Syntheses and structures of intramolecularly coordinated azidoalanes

Article abstract of DOI:10.1021/om9706875

The four intramolecularly coordinated azidoalanes R₂Al(N₃) and RAltBu(N₃) (R = (CH₂)3-NMe₂ (1b, 3b), 2-(Me₂NCH₂)C₆H₄ (2b, 4b)) were synthesized by reaction

Full text of DOI:10.1021/om9706875

Organometallics 1998, 17, 161-166
161
Syn th eses a n d Str u ctu r es of In tr a m olecu la r ly
Coor d in a ted Azid oa la n es
J ens Mu¨ller,*,†,‡ Roland A. Fischer,*,§,| Harald Sussek,§ Peter Pilgram,†
Ruimin Wang,† Hans Pritzkow,§ and Eberhard Herdtweck
Institut fu¨r Anorganische Chemie der RWTH Aachen, Professor-Pirlet-Strasse 1,
D-52056 Aachen, Germany, Anorganisch-chemisches Institut der Ruprecht-Karls Universita¨t,
Im Neuenheimerfeld 270, D-69120 Heidelberg, Germany, and Anorganisch-chemisches Institut
der Technischen Universita¨t Mu¨nchen, Lichtenbergstrasse 4, D-85747 Garching, Germany
Received August 5, 1997X
The four intramolecularly coordinated azidoalanes R2Al(N3) and RAltBu(N3) (R ) (CH2)3-
NMe2 (1b, 3b), 2-(Me2NCH2)C6H4 (2b, 4b)) were synthesized by reaction of the corresponding
aluminum chlorides (1a -4a ) with an excess of dry sodium azide in refluxing toluene or
toluene/THF. The structures of the products were deduced from 1H, 13C, and 27Al NMR
spectra and were confirmed by X-ray structural determinations of 1a , 1b, and 2b. The
compounds of type 1 and 2 contain pentacoordinated Al atoms, whereas the alanes of type
3 and 4 show tetracoordination of the central Al atoms.
Sch em e 1
In tr od u ction
The group 13 nitrides AlN, GaN, and InN are candi-
dates for advanced microelectronic and optoelectronic
devices such as light-emitting diodes and lasers and
high-temperature and high-power devices, as well as
chemical sensors, acoustic surface wave conductors, and
isolating passivation layers.1,2 Recently, group 13 metal
azides containing a 3-(dimethylamino)propyl ligand,
capable of intramolecular donor stabilization, were
shown to be suitable single-source precursors for the
deposition of AlN,3 GaN,4 and InN5 at relatively low
temperatures. To date, only a few monoazido alanes
have been structurally characterized, namely [R2Al-
7
(N3)]3 (R ) Me, Et)6 and [EtClAl(N3)]3 by vibrational
8
spectroscopy and [{(SiMe3)2CH}2Al(N3)]3 by single-
crystal X-ray diffraction.9 The compound with the bulky
† RWTH Aachen.
‡ E-mail: jens.mueller@ac.rwth-aachen.de.
§ Ruprecht-Karls Universita¨t.
| E-mail: FISCHER@akcomba.oci.uni-heidelberg.de.
Technischen Universita¨t Mu¨nchen.
“disyl” ligand trimerizes via γ-nitrogen atoms and not
like the others via R-nitrogen atoms. Recently, we
reported the synthesis and characterization of Me2Al-
(N3)NH2tBu and [Me2N(CH2)3]2Al(N3) (1b).3 These two
Lewis acid/base adducts are the first known monomeric
azidoalanes. We describe here the continuation of our
investigations on intramolecularly Lewis-base-stabilized
aluminum azides using the well-known and related
ligands 3-(dimethylamino)propyl and 2-[(dimethylami-
no)methyl]phenyl.
X Abstract published in Advance ACS Abstracts, December 15, 1997.
(1) Neumayer, D. A.; Ekerdt, J . G. Chem. Mater. 1996, 8, 9 and
references therein.
(2) J ones, A. C.; O’Brien, P. CVD of Compound Semiconductors;
VCH: Weinheim, Germany, 1997.
(3) Fischer, R. A.; Miehr, A.; Sussek, H.; Pritzkow, H.; Herdtweck,
E.; Mu¨ller, J .; Ambacher, O.; Metzger, T. J . Chem. Soc., Chem.
Commun. 1996, 2685.
(4) (a) Miehr, A.; Mattner, M. R.; Fischer, R. A. Organometallics
1996, 15, 2053. (b) Miehr, A.; Ambacher, O.; Rieger, W.; Metzger, T.;
Born, E.; Fischer, R. A. Chem. Vap. Deposition 1996, 2, 51. (c) Fischer,
R. A.; Miehr, A.; Herdtweck, E.; Mattner, M. R.; Ambacher, O.;
Metzger, T.; Born, E.; Weinkauf, S.; Pulham, C. R.; Parsons, S. Chem.
Eur. J . 1996, 2, 1353.
(5) Fischer, R. A.; Miehr, A.; Metzger, T.; Born, E.; Ambacher, O.;
Angerer, H.; Dimitrov, R. Chem. Mater. 1996, 8, 1356.
(6) (a) Prince, M. I.; Weiss, K. J . Organomet. Chem. 1966, 5, 584.
(b) Dehnicke, K.; Stra¨hle, J .; Seybold, D.; Mu¨ller, J . J . Organomet.
