Applied Catalysis A: General 469 (2014) 132–138 Contents lists available at ScienceDirect Applied Catalysis A: General j ourna l h omepa ge: www.elsevier.com/locate/apcata Pd-nanoparticles supported onto functionalized poly(lactic acid)-based stereocomplexes for partial alkyne hydrogenation Giorgio Petrucci a , Werner Oberhauser b,∗ , Mattia Bartoli a , Guido Giachi a , Marco Frediani a,∗ , Elisa Passaglia c , Laura Capozzoli d , Luca Rosi a a Dipartimento di Chimica, Università di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Firenze, Italy b Istituto di Chimica dei Composti OrganoMetallici (ICCOM)-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy c ICCOM-CNR, UOS Pisa, Area della Ricerca, via Moruzzi 1, 56124 Pisa, Italy d Centro di Microscopie Elettroniche “Laura Bonzi” (Ce.M.E.)-ICCOM, Area di Ricerca CNR di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze Italy a r t i c l e i n f o Article history: Received 15 July 2013 Received in revised form 6 September 2013 Accepted 26 September 2013 Available online 6 October 2013 Keywords: Polyesters Stereocomplexes Alkyne hydrogenation Palladium nanoparticles a b s t r a c t Bipyridine-functionalized poly(lactic acid) (PLA)-based stereocomplexes were employed to stabilize Pd- nanoparticles (NPs). The well defined heterogeneous catalysts were suitable to catalyze the partial hydrogenation reaction (i.e. p(H 2 ) = 3 bar, 25 and 60 ◦ C) of phenylacetylene and diphenylacetylene in THF to give styrene and cis-stilbene with a chemoselectivity of 96% and 91%, respectively. Since the polymer support revealed stable under real catalytic conditions, stabilizing also efficiently the Pd-NPs in the course of the catalytic reaction, the heterogeneous catalytic system was easily recyclable. The catalytic activity as well as the chemoselectivity of the supported catalyst proved to be comparable in four consecutive catalytic cycles even by recovering the catalyst in air atmosphere after each cycle. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The catalytic partial hydrogenation of alkynes to alkenes is of special relevance in bulk, and fine chemical industries [1,2]. This latter catalytic process is most conveniently performed with the Lindlar catalyst (i.e. palladium nanoparticles (NPs) supported onto quinoline-promoted CaCO 3 which is partially poisoned with lead [3]). A further development of the latter catalyst using BaSO 4 as support and quinoline as modifier gave results which were found superior to that obtained by Lindlar’s catalyst in terms of reproducibility and ease of preparation [4]. The presence of an organic surface modifier [5–8], which is mainly involved in the rearrangement process of the Pd-(NPs) [9] revealed mandatory for obtaining high chemo- and regioselectivity in the partial hydrogenation of terminal and internal alkynes to terminal olefins and internal cis-olefins, respectively, avoiding hence the over-hydrogenation of the substrate giving alkanes. The organic modifier has always to be added to the catalytic reaction solution after each catalytic cycle and consequently separated from the catalytic solution, which is a clear drawback ∗ Corresponding authors. Tel.: +39 55 5225284/+39 55 4573459; fax: +39 55 5225203/+39 55 4573531. E-mail addresses: werner.oberhauser@iccom.cnr.it (W. Oberhauser), marco.frediani@unifi.it (M. Frediani). of the latter heterogeneous catalyst. Hence other heteroge- neous catalysts have been developed such as carbon-based nanomaterials [10–13], inorganic materials [14–17], func- tional organic polymers [18,19] (e.g. poly(ethylenimine) [20,21], polyaniline [22], poly(ethylene glycol) [23], poly(methacryalate) [24], poly(N-vinyl-2-pyrrolidone) [25]), resins [26–28], porous organic polymers [29,30] and organic-inorganic composite materials [31,32]. Since functional polymer-based catalytic systems generally exhibit important advantages over traditional catalysts such as: (i) the possible control of the particle shape exerted by func- tional groups located in the polymer chain; (ii) the improvement of catalytic selectivity; (iii) the stabilization of NPs by suppres- sion of their aggregation [18,19,33]. In this context we propose bipyridine-functionalized poly(lactic acid) (PLA)-based stereocom- plexes [34–39] as heterogeneous polymer support for Pd-(NPs), which efficiently catalyzed the partial hydrogenation of pheny- lacetylene and diphenylacetylene to styrene and cis-stilbene as major organic compounds. The effect of the Pd-(NPs)-localization in different polymer environments on the catalysts’ performance was studied. Stereocomplexation of PLA (i.e. interaction between PLA chains with opposite stereoconfiguration) which is based on the CH 3 . . .O(carbonyl oxygen atom) hydrogen bonds as proved by IR-spectroscopy [40] confers high mechanical performance [41], thermal stability [42] and hydrolysis resistance [43] to PLA. 0926-860X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcata.2013.09.053