Synthesis of organocobalt complexes via cobalt I reagents

Despite the sensitivity of cobalt(I) reagents to air oxidation, the extremely high nucleophilicity of these reagents makes them attractive substrates for alkylation reactions. Since cobalt(I) reagents must always be prepared in situ from complexes in a higher oxidation state, this route is commonly referred to as reductive alkylation. 

All cobalt(I) nucleophiles (Eqn. 4) as well as their conjugate acids (Eqn. 5) react rapidly with alkyl halides to produce the appropriate alkyl cobalt complexes. 

Kinetic studies of the reactions of cobalt(I) nucleophiles with alkyl halides [45] are consistent with an 8, 2 mechanism for these reactions. Indeed, inversion of configuration at the displacement center has been observed both for secondary [46] and primary [47,48] alkylating agents. However, for some alkylating agents for which inversion of configuration is not possible [44,49] as well as in certain other instances 

Both cobalt(I) supernucleophiles (Eqn. 8) and hydridocobalt species (Eqn. 9) will 

Co (Chelate)L-+ XCH=CH2 XCH2CH2Co(Chelate)L HCo(Chelate)L + XCH=CH2 CH3CHXCo(Chelate)L 

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