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Activation of C—H bonds by transition

The interaction of saturated C—H and C—C bonds with heterogeneous metal catalysts forms the basis of widely applied reactions such as isomerization, cracking, and re-forming of alkanes. In recent years, much attention has been devoted to the selective activation of C—H bonds by transition metal complexes in homogeneous solution under mild conditions.601 604 In principle, an alkane can undergo oxidative addition to a noble metal complex according to... [Pg.374]

Even the activation of C-H bonds by transition metal carbene complexes has parallels in phosphane chemistry [215]. However, the reasons for the C-H activation by transition metal carbene complexes are still poorly understood and the reaction cannot as yet be predicted, although interesting applications in catalysis might be envisaged. [Pg.251]

Hietkamp S, Stufkens DJ, Vrieze K (1979) Activation of C-H bonds by transition metals V. A study of the mechanism of metalation reactions of benzyl- and rneta-fluorobenzylphosphines with Rh(I), Ir(I), Pd(II), and Pt(II) compounds. J Organomet Chem 168 351-361... [Pg.277]

The effects of ligands in the activation of C-H bonds by transition metal complexes were discussed in certain works. It has been suggested [66a] that a combination of hydride and lone-pair ligands with a minimum of 7c-bonding should be an optimal combination for the reaction between methane and some model Rh(I) and Ru(II) complexes. For example, it should be advantageous to... [Pg.248]

The activation of C-H bonds by an electrophilic pathway is shown schematically in eq. (12) and has been observed with a number of late transition metal ions [9], A driving force for the reaction shown in eq. (12) is the stabilization of the leaving group, H", by solvation in polar solvents. The related four-center electrophilic activation by transition, lanthanide, and actinide metal centers has also been reported, (eqs. (13a) and (13b)) [9b,c,g, 27]. In these instances, a ligand on the metal assists the reaction by acting as the base. [Pg.1231]

The activation of C—H bonds by a o-bond metathesis pathway involves coordination of the C—H group followed by concerted C—H bond breaking of the activated substrate and C—H bond formation with a hydrocarbyl ligand. Thus, the reaction proceeds through a four-centered transition state (Scheme 11.8). [Pg.521]

The activation of C-H bonds by early transition metals or /-block elements in their highest possible formal oxidation states, for some of which the first direct observations of methane activation were verified, " is particularly interesting from a mechanistic point of view since their r/ - (or r/ /"-) electron configurations preclude any of the... [Pg.101]

Evidence of the activation of C—H bonds in ligands by the transition metal to which the ligand is attached has come from three sources. [Pg.149]

The contents of Sections II, III, and IV show that the activation of C—H bonds in alkanes by transition metal compounds has much in common with the activation of C—H bonds in aromatic compounds. It appears, therefore, to be more profitable at the present time to draw mechanistic parallels between alkanes and aromatic systems, as has been done here, than, say, between alkanes and molecular hydrogen, although, of course, much work has been done on hydrogen activation (59). [Pg.185]

In connection with the activation of C—H bonds the cyclometalation has become a very general reaction, intensively investigated by Kaesz and coworkers4 and reviewed by Bruce.5 In transition metal complexes an organic ligand reacts with the transition metal resulting in the formation of a metal-... [Pg.142]

Kagan H, Namy JL (1999) Influence of Solvents or Additives on the Organic Chemistry Mediated by Diiodosamarium. 2 155-198 Kakiuchi F, Murai S (1999) Activation of C-H Bonds Catalytic Reactions. 3 47-79 Kakiuchi F, Chatani N (2004) Activation of C-H Inert Bonds. 11 45-79 Kant J (2004) Stereospecific Introduction of Cephalosporin Side Chains Employing Transition Metal Complexes. 6 247-262 Keen SP see Gibson SE (nde Thomas) (1998) / 155-181 Kiessling LL, Strong LE (1998) Bioactive Polymers. 1 199-231 Kim DD see Beak P (2003) 5 139-176... [Pg.338]

The activation of C-H bonds is currently one of the most fascinating challenges encountered for the construction of organic molecules. Two recent reviews pointed out how important this process is from an economical point of view [46, 47]. In particular C-H activation initiated by transition metal complexes has... [Pg.66]

The search for new reactivity and new reactions is an important target in homogeneous catalysis. A declared goal is the selective activation of C-H bonds under mild conditions. Although there are numerous examples of stoichiometric C-H bond oxidative additions to transition metal centers, successful examples regarding catalytic functionalization of C-H bonds have been made only during the last five years. Notable advances have been achieved by Moore and coworkers who described in 1992 the ortAo-acylation of pyridine with olefins and carbon monoxide. The cluster compound triruthenium dodecacarbonyl has been used as catalyst (Scheme 10). [Pg.9]

Over the past 30 years there has been a massive effort to achieve selective C-H bond activation by transition metal catalysis and there now exists a variety of mechanisms for the activation of C-H bonds using a range of transition metal catalysts (Scheme 4) [8-18]. [Pg.89]

Hydrocarbons can also be activated through reactions that do not involve an oxidative addition to an unsaturated metal complex but rather proceed by a four-centered mechanism. This is usually called heterolytic activation of C-H bonds because these bonds are polarized in the transition state, by action of an electrophilic metal and a... [Pg.625]

In this chapter, the transition of metal catalyzed carbonylative activation of C-H bonds has been discussed. This area is dominated by Pd, Ru and Rh catalysts, whereas the ability of other metals, such as Cu and Fe, have still not been explored. From the reaction mechanism point of view, the first step is the palladation of arene to produce an Ar-Pd bond, and then be followed by CO insertion. [Pg.129]


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Activation of C-H bond

Activation, C—H bond

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H activation

H-Bonding Activation

Transition active

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