Permethylscandocene-alkyl complex

An example of an alkyne insertion involving an early metal complex is shown in Equation 9.72. The insertion of dimethylacetylene into the permethylscandocene-alkyl complex occurs in a manner similar to that for the insertion of olefins into d metal-alkyl complexes. This reaction gave the product of a cis addition. The competition experiment shows that there is no measurable isotope effect of the a-hydrogen, implying that the modified Green-Rooney mechanism is not followed in this case. 

Burger, B. J. Thompson, M. E. Cotter, W. D. Bercaw, J. E. Ethylene insertion and -hydrogen elimination for permethylscandocene alkyl complexes. A study of the chain propagation and termination steps in Ziegler-Natta polymerization of ethylene. J. Am. Chem. Soc. 1990,112, 1566-1577. 

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