ELECTRON-SPIN-RESONANCE AND ELECTROSPRAY-IONIZATION MASS SPECTROSCOPIC STUDIES OF THE INTERACTION OF ALKALI AND ALKALINE-EARTH CATIONS WITHMANGANESE BIS(MU-OXO) DIMERS

The dimer [(3,3'-17-crown-6-SALPN)Mn-IV(mu-O)](2) (2) was prepared by the reaction of (3,3'-17-crown-6-SALPN)Mn(II) with O-2 in CH3CN. Dimer 2 when reacted with two molar equivalents of NaPF6, KPF6, CaTf(2) or BaTf(2) (Tf(-) is SO3CF3-) formed the complexes 2 . 2NaPF(6), 2 . 2KPF 6, 2 . 2CaTf(2) or 2 . 2BaTf(2), respectively. The dimers were reduced to the mixed-valent Mn-III,Mn-IV state either chemically with Cp(2)Co or electrochemically and their ESR spectra recorded. The ESR spectrum of each mixed-valent dimer showed a 16-line pattern characteristic of a valence trapped antiferromagnetically coupled species. The cation c ontaining Mn-IV,Mn-IV bis(mu-oxo) dimers were also analyzed by electro spray ionization mass spectrometry using CH2Cl2 and CH3CN as solvents. Singly charged cations corresponding to the loss of one anion from th e parent complex were observed for all four compounds. In addition, io ns were detected in which cation exchange had occurred.