Synthesis, characterization, and reaction of aluminum halide amides supported by a bulky β-diketiminato ligand

Article abstract of DOI:10.1021/ic701896r

Monomeric aluminum chloride amides with the general formula LAI(Cl)NR ₂ (1, R = Me; 2, R = iPr; 3, R = SiMe₃; L = HC[C(Me)N(Ar)]₂; Ar = 2,6-iPr₂C₆H₃) were prepared by selected routes. Treatment of LAIBr₂ (4) and LAII₂ with LiNMe₂ yielded LAI(Br)NMe₂ (5) and LAI(I)NMe₂ (6), respectively. The alkylation of 1 and 2 with MeLi gave the corresponding methylated compounds LAI(Me)NR₂ (7, R = Me; 8, R = iPr); however, no reaction of 3 with MeLi was observed because of steric hindrance. Subsequent fluorination of 1-3 afforded LAI(F)NR₂ (9, R = Me; 10, R = iPr; 11, R = SiMe₃). Compounds 1-11 were characterized by multinuclear NMR, electron impact mass spectrometry, and IR. The constitution of compounds 1-3 was confirmed by single-crystal X-ray diffraction studies.

Full text of DOI:10.1021/ic701896r

Inorg. Chem. 2008, 47, 2585-2592
Synthesis, Characterization, and Reaction of Aluminum Halide Amides
Supported by a Bulky ꢀ-Diketiminato Ligand
Ying Yang,†,‡ Thomas Schulz,‡ Michael John,‡ Arne Ringe,‡ Herbert W. Roesky,*,‡ Dietmar Stalke,‡
Jörg Magull,‡ and Hongqi Ye†
School of Chemistry and Chemical Engineering, Central South UniVersity,
410083 Changsha, People’s Republic of China, and Institut für Anorganische Chemie,
UniVersität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany
Received September 25, 2007
Monomeric aluminum chloride amides with the general formula LAl(Cl)NR2 (1, R ) Me; 2, R ) iPr; 3, R ) SiMe3;
L ) HC[C(Me)N(Ar)]2; Ar ) 2,6-iPr2C6H3) were prepared by selected routes. Treatment of LAlBr2 (4) and LAlI2 with
LiNMe2 yielded LAl(Br)NMe2 (5) and LAl(I)NMe2 (6), respectively. The alkylation of 1 and 2 with MeLi gave the
corresponding methylated compounds LAl(Me)NR2 (7, R ) Me; 8, R ) iPr); however, no reaction of 3 with MeLi
was observed because of steric hindrance. Subsequent fluorination of 1-3 afforded LAl(F)NR2 (9, R ) Me; 10,
R ) iPr; 11, R ) SiMe3). Compounds 1–11 were characterized by multinuclear NMR, electron impact mass
spectrometry, and IR. The constitution of compounds 1-3 was confirmed by single-crystal X-ray diffraction studies.
Introduction
few examples known of monomeric aluminum halide amides
with two different substituents.10 Nevertheless, several
analogues are found in ytterbium-, samarium-, and scandium-
containing compounds,11–13 where the halogen can be
eliminated by metathesis reactions, while in some cases of
alkaline-earth metal and zinc amides,14,15 it is the amido
group that plays the role as a facile leaving group. These
facts prompted us to prepare aluminum halide amides of the
general formula LAl(X)NR2 (L ) ligand; X ) halogen) and
to explore their reactivity. Herein, we report on the synthesis
and characterization of LAl(X)NR2 (X ) Cl, Br, I; R ) Me,
iPr, SiMe3; L ) HC[C(Me)N(Ar)]2; Ar ) 2,6-iPr2C6H3).
Aluminum amides have found widespread application as
precursors for AlN materials1 and are of interest in catalysis
and organic synthesis.2 Oligomeric nitrogen-rich com-
pounds3,4 or structurally characterized monomers5–9 have
been developed for this purpose. There are, however, only a
* To whom correspondence should be addressed. Email: hroesky@
gwdg.de. Fax: (+49) 551-393373.
†
Central South University.
Universität Göttingen.
‡
(1) (a) Bradley, D. C.; Frigo, D. M.; White, E. A. D. Eur. Patent 0331448,
1989. (b) Interrante, L. V.; Lee, W.; McConnell, M.; Lewis, N.; Hall,
E. J. Electrochem. Soc. 1989, 136, 472–478. (c) Takahashi, Y.;
Yamashita, K.; Motojima, S.; Sugiyama, K. Surf. Sci. 1979, 86, 238–
245.
(10) Chang, C. C.; Hsiung, C. S.; Su, H. L.; Srinivas, B.; Chiang, M. Y.;
Lee, G. H.; Wang, Y. Organometallics 1998, 17, 1595–1601.
(11) Cui, C.; Shafir, A.; Schmidt, J. A. R.; Oliver, A. G.; Arnold, J. Dalton
Trans. 2005, 1387–1393.
(2) (a) Rowley, C. N.; DiLabio, G. A.; Barry, S. T. Inorg. Chem. 2005,
44, 1983–1991. (b) Hoerter, J. M.; Otte, K. M.; Gellman, S. H.; Stahl,
S. S. J. Am. Chem. Soc. 2006, 128, 5177–5183.
(3) (a) Brask, J. K.; Chivers, T.; Yap, G. P. A. Chem. Commun. 1998,
2543–2544. (b) Kovar, R. A.; Ashby, E. C. Inorg. Chem. 1971, 10,
893–899.
(12) Chai, J.; Jancik, V.; Singh, S.; Zhu, H.; He, C.; Roesky, H. W.;
Schmidt, H.-G.; Noltemeyer, M.; Hosmane, N. S. J. Am. Chem. Soc.
2005, 127, 7521–7528.
(4) Waggoner, K. M.; Olmstead, M. M.; Power, P. P. Polyhedron 1990,
9, 257–263.
(13) Knight, L. K.; Piers, W. E.; Fleurat-Lessard, P.; Parvez, M.; McDonald,
R. Organometallics 2004, 23, 2087–2094.
(5) Jancik, V.; Pineda, L. W.; Pinkas, J.; Roesky, H. W.; Neculai, D.;
Neculai, A. M.; Herbst-Irmer, R. Angew. Chem., Int. Ed. 2004, 43,
2142–2145.
(14) (a) Cheng, M.; Moore, D. R.; Reczek, J. J.; Chamberlain, B. M.;
Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc. 2001, 123, 8738–
8749. (b) Nembenna, S.; Roesky, H. W.; Mandal, S. K.; Oswald, R. B.;
Pal, A.; Herbst-Irmer, R.; Noltemeyer, M.; Schmidt, H.-G. J. Am.
Chem. Soc. 2006, 128, 13056–13057. (c) Nembenna, S.; Roesky,
H. W.; Nagendran, S.; Hofmeister, A.; Magull, J.; Wilbrandt, P. J.;
Hahn, M. Angew. Chem., Int. Ed. 2007, 46, 2512–2514.
(6) Kenney, A. P.; Yap, G. P. A.; Richeson, D. S.; Barry, S. T. Inorg.
Chem. 2005, 44, 2926–2933.
(7) Gardiner, M. G.; Koutsantonis, G. A.; Lawrence, S. M.; Raston, C. L.
Inorg. Chem. 1996, 35, 5696–5702.
(8) Atwood, D. A.; Rutherford, D. Main Group Chem. 1996, 1, 431–
442.
(15) (a) Chisholm, M. H.; Gallucci, J.; Phomphrai, K. Chem. Commun.
2003, 48–49. (b) Chisholm, M. H.; Gallucci, J. C.; Phomphrai, K.
Inorg. Chem. 2004, 43, 6717–6725. (c) Avent, A. G.; Crimmin, M. R.;
Hill, M. S.; Hitchcock, P. B. Dalton Trans. 2005, 278–284.
(9) Zhu, H.; Yang, Z.; Magull, J.; Roesky, H. W.; Schmidt, H.-G.;
Noltemeyer, M. Organometallics 2005, 24, 6420–6425.
