RASSCF-SO calculations were then carried out with RAS1 as the 3 highest-energy phosphorus 3p orbitals and RAS3 as the 3 lowest-energy virtual orbitals. These suffered from rotation of the RAS1 orbitals during the SCF procedure to become metal 4d and 5p orbitals. Further RASSCF-SO calculations were carried out with RAS1 as all 9 phosphorus 3p orbitals and RAS 3 as the 9 lowestenergy virtual orbitals. These saw significantly less rotation to metal orbitals, and in the case of 1-Nd all RAS1 orbitals remained predominantly phosphorus 3p in character. The orbitals from the 1-Nd RASSCF-SO were used for a RASCI-SO calculation, with RAS1 as the phosphorus 3s and 3p orbitals and as the 12 lowest-energy virtual orbitals. pNMR shifts calculated from the results of the RASSCF-SO calculations with all of the phosphorus 3p orbitals as RAS1 and this RASCI-SO calculation are shown in Table .