Information about the functionalization of fluorinated molecules by transition-metal-mediated C-F bond activation is presented. Topics discussed include C-F activation and C-heteroatom bond formation.
'Al'l about F: Aluminum chlorofluoride (ACF) catalyzes the hydrodefluorination, as well as Friedel–Crafts reactions of fluorinated methanes in the presence of Et3SiH. A surface‐bound ...silylium‐ion‐like species is considered to be a crucial intermediate in achieving the CF bond cleavage.
The reaction of the silyl complex Rh{Si(OEt)
}(PEt
)
(1) with 3,3,3-trifluoropropene afforded the rhodium complex Rh(CH
CHCF
){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)(CH
CHCF
)(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.
In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation ...catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process.
The use of operando FTIR indicates that the high efficiency for NO2 removal from ambient air of iron-containing zeolites comes from their ability to condensate nitric acid. The NO2 removal ...performance of Fe-modified H-BEA and H-ZSM-5 has been investigated in detail by means of in situ and operando FTIR spectroscopy. The surface characterization using NO2 and NO as probe molecules revealed important contributions of redox processes involving Fe3+ -OH and/or alpha-oxygen species as well as Fe2+ -NO species. In these anhydrous conditions, the NO2 storage performance is mainly due to the disproportion of NO2 leading to NO+ and nitrate species. However, under flow and in the presence of humidity, and thus in more realistic conditions, nitrates and NO+ formation are suppressed. The main mechanism responsible for the wet NO2 removal consists in the formation of both adsorbed nitric acid and gaseous NO. According to the proposed mechanism, a strong positive water-effect is established: the total suppression of NO2 in the presence of humidity together with the formation of NO, which is less toxic than NO2 , makes the investigated zeolites promising candidates for efficient materials used in indoor air treatment. PUBLICATION ABSTRACT
The hydrofluorocarbon 245 isomers, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2- pentafluoropropane, and 1,1,1,2,3-pentafluoropropane (HFC-245fa, HFC-245cb, and HFC-245eb) were activated through C-F bond ...activations using aluminium chlorofluoride (ACF) as a catalyst. The addition of the hydrogen source Et
SiH is necessary for the activation of the secondary and tertiary C-F bonds. Multiple C-F bond activations such as hydrodefluorinations and dehydrofluorinations were observed, followed by hydroarylation and Friedel-Crafts-type reactions under mild conditions.
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•Unusual reactions of 1,1,-difluoroallene towards rhodium complexes are described.•Coordination and insertion into RhH or RhSi bonds were observed as supported by NMR spectroscopy, ...X-ray crystallographyand DFT calculations.•Surprisingly, with hexafluoropropene metallacyclopropane formation and no C-F activation occurred.
The reaction of rhodium(I) complexes Rh(E)(PEt3)3 (E = H (2), Si(OEt)3 (4)) with 1,1-difluoroallene provides the rhodium (III) complexes Rh(η2-CH2CCF2)(η3-CH2C(E)CF2)(PEt3)2 (E = H (3), Si(OEt)3 (5)). The conversions involve the coordination of one equivalent of difluoroallene to form a rhodiumcyclopropane and the insertion of a second equivalent into the Rh-E bond. X-ray crystallography as well as DFT calculations support the suggested structures as well as the arrangement of the fluorinated ligands. In contrast, when Rh{Si(OEt)3}(PEt3)3 (4) reacted with hexafluoropropene, only the coordination of the fluorinated olefin was observed resulting in the formation of Rh(CF2CFCF3){Si(OEt)3}(PEt3)2 (6).
