Formation of elastomeric polypropylene promoted by the dynamic complexes [TiCl 2{N(PPh 2) 2} 2] and [Zr(NPhPPh 2) 4]

• Published in: Journal of organometallic chemistry Vol. 604; no. 1; pp. 116 - 125
• Main Authors: Kühl, Olaf, Koch, Thomas, Somoza, Fernando B, Junk, Peter C, Hey-Hawkins, Evamarie, Plat, Dorit, Eisen, Moris S
• Format: Journal Article
• Language: English
• Published: LAUSANNE Elsevier B.V 05.06.2000; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Homoleptic zirconium phosphinoamide complex; Molecular structure; Physical Sciences; Polymerisation of propylene; Science & Technology; Titanium bisamido dichloride complex; Homoleptic zirconium phosphinoamide complex; Polymerisation of propylene; Titanium bisamido dichloride complex; Molecular structure; OLEFIN POLYMERIZATION CATALYSTS; homoleptic zirconium phosphinoamide complex; METALLOCENE CATALYSTS; MOLECULAR-STRUCTURE; ZIRCONIUM COMPLEXES; REACTIVITY; TITANIUM COMPLEXES; molecular structure; HETEROALLYLIC LIGANDS; BENZAMIDINATE COMPLEXES; polymerisation of propylene; titanium bisamido dichloride complex; PROPENE POLYMERIZATION; STEREOERROR FORMATION
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(00)00214-X

The homoleptic phosphinoamide complex [Zr(NPhPPh 2) 4] ( 1) and the bisamido complex [TiCl 2{N(PPh 2) 2} 2] ( 2) were prepared from ZrCl 4 and four equivalents of LiNPhPPh 2 and from TiCl 4 and one equivalent of [Li(THF)N(PPh 2) 2] 2. In the solid state, the four NPhPPh 2 ligands in 1 exhibit η 2 coordination. The ZrN 4P 4 fragment is highly symmetrical and almost of D 2 symmetry. Hence, the complex is chiral, and the two enantiomers cocrystallize in the asymmetric unit. In solution, 1 exhibits signals for the six-coordinate complex [Zr(η 2-NPhPPh 2) 2(η 1-NPhPPh 2) 2]. In the presence of methylalumoxane (MAO), 1 and 2 are active catalysts for the formation of high-molecular-weight elastomeric polypropylene. The formation of elastomeric polypropylene is a consequence of an epimerization mechanism of the last-inserted monomer, indicating no detachment of the growing polymer chain from the metal center during this process. Fractionation studies of all the elastomeric polymers show no atactic fractions. As corroboration for this mechanism, we have shown that these complexes are active catalysts for the isomerization and oligomerization of 1-octene, as well as for the rapid isomerization of allylbenzene to trans-methylstyrene.