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Chem. Mater. 1996, 8, 318-320
Toward Pillared Layered Metal Sulfides. Intercalation of the Chalcogenide Clusters Co6Q8(PR3)6 (Q ) S, Se, and Te and R ) Alkyl) into MoS2
where the MoS2 layers sandwich the Co6Q8(PR3)6 clusters, and results in new intercalated phases. Equations 1 and 2 illustrate the intercalation process, with Co6S8(PPh3)6 as an example.
Rabin Bissessur, Joy Heising, Wakgari Hirpo, and Mercouri Kanatzidis*,†
LiMoS2 + H2O f (MoS2)single layers + LiOH + 1/2H2 (1)
Department of Chemistry and the Center for Fundamental Materials Research Michigan State University East Lansing, Michigan 48824 Received August 14, 1995 Revised Manuscript Received November 28, 1995 Materials with open frameworks and void spaces are important in the field of separation science and catalysis. Depending upon the pore diameter, which can range from 5 to 1000 Å,1 these materials can be classified as microporous (5-20 Å), mesoporous (20500 Å), or macroporous (500-1000 Å). In addition to zeolites2a and the newly discovered mesoporous phases,2b pillaring of layered structures offers the promise of achieving micro- and mesoporosity in a controlled manner. This is done via judicious choice of the pillar and control of the pillar spacing in the galleries. In addition to tetraalkylammonium ions, polynuclear hydroxyl metal cations,3a metal chelate complexes,3b bicyclic amine cations,4 and polyoxocations such as [Al13O4(OH)24]7+ and [Zr4(OH)16-x]x+ 3a have been used as pillaring agents for clays. Unlike pillared layered oxides, there have been no reports on pillared layered chalcogenides. From the latter perspective, the intercalation of [Al13O4(OH)24]7+ and [Bi6(OH)12]6+ into MoO3 and TaS25 and of [Fe6S8(PEt3)6]2+ into TaS2 are noteworthy.6 In this communication we report a new family of materials based on layered transition metal dichalcogenides of the type [M′xQyLz]n[MoS2] (Q ) S, Se, Te) prepared as a first step toward pillared layered sulfides. The addition of Co6Q8(PR3)67,8 solutions in CH2Cl2 to exfoliated suspensions of LiMoS29 causes flocculation †
Camille and Henry Dreyfus Teacher Scholar 1993-95. (1) (a) Behrens, P. Adv. Mater. 1993, 5, 127-132. (b) Barrer, R. M.; MacLeod, D. M. Trans. Faraday Soc. 1955, 51, 1290-1300. (2) (a) Davis, M. E. Acc. Chem. Res. 1993, 26, 111-115. (b) Kresge, C. T.; Leonowicz, M. E. Roth, W. J.; Vartuli, J. C. Beck, J. S. Nature 1992, 359, 710-712. (3) (a) Brindley, G. W.; Sempels, R. E. Clay Miner. 1977, 12, 229. (b) Yamanaka, S.; Brindley, G. W. Clays Clay Miner. 1978, 26, 21. (c) Knudson. M. I.; McAtee, J. L. Clays Clay Miner. 1973, 21, 19. (d) Traynor, M. F.; Mortland, M. M.; Pinnavaia, T. J. Clays Clay Miner. 1978, 26, 318-326. (4) (a) Mortland, M. M.; Berkheiser, V. E. Clays Clay Miner. 1976, 24, 60. (b) Shabtai, J.; Frydman, N.; Lazar, R. Proc. 6th Int. Congr. Catal. 1976, B5, 1. (5) (a) Nazar, L. F.; Yin, X. T.; Zinkweg, D.; Zhang, Z.; Liblong, S. Mater. Res. Soc. Symp. Proc. 1991, 210, 417-422. (b) Lerf, A., Lalik, E.; Kolodziejski, W.; Klinowski, J. J. Phys. Chem. 1992, 96, 73897393. (6) (a) Nazar, L. F.; Jacobson, A. J. J. Chem. Soc., Chem. Commun. 1986, 570-571. (b) Nazar, L. F.; Jacobson, A. J. J. Mater. Chem. 1994, 4, 149. (7) (a) Stuczynski, S. M.; Kwon, Y.-U.; Steigerwald, M. L. J. Organomet. Chem. 1993, 449, 167-172. (b) Steigerwald, M. L.; Siegrist, T.; Stuczynski, S. M. Inorg. Chem. 1991, 30, 4940-4945. (8) (a) Hong, M.; Huang, Z.; Lei, X.; Wei, G.; Kang, B.; Liu, H. Polyhedron 1991, 10, 927-934. (b) Hong, M.; Huang, Z.; Lei, X.; Wei, G.; Kang, B.; Liu, H. Inorg. Chim. Acta 1989, 159, 1-2. (9) A literature procedure was used in the synthesis of LiMoS2. Murphy, D. W.; DiSalvo, F. J.; Hull, G. W.; Waszczak, J. V. Inorg. Chem. 1976, 15, 17-21.
0897-4756/96/2808-0318$12.00/0
(MoS2)single layers + xCo6Q8(PR3)6 f [Co6Q8(PR3)y]xMoS2 (2) Table 1 summarizes all the intercalated phases synthesized along with their respective interlayer spacing, interlayer expansions relative to pristine MoS2, and elemental compositions. Elemental analyses show evidence of partial loss of phosphine ligands in most of the intercalated products. The loss of two to three triphenylphosphine ligands per cluster in [Co6Q8(PR3)x]nMoS2 is explained by steric crowding in the gallery space of the layered host. Partial ligand loss was also observed in [Fe6S8(PEt3)3]0.05TaS2,6 and it too was attributed to steric crowding in the gallery space of the host. In general, less phosphine is lost from the cluster when the concentration ratio of cluster to MoS2 is low. X-ray powder diffraction patterns of the intercalated compounds reveal their lamellar character as depicted by well-defined (001) reflections, see Figure 1i. The maximum d spacing of 21.5 Å with an interlayer expansion of 15.3 Å was found in [Co6S8(PPh3)3]0.09MoS2, which is in good agreement with the cluster dimensions and consistent with the inclusion of the cluster molecule in between the MoS2 slabs; see Figure 1ii. Despite the fact that the 21.5 Å d spacing is consistent with the C4fold axis of the cluster being oriented perpendicular to the layers, we need additional evidence to establish the actual cluster orientation. Pyrolysis mass spectroscopy showed no evidence for the co-intercalation of CH2Cl2. Under nitrogen, these materials are thermally stable, with respect to weight loss, up to 200 °C. The stability depends on the nature of the chalcogen atom and/or the nature of the phosphine ligands in the cluster.11 In general, the tellurides are the least thermally stable, especially when the ligand is PBu3. This is attributed to some ligand loss from the cluster. The thermal gravimetric analysis data of all the intercalates are given in Table 1. Variable temperature magnetic susceptibility measurements on [Co6S8(PPh3)3]0.09MoS2 (I) and [Co6S8(PPh3)4]0.05MoS2 (II) show Curie-Weiss law behavior with a slight deviation at low temperature (
