Iridium-catalyzed dehydrogenation reaction conditions

The success of derivatives of 1 and 2 as dehydrogenation catalysts has led to the investigation of numerous different pincer ligands for iridium-catalyzed alkane dehydrogenation. The Anthraphos pincer iridium complex (3-H2) was expected to afford even greater thermal stability (Eig. 1), and indeed, the catalyst can tolerate reaction temperatures up to 250°C [42]. The catalytic activity of 3-H2, however, is much less than that of I-H2 under comparable conditions. 

Some other catalytic events prompted by rhodium or ruthenium porphyrins are the following 1. Activation and catalytic aldol condensation of ketones with Rh(OEP)C104 under neutral and mild conditions [372], 2. Anti-Markovnikov hydration of olefins with NaBH4 and 02 in THF, a catalytic modification of hydroboration-oxidation of olefins, as exemplified by the one-pot conversion of 1-methylcyclohexene to ( )-2-methylcycIohexanol with 100% regioselectivity and up to 90% stereoselectivity [373]. 3. Photocatalytic liquid-phase dehydrogenation of cyclohexanol in the presence of RhCl(TPP) [374]. 4. Catalysis of the water gas shift reaction in water at 100 °C and 1 atm CO by [RuCO(TPPS4)H20]4 [375]. 5. Oxygen reduction catalyzed by carbon supported iridium chelates [376]. - Certainly these notes can only be hints of what can be expected from new noble metal porphyrin catalysts in the near future. 

Complexes of ruthenium and rhodium have been identified that catalyze the hydrogenation of nitriles under mild conditions with very good selectivities to the primary amine. In particular, Otsuka and co-workers showed that [RhHfP Prj) ] catalyzes the hydrogenation of a variety of nitriles to amines under mild conditions (1 atm pressure, 20 °C, 2 h Equation 15.119). The reaction is reversible primary amines undergo dehydrogenation in the presence of [Rl iHfP Prj) ] to form nitriles (Equation 15.120). Iridium catalysts for the dehydrogenation of nitriles have also been reported recently. ... 

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