Associate Professor Mark Mason's Faculty Page

Inorganic and Organometallic Chemistry:
Synthesis, characterization, and reactivity of molecules and materials with catalytic applications; microporous group 13 phosphates and phosphonates, crystal engineering; Lewis acids, alkylaluminoxane analogues; epoxide polymerization catalysts.

My group is pursuing two areas of research: (1) The synthesis of group 13 phosphate and phosphonate materials via a molecular precursor approach. (2) The development of new catalysts and cocatalysts for the polymerization of epoxides and olefins. Our interest in group 13 phosphates and phosphonates is driven by need for rational construction principles for preparation of porous materials. Porous materials with zeolitic structures have applications in molecular separations and membrane technology, and as catalysts and catalyst supports for a variety of reactions, including the catalytic cracking of petroleum. At present, several AlPO4 and GaPO4 materials are known with pore sizes of up to 13 ª. These materials were discovered by varying reactant stoichiometries and reaction conditions in hydrothermal reactions until new products were observed. This approach is time-consuming and does not allow designed synthesis of materials with specific structures and pore sizes. My group aims to synthesize AlPO4 and GaPO4 materials with pore diameters in the 5-25 ª range via preformed molecular building blocks. We have already synthesized and fully characterized a range of aluminophosphonate and gallophosphonate precursors which have core structures analogous to the secondary building units common to many of the known phosphate molecular sieves. We are developing methods to remove organic substituents from these precursors under mild conditions without disrupting the inorganic cores. We aim to concurrently link the remaining inorganic building blocks to give porous networks. Physical properties and catalytic utility of the resulting materials will be probed.

Our second area of emphasis is the development of Lewis acid catalysts for the polymerization of epoxides to yield high molecular weight polyether elastomers. Polyether elastomers continue to find use in automotive and industrial applications which require materials with low gas permeability, retention of flexibility at both low and high temperatures, and stability upon extended exposure to heat, hydrocarbons, and ozone. Traditional catalysts for the commercial production of polyether elastomers are based on partially hydrolyzed trialkylaluminum reagents prepared in a nonpolar hydrocarbon solvent. The resulting alkylaluminoxane solutions are complicated mixtures of structurally ill-defined components. Since the structure and composition of the active component(s) of the catalyst solution are unknown, rational improvements to the catalyst which would increase activity and reduce polydispersities of the resulting polymers are difficult to achieve. Our objective is to develop structurally well-defined catalysts with which polymer properties can be precisely controlled. Although our quest spans complexes of both the p-block and d-block elements, we are currently exploring alkylaluminophosphonates as alkylaluminoxane analogues based on the isolobal relationship of m3-oxo and m3-phosphonate units.

Additional research interests include the synthesis of novel phosphorus ligands with applications in homogeneous catalysis, and molecular precursors for the chemical vapor deposition of metal containing thin films. Consistent with our breadth of research interests, my group utilizes a broad range of synthetic and characterization techniques, including the handling of air- and moisture sensitive reagents, solvothermal synthesis, solution and solid-state multinuclear NMR spectroscopy, infrared spectroscopy, X-ray crystallography, and thermal gravimetric analysis.