Palladium Bisphosphine Monoxide Complexes: Synthesis, Scope, Mechanism, and Catalytic Relevance.

Recent studies in transition metal catalysis employing chelating phosphines have suggested a role for partial ligand oxidation in formation of the catalytically active species, with potentially widespread relevance in a number of catalytic systems. We examine the internal redox reaction of Pd(bisphosphine)X (X = Cl, OAc, ) complexes to reveal previously underexplored aspects of bisphosphine monoxides (BPMOs), including evaluation of ligand structure and development of general reaction conditions to access a collection of structurally diverse BPMO precatalysts based on organopalladium oxidative addition complexes. In particular, a series of Pd(BPMO)(R)(X) (R = aryl, alkyl; X = I, Br) oxidative addition complexes bearing 24 different BPMO ligands were characterized by NMR and X-ray crystallography.

Cosmological inflation and meta-empirical theory assessment.

I apply Dawid's Meta-Empirical Assessment (MEA) methodology to the theory of cosmological inflation. I argue that applying this methodology does not currently offer a compelling case for ascribing non-empirical confirmation to cosmological inflation. In particular, I argue that despite displaying strong instances of Unexpected Explanatory Coherence (UEA), it is premature to evaluate the theory on the basis of the No Alternatives Argument (NAA).

Methodological reflections on the MOND/dark matter debate.

The paper re-examines the principal methodological questions, arising in the debate over the cosmological standard model's postulate of Dark Matter vs. rivalling proposals that modify standard (Newtonian and general-relativistic) gravitational theory, the so-called Modified Newtonian Dynamics (MOND) and its subsequent extensions. What to make of such seemingly radical challenges of cosmological orthodoxy? In the first part of our paper, we assess MONDian theories through the lens of key ideas of major 20th century philosophers of science (Popper, Kuhn, Lakatos, and Laudan), thereby rectifying widespread misconceptions and misapplications of these ideas common in the pertinent MOND-related literature.

Edge Modes and Dressing Fields for the Newton-Cartan Quantum Hall Effect.

It is now well-known that Newton-Cartan theory is the correct geometrical setting for modelling the quantum Hall effect. In addition, in recent years edge modes for the Newton-Cartan quantum Hall effect have been derived. However, the existence of these edge modes has, as of yet, been derived using only orthodox methodologies involving the breaking of gauge-invariance; it would be preferable to derive the existence of such edge modes in a gauge-invariant manner.

An Efficient Synthesis of Geminal-Dialkyl Dienes for Olefin Metathesis Polymerization.

A robust synthesis of -dialkyl acyclic diene monomers has been developed. This route is scalable, flexible, and biorenewable, allowing for the production of a wide range of diene monomers of different lengths and different -dialkyl substitution starting from unsaturated esters derived from seed oils. The metathesis polymerization of these monomers and the hydrogenation of the resulting polyolefins leads to telechelic -dialkyl polyethylenes, which can be used as elastomers in the synthesis of polyurethanes and other block polymers.

Standard Sirens as a Novel Probe of Dark Energy.

Cosmological models with a dynamical dark energy field typically lead to a modified propagation of gravitational waves via an effectively time-varying gravitational coupling G(t). The local variation of this coupling between the time of emission and detection can be probed with standard sirens. Here we discuss the role that lunar laser ranging (LLR) and binary pulsar constraints play in the prospects of constraining G(t) with standard sirens.

Examining the Effects of Monomer and Catalyst Structure on the Mechanism of Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization.

The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a monomer-dependent mechanism for polymerization of norbornene monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating monomers and determining the effect of chelation on the polymerization mechanism.

Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells.

Fluoride ion batteries are potential "next-generation" electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion-conducting electrolytes are known only in the solid state. We report a liquid fluoride ion-conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents.

High-spatial-resolution mapping of catalytic reactions on single particles.

The critical role in surface reactions and heterogeneous catalysis of metal atoms with low coordination numbers, such as found at atomic steps and surface defects, is firmly established. But despite the growing availability of tools that enable detailed in situ characterization, so far it has not been possible to document this role directly. Surface properties can be mapped with high spatial resolution, and catalytic conversion can be tracked with a clear chemical signature; however, the combination of the two, which would enable high-spatial-resolution detection of reactions on catalytic surfaces, has rarely been achieved.

Phosphonium Formation by Facile Carbon-Phosphorus Reductive Elimination from Gold(III).

A recent trend in homogeneous gold catalysis has been the development of oxidative transformations relying on Au(I)/Au(III) redox cycling. Typically, phosphine-supported Au(I) precatalysts are used in the presence of strong oxidants to presumably generate phosphine Au(III) intermediates. Herein, we disclose that such Au(III) complexes can undergo facile C(aryl)-P reductive elimination to afford phosphonium salts, which have been spectroscopically and crystallographically characterized.

Photoinitiated oxidative addition of CF3I to gold(I) and facile aryl-CF3 reductive elimination.

Herein we report the mechanism of oxidative addition of CF3I to Au(I), and remarkably fast Caryl-CF3 bond reductive elimination from Au(III) cations. CF3I undergoes a fast, formal oxidative addition to R3PAuR' (R = Cy, R' = 3,5-F2-C6H4, 4-F-C6H4, C6H5, 4-Me-C6H4, 4-MeO-C6H4, Me; R = Ph, R' = 4-F-C6H4, 4-Me-C6H4). When R' = aryl, complexes of the type R3PAu(aryl)(CF3)I can be isolated and characterized.

Exceptionally fast carbon-carbon bond reductive elimination from gold(III).

Reductive elimination of carbon-carbon bonds occurs in numerous metal-catalysed reactions. This process is well documented for a variety of transition metal complexes. However, carbon-carbon bond reductive elimination from a limited number of Au(III) complexes has been shown to be a slow and prohibitive process that generally requires elevated temperatures.

Bis(η-naphthalene)-molybdenum(0).

The title compound, [Mo(C(10)H(8))(2)], was prepared from the naphthalene radical anion and MoCl(4)(thf)(2) (thf is tetra-hydro-furan). In the crystal, the mol-ecule is located on an inversion center. The Mo atom is equally disordered over two positions; the range of Mo-C distances is 2.