Reactions of MAIH4 (M = Li, Na) with primary amines - Synthetic and structural studies of alkali metal tetrakis(amido)aluminates and related dinuclear complexes

Article abstract of DOI:10.1139/V06-018

The reactions of MAlH₄ (M = Li, Na) with primary amines NH ₂R (R = t-Bu, i-Pr, p-tolyl) in a 1:4 molar ratio in THF produce the tetrakis(amido)aluminates, [M(THF)_n][Al(NHR)₄], in yields of 46%-82% together with secondary products. The extent of solvation of the alkali-metal cation varies from none (n = 0) for M[Al(NH-i-Pr)₄] (2b, M = Li; 3b, M = Na) to n = 4 in the complex [Li(THF)₄][Al(NH-p- tolyl)₄] (2c), which exists as a solvent-separated ion pair. The complexes 2b, 3b, and [Na(THF)][Al(NH-p-tolyl)₄]_∞ (3c) all exhibit one-dimensional polymeric structures in which the bis-N,N′-chelating tetrakis(amido)aluminate anions are bridged by four- (2b, 3b) and five-coordinate (3c) metal ions, respectively. The structures of two of the secondary products, {[Na(THF)₂][(NH-t-Bu)Al(H)(μ-N-t- Bu)]}₂ (4) and {[Na(THF)₃][(NH-p-tolyl) ₂Al(μ-N-p-tolyl)]}₂ (5), were established by X-ray crystallography. Complex 4 is a dimer of the [HAl(NH-t-Bu)(N-t-Bu)]^- anion, which forms a central Al₂N₂ ring with each monoanion N,N′-chelated to a [Na(THF)₂]⁺ cation. Complex 5 is a dimer of the [Al(NR)(NHR)₂]^- (R = p-tolyl) anion in which the bridging p-tolyl groups are coordinated in an N-monodentate fashion to the trisolvated [Na(THF)₃]⁺ cations.

Full text of DOI:10.1139/V06-018

443
Reactions of MAlH4 (M = Li, Na) with primary
amines — Synthetic and structural studies of
alkali metal tetrakis(amido)aluminates and related
dinuclear complexes
Dana J. Eisler and Tristram Chivers
Abstract: The reactions of MAlH4 (M = Li, Na) with primary amines NH2R (R = t-Bu, i-Pr, p-tolyl) in a 1:4 molar
ratio in THF produce the tetrakis(amido)aluminates, [M(THF)n][Al(NHR)4], in yields of 46%–82% together with sec-
ondary products. The extent of solvation of the alkali-metal cation varies from none (n = 0) for M[Al(NH-i-Pr)4] (2b,
M = Li; 3b, M = Na) to n = 4 in the complex [Li(THF)4][Al(NH-p-tolyl)4] (2c), which exists as a solvent-separated
ion pair. The complexes 2b, 3b, and [Na(THF)][Al(NH-p-tolyl)4]∞ (3c) all exhibit one-dimensional polymeric structures
in which the bis-N,N ′-chelating tetrakis(amido)aluminate anions are bridged by four- (2b, 3b) and five-coordinate (3c)
metal ions, respectively. The structures of two of the secondary products, {[Na(THF)2][(NH-t-Bu)Al(H)(µ-N-t-Bu)]}2
(4) and {[Na(THF)3][(NH-p-tolyl)2Al(µ-N-p-tolyl)]}2 (5), were established by X-ray crystallography. Complex 4 is a
dimer of the [HAl(NH-t-Bu)(N-t-Bu)]– anion, which forms a central Al2N2 ring with each monoanion N,N′-chelated to
a [Na(THF)2]+ cation. Complex 5 is a dimer of the [Al(NR)(NHR)2]– (R = p-tolyl) anion in which the bridging p-tolyl
groups are coordinated in an N-monodentate fashion to the trisolvated [Na(THF)3]+ cations.
Key words: aluminohydrides, alkali metals, primary amines, tetrakis(amido)aluminates, structures.
Résumé : Les réactions des MAlH4 (M = Li, Na) avec des amines primaires, NH2R (R = t-Bu, i-Pr, p-tolyle), dans un
rapport molaire de 1 : 4, dans le THF, conduit à la formation des tétrakis(amido)aluminates, [M(THF)n][Al(NHR)4],
avec des rendements allant de 46 % à 82 % aux côtés de produits secondaires. Le degré de solvatation du cation du
métal alcalin varie de zéro (n = 0) pour M[Al(NH-i-Pr)4] (2b, M = Li; 3b, M = Na) à n = 4 pour le complexe
[Li(THF)4]-[Al(NH-p-tolyl)4] (2c) qui existe sous la forme de paire d’ions séparés par le solvant. Les complexes 2b, 3b
et [Na(THF)][Al(NH-p-tolyl)4]∞ (3c) présentent tous des structures polymériques monodimensionnelles dans lesquelles
les anions tétrakis(amido)aluminates bis-N,N′-chélatants sont liés par des ponts d’ions métalliques respectivement tétra-
(2b, 3b) et penta-coordinés (3c). Les structures de deux des produits secondaires, le {[Na(THF)2][(NH-t-Bu)Al(H)(µ-N-
t-Bu]}2 (4) et {[Na(THF)3)][(NH-p-tolyl)2Al(µ-N-p-tolyl)]}2 (5) ont été établies par diffraction des rayons X. Le
complexe 4 est un dimère de l’anion [HAl(NH-t-Bu)(N-t-Bu)]– qui forme un cycle Al2N2 central dans chacun des
monoanions N,N ′-chélatés à un cation [Na(THF)2]+. Le complexe 5 est un dimère de l’anion [Al(NR)(NHR)2]– (R =
p-tolyle) dans lequel les groupes p-tolyles servant de pont sont coordinés d’une façon N-monodentate aux cations
[Na(THF)3]+ trisolvatés.
Mots clés : hydrures d’aluminium, métaux alcalins, amines primaires, tétrakis(amido)aluminates, structures.
[Traduit par la Rédaction] Eisler and Chivers 452
Introduction
be prepared by treatment of primary amines with MAlH4
(M = Li, Na) in a 1:1 molar ratio in boiling hydrocarbon sol-
vents (M = Li) or diethyl ether (M = Na) (5a) (eq. [1]) or by
reaction of RNH2·HCl with LiAlH4 in diethyl ether at room
temperature (5b). The value of n is determined by the nature
of the R group and by the solvent used for the reaction (6).
