Aluminium complexes of a sterically demanding bis(iminophosphorane) methandiide

Article abstract of DOI:10.1071/CH13229

The reaction of the sterically demanding bis(iminophosphorane)methane, {DipN≤P(Ph2)}2CH2, H2L 1 (where Dip≤2,6-iPr2C6H3), with one or two equivalents of AlMe3 in toluene under varying conditions led to the methanide complex [HLAlMe2] 4, and the methandiide complex [L(AlMe2)2] 5, respectively. Iterative iodination of complex 5 with I2 in toluene yielded the complexes [L(AlMeI)2] 6 and [L(AlI2)2] 7. The complexes 4-7 were structurally characterised. The methanide 4 forms a puckered six-membered ring without Al-C(methanide) contact and the complexes 5 and 6 show coordination of the methandiide ligand to two Al atoms forming two four-membered rings on the central spirocyclic carbon centre. Complex 7 shows an asymmetric coordination mode of the two Al centres to the methandiide ligand in the solid state with an almost planar, severely distorted three-coordinate methandiide carbon atom and only one short Al-C bond.

Full text of DOI:10.1071/CH13229

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 1219–1225
Full Paper
http://dx.doi.org/10.1071/CH13229
Aluminium Complexes of a Sterically Demanding
Bis(iminophosphorane)methandiide
A B
,
B C
,
Christian P. Sindlinger
and Andreas Stasch
A
Institut fur Anorganische Chemie, Auf der Morgenstelle 18, 72076 Tubingen, Germany.
¨
¨
B
School of Chemistry, Monash University, PO Box 23, Melbourne, Vic. 3800, Australia.
C
Corresponding author. Email: Andreas.Stasch@monash.edu
The reaction of the sterically demanding bis(iminophosphorane)methane, {DipN¼P(Ph2)}2CH2, H2L 1 (where Dip ¼
2,6-iPr2C6H3), with one or two equivalents of AlMe3 in toluene under varying conditions led to the methanide complex
[HLAlMe2] 4, and the methandiide complex [L(AlMe2)2] 5, respectively. Iterative iodination of complex 5 with I2 in
toluene yielded the complexes [L(AlMeI)2] 6 and [L(AlI2)2] 7. The complexes 4–7 were structurally characterised. The
methanide 4 forms a puckered six-membered ring without Al-C(methanide) contact and the complexes 5 and 6 show
coordination of the methandiide ligand to two Al atoms forming two four-membered rings on the central spirocyclic
carbon centre. Complex 7 shows an asymmetric coordination mode of the two Al centres to the methandiide ligand in the
solid state with an almost planar, severely distorted three-coordinate methandiide carbon atom and only one short Al–C
bond.
Manuscript received: 1 May 2013.
Manuscript accepted: 30 May 2013.
Published online: 27 June 2013.
Introduction
have also undergone reactions with (unsaturated) organic sub-
strates though this reactivity has been described as modest[1b]
taking the high negative charge of the methandiide into consid-
eration. As sterically demanding and anionic ligands, these
substance classes have also found their way into stabilising rare
bonding modes and oxidation states of metal ions. For instance,
some Zn–Zn bonded complexes of substituted bis(iminopho-
sphorane)methanides were recently obtained by the facile reac-
tion of Cp*ZnZnCp* with CH-acidic bis(iminophosphorane)
methanes.[2]
In recent years, several aluminium complexes of bis
(iminophosphorane)methanides and -methandiides have been
reported,[3–7] as well as some chalcogen analogues and related
complexes.[8–15] Along the study of metal-ligand, and especially
metal-carbon interactions, these complexes are also of interest
as transition metal free olefin polymerisation pre-catalysts,[4,7]
e.g. compound 2 (Fig. 2), and have been found to add the
methandiide fragment of 2 to heterocumulenes,[5] yielding 3
(Fig. 2). Herein, we report on new AlIII complexes derived from
the sterically demanding compound 1, their conversion to iodide
complexes, and initial attempts to synthesise novel low oxida-
tion state derivatives.
Substituted bis(iminophosphorane)methanes (Fig. 1, where
Mes ¼ mesityl (2,4,6-trimethylphenyl) and Dip ¼ 2,6-diisopro-
pylphenyl) such as H2L 1 (R ¼ Dip), and related sterically less
demanding chalcogen analogues, are CH acidic compounds that
can be deprotonated to substituted methanide (Fig. 1a) com-
plexes and even doubly deprotonated forming substituted
methandiide (Fig. 1b, c) complexes with suitable organometallic
reagents, and can undergo subsequent metathesis chemistry.[1]
The methandiide complexes are of particular interest because of
their unusual metal-carbon interactions including a varying
degree of metal-carbon double bonding. In complexes with
electropositive metal ions, the majority of charge accumulation
on the metal-carbon fragment is located on the methandiide
carbon atom having typical charges of , ꢀ1.7 to ꢀ1.9.[1] This
dianionic charge (see Fig. 1c) is mainly located in two orbitals
that can be described for most compounds as approximately sp2
and p in character. The highly ionic character of the metal-
carbon interaction for electropositive metal ions has led to
descriptions that favour a methandiide formulation rather than a
covalent metal carbene bond. In addition, these substituted
methanide and methandiide ligands afforded a range of metal
complexes with different and flexible metal-ligand coordina-
tion modes to the anionic C and N atoms.[1] For bis(imino-
Results and Discussion
phosphorane)methandiide complexes,
a
formulation with
The reaction of H2L 1 with one equivalent of AlMe3 in toluene
afforded the methanide complex [HLAlMe2] 4 in good yield, see
Fig. 3. The complex was structurally characterised (see Fig. 4),
crystallographic details are summarised in Table 1, and selected
interatomic distances and angles are collected in Table 2.
