Acetylides of cycloplatinated ferrocenylamines; synthesis and redox chemistry

Abstract

Sonogashira coupling of a terminal alkyne with cycloplatinated ferrocenylamine complexes gave the acetylides Pt{[RCC][Me₂NCH₂(σ-Fc)]dmso}, which were characterised by analysis, spectroscopy and, for the R = SiMe₃3, Fc 5 complexes, X-ray structural analyses. A butadiyne complex was also isolated in reactions of 3. Equivalent reactions with LDA led to an unusual deplatination reaction to give the ethynylferrocenylamine. The Pt(II) centre functions as a redox switch at E^+/0 = ∼0.21 V and the spectroscopic and electrochemical data show that the acetylide is a π-donor ligand. There is a strict delineation of the electronic requirements for the trans Pt–N and trans Pt–C(Cp) groups in these cycloplatinated compounds. Oxidation of 3 gives rise to low energy bands based on the Pt(II) unit; an additional broad band at 1100 nm occurs in 5⁺ but not 5²⁺.