Imido analogs of aluminophosphates: Syntheses and X-ray structures of {LiA1[OP(NtBu)2 (NMtBu)]2}2 and the mono- and di-methylaluminum complexes of the anions [OP(NtBu)x (NHt

Article abstract of DOI:10.1016/S0022-328X(01)01100-7

The reaction of OP(NH^tBu)₃ with trimethylaluminum in 1:1 or 2:1 molar ratios in hydrocarbon solvents yields the complexes {Me₂Al(μ-N^tBu)₂P(μ-O) (NH^tBu)A1Me₂[OP(NH^tBu)<

Full text of DOI:10.1016/S0022-328X(01)01100-7

Journal of Organometallic Chemistry 646 (2002) 107–112
www.elsevier.com/locate/jorganchem
Imido analogs of aluminophosphates: syntheses and X-ray
structures of {LiAl[OP(NtBu)2(NHtBu)]2}2 and the mono- and
di-methylaluminum complexes of the anions
x−
[OP(NtBu)x(NHtBu)3−x
]
(x=1, 2)
Pierre Blais, Tristram Chivers *, Gabriele Schatte, Mark Krahn
Department of Chemistry, Uni6ersity of Calgary, Calgary, Alta., Canada T2N 1N4
Received 3 May 2001; accepted 5 July 2001
Abstract
The reaction of OP(NHtBu)3 with trimethylaluminum in 1:1 or 2:1 molar ratios in hydrocarbon solvents yields the complexes
{Me2Al(m-NtBu)2P(m-O)(NHtBu)AlMe2[OP(NHtBu)3]} (1) and MeAl[(m-NtBu)(m-O)P(NHtBu)2]2 (2). The dimeric complex
{LiAl[OP(NtBu)2(NHtBu)]2}2 (3) is obtained by treatment of OP(NHtBu)3 with LiAlH4 in toluene. Complexes 1–3 were
characterized by multinuclear NMR spectroscopy and by X-ray crystallography, which revealed different bonding modes for the
anions [OP(NtBu)(NHtBu)2]2− and [OP(NtBu)2(NHtBu)]2−. © 2002 Published by Elsevier Science B.V.
Keywords: Aluminum; Phosphate; Imido derivatives; Structures; X-ray diffraction
1. Introduction
fundamental building block in polycyclic lithium imi-
dosulfites [14] and bis(imido)sulfates [15].
Aluminophosphates (AlPOs) are the subject of much
interest because they form microporous materials with
possible applications as molecular sieves or in catalysis
[1]. Several methods have been explored for generating
AlPOs with different molecular architectures, viz. tem-
plation by fluoride ions [2] or organic ammonium
cations [3,4]. Attention has also been directed recently
to Group 13 phosphonates as soluble models for phos-
phate materials [5–13]. A possible alternative approach
to the generation of AlPOs with unique properties is
In a preliminary investigation of the synthesis and
structures of imido derivatives of aluminophosphates,
e.g. Al[OP(NtBu)3], we have carried out the reactions of
OP[NHtBu)]3 with (a) trimethylaluminum and (b)
lithium aluminum hydride. We report here the synthe-
sis, spectroscopic characterization and X-ray struc-
tures of {Me2Al(m-NtBu)2P(m-O)(NHtBu)AlMe2[OP-
(NHtBu)3]} (1), MeAl[(m-NtBu)(m-O)P(NHtBu)2]2 (2),
and{LiAl[OP(NtBu)2(NHtBu)]2}2 (3).
the substitution of one (or more) of the oxo (O2−
)
ligands with isoelectronic imido (NR2−) groups. The
ability to change the size of the R groups allows the
possibility of controlling the structure of the clusters
formed by alkali-metal derivatives of heteroleptic
imido/oxo anions with p-block element centers. In re-
cent studies, we have demonstrated that subtle changes
in the R group can significantly alter the size of the
2. Experimental
Solvents (n-hexane, toluene (Na/benzophenone))
were dried and distilled before use. The reagents
NHt2Bu and Me3Al (2.0 M in hexanes) were commercial
samples (Aldrich) used as received. LiAlH4 was purified
by extraction with diethyl ether followed by filtration
and removal of the solvent from the filtrate under
vacuum. The compound OP(NHtBu)3 was prepared
from OPCl3 and the primary amine NHt2Bu by a
modified literature procedure [16]. The handling of air-
and moisture-sensitive materials was performed under
* Corresponding author. Tel.: +1-403-220-5741; fax: +1-403-289-
9488.
