Reactions of the aluminum(I) monomer LAl [L = HC{(CMe)(NAr)}2; Ar = 2,6-iPr2C6H3] with imidazol-2-ylidene and diphenyldiazomethane. A hydrogen transfer from the L ligand to the central aluminum atom and formatio

Article abstract of DOI:10.1002/ejic.200400159

The solid-state reaction of LAl and imidazol-2-ylidene at elevated temperature (120 °C) yielded the aluminum monohydride N-heterocyclic carbene adduct [{HC[C(CH₂)NAr] (CMeNAr)}AlH-{CN(R)C₂Me ₂N(R)}] [R = iPr (1), Me (2)].

Full text of DOI:10.1002/ejic.200400159

FULL PAPER
Reactions of the Aluminum( ) Monomer LAl [L ؍ HC{(CMe)(NAr)}2; Ar ؍
I
2,6-iPr2C6H3] with Imidazol-2-ylidene and Diphenyldiazomethane. A Hydrogen
Transfer from the L Ligand to the Central Aluminum Atom and Formation of
the Diiminylaluminum Compound LAl(N؍CPh2)2
Hongping Zhu,[a] Jianfang Chai,[a] Andreas Stasch,[a] Herbert W. Roesky,*[a]
Torsten Blunck,[a] Denis Vidovic,[a] Jörg Magull,[a] Hans-Georg Schmidt,[a] and
Mathias Noltemeyer[a]
Dedicated to Professor Axel Zeeck on the occasion of his 65th birthday
Keywords: Aluminum / Carbenes / Diazo compounds / Hydrogen transfer / N ligands
The solid-state reaction of LAl and imidazol-2-ylidene at ele-
methane afforded the diiminylaluminum compound LAl(N=
vated temperature (120 °C) yielded the aluminum monohy- CPh2)2 (3), while an excess of diphenyldiazomethane re-
dride N-heterocyclic carbene adduct [{HC[C(CH2)NAr]
(CMeNAr)}AlH-{CN(R)C2Me2N(R)}] [R = iPr (1), Me (2)].
Compounds 1 and 2 have been characterized by spectros-
copic (IR, and 1H and 13C NMR), mass spectrometric, and
elemental analyses, and 1 was further characterized by X-
ray structural analysis. These experimental data indicate that
the Al−H bond is formed by hydrogen migration from one of
the methyl groups of the β-diketiminato ligand backbone.
The reaction of LAl with two equivalents of diphenyldiazo-
sulted in the formation of Ph2C=N−N=CPh2. This suggests
that Ph2C=N−N=CPh2 is initially generated and then reacts
further by oxidative addition to yield 3. The X-ray structural
analysis reveals that compound 3 contains the shortest
Al−Niminyl bond among those with a four-coordinate alumi-
num center.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
its reactivity, leading to the formation of a five-membered
AlN4 heterocycle [LAl{(NSiMe3)2N2}],
a monomeric
Monovalent group-13 species are of considerable interest
not only for their syntheses, structures, and theoretical in-
vestigations,[1] but also for their reactivity.[2] In the last dec-
ade, a variety of new reactions has been intensively explored
for generating tetrameric aluminum() compounds.[3] The
compound (Cp*Al)4 has been reported to have a remark-
able tendency to dissociate in solution and give a mono-
meric fragment in the gas phase.[4] Reactions involving such
species have also been investigated to some extent and a
number of novel compounds have been isolated and struc-
aluminum imide [LAl(N-2,6-trip2C6H3)] (trip ϭ 2,4,6-
iPr3C6H2), and a sandwich compound [(LAl)2P4] contain-
ing a P44Ϫ unit.[7] These results are markedly different from
those in which (Cp*Al)4 is used in related reactions. Obvi-
ously, the steric and electronic stabilization of the bulky β-
diketiminato ligand enables its monomeric nature and
therefore its unique chemical behavior, and allows further
investigation of its reactivity.
Imidazol-2-ylidene is a stable neutral N-heterocyclic car-
turally characterized.[5] Recently, we have prepared the first bene which has been prepared in recent years.[8] Diphenyldi-
monomeric
aluminum()
complex
LAl
[L
ϭ
azomethane can be used as an effective precursor for the
HC{(CMe)(NAr)}2, Ar ϭ 2,6-iPr2C6H3], which is stable at generation of transient :CPh2.[9] The reaction of imidazol-
room temperature.[6] Ab initio calculations show that this 2-ylidene with monovalent group-13 compounds has only
monomer possesses a nonbonded electron pair at the cen- been reported for InBr; a disproportionation reaction is ob-
tral two-coordinate Al atom and is isoelectronic with a sing- served.[10] More recently, a handful of reactions involving
let carbene. Subsequent reaction of LAl with organic azides treatment of imidazol-2-ylidene with trivalent group-13
at low temperature or with P4 at room temperature indicates species have been investigated; the N-heterocyclic carbene
functions as a Lewis base.[11] The corresponding reactions
[a]
Institut für Anorganische Chemie der Universität Göttingen,
of diphenyldiazomethane with monovalent group-13 species
have not been described so far. We now report on the reac-
tion of LAl with imdazol-2-ylidene and diphenyldiazome-
Tammannstrasse 4, 37077 Göttingen, Germany
Fax: ϩ49-551-39-3373
E-mail: hroesky@gwdg.de
4046
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400159
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051

Reactions of an Aluminum(I) Monomer Imidazol-2-ylidene and Diphenyldiazomethane
FULL PAPER
thane. The formation of the aluminum monohydride N-het-
Complex 1 was also characterized by X-ray structural
erocyclic carbene adduct of composition [{HC[C(CH2)- analysis. The molecular structure of 1 is shown in Figure 1.
