Intercalation of n-alkylamines into misfit layer sulfides Lourdes Hernan, Pedro Lavela, Julian Morales," Luis Sanchez and JosC L. Tirado Laboratorio de Quimica Inorghnica, Facultad de Ciencias, Universidad de Cbrdoba, Avda. San Albert0 Magno sln, El 4004 Cbrdoba, Spain Novel intercalation complexes of (PbS)'.'8( TiS,), and (PbS)1.14( TaS&, two representative compounds of misfit layer sulfides, have been prepared by direct reaction with n-alkylamines (C,H2,+1NH2) (n=1-9). From the observed amine stoichiometry and lattice expansions, the most likely configuration for the intercalated amine molecules is one in which the latter are located at the van der Waals gap between two adjacent TS, slabs as a monolayer with the alkyl chain oriented parallel to the layers.Thermal deintercalation of the new phases occurred at temperatures below 250 "Cand in the case of Ti intercalates, H,S was released simultaneously with the amine deintercalation process. The intercalation process was confirmed to be reversible. Thus, the product obtained from the thermal treatment recovered the main features of the original host structure and, when mixed with the amine, yielded an intercalate of similar structural characteristics to those found using the original sulfide. Composite layered sulfides of formula (MS),,,(TS,), (M = lanthanides, Sn, Pb, Bi, Sb; T =Ti,V,Cr,Nb,Ta) are a relatively new class of layered compounds that have received special attention over the last five years, because of their peculiar structures and physical properties.' Their structures consist of alternation of two-atom-thick layers of MS and rn times three- atom-thick sandwiches of TS, stacked along the c axis.The atomic arrangement of MS layers is based on a distorted rock- salt structure and the TS, units are geometrically identical to the layers found in the binary TS, layer compounds. The unit- cell axes of both sublattices MS and TS, are equal in the b direction and incommensurate in the u direction. This intro- duces a certain degree of non-stoichiometry, y, which can be determined from uTS2/uMS. The number of well known compounds belonging to the family with rn= 1 is very large, while for the family with m=2, so far X-ray single-crystal structures have only been determined for (PbS)1.14(NbS2)2,2 and(PbS)1.18(TiS2)23 (PbSe)l,12( NbSe,),.4 Recently, the single-crystal structure of the trilayer misfit compound (Gd,Sn, -&s)1.16(NbsZ)3 has been reported.' From the point of view of intercalation reactions, these two latter families of compounds have a relevant characteristic, namely, the formation of van der Waals gaps between adjacent TS, slabs of similar geometry to that found in binary metal disulfides.This feature is the accommodation of metal ions, inorganic and organic molecules between the layers.6 In this context, lithi~m,~ sodium,' hydrazine, and even cobaltocene'' can be easily and successfully intercalated into misfit layer chalcogenides. A common aspect of all these guest species is their strong reducing power. In continuing our research on the intercalation properties of these novel layered chalcogenides we have extended our study to the intercalation of organic Lewis bases as prototypical guest species.In this paper we describe the preparation and characterization of novel intercalates with linear aliphatic amines (C,-C,) as guest molecules. The comparison of the results obtained with those reported for binary intercalated dichalcogenides with the same guest molecules provides valu- able information on the interactions between the two subcells in these incommensurated intergrowths. Experiment a1 The layered host materials (PbS)1,18(TiS2)2 and (PbS)1.14(TaS2)2used in this study were prepared from the corresponding elements (supplied by Strem. Chem) as reported earlier.3*'' The materials were obtained as high-purity plate- like crystals with a metallic lustre.All the amines were of reagent grade (Merck) and were used as supplied. Intercalation was accomplished by mixing the reactants (sulfide, 70 mg; amine, 3 ml) in sealed Pyrex tubes and then heating at 50-90 "C, depending on the hydrocarbon chain length of the amine. Times for complete intercalation ranged from 1 day for methylamine (50"C) to 10 days for n-nonylamine (70"C). The absence of the (001)reflections of the host was considered as evidence for complete intercalation. Solids were filtered, washed with pure ethanol, air-dried and stored in a dry glove-box. The amounts of intercalated amine were determined by C,H,N analyses while occasionally water content was calculated by combining these data and those obtained from TG curves recorded with a Cahn 2000 thermob-alance under a dynamic nitrogen atmosphere.The chemical identity of the intercalated species was checked by temperature- programmed deintercalation (TPD) measurements that were carried out in a quartz reactor coupled to a quadrupole mass spectrometer (model VG sensorlab). The gas carrier used was nitrogen. X-Ray powder diffraction (XRD) patterns were recorded in a Siemens D500 Instrument using Cu-Ka radiation, operating at 35 kV and 20 mA. For identification purposes, the intensities were collected with steps of 0.02" (28) and times of 0.6 s per step. For the broadening analysis of the Bragg lines, the intensities were collected with the same scan step and a time of 4 s per step. Results and Discussion The amine contents of the two sets of intercalates deduced from C,H,N analysis are shown in Table 1.In most compounds the agreement between the experimental and calculated per- centages is fairly acceptable (usually <5%). The larger differ- ences appeared for the methylamine and ethylamine intercalates, in particular for the hydrogen content, probably owing to the fact that these amines are supplied in aqueous solutions (50% and 70%, respectively). From these data, the degree of water content was also calculated and is shown in Table 1. The presence of water will be discussed below. Two interesting findings deserve an additional comment.First, amine contents are low and show only small fluctuations with the amine length and there is no correlation between the composition of the intercalates and the molecular volumes or J. Muter. Chem., 1996, 6(5), 861-866 861 Table 1 Compositions of ( PbS), 18 ( TiS,), (n-alkylamme),(H,O), and ( PbS)l 14 (TaS,), (n-alkylamine), (H,O), intercalates" (PbS)l 18 (TiS,),(n-alkylamine),( H20), n-alk ylamine C H N X met h ylamine 0 28 ethylamine 0 28 prop ylamine 0 28 butylamine 0 24 pentylamine 0 23 hex ylamine 0 25 hept ylamine 0 26 oct ylamine 0 26 non ylamine 0 21 "Calculated values are shown in parentheses the amine basicity This behaviour contrasts with that found in the intercalates (n-CnH2,,+ iNH2),TiS,,i2 for which an amine content about five times greater was observed, with a small tendency to increase as the amine molecular volume increases In the case of 2H-TaS2I3 the stoichiometry (x=O 5) reported for the intercalation of methylamine and ethylamine by direct reaction is also notably higher than that found in (PbS)l 14(TaS,)2 (see Table 1) These differences in the amine stoichiometry can be discussed in terms of the role played by the MS layers on electron-accepting potential of the TS, layer Although there is some controversy concerning the evaluation of the charge transfer from MS to TS2, both spectroscopici4 and electrical transporti5 data support the occurrence of interactions between MS (which acts as the electron donor part) and TS, sublattices (which act as electron acceptors) This should reduce the electron-accepting ability of TS2, thus decreasing their intercalation properties The second finding refers to the amine content measured in the Ti compound, which is somewhat higher than that found in the Ta compound This difference in reactivity cannot be due to particle size In fact, the average particle sizes deduced from scanning electron microscopy images were 50-60 pm and 10-20 pm for the Ti and Ta compounds, respectively Similar results have been obtained with other guest species such as cobaltocene," and they have been explained on the basis of the band structure of the component sublattices l6 According to studies of