phosphite and related compounds

208

Materids

Chemhy

and Physics, 35 (1993) 208-216

Preparation of layered zirconium phospho~ate/phosphate, phosphonate/phosphite and related compounds J. Don Wang and Abraham Depumnent

Clearfield*

of ~~~~~, Texas A&M University, Co&e

Guang-Zhi

zirconium

St&ion, TX 77843 (USA)

Peng

Qinghai Institute of the Salt Lakes, Xining, Qinghai, 810008 (China)

Abstract The preparation and characterization of a number of layered zirconium compounds containing inorganic phosphorus groups as well as organic phosphonate groups are described. Thermal decomposition of ZrF,*- in the presence of mixed phosphoric and phenylphosphonic acids leads to formation of a staged compound in which the organic and inorganic groups are separated in adjacent layers. Reaction of ZrOC12~8H,0 with a mixture of phosphorus acid and phenylphosphonic acid produces a differently staged compound in which each phosphonate group is situated opposite a phosphite group. Reaction of a mixed solution of phosphoric acid and 1,4-phenyldiphosphonic acid with a solution of ZrOClz.8H20 without HF results in the preparation of a series of amorphous mixedcomponent compounds that are found to be highly selective ion-exchangers toward Csc, etc. and can be used in nuclear waste disposal.

( Q

Introduction It was three decades ago [l] that Abraham Clearfield and co-workers crystallized cu-zirconium phosphate (CXZrP) [2]; in 1969 they determined its structure [3, 41. Based upon that structure, a large variety of layered compounds has since been developed all over the world [5,6], including the organic-containing zirconium phenylphosphonate, Zr(C6H5P0& (abbreviated as ZrP+), which was first prepared by Alberti et al. in 1978 {7, S] and recently structurally characterized via a combination of powder diffraction methods by Clearfield and co-workers [9]. The discovery of cr-ZrP has led to a wide range of applications of inorganic ion-exchangers 161, while that of ZrP4 has opened up tremendous possibilities for further modification and control of the structure and properties of such ion-exchangers [lo]. For instance, many mixed-component compounds, i.e., single-phase materials containing both organic phosphonate groups (PR) and inorganic phosphate (POH) or phosphite (PH) groups situated in either ordered or random fashion, have been and continue to be designed and produced. Some of the mixing patterns are illustrated in Scheme 1. Several laboratories, including ours, have been very active in carrying out synthetic studies on these mixed*Author to whom correspondence

0254-0584/93/$6.00

should be addressed.

-0 =PHorPOH)

= PR;

Type B Scheme

i-

1.

=P-R-P. whereR = (C&l&,;

TYW

Scheme

TYP@ C

-0

=

POH )

0

2.

component compounds in general. A patented family of compounds [ 1l] consists of phosphate as the inorganic component and 1,4-phenyldiphosphonate, 4,4’-biphenyldiphosphonate or 4,4”-te~henyldiphosphonate as the organic component or, as it is commonly known, the pillar (Scheme 2). The synthesis, characterization and subsequent chemical behavior of solid state two-dimensional molecular assemblies with to~graphically separated functional groups are receiving increasing attention. The importance of such systems to the fields of electrochemistry

0 1993 - Elsevier

Sequoia.

All rights reserved

[12, 131, microelectronics [14], biological membranes [15, 161, photochemical mechanisms [17] and catalysis [18] has widely been recognized. Organized molecular assemblies have been prepared by both Langmuir-Blodgett [19] and spontaneous adsorption [20, 211 techniques. Recently, highly stable zirconium-containing assemblies have been prepared by variations of the latter method [22, 231. We have had a long and persistent interest in producing organized media in which an electron donor and an electron acceptor are compartmentalized in an orderly fashion within a solid substrate. Our work has involved the use of layered zirconium phosphates and derivatized organic phosphonates. As illustrated in Scheme 3, among the three simple staged structure types involving zirconium phenylphosphonate and phosphate or phosphite, Type F provides separate interlayer spaces that are alternately organic and inorganic and was thus chosen as the basis to facilitate our task of compartmentalizing organic and inorganic guest molecules. Photoactive molecules encapsulated in the interlayers of both clays [17, 181 and zirconium phosphate [24] are greatly affected by the microenvironment of the layered compounds. However, in our initial study [25], Ru(bpy),‘+ (bpy = 2,2’-bipyridine) was encapsulated between the layers of zirconium phosphate sulfophenylphosphonate (ZrPS), which has the approximate composition Zr(HPO,)(O,PC,H,SO,H), and used as a probe of the chemical microenvironment. In this case, the observed spectral shifts were found to result from interactions of the probe molecule with the phenyl rings of the host. Subsequently, both Ru(bpy),” and methylviologen were incorporated within the ZrPS layers and the photo-induced electron transfer reaction was examined [26]. The microenvironment within ZrPS was found to restrict the movement of ions through the interlayer space, probably because of the high concentration of sulfophenyl groups in the interlayer space. However, diffusion leading to dynamic quenching reactions did occur, and these were accounted for by a model combining diffusional quenching and sphere-ofaction quenching of Ru(bpy),*’ by the methylviologen. We are attempting to synthesize new derivatives of ZrPS in which the distance between phenyl rings is systematically increased. This larger space should in-

Type

Scheme

E

3.

