Syntheses and X-ray structures of base-stabilized iminoalanes

Article abstract of DOI:10.1021/om0509286

Reactions between low-valent [Cp*Al]₄ and trialkylsilyl azides RR′₂SiN₃ proceed with N₂ elimination and subsequent formation of iminoalanes [Cp*AlNSiRR′₂]_x (R, R′ = Et 1, i-Pr 2, t-Bu 3; R

Full text of DOI:10.1021/om0509286

1392
Organometallics 2006, 25, 1392-1398
Syntheses and X-ray Structures of Base-Stabilized Iminoalanes§
Stephan Schulz,*,† Florian Thomas,‡ Wolfgang M. Priesmann,‡ and Martin Nieger‡
Department of Chemistry, UniVersita¨t Paderborn, Warburger Strasse 100,
33098 Paderborn, Germany, and Institut fu¨r Anorganische Chemie der UniVersita¨t Bonn,
Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany
ReceiVed October 27, 2005
Reactions between low-valent [Cp*Al]4 and trialkylsilyl azides RR′2SiN3 proceed with N2 elimination
and subsequent formation of iminoalanes [Cp*AlNSiRR′2]x (R, R′ ) Et 1, i-Pr 2, t-Bu 3; R ) t-Bu R′
) Me 4), which further react with an equimolar amount of 4-(dimethylamino)pyridine (dmap) with
formation of dmap-stabilized iminoalanes of the general type [dmap-Al(Cp*)NSiRR′2]2 (R, R′ ) Et 5,
i-Pr 6; R ) t-Bu R′ ) Me 7). No reaction was observed for [Cp*AlNSi(t-Bu)3]2, 3. In contrast, Cp*Al
and RR′2SiN3 react in the presence of dmap at elevated temperatures with C-H activation of the ortho-
Hdmap and formation of dihydroanthracene-type compounds of the type [o-Al(Cp*)N(H)SiRR′2-dmap]2
(R, R′ ) Et 8, i-Pr 9, t-Bu 10; R ) t-Bu R′ ) Me 11). The reaction of Cp*Al and t-Bu3SiN3 with 2 equiv
of dmap proceeds with o-C-Hdmap activation of only one dmap molecule and formation of the dmap-
stabilized monomeric aminoalane [o-Al(dmap)(Cp*)N(H)Si(t-Bu)3-dmap], 12. Compounds 3 and 5-12
were characterized by IR, mass, and multinuclear NMR spectroscopy (1H, 13C), and 3, 7, 8, 9, 11, and
12 also by single-crystal X-ray structure analysis.
Scheme 1. General Reaction Sequence of the AlH3/NH3
Reaction
Introduction
Compounds containing Al-N bonds have a long-standing
history in main group organometallic chemistry due to their
fascinating structures, interesting bonding properties, and ver-
satility in organic and inorganic syntheses.1 In addition, their
potential application to serve as precursors for the synthesis of
aluminum nitride, AlN, which finds several applications as
ceramic material, has stimulated their synthesis. Early studies
by Wiberg et al. perfectly illustrate some general reaction
patterns in aluminum-nitrogen chemistry. AlH3 and NH3 react
with formation of the Lewis acid-base adduct H3Al-NH3,
which is stable only at very low temperature. At higher
temperatures, H2 is eliminated with stepwise formation of
aminoalane [H2AlNH2]x and iminoalane [HAlNH]x. Finally,
aluminum nitride, AlN, is formed.2 Comparable findings have
been observed for reactions of trialkylalanes with primary,
secondary, and tertiary amines. Numerous adducts (type I) and
aminoalanes (type II), which typically form four- or six-
membered rings, have been prepared in the last decades,3
whereas iminoalanes [RAlNR′]x have been structurally charac-
terized to a far lesser extent.4 They typically adopt oligomeric
structures in the solid state (x ) 4, 6, 7, 8, and higher) with the
central aluminum and nitrogen atoms featuring tetrahedral
coordination environments. The degree of oligomerization is
controlled by the steric demand of the organic substituents (R,
R′). In addition, a very few lower aggregated species such as
monomeric,5 dimeric,6 and trimeric iminoalanes7 containing 2-
and 3-fold coordinated Al and N centers have been synthesized.
These are of particular interest due to their bonding properties.
Six-membered rings are isoelectronic to benzene (C6H6) and
borazine (B3N3H6), sometimes referred to as “inorganic ben-
zene”. Monomeric compounds RAlNR′ are also a challenging
goal since they should exhibit multiple bonding character, as
was observed for iminoboranes. Unfortunately, they have a
strong oligomerization tendency. Theoretical calculations for
HAlNH demonstrated that dimerization is strongly exothermic
(140 kcal/mol) and occurs without any activation barrier.8
(4) (a) Veith, M. Chem. ReV. 1990, 90, 3. (b) Perego, G.; del Piero, G.;
Cesari, M.; Zazzetta, A.; Dozzi, G. J. Organomet. Chem. 1975, 87, 53. (c)
del Piero, G.; Cesari, M.; Dozzi, G.; Mazzei, A. J. Organomet. Chem. 1977,
129, 281. (d) Cesari, M.; Perego, G.; del Piero, G.; Cucinella, S.; Cernia,
E. J. Organomet. Chem. 1974, 78, 203. (e) del Piero, G.; Perego, G.;
Cucinella, S.; Cesari, M.; Mazzei, A. J. Organomet. Chem. 1977, 136, 13.
(f) Perego, G.; Dozzi, G. J. Organomet. Chem. 1981, 205, 21. (g) Perego,
G.; Cesari, M.; del Piero, G.; Balducci, A.; Cernia, E. J. Organomet. Chem.
1975, 87, 33. (h) del Piero, G.; Cucinella, S.; Cesari, M. J. Organomet.
Chem. 1979, 173, 263. (i) Harlan, C. J.; Bott, S. G.; Barron, A. R. J. Chem.
Soc., Dalton Trans. 1997, 637.
(5) Hardman, N. J.; Cui, C.; Roesky, H. W.; Fink, W. H.; Power, P. P.
Angew. Chem., Int. Ed. 2001, 40, 2172.
§ Dedicated to Prof. Hansgeorg Schno¨ckel on the occasion of his 65th
birthday.
* To whom correspondence should be addressed. Phone: + 49 5251-
602493. Fax: + 49 5251-603423. E-mail: stephan.schulz@upb.de.
† Universita¨t Paderborn.
