On the mercuration, palladation, transmetalation and direct auration of a C^N^C pincer ligand

The C^N^C ligand 2,6-bis(2,3-dialkoxyphenyl)pyridine forms dimercury and orthopalladated complexes, both of which may be transmetallated to gold(iii) complexes; the gold complexes may also be formed directly in a Rh(iii)-catalysed process, hence it is possible to circumvent the use of organomercury intermediates in the synthesis of this important class of compound

Enhancing the Air Stability of Dimolybdenum Paddlewheel Complexes : Redox Tuning through Fluorine Substituents

The optical and electrochemical properties of quadruply bonded dimolybdenum paddlewheel complexes (Mo2PWCs) make them ideal candidates for incorporation into functional materials or devices, but one of the greatest bottlenecks for this is their poor stability toward atmospheric oxygen. By tuning the potential at which the Mo2 core is oxidized, it was possible to increase the tolerance of Mo2PWCs to air. A series of homoleptic Mo2PWCs bearing fluorinated formamidinate ligands have been synthesized and their electrochemical properties studied. The oxidation potential of the complexes was tuned in a predictable fashion by controlling the positions of the fluorine substituents on the ligands, as guided by a Hammett relationship. Studies into the air stability of the resulting complexes by multinuclear NMR spectroscopy show an increased tolerance to atmospheric oxygen with increasingly electron-withdrawing ligands. The heteroleptic complex Mo2(DFArF)3(OAc) [where DFArF = 3,5-(difluorophenyl)formamidinate] shows remarkable tolerance to oxygen in the solid state and in chloroform solutions. Through the employment of easily accessible ligands, the stability of the Mo2 core toward oxygen has been enhanced, thereby making Mo2PWCs with electron-withdrawing ligands more attractive candidates for the development of functional materials

Gold(III), Mercury(II), and Palladium(II) Complexes of a Series of Isomeric Bis(mono- and dialkoxyphenyl)pyridines : Introduction of Gold through Transmetalation and Catalysis

A series of isomeric bis-2,6-(monoalkoxyphenyl)pyridine and bis-2,6-(dialkoxyphenyl)pyridine ligands were synthesized and characterized. In order to prepare their chlorogold(III) complexes, intermediate chloromercury(II) complexes were first prepared, but unlike observations from previous studies where they were obtained impure and at best in moderate yield, here pure complexes were synthesized, many in rather high yields. Depending on the substitution pattern of the alkoxy chains on the ligands, mono- and/or dimercurated complexes were obtained, characterized by 1H, 13C{1H}, and 199Hg NMR spectroscopy as well as, in several cases, by X-ray crystallography. Factors that may explain this unusual reactivity are discussed. In most cases, transmetalation to the related chlorogold(III) complex proceeded smoothly, although lower yields were obtained when starting from doubly mercurated precursors. Prompted by the propensity of these ligands to mercurate, attempts were made to effect direct auration, but none was successful. However, dimeric, orthometalated complexes of palladium(II) could be prepared and were also amenable to transmetalation to the chlorogold(III) complex, providing for a mercury-free synthesis

Chemical shift tensors as a direct probe in metal-carbon bonding

Chemical shift tensors, the three-dimensional representation of chemical shift, have been recovered for a range of organometallic complexes through the collection of solid-state (SS) nuclear magnetic resonance (NMR) spectroscopy. Quantum chemical calculations using density functional theory (DFT) have also been performed to predict the chemical shift tensors. The chemical shift interaction is encoded with electronic information and can be decomposed into two contributions: diamagnetic shielding (d dia) and paramagnetic shielding (d para). dpara dominates the observed change in shielding in large nuclei and is associated with magnetically coupled transitions between frontier molecular orbitals (FMOs). In this thesis, chemical shift tensors have been used to analyse the FMOs of organometallic compounds with a focus on metal-carbon bonding. The fluorine effect has been explored on ruthenium alkynyl and vinylidene moieties. The metal-bound carbon (C a) undergoes a large change in isotropic chemical shift between fluorinated and non-fluorinated moieties: d C ≈ 380 vs d C ≈ 350. This has been shown to be a 236 ppm deshielding shift in the dz tensor associated with the HOMO→LUMO transition. The increased deshielding arises from the contraction of the HOMO→LUMO energy and an improved magnetic coupling. The opposite trend has been explored in C between fluorinated and non-fluorinated alkynyl moieties: d C ≈ 36 vs d C ≈ 120. A 100 ppm shielding shift in the dx and dy tensors is responsible. Inclusion of fluorine decreases the energy of the sigma-bonding orbital reducing the deshielding. High resolution 195Pt SS NMR spectra have been recorded. 103Rh solid-state NMR spectra were too technically demanding to record. Platinum chemical shift tensors have been used as a model for exploring the FMOs of metal complexes directly at the metal. This has been expanded to study a range of rhodium complexes relevant to hydroformylation looking at the effect of pnictogen and phosphine bite angle on 103Rh tensors

