Four electron aromaticity in η3-Allyltetrylenes Ar-E-η3-Allyl E= Si, Ge, Sn, Pb

Abstract

The electronic structure and the conjugation in allyltetrylenes Ar-E-η3-C3H4 (E= Si, Ge, Sn, Pb; Ar = С6H3Trip2 (1), Ph (1′)), which exhibit the unique symmetric η3-coordination among the allyl compounds of the main groups, were studied by the DFT based methods. The QTAIM molecular graph exhibits two metal-allyl bond paths, which form 4-membered metallacycles. The advance aromaticity criteria NICS-scan, electron density of delocalized bonds (EDDB) and gauge-including magnetically induced currents (GIMIC) were firstly applied to the 1. The method results demonstrate a strong cyclic delocalization for organometallics. According to the NICS and GIMIC values, the aromaticity degree diminishes in the series Si ~ Ge > Sn > Pb. According to the EDDB results, it increases in the series Si < Ge < Sn < Pb from 38 % to 65%. The CMO and NODB population analyses reveal the unprecedented type of aromaticity, namely the four electron in-plane Möbius type.