Structural motifs of diiodine complexes with amides and thioamides

Abstract

The reaction of 2-pyrimidone hydrochloride ([C₄H₅N₂O]⁺[Cl]⁻ or [PMOH₂]⁺[Cl]⁻) with diiodine in a dichloromethane–methanol solution resulted in the formation of ([C₄H₅N₂O]⁺)₂[I₂Cl₂]²⁻ (1) complex. The compound was characterized by elemental analysis, FT-IR, DTA-TG and conductivity titrations. The crystal structure of 1 was also determined by X-ray diffraction at 294(1) K. Compound 1 is monoclinic, space group P2₁/n, consisting of two cationic [PMOH₂]⁺ species and a [I₂Cl₂]²⁻ counter dianion. The cation is in its keto form. Direct reaction of thiazolidine-2-thione (tzdtH), with diiodine in dichloromethane solution, on the other hand, led to the formation of a crystalline solid which contained two complexes of formulae [(tzdtH)₂I]⁺[I₃]⁻·2I₂ (2) and [(tzdtH)I₂]₂·I₂ (2a) in a ratio of 90 to 10%. Complex 2a was characterized by X-ray analysis at 180(2) K. Compound 2a is monoclinic, space group C2/c and contains two units of [(tzdtH)I₂] “spoke” structures. Compound 1, as well as the known species iodonium salt [(tzdtH)₂I]⁺[I₃]⁻·2I₂ (2) and the charge transfer (CT) iodine complexes of formulae [(bztzdtH)I₂] (3) and [(bztzdtH)I₂]·I₂ (4) (bztzdtH = 2-mercaptobenzothiazole) with “spoke” and extended “spoke” structures respectively, were tested for their oxidizing activity towards 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone.