576 results on '"T. Don Tilley"'
Search Results
2. Expanded [23]-Helicene with Exceptional Chiroptical Properties via an Iterative Ring-Fusion Strategy
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Gavin R. Kiel, Harrison M. Bergman, Adrian E. Samkian, Nathaniel J. Schuster, Rex C. Handford, August J. Rothenberger, Rafael Gomez-Bombarelli, Colin Nuckolls, and T. Don Tilley
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Colloid and Surface Chemistry ,Circular Dichroism ,Polycyclic Compounds ,General Chemistry ,Biochemistry ,Carbon ,Catalysis - Abstract
Expanded helicenes are an emerging class of helical nanocarbons composed of alternating linear and angularly fused rings, which give rise to an internal cavity and a large diameter. The latter is expected to impart exceptional chiroptical properties, but low enantiomerization free energy barriers (Δ
- Published
- 2022
3. Late 3d-Transition Metal Complexes Bearing a Bis-Phosphine Borane Ligand, PhB(CH2PtBu2)2
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Rex C. Handford, Lingfei Zhong, and T. Don Tilley
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Inorganic Chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry - Published
- 2022
4. Synthesis and Reactivity of a Dimeric Ni(I) Methyl Complex
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T. Don Tilley and Ryan Witzke
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Inorganic Chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry - Published
- 2022
5. Synthesis, Characterization, and Reactivity of Low-Coordinate Titanium(III) Amido Complexes
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Alejandro Cuellar De Lucio, Ryan Witzke, Addison Desnoyer, Irene Cai, and T. Don Tilley
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Inorganic Chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry - Published
- 2022
6. Copper(III) Metallacyclopentadienes via Zirconocene Transfer and Reductive Elimination to an Isolable Phenanthrocyclobutadiene
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Harrison M. Bergman, D. Dawson Beattie, Rex C. Handford, Elliot Rossomme, Benjamin A. Suslick, Martin Head-Gordon, Thomas R. Cundari, Yi Liu, and T. Don Tilley
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Colloid and Surface Chemistry ,Organometallic Compounds ,Zirconium ,General Chemistry ,Oxidation-Reduction ,Biochemistry ,Copper ,Catalysis - Abstract
Despite the widespread use of copper catalysis for the formation of C-C bonds, debate about the mechanism persists. Reductive elimination from Cu(III) is often invoked as a key step, yet examples of its direct observation from isolable complexes remain limited to only a few examples. Here, we demonstrate that incorporation of bulky mesityl (Mes) groups into the α-positions of a phenanthrene-appended zirconacyclopentadiene, Cp
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- 2022
7. Mechanistic Aspects of Cobalt–Oxo Cubane Clusters in Oxidation Chemistry
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Jaruwan Amtawong, Andy I. Nguyen, and T. Don Tilley
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Abstract
Cobalt oxides are recognized as one of the most efficient earth-abundant catalysts for challenging oxidation chemistry, with substrates ranging from water to organic compounds. In these oxidations, cobalt-oxo species with formal oxidation states greater than 3 are commonly invoked as reactive intermediates. However, there is a dearth of mechanistic information regarding how these high-valent cobalt catalysts operate. This Perspective describes how the study of molecular cobalt oxo clusters, with an emphasis on [Co
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- 2022
8. Switchable Product Selectivity in Diazoalkane Coupling Catalyzed by a Two-Coordinate Cobalt Complex
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T. Don Tilley, Julien A. Panetier, Ryan J. Witzke, Michael I. Lipschutz, and Yuyang Dong
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Coupling (electronics) ,chemistry ,Product (mathematics) ,chemistry.chemical_element ,General Chemistry ,Selectivity ,Cobalt ,Combinatorial chemistry ,Catalysis - Published
- 2021
9. C–H Activation by RuCo3O4 Oxo Cubanes: Effects of Oxyl Radical Character and Metal–Metal Cooperativity
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David Balcells, Benjamin A. Suslick, Bastian Bjerkem Skjelstad, Rex C. Handford, T. Don Tilley, and Jaruwan Amtawong
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Steric effects ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Ligand ,Cooperativity ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Redox ,Catalysis ,0104 chemical sciences ,Electron transfer ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Cubane ,Reactivity (chemistry) - Abstract
High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo3O4 cubane complexes bearing a terminal RuV-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical. Radical intermediates are subsequently trapped by another equivalent of the terminal oxo to afford isolable radical-trapped cubane complexes. Density functional theory (DFT) reveals a barrierless radical combination step that is more favorable than an oxygen-rebound mechanism by 12.3 kcal mol-1. This HAA reactivity to generate organic products is influenced by steric congestion and the C-H bond dissociation energy of the substrate. Tuning the electronic properties of the cubane (i.e., spin density localized on terminal oxo, basicity, and redox potential) by varying the donor ability of ligands at the Co sites modulates C-H activations by the RuV-oxo fragment and enables construction of structure-activity relationships. These results reveal a mechanistic pathway for C-H activation by high-valent metal-oxo species with oxyl radical character and provide insights into cooperative effects of multimetallic centers in tuning PCET reactivity.
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- 2021
10. Binding, Release and Functionalization of Intact Pnictogen Tetrahedra Coordinated to Dicopper Complexes
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Martin Piesch, Amélie Nicolay, Maria Haimerl, Michael Seidl, Gábor Balázs, T. Don Tilley, and Manfred Scheer
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Models, Molecular ,Anions ,coordination modes ,Molecular Structure ,ddc:540 ,Organic Chemistry ,Molecular ,General Chemistry ,Ligands ,metal-metal interactions ,carbenes · coordination modes · copper · metal-metal interactions · pnictogens ,Catalysis ,carbenes ,Models ,540 Chemie ,copper ,Chemical Sciences ,pnictogens ,Copper - Abstract
The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu2 (μ,η1 : η1 -MeCN)][X]2 (X=weakly coordinating anion, NTf2 (1 a), FAl[OC6 F10 (C6 F5 )]3 (1 b), Al[OC(CF3 )3 ]4 (1 c)) was replaced by white phosphorus (P4 ) or yellow arsenic (As4 ) to yield [(DPFN)Cu2 (μ,η2 : η2 -E4 )][X]2 (E=P (2 a-c), As (3 a-c)). The molecular structures in the solid state reveal novel coordination modes for E4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E4 tetrahedra with release of P4 or As4 and formation of [(DPFN)Cu2 (μ,η1 : η1 -Me NHC)][X]2 (4 a,b) or to an opening of one E-E bond leading to an unusual E4 butterfly structural motif in [(DPFN)Cu2 (μ,η1 : η1 -E4 Dipp NHC)][X]2 (E=P (5 a,b), E=As (6)). With a cyclic alkyl amino carbene (Et CAAC), cleavage of two As-As bonds was observed to give two isomers of [(DPFN)Cu2 (μ,η2 : η2 -As4 Et CAAC)][X]2 (7 a,b) with an unusual As4 -triangle+1 unit.
