Synthesis and some properties of neodymium(III) and dysprosium(III) iodide hydrides LnI2H

Article abstract of DOI:10.1007/s11172-007-0303-x

The iodide hydrides NdI₂H (1) and DyI₂H (2) were obtained by the reactions of diiodides NdI₂ (3) and DyI₂ (4) with hydrogen at atmospheric pressure and temperature of 120-200 °C. Hydrolysis of products 1 and 2 gives hydrogen in a high yield. The reactions of 1 with phenol and of 2 with isopropyl alcohol in THF afford the iodide phenoxide NdI₂(OPh)(THF)₄ and iodide isopropoxide DyI ₂(OPrⁱ)(PrⁱOH)₃, respectively. The reaction of 2 with cyclopentadiene is accompanied by disproportionation and gives, besides dihydrogen, Cp₂DyI(THF)₂ and DyI ₃(THF)₃.

Full text of DOI:10.1007/s11172-007-0303-x

Russian Chemical Bulletin, International Edition, Vol. 56, No. 10, pp. 1953—1955, October, 2007
1953
Synthesis and some properties of neodymium(III) and dysprosium(III)
iodide hydrides LnI2H
M. N. Bochkarev,ꢀ A. A. Logunov, and M. E. Burin
G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831) 462 4021. Eꢀmail: mboch@iomc.ras.ru
The iodide hydrides NdI2H (1) and DyI2H (2) were obtained by the reactions of diiodides
NdI2 (3) and DyI2 (4) with hydrogen at atmospheric pressure and temperature of 120—200 °C.
Hydrolysis of products 1 and 2 gives hydrogen in a high yield. The reactions of 1 with phenol
and of 2 with isopropyl alcohol in THF afford the iodide phenoxide NdI2(OPh)(THF)4 and
iodide isopropoxide DyI2(OPri)(PriOH)3, respectively. The reaction of 2 with cyclopentadiene
is accompanied by disproportionation and gives, besides dihydrogen, Cp2DyI(THF)2 and
DyI3(THF)3.
Key words: diiodides, hydrides, dysprosium, neodymium, isopropoxide, cyclopentadienide.
The reactivities of divalent neodymium and dysproꢀ
sium diiodides LnI2 are similar to those of alkali and rare
earth metals.1 The latter easily react with H2 to form
hydride phases with a composition close to LnH3 or, at
elevated temperature, to LnH2 (see Ref. 2). To our knowlꢀ
edge, the reactions of the diiodides LnI2 with hydrogen
have not been studied earlier, and the chemical properties
of the probable products such as LnI2H have not been
studied either. Meanwhile, such hydrides can be of conꢀ
siderable interest as synthons and catalysts of hydrogenaꢀ
tion of organic and organometallic compounds. So far,
only rare earth metal organic hydrides, i.e., molecular
complexes containing organic ligands bound to the metal
atom, apart from the Ln—H group, have been used in the
synthetic practice.3 This study deals with the reactions of
diiodides 3 and 4 with hydrogen and some properties of
the iodide hydrides 1 and 2 thus formed.
absorbed hydrogen in reactions with compounds 3 and 4
were 52 and 80%, respectively, relative to the value calcuꢀ
lated from the equation
,
(1)
Ln = Nd (1, 3), Dy (2, 4).
Thulium(II) diiodide, whose reduction potential
(–2.3 V)4 is considerably lower than the potentials of
neodymium(II) and dysprosium(II), does not react with
hydrogen under comparable conditions.
The considerable difference between the calculated
and absorbed amounts of hydrogen in reaction (1) is probꢀ
ably due to shielding of the particle surface of diiodides 3
and 4 by the iodide hydrides 1 and 2 formed. Presumably,
the density of the layer of product 1 is higher, which is
reflected in the reaction rate and degree of conversion.
The rate of reaction (1) and the amount of absorbed hyꢀ
drogen depend appreciably on the degree of dispersion of
the initial iodide powders. Compounds with particle size
of 0.01—0.05 mm were used in the work.