E-mail address: chivers@ucalgary.ca (T. Chivers).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01100-7

108
P. Blais et al. / Journal of Organometallic Chemistry 646 (2002) 107–112
an atmosphere of argon gas using standard Schlenk
techniques or a glove box.
2.3. Synthesis of {LiAl[OP(NtBu)2(NHtBu)]2}2 (3)
1H-NMR spectra were collected with a Bruker AM-
200 spectrometer. 31P-NMR spectra were obtained with
a Varian XL-200 spectrometer and chemical shifts are
reported relative to 85% H3PO4. Solid-state 13C-, 27Al-,
and 31P-NMR studies were performed using a Bruker
AMX-300 spectrometer operating at 75.48, 78.20 and
121.50 MHz, respectively, with a BL4 probe and a spin
range of 8–14 kHz; chemical shifts are reported relative
to Me4Si, Al(NO3)3 and Na2HPO4, respectively. The
Analytical Services Laboratory of the Department of
Chemistry, University of Calgary, provided elemental
analyses.
A slurry of LiAlH4 (0.190 g, 4.75 mmol) in toluene
(15 ml) was added dropwise to a slurry of OP(NHtBu)3
(2.50 g, 9.50 mmol) in toluene (20 ml). Bubbles of H2
gas were evolved slowly and the mixture was stirred for
18 h at 23 °C. The solvent was removed from the
cloudy solution under vacuum to give a fine pale-yellow
powder, which was washed with toluene (3×10 ml).
The remaining solvent was removed under vacuum and
{LiAl[OP(NtBu)2(NHtBu)]2}2 (3) was obtained as a fine
white powder (2.330 g, 1.93 mmol, 81%). Clear plates
of 3·C7H8 were obtained from a concentrated solution
of 3 in toluene kept at room temperature for 8 days.
1H-NMR (C6D6): l 1.67 (d, 9H, 4JPNCCH=0.68 Hz,
4
t
tBu), 1.58 (d, 9H, JPNCCH=0.70 Hz, Bu), 1.52 (d, 9H,
t
4
4JPNCCH=0.69 Hz, Bu), 1.47 (d, 9H, JPNCCH=0.69
2.1. Synthesis of {Me2Al(v-NtBu)2P(v-O)(NHtBu)-
AlMe2[OP(NHtBu)3]} (1)
t
4
t
Hz, Bu), 1.45 (d, 9H, JPNCCH=0.68 Hz, Bu), 1.36 (s,
9H, Bu). 27Al-NMR (solid state): l −183.14 (W1/2
=
t
278 Hz). 13C-NMR (solid state): l 52.65 (C(CH3)3),
51.35 (2×C(CH3)3), 50.70 (2×C(CH3)3), 50.18
(C(CH3)3), 36.19 (C(CH3)3), 34.39 (C(CH3)3), 34.02
(2×C(CH3)3), 32.91 (2×C(CH3)3). 31P-NMR (solid
state): l 12.17, −4.88. Anal. Found: C, 51.59; H,
10.04; N, 14.93. Calc. for C55H120N12Al2Li2O4P4: C,
51.79; H, 10.14; N, 15.10%.
A clear solution of Me3Al (2 M, 1.14 ml, 2.28 mmol)
was added dropwise to a stirred slurry of OP(NHtBu)3
(0.600 g, 2.28 mmol) in n-hexane or toluene (20 ml) at
23 °C and the mixture was stirred for 18 h. The volume
of the solution was reduced by approximately one-half
under vacuum. After 12 h at 23 °C, colorless crystals
were formed and the mother liquor was decanted by a
cannula. The crystalline solid was dried under dynamic
vacuum and identified as {Me2Al(m-NtBu)2P(m-
O)(NHtBu)AlMe2[OP(NHtBu)3]} (0.378 g, 0.59 mmol,
52%). 1H-NMR (C6D6): l 2.39 (d, 2JPNH=10 Hz, NH),
2.27 (d, 2JPNH=10 Hz, NH), 1.60 (s, 18H, tBu), 1.47 (s,
9H, tBu), 1.45 (s, 27H, tBu), −0.09 (s, 3H, Me), −0.11
(s, 3H, Me), −0.28 (s, 6H, Me). 31P-NMR (C6D6): l
3.27 (s), −0.49 (s). Anal. Found: C, 52.34; H, 11.48; N,
12.77. Calc. for C28H70N6Al2O2P2: C, 52.65; H, 11.04;
N, 13.16%.
