Photoactivation of Cluster Catalysis: A Comparison of 1-Pentene Isomerization by Tetracarbonyl(Triphenylphosphine)Ruthenium and 1,1,1,2,2,2,3,3,3- Nonacarbonyl-1,2,3-Tris(Triphenylphosphine)-Triangulo-Triruthenium.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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The photocatalyzed isomerization of 1-pentene to trans- and cis-2-pentene by RuCO4PPh3 and Ru3CO9PPh33 is reported along with data for Ru3CO12, Fe3CO12, and FeCO5. The primary photoprocess in RuCO4PPh3 is dissociative loss of CO giving a coordinatively unsaturated species having the same empirical formula Ru3CO9PPh33 the trinuclear species undergoes Ru-Ru bond rupture and ultimate declusterification subsequent to photo-excitation giving a quantitative yield of RuCO4PPh3 under CO or RuCO3PPh32 in the presence of PPh3. The crucial result is that the cluster yields a different catalytically active species compared to RuCO4PPh3, since the initial ratio of trans- and cis-2-pentene is different for the two photocatalysts. The photocatalysis and primary photoprocesses suggest that the isomerization from the Ru3CO9PPh33 results from an active form of the cluster. By way of contrast, FeCO5 and Fe3CO12 yields the same initial ratio of photocatalytic products, implicating a common, mononuclear catalytic species. Since the clusters are good visible absorbers compared to the mononuclear species, photoactivation of cluster catalysis can be effected with low energy visible light.
- Organic Chemistry
- Radiation and Nuclear Chemistry