화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.118, No.7, 1247-1257, 2014
CASPT2 Study of Inverse Sandwich-Type Dinuclear Cr(I) and Fe(I) Complexes of the Dinitrogen Molecule: Significant Differences in Spin Multiplicity and Coordination Structure between These Two Complexes
Inverse sandwich-type complexes (ISTCs), (mu-N-2)[M(AIP)](2) (AIPH = (Z)-1-amino-3-imino-prop-1-ene; M = Cr and Fe), were investigated with the CASPT2 method. In the ISTC of Cr, the ground state takes a singlet spin multiplicity. However, the singlet to nonet spin states are close in energy to each other. The thermal average of effective magnetic moments (mu(eff)) of these spin multiplicities is close to the experimental value. The eta(2)-side-on coordination structure of N-2 is calculated to be more stable than the eta(1)-end-on coordination one. This is because the d-orbital of Cr forms a strong d(pi)-pi* bonding interaction with the pi* orbital of N-2 in molecular plane. In the ISTC of Fe, on the other hand, the ground state takes a septet spin multiplicity, which agrees well with the experimentally reported mu(eff) value. The eta(1)-end-on structure of N-2 is more stable than the eta(2)-side-on structure. In the eta(1)-end-on structure, two doubly occupied d-orbitals of Fe can form two d(pi)-pi* bonding interactions. The negative spin density is found on the bridging N-2 ligand in the Fe complex but is not in the Cr complex. All these interesting differences between ISTCs of Cr and Fe are discussed on the basis of the electronic structure and bonding nature.