Triel Bonds with Au Atoms as Electron Donors

The novel triel bonds of BX₃ (X=H, F, Cl, Br, and I) and C₅H₅B as electron acceptors and AuR₂ (R=Cl and CH₃) as an electron donor were explored. The triel bond is a primary driving force for most complexes, while the contribution from a halogen-chlorine interaction in BX₃−AuCl₂ (X=Cl, Br, and I) and an iodine-Au interaction in BI₃−Au(CH₃)₃ is also very important. Interestingly, the positively charged Au atom of AuCl₂ can attractively bind with the holes of BX₃ and C₅H₅B. The interaction energy lies in the range of 1 and 80 kcal/mol, in the order X=F5H₅B is stronger than the triel bond of BX₃. In the formation of B−Au triel bond, electrostatic energy is not dominant, while polarization energy including orbital interaction has the largest contribution for the strongly bonded complexes and dispersion energy for the weak triel bond.