NEW CLASS OF OLIGONUCLEAR PLATINUM-THALLIUM COMPOUNDS WITH A DIRECT METAL-METAL BOND - 2 - STRUCTURAL CHARACTERIZATION OF THE COMPLEXES

A new series of four binuclear platinum-thallium cyano compounds conta ining a direct and unsupported by ligands metal-metal bond has been pr epared in aqueous solution. The structure of these compounds represent ed by the formula [NC)(5)Pt-T1(CN)(n-1)]((n-1)-) (n = 1-4 for compound I, II, III, and IV, respectively) was determined by means of multinuc lear NMR (Pt-195, Tl-205, C-13) supported by Raman spectroscopy. In ad dition, a trinuclear complex with the formula [(NC)(5)Pt-Tl-Pt(CN)(5)] (3-) is formed in solutions where the Pt/Tl ratio is larger than 1. Th e compounds exhibit very large one-bond Pt-195-Tl-205 spin-spin coupli ng constants, 25-71 kHz; the value for compound I, 71 060 Hz, is the l argest reported coupling constant between two different nuclei. The po ssible reasons for this strong coupling, as well as its variation alon g the series of the binuclear compounds I-IV, are discussed in terms o f the metal-metal bond strength, varying participation of s-electrons in this bond and oxidation state of the metal ions.