by Shan-Ming Kuang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 135-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

In Chapter 1, I discuss the synthesis and characterization of lithium tris(pyrazolyl)hydroborato complexes, [TpR1,R2]Li. Group 1 [TpR1,R2]M complexes serve as key starting points to access many other main group and transition metal complexes; however, the synthesis and crystal structures of [Tp R1,R2]Li has not been reported. Molecular structures of [TpBut]Li and [TpBut,Me]Li show these complexes are trigonal pyramidal, an unusual geometry for lithium. These complexes are also able to bind small molecules to form four-coordinate pseudo-tetrahedral complexes, [Tp]Li-L (L = MeCN, pzButH, and H2O). The binding constants for the association of acetonitrile to [TpBut]Li and [TpBut,Me]Li are 0.84M-1 and 0.96M-1, respectively, indicating that the dissociation of MeCN is facile in solution. In addition, [TpBut,Me]Li serves as transmetallating agent to yield the cadmium halide complexes, [TpBut,Me]CdX (X = Cl, Br, I). In Chapter 2, I discuss the synthesis and characterization of organometallic cadmium complexes supported by the nitrogen-rich multidentate ligands, tris(pyridylthio)methane, [Tptm]H; tris(1-methyl-imidazolylthio)methane, [TitmMe]H; and tris(1-methyl-benzimidazolylthio)methane, [TitmiPrBenz]H. These ligands are in the nascent stages of development and there are only a few metal [Tptm] and [TitmMe] complexes in the literature. An investigation of the reactivity of [L]CdN(SiMe3)2, [L]CdOSiMe3, and [L]CdOSiPh3 ([L] = [Tptm], [TitmMe], [TitmiPrBenz]) shows these complexes provide access to a variety of organometallic cadmium complexes, [L]CdX, (X = OAc, Cl, Br, O2CH, NCO). The characterization of cadmium acetate and formate complexes is significant due to their structural similarity with the metal bicarbonate intermediate formed by zinc and cadmium-substituted carbonic anhydrase. In addition, the synthesis and characterization of cadmium methyl complexes, [L]CdMe, is discussed. The application of heat to a mixture of [TitmiPrBenz]H and CdMe2 results in isomerization of the ligand to [S3-TitmiPrBenz]CdMe. This sulfur-rich [S3-TitmiPrBenz] ligand is not reported in the literature and is ripe for further investigation. The solid state structures of these compounds provide a comparison with biologically relevant [Tp] or [Tm] cadmium methyl complexes in the literature. In Chapter 3, I describe the synthesis and structural characterization of [BmButBenz]M (M = Na, K) and [BmRBenz]Ca(THF)2 (R = Me, But) are discussed. The sulfur-rich tripodal ligand tris(imidazolylthio)hydroborato, [Tm], was previously designed to serve as a softer version of the [Tp] ligand. Metal [Tm] complexes are prevalent in the literature and have often been used as molecular mimics of sulfur-rich enzyme active sites. Recently, the benzannulated [TmRBenz]M complexes were reported and were found to promote k3 coordination toward the metal center. To allow for an in-depth investigation of the newly synthesized [BmRBenz] class of ligand, the [BmButBenz]M (M = Na, K, Ca) complexes were synthesized and compared to previously reported metal [BmMeBenz]M complexes. Additionally, the [BmMeBenz]2Ca(THF)2 was synthesized and characterized via X-ray diffraction. The molecular structure of [BmMeBenz]2Ca(THF)2 shows the complex is monometallic with an uncommon eight-coordinate dodecahedral calcium center. [BmMeBenz]2Ca(THF)2 is the first molecular structure of calcium coordinated to the [Tm] or [Bm] ligand class. In Chapter 4, I discuss the synthesis and characterization of mercury alkyl complexes supported by the [TmMe], [BmR], [TmRBenz] and [BmRBenz] ligands (R = Me or But). As previously mentioned, [Tm]M complexes are considered biologically relevant molecular models of enzyme active sites. With this in mind, [TmBut]HgR (R = Me,Et) complexes have served as mimics for the mercury detoxification enzyme MerB. A previous study by our group showed that the adoption of multiple coordination modes of the ligand in [TmBut]HgR plays a significant role in the activation of the Hg-C bond toward protonolysis. The molecular structures of the [TmR], [BmR], [TmRBenz], and [BmRBenz] mercury alkyl complexes show that they adopt various coordination modes, ranging from k1 to k3. Preliminary competition experiments in which benzenethiol was added to [TmR]HgEt and [TmRBenz]HgEt indicate that the Hg-C bond in [TmMeBenz]HgEt was cleaved faster than that in [TmMe]HgEt. Conversely, the Hg-C bond in [TmBut]HgEt was cleaved faster than that in [TmButBenz]HgEt, indicating that benzannulation and the size of the R-group on the [Tm] ligand play important roles in Hg-C bond cleavage.

In chapter 1, I discuss how ligand architecture in tripodal nitrogen-rich ligands can drastically affect the structure of zinc complexes featuring these ligands. The synthesis and characterization of zinc tris(1-methylimidazol-2-ylthio)methyl ([Titm^Me]) and tris(1-Pribenzimidazol-2-ylthio)methyl ([Titm^iPr,benzo]) complexes is presented. The ligand in [Titm^Me]Zn complexes binds the metal to form carbatrane structures that exhibit unusually long and flexible Zn–C bonds. The bonding between the zinc and the carbon in these complexes can therefore be more accurately described as a zwitterionic interaction between a carbanion and a zinc cation. Density functional theory calculations demonstrate that the energy profile for the Zn–C bond is shallow, such that large variations of the Zn–C distance result in very little change in the energy of the complex. The benzannulated ligand [Titm^iPr,benzo] allows access to a rare monomeric zinc hydride species [κ³-Titm^iPr,benzo]ZnH that can react with either CO₂ to produce a zinc formate, or B(C₆F₅)₃ to form the ion pair [κ⁴-Titm^iPr,benzo]ZnHB(C₆F₅)₃. The coordination chemistry of the [Titm^iPr,benzo] ligand also extends to the other metals of group 12. In chapter 2, I report the use of the [Titm^Me] and [Titm^iPr,benzo] zinc complexes presented in chapter 1 as biomimetic models for zinc enzymes. First, [Titm^Me] zinc complexes present structural similarities with the active site of carbonic anhydrase, and can be used to study the binding of carbonic anhydrase inhibitors to the enzyme active site. Then, [κ⁴-Titm^iPr,benzo]ZnX (X = MeB(C₆F₅)₃, BPh₄) complexes and their interactions with ligands of relevance towards antibiotic resistance is reported. The non coordinating nature of the anions in [κ⁴-Titm^iPr,benzo]ZnX (X = MeB(C₆F₅)₃, BPh₄) lead to the formation of a Lewis acidic zinc cationic center, which can be coordinated by an additional ligand of biological interest. The binding of simple β-lactams to the [κ⁴-Titm^iPr,benzo]ZnX complexes can be probed using X-ray diffraction and Nuclear Magnetic Resonance (NMR) spectroscopy, thereby providing a way to model the binding of antibiotics to the active site of the metallo-β-lactamases enzymes responsible for broad antibiotic resistance. The binding of β-lactams can be compared to larger ring size lactams and linear amides. [κ⁴-Titm^iPr,benzo]ZnX (X = MeB(C₆F₅)₃, BPh₄) also allows for the study of the binding of potential metallo-β-lactamases inhibitors, such as, for example, glycinamide, picolinamide, and piperazine-2,3-dione. Binding studies between [κ⁴-Titm^iPr,benzo]ZnX and substrates bearing structural similarities to antibiotics reveal secondary interactions involving peripheral functional groups the cationic zinc center in [κ⁴-Titm^iPr,benzo]ZnX. These