Researchers in the UK have a quick and mild way to break down SF. developed6th. The method converts the potent greenhouse gas into stable aluminum (iii) Fluoride and sulphide compounds, which are used as nucleophilic sources for F. can serve and S.2- in further reactions to valuable organic products.

A picture with sulfur hexafluoride circuit breakers

Due to its very inert nature and excellent thermal conductivity, SF6th used in industry as an electrical insulator in circuit breakers, transmission lines and transformers. However, this inert nature resulting from its high symmetry implies the activation and decomposition of SF6th is extremely demanding. SF6th has an estimated global warming potential 23,900 times greater than that of CO2, and while its inertia makes it a useful gas here on Earth once it is released into the atmosphere, SF6th will stay there for thousands of years.

“The main problem is that there is no conventional and accepted method for the destruction or recycling of SF. gives6th produced in industry, ”explains Daniel Sheldon, who developed the method at Imperial College London together with Mark Crimmin. Thermal decomposition of SF6th requires temperatures above 1100 ° C; electrical discharge decomposition can also be used, but either method can produce toxic or corrosive by-products. Activation of SF6th often requires transition metals or strong reducing agents, so there remains a need for mild and efficient methods of recycling or destroying SF6th prevent its release into the atmosphere.

Crimmins group previously had an Al (I) Connection for the activation of fluorocarbons, which Crimmin and Sheldon now use SF. have put to the test6th. First they have SF. added6th to a C6thD.6th Solution of Al (I) Connection with a supporting ligand ([{(ArNCMe)2CH}Al], where Ar = 2,6-diisopropylphenyl) at 22 ° C. Within 15 minutes the Al (I) Compound was consumed and they observed the formation of a fluorinated product ([{(ArNCMe)2CH}AlF2]) by 1Dog 19thF-NMR spectroscopy. They also found a colorless precipitate that was not detected by NMR. When repeating the reaction with slow SF6th Diffusion to obtain single crystals of the precipitate, they identified a sulfur-containing by-product by X-ray diffraction.

“The fact that the products separate on their own makes further conversion of the resulting aluminum fluoride and sulfide much more convenient,” said Ching-Wen Chiu, an expert on major organometallic groups at National Taiwan University.

Reaction scheme for SF6 activation [{(ArNCMe)2CH}Al]

‘Given its remarkable chemical inertness, we were pleasantly surprised by the ready reactivity of SF6th with the Al (I) Compound, “says Sheldon. Crimmin and Sheldon investigated the mechanism with DFT and calculated the degradation pathway through several SF bond cleavages. These calculations revealed a nucleophilic attack mechanism that differed from most previous reports on single-electron transfer to SF6th. “This article illustrates the enormous untapped potential of main-group metal compounds to activate small molecules in a way that has been considered the exclusive domain of transition-metal chemistry for decades,” notes Eva Hevia, whose research at the University of Bern in Switzerland focuses on polar organometallic chemistry.

“Lately the field has focused on developing reactions that allow the reuse of fluorine and sulfur from SF6thwhich creates a way to reuse the atomic content, ”says Sheldon. Here they could use the aluminum (iii) Fluoride and aluminum (iii) Sulphide products to transfer sulfur and fluorine to useful organic products such as acyl fluorides and a sulfur heterocycle.

Sheldon and Crimmin plan to expand their methodology to address the degradation of other industrially relevant and environmentally stable fluorinated gases.


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