No description available.

No description available.

No description available.

Full X-ray structure analyses ot sixteen .etal cluster compounds of nuclearity 3 to 11 have been carried out to investigate to what extent the attached surface ligands govern the structure in the solid state and how this relates to the chemistry of the cluster in solution. The structure of the tetranuclear cluster [AgRu,(CO),(CzBut)(PPh,)] has completed a series of related clusters [MRu,(CO),(CzBut)(PPh,)] [M a Cu, Ag or Au]. This is only the second example of a complete series of Group IB cluster analogues and confirms earlier evidence that the bonds fro. gold are different in character to those trom silver and copper. The structures of the copper clusters [Cu,Ru.(~,-H),(CO)'Z{P(C6H'1)'}Z] and [Cu,Ru.(~,-H)Z (CO)tZ {P(CHMel ) l} l ] compared to the reported structure [Cu,Ru"(~J-H)z(CO)tZ(PPhl)l] indicate that the 'bulk' of the organophosphine groups is a major factor in determining the type of metal geometry adopted by this type of compound in the solid state. Comparison of the structural results obtained for the hexanuclear clusters [M,Ru,,(CO).,(PPh,),] [M a Cu or Ag] to those reported for the hydrido analogues [MlRu.(~,-H)z(CO)'l(PPh')l] have shown that small changes in the surface ligand set can have marked effects on the metal geometry in the solid state, providing further evidence that the energy differences between the various structural types are small for heteronuclear clusters containing Group IB metal atoms. The X-ray structure analyses of [AulRu.(~-H)(~,-H)(CO)ll{~-Ph,PCH=CHPPhz}] and [Au,Ru,,(~-H)(CO),,{~-PhzPCH,PPhz}(PPhJ)] have enabled the correlation of earlier structural data of related hexanuclear and heptanuclear mixed-metal clusters to account tor the marked differences between the structures of gold-ruthenium clusters with monodentate organophosphines, -compared to those with bidentate phosphine ligands. The X-ray structures ot the isomers [Os,Hz(CCHOEt)(CO).l and [Os.H,(HCCOEt) (CO),] provide a rare exaaple of cluster isomers differing only in the nature of the organo ligands. The structures of the high nuclearity hydrido clusters [Os.HZ(CO)'7- P(OMe),]' [Os7HZ (CO)u], and [Os7HZ (CO)..{MeCaCMe}] have shown nove1 metal fraaeworks, supporting previous observations that when hydrido ligands are present, osmium cluster geo.etries can often be unpredictable in the solid state. The structural characterisation of the large hydrido cluster monoanions [HsOs,o(CO),.]- and [HOs"C(CO)Z7]- have provided evidence for the presence of intersU Ual hydrido ligands. Comparison of these results to those reported for related compounds supports the view that in some cases. interstitial ligands become important in preventing surface ligand. overcrowding.

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No description available.

The high temperature and pressure synthesis of chlorophosphines from an alkene, white phosphorus and phosphorus trichloride yielded both mono- and diphosphine products. Chain and cyclic alkenes, dienes and terpenes were used as substrates forming chain, ring and bicyclic mono- and diphosphines. Many novel, even unique, chlorophosphines were prepared in good yield and characterised using (^31)P and (^13)C NMR, mass spectroscopy and elemental analysis. Simple alkenes readily reacted forming mono- and 1,2-diphosphines. However 1,5-cyclooctadiene formed a 1,4-addition product after double bond conjugation. Butadiene dimerised prior to reaction, generating either a 2,2'-diphospholane or a 1,4-bridged phosphabicyclic alkane in addition to 1,2- and 1,4-diphosphines. Terpenoid dichlorophosphines were prepared but could not be isolated or characterised, because the substrate isomerised under the reaction conditions generating many similar products. Aromatic rings did not react, although the exocyclic double bond of styrene did undergo reaction. Chiral phosphines were readily produced from unsymmetric pro-chiral, alkenes. Chlorophosphines are versatile precursors and, using standard organophosphorus techniques, were readily converted to phosphines, phosphites and other organophosphorus ligands suitable for chelation. Grignard reagents were used to prepare dimethyl derivatives, alcohols reacted with dichlorophosphines producing diethyl-, dimenthyl- or 1,4-butylphosphite derivatives, Piperazine also reacted although the products could not be fully characterised. Electronic properties (^Mn)χ) of the phosphines in manganese carbonyl halide derivatives were measured as a function of the A(_1)carbonyl stretching frequency. Substituent electronegativity was the most important factor in determining the π-acidity. Some dichloropalladium complexes were studied using 3ip NMR, although phosphine impurities complicated spectral interpretation. Iron and molybdenum hydrides reacted with dichlorophosphines to produce some unusual metal-phosphine compounds.

The electronic structure of substituted cyclic phosphazenes has been investigated using Density Functional Theory (DFT) and Natural Bond Order (NBO) analysis. NBO analysis shows covalent, ionic and negative hyper-conjugation interactions all contribute to the electronic structure of cyclic phosphazenes. The geometric and electronic structural changes that occur when transition metals are coordinated to the nitrogen atom of the phosphazene ring have been analyzed using the NBO model. The bonding of transition metal ions with the ring nitrogen on the phosphazene was investigated by modeling hexakis(2-pyridyloxy)cyclotriphosphazene, hexakis(4-methyl-2-pyridyloxy)cyclotriphosphazene and octakis(2- pyridyloxy)cyclotetraphosphazene with different metal ions (Co(II), Ni(II), Cu(II), Zn(II)) in their assorted configurations with DFT as implemented in the Gaussian03 package. First-row transition metals bind to the phosphazene ring with simple s donor behaviour via the ring nitrogen. The lengthening of the PN bonds adjacent to the coordinated metal centre is a result of electron density being removed from the PN bonding orbitals and going into the 4s orbital of the metal ion. Investigating the pyridine substituents on the phosphazene ring showed that these can affect the PN bonds in a similar fashion, although weaker, to the transition metals. This effect is the result of the pyridine nitrogen lone pair affecting the negative hyperconjugation component of the PN bond. Coupling between two metal atoms coordinated to the phosphazene ring was investigated by DFT calculations, which showed molecular orbitals in both the tricyclic and tetracyclic phosphazene capable of providing an ‘electron density bridge’ between the metal centres. These results are in accord with ESR and magnetic susceptibility results, which can be explained in terms of weak antiferromagnetic coupling between metal ions. The cyclic phosphazenes are model compounds for polyphosphazenes and the results obtained from this work will provide insight into the electronic properties of this important class of inorganic polymers.

The development of new unconventional routes to small functionalized fluorocarbons (FCs) continues to be an attractive target due to the high utility of FCs in a broad range of applications, including their use as refrigerants, solvents, and surfactants. With the phasing out of hydrofluoroalkanes as refrigerants, there is a growing interest in the synthesis of new hydrofluoroolefins (HFOs), which are known to have significantly reduced global warming potential relative to hydrofluoroalkanes. Currently, energy-intensive conditions and toxic starting materials are typically necessary for their syntheses, making these processes environmentally problematic. The approach we have proposed for alternative ‘greener’ methods for functionalized FC production targets a transition metal-catalyzed synthesis involving the formation of metallacyclic intermediates through the oxidative cycloaddition of simple fluorinated alkenes, e.g., tetrafluoroethylene (TFE) and trifluoroethylene (TrFE), at low-valent nickel centres. There is precedent for the generation of short fluoroalkyl chain (C4-C6) compounds through homogeneous catalysis. For example, Baker et al. showed that you could catalytically hydrodimerize two molecules of tetrafluoroethylene (TFE) or one molecule of TFE with one molecule of ethylene using low valent Ni catalysts and π-acidic monodentate ancillary ligands, affording octafluorobutane and 1,1,2,2-tetrafluorobutane respectively. The objective of this Thesis is to further the state-of-the-art in fluoroorganometallic chemistry by gaining a deeper understanding of transition metal fluoroalkyl complexes as a function of metal-fluoroalkyl and carbon-fluorine bond reactivity. The over-arching goal is to harness said reactivity for the synthesis of new value-added fluorocarbons. Due to the robust nature of carbon-fluorine and metal-fluoroalkyl bonds in transition metal fluoroalkyl complexes, intensive conditions are often necessary to achieve any reactivity. Recently, bifunctional ligands have proven to be useful at effecting challenging transformations through unconventional ligand-assisted substrate activation pathways. Chapters 2 and 3 herein explore the use of a bidentate phosphinothiol ligand in the context of perfluoronickelacyclopentane reactivity. Synthetic approaches for the formation of phosphinothioether- and phosphinothiolate-supported perfluorometallacycles are outlined along with ensuing reactivity studies, including examples of Cα-F, Cβ-F, and Ni-Cα bond activation. Furthermore, a metal-mediated synthesis of functionalized FC, (E)-1,2,3,3,4,4-hexafluoro-1-butene, is provided. Chapter 4 sheds light on the comparatively underdeveloped chemistry of fluorinated nickelacycles generated from TrFE. A systematic study of monodentate phophine and phosphite ligand effects on metallacyclopentane regio-/stereochemistry is presented. The behaviour of the generated hydrofluoronickelacyclopentanes in the presence of acidic additives allows for a direct analogy to be made regarding the effects of the extent of metallacycle fluorination on C-F and Ni-C activation. In search of new approaches to novel functionalized FC synthesis, Chapter 5 will re-visit the use of bifunctional ligands, investigating the formation and reactivity of new perfluoronickelacycles featuring [P,NH] and [P,Nˉ] bidentate ligands. Finally, Chapter 6 summarizes the findings of this Thesis and discusses some of the future opportunities that will build on this work. The increased understanding of the stoichiometric systems presented herein will be directly important to the development of nickel-catalyzed routes to HFOs. As the demand for new “greener” refrigerants and propellants increases, the synthesis of small-molecule functionalized FCs using transition metal catalysis and waste fluorinated feedstocks can offer a mild, atom economical approach to new, unique candidates that will be appealing to industrial partners.

<p dir="ltr">This work describes the electronic and geometric structure of molecular metal complexes involving different ligand environments. These include the Cu-redox active ligand reduction series, Tp*₂U imido and anilido transformations, Lewis base activation by Tp*₂U, silyluranium synthesis and reactivity, and electrochemistry of plutonyl.</p>