16 Borane Activators for Late-Transition Metal Catalysts in Norbornene Polymerization Dedicated to Prof. Dr. Gerhard Herberich on the occasion of his 65 th birthday Paul-Gerhard Lassahn, 1 Christoph Janiak,* 1 Jae-Seung Oh 2 1 Institut für Anorganische Chemie, Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany Fax: +49(0)761-2036147; E-mail: janiak@uni-freiburg.de 2 LG Chem Research Park, 104-1, Moonji-dong, Yusong-gu, Taejon 305-380, Korea Keywords: borane catalysts; methylaluminoxane; polynorbornene; polyolefins; transition metal chemistry; Introduction The majority of polyolefins is produced with titanium- (Ziegler catalysts), zirconium- (metallocene catalysts), and chromium-based catalysts (Unipol, Phillips catalysts) or by a free radical process (low-density polyethylene (LDPE)). Recently, late-transition metals, in particular nickel and palladium, are seeing a renewed interest as olefin polymerization catalysts. [1–3] Some of these late- transition metal complexes are directly active polymeri- zation catalysts, mostly towards ethene, because they are cationic species with weakly bound ligands. [3, 4] Others have to be activated with methylaluminoxane (MAO) [5] or so-called phosphane scavengers, such as Ni(cod) 2 (cod: 1,5-cyclooctadiene) or rhodium complexes to abstract phosphorus-bound ligands. [6] The use of the organic Lewis acid tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 , 1) [7] in combination with and without TEA as an activator of late-transition metal complexes in olefin polymerization is also known and described in the litera- ture. [8] Tris(perfluoroaryl)boranes also play an important role in catalyst activation and in the mechanistic under- standing of early-transition-metal group IV metallocene catalysts in olefin polymerization. [9–11] The borane abstracts an alkyl or hydride group from the metallocene precatalysts, becomes an anion and generates a highly active cationic metallocenium olefin polymerization cata- lyst. To the best of our knowledge, the use of the cocata- lyst system 1/TEA in the polymerization of norbornene has been described only once in a patent of the B.F. Goodrich Company (USA) [12] and communicated by the same author at conferences [13] but not published in regular journals. Here, we describe the use of 1, in comparison to MAO as an activator towards nickel and palladium com- plexes 2 – 5 in the vinyl polymerization of norbornene. Phosphane complexes 2 – 5 have not been mentioned before for norbornene polymerization as well. [14] The homopolymer vinyl-polynorbornene (6) is of inter- est as a specialty polymer with good mechanical strength, heat resistivity, and optical transparency for applications, such as deep ultraviolet photoresists, interlevel dielectrics in microelectronics applications, or as cover layers for liquid-crystal displays. Catalysts described in the litera- Communication: Nickel(II) and palladium(II) complexes of the general type [MCl 2 {Ph 2 P(CH 2 ) n PPh 2 }] with n = 2, 3 and M = Ni (2, 3), Pd (4, 5) have been utilized as catalysts for the polymerization reaction of norbornene. It was found that the use of B(C 6 F 5 ) 3 /triethylaluminium (TEA) in comparison to methylaluminoxane as an activator towards complexes 2, 3 and 5 gave comparable polymerization activities, and the system 4/B(C 6 F 5 ) 3 /TEA even led to an extremely high polymerization activity of 10 7 g polymer / mol metal N h. Macromol. Rapid Commun. 2002, 23, No. 1 i WILEY-VCH Verlag GmbH, 69451 Weinheim 2002 1022-1336/2002/0101–0016$17.50+.50/0 Macromol. Rapid Commun. 2002, 23, 16–20