(6) (a) Schulz, S.; Ha¨ming, L.; Herbst-Irmer, R.; Roesky, H. W.;
Sheldrick, G. M. Angew. Chem., Int. Ed. Engl. 1994, 33, 969. (b) Fisher,
J. D.; Shapiro, P. J.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem. 1996,
35, 271. (c) Wehmschulte, R. J.; Power, P. P. J. Am. Chem. Soc. 1996,
118, 791. (d) Schulz, S.; Voigt, A.; Roesky, H. W.; Ha¨ming, L.; Herbst-
Irmer, R. Organometallics 1996, 15, 5252. (e) Wehmschulte, R. J.; Power,
P. P. Inorg. Chem. 1998, 37, 6906. (f) Uhl, W.; Molter, J.; Koch, R. Eur.
J. Inorg. Chem. 1999, 2021.
‡ Universita¨t Bonn.
(1) Hudlicky, M. In Reductions in Organic Chemistry, 2nd ed.; American
Chemical Society: Washington, DC, 1996.
(2) Wiberg, E.; May, A. Z. Naturforsch. B 1955, 10, 229.
(3) See the following and references therein: (a) Chang, C.-C.; Ameerun-
isha, M. S. Coord. Chem. ReV. 1999, 189, 199. (b) Bauer, T.; Schulz, S.;
Hupfer, H.; Nieger, M. Organometallics 2002, 21, 2931.
(7) (a) Wagonner, K. M.; Hope, H.; Power, P. P. Angew. Chem., Int.
Ed. 1988, 27, 1699. (b) Wagonner, K. M.; Power, P. P. J. Am. Chem. Soc.
1991, 113, 3385.
10.1021/om0509286 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/11/2006

Syntheses of Base-Stabilized Iminoalanes
Organometallics, Vol. 25, No. 6, 2006 1393
Scheme 2. Formation of dmap-Stabilized Four-Membered
Iminoalanes
Figure 1. Molecular structure and atom-numbering scheme of
compound 3. Thermal ellipsoids are drawn at the 50% probability
level. H atoms have been omitted for clarity.
Dimerization of [HAlNH]2 to the heterocubane [HAlNH]4 again
occurs with an energy release of 66 kcal/mol.
The most common principles for the stabilization of mono-
meric group 13-imides are kinetic (bulky organic substituents)
and electronic stabilization (electron-withdrawing substituents
at Al, electron-donating substituents at N (push-pull substitution
pattern)).9 These general principles have been successfully
applied for the synthesis of [{HC(MeCDippN)2}AldNR] (R
) 2,6-Trip2C6H3) by reaction of the low-valent Al(I) compound
{HC(MeCDippN)2}Al with the sterically encumbered azide N3R
at ambient temperature.5 In contrast, comparable reactions
between [Cp*Al]4 and N3SiR′3 (R′ ) Me, Et, Ph, i-Pr, t-Bu)
between 60 and 80 °C yielded dimeric iminoalanes.6a,d Obvi-
ously, the mild reaction conditions and the high degree of steric
crowding favor the formation of monomeric species. In addi-
tion, the increase of the coordination number of the Al center
from two (“normal” iminoalane RAldNR′) to three ([{HC-
(MeCDippN)2}AldNR]) by use of the â-ketiminato ligand
seems to play a key role for the stabilization of low-aggregated
iminoalanes. Comparable findings have been reported very
recently for the synthesis of base-stabilized, dimeric iminoalanes
containing sterically less hindered substituents. Coordination of
a Lewis base such as NMe33b or THF6f increases the coordina-
tion number of a dimeric iminoalane [RAlNR′]2 from three to
four and hence decreases its oligomerization tendency.
In an attempt to stabilize low-aggregated iminoalanes, we
became interested in their general reactivity toward strong Lewis
bases, and we re-examined reactions of univalent [Cp*Al]4 with
trialkylsilyl azides RR′2SiN3. Unlike the studies reported
previously,6a,d the reactions were performed in the presence of
the strong Lewis base 4-(dimethylamino)pyridine (dmap). The
resulting compounds 3-12 were characterized by elemental
analyses, IR, mass, and multinuclear NMR spectroscopy (1H,
13C), and 3, 7, 8, 9, 11, and 12 also by single-crystal X-ray
structure analysis.
Figure 2. Molecular structure and atom-numbering scheme of
compound 7. Thermal ellipsoids are drawn at the 50% probability
level. H atoms have been omitted for clarity.
5-7 show resonances due to the trialkylsilyl group, the Cp*
substituent, and the dmap base.10 The Cp* substituents in 5-7
show different numbers of resonances in the 1H NMR spectra,
indicating an expressed bonding flexibility (η1-η5) in solution.
The EI mass spectra of 5-7 show peaks due to typical
fragmentation reactions. In contrast, the molecular ion peak was
observed for 3.
The solid-state structures of 3 and 7 were determined by
single-crystal X-ray diffraction. Suitable crystals were obtained
after storage of solutions of 3 and 7 in toluene at 4 °C for 48
h. Figures 1 and 2 show their solid-state structures. 3 crystallizes
in the orthorhombic space group Pbcn (No. 60) and 4 in the
monoclinic space group C2/c (No. 15), both with one toluene
molecule per formula unit (3: 1 toluene per molecule (no
crystallographic symmetry); 7: 1/2 toluene per 1/2 molecule
(crystallographic C2 symmetry)). Since 3 has been described
previously,6d the bonding parameters will not be discussed in
detail. It should only be mentioned that the central, noncen-
trosymmetric Al2N2 ring in 3 adopts a butterfly-type conforma-
tion (19.5° along the Al‚‚‚Al axis), in contrast to previously
described four-membered heterocyclic iminoalanes, which typi-
cally exhibit planar Al2N2 ring geometries. This is most likely
due to the presence of very bulky t-Bu3Si substituents at the N
centers. The N centers in 7 adopt a trigonal-planar coordination
sphere (sum of bond angles ) 360°), whereas the Al centers
adopt slightly distorted tetrahedral coordination environments.
Results and Discussion
Reactions of [Cp*Al]4 and trialkylsilyl azides RR′2SiN3
between 60 and 80 °C proceed with smooth elimination of N2
and subsequent formation of iminoalanes [Cp*AlNSiRR′2]x (R,
R′ ) Et 1, i-Pr 2, t-Bu 3; R ) t-Bu R′ ) Me 4), which further
react at ambient temperature with an equimolar amount of dmap
with formation of dmap-stabilized dimeric iminoalanes of the
general type [dmap-Al(Cp*)NSiRR′2]2 (R, R′ ) Et 5, i-Pr 6; R
) t-Bu, R′ ) Me 7). Only [Cp*AlNSi(t-Bu)3]2 (3) did not react
with dmap under these conditions, most likely due to the steric
1
crowding of the t-Bu groups. The H and 13C NMR spectra of
(8) Hamilton, T. P.; Shaikh, A. W. Inorg. Chem. 1997, 36, 754.
