Synthesis, spectroscopic and structural aspects of mono- and diorganothallium(III) complexes of 2,6-diacetylpyridine bis(thiosemicarbazone) (H2DAPTSC) -: A new coordination mode of the HDAPTSC- anion

The reaction of 2,6-diacetylpyridine bis(thiosemicarbazone) (H(2)DAPTSC) with dimethylthallium hydroxide yielded the complexes [(TlMe2)(2)(DAPTSC)] and [TlMe2(HDAPTSC)]. The structure of [TlMe2(HDAPTSC)], determined by X-ray diffractometry, exhibits a hitherto unknown coordination model of the HDAPTSC(-) anion in which its deprotonated thiosemicarbazone chain coordinates one metal atom through its sulphur and hydrazinic N atoms while a second metal atom is weakly coordinated through the S atom of the undeprotonated thiosemicarbazone chain. Each thallium atom is coordinated in both ways, with the result that the [TlMe2(HDAPTSC)] units are linked in infinite helical chains in the direction of the b axis. When reacting with diphenylthallium(III) hydroxide, H(2)DAPTSC induced a dephenylation process which led to the monophenylthallium(III) complex [TlPh(DAPTSC)]. Recrystallization from acetone yielded crystals of [TlPh(DAPTSC)] C3H6O in which X-ray diffractometry showed DAPTSC(2-) to be pentadentate. coordinating through its sulphur, azomethine N and pyridine N atoms. The H-1, C-13 and Tl-205 NMR data of [TlPh(DAPTSC)] indicate that its solid state molecular structure persists in DMSO solution, while those of [TlMe2(HDAPTSC)] indicate rapid alternation between coordination of the metal atom to one of the HDAPTSC thiosemicarbazone chains and its coordination to the other.