Noble Gas Atoms as Electron Donors: Is the Stabilization of Strongly Electrophilic Borylnitrenes Feasible?

Abstract

AbstractThe possible interaction between an electrophilic borylnitrene, CatBN (Cat = Catecholato), with the noble gas atoms Rg (Rg = Kr, Xe) is probed by computational chemistry techniques including hybrid density functional (B3LYP), second‐order Møller–Plesset perturbation (MP2), and coupled‐cluster theory with singles, doubles, and a perturbative estimate of triple excitations [CCSD(T)] in conjunction with aug‐cc‐pVDZ and cc‐pVTZ and the corresponding small‐core pseudopotential correlation consistent basis sets for krypton and xenon. In the triplet manifold the interaction between CatBN and Rg is of the van der Waals type with a small N–Rg bond dissociation energy. In contrast, the singlet CatBNRg(1A′) has a short N–Rg distance (Kr: 1.962 Å; Xe: 2.029 Å) in agreement with a single bond character. The N–Xe bond dissociation energy is 17 kcal·mol–1 at the highest level of theory, while the N–Kr bond is significantly weaker. Experiments in xenon or xenon doped argon matrices do not give any indication for the formation of the CatBNXe(1A′) compound in spite of the strong N–Xe interaction predicted by theory. The experimental observation is explained by the existence of a crossing of singlet and triplet potential energy surfaces. At the geometry of triplet CatBNRg (large N–Rg distance) the singlet state is higher in energy whereas at the geometry of singlet CatBNRg (short N–Rg distance) the triplet is higher. Fast intersystem crossing to the lower lying triplet surface in the presence of Xe is assumed to preclude the formation of CatBNXe(1A′).