Electrospray ionization tandem mass spectrometric determination of ligand binding energies in platinum(II) complexes

Energy-resolved collision-induced dissociation (CID) cross sections were measured and deconvoluted to determine ligand binding energies for 2,2,2-trifluoroethanol, water, and acetonitrile to a cationic (diimine)Pt-II complex involved in recent C-H activation studies for which ligand exchange is rate-determining. The binding energies agree well with predictions based on DFT calculations. Practical considerations in the use of CID cross sections for large organometallic complexes are discussed. Results using a simplifying approximation for the deconvolution of the binding energy are then introduced and shown to lead to acceptable binding energies when the molecule is large.