2.4. Crystal structures of 1, 2 and 3·C7H8
Crystal data for 1, 2 and 3·C7H8 are summarized in
Table 1. All data collections were carried out with a
Bruker AXS P4/RA/SMART 1000 CCD instrument
using monochromated Mo–Ka radiation (u=0.71073
,
A).
1: Cell parameters were determined using SMART [17]
software and refined with SAINT [18]. The structure was
solved using the heavy atom method (Patterson) in the
centrosymmetric space group Pnma (No. 62) (SHELXS-
2.2. Synthesis of MeAl[(v-NtBu)(v-O)P(NHtBu)2]2 (2)
97, [19]) and refined by full-matrix least-squares method
A clear solution of Me3Al (2 M, 1.14 ml, 2.28 mmol)
was added dropwise to a stirred slurry of OP(NHtBu)3
(1.200 g, 4.56 mmol) in n-hexane (30 ml) at 23 °C. The
mixture was heated to reflux and stirred for 18 h. The
volume of the solution was reduced to approximately
one-quarter of the original volume under vacuum and
the solution was then heated to 70 °C and allowed to
deposit crystals for 3 h at 23 °C. The crystallization
procedure was repeated twice to give MeAl[(m-NtBu)(m-
O)P(NHtBu)2]2 (1.100 g, 1.94 mmol, 85%). 1H-NMR
on F2 with SHELXL-97-2 [20].
The nitrogen atom and one carbon atom of one
NtBu group (N(4A), N(4B), C(43A), C(43B)) were dis-
ordered over two sites with partial occupancy factors of
0.5 each in both cases. The other non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were in-
cluded at geometrically idealized positions and were not
refined.
2 and 3·C7H8: The procedures used for data collec-
tion and the refinement of the structures of 2 and
3·C7H8 were the same as those described above for 1.
Both structures were solved by direct methods. Three
carbon atoms of the disordered toluene molecule in
3·C7H8 were positioned over two sites with partial
occupancy factors of 0.50 each.
t
(C6D6): l 2.25 (broad, s, NH), 1.55 (s, 18H, Bu), 1.30
t
(s, 36H, Bu), −0.09 (s, 3H, Me). 31P-NMR (C6D6): l
11.50 (s). Anal. Found: C, 51.89; H, 10.51; N, 14.43.
Calc. for C25H61N6AlO2P2: C, 52.98; H, 10.85; N,
14.83%.

P. Blais et al. / Journal of Organometallic Chemistry 646 (2002) 107–112
109
Table 1
Crystal data and structure refinement parameters for 1, 2 and 3
1
2
3·C7H8
Empirical formula
Formula weight
Temperature (°C)
Crystal system
Space group
Unit cell dimensions
C28H70N6Al2O2P2
638.80
−80(2)
Orthorhombic
Pnma (c62)
C25H61N6AlO2P2
566.72
−80(2)
Orthorhombic
Iba2 (c45)
C55H120N12Al2Li2O4P4
1205.35
−80(2)
Monoclinic
P21/n (c14)
,
a (A)
25.1500(17)
14.7597(10)
11.0507(7)
19.561(3)
11.028(2)
16.023(3)
15.1850(8)
10.6573(6)
23.4217(11)
103.9232(9)
3679.0(3)
2
1.088
0.173
6968
,
b (A)
,
c (A)
i (°)
V (A )
3
,
4102.1(5)
4
1.034
0.178
4371
3456.2(11)
4
1.089
0.180
2688
Z
Dcalc (g cm−3
)
Absorption coefficient (mm−1
)
Unique data
Observed data
3390
2295
5662
Parameters refined
220
165
370
R
Rw
0.0653
0.1827
0.0426
0.1002
0.0545
0.1597
R1=[ꢀꢁ ꢁFoꢁ−ꢁFcꢁ ꢁ]/[ꢀꢁFoꢁ] for [F2o\2|(Fo2)]e. wR2={[ꢀw(Fo2−Fc2)2]/[ꢀw(Fo2)2]}1/2 (all data).
