Divalent propargylenic C2H2M group 14 elements:Structures and singlet-triplet energy splittings (M=C, Si, Ge, Sn and Pb)

Relative stabilities and singlet (s)-triplet (t) energy splittings (ΔEs-t) of divalent propargylenic H-CC-M-H group 14 elements are investigated at B3LYP/6-311++G** and MP2/6-311++G** levels of theory (M=C, Si, Ge, Sn and Pb). Plotting B3LYP calculated relative energies of each H-CC-M-H as a function of the divalent bond angle ∠HMC, gives cross points between the singlet and triplet states of divalent C, Si, Ge, Sn and Pb. A linear correlation is found between the LUMO-HOMO energy gaps of the singlet species, and their corresponding ΔEs-t. No significant group 14 element d orbital valence participation is found for any of the scrutinized structures. Comparisons between relative stabilities and geometrical parameters for structures with different divalent atoms and multiplicities are discussed.