Synthesis and Spectral Studies on Metal Chelates of Heterocyclic Carboxaldehyde Thiosemicarbazones

National Chemical Laboratory, Poona-411 008 Manuscript received 18 September 1984, revised 16 August 1985, accepted 12 August 1986 Square-planar neutral metal chelates of aldehyde thiosemicarbazones of the type ML,. where M=NiII, PdlI or PtII and HL =thiosemicarbazone or 4-phenyl- or 4-­methytthlosemicarbazone of 2-furaldehyde or thiopbene-2-carboxaldehyde or o-nitro­benzaldehyde. have been synthesised and characterised. Jr. uv-visible. 1H and 13C nmr and polarographic techniques have been utilised to study and characterise the free ligands and their metal chelates. The data suggest that the heterocyclic carboxal­dehyde thiosemicarbazones exist predominantly in thioenol form in DMSO solutions or in solvents with pH ~7.7, and above. The ligands act as N, S bidentate chelating agents coordinating through the nitrogen(I) and the thiolate sulphur atom