X-ray crystal structures and the facile oxidative (Au-C) cleavage of the dimethylaurate(I) and tetramethylaurate(III) homologues

Dimethylaurate(I) has been prepared as the crystalline tetrabutylammonium s alt for comparison with the known tetramethylaurate(III) analogue. The line ar structure of dimethylaurate(I) and the square-planar structure of tetram ethylaurate(III) have both been confirmed by X-ray crystallography. One-ele ctron oxidation of dimethylaurate(I) by either ferrocenium or arenediazoniu m cations produces the metastable dimethylgold(II) intermediate, which can be trapped as the paramagnetic 9,10-phenanthrenequinone (PQ) adduct. Otherw ise, dimethylgold(II) is subject to rapid reductive elimination of ethane a nd affords metallic gold (mirror). The analogous oxidation of tetramethylau rate(III) by ferrocenium, arenediazonium, or nitrosonium cations also proce eds via electron transfer to generate the putative tetramethylgold(IV) inte rmediate. The highly unstable (CH3)(4)Au-IV spontaneously undergoes homolyt ic cleavage to produce methyl radical and the coordinately unsaturated trim ethylgold(III), which can be intercepted by added triphenylphosphine to aff ord (Me3AuPPh3)-P-III..