(9) See for instance: Power, P. P. Chem. ReV. 1999, 99, 3463.
(10) 13C NMR spectra of some compounds could not be recorded due
to their poor solubility in organic solvents.

1394 Organometallics, Vol. 25, No. 6, 2006
Schulz et al.
Table 1. Selected Bond Lengths [Å] and Bond Angles [deg]
of 3 and 7
[Cp*AlNSi(t-Bu)3]2 (3)
Al1-N1
Al1-N2
Al2-N1
Al2-N2
Al1-C1
Al2-C11
N1-Si1
N2-Si2
1.840(1)
1.837(1)
1.841(1)
1.841(1)
2.025(1)
2.034(2)
1.730(1)
1.732(1)
N1-Al1-N2
N1-Al2-N2
Al1-N1-Al2
Al1-N2-Al2
C1-Al1-N1
C1-Al1-N2
C11-Al2-N1
C11-Al2-N2
Si1-N1-Al1
Si1-N1-Al2
Si2-N2-A1
93.3(1)
93.0(1)
85.1(1)
85.2(1)
130.8(1)
125.4(1)
125.9(1)
131.4(1)
129.2(1)
138.8(1)
138.9(1)
130.1(1)
Si2-N2-Al2
[dmap-Al(Cp*)NSi(t-Bu)Me2]2 (7)
Al1-N1#a
Al1-N1
Al1-N1D
Al1-C1
N1-Si1
1.856(2)
1.863(2)
2.007(2)
2.083(2)
1.699(2)
N1-Al1-N1#a
Al1-N1-Al1#a
N1-Al1-N1D
C1-Al1-N1D
C1-Al1-N1
92.2(1)
87.7(1)
106.1(1)
108.3(1)
117.6(1)
129.7(1)
142.7(1)
Figure 3. Molecular structure and atom-numbering scheme of
compound 8 (one independent molecule). Thermal ellipsoids are
drawn at the 50% probability level. H atoms, except those attached
to N, have been omitted for clarity.
Si1-N1-Al1
Si1-N1-Al1#a
a Symmetry operator: -x+1, y, -z+0.5.
Scheme 3. Formation of Dihydroanthracen-Type
Compounds
Figure 4. Molecular structure and atom-numbering scheme of
compound 9. Thermal ellipsoids are drawn at the 50% probability
level. H atoms, except those attached to N, have been omitted for
clarity.
The central four-membered ring in 7 also deviates from planarity
(5.1° along the Al‚‚‚Al axis) due to the coordination of the dmap
bases. The Al-N distances within the Al2N2 ring of 7 (1.856-
(2), 1.863(2) Å) are slightly elongated compared to those of 3
(av 1.839 Å) as a result of the higher coordination number of
the Al centers (4 vs 3). The Al-Ndmap distance in 7 (2.007(2)
Å) is significantly longer, as is typical for dative Al-N bonds.
The Cp* substituents in 3 and 7 are σ-bonded to the Al centers
with Al-C distances of 2.034(2) [2.025(2)] Å (3) and 2.083(2)
Å (7), respectively, again reflecting the different coordination
numbers of the Al centers. The endocyclic Al-N-Al bond
angles (av 85.2° 3; 87.7(1)° 7) are smaller than the N-Al-N
bond angles (av 93.2° 3; 92.2(1)° 7), consequently leading to
relatively short transannular Al‚‚‚Al distances (2.490(1) Å 3;
2.575(1) Å 7; for comparison 2.60 Å in Al2Me6). Reactions of
[Cp*Al]4 and RR′2SiN3 in refluxing toluene in the presence of
an equimolar amount of dmap also proceed with smooth N2
elimination. However, in contrast to the previously described
reactions, dark-colored solutions were formed, from which
colorless crystals of dihydroanthracene-type compounds of the
general type [o-Al(Cp*)N(H)SiRR′2-dmap]2 (R, R′ ) Et 8, i-Pr
9, t-Bu 10; R ) t-Bu R′ ) Me 11) were isolated after storage
at -60 °C. Compounds 8, 9, and 11 were also formed when
dmap-stabilized iminoalanes 5-7 were heated in toluene at 110
°C for 1 h. The 1H and 13C NMR spectra of 8-11 again show
resonances due to the trialkylsilyl group and the Cp* substituent.
In contrast, the aromatic protons of the dmap molecules in 8-11
no longer show the typical AA′XX′ peak pattern as was
observed for 5-7. Instead, three sets of resonances are observed,
Figure 5. Molecular structure and atom-numbering scheme of
compound 11. Thermal ellipsoids are drawn at the 50% probability
level. H atoms, except those attached to N, have been omitted for
clarity.
indicating the presence of three nonequivalent ring protons.
