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The nitrogen oxides NO 2 ,NO, and N 2 Oare among the most potent air pollutants of the 21 st century.Abimetallic Rh I -Pt II complex containing an especially designed multidentate phosphine olefin ligand is capable of catalytically detoxifying these nitrogen oxides in the presence of hydrogen to form water and dinitrogen as benign products.The catalytic reactions were performed at room temperature and low pressures (3-4 bar for combined nitrogen oxides and hydrogen gases). Aturnover number (TON) of 587 for the reduction of nitrous oxide (N 2 O) to water and N 2 was recorded, making these Rh I -Pt II complexes the best homogeneous catalysts for this reaction to date.L ower TONs were achieved in the conversion of nitric oxide (NO,TON = 38) or nitrogen dioxide (NO 2 ,T ON of 8). These unprecedented homogeneously catalyzedh ydrogenation reactions of NO x were investigated by ac ombination of multinuclear NMR techniques and DFT calculations,w hich provide insight into ap ossible reaction mechanism. The hydrogenation of NO 2 proceeds stepwise,t o first give NO and H 2 O, followed by the generation of N 2 Oand H 2 O, whichi st hen further converted to N 2 and H 2 O. The nitrogen À nitrogen bond-forming step takes place in the conversion from NO to N 2 Oa nd involves reductive dimerization of NO at ar hodium center to give ah yponitrite (N 2 O 2 2À ) complex, whichw as detected as an intermediate.

The nitrogen oxides NO 2 ,NO, and N 2 Oare among the most potent air pollutants of the 21 st century.Abimetallic Rh I -Pt II complex containing an especially designed multidentate phosphine olefin ligand is capable of catalytically detoxifying these nitrogen oxides in the presence of hydrogen to form water and dinitrogen as benign products.The catalytic reactions were performed at room temperature and low pressures (3-4 bar for combined nitrogen oxides and hydrogen gases). Aturnover number (TON) of 587 for the reduction of nitrous oxide (N 2 O) to water and N 2 was recorded, making these Rh I -Pt II complexes the best homogeneous catalysts for this reaction to date.L ower TONs were achieved in the conversion of nitric oxide (NO,TON = 38) or nitrogen dioxide (NO 2 ,T ON of 8). These unprecedented homogeneously catalyzedh ydrogenation reactions of NO x were investigated by ac ombination of multinuclear NMR techniques and DFT calculations,w hich provide insight into ap ossible reaction mechanism. The hydrogenation of NO 2 proceeds stepwise,t o first give NO and H 2 O, followed by the generation of N 2 Oand H 2 O, whichi st hen further converted to N 2 and H 2 O. The nitrogen À nitrogen bond-forming step takes place in the conversion from NO to N 2 Oa nd involves reductive dimerization of NO at ar hodium center to give ah yponitrite (N 2 O 2 2À ) complex, whichw as detected as an intermediate.

A number of stable group 6 metal complexes bearing 2,4,6-oxy functionalised 1,3,5-triphosphinines, phosphorus containing heterocyclic ligands with a central C3P3 core, were synthesised such that a complete series of [M{P3C3(OX)3}(CO)3]...