An unexpected bonding interaction between dxy and a1u orbitals mediated by porphyrin deformation.

Through density functional calculation and NMR spectroscopy, an unusual intermediate-spin electronic structure (d(xz)d(yz))3(d(xy))1(d(z)2)1 has been assigned to the six-coordinate saddled [Fe(OETPP)(THF)2]+ complex instead of the corresponding ruffled [Fe(TiPrP)(THF)2]+ complex.