A bulky chelating diamidoaluminum monohydride - Synthesis, structure and reactions with Me3SnF and heavy group 16 elements

Article abstract of DOI:10.1002/ejic.200300182

The bulky chelating diamidoaluminum monohydride [ArN(CH₂) ₃NAr]AlH(NMe₃) (Ar = 2,6-iPr₂C ₆H₃; 1) was prepared in excellent yield from the reaction of the diamine ArNH(CH₂)₃HNAr with a small excess of AlH₃·NMe₃ in toluene. Subsequent fluorination of 1 with Me₃SnF resulted in the formation of the aluminum monofluoride [ArN(CH₂)₃N-Ar]AlF(NMe₃) (2). Reaction of 1 with elemental E (E = S, Se and Te) proceeded in toluene with heating to yield the aluminum chalcogenides {[ArNH(CH₂)₃NAr]Al(μ -E)}₂ [E = S (3), Se (4), and Te (5)]. The structures of complexes 1, 2 and 4 have been determined by X-ray diffraction analyses. Compounds 1 and 2 are well-separated monomers with a central aluminum atom in a tetrahedral environment. The diamide ligand [ArN(CH₂)₃NAr] ^2- chelates the Al atom to form a distorted six-membered AlN ₂C₃ ring which features a boat conformation for 1 and a flattened chair conformation for 2. Compound 4, however, is a dimer with a central Al₂Se₂ core bearing an ideal four-membered planar ring and two six-membered AlN₂C₃ rings, both displaying a boat conformation. The latter two rings are arranged perpendicularly to the Al₂Se₂ core in a trans configuration. The IR spectra and ¹H NMR spectroscopic data of compounds 3-5 suggest that the migration of the hydrogen from selenium to one of the nitrogens at the diamide ligand is involved in the course of the reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300182

FULL PAPER
A Bulky Chelating Diamidoaluminum Monohydride ؊ Synthesis, Structure and
Reactions with Me3SnF and Heavy Group 16 Elements
Hongping Zhu,[a] Jianfang Chai,[a] Herbert W. Roesky,*[a] Mathias Noltemeyer,[a]
Hans-Georg Schmidt,[a] Denis Vidovic,[a] and Jörg Magull[a]
Dedicated to Professor Helmut Werner on the occasion of his 70th birthday
Keywords: Aluminum / Hydride / Chalcogens / Fluorine
The bulky chelating diamidoaluminum monohydride
[ArN(CH2)3NAr]AlH(NMe3) (Ar = 2,6-iPr2C6H3; 1) was pre-
pared in excellent yield from the reaction of the diamine
ArNH(CH2)3HNAr with a small excess of AlH3·NMe3 in tolu-
ene. Subsequent fluorination of 1 with Me3SnF resulted in
the formation of the aluminum monofluoride [ArN(CH2)3N-
Ar]AlF(NMe3) (2). Reaction of 1 with elemental E (E = S, Se
and Te) proceeded in toluene with heating to yield the alumi-
num chalcogenides {[ArNH(CH2)3NAr]Al(µ-E)}2 [E = S (3), Se
(4), and Te (5)]. The structures of complexes 1, 2 and 4 have
been determined by X-ray diffraction analyses. Compounds
[ArN(CH2)3NAr]2− chelates the Al atom to form a distorted
six-membered AlN2C3 ring which features a boat conforma-
tion for 1 and a flattened chair conformation for 2. Compound
4, however, is a dimer with a central Al2Se2 core bearing an
ideal four-membered planar ring and two six-membered
AlN2C3 rings, both displaying a boat conformation. The latter
two rings are arranged perpendicularly to the Al2Se2 core in
a trans configuration. The IR spectra and 1H NMR spectro-
scopic data of compounds 3−5 suggest that the migration of
the hydrogen from selenium to one of the nitrogens at the
diamide ligand is involved in the course of the reaction.
