Chromium Complexes with Acenaphthene Imine Derivative Ligands Synthesis and Catalysis on Diene Polymerization

Treatment of the bis(arylimino)acenaphthene (BIAN) ligands with CrCl₂(THF)₂ in THF affords mononuclear complexes of ^ArBIANCrCl₂(THF)₂ (3a, Ar = 2-ⁱPrC₆H₄; 3b, Ar = 2,6-Me₂C₆H₃) and chlorine-bridging dinuclear complexes ^ArBIANCrCl(μ-Cl)₃Cr(THF)^ArBIAN (3c, Ar = 2,6-Et₂C₆H₃; 3d, Ar = 2,6-ⁱPr₂C₆H₃). The molecular structures of 3b–3d were characterized by X-ray diffraction analysis, and all the chromium atoms are in octahedral geometries. Similar reactions of N-(arylimino)acenaphthenones with CrCl₂(THF)₂ afford the dinuclear chromium complexes with 1,1′-bis(2-aryliminoacenaphthene-1-olate) tetradentate ligands ArBIAOCr₂Cl₄(THF)₂ (4b, Ar = 2,6-Me₂C₆H₃; 4c, Ar = 2,6-Et₂C₆H₃) via a pinacol cross-coupling reaction. Upon activation with MAO, these complexes show moderate-to-high activities in butadiene and isoprene polymerization, affording a cis-1,4-enriched polymer.