Photochemistry of Cobalt(III) Complexes. II. Cobalt(III) Complex with a Co–C–S Three-Membered Ring Prepared by Photodecarboxylation of 2,2′-Thiodiacetato Complex. Crystal Structure of (−)537CD-fac-trans(NH,O)-[Co(CH2SCH2COO)(dien)]ClO4

The diethylenetriamine (dien) cobalt(III) complex with a three-membered ring, fac-trans(NH, O)-[Co(CH2SCH2COO)(dien)]+ (1), has been prepared in an aqueous solution by the photodecarboxylation of u-fac- (2) or s-fac-[Co(2,2′-thiodiacetato)(dien)]+ (3). Perchlorate salt of 1 was subject to spontaneous resolution, and the crystal structure and absolute configuration for the isomer were determined by X-ray diffraction. The crystal is monoclinic, space group P21, a = 6.962(1), b = 13.411(1), c = 7.663(1) A, β = 101.921(8)°, V = 700.1(2) A3, Z = 2, and R = 0.032. The formation of the three-membered ring introduces a significant distortion into the octahedral coordination around the Co atom (∠C–Co–S = 49.4(1)°), although the bond lengths in the ring are within the range normally observed for other complexes. For the isomer the chiral configuration is regulated to ΔΛΔ and R for the sulfur atom. The racemization rate of 1 is very fast in water and DMSO. The position of the first d–d band of 1 is red-shifted by 16...