Dissertations / Theses on the topic 'Ditopic ligand'

This thesis deals with the design and syntheses of chiral,enantiopure pyridinecontaining ligands and their applicationsin asymmetric catalyis.

Chiral pyridyl pyrrolidine ligands and pyridyl oxazolineligands were synthesized and employed in thepalladium-catalysed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. Theinfluence of the steric properties of the ligands wereinvestigated.

Ditopic ligands, containing crown ether units as structuralelements, were synthesized and some of the ligands were used asligands in the palladiumcatalysed allylic alkylation of1,3-diphenyl-2-propenyl acetate with dimethyl malonate. A smallrate enhancement was observed, compared with analogous ligandslacking the crown ether unit, when these ditopic ligands wereused in dilute systems.

A modular approach was used to synthesize chiralenantiomerically pure pyridyl alcohols and C2-symmetric2,2’-bipyridines, with the chirality originating from thechiral pool. Electronic and steric properties of the compoundswere varied and they were used as ligands in theenantioselective addition of diethylzinc to benzaldehyde. Thesense of asymmetric induction was found to be determined by theabsolute configuration of the carbinol carbon atom. Theelectronic properties of the ligands had a minor influence onthe levels of enantioselectivity induced by the ligands.

Chiral pyridyl phosphinite ligands and pyridyl phosphiteligands were synthesized from the pyridyl alcohols andevaluated as ligands in palladiumcatalysed allylic alkylations.With the phosphinite ligands, the sense of chiral induction wasfound to be determined by the absolute configuration of theformer carbinol carbon atom. A kinetic resolution of theracemic starting material was observed with one of thephosphite ligands. Moderate enantioselectivities wereachieved.

Kewords:asymmetric catalysis, chiral ligand, chiralpool, oxazoline, crownether, ditopic receptor, bipyridine,pyridyl alcohol, modular approach, P,Nligand, diethylzinc,allylic alkylation.

A series of unsymmetrical xylenyl-backboned diphosphine ligands are reported: o-C6H4(CH2ptSU2)(CH2PRR'), R = Ph, R' = 2-Py (L1) and O-C6H4(CH2ptSU2)(CH2PR2), R = 2-Py (L2), R = 2-(3-Me-Py) (L3), R = 2-(4- Me-Py) (L4), R = 2-(6-Me-Py) (Ls) and R = 2-Pyrim (Ls). The ligands have all been characterised by 31p, 1H and 13C NMR spectroscopy and high resolution mass spectrometry. Studies of [PtCI(CH3)(L)] and [PdCI(CH3)(L)] (L = L1-LS) have shown that the favoured isomers have the more strongly a-donating CH3 ligand trans to the bulkier ptSU2 donor. Studies with [PdCI2(L)], [PtCI2(L)] and [Pt(CH3h(L)] (L = L1-LS) show that the donor strength of the two phosphorus centres is not averaged in these complexes, in contrast to the related complexes of o-C6H4(CH2ptSu2)(CH2PPh2) (TP). These complexes have been characterised by a combination of NMR spectroscopy, high resolution mass spectrometry, elemental analysis and X-ray crystallography. The coordination chemistry of PR3, R = 2-(3-Me-Py), R = 2-(4-Me-Py), R = 2-(6-Me-Py), with LiCI and LiSr is also reported. Tripodal coordination to lithium by the three pyridyl nitrogen donors is detected for each ligand. These [LiX(PR3)] complexes have been characterised by 31p, 1H and 13C NMR spectroscopy and X-ray crystallography. Protonation studies with [PdCI2(L)] and [PtCh(L)] (L = L1-LS) suggest that the pendant pyridyl and pyrimidyl groups of L1-LS are protonated in methanolic solutions when treated with acids such as HSF 4, CH3S03H (MSA) and CF3C02H (TFA). The evidence for protonation came from 31p NMR spectroscopy and X-ray crystallography. Protonation studies with [Pt(CH3h(L2)] have shown that tridentate coordination of platinum by L2 (through both P donors and one pyridyl N donor) occurs. Catalysts derived from the new ligands were tested in the palladiumcatalysed methoxycarbonylation of ethene. The systems based upon L1, L2, L4 and Ls are shown to be active and selective for the production of methyl propionate (MeP) over polyketone (PK). Those derived from L2 and Ls are comparable in activity to the best reported system (which is based upon o-C6H4(CH2ptSU2h, dtbpx) when promoted by the strong acid MSA. The L2 and Ls systems are more active than dtbpx with the weaker acids TFA and PA. Complexes derived from L3 and Ls are inactive in methoxycarbonylation catalysis. Catalysts derived from L1-LS are also shown to be active in palladium-catalysed styrene methoxycarbonylation. Mechanistic studies suggest that catalysts derived from L2 produce MeP following the hydride mechanism. Competition between the coordination of palladium by the nitrogen donor of a pendant pyridyl group and acid anions was observed under catalytically relevant conditions. Complexes derived from L3 appear to be inactive in MeP catalysis due to persistent tridentate coordination of palladium (via the two P donors and one pyridyl N donor) blocking substrate coordination. Complexes derived from Ls may be inactive in MeP catalysis due to the electron deficient nature of the PPyrim2 donor. Carbonylation studies with isotopically labelled 13CO support the conclusion that MeP preference is a balance between kinetic and thermodynamic influences - the minor palladium-ethyl complex isomer may react faster to generate the more stable palladium-acyl isomer.

