Homoleptic and Heteroleptic Borylones L1-B(Ph)-L2

Abstract

Quantum chemical calculation using density functional theory at the BP86-D3(BJ)/def2-TZVPP level and ab initio theory at the CCSD(T)/def2-TZVPP level have been carried out for the homoleptic and heteroleptic borylones L1-B(Ph)-L2 with the ligands L1, L2 = PPh₃, SPh₂, N₂, CO, CS, NHC^Me, CAAC^Me. The computation of the bond dissociation energy suggests that all borylones considered in this work should be stable enough to be observed experimentally. A surprising result is the finding that the homoleptic borylones B(Ph)(N₂)₂ and B(Ph)(SPh₂)₂ have a higher BDE than the corresponding carbones. It seems possible that bis-dinitrogen borylones can be synthesized and structurally characterized under appropriate conditions. The boron-ligand bonds of the heteroleptic borylones L1-B(Ph)-L2 influence each other, so that one bond becomes stronger and the other weaker, but to different degrees. The BDEs do not always show the same trend, as the electronic and geometric relaxation of the fragments can strongly influence the energy change due to bond breaking, which affects the thermodynamic stability of the compounds. The EDA-NOCV results show that Pauli repulsion is often the strongest energy component of the chemical bond, determining the bond strength and bond length.