TYPO F

TYPO G

crease the mobility of the ions between the ZrPS layers. In addition, we have attempted to produce staged layered compounds of type F structure in such a way that the electron donor would reside in one layer and the acceptor in an adjacent layer. Some preliminary results on staged compounds and otherwise organized layers are reported here. These results build on earlier studies in which two different functional groups were incorporated into the zirconium phosphate layers. Alberti et al. [27] used the slow decomposition of ZrF,‘- in the presence of a mixture of two phosphonic acids to prepare zirconium phosphonates containing both organic groups in the same compound. Three types of derivatives were obtained: (1) Zr(O,PR),_,(O,POH), with 1 GXQ 1.3; (2) Zr(O,PR),_,(O,PR’), with x= 1.25; (3) Zr(O,PR),_,(O,PH), with 0.8
Experimental

Materials and instrumentation

The starting material, 1,4-phenyldiphosphonic acid, was prepared from commercially available C,H,Br,, NiCl, and P(OGH,), by a known procedure [29] with slight modifications [30]. Zirconyl chloride was obtained as a commercial product (Magnesium Elektron, Inc.) and recrystallized from 8 M HCl twice. Phosphorus acid (Fisher, certified), phosphoric acid (Fisher, reagent grade), phenylphosphonic acid (Alfa) and hydrofluoric acid (Fisher, reagent) were used as purchased. X-ray powder diffraction patterns were obtained with a SeifertScintag PAD-V instrument with Cu Kafiltered radiation (A = 1.5418 A). Thermogravimetric analyses were performed with a DuPont Thermal Analyst 2000 system at a heating rate of 5 “C min-’ under a nitrogen atmosphere. For samples difficult to oxidize, a 50:50 mixture of 0, and Nz was used. Infrared spectra were obtained mainly by the KBr disk method on a BioRad ITS-40 Fourier-transform infrared spectrophotometer. Solid-state NMR spectra were recorded on a Bruker MSL300 (31P, 121.493 MHz) spectrometer.

210

Synthesis of staged zirconium phenylphosphonate phosphate

A ZrF,*- solution was prepared by first dissolving 5.43 g (16.8 mmol) of zirconyl chloride, ZrOClz.8H,0, in 30 ml of distilled water in a plastic beaker and then adding 12.4 ml of 48% hydrofluoric acid. A second solution was prepared by dissolving 2.16 g (13.7 mmol) of phenylphosphonic acid, CdHSPO,H,, in 45 ml of water and adding 84.6 ml of cont. H,PO, (1.4 mol). The zirconyl fluoride solution was then added slowly at room temperature to the phosphorus-containing solution and then the container was rinsed with 28 ml of water, which was added to the mix. The combined volume was then approximately 200 ml. This mixture was heated in an oil bath at 60-70 “C for several days to gradually reduce the volume, whereupon a precipitate began to form. The reaction was stopped after 24 h of additional heating. The yield was 3.6 g, or 62% based upon recovered zirconium. Synthesis of staged zirconium phenylphosphonate phosphite 2.76 g (8.54 mmol) of ZrOC1,*8H,O were dissolved

in 20 ml of water in a polyethylene beaker and 6.4 ml of cont. HF were added to it. In a separate vessel, 2.34 g (14.8 mmol) of phenylphosphonic acid were dissolved in 100 ml of water and 48 g (585 mmol) of phosphorus acid were added. This mixed acid solution was then added to the zirconyl chloride solution and the beaker was rinsed with 40 ml of water. This rinse was also added to the zirconyl chloride and the whole was then diluted to 200 ml. The polyethylene beaker was then placed in an oil bath and kept at 60-70 “C for 7 days. This procedure reduced the volume by one half and yielded 1.54 g of product, or 55% based on the formula Zr(HP03)(03PCsH,). This preparation is essentially that described by Alberti et al. [27], in which P/Zr = 70, the mole fraction C,H,PO,H,/(total P) = 0.024, F/Zr = 20 and the total phosphorus concentration is 3 M. Several variants of this procedure were tried, of which only one is described. 4 g (12.4 mmol) of zirconyl chloride were dissolved in 20 ml of water in a plastic beaker, and 9 ml of concentrated HF were added. A second solution, containing 1.06 g (6.7 mmol) of phenylphosphonic acid and 26.8 g (32.7 mmol) of H,PO, in 50 ml of water, was prepared. The zirconyl chloride hydrofluoric acid solution was added to the acid solution and the beaker was rinsed with 14 ml of water and combined with the reactant solution. The beaker was held in a water bath kept at 60-70 “C until 24 h after the first appearance of solid. The yield was 2.6 g (65%). Based on the results obtained in the above reactions, another series was run without the inclusion of HF. 1.00 g (6.33 mmol) of phenylphosphonic acid and 1.04

