1984 Volume 57 Issue 6 Pages 1494-1498
The crystal structure and the absolute configuration of the spontaneously resolved title complex cation, (−)500CD-[Co(aesei)(en)2]2+, has been determined by X-ray diffraction. The red crystalline needle was monoclinic, space group P21, a=9.572(4), b=10.410(3), c=8.838(5) Å, β=115.35(3)°, Z=2, and the final R value was 0.035 for 2358 independent reflections with |F0|>3σ(|F0|). The crystal used showed a negative CD value at 500 nm and had Δ configuration. The 2-aminoethaneseleninate is bound to the cobalt atom by the nitrogen and oxygen atoms, and the asymmetric selenium atom takes an S configuration. The value of the protonation constant (pKa) was determined to be 1.91±0.05, on the basis of the major absorption spectral change at 304 nm of the title complex by spectrophotometric titration (μ=1.0 mol dm−3 (NaClO4) and 25 °C). The electronic absorption and CD spectral behavior were compared with those of the related sulfinato complexes, in which the S-bonded sulfinato complex, (+)500CD-[Co(S(O)2CH2CH2NH2)(en)2]2+, was resolved in this work.
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