Conceiving the records continuum in Canada and the United States

This thesis surveys the efforts made by Canadian and American records administrators, both records managers and archivists, to ensure that records are created, received, stored, used, preserved, and disposed of in a manner which is both efficient and effective. Beginning with the French Revolution and continuing to modern times, it investigates how approaches in North American archival thinking, government records programs, and applicable records legislation were often flawed because of fundamental misconceptions of the nature of the records themselves. The thesis traces how the most widely accepted approach for administering records, which called for the division of responsibilities amongst records professionals according to the records' "life status" — active, semi-active, or inactive — was incorrect because it was not compatible with the reality that records exist as a conceptual whole and are best administered in a manner which reflects this realization. The records, which should have been managed as a coherent and complete fonds of an institution, suffered from these divisions which had eventually led to the evolution of separate records occupations: those who looked after active records, called records managers, and those who handled inactive ones, labelled archivists. What was required was an "integrated" or "unified" approach such as that articulated by the Canadian archivist Jay Atherton. Like others, he called for the management of records in a manner which reflected the singular nature of the records, an approach which did not make arbitrary divisions where none existed, but instead viewed records from a wider and more complete perspective. Support for this approach amongst some records administrators was precipitated by a number of factors, not the least of which were the demands of handling information in modern society. The thesis concludes by examining what is required for the integrated ideas to be implemented as part of a practical model in today's institutions. It suggests that for the best results to be achieved, records administrators will have to learn to work with others in related information professions, or risk losing the ability to make valid contributions in the modern information age.Arts, Faculty ofLibrary, Archival and Information Studies (SLAIS), School ofGraduat

Hydrogen-Halogen Exchange of Phosphines for the Rapid Formation of Cyclopolyphosphines

The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton “donor phosphine” makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP)5 have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (Ar2P)2 and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP)n, where n = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac)3 suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction

Erratum : Correction: On the mercuration, palladation, transmetalation and direct auration of a C^N^C pincer ligand (Dalton transactions (Cambridge, England : 2003) (2023) 52 4 (872-876))

Correction for 'On the mercuration, palladation, transmetalation and direct auration of a C^N^C pincer ligand' by Alice Jane McEllin et al., Dalton Trans., 2023, 52, 872-876, https://doi.org/10.1039/d2dt04114f

The IDOL–UBE2D complex mediates sterol-dependent degradation of the LDL receptor

We previously identified the E3 ubiquitin ligase IDOL as a sterol-dependent regulator of the LDL receptor (LDLR). The molecular pathway underlying IDOL action, however, remains to be determined. Here we report the identification and biochemical and structural characterization of an E2–E3 ubiquitin ligase complex for LDLR degradation. We identified the UBE2D family (UBE2D1–4) as E2 partners for IDOL that support both autoubiquitination and IDOL-dependent ubiquitination of the LDLR in a cell-free system. NMR chemical shift mapping and a 2.1 Å crystal structure of the IDOL RING domain–UBE2D1 complex revealed key interactions between the dimeric IDOL protein and the E2 enzyme. Analysis of the IDOL–UBE2D1 interface also defined the stereochemical basis for the selectivity of IDOL for UBE2Ds over other E2 ligases. Structure-based mutations that inhibit IDOL dimerization or IDOL–UBE2D interaction block IDOL-dependent LDLR ubiquitination and degradation. Furthermore, expression of a dominant-negative UBE2D enzyme inhibits the ability of IDOL to degrade the LDLR in cells. These results identify the IDOL–UBE2D complex as an important determinant of LDLR activity, and provide insight into molecular mechanisms underlying the regulation of cholesterol uptake