,
A is significantly shorter than the exocyclic P(1)ꢀN(1)
3. Results and discussion
,
bond (1.657(3) A). Surprisingly, there is no significant
The reaction of OP(NHtBu)3 with trimethylalu-
minum in a 1:1 molar ratio in hexane or toluene at
23 °C produces a mixture of products. The major
component, which was isolated in 52% yield, was iden-
tified by X-ray crystallography as {Me2Al(m-NtBu)2P(m-
O)(NHtBu)AlMe2[OP(NHtBu)3]} (1). The structure of 1
is depicted in Fig. 1 and selected bond distances and
bond angles are summarized in Table 2. The reagent
OP(NHtBu)3 is doubly deprotonated by two equivalents
of Me3Al to give the [OP(NtBu)2(NHtBu)]2− dianion,
which is N,N%-chelated to one Me2Al+ cation and
connected in an O-monodentate fashion to the second
Me2Al+ cation. The coordination sphere of the latter
Al center is completed by the neutral O-donor ligand
difference in the Al–O distances involving the neutral
OP(NHtBu)3 ligand and the anionic {Me2Al(m-
NtBu)2P(O)(NHtBu)]− fragment whereas the P–O dis-
,
tance in the former (1.466(3) A) is, as expected,
,
significantly shorter than that in the latter (1.539(3) A).
The bond angles at Al(2) range from 101.04(15)
(ÚOAlO) to 114.1(5)° (ÚCAlC).
NMR data indicate that the solid-state structure of 1
1
is maintained in solution. The H-NMR spectrum of 1
in C6D6 exhibits three resonances for NtBu groups in
the integrated area ratio 2:1:3 corresponding to the two
OP(NHtBu)3.
The
N,N%
bonding
mode
of
[OP(NtBu)2(NHtBu)]2- is reminiscent of the ligand be-
havior of [O2S(NtBu)2]2− in covalent P(III) derivatives
[21,22].
As a result of a crystallographic mirror plane, an
interesting feature of the structure of 1 is the coplanar-
ity of the ten-atom sequence C(1)/C(2), Al(1), P(1),
O(1), Al(2), O(2), P(2), N(3) and C(30). The four-mem-
bered AlN2P ring is essentially planar with distorted
tetrahedral geometries at Al(1) and P(1). The endo-
cyclic bond angles ÚNAlN and ÚNPN are 77.62(16)
and 95.2(2)°, respectively. The geometry at the bridging
nitrogens is almost planar (ꢀÚN(2)=357.1°) with
ÚP(1)N(2)Al(1)=93.54(15)°. The Al–N distance of
Fig. 1. ORTEP diagram of {Me2Al(m-NtBu)2P(m-O)(NHtBu)AlMe2-
[OP(NHtBu)3]} (1). Ellipsoids are drawn at the 30% level. For clarity,
only the a-carbon atoms of Bu groups are shown.
,
1.900(3) A is typical for four-coordinate Al complexes
t
[23]. The endocyclic bond length [P(1)ꢀN(2)] of 1.612(3)

110
P. Blais et al. / Journal of Organometallic Chemistry 646 (2002) 107–112
bridging NtBu groups, the terminal NHtBu group, and
Table 2
a
,
Selected bond lengths (A) and bond angles (°) for 1
the three NHtBu groups of the OP(NHtBu)3 ligand,
respectively. The latter resonance (l 1.05) is shifted
upfield compared to that of the free ligand (l 1.30).
Three resonances at l −0.09, −0.11 and −0.28 in the
ratio 1:1:2 are observed for the two Me2Al units. The
first two signals are attributed to the inequivalent
methyl groups of the Me2Al+ cation in the four-mem-
bered ring. The 31P-NMR spectrum of 1 shows two
equally intense resonances at l 3.27 and −0.09, cf. l
5.53 for OP(NHtBu)3 in C6D6.
Bond lengths
P(1)ꢀO(1)
P(2)ꢀO(2)
P(1)ꢀN(2)
P(2)ꢀN(3)
P(2)ꢀN(4A)
Al(1)ꢀN(2)
Al(2)ꢀO(2)
Al(2)ꢀO(1)
1.539(3)
1.466(3)
1.612(3)
1.606(3)
1.592(3)
1.900(3)
1.774(3)
1.773(3)
P(1)ꢀN(1)
Al(1)ꢀC(2)
Al(1)ꢀC(1)
Al(2)ꢀC(3)
1.657(3)
1.988(6)
1.990(6)
1.945(3)
Bond angles
When the reaction of OP(NHtBu)3 with trimethylalu-
minum is carried out in a 2:1 molar ratio in n-hexane at
reflux or in toluene at 75 °C, the complex MeAl[(m-
NtBu)(m-O)P(NHtBu)2]2 (2) is isolated in ca. 85% yield.
