Manganese(II) Indenyl Compounds: Synthesis, Characterization, and Reactivities with Oxygen Donor Ligands

Abstract

A series of bis(indenyl)manganese(II) complexes have been synthesized with methyl substituents. These species appear to be high spin with no-evidence of spin-crossover. However, the physical structures of these compounds are unique in comparison other bis(indenyl) complexes of first row transition metal complexes. The bis(indenyl)manganese compounds display a very flexible Mn-indenyl interaction that results in oligomerization and polymerization of the compounds unless sufficient steric bulk can be provided. Dimeric (indenyl)manganese halides can be synthesized by salt metathesis reactions of the appropriate stoichiometries. A few of these compounds react with elemental oxygen at low temperature (-78 °C) and very low oxygen concentrations (< 5ppm). Spectroscopic data suggests the formation of a manganese(III) superoxide complex. A new synthetic route for the preparation of manganese(II) aryloxide compounds has been developed. Of interesting note is the observation that manganese(II) preferentially coordinates an aryloxide ligand over an indenyl ligand; however, these compounds appear to require sterically bulky phenoxide ligands in order to prevent polymerization and to help solubility.