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

700 MHz H-1 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 (1)JC-H coupling constant. Density functional theory (DFT) calculations were used to compare characteristic features of the putative agostic intermediate when the acetato ligand C & boxH;OH-C interaction is present as in the CMD/AMLA mechanism and when it is not. With the C & boxH;OH-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-H sigma orbital donation to Pd-based orbitals is significantly greater, pi-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 & boxH;OH-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 eta(1)-sigma-lone pair donor complexes and S- produces a Pd-C-H sigma-bond. Overall, the presence of the C & boxH;OH-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.