Periodic Reporting for period 1 - cAAC-Light (New Strategies for Bond Activation and Catalysis with subvalent Main Group Complexes)
Período documentado: 2021-09-01 hasta 2022-08-31
Catalysis is the base of the Chemical industry, which is related with the 20-30% of the world GDP. The development of catalyst have an impact of 3- 4 billion of euros in Europe. Catalysis is at the centre of promising solutions to many of the EU Societal Challenges, being a key technology in the European future economy, industry and sustainable growth. However, there are still many challenges to be addressed such as cost efficiency, selectivity or substrate scope. Our study is in clear alignment with the design of new more efficient catalyst and the study of the cooperativity in catalysis. Focusing on unexplored synergies between Main Group (MG) and Transition Metals (TM), we expect to reveal new reactivity concepts for small molecules and the activation of uncommon bonds for TM systems such as N-H bond of the ammonia.
The main objectives of this projects are:
To synthesize a variety of MG-carbene complexes to explore their capacity towards the activation of small molecules.
To test the capacity of the MG-carbene and MG-TM complexes for the light-driven activation of non-classical bonds.
To explore the cooperativity of the MG/TM complexes on the reversible activation of E-H bonds.
To synthesize and characterize a variety of hybrid MG/TM complexes based on P,carbene chelating scaffolds functionalised with bulky moieties or N,P ligands.
The main objectives of this projects are:
To synthesize a variety of MG-carbene complexes to explore their capacity towards the activation of small molecules.
To test the capacity of the MG-carbene and MG-TM complexes for the light-driven activation of non-classical bonds.
To explore the cooperativity of the MG/TM complexes on the reversible activation of E-H bonds.
To synthesize and characterize a variety of hybrid MG/TM complexes based on P,carbene chelating scaffolds functionalised with bulky moieties or N,P ligands.
The first step of the work was the synthesis of the carbene ligands (cyclic (alkyl)amino carbenes (cAACs) and mesoinic carbenes (MICs)) due to the great background of the outgoing host group in this area and their frontier orbitals with relatively small energy gaps which should enable bond activation by oxidative addition. Also we prepared terphenyl ligands due to the stability that this kind of bulky ligands conferee to the complexes and the expertise of the host group.
Once the synthesis of the ligands was performed, the following step was the preparation of the MG complexes. GeCl2 was the precursor chosen for this aim. The reactivity of the GeCl2 with cAAC in the presence of catalytic amounts of lithium diisopropylamide (LDA) leads to the Ge(cAAC)Cl2. Using the same procedure for the MICs carbenes the formation of Ge(MIC)Cl2 was performed. Also, we prepared Ge(terpenyl)Cl and Ge(terphenyl)2 compounds following the synthesis previously reported by Power´s group (Figure 1).
The next step was the abstraction of one or two chlorides ligands of the Ge(MIC)Cl2 and Ge(cAAC)Cl2 for the preparation of Ge(II)(Carbene)Cl+ or Ge(0)(carbene) complexes. These species should be more reactive for the activation of small molecules. We are still working on the characterization and isolation of these species due to their great instability.
In the area of Ge(terphenyl)Cl and Ge(terphenyl)2 complexes, Ge-TM complexes were isolated and characterized. Also the activation of small molecules and the catalytic hydrogenation, hydrosilylation and isomerization of olefins were performed (Figure 2), revealing an unusual selectivity pattern that we attribute to the combination of a germanium centre with rhodium, one of the core ideas of this Marie Curie proposal. These results have already led to a publication in ChemCatChem (2022, 14, e2022001).
Once the synthesis of the ligands was performed, the following step was the preparation of the MG complexes. GeCl2 was the precursor chosen for this aim. The reactivity of the GeCl2 with cAAC in the presence of catalytic amounts of lithium diisopropylamide (LDA) leads to the Ge(cAAC)Cl2. Using the same procedure for the MICs carbenes the formation of Ge(MIC)Cl2 was performed. Also, we prepared Ge(terpenyl)Cl and Ge(terphenyl)2 compounds following the synthesis previously reported by Power´s group (Figure 1).
The next step was the abstraction of one or two chlorides ligands of the Ge(MIC)Cl2 and Ge(cAAC)Cl2 for the preparation of Ge(II)(Carbene)Cl+ or Ge(0)(carbene) complexes. These species should be more reactive for the activation of small molecules. We are still working on the characterization and isolation of these species due to their great instability.
In the area of Ge(terphenyl)Cl and Ge(terphenyl)2 complexes, Ge-TM complexes were isolated and characterized. Also the activation of small molecules and the catalytic hydrogenation, hydrosilylation and isomerization of olefins were performed (Figure 2), revealing an unusual selectivity pattern that we attribute to the combination of a germanium centre with rhodium, one of the core ideas of this Marie Curie proposal. These results have already led to a publication in ChemCatChem (2022, 14, e2022001).
We have already in hand many of the proposed mixed MG/TM complexes. Now, progress beyond the state of the art will come from the study of them for the activation of small molecules and catalysis. The cooperativity of MG and TM, because of the unexplored synergies between them, will provide the activation of strong bonds which could not be possible with the general methods reported until now. We also anticipate divergent selectivity to be observed in the investigated catalytic reactions. Preliminary results in this area suggest options of success but the study has to be continued during the following period. These results could have an impact in the cost and sustainability of many chemical transformations of interest for the industry.