A series of soluble .alpha.-diimine late transition metal catalysts has been invented comprising a substituted or unsubstituted catecholate ligand. The catalysts demonstrate high activity and selectivity for linear .alpha.-olefins. As such, these catalysts conveniently oligomerize ethylene. Typical activators as known to those of ordinary skill in the art are used to activate these transition metal catalysts. These catalysts can be used in a supported or unsupported form.