Ligand-tetrahydrofuran coupling in chelated aluminum phosphinates

Article abstract of DOI:10.1021/ic0110326

When the reagents LAIMe (L = N,N-(alkylene or arylene)bis(3,5-di-tert-butyl)salicylideneimine (alkylene = ethylene (Salen(tBu)) (1); propylene (Salpen(tBu)) (2), and butylene (Salben(tBu)) (3); arylene = phenylene (Salophen(tBu) (4), 3,4-dimethylphenylene (Salomphen(tBu) (5)) are combined with Ph(H)P(O)OH in tetrahydrofuran (thf) the unique aluminophosphinate compounds, [L(tBu)Al{O₂P(H)Ph}]_n with L, n = Salen, ∞ (6), Salpen, 2 (7), Salben, 2 (8), Salophen, ∞ (9) and Salomphen, ∞ (10) are produced. The yields for the latter two reactions are low and it was subsequently found that the unique thf-coupled compounds appear in the thf filtrates of the original reaction mixture. These compounds are, [L-thf(tBu)Al{O₂P(H)Ph}]₂, L = Salophen (13) and Salomphen (14). The thf connects through an α-carbon to only one of the two possible imine carbons of the ligand. While trying to determine how this coupling proceeds, the six-coordinate, solution-state species LAIMe(thf) (L = Salophen (11) and Salomphen (12) were discovered and implicated as intermediates. All of the compounds are characterized by melting point, NMR, IR, and X-ray analyses for 5-8, 13, and 14. A possible mechanism for the thf coupling event is presented.

Full text of DOI:10.1021/ic0110326

Inorg. Chem. 2002, 41, 558−565
Ligand−Tetrahydrofuran Coupling in Chelated Aluminum Phosphinates
Y. Wang, S. Parkin, and D. Atwood*
Department of Chemistry, UniVersity of Kentucky, Lexington, Kentucky 40506-0055
Received October 5, 2001
When the reagents LAlMe (L ) N,N′−(alkylene or arylene)bis(3,5-di-tert-butyl)salicylideneimine (alkylene ) ethylene
(Salen(tBu)) (1), propylene (Salpen(tBu)) (2), and butylene (Salben(tBu)) (3); arylene ) phenylene (Salophen(tBu)
(4), 3,4-dimethylphenylene (Salomphen(tBu) (5)) are combined with Ph(H)P(O)OH in tetrahydrofuran (thf) the unique
aluminophosphinate compounds, [L(tBu)Al{O P(H)Ph}]n with L, n ) Salen, ∞ (6), Salpen, 2 (7), Salben, 2 (8),
2
Salophen, ∞ (9) and Salomphen, ∞ (10) are produced. The yields for the latter two reactions are low, and it was
subsequently found that the unique thf-coupled compounds appear in the thf filtrates of the original reaction mixture.
These compounds are, [L−thf(tBu)Al{O P(H)Ph}]2, L ) Salophen (13) and Salomphen (14). The thf connects
2
through an R-carbon to only one of the two possible imine carbons of the ligand. While trying to determine how
this coupling proceeds, the six-coordinate, solution-state species LAlMe(thf) (L ) Salophen (11) and Salomphen
(12) were discovered and implicated as intermediates. All of the compounds are characterized by melting point,
NMR, IR, and X-ray analyses for 5−8, 13, and 14. A possible mechanism for the thf coupling event is presented.
Introduction
There are three general classes of compounds which
possess an Al-O-P linkage: phosphates, phosphonates, and
phosphinates (Figure 1). In materials chemistry, nanoporous
and open-framework1 group 13 phosphates have far-ranging
applications2 in catalysis,3 in separations,4 and in many other
areas.5,6 Synthetic chemistry is responsible for the majority
of these materials since there are relatively few that are
Figure 1. General representation and example of a group 13 phosphinate
naturally occurring. One noteworthy example is turquoise
(CuAl6(PO4)4(OH)8‚4H2O). The vast majority of these solid-
state materials contain aluminum in a four-coordinate
geometry. This is true, also, for molecular aluminum phos-
phonates that model some of the naturally occurring minerals
and synthetic large-pore zeolitic materials.7-10
(X, Y ) alkyl), phosphonate (X ) alkyl; Y ) alkoxide), and phosphate (X
) Y ) alkoxide).
Such materials containing six-coordinate aluminum are
extremely rare. This coordination number may be observed,
for example, in KAl2(PO4)2(OH)‚nH2O 11 and in phosphonate
composite materials containing both an inorganic and an
organic component.12 Furthermore, there are relatively few
molecules containing higher coordinate aluminum bound to
* To whom correspondence should be addressed. E-mail: datwood@
pop.uky.edu.
(1) Cheatham, A. K.; Ferey, G.; Loiseau, T. Angew. Chem., Int. Ed. Engl.
1999, 38, 3268.
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558 Inorganic Chemistry, Vol. 41, No. 3, 2002
10.1021/ic0110326 CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/05/2002

Ligand-thf Coupling in Aluminum Phosphinates
either a phosphate, phosphonate, or phosphinate. Group 13
phosphinates, [R2MO2P(X)(Y)]2 (R ) alkyl; X, Y ) halide,
alkyl, etc.; M ) Al,13,16,18 Ga,14-19 In,15,16,18 Tl18), the most
developed class of these molecular species, for example, are
predominantly four-coordinate and dimeric (as shown gener-
ally in Figure 1). In a unique example, a five-coordinate
aluminum atom is found in [Al(OiPr)2O2P(OtBu)2]4.20
The present work will demonstrate that molecular six-
coordinate aluminum phosphinates may be readily obtained
using tetradentate Salen chelate ligands. In these chelated
phosphinates, [Salen(tBu)AlO2P(H)Ph]n, the degree of ag-
gregation may be manipulated by changing the length of the
ligand “backbone”. This is observed, for instance, in the
formation of a dimer having n ) 2 with the ligands con-
taining a two-carbon backbone, while polymeric compounds
result when the backbone contains three or more carbon
atoms between the nitrogens.
In the course of the preparation of these compounds, an
unprecedented thf coupling reaction between the R-carbon
of tetrahydrofuran (thf) and an imine carbon of the ligand
was discovered. These reactions and the means by which
they proceed will be described in the context of traditional
inorganic characterization techniques including X-ray crys-
tallography.
Figure 2. Molecular structure of Salomphen(tBu)AlMe (5).
indication that these compounds are polymeric. Remarkably,
however, compounds 6-10 were of similar solubility in
organic solvents. Nevertheless, the solubility of 6, 9, and 10
was not sufficient to homogenize the aluminum environ-
ments.