Products 1 and 2 are rapidly hydrolyzed in air; howꢀ
ever, they are quite stable in dry inert atmosphere. Heatꢀ
ing to 150 °C in vacuo does not induce visible changes or
hydrogen evolution. The IR spectra of compounds 1 and 2
in the 400—4000 cm–1 range contain a broad band with
peaks at 930 (Nd) and 950 cm–1 (Dy), which may be
assigned to Ln—H vibrations. In the spectra of the comꢀ
plexes LnH2(THF)3 (Ln = Sm, Eu, Yb), the bands for
hydride groups occur at 1250 cm–1 (see Refs 5 and 6).
Results and Discussion
Heating of powders 3 and 4 under atmospheric presꢀ
sure of H2 to a temperature of 120 °C was found to induce
slow gas absorption, which is considerably accelerated at
higher temperatures. During the reaction, the color of
NdI2 does not change, while the color of the DyI2 powder
gradually changes from dark violet to black. Despite the
higher reduction potential of NdII (–2.62 V) compared to
DyII (–2.45 V),4 iodide 3 reacts more slowly than dysproꢀ
sium salt 4. At 200 °C, hydrogen absorption stopped after
10 h in the case of 3, whereas in the case of iodide 4, the
reaction was almost completed after 2 h. The amounts of
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1887—1889, October, 2007.
1066ꢀ5285/07/5610ꢀ1953 © 2007 Springer Science+Business Media, Inc.

1954
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 10, October, 2007
Bochkarev et al.
Lanthanide cyclopentadienyl hydrides have typically two
absorption regions for the Ln—H groups: 650—900 cm–1
and 1100—1350 cm–1 (see Ref. 7).
tion of the precipitate, the complex Cp2DyI(THF)2 was
isolated from the solution by lowꢀtemperature crystalliꢀ
zation.
Hydrides 1, 2 are insoluble in hexane, toluene, and
ether; they are slowly dissolved in pyridine and acetoniꢀ
trile, but dissolution is accompanied by chemical transꢀ
formations, which are currently under study. The powꢀ
ders of 1 and 2 are insoluble in THF; however, the soluꢀ
tion acquires violet (1) or green (2) color due to dissoluꢀ
tion of the impurities of initial iodides 3 and 4 present in
the sample. These can be isolated from solutions by lowꢀ
temperature crystallization as the complexes LnI2(THF)5
(see Ref. 8). After treatment with tetrahydrofuran and
drying in vacuo at 40 °C for 4 h, the hydrides contain no
THF, as indicated by the absence of new bands in the
IR spectrum of the powders and good agreement of the
metal and iodine contents with the formulas NdI2H and
DyI2H. Since products 1 and 2 are insoluble in THF and
do not retain it in the coordinated state, one can conclude
that THF molecules do not destroy the crystal lattice
of LnI2H. The magnetic moment of hydride 1 (3.8 µB) is
markedly higher than the µeff value of the initial iodide 3
(2.7 µB) and corresponds to trivalent neodymium,9 which
thus confirms the redox nature of reaction (1) and the
saltꢀlike nature of products 1 and 2.
.
(4)
The formation of dysprosium triiodide in 46% yield
and the dicyclopentadienyl complex attest to disproporꢀ
tionation of the monocyclopentadienyl product CpDyI2,
which must have formed in the initial stage. Substituent
redistribution processes of this type are usual for rare earth
metal cyclopentadienyl halides.7 No disproportionation
was noted in the homogeneous reaction of diiodides 3
and 4 with cyclopentadiene in a THF solution, resulting
in the complexes CpLnI2(THF)3.10
Thus, divalent neodymium and dysprosium iodides 3
and 4 add hydrogen under relatively mild conditions to
give iodide hydrides 1 and 2. The metal is simultaneously
oxidized to the trivalent state. Hydrogen within comꢀ
pounds 1 and 2 is highly reactive, thus making these comꢀ
pounds promising as hydrogenating agents.
Experimental
Hydrolysis of the iodide hydrides with water proceeds
vigorously and is accompanied by hydrogen evolution.
The yield of the gas (98% for 1 and 85% for 2) is someꢀ
what lower than the stoichiometric yield, because of the
presence of triiodide LnI3 impurity in diiodides 3 and 4.
The reaction of compound 2 with isopropyl alcohol is
very slow; however, in the presence of THF, the reaction
is nearly as vigorous as that with water. As the metalꢀ
containing product, the isopropoxide DyI2(OPri)(PriOH)3
was isolated as colorless crystals.
