Yu
Wanga and J.J. Leeb
aDepartment of Chemistry, National Taiwan University, Taipei, Taiwan;
bNational Synchrotron Radiation Research
Center, Hsin-Chu, Taiwan (yuwang@xtal.ch.ntu.edu.tw)
Charge density and bond characterization have
been investigated on an Iron-nitrosyl dithiocarbamate complex, [Fe (NO)(S2CNC2H6)2]
in terms of accurate single crystal diffraction at 100K and an open-shell DFT
calculation. The iron atom is five- coordinated with four sulfur and one
nitrogen atoms in a square pyramidal geometry, the site symmetry is roughly C2v. The iron atom is 0.6261(1) above the
plane of four sulfur atoms, the nitrosyl group (NO) is in the axial direction
perpendicular to the plane. Unfortunately, the oxygen atom exhibits positional
disorder.
The complex is related to a potential free radical scavenger, this
study may shine some light on how it is so via electron density distribution,
especially at the iron site and at the NO group. It is known that NO ligand
could be served as a radical neutral species or NO+, a nitrosyl, or NO- ,
a nitroxide group. Thus the unpaired electron can be located either at Fe or at
the NO group. According to the electron density distribution based on the
multipole model and on the DFT calculation, the electronic configuration of iron
atom is 4s13d6, therefore a FeI and NO+ ligand is a nitrosyl group. In other words, the unpaired
electron is mostly localized at Fe not on the NO ligand, which is consistent
with the conclusion made from single crystal EPR and Moessbauer measurements.
Topological analysis on the total electron density will give the bond
characterization in terms of topological properties associated with bond
critical points. The VSCC of Fe in this five coordinated complex is quite
interesting, the detail description and its correlation to the metal ligand
bond will be presented.