In 1997 Roesky and co-workers (7) prepared the first alumi-
num amides derived from primary amines via the reaction of
LiAlH4 with the sterically demanding amine, DippNH2
(Dipp = 2,6-diisopropylphenyl). Molar ratios of 1:2 and 2:5
The reactions of secondary amines with LiAlH4 have been
studied extensively (1–4). Several tetrakis(amido)aluminate
complexes of the type [L2Li][Al(NR2)4] (L = electron-pair
donor ligand) (1, 2) as well as the intermediate lithium
amidohydridoaluminates formed in this process, e.g.,
[H3AlN(SiMe3)2Li(Et2O)2]2 (3) and [Li(THF)4][HAl(NPh2)3]
(4), have been structurally characterized. Aluminum-nitrogen
cage compounds of the type (HAlNR)n (imidoalanes) may
Received 17 November 2005. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 31 March 2006.
D.J. Eisler and T. Chivers.1 Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4, Canada.
1Corresponding author (e-mail: chivers@ucalgary.ca).
Can. J. Chem. 84: 443–452 (2006)
doi:10.1139/V06-018
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Can. J. Chem. Vol. 84, 2006
produced structurally characterized dinuclear complexes
containing either one or two Al-H functionalities, respec-
tively.
the potentially useful tetradentate, monoanionic ligands
[Al(NH-t-Bu)4]–. We describe here the synthesis of six alkali
metal tetrakis(amido)aluminates; the X-ray structures of four
of them are compared with those of 1a, 1b, and 2a. We also
report the X-ray structures of two of the secondary products
of these reactions, both of which are novel dinuclear clusters
containing amido–imido aluminum anions.
[1]
MAlH4 + RNH2 → 1/n(HAlNR)n + 2H2
+ MH (M = Li, Na)
The reactions of lithium amides with aluminum(III) com-
pounds have also been investigated. Tetrakis(amido)alumi-
nates of the type [Al(NHR)4]– are obtained as the
monomeric ion-paired complex [(DippNH)2Al(µ-NHDipp)2-
Li·THF] (1a) (8) or the dimer [(t-BuNH)Al(µ-NH-t-
Bu)2Li(µ-NH-t-Bu)]2 (2a) (9) from reactions of LiNHR (R =
Dipp, t-Bu) with AlCl3 in THF or hexane, respectively. The
related complex, [{(Me2N)3SiNH}2Al(µ-NHSi(NMe2)3}2-
Li·2THF], which is structurally analogous to 1a but incorpo-
rates a bis-solvated Li+ cation, is prepared from AlCl3 and
(Me2N)3SiNHLi in a 1:4 molar ratio in pentane (followed by
recrystallization from THF) (10). The diethyl-ether-solvated
complex, [(DippNH)2Al(µ-NHDipp)2Li·OEt2] (1b), iso-
structural with 1a, was obtained as a minor product from the
reaction of H3Al·NMe3 with DippNH2 (11). The open
rhombododecahedral cage [(HAl)4(NPh)6{Li(OEt2)}3]– is
formed by treatment of the adduct AlH3·N(Me)C5H8 with
LiNHPh (12).
Experimental section
Reagents and general procedures
Solvents were dried and distilled before use (n-hexane,
THF, diethyl ether, and toluene (Na/benzophenone)). The re-
agents NH2-t-Bu, NH2-i-Pr, and NH2-p-tolyl were commer-
cial samples (Sigma-Aldrich) and used as received. A
commercial sample of NaAlH4 was dissolved in THF and,
after 45 min at 23 °C, insoluble black material was removed
by filtration to give pure NaAlH4 as an off-white solid after
the removal of solvent. LiAlH4 was purified by recrystalli-
zation from diethyl ether. The handling of air- and moisture-
sensitive materials was performed under an atmosphere of
argon gas using standard Schlenk techniques or a glovebox.
7
1H, Li, 13C, and 27Al NMR spectra were collected on a
Bruker AMX-300 spectrometer and chemical shifts are re-
ported relative to Me4Si in CDCl3 (1H, 13C), LiCl in D2O
(7Li), or Al(NO3)3 in D2O (27Al). All NMR spectra were col-
lected at 23 °C unless otherwise stated. Fourier transform in-
frared (FT IR) spectra were obtained as Nujol mulls using
KBr windows on a Mattson Genesis Series instrument. The
Analytical Services Laboratory of the Department of Chem-
istry, University of Calgary, provided elemental analyses.
Preparation of Li[Al(NH-t-Bu)4] (2a)
A slurry of LiAlH4 (0.125 g, 3.30 mmol) in n-hexane or
toluene (10 mL) was added to a clear colorless solution of
NH2-t-Bu (2.74 mL, 1.907 g, 26.1 mmol) in n-hexane or to-
luene (10 mL) at 23 °C. Immediate, vigorous bubbling was
observed. The mixture was stirred for 3 h and then the vol-
ume of solution was reduced to 10 mL under vacuum. The
resulting clear solution was cooled to –25 °C for 24 h to
give colorless crystals of LiAl(NH-t-Bu)4 (0.872 g,
2.70 mmol, 82%) with n-hexane as solvent and (0.810 mg,
2.51 mmol, 76%) when toluene was used. 1H NMR (in
C6D6) δ: 1.45 (s, CMe3), cf. lit. δ 1.43 in C6D6 (7).
In connection with our interest in generating polyimido
anions of p-block elements (13), we have previously investi-
gated the reaction of the trialkylamidoalane dimer [(t-
BuNH)2Al(µ-NH-t-Bu)2Al(NH-t-Bu)2] with alkyl-lithium re-
agents and shown by NMR spectroscopy that the initial
lithiation occurs at a bridging NH-t-Bu group to give mono-
and di-lithiated derivatives, Lix[Al2(N-t-Bu)x(NH-t-Bu)6–x
]
(x = 1, 2) (14). In the case of n-BuLi, the use of 5 equiv. of
the organolithium reagent (per dimer) generates the
trilithiated derivative, which acts as a template to trap the
unsolvated dimer (n-BuLi)2. By contrast, the reaction of the
tris(arylamido) alane, [Al(NHAr)3] (Ar = 2-MeOC6H4),
which is assumed to be dimeric (15), with 3 equiv. of n-
BuLi (per monomer) leads to lithiation of all three N-H pro-
tons and nucleophilic addition of the n-Bu group to alumi-
num to give a tetraanionic organotriimidoaluminate, [n-
BuAl(NAr)3]4– (16). This anion, as the tetralithium deriva-
tive, forms the dimeric ion-separated cluster, [Li(THF)4]2-
[Li6{n-BuAl(NAr)3}2] (16).
