Palladium N(CH₂CH₂PiPr₂) ₂-Dialkylamides: Synthesis, structural characterization, and reactivity

Palladium(II) aminodiphosphine PNP pincer complexes [PdR(PNP^H )]PF6 (1^R; R ) Cl Me, Ph; PNP^H ) HN(CH₂CH ₂P'Pr₂)₂) were prepared. Deprotonation with KO'Bu affords dialkylamides [PdR(PNP)] (2^R; R ) Cl Me, Ph; PNP = (NCH₂CH₂P'Pr₂)₂) in high yield which are stable toward ß-H elimination. While AgPF₆ oxidizes the amides, cationic amido complexes [PdL(PNP)]PF₆ (3^L; L = CN'Bu, PMe₃) were obtained upon chloride abstraction from 1 ^Cl with TlPF₆. The reaction of amide 2^Cl with MeOTf results in A/-methylation yielding [PdCl(PNP^Me)]OTf (5) quantitatively. N-H acidities of the amino complexes 1^Me (pk = 24.2(1)) and 1^Ph (pk = 23.2(1)) were determined in dmso. Complexes 1^Cl, 1^Me, 2^Cl 2^Me, 3 ^CNIBu, and 5 were structurally characterized by single crystal X-ray diffraction. The amido complexes feature pyramidal nitrogen atoms in the solid state. The molecular structures, high A/-basicity, and reactivity of the amido complexes can be explained with Pd-N^amido bonding that is characterized by strong N→Pd σ-donation and repulsive dπ-pπ π-interactions. This interpretation was confirmed by density functional theory (DFT) calculations of 2^Cl.