BINDING-ENERGIES OF PALLADIUM CARBONYL CLUSTER ANIONS - COLLISION-INDUCED DISSOCIATION OF PD-3(CO)(N)(-) (N=0-6)

The bond dissociation energies of palladium trimer anion, Pd-3(-), and its carbonyls, Pd-3(CO)(n)(-) (n = 1-6), are measured in the gas phas e by the energy-resolved collision-induced dissociation method. The va lues obtained are D-0(Pd-2(-)-Pd) = 2.26+/-0.36 eV for the bare cluste r and D-0(Pd-3(CO)(n-1)(-)-CO) = 1.78+/-0.32 eV, 1.74+/-0.22 eV, 1.47/-0.22 eV, 1.13+/-0.15 eV, 1.11+/-0.15 eV, and 1.14+/-0.17 eV for n = 1-6, respectively, for the carbonyls. The results show a general decre ase of the bond energy with an increasing number of carbonyls, with tw o relatively stable structures, Pd-3(CO)(2)(-) and Pd-3(CO)(6)(-). A s ymmetric Pd-3(CO)(2)(-) structure with two three-fold bridged carbonyl s is postulated. (C) 1998 American Institute of Physics. [S0021-9606(9 8)02837-2].