In view of the lack of a general, high-yield synthesis to
tetrakis(amido)aluminates, we have undertaken a systematic
investigation of the reactions of alkali metal aluminum hy-
drides, M[AlH4] (M = Li, Na), with primary amines, RNH2
(R = t-Bu, i-Pr, p-tolyl), under mild conditions as a route to
Preparation of Li[Al(NH-i-Pr)4] (2b)
A solution of LiAlH4 (0.223 g, 5.88 mmol) in THF
(40 mL) was added to a solution of NH2-i-Pr (2.00 mL,
1.388 g, 23.48 mmol) in THF (15 mL) at 23 °C resulting in
immediate, vigorous evolution of H2. The mixture was
stirred for 1 h and the resulting slightly cloudy solution was
filtered though a 0.45 µm pore size filter disk. The solvent
was removed in vacuo and the residue was washed with di-
ethyl ether (20 mL) leaving a white solid (0.892 g, 57%). IR
1
(cm–1): 3365 ν(N-H). H NMR (in D8-THF) δ: 3.05 (m, 1H,
3
CHMe2), 0.98 (d, 6H, CHMe2, J(1H-1H) = 6 Hz), –0.94 (d,
3
1H, NH, J(1H-1H) = 11 Hz). 13C NMR δ: 45.3 (CHMe2),
31.0 (CHMe2). 27Al NMR δ: 107.1. 7Li NMR δ: –1.31. Anal.
calcd. for C12H32AlLiN4 (%): C 54.12, H 12.11, N 21.01;
found: C 53.60, H 13.08, N 20.92.
© 2006 NRC Canada

Eisler and Chivers
445
(1.00 g, 9.33 mmol) in THF (15 mL) at 23 °C resulting in
immediate, vigorous evolution of H2. The mixture was
stirred for 1 h and the resulting slightly cloudy solution was
filtered though a 0.45 µm pore size filter disk. The solvent
was removed in vacuo and the residue was washed with di-
Preparation of [Li(THF)4][Al(NH-p-tolyl)4] (2c)
A solution of LiAlH4 (0.089 g, 2.35 mmol) in THF
(40 mL) was added slowly to a solution of p-toluidine
(1.00 g, 9.33 mmol) in THF (15 mL) resulting in immediate,
vigorous evolution of H2. The mixture was stirred for 1 h
and the resulting slightly cloudy solution was filtered though
a 0.45 µm pore size filter disk and then concentrated to ca.
10 mL. Slow addition of n-hexane (25 mL) combined with
vigorous stirring of the solution resulted in the precipitation
of [Li(THF)4][Al(NH-p-tolyl)4] as a white solid. The solu-
tion was decanted and the solid dried in vacuo (1.385 g,
1
ethyl ether (40 mL) leaving a white solid (0.893 g, 70%). H
NMR (in D8-THF) δ: 6.54 (m, 4H, C6H4), 3.63 (m, THF),
3.15 (s, 1H, NH), 2.06 (s, 3H, Me), 1.78 (m, THF). 13C
NMR δ: 154.0, 129.7, 120.6, 116.7 (C6H4), 68.4 (THF), 26.4
(THF), 20.8 (Me). 27Al NMR δ: 95.4. Anal. calcd. for
C32H40AlN4NaO (%): C 70.31, H 7.38, N 10.25; found: C
69.74, H 6.67, N 9.98.
1
1.85 mmol, 79%). H NMR (in D8-THF) δ: 6.55 (m, 4H,
C6H4), 3.63 (m, THF), 3.16 (s, 1H, NH), 2.08 (s, 3H, Me),
1.78 (m, THF). 13C NMR δ: 154.1, 129.6, 120.2, 116.5
(C6H47), 68.4 (THF), 26.4 (THF), 20.8 (Me). 27Al NMR δ:
96.7. Li NMR δ: –2.68. Anal. calcd. for C44H64AlLiN4O4
(%): C 70.65, H 8.64, N 7.50; found: C 69.97, H 8.52, N
7.21.
Preparation of {[Na(THF)2][(NH-t-Bu)Al(H)(␮-N-t-
Bu)]}2 (4)
This complex is a minor product (ca. 20%) obtained in the
preparation of 3a. In addition to complex 4, an additional
minor product (ca. 10%), which was not identified, is also
present in reaction solutions of 3a. Significantly larger quan-
tities of 4 and this unidentified complex (ca. 50% combined)
are observed when the reaction is carried in a 1:2 mixture of
THF and n-hexane. An analytically pure sample of 4 could
not be obtained, as this material was always contaminated
with the other reaction products. X-ray quality crystals of 4
were isolated manually from a mixture of crystals of 3a and
4 grown from a concentrated solution of the complexes in
Preparation of [Na(THF)][Al(NH-t-Bu)4] (3a)
A solution of NaAlH4 (0.251 g, 4.65 mmol) in THF
(40 mL) was added to a solution of NH2-t-Bu (2.0 mL,
1.358 g, 18.57 mmol) in THF (10 mL) at 23 °C resulting in
immediate, slow evolution of H2. The mixture was stirred
for 3 h and the resulting slightly cloudy solution was filtered
though a 0.45 µm pore size filter disk. The volume of
solution was then reduced to 10 mL in vacuo and cooled to
1
THF–hexane at –10 °C. H NMR (in D8-THF, 298 K) δ:
–10 °C for
2
h
to give colorless crystals of
3.63 (m, THF), 1.78 (m, THF), 1.22 (s, 9H, CMe3), 1.18 (s,
9H, CMe3), 0.46 (s, 1H, NH). 13C NMR δ: 68.4 (THF), 52.9,
1
[Na(THF)][Al(NH-t-Bu)4] (0.872 g, 2.12 mmol, 46%). H
NMR (in D8-THF) δ: 3.63 (m, 4H, THF), 1.78 (m, 4H,
THF), 1.13 (s, 36H, CMe3), –0.68 (s, 4H, NH). 13C NMR δ:
68.4 (THF), 49.9 (CMe3), 36.4 (CMe3), 26.4 (THF). 27Al
NMR δ: 110.0. Anal. calcd. for C20H48AlN4NaO (%): C
58.50, H 11.78, N 13.65; found: C 56.15, H 10.74, N 13.10.
The obtained carbon analysis for this complex was consis-
1
50.9 (CMe3), 38.9, 36.3 (CMe3), 26.4 (THF). H NMR (in
D8-THF, 233 K) δ: 4.38 (v br, ∆ω1/2 - 70 Hz, 1H, Al-H),
3.63 (m, THF), 1.78 (m, THF), 1.19 (s, 9H, CMe3), 1.14 (s,
9H, CMe3), 0.60 (s, 1H, NH). 27Al NMR δ: 110.0.
Preparation of {[Na(THF)3][(NH-p-tolyl)2Al(␮-N-p-
tolyl)]}2 (5)
1
tently low, however, the complex was pure by both H and
13C NMR spectroscopy.
This complex is the minor product (ca. 30%) obtained in
the preparation of complex 3c. An analytically pure sample
of 5 could not be obtained, as this material was always con-
taminated with 3c. X-ray quality crystals of 5 were isolated
manually from a mixture of crystals of 3c and 5 grown from
a concentrated solution of the complexes in THF–hexane at
Preparation of [Na][Al(NH-i-Pr)4] (3b)
A solution of NaAlH4 (0.315 g, 5.83 mmol) in THF
(40 mL) was added to a solution of NH2-i-Pr (2.00 mL,
1.388 g, 23.48 mmol) in THF (15 mL) at 23 °C resulting in
immediate, vigorous evolution of H2. The mixture was
stirred for 1 h and the resulting slightly cloudy solution was
filtered though a 0.45 µm pore size filter disk. The solvent
was removed in vacuo and the residue was washed with di-
1
–10 °C. H NMR (in D8-THF) δ: 6.72 (m, 8H, C6H4), 6.70
(m, 16H, C6H4), 3.63 (m, THF), 3.28 (s, 4H, NH) 2.06 (s, br,
18H, Me), 1.78 (m, THF). 13C NMR δ: 157.4, 152.8, 130.4,
130.2, 122.5, 122.0, 117.3, 116.8 (C6H4), 68.4 (THF), 26.4
(THF), 20.6 (Me). 27Al NMR δ: 97.2.
1
ethyl ether (20 mL) leaving a white solid (1.068 g, 65%). H
NMR (in D8-THF) δ: 3.12 (m, 1H, CHMe2), 0.98 (d, 6H,
3
3
CHMe2, J(1H-1H) = 6 Hz), –0.85 (d, 1H, NH, J(1H-1H) =
9 Hz). 13C NMR δ: 45.5 (CHMe2), 31.1 (CHMe2). 27Al
NMR δ: 108.5. Anal. calcd. for C12H32AlN4Na (%): C 51.04,
H 11.42, N 19.84; found: C 50.31, H 11.81, N 19.44.
X-ray structural analyses
Crystal data for 2b, 2c, 3b, 3c, 4, and 5 are summarized in
Table 1.2 A suitable crystal of the complex was selected,
coated in Paratone oil, and mounted on a glass fibre. Data
were collected at 173 K on a Nonius Kappa CCD
diffractometer using Mo Kα radiation (λ = 0.710 73 Å) via ω
and φ scans. The unit cell parameters were calculated and re-
fined from the full data set. Crystal cell refinement and data
Preparation of [Na(THF)][Al(NH-p-tolyl)4] (3c)
A solution of NaAlH4 (0.126 g, 2.33 mmol) in THF
(40 mL) was added slowly to a solution of p-toluidine
2 Supplementary data for this article are available on the journal Web site (http://canjchem.nrc.ca) or may be purchased from the Depository
of Unpublished Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 5011. For more
information on obtaining material refer to http://cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 290050–290055 contain the crystallo-
graphic data for this manuscript. These data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
© 2006 NRC Canada

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Eisler and Chivers
447
reduction were carried out using the Nonius DENZO pack-
age. After data reduction, the data were corrected for ab-
sorption based on equivalent reflections using SCALEPACK
(Nonius, 1998). The structures were solved by direct meth-
ods using SHELXS-97 (17) and refinement was carried out
on F2 against all independent reflections by the full-matrix
least-squares method using the SHELXL-97-2 program (18).
The hydrogen atoms were calculated geometrically and were
riding on their respective atoms unless otherwise noted. Ex-
cept as mentioned, all non-hydrogen atoms were refined
with anisotropic thermal parameters.
Results and discussion
Synthesis of lithium and sodium
tetrakis(amido)aluminates
The reaction of lithium or sodium aluminum hydride with
4 equiv. of primary amine RNH2 in THF at room tempera-
ture results in the immediate evolution of H2 gas to give the
corresponding lithium or sodium tetrakis(amido)aluminate
(eq. [2]), as well as secondary products, which are observed
in varying quantities (<5% to ca. 30%). However, the
tetrakis(amido)aluminate complexes are readily purified
owing to the higher solubility of the secondary products in
diethyl ether, in comparison to the desired tetra-
kis(amido)aluminates. Although the quantities of the minor
components formed vary with reaction conditions, the iden-
tities of the products do not change. All attempts to obtain
analytically pure samples of the secondary products were
unsuccessful owing to persistent contamination with the
tetrakis(amido)aluminate complexes.
2b
The molecule was well-ordered and no special consider-
ations for the refinement were necessary. The complex crys-
tallizes with two independent, but chemically equivalent
molecules in the unit cell, for which two independent halves
of the molecules are present in the asymmetric unit (the
other half in each case being generated by the crystallo-
graphic twofold axis). The lithium atoms were refined
isotropically.
[2]
MAlH4 + 4NH2R → M[Al(NHR)4] + 4H2
2c
(2a, M = Li, R = t-Bu; 3a, M = Na, R = t-Bu; 2b, M = Li,
R = i-Pr; 3b, M = Na, R = i-Pr; 2c, M = Li, R = p-tolyl; 3c,
M = Na, R = p-tolyl)
The amidoaluminate anion was well-ordered, however the
[Li(THF)4]+ cation was highly disordered around a crystallo-
graphic twofold rotation axis. Only one-half of the anion and
cation are present in the asymmetric unit, with the second
half of each being generated by the twofold axis. One of the
THF molecules of the cationic moiety was modeled with a
75:25 disorder of the oxygen and one carbon atom; the 25%
component of this disorder was refined isotropically. The
second THF molecule was severely disordered and was
modeled as a 25:25:25:25 isotropic mixture with geometric
restraints applied.
