In Chemistry, Does 4 – 2 = 2?

Chemical reactions that involve oxidation or reduction of organic molecules typically take place in two-electron steps.  We recently developed a novel reaction that involves a metal center undergoing a four-electron change, while its attached ligands undergo a two-electron change in the opposite direction, to achieve a net two-electron change.  This bit of molecular gymnastics allowed us to access a previously unknown oxidation state of iridium, Ir(VII).  We are now curious about whether this "4 – 2" pathway has any noticeable differences from a more traditional two-electron redox change.  This project will allow a student to address this question by studying the reactivity of our novel iridium(VII) nitrides with triarylphosphines, and comparing that to the reactivity of osmium(VI) nitrides, which are known to undergo traditional two-electron chemistry.  Students will measure the rates of these reactions using UV-visible spectroscopy or NMR, and will assay the sensitivity of the rates to changes in the structure of either the phosphines or the groups on the metal center.  This will allow us to build a picture of the electron distribution in the reactions of the two types of reagents.