Synthesis and catalytic behavior in ethene polymerization of half-sandwich amido complexes activated with MAO

Abstract

The half‐sandwich complexes, [η1:η5‐C9H6(CH2)2NEt]Ti(NEt2)2 and [η1:η5‐C13H8(CH2)2NEt]Ti(NEt2)2, were synthesized and characterized by spectroscopy techniques. These compounds were activated by methylaluminoxane (MAO) for homogeneous ethene polymerization. The effect of the ligand and Al/Ti molar ratio on the polymerization activity, the molecular masses and the thermal properties of the polymers were studied and compared with previous data obtained for the case of analogous cyclopentadienyl (Cp) complexes. The activity and molecular weight decreases in the following order: Cp‐half‐sandwich > indenyl‐half‐sandwich > fluorenyl‐half‐sandwich, as consequence of the interaction of steric and electronic effects.

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.…”

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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).…”