From perfluoroacyl halides

Perfluoroacyl halides readily form perfluoroacyl-metal complexes, M—CORf, from which the perfluoroalkyl derivatives are easily prepared by decarbonylation, e.g. 

In some cases, thermal decarbonylation is preferable to photochemical techniques [51]. Using this synthetic approach, perfluoroacyl and alkyl complexes of Mn(CO)s [210, 211, 212, 213, 214], Re(CO)s [210], iron carbonyls [51, 215, 216], cobalt carbonyls [211, 213, 217, 218] and jr-C5HsMo(CO)3 [51] have been isolated. Perfluoroacyl derivatives may also be prepared using perfluoroacid anhydrides [213]. 

Unlike alkyl halides, perfluoroalkyl halides do not give perfluoroalkyl derivatives when they react with metal carbonyl anions. 

The electronegativities of perfluoroalkyl groups are so large that the perfluoroalkyl halides may be regarded, to some extent, as pseudo-interhalogen compounds. Stone and co-workers have demonstrated this analogy in the reactions between RfX and metal carbonyls, e.g. 

Perfluoroalkyl halides also add across metal-metal bonds, as do the halogens. 

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Acyl fluorides have been used as intermediates to prepare fluoroethers from perfluoroacyl halides. Some of the perfluoroethers prepared are found to be not ozone-depleting and are therefore useful as detergents, solvents, heat-transfer media, etc.39... 

Hydrosilation of ajS-unsaturated esters has been achieved using tris(triphenyl-phosphine)-chlororhodium as catalyst yields are excellent, and to a large extent the additions are regioselective, although the precise orientation of addition varies remarkably with the nature of the starting ester. Various perfluoro esters have been prepared directly from perfluoroacyl halides and organosilicon hydrides. ... 

For acyl halides or anhydrides which do not afford ketenes in the presence of base (such as perfluoroacyl halides), however, the a-acylmethylenephosphoranes can be prepared directly in one step from the phosphonium salts by using two equivalents of base by the present procedure (Table I).2 Both tetrahydrofuran and methylene chloride have been used as solvents and in the case of the title compound, tetrahydrofuran provides the best results. Good yields of the phosphoranes are generally obtained when R1 is an electron-withdrawing group such as ester or nitrile. The yields of phosphoranes obtained for the thiomethyl or phenyl cases can be... 

Although those Michaelis-Arbuzov reactions which involve acyl halides and phospho-rus(III) esters are yet a further route to phosphorus-carbon bond formation and will be discussed later in Section VI, the use of halogenated acyl halides has led to some unusual results which, conveniently, can be summarized here. The products obtained from reactions between trialkyl phosphites and perfluoroacyl chlorides contain both phosphonate and phosphate moieties and are structurally dependent on reaction temperature. The initial product (Scheme 4) is thought to be the ylide 66. In an ethereal solvent at low temperature, decomposition of the ylide yields [l-(dialkoxyphosphinoyl)oxy-l/f-perfluo-roalkyl]phosphonates (67) exclusively, but at -20 °C and above, and in the absence of a solvent, the products consist of (Z)-[l-(dialkoxyphosphinoyl)oxyperfluoroalkene]phos-phonates (68) . The treatment of the compounds 67 with Ida yields 68, and the action of BuLi-CuI on 68 results in loss of the phosphate moiety to give the esters 69 The structural isomers 70 of the compounds 68 have been obtained as illustrated in equation... 

Mn(CO)5] reacts with allyl halides at room temperature to produce the hexacoordinate a-allyl derivative C3H5Mn(CO)5 which must be heated to 60° C before carbon monoxide is lost at an appreciable rate to form the ir-allyl derivative C3HsMn(CO)4 (99,100). In addition, the pentacoordinate perfluoroacyl derivatives of cobalt, RfCOCo(CO)4 (38, 111, 112), lose carbon monoxide to form RfCo(CO)4 at a lower temperature than the hexacoordinate perfluoroacyl derivatives of manganese, RfCOMn(CO)5 (38,113), form the perfluoroalkyl derivatives, RfMn(CO)s. On the basis of present data, however, it is diflicult to separate the effect of coordination number on the general stability of the molecule from the effect of coordination number on the stability of the metal-carbon monoxide bond. 

No stable compounds of the type R2Fe(CO)4 with iron-carbon a bonds have been isolated by the reaction between [Fe(CO)4] and alkyl halides such as methyl iodide. However, the perfluoroalkyl derivatives (Rf)2Fe (CO)4 (Rf = C2F5 and C3F7) have been obtained as air-stable very pale yellow crystals by the reaction between Na2[Fe(CO)4] prepared in tetra-hydrofuran and the perfluoroacy/ chlorides RfCOCl. The intermediate perfluoroacyl derivatives (RfCO)2Fe(CO)4 were not isolated, but instead were decarbonylated spontaneously in the boiling tetrahydrofuran 50). For reasons which are not clear at the present time the yields of the perfluoroalkyl compounds (Rf)2Fe(CO)4 in this reaction were only about 15%. Attempts to prepare (CF3)2Fe(CO)4 by this technique have been unsuccessful. A related compound is the extremely stable perfluorotetramethylene derivative C4FgFe(CO)4 (XXIX) 182) obtained from tetrafluoroethylene and iron pentacarbonyl. This fluorocarbon derivative was first erroneously formulated as a tricarbonyl derivative 183). 

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