g (12.7 mmol) of phosphonic acid were dissolved in 20 ml of water. To this solution was added 2.04 g of ZrOC1,+8H,O dissolved in 5 ml of water. The mixture was then heated at 90 “C or under reflux for l-2 days and the solid was recovered, washed with water and air dried. Several different mole ratios of the reactants were tried. Synthesis of amorphous zirconium 1, I-phenyldiphosphonate phosphate

A mixed acid solution was prepared by dissolving 0.44 g (1.85 mmol) of 1,4-phenyldiphosphonic acid in 4.5 ml of water and then adding 1.0 ml (14.7 mmol) of 85% H,PO, in a plastic bottle. In a separate container, 2.98 g (9.20 mmol) of ZrOCl,.8H,O were dissolved in 45 ml of water. The zirconyl chloride solution was added to the mixed acid solution. The reaction mixture in the capped plastic bottle was placed in a 65 “C constant-temperature oven and digested for 7 days. The white solid was filtered, washed with water and dried at 60 “C. Compounds with different phosphonate-to-phosphate ratios were made by varying the molar ratio of 1,4phenyldiphosphonic acid to phosphoric acid but keeping the zirconyl chloride equimolar to the sum C,H,(PO,H,), + tH,PO,. For instance, in a synthesis for a product with higher phosphonate content, 14.7 mm01 of H,PO,, 7.35 mm01 of C,H,(PO,H,),, and 14.70 mm01 of ZrOCl,. 8H,O were used as reactants under identical conditions. Furthermore, longer-chain aryldiphosphonic acids and derivatized acids may be used in place of the 1,4-phenyldiphosphonic acid. Results and discussion Type F zirconium phenylphosphonate phosphate

The product obtained by the slow thermal decomposition of ZrF,‘in the presence of H,PO, and C6HSP0,H, displays an X-ray diffraction pattern (Fig. 1) that is clearly of a layered compound, because it exhibits a high degree of preferred orientation. In fact, the X-ray pattern represents a mixture of phases, which can be identified as follows. The first reflection has an interlayer spacing (001) of 22.5 A. This spacing is expected for a staged compound in which one layer contains phenylphosphonate groups and alternates with an exclusive phosphate layer (Fig. 2). Pure zirconium phen lphosphonate, ZrP4 has an interlayer spacing of 14.8 81 [7,9], while the value for cu-zirconium phosphate, Zr(HPO,),-H,O, is 7.6 8, [4]. The sum of these two values, 22.4 A, is then the expected value for the (001) reflection, and 11.2 8, is expected for the (002) reflection of the phase pictured in Fig. 2. In fact, the first five orders of (001) are present in the diffractogram. Also present is a small peak at 20=6” corresponding to a

211

22.5A

Fig. 1. X-ray powder diffraction pattern of the staged zirconium phenylphosphonate/phosphate prepared from the thermal decomposition reaction of ZrF, *- in the presence of mixed phenylphosphonic and phosphoric acids.

Oli

OH

OH OH

OH

OH

OH OH

OH

OH

7.6 A

14.8 A

+

Fig. 2. Schematic representation of the staged zirconium ylphosphonate/phosphate, Zr(C&P03)(HOP0,).

phen-

d-spacing of 14.7 A, which undoubtedly indicates the presence of some pure ZrP+. It will be shown in the following that a small amount of cu-ZrP is also present. Elemental analysis of the solid indicated an empirical formula of Zr(C,&PO,),,,(HPO,),, .0.5H,O: 27.0% Zr, 18.15% P, 16.88% C, 1.90% H. These results give the overall composition, which needs to be evaluated in terms of the fact that the solid is not pure, but contains small amounts of ZrP4 and cr-ZrP. Alberti ef al. [28] reported a basal spacing of 24.5 8, for a similar staged compound. On the supposition that this higher value is the result of water sorption, we exposed our staged compound (d,, =22.4 A) to a moist atmosphere for 17 h. The X-ray pattern now showed that the initial reflection was, indeed, 24.5 8, with five higher orders, but the 22.4 A reflection also aDDeared. as a shoulder with five higher orders of the