These results were confirmed by 13C NMR spectroscopy, also
demonstrating the ring-Cdmap atoms to be chemically nonequiva-
lent. The 1H NMR spectra of 8-11 also show additional
resonances at very high field (-0.30 to -0.60 ppm) for the
N-H group. IR spectra of 8-11 also show typical absorption
bands between 3100 and 3300 cm-1. The EI mass spectra of
8-11 do not show the molecular ion peak. However, the central
dihydroanthracene-type core was found to be thermally very

Syntheses of Base-Stabilized Iminoalanes
Organometallics, Vol. 25, No. 6, 2006 1395
Table 2. Selected Bond Lengths [Å] and Bond Angles [deg] of 8, 9, and 11
[o-Al(Cp*)N(H)SiEt3-dmap]2 (8) [second molecule]
Al1-N11D
Al1-C12D#a
Al1-N1
1.935(3) [1.943(3)]
2.013(3) [2.021(4)]
1.811(3) [1.801(3)]
2.121(4) [2.128(4)]
1.381(4) [1.382(4)]
1.706(3) [1.715(3)]
N1-Al1-N11D
N1-Al1-C12D#a
N1-Al1-C11
N11D-Al1-C11
C11-Al1-C12D#a
Al1-N11D-C12D
Al1#a-C12D-N11D
Al1-N1-Si1
107.2(1) [109.1(2)]
113.6(1) [114.6(1)]
115.3(1) [110.3(1)]
111.8(1) [99.6(2)]
102.3(1) [115.4(1)]
123.5(2) [124.4(2)]
125.0(2) [123.7(2)]
137.3(2) [142.2(2)]
Al1-C11
N11D-C12D
N1-Si1
N11D-Al1-C12D#a
104.4(1) [106.4(1)]
[o-Al(Cp*)N(H)Si(i-Pr)3-dmap]2 (9)
Al1-N1D
Al1-C2D#b
Al1-N1
1.936(2)
2.020(2)
1.814(2)
2.101(2)
1.390(3)
1.714(2)
N1-Al1-N1D
N1-Al1-C2D#b
N1-Al1-C1
N1D-Al1-C1
C1-Al1-C2D#b
Al1-N1D-C2D
Al1#b-C2D-N1D
Al1-N1-Si1
110.0(1)
118.4(1)
109.5(1)
109.8(1)
103.6(1)
123.5(2)
123.2(2)
146.3(2)
Al1-C1
N1D-C2D
N1-Si1
N1D-Al1-C2D#b
105.2(1)
[o-Al(Cp*)N(H)Si(t-Bu)Me2-dmap]2 (11)
Al1-N1D
Al1-C2D#c
Al1-N1
1.933(2)
2.028(3)
1.819(3)
2.701(3)
1.375(3)
1.696(3)
N1-Al1-N1D
105.4(1)
113.9(1)
110.1(1)
113.9(1)
107.9(1)
124.5(2)
126.2(2)
135.5(2)
N1-Al1-C2D#c
N1-Al1-C1
Al1-C1
N1D-Al1-C1
C1-Al1-C2D#c
Al1-N1D-C2D
Al1#c-C2D-N1D
Al1-N1-Si1
N1D-C2D
N1-Si1
N1D-Al1-C2D#c
105.7(1)
a Symmetry operator: -x+1, -y+1, -z+1 (first molecule); -x+2, -y+2, -z (second molecule). b Symmetry operator: -x, -y+1, -z+1. c Symmetry
operator: -x+1, y, -z+0.5.
robust since peaks with the highest mass typically correspond
to the molecular ion peak minus one alkyl substituent from the
silyl group or minus one Cp* group.
(4) Å [2.128(4) Å] 8, 2.101(2) Å 9, 2.071(3) Å 11), as was
observed for 3 and 7. The endocyclic bond angles [deg] within
the central (AlCN)2 rings (N-Al-C: 106.4(1) [106.4(1)] 8,
105.2(1) 9, 105.7(1) 11; Al-C-N: 125.0(2), [123.7(2)] 8,
123.2(2) 9, 125.0(2) 11; C-N-Al: 123.5(2), [124.4(2)] 8,
123.5(2) 9, 124.5(2) 11) clearly reflect the different coordination
numbers (Al 4, C 3, N 3) and hybridization states (Al sp3, C
sp2, N sp2) of the central ring atoms. Ortho-C-H activation of
dmap has been described twice in the literature.12 In both
reaction types, the presence of a very strong basic reaction
center, which was formed as a result from the coordination of
the Li cation of the metalation reagent (n-BuLi, tmpLi (tmp )
2,2,6,6-tetramethylpiperidyl)) to the heteroatom (O, F) of the
BF3- or LiOC2H4NMe2-mediated reaction, was found to be
essential. According to these findings, the formation of 8-11
most likely proceeds through the intermediate formation of
monomeric iminoalanes Cp*AlNSiRR′2, which are expected to
be highly reactive species due to the presence of both coordi-
natively and electronically unsaturated central atoms. Reactions
with dmap yield monomeric, dmap-stabilized iminoalanes dmap-
Al(Cp*)NSiRR′2, which contain a very strong basic imine
center. Ortho-C-Hdmap activation occurs either through the
formation of a weakly bonded dimer (pathway I), which
subsequently undergoes intermolecular N-H and Al-C bond
formation reactions, or by intramolecular deprotonation and
formation of a monomeric, zwitterionic compound (pathway II),
which dimerizes with formation of the dihydroanthracene-type
compounds 8-11. To investigate the role of dmap in more
detail, the reaction of Cp*Al, t-Bu3SiN3, and 2 equiv of dmap
in refluxing toluene was investigated, yielding the dmap-
stabilized monomer [o-Al(dmap)(Cp*)N(H)Si(t-Bu)3-dmap], 12.
The 1H NMR spectrum of 12 shows two different sets of
resonances due to the aromatic H atoms of the dmap molecule.
The signal patterns indicate the presence of both an activated
and a nonactivated dmap molecule. These results were con-
Colorless crystals of 8, 9, and 11 suitable for X-ray structure
analyses were grown from solutions in toluene at -60 °C.
Figures 3-5 show their solid-state structures. They crystallize
in different space groups (P1h (No. 2), two half independent
molecules in the asymmetric unit 8, C2/c (No. 15) 9, C2/c (No.
15) 11). The central skeleton of 8, 9, and 11 contains three
annelated six-membered rings, which adopt a dihydroanthracene-
type conformation.
8 and 9 show crystallographic Ci symmetry, whereas 11
exhibits C2 symmetry. The structures can alternatively be
described as dimers of ortho-metalated dmap (head-to-tail
Al-Nimin adducts). The central (AlCN)2 six-membered rings
in 8 and 9 both adopt a flattened chair-like conformation
(convolution degree 24.1° (8), 25.3° (9); for comparison 55° in
cyclohexane) with the Cp* and N(H)SiRR′2 groups in transoid
orientations. The annelated dmap rings are in plane with the
plane of the (AlCN)2 chair (Figures 3 and 4), and the Cp* rings
adopt an almost coplanar orientation to the central dihydroan-
thracene-type system. In contrast, the (AlCN)2 ring of 11 forms
a distorted envelope-type conformation. The Cp* rings and the
N(H)Si(t-Bu)3 groups adopt a cisoid orientation, most likely due
to the higher steric demand of the t-Bu groups. As a conse-
quence, the central dihydroanthracene-type ring system signifi-
cantly deviates from planarity, as can be seen in Figure 5. The
endocyclic Al-N bond lengths (1.935(3) Å [1.943(3) Å] 8,
1.936(2) Å 9, 1.933(2) Å 11) are longer than the exocyclic ones
(1.811(3) Å [1.801(3) Å] 8, 1.814(2) Å 9, 1.819(3) Å 11),
indicating a rather dative bonding character of the endocyclic
Al-Ndmap bond, even though these bond lengths are significantly
shorter compared to that in dmap-AlMe3 (av 201.4 Å).11 The
Cp* substituents in 8, 9, and 11 are σ-bonded (Al-C: 2.121-
(11) Thomas, F.; Bauer, T.; Schulz, S.; Nieger, M. Z. Anorg. Allg. Chem.
