# Why are organolithium and organomagnesium compounds nucleophilic in nature?

My textbook doesn't say anything about this but does say that on addition of organolithium compounds to carbon dioxide, they give ketones and not carboxylic acids like grignard reagents. This has been attributed to the greater nucleophilic character of Organolithium compounds compared to grignard reagents. I see that greater polarity of the C-Metal bond must relate to this according to many websites but I cannot understand why! Also, during formation of the RLi compounds using alkyl halides, what does the alkyl halide dissociate into? Please help!

When Li reacts with an alkyl halide, a salt (lithium halide) is formed, whose stability is the primary thermodynamic driving force of the reaction: $\mathrm{2Li}+\mathrm{RCl} \rightarrow \mathrm{RLi}+\mathrm{LiCl}$.