(001) reflections. The solid, in this hydrated condition, gave a thermogravimetric curve containing two weight losses. The end product of the thermal decomposition is ZrPz07, which, based on a weight loss of 23.76%, indicates an initial formula weight of 347.8 (2% Hf in zirconium assumed in calculations). The first weight loss is due to water evolution and amounts to 0.93 H,O. The second weight loss is the result of split-out of phenyl groups followed by condensation to ZrP,O-I. Pure cr-ZrP contains 1 mole of water for every 2 moles of phosphate, with an interlayer distance of 7.6 A. Thus, we would expect an ideal formula of Zr(O,PC&)(HPO,).tH,O to yield an interlayer spacing of 22.4 A. The excess 0.43 moles of water are then the cause of the expansion to 24.5 A. The infrared spectrum contains very broad bands due to the OH stretch at 3424 and 3183 cm-’ and narrow, weak bands at 1618 and 1590 cm-’ for water bending vibrations. The C-H stretching bands of the aromatic ring are observed to be very weak and are located at 3073, 3058 and 3020 cm-‘. A very sharp, medium-intensity band located at 1439 cm-’ is probably an aromatic ring vibration. The PO, and PO, vibrations are centered in very strong, broad bands at 1041 and 1133 cm-‘. Additional sharp, medium-intensity bands are located at 748, 730 and 692 cm-’ and are characteristic of the out-of-plane C-H vibrations. In the solid state MAS 31P NMR spectrum of the d =22.4 8, compound (Fig. 3), there are two major resonances present, one at -5.3 ppm and the other at -20.2 ppm. A spectrum for pure zirconium phenylphosphonate exhibited a single resonance peak at - 5.3 ppm, and Clayden has shown that Zr(HPO,),. H,O yields a single resonance at - 18.7 ppm [31]. Thus the spectra reveal that the two phosphorus-containing groups retain almost the same environment in this staged compound as they possessed in their pure compounds.

-202

-5.31

*

*

*

* *

*

*

*

.li(;_!:_ 80

_ IO

40

20

:

&._ -:.

4.

-L

-a

-b

Fig. 3. Solid-state 3’P MAS NMR spectrum of the staged Zr(C&P03)(HOP03) prepared from the thermal decomposition of ZrF,‘-: asterisks denote spinning sidebands.

212

Amines are readily intercalated into cu-zirconium phosphate [32] with an expansion of the interlayer distance. For example, intercalation of butylamine into cy-ZrP causes the d-spacing to increase from 7.6 to 18.6 A. This large expansion is due to the formation of an amine bilayer inclined at an angle of =55” relative to the layers 1331. In order to show that a compound in which the two ligands are ~ncentrated in separate layers had indeed been prepared, the solid was slurried in a solution of butylamine. The X-ray powder pattern for the intercalated phase (Fig. 4) revealed the presence of several phases. The major one is represented by reflections at 34.7, 17.3 and 11.4 A, which represent the first three (~~ reflections of the staged butylamine intercalate Zr(C,H,NH, .HPO,),,,(O,PC,H,),,. If a bilayer of amine forms in the phosphate layer and this layer expands to 18.6 A, then the repeat interlayer distance should be 18.6+ 14.8=33.4 A. There are actually seven orders of this basal spacing present in the dilfractogram. Consistent with this structure assignment is the observation in the 31P NMR spectra that the resonance for the phosphate group is shifted downfield (from -20.2 to - 18.7 ppm) and broadened upon intercalation of amine, whereas the phenylphosphonate resonance ( - 5.3 ppm) remains unaffected. There is also a medium-sized reflection at 18.6 A resulting from amine intercalation into a-ZrP. It will be remembered (Fig. 1) that a small reflection was present at 7.6 8, (28= 11.65”), which represents the interlayer separation for cr-ZrP. In addition, the diffraction pattern, shown in Fig. 1, contained a small reflection for zirconium phenylphosphonate. This peak is not seen in Fig. 4, but it is probably overlapped by the large one at 17.3 A.

7.3A

Fig. 4. X-ray powder diffraction pattern of the butylamine inter&ate of the staged zirconium phenyIphosphonate/phosphate.

We have shown previously [34] that bringing the bu~lamine inter&ate of G-ZrP into contact with CaCl, results in exchange of Ca2+ for C,H,NH,+: Zr(C4H9NH3P0,&

+ Ca2+ z Zr(PO&(Ca)

- 4&O

-I- 2C4HNH3+

The ~lcium-exchanged t+ZrP has an interlayer spacing of 9.8 A [34, 351. Thus, when a similar reaction was carried out with our staged butylamine intercalate the major phase had an interlayer spacing of 24.8 A, which is close to the expected value of 24.5 8, (14.7 + 9.8 A). The reaction did not proceed to completion, as roughly 25% of the original bu~lamine phase remained. Washing the solid with dilute HCl removed both Ca2’ and butylamine, with recovery of the original staged compound. In a separate experiment, ethylenediamine was intercalated between the phosphate layer of the same staged compound. The product has an X-ray pattern that contains sharp, intense (001) reflections at 25.3, 12.5, 8.3 and 4.9 A. The thermogravimetric analysis (TGA) showed three weight losses: the first one (2%) of H,O before 150 “C, the second (4.6%) of ethylenediamine around 350 “C, and the last (I9.6%) of the phenylphosphonate at 567 “C. This leads to the empirical formula Zr(C,H,PO,)(HPO,)(H,NC&NH,),,~ 0.34H20. The 31P NMR spectrum confirms the presence of the phosphate and phosphonate groups. The collective results of the characterization of products from the slow precipitation reactions with ZrF,‘consistently indicate a staged layered compound of structure type F (Scheme 3). While some of the results could be interpreted in terms of type G as well, the X-ray diffraction patterns for that type would have shown the systematic absence of the first-order reflection owing to the existence of a mirror plane between the repeating layers [9]. This systematic absence was not observed. The type F compound provides a framework in which two different interlayer environments, one inorganic and the other organic in nature, are adjacent to each other. Subsequent amine intercalation experiments have shown that the guest molecules occupy only one interlayer space but not the other. Further modification of the phenyl interlayer space would enable intercalation of another type of guest molecule responding to the functionalized phenyl groups and thus realize our goal of ~mpar~entalizing an electron donor-acceptor pair within one solid substrate. Even though some residual phosphite or phosphate groups, as Alberti suggested, might be mixed in the phosphonate layer [36] of type F, those groups would not participate in the separate ion-exchange procedures owing to steric hindrance and thus would hardly affect the construction of our ‘electron transfer compartments’.

213

Type E zirconium phenylphosphonate phosphite

The staged Zr phosphite phenylphosphonates (type F) should have a basal spacing of 14.8 + 5.6= 20.4 A. Alberti et al. [28] obtained an initial product with a value of 21.1 A. In our experiments involving phosphite, with HF added to complex the Zr4+, one of the products has a d-spacing of 25.5 A. This layer distance indicates that the product may have a full mole of water present in the phosphite layer, which would increase the spacing by 2.5 A. 0 nce this water was removed b slow dehydration, the d value decreased to 21 8: and the compound could not be rehydrated owing to the hydrophobic nature of the interlayer environments. The presence of phenylphosphonate and phosphite groups was reconfirmed by NMR. In a second experiment all the conditions were the same, except that the F/Zr ratio was 30. This increased the time required for precipitation to 21 days and yielded zirconium phosphite (5.6 8, basal spacing) as the major product, zirconium phenylphosphonate containing a small amount of phosphite (14.7 A), and a phase with an interlayer spacing of 30.4 A. This latter spacing, as well as that of 25.5 A, can be explained on the basis of more highly interstratified products. For example, two phosphite layers plus one phenylphosphonate layer yields a basal spacing of 25.9 A, while three phosphite layers plus a phenylphosphonate layer leads to a (001) reflection of 31.5 A. Thus, approaching equilibrium very slowly, as in this experiment, yields mainly a pure phosphite phase together with more highly staged products. We have also reacted ZrOC1,*8H,O directly, without HF, with a mixture of phosphorus and phenylphosphonic acids. As soon as the zirconyl chloride is added to the mixture of acids a white precipitate forms and remains suspended in the water. This precipitate was digested at an ambient temperature of 90 “C or under reflux. An X-ray pattern of the solid before digestion showed it to be poorly crystalline but with a broad peak at = 15 A, representing the interlayer spacing. This solid is apparently a mixed phosphite phosphonate derivative with sufficient phenyl groups in the interlamellar space to require the larger d-spacing in which phenyl groups in adjacent layers are separated by slightly greater than the van der Waals distance. The layer spacing must arise from the disorder of the poorly crystalline product. When this solid was heated in its mother liquor at 90-100 “C, the product obtained depended upon the ratio of phosphite to phosphonate in the reactant mix. This ratio in turn determines the relative amounts of these ligands incorporated. Thus when this ratio was 1:l the product had a = 15 %,interlayer spacing. Analysis of one of the products gave 20.36% C, 2.62% H and a total weight loss of 29.9%, with 12.6% being water. These values yield an empirical formula of

