only compound XII was crystalline and
revealed sufficiently high solubility in the aqueous
medium (yet the solubility was lower than that of the
amorphous compounds).
The product cooling gave a transparent glassy
substance that could be broken into smaller pieces and
ground into white powder in a porcelain mortar.
According to the elemental analysis data, the obtained
salt X was of the Н4L·4NH2C(CH2OH)3 composition,
with four molecules of compound II being bound to a
single molecule of the four-basic (1-hydroxy-
ethylidene)diphosphonic acid. The salt X was formed
at the reactants ratio of 1 : 4 or 1 : 3 in any of the
above-mentioned solvents. Solubility of compound X
in methanol was of 1.8 g in 100 mL.
IR spectra of the metal complexes and the salts of
(1-hydroxyethylidene)diphosphonic acid with 2-amino-
ethanol and 2-amino-2-(hydroxymethyl)propane-1,3-
diol were identical and contained three absorption
regions at 3700–2000, 1700–1500, and 1200–900 cm–1.
The bands were assigned using the information
provided in [10, 11]. In particular, the strong broad
overlapping bands at 3700–2000 cm–1 corresponded to
stretching of О–Н bonds in alcohol hydroxyl groups as
well as N–H and О–Н bonds in the H3N+–C and Р(О–Н)
groups. The two medium-intensity bands at 1620 and
1530 cm–1 were assigned to the N–H deformation
vibration, whereas the very strong structured band with
maximum at 1050 cm–1 was due to vibrations of the
С–О, С–N, and Р(О)ОН fragments.
Hence, the products of the reaction between (1-
hydroxyethylidene)diphosphonic acid with amines I
and II were significantly different. The salt IV readily
crystallized, whereas the resin-like compound X turned
into amorphous glass upon heating. Likely, the latter
compound was a coordination polymer due to
formation of strong intermolecular hydrogen bonds
between the Р=Оδ– and δ+Н–О–С fragments. The three
electronegative hydroxyl groups (ОН, σI = 0.25) [9]
were linked to the same carbon atom in the molecule
of 2-amino-2-(hydroxymethyl)propane-1,3-diol; there-
fore, their acidity was significantly enhanced to exceed
that of the hydroxyl group in the 2-aminoethanol
molecule (СН2ОН, σI 0.05). The salt formation
induced the appearance of positive charge at the
nitrogen atom and further increase of the acidic
properties of compound II. In the 2-aminoethanol
molecule, nitrogen atom was separated from the
hydroxyl group by an additional methylene bridge, and
the positive charge was better compensated.
The reactions with amines I and II were more
convenient ways to prepare water-soluble forms of
iron and manganese coordination compounds as com-
pared to the earlier developed procedure of accurate
titration of the poorly soluble salts with (1-
hydroxyethylidene)diphosphonic acid by potassium or
ammonium hydroxides [1]. Good results were
achieved only in the cases of the amines containing
hydroxyl groups, becoming readily water-soluble
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PREPARATION OF AMORPHOUS WATER-SOLUBLE COMPLEXES
owing to the presence of the latter. The required amine
1121
I
amount could be easily calculated taking into account
the number of Р(О)ОН groups in the coordination
compounds (6 mol per 1 mol of Fe2(H2L)3·4H2O and
2 mol per 1 mol of MnH2L·2H2O. The experiments
revealed that the complexes could be dissolved even
with a slight lack of the amine (10–15%) with respect
to the calculated amount. The sharp solubility
enhancement was due to both formation of the salts via
the free (not bound to the cation) groups of the protic
acid and to the presence of hydroxyl groups in the
organic amines.
In the absence of the С(ОН) groups in the amines
they did not react with the compounds of iron and
manganese. That was observed as preservation of the
two-phase system upon prolonged vigorous stirring of
the complex aqueous suspension in the presence of the
amine at 80–90°С.
2θ, deg
Fig. 4. X-ray powder diffraction patterns of compounds
(1) III, (2) V, (3) VII, (4) VIII, and (5) IX.
