Synthesis and structural characterization of aluminum lminophosphonamide complexes

Article abstract of DOI:10.1021/ic9011179

Monoanlonic lminophosphonamide ligands have a N-P-N linkage and undergo four-membered ring N,N-ligand formation when treated with aluminum compounds. The reaction of LLi (L = [Ph₂P(NSIMe₃)₂]) with equivalent amounts of AIC

Full text of DOI:10.1021/ic9011179

9174 Inorg. Chem. 2009, 48, 9174–9179
DOI: 10.1021/ic9011179
Synthesis and Structural Characterization of Aluminum Iminophosphonamide
Complexes
Bijan Nekoueishahraki, Herbert W. Roesky,* Gerald Schwab, Daniel Stern, and Dietmar Stalke
::
:: ::
::
Institut fur Anorganische Chemie, Universitat Gottingen, Tammannstrasse 4, 37077 Gottingen, Germany
Received June 9, 2009
Monoanionic iminophosphonamide ligands have a N-P-N linkage and undergo four-membered ring N,N-ligand
formation when treated with aluminum compounds. The reaction of LLi (L = [Ph2P(NSiMe3)2]) with equivalent
amounts of AlCl3 and AlMeCl2 in toluene afforded LAlCl2 (3) and LAlClMe (4), respectively. L2AlH (5), LAlEt2 (6), and
LAl(NMe2)2 (7) respectively were prepared by the reaction of LH with AlH3 NMe3, AlEt3, and Al(NMe2)3 in n-hexane.
3
Subsequently compounds 3-7 were characterized by elemental analysis, 1H, 13C, and 31P NMR spectroscopy and
X-ray crystallographic studies (for 3, 4, 5, and 7).
Introduction
reactive oxygen containing species which leads to the pre-
paration of alumoxanes.3
The importance of organoaluminum compounds is due to
their use in a variety of applications, including organic
syntheses and industrial catalytic processes. They have also
been utilized as precursors in chemical vapor deposition
(CVD) processes.1 It has been observed that stable aluminum
compounds involving nitrogen substituents or neutral nitro-
gen donors are useful in the preparation of aluminum nitride
or AlN-containing materials. As a result, there is consider-
able interest in the structures, properties, and transforma-
tions of molecules containing Al-N bonds.2 Particularly,
there has been immense research interest in synthesizing
aluminum chlorides and methyl derivatives which can act
as precursors in the controlled hydrolysis with water or
There are very few reports on structurally characterized
four-membered aluminum rings bearing halide, methyl, and
hydride substituents probably because of the steric and
electronic properties. The interest in these ligands is currently
growing as a result of their specific steric and electronic
features, and these properties can efficiently control the
geometry at the metal center. Herein we report the synthesis
and structural characterization of aluminum complexes with
chloride, hydride, methyl, amide, and diethyl substituents
based on an iminophosphonamide ligand.
Results and Discussion
Synthesis of LAlCl2 (3), LAlMeCl (4). Compound
Ph2P(NSiMe3)2H (1) was prepared by a previously re-
ported method.4,5 Treatment of iminophosphonamide
with MeLi or nBuLi yielded the lithium salt of iminopho-
sphonamide LLi (2) (L = Ph2P(NSiMe3)2) in high yield.6
Further reactions were carried out either by isolating 2 or
by in situ reaction of 2 with the corresponding aluminum
compounds. Synthesis of LAlCl2 (3) (Scheme 1) was
accomplished by reacting the lithiated precursor 2 with
AlCl3 under the elimination of LiCl in moderate yield.
The solution of AlCl3 in toluene was added drop by drop
to the solution of 2 in a 1:1 stoichiometric ratio in toluene
and stirred at 25 °C for 14 h to yield the colorless complex
3. In a similar route, complex 4 was prepared by slow
*Towhomcorrespondence shouldbeaddressed. E-mail: hroesky@gwdg.de.
Fax: þ49-551-393373.
(1) (a) Barron, A. R. Adv. Mater. Opt. Electron. 1995, 5, 245–258. (b)
Atwood J. L. In Coordination Chemistry of Aluminum; Robinson, G. H., Ed.;
VCH: New York, 1993; pp 197-232. (c) Sinn, H.; Kaminsky, W.; Vollmer, H.-J.;
Woldt, R. Angew. Chem. 1980, 92, 396–402. Angew. Chem., Int. Ed. Engl.
