Synthesis and Structure of Lewis-Base-Free Phosphinoalumane Derivatives

Article abstract of DOI:10.1002/ejic.201501141

Lewis-base-free diphosphinoalumane and 1-hydro-2-chlorophosphinoalumane derivatives bearing a bulky aryl substituent were synthesized by the reaction of the corresponding lithium phosphide and dichloroalumane. Structures of these phosphinoalumane derivatives were determined by spectroscopic and X-ray crystallographic analyses. Because of the efficient steric protection by the bulky aryl substituent, the aluminum centers in these phosphinoalumane derivatives have tricoordinate geometry. Reactions of the phosphinoalumane derivatives with organolithium reagents and bases were investigated.

Full text of DOI:10.1002/ejic.201501141

DOI: 10.1002/ejic.201501141
Communication
CLUSTER
ISSUE
Phosphinoalumanes
Synthesis and Structure of Lewis-Base-Free Phosphinoalumane
Derivatives
[a]
[a]
[a]
[a]
Tomohiro Agou, Shin Ikeda, Takahiro Sasamori, and Norihiro Tokitoh*
Abstract: Lewis-base-free diphosphinoalumane and 1-hydro-2- scopic and X-ray crystallographic analyses. Because of the effi-
chlorophosphinoalumane derivatives bearing a bulky aryl sub- cient steric protection by the bulky aryl substituent, the alumi-
stituent were synthesized by the reaction of the corresponding num centers in these phosphinoalumane derivatives have trico-
lithium phosphide and dichloroalumane. Structures of these ordinate geometry. Reactions of the phosphinoalumane deriva-
phosphinoalumane derivatives were determined by spectro- tives with organolithium reagents and bases were investigated.
Introduction
–113 ppm, 1JPH = 203 Hz).[8] Addition of an excess amount of
1
31
THF or Et O to a C D solution of 1 did not affect its H and
P
2
6 6
Group 13–15 single-bond compounds with the formula R E–
2
NMR chemical shifts, which indicates that the aluminum center
PnR (E = B, Al, Ga, In, and Tl, Pn = N, P, As, Sb, and Bi) potentially
2
in 1 keeps a tricoordinate structure even in the presence of
–
+
possess E =Pn double bonds because of the donation of the
lone-pair electrons on the Pn atom to the vacant p orbital on
1
these Lewis bases. At 300 K, one broad H NMR signal was
observed for the ortho-tert-butyl substituents of the two Mes*
[
1]
the E atom. A number of Lewis-base-free aminoboranes have
groups on the phosphorus atoms, which was split into two sin-
–
+
been synthesized, and their B =N double-bond character has
1
glets at 278 K. Meanwhile, one sharp H NMR signal was ob-
[
2]
been elucidated. However, examples of their heavier element
congeners, such as phosphinoalumanes R P–AlR , have re-
served for the ortho-tert-butyl substituents of the Mes* group
on the aluminum atom, and no notable change was observed
for this signal in the temperature range between 278 and 300 K.
2
2
mained sparse. Unlike aminoboranes, phosphinoalumanes
readily oligomerize or are coordinated by a Lewis base at the
aluminum atom in the absence of sterically demanding groups
around the P–Al moieties. Therefore, there have been a lim-
ited number of monomeric and Lewis-base-free phosphino-
alumane derivatives so far. Especially, Lewis-base-free phos-
phinoalumanes bearing reactive functional groups, such as
hydrogen and halogen substituents, on their P–Al moieties
have not been reported. In this communication, we describe
the synthesis and structure of the first diphosphinoalumane
and 1-hydro-2-chlorophosphinoalumane derivatives free from
Lewis-base coordination. Their reactivity toward organolithium
compounds and bases is also described.
These NMR spectroscopic data suggest a C -symmetric struc-
2
ture for 1 with a twofold rotation axis passing through the Al–
C(Mes*) bond. The observed signal splitting for the ortho-tert-
butyl substituents of the phosphorus-bound Mes* groups is
possibly due to the restricted rotation around the P–C(Mes*)
bonds.