During the 2014 vegetation period, we performed a
series of model, laboratory, and vegetation tests to
estimate the agricultural efficiency of the novel micro-
fertilizers. Spring rape was utilized as a biological
model. Aqueous solutions of the (1-hydroxyethyl-
idene)diphosphonic acid complexes with copper, zinc,
manganese, and iron were prepared. The copper Cu(H3L)2·
5H2O and zinc ZnH2L·4H2O compounds revealed
sufficiently high solubility in aqueous media. Due to
the higher solubility of the Fe(H3L)3·4H2O and
Mn(H3L)2·4H2O salts as compared to that of Fe2(H2L)3·
4H2O and MnH2L·2H2O, the following pairs of iron
and manganese complexes with (1-hydroxyethylidene)
diphosphonic acid (with and without 2-aminoethanol
as the solubility promotor) were selected for the tests:
Fe(H3L)3·4H2O and Fe(H3L)3·6H2NCH2CH2OH·2Н2О
ХI; Mn(H3L)2·4H2O and Mn(H3L)2·3H2NCH2CH2OH·
4H2O XII. Moreover, the readily soluble MnH2L·
2H2NCH2CH2OH·2H2O VII complex was tested as
well.
yield than conventional copper sulfate. Compounds
VII and XII when used for out-root fertilization were
the most efficient of the manganese compounds; the
total biomass increase was of 91 and 45 g/vessel,
respectively, and the increase of pods mass was of 58
and 45 g/vessel, respectively. The iron complexes
showed no advantages over iron sulfate.
The amine should be introduced into the reaction
mixture after complete dissolution of the metal
compound (iron hydroxide or basic manganese
carbonate) during commercial production of the
aqueous solutions of iron and manganese aminium(1-
hydroxyethylidene)diphosphonates. The so prepared
concentrated solutions were stable upon long-term
storage under conditions of alternating temperatures,
revealing no precipitation of crystalline solids.
Dry powders of the water-soluble aminium salts
were wetted after addition of the minimal amount of
water, and turned into transparent viscous liquids 1–
2 h later. Further addition of water decreased the
viscosity, and the solutions rapidly became the low-
viscous colored fluids. In view of that, it was not
possible to determined the compounds solubility
quantitatively; instead, the prepared complexes should
be regarded as the compounds with infinitely high
solubility.
The one-year results concluded on the possibility of
application of the prepared compounds as micro-
fertilizers. The suggested form of zinc-containing
fertilizer (ZnH2L·4H2O) showed much better results
when applied to spring rape than zinc sulfate. The
highest effect was achieved out-root fertilization,
yielding additional 105 g of the total mass (including
55 g of pods) per 5 kg of soil in the vegetation vessel
as compared to the zinc-free reference test. Copper
compounds were more efficient in the case of the seeds
treatment. The novel fertilizer formulation Cu(H3L)2·
5H2O was 1.4 times more efficient towards rape pods
EXPERIMENTAL
IR spectra of the suspensions in vaseline oil placed
between KBr plates were recorded using a FSM 1201
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 5 2015

1122
SEMENOV et al.
IR-Fourier spectrometer. Electronic absorption spectra
of the aqueous solutions were registered using a
Perkin-Elmer Lambda 25 spectrophotometer.
diphosphonic acid in a porcelain mortar, and the
mixture was stirred. The formed viscous mass
solidified after 15 min. Re-crystallization from hot
methanol yielded 5.49 g (0.95 × 10–2 mol, 67%) of the
Н4L·3NH2CH2CH2OH salt; well soluble in water and
poorly soluble in methanol. IR spectrum, ν, cm–1:
3500–2200 br, 2145, 2046, 1596, 1552, 1281, 1084 sh,
1033, 938, 813, 723. Found, %: С 24.26; Н 7.47; N
11.06; P 16.31. C8H29N3O10P2. Calculated, %: С 24.68;
Н 7.51; N 10.79; P 15.91.
X-ray diffraction data were obtained using a Smart
APEX diffractometer (graphitic monochromator,
MoKα radiation, λ 0.71073 Å, ω- and φ-scans, 100 K).
Absorption was accounted for taking advantage of
SADABS software [12]. Structure of compound III
was solved via direct method and refined via least
squares method over F2hkl in the anisotropic approxi-
mation for all the non-hydrogen atoms. Hydrogen
atoms were placed into the geometrically defined
positions and refined in rider model [Uiso(H) =
1.2Ueq(C), 1.5Ueq(O)]. Positions of hydrogen atoms at
the O6 and O7 oxygen atoms [OH groups of (1-hyd-
roxyethylidene)diphosphonic acid] and the N(1A–C)
atoms of HOCH2CH2NH3+ molecules were fund via
differential Fourier synthesis of the electronic density
and refined under isotropic approximation. All
computations were performed using SHELXTL v.6.12
software package [13]. The selected bond lengths and
angles of compound IV are collected in Table 1. Basic
parameters of the X-ray diffraction experiment and the
solved structure of compound IV are given in Table 2.
