1. OrganoLithium Compounds Peter H.M. Budzelaar

2. OrganoLithium Compounds 2 Organo-lithium compounds Ionic character, electron-deficient –oligomeric or polymeric structures Strongly basic and nucleophilic –applications in organic synthesis Reducing –unwanted side reactions

3. OrganoLithium Compounds 3 Organo Na, K compounds "Purely" ionic –polymeric structures –pyrophoric solids –mostly insoluble in any solvent they don't react with Very strong bases, not that good as nucleophiles –few applications –organoLi compounds are much easier to handle

4. OrganoLithium Compounds 4 Driving force for oligomerization ionic interpretation: Ionic interactions are "soft" but not weak!

5. OrganoLithium Compounds 5 Driving force for oligomerization covalent interpretation 2e-3c and 2e-4c bonds are not just bonding between Li and C, but also bonding between the Li atoms

6. OrganoLithium Compounds 6 Structure of [EtLi] 4

7. OrganoLithium Compounds 7 Structure of [CyLi] 6

8. OrganoLithium Compounds 8 Structure of [BuLi(THF)] 4

9. OrganoLithium Compounds 9 Structure of [o-Me 2 NCH 2 C 6 H 4 Li] 4

10. OrganoLithium Compounds 10 Structure of [2,6-(MeO) 2 C 6 H 3 Li]4

11. OrganoLithium Compounds 11 Structure of [MeLi(sparteine)] 2 used for enantioselective deprotonation not all hydrogen positions well-determined

12. OrganoLithium Compounds 12 Structure of PhLi(pmdta)

13. OrganoLithium Compounds 13 Structure of (Allyl)Li(pmdta) 2.25 2.33 2.72

14. OrganoLithium Compounds 14 Structure of [BzNa(pmdta)] ∞

15. OrganoLithium Compounds 15 Structure of [(Me 3 Si) 3 CRb] ∞

16. OrganoLithium Compounds 16 Structure of (naphthalene)[Li(tmeda)] 2

17. OrganoLithium Compounds 17 Synthesis of OrganoLi Compounds Direct synthesis –Reactivity: alkyl > aryl, Cl < Br < I etc –Commercial synthesis: mostly from chlorides –In laboratory: usually from alkyl bromides/iodides (easier to start) –Complication: Li reacts with N 2, do reaction under Ar ! –Side reaction: Wurtz coupling, especially for X = I –In apolar or weakly polar solvents –Radical mechanism Transmetallation –M less electropositive than Li –Infrequently used

18. OrganoLithium Compounds 18 Reactions of OrganoLi Compounds Metallation –Faster for more basic R - –Faster in polar and/or coordinating solvents –Works well if product capable of intramolecular coordination Metal-halogen exchange –Facile for I and Br, usually (too) slow for Cl, F –Regioselective synthesis of R'Li –Side reaction: Wurtz coupling –Usually done at low temperature (-80 to -20°C)

19. OrganoLithium Compounds 19 Reactions of OrganoLi Compounds Metathesis –Driving force: stability of LiCl (lattice energy!) –Selective synthesis of R l MX m often hard –With excess RLi often "ate" complexes (R n+1 M - )

20. OrganoLithium Compounds 20 Structure of [(tmeda)LiMe 2 ] 2 Mg