The chemistry of cyclometalation : a comprehensive study on cycloiridated 1-arylalkylamine and imine complexes

Abstract

As fundamental ligand frameworks within the field of cyclometalation, the 1arylalkylamine and imine motifs have a widespread presence as cyclometalating ligands for an extensive number of transition metal elements. In the thesis, we investigate the outcome of cycloiridation of various 1-arylalkylamine and imine ligands with [IrCp*Cl2]2. A good balance of steric factors within the organic scaffold was found to be vital for the formation and stability of amino-derived iridacycles. While excessive steric hindrance would lead to numerous side reactions affording an assortment of byproducts, the lack of steric bulk within the amine ligands would lead to an internal oxidation to its imine functionality within the cyclometalated ring. Investigations into the failed cyclization procedure revealed a consistent competing pathway leading to either a strained ring system or an iminium species. The postulated intermediates can then readily undergo hydrolysis to provide a N-dealkylated amine moiety and a carbonyl compound. Optically-active cycloiridated complexes from successful direct ortho-metalation procedures were characterized for its conformational lock and evaluated for its efficiency in the catalytic asymmetric hydrogen transfer reaction. Lastly, we examine the crystallographic structures of the synthesized iridacycles to gain insights into their bonding. III ACKNOWLEDGEMENTS As I progress to the next stage of life after Ph.D. studies, feelings of sweet and bitterness came as I recall the seven years I had (including two and a half years from my undergraduate days) in this very group. The journey has been awesome, and there are many people whom I must thank for their support and encouragements over the years. First and foremost, I would like to express my gratitude to my supervisor, Professor Leung Pak-Hing. Without his support, whether research or otherwise, I would have not come so far to where I am today. His motivation, patience and cheerfulness has kept me going strong over the ups and downs in the course of my Ph.D. studies. I also truly appreciate the scientific freedom he has granted to me, which left me with a satisfying and enriching learning experience. My gratitude also extends to my co-supervisor, Dr. Sumod A. Pullarkat, for his continual support, guidance, encouragement and patience with me throughout these years. His door was always open to us, providing much support, and the occasional chats, whenever we needed it. Your advice, whether research or otherwise, will always be invaluable to me. Next, I would like to specifically show my gratitude to Jonathan Wong, who have shared my successes, failures and frustrations over research and life. Your advice and assistance over these years has been extremely invaluable. I will also always recall our extremely fun early days when we took over from each other between lessons and having no idea what experiment we are conducting in the lab.