FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY OF ORGANOMETALLIC PALLADIUM COMPLEXES CONTAINING TERDENTATE NITROGEN LIGANDS

Fast atom bombardment and collisonal-induced dissociation tandem mass spectrometry were used to analyze 12 cationic organometallic palladium [Pd(L)(R)](OTf) complexes containing three different terdentate nitrogen ligands (L), an organic group (R) attached in the sigma bonding mode, and a trifluoromethanesulfonate anion (OTf is CF3SO3-) using m-nitrobenzyl alcohol as a matrix. FAB ionization gives abundant Pd(L)(R) cations and some fragment ions. Tandem mass spectrometry of collisionally activated monoisotopic Pd-108(L)(R) cations affords additional information on fragmentation mechanisms and enables discrimination between isomeric complexes. The MS/MS experiments also provided evidence for the occurrence of an abundant gas-phase cyclopalladation reaction of the Pd-108(L)(R) cations by activation of a sp(3) C-H bond according to an oxidative addition/reductive elimination or a multicentered pathway.