.,(HPO,),,, .2.6H,O. The 31P NMR spectrum confirms the presence of the P+ and PH groups. From this we may conclude that the product is a single phase in which the excess of phenyl groups over phosphites on the layers requires that the interlayer spacing be close to that of the zirconium phenylphosphonate. Increasing the H,PO,:C,H,PO,H, ratio to 2:l decreases the interlayer spacing to 11.8 A, and the analytical and TGA data indicate a formula of Zr(C6H~P03)1.01(HP03)0,99.3.5H20, which is supported by NMR and IR spectra. As the ratio of phosphorus acid to phenylphosphonic acid increases, the interlayer spacing further decreases to 118, (Zr(C,H,PO,)(HPO,) when the starting acid ratio was 3:l) and finally attains a value of 10.6 A (starting acid ratioa5:l). This last solid has an empirical formula of Zr(C,H,PO,),,,(HP03)1.52 (TGA weight loss 8.6%). The 31P NMR spectrum (Fig. 5) confirms the presence of both the P+ and PH groups with S values -5 and - 16 ppm, respectively, the latter being ‘H-coupled. In these solids with much smaller interlayer spacings than the 14.8 A value for ZrP4, each phenyl group faces a phosphite group from the adjacent layer. For the idealized structure of type E (Scheme 3), each phenyl group in a layer is situated opposite a phosphite group, and therefore the interlayer spacing is half the sum of the distances in pure zirconium phosphite (5.6 A) and ZrP+ (14.8 A). A phase with an interlayer distance of 10.4 A, exactly that calculated for type E, has been observed in several of the mixed-phase products from our hydrothermal or thermal reactions. The pure products with phosphite-to-phosphonate ratios approximating one would most closely resemble structure type E, whereas the last product with a formula of

~4.85

-Ih 3

Fig.

5.

Solid-state

Zr(C~sP03)l.m(HP03)a97 (A) and off (B); asterisks

3’P MAS NMR spectra recorded with proton decoupler denote spinning sidebands.

of on

214

and a d-spacing of 10.6 A Zr(CsH5Pu,),.,(HPO,)1,, would have an interlayer ~~~o~~n~ where one side is fu&~ a phosphite layer and the other side a mixed layer of phosphite and phenylphosphonate groups. It should be pointed out that we do not, however, have exclusive evidence to show whether the phosphonate and phosphite groups in the mixed layer are distributed in a random or an orderly way, Zirconium p-phenyldiphmphonate phaspha te and related cmnpmmds The reactions between the fluoride complex of Zr4’ and the mixed acid of 1~4-phenyldiphosphonic acid and phosphoric acid have previously been reported fll], The product was a crystalline layered compound with d = 9.67 A (Fig. 6). Peng et al. [37] discovered that a similar reaction took place in the absence of fluoride (HF). Upon mixing a ZrOCl, solution directly with the ~phosphonic/phospho~c mixed acids at arbitrary PR/ PUH ratios, a white precipitate formed, which was then digested at. 60-70 “C for several days. X-ray diffraction shows that the solids so produced are amorphous, with a very broad reflection centered at about 10 A (Fig. 7). Hydrothermal treatment of this solid increased the X-ray diffraction intensity only slightly, The phosphateto-diphosphonate ratio in these amorphous products varies and correlates closely with the molar ratios of phosphoric acid to diphosphonic acid in the starting mixed acid solution (Table l), unlike the crystalline product, whose ~m~sition seems to be independent of the reactant ratio. Synthetic experiments have been carried out with a variety of phosphoric-acid-to-diphosphonic-acid ratios (ranging from 1:I to 1:16), with

3.67 &

Fig. 6. X-ray powder diffraction pattern of the crystalhne zirconium l,~pheny~d~phosphonate/phosphate prepared from the thermal decomposition of ZrFez- in the presence of mixed 1,4phenyldiphosphonic and phosphoric acids.

t

Fig. 7. X-ray powder dieaction pattern of the amorphous zirconium 1,4-phenyldiphosphonate/phosphate (lP-Qprepared from the direct reaction ofZr4’ with the mired 1,4-phenyldiphosphonic and phosphoric acids followed by thermai digestion. TABLE 1. Reactant ratios (1,4-phenyldiphosphonic acid to phosphoric acid) and empirical formulae for the amorphous zirconium p-phenyldiphosphonate/phosphate compounds Sample no.

