Sequential Deoxygenation of CO 2 and NO 2 - via Redox-Control of a Pyridinediimine Ligand with a Hemilabile Phosphine.

The deoxygenation of environmental pollutants CO 2 and NO 2 - to form value-added products is reported. CO 2 reduction with subsequent CO release and NO 2 - conversion to NO are achieved via the starting complex Fe( PPh PDI)Cl 2 ( 1 ). 1 contains the redox-active pyridinediimine (PDI) ligand with a hemilabile phosphine located in the secondary coordination sphere. 1 was reduced with SmI 2 under a CO 2 atmosphere to form the direduced monocarbonyl Fe( PPh PDI)(CO) ( 2 ). Subsequent CO release was achieved via oxidation of 2 using the NO x - source, NO 2 - . The resulting [Fe( PPh PDI)(NO)] + ( 3 ) mononitrosyl iron complex (MNIC) is formed as the exclusive reduction product due to the hemilabile phosphine. 3 was investigated computationally to be characterized as {FeNO} 7 , an unusual intermediate-spin Fe(III) coupled to triplet NO - and a singly reduced PDI ligand.