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

Abstract

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