Articles
Aluminum Phenylphosphonates: A Fertile Family of Compounds
Aurelio Cabeza,
²
Miguel A. G. Aranda,
²
Sebastian Bruque,*
,²
Damodara M. Poojary,
‡,§
Abraham Clearfield,
‡
and Jesus Sanz
|
Departamento de Quı ´mica Inorga ´nica, Universidad de Ma ´laga, 29071 Ma ´laga, Spain, Department of
Chemistry, Texas A&M University, College Station, Texas 77843, and Instituto de Ciencia de
Materiales, CSIC, Cantoblanco, 28049 Madrid, Spain
ReceiVed March 5, 1998
Six aluminum phenylphosphonates have been synthesized depending upon the synthetic conditions: Al
2
(O
3
-
PC
6
H
5
)
3
‚2H
2
O(I), Al
2
(O
3
PC
6
H
5
)
3
(II), R-Al(HO
3
PC
6
H
5
)(O
3
PC
6
H
5
)‚H
2
O(III), -Al(HO
3
PC
6
H
5
)(O
3
PC
6
H
5
)‚H
2
O
(IV), Al(HO
3
PC
6
H
5
)
3
‚H
2
O(V), and Al(OH)(O
3
PC
6
H
5
)(VI). Thermal analysis, X-ray powder thermodiffractometry,
IR spectroscopy, and
27
Al and
31
P MAS NMR data have been obtained to study the structure and thermal stability
of these materials. III crystallizes in the orthorhombic system, space group Pbca, with a ) 9.7952(1) Å, b )
29.3878(4) Å, c ) 9.3537(3) Å, and Z ) 8. The structure was solved ab initio, from synchrotron data (λ ≈ 0.4
Å), using direct methods, and refined by Rietveld methods. The final agreement factors were R
wP
) 6.73%, R
P
) 5.24%, and R
F
) 6.8%. The compound is layered with the aluminum atoms in an octahedral environment of
oxygens and two crystallographically independent phosphonate groups, one being protonated. The powder patterns
of V and VI have been indexed, and the experimental observations are consistent with layered structures. The
unit cell of V contains one octahedral site for Al and three tetrahedral sites for P. Phosphonate I seems to have
a three-dimensional tubular structure with aluminum atoms in both octahedral and tetrahedral environments and
phosphorus atoms in three different types of sites.
Introduction
The metal phosphonates are a class of inorganic-organic
hybrid materials, characterized by the presence of covalent bonds
between the inorganic and organic moieties. In this family, the
chemistry of metal phosphonates has received increasing
attention for the last 15 years. The main research effort in the
metal phosphonates field was initially directed toward tetravalent
cations. A wide variety of tetravalent metal phosphonates (for
instance, Zr, Ti, Sn, and Ce) have been known since the early
1980s.
1
The crystal structure of these materials was assumed
to be related to that of R-zirconium phosphate, Zr(O
3
POH)
2
‚
H
2
O.
2
Later, the structure of zirconium phenylphosphonate,
Zr(O
3
PC
6
H
5
)
2
, was solved from powder diffraction data
3
and
the close relationship between the structures became clear. Many
other investigations have been reported about the synthesis,
crystal structures, and properties of divalent metal phospho-
nates,
4-8
and more recently about trivalent metal phospho-
nates.
7b,9,10
The general interest in the chemistry of metal
organophosphonates is mainly due to the unusual compositional
and structural diversity varying from one-dimensional arrange-
ments to three-dimensional microporous frameworks, passing
by the most common layered networks. The importance of such
systems in several research areas such as electrochemistry,
11,12
microelectronics,
13
biological membranes,
14,15
photochemical
mechanisms
16
and catalysis
17,18
has been widely recognized.
Several studies of trivalent metal phenylphosphonates have
been carried out. Two iron(III) derivatives, FeH(HO
3
PC
6
H
5
)
4
and Fe(HO
3
PC
6
H
5
)(O
3
PC
6
H
5
)‚H
2
O, were synthesized, and the
structure of the first compound was solved from single-crystal
data. The main structural features are linear chains with iron
*
To whom correspondence should be addressed.
²
Universidad de Ma ´laga.
‡
Texas A&M University.
§
Current address: Symyx Technologies, 3100 Central Expressway, Santa
Clara, CA 95051.
|
CSIC.
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S0020-1669(98)00235-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 08/06/1998