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 ≈5 for the octyl
and dodecyl systems and ≈8 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.