Novel disilyleno- and digermylenocarbenes and SiSi containing cyclopropenylidenes at theoretical levels

Following our quest for silylenes and germylenes, we have reached at W shaped novel triplet disilyleno- and digermylenocarbenes through optimization of 2,3-di(X)disilacyclopropenylidenes and 2,3-di(X)digermacyclopropenylidenes, respectively, at five ab initio and DFT levels (M = Si, Ge; X = H, F, Cl, Br). Also, we have met the challenge of confining SiSi double bonds in singlet cyclopropenylidene ground states by optimizing singlet 2,3-di(X)disilacyclopropenylidenes, at the same levels of theory. Results are compared and contrasted to the corresponding singlet and triplet 2,3-di(X)cyclopropenylidenes.