名称:
Synthesis, Crystal Structures, and Spectroscopic Characterization of Two Pairs of Racemic Isomers of [{Co2(aet)2}{Co(aet)3}2]4+ (aet = 2-Aminoethanethiolate): A Novel S-Bridged Tetranuclear Cobalt(III) Complex Formed by Ligand Transfer from Nickel(II) to Cobalt(III)
摘要:
A novel S-bridged tetracobalt(III) complex, [{Co-2(aet)(2)}{Co(aet)(3)}(2)](4+) (1), was prepared by reacting [Ni(aet)(2)] (aet = 2-aminoethanethiolate) with [CoCl(NH3)(5)](2+) Or [CoCl2(en)(2)](+) (en = ethylenediamine) in water. 1 formed two pairs of racemic isomers, la and Ib, which were separated by fractional crystallization and/or cation-exchange column chromatography. The crystal structures of la and Ib were determined by X-ray crystallography. la(NO3)(4).2H(2)O, empirical formula C16H52N12O14S8Co4, crystallizes in the triclinic space group P (1) over bar with a = 13.585(3) Angstrom, b = 15.132(3) Angstrom, c = 10.699(2) Angstrom, alpha = 101.46(1)degrees, beta = 104.78(1)degrees, gamma = 95.89(1)degrees, and Z = 2. 1b(NO3)(4).2H(2)O crystallizes in the monoclinic space group Cc with a = 26.633(6) Angstrom, b = 10.204(1) Angstrom, c = 15.907(4) Angstrom, beta = 110.33(1)degrees, and Z = 4. Each of la and 1b contains four cobalt atoms which are linked by one double and two triple sulfur bridges in a boat-type metal array. The two outer cobalt atoms have a fac-Co(N)(3)(S)(3) chromophore, while the two inner cobalt atoms have a Co(N)(S)(5) chromophore. The isomers possible for 1 are discriminated by a combination of the Delta or Lambda configuration for the outer cobalt centers and the C or A configuration for the inner cobalt centers, and X-ray analyses indicated that la and Ib have the Delta AA Delta/Lambda CC Lambda and Delta CC Delta/Lambda AA Lambda configurations, respectively. Each of la and Ib was optically resolved, and their electronic absorption, circular dichroism (CD), and NMR spectral properties are also reported. The additivity on CD was considered to assign the absolute configuration for the optically resolved isomers of 1a and 1b.