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Organotransition metal compounds

The first organometallic compound of the transition metals to be characterized (1827) was Zeise s salt, K[(C2H4)PtCl3]-H20 (Fig. 18.1). It forms when K2[PtCl4] in aqueous ethanol is exposed to ethylene (ethene) a dimeric Pt—C2H4 complex with Cl bridges is also formed. In both species, the ethylene is bonded sideways to the platinum(II) center so that the two carbon atoms are equidistant from the metal. This is called the dihapto-or jf mode. A ligand such as an allyl radical with three adjacent carbons directly bonded to a metal atom would be trihapto- or rf, and so on. [Pg.395]

The nature of the bonding in Zeise s anion and other 7 -olefin complexes is illustrated in Fig. 18.2. Without the push-pull mechanism, the tt electrons of the olefin would have little or no tendency to allow themselves [Pg.395]

Aromatic hydrocarbons such as benzene (CeHe) and the anion CsHs ( Cp ) of cyclopentadiene (CsHe, CpH ) are side-on bonders par excellence. They bond to the metal atom perpendicularly to the plane of the aromatic ring by multiple interactions involving the several bonding and antibonding orbitals of the 7r-electron systems. Thus, two cyclopenta-dienide units can form a sandwich complex with Fe known as ferrocene, Fe(7 5-C5H5)2 (Fig. 18.3). [Pg.396]


More than 80 % of all organotransition metal compounds are cyclopentadienyl complexes with Cp (C5H5) and Cp (CsMes) being the most prominent cyclopentadienyl systems used [1]. However, during the past few years functionalized cyclopentadienyl systems which do not just act as innocent spectator ligands have become very attractive. [Pg.193]

Reductive and oxidative transformations of small ring compounds form the basis of a variety of versatile synthetic methods which include functionalization and carbon skeleton construction. Redox mechanisms of organotransition metal compounds play an important role in inducing or catalyzing specific reactions. Another useful route in this area is based on one-electron redox reactions. The redox tautomerism of dialkyl phosphonate also contributes to the efficiency of the reductive transformation of small ring compounds. This review summarizes selective transformations which have a high potential for chemical synthesis. [Pg.107]

B. L. Shaw and N. I. Tucker, "Organotransition Metal Compounds and Related Aspects of Homogeneous Catalysis." Pergamon, Oxford, 1975. [Pg.391]

In principle, carbometallation of an alkene (RCH=CH2) with a coordinatively unsaturated organotransition metal compound (R1 M I. ) can produce a monomeric carbometallation product 1 (Scheme 6). This reaction may not, however, stop at this stage. It can be accompanied by other processes of which (i) hydrogen-transfer hydrometallation to produce a potentially thermodynamically more favorable mixture of a 1,1-disubstituted alkene and a hydrometallation product 2 and (ii) polymerization to produce polyalkenes 3 are representative. The extents to which these side-reactions occur are functions of relative rates of various competing processes. For example, accumulation of the monomeric carbometallation product 1 can be favored in cases where the starting R1 MTL is more reactive toward alkenes than 1. The organometal/alkene ratio is also an important parameter, since neither of the two side-reactions can proceed after all of the starting alkene has reacted. [Pg.255]

To summarize, the special bonding characteristics of 7r-acceptor ligands in organotransition metal compounds enable these complexes to coordinate small molecules such as ethylene, CO, and H2 and also provide an electronic buffer system to facilitate changes of metal oxidation state and coordination... [Pg.398]

Fig. 1. Schematic representation of energy levels for organotransition metal compounds (a) without n bonding and (b) with ir bonding (12). Fig. 1. Schematic representation of energy levels for organotransition metal compounds (a) without n bonding and (b) with ir bonding (12).
Covalent bond classification method, organotransition metal compounds ([Pg.87]

The mechanistic basis to radical reactivity of organotransition metal compounds is still not very well developed. Mechanisms very often remain speculative, since the information about involved intermediates is scarce. Mechanistic information can be gathered by using physical methods, such as ESR spectroscopy. Changes in the oxidation state of metal complexes indicating SET, paramagnetic metal centers or the radicals themselves, provided their lifetime allows it, can be detected (selected reviews [73-75]). CIDNP measurements can also provide valuable information, but were rarely used in the past [76-78]. [Pg.129]

Hartwig, J. (2009). Organotransition Metal Chemistry From Bonding to Catalysis. Sausalito, CA University Science Books. Provides comprehensive and up to date coverage of structure, bonding, and reactions of organotransition metal compounds. [Pg.547]

For an excellent review concerning chiral tetrahedral organotransition metal compounds, see Brunner, H. Adv. Organomet. Chem. 18, 151 (1980)... [Pg.54]

In this section the main types of transition metal organometallic compounds will be briefly introduced. Specific examples are cited in Chapters 17 and 18 under the individual elements. The many sorts of reactions that organotransition metal compounds undergo, with particular emphasis on their relationship to catalysis, are reviewed in detail in Chapter 21. Catalysis via organometallic compounds is presented in Chapter 22. [Pg.674]

The photochemistry of metal-metal bonded complexes has been the subject of several reviews see Luminescence Behavior Photochemistry of Organotransition Metal Compounds and Photochemistry of Transition Metal Complexes Theory). Strong a bonding to a antibonding transitions are often observed in metal - metal bonded systems. These lead to photogenerated fragments that undergo reactions and may ultimately recombine (equation 72). [Pg.1154]

Coordination Chemistry Supported Organotransition Metal Compounds Titanium Organometallic Chemistry Vanadium Organometallic Chemistry Zirconium Hafnium Organometallic Chemistry. [Pg.3215]

For catalytic purposes, MTO has also been supported on zeolites, niobia and polymers a useful means of preparing quinones in high yields (see Supported Organotransition Metal Compounds).Other useful variations use the urea-H2O2 adduct as an oxidant in water-free reactions or ionic liquids as solvents. [Pg.4024]


See other pages where Organotransition metal compounds is mentioned: [Pg.511]    [Pg.131]    [Pg.395]    [Pg.395]    [Pg.397]    [Pg.185]    [Pg.325]    [Pg.86]    [Pg.134]    [Pg.134]    [Pg.152]    [Pg.171]    [Pg.127]    [Pg.318]    [Pg.3]    [Pg.658]    [Pg.795]    [Pg.3537]    [Pg.3594]    [Pg.3910]    [Pg.3911]    [Pg.3931]    [Pg.3964]    [Pg.4012]    [Pg.4047]   
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See also in sourсe #XX -- [ Pg.127 , Pg.128 , Pg.129 , Pg.130 , Pg.131 , Pg.132 , Pg.133 , Pg.134 , Pg.135 , Pg.136 ]




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