A comparative study on photocatalytic hydrogen transfer and catalytic hydrogenation of norbornadiene and quadricyclane catalyzed by [Rh 6(CO) 16]

• Published in: Journal of molecular catalysis. A, Chemical Vol. 202; no. 1; pp. 31 - 39
• Main Authors: Akioka, Takanori, Inoue, Yoshiharu, Yanagawa, Akihisa, Hiyamizu, Makoto, Takagi, Yuzuru, Sugimori, Akira
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2003; Elsevier
• Subjects: Catalysis; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; Hydrogen transfer reaction; Norbornadiene; Photocatalyst; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Quadricyclane; Rh carbonyl cluster catalyst; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Quadricyclane; Rh carbonyl cluster catalyst; Photocatalyst; Hydrogen transfer reaction; Norbornadiene; Hydrogen transfer; Catalytic reaction; Photocatalysis; Transition metal Carbonyl; Dienic compound; Hydrogenation; Bicyclic compound; Rhodium Carbonyl; Platinoid Carbonyl; Comparative study
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(03)00201-2

A comparative study on the hydrogenation of norbornadiene ( I) and quadricyclane ( II) was performed over photo-assisted activated [Rh 6(CO) 16] with or without UV-light irradiation. The photochemical and usual hydrogenations proceeded similarly as shown in reaction scheme. The photo-assisted catalytic transfer hydrogenation and the catalytic hydrogenation of norbornadiene ( I) and quadricyclane ( II) over a photo-activated Rh cluster in 2-propanol in the presence of acetone was studied under comparative conditions. With the photo-assisted catalytic transfer hydrogenation, the hydrogen produced by dehydrogenation of 2-propanol is used very effectively for the addition to the reactants without evolving H 2. Norbornane ( IV) and nortricyclene ( V) are formed in parallel in the photo-assisted hydrogen transfer reaction of II. In the reaction of I, the acetone-sensitized isomerization of I to II occurs prior to hydrogenation in a concentration of 58 mmol/l of I. However, at a lower concentration, we observed a stepwise hydrogenation of I to IV via norbornene ( III). The yield of III formed in the catalytic hydrogenation was larger than that in the photo-assisted catalytic transfer hydrogenation. Compound II was not observed in the catalytic hydrogenation of I, and the yield of V was less than 1%. Compound II behaves in catalytic hydrogenation similar to as in photo-assisted catalytic transfer hydrogenation. The hydrogenation paths of I and II in both the reactions are discussed on the basis of a reaction mechanism shown in Scheme 1.