Synthesis and reactivity of the 2-phosphaethynolate anion and phosphinecarboxamide

Thesis

This thesis describes a novel synthesis of the 2-phosphaethynolate anion, [PCO]^–, via reaction of the [P₇]^3– Zintl cluster with carbon monoxide. The ligand properties of this fundamental molecule have been probed and compared to common isoelectronic pseudohalides: cyanate and isocyanate. The first ambient-temperature synthesis of the heavier congener, [PCS]^–, is also reported, and studies show that this anion can act as an ambidentate ligand.

The cycloaddition chemistry of [PCO]^– with heteroallenes afforded a range of novel anionic phosphorus-containing heterocycles. A collaborative study has shown that [PCO]^– can act as a catalyst for the trimerisation of isocyanates, and potential intermediates in this catalytic cycle have been isolated.

By analogy with Wöhler's historic synthesis of urea, the reaction of [PCO]^– with ammonium salts yields phosphinecarboxamide. This unprecedented molecule is a rare example of an air-stable "user-friendly" primary phosphine, and its structure and ability to coordinate to metal centres were explored. It was found that this species has similar σ donor and π acceptor properties to phosphine, PH₃.

This reactivity has been extended to incorporate N-functionalised phosphinecarboxamides with a range of different functional groups. The Brønsted acidity, P-functionalisation and oxidation chemistry of these species was subsequently investigated to afford a diverse family of carbamoyl-bearing phosphides, phosphines and phosphine oxides. Some of these species have great potential to become industrially relevant molecules in the future. Preliminary results showing the generality of the reaction of [PCO]^– with other protic nucleophiles are additionally presented.

Authors: Jupp, A

• DOI: 10.5287/ora-6gdngj7yb
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford