Aromatic heterocyclic chemistry has been prolifically investigated for over a century. However, most of the known heteroaromatics involve only a few elements (C, O, N and S). Our group has expanded this field by the preparation of new heteroaromatics with unusual heteroatoms (B, P, As, etc.). This work involves challenging syntheses, while the study of these molecules focuses on fundamental questions of chemical bonding.
This heterocyclic aromatic chemistry has been applied to the preparation of new catalysts for olefin polymerization. Borata-benzenes, the boron analogs of benzene, are negatively charged like cyclopentadienide (Cp). It has been found that boratabenzenes can be substituted for Cp in metallocene catalysts with undiminished activity. However, since boron interacts strongly with its exocyclic substituents, electron density and consequent reactivity at the metal center can be modulated in a unique manner not available using Cp ligands using the rationale we have recently developed a series of novel catalysts for polymerization of ethylene and propylene. Our best catalysts exceed the activity of widely used industrial catalysts.
J. Chen, Z. Bajko, J. W. Kampf and A. J. Ashe, III Organometallics 2007, 26, 1563, “1,2-Dihydro-1,2-oxaborine: A Boron-Oxygen Heterocycle Isoelectronic with Benzene.”
J. Pan, J. W. Kampf and A. J. Ashe,III , Organometallics 2008, 27, 1345, “The Preparation and Crystal Structures of ?1-Derivatives of 2-Phenyl-1,2-azaboratabenzene.”
J. Chen, J. W. Kampf and A. J. Ashe, III Organometallics 2008, 27, 3639, “Syntheses and Structures of 6,13-Dihydro-6,13-diborapentacenes: p-Stacking in Heterocyclic Analogs of Pentacene.”
J. Pan, J. W. Kampf and A. J. Ashe, III Organometallics 2009, 28, 506, “Tricarbonylchromium Complexes of 1,2-Dihydro-1,2-benzazaborines.”
J. Pan, J. W. Kampf and A. J. Ashe, III J. Orgomet. Chem. 2009, 694, 1036, “The ligand properties of 2-vinyl-1,2-azaboratabenzene.”
A. J. Ashe, III Organometallics 2009, 28, 4236, “Aromatic Borataheterocycles: Surrogates for Cyclopentadienyl in Transition Metal Complexes.”