[
3]
[
4]
Results and Discussion
Treatment of Lewis-base-free dichloroalumane Mes*AlCl2[5]
[
Mes* = 2,4,6-(tBu) C H ] with 2 equiv. of lithium phosphide
3 6 2
[
6]
Mes*PHLi, prepared from Mes*PH and nBuLi in Et O, afforded
2
2
diphosphinoalumane Mes*Al(PHMes*) (1) as a colorless solid
Scheme 1. Synthesis of Mes*Al(PHMes*)
[Mes* = 2,4,6-(tBu) ].
2
(1) and Mes*(Cl)Al–PHMes* (2)
2
3
1
3 6 2
C H
(
Scheme 1). The P NMR chemical shift (δ = –120 ppm) and
JPHcouplingconstant(220Hz)of1arecomparabletothosereported
P
1
The molecular structure of compound 1 was elucidated by
X-ray crystallographic analysis (Figure 1). The aluminum center
has trigonal planar geometry (Σ∠Al1 = 360°), whereas the phos-
phorus atoms are pyramidalized (Σ∠P1 = 304°, Σ∠P2 = 307°).
There are close contacts between the aluminum atom and the
hydrogen atoms of the ortho-tert-butyl substituents of the Mes*
for structurally related diphosphinogallanes Mes*Ga(PHMes*)
2
1
[7]
(δP = –96 ppm, JPH = 222 Hz) and tBuGa(PHMes*)2 (δP
=
[
a] Institute for Chemical Research, Kyoto University
Gokasho, Uji, Kyoto 611-0011, Japan
E-mail: tokitoh@boc.kuicr.kyoto-u.ac.jp
http://boc.kuicr.kyoto-u.ac.jp/www/index-e.html
[
9]
group on the aluminum atom (ca. 2.3 Å). As shown in Fig-
Eur. J. Inorg. Chem. 2016, 623–627
623
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
ure 1b, compound 1 has a nearly C symmetry in the crystalline Al–PHMes* (2) was formed along with a trace amount of 1
2
state, corroborating the interpretation of the NMR spectro- (Scheme 1). In contrast, related gallium and indium species
scopic data mentioned above. The Al–P bond lengths [2.405(2) Mes*(Cl)E–PHMes* (E = Ga, In) have not been obtained in the
[
7]
and 2.417(2) Å] are elongated with respect to those observed reactions between Mes*ECl and 1 equiv. of Mes*PHLi. Com-
2
in phosphinoalumane Tip Al–P(SiPh )(1-adamantyl) [2.342- pound 2 was isolated as a colorless solid by fractional crystalli-
2
[
3
4a]
(
2) Å, Tip = 2,4,6-(iPr) C H ]
and Al3P3 six-membered-ring zation and was characterized by NMR spectroscopy, mass spec-
3
6 2
[
10]
compound (Mes*AlPPh) [2.323(3)–2.336(3) Å], which are ex- trometry, and X-ray crystallographic analysis. To the best of our
3
amples of molecules with bonding between tricoordinate alu- knowledge, compound 2 is the first monomeric phosphino-
minum and phosphorus atoms. The P–Al bonds of 1 are even alumane derivative bearing a halogen substituent on the alumi-
[
4b,13]
31
longer than those of Lewis-base-coordinated phosphino- num moiety.
The P NMR spectrum of 2 shows a signal
1
alumanes (dmap)Me Al–P(SiMe ) [P–Al 2.379(1) Å, dmap = 4- at δ = –133 ppm ( J = 210 Hz), which is slightly shifted to
2
3 2
PH
[
11]
1
(
2
dimethylamino)pyridine]
and (Me N)H Al–PMes [P–Al higher field compared to that of 1. In the H NMR spectrum of
These structural data suggest that the P–Al 2, each Mes* group shows only one signal for the ortho-tert-
3 2 2
[
12]
.409(3) Å].
