Cp Systems with Covalently Bound Additional Donor Functions

Cp Systems with Covalently Bound Additional Donor Functions 

Jolly and coworkers [16] reported highly active chromium complexes such as compound 9 in 1997. The corresponding dimethyl complex shows even higher activity, and ultrahigh molecular weight PE M = 2 X 10 g mol ) is formed within only 4 min of reaction time [17]. From these data, a turnover frequency of 300 s can be calculated with 37% of the Cr centers to be active. In addition to the N-donor systems, P, O, and S donors have also been tested but with much lower activities and lower molecular weights [18]. 

Compounds 9-10 differ in the length of the spacer between the Cp ring and the N donor atom. Only the complexes with a C2 spacer and a neutral N donor give both high activities and high molecular weights. Complexes of the type 11 were activated with AlMeg or AlEtj. The active catalyst from complex 12 suffers from low stability. 

We developed rigid donor-functionalized Cp ligands in 1996 [19] and were able to coordinate them in to Cr(III) complexes of the type 13 in 2001 [20]. These complexes give excellent polymerization catalysts when activated with MAO. 

Polymerization Behavior of Donor-Functionalized Cp Chromium Complexes Developed in Heidelberg 

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