1
Single H NMR resonances for the tBu groups and the
imine proton indicated a symmetric solution state geometry
for the compounds.22 The P-H group appeared in the range
6.66-7.30 ppm with a coupling constant of 500-550 Hz.
By comparison, the phosphorus atom in phosphinates
([O2PR2]-, R ) alkyl or aryl) bridging either titanium (37.1
ppm)22 or antimony (57.7 ppm)23 appear more deshielded.
This may be due to the presence of alkyls in these systems
as opposed to the phenyl/hydride combination in 6-10.
Interestingly, the 31P NMR resonances increased from δ 7.08
to 7.81 ppm for 6-8 in step with the increasing length of
the backbone connection between the two nitrogens. An even
more pronounced increase was observed for 9 and 10, 7.97
and 9.16 ppm, respectively.
The mass spectral data (EI, positive) contained a highest
molecular weight peak attributable to a dimer for 6-10.
However, the distinction between dimeric or polymeric
structures in the native compounds could not be made. From
past work it is clear, however, that the Salen, Salophen, and
Salomphen ligands adopt planar geometries around a central
metal,21 while the Salpen and Salben ligands are more
variable due to the flexibility inherent to the ligand backbone.
Through a crystallographic study of 6-8 the distinction
between dimer and polymer for 6-10 could be made. Details
of the study and selected bond lengths and angles are located
in Tables 1 and 2, respectively. Compound 6 was found to
consist of polymeric chains of -[LAl(OP{(H)Ph}O]- units
(Figure 3). The -[O-Al-O-P]- backbones are not linear
but curved at the O-P-O junctions with angles in the range
∼ 119.1(3)°. Adjacent ligand-tBu groups are arranged in a
staggered conformation to reduce steric contacts. The effect
of this arrangement is to make the polymer appear as columns
in the packing diagram (see figure in Supporting Informa-
tion). These columns are arranged so that the tBu groups
point inward toward channels containing thf molecules. In
this manner the structure of 6 is loosely comparable to the
structures of other inorganic phosphate solid-state materials.12
Results and Discussion
Six-Coordinate Aluminum Phosphinates. The combina-
tion of AlMe3 with the appropriate ligand leads to the
formation of the five-coordinate compounds, 1-5.21 This
coordination number is evident in solution, as demonstrated
by 27Al NMR: the spectra of all five compounds contain a
single resonance at ∼50 ppm, the appropriate region for five-
coordinate aluminum. There is a structural difference in these
starting materials. The Salpen(tBu) and Salben(tBu) deriva-
tives are trigonal bipyramidal, and the others are square
pyramidal. As a square pyramidal representative the structure
of compound 5 is shown in Figure 2. Selected bond lengths
and angles are listed in Table 1.
These compounds readily undergo alkane elimination re-
actions when combined with protic reagents. Thus, the addi-
tion of phenylphosphinic acid to 1-5 leads to the formation
of 6-10 (respectively; Scheme 1). Compounds 7 and 8
feature a single 27Al NMR resonance in the vicinity expected
for six-coordinate aluminum (∼0 ppm). No peak could be
detected for compounds 6, 9, and 10, even with prolonged
acquisition times on the spectrometer (48 h). This is a partial
(13) Coates, G. E.; Mukherjee, R. N. J. Chem. Soc. 1964, 1295.
(14) Schaible, B.; Weidlein, J. J. Organomet. Chem. 1972, 35, C7.
(15) Hahn, F. E.; Schneider, B. Z. Naturforsch. 1990, 45b, 134.
(16) Olapinski, H.; Schaible, B.; Weidlein, J. J. Organomet. Chem. 1972,
43, 107.
(17) Weidlein, J.; Schaible, Z. Anorg. Allg. Chem. 1971, 386, 176.
(18) Schaible, B.; Haubold, W.; Weidlein, J. Z. Anorg. Allg. Chem. 1974,
403, 289. Schaible, B.; Weidlein, J. Z. Anorg. Allg. Chem. 1974, 403,
301.
(19) Landry, C. C.; Hynes, A.; Barron, A. R.; Haiduc, I.; Silvestru, C.
Polyhedron 1996, 15, 391.
(20) Lugmair, C. G.; Tilley, T. D.; Rheingold, A. L. Chem. Mater. 1999,
11, 1615.
(21) Atwood, D. A.; Hill, M. S.; Jegier, J. A.; Rutherford, D. Organome-
tallics 1997, 16, 2659.
(22) Shah, S. A. A.; Dorn, H.; Gindl, J.; Noltemeyer, M.; Schmidt, H.-G.;
Roesky, H. W. J. Organomet. Chem. 1998, 550, 1.
(23) Said, M. A.; Swamy, K. C. K.; Poojary, D. M.; Clearfield, A.; Veith,
M.; Huch, V. Inorg. Chem. 1996, 35, 3235.
Inorganic Chemistry, Vol. 41, No. 3, 2002 559

Wang et al.
