Olefin complexes classification

The mass spectra of a considerable number of 77--bonded complexes of the group VIA metals have been reported, but in many cases mass spectrometry has only been used to determine the molecular weight, so that a detailed examination of the fragmentation processes involved has not been attempted, and only the molecular ion and perhaps a few other major peaks are reported. Within this section it is more convenient to discuss the compounds in terms of the attached ligands rather than in terms of the central metal atom. The classifications are (A) cyclopentadienyl compounds (B) arene compounds and (C) olefin, acetylene, and allyl compounds. 

Molybdenum complexes are the most effective catalysts known for the selective epoxidation of olefins with alkyl hydroperoxides (210-212). Commonly known is the Arco or Halcon process for the large-scale manufacture of propylene oxide from propylene. This process uses t-BuOOH or ethyl benzene hydroperoxide (EBHP) as an oxidant and Mo(CO)6, for example, as a source of Mo. The Mo(CO)6 acts as a catalyst precursor, which is converted into a soluble active form by complexation with diols (3). Chemists have designed several supported versions of the catalysts for this epoxidation chemistry. A clear classification can be made on the basis of the nature of the support. 

The Sabine River Works of the DuPont Company Plant in Orange, Texas, shared their process interlock classification and test program in 1988. [26] At that time, this large DuPont chemical complex employed about 2,500 individuals and consists of large singletrain processing units. Most of the units are continuous processes for the manufacture of olefins, polyolefins, and chemical intermediates for nylon. 

The chemical composition of diesel fuel is extremely complex, with an enormous number of compounds normally present (Table 8.2). For this reason, it usually is not practical to analyze diesel fuel for individual compounds but it is often advantageous to define the compounds present as broad classifications of compound types, such as aromatics, paraffins, naphthenes and olefins. 

The chemical composition of fuel oil is extremely complex, and an extremely high number of compounds can be present through the hydrocarbon types, the range of isomeric hydrocarbons (Table 9.2), and the various types and isomers of heteroatom constituents. Therefore, it is not practical to perform individual compound analyses but it is often helpful to define the compounds present under broad classifications, such as aromatics, paraffins, naphthenes, and olefins. 

During the past few decades, a wide variety of molecules with transition metal-carhon mulhple bonds have been studied. The chemistry of doubly bonded species - carbenes - is particularly interesting because it leads to several synthetically important transformations, and for this reason, metal carbenes are the main subject of this chapter. Our discussion begins with a classification of metal-carbene complexes based on electronic structure, which provides a way to understand their reactivity patterns. Next, we summarize the mechanistic highlights of three metal-carbene-mediated reactions carbonyl olefinafion, olefin cyclopropanafion, and olefin metathesis. Throughout the second half of the chapter, we focus mainly on ruthenium-carbene olefin metathesis catalysts, in part because of widespread interest in the applications of these catalysts, and in part because of our expertise in this area. We conclude with some perspectives on the chemistry of metal carbenes and on future developments in catalysis. 

The classification of metal 7r-complexes has customarily been based on the types of organic 7c-ligands rather than on the metal elements in the TT-complex. In accordance with this classification, the three major groups of olefin, Ti-cyclopentadienyl, and arene metal Tc-complexes as well as their subgroups are described in the following by illustration of typical 7c-complexes. 

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