1980, 19, 390-392. (d) Sinn, H.; Kaminsky, W. Adv. Organomet. Chem. 1980,
18, 99–149.
(2) (a) Liu, H.; Bertolet, D. C.; Rogers, J. W. Surf. Sci. 1994, 320, 145–160.
(b) Chemistry of Aluminum, Gallium, Indium and Thallium; Downs A. J., Ed.;
Blackie: Glasgow, 1993. (c) Jones, A. C.; O'Brien, P. In CVD of Compound
Semiconductors; VCH: Weinheim, 1997. (d) Neumayer, D. A.; Ekerdt, J. G.
Chem. Mater. 1996, 8, 9–25.
(3) (a) Storre, J.; Klemp, A.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer,
M.; Fleischer, R.; Stalke, D. J. Am. Chem. Soc. 1996, 118, 1380–1386. (b)
Storre, J.; Schnitter, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.;
Fleischer, R.; Stalke, D. J. Am. Chem. Soc. 1997, 119, 7505–7513. (c) Zheng,
::
W.; Mosch-Zanetti, N. C.; Roesky, H. W.; Noltemeyer, M.; Hewitt, M.; Schmidt,
(4) Stapleton, R. L.; Chai, J.; Taylor, N. J.; Collins, S. Organometallics
2006, 25, 2514–2524.
H.-G.; Schneider, T. R. Angew. Chem. 2000, 12, 4446–4449. Angew. Chem., Int.
Ed. 2000, 39, 4276-4279. (d) Lewinski, J.; Bury, W.; Justyniak, I.; Lipkowski, J.
Angew. Chem. 2006, 118, 2938–2941. Angew. Chem., Int. Ed. 2006, 45,
2872-2875. (e) Gonzalez-Gallardo, S.; Jancik, V.; Cea-Olivares, R.; Toscano,
R. A.; Moya-Cabrera, M. Angew. Chem. 2007, 119, 2953–2956. Angew.Chem.,
Int. Ed. 2007, 46, 2895-2898.
(5) (a) Schmidbaur, H.; Schwirten, K.; Pickel, H.-H. Chem. Ber. 1969,
102, 564–567. (b) Wolfsberger, W.; Hager, W. Z. Anorg. Allg. Chem. 1976, 425,
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r
pubs.acs.org/IC
Published on Web 09/09/2009
2009 American Chemical Society

Article
Inorganic Chemistry, Vol. 48, No. 19, 2009 9175
Scheme 1. Preparation of Aluminum Iminophosphonamide
Complexes
Figure 1. Molecular structure of 3. Table 1 contains selected bond
˚
lengths [A] and angles [deg]. Anisotropic displacement parameters are
drawn at the 50% probability level. Only one of the two crystallographi-
cally independent molecules is shown. H atoms are omitted for clarity.
addition of AlMeCl2 (1.0 M in n-hexane) to the toluene
solution of 2 and stirring at room temperature for 14 h.
Compounds 3 and 4 are soluble in common organic
solvents such as toluene, tetrahydrofuran (THF), and
n-hexane, and they are stable in the solid state at room
temperature for several months under an inert atmo-
sphere. 3 is easily oxidized and hydrolyzed on exposure
to air as indicated by a color change from colorless to a
light yellow oily solid, and we were not able to measure
the elemental analysis of 3 because of its sensitivity.
The 31P NMR spectra of 3 and 4 exhibit downfield shifts
when compared with those of complex 2 (37.8 ppm for 3,
33.2 ppm for 4, 7.4 ppm for 2). The 1H NMR of 4 exhibits
a single resonance (0.04 ppm) which can be assigned to
Al-Me. The 18 protons of SiMe3 resonate as a singlet at
-0.03 ppm, and the aromatic protons of Ph are shown at
7.46-7.79 ppm.
Crystal Structures of LAlCl2 (3), LAlMeCl (4). Com-
plexes 3 and 4 were characterized further by X-ray crystal-
lography, and the molecular structures are presented in
Figures 1 and 2. Table 1 contains important bond para-
meters of compounds 3 and 4, and crystallographic data for
the structural analyses are listed in Table 2. Compound
[Ph2P(NSiMe3)2AlCl2] (3) crystallizes in the triclinic space
group P1 with two molecule in the asymmetric unit whereas
[Ph2P(NSiMe3)2AlMeCl] (4) is monomeric in the solid
state and crystallizes in the monoclinic space group P21/c.
Colorless crystals of 3 and 4 suitable for X-ray structure
analysis were grown from toluene and n-hexane at -78
°C, respectively. In both structures the aluminum atoms
Figure 2. Molecular structure of 4. Table 1 contains selected bond
˚
lengths [A] and angles [deg]. Anisotropic displacement parameters are
drawn at the 50% probability level. H atoms (except for those of C19) and
half toluene solvent molecule are omitted for clarity.
show a distorted tetrahedral environment, and the me-
trical parameters associated with the PN2 ligand are quite
similar.7 All N atoms bearing SiMe3 groups show a planar
arrangement; the Si-N bonds are slightly shorter than
8
˚
the sum of the covalent radii of 1.87 A, and the P-N
˚
distances in the range of 1.614(12)-1.629(16) A have been
previously rationalized to range between single and dou-
ble P-N bonds.9 However, recent experimental charge
density studies proved the shortening mainly to be caused
by electrostatic contributions.10 In addition to the P-N
σ-bonds, there is Coulomb attraction between the posi-
tively charged phosphorus atoms and the negatively
charged nitrogen atoms and, in return, repulsion between
the competing N-atoms across the central P-atom. This
“seesaw” effect is most prominent in the structures from
the tetra(amino) phosphonium cation, [P(NHPh)4]þ, to
the tetra(imino) phosphate trianion, [P(NPh)4]3-: De-
spite the diversity of the P-N bond lengths, the average
P-N bond length within the PN4 tetrahedra is very
(8) Huheey, E. Inorganic Chemistry, 3rd ed.; Harper and Row: New York,
1983.
(9) Allcock, H. R. Phosphorus-Nitrogen Compounds; Academic Press: New
York, 1972.
(10) Kocher, N.; Leusser, D.; Murso, A.; Stalke, D. Chem.;Eur. J. 2004,
10, 3622–3631.
(7) Fleischer, R.; Stalke, D. Inorg. Chem. 1997, 36, 2413–2419.

9176 Inorganic Chemistry, Vol. 48, No. 19, 2009
Nekoueishahraki et al.
P
similar ( (dP-N)}/4 = 1.62(1)A).11 On this basis we state
˚
that there is no PdN double bonding and hence no
hypervalent phosphorus present in the iminophosphona-
mide ligands presented in this paper.12
The Al-Cl bond lengths in compound 3 are shorter
than those of compound 4, while the ligand bite
(N1-Al1-N2) in 3 (av 81.09°) is slightly bigger than that
˚
in 4 (80.04(5)°). The Al-Cl distances in 3 (av 2.129 A) are
quite similar to those observed in the mono 1-aza-allyl
˚
complex [N(SiMe3)C(Ph)C(SiMe3)2]AlCl2 (av 2.071 A),
but the core angle is significantly different because of non
equivalent chelating backbone.13
Synthesis of L2AlH (5), LAlEt2 (6), and LAl(NMe2)2 (7).
Reaction of iminophosphonamide 1 with AlH3 NMe3 in
3
2:1 stoichiometric ratio in n-hexane/THF at -78 °C
afforded the iminophosphonamide aluminum complex
[Ph2P(NSiMe3)2]2AlH (5) in moderate yield. The 1H
NMR spectrum of 5 exhibits a broad singlet at 5.1 ppm
assigned to the AlH and two singlets at -0.22 and
-0.13 ppm, which can be assigned to the 36 protons of
the SiMe3 units. The presence of two non equivalent
SiMe3 groups indicates a restricted fluctionality of these
groups at room temperature. In the IR spectrum one
weak absorption for the AlH stretching frequency is
observed at 1853 cm-1. Compound 6 was prepared as a
white crystalline solid from the reaction of iminopho-
sphonamide 1 with AlEt3 in n-hexane at -78 °C. Reaction
of 1 with Al(NMe2)3 in n-hexane at reflux temperature for
6 h afforded the aluminum amide complex 7. Both
compounds are soluble in common organic solvents such
as n-hexane, toluene, and THF. 5 and 7 are stable in the
solid state under an inert atmosphere and are slowly
oxidized and hydrolyzed on exposure to air whereas 6 is
not stable and very sensitive to air. Therefore we were not
able to determine the elemental analysis. 31P NMR
spectra of 6 and 7 exhibit single resonances at 30.3 and
28.6 ppm, respectively. In both compounds the 1H
NMR and 29Si NMR spectra exhibit only one singlet
for the SiMe3 groups. In compound 7 the 12 protons
correspond to two NMe2 and resonate at 3.06 ppm while
the aromatic protons appear between 7.03 and 7.83 ppm.
