Summary: A [TiCl2(salen)] complex and its derivatives with the formula [TiCl2(L)] [L = salen(tBu), salen(di‐Me), salen(di‐tBu), salen(Me)] were synthesized in high yield by reacting the Schiff‐base ligands with TiCl4. [TiCl2{salen(tBu)}] and [TiCl2{salen(di‐tBu)}] have been characterized by single‐crystal X‐ray diffraction. Styrene polymerizations carried out with [TiCl2(salen)] and its derivatives co‐catalyzed by MAO yielded syndiotactic polystyrenes. The catalytic activity and syndiospecificity were dependent on the bulkiness of the ortho substituents in the aryl ring of ligand. magnified image

Polymerizations of vinyl ethers are carried out with (α‐diimine)nickel(II) catalysts in the presence of methylaluminoxane. Effects of structural variations of the ligand on the activities of catalysts and polymer microstructure are described. The catalysts prepared by changing the bulkiness of ligand substituents in the ortho aryl position result in no specific trends terms of the yield and molecular weight of polymer. Poly(vinyl ether)s are atactic regardless of the structure of the catalyst used. magnified image

Summary: The polymerizations of ethyl vinyl ether, n‐butyl vinyl ether and isobutyl vinyl ether were investigated with a series of pyridine bis(imine) complexes of iron(II) and cobalt(II) in the presence of methylaluminoxane. The cobalt catalysts showed much higher activity and produced higher molecular weight polymers than their iron analogues. Both catalyst systems produced predominantly atactic polymers. There were no specific trends in the activity and the polymer molecular weight, according to the steric bulk around the metal center.The iron(II) and cobalt(II) catalysts used here.imageThe iron(II) and cobalt(II) catalysts used here.