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Metal-arene complexes displacement reactions

Arene-displacement reactions, characteristics, 1, 97 Arene-ene substrates, in C-H bond alkylation, 10, 218 Arene-ferracarboranes, characteristics, 3, 225-226 I // -Arene liruliiim complexes, preparation, 7, 388 (Arene)metal(diborolyl) sandwiches, synthesis, 3, 12... [Pg.55]

Complexes of Cr, W, Mo, Fe, Ru, V, Mn and Rh form stable, isolable arene if -complexes. Among them, arene complexes of Cr(CO)3 have high synthetic uses. When benzene is refluxed with Cr(CO)6 in a mixture of dibutyl ether and THF, three coordinated CO molecules are displaced with six-7r-electrons of benzene to form the stable i/fi-benzene chromium tricarbonyl complex (170) which satisfies the 18-electron rule (6 from benzene + 6 from Cr(0) + 6 from 3 CO = 18). Complex formation is facilitated by electron-donating groups on benzene, and no complex of nitrobenzene is formed. Complex formation has a profound effect on reactivity of arenes, and the resulting complexes are used in synthetic reactions. The metal-free reaction products can be isolated easily after decomplexation by mild oxidation using low-valent Cr. Cycloheptatriene also forms a stable complex with Cr(CO)3 and its synthetic applications are discussed below. [Pg.371]

Arene complexes are usually prepared by the displacement of more weakly bound, monodentate ligands, by oxidation or evolution of CO ligands, or by reducing a metal from a higher oxidation state in the presence of an arene. These methods have been reviewed. - In some cases, one arene will displace another. For example, hexamethylbenzene replaces p-diisopropyl benzene in the tungsten complex of Equation 2.13. This reaction is imdoubt-edly controlled by steric effects. The mechanisms of these arene exchange reactions have been clarified by Traylor and are discussed in Section 4.55. [Pg.54]

The photochemical displacement of the arene is also observed for the complexes ( / -cp)(7 -arene)M (M = Fe, Ru). This reaction occurs from the photoactive a E ligand field excited state. A linear correlation exists between log (0/(l-0)) and o-p, the Hammett parameter for a series of complexes with chloro-and methyl-substituted arenes. The data indicate that a small amount of negative charge builds up at the arene in the transition state for the reaction that results in arene dissociation in these systems. The temperature dependence for the photodissociation of the arene ligand indicates that the metal-arene bond is almost broken in the a E excited state. When the analogous pentamethylcyclopentadienyl complexes (7 -cp )( / -arene)M (M = Fe, Ru) are photolyzed, the quantum yields for arene release are lower than those found for the unsubstituted compounds... [Pg.281]

Bis ( -arene) metal complexes have been made for many transition metals by the AI/AICI3 reduction method and cationic species [M( j -Ar)2]"" " are also well established for n = 1, 2, and 3. Numerous arenas besides benzene have been used, the next most common being l,3,5-Mc3C6H3 (mesitylene) and CeMce. Reaction of arenas with metal carbonyls in high-boiling solvents or under the influence of ultraviolet light results in the displacement of 3CO and the formation of arena-metal carbonyls ... [Pg.940]

The known reactions of fluorinated olefins, arenes, and heterocycles with metal carbonyl anions, to afford fluorovinyl or fluoroaryl complexes resulting from net displacement of fluoride ion (see Section II1,G), prompted us to attempt such substitution reactions with OFCOT, in order to generate the required metal-substituted heptafluorocyclooctatetraenes. [Pg.247]

Apart from the metal atom aggregation reactions described below, bis(arene)metal complexes of the early transition metals are resistant to ligand displacement The rings on the corresponding bis(naphthalene)metal species (41) are by, contrast, labile. Polymer-supported analogs of these naphthalene compounds with vanadium and chromium are known (42), but Ti atoms attack the polymer at the silicon ether linkage. These and other hybrid polymers can be further modified once the metal atom is incorporated. Thus a-methyl naphthalene is displaced from the hybrid organometallic polymer shown in Scheme 7 (43). [Pg.250]

Zeiss and co-workers further found that acetylenes displace THF molecules in the coordination sphere of chromium and other metals in analogous complexes. The acetylenes subsequently condense in cyclic arrangements, and such cyclic condensation reactions have provided important new routes to both arene-metal complexes and uncomplexed arenes. Further details on these novel reactions are contained in the reviews at the end of this section. [Pg.510]

Halogen-substituted arene chromium tricarbonyl complexes undergo nucleophilic substitution by alkoxide ions at a considerably enhanced rate over the free arene 39, 327, 444). The effect of the chromium tricarbonyl moiety on the rate of substitution of the arene is approximately equal to that of a -nitro group (39). Treatment of ethylbenzene chromium tricarbonyl with fcrf-butyl lithium followed by hydrolysis and decomposition of the resulting complexes with Ce(IV) yielded m- and p-ethyl-tcrt-butylbenzene along with some unsubstituted ethylbenzene (55). The reaction represents a novel nucleophilic displacement of a hydride ion and contrasts with the metalation reaction observed with w-butyl lithium (304). [Pg.86]

Methyl-substituted thiophenes bind more strongly to transition metals than the unsubstituted ligand, as illustrated by ligand-exchange reactions of CpRu(77 -Th) complexes. The equilibrium constant measured by NMR increases by a factor of about 6 for each methyl group added on the thiophene " benzene, BT, and DBT also displace T. These observations can be related to the inhibition effect of benzene and other aromatic hydrocarbons on FIDS of BT over solid catalysts, ascribed to a stronger binding of arenes on metal sulfide surfaces as compared to common sulfur... [Pg.768]


See other pages where Metal-arene complexes displacement reactions is mentioned: [Pg.311]    [Pg.334]    [Pg.231]    [Pg.3313]    [Pg.4111]    [Pg.553]    [Pg.74]    [Pg.448]    [Pg.3312]    [Pg.4110]    [Pg.325]    [Pg.243]    [Pg.97]    [Pg.444]    [Pg.469]    [Pg.74]    [Pg.183]    [Pg.614]    [Pg.49]    [Pg.56]    [Pg.36]    [Pg.305]    [Pg.322]    [Pg.2625]    [Pg.23]    [Pg.192]    [Pg.503]    [Pg.824]    [Pg.267]    [Pg.311]    [Pg.324]    [Pg.41]    [Pg.60]    [Pg.173]    [Pg.1422]    [Pg.2624]    [Pg.108]    [Pg.302]   
See also in sourсe #XX -- [ Pg.66 , Pg.67 ]




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Arene complexe

Arene complexes

Arene reaction

Arenes complexes

Arenes metal complexes

Arenes metalation

Arenes metalations

Arenes metallation

Arenes reaction

Complex displacement

Metal arene

Metal arenes

Metal complexes reactions

Metal displacement

Metal displacement reactions

Metal-arene complexes

Metalated arenes

Metalation arene

Reaction displacement

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