1 and 2 are well-separated monomers with a central alumi- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
num atom in a tetrahedral environment. The diamide ligand
Germany, 2003)
[6a]
Introduction
LAl(SeH)Se(SeH)AlL,[3] LAl(SH)2
[L ϭ N(Ar)C(Me)-
CHC(Me)N(Ar), Ar ϭ 2,6-iPr2C6H3); (RAlE)2 (R ϭ 2,4,6-
tBu3C6H2, E ϭ S;[5] R ϭ N(SiMe3)C(Ph)C(SiMe3)2,[6b] 2,6-
(Et2NCH2)2C6H3, 2-Et2NCH2-6-MeC6H3;[6c] E ϭ Se, Te],
Studies of aluminum hydrides have received considerable
attention due to their scientific importance and numerous
applications.[1] In recent years, much work has been devoted
to aluminum hydrides of low aggregation, especially the
monomeric forms. The synthesis of monomeric aluminum
hydrides helps us to understand the reaction chemistry of
surface-bound AlHn groups formed during thin-film growth
from organoaluminum sources.[2] Moreover, aluminum hy-
drides of low aggregation can be very effective precursors
for preparing aluminum chalcogenides.[3] However, reac-
tions involving aluminum hydrides of low aggregation with
chalcogen or organochalcogenides have been reported to a
lesser extent. Raston et al.[4] have investigated the reaction
of the trimethylamine adduct of alane Me3N·AlH3 with
chalcogen or organochalcogenides. Power et al.[5] have re-
ported one example of the reaction of an aluminum dihy-
dride with an organochalcogenide and our group has dis-
cussed the reaction of a series of aluminum dihydrides with
chalcogen,[3,6] where the isolation and structural charac-
terization of some novel compounds {such as LAl(SeH)2,
trans-[{Me3N(H)Al(µ-E)}2] (E
ϭ
Se, Te),[4b] trans-
[{Me3N(PhTe)Al(µ-Se)}2];[4c]
[(η1-3,5-tBu2pz(µ-Al)H]2E
(E ϭ S, Se, Te);[6d] Me3NAl(ER)3 (E ϭ Se, R ϭ Et, Ph,
[4c]
CH2Ph; E ϭ Te, R ϭ Ph)[4a] and Al4Se5(H)2(NMe3)4
}
showed a rich chemistry. Although further reaction of the
dimeric chalcogenidoalane, trans-[{Me3N(H)Al(µ-E)}2]
(E ϭ Se, Te) with chalcogen or organochalcogenides has
been investigated,[4b] studies of the reaction of bulky, mono-
meric aluminum monohydrides with chalcogens, which
might generate the corresponding monomeric Al-EH moi-
eties, have not been reported so far. Therefore we became
interested in finding a sufficiently bulky ligand to synthesize
an intramolecularly stabilized aluminum monohydride, and
further studies on its reactivity with the fluorinating agent
Me3SnF and heavy group 16 elements.
The divalent bulky chelating diamide ligand
[ArN(CH2)3NAr]2Ϫ (Ar ϭ 2,6-iPr2C6H3) is increasingly be-
ing used as a ligand[7] due to its special steric and electronic
properties that help to control effectively the geometry at
the metal center. Known complexes containing this ligand
include main group metal (Li, K, Al) and transition metal
(Ti, Zr, Y, Lu) derivatives.[7Ϫ11] The only reported alumi-
[a]
Institut für Anorganische Chemie der Universität Göttingen
Tammannstrasse 4, 37077 Göttingen, Germany
Fax: (internat.) ϩ49-(0)551/393-373
E-mail: hroesky@gwdg.de
Eur. J. Inorg. Chem. 2003, 3113Ϫ3119
DOI: 10.1002/ejic.200300182
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3113

H. W. Roesky et al.
FULL PAPER
num complexes are a series of compounds containing alkyl
δ
ϭ
Ϫ175.0 ppm;
R
ϭ
2,4,6-Me3C6H2,
δ
ϭ
and aryl groups [ArN(CH2)3NAr]AlR (R ϭ Me, iBu, Ϫ175.9 ppm}.[15] In the H NMR spectra of 1 and 2 the
C6F5).[11] Herein we report on the synthesis and charac- presence of complex resonances for the backbone protons
terization of the bulky chelating diamidoaluminum of the diamide ligand [two isopropyl methine (CHMe2),
monohydride [ArN(CH2)3NAr]AlH(NMe3) (Ar ϭ 2,6- four isopropyl methyl (CHMe2), two methene (NCH2) and
iPr2C6H3; 1). The metathesis of 1 with Me3SnF to give the two methene (NCH2CH2) resonances] is consistent with a
monofluoride [ArN(CH2)3NAr]AlF(NMe3) (2) and the re- pseudotetrahedral geometry and Cs symmetry at alu-
action with heavy group 16 elements to afford the dimeric minium. Similar resonances are observed in compounds
aluminum chalcogenides {[ArNH(CH2)3NAr]Al(µ-E)}2 [M{ArN(CH2)3NAr}(η-C5H5)Cl] (M ϭ Zr, Y; Ar ϭ 2,6-
1
[E ϭ S (3), Se (4), and Te (5)] are also described.
iPr2C6H3).[7,9] The resonance for the AlϪH proton is not
seen, which is typical for amidoaluminum hydride spec-
ies.[13b] Substitution of AlϪH in 1 by AlϪF has a stronger
effect on the chemical shift of the NMe3 group (1: δ ϭ
1.66 ppm; 2: δ ϭ 1.75 ppm), while a smaller effect is ob-
served for the backbone protons of the ligand. The MS (EI)
spectrum shows the molecular ion of [Mϩ Ϫ NMe3] for 1,
and [Mϩ] and [Mϩ Ϫ NMe3] for 2 and the single-crystal X-
ray structural determinations of 1 and 2 confirm the com-
position of [ArN(CH2)3NAr]AlR(NMe3) (R ϭ H, 1; F, 2),
where the former contains half a molecule of n-hexane per
molecule of complex 1 in the asymmetric unit.
Results and Discussion
Syntheses and Characterization of
[ArN(CH2)3NAr]AlH(NMe3) (1) and
[ArN(CH2)3NAr]AlF(NMe3) (Ar ؍ 2,6-iPr2C6H3) (2)
The synthesis of aluminum hydrides has been reported in
a number of publications.[12] The use of AlH3·NMe3 as a
precursor to react with N-substituted diamine, diimine and
analogues containing N-H groups or E(SiMe3)2 (E ϭ P, As)
with elimination of H2 or HSiMe3 has been shown to be a
facile route to aluminum hydrides of low aggregation.[3,13]
Reaction of the diamine [ArNH(CH2)3HNAr] with a small
excess of AlH3·NMe3 in toluene under heating (80 °C) af-
fords the intramolecularly stabilized diamidoaluminum
monohydride [ArN(CH2)3NAr]AlH(NMe3) (1) in excellent
yield. Subsequent fluorination of 1 with Me3SnF either at
room temperature or at high temperature (80 °C) results in
the formation of the aluminum monofluoride [ArN(CH2)3-
NAr]AlF(NMe3) (2; Scheme 1).
Compounds 1 and 2 are well-separated monomers both
of which contain a central aluminum atom in a distorted
tetrahedral environment (Figures 1 and 2). Selected bond
lengths and angles are listed in Table 1. The terminal AlϪH
˚
bond length (1.52 A) is closer to those in compounds (2,4,6-
tBu3C6H2)2AlH[16] [1.53(4) A] and [HAl(NMe2)3]Ϫ[17]
˚
˚
[1.52(2) A], but shorter than those in AlH(Cl)-
[tBuNCH2CH2N(tBu)H][13a] (1.60 A), Al2(µ-NEt2)2-
˚
[18]
˚
˚
[N(iPr)2]2H2
(1.67
A)
and
(2,4,6-
tBu3C6H2)Al(H)Cl·THF[19] [1.73(5) A]. The terminal AlϪF
separation [1.678(1) A] is in the range of 1.657Ϫ1.681 A
˚
˚
Scheme 1
Complexes 1 and 2 were characterized by NMR, MS (EI)
and IR spectroscopy, and elemental analyses. The presence
of the hydride in 1 is evident from the IR spectrum. The
broad IR band at 1799 cmϪ1 can be assigned to the AlϪH
stretching absorption.[14] In the IR spectrum of 2, this ab-
sorption disappears, indicating that compound 1 is com-
pletely fluorinated. The 19F NMR spectrum of 2 exhibits
one singlet resonance (δ ϭ Ϫ175.4 ppm), which is similar
to the terminal AlϪF resonance in a closely related series
of compounds {ArN[Si(R)Me2]AlF2·THF: Ar ϭ 2,6-
iPr2C6H3, R ϭ Me, δ ϭ Ϫ178.1; R ϭ iPr, δ ϭ Ϫ177.0 ppm;
Figure 1. Molecular structure of 1 with the thermal ellipsoids at
30% probability level; H atoms are omitted for clarity except for
R ϭ tBu, δ ϭ Ϫ175.1 ppm; Ar ϭ 2,6-Me2C6H3, R ϭ tBu, the AlϪH hydrogen atom
3114
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Eur. J. Inorg. Chem. 2003, 3113Ϫ3119

A Bulky Chelating Diamidoaluminum Monohydride
FULL PAPER
tion. The diamide ligand chelates the Al atom to form an
AlN2C3 six-membered non-planar ring, in which Al(1) and
C(2) occupy the head positions with distances to the quasi-
plane N(1)ϪN(2)ϪC(3)ϪC(1) (mean deviation ∆ ϭ 0.0716
˚
˚
A) of 0.1034 and 0.6852
A
in
1
and the plane
˚
N(1)ϪN(2)ϪC(3)ϪC(1) (∆ ϭ 0.0316 A) of Ϫ0.0109 and
0.6730 A in 2. It is obvious that the former displays a boat
˚
conformation and the latter a flattened chair conformation,
and this can be explained in terms of the strain imposed by
the Ar group. The F atom has a stronger electron-attracting
tendency than the H atom, which generates different charge
distributions at the central Al atom of 1 and 2. This gives
rise to the small difference in the AlϪNdiamide bond length
˚
between 1 and 2 (average 1.824, 1; 1.807 A, 2), as well as
˚
the Al-NNMe bond length [2.024(2), 1; 2.000(2) A, 2] and
3
the N(1)ϪAl(1)ϪN(2) chelating angle [106.52(6)°, 1;
107.45(7)°, 2]. The AlϪNdiamide distances in 1 and 2 can
be compared with the terminal AlϪN(amide) distances in
[13h]
˚
CH2(CH2CMe2)2NAlH2·NMe3
[1.838(2)
A],
AlH(Cl)[tBuNCH2CH2N(tBu)H][13a] [1.80(1) A] and {Al(µ-
˚
[22]
˚
H)[N(CMe2CH2)2CH2]2}2
[1.836(3) A], and are longer
than the AlϪNdiamide bond lengths in the three-coordinate
aluminum compound [ArN(CH2)3NAr]AlMe[11] [1.760(3),
˚
1.766(3) A]. The AlϪNNMe distances in 1 and 2 are as ex-
3
Figure 2. Molecular structure of 2 with the thermal ellipsoids at
30% probability level; H atoms are omitted for clarity
pected.[13h,23,24]
Syntheses of {[ArNH(CH2)3NAr]Al(µ-E)}2 [E ؍ S (3), Se (4)
and Te (5)] and X-ray Structural Analysis of Compound 4
˚
Table 1. Selected bond lengths [A] and bond angles [°] for com-
pounds 1·1/2 n-hexane, 2 and 4·2 toluene
The successful fluorination of 1 using Me3SnF is indica-
tive of its reactivity despite the steric hindrance of the bulky
ligand. Treatment of 1 with equivalent amounts of sulfur,
selenium or tellurium proceeded in toluene at elevated tem-
perature to afford the solvated aluminum sulfide 3 as light
yellow crystals, the selenide 4 as yellow crystals and the tel-
luride 5 as green-yellow crystals. The former two com-
pounds were obtained in good yield and the latter in mod-
erate yield [Equation (1)].
