It Is Not All about the Ligands: Exploring the Hidden Potentials of tBu(3)P through Its Oxidative Addition Complex as the Precatalyst

A series of oxidative addition complexes with a generalformula(tBu(3)P)Pd(Ar)X, as a class of precatalysts,were synthesized for challenging Suzuki-Miyaura coupling involvingcoupling partners, such as (i) sensitive polyfluorinated arylboronicacids or their corresponding boronic esters, (ii) sterically hinderedelectrophiles, and (iii) sterically hindered nucleophiles. A totalof 89 examples are reported, of which 39 examples are in the SupportingInformation. These precatalysts, in particular (tBu(3)P)Pd(4-CF3Ph)Br, were demonstrated to bepowerful catalytic systems in general for cross coupling reactionsin comparison to the in situ systems created by mixing tBu(3)P ligand with a palladium precursor. Theprecatalysts are also superior to the other monoligated systems, suchas Buchwald's biaryl based G3 or G4 palladacycles. In addition,the (tBu(3)P)Pd(4-CF3Ph)Br precatalystis also highly effective for the second most popular coupling reaction,namely the Buchwald-Hartwig coupling. In this study, hinderedand electron-deficient amines were coupled with hindered (hetero)arylbromides and chlorides with 34 examples, of which 8 are in the SupportingInformation. Interestingly, the results obtained for both C-Cand C-N couplings were on par with or superior to that of the"state-of-the-art" catalysts containing Ad(3)P and Np3P ligands for the same or similar substrates,suggesting that it is not all about the ligands.