Structure bonding and reactivity of low valent group 14 and 15 compounds

Abstract

The synthesis and isolation of low-valent main group compounds break up the newlineorthodoxy of traditional bonding concepts in the main group elements. The presence of newlinestereochemically active/hidden lone pairs or a vacant coordination site on the low-valent newlineelement makes them highly reactive. The reactivity varies depending on the nature of the newlinemain group element and the substituent attached to it. Although the structural diversity newlineof these compounds has been expanded in the last few decades, pursuits for newlineunderstanding the electronic requirement and bonding in these compounds need to be newlineexplored. The donor-acceptor interaction has been shown to play a vital role in stabilizing newlinemain group compounds in their low-valent state. The role of the substituents in newlinestabilizing the low-valent groups 14 and 15 compounds and their reactivity is the prime newlinefocus of the thesis. The cyclopropenylidenes with various substituents at the olefinic newlinecarbons, neutral carbon (I) compounds with three non-bonding electrons, gallium ligand newlinecoordinated group 15 compounds having low-valent group 15 elements and newlinebenzamidinate tetrylene-oxygen complexes have been selected for the detailed newlinetheoretical study. All the calculations in the thesis were carried out within the density newlinefunctional theory framework. newlineTheoretical analysis of the effect of different substituent on the electronic newlinestructure and bonding in cyclopropenylidenes indicates that the bonding interaction newlinebetween the carbene carbon and the acetylenic fragment changes from classical electron- newlinesharing to two donor-acceptor and#61555;-interactions when the substituent changes from newlinehydrogen to electron-withdrawing groups ( CHO and COOH). Whereas the and#61555;- newlineinteractions changes to one electron-sharing and one donor-acceptor type when the newlinesubstituents are electron-donating groups. Significant stabilization from and#61552;-interaction is