Stereoselective formation and reactions of tetraalkylaurates(III)

Article abstract of DOI:10.1016/0022-328X(92)80159-U

Reactions of cis- (or trans-) dimethylalkyl(triphenylphosphine)gold(III), Au(R¹)(R²)R³)(PPh3) with alkyllithiums (R⁴Li) lead to selective displacement of the triphenylphosphine ligand by the alkyl anion to give square planar cis- (or trans-)tetraalkylaurates(III), 1)(R²)(R³)(R⁴)>^-Li⁺ (R¹ = Me, R² = R³ = Me or Et, R⁴ = Me, Et, nPr, iPr, nBu or Ph) in benzene.The reactions are stereoselective and no isomerization is observed.Rates of the reactions between the trialkylgold(II) complex and alkyllithiums are first order in the concentrationof the gold(III) complex, and an associative mechanism involving the neutral trimethylgold(III) complex and alkyllithiums for the formation of tetraalkylaurates(III) has been proposed as a result from the kinetic study.Hydrolyses of cis- or trans-dimethyldiethylaurates(III) in the presence of triphenylphosphine afford cis-methyldiethyl(triphenylphosphine)gold(III) or trans-dimethylethyl(triphenylphosphine)gold(III) with liberation of an equimolar amount of the corresponding alkane, reflecting the strong trans effect of the alkyl group in the reaction.Molecular structure of cis-methyldiethyl(triphenylphosphine)gold(III) has been unequivocally determined by X-ray structure analysis (monoclinic, P2₁/c, a 10.972(6), b 19.898(9), c 10.683(7) Angstroem, γ 112.42(4) deg, V 2156(2) Angstroem³, R = 7.8, R_w = 11.6 for 3947 reflections (<*>F₀<*> > 3<*>F₀<*>).