Photochemical synthesis and characterization of linkage isomers of (2,4-dithiouracilato-N,S)bis(ethane-1,2-diamine or propane-1,3-diamine)cobalt(III) complexes

Abstract

Bis(diamine)cobalt(III) type complexes containing 2,4-dithiouracilate (dtuc^2–) have been photochemically prepared from robust [Co(diamine)₃]³⁺[diamine = ethane-1,2-diamine (en) or propane-1,3-diamine (tn)], H₂dtuc and NaOH. Column chromatography yielded two and three linkage isomers of [Co(dtuc)(en)₂]⁺ and [Co(dtuc)(tn)₂]⁺, respectively, which were characterized by elemental analysis, UV/VIS absorption and NMR spectroscopy. The crystal structure of [Co(dtuc)(en)₂]ClO₄(main product) was determined from 4952 unique reflections to R= 0.047 (R′= 0.045): space group Pa(monoclinic), a= 13.394(4), b= 8.819(3), c= 13.813(2)Å, β= 102.75(2)°, and Z= 4. The dtuc ligand co-ordinates through the 3-N and 2-S donors and the complex adopts an adjacent linkage form. A characteristic intramolecular hydrogen bond N–H ⋯ S [3.210(7)Å] was found between the 4-sulfur atom of the dtuc and an amine proton of en. Proton NMR spectroscopy showed that this hydrogen bond is present even in D₂O and (CD₃)₂SO solutions.