The structure of 2 was determined by X-ray crystallog-
raphy (see Fig. 2) and selected bond distances and bond
angles are given in Table 3. Complex 2 consists of two
monoanionic [OP(NtBu)(NHtBu)2]− ligands, which are
both N,O-chelated to the MeAl2+ dication. The alu-
minum atom is in a distorted trigonal bipyramidal
geometry with equatorial bond angles ÚNAlN=123.1
and ÚNAlC=118.5° and a distinctly non-linear axial
arrangement, ÚOAlO=161.2° (cf. 156.2–158.8° for
related five-coordinate aluminum complexes [24]). The
CH3–Al unit occupies a crystallographic twofold axis.
The four-membered AlNPO rings are essentially planar.
O(1)P(1)N(1)
N(1)P(1)N(2)
N(2)Al(1)C(1)
C(2)Al(1)C(1)
P(1)O(1)Al(2)
O(2)Al(2)C(3)
O(1)Al(2)O(2)
100.94(17)
115.49(12)
116.33(17)
110.93(3)
145.4(2)
O(1)P(1)N(2)
N(2)P(1)N(2) b
N(2)Al(1)N(2) b
N(2)Al(1)C(2)
P(1)N(2)Al(1)
P(2)O(2)Al(2)
O(1)Al(2)C(3)
C(3)Al(2)C(3) b
115.34(14)
95.2(2)
77.62(16)
116.10(17)
93.54(15)
161.0(2)
111.7(2)
114.1(5)
108.7(2)
101.04(15)
a Symmetry transformation used to generate equivalent atoms.
b x, −y+1/2, z.
,
The Al–O distance of 1.9847(18) A falls outside the
,
range of 1.779–1.928 A observed for 5-coordinate Al
,
complexes whereas the Al–N distance of 1.928(2) A is
typical [24]. The PꢀO bond length of 1.519(2) A is
unexceptional and the endocyclic d(PꢀN) is ca. 0.04 A
,
,
shorter than the mean value of the exocyclic PꢀN bond
length, as found for 1. The monoanionic ligand
[(tBuNH)2P(O)(NtBu)]− subtends an angle of 74.07(9)°
at Al.
Fig. 2. ORTEP diagram of MeAl[(m-NtBu)(m-O)P(NHtBu)2]2 (2). Ellip-
soids are drawn at the 30% level. For clarity, only the a-carbon atoms
Consistent with the solid-state structure, the 1H-
NMR spectrum of 2 in C6D6 shows three resonances at
l −0.09, 1.30 and 1.55 in the ratio 1:12:6 attributable
to the MeAl unit, the four terminal NHtBu groups, and
the two bridging NtBu groups, respectively. The reso-
nance for the NH protons appears as a broad singlet at
l 2.25. The 31P-NMR spectrum of 2 exhibits a singlet at
l 11.50.
t
of Bu groups are shown.
Table 3
a
,
Selected bond lengths (A) and bond angles (°) for 2
Bond lengths
P(1)ꢀO(1)
P(1)ꢀN(2)
AlꢀN(1)
AlꢀO(1)
1.519(2)
1.645(3)
1.928(2)
1.9847(18)
P(1)ꢀN(1)
P(1)ꢀN(3)
AlꢀC(1)
1.606(4)
1.646(3)
1.978(5)
In summary, as indicated in Scheme 1, the reaction
of OP(NHtBu)3 with Me3Al in n-hexane or toluene in a
1:1 molar ratio generates 1 as the major product. The
presence of 2 (and other unidentified products) can be
Bond angles
O(1)P(1)N(1)
N(1)P(1)N(2)
N(1)P(1)N(3)
N(1)AlN(1) b
N(1)AlO(1)
C(1)AlO(1)
97.88(11)
121.86(13)
110.13(13)
123.10(16)
74.07(9)
99.39(7)
161.21(13)
93.73(10)
O(1)P(1)N(2)
O(1)P(1)N(3)
N(2)P(1)N(3)
N(1)AlC(1)
109.91(14)
117.56(13)
100.65(14)
118.45(8)
96.84(9)
1
detected in the reaction mixture by H- and 31P-NMR
spectroscopy. The formation of 2 is favored by increas-
ing the temperature of the reaction and the yield of 2 is
optimized, at ca. 85%, by using a 2:1 molar ratio of the
reagents in boiling n-hexane.
