Formation of elastomeric polypropylene promoted by the dynamic complexes [TiCl₂{N(PPh₂)₂}₂] and [Zr(NPhPPh₂)₄]

TY - JOUR

T1 - Formation of elastomeric polypropylene promoted by the dynamic complexes [TiCl2{N(PPh2)2}2] and [Zr(NPhPPh2)4]

AU - Kühl, Olaf

AU - Koch, Thomas

AU - Somoza, Fernando B.

AU - Junk, Peter C.

AU - Hey-Hawkins, Evamarie

AU - Plat, Dorit

AU - Eisen, Moris S.

N1 - Funding Information: We gratefully acknowledge support from the German-Israeli-Foundation grant no. I-142/95, the Fonds der Chemischen Industrie, the Deutscher Akademischer Austauschdienst (P.C.J.), the Funds for the Promotion of Research at the Technion, the E. and J. Bishop Research Fund administered by the Technion V.P.R. Fund and to The Ministry of Science.

PY - 2000/6/5

Y1 - 2000/6/5

N2 - The homoleptic phosphinoamide complex [Zr(NPhPPh2)4] (1) and the bisamido complex [TiCl2{N(PPh2)2}2] (2) were prepared from ZrCl4 and four equivalents of LiNPhPPh2 and from TiCl4 and one equivalent of [Li(THF)N(PPh2)2]2. In the solid state, the four NPhPPh2 ligands in 1 exhibit η2 coordination. The ZrN4P4 fragment is highly symmetrical and almost of D2 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(η2-NPhPPh2)2(η 1-NPhPPh2)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.

AB - The homoleptic phosphinoamide complex [Zr(NPhPPh2)4] (1) and the bisamido complex [TiCl2{N(PPh2)2}2] (2) were prepared from ZrCl4 and four equivalents of LiNPhPPh2 and from TiCl4 and one equivalent of [Li(THF)N(PPh2)2]2. In the solid state, the four NPhPPh2 ligands in 1 exhibit η2 coordination. The ZrN4P4 fragment is highly symmetrical and almost of D2 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(η2-NPhPPh2)2(η 1-NPhPPh2)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.

KW - Homoleptic zirconium phosphinoamide complex

KW - Molecular structure

KW - Polymerisation of propylene

KW - Titanium bisamido dichloride complex

UR - http://www.scopus.com/inward/record.url?scp=0041783133&partnerID=8YFLogxK

U2 - 10.1016/S0022-328X(00)00214-X

DO - 10.1016/S0022-328X(00)00214-X

M3 - 文章

AN - SCOPUS:0041783133

SN - 0022-328X

VL - 604

SP - 116

EP - 125

JO - Journal of Organometallic Chemistry

JF - Journal of Organometallic Chemistry

IS - 1

ER -