CuI complexes containing the bulky dialkylbiarylphosphane 2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl (tBuXPhos, L) and an ancillary ligand (Cl-, Br-, I-, MeCN, ClO4- or SCN-) have been structurally characterized, namely, chlorido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuCl(C29H45P)], 1, bromido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuBr(C29H45P)], 2, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]iodidocopper(I), [CuI(C29H45P)], 3, (acetonitrile-κN)[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I) hexafluoridophosphate, [Cu(CH3CN)(C29H45P)]PF6, 4, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP](perchlorato-κO)copper(I), [Cu(ClO4)(C29H45P)], 5, and di-μ-thiocyanato-κ2S:N;κ2N:S-bis{[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I)}, [Cu2(NCS)2(C29H45P)2], 6. Iodide complex 3 shows significant CuI-arene interactions, in contrast to its chloride 1 and bromide 2 counterparts, which is attributed to the weaker interaction between the iodide ion and the CuI centre. When replacing iodide with an acetonitrile (in 4) or perchlorate (in 5) ligand, the reduced interaction between the CuI atom and the ancillary ligand results in stronger CuI-arene interactions. No CuI-arene interactions are observed in dimer 6, due to the tricoordinated CuI centre having sufficient electron density from the coordinated ligands.

In this paper, we present our findings on a series of copper(ii) 2,2′-bipyridyl (bipy) complexes that inhibit the oxidation of thiosulfate, a current problem in the gold leaching process. The formation of six complexes, five of which have been structurally characterized by X-ray crystallography, illustrate a thermally induced, controllable switching between oxidation states, which in turn inhibits the oxidation of thiosulfate. These findings give further insight and understanding into the rich chemistry of the coinage metals and the hydrolytic processes involved with gold leaching.

The results reported in this thesis are an investigation into the synthesis: characterisation, and coordination ability of some new Schiff base f errocenyl derivatives. Chapter One gives a brief overview of the practical applications that ferrocene based compounds have been put to, since f errocenes first synthesis in 1951. Chapter Two outlines the preparation and characterisation of six new Schiff base ferrocenyl derivatives, along with a new synthesis and full characterisation of a f errocenyl thiosemicarbazide derivative which was first synthesised in 1968. The X-ray structure of bis-N-(a-hydroxybenzylidene) ferrocenylimine, (Ll 1), was established, showing relatively strong intramolecular hydrogen bonding between the Schiff base nitrogen and the hydrogen of the hydroxy group on Jhe phenol. In Chapter three reduction attempts of the f errocene derirntives in Chapter 2 are reported. The synthesis and characterisation of a borane adduct of the N-(ahydrazonylpyridine) ferrocenimine ligand, (L2.Bf-\) , is studied. Its single crystal X-ray structure is determined and the adduct is compared to the parent L2 ligand. Chapter Four contains the preparation and characterisation of the complex [Zn(Ll)Cl]i, which is based on the N-(a-hydroxybenzylidene) ferrocenylimine ligand, (Ll). Five new metal complexes are reported, [Co(L2)Cl 2 ], [Ni(L2)Br2], [Cu(L2)Cl 2], [Co(L2)Br2] and [Zn(L2)Cl2] based on the L2 ligand, and these are characterised by mass and infra-red spectroscopies. In Chapter Five the ligands are studied by cyclic voltarnmetry and Mossbauer spectroscopies, with further cyclic voltarnmetry studies undertaken on the complexes. The electrochemical oxidation trends observed in the cyclic voltarnmetry studies on the Schiff base derivatives are in parallel with the Mossbauer studies, which have the results rationalised in terms of electron population movements within the 57 Fed-orbitals and the porbitals of the cyclopentadienyl rings.

Tribenzylphosphane sulfide (SPBn3) reacts with [Cu(CH3CN)(4)]PF6 in a 2:1 ratio to give [Cu(CH3CN) (SPBn3)(2)]PF6 whereas with [Ag(CH3CN)(4)]PF6 in the same ratio it forms [Ag-2(SPBn3)(3)](PF6)(2). The crystal structure of the Cu(I) complex shows it to contain discrete 3-coordinate [Cu(CH3CN)(SPBn3)(2)](+) cations and [PF6](-) anions with the Cu atom lying in the plane formed by the two coordinated sulfur atoms and the nitrogen from the coordinated acetonitrile molecule. The Ag complex is a dinuclear species with the one silver atom being 3-coordinate and the other 4-coordinate. Each of the SPBn3 molecules forms a Ag-C eta(1)-bond with one of the aromatic rings thus blocking the coordination of further SPBn3 ligands. The two Ag centers are linked by a bridging sulfur and a weaker interaction with carbon from the aromatic ring of the same tribenzylphosphane sulfide. (C) 2015 Elsevier Ltd. All rights reserved.

