Aryl–Phenyl Scrambling in Intermediate Organopalladium Complexes: A Gas‐Phase Study of the Mizoroki–Heck Reaction

Abstract

The intramolecular aryl-phenyl scrambling reaction within palladium-DPPP-aryl complex (DPPP=1,3-bis(diphenylphosphino)propane) ions was analyzed by state-of-the-art tandem MS, including gas-phase ion/molecule reactions. The Mizoroki-Heck cross-coupling reaction was performed in the gas phase, and the intrinsic reactivity of important intermediates could be examined. Moreover, linear free-energy correlations were applied, and a mechanism for the scrambling reaction proceeding via phosphonium cations was assumed.

Elusive Reaction Intermediates in Solution Explored by ESI‐MS: Reverse Periscope for Mechanistic Investigations

“…[46] In this recent contribution, the reaction was investigated by using acetonitrile and as odium arylsulfinate as starting materials.T he analysis of the reaction mixture resulted in the observation and characterization of the cationic portion of five palladium-containing intermediates.T his finding confirmed the formation of the Pd-aryl [47] bond by loss of SO 2 , which was replaced by CH 3 CN,inthe palladium coordination sphere.T he next step was the crucial carbopalladation of acetonitrile.…”

Gas-Phase Intramolecular Cyclization of Argentinated N-Allylbenzamides

“…Its first application in gas phase was conducted by McLafferty in 1959 [46], who found out that the logarithm of the ratio of the fragment ion to the precursor ion increases linearly with the increase in the substituent constants. From then on, Hammett plots have been extensively employed in the study of gas-phase chemistry [47][48][49][50] owing to its intuitive presentation of the substituent effect on the direct cleavage as well as on competitive fragmentation pathways. To get a more direct understanding on the relationship between substituents and competitive pathways, the logarithm of the intensity ratios of these two competitive product ions are usually utilized to plot with the substituent constants [31,37,50,51].…”

Mechanistic insights from mass spectrometry: examination of the elementary steps of catalytic reactions in the gas phase

“…These new alkyl complexes containing beta-hydrogens, unstable in solution, are prone to alkene elimination in the gas phase. The Mizoroki-Heck example alluded to in the ligand exchange reaction also exemplifies the β-hydride elimination to generate the final product [27].…”

“…Ligand scrambling phenomena can be important side-reactions in various catalytic processes. The Mizoroki-Heck reaction was recently investigated by ESI-MS/MS and gas-phase ion-molecule reactions [27]. The authors of this contribution orchestrated the Mizoroki-Heck reaction in the gas phase by ion-molecule reaction and CID and were able to measure the extent of the aryl/phenyl scrambling on the basis of the palladiumhydride complex ion abundances (Fig.…”