Intercalation of nitrogenous substances into HUO2PO4·4H2O

Mat. Res. Bull., Vol. 22, pp. 19-27, 1987. Printed in the USA. 0025-5408/87 $3.00 + .00 Copyright (c) 1987 Pergamon Journals Ltd.

INTERCALATION L.Noreno Departamento

de

OF NITROGENOUS

Real,

R.Pozas

SUBSTANCES

Tormo,

M.Martinez

INTO H U ~ P ~

.4H20

Lara and S.Bruque

Ouimica Inorg~nica, Universidad n Q 59, 29080 MALAGA (Spain)

de

M~laga,

Apartado

(Received April 30, 1986; Refereed)

ABSTRACT The laminar compound HUO 2 PO .4H 2 0 (HUP) interacts with piperidine, hydrazine, p y r l d i n e ~ pyrazlne and (dimethylaminomethyl)ferrocene to produce intercalation reactions. The intercalate materials exhibit a layered structure derived from the starting solid. The only observed structural modifications were dimensional changes in the crystal c axes . The amount of a@sorbate taken up by the NUP is related to the size and geometry of the guest molecule and its basicity. The guest-host reactions are of the acid-base type as shown by i.r. spectra. MATERIALS substances.

INDEX:

Hydrogen

Uranyl

Phosphate,

Nitrogenous

INTRODUCTION Within the field of solid state chemistry the chemistry of the intercalated compounds has become increasingly important in the space of a few years. Among these substances those which offer the most interest and application potential at the present time are the inorganic laminar compounds because their different solid structural lattices show very high surface reactivities and their original structures remain practically intact during and after the intercalation process. HUO 2 P O 4 . 4 H 2 0 (HUP) is a member of the large family of uranium-mica compounds with the general formula M ( U O ~ P 0 4 )z .nH20, where M may be a mono or divalent cation. Their typlcal structure

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L. MORENO REAL, et al.

Vol. 22, No. 1 n-

consists of negatively charged layers of (UO 2 PO4)n ,separated by staggered layers of water molecules and compen-sating~eations. In the HUP, the latter are H +, but these may be substituted by almost any other cations (1),(2). The layer may be stacked in one of two ways (metaautunite and autunite) as shown in figure i (3). HUP crystallizes in the tetragonal system in which the inter laminar distance is 8.8 A. The intercalation of alkylamines causes a n increase of the interlaminar space the values of which are a function of the number of carbon atoms in the alkyl chains(4).These intercalated compounds show very high crystallinity and the original HUP tetragonal structure is preserved (5).

UO2

lal

(bl

FIGURE l.-Uranyl phosphate layers the meta autunite structure (b).

in

the

autunite

structure

(a)

and

The sorbates chosen for this present study were nitrogenated substances with different degrees of basicity: piperidine was chosen as the strong base (PKb= 2.88),and as weak bases, hydrazine (PKb= 5.77) and pyridine (pKb =8.75). The almost amphiprotic molecule, pyrazine, and one basic organometallie species,(dimethylaminomethyl)ferrocene (DMAMFe), were also employed. The study of the intercalation of the above molecules by the HUP centered on the composition of the products, the arrangement of the guest molecules in the interlaminar spaces, and spectroscopic characteristic of the intercalated compounds.

EXPERIMENTAL The HUO P O ~ . 4 H 0 was prepared by the method proposed by Schreyer and Baes (~) ~from2uranyl nitrate and orthophosphoric acid in aqueous solution with an acid/nitrate ratio of i.i/i. The resulting yellow solid was kept in controlled humidity conditions (p H 2 0 = 9.1 torr).

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N I T R O G E N O USUBSTANCES S

21

P y r i d i n e and piperidine, the most volatile of the liquids, were a d s o r b e d by s o l i d - v a p o r reactions. Hydrazine, pyrazine and DMAMFe were a d s o r b e d in s o l i d - l i q u i d reactions; h y d r a z i n e was employed as the pure liquid but p y r a z i n e (0.i M) was d i s s o l v e d in methanol and the DMAMFe, was in the form of an aqueous emulsions. In each case, following the i n t e r c a l a t i o n reactions, the final products were r e p e a t e d l y washed until the w a s h - l i q u i d s showed no trace of sorbates. The dimensions of the i n t e r c a l a t e d m o l e c u l e s were c a l c u l a t e d using the "Tables of i n t e r a t o m i c distances and configurations
RESULTS

AND D I S C U S S I O N

The uranyl hydrogen p h o s p h a t e tetrahydrate retains sorbates and its basal s p a c i n g is modified, as shown in Table i. table also shows the c o m p o s i t i o n of the intercalates obtained for sorbate.

the This each

'FABLE 1

Intercalate c o m p o s i t i o n s and basal spacing " H U P + n i t r o g e n o u s substances" Sorbate piperidine

(pip)

hydrazine pyridine

(py)

pyrazine

(pz)

dimethylaminomethylferrocene(DMAMFe)

Composition

of

d 002

HUP.