The sterically bulky di(1-adamantyl)benzylphosphane (L) reacts with the copper(I) compounds, CuX (X = CI, Br, I and SCN), in a 1:1 ratio to give the salts CuXL. Single crystal X-ray structures for X = Cl, Br and SCN, show that the complexes exist as dimeric species of the type [Cu2X2L2] with the X groups bridging to give each copper a distorted trigonal-planar coordination geometry with a 'PX2' donor site. When [Cu(CH3CN)(4)]BF4 reacts with L in a 1:2 ratio, the two-coordinated complex [CuL2]BF4 was formed which has a P-Cu-P angle of 169.46(6)degrees, reflecting the influence of the adamantyl groups. The silver(I)1:2 compound, [AgCIL2], has a 'CIP2' donor set with a distorted P-Ag-P bond angle of about 149.02(5)degrees. The reduced coordination numbers, irregular structures and distortions of selected angles are a result of the steric bulk (large cone angle) of L. Some of these structural features may also assist in understanding why Pd(0) complexes of L are effective catalysts for the Sonogashira coupling reactions of arylchlorides and alkynes. (C) 2016 Elsevier Ltd. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Six complexes consisting of either 2,6-bis(1H-benzimidazol-2-yl)pyridine (bbp) or 2,2':6',2 ''-terpyridine (tpy) moieties coordinated to ruthenium(II) and attached to (pentaphenoxy)cyclotriphosphazene were synthesised and structurally characterised by single-crystal X-ray diffraction techniques. Two of the complexes are the first examples of structurally characterised mono-protonated Ru(bbp)(tpy) complexes. The new complexes were studied by NMR, electronic absorption and vibration spectroscopy to gain an understanding of their physical characteristics. Remarkably the mono-deprotonated form of the bbp ligand, but only when attached to (pentaphenoxy)cyclotriphosphazene by a pyridyl phosphoester linker, shows an equivalence of the benzimidazole/benzimidazolate moieties on the NMR time scale, but not on the electronic time scale, as evidenced by UV-Vis and resonance Raman spectroscopy. (C) 2015 Elsevier Ltd. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The synthesis of a series of cyclotriphosphazene and polyphosphazene ruthenium(II) compounds is reported using 2,2′:6′,2″-terpyridine (terpy) and 2,6-di(1H-pyrazol-1-yl)pyridine (bpp) pendant ligands. X-ray crystallography, UV–Vis and resonance Raman spectroscopy have been employed to gain an insight into the physical and coordination behaviour of these complexes and indicate that both the small molecule and their polymeric analogues contain coordinated Ru in an octahedral ‘N6’ environment. The results reveal a difference between the chemistry of the ruthenium(II)-bpp-terpy and ruthenium(II)-bis-terpy complexes and demonstrate a means of grafting functional groups to a polyphosphazene backbone under mild conditions.

Two new polyphosphazene ligands containing 1,10-phenanthrolin-2-olate (L-1) and 2,2 -bipyridine-6-olate moieties (L-2) with 5,5 -di-tert-butylbiphenyl-2,2 -bis(olate) co-substituents were synthesised and then reacted with Fe(Pyridine)(4)(NCS)(2). Variable temperature Mossbauer and electronic absorbance spectroscopies were used to establish the physical behaviour of the new iron-polyphosphazenes. By attaching two bidentate ligands to a geminal phosphorus atom a pseudo tetradentate ligand can be formed that prevents cross-linking when iron is coordinated to the polyphosphazene. (C) 2014 Elsevier B.V. All rights reserved.