Table 1. Selected Bond Lengths and Angles for 5-7, 8a, 13, and 14
[Salomphen(tBu)AlMe‚2thf] (5)
Al(1)-O(1)
1.812(3)
1.962(5)
89.4(2)
88.3(2)
98.6(2)
Al(1)-O(2)
1.811(4)
Al(1)-N(1)
2.023(4)
Al(1)-N(2)
2.038(4)
Al(1)-C(39)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
C(39)-Al(1)-N(2)
O(2)-Al(1)-C(39)
C(39)-Al(1)-N(1)
N(2)-Al(1)-N(1)
111.1(2)
106.1(2)
77.7(2)
O(1)-Al(1)-C(39)
O(2)-Al(1)-N(2)
107.5(2)
87.5(2)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
141.6(2)
153.0(2)
[Salen(tBu)AlO2P(H)Ph]∞ (6)
Al(1)-O(1)
1.816(3)
2.004(3)
97.8(1)
90.5(1)
89.6(1)
86.1(1)
158.5(2)
Al(1)-O(2)
1.821(3)
2.008(3)
91.4(1)
174.1(1)
86.9(1)
88.7(1)
160.8(3)
Al(1)-O(3)
1.896(3)
1.444(4)
92.3(1)
90.8(1)
170.9(1)
80.4(1)
Al(1)-O(4)
1.895(3)
1.476(3)
93.4(1)
171.2(1)
91.1(1)
Al(1)-N(1)
Al(1)-N(2)
P(1)-O(3)
P(1)-O(4)
O(1)-Al(1)-O(2)
O(2)-Al(1)-O(3)
O(4)-Al(1)-N(1)
O(4)-Al(1)-N(2)
P(1)-O(3)-Al(1)
O(1)-Al(1)-O(4)
O(4)-Al(1)-O(3)
O(3)-Al(1)-N(1)
O(3)-Al(1)-N(2)
P(1)-O(4)-Al(1)
O(2)-Al(1)-O(4)
O(1)-Al(1)-N(1)
O(1)-Al(1)-N(2)
N(1)-Al(1)-N(2)
O(1)-Al(1)-O(3)
O(2)-Al(1)-N(1)
O(2)-Al(1)-N(2)
O(3)-P(1)-O(4)
119.1(3)
[Salpen(tBu)AlO2P(H)Ph]2 (7)
Al(1)-O(2)
1.830(2)
2.034(2)
1.801(2)
1.474(3)
92.09(7)
174.68(7)
174.87(7)
92.33(7)
140.6(1)
Al(1)-O(1)
1.830(2)
2.052(2)
1.313(2)
1.286(3)
93.59(7)
90.19(7)
86.03(7)
86.97(7)
140.56(9)
Al(1)-O(4)
1.890(2)
1.507(2)
1.316(2)
1.478(3)
90.28(7)
90.08(7)
174.07(7)
84.01(7)
Al(1)-O(3)
P(1)-O(3)
N(1)-C(15)
1.917(2)
1.507(2)
1.290(3)
Al(1)-N(2)
Al(1)-N(1)
P(1)-O(4)
P(1)-C(34)
N(1)-C(16)
O(2)-Al(1)-O(1)
O(1)-Al(1)-O(3)
O(4)-Al(1)-N(2)
O(4)-Al(1)-N(1)
P(1)-O(3)-Al(1)
O(1)-C(1)
N(2)-C(19)
O(2)-Al(1)-O(4)
O(4)-Al(1)-O(3)
O(3)-Al(1)-N(2)
O(3)-Al(1)-N(1)
P(1)-O(4)-Al(1)
O(2)-C(21)
N(2)-C(18)
O(1)-Al(1)-O(4)
O(2)-Al(1)-N(2)
O(2)-Al(1)-N(1)
N(2)-Al(1)-N(1)
O(2)-Al(1)-O(3)
O(1)-Al(1)-N(2)
O(1)-Al(1)-N(1)
O(4)-P(1)-O(3)
93.18(7)
93.16(7)
87.71(7)
116.81(8)
[Salben(tBu)AlO2P(H)Ph]2 (8)
Al(1)-O(1)
1.835(2)
2.061(2)
1.792(2)
1.484(3)
92.92(7)
90.19(7)
88.20(7)
91.07(7)
132.7(1)
Al(1)-O(2)
1.839(2)
2.065(2)
1.323(3)
1.292(3)
89.52(7)
90.52(7)
90.30(7)
177.55(8)
136.4(1)
Al(1)-O(3)
1.890(2)
1.508(2)
1.306(3)
1.482(3)
177.42(8)
176.16(8)
89.07(7)
87.89(8)
Al(1)-O(4)
P(1)-O(3)
N(1)-C(15)
1.906(2)
1.512(2)
1.289(3)
Al(1)-N(2)
Al(1)-N(1)
P(1)-O(4)
P(1)-C(35)
N(1)-C(16)
O(1)-Al(1)-O(2)
O(2)-Al(1)-O(4)
O(3)-Al(1)-N(2)
O(3)-Al(1)-N(1)
P(1)-O(3)-Al(1)
O(1)-C(1)
N(2)-C(20)
O(1)-Al(1)-O(3)
O(3)-Al(1)-O(4)
O(4)-Al(1)-N(2)
O(4)-Al(1)-N(1)
P(1)-O(4)-Al(1)
O(2)-C(22)
N(2)-C(19)
O(2)-Al(1)-O(3)
O(1)-Al(1)-N(2)
O(1)-Al(1)-N(1)
N(2)-Al(1)-N(1)
O(1)-Al(1)-O(4)
O(2)-Al(1)-N(2)
O(2)-Al(1)-N(1)
O(4)-P(1)-O(3)
92.81(7)
89.32(7)
88.13(7)
116.16(9)
[Salophen(thf)(tBu)AlO2P(H)Ph]2 (13)
Al(1)-O(1)
1.835(5)
2.100(6)
1.798(8)
1.451(9)
1.51(2)
Al(1)-O(2)
Al(1)-N(2)
O(1)-C(1)
N(2)-C(21)
1.812(5)
2.023(6)
1.337(9)
1.423(9)
Al(1)-O(3)
P(1)-O(3)
O(2)-C(24)
N(2)-C(22)
1.860(5)
1.491(5)
1.312(8)
1.286(9)
Al(1)-O(4)
P(1)-O(4)
N(1)-C(15)
O(5)-C(43)
1.942(5)
1.494(5)
1.51(1)
1.43(1)
Al(1)-N(1)
P(1)-C(37)
N(1)-C(16)
O(5)-C(46)
O(1)-Al(1)-O(2)
O(1)-Al(1)-O(4)
O(3)-Al(1)-N(2)
O(3)-Al(1)-N(1)
P(1)-O(3)-Al(1)
93.9(2)
O(2)-Al(1)-O(3)
O(3)-Al(1)-O(4)
O(4)-Al(1)-N(2)
O(4)-Al(1)-N(1)
P(1)-O(4)-Al(1)
97.8(2)
87.0(2)
84.6(2)
82.6(2)
138.8(3)
O(1)-Al(1)-O(3)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(1)
N(2)-Al(1)-N(1)
93.0(2)
94.5(2)
169.5(3)
80.2(3)
O(2)-Al(1)-O(4)
O(2)-Al(1)-N(2)
O(1)-Al(1)-N(1)
O(4)-P(1)-O(3)
93.0(2)
90.0(2)
90.5(2)
119.1(3)
173.0(2)
168.8(2)
91.5(2)
146.8(3)
[Salomphen(thf)(tBu)AlO2P(H)Ph]2 (14)
Al(1)-O(1)
1.828(2)
2.042(3)
1.793(3)
1.424(4)
1.444(4)
93.1(1)
94.5(1)
169.6(1)
91.9(1)
Al(1)-O(2)
Al(1)-N(2)
O(1)-C(1)
N(2)-C(23)
1.820(2)
2.085(3)
1.309(4)
1.454(4)
Al(1)-O(3)
P(1)-O(3)
O(2)-C(26)
N(2)-C(24)
1.927(2)
1.501(2)
1.335(4)
1.513(4)
Al(1)-O(4)
P(1)-O(4)
N(1)-C(15)
O(5)-C(42)
1.839(2)
1.495(2)
1.296(4)
1.368(5)
Al(1)-N(1)
P(1)-C(43)
N(1)-C(16)
O(5)-C(39)
O(2)-Al(1)-O(1)
O(1)-Al(1)-O(3)
O(4)-Al(1)-N(1)
O(4)-Al(1)-N(2)
P(1)-O(3)-Al(1)
O(2)-Al(1)-O(4)
O(4)-Al(1)-O(3)
O(3)-Al(1)-N(1)
O(3)-Al(1)-N(2)
P(1)-O(4)-Al(1)
92.0(1)
88.4(1)
83.3(1)
82.7(1)
151.5(1)
O(1)-Al(1)-O(4)
O(2)-Al(1)-N(1)
O(2)-Al(1)-N(2)
N(2)-Al(1)-N(1)
C(42)-O(5)-C(39)
95.8(1)
95.5(1)
89.6(1)
80.9(1)
110.8(3)
O(2)-Al(1)-O(3)
O(1)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(4)-P(1)-O(3)
172.3(1)
91.1(1)
171.8(1)
118.6(1)
143.2(1)
Scheme 1. General Synthesis of Compounds 6-10
atoms are in an octahedral environment. The Al-O(ligand)
distances, ∼1.83 Å, are marginally shorter than the Al-O-P
distances, ∼1.93 Å. These are the first structurally character-
ized phosphinates of aluminum but similar to the analogous
Ga and In compounds which are also dimeric.24 The bond
distances in 7 and 8 are similar to that observed in an
aluminum phenylphosphonate (O3PR) with Al-O distances
in the range 1.786(6)-1.951(6) Å. By comparison, these
distances are just slightly shorter in derivatives containing
The structures of 7 and 8 (from either CH2Cl2 or toluene)