N(1) bAlO(1)
N(1)AlO(1) b
P(1)O(1)Al
96.84(9)
94.29(9)
O(1)AlO(1) b
P(1)N(1)Al
In a previous study, we showed that the reagent
LiAlH4 readily deprotonates SO2(NHtBu)2 in THF at
room temperature to give the single-strand polymer
a Symmetry transformation used to generate equivalent atoms.
b −x, −y+1, z.

P. Blais et al. / Journal of Organometallic Chemistry 646 (2002) 107–112
111
{Li(THF)2Al[SO2(NtBu)2]2}ꢀ [15]. As an extension of
Table 4
a
,
Selected bond lengths (A) and bond angles (°) for 3
this approach to complex imido/oxo anions of p-block
elements, we attempted to triply deprotonate
OP(NHtBu)3 by reaction with LiAlH4. However, only
the [OP(NtBu)2(NHtBu)]2− dianion is generated even
after prolonged reflux in toluene with an excess of
LiAlH4. When this reaction is carried out in a 1:2 molar
ratio, the complex {LiAl[OP(NtBu)2(NHtBu)]2}2 (3) is
obtained in 80% yield. The structure of 3·C7H8 was
determined by X-ray crystallography (see Fig. 3). Se-
lected bond distances and bond angles are given in
Table 4. Interestingly, the [OP(NtBu)2(NHtBu)]2− lig-
and adopts two different chelating modes, N,N% and
Bond lengths
P(1)ꢀN(6)
P(1)ꢀN(5)
P(2)ꢀO(2)
P(2)ꢀN(2)
AlꢀO(1)
1.558(2)
1.650(2)
P(1)ꢀO(1)
P(1)ꢀN(4)
P(2)ꢀN(1)
P(2)ꢀN(3)
AlꢀN(2)
AlꢀN(4)
O(2)ꢀLi(1)
1.6056(14)
1.6538(17)
1.6500(18)
1.6588(18)
1.8348(18)
1.8518(18)
1.796(4)
1.4931(15)
1.6515(18)
1.8055(15)
1.8408(18)
1.983(4)
AlꢀN(1)
O(1)ꢀLi(1) b
N(6)ꢀLi(1) b
2.000(4)
Bond angles
N(6)P(1)O(1)
O(1)P(1)N(5)
O(1)P(1)N(4)
O(2)P(2)N(1)
N(1)P(2)N(2)
N(1)P(2)N(3)
O(1)AlN(2)
N(2)AlN(1)
N(2)AlN(4)
P(1)O(1)Al
101.38(9)
112.15(9)
92.56(8)
117.68(9)
91.62(9)
112.01(9)
121.57(8)
80.20(8)
131.82(8)
95.19(7)
131.10(16)
93.99(9)
145.2(2)
75.85(15)
91.85(8)
N(6)P(1)N(5)
N(6)P(1)N(4)
N(5)P(1)N(4)
O(2)P(2)N(2)
O(2)P(2)N(3)
N(2)P(2)N(3)
O(1)AlN(1)
115.99(11)
127.32(11)
104.45(9)
117.92(9)
106.39(9)
110.86(9)
124.01(7)
80.19(7)
125.56(8)
90.72(13)
143.41(16)
94.15(9)
O(1)AlN(4)
N(1)AlN(4)
P(1)O(1)Li(1) b
P(2)O(2)Li(1)
P(2)N(2)Al
AlO(1)Li(1) b
P(2)N(1)Al
O(2)Li(1)N(6)
O(1) bLi(1)N(6)
P(1)N(4)Al
O(2)Li(1)O(1) b
O(2)Li(1)P(1) b
P(1)N(6)Li(1) b
135.30(2)
163.50(3)
91.52(15)
a Symmetry transformation used to generate equivalent atoms.
b −x, −y+1, −z.
