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), th e 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 substit uents. This angular distortion is thought to encourage the partial los s of TMEDA from Mg centres in solution.