the photoelectron spectra, the band structure of the misfit layer compounds is approximately a superposition of the band structure of the two component sublattices As the TS, sublattice has an atomic arrangement identical to the TS2 unit of the binary transition-metal disulfide, for the compound with Ti as the transition metal the Fermi level lies at the t2g band which is formally empty, while for the Ta compound, the Fermi level lies at the dZ2 band which is formally half filled l6 This occupancy should hinder the charge transfer from the intercalated molecule to the host lattice and hence the poorer intercalation properties of the Ta compound Taking into account the low guest stoichiometry (see Table l),the amount of guest-host charge transfer must be low and it therefore seems unlikely that the amine contents of these compounds are determined solely by the host band structure In this context, one can find a correlation between the amine content and the volume of TS2 subcells (T=Ti, Ta) Thus, the greater amine content occu~s in the Ti tompound, which has a greater cell volume (347 9 A3 us 343 3 A3) The relatively small change observed for the amount of 862 J Muter Chem, 1996, 6(5),861-866 ( PbS), (TaS,),(n-alkylamine), ( H20),, Y C H N X Y 0 21 0 36 0 19 0 20 -0 22 -0 20 0 23 -0 18 -0 19 -0 19 -0 19 -intercalated amine with the change in alkyl chain length can be explained as a consequence of two different effects First, molecular size considerations would favour the intercalation of the amines with small chain lengths Second, for the heavier amines, the increasing contribution of van der Waals forces between the hydrophobic part of the alkylamines has a tend- ency to stabilize the molecular aggregates at the interlayer space l7 This facilitates the intercalation process The XRD patterns of the amine-intercalated powdered samples of the Ta compound showed a set of multiple order reflections (001) of high intensity together with additional broad and weak lines that were indexed on an orthorhombic lattice like that of the parent compound l1 Unit-cell parameters of both sublattices of some intercalated compounds, together with those of the pristine compound, are included in Table 2 Note that the a and b axes hardly changed upon intercalation, which indicates that the deformation of the layers in the ab plane is very small However, a significant expansion along the c axis direction was observed For the Ti intercalates, the XRD patterns showed only peaks associated with (001) reflec-tions as a consequence of a strong preferred orientation of the particles, even though the spectrum was recorded by sprinkling the powder on silicone grease For this reason, we could not calculate the unit-cell constants of these intercalates and only the periodic length, which defines the thickness of a PbS-TiS2-TiS2 unit stacked along the c axis, was computed The lattice expansion of the various amine intercalates per PbS-TS2-TS, unit packing is plotted in Fig 1as a function of the chain length, together with those values of (n-alkylamine),TaS, intercalates taken from the literature A relevant feature of the data in Fig 1 is the limited change of lattice expansion on moving from methylamine to n-nonyl- amine, which implies that the hydrocarbon chains lie practically parallel to the layers The increase in the interlayer spacing can be compared wi!h the van der Waals diameter of the methyl group, ca 3 6 A The difference which appears in going from methylamine to n-nonylamine probably reflects a very small deviation of the alkylamine guest orientation from host- layer parallel A constant interlayer spacing has also been observed for TaS, n-alkylamine complexes for carbon numbers up to 4 For longer amine chains in TaS," and TiS2,l2 the interplanar separation increases gradually with n (see Fig 1) Moreover, the composition and the c-axis separation suggests that in these binary sulfides, n-alkylamines form double layers in the interlayer space Table 2 Lattice constants of (PbS)1.14 (TaS,), intercalated with n-alkylamine compound subcell PbS(PbS)1.14 (TasZ)2 TaS, ( PbS)l.14 ( Tas2 )Z (methylamine)O.Zl PbS TaS, (PbS)l.14 (TasZ)Z (ethy1amine)0.19 PbS TaS2 ( PbS)I. 14 (TasZ)Z ( hexy1amine)0.18 PbS TaS, 25 20 V V V3 15 vQ 10 4 3 0 2 46810 "C Fig. 1 Change in the lattice expansion as a function of the number of carbon atoms in the alkylamine intercalation compounds of (PbS)l.18(TiS,), (0) For comparison the and (PbS)1.14(TaS2)2 (0).alkylamine intercalation compounds of TaS, have been included [data taken from refs. 18 (A)and 19 (V )]. The different intercalation properties of misfit layer sulfides can be explained by taking into account their peculiar struc- tural characteristics. As described earlier, the stacking sequence of PbS and TS, (T=Ti,Ta) slabs along the c axis is PbS-TS2-TS2-PbS. Of the two interlayer spaces available for the location of the amine, defined as the PbS-TS2 and TS,-TS, interfaces, the latter is more favoured for two reasons. First, the distance between T!S2-TiS2 slabs is greater than that of PbS-TiS, slabs (2.934A us. 2.689 A).3 Moreover, Pb atoms protrude from the sulfur planes on both sides of the PbS double layer, and are bonded to the S atoms of the neighboring TiS, sandwiches by weakly covalent interactions.Indirect evidence of the location of the guest molecules was obtained by using ( PbS)l.18TiS, and (PbS),.,,TaS, as host materials. The compounds have a PbS-TS,-PbS stacking sequence, whose host lattice only contains PbS-TS, interfaces. We failed to intercalate n-alkylamines into these hosts under the same experimental conditions as described above. One-dimensional electron-density projections on the c axis of the Ti compounds were examined by using (001) reflections. The intensities were corrected for Lorentz and polarization effects and the structure factor phases were calculated from the known host structure.The electron density maps were then computed from the phased data. Some of them are shown as illustrative examples in Fig. 2. This plot reveals the expected sequence of atoms along Cool] in the pristine solid: (S,Pb)-S-Ti-S-S-Ti-S-( S,Pb), as the Pb atoms protrude from sulfur planes on both sides of the PbS double layer. After amine intercalation, the (S,Pb)-S-Ti-S and S-Ti-S-( S,Pb) sheets remained basically unaltered while there was a signifi- cant increase in the electron density in the region between successive TiS, layers. This means that the guest molecules are located in the S-S interlayer spaces. Moreover, the presence of a main peak between the layers is in good agreement with an orientation of the amine almost parallel to the TiS, layers a/A bfA c/A 5.820( 1) 3.303( 3) 5.771 (2) 5.778 (4) 18.00(2) 17.99(3) 5.833( 3) 3.304( 2) 5.734( 7) 5.734( 5) 21.23 (7) 21.24( 3) 5.71 1 (6) 3.3 13( 2) 5.795( 7) 5.759(3) 21.63(2) 21.61( 1) 5.809( 3) 3.307( 5) 5.785( 3) 5.754(8) 21.90( 2) 21.89( 4) I P ~ Sl I Pristine I I 1 1 1 1 1 1 1111II11111 distanceIA Fig.2 One-dimensional electron-density projection on the c axis of ( PbS)1.18(TiS,), and three representative examples of alkylamines in a monolayer arrangement. A schematic model of this arrangement is shown in Fig. 3. The different arrangement of n-alkylamines ( PbS)l + ,,( TS2)2 (T= Ti,Ta), compared with transition-metal layer disulfides, can be explained by taking into account the presence of the PbS layer between two consecutive TS2 slabs.According to SolinY2' layered solids can be classified into three groups based on the rigidity of their layers with respect to the distortions involving displacements transverse to the layer planes. Layer dichalcogenides belong to class 11. These compounds consist of three distinct planes of strongly bonded atoms and can undergo a significant transverse distortion due to the relatively high flexibility of the structure. These solids can sometimes accommodate bilayers and even trilayers o{ intercalant, and thus lattice expansions of as much as 50A have been ob- served for the neutral anisometric guest species, e.g. (octadecylamine),,,TaS, .18 According to the intercalation model described above and depicted in Fig. 3, the insertion of the PbS layers between two consecutive TS2 slabs increases the thickness of the layers that now are composed of as many J.Muter. Chem., 1996, 6(5), 861-866 863 Fig. 3 Idealised model of the structure of ( PbS)l +,,(TS,),(n-alkylam- me), complexes as five planes of strongly bonded atoms One can accept that the structures of these misfit layer sulfides will increase in rigidity against transverse layer distortions This increased host rigidity is likely to act as a kinetic barrier both to the uptake of guest molecules and to lattice expansion, and the amine should adopt a parallel orientation In fact, the dependence of lattice expansion on chain length shown in Fig 1 is similar to the expected behaviour for an infinitely rigid solid such as silicate clays The stability of the intercalates was examined from both thermogravimetric data and the results of the desorbed mol- ecules analysed by mass spectrometry The temperature range studied was 30-300°C and the base peaks of the mass spectra of amine, ammonia, carbon dioxide, dihydrogen sulfide and hydrogen compounds were recorded Of all these chemicals only the presence of amine together with H,S in the case of Ti intercalates was detected The samples may pick up some water during air handling, in particular during the transfer of the intercalated material to the TG and MS apparatus, but the water spectrum could not be recorded owing to the background of HzO in the spectrometer The TPD curves of the methylamine, ethylamine and n-butylamine intercalates are shown in Fig 4 The TPD profiles of heavier amine samples were more complicated, because of the increasing possibility of side reactions which may have taken place in the gas phase The thermogravimetric curves of all intercalation compounds showed a continuous mass loss with no sharp steps, so that it was difficult to define the temperature of the amine deintercal- ation with accuracy However, the amine profile of the TPD spectra showed a single peak centred at ca 175"C and 225 "C for Ti and Ta intercalates, respectively This is also indicative of the presence of one type of amine species at the interlayer, and the rather low temperature of deintercalation suggests that these species are weakly bonded within the layers, prob- ablj through an interaction between the nitrogen lone pair and antibonding or non-bonding empty cation states Another point of interest in the case of Ti intercalates is the simultaneous appearance of H,S with amine deintercalation The formation of H,S was recently reported in the deintercal- ation process of FePS3(CH3NH2)" and MnPS, (pyridine)?' intercalates, and was explained by assuming the presence of alkylammonium and pyridinium cations, respectively, solvated by neutral amines as the intercalated species The source of protons is probably the H,O molecules which are always associated with the amines However, in MPS, materials, charge neutrality is preserved by the loss of M2+ from the lattice, based on the ability of the lattice to exchange a fraction 864 J Muter Chem , 1996, 6(5),861-866 1 1 1 1 I I I I I I 30 100 150 200 50 100 130 200 250 300 TPC Fig.4 Temperature-programmed deintercalation spectra of different (PbS), 18(T1S2)2 and ( PbS)l 14(TaS2)2 intercalates I, methylamme, 11, ethylamine, 111, n-butylamine The profiles correspond to (a)amine base peak (m/z30) and (b)H2S (m/z 34) of the M2+ intralayer cations 23 Such an intercalation mechan- ism cannot be applied to misfit layer sulfides Two reaction models can account for the liberation of H2S First, by considering that the amines were present as alkylam- monium hydroxide, and amine and H2S are produced by reaction (I) 21 R-"H30H+S2-(*attlce)-)R-NH2+H2S+02-(latt,ce)(1) An alternative mechanism for the formation of ammonium cations in the presence of water has been outlined according to reaction (2) 24 .Y(NH3)+ TS, + xH,O+( NH4 + )Zx( NH3),-Zx( TS2 -xOx)2x-+(XlY)S, (2) This mechanism was extended by Johnson25 to the aniline intercalation reaction in TaS, in the presence of water by suggesting that some amine molecules are found as protonated amine cations while the sulfide lattice is reduced In our case, simple calculations for the methylamine intercalates, supposing that all amine molecules are protonated cations, suggest that cu 3% of the lattice sulfide should be replaced and oxidized This means that the amount of sulfur released should be < 1% of the original sulfide, too low to be unambiguously measured Unfortunately, IR spectra, which can shed light on the actual intercalated species, could not be recorded because of the high absorbance of the samples However, evidence to discard the possibility of the formation of protonated amine cations was obtained from TPD studies, as no hydrogen was evolved during the deintercalation process The appearance of this molecule can be indicative of the presence of co-intercalated alkylammonium ions as exhibited by ammonia-intercalated TiS, This Ti compound contains both ammonia and ammonium, with ammonium decomposing to ammonia and hydrogen during the thermal deintercalation process 26 Moreover, attempts to intercalate methylammonium cations from methylammonium hydroxide were unsuccessful A second scheme for the release of H2S could involve a direct attack to the lattice by water molecules [reaction (3)]: H2O +S2-(lattice) -+H2S +O2-(lattice) (3) Unfortunately, for the Ti intercalates it was not possible to estimate the water content from the TG data owing to the loss of H2S.These calculations, carried out in the methylamine and ethylamine Ta intercalates, yielded water contents in fairly good agreement with those obtained from C,H,N analyses (Table 1). Moreover, for the heavier amines, the amounts of water deter- mined were insignificant. We have no direct proof of the location of the H,O molecules in the host lattices, but both Ti and Ta compounds remained unaltered after treatment with pure water under the same experimental conditions used for the alkylamine intercalation.Moreover, the intercalated phases obtained with methylamine vapours had identical lattice expansions to those given in Fig. 1, which were prepared with the amine dissolved in water. The TPD spectra were also similar to those included in Fig. 41. Joy and Vasudevan21.22 suggested an exchange reac- tion between physically adsorbed water during the transfer of the intercalated material to the mass spectrometer apparatus and neutral amine molecules. This exchange reaction is probably enhanced for the intercalation complexes containing short-chain amines. In fact, for the n-butylamine intercalate, the intensity of the H2S peak notably decreased (see Fig.4III), whereas for heavier amines this signal practically disappeared. This feature can be correlated with the increasing hydrophobic nature of the guest species, which may limit water uptake. According to this explanation, a strong association between amine and water molecules in the intercalated state accounts for the simultaneous liberation of amine and H2S. The absence of H2S loss in the deintercalation process of Ta intercalates, in spite of their water content, should be correlated with the free energies of formation of TiO, and TaO,, -21 1.4 and -43 kcal mol- ', re~pectively.~'t Thus, the greater stability of Ti02 should favour reaction (3), and this might be the origin of the lower deintercalation temperatures exhibited by the Ti intercalates.Moreover, this behaviour is in accordance with that reported by Whittingham,' concerning the ease of preparation of A,(H20),TaS2 (A =NH,, Li, Na, K) intercalates by immersion of the sulfide in aqueous solutions. In contrast, the alkali-metal hydrates of other sulfides, particularly those of group 4, were more difficult to obtain because these sulfides are more easily hydrolysed than TaS,. The reversibility of the intercalation process was confirmed by mixing the product obtained from the TPD measurements with the intercalant under the same experimental conditions as described above. The results obtained, referred to ethylamine and (PbS)1.18(TiS2)2, are shown in Fig.5, and clearly demon- strate the formation of the intercalate of similar structural characteristics to that found using