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- 2022
11. Controlled monodefluorination and alkylation of C(sp
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Amy E, Kynman, Luca K, Elghanayan, Addison N, Desnoyer, Yan, Yang, Laurent, Sévery, Andrea, Di Giuseppe, T Don, Tilley, Laurent, Maron, and Polly L, Arnold
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The controlled functionalization of a single fluorine in a CF
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- 2022
12. Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations
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Serene Kuramarohit, Amélie Nicolay, Chungkeun Shin, David Balcells, Julie Héron, T. Don Tilley, and Micah S. Ziegler
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Inorganic Chemistry ,chemistry.chemical_compound ,Chemistry ,Organic Chemistry ,Polymer chemistry ,Carbon–hydrogen bond activation ,Physical and Theoretical Chemistry - Published
- 2021
13. Scalable, Divergent Synthesis of a High Aspect Ratio Carbon Nanobelt
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Rex C. Handford, Gavin R. Kiel, T. Don Tilley, Yi Liu, and Harrison M. Bergman
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Molecular Structure ,Nanotubes, Carbon ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Aspect ratio (image) ,Catalysis ,Cycloaddition ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Monomer ,chemistry ,law ,Scalability ,Molecule ,Carbon ,Divergent synthesis - Abstract
Carbon nanobelts are molecules of high fundamental and technological interest due to their structural similarity to carbon nanotubes, of which they are molecular cutouts. Despite this attention, synthetic accessibility is a major obstacle, such that the few known strategies offer limited structural diversity, functionality, and scalability. To address this bottleneck, we have developed a new strategy that utilizes highly fused monomer units constructed via a site-selective [2 + 2 + 2] cycloaddition and a high-yielding zirconocene-mediated macrocyclization to achieve the synthesis of a new carbon nanobelt on large scale with the introduction of functional handles in the penultimate step. This nanobelt represents a diagonal cross section of an armchair carbon nanotube and consequently has a longitudinally extended structure with an aspect ratio of 1.6, the highest of any reported nanobelt. This elongated structure promotes solid-state packing into aligned columns that mimic the parent carbon nanotube and facilitates unprecedented host-guest chemistry with oligo-arylene guests in nonpolar solvents.
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- 2021
14. Two-Coordinate Iron(I) Complexes on the Edge of Stability: Influence of Dispersion and Steric Effects
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Ryan J. Witzke, T. Don Tilley, Diptarka Hait, and Martin Head-Gordon
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Inorganic Chemistry ,Steric effects ,Chemical physics ,Chemistry ,Organic Chemistry ,Dispersion (optics) ,Physical and Theoretical Chemistry ,Edge (geometry) ,Stability (probability) - Published
- 2021
15. A Dicopper Nitrenoid by Oxidation of a CuICuI Core: Synthesis, Electronic Structure, and Reactivity
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K. V. Lakshmi, Amélie Nicolay, Addison N. Desnoyer, T. Don Tilley, Micah S. Ziegler, and Thomas R. Cundari
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General Chemistry ,Electronic structure ,Bond formation ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Oxidative addition ,Catalysis ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Phenol ,Amine gas treating ,Reactivity (chemistry) ,Protonolysis - Abstract
A dicopper nitrenoid complex was prepared by formal oxidative addition of the nitrenoid fragment to a dicopper(I) center by reaction with the iminoiodinane PhINTs (Ts = tosylate). This nitrenoid complex, (DPFN)Cu2(μ-NTs)[NTf2]2 (DPFN = 2,7-bis(fluorodi(2-pyridyl)methyl)-1,8-naphthyridine), is a powerful H atom abstractor that reacts with a range of strong C-H bonds to form a mixed-valence Cu(I)/Cu(II) μ-NHTs amido complex in the first example of a clean H atom transfer to a dicopper nitrenoid core. In line with this reactivity, DFT calculations reveal that the nitrenoid is best described as an iminyl (NR radical anion) complex. The nitrenoid was trapped by the addition of water to form a mixed-donor hydroxo/amido dicopper(II) complex, which was independently obtained by reaction of a Cu2(μ-OH)2 complex with an amine through a protonolysis pathway. This mixed-donor complex is an analogue for the proposed intermediate in copper-catalyzed Chan-Evans-Lam coupling, which proceeds via C-X (X = N or O) bond formation. Treatment of the dicopper(II) mixed donor complex with MgPh2(THF)2 resulted in generation of a mixture that includes both phenol and a previously reported dicopper(I) bridging phenyl complex, illustrating that both reduction of dicopper(II) to dicopper(I) and concomitant C-X bond formation are feasible.
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- 2021
16. A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole cycloadditions
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Harrison M. Bergman, D. Dawson Beattie, Gavin R. Kiel, Rex C. Handford, Yi Liu, and T. Don Tilley
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Chemical Sciences ,Bioengineering ,General Chemistry - Abstract
The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels-Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations via the marriage of two powerful cycloaddition strategies. First, a formal Cp2Zr-mediated [2 + 2 + 1] cycloaddition is used to generate a stannole-annulated PAH. Secondly, the stannoles are employed as diene components in a [4 + 2] cycloaddition/aromatization cascade with an aryne, enabling π-extension to afford a larger PAH. This discovery of stannoles as highly reactive - yet stable for handling - diene equivalents, and the development of a modular strategy for their synthesis, should significantly extend the structural scope of PAHs accessible by a [4 + 2] cycloaddition approach.
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- 2022
17. Olefin Hydroarylation Catalyzed by a Single-Component Cobalt(-I) Complex
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T. Don Tilley and Benjamin A. Suslick
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Reaction conditions ,Olefin fiber ,010405 organic chemistry ,Chemistry ,Aryl ,Single component ,Organic Chemistry ,Imine ,Regioselectivity ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Physical and Theoretical Chemistry ,Cobalt - Abstract
A single-component Co(-I) catalyst, [(PPh3)3Co(N2)]Li(THF)3, has been developed for olefin hydroarylations with (N-aryl)aryl imine substrates. More than 40 examples were examined under mild reaction conditions to afford the desired alkyl-arene product in good to excellent yields. Catalysis occurs in a regioselective manner to afford exclusively branched products with styrene-derived substrates or linear products for aliphatic olefins. Electron-withdrawing functional groups (e.g., -F, -CF3, and -CO2Me) were tolerated under the reaction conditions.
