Ru3(CO)12
Cluster Versus Non-Cluster Catalysis in Olefin Thermal Isomerization and Hydrosilylation in the Presence of Ru3(CO)12
Mon, 2014-03-24 14:59 — Shukri Mohammed KhalafThe ruthenium cluster Ru3(CO)12 (1) has been evaluated as a catalyst precursor for the thermal reactions of 1-octene with (EtO)3SiH in a mixture of dioxane and benzene at temperatures of 50–75°C. At 70°C or higher, olefin isomerization and hydrosilylation reactions were observed; the products,trans-2-octene and C5H11CH2CH2CH2Si(OEt)3 (2) were identified. The reactions were accompanied by a side reaction that involved generation of hydrogen gas. The sum of the rates of appearance of 2 and H2 equalled the rate of disappearance of (EtO)3SiH. No significant isomerization was observed in the absence of (EtO)3SiH. Maximum turnover number values of 750, 70, and 70 were obtained for isomerization, hydrosilylation, and H2production reactions, respectively. At 60°C or lower, no hydrosilylation or hydrogen production was observed, and the only product was trans-2-octene. No detectable disappearance of (EtO)3SiH was observed. Acetophenone was also hydrosilated by use of cluster 1, as catalyst; the only product obtained was (EtO)3SiOC(Ph)(H)(CH3). Kinetic studies indicated that the reactions of 1-octene and the reaction of acetophenone involved a catalytically active species of lower nuclearity. There was evidence of concurrent cluster catalysis, especially during the first few minutes of the reaction.
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Short Communication: The Mechanism of 1- Octene Isomerization and Hydrosilylation Reaction Catalysed by Ru3(CO)12
Wed, 2010-04-21 14:32 — Hikmat S. Hilal, D.Sc.
Isomerization and hydrosilylation reactions of terminal olefins have been reported under thermal and photochemical conditions using Ru3 (C0) 12, 1, and HRu3 (CO)!!, 2,11 '0 In a very recent work, we reported E LI that 1 catalyses both Isomerization and hydrosilylation reactions of 1-octene (eq. 1). It has been found that the isomerization reaction occurs via lower nuclearity catalytic species that result from fragmentation of the mother cluster 1. Evidence in favour of concurrent cluster catalysis was also reported. On the other hand, the hydrosilylation reaction occurred via cluster catalysis at first and after some-time fragment catalysis occurred.
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Cluster Vs. Non-Cluster Catalysis in Olefin Thermal Hydrosilylation And Isomerization Reactions Using Ru3(CO)12
Wed, 2010-04-21 14:32 — Hikmat S. Hilal, D.Sc.The ruthenium cluster Ru3(CO)12 (1) has been evaluated as a catalyst precursor for the thermal reactions of 1-octene with (EtO)3SiH in a mixture of dioxane and benzene at temperatures of 50–75°C. At 70°C or higher, olefin isomerization and hydrosilylation reactions were observed; the products, trans-2-octene and C5H11CH2CH2CH2Si(OEt)3 (2) were identified. The reactions were accompanied by a side reaction that involved generation of hydrogen gas. The sum of the rates of appearance of 2 and H2 equalled the rate of disappearance of (EtO)3SiH. No significant isomerization was observed in the absence of (EtO)3SiH. Maximum turnover number values of 750, 70, and 70 were obtained for isomerization, hydrosilylation, and H2 production reactions, respectively. At 60°C or lower, no hydrosilylation or hydrogen production was observed, and the only product was trans-2-octene. No detectable disappearance of (EtO)3SiH was observed. Acetophenone was also hydrosilated by use of cluster 1, as catalyst; the only product obtained was (EtO)3SiOC(Ph)(H)(CH3). Kinetic studies indicated that the reactions of 1-octene and the reaction of acetophenone involved a catalytically active species of lower nuclearity. There was evidence of concurrent cluster catalysis, especially during the first few minutes of the reaction.
Olefin Hydrogenation and Isomerization Catalysed by Ru3(CO)12 and its Derivatives. Cluster vs. Non-Cluster Catalysis
Wed, 2010-04-21 14:32 — Hikmat S. Hilal, D.Sc.The systems Ru3(CO)12·nL, (L = PPh3, CH3CN, (EtO)3Si(CH2)3NH2; n = 0–3, 15) have been employed as catalysts and/or catalyst precursors for thermal hydrogenation and isomerization reactions of 1-octene under moderate reaction conditions (1 atm at 70°C or below). In the hydrogenation reaction the system Ru3(CO)12/15CH3CN showed the highest activity, with turnover numbers up to 1000. For this system the kinetics indicated that the hydrogenation occurs via a lower nuclearity catalytic species formed by fragmentation of the mother cluster. On the other hand the isomerization reaction occurs, after a 10–20 min induction period, by higher-nuclearity catalytic species. The isomerization gave trans-2-octene only, and none of the cis-isomer. The effects of other factors on the rates of hydrogenation and isomerization reactions are described.
