Et(2)C(2)B(4)H(4)-titanium-phosphine complexes: Synthesis, characterization, and ethylene polymerization activity, and, Preliminary studies in combinatorial catalysis: Synthesis and catalytic testing of a resin-tethered 1,1'-2-binapthol.

摘要

Two projects involving titanium based catalysis are described. The first project involved the synthesis of a series of 14-electron Et ₂C₂B₄H₄-titanium-phosphine complexes for olefin polymerization. Traditional polymerization systems, which rely on cyclopentadienide, can be significantly improved by introduction of Et ₂C₂B₄H₄−2. The dinegative carborane ligand can replace two cyclopentadienide ligands, significantly reducing the steric crowding around the metal center. In addition, the C ₂B₄ cage can be easily modified allowing systematic adjustment of steric; and electronic factors. The titanium carborane complexes serve as catalyst precursors for the polymerization of ethylene at 1 atm in the presence of methylaluminoxane. The presence of reduced titanium species, the role of phosphine, and properties of the polymers produced are all discussed. The second project involved preliminary efforts in the development of a combinatorial approach to catalysis. The synthesis of a 1,1′-2-binapthol (BINOL) ligand suitable for attachment to resin is outlined along with initial testing in titanium catalyzed reactions displaying strong nonlinear effects. The use of the resin-attached BINOL in titanium catalyzed diethylzinc additions to aldehydes is also described. A comparison between catalysis using resin-attached BINOL and BINOL in solution is reported, and the implications to combinatorial catalysis discussed. Finally, the importance of carefully choosing the point of ligand attachment to resin is examined, along with the perceived need of maintaining C₂ symmetry in the resulting catalytic systems.