bonds in 1 are single bonds rather than double bonds. The butyl substituents, suggesting fast rotation around the Al–C
substantial pyramidalization of the phosphorus atoms as well and P–C bonds. Meanwhile, peak shifts were observed in the
1
31
as the large dihedral angles between the Al–P–P–C(Al) plane
H and P NMR spectra upon addition of excess amount of
and the Al–H–C(P) planes (37° and 33°) also suggests negligible THF or Et O to a C D solution of 2, indicating the Lewis-acid–
2
6 6
P=Al double-bond character in 1. Overall, the structure of 1 is base complexation.
very similar to those of its gallium analogue, Mes*Ga-
The molecular structure of 2 determined by X-ray crystallo-
graphic analysis is shown in Figure 2, though the results are
preliminary as a result of the poor crystal quality. The geome-
tries around the aluminum and phosphorus atoms are trigonal
planar (Σ∠Al1 = 359°) and pyramidal (Σ∠P1 = 293°), respec-
tively. The closest approach between the aluminum center and
the hydrogen atom of the ortho-tert-butyl substituents of the
[
7]
(
PHMes*)2.
[
9]
aluminum-bound Mes* group is 2.1 Å. The Al–P bond length
2.379(3) Å] is close to those in 1 and is comparable to those
in Lewis-base-coordinated phosphinoalumanes (dmap)Me Al–
[
2
[
11]
P(SiMe3)2 [P–Al 2.379(1) Å]
and (Me N)H Al–PMes [P–Al
3 2 2
[
12]
2
.409(3) Å], which indicates the single-bond character of the
Al–P bond in 2. The pyramidalized phosphorus atom and the
large dihedral angle between the Al1–P1–Cl1–C1 plane and the
Al1–H1–C2 plane (34°) corroborate negligible P=Al double-
bond character in 2. The Al–Cl bond length is 2.174(3) Å, which
2
Figure 1. (a) Molecular structure of Mes*Al(PHMes*) (1) (50 % probability
level). Hydrogen atoms, except those attached to the phosphorus atoms, are
omitted for clarity. Selected bond lengths [Å] and angles [°]: Al1–P1 2.405(2),
Al1–P2 2.417(2), Al1–C1 1.990(5), P1–C2 1.869(5), P2–C3 1.868(5); P1–Al1–P2
1
14.72(8), P1–Al1–C1 127.6(2), P2–Al1–C1 117.6(2), Al1–P1–C2 106.4(2), Al1–
P1–H1 93(1), C2–P1–H1 105(1), Al1–P2–C3 107.2(2), Al1–P2–H2 93(1), C3–P2–
H2 107(1). (b) Side view. The tert-butyl substituents and hydrogen atoms,
except those attached to the phosphorus atoms, are omitted.
Figure 2. Molecular structure of Mes*(Cl)Al–PHMes* (2) (50 % probability
level). Hydrogen atoms, except that attached to the phosphorus atom, are
omitted for clarity. Selected bond lengths [Å] and angles [°]: Al1–P1 2.379(3),
Al1–Cl1 2.174(3), Al1–C1 1.966(6), P1–C2 1.873(6); P1–Al1–Cl1 112.8(1), P1–
Al1–C1 131.7(2), Cl1–Al1–C1 114.5(2), Al1–P1–C2 103.3(2), Al1–P1–H1 90(2),
C2–P1–H1 100(2).
By changing the stoichiometry of Mes*PHLi to
Mes*AlCl2,
1-hydro-2-chlorophosphinoalumane
Mes*(Cl)-
Eur. J. Inorg. Chem. 2016, 623–627
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624
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
is slightly longer than those found in the starting material
[
5]
Mes*AlCl [2.120(1)–2.129(1) Å].
2
Deprotonation reactions of compound 1 were investigated
with the expectation that anionic species 3 would be generated
(
Scheme 2). However, no reaction was observed when 1 was
treated with nBuLi, tBuLi, or MesLi in Et O or C D , which sug-
2
6 6
gests the low acidity of the P–H groups in 1. Treatment of 1
with tBuOK or 1,8-diazabicycloundec-7-ene (DBU) gave a mix-
ture of compounds including Mes*PH as a phosphorus-con-
2
taining product.
