Theoretical Insights into Boron Heterocycles and Donor Ligands

A Thesis Submitted in Total Fulfillment of the Requirements for the Degree of Doctor of Philosophy to the School of Agriculture, Biomedicine and Environment, La Trobe University, Victoria, Australia. </p

Ligand-stabilized heteronuclear diatomics of group 13 and 15

A theoretical investigation of ligand-stabilized MX diatomics (M = group 13, X = group 15 element) with N-heterocyclic carbene (NHC) ligands has been carried out to assess bonding and electronic structure. Binding of two ligands in the form L-MX-L is generally preferred over binding of a single ligand as L-MX or MX-L. Binding of carbene donor ligands is predicted to be thermodynamically favorable for all the systems, and is very favorable for the lighter group 15 systems (nitrogen and phosphorus). Detailed analysis of the bonding in these complexes has been carried out with energy decomposition analysis (EDA). In all cases, the carbene to boron and carbene to nitrogen bonding is described as an electron-sharing double bond with both σ and π bonding interactions. For the heavier elements, bonding to C (except for P-C interactions) is best described as a donor-acceptor σ single bond

Borataalkene Hydrofunctionalization Reactions

The hydrofunctionalization of alkenes is a foundational class of reactions; however, the analogous reactions for B═C bond-containing species have been virtually unexplored. This work unearths a range of B═C hydrofunctionalization reactions with the 9-borataphenanthrene anion, including hydroalkylation, hydroarylation, hydroalkynylation, hydroamination, hydroalkoxylation, and hydration. The unique reactivity represents an addition to the synthetic chemist's toolbox to access functionalized tetracoordinate borates.</p

PhICl₂ is activated by chloride ions

A study on the potential activating role of pyridine in the electrophilic chlorination of anisole by PhICl2 has led to the discovery that soluble sources of chloride ions activate PhICl2 in the reaction at catalytic loadings, greatly increasing the rate of chlorination. It is further shown that presence of chloride increases the rate of decomposition of PhICl2 into PhI and Cl2. The specific mechanism by which chloride induces electrophilic chlorination and decomposition of PhICl2 remains an open question.</p

Isolation of Stable Borepin Radicals and Anions

Borepin, a 7-membered boron-containing heterocycle, has become an emerging molecular platform for the development of new materials and optoelectronics. While electron-deficient borepins are well-established, reduced electron-rich species have remained elusive. Herein we report the first isolable, crystalline borepin radical (2 a, 2 b) and anion (3 a, 3 b) complexes, which have been synthesized by potassium graphite (KC8) reduction of cyclic(alkyl)(amino) carbene-dibenzo[b,d]borepin precursors. Borepin radicals and anions have been characterized by EPR or NMR, elemental analysis, X-ray crystallography, and cyclic voltammetry. In addition, the bonding features have been investigated computationally using density functional theory