Transfer of cyclopentadienyl groups between platinum atoms

Abstract

Replacement of a chloride ion of cis-[PtCl₂(CO)(PR₃)](PR₃= tertiary phosphine) by a cyclopentadienyl group from Tl(C₅H₅) or Hg(C₅H₅)₂ results exclusively in the isomers of [PtCl(σ-C₅H₅)(CO)(PR₃)] with C₅H₅trans to PR₃. The second chloride can be replaced when excess Tl(C₅H₅) is used. The σ-bonded cyclopentadienyl groups of either mono- or di-substituted compounds can readily exchange in solution with a chloride of cis-[PtCl₂(CO)(PR₃)] again producing exclusively the same isomers of [PtCl(σ-C₅H₅)(CO)(PR₃)]. The cyclopentadienyl groups do not transfer as fast as chloride ions between the same species, but do so considerably faster than any accompanying CO scrambling processes. Cyclopentadienyl groups from the σ-bonded complexes, and from [Pt(η⁵-C₅H₅)(PR₃)₂]Cl, can also be readily transferred to mercury when treated with HgCl₂.