Structures of 2,4,6-tri-α-pyridyl-1,3,5-triazine complexes of the lanthanoid nitrates: A study in the lanthanoid contraction

The structures are reported of 20 1:1 complexes formed between 2,4,6-tri-α-pyridyl-1,3,5-triazine (tptz) and the nitrates of yttrium and the lanthanoids (La–Lu except Pm). The complexes can be divided up into a series of structural types. The majority of the characterised complexes belong to the isostructural family [Ln(tptz)(NO3)3(H2O)] · 2C2H5OH (Ln = Y (3), La–Yb (4–16)), which have three bidentate nitrate groups as well as a co-ordinated water molecule, and the metal ion is 10 co-ordinate, whilst a similar lanthanum complex [La(tptz)(NO3)3(H2O)] · Me2CO (2) has been prepared. Eleven co-ordinate [La(tptz)(NO3)3(CH3OH)2] (1), which has three bidentate nitrate groups as well as two co-ordinated methanol molecules, is also reported. By varying the solvent used, three different lutetium complexes can be obtained; [Lu(tptz)(NO3)3(C2H5OH)] · C2H5OH (18) and [Lu(tptz)(NO3)3(H2O)] · MeCN (19), both featuring two bidentate nitrate groups, a monodentate nitrate group and a co-ordinated solvent molecule, and [Lu(tptz)(NO3)2(H2O)2]NO3 · 3MeOH (20), whose cation contains two bidentate nitrate groups as well as two co-ordinated water molecules. The ytterbium complex [Yb(tptz)(NO3)3(C2H5OH)] · C2H5OH (17) is also described.

The structures of 20 new lanthanoid complexes all containing the 2,4,6-tri-α-puridyl-1,3,5-triazine ligand have been determined crystallographically. The majority of the complexes have the formula [Ln(tptz)(NO)3(H2O)] · 2EtOH, with the two ethanol molecules hydrogen bonded to the complex. The lanthanoid ions are 10 co-ordinate and an analysis of the metal–ligand bond lengths is consistent with the lanthanide contraction across the series.Figure optionsDownload as PowerPoint slide