Estimating the stability and reactivity of acyclic and cyclic mono-heteroatom substituted germylenes: A density functional theory investigation

DFT computations coupled with appropriate isodesmic reactions are employed to investigate the effects of mono-heteroatom substitution, cyclization and unsaturation on the stability, multiplicity and reactivity of amino-, oxy-, silyl-, phosphino-, and thioalkylgermylenes. The results are based on the references to the parent symmetrical acyclic, saturated/unsaturated cyclic dialkylgermylenes. The calculated singlet-triplet energy gaps (ΔE_S-T) demonstrate the following trend: (amino≈oxy)>thio>alkyl>phosphino>silyl. Cyclization increases the ΔE_S-T of the all germylenes, but unsaturation considerably decreases it. Isodesmic reactions show that π-donor/σ-acceptor amino, oxy and thio stabilize both singlet and triplet germylenes but with a more considerable effect on the former while phosphino acts reversely. The reactivity of the species is discussed in terms of nucleophilicity, electrophilicity and proton affinity issues showing silyl and phosphinoalkylgermylenes more nucleophilic and more basic than amino and oxyalkylgermylenes.