Synthesis, structure, and stereochemistry of double-chain surfactant Co(III) complexes

Double-chain surfactant octahedral Co(III) complexes 1 and 2 (X = ClO4) (a, R = C6H13; b, R = C8H17; c, R C10H21; d, R - C12H25; e, R = C14H29, f, R = C16H33) were synthesized in H2O and 20:1 (v/v) EtOH-H2O by the reaction of RNHCH2CH2NH2 (5) with Na3Co(NO2)(6), followed by the addition of NaClO4. The cisoid 1/transoid 2 diastereomer ratio increased upon going from EtOH-H2O to H2O, in particular by a factor of approximate to5 for the octyl and dodecyl systems and approximate to8 for the hexadecyl system. The increase in the relative amount of cisoid 1 was attributed to the hydrophobic effect associated with the aggregation of ligand 5 in H2O. Surfactant complexes 3 and 4 (X = NO3) were also prepared in EtOH(MeOH)-H2O. The characterization of 1-4 included single-crystal X-ray diffraction studies of 1e and 3a, measurement of their Krafft temperatures, and demonstration of the cleavable nature of 3a and 4a.