Chem. 1966, 6, 298. (c) Dehnicke, K.; Mu¨ller, J . Z. Anorg. Allg. Chem.
1966, 348, 261. (d) Wiberg, N.; J oo, W.-Ch.; Henke, H. Inorg. Nucl.
Chem. Lett. 1967, 3, 267. (e) Mu¨ller, J .; Dehnicke, K. J . Organomet.
Chem. 1968, 12, 37.
Resu lts a n d Discu ssion
Syn th eses. The new azidoalanes 1b-4b (Scheme 1)
were synthesized by reaction of the aluminum chlorides
1a -4a with an excess of dry sodium azide in refluxing
toluene or toluene/THF for several days. The gallium
(7) Krieg, V.; Weidlein, J . Z. Anorg. Allg. Chem. 1969, 368, 44.
(8) Uhl, W.; Gerding, R.; Pohl, S.; Saak, W. Chem. Ber. 1995, 128,
81.
(9) AlCl2(N3) (structure unknown): Wiberg, N.; J oo, W.-Ch.; Schmid,
K. H. Z. Anorg. Allg. Chem. 1972, 394, 197.
S0276-7333(97)00687-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 01/19/1998

162 Organometallics, Vol. 17, No. 2, 1998
Mu¨ller et al.
azides [Me2N(CH2)3]Ga(N3)2 and [Me2N(CH2)3]GaR(N3)
(R ) Me, tBu)4a had been obtained earlier by a similar
method. The syntheses of the aluminum compounds
described here required higher temperatures and longer
reaction times. The progress of the substitution reac-
tions was followed by 27Al NMR spectroscopy, the
signals of the starting chlorides and the respective
azides being well-separated (see discussion below). The
synthesis of compound 1b was reported in an earlier
communication.3 This azide was an unexpected product
in the attempted preparation of [Me2N(CH2)3]Al(N3)2 by
reaction of the dichloride10 [Me2N(CH2)3]AlCl2 and
sodium azide. Instead of the expected diazido com-
pound, the monoazide 1b was isolated in about 50%
yield (eq 3). Treatment of [Me2N(CH2)3]AlCl2 with
F igu r e 1. Molecular structure of 1a (thermal ellipsoids
at 50% probability).
sodium azide in toluene gave only traces of 1b. The
presence of THF was necessary to achieve quantitative
formation of 1b according to eq 3. However, in contrast
to the case of gallium, the aluminum diazido compound
could not be isolated from the reaction mixture. The
azide 1b, a volatile, low-melting solid, is a potential
single-source precursor for the deposition of AlN films,3
and a straightforward synthesis of 1b was needed.
Chloride 1a , prepared by the reaction of 2 equiv of Li-
(CH2)3NMe2 with aluminum trichloride in 84% yield,
gave 1b on reaction with NaN3. The analogous bromide
[Me2N(CH2)3]2AlBr (1c), which is accessible by a similar
route, also was tested as a starting material. In
principle it makes no difference if the chloride or the
bromide is used (eq 1, Scheme 1); the reaction times
needed rather are a function of the solvent used. With
a 2:1 toluene/THF mixture the substitution is complete
within 15 h, whereas in pure toluene more than 60 h is
required, probably due to the higher solubility of NaN3
in the presence of THF.
F igu r e 2. Molecular structure of 1b (Platon;22 thermal
ellipsoids at 30% probability).
Ta ble 1. Cr ysta l Da ta , Da ta Collection
P a r a m eter s, a n d Con ver gen ce Resu lts for 1a ,
1b, a n d 2b
1a
10H24AlClN2 C10H24AlN5
234.70 241.32
orthorhombic monoclinic
1ba
2b
formula
fw
cryst syst
C
C18H24AlN5
337.41
orthorhombic
P212121 (19)
9.048(2)
10.007(1)
20.844(3)
90
space group (No.) Pcab (61)
P21/n (14)
7.234(1)
11.236(1)
17.525(3)
100.409(12)
1401.0(3)
4
a, Å
b, Å
c, Å
â, deg
U, Å3
Z
11.024(6)
15.062(8)
16.557(8)
90
2749(3)
8
The starting compounds required for the syntheses
of azides equipped with the “one-arm phenyl” ligand (2b
and 4b) were published recently.11 Applying the method
used for the chloride 4a 11 and the gallane [Me2N(CH2)3]-
GatBu(Cl),4a we prepared 3a by reaction of [Me2N(CH2)3]-
1887.2(9)
4
d
calc, g cm-3
µ, cm-1
max, deg
1.134
1.144
1.187
9.77
71.9
3.13
1.3
θ
26.0
25.6
cryst dimens,
0.5 × 0.5 ×
0.20 × 0.20 × 0.28 × 0.48 ×
10
AlCl2 and 1 molar equiv of t-BuLi.
mm3
0.5
0.51
0.710 73
12795
2466
0.60
1.541 84
9234
The four azides 1b-4b are not pyrophoric, are not
explosive, and sublime or distill in the range of 60-140
°C under high vacuum.
