Supporting Information for the paper: Tailoring the Physical Properties of Isotactic Polypropylene Through Incorporation of Comonomers and the Precise Control of Stereo- and Regio-Regularity by Metallocene Catalysts. Claudio De Rosa,* ,† Finizia Auriemma, † Odda Ruiz de Ballesteros, † Luigi Resconi, ‡ Isabella Camurati ‡ Dipartimento di Chimica, Università di Napoli "Federico II", Complesso Monte S.Angelo, Via Cintia, I- 80126 Napoli, Italy and Basell Polyolefins, Centro Ricerche G. Natta, P.le G. Donegani 12, I-44100 Ferrara, Italy. Experimental section Samples of isotactic polypropylene (iPP) homopolymer and propylene-ethylene (iPPEt), propylene- butene (iPPBu) and propylene-hexene (iPPHe) copolymers have been prepared at temperatures between 60 and 70 °C with the four metallocene catalysts shown in Chart 1, activated with methylalumoxane (MAO). All iPP samples and iPPEt and iPPBu copolymer samples have been prepared in liquid monomers, whereas iPPHe copolymers have been prepared in hexane solutions. The C 2 -symmetric catalysts A and B are highly stereoselective but not fully regioselective. S1-S3 These catalysts produce high molecular mass and highly stereoregular iPP homopolymer samples and iPPEt, S1 † Università di Napoli "Federico II", Italy ‡ Basell Polyolefins, Italy