Theoretical exploitation of donor-acceptor ability in low-valent group-14 elements complexes [E(PPh₃)₂→SiH₂]²⁺ (E = C to Pb) using energy decomposition analysis

Abstract

The structure and bonding of complexes containing subvalent group-14 elements [E(PPh₃)₂→SiH₂]²⁺ (Si-EP) with E = C to Pb have been researched using charge - and EDA-NOCV methods. The optimized equilibrium geometries for complexes have the most stable structure which has been found for carbone ligand CP as the nearly end-on bonded form in Si-CP. In contrast to this, the heavier ligands SiP to PbP in the heavier complexes Si-SiP to Si-PbP exhibit strongly side-on manners. Bond dissociation energies, -Dc (kcal.mol⁻¹), increase from Si-CP to the stronger bonded complexes Si-SiP to Si-PbP EDA-NOCV calculations revealed that the donation [E(PPh₃)₂→SiH₂]²⁺ displays the significant σ-interactions of the ligands while the π-electron sharing exhibits the charges transfer between E(PPh₃)₂ and SiH₂²⁺. Bonding analysis indicated that the Si-E bond results from the decrease in the donation [E(PPh₃)₂→SiH₂]²⁺ and electrostatic attraction. The investigated complexes possessed E(PPh₃)₂→SiH₂²⁺ strong σ-donors and E(PPh₃)₂↔ SiH₂²⁺ π-π electrons shared between the two fragments.