Post Hartree–Fock calculations of pnictogen–uranium bonding in EUF₃ (E = N–Bi)

NUF₃ is identified as having a NU triple bond, as has been previously found (Andrews et al., Angew. Chem. Int. Ed., 2008, 47, 5366). By contrast, while previously reported calculations on PUF₃ and AsUF₃ (Andrews et al., Inorg. Chem., 2009, 48, 6594) gave a EU triple bond, our calculations suggest a single bond for both molecules, with antibonding π* and non-bonding 5f_U orbitals significantly occupied, and highly multiconfigurational wavefunctions. We propose this difference to be due to the smaller [6,6] active space used (σ, π, π* and σ*) in the previous studies. In our calculations, a [6,16] active space was employed in order to include uranium f-orbitals and pnictogen d-orbitals.