The [(CN)5Pt–Tl(edta)]4− complex, having direct metal–metal bond, has been prepared in solution by two different reactions: (a) dissolution of [(CN)5Pt–Tl](s) in aqueous solution of edta ligand, (b) from Pt(CN)42− and Tl(edta)(CN)2− reactants. The decomposition reaction is greatly accelerated by cyanide and significantly inhibited by edta. It proceeds through the [(CN)5Pt–Tl(CN)3]3− intermediate. This complex decomposes to Pt(CN)42− and Tl(CN)4−. To complete the reaction, Tl(CN)4− and edta4− react in relatively fast equilibrium step(s) giving Tl(edta)(CN)2−.The formation of [(CN)5Pt–Tl(edta)]4− complex can proceed via two different pathways depending on the ratio of the cyanide and the edta ligand. The ‘direct path’ at excess of edta means the formation of a [(CN)4Pt…Tl(CN)(edta)]4− intermediate followed by the release of the cyanide from the Tl-center than the coordination of a cyanide from the bulk to the Pt-center of the intermediate. The ‘indirect path’ dominates in the absence of extra edta and the formation of the Pt–Tl bond happens between Pt(CN)42− and Tl(CN)4− as studied earlier in our laboratories.