Ziegler-Natta catalysis homogeneous systems

Unfortunately, despite the great number of papers and the doubtless interest in both kinetic and mechanistic studies on the behavior of the homogeneous catalytic systems, many aspects of this part of Ziegler-Natta catalysis remain in the dark. To this point reference is made to the works and reviews of Henrici-01iv6 and Olive b92), Ballard , Reichert and finally of Fink et al. on the MWD... 

Progress in (heterogeneous) Ziegler-Natta catalysis has continued unabated over the last 50 years, while the last 20 years have seen the advent of homogeneous (metallocene and other single-site) catalysts. However, despite the enormous research effort and many advances made in the field of homogeneous catalysis, polyolefins manufacture is still dominated by Ziegler-Natta systems. 

The catalytic cyclo-oligomerization of 1,3-butadiene mediated by transition-metal complexes is one of the key reactions in homogeneous catalysis.1 Several transition metal complexes and Ziegler-Natta catalyst systems have been established that actively catalyze the stereoselective cyclooligomerization of 1,3-dienes.2 Nickel complexes, in particular, have been demonstrated to be the most versatile catalysts.3... 

Much effort has been devoted during the last 30 years toward understanding the mechanisms operative in the coordination catalysis of ethylene and a-olefin polymerization using Ziegler-Natta systems (metal halide and aluminum alkyl, sometimes with Lewis base modifiers). Aspects of the complex heterogeneous reactions have been elucidated (jL- ) but the intimate mechanistic detail - for example the role of inhibitors and promoters, kinetics and thermodynamics of chain growth, modes of chain transfer and termination - comes primarily from studies of homogeneous catalysts ... 

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