0.62pip.

H20

12.56

HUP.

N2H 4. 1.6H20

8.96

HUP.

9.30

HUP.

py

O.32pz.

HUP.O.8DMAMFe.

H20

0.4H20

(A)

8.26 18.80

The i n t e r c a l a t i o n r e a c t i o n s were topotactic,all the products showed high c r y s t a l l i n i t y and their d i f f r a c t i o n lines can be indexed in tetragonal s i s t e m . T h e starting p r o d u c t hkO r e f l e c t i o n s are m a i n t a i n e d in the intercalates, this indicates that the ab plane of the crystal lattice remains unchanged. The only observed structural m o d i f i c a t i o n s were dimensional changes in the crystal c axes because of the intrusion of the sorbate m o l e c u l e s into the i n t e r l a m i n a r space of the HUP.

the

size

The amount and g e o m e t r y

of adsorbate taken up by the HUP is of the guest molecule and to its

related [o basicity .

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L. MORENO R E A L , et al.

Vo].

22, No.

Consequently the basal spacing of the piperidine intercalate allows the molecule to lodge in such away that the plane which contains four methylene groups is parallel to the host layers. Piperidine lodged in this way occupies an area of 33 A 2 ,so, takin~ into accoun~ that the total available area of each active center (H T) is 24.4 A - (9) then complete saturation of this possible active sites accessible is achieved by the occupation of some two-thirds of the total available area and this determines the maximum composition of the HUP-pip intercalate of 0.62 moles of pip per mol of HUP. However, for the hydrazine-HUP intercalates the H U P / N ^ H ratio is unity and the observed basal spacing is compatible with t ~ e ~ N p H ~ molecule being orientated in such aw~y_ that the N-N axis is situated parallel to the host layers ( U O 2 P 0 4 ~ in a autunite type structure (Figure I). The composition data suggest that two hydrazine molecules occupy each cavity and that space remains to accommodate the water molecules. The pyridine intercalate has no water in its composition and the observed d(O02) spacing is 9.30 A. Taking into account that the Van der Waals area occupied by pyridine is 43 A and that the HUP/py is unity,the sorbate molecules should be situated two to each structural cavity with their CA axis perpendicular to the host layer planes. This type of arrangement~ v and the slight increase of the substrate laminar spacing, precludes the presence of water molecules,so that those of the host HUO 2 P O 4 . 4 H 2 0 , are progressively displaced as the pyridine penetrates. Pyrazine is and aromatic molecules and only very weakly basic (PKb= 13.55) and so it is to be expected that it is only slightly retained: only 0.32 molecules per formula of HUP. The basal spacing of the inZercalate H U P . O . 3 2 p z . H 2 0 (8.26 A) is compatible with the pyrazine molecules occupying the spaces in the autunite type of structure with the aromatic ring planes orientated parallel to the layer planes. The composition obtained indicates that only 64% of the cavities are occupied so that there is ample space for the water molecules. Attempts to intercalate DMAMFe failed in aprotic solvents (acetone) and only occurred to a very small extent in acetone/water mixture. In spite of being insoluble in water, DMAMFe forms stable emulsion which effectively react with suspensions of HUP to produce an intercalate with the composition shown in Table i. The basal spacing suggests a bi-laminar arrangement of this complex molecule which is depicted in Figure 2. Probably the orientation of the cyclopentadiene ring planes is parallel to the layer planes of (UO^POA)D-O,)Lkl as the molecular thickness when orientated in this way is 6~65 ~ and so the thickness or the bi-laminar arrangement should be 13.3 A. The d(O02) value obtained was 18.8 A,very closed to the sum of the laminar packet (6.38 A) and the molecules thickness described above. The difference between the expected and experimentally obtained is only 0.88 A. This may be due to the molecules being only partially enclosed in the cavities formed by the host layer oxygen molecule surfaces. On the other hand the Van der Waals surface of the DMAMFe molecule which lines !7bc layer faces2is slightly less than the available area of each active centre (48.2 A against 48.8 A 2 for the bilaver). Nevertheless, the

1

Vol. 22, No. 1

NITROGENOUS SUBSTANCES

23

irregular contours of this molecule must be taking into account as this increases the effective area. One calculation made by assuming lO molecules arranged in the_closest packing order gave an effective area value per molecule of 69 A . Consequently, the maximum saturation is reached with a composition of 0.8 molecules of DMAMFe per active centre.

H '2N M e.: Ye

FIGURE

2.-

Scheme

of

the

(dimethylaminomethyl)ferrocene

molecule.