This thesis extends earlier work at the University of Edinburgh aimed at opening up new flowsheets for the hydrometallurgical recovery of base metals using tetradentate ligands which are capable of transporting metal salts {both a metal cation and its attendant anion(s)}. Prototypes were based on salicylaldimine derivatives of diamines, “salen” ligands in which coordination of a metal dication releases the two phenolic protons which are captured by pendant secondary amine groups generating a preorganised dicationic binding site for the anion(s). The thesis initially deals with the design, synthesis and evaluation of ligands to improve the strength, selectivity and speed of binding of nickel(II) sulfate by incorporating two additional donors in the salen unit to generate N₂X₂O₂^2- binding sites for the nickel yielding pseudo octahedral complexes. The ligands N,N or O,O or S,S o-aminophenyl-substituted 1,2-diaminoethane, 1,2-dioxaethane, 1,3-dioxapropane or 1,2-diethioethane were also used in a screening study with some other divalent metal salts (calcium, cobalt, copper, magnesium, manganese and zinc) commonly found in the feed solutions in commercial processes. Chapter two deals with the nickel(II) coordination chemistry of a series of sexadentate (N₂X₂O₂^2-) ligands. Nickel-ligand-anion complexes have been synthesised for sulfate, nitrate and chloride salts and neutral nickel-ligand complexes have been made. Crystal structures of complexes all contain the same isomer which has a planar mer arrangement of the salicylaldimato XNO^- units. A “nickel only” complex for an X₂N₂O₂^2- ligand with pendent piperidine groups shows that these could provide a cavity to encapsulate a single sulfate anion. All the ligands were found to be very weak extractants and showed slow complexation kinetics and phase transfer of nickel sulfate. The synthesis and characterisation of a series of tridentate ligands related to the sexadentate ligands, with NXO^- binding sites, are reported in chapter three. In theory these could form complexes with a ligand: nickel ratio of 2:1, with a more nearly “ideal” octahedral donor set. Solid state structures of the ligands show them to be pre-organised with an approximately 90° X˙˙˙N˙˙˙O angle. Nickel complexes have been synthesised for sulfate, chloride and acetate salts. Analysis indicates that complexes with ligand: nickel: dianion ratios of 2:1:1 were formed. The tridentate ligands were found to be very weak extractants for nickel sulfate. Chapter four describes the screening of the potentially sexadentate N₂X₂O₂^2-, tridentate NXO^- and the tetradentate “salen” ligands N₂O₂^2- in which the complexation and phase transfer of calcium(II), cobalt(II), copper(II), magnesium(II), manganese(II), nickel(II) and zinc(II) sulfates and chlorides were studied.