2003, 629, 2018.
(12) (a) Vedejs, E.; Chen, X. J. Am. Chem. Soc. 1996, 118, 1809. (b)
Cuperly, D.; Gros, P.; Fort, Y. J. Org. Chem. 2002, 67, 238.

1396 Organometallics, Vol. 25, No. 6, 2006
Schulz et al.
Scheme 4. Proposed Reaction Pathway for the Activation of
o-C-H
Figure 6. Molecular structure and atom-numbering scheme of
compound 12. Thermal ellipsoids are drawn at the 50% probability
level. H atoms, except those attached to N, have been omitted
for clarity. Selected bond lengths [Å] and angles [deg]: Al1-N1
1.829(2), Al1-N1D 1.942(2), Al1-C1 2.098(2), Al1-C12D
2.004(2), N1-Si1 1.725(2); N1-Al1-N1D 107.9(1), N1-Al1-
C12D 115.7(1), N1-Al1-C1 109.3(1), N1D-Al1-C12D
108.4(1), N1D-Al1-C1 105.1(1), C12D-Al1-C1 110.0(1),
Al1-N1-Si1 149.0(1).
Scheme 6. Summary of the Reactions of [Cp*Al]4 with
Trialkylsilyl Azides RR′2SiN3 and dmap
Scheme 5. Formation of dmap-Stabilized Monomer 12
N centers, and the Al-Ndmap bond distance (1.942(2) Å) is
relatively short, as was observed for 8, 9, and 11.
Conclusions. Reactions of equimolar amounts of [Cp*Al]4,
trialkylsilyl azides RR′2SiN3, and 4-(dimethylamino)pyridine
(dmap) were investigated. The reactions proceed with elimina-
tion of N2 and subsequent formation of dmap-stabilized dimers
or dihydroanthracene-type compounds. The latter are formed
by ortho-C-H activation of the coordinating dmap base. In
addition, the reaction of Cp*Al, t-Bu3SiN3, and 2 equiv of dmap
yielded a base-stabilized, monomeric aluminum amide.
firmed by 13C NMR spectroscopy. The IR spectra also show
the formation of an N-H group (3315 cm-1). The EI mass
spectrum of 12 shows the molecular ion peak with almost 20%
intensity, indicating 9 to be thermally very stable.
Colorless crystals of 12 were obtained from a solution in
toluene at -60 °C. Figure 6 shows the solid-state structure of
12, which crystallizes in the triclinic space group P1h (No. 2).
The central Al atom in 12 is coordinated by one Cp* substituent,
one amido group (NH(Sit-Bu3)), and one activated (ortho-
position) dmap molecule. The tetrahedral coordination sphere
is completed by one additional dmap molecule. Obviously, the
strong Lewis base dmap disaggregates the dihydroanthracene-
type dimer 10, which can be described as a head-to-tail adduct,
with subsequent formation of 12. Comparable findings have
been previously observed for the reactions of four- and six-
membered Al/group15 heterocycles [R2AlER′2]x (E ) P, As,
Sb, Bi) with dmap, yielding the base-stabilized monomers dmap-
AlR2ER′2.13 The Al-CCp* bond length (2.098(2) Å) is signifi-
cantly longer than the Al-Cdmap distance (2.004(2) Å), as was
observed for 8, 9, and 11. The Al-Namido bond distance (1.829-
(2) Å) is in the typical range as observed for 3-fold-coordinated
Experimental Section
General Procedures. All manipulations were performed in a
glovebox under an N2 atmosphere or with standard Schlenk
techniques. Solvents were dried over sodium/potassium and de-
gassed prior to use. 4-(Dimethylamino)pyridine was purchased from
14
Aldrich and sublimed prior to use. [Cp*Al]4 and silyl azides
RR′2SiN315 were prepared according to literature methods. A Bruker
1
AMX 300 spectrometer was used for NMR spectroscopy. H and
(13) (a) Schulz, S.; Nieger M. Organometallics 2000, 19, 2640. (b)
Schulz, S.; Thomas, F.; Kuczkowski, A.; Hupfer, H.; Nieger M. Organo-
metallics 2000, 19, 5758. (c) Thomas, F.; Schulz, S.; Nieger, M. Eur. J.
Inorg. Chem. 2001, 161.
(14) Schulz, S.; Roesky, H. W.; Koch, H. J.; Sheldrick, G. M.; Stalke,
D.; Kuhn, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1729.

Syntheses of Base-Stabilized Iminoalanes
Organometallics, Vol. 25, No. 6, 2006 1397
13C{1H} NMR spectra were referenced to internal C6D5H (1H: δ
) 7.154; 13C: δ ) 128.0) or internal toluene-d8 (1H: δ ) 2.03
(q), 6.98 (m), 7.00 (br), 7.09 (m); 13C: δ ) 20.4 (sept), 125.2 (t),
128.0 (t), 128.9 (t), 137.5 (s) ppm). Mass spectra (EI) were re-
corded on a VG Masslab 12-250 spectrometer and a Finnigan MAT
8230. Infrared spectra were recorded in Nujol between KBr plates
with a Nicolet Magna 550 and are reported in wavenumbers.
Melting points were measured in sealed capillaries and were not
corrected. Elemental analyses were performed at the Elementar-
analyse Labor der Universita¨t Paderborn. Yields are given for the
pure products.
due to the very poor solubility of 7 in organic solvents. EI-MS (16
eV, 350 °C): m/z (%) 628 (14) [Cp*(dmap)AlN(Si(t-Bu)Me2)2N-
(Si(t-Bu)H]+), 391 (100) [Cp*AlN(Si(t-Bu)Me2)N(Si(H)t-Bu)]+,
268 (21) [C5Me4CH2]2+, 162 (4) [Cp*Al]+, 135 (63) [Cp*]+, 134
(60) [C5Me4CH2]+.
General Synthesis of [o-Al(Cp*)N(H)SiRR′2-dmap]2. A sus-
pension of 1 mmol of RR′2SiN3, 0.16 g (0.25 mmol) of [Cp*Al]4,
and 0.12 g (1 mmol) of dmap was heated in 50 mL of toluene to
reflux for 30 min. The resulting solution was stored at -50 °C,
yielding colorless crystals.
