Synthesis, characterization and l-lactide polymerization behavior of bis(amidinate) rare earth metal amide complexes

A family of neutral and solvent-free bis(amidinate) rare earth metal amide complexes with a general formula [RC(N-2,6-Me2C6H3)2]2LnN(SiMe3)2 (R = phenyl (Ph), Ln = Y (1), Nd (2); R = cyclohexyl (Cy), Ln = Y (3), Nd (4)) were synthesized in high yields by one-pot salt metathesis reaction of anhydrous LnCl3, amidinate lithium salt [RC(N-2,6-Me2C6H3)2]Li, and NaN(SiMe3)2 in THF at room temperature. Single crystal structural determination of complexes 1, 2 and 4 revealed that the central metal adopts distorted pyramidal geometry. In the presence of 1 equivalent of iPr-OH, all these complexes were active for l-lactide polymerization in toluene at 70 °C to give high molecular weight (Mn > 104) polymers.