The conversion of aldehydes to carboxylic acids was investigated using a (hexamethylbenzene)ruthenium dimer and a series of (hexamethylbenzene)ruthenium monomers. As opposed to traditional heavy metal oxidants which produce hazardous waste, this reaction, the Aldehyde Water Shift (AWS), uses water as the oxidant and produces dihydrogen as a byproduct. A variety of aldehyde substrates were screened for selectivity of the acid product as well as the yield. High acid selectivity was found across precatalysts and substrates, but acid yield was highly dependent on the system. Precatalysts investigated were superior to previous catalysts systems for the AWS.