The structure of complex 4 shows the expected distorted
four-coordinate environment around the Al3þ centre with a
puckered six-membered ring similar to previously characterised
alternating negative and positive charges and a dianionic central
carbon atom (Fig. 1c) seems to be the appropriate description.[1]
The majority of investigations into bis(iminophosphorane)
methanide and methandiide complexes have been carried out
with trimethylsilyl and mesityl substituents on the nitrogen
atoms, while complexes with the more sterically demanding
Dip aryl group are less common.[1] Methandiide complexes
Journal compilation Ó CSIRO 2013
www.publish.csiro.au/journals/ajc

1220
C. P. Sindlinger and A. Stasch
R
R
(a)
(b)
(c)
R
2ꢀ
ꢀ
ꢀ
N
Ph
P
N
N
R
R
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
ꢂ
P
P
P
P
N
N
Ph
Ph
CH2
N
2ꢀ
H
C
C
N
C
P
P
R
ꢂ
P
Ph
Ph
ꢀ
N
R
R
R ꢁ SiMe3, Mes, Dip
H2L 1, R ꢁ Dip
Fig. 1. Bis(iminophosphorane)methane, -methanide (a) and -methandiide (b, c).
geometry as found for compound 5. The two Al-C-P-N least-
square-planes intersect at an angle of ,68.28. The two large iodo
ligands are arranged in a trans-like fashion on the LAl2 core
placing them almost as far as possible away from each other with
an I-Al ꢁ ꢁ ꢁ ꢁ Al-I torsion angle of ,1678. The bond lengths and
angles are comparable to those of 5 though with slightly
shortened Al–N and Al–C(ligand) distances and slightly elon-
gated Al-CH3 and P–C(ligand) distances. The bond lengths ratio
M–Cmethandiide/M–N for some dimeric complexes of the anionic
ligand {(Me3Si)NPPh2}C2ꢀ have been compared and suggest
increasingly covalent metal-ligand interactions with a lower
ratio (,1.0).[1b] Complexes 5 and 6 show M–C/M–N ratios of
,1.13 and 1.14, respectively, which are close to the ratios for
group 2 metal methandiides of ,1.11.[1b] If comparisons can be
drawn with the complexes reported herein, then this underpins
the highly ionic character of the metal-ligand interaction in 5
and 6. Complex 6 shows four broad resonances for the iPr
methyl protons, two broad resonances for the iPr methine
protons and a singlet for the Al-methyl protons at 278C in the
1H NMR spectrum. Upon heating, the iPr protons broaden
significantly and start merging at around 608C.
The first bis-iodination (5 to 6) is rapid at 08C. Further
iodination is slowed down and proceeds slowly at room tempera-
ture and a small excess of I2 is required in the reaction mixture.
After completion, workup afforded brown-yellow crystalline
[L(AlI2)2] 7 in moderate yield, see Fig. 5. Complex 7 ꢁ 0.5
C6H14 crystallised with a full molecule in the asymmetric unit
(Fig. 6; see also Tables 1 and 2 for further details). The two Al
atoms coordinate to the methandiide ligand in an asymmetric
fashion. Complex 7 comprises one Al-C-P-N four-membered
ring and an Al-C-P-N-Al-I six-membered ring with a bridging
iodide between the two Al centres. One Al–C bond is broken
compared with the structures of 5 and 6 and replaced with an
additional Al–I interaction to still yield two four-coordinate Al
centres. This change in coordination environment is likely caused
by an increased steric demand of the iodide ligands and possibly
by a different ionic character of the AlIþ2 fragments compared
with the AlMeþ2 or AlMeIþ fragments in 5 and 6, respectively. In
addition, substituted bis(iminophosphorane)methanides and
-methandiides have previously been described as very flexible
ligands[1] and changes in the coordination mode are likely low in
energyand could tosome degree beinfluencedbycrystal packing
effects. The Al–I bond lengths for the bridging iodide are
naturally longer compared with those for the terminal Al–I bonds,
and the Al–I2 distance is somewhat shorter for Al1 than for Al2.
