Reactions of dialkylaurate(I) with electrophiles: synthesis of trialkylgold(III) compounds

Abstract

The formation of new dialkylaurate(I) species from alkylgold(I) complexes and alkyl-lithium is described. Lithium dimethyl(triphenylphosphine)aurate(I) is stable only in ether solutions, but the crystalline bis-pyridine analogue can be isolated. A variety of mixed primary, secondary, and tertiary dialkylaurate(I) analogues can also be prepared in situ and reacted directly with alkyl halides in the convenient synthesis of trialkylgold(III) complexes. The stereospecific synthesis of trans- or cis-alkyldimethyl(triphenylphosphine)gold compounds is possible from the reaction of dimethyl(triphenylphosphine)aurate(l) and alkyl halide or cis-dimethyliodo(triphenylphosphine)gold and alkyl-lithium, respectively. Bromination and protonolysis of dialkylaurate(I) proceed readily at 0 °C. The lack of selectivity in the cleavage of mixed alkylmethylaurate(I) with hydrogen chloride suggests that it proceeds by oxidative addition, in contrast with the direct proton transfer to the alkyl ligand as in many other electrophilic cleavages. Unsuccessful attempts to add alkenes and co-ordinated olefinic ligands to dialkylaurate(I) are described.