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Organo Be and Mg Compounds

Organo Be and Mg Compounds. Ionic character Electron-deficient Basic Nucleophile Reducing. oligomeric or polymeric structures Mg: applications in organic synthesis (Grignard) Be: extremely toxic. Organo Ca, Sr, ... Compounds. Very ionic Strongly basic. polymeric structures,

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Organo Be and Mg Compounds

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  1. Organo Be and Mg Compounds • Ionic character • Electron-deficient • Basic • Nucleophile • Reducing oligomeric or polymeric structures Mg: applications in organic synthesis (Grignard) Be: extremely toxic Organomagnesium Compounds

  2. Organo Ca, Sr, ... Compounds • Very ionic • Strongly basic polymeric structures, usually insoluble few applications Organomagnesium Compounds

  3. Grignards RMgX Direct synthesis ("Grignard reaction"): Mechanism is not simple! Almost certainly involves SET (Single Electron Transfer). Very sensitive to traces of impurities (Na, K, transition metals) in the Mg, and to the nature of the Mg surface. Organomagnesium Compounds

  4. Direct Synthesis Reactivity: I > Br > Cl >> F Selectivity: I gives largest amounts of side products In ethers • In Et2O cleaner than in THF, but also slower • Also in ether/hydrocarbon mixtures Side reactions: • Wurtz coupling • Radical rearrangements Organomagnesium Compounds

  5. Main application of Grignards:Addition to C=X Sometimes radical mechanism(especially for aromatic ketones) : Organomagnesium Compounds

  6. Complication in C=X addition:Reduction For Grignards having a b-hydrogen: Organomagnesium Compounds

  7. Grignards RMgX "Barbier reaction": • Selectivity differs from that of Grignard addition. • Probably radical mechanism. Organomagnesium Compounds

  8. RMgX en R2Mg "Schlenk" equilibrium: (is really more complicated) Shifts through addition of ligands: Organomagnesium Compounds

  9. MeMgBr(THF)3 Organomagnesium Compounds

  10. Me2Mg(pmdta) Organomagnesium Compounds

  11. (diiminate)MgMe Organomagnesium Compounds

  12. Me2Mg4Cl6(THF)6 Organomagnesium Compounds

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