New Frontiers on Cooperative Chemistry of Rarely Employed Metals

  • Marina Uzelac

Student thesis: Doctoral Thesis

Abstract

This project sought to extend the concept of enhanced cooperative reactivity in bimetallic chemistry to metals beyond Mg, Zn or Al, especially, Ga and Mn.Towards new applications of trisalkylgallium in synthesis, studies on gallium NHC (N-heterocyclic carbene) chemistry afforded a novel series of normal, abnormal and anionic NHC complexes derived from Ga(CH2SiMe3)3. These complexes proved excellent platforms for accessing functionalised aNHC ligands via metallation/electrophilic interception and/or thermal isomerisation. Capitalising on these advances, a new FLP system incorporating Ga(CH2SiMe3)3 and bulky NHCs as effective Lewis acid Lewis base combinations was developed. By exploring their reactivity towards carbonyl compounds two distinct types of FLP activation processes were uncovered. Adding the FLP pair across the C=O functionality can occur, forming new C-C and Ga-O bonds, in which NHC can participate through its normal or abnormal position. Alternatively, C-H bond activation can proceed by treating enolizable ketones, or other C-H acidic substrates such as nitriles or terminal alkynes, with the same mixtureExporting such steric incompatibility into bimetallic chemistry a new multicomponent LiTMP/GaR3 metallating mixture that works in a tandem manner has been established. Lack of co-complexation between the bulky lithium amide LiTMP and trisalkylgallium facilitates substrate deprotonation by LiTMP (the base) and anion trapping by GaR3 (the trap). Thus, introducing the concept of gallium trans-metal-trapping, for the first time formal gallation of aromatic substrates (i.e. diazines and anisole) has been accomplished.The project also developed alkali-metal manganate chemistry. A new family of homoleptic alkali-metal manganates has been prepared and characterized by X-ray crystallographic, EPR spectroscopic and SQUID magnetometric studies. Intriguing structural/synthetic/magnetic correlations were revealed in which aggregation and reactivity of different manganates were largely determined by the alkali-metal. Furthermore, addressing the issue of ill-defined manganese species participating in organic transformations, lithium manganate [(TMEDA)2Li2Mn(CH2SiMe3)4] was disclosed as an effective reagent to promote direct Mn-I exchange and homocoupling processes.
Date of Award1 Apr 2016
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorEva Hevia (Supervisor) & Robert Mulvey (Supervisor)

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