Tris(2-cyanoethyl)phosphine (tcep) reacts with the copper(I) compounds, CuX (X = Cl, Br, I and SCN), in a 1:1 ratio to give 1:1 complexes, CuX(tcep), whereas it reacts with CuY (Y = PF6, ClO4, NO3, BH4, CN and CF3COO) in a 2:1 ratio to give the 2:1 complexes, CuY(tcep)(2). Single crystal X-ray structures show that for the anions X = Br and SCN, the complexes are coordination polymers, [CuX(tcep)](n), with the Cu centres being bridged by the anion, and as well, one nitrile arm per tcep ligand coordinates intermolecularly to the Cu to give tetrahedral 'PBr2N' and 'PSN2' coordination spheres respectively. The 2:1 compounds exhibit a variety of structures. For Y = ClO4, CN and CF3COO polymeric structures are formed except for Y = BH4 where the compound is a discrete monomer, [Cu(BH4)(tcep)(2)], with a chelating anion and two monodentate P-bound tcep ligands. Both the compounds obtained with Y = CN and CF3COO also contain coordinated anions and are formulated as [Cu(CN)(tcep)(2)](n) and [Cu(CF3COO)(tcep)(2)](n) respectively. In the case of Y = CN the anion is bridging and the tcep ligands are only P-bound giving a 'P2NC' coordination sphere. In contrast, for Y = CF3COO, the anion is an O-bound monodentate and the tcep ligands bridge to give a 'P2NO' environment for the copper. In the case of Y = ClO4, the anion is not coordinated but a polymeric structure, [Cu(tcep)(2)](n)(ClO4)(n), is formed via bridging tcep ligands linking Cu centres intermolecularly resulting in a 'P2N2' coordination sphere. (C) 2014 Elsevier Ltd. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The pyridyloxy-substituted cyclotetraphosphazene ligands, octakis(2-pyridyloxy) cyclotetraphosphazene (L), and octakis(4-methyl-2-pyridyloxy) cyclotetraphosphazene (MeL), react with [Ag(CH3CN)(4)]PF6 and [Ag(CF3SO3)] to form the complexes {[AgL](PF6)center dot 0.5CH(3)CN center dot 0.5C(4)H(10)O}(n) (1), {[Ag2L](PF6)(2)}(n) (2), [Ag2L](CF3SO3)(2) (3), {[Ag2L](CF3SO3)(2)center dot C4H10O}(n) (4), {[Ag-3(MeL)(CH3CN)(2)](PF6)(3)center dot 2CH(3)CN}(n) (5), and [Ag-4(MeL)(CF3SO3)(CH3CN)(3)](CF3SO3)(3) (6), which have been characterized by single crystal X-ray crystallography. The structure of (1) is a coordination polymer containing repeating [AgL](+) units that form 1-D chains. The PF6- anions lie between the sheets formed when the individual chains approach each other such that the pendant pyridyloxy rings have numerous close intermolecular contacts. The triflate solvated salt (4) also is a 1-D coordination polymer, with the individual chains packed close together due to multiple hydrogen bonding contacts between the coordinated triflate fluorine atoms and aromatic hydrogen atoms on adjacent chains, whereas the unsolvated form (3) contains discrete molecules of a dimetallic complex. For the latter two complexes the influence of the solvent on the structures is notable and shows the flexibility of the ligand system. Complex (5) forms a 1-D coordination polymer with the chain being propagated by a silver bound in a near linear manner by a pyridyloxy pendant from one molecule, and by a pyridyloxy from an adjacent molecule. Apart from (4) and (6) all the compounds show this or a similar way of linking the units. Complex (6) forms discrete molecules of a tetra-metallic complex but with one silver involved in an argentophilic interaction at 3.408 angstrom from its symmetry equivalent. This complex is the most metal-rich phosphazene reported for this ligand type, with all eight of the pyridine ligand arms involved in binding the four Ag(I) centres. The formation of silver-ligand bonds, hydrogen bonds, pi-pi stacking, argentophilic and anionic interactions along with subtle kinetic factors influence the self-assembly process.

Mössbauer and electronic absorbance spectroscopy along with variable temperature magnetic moment measurements demonstrate that a cyclotriphosphazene substituted with an iron(II)-bis-2,6-di(1H-pyrazoly-yl)pyridine moiety (1) and its polyphosphazene analogue (2) differ significantly in magnetic behaviour.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The synthesis of the new cyclotriphosphazene (CTP) ligand substituted with a pendant 2,6-bis(benzimidazole-2-yl)pyridine (bbp), namely (pentaphenoxy)[4-{2,6-bis(benzimidazole-2-yl)pyridine-4-yl}phenoxy]cyclotriphosphazene L is reported. The single crystal structure of L shows that the bbp group is attached to the CTP via the oxygen. L reacts with FeX2 (X=ClO4− or BF4-) salts forming the [FeL2]X2 complexes 1 and 2 respectively. For [FeL2](BF4)2 (2), the single crystal structure shows an ‘N6’ coordination sphere around the iron atom. UV–Vis, resonance Raman and Mössbauer spectroscopies and magnetic susceptibility measurements, aided by density functional theory (DFT) calculations, determine the complexes are low spin below 300K but display spin crossover (SCO) behavior above this temperature, hence showing that the addition of a phosphazene to a SCO moiety does not prevent SCO.

