Competing reaction pathways of 3,3,3-trifluoropropene at rhodium hydrido, silyl and germyl complexes: C–F bond activation versus hydrogermylation

Abstract

The reaction of the silyl complex [Rh{Si(OEt)}(PEt)] (1) with 3,3,3-trifluoropropene afforded the rhodium complex [Rh(CHCHCF){Si(OEt)}(PEt)] (2) which features a bonded fluorinated olefin. In contrast the rhodium hydrido complex [Rh(H)(PEt)] (3) yielded on treatment with 3,3,3-trifluoropropene in the presence of a base the fluorido complex [Rh(F)(PEt)] (4) together with 1,1-difluoro-1-propene by C-F bond activation. At low temperature the intermediate fac-[Rh(H)(CHCHCF)(PEt)] (5) was detected by NMR spectroscopy. The germyl complex [Rh(GePh)(PEt)] (6) reacted also with 3,3,3-trifluoropropene by C-F bond activation affording again the fluorido complex [Rh(F)(PEt)] (4) as well as the (3,3-difluoroallyl)triphenylgermane 7. The catalytic hydrogermylation of 3,3,3-trifluoropropene in the presence of various germanium hydrides under mild conditions was developed by employing complex 6 as a catalyst. The molecular structures of both germane derivatives (3,3-difluoroallyl)triphenylgermane 7 and 1,1,1-trifluoropropane-3-triphenylgermane 8 were determined by X-ray crystallography.

Reactivity of 3,3,3‐Trifluoropropyne at Rhodium Complexes: Development of Hydroboration Reactions

“…[13,20] The 31 P{ 1 H} NMR spectrum is also consistent with the structure proposed showingt wo signals in a2 :1 ratio at d = 18.9 and À3.2 ppm as ad oublet of doublets of multiplets and ad oublet of triplets of multiplets, respectively.T he rhodium-phosphorus coupling constantso fJ = 89.6 and 78.5 Hz, respectively,f urtherc onfirmt he oxidation state (III) of the rhodium center. The hydrido ligand is undoubtedlyc onfirmed by the 1 HNMR spectrum with as ignal at d = À10.25 ppm as ad oublet of pseudoquartets.…”

“…hydrido ligand is in the trans position to the phosphorus atom. [13,20] The 31 P{ 1 H} NMR spectrum is also consistent with the structure proposed showingt wo signals in a2 :1 ratio at d = 18.9 and À3.2 ppm as ad oublet of doublets of multiplets and ad oublet of triplets of multiplets, respectively.T he rhodium-phosphorus coupling constantso fJ = 89.6 and 78.5 Hz, respectively,f urtherc onfirmt he oxidation state (III) of the rhodium center. [13, 16a, 21] In the 19 FNMR spectrum, as ignal at d = À44.8 ppm as ap seudoquartet due to the coupling to the phosphorus atoms of approximately J = 4Hzconfirms the presence of the CF 3 groups.F inally,t wo of the typical signals for the alkyne moieties in the 13 C{ 1 H} NMR spectrum are observed at d = 95.1 and 113.5 ppm forC b and C g with typical C,F coupling constants of J = 47.6 and 251.6 Hz, respectively.T he acarbon atoms are only observed as resonances at d = 118.1 ppm with ac oupling constantt of luorine of J = 7Hzb ya 19 F, 13 CHMBCNMR experiment.…”

Reactions of Fluoroalkenes with an Aluminium(I) Complex

“…Thef ormation of ar elated organometallic species from trifluoropropene has previously been reported upon reaction with [Cp*Ir(PMe 3 )H]Li and [(PEt 3 ) 3 Rh(GePh 3 )]. [34,37] A similar fluorine elimination followed by transposition of the double bond is observed in Lewis-acid-mediated 3,3-difluoroallylation reactions between 2-bromo-3,3,3-trifluoropropene and arenes. [38] In combination, the reactions of 1 with fluoroalkenes possess as eries of interesting mechanistic features that require comment.…”

C−H and C−F Bond Activation Reactions of Fluorinated Propenes at Rhodium: Distinctive Reactivity of the Refrigerant HFO‐1234yf

“…Carbon–fluorine bond activation– can occur through the formation of a thermodynamically favored F−B, F−Si, or F−H bond, among others, implying that metal complexes bearing boryl, silyl, or hydrido ligands are useful for C−F bondactivation reactions . In recent years, we have shown the capabilities of various rhodium(I) complexes [Rh(E)(PEt 3 ) 3 ] (E=H ( 1 ), Bpin ( 6 , pin=pinacolate, O 2 C 2 Me 4 ), Si(OEt) 3 , GePh 3 ) in C−F bond activation reactions of olefins such as hexafluoropropene, 3,3,3‐trifluoropropene, and cis ‐1,2,3,3,3‐pentafluoropropene . In contrast, C−H activation steps at fluoroolefins are very rare and usually restricted to olefins not fluorinated at the double bond.…”

“…Treatment of [Rh(H)(PEt 3 ) 3 ] ( 1 ) with HFO‐1234yf at room temperature provided selectively the rhodium fluorido complex [Rh(F)(PEt 3 ) 3 ] ( 3 ) and 3,3,3‐trifluoropropene conveniently and efficiently, in contrast to previous methods to access 3 , which require sources of HF and longer reaction times . The intermediate of this reaction fac ‐[Rh(H)(CH 2 =CFCF 3 )(PEt 3 ) 3 ] ( 2 ) was identified by NMR spectroscopy at 253 K (see the Supporting Information) and exhibits a coordination of the olefin at the rhodium center of 1 (Scheme ).…”