Organometallic Approaches to Abnormal Bonds and Fleeting Molecules
Name of applicant
Anders Reinholdt
Institution
University of Pennsylvania, PA, USA
Amount
DKK 1,281,729
Year
2021
Type of grant
Reintegration Fellowships
What?
Some of the questions that chemists have asked throughout time are: Why do some chemical bonds predominantly break, while others form? What constitutes a stable molecule, and can we push the boundaries for stability? Nitrogen is among the five most electronegative elements, and therefore most chemical bonds are polarized toward it. Late transition metals such as osmium can reverse this polarity by forming osmium nitrides. We will take advantage of this polarity reversal when 1) converting atmospheric dinitrogen into unstable molecules such as azides and when 2) generating elusive two-atom molecules such as NP and NAs. The first topic targets thermodynamically disfavored reactions while the second topic targets fundamental and unexplored chemical building blocks.
Why?
In synthetic chemistry there is a constant need for inventing methods for constructing chemical bonds and assembling molecules. Azides are heat and shock sensitive molecules that are used for airbags and explosives. Reversing the propensity for azides to fracture into dinitrogen and nitrene fragments is a pursuit toward understanding and designing chemical pathways that generate high-energy molecules in spite of their thermodynamic tendency to fall apart. Heavy-atom analogs of dinitrogen (such as NP or NAs) were first observed in interstellar media, but on Earth, these molecules are fleeting and little is known about their chemistry. Even so, NP and NAs are among the simplest conceivable building blocks in chemistry and could unlock a range of fundamental organic and inorganic reactions.
How?
Our pivotal idea is to use synthetic organometallic techniques to tame chemical fragments that under normal circumstances are either unreactive or unstable, precluding use in chemical synthesis. Simple electrostatic considerations suggest that free dinitrogen lacks coupling reactivity due to its nonpolar nature. We will activate atmospheric dinitrogen by coordination to electron-rich metal centers and combine these polarized molecules with osmium-nitride fragments to assemble azides. Osmium nitrides will also provide entry to elusive two-atom molecules when combined with P and As atom transfer reagents. To understand and ideally control bonding and reactivity, we will study the systems by spectroscopy and quantum theoretical methods in partnership with international collaborators.