Formation of metal-carbon bonds by other insertion reactions

Formation of metal-carbon bonds by other insertion reactions 

The addition of metal hydrides to carbon-carbon double or triple bonds is a special case of a very general reaction type, which involves the addition of a species A—B to an unsatrirated system X=Y (or X=Y). 

In this section we discuss examples of this general type, which involve the addition of bonds between metals and elements other than hydrogen (A = Metal B = — C, — N, — P, — O, —Hal, —Metal, etc.), to olefins and acetylenes. Formally similar reactions which involve addition of these bonds to species X=Y, where Y 7 C (e.g. to C=0, C=N, etc.) are described briefly elsewhere, as these do not lead to the formation of new M—C bonds. 

Polar metal-carbon bonds, such as are found in the organometallic compounds of the most electropositive elements, can add to olefins and acetylenes, especially when the latter bear electron-withdrawing substituents, which either increase the polarity of the C=C or C=C bond or can stabilize a negative charge in the transition state. Thus butyl-lithium adds to diphenylacetylene in diethyl ether, thought not in pentane, and trans-butylstilbene may be isolated after hydrolysis, showing that cis- addition occurs  

A series of insertion reactions occurs when n-butyl-lithium reacts with ethylene under high pressure (10000 to 15000 psi). Waxy polythene of molecular weight up to about 17 000 is produced, 

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