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Tandem mass spectrometry and hydrogen/deuterium exchange studies of protonated species of 1,1′‐bis(diphenylphosphino)‐ferrocene oxidative impurity generated during a Heck reaction
Author(s) -
Wu Lianming,
HernandezSoto Heriberto,
Liu David Q.,
Vogt Frederick G.,
O'NeillSlawecki Stacy A.,
Su Qiaogong
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3369
Subject(s) - chemistry , protonation , dissociation (chemistry) , deuterium , proton affinity , collision induced dissociation , ferrocene , hydrogen–deuterium exchange , mass spectrometry , fragmentation (computing) , photochemistry , medicinal chemistry , tandem mass spectrometry , ion , organic chemistry , physics , chromatography , quantum mechanics , electrode , computer science , electrochemistry , operating system
Oxidation of 1,1′‐bis(diphenylphosphino)‐ferrocene (DPPF) was found to occur when it served as the ligand for Pd(II)(CH 3 COO) 2 in a Heck reaction. This oxidative impurity of DPPF, referred to as DPPF(O), was identified by high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) and exact mass measurements. Protonated DPPF(O) exhibited unique fragmentation pathways in the gas phase. Hydrogen/deuterium (H/D) exchange experiments provided important insights into the dissociation mechanisms of protonated DPPF(O), suggesting the existence of isomeric structures of the product ions by retaining or losing a proton (or deuteron) upon collision‐induced dissociation (CID). The specific fate of the proton (or deuteron) upon CID is postulated to be dependent on the distance between the exchangeable proton (or deuteron) and the sites of bond cleavage. Density functional theory (DFT) calculations at the B3LYP/LANL2DZ level of theory showed that oxygen in DPPF(O) plays a pivotal role in invoking π ‐cation interactions between the p‐type lone pair electrons (n π ) in oxygen and the anti‐bonding orbital of Fe(II), accounting for the major fragmentation pathways of protonated DPPF(O). Facile formation of organometallic distonic ions in dissociation of protonated DPPF(O), and especially of protonated DPPF, could be useful for further exploration of their chemical properties by gas‐phase ion/molecule reactions. Copyright © 2008 John Wiley & Sons, Ltd.