Synthesis and catalytic applications of new heavy s-block metal amides

Student thesis: Doctoral Thesis

Abstract

Sustainability issues are becoming ever more important within the scientific world. Many commercial chemical processes require precious d-block metals. Research within this project offers a glimpse into pushing past some of the uses of these metals, to find sustainable alternatives. While lithium has long been indispensable for synthesising fine chemicals and pharmaceuticals via organolithium reagents, the seismic shift towards energy transition, fronted by lithium-ion batteries for electric vehicles, means there is a rising threat to lithium's long-term sustainability. With heavier alkali metals rubidium and caesium accessible as by-products of lithium mining and both sodium and potassium abundant in the earth's crust and oceans, stoichiometric reagents or catalysts based on these lesser studied alkali metals could with creative development replace lithium in both stoichiometric reactions and precious transition metals in homogeneous catalysis. Much of this research has focused on the synthesis and characterisation of the 1-metallo-2-t-butyl-1,2-dihydropyridyl (DHP) complexes of rubidium and caesium, thereby completing the homologous alkali metal series. From there we were able to test the full series for catalytic reduction of a representative set of imines, establishing a definite trend in catalyst efficiency with the heavier alkali metal tBuDHPs outperforming lighter congeners. Co complexation of these dihydropyridyl units containing a surrogate hydride with [(iBu)2Al(TMP)] afforded group 1 hydrocarbon-soluble donor free aluminates [AM(tBuDHP)(TMP)Al(iBu)2] (AM = Li, Na, K, Rb). Modifying the dihydropyridyl scaffold to include a dimethylamino group in the 4-position produced the monomer [Na-1,2-tBu-DH(DMAP)]·Me₆TREN, which proved effective in transfer hydrogenation catalysis of the representative alkene 1,1-diphenylethylene to the alkane 1,1-diphenylethane using 1,4- cyclohexadiene as the hydrogen source. The success of this sodium monomer can be attributed to its high solubility and reactivity in organicsolvents. Moreover, this DH(DMAP) ligand has provided another full group 1 series of compounds which could have vast potential in future catalytic applications.
Date of Award6 Sept 2024
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorRobert Mulvey (Supervisor) & Stuart Robertson (Supervisor)

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