Nitrogen is a major contaminant in much of the world’s natural gas.Because no economical method currently exists for removing the N2 from natural gas,we have been developing new materials that can carry out the purification.Our work has shown that complexes of the type trans-Fe(PR3)4X2 can be used as absorbents for the removal of N2 in the pressure-swing purification of natural gas.The efficiency of the purification process depends on the nature of the R groups in the phosphine ligand,and this talk will describe our research effort to synthesize Fe complexes with the best absorption and purification properties.