A challenging and dynamic research area in organometallic and coordination chemistry is directed toward the stabilization of low-coordinate transition metal (TM) complexes that show relevance as intermediates/reactive species in biological and molecular catalysis. Since their first use as supporting ligands to stabilize 3d TM complexes, the easily and sterically tunable beta-diketiminate (BDI) framework has emerged as one of the most popular and widely used ligand for this purpose stabilizing a range of metal ions in multiple oxidation states. Earth-abundant 3d late TM have inherent features that can offer complementary reactivity compared to their heavier d-block congeners and open up new reactivity avenues in sustainable catalysis. The rich landscape of variable redox, spin states and coordination geometries associated with 3d late TM complexes has the potential for accessing reactivity that is largely unavailable to 4d/5d complexes. Moreover, the association of these elements with weak/intermediate field ligands such as N-containing BDI, particularly in a low coordinate environment, open the door for a two-state reactivity, meaning that spin-state changes for the reactive organometallic species could occur during the reaction course to lower or avoid high energy barriers leading to rate acceleration or reactivity. This proposal aims to harness the versatility of the BDI ligand platform and the intrinsic properties of low-coordinate iron and cobalt complexes in sustainable catalysis to tackle the main challenges related to metal-catalyzed Suzuki-Miyaura cross-coupling (SMC) for sp3-hydridized partners. The transition-metal catalyzed Suzuki-Miyaura cross-coupling of organohalide (or pseudo-halide) electrophiles and organoboron nucleophiles is one of the most commonly applied strategy for carbon-carbon bond formation in the pharmaceutical, agricultural and fine chemical industries. In this proposal, structurally-defined iron and cobalt complexes featuring task-specific functionality on the ligand skeleton will be designed to accommodate the steric and electronic metal needs for particular and demanding reactivities occurring in SMC with sp3-hydridized partners. Our strategy will rely on a synergistic approach based on the complementarity between experimental and computational studies. State-of-the art theoretical DFT calculations to properly understand the SMC mechanism for first row transition metals will be conducted. Computations are the only available method to identify spin state changes over a reaction course and are compulsory to correlate structure, geometry and spin states of species with reactivity/selectivity. This will be of critical importance to gain information on factors controlling these reaction data. Solid-state structure determinations, magnetic moment measurements, EPR and UV-vis spectroscopy and stoichiometric reactivity patterns designed to mimic SMC elementary steps with a special focus on the key transmetalation step will also be considered to support the calculations and target a comprehensive picture of the mechanistic aspects of the reactions.
Monsieur Jérôme Hannedouche (Université Paris-Saclay)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ICMMO Université Paris-Saclay
Computational BioNanoCat, Universitat Autonoma de Barcelona
Help of the ANR 253,097 euros
Beginning and duration of the scientific project: September 2022 - 42 Months