Degradation of the First-Generation Grubbs Metathesis Catalyst with Primary Alcohols, Water, and Oxygen. Formation and Catalytic Activity of Ruthenium(II) Monocarbonyl Species

The first-generation Grubbs metathesis catalyst (PCy 3 ) 2 Ru( CHPh)(Cl) 2 ( 1 ) was reacted with primary alcohols at 70 °C to give the monohydride species (PCy 3 ) 2 (CO)Ru(Cl)(H) ( 4 ) in ∼20% yield. Addition of either an inorganic or organic base greatly facilitated the formation of the hydride, and 4 could be isolated in >70% yield in the case of 1-propanol and triethylamine. Analysis of the reaction products and labeling experiments revealed that 4 was formed via a noncatalytic alcohol dehydrogenation pathway. When benzyl alcohol was used, (PCy 3 ) 2 (CO)Ru(Cl)(Ph) ( 5 ) was formed, this also being one of the products of the decomposition of 1 by oxygen in both solid and solution states. Complexes 4 and 5 were found to be active and selective alkene double-bond isomerization catalysts.