The Curious Case of Co-Planarity in Di-nuclear Triel Complexes: A Density Functional Investigation

Density functional investigation of intramolecular triel (Tr) bonding present in di-nuclear aryl complexes of group 13 elements having general formula [(Tr)Me2(2,6- (X)2C6H3O)]2 (Tr = B, Al, Ga, In & Tl and X = OMe, OEt, OH, OPh, NH2, SH, Cl, F) has been performed. Conclusive evidence of the concurrent two σ-hole interaction has been provided by analysis of Tr bond length, interaction energy (∆E), second order perturbation energy (E2), charge transfer (∆q), Quantum theory of atom in molecules (QTAIM) and Noncovalent Interaction (NCI) Plots for 12 complexes. The Tr bond length in the optimized geometry varies from 2.49 to 2.89 Å in Al complexes (1-8) and 2.66 to 2.83 Å in other group 13 element complexes (9-12) at PBE0-D3 functional. The interaction energy calculation reveals that the co-planer structure of complexes containing Al (1-8) are more stable than its rotamer by 8-15 kcal/mol, whereas the di-nuclear complexes of other group 13 (9-12) orient in non-planer pocket structure. This loss of co-planarity reveals the fact that it presence relies on the Tr atom, not the intramolecular Tr bonding, which has a striking impact on the crystal engineering of di-nuclear complexes of Group 13.