Activation of carbon dioxide and carbon disulfide by a scandium N-heterocyclic carbene complex

A Sc NHC complex readily activates three equivalents of CO2 showing ‘Frustrated Lewis Pair’ type reactivity with each metal–carbene bond, but whilst CS2 is also activated by the labile carbenes, no metal involvement is observed. Graphical abstract: Activation of carbon dioxide and carbon disulfide by a scandium N-heterocyclic carbene comple

Synthesis of Well-Defined, Surfactant-Free Co₃O₄ Nanoparticles:The Impact of Size and Manganese Promotion on Co₃O₄ Reduction and Water Oxidation Activity

Abstract: A surfactant-free synthetic route has been developed to produce size-controlled, cube-like cobalt oxide nanoparticles of three different sizes in high yields. It was found that by using sodium nitrite as salt-mediating agent, near-quantitative yields could be obtained. The size of the nanoparticles could be altered from 11 to 22 nm by changing the cobalt concentration and reaction time. These surfactant-free nanoparticles form ideal substrates for facile deposition of further elements such as manganese. The effect of size of the cobalt oxide nanoparticles and the presence of manganese on the reducibility of cobalt oxide to metallic cobalt was investigated. Similarly, the effect of these parameters was investigated with a visible light promoted water oxidation system with cobalt oxide as catalyst, together with [Ru(bpy) 3] 2+ light harvester dye and an electron acceptor. Graphical Abstract: A novel surfactant-free synthetic route has been developed to produce size-controlled, cube shaped cobalt oxide nanoparticles in high yields. [Figure not available: see fulltext.]. </p

Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N-H and C-H bonds

The reactivity of a series of organometallic rare earth and actinide complexes with hemilabile NHC-ligands towards substrates with acidic C–H and N–H bonds is described. The synthesis, characterisation and X-ray structures of the new heteroleptic mono- and bis(NHC) cyclopentadienyl complexes LnCp2(L) 1 (Ln = Sc, Y, Ce; L = alkoxy-tethered carbene [OCMe2CH2(1-C{NCHCHNiPr})]), LnCp(L)2 (Ln = Y) 2, and the homoleptic tetrakis(NHC) complex Th(L)44 are described. The reactivity of these complexes, and of the homoleptic complexes Ln(L)3 (Ln = Sc 3, Ce), with E–H substrates is described, where EH = pyrrole C4H4NH, indole C8H6NH, diphenylacetone Ph2CC(O)Me, terminal alkynes RC[triple bond, length as m-dash]CH (R = Me3Si, Ph), and cyclopentadiene C5H6. Complex 1-Y heterolytically cleaves and adds pyrrole and indole N–H across the metal carbene bond, whereas 1-Ce does not, although 3 and 4 form H-bonded adducts. Complexes 1-Y and 1-Sc form adducts with CpH without cleaving the acidic C–H bond, 1-Ce cleaves the Cp–H bond, but 2 reacts to form the very rare H+–[C5H5]−–H+ motif. Complex 1-Ce cleaves alkyne C–H bonds but the products rearrange upon formation, while complex 1-Y cleaves the C–H bond in diphenylacetone forming a product which rearranges to the Y–O bonded enolate product

Surface ligand mediated growth of CuPt nanorods

CuPt alloy nanorods have been synthesized via one dimensional assembly of randomly orientated nanocrystallites in the presence of hexadecanoic acid and hexadecylamine as surface ligands. When hexadecanoic acid was added into the synthetic system first followed by a second step of adding hexadecylamine, strands of ultrathin CuPt nanowires were produced. The roles of the amine and organic acid are discussed. A novel ligand mediated mechanism is proposed, in which the formation of a stable monolayer structure of the ligands is the driving force to guide the 1D growth of the alloy nanorods without the influence of the crystal orientation. Photocatalytic hydrogen production from water has been performed using CuPt nanorods as a cocatalyst, which has a higher production rate (234.08 μmol h−1 g−1) than that of Pt nanorods under the same conditions (~66.35 μmol h−1 g−1). Our results suggest that polycrystalline CuPt nanorods with a large amount of defects are probably promising cocatalyst for photocatalysis.PostprintPeer reviewe

One-step synthesis and shape-control of CuPd nanowire networks

An effective one-step method has been developed to synthesize CuPd bimetallic nanowire networks. Investigation of the growth process revealed that the nanowires were formed by attachment of spherical particles and strongly influenced by interactions between surface ligands and metals. The morphology of CuPd nanoparticles is tuned via changing the molecular weight of polyvinylpyrrolidone (PVP) and solvents. The versatility of this method was further demonstrated by preparation of AgPd nanowires. An electrochemical study of CuPd nanowire networks shows morphology dependent activity in oxygen reduction reaction (ORR), which is comparable to that of platinum.</p

Facile Synthesis of Branched Ruthenium Nanocrystals and Their Use in Catalysis

Our novel and facile synthesis of ruthenium nanostars opens the door to the shape control of previously inaccessible sophisticated and monodisperse ruthenium nanomaterials. The metallic state and hexagonal close-packed (hcp) structure of the Ru nanostars, which are approximately 15 nm across, were determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). These materials can also act as seeds for the first preparation of ruthenium nanourchins. In addition, we have shown that they are as catalysts for the activation of CO and C=C bonds, since Fischer-Tropsch and solvent-free hydrogenation reactivities were observed on these unsupported materials.</p

Metathesis of renewable unsaturated fatty acid esters catalysed by a phoban-indenylidene ruthenium catalyst

The phoban-indenylidene complex is a robust catalyst for self-metathesis and ethenolysis reactions of methyl oleate. The phobanindenylidene catalyst was characterized by X-ray analysis, NMR and microanalysis and was used in various self-metathesis and ethenolysis of methyl oleate, giving rise to significantly higher end of run conversions compared to Grubbs 1st generation catalyst. These complexes are more stable and active than commercial Grubbs 1st generation catalyst, can be accessed from simple precursors and should give rise to more economical metathesis processes. (c) 2006 Elsevier B.V. All rights reserved.</p