[lutesium]

Why is always Li used in Organometallic compounds??? Eventhough Na/K is more reactive than Li??? Why not BuK or KDA (Potassium diisopropyl Amide) but always BuLi/LDA???
Is this case associated with the lesser risk of explosion associated with the contact of Li with the halides???

[Chump0]

A quick review in Bruice tells me that: "The electrostatic potential map shows that the carbon attached to the halogen in the alkyl halide is an electrophile, whereas the carbon attached to the metal ion Lithium in the organometallic compound is a nucleophile"

Maybe this helps, I'm a 1st year undergraduate sorry if it's doesn't help.

[orgopete]

This is a good question, but one for which a simple good answer may not be available. The correct answer probably involves cost, ease of preparation, solubility, stability, and reactivity (or hazard). For those who may have used even some of the more reactive alkyllithium reagents, you know that the titer or shelf life is limited. If a more reactive equivalent were prepared, would it be sufficiently stable for use as a commercial reagent (arguably a significant factor in degree of use)?

A variety alkyllithium reagents are commercially available and are reasonably cheap and stable. I think that probably explains their popularity.

If anyone has experience with equivalent organometallic sodium or potassium reagents, please comment on their properties.

[movies]

I think the answer is definitely stability.  Alkyl lithiums are reasonably stable and can be kept around the lab for a while before they lose their effectiveness.

You can pretty readily make a variant of an alkyl-potassium reagent by mixing an alkyl lithium with KOt-Bu.  These are sometimes used when you need a slightly stronger nucleophile, but as far as I know they are always prepared and used immediately, not stored.

[Doc Oc]

Ha ha!  Schlosser's base!  I'll never forget that after getting cornered during a practice talk for one of my grad student seminars.

[408]

I would also be inclined to stress solubility.  Lithium salts of organic compounds are often the most soluble as solvent can coordinate to the Li centre, solubilizing the compound.