摘要:
The reaction of equimolar amounts of 2-(2,4,6-Me3C6H2N = CH)(6-Bu')C6H3OH (HL') with M(CH2SiMe3)(3)(THF)(3) (M = Sc or Y) under mild conditions gives M(CH2SiMe3)(2)(THF)(L-1). The trigonal-bipyramidal structure of these dialkyls was confirmed crystallographically for M = Sc. Whereas the scandium complex is stable in solution at room temperature, the yttrium derivative slowly disproportionates to give Y(L-1)(3) which is also accessible from Y(CH2SiMe3)(3)(THF)(3) and three HL'. The X-ray structure of Y(L)3 indicates a chiral tris-chelate complex. While the reaction of the related ligand (2-CyN = CH)(6-Bu')C6H3OH (HL2, CY = cyclohexyl) with Sc(CH2SiMe3)(3)(THF)(3) gives the expected dialkyl Sc(CH2SiMe3)(2)(THF)(L-2), the reaction with the yttrium analogue affords the six-coordinate monoalkyl product Y(CH2SiMe3)(THF)(L-2)(2). This product is stable in solution towards disproportionation. The reaction of Y[N(SiMe3)(2)](3) with (2-C6F5N = CH)(6-Bu')C6H3OH (HL3) affords Y{N(SiMe3)(2)}(L-3)(2) and Y(L-3)(3). Both complexes are seven-coordinate in the solid state due to Y...F co-ordination to the C6F5 substituents. The scandium alkyl complexes are efficient catalysts for the ring-opening polymerisation of F-caprolactone. (C) 2002 Elsevier Science B.V. All rights reserved.