10.1021/ic701896r CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 7, 2008 2585
Published on Web 03/04/2008

Yang et al.
Scheme 1
together in toluene, surprisingly an almost clear solution with
only a small amount of insoluble material is formed. No
precipitate was produced in this system even after stirring
at room temperature for 1 week. To explain this, we postulate
the formation of an intermediate of composition K[Cl3AlN
(SiMe3)2], which is soluble or finely dispersed in toluene
and evidently stable with respect to KCl elimination at room
temperature. Treatment of this intermediate with LLi · OEt2
followed by filtration and purification resulted in the recovery
of LAl(Cl)N(SiMe3)2 (3) as a colorless microcrystalline solid.
1
The H NMR spectrum of 3 shows two equally intense
singlets (δ 0.30 and 0.42 ppm) for the N(SiMe3)2 group with
corresponding resonances in the 29Si NMR spectrum (δ
-3.20 and +2.24 ppm). The mass spectrum confirms the
composition with the base peak for the fragment [M+ - Me].
In a previous contribution, we reported that the aluminum
diamide LAl(NH2)2 was obtained by treating LAlCl2 with
ammonia in the presence of an N-heterocyclic carbene.5 In
the current case, however, the preparation of the NiPr2- or
N(SiMe3)2-substituted derivatives using LAlCl2 as a precursor
was not successful probably because of steric hindrance of
the substituents. Aluminum has a relatively small atomic
radius, and it is more easily shielded by the bulky ꢀ-diketim-
inato ligand when compared with ytterbium and samari-
um.11,12 The procedure for the preparation of compounds 2
and 3 is an example for a successful introduction of a further
bulky group on aluminum by changing the sequence of
adding the components to the reaction mixture. A similar
method was also found for the preparation of alkaline-earth
metal derivatives.15
Furthermore, the reactivity of these compounds was inves-
tigated toward alkylation, fluorination, and hydrolysis. All
compounds were characterized by multinuclear NMR, IR,
and electron impact mass spectrometry (EI-MS) measure-
ments as well as by elemental analysis.
Results and Discussion
Synthesis of Chloride Derivatives 1–3. Aluminum amides
are generally available under elimination of alkali halides,
alkanes,16 or hydrogen.17,18 Using such a strategy, compound
LAl(Cl)NMe2 (1) was obtained in good yield by the reaction
of LAlCl2 with 1 equiv of LiNMe2 in toluene (Scheme 1).
1
The H NMR spectrum of 1 displays one singlet (δ 2.64
ppm) corresponding to the methyl proton resonance of the
NMe2 group. The remaining resonances are attributed to the
ꢀ-diketiminato ligand. In the mass spectrum, the most intense
peak corresponds to the elimination of one methyl group and
one amido group from the molecular ion.
Synthesis of Bromide and Iodide Derivatives 5 and
6. The dibromide precursor LAlBr2 (4) was readily prepared
from LLi ·OEt2 with AlBr3 in toluene. The 1H NMR spectrum
of 4 gives a pattern comparable to that of LAlCl2 with one
isopropyl methine septet and two methyl doublets of the
ꢀ-diketiminato ligand,19 demonstrating that the C2V symmetry
is kept in solution. The 27Al NMR spectrum shows a
resonance at δ 99.25 ppm, which is in the typical range for
four-coordinate aluminum compounds.20 The melting point
of 4 (215 °C) is very close to that of its dichloride analogue
(211–213 °C).19 In the mass spectrum, the molecular ion is
observed as the base peak, consistent with the observation
for a related organoaluminum dibromide HC[C(Me)N
(C6F5)]2AlBr2.21
The synthesis of LAl(Br)NMe2 (5) parallels that used for
the preparation of 1, from the reaction of 4 with 1 equiv of
LiNMe2 to afford a light-pink solid in moderate yield.
However, the analogous reactions aiming at LAl(Br)NiPr2
and LAl(Br)N(SiMe3)2 gave the target product containing
always an equivalent amount of 4 as determined by 1H NMR
spectroscopy. All attempts to isolate the pure compounds
The reaction of LAlCl2 with LiNiPr2, however, led to a
mixture of products, most of which were recognized as the
starting material. We suggest that the steric bulk of the iPr
substituent prevents the metathesis at the Al atom. To
overcome this difficulty, a one-pot strategy was proposed.
The reaction of AlCl3 and LiNiPr2 followed by the addition
of 1 equiv of LLi · OEt2 finally afforded the target product
LAl(Cl)NiPr2 (2). The 1H NMR spectrum of 2 exhibits one
septet (δ 3.10 ppm) and one doublet (δ 0.84 ppm) represent-
ing the isopropyl methine and methyl proton resonances of
the NiPr2 group, respectively. The base peak in the mass
spectrum is assigned to the fragment [M+ - NiPr2].
An attempt to react LAlCl2 with the even more bulky
MN(SiMe3)2 (M ) Li, Na, K) was not successful either,
although analogous reactions with Mes2AlCl(THF),8
12
LSmCl2,11 and LYbCl2 have been reported. Then the
above-mentioned one-pot strategy was tentatively employed
to this system. When AlCl3 and KN(SiMe3)2 are placed
(16) (a) Bradley, D. C. AdV. Inorg. Chem. Radiochem. 1972, 15, 259. (b)
Rutherford, D.; Atwood, D. A. Organometallics 1996, 15, 4417–4422.
(c) Passarelli, V.; Carta, G.; Rossetto, G.; Zanella, P. Dalton Trans.
2003, 1284–1291.
(19) Stender, M.; Eichler, B. E.; Hardman, N. J.; Power, P. P.; Prust, J.;
Noltemeyer, M.; Roesky, H. W. Inorg. Chem. 2001, 40, 2794–2799.
(20) Cui, C.; Köpke, S.; Herbst-Irmer, R.; Roesky, H. W.; Noltemeyer,
M.; Schmidt, H.-G.; Wrackmeyer, B. J. Am. Chem. Soc. 2001, 123,
9091–9098.
(17) Heine, A.; Stalke, D. Angew. Chem., Int. Ed. Engl. 1992, 31, 854–
855.
(21) Yang, Z.; Zhu, H.; Ma, X.; Chai, J.; Roesky, H. W.; He, C.; Magull,
J.; Schmidt, H.-G.; Noltemeyer, M. Inorg. Chem. 2006, 45, 1823–
1827.
(18) Montero, M. L.; Wessel, H.; Roesky, H. W.; Teichert, M.; Usón, I.
Angew. Chem., Int. Ed. Engl. 1997, 36, 629–631.
2586 Inorganic Chemistry, Vol. 47, No. 7, 2008

Aluminum Halide Amides
Scheme 2
by repeated recrystallization from various organic solvents
were not successful. Possibly an equilibrium exists in these
systems, which could not be driven further by the elimination
of alkali bromide.
Treatment of LAlI2 with 1 equiv of LiNMe2 in toluene
smoothly afforded LAl(I)NMe2 (6). A reference reaction of
LAl(I)Cl with a stoichiometric amount of LiNMe2 selectively
gave the expected 1 under elimination of lithium iodide, due
to the weaker Al-I bond strength. Similarly, in a recent
example of the stepwise hydrolysis of LAl(I)Cl, the iodide
is more easily removed than chloride by the elimination of
Figure 1. Molecular structure of 1. All H atoms are omitted for clarity.
Hydrolysis of Compounds 1 and 7. Controlled hydrolysis
of compound 1 in the presence of an N-heterocyclic
carbene5,22,24 resulted in the free ligand LH rather than the
desired aluminum hydroxide LAl(OH)NMe2 (Scheme 2).
Probably under these conditions, the coexistence of both a
hydroxyl group and an amido group on the Al atom [as an
intermediate LAl(OH)NMe2] may be unstable and prone to
decomposition by intramolecular elimination of LH. In
contrast, direct hydrolysis of 1 and 7 by 1 equiv of distilled
water in toluene at 0 °C led to the isolation of the known
22
1
[H:C]+I- as a precipitate. The H NMR spectra of 5 and
6 show a pattern similar to that of 1, confirming the
analogous composition.
