Tetrafluoroethylene complexes, bonding

One complex with a metal—metal bond that has been added to an olefin is cobalt octacarbonyl. It reacts with tetrafluoroethylene and it seems reasonable that this is an insertion reaction but again it has not been proved. 

Under similar experimental conditions (SIFT at room temperature), however, F adds to the C—C double bond of perfluoroalkenes such as tetrafluoroethylene and hexafluo-ropropene, which are industrially important monomers290. In the case of hexafluoro-propene a second addition step is also observed (Scheme 43). These reactions are believed to involve covalent addition rather than cluster formation for a number of reasons. First, ab initio calculations show that QF5 and C3Ff are stable ions and that the chemically bonded species 132 is more stable than the 7r-complex structure 133291. Second, these reactions... 

The parent TMM complex (190 R = H) undergoes photochemical ligand substitution with trifluorophosphine or trimethylamine Al-oxide assisted substitution with tertiary phosphines or t-butyl isocyanide (Scheme 5A) Trimethylamine A-oxide assisted substitution using isoprene as the incoming ligand results in C-C bond formation to afford the bis-TT-allyl complex (197). An intramolecular version of this reaction is also known.The parent complex (190 R = H) reacts with electrophiles. Addition of HCl or Br2 gives the methallyl complexes (192) and (198), respectively. Tetrafluoroethylene adds across the Fe bond to afford (199) under photochemical conditions. Complex (190) undergoes Friedel-Crafts-type acylation with... 

Alkylcobalts form in stoichiometric reactions of pentacyanocobalt(III) hydride and alkenes. This reaction occurs both for halogenated alkenes such as tetrafluoroethylene and for alkenes that contain other electron-withdrawing groups such as carbonyls, nitriles and arenes as substituents (see Table 6) . The addition is regiospedfic, forming the more substituted alkylcobalt. Prior coordination of alkene to cobalt to form an alkene(hydrido)cobalt complex, an intermediate in hydrometalation reactions, is not important. This reaction is a radical process however, by NMR, additions of [HCo(CN)5 ] " to diastereomeric alkenes such as fumaric and maleic add salts lead to a cr-alkylcobalt by stereospecific cis addition of Co and H to the double bond . The overall reduction is not stereospecific. (r-Alkylcobalt bond formation proceeds by either a concerted addition or a rapid collapse of a radical cage. 

A catalytic addition of acidic alcohols or phenols to hexafluoropropene is induced by the complex Pd(PPh3)4 [110]. Catalytic activity is increased in the presence of cocatalytic l,4-bis-(diphenylphosphino)butane (dppb) (Scheme 19). The authors propose a mechanism involving external protonation of a Pd(0)-coordinated olefin and reductive elimination to the ether product, but both steps appear improbable. There is literature precedence for insertion of tetrafluoroethylene into the Pt-O bond of (dppe)PtMe(OMe) to give (dppe)PtMe(CF2CF20Me), but proto-demetallation of the resulting complex has not been reported [111, 112]. 

Tetrafluoroethylene reacts with Fe(CO)3(butadiene) by a two-step oxidative addition process to give (43). The reaction of the rhodium(i) complex Rh(acac)(cod) with hexafluorobut-2-yne results both in trimer-ization of this alkyne, and either its insertion into a y-bonded acetyl-acetonate intermediate or a concerted addition to the acetylacetonate ring, to produce (44), RhCl3,3H20 reacts with 2-methylallyl alcohol, in the presence of 4-methylpyridine (pic), probably via two insertion reactions, to... 

Treatment of poly tetrafluoroethylene with sodium complexes also gave strong evidence of surface oxidation, and resulted in up to tenfold increases in bond strength with epoxy adhesives [40]. 

Reactions of perfluoro olefinic compounds with iron carbonyls are also found to be somewhat unusual due undoubtedly to the high electronegativity of the fluorine atom. Tetrafluoroethylene was found to react with Fe3(CO)i2 to give a complex, first thought to be (LXV) 81) but subsequently shown to be the o-bonded Fe(CO)4 complex (LXVI) 82, 83). The formation of (LXVI) in this manner is related to the fact that whereas Fe-alkyl bonds are very unstable, Fe-perfluoroalkyl bonds, as in the complex (CF3—CF2)2—Fe (CO)4, are found to be quite stable 84). 

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