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.