The following paragraphs cover the work carried out within this ERC project from February 2018 to the end of the project (see Figure).
Objective 1: We have investigated many bimetallic FLP combinations and acquired a deep understanding on how they operate. Some of them activate rather strong bonds (Chem. Commun. 2019). In addition, our mechanistic investigations allowed us to provide evidence for the genuine frustrated character of our gold/platinum TMFLPs (CEJ2020), while subtle modifications of the ligands permit rational control of regioselectivity (Organometallics 2020, 2021; Chem. Commun. 2022). Our Lewis acid/base bimetallic combinations have also allowed us to identify the non-innocent character of the very common Cp* ligand (Angew. Chem. 2020; JACS, 2019, Dalton Trans. 2023, Inorg. Chem. 2023). Also, we have started to explore bimetallic FLPs based on Earth abundant metals (Angew. Chem. 2022). Our continuous interest on accessing extremely bulky and electrophilic synthons led us to discover a novel mechanism for C-C bond formation (JACS, 2021) and to disclose a highly constrained cavity-shaped gold system (Chem. Commun. 2021, ACS Catal. 2022, ChemPlusChem 2022, Inorg. Chem. 2022). Additionally, our attempts to access radical FLPs led us to an intriguing open-shell Ir(II) system (Angew. Chem. 2022).
Objective 2: We have examined the coordination chemistry of sterically congested germylene compounds with a variety of transition metals. From there, we have obtained dynamic information from X-ray diffraction studies on metalogermlenium cations (CEJ2020), demonstrated the potential of TM-Ge cooperation during bond activation (CEJ2021) and catalysis (ChemCatChem 2022, Chem. Commun. 2022). We investigated the synthesis and tuning of their clusters (CEJ 2024). The combination of alkali and transition metals was also explored (Chem. Sci. 2022). In addition, we have investigated the reactivity of a gold/platinum FLP towards tetrylene dihalides (combining WP1 and W2; Dalton Trans. 2019). With the same spirit of combining WP1 and WP2 we have explored the bonding in metal-only Lewis pairs formed between a Rh(I) Lewis base and main group Lewis bases (CEJ2020).
Objective 3: We have prepared a number of transition metal clusters. We have combined cationic versions of these clusters with commercial polyoxometalates and obtained a family of heterogeneous intercluster compounds. Despite our success in synthetic aspects, the prepared materials do not show remarkable results in terms of catalysis yet. We continue exploring other related systems, as described in our contingency plans (e.g. Molecules, 2020).
Objective 4: We have not yet found catalytic applications of the cooperative systems targeted in WP4. Some of them have been prepared, but their characterization is rather difficult and still evolved into nanoparticles which, although interesting, were beyond our scope. We have explored an alternative approach based on solid-state organometallic chemistry based on extremely bulky systems that still holds the porosity of a molecular heterogeneous material and that set the grounds for much future work in our group. The first contribution is currently under evaluation.