Molecular design and function of ate complexes

Abstract

Lithium trialkylzincates were known to be convenient and synthetically useful for transferring various organic moieties and for metallating aromatic halides or vinyl halides. The outer shell of the zinc atom in lithium trialkylzincates is filled with 16 electrons, and there is a room for an additional ligand to coordinate to form a favorable state with 18 electrons. As a new type of zincate, the reactivities of this tetraalkylorganozincates and related modified organozincates were then studied. 1H-NMR study of organozincates indicated the difference between these highly coordinated zincates and lithium trimethylzincate. And the studies on the reactivity disclosed the difference of regioselectivity for epoxide opening reaction and the different reactivity toward halogen-metal exchange reaction. These results support that these highly coordinated zincates should be distinguished from ordinary lithium trialkylzincates in the structure and the reactivity. On the other hand, various dialkylzinc hydride "ate" complexes were also designed and the reactivities of these zincates toward the carbonyl compounds were investigated. The results clearly reveal that dimethylzinc hydrides are the most powerful and selective zincate for the reduction of the carbonyl group.