[o-Al(Cp*)N(H)SiEt3-dmap]2 (8). Yield: 0.58 g (71%). Mp:
232-240 °C (dec). Anal. Found (calcd) for C46H80Al2N6Si2 (827.3
General Synthesis of [dmap-Al(Cp*)NSiRR′2]2. A suspension
of 1 mmol of RR′2SiN3 and 0.16 g (0.25 mmol) of [Cp*Al]4 in 30
mL of toluene was heated for 30 min between 60 and 80 °C until
gas evolution has stopped. The resulting clear solution was cooled
to ambient temperature, combined with a solution of 1 mmol (0.12
g) of dmap in 5 mL of toluene, and stirred for 5 min, yielding
yellowish to brownish suspensions. Addition of THF (20-30 mL)
gave clear solutions (5, 6), which were stored at -30 °C. 5 and 6
were obtained as colorless solids. 7 was obtained as a colorless
crystalline solid after slow cooling of a hot solution in 40 mL of
toluene. 3 did not react with dmap under these conditions.
[Cp*AlNSi(t-Bu)3]2 (3). Yield: 0.64 g (85%). Mp: 244 °C (dec).
Anal. Found (calcd) for C44H84Al2N2Si2-C7H8 (843.4 g/mol): H:
1
g/mol): H: 9.62 (9.75); C: 66.61 (66.81); N: 10.04 (10.16). H
NMR (300 MHz, toluene-d8, 30 °C): δ -0.31 (s, 1H, NH), 0.79
3
3
(q, JHH ) 7.8 Hz 6H, CH2CH3), 1.23 (t, JHH ) 7.8 Hz, 9H,
CH2CH3), 1.79 (s, 15H, C5Me5), 2.49 (s, 6H, NMe2), 6.09 (dd, 3JHH
4
4
) 7.0 Hz, JHH ) 3.4 Hz, 1H, C5-H-dmap), 7.25 (d, JHH ) 3.4
Hz, 1H, C3-H-dmap), 8.23 (d, 3JHH ) 7.0 Hz, 1H, C6-H-dmap). A
13C NMR spectrum could not be recorded due to the very poor
solubility of 8 in organic solvents. IR (Nujol): νj 3243, 3232
(N-H) cm-1. EI-MS (12 eV, 450 °C): m/z (%) 797 (2) [M - Et]+,
691 (76) [M - Cp*]+, 278 (8) [M/2 - Cp*]+, 206 (100) [M/2 -
Cp* - Et - NMe2]+, 135 (48) [Cp*]+, 122 (64) [dmap]+.
[o-Al(Cp*)N(H)Si(i-Pr)3-dmap]2 (9). Yield: 0.67 g (74%).
Mp: 270-275 °C (dec). Anal. Found (calcd) for C52H92Al2N6Si2
(911.5 g/mol): H: 10.09 (10.17); C: 68.43 (68.52); N: 9.19 (9.22).
1H NMR (300 MHz, toluene-d8, 30 °C): δ -0.60 (br, 1H, N-H),
0.90-1.17 (m, 21H, i-Pr), 1.64 (s, 15H, C5Me5), 2.55 (s, 6H, NMe2),
6.18 (dd, 3JHH ) 6.9 Hz, 4JHH ) 3.3 Hz, 2H, C5-H-dmap), 7.31 (s,
1
10.76 (10.91); C: 72.28 (72.66); N: 3.23 (3.32). H NMR (300
MHz, C6D6, 25 °C): δ 1.08 (s, 6H, Cp*), 1.17 (s, 27H, t-Bu), 1.91
(s, 6H, Cp*), 2.09 (s, 3H, Cp*). 13C NMR (75 MHz, C6D6, 25 °C):
δ 15.1 (C5Me5), 22.8 (t-Bu), 32.2 (t-Bu), 122.4 (C5Me5). EI-MS
(35 eV, 200 °C): m/z (%) 750 (3) [M]+, 693 (8) [M - t-Bu]+, 558
(34) [M - Cp* - t-Bu]+, 375 (21) [M/2]+, 135 (85) [Cp*]+, 57
(100) [t-Bu]+.
4JHH ) 3.1 Hz, 2H, C3-H-dmap), 8.41 (dd, 3JHH ) 6.9 Hz, 5JHH
)
0.4 Hz, 2H, C6-H-dmap). 13C{1H} NMR (75 MHz, toluene-d8, 95
°C): δ 1.4 (CH(CH3)2), 13.0 (C5Me5), 15.0 (CH(CH3)2), 38.5
(NMe2), 104.8 (C3/C5dmap), 118.5 (C5Me5), 119.6 (C6dmap), 149.0
[dmap-Al(Cp*)NSiEt3]2 (5). Yield: 0.50 g (60%). Mp: 145 °C.
Anal. Found (calcd) for C46H80Al2N6Si2 (827.3 g/mol): H: 9.65
1
(C2dmap), 153.5 (C4dmap). IR (Nujol): νj 3179, 3236 (N-H) cm-1
.
(9.75); C: 66.68 (66.81); N: 10.09 (10.16). H NMR (300 MHz,
3
EI-MS (16 eV, 400 °C): m/z (%) 868 (1) [M - i-Pr]+, 776 (49)
[M - Cp*]+, 640 (2) [M - 2Cp*]+, 135 (40) [Cp*]+, 130 (100)
[(i-Pr)2SiNH2]+, 121 (65) [dmap - H]+.
C6D6, 25 °C): δ 0.47 (q, JHH ) 7.9 Hz, 6H, CH2CH3), 0.94 (t,
3JHH ) 7.7 Hz, 9H, CH2CH3, 1.69 (s, 6H, C5Me5), 1.75 (s, 9H,
3
C5Me5), 2.49 (s, 6H, NMe2), 6.21 (d, JHH ) 5.7 Hz, 2H, C3/C5-
H-dmap), 8.27 (d, 3JHH ) 6.3 Hz, 2H, C2/C6-H-dmap). 13C NMR
(75 MHz, toluene-d8, 30 °C): δ 6.5 (CH2CH3) 11.6 (C5Me5), 14.3
(CH2CH3), 35.4 (NMe2), 95.6 (C5Me5), 107.2 (C3dmap), 121.9
(C2dmap), 138.0 (C4dmap). EI-MS (12 eV, 350 °C): m/z (%) 797 (1)
[M - Et]+, 691 (42) [M - Cp*]+, 553 (80) [M - 2dmap - Et]+,
122 (100) [dmap]+.
[o-Al(Cp*)N(H)Si(t-Bu)3-dmap]2 (10). Yield: 0.82 g (85%).
Mp: 250-255 °C (dec). Anal. Found (calcd) for C58H104Al2N6Si2
(995.6 g/mol): H: 10.37 (10.53); C: 69.72 (69.97); N: 8.31 (8.43).