Alkylation of Compounds 1–3. Treatment of compounds
1 and 2 with MeLi, respectively, resulted in the formation
of the corresponding methylated compounds LAl(Me)NR2
(7, R ) Me; 8, R ) iPr). An alternative route allowed access
to compound 7 from the reaction of LAl(Me)Cl with LiNMe2
in toluene in modest yield. In contrast, no reaction of 3 could
be observed with the bulky N(SiMe3)2 group.
The 1H NMR spectrum of 7 exhibits a singlet at high field
(δ -0.87 ppm), demonstrating the presence of a methyl
group at the Al atom. The proton resonance of NMe2 is again
observed as a singlet (δ 2.68 ppm). In the mass spectrum,
the base peak is assigned to the fragment [M+ - Me -
NMe2]. The methyl proton resonance of 8 (δ -0.09 ppm) is
shifted downfield relative to those found in 7 and LAl(Me)Cl
(δ -0.64 ppm).22 The highest peak in the mass spectrum of
8 corresponds to the fragment [M+ - NiPr2].
Fluorination of Compounds 1–3. The reaction of 1-3
with 1 equiv of Me3SnF in toluene under reflux overnight
readily produced LAl(F)NR2 (9, R ) Me; 10, R ) iPr; 11,
R ) SiMe3) in high yield. Again, it is demonstrated that
Me3SnF can be used in stoichiometric amounts rather than
in an excess for metathesis reactions.23
The 1H NMR spectra of 9 and 10 are very similar to those
of the respective chloride analogues. In the 1H NMR
spectrum of 11, it is interesting to note that one of the
N(SiMe3)2 proton resonances (δ 0.15 ppm) is split into a
doublet with a long-range coupling constant of 5JF-H ) 1.8
Hz. In the mass spectra of 9-11, the most intense peak is
assigned to the fragment [M+ - Me].
22
compounds [LAlCl(µ-OH)]2 and LAl(Me)OH,25 respec-
tively, in low yield. The latter compounds had before been
accessed by controlled hydrolysis under elimination of
hydrogen halide,22,25 as shown in Scheme 2.
Structural Characterization of 1-3. Molecular structures
of 1-3 were determined by X-ray diffraction. Single crystals
of 1 and 3 were recovered from a concentrated toluene
solution at room temperature, while those of 2 were grown
from a THF solution. The structures of compounds 1-3 are
shown in Figures 1-3, with selected bond lengths and angles
provided in Table 1. Details for crystal data and structure
refinement are listed in Table 2.
Compounds 1-3 each adopt a monomeric structure in
which the Al atom is coordinated to one Cl atom and three
N atoms (one from the amido group and the other two from
the ꢀ-diketiminato ligand).
j
1 crystallizes in the triclinic space group P1. The six-
membered C3N2Al ring is slightly folded in a typical
envelope conformation,11 where the C atoms are displaced
by 34° from the N(1)-Al-N(2) plane. The Cl atom and the
amido group are located on opposite sides of the six-
membered C3N2Al ring. The Al-Cl bond length [2.1339(7)
Å] is comparable to that of LAlCl2 [2.1344(4) and 2.1185(4)
Å].19 The Al-N(3) bond length [1.7882(15) Å] is near the
(22) Zhu, H.; Chai, J.; He, C.; Bai, G.; Roesky, H. W.; Jancik, V.; Schmidt,
H.-G.; Noltemeyer, M. Organometallics 2005, 24, 380–384.
(23) (a) Herzog, A.; Liu, F.-Q.; Roesky, H. W.; Demsar, A.; Keller, K.;
Noltemeyer, M.; Pauer, F. Organometallics 1994, 13, 1251–1256. (b)
Guzyr, O. I.; Schormann, M.; Schimkowiak, J.; Roesky, H. W.;
Lehmann, C.; Walawalkar, M. G.; Murugavel, R.; Schmidt, H.-G.;
Noltemeyer, M. Organometallics 1999, 18, 832–836.
(24) (a) Pineda, L. W.; Jancik, V.; Roesky, H. W.; Neculai, D.; Neculai,
A. M. Angew. Chem., Int. Ed. 2004, 43, 1419–1421. (b) Singh, S.;
Jancik, V.; Roesky, H. W.; Herbst-Irmer, R. Inorg. Chem. 2006, 45,
949–951.
(25) Bai, G.; Singh, S.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.
J. Am. Chem. Soc. 2005, 127, 3449–3455.
Inorganic Chemistry, Vol. 47, No. 7, 2008 2587

Yang et al.
Table 2. Crystal Data and Structure Refinement of 1-3
1
2
3
CCDC
formula
fw
temp, K
cryst syst
space group
a, Å
659515
659516
660534
C31H47AlClN3 C35H55AlClN3 C35H59AlClN3Si2
524.15
100(2)
triclinic
580.25
100(2)
640.46
133(2)
orthorhombic
Pbcn
20.3830(5)
18.1958(4)
20.0821(5)
90
90
90
7448.1(3)
8
monoclinic
P2(1)/n
10.0276(8)
20.3125(16)
16.7958(13)
90
97.4050(10)
90
3392.5(5)
4
j
P1
10.5043(8)
12.3521(10)
13.4442(11)
66.4120(10)
72.1260(10)
72.6120(10)
1490.2(2)
4
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
Fc, Mg/m3
µ, mm-1
F(000)
θ range, deg
index ranges
1.168
0.181
568
1.69-26.41
1.136
0.165
1264
2.64-25.21
1.142
0.218
2784
1.50-24.84
Figure 2. Molecular structure of 2. All H atoms are omitted for clarity.
-12 e h e 13 -12 e h e 11 -23 e h e 24
-13 e k e 15 0 e k e 24
0 e l e 16
27 557
-21 e k e 21
-23 e l e 23
72 208
0 e l e 20
38 060
reflns collected
indep reflns (Rint
)
6084 (0.0309) 6089 (0.0264) 6420 (0.0394)
data/restraints/param 6084/0/337
6089/0/375
1.039
6420/0/395
1.065
GOF on F2
1.034
R1, wR2 [I > 2σ(I)] 0.0394, 0.1026 0.0329, 0.0877 0.0294, 0.0823
R1, wR2 (all data) 0.0502, 0.1098 0.0379, 0.0918 0.0341, 0.0845
largest diff peak/
0.503/-0.289 0.286 /-0.282 0.218/-0.253
hole, e/Å3
2 crystallizes in the monoclinic space group P2(1)/n. The
same envelope conformation as that found in 1 is also
recognized in this structure, with a folding angle of 43°.
Compared to 1, however, the positions of the Cl atom and
the amido group are exchanged. The Al-Cl bond length
[2.1576(5) Å] is consistent with those reported for LAl-
(Me)Cl [2.158(1) Å]28 and LAl(I)Cl [2.151(1) Å]22 but a
little longer than that of 1 [2.1339(7) Å]. The Al-N(3)
distance [1.7996(11) Å] agrees well with the average value
of 1.795(5) Å in Al(NiPr2)3.26
3 crystallizes in the orthorhombic space group Pbcn.
