Precision X-ray study of mononuclear dinitrosyl iron complex [Fe(SC2H3N3)(SC2H2N3)(NO)2]·0.5H2O at low temperatures

X-ray analysis of mononuclear dinitrosyl iron complex [Fe(SC2H3N3)(SC2H2N3)(NO)2]·0.5H2O (1) has been performed at 100 K (the crystallographic data are: a = 18.5006(3) Å, b = 9.5207(1) Å, c = 13.5719(2) Å, β = 99.8860(7)°, V = 2355.04(6) Å3, space group C2/c, Z = 8). From precision study of 1, distribution maps of deformation electron density (DED) have been obtained. Both DED and topological parameters clearly indicate that Fe-S bonds in 1 are similar, though originally one of the molecules of ligand 1,2,3-triazole-3-thione coordinates the Fe atom in a thiol form (A), while the other in a thione form (B). These bonds can be described as interatomic interactions of a peak-peak type. The geometry and bond lengths in 5-membered cycles for A and B forms are rather similar. Fe-NO bonds can be described as interactions of a peak-hole type. The thermal motion of NO groups (even at 100 K) is highly anisotropic (this being an intrinsic feature of NO groups), thus suggesting mobility of the Fe-NO bond.