Co-ordination chemistry of S-methyl 2-methyldithiocarbazate and formation of [M≡N]2+(M = Tc or Re) species

Reaction of [TcOCl4]- and [ReOCl3(PPh3)2] with S-methyl 2-methyldithiocarbazate [H2L = H2NNMeC(S)SMe] under mild conditions gave the oxo-technetium(V) and -rhenium(V) S,N-chelated complexes [MO(HL)2]Cl (M = Tc or Re). These were transformed to the corresponding nitrido-complexes [MNCl2(PPh3)2] under reflux and in the presence of HCl and PPh3. The technetium(IV) complex [TcCl4(PPh3)2] under reflux and in presence of an excess of H2L and NEt3 gave the nitrido-compound [TcN(HL)2]. This was also obtained when [TcNCl2(PPh3)2] was used as precursor in the presence of NEt3. The complex [TcNCl2{NPr(CH2CH2PPh2) 2}] reacted with an excess of H2L to give the monosubstituted compound [TcN(HL){NPr(CH2CH2PPh2)2}]X (X = Cl, BF4 or BPh4). A crystal structure determination of the complex [ReO(HL)2]Cl showed a distorted square-pyramidal geometry with the oxygen atom in apical position. The Cl- ion is bound to NH groups by means of two hydrogen bonds. A set of reactions using 99mTc were carried out in order to understand the formation of the 99mTcN core.