Competing C–H and C–F bond activation reactions of a fluorinated olefin at Rh: a fluorido vinylidene complex as an intermediate in an unprecedented dehydrofluorination step. Issue 4 (12th January 2022)

• Record Type: Journal Article
• Authors: Talavera, Maria; Braun, Thomas
• Is Part Of: Chemical science. Volume 13:Issue 4(2022)
• Page Start: 1130
• Page End: 1135
• Publication Date: 2022-01-12
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1sc06713c
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Dehydrofluorination of a fluorinated vinyl ligand takes place after C–H bond activation of Z -1, 3, 3, 3-tetrafluropropene at a rhodium vinyl complex. Model studies support a vinylidene as reaction intermediate for the dehydrofluorination. Abstract : The hydrofluoroolefin Z -1, 3, 3, 3-tetrafluoropropene has been activated via an initial C–F bond activation and subsequent C–H bond activation using [Rh(H)(PEt3 )3 ] (1 ) or via C–H bond activation at [Rh(CH3 )(PEt3 )3 ] (8 ). In both cases the formation of [Rh{( E )-CFCHCF3 }(PEt3 )3 ] (3 ) was observed. Importantly, the C–F activation product [Rh{( E )-CHCHCF3 }(PEt3 )3 ] (2 ) reacts in the presence of Z -1, 3, 3, 3-tetrafluoropropene into 3 . The latter converted into [Rh(CCCF3 )(PEt3 )3 ] (6 ) by an unprecedented dehydrofluorination reaction, presumably via a vinylidene complex as intermediate. When the carbonyl complex [Rh(CCCF3 )(CO)(PEt3 )3 ] (12 ) was treated with an excess of NEt3 ·3HF or HBF4 at low temperature, the formation of the phosphonioalkenyl compounds [Rh{( Z )-C(PEt3 )CHCF3 }(CO)(PEt3 )2 ]X (X = F(HF) x, BF4 ) (13 ) was observed. The formation of 13 can be explained by an attack of PEt3 at the electrophilic α-carbon atom of an intermediate vinylidene complex. The employment of P i Pr3 derivatives as model compounds allowed for the isolation of the unique fluorido vinylidene complex trans -[Rh(F)(CCHCF3 )(P i Pr3 )2 ] (16 ), which in the presence of PEt3 transforms into [Rh(CCCF3 )(PEt3 )3 ] (6 ).