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- 2021
18. Siloxyaluminate and Siloxygallate Complexes as Models for Framework and Partially Hydrolyzed Framework Sites in Zeolites and Zeotypes
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Alexis T. Bell, T. Don Tilley, Erum Mansoor, Micah S. Ziegler, Neelay M. Phadke, Ryan J. Witzke, Martin Head-Gordon, James P. Dombrowski, and Daniel S. Levine
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Molecular model ,010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,Infrared spectroscopy ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Monomer ,chemistry ,Benzyl alcohol ,Salt metathesis reaction ,Lithium - Abstract
Author(s): Dombrowski, James P; Ziegler, Micah S; Phadke, Neelay M; Mansoor, Erum; Levine, Daniel S; Witzke, Ryan J; Head-Gordon, Martin; Bell, Alexis T; Tilley, T Don | Abstract: Anionic molecular models for nonhydrolyzed and partially hydrolyzed aluminum and gallium framework sites on silica, M[OSi(OtBu)3 ]4 - and HOM[OSi(OtBu)3 ]3 - (where M=Al or Ga), were synthesized from anionic chlorides Li{M[OSi(OtBu)3 ]3 Cl} in salt metathesis reactions. Sequestration of lithium cations with [12]crown-4 afforded charge-separated ion pairs composed of monomeric anions M[OSi(OtBu)3 ]4 - with outer-sphere [([12]crown-4)2 Li]+ cations, and hydroxides {HOM[OSi(OtBu)3 ]3 } with pendant [([12]crown-4)Li]+ cations. These molecular models were characterized by single-crystal X-ray diffraction, vibrational spectroscopy, mass spectrometry and NMR spectroscopy. Upon treatment of monomeric [([12]crown-4)Li]{HOM[OSi(OtBu)3 ]3 } complexes with benzyl alcohol, benzyloxide complexes were formed, modeling a possible pathway for the formation of active sites for Meerwin-Ponndorf-Verley (MPV) transfer hydrogenations with Al/Ga-doped silica catalysts.
- Published
- 2020
19. Elucidation of Diverse Solid‐State Packing in a Family of Electron‐Deficient Expanded Helicenes via Microcrystal Electron Diffraction (MicroED)**
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Harrison M. Bergman, Julia Oktawiec, T. Don Tilley, Adrian E. Samkian, Hosea M. Nelson, Gavin R. Kiel, and Christopher G. Jones
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Materials science ,010405 organic chemistry ,Resolution (electron density) ,Space group ,General Medicine ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,law.invention ,Crystal ,Crystallography ,chemistry.chemical_compound ,Helicene ,chemistry ,Electron diffraction ,law ,Self-assembly ,Homochirality ,Crystallization ,Single crystal ,Divergent synthesis - Abstract
Solid-state packing plays a defining role in the properties of a molecular organic material, but it is difficult to elucidate in the absence of single crystals that are suitable for X-ray diffraction. Here, we demonstrate the coupling of divergent synthesis with microcrystal electron diffraction (MicroED) for rapid assessment of solid-state packing motifs, using a class of chiral nanocarbons – expanded helicenes – as a proof of concept. Two highly selective oxidative dearomatizations of a readily-accessible helicene provided a divergent route to four electron-deficient analogues containing quinone or quinoxaline units. Crystallization efforts consistently yielded microcrystals that were unsuitable for single crystal X-ray diffraction, but ideal for MicroED. This technique facilitated the elucidation of solid-state structures of all five compounds with
- Published
- 2020
20. Shape-Selective Synthesis of Pentacene Macrocycles and the Effect of Geometry on Singlet Fission
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Ryan J. Witzke, David P. Nenon, T. Don Tilley, Yi Liu, Adam M. Schwartzberg, Harrison M. Bergman, and Gavin R. Kiel
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chemistry.chemical_classification ,Intermolecular force ,Alkyne ,General Chemistry ,Crystal structure ,Chromophore ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Pentacene ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Chemical physics ,Covalent bond ,Singlet fission ,Singlet state ,Physics::Chemical Physics - Abstract
Pentacene's extraordinary photophysical and electronic properties are highly dependent on intermolecular through-space interactions. Macrocyclic arrangements of chromophores have been shown to provide a high level of control over these interactions, but few examples exist for pentacene due to inherent synthetic challenges. In this work, zirconocene-mediated alkyne coupling was used as a dynamic covalent C-C bond forming reaction to synthesize two geometrically distinct, pentacene-containing macrocycles on a gram scale and in four or fewer steps. Both macrocycles undergo singlet fission in solution with rates that differ by an order of magnitude, while the rate of triplet recombination is approximately the same. This independent modulation of singlet and triplet decay rates is highly desirable for the design of efficient singlet fission materials. The dimeric macrocycle adopts a columnar packing motif in the solid state with large void spaces between pentacene units of the crystal lattice.
- Published
- 2020
21. Robust dicopper(I) µ-boryl complexes supported by a dinucleating naphthyridine-based ligand
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Pablo Ríos, Matthew S. See, Rex C. Handford, and T. Don Tilley
- Abstract
Copper boryl species have been widely invoked as reactive intermediates in Cu-catalysed C−H borylation reactions, but their isolation and study have been challenging. Use of the robust dinucleating ligand DPFN (2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine) allowed for the isolation of two very thermally stable dicopper(I) boryl complexes, [(DPFN)Cu2(µ-Bpin)][NTf2] (2) and [(DPFN)Cu2(µ-Bcat)][NTf2] (4) (pin = 2,3-dimethylbutane-2,3-diol; cat = benzene-1,2-diol). These complexes were prepared by cleavage of the corresponding diborane via reaction with the alkoxide [(DPFN)Cu2(µ-OtBu)][NTf2] (3). Reactivity studies illustrated the exceptional stability of these boryl complexes (thermal stability in solution up to 100 °C) and their role in the activation of C(sp)−H bonds. X-ray diffraction and computational studies provide a detailed description of the bonding and electronic structures in these species, and suggest that the dinucleating character of the naphthyridine-based ligand is largely responsible for their remarkable stability.
- Published
- 2022
22. Controlled monodefluorination and alkylation of C(sp3)–F bonds by lanthanide photocatalysts: importance of metal–ligand cooperativity
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Amy E. Kynman, Luca K. Elghanayan, Addison N. Desnoyer, Yan Yang, Laurent Sévery, Andrea Di Giuseppe, T. Don Tilley, Laurent Maron, and Polly L. Arnold
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General Chemistry - Abstract
The controlled functionalization of a single fluorine in a CF3 group is difficult and rare. Photochemical C–F bond functionalization is achieved using catalysts made from a range of earth-abundant lanthanides by using a ligand that enables M–L cooperativity.