Les assemblages polymériques métallo-supramoléculaires constituent une nouvelle classe de matériaux apparue au cours des dernières décennies. Ces matériaux présentent un large éventail de propriétés qui dépendent de la nature des métaux et des ligands ditopiques utilisés. La réversibilité des liaisons de coordination offre également un caractère dynamique au système qui peut répondre à un stimulus externe. En introduisant de la chiralité dans ces systèmes moléculaires, nous pouvons étudier la capacité de ces structures moléculaires à s’associer ou à se désolidariser pour former des espèces homochirales ou hétérochirales. Ce manuscrit se concentre sur la synthèse et la chimie de coordination de ligands chiraux avec une symétrie C2, tels que les bisoxazolines, les bisimidazolines et les dérivés du 1,2-diaminocyclohexane. La complexation de deux ligands sur un métal de transition donne formation à des complexes homoleptiques ML2 dans lesquels la chiralité des ligands et la géométrie de coordination sont des paramètres importants pour observer une auto-association ou une hétéro-association des ligands. Tous ces complexes ont été étudiés et caractérisés à l’état solide ou en solution et l’impact des groupements chiraux sur les ligands a également été analysée. Afin de convertir ces complexes en assemblages polymériques, des ligands ditopiques chiraux ont également été conçus, synthétisés et étudiés
Metallo-supramolecular polymeric assemblies are a new class of materials that have emerged in recent decades. These materials exhibit a wide range of properties depending on the nature of the metals and the ditopic ligands used. The reversibility of the coordination bonds also gives the system a dynamic character that can response to an external stimulus. By introducing chirality into these molecular systems, we can study the ability of these molecular structures to associate or disassociate to form homochiral or heterochiral species.This manuscript focuses on the synthesis and coordination chemistry of chiral ligands with C2-symmetry, i.e. bisoxazolines, bisimidazolines and derivates of 1,2-diamonocyclohexane. The complexation of two ligands to a transition metal gives rise to homoleptic ML2 complexes, in which the chirality of the ligands and the coordination geometry are important parameters for observing self-association or hetero-association of the ligands. All these complexes have been studied and characterized in the solid state or in solution and the influence of the chiral groups of the ligands has also been analysed. In order to convert these complexes into polymeric assemblies, chiral ditopic ligands have also been designed, synthesized and studied

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2009.
Title from first page of PDF file (viewed November 17, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

The thesis considers the development of new reagents which could transport transition metal salts in extractive hydrometallurgy and addresses the ligand design features which are needed to control the strength and selectivity of binding of both a particular metal cation and its attendant anions(s). Extractive metallurgy of base metals is surveyed in chapter 1 and suggests that more efficient recovery processes are needed. One new approach, which could lead to much better materials balances in many cases, is to use hydrometallurgical techniques which involve co-extraction and transport of metal cations and their attendant anion(s). The problems in obtaining the selective extraction of anions makes the development of such a process very challenging, especially for hydrophilic anions such as sulphate which would be present in many pregnant solutions generated in processing sulfides ores. The rapidly emerging field of anion coordination chemistry and approaches to the development of selective ligands are discussed. Chapter 2 focuses on the pH dependence of sulfate-loading from an aqueous solution into chloroform solutions of a selection of zwitterionic ditopic ligands containing two 3-dialkylaminomethylsalicylaldimine units. These “salen-type2 ligands have quadridentate N₂O₂^2- binding sites for divalent metal cations and the cis-coordination of the phenolate aligns the pendant protonated 3-dialkylaminomethyl groups to bind to a sulfate dianion. Studies of the pH dependence of sulfate-loading confirm that sulfate binding is enhanced significantly by the incorporation of a divalent cation such as Cu²⁺ in the salen N₂O₂^2- site. Metal dication loading is very dependent on the nature of the bridging group between the two imines in the “salen” unit; Cu²⁺ loading follows the order ortho-phenylene > 1,2-ethane > 2,2’-biphenyl. The ethane-bridged ligand, 4,4’-di-tert-butyl-6,6’-bis(dihexylaminomethyl)-2,2’-(ethylenedinitrilodimethylidyne) diphenol, was found to have a nearly ideal loading profile for CuSo₄. Stability to hydrolysis and oxidation is a key requirement for commercial metal solvent extractants. The stability of the imine bond in the “salen-type” extractants investigated in chapter 2 was tested in a two phase chloroform: water systems under conditions likely to be used for loading or stripping of metal salts. Stability is dependent on the nature of the bridging unit between the two imines varying in this order 2,2’-biphenyl > ortho-phenylene > 1,2-ethane. Two new ligands, 4,4’-di-tert-butyl-6,6’-bis(dihexylaminomethyl)-2,2’-(ethylenedinitrilo-1,1’-phenyldimethylidyne) diphenol and N,N’-dimethyl-N,N’-bis(2-hydroxy-3-[(E)-phenyliminomethyl]-5-tert-butylbenzyl)hexane-1,6-diamine, which exhibit improved stabilities at low pH are also discussed.