Compounds 3 and 1 are structurally similar concerning the
arrangement of the Cl atom and the amido group relative to
the six-membered C3N2Al ring. The folding angle (33°) is
also close to that of 1 (34°). The Al-Cl bond length
[2.1532(5) Å] is slightly shorter but comparable to that of 2
[2.1576(5) Å]. The Al-N(3) separation [1.8361(12) Å] is
very close to those of [((Me3Si)2N)2Al(µ-CH2)]2 [1.832(3)
and 1.837(3) Å]29 while longer than those of Mes2AlN
(SiMe3)2 [1.813(7) Å]8 and of the dimeric iminoalane [1.790
and 1.818. Å] containing three-coordinate Al centers30 and
shorter than that of [(Me3Si)2N]2AlH2Li ·2Et2O (av 1.862 Å)
with the four-coordinate Al center.17
Figure 3. Molecular structure of 3. All H atoms are omitted for clarity.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 1-3
1a
2b
3c
Al-N(1)
1.8912(14)
1.9054(14)
1.7882(15)
2.1339(7)
96.15(6)
110.59(5)
113.00(14)
119.48(12)
127.18(12)
1.8992(11)
1.9291(11)
1.7996(11)
2.1576(5)
96.56(5)
112.21(4)
113.19(10)
119.89(9)
126.89(9)
1.9178(12)
1.9031(12)
1.8361(12)
2.1532(5)
98.07(5)
110.92(4)
118.36(7)
116.20(6)
125.25(7)
Al-N(2)
Al-N(3)
Al-Cl
N(2)-Al-N(1)
N(3)-Al-Cl
C′-N(3)-C′′
C′-N(3)-Al
C′′-N(3)-Al
a C′ ) C(30); C′′ ) C(31). b C′ ) C(33); C′′ ) C(30). c C′ ) Si(1); C′′
) Si(2).
lower end of the predicted range of 1.79-1.85 Å26 and close
to those in [Me2NC(NiPr)2]Al(NMe2)2 [1.788(3) and 1.797(3)
Å].6 However, in some related examples for Al-bound
terminal NMe2 groups, the Al-N distances are found to be
variable with the steric crowding, ranging from 1.775(4) Å
in [AlCl(MeNCH2CH2NMe)2(Al(NMe2)Cl)(Al(NMe2)2)]27 to
The Al-N(1) and Al-N(2) bond lengths (1.891–1.929
Å) in 1-3 are close to the ones reported9,22,28,31 and
obviously longer than the Al-N(3) distances (1.788–1.836
(28) Singh, S.; Ahn, H. J.; Stasch, A.; Jancik, V.; Roesky, H. W.; Pal, A.;
Biadene, M.; Herbst-Irmer, R.; Noltemeyer, M.; Schmidt, H.-G. Inorg.
Chem. 2006, 45, 1853–1860.
4
1.802 Å (av) in [Al(NMe2)3]2 and even 1.822(2) Å in
[Me2NC(NiPr)2]2AlNMe2.6
(29) Knabel, K.; Nöth, H.; Seifert, T. Z. Naturforsch. B 2002, 57, 830–
833.
(26) Brothers, P. J.; Wehmschulte, R. J.; Olmstead, M. M.; Ruhlandt-Senge,
K.; Parkin, S. R.; Power, P. P. Organometallics 1994, 13, 2792–2799.
(27) Leggett, G.; Motevalli, M.; Sullivan, A. C. J. Organomet. Chem. 2000,
598, 36–41.
(30) Schulz, S.; Häming, L.; Herbst-Irmer, R.; Roesky, H. W.; Sheldrick,
G. M. Angew. Chem., Int. Ed. Engl. 1994, 33, 969–970.
(31) Qian, B.; Ward, D. L.; Smith, M. R., III. Organometallics 1998, 17,
3070–3076.
2588 Inorganic Chemistry, Vol. 47, No. 7, 2008

Aluminum Halide Amides
Å), resulting from the electronically delocalized ꢀ-diketimi-
nato ligand. Furthermore, the Al-N(3) bond lengths in 1-3
increase with the steric demand of the amido substituents,
which is in accordance with the trend in a previous theoretical
study of the electronic structure of Al(NR2)3 (R ) H, Me,
iPr, SiMe3).32 In each case of 1-3, the N(3) atom favors a
nearly trigonal coordination geometry because the sum of
the angle at the nitrogen of the amido groups is very close
to 360° (1, 359.66°; 2, 359.97°; 3, 359.81°). The NC2 plane
in 1 is almost perpendicular to the quasi-NCCN plane
(89.73°), while the NC2 plane in 2 and the NSi2 plane in 3
are tilted to some degree as a result of diminishing steric
repulsion (2, 63.83°; 3, 87.33°).26,32
NMR Characterization of 1–11. As was previously noted
for the mixed halide LAl(I)Cl,22 an asymmetric substitution
of the Al atom with one halogen and one amido group in
LAl(X)NR2 results in two nonequivalent sides of the six-
membered C3N2Al ring of the ꢀ-diketiminato ligand. Sub-
sequently, each subspectrum of the ligand contains two
isopropyl groups (evident as two isopropyl methine septets
and four distinct methyl doublets) and three distinct aromatic
CH groups, representing both symmetry-related Ar substit-
uents.
amido 1H NMR resonance is shifted increasingly upfield (δ
2.48 to av 2.72 ppm) with increasing electronegativity of
the halogen.
Surprisingly, 2 and 10 exhibit a single septet and a single
doublet for the methine and methyl protons of the NiPr2
group and also single resonances in the 13C NMR spectra
under all conditions studied. With regard to the steric demand
of an isopropyl group, the Al-N(3) bond would be expected
to rotate rather slowly. Possibly, as seen in the structure of
2 (Figure 2), the NiPr2 group stretches itself out away from
the clasp of the Ar flanks and adopts a pseudoequatorial
position with respect to the six-membered C3N2Al ring,
thereby gaining more space for a flexible Al-N(3) bond
rotation.
Further increasing the steric demand of the amido group
in 3 and 11 gave separate 1H, 13C, and 29Si NMR resonances
for the two SiMe3 substituents, owing to the restricted
rotation of the bulky N(SiMe3)2 group along the Al-N(3)
linkage. Nevertheless, a plane of symmetry through the
Al-X and Al-N(3) bonds is conserved in the NMR spectra,
in agreement with the crystal structure of 3, which shows
the N(3) atom in a nearly sp2-hybridized state. No exchange
peaks between the two proton resonances for SiMe3 substit-
uents were observed in the NOESY spectra even at elevated
temperature (60 °C), indicating that the rate of Al-N(3) bond
rotation is extremely slow (<0.01 s-1). The NOESY
spectrum of 11 also revealed that the SiMe3 group that shows
a split 1H NMR resonance (5JH-F ) 1.8 Hz) is the one cis to
the F atom. A similar behavior was observed for the
corresponding 13C NMR resonance (4JC-F ) 4.3 Hz), whereas
both 29Si NMR resonances are doublets (3JSi-F ) 3.4 and
3.2 Hz). Possibly, the spatial proximity of the cis-SiMe3
group and the F atom favors a “through-space” coupling due
Using NOESY (nuclear Overhauser enhancement) spectra,
1
all H NMR resonances can be stereospecifically assigned
to individual atoms in the 3D structure. For example, in 1
only one methyl group of the ꢀ-diketiminato ligand shows
a NOE correlation with the NMe2 group, while two show
NOE correlations with the protons of the ꢀ-diketiminato core
on the reverse side of the Ar ring. No N-Ar bond rotation
was observed. The corresponding 13C NMR resonances were
identified from 2D 1H-13C correlation spectra optimized for
single and multiple bond correlations.
5
4
3
to the JH-F, JC-F and, JSi-F (partly) couplings.
1
1 and 9 exhibit single H and 13C NMR resonances for
the NMe2 group, indicating that the rotation about the
Conclusion
Al-N(3) bond is fast in solution. For 5, however, we noticed
Monomeric aluminum halide amides with the general
formula LAl(X)NR2 were prepared. Treatment of LAlX2 with
LiNMe2 gives the compounds 1, 5, and 6, respectively. When
more bulky substituents were employed, 2 and 3 are
accessible by the one-pot reaction of AlCl3, LiNiPr2 or
KN(SiMe3)2 and LLi · OEt2. The methylated compounds 7
and 8 were prepared by the reaction of MeLi with 1 and 2.
Using Me3SnF as a fluorinating agent, 1-3 were converted
by metathesis to 9-11. The hydrolysis of 1 and 7 resulted
in the known aluminum hydroxides [LAlCl(µ-OH)]2 and
LA(Me)OH, while the protocol of hydrolyzing Al-Cl of 1
led to decomposition. Presently, the reduction of LAl(X)NR2
as a precursor to generate either a stable radical or a
compound with an Al-Al bond is in progress.