NAr](CMeNAr)}AlH{CN(R)C2Me2N(R)}] [R ϭ iPr (1), Due to the poor quality of the crystal data the bond lengths
Me (2)] indicates a hydrogen transfer from the L ligand to and angles for 1 will not be discussed in detail. The quality
the aluminum center. The formation of a diiminylaluminum of the crystals gave no improvement in the refinement of the
compound [LAl(NϭCPh2)2] (3) might proceed through the structure even after recrystallization from several different
initial generation of Ph2CϭNϪNϭCPh2 followed by its solvents. Nonetheless, the structural solution of 1 offers im-
oxidative addition to LAl.
portant structural information which is in agreement with
its spectral analysis. Compound 1 is monomeric and the
central Al atom adopts a distorted tetrahedral geometry.
˚
Results and Discussion
The AlϪN bond lengths [1.844(3) and 1.853(2) A] appear
to be shorter than other AlϪNβ-diketiminato bonds
Reaction of LAl with Imdazol-2-ylidenes
[5,14]
˚
[1.875(4)Ϫ1.957(2) A],
and are closer to those found in
diamidoaluminum
AlH(NMe3)] [1.820(1) and 1.828(1) A].
monohydride [{ArN(CH2)3NAr}-
The initial reaction of LAl with 1,3-diisopropyl-4,5-di-
methylimidazol-2-ylidene was conducted in toluene in the
temperature range from 25 to 80 °C. However, due to the
low solubility of the N-heterocyclic carbene, this reaction
was not successful. Therefore both starting materials were
mixed in the solid state at 120 °C for 5 h. A softening of
1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene and a sub-
sequent color change of LAl from red black to light yellow
were observed. Extraction of the product with hot toluene
and keeping the eluate at room temperature afforded crys-
talline [{HC[C(CH2)NAr](CMeNAr)}AlH{CN(iPr)C2Me2-
N(iPr)}] (1, Scheme 1).
[13c]
˚
In the ligand
backbone, the terminal CϪC bond lengths [C(4)ϪC(5):
˚
˚
1.507(4) A; C(1)ϪC(2): 1.363(4) A] are indicative of a single
and double bond, respectively, as are the others within the
backbone [C(2)ϪC(3): 1.458(4) A; C(3)ϪC(4): 1.351(4) A].
The adjacent NϪC bond lengths [1.411(3) and 1.413(3) A]
are intermediate between NϪC double and single bonds.
˚
˚
˚
Scheme 1
Compound 1 is colorless and soluble in hot toluene and
benzene while sparingly soluble in n-hexane and pentane. It
was characterized by spectroscopic and elemental analyses.
The mass spectrum exhibits the molecular ion of 1 {m/z
(%) ϭ 624 (5) [Mϩ], 609 (40) [Mϩ Ϫ Me], 581 (100) [Mϩ
Figure 1. Molecular structure of 1; H atoms are omitted for clarity
except for the AlϪH hydrogen atom
1
Ϫ iPr]}. The H and 13C NMR spectra recorded in C6D6
are consistent with a pseudo-tetrahedral geometry and Cs
symmetry about aluminum, giving rise to six isopropyl CH
resonances and twelve diastereotopically split isopropyl
Obviously, the AlϪH hydrogen comes from one of the
CH3 resonances due to the chiral environment of the Al terminal methyl groups of the L ligand, although whether
center. The proton resonance of the β-CH3 group on the L this hydrogen transfer occurs via a proton, a hydrogen rad-
ligand backbone (δ ϭ 1.72 ppm) integrates for three pro- ical, or a hydride is not clear.
