Metal Phenolates as Polymerization Catalysts

Abstract

Phenolates represent versatile ligand scaffolds capable of stabilizing a large variety of both oxophilic metal centers and late transition elements. Over the past 50 years, they have played a prominent role in the rise of discrete metal complexes employed to promote, initiate and/or catalyze a variety of controlled homogeneous polymerization reactions. This chapter features a selection of the most remarkable metal phenolate complexes used in the polymerization of olefins, styrene and dienes, cyclic esters and (meth)acrylates. Coordination-insertion polymerization reactions are emphasized, but other types of mechanisms are also treated. Specifically highlighted are catalytic systems where the phenolate ligands have proved valuable ancillaries, to provide either exceptional stability to active species and to generate highly productive catalysts, and/or to control the polymerization reactions, imparting a unique capacity to obtain polymers with tailored macromolecular features: molecular weights and their dispersion, (co)monomer distribution and regio/stereoselectivity

PolymerizationCatalysis by Metal Phenolates

“…The guanidinate-supported mono-phenolate CpTi IV species 1 (Figure 1) was recently reported to be highly active in ethylene polymerization to afford high-molecular-weight polyethylene (HMWPE) when activated with AlMe3-free methylaluminoxane (MAO) (typical run: [MAO]/ [1] = 1000, 2 bar of ethylene, 50 °C, 15 min, activity = 760 kg PE mol -1 h -1 bar -1 , Mw = 369000 g mol -1 , PDI = 1.8). 5 In contrast, the use of standard MAO as co-catalyst decreased dramatically both the activity and level of control of the polymerization process.…”

“…Initially reported by Fujita and co-workers nearly fifteen years ago, group 4 metal species bearing fluorinated phenolate-imine ligands are well-established high performance catalysts for the living (and stereoselective) polymerization of ethylene (and propene). 1 Recently, Ma and co-workers investigated the dinuclear phenoxyimine Ti IV catalyst 35 (Figure 14) in ethylene/1,5-hexadiene co-polymerization. 38 The possible cooperativity between metallic sites in species 35 may favor co-monomer incorporation in the final copolymeric material.…”

“…A Patai contribution entitled « Metal phenolates as polymerization catalysts » was published in 2014. 1 It included an up-to-date literature coverage till 2012 in olefin, dienes and cyclic esters/carbonates polymerization mediated by metal phenolate species. Therefore, for the latter polymerization reactions, only an update since 2012 is provided herein with an emphasis on the most significant developments.…”

Selective substitution of long-acyl groups into alcohols of kraft lignin over transesterification using ionic liquid

“…Notably, the Ar-OH group is a valuable functional group, because it is more chemically reactive than the R-OH group and can easily serve as a reaction point for thermosetting and chemical crosslinking of kraft lignin. Furthermore, the Ar-OH group is known to have antioxidant ability [2,3] and adsorption capability for metals [4,5]. We hypothesized that if the poor processability of kraft lignin was improved by a certain modification method while retaining the rich Ar-OH group, the resultant kraft lignin derivative would be a valuable precursor for polymeric materials with the unique functions in addition to the inherent high thermal stability of aromatic polymers.…”

Monometallic and Bimetallic Titanium κ1-Amidinate Complexes as Olefin Polymerization Catalysts

“…With specific regard to the Group 4 metals, the spectacular success of metallocene systems as single-site olefin polymerization catalysts was followed by the development of a range of half-sandwich compounds, starting with the cyclopentadienyl-amido “constrained geometry catalysts” (CGCs) and then other systems of the type (η-C 5 R 5 )­M­(X)­R 2 , in which the ‘X’ ligand is a heteroatom-donor moiety such as aryloxide (OAr), , phosphinimide (NPR 3 ), cyclic or noncyclic guanidine­(NC­(NR 2 ) 2 ), ketimide (NCR 2 ), or κ 1 -benzamidine (NC­(Ar)­NR 2 ) . Non-cyclopentadienyl systems were also developed featuring bis­(amide)-type ligands and their bis­(phenoxide) and related analogues, typically incorporating additional Lewis base donors. Catalyst systems based on imido ligands with additional fac-N 3 donor ligand sets were also developed, building on and exploiting the isolobal analogy between cyclopentadienide and these N-donor ligand sets …”