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Carbonylation reactions of intramolecular vicinal frustrated phosphane/borane Lewis pairs.

Research paper by Muhammad M Sajid, Arunlibertsen A Lawzer, Weishi W Dong, Christoph C Rosorius, Wolfram W Sander, Birgitta B Schirmer, Stefan S Grimme, Constantin G CG Daniliuc, Gerald G Kehr, Gerhard G Erker

Indexed on: 24 Oct '13Published on: 24 Oct '13Published in: Journal of the American Chemical Society



Abstract

The intramolecular frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 4 adds cooperatively to carbon monoxide to form the five-membered heterocyclic carbonyl compound 5. The intramolecular FLP 7 contains an exo-3-B(C6F5)2 Lewis acid and an endo-2-PMes2 Lewis base functionality coordinated at the norbornane framework. This noninteracting FLP adds carbon monoxide in solution at -35 °C cooperatively to yield a five-membered heterocyclic FLP-carbonyl compound 8. In contrast, FLP 7 is carbonylated in a CO-doped argon matrix at 25 K to selectively form a borane carbonyl 9 without involvement of the adjacent phosphanyl moiety. The free FLP 7 was generated in the gas phase from its FLPH2 product 10. A DFT study has shown that the phosphonium hydrido borate zwitterion 10 is formed exergonically in solution but tends to lose H2 when brought into the gas phase.