Fluorinated ions, reactions

The fluorine titration of chromium oxide was carried out at the Elf-Atochem Research Center, Pieire-Benite.The catalyst mineralization was carried out in a Parr bomb by reaction with sodium peroxyde. Fluorine ions were then titrated by a potentiometric method with a specific fluoride electrode. 

If we examine the reactant, we find that the compound, KF, is an ionic compound containing potassium ions and fluoride ions. For this reason, we could replace the KF(1) in the original equation with K+(l) + F (l). These two ions, either alone or in combination, are the only substances, other than electrons, that can appear on the reactant side of the half-reactions. One of these ions, the fluoride ion, appears in the fluorine half-reaction. Since KF, and therefore F, is a reactant, we must reverse the fluorine half-reaction to place the fluoride ion on the reactant side. The original KF has no F2, so F2 cannot be a reactant. 

We need to reverse the fluorine half-reaction to place the fluoride ion on the reactant side ... 

The reaction between gaseous magnesium ions and gaseous fluorine ions is highly exothermic. Chemists have determined that 2957 kj of energy is released when 1 mol of Mg " (g) and 2 mol of F (g) react to form 1 mol of the stable ionic solid, MgF2. 

Dinucleoside phosphorofluoridites are readily available (Example 47). The Me3SiCF3 reagent reacts with this type of compounds in the presence of a catalytic amount of CsF (step a) and the trifluoromethylphosphonite formed was oxidized to trifluoromethylphosphonate by TBHP (step b). The method is particularly valuable as it is compatible with a sequential procedure combining the formation of phosphorus-fluorine compounds from pi haryloxy precursors with the reaction leading to P cp groups. Both reactions require the presence of fluorine ions as a substrate or catalyst. 

As well as the Bingel reaction and its modifications some more reactions that involve the addition-elimination mechanism have been discovered. 1,2-Methano-[60]fullerenes are obtainable in good yields by reaction with phosphorus- [44] or sulfur-ylides [45,46] or by fluorine-ion-mediated reaction with silylated nucleophiles [47]. The reaction with ylides requires stabilized sulfur or phosphorus ylides (Scheme 3.9). As well as representing a new route to l,2-methano[60]fullerenes, the synthesis of methanofullerenes with a formyl group at the bridgehead-carbon is possible. This formyl-group can be easily transformed into imines with various aromatic amines. 

Benzene derivatives such as m-methylanisole (40) can be converted to distonic carbene ions. Reaction of 40 with O occurs with loss of H2, generating the conventional carbene anion 41 this anion reacts with molecular fluorine by dissociative ET, followed by nucleophilic attack of F on the methyl group, forming 42. In contrast to phenyhnethylene, 42 has a singlet ground state however, upon protonation it gives rise to the triplet state of m-hydroxyphenyl-methylene. This interesting reaction can be viewed as a spin-forbidden proton-transfer reaction. 

The trimethylsilylated ylides (1), easily generated from trimethyl chlorosilane and ylides, react with aldehydes 2 to form vi-nylsilanes 3 (2,3). The vinylphosphonium silanolates 4 are also formed. Compounds 3 are versatile reagents for further reactions (4). The ylide J (with R1 =H) reacts with aldehydes 2 to give the dienes j). The oxidation of with the adduct 6, from triphenyl-phosphite and ozone, gives access to a generaT synthesis of acyl-silanes (trimethylsilylketones) (2). The silylated ylides react to form phosphonium salts 7 with halogen compounds. The salts 7.can be desilylated by fluorine ions. The disubstituted ylides JO Tormed can be converted in statu nascendi with aldehydes V[ into the tris-substituted olefin J2 (2,3). In the case of R3-I, vinyl... 

Fukada, S., et al. (2007b), Reaction Rate of Beryllium with Fluorine Ion for Flibe Redox Control , Journal of Nuclear Materials, 367-370,1190-1196. 

The mechanism follows initial fluorine ion attack on the silicon atom yielding an ion which transfers the trifluoroviiiyl anion to the alkene, leading to formation of fluorotrimethylsilane and a carbanion. Stabilization of this species by fluoride ion elimination may give a mixture of isomeric dienes which isomerize in the presence of cesium fluoride under the reaction conditions to the end product 3. ... 

Only fluoride compounds of Au are known, and they all have octahedral stereochemistry as expected for a d metal ion. Reaction between AuFs, fluorine, and Xep2 yielded the first gold(V) complex [XeFu][AuF6] (equation (14)). 

Evidence has been presented that hypofluorites (see Section IIIB) can act as sources of electrophilic fluorine for reactions with electron-rich double bonds [11, 93]. Syn addition usually occurs and a tight ion-pair intermediate similar to that postulated to occur in the direct fluorination of alkenes can be envisaged. However, electron-transfer processes have been invoked [93] to explain some anomalous results and cannot be discounted [281] (Figure 3.64). 

Fluoride ion reactions are somewhat puzzling. Oxidation of fluoride ion by a cation radical is out of the question and nucleophilic attack would appear to be certain. However, this reaction has failed completely with several cation radical perchlorates, such as those from perylene (Ristagno and Shine, 1971b), and phenothiazine (Shine et al., 1972). It appears that fluoride ion is too weak a nucleophile to participate in such substitution reactions. On the other hand, several cases of anodic fluorination are known oxidation of some aromatics, in solutions containing fluoride ion and at potentials lower than the oxidation potential of fluoride ion, has led to fluorination. This has occurred with naphthalene, which gave... 

---