A Cationic Ag-I(PNPtBu) Species Acting as PNP Transfer Agent: Facile Synthesis of Pd(PNPtBu)(alkyl) Complexes and Their Reactivity Compared to PCPtBu Analogues

The straightforward Synthesis of cationic complex 1, [Ag(PNtBu)]BF4 (PNPtBu = 1,2-bis[(di-tert-butylphosphino)methyl]pyridine), and its facile transmetalating properties toward gold and palladium are described. The corresponding Au complex [Au(PNPtBu)](2)(BF4)(2) (2) exists its a dimer in the solid state, its deduced by X-ray crystallography. The transmetalating properties were expanded to include the formation of Pd-alkyl species. Reaction of I with 0.5 equiv of Pd(allyl)(mu-Cl) dirner led to clean formation of the [Pd(PNPtBu)(eta(1)-allyl)]BF4 complex 3. The analogous cationic methyl (4), cyanophenyl (5), and chloro species (6) could also be prepared in good yields from appropriate Pd Precursors Via this transmetalation methodology. The molecular structures for complexes 3-5 were established by X-ray crystallography. Reaction of complexes 4 and 6 with NaN(SiMe3)(2) led to deprotonation and dearomatization of the PNP backbone with formation of the neutral Pd species 7 and 8, which can be regarded as the diphosphino-rnonoamido N-ligated analogues of well-studied Pd(PCPtBu) complexes. These neutral Pd((PN-PtBu)) complexes 7 and 8 displayed reasonable activity in the Suzuki-Miyaura Coupling Of phenylboronic acid pinacol ester and bromoarenes.