skip to main content


Search for: All records

Creators/Authors contains: "Schlenker, Kevin"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Pincer-ligated catalysts that can undergo metal–ligand cooperativity (MLC), whereby H 2 is heterolytically cleaved (with proton transfer to the ligand and hydride transfer to the metal), have emerged as potent catalysts for the hydrogenation of CO 2 and organic carbonyls. Despite the plethora of systems developed that differ in metal/ligand identity, no studies establish how variation of the metal impacts the pertinent thermochemical properties of the catalyst, namely the equilibrium with H 2 , the hydricity of the resulting hydride, and the acidity of the ligand. These parameters can impact the kinetics, scope, and mechanism of catalysis and hence should be established. Herein, we describe how changing the metal (Co, Fe, Mn, Ru) and charge (neutral vs. anionic) impacts these parameters in a series of PNP-ligated catalysts (PNP = 2,6-bis[(di- tert -butylphosphino)methyl]pyridine). A linear correlation between hydricity and ligand p K a (when bound to the metal) is found, indicating that the two parameters are not independent of one another. This trend holds across four metals, two charges, and two different types of ligand (amine/amide and aromatization/de-aromatization). Moreover, the effect of ligand deprotonation on the hydricity of (PNP)(CO)(H)Fe–H and (PNP)(CO)(H)Ru–H is assessed. It is determined that deprotonation to give anionic hydride species enhances the hydricity by ∼16.5 kcal mol −1 across three metals. Taken together, this work suggests that the metal identity has little effect on the thermodynamic parameters for PNP-ligated systems that undergo MLC via (de)aromatization, whilst the effect of charge is significant; moreover, ion-pairing allows for further tuning of the hydricity values. The ramifications of these findings for catalysis are discussed. 
    more » « less