tons, while two other singlets are observed downfield (δ ϭ
The reaction of LAl with less bulky N-substituted 1,3,4,5-
3.98 and 3.30 ppm) and integrate for one proton each. The tetramethylimidazol-2-ylidene was also performed in a simi-
former corresponds to the normal terminal CH3ϪC group, lar manner (method A) to the preparation of 1 in order to
and the latter is assigned to the terminal CH2ϭC group investigate the effect of the steric bulk on the reaction prod-
which gives rise to two nonequivalent protons due to the uct. As
a result, [{HC[C(CH2)NAr](CMeNAr)}AlH-
restricted rotation about the CϭC double bond. One broad {CN(Me)C2Me2N(Me)}] (2) was obtained in a relatively
1
proton resonance centered at δ ϭ 4.80 ppm is characteristic low yield. All the spectroscopic data (IR, EI mass, and H
for aluminum hydrides.[12] The IR spectrum exhibits a single and 13C NMR) confirm a structure analogous to that of 1.
band at 1809 cmϪ1 for AlϪH absorption.[13]
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4047

H. W. Roesky et al.
FULL PAPER
Reaction of LAl with N2CPh2
Complex 3 is an orange-yellow crystalline solid that is
thermally stable, as indicated by its high melting point
(344Ϫ346 °C). The most intense ion in the EI mass spec-
trum appears at m/z ϭ 624 [Mϩ Ϫ NCPh2]; the peak at
m/z ϭ 805 (20%) is assigned to the molecular ion [Mϩ].
In the majority of organic and organometallic reactions
diphenyldiazomethane is used as a precursor for the genera-
tion of transient :CPh2 carbene.[9] Therefore, it was selected
as another electron-rich species for the reaction with LAl.
However, treatment of LAl with two equivalents of N2CPh2
under heating unexpectedly afforded [LAl(NϭCPh2)2] (3;
Scheme 2), the first example of a diiminylaluminum com-
pound. When LAl was treated with an excess of N2CPh2
under the same conditions Ph2CϭNϪNϭCPh2 was iso-
lated.[15] Therefore, we assumed that the formation of 3 pro-
ceeds by the initial generation of Ph2CϭNϪNϭCPh2 fol-
lowed by its oxidative addition to LAl. In order to test this
assumption a toluene solution of LAl was heated under re-
flux with one equivalent of Ph2CϭNϪNϭCPh2 and com-
plex 3 was formed, as expected, in an almost quantitative
yield.[16]
X-ray quality single crystals of 3 had formed from a 1:1
solvent mixture (n-hexane, diethyl ether) at 4 °C after two
days. The structural analysis unambiguously ascertains
the composition of 3. The molecular structure is shown in
Figure 2 and selected bond lengths and angles are listed in
Table 1. The central Al atom is bound to two β-diketimin-
ato nitrogen atoms and two iminyl nitrogen atoms. The
AlN4 core exhibits a distorted tetrahedral geometry with
trans-NϪAlϪN angles ranging from 97.23(18)° to
117.6(2)°. The AlϪNβ-diketiminato bond lengths [1.899(4) and
˚
1.901(4) A] are in the expected range [1.875(4)Ϫ1.957(2)
[5,14]
˚
A].
However, the AlϪNiminyl distances [1.774(4) and
˚
1.785(4) A] are the shortest yet found in four-coordinate
AlϪN complexes.[17] Comparable AlϪN bond lengths
have
only
been
observed
in
three-coordinate
[MeAl(Ndipp)]3
[18a]
˚
[trip2Al{N(H)dipp}] [1.784(3) A],
[1.782(4) A]
[18b]
and Al[N(SiMe3)2]3 [1.78(2) A].[18c] Surpris-
˚
˚
ingly, the NϪC distances of the iminyl group [1.249(6) and
[19]
˚
1.269(6) A] are shorter than that of a CϭN bond.
The
short AlϪNiminyl bond can be considered to be highly ionic,
and the shortening of the NϭC bond may be due to a
charge delocalization over the phenyl groups. The
Al(1)ϪN(4)ϪC(50) [163.4(5)°] and Al(1)ϪN(3)ϪC(30)
Scheme 2
Figure 2. Molecular structure of 3; H atoms are omitted for clarity
4048
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051

Reactions of an Aluminum(I) Monomer Imidazol-2-ylidene and Diphenyldiazomethane
FULL PAPER
(ca. 5 mL) and kept at 4 °C for 24 h to give another crop of color-
less crystals (0.25 g). Total yield of 1: 0.67 g {47%, based on
[CN(iPr)C2Me2N(iPr)]}. M.p. 298Ϫ300 °C (Ͼ250 °C decomp.). 1H
NMR (C6D6, 300 K): δ ϭ 0.38, 0.50, 0.76, 0.82, 1.19, 1.32, 1.46,
1.50, 1.53, 1.55, 1.57, 1.59 [d, 12 ϫ 3 H, CHMe2 and N(CHMe2)],
1.38, 1.62 (s, 2 ϫ 3 H, C2Me2), 1.72 (s, 3 H, β-CH3), 3.30, 3.98 (s,
2 ϫ 1 H, β-CH2), 3.28, 3.62, 4.18, 4.26 (sept, 4 ϫ 1 H, CHMe2),
4.80 (br., 1 H, Al-H), 5.60 (s, 1 H, γ-CH), 5.44, 5.62 [sept, 2 ϫ 1
H, N(CHMe2)], 7.10Ϫ7.38 (m, 6 H, Ar) ppm. 13C NMR (C6D6,
300 K): δ ϭ 9.9, 10.0 (C2Me2), 20.7, 21.1, 21.4, 22.0, 23.3, 23.7,
23.8, 24.4, 24.5, 24.7, 25.6, 25.7, 26.4, 27.1, 27.7, 28.4, 28.9
[N(CHMe2), CHMe2, CHMe2 and β-CH3], 50.9, 53.0 [N(CHMe2)],
80.8 (β-CH2), 106.6 (γ-C), 123.0, 124.5, 124.7, 124.9, 125.6, 126.6,
127.8, 128.5, 129.3, 143.4, 144.7, 145.6, 146.1, 147.2, 148.4, 149.0
(Ar, CN and C2Me2), 154.5 (Al-C) ppm. 27Al NMR ([D8]toluene,
300 K): no resonances were observed. IR (Nujol): νAlϪH ϭ 1809
cmϪ1 (m), νCϭC ϭ 1619 (m). MS (EI): m/z (%) ϭ 624 (5) [Mϩ],
609 (40) [Mϩ Ϫ Me], 581 (100) [Mϩ Ϫ iPr]. C40H61AlN4 (624.94):
calcd. C 76.87, H 9.84, N 8.97; found C 77.07, H 9.55, N 8.86.
[169.4(4)°] angles show a less-bent arrangement of the
AlϪNϭC group. The observation of two sets of resonances
for the iminyl phenyl rings in the 1H and 13C NMR spectra
suggests a restricted rotation of the phenyl rings around the
NϭC bond. This was confirmed by a high-temperature pro-
ton NMR spectral analysis (40, 60, and 80 °C), where two
corresponding sets of resonances are always observed.
˚
Table 1. Selected bond lengths (A) and angles (deg) for com-
pound 3
Al(1)ϪN(1)
Al(1)ϪN(3)
N(3)ϪC(30)
1.901(4) Al(1)ϪN(2)
1.774(4) Al(1)ϪN(4)
1.249(6) N(4)ϪC(50)
1.899(4)
1.785(4)
1.269(6)
N(1)ϪAl(1)ϪN(2)
97.23(18) N(3)ϪAl(1)ϪN(4) 116.1(2)
N(1)ϪAl(1)ϪN(3) 117.6(2)
N(2)ϪAl(1)ϪN(3) 109.5(2)
C(30)ϪN(3)ϪAl(1) 169.4(4)
N(1)ϪAl(1)ϪN(4) 107.4(2)
N(2)ϪAl(1)ϪN(4) 106.9(2)
C(50)ϪN(4)ϪAl(1) 163.4(5)
Method B:
A
suspension of LAlI2 (2.08 g, 3.0 mmol),
Conclusions
[CN(iPr)C2Me2N(iPr)] (0.54 g, 3 mmol) and finely divided potass-
ium (0.25 g, 6.3 mmol) in toluene (50 mL) was stirred vigorously
In summary, we have reacted the aluminum() monomer for 3 d at room temperature until all the potassium had disap-
peared. After filtration the orange filtrate was concentrated (ca.
20 mL) and n-hexane (20 mL) was added. The solution was kept at
4 °C for one week to afford colorless block crystals (0.72 g). The
mother liquor was further concentrated (ca. 5 mL) and kept at 4
°C for 2 d to give another crop of colorless crystals (0.32 g). Total
yield of 1·toluene: 1.04 g (48%). The IR, 1H and 13C NMR spectro-
scopic data are essentially the same as those of 1 except for one
extra molecule of toluene.
LAl with imidazol-2-ylidene and diphenyldiazomethane
and obtained the new compounds [{HC[C(CH2)NAr]-
(CMeNAr)}AlH{CN(R)C2Me2N(R)}] [R ϭ iPr (1), Me
(2)] and [LAl(NϭCPh2)2] (3). This further shows the unique
reaction behavior of LAl, and exhibits its properties as a
carbene analog. Inspired by these results, we are now ex-
ploring the reaction of LAl with metal carbonyl complexes
to compare the electronic equivalence of LAl with CO.
Synthesis
of
[{HC[C(CH2)NAr](CMeNAr)}AlH{CN(Me)C2-
Me2N(Me)}] (2): Compound 2 was prepared in a similar manner
(method A) as 1. LAlI2 (2.08 g, 3.0 mmol), finely divided potassium
(0.25 g, 6.3 mmol) and [CN(Me)C2Me2N(Me)] (0.24 g, 2.0 mmol)
were used. The extract (10 mL) was added to n-hexane (10 mL) and
kept at Ϫ26 °C for 48 h to afford colorless crystals of 2 {yield:
0.42 g, 25%, based on [CN(Me)C2Me2N(Me)]}. M.p. 252Ϫ253 °C.
