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Exploring Lewis Acid/Base Frustration in Carbodi-Phosphoranes: A Study at -78°C

This study delves into the unique interactions of carbodi-phosphoranes displaying high proton affinity. We investigate reactions with B(C6F5)3 at low temperatures, focusing on adduct formation and the challenges posed by frustration with Lewis acids. Key reactions include the nucleophilic attack on Si-H under extreme conditions involving terminal alkynes and various substrates, revealing unprecedented reactivity. Our findings underscore the significance of base interactions and the exploration of proton affinities, contributing to the understanding of frustrated Lewis pairs.

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Exploring Lewis Acid/Base Frustration in Carbodi-Phosphoranes: A Study at -78°C

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  1. Lewis Acid/Base Adduct FLP – Frustration -> activity Carbodiphosphoranes ( C(0) ) – high proton affinity ( > amines, phosphines, N-heterocyclic carbenes) - frustration with B(C6F5)3

  2. Reaction with B(C6F5)3 / H-H Frustration at -78 ℃ (purging H2) (H-H) Adduct at RT

  3. C-O / C-F Ring opening of THF at -78 ℃ (C-O) Ethylene carbonate at -78 ℃ (C-O) 1-fluoropentane at -78 ℃ (C-F) (unprecedented)

  4. Reaction with terminal alkynes / Phenylacetylene at -78 ℃ Basic deprotonation (stronger than tBu3P) Frustration -> nucleophilic attack

  5. Si-H Ph2SiH2 at -78 ℃ EtMe2SiH at -78 ℃ Me3SiOMe at -78 ℃ (C-O) Si-F (X), Si-O (X)

  6. Second proton affinity (-193.4 kcal/mol) (first example of a cationic base in FLP) MeOH at RT (O-H) H-H (X), N-H (X)

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