Ethene homo- and ethene/propene copolymerization using a MAO activated cyclopentadienyl-amido half-sandwich complex

Abstract

The half‐sandwich complex [{η5:σ‐C5H4(CH2)2NEt}Ti(NEt2)2] was synthesized and characterized by means of IR‐spectroscopy. This compound was activated by methylaluminoxane (MAO) for homogeneous ethene polymerization and ethene/propene copolymerization. The effect of the Al/Ti molar ratio on the polymerization activity, the molecular masses, and the thermal properties of the polymers was studied. The molecular weight distributions and the DSC measurements of the copolymers show the presence of two different catalytic sites.

Ethene Polymerisation with Titanium Half-Sandwich Amido-Complexes

“…Both catalysts showed a maximum of the activity at a ratio Al/Ti = 4000. As found before in different catalytic systems, 3,4,7,8 increasing the MAO amount leads to lower activity, because of the poisoning effect by MAO at high Al/Ti ratios. On the other hand, a low MAO amount is not sufficient for total conversion to the active species.…”

“…The titanium content was determined by a colorimetric method. 9 Compound 1 was synthesised in the following way: a solution of LiN(CH 2 CH 3 ) 2 (from 7 mmol of n-butyllithium and 6 mmol of diethylamine in hexane) was added slowly to 0.498 g (2 mmol) of [(η 5 -C 5 H 5 ) 2 TiCl 2 ] in hexane (40 ml). After stirring for 72 h, the mixture was filtered with a celite column and the volatiles removed in vacuum.…”

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Half-sandwich metal amido-complexes are potential catalytic precursors for homogeneous olefin polymerization. [1][2][3][4] Amine groups directly linked to the metal atom may affect both the catalytic activity and polymer properties through their steric and/or electronic influence, as well as playing a fundamental role in the stability of active species during polymerisation. This latter characteristic has great importance for understanding catalytic behaviour in homogenous olefin polymerisation.In this work, using two different alkyl-amines as substituents (-NCH 2 CH 3 and -NCH 2 CH 2 CH 3 ) in half-sandwich titanium complexes of the type [CpTi(NR 2 ) 3 ], a comparison of the amido-substituent effect on the catalyst performance toward ethene polymerisation was made.

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“…This synthetic route is an alternative to the traditional amine elimination route used before for Cp-amido complexes. [3][4][5][6] Scheme 1 Synthesis of [CpTi{(N(CH 2 CH 3 ) 2 }] 3 ] (1) and [CpTi{N(CH 2 CH 2 CH 3 ) 2 } 3 ] (2).…”