1H NMR ([D8]toluene, 300 K): δ ϭ 1.45, 1.47 (s, 2 ϫ 3 H, C2Me2),
0.29, 0.30, 1.16, 1.46, 1.58, 1.60, 1.61, 1.62 (d, 8 ϫ 3 H, CHMe2),
1.69 (s, 3 H, β-CH3), 3.70, 3.75 (s, 2 ϫ 3 H, N(Me)), 3.10, 3.85 (s,
2 ϫ 1 H, β-CH2), 3.21, 3.25, 4.15, 4.21 (sept, 4 ϫ 1 H, CHMe2),
Experimental Section
All manipulations were carried out under a purified nitrogen at-
mosphere using Schlenk techniques. The solvents were dried by
standard methods. Chemicals were purchased from Aldrich or
Fluka and used as received. LAl,[6] [CN(R)C2Me2N(R)] (R ϭ Me,
iPr),[8] and N2CPh2 [9a] were prepared as described in the literature.
Elemental analyses were performed by the Analytisches Labor des
1
Instituts für Anorganische Chemie der Universität Göttingen. H 4.80 (br., 1 H, Al-H), 5.39 (s, 1 H, γ-CH), 7.04Ϫ7.38 (m, 6 H, Ar)
(300.13 MHz), 13C (125.76 MHz) and 27Al NMR (65.17 MHz)
spectra were recorded on a Bruker AM 200 or a Bruker AM 250
spectrometer and IR spectra on a Bio-Rad Digilab FTS-7 spec-
ppm. 13C NMR ([D8]toluene, 300 K): δ ϭ 7.9, 8.0 (C2Me2), 23.6,
24.0, 24.2, 24.3, 24.8, 24.9, 25.4, 25.8, 26.0, 26.4, 26.5, 27.1, 27.8,
28.7, 29.0 [N(Me), CHMe2, CHMe2 and β-CH3), 80.1 (β-CH2),
trometer. EI mass spectra were measured on a Finnigan MAT 8230 102.3 (γ-C), 122.9, 123.7, 124.2, 124.6, 124.9, 125.1, 125.3, 127.7,
or a Varian MAT CH5 instrument. Melting points were measured
in sealed glass tubes and are not corrected.
128.0, 143.2, 143.8, 145.4, 146.3, 147.4, 148.2, 149.0 (Ar, CN and
C2Me2), 155.2 (Al-C) ppm. MS (EI): m/z (%) ϭ 568 (15) [Mϩ], 553
(100) [Mϩ Ϫ Me]. IR (Nujol): νAlϪH ϭ 1810 cmϪ1 (m), νCϭC
ϭ
Synthesis of [{HC[C(CH2)NAr](CMeNAr)}AlH{CN(iPr)C2Me2-
N(iPr)}] (1). Method A: A suspension of LAlI2 (2.08 g, 3.0 mmol)
and finely divided potassium (0.25 g, 6.3 mmol) in toluene (50 mL)
was stirred vigorously for 3 d at room temperature until all the
potassium had disappeared. After filtration the dark-red filtrate
was slowly dried in vacuo and some red microcrystals of LAl were
observed to deposit on the walls of the flask. [CN(iPr)C2Me2N-
(iPr)] (0.36 g, 2 mmol) was added to the resulting solid. The mixture
was heated slowly to about 120 °C and kept for 5 h. After cooling
1616 (m). C36H53AlN4 (568.83): calcd. C 76.01, H 9.29, N 9.85;
found C 76.50, H 9.60, N 9.40.
Synthesis of LAl(NCPh2)2 (3): A solution of N2CPh2 (0.37 g,
1.90 mmol) in toluene (15 mL) was added to a solution of LAl
(0.42 g, 0.94 mmol) in toluene (25 mL) at room temperature. The
mixture was slowly heated to 60 °C and kept for 12 h; a yellow
solution developed. All volatiles were then removed in vacuo and
the residue was washed with n-hexane (5 mL) to afford an orange-
to room temperature, the yellow product was extracted with hot yellow crystalline solid of 3 (0.36 g, 48%). M.p. 344Ϫ346 °C. 1H
toluene (30 mL) and the extract was kept at room temperature for NMR (C6D6, 300 K): δ ϭ 0.82, 1.02 (d, 8 ϫ 3 H, CHMe2), 1.64
24 h to afford X-ray quality colorless block crystals, which were (s, 2 ϫ 3 H, β-CH3), 3.21 (sept, 4 ϫ 1 H, CHMe2), 5.28 (s, 1 H, γ-
collected by filtration (0.42 g). The mother liquor was concentrated CH), 6.92Ϫ7.00 (m, 2 ϫ 5 H, Ph), 7.00Ϫ7.08 (m, 2 ϫ 5 H, Ph),
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4049

H. W. Roesky et al.
FULL PAPER
7.18Ϫ7.32 (m, 6 H, Ar) ppm. 13C NMR (C6D6, 300 K): δ ϭ 23.8,
24.4, 24.9, 28.5 (CHMe2, CHMe2, β-CH3), 98.8 (γ-C), 124.5, 126.9,
127.6, 127.6, 127.9, 128.1, 128.3, 128.3, 129.4, 142.4, 143.1, 144.7
(Ar, Ph), 166.9 (NCPh2), 171.0 (CN) ppm. MS (EI): m/z (%) ϭ 805
(20) [Mϩ], 790 (30) [Mϩ Ϫ Me], 624 (100) [Mϩ Ϫ NCPh2]. IR
(Nujol): νCϭC ϭ 1667 cmϪ1 (w), νCϭN ϭ 1624, 1554 (w).
C55H61AlN4 (805.10): calcd. C 82.05, H 7.64, N 6.96; found C
82.11, H 7.74, N 7.05. X-ray quality crystals were obtained by
recrystallization from a 1:1 n-hexane/diethyl ether solution at 4 °C
for one week.
Acknowledgments
This work was supported by the Deutsche Forschungsgemeinsch-
aft, the Fonds der Chemischen Industrie and the Göttinger Akade-
mie der Wissenschaften.
[1] [1a]
P. P. Powe r, J. Chem. Soc., Dalton Trans. 1998, 2939Ϫ2951.
[1b]
P. P. Powe r, Chem. Rev. 1999, 99, 3463Ϫ3503.
[2] [2a]
W. Uhl, Rev. Inorg. Chem. 1998, 18, 239Ϫ282, and refer-
[2b]
ences cited therein.
M. N. S. Rao, H. W. Roesky, G. Anan-
X-ray Structure Determination and Refinement: The crystallo-
graphic data for compound 1 were collected on a Stoe IPDS II-
array detector system and for 3 on a StoeϪSiemensϪHuber four-
circle-diffractometer coupled to a Siemens CCD area-detector. In
both cases graphite-monochromated Mo-Kα radiation (λ ϭ 0.71073
tharaman, J. Organomet. Chem. 2002, 646, 4Ϫ14, and refer-
ences cited therein.
[3] [3a]
C. Dohmeier, C. Robl, M. Tacke, H. Schnöckel, Angew.
Chem. 1991, 103, 594Ϫ595; Angew. Chem. Int. Ed. Engl. 1991,
[3b]
30, 564Ϫ565.
E. P. Schram, N. Sudha, Inorg. Chim. Acta
[3c]
1991, 183, 213Ϫ216.
S. Schulz, H. W. Roesky, H. J. Koch,
˚
A) was used. Both structures were solved by direct methods
G. M. Sheldrick, D. Stalke, A. Kuhn, Angew. Chem. 1993, 105,
(SHELXS-96) and refined against F2 using SHELXL-97.[20,21] All
non-hydrogen atoms were located by difference Fourier synthesis
and refined anisotropically, and hydrogen atoms were included
using the riding model with Uiso tied to the Uiso of the parent
atoms, except for the AlϪH hydrogen atom, which was located by
difference Fourier synthesis and refined isotropically. A summary
of cell parameters, data collection, and structure solution and re-
finement is given in Table 2.
1828Ϫ1830; Angew. Chem. Int. Ed. Engl. 1993, 32, 1729Ϫ1731.
[3d]
C. Schnitter, H. W. Roesky, C. Röpken, R. Herbst-Irmer,
H.-G. Schmidt, M. Noltemeyer, Angew. Chem. 1998, 110,
[3e]
2059Ϫ2062; Angew. Chem. Int. Ed. 1998, 37, 1952Ϫ1955.
M. Schormann, K. S. Klimek, H. Hatop, S. P. Varkey, H. W.
Roesky, C. Lehmann, C. Röpken, R. Herbst-Irmer, M. Nolte-
[3f]
meyer, J. Solid State Chem. 2001, 162, 225Ϫ236.
M. Schie-
fer, N. D. Reddy, H. W. Roesky, D. Vidovic, Organometallics
2003, 22, 3637Ϫ3638.
CCDC-231677 (for 1) and -231678 (for 3) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
[or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; fax: ϩ44-1223-336-033; E-mail:
deposit@ccdc.cam.ac.uk].
[4] [4a]
J. Gauss, U. Schneider, R. Ahlrichs, C. Dohmeier, H.
[4b]
Schnöckel, J. Am. Chem. Soc. 1993, 115, 2402Ϫ2408.
A.
Haaland, K.-G. Martinsen, S. A. Shlykov, H. V. Volden, C.
Dohmeier, H. Schnöckel, Organometallics 1995, 14,
3116Ϫ3119.
