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The synthesis of half-sandwich transition-metal complexes containing the Cab (N) and Cab (N, S) chelate ligands (HCab (N) = HC2B10H10CH2C5H4N (1), LiCab (N, S) = LiSC2B10H10CH2C5H4N (4) ) is described. Compounds 1 and 4 were treated with chloride-bridged dimers Ir (Cp*) Cl22 (Cp* = eta5-C5Me5), Ru (p-cymene) Cl22 and Rh (Cp*) Cl22 to give half-sandwich complexes Ir (Cp*) Cl (Cab (N) ) (2), Ru (p-cymene) Cl (Cab (N) ) (3), and Rh (Cp*) Cl (Cab (N, S) ) (5), respectively. Addition reaction of LiCab (S) (Cab (S) = SC2 (H) B10H10) to the rhodium complex 5 yields Rh (Cp*) (Cab (S) ) (Cab (N, S) ) (6). All the complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. In addition, X-ray structure analyses were performed on complexes 2, 3, 5, and 6, in which the potential C, N- and N, S-chelate ligands were found to coordinate in a bidentate mode. The carborane complex 2 shows catalytic activities up to 3. 7x10 (5) g PE mol (-1) Ir h (-1) for the polymerization of ethylene in the presence of methylaluminoxane (MAO) as cocatalyst. The polymer obtained from this homogeneous catalytic reaction has a spherical morphology. Catalytic activities and the molecular weight of polyethylene have been investigated for various reaction conditions.
Wang et al. (2005) studied this question.