Selective crystallization of di-sec-butylmagnesium. N,N,N',N'-tetramethylethylenediamine from solutions containing mixtures of normal-butyl and secondary-butyl isomers

Found to crystallise selectively from treatment of commercial (s)Bu((n)Bu)Mg solutions with N,N,N',N'-tetramethylethylenediamine (TMEDA), the complex ((s)Bu(2)Mg . TMEDA) is mononuclear in the crystal state and undergoes a solvation-desolvation equilibrium in arene solution. The crystal structure is noteworthy for the large C-Mg-C bond angle of 133.6(2)degrees, attributable to the branched nature of the alkyl substituents. This angular distortion is thought to encourage the partial loss of TMEDA from Mg centres in solution.