Scheme 4. Proposed mechanism for the formation of 1 by the reaction of 2
with organolithium compounds (R = nBu, tBu, Mes, Tip).
Conclusions
Lewis-base-free diphosphinoalumane and 1-hydro-2-chloro-
phosphinoalumane have been synthesized by taking advantage
of the bulky Mes* group. The 1-hydro-2-chlorophosphino-
alumane is the first example of monomeric phosphinoalumane
derivatives with an Al–X bond (X = halogen group). Reactions
of the 1-hydro-2-chlorophosphinoalumane with organolithium
reagents resulted in the generation of the diphosphinoalumane
as the sole phosphorus-containing product.
Scheme 2. Reactions of 1 with organolithium compounds or bases.
Deprotonation reactions of compound 2 were also investi-
gated, because the dehydrochlorination of 2 would afford so
far unknown P=Al double bond species 4 (Scheme 3). Reaction
of 2 with DBU gave a complicated mixture, and none of the
products could be characterized. The 3 P NMR spectra of the
reaction mixtures of 2 and MesLi or TipLi suggested the forma-
tion of 1 as the sole phosphorus-containing product. Com-
pound 1 was also observed in the reaction mixtures of 2 with
n- or tBuLi, although several uncharacterized phosphorus-con-
taining products were generated.
1
Experimental Section
General Procedures: All the manipulations were performed under
an argon atmosphere by using a vacuum line or a glove box. Sol-
vents were dried and deoxygenated by using the Ultimate Solvent
[
15]
System, Glass Contour Company,
or by trap-to-trap distillation
from a potassium mirror. H, C, and 31P NMR spectra were meas-
ured with a JEOL AL-300 spectrometer. Al NMR spectra were re-
corded with a JEOL Delta 600 NMR spectrometer. H and C NMR
signals were assigned with the aid of HSQC and HMBC techniques.
Melting points were measured with a Yanaco micro melting point
apparatus. High-resolution mass spectra were measured with a
Bruker microTOF mass spectrometer equipped with an AMR DART-
1
13
27
1
13
[6]
SVP ion source by using He as ionization gas. Mes*PHLi and
Mes*AlCl2 were prepared according to literature procedures.
[
5]
Mes*Al(PHMes*) (1): To a solution of Mes*PHLi in Et O (5 mL),
2
Scheme 3. Reactions of 2 with DBU or organolithium compounds.
prepared from Mes*PH2 (0.20 g, 0.72 mmol) and nBuLi (1.6
M in
hexane, 0.48 mL, 0.72 mmol), was added a solution of Mes*AlCl in
2
Et O (5 mL, 0.12 g, 0.36 mmol) at –35 °C. The mixture was stirred
2
A possible explanation for the formation of 1 is shown in
Scheme 4. In the first step, organolithium reagents RLi (R = nBu,
tBu, Mes, Tip) attack the aluminum center in 2 to afford ate
complex 5. The Al–Cl or Al–P bond cleavage from 5 gives phos-
at –35 °C for 2 h. After removal of the solvents under reduced pres-
sure, the residue was dissolved in hexane and filtered. The solvent
was removed under reduced pressure, and recrystallization from
hexane at –35 °C gave 1 as colorless crystals (80 mg, 0.21 mmol,
1
phinoalumane 6 or the mixture of Mes*PHLi and chloro- 58 %). M.p.: 147 °C (dec.). H NMR (300 MHz, C D ): δ = 1.23 [s, 9 H,
6
6
alumane 7, respectively. The DFT calculations on the model Mes*(Al) p-tBu], 1.30 [s, 18 H, Mes*(P) p-tBu], 1.33 [s, 18 H, Mes*(Al)
1
compound of 5 suggest the comparable energy gain for the P– o-tBu], 1.62 [s, 36 H, Mes*(P) o-tBu], 4.77 (d, JHP = 220 Hz, 2 H, P–
[
14]
H), 7.28 [s, 2 H, Mes*(Al) m-ArH], 7.46 [s, 4 H, Mes*(P) m-ArH] ppm.
