Technetium diazenido-complexes. Part 2. Substitution chemistry of [TcCl(NNC6H4Cl-4)2(PPh3)2] and the synthesis of technetium diazenido-complexes directly from [NH4][TcO4]

The bis(diazenido)technetium(III) complex [TcCl(NNR)2(PPh3)2](R = C6H4Cl-4) reacted with bidentate ligands L with loss of one diazenide ligand to give [Tc(NNR)L2(PPh3)](L = S2CNR2) and [TcCl(NNR)L(PPh3)2](HL = maltol) in high yield. With dianionic tetradentate ligands L′ complexes of the type cis-[Tc(NNR)L′(PPh3)][L′= dianion of N,N′-bis(salicylidene)ethane-1,2-diamine (salen), S(CH2)2NMe(CH2)2NMe(CH2)2S or O2S(CH2)2NMe(CH2)2NMe(CH2)2SO2] were obtained. The crystal structure of the complex with L′= salen has been determined. It shows pseudo-octahedral co-ordination about the Tc with the NNR and PPh3 ligands cis. Direct reaction of [TcO4]– with arylhydrazine hydrochlorides generated a diazenide species in situ which reacts with S2CNR2 to give [TcCl(NNR)2(S2CNR2)2] and 2,2′-bipyridine (bipy) to give [TcCl(NNR)(bipy)2]+ isolated as a BPh4– salt.