Complex 2a is obtained in 82% yield when n-hexane is
used as solvent, cf. 60% yield of 2a from the reaction of
AlCl3 with LiNH-t-Bu in hexane (9); it was identified by
1
comparison of the H NMR chemical shift (a broad singlet
at δ 1.45) and unit cell constants with those reported in the
literature (9).3 The other tetrakis(amido)aluminate com-
plexes (2b, 2c, 3a–3c), four of which have been identified by
X-ray structural analyses (vide infra), were prepared in THF
in yields ranging from 46% to 79%. They are accompanied
by the formation of secondary products, and two of these
have also been structurally characterized. The complexes 2b,
2c, and 3a–3c are each obtained with a varying degree of
THF-solvation of the alkali metal cations, as indicated by
3b
The molecule was well-ordered and no special consider-
ations for the refinement were necessary. Due to symmetry
only one-quarter of the molecule was located in the differ-
ence Fourier map, as the molecule is situated on a fourfold
rotary inversion axis.
1
the H NMR spectra. For example, the isopropyl complexes
2b and 3b are isolated as the unsolvated complexes
M[Al(NH-i-Pr)4], whereas the arylamido complex 2c is ob-
tained as a highly solvated complex with four molecules of
THF for each Li+ ion.
3c
The molecule was well-ordered with the exception of the
coordinated THF molecule, which was modeled with a
65:35 isotropic mixture of two of the carbon atoms with
mild geometric restraints.
X-ray structures of lithium and sodium
tetrakis(amido)aluminates
The solid-state structure of complex 2c, which was deter-
mined crystallographically, confirmed the presence of an
ion-separated complex consisting of a [Li(THF)4]+ cation
and a [Al(NH-p-tolyl)4]– anion, in contrast to the solvated
monomeric structure of 1a and the unsolvated dimeric struc-
ture of 2a. The anion in 2c is depicted in Fig. 1. The Al—N
4
The molecule was well-ordered and no special consider-
ations for the refinement were necessary. The hydrogen at-
oms on the amido nitrogen and aluminum centers (H2D and
H1D, respectively) were located and refined.
distances are identical within error (Al(1)—N(1)
=
5
1.841(2) Å, Al(1)—N(2) = 1.844(2) Å), and are comparable
to those observed for the terminal DippNH ligands in 1a
(1.845(9) Å) (8). The aluminum centre in 2c adopts a dis-
torted tetrahedral geometry with the N-Al-N bond angles
ranging from 105.5(1)° to 116.6(2)°.
The molecule was well-ordered with the exception of one
THF molecule, which was modeled with a 55:45 disorder of
two of the carbon atoms that were refined with isotropic
thermal parameters.
1
3 As reported by Cowley and co-workers (9), the NH resonances of 2a were not observed in the H NMR spectrum. The broad singlet ob-
served for the t-Bu groups at 23 °C is indicative of dynamic behaviour.
© 2006 NRC Canada

448
Can. J. Chem. Vol. 84, 2006
Fig. 1. Molecular structure of the anion [Al(NH-p-tolyl)4]– in 2c.
Thermal ellipsoids are shown at 30% probability. Hydrogen at-
oms on carbon atoms have been removed for clarity. Selected
bond lengths (Å) and angles (°): Al(1)—N(1), 1.841(2) Å;
Al(1)—N(2), 1.844(2) Å; N(1)-Al(1)-N(1A), 116.6(2)°; N(1)-
Al(1)-N(2), 107.3(1)°; N(1)-Al(1)-N(2A), 105.5(1)°; N(2)-Al(1)-
N(2A), 115.2(2)°.
Fig. 2. Top left: Molecular structure of 2b. Top right: Molecular
structure of 3b. Bottom: Polymeric crystal structure of 3b. Ther-
mal ellipsoids are shown at 30% probability. Hydrogen atoms on
carbon atoms have been removed for clarity. Selected bond
lengths (Å) and angles (°): 2b: Al(1)—N(1), 1.857(2) Å; Al(1)—
N(2), 1.863(2) Å; Li(1)—N(1), 2.166(6) Å; N(1)-Al(1)-N(2),
113.5(1)°; N(1)-Al(1)-N(1A), 101.5(2)°; N(1)-Al(1)-N(2A),
113.8(1)°; N(2)-Al(1)-N(2A), 101.4(2)°. 3b: Al(1)—N(1),
1.862(2) Å; Na(1)—N(1), 2.532(2) Å; N(1)-Al(1)-N(1A),
107.61(9)°; N(1)-Al(1)-N(1B), 110.41(5)°.
An X-ray analysis of the solid-state structures of com-
plexes 2b and 3b verified that there are no solvent molecules
present in either case (Fig. 2). The two structures are very
similar, although there are variations that arise from the
presence of different alkali metal cations. For complex 2b,
two independent, but chemically equivalent, molecules are
present in the asymmetric unit, and only one is shown in
Fig. 2. The two molecules are adjacent to each other, but are
slightly skewed along the crystallographic twofold axis (tor-
sion angles N-Al-Al-N, ca. 34°). In contrast, the (HN-i-
Pr)2Al(HN-i-Pr)2Na molecule in 3b is highly symmetrical,
with both the sodium and the aluminum centres situated on a
fourfold rotary inversion axis. Presumably, the lower sym-
metry in 2b arises owing to distortions resulting from the
smaller size of the lithium cation in comparison to the so-
dium cation in 3b. This rationale is supported by the ob-
served distortions from regular tetrahedral geometry around
the aluminum centres in 2b. The smallest N-Al-N angles are
those involved in the AlN2Li rings (range 100.5(2)°–
101.5(2)°). The exocyclic N-Al-N angles are considerably
larger, ranging from 113.5(1)° to 114.2(1)°. By comparison,
the aluminum centre in 3b is only slightly distorted from tet-
rahedral, with bond angles in the narrow range of
107.61(9)°–110.41(5)°; the smallest angles are those in the
AlN2Na rings. The Al—N bond distances are identical
within experimental error in both structures (2b, 1.857(2)–
1.865(2) Å; 3b, 1.862(2) Å) and are comparable to those ob-
served for complex 2c. Interestingly, the overall crystal
structures of complexes 2b and 3b are one-dimensional
polymers (Fig. 2, bottom). The polymeric structure is a re-
sult of the coordination of the lithium or sodium cation to
two amido nitrogen centres from each of two adjacent
tetrakis(amido)aluminate anions. The lithium and sodium
cations are thus four-coordinate, and are highly distorted
from tetrahedral (2b, N-Li-N bond angles 83.2(3)°–84.3(3)°
in the AlN2Li rings and exocyclic bond angles of
107.58(9)°–143.76(9)°; 3b, N-Na-N bond angles of
72.80(7)° in the AlN2Na rings and exocyclic N-Na-N bond
angles of 130.38(4)°). A similar structure has been observed
for the methyl derivative, Li[Al(NHMe)4] (19).