The asymmetric coordination and the bond lengths suggest that
[L(AlI2)2] 7 approaches an intramolecularly ionised [L(AlIþ)
(AlIꢀ3 )] formulation. It is worthy to mention that the olefin
polymerisation activity generated from pre-catalyst 2 stems from
Me3Si
Me3Si
AIMe2
N
N
Ph
Ph
Ph
Ph
Ph
Ph
AIMe2
AIMe2
2
P
P
N
C
R
R ꢁ Cy, X ꢁ NCy
R ꢁ Ad, X ꢁ O
P
P
C
C
Ph
Ph
X
AIMe2
N
N
Me3Si
Me3Si
3
Fig. 2. Previously reported aluminium complexes 2 and 3; Cy ¼ cyclo-
hexyl, Ad ¼ 1-adamantyl.
examples,[3,6,7] though some known examples are found in a
boat conformation. The Al–N and Al–C bond lengths are very
similar to those found for related methanide-AlMe2 com-
plexes[6,7] though the Al–N bond lengths are longer than in
related methanide-AlX2 (X ¼ Cl, Br, I) complexes.[3,7] The
spectroscopic data of 4 is as expected and similar to related
examples. Heating complex 4 in boiling toluene did not lead to
further methane elimination which could form a mono-
aluminium methandiide complex. Treatment of complex 4 with
a second equivalent of AlMe3 in toluene at ,1008C or under
reflux afforded the bisaluminium methandiide complex
[L(AlMe2)2] 5 in good yield (Fig. 3). The crystal structure of
complex 5 ꢁ 3C7H8 (Fig. 4, Table 1, Table 2) shows two spiro-
cyclic Al-C-P-N rings about the central carbon atom, as found
for the previously characterised related example 2.[6] The least-
square-planes of the two four-membered Al-C-P-N rings are
twisted by ,72.48 which is close to the value for the related
complex 2 (,75.38). At 278C, the 1H NMR spectrum of 5 dis-
plays two very broad resonances for the iPr methyl protons and
one broad resonance for the iPr methine protons. These two
resonances merge at a coalescence temperature of ,408C to one
(broad) resonance and one sharp septet is observed for the iPr
methine protons. Between 278C and 708C, two singlets with an
integration of 6H each are found for the Al-methyl protons, the
broader resonance appears at highest field.
In order to substitute the Al-methyl groups in compound 5
with halide groups, we treated a solution of 5 with iodine (I2) in
toluene, see Fig. 5. The reaction was carried out as a titration
experiment, following the decolourisation of iodine. The reac-
tion proceeds rapidly at 08C for the addition of the first two
equivalents of I2 and the mixed iodo methyl complex
[L(AlMeI)2] 6 can be isolated and structurally characterised
(Fig. 6, Table 1, Table 2). Complex 6 ꢁ 2 C7H8 crystallised with a
full molecule in the asymmetric unit and shows the same overall

Main Group Chemistry
1221
Dip
P
Dip
P
CH3
N
Ph
P
Dip
AI
N
Ph
Ph
Ph
Ph
Ph
Ph
AI
AI
N
N
AIMe3
AIMe3, Δ
ꢀMeH
CH3
CH3
CH3
CH3
Ph
Ph
CH2
H
C
C
ꢀMeH
P
P
P
Ph
Ph
N
Dip
CH3
Ph
N
Dip
Dip
1
4
5
Fig. 3. Synthesis of complexes 4 and 5.
(a)
(b)
Fig. 4. Molecular structures of complexes (a) 4 and (b) 5 ꢁ 3C7H8 (30 % thermal ellipsoids). Hydrogen atoms with the
exception of C(1)H on 4 and solvent molecules are omitted for clarity.
its conversion to a cationic complex after a methyl anion
abstraction in solution.[4] The methandiide carbon atom is
three-coordinate with one acute (Al1-C1-P1 87.93(13)8) and
two obtuse (Al1-C1-P2 135.74(14)8 and P1-C1-P2 134.01(18)8)
angles and is very close to a planar geometry (sum of angles
that low energy exchange or isomerisation processes are respon-
sible for the methandiide coordinated AlIþ2 fragments in solution
and further supports the high flexibility of the ligand class.[1]
The 13C{1H} NMR spectra show a triplet for the methanide
carbon atom of 4 at d 15.1 with a large 1JC-P coupling constant of
138 Hz, though no comparable resonances were observed for the
methandiide complexes 5–7 despite long acquisition times. This
is not surprising given the coordination of this quaternary carbon
˚
,3588). Notable is the short Al1–C1 bond length of 1.942(3)A
˚
incomplex 7, thatis,0.2 A shorterthanthe Al–Cdistances tothe
four-coordinate methandiide centres in 5 and 6 (2.126(3)-2.1607
atom to two 27Al nuclei (I ¼ 5/2) and further splitting by two 31
P
nuclei. This has also previously been observed for the related
˚
(13)A). To the best of our knowledge, the coordination of the two
Al centres to the methandiide in the monomeric complex 7
represents a new structurally characterised coordination mode
for this ligand class. A somewhat related asymmetric coordina-
tion mode of two metals to one methandiide unit has been
characterised for the dimeric structure [[(Ph2PNSiMe3)(Ph2PS)
CAlMe]2].[9]
complex 2.[6]
1
We carried out small scale experiments, monitored by H
and 31P{1H} NMR spectroscopy, of complex 5 with I2 in
various stoichiometries including those with approximately
one and three equivalents of I2 in [D6]benzene, respectively.