were found to be dimeric (Figures 4 and 5 (for the core of
8)). Apparently the flexible nature of the ligand backbones
in these compounds allows for dimerization to occur rather
than polymerization. In all three structures the aluminum
(24) Hahn, F. E.; Schneider, B.; Reier, F.-W. Z. Naturforsch. 1990, 45B,
134. Landry, C. C.; Hynes, A.; Barron, A. R.; Haiduc, I.; Silvestru,
C. Polyhedron 1996, 15, 391.
560 Inorganic Chemistry, Vol. 41, No. 3, 2002

Ligand-thf Coupling in Aluminum Phosphinates
Table 2
compd 5
compd 6
compd 7
compd 8
compd 13
compd 14
formula
fw
color
C47H69AlN2O4
753.06
yellowish red
C142H209.5Al3N6O19P3 C82H116Al2Cl8N4O8P2 C42H60AlCl4N2O4P C50.2H64.8AlN2O5P C49H66AlCl2N2O5P
2478.51
pale yellow
1685.29
yellow
856.67
yellow
834.22
yellow
891.89
yellow
cryst size (mm3)
cryst system
space group
a (Å)
0.05 × 0.08 × 0.25 0.25 × 0.20 × 0.18
0.40 × 0.38 × 0.28
Triclinic
P1h
0.24 × 0.18 × 0.16 0.24 × 0.11 × 0.11 0.34 × 0.30 × 0.18
monoclinic
C2/c
monoclinic
P21/c
16.6500(10)
27.518(2)
31.149(2)
90
92.280(10)
90
14260.4(16)
4
triclinic
P1h
triclinic
P1h
orthorhombic
Pbca
35.539(6)
10.2870(15)
27.986(5)
90
119.965(4)
90
9.3370(10)
16.245(2)
16.297(2)
66.953(10)
73.913(10)
78.892(10)
2175.6(4)
1
12.101(2)
12.533(2)
16.136(2)
91.552(10)
106.656(10)
104.090(10)
2261.6(6)
2
13.214(5)
13.480(5)
15.347(5)
109.56(3)
96.48(3)
93.56(3)
2544.8(16)
2
21.384(2)
18.039(2)
25.375(3)
90
90
90
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
8864(2)
8
9788.3(18)
8
Z
F (000)
3264
1.123
0.087
5782
5358
1.154
0.124
18627
13676
1730
892
1.286
0.370
7657
5785
481
908
1.258
0.357
7954
6280
516
983
1.199
0.121
5473
3895
577
3808
D(calcd) (g cm-3
)
1.210
0.229
8617
6777
542
(mm-1
)
unique data measd
obsd data, n [F g 4σ(F)] 4498
no. of variables, p
489
R1
wR2
S (goodness of fit)
0.0908
0.2042
1.12
0.0765
0.1896
1.04
0.0425
0.1031
1.03
0.0507
0.1179
1.04
0.1112
0.3087
1.13
0.0747
0.1595
1.11
Figure 5. Molecular structure of [Salben(tBu)Al{O2P(H)Ph}]2 (8) em-
phasizing the coordination environment around the aluminum atoms.
still serve to demonstrate that molecular phosphinates of six-
coordinate aluminum can be obtained.
Figure 3. Molecular structure of [Salen(tBu)Al{O2P(H)Ph}]∞ (6).
A similar arrangement to 6 is observed in the carboxylate,
[SalenMn(O2CPr)]n while the Salpen derivative is mono-
meric, SalpenMn(O2CnBu).26 Thus, both carboxylate and
phosphinate follow the same general trend in oligomerization
for Salen-chelated metals: for Salen, Salophen, and Salom-
phen, polymers are observed. With ligands having more than
two carbons in the backbone, lower oligomers, either dimers
(for the phosphinates) or monomers (for the carboxylates),
are observed.
Thf-Salen Ligand Coupling. One of the main reasons
for the popularity of the Salen ligands is the fact that they
are stable under a broad range of conditions.27 The ligands
do not decompose or undergo side reactions. Indeed, the only
known instances where an inorganic or organometallic
compound undergoes a reaction at the ligand is in the
coupling of two ligands following reduction in thf.28-30
Figure 4. Molecular structure of [Salpen(tBu)Al{O2P(H)Ph}]2 (7).
four-coordinate aluminum such as [Me2AlO2P(OtBu)2]2
(Al-O ∼ 1.77 Å). The dimerization of 7 and 8 follows the
precedent set with the previously reported compounds which
have most often been dimeric, including, [Me2Al(O2PPh2)]2,
first reported by Coates in 1964.25 Although the bonding
within compounds 7 and 8 are not unusual, the compounds
(25) Coates, G. E. J. Chem. Soc. 1964, 1295.
(26) Aurangzeb, N.; Hulme, C. E.; McAuliffe, C. A.; Pritchard, R. G.;
Watkinson, M.; Garcia-Deibe, A.; Bermejo, M. R.; Sousa, A. J. Chem.
Soc., Chem. Commun. 1992, 1525.
(27) Atwood, D. A.; Harvey, M. J. Chem. ReV. 2001, 101, 37.
(28) Gambarotta, S.; Urso, F.; Floriani, C.; Chiesi-Villa, A.; Guastini, C.
Inorg. Chem. 1983, 22, 3966.
(29) Dube, T.; Gambarotta, S.; Yap, G. Organometallics 1998, 17, 3967.
Inorganic Chemistry, Vol. 41, No. 3, 2002 561

Wang et al.
thf is apparently sufficient to deactivate the compound to a
second coupling reaction. Thus, conjugation throughout the
compound must play a role. Another consideration is the
fact that 27Al NMR studies indicate that 4 and 5 exist as the
six-coordinate thf-solvates (compounds 11 and 12) in
solution. They feature 27Al resonances at 18.01 ppm (W1/2
) 1094 Hz) and 17.06 ppm (W1/2 ) 2396 Hz), respectively.
However, thf coordination (and attendant activation) is not
sufficient alone, otherwise coupled products would have been
observed in the now commonplace cations, [SalenAl-
(base)2]+X- (where base ) H2O,33 MeOH,34 thf,35 etc.).
To explore the possibility that protic reagents, in general,
effect the thf coupling, Ph3SiOH was employed in place of
phenylphosphinic acid. It had already been demonstrated that
silanol could induce alkane elimination and form compounds
of the type SalenAlOSiPh3 in toluene.22 When this reagent
is combined with 1-5 in thf, however, the same product is
obtained.
Thus, for thf coupling to occur two components appear to
be necessary: an aryl backbone on the ligand (providing an
extended resonance structure and allowing the coordination
of thf) and phenylphosphinic acid. Moreover, the acid is not
simply a proton donor but must operate in another capacity.
It is known that compounds containing a PdO bond can
undergo a variety of hydrogen bonding interactions.36-39
Additionally, the hydrogen of the R-carbon on thf is
sufficiently protic to be involved in this type of interaction40
and can be readily activated.41 One scenario then is that the
phosphinic acid serves to activate the coordinated thf through
a hydrogen bonding interaction (Scheme 2b). The same
interaction could be made with the imine nitrogen and the
acid proton. The last step would be coupling of the thf
carbanion with the ligand carbocation (Scheme 2d).
Figure 6. Molecular structure of [Salophen(thf)(tBu)Al{O2P(H)Ph}]2 (13).
However, it was found that when 4 or 5 are combined
with phenylphosphininc acid in thf, one molecule of thf adds
to the imine carbon of the ligand forming [Salophen(thf)-
(tBu)AlO2P(H)Ph]2 (13) and [Salomphen(thf)(tBu)AlO2P(H)-
Ph]2 (14). The presence of the newly formed amine linkage
is signaled by a new IR resonance at ∼3260 cm-1. One imine
1
remains at ∼1620 cm-1. In the H NMR there are two sets
of resonances attributable to a cyclic ether: one for free thf
(1.85 and 3.76 ppm) and one for the coupled thf (broadened
peaks in the ranges 1.60-1.85 and 3.50-4.60 ppm).
Otherwise, the spectroscopic data for 13 and 14 are very
similar to those of 6-10.
X-ray analyses confirm the formulations for 13 and 14
(the two are isostructural; only 13 is shown in Figure 6).
The degree of oligomerization of both compounds is no
longer dictated by the nature of the ligand backbone. The
increased flexibility in the ligand resulting from the thf
coupling apparently allows dimerization to occur rather than
polymerization, as observed for compounds 9 and 10. Thus,
the structures of 7, 8, 13, and 14, as dimers, are very similar.
The C-C bond to the coupled thf is ∼1.5 Å. The distance
in the newly formed amine is lengthened (∼1.6 Å) compared
to the imine. Otherwise, the structures of 7, 8, 13, and 14
differ very little. Compounds 6-8 do not produce the thf-
coupled products.
Imines have been known to undergo one or both of either
C-C or C-solvent coupling. For example, both occur when
N-benzylideneaniline is reduced with Na.31 Furthermore, thf
coupling to benzaniline occurs photolytically. In this process
the thf is ionized and the resulting benzaniline radical anion
couples with the thf.32 A common feature of the literature
on this reaction (and for the known Salen coupling
reactions),29-31 then, is that an anionic substrate undergoes
the coupling. For 13 and 14, however, it is not clear how an
anion might be produced during the course of the reaction.
There must be an electronic consideration, however, since
only those compounds having an aryl backbone produce the
coupled product. Furthermore, the presence of one coupled
Conclusion
It has been demonstrated that six-coordinate phosphinates
of aluminum can be prepared when utilizing Salen-based
starting materials. These phosphinates are polymeric when
the “backbone” of the ligand contains two carbon atoms (as
Salen or Salophen, for example). With “backbones” contain-
ing long-chain alkanes, the resulting compounds are dimeric.
In the presence of thf the formation of these phosphinates
occurs concurrently to the coupling of thf to the Salen ligand.
In this coupling it appears that phosphinic acid is ideally
(33) Atwood, D. A.; Jegier, J. A.; Rutherford, D. J. Am. Chem. Soc. 1995,
117, 6779. Atwood, D. A.; Jegier, J. A.; Rutherford, D. Inorg. Chem.
1996, 35, 63.
(34) Jegier, J. A.; Munoz-Hernandez, M.-M.; Atwood, D. A. J. Chem. Soc.,
Dalton Trans. 1999, 2583.
(35) Keizer, T. S.; Parkin, S.; Yearwood, B.; Atwood, D. A. Inorg. Chim.
Acta, submitted for publication.
(36) Kariuki, B. M.; Harris, K. D. M.; Philp, D.; Robinson, J. M. A. J.
Am. Chem. Soc. 1997, 119, 12679.
(37) Steiner, T.; van der Maas, J.; Lutz, B. J. Chem. Soc., Perkin Trans.
1997, 2, 1287.
(38) Burrow, R. A.; Farrar, D. H.; Lough, A. J.; Siqueira, M. R.; Squizani,
F. Acta Crystallogr. C 2000, 56, 357.
(30) Solari, E.; Maltese, C.; Franceschi, F.; Floriani, C.; Chiesi-Villa, A.;
Rizzoli, C. J. Chem. Soc., Dalton Trans. 1997, 2903.
(31) Smith, J. G.; Ho, I. J. Org. Chem. 1972, 37, 4260.
(32) Ishida, A.; Sugita, D.; Itoh, Y.; Takamuku, S. J. Am. Chem. Soc. 1995,
117, 11687.
(39) Rohovec, J.; Kyvala, M.; Vojtisek, P.; Hermann, P.; Lukes, I. Eur. J.
Inorg. Chem. 2000, 195.
(40) Laarhoven, L. J. J.; Mulder, P. J. Phys. Chem. 1997, 101, 73.
