Electrospray ionization and tandem mass spectrometry characterization of novel heterotrimetallic Ru(η5-C5H5)(dppf)SnX3 complexes and their heterobimetallic Ru(η5-C5H5)(dppf)X precursors

Electrospray ionization and tandem mass spectrometry were used to characterize some novel heterotrimetallic complexes Ru(η5-C5H5)(dppf)SnX3 (1) (dppf = diphenylphosphine ferrocene; X = Cl, Br) and their heterobimetallic precursors Ru(η5-C5H5)(dppf)X (2) (X = Cl, Br, I, N3). The positive-ion ESI mass spectra of 1 and 2 in acetonitrile solution showed the predominant presence of the [Ru(5-C5H5)(dppf)]+ cation (3) of m/z 721. In the positive-ion ESI mass spectrum of the complex Ru(η5-C5H5)(dppf)N3 (2d), another prominent cation of m/z 735, [Ru(η5-C5H5)(dppf)N]+ (4), was also observed. Its formation was proposed to occur via the oxidation of the ruthenium atom followed by the loss of N2. Cation 3 was proposed to be the catalytic active species in the single-step conversion of methanol to acetic acid.