This thesis considers methods which can be employed to increase the mass of copper transferred into and out of the organic phase during the load and strip stages of commercial solvent extraction processes. Conventional 5-alkylsalicylaldoxime reagents transfer 1 mol of divalent copper per 2 mol of ligand in a neutral complex of the type [Cu(L-H)2] via a pH-swing process. New triacidic ligands have been designed which triple the molar transport of copper to form [Cu3(L-3H)2]. Until recently copper recovery by solvent extraction has been confined to oxidic ores which are leached with sulfuric acid. New leaching technologies generate high tenor copper sulfate feed streams from sulfidic ores. The conventional 5- alkylsalicylaldoxime reagents do not work effectively in conjunction with these leach processes as they do not consume the acid which is generated on loading the oxime. To address this problem ditopic zwitterionic ligands have been designed which can transfer both metal cation and attendant anion. These new metal salt reagents are diacidic, therefore not only transfer metal salts but also increase the molar transport relative to the conventional reagents. Equilibrium-modifiers are often added to improve the mass transport efficiency of conventional solvent extraction processes. The nature of their interaction with the species in solution is poorly understood. This thesis investigates their interaction with the free ligands and copper complexes to gain an understanding of their mode of action in order to rationalise the design of future modifiers to optimise recovery efficiencies. Increased molar transport is addressed in Chapter 2. The diacidic ligand 5- methylsalicylaldehyde-pivaloylhydrazide (L2) and its dinuclear copper complex [Cu2(L2-2H)2] were synthesised and characterised to gain an understanding of their speciation in solution. X-ray structural analysis of [Cu2(L2-2H)2] confirmed that the phenolate oxygen atoms bridge the copper centres rather than the amidato oxygen atoms of the hydrazone. Variable temperature magnetic susceptibility data confirm that the copper centres are antiferromagnetically coupled as expected for the Cu-OCu angle (99.6(2)°). An understanding of the coordination geometry of the dinuclear systems lead to design of triacidic ligands. A series of 3-hydrazono- and 3- hydroxyanil- 5-alkylsalicylic acids were synthesised. The prototype ligand 5-methyl 3-octanoylhydrazonosalicylic acid (L6) was demonstrated to triple molar transport and increase mass transport by 2.5 fold. Solvent extraction results indicate that copper is sequentially loaded as pH is increased. The plateaux observed in loading curves suggest formation of stable mono-, di-, and tri-nuclear copper complexes within the pH-ranges 1.75 - 2.75, 3.25 - 4.0 and > 4.25 respectively. The triacidic ligands were also demonstrated to double the molar transport of the conventional salicylaldoximes when used in 1:1 blends by formation of a ternary complex. Chapter 3 describes the incorporation of two tertiary amine groups into diacidic salicylaldehydehydrazone ligands to form dinucleating metal salt extractants. Piperidinomethyl, piperazinomethyl and dihexylamino groups were incorporated into various positions of the ligand including 3- and/or 5- positions of the salicylaldehyde or incorporated into the hydrazone. Solvent extraction results obtained for 3,5- bis((dihexylamino)methyl)salicylaldehyde-octanoic hydrazone (L20) are consistent with transfer of 1 mol of copper sulfate per mol of ligand in the organic phase between pH 2.0 and 2.5. This result is indicative of the formation of [Cu2(L20)2(SO4)2]. Conventional salicylaldoximes are “strong” copper extractants which require concentrated acid electrolyte to efficiently strip the copper from the organic phase. However, as the use of concentrated acid affects the quality of the copper cathodes, oxygen-containing equilibrium modifiers are often added. These facilitate copper stripping without adversely affecting the loading. The affect of 2-ethylhexanol (2- EH) and trioctylphosphine oxide (TOPO) on the extractive ability of 5-toctylsalicylaldoxime (19) in n-heptane is reported. Both are found to decrease copper extraction more under stripping conditions than loading conditions. 2-EH shows little affect at pH greater than 2.5. TOPO does not significantly affect copper loading at pH greater than 3.0. Evidence for the formation of the adduct [Cu(19-H)2)(TOPO)] was obtained from UV/Vis, IR, EPR and sonic spray mass spectrometry.

