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 (PCy3)(2)Ru(=CHPh)(Cl)2 (1) was reacted with primary alcohols at 70 degreesC to give the monohydride species (PCy3)(2)(CO)Ru(Cl)(H) (4) in similar to20% 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, (PCy3)(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.