These reactions afforded product mixtures and we assigned two
broad resonances at ,d 23 and ,d 33 (31P{1H} NMR) to the
mixed species [L(AlMe2)(AlMeI)], and two doublets at d 28.3
and d 36.1 (br) with J ¼ 36.6 Hz for [L(AlMeI)(AlI2)]. These
experiments also confirmed the generation of MeI (d 1.44 by
1H NMR) as the by-product in the iodination reactions. The end
product [L(AlI2)2] 7 can be synthesised in good yield according
to these NMR experiments and work-up and possibly separa-
tion from small amounts of excess I2 or polyiodinated products
(e.g. with Iꢀ3 ligands) only seemed to limit the isolated yield for
the larger scale reactions. Initial reduction experiments of
complexes 6 and 7 with potassium metal have so far only led
to product mixtures. The attempted reduction of these com-
pounds with the stoichiometric and hydrocarbon-soluble
dimeric magnesium(I) complex[16] [[(Mesnacnac)Mg]2]
The 1H NMR spectrum of compound 7 largely resembles that
of complex 6 though without the Al-CH3 peak and slightly
shifted resonances. The four broad resonances for the iPr methyl
protons and two broad resonances for the iPr methine protons
broaden at elevated temperatures and the two methine reso-
nances merge at ,658C. Complexes 4 (d 30.5), 5 (d 31.6),
6 (d 40.1), and 7 (d 32.9) all display one sharp resonance in their
31P{1H} NMR spectra. This, together with 1H NMR data, shows
average symmetric solution behaviour for complex 7. We
further investigated this situation for the asymmetrically coor-
dinated complex [L(AlI2)2] 7 with a low temperature NMR
1
study and found broadening of the resonances in the H and
31P{1H} NMR spectra at very low temperatures in deuterated
toluene down to ꢀ758C, the limit of this experiment, though no
splitting of the 31P{1H} resonance was observed. This shows

1222
C. P. Sindlinger and A. Stasch
Table 1. Selected crystallographic data for compounds 4 7
]
Compound
4
5 ꢁ 3C7H8
6 ꢁ 2 C7H8
7 ꢁ 0.5 C6H14
CCDC number
Empirical formula
Formula weight
T [K]
936379
936380
936381
936382
C51H61AlN2P2
790.94
C74H90Al2N2P2
1123.38
C65H76Al2I2N2P2
1254.98
C52H61Al2I4N2P2
1337.53
173(2)
100(2)
123(2)
100(2)
˚
l [A]
Crystal system
0.71073
0.71068
0.71073
0.71080
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/c
Space group
˚
a [A]
˚
b [A]
9.4621(19)
24.198(5)
19.854(4)
90
10.298(2)
27.243(5)
23.307(5)
90
13.6466(3)
21.7276(3)
20.5625(4)
90
12.920(3)
18.830(4)
22.100(4)
90
˚
c [A]
a [8]
b [8]
g [8]
100.69(3)
90
100.40(3)
90
90.573(2)
90
96.39(3)
90
3
˚
V [A ]
4467.0(15)
4
6431(2)
6096.6(2)
4
5343.2(19)
4
Z
4
r [Mg mꢀ3
]
1.176
1.160
1.367
1.663
m [mmꢀ1
F(000)
]
0.153
0.138
1.153
2.461
1696
2416
2568
2620
Crystal size [mm3]
Theta range [8]
Index ranges
0.30 ꢂ 0.12 ꢂ 0.12
3.09 to 25.99
ꢀ11 # h # 11,
ꢀ29 # k # 29,
ꢀ24 # l # 24
17210
0.04 ꢂ 0.03 ꢂ 0.03
1.16 to 27.09
ꢀ13 # h # 12,
ꢀ28 # k # 28,
ꢀ28 # l # 28
91715
0.50 ꢂ 0.45 ꢂ 0.40
1.98 to 28.00
ꢀ18 # h # 18,
ꢀ28 # k # 18,
ꢀ27 # l # 27
33728
0.04 ꢂ 0.03 ꢂ 0.02
1.42 to 27.18
ꢀ16 # h # 16,
ꢀ24 # k # 24,
ꢀ28 # l # 28
84700
Refl. collected
Indep. refl.
