Ethylene polymerization using novel titanium catalytic precursors bearing N,N‐dialkylcarbamato ligands

Abstract

Polymerization catalysts based on N,N-dialkylcarbamato complexes of titanium(IV) appear particularly interesting, because these novel catalytic precursors are rather cheap and easy to synthesize and handle. This contribution reports ethylene polymerization behavior of titanium(IV) complexes of general formula Ti(O2CNR2)4 R ¼ Me (I) and Et (II) and TiCl2(O2CNMe2)2 (III). These precursors in conjunction with methylaluminoxane resulted active catalysts for the polymerization of ethylene, affording high-density polyethylene with limited branch content. The influence of the polymerization parameters was studied with particular reference to the type of catalyst components, solvent, temperature, monomer concentration, and Al/Ti ratio. The nature of the solvent appears crucial for catalytic performances: when toluene was replaced by chlorobenzene, a significant increase of the productivity was ascertained. The obtained polymers were characterized by DSC, size exclusion chromatography, FTIR, and NMR techniques

Titanium complexes bearing carbamato ligands as catalytic precursors for propylene polymerization reactions

“…and Table ). The molecular structure of IV closely resembles those previously reported for the analogous compounds Ti(O 2 CNR 2 ) 4 (R = Me, Et, and i Pr ). Thus, the Ti(IV) centre displays a pseudo ‐dodecahedral geometry being coordinated to eight O‐atoms.…”

“…The colourless solid was recovered by filtration and dried under vacuum at room temperature . Complexes I–III were prepared according to the literature …”

“…More recently, N , N ‐dialkylcarbamato complexes of titanium have been used as catalyst precursors for polymerization of ethylene. These complexes, upon activation with MAO, gave rise to the formation of ethylene homopolymers with a moderate activity (31–1390 kg polymer /mol catalyst ⋅hour) and limited branch content . (a) The same catalysts resulted almost inactive in the homopolymerization reactions of styrene and of 1‐hexene, while afforded ethylene/1‐hexene random copolymers with high 1‐hexene content, up to 30 mol % .…”

A new post-metallocene catalyst for alkene polymerization: copolymerization of ethylene and 1-hexene with titanium complexes bearingN,N-dialkylcarbamato ligands

“…The colorless solid was recovered by filtration and dried under vacuum at room temperature . Complexes I , II and III were prepared according to the previously published methods.…”

“…As a part of our investigation of the coordination behavior of titanium N,N ‐dialkylcarbamato complexes, we have found that these compounds, upon activation with methylalumoxane (MAO), catalyze ethylene homopolymerization reactions . As an expansion of this preliminary work, we synthesized two Ti(O 2 CNR 2 ) 4 complexes with R = Et ( I ) and R = Me ( II ) and the mixed chlorocarbamato derivative Ti(O 2 CNMe 2 ) 2 Cl 2 ( III ) and explored their catalytic potential in copolymerization reactions of ethylene with 1‐hexene (Scheme ).…”