studies provide guidelines to modify existing antibiotics, in order to decrease their sensitivity to metallo-β-lactamases. In chapter 3, I explore the reactivity of previously characterized tris(2-pyridylthio)methyl [Tptm] zinc complexes. First, an improved synthesis of [κ⁴-Tptm]ZnF using Me₃SnF as the fluorinating agent is reported. The fluorine atom in [κ⁴-Tptm]ZnF acts as a Lewis base, as illustrated by its reaction with B(C₆F₅)₃ to form [κ⁴-Tptm]ZnFB(C₆F₅)₃, in which the fluorine is transferred to the borane group. The fluoride ligand in [κ⁴-Tptm]ZnF also acts as a hydrogen bond and halogen bond acceptor and is capable of forming adducts with H₂O, indole, and iodopentafluorobenzene. [κ⁴-Tptm]ZnF undergoes metathesis with Ph₃CCl to form Ph₃CF, thereby providing a rare example of C–F bond formation promoted by a zinc complex. Then, [κ³-Tptm]ZnH is used as a catalyst for the hydrosilylation of aldehydes and ketones using phenylsilane to produce tris alkoxysilane products. The catalyst is very active with aldehydes, and shows slower reactivity towards dialkyl ketones. The reaction proceeds via insertion of the carbonyl group in the Zn–H bond to form a zinc alkoxide, which then undergoes metathesis with the silane to generate the desired product and regenerate the zinc hydride species. The complicated NMR spectroscopic features of the products resulting from the hydrosilylation of prochiral ketones are explained by the presence of different diastereomers. Finally, we report that [κ³-Tptm]ZnH is a catalyst for the hydrosilylation of silylformates to methoxy silanes with (EtO)₃SiH, (MeO)₃SiH and κ⁴-N(CH₂CH₂O)₃SiOMe. We show that CO₂ can be reduced to methoxy silane species in a one pot reaction using (MeO)₃SiH and catalytic amounts of [κ³-Tptm]ZnH. In chapter 4, I report the synthesis and characterization of a silicon based analogue of [Titm^iPr,benzo], namely the tris(1-Pribenzimidazol-2-yldimethylsilyl)methyl [Tism^iPr,benzo] ligand. The ligand possesses unique structural features, due to the proximity between the dimethylsilyl groups and the methyl carbanion. The formation of [κ⁴-Tism^iPr,benzo]Li proceeds via the doubly base stabilized silene intermediate [κ³-C(SiMe₂benzimid^iPr)₂]SiMe₂. [κ⁴-Tism^iPr,benzo]Li can be used as a precursor for copper and nickel [Tism^iPr,benzo] and [C₃-Tism^iPr,benzo] complexes, where [C3-Tism^iPr,benzo] represents the isomerized tris carbene version of [Tism^iPr,benzo]. [κ³-C(SiMe₂benzimid^iPr)₂]SiMe₂ reacts with ZnMe₂ to produce [κ³-C(SiMe₃)(SiMe₂benzimid^iPr)₂]ZnMe, which can be transformed to the phenoxide compound. This compound acts as a catalyst for the hydrosilylation of CO₂ to silyl formates and methoxy silanes. [κ³-C(SiMe₂benzimid^iPr)₂]SiMe₂ itself reacts with CO₂ to produce an unusual β-lactone.

Descritores moleculares são essenciais em muitas aplicações de física e química computacional, como na análise de similaridade entre ligantes baseada em sua estrutura. Harmônicos esféricos têm sido utilizados como descritores da superfície molecular por serem uma forma compacta de descrição geométrica e por possuírem um descritor invariante por rotação. Assim, este trabalho propõe um método de análise de similaridade estrutural entre ligantes no qual se modela a superfície de uma molécula através de uma expansão em harmônicos esféricos realizada pelo programa LIRA. Os coeficientes encontrados são utilizados para percorrer o banco de dados DUD-E, com descritores previamente calculados, utilizando Distância Euclidiana e diversos valores de corte para selecionar compostos mais semelhantes. O potencial do método é avaliado usando o Ultrafast Shape Recognition (USR) como método padrão, pelo fato de ser uma excelente e rápida métrica para análise da similaridade de ligantes. Foram selecionadas 50 moléculas de diferentes tamanhos e composição de forma a representar todos os grupos moleculares presentes na DUD-E. Em seguida, cada molécula foi submetida à busca de similares variando-se valores de corte para o LIRA em que o conjunto de moléculas selecionadas foi comparado com as selecionadas pelo USR através de um processo de classificação binária e criação e interpretação de curvas ROC. Além do benchmarking, foi realizada a análise das componentes principais para determinar quais descritores são os mais importantes e carregam as melhores informações utilizadas na descrição da superfície da molécula. A partir das componentes principais, foi realizado um estudo do uso de funções peso, associando mais importância aos descritores adequados, e a redução da dimensionalidade do banco de dados, seleção de um novo conjunto de autovetores que formam as bases do espaço vetorial e uma nova descrição das moléculas para o novo espaço, no qual cada variação foi avaliada através de um novo benchmarking. O LIRA se mostrou tão rápido quanto o USR e apresentou grande potencial de seleção de moléculas similares, para a maioria das moléculas testadas, pois as curvas ROC apresentaram pontos acima da linha do aleatório. Tanto a redução da dimensionalidade quanto o uso de funções de ponderação agregaram valor à métrica deixando-a mais veloz, no caso da redução da quantidade de descritores, e seletiva, em ambos os casos. Dessa forma, o método proposto se mostrou eficiente em mensurar a similaridade entre ligantes de forma seletiva e rápida utilizando somente informações a respeito da superfície molecular. / Molecular descriptors are essential for many applications in computational chemistry and physics, such as ligand-based similarity searching. Spherical harmonics have previously been suggested as comprehensive descriptors of molecular structure due to their properties, orthonormality and rotationally invariant. Here we proposed a ligand similarity analysis method where molecule\'s surface is modeled by an expansion in Spherical Harmonics, called LIRA, whose coefficient are used to perform a search in DUD-E database, with all descriptors previously calculated, measured by Euclidian Distance and different cutoff\'s values to select similar compounds. Method\'s potential is evaluated against Ultrafast Shape Recognition (USR), due to it is an excellent a fast metric to ligand similarity analysis, in a benchmarking. Fifty molecules are selected varying chemical composition and size to represent all molecular groups of DUD-E. After that, which one was submitted in a search with different values of cutoff for LIRA and the subset selected was compared with the ones selected by USR through binary classification and ROC curves analysis. Beyond benchmarking, it was performed a principal component analysis to identify which are the most valuable coefficient for shape description. Using principal components two other studies are made, weight functions are applied to descriptors, providing more value for those carry more information, and dimensionality reduction, where a subset of eigenvectors are select to form the new basis of the vector space and the new molecule\'s description was made in the new space, which variation was tested in a new benchmarking. Lira showed to be as fast as USR and a big potential to select similar molecules, for the majority of the molecules tested, because ROC curves had points over the random line. Dimensionality reduction and weight functions improved LIRA results raising velocity, due to the use of less descriptors to model molecule\'s surface, and the selection power, for both cases. In summary, the proposed method showed to be an efficient and fast tool for measure similarity between ligands based in molecular shape.

Chapter 1 gives a brief introduction to metal complexes supported by anionic nitrogen-based ligands. / Chapter 2 describes the synthesis, structural characterization and reactivity of Mn(II), Fe(II) and Co(II) amides derived from the strongly electron-withdrawing [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). Twelve new compounds, including the ligand precursor HL 1, and three alkali-metal and eight late transition metal derivatives of L1, were prepared. Reactions of MCl2 (M = Mn, Fe, Co) with [Li(L1)(TMEDA)] (2) yielded the monoamido complexes [M(L1)Cl(TMEDA)] [M = Mn (5), Fe ( 6), Co (7)]. Treatment of [Li(L1)(THF) 3] with MCl2 (M = Fe, Co) afforded the diamido complexes [M(L1)2(mu-Cl)Li(THF)3] [M = Fe ( 8), Co(9)]. The reaction chemistry of the Co(II) complex 7 was investigated. Treatment of the Co(II) derivative 7 with LiMe, NaN3 and NaOMe gave the corresponding methyl-, azido- and methoxide-amide complexes, namely [Co(L1)(Me)(TMEDA)] ( 10), [Co(L1)(N3)(TMEDA)] (11) and [Co(L1)2(mu-OMe)Na(TMEDA)] (12), respectively. The solid-state structures of complexes 5--12 were determined by X-ray crystallography. / Chapter 3 reports on the synthesis and catalytic properties of lanthanide(III) complexes derived from the unsymmetrical [PhC(NSiMe3)(NC6 H3Pri2-2,6)] - ligand (L2). The lithium and potassium salts of L2, and eight lanthanide(III) derivatives of L2 were synthesized. A series of Ln(III) complexes of the general formula [Ln(L 2)2(mu-Cl)2Li(TMEDA)] [Ln = Y (17), Eu (18), Er (19), Lu (20)] and [Li(THF) 4][Ln(L2)2Cl2] [Ln = Ce ( 21), Nd (22), Sm (23)] were synthesized by the reactions of anhydrous LnCl3 with two molar equivalents of [Li(L2)(TMEDA)] (15). In addition, the neutral dimeric yttrium(III) complex [Y(L2)2(mu-Cl)] 2 (24) was also prepared by the reaction of anhydrous YCl 3 with the potassium amidinate [K(L2)]n (16). The catalytic properties of complexes 20--22 towards the ring-opening polymerization of epsilon-caprolactone were also studied in this work. / Chapter 4 reports on the coordination chemistry of L2 towards divalent lanthanide metal ions. Three neutral divalent lanthanide complexes, [Ln(L2)2(THF)n] [Ln = Sm, n = 2 (25); Ln = Eu, n = 2, (26); Ln = Yb, n = 1 (27)], were prepared by treatment of LnI2(THF) 2 with the potassium amidinate [K(L2)]n . The reaction chemistry of 25--27 as one-electron transfer reagents has been examined. This led to the isolation of six lanthanide(III) complexes (28--33). Treatment of 25--27 with PhEEPh (E = Se, Te) gave the corresponding Ln(III) chalcogenolate complexes [Ln(L2)2(mu-EPh)]2 [Ln = Sm, E = Se (28); Ln = Eu, E = Se (29); Ln = Sm, E = Te ( 31)] and [Yb(L2)2(SePh)(THF)] (30). Besides, the reaction of 27 with iodine resulted in the isolation of the iodide complex [Yb(L2)2(I)(THF)] ( 32), whilst treatment of 25 with dicyclohexylcarbodiimide led to [Sm(L2)2{CyNC(H)NCy}] (33). / Chapter 5 summarizes the results of this research work. A brief suggestion on future directions of this research project is also discussed. / The present research work was focused on the coordination chemistry of the highly electron-withdrawing [N(C6F5)(C6H 3Pri2-2,6)]- ligand and the unsymmetrical [PhC(NSiMe3)(NC6H 3Pri2-2,6)- ligand. The first part of this work was centered on the synthesis, structure and reactivity of late transition metal complexes supported by the [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). The second part of this work dealed with the chemistry of trivalent and divalent lanthanide complexes derived from the bulky [PhC(NSiMe3 )(NC6H3Pri 2-2,6)]- ligand (L2). / Yao, Shuang. / Adviser: Hung Kay Lee. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0317. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Alkylation of [eta5:sigma-Me2C(C5 H4)(C2B10H10)]TiCl(NMe 2) generates [eta5:sigma-Me2C(C5 H4)(C2B10H10)]Ti(R)(NMe 2) (R = Me, CH2TMS), which offers a unique opportunity to observe the direct competition among Ti-C(alkyl), Ti-N and Ti-C(cage) bonds in the insertion reactions with unsaturated molecules. The results indicate that unsaturated molecules insert preferably into the Ti-C (alkyl) bond over the Ti-N bond, while the Ti-C (cage) bond remains intact in all reactions. Several imido-titanium complexes [eta5:sigma-Me2C(C 5H4)(C2B10H10)]Ti(=NR)(Py) and [eta5:sigma-Me2C(C9H6)(C 2B10H10)]Ti(=NtBu)(Py) have been prepared by salt metathesis reactions or imido exchange reactions. These imido complexes can react with a variety of unsaturated molecules to give imido exchange products or [2+2] cycloaddition species. The imido complex [eta5:sigma-Me2C(C5H4)(C 2B10H10)]Ti(=NtBu)(Py) can also catalyze the hydroamination of phenyl acetylene. The key intermediate metallacyclic complex has been isolated and structurally characterized. / By taking the advantage of a cyclic organic group and an icosahedral carborane as well as the bridging ligand, trivalent phosphorus-bridged ligand iPr2NP(C9H7)(C2B 10H11) is designed and successfully synthesized. It is readily converted into the corresponding mono- and di-lithium salts, which have found many applications in transition metal chemistry. A series of organolanthanide and group 4 metal complexes derived from this new ligand have been prepared and structurally characterized. It is found that this ligand can effectively prevent lanthanocene chlorides from ligand redistribution reactions. [eta 5:sigma-iPr2NP(C 9H6)(C2B10H10)]Zr(NMe 2)2 can catalyze ethylene polymerization upon activation with MMAO and initiate the polymerization of epsilon-caprolactone. / iPr2NP(C9H 7)(C2B10H11) can be converted into the pentavalent derivative iPr2NP(O)(C9H 7)(C2B10H11) by treatment with H 2O2. Interactions of M(NMe2)4 with iPr2NP(O)(C9H7)(C2 B10H11) give unexpected products [sigma.sigma- iPr2NP(O)(C9H6)(C2 B10H11)]M(NR2)2. To investigate the similarities and differences between iPr2NP(O)(C 9H7)(C2B10H11) and its fluorenyl derivative in chemical properties, iPr 2NP(O)(C13H9)(C2B10H 11) is also prepared in a similar manner. It reacts easily with Zr(NMe 2)4 to give the amine elimination product [sigma.sigma- iPr2NP(O)(C13H8)(C 2B10H10)]Zr(NMe2)2(THF). However, treatment of iPr2NP(O)(C 2B10B11)(C2B10H11) with Ti(NMe2)4 affords amine elimination/deboration complex [sigma:eta5-iPr 2NP(O)(C13H9)(C2B9H 10)]Ti(NMe2)2. / Wang Hong. / "February 2005." / Adviser: Xie Zuomei. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0265. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 168-180). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

"January 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Chapter 1 provides the general review of phosphoranoimines and 1-azaallyls as ligands for group 4 and 14 metal complexes. / Chapter 2 describes the development of low-valent group 14 1,3-dimetallacyclobutanes from phosphoranoimines. Three low-valent 1,3-distannacyclobutanes 1,3-[Sn{C(Pr i2P=NSiMe3)(2-Py)}]2 ( 95), 1,3-[Sn{C(Ph2P=NSiMe3)(C6H 5)}]2 (97) and 1,3-[Sn{C(Ph2P=NSiMe 3)(PPh2)}]2 (100) were synthesized from the phosphoranoimine ligands [CH2(Pri 2P=NSiMe3)(2-Py)] (92), [CH2(Ph 2P=NSiMe3)(C6H5)] (96) and [CH2(Ph2P=NSiMe3)(PPh 2)] (99), respectively. A novel cationic tin(IV) species [HC(Pri2P=NSiMe3)(Ar)] -[SnCl3]+ (Ar = 9-anthryl) ( 104) was synthesized from [CH2(Pri 2P=NSiMe3)(Ar)] (Ar = 9-anthryl) (103). / Chapter 3 describes the reactivies of low-valent group 14 1,3-distannacyclobutanes (95 and 111) and the isolation of the enantiomers of 95 and [1-Sn{C(Pri2P=NSiMe 3)(2-Py)}3-Pb{C(Pri2P=NSiMe 3)(2-Py)}] (120). The reactions of 95 or 111 with M(CO)5(THF) (M = Cr, Mo, W), CpMn(CO)2THF (Cp = eta-C5H5), MeI and Br2 were performed. Three isomers of compound 95 (95R, 95S and 95I) and two enantiomers of compounds 120 ( 120R and 120S) and 122 (122R and 122S) were obtained by the method of recrystallization from different solvents. Heteroleptic lead(II) compound [{(Pri 2P=NSiMe3)(2-Py)CH}Pb{N(SiMe3)2} 2] (121) was synthesized, which further react with 94 to give 1,3-[Pb{C(Pri2P=NSiMe 3)(2-Py)}]2 (122). / Chapter 4 describes the development of group 4 metal complexes from phosphoranoimines. Group 4 metal imido complexes [(Me2N)2M{CH(Ph2 PN)(2-Py)}]2 (M = Zr (133), Hf (134)) and ionic compounds [ML2Cl]+2[MCl 6]2- (L = {CH(R2PNSiMe3)(2-Py)}) (135 M = Zr, R = Ph, 136 M = Hf, R = Ph, 137 M = Zr, R = Pri, 138 M = Hf, R = Pri) were synthesized. The neutral zirconium(IV) dichloride compound [ZrCl2{CH(Ph2P=NSiMe 3)(C6H5)}2] (139) was prepared by the reaction of lithium compound [(THF)2Li{CH(Ph 2PNSiMe3)(C6H5)}] (97) with ZrCl4. The catalytic activity of the compounds toward ethylene polymerization has been investigated. / Chapter 5 describes the development of group 4 metal complexes from 1-azaallyls. Lithium cyclohexenyl-1-azaallyl compound [(TMEDA)LiN(SiMe3)C(Ph)= CHCHC&parl0;SiMe3&parr0;CH2CH 2C H2] (149) and zirconium(IV) dichloride compound [Zr{N(SiMe3)C(Ph)(L)}2Cl2] (L = CHCHC&parl0;SiMe3&parr0;CH2CH 2C H2) (150) were synthesized. Novel anionic one-dimensional bifunctional lithium compound [{(THF)Li(N(SiMe3))2C}(CN)C 6H4-1,4)]n (151) has also been synthesized. Similar reactions of 1,2-dicyanobenzene, 1,3-dicyanobenzene or 1,4-dicyanobenzene with lithium amide [(Et2O)2LiN(SiMe3) 2] afforded lithium bis(1,3-diazaallyl) compounds [{(THF)2Li(N(SiMe 3))2C}C6H4-1,2)] (152), [{(THF)2Li(N(SiMe3))2C}C6H 4-1,3)] (153) and [{(THF)2Li(N(SiMe3)) 2C}C6H4-1,4)] (154), respectively. / The work presented in this thesis is mainly focused in two parts: (i) the synthesis and reactivities of low-valent main group 14 metal complexes derived from phosphoranoimines, (ii) the synthesis and catalytic studies of transition group 4 metal complexes derived from phosphoranoimines and 1-azaallyl ligands. / Wong Kam Wing. / "December 2006." / Adviser: Kevin Wing-Por Leung. / Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5233. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

This work aims to define the modes of action of a series of metal extraction ligands with particular focus on how these depend on the formation of supramolecular assemblies. Though solvent extraction processes are well established industrially often the understanding, particularly of the metal coordination chemistry, is less so. A greater understanding of a variety of solvent extraction systems can lead to the development of stronger and more specific extractants. Chapter 2 examines the role of inter-ligand interactions in the extraction of copper by phenolic oximes and pyrazoles. Computational methods are used to understand the importance of inter-ligand outer-sphere interactions in square-planar copper complexes. It is shown that functionalisation at different positions on the phenol ring can either stabilise or destabilise the copper complex and it is possible to predict the strength of extractants