8746 [R(int) ¼ 0.0401]
99.8 %
13803 [R(int) ¼ 0.0597]
99.2 % (at 25.008)
13803/80/864
1.055
14697 [R(int) ¼ 0.0248]
99.9 %
11858 [R(int) ¼ 0.0562]
99.7 %
Completeness to theta max
Data/restraints/parameter
GooF
6280/0/369
1.027
14697/52/735
1.148
11858/9/596
1.067
Final R indices, [I .2sigma(I)] R1 ¼ 0.0454, wR2 ¼ 0.1004 R1 ¼ 0.0428, wR2 ¼ 0.01143 R1 ¼ 0.0400, wR2 ¼ 0.0975 R1 ¼ 0.0330, wR2 ¼ 0.0832
R indices (all data)
R1 ¼ 0.0788, wR2 ¼ 0.1149 R1 ¼ 0.0458, wR2 ¼ 0.1167
R1 ¼ 0.0567, wR2 ¼ 0.1080 R1 ¼ 0.0370, wR2 ¼ 0.0853
1.931 and ꢀ1.419 0.953 and ꢀ1.593
Largestꢀd3iff. peak and hole
˚
0.331 and ꢀ0.433
0.375 and ꢀ0.582
[e ꢁ A
]
˚
Table 2. Selected interatomic distances [A] and angles [8] for compounds 4 7
(av) describes an average value
]
4
5 ꢁ 3C7H8
6 ꢁ 2 C7H8
7 ꢁ 0.5 C6H14
M–N/I
Al1–N1: 1.9461(18)
Al1–N2: 1.9461(17)
Al1–N1: 1.9250(11)
Al2–N2: 1.9095(12)
Al1–N1: 1.865(3)
Al2–N2: 1.864(2)
Al1–I1: 2.6115(9)
Al2–I2: 2.5830(10)
Al1–N1: 1.858(3)
Al2–N2: 1.854(3)
Al1–I1: 2.5267(10)
Al1–I2: 2.6145(11)
Al2–I2: 2.6840(12)
Al2–I3: 2.5067(10)
Al2–I4: 2.5271(11)
Al1–C1: 1.942(3)
Al2 ꢁ ꢁ ꢁ ꢁ C1: ca. 3.228
M–C
Al1 ꢁ ꢁ ꢁ C1: ca. 3.383
Al1–C1: 2.1565(14)
Al2–C1: 2.1607(13)
Al-CH3: 1.972 (av)
P1–N1: 1.6323(11)
P2–N2: 1.6300(11)
P1–C1: 1.7552(13)
P2–C1: 1.7399(13)
P1-C1-P2: 126.48(7)
Al1-C1-Al2: 100.51(5)
Al1–C1: 2.134(3)
Al2–C1: 2.126(3)
Al–C50: 2.015(3)
P1–N1: 1.640(2)
Al-CH3: 1.977 (av)
P–N
P–C
P1–N1: 1.6452(18)
P2–N2: 1.6424(17)
P1–C1: 1.702(2)
P2–C1: 1.708(2)
P1-C1-P2: 124.47(12)
–
P1–N1: 1.666(3)
P2–N2: 1.640(2)
P2–N2: 1.670(3)
P1–C1: 1.775(3)
P1–C1: 1.727(3)
P2–C1: 1.784(3)
P2–C1: 1.695(3)
P–C–P
P1-C1-P2: 124.08(16)
Al1-C1-Al2: 100.40(12)
P1-C1-P2: 134.01(18)
Al1-C1 ꢁ ꢁ ꢁ ꢁ Al2: ca. 87.98
M–C–M
(
Mesnacnac ¼ [HC(MeCNMes)2])[17] at elevated temperatures
and the bis(iminophosphorane)methandiide aluminium com-
plexes [L(AlMe2)2] 5, [L(AlMeI)2] 6, and [L(AlI2)2] 7, using a
sterically demanding methandiide ligand. The latter two com-
plexes were prepared in a facile manner from complex 5 and
iodine. The single crystal structures of complexes 4–7
were determined and support largely ionic metal-ligand inter-
actions and flexible coordination modes for the employed
also led to product mixtures and no reduced pure compound has
been isolated so far.
Conclusions
We have successfully synthesised and characterised the bis(imi-
nophosphorane)methanide aluminium complex [HLAlMe2] 4

Main Group Chemistry
1223
Dip
Dip
P
Dip
P
I
I
CH3
I
N
C
N
N
C
N
N
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
AI
AI
AI
AI
AI
P
CH3
CH3
CH3
CH3
CH3
ꢂ 2 I2
ꢂ 2 I2
C
I
ꢀ 2MeI
ꢀ 2MeI
Ph
Ph
Ph
Ph
P
P
I
P
AI
N
I
Dip
Dip
Dip
7
5
6
Fig. 5. Synthesis of complexes 6 and 7.
