Solution Phase Cationic Niobium and Tantalum Alkoxide Clusters: Insights into Formation and Structure

Electrospray mass spectrometry (ESMS) is used to investigate cationic niobium and tantalum alkoxide clusters generated in solution by adding equal molar amounts of B(C6F5)3 to the metal ethoxide, M(OEt)5. The dominant metal ethoxide cations that were observed in the electrospray mass spectrum correspond to M(OEt)4+, M2O(OEt)7+, M2(OEt)9+, and M3O(OEt)12+, where M is niobium or tantalum. In separate experiments heterometallic Nb/Ta ethoxide clusters were produced, and the heterometallic cations present in the electrospray mass spectrum are NbTaO(OEt)7+, NbTa(OEt)9+, Nb2TaO(OEt)12+, and NbTa2O(OEt)12+. Collision-induced dissociation (CID) experiments were completed to provide structural information about the observed metal ethoxide cations. At low collision energy (ECM < 2 eV), the CID fragmentation pattern of Nb3O(OEt)12+ favors loss of Nb2(OEt)9+ and neutral NbO(OEt)3, whereas the fragmentation pattern of Ta3O(OEt)12+ favors loss of Ta2O(OEt)7+ and neutral Ta(OEt)5. In addition, the major CID product of M...