The solid-state structure for 3c, which is depicted in
Fig. 3, was determined by X-ray crystallography; pertinent
metrical parameters are given in Table 2. The molecular
structure is similar to that of 3b except that the sodium ion is
monosolvated by THF. The four-coordinate aluminum centre
adopts a distorted tetrahedral geometry, with the N-Al-N an-
gles ranging from 106.9(1)° to 114.6(1)°. The Al—N bond
lengths are equal within the limits of error, falling in the nar-
row range of 1.843(3)–1.855(3) Å.
Similar to the structures of 2b and 3b, complex 3c forms a
one-dimensional polymer involving coordination of the so-
dium cations to amido groups of adjacent aluminate anions.
In addition to the amido substituents and the single molecule
of THF, each sodium ion displays interactions with the aro-
matic rings of two p-tolyl substituents. Thus, the sodium
ions are overall seven-coordinate. The strongest Na—C in-
teractions are with the ipso carbon atoms of the two rings
with distances of 2.839(3) Å (C8A—Na1) and 2.868(3) Å
(C22—Na1). There are also weaker contacts with one of the
ortho carbon atoms (C13A—Na1 = 3.174(3) Å; C23—Na1 =
3.063(3) Å). These distances are within the typical range of
2.6–3.2 Å observed for Na—C aromatic interactions (20).
The Na—N bond distances are considerably longer and
more varied in 3c (2.561(3)–2.785(3) Å) than those in 3b
(2.532(2) Å), presumably as a result of the higher coordina-
tion number of the sodium centre.
NMR spectra of lithium and sodium
tetrakis(amido)aluminates
The NMR spectra for 2b, 2c, 3b, and 3c should provide a
good indication of whether the solid-state structures (vide
supra) are maintained in solution. In addition, the NMR
© 2006 NRC Canada

Eisler and Chivers
449
Fig. 3. Top: Molecular structure of 3c; portions of an adjacent
molecule are shown, and all hydrogen atoms and THF carbon at-
oms have been removed to clarify the full coordination environ-
ment of the sodium centre. Bottom: Polymeric crystal structure
of 3c; hydrogen atoms on carbon atoms have been removed for
clarity. Thermal ellipsoids are shown at 30% probability.
Table 2. Selected bond lengths (Å) and bond
angles (°) for 3c.
Bond lengths (Å)
Al(1)—N(1)
Al(1)—N(2)
Al(1)—N(3)
Al(1)—N(4)
Na(1)—N(1A)
Na(1)—N(2A)
Na(1)—N(3)
Na(1)—N(4)
1.855(3)
1.843(3)
1.853(2)
1.847(2)
2.561(3)
2.785(3)
2.613(3)
2.625(3)
Bond angles (°)
N(1)-Al(1)-N(2)
N(1)-Al(1)-N(3)
N(1)-Al(1)-N(4)
N(2)-Al(1)-N(3)
N(2)-Al(1)-N(4)
N(3)-Al(1)-N(4)
Al(1)-N(1)-Na(1)
Al(1)-N(2)-Na(1)
O(1)-Na(1)-N(1A)
O(1)-Na(1)-N(3)
O(1)-Na(1)-N(4)
N(1A)-Na(1)-N(2A)
N(1A)-Na(1)-N(3)
N(2A)-Na(1)-N(3)
N(2A)-Na(1)-N(4)
N(3)-Na(1)-N(4)
110.2(1)
108.0(1)
107.3(1)
106.9(1)
114.6(1)
109.7(1)
93.6(1)
86.9(1)
92.79(9)
89.94(8)
139.59(9)
69.01(8)
175.70(9)
110.88(8)
82.24(8)
70.57(8)
However, the complexes 2b and 3b are completely insoluble
in noncoordinating solvents such as benzene and toluene,
whereas they are freely soluble in THF. Presumably, there is
some degree of solvation of the alkali metal cations that al-
lows the complex to dissolve in the coordinating solvent,
1
THF. In the respective H NMR spectra for these isopropyl
complexes, the methyl groups appear as a doublet owing to
coupling with the methine protons. The resonances for the
N-H protons appear as doublets owing to long-range
coupling with the methine protons, which in turn appear as
two overlapping septets. A single resonance is observed in
each 27Al NMR spectrum. In addition, a singlet is observed
7
spectra will furnish information about the solution structure
of 3a, which could not be determined in the solid state. The
multinuclear NMR data obtained for 2c were in keeping
with the observed solid-state structure. For example, a single
resonance was observed for the methyl groups of the p-tolyl
substituents in the 1H and 13C NMR spectra, as well as a sin-
at δ –1.31 in the Li NMR spectrum of 2b, which is in keep-
ing with a THF-solvated lithium ion (typical range -δ –0.5
to –2.5) (21). These data suggest that these complexes exist
in THF solution either as solvent-separated cation–anion
pairs, as was observed for 2c, or that the cation is partially
solvated, and the complexes are present as contact-ion pairs.
In the latter case, any association between the cation and the
complex would have to be dynamic on the NMR timescale
as all of the amido substituents are equivalent in solution,
even down to –80 °C.
1
gle resonance for the four equivalent N-H protons in the H
1
NMR spectrum. The integration of the H NMR spectrum
indicated the presence of four THF molecules of solvation.
A single broad resonance (∆ω1/2 - 390 Hz) was observed
in the 27Al NMR spectrum, and a singlet was observed at δ
–2.68 in the 7Li NMR spectrum attributable to the
[Li(THF)4]+ cation.
Complex 3c is also insoluble in noncoordinating solvents,
but it is freely soluble in THF. In keeping with the solid-
state structure, resonances attributable to a single molecule
1
The NMR data obtained for the isopropyl derivatives 2b
of coordinated THF were present in the H NMR spectrum
and 3b were consistent with the observed solid-state struc-
of 3c. However, in contrast to the solid-state structure, the
multinuclear NMR data obtained for complex 3c are consis-
tent with a highly symmetrical structure, with only a single
1
tures. There were no observable resonances in the H or 13C
NMR spectra attributable to coordinated solvent molecules.
© 2006 NRC Canada

450
Can. J. Chem. Vol. 84, 2006
Table 3. Selected bond lengths (Å) and bond
Fig. 4. Molecular structure of 4. Thermal ellipsoids are shown at
30% probability. Hydrogen atoms on carbon atoms have been re-
moved for clarity.
angles (°) for 4.
Bond lengths (Å)
Al(1)—N(1)
Al(1)—N(1A)
Al(1)—N(2)
Na(1)—N(1A)
Na(1)—N(2)
1.858(2)
1.869(2)
1.891(2)
2.486(2)
2.493(2)
Bond angles (°)
N(1)-Al(1)-N(1A)
N(1)-Al(1)-N(2)
Al(1)-N(1)-Al(1A)
Al(1)-N(1)-Na(1A)
Al(1A)-N(1)-Na(1A)
88.69(6)
111.86(7)
91.31(6)
98.06(7)
84.68(6)
donation of the lone pair on the imido nitrogen centre to the
sodium cation is evident from the pyramidal geometry of the
nitrogen (bond angles range from 84.68(6)° to 98.06(7)°).
The Na—N bond lengths are shorter than those observed for
any of the previous complexes reported here. Presumably,
the shorter distances are a reflection of the higher ionic char-
acter of these bonds in the dianionic complex 4 in compari-
son to that in the monoanionic complexes 3b and 3c.
The NMR data obtained for 4 indicate that the solid-state
resonance observed for the N-H and methyl protons, for ex-
ample. These data suggest that, like the isopropyl com-
plexes, 3c exists in solution as a solvent-separated cation–
anion pair, or that the complex is present as a dynamic
contact-ion pair.
All attempts to obtain crystals of 3a suitable for X-ray dif-
fraction studies were unsuccessful, and so the complex was
1
characterized by multinuclear NMR spectra. In the H NMR
1
spectrum, a single resonance is observed for the tert-butyl
structure is maintained in solution. In the H NMR spec-
methyl protons, as well as a single N-H resonance. Further-
more, the integrated H NMR spectrum indicates that the
trum, two resonances of equal intensity are apparent for the
methyl groups of the two different tert-butyl substituents. A
single resonance is observed for the N-H protons of the two
amido substituents. At room temperature, no resonance was
observed for the Al-H proton. However, at 233 K, a single
broad resonance (∆ω1/2 - 70 Hz) at δ 4.38 was detected for
this proton. While a large range of values has been reported
for Al-H chemical shifts, values in the range of 4.3–5.8 ppm
are typical (22), and the value observed for 4 correlates well
with the shift δ 4.31 obtained for the structurally similar
complex [(SiMe3N-CH2CH2-µ-N-SiMe3)AlH]2 (22c).
1
complex is isolated in the solid state with a single molecule
of THF, presumably coordinated to the sodium cation. A
broad resonance is observed in the 27Al NMR spectrum,
similar to the resonances of the other complexes reported
here. Thus, while the NMR data are in keeping with a sym-
metrical tetrakisimidoaluminate anion, the exact structure of
the complex cannot be unambiguously established from
these data.
The by-product obtained from the reaction of p-toluidine
with NaAlH4 is related to complex 4, and the structure is
shown in Fig. 5 with selected bond distances and angles
given in Table 4. In complex 5 a dimeric, dianionic
aluminate core structure is observed, however, the hydrido
ligand that was present in 4 has been replaced by an addi-
tional amido ligand. Thus, the dianion in 5 is {[(NH-p-
X-ray structures and NMR spectra of the dinuclear
complexes {[Na(THF)2][(NH-t-Bu)Al(H)(␮-N-t-Bu)]}2 (4)
and {[Na(THF)3][(NH-p-tolyl)2Al(␮-N-p-tolyl)]}2 (5)
As mentioned previously, the reactions of MAlH4 with a
primary amine result in the formation of small amounts of
secondary products in addition to the desired tetra-
kis(amido)aluminate anion. We were able to unambiguously
identify the minor products formed in two of the syntheses.
The first of these is the dimeric complex {[Na(THF)2][(NH-
t-Bu)Al(H)(µ-N-t-Bu)]}2 (4), obtained from the reaction of
NaAlH4 with t-BuNH2. Complex 4 was identified by an X-
ray structural determination (Fig. 4); pertinent metrical pa-
rameters are given in Table 3.
Complex 4 can be viewed as a contact-ion pair involving
the dianion {[(NH-t-Bu)Al(H)(µ-N-t-Bu)]2}2–, a dimer of the
[AlH(N-t-Bu)(NH-t-Bu)]– monoanion, and two THF-solvated
sodium ions. The exocyclic amido groups in the dianion ex-
hibit a slightly elongated Al—N bond (1.891(2) Å) in com-
parison to the bridging imido Al—N bonds (1.858(2) and
1.869(2) Å). The aluminum centres are highly distorted tet-
rahedral, with the bond angles ranging from 88.69(6)° to
111.86(7)°. The amido and imido Na—N bond distances are
nearly identical (2.486(2) and 2.493(2) Å, respectively). The
tolyl)2Al(µ-N-p-tolyl)]2}2–,
a dimer of the monoanion
[Al(NH-p-tolyl)2(N-p-tolyl)]–. The Al—N bond distances
fall in a narrow range (1.841(2)–1.860(2) Å), and the alumi-
num centres exhibit distorted tetrahedral geometries (Ta-
ble 4). The Na—N distance of 2.493(2) Å is similar to that
observed in complex 4, presumably as a result of the ionic
character of the bonding. The sodium centre is only coordi-
nated to the pyramidal imido centre (and three molecules of
THF), which suggests a preference for the more ionic imido
nitrogen centre in comparison to the amido centres.
The multinuclear NMR data obtained for complex 5 are in
1
accordance with the solid-state structure. In the H NMR
spectrum, two sets of resonances in a 2:1 ratio are apparent
for the aromatic protons of the amido and imido p-tolyl sub-
stituents, respectively. Consistently, eight carbon resonances
for these inequivalent p-tolyl groups were observed in the
© 2006 NRC Canada

Eisler and Chivers
451
Scheme 1. Possible pathways in the reactions of MAlH4 with primary amines.