the original compound as the host lattice. This means that the release of produced H,S has little effect on the host lattice (according to XRD results), probably owing to the small extent of reaction (3). Additional information about the microstructural changes induced by the intercalation-deintercalation process in the host lattice was obtained by X-ray diffraction line-broadening analysis. The experimental X-ray powder diffraction patterns of multiple-order (001) lines were used to obtain the profiles (h)and a highly crystalline silicon standard was used to provide the instrumental broadening (g),after Ka, elimination by the Rachinger method.,' The cosines of Fourier coefficients of the pure diffraction profiles (f) were then obtained by the Stokes3' method of deconvolution [eqn.(4)]: Fn =HnIGn (4) where F, G and H are the cosines of the Fourier coefficients off, g and h profiles, respectively, and n is the order of the Fourier coefficient. t 1 calz4.184 J. I I II' 'I (C) ~ 10 20 30 40 50 60 2Wdegrees Fig. 5 XRD patterns of (a) (PbS)l,18(TiS2)2;(b) (PbS), 18(TiS2)2-(ethylamine),,,,; (c) sample (b)after thermal treatment; (d) sample (c) mixed with ethylamine, prepared under the same experimental condition as sample (b) Crystallite sizes and microstrains were then computed by the Warren-Averbach method,31 using eqn. (5): In F,( l/d) =In F,"-2n2(cn2)n2PL2/d2 (5) where F," are the size coefficients, (E,~) is the mean-square value of the component of strain, P, is the (001) periodic length, and d the (001) spacing.The crystallite size, (Do,,), was computed from the derivative dF,s/dnl,,o. Selected Warren-Averbach plots are shown in Fig. 6. The pristine misfit layer compounds showed negligible slopes for all n values, thus indicating that the microstrain content is low in the solids obtained at high temperatures. The values of crystallite size were also high (Table 3), irrespective of the exfoliation properties of these materials in directions normal to [0011. After ethylamine intercalation, a significant increase in the slopes of the plots evidenced an enhanced microstrain content.This behaviour can be interpreted in terms of a broad but symmetric distribution of interlayer spacings after the intercalation of the organic molecule. Slight changes in the angle formed between the hydrocarbon chain and the host layers could also account for the observed broadening. These changes may be either static or dynamic, as in other oxosalt intercalates. The values of the crystallite size reveal a significant decrease upon intercalation, as referred to the number of layers in each crystallite, probably as a consequence of the rupture of coherency of diffraction between consecutively stacked layered domains. On the other hand, after alkylamine thermal deintercalation the slopes decrease again, reaching values close to the pristine compounds, in good agreement with the above interpretation. A significant exfoliation also takes place on deintercalation.Conclusion We have shown that (PbS)1.1~(TiS2)2, and (PbS),.,4(TaS2), two representative compounds of misfit layer sulfides with MS :TS, =1:2, undergo a direct reaction with n-alkylamines C,H,, + ,NH2, with the subsequent formation of a complete series of intercalation compounds for n =1-9. In addition, compared with other families of related layer compounds such as transition-metal disulfides, the c axis expansion hardly changes with the chain length, and the experimental values suggest that the hydrocarbon chains are oriented parallel to the layers. This unusual finding is probably a consequence of the PbS layers that reduce the flexibility of the TS, layer structure.The intercalation reaction is reversible. J. Muter. Chern., 1996,6(5), 861-866 865 I II I References v n=3 0 05 0.10 0.1 5 0.20 2.5 1 I I n=3 2.0 I n=4 n G 1.5 c 7 1.0 0.5 - 0.0 I- 1 1 0 0.00 0.05 0.10 0.15 0.20 r I I 1 I 1 0.5 -n=l -n=O 0.0 2 1 1 1 1. 