N,O, towards the aluminum center in 3. The two halves
of the centrosymmetric dimer are linked by two three-
coordinate Li+ ions, which display O-monodentate co-
ordination to the N,N%-chelated ligand and O,N
chelation of the other [OP(NtBu)2(NHtBu)]2− dianion.
Access to the cavity of the resulting twelve-membered
t
Al2P2O4N2Li2 ring is partially impeded by Bu sub-
stituents (on N(1)).
Scheme 1.
As indicated in Table 4, one of the PꢀN bond lengths
,
(P(1)ꢀN(6)) in 3 is ca. 0.1 A shorter than the other five
PꢀN bonds, which fall within the narrow range 1.650–
,
1.659 A. Furthermore, the P(1)–O(1) distance is sub-
stantially longer than the P(2)ꢀO(2) bond, 1.6056(14)
,
,
versus 1.4931(15) A (cf. d(PꢁO)=1.5016(12) A in
Al(NMe2)3·OPPh3 [25]). Although this difference may
be partly attributable to the different coordination
numbers of the two oxygen atoms, 3 versus 2, it may
also indicate delocalization of the negative charge of
the complex anion [(tBuN)(tBuNH)P(m-O)(m-NtBu)Al-
(m-NtBu)2P(O)(NHtBu)]− over the N(6)ꢀP(1)ꢀO(1) unit.
The mean AlꢀN and AlꢀO bond distances of 1.842 and
,
1.805 A, respectively, are typical for 4-coordinate Al
[26,27]. There is a substantial difference of almost 0.2 A
for the Li–O distances involving the two- and three-co-
ordinate oxygen atoms, as has been observed previously
[28].
,
The four-membered PN2Al, PONAl and PONLi are
all almost planar with maximum deviations from pla-
Fig. 3. ORTEP diagram of {LiAl[OP(NtBu)2(NHtBu)]2}2 (3)·C7H8.
Ellipsoids are drawn at the 30% level. For clarity, only the a-carbon
atoms of tBu groups are shown. The toluene molecule is not included.
,
narity of 0.0125(7), 0.0284(7) and 0.0497(13) A, respec-

112
P. Blais et al. / Journal of Organometallic Chemistry 646 (2002) 107–112
tively. The [OP(NtBu)2(NHtBu)]2− ligands subtend
identical bond angles of 80.2° at Al via either N,O or
N,N chelation. The endocyclic bond angle ÚOLiN is
75.85(15)°.
[2] Y. Yang, J. Pinkas, M. Scha¨fer, H.W. Roesky, Angew. Chem.
Int. Ed. Engl. 37 (1998) 2650.
[3] I.D. Williams, Q. Gao, J. Chen, L.-Y. Ngai, Z. Lin, R. Xu,
Chem. Commun. (1996) 1781.
[4] W. Yan, J. Yu, Z. Shi, R. Xu, Inorg. Chem. 40 (2001) 379.
[5] M.G. Walawalkar, H.W. Roesky, R. Murugavel, Acc. Chem.
Res. 32 (1999) 117.
The 1H-NMR spectrum of 3 in C6D6 shows six
equally intense resonances in the region l 1.36–1.67
t
[6] M.R. Mason, J. Cluster Sci. 9 (1998) 1.
corresponding to the six inequivalent Bu groups at-
[7] Y. Yang, M.G. Walawalkar, J. Pinkas, H.W. Roesky, H.-G.
Schmidt, Angew. Chem. Int. Ed. Engl. 37 (1998) 96.
[8] Y. Yang, H.-G. Schmidt, M. Noltemeyer, J. Pinkas, H.W.
Roesky, J. Chem. Soc. Dalton. Trans. (1996) 3609.
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H.-G. Schmidt, J. Am. Chem. Soc. 119 (1997) 4656.
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H.-G. Schmidt, Organometallics 16 (1997) 516.
[11] K. Dimert, U. Englert, W. Kuchen, F. Sandt, Angew. Chem.
109 (1997) 251 (Angew. Chem. Int. Ed. Engl. 36 (1997) 241).
[12] M.R. Mason, M.S. Mashuta, J.F. Richardson, Angew. Chem.
109 (1997) 239 (Angew. Chem. Int. Ed. Engl. 36 (1997) 239).
[13] A. Keys, S. Bott, A.R. Barron, Chem. Commun. (1996) 2339.
