The agreement achieved with this functional is most likely due to cancellation of errors, however, especially from the neglect of dynamics in our calculations; B3LYPHF30 should not be expected to give an improved description of the electronic structure of the complex. This interpretation is supported by the very different optimal exact exchange contribution found by the previous fit to f-element bound 31 P NMR data. The DFT-calculated 31 P NMR parameters are those of a static 1-La structure. However, at ambient temperature, where the experimental NMR measurements were recorded, there will be dynamic averaging owing to local motions, if these are present. For instance, librational motion of the La-P bond will reduce the effective 31 P shielding span. Simulating a fast (on the NMR time-scale) librational motion of the calculated 31 P shielding tensor with amplitude of ± 32° gives an averaged spectrum (see Figure ) that corresponds to the spectrum measured experimentally. Note that this librational motion is one of many possible solutions but highlights that 1-La is not static. Natural bond orbital (NBO) analysis was carried out using the NBO 6.0 software in Orca, with the aim of characterizing the Ln-P bonds. The results presented in Table use B3LYPHF20 with optimized H-positions (see Supporting Information Table for results from other methods). These data indicate relatively weak covalent bonding that is slightly stronger for phosphorus atoms with a lower degree of pyramidalization. The bonding interaction can be split into σ and π components, and as expected, the σ NBO has significant contributions form phosphorus 3s and 3p orbitals and lanthanum 4f, 5d and 6s orbitals, with the 5d contribution being most significant from lanthanum. The π NBO is similar but without significant contributions from the s orbitals.