Chasing the CMD/AMLA Mechanism C-H···Pd Interactions in the Cyclopalladation Reaction of N,N-Dimethylbenzylamine with Pd(OAc)₂

700 MHz ¹H NMR spectral examination of the reaction between Me₂NCH₂Ph and Pd(OAc)₂ in CDCl₃ reveals that several anagostic complexes form, but an agostic intermediate is not identified by way of a lowered ¹JC-H coupling constant. Density functional theory (DFT) calculations were used to compare characteristic features of the putative agostic intermediate when the acetato ligand C═O···H-C interaction is present as in the CMD/AMLA mechanism and when it is not. With the C═O···H-C interaction present, the agostic C-H bond is significantly longer, the H and C atoms are closer to the metal, natural bond orbital (NBO) analysis indicates that agostic C-Hσ orbital donation to Pd-based orbitals is significantly greater, π-syndetic donation is similar, and coulombic attraction between the agostic carbon and the Pd center is greater as is the repulsion between the H and Pd atoms. Whether the C═O···H-C interaction is present or not, the electron withdrawal substituents SO₂Cl and NO₂ at the para position of the ligand on energy minimization reduce the effect of the interaction, whereas the electron-donating groups B(OH)₃^- and NMe₂ give η¹-σ-lone pair donor complexes and S^- produces a Pd-C-H σ-bond. Overall, the presence of the C═O···H-C interaction enhances the agostic interaction produced during the reaction of the N,N-dimethylbenzylamine with Pd(OAc)₂, which gives credence to the importance of the AMLA mechanism.