Synthesis, structures, and spectra of cobalt(III) complexes of the novel branched cyclic ligands 6-methyl-6-(4-amino-2-azabutyl)-1-thia-4-azacycloheptane and N-(2-aminoethyl)-3-methyl-3-(4-amino-2-thiabutyl)azetidine

Abstract

The preparation and properties of two cobalt(III) complexes, [Co(atac)(en)](NO)(C10)and [Co(amta.)(en)]ICl, are described, where atac is 6-methyl-6-(4-amino-2-azabutyl)-l-thia-4-azacycloheptane, amta is A-(2-aminoethyl)-3-methyl-3-(4-amino-2-thiabutyl)azetidine, and en is ethylenediamine. Both atac and amta arise from reaction between en and the benzenesulfonate of 2-methyl-2-(4-phthalimido-2-thiabutyl)-1,3-propanediol. The absolute configuration of one of the enantiomeric forms of [Co-(amta)(en)]([co(cHNS)]C1I) with ΔE= -2.61 Mcmhas been determined by single-crystal X-ray diffraction techniques (orthorhombic; space group P222; a = 11.657 (2), b = 11.670 (2), c = 14.870 (2) A; Z = 4; R = 0.036) and the complex shown to be Δ-[Co(amta)(en)]. The crystal structure of [Co(atac)(en)](NO)(ClO)([Co(CHHS)](NO)(ClO)) is also reported (monoclinic; space group P2/c; a = 9.054 (2), b = 17.561 (3), c = 14.506 (2) A; β = 92.23 (1)°; Z = 4; R = 0.059). In each case the cobalt(III) ion is surrounded by five nitrogen donors (three from atac or amta; two from en) and the thioether atom. The effects of complexation of the strained four-membered azetidine and seven-membered 1,4-disubstituted cycloheptane rings manifest themselves in long Co-N bonds associated with the nitrogen donors of the strained rings (Co(l)-N(2) = 1.99 A in [Co(amta)(en)]and Co(l)-N(l) = 2.05 A in [Co(atac)(en)]), shifts in the ligand field absorption spectra compared to those of other Co(NS)cobalt(III) complexes, and unusual chemical shifts observed in theC NMR spectra.