The syntheses were carried out under conditions excluding
contact with oxygen or air moisture using Schlenk type glassꢀ
ware. Tetrahydrofuran was distilled from NaOH, deaerated,
dried by adding NdI2 (THF, 500 mL; NdI2,2 g; 20 °C, 30 min),
and condensed into the reaction vessel directly prior to use.
Isopropyl alcohol was dried by a standard procedure. The
diiodides NdI2 and DyI2 were prepared by a previously deꢀ
veloped procedure.8,11 The IR spectra were recorded on a
FSMꢀ1201 FT IR spectrometer in the 4000—400 cm–1 range.
The samples were prepared as mineral oil mulls. The lanthanide
content in the obtained compounds was determined by
complexometry and the iodine content, by back titration. Magꢀ
netic measurements were carried out by a known procedure.12
Synthesis of diiodide hydride NdI2H (1). A tube containing a
powder of 3 (4.52 g, 11.35 mmol) was connected to a hydrogenꢀ
filled gas burette and heated at 200 °C. Hydrogen was gradually
absorbed. The reaction stopped after 10 h after absorption of
66 mL (52%; standard conditions) of H2. The resulting powder
was washed with tetrahydrofuran (6×25 mL) at room temꢀ
perature and dried for 4 h in vacuo at 40 °C to give 2.16 g (56%)
of hydride 1. Found (%): I, 62.50; Nd, 36.78. HI2Nd. Calꢀ
culated (%): I, 63.60; Nd, 36.15. IR (mineral oil, KBr,
ν/cm–1): 930. µ (293 K) = 3.8 µ .
.
(2)
Hydride 1 showed a lower reactivity toward compounds
containing an active hydrogen atom. Deprotonation of
isopropyl alcohol even in a THF solution at room temꢀ
perature proceeds during 7 days and gives an intractable
mixture of products. The reaction of 1 with phenol, which
was accelerated by sonication of the mixture, gave the
phenoxide PhONdI2(THF)4 (yield 83%).
eff
B
.
(3)
Synthesis of diiodide hydride DyI2H (2). Compound 4 (2.97 g,
7.13 mmol) was kept under hydrogen for 2 h under conditions of
the previous experiment. The color of the powder of 4 changed
from dark violet to black; 63 mL (79%; standard conditions)
of H2 was absorbed. The product was washed with THF
(6×25 mL) at room temperature and dried for 4 h in vacuo at
40 °C to give 2.4 g (80%) of hydride 2. Found (%): Dy, 38.65;
I, 59.81. HDyI2. Calculated (%): Dy, 38.92; I, 60.83. IR (mineral
oil, KBr, ν/cm–1): 950.
An equally pronounced difference between the reacꢀ
tivities of hydrides 1 and 2 was manifested in the reaction
with cyclopentadiene. Whereas hydride 1 is absolutely
inert toward CpH, hydride 2 readily reacts with it at room
temperature. The reaction is accompanied by hydrogen
evolution and precipitation of DyI3(THF)3. After separaꢀ

Iodide hydrides of neodymium and dysprosium
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 10, October, 2007
1955
Hydrolysis of complexes 1 and 2. Water (10 mL) was added
at room temperature to a powder of 1 (0.18 g, 0.45 mmol).
Vigorous gas evolution was observed. After 1 min, the reaction
was completed; 9.9 mL (98%; standard conditions) of hydrogen
was evolved.
IR (mineral oil, KBr, ν/cm–1): 1343 w, 1293 w, 1260 w, 1176 w,
1038 m, 1010 s, 953 w, 913 m, 851 s, 784 s, 670 m.
References
Under similar conditions hydride 2 (0.47 g, 1.13 mmol) gave
21.2 mL (85%; standard conditions) of hydrogen.
1. M. N. Bochkarev, Coord. Chem. Rev., 2004, 248, 835.
2. M. E. Kost, A. L. Shilov, V. I. Mikheeva, S. I. Uspenskaya,
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A. A. Eliseev, G. M. Kuz´micheva, and G. B. Seifer,
Soedineniya redkozemel´nykh elementov. Gidridy, boridy,
karbidy, fosfidy, pniktidy, khal´kogenidy, psevdogalogenidy
[Rare Earth Element Compounds. Hydrides, Borides, Carbides,
Phosphides, Pnictides, Chalcogenides, Pseudohalides] Nauka,
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Penyagina, S. Ya. Khorshev, and A. V. Protchenko,
Metalloorgan. Khim., 1989, 2, 703 [Organomet. Chem. USSR,
1989, 2, 363].
