Syntheses of {(MeC5H4)2Ln[O⋯C̄⋯N(CH2)4CH2]}2 (Ln=Yb, Y, Er) and the X-ray crystal structure of the ytterbium complex

Reaction of (MeC5H4)2LnCl (Ln=Yb, Y, Er) with LiNH2 in toluene at 0°C yielded the complexes {(MeC5H4)2Ln[OC̄H2]}2 [Ln=Yb (1), Y (2), Er (3)] in fairly good yields. The crystal structure of 1 [monoclinic, space group P21/n (#14); a=12.247(1), b=11.137(2), c=12.708(3) Å; β=107.36(1)°, V=1654.2(5) Å3, Z=2, Dcalc=1.780 g cm−3] was identified by X-ray diffraction analysis. The two trivalent (MeC5H4)2Yb units are bridged by two deprotonated ε-caprolactam ligands via Yb–N (2.374(4) Å) and Yb–O* (2.277(3) Å) bonds. All the complexes exhibit good catalytic activity for the ring-opening polymerization of ε-caprolactone.