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Int. Ed. Engl. 36 (1997) 1986.
tached to nitrogen atoms N(1)–N(6), suggesting that
the solid-state structure is maintained in C6D6 solution.
The solid-state 31P-NMR spectrum exhibits two reso-
nances at l 12.17 and −4.88 and the solid-state 27Al-
NMR spectrum revealed one signal at d −183.1.
4. Conclusions
These preliminary studies of imido analogs of alu-
minophosphate show that the AlPO analog Al[OP-
(NtBu)3] is not accessible from the reaction of OP[NHt-
Bu]3 and trimethylaluminum. Partial deprotonation oc-
x−
curs to give the anions [OP(NtBu)x(NHtBu)3−x
]
[15] P. Blais, J.K. Brask, T. Chivers, G. Schatte, Inorg. Chem. 40
(2001) 384.
[16] R.R. Holmes, J.A. Forstner, Inorg. Chem. 2 (1963) 380.
[17] SMART version 5.0: Software for the CD Detector System,
Bruker AXS, Inc., Madison, WI, 1998.
(x=1, 2) which engage in O,N or N,N chelation to the
aluminum center. The prevalence of four-membered
ring formation in 1–3, in contrast to the eight-mem-
bered rings observed for aluminophosphonates [29],
[18] SAINT version 5.0: Software for the CCD Detector System,
Bruker AXS, Inc., Madison, WI, 1998.
t
likely results from the steric influence of bulky Bu
groups. Future attempts to generate imido analogs of
AlPO materials will target derivatives with a lower N/O
ratio, e.g. Al[O3P(NR)], and smaller R groups.
[19] G.M. Sheldrick, SHELXS-97: Program for the Solution of Crys-
tal Structures, Universita¨t of Go¨ttingen, Go¨ttingen, Germany,
1997.
[20] G.M. Sheldrick, SHELXS-97-2: Program for the Solution of
Crystal Structures, Universita¨t of Go¨ttingen, Go¨ttingen, Ger-
many, 1997, Function minimized: ꢀw(ꢁFoꢁ−ꢁFcꢁ)2.
[21] E. Flu¨ck, H. Riffel, H. Richter, Phosphorus and Sulfur 4 (1985)
273.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 162602, 162603 and 162604
for compounds 1, 2 and 3, respectively. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
[22] A. Cowley, S.K. Mehrotra, H.W. Roesky, Inorg. Chem. 20
(1981) 712.
[23] (a) J.K. Brask, T. Chivers, G.P.A. Yap, Chem. Commun.
(1998) 2543;
(b) J.K. Brask, T. Chivers, G. Schatte, G.P.A. Yap,
Organometallics 19 (2000) 5683.
[24] (a) J.P. Corden, W. Errington, P. Moore, M.G.H. Wallbridge,
Chem. Commun. (1999) 323;
(b) J.P. Duxburg, A. Cowley, M. Thornton-Pett, L. Wantz,
J.N.D. Warner, R. Gretrex, D. Brown, T.P. Kee, Tetrahedron
Lett. 40 (1999) 4403;
Acknowledgements
(c) W. Liu, A. Hassan, S. Wang, Organometallics 16 (1997)
4257;
(d) J. Jewinski, J. Zachara, T. Kopen, Z. Ochal, Polyhedron 16
(1997) 1337;
(e) D.A. Atwood, M.S. Hill, J.A. Jegier, D. Rutherford,
Organometallics 16 (1997) 2659.
We thank Dr R. MacDonald (University of Alberta)
for the data collections for 1, 2 and 3 and the Natural
Sciences and Engineering Research Council of Canada
(NSERC) for financial support. Helpful discussions
about the structure of 1 with Dr M. Parvez (University
of Calgary) are gratefully acknowledged.
[25] J. Pinkas, H. Wessel, Y. Yang, M.L. Montero, M. Noltemeyer,
M. Fro¨ba, H.W. Roesky, Inorg. Chem. 37 (1998) 2450.
[26] M.S. Hill, D.A. Atwood, Main Group Chem. 2 (1998) 285.
[27] H. No¨th, A. Schlegel, J. Knizek, I. Krossing, W. Ponikwar, T.
Seifert, Chem. Eur. J. 4 (1998) 2191.
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[1] For a review see: A.K. Cheetham, G. Ferey, T. Louseau,
Angew. Chem. Int. Ed. Engl. 38 (1999) 3268.