Single crystals suitable for XRD studies were obtained for all Error! Reference source not found.1-M complexes, which confirmed the proposed connectivity in all cases. The crystal structure of 1-Mg (Figure ), is reminiscent of the magnesium bis(phosphoranimine)methanide hexagonal P6322 space group, with the three (NPC-H) -ligands symmetrically related (Figure )the two donor atoms (methanide C and imide N) are completely equivalent in the model, exemplified by the asymmetric unit featuring only half of the NPC-H ligand. All four complexes adopt a twisted trigonal prismatic coordination environment about the metal, rather than the more familiar octahedral 6-coordinate shape (Figure ). This is due to the small bite angle (ca. 65°) of the (NPC-H) -ligand. In each complex, the three phosphorus atoms and lanthanide atom all lie in the same plane (average of sum of P-RE-P angles: