Acceptorless alkane dehydrogenation

The first example of thermochenfical catalytic system for acceptorless alkane dehydrogenation was reported by Fujii and Saito [117]. Their approach was to purge the reactor continuously with an inert gas in order to prevent the reversible hydrogenation of alkenes by the evolving H2. Unfortunately, these thermochemical catalytic systems are limited by low catalytic activities and catalyst instability. 

If alkyl groups having (3-hydrogens are present on platinum cis to an open site, (3-H-elimination will indeed occur, reversibly sometimes, and it can occur both from Pt(II) and Pt(IV) (52,97,213-219). Catalytic dehydrogenation of an alkane using a soluble platinum complex has been reported in an early study on acceptorless thermal dehydrogenation. At 151 °C, cyclooctane was catalytically dehydrogenated (up to 10 turnovers)... 

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. 

Figure 9.12 Transfer dehydrogenation and acceptorless dehydrogenation of alkanes catalyzed by complexes 47. (According to Chianese [16a].)...

Goldman and co-workers have reported an acceptorless PCP B(in) pin-cer complex that is among the most efficient m date for alkane dehydiogenation (Eq. 12.34). It has been applied to the introduction of C=C double bonds into aliphatic polymers and to the formation of enamines by dehydrogenation of tm -tiary amines. 

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