Hydrophobic Control of Diastereoselectivity in the Synthesis of Double-Chain Surfactant Co(III) Complexes

A series of double-chain surfactant octahedral Co(III) complexes 1 − 4 has been prepared in both water and 20:1 (v/v) ethanol−water by the reaction of an N -alkylethylenediamine ligand ( 5 ) with sodium hexanitrocobaltate(III), followed by the addition of sodium perchlorate or sodium nitrate: trans -dinitro- cisoid -bis( N -alkylethylenediamine)cobalt(III) perchlorate ( 1 ) and nitrate ( 3 ), and trans -dinitro- transoid -bis( N -alkylethylenediamine)cobalt(III) perchlorate ( 2 ) and nitrate ( 4 ) (alkyl = hexyl, octyl, decyl, dodecyl, and hexadecyl). The cisoid 1 ( 3 )/t ransoid 2 ( 4 ) diastereomer ratio increased on going from 20:1 ethanol−water to water, in particular by a factor of approximately 5 for the octyl and dodecyl perchlorate systems and approximately 8 for the hexadecyl perchlorate system. The increase in the relative amount of cisoid 1 ( 3 ) is attributed to the hydrophobic effect associated with the aggregation of ligand 5 in water.