The Interplay of Alkylidyne and Carbaborane Ligands at Metal Centers II: Proton-Mediated Reactions1

Methane activation by ZSM-5-supported transition metal centers

Chemical Society Reviews ◽

10.1039/d0cs01016b ◽

2021 ◽

Author(s):

Daniyal Kiani ◽

Sagar Sourav ◽

Yadan Tang ◽

Jonas Baltrusaitis ◽

Israel E. Wachs

Keyword(s):

Transition Metal ◽

Methane Activation ◽

Group V ◽

Metal Centers ◽

Methane Dehydroaromatization

The literature on methane dehydroaromatization (MDA) to benzene using ZSM-5 supported, group V–VIII transition metal-based catalysts (MOx/ZSM-5) is critically reviewed with a focus on in situ and operando molecular insights.

Download Full-text

Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

10.26434/chemrxiv.10316681.v1 ◽

2019 ◽

Author(s):

Andrew Rosen ◽

M. Rasel Mian ◽

Timur Islamoglu ◽

Haoyuan Chen ◽

Omar Farha ◽

...

Keyword(s):

Density Functional ◽

Metal Organic Frameworks ◽

Redox Activity ◽

Screening Methods ◽

Bridging Ligands ◽

Metal Centers ◽

Computational Screening ◽

Open Metal Sites ◽

Metal Organic ◽

Unsaturated Metal Sites

Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O2 and N2 adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br-, μ-Cl-, μ-F-, μ-SH-, or μ-OH- groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O2 affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O2. In contrast with O2 adsorption, N2 adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V2+ open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl- ligands of M2Cl2(BBTA) (H2BBTA = 1H,5H-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH- groups would significantly enhance the strength of O2 adsorption at the open metal sites without a corresponding increase in the N2 affinity. Experimental investigation of Co2Cl2(BBTA) and Co2(OH)2(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O2 at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH- ligands and the presence of H-bonding interactions between the μ-OH- bridging ligands and the O2 adsorbate.

Download Full-text

Electron Density Modulation of Catalytic Metal Centers by Substituted Aryl-Isocyanide Ligands

10.21236/ada212875 ◽

1989 ◽

Author(s):

Randy F. Johnston

Keyword(s):

Electron Density ◽

Metal Centers ◽

Isocyanide Ligands ◽

Density Modulation ◽

Catalytic Metal

Download Full-text

Structural tuning of heterogeneous molecular catalysts for electrochemical energy conversion

Science Advances ◽

10.1126/sciadv.abf3989 ◽

2021 ◽

Vol 7 (13) ◽

pp. eabf3989

Author(s):

Jiong Wang ◽

Shuo Dou ◽

Xin Wang

Keyword(s):

Energy Conversion ◽

Model Systems ◽

Structural Variations ◽

Metal Centers ◽

Electrochemical Energy Conversion ◽

Electronic Configurations ◽

Coordination Spheres ◽

The Stability ◽

Molecular Catalysts ◽

Electrochemical Energy

Heterogeneous molecular catalysts based on transition metal complexes have received increasing attention for their potential application in electrochemical energy conversion. The structural tuning of first and second coordination spheres of complexes provides versatile strategies for optimizing the activities of heterogeneous molecular catalysts and appropriate model systems for investigating the mechanism of structural variations on the activity. In this review, we first discuss the variation of first spheres by tuning ligated atoms; afterward, the structural tuning of second spheres by appending adjacent metal centers, pendant groups, electron withdrawing/donating, and conjugating moieties on the ligands is elaborated. Overall, these structural tuning resulted in different impacts on the geometric and electronic configurations of complexes, and the improved activity is achieved through tuning the stability of chemisorbed reactants and the redox behaviors of immobilized complexes.

Download Full-text

ChemInform Abstract: Intramolecular Alkane Dehydrogenation and Functionalization at Niobium Metal Centers.

ChemInform ◽

10.1002/chin.199106227 ◽

2010 ◽

Vol 22 (6) ◽

pp. no-no

Author(s):

J. S. YU ◽

P. E. FANWICK ◽

I. P. ROTHWELL

Keyword(s):

Alkane Dehydrogenation ◽

Metal Centers

Download Full-text

Dioxygen splitting at room temperature over distant binuclear transition metal centers in zeolites for direct oxidation of methane to methanol

Chemical Communications ◽

10.1039/d1cc00909e ◽

2021 ◽

Author(s):

Kinga Mlekodaj ◽

Mariia Lemishka ◽

Stepan Sklenak ◽

Jiri Dedecek ◽

Edyta Tabor

Keyword(s):

Transition Metal ◽

Room Temperature ◽

Direct Oxidation ◽

Metal Centers ◽

Oxidation Of Methane ◽

First Time

Here we demonstrate for the first time the splitting of dioxygen at RT over distant binuclear transition metal (M = Ni, Mn, and Co) centers stabilized in ferrierite zeolite. Cleaved...

Download Full-text

Methane to Methanol Conversion Facilitated by Anionic Transition Metal Centers: The Case of Fe, Ni, Pd, and Pt

The Journal of Physical Chemistry A ◽

10.1021/acs.jpca.0c10577 ◽

2021 ◽

Author(s):

Safaa Sader ◽

Evangelos Miliordos

Keyword(s):

Transition Metal ◽

Methanol Conversion ◽

Metal Centers

Download Full-text

Iron(II) complexes of dimethyltriazacyclophane

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229618015255 ◽

2018 ◽

Vol 74 (12) ◽

pp. 1641-1649

Author(s):

Wei-Tsung Lee ◽

Matthias Zeller ◽

David Upp ◽

Yuliya Politanska ◽

Doug Steinman ◽

...

Keyword(s):

Density Functional Theory ◽

Solid State ◽

Dft Calculations ◽

Density Functional Calculations ◽

Density Functional ◽

Coordination Mode ◽

Functional Theory ◽

Metal Centers ◽

Bonding Interaction

Treatment of the ortho-triazacyclophane 1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-triene [(C6H5)3(NH)(NCH3)2, L1] with Fe[N(SiMe3)2]2 yields the dimeric iron(II) complex bis(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido)bis[(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido)iron(II)], [Fe(C20H18N3)4] or Fe2(L1)4 (9). Dissolution of 9 in tetrahydrofuran (THF) results in solvation by two THF ligands and the formation of a simpler monoiron complex, namely bis(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido-κN 7)bis(tetrahydrofuran-κO)iron(II), [Fe(C20H18N3)2(C4H8O)2] or (L1)2Fe(THF)2 (10). The reaction is reversible and 10 reverts in vacuo to diiron complex 9. In the structures of both 9 and 10, the monoanionic triazacyclophane ligand L1− is observed in only the less-symmetric saddle conformation. No bowl-shaped crown conformers are observed in the solid state, thus preventing chelating κ3-coordination to the metal as had been proposed earlier based on density functional theory (DFT) calculations. Instead, the L1− ligands are bound in either a η2-chelating fashion through the amide and one amine donor (for one of the four ligands of 9), or solely through their amide N atoms in an even simpler monodentate η1-coordination mode. Density functional calculations on dimer 9 revealed nearly full cationic charges on each Fe atom and no bonding interaction between the two metal centers, consistent with the relatively long Fe...Fe distance of 2.912 (1) Å observed in the solid state.

Download Full-text