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- 2022
23. Bimetallic Mechanism for Alkyne Cyclotrimerization with a Two-Coordinate Fe Precatalyst
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Khetpakorn Chakarawet, Ryan J. Witzke, T. Don Tilley, Diptarka Hait, and Martin Head-Gordon
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chemistry.chemical_classification ,010405 organic chemistry ,Chemistry ,Polymer chemistry ,Alkyne ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Bimetallic strip ,Catalysis ,0104 chemical sciences - Abstract
The two-coordinate compound (IPr)Fe[N(SiMe3)DIPP] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; DIPP = 2,6-diisopropylphenyl) catalyzes the cyclotrimerization of alkynes to arenes. Tre...
- Published
- 2020
24. A Dicopper Platform that Stabilizes the Formation of Pentanuclear Coinage Metal Hydride Complexes
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Addison N. Desnoyer, Amélie Nicolay, Micah S. Ziegler, Nicole A. Torquato, and T. Don Tilley
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General Medicine - Published
- 2020
25. Expanded Helicenes as Synthons for Chiral Macrocyclic Nanocarbons
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Katherine L. Bay, T. Don Tilley, Kendall N. Houk, Gavin R. Kiel, Rex C. Handford, Janice B. Lin, Nathaniel J. Schuster, Colin Nuckolls, and Adrian E. Samkian
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Macrocyclic Compounds ,Lability ,Stereochemistry ,Dimer ,Synthon ,Stereoisomerism ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Helicene ,chemistry ,Alkyne metathesis ,Polycyclic Compounds ,Density functional theory - Abstract
Expanded helicenes are large, structurally flexible π-frameworks that can be viewed as building blocks for more complex chiral nanocarbons. Here we report a gram-scale synthesis of an alkyne-functionalized expanded [11]helicene and its single-step transformation into two structurally and functionally distinct types of macrocyclic derivatives: (1) a figure-eight dimer via alkyne metathesis (also gram scale) and (2) two arylene-bridged expanded helicenes via Zr-mediated, formal [2+2+n] cycloadditions. The phenylene-bridged helicene displays a substantially higher enantiomerization barrier (22.1 kcal/mol) than its helicene precursor (
- Published
- 2020
26. Structure and Bonding in a Diamond‐Shaped Tin Cluster Possessing a cyclo ‐Sn 4 Core
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Rex C. Handford, T. Don Tilley, and T. Alex Wheeler
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010405 organic chemistry ,Chemistry ,Aryl ,Organic Chemistry ,Cluster chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Core (optical fiber) ,chemistry.chemical_compound ,Crystallography ,Cluster (physics) ,Molecule ,Density functional theory ,Tin ,Single crystal - Abstract
A tetrameric cluster composed entirely of (aryl)Sn units, [DMPSn]4 (DMP=2,6-dimesitylphenyl), has been prepared by reduction of [DMPSnCl]2 with a variety of reductants. This cluster was characterized in solution by multinuclear NMR spectroscopies, as well as in the solid-state by single crystal X-ray diffraction analysis. This species is stereochemically nonrigid in solution and possesses a cyclo-Sn4 core whose DMP substituents are equivalent at higher temperatures. The solid-state molecular structure is remarkably unsymmetrical and possesses a nearly planar cyclo-Sn4 core. The DMP substituents are arranged such that three are approximately coplanar, while one is nearly perpendicular to the cyclo-Sn4 core. Density functional theory calculations for a [PhSn]4 model system show that this distorted geometry about the cyclo-Sn4 core maximizes σ-bonding between the Sn centers in a manner reminiscent of trans-bent bonding in the heavy group 14 analogues of alkenes and alkynes.
- Published
- 2020
27. Isolation and Study of Ruthenium–Cobalt Oxo Cubanes Bearing a High-Valent, Terminal RuV–Oxo with Significant Oxyl Radical Character
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Jaruwan Amtawong, R. David Britt, Andy I. Nguyen, Jarett Wilcoxen, Naomi Biggins, David Balcells, Rex C. Handford, and T. Don Tilley
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Models, Molecular ,Free Radicals ,Radical ,Molecular Conformation ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Article ,Ruthenium ,Catalysis ,Coupling reaction ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Pyridine ,Organometallic Compounds ,Moiety ,Ligand ,Cobalt ,General Chemistry ,Hydrocarbons ,0104 chemical sciences ,Oxygen ,chemistry ,Cubane ,Natural bond orbital - Abstract
High-valent Ru(V)–oxo intermediates have long been proposed in catalytic oxidation chemistry, but investigations into their electronic and chemical properties have been limited due to their reactive nature and rarity. The incorporation of Ru into the [Co(3)O(4)] subcluster via the singlestep assembly reaction of Co(II)(OAc)(2)(H(2)O)(4) (OAc = acetate), perruthenate (RuO(4)(−)), and pyridine (py) yielded an unprecedented Ru(O)Co(3)(μ(3)-O)(4)(OAc)(4)(py)(3) cubane featuring an isolable, yet reactive, Ru(V)–oxo moiety. EPR, ENDOR, and DFT studies reveal a valence-localized [Ru(V)(S = 1/2)Co(III)(3)(S = 0)O(4)] configuration and non-negligible covalency in the cubane core. Significant oxyl radical character in the Ru(V)–oxo unit is experimentally demonstrated by radical coupling reactions between the oxo cubane and both 2,4,6-tri-tert-butylphenoxyl and trityl radicals. The oxo cubane oxidizes organic substrates and, notably, reacts with water to form an isolable μ-oxo bis-cubane complex [(py)(3)(OAc)(4)Co(3)(μ(3)-O)(4)Ru]–O–[RuCo(3)(μ(3)-O)(4)(OAc)(4)(py)(3)]. Redox activity of the Ru(V)–oxo fragment is easily tuned by the electron-donating ability of the distal pyridyl ligand set at the Co sites demonstrating strong electronic communication throughout the entire cubane cluster. Natural bond orbital calculations reveal cooperative orbital interactions of the [Co(3)O(4)] unit in supporting the Ru(V)–oxo moiety via a strong π-electron donation.
- Published
- 2019
28. C-H Activation by RuCo
- Author
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Jaruwan, Amtawong, Bastian Bjerkem, Skjelstad, Rex C, Handford, Benjamin A, Suslick, David, Balcells, and T Don, Tilley
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Electron Transport ,Oxygen ,Coordination Complexes ,Molecular Conformation ,Cobalt ,Protons ,Rubidium ,Density Functional Theory - Abstract
High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo
- Published
- 2021
29. Site-selective [2 + 2 +
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Gavin R, Kiel, Harrison M, Bergman, and T Don, Tilley
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Chemistry - Abstract
Polycyclic aromatic hydrocarbons (PAHs) are attractive synthetic building blocks for more complex conjugated nanocarbons, but their use for this purpose requires appreciable quantities of a PAH with reactive functional groups. Despite tremendous recent advances, most synthetic methods cannot satisfy these demands. Here we present a general and scalable [2 + 2 + n] (n = 1 or 2) cycloaddition strategy to access PAHs that are decorated with synthetically versatile alkynyl groups and its application to seven structurally diverse PAH ring systems (thirteen new alkynylated PAHs in total). The critical discovery is the site-selectivity of an Ir-catalyzed [2 + 2 + 2] cycloaddition, which preferentially cyclizes tethered diyne units with preservation of other (peripheral) alkynyl groups. The potential for generalization of the site-selectivity to other [2 + 2 + n] reactions is demonstrated by identification of a Cp2Zr-mediated [2 + 2 + 1]/metallacycle transfer sequence for synthesis of an alkynylated, selenophene-annulated PAH. The new PAHs are excellent synthons for macrocyclic conjugated nanocarbons. As a proof of concept, four were subjected to alkyne metathesis catalysis to afford large, PAH-containing arylene ethylene macrocycles, which possess a range of cavity sizes reaching well into the nanometer regime. Notably, these high-yielding macrocyclizations establish that synthetically convenient pentynyl groups can be effective for metathesis since the 4-octyne byproduct is sequestered by 5 Å MS. Most importantly, this work is a demonstration of how site-selective reactions can be harnessed to rapidly build up structural complexity in a practical, scalable fashion., An orthogonal [2 + 2 + n] cycloaddition/alkyne metathesis reaction sequence enables streamlined access to conjugated macrocyclic nanocarbons.
- Published
- 2021
30. A Dicopper Nitrenoid by Oxidation of a Cu
- Author
-
Addison N, Desnoyer, Amélie, Nicolay, Micah S, Ziegler, K V, Lakshmi, Thomas R, Cundari, and T Don, Tilley
- Subjects
Models, Molecular ,Molecular Structure ,Coordination Complexes ,Electrons ,Imines ,Oxidation-Reduction ,Copper - Abstract
A dicopper nitrenoid complex was prepared by formal oxidative addition of the nitrenoid fragment to a dicopper(I) center by reaction with the iminoiodinane PhINTs (Ts = tosylate). This nitrenoid complex, (DPFN)Cu
- Published
- 2021
31. Early-Transition-Metal Complexes of Functionalized Nonagermanide Clusters: Synthesis and Characterization of [Cp2(MeCN)Ti(η1-Ge9{Si(TMS)3}3)] and K3[Cp2Ti(η1-Ge9{Si(TMS)3}2)2]
- Author
-
Thomas F. Fässler, Felix S. Geitner, Oksana Storcheva, Wilhelm Klein, and T. Don Tilley
- Subjects
Inorganic Chemistry ,Core (optical fiber) ,Crystallography ,Transition metal ,010405 organic chemistry ,Chemistry ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Characterization (materials science) - Abstract
Anionic clusters with a homoatomic [Ge9] core are species with Ge atoms in low oxidation states. In this study their reaction with early-transition-metal complexes was investigated. We report the s...
- Published
- 2019
32. Stabilization of reactive Co 4 O 4 cubane oxygen-evolution catalysts within porous frameworks
- Author
-
Micah S. Ziegler, K. V. Lakshmi, T. Don Tilley, Jaruwan Amtawong, Maxwell W. Terban, James P. Dombrowski, Walter S. Drisdell, Julia Oktawiec, Junko Yano, Michal Bajdich, Simon J. L. Billinge, Kurt M. Van Allsburg, and Andy I. Nguyen
- Subjects
chemistry.chemical_compound ,Multidisciplinary ,chemistry ,Molecular model ,Cubane ,Reactive intermediate ,Intermolecular force ,Oxygen evolution ,Decomposition ,Combinatorial chemistry ,Artificial photosynthesis ,Catalysis - Abstract
A major challenge to the implementation of artificial photosynthesis (AP), in which fuels are produced from abundant materials (water and carbon dioxide) in an electrochemical cell through the action of sunlight, is the discovery of active, inexpensive, safe, and stable catalysts for the oxygen evolution reaction (OER). Multimetallic molecular catalysts, inspired by the natural photosynthetic enzyme, can provide important guidance for catalyst design, but the necessary mechanistic understanding has been elusive. In particular, fundamental transformations for reactive intermediates are difficult to observe, and well-defined molecular models of such species are highly prone to decomposition by intermolecular aggregation. Here, we present a general strategy for stabilization of the molecular cobalt-oxo cubane core (Co4O4) by immobilizing it as part of metal-organic frameworks, thus preventing intermolecular pathways of catalyst decomposition. These materials retain the OER activity and mechanism of the molecular Co4O4 analog yet demonstrate unprecedented long-term stability at pH 14. The organic linkers of the framework allow for chemical fine-tuning of activity and stability and, perhaps most importantly, provide "matrix isolation" that allows for observation and stabilization of intermediates in the water-splitting pathway.
- Published
- 2019
33. Element–Hydrogen Bond Activations at Cationic Platinum Centers To Produce Silylene, Germylene, Stannylene, and Stibido Complexes
- Author
-
Rex C. Handford, Rory Waterman, and T. Don Tilley
- Subjects
Silanes ,Silylation ,010405 organic chemistry ,Hydride ,Hydrogen bond ,Organic Chemistry ,Cationic polymerization ,Silylene ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Disilane ,Physical and Theoretical Chemistry ,Platinum - Abstract
Reactions of [(dippe)PtMe(Et2O)][BArf4] (4[BArf4], dippe = 1,2-bis(diisopropylphosphino)ethane; Arf = 3,5-(CF3)2C6H3) with Mes2EH2 (Mes = mesityl) liberate methane and produce silylene, germylene, or stannylene products [(dippe)Pt(H)═EMes2][BArf4] (E = Si, 1[BArf4]; Ge, 8; Sn, 9). In contrast, treatment of 4[BArf4] with tertiary silanes HSiR3 (R = Ph, Et, OEt) failed to give the expected cationic silyl complexes but instead produced the bridging hydride [(dippe)Pt(μ-H)]2[BArf4]2 (10) along with the corresponding disilane Si2R6. Complex 10 reacts with primary stibines RSbH2 (R = Mes, dmp) to afford dimeric stibido complexes [(dippe)Pt(μ-SbHR)]2[BArf4]2 (R = Mes, 11; dmp, 12) via Sb–H bond activation.
- Published
- 2019
34. Monomeric, Divalent Vanadium Bis(arylamido) Complexes: Linkage Isomerism and Reactivity
- Author
-
Patrick W. Smith, Vidmantas Kalendra, Irene C. Cai, Amélie Nicolay, Philip C. Bunting, Micah S. Ziegler, K. V. Lakshmi, Daniel S. Levine, and T. Don Tilley
- Subjects
010405 organic chemistry ,Ligand ,Aryl ,Organic Chemistry ,Vanadium ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,law ,Structural isomer ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Linkage isomerism ,Homoleptic ,Electron paramagnetic resonance - Abstract
Divalent complexes of vanadium were synthesized employing bulky silyl(aryl)amido ligands −N(SiiPr3)DIPP and −N(SitBu2Me)DIPP (DIPP = 2,6-iPr2C6H3). Solid-state structural characterization revealed that although the ligand −N(SiiPr3)DIPP supports a monomeric, bis(amido) complex of vanadium, its constitutional isomer −N(SitBu2Me)DIPP affords a homoleptic complex in which the vanadium center is sandwiched between the arene rings, an unusual binding mode for arylamido ligands. Magnetometry studies indicate that V[N(SiiPr3)DIPP]2 and V[(η5-DIPP)N(SitBu2Me)]2 have similar high-spin d3 electron configurations. However, spectroscopic methods, including electron paramagnetic resonance, nuclear magnetic resonance, infrared, and UV–visible spectroscopies, in addition to cyclic voltammetry and reactivity studies, suggest that V[N(SiiPr3)DIPP]2 is stereochemically nonrigid in solution, while V[(η5-DIPP)N(SitBu2Me)]2 is not. This nonrigidity explicitly impacts the reactivity of V[N(SiiPr3)DIPP]2, which can be used to a...
- Published
- 2019
35. An Anionic Ruthenium Dihydride [Cp*(iPr2MeP)RuH2]− and Its Conversion to Heterobimetallic Ru(μ-H)2M (M = Ir or Cu) Complexes
- Author
-
Scott R. Ellis, T. Don Tilley, Rex C. Handford, and Patrick W. Smith
- Subjects
Chemistry ,Sodium ,Organic Chemistry ,Resonance Raman spectroscopy ,Diastereomer ,chemistry.chemical_element ,Metathesis ,Medicinal chemistry ,Chloride ,Ruthenium ,Inorganic Chemistry ,Transition metal ,medicine ,Physical and Theoretical Chemistry ,Enantiomer ,medicine.drug - Abstract
A novel dihydridoruthenate, [(solv)Na][Cp*(iPr2MeP)RuH2] (2; solv = THF or OEt2), was synthesized from Cp*(iPr2MeP)RuCl (1) and sodium triethylborohydride. Compound 2 was used to generate “Cp*(iPr2MeP)RuH” equivalents by salt metathesis with 1, which resonance Raman spectroscopy indicates is a mixture of the terminal dinitrogen complex, Cp*(iPr2MeP)RuH(N2) (4), and diastereomers of the bridging dinitrogen complex [Cp*(iPr2MeP)RuH]2(μ-N2) (meso, 5, and a pair of enantiomers, 6). Compound 2 also reacted with the late transition metal chloride complexes [(COD)IrCl]2 and (IPr)CuCl [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] to form hydride-bridged heterobimetallic complexes Cp*(iPr2MeP)Ru(μ-H)2Ir(COD) (7) and Cp*(iPr2MeP)Ru(μ-H)2Cu(IPr) (8), respectively, that feature weakened Ru–H interactions relative to those of 2.
- Published
- 2019
36. A two-coordinate Ni(<scp>i</scp>) silyl complex: CO2 insertion and oxidatively-induced silyl migrations
- Author
-
T. Don Tilley and Ryan J. Witzke
- Subjects
Silylation ,010405 organic chemistry ,Ligand ,Metals and Alloys ,Silylene ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Chloride ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Ceramics and Composites ,medicine ,Reactivity (chemistry) ,medicine.drug - Abstract
The synthesis and reactivity of the first open-shell two-coordinate silyl complex, (IPr)Ni–Si(SiMe3)3, (IPr = 1,3-di(2,6-di-iso-propylphenyl)imidazolin-2-ylidene) is reported. Reaction with CO2 results in a novel insertion product that possesses a distorted geometry. Oxidations of the Ni center, with [Cp2Fe][B(C6F5)4] and Ph3CCl, result in migratory rearrangements of the silyl ligand, apparently via related silylene intermediates. The distinct oxidation products are interconverted by reactions that introduce or remove chloride.
- Published
- 2019
37. Synthesis, structure and DFT calculations of mononuclear cyclic (alkyl)(amino) carbene supported titanium(<scp>ii</scp>) complexes
- Author
-
T. Don Tilley, Zhenyang Lin, Qing Ye, Wangyang Ma, and Jing-Xuan Zhang
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Chemistry ,Potassium ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Chloride ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,medicine ,Carbene ,Alkyl ,medicine.drug ,Titanium - Abstract
The mononuclear cyclic (alkyl)(amino)carbene (cAAC) supported titanium(iii) chloride complex [(cAAC)2TiCl3] has been synthesized by treatment of free cAAC with TiCl3(THF)3. Further reduction of (cAAC)2TiCl3 with potassium graphite (KC8) afforded the desired (cAAC)2TiCl2 complex, which features a small S-T energy gap. Both complexes were structurally characterized and represent the first cAAC supported Ti complexes.
- Published
- 2019
38. Catalytic Olefin Hydrosilations Mediated by Ruthenium η3-H2Si σ Complexes of Primary and Secondary Silanes
- Author
-
Mark C. Lipke, Odile Eisenstein, T. Don Tilley, Christophe Raynaud, Marie-Noëlle Poradowski, Rutgers, The State University of New Jersey [New Brunswick] (RU), Rutgers University System (Rutgers), Department of Chemistry [Berkeley], University of California [Berkeley], University of California-University of California, Interface Theory Experiment : Mechanism & Modeling (ITEMM), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie du CNRS (INC)-École Supérieure Chimie Physique Électronique de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie du CNRS (INC)-École Supérieure Chimie Physique Électronique de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)
- Subjects
Allyl chloride ,Olefin fiber ,Silanes ,010405 organic chemistry ,Chemistry ,Silylene ,Cationic polymerization ,chemistry.chemical_element ,General Chemistry ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,Ruthenium ,chemistry.chemical_compound ,Proton NMR ,ComputingMilieux_MISCELLANEOUS - Abstract
Unambiguous examples of η3-H2SiH(R) complexes featuring a terminal Si–H bond have been prepared and examined as possible intermediates in olefin hydrosilation. These species were generated by displacement of the secondary silane ligands in [PhBPPh3]RuH[η3-H2SiMePh] (1b) (PhBPPh3 = PhB(CH2PPh2)3− by primary silanes RSiH3 to generate [PhBPPh3]RuH[η3-H2SiH(R)] (R = Cy (1d), CH2CH2Ph (1e), Trip = 2,4,6-iPr3C6H2 (1f)). Complexes 1d and 1e were characterized in solution, whereas 1f was isolated and studied in detail. Complex 1b is not a competent precatalyst for the hydrosilation of 1-hexene with CySiH3, whereas comparable conditions gave reasonable yields for the selective anti-Markovnikov hydrosilations of Cl3SiCH2CH═CH2 (89%), p-chlorostyrene (73%), and allyl chloride (70%). The 1H NMR spectrum of 1f collected at −30 °C displays a downfield signal (δ = 8.26 ppm) for the terminal Si–H bond that suggests electronic similarities between 1f and cationic silylene dihydrides [Cp*(iPr3P)Ru(H)2═SiH(R)]+ that mediate...
- Published
- 2018
39. Activation and Functionalization of C—H Bonds
- Author
-
Alan S. Goldman, Karen I. Goldberg, Alan S. Goldman, Karen I. Goldberg, Steven R. Klei, Kian L. Tan, Jeffrey T. Golden, Cathleen M. Yung, Reema K. Thalji, Kateri A. Ahrendt, Jonathan A. Ellman, T. Don Tilley, Robert G. Bergman, William D. Jones, Andrew J. Vetter, Douglas D. Wick, Todd O. Northcutt and Alan S. Goldman, Karen I. Goldberg, Alan S. Goldman, Karen I. Goldberg, Steven R. Klei, Kian L. Tan, Jeffrey T. Golden, Cathleen M. Yung, Reema K. Thalji, Kateri A. Ahrendt, Jonathan A. Ellman, T. Don Tilley, Robert G. Bergman, William D. Jones, Andrew J. Vetter, Douglas D. Wick, Todd O. Northcutt
- Published
- 2004
40. Concerted Proton-Electron Transfer Reactivity at a Multimetallic Co
- Author
-
Jaruwan, Amtawong, Bastian B, Skjelstad, David, Balcells, and T Don, Tilley
- Abstract
High-valent oxocobalt(IV) species have been invoked as key intermediates in oxidative catalysis, but investigations into the chemistry of proton-coupled redox reactions of such species have been limited. Herein, the reactivity of an established water oxidation catalyst, [Co
- Published
- 2020
41. Shape-Selective Synthesis of Pentacene Macrocycles and the Effect of Geometry on Singlet Fission
- Author
-
Harrison Bergman, Gavin Kiel, Ryan J. Witzke, David P. Nenon, Adam M. Schwartzberg, Yi Liu, and T. Don Tilley
- Subjects
Physics::Chemical Physics - Abstract
Pentacene’s extraordinary photophysical and electronic properties are highly dependent on intermolecular, through-space interactions. Macrocyclic arrangements of chromophores have been shown to provide a high level of control over these interactions, but few examples exist for pentacene due to inherent synthetic challenges. In this work, zirconocene-mediated alkyne coupling was used as a dynamic covalent C-C bond forming reaction to synthesize two geometrically distinct, pentacene-containing macrocycles on a gram scale and in four or fewer steps. Both macrocycles undergo singlet fission in solution, with rates that differ by an order of magnitude while the rate of triplet recombination is approximately the same. This independent modulation of singlet and triplet decay rates is highly desirable for the design of efficient singlet fission materials. The dimeric macrocycle adopts a columnar packing motif in the solid state, with large void spaces between pentacene units of the crystal lattice.
- Published
- 2020
42. Gauging aromatic conjugation and charge delocalization in the aryl silanes Ph
- Author
-
Nicholas A, Phillips, Patrick W, Smith, T Don, Tilley, and Stefan G, Minasian
- Abstract
Si K-edge X-ray absorption spectra (XAS) have been measured experimentally and calculated using time-dependent density functional theory (TDDFT) to investigate electronic structure in aryl silanes, PhnSiH4-n (n = 0-4). Adding aryl groups to SiH4 splits the Si-H σ-antibonding orbitals into new orbitals with Si-Ph π-bonding (πb) and π-antibonding (π*) character. Greater aryl substitution is reflected by increasingly intense Si 1s → πb and Si 1s → π* transitions, and weaker transitions into the Si-H and Si-C σ* orbitals. These observations are consistent with known trends in the hydride donor ability of aryl silanes, which is driven in part by the composition of the LUMOs and the accessibility of pathways for electron delocalization through aromatic conjugation. Methodology developed for liquid-phase Si K-edge XAS measurements on PhSiH3 and Ph2SiH2 will enable dynamic studies of chemical transformations involving silicon-containing catalysts, intermediates, and substrates.
- Published
- 2020
43. MicroED Elucidation of Diverse Solid-State Packing in a Family of Electron-Deficient Expanded Helicenes
- Author
-
Christopher G. Jones, Adrian E. Samkian, Hosea M. Nelson, Julia Oktawiec, Harrison M. Bergman, Gavin R. Kiel, and T. Don Tilley
- Subjects
Materials science ,law.invention ,Crystal ,Crystallography ,chemistry.chemical_compound ,Electron diffraction ,Helicene ,chemistry ,law ,Self-assembly ,Homochirality ,Crystallization ,Single crystal ,Divergent synthesis - Abstract
Solid-state packing plays a defining role in the properties of a molecular organic material, but it is difficult to elucidate in the absence of single crystals that are suitable for X-ray diffraction. Here, we demonstrate the coupling of divergent synthesis with microcrystal electron diffraction (MicroED) for rapid assessment of solid-state packing motifs, using a class of chiral nanocarbons – expanded helicenes – as a proof of concept. Two highly selective oxidative dearomatizations of a readily-accessible helicene provided a divergent route to four electron-deficient analogues containing quinone or quinoxaline units. Crystallization efforts consistently yielded microcrystals that were unsuitable for single crystal X-ray diffraction, but ideal for MicroED. This technique facilitated the elucidation of solid-state structures of all five compounds with
- Published
- 2020
44. MicroED Elucidation of Diverse Solid-State Packing in a Family of Electron-Deficient Expanded Helicenes
- Author
-
Adrian Samkian, Gavin R. Kiel, Christopher G. Jones, Harrison Bergman, Julia Oktawiec, Hosea Nelson, and T. Don Tilley
- Abstract
Solid-state packing plays a defining role in the properties of a molecular organic material, but it is difficult to elucidate in the absence of single crystals that are suitable for X-ray diffraction. Here, we demonstrate the coupling of divergent synthesis with microcrystal electron diffraction (MicroED) for rapid assessment of solid-state packing motifs, using a class of chiral nanocarbons – expanded helicenes – as a proof of concept. Two highly selective oxidative dearomatizations of a readily-accessible helicene provided a divergent route to four electron-deficient analogues containing quinone or quinoxaline units. Crystallization efforts consistently yielded microcrystals that were unsuitable for single crystal X-ray diffraction, but ideal for MicroED. This technique facilitated the elucidation of solid-state structures of all five compounds with
- Published
- 2020
45. Bimetallics in a Nutshell: Complexes Supported by Chelating Naphthyridine-Based Ligands
- Author
-
T. Don Tilley, Addison N. Desnoyer, Micah S. Ziegler, Pablo Ríos, and Amélie Nicolay
- Subjects
biology ,010405 organic chemistry ,Ligand ,Chemistry ,Aryl ,Active site ,General Medicine ,General Chemistry ,010402 general chemistry ,Metathesis ,01 natural sciences ,Combinatorial chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,biology.protein ,Moiety ,Azide ,Isostructural ,Bimetallic strip - Abstract
Bimetallic motifs are a structural feature common to some of the most effective and synthetically useful catalysts known, including in the active sites of many metalloenzymes and on the surfaces of industrially relevant heterogeneous materials. However, the complexity of these systems often hampers detailed studies of their fundamental properties. To glean valuable mechanistic insight into how these catalysts function, this research group has prepared a family of dinucleating 1,8-naphthyridine ligands that bind two first-row transition metals in close proximity, originally designed to help mimic the proposed active site of metal oxide surfaces. Of the various bimetallic combinations examined, dicopper(I) is particularly versatile, as neutral bridging ligands adopt a variety of different binding modes depending on the configuration of frontier orbitals available to interact with the Cu centers. Organodicopper complexes are readily accessible, either through the traditional route of salt metathesis or via the activation of tetraarylborate anions through aryl group abstraction by a dicopper(I) unit. The resulting bridging aryl complexes engage in C-H bond activations, notably with terminal alkynes to afford bridging alkynyl species. The μ-hydrocarbyl complexes are surprisingly tolerant of water and elevated temperatures. This stability was leveraged to isolate a species that typically represents a fleeting intermediate in Cu-catalyzed azide-alkyne coupling (CuAAC); reaction of a bridging alkynyl complex with an organic azide afforded the first example of a well-defined, symmetrically bridged dicopper triazolide. This complex was shown to be an intermediate during CuAAC, providing support for a proposed bimetallic mechanism. These platforms are not limited to formally low oxidation states; chemical oxidation of the hydrocarbyl complexes cleanly results in formation of mixed valence CuICuII complexes with varying degrees of distortion in both the bridging moiety and the dicopper core. Higher oxidation states, e.g., dicopper(II), are easily accessed via oxidation of a dicopper(I) compound with air to give a CuII2(μ-OH)2 complex. Reduction of this compound with silanes resulted in the unexpected formation of pentametallic copper(I) dihydride clusters or trimetallic monohydride complexes, depending on the nature of the silane. Finally, development of an unsymmetrical naphthyridine ligand with mixed donor side-arms enables selective synthesis of an isostructural series of six heterobimetallic complexes, demonstrating the power of ligand design in the preparation of heterometallic assemblies.
- Published
- 2020
46. Mechanistic Interrogation of Alkyne Hydroarylations Catalyzed by Highly Reduced, Single-Component Cobalt Complexes
- Author
-
T. Don Tilley and Benjamin A. Suslick
- Subjects
inorganic chemicals ,chemistry.chemical_classification ,organic chemicals ,Single component ,Alkyne ,chemistry.chemical_element ,General Chemistry ,Cobalt ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Benzylidene Compounds ,Catalysis ,0104 chemical sciences ,Kinetics ,Colloid and Surface Chemistry ,chemistry ,Models, Chemical ,Coordination Complexes ,Reagent ,Alkynes ,heterocyclic compounds - Abstract
Highly reactive catalysts for ortho-hydroarylations of alkynes have previously been reported to result from activation of CoBr2 by Grignard reagents, but the operative mechanism and identity of the...
- Published
- 2020
47. A Dicopper Platform that Stabilizes the Formation of Pentanuclear Coinage Metal Hydride Complexes
- Author
-
Nicole A. Torquato, T. Don Tilley, Addison N. Desnoyer, Micah S. Ziegler, and Amélie Nicolay
- Subjects
Silanes ,010405 organic chemistry ,Hydride ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Copper ,Catalysis ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,visual_art.visual_art_medium ,Copper hydride ,Hydroxide ,Dehydrogenation - Abstract
Reduction of a dicopper(II) bis(hydroxide) complex with silanes in the presence of external copper or silver cations results in the formation of multinuclear hydride clusters, which were characterized by a variety of NMR spectroscopic experiments and X-ray crystallography. In particular, the pentanuclear complexes adopt an unusual planar "bow tie" configuration. The copper hydride complexes are efficient catalysts for the dehydrogenation of formic acid to H2 and CO2 .
- Published
- 2020
48. Site-selective [2 + 2 + n] cycloadditions for rapid, scalable access to alkynylated polycyclic aromatic hydrocarbons
- Author
-
Harrison M. Bergman, T. Don Tilley, and Gavin R. Kiel
- Subjects
Chemistry ,Synthon ,Arylene ,Chemical Sciences ,Alkyne metathesis ,Bioengineering ,General Chemistry ,Metallacycle ,Conjugated system ,Metathesis ,Ring (chemistry) ,Combinatorial chemistry ,Cycloaddition - Abstract
Polycyclic aromatic hydrocarbons (PAHs) are attractive synthetic building blocks for more complex conjugated nanocarbons, but their use for this purpose requires appreciable quantities of a PAH with reactive functional groups. Despite tremendous recent advances, most synthetic methods cannot satisfy these demands. Here we present a general and scalable [2 + 2 + n] (n = 1 or 2) cycloaddition strategy to access PAHs that are decorated with synthetically versatile alkynyl groups and its application to seven structurally diverse PAH ring systems (thirteen new alkynylated PAHs in total). The critical discovery is the site-selectivity of an Ir-catalyzed [2 + 2 + 2] cycloaddition, which preferentially cyclizes tethered diyne units with preservation of other (peripheral) alkynyl groups. The potential for generalization of the site-selectivity to other [2 + 2 + n] reactions is demonstrated by identification of a Cp2Zr-mediated [2 + 2 + 1]/metallacