Acetylides of cycloplatinated ferrocenylamines; synthesis and redox chemistry

Sonogashira coupling of a terminal alkyne with cycloplatinated ferrocenylam ine complexes gave the acetylides Pt{[RC=C][Me2NCH2(sigma -Fc)]dmso}, which were characterised by analysis, spectroscopy and, for the R = SiMe3 3, Fc 5 complexes, X-ray structural analyses. A butadiyne complex was also isolat ed in reactions of 3. Equivalent reactions with LDA led to an unusual depla tination reaction to give the ethynylferrocenylamine. The Pt(li) centre fun ctions as a redox switch at E+/0 = similar to0.21 V and the spectroscopic a nd electrochemical data show that the acetylide is a ir-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 br oad band at 1100 nm occurs in 5(+) but not 5(2+).