The existence and structure, (I), of strong sparteine R2Mg complexes, which undergo inversion, carbon-magnesium bond exchange, and magnesium ligand exchange unusually slowly, have been established by n.m.r. studies.

of the solvent, the residue was recrystallized from chloroformethanol, white needles, mp 239°(lit.27 239-240°), 92% after recrystallization. The uv absorption spectrum agreed with that published for DPP.9Techniques and apparatus used for voltammetry and coulometry have previously been described.11.28 TFA was reagent grade and used without further purification. Reagent grade dichloromethane was passed through a column of neutral aluminum immediately before use. Reagent grade TPE was recrystallized before use.

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