The synthesis, reactions, and dynamic behaviour of allyl(cyclopentadenyl)platinum complexes

Abstract

Reaction of [PtCl(σ-allyl)(cod)][allyl = CH₂CHCH₂, CH₂C(Me)CH₂, CH₂CHCHMe, or CH₂CHCHPh; cod = cyclo-octa-1,5-diene] with Tl[C₅H₅] affords the crystalline complexes [Pt(η³-allyl)(η-C₅H₅)]. In the case of the cinnamyl ligand the precursor, [Pt(σ-CH₂CHCHPh)(cod)(σ-C₅H₅)], of the η³-allyl species could be isolated as an orange crystalline material. Treatment of the η³-allylic species with an excess of CNBu^t affords the complexes trans-[Pt(CNBu^t)₂(σ-allyl)(σ-C₅H₅)], there being no evidence for the intermediacy of isocyanide analogues of [Pt(CO)(σ-allyl)(η-C₅H₅)]. The trans-isocyanide complexes rearrange in solution to give thermodynamically controlled mixtures whose major component is the cis isomer. The mechanisms of these reactions are discussed, together with the ¹H and ¹³C n.m.r spectra of the complexes isolated.