Experimental Gas-Phase and in Silico Investigation of β-Methyl Elimination from Cationic Palladium Alkyl Species

Abstract

Herein we disclose experimental and in silico gas-phase studies of β-methyl and β-hydride elimination from cationic diphosphine palladium(II) neopentyl and isobutyl complexes. In particular, we have determined activation barriers for these transformations through mass-spectrometric threshold collision-induced dissociation (T-CID) studies. These systems can undergo at least one of the several competitive processes: (1) β-methyl elimination, (2) Pd–C bond homolysis, or (3) β-hydride elimination. We also confirm that qualitative trends in the branching ratios between these processes depend on the diphosphine bite angle, whereas electronic modifications of phosphine electron-donating ability have no significant effect on the barriers for β-methyl elimination within the experimental error. The full reaction manifold has been investigated with density functional theory (DFT) and affords a valuable experimental benchmark for types of organometallic transformations described herein.