Umpolung of electrophilic terminal phosphinidene complexes: coordination chemistry to phosphorus and gateway to the chemistry of low-coordinate P-based super-electrophiles

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Major aim of the research project is to develop new methodologies to generate novel, highly electrophilic low valent phosphorus species, able to activate small molecules. Starting point for the study should be end-on donor-stabilized terminal, electrophilic phosphinidene complexes (EPCs), i.e. "umgepolte" EPCs. Their structure/reactivity relationship shall be studied, focusing on the following processes at the phosphorus centre: oxidation/oxidative addition (A) and protonation (B). In part A we will study oxidation reactions of end-on donor EPC adducts in order to synthesize highly electrophilic phosphinidene-oxide complexes (EPOCs), but also pathways of oxidative addition reactions of species having differently polarized polar E-E’ bonds. In part B we will react end-on donor EPC adducts with strong Brønsted acids (i) or 1,1’-bifunctional chlorophosphane complexes with chloride abstractors (ii). This should open the gateway to novel protonated EPCs (PEPCs), and important for their reactivity is that reactants in i) and ii) possess weakly coordinating anions (WCAs). Such PEPCs will be examined in small molecule activation such as CO2, N2 and P4. In total, the project should not only lead to new fundamental insights into the coordination/ organometallic chemistry of the non-metal element phosphorus, but also create new mild, powerful synthetic methods. Theoretical studies will be performed in close collaboration with A. Espinosa (Spain).