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

Reaction of (MeC5H4)(2)LnCl (Ln = Yb, Y, Er) with LiNCO(CH2)(4)CH2 in tolue ne at 0 degreesC yielded the complexes {(MeC5H4)(2)Ln[O=C=N(CH2)(4)]}(2) [L n = Yb (1), Y (2), Er (3)] in fairly good yields. The crystal slrudure of 1 [monoclinic, space group P2(1)/n ( not equal 14); a = 12.247(1), b = 11.13 7(2), c = 12.708(3) Angstrom; beta = 107.36(1)degrees, V = 1654.2(5) Angstr om (3), Z = 2, D-calc = 1.780 g cm(-3)] was identified by X-ray diffraction analysis, The two trivalent (MeC5H4)(2)Yb units are bridged by two deproto nated epsilon -caprolactam ligands via Yb-N (2.374(4) Angstrom) and Yb-O* ( 2.277(3) Angstrom) bonds. All the complexes exhibit good catalytic activity for the ring-opening polymerization of epsilon -caprolactone. (C) 2001 Els evier Science B.V. All rights reserved.