(41) Gutierrez-Puebla, E.; Monge, A.; Nicasio, M. C.; Perez, P. J.; Poveda,
M. L.; Carmona, E. Chem. Eur. J. 1998, 4, 2225.
562 Inorganic Chemistry, Vol. 41, No. 3, 2002

Ligand-thf Coupling in Aluminum Phosphinates
Scheme 2. General Route for the Formation of Compounds 11 and
12 (a) and a Proposed Mechanism (b, c) for the Formation of 13 and
14 (d)
groups, all non-hydrogen atoms were refined with anisotropic
displacement parameters. The majority of hydrogen atoms were
found in difference Fourier maps, but some belonging to disordered
groups could not be found. All hydrogens were subsequently placed
at calculated positions and refined using an appropriate riding
model. Absorption corrections were not strictly applied, but the
data-reduction program Scalepack (Otwinowski & Minor, 1997)
effectively provides a satisfactory correction for the gross effects
of anisotropic absorption in cases where absorption is not severe.
Further details of the structure analyses are given in Table 2. The
high R-values for these refinements are largely a consequence of
poor crystal quality. This is a perennial problem for compounds of
salen-type ligands, especially those that contain occluded solvent,
where extensive disorder is common. In such cases the spatial
quality of the fit, as obtained by the R-tensor (Parkin, 2000), can
be invaluable in distinguishing between poor counting statistics and
an inadequate model as the source of high R-values. For the
structures presented here, the anisotropy of the fit clearly implicates
poor counting statistics, which are a direct consequence of crystal
quality. An X-ray analysis of compound 8 was obtained in both
CH2Cl2 (data for 8‚2CH2Cl2 presented herein) and from toluene
(data for 8‚toluene in Supporting Information). The dimeric
aluminum-containing units of each were found to be identical.
[Salomphen(tBu)AlMe]‚2thf (5). Salomphen(tBu)AlMe (0.500
g, 0.766 mmol) was dissolved in a mixed solution of thf (20 mL)
and CH2Cl2 (10 mL). Storage of it at -30 °C for 1 week yielded
orange needle crystals suitable for X-ray analysis. Yield: 0.487 g,
1
79%. Mp: 304-307 °C. H NMR (CDCl3, 200 MHz): δ -1.25
(s, 3H, AlCH3), 1.31 (s, 18H, C(CH3)3), 1.53 (s, 18H, C(CH3)3),
1.83 (m, thf), 2.34 (s, 6H, PhCH3), 3.73 (m, thf), 7.13-7.54 (m,
6H, PhH), 8.73 (s, 2H, PhCH). IR(KBr; ν, cm-1): 2960(s), 2905-
(m), 2869(m), 1619(vs), 1592(m), 1559(m), 1539(s), 1520(w), 1472-
(m), 1387(m), 1256(m), 1202(w), 1177(s), 1089(m), 1022(m),
845(m), 788(m), 750(m).
suited to activate both the thf and the imine of the ligand
through hydrogen bonding contacts. This is an unprecedented
reaction and differs from other coupling reactions involving
these ligands in that an anion or radical is not involved.
Experimental Section
[Salen(tBu)AlO2P(H)Ph]∞ (6). To a stirring solution of Salen-
(tBu)AlMe (0.540 g, 1.01 mmol) in thf (40 mL) was added a
solution of phenylphosphinic acid (0.144 g, 1.01 mmol) in 20 mL
of thf at -78 °C. After 3 h of stirring, the solution stand at ambient
temperature overnight to yield clear and yellow crystals. Yield:
0.529 g, 79%. Mp: The color of the crystal became darker at 340
General Considerations. All manipulations were conducted
using Schlenk techniques in conjunction to an inert atmosphere
glovebox. Solvents were dried over activated alumina or iron and
dispensed under pressure into the drybox prior to use. NMR data
were obtained on JEOL-GSX-400 and -270 instruments operating
at 270.17 and 399.78 MHz and are reported relative to SiMe4 and
are in ppm. 27Al NMR data were obtained in CDCl3 at 52.1 MHz.
Elemental analyses were obtained on a Perkin-Elmer 2400 analyzer.
Infrared data were recorded as KBr pellets on a Matheson
Instruments 2020 Galaxy Series spectrometer and are reported in
cm-1. The reagent 3,5-di-tert-butyl-2-hydroxybenzaldehyde was
prepared according to the literature.42 The ligands were prepared
by combining various diamines with the aldehyde following the
literature precedent. The reagents, L(tBu)AlMe (L ) Salen, Salpen,
Salben, Salophen, and Salomphen), were prepared as described
previously.22 X-ray data were collected on a Nonius Kappa-CCD
unit using Mo KR radiation. The structures were refined using the
Siemens software package SHELXTL 4.0. All of the non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were put
into calculated positions. Absorption corrections were not employed.
Further details of the structure analyses are given in Table 2.
The structures were solved using Shelxs and refined using Shelxl
from the Shelx-97 program package. Molecular fragment editing,
including the construction of suitable disorder models, was
performed using the XP program of Siemens Shelxtl 5.0. With the
exception of a few minor component atoms of some disordered
1
°C, and the crystal melt at 361-362 °C. H NMR (CDCl3, 200
MHz): δ 1.19 (s, 18H, C(CH3)3), 1.28 (s, 18H, C(CH3)3), 3.05(br,
1
4H, NCH2), 6.66 (d, JPH ) 552 Hz, 1H, PH), 6.51, 6.70, 6.92,
7.43 (m, 9H, PhH), 7.28 (s, 2H, PhCH). 31P{1H}NMR (CDCl3,
80.9 MHz): δ 7.08 (s). IR(KBr; ν, cm-1): 3054(w), 2954(s), 2905-
(m), 2867(m), 2385(w), 1656(s), 1548(m), 1536(m), 1477(m), 1462-
(m), 1441(s), 1416(m), 1390(m), 1335(m), 1197(s), 1171(s),
1141(m), 1080(m), 1021(w), 970(m), 875(m), 770(m), 760(m), 610-
(m). MS(EI, positive): 1317.7 (2.1%, Dimer+), 658.3 (100%, M+).
Anal. Calcd: C, 69.28; H, 7.96. Found: C, 69.27; H, 8.17.
[Salpen(tBu)AlO2P(H)Ph]2 (7). To a stirring solution of Salpen-
(tBu)AlMe (0.500 g, 0.91 mmol) in thf (40 mL) was added a
solution of phenylphosphinic acid (0.129 g, 0.91 mmol) in 20 mL
of thf at -78 °C. After 3 h of stirring, the thf was removed under
vacuum yielding a yellow solid which was dissolved in CH2Cl2
(20 mL) and allowed to stand for several days at room temperature
during which time yellow crystals formed. Yield: 0.450 g, 73%.
1
Mp: >400 °C. H NMR (CDCl3, 200 MHz): δ 1.06 (s, 36H,
C(CH3)3), 1.31 (s, 36H, C(CH3)3), 2.14(m, 4H, CH2CH2CH2), 3.25,
3.49 (m, 8H, NCH2), 7.25 (d, 1JPH ) 556 Hz, 2H, PH), 6.61, 6.96,
7.20, 7.42 (m, 18H, PhH), 7.91 (s, 4H, PhCH). 31P{1H}NMR
(CDCl3, 80.9 MHz): δ 7.24 (s). 27Al NMR (CDCl3, 52.1 MHz):
δ 0.53 (W1/2 ) 1615 Hz). IR (KBr; ν, cm-1): 3053(m), 2956(s),
(42) Casiraghi, G.; Casnati, G.; Puglia, G.; Sartori, G.; Terenghi, G. J.
Chem. Soc., Perkin Trans. 1980, 1862.
Inorganic Chemistry, Vol. 41, No. 3, 2002 563

Wang et al.
2902(s), 2867(s), 2420(w), 1632(s), 1548(s), 1536(s), 1475(s), 1462-
(s), 1440(s), 1416(s), 1386(s), 1360(s), 1341(m), 1327(s), 1277-
(m), 1259(s), 1234(s), 1207(s), 1172(s), 1140(s), 1087(m), 1071(s),
1018(w), 974(s), 841(m), 787(m), 750(m). MS (EI, positive):
1346.5 (8.2%, Dimer+), 672.0 (9.1%, M+). Anal. Calcd: C, 69.62;
H, 8.09. Found: C, 69.64; H, 8.30.
MHz): δ 9.16. IR (KBr; ν, cm-1): 3051(w), 3011(w), 2951(s),
2903(s), 2866(s), 2361(w), 2340(w), 1653(w), 1621(s), 1595(s),
1532(s), 1505(m), 1474(s), 1444(s), 1418(m), 1386(s), 1359(s),
1331(w), 1279(m), 1255(m), 1234(s), 1197(s), 1138(s), 1087(m),
1073(w), 1018(w), 1003(w), 981(s), 868(m), 847(m), 788(m), 743-
(m), 693(m), 597(m), 561(m), 509(m), 419(s), 409(m). MS (EI,
positive): 1468.1(2.6%, Dimer+), 734.2 (100%, M+). Anal. Cal-
cd: C, 71.91; H, 7.68. Found: C, 71.46; H, 7.97.
[Salben(tBu)AlO2P(H)Ph]2 (8). Two routes were used: (1) To
a stirring solution of salben(tBu)AlMe (1.000 g, 1.78 mmol) in thf
(40 mL) was added a solution of phenylphosphinic acid (0.253 g,
1.78 mmol) in 20 mL of thf at -78 °C. The reaction was allowed
to proceed at -78 °C for 3 h. The solution was brought to room
temperature slowly and stirred overnight. The thf was removed
under vacuum yielding a yellow solid which was dissolved in
toluene (10 mL) and refluxed for 30 min. The resulting solution
was allowed to stand for 1 week during which time yellow crystals
formed. Yield: 0.850 g, 69%). (2) To a stirring solution of salben-
(tBu)(AlMe2)2 (1.000 g, 1.58 mmol) in thf (40 mL) was added a
solution of phenylphosphinic acid (0.225 g, 1.58 mmol) in 20 mL
of thf at -78 °C. The reaction was allowed to proceed at -78 °C
for 3 h. The solution was brought to room temperature slowly and
stirred overnight. The thf was removed under vacuum yielding a
yellow solid which was dissolved in CH2Cl2 (15 mL) and allowed
to stand for 1 week at room temperature during which time yellow
crystals formed. Yield: 0.900 g, 83%. Mp: 316-319 °C. 1H NMR
[Salophen(thf)(tBu)AlO2P(H)Ph]2 (13). To a stirring solution
of salophen(tBu)AlMe (1.000 g, 1.72 mmol) in thf (40 mL) was
added a solution of phenylphosphinic acid (0.245 g, 1.72 mmol)
in 20 mL of thf at -78 °C. The reaction was allowed to proceed
at -78 °C for 24 h. The solution was brought to room temperature
slowly and stirred overnight, after which the thf was filtered off.
For the filtered solution, the thf was removed under vacuum yielding
an orange solid. It was then dissolved in toluene (15 mL) and
allowed to stand for 7 days at room temperature during which time
yellow crystals formed. Yield: 0.511 g, 38%. Mp: melt and
1
decomposed at 273-277 °C. H NMR (toluene-d8, 200 MHz): δ
1.19 (s, 18H, C(CH3)3), 1.21 (s, 18H, C(CH3)3), 1.38 (s, 18H,
C(CH3)3), 1.41 (s, 18H, C(CH3)3), 1.68-1.85 (m, 8H, thf), 3.52-
4.30 (m, 8H, thf and PhCH(thf)), 6.38 (d, 1JPH ) 544 Hz, 2H, PH),
6.30, 6.50, 6.71, 7.32 (m, 26H, PhH), 8.14 (s, 2H, PhCH).
31P{1H}NMR (toluene-d8, 80.9 MHz): δ 4.71. 27Al NMR (toluene-
d8, 52.1 MHz): δ 3.08 (W1/2 ) 721.4 Hz). IR (KBr; ν, cm-1): 3260-
(w), 2953(s), 2903(m), 2866(m), 2361(m), 2344(m), 1621(s),
1589(m), 1534(s), 1496(s), 1438(s), 1414(m), 1388(m), 1258(m),
1215(s), 1169(s), 1142(s), 1086(m), 1072(w), 1021(m), 975(s), 842-
(m), 749(M), 693(m), 668(m), 566(m). MS (MALDI-TOF, posi-
tive): 1274 (100%, [dimer - 2thf - P(H)(Ph)O2]+), 778 (3.0%,
M+), 638 (81.5%, [M - P(H)(Ph)O2]+). Anal. Calcd: C, 70.93;
H, 7.76. Found: C, 71.41; H, 7.91.
(CDCl3, 200 MHz): δ1.29 (s, 36H, C(CH3)3), 1.43 (s, 36H,
1
C(CH3)3), 1.79 (m, 8H, CH2), 3.61(m, 8H, CH2), 7.15(d, JPH
)
553 Hz, 2H, PH), 7.06, 7.18, 7.24, 7.36 (m, 18H, PhH), 8.35 (s,
4H, PhCH). 31P{1H}NMR (CDCl3, 80.9 MHz): δ 7.81 (s). 27Al
NMR (CDCl3, 52.1 MHz): δ 3.10 (W1/2 ) 1824 Hz). IR (KBr; ν,
cm-1): 2959(s), 2910(m), 2867(m), 2424(w), 1628(s), 1554(m),
1539(m), 1476(m), 1457(m), 1438(m), 1419(m), 1360(m), 1276-
(m), 1258(m), 1233(m), 1182(s), 1139(s), 1080(m), 1060(m), 1037-
(w), 1022(m), 983(m), 875(m), 841(m), 787(m), 596(m). MS (EI,
positive): 1372.4 (2.4%, Dimer+), 686.4 (5.1%, M+). Anal.
