Oligomerization–transmetalation reactions of Cp*CrMe2(PMe3)/methylaluminoxane catalysts

Rogers, Jonathan S.; Bazan, Guillermo C.

doi:10.1039/b002146f

Cited by 84 publications

(52 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Boratabenzenyl and cyclopentadienyl anions are often considered to be isoelectronic [35] and by analogy to the systems discussed in Sections 2.1.2 and 2.1.3, one would also expect the existence of a trimerisastion catalyst system based on these ligands. Mitsubishi Chemical Industries did indeed investigate these ligands and found them to promote 1-hexene formation, although at very moderate catalyst activities [36].…”

Section: Boratabenzenyl Ligandsmentioning

confidence: 98%

Advances in selective ethylene trimerisation – a critical overview

Dixon

Green

Hess

et al. 2004

Journal of Organometallic Chemistry

430

378

View full text Add to dashboard Cite

Section: Boratabenzenyl Ligandsmentioning

confidence: 98%

Advances in selective ethylene trimerisation – a critical overview

Dixon

Green

Hess

et al. 2004

Journal of Organometallic Chemistry

430

378

View full text Add to dashboard Cite

“…Reports on transition-metal-based catalyst systems can be divided into, reports on single-catalyst systems [17,18,19] and systematically accomplished studies, in which one CGS was investigated with regard to a variety of main-group alkyls [20] and vice versa. [21] Systems identified by the authors as very fast, reversible, PE chain-transfer catalysts are only taken for discussion.…”

Section: Transition-metal-based Catalyst Systemsmentioning

confidence: 99%

“…(5), a previously prepared and characterised compound, [22] has been used as a CGS after activation by methylaluminoxane (MAO), BA C H T U N G T R E N N U N G (C 6 F 5 ) 3 or perflouroaryl borates; [17] TMA and TEA (TM/EA = trimethyl/ethyl aluminium) act as the maingroup alkyls. Selected results of the Cr + /Al catalyst system are shown in Table 3.…”

Section: Reports On Single-catalyst Systems: [Crcp*(me) 2 a C H T U Nmentioning

confidence: 99%

How to Polymerize Ethylene in a Highly Controlled Fashion?

Kempe

2007

Chemistry A European J

256

212

View full text Add to dashboard Cite

Very fast, reversible, polyethylene (PE) chain transfer or complex-catalysed "Aufbaureaktion" describes a "living" chain-growing process on a main-group metal or zinc atom; this process is catalysed by an organo-transition-metal or lanthanide complex. PE chains are transferred very fast between the two metal sites and chain growth takes place through ethylene insertion into the transition-metal- or lanthanide-carbon bond-coordinative chain-transfer polymerisation (CCTP). The transferred chains "rest" at the main-group or zinc centre, at which chain-termination processes like beta-H transfer/elimination are of low significance. Such protocols can be used to synthesise very narrowly distributed PE materials (M(w)/M(n)<1.1 up to a molecular weight of about 4000 g mol(-1)) with differently functionalised end groups. Higher molecular-weight polymers can be obtained with a slightly increased M(w)/M(n), since diffusion control and precipitation of the polymers influences the chain-transfer process. Recently, a few transition-metal- or lanthanide-based catalyst systems that catalyse such a highly reversible chain-growing process have been described. They are summarised and compared within this contribution.

show abstract

“…[3a] Transition-metal-based chain-transfer catalyst systems [5] are intended to work at room temperature, which restricts the production of long-chain polymers, most likely because of solubility problems. Molecular weights with a dispersity of around 1.1 up to a M w of about 1200 g mol À1 are Influence of polymer precipitation on the molecular-weight distribution (SEC); before (15 min), at the beginning of (22 min,) and after (30 min) precipitation (Table 4, entries 4, 6, and 7).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…[ 5] We report here on aminopyridinato-ligandstabilized [6] organoyttrium cations and the reversible PE chain transfer between these cations and aluminum to synthesize aluminium-terminated PE chains with a very narrow molecular-weight distribution. The rather high thermal stability of these cations in combination with suppressed b-H transfer allows for the synthesis of relatively high-molecularweight Al-terminated PE, functionalized polyethylene blocks to build novel polymer architectures.…”

Section: Introductionmentioning

confidence: 99%

Reversible Chain Transfer between Organoyttrium Cations and Aluminum: Synthesis of Aluminum‐Terminated Polyethylene with Extremely Narrow Molecular‐Weight Distribution

Kretschmer

Meetsma

Hessen

et al. 2006

Chemistry A European J

150

101

View full text Add to dashboard Cite

Aminopyridinato-ligand-stabilized organoyttrium cations are accessible in very good yield through alkane elimination from trialkyl yttrium complexes with sterically demanding aminopyridines, followed by abstraction of one of the two alkyl functions using ammonium borates. At 80 degrees C and in the presence of small amounts of aluminum alkyl compounds, very high ethylene polymerization activities are observed if very bulky aminopyridinato ligands are used. During these polymerizations a reversible polyethylene chain transfer is observed between the organoyttrium cations and aluminum alkyls. The chain-transfer catalyst system described here is able to produce relatively long-chain (up to 4000 g mol-1) Al-terminated polyethylene with a molecular-weight distribution<1.1. In the synthesis of higher molecular PE a slight increase in polydispersity with increasing chain length (15,600 g mol-1, approximately 1.4) is observed owing to reduced reversibility caused by higher viscosity and precipitation of polymer chains (temperature of 80-100 degrees C).

show abstract

Oligomerization–transmetalation reactions of Cp*CrMe2(PMe3)/methylaluminoxane catalysts

Abstract: Chain growth in the reaction of ethylene with Cp*CrMe 2 (PMe 3 ) activated with methylaluminoxane is restricted by a fast Cr/Al transmetalation process.

Cited by 84 publications

References 19 publications

Advances in selective ethylene trimerisation – a critical overview

Advances in selective ethylene trimerisation – a critical overview

How to Polymerize Ethylene in a Highly Controlled Fashion?

Reversible Chain Transfer between Organoyttrium Cations and Aluminum: Synthesis of Aluminum‐Terminated Polyethylene with Extremely Narrow Molecular‐Weight Distribution

Contact Info

Product

Resources

About