The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4- was found to be a highly effective catalyst for a number of dehydrative C–H coupling reactions of aliens and arenas with alcohols and carbonyl compounds. The ruthenium catalyst mediates regioselective dehydrative C–H alkylation of alkenes with alcohols to yield elaborated alkene products. The dehydrative C–H coupling of phenols with alcohols and 1,2-diols formed ortho-alkylated phenol and benzofuran derivatives, respectively. The ruthenium catalyst with phenol ligand was found to mediate chemoselective hydrogenolysis of aldehydes and ketones to form the aliphatic products. Detailed kinetics and mechanistic studies for the hydrogenolysis reaction will be discussed.