Tetraorganylargentate(III) Complexes: Key Intermediates in Silver-Mediated Cross-Coupling Reactions

The
use of silver as a catalyst in cross-coupling reactions remains underdeveloped.
We show by means of electrospray-ionization mass spectrometry that
the diorganylargentates LiAgR′2·Li­(CN) (R′
= Me, Bu) formed in situ react with a wide scope
of alkyl and aryl halides RX to afford the tetraorganylargentate­(III)
complexes R′3AgR–. Upon fragmentation
in the gas phase, these high-valent species readily undergo reductive
elimination. The trimethylorganylargentates Me3AgR– furnish the synthetically desired cross-coupling products
MeR with high selectivity, whereas the tributylorganylargentates Bu3AgR– yield more of the homocoupling product
Bu2. Quantum chemical calculations reproduce the experimentally
observed trends in reactivity and moreover provide insight into the
structures and energetics of the species involved. Our findings indicate
that the facile formation of tetraorganylargentate complexes and their
high tendency toward reductive elimination can be exploited for the
development of silver-mediated cross-coupling reactions as a viable
alternative to established synthetic methods.