The chapter one introduces the reported examples of rare earth metal (RE) complexes with different oxidation states. It also reviews the synthesis and reactivity study of N-heterocyclic carbene (NHC) supported transition metal and RE metal complexes. Chapter two focusses on the synthesis and characterisation of a series of tetraaryloxide Ce and Pr complexes. With the reaction of bulky tetraphenol proligand H4LR(R = P, PT, M) with four equivalents of KN"(N" = N(SiMe3)2), a dimerised complex of [K4LP]2(thf)11 was synthesised and characterised. The salt metathesis reactions of this complex with RECl3(thf)2 afford bimetallic aryloxide complexes of K2L2RE2(thf)11 (RE = Ce, Pr), which display divergent structures under different conditions. Reactions of the CeIII complex of K2L2Ce2(thf)11 with a variety of oxidants(I2, CuCl2 and O2, etc.) lead to the oxidation of CeIII to CeIV, affording purple ceric dimer of L2Ce2. The reaction of the PrIII complexes with I2 under 60 °C affords a mixture from which PrIII iodide (LPr2I2) has been isolated and characterised. This chapter also discusses the reactivity of the bimetallic aryloxide complexes towards different substrates, such as MeLi, KC8 and KBn (Bn = benzyl). Bimetallic complexes of L(REX)2(py)8 (RE = Ce, Pr; X = Cl, BH4) are synthesised and characterised. The preliminary study on the copolymerization of cyclohexene oxide (CHO) and CO2 is conducted for CeIII and PrIII complexes. Chapter three details the work on two different types of NHC ligand. The first ligand is the β-ketoimidazolinium salts H2LBr {L = RC(O)CH2{CH[NCH2CH2NMes], R = tBu, naphth} which reacts with MHBEt3 (M = Na, K) to form carbene-borane adducts RC(O)CH2{C(BEt3[NCH2CH2NMes]}. This type of reactivity differs from the previous work on imidazole derivatives. The possible mechanism of these reactions is provided and discussed. The other ligand is p-aryloxy-tethered imidazolinium salt H2LX (L = N-3,5-di-tert-butyl-4-hydrooxyphenyl-N’-mesityl-imidazolinium, X = Cl, Br, PF6 ), which have been synthesised and characterised. The reactions of these salts with MN"(M = Na, K) enabled the characterisation of polymerised complexes of [NaL]n and [KL(thf)2]n. The yttrium complex YL3 is synthesised and its reactivity towards small molecules such as boranes, CO2 and CS2 is discussed. Chapter four presents the primary results on the study of macrocyclic NHC based cyclophane ligand H6LPF6 (L = calix[4]imidazolylidene[2]pyrazolato). Investigations on the reactivity of the ligand towards different bases (NaN", KN", KBn etc.) are examined and subsequent metathesis reactions with RE complexes are explored. Chapter five concludes the work presented in this thesis. Chapter six contains all experimental and characterisation details.

Various ways of preparing enantiomerically pure 2-amino[6]helicene derivatives were explored. Ni(0) mediated cyclotrimerization of enantiopure triynes provided (M)- and (P)-7,8-bis(p-tolyl)hexahelicene-2-amine in >99% ee as well as its benzoderivative in >99% ee. The stereocontrol was found to be inefficient for a 2- aminobenzo[6]helicene congener with an embedded five-membered ring. Helically chiral imidazolium salts bearing one or two helicene moieties have been synthesized and applied in enantioselective [2+2+2] cyclotrimerization catalyzed by an in situ formed Ni(0)-NHC complex. The synthesis of the first helically chiral Pd- and Ru- NHC complexes and their application in enantioselective catalysis was demonstrated. The latter shows promising results in enantioselective olefin metathesis reactions. A mechanistic proposal for asymmetric ring closing metathesis is provided.

This thesis describes the catalysed addition of X-H bonds (X = S, O and N) to alkynes using a range of novel rhodium(I) and iridium(I) complexes containing hybrid bidentate phosphine-pyrazolyl, phosphine-imidazolyl and phosphine-N heterocyclic carbene (NHC) donor ligands. The synthesis of novel bidentate phosphine-pyrazolyl, phosphine-imidazolyl (P-N) and phosphine-NHC (PC) donor ligands and their cationic and neutral rhodium(I) and iridium(I) complexes [M(P N)(COD)]BPh4, [M(PC)(COD)]BPh4, [Ir(P-N)(CO)2]BPh4 and [M(P-N)(CO)Cl] were successfully performed. An unusual five coordinate iridium complex with phosphine-NHC ligands [Ir(PC)(COD)(CO)]BPh4 was also obtained. Seventeen single crystal X-ray structures of these new complexes were determined. A range of these novel rhodium and iridium complexes were effective as catalysts for the addition of thiophenol to a variety of alkynes. Iridium complexes were more effective than rhodium analogues. Cationic complexes were more effective than neutral complexes. Complexes with hybrid phosphine-nitrogen donor were more effective than complexes containing bidentate nitrogen donor ligands. An atom-economical, efficient method for the synthesis of cyclic acetals and bicyclic O,O-acetals was successfully developed based on the catalysed hydroalkoxylation. Readily prepared terminal and non-terminal alkyne diols were cyclised into bicyclic O,O-acetals in quantitative conversions in most cases. The efficiency of a range of rhodium and iridium complexes containing bidentate P-N and PC donor ligands as catalysts for the cyclisation of 4-pentyn-1-amine to 2-methyl-1-pyrroline varied significantly. The cationic iridium complexes with the bidentate phosphine-pyrazolyl ligands, [Ir(R2PyP)(COD)]BPh4 (2.39-2.42) were extremely efficient as catalysts for this transformation. Increasing the size of the substituent on or adjacent to the donor led to improvement in catalytic activity of the corresponding metal complexes. The mechanism of the catalysed hydroalkoxylation was proposed to proceed by the initial activation of the alkyne via ?? coordination to the metal centre. The ?? binding of both aliphatic and aromatic alkynes to [Ir(PyP)(CO)2]BPh4 (2.44) was observed by low temperature NMR and no reaction between 2.44 and alcohols was observed. In contrast, the facility in which thiol and amine oxidatively added to 2.44 led the proposal that in the hydrothiolation and hydroamination reaction, the catalytic cycle commences with the activation of the X-H bond (X = S, N) by an oxidative addition process.

This thesis describes the catalysed addition of X-H bonds (X = S, O and N) to alkynes using a range of novel rhodium(I) and iridium(I) complexes containing hybrid bidentate phosphine-pyrazolyl, phosphine-imidazolyl and phosphine-N heterocyclic carbene (NHC) donor ligands. The synthesis of novel bidentate phosphine-pyrazolyl, phosphine-imidazolyl (P-N) and phosphine-NHC (PC) donor ligands and their cationic and neutral rhodium(I) and iridium(I) complexes [M(P N)(COD)]BPh4, [M(PC)(COD)]BPh4, [Ir(P-N)(CO)2]BPh4 and [M(P-N)(CO)Cl] were successfully performed. An unusual five coordinate iridium complex with phosphine-NHC ligands [Ir(PC)(COD)(CO)]BPh4 was also obtained. Seventeen single crystal X-ray structures of these new complexes were determined. A range of these novel rhodium and iridium complexes were effective as catalysts for the addition of thiophenol to a variety of alkynes. Iridium complexes were more effective than rhodium analogues. Cationic complexes were more effective than neutral complexes. Complexes with hybrid phosphine-nitrogen donor were more effective than complexes containing bidentate nitrogen donor ligands. An atom-economical, efficient method for the synthesis of cyclic acetals and bicyclic O,O-acetals was successfully developed based on the catalysed hydroalkoxylation. Readily prepared terminal and non-terminal alkyne diols were cyclised into bicyclic O,O-acetals in quantitative conversions in most cases. The efficiency of a range of rhodium and iridium complexes containing bidentate P-N and PC donor ligands as catalysts for the cyclisation of 4-pentyn-1-amine to 2-methyl-1-pyrroline varied significantly. The cationic iridium complexes with the bidentate phosphine-pyrazolyl ligands, [Ir(R2PyP)(COD)]BPh4 (2.39-2.42) were extremely efficient as catalysts for this transformation. Increasing the size of the substituent on or adjacent to the donor led to improvement in catalytic activity of the corresponding metal complexes. The mechanism of the catalysed hydroalkoxylation was proposed to proceed by the initial activation of the alkyne via ?? coordination to the metal centre. The ?? binding of both aliphatic and aromatic alkynes to [Ir(PyP)(CO)2]BPh4 (2.44) was observed by low temperature NMR and no reaction between 2.44 and alcohols was observed. In contrast, the facility in which thiol and amine oxidatively added to 2.44 led the proposal that in the hydrothiolation and hydroamination reaction, the catalytic cycle commences with the activation of the X-H bond (X = S, N) by an oxidative addition process.