Acceptorless Reaction

A recent study shows that the (RAP)IrH2 complex can catalytically convert alkane to alkene at temperatures ranging from 150 to 250 °C through an acceptorless, thermal reaction. Three suggested reaction mechanisms, associative (A), dissociative (D) and interchange (I) will 

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Fig. 3. The important intermediates involved in the transfer and acceptorless reactions of the pincer complex (anthraphos species are similar).

The thermodynamic parameters for the alkane dehydrogenation reaction are calculated for both the pincer and anthraphos iridium(III) complexes. The mechanism of the transfer reaction, and the associative, dissociative and interchange mechanisms for the acceptorless reactions are discussed and compared. As these reactions typically occur at conditions very different from STP, important corrections for high temperature, high reactant (alkane) concentration and low product (H2, olefin) concentration are important. 

Alan Goldman developed much improved catalysts and also obtained detailed mechanistic information in the 1990s [35, 36]. An unexpected variant developed by Saito, by our own group and most extensively by Goldman, was acceptorless dehydrogenation. It turned out that the reaction could be driven by reflux because the hydrogen was continuously pumped out of the solvent by the reflux action [37-39]. 

The catalyst 18 has also been immobilized on a silica sol gel and applied in the same acceptorless dehydrogenation reaction, resulting in a slower reaction although with a clear advantage in recyclabihty and stabilization compared to the... 

The isoelectronic [Ru -Ru ] complexes are relatively more accessible, and such complexes are proving to be useful for a range of chemical reactions. This article collects the chemistry at sites trans to the [Ru-Ru] single bond. The C-H activation, C-C bond formation, acceptorless alcohol dehydrogenation, cyclo-propanation, carbenoid C-H insertion, and C-H amination reactions are covered. Reactivity studies at axial sites on [Ru-Ru] multiply bonded systems are also included because of their direct relevance in catalytic chemistry. The purpose of this article is to highlight the recent progress on the axial-site chemistry on [Ru -Ru ] platforms with intent to infuse interests for further development. 

Fullerene is reported to be used as as a stabilizer in the synthesis of liquid-crystalline polyesters. The use of fullerene (-0.01 wt % based on the monomer weight) as a stabilizer in the synthesis of a liquid-crystalline (LC) polyesters enabled it for high-temperature acceptorless poly-condensation. The temperature interval of reaction may be widened to 220°C. The presence of fullerene also makes it possible to eliminate high temperature crosslinking side reaction [154]. 

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