Argentate(i) and (iii) complexes as intermediates in silver-mediated cross-coupling reactions.

Despite the potential of silver to mediate synthetically valuable cross-coupling reactions, the operating mechanisms have remained unknown. Here, we use a combination of rapid-injection NMR spectroscopy, electrospray-ionization mass spectrometry, and quantum chemical calculations to demonstrate that these transformations involve argentate(i) and (iii) complexes as key intermediates.

First X-ray crystal structure and internal reference diffusion-ordered NMR spectroscopy study of the prototypical Posner reagent, MeCu(SPh)Li(THF)3.

Grow slow: The usual direct treatment of MeLi and CuSPh did not yield X-ray quality crystals of MeCu(SPh)Li. An indirect method starting from Me2CuLi⋅LiSPh and chalcone afforded the desired crystals by the slow reaction of the intermediate π-complex (see scheme). This strategy produced the first X-ray crystal structure of a Posner cuprate. A complementary NMR study showed that the contact ion pair was also the main species in solution.

Aldehydes and ketones form intermediate π complexes with the Gilman reagent, Me2CuLi, at low temperatures in tetrahydrofuran.

Typical aldehydes and ketones form π complexes with Me2CuLi at low temperatures in tetrahydrofuran. They range in stability from fleeting intermediates at -100 °C to entities that persist up to -20 °C. Three subsequent reaction pathways have been identified.

π-Complexes from acyl cyanides and lithium dimethylcuprate(I).

Rapid injection of pyruvonitrile or benzoyl cyanide into solutions of Me2CuLi in THF-d8 at -100 °C gave complexes that were stable at this temperature. 1D NMR with multiply labelled substrates ((13)C/(15)N) and 2D NMR ((1)H/(13)C) identified them as the first cuprate-carbonyl π-complexes.

Rapid injection NMR reveals η3 'π-allyl' Cu(III) intermediates in addition reactions of organocuprate reagents.

By using rapid injection NMR, it has now been possible to prepare and characterize the η(3) 'π-allyl' copper(III) intermediate that has been proposed for addition reactions of organocopper(I) reagents and α,ß-unsaturated carbonyl compounds.

Minimization of organocuprate complexity through self-organization: remarkable orientation effect in mixed cuprate π complexes.

They "know" where to go: a powerful orientation effect has been observed in complexes of mixed organocuprates [R(T)R(NT)CuLi] and substrates with C-C, C-N, and C-S double bonds (see scheme; Th=thienyl). The preferred geometry of the intermediate complex sets up the facile addition of R(T) to the double bond, rather than addition of the "dummy ligand", R(NT) .