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Homogeniczne uwodornienie arenów

Borowski A.F.

Wiadomości Chemiczne

2000

[Z] 54, 7-8

565-589

Catalytic activity of soluble metal complexes in homogeneous hydrogenation of aromatic hydrocarbons has been reviewed based on 86 articles. The catalysts of different structural types (e. g. metal carbonyls, complexes containing coordinated arenes, allyls, dihydrogen ligands) as well as some complexes of the early transition metals (Nb, Ta) are catalytically active in reduction of aromatic rings of mono and polynuclear aromatic hydrocarbons. Where available, mechanisms of hydrogenation reactions have been presented. Most of the proposed mechanisms involve coordination of arene in an n4-mode. E. g. benzene hydrogenation requires coordination of the substrate as n6, n4 or h2-arene. Transition n6-n4 leads to a noncoplanar C6 skeleton and a highly disturbed aromatic system lowers the aromatic resonance stabilization energy (bent arene) and provides a driving force for arene ring hydrogenation. From among studied complexes the highest activity in benzene hydrogenation has been observed in the presence of [{Rh(h5-C5Me5)Cl2}2] in homogeneous systems and in the presence of a water-soluble complex [(h6-C6H6) 2Rh2Cl4] used in two-phase system. [(h6-C6Me6v)Ru(m-H) 2 (m-Cl)Ru(h6-C6Me6)]Cl turned out to be the most active naphthalene hydrogenation catalyst, while the best results in anthracene reduction has been obtained using the dihydrogen complex [Ru(H) 2 (H2) 2 (PCy3) 2]. Some aspects of homogeneiety control of arene hydrogenation reactions catalysed by metal complexes are discussed.