Cl and P–Al bond cleavage from 5.
2
Because the reaction of
13
1
C{ H} NMR (75 MHz, C D ): δ = 31.31 [s, Mes*(Al) p-CMe ], 31.67
6
6
3
with MesLi or TipLi afforded not 6 but 1, the Al–Cl bond
[
s, Mes*(P) p-CMe ], 32.81 [s, Mes*(Al) o-CMe ], 33.45 [s, Mes*(P) o-
3
3
breaking from 5 is seemingly unfavorable. In the second step,
Mes*PHLi reacts with the remaining 2 to give 1. The nucleophil-
lic attack of Mes*PHLi on 7 would be hampered, when the R is
a Mes or Tip group, by the steric repulsion. In contrast, when R
is an nBu or tBu group, several side reactions, such as
CMe ], 34.69 [s, Mes*(Al) p-CMe ], 34.87 [s, Mes*(P) p-CMe ], 37.69
3
3
3
[
s, Mes*(Al) o-CMe ], 38.36 [s, Mes*(P) o-CMe ],121.81 [s, Mes*(Al)
3
3
1
m-ArC], 122.54 [s, Mes*(P) m-ArC], 131.59 [d, J = 40.5 Hz, Mes*(P)
CP
ipso-ArC], 147.01 [s, Mes*(Al) p-ArC], 150.85 [s, Mes*(P) p-ArC],
2
1
53.55 [d, J = 3.39 Hz, Mes*(P) o-ArC], 157.02 [s, Mes*(Al) o-ArC]
CP
nucleophillic attack of the Mes*PHLi on 7, might occur, giving ppm. A signal corresponding to the carbon atom directly attached
a complicated mixture containing 1.
to the aluminum moiety could not be observed, probably because
625 © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2016, 623–627
www.eurjic.org

Communication
of signal broadening due to the quadrupolar 27Al nucleus. 31P NMR
AFIX instructions, while all other atoms were refined anisotropically.
The hydrogen atoms attached to the phosphorus atoms in 1 and 2
were found in the difference Fourier maps, and they were refined
isotropically by using the DFIX instruction.
1
(
120 MHz, C D ): δ = –120 (d, J = 220 Hz) ppm. No signal was
6
6
PH
27
observed in the Al NMR spectrum even after a long-time measure-
+
ment. HRMS (DART-TOF): calcd. for C H AlP [M + H] 827.6333;
5
4
90
2
found 827.6364.
CCDC-977526 (for 1·C H ) and -977525 (for 2·C H ) contain the sup-
7
8
6 6
plementary 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.
Mes*(Cl)Al–PHMes* (2): To a solution of Mes*PHLi in Et O (5 mL),
2
prepared from Mes*PH2 (0.20 g, 0.72 mmol) and nBuLi (1.6
M in
hexane, 0.48 mL, 0.72 mmol), was added a solution of Mes*AlCl in
2
Et O (5 mL, 0.25 g, 0.72 mmol) at –35 °C. The mixture was stirred
2
Crystallographic Data for 1·C H : C H AlP , M = 919.31, crystal
size 0.22 × 0.21 × 0.20 mm, temperature –170 °C, λ = 0.71070 Å,
7
8
61 97
2
r
at –35 °C for 0.5 h. The solvent was removed under reduced pres-
sure, and the residue was dissolved in hexane and filtered. The fil-
monoclinic, space group P2 /a (#14), a = 18.6807(6) Å, b =
1
1
31
trate was concentrated to afford the crude product. The H and
P
3
1
6.9204(6) Å, c = 18.7617(6) Å, β = 100.6182(12)°, V = 5828.7(3) Å ,
Z = 4, Dcalcd. = 1.048 g cm , μ = 0.124 mm , θ
NMR spectra indicated the formation of 2 along with a trace
amount of 1. Recrystallization of the crude product from hexane at
–3
–1
= 25.50°, 55050
max
reflections measured, 10507 independent reflections (Rint = 0.1134),
38 refined parameters, GOF = 1.063, R [I > 2σ(I)] = 0.0856, wR (all
–
1
35 °C gave 2 as colorless crystals (40 mg, 0.068 mmol, 9 %). M.p.:
6
1
2
1
17 °C (dec.). H NMR (300 MHz, C D ): δ = 1.27 [s, 9 H, Mes*(P) p-
–3
6
6
data) = 0.2153, largest diff. peak and hole 0.498 and –0.654 e Å .
tBu], 1.30 [s, 9 H, Mes*(Al) p-tBu], 1.41 [s, 18 H, Mes*(Al) o-tBu], 1.59
Crystallographic Data for 2·C H : C H AlClP, M = 663.34, crystal
1
6
6
42 65
r
[
s, 18 H, Mes*(P) o-tBu], 4.70 (d, JHP = 210 Hz, 1 H, P–H), 7.37 [s, 2
size 0.01 × 0.01 × 0.01 mm, temperature –170 °C, λ = 0.78215 Å,
1
3
1
H, Mes*(Al) m-ArH], 7.44 [s, 2 H, Mes*(P) m-ArH] ppm. C{ H} NMR
75 MHz, C D ): δ = 31.39 [s, Mes*(Al) p-CMe ], 31.68 [s, Mes*(P) p-
triclinic, space group P1¯ (#2), a = 9.867(6) Å, b = 14.520(12) Å, c =
(
6
6
3
1
2
2
6.181(10) Å, α = 106.63(3)°, β = 107.13(2)°, γ = 100.79(4)°, V =
CMe ], 32.87 [s, Mes*(Al) o-CMe ], 33.25 [s, Mes*(P) o-CMe ], 34.85
3
3
3
3
–3
–1
027(2) Å , Z = 2, D
= 1.087 g cm , μ = 0.201 mm , θ
=
calcd.
max
[
s, Mes*(Al) p-CMe ], 35.15 [s, Mes*(P) p-CMe ], 37.81 [s, Mes*(Al) o-
3
3
7.38°, 14194 reflections measured, 6584 independent reflections
CMe ], 38.22 [s, Mes*(P) o-CMe ], 121.62 [s, Mes*(Al) m-ArC], 122.57
3
3
(Rint = 0.1292), 459 refined parameters, 37 restraints used, GOF =
3
1
[
d, J = 3.70 Hz, Mes*(P) m-ArC], 129.51 [d, J = 35.5 Hz, Mes*(P)
CP CP
1
.038, R1 [I > 2σ(I)] = 0.0902, wR2 (all data) = 0.2674, largest diff.
ipso-ArC], 147.56 [s, Mes*(Al) p-ArC], 151.62 [s, Mes*(P) p-ArC] 153.95
–
3
peak and hole 0.460 and –0.459 e Å .
2
[
d, J = 6.47 Hz, Mes*(P) o-ArC], 157.50 [s, Mes*(Al) o-ArC] ppm. A
CP
signal corresponding to the carbon atom directly attached to the
aluminum moiety could not be observed, probably because of sig- Acknowledgments
2
7
31
nal broadening due to the quadrupolar Al nucleus. P NMR
1
This work was partially supported by the Japan Society for the
Promotion of Science (JSPS) Grants-in-Aid for Scientific Research
(KAKENHI) (nos. 24109013, 24550048, 2662028, and 15H05477),
the Ministry of Education, Culture, Sports, Science and Technol-
ogy (MEXT), Japan, Project of Integrated Research on Chemical
Synthesis, the RIKEN Advanced Science Institute (“Molecular
Systems Research” project), and the Collaborative Research Pro-
gram of the Institute for Chemical Research, Kyoto University.
(
120 MHz, C D ): δ = –133 (d, J = 210 Hz) ppm. No signal was
observed in the Al NMR spectrum even after a long-time measure-
ment. HRMS (DART): calcd. for C H Al ClP [M] 584.3858, found
6 6 PH
27
3
5
+
3
6 59
5
84.3890.
