Mechanistic study on the coupling reaction of aryl bromides with arylboronic acids catalyzed by (iminophosphine)palladium(0) complexes. Detection of a palladium(ii) intermediate with a coordinated boron anion

Bruno Crociani, Simonetta Antonaroli, Alessia Marini, Ugo Matteoli, Alberto Scrivanti
2006 Dalton Transactions  
3 and activated olefins (ol = dmfu, fn), the latter compounds react with an excess of 4-R 2 C 6 H 4 B(OH) 2 (R 2 = H, Me, OMe, Cl) to give [Pd(g 2 -ol)(P-N)] and the corresponding biaryl through transmetallation and fast reductive elimination. The transmetallation proceeds via a palladium(II) intermediate with an O-bonded boron anion, the formation of which is markedly retarded by increasing the bulkiness of R. The intermediate was isolated for R = CHMe 2 , R 1 = CF 3 and R 2 = H. The boron
more » ... = H. The boron anion is formulated as a diphenylborinate anion associated with phenylboronic acid and/or as a phenylboronate anion associated with diphenylborinic acid. In general, the oxidative addition proceeds at a lower rate than transmetallation and represents the rate-determining-step in the coupling reaction of aryl bromides with arylboronic acids catalyzed by [Pd(g 2 -dmfu)(P-N)].
doi:10.1039/b514405a pmid:16804582 fatcat:ylhqn4rgr5ftbi5zllbf3h7nca