Carbenes and Carbene Ligands in Organometallic Chemistry

Since Bertrand et al. and Arduengo et al. described the first stable carbenes in the 1990s the chemistry of carbenes has witnessed tremendous development in 

Carbenes are divalent carbon species, and are two electrons short of their octet Most carbenes are highly reactive. 

This chapter has discussed how carbenes can be formed and how they can react to give stable compounds or yet more reactive intermediates. Below is a summary of the main relationships between carbenes and other intermediates  

Each of the following carbenes has been predicted to have a sin et ground state. Indicate what structural feature in each case might lead to stabilization of the singlet state. 

A reaction between methylene and ds-2-butene gave tra s-l,2-dimethylcyclopropane. What does this tell us about the electronic configuration of the carbene in this reaction  

---