Mapping the chemistry of phosphorus-containing analogues of urea. From fundamental chemistry to high-performance compounds and materials.

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The isolobal analogy is frequently invoked to draw comparisons between the fundamental chemistry of small inorganic molecules and more established organic species. For example, the diagonal relationship between a methine fragment (C-H) and phosphorous has led to the latter being nicknamed a "carbon-copy". This has resulted in extensive chemistry aimed at developing phosphorus-containing analogues of organic molecules such as phospha-alkenes (RP=PR) and -alkynes (PCR), amongst many other examples. However, an isolobal relationship does not imply that phosphorus-containing congeners of specific organic molecules can be readily synthesized. In fact, the synthesis of relatively simple molecules where a C-H unit, or even an isoelectronic element such as nitrogen, has been replaced by a phosphorus atom still represents a significant technical and intellectual challenge. In this regard synthetic inorganic chemistry lags far behind organic synthesis.As a case in point, while urea was first synthetically isolated in 1829, it was not until late 2013 that our research group succeeded in the isolation of a phosphorus analogue, phosphinecarboxamide. Considering the importance of urea as a chemical feedstock, we propose to utilize this heavier analogue (and other related species) for the synthesis of novel molecules and solids. This is a completely new approach to organophosphorus compounds which, while inherently risky, has the potential to generate fascinating new species that are related to those derived from urea, but that have fundamentally different chemical and physical properties. Current methods for the synthesis of phosphorus-containing chemicals (employed, for example, in pharmaceuticals and specialty chemicals such as photo-initiators) require the use of phosphorus (III) chloride as a feedstock. While such processes currently represent the industrial state-of-the-art, the use of alternative non-toxic precursors remains a highly desirable objective. Alternative strategies to organophosphorus compounds based on the chemical activation of white phosphorus are possible (and well-documented in the literature), however such transformations are often marred by low selectivities or require multiple subsequent manipulations to be competitive with industrial processes. Moreover, white phosphorus is itself highly pyrophoric and dangerous to manipulate. The risks associated with these precursors make the identification of novel phosphorus-atom feedstocks highly desirable.We propose to develop the chemistry of a new class of phosphorus-containing small molecules that are accessible using red phosphorus, a non-pyrophoric allotrope of the element. Ultimately, this will allow us to reduce the safety risks typically encountered when manipulating conventional precursors for the synthesis of specialty chemicals. Building on recent breakthroughs in our laboratory, we will explore the chemistry of the 2-phosphaethynolate anion and phosphinecarboxamide, two novel phosphorus-containing analogues of otherwise ubiquitous chemicals (the cyanate ion and urea, respectively). Our ultimate goal is to access novel molecular, supramolecular and polymeric species with potential applications in catalysis, chemical sensing and materials chemistry. This proposal represents an entirely novel approach to the development of phosphorus-containing molecules and solids of enormous potential societal and economic impact.