λ, Å
no. of rflns
0.710 73
2699
no. of indep rflns 2699
3733
abs cor
empirical
0.836/0.768
empirical
0.999/0.872
X-r a y Str u ctu r a l An a lyses. Molecu la r Str u c-
tu r es of 1a a n d 1b. The chloroalane 1a crystallizes
in the orthorhombic space group Pcab, and the azi-
doalane 1b3 crystallizes in the monoclinic space group
P21/n with no unusual intramolecular contacts in each
case (Figures 1 and 2 and Tables 1 and 2). The
coordination geometries around the Al centers reflect
distorted trigonal bipyramids with the two amine N-
donor atoms at the apical positions and the alkyl carbon
atoms of the propyl groups as well as Cl and N3 (of the
azide), respectively, in the equatorial plane. The N1-
Al1-N2 axes are very close to linearity. The angles
transmissn
(min/max)
no. of indep
obs rflns
no. of vars
R
1994 (I >
2.0σ(I))
224
2051 (I >
2.0σ(I))
241
1893 (I >
1.0σ(I))
217
0.055
0.045
0.037
0.051
Rw (w-1 ) σ2(Fo))
wR2
GOF
0.086
1.040
0.211
0.092
1.024
0.309
0.888
0.331
resid electron
dens, e Å-3
a
Data taken from ref 3.
C1-Al-C6 for both compounds (1a and 1b) are 136°,
larger than the ideal value of 120° as a result of the
steric requirements of the chelating aminopropyl ligands.
The Al-Cl bond distance of 2.224(1) Å (1a ) is compa-
rable to the mean Al-N distance of 2.18 Å in (HMe2N)2-
(10) (a) Schumann, H.; Hartmann, U.; Wassermann, W.; J ust, O.;
Dietrich, A.; Pohl, L.; Hostalek, M.; Lokai, M. Chem. Ber. 1991, 124,
1113. (b) Du¨michen, U.; Thiele, K.-H.; Gelbrich, T.; Sieler, J . J .
Organomet. Chem. 1995, 195, 71.
(11) Mu¨ller, J .; Englert, U. Chem. Ber. 1995, 128, 493.

Intramolecularly Coordinated Azidoalanes
Organometallics, Vol. 17, No. 2, 1998 163
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 1a , 1b, a n d 2b
Compound 1a
Al-N1
Al-C1
C3-N1
C7-C8
2.210(2)
1.981(3)
1.486(3)
1.515(4)
Al-N2
C1-C2
Al-C6
C8-N2
2.189(2)
1.529(3)
1.989(2)
1.487(3)
Al-Cl
C2-C3
C6-C7
2.224(1)
1.518(4)
1.533(3)
N1-Al-N2
Al-N1-C3
Al-N2-C8
C1-Al-C6
176.2(1)
101.1(2)
102.0(2)
136.0(2)
N1-Al-Cl
N2-Al-Cl
Cl-Al-C1
91.3(1)
92.5(1)
111.1(1)
N1-Al-C1
N2-Al-C6
Cl-Al-C6
83.6(1)
84.0(1)
112.9(1)
Compound 1b
Al-N1
N3-N4
C1-C2
Al-C6
C8-N2
2.167(2)
1.191(2)
1.534(3)
1.991(2)
1.483(3)
Al-N2
N4-N5
C2-C3
C6-C7
2.199(2)
1.145(2)
1.514(2)
1.536(3)
Al-N3
Al-C1
C3-N1
C7-C8
1.897(2)
1.982(2)
1.483(2)
1.518(3)
N1-Al-N2
N1-Al-C1
N2-Al-C6
N3-Al-C6
178.3(1)
84.0(1)
84.1(1)
112.4(1)
N1-Al-N3
Al-N1-C3
Al-N2-C8
C1-Al-C6
89.6(1)
101.7(1)
102.7(1)
135.9(1)
N3-N4-N5
N2-Al-N3
N3-Al-C1
176.9(2)
91.5(1)
111.7(1)
Compound 2b
Al-N1
2.168(5)
1.161(6)
1.429(7)
1.988(6)
1.512(7)
Al-N2
2.209(4)
1.153(7)
1.510(8)
1.397(7)
Al-N3
1.864(6)
1.985(5)
1.469(7)
1.507(7)
N3-N4
C10-C11
Al-C20
C26-N2
N4-N5
Al-C10
C16-N1
C21-C26
C11-C16
C20-C21
N1-Al-N2
N1-Al-C10
N2-Al-C20
N3-Al-C20
176.9(2)
82.0(2)
80.1(2)
120.4(2)
N1-Al-N3
Al-N1-C16
Al-N2-C26
C10-Al-C20
85.8(2)
101.2(3)
100.2(3)
125.6(2)
N3-N4-N5
N2-Al-N3
N3-Al-C10
175.5(7)
91.3(2)
113.9(2)
AlCl3.12 The azido unit of 1b shows a characteristic
bending (Al-N3-N4 ) 133.1(1)°) and is almost linear
(N3-N4-N5 ) 176.9(2)°). The Al-N3 bond length of
1.897(2) Å compares well with the values of 1.901(1) and
1.864(6) Å for Me2(N3)Al(NH2tBu)3 and 2b, respectively,
which represent the only known structurally character-
ized monoazido alanes to date. The Al-Nazide bonds in
(N3)3Al(py)3 of 1.952(3), 1.953(2), and 2.007(3) Å are
significantly longer.3 The donor-acceptor bonds of 1a
(2.189(2) and 2.210(2) Å) are insignificantly longer than
those of the azide 1b (2.167(2) and 2.199(2) Å). Com-
pounds 1a and 1b both exhibit two fused five-membered
metallacyclic rings, each in an expected envelope con-
formation. The “flap” atoms are C3 and C8 for both
alanes. Two envelope conformations could lead to
several isomers, depending on the “bending directions”
of the carbon tips. The one adopted by 1a and 1b could
be called an exo/exo isomer, i.e., C3 and C8 are both bent
toward the chloride or the azide, respectively. A similar
conformation is adopted by the related chlorogallane
[Me2N(CH2)3]2GaCl.13 The related azidoindane [Me2-
N(CH2)3]2In(N3), however, exhibits an exo/endo orienta-
tion. However, in contrast to 1a and 1b, this indium
compound is associated in the solid state via linear
bridging azide units, similar to the related halides
[Me2N(CH2)3]2InX (X ) Br, I).13
F igu r e 3. Molecular structure of 2b (Platon;22 thermal
ellipsoids at 30% probability).
nitrogen atoms N1 and N2 are in apical positions. The
N1-Al-N2 axis is close to linearity (176.9(2)°), and the
three angles in the equatorial plane sum up to 360°.
The deviation from an ideal trigonal-bipyramidal ge-
ometry may be described by the tilt angle of 101°
between the least-squares plane N1, Al, N2, and N314
and the equatorial plane. The linear N3 group (N3-
N4-N5 ) 175.5(7)°) is bent in a similar way (Al-N3-
N4 ) 139.5(5)°) as that of 1b discussed earlier. The two
donor-acceptor bond lengths of 2.168(5) Å (Al-N1) and
2.209(4) Å (Al-N2) match well those of the chloride 1a
and of the azide 1b. The closely related alane [2-(Me2-
NCH2)C6H4]2AlMe11 exhibits with 2.245(2) and 2.290-
(2) Å significantly longer Al-N bonds, but it is known
that Al-N bond lengths are very sensitive to substituent
effects and, therefore, cover quite a large range.15
Compound 2b contains two fused five-membered
rings, each in an envelope conformation. Compared
Molecu la r Str u ctu r e of 2b. The azidoalane 2b
crystallizes in the space group P212121 with no unusual
intermolecular contacts (Figure 3). The metal center
is distorted trigonal bipyramidal coordinated. Two
carbon atoms (C10, C20) and the azide nitrogen atom
N3 form the equatorial plane, whereas the two amino
(12) Ahmed, A.; Schwarz, W.; Weidlein, J .; Hess, H. Z. Anorg. Allg.
Chem. 1977, 434, 207.
(13) Schumann, H.; Seuss, T. D.; J ust, O.; Weimann, R.; Hemling,
H.; Gorlitz, F. H. J . Organomet. Chem. 1994, 479, 171.
(14) Orthogonal distances from the least-squares plane (Å): N1,
0.008(4); Al, 0.015(1); N2, 0.007(4); N4, 0.000(4).
(15) Haaland, A. In Coordination Chemistry of Aluminum; Robinson,
G. H., Ed.; VCH: Weinheim, Germany, 1993; Chapter 1.

164 Organometallics, Vol. 17, No. 2, 1998
Mu¨ller et al.
Ta ble 3. 27Al NMR Sh ifts (p p m )
with the alanes of type 1, however, the “flap” atoms of
2b are the nitrogen ring atoms; i.e., N1 and N2 are
displaced 0.77 and 0.84 Å outside their respective planes
(Al-C10-C11-C16 and Al-C20-C21-C26). The dif-
ference between the “one-arm phenyl” ligand and its
aminopropyl counterpart obviously is a consequence of
the rigidity of the aryl systems incorporated into the
chelate. As in the case of 1a and 1b, the envelope
conformations give rise to several isomers, depending
on the “bending directions” of the nitrogen tips. The
one adopted by 2b could be called an endo/exo isomer,
i.e., N1 is bent toward the gap between the two aromatic
rings (endo), whereas N2 is bent in the opposite direc-
tion (exo). A related endo/exo isomer was revealed by
single-crystal analysis of [2-(Me2NCH2)C6H4]2AlMe.11
a
b
1
2
3
4
118
109
87
96a
158
145
145
134
a
Taken from ref 11.
2b fully resemble those of the chloride 2a . Therefore,
we assume the same dynamic processes in solution.
The asymmetrically substituted alanes 3 and 4 (C1
point group) show the expected NMR signals; for
example, 3a and 3b give six multiplets for the three CH2
groups, with separation trends similar to those found
for the alanes of type 1, plus two singlets for the NMe2
1
and one for the tBu group in the H NMR spectra. A
Sp ectr oscop y. The pentacoordination of aluminum
in 1 and 2 is revealed by NMR spectroscopy. At ambient
temperature, the azide 1b shows C2 symmetry with
respect to the NMR time scale (500 MHz instrument);
i.e., three different CH2 groups and two different NMe
groups. This gives rise to five 13C and eight 1H
respective pattern can be seen in the 13C NMR spectra.
