Zheng, Yang. Rational design and synthesize sterically less hindered pincer-iridium catalysts for alkane dehydrogenation. Retrieved from https://doi.org/doi:10.7282/T3NG4SHK
DescriptionDehydrogenation of alkane, which can convert alkane to alkene effectively and atom economically, is one of the most important and challenge goal in modern catalysis since the dehydrogenation product, alkenes, are ubiquitous as reagents and intermediates for a variety of useful transformation. Our group focused on the development of PCP Iridium catalysts for alkane dehydrogenation in the last decades and made lots of significant breakthroughs. One of them was that we found the steric hindrance of the PCP ligand backbone can affect the activity of the catalysts for dehydrogenation of alkane observably. The work presented in this thesis studied one new sterically less hindered pincer-ligated Iridium complex, (tBu2PCPMe2)IrH4, as the perfection of the study of the steric effect of PCP Iridium complexes for alkane dehydrogenation. (tBu2PCPMe2)IrH4 is the least steric PCP Iridium complex we have every made. It was expected to have all the advantage as another small steric complex (tBu2Me2PCP)IrH4, which had shown very high reactivity for alkane dehydrogenation but was hard to synthesis. (tBu2PCPMe2)IrH4 has the comparable satiric and electronic effects as (tBu2Me2PCP)IrH4 and is relatively easier to synthesis compared with the latter. What’s more, without the β-H in Me2- side, the stability of complex may be improved due to the less chance undergoing Cyclometalation. As such, (tBu2PCPMe2)IrH4 is a good complex to study the steric effect of PCP Iridium complexes for alkane dehydrogenation. tBu2PCPMe2-H ligand was successfully synthesized by a revised procedure. The corresponding Iridium complexes (tBu2PCPMe2)IrH4 and (tBu2PCPMe2)Ir(C2H4) were made as well. Addition of small molecules, H2, N2, CO, to (tBu2PCPMe2)IrH4 and (tBu2PCPMe2)Ir(C2H4) was then studied to investigate the properties of such complexes. The alkane transfer dehydrogenation of cyclooctane by (tBu2PCPMe2)IrH4 and (tBu2PCPMe2)Ir(C2H4) was studied to compare the activity of this new complex with our previous PCP Iridium catalysts. Finally, the effect of different acceptor and the effect of acceptor’s concentration were also studied.