Factors influencing chain transfer with monomer and with hydrogen in propene polymerization using MgCl2-supported Ziegler-Natta catalysts

Effects of Internal and External Donors on the Regio- and Stereoselectivity of Active Species in MgCl2-Supported Catalysts for Propene Polymerization

“…The DIBP/silane system gave the lowest proportion of vinylidene-terminated oligomers, 6% of the C 12 fraction, as opposed to 11 and 9% respectively for the ethyl benzoateand diether-based systems. This is also in line with the observed differences in regio-and stereochemical distribution, recent studies [28] having shown that the incidence of chain transfer to monomer, generating vinylidene-terminated chains, is unaffected by hydrogen but increases with decreasing site selectivity.…”

Mimicking Ziegler-Natta Catalysts in Homogeneous Phase, 1.C2-Symmetric Octahedral Zr(IV) Complexes with Tetradentate [ONNO]-Type Ligands

“…[1,4] It should be added that the two signals of the vinylidene protons were the only ones observed in the olefinic region of the 1 H NMR spectrum. All chain ends, therefore, are indicative of a 1,2 (primary) propene insertion mode, with no evidence of regioerrors even for the first propene insertion into a Zr1H bond (which contrasts with what has been found for a number of Ziegler-Natta [11] and C 2 -symmetric metallocene catalysts, [1 b, 12] for which such insertion is only weakly regioselective).…”

Coadsorption model for first-principle description of roles of donors in heterogeneous Ziegler–Natta propylene polymerization

“…6 illustrates all the pathways examined for propylene insertion and chain transfer to propylene. The chain transfer to monomer is known as one of the major chain-transfer pathways in the absence of hydrogen [78,79]. In order to fully consider stereo and regio aspects of these reactions, the position of the methyl group of propylene was varied at either of R [1][2][3][4] .…”