La presente memoria ha profundizado en el diseño de nuevos catalizadores al utilizar dos nuevos tipos de ligandos diferenciados: triazolil-di-ilideno y bis-alquenil-NHCs. El uso del ligando trimetiltriazolil-di-ilideno, ha permitido obtener series de compuestos de tipo homo- y hetero-bimetálicos, estableciéndose criterios claros de coordinación que garantizan que el mismo ligando se puede utilizar de manera amplia en su coordinación a prácticamente cualquier par de fragmentos metálicos. La preparación y la caracterización de los compuestos heterobimetálicos establece un gran avance en el diseño de catalizadores tándem que permitan catalizar secuencias catalíticas formadas por reacciones muy diferentes. La utilización de los ligandos de tipo bis-alquenil-NHC, ha permitido diseñar de forma sistemática compuestos en los que el ligando actúa como mono-, bi- y tri-dentado. Los compuestos derivados de la coordinación de los ligandos bis-alquenil-NHC han sido probados como catalizadores en reacciones de hidrosililación de alquinos, observándose que la actividad catalítica depende del grado de coordinación del ligando NHC. De este modo, los complejos monocoordinados y bisquelatos han mostrado las mejores actividades, junto a una elevada selectividad hacia los isomeros Z.

The aim of this research was to synthesise a series of novel organic multidentate ligands which contain N-donor domains for the coordination of metal ions and amide or amine hydrogen atoms which are capable of interaction with anions. It was envisaged that incorporation of these two binding units would produce a system where the metal ions would control the ability of the ligand to interact with anions or vice versa. Ligand 1 contains a tetradentate N-donor domain formed by a central bipyridine, two thaizole units and two amide units attached in the 4,4’-position of the bipyridine unit. Reaction of this with divalent metal ions results in a mono-nuclear complex where the metal is bound by the N-donor atoms and the amides interact with a variety of anions. Reaction with monovalent metal ions results in the formation of a dinuclear double helicate with the metal again coordinated by the N-donor domains and the anions interacting with the amide hydrogen atoms. This results in a polymeric assembly in the solid state. Ligand 2 contains an identical tetradentate domain comprised of the same N-donor units; however the single amides in the 4,4’-position have been removed and a diamide attached in the 3,3’-position of the bipyridine unit. Reaction of [L2 with divalent cations results in a similar mono-nuclear species. The metal centre is coordinated by the N-donor atoms and one of the acetyl units from two adjoining ligands with the counter ions undergoing interactions with the diamide hydrogen atoms. Coordination of the same ligand with a monovalent cation resulted in a di-nuclear double helicate, each metal centre is fulfilled by the N-donor atoms of the ligand strand and the hydrogen atoms of the diamide units interact with anions. This too results in a polymeric assembly in the solid state. Ligands 3 and 4 contain the iso-structural tetradentate N-donor domain seen in [L1] and [L2] but their functionality in the 3,3’-position differ. Ligand 3 contains a urea group while ligand 4 has a single amide group attatched to an indole unit. Coordination of [L3] and a divalent metal ion results in the formation of a mono-nuclear species with the metal