Electronic structure and feno conformation of nonheme iron-thiolate-no complexes : An experimental and DFT study

Reactions of NO and CO with Fe(II) complexes of the tripodal trithiolate ligands NS3 and PS3* yield trigonal-bipyramidal (TBP) complexes with varying redox states and reactivity patterns with respect to dissociation of the diatomic ligand. The previously reported four-coordinate [FeII(NS3)]- complex reacts irreversibly with NO gas to yield the S = 3/2 {FeNO}7 [Fe(NS3)(NO)]- anion, isolated as the Me4N+ salt. In contrast, the reaction of NO with the species generated by the reaction of FeCl2 with Li3PS3* gives a high yield of the neutral, TBP, S = 1 complex, [Fe(PS3*)(NO)], the first example of a paramagnetic {FeNO}6 complex. X-ray crystallographic analyses show that both [Fe(NS3)(NO)]- and [Fe(PS3*)(NO)] feature short Fe−N(NO) distances, 1.756(6) and 1.676(3) A, respectively. However, whereas [Fe(NS3)(NO)]- exhibits a distinctly bent FeNO angle and a chiral pinwheel conformation of the NS3 ligand, [Fe(PS3*)(NO)] has nearly C3v local symmetry and a linear FeNO unit. The S = 1 [FeII(PS3)L] complexes, where ...