2-
R
N
2M+
-3H2
II
NHR
H
H
MAlH4 + 3RNH2
[M][(H)Al(NHR)3]
Al
Al
+ [M][(H)Al(NHR)3]
- 2RNH2
N
R
RHN
I
+ 2RNH2
- 2H2
+ RNH2
- H2
III
-
M+
2-
NHR
R
2M+
IV
NHR
NHR
N
RHN
NHR
NHR
Al
Al
+ [M][Al(NHR)4]
- 2RNH2
Al
N
R
RHN
RHN
Fig. 5. Molecular structure of 5. Thermal ellipsoids are shown at
30% probability. Hydrogen atoms on carbon atoms have been re-
moved for clarity.
Table 4. Selected bond lengths (Å) and bond
angles (°) for 5.
Bond lengths (Å)
Al(1)—N(1)
Al(1)—N(2)
Na(1)—N(2)
Al(1)—N(2A)
Al(1)—N(3)
1.841(2)
1.860(2)
2.493(2)
1.862(2)
1.857(2)
Bond angles (°)
N(1)-Al(1)-N(2)
N(1)-Al(1)-N(2A)
N(1)-Al(1)-N(3)
N(2)-Al(1)-N(2A)
N(2)-Al(1)-N(3)
N(2A)-Al(1)-N(3)
Al(1)-N(2)-Al(1A)
Al(1)-N(2)-Na(1)
Al(1A)-N(2)-Na(1)
109.60(9)
117.48(9)
115.69(9)
87.86(8)
116.78(9)
106.55(9)
92.14(8)
99.06(8)
105.65(8)
2 equiv. of primary amine (RNH2) and the formation of the
dianion [(RNH)Al(H)(µ-NR)]22–, as observed in complex 4
(R = t-Bu). Reaction of the Al-H functionality in this
dianion with two additional equivalents of amine (III,
Scheme 1) would result in the formation of the diamido
imido dianion[(RNH)2Al(µ-NR)]22–, which was identified in
5 (R = p-tolyl). Alternatively, condensation of two tetra-
kis(amido)aluminate anions, with the loss of primary amine
(IV, Scheme 1), could also result in the production of the
dianion [(RNH)2Al(µ-NR)]22–. However, this pathway seems
unlikely since it was possible to isolate the pure tetra-
kis(amido)aluminate complexes in good to excellent yields.
Under more forcing conditions, the reactions of primary
amines with MAlH4 proceed according to eq. [1] (vide su-
pra).
13C NMR spectrum. Curiously, however, the methyl groups
of the p-tolyl substituents exhibit only a single resonance in
1
both the H and 13C NMR spectra, indicating coincidental
equivalence of these substituents.
The isolation and structural characterization of complexes
4 and 5 provides some insight into the possible different
pathways for the reactions of MAlH4 with primary amines.
As illustrated in Scheme 1, under mild conditions these reac-
tions likely proceed readily to the formation of the trisamido
complex [M][(RNH)3Al(H)], cf. the formation of
[Li(THF)4][HAl(NPh2)3] (4). Once this complex is formed,
there is a competition among two possible reaction path-
ways. The first, predominant route involves reaction with a
fourth equivalent of amine, resulting in the substitution of
the final hydrido ligand with an amido ligand, to form the
tetrakis(amido)aluminate complexes (I, Scheme 1). The sec-
ond route, (II, Scheme 1), involves the condensation of two
[(RNH)3Al(H)]– anions, resulting in the elimination of
Conclusions
The reactions of alkali metal aluminum hydrides MAlH4
(M = Li, Na) with primary alkyl- or aryl-amines produces
tetrakis(amido)aluminate complexes in good to excellent
yields. For the lithium derivatives, the established solid-state
© 2006 NRC Canada

452
Can. J. Chem. Vol. 84, 2006
8. M.A. Beswick, N. Choi, C.N. Harmer, M. McPartlin, M.E.G.
Mosquera, P.R. Raithby, M. Tombul, and D.S. Wright. Chem.
Commun. (Cambridge), 1383 (1998).
9. J.S. Silverman, C.J. Carmalt, D.A. Neumayer, A.H. Cowley,
B.G. McBurnett, and A. Decken. Polyhedron, 17, 977 (1998).
10. J.S. Bradley, F. Cheng, S.J. Archibald, R. Supplit, R. Rovai,
C.W. Lehmann, C. Krüger, and F. Lefebvre. Dalton Trans.
1846 (2003).
structures of these complexes include mono- or bis-solvated
monomeric contact-ion pairs, a solvent-separated ion pair,
an unsolvated dimeric contact-ion pair, and a polymeric
structure. By contrast, only polymeric structures, either
unsolvated or monosolvated, are observed for sodium deriv-
atives of the same primary amines. The [Al(NHR)4]– anions
represent potentially interesting tetradentate ligands. Al-
though they have been known since 1998 (8, 9), their coor-
dination chemistry has yet to be investigated. The facile
synthetic procedure reported herein will facilitate such stud-
ies.
11. T. Bauer, S. Schulz, H. Hupfer, and M. Nieger. Organo-
metallics, 21, 2931 (2002).
12. K.W. Henderson, A.R. Kennedy, A.E. McKeown, and R.E.
Mulvey. Angew. Chem. Int. Ed. 39, 3879 (2000).
13. For recent reviews, see: (a) J.K. Brask and T. Chivers. Angew.
Chem. Int. Ed. 40, 3960 (2001); (b) G.M. Aspinall, M.C.
Copsey, A.P. Leedham, and C.A. Russell. Coord. Chem. Rev.
227, 217 (2002).
Acknowledgements
We thank P. Blais and Dr. G. Schatte for carrying out pre-
liminary investigations of the reactions of primary amines
with LiAlH4. We gratefully acknowledge the Natural Sci-
ences and Engineering Research Council of Canada
(NSERC) and The Alberta Ingenuity Fund (AIF) for finan-
cial support.
14. J.K. Brask, T. Chivers, G. Schatte, and G.P.A. Yap.
Organometallics, 19, 5683 (2000).
15. J.K. Brask, T. Chivers, and G.P.A. Yap. Chem. Commun.
(Cambridge), 2543 (1998).
16. M.C. Copsey, J.C. Jeffery, C.A. Russell, J.M. Slattery, and J.A.
Straughan. Chem. Commun. (Cambridge), 2356 (2003).
17. G.M. Sheldrick. SHELXS-97. University of Göttingen,
Göttingen, Germany. 1997.
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