Organometallic reagents acetylide anions

The acetylide anions discussed in Chapter 11 are another example of organometallic compounds. These reagents are prepared by an acid-base reaction of an alkyne with a base such as NaNH2 or NaH. We can think of these compounds as organosodium reagents. Because sodium is even more electropositive (less electronegative) than lithium, the C-Na bond of these organosodium compounds is best described as ionic, rather than polar covalent. 

The two perpendicular pi bonds of a triple bond can be considered separately, and thus this source becomes merely a subset of the double-bond sources. Alkynes are slightly poorer electron sources than alkenes because the vinyl cation formed upon electrophile attack is relatively unstable. Acetylide anions, RC=C M+, are treated as organometallic reagents (Section 5.3.1) and not as alkyne sources. 

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