Diiron(III) tris(1-hydroxyethylidenediphospho-
nate) penta(2-hydroxyethanaminium) tetrahydrate
(V). 0.68 g (1.12 × 10–2 mol) of 2-aminoethanol was
added to a stirred suspension of 1.29 g (1.62 ×
10–3 mol) of the finely ground Fe2(H2L)3·4H2O iron
complex in 15 mL of distilled water. 12 h later water
was removed, the glassy mass was ground, and the
obtained orange powder was incubated in vacuum at
100°С. Yield 1.53 g (1.39 × 10–3 mol, 86%), IR
spectrum, ν, cm–1: 3700–2000 br, 1623, 1525, 1278,
1087, 1000, 813, 724, 664. Found, %: С 17.91; H 5.36;
N 6.74; Fe 10.18; P 16.94. C16H61N5Fe2O30P6. Cal-
culated, %: C 17.45; H 5.58; N 6.36; Fe 10.14; P 16.87.
Manganese(II) (1-hydroxyethylidene)diphospho-
nate bis(2-hydroxyethanaminium) dihydrate (VII)
was prepared similarly from 1.78 g (5.70 × 10–3 mol)
of the MnH2L·2H2O manganese complex, 10 mL of
distilled water, and 1.43 g (2.34 × 10–2 mol) of 2-
aminoethanol. Yield 2.26 g (5.0 × 10–3 mol, 88%). IR
spectrum, ν, cm–1: 3125 br, 2800–2000 br, 1620, 1528,
1066, 995, 950, 819, 721, 658. Found, %: С 16.96; H
5.94; N 6.84; Mn 13.06; P 14.75. C6H26N2MnO12P2. Cal-
culated, %: C 16.56; H 6.02; N 6.44; Mn 12.62; P 14.24.
(1-Hydroxyethylidene)diphosphonic acid (“pure”
grade, Khimprom, TU 2439-363-05783441-2002) was
used; zinc (1-hydroxyehtylidene)diphosphonate tetra-
hydrate [14] and copper bis(1-hydroxyethylidene)
diphosphonate pentahydrate [15] were prepared as
described in the corresponding references.
Diiron(III) tris[(1-hydroxyethylidene)diphospho-
nate] nona(2-hydroxyethanaminium) (III).
A
mixture of 1.52 g (1.91 × 10–3 mol) of the finely ground
Fe2(H2L)3·4H2O iron complex and 10 mL (1.67 ×
10–1 mol) of 2-aminoethanol was stirred at 50°С. After
40 min, 2-aminoethanol was distilled off, and the
residue was heated in vacuum during 1 h at 110–130°С.
Yield 1.56 g (1.23 × 10–3 mol, 64%), light-brown powder,
well soluble in water, poorly soluble in methanol, and
insoluble in ethanol, DMSO, and acetonitrile. IR
spectrum, ν, cm–1: 3500–2200 br, 2127, 1623, 1531,
1278, 1087, 1006, 813, 723, 664. Found, %: С 21.83;
H 6.88; N 10.15; Fe 8.90; P 14.80. C24H81N9Fe2O30P6.
Calculated, %: С 22.63; H 6.41; N 9.90; Fe 8.77; P
14.59.
Diiron(III) tris[(1-hydroxyethylidene)diphospho-
nate] hexa[1,3-dihydroxy-2-(hydroxymethyl)propan-
2-aminium]) tetrahydrate (VIII). 3.11 g (2.56 ×
10–2 mol) of 2-amino-2-(hydroxymethyl)propane-1,3-
diol ground in a mortar was added portionwise to a
stirred suspension of 3.39 g (4.26 × 10–3 mol) of the
finely ground Fe2(H2L)3·4H2O iron complex in 25 mL
of distilled water. The dissolution was complete after
30 min at 80–90°С. Water was removed; the residue
was dried at 110–115°С, ground, and dried in vacuum
at 200°С. Yield 5.62 g (3.69·10–3 mol, 87%), yellow
powder, well soluble in water. IR spectrum, ν, cm–1:
3208 br, 2750–2090 br, 1617, 1522, 1054, 813, 723,
664, 580, 473. Found, %: С 24.07; H 6.35; Fe 7.40; P
12.31. C30H92N6Fe2O43P6. calculated, %: С 23.66; H
6.09; Fe 7.34; P 12.21.
Tris(2-hydroxyethanaminium)(1-hydroxyethyl-
idene)diphosphonate (IV). 3.45 g (5.64 × 10–2 mol)
of 2-aminoethanol was added to 3.16 g (1.41 ×
10–2 mol) of finely ground (1-hydroxyethylidene)-
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PREPARATION OF AMORPHOUS WATER-SOLUBLE COMPLEXES
1123
Manganese(II) (1-hydroxyethylidene)diphosphonate
bis[1,3-dihydroxy-2-(hydroxymethyl)propan-2-
aminium] dihydrate (IX) was prepared similarly from
4.13 g (1.32 × 10–2 mol) of the MnH2L·2H2O manga-
nese complex, 50 mL of distilled water, and 3.35 g
(2.77 × 10–2 mol) of 2-amino-2-(hydroxymethyl)-
propane-1,3-diol. Yield 6.47 g (1.17 × 10–2 mol, 87%),
coarsely dispersed light-grey powder. IR spectrum, ν,
cm–1: 3600–3020 br, 2750–2200 br, 2077, 1609, 1527,
1056, 994, 950, 905 sh, 819, 721, 657, 559, 479.
Found, %: С 21.31; H 6.05; Mn 9.82; P 11.07.
C10H34N2MnO16P2. Calculated, %: C 21.63; H 6.17;
Mn 9.89; P 11.16.
rate (XII) was prepared similarly form 11.01 g (2.05 ×
10–2 mol) of the Mn(H3L)2·4H2O complex, 100 mL of
water, and 4 mL (4.08 g, 6.69 × 10–2 mol) of 2-
aminoethanol. Yield 11.37 g (1.58·10–2 mol, 77%),
light-brown powder. IR spectrum, ν, cm–1: 3600–2100
br, 1624, 1509, 1302, 1272, 1139, 1071, 1021, 988,
929 sh, 893, 787, 725, 663, 642, 580, 538. Found, %:
С 17.04; H 6.55; Mn 7.66; P 17.27. C10H43N3MnO21P4.
Calculated, %: С 16.67; H 6.02; Mn 7.63; P 17.20.
Solubility 1.94 g in 100 mL of the solution.
ACKNOWLEDGMENTS
The studies were performed at Analytical Center of
Institute of Organometallic Chemistry, Russian Academy
of Sciences.
Tris[1,3-dihydroxy-2-(hydroxymethyl)propan-2-
aminium] (1-hydroxyethylidene)diphosphonate (Х).
5.3 mL of 0.72 M of (1-hydroxyethylidene)diphos-
phonic acid solution in ethanol (0.86 g, 3.82 ×
10–3 mol) was added dropwise at stirring to a hot solu-
tion of 1.39 g (1.15 × 10–2 mol) of 2-amino-2-(hydroxy-
methyl)propane-1,3-diol in 10 mL of ethanol. 12 h
later the solvent was decanted; the residue was dried in
air during 7 h at 115°С and in vacuum at 200°С. Yield
1.89 g (2.74 × 10–3 mol, 72%), colorless glassy mass.
IR spectrum, ν, cm–1: 3650–3000 br, 2800–2000 br,
1617, 1528, 1293, 1125, 1057, 968, 905, 807, 724, 643,
539, 464. Found, %: С 31.87; H 7.97; P 9.03. C18H52N4O19P2.
Calculated, %: С 31.31; H 7.59; P 8.97.
This work was financially supported by Presidium
of Russian Academy of Sciences in the frame of the
“Targeted synthesis of compounds with desired
properties and development of functional materials
based thereof” program.
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The reactions in mixed solvents were performed
similarly, adding ethanolic solution of (1-hydroxy-
ethylidene)diphosphonic acid to a hot solution or
suspension of compound II in methanol, acetone,
toluene, or DMSO. Compound II was completely
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Iron(III) tris[(1-hydroxyethylidene)diphospho-
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added upon stirring to a suspension of 18.62 g (2.50 ×
10–2 mol) of the finely ground Fe(H3L)3·4H2O complex
in 200 mL of water. 15 min later the mixture was
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