1
a substantial broadening of the H NMR resonance for the
NMe2 group at 500 vs 200 MHz, concomitant with a
broadening of the 13C NMR resonance at 125 MHz. It is
suggested that in this compound the Al-N(3) bond rotation
is somewhat slowed down because of a steric effect of the
larger Br atom and thus approaches the chemical shift time
scale. This observation could be confirmed by further
1
broadening (by a factor of 2.7) of the H and 13C NMR
resonances for the NMe2 group when the temperature was
lowered to 10 °C. In the case of 6, we observed a very broad
1H NMR resonance at ambient temperature at 200 MHz,
which splits into two broad resonances (δ 2.79 and 2.64 ppm)
at 500 MHz. Here, lowering the temperature (10 °C) resulted
in approximately a 2.7-fold narrowing of both resonances.
From the line width, we calculated that the rate of Al-N(3)
bond rotation for 6 is in the order of 120 s-1 at 25 °C and
45 s-1 at 10 °C, but in its bromide analogue 5, it is at least
20 times faster. In the series of the dimethylamides LAl(X)-
NMe2 (9, X ) F; 1, X ) Cl; 5, X ) Br; 6, X ) I), the
Experimental Section
General Remarks. All manipulations were carried out under
an atmosphere of purified nitrogen using standard Schlenk tech-
niques. The samples for reactions as well as for analytical
measurements were manipulated in a glovebox. Solvents were
purified and dried using conventional procedures and were freshly
distilled under nitrogen and degassed prior to use. AlCl3, AlBr3,
(32) Fleurat-Lessard, P.; Volatron, F. Inorg. Chem. 2000, 39, 1849–1854.
Inorganic Chemistry, Vol. 47, No. 7, 2008 2589

Yang et al.
LiNMe2, LiNiPr2, LiN(SiMe3)2, NaN(SiMe3)2, KN(SiMe3)2, and
MeLi were purchased from Aldrich. LH,31,33 LLi ·OEt2,31,33
LAlCl2,19 LAl(Me)Cl,25 LAl(I)Cl,22 LAlMe2,31 LAlI2,34 Me3SnF,35
and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (abbreviated as
:C)36 were prepared as described in the literature.
for C35H55AlClN3 (580.30): C, 72.45; H, 9.55; N, 7.24. Found: C,
72.35; H, 9.52; N, 7.22.
LAl(Cl)N(SiMe3)2 (3). A solution of KN(SiMe3)2 (1.05 g, 5
mmol) in toluene (30 mL) was added to the suspension of freshly
sublimed AlCl3 (0.67 g, 5 mmol) in toluene (30 mL) at -78 °C.
The mixture was stirred for 4 h at room temperature, and a solution
of LLi ·OEt2 (2.49 g, 5 mmol) in toluene (20 mL) was added at
-78 °C. The mixture was allowed to warm to room temperature
and stirred overnight. After filtration, the filtrate was evaporated
and washed with cold n-hexane (5 mL) to afford LAl(Cl)N(SiMe3)2
as a white solid. Single crystals of X-ray-quality were grown from
toluene solution. Yield: 1.48 g (46%). Mp: 173–175 °C. 1H NMR
(500.13 MHz, C6D6): δ 0.30 (s, 9 H, Si(CH3)3), 0.42 (s, 9 H,
LAl(Cl)NMe2 (1). A solution of LiNMe2 (0.11 g, 2 mmol) in
toluene (30 mL) was added at -78 °C to a solution of LAlCl2 (1.03
g, 2 mmol) in toluene (30 mL). The mixture was allowed to warm
to room temperature and stirred overnight. Volatile components
were removed in vacuo, and the crude product was extracted with
Et2O (60 mL). The extract was evaporated to dryness to afford 1
as a white solid. Single crystals of X-ray-quality were grown from
the concentrated toluene solution at room temperature. Yield: 0.81 g
1
(77%). Mp: 186–187 °C. H NMR (500.13 MHz, C6D6): δ 1.08
Si(CH3)3), 1.08 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.19 (d, J ) 6.6
(d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.21 (d, J ) 7.0 Hz, 6 H,
CH(CH3)2), 1.33 (d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.45 (d, J ) 6.8
Hz, 6 H, CH(CH3)2), 1.52 (s, 6 H, CMe), 2.64 (s, 6 H, N(CH3)2),
3.30 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 3.53 (sept, J ) 6.8 Hz, 2
H, CH(CH3)2), 4.87 (s, 1 H, γ-CH), 7.10–7.16 (m, Ar) ppm. 13C
NMR (125.76 MHz, C6D6): δ 170.9 (CN), 145.0, 144.4, 140.1,
127.7, 124.9, 124.6 (o-, o-, i-, p-, m-, m-Ar), 97.9 (γ-CH), 40.8
(N(CH3)2), 29.0, 28.3 (CH(CH3)2), 25.5, 24.8, 24.7, 24.6
(CH(CH3)2), 23.5 (ꢀ-CH3) ppm. IR (Nujol mull, cm-1): ν˜ 1589
(w), 1527 (m), 1318 (m), 1261 (m), 1162 (w), 1101 (w), 1057 (w),
1019 (w), 981 (w), 937 (w), 877 (w), 834 (w), 801 (m), 759 (w),
722 (w), 649 (w), 634 (w). EI-MS: m/z (%) 523.4 (8) [M+], 508.3
(40) [M+ - Me], 479.3 (8) [M+ - NMe2], 463.3 (100) [M+ - Me
- NMe2]. Anal. Calcd for C31H47AlClN3 (524.20): C, 71.03; H,
9.04; N, 8.02. Found: C, 70.67; H, 8.90; N 7.90.
Hz, 6 H, CH(CH3)2), 1.39 (d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.44
(s, 6 H, CMe), 1.45 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 3.24 (sept, J
) 6.8 Hz, 2 H, CH(CH3)2), 3.69 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2),
5.02 (s, 1 H, γ-CH), 7.10–7.16 (m, Ar) ppm. 13C NMR (125.76
MHz, C6D6): δ 172.5 (CN), 145.3, 144.5, 141.6, 127.8, 125.4, 124.8
(o-, o-, i-, p-, m-, m-Ar), 102.2 (γ-CH), 28.8, 28.2 (CH(CH3)2),
25.8, 25.4, 25.4 (CH(CH3)2), 25.1 (ꢀ-CH3), 24.9 (CH(CH3)2), 7.13,
6.00 (Si(CH3)3) ppm. 29Si NMR (99.36 MHz, C6D6): δ 2.24, -3.20
ppm. IR (Nujol mull, cm-1): ν˜ 3064 (m), 1519 (m), 1318 (m), 1259
(m), 1246 (m), 1168 (w), 1109 (w), 1056 (w), 1019 (w), 937 (w),
907 (m), 877 (m), 837 (m), 798 (m), 773 (w), 758 (w), 724 (w),
668 (w), 649 (w), 607 (w), 554 (w), 538 (w), 485 (w), 451 (w),
396 (w). EI-MS: m/z (%) 639.4 (4) [M+], 624.4 (100) [M+ - Me].
