The combination of Lewis acidic f-block metals and a labile nucleophilic
carbene can be an excellent means to activate small molecules such as silanes, CO2 and
other traditionally inert substrates. Furthermore, bidentate alkoxy-NHC ligands have
shown promise in the support of unusual high oxidation state organometallic complexes,
including examples of CeIV, PdIV and UVI. In this thesis the synthesis and reactivity of a
series of f-block metal NHC complexes is described.
Chapter One introduces N-heterocyclic carbenes and their f-block metal
complexes, in particular of cerium, praseodymium and uranium. Furthermore, it will
give an overview of small molecule activation by NHCs, lanthanides and specifically
[Ce(LAr)N"], (L = OC(CH3)2CH2(CNCH2CH2NMes) the magnetic properties and use of
lanthanides e.g. as single molecule magnets and oxo-functionalisation of the uranyl
moiety.
Chapter Two describes the addition-elimination reaction chemistry of CeIII and
UIV NHC complexes in which polar reagents add in a heterocyclic fashion across the MNHC
bond. It also describes the synthesis of the lithium salt of the alkoxycarbene
proligand [LiLAr]4 and its reactivity towards f-element halide and aryloxide salts. A
series of reactions to target the formation of metal-metal bonds is described.
Chapter Three focuses on the synthesis of novel cerium and praseodymium
complexes [Pr(LAr)N"2], [Pr(LAr)2N"], [Pr(OAr2,6-tBu)3] and [Ce(OAr2,6-tBu)3] and their
reactivity towards oxidants. A series of alkoxide bridged lanthanide dimers [(Cl)Ce(μ-
LAr)2Ce(Cl)2], [N"(LAr)Ce(μ-OAr2,6-tBu)OAr2,6-
2Ce(LAr)N"] and [N"(Cl)Pr(μ
LAr)2Pr(Cl)N"] have been made and characterised including by SQUID variable
temperature magnetometry.
Chapter Four evaluates the synthesis and reactivity of uranyl complexes
[UO2(LAr)2], [UO2N"2(py)2] and [UO2(OAr2,6-tBu)2(py)2], specifically their reactivity
towards haloboranes in different solvents. Additionally, the oxo-functionalisation of
uranyl compounds with haloboranes is discussed.
Chapter Five draws conclusions and provides a summary of the work presented.
Chapter Six comprises the experimental details and analytical data