Brian L. Conley

Discovery, Applications, and Catalytic Mechanisms of Shvo's Catalyst

7.1. Proposed Mechanisms 2306 7.2. Kinetic Isotope Effect Studies 2306 7.3. Amine Coordination and Exchange 2306 7.4. Computational Studies 2307 7.5. Summary 2307 8. Analogous Systems 2308 8.1. Structural Analogues 2308 8.1.1. Cyclopentadienyl Amine Derivatives 2308 8.1.2. μ-Iodo Homologue 2308 8.1.3. Silica-Supported Homologue 2309 8.1.4. Phosphine-Substituted Homologue 2309 8.2. Osmium 2309 8.3. Iron 2310 9. Outlook 2311 10. Acknowledgments 2311 11. References 2311

A Robust, Air-Stable, Reusable Ruthenium Catalyst for Dehydrogenation of Ammonia Borane

We describe an efficient homogeneous ruthenium catalyst for the dehydrogenation of ammonia borane (AB). This catalyst liberates more than 2 equiv of H(2) and up to 4.6 system wt % H(2) from concentrated AB suspensions under air. Importantly, this catalyst is robust, delivering several cycles of dehydrogenation at high [AB] without loss of catalytic activity, even with exposure to air and water.

Facile Oxy‐Functionalization of a Nucleophilic Metal Alkyl with a cis‐Dioxo Metal Species via a (2+3) Transition State

Selective, low-temperature hydroxylation of alkanes catalyzed by transition-metal complexes is an important area of study, given its possible applications to natural-gas conversion as well as to more efficient production of bulk chemicals and energy. Several promising electrophilic catalysts that couple C–H activation to facile oxy-functionalization of the resulting electrophilically activated M R intermediates have been reported (Figure 1). To address practical challenges with

Thermochemistry and Molecular Structure of a Remarkable Agostic Interaction in a Heterobifunctional Ruthenium−Boron Complex

A boron-pendant ruthenium species forms a unique agostic methyl bridge between the boron and ruthenium atoms in the presence of a ligating solvent, acetonitrile. NMR inversion-recovery experiments enabled the activation and equilibrium thermochemistry for formation of the agostic bridge to be measured. The mechanism for bridge formation involves displacement of an acetonitrile ligand; thus, this is a rare example of a case where an agostic C-H ligand competitively displaces another tightly binding ligand from a coordinatively saturated complex. Characterization of this complex gives unique insights into the development of C-H activation catalysis based on this ligand-metal bifunctional motif.

Oxy-Functionalization of Nucleophilic Rhenium(I) Metal Carbon Bonds Catalyzed by Selenium(IV)

We report that SeO2 catalyzes the facile oxy-functionalization of (CO)5Re(I)-Me(delta-) with IO4(-) to generate methanol. Mechanistic studies and DFT calculations reveal that catalysis involves methyl group transfer from Re to the electrophilic Se center followed by oxidation and subsequent reductive functionalization of the resulting CH3Se(VI) species. Furthermore, (CO)3Re(I)(Bpy)-R (R = ethyl, n-propyl, and aryl) complexes show analogous transfer to SeO2 to generate the primary alcohols. This represents a new strategy for the oxy-functionalization of M-R(delta-) polarized bonds.

DUAL SITE CATALYSTS FOR HYDRIDE MANIPULATION

This comment describes our efforts to develop dual site catalysts for hydride manipulation. We began by analyzing the mechanism of alcohol oxidation with the ruthenium-based Shvo catalyst, which utilizes a proton transfer to template a hydride transfer from carbon to ruthenium in a single transition state. In our project we are working to extend this concept of reactivity from the use of proton transfer as a templating interaction for hydride transfer to the use of a Lewis acid to coordinate and direct a substrate to a metal. Along these lines, we have found that ammonia borane, a popular and high-weight-content hydrogen storage material, has been one of our best model substrates with which to study hydride transfer mechanisms. Our ongoing studies have thus far given new insight into the reactivity of the Shvo system, particularly regarding dehydrogenation of ammonia borane, and have enabled us to design a new, prolific, air- and water-tolerant, and reusable catalyst for ammonia borane dehydrogenation.