DOI: 10.1002/adsc.200606077 Preparation, Characterization and Catalytic Properties of Polyaniline-Supported Metal Complexes Boyapati M. Choudary, a, * Moumita Roy, b Sarabindu Roy, b M. Lakshmi Kantam, b, * Bojja Sreedhar, b and Karasala Vijay Kumar b a Ogene Systems (I) Pvt. Ltd. #11-6-56, GSR Estates, Hyderabad 500037, India Fax: (+ 91)-40-23775566; e-mail: bmchoudary@gmail.com b Inorganic & Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500 007, India Fax: (+ 91)-40-27160921; e-mail: mlakshmi@iict.res.in Received: March 3, 2006; Accepted: June 13, 2006 Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/. Abstract: Polyaniline-supported Sc, In, Pd, Os and Re catalysts were prepared by using a simple proto- col and the thus prepared catalysts were well charac- terized using FTIR, XPS, UV-Vis/DRS, TGA-DTA. All the catalysts were successfully employed in a wide range of organic transformations such as cyana- tion and allylation of carbonyl compound, Suzuki coupling of aryl halides and boronic acids, and, most importantly, in asymmetric dihydroxylation of olefins to afford optically active vicinal diols. All the cata- lysts were separated from the reaction mixture by simple filtration and reused with consistent activity for five cycles without noticeable leaching of metal from the support. Keywords: allylation; asymmetric dihydroxylation; cyanation; polyaniline; Suzuki coupling Introduction Although a number of homogeneous catalysts have gained wide acceptance in terms of efficiency and se- lectivity, the contribution of these catalysts in the overall production of chemicals is much lower than originally expected. The major drawback of homoge- neous catalysis is the need to separate the relatively expensive catalyst from the reaction mixture at the end of the process. One of the most promising solu- tions to this problem seems to be the immobilization of the soluble catalysts onto an insoluble matrix usu- ally polymers using a simplified protocol. [1] Microen- capsulation [1c–f] and incarceration [1k–l] are newly de- veloped, advanced techniques using polymers to con- tain the metal complexes inside the polymer wrap via pi (p) interaction and physical forces. But the prepa- ration of polystyrene and polystyrene-derived materi- als for microencapsulation requires a complex proce- dure and the incarceration technique is tedious. Polyaniline (PANI) is one of the most widely stud- ied conducting polymers for electronic and optical ap- plications [2] due to its environmental stability and in- teresting redox properties but only a few reports are available using not well characterized PANI-support- ed metal catalysts. [3] We conceived the use of interac- tive PANI prompted by its highly conducting and redox properties as a support that holds metal com- plexes securely during catalytic reactions. Further- more, its easy preparative protocol from non-expen- sive starting material (aniline), controllable doping levels through an acid doping/base dedoping process, inert nature, and non-solubility in most of the organic solvents and water are essential qualities for using it as support in heterogeneous catalysis. We chose proven metal catalysts such as scandium, indium, pal- ladium salts, osmium and rhenium oxides, which have impacted immensely on modern organic synthesis. [4] We herein disclose the preparation, characterization and evaluation of polyaniline-supported metal cata- lysts in a wide diversity of organic reactions. Results and Discussion Preparation of Polyaniline-Supported Catalysts Scandium-doped PANI (PANI-Sc) was prepared by adopting a very simple protocol of stirring the solu- tions of ScACHTUNGTRENNUNG(OTf) 3 in acetonitrile with PANI at room temperature for a specified time and then the catalyst was filtered, washed, and dried. Similarly PANI-In 1734 # 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Adv. Synth. Catal. 2006, 348, 1734 – 1742 FULL PAPERS