C-H Borylation Catalysis of Heteroaromatics by a Rhenium Boryl Polyhydride
Liam J. Donnelly, Teresa Faber, Carole A. Morrison, Gary S. Nichol, Stephen P. Thomas and Jason B. Love
ACS Catalysis, 2021, accepted
ABSTRACT: Transition metal complexes bearing metal-boron bonds are of particular relevance to catalytic C-H borylation reactions, with iridium polyboryl and polyhydrido-boryl complexes the current benchmark catalysts for these transformations. Herein, we demonstrate that polyhydride boryl phosphine rhenium complexes are accessible and catalyze the C-H borylation of heteroaromatic substrates. Reaction of [K(DME)(18-c-6)][ReH4(Bpin)(η2-HBpin)(κ2-H2Bpin)] 1 with 1,3-bis(diphenylphosphino)propane (dppp) produced [K(18-c-6)][ReH4(η2-HBpin)(dppp)] 2 through substitution of two equivalents of HBpin, and protonation of 2 formed the neutral complex [ReH6(Bpin)(dppp)] 3. Combined X-ray crystallographic and DFT studies show that 2 is best described as a s-borane complex, whereas 3 is a boryl complex. Significantly, the boryl complex 3 acted as a catalyst for the C(sp2)-H borylation of a variety of heteroarenes (14 examples including furan, thiophene, pyrrole and indole derivatives) and displayed similar reactivity to the iridium analogues.
Simple Amides and Amines for the Synergistic Recovery of Rhodium from Hydrochloric Acid by Solvent Extraction
Andrew Carrick, Euan Doidge, Alexander Bouch, Gary Nichol, Jane Patrick, Emma Schofield, Carole Morrison, Jason Love
Chem. Eur. J., 2021, DOI:10.1002/chem.202100630
A synergistic combination of a simple primary amine (LA) and a simple primary amide (L1) is shown to extract rhodium from hydrochloric acid. A range of experimental and computational techniques are used to elucidate the structures of two different complexes in the organic phase; the ion-pair [HLA]3[RhCl6] and the amide complex [HLA]2[RhCl5(L1)]. In the latter complex, the amide is tautomerized to its enol form and coordinated through the nitrogen atom.
Recycling copper and gold from e-waste by a two-stage leaching and solvent extraction process
M. Dhanunjaya Rao, Kamalesh K. Singh, Carole A. Morrison, and Jason B. Love
Separ. Pur. Technol., 2021, 10.1016/j.seppur.2021.118400
The recycling of metals such as gold and copper from discarded end-of-life electronic waste (e-waste or WEEE) is an important aspect to the development of environmentally benign manufacturing processes that exhibit circularity in materials flow. Global e-waste production is increasing at a 3-5 % rate, so it is concerning that only 30 % is recycled using regulated processes. We present here a new hydrometallurgical route for the technically feasible recycling of copper and gold from waste printed circuit boards (WPCBs) of mobile phones. This process comprises the liberation of the metallic fractions from downsized WPCBs, a two-stage acid leaching process to provide a bulk separation of copper and gold from the other metals present, and subsequent purification of the copper and gold-containing solutions by solvent extraction using highly selective phenolic oxime and amide extractants, respectively. Complete dissolution of the base metals was seen using 3 M nitric acid at 30 °C and the selective separation of copper from this leach liquor was achieved by solvent extraction using ACORGA M5640 dissolved in kerosene. The residues from base-metal leaching were treated with a mixture of 3 M sulfuric acid and 3 M sodium bromide at 70 °C, resulting in greater than 95 % gold dissolution. The selective separation of gold from this precious metal leachate was achieved by solvent extraction using 0.1 M primary amide extractant dissolved in toluene. This process delivers complete copper and gold recycling from WPCBs under relatively benign laboratory conditions and represents a proof of concept for liberating valuable and critical metals back into active service from end-of-life electronic devices.
Synthesis and complexes of a constrained-cavity Schiff-base dipyrrin macrocycle
Karlotta van Rees and Jason B. Love
Dalton Transactions, 2021, DOI: 10.1039/D1DT00175B
A new constrained-cavity [1+1] Schiff-base dipyrrin macrocycle comprising an N4 donor-pocket has been synthesised by spontaneous oxidation and in-situ crystallisation. Access to Fe(II) and Zn(II) complexes is achieved by salt elimination reactions of the lithium salt. All compounds have been characterised by NMR and UV-vis spectroscopy, X-ray crystallography, and DFT analysis.
