1434
Inorg. Chem. 1991, 30, 1434-143s
Articles Contribution from the Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712-1167
Shape-Selective Intercalation Reactions of Layered Zinc and Cobalt Phosphonates Guang Cao and Thomas E. Mallouk* Received September 4, 1990 Dehydration of layered metal phosphonates M(03PCH3).H20(M = Mg, Zn, Co) occurs topochemically to give anhydrous salts M(03PCH3)with similar unit cell dimensions in the space group Pmn2,. Mg(03PCH3)absorbs water rapidly from air, forming Mg(03PCH3).H20;Co(03PCH3)does so less readily, and Zn(03PCH3)is unreactive even with liquid water. Anhydrous Co and Zn salts M(03PCH3)react with ammonia and primary amines to form intercalation compounds M(03PCH3)(RNH2),R = H to n-C8H17. The intercalation reaction is shape-selective, as amines with branching at the a-carbon cannot access the metal coordination site. The packing of alkyl chains is different for primary amine intercalation compounds containing Co and Zn. In all C O ( O ~ P C H ~ ) ( ~ - C , H ~ ~ compounds, + , N H ~ ) the chains pack as double layers. In the Zn(03PCH3)(n-C,H2n+lNH2)series, compounds with even n also adopt double-layer structures, while odd n compounds form more efficiently packed interdigitated monolayers in the interlamellar region.
Introduction
Layered metal phosphonates have received considerable a t tention since t h e late 1970s because of properties which lend themselves to various potential practical uses, such as serving as sorbents, catalysts and catalyst supports, and ion exchangers.'" All these properties are related to easy access of molecules to the large internal surface area of the layered structures. Since these layered materials have structurally and chemically well-defined internal void spaces and coordination sites and these internal sites are often preparatively easy t o alter, in favorable cases so-called "structurally tailored" materials' can be obtained. Examples of structurally tailored materials include pillared tetravalent metal phosphates whose internal surface area becomes accessible upon ~illaring.~,~ A recent example of this kind of chemistry is the work of Johnson et alesbwho demonstrated shape-selective intercalation of alcohols into vanadyl phosphonates, VO(0,PR).H20. These compounds, prepared by thermal loss of benzyl alcohol from VO(03PR).H20.C,H5CH20H, have a vacant coordination site a t the VIv atom. A variety of primary alcohols can bind at such sites, while secondary and tertiary alcohols are excluded. VO( I ) Mikulski, C. M.; Karayannis, N. M.; Minkiewicz, J. V.; Pytlewski, L. L.;Labes, M. M. Inorg. Chim. Acra 1969, 3, 523. (2) Yamanaka, S.Inorg. Chem. 1976, 15, 2811. ( 3 ) (a) Alberti, G.;Constantino, U.; Alluli, S.;Tomassini, J. J . Inorg. Nucl. Chem. 1978, 40, 1 1 13. (b) Alberti, G.; Constantino, U.; Giovagnotti, M. L.L.J . Chromarogr. 1979, 180,45. (c) Casciola, M.; Constantino, U.; Fazzini, S . ; Tosoratti, G. Solid State Ionics 1983, 8, 27. (4) (a) Dines, M. B.; DiGiacomo, P. Inorg. Chem. 1981,20,92. (b) Dines, M. B.; DiGiacomo, P.; Callahan, K.P.; Griffith, P. C.; Lane, R.; Cooksey, R. E. In Chemically Modified Surfaces in Catalysis and Elecrrocatalysis; Miller, J., Ed.; ACS Symposium Series 192; American Chemical Society: Washington, DC, 1982; p 223. (c) Dines, M. B.; Griffth, P. C. Inorg. Chem. 1983,22,567. (d) Dines, M. B.; Cooksey, R. E.; Griffith, P . C. Inorg. Chem. 1983, 22, 1003. (e) Dines, M.B.; Griffith, P. C. Polyhedron 1983, 2, 607. ( 5 ) (a) Johnson, J. W.; Jacobsen, A. J.; Brody, J. F.; Lewandowski, J. T. Inorg. Chem. 1984, 23, 3844. (b) Johnson, J. W.; Jacobsen, A. J.; Butler, W. M.; Rosenthal, S.E.;Brody, J. F.;Lewandowski, J. T. J. Am. Chem. Soc. 1989, 1 1 1 , 381. (c) Huan, G.; Jacobsen, A. J.; Johnson, J. W.;Corcoran, E. W., Jr. Chem. Mater. 1990, 2, 91. (d) Johnson, J. W.; Brody, J. F.;Alexander, R. M.; Pilarski, B.; Katritzky, A. R. Chem. Mater. 1990, 2, 198. (6) (a) Cheng. S.;Peng, G.-2.; Clearfield, A. Ind. Eng. Chem. Prod. Res. Deo. 1984, 23, 219. (b) Wan, B.-Z.; Anthony, R. G.; Peng, G. 2.; Clearfield, A. J . Caral. 1986, 101, 19. (c) Clearfield, A. In Design of New Materials; Clearfield, A., Cocke, D. A., Eds.; Plenum: New York, 1986; p 121. (d) Peng, G.-2.; Clearfield, A. J. Inclusion Phenom. 1988, 6,49. ( e ) Clearfield, A. Chem. Rev. 1988,88, 125. (f) Yang, C.-Y.; Clearfield, A. Reacriue Polym. 1987, 5 , 13. (g) Colon, J. L.;Yang, C. Y.; Clearfield, A.; Martin, C. R. J . Phys. Chem. 1988, 92, 5777. (7) Mallouk, T. E.;Lec, H. J . Chem. Educ. 1990, 67, 829.
