Ligand-exchange reactivity patterns of oxotechnetium(V) complexes

The ligand-exchange reactions of various oxotechnetium(V) complexes with 1,2-dithiols have been investigated. The complexes (TcO(OCH/sub 2/CH/sub 2/O)/sub 2/)/sup -/(1), (TcO(O/sub 2/C/sub 6/H/sub 4/)/sub 2/)/sup -/(2), and (TcO(SCH/sub 2/CH/sub 2/O)/sub 2/)/sup -/(3) all react with 2 equiv of 1,2-ethanedithiol to ultimately form (TcO(SCH/sub 2/CH/sub 2/S)/sub 2/)/sup -/(4). However, different mechanisms and/or intermediates are observed in each case. The reaction of 1 proceeds without evidence for the formation of intermediates. In the reaction of 2, an intermediate is detected, which is probably a mixed-ligand oxotechnetium monomer; and in the reaction of 3 the spectrum of the intermediate formed is similar to that of the dimer species ((TcO)/sub 2/(SCH/sub 2/CH/sub 2/S)/sub 3/) (5). The relation of these results to ligand-exchange reactions of 1,2-dithiols with citrate complexes of technetium is discussed. Reaction of 1,3-propanedithiol with (TcOCl/sub 4/)/sup -/ gives a compond formulated as ((TcO)/sub 2/(SCH/sub 2/CH/sub 2/CH/sub 2/S)/sub 3/), which does not react with further amounts of ligand to form the bis(1,3-dithiolato) monomer, as would be anticipated from the sequential formation of 4 from 5 in the reacton of (TcOCl/sub 4/)/sup -/ with 1,2-ethanedithiol.