Crystal Structures of L2AlH (5) and LAl(NMe2)2 (7).
Complexes 5 and 7 were characterized further by X-ray
crystallography, and the molecular structures are pre-
sented in Figures 3 and 4. Table 1 contains important
bond parameters of compounds 5 and 7, and crystal-
lographic data for the structural analyses are listed in
Table 2. The X-ray structure reveals that in 5 the alumi-
num is five coordinate and in a distorted trigonal bipyr-
amidal geometry with N1 and N4 in axial positions and
N2, N3, and H in the equatorial plane. The N1-Al1-N4
axis is almost linear [N1-Al1-N4 175.80(5)°] in which
Figure 3. Molecular structure of 5. Table 1 contains selected bond
˚
lengths [A] and angles [deg]. Anisotropic displacement parameters are
drawn at the 50% probability level. H atoms (except for those of Al1) and
one THF solvent molecule are omitted for clarity.
Figure 4. Molecular structure of 7. Table 1 contains selected bond
˚
lengths [A] and angles [deg]. Anisotropic displacement parameters are
drawn at the 50% probability level. H atoms are omitted for clarity.
torial Al1-N1 and Al1-N3 having almost the same bond
˚
˚
lengths. [Al1-N2 1.94(13) A, Al1-N3 1.93(13) A]. The
deviation from the ideal trigonal-bipyramidal geometry
can be described by an angle of 73.94(26)° between the
least-squares plane of N1, Al, N4, H and the equatorial
plane. Clearly, the deviation from ideal trigonal-bypyr-
amidal geometry arises from the steric requirements of
the two chelating ligands. The axial Al-N bond lengths
are in good agreement with those which are observed in
similar five coordinate aluminum complexes14 where
Al-N bond lengths are found in the range from
˚
˚
2.051(18) A to 2.179(7) A. Colorless compound 7 crystal-
lizes in the monoclinic space group P21/n, with one
monomer in the asymmetric unit from n-hexane at -78
°C. The coordination polyhedron around the aluminum
atom features a distorted tetrahedral environment and
the metrical parameters associated with the PN2 ligand
are quite similar to those of 2 and 3. The Al-N3 and
Al-N4 bond distances are comparable to those reported
in structurally characterized Al-bound terminal NMe2
groups.15 The Al-N1 and Al-N2 bond lengths
˚
the Al-N bond lengths of 2.08(13) A for Al-N1 and
˚
2.100(13) A for Al1-N4 are almost the same. The equa-
(11) Bickley, J. F.; Copsey, M. C.; Jeffery, J. C.; Leedham, A. P.; Russell,
C. A.; Stalke, D.; Steiner, A.; Stey, T.; Zacchini, S. J. Chem. Soc., Dalton
Trans. 2004, 989–995.
˚
(1.937(12)-1.950(12) A) are longer than the Al-N3 and
(12) (a) Leusser, D.; Henn, J.; Kocher, N.; Engels, B.; D.; Stalke, D. J.
Am. Chem. Soc. 2004, 126, 1781–1793. (b) Kocher, N.; Henn, J.; Gostevskii, B.;
Kost, D.; Kalikhman, I.; Engels, B.; Stalke, D. J. Am. Chem. Soc. 2004, 126,
5563–5568.
(13) Cui, C.; Roesky, H. W.; Noltemeyer, M.; Lappert, M. F.; Schmidt,
H.-G.; Hao, H. Organometallics 1999, 18, 2256–2261.
::
::
(14) (a) Muller, J.; Schroder, R.; Wang, R. Eur. J. Inorg. Chem. 2000, 153–
157. (b) Yu, R.-C.; Hung, C.-H.; Huang, J.-H.; Lee, H.-Y.; Chen, J.-T. Inorg.
