An insight into the structure of model germaphosphaallenes

Abstract

The geometries of all possible isomers of the model compound H₂Ge=C=PH were optimized at the B3LYP/6-31G(d,p) level of the theory. The calculation were repeated at higher correlated methods with similar results and for the the isomers of the methyl-substituted phosphagermaallene MeP=C=GeMe₂. As another way to stabilise the P=C=Ge unit consists in the use electronic effects, a NBO study was carried out in order to identify the influence that the nature (electropositive or electronegative) of several substituents would have on the strength of the C=Ge bond. Model compounds HP=C=GeR₂ and HP=C=GeRR′ were investigated (R = BH₂, CH₃, SiH₃, NH₂, OMe, F; R′ = H). It was found that the main interaction contributing to the weakening of the C=Ge bond is a transfer of electron density from the lone pair of the phosphorus atom to the molecular antibonding orbital localized on the Ge–C bond.

Keywords:

• phosphagermaallenes
• B3LYP
• CCSD
• MP4
• theoretical study

Acknowledgements

The authors are grateful to Professor Romuald Poteau (Université Paul Sabatier, Toulouse) for helpful discussions. Financial support from the French Ministery of Foreign Affairs (ECO-NET program no 18824SD) is acknowledged. We thank Dr Joaquin Barosso-Flores for useful discussion on the NBO analysis.