1 Fig. 6 Warren-Averbach plots of (001) reflections for (a)(PbS)l 18(T1S2)2, (b)(PbS)l 18(TiS,)2(ethy1amine)0 28, (c) (b)after thermal treatment Table 3 Results of the X-ray diffraction line-broadening analysis along [OOl] by the Warren-Averbach method intercalate/ misfit layer compound treatment (Dool)a/A n((Dool)/PL)b (PbS)I 18 (T1S2)2 pristine 242 14 ethylamine 209 10 300 "C 71 4 (PbS)114(TaS2)2 pristine 173 10 ethylamine 159 7 300 "C 120 6 "(Do,, )=size of coherently diffracting domains bn=number of layers per crystallite, P, =periodic length The authors gratefully acknowledge support from CICYT (MAT 93-1204) and Junta de Andalucia (Group 6036) and the help of Dr M A Aramendia and Mr A Porras from the Organic Chemistry Department and Mass Spectrometry Service in recording TPD spectra 1 G A Wiegers and A Meerschaut, in Sandwiched Incommensurated Layered Compounds, ed A Meerschaut, Trans Tech Pub Zurich, 1992 and references therein 2 A Meerschaut, L Guemas, C Auriel and J Rouxel, Eur J Solid State Inorg Chem , 1990, t27, 557 3 A Meerschaut, C Auriel and J Rouxel, J Alloys Comp, 1992, 183,129 4 C Auriel, A Meerschaut, R Roesky and J Rouxel, Eur J Solid State Inorg Chem , 1992,29,557 5 L M Hoistad, A Meerschaut, P Bonneau and J Rouxel, J Solid State Chem, 1995,114,435 6 A J Jacobson, in Intercalation Chemistry, ed M S Whittingham and A J Jacobson, Academic Press, New York, 1982, p 229 7 (a)C Auriel, A Meerschaut, P Deniard and J Rouxel, C R Acad Sci Paris, 1991, t313, 1255, (b)C Barriga, P Lavela, J Morales, J Pattanayak and J L Tirado, Chem Muter, 1992, 4, 1021, (c) P Lavela, J Morales and J L Tirado, J Muter Chem, 1994, 4,1413 8 L Hernan, J Morales, L Sanchez and J L Tirado, Chem Muter, 1993,5,1167 9 Y Oosawa, Y Gotoh, J Akimoto, T Tsunoda, H Sohma, H Hayakawa and M Onoda, Solid State Ionics, 1994,67,287 10 L Hernan, J Morales, L Sanchez, J L Tirado and A R Gonzalez-Elipe, J Chem SOC Chem Commun, 1994, 1081, L Hernan, J Morales, L Sanchez, J L Tirado, J P Espinos and A R Gonzalez Elipe, Chem Muter, 1995,7, 1576 11 Y Goto, J Akimoto, M Sakorai, Y Kiyozumi, K Suzuki and Y Oosawa, Chem Lett, 1990, 2057, L Hernan, J Morales, L Sanchez and J L Tirado, Electrochim Acta, 1994,39,2665 12 A Weiss and R Ruthardt, Z Naturforsch, Teil B, 1973,28,249 13 S F Meyer, R E Howard, G R Stewart, J V Acrivos and T H Geballe, J Chem Phys ,1975,62,4411 14 Y Ohno, Solid Stute Commun , 1991,72, 1081, Phys Rev B, 1991, 44, 1281, J C Jumas, J Olivier-Fourcade, P Lavela, J Morales and J L Tirado, Chem Muter, 1995,7, 1193, A R H F Ettema and C Haas, J Phys Condens Matter, 1993, 5, 3817, A R H F Ettema, G A Wiegers, C Haas and T S Turner, Surf Sci , 1992, 269/270,1161 15 G A Wiegers, A Meetsma, J R Haange and J L de Boer, Muter Res Bull, 1988, 23, 1551, G A Wiegers and R J Haange, Eur J Solid State Inorg Chem, 1991,28, 1071 16 A R H F Ettema, PhD Thesis, University of Groningen, Netherlands, 1993, A R H F Ettema, C Haas and T Turner, Phys Rev B, 1993,47,2794 17 C Rosner and G Lagaly, J Solid State Chem ,1984,53,249 18 F R Gamble, J H Osiecki, M Cam, R Pisharody, F J Disalvo and T H Geballe, Science, 1971,174,493 19 R Schollhorn, E Sick and A Weiss, Z Naturforsch Ted B, 1973, 28,168 20 S A Solin, in Intercalation in Layered Materials, ed M S Dresselhaus, NATO AS1 Series, Plenum Press, New York, 1986,p 145 21 P A Joy and S Vasudevan, Chem Muter, 1993,5,1182 22 P A Joy and S Vasudevan, J Am Chem SOC,1992,114,7792 23 R Clement, 0 Garnier and J Jegoudez, Inorg Chem, 1986, 25, 1904 24 R Schollhorn, E Sick and A Lerf, Muter Res Bull, 1975, 10, 1005, R Schollhorn, in Progress in Intercalation Research, ed W Muller-Warmuth and R Schollhorn, Kluwer Academic Publisher, Dordrecht, 1994, p 1 25 J W Johnson, Physica B, 1980,99,141 26 M J Mckelvy and W Glaunsinger, Annu Rev Phys Chem ,1990, 41,497 27 R H Shumn, D D Wagman, S Bailey, W H Evans and V B Parker, Selected Values of Chemical Thermodynamic Properties, NBS Technical Notes, Washington, 1974 28 M S Whittingham, Muter Res Bull, 1974,9, 1681 29 W A Rachinger, J Sci Instrum, 1948,25,254 30 A R Stokes, Proc Phys SOC London, 1948,61,382 31 B E Warren, X-Ray Digraction, Dover Publications, New York, 1990,p 251 Paper 5/067676, Received 12th October 1995 866 J Muter Chem , 1996, 6(5), 861-866