Studies of gas‐phase fragmentation reactions of [Pd(PPh 3 ) 2 (OCOR)] + by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Gas‐phase fragmentation reactions of [Pd(PPh 3 ) 2 (OCOR)] + (R = H, CH 3 , CD 3 , C 2 H 5 , n ‐C 3 H 7 , n ‐C 6 H 13 and C 6 H 5 ) were studied by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FTICRMS). In sustained off‐resonance irradiation collision‐activated dissociation (SORI‐CAD) experiments, the complexes all dissociated to yield the same product ion at m/z 629.1. We propose that the fragmentation pathway occurs through the elimination of RCOOH and a palladium(IV) hydride intermediate. Semi‐empirical (PM3) calculations shed light on the mechanism for the fragmentation reactions of these compounds. The results of deuterium‐labeling experiments indicate that the protons of RCOOH lost from [Pd(PPh 3 ) 2 (OCR)] + originate from the phenyl in the triphenylphosphine ligand. [Pd(PPh 3 ) 2 (OCOH)] + undergoes two competitive pathways in SORI‐CAD experiments, one of which is similar to that of [Pd(PPh 3 ) 2 (OCOR)] + (R = CH 3 , CD 3 , C 2 H 5 , n ‐C 3 H 7 , n ‐C 6 H 13 and C 6 H 5 ), and the other involves decarboxylation. The present study demonstrates that MS could play an important role in studying the gas‐phase chemistry of palladium hydrides. Copyright © 2006 John Wiley & Sons, Ltd.