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 unsymmetrically substituted ligand 5-methyl-5-(4-amino-2-azabutyl)-3,7-dithianonane-1,9-diamine (N4S2) has been prepared. The complex reacts with formaldehyde and ammonia, and formaldehyde and nitromethane, to form the encapsulated complexes [(8-methyl-6,10-dithia-1,3,13,16,19-pentaaza-bicyclo[6.6.6]icosane)cobalt(III)] perchlorate ([Co(AZAN4S2sar)](ClO4)3) and [(1-methyl-8-nitro-3,13-dithia-6,10,16,19-tetraazabicyclo[6.6.6]icosane)cobalt(III)] perchlorate ([Co(NON4S2sar)](ClO4)3), respectively. The nitro-substituted encapsulated metal complex is readily reduced to the NH3+-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, P2(1)2(1)2(1), a = 8.963 (2) angstrom, b = 13.293 (2) angstrom, c = 18.229 (6) angstrom, Z = 4, R = 0.030 (1756 F); crystals of the latter are monoclinic, space group, P2(1)/n, a = 15.669 (6) angstrom, b = 9.620 (2) angstrom, c = 17.772 (2) angstrom, beta = 105.26 (2)-degrees, 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(N6-nSn) complexes reveals that the net positive rotational strength for the A absolute configuration increases with the number of thioether groups coordinated to the metal.