Ratio

lP-1 lP-2 IP-3 1P4 IP-5

1:l 1:2 1:4 1:6 1:8

Formula ~(~p2~,),,(wpo4~U.~*2.19H2~

zr(C~P,o,),,(HPo4),,~ -233-W Zr(Cb~P206)0.33(HP04)*.51 *2.~W3 zr(~~PzO,),,,(HPO4)l,.2.56H20 zr(~~P,O,),.,,,(Hpo,)t.~~ -3.13L-W

TABLE 2. Values of the distribution coefficients for the amorphous zirconium 1,4-diphosphonatelphosphates Sample no. Li

Na

lP-f. lP-2 lP-3 lP4 lP-5


<1 <1 5.8 1.9 <1

K

Rb

Cs

Mg Ca

38 65 27 22 140 277 44 27 288 2090 188 457 522 3350 320 589 220 4500 187 361

Sr

Ba

208 140 595 613 461

154 72 292 420 285

or without HF, and the two sets of products (amorphous and crystalline, respectively) have been studied. The amorphous products display IR and NMR spectra that are quite different from those for the crystalline products, indicating that these are fund~~ntally different compounds. More importantly, they show very interesting ion-exchange properties toward Cs and other large cations. As summarized in Table 2, a gradual increase is obvious from the compound with the highest organic content (IP-1) to lowest organic content flP5). For every compound, the distribution coefkient for Cs is much higher than that for Na ion, making these highly selective ion-exchange materials for separation

215

of es+ and other large cations from Na’. We are currently engaged in development of these materials for separation and disposal of nuclear wastes*. We have also synthesized and characterized similar amorphous compounds with an array of aryl- and derivatized aryldiphosphonic acids.

Conclusions

We have presented several types of zirconium phenylphosphonate/phosphate and phenylphosphonate/ phosphite compounds, including staged compounds in which similar groups (for instance, groups of the same polarity or same size) are preferentially situated on the same side of a layer. Depending on the relative organization of these layers, a number of staged structures are possible. By varying the reactant ratio and reaction conditions, a large number of zirconium aryldiphosphonate/phosphate compounds could be produced in either amorphous or crystalline form. Among the Zr(C,H,P0,)(HOP03) -xH,O systems, a product of type F has been synthesized from slow reaction utilizing HF. Intercalation of this compound with amines or diamines leads to increases in the interlayer distance corresponding to insertion of a bilayer or monolayer, respectively, between the phosphate layers. The observation of a monolayer of intercalated ethylenediamine rules out the possibility of having structure type G. Sulfonation of the phenylphosphonate groups and further exchange of a second type of ion into the sulfonated phosphonate interlayer space are being pursued actively in our laboratory in order to realize the compartmentalization of electron donors and acceptors. On the other hand, in the Zr(C,H,PO,),_,(HPO,), system, compounds with x values of either = 1 or = 1.5 have been prepared from thermal reactions. The compound in which x= 1 and d= 10.811.3 8, is probably zirconium phenylphosphonate/phosphite of pe A, whereas the product with x = 1.5 and d = 10.6 1 seems to be consistent with a structure in which one side of the layer is entirely phosphite and the other side consists of mixed phenylphosphonate and phosphite groups. Preliminary experiments on the reaction of these phosphite-containing compounds with sulfuric acid have indicated that the phosphite groups can be oxidized and the phenyl groups sulfonated. A more systematic investigation is being conducted to fully elucidate the structural features and reactivities of these staged compounds. *Technical details are not available owing to the proprietary nature of the research.

A more detailed report on the complete range of staged phenylphosphonate/phosphates and phenylphosphonate/phosphites will be forthcoming [38]. Numerous amorphous aryl- and derivatized aryldiphosphonate/phosphates have been prepared from direct precipitation without HF, and the products have been shown to be structurally distinguishable from their crystalline counterparts. These amorphous compounds are highly selective ion-exchangers, and we are actively developing them for applications including nuclear waste treatment. We are also exploring the detailed structural characteristics of these amorphous materials and comparing them with those of the crystalline compounds.

Acknowledgements

These research projects have been supported, in part, by the National Science Foundation under grant numbers CHE-8921859 and INT-8910902, for which grateful acknowledgement is made. The authors wish to express their gratitude to Dr C.-Y. Yang for preliminary results on the staged compounds and to Ying Tian for experimental work on all three aspects of the chemistry in this paper. Without their contributions this paper would not have been possible. J.D.W. thanks Professor Giulio Alberti for a stimulating discussion on possible defects in the type F zirconium phenylphosphonate/ phosphate.

References J.A. Stynes, M.S. 7%esis, Niagara University, Niagara Falls, NY, 1961. A. Cleatield and J.A. Stynes, J. Inorg. Nucl. Chem., 26 (1964) 117. A. Clearfield and G.D. Smith, Inorg. Chem., 8 (1969) 431. J.M. Troup and A. Clearfield, Inorg. Chem., 16 (1977) 3311. A. Clearfield (ed.), Inorganic Zon Exchange Materials, CRC Press, Boca Raton, FL, 1982. A. Clearfield, Comments Inorg. Chem., 10 (1990) 89. G. Alberti, U. Costantino, S. Allulli and N. Tomassini, /. Inorg. Nucl. Chem., 40 (1978) 1113. G. Alberti and U. Costantino, in J.L. Atwood and J.E.O. Davies (eds.), Inclusion Compounds, Vol. 5, Oxford University Press, Oxford, UK, 1991, Ch. 5. 9 M.D. Poojaty, H.-L. Hu and A. Clearfield, Acta Crystabgr., Sect. B, submitted. 10 M.B. Dines and P.M. DiGiacomo, Inorg. Chem., 20 (1981)

92. 11 M.B. Dines, P.M. DiGiacomo, K.P. Callahan, P.C. Griffith, R.H. Lane and R.E. Cooksey, ACS Symp. Ser., 192 (1982) Ch. 13. 12 R.W. Murray, Act. Chem. Res., 13 (1980) 13.5. 13 J.S. Facci, Langmuir, 2 (1987) 525. 14 G.G. Roberts, Adv. Phys., 54 (1985) 475.

216 15 (a) T.H.

16 17 18 19

20 21 22 23 24

Watts, H.E. Gaub and H.M. McConnel, Nature (London), 320 (1986) 179; (b) A. Laschewsky, H. Ringsdorf, G. Schmidt and J. Schneider, L Am. Chem. Sot., 109 (1987) 788; (c) H. Ringsdorf, G. Schmidt and J. Schneider, Thin Solid Films, 152 (1987) 207. J.H. Fendler, Membrane Mimetic Chemistry, Wiley, New York, 1982. (a) M. Gratzel, Pure A&. Chem., 54 (1982) 2369; (b) J.K. Thomas, Act. Chem. Res., 21 (1988) 275. M.A. Richard, J. Deutsch and G.M. Whitesides, .I. Am. Chem. Sot., 100 (1979) 6613. H. Kuhn, D. Mobius and H. Bucher, in A. Weissberger and B.W. Rossiter (eds.), Techniques of Chemistry, Vol. 1, Wiley, New York, 1972, p. 577. J. Sagiv, J. Am. Chem. Sot., 102 (1980) 92. D.L. Allara and R.G. Nuzzo, Langmuir, 1 (1985) 45; I (1985) 52. H.-G. Hong, D.D. Sackett and T.E. Mallouk, Chem. Muter., 3 (1991) 521. T.M. Putvinski, M.L. Schilling, H.E. Katz, C.E.D. Chidsey, A.M. Mujsce and A.B. Emerson, Langmuir, 6 (1990) 1567. R.A. Schoonheydt, J. Mol. Cutal., 27 (1984) 111.

25 J.L. Colon,

26 27 28 29 30 31 32 33 34 35 36 37 38

C.-Y. Yang, A. Clearfield and C.R. Martin, I; Phys. Chem., 92 (1988) 5777. J.L. Colon, C.-Y. Yang, A. Clearfield and C.R. Martin, J. Phys. Chem., 94 (1990) 874. G. Alberti, U. Gxtantino, J. Kornyei and M.L. LucianiGiovognotti, React. Polym., 4 (1985) 1. G. Alberti, U. Costantino and G. Perego, J. Solid Stute Chem., 63 (1986) 455. (a) P. Tavs, Chem. Ber., 103 (1970) 2428; (b) A. Michaelis, Justus Liebigs Ann. Chem., 293 (1896) 193. G.-Z. Peng et al., unpublished results, 1991. N.J. Clayden, J. Chem. Sot., Dalton Trans., (1987) 1877. A. Cleartield and R.M. Tindwa, J. Inorg. Nucl. Chem., 41 (1979) 871. R.M. Tindwa, D.K. Ellis, G.-Z. Peng and A. Clearheld, J. Chem. Sot., Faraday Trans. 1, 81 (1985) 545. G.-Z. Peng and A. Clearfield, J. Inclusion Phenom., 6 (1988) 49. A. Clearfield and H. Hagiwara, J. Znorg. Nucl. Chem., 40 (1978) 907. G. Alberti, University of Perugia, Perugia, Italy, personal communication. G.-Z. Peng et al. and A. Clearfield, manuscripts in preparation, J.D. Wang, C.-Y. Yang, C. Bhardwaj and A. Clearfield, manuscripts in preparation.