Anal. Calcd for C35H59AlClN3Si2 (640.50): C, 65.64; H, 9.29; N,
6.56. Found: C, 65.59; H, 9.16; N, 6.51.
LAl(Cl)NiPr2 (2). A solution of LiNiPr2 (0.55 g, 5 mmol) in
toluene (30 mL) was added at -78 °C to the suspension of freshly
sublimed AlCl3 (0.67 g, 5 mmol) in toluene (30 mL). The mixture
was allowed to warm to room temperature, and a white precipitate
was observed. After this mixture was stirred overnight, a solution
of LLi ·OEt2 (2.49 g, 5 mmol) in toluene (20 mL) was added at
-78 °C. Then the cold bath was removed to allow the mixture to
warm to room temperature under stirring for another 12 h. After
filtration, the filtrate was evaporated to dryness to afford 2 as a
white solid. Single crystals of X-ray-quality were grown from THF
solution. Yield: 0.78 g (27%). Mp: 263 °C. 1H NMR (500.13 MHz,
C6D6): δ 0.84 (d, J ) 6.7 Hz, 12 H, N(CH(CH3)2)2), 0.98 (d, J )
6.7 Hz, 6 H, CH(CH3)2), 1.17 (d, J ) 6.8 Hz, 6 H, CH(CH3)2),
1.29 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.56 (d, J ) 6.6 Hz, 6 H,
CH(CH3)2), 1.60 (s, 6 H, CMe), 3.10 (sept, J ) 6.8 Hz, 2 H,
N(CH(CH3)2)2), 3.16 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 3.89 (sept,
J ) 6.8 Hz, 2 H, CH(CH3)2), 5.11 (s, 1 H, γ-CH), 7.05–7.20 (m,
Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ 171.6 (CN), 146.1,
142.7, 141.9, 127.4, 125.5, 123.9 (o-, o-, i-, p-, m-, m-Ar), 99.9
(γ-CH), 46.9 (N(CH(CH3)2)2), 29.4, 28.2 (CH(CH3)2), 26.4
(N(CH(CH3)2)2), 25.7, 25.1, 24.8 (CH(CH3)2), 24.5 (ꢀ-CH3), 23.8
(CH(CH3)2) ppm. IR (Nujol mull, cm-1): ν˜ 3059 (s), 2727 (s), 1938
(w), 1870 (w), 1590 (w), 1549 (s), 1533 (s), 1518 (s), 1313 (s),
1297 (s), 1251 (s), 1193 (s), 1173 (s), 1156 (s), 1124 (m), 1098
(m), 1056 (m), 1018 (s), 1008 (s), 972 (s), 936 (m), 885 (m), 877
(m), 832 (w), 802 (m), 794 (m), 770 (m), 759 (m), 724 (m), 711
(w), 645 (m), 631 (m), 593 (m), 560 (s). EI-MS: m/z (%) 579 (4)
[M+], 564 (40) [M+ - Me], 479 (100) [M+ - NiPr2]. Anal. Calcd
LAlBr2 (4). A toluene solution (40 mL) of LLi ·OEt2 (1.50 g, 3
mmol) was added drop by drop to a suspension of freshly sublimed
AlBr3 (0.80 g, 3 mmol) at -32 °C with rapid stirring. The mixture
was allowed to warm to room temperature overnight. After filtration,
the concentrated solution was kept at -4 °C overnight to afford
colorless crystals. Yield: 1.12 g (62%). Mp: 215 °C. 1H NMR (C6D6,
300.13 MHz): δ 1.08 (d, 12 H, J ) 6.8 Hz, CH(CH3)2), 1.42 (d,
12 H, J ) 6.8 Hz, CH(CH3)2), 1.50 (s, 6 H, CMe), 3.49 (sept, 4 H,
J ) 6.8 Hz, CH(CH3)2), 4.96 (s, 1 H, γ-CH), 7.09–7.15 (m, Ar)
ppm. 13C NMR (75.48 MHz, C6D6): δ 172.4 (CN), 144.8, 144.8,
138.5, 127.7, 125.0, 125.0 (o-, o-, i-, p-, m-, m-Ar), 99.6 (γ-CH),
28.9 (CH(CH3)2), 25.9, 24.6 (CH(CH3)2), 23.8 (ꢀ-CH3) ppm. 27Al
NMR (78.21 MHz, C6D6): δ 99.25 ppm. IR (Nujol mull, cm-1): ν˜
1590 (w), 1537 (m), 1515 (m), 1315 (s), 1297 (m), 1250 (m), 1189
(w), 1171 (m), 1106 (w), 1055 (w), 1021 (m), 936 (w), 891 (w),
799 (m), 788 (m), 758 (m), 722 (m), 645 (w). EI-MS: m/z (%)
604.1 (100) [M+], 589.1 (20) [M+ - Me]. Anal. Calcd for
C29H41AlBr2N2 (604.4): C, 57.63; H, 6.84; N, 4.63. Found: C, 57.27;
H, 7.00; N, 4.52.
LAl(Br)NMe2 (5). The preparation of 5 was accomplished like
that of 1 from 4 (1.81 g, 3 mmol) and LiNMe2 (0.16 g, 3 mmol) to
afford a light-pink solid. Yield: 0.78 g (46%). Mp: 202–203 °C.
1H NMR (500.13 MHz, C6D6): δ 1.07 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.21 (d, J ) 7.0 Hz, 6 H, CH(CH3)2), 1.31 (d, J ) 6.8
Hz, 6 H, CH(CH3)2), 1.45 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.51
(s, 6 H, CMe), 2.67 (br, 6 H, N(CH3)2), 3.31 (sept, J ) 6.8 Hz, 2
H, CH(CH3)2), 3.33 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 4.88 (s, 1
H, γ-CH), 7.10–7.17 (m, Ar) ppm. 13C NMR (125.76 MHz, C6D6):
δ 170.9 (CN), 145.0, 144.2, 140.2, 127.7, 124.6, 124.5 (o-, o-, i-,
p-, m-, m-Ar), 98.3 (γ-CH), 41.1 (br, N(CH3)2), 29.1, 28.3
(CH(CH3)2), 25.6, 24.8, 24.7, 24.7 (CH(CH3)2), 23.7 (ꢀ-CH3) ppm.
IR (Nujol mull, cm-1): ν˜ 2785 (s), 2768 (s), 1660 (m), 1591 (m),
1546 (m), 1527 (m), 1317 (m), 1261 (m), 1174 (m), 1160 (m),
1099 (m), 1019 (m), 981 (m), 937 (w), 876 (w), 834 (w), 800 (m),
(33) Budzelaar, P. H. M.; van Oort, A. B.; Orpen, A. G. Eur. J. Inorg.
Chem. 1998, 1485–1494.
(34) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao, H.;
Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4274–4276.
(35) Krause, E. Ber. Dtsch. Chem. Ges. 1918, 51, 1447–1456.
(36) Kuhn, N.; Kratz, T. Synthesis 1993, 561–562.
2590 Inorganic Chemistry, Vol. 47, No. 7, 2008

Aluminum Halide Amides
768 (w), 722 (w), 648 (w). EI-MS: m/z (%) 569.3 (10) [M+], 552.3
(sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 5.00 (s, 1 H, γ-CH), 7.10–7.18
(m, Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ 170.6 (CN), 145.1,
143.3, 143.0, 126.8, 124.8, 124.1 (o-, o-, i-, p-, m-, m-Ar), 96.5
(γ-CH), 46.6 (N(CH(CH3)2)2), 29.1, 28.0 (CH(CH3)2), 26.8
(N(CH(CH3)2)2), 25.2, 25.1, 25.0 (CH(CH3)2), 24.5 (ꢀ-CH3), 23.1
(CH(CH3)2), -8.1 (br, AlMe) ppm. IR (Nujol mull, cm-1): ν˜ 3171
(w), 3058 (w), 1935 (w), 1867 (w), 1546 (w), 1524 (m), 1313 (m),
1251 (m), 1190 (w), 1172 (m), 1156 (w), 1107 (w), 1056 (w), 1011
(w), 964 (m), 937 (m), 868 (w), 833 (m), 793 (w), 765 (m), 744
(w), 724 (m), 680 (w), 642 (w), 603 (w). EI-MS: m/z (%) 544.42
(10) [M+ - Me] 459.3 (100) [M+ - NiPr2]. Anal. Calcd for
C36H58AlN3 (559.8): C, 77.23; H, 10.44; N, 7.51. Found: C, 76.98;
H, 10.05; N, 7.28.
(40) [M+ - Me], 523.2 (20) [M+ - NMe2], 507.3 (100) [M+
-
Me - NMe2]. Anal. Calcd for C31H47AlBrN3 (568.60): C, 65.48;
H, 8.33; N, 7.39. Found: C, 64.88; H, 8.33; N, 7.23.