[5] [5a]
C. Dohmeier, H. Schnöckel, C. Robl, U. Schneider, R.
Ahlrichs, Angew. Chem. 1994, 106, 225Ϫ227; Angew. Chem.
Int. Ed. Engl. 1994, 33, 199Ϫ201. [5b] S. Schulz, L. Häming, R.
Herbst-Irmer, H. W. Roesky, G. M. Sheldrick, Angew. Chem.
1994, 106, 1052Ϫ1054; Angew. Chem. Int. Ed. Engl. 1994, 33,
969Ϫ971. [5c] C. Dohmeier, H. Krautscheid, H. Schnöckel, An-
Table 2. Crystallographic data for compounds 1 and 3
1
3
gew. Chem. 1994, 106, 2570Ϫ2571; Angew. Chem. Int. Ed. Engl.
[5d]
1994, 33, 2482Ϫ2483.
S. Schulz, T. Schoop, H. W. Roesky,
Empirical formula
Formula mass
Temp. (K)
C40H61AlN4
624.91
133(2)
C55H61AlN4
805.06
203(2)
L. Häming, A. Steiner, R. Herbst-Irmer, Angew. Chem. 1995,
107, 1015Ϫ1016; Angew. Chem. Int. Ed. Engl. 1995, 34,
[5e]
919Ϫ920.
S. Schulz, A. Voigt, H. W. Roesky, L. Häming,
Crystal system
Space group
monoclinic
P21/c
10.161(2)
17.380(4)
22.274(5)
orthorhombic
P2(1)2(1)2(1)
12.285(2)
12.981(2)
30.001(6)
R. Herbst-Irmer, Organometallics 1996, 15, 5252Ϫ5263.
C. Cui, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, H. Hao,
F. Cimpoesu, Angew. Chem. 2000, 112, 4444Ϫ4446; Angew.
Chem. Int. Ed. 2001, 39, 4274Ϫ4276.
[6]
[7]
˚
a (A)
˚
b (A)
c (A)
[7a] C. Cui, H. W. Roesky, H. Hao, H.-G. Schmidt, M. Nolteme-
˚
α (°)
β (°)
γ (°)
yer, Angew. Chem. 2000, 112, 4705Ϫ4707; Angew. Chem. Int.
[7b]
101.89(3)
Ed. 2000, 39, 4531Ϫ4533.
N. J. Hardman, C. Cui, H. W.
Roesky, W. H. Fink, P. P. Power, Angew. Chem. 2001, 113,
3
[7c]
˚
V (A )
3849.1(13)
4
1.078
0.084
1386
4784.4(16)
4
1.118
0.082
1728
2230Ϫ2232; Angew. Chem. Int. Ed. 2001, 40, 2172Ϫ2174.
Z
Y. Peng, H. Fan, H. Zhu, H. W. Roesky, J. Magull, Angew.
Chem. 2004, 116, 3525Ϫ3527; Angew. Chem. Int. Ed. 2004,
43, 3443Ϫ3445.
ρc (Mg/m3)
µ (mmϪ1
F(000)
)
[8]
N. Kuhn, T. Kratz, Synthesis 1993, 561Ϫ562.
[9] [9a]
θ range (°)
Index ranges
1.87Ϫ24.71
3.55Ϫ25.01
H. Staudinger, E. Anthes, F. Pfenninger, Ber. Dtsch. Chem.
[9b]
Ϫ11 Յ h Յ 11 0 Յ h Յ 14
Ϫ20 Յ k Յ 20 Ϫ1 Յ k Յ 15
Ϫ26 Յ l Յ 24 Ϫ35 Յ l Յ 35
Ges. 1916, 49, 1928Ϫ1941.
K. Ziegler, H.-G. Gellert, H.
Lehmkuhl, W. Pfohl, K. Zosel, Justus Liebigs Ann. Chem. 1960,
[9c]
629, 1Ϫ13.
W. A. Herrmann, J. L. Hubbard, I. Bernal, J.
No. of reflections collected
No. of independent reflns. (Rint
33356
4675
D. Korp, B. L. Haymore, G. L. Hillhouse, Inorg. Chem. 1984,
)
6560 (0.1511) 4658 (0.0188)
23, 2978Ϫ2983.
[10]
No. of data/restraints/parameters 6560/0/424
4658/0/555
1.096
R. J. Baker, R. D. Farley, C. Jones, M. Kloth, D. M. Murphy,
Chem. Commun. 2002, 1196Ϫ1197.
GoF/F2
0.911
R1,[a] wR2[b]
[I Ͼ 2σ (I)]
0.0541, 0.0974 0.0614, 0.1530
[11] [11a] A. J. Arduengo III, H. V. R. Dias, J. C. Calabrese, F. David-
[11b]
son, J. Am. Chem. Soc. 1992, 114, 9724Ϫ9725.
