Some New exo,exo-Bis(isodicyclopentadienyl)titanium and -zirconium Dichloride Derivatives:  Synthesis, Characterization, and Evaluation as Propene Polymerization Catalysts

Abstract

Exo,exo derivatives of the efficient catalyst precursors (diisodicyclopentadienyl)titanium and -zirconium dichloride substituted at the central position have been synthesized. These compounds have been characterized by solution NMR measurements, which also permitted the calculation of rotational barriers. The solid-state structures of exo,exo-bis(3-diphenylphosphinoisodicyclopentadienyl)titanium and -zirconium dichloride were determined by X-ray crystallography. Unfortunately, after activation by methylalumoxane, these complexes are shown to serve as poor catalysts for the polymerization of propene.

ansa-[(tert-Butylamino)(isodicyclopentadienyl)dimethylsilane]Zr(NMe2)2prepared by an amine-elimination reaction

“…As expected on the basis of experimental reaction conditions and prior results in this ®eld (Paquette et al, 1989;Sornay et al, 1991;Zaegel et al, 1995;Gobley et al, 1998;Gentil et al, 2000Gentil et al, , 2002, the molecular structure of (I) indicates that exo complexation of the isodicyclopentadienyl ligand to Zr has occurred. This structure exhibits the classical half-sandwich pseudo-tetrahedral geometry about the Zr atom.…”

A Silylene-Bridged (Isodicyclopentadienyl)(Fluorenyl) Complex of Zirconium for Homogeneous Olefin Polymerization

“…No steric consequences from the silylene bridge are noted compared to unbridged isodicyclopentadienyl complexes. The angles about the metal atom are in the same range in the silylene-bridged complex 5 as in the nonbridged isodicyclopentadienyl zirconium dichloro derivatives. ,, As observed in all isodicyclopentadienyl molecular structures, the norbornane fragment is slightly bent to the endo side of the ligand. This bending, as defined by the dihedral angle between the least-squares plane C(6)−C(5)−C(1)−C(9) and the plane C(3)−C(2)−C(1)−C(5)−C(4), is 10.2(1)° in 5 .…”

“…The methano 14 and ethano 13 bridge protons give rise to two sets of double multiplets between 1.01 and 2.51 ppm. The syn- methano bridge proton chemical shift at 2.51 ppm is observed to be 0.5 ppm more shielded than in classical nonbridged isodicyclopentadienyl complexes. − The corresponding chemicals shifts of the fluorenyl ligand protons are within the range of δ 7.23−8.23 ppm and appear as two sets of double triplets centered at δ 7.45 and 8.03 ppm and two sets of triple multiplets at 7.23 and 7.59 ppm.

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“…It has been assumed that even with a large centroid−metal−centroid angle, syndiospecificity can be realized when complexes contain a cyclopentadienyl ligand bulky enough to force the orientation of the methyl group of the incoming monomer unit to the open region of the flat fluorenyl ligand. Our investigations involving isodicyclopentadienyl ligand utilization for the synthesis of group 4 metallocene − complexes allowed us to anticipate that the presence of fluorenyl and isodicyclopentadienyl ligands in the same complex could lead to syndiotactic polypropylene when activated with MAO. We report below the synthesis, characterization, and polymerization behavior of complex 5 , the first isodicyclopentadienyl-bridged complex.…”

Stereoselective Access to New Half-Sandwich Complexes Containing an Isodicyclopentadienyl Ligand

“…For this reason, so-called half-sandwich metallocenes featuring an isodicyclopentadienyl ligand hold considerable attraction. The isodicyclopentadienyl ligand has already been used in Ziegler−Natta catalysts synthesis, and the combination of bis(isodicyclopentadienyl)titanium and zirconium dichlorides with methylalumoxane exhibits interesting activity …”