Bonding, reactivity and aromaticity in some beryllocene derivatives

Abstract

Geometries of [X₃-M-Y₃]²⁻: X, M, Y = Be, Mg; [Cp-M-Y₃]⁻: M, Y = Be, Mg and [Cp-M-Cp]; M = Be, Mg; Cp⁻ = C₅H₅⁻ are optimized at the B3LYP/6-311+G(d) level of theory and the frequencies are also calculated at the same level of theory. Interesting bonding, reactivity and aromaticity trends emerge as one keeps on changing Cp⁻ units of beryllocene by the triangular aromatic dianions, X₃²⁻ (X = Be, Mg) as well as by replacing the central Be by Mg. Similar substitution of Cp⁻ by Al₄²⁻ and the additional change in the number of electrons yield all - metal complexes devoid of the original square planar Al₄²⁻ rings and with newly formed roughly rectangular aromatic rings. Atomic charges and Fukui functions lend additional insights into the local reactivity patterns of individual atomic centers.