The (β‐ketiminato)rhodium complex Rh{κ2‐(N,O)‐(tBu)(O)CCHC(tBu)N(C6F5)}(cod) (1) cod = (1Z,5Z)‐1,5‐cyclooctadiene and (β‐diketiminato)rhodium complexes Rh{κ2‐(N,N)‐(Ar)NC(Me)CHC(Me)N(Ar)}(L1)(L2) 2: ...Ar = C6F5, (L1)(L2) = cod; 3: Ar = C6F5, L1 = L2 = C2H4; 4: Ar = C6F5, L1 = L2 = CNtBu; 5: Ar = 2,6‐MeC6H3, L1 = L2 = CNtBu; 6a: Ar = C6F5, L1 = L2 = CO; 7a: Ar = C6F5, L1 = CO, L2 = NCMe; 8a: Ar = C6F5, L1 = CO, L2 = PEt3; 9a: Ar = C6F5, L1 = CO, L2 = NH3 were synthesized. Treatment of Rh{κ2‐(N,N)‐(C6F5)NC(Me)CHC(Me)N(C6F5)}(CO)(NCMe) (7a) with tertiary silanes HSiR3 gave the (β‐diketiminato)(hydrido)(silyl)rhodium complexes Rh{κ2‐(N,N)‐(C6F5)NC(Me)CHC(Me)N(C6F5)}(H)(SiR3)(CO) (10a: R = Me; 11: R = Et; 12: R = iPr; 13: R = Ph; 14: R = OMe; 15: R = OEt). When using an excess amount of HSiMe3 the dihydridobis(silyl) complex Rh{κ2‐(N,N)‐(C6F5)NC(Me)CHC(Me)N(C6F5)}(H)2(SiMe3)2 (16) was formed in addition to 10a.
A series of rhodium complexes with a fluorinated β‐diketiminato ligand as well as a fluorinated β‐ketiminato ligand has been synthesized. Treatment of Rh{κ2‐(N,N)‐(C6F5)NC(Me)CHC(Me)N(C6F5)}(CO)(NCMe) with tertiary silanes HSiR3 (R = Me, Et, iPr, Ph, OMe, OEt) gave the (β‐diketiminato)(hydrido)(silyl)rhodium complexes Rh{κ2‐(N,N)‐(C6F5)NC(Me)CHC(Me)N(C6F5)}(H)(SiR3)(CO).
A substantial fraction of insects and other terrestrial arthropods are infected with parasitic, maternally transmitted endosymbiotic bacteria that manipulate host reproduction. In addition to ...imposing direct selection on the host to resist these effects, endosymbionts may also have indirect effects on the evolution of the mtDNA with which they are cotransmitted. Patterns of mtDNA diversity and evolution were examined in Drosophila recens, which is infected with the endosymbiont Wolbachia, and its uninfected sister species D. subquinaria. The level of mitochondrial, but not nuclear, DNA diversity is much lower in D. recens than in D. subquinaria, consistent with the hypothesized diversity-purging effects of an evolutionarily recent Wolbachia sweep. The d(N)/d(S) ratio in mtDNA is significantly greater in D. recens, suggesting that Muller's ratchet has brought about an increased rate of substitution of slightly deleterious mutations. The data also reveal elevated rates of synonymous substitutions in D. recens, suggesting that these sites may experience weak selection. These findings show that maternally transmitted endosymbionts can severely depress levels of mtDNA diversity within an infected host species, while accelerating the rate of divergence among mtDNA lineages in different species.
Abstract The κ 2 ‐(P,N)−phosphine ligand precursor NH(CH 2 CH 2 PCy 2 ) 2 can be used for the synthesis of the rhodium(I) complex Rh(CO){ ĸ 3 ‐(P,N,P)−Cy 2 PC 2 H 4 NHC 2 H 4 PCy 2 }Cl ( 1 ). The ...deprotonated complex Rh(CO){ ĸ 3 ‐(P,N,P)−Cy 2 PC 2 H 4 NC 2 H 4 PCy 2 } ( 2 ) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO 2 F 2 to yield the rhodium fluorido complex trans ‐Rh(F)(CO){ ĸ 2 ‐(P,P)−Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 } 2 ( 3 ) by S−F bond cleavage. It is remarkable that no reaction was observed when 3 was treated with hydrogen sources e. g. dihydrogen, organosilicon compounds such as triethylsilane or TMS−CF 3 and different fluorine sources such as SF 4 or Selectfluor®. However, the treatment of complex 3 with XeF 2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis , trans ‐Rh(F) 3 (CO){ ĸ 2 ‐(P,P)−Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 } 2 ( 4 ). In the presence of pyridine(HF) X or BF 3 the fluorido complex 3 converted into the dicationic complexes Rh(CO){ ĸ 2 ‐(P,P)−Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 } 2 XF 2 , X=HF ( 5 ) or BF 3 ( 6 ), respectively.
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