{Bis(3,5-Di-tert-butyl-2-oxidobenzyl)- [2-(N,N-dimethylamino)ethyl]amine- j4N,N0,O,O0}zinc(II) and {bis(3-tert- butyl-5-methyl-2-oxidobenzyl)- [2-(N,N-dimethylamino)ethyl]amine- j4N,N0,O,O0}(tetrahdyrofuran)zinc(II)

The title zinc(II) complexes, [Zn(C34H54N2O2)], (II), and [Zn(C28H42N2O2)(C4H8O)], (III), were obtained as monomeric 1:1 complexes, in contrast with the calcium complexes supported by the same ligand class. Complex (II) crystallizes with two independent molecules in the asymmetric unit, which have similar geometric parameters. The donor atoms in (II) form a distorted trigonal±pyramidal arrangement around the zinc centre. Complex (III) contains a coordinated tetrahydrofuran molecule, resulting in a ®ve-coordinate trigonal± bipyramidal arrangement around the Zn atom. The electron density provided by the coordination of this tetrahydrofuran molecule elongates the ZnÐO and ZnÐN bonds by approximately 0.07 and 0.10 AÊ , respectively, in comparison with (II). Neither (II) nor (III) is active as an "-caprolactone polymerization catalyst. The data presented here demonstrate that Zn may bind both an ONNO ligand and an additional oxygen-based ligand. The lack of activity is thus not due to steric hinderance at the metal atom.