27Al NMR spectroscopy often is used to deduce the
coordination number of aluminum. Besides the number
of ligands, the electronic nature of the substituents
governs the 27Al NMR chemical shifts.16 The δ (27Al)
values for 1-4 are compiled in Table 3. Inspection of
the data in Table 3 shows that the compounds with
pentacoordination resonate in the range of 87-118 ppm,
whereas the signals for the substances 3 and 4, with
only tetracoordinated centers, are found at lower field
strength (134-158 ppm). The resonances of the chlo-
rides 1a and 2a are deshielded by 9 ppm compared with
their azide counterparts 1b and 2b , respectively. In
addition, the “exchange” of two aminopropyl ligands in
1a and 1b by two “one-arm phenyl” substituents (2a
and 2b) is accompanied by an upfield shift of 22 ppm.
Similar effects can be seen with the compounds 3a , 3b,
4a , and 4b. The chloride/azide substitution results in
a difference of 13 ppm for the 3a /3b couple and 11 ppm
for the 4a /4b couple, whereas the “propyl/phenyl”
exchange yields 13 ppm for the chlorides 3a /4a and 11
ppm for the azides 3b/4b. The 27Al shift is affected
neither by the change of the solvent, i.e., THF instead
of toluene-d8, nor by a variation of the concentration of
the substance, as was found for the compounds 1a and
1b.
1
resonances. In the H NMR spectrum the differences
between two multiplets of one CH2 group increase from
AlCH2- (∆ ) 0.10 ppm) to -CH2- (∆ ) 0.35 ppm) and
-H2CN (∆ ) 0.71 ppm). The starting compounds 1a
and 1c exhibit similar NMR patterns. Temperature-
dependent measurements using a 200 MHz NMR in-
strument were undertaken for 1a and 1b. In the case
of the two proton resonances for the NMe units the
coalescence temperature is about 300 K. Above 330 K
a simple spectrum is obtained, i.e., on the NMR time
scale the symmetry of the molecule is C2v, indicating a
fast equilibrium between the possible isomers. Neither
the presence of a coordinating solvent (THF-d8) nor the
variation of the concentration of the solutions interferes
with this process; the temperature of coalescence is
unaffected. These results, together with the unchanged
chemical shifts of the 27Al atoms (see below), are strong
evidence for the persistence of 5-fold-coordinated Al
species in solution.
In addition to the expected resonances of the aromatic
ring (ABCD spin system), the azide 2b shows four broad
1
singlets in the H NMR spectrum; two for the diaste-
Exp er im en ta l Section
reotopic protons of CH2 and two for the NMe groups.
Accordingly, these groups give only one sharp 13C
resonance (CH2) and two broad ones (NMe) in the 13C
NMR spectrum. At higher temperature (70 °C; toluene-
d8, 500 MHz instrument) the CH2 and the NMe groups
each give only one singlet in the 1H NMR spectrum,
while at -80 °C these groups result in four doublets
(CH2) and four singlets (NMe). The related compounds
2a and [2-(Me2NCH2)C6H4]2AlMe were investigated in
All procedures were carried out under a dry nitrogen
atmosphere using standard Schlenk techniques. Solvents were
dried by standard procedures, distilled, and stored under
nitrogen and molecular sieves (4 Å). NaN3 was dried at 110
°C under high vacuum for 12 h. The reagents [2-(Me2-
NCH2)C6H4]2AlCl (2a ),11 [2-(Me2NCH2)C6H4]AltBuCl (4a ),11
10b
Li(CH2)3NMe2,17 and [Me2N(CH2)3]AlCl2 were prepared ac-
cording to the literature methods.
NMR spectra were obtained on a Varian Unity 500 at
ambient temperature (1H, 499.843 MHz; 27Al, 130.195 MHz;
13C, 125.639 MHz) and calibrated against residual protons of
the deuterated solvents. 1H and 13C chemical shifts are
reported relative to TMS and 27Al values relative to the
external standard [Al(acac)3] in C6D6. As a result of the electric
quadrupole moment of the 27Al nucleus, not all of the carbon
atoms bound to aluminum could be detected in 13C NMR
experiments. The assignments of the 1H and 13C NMR signals
1
detail by variable-temperature H NMR spectroscopy.11
As deduced from these experiments, the equilibrium
geometry corresponds to an endo/exo configuration (C1
point group), in accordance with the structure of the
methylalane in the solid state. The dynamic behavior
in solution was explained by assuming two processes.
First, an envelope inversion converts an endo/exo isomer
into an exo/endo species, which results in a C2-sym-
metrical molecule. Second, there is an interchange of
the two chelating ligands, i.e., an interconversion of the
two C2-symmetrical enantiomers, which results in a C2v-
symmetrical molecule on time average. The spectra of
1
were made either with the aid of H/13C-HMQC experiments
(16) Benn, R.; J anssen, E.; Lehmkuhl, H.; Rufinska, A. J . Orga-
nomet. Chem. 1987, 333, 155.
(17) Thiele, K.-H.; Langguth, E.; Mu¨ller, G. E. Z. Anorg. Allg. Chem.
1980, 462, 152.

Intramolecularly Coordinated Azidoalanes
Organometallics, Vol. 17, No. 2, 1998 165
(1c and 3b) or according to the literature.11 The IR spectra
were recorded on a Perkin-Elmer FTIR 1720x in toluene.
Mass spectra were obtained on a Finnigan MAT 95 (70 eV).
Elemental analyses (C, H, N) were measured on either a Carlo-
Erba elemental analyzer (Model 1106) or an Elementar Vario
EL. Melting points were obtained in sealed glass capillaries
under N2 and are uncorrected.
