Stabilization of poly-iodides: structural influences of the cationic disulfides of 2-mercapto-3,4,5,6-tetrahydro-pyrimidine and 2-mercatpo-pyrimidine

Abstract

The reaction of 2-mercapto-3,4,5,6-tetrahydro-pyrimidine (tHPMT) or 2-mercaptopyrimidine (PMTH) with hydroiodic or hydrochloric acids in the presence or absence of di-iodine in dichloromethane solutions resulted in the formation of complexes with formulae [2{(tHPMT)₂²⁺} 2(I⁻) (I₄²⁻)] (1), [2{(tHPMT)₂²⁺} Cl⁻ 3(I₃⁻)] (2), [6{(tHPMT)₂²⁺} 3(Cl⁻) 2(I⁻) 5(I₃⁻)] (3) and [2{(PMTH₂)⁺} I₄²⁻] (4). The compounds were characterized by FT-IR, and Raman spectroscopic techniques. The crystal structures of 1–4 were also determined by X-ray diffraction. Complexes 1 and 4 contain tetra-iodides di-anions (I₄²⁻) as counter parts. The linear geometry of tetra-iodides species is broken in case of 1 and the deviation from the linearity for this di-anion is greater than in any such molecule described thus far. Moreover in complex 3 with a hexa-iodide di-anion, (I₆²⁻) is detected by considering the distance of 3.67 Å as a bonding interaction.