1H NMR (300 MHz, toluene-d8, 95 °C): δ -0.53 (s, 1H, NH),
1.29 (s, 27H, t-Bu), 1.74 (s, 15H C5Me5), 2.63 (s, NMe2), 6.36 (dd,
4
4
3JHH ) 7.2 Hz, JHH ) 3.2 Hz, 1H, C5-H-dmap), 7.56 (d, JHH
3.2 Hz, 1H, C3-H-dmap), 8.81 (d, 3JHH ) 7.2 Hz, 1H, C6-H-dmap).
13C NMR spectrum could not be recorded due to the very poor
)
[dmap-Al(Cp*)NSi(i-Pr)3]2 (6). Yield: 0.82 g (90%). Mp:
160-165 °C (dec). Anal. Found (calcd) for C52H92Al2N6Si2 (911.5
A
1
g/mol): H: 10.12 (10.17); C: 68.37 (68.52); N: 9.16 (9.22). H
solubility of 10 in organic solvents. IR (Nujol): νj 3215, 3304
(N-H) cm-1. EI-MS (16 eV, 400 °C): m/z (%) 820 (5) [M -
Cp*]+, 342 (16) [M/2 - Cp*]+, 214 (21) [N(H)Si(t-Bu)3]+, 135
(84) [Cp*]+, 121 (35) [dmap - H]+, 57 (100) [t-Bu]+.
NMR (300 MHz, toluene-d8, 95 °C): δ 1.15 (m, 21H, i-Pr), 1.71
(s), 1.83 (s), 2.19 (s) (15H, C5Me5), 2.27 (s, 6H, NMe2), 6.24 (d,
4
4JHH ) 5.9 Hz, 2H, C3/C5-H-dmap), 8.74 (d, JHH ) 4.7 Hz, 2H,
C2/C6-H-dmap). 13C NMR (75 MHz, toluene-d8, 95 °C): δ 1.4
(CHMe2), 9.3, 10.9, 17.0 (C5Me5), 15.0 (CHMe2), 38.4 (NMe2),
106.6 (C3dmap), 109.7 (C5Me5), 121.7 (C2dmap), 137.8 (C4dmap).
EI-MS (12 eV, 150-250 °C): m/z (%) 667 (1) [M - 2dmap]+,
623 (1) [M - 2dmap - i-Pr]+, 532 (6) [M - 2dmap - Cp*]+,
489 (6) [M - 2dmap - i-Pr - Cp*]+, 135 (35) [Cp*]+, 122 (100)
[dmap]+.
[o-Al(Cp*)N(H)Si(t-Bu)Me2-dmap]2 (11). Yield: 0.58 g (71%).
Mp: 225-230 °C (dec). Anal. Found (calcd) for C46H80Al2N6Si2-
2C7H8 (1011.8 g/mol): H: 9.31 (9.49); C: 71.07 (71.21); N: 8.21
1
(8.31). H NMR (300 MHz, toluene-d8, 30 °C): δ -0.36 (s, 1H,
NH), 0.18 (s, 3H, Si(t-Bu)Me2), 0.21(s, 3H, Si(t-Bu)Me2), 1.14 (s,
9H, Si(t-Bu)Me2), 1.72 (s, 15H, C5Me5), 2.63 (s, 6H, NMe2), 6.19
(dd, 3JHH ) 6.9 Hz, 4JHH ) 3.2 Hz, 1H, C5-H-dmap), 7.27 (d, 4JHH
[dmap-Al(Cp*)NSi(t-Bu)Me2]2 (7). Yield: 0.53 g (64%). Mp:
184-187 °C (dec). Anal. Found (calcd) for C46H80Al2N6Si2-C7H8
(919.4 g/mol): H: 9.43 (9.57); C: 69.03 (69.27); N: 9.08 (9.14).
1H NMR (300 MHz, toluene-d8, thf-d8 (2:1), 65 °C): δ -0.04 (s,
6 H, Si(t-Bu)Me2), 0.64 (s, 9 H, Si(t-Bu)Me2), 1.96 (s, 15 H, Cp*),
2.70 (s, 6 H, NMe2), 6.34 (br, 2 H, C3/C5-H-dmap), 8.49 (br, 2 H,
C2/C6-H-dmap). A 13C NMR spectrum could not be recorded
3
) 3.1 Hz, 1H, C3-H-dmap), 8.26 (d, 1H, JHH ) 6.8 Hz, C6-H-
dmap). 13C{1H} NMR (75 MHz, toluene-d8, 30 °C): δ 1.6 (Si(t-
Bu)Me2), 13.1 (C5Me5), 23.5 (Si(CMe3)Me2), 30.2 (Si(CMe3)Me2),
38.7 (NMe2), 104.6 (C3/C5dmap), 117.2 (C5Me5), 119.0 (C6dmap),
148.1 (C2dmap), 153.6 (C4dmap). IR (Nujol): νj 3101, 3330 (N-H)
cm-1. EI-MS (12 eV, 400-500 °C): m/z (%) 812 (1) [M - Me]+,
771 (1) [M - t-Bu]+, 691 (100) [M - Cp*]+, 135 (5) [Cp*]+, 57
(35) [t-Bu]+.
(15) Moberg, C.; Adolfson, H. In Catalysis 1: Organometallics, Vol. 4:
Compounds of Group 15 (As, Sb, Bi) and Silicon Compounts; Flemming,
I. (Hrsg.); Science of Synthesis: Houben-Weyl, Methods of Molecular
Transformations, Thieme, 2001.
[o-Al(dmap)(Cp*)N(H)Si(t-Bu)3-dmap] (12). A 0.24 g amount
of t-Bu3SiN3 (1 mmol), 0.16 g (0.25 mmol) of [Cp*Al]4, and 0.24
g (2 mmol) of dmap were heated in 50 mL of toluene at 75 °C,

1398 Organometallics, Vol. 25, No. 6, 2006
Table 3. Crystallographic Details for 3, 7, 8, 9, and 11
Schulz et al.
