Nitrobenzene Reduction with AuNPs supported onto a polymeric matrix

Nitrobenzene Reduction with AuNPs supported onto a polymeric matrix Annarita Noschese1*, Antonio Buonerba1, Carmine Capacchione1, Stefano Milione1, Alfonso Grassi1 1 - Dipartimento di Chimica e Biologia, Università degli Studi di Salerno, Via Giovanni Paolo II - 84084 Fisciano (SA), Italy, and CIRCC-Bari, Italy annaritanoschese@gmail.com Gold Nanoparticles (AuNPs) are a powerful and versatile catalyst suitable in a variety of oxidation and reduction reactions under sustainable conditions [1]. E.g. aerobic oxidation of alcohols and cross coupling reactions of alcohols to esters, amide, imine have been widely and successfully explored [2]. On the other side the reduction of nitroarenes to anilines using NaBH4, H2, silanes, formic acid, CO/H2O is a benchmark reaction for testing the catalytic performances of AuNPs in reduction reactions [3]. In this scenario, AuNPs embedded in a polymeric matrix consisting of syndiotactic polystyrene-co-cis-1,4-polybutadiene (AuNPs-sPSB) were found extremely active in oxidation catalysis [4]; thus herein we report on the use of the AuNPs-sPSB catalyst in the reduction of nitrobenzene to aniline using NaBH4. The polymorphic behaviour of the host polymer matrix has been studied in order to optimize the catalyst performances. The nanoporous crystalline forms, namely  and , of the sPSB matrix allowed a total conversion of nitrobenzene in 40 min at room temperature, with 100% selectivity in aniline. The not permeable  crystalline form produced a less reactive and selective catalyst; actually azobenzene and azoxybenzene were detected as intermediates compounds providing information on the cascade of reactions and the global reaction mechanism. The catalyst is very stable under the reaction conditions and reusable for at least three times without any loss of catalytic activity. [1] M. Stratakis, H. Garcia, Chem. Rev. 112 (2012). 4469. [2] A. Corma, H. Garcia, Chem. Soc. Rev. 37 (2008) 2096. [3] S. Fountoulaki, V. Daikopoulou, P. L. Gkizis, I. Tamiolakis, G.S. Armatas, I. N. Lykakis*, ACS Catal. 4 (2014) 3504; X. Liu, S. Ye, H.-Q. Li, Y.-M. Liu, Y. Cao, K.-N. Fan, Catal. Sci. Technol. 3 (2013) 3200. [4] A. Buonerba, C. Cuomo, S. Ortega Sánchez, P. Canton, A.Grassi, Chem. Eur. J. 18 (2012) 709 ; A. Buonerba, A. Noschese, A. Grassi, Chem. Eur. J. 20 (2014) 5478.