One-dimensional metal atom chain [Ru(CO)4]n as a catalyst precursor—Hydroformylation of 1-hexene using carbon dioxide as a reactant

The catalytic activity of the polymeric 1D metal atom chain [Ru(CO)4]n was studied in the context of the hydroformylation of 1-hexene utilizing CO2 as a source of CO. In the multi-step process, CO2 is first reduced via a reversed water–gas shift reaction to CO, which is then used in situ in conventional hydroformylation. A promoter is needed to prevent the direct hydrogenation of alkenes that occurs as a side reaction. Thus, the effect of the promoter and the solvent was also studied. Linear chain compounds can act as catalysts or as precursors for active species. The results show that the ruthenium complexes derived from a [Ru(CO)4]n precursor can effectively catalyze both the reversed water–gas shift reaction and the hydroformylation. The polymeric [Ru(CO)4]n favors the direct hydrogenation of the aldehydes, permitting the selective production of alcohols. Compared to the better known Ru3(CO)12 catalyst, the activities of polymeric [Ru(CO)4]n were found to be at the same level. The best yields of hydroformylation products were achieved when DMF was used as a solvent with a LiCl promoter. The ESI-MS analysis of the reaction products indicated that the catalytically active species in the [Ru(CO)4]n catalyzed reactions were essentially the same as those found in [Ru3(CO)12] reactions. This indicates that the original linear framework of [Ru(CO)4]n is not retained during the reaction, but that [Ru(CO)4]n serves as an effective precursor for a catalytically active mononuclear and oligonuclear species.

Graphical abstractPolymeric 1D metal atom chain [Ru(CO)4]n was studied as a catalyst for hydroformylation of 1-hexene utilizing CO2 as a source of CO. The linear chain [Ru(CO)4]n acts as a precursor for active oligonuclear and mononuclear ruthenium carbonyl species, which prefer direct formation of alcohols. Compared to the better known Ru3(CO)12 catalyst, the activity of the [Ru(CO)4]n-based catalyst was found to be at the same level.Figure optionsDownload full-size imageDownload as PowerPoint slide