A New Class of Oligonuclear Platinum-Thallium Compounds with a DirectMetal2Metal Bond3. Unusual Equilibria in Aqueous Solution

M Maliarik, J Glaser, Imre Toth, Mateus Webba da Silva, L Zekany

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24 Citations (Scopus)

Abstract

A new series of four binuclear platinum-thallium cyano compoundscontaining a direct and unsupported by ligands metal2metalbond has been prepared in aqueous solution. Thesecompounds are represented by the formula[(NC)5Pt2Tl(CN)n21](n21)2 (n = 124 for compounds I, II, IIIIV, respectively) and [(NC)5Pt2Tl2Pt(CN)5]32 (for compoundV). The oligonuclear complexes are synthesised accordingto the reaction mPt(CN)422 + Tl3+ + nCN2 v [PtmTl-(CN)4m+n]322m2n. Thus, there occurs a change of the coordinationnumber of the Pt center from four (square planar) tosix (octahedral). Consequently, the formation of binuclearplatinum-thallium cyano compounds involves at least twosteps: (i) formation of metal2metal bond and (ii) formation of(NC)5Pt2 unit by a cyanide transfer process. 2 The complexes exist in an equilibrium, which also includes the parentcomplexes Pt(CN)422 and Tl(CN)n32n (n = 024), and can becontrolled by varying the cyanide concentration and/or pHof the solution. The stability constants of the compounds âN =[PtmTl(CN)4m+n322m2n] / {[Pt(CN)422]m· [Tl3+] ·[CN2]n} havebeen determined by means of multinuclear NMR (195Pt,205Tl): logâN = 19.9±0.4, 30.7±0.3, 38.6±0.3, and 44.8±0.2 forI, II, III, and IV (m = 1, n = 124), and 32.1±0.3 for V (m = 2,n = 2), respectively, (in 1 M NaClO4 as ionic medium, at 25oC). To our knowledge, the present work constitutes the firstdetailed equilibrium study of metal2metal bonded compounds;it indicates that also other cluster formation reactionsdescribed in the literature may represent real equilibria.
Original languageEnglish
Pages (from-to)565-570
JournalEuropean Journal of Inorganic Chemistry
Volume1998
Publication statusPublished - 1998

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