Novel functionalised phosphines relevant to the methoxycarbonylation of ethylene

Abstract

Several novel o-xylene bridged diphosphine ligands have been synthesised, and their activity tested in the palladium catalysed methoxycarbonylation of ethylene. Particular interest has been paid to the synthesis of phosphine ligands with tertiary-alkyl groups pendant to the phosphorus atoms. Results obtained from catalysis compare favourably with ligand systems described in the chemical literature, with l,2-Z>/s(di-l-adamantylphosphinomethyl)benzene and l,2-Z>/5(di-l-methylcyclopentylphosphinomethyl)benzene providing highly active catalyst systems, with selectivity towards methylpropionate. Alternative synthetic strategies are described, which have provided novel routes to the phosphines of interest. These methodologies having increased the scope of phosphine ligand synthesis with di-terr/ary-alkyl substituted species. Several complexes of the new ligands have been prepared and characterised, giving insight into the properties of the novel ligands