Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - VAIM (Stereoregular Inorganic Polymer Analogues of Polyolefins)

Teaser

Inorganic polymers contain elements other than carbon in the backbone and are promising as new materials with unique physical and chemical properties. Controlling stereoregularity within polymers can also have a drastic impact on the resulting material properties, and the...

Summary

Inorganic polymers contain elements other than carbon in the backbone and are promising as new materials with unique physical and chemical properties. Controlling stereoregularity within polymers can also have a drastic impact on the resulting material properties, and the range of potential applications. This project aimed to address the synthesis of stereoregular inorganic polymers using chiral transition metal catalysts for the dehydrocoupling reaction, where the resulting materials should be of interest for a range of applications especially those where polymer thermal properties and crystallinity are important.

While the initial objective of the project was the generation of stereoregular inorganic polymers this proved to be hindered by the general lack of understanding of the mechanism of dehydrocoupling reaction. The major conclusions from the project were a much deeper understanding of the mechanisms for dehydrocoupling reactions used to generate inorganic polymers and small molecules through element-element bond formation. Several of the new routes to phosphorus-containing materials could be performed under more environmentally friendly or mild conditions compared to traditional routes, and avoid the use of expensive and scarce transition metal catalysts.

Work performed

Several new chemical reactions were developed over the course of the project. This included the development of an inorganic ‘click’ reaction which could be used to generate new phosphorus-containing ligands or polymers (Fig 1a). Metal-free approaches to dehydrocoupling using a main-group Lewis acid catalyst allowed access to silylphosphines, a synthetically versatile class of compounds (Fig 1b). A metal-free approach using carbenes as a hydrogen-acceptor which allowed for the formal dehydropolymerisation of phosphine-boranes, including the synthesis of unprecedented P-disubstituted polyphosphinoboranes (Fig 1c). We were also able to develop the synthesis of new inorganic polymers which possess a PV–O main chain and found that their depolymerisation could be triggered which may hold promise for new recyclable polymers (Fig 1d). We also discovered a highly general transition metal-free approach using inexpensive alkali metal-based catalysts for the dehydrocoupling of phosphines to generate compounds featuring a new P–E (where E= P, N, O, S) (Fig 1e). All these results have been published in top-ranking journals, and presented at conferences, symposia, and to the general public at University open days, and EU researchers’ events.

Final results

The progress beyond the state of the art is the potentially environmentally greener synthesis of phosphorus-based molecules and materials. Catalytic dehydrocoupling routes where molecular dihydrogen (H2) is the only by-product have the potential advantages of generating less waste than traditional salt metathesis syntheses of main-group molecules and polymers. The exciting prospects of expanding the synthetic toolkit used by chemists to make inorganic polymers and small molecules could find use in a wide variety of industries, especially in fine chemical synthesis and polymeric materials.

Website & more info

More info: http://www.inchm.bris.ac.uk/people/manners/home.html.