Configuring first-row metal-metal bonded complexes to boost redox flexibility and N2 reduction activity

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Nitrogen is essential to life and has many important uses including fertilizers, components of plastics, and ingredients of pharmaceuticals. Actually, nitrogen is abundant and easily accessible as it makes up 78% of the Earth's atmosphere. However, atmospheric nitrogen gas is very difficult to convert into forms that can be used for practical applications. In fact, the industrial conversion of atmospheric nitrogen into ammonia (the basic component of agricultural fertilizer and many industrial processes) utilizes extreme amounts of energy and the conversion of atmospheric nitrogen directly to a number of other industrial chemicals is not developed. In this project funded by the Chemical Synthesis program of the Chemistry Division, Professor Connie Lu of the University of Minnesota, Twin Cities is addressing these problems by developing ways to convert atmospheric nitrogen into chemicals other than ammonia. The methods utilize cobalt and iron compounds to transfer electrons to nitrogen. This activates the nitrogen and permits it be converted to a class of compounds know as amines, which are the basic building blocks for many industrially important chemicals. The project contains a strong educational component in which undergraduate and graduate students are trained for future careers in science and technology. Additionally, an outreach component provides experimental modules for middle and high-school students to teach topics of sustainability and catalysis. The redox processes available to first-row metal-metal bonded complexes can be more flexible than those of individual metals. This effect is seen in multi-metallic compounds, which are versatile catalysts for a broad range of organic and inorganic transformation. This property is utilized to prepare catalysts for the conversion of dinitrogen to amines. A series of bimetallic Co-M and Fe-M (M = Al, Ti, V, Cr, and Co) complexes are prepared and their redox flexibility characterized by synchrotron and theoretical methods. The ability of these species to catalyze the silylation of dinitrogen is investigated and the mechanism of this process is determined by chemical and theoretical studies. The goal is to devise catalytic N−C bond formation directly from dinitrogen. Throught these activities undergraduate and graduate students become skilled in syntheis, catalyst development, and mechanistic studies. A further outreach component targets middle and high school girls through experimentally based catalysis workshops. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.