General Procedure for the Reactions of 1 with Bases: In a NMR
tube with a J. Young valve, to a C D (0.5 mL) solution of 1 (10.0 mg,
6
6
0
.012 mmol) was added tBuOK (1.3 mg, 0.012 mmol) at room tem-
1
31
perature. The reaction was monitored by H and P NMR spectro-
scopy. After 2 h, 1 was consumed completely to give a complicated T. A. is thankful for the Ube Industries Award in Synthetic Or-
mixture containing Mes*PH2.
ganic Chemistry, Japan. The authors are grateful to Dr. Nobuhiro
Yasuda (SPring-8/JASRI) for his kind assistance in performing X-
ray diffraction measurements for 2·C H .
General Procedure for the Reactions of 2 with Organolithium
Compounds: In a NMR tube with a J. Young valve, to a C D6
6
6
6
(0.5 mL) solution of 2 (10.0 mg, 0.017 mmol) was added MesLi
(
2.1 mg, 0.017 mmol), and the mixture was heated at 70 °C for 2 h. Keywords: Aluminum · Phosphorus · Phosphanes ·
1
31
The H and P NMR spectra of the mixture showed the formation
of 1 as the sole phosphorus-containing product.
Phosphinoalumanes
X-ray Crystallographic Analysis
[
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7
8
6 6
from toluene (at –35 °C) and benzene (at room temperature), re-
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17]
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6
6
3
posal No. 2011B1545) with a Rigaku Saturn 724 CCD system by
using synchrotron X-ray radiation. The reflection data were inte-
grated, scaled, and averaged by using the Rigaku Rapid Auto soft-
ware (Rigaku Corp.). The structures were solved by direct methods
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[
[
(
F
SHELXS-97) and refined by full-matrix least-squares procedures on
for all reflections (SHELXL-97).
1982, 104, 5820.
2
[18]
All hydrogen atoms, except
[7] W.-P. Leung, C. M. Y. Chan, B.-M. Wu, T. C. W. Mak, Organometallics 1996,
15, 5179–5184.
those attached to the phosphorus atoms, were placed by using
Eur. J. Inorg. Chem. 2016, 623–627
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© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
[
[
8] D. A. Atwood, A. H. Cowley, R. A. Jones, M. A. Mardones, J. Am. Chem.
Soc. 1991, 113, 7050–7052.
9] Short contacts between the tricoordinate aluminum center and the
hydrogen atoms of the ortho-tert-butyl substituents were reported for
energy for the Al–Cl bond cleavage from 5′ giving 6′ (+39.32 kcal mol–1
)
–
is comparable to that for the Al–P bond cleavage giving 7′ and MeHP
–
1
(
+48.29 kcal mol ).
2
Mes*AlX (X = Cl, Br): M. A. Petrie, P. P. Power, H. V. Rasika Dias, K. Ruhl-
andt-Senge, K. M. Waggoner, R. J. Wehmschulte, Organometallics 1993,
[
5]
1
2, 1086–1093. See also ref.
[
10] R. J. Wehmschulte, P. P. Power, J. Am. Chem. Soc. 1996, 118, 791–797.
[
[
11] F. Thomas, S. Schulz, M. Niger, Eur. J. Inorg. Chem. 2001, 161–166.
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Organometallics 1993, 12, 17–18.
[
15] A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, F. J. Timmers,
Organometallics 1996, 15, 1518–1520.
[16] Z. Otwinoski, W. Minor, Methods Enzymol. 1997, 276, 307–326.
[17] R. H. Blessing, Acta Crystallogr., Sect. A 1995, 51, 33–38.
[18] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[
13] Oligomers of phosphinoalumanes with Al–Cl bonds: a) C. von Hänisch,
F. Weigend, Z. Anorg. Allg. Chem. 2002, 628, 389–393; b) C. von Hänisch,
Z. Anorg. Allg. Chem. 2003, 629, 1496–1500.
[
14] The Gibbs free energies for the following model reactions were calcu-
lated at the B3PW91/6–31+G(d) level of theory. The reaction Gibbs free
Received: October 8, 2015
Published Online: October 13, 2015
Eur. J. Inorg. Chem. 2016, 623–627
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627
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim