Ambiphilic Phosphinines: a paradigm shift for aromatic phosphorus heterocycles?

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In this continuation proposal, the very successful project on the chemistry of ambiphilic phosphinines is to be continued. Since the first successful synthesis of a phosphinine derivative by G. Märkl in 1966, the reactivity, coordination chemistry and application of these higher homologues of the pyridines have been determined by their electronic (and partly steric) properties: Phosphinines are characterised by an intrinsically weak nucleophilicity and basicity of the phosphorus atom, whereby its embedding in an aromatic system simultaneously gives rise to significant, electrophilic properties at the donor atom. This combination undoubtedly allows for interesting (follow-on) chemistry, but on the other hand also prohibits access to compounds typical for classical organophosphorus(III) compounds. In the course of the first funding phase, it became apparent that many of the originally postulated ideas and concepts for modifying the nucleophilic and electrophilic properties of phosphinines by introducing suitable substituents on the phosphorus heterocycle could be implemented very successfully. The diversity of the results promises a very multifaceted chemistry also in the second phase, whereby here, in addition to further research into the fundamental properties of functionalised phosphinines and access to still unknown diazaboryl-substituted phosphinines, applications in the field of (catalytic) bond activation reactions will be mainly targeted. The following goals are in focus: (i) diazaboryl-substituted phosphinines and their follow-up chemistry; (ii) insertion and cycloaddition reactions on phosphinine-borane/alane Lewis pairs; (iii) catalytic reactions with phosphinine-borane/alane Lewis pairs; (iv) bond activation reactions with electrophilic phosphinines; (v) reactions of electrophilic phosphinines with carbenes and fluorides. The previous results and preliminary work from the first funding period promise a successful implementation of the planned extensive studies also in the second project phase.