Reduction of the groups C=O and C=N with neodymium and dysprosium diiodide hydrides

Article abstract of DOI:10.1007/s11172-011-0236-2

Neodymium diiodide hydride under mild conditions adds at the carbonyl group of benzo-phenone to give (diphenylmethoxy)(diiodo)neodymium(_III) of the formula I₂Nd(OCHPh2)(THF)₄. In reactions of NdI ₂H and DyI

Full text of DOI:10.1007/s11172-011-0236-2

Russian Chemical Bulletin, International Edition, Vol. 60, No. 8, pp. 1586—1590, August, 2011
1586
Reduction of the groups C=O and C=N
with neodymium and dysprosium diiodide hydrides
M. E. Burin, A. A. Logunov, N. O. Druzhkov, G. K. Fukin, and M. N. Bochkarev
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 462 7497. Eꢀmail: mboch@iomc.ras.ru
Neodymium diiodide hydride under mild conditions adds at the carbonyl group of benzoꢀ
phenone to give (diphenylmethoxy)(diiodo)neodymium(III) of the formula I2Nd(OCHPh2)(THF)4.
In reactions of NdI2H and DyI2H with Nꢀ(2,6ꢀdiisopropylphenyl)ꢀ9,10ꢀphenanthrenequinonꢀ
imine, the system of conjugated C=N and C=O groups of the quinone is reduced. The resulting
oꢀaminophenanthrolate complexes are structurally characterized by Xꢀray diffraction.
Key words: neodymium diiodide hydride, dysprosium diiodide hydride, ketones, imines,
reduction, Xꢀray diffraction analysis.
Scheme 1
In the synthesis of organic derivatives of rareꢀearth
metals, common starting reagents include free lanthanides,
halides LnX2 and LnX3 (X = Cl and I), or their hydrates.1—7
Other inorganic compounds such as oxides Ln2O3, hydrides
LnH3, and carboxylates Ln(RCO2)3 are not employed,
though being accessible, as sources of rare earth metals in
the organolanthanide synthesis because of their low reacꢀ
tivity. Recently, we have found8 that neodymium(III) and
dysprosium(III) diiodide hydrides (NdI2H and DyI2H, reꢀ
spectively) can serve as promising lanthanide reagents.
These compounds, which are directly prepared from diꢀ
iodides LnI2 and hydrogen, react with alcohols, phenol,8
cyclopentadienylpotassium,9 and potassium naphthalene10
under mild conditions to give the corresponding complexꢀ
es containing, apart from the Ln—I bonds, the Ln—OR,
Ln—Cp, and Ln—C10H8 bonds, respectively. In a search
for other possible applications of NdI2H and DyI2H, here
we studied the reactivities of these compounds toward some
carbonylꢀ and iminoꢀcontaining substrates.
the diphenylmethoxy ligand OCHPh2 and the I(1) atom
in the axial positions (Fig. 1, Table 1). The angle
Nd(1)—O(1)—C(1) (170.4(2)°) and the Nd(1)—O(1)
bond length (2.111(2) Å) are typical of rare earth metal
I(1)
O(4S)
O(3S)
O(1S)
Nd(1)
O(1)
Results and Discussion
C(8)
H(1A)
C(1)
C(2)
Heating of an equimolar mixture of benzophenone and
NdI2H in THF at 60 °C for 2 h (Scheme 1) produced
a reddish violet solution. Subsequent workup involving
concentration and addition of diethyl ether afforded adꢀ
duct 1 as airꢀunstable colorless crystals. According to Xꢀray
diffraction data, complex 1 results from the addition of
the hydride fragment Nd—H of the starting diiodide hyꢀ
dride to the carbonyl group of benzophenone.
I(2)
O(2S)
The coordination polyhedron of the Nd atom is a disꢀ
torted pentagonal bipyramid made up of four THF moleꢀ
cules and the I(2) atom in the equatorial plane and
Fig. 1. Molecular structure of the complex I2Nd(OCHPh2)—
(THF)4 (1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1562—1565, August, 2011.
1066ꢀ5285/11/6008ꢀ1586 © 2011 Springer Science+Business Media, Inc.

Reduction of ketones with LnI2H
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011
1587
Table 1. Selected bond lengths (d) and bond angles (ω) in structure 1
Scheme 2
Bond
d/Å
Angle
ω/deg
Nd(1)—O(1)
O(1)—C(1)
2.111(2)
1.376(4)
2.495(2)
2.493(2)
2.536(2)
2.520(2)
3.1752(3)
3.2054(3)
C(2)—C(1)—C(8)
O(1)—C(1)—C(2)
O(1)—C(1)—C(8)
C(1)—O(1)—Nd(1) 170.4(2)
O(1)—Nd(1)—I(1)
O(1)—Nd(1)—I(2)
110.8(3)
114.3(3)
110.0(3)
Nd(1)—O(1S)
Nd(1)—O(2S)
Nd(1)—O(3S)
Nd(1)—O(4S)
Nd(1)—I(1)
Nd(1)—I(2)
174.51(6)
95.40(6)
alkoxides.11—14 The C(1)—O(1) bond length (1.376(4) Å)
in the diphenylmethoxy ligand is comparable with an anaꢀ
logous bond in the complex Yb(OCHPh2)2(OAr)(HMPA)2
(1.369 Å).11
Dysprosium diiodide hydride reacts with benzoꢀ
phenone in a similar way, yielding a fine crystalline light
yellow product. According to elemental analysis and IR
spectroscopic data, this compound can be formulated as
(I2DyOCHPh2)2(THF). However, we failed to obtain its
crystals suitable for Xꢀray diffraction experiments.
Reactions of NdI2H and DyI2H with 9,10ꢀphenanꢀ
threnequinonimine in THF occurred under more drastic
conditions: even exposure to ultrasound at 70 °C for 7 days
provided only 40—50% conversion of the starting hydride.
During the reaction, the initial green solutions characterꢀ
istic of the neutral ligand turned reddish brown. By adding
DME, we isolated yellow crystals of complexes 2 and 3 in
77 and 86% yields, respectively (Scheme 2). Note that the
reaction in boiling acetonitrile resulted in complete dissoꢀ
lution of the starting iodide hydrides in 6 h. However, the
yields of products 2 and 3 in this case did not exceed 50%
(probably because of intense side processes).
Ln = Nd (2), Dy (3)
172.50(16)°, respectively) are smaller only by 4° than the
corresponding angles in complexes 4 and 5, while the anꢀ
gles O(1)—C(1)—C(2) and C(1)—C(2)—N(1) in comꢀ
plexes 2—5 vary within 1°. However, the pairs of comꢀ
plexes 2, 3 and 4, 5 differ substantially in nature. In comꢀ
plexes 4 and 5, one ligand is neutral and is coordinated to
the metal center, while the other is 9,10ꢀphenanthrenꢀ
esemiquinonimine with the unpaired electron at the Cmeta
atom of the central ring of the phenanthrene fragment. In
complexes 2 and 3, the phenanthrolate ligand contains
the substituent 2,6ꢀPri2C6H3NH at the C(2) atom. The
protonation of the N(1) atom in these complexes is eviꢀ
dent from both Xꢀray diffraction data and IR spectra (an
absorption band at 3315—3320 cm–1).
Both compounds are very unstable in air; they are well
soluble in THF but virtually insoluble in hexane.
According to Xꢀray diffraction data, complexes 2 and
3 are isostructural NdIII and DyIII aminophenanthrolate
diiodides with a distorted pentagonalꢀbipyramidal coordiꢀ
nation of the Ln cation. The equatorial plane consists of
the O atoms of the DME molecules and the aminophenanꢀ
throlate ligand, while the iodide anions are in the axial
positions (Fig. 2, Table 2).
Complexes 2 and 3 are first representatives of a novel
class, namely, lanthanide aminophenanthrolates. Their
closest semiquinonimine analogs 4 and 5 have been obꢀ
tained recently15 from appropriate diiodides LnI2 and
9,10ꢀphenanthrenequinonimine (Scheme 3).
Interestingly, the complexes of both groups show
monodentate coordination of the ligands. In view of comꢀ
pounds 4 and 5, this is unusual for iminoquinone comꢀ
plexes. As a consequence, the geometrical parameters of
the fragments Ln—L are similar. For instance, the angles
Ln(1)—O(1)—C(1) in products 2 and 3 (172.1(2)° and
I(1)
O(5)
O(4)
C(2)
Ln
C(1)
O(1)
H(1)
N(1)
O(3)
2,6ꢀPriC6H3
O(2)
I(2)
Fig. 2. Molecular structures of the complexes LnI2LH(DME)2
(Ln = Nd (2), Dy (3)). For the coordinated DME molecules, the
O atoms are shown only.

