Organometallic fluorinated

Systems usually fluonnated by electropositive fluorine reagents include acti-vated alkenes (enol ethers, enol acetates, silyl enol ethers, and enamines), activated aromatic systems, certain slightly activated carbon-hydrogen bonds, and selected organometallics. 

The preparation of aromatic fluorine compounds may be accomplished by direct fluorination or by fluonnation of organometallic intermediates. Tlte ipso fluorination of an aryl organometallic derivative with a positive fluorine reagent allows control over the regioselectivity of the fluorination and offers advantages in the preparation of F-labeled materials [II, 50],... 

The fluorination of organometallics with Al-fluoroamide reagents has received Only limited attention. Grignard reagents, both aliphatic and aromatic, are converted to organofluonne compounds. Both the electron transfer and the Sf,j2 ntechamsms have been considered in these processes [SO, 81, 82], The reactions 0 exemplified in equation 46 [48, 69, 70, 71, 75] Organosilanes are also fluonnated [71] (equation 47)... 

After a vigorous initial activity, whereby new fluorinated organometallic compounds were first synthesized, much of the research effort has decreased Some activity has been concerned with the reactions of perfluoroaromatic magnesium compounds... 

The insertion of calcium atoms into vinyl and aryl carbon-fluorine bonds has been reported Only the resulting organometallic from the aryl derivatives appears to live long enough to be trapped by water [J]... 

Also in the divalent state, Pd and Pt show the class-b characteristic of preferring CN and ligands with nitrogen or heavy donor atoms rather than oxygen or fluorine. Platinum(IV) by contrast is more nearly class-a in character and is frequently reduced to Pt by P- and Aj-donor ligands. The organometallic chemistry of these metals is rich and varied and that involving unsaturated hydrocarbons is the most familiar of its type. 

Reactions of heterocycles with fluorinated organometallic compounds 97MI31. 

Deletion of the 17a-hydroxy group similarly leads to an effective topical antiinflammatory agent. Treatment of 16a-methylpregnenolone (244) (obtained by conjugate addition of an organometallic to pregnenolone) sequentially with bromine and acetate ion affords the 21 acetate, 245 (see, for example, the transformation of 196 to 198). In an interesting variation on the method for the introduction of a fluorine atom at 6, the... 

Fluorination of organometallics, e.g., Me3Sn-imidazoles, has been used to improve selectivity with the aromatic—metal bond being broken preferentially (86BSF930). 

IV. Synthesis of Trifluoromethyl Organometallic Compounds by Direct Fluorination... 

A quite surprising development, even to experienced workers in elemental-fluorine chemistry, has been the synthesis of trifluoromethyl organometallic compounds by direct fluorination of metal alkyls (25). Even more surprising is the fact that, for certain metal and metalloid systems, such as the reaction of elemental fluorine with tetramethyl-germane, this t5rpe of low-temperature synthesis is a practical method 26) for the laboratory preparation of the perfluoro analog. 

This method of low-temperature, direct fluorination involves very precise control of fluorine concentrations during the reaction, and initial high dilution of the fluorine with helium. The reaction of elemental fluorine with organometallic compounds is conducted (27) in a cryogenic-zone reactor (see Fig. 8) at temperatures in the range of - 78 to... 

As outlined above, immobilization in a fluorinated liquid phase demands the functionahzation of the ligand with perfluoroalkyl chains and, even then, the solubihty is strongly influenced by the nature of the complex. Ionic hquids of the alkylmethyhmidazolium type (Fig. 4) have been recently developed as alternative solvents for organometallic catalysis and have the practical advantage of using directly the commercially available chiral hgands and complexes. 

The bond dissociation energy of fluoromethane is 115 kcal mol , which is much higher than the other halides (C-Cl, C-Br and C-1, respectively 84, 72 and 58 kcal mol ) [6], Due to its strength, the carbon-fluorine (C-F) bond is one of the most challenging bonds to activate [7], A variety of C-F bond activation reactions have been carried out with different organometallic complexes [8], Among them, nickel [9] and ruthenium complexes have proven to proceed selectively under mild conditions [10],... 

Y. Wang, N. Herron, V.V. Grushin, D. LeCloux, and V. Petrov, Highly efficient electroluminescent materials based on fluorinated organometallic iridium compounds, Appl. Phys. Lett., 79 449-451 (2001). 

Tho main routes for the insertion of fluorinated alkyl groups in the silicones are suggested either by organometallic or by hydrosilylation methods as shown in Scheme 2. Consequently, research can be pursued in two directions (a) synthesis of fluorohalides and alkenes, and (b) introduction in siliconated groups and polymerization. 

There are two possible ways to introduce fluorinated groups into silanes and silicones through the use of fluorinated organometallic reactants (mainly orga-nomagnesians and organolithians) or by hydrosilylation of fluorinated alkenes. 

The direct fluorination of inorganic,1,2 organometallic,3 5 and organic compounds,6-8 employing the LaMar9,10 and Exfluor-Lagow" methods, has impacted the synthesis of fluorinated compounds over the past 25 years. Among the most important applications of direct fluorination are the synthesis of fluoropolymers from hydrocarbon polymers and the conversion of the surface of the hydrocarbon polymers to fluoropolymer surfaces.12,13 The direct fluorination process is an excellent approach to the synthesis of fluoropolymers. 

Organic compound removal, with ion-exchange resins, 14 423 Organic compounds. See also Organic fluorine compounds Organics Organometallic compounds addition to reaction mixtures, 16 409—411... 

Another approach to isolate the catalyst from the products is the application of perfluorinated catalytic systems, dissolved in fluorinated media [63], which are not non-miscible with the products and some commonly used solvents for catalysis like THE or toluene at ambient temperature. Typical fluorinated media include perfluorinated alkanes, trialkylamines and dialkylethers. These systems are able to switch their solubility properties for organic and organometallic compounds based on changes of the solvation ability of the solvent by moving to higher temperatures. This behavior is similar to the above-mentioned thermomorphic multiphasic PEG-modified systems [65-67]. 

Example 52 replacement of the fluorine ligand by the alkyl (aryl) group by the action of organometallic reagent has been studied by Michalski and associates. Preliminary successful results have been achieved with Grignard reagents [30]. 

---