Fluorocarbon transition metal compound

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 ... 

One concrete measure of the amount of knowledge which is currently available about fluorocarbon-transition metal complexes is that until recently the entire field could be comprehensively surveyed in one very short chapter in a larger review (9-12). Within the past few years, however, the volume of work has grown to the extent that this type of treatment is no longer possible. Therefore the present discussion narrowly focuses upon only one aspect of fluorocarbon chemistry the synthesis of compounds that contain trifluoromethyl groups bonded to transition metals. 

A variety of reviews is available on the subject of (7-bonded, organotransition metal compounds. The most recent of these (1965) is a detailed review by Razuvaev and Latyaeva 209) which has recently been translated from the original Russian text. As mentioned earlier, the review by Cotton 63) comprehensively and critically covers the literature up to 1955. Several other reviews, by Coates and Clocking 46) and by Chatt 28, 30), appeared in 1960. The specific area of fluorocarbon-transition metal chemistry has been covered in recent reviews by Clark 4I) in 1963, Treichel and Stone 236) in 1964, and Rausch 203) in 1966. 

Organo-transition-metal compounds containing a variety of ligands on the metal have been prepared. Of these, the fluorocarbons perhaps deserve particular attention 261). The bonds between these and the metal are almost always a-bonds, even for aromatic fluorocarbons, and they are appreciably more stable thermally than the corresponding hydrocarbons. 

Transition metal compounds containing o--bonded alkyl or aryl groups were rare until the 1960 s. It has been found that the presence of ligands such as CO, C5H5, or PR3 on transition metals greatly enhances the ability of transition metals to form o--bonded organometallic compounds. Transition metal-carbon a bonds are often produced by metathesis reactions in which one product is the organometallic compound and the other is a simple salt, reactions (11), (12). Transition metal fluorocarbon derivatives have also been... 

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. 

Fluoro compounds, particularly fluorocarbon molecules, are generally regarded as being less reactive than other halo molecules. The compound SF6 has been regarded as inert and often used as a collision gas in gas-phase experiments, but this molecule reacts with some bare metal ions. The group 3 (IIIB), 4 (IVB), and 5 (VB) transition metal ions (92) and Pr+ (120), remove fluorine atoms from SF6. In the most extreme case, Ta+ forms a series of T iFJ+ and SF ions. 

Studies on the organo-transition metal chemistry of OFCOT and other fluorocarbons indicate that organometallic molecules with perfluorinated carbon skeletons possess structural and chemical properties equally as rich as their hydrocarbon analogues. Their structures and chemistry have helped our understanding of the effects of fluorine substitution on the physical and chemical behavior of organometallic compounds. 

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. 

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. 

There appear to be limitations on the extent to which reactions between transition metal hydrides and fluoroolefins can be used to make o-bonded fluorocarbon-metal compounds. Unsuccessful attempts have been made to add manganese pentacarbonyl hydride to 1,1-difluoroethylene, 1-chloro-... 

Recently several compounds have been described in which transition metals are bonded to carbon atoms which are in turn joined to a CF3 group. These substances are obtained from reactions between the acetylene hexafluorobut-2-yne and certain metal carbonyls and related compounds. They are obviously closely related to the other fluorocarbon-metal compounds described earlier. 

In concluding this survey of fluorocarbon tt complexes of transition metals it is of interest to me ntion two compounds which, although they do not have... 

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