http://utw10193.utweb.utexas.edu/Archive/RuoffsPDFs/150.pdf

Synthesis and exfoliation of isocyanate-treated graphene oxide nanoplatelets

Since it was first suggested1 that a single molecule might function as an active electronic component, a number of techniques have been developed to measure the charge transport properties of single molecules2,3,4,5,6,7,8,9,10,11,12. Although scanning tunnelling microscopy observations under high vacuum conditions can allow stable measurements of electron transport, most measurements of a single molecule bonded in a metal–molecule–metal junction exhibit relatively large variations in conductance. As a result, even simple predictions about how molecules behave in such junctions have still not been rigorously tested. For instance, it is well known13,14 that the tunnelling current passing through a molecule depends on its conformation; but although some experiments have verified this effect15,16,17,18, a comprehensive mapping of how junction conductance changes with molecular conformation is not yet available. In the simple case of a biphenyl—a molecule with two phenyl rings linked by a single C–C bond—conductance is expected to change with the relative twist angle between the two rings, with the planar conformation having the highest conductance. Here we use amine link groups to form single-molecule junctions with more reproducible current–voltage characteristics19. This allows us to extract average conductance values from thousands of individual measurements on a series of seven biphenyl molecules with different ring substitutions that alter the twist angle of the molecules. We find that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems13.

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Dependence of single-molecule junction conductance on molecular conformation

This report details the effects of ligand variation on the mechanism and activity of ruthenium-based olefin metathesis catalysts. A series of ruthenium complexes of the general formula L(PR3)(X)2RuCHR1 have been prepared, and the influence of the substituents L, X, R, and R1 on the rates of phosphine dissociation and initiation as well as overall activity for olefin metathesis reactions was examined. In all cases, initiation proceeds by dissociative substitution of a phosphine ligand (PR3) with an olefinic substrate. All of the ligands L, X, R, and R1 have a significant impact on initiation rates and on catalyst activity. The origins of the observed substituent effects as well as the implications of these studies for the design and implementation of new olefin metathesis catalysts and substrates are discussed in detail.

Mechanism and Activity of Ruthenium Olefin Metathesis Catalysts

Reduction of the five-coordinate iron(II) dihalide complexes (iPrPDI)FeX2 (iPrPDI = ((2,6-CHMe2)2C6H3NCMe)2C5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (iPrPDI)Fe(N2)2. In solution, (iPrPDI)Fe(N2)2 loses 1 equiv of N2 to afford the mono(dinitrogen) adduct (iPrPDI)Fe(N2). Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (≤0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) σ-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C−H and catalytic C−Si bond formation.

Preparation and molecular and electronic structures of iron(0) dinitrogen and silane complexes and their application to catalytic hydrogenation and hydrosilation.

Serendipity has long been a welcome yet elusive phenomenon in the advancement of chemistry. We sought to exploit serendipity as a means of rapidly identifying unanticipated chemical transformations. By using a high-throughput, automated workflow and evaluating a large number of random reactions, we have discovered a photoredox-catalyzed C–H arylation reaction for the construction of benzylic amines, an important structural motif within pharmaceutical compounds that is not readily accessed via simple substrates. The mechanism directly couples tertiary amines with cyanoaromatics by using mild and operationally trivial conditions.

Discovery of an α-Amino C–H Arylation Reaction Using the Strategy of Accelerated Serendipity

Safe and Convenient Procedure for Solvent Purification

Compounds and metal complexes comprising a polycyclic, fused ring ligand or inertly substituted derivative thereof having up to 60 atoms other than hydrogen, said ligand comprising at least: (1) a cyclopentadienyl ring, (2) a 6,7, or 8 membered ring other than a 6-carbon aromatic ring, and (3) an aromatic ring, with the proviso that said 6, 7, or 8 membered ring (2), is fused to both the cyclopentadienyl ring (1), and the aromatic ring (3), polymerization catalysts, a process to prepare the novel compounds and complexes, and olefin polymerization processes using the same are disclosed.

Polycyclic, fused ring compounds, metal complexes and polymerization process

An olefin polymerization process

Metal complexes comprising a polycyclic, fused ring ligand or inertly substituted derivative thereof comprising at least: (1) a cyclopentadienyl ring, (2) a 7 membered polyatomic ring, and (3) one or more aromatic ring systems, with the proviso that said 7 membered ring (2), is fused to both the cyclopentadienyl ring (1), and said one or more aromatic ring systems (3), and substituted in at least one ring position with a substituent group resulting in sp 2 hybridization on the ring atom bonded thereto; polymerization catalysts; and olefin polymerization processes using the same are disclosed.

Substituted polycyclic, fused ring compounds, metal complexes and polymerization process

COORDINATING METAL COMPLEXES CONTAINING METAL GROUP 3 (except SC) 4-10 OR lanthanide series AND A HALF WITH NO SPECIAL LINK LOCATED SUCH THAT HAS REPLACED WITH HALF A PART TO INDUCE constriction, reducing the angle METAL BETWEEN THE CENTER OF SUCH LINKED ESPECIALLY HALF AND at least one substituent REMNANT. Preferably, the complexes contain a cyclopentadienyl or substituted cyclopentadienyl GROUP part of a ring structure in which the metal is covalently LINKED LINKED TO A HALF AND REMAINS IN ASSOCIATION WITH HALF cyclopentadienyl (REPLACED). COMPLEX STRUCTURE SUCH ARE NOT NECESSARILY PREFERRED Constrained ENOUGH TO REDUCE said angle. Preferred compounds PARTICULARLY amidosilane And amidoalkanediyl. The complexes of the invention form addition polymerization catalysts, which activate cocatalysts LEWIS such as acids, ammonium salts, oxidizing agents and especially aluminum compounds, PARTICULARLY aluminum trialkyls. NEW polymers, including resins and copolymers EIPE pseudorandom, can be obtained using the catalysts of the invention.

Addition polymerization catalysts constrained geometry, processes for their preparation, their precursors, methods of use and new polymers formed therefrom.

Robert K Rosen

Papers

Safe and Convenient Procedure for Solvent Purification

Polycyclic, fused ring compounds, metal complexes and polymerization process

An olefin polymerization process

Substituted polycyclic, fused ring compounds, metal complexes and polymerization process

Addition polymerization catalysts constrained geometry, processes for their preparation, their precursors, methods of use and new polymers formed therefrom.