1. OrganoLithium Compounds
Peter H.M. Budzelaar

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

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

6. Structure of [EtLi]4
OrganoLithium Compounds

7. Structure of [CyLi]6
OrganoLithium Compounds

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

9. Structure of [o-Me2NCH2C6H4Li]4
OrganoLithium Compounds

10. Structure of [2,6-(MeO)2C6H3Li]4
OrganoLithium Compounds

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

12. Structure of PhLi(pmdta)
OrganoLithium Compounds

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

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

15. Structure of [(Me3Si)3CRb]∞
OrganoLithium Compounds

16. Structure of (naphthalene)[Li(tmeda)]2
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 N2, 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
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)
OrganoLithium Compounds

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

20. Structure of [(tmeda)LiMe2]2Mg
OrganoLithium Compounds