[PtCl2(phen)] reacts with thiosemicarbazones derived from β-diketones (H2LR) leading to an intramolecular C-C coupling between phen and the ketone upon formation of tetradentate N,N,N,S chelates [PtII(LRphen)]. The reactions proceed via bidentate coordination of the doubly deprotonated (LR)2- followed by an intra-nucleophilic attack and consecutive C-C bond formation.