ion bound by the central bipyridine and the N-donor of two thaizole units. Furthermore each of the urea groups in the 3,3’-position undergo favourable interactions with the perchlorate counter ions. A solid state structure of Ligand 4 was only successful with a monovalent cation resulting in the formation of a dinuclear double stranded species. Each metal centre exhibits a distorted trigonal planar geometry through coordination with a pyridine and thiazole ring of one strand and a single thiazole ring of another. The indole and amide of each ligand strand undergo two sets of interactions; anion interactions through the amide and indole hydrogen atoms as well as complementary intermolecular interactions between the indole N···H units of one ligand and the carbonyl C···O units of another complex. Both [L3] and [L4] exhibit long range order through favourable anion-NH interactions however [L4] also displays complimentary indole/acetyl interactions to develop a larger aggregate species. In all these cases the resultant complex is independent upon which anion is used. However, this is not the case with ligand 5. Reaction of [L5] with Cu(BF4)2 or Cu(ClO4)2 gave a dinuclear double helicate with a cleft within the helicate assembly in which an anion is bound. However, reaction of this with half an equivalent of either sulphate (SO4 2-) or dihydrogen phosphate (H2PO4 -) results in the formation of a different dinuclear double helicate whereby the cleft is occupied by either a dihydrogen phosphate or sulphate anion which bridges the metal centres. Further addition of sulphate results in no change of the ESI-MS indicating the dinuclear double helicate persist however addition of one equivalent of di-hydrogen phosphate leads to the formation of a pentanuclear circular helicate. Each metal centre is coordinated by the pyridine and thiazole units of two different ligand strands and a single Cu···O interaction from one of the dihydrogen phosphates. The inclusion of three dihydrogen phosphates into the centre of the assembly as well as a series of phosphate-ligand and phosphate-phosphate interactions leads to the dimerization of the structure with another set of phosphates from a second assembly. Further reaction of this dinuclear species with one equivalent of (Bu4N)NO3 resulted in the formation of a hexanuclear circular meso-helicate (or mesocate). In this structure each Ndonor domain of a thiazole and pyridine ring coordinate two different Cu2+ metal centres. Each metal centre exhibits a distorted octahedral arrangement with two ligand strands completing 4 of its 6 coordination sites, the remaining sites are occupied by two O-donors of a nitrate anion. In addition an amine of each ligand strand points into the centre of the complex creating a cavity capable of hosting two nitrate anions. Ligand 6 is made up of the same bis-bidentate donors as ligand 5 with the addition of a nitrogen atom into the central phenyl spacer. On reaction of [L6] with a divalent metal ion (e.g. Cu(II)) a simple mono-nuclear structure is observed. Although a mono-nuclear assembly is expected, it is interesting that even a simple change in the ligand strand can have a dramatic affect on the self-assembly process. When a central 1,3-phenylene spacer is employed (i.e. [L5]) a dinuclear double helicate is formed, however, when a 1,3-pyridine unit is contained within the ligand strand (i.e. [L6]) a simple mono-nuclear species is produced.

Das Ziel der vorliegenden Arbeit bestand in der Synthese von neuen funktionalisierten tripodalen Azaliganden auf Basis von Tris(2-aminoethyl)amin (Tren) und ihrer Charakterisierung als Rezeptoren und Extraktionsmittel für Kationen, Anionen sowie Salze. Die Komplexbildungs- und Phasentransfereigenschaften gegenüber den Kationen Ag(I), Co(II), Ni(II), Cu(II), Zn(II) und Cd(II) sowie den Anionen Cl-, Br-, I-, H2PO4-, SO42- und HCrO4- wurden durch Flüssig-Flüssig-Extraktion und Flüssigmembrantransport, 1H-NMR-Spektroskopie sowie Silberpotentiometrie untersucht; Struktur-Wirkungsbeziehungen für die jeweiligen Wirt/Gast-Systeme wurden abgeleitet. Röntgenkristallstrukturanalysen ausgewählter Komplexe mit den Kationen Ag(I), Ni(II) und Cu(II), den Anionen Br- und BF4- sowie dem Salz Hg(ClO4)2 ergänzten die gewonnenen Aussagen durch detaillierte Informationen zur Struktur und zu den auftretenden Wechselwirkungen. In die Betrachtungen wurden vergleichende Untersuchungen zur Ag(I)-Bindung durch strukturverwandte tripodale Schiffsche Basen einbezogen. Zusammenfassend wird der Einfluss der unterschiedlichen ligandspezifischen Charakteristika sowie der Substratspezies auf die Komplexbildung in Lösung und die Festkörperstruktur diskutiert. Die untersuchten tripodalen Aminverbindungen auf Basis von Tren zeigten in Abhängigkeit von ihrer Struktur ein differenziertes Extraktionsverhalten im System Metallsalz-Puffer-Wasser/Ligand-Chloroform. Als wesentliche Einflussfaktoren auf die Extraktion erwiesen sich Art, Anzahl und Anordnung der Donoratome sowie die differenzierte Lipophilie der Liganden. Die Zusammensetzung der extrahierten Komplexe in der organischen Phase ergab sich in den meisten Fällen zu 1:1 (Ag(I) : Ligand). Die bestimmte Reihe steigender Komplexstabilität für die 1:1-Komplexe von Ag(I) in Methanol unterstreicht in Analogie zu den Extraktionsuntersuchungen den Einfluss der Ligandcharakteristika auf die Komplexbildung. So führten Liganden mit tertiären Aminstickstoffatomen, zusätzlichen O-Donoratomen sowie sterisch anspruchsvollen Substituenten im Molekül zu geringeren Komplexstabilitäten, während zusätzliche S- und Pyridin-N-Donoratome in den untersuchten Aminverbindungen eine deutliche Steigerung der bestimmten Konstanten ergaben. Vergleichende Untersuchungen mit tripodalen Iminopodanden zeigten mit Ausnahme des 2-pyridylmethyl-substituierten Liganden generell niedrigere Stabilitäten der Ag(I)-Komplexe. 1H-NMR-Untersuchungen zur Komplexbildung in Lösung deuten unter veränderten Bedingungen auch auf einen möglichen Wechsel in der Komplexzusammensetzung und im Bindungsmuster für Ag(I) in Abhängigkeit von den im Molekül vorhandenen Donorfunktionen hin. Während für N4-Liganden ohne zusätzliche Donoratome sowie in Anwesenheit von S- und N-Donoratomen eine Zusammensetzung (Ag(I) : Ligand) von 1:1 bestimmt wurde, führen zusätzliche Pyridin-N-Donoratome zu einem stöchiometrischen Verhältnis von 3:2. Die Röntgenstrukturanalysen der Ag(I)-Komplexe von tripodalen Schiffschen Basen mit unterschiedlichen Substituenten unterstreichen die Variabilität der Koordinationsgeometrie von Ag(I) in Abhängigkeit vom Liganden. Interessant ist die Ausbildung von schwachen C-H···Ag-Wasserstoffbrücken in den Ag(I)-Komplexen der benzyl- und 4-biphenylmethyl-substituierten Liganden. Für die Kationen Co(II) und Zn(II) wurden mit den untersuchten Liganden generell nur geringe