Fixation of Small Molecules and Homogeneous Catalysis by Boron and Aluminum Based Compounds

Kumar, Vardhanapu Pavan (2019) Fixation of Small Molecules and Homogeneous Catalysis by Boron and Aluminum Based Compounds. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Vardhanapu Pavan Kumar (11RS028)) 11RS028.pdf - Submitted Version Restricted to Repository staff only Download (15MB)

Abstract

The main group compounds are easily available, cost effective and less toxic, and are benign to the environment compared to that of highly expensive, more toxic transition metal compounds. Among main group elements, Group 13 consists of the most abundant metal in the Earth crust, aluminum (7-8%), and boron which is a non-metal and the lightest of the elements in this group. Because of high abundance, less toxicity, boron and aluminum compounds became very attractive in designing catalysts to replace more toxic transition metal-based catalysis. In recent years, highly abundant main group metal, aluminum has drawn huge attention in the field of transition metal free catalysis and non-metal like boron has drawn huge attention in the field of metal free catalysis (organocatalysis). Given this importance of Earth-abundant main group compounds in the field of synthetic chemistry for various organic transformations, we were motivated to develop boron and aluminum based compounds for the fixation and activation of small molecules, and also in the field of homogenous catalysis, which traditionally carried out by expensive transition metals. The major objectives of the present investigation have been; developments of boron and aluminum based compounds using abnormal N-heterocyclic carbene (aNHC), cyclic (alkyl)amino carbene (cAAC) and phenalenyl (PLY) ligands as the backbone for the fixation and activation of small molecules and also in homogeneous catalysis with an emphasis on both synthetic outcome and mechanism. Chapter 1 provides a brief overview on the fixation and activation of small molecules by boron and aluminum based compounds as well as boron and aluminum compounds in homogenous catalysis involving C-C and C-N coupling reactions, hydroamination, hydroboration, hydrosilylation, etc. The aim and the scope of the present investigation are outlined at the end of this chapter. Chapter 2 represents the results obtained in the present investigation and a discussion of these results. This chapter is subdivided into three different sections; first section deals with the abnormal N-heterocyclic carbene mediated fixation and activation of small molecules under ambient conditions. Second section deals with the cyclic (alkyl)amino carbene complex of aluminum(III) in catalytic guanylation reaction of carbodiimides and the third section deals with the phenalenyl based aluminum compound for catalytic C-H arylation of arene and heteroarenes at room temperature. The highlights of the present investigation and possible future directions are summarized at the end of each section. Chapter 3 contains relevant details of the experimental procedures for the synthesis of these boron and aluminum compounds bearing abnormal N-heterocyclic carbene (aNHC), cyclic (alkyl)amino carbene (cAAC) and phenalenyl ligand backbone. Detailed procedure including catalysis reaction as well as single crystal diffraction studies are also given in this chapter. The references to the literature are compiled at the end of each chapter and are indicated in the relevant text by appropriate numbers appearing as superscripts. The abbreviations employed in this thesis are those generally used in Chemical Abstracts.

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