Sequential Bond Dissociation Energies of M+(NH3)x (x = 1−4) for M = Ti−Cu

Abstract

The sequential bond dissociation energies (BDEs) for M+(NH3)x (x = 1−4) for M = Ti−Cu are determined by examining the collision-induced dissociation reactions with xenon in a guided ion beam mass spectrometer. In the cases of Fe, Co, Ni, and Cu, the BDE for the second ammonia molecule is determined to be greater than the BDE for the first ammonia molecule. For all metal ions but Ti+, the BDEs for the first two ammonia molecules are large in comparison to the BDEs for the third and fourth ammonia molecules. In general, the results of this study for the BDEs of the first and second ammonia molecules agree well with the results of previous experimental and theoretical studies. Previous studies are available only for M+(NH3)3 (M = V, Mn, Ni, and Cu) and M+(NH3)4 (M = V and Cu) complexes, such that this study provides the first determination of all other (NH3)2M+−NH3 and (NH3)3M+−NH3 BDEs. The trends in BDEs are discussed in terms of hybridization, dative interactions, and spin changes and compared to trends for other comprehensively studied ligands, H2O and CO.