Complexes of Lanthanide Nitrates with Tri Tert Butylphosphine Oxide
2012-04-02T00:00:00Z (GMT) by
Reaction of lanthanide nitrates with tBu3PO (=L) lead to the isolation of complexes Ln(NO3)3L2·H2O·nEtOH (Ln = La (1), Nd(2)), Ln(NO3)3L2 ·nEtOH (Sm(3), Eu(4)), and Ln(NO3)3L2 (Dy(5), Er(6), Lu(7)). These have been characterized by elemental analysis, infrared and NMR(1H, 13C and 31P) spectroscopy and single-crystal X-ray diffraction. The structures show L to be positioned on opposite sides of the metal with the nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct molecules are present in the unit cell. A major isomer (70%) has a (P)O–Ln–O(P) angle of less than 180° with one of the nitrate ligands twisted out of the plane of the other nitrates while the lower abundance isomer is more symmetric with the (P)O–Ln–O(P) angle of 180° and the nitrate ligands coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be observed by variable temperature solution 31P NMR measurements but are clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln(NO3)2L3]+[PF6]− have not been totally successful and led to the isolation of crystals of Lu(NO3)3L2 and Tb(NO3)3L2.CH3CN (8).