Aluminum hydrides with radical-anionic and dianionic acenaphthene-1,2-diimine ligands

Article abstract of DOI:10.1007/s11172-017-1926-1

The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with LiAlH₄ affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether). These products were isolated as green and colorless crystals. Green

Full text of DOI:10.1007/s11172-017-1926-1

Russian Chemical Bulletin, International Edition, Vol. 66, No.9, pp. 1569—1579, September, 2017
1569
Aluminum hydrides with radicalꢀanionic and dianionic
acenaphtheneꢀ1,2ꢀdiimine ligands*
V. G. Sokolov, T. S. Koptseva, M. V. Moskalev, A. V. Piskunov, M. A. Samsonov, and I. L. Fedushkin
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603137 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 462 7497. Eꢀmail: igorfed@iomc.ras.ru
The reaction of 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene (dppꢀbian) with
LiAlH4 affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether).
These products were isolated as green and colorless crystals. Green crystals of the complex
[(dppꢀbian)Al(H)2Li(THF)3] (1) were obtained from tetrahydrofuran; colorless crystals of
the complex [{dppꢀbian(H2)}Al(H)2Li(Et2O)2] (2), from diethyl ether. The reactions of comꢀ
pound 1 with 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylphenol and benzophenone gave monohydrides [(dppꢀ
bian)Al(H)(OC6H2ꢀ2,6ꢀBut2ꢀ4ꢀMe)][Li(THF)4] (3) and [(dppꢀbian)Al(H)(OCHPh2)ꢀ
Li(THF)2] (4), respectively. The diamagnetic aluminum hydride [(dppꢀbian)AlH(THF)] (5)
was synthesized by the reaction of dichloroalane HAlCl2 (in situ) with the disodium salt of
dppꢀbian in THF; the paramagnetic hydride [(dppꢀbian)AlH(Cl)] (6) containing the dppꢀ
bian radical anion was synthesized by the reaction of the monosodium salt (dppꢀbian)Na with
monochloroalane H2AlCl (in situ) in diethyl ether. The reaction of compound 6 with tertꢀ
butyllithium gives the complex [(dppꢀbian)AlBut(Et2O)] (7). Diamagnetic derivatives 1—5
1
and 7 were characterized by Н NMR spectroscopy; paramagnetic compound 6, by ESR specꢀ
troscopy. The molecular structures of compounds 1—7 were determined by singleꢀcrystal
Xꢀray diffraction.
Key words: aluminum, hydrides, redoxꢀactive ligands, diimine ligands, molecular structure.
Aluminum hydrides are widely used in different inꢀ
dustrial applications as components of Ziegler—Natta
catalyst systems for αꢀolefin polymerization and oligoꢀ
merization and for the synthesis of stereoregular diene
rubbers.1,2 Besides, these compounds proved to be effiꢀ
cient reagents for the preparation of aluminum chalcoꢀ
genides3—6 and alumoxanes by controlled hydrolysis,7 as
well as reducing agents.8 In some cases, the use of hydrides
as selective reducing agents is limited by their high reducꢀ
tion potentials. One way to modify the reactivity of aluꢀ
minum hydrides is to combine them with nitrogenꢀconꢀ
taining ligands. This approach was successfully applied
to coordination compounds of dꢀblock elements and
to mainꢀgroup metal complexes with redoxꢀactive
1,2ꢀacenaphthenediimine ligands. In the latter case, the
molecular systems containing mainꢀgroups metals exhibit
reactivity toward organic and inorganic molecules simiꢀ
lar to that observed in elementary steps of the catalytic
cycles involving transition metal compounds.9—14 This is
made possible due to the presence of a redoxꢀactive ligand,
which can reversibly accept and release electrons and be
directly involved in the formation and cleavage of chemiꢀ
cal bonds with substrates.
Aluminum hydrides with nitrogen ligands, such as
bis(imino)pyridine,15—17 βꢀdiketiminate, (bis)amide,18,19
and aminotroponiminate ligands,20 have attracted much
attention in recent years. However, no aluminum hydrides
with the anionic diimine ligand have been reported. In
this work, we present the synthesis, structures, and some
properties of aluminum hydrides with radicalꢀanionic and
dianionic acenaphtheneꢀ1,2ꢀdiimine ligands.
Results and Discussion
Synthesis and characterization of compounds 1—7. The
reaction of the diimine dppꢀbian with one equivalent of
lithium aluminum hydride LiAlH4 proceeds in tetrahydroꢀ
furan (80 °C) or diethyl ether (20 °C) over 1 and 6 h, resꢀ
pectively. Hydrogen that was eliminated in the course of the
reaction was removed by shortꢀterm evacuation of the tube.
In both cases, the color of the reaction mixture changes
from yellow to green. The products [(dppꢀbian)Al(H)2Liꢀ
(THF)3] (1, 29%) and [{dppꢀbian(H2)}Al(H)2Li(Et2O)2]
(2, 44%) were isolated as darkꢀgreen and colorless crysꢀ
tals from tetrahydrofuran and diethyl ether, respectively.
* Dedicated to Academician of the Russian Academy of Sciences
G. A. Abakumov on the occasion of his 80th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1569—1579, September, 2017.
1066ꢀ5285/17/6609ꢀ1569 © 2017 Springer Science+Business Media, Inc.

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Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017
Sokolov et al.
at δ 3.96 (4 H) assigned to isopropyl groups of 2,6ꢀ
Pri2C6H3 substituents, as well as a doublet at δ 5.50 (2 H)
and multiplets at δ 6.41—6.62 (4 H) and 6.86—7.03 (6 H)
belonging to aromatic protons. Protons of THF moleꢀ
cules appear as two multiplets at δ 1.72 (10 H) and 3.57
(10 H). Minor signals observed in the NMR spectrum are
attributed to the presence of an impurity of the hydrolysis
product of compound 1. Their total integrated intensity is
not higher than 4 H. Thus, the signal of the N—H proton
of the diamine dppꢀbianH2 appears as a singlet at δ 5.28
(0.1 H).
1
In the H NMR spectrum of compound 2 (Fig. 2),
four pairwise equivalent methine protons of isopropyl
groups of 2,6ꢀPri2C6H3 substituents appear as septets at δ
3.96 (2 H) and 4.36 (2 H). Protons of eight pairwise
equivalent methyl groups of isopropyl substituents give
four doublets at δ 1.62 (6 H), 1.50 (6 H), 1.11 (6 H), and
1.07 (6 H). The latter two doublets overlap and look like
as a triplet. It should be noted that there are two mirror
planes in the free diamine dppꢀbian; one plane coincides
with the plane of the diimine moiety, whereas another
one is perpendicular to the first plane and passes through
the midpoint of the C—C bond of the diimine moiety.
A singlet of methine protons of the 1,2ꢀdihydroacenaphthꢀ
ylene moiety appears at δ 5.76 (2 H). Aromatic protons of
the naphthalene moiety and phenyl substituents at the
nitrogen atoms are observed as two doublets at δ 7.01
(2 H) and 7.54 (2 H) and a multiplet at δ 7.16—7.35 (8 H).
Signals of two coordinated ether molecules appear as
a triplet and a quartet at δ 0.65 (12 H) and 2.86 (8 H),
respectively.
Ar = 2,6ꢀPri2C6H3
The use of a fiveꢀfold excess of lithium aluminum
hydride and an increase in the reaction time to 18 h do
not lead to a significant change in the product ratio. The
formation of complex 1 occurs via the replacement of
two hydrogen atoms in LiAlH4 with diimine and the reꢀ
duction of the latter to the dianion; the formation of comꢀ
pound 2 proceeds via the reduction of the C—C bond in
the diimine moiety of the dppꢀbian ligand. Apparently,
hydride 2 was obtained for the first time in the synthesis
of (1R,2S)ꢀN,Nꢀbis(aryl)ꢀ1,2ꢀdihydroacenaphthyleneꢀ
1,2ꢀdiamine. However, this compound has not been isoꢀ
lated and structurally characterized at that time.21 More
recently, it was demonstrated22 that the reduction of the
diimine [(2,6ꢀPri2C6H3)NC(Me)]2 with an equivalent
amount of H3Al•N(Ме) affords the only product — the
3
complex [(2,6ꢀPri2C6H3)NCH(Me)]2AlH(NMe3).
The IR spectra of hydrides 1 and 2 show intense abꢀ
sorption bands at 1757 and 1662 cm–1 (1) and at 1662
and 1537 cm–1 (2) characteristic of Al—H stretching
vibrations. In the spectrum of lithium aluminum hydride,
these vibrations appear as intense bands at 1462 and
1377 cm–1. The 1H NMR spectrum of compound 1
(Fig. 1) shows signals of the symmetrical dppꢀbian ligand:
two doublets at δ 1.01 (12 H) and 1.15 (12 H) and a septet
The reaction of compound 1 with 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀ
methylphenol (1 : 1) proceeds in THF at room temperaꢀ
ture via protonolysis of the Al–H bond (Scheme 1). The
reaction product [(dppꢀbian)Al(H)(OC6H2ꢀ2,6ꢀBut2ꢀ4ꢀ
Me)][Li(THF)4] (3) was isolated as a finelyꢀcrystalline
green powder. The crystals that formed from C4D8O in
an NMR tube were suitable for Xꢀray diffraction.
Recently, the heterolytic cleavage of water15 and
anilines16 in the presence of bis(imino)pyridineꢀligated
6.5
5.5
4.5
3.5
2.5
1.5
0.5
δ
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0.5
δ
Fig. 1. 1H NMR spectrum of compound 1 (200 MHz, C4D8O,
Fig. 2. 1H NMR spectrum of compound 2 (200 MHz, C6D6,
298 K).
298 K).

Aluminum hydrides
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017 1571
Scheme 1
(2 H) and 7.07 (2 H) and a pseudoꢀtriplet at δ 6.88 (2 H)
assigned to protons of the naphthalene moiety. Signals
of aromatic protons of 2,6ꢀPri2C6H3 substituents and
the aroxy ligand 2,6ꢀBut2ꢀ4ꢀMeC6H2O are observed at
δ 7.26—7.38 (8 H). The presence of two mirror planes in
the ligand of compound 3 is apparently attributed to the
rapid exchange between the hydride ion and the aroxy
ligand. Singlets at δ 1.72 (18 H) and 2.44 (3 H) belong to
tertꢀbutyl and methyl groups, respectively. Signals of four
coordinated THF molecules appear as two multiplets at
δ 1.17 (16 H) and 3.38 (16 H).
The reaction of compound 1 with benzophenone (1 : 1)
proceeds in toluene at 50 °C for 15 min. The reaction
product — the complex [(dppꢀbian)Al(H)(OCHPh2)ꢀ
Li(THF)2] (4) (Scheme 2) — was isolated as blueꢀgreen
crystals by concentrating the solution. It should be noted
that the reaction of 4,4´ꢀdimethoxybenzophenone with
[(dppꢀbian)AlEt(Et2O)] is accompanied only by the reꢀ
placement of the coordinated solvent molecule at the
aluminum atom by ketone. 14
Ar = 2,6ꢀPri2C6H3
aluminum hydride complexes was described. In these proꢀ
cesses, acidic N—H and O—H substrates are inserted
into the Al—N bond but do not protonate the Al—H
bond. The derivative [(dppꢀbian)AlEt(Et2O)] reacts in
a similar manner with 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylphenol,
the latter being inserted into the Al—N bond to form the
amino amide complex.14 It is noteworthy that similar
processes are observed in the reactions of compounds conꢀ
taining labile hydrogen atoms with Group 2 metal comꢀ
plexes containing the dppꢀbian dianion.23—25 Therefore,
it can be concluded that the hydride ion has a higher
basicity compared to the amide nitrogen atoms in comꢀ
plex 1 and the alkyl carbon atom in the compound [(dppꢀ
bian)AlEt(Et2O)]. Hydride 1 proved to be unreactive toꢀ
ward such substrates as PhC≡CH, Me3SiC≡CH, and
Pri2NH. As opposed to complex 1, the IR spectrum of
which has two bands (1757 and 1662 cm–1) assigned to
Al—H bonds, the IR spectrum of compound 3 exhibits
a single band (1776 cm–1) corresponding to Al—H
stretching vibrations.
Scheme 2
Ar = 2,6ꢀPri2C6H3
In the IR spectrum of compound 4, the Al—H stretchꢀ
ing vibrations appear as a strong band at 1691 cm–1. In
the 1H NMR spectrum (Fig. 4), two partially overlapping
septets of four pairwise equivalent methine protons of
2,6ꢀPri2C6H3 substituents are observed at δ 4.03 (2 H)
and 4.11 (2 H); protons of eight pairwise equivalent
methyl groups of isopropyl substituents, as three doublets
Unexpectedly, the 1H NMR spectrum of compound 3
(Fig. 3) shows only signals of the symmetrical dppꢀbian
ligand: doublets at δ 1.24 (12 H) and 1.27 (12 H) and
a septet at δ 3.82 (4 H) belonging to isopropyl groups of
2,6ꢀPri2C6H3 substituents and also two doublets at δ 6.32
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0.5
δ
7.0
6.0
5.0
4.0
3.0
2.0
1.0
δ
Fig. 3. 1H NMR spectrum of compound 3 (200 MHz, C6D6,
Fig. 4. 1H NMR spectrum of compound 4 (200 MHz, C6D6,
298 K).
298 K).

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Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017
Sokolov et al.
Scheme 4
at δ 1.20 (12 H), 1.29 (6 H), and 1.43 (6 H). The aliphatic
region also has a singlet at δ 2.11 (3 H) assigned to the
methyl group of toluene that is present in the crystal
lattice. Aromatic protons appear as a doublet at δ 6.27
(2 H) and a set of signals at δ 6.82—7.39 (25 H). The
singlet at δ 6.35 (1 H) belongs to the methine proton of
the OCHPh2 substituent. Protons of two coordinated
THF molecules give signals at δ 1.08 (8 H) and 3.04 (8 H).
The complex [(dppꢀbian)AlH(THF)] (5) was syntheꢀ
sized by the reaction of dichloroalane HAlCl2 with the
disodium salt of dppꢀbian (Scheme 3). The reaction proꢀ
ceeds at room temperature at a rate with which the reꢀ
agents are mixed and is accompanied by a change in the
color of the solution from green to blue. Darkꢀblue crystals
of compound 5 were obtained by concentrating its solution
in diethyl ether; crystals suitable for Xꢀray diffraction
were obtained from a diethyl ether—benzene mixture (10 : 1).
Ar = 2,6ꢀPri2C6H3
containing a paramagnetic radicalꢀanionic ligand. First
aluminum derivatives with free–radical ligands were synꢀ
thesized 45 years ago.26 They are generated by the reacꢀ
tion of aluminum halides with orthoꢀbenzoquinones in
tetrahydrofuran, benzene, or acetone. The reaction proꢀ
ceeds through the activated complexation followed by
electron transfer from the halide ion to the quinone to
form the semiquinolate ligand.
Scheme 3
In the IR spectrum of compound 6, Al—H stretching
vibrations appear as a mediumꢀintensity band at
1876 cm–1, which is close to the corresponding value for
compound 5 (1864 cm–1) but substantially differs from
those for compounds 3 and 4 (1776 and 1691 cm–1, reꢀ
spectively). This difference can be attributed to the fact
that the hydride ion in complexes 5 and 6 is not coordiꢀ
nated to the lithium atom as opposed to compounds 3
and 4, resulting in that the energy of Al—H stretching
vibrations is higher in the latter case. Paramagnetic comꢀ
pound 6 was characterized by ESR spectroscopy (Fig. 5).
The hyperfine structure of the ESR signal in solution is
associated with splitting of an unpaired electron at 27Al
(I = 5/2, 100%), two pairs of protons (I = 1/2, 99.99%)
of the naphthalene system, two equivalent 14N nuclei of
the diimine moiety (I = 1, 99.6%), magnetic isotopes of
the chlorine 35Cl (I = 3/2, 75.77%) and 37Cl (I = 3/2,
24.23%), and the hydride ion (I = 1/2, 99.99%). Some
difference between the calculated and experimental
spectra is apparently attributed to the dynamic process in
the coordination sphere of the aluminum atom, which
Ar = 2,6ꢀPri2C6H3
In the IR spectrum of complex 5, the Al—H stretchꢀ
ing vibrations appear as an intense band at 1864 cm–1
.
This value is similar to the corresponding value for the
compound [{(2,6ꢀPri C6H3)NCH(Me)}2AlH(NMe3)]
2
(1851 cm–1).22 The H NMR spectrum of compound 5
1
in deuterobenzene has a broadened signal of methyl proꢀ
tons of 2,6ꢀPri2ꢀC6H3 substituents at δ 1.15—1.38 (24 H)
and a septet of methine protons of these substituents at
δ 3.82 (4 H). Two doublets at δ 6.30 (2 H) and 7.07 (2 H)
and multiplets at δ 6.88 (2 H) and 7.33 (6 H) belong to
aromatic protons of the naphthalene moiety and phenyl
substituents at the nitrogen atoms. Signals of the coordiꢀ
nated THF molecule appear as two multiplets at δ 1.06
(4 H) and 3.59 (4 H).
Aluminum hydride with the dppꢀbian radical anion
was synthesized by the reaction of H2AlCl with the monoꢀ
sodium salt of dppꢀbian taken in a ratio of 1:1. Unfortuꢀ
nately, we failed to prepare the target complex [(dppꢀ
bian)AlH2]. The reaction of equimolar amounts of HAlCl2
and (dppꢀbian)Na produces the compound [(dppꢀbian)ꢀ
AlH(Cl)] (6) in a very low yield (5%). Meanwhile,
hydride 6 is generated in a yield of up to 78% in the
reaction of (dppꢀbian)Na with two equivalents of H2AlCl
(Scheme 4).
15 G
1
2
3380 3400 3420 3440 3460 3480 3500 H/G
Fig. 5. Experimental (1) and simulated (2) ESR spectra of
complex 6 in toluene at 293 K (gi = 2.0024; ai(27Al) = 3.0,
ai(35Cl) = 9.6, ai(37Cl) = 8.0, ai(2 14N) = 4.7, ai(4 1H) = 1.1,
ai(1H) = 10.8 Oe).
Compound 6 was isolated from toluene as darkꢀbrown
crystals and it is the first example of aluminum hydrides

Aluminum hydrides
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017 1573
can involve changes in the bond angles and, as a conseꢀ
quence, in hyperfine constants.
nitrogen atoms are observed at δ 5.83—7.22 (12 H). The
singlet at δ 0.93 (9 H) is assigned to protons of the
tertꢀbutyl group.
In order to synthesize a mixed alkyl aluminum hydrꢀ
ide complex, we performed the reaction of compound 6
with tertꢀbutyllithium in diethyl ether. The color of the
reaction mixture changed from brown to blueꢀgreen at
room temperature within 60 min. The reaction was
accompanied by gas evolution (presumably hydrogen).
The reaction product — the compound [(dppꢀbian)AlButꢀ
(Et2O)] (7) (Scheme 5) — was isolated as blue crystals by
concentrating the reaction mixture. Compound 7 is apꢀ
parently generated from the unstable intermediate [(dppꢀ
bian)AlH(But)] through the reductive elimination of
hydrogen accompanied by the reduction of the radicalꢀ
anionic diimine ligand to the dianion. It should be noted
that the reaction of compound 6 with one molar equivaꢀ
lent of benzyl potassium in toluene affords a difficultꢀtoꢀ
separate mixture of reaction products.
Structures of compounds 1—7. The structures of comꢀ
pounds 1—7 were established by Xꢀray diffraction. The
molecular structures of compounds 1—7 are shown in
Figs 7—13, respectively In the crystalline state, complex 1
(Fig. 7) exists as a contact ion pair, in which aluminum
and lithium atoms are bridged by a hydride ion. Both
metal atoms have slightly distorted tetrahedral coordinaꢀ
tion. The N(1)—C(1), N(2)—C(2), and C(1)—C(2) bond
lengths (1.387(2), 1.394(2), and 1.372(3) Å, respectively;
Table 1) in the diimine moiety are indicative of the dianꢀ
ionic reduction state of dppꢀbian.
For instance, these distances in the compound [(dppꢀ
bian)AlMe(Et2O)] are 1.407(4), 1.409(4), and 1.371(4) Å,
respectively.27 The Al—H(1) and Al—H(2) bond lengths
Scheme 5
O(1)
H(1)
Li
N(2)
O(2)
C(2)
C(1)
O(3)
Al
N(1)
Ar = 2,6ꢀPri2C6H3
H(2)
In the 1H NMR spectrum of compound 7 (Fig. 6), the
chemical shifts of two septets of methine protons virtualꢀ
ly coincide and partially overlap with the signal of the
residual protons of deuterated tetrahydrofuran. Protons
of four nonequivalent pairs of methyl groups of isopropyl
substituents appear as four doublets at δ 0.83 (6 H),
1.16 (6 H), 1.22 (6 H), and 1.35 (6 H). Aromatic protons
of the naphthalene moiety and phenyl substituents at the
Fig. 7. Molecular structure of compound 1 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms, except for the H(1) and H(2) atoms, are not shown.
H(1)
N(2)
C(2)
O(2)
Al
C(1)
N(1)
Li
O(1)
H(1´)
H(2´)
H(2)
Fig. 8. Molecular structure of compound 2 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms, except for the H(1), H(2), H(1´), and H(2´) atoms, are
not shown.
7.5
6.5
5.5 3.5
2.5
1.5
0.5
δ
Fig. 6. 1H NMR spectrum of compound 7 (200 MHz, C4D8O,
298 K).

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Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017
Sokolov et al.
N(2)
O(1)
H(1)
C(2)
C(1)
O(1)
Al
N(2)
N(1)
C(2)
C(1)
N(1)
Al
H(1)
Fig. 9. Molecular structure of the anion of compound 3 with
displacement ellipsoids drawn at the 30% probability level. The
hydrogen atoms, except for the H(1) atom and the [Li+(THF)4]
cation, are not shown.
Fig. 11. Molecular structure of compound 5 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms, except for the H(1) atom, are not shown.
Compound 2 (Fig. 8) exists as a contact ion pair,
in which aluminum and lithium atoms are linked by
two hydride ions. In compound 2, the N(1)—C(1)
(1.4634(15) Å), N(2)—C(2) (1.4690(15) Å), and C(1)—C(2)
(1.5897(16) Å) bonds are longer than those in hydride 1
(1.387(2), 1.394(2), and 1.372(3) Å, respectively). This is
apparently due to the lack of conjugation in the metalloꢀ
cycle —Al—N(1)—C(1)—C(2)—N(2)— in compound 2.
Meanwhile, the Al—H(1) (1.555(17) Å) and Al—H(2)
(1.557(17) Å) distances in complex 2 are similar to those
in hydride 1 (1.588(18) and 1.553(19) Å).
H(37)
O(1)
N(2)
C(2)
O(2S)
Li
Al
C(1)
N(1)
O(1S)
H(1)
Compounds 3 and 4 are aroxy and alkoxy aluminum
hydride complexes. Complex 3 is composed of the solꢀ
ventꢀseparated [Li(THF)4]+ cation and [(dppꢀbian)ꢀ
Al(H)O(2,6ꢀBut2ꢀ4ꢀMeC6H2)]– anion. As opposed to
compound 3, the [Li(THF)2]+ cation in complex 4 is
coordinated by both the oxygen atom and the hydride
ligand. The difference in the geometry of complexes 3
and 4 (Table 2) is apparently attributed to the different
steric volume of RO groups.
Unlike compounds 1—4, complexes 5—7 do not conꢀ
tain lithium cations.
Compounds 5 (Fig. 11), 6 (Fig. 12), and 7 (Fig. 13)
are monomeric fourꢀcoordinate aluminum complexes. An
Fig. 10. Molecular structure of compound 4 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms, except for the H(1) and H(37) atoms, are not shown.
in complex 1 (1.588(18) and 1.553(19) Å, respectively)
are somewhat larger than the Al—H distances in the imiꢀ
nopyridinate derivatives of aluminum [(PhI2P2–)AlHꢀ
(THF)] (1.51(6) Å) and [(PhHI2P )AlH(NHAr)] (1.54(2) Å)
(
PhI2P = 2,6ꢀ(2,6ꢀPri2C6H3N=CPh)2C5H3N).16
Table 1. Selected bond lengths (d) and bond angles (ω) in compounds 1 and 2
Bond
d/Å
Bond
d/Å
Angle
ω/deg
1
2
1
2
1
2
Al—N(1)
Al—N(2)
Al—H(1)
Al—H(2)
1.8632(17) 1.8339(10)
1.8725(16) 1.8179(11)
1.588(18) 1.555(17)
1.553(19) 1.557(17)
N(1)—C(1) 1.387(2) 1.4634(15)
N(2)—C(2) 1.394(2) 1.4690(15)
C(1)—C(2) 1.372(3) 1.5897(16)
N(1)—Al—N(2)
N(1)—Al—H(1)
N(2)—Al—H(1)
N(1)—Al—H(2)
N(2)—Al—H(2)
H(1)—Al—H(2)
90.28(7) 92.34(5)
114.0(7) 121.7(6)
116.4(7) 118.1(6)
115.3(7) 114.6(6)
117.0(7) 117.8(6)
104.1(10) 94.4(9)

Aluminum hydrides
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017 1575
O(1)
Cl
C(1)
N(1)
N(2)
N(1)
C(2)
Al
C(2)
Al
N(2)
C(37)
C(1)
H(1)
Fig. 13. Molecular structure of compound 7 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms are not shown.
Fig. 12. Molecular structure of compound 6 with displacement
ellipsoids drawn at the 30% probability level. The hydrogen
atoms, except for the H(1) atom, are not shown.
bonds in complexes 5 and 7 (see Figs 11—13) and in
compounds 1—4 (see Figs 7—10). For comparison, the
N(1)—C(1) and N(2)—C(2) distances in the dimethyl
aluminum complex with the radicalꢀanionic dppꢀbian
ligand, (dppꢀbian)AlMe2, are 1.330(3) and 1.331(3) Å
(see Ref. 28); the N(1)—C(1) and N(2)—C(2) distances
in the methyl aluminum complex with the dppꢀbian diꢀ
analysis of the bond lengths in the metallocycles of comꢀ
plexes 5—7 (Table 3) shows that the dppꢀbian ligands in
these complexes are in different oxidation states. In comꢀ
pound 6, the C(1)—N(1) (1.3335(19) Å) and C(2)—N(2)
(1.3364(19) Å) bonds are shorter than the corresponding
Table 2. Selected bond lengths (d) and bond angles (ω) in compounds 3 and 4
Bond d/Å Bond d/Å
Angle
ω/deg
3
4
3
4
3
4
Al—O(1) 1.7495(10) 1.7597(11)
Al—N(1) 1.8945(12) 1.8659(13)
Al—N(2) 1.8840(12) 1.8578(13)
N(1)—C(1) 1.4055(18) 1.4023(19)
N(2)—C(2) 1.3937(18) 1.3997(18)
O(1)—Al—N(1) 119.81(5) 118.90(6)
O(1)—Al—N(2) 113.38(5) 118.59(6)
N(2)—Al—N(1) 90.91(5) 92.63(6)
C(1)—C(2) 1.382(2)
1.380(2)
Al—H(1) 1.537(16)
1.538(19)
O(1)—Al—H(1) 106.5(6)
96.3(7)
N(2)—Al—H(1) 117.8(6) 118.3(7)
N(1)—Al—H(1) 108.5(6) 113.8(7)
Table 3. Selected bond lengths (d) and bond angles (ω) in compounds 5, 6, and 7
Bond
d/Å
Angle
ω/deg
5
6
7
5
6
7
Al—N(1)
Al—N(2)
Al—O(1)
Al—Cl
Al—C(37)
Al—H(1)
N(1)—C(1)
N(2)—C(2)
C(1)—C(2)
1.8451(11)
1.8542(11)
1.8798(10)
—
1.9064(13)
1.9119(13)
—
2.1311(8)1
—
1.492(5)11
1.3335(19)
1.3364(19)
1.435(2)11
1.8586(9)1
1.8606(9)1
1.9341(8)1
—
1.9852(11)
—
1.4072(13)
1.4018(13)
1.3825(15)
N(1)—Al—–N(2)
N(1)—Al—O(1)
N(1)—Al—Cl
N(2)—Al—O(1)
N(2)—Al—Cl
N(1)—Al—C(37)
N(2)—Al—C(37)
N(1)—Al—H(1)
N(2)—Al—H(1)
O(1)—Al—H(1)
O(1)—Al—C(37)
Cl—Al—H(1)
192.43(5)
107.64(5)
—
112.06(5)
—
—
—
121.7(7)
121.7(6)
101.2(6)
—
187.85(6)
—
114.33(5)
—
112.72(5)
—
193.86(4)
100.60(4)
—
103.27(4)
—
120.14(4)
121.69(5)
—
—
1.533(17)1
1.4007(16)
1.4006(16)
1.3783(17)
—
126.7(12)
115.8(12)
—
—
—
—
113.53(4)
—
199.9(13)

1576
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017
Sokolov et al.
Synthesis of complexes 1 and 2. A mixture of dppꢀbian (2.0 g,
4 mmol) and LiAlH4 (0.16 g, 4.2 mmol) was stirred in tetraꢀ
hydrofuran (60 mL) at 80 °C for 1 h with the removal, from
time to time, of the hydrogen that formed by shortꢀterm evacuꢀ
ation of the tube. In the course of the reaction, the color of the
mixture changed from yellow to darkꢀgreen. Then the solvent
was replaced with toluene, and the solution was separated from
the gray precipitate by filtration (Schott filter no. 4) and conꢀ
centrated to 15 mL. Darkꢀgreen crystals of compound 1 (0.49 g),
which precipitated overnight, were washed with toluene and
dried in vacuo. The mother liquor was again concentrated
(5 mL). A mixture (1.53 g) of darkꢀgreen and colorless crystals
of compounds 1 and 2, respectively, was isolated after one day.
The ratio of products 1 and 2 in the mixture was 1 : 4, as
determined by NMR spectroscopy. Therefore, the total yield of
compound 1 was 0.79 g (29%); of complex 2, 1.22 g (44%).
Crystals of hydride 2, which were suitable for Xꢀray diffraction
and were used for measuring spectra, were isolated after recrysꢀ
tallization from diethyl ether.
Lithium 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene
aluminum dihydride tris(tetrahydrofuranate) (1). M.p. >178 °C
(decomp.). Found (%): C, 76.31; H, 9.36. C48H66AlLiN2O3.
Calculated (%): C, 76.57; H, 8.84. 1H NMR (200 MHz, C4D8O,
298 K), δ: 7.03—6.86 (m, 6 H); 6.62—6.41 (m, 4 H); 5.50
(d, 2 H, J = 6.1 Hz); 3.96 (sept, 4 H, J = 6.8 Hz); 3.57 (m, 10 H);
1.72 (m, 10 H); 1.15 (d, 12 H, J = 6.8 Hz); 1.01 (d, 12 H,
J = 6.8 Hz). IR (Nujol mulls), ν/cm–1: 2043 w, 1959 w, 1904 w,
1757 s, 1662 s, 1615 w, 1588 w, 1505 s, 1445 m, 1428 s, 1341 s,
1265 m, 1253 m, 1210 m, 1191 w, 1176 m, 1159 w, 1137 m,
1112 w, 1102 m, 1044 m, 956 m, 996 m, 933 m, 924 m, 888 m,
838 w, 804 m, 780 w, 759 m, 704 m, 661 w, 635 w, 620 w, 588 w,
578 w, 563 w, 546 w, 530 w.
Lithium 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)ꢀ1,2ꢀdiamino]ꢀ1,2ꢀ
dihydroacenaphthylene aluminum dihydride tris(tetrahydroꢀ
furanate) (2). M.p. >130 °C (decomp.). Found (%): C, 76.17;
H, 9.13. C44H64AlLiN2O2. Calculated (%): C, 76.93; H, 9.39.
1H NMR (200 MHz, C6D6, 298 K), δ: 7.54 (d, 2 H, J = 8.08 Hz);
7.35—7.16 (m, 8 H); 7.01 (d, 2 H, J = 6.8 Hz); 5.76 (s, 2 H);
4.36 (sept, 2 H, J = 6.8 Hz); 3.96 (sept, 2 H, J = 6.8 Hz); 2.86
(q, 8 H, J = 7.0 Hz); 1.62 (d, 6 H, J = 6.8 Hz); 1.50 (d, 6 H,
J = 6.8 Hz); 1.11 (d, 6 H, J = 6.8 Hz); 1.07 (d, 6 H, J = 6.8 Hz);
0.65 (t, 12 H, J = 7.0 Hz). IR (Nujol mulls), ν/cm–1: 1933 w,
1847 w, 1662 s, 1601 w, 1586 w, 1570 w, 1537 s, 1485 w, 1433 m,
1361 m, 1322 m, 1310 m, 1295 w, 1258 m, 1246 m, 1216 w,
1200 m, 1182 w, 1170 w, 1153 w, 1103 m, 1089 m, 1064 m,
1038 m, 1021 m, 982 m, 967 m, 944 m, 921 m, 897 m, 889 w,
847 m, 836 m, 825 m, 804 m, 800 m, 781 m, 760 s, 750 m,
705 m, 687 m, 660 w, 620 w, 600 w, 592 w, 562 w, 545 w.
Lithium 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene
aluminum hydride 2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylphenoxide tetrakisꢀ
(tetrahydrofuranate) (3). 2,6ꢀDiꢀtertꢀbutylꢀ4ꢀmethylphenol
(0.12 g, 0.53 mmol) was added to a solution of compound 1
(0.4 g, 0.53 mmol) in THF (20 mL). The mixture was stirred for
60 min at room temperature with the removal, from time to
time, of the hydrogen that formed under reduced pressure. The
resulting green solution was concentrated to 5 mL and allowed
to stand for 24 h at 10 °C. The green crystals of compound 3
that precipitated were separated from the solution by decantaꢀ
tion, washed with cold THF, and dried in vacuo. Yield 0.37 g
(65%). M.p. > 195 (decomp.). Found (%): C, 75.31; H, 11.58.
C67H64AlD32LiN2O5. Calculated (%): C, 74.82; H, 11.99.
anion, [(dppꢀbian)AlMe(Et2O)], are 1.407(4) and
1.409(4) Å, respectively.27 Meanwhile, the Al—N disꢀ
tances in complex 6 (1.9064(13) and 1.9119(13) Å) are
substantially longer than the Al—N distances in all comꢀ
pounds considered in the present study, which is indicaꢀ
tive of a stronger binding between the aluminum atom
and the dppꢀbian dianion compared to its radical anion.
