Fluorocarbon-metal derivatives

The F nucleus is almost as suitable as the proton for NMR work and the large fluorine chemical shifts minimize second order effects, thereby permitting meaningful deductions to be made about molecular structure. The F spectra of many of the recently described fluorocarbon-metal derivatives have been recorded, and the chemical shifts and spin coupling constants listed. References to these studies are collected in Table VIII. 

Brennessel, W. W. et al., J. Amer. Chem. Soc., 2002, 124(35), 10258 Pyrophoric, and spontaneously ignites with fluorocarbon solvents even under argon. See also METAL DERIVATIVES OF ORGANOFLUORINE COMPOUNDS See other ORGANOMETALLICS... 

Factors affecting the stability of transition-metal bonds to carbon are of continued interest and fluorocarbon transition-metal derivatives are especially interesting [115-117] because of their generally enhanced stability, relative to hydrocarbon analogues. Factors... 

For a wider discussion of fluorocarbon-transition-metal derivatives, and aspects such as their bonding, the reader is referred to other sources [115-117]. 

Various approaches to other transition-metal derivatives have been applied which are not covered here, but some involve reactions that exploit the properties of the fluorocarbon... 

Another possible explanation for enhanced stabilities of perfluoro-alkyltransition metal compounds concerns possible multiple bonding between the metal and the fluorocarbon group 230). Whatever the reason, a large number of fluorocarbon derivatives of the transition metals have now been described, and a study of their synthesis, properties, and reactions constitutes an important new branch of organotransition metal chemistry. Fluoroalkyltransition metal compounds were first described in 1959 J 8), while perfluoroary 1-transition metal derivatives were discovered in 1963 201, 234). Some typical syntheses of fluorocarbon-transition, metal compounds are shown below ... 

In this review compounds of metals of the main groups are discussed systematically according to the Periodic Table, and this is followed by a survey of fluorocarbon derivatives of the transition metals and the zinc subgroup. Compounds of boron and silicon will be considered even though these elements are not metals in the real sense of the term. Nevertheless, studies on fluorocarbon derivatives of boron and silicon established important principles applicable to fluorocarbon-metal compounds in general, and, moreover, surveys of organometallic chemistry customarily discuss boron and silicon compounds. Compounds of the heavier Group V elements are not reviewed, principally because of the availability of fairly up to date surveys (5, 5a). The review is concluded with some remarks about spectroscopic studies. 

Frequently, fluorocarbon-metal compounds are known where the comparable alkyl or aryl derivatives are not. To some extent this may be because no serious attempts have been made to prepare the particular alkyl or aryl metal compounds, thus making them unavailable for comparison piuq>oses. However, in many instances either unsuccessful attempts at synthesis have been made, or the hydrocarbon derivative is known but is thermally much less stable than the fluorocarbon analog. At the time of writing much less common are situations where a o--bonded alkyl transition metal group is thermally as robust as the analogous o-bonded fluorocarbon-transition metal group. 

As mentioned in the Introduction, the first fluorocarbon-metal compounds to be discovered were derivatives of mercury (/-5). Since they (Table VII) were the subject of a recent review (5) a less thorough treatment will be given here, with the exception of those compounds reported since 1960. 

Fluorocarbon groups show very strong C—F absorptions in the 1400-1000 cm region of the spectrum. This property has been extremely useful in the preparation of fluorocarbon-metal compounds. By examining the infrared spectrum of the reaction products it is possible to establish immediately whether the synthesis of a fluorocarbon derivative of a metal has been successful or not. The strong C—F absorptions reveal themselves immediately, even if the desired compound is diluted considerably with nonfluorine-containing material. 

Release agents function by either lessening intermolecular interactions between the two surfaces in contact or preventing such close contact. Thus, they can be low surface-tension materials based on aUphatic hydrocarbon, fluorocarbon groups, or particulate soHds. The principal categories of material used are waxes, fatty acid metal soaps, other long-chain alkyl derivatives, polymers, and fluorinated compounds. 

Electronic Effects in Metallocenes and Certain Related Systems, 10, 79 Electronic Structure of Alkali Metal Adducts of Aromatic Hydrocarbons, 2, 115 Fast Exchange Reactions of Group I, II, and III Organometallic Compounds, 8,167 Fluorocarbon Derivatives of Metals, 1, 143 Heterocyclic Organoboranes, 2, 257... 

Miller (90), King (209, 210), and Bruce (211) first observed the formation of neutral metal fluoride species and metal fluoride-containing ions in the mass spectra of pentafluorophenyl derivatives of phosphorus, germanium, silicon, and phosphido-bridged iron carbonyls (90) and aliphatic and aromatic fluorocarbon derivatives of iron, cobalt (209-211),... 

Henry Gilman and Gerald L. Schwebke Fluorocarbon Derivatives of Metals... 

I. Mass Spectra of Fluorocarbon Derivatives of Transition Metals. 113... 

The first mass spectral studies on fluorocarbon derivatives of metal carbonyls were reported in 1961 68> the octafluorotetramethylene derivative C4FsFe(CO)4 (34) and the octafluoro-l,3-cydohexadiene... 

Metallocenes and related compounds for which mass spectral data have been reported are given in Tables I-XII, but in many cases only the molecular ion is reported. Metal carbonyls, nitrosyls and their derivatives, and fluorocarbon complexes are not discussed in this review, but Table XIX summarizes the compounds for which mass spectral data have been reported since Bruce s review (27). 

The fact that exchange occurs to produce, in each case, the fluorocarbon derivative is quite consistent with the general observation that exchange generally proceeds to give a product where the metal is bonded preferentially to the most electronegative group [33]. 

Perfluoroalkyl derivatives of mercury were the first fluorocarbon-organometallic compounds to be reported. Alkylmercurials are valuable in that they are able to alkylate other metals, but the toxicity of mercurials greatly inhibits the use of these systems. Perfluoroalkyl iodides react with mercury on heating or irradiation with ultraviolet light to give perfluoroalkylmercury(ll) iodides [58-60] (Figure 10.17). 

Alkenyl and aryl derivatives of transition metals are generally more stable than the corresponding alkyl derivatives. This has been attributed to the unsaturated groups being able to accept charge from the metal via tt orbitals. This process should be enhanced by the introduction of fluorine or fluorocarbon groups into the alkene or aromatic compound. 

Fluorocarbon derivatives of copper have been studied quite widely, probably because there is little evidence for the elimination of metal fluoride being a limitation in these systems. Early work [118] showed that when perfluoroiodoalkanes are heated with copper in DMSO or DMF, then the copper compounds are formed in solution and these have been successfully applied in a variety of coupling reactions. High-dielectric media are essential to the success of these processes (Figure 10.57). 

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