Addition Polymerization of Norbornene-Type Monomers Using Neutral Nickel Complexes Containing Fluorinated Aryl Ligands

• Published in: Macromolecules 2003-04, Vol.36 (8), p.2623-2632
• Main Authors: Barnes, Dennis A, Benedikt, George M, Goodall, Brian L, Huang, Shyhchang S, Kalamarides, Heather A, Lenhard, Susan, McIntosh, Lester H, Selvy, K. T, Shick, Robert A, Rhodes, Larry F
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma030001m

The strong Lewis acid B(C6F5)3 was found to activate complexes of nickel toward the polymerization of norbornene-type monomers. The active species in this reaction is created by the transfer of C6F5 from boron to nickel. As a result, a class of neutral, single-component nickel complexes was developed containing two electron-withdrawing aryl ligands that polymerize norbornene and norbornenes with functional pendant groups. Active complexes include Ni(C6F5)2(PPh2CH2C(O)Ph), (η6-toluene)Ni(C6F5)2, and Ni(2,4,6-tris(trifluoromethyl)phenyl)2(1,2-dimethoxyethane). In the case of (η6-toluene)Ni(C6F5)2, isolation and characterization of low molecular weight norbornene polymers, using ethylene, indicated that each polymer chain contained a C6F5 headgroup. This points to the initiation step as being the insertion of norbornene into the Ni−C6F5 bond. The polymer microstructure as revealed by 1H and 13C NMR spectrometry is entirely different from that produced using the cationic nickel catalyst, [(η-crotyl)Ni(1,4-COD)]PF6. This difference in microstructure led to improved mechanical properties for 80:20 copolymers of norbornene and 5-triethoxysilylnorbornene.