Extrahierbarkeiten erzielt. Dabei ist der Einfluss von Ligandstruktur sowie Lipophilie der Verbindungen auf die Extraktion stärker ausgeprägt als für Ag(I). Die Extraktion aus einem Gemisch von Co(II), Ni(II), Cu(II), Zn(II) und Cd(II) zeigte generell einen Anstieg der Extraktion in der Reihe Co(II) < Ni(II) < Zn(II) < Cd(II) < Cu(II). Lediglich die Verbindung mit einer OH-Funktion in 2-Position der aromatischen Substituenten führte zu höheren Extraktionsausbeuten für Co(II), Ni(II) und Cd(II) gegenüber Cu(II) und Zn(II). Röntgenstrukturanalysen von vier Cu(II)- bzw. Ni(II)-Komplexen veranschaulichen die bevorzugte höhere Koordinationszahl dieser Metallionen in relevanten Komplexen im Vergleich zu Ag(I). Die höhere Koordinationszahl wird dabei durch eine zusätzliche Koordination von Anionen oder Lösungsmittelmolekülen erreicht. Im Gegensatz zu den Kationen ist die Anionenextraktion wesentlich sensitiver gegenüber wechselnden experimentellen Bedingungen. Das hängt insbesondere mit den veränderten Bindungsverhältnissen in Anionenkomplexen zusammen. So wird die Extraktionsausbeute stark durch die Lipophilie der Liganden beeinflusst; ein signifikanter Anionentransport in die organische Phase wurde lediglich mit lipophilen Liganden erzielt. Die beobachtete Abstufung steigender Extraktion SO42- < Cl- < HCrO4- < I- ist in Übereinstimmung mit der zunehmenden Lipophilie dieser Anionen. In Abhängigkeit von der Natur der vorhandenen N-Donorfunktionen im Liganden und der Struktur der Liganden insgesamt wurde ein ausgeprägter pH-Einfluss auf die Extraktion der Anionen beobachtet. Während für die Liganden mit sekundären Aminfunktionen hohe Extrahierbarkeiten bei einem pH-Wert von ca. 5 auftraten, stiegen die Extraktionsausbeuten für Verbindungen mit tertiären Aminstickstofffunktionen mit abnehmenden pH-Wert kontinuierlich an. Die untersuchten Anionen wurden vorwiegend unter Bildung von 1:1- und 1:2-Komplexen (Anion : Ligand) in die organische Phase überführt. Für den Membrantransport war eine steigende Transportrate entsprechend der Dominanz der Lipophilie in der Reihe H2PO4- < SO42- < Cl- < Br- charakteristisch. Ein bevorzugter Transport von Cl- gegenüber Br- wurde hingegen mit sterisch anspruchsvollen Liganden sowie ausgeprägt lipophilen Verbindungen erreicht. Die Strukturen von zwei Anionenkomplexen mit BF4- bzw. Br- zeigen differenzierte Bindungsmuster. Einmal verhindern in einem Iminopodanden starke intramolekulare Wasserstoffbrücken zwischen dem protonierten Brückenstickstoff und den Iminfunktionen der Podandarme einen Einschluss des BF4--Anions in den vorliegenden Pseudokäfig, so dass die Koordination des Anions lediglich über schwache C-H···F-Kontakte an der Ligandperipherie erfolgt. Im Gegensatz dazu sind in einem N4-Aminliganden die drei Aminfunktionen der Podandarme protoniert. Die Br--Ionen werden sowohl durch ladungsunterstützte N-H···Br- als auch durch C-H···Br-Wasserstoffbrücken vom Liganden koordiniert. Weiterhin konnte in der Arbeit der Nachweis geführt werden, dass durch die Kombination von kationen- und anionenbindenden Funktionseinheiten in einem tripodalen Liganden die simultane Bindung und Extraktion von Kationen und Anionen möglich wird. Die Röntgenkristallstruktur eines Hg(ClO4)2-Komplexes bestätigt dabei die gleichzeitige Koordination von Kation und Anion durch die unterschiedlichen spezifischen Funktionseinheiten im Molekül.