Efficient Synthesis of Aluminium‐Terminated Polyethylene by Means of Irreversible Coordinative Chain‐Transfer Polymerisation Using a Guanidinatotitanium Catalyst

Abstract

A series of guanidinato‐ligand‐stabilised titanium complexes has been synthesised and characterised. These compounds can be prepared by carbodiimide insertion into titanium–amide bonds. Reaction of carbodiimides N,N′‐bis(2,6‐diisopropylphenyl)carbodiimide, N,N′‐bis(2,6‐dimethylphenyl)carbodiimide and N‐tert‐butyl‐N′‐(2,6‐diisopropylphenyl)carbodiimide (2a–2c, respectively) with [(Et2N)TiCl3] led to mono(guanidinato)trichloridotitanium(IV) complexes (3a–3c). Subsequent conversion with methylmagnesium chloride gave the corresponding trimethyl complexes (4a and 4b). Single‐crystal X‐ray diffraction analyses were carried out for all complexes. Compound 4a showed very high activities in the polymerisation of ethylene in the presence of very high amounts of triethylaluminium and undergoes polymeryl chain transfer to aluminium. Irreversible coordinative chain‐transfer polymerisation and a unique combination of catalyst economy and high activity were observed. In the presence of 1000 equivalents of aluminium, a chain elongation of 83.3 % could be achieved with an activity of 9900 kgPE molcat–1 h–1 bar–1. The influence of the steric demand of the ligand on the polymerisation capability is significant and was investigated too.

Coordinative Chain Transfer Polymerization of Butadiene with Functionalized Aluminum Reagents

“…While 1,2-enchainment is consistently low in the range of 1-2%,t he 1,4-cis selectivity drops down to 53 %f or 1f at its highest investigated concentration (Table 1, entry 11). However,a se xemplified for 1c,s ignificant improvement with as electivity for 1,4-cis enchainment of BD of 90-95 %i s feasible by lowering the reaction temperature ( Table 2, entries [3][4][5][6][7][8][9].…”

“…This reversible chain transfer of polymeryl chains between chain-growth-active metal centers and chain-growth-inactive metal centers (Scheme 1) reduces the amount of polymerization catalyst required, controls the molecular weight and molecular weight distribution of polymers,a nd enables chain-end functionalization by appropriate quenching of the main group metal polymeryl species. [1][2][3][4][5][6][7][8][9][10] An obvious major potential of CCTP is chain-end functionalization by the main group metal initiator. This approach to functionalize the initiating chain end, however, has been hardly developed (Scheme 1).…”

Coordinative Chain Transfer Polymerization of Butadiene with Functionalized Aluminum Reagents

“…[1][2][3][4][5][6][7][8][9][10] An obvious major potential of CCTP is chain-end functionalization by the main group metal initiator. This reversible chain transfer of polymeryl chains between chain-growth-active metal centers and chain-growth-inactive metal centers (Scheme 1) reduces the amount of polymerization catalyst required, controls the molecular weight and molecular weight distribution of polymers,a nd enables chain-end functionalization by appropriate quenching of the main group metal polymeryl species.…”

Facile Synthesis of Hydroxyl‐Terminated Oligoethylenes

“…A significant improvement in controlling the molecular weight (distribution) is the approach of the coordinative chain transfer polymerization (CCTP) of ethylene. [25][26][27][28][29][30][31][32][33][34] This catalyzed version of the ''Aufbaureaktion'' has a low rate of b-hydride elimination relative to ethylene insertion and metal transfer reactions. [10] Thus, most of the time the alkyl chains remain bound to aluminum where b-hydride elimination is not prominent (Figure 1).…”

“…The polymerization affords high molecular linear PE with a broader distribution than in the ZIEGLER process due to the more frequent chain termination reactions. A significant improvement in controlling the molecular weight (distribution) is the approach of the coordinative chain transfer polymerization (CCTP) of ethylene . This catalyzed version of the “Aufbaureaktion” has a low rate of β ‐hydride elimination relative to ethylene insertion and metal transfer reactions .…”