Two new cyclotriphosphazene ligands with pendant 2,2':6',2″-terpyridine (Terpy) moieties, namely, (pentaphenoxy){4-[2,6-bis(2-pyridyl)]pyridoxy}cyclotriphosphazene (L(1)), (pentaphenoxy){4-[2,6-terpyridin-4-yl]phenoxy}cyclotriphosphazene (L(2)), and their respective polymeric analogues, L(1P) and L(2P), were synthesized. These ligands were used to form iron(II) complexes with an Fe(II)Terpy(2) core. Variable-temperature resonance Raman, UV-visible, and Mössbauer spectroscopies with magnetic measurements aided by density functional theory calculations were used to understand the physical characteristics of the complexes. By a comparison of measurements, the polymers were shown to behave in the same way as the cyclotriphosphazene analogues. The results showed that spin crossover (SCO) can be induced to start at high temperatures by extending the spacer length of the ligand to that in L(2) and L(2P); this combination provides a route to forming a malleable SCO material.

The synthesis and characterization of the fluxional, d(10) cyclotriphosphazene complexes, [MLCl(2)] (M = Zn, Cd, and Hg; L = spiro-[(1,1'-biphenyl)-2,2'-dioxy]tetrakis(4-methyl-2-pyridyloxy)cyclotriphosphazene), are described. Single-crystal X-ray structures show that the zinc complex has crystallized into two crystal forms: one as a tetrahedral species, with a N(2)Cl(2) donor set in which a geminal pair of the pendant pyridyloxy nitrogen atoms binds to the zinc, and the other as a trigonal-bipyramidal (tbp) one, with an N(3)Cl(2) donor set. The third nitrogen atom comes from the phosphazene ring and the two pyridyl ligands are non-geminal. The asymmetric unit of the cadmium complex contains three structurally distinct molecules. One molecule has a tbp structure similar to that of the zinc complex. The second molecule has a six-coordinate, distorted octahedral geometry around the cadmium center with a N(4)Cl(2) donor set, with three of the nitrogen donor atoms coming from the pendant pyridyloxy arms. The third site contains a tbp complex and a distorted octahedral species with a relative occupancy of 3:1. The identification of these three different forms in the one crystal suggests that the energy difference between the tbp and distorted octahedral isomers is not large. Quantitative analysis of the (1)H NMR and variable-temperature (31)P NMR spectra of the zinc, cadmium, and mercury complexes in a CD(2)Cl(2) solution, coupled with the X-ray structural results, shows that an associative fluxional mechanism (ΔS(++) < -65 J mol(-1) K(-1)) is operating.

A series of small phosphazene ligands with pendant 6-phenyl-2,2'-bipyridyl moieties, namely L-1 [N3P3(OPh)(5)-(OPhbpyPh)], L-2 [N3P3(biph)(2)(OPhbpyPh)(2)], L-3 [N3P3(tBubiph)(2)(OPhbpyPh)(2)], L-4 [N3P3(biph)(2)(OPhbpyPh)Cl] and L-5 [N3P3(biph)(2)(OPhbpyPh)(OPh)] [OPhbpyPh = 4-(4-phenoxy)-6-phenyl-2,2'-bipyridine, OPh = phenoxy, biph = 2,2'-oxybiphenyl and tBubiph = 4,4'-di-tert-butyl-2,2'-oxybiphenyl], have been used to synthesise the new cyclometallated palladium(II) and platinum(II) complexes [(L-1-H)PdCl], [(L-1-H)PtCl], [(L-1-H)(PdCl)(2)], [(L-3-H)(PdCl)(2)], [(L-4-H)PtCl], [(L-5-H)PtCl] and the rhenium(I) complex [(LRe)-Re-5(CO)(3)Cl]. Singlecrystal X-ray diffraction analysis was performed on the free ligand L-2 and the palladium complexes [(L-1-H)PdCl] and [(L-3-H)(PdCl)(2)]. In both Pd-II complexes, the metal centre lies in a distorted square-planar geometry with an "N2CCl" donor set confirming the cyclopalladation. The ligand pendant arms are involved in intermolecular stacking interactions with adjacent molecules. A polyphosphazene (L-6) with 4-tert-butylphenoxy (OtBuPh) and the potential donor OPhbpyPh as pendant groups was prepared and used to synthesise metallopolymers with Re-I and Pt-II. Spectroscopic and computational studies were conducted to compare the discrete complexes with the polymers with similar metal pendants as well as to model compounds in the literature. By using UV/Vis and resonance Raman spectroscopic techniques it was found that very few deviations from known metal chromophores exist for both the triphosphazene- and polyphosphazene-based complexes. The transient resonance Raman spectra of the Pt-II complexes revealed a ligand radical anion signature associated with the N2C unit.