Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Arene-metal bond

Arene complexes with mint metals are rather rare. The arene metal bond is weaker compared to the other transition metals and hapticity is lower. For this reason the stronger rr-donor properties of the cyclophanes compared to open chained arenes [109c] make the preparation in benzene solution possible. The cyclophane is simply heated with silver-I (Fig. 29a) [109a] or copper-I (Fig. 29b) [109b] and yields the respective complex formed in almost quantitative yield. It is noteworthy that the silver ion in 128 shows no interaction with the benzene ring at all the naphthalene unit acts as 7t-donor only [109a]. [Pg.62]

Arene tricarbonyl molybdenum complexes are yellow, often crystalhne compounds. They are weakly air-sensitive in the sohd state and have to be stored under inert atmosphere and out of hght. They are best purified by crystaUization. In solution, they are unstable to air. The trait that has most hampered development of the use of (arene)Mo(CO)3 complexes in organic synthesis, however, is the lability of the arene metal bond. Lewis basic solvents such as THF, DMF, DM-SO, acetone and acetonitrile rapidly displace benzene in (benzene)Mo(CO)3. This lability of the arene-Mo bond, while making handling difficult, holds promise for the catalytic use of this class of compounds. [Pg.8]

The (arene)RuCp complexes share many characteristics with the analogous iron compounds such as their robustness, stability to air and mild oxidants, and the photo lytic cleavage of the arene metal bond. It has to be pointed out though that there are substantial differences in both the efficiency of the photolytic cleavage (Fe>Ru) and the stability of the resulting cationic CpM(solvate)3 complexes (Ru>Fe).As will be detailed below the latter will form the basis for the best synthetic routes to the title compounds. [Pg.15]

S coordinating solvent (e.g. THF, acetone,..) Fig.1 General mechanism of dissociation of arene-metal bonds... [Pg.182]

An alternative approach to arene complex catalysis involves generation of cata-lytically active species without breaking arene-metal bonds. In the event, open sites of coordination on the metal center are created by the dissociation of lig-... [Pg.193]

In addition to transfer hydrogenation reactions, arene ruthenium complexes also display excellent activity in the catalytic hydrogenation of olefins and alkynes including asymmetric reduction [40]. Remarkably, this process occurs under milder conditions, than required for catalysis with the dissociation of arene-metal bond. Lately, arene iridium complexes have also been found to be effective hydrogenation catalysts [41 ]. It is noteworthy that iridium can also promotes addition to the carbon-nitrogen double bond. [Pg.195]

Metal-assisted dehydrogenative coupling of silanes with nucleophiles can also lead to the silicon-heteroatom bond formation. Thus, in the presence of catalytic amount of (ri -benzene)(R -HSiHPh2)Cr(CO)2 124 diphenylsilane 125 reacts smoothly with either aniline or thiophenol to afford the products 126 or 127 respectively (Scheme 34) [60]. This process represents a rare example of arene-chro-mium complex catalysis, which proceeds without breaking arene-metal bonds. [Pg.201]

A set of oxygen donor atoms, providing both a and tt donation to a metal center, is not appropriate to stabilize any low oxidation state of a metal.19 This is, however, a synthetic advantage since very reactive, unstable, low-valent metalla-calix[4]arenes can be generated in situ and intercepted by an appropriate substrate. In the absence of a suitable substrate, the reactive fragment, however, can collapse to form metal-metal bonded dimers. The formation of metal-metal bonds has been, however, so far observed in the case of Group V and VI metals only. The most complete sequence so far reported has been for tungsten, molybdenum, and niobium. [Pg.172]

Table 10. Bond enthalpy contributions, D(M-ArH) kJ mol, in bis(arene) metal compounds... Table 10. Bond enthalpy contributions, D(M-ArH) kJ mol, in bis(arene) metal compounds...
Much of the interest in the polysilanes, polygermanes, and polystannanes involves their sigma delocalization and their sigma-pi delocalization when coupled with arenes or acetylenes. This is not unexpected since silicon exists as a covalent network similar to diamond. In exhibiting electrical conductivity, germanium and tin show more typical metallic bonding. Some polystannanes have been referred to as molecular metals. ... [Pg.373]

Although attempts to acylate bisbenzenechromium under Friedel-Crafts conditions have thus far resulted in cleavage of the ring-metal bond, the successful metalation of this 7r-arene complex has been recently reported, using amylsodium (10). The resulting dimetalated product has been characterized as a dicarb-methoxy derivative, although the position of the two substituents has not yet been determined. [Pg.74]

The addition-protonation procedure maintains the arene-chromium bond and allows further application of the activating effect of the metal. In an approach to the synthesis of anthraquinone antibiotics, the dihydronaphthalene complex (79) was allowed to react with a cyanohydrin acetal anion and then quenched with acid.129 The resulting tetralin complex (80) could be metallated effectively and carried on to a key intermediate (81) in anthraquinone construction (equation 54)... [Pg.546]

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]


See other pages where Arene-metal bond is mentioned: [Pg.452]    [Pg.50]    [Pg.283]    [Pg.313]    [Pg.7]    [Pg.181]    [Pg.181]    [Pg.182]    [Pg.183]    [Pg.183]    [Pg.60]    [Pg.172]    [Pg.452]    [Pg.50]    [Pg.283]    [Pg.313]    [Pg.7]    [Pg.181]    [Pg.181]    [Pg.182]    [Pg.183]    [Pg.183]    [Pg.60]    [Pg.172]    [Pg.62]    [Pg.161]    [Pg.194]    [Pg.277]    [Pg.1266]    [Pg.204]    [Pg.49]    [Pg.1223]    [Pg.334]    [Pg.23]    [Pg.764]    [Pg.520]    [Pg.544]    [Pg.301]    [Pg.81]    [Pg.97]    [Pg.98]    [Pg.100]    [Pg.175]   
See also in sourсe #XX -- [ Pg.452 ]




SEARCH



Arenes metalation

Arenes metalations

Arenes metallation

Metal arene

Metal arenes

Metal-arene bonding

Metalated arenes

Metalation arene

© 2024 chempedia.info