Synthesis, Structure, and Paramagnetism of Manganese(II) Iminophosphate Complexes

The coordination chemistry of the bidentate bis­(imino)­bis­(amino)­phosphate ligands [Me₃SiNP­{NR}­{N­(H)­R}₂]⁻, where R = <i>n</i>-propyl is [L¹H₂]⁻, R = cyclohexyl is [L²H₂]⁻, and R = <i>tert</i>-butyl is [L³H₂]⁻, with manganese­(II), is described. The bis­(imino)­bis­(amino)­phosphate-manganese­(II) complexes [(η⁵-Cp)­Mn­(μ-L¹H₂)]₂ (<b>1</b>), [Mn­(L²H₂)₂]·THF (<b>2</b>·THF), and [(η⁵-Cp)­Mn­(L³H₂)] (<b>3</b>) were synthesized by monodeprotonation of the respective pro-ligands by manganocene, Cp₂Mn. The molecular structures of <b>1</b>–<b>3</b> reveal that the steric demands of the ligand N-substituents play a dominant role in determining the aggregation state and overall composition of the manganese­(II) complexes. The coordination geometries of the Mn­(II) centers are six-coordinate pseudotetrahedral in <b>1</b>, four-coordinate distorted tetrahedral in <b>2</b>, and five-coordinate in <b>3</b>, resulting in formal valence electron counts of 17, 13, and 15, respectively. EPR studies of <b>1</b>–<b>3</b> at Q-band reveal high-spin manganese­(II) (<i>S</i> = ⁵/₂) in each case. In the EPR spectrum of <b>1</b>, no evidence of intramolecular magnetic exchange was found. The relative magnitudes of the axial zero-field splitting parameter, <i>D</i>, in <b>2</b> and <b>3</b> are consistent with the symmetry of the manganese environment, which are <i>D</i>_2<i>d</i> in <b>2</b> and <i>C</i>_2<i>v</i> in <b>3</b>

Oscillatory Template Exchange in Polyoxometalate Capsules: A Ligand-Triggered, Redox-Powered, Chemically Damped Oscillation

The redox-controlled driven oscillatory template exchange between phosphate (P) and vanadate (V) anions enclosed in an {X₂M₁₈} cluster is reported. Extensive investigations using a range of techniques, including correlated ESI-MS, EPR, and UV–vis as a function of reaction time, showed that six complete oscillations interconverting the capsule species present in solution from {P₂M₁₈} to {V₂M₁₈} were possible, provided that a sufficient concentration of the TEA reducing agent was present in solution