Synthesis, structure, and reactivity of C2-symmetric bis(phospholyl)zirconium and bis(phospholyl)hafnium complexes

Several C-2-symmetric bis(phospholyl) adducts of group 4 metals, including the first example of an eta (5)-phospholyl complex of hafnium, have been synthesized and structurally characterized. These complexes undergo rac/meso isomerization in a process that is accelerated by Lewis bases. A C-2-symmetric bis(phospholyl)zirconium dichloride binds as a bidentate ligand to MO(CO)(4), In the presence of methylalumoxane, bis(phospholyl)zirconium complexes serve as active catalysts for ethylene-hexene copolymerization reactions.