Synthesis and reactivity of hydroxo-bridged binuclear platinum complexes. Crystal structure of [NBu4]2[{Pt(C6F5)2(µ-OH)}2]

Abstract

The reaction of [NBu₄]₂[{Pt(C₆X₅)₂(µ-Cl)}₂] with NBu₄OH(aq) in acetone leads to the formation of the hydroxo-complexes [NBu₄]₂[{Pt(C₆X₅)₂(µ-OH)}₂](X = F 1 or Cl 2). These react with weak protic acids such as acetylacetone (Hacac), benzoylacetone (Hbzac) and 8-hydroxyquinoline (Hquin) yielding the mononuclear complexes [NBu₄][Pt(C₆X₅)₂(L–L)](X = F, L–L = acac 3, bzac 4, or quin 5; X = Cl, L–L = acac 6, bzac 7, or quin 8). Treatment of complexes 1 and 2 with PhCN in the presence of HBF₄ gives the mononuclear compounds cis-[Pt(C₆X₅)₂(PhCN)₂](X = F 9 or Cl 10). When the benzonitrile complexes are treated with aniline the corresponding cis-[Pt(C₆X₅)(NH₂Ph)₂](X = F 11 or Cl 12) are formed. The benzamido derivatives [NBu₄][Pt(C₆X₅)₂(HNOCPh)(H₂O)](X = F 13 or Cl 14) are formed when complexes 9 and 10 are treated with NBu₄OH(aq) in acetone, and thermal treatment of 13 yields [NBu₄]₂[{Pt(C₆F₅)₂(µ-HNOCPh)}₂]15. Complexes 9 and 10 react with methanol in the presence of NBu₄OH to give the corresponding imido ester derivatives [Pt(C₆X₅)₂{HNC(OMe)Ph}₂](X = F 16 or Cl 17). Spectroscopic (IR, ¹H and ¹⁹F) data have been used for structural assignments, and an X-ray structure determination carried out for [NBu₄]₂[{Pt(C₆F₅)₂(µ-OH)}₂] has established the centrosymmetric binuclear nature of the anion [(C₆F₅)₂Pt(µ-OH)₂Pt(C₆F₅)₂]^2–. The structure has been solved and refined up to R= 0.049 and R′= 0.056 based on 2278 observed reflections. The Pt atoms are four-co-ordinated and show slight deviations from a square-planar arrangement.