Novel .alpha.-diimine metal complexes, particularly iron complexes are
disclosed. The .alpha.-diimine metal complexes are produced by forming
one of the .alpha.-diimine metal complex imine bonds in the presence of a
metal salt or an .alpha.-acylimine metal complex. .alpha.-diimine metal
complexes having two different .alpha.-diimine nitrogen groups may be
produced. The .alpha.-diimine metal complexes are useful for polymerizing
or oligomerizing olefins.