The g u e s t - h o s t reactions are of the acid-base is shown by the i.r. spectra of the intercalates. In all of v i b r a t i o n b~nds are detected: piperidinium ( Q N H ~ = 2950 --± + L = 1590 cm ~(ii); hydrazinium ( S NH~ : 1585 ~ cm-') (12); (BI= 1545 cm--)(13) (14).

type, this them ionic cm-±, ~ N H : L pyridinium

Another common characteristic of the i.r. spectra of all the intercalates is the disappearance of the wide band of HUP (to 1750 cm -1 ) due to the vibration bending of the mobile H30+ ions. In the intercalates of piperidine, pyrazine and DMAMFe, the residual protons which where not involved in the H+-amine reactions r e m a i n _ ~ i x e d to the phosphate groups. Other bands are also seen at 117080 ~ m - a n d 850-80 cm-- which caused by POH groups. The bands at 1170 cm may be assigned to the Q mode of the PO with an assymetric 3 4 configuration such as that produced when one or more oxygen atoms are united to atoms of hydrogen. In this case the ~ mode might develop into two or three components (~ ( P O ) , ~ (PO~) and ~ (P-OH))~ ~he first • as J s a -± zs seen clearly in m o n o h y d r o g e n p h o s p h a t e s c~ose to ~170 cm (15). In addition t h ~ "0 (P-OH) should appear which some authors attributed to the 870 cm - ± b~nd. Other authors (15),(16) postulate that the 1170 and 870 cm-I bands correspond to deformations within and outside the plane of the POH groups respectively. However, the closeness of the two frequencies 0 (UO~) and ~ (P-OH) ( o r ~ ~P-OH)), makes this assignment • s L rather rzsky. Consequently, the i170 cm band is the most important indication of the presence of POH. In the pyridine intercalate, although the r_~tio H + /py =i one can see in the i.r. spectrum a weak band at 1170 cm which is not present in the HUP.N2H4.1$6H20. This could be due to two factors: i) pyridine basicity is i0 times weaker than hydrazine, and ii)the spacial orientation of the pyridine, in the interlaminar cavity could weaken the p r o t o n a t i o n of the intercalated molecules.

show

i.r.

Those intercalates which have water in their composition bands corresponding to the Q O H and ~ H O H vibrations.

24

L. MORENO REAL, et al.

Vol. 22, No. I

Figures 3 to 5 give the observed i.r. frequencies with their corresponding assignations for the HUP+Nitrogenous substance compounds. In every case there are bands at frequencies which correspond to the uranyl and phosphate groups ( ~ a s P 0 4 = 1125 cm -I, ~ s P 0 4 = i010 cm-l, asU02 = 925 cm ,'OsU02 = 820 cm ).

' ~-~

b

! )

l 3500

I ~

m

i 25(x)

)

, )

I

~ I

I)

WXVlmUimen

140(2)

,#,

I

I)

1000

(,~m- 1 )

FIGURE 3.- Infrared Spectra of HUP.O.8DMAMFe. O.4H20

I BOO

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Vol. 22, No. 1

N I T R O G E N O U SUBSTANCES S

25

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L. MORENO R E A L , et al.

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Vol.

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NITROGENOUS

SUBSTANCES

ACKNOWLEDGEMENTS We acknowledge financial help from the C.A.I.C.Y.T. and we express our thanks to the "Instituto de Fisico-Quimica Mineral (CSIC; Madrid) for i.r. mesurements. We are grateful to Mr. David W. Schofield for reviewing the english version.

REFERENCES i. V. Pekarek and V. Vesely, J. Inorg. Nucl. Chem., 2__7, 1151 (1965). 2. R. Pozas, Thesis, Universidad de M~laga, Espa~a, (1986). 3. J. Beintema, Rec. Travaux Chim.,Pays-Bas et Belgique, 57, 155

(1938). 4. A. Weiss, 5. R. Pozas,

K. Hartl and U. Hoffman, Z. Naturforsch, 12b,351, (1957). L. Moreno-Real, M. Martinez-Lara and S.Bruque, Can. J.Chem.,

64, 30 (1986), 6. J.M. Schreyer and J. Baes, J. Am. Chem. Soc., 76, B54 (1954). 7. Tables of Interatomic Distances and Configurations in Molecules and Ions, The Chemical Soc., London (1956). 8. L. Pauling, "The Nature of Chemical Bond", Cornell University Press, N. Y. ( 1 9 6 0 ) . 9. C.B. Amphlett, "Inorganic Ion Exchangers", Elsevier, Amsterdam (1964). i0. N.M. Greenwood and A. Earnshaw, "Chemistry of the Elements", Pergamon Press, Oxford (1984). ll. P. Sauvageau and C. Sandorfy, Can. J. Chem.,S8, 1901 (1960). 12. J.C. Decius and D.P.Pearson, J. Am. Chem. Soc.,Z_5, 2436 (1953). 13. V.C. Farmer and M.M. Mortland, J. Chem. S o c . , ~ j , 344 (1966). 14. J.M. Serratosa, Clays Clay Min., 14, 385 (1966). 15. V.C. Farmer, "The Infrared Spectra of Minerals", Mineralog. Soc., London (1974). 16. L.V. Kobets and D.S. Umreiko, Russ. Chem. Rev., 52, 509,(1983).

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