A mechanistic investigation of hydrodehalogenation using ESI-MS

Abstract

The rate of hydrodehalogenation of aryl iodides with a palladium catalyst in methanol exhibits a strong primary kinetic isotope effect from both CD3OD and CH3OD, suggesting that deprotonation plays a major role in the mechanism.

The application of electrospray ionization mass spectrometry to homogeneous catalysis

“…When the charged aryl iodide A c c e p t e d M a n u s c r i p t 43 reaction conditions was selected which involved the addition of a stronger base to more effectively sequester the generated H + . The observed formation of a dehalogenated byproduct in the reaction was also investigated in detail by PSI-MS in similar fashion (Figure 25), and unusually strong primary kinetic isotope effects were detected, suggesting an alternative mechanism at play under these conditions [104]. Reprinted with permission from reference [104].…”

Spatial effects on electrospray ionization response

“…In particular, it is important for reproducibility purposes across different concentration ranges that we are not perturbing the relative response of different ions, because such effects may provide misleading kinetic data. M a n u s c r i p t 4 Because we mostly use permanently charged ions in our analyses of catalytic reactions by ESI-MS, [9][10][11] we selected two such cations of drastically different mass and shape. [NMe 4 ] + is small (m/z 74; tetramethylammonium = TMA) and near-spherical; [(Ph 3 P) 2 N] + is large (m/z 538; bis(triphenylphosphine)iminium = PPN) and dumbbell-shaped ( Figure 1).…”

Alkylation of [Pt2(μ-S)2(PPh3)4] with boronic acid derivatives

“…An overpressure of 2 -4 psi is applied displacing the reacting solution into the MS. This allows for real-time observation of all charged species and how they behave over the course of the reaction, [31][32][33][34] and providing a better understanding of mechanism and optimization of synthetic protocols. For this report speciation and dynamic behavior in the reaction of 1 with 4-(bromomethyl)phenylboronic acid pinacol ester, BrCH2(C6H4)B{OC(CH3)2}2, 2 was monitored.…”