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Burin et al.
Table 2. Selected bond lengths (d) and bond angles (ω) in structures 2 and 3
Bond
d/Å
Angle
ω/deg
2
3
2
3
Ln(1)—O(1)
Ln(1)—O(2)
Ln(1)—O(3)
Ln(1)—O(4)
Ln(1)—O(5)
Ln(1)—I(1)
Ln(1)—I(2)
C(1)—O(1)
C(1)—C(2)
C(2)—N(1)
N(1)—C(15)
2.155(2)
2.507(2)
2.526(2)
2.545(2)
2.512(2)
3.0849(3)
3.1055(3)
1.343(4)
1.384(4)
1.398(4)
1.429(4)
2.085(2)
2.434(2)
2.441(2)
2.463(2)
2.439(2)
3.0042(2)
3.0281(2)
1.342(3)
1.389(4)
1.391(3)
1.437(3)
O(1)—Ln(1)—I(1)
O(1)—Ln(1)—I(2)
O(1)—Ln(1)—O(2)
O(1)—Ln(1)—O(3)
O(2)—Ln(1)—O(3)
Ln(1)—O(1)—C(1)
O(1)—C(1)—C(2)
C(1)—C(2)—N(1)
C(2)—N(1)—C(15)
96.77(6)
93.33(6)
79.92(8)
145.82(8)
65.98(8)
172.1(2)
119.5(3)
116.8(3)
128.1(3)
96.40(5)
93.27(5)
78.62(7)
145.90(7)
67.37(6)
172.50(16)
119.3(2)
116.9(2)
127.8(2)
Scheme 3
sponding alkoxide diiodides I2LnOCHPh2. Under more
drastic conditions (ultrasound, 70 °C), the same iodide
hydrides react with Nꢀ(2,6ꢀdiisopropylphenyl)ꢀ9,10ꢀ
phenanthrenequinonimine in THF, yielding lanthanide
complexes of a novel type, namely, (oꢀaminophenanꢀ
throlato)(diiodo)neodymium and (oꢀaminophenanthroꢀ
lato)(diiodo)dysprosium.
Experimental
Reactions were carried out using standard Schlenk equipꢀ
ment to prevent any contact with atmospheric oxygen or moisꢀ
ture. The solvent THF and DME were dried and stored over
Na/benzophenone and distilled in vacuo immediately before use.
Iodide hydrides NdI2H and DyI2H and Nꢀ(2,6ꢀdiisopropylpheꢀ
nyl)ꢀ9,10ꢀphenanthrenequinonimine were prepared as described
earlier.8,17 IR spectra were recorded on a FSMꢀ1201 FTIR specꢀ
trometer in the 4000—400 cm–1 range. Magnetic measurements
were effected according to a known procedure.18
Xꢀray diffraction studies were carried out on a Bruker AXS
SMART APEX diffractometer (MoꢀKα radiation, graphite
monochromator, ϕ—ω scan mode) at 100 K. The structures were
solved by the direct methods and refined anisotropically by the
fullꢀmatrix leastꢀsquares method on F2 for all nonꢀhydrogen
atoms with the SHELXTL program package.19 Absorption corꢀ
rections were applied using the SADABS program.20 The hydroꢀ
gen atoms were located geometrically and refined isotropically
using a riding model. The crystallographic parameters and the
data collection statistics for structures 1—3 are summarized
in Table 3.
Reduction of benzophenone with NdI2H. A solution of benꢀ
zophenone (0.35 g, 1.92 mmol) in THF (4 mL) was added to
a suspension of NdI2H (0.768 g, 1.92 mmol) in THF (10 mL). The
reaction mixture was stirred at 60 °C for 2 h. The resulting redꢀ
dish violet solution was filtered; the greater part of the solvent
was removed from the vessel in vacuo and collected in a cooled
trap. Then diethyl ether (10 mL) was slowly added to the reddish
violet concentrate by diffusion under reduced pressure. The
colorless crystalline precipitate that formed was washed with
THF and dried in vacuo. The yield of product 1 was 0.35 g
(20%). Found (%): C, 39.84; H, 5.65. C29H43O5NdI2. Calculatꢀ
Ln = Nd (4), Dy (5)
The magnetic moment of product 2 (3.3 μB) correꢀ
sponds to that of the Nd3+ cation (μeff = 3.68 μB);16 i.e.,
the metal undergoes no redox transformations during this
complexation reaction.
Attempted addition of NdI2H and DyI2H to the C=O
(carbon monoxide), C=C (styrene), C≡C (phenylacetylene
and diphenylacetylene), and N=N bonds (azobenzene)
were unsuccessful: even upon exposure of the reaction mixꢀ
ture to ultrasound at 70 °C for many hours, the starting
reactants were recovered intact.
To sum up, we found that NdI2H and DyI2H readily
add at the C=O bond of benzophenone to give the correꢀ

