Formation of platinum–enamine complexes by reaction of Zeise's salt with secondary amines

Abstract

Enamine complexes of platinum [Pt(CH₂CHNRR′)Cl₂(NHRR′)] are obtained in the reaction of secondary amines [HNRR′= piperidine, HNEt₂, or HNMe(CHMePh)] with Zeise's salt K[Pt(η²-C₂H₄)Cl₃]. The enamine ligand results from addition of the amine to the platinum-bonded olefin and subsequent loss of two hydrogen atoms. In the case of HNMe(CHMePh)(which has two different alkyl substituents at the nitrogen atom) two isomeric enamine ligands can be formed (having configurations E and Z respectively). Isomer E(NMe group cis to the metal atom) is ca. ten times more favoured than the other and exhibits ⁵J(Pt–H) 12.5 Hz which is indicative of a through-space interaction between the methyl group and the metal.