PhD Project - PhD in Chemistry: Single or Double? A Radical Approach to Catalysis - Competitive EPSRC funded post at Cardiff University, listed on FindAPhD.com

We are hiring a Postdoc! If you have PhD/PDRA experience in air sensitive, platinum group metal organometallics, are interested in using this expertise in single-crystal SMOM synthesis and reactivity,...

Advanced fibers enable the fabrication of structures and composites for applications reliant on lightweight, oxidation resistant, mechanically strong, and electrically insulating materials, e.g. in all forms of land, air, and space transportation and in applications within extreme environments. Hexagonal boron nitride (h-BN) fibers harness these advantages, and in addition, offer ultra-high-strength-to-weight ratio and low density. Yet, existing precursors for polymer-derived BN fibers are limited to insoluble and air/moisture sensitive polyborazylenes, hindering fiber production at scale. In this contribution, we report a reliable, controllable, and scalable synthesis methodology for producing pure micro- and nano-h-BN fibers, offering a competitive alternative to NASA’s energy-intensive h-BN nanotubes production. The single-source precursor, N-methyl polyaminoborane (PMeAB), plays a pivotal role in this process. The catalytic, and scalable, synthesis of PMeAB with controlled molecular weights (Mw = 110,500–290,500 g·mol−1) enables the production of h-BN fibers by electrospinning method and thermolysis under ammonia. PMeAB molecular weight and concentration were identified as key factors dictating the viscosity and surface tension, and thus influencing the overall spinnability of the PMeAB solution. We reveal that the subsequent formation of a cross-linked intermediate during PMeAB thermolysis is essential to retain the fibrous morphology during the conversion to h-BN fibers. Comprehensive characterization demonstrated the purity and homogeneity of the h-BN fibers, with ~ 97 at.% of B and N contents combined throughout the fiber body. This newly disclosed route to h-BN fibers offers a route to potentially valuable multifunctional filler material for advanced lightweight composites suitable for applications in extreme environments.

The perfluoropinacol borate-based anion [B(O2C2(CF3)4)2]−, [FPB]–, is developed as a weakly coordinating anion for single-crystal to single-crystal organometallic solid/gas reactivity, resulting in the isolation and characterization (including periodic DFT and IGMH analysis) of the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(exo-η2η2-norbornane)][FPB]. The synthetically useful solvent-free Na+ salt, Na[FPB], and oxonium acid [H(OEt2)2][FPB] are also reported.

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Project opportunity - Digital and Flow Materials Chemistry for Metal-Organic Frameworks Production at the University of Leeds

The reactivity of an unsupported phosphinidene oxide, BnArNP═O (Bn = benzyl; Ar = bulky aryl group), as the electrophilic partner in Wittig reactions with ylides is described. Reactions with methylene-triphenylphosphorane (H2C═PPh3) and ethylidene-triphenyl-phosphorane (HMeC═PPh3), proceed as expected, giving rise to the phosphaalkene metathesis products and triphenylphosphine oxide. This reaction can be extended to other ylides such as N-(triphenylphosphoranylidene)methanamine (MeN═PPh3), to afford an aminoiminophosphane BnArNP═NMe. In these reactions the phosphinidene oxide plays the role of an electrophile, which would typically be the remit of an organic carbonyl in classical Wittig reactions. Further mechanistic insight into such transformations can be gained by altering the nature of the phosphorus-ylide. Upon reacting BnArNP═O with H2C═PMe3 (which possesses a smaller, more Lewis basic, phosphine) an alternative product is formed. This transformation supports the formation of a betaine intermediate that subsequently undergoes hydrogen-migration to afford an oxidized phosphorus(V) compound related to phosphorus acid.

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The known complex [Ir(tBu-PONOP)MeH][BArF4], 1[BArF4] [tBu-PONOP = κ3-2,6-(tBu2PO)2C5H3N); ArF = 3,5-(CF3)2(C6H3); J. Am. Chem. Soc. 2009, 131, 8603], is a robust precursor for in crystallo single-cry...

In this study, we have employed high-resolution charge density (HRCD) techniques using X-ray diffraction data collected at 10 K to reanalyze the intermetallic electron density topologies of two repres...

Posted 9:23:25 PM. The Department of Chemistry at Queen's University invites applicants for a tenure-track faculty…See this and similar jobs on LinkedIn.

The catalytic transformation of glycerol (GLY) using [(iPr2PNHP)Ir(COD)]Cl [iPr2PNHP = κ3-(iPr2PCH2CH2)2NH] affords hydrogen and lactic acid (LA), trapped as its sodium salt (Na[LA]) with high yield (96%) and selectivity (99%) in the presence of an equivalent of in situ generated NaOEt at 140 °C within 4 h. A diminution in activity was observed when the PNMeP ligand was used instead of PNHP, or when Cl– was replaced by [BArF4]−. An Ir to Rh substitution also resulted in poor activity. Kinetic studies show a first-order dependence of the initial rate of turnovers on the concentrations of [(iPr2PNHP)Ir(COD)]Cl, NaOEt, and glycerol. An outer-sphere mechanism does not explain the activity of [(iPr2PNMeP)Ir(COD)]Cl, and DFT studies support an inner-sphere mechanism, with oxidative addition of glycerol to the 14-electron intermediate [(iPr2PNHP)Ir]Cl determined as the rate-determining step (RDS). A kH/kD of 2.7 obtained with glycerol-d8 shows a major contribution from O–H activation in the RDS. The kinetics of the reaction become favorable (ΔG140⧧ = 27.01 kcal/mol) when one of the terminal O–H’s of glycerol is hydrogen bonded to the N–H of the pincer backbone, in contrast to cases where no hydrogen bonds are invoked (ΔG140⧧ = 31.96 kcal/mol) or are not possible [(iPr2PNMeP)Ir]Cl (ΔG140⧧ = 30.36 kcal/mol).