In situ synthesis of magnesium hydroxides modified with tripodal ligands in an organic medium

Layered magnesium hydroxides modified organically with tris(hydroxymethyl)aminomethane (Tris-NH₂) were directly synthesized from magnesium chloride dissolved in a polar organic solvent, like dimethyl sulfoxide (DMSO), containing a small amount of water. Tris-NH₂ acted as a base for precipitating magnesium hydroxides as well as an organic modifier. In contrast to the case of an aqueous solution, the use of organic solvents substantially increased the degree of modification of layered magnesium hydroxides with Tris-NH₂ owing to the formation of bidentate Mg-O-C linkages by Tris-NH₂ in addition to its tridentate bonding mode. Bidentate linkages, hydrolyzed readily in water, are stable in the organic media. Pentaerythritol (Tris-CH₂OH), trimethylolethane (Tris-CH₃), and trimethylolpropane (Tris-C₂H₅) were also successfully used for the synthesis of organically-modified layered magnesium hydroxides by the addition of tetrabutylammonium hydroxide as a base with DMSO as the solvent. The synthesis of hybrid magnesium hydroxides in organic solvents is expected to expand the chemistry of organically modified layered metal hydroxides with various metallic species and a wide variety of organic functional groups.