3
7
8
9
11
12
empirical formula
C44H84Al2N2Si2-
toluene
843.4
orthorhombic
Pbcn (no. 60)
28.6468(3)
17.3400(2)
20.9183(2)
90
C46H80Al2N6Si2-
toluene
919.4
monoclinic
C2/c (no. 15)
15.2494(2)
24.9648(4)
14.5470(3)
90
100.894(1)
90
5438.2(2)
4
C46H80Al2N6Si2
C52H92Al2N6Si2
C46H80Al2N6Si2-
2 toluene
1011.8
monoclinic
C2/c (no. 15)
15.8746(9)
14.8353(8)
25.8986(15)
90
92.351(3)
90
6094.1(6)
4
C36H62AlN5Si
molecular mass
cryst syst
space group
a [Å]
b [Å]
c [Å]
827.3
911.5
620.0
triclinic
P1h (no. 2)
11.0466(5)
13.0505(7)
17.4302(10)
102.797(2)
95.132(3)
97.467(3)
2411.4(2)
2 ) 4 × 0.5
123(2)
monoclinic
C2/c (no. 15)
30.6476(6)
9.1764(2)
24.2053(7)
90
127.180(1)
90
5423.7(2)
4
triclinic
P1h (no. 2)
8.5764(1)
12.7498(1)
17.4072(2)
101.112(1)
96.038(1)
93.532(1)
1843.9(1)
2
R [deg]
â [deg]
90
90
γ [deg]
V [Å3]
10390.9(2)
8
123(2)
Z
T [K]
123(2)
123(2)
123(2)
123(2)
radiation (λ [Å])
Mo KR
(0.71073)
0.136
Mo KR
(0.71073)
0.137
Mo KR
Mo KR
(0.71073)
0.137
Mo KR
(0.71073)
0.128
Mo KR
(0.71073)
0.118
(0.71073)
0.147
µ [mm-1
]
D
calcd [g cm-3
]
1.078
1.123
1.139
1.116
1.103
1.117
2θmax [deg]
cryst dimens [mm]
50
50
50
50
50
50
0.25 × 0.20 ×
0.55 × 0.35 ×
0.30 × 0.20 ×
0.40 × 0.15 ×
0.30 × 0.25 ×
0.50 × 0.30 ×
0.15
0.20
0.10
0.10
0.15
0.10
no. of reflns
no. of unique reflns
Rmerg
78 227
9157
0.0450
523/0
29 093
4785
0.0373
276/14
22 391
8386
0.0409
517/0
17 829
4728
0.0613
289/1
14 167
4879
0.0377
297/57
31 599
6497
0.0438
399/1
no. params refined/
restraints
R1a
0.0367
0.1058
1.058
0.277/-0.264
0.0447
0.1350
1.069
0.797/-0.491
0.0794
0.2281
1.033
1.856/-0.551
0.0438
0.0967
0.900
0.252/-0.206
0.0583
0.1705
1.053
0.463/-0.453
0.0380
0.1113
1.038
0.420/-0.220
wR2b
goodness of fitc
final max./min.
∆F, e Å-3
2 2
2 2
2
2
a R1 ) ∑(||Fo| - |Fc||)/∑|Fo| (for I > 2σ(I)). b wR2 ) {∑[w(Fo2 - Fc ) ]/∑[w(Fo ) ]}1/2
.
c Goodness of fit ) {∑[w(|Fo | - |Fc |)2]/(Nobservns - Nparams)}1/2
.
pically and hydrogen atoms by a riding model (H(N) free). The
crystallographic data of 3, 7, 8, 9, 11, and 12 (excluding structure
factors) have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication nos. CCDC-285233 (3),
CCDC-285231 (7), CCDC-285236 (8), CCDC-285232 (9), CCDC-
285234 (11), and CCDC-285235 (12). Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
Cambridge, CB21EZ, UK (fax: (+44) 1223/336033; e-mail:
deposit@ccdc.cam-ak.uk).
until gas evolution was finished. The resulting blue solution was
stored at -50 °C for 5 days, yielding colorless crystals of 12.
Yield: 0.25 g (41%). Mp: 175-185 °C (dec). Anal. Found (calcd)
for C36H62AlN5Si (620.0 g/mol): H: 9.97 (10.08); C: 69.53 (69.74);
N: 11.18 (11.29). 1H NMR (300 MHz, toluene-d8, 30 °C): δ -0.51
(s, 1H, NH), 1.02 (s, 27H, t-Bu), 1.68 (s, 15H, C5Me5), 2.65 (s,
3
4
6H, NMe2), 2.77 (s, 6H, NMe2), 6.22 (dd, JHH ) 5.9 Hz, JHH
)
3.0 Hz, 1H, C5-H-dmap), 6.31 (d, 3JHH ) 7.3 Hz, 2H, C3′/C5′-H-
4
3
dmap), 7.24 (d, JHH ) 2.8 Hz, 1H, C3-H-dmap), 8.34 (d, JHH
)
5.8 Hz, 1H, C6-H-dmap), 8.90 (d, 3JHH ) 7.3 Hz, 2H, C2′/C6′-H-
dmap). 13C{1H} NMR (75 MHz, toluene-d8, 30 °C; ) acti-
Acknowledgment. S.S. gratefully acknowledges generous
financial support by the Deutsche Forschungsgemeinschaft
(DFG), the Fonds der Chemischen Industrie (FCI), and the
Bundesministerium fu¨r Bildung, Wissenschaft, Forschung and
Technologie (BMBF).
a
vated dmap, b ) nonactivated dmap): 13.1 (C5Me5), 23.6 (CMe3),
30.5 (CMe3), 38.5, 41.1 (2 × NMe2), 105.3 (C3/C3′dmapb), 107.1
a
(C3/C5dmap ), 118.4 (C5Me5), 119.8 (C6dmapa), 127.7 (C2dmapb), 137.4
(C4dmapb), 149.3 (C2dmapa), 167.7 (C4dmapa). IR (Nujol): νj 3315
(N-H) cm-1. EI-MS (12 eV, 450 °C): m/z (%) 618 (20) [M]+,
562 (11) [M - t-Bu]+, 484 (100) [M - Cp*]+, 441 (14) [M -
t-Bu - dmap]+, 427 (9) [M - t-Bu - Cp*]+, 135 (28) [Cp*]+,
122 (31) [dmap]+, 57 (100) [t-Bu]+.
X-ray Structure Solution and Refinement. Crystallographic
data of 3, 7, 8, 9, 11, and 12 are summarized in Table 3. Figures
1-6 show ORTEP diagrams of the solid-state structures of 3, 7, 8,
9, 11, and 12. Data were collected on a Nonius Kappa-CCD
diffractometer. The structures were solved by direct methods
(SHELXS-97)16 and refined by full-matrix least-squares on F2
(SHELXL-97).17 All non-hydrogen atoms were refined anisotro-
Supporting Information Available: Tables of bond distances,
bond angles, anisotropic temperature factor parameters, and frac-
tional coordinates for 3, 7, 8, 9, 11, and 12. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM0509286
(16) Sheldrick, G. M. SHELXS-97, Program for Structure Solution: Acta
Crystallogr. Sect. A 1990, 46, 467.
(17) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; Universita¨t Go¨ttingen, 1997.