Computational Study of General Relationships in Chemistry C C C N and B B Coupling B B Catenation and 2D Metal Borides

Abstract

Elements in the periodic table are categorized into four major blocks, main group (MG) elements, transition metals (TM), lanthanides (Ln), and actinides (An), which differ dramatically. Recent studies revealed some interesting relationships among them, such as structural similarities of An-metallacycle with TM-metallacycle, low-valent MG-complexes mimicking TM-chemistry and boron mimicking carbon chemistry. The present thesis discusses the possible relationships among these areas of chemistry by studying different coupling reactions computationally, mainly using density functional theory Chapter 2 analyzes acetylide coupling reaction across selected elements from main group (MG) elements, transition metals (TM), lanthanides (Ln), and actinides (An). Here, we discuss the geometric and electronic structure of di-acetylide bridged bimetallic complexes of formula [L]M(and#956;-CCR)2M[L] and their C-C coupled product [L]M(and#956;-RC4R)M[L], where M = MG, TM, Ln and An, considering all the available examples in the Cambridge Structural Database (CSD) and show how the central (and#956;-CCR)2 and (and#956;-RC4R) units reorganize as M traverses across the periodic table. In this context, transition metal and actinide complexes are similar, while lanthanide and main group complexes show similarity. The ground state electronic configuration and metal oxidation state control these striking differences. Replacement of and#956;-C4R2 unit by and#956;-C2N2R2 unit having two extra electrons is an effective strategy to make a cross connection between two sets. At the end, we show the possible extension of the generalization from acetylide Cand#8722;C coupling to isocyanide, the valence isomer of acetylide, Cand#8722;C coupling. In chapter 3, we discuss reductive coupling of isocyanide and CO mediated by Crand#8722;Cr quintuple bonded complex and Band#8722;B multiple bonded complexes. The ground state electronic configurations of different products are discussed using electron counting scheme. A detailed mechanistic study shows that CO coupling reaction mediated by Crand#8722;Cr quintuple bond follows only...