Precipitation of Spherical Magnesium(II) Cresolate Particles

Magnesium bis-o-cresol (or o-methylphenoxide), [Mg(oMP)2]n (1), was prepared through a variety of synthetic routes that involved the stoichiometric reaction of o-methylphenol (H-oMP), with Mg(Bu)2, Mg{N(Si(CH3)3)2}2(THF)2, or the bulk metal (Mg0). In all cases the low-temperature product was found to be soluble, while precipitation occurred at higher temperatures. The precipitate could only be redissolved by the addition of pyridine or a similarly strongly coordinating Lewis base. The pyridine and NH3 adducts of 1 were isolated as monomeric species, whereas the THF adduct proved to be the dimeric [Mg(μ-oMP)(oMP)(THF)2]2, 2. For a limited set of conditions, sufficient control over the precipitation kinetics of the reaction between Mg(Bu)2 and H-oMP was realized to yield spherical morphologies. The window of spherulitic growth was small and could only be partially controlled by varying reaction conditions during the precipitation. Use of seed particles to control nucleation events during precipitation was found to lead to increased monodispersity of spherical [Mg(oMP)2]n precipitate powders.