José Vicente

Providing Support in Favor of the Existence of a PdII/PdIV Catalytic Cycle in a Heck‐Type Reaction

The complex [Pd(O,N,C-L)(OAc)], in which L is a monoanionic pincer ligand derived from 2,6-diacetylpyridine, reacts with 2-iodobenzoic acid at room temperature to afford the very stable pair of Pd(IV) complexes (OC-6-54)- and (OC-6-26)-[Pd(O,N,C-L)(O,C-C(6)H(4)CO(2)-2)I] (1.5:1 molar ratio, at -55u2009°C). These complexes and the Pd(II) species [Pd(O,N,C-L)(OX)] and [Pd(O,N,C-L)(NCMe)]ClO(4), (X = MeC(O) or ClO(3), L = another monoanionic pincer ligand derived from 2,6-diacetylpyridine), are precatalysts for the arylation of CH(2)=CHR (R = CO(2)Me, CO(2)Et, Ph) using IC(6)H(4)CO(2)H-2 and AgClO(4). These catalytic reactions have been studied and a tentative mechanism is proposed. The presence of two Pd(IV) complexes was detected by ESI(+)-MS during the catalytic process. All the data obtained strongly support a Pd(II)/Pd(IV) catalytic cycle.