Bonding analysis of telluroketones H₂A = Te (A = C, Si, Ge)

Quantum chemical calculations using density functional theory BP86/def2-TZVPP and ab initio methods at CCSD(T)/def2-TZVPP have been carried for the telluroketones H₂A=Te (A = C, Si, Ge). DFT calculations have also been carried out for the ketones H₂C=E (E = O, S, Se, Te) and for the complexes NHC → [H₂A=Te] → B(C₆F₅)₃. The nature of the bonding has been investigated with charge- and energy decomposition analyses. The calculated bond dissociation energies for the double bonds of the H₂C = E and H₂A = Te molecules show the expected trends O > S > Se > Te for atom E and C > Si > Ge for atom A. Complexation of the telluroketones in NHC → [H₂A = Te] → B(C₆F₅)₃ leads to longer and weaker A-Te bonds which exhibit the surprising trend for the bond dissociation energy Si > Ge > C. The contribution of the π bonding in H₂A = Te increases for the heavier atoms with the sequence C < Si < Ge.