Reduction of ketones with LnI2H
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 8, August, 2011
1589
Table 3. Crystallographic parameters and the data collection statistics for complexes 1—3
Parameter
1
2
3
Molecular formula
Molecular weight
Crystal system
Space group
a/Å
C29H43I2NdO5
869.67
C36H51I2NNdO6
991.82
C36H51DyI2NO6
1010.08
Monoclinic
P2(1)/c
Monoclinic
P2(1)/c
9.4197(4)
17.9246(7)
19.4114(8)
95.480(1)
3262.5(2)
4
Monoclinic
P2(1)/c
11.7045(8)
12.9607(9)
26.7027(18)
101.133(1)
3974.5(5)
4
11.6620(6)
12.8756(7)
26.543(1)
101.331(1)
3907.8(4)
4
b/Å
c/Å
β/deg
3
V/Å
Z
dcalc/g cm–3
1.771
3.517
1.658
2.901
1.717
3.533
μ/mm–1
F(000)
1692
1952
1976
Crystal dimensions/mm
0.16×0.11×0.07
27.50
0.32×0.18×0.10
26.00
0.30×0.10×0.09
26.50
θ
max/deg
Number of measured/independent reflections
Rint
S(F 2)
30723/7461
0.0263
33319/7798
0.0236
24206/8094
0.0241
1.055
1.085
1.067
R factor (I > 2σ(I))
R1
wR2
0.0349
0.0811
0.0294
0.0702
0.0292
0.0688
R factor for all reflections
R1
wR2
0.0482
0.0853
0.0342
0.0725
0.0349
0.0709
Residual electron density,
(max/min)/e Å
2.217/–0.591
1.875/–1.195
2.079/–1.000
–3
ed (%): C, 40.04; H, 4.95. IR (Nujol, KBr), ν/cm–1: 1458 s,
1378 m, 1367 m, 1317 w, 1270 m, 1182 w, 1172 m, 1037 m,
1032 m, 1019 m, 927 w, 911 w, 754 m, 735 s, 698 s, 655 m,
603 m, 544 w.
(Nujol, KBr), ν/cm–1: 3317 s, 1603 m, 1575 s, 1517 w, 1488 w,
1206 m, 1190 w, 1178 w, 1119 s, 1076 s, 1031 s, 1012 s, 975 m,
932 m, 856 s, 788 m, 753 m, 696 m, 675 m.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 10ꢀ03ꢀ00190).
Reduction of Nꢀ(2,6ꢀdiisopropylphenyl)ꢀ9,10ꢀphenanthreneꢀ
quinonimine with NdI2H. Tetrahydrofuran (8 mL) was added to
a mixture of NdI2H (0.45 g, 1.12 mmol) and the quinonimine
(0.41 g, 1.12 mmol). The suspension was heated in an ultrasound
bath at 70 °C for five days. The resulting reddish brown solution
was decanted from the precipitate of the starting iodide hydride
NdI2H (0.24 g) and concentrated in vacuo. The solid residue was
washed with hexane (2×10 mL). The resulting brown powder
was dissolved in THF (1 mL) and DME (5 mL) was added. The
yellow crystals of complex 2 that formed were separated by deꢀ
cantation, washed with cold DME, and dried in vacuo. The
yield was 0.40 g (77% with respect to the consumed NdI2H);
m.p. >180 °C (decomp.); μ = 3.3 μ . One crystal was used
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Received December 15, 2010