X.-X. Li,
R1,[a] wR2[b] (all data)
0.1198, 0.1096 0.0848, 0.1740
J. Su, G. H. Robinson, Chem. Commun. 1996, 2683Ϫ2684. [11c]
largest difference peak/hole (e·AϪ3) 0.313/Ϫ0.271 0.271/Ϫ0.282
C. J. Carmalt, A. H. Cowley, Adv. Inorg. Chem. 2000, 50, 1Ϫ61,
˚
[11d]
and references cited therein.
R. J. Baker, A. J. Davies, C.
[a]
[b]
2
2 2
2
R ϭΣ||Fo| Ϫ |Fc||/Σ|Fo|. wR2 ϭ [Σw(Fo Ϫ Fc ) /Σw(Fo )]1/2
.
Jones, M. Kloth, J. Organomet. Chem. 2002, 656, 203Ϫ210. [11e]
4050
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051

Reactions of an Aluminum(I) Monomer Imidazol-2-ylidene and Diphenyldiazomethane
FULL PAPER
[16]
J. D. Gorden, C. L. B. Macdonald, A. H. Cowley, J. Or-
ganomet. Chem. 2002, 643Ϫ644, 487Ϫ489.
A mixture of equivalent amounts of LAl and Ph2CϭNϪNϭ
CPh2 in toluene (20 mL) was allowed slowly to heat to reflux
and kept for 3 h. After cooling to room temperature, the solu-
tion was dried in vacuo and the residue was washed with n-
hexane (5 mL) to give an orange-yellow crystalline solid in al-
most quantitative (yield, Ͼ 90%). The melting point and the
spectroscopic data (EI mass and IR) are essentially the same
as those of 3.
[12]
C. Cui, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, Inorg.
Chem. 2000, 29, 3678Ϫ3689.
[13] [13a]
A. H. Cowley, H. S. Isom, A. Decken, Organometallics
[13b]
1995, 14, 2589Ϫ2592.
C. Klein, H. Nöth, M. Tacke, M.
Thomann, Angew. Chem. 1993, 105, 923Ϫ926; Angew. Chem.
[13c]
Int. Ed. Engl. 1993, 32, 886Ϫ889.
H. Zhu, J. Chai, H. W.
[17]
Roesky, M. Noltemeyer, H.-G. Schmidt, D. Vidovic, J. Magull,
Eur. J. Inorg. Chem. 2003, 17, 3113Ϫ3119.
C. Cui, S. Köpke, R. Herbst-Irmer, H. W. Roesky, M. Nolteme-
yer, H.-G. Schmidt, B. Wrackmeyer, J. Am. Chem. Soc. 2001,
123, 9091Ϫ9098.
The azine Ph2CϭNϪNϭCPh2 was obtained as colorless crys-
tals with a melting point of 174 °C. Its spectroscopic data (EI
mass, IR, 1H and 13C NMR) and elemental analysis confirmed
the composition. It is well-known that many salts and com-
plexes of CuI and CuII are used as catalysts for the decompo-
sition of diphenyldiazomethane. The reaction of LAl and di-
P. J. Brothers, P. P. Power, Adv. Organomet. Chem. 1996, 39,
1Ϫ69.
[14]
[15]
[18] [18a]
K. M. Waggoner, H. Hope, P. P. Power, Angew. Chem.
1988, 100, 1765Ϫ1766; Angew. Chem. Int. Ed. Engl. 1988, 27,
[18b]
1699Ϫ1700.
K. M. Waggoner, P. P. Power, J. Am. Chem.
[18c]
Soc. 1991, 113, 3385Ϫ3393.
rick, J. Chem. Soc. A 1969, 2279Ϫ2293.
G. M. Sheldrick, W. S. Sheld-
[19]
For the structural model X1,2ϪCϭNϪY, the range of CϭN
double-bond lengths is 1.279Ϫ1.302 A. [19a] F. H. Allen, P. Ken-
˚
nard, D. G. Waston, L. Brammer, A. G. Orpen, R. Taylor, J.
Chem. Soc., Perkin Trans. 2 1987, S1ϪS19.
G. M. Sheldrick, SHELXS-90, Program for Structure Solution,
Acta Crystallogr., Sect. A 1990, 46, 467Ϫ473.
G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
Refinement, University of Göttingen, Germany, 1997.
Received February 25, 2004
[20]
[21]
phenyldiazomethane to give Ph2CϭNϪNϭCPh2 may indicate
[15a]
that the LAl plays a catalytic role.
W. Kirmse, Carbene
Chemistry 2nd edition, Academic Press, New York, 1971,
[15b]
85Ϫ128, and references cited therein.
D. Bethell, K. L.
Handoo, S. A. Fairhurst, L. H. Sutcliffe, J. Chem. Soc., Chem.
Commun. 1977, 326Ϫ328.
Eur. J. Inorg. Chem. 2004, 4046Ϫ4051
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4051