Some 5- and 6-coordinate base adducts of Bis(acetylacetonato)manganese(II)

Abstract

From diaquobis(acetylacetonato)manganese(II) we have obtained mono- and bis(pyridine)acetylacetonatomanganese(II), corresponding 4-methylpyridine compounds, bis-2-methylpyridine-, aquo-2-methylpyridine-, and o-phenanthroline- derivatives and some compounds in which all or part of the water is replaced by ethanol. All these compounds have magnetic moments which are normal for spin-free d5 complexes, but anhydrous bis(acetylacetonato)manganese(II) has a slightly lower moment. Molecular weight determinations show that the anhydrous compound is trimeric; the adducts with one molecule of base, though monomeric and 5-coordinate in freshly prepared benzene solutions, slowly decompose in solution, probably to condensed 6-coordinate species; the bispyridine, bis-4-methylpyridine, and o-phenanthroline adducts also dissociate in solution, an indication that manganese(II) forms unstable complexes with nitrogen as donor atom. The dark colour of these solutions appears to be due to manganese(IV) oxide.