Electrooxidation of ruthenium cyclopentadienyl PTA complexes in DMF: ESI-MS, cyclic voltammetry and on-line electrochemistry/ESI-MS s

Halogen complexes of ruthenium cyclopentadienyl CpRuPTA2X; CpRuPTAPPh3X; CpRuPPh32Cl, andCpRumPTAPPh3X+ Cp = C5H5; PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA+ = 1-methyl-1,3,5-triaza-7-phosphaadamantane+; X = Cl-, I- were investigated by electrospray mass spectrometry ESI-MS, in flow-cell cyclic voltammetry,by microelectrodes, and by combined online electrochemistry and electrospray mass spectrometry EC/ESI-MS in dimethylformamide solution. Coordination changes and the structures of the initial compounds and the products of the electrooxidationof the RuII complexes were traced by in situ EC/MSn experiments which revealed their fragmentation pathways.ESI-MS collision-induced dissociation fragmentations of the initial reactants and the oxidation products were explained by softacid-hard base considerations taking into account the different nature of RuII--RuIV centers. The electrochemical studies showthat it is possible to tune the formal potentials for the oxidation of CpRuL2X complexes by over 300 mV by proper selection ofthe ligands. The increase of the redox potential by the different ligands follows the order PTA PPh3 mPTA+. We demonstratea similarity between the propensity of the ligand to fragment out in the gas phase and its relationship to the formal potential of thecomplex.