Calcd: C, 69.95; H, 8.22. Found: C, 70.39; H, 8.41.
[Salomphen(thf)(tBu)AlO2P(H)Ph]2 (14). To a stirring solution
of salomphen(tBu)AlMe (1.000 g, 1.64 mmol) in thf (40 mL) was
added a solution of phenylphosphinic acid (0.233 g, 1.64 mmol)
in 20 mL of thf at -78 °C. The reaction was allowed to proceed
at -78 °C for 24 h. The solution was brought to room temperature
slowly and stirred overnight, after which the thf was filtered off.
For the filtered solution, the thf was removed under vacuum yielding
an orange solid. It was then dissolved in dichloromethane (10 mL)
and allowed to stand for 1 day at room temperature during which
time yellow crystals formed. Yield: 0.426 g, 32%. Mp: melt and
decomposed at 278-280 °C. 1H NMR (CDCl3, 200 MHz): δ 1.18
(s, 18H, C(CH3)3), 1.20 (s, 18H, C(CH3)3), 1.33 (s, 18H, C(CH3)3),
1.40 (s, 18H, C(CH3)3), 1.60-1.85 (m, 8H, thf), 2.09 (s, 6H,
PhCH3), 2.10 (s, 6H, PhCH3), 3.60-4.60 (m, 8H, thf and PhCH-
(thf)), 7.30 (d, 1JPH ) 550 Hz, 2H, PH), 6.31-7.35 (m, 22H, PhH),
8.38 (s, 2H, PhCH). 31P{1H}NMR (CDCl3, 80.9 MHz): δ 11.59
(s). 27Al NMR (CDCl3, 52.1 MHz): δ 4.86 (W1/2 ) 938 Hz). IR
(KBr; ν, cm-1): 3264(w), 2953(s), 2904(m), 2866(m), 2378 (w),
1621(s), 1601(m), 1534(m), 1479(s), 1463(s), 1415(m), 1388(m),
1359(m), 1255(m), 1233(s), 1170(s), 1143(s), 1085(m), 1067(m),
1021(m), 1001(w), 978(m), 872(m), 807(m), 788(m), 710(m), 694-
(w), 614(w), 557(m). MS (EI, positive): 1330 (2.7%, [dimer -
2thf - P(H)(Ph)O2]+), 807 (2.0%, M+), 664 (24.0%, [M - P(H)-
(Ph)O2]+). Anal. Calcd: C, 71.44; H, 7.99. Found: C, 71.29; H,
7.89.
[Salophen(tBu)AlO2P(H)Ph]∞ (9). To a stirring solution of
salophen(tBu)AlMe (1.000 g, 1.72 mmol) in thf (40 mL) was added
a solution of phenylphosphinic acid (0.245 g, 1.72 mmol) in 20
mL of thf at -78 °C. The reaction was allowed to proceed at -78
°C for 24 h. The solution was brought to room temperature slowly
and stirred overnight, after which the thf was filtered off to leave
a yellow solid. Yield: 0.365 g (30%). Mp: melt and decomposed
at 316-320 °C. 1H NMR (DMSO-d6, 200 MHz): δ 1.32 (s, 18H,
1
C(CH3)3), 1.51 (s, 18H, C(CH3)3), 6.89 (d, JPH ) 511 Hz, 1H,
PH), 6.97, 7.22, 7.46, 8.04 (m, 13H, PhH), 9.06 (s, 2H, PhCH).
31P{1H}NMR (DMSO-d6, 80.9 MHz): δ 7.97. IR (KBr; ν, cm-1):
2964(s), 2903(s), 2870(m), 2387(w), 1619(s), 1586(s), 1546(s),
1532(s), 1488(m), 1473(s), 1445(m), 1414(m), 1389(s), 1359(s),
1263(m), 1238(m), 1198(s), 1175(s), 1140(s), 1111(m), 1096(m),
1070(w), 1025(w), 845(m), 788(m), 744(s), 693(m). MS (EI,
positive): 1412.0 (2.0%, Dimer+), 706.4 (91.8%, M+). Anal.
Calcd: C, 71.37; H, 7.42. Found: C, 71.36; H, 7.62.
[Salomphen(tBu)AlO2P(H)Ph]∞ (10). To a stirring solution of
salomphen(tBu)AlMe (1.000 g, 1.64 mmol) in thf (40 mL) was
added a solution of phenylphosphinic acid (0.233 g, 1.64 mmol)
in 20 mL of thf at -78 °C. The reaction was allowed to proceed
at -78 °C for 24 h. The solution was brought to room temperature
slowly and stirred overnight, after which the thf was filtered off to
leave a yellow solid. Yield: 0.484 g, 40%. Mp: melt and
decomposed at 342-344 °C. 1H NMR (CDCl3, 200 MHz): δ 1.34
(s, 18H, C(CH3)3), 1.48 (s, 18H, C(CH3)3), 2.35(s, 6H, PhCH3),
Acknowledgment. This work was supported by the
National Science Foundation NSF-CAREER award (Grant
CHE 9816155). NMR instruments used in this research were
obtained with funds from the CRIF program of the National
1
7.07(d, JPH ) 546 Hz, 1H, PH), 6.95, 7.13, 7.21, 7.40, 7.58 (m,
11H, PhH), 8.58 (s, 2H, PhCH). 31P{1H}NMR (CDCl3, 80.9
564 Inorganic Chemistry, Vol. 41, No. 3, 2002

Ligand-thf Coupling in Aluminum Phosphinates
(5), [Salen(tBu)Al{O2P(H)Ph}]∞ (6), [Salpen(tBu)Al{O2P(H)Ph}]2
(7), [Salben(tBu)Al{O2P(H)Ph}]2 (8), [Salophen-thf(tBu)Al{O2P-
(H)Ph}]2 (13), and [Salomphen-thf(tBu)Al{O2P(H)Ph}]2 (14). This
material is available free of charge via the Internet at http://
pubs.acs.org.
Science Foundation (Grant CHE 997841) and from the
Research Challenge Trust Fund of the University of Ken-
tucky.
Supporting Information Available: Tables of crystal data,
structure solution and refinement, atomic coordinates, bond lengths
and angles, and anisotropic parameters for (Salomphen(tBu)AlMe
IC0110326
Inorganic Chemistry, Vol. 41, No. 3, 2002 565