LAl(I)NMe2 (6). The preparation of 6 was accomplished like
that of 1 from LAlI2 (1.39 g, 2 mmol) and LiNMe2 (0.11 g, 2 mmol).
1
Yield: 0.85 g (69%). Mp: 192–195 °C. H NMR (500.13 MHz,
C6D6): δ 1.05 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.21 (d, J ) 6.8
Hz, 6 H, CH(CH3)2), 1.35 (d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.46
(d, J ) 7.0 Hz, 6 H, CH(CH3)2), 1.52 (s, 6 H, CMe), 2.79 (br, 3 H,
N(CH3)2), 2.64 (br, 3 H, N(CH3)2), 3.29 (sept, J ) 6.8 Hz, 2 H,
CH(CH3)2), 3.34 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 4.89 (s, 1 H,
γ-CH), 7.00–7.16 (m, Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ
170.7 (CN), 145.2, 143.9, 140.5, 127.7, 124.7, 124.6 (o-, o-, i-, p-,
m-, m-Ar), 98.6 (γ-CH), 40.2, 40.5 (br, N(CH3)2), 29.3, 29.2
(CH(CH3)2), 25.7, 24.7, 24.7, 24.5 (CH(CH3)2), 24.0 (ꢀ-CH3) ppm.
IR (Nujol mull, cm-1): ν˜ 2786 (s), 2764 (s), 1589 (w), 1544 (m),
1524 (s), 1314 (s), 1253 (s), 1174 (m), 1156 (s), 1106 (m), 1067
(m), 1057 (m), 1017 (s), 978 (s), 936 (m), 875 (m), 798 (s), 758
(m), 727 (s), 694 (w), 646 (m), 631 (m), 551 (m). EI-MS: m/z (%)
615.3 (4) [M+], 600.2 (12) [M+ - Me], 571.2 (100) [M+ - NMe2].
Anal. Calcd for C31H47AlIN3 (615.6): C, 60.48; H, 7.70; N, 6.83.
Found: C, 60.32; H, 7.58; N, 6.58.
LAl(F)NMe2 (9). Toluene (40 mL) was added to a mixture of 1
(0.84 g, 1.61 mmol) and Me3SnF (0.30 g, 1.61 mmol). The mixture
was then heated to reflux overnight until a clear solution was
obtained. After filtration and removal of all of the volatiles, the
residue was extracted with n-hexane (30 mL). The solution was
concentrated and kept at 4 °C overnight to afford a colorless
crystalline solid. Yield: 0.76 g (93%). Mp: 118–120 °C. 1H NMR
(500.13 MHz, C6D6): δ 1.13 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.19
(d, J ) 7.0 Hz, 6 H, CH(CH3)2), 1.31 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.44 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.54 (s, 6 H,
CMe), 2.48 (br, 6 H, N(CH3)2), 3.26 (sept, J ) 6.8 Hz, 2 H,
CH(CH3)2), 3.46 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 4.88 (s, 1 H,
γ-CH), 7.05–7.20 (m, Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ
170.8 (CN), 144.8, 144.7, 140.0, 127.5, 124.7, 124.4 (o-, o-, i-, p-,
LAl(Me)NMe2 (7). Route a: At -78 °C, MeLi (1 mL, 1.6 M,
1.6 mmol) was added to a solution of 1 (0.84 g, 1.6 mmol) in
toluene (40 mL). The mixture was allowed to warm to room
temperature and stirred overnight. After filtration, the solution was
concentrated to give a colorless crystalline solid. Yield: 0.48 g
(59%). Route b: A solution of LAl(Me)Cl (0.99 g, 2 mmol) in
toluene (30 mL) was added at -78 °C to the suspension of LiNMe2
(0.11 g, 2 mmol) in toluene (20 mL). The mixture was allowed to
warm to room temperature and stirred overnight. After filtration,
the solution was concentrated to give a colorless crystalline solid.
m-, m-Ar), 97.4 (γ-CH), 40.4 (N(CH3)2), 28.6 (d, 5JC-F ) 1.9 Hz,
6
CH(CH3)2), 28.5 (CH(CH3)2), 25.1 (CH(CH3)2), 24.9 (d, JC-F
)
F
2.4 Hz, CH(CH3)2), 24.7, 24.6 (CH(CH3)2), 23.2 (ꢀ-CH3) ppm. 19
NMR (188.23 MHz, C6D6): δ -15.03 ppm. IR (Nujol mull, cm-1):
ν˜ 3121 (w), 3059 (w), 2778 (m), 1587 (w), 1535 (s), 1316 (m),
1276 (w), 1261 (m), 1195 (w), 1171 (m), 1101 (w), 1071 (w), 1057
(w), 1021 (m), 986 (m), 937 (w), 888 (w), 798 (m), 771 (m), 757
(w), 726 (w), 646 (w), 633 (w). EI-MS: m/z (%) 507.3 (20) [M+],
492.3 (100) [M+ - Me]. Anal. Calcd for C31H47AlFN3 (507.7): C,
73.34; H, 9.33; N, 8.28. Found: C, 73.06; H, 9.15; N, 8.02.
LAl(F)NiPr2 (10). The preparation of 10 was accomplished like
that of 9 from 2 (0.58 g, 1 mmol) and Me3SnF (0.19 g, 1 mmol).
1
Yield: 0.54 g (53%). Mp: 196–198 °C. H NMR (500.13 MHz,
C6D6): δ -0.87 (s, 3 H, AlMe), 1.06 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.26 (d, J ) 7.0 Hz, 6 H, CH(CH3)2), 1.31 (d, J ) 7.0
Hz, 6 H, CH(CH3)2), 1.36 (d, J ) 7.0 Hz, 6 H, CH(CH3)2), 1.56
(s, 6 H, CMe), 2.68 (s, 6 H, N(CH3)2), 3.25 (sept, J ) 7.0 Hz, 2 H,
CH(CH3)2), 3.47 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 4.90 (s, 1 H,
γ-CH), 7.09–7.17 (m, Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ
169.1 (CN), 145.6, 143.64, 141.6, 127.1, 124.7, 124.1 (o-, o-, i-,
p-, m-, m-Ar), 97.7 (γ-CH), 41.8 (N(CH3)2), 28.9, 28.1 (CH(CH3)2),
25.9, 24.9, 24.7, 24.3 (CH(CH3)2), 23.4 (ꢀ-CH3), -15.0 (br, AlMe)
ppm. IR (Nujol mull, cm-1): ν˜ 2759 (w), 2729 (w), 1934 (w), 1624
(w), 1546 (w), 1525 (w), 1316 (m), 1258 (w), 1192 (w), 1174 (w),
1162 (w), 1100 (w), 1065 (w), 1056 (w), 1017 (w), 978 (w), 936
(w), 870 (w), 797 (w), 761 (w), 723 (w), 680 (w), 650 (w). EI-
MS: m/z (%) 503.4 (4) [M+], 488.36 (16) [M+ - Me], 459.3 (36)
[M+ - NMe2], 443.3 (100) [M+ - Me - NMe2]. Anal. Calcd for
C32H50AlN3 (503.7): C, 76.30; H, 10.00; N, 8.34. Found: C, 75.91;
H, 10.11; N, 8.17.
