High-coordinated lanthanum(III) complexes with new mono- and bidentate phosphoryl donors; spectroscopic and structural aspects

Monodentate and bidentate ligands PhNHP(O)(NC4H8O)2 (1) and PhC(O)NHP(O)(NH(tert-C4H9))2 (2) were used to prepare new 7, 9 and 10-coordinated lanthanum(III) complexes; La(1)2Cl3(H2O)2 (3), La(1)2(NO3)3H2O.La(1)2(NO3)3CH3CN (4) and La(2)2(NO3)3 (5), respectively. Crystallization of compound 2 in CH3OH:CH3CN leads to one conformer in contrast to the crystallization result from CHCl3:n-C7H16 (two conformers). Compound 4 contains two independent nine-coordinated La(III) complexes that are different in the solvated molecules (H2O and CH3CN). Some structural and electronic perturbations in coordinated ligand were occurred upon complexation, that are confirmed by increase of 2JPH, 3JPH and 6JPH coupling constants from the free ligand 1 to complexes 3 and 4. The steric repulsions in the first coordination sphere of La3+ ion, metal–ligand (M–L) binding strength and PO stretching frequency are very influenced by changing the counter ion from Cl− to NO 3 - . Comparing the X-ray crystallography data of free ligand 2 with bis-chelated complex 5, it is found that the phosphoryl group is more reactive than carbonyl counterpart. A blue shift of the ν(N–H) vibration is observed in line with the weakening of the hydrogen bond from N–H···OPhosphoryl in 1 to N–H···Cl in 3. Three dimensional butterfly-shape structures are seen in the unit cell of complex 3, which are produced by OWater–H···OMorpholine hydrogen bonds.