(a)
(b)
Fig. 6. Molecular structures of compounds (a) 6 ꢁ 2 C7H8 and (b) 7 ꢁ 0.5 C6H14 (30 % thermal ellipsoids). Hydrogen atoms and solvent molecules have been
omitted for clarity.
bis(iminophosphorane)methandiide ligand. An unusual asym-
metric coordination mode of the Al atoms to the methandiide
ligand in compound 7 was observed in the solid state with an
almost planar, severely distorted three-coordinate methandiide
carbon atom and one short Al–C interaction.
1.84 mmol, 1.0 equiv.) in toluene (20 mL). The mixture was
stirred at room temperature overnight and at ,608C for 4 h. The
mixture was concentrated (to ,8 mL) while still warm, hexane
(15 mL) was added and cooled to 48C. Precipitated product was
filtered off and the supernatant solution was stored at ꢀ308C to
yield a second crop of 4 (1.18 g, 81 %); (Found: C 76.8, H 7.6, N
3.5. C51H61AlN2P2 requires C 77.4, H 7.8, N 3.5 %); 1H NMR
([D6]benzene, 400.2 MHz): d 0.01 (s, 6H, AlCH3), 0.42 (d,
JH-H ¼ 6.8 Hz, 12H, CH(CH3)2), 1.31 (d, JH-H ¼ 6.8 Hz, 12H,
CH(CH3)2), 1.37 (s, 1H, CH), 3.95 (sept, JH-H ¼ 6.8 Hz, 4H, CH
(CH3)2), 6.91–7.18 (m, 18H, Ar-H), 7.52–7.61 (m, 8H, Ar-H);
13C{1H} NMR ([D6]benzene, 100.6 MHz): d ꢀ3.8 (AlCH3),
15.1 (t, JC-P ¼ 138 Hz, PCP), 23.0 (CH(CH3)2), 28.3 (CH
(CH3)2), 28.8 (CH(CH3)2), 124.9 (vtr, Ar-C), 125.5 (vtr, Ar-C),
Experimental
General Considerations
All manipulations were carried out using standard Schlenk and
glove box techniques under an atmosphere of high purity dini-
trogen. Benzene, toluene, and hexane were dried and distilled
over molten potassium. 1H, 13C{1H}, and 31P{1H} NMR spectra
were recorded on a Bruker DPX 300 or Bruker Avance 400
spectrometer in dried and degassed deuterated benzene or tolu-
ene, were referenced to the residual 1H or 13C{1H} resonances of
the solvent used or external aqueous H3PO4 solutions, and were
obtained at 303 K unless otherwise specified. IR spectra were
recorded using a Perkin Elmer RXI FT-IR spectrometer as Nujol
mulls between NaCl plates. Melting points were determined in
sealed glass capillaries under dinitrogen and are uncorrected.
H2L 1,[18] and [[(Mesnacnac)Mg]2][17] were prepared according to
literature procedures. All other reagents were used as received
(Aldrich chemical company). Abbreviations: br¼ broad, vbr ¼
very broad, vtr ¼ virtual triplet, m ¼ multiplet. Note that the PCP
13C{1H} resonances were not observed for compounds 5, 6, and
7. The number of 13C{1H} ArC resonances may be low due to
overlap in broadened or multiplet resonances, or hidden by the
strong residual solvent resonances.
130.7 (Ar-C), 133.9 (vtr, JC-P ¼ 8.9 Hz, Ar-C), 135.1 (dd, JC-P
¼
97.6, 1.9 Hz, Ar-C), 140.2 (vtr, JC-P ¼ 4.6 Hz, Ar-C), 148.6 (vtr,
JC-P ¼ 2.7 Hz, Ar-C); 31P{1H} NMR ([D6]benzene,
162.0 MHz): d 30.5 (s); nmax (Nujol)/cmꢀ1 1589w, 1464s,
1433s, 1381m, 1311m, 1253m, 1236m, 1203m, 1171s, 1101s,
1051m, 1043m, 1032m, 1006m, 991s, 966s, 931m, 840m, 830m,
796s, 790s, 749m, 737m, 715m, 703s, 693s, 656s, 654s.
Synthesis of [L(AlMe2)2] (5)
AlMe3 (1.50 mL, 2.0 M in toluene, 3.00 mmol, 2.32 equiv.) was
added at room temperature to a solution of H2L 1 (0.95 g,
1.29 mmol, 1.0 equiv.) in toluene (13 mL). The mixture was
briefly stirred at room temperature and then at ,1058C for 2 h.
The mixture was concentrated (to ,4–5 mL) while still warm
and slowly cooled to ꢀ308C to yield colourless crystals of
5 ꢁ nC7H8 (0.85 g, 64 %). Crystals suitable for structural deter-
mination show n ¼ 3; after drying under vacuum, the solid
contained n ¼ 2. Mp ,2408C softer, 245–2488C melts with
Synthesis of [HLAlMe2] (4)
AlMe3 (0.96 mL, 2.0 M in toluene, 1.92 mmol, 1.04 equiv.) was
added to a cooled (, ꢀ308C) solution of H2L 1 (1.35 g,

1224
C. P. Sindlinger and A. Stasch
foaming (Found: C 77.8, H 8.0, N 2.7. C67H82Al2N2P2 requires
1
C 78.0, H 8.0, N 2.7 %); H NMR ([D6]benzene, 400.2 MHz):
ꢀ308C afforded a second crop (0.28 g, 43 %). Mp ,1408C
1
softer, 150–1558C melts with gas formation; H NMR ([D6]
d ꢀ0.22 (br s, 6H, AlCH3), 0.15 (br s, 6H, AlCH3), 0.2–0.8 (vbr,
12H, CH(CH3)2), 0.9–1.5 (vbr, 12H, CH(CH3)2), 3.63 (br, 4H,
CH(CH3)2), 6.45–6.79 (br m, 6H, Ar-H), 6.88–6.20 (br m, 16H,
Ar-H), 7.77–7.86 (vbr, 4H, Ar-H); 1H NMR ([D6]benzene,
300.1 MHz, 343 K): d ꢀ0.28 (br s, 6H, AlCH3), 0.28 (s, 6H,
AlCH3), 0.85 (br, 24H, CH(CH3)2), 3.72 (sept, JH-H ¼ 6.8 Hz,
4H, CH(CH3)2), 6.55–6.80 (m, 6H, Ar-H), 6.96–7.24 (m, 16H,
Ar-H), 7.70–8.00 (vbr, 4H, Ar-H); 13C{1H} NMR ([D6]ben-
zene, 75.5 MHz, 333 K): d ꢀ1.8 (br, AlCH3), ꢀ0.2 (br, AlCH3),
25.2 (vbr, CH(CH3)2), 28.7 (CH(CH3)2), 124.5 (br, Ar-C), 125.4
(vtr, JC-P ¼ 1.5 Hz, Ar-C), 130.9 (br, Ar-C), 131.8 (vtr, Ar-C),
133.6 (vtr, JC-P ¼ 5.0 Hz, Ar-C), 133.6 (vtr, JC-P ¼ 4.6 Hz,
Ar-C), 138.0 (vtr, Ar-C), 147.7 (vtr, Ar-C); 31P{1H} NMR ([D6]
benzene, 162.0 MHz): d 31.6 (s); nmax (Nujol)/cmꢀ1 1604w,
1590w, 1495m, 1463s, 1435s, 1383m, 1362m, 1318m, 1253m,
1203m, 1098s, 1049s, 976s, 838m, 796s, 729s, 719s, 694s,
666m, 648m, 597m.
benzene, 400.2 MHz): d 0.34 (br, 6H, CH(CH3)2), 0.60 (br, 6H,
CH(CH3)2), 1.35 (br, 6H, CH(CH3)2), 1.63 (br, 6H, CH(CH3)2),
3.38 (br, 2H, CH(CH3)2), 4.31 (br, 2H, CH(CH3)2), 6.67–7.20
(br m, 22H, Ar-H), 7.42–7.61 (m, 4H, Ar-H); 13C{1H} NMR
([D6]benzene, 75.5 MHz, 298 K): d 23.1 (br, CH(CH3)2), 25.6
(br, CH(CH3)2), 26.8 (br, CH(CH3)2), 28.8 (br and sharp, CH
(CH3)2, CH(CH3)2), 29.7 (br, CH(CH3)2), 125.0 (vbr, Ar-C),
127.2 (vtr, br, JC-P E 6.0 Hz, Ar-C), 127.6 (vtr, JC-P ¼ 6.0 Hz,
Ar-C), 131.4 (Ar-C), 131.7 (Ar-C), 134.2 (vtr, JC-P ¼ 5.4 Hz,
Ar-C), 135.2 (vtr, JC-P ¼ 4.7 Hz, Ar-C), 147.7 (m br, Ar-C),
149.0 (m br, Ar-C); 31P{1H} NMR ([D6]benzene, 121.5 MHz): d
32.9 (s); nmax (Nujol)/cmꢀ1 1589w, 1459s, 1435s, 1381m,
1378m, 1364m, 1315m, 1308m, 1253m, 1144s, 1100s, 1042m,
946m, 925s, 885m, 868m, 839s, 800s, 771m, 745m, 716s, 693m,
616m.
