(Imido)vanadium Complexes as Efficient Catalyst Precursors for Olefin Polymerization/Oligomerization

Abstract

Arylimido)vanadium(V) complexes containing anionic ancillary donor ligands of type, V(NAr)Cl 2 (L) (Ar = 2,6-Me 2 C 6 H 3 , L = aryloxo, ketimide phenoxyimine, etc.) exhibited high catalytic activities for ethylene polymerization in the presence of Al cocatalyst; V(NAr)Cl 2 (O-2,6-Me 2 C 6 H 3 ) showed the exceptionally high activities in the presence of halogenated Al alkyls such as Et 2 AlCl, EtAlCl 2 , etc. (Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe 3 ) (NAr)(L 0 ) (L 0 = N=C t Bu 2 , O-2,6-i Pr 2 C 6 H 3 ) exhibited the remarkable catalytic activities for ring-opening metathesis polymerization of norbornene. (Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl 2 [2-Ar 0 NCH 2 (C 5 H 4 N)] (R = 1-adamantyl, cyclohexyl, phenyl, Ar 0 = 2,6-Me 2 C 6 H 3 , 2,6-i Pr 2 C 6 H 3 ), exhibit the remarkable activities for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to [99%). The steric bulk of the imido ligand plays an important role in the selectivity, and the electronic nature directly affects the activity.

Pogo-Stick Iron and Cobalt Complexes: Synthesis, Structures, and Magnetic Properties

“…There has been a long-standing interest in metal–ligand multiple bonds involving late 3d transition metals, in particular those compounds containing an imido functionality. − Imido ligands can donate up to six electrons by acting as a 2σ, 4π donor ligand. , Furthermore, the imido functionality not only acts as an ancillary ligand in homogeneous catalysis − but also acts to actively participate in organic reactions − and stabilize highly reactive species. Nevertheless, reactivity always correlates with the electronic structure of the central metal atom.…”

Novel SiO2‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution

“…Ghosh found that the imido vanadium catalyst supported on the SiO 2 with MAO as the co‐catalyst had higher activity than that supported on the other supports. Zhang and Nomura focused on high oxidation state imido vanadium complexes containing anionic ancillary donor ligands because the olefin coordination onto the highest oxidation state vanadium–alkyl complexes would be suitable for the subsequent insertion. Several researchers suggested that the use of vanadium‐based catalysts usually allows the preparation of high‐molecular‐weight polymers with narrow MWD, and ethylene/α‐olefin copolymers with high α‐olefin incorporation …”

Ethylene polymerization and ethylene/hexene copolymerization by vanadium(III) complexes bearing bidentate phenoxy-phosphine oxide ligands

“…One way to overcome this problem is adding Cl 3 CCOOEt or chlorinated hydrocarbons (viz., “rejuvenators” or “promoters” in the literature), which has proven to be effective reagents for maintaining the higher (active) oxidation state of vanadium systems . The introduction of ancillary ligands is another powerful method of stabilizing the catalytically active species by way of variation of the number, size and electronic properties of ligands . In recent years, great advances in vanadium catalytic systems with improved catalytic activity and thermal stability have been achieved .…”

“…For example, Redshaw et al reported various aryloxide‐based vanadium complexes which exhibit excellent performance for ethylene polymerization at an elevated temperature . Golisz and Bercaw discovered that a vanadium (III) complexes containing bis(phenoxy)pyridine ligand showed remarkable catalytic activity for propylene polymerization and afforded high molecular weight polypropylene with uniform weight distributions . Nomura and Zhang obtained series of vanadium (V) imido complexes with aryloxide coligands as efficient catalysts for olefin (co)polymerization, and some systems exhibited remarkable catalytic activities, excellent comonomer incorporation ability at high temperature .…”