0020-1669/91/1330-1434%02.50/0
Table I. Unit Cell Parameters for M(03PCH3) from Indexing the Powder Patterns in the Orthorhombic System (PmnZI) cell params, A M a b C Mg 5.44 (1) 6.97 (1) 5.23 (1) Zn 5.42 ( I ) 6.94 ( I ) 5.22 ( I ) co 5.44 ( I ) 6.85 ( I ) 5.24 ( I ) (O3PR)-H20exhibits this selectivity in absorbing alcohols because of the steric constraints imposed by the R groups of the phosphonate surrounding the binding site. In continuing our studies of divalent metal phosphonates MT1(03PR).H20,we have found that they can be dehydrated and that the resulting dehydrated phosphonates remain crystalline. In some favorable cases the dehydrated phases remain in the same space group as the initial starting materials and have similar unit cell dimensions. These topochemically dehydrated metal phosphonates show shape selectivity in forming intercalation compounds; i.e., only primary amines are absorbed, while amines with branching at the a-position are excluded. The new intercalation compounds have the general formula M"(03PR).(RNH2). In a parallel study, Frink et al. have found that size-selective intercalation of the closely related anhydrous phenylphosphonates M " ( O ~ P C ~ H (SM ) = Zn, Co) occurs. In this case the size of the bonding pocket is restricted by the phenyl rings, so that only ammonia and water, and not larger amines, can intercalate.*e
Experimental Section Materials and Methods. Divalent metal phosphonates were synthesized according to literature procedures.8 All other chemicals were from commercial sources and were used without purification. Methods and instruments used in the characterization of these compounds are also described in previous Dehydration of M(0,PR).H20 and Intercalation of Amines into the Resulting Layered Hosts. The dehydration of M(03PR).H20 (M = Zn, Co, Ni, Mg) was carried out in air at temperatures predetermined from TGA experiments. (The measured water loss agrees well with the formulation M(03PR).H20.) In cases where good crystallinity of the dehydrated phase is desired (e&, for obtaining indexable X-ray powder (8) (a) Cunningham, D.; Hennelly, P.J. D.; Deeney, T. Inorg. Chim. Acra 1979,37,95. (b) Cao, G.; Lee,H.; Lynch, V. M.; Mallouk, T. E.Inorg. Chem. 1988,27, 2781. (c) Cao, G.; Lee, H.; Lynch, V. M.; Mallouk, T. E. Solid Stare Ionics 1988, 26, 63. (d) Martin, K.;Squattrito, P. J.; Clearfield, A. Inorg. Chim. Acra 1989, 155, 7. (e) Ortiz-Avila, Y.; Rudolf, P.; Clearfield, A. Inorg. Chem. 1989, 28, 2147. ( f ) Cao, G.; Lynch, V. M.; Swinnea. J. S.; Mallouk, T. E. Inorg. Chem. 1990, 29, 2112. (g) Frink, K. J.; Wang, R.-C.; Colon, J. L.; Clearfield, A.
Following article in this issue.
0 1991 American Chemical Society
Inorganic Chemistry. Vol. 30, No.7, 1991 1435
Layered Zinc and Cobalt Phosphonates
Onsets of Dehydration Temperature and Cell Parameters for M(0,PCHI).H20 (Indexed in Orthorhombic System, Pmn2,)
Table Ill.
To Vacuum
t
cell params,
M Me
a
-
5.68 5.68 5.66 5.67
Zn
CO Ni
b 8.72 8.73 8.69 8.68
C
dehydration temp (onset), OC
4.79 4.78 4.79 4.73
159 70 155 260
A
Fipurr 1. Apparatus used in the dehydration and subscqucnt inlcrcalalion
rcactions of W(O,PCH,).H,O
a
X-ray Powder Diffraction Data for Zn 0,PCHJ (Orthorhombic: a = 5.425 (2) A, b = 6.938 (3) , c = 5.221 (3) A) d,, A daksA hkl 1, d,,A dak.A hkl I,
Table 11.
6.93 4.277 4.175 3.761 3.469 3.301 2.930 2.896 2.706 2.610
6.94 4.274 4.172 3.762 3.469 3.307 2.927 2.888 2.712 2.610
010 110 Oll
101 020 Ill 120 021 200 002
100 10.7 9.8 1.1 3.5 15.3 5.0 4.4 3.5 3.7
2.547 2.445 2.119 2.088 1.971 1.746 1.732 1.654 1.608
2.550 2.443 2.114 2.086 1.970 1.750 1.731 1.653 1.612
I21 012 031 022 131 310 032 222
12.6 3.7 3.8 2.7 10.3 1.3 1.4
