Tetrahydrothiophene complexes of technetium(IV)

A technetium(IV) complex of the composition trans-[TcCl4(tht)2] (tht = tetrahydrothiophene) is formed during heating of K2TcCl6 in a mixture of tht and aqueous HCl. The thioether ligands are only weakly bonded and the red crystals slowly decompose under release of tht. The weak technetium–sulphur bonds are confirmed by Tc–S distances of 2.494(1) Å. The anionic thioether technetium(IV) complex [TcBr5(tht)]− is formed by the reaction of (NBu4)2[TcBr6] with neat tht. The tetrabutylammonium salt of the complex is indefinitely stable in air.