The direct utilization of O2 in the controlled oxidation of organic substrates remains an area of intense interest in the chemical community. Research over the past century has only partially addressed the fundamental issues behind productive O2 activation (i.e., the absence of freely diffusing oxygen-based radicals) and its use. Advances in mechanistic and structural/spectroscopic metalloenzymology have generated a new understanding of how Nature activates O&lt;font size="1"&gt;2&lt;/font&gt;. Based on these insights, we have developed a series of mononuclear and binuclear iron complexes that react with either O2 directly or with activated forms of oxygen (peroxides, peracids, oxygen atom donor (OAD) molecules) to generate transient iron-based reactive intermediates capable of oxidizing alkane C-H bonds to alcohol C-OH moieties. Temperature-dependent kinetic studies of a binuclear ferrous complex that induces heterolytic O-O bond cleavage of (i) the mechanistic probe alkyl peroxide 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) or (ii) phenylperacetic acid (PPAA), and (iii) reacts with OAD species to generate an equivalent intermediate, will be presented along with data demonstrating the ability of the iron complex to tightly couple intermediate formation to the oxidation of cyclohexane to cyclohexanol. A long-standing scientific challenge has been the direct activation of O2&lt;font size="1"&gt; &lt;/font&gt;at a single metal center, and use of the subsequent metal-based oxidant for substrate oxidation reactions. Towards this end, computational, spectroscopic, and synthetic methods have been utilized to develop model systems capable of this chemistry, and to better understand the electronic and mechanistic properties of the observed catalytic reactivity. We will report on a catalyst that is capable of utilizing alpha-keto acids in the activation of O2 and oxidation of organic substrates in a highly coupled manner. This reactivity takes place at room temperature and standard pressure, and resembles the type of chemistry performed by mononuclear non-heme enzymes, which inspired the design of the catalyst. The implications derived from stopped-flow kinetic studies will be presented in light of the development of new catalytic processes.

Exploring synthetic iron model oxidation pathways by kinetic and mechanistic techniques: Insights and challenges

2019 Spring National Meeting

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