A comparative study of the reactivity of the σ(Pd-Csp2,ferrocene) and σ(Pd-Csp2,biphenyl) bonds in cyclopalladated complexes derived from [Fe(η5-C5H5)(η5-C5H4CH=NC6H4C6H5-2)]

A study has been made of the reactivity of the sigma (Pd-C-sp(2)) bond in the di-mu -chloro-bridged cyclopalladated complexes [Pd{(eta (5)-C5H3CH=NC6H4C6H5-2)Fe(eta (5)-C5H5)}(mu -Cl)](2) 1a and [Pd{(C6H4-2-C6H4)N=CH(eta (5)-C5H4)Fe(eta (5)-C5H5)}(mu -Cl)](2) 1b {which differ in the nature of the metallated carbon atom C-sp(2),(ferrocene) or C-sp(2),(biphenyl), respectively} towards the alkynes, (RC)-C-1=CR2 {with R-1=R-2=Et; R-1=H, Me or Ph, and R-2=Ph; or R-1=R-2=CO2Me}. Thus palladacycles containing seven-, eight-, nine- and ten-membered rings have been isolated and characterized. The crystal structure of [Pd{(EtC=CEt)(2)(C6H4-2-C6H4)N=CH(eta (5)-C5H4)Fe(eta (5)-C5H5)}Cl] has also been determined and confirms the presence of a [6, 6, 10] tricyclic system arising from fusion of the two hexagonal rings of the biphenyl group and a ten-membered palladacycle generated through bis(insertion) of hex-3-yne into the sigma (Pd-C-sp(2),(biphenyl)) bond in 1b.