Exploration of the chemistry of diazine-based redox-active ligands in iron chemistry
Final Report Abstract
This project explores the electronic structure and catalytic properties of iron complexes with redoxactive diazine- and phopshorus-based ligands. The project developed around two axes: (1) The exploration of various metal-ligand cooperativities which extend beyond the first coordination sphere of the metal and (2) the use of these effects in developing highly efficient catalytic applications. By focusing on pyrazinediimine ligands scaffolds the research examines how metal-ligand cooperativity and secondary interactions, such as hydrogen bonding, influence the reactivity and stability of iron centres. The study expands the knowledge on mesoionic N-heterocyclic carbenes which can function as ditopic ligands for redox-active systems and are highly active redox-switchable catalysts. Nevertheless, synthetical challenges in ligand synthesis prevented the development of catalytic applications beyond hydroelementation reactions. The development of iron complexes with phosphino-α-iminopyridine (PNN) ligands is detailed, which enable both chemical and redox cooperativity, leading to labilisation of nitrogen (N₂) and olefin hydrogenation. It also explores how hydrogen bonding in the secondary coordination sphere, via a pyrrolidine-functionalized pyridinediimine ligand, can influence the reactivity of reduced iron centers. Additionally, iron complexes with pyrimidinediimine ligands show improved catalytic performance in cycloaddition reactions, surpassing their pyridine-based counterparts, with catalyst loadings as low as 0.1 mol% being achieved. These findings suggest that modifying ligands and incorporating hydrogen bonding can optimize the electronic properties of iron complexes, offering new strategies for substrate activation and for the use of earth-abundant 3d transition metals in catalysis. This work advances coordination chemistry by deepening the understanding of how ligand design affects metal-ligand interactions and catalytic efficiency, which our group will explore in the coming years.
Publications
-
Redox Activity of Iron Diazine-Diimine Carbonyl and Dinitrogen Complexes: A Comparative Study of the Influence of the Heterocyclic Ring. Inorganic Chemistry, 61(1), 520-532.
Doll, Julianna S.; Regenauer, Nicolas I.; Bothe, Viktoria P.; Wadepohl, Hubert & Roşca, Dragoş-Adrian
-
Metal–Ligand Cooperativity in Iron Dinitrogen Complexes: Proton-Coupled Electron Transfer Disproportionation and an Anionic Fe(0)N2 Hydride. Inorganic Chemistry, 61(19), 7426-7435.
Regenauer, Nicolas I.; Wadepohl, Hubert & Roşca, Dragoş-Adrian
-
Redox‐Switchable Catalysis. Encyclopedia of Inorganic and Bioinorganic Chemistry, 1-21. Wiley.
Regenauer, Nicolas I.; Doll, Julianna S. & Roșca, Dragoș‐Adrian
-
Terminal N2 Dissociation in [(PNN)Fe(N2)]2(μ‐N2) Leads to Local Spin‐State Changes and Augmented Bridging N2 Activation. Chemistry – A European Journal, 28(58).
Regenauer, Nicolas I.; Wadepohl, Hubert & Roşca, Dragoş‐Adrian
-
Diazines and Triazines as Building Blocks in Ligands for Metal-Mediated Catalytic Transformations. ACS Organic & Inorganic Au, 4(1), 41-58.
Doll, Julianna S.; Becker, Felix J. & Roşca, Dragoş-Adrian
-
Iron-Catalyzed Synthesis of Conformationally Restricted Bicyclic N-Heterocycles via [2+2]-Cycloaddition: Exploring Ring Expansion─Mechanistic Insights and Challenges. ACS Catalysis, 13(9), 6416-6429.
Hertwig, Leif E.; Bender, Thilo; Becker, Felix J.; Jäger, Patrick; Demeshko, Serhiy; Gross, Sophie Jana; Ballmann, Joachim & Roşca, Dragoş-Adrian
-
The Atmosphere Matters: The Effect of “Inert” Gas on the Catalytic Outcomes in Cobalt-Mediated Alkyne and Olefin Hydroboration. ACS Catalysis, 13(13), 8770-8782.
Doll, Julianna S.; Heldner, Maxi L.; Scherr, Matthias; Ballmann, Joachim & Roşca, Dragoş-Adrian
-
Transition‐Metal Catalyzed, Thermally Driven [2π+2π]‐Cycloadditions of Olefins and Alkynes. European Journal of Organic Chemistry, 28(13).
Hertwig, Leif E.; Becker, Felix J. & Roşca, Dragoş‐Adrian
