A Route to Pd^o from Pd^II Metallacycles in Animation and Cross-Coupling Chemistry

Pd^II/Pd^IV or Pd^II/Pd⁰? The unusual Pd^II catalyst 1 was reduced to a Pd⁰ complex by reaction with an amine and a base. β-Hydrogen elimination and subsequent CH bond-forming reductive elmination generate a coordinated tris(o-tolyl)phosphane. The same palladium(II) metallacycle was reduced to Pd⁰ in a cross-coupling reaction by CC bond-forming reductive elimination to form coordinated P(oTol)₂-(C₆H₄CH₂Ar). Thus, these compounds can react by a Pd^II/Pd⁰-containing catalytic cycle.