Shibo Shao, Jialin Yu, Jason B. Love, Xianfeng Fan
An economic approach to produce iron doped TiO2 nanorods from ilmenite for photocatalytic applications
Journal of Alloys and Compounds, 2020, DOI:10.1016/j.jallcom.2020.158388
Abstract: Titanium dioxide (TiO2) is one of the most promising photocatalytic materials, but its practical applications are always limited since it could be only excited in the UV and has low photocatalytic efficiency due to its wide band gap and fast recombination rate. To overcome these problems, transition metals have been used as dopants to improve the photocatalytic performance of titanium dioxide. However, doping by hydrothermal, sol-gel or other synthetic pathways in the catalyst synthesis in previous investigations which are difficult to scale-up for mass production. Herein, ilmenite (FeTiO3), the most abundant titanium mineral was used as the raw material to produce iron-doped titanium oxide nanorods by an economic acid treatment approach. Compared with commercial titanium oxide nanomaterials, the photocatalytic performance for Rhodamine B (RHB) degradation of as-prepared materials were significantly improved and could be activated by visible light irradiation. The results from characterization also shows the band gap and recombination rate are modified by the iron dopant. This work provides a possible method which can significantly reduce the cost for producing iron doped TiO2 in high yield for photocatalytic application
Profs. Jason Love, Carole Morrison, and Bryne Ngwenya with PhD student Luke Kinsman and UG students Rosa Crevecoeur and Amrita Singh-Morgan have won the 2020 Anders Gustav Ekeberg Prize for their paper on tantalum recycling https://www.mdpi.com/2075-4701/10/3/346.
More information can be found at https://www.tanb.org/view/ekeberg-prize-2020—winner
Synthesis and Structures of Anionic Rhenium Polyhydride Complexes of Boron-Hydride Ligands and their Application in Catalysis
Chem. Sci., 2020, DOI: 10.1039/d0sc03458d
The rhenium complex, [K(DME)(18-c-6)][ReH4(Bpin)(h2-HBpin)(k2-H2Bpin)] 1, comprising hydride and boron ligands only, has been synthesized by exhaustive deoxygenation of the commercially available perrhenate anion (ReO4−) with pinacol borane (HBpin). The structure of 1 was analysed by X-ray crystallography, NMR spectroscopy, and DFT calculations. While no hydrides were located in the X-ray crystal structure, it revealed a trigonal arrangement of pinacol boron ligands. Variable-temperature NMR spectroscopy supported the presence of seven hydride ligands but further insight was hindered by the fluxionality of both hydride and boron ligands at low temperature. Further evaluation of the structure by Ab Initio Random Structure Searching (AIRSS) identified the presence of hydride, boryl, s-borane, and dihydroborate ligands. This complex, either isolated or prepared in situ, is a catalyst for the 1,4-hydroboration of N-heteroaromatic substrates under simple operating procedures. It also acts as a reagent for the stoichiometric C-H borylation of toluene, displaying high meta regioselectivity in the borylated products. Reaction of 1 with 9-BBN resulted in HBpin substitution to form the new anionic tetra(dihydroborate) complex [K(DME)(18-c-6)][Re(k2-H-9-BBN)4] 4 for which the hydride positions were clearly identified by X-ray crystallography. The method used to generate these isolable yet reactive boron-hydride complexes is direct and straightforward and has potential utility for the exploitation of other metal oxo compounds in operationally simple catalytic reactions.
Reducing the Competition: A Dual-Purpose Ionic Liquid for the Extraction of Gallium from Iron Chloride Solutions
Molecules, 2020, 25, 4047; doi:10.3390/molecules25184047
The separation of gallium from iron by solvent extraction from chloride media is challenging because the anionic chloridometalates, FeCl4− and GaCl4−, display similar chemical properties. However, we report here that the selective separation of gallium from iron in HCl solution can be achieved using the dual-purpose ionic liquid methyltrioctylammonium iodide in a solvent extraction process. In this case, the reduction of Fe3+ to Fe2+ by the iodide counterion was found to inhibit Fe transport, facilitating quantitative Ga extraction by the ionic liquid with minimal Fe extraction from 2 M HCl.
Jason provides some comments on e-waste recycling by Mint Innovation in The Guardian.
Also commentary and analysis on the Dotun Adebayo Show on BBC Radio 5Live