Chem. 2002, 41, 6450–6455.
(15) Ying, Y.; Schultz, T.; John, M.; Ringe, A.; Roesky, H. W.; Stalke, D.;
Magull, J.; Hongqi, Y. Inorg. Chem. 2008, 47, 2585–2592.

Article
Inorganic Chemistry, Vol. 48, No. 19, 2009 9177
a
˚
Table 1. Selected Bond Lengths [A] and Angles [deg] of 3 , 4, 5, and 7
3a(R1 = R2 = Cl)
3b(R1 = R2 = Cl)
4 (R1 = Cl, R2 = Me)
5 (R1 = N3, R2 = N4)
7 (R1 = N3, R2 = N4)
Al1-N1
Al1-N2
Si1-N1
Si2-N2
P1-N1
P1-N2
Al1-R1
Al1-R2
1.880(17)
1.885(17)
1.739(16)
1.747(17)
1.629(16)
1.623(16)
2.132(8)
1.890(18)
1.874(18)
1.744(18)
1.742(18)
1.625(17)
1.628(17)
2.122(8)
1.899(13)
1.909(13)
1.736(12)
1.733(12)
1.614(12)
1.617(12)
2.155(6)
2.080(13)
1.947(13)
1.937(12)
1.950(12)
1.727(12)
1.728(12)
1.614(11)
1.606(12)
1.795(12)
1.790(13)
1.7252(13)c
1.7381(13)c
1.5923(13)c
1.6162(12)c
1.939(13)
2.130(8)
2.131(8)
1.947(15)
2.100(13)
R1-Al1-R2
Al1-N1-P1
Al1-N2-P1
N1-P1-N2
N1-Al1-N2
C1-P1-C7
Si1-N1-Al1
Si1-N1-P1
Si2-N2-Al1
Si2-N2-P1
R1-Al1-N1
R2-Al1-N1
R1-Al1-N2
R2-Al1-N2
109.51(3)
90.59(8)
90.57(8)
97.65(8)
81.11(7)
107.16(9)
132.34(9)
132.44(10)
132.11(9)
137.02(10)
114.04(6)
116.42(6)
115.83(6)
117.67(6)
108.95(3)
90.44(8)
90.90(8)
97.50(9)
81.07(7)
106.72(9)
128.49(10)
135.25(11)
132.31(10)
134.97(10)
112.37(6)
119.22(6)
116.73(6)
116.49(6)
111.89(6)
90.89(6)
90.41(6)
98.56(6)
80.04(5)
106.846(7)
131.52(7)
136.69(8)
128.83(7)
134.17(8)
110.81(4)
120.92(7)
109.69(4)
119.69(6)
75.66 (5)
89.23(6)c
93.90(6)c
101.10(6)c
75.75(5)
111.61(6)
91.38(6)
91.14(6)
99.15(6)
78.21(5)
104.23(7)
131.04(6)
133.52(7)
130.33(6)
133.57(7)
113.12(6)
118.87(6)
119.33(6)
112.27(6)
106.58(7)c
133.46(7)c
133.13(8)c
135.69(7)c
128.08(8)c
102.38(5)
175.80(5)
110.34(6)
101.33(5)
a a and b are the two independent molecules. c Averaged values, esds are extremes.
Figure 5. Superposition of 3, 4, 5, and 7, depicting the response of the trimethylsilyl group at N1 to the bulk of the two other substituents at the aluminum
atom.
˚
Al-N4 distances (1.790(13)-1.795(12) A), because of the
electronically delocalized PN2 ligand.
in 4 leaves the angle sum at the nitrogen atom virtually
unchanged (359.7 vs 359.1°), and the silyl atom almost
shares the plane with the PN2Al four-membered ring.
Only the second iminophosphonamide ligand in 5 and the
two dimethylamino groups in 7 remove that silyl group
from the plane, indicated by an angle sum of only 356.16
and 355.94°, respectively.
Structural Comparison of LAlCl2 (3), LAlMeCl (4),
L2AlH (5), and LAl(NMe2)2 (7). The superposition of
the PN2Al four-membered rings in the four structures in
Figure 5 reveals that not only does this motif remains
widely unchanged but even the phenyl groups adopt the
same orientation. Also the remaining substituents at
aluminum stay almost in place. Remarkably, only one
of the two Me3Si groups responds to the various steric
requirements of those two exocyclic substituents. Switch-
ing one of the chlorine substituents in 2 to a methyl group
Experimental Section
General Procedures. All experimental manipulations were
carried out under an atmosphere of dry nitrogen using standard
Schlenk techniques. The samples for spectral measurements

9178 Inorganic Chemistry, Vol. 48, No. 19, 2009
Nekoueishahraki et al.
Table 2. Crystal Data and Structure Refinement for Compounds 3, 4, 5, and 7
3
4 0.5 C7H8
5 1 THF
7
empirical formula
formula weight
T [K]
C
457.45
100(2)
triclinic
P1
9.8445(7)
10.1246(7)
28.090(2)
81.2820(10)
89.0870(10)
61.8080(10)
2434.2(3)
4
18H28AlCl2N2PSi2
C22.5H35AlClN2PSi2
483.11
100(2)
monoclinic
P21/c
10.8667(10)
10.8034(10)
23.915(2)
90
102.5070(10)
90
2740.9(4)
4
1.171
0.329
1028
C40H65AlN4OP2Si4
819.24
100(2)
monoclinic
P21/n
12.7603(12)
19.0226(18)
19.412(2)
90
96.103(2)
90
4685.3(8)
4
1.161
0.248
1760
C22H40AlN4PSi2
474.71
100(2)
monoclinic
P21/n
11.2941(8)
17.1485(12)
14.4640(10)
90
91.8650(10)
90
2799.9(3)
4
1.126
0.231
1024
crystal system
space group
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
F
calcd, Mg m-3
1.248
0.473
960
μ, mm-1
F(000)
θ range for data collcn [deg]
no. of reflections collected
no. of indept reflections
data/restraints/parameters
GoF
2.68-26.36
53683
9866
9866/0/481
1.057
0.0341, 0.0722
0.0465, 0.0771
0.66/-0.326
1.74-26.05
52109
5405
5405/0/288
1.068
0.0298, 0.0799
0.0329, 0.0818
0.409/-0.364
1.50-26.74
41456
9929
9929/0/484
1.047
0.0318, 0.0809
0.0394, 0.0842
0.441/-0.254
1.84-27.51
72209
6427
6427/0/292
1.077
0.0361, 0.0943
0.0448, 0.0989
0.342/-0.280
R1, wR2[ I > 2σ(I)]a
R1, wR2 (all data)
largest diff peak, hole (e A
-3
˚
)
P
P
P
P
a R1 = ||Fo| - |Fc||/ |Fo|; wR2 = [ w(Fo2 - Fc2)2/ w(Fo2)2]0.5
.
were prepared in a glovebox. The solvents were purified accord-
ing to conventional procedures and were freshly distilled prior to
use. AlEt3, MeAlCl2, and AlCl3 were purchased from Aldrich,
NMR (125.76 MHz, C6D6, 298 K): δ 1.91, 1.93, 132.3-127.4.
31P NMR (121.50 MHz, C6D6): δ 37.8.
Synthesis of LAlMeCl (4). AlMeCl2 (1.0 M in n-hexane,
1.4 mL, 1.4 mmol) was added drop by drop to the solution
of freshly prepared 2 (0.5 g, 1.36 mmol) in toluene (70 mL) at
-78 °C. The mixture was stirred at -78 °C for 1 h, and then the
temperature was slowly raised to 0 °C and stirring was continued
for 3 h. After that the solution was allowed to attain room
temperature, and stirring was continued for 12 h. Then the mixture
was extracted with n-hexane (70 mL), and the concentrated solution
was stored in a freezer at -30 °C to obtain colorless crystals. Yield
and AlH3 NMe3 was prepared by published methods.16 NMR
3
spectra were recorded either on a Bruker Avance 200 or on
500 NMR spectrometers and referenced to the deuterated
solvent in the case of the 1H and 13C NMR spectra. 29Si NMR
spectra were referenced to SiMe4 and those of 31P NMR to
85% H3PO4. All NMR measurements were carried out at room
temperature. Melting points were measured in sealed glass tubes
on a Buchi B-540 melting point apparatus and are uncorrected.
Elemental analyses were performed at the Analytical Labora-
::
1
(0.41 g 68%); mp 135 °C; H NMR (200 MHz, C6D6, 298 K):
::
tory of the Institute of Inorganic Chemistry at Gottingen.
δ -0.03 (s, 18H, Si-Me), 0.04 (s, 3H, Al-Me), 7.65-7.85 (m, 4H,
o-Ar), 6.92-7.07 (m, 6H, p-/m-Ar). 13C NMR (125.76 MHz, C6D6,
298 K): δ -0.69, 1.71, 1.66, 131.6-129.2. 31P NMR (121.50 MHz,
C6D6, 298 K): δ33.2. 29Si NMR (59.6 MHz, C6D6, 298 K): δ-0.31,
-0.34. Anal. Calcd for C19H31AlClN2PSi2: C, 52.22; H, 7.15; N,
6.41. Found C, 52.54; H, 7.15; N, 6.21.
N,N0-Bis(trimethylsilyl)diphenyliminophosphonamide4 and [Al-
(NMe2)3]217were prepared according to literature procedure.
Synthesis of LLi (2). To a solution of 15 (3.0 g, 8.33 mmol) in
toluene (80 mL) at -78 °C was added nBuLi (2.5 M, 3.4 mL,
8.5 mmol). The mixture was warmed to room temperature and
stirred overnight. Toluene was removed under reduced pressure,
and the product was recrystallized from a mixture of toluene and
n-hexane. [LiPh2P(NSiMe3)2] formed colorless crystals. Yield
(0.84 g, 83%), whose spectral data agreed with those reported in
literature.6 1H NMR (200 MHz, C6D6, 298 K): δ 0.12 (s, 18H,
Si-Me), 7.61-7.80 (m, 4H, o-Ar), 6.98-7.07 (m, 6H, p-/m-Ar).
31P NMR (121.50 MHz, C6D6, 298 K): δ 7.4.
Synthesis of L2AlH (5). The n-hexane solution (30 mL) of 1
(1.0 g, 2.7 mmol) was added drop by drop to a cold suspen-
sion of freshly sublimed AlH3 NMe3 in THF (30 mL), (0.12 g,
3
1.39 mmol) at -78 °C. The mixture was stirred at -30 °C for 1 h
and then the temperature was slowly raised to 0 °C and the stirring
was continued for 3 h. Then the solution was allowed to attain
room temperature under stirring for 12 h. Then the mixture was
concentrated and stored in a freezer at -30 °C to obtain color-
Synthesis of LAlCl2 (3). A toluene solution of freshly pre-
pared 2 (1.0 g, 2.73 mmol) was added drop by drop to a cold
suspension of freshly sublimed AlCl3 (0.36 g, 2.73 mmol) in
toluene at -78 °C. The temperature was raised to 0 °C and
stirred for 1 h, and stirring was continued for 3 h. The solution
was allowed to attain room temperature, and stirring was
continued for 12 h. Then the mixture was filtered, and the
concentrated solution was stored in a freezer at -30 °C to
obtain colorless crystals. Yield (0.76 g 61%); mp 135 °C (dec);
1H NMR (200 MHz, C6D6, 298 K): δ -0.2 (s, 18H, Si-Me),
7.65-7.81 (m, 4H, o-Ar), 6.95-7.07 (m, 6H, p-/m-Ar). 13C
1
less crystals. Yield: (0.64 g 61%); mp 107 °C (dec); H NMR
(200 MHz, CDCl3, 298 K): δ -0.22 (s, 18H, Si-Me), -0.13 (s,
18H, Si-Me), 5.1 (very br, 1H, Al-H), 7.78-7.92 (m, 4H, o-Ar),
7.45-7.59 (m, 6H, p-/m-Ar). 13C NMR (125.76 MHz, C6D6,
298 K): δ 1.52, 1.56, 3.75, 3.80, 133.1-131.2. 31P NMR (121.50
MHz, C6D6, 298 K): δ 29.2, 34.6. 29Si NMR (59.6 MHz, C6D6,
298 K): δ -4.15, -4.22. IR (cm-1): ν~ (AlH) 1853. Anal. Calcd for
C37H60AlN4P2Si4: C, 58.31; H, 7.93; N, 7.35. Found C, 57.94; H,
7.83; N, 7.21.
