Carbene complexes. Part II. Thermally-induced isomerisations of trans-platinum(II) and palladium(II) complexes and the chemistry of the cis- and trans-isomers

Abstract

trans-Dihalogenoplatinum(II) or palladium(II)(carbene) complexes are isomerised either thermally or in polar solvents to the thermodynamically more stable cis-isomers. Reactivity decreased from Pd^II to Pt^II and with increasing n-alkyl chain-length of a tertiary phosphine trans to the carbene ligand. Properties of cis- and trans-carbene complexes are compared and certain generalisations emerge. Dichloro-complexes undergo Cl^– displacement (cis- more readily than trans- and Pd^II more than Pt^II) by Br^–(LiBr), Me^–(LiMe), H^–(Et₃SiH), and PR₃(NaBF₄/PR₃). trans-Hydrido(chloro)platinum(II) and dimethylplatinum(II) carbene complexes are of particular interest.