CO Reduction to CH_3OSiMe_3: Electrophile-Promoted Hydride Migration at a Single Fe Site

One of the major challenges associated with developing molecular Fischer–Tropsch catalysts is the design of systems that promote the formation of C–H bonds from H_2 and CO while also facilitating the release of the resulting CO-derived organic products. To this end, we describe the synthesis of reduced iron-hydride/carbonyl complexes that enable an electrophile-promoted hydride migration process, resulting in the reduction of coordinated CO to a siloxymethyl (LnFe-CH_2OSiMe_3) group. Intramolecular hydride-to-CO migrations are extremely rare, and to our knowledge the system described herein is the first example where such a process can be accessed from a thermally stable M(CO)(H) complex. Further addition of H_2 to LnFe-CH_2OSiMe_3 releases CH_3OSiMe_3, demonstrating net four-electron reduction of CO to CH_3OSiMe_3 at a single Fe site

Dihydrogen Adduct (Co-H₂) Complexes Displaying H-atom and Hydride Transfer

The prototypical reactivity profiles of transition metal dihydrogen complexes (M‐H₂) are well‐characterized with respect to oxidative addition (to afford dihydrides, M(H)₂) and as acids, heterolytically delivering H⁺ to a base and H⁻ to the metal. In the course of this study we explored plausible alternative pathways for H₂ activation, namely direct activation through H‐atom or hydride transfer from the σ‐H₂ adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S = ½ and an anionic S = 0 Co‐H₂ adduct, both supported by a trisphosphine borane ligand (P₃^B). The thermally stable metalloradical, (P₃^B)Co(H₂), serves as a competent precursor for hydrogen atom transfer to ᵗBu₃ArO·. What is more, its anionic derivative, the dihydrogen complex [(P₃^B)Co(H₂)]¹⁻, is a competent precursor for hydride transfer to BEt₃, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M‐H₂ complexes known

Dihydrogen Adduct (Co-H₂) Complexes Displaying H-atom and Hydride Transfer

The prototypical reactivity profiles of transition metal dihydrogen complexes (M‐H₂) are well‐characterized with respect to oxidative addition (to afford dihydrides, M(H)₂) and as acids, heterolytically delivering H⁺ to a base and H⁻ to the metal. In the course of this study we explored plausible alternative pathways for H₂ activation, namely direct activation through H‐atom or hydride transfer from the σ‐H₂ adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S = ½ and an anionic S = 0 Co‐H₂ adduct, both supported by a trisphosphine borane ligand (P₃^B). The thermally stable metalloradical, (P₃^B)Co(H₂), serves as a competent precursor for hydrogen atom transfer to ᵗBu₃ArO·. What is more, its anionic derivative, the dihydrogen complex [(P₃^B)Co(H₂)]¹⁻, is a competent precursor for hydride transfer to BEt₃, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M‐H₂ complexes known

CO Reduction to CH_3OSiMe_3: Electrophile-Promoted Hydride Migration at a Single Fe Site

One of the major challenges associated with developing molecular Fischer–Tropsch catalysts is the design of systems that promote the formation of C–H bonds from H_2 and CO while also facilitating the release of the resulting CO-derived organic products. To this end, we describe the synthesis of reduced iron-hydride/carbonyl complexes that enable an electrophile-promoted hydride migration process, resulting in the reduction of coordinated CO to a siloxymethyl (LnFe-CH_2OSiMe_3) group. Intramolecular hydride-to-CO migrations are extremely rare, and to our knowledge the system described herein is the first example where such a process can be accessed from a thermally stable M(CO)(H) complex. Further addition of H_2 to LnFe-CH_2OSiMe_3 releases CH_3OSiMe_3, demonstrating net four-electron reduction of CO to CH_3OSiMe_3 at a single Fe site

Microbial associations with macrobiota in coastal ecosystems : patterns and implications for nitrogen cycling

Author Posting. © Ecological Society of America, 2016. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Frontiers in Ecology and the Environment 14 (2016): 200-208, doi:10.1002/fee.1262.In addition to their important effects on nitrogen (N) cycling via excretion and assimilation (by macrofauna and macroflora, respectively), many macrobiota also host or facilitate microbial taxa responsible for N transformations. Interest in this topic is expanding, especially as it applies to coastal marine systems where N is a limiting nutrient. Our understanding of the diversity of microbes associated with coastal marine macrofauna (invertebrate and vertebrate animals) and macrophytes (seaweeds and marine plants) is improving, and recent studies indicate that the collection of microbes living in direct association with macrobiota (the microbiome) may directly contribute to N cycling. Here, we review the roles that macrobiota play in coastal N cycling, review current knowledge of macrobial–microbial associations in terms of N processing, and suggest implications for coastal ecosystem function as animals are harvested and as foundational habitat is lost or degraded. Given the biodiversity of microbial associates of macrobiota, we advocate for more research into the functional consequences of these associations for the coastal N cycle.University of Chicago-Marine Biological Laboratories (MBL

CO Reduction to CH₃OSiMe₃: Electrophile-Promoted Hydride Migration at a Single Fe Site

One of the major challenges associated with developing molecular Fischer–Tropsch catalysts is the design of systems that promote the formation of C–H bonds from H₂ and CO while also facilitating the release of the resulting CO-derived organic products. To this end, we describe the synthesis of reduced iron-hydride/carbonyl complexes that enable an electrophile-promoted hydride migration process, resulting in the reduction of coordinated CO to a siloxymethyl (L_<i>n</i>Fe-<i>CH</i>_<i>2</i><i>OSiMe</i>₃) group. Intramolecular hydride-to-CO migrations are extremely rare, and to our knowledge the system described herein is the first example where such a process can be accessed from a thermally stable M­(CO)­(H) complex. Further addition of H₂ to L_<i>n</i>Fe-CH₂OSiMe₃ releases CH₃OSiMe₃, demonstrating net four-electron reduction of CO to CH₃OSiMe₃ at a single Fe site

Synthesis and Structure of Metal Complexes of P‑Stereogenic Chiral Phosphiranes: An EDA-NOCV Analysis of the Donor–Acceptor Properties of Phosphirane Ligands

Reaction of the enantiomerically enriched P-stereogenic phosphiranes <i>syn</i>-(<i>R</i>_P<i>,S</i>_C)-Mes*PCH₂CH­(Ph) (<i>syn-</i><b>1</b>) and <i>anti</i>-(<i>S</i>_P,<i>S</i>_C)-Mes*PCH₂CH­(Ph) (<i>anti-</i><b>2</b>, Mes* = 2,4,6-(<i>t</i>-Bu)₃C₆H₂) with metal complex precursors gave Au­(L)­(Cl) (L = <b>1</b> (<b>3</b>); L = <b>2</b> (<b>4</b>)), <i>trans</i>-ML₂Cl₂ (L = <b>1</b>, M = Pd (<b>5</b>), Pt (<b>6</b>)), Pd­(η³-C₃H₅)­(L)­(Cl) (L = <b>1</b> (<b>7</b>)), and <i>trans</i>-RhL₂(CO)­(Cl) (L = <b>1</b> (<b>8</b>); L = <b>2</b> (<b>9</b>)); <b>3</b>, <b>4</b>, <b>7</b>, and <b>9</b> were crystallographically characterized. Phosphirane coordination resulted in shortening of the P–C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in determining the strength of these metal–ligand interactions

Synthesis and Structure of Metal Complexes of P‑Stereogenic Chiral Phosphiranes: An EDA-NOCV Analysis of the Donor–Acceptor Properties of Phosphirane Ligands

Reaction of the enantiomerically enriched P-stereogenic phosphiranes <i>syn</i>-(<i>R</i>_P<i>,S</i>_C)-Mes*PCH₂CH­(Ph) (<i>syn-</i><b>1</b>) and <i>anti</i>-(<i>S</i>_P,<i>S</i>_C)-Mes*PCH₂CH­(Ph) (<i>anti-</i><b>2</b>, Mes* = 2,4,6-(<i>t</i>-Bu)₃C₆H₂) with metal complex precursors gave Au­(L)­(Cl) (L = <b>1</b> (<b>3</b>); L = <b>2</b> (<b>4</b>)), <i>trans</i>-ML₂Cl₂ (L = <b>1</b>, M = Pd (<b>5</b>), Pt (<b>6</b>)), Pd­(η³-C₃H₅)­(L)­(Cl) (L = <b>1</b> (<b>7</b>)), and <i>trans</i>-RhL₂(CO)­(Cl) (L = <b>1</b> (<b>8</b>); L = <b>2</b> (<b>9</b>)); <b>3</b>, <b>4</b>, <b>7</b>, and <b>9</b> were crystallographically characterized. Phosphirane coordination resulted in shortening of the P–C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in determining the strength of these metal–ligand interactions