Technetium Tetrachloride as A Precursor for Small Technetium(IV) Complexes

Polymeric technetium tetrachloride reacts with monodentate donor ligands such as THF, acetonitrile, DMSO, thioxane
(1-oxa-4-thiacyclohexane), PMe2Ph, PPh3, OPPh3, or OH2 via cleavage of the polymeric network and the formation
of [TcCl4(L)2] complexes. The configuration of the products is dependent on the donor atoms such that trans
coordination is established with ‘soft' donor atoms such as sulfur or phosphorus, while cis-[TcCl4(L)2] complexes
are formed with the ‘harder' donors oxygen or nitrogen. The ambivalent thioxane binds to technetium via the sulfur
atom. The trans products are air stable and resistant to hydrolysis. The cis complexes, however, undergo stepwise
hydrolysis, during which complexes of the composition [Cl3(L)2TcOTc(L)2Cl3] (L = CH3CN, DMSO, or OH2) are
formed. They are the first representatives of a new class of technetium(IV) complexes with a bridging oxo ligand.
The Tc−O bond lengths in these bridges are between 1.803(1) and 1.823(2) Å.