Titanium(II) or zirconium(II) complexes and addition polymerization catalysts therefrom

DETAILED DESCRIPTION According to the present invention there are provided metal complexes containing one and only one cyclic, delocalized, anionic, .
pi.
-bonded group, said complexes corresponding to the formula: ##STR1## wherein: M is titanium or zirconium in the +2 formal oxidation state; L is a group containing a cyclic, delocalized, anionic, .
pi.
-system through which the group is bound to M, and which group is also bound to Z; Z is a moiety bound to M via a .
sigma.
-bond, comprising boron, or a member of Group 14 of the Periodic Table of the Elements, and also comprising nitrogen, phosphorus, sulfur or oxygen, said moiety having up to 60 nonhydrogen atoms; and X is a neutral, conjugated or nonconjugated diene, optionally substituted with one or more hydrocarbyl groups, said X having up to 40 carbon atoms and forming a .
pi.
-complex with M.
Additionally according to the present invention there is provided a process for preparing a metal complex containing one and only one cyclic, delocalized .
pi.
-bonded group, said complex corresponding to the formula: ##STR2## wherein M, L, Z and X are as previously defined, comprising: contacting a compound according to the formula M(X*).
sub.
2 or a solvated adduct thereof wherein X* is halo and M is as previously defined, with a conjugated or nonconjugated C.
sub.
4-40 diene compound corresponding to X and a source of a dianion ligand, (Z--L).
sup.
-2.
In a preferred embodiment the compound according to the formula M(X*).
sub.
2 is prepared by contacting a compound according to the formula M*(X*).
sub.
3 or M**(X*).
sub.
4, or a solvated adduct thereof, in a solvent, with a reducing agent under reducing conditions wherein, M* is titanium or zirconium in the +3 formal oxidation state; M** is titanium or zirconium in the +4 formal oxidation state; and X* is as previously defined.
In another embodiment of the present invention there is provided a process for preparing a metal complex containing one and only one cyclic, delocalized .
pi.
-bonded group, said complex corresponding to the formula: ##STR3## wherein M, L, Z and X are as previously defined, the steps of the process comprising: 1) a) contacting a conjugated or nonconjugated C