Electride Characteristics of Some Binuclear Sandwich Complexes of Alkaline Earth Metals, M2(η5-L)2 (M = Be, Mg; L = C5H5–, N5–, P5–, As5–)

Abstract

Ab initio calculations have been performed for a series of binuclear sandwich complexes, M2(η5-L)2. It has been observed that the eclipsed and staggered conformations have almost equal amount of energies. The M–M bond lengths are comparable with those in the free M2 molecules (M = Be, Mg). The nuclear-independent chemical shift (NICS) values indicate the aromaticity of these complexes. The stability of Be2(η5-L)2 complexes is higher than that of the Mg2(η5-L)2 complexes. The natural bond orbital (NBO) analysis and electron density descriptors proved the existence of a single covalent M–M bond in an M22+ fragment. It has been observed that each M–M bond contains a non-nuclear attractor (NNA) at the center of the respective bond. The Laplacian of electron density [∇2ρ(r)] is negative at the NNAs. The energy decomposition analysis (EDA) showed that M22+ and 2L– represent the bonding interaction in the complexes. All of the designed binuclear sandwich complexes behave as electrides.