Synthesis of LAlEt2 (6). AlEt3 (2.2 mL, 2.2 mmol) was added to
a n-hexane (50 mL) solution of 1 (0.8 g, 2.2 mmol) at -78 °C. The
mixture was stirred for 1 h at this temperature and then was allowed
to attain room temperature, and stirring was continued for 12 h.
The mixture was concentrated and stored in a freezer at -30 °C to
(16) Ruff, J. K.; Hawthorne, M. F. J. Am. Chem. Soc. 1961, 83, 535–538.
(17) Waggoner, M.; Olmstead, M. M.; Power, P. P. Polyhedron 1990, 9,
257–263.
1
give white microcrystalline solid. Yield: (0.86 g, 88%); H NMR

Article
Inorganic Chemistry, Vol. 48, No. 19, 2009 9179
(500 MHz, C6D6, 298 K): δ -0.05 (s, 18H, Si-Me), 0.45 (q, 4H,
CH2), 1.52 (t, 6H, CH3), 7.71-7.81 (m, 4H, o-Ar), 6.97-7.11 (m,
6H, p-/m-Ar). 13C NMR (125.8 MHz, C6D6, 298 K): δ 1.99, 2.04,
10.4, 134.5-131.9. 31P NMR (121.50 MHz, C6D6, 298 K): δ 30.3.
29Si NMR (59.6 MHz, C6D6, 298 K): δ -2.61, -2.54.
Synthesis of LAl(NMe2)2 (7). n-Hexane (30 mL) solution of 1
(0.9 g, 2.5 mmol) was added to [Al(NMe2)3]2 (0.4 g, 1.25 mmol)
in n-hexane (20 mL), and then heated under reflux for 6 h. The
mixture was cooled to room temperature, concentrated, and stored
in a freezer at -30 °C to obtain a colorless microcrystalline solid.
Yield: (0.69 g, 58%); mp 156 °C; 1H NMR (500 MHz, C6D6, 298
K): δ 0.024 (s, 18H, Si-Me), 3.06 (s, 12H, CH3), 7.73-7.83 (m, 4H,
o-Ar), 7.03-7.08 (m, 6H, p-/m-Ar). 13C NMR (125.8 MHz, C6D6,
298 K): δ 1.86, 1.92, 41.8, 134.3-132.0. 31P NMR (121.50 MHz,
C6D6, 298 K): δ 28.6. 29Si NMR (59.6 MHz, C6D6, 298 K):
δ -2.67, -2.72. Anal. Calcd for C22H40AlN4PSi2: C, 55.66; H,
8.49; N, 11.80. Found C, 55.11; H, 8.63; N, 11.94.
X-ray Structure Determination of 3, 4, 5, and 7. All data were
collected from shock-cooled crystals on Bruker SMART-APEX
II diffractometers with D8 goniometers at 100 K18 (Mo KR
radiation, λ = 71.073 pm; 3: graphite-monochromated; 4 and 5:
INCOATEC Helios mirror optics; 7 INCOATEC Quazar
mirror optics). The data were integrated with SAINT,19 and
an empirical absorption correction (SADABS) was applied.20
The structures were solved by direct methods (SHELXS)21 and
refined on F2 using the full-matrix least-squares methods of
SHELXL.22 All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. With the exception of H1 (5),
all hydrogen atoms bonded to sp2 (sp3) carbon atoms were
assigned ideal positions and refined using a riding model with
Uiso constrained to 1.2 (1.5) times the Ueq value of the parent
carbon atom; the position of the Al-bonded hydrogen atom
H1 (5) was taken from the difference map and refined freely
(Table 2).
(18) (a) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615–619. (b)
Kottke, T.; Lagow, R. J.; Stalke, D. J. Appl. Crystallogr. 1996, 29, 465–468.
(19) SAINT v7.34A in Bruker APEX v2.1-0; Bruker AXS Inst. Inc.:
Madison, WI, 2005.
::
(20) Sheldrick, G. M. SADABS 2004/1; Gottingen, Germany, 2004.
Supporting Information Available: X-ray data for 3, 4, 5, and
7 (CIF). This material is available free of charge via the Internet
at http://pubs.acs.org.
(21) Sheldrick, G. M. SHELXS in SHELXTL, v6.12; Bruker AXS Inst.
Inc.: Madison, WI, 2000.
(22) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.