Sulfur- and Carbon-Bonded Forms of the Cobalt(III) Complex With the Ligands 2-Aminoethyl 3-Aminopropyl Sulfide and 1,1,1-Tris(aminomethyl)ethane

Abstract

The new sulfur-bonded compound [Co(tame)( aeaps )] Cl₃.H₂O has been synthesized by the reaction of aeaps with Co(tame)Cl₃ [tame = 1,1,1-tris( aminomethyl )ethane, and aeaps = 2- aminoethyl 3-aminopropyl sulfide or 3-thiahexane-1,6-diamine]. The Co(tame)( aeaps )³⁺ ion equilibrates in basic solution with the corresponding carbon-bonded species:

Co(tame)( aeaps )³⁺+HO^-↔ Co(tame)(C-aeaps )²⁺+H₂O

A salt of the carbon-bonded species, [Co(tame)(C- aeaps )](S₂O₆), has been isolated and its structure solved by X-ray diffraction analysis ( C- aeaps = 1,6-diamino-3-thiahexan-4-ide). The crystals are orthorhombic, Pna2₁, with cell dimensions a 20.455(10), b 9.960(10), c 8.982(10) Ǻ at 122(2) K.

Preliminary thermodynamic and kinetic data are similar to the recently reported values for the corresponding coordination ion Co( tacn )( aeaps )³⁺ ( tacn = 1,4,7-triazacyclononane). In basic solution the Co(tame)( aeaps )³⁺ species exchanges one of its methylene protons orders of magnitude faster than any other methylene protons and also much faster than it forms the alkyl complex as shown by ¹³C n.m.r. measurements.