The Al—H bond in complex 6 (1.492(5) Å) is similar to the
corresponding distances in compounds 3 (1.537(16) Å),
4 (1.538(19) Å), and 5 (1.533(17) Å).
In summary, in the present work we synthesized aluꢀ
minum hydrides with the redoxꢀactive acenaphtheneꢀ1,2ꢀ
diimine ligand dppꢀbian. Aluminum hydrides can be staꢀ
bilized by both the dianion of dppꢀbian and its radical
anion. The preliminary investigation of the reactivity of
the resulting hydrides demonstrated that these compounds
are chemically more inert than other aluminum hydrides,
including those containing redoxꢀinactive amide ligands.
Thus, compounds 1 and 5 do not react with terminal
alkynes and heptꢀ1ꢀene. Meanwhile, the hydrides deꢀ
scribed in this work are thermodynamically stable crysꢀ
talline compounds, the oxidation and hydrolytic stability
of which is higher, according to the preliminary data,
compared to other aluminum hydrides. Therefore, the
handling of these compounds in vacuo or under inert
atmosphere, both in the individual crystalline state and
solution, is not difficult.
In order to enhance the reactivity of aluminum hyꢀ
drides with the dppꢀbian ligand, we intend to synthesize
cationic derivatives, which, in our opinion, can coordiꢀ
nate unsaturated substrates and involve them in further
chemical transformations.
Experimental
Since all the synthesized compounds are sensitive to oxyꢀ
gen and moisture, all operations during their synthesis, isolaꢀ
tion, and identification of these compounds were carried out in
vacuo using the Schlenk technique or under a nitrogen atmoꢀ
sphere (Glovebox M. Braun). 1,2ꢀBis[(2,6ꢀdiisopropylphenyl)ꢀ
imino]acenaphthene (dppꢀbian) was prepared by the condenꢀ
sation of acenaphthenequinone and 2,6ꢀdiisopropylaniline
(Aldrich) in acetonitrile. Tetrahydrofuran, diethyl ether, benzꢀ
ene, and toluene were dried and stored over sodium benzoꢀ
phenone; hexane, over sodium mirror. All solvents were withdrawn
by vacuum condensation immediately before use. The IR spectra
were recorded on a FSMꢀ1201 spectrometer. The 1H NMR
spectra were measured on a Bruker DPXꢀ200 spectrometer
(200 MHz). Deuterobenzene (Aldrich) and deuterotetrahydroꢀ
furan (Aldrich) were dried over sodium benzophenone and
withdrawn by vacuum condensation to NMR tubes containing
samples of the compounds under study. The melting points
were measured in sealed evacuated tubes. The compounds (dppꢀ
bian)Na,29 (dppꢀbian)Na2,29 HAlCl2,16 and H2AlCl30 were preꢀ
pared by known procedures and used in the synthesis without
isolation. The elemental analysis was performed by combustion
of the samples in oxygen using the Pregl technique.

Aluminum hydrides
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017 1577
1H NMR (200 MHz, C6D6, 298 K), δ: 7.38—7.26 (m, 8 H);
7.07 (d, 2 H, J = 8.3 Hz); 6.88 (pseudoꢀt, 2 H, J = 6.8 Hz,
J = 8.2 Hz); 6.32 (d, 2 H, J = 6.8 Hz); 3.82 (sept, 4 H, J = 6.8 Hz);
3.38 (m, 16 H); 2.44 (s, 3 H); 1.72 (s, 18 H); 1.27 (d, 12 H,
J = 6.8 Hz); 1.24 (d, 12 H, J = 6.8 Hz); 1.17 (m, 16 H).
IR (Nujol mulls), ν/cm–1: 1909 w, 1846 w, 1776 s, 1668 w,
1613 w, 1586 w, 1507 m, 1335 m, 1311 m, 1276 m, 1251 m,
1205 m, 1177 m, 1150 m, 1121 m, 1090 m, 1057 m, 1023 m,
1001 w, 923 m, 899 m, 860 m, 835 w, 806 m, 778 m, 763 s,
685 w, 670 w, 654 w, 635 m, 587 m, 526 w.
J = 6.8 Hz); 1.08 (m, 8 H). IR (Nujol mulls), ν/cm–1: 1954 w,
1909 w, 1852 w, 1691 s, 1612 w, 1602 w, 1590 m, 1502 s, 1434 s,
1335 s, 1316 s, 1255 m, 1209 m, 1189 m, 1180 m, 1155 w, 1136 m,
1100 m, 1070 m, 1044 m, 1000 m, 957 m, 935 m, 922 m, 908 m,
886 m, 809 m, 803 m, 781 m, 761 m, 736 m, 726 m, 703 m, 693 m,
671 m, 659 w, 644 m, 631 w, 620 m, 606 m, 565 w, 536 w,
501 w, 463 m.
1,2ꢀBis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene alumiꢀ
num hydride tetrahydrofuranate (5). A suspension of dichloroꢀ
alane HAlCl2 (in situ from anhydrous aluminum chloride
(0.1 g, 0.75 mmol) and LiAlH4 (0.01 g, 0.3 mmol) in THF (10 mL))
was added to a solution of the compound (dppꢀbian)Na2
(in situ from dppꢀbian (0.5 g, 1.0 mmol) and sodium (0.046 g,
2.0 mgꢀatom)) in tetrahydrofuran (30 mL). The mixture was
stirred for 15 min at room temperature. After the replacement
of tetrahydrofuran with diethyl ether, the colorless precipitate
was separated by filtration, and the blue solution was concenꢀ
trated to 10 mL. The blue crystals of compound 5 that precipiꢀ
tated within 24 h at 10 °C were separated by decantation, washed
with cold diethyl ether, and dried in vacuo. Yield 0.5 g (84%).
M.p. >290 °C (decomp.). Found (%): C, 79.51; H, 7.98.
C40H49AlN2O. Calculated (%): C, 79.96; H, 8.22. 1H NMR
(200 MHz, C6D6, 298 K), δ 7.33 (m, 6 H); 7.07 (d, 2 H, J = 8.2 Hz);
6.88 (m, 2 H); 3.82 (sept, 4 H, J = 6.8 Hz); 3.59 (m, 4 H);
Lithium 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene
aluminum diphenylcarbinolate hydride bis(tetrahydrofuranate)
(4). Diphenyl ketone (0.11 g, 0.58 mmol) was added to a soluꢀ
tion of compound 1 (0.44 g, 0.58 mmol) in toluene (20 mL).
The mixture was stirred for 15 min at 50 °C. After cooling to
room temperature, the resulting blue solution was concentrated
(5 mL) and allowed to stand for 24 h at 10 °C. The blueꢀgreen
crystals of compound 4 that precipitated were separated from
the solution by decantation, washed with cold toluene, and
dried in vacuo. Yield 0.35 g (67%). M.p. >225 °C (decomp.).
Found (%): C, 79.56; H, 8.43. C60.50H72AlLiN2O3. Calculated
1
(%): C, 79.93; H, 7.98. H NMR (200 MHz, C6D6, 298 K), δ:
7.39—7.26 (m, 10 H); 7.16 (s); 7.15—6.82 (m, 15 H); 6.35
(s, 1 H); 6.27 (d, 2 H, J = 6.8 Hz); 4.11 (sept, 2 H, J = 6.8 Hz);
4.03 (sept, 2 H, J = 6.8 Hz); 3.04 (m, 8 H); 2.11 (s, 3 H); 1.43
(d, 6 H, J = 6.8 Hz); 1.29 (d, 6 H, J = 6.8 Hz); 1.20 (d, 12 H,
1.38—1.15 (m, 24 H); 1.06 (m, 4 H). IR (Nujol mulls), ν/cm–1
1864 s, 1614 w, 1590 m, 1542 w, 1506 m, 1439 s, 1360 m, 1326 m,
:
Table 4. Crystallographic data and the Xꢀray data collection and structure refinement statistics for compounds 1—4
Parameter
1
2
3
4
Molecular formula
Molecular weight
Т/K
C48H66AlLiN2O3
752.94
C44H64AlLiN2O2
686.89
C67H64AlD32LiN2O5
1075.57
C60.50H72AlLiN2O3
909.12
100(2)
100(2)
100(2)
100(2)
Crystal system
Space group
a/Å
b/Å
c/Å
Monoclinic
P21/n
12.272(3)
16.797(3)
21.225(4)
90
Monoclinic
P21/n
12.0834(6)
20.0024(9)
18.2233(9)
90
Orthorhombic
Pbca
22.7673(2)
21.8432(2)
24.6453(2)
90
Monoclinic
P21/n
11.2291(8)
20.3101(14)
23.0107(16)
90
α/deg
β/deg
90.735(6)
90
4374.8(15)
4
1.143
0.088
106.9310(10)
90
4213.6(4)
4
90
90
90.9744(12)
90
5247.2(6)
4
γ/deg
V/Å3
12256.37(18)
8
Z
d/g cm–3
μ/mm–1
F(000)
1.083
0.084
1496
1.166
0.082
4544
1.151
0.085
1956
1632
Crystal size/mm
θꢀScan range/deg
h, k, l indices
0.35×0.28×0.21
2.270—26.999
–15 ≤ h ≤ 15
–21 ≤ k ≤ 21
–27 ≤ l ≤ 27
27777
0.60×0.51×0.18
1.549—29.130
–16 ≤ h ≤ 16
–27 ≤ k ≤ 27
–24 ≤ l ≤ 24
60077
0.594×0.420×0.379
2.959—28.000
–30 ≤ h ≤ 30
–28 ≤ k ≤ 28
–32 ≤ l ≤ 32
207951
0.65×0.21×0.10
1.770—27.999
–14 ≤ h ≤ 14
–26 ≤ k ≤ 26
–30 ≤ l ≤ 30
52142
Number of observed reflections
Number of unique
9514 (0.0892)
11324 (0.0309)
14771 (0.0916)
12649 (0.0432)
reflections (Rint
)
Goodnessꢀofꢀfit (F2)
1.020
1.026
1.026
1.044
R1/wR2 (I > 2σ(I))
0.0609/0.1092
0.1234/0.1221
0.312/–0.275
0.0517/0.1257
0.0615/0.1342
0.467/–0.317
0.0509/0.1191
0.0801/0.1288
0.389/–0.352
0.0543/0.1319
0.0794/0.1436
0.459/–0.208
R1/wR2 (based on all reflections)
Residual electron density
(max/min)/e Å–3, ρmax/ρmin

1578
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017
Sokolov et al.
Table 5. Crystallographic data and the Xꢀray data collection and structure refinement statistics for compounds 5—7
Parameter
5
6
7
Molecular formula
Molecular weight
Т/K
C46H55AlN2O
678.90
C36H41AlClN2
564.14
C44H59AlN2O
658.91
100(2)
100(2)
100(2)
Crystal system
Space group
a/Å
b/Å
c/Å
Monoclinic
P21/n
10.5801(3)
24.3422(7)
15.4384(5)
90
Monoclinic
P21/c
10.4281(2)
20.0166(3)
15.7969(3)
90
Monoclinic
P21/c
11.04380(10)
22.1793(2)
16.3191(2)
90
α/deg
β/deg
104.9530(10)
90
3841.4(2)
4
104.700(2)
90
3189.44(10)
4
107.4750(10)
90
3812.78(7)
4
γ/deg
V/Å3
Z
d/g cm–3
μ/mm–1
F(000)
1.174
0.090
1464
1.175
0.174
1204
1.148
0.088
1432
Crystal size/mm
θꢀScan range/deg
h, k, l indices
0.47×0.22×0.08
2.160—29.999
–14 ≤ h ≤ 14
–34 ≤ k ≤ 34
–21 ≤ l ≤ 21
48656
0.751×0.432×0.367
2.938—27.999
–13 ≤ h ≤ 13
–26 ≤ k ≤ 26
–20 ≤ l ≤ 20
54678
0.440×0.234×0.178
3.198—28.000
–14 ≤ h ≤ 14
–29 ≤ k ≤ 29
–21 ≤ l ≤ 21
65936
Number of observed reflections
Number of unique reflections (Rint
Goodnessꢀofꢀfit (F2)
)
11187 (0.0488)
1.031
7672 (0.0322)
1.045
9200 (0.0362)
1.019
R1/wR2 (I > 2σ(I))
R1/wR2 (based on all reflections)
Residual electron density (max/min)/e Å–3, ρmax/ρ
0.0532/0.1240
0.0717/0.1300
0.398/–0.383
0.0523/0.1292
0.0606/0.1333
0.365/–0.573
0.0391/0.0998
0.0503/0.1050
0.357/–0.203
min
1312 m, 1254 m, 1208 m, 1191 w, 1178 m, 1159 w, 1134 m,
1109 m, 1075 w, 1057 w, 1040 w, 994 m, 924 m, 894 w, 854 m,
836 m, 811 m, 803 m, 781 w, 760 m, 684 w, 667 m, 634 m,
617 w, 598 m, 556 w, 528 w, 460 w.
(0.33 g) in pentane (18%, 0.92 mmol) was added to a solution of
compound 6 (0.52 g, 0.92 mmol) in diethyl ether (20 mL). The
mixture was stirred for 60 min at room temperature with the
removal, from time to time, of the hydrogen that formed under
reduced pressure. The precipitate of lithium chloride that
formed was separated by filtration. The resulting blueꢀgreen
solution was concentrated to 10 mL and allowed to stand for
24 h at 10 °C. The blue crystals of compound 7 that precipitated
were separated from the solution by decantation, washed with
cold diethyl ether, and dried in vacuo. Yield 0.38 g (63%).
M.p. >175 °C (decomp.). Found (%): C, 79.82; H, 8.78.
C44H59AlN2O. Calculated (%): C, 80.20; H, 9.03. 1H NMR
(200 MHz, C4D8O, 298 K), δ: 7.22—7.09 (m, 6 H); 6.99 (d, 2 H,
J = 8.2 Hz); 6.79 (d, 1 H, J = 6.9 Hz); 6.75 (d, 1 H, J = 6.9 Hz);
5.83 (d, 2 H, J = 6.7 Hz); 3.69 (sept, 2 H, J = 6.8 Hz); 3.68
(sept, 2 H, J = 6.8 Hz); 3.58 (s, C4D8O); 3.39 (q, 4 H, J = 6.9 Hz);
1.35 (d, 6 H, J = 6.8 Hz); 1.22 (d, 6 H, J = 6.8 Hz); 1.16
(d, 6 H, J = 6.8 Hz); 0.93 (s, 9 H); 0.83 (d, 6 H, J = 6.8 Hz). IR
(Nujol mulls), ν/cm–1: 1639 w, 1613 w, 1589 w, 1573 w, 1508 m,
1438 m, 1364 m, 1327 m, 1309 m, 1252 m, 1205 w, 1192 w,
1181 w, 1161 w, 1149 w, 1132 w, 1122 w, 1109 w, 1057 w,
1043 w, 1010 m, 998 w, 991 w, 996 w, 937 m, 918 m, 883 w,
831 w, 812 w, 798 w, 759 m, 687 w, 660 w, 621 w, 602 w, 576 w,
549 w, 540 w, 515 w, 504 w.
1,2ꢀBis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene alumiꢀ
num hydride chloride (6). An ethereal solution of monochloroꢀ
alane H2AlCl (in situ from anhydrous aluminum chloride
(0.13 g, 1.0 mmol) and LiAlH4 (0.03 g, 1.0 mmol) in diethyl
ether (10 mL)) was added to a solution of the compound
(dppꢀbian)Na (in situ from dppꢀbian (0.5 g, 1.0 mmol) and
sodium (0.023 g, 1.0 mgꢀatom)) in diethyl ether (30 mL). The
mixture was stirred for 30 min at room temperature. After the
replacement of diethyl ether with toluene, the colorless precipꢀ
itate was separated by centrifugation, and the resulting brown
solution was concentrated to 10 mL. The brown crystals of
compound 6 that formed within 24 h at 10 °C were separated by
decantation of the solution, washed with cold toluene, and dried
in vacuo. Yield 0.44 g (78%). M.p. > 260 (decomp.). Found (%):
C, 76.33; H, 7.70. C36H41AlClN2. Calculated (%): C, 76.64;
H, 7.33. ESR (toluene, 293 K): gi = 2.0024; ai(27Al) = 3.0,
ai(35Cl) = 9.6, ai(37Cl) = 8.0, ai(2 14N) = 4.7, ai(4 1H) = 1.1,
ai(1H) = 10.8 Oe. IR (Nujol mulls), ν/cm–1: 1876 m, 1832 m,
1800 m, 1594 m, 1535 m, 1364 m, 1322 m, 1254 m, 1211 m,
1188 m, 1178 w, 1151 m, 1112 m, 1102 w, 1080 w, 1055 m, 3037 w,
963 w, 950 w, 933 w, 896 w, 879 w, 821 m, 803 m, 781 m, 771 m,
761 m, 673 m, 629 w, 593 w, 571 w, 546 w, 523 w, 484 m, 459 w.
1,2ꢀBis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene alumiꢀ
num tertꢀbutyl etherate (7). A solution of tertꢀbutyllithium
Xꢀray diffraction studies of compounds 1—7. The Xꢀray difꢀ
fraction studies of compounds 1—7 were performed on Bruker
Smart Apex (2, 4), Bruker D8 Quest (1, 5), and Agilent Xcaliꢀ
bur E (3, 6, 7) diffractometers (ωꢀscanning technique, МOꢀКα

Aluminum hydrides
Russ. Chem. Bull., Int. Ed., Vol. 66, No. 9, September, 2017 1579
radiation, λ = 0.71073 Å, T = 100 K). The experimental intenꢀ
sity data were integrated using the SAINT31 (1, 2, 4, 5) and
CrysAlisPro32 (3, 6, 7) programs. All structures were solved by
direct methods using the SHELXTL program package17—19 and
13. I. L. Fedushkin, O. V. Kazarina, A. N. Lukoyanov, A. A.
Skatova, N. L. Bazyakina, A. V. Cherkasov, E. Palamidis,
Organometallics, 2015, 34, 1498.
14. M. V. Moskalev, A. N. Lukoyanov, E. V. Baranov, I. L.
Fedushkin, Dalton Trans., 2016, 45, 15872.
refined by the fullꢀmatrix leastꢀsquares method based on F 2
hkl
with anisotropic displacement parameters for all nonhydrogen
atoms using the SHELX program package.33 The hydrogen
atoms were positioned geometrically and refined isotropically.
Absorption corrections were applied with the SADABS34 and
SCALE3 ABSPACK35 programs. Crystallographic data and
the Xꢀray data collection and structure refinement statistics
for the compounds are given in Tables 4 and 5. The strucꢀ
tures were deposited with the Cambridge Crystallographic
Data Centre (CCDC 1559869—1559875) and are available at
ccdc.cam.ac.uk/getstructures.
15. T. W. Myers, L. A. Berben, Organometallics, 2013, 32, 6647.
16. T. W. Myers, L. A. Berben, J. Am. Chem. Soc., 2013,
135, 9988.
17. T. J. Sherbow, C. R. Carr, T. Saisu, J. C. Fettinger, L. A.
Berben, Organometallics, 2016, 35, 9.
18. A. E. Nako, S. J. Gates, A. J. P. White, M. R. Crimmin,
Dalton Trans., 2013, 42, 15199.
19. A. E. Nako, Q. W. Tan, A. J. P. White, M. R. Crimmin,
Organometallics, 2014, 33, 2685.
20. A. V. Korolev, E. Ihara, I. A. Guzei, V. G. Young, Jr., R. F.
Jordan, J. Am. Chem. Soc., 2001, 123, 8291.
This study was financially supported by the Russian
Science Foundation (Project No. 14ꢀ13ꢀ01063).
21. S. Dastgir, K. S. Coleman, A. R. Cowley, M. L. H. Green,
Dalton Trans., 2009, 7203.
22. Y. Ju, Z. Yang, X. Ma, Y. Yang, H. W. Roesky, Z. Anorg.
Allg. Chem., 2015, 641, 521.
23. I. L. Fedushkin, N. M. Khvoinova, A. A. Skatova, G. K.
Fukin, Angew. Chem., Int. Ed., 2003, 42, 5223.
24. I. L. Fedushkin, A. G. Morozov, O. V. Rassadin, G. K.
Fukin, Chem. Eur. J., 2005, 11, 5749.
25. I. L. Fedushkin, A. A. Skatova, G. K. Fukin, M. Hummert,
H. Schumann, Eur. J. Inorg. Chem., 2005, 2332.
26. G. A. Abakumov, E. S. Klimov, Dokl. AN SSSR, 1972, 202,
827 [Dokl. Chem. (Engl. Transl.), 1972].
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Received July 5, 2017