Synthesis and Spectroscopic Properties of the Encapsulated Cobalt(III) Complexes Derived from the Unsymmetrically Substituted Ligand 5-Methyl-5-(4-Amino-2-Azabutyl)-3, 7-Dithianonane-1, 9-Diamine (N4S2)

The cobalt(III) complex of the unsymmetricallysubstitutedligand5-methyl-5-(4-amino-2-azabutyl)-3, 7-dithianonane-1, 9-diamine (NS) has been prepared. The complex reacts with formaldehyde and ammonia, and formaldehyde and nitromethane, to form the encapsulated complexes [(8-methyl-6, 10-dithia-l, 3, 13, 16, 19-pentaaza-bicyclo[6.6.6]icosane)cobalt(III)] perchlorate ([Co(AZANSsar)](ClO)) and [(l-methyl-8-nitro-3, 13-dithia-6, 10, 16, 19-tetraazabicyclo[6.6.6]icosane)cobalt(III)] perchlorate ([Co(NONSsar)](ClO)), respectively. The nitro-substituted encapsulated metal complex is readily reduced to the NH -substituted compound; this substituent is replaced to form, successively, chloro- and proteo-capped complexes. The uncapped and the nitro-capped complexes have been characterized by single-crystal X-ray study: crystals of the former complex are orthorhombic, space group, P222, a = 8.963 (2) Å, b = 13.293 (2) Å, c = 18.229 (6) Å, Z = 4, R = 0.030 (1756 F); crystals of the latter are monoclinic, space group, P2/n, a = 15.669 (6) Å, b = 9.620 (2) Å, c = 17.772 (2) Å, β = 105.26 (2)°, Z = 4, R = 0.040 (3317 F). The octahedral ligand-field parameters 10Dq and B are progressively reduced as the number of thioether donors increases, a result of the increased covalency associated with the thioether coordination. Comparison of the solution circular dichroism for Co(NS) complexes reveals that the net positive rotational strength for the A absolute configuration increases with the number of thioether groups coordinated to the metal