Multinuclear Olefin Polymerization Catalysts

Delferro, Massimiliano; Marks, Tobin J.

doi:10.1021/cr1003634

Cited by 555 publications

(406 citation statements)

References 300 publications

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“…The catalysts of choice should be both cheap and non-toxic, whilst being highly active and are, hopefully, constructed in such a way that they can be readily modified and thereby allow for a high degree of control over the ring opening polymerization (ROP) process. It is now well established that the use of bimetallic catalysts versus their monometallic counterparts can impart improved activities and selectivities over the catalytic process, be it α-olefin polymerization [2] or for the ROP of lactides [3]. In order to synthesize such bimetallic catalysts, suitable pro-ligand frameworks need to be available, whose coordination chemistry is well suited to binding more than one metal simultaneously in close proximity.…”

Section: Introductionmentioning

confidence: 99%

Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

Redshaw

2017

Catalysts

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Schiff base macrocycles are emerging as useful scaffolds for binding two or more catalytic metals in close proximity. Such coordination chemistry allows for the evaluation of potentially beneficial catalytic cooperative effects. In the field of ring opening polymerization (ROP) of cyclic esters, only a handful of metal systems bound by Schiff base [2 + 2] type macrocycles have been studied. Nevertheless, results to date have, for certain metals, identified some interesting structure activity relationships, whilst for other systems results have revealed particular combinations of metals and macrocycles to be virtually inactive. This perspective review takes a look at two types of recently-reported Schiff base macrocycles that have been employed as pro-ligands in the metal-catalyzed ROP of cyclic esters, specifically ε-caprolactone and rac-lactide.

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Section: Introductionmentioning

confidence: 99%

Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

Redshaw

2017

Catalysts

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“…At the beginning of the 1990s, new generations of ''nonmetallocene'' [32][33][34][35] catalysts based on various phenoxyiminato ligands were reported by Fujita and co-workers (Group 4, Fig. 5) [36][37][38][39][40][41][42] and Grubbs and co-workers (Group 10, Fig.…”

Section: Introductionmentioning

confidence: 99%

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

2014

Self Cite

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Single-site organometallic catalysts supported on solid inorganic or organic substrates are making an important contribution to heterogeneous catalysis. Early and late transition metal single-site catalysts have changed the polyolefin manufacturing industry and research with their ability to produce polymers with unique properties. Moreover, several of these catalysts have been commercialized on a large scale. Their heterogenization for slurry or gas phase olefin polymerization is important to produce polyolefin as beads and to avoid reactor fouling. The large majority of supports currently used in industry are inorganic materials (SiO 2 , Al 2 O 3 , MgCl 2 ), with silica being the most important. Single-site supported catalysts are most commonly prepared by molecular-level anchoring/chemisorption, in which a molecular precursor undergoes reaction with the surface while maintaining most of the ligand sphere of the parent molecule. Chemisorption of discrete organometallic complexes on solid supports yields catalysts with well-defined active sites, greater thermal stability than the homogeneous analogues, and decreased reactor fouling versus the homogeneous analogues. This review presents a detailed account of the synthesis, characterization and polymerization properties of single-site catalysts supported on metal oxides and metal sulfated oxides, primarily carried out at Northwestern University.

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“…Low polydispersities of the polymers were observed which indicate the single-site nature of these catalysts. Higher M n obtained for complexes 57 and 59 could be explained by steric hindrance due to the methyl groups on Cp ligand which mimics the b-hydride elimination resulting into the formation of long-chain syndiotactic polystyrene [63,66,74]. Decrease in ligand steric bulk decreased the activity as well as M n , and thus, it could also be inferred that cationic catalyst is better protected with sterically bulky ligands.…”

Section: N-trimethylsilylamido Complexes For Styrene Polymerizationmentioning

confidence: 94%

“…Presumably, the greater ionic radius and less electrophilicity of electron-deficient Hf-centre in 67 is helpful for getting very high molecular weight polymer. Whereas smaller ionic radius and greater electrophilicity in case of Zr-complex 66 enhances its activity but produces polymers of lower molecular weight which might be attributed to the faster chain transfer rate in case of 66 [72][73][74]81].…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

Aminopyridine stabilized group-IV metal complexes and their applications

Hafeez

Muhammad

2016

Appl Petrochem Res

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During the last two decades, group-IV metalsbased aminopyridinato complexes have attracted a tremendous research interest because of immense industrial needs for the catalyst which would be of higher activity and selectivity with lower toxicity and lower cost. Chemistry of titanium (Ti) and zirconium (Zr) complexes was more extensively explored as compared to hafnium (Hf) complexes. Direct synthesis, salt metathesis, amine elimination, alkane elimination, silyl chloride elimination, hydrogen chloride elimination and toluene elimination protocols have been used for the synthesis of group-IV metal complexes. Changes in ligand and complex design were made to optimize these catalysts for olefin polymerization. Most of these complexes have shown good catalytic activities when activated with dry methyl aluminoxane. Ligand transfer to aluminum was found in these complexes, particularly with less bulky ligands, and this ligand transfer problem was overcome by tridentate ligands but the activities of these complexes were not competitive to complexes with bidentate aminopyridinato ligands. Majority of these complexes produce high-molecularweight polymers with broader molecular weight distributions, and Hf-complexes produce longer chain polymers than their comparative Ti and Zr aminopyridinato complexes. It could be deduced that group-IV metals inherit the potential for optimal polymerizing catalysts probably, because of their almost vacant d-orbitals, these act as hard acids which on combination with soft bases carry the opportunity to design and develop polymerization catalysts which could overcome the problems associated with existing systems.

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Multinuclear Olefin Polymerization Catalysts

Cited by 555 publications

References 300 publications

Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Aminopyridine stabilized group-IV metal complexes and their applications

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