Magneto-Structural Relationship Of Tetragonally-Compressed Octahedral Iron(Ii) Complex Surrounded By A Pseudo-S-6 Symmetric Hexakis-Dimethylsulfoxide Environment

Since the octahedral high-spin iron(II) complex has the T-5(2g) ground term, the spin-orbit coupling should be considered in magnetic analysis; however, such treatment is rarely seen in recent papers, although the symmetry-sensitive property is of interest to investigate in detail. A method to consider the T-term magnetism was well constructed more than half a century ago. On the other hand, the method has been still improved in recent years. In this study, the octahedral high-spin iron(II) complex [Fe(dmso)(6)][BPh4](2) (dmso: dimethylsulfoxide) was newly prepared, and the single-crystal X-ray diffraction method revealed the tetragonal compression of the D-4-symmetric coordination geometry around the iron(II) ion and the pseudo-S-6 hexakis-dmso environment. From the magnetic data, the sign of the axial splitting parameter, Delta, was found to be negative, indicating the E-5 ground state in the D-4 symmetry. The DFT computation showed the electronic configuration of (d(xz))(2)(d(x)(-y)(2)(2))(1)(d(yz))(1)(d(xy))(1)(d(z)(2))(1) due to the tetragonal compression and the pseudo-S-6 environment of dmso pi orbitals. The electronic configuration corresponded to the E-5 ground term, which was in agreement with the negative Delta value. Therefore, the structurally predicted ground state was consistent with the estimation from the magnetic measurements.