(4.22 g, 12.8 mmol) in 120 mL of toluene was heated at reflux
for 140 h. The reaction mixture was filtered, and the solid
was washed with two 10 mL portions of toluene. After removal
of the solvent under high vacuum, sublimation (140 °C, 10-3
Torr) gave pure, crystalline 2b (3.25 g, 76%). Single crystals
suitable for X-ray diffraction were obtained from Et2O at -20
°C (mp 147-149 °C). Anal. Calcd for C18H24AlN5 (337.41):
C, 64.08; H, 7.17; N, 20.76. Found: C, 64.14; H, 7.39; N, 21.50.
MS: m/z 337 (M+, 2), 322 (M+ - CH3, 13), 295 (M+ - N3, 27),
203 (M+ - C9H12N, 21), 135 (C9H13N+, 57), 134 (C9H12N+, 47),
91 (C7H7+, 69), 58 (C3H8N+, 100). 1H NMR (C6D6): δ 2.04 (s,
broad, 6H, N(CH3)(CH3)), 2.23 (s, broad, 6H, N(CH3)(CH3)),
3.26 (s, broad, 2H, CHH), 3.65 (s, broad, 2H, CHH), 6.91 (m,
2H, 3-H), 7.20 (m, 4H, 4,5-H), 7.63 (m, 2H, 6-H). 13C{1H} NMR
(C6D6): δ 45.18 (broad, NCH3), 46.05 (broad, NCH3), 66.63
(CH2), 125.90 (CH), 126.05 (CH), 127.65 (CH), 138.31 (C-6),
147.07 (C-2), 147.4 (broad, C-ipso). 27Al NMR (C6D6): δ 87 (h1/2
) 4400 Hz). IR (toluene; νas(N3), cm-1): 2124.
Ch lor obis[3-(d im eth yla m in o)p r op yl]a lu m in u m (1a ).
17
A suspension, prepared with Li(CH2)3NMe2 (9.31 g, 100.0
mmol) in 200 mL of Et2O, was added dropwise to a solution of
AlCl3 (6.66 g, 49.9 mmol) in 200 mL of Et2O at -78 °C. The
dry-ice bath was removed, and the reaction mixture was
stirred overnight. The solution was filtered, and after removal
of volatiles at ambient temperature, 1a crystallized as large,
colorless needles (9.81 g, 84%, mp 54 °C). Anal. Calcd for
C
10H24AlClN2 (234.75): C, 51.17; H, 10.31; N, 11.93; Al, 11.49.
Found: C, 49.21; H, 9.80; N, 11.53; Al, 11.86. HRMS: m/z
calcd for C10H24Al35ClN2 234.1444, found 234,1476. MS: m/z
234 (M+, 4), 199 (M+ - Cl, 6), 148 (M+ - C5H12N, 72). 1H NMR
(toluene-d8, 293 K): δ 0.13 (m, 4H, AlCH2), 1.46 (m, 2H,
-CHH-), 1.72 (m, 4H, NCHH, -CHH-), 1.95 (s, broad, 12H,
NCH3), 2.71 (m, 2H, NCHH). 13C{1H} NMR (toluene-d8): δ
1.69 (broad, AlCH2), 20.85 (AlCH2CH2), 44.98 (broad, NCH3),
60.92 (NCH2). 27Al NMR (toluene-d8): δ 118 (h1/2 ) 1750 Hz).
Azid ob is[3-(d im et h yla m in o)p r op yl]a lu m in u m (1b ).
Meth od A. A solution of 1a (5.00 g, 21.3 mmol) in 100 mL of
toluene and 50 mL of THF were added to NaN3 (2.76 g, 42.5
mmol), and the mixture was heated at reflux for 15 h. After
removal of the solvent under vacuum, the residue was purified
by sublimation (100 °C, 10-4 Torr) with a -15 °C cold finger.
1b was obtained as small, colorless crystals (4.72 g, 92%).
Meth od B. A mixture of NaN3 (3.16 g, 48.6 mmol) and 1c
(1.36 g, 4.9 mmol) in 40 mL of toluene was heated at reflux
for 64 h. The reaction mixture was filtered, and the solid was
washed with two 10 mL portions of toluene. After removal of
the solvent under high vacuum, trap-to-trap distillation (60-
70 °C, 10-3 Torr) gave pure 1b as a colorless liquid (0.94 g,
80%), which slowly solidified on storage at -15 °C. Anal. Calcd
for C10H24AlN5 (241.31): C, 49.77; H, 10.03; N, 29.02; Al, 11.18.
Found: C, 48.19; H, 10.08; N, 29.26; Al, 11.05. HRMS: m/z
calcd for C10H24AlN5 241.1847, found 241,1848. MS: m/z 241
t er t -Bu t ylch lor o[3-(d im e t h yla m in o)p r op yl]a lu m i-
n u m (3a ). A 1.7 M solution of t-BuLi in pentane (13.0 mL,
22.1 mmol) was added to [Me2N(CH2)3]AlCl2 (4.06 g, 22.1
mmol) dissolved in 120 mL of Et2O at -78 °C. The dry-ice
bath was removed, and the solution was stirred overnight.
Subsequently, volatiles were distilled under high vacuum at
ambient temperature. The residue was extracted with hexane
(60 mL). The solution was filtered, and the solid was washed
with two 10 mL portions of hexane. After removal of the
solvent from the extracts under high vacuum, trap-to-trap
distillation (70-80 °C, 10-3 Torr) yielded 3a (3.81 g, 81%) as
a colorless liquid. Further purification was effected by short-
path distillation (60 mm Vigreux, bp 42-45 °C, 10-3 Torr) (3.11
g, 66%). HRMS: m/z calcd for C9H21AlClN 205.1178, found
205.1179. MS: m/z 205 (M+, 1), 170 (M+ - Cl, 5), 148 (M+
-
C4H9, 100), 58 (C3H8N+, 92). 1H NMR (C6D6): δ 0.21 (m, 2H,
AlCH2), 1.14 (s, 9H, C(CH3)3), 1.30 (m, 1H, AlCH2CHH), 1.53
(m, 1H, NCHH), 1.70 (s, 3H, NCH3), 1.73 (m, 1H, AlCH2CHH),
1.99 (s, 3H, NCH3), 2.18 (m, 1H, NCHH). 13C{1H} NMR (C6D6):
δ 0.40 (broad, AlCH2), 20.66 (AlCH2CH2), 29.63 (C(CH3)3),
43.43 (NCH3), 46.43 (NCH3), 63.70 (NCH2). 27Al NMR (C6D6):
δ 158 (h1/2 ) 1700 Hz).
Azid o -t er t -b u t y l[3-(d im e t h y la m in o )p r o p y l]a lu m i-
n u m (3b). A mixture of NaN3 (7.60 g, 116.9 mmol) and 3a
(2.41 g, 11.7 mmol) in 100 mL of toluene was heated at reflux
for 88 h. The reaction mixture was filtered, and the solid was
washed with two 10 mL portions of toluene. After removal of
the solvent under high vacuum, trap-to-trap distillation (75-
85 °C, 10-3 Torr) gave pure 3b as a colorless liquid (1.39 g,
56%). Anal. Calcd for C9H21AlN4 (212.28): C, 50.92; H, 9.97;
N, 26.39. Found: C, 51.29; H, 10.55; N, 26.97. HRMS: m/z
calcd for C9H21AlN4 212.1582, found 212.1583. MS: m/z 212
(M+, 1), 170 (M+ - N3, 3), 155 (M+ - C4H9, 100), 58 (C3H8N+,
22). 1H NMR (C6D6): δ 0.02 (m, 1H, AlCHH), 0.10 (m, 1H,
AlCHH), 1.09 (s, 9H, C(CH3)3), 1.19 (m, 1H, AlCH2CHH), 1.43
(m, 1H, NCHH), 1.53 (s, broad, 3H, NCH3), 1.58 (m, 1H, AlCH2-
CHH), 1.79 (s, broad, 3H, NCH3), 1.93 (m, 1H, NCHH). 13C-
{1H} NMR (C6D6): δ -1.89 (broad, AlCH2), 20.77 (AlCH2CH2),
29.49 (C(CH3)3), 43.14 (NCH3), 45.50 (NCH3), 63.92 (NCH2).
27Al NMR (C6D6): δ 145 (h1/2 ) 1850 Hz). IR (toluene; νas(N3),
cm-1): 2125.
Azid o-ter t-b u t yl{2-[(d im et h yla m in o)m et h yl]p h en yl}-
a lu m in u m (4b). A mixture of NaN3 (14.08 g, 216.6 mmol)
and 4a (5.75 g, 22.7 mmol) in 150 mL of toluene was heated
at reflux for 90 h. The reaction mixture was filtered, and the
solid was washed with two 10 mL portions of toluene. After
removal of the solvent under high vacuum, trap-to-trap
distillation (110-120 °C, 10-3 Torr) gave pure 4b as a colorless
liquid (4.99 g, 85%). The compound crystallized slowly at room
temperature (mp 38-41 °C). Anal. Calcd for C13H21AlN4
(260.32): C, 59.98; H, 8.13; N, 21.52. Found: C, 59.20; H, 8.40;
N, 22.07. HRMS: m/z calcd for M+ - C4H9 (C9H12AlN4)
203.0877, found 203.0879. MS: m/z 203 (M+ - C4H9, 33), 135
(M+, 7), 199 (M+ - N3, 32), 155 (M+ - C5H12N, 100), 113 (C5H12
-
AlN+, 9). 1H NMR (C6D6): δ -0.15 (m, 2H, AlCHH), -0.05
(m, 2H, AlCHH), 1.38 (m, 2H, AlCH2CHH), 1.60 (s, broad, 6H,
N(CH3)(CH3)), 1.67 (m, 2H, NCHH), 1.73 (m, 2H, AlCH2CHH),
2.05 (s, broad, 6H, N(CH3)(CH3)), 2.38 (m, 2H, NCHH). 13C-
{1H} NMR (C6D6): δ 0.25 (broad, AlCH2), 20.99 (AlCH2CH2),
43.46 (broad, N(CH3)(CH3)), 45.51 (broad, N(CH3)(CH3)), 61.73
(NCH2). 27Al NMR (C6D6): δ 109 (h1/2 ) 1550 Hz). IR (toluene;
νas(N3), cm-1): 2113.
