Ligand and metal binding energies in platinum carbonyl cluster anions: Collision-induced dissociation of Pt-m(-) and Pt-m(CO)(n)(-)

The collision induced dissociation (CID) of small pas phase platinum and platinum carbonyl cluster anions, Pt-m(-) and Pt-m(CO)(n)(-) (m=3-6), has been studied using a guided ion beam tandem mass spectrometer. The threshold energies obtained from analysis of the CID cross sections for carbonyl and metal atom loss are equated with binding energies. The binding energies of CO to the platinum cluster anions are indicative of two different binding sites, terminal (about 80-110 kJ/mol) and bridged (220-250 kJ/mol). Energies required to removed platinum atoms from the bare cluster anions are 410-470 kJ/mol, a substantial fraction of the bulk enthalpy of vaporization, 570 kJ/mol. Using threshold energies for both primary and secondary CID products in thermodynamic cycles, we have determined thermochemical stabilities of additional neutral and anionic platinum carbonyl species, (C) 1997 American Institute of Physics.