JOURNAL OF CATALYSIS 31, 369-371 (1973) Platinum Bronzes III. A Reinvestigation of the Composition of Adams’ Catalyst (7) DAVID CAHEN” AND JAMES A. IBERS Department of Chemistry and Materials RRsearch Center, Nodhwestern University, Evanston, Zllinois 60301 Received May 18, 1973 The platinum oxide, commonly known as Adams’ catalyst and formulated as PtOz.H,O, has been found to be a mixture of Pt, cu-PtOz (possibly hydrated) and NaGPt304, sodium platinum bronze. Both a-PtO, and Na,Pt30a are active as hydro- genating agents for cyclopentene and benzene, but ol-Pt02 is converted completely to Pt metal, while only minor decomposition to the metal occurs for Na,PtaOa. It is suggested that the irreproducibility of the activity of Adams’ oxide might be caused by a variation of the relative amounts of Pt metal and the oxides in the mixture. Methods for preparing a more consistent catalyst are discussed. More than half a century ago Adams and Voorhees (2) introduced platinum oxide as a catalyst in the reduct’ion of organic compounds. The simplicity of the preparation and the activity of the oxide as a catalyst led to its considerable pop- ularity, which makes it still a frequently used cat,alyst in synthetic organic chem- istry. It is by now generally accepted that the oxide, formulated by Adams as PtOZ.H20, is not the actual catalyst, but rather a precursor to an extremely finely divided form of metallic platinum (3). Therefore, the oxide is not a catalyst, strictly speaking; it is used up in the re- duction of the organic material and thus not reusable. The exact stoichiometry of this oxide has never been clearly est’ab- lished and seems t,o depend on the mode of preparation (g). In t,he course of an investigation of platinum bronzes Cl), ternary platinum oxides with the general formula M,Pt’,O,, where the counterion 14 is generally a group I or II cation and 0 < R:< 1, we became interested in the *To whom correspondence should be ad- dressed: Department of Polymer Research. Fac- ulty of Biophysics and Biochemistry, Weizmann Institute of Science, Rehovot, Israel. true nature of Adams’ oxide. Inoue (4) reported some years ago that thermal deg- radation of PtO,, prepared by WGhler’s (5) method, results in a material that con- tains besides other phases, Pt304. Recently Sukhotin and co-workers (6) reported that thermal decomposition of Adams’ ox- ide yields Pt,O, and Pt metal at tem- peratures above 650°C. In this note we report our results concerning the true composition of Adams’ oxide and the hydrogenating activity of the individual components. In order t’o try to improve the yield of P&O, from the decomposition of Adams’ oxide, we investigated this decom- position reaction in detail. X-ray powder diffract’ion provides a convenient way of following the reaction. Met’allic platinum has its strongest peak at 20 = 39.8” [(ill) reflection] (7) and cu-PtO, gives the st’rongest peak at 26’ z 33” [ (100) re- flectionl (8). The strongest reflection for the platinum bronzes, the (110) reflection, comes arolmd 28 = 35” (91, depending on the exact lattice parameter, which can vary by 5% with temperature and counterion. No change in P&O, cont,ent of the de- composition product was obtained by 369 Copyright @ 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.