Br om obis[3-(dim eth ylam in o)pr opyl]alu m in u m (1c). Li-
(CH2)3NMe2 (2.48 g, 26.6 mmol) was added to a solution of
AlBr3 (3.55 g, 13.3 mmol) in 50 mL of toluene at -78 °C. The
dry-ice bath was removed, and the reaction mixture was
stirred overnight and subsequently filtered. The solid was
washed with two 10 mL portions of toluene. After removal of
volatiles at ambient temperature, sublimation (60 °C, 10-3
Torr) gave pure 1c (3.02 g, 81%, mp 82-84 °C). Anal. Calcd
for
Found: C, 42.95; H, 8.72; N, 10.60. HRMS: m/z calcd for
10H24AlBrN2 278.0938, found 278.0938. MS: m/z 278 (M+,
C10H24AlBrN2 (279.20): C, 43.02; H, 8.67; N, 10.03.
C
5), 263 (M+ - CH3, 3), 235 (M+ - C3H7, 31), 199 (M+ - Br,
25), 192 (M+ - C5H12N, 100), 87 (C5H13N+, 16), 86 (C5H12N+,
17). 1H NMR (C6D6): δ 0.09 (m, 2H, AlCHH), 0.20 (m, 2H,
AlCHH), 1.45 (m, 2H, AlCH2CHH), 1.65 (m, 2H, NCHH), 1.77
(m, 2H, AlCH2CHH), 1.95 (s, broad, 12H, NCH3), 2.88 (m, 2H,
NCHH). 13C{1H} NMR (C6D6): δ 1.89 (broad, AlCH2), 20.56
(AlCH2CH2), 44.99 (broad, NCH3), 60.47 (NCH2). 27Al NMR
(C6D6): δ 118 (h1/2 ) 1750 Hz).
Azid ob is{2-[(d im et h yla m in o)m et h yl]p h en yl}a lu m i-
n u m (2b). A mixture of NaN3 (8.47 g, 130.3 mmol) and 2a

166 Organometallics, Vol. 17, No. 2, 1998
Mu¨ller et al.
(C9H13N+, 98), 134 (C9H12N+, 76), 91 (C7H7+, 91), 58 (C3H8N+,
100). 1H NMR (C6D6): δ 1.15 (s, 9H, C(CH3)3), 1.57 (s, 3H,
NCH3), 1.84 (s, 3H, NCH3), 2.73 (d, J ) 14.0 Hz, 1H, CH2),
3.28 (d, J ) 14.0 Hz, 1H, CH2), 6.74 (m, 1H, 3-H), 7.15 (m,
2H, 4,5-H), 7.70 (m, 1H, 6-H). 13C{1H} NMR (C6D6): δ 29.36
(C(CH3)3), 44.27 (NCH3), 45.47 (NCH3), 67.05 (CH2), 124.36
(CH), 127.39 (CH), 128.57 (CH), 137.66 (C-6), 143.82 (C-2). 27Al
NMR (C6D6): δ 134 (h1/2 ) 2900 Hz). IR (toluene; νas(N3), cm-1):
2129.
X-r a y Str u ctu r e Deter m in a tion of C18H24AlN5 (1a ).
Geometry and intensity data were collected with Mo KR
radiation at -70 °C on a Siemens Stoe AED2 diffractometer
equipped with a graphite monochromator (λ ) 0.710 73 Å). A
summary of crystal data, data collection parameters, and
convergence results is compiled in Table 1. An empirical
absorption correction (ψ scans) was applied.18 The structure
was solved by direct methods and refined with all data based
on F2.19 In the full-matrix least-squares refinement, all non-
hydrogen atoms were assigned anisotropic displacement pa-
X-r a y Str u ctu r e Deter m in a tion of C18H24AlN5 (2b).
Geometry and intensity data were collected with Cu KR
radiation at room temperature on an Enraf-Nonius CAD4
diffractometer equipped with a graphite monochromator (λ )
1.541 84 Å). A summary of crystal data, data collection
parameters, and convergence results is compiled in Table 1.
An empirical absorption correction (ψ scans) was applied.18 The
structure was solved by direct methods20 and refined on
structure factors with the local version of the SDP program
suite.21 In the full-matrix least-squares refinement, all non-
hydrogen atoms were assigned anisotropic displacement pa-
rameters. Hydrogen atoms were not refined but included
isotropically as riding on the corresponding carbon atoms
(C-H ) 0.98 Å, Uiso(H) ) 1.3[Ueq(C)]).
Ack n ow led gm en t. We are grateful to the Deutsche
Forschungsgemeinschaft for generous financial support.
Su p p or tin g In for m a tion Ava ila ble: Listings of the bond
lengths and angles, atomic coordinates, and displacement
parameters (7 pages). Ordering information is given on any
current masthead page.
rameters. Hydrogen atoms were located in
Fourier map and refined anisotropically.
a difference
X-r a y Str u ctu r e Deter m in a tion of C18H24AlN5 (1b). See
reference 3.
OM9706875
(18) North, A. C. T.; Phillips, D. C.; Mathewes, F. S. Acta Crystallogr.
1968, A24, 351.
(19) Sheldrick, G. M. SHELXL 93, Program for Structure Solution;
University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(20) Sheldrick, G. M. SHELXS86, Program for Structure Solution;
University of Go¨ttingen, Go¨ttingen, Germany, 1986.
(21) ENRAF-Nonius SDP Version 5.0, 1989.
(22) Spek, A. L. Acta Crystallogr. 1990, A46, C34.