1
Yield: 0.50 g (89%). Mp: 223–225 °C. H NMR (500.13 MHz,
C6D6): δ 0.80 (d, J ) 6.8 Hz, 12 H, N(CH(CH3)2)2), 0.99 (d, J )
6.8 Hz, 6 H, CH(CH3)2), 1.19 (d, J ) 6.8 Hz, 6 H, CH(CH3)2),
1.37 (d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.54 (d, J ) 6.6 Hz, 6 H,
CH(CH3)2), 1.59 (s, 6 H, CMe), 2.96 (sept, J ) 6.6 Hz, 2 H,
N(CH(CH3)2)2), 3.18 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 3.69 (sept,
J ) 6.8 Hz, 2 H, CH(CH3)2), 5.01 (s, 1 H, γ-CH), 7.05–7.20 (m,
Ar) ppm. 13C NMR (125.76 MHz, C6D6): δ 171.2 (CN), 145.4,
142.7, 142.2, 127.3, 124.0, 123.9 (o-, o-, i-, p-, m-, m-Ar), 98.6
5
(γ-CH), 46.2 (N(CH(CH3)2)2), 29.3 (CH(CH3)2), 27.8 (d, JC-F
)
3.1 Hz, CH(CH3)2), 25.8 (d, 4JC-F ) 0.8 Hz, N(CH(CH3)2)2), 25.1
(d, 6JC-F ) 1.5 Hz, CH(CH3)2), 24.9 (CH(CH3)2), 24.7 (CH(CH3)2),
24.2 (ꢀ-CH3), 23.7 (CH(CH3)2) ppm. 19F NMR (188.23 MHz,
C6D6): δ 6.95 ppm. IR (Nujol mull, cm-1): ν˜ 3060 (m), 1939 (w),
1872 (w), 1667 (w), 1623 (w), 1590 (w), 1550 (w), 1531 (s), 1518
(s), 1340 (w), 1316 (m), 1297 (m), 1252 (m), 1192 (m), 1169 (s),
1126 (m), 1107 (m), 1098 (m), 1057 (m), 1018 (m), 968 (m), 937
(m), 886 (w), 878 (m), 830 (w), 795 (m), 767 (m), 755 (m), 712
(w), 644 (w), 628 (m). EI-MS: m/z (%) 563.4 (10) [M+], 548.4
(100) [M+ - Me]. Anal. Calcd for C35H55AlFN3 (563.8): C, 74.56;
H, 9.83; N, 7.45. Found: C, 74.22; H, 9.64; N, 7.61.
LAl(Me)NiPr2 (8). At -78 °C, MeLi (0.94 mL, 1.6 M, 1.5
mmol) was added to a solution of 2 (0.58 g, 1 mmol) in toluene
(40 mL). The mixture was allowed to warm to room temperature
and stirred overnight. After filtration and removal of all of the
volatiles, the residue was dissolved in toluene (10 mL) and kept at
4 °C overnight to afford a colorless crystalline solid. Yield: 0.35 g
(62%). Mp: 245–247 °C. 1H NMR (500.13 MHz, C6D6): δ -0.09
(s, 3 H, AlMe), 0.82 (d, J ) 6.4 Hz, 12 H, N(CH(CH3)2)2), 1.06
(d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.16 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.35 (d, J ) 6.6 Hz, 6 H, CH(CH3)2), 1.48 (d, J ) 6.6
Hz, 6 H, CH(CH3)2), 1.58 (s, 6 H, CMe), 3.10 (sept, J ) 6.8 Hz,
2 H, N(CH(CH3)2)2), 3.30 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 3.47
LAl(F)N(SiMe3)2 (11). The preparation of 11 was accomplished
like that of 9 from 3 (1.03 g, 1.61 mmol) and Me3SnF (0.30 g,
1.61 mmol). Yield: 0.91 g (91%). Mp: 173–175 °C. 1H NMR
Inorganic Chemistry, Vol. 47, No. 7, 2008 2591

Yang et al.
5
(500.13 MHz, C6D6): δ 0.15 (d, JF-H ) 1.8 Hz, 9 H, Si(CH3)3),
was applied.39 The data collection and reduction of 3 were
performed with X-Area and X-RED32.40 The structures were solved
by direct methods (SHELXS-97)41 and refined by full-matrix least-
squares methods against F2 (SHELXL-97).42 All non-H atoms were
refined with anisotropic displacement parameters. The H atoms were
refined isotropically on calculated positions using a riding model
with their Uiso values constrained to equal to 1.5 times the Ueq of
their pivot atoms for terminal sp3 C atoms and 1.2 times for all
other C atoms. Other structural details are listed in Table 2.
Crystallographic data for the structures 1-3 have been deposited
with the Cambridge Crystallographic Data Centre. The CCDC
numbers are listed in Table 2. Copies of this information may be
obtained free of charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K.; fax (int code) +44(1223)336-033; or
e-mail deposit@ccdc.cam.ac.uk.
0.42 (s, 9 H, Si(CH3)3), 1.10 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.19
(d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.37 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.41 (s, 6 H, CMe), 1.45 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 3.24 (sept, J ) 6.8 Hz, 2 H, CH(CH3)2), 3.68 (sept, J
) 6.8 Hz, 2 H, CH(CH3)2), 4.98 (s, 1 H, γ-CH), 7.05–7.20 (m, Ar)
ppm. 13C NMR (125.76 MHz, C6D6): δ 171.9 (CN), 145.1, 144.0,
141.0, 127.3, 125.1, 124.4 (o-, o-, i-, p-, m-, m-Ar), 100.8 (γ-CH),
6
28.2, 27.9 (CH(CH3)2), 25.7 (d, JC-F ) 2.3 Hz, CH(CH3)2), 25.2,
4
24.8, 24.4 (CH(CH3)2), 24.1 (d, JC-F ) 1.0 Hz, ꢀ-CH3), 5.7
(Si(CH3)3), 5.0 (d, JC-F ) 4.3 Hz, Si(CH3)3) ppm. 19F NMR
4
(188.23 MHz, C6D6): δ 8.62 ppm. 29Si NMR (99.36 MHz, C6D6):
3
3
δ 2.00 (d, JSi-F ) 3.2 Hz), -4.34 (d, JSi-F ) 3.4 Hz) ppm. IR
(Nujol mull, cm-1): ν˜ 3063 (s), 1866 (m), 1698 (m), 1662 (m),
1587 (m), 1531 (s), 1314 (m), 1259 (s), 1169 (m), 1096 (m), 1060
(m), 1021 (m), 931 (s), 882 (s), 833 (w), 820 (m), 798 (s), 761
(m), 724 (w), 673 (w), 651 (w). EI-MS: m/z (%) 623.4 (4) [M+],
608.4 (100) [M+ - Me]. Anal. Calcd for C35H59AlFN3Si2 (624.0):
C, 67.37; H, 9.53; N, 6.73. Found: C, 66.73; H, 9.35; N, 6.59.
X-ray Structure Determination of 1-3. The data for 1 were
collected from shock-cooled crystals at 100(2) K on a Bruker
SMART-APEX II diffractometer with a D8 goniometer,37 for 2 at
100(2) K on a Bruker TXS-Mo rotating anode with an APEX II
detector on a D8 goniometer, and for 3 at 133(2) K on a Stoe IPDS-
2. All diffractometers were equipped with a low-temperature device.
The Bruker SMART-APEX II diffractometer and the Stoe IPDS-2
used graphite-monochromated Mo KR radiation, λ ) 0.71073 Å.
The Bruker TXS-Mo rotating anode used INCOATEC Helios mirror
optics as the radiation monochromator. The data of 1 and 2 were
integrated with SAINT,38 and an empirical absorption (SADABS)
Acknowledgment. This work was supported by the
Deutsche Forschungsgemeinschaft, the Fonds der Chemis-
chen Industrie, and the Göttinger Akademie der Wissen-
schaften. Y.Y. thanks the Chinese Scholarship Council for
a fellowship.
Supporting Information Available: X-ray structural information
in CIF format for 1-3. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC701896R
(39) Sheldrick, G. M. SADABS 2.0; Universität Göttingen: Göttingen,
Germany, 2000.
(40) X-Area (Version 1.18) and X-RED32 (Version 1.04); Stoe & Cie:
Darmstadt, Germany, 2002.
(41) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467–473.
(42) Sheldrick, G. M. SHELX-97: Program for the Solution and Refinement
of Crystal Structures; Universität Göttingen: Göttingen, Germany,
1997.
(37) (a) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615–619. (b)
Stalke, D. Chem. Soc. ReV. 1998, 27, 171–178.
(38) SAINT-NT; Bruker AXS Inc.: Madison, WI, 2000.
2592 Inorganic Chemistry, Vol. 47, No. 7, 2008