Olefin Polymerization with Non-metallocene Catalysts (Early Transition Metals)

Abstract

In this chapter, recent developments of so called non-metallocene early transition metal (group 3-5) complexes as the catalyst precursors for olefin polymerization have been described. These catalysts display unique characterisitics especially for ethylene (co)polymerization, and high isospecificity ([mmmm] [ 99.6 %) in propylene polymerization has been achieved in some catalyses. The ligand modification plays an essential key role not only for the catalytic activity, but also for control of tacticity and/or living nature in these catalyses.

Reactions of (Arylimido)vanadium(V)–Trialkyl Complexes with Phenols: Effects of Arylimido Ligands and Phenols for Formation of the Vanadium Phenoxides

“…Transition-metal alkyl complexes are among the most important reagents or intermediates in organic reactions, − and the study of their reaction chemistry has been recognized as an important subject for better understanding especially in catalysis cycles, reaction pathways, and design of efficient catalysts. − The metal alkyl species play a key role in olefin polymerization, the core technology for the production of polyolefins in the chemical industry. − Since classical Ziegler type vanadium catalyst systems display unique characteristics (highly reactive toward olefins exemplified as production of ultrahigh molecular weight polyethylene with narrow molecular weight distributions), − the reaction chemistry of vanadium–alkyl complexes − should be considered as an important subject in the field of catalysis ,− and organometallic chemistry. − …”

“…Early transition-metal–alkyl bonds have been known to be more nucleophilic than those with late transition metals, and these are thus highly reactive toward Brönsted/Lewis acids. − For example, cationic alkyl complexes, proposed active species for olefin polymerization, are formed by treating the dialkyl analogues with Al alkyls or borate through protonolysis or alkyl abstraction. − ,, These metal alkyls are generally rapidly reacted with alcohols (or phenols, ArOH) via protonation or coordination and a subsequent hydrogen transfer pathway (Scheme ). It has been, however, reported that steric crowding in tetrakis­(alkyl)-chromium­(IV) , and zirconium­(IV) complexes [exemplified as Cr t Bu 4 and Zr­(CH 2 t Bu) 4 ] and (arylimido)­vanadium­(V) trialkyl complex (described below) contributes to greater stability toward oxygen and alcohols.…”

Synthesis and Structural Analysis of (Imido)vanadium Dichloride Complexes Containing 2-(2′-Benz-imidazolyl)pyridine Ligands: Effect of Al Cocatalyst for Efficient Ethylene (Co)polymerization

“…; employed as catalysts for production of EPDM (synthetic rubber) etc. ], 24,34−45 development of efficient vanadium complex catalysts is considered to be an attractive and important subject. 24,42−45 It has been reported that (imido)vanadium(V) complexes containing the anionic ancillary donor ligand (aryloxo, 46−49 imidazolidin-2-iminato, 50 etc.)…”

“…], 24,34−45 development of efficient vanadium complex catalysts is considered to be an attractive and important subject. 24,42−45 It has been reported that (imido)vanadium(V) complexes containing the anionic ancillary donor ligand (aryloxo, 46−49 imidazolidin-2-iminato, 50 etc.) 24,42−50 and the chelate anionic donor ligand, 51−58 as shown in Chart 1, exhibit promising catalyst behaviors in the presence of the Al cocatalyst.…”

Ligand-Induced Product Switching between 4-Methyl-1-pentene and 2-Methyl-1-pentene in Bis(imino)pyridine/V(III)-Catalyzed Propylene Dimerization: Cossee–Arlman Versus Metallacycle Mechanism

“…Since the late 1990s, interest in developing new complexes that can be used as olefin oligo-/polymerization catalysts has once again attracted considerable attention. − Several complexes with different metal centers were used to study the effect of ligand substitution on olefin oligomerization and polymerization activity and selectivity. Iron- and cobalt-based catalysts with bis­(imino)­pyridine olefins have high activity and selectivity for ethylene oligomerization and co-polymerization with methylaluminoxane (MAO). − Alt and colleagues reported the use of the bis­(imino)­pyridine–vanadium­(III) complex with MAO as a co-catalyst for olefin-selective oligomerization. ,, The structure of the pre-catalyst has no great influence on the activity of the dimer, but it has a great influence on the distribution of the product.…”