from DFT calculations. Substitution ortho to the phenolic oxygen in the oximes and pyrazoles can have a major effect of enhancing the strength of extractants by “buttressing” the H-bonding between ligands. However, in the amino-methyl substituted oximes buttressing is so strong that is has an adverse effect on complex formation. Crystal structures are confirmed by both ENDOR EPR spectroscopy and DFT structures. A series of 6-X-4-methyl-2-(5-alkyl-1H-pyrazol-3-yl)- phenols (X = H, OMe, Br and NO2) was synthesised and characterised (X = H, OMe, Br and NO2) and the copper extractant found to be 6-nitro-4-methyl-2-(5-(1,3,5-tri-methyl-pentyl)- 1H-pyrazol-3-yl)-phenol extractants. Computational DFT studies in the gas phase were carried out to calculate the formation energies of analogous phenolic pyrazole copper complexes. The predicted order of these energies followed the same trend shown by experimental solvent extraction studies. Studies also showed that substitution can affect not only complex stability through inter-ligand interactions through hydrogen bonding in the outer-sphere but also the strength of metal-ligand bonds. Chapter 3 looks at synergistic solvent extraction systems: where more than one extractant works together to provide additional strength and selectivity. Combinations of neutral N and O donor ligands with carboxylic, phosphinic and sulfonic acids were studied by solvent extraction, crystallographic and computational methods. Crystal structures and DFT-optimised structures show that ligands and acid form pseudo-tridentate ligands where both the neutral ligand and the deprotonated acid are coordinated directly to the metal centre with inter-ligand hydrogen bonding allowing for a more flexible backbone than a classic tridentate system. Although synergistic extractions systems often utilise carboxylic acids many of the structures show the similarities with systems containing phosphinic acids and it was shown experimentally that some extraction systems show greater synergism with phosphinic than carboxylic acid in the recovery of nickel. Chapter 4 deals with the extraction of molybdenum with commercial phosphinic acid extractant Cyanex 600. The propensity for molybdenum to form oxo clusters in aqueous solutions and the influence pH in both the speciation of the Mo species and extraction conditions contributes to a complex extraction profile. The pH dependence of extraction shows that different mechanisms operate at low (pH < 0) and high (pH > 0) pH. The extraction curve shows a conventional S-curve between pH 0 and 1.5 and slope analysis within this pH range gives a value very close to two but identification of structures which match this profile is complex. Maximum pH extraction is see at ~ pH 1.5. ESMS studies identified very similar species in the organic phase despite the variation seen in the S-curve. A survey of the structures of metal complexes of phosphinate ligands suggests that molybdenum-phosphinate complexes can often form cubane-like structure and negative ion ESMS data supports the concept of cluster formation in the organic phase. A common feature of the spectra are tetra- tri- and bi-metal- oxo species and spectra show a large number of peaks. It is very probable that the extraction of molybdenum(VI) with phosphinic acids is a dynamic system as extraction is influenced by the molybdenum speciation in the aqueous phase which is in turn influenced by both the pH and the molybdenum concentration both of which change over the course of a conventional extraction.

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