Preparation, Structure, and Olefin Polymerization Behavior of a Picolyl-Functionalized Carborane Nickel(II) Complex

The picolyl-functionalized o-carborane ligand CabNH (1; CabNH = 1-(2‘-picolyl)-o-carborane) was prepared from the monolithium carborane LiHC2B10H10 (=LiCab) and picolyl chloride (2-CH2ClC5H5N). 1 was lithiated with n-BuLi and then reacted with Ni(PPh3)2Cl2 to give the mononuclear Ni complex [(CabN)2]Ni (2). 2 was characterized by IR and NMR spectroscopy and elemental analysis. In addition, an X-ray structure analysis was performed on the complex, where the potential C,N-chelate ligand 1 was found to coordinate in a bidentate mode. The carborane complex 2 shows moderate catalytic activities of up to 3 × 106 g of PNB (mol of Ni)-1 h-1 for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities, molecular weights, and molecular weight distributions of polynorbornene (PNB) have been investigated under the various reaction conditions.