Platinum carbonyl derived catalysts on inorganic and organic supports: a comparative study Himadri Paul b , Susmit Basu b , Sumit Bhaduri a, * , Goutam Kumar Lahiri b, * a Reliance Industries Limited, Swastik Mills Compound, V.N. Purav Marg, Chembur, Mumbai 400071, India b Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India Abstract Fumed silica, silica gel, silica–alumina and cross-linked (5.5%) polystyrene have been functionalized with quaternary ammonium groups and the Chini cluster [Pt 12 (CO) 24 ] 2 has been anchored onto these functionalized materials by ion pairing. A catalyst has also been prepared by the adsorption of Na 2 [Pt 12 (CO) 24 ] on unfunctionalized fumed silica. The catalytic activities of the resultant materials, and that of commercially purchased 5% platinum on alumina have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: a-acetamidocinnamic acid, cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate, nitrobenzene and benzonitrile. Compared to the polystyrene supported catalyst, the inorganic oxide supported catalysts have higher surface areas and for most of the substrates have notably higher activities. The functionalized fumed silica- based catalyst gives higher conversions than functionalized silica gel and silica–alumina-based catalysts. In the hydrogenation of acetophenone and ethyl acetoacetate, the functionalized fumed silica-based catalyst show superior activity compared to the com- mercial platinum catalyst, and the catalyst made by conventional adsorption method. In benzonitrile hydrogenation with all the cluster-derived catalysts a hydrazine derivative is selectively formed, but when the commercial platinum catalyst is used benzyl amine is the main product. Keywords: Platinum carbonyl cluster; Hydrogenation; Catalysis; Polystyrene; Inorganic oxides 1. Introduction Anchoring of homogeneous catalysts onto insoluble polymeric supports has been much investigated for achieving a simple and easy method for the separation of the catalyst [1]. Supported carbonyl clusters in addi- tion have the potential to generate small metal crystal- lites of novel catalytic properties [2]. Because of these two reasons catalysts made by supporting carbonyl clusters on inorganic or organic polymeric materials continues to be an area of active research [1,2]. While considerable progress has been made elucidating struc- tural details of cluster derived particles, the practical advantages of such an approach for making catalysts remain to be firmly established. The physico-chemical properties of the Chini clusters, [Pt 3 (CO) 6 ] 2 n (n ¼ 3; 4; 5), have been much studied and we have reviewed and reported their use both as sup- ported and as homogeneous catalysts [3a,3b,3c]. We had also reported the use of commercial anion exchange resin as a support material for a number of anionic carbonyl clusters, including the Chini clusters, many years ago [3d]. Later on this method of ion-paring Chini clusters on suitable organic supports was found to be of special interest because of the ability of the resultant materials to catalyze hydrogen driven reductions of re- dox active biomolecules, and asymmetric hydrogenation of methyl pyruvate [4–6]. Very recently we communi- cated the catalytic performance of [Pt 12 (CO) 24 ] 2 (1), ion-paired on functionalized fumed silica, in hydroge- nation reactions [7].