X-Ray Crystallography
Suitable crystals were mounted in silicone oil and were either
measured using a Nonius Kappa CCD diffractometer (4), an
Oxford Xcalibur Gemini Ultra diffractometer (6 ꢁ 2 C7H8)
Synthesis of [L(AlMeI)2] (6)
A solution ofI2 (0.33 g, 1.30 mmol, 2.1 equiv.) in toluene (15 mL)
was added dropwise (titration) to a cooled (08C) solution of [L
(AlMe2)2] 5 ꢁ 2 C7H8 (0.64 g, 0.620 mmol, 1.0 equiv.) in toluene
(15 mL) in a way that the decolourisation of the iodine is rea-
sonably fast at this temperature. The decolourisation slows down
when ,90–95% of the solution was added and the addition was
stopped. The lightly coloured solution was briefly stirred at room
temperature (resulting in complete decolourisation), concentrat-
ed to ,6 mL, and stored at 48C to afford a first crop of colourless
crystals of 6 ꢁ 2C7H8. Concentration of the supernatant solution to
,2 mL and cooling to ꢀ308C afforded a second crop of 6 ꢁ 2C7H8
(0.40 g, 51 %). Mp 251–2558C; 1H NMR ([D6]benzene,
400.2MHz): d 0.28 (br, 6H, CH(CH3)2), 0.60 (br, 6H, CH
(CH3)2), 0.62 (s, 6H, AlCH3), 1.20 (br, 6H, CH(CH3)2), 1.55 (br,
6H, CH(CH3)2), 3.25 (br, 2H, CH(CH3)2), 4.47 (br, 2H, CH
(CH3)2), 6.52–7.65 (br m, 22H, Ar-H), 8.02–8.18 (vbr, 4H,
Ar-H); 13C{1H} NMR ([D6]benzene, 75.5MHz, 333 K): d 10.8
(br, AlCH3), 23.4 (br, CH(CH3)2), 24.7 (br, CH(CH3)2), 27.2 (br,
CH(CH3)2), 27.5 (br, CH(CH3)2), 28.6 (br, CH(CH3)2), 29.2 (br,
CH(CH3)2), 125.0 (Ar-C), 126.6 (Ar-C), 127.3 (vtr, JC-P ¼ 6.4
Hz, Ar-C), 131.7 (Ar-C), 132.5 (Ar-C), 135.1 (vtr, JC-P ¼ 5.6 Hz,
Ar-C), 135.8 (vtr, JC-P ¼ 4.8 Hz, Ar-C), 147.1 (m br, Ar-C), 148.0
(m br, Ar-C); 31P{1H} NMR ([D6]benzene, 121.5 MHz): d 40.1
(s); nmax (Nujol)/cmꢀ1 1603w, 1588w, 1494m, 1463s, 1436s,
1383m, 1365m, 1336m, 1317m, 1247m, 1232m, 1200m, 1192m,
1101s, 994s, 963s, 933m, 848s, 799s, 746m, 727s, 720s, 693s,
680m, 654m, 643m, 632m.
´
˚
with MoKa radiation (l ¼ 0.71073 A), or at the MX1 beamline at
the Australian Synchrotron (5 ꢁ 3 C7H8, 7 ꢁ 0.5 C6H14) with
synchrotron radiation with a wavelength close to MoKa radia-
tion. All structures were refined using SHELX.[19] All non-
hydrogen atoms were refined anisotropically. Semi-empirical
(multi-scan) absorption corrections were performed on all
datasets. Two of the three toluene molecules are disordered in
the structure of 5 ꢁ 3 C7H8, and were modelled with two positions
for each carbon atom (75 % and 25 % occupancy) using geom-
etry restraints. One of the two toluene molecules in the structure
of 6 ꢁ 2 C7H8 is disordered and was modelled with two positions
for each carbon atom (55 % and 45 % occupancy) using geom-
etry restraints. C51 shows an asymmetric thermal ellipsoid and
some residual electron density peaks are near this atom. The
spectroscopic data of this sample fully support the formulation
as a methyl group. In the structure of 7 ꢁ 0.5 C6H14, half a mol-
ecule of n-hexane is disordered in the asymmetric unit and was
modelled using geometry restraints. Refinement details are
summarised in Table 1 and further information can be found in
the crystallographic information files. CCDC 936379 – 936382
contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Acknowledgements
A.S. is grateful to the Australian Research Council for support and a fel-
lowship. C.P.S. thanks the DAAD for RISE program funding. The Monash
University Research Accelerator Program is highly acknowledged. Part of
this research was undertaken on the MX1 beamline at the Australian Syn-
chrotron, Victoria, Australia.
Synthesis of [L(AlI2)2] (7)
A solution of I2 (0.58 g, 2.29 mmol, 4.71 equiv.) in toluene
(30 mL) was slowly added to a cooled (08C) solution of
[L(AlMe2)2] 5 ꢁ 2 C7H8 (0.50 g, 0.485 mmol, 1.0 equiv.) in tol-
uene (15 mL) for the first ,50 % of the I2 solution. The mixture
was allowed to warm to room temperature and the addition of
the remaining I2 solution was continued dropwise at room
temperature over several hours in a way that the iodine colour of
the solution is only light red. Once ,85 % of the solution was
added, the mixture was stirred overnight giving a red-brown
solution. The mixture was concentrated to ,4 mL, some warm
hexane (20 mL) was added and the mixture was quickly filtered.
Standing at room temperature afforded a crop of brown-yellow
crystals of 7.0.5 C6H14. Storing the supernatant solution at
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