Reaction of 1 with phenol. A solution of PhOH (0.18 g,
1.91 mmol) in THF (15 mL) was added at room temperature to
a tube containing compound 1 (0.59 g, 1.48 mmol). The tube
was placed into an ultrasonic bath and kept for 8 h at 40 °C until
the black powder of 1 completely dissolved and a pale blue finely
crystalline precipitate formed. THF (20 mL) was added to the
reaction mixture and the resulting solution was filtered through
a glass filter. Slow removal of THF resulted in the precipitation
of paleꢀblue crystals of PhONdI2(THF)4, which were separated
by decantation, washed with cold THF, and dried in vacuo. The
product yield was 0.95 g (83%); m.p. 145—147 °C (decomp.).
Found (%): I, 33.10; Nd, 19.00. C22H37I2NdO5. Calculated (%):
I, 32.56; Nd, 18.50. IR (mineral oil, KBr, ν/cm–1): 1585 m,
1500 s, 1344 s, 1280 m, 1219 m, 1065 s, 1019 s, 921 w, 860 s,
772 m, 699 m, 596 m, 560 m.
6. E. A. Fedorova, A. A. Trifonov, E. N. Kirillov, and M. N.
Bochkarev, Izv. Akad. Nauk. Ser. Khim., 2000, 947 [Russ.
Chem. Bull., Int. Ed., 2000, 49, 946].
7. M. N. Bochkarev, L. N. Zakharov, and G. S. Kalinina,
Organoderivatives of Rare Earth Elements, Kluwer Academic
Publishers, Dordrecht, 1995, 532 p.
8. M. N. Bochkarev and A. A. Fagin, Chem. Eur. J., 1999,
5, 2990.
9. W. J. Evans and M. A. Horzbor, J. Organomet. Chem., 1987,
326, 299.
10. G. V. Khoroshen´kov, A. A. Fagin, M. N. Bochkarev,
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2003, 1627 [Russ. Chem. Bull., Int. Ed., 2003, 52, 1715].
11. M. A. Katkova, G. K. Fukin, A. A. Fagin, and M. N.
Bochkarev, J. Organomet. Chem., 2003, 682, 218.
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eksperimenta [Experimental Instruments and Techniques],
Nauka, Moscow, 1990, 1, 194 pp. (in Russian).
Reaction of 2 with isopropyl alcohol. Isopropyl alcohol (5 mL)
and THF (0.5 mL) were added in vacuo to hydride 2 (0.34 g,
0.82 mmol). Gas evolution and gradual dissolution of 2 were obꢀ
served. The mixture was stirred for 1.5 h until hydrogen evoluꢀ
tion ceased. The solution thus formed was centrifuged, decanted
from the precipitate, and concentrated in vacuo. The finely crysꢀ
talline precipitate formed was separated by decantation, washed
with cold THF, and dried in vacuo at room temperature to give
0.40 g (75%) of the compound I2Dy(OPri)(PriOH)3 as colorless
crystals. Found (%): Dy, 24.40; I, 40.11. C12H31DyI2O4. Calcuꢀ
lated (%): Dy, 24.79; I, 38.80. IR (mineral oil, KBr, ν/cm–1):
1285 m, 1159 m, 1142 m, 1112 m, 1080 s, 942 s, 917 s, 797 s,
743 w, 533 m.
Reaction of 2 with cyclopentadiene. A solution of CpH (1 mL)
and THF (5 mL) were added in vacuo to hydride 2 (0.44 g,
1.05 mmol). Hydrogen evolution and gradual dissolution of 2
were observed. The mixture was centrifuged, decanted from the
precipitate, and concentrated by slow removal of the solvent.
The resulting colorless needle crystals were separated by decanꢀ
tation, washed with cold THF, and dried in vacuo to give 0.17 g
(30%) Cp2DyI(THF)2; m.p. 180 °C. Found (%): Dy, 29.30;
I, 30.11. C18H26DyIO2. Calculated (%): Dy, 28.84; I, 23.50.
Received April 4,2007;
in revised form August 22, 2007