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

Abstract

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.