Compound 1·1/2 n-hexane
Al(1)ϪN(1)
Al(1)ϪN(2)
N(1)ϪAl(1)ϪN(2)
N(1)ϪAl(1)ϪN(3)
N(2)ϪAl(1)ϪN(3)
1.820(1)
1.828(1)
Al(1)ϪN(3)
Al(1)ϪH(1)
2.024(2)
1.52
116.1
120.2
96.0
106.52(6)
111.31(7)
105.74(7)
H(1)ϪAl(1)ϪN(1)
H(1)ϪAl(1)ϪN(2)
H(1)ϪAl(1)ϪN(3)
Compound 2
Al(1)ϪF(1)
Al(1)ϪN(1)
N(1)ϪAl(1)ϪN(2)
N(1)ϪAl(1)ϪN(3)
N(2)ϪAl(1)ϪN(3)
1.678(1)
1.810(2)
107.45(7)
108.55(8)
112.69(8)
Al(1)ϪN(2)
Al(1)ϪN(3)
F(1)ϪAl(1)ϪN(1)
F(1)ϪAl(1)ϪN(2)
F(1)ϪAl(1)ϪN(3)
1.804(2)
2.000(2)
119.12(6)
115.24(6)
93.00(6)
Compound 4·2 toluene
Compounds 3Ϫ5 are air and moisture sensitive and sol-
uble in hot toluene and benzene, while poorly soluble in
THF, CHCl3 and n-hexane. They were characterized by IR
and NMR spectroscopy and MS (EI) spectrometry, as well
as by elemental analyses. The MS (EI) spectra of 3Ϫ5 show
the dimeric molecular ion with the correct isotope pattern
and their 1H NMR spectra show the very similar characters
of the ligand, including the resonances of solvent toluene
protons. The doublets in the range of δ ϭ 1.10Ϫ1.25 ppm,
one septet centered at ca. δ ϭ 3.38 ppm and a multiplet at
δ ϭ 7.02Ϫ7.10 ppm correspond to the protons of the 2,6-
Al(1)ϪSe(1)
Al(1)ϪSe(1A)
Al(1)ϪAl(1A)
Al(1)ϪSe(1)ϪAl(1A)
N(1)ϪAl(1)ϪSe(1)
N(2)ϪAl(1)ϪSe(1)
Al(1)ϪN(1)ϪC(1)
Al(1)ϪN(1)ϪC(16)
C(1)ϪN(1)ϪC(16)
2.339(1)
2.381(1)
2.988(2)
78.56(5)
119.2(4)
118.6(4)
119.6(8)
126.4(8)
113.2(9)
Al(1)ϪN(1)
Al(1)ϪN(2)
1.932(11)
1.916(11)
101.44(5)
98.13(14)
109.7(4)
109.7(4)
121.1(9)
130.1(7)
108.0(9)
Se(1)ϪAl(1)ϪSe(1A)
N(1)ϪAl(1)ϪN(2)
N(2)ϪAl(1)ϪSe(1A)
N(1)ϪAl(1)ϪSe(1A)
Al(1)ϪN(2)ϪC(3)
Al(1)ϪN(2)ϪC(4)
C(3)ϪN(2)ϪC(4)
observed in [(Me3Si)3CAlF2]3 [20] and somewhat longer than iPr2C6H3 group. One broad singlet at ca. δ ϭ 1.36 ppm can
those in [{(2,6-iPr2C6H3)N(SiMe3)AlF2}3][15] (1.634Ϫ1.642 be assigned to the NH resonance,[13a,13c] with a satisfactory
[21]
˚
˚
A) and AlF3
(1.63 A), as determined by electron diffrac- integral intensity indicating two protons, and two areas of
Eur. J. Inorg. Chem. 2003, 3113Ϫ3119
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H. W. Roesky et al.
FULL PAPER
unresolved multiplet resonances centered at ca. δ ϭ 1.78
and 3.00 ppm arising from the six non-equivalent methylene
protons, with the latter probably coming from the overlap-
ping proton resonances of the two amido NCH2 and two
amine HNCH2 groups. The IR spectra exhibit the NH ab-
sorption in the νN-H region[13a,13b] (3: 3190; 4: 3187; 5: 3185
cmϪ1). All these data indicate that compounds 3, 4 and 5
have the same structure corresponding to the formula
{[ArNH(CH2)3NAr]Al(µ-E)}2.
The reaction of aluminum dihydride with selenium has
been reported by our group,[3,6b,6c] where the formation of
a dimeric compound might proceed through an AlϪSeH
intermediate. In a similar way the reaction of the aluminum
monohydride 1 with selenium might involve the formation
of intermediate [ArN(CH2)3NAr]Al(SeH)(NMe3), which
dimerizes to produce {[ArN(CH2)3NAr]Al(µ-SeH)}2 with
elimination of gaseous NMe3. However, with reference to
the related Al-SeH compounds LAl(SeH)2 and LAl-
(SeH)Se(SeH)AlL [L ϭ N(Ar)C(Me)CHC(Me)N(Ar), Ar ϭ
2,6-iPr2C6H3],[25] no absorptions in the range of 2000Ϫ2500
cmϪ1 in the IR spectrum are observed to indicate the for-
mation of an Al-SeH moiety. This suggests that the dimer
{[ArN(CH2)3NAr]Al(µ-SeH)}2 is not stable under heating
and the hydrogen atom attached to the selenium atom mi-
grates quickly to one of the nitrogen atoms of the diamide
ligand to afford stable compound 4. The most likely mecha-
Scheme 2
Figure 3. Molecular structure of 4 with the thermal ellipsoids at 30% probability level; H atoms are omitted for clarity
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Eur. J. Inorg. Chem. 2003, 3113Ϫ3119

A Bulky Chelating Diamidoaluminum Monohydride
FULL PAPER
nism is given in Scheme 2. The formation of compounds 3 under migration of the hydrogen to an adjacent nitrogen
and 5 is probably similar to that of 4. of the chelating ring. The latter reaction does not yield an
A suitable single crystal of compound 4 was measured by aluminium chalcogen double bond system but rather a four-
X-ray diffraction. The structure analysis of compound 4 membered ring of composition Al2E2 (E ϭ S, Se, Te).
shows a dimeric species containing two molecules of tolu-
ene. Unfortunately, the quality of the crystal structure did
Experimental Section
not allow the location of the hydrogen atoms on the nitro-
gen atoms. Nevertheless, the presence of NH groups was
established by IR and 1H NMR spectroscopy. The molecu-
lar structure is shown in Figure 3, and selected bond lengths
and angles are listed in Table 1. The Al(1)ϪN(1) [1.932(11)
General: All operations were carried out under purified nitrogen
atmosphere using Schlenk techniques. Solvents were purified
and dried by distillation over sodium under nitrogen prior to use.
Elemental sulfur, selenium and tellurium were purchased from Ald-
˚
˚
A] and Al(1)ϪN(2) [1.916(11) A] bond lengths are midway
between the AlϪNamine and AlϪNamido bond lengths ob-
served in AlH(Cl)[tBuNCH2CH2N(tBu)H][13a] [AlϪN(1)
rich and used as received. ArNH(CH2)3HNAr (Ar
ϭ 2,6-
iPr2C6H3),[7] AlH3·NMe3 [26]and Me3SnF[27] were prepared accord-
ing to the literature.
˚
˚
(amine): 2.00(1) A; AlϪN(2) (amido): 1.80(1) A], and are
longer than those AlϪN distances found in
Al[tBuNCH2CH2N(tBu)][tBuNCH2CH2NH(tBu)],[13b]
where the NH hydrogen atom is disordered over all four
nitrogen centers [1.850(5), 1.870(5) A], and much longer
than AlϪNamido distances in 1 [1.820(1), 1.828(1) A] and 2
1H (200.13 MHz), 19F (188.29 MHz) and 77Se NMR (500 MHz)
spectra were recorded on a Bruker AM 200 or a Bruker AM 250
spectrometer and the chemical shifts were externally referenced to
SiMe4 for 1H nuclei, C6F6 for 19F and Me2Se for 77Se. (In this
paper the chemical shift for 19F NMR spectroscopy was adjusted
to the scale where CFCl3 is used as external reference). The IR
spectra were measured on a Bio-Rad Digilab FTS-7 spectrometer.
EI (70 eV) mass spectra were measured on a Finnigan MAT 8230
or a Varian MAT CH5 instrument. Elemental analyses were per-
formed by the Analytisches Labor des Instituts für Anorganische
Chemie der Universität Göttingen. Melting points were measured
in sealed glass tubes and were not corrected.
˚
˚
˚
[1.804(2),
1.810(2)
A]. However,
compared
to
AlH(Cl)[tBuNCH2CH2N(tBu)H],[13a] where a remarkable
˚
difference (0.20 A) between AlϪN(1) (amine) and AlϪN(2)
(amido) distances was observed, the very slight difference
˚
(0.016 A) between Al(1)ϪN(1) and Al(1)ϪN(2) in 4 may
imply the disorder of the two hydrogen atoms over the sides
of all four nitrogen centers. Moreover, the similar coordi-
nation environments and approximately planar coordi-
nation geometries at N(1) and N(2) [at N(1),
Al(1)ϪN(1)ϪC(1) 119.6(8)°, Al(1)ϪN(1)ϪC(16) 126.4(8)°,
C(1)ϪN(1)ϪC(16) 113.2(9)°; at N(2), Al(1)ϪN(2)ϪC(3)
121.1(9)°, Al(1)ϪN(2)ϪC(4) 130.1(7)°, C(3)ϪN(2)ϪC(4)
108.0(9)°, (CϪNϪAl, C) ϭ 359.2°] do not allow us to dis-
tinguish between the amine nitrogen and the amido nitro-
gen centers. In summary, it is assumed that the almost equal
possibility of the hydrogen migration from the selenium
atom to any nitrogen atom at the diamide ligand is included
in the course of the reaction.
[ArN(CH2)3NAr]AlH(NMe3) (1): A solution of ArNH(CH2)3-
HNAr (4.03 g, 10.24 mmol) (Ar ϭ 2,6-iPr2C6H3) in toluene
(20 mL) was added to
a solution of AlH3·NMe3 (1.18 g,
13.24 mmol) in toluene (30 mL). While stirring, gas evolution was
observed. The mixture was slowly heated to 80 °C and stirred for
5 h. All volatiles were removed in vacuo and the residue was ex-
tracted with n-hexane. After filtration through Celite, the extract
was evaporated to dryness to afford [ArN(CH2)3NAr]AlH(NMe3)
as a white solid (4.41 g, 90%). X-ray quality crystals were grown
1
from n-hexane. M.p. 196Ϫ197 °C. H NMR (200.13 MHz, C6D6):
δ ϭ 1.22, 1.37, 1.47, 1.66 (d, 24 H, CHMe2), 1.66 (s, 9 H, NMe3),
2.10, 3.00 (m, 2 H, NCH2CH2), 3.25Ϫ3.45 (m, 4 H, NCH2), 3.63,
4.25 (sept, 4 H, CHMe2), 7.10Ϫ7.16 (m, 6 H, Ar) ppm. MS (EI):
m/z ϭ 420 [Mϩ Ϫ NMe3]. IR (KBr, Nujol mull): νAl-H ϭ 1799
cmϪ1(br. sh.). C33H57AlN3 (522.02) (1·1/2 n-hexane): calcd. C
75.93, H 11.00, N 8.05; found C 75.44, H 10.64, N 8.26.
The Al2Se2 core exhibits an ideal planar ring (least-
square deviation ∆ of 0.0005) with an Al(1)ϪSe(1) distance
˚
˚
of 2.339(1) A, an Al(1)ϪSe(1A) distance of 2.381(1) A and
an Al(1)ϪSe(1)ϪAl(1A) bond angle of 78.56(5)°, which are
as expected for Al2Se2 core compounds,[4a,4b,6b,6c] while the
Al(1)ϪSe(1) and Al(1)ϪSe(1A) distances differ by ca. 0.042
[ArN(CH2)3NAr]AlF(NMe3) (2). Method 1: A suspension of 1
(1.44 g, 3 mmol) and Me3SnF (0.55 g, 3 mmol) in toluene (30 mL)
was heated to 80 °C and stirred for 12 h. After filtration, the filtrate
was concentrated to ca. 10 mL in vacuo and kept at 4 °C for 48 h
to afford colorless block-shaped crystals of 2 (1.20 g, 80%). M.p.
˚
A probably due to the steric effects of the backbone ligand
on the Al2Se2 ring. The ligand chelates the Al atom to fuse
two six-membered AlN2C3 rings, which are arranged in
trans positions on each side of the Al2Se2 core. The two
AlN2C3 rings both display a boat conformation with Al(1)
and Al(1A) at the bow and C(2) and C(2A) at the stern,
respectively, and are arranged almost perpendicularly to the
Al2Se2 ring (the dihedral angle between the ring (Al2Se2)
1
220Ϫ222 °C. H NMR (200.13 MHz, C6D6): δ ϭ 1.22, 1.35, 1.47,
1.71 (d, 24 H, CHMe2), 1.75 (s, 9 H, NMe3), 2.00, 3.00 (m, 2 H,
NCH2CH2), 3.27, 3.40 (m, 4 H, NCH2), 3.64, 4.29 (sept, 4 H,
CHMe2), 7.10Ϫ7.32 (m, 6 H, Ar) ppm. 19F NMR (188.29 MHz,
C6D6): δ ϭ Ϫ12.4 (adjusted value, Ϫ175.4) ppm. MS (EI): m/z ϭ
497 [Mϩ], 438 [Mϩ Ϫ NMe3]. C30H49AlFN3 (497.72): calcd. C
72.40, H 9.92, N 8.44; found C 72.31, H 9.71, N 8.28.
˚
and the N(1)ϪN(2)ϪC(3)ϪC(1) plane (∆ ϭ 0.0238 A) be-
Method 2: A suspension of 1 (1.44 g, 3 mmol) and Me3SnF (0.55 g,
3 mmol) in toluene (30 mL) was stirred for 4 days at room tempera-
ture until Me3SnF was almost consumed. After filtration, the fil-
trate was concentrated to ca. 10 mL in vacuo and kept at 4 °C for
a week to afford colorless crystals. All spectroscopic data con-
ing 90.5°).
In summary we have shown that the [ArNCH2-
CH2NAr]2Ϫ ligand forms a stable chelate with the alu-
minium hydride. The hydride functionally can be replaced
by a fluorine atom or substituted by a chalcogen (S, Se, Te) firmed the same compound as that obtained from method 1.
Eur. J. Inorg. Chem. 2003, 3113Ϫ3119
www.eurjic.org  2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3117

H. W. Roesky et al.
FULL PAPER
Table 2. Summary of crystallographic data for compounds 1·1/2 n-hexane, 2 and 4·2 toluene
1·1/2 n-hexane
2
4·2 toluene
Empirical formula
Molecular weight
Temperature [K]
Crystal system
Space group
C33H57AlN3
522.80
203(2)
monoclinic
P21/n
12.285(3)
20.125(4)
14.274(3)
110.47(3)
3306.2(12)
4
C30H49AlFN3
497.70
200(2)
monoclinic
P21/n
13.323(6)
12.480(2)
17.979(5)
92.57(5)
2986.5(16)
4
1.107
0.096
1088
C68H96Al2N4Se2
1181.37
133(2)
monoclinic
C2
19.104(4)
17.561(4)
12.286(3)
129.10(3)
3198.5(11)
2
˚
a (A)
˚
b (A)
˚
c (A)
β [°]
3
˚
Volume [A ]
Z
Density (calcd.) [Mg·mϪ3
]
1.050
0.085
1156
1.227
1.225
1252
Absorption coefficient [mmϪ1
F(000)
]
θ range [°]
3.52Ϫ25.00
Ϫ14 Յ h Յ 14
Ϫ23 Յ k Յ 23
Ϫ16 Յ l Յ 16
11566
3.61Ϫ25.04
Ϫ15 Յ h Յ 15
Ϫ10 Յ k Յ 14
Ϫ16 Յ l Յ 21
5643
1.80Ϫ24.81
Ϫ22 Յ h Յ 22
Ϫ20 Յ k Յ 20
Ϫ14 Յ l Յ 13
18430
Index ranges
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
5786 (Rint ϭ 0.0346)
5786/0/350
1.004
R1 ϭ 0.0418
wR2 ϭ 0.0994
R1 ϭ 0.0586
wR2 ϭ 0.1101
0.200, Ϫ0.228
5249 (Rint ϭ 0.1332)
5249/0/327
1.069
R1 ϭ 0.0486
wR2 ϭ 0.1282
R1 ϭ 0.0532
wR2 ϭ 0.1340
0.519, Ϫ0.300
5488 (Rint ϭ 0.0718)
5488/1/312
0.996
R1 ϭ 0.0433
wR2 ϭ 0.1112
R1 ϭ 0.0529
wR2 ϭ 0.1164
0.694, Ϫ0.514
R indices (all data)
Ϫ3
˚
Largest different peak and hole (e·A
)
{[ArNH(CH2)3NAr]Al(µ-S)}2 (3):
A
suspension of
1
(1.48 g,
was concentrated to ca. 10 mL and n-hexane (5 mL) was added.
3 mmol) and elemental S (0.096 g, 3 mmol) in toluene (30 mL) was The solution was kept at 4 °C for 24 h to afford green-yellow crys-
1
heated to 80 °C and stirred for 12 h. After filtration, the orange-
red filtrate was concentrated to ca. 10 mL and kept at 4 °C for (200.13 MHz, C6D6): δ ϭ 1.17, 1.22 (d, 48 H, -CHMe2), 1.35 (s, 2
48 h to afford light yellow crystals of 3·toluene (1.00 g, 67%). M.p. H, NH), 1.75 (m, 4 H, NCH2CH2), 2.1 (s, 3 H, MePh), 3.00 (t, 8
278Ϫ279 °C (Ͼ 250 °C, decomp.). H NMR (200.13 MHz, C6D6): H, NCH2), 3.37 (sept, 8 H, CHMe2), 6.94Ϫ7.04 (m, 5 H, MePh),
tals of 5·toluene (0.85 g, 48%). M.p. 320 °C (decomp.). H NMR
1
δ ϭ 1.17, 1.22 (d, 48 H, CHMe2), 1.36 (s, 2 H, NH), 1.78 (m, 4 H,
7.02Ϫ7.10 (m, 12 H, Ar) ppm. MS (EI): m/z ϭ 1096 [Mϩ]. IR
NCH2CH2), 2.1 (s, 3 H, MePh), 3.00 (t, 8 H, NCH2), 3.38 (sept, 8 (KBr Nujol mull): ν˜N-H ϭ 3185 cmϪ1. C61H90Al2N4Te2 (1188.1)
H, CHMe2), 6.96Ϫ7.04 (m, 5 H, MePh), 7.02Ϫ7.10 (m, 12 H, Ar) (5·toluene): calcd. C 61.67, H 7.63, N 4.71; found C 61.72, H 7.61,
ppm. MS (EI): m/z ϭ 904 [Mϩ]. IR (KBr Nujol mull): ν˜N-H ϭ 3190 N 4.76.
cmϪ1. C61H90Al2N4S2 (996.8) (3·toluene): calcd. C 73.50, H 9.10,
N 5.62; found C 73.25, H 8.90, N 5.07.
X-ray Structural Determinations and Refinements for 1, 2 and 4: The
crystallographic data for compounds 1 and 2 were collected on a
StoeϪSiemensϪHuber four-circle diffractometer coupled to a Sie-
mens CCD area-detector and for 4 on a Stoe IPDS II-array detec-
tor system. In both cases graphite-monochromated Mo-Kα radi-
{[ArNH(CH2)3NAr]Al(µ-Se)}2 (4): A suspension of 1 (1.44 g,
3 mmol) and elemental Se powder (0.24 g, 3 mmol) in toluene
(30 mL) was refluxed for 12 h until almost all the selenium was
consumed. In the course of hot filtration, yellowish crystals grew
from the orange filtrate, and these were collected by filtration.
(0.10 g). The mother liquor was concentrated to ca. 10 mL and kept
at 4 °C for 24 h to afford another crop of yellowish crystals of 4·2
toluene (1.00 g). Total yield: 1.10 g (62%). M.p. 291 °C (Ͼ 259 °C,
˚
ation (λ ϭ 0.71073 A) was used. All structures were solved by direct
methods (SHELXS-96)[28] and refined against F2 using SHELXL-
97.[29] In 1 and 2, all non-hydrogen atoms were refined aniso-
tropically and hydrogen atoms were included using the riding
model with Uiso tied to the Uiso of the parent atoms, except for the
AlϪH hydrogen atom in 1, which was located by difference Fourier
synthesis and refined isotropically. In 4 the non-hydrogen atoms in
the dimeric structure were refined anisotropically while those in
the two solvent molecules were refined isotropically. Treatment of
hydrogen atoms was the same as those in 1 and 2, except for the
two NH hydrogen atoms, which could not be located. A summary
of cell parameters, data collections, and structure solutions is given
in Table 2.
1
decomp.). H NMR (200.13 MHz, C6D6): δ ϭ 1.17, 1.22 (d, 48 H,
CHMe2), 1.36 (s, 2 H, NH), 1.78 (m, 4 H, NCH2CH2), 2.1 (s, 6 H,
MePh), 3.00 (t, 8 H, NCH2), 3.38 (sept, 8 H, CHMe2), 6.94Ϫ7.04
(m, 10 H, MePh), 7.02Ϫ7.10 (m, 12 H, Ar) ppm. 77Se NMR
(500 MHz, C6D6, CDCl3, or C7D8): no resonances were observed.
MS (EI): m/z ϭ 998 [Mϩ]. IR (KBr Nujol mull): ν˜N-H ϭ 3187
cmϪ1. C68H98Al2N4Se2 (1182.9) (4·2 toluene): calcd. C 69.04, H
8.35, N 4.74; found C 68.79, H 8.22, N 4.63.
{[ArNH(CH2)3NAr]Al(µ-Te)}2 (5): A suspension of 1 (1.44 g,
3 mmol) and elemental Te powder (0.39 g, 3 mmol) in toluene
(40 mL) was refluxed for 5 days and a small amount of unreacted
Te powder still remained. After filtration, the green-yellow filtrate
CCDC-207050 (1), -207051 (2), and -207052 (4) contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data Centre, 12,
3118
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 3113Ϫ3119

A Bulky Chelating Diamidoaluminum Monohydride
FULL PAPER
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See ref.[3] and some spectroscopic data are listed for [LAl(-
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(KBr, Nujol): ν˜SeH ϭ 2318 cmϪ1; [L(HSe)AlSeAl(SeH)L]: 1H
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[8]
(500 MHz, C6D6): δAl-SeH ϭ Ϫ341 and δ
ϭ Ϫ535 ppm.
Al-Se-Al
IR (KBr, Nujol): ν˜SeH ϭ 2276, 2292 cmϪ1
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[26]
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Received March 31, 2003
Eur. J. Inorg. Chem. 2003, 3113Ϫ3119
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3119