High H Solubility of Perfluorocarbon Solvents and Their Use in Reversible Polarization Transfer from -Hydrogen.

This research uses perfluorocarbons (PFCs) as effective alternatives to traditional toxic solvents in reversible -hydrogen-induced polarization (PHIP) for NMR signal enhancement. Hydrogen solubility in PFCs is shown here to be an order of magnitude higher than in typical organic solvents by determination of Henry's constants. We demonstrate how this high H solubility enables the PFCs to deliver substantial polarization transfer from -hydrogen, achieving up to 2400-fold signal gains for H NMR detection and 67,000-fold (22% polarization) for N NMR detection at 9.

Solid/Gas Reactivity of an Ir(I) Methylidene Complex.

stabilization of known, but solution unstable, methylidene complex [Ir(Bu-PONOP)(=CH)][BAr ] allows single-crystal to single-crystal solid/gas reactivity associated with the {Ir=CH} group to be studied. Addition of H results in [Ir(Bu-PONOP)(H)][BAr ]; exposure to CO forms iridium(I) carbonyl [Ir(Bu-PONOP)(CO)][BAr ], and reaction with NH gas results in the formation of methylamine complex [(Bu-PONOP)Ir(NHMe)][BAr ] via an aminocarbene intermediate. Periodic density functional theory and electronic structure analyses confirm the Ir=CH bond character but with a very low barrier to rotation around the Ir=CH bond.

The ubiquitous P(-tol) ligand promotes formation of catalytically-active higher order palladacyclic clusters.

The Herrmann-Beller catalyst, Pd[(C^P)(μ-OAc)], is readily formed by reaction of the cyclic trimer of 'Pd(OAc)' with P(-tol). In the presence of hydroxide, Pd(C^P)(μ-OAc)] converts to [Pd(C^P)(μ -OH)]. Here, we report how this activated Pd precatalyst species, and related species, serve as a conduit for formation of higher order Pd clusters containing multiple cyclopalladated P(-tol) ligands.

Ligand-to-metal charge transfer facilitates photocatalytic oxygen atom transfer (OAT) with -dioxo molybdenum(vi)-Schiff base complexes.

Systems incorporating the -Mo(O) motif catalyse a range of important thermal homogeneous and heterogeneous oxygen atom transfer (OAT) reactions spanning biological oxidations to platform chemical synthesis. Analogous light-driven processes could offer a more sustainable approach. The -Mo(O) complexes reported here photocatalyse OAT under visible light irradiation, and operate a non-emissive excited state with substantial ligand-to-metal charge-transfer (LMCT) character, in which a Mo[double bond, length as m-dash]O π*-orbital is populated transfer of electron density from a chromophoric salicylidene-aminophenol (SAP) ligand.

Revealing the Hidden Complexity and Reactivity of Palladacyclic Precatalysts: The P(-tolyl) Ligand Enables a Cocktail of Active Species Utilizing the Pd(II)/Pd(IV) and Pd(0)/Pd(II) Pathways for Efficient Catalysis.

The ligand, P(-tolyl), is ubiquitous in applied synthetic chemistry and catalysis, particularly in Pd-catalyzed processes, which typically include Pd(OAc) (most commonly used as Pd(OAc)) as a precatalyst. The Herrmann-Beller palladacycle [Pd(C^P)(μ-OAc)] (where C^P = monocyclopalladated P(-tolyl)) is easily formed from reaction of Pd(OAc) with P(-tolyl). The mechanisms by which this precatalyst system operates are inherently complex, with studies previously implicating Pd nanoparticles (PdNPs) as reservoirs for active Pd species in arylative cross-coupling reactions.