METHANOL AS A HYDROGEN DONOR IN REACTIONS HOMOGENEOUSLY CATALYSED BY RUTHENIUM AND RHODIUM COMPLEXES

Article abstract of DOI:10.1016/0022-328X(85)87415-5

Under suitable conditions methanol can act as a hydrogen donor towards organic substrates, especially for the reduction of ketones to alcohols.A variety of complexes of rhodium, iridium, ruthenium, and osmium have been shown to be active for this reaction; the highest activity observed so far is that of t-phosphine-ruthenium-chloride systems such as .In all the reactions the methanol is oxidised to methyl formate; some carbon dioxide is also formed.Cyclohexanone is reduced to cyclohexanol, methyl vinyl ketone and mesityl oxide to the corresponding saturated ketones, and 4-t-butylcyclohexanone to a 4/1 mixture of the trans and cis 4-t-butylcyclohexanols; aldehydes are reduced with more difficulty and cyclohexene is comparatively unreactive.Possible mechanisms for the reaction are discussed in the light of observations of changes in the catalyst precursors that take place during the rections.The reactions with methanol are also contrasted with those in wich ethanol is used as hydrogen donor.