Nature and strength of group-14 A-A′ bonds

• Published in: Chemical science (Cambridge) Vol. 15; no. 5; pp. 1648 - 1656
• Main Authors: Rodrigues Silva, Daniela, Blokker, Eva, van der Schuur, J. Martijn, Hamlin, Trevor A, Bickelhaupt, F. Matthias
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 31.01.2024; The Royal Society of Chemistry
• Subjects: Bonding strength; Bulk density; Chemistry; Density functional theory; Germanium; Lead; Silicon; Tin
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d3sc06215e

We have quantum chemically investigated the nature and stability of C-C and Si-Si bonds in R 3 A-AR 3 (A = C, Si; R 3 = H 3 , Me 3 , Me 2 Ph, MePh 2 , Ph 3 , t -Bu 3 ) using density functional theory (DFT). Systematic increase of steric bulk of the substituents R has opposite effects on C-C and Si-Si bonds: the former becomes weaker whereas the latter becomes stronger. Only upon going further, from R = Ph to the bulkiest R = t -Bu, the R 3 Si-SiR 3 bond begins to weaken. Our bonding analyses show how different behavior upon increasing the steric bulk of the substituents stems from the interplay of (Pauli) repulsive and (dispersion) attractive steric mechanisms. Extension of our analyses to other model systems shows that C-Si bonds display behavior that is in between that of C-C and Si-Si bonds. Further increasing the size of the group-14 atoms from C-C and Si-Si to Ge-Ge, Sn-Sn and Pb-Pb leads to a further decrease in the sensitivity of the bond strength with respect to the substituents' bulkiness. Our findings can be used as design principles for tuning A-A and A-A′ bond strengths. Quantum-chemical analyses reveal: Si-Si bonds are longer, weaker, and react oppositely to introducing bulkier substituents than C-C bonds.