Synthesis, Bonding, and Reactivity of Group 15 Amides

Abstract

This thesis discusses the effects of ligand design on the chemistry of heavy Group 15 elements. The correlation of molecular geometry with frontier molecular orbital energies is a well-known principal. This principle was exploited to systematically tune the frontier molecular orbitals in heavy Group 15 amides. The geometry of antimony and bismuth complexes tethered with a N,N,N-triamido ligand deviate from idealized pyramidal geometries and showed planar metal centers. These compounds were examined in the solid, solution, and gas-phase. Gas-phase calculations were used to assess the change in properties of the bismuth compound upon planarization, such as the lower LUMO energies, and increased Lewis acidity, for which both steric and electronic effects were examined.

A new class of antimony hydrides that participate in the first example of additive-free hydrostibanation of \ch{C+C}, C=C, C=O, and N=N bonds was developed. These hydrometallation reactions were unlocked through changing the geometry of the ligand, and consequently tuning the energy of the \acrfull{fmos}. The careful choice of a bis(silylamino)naphthalene ligand accomplished the desired outcome and provides a second example of frontier molecular orbital engineering in this work. Mechanistic studies suggest that hydrostibanation proceeds via a radical mechanism. Recycling of the stinbinyl hydride during the hydrostibanation of terminal alkynes to yield the Z-olefin product was also achieved.

A one-step, high yield synthesis of thermally-robust bismuthanylstibanes provided the first examples of neutral Bi–Sb $\sigma$-bonds in the solid-state. The reaction chemistry of the Bi–Sb bond was debuted by showing the insertion of a sulfur atom, providing the first documented example of a Bi–S–Sb bonding moiety. DFT calculations indicated that the bis(silylamino)naphthalene scaffold is particularly efficient in increasing interaction energies through a combination of inductive effects and dispersion donor effects, foreshadowing the use of this ligand in the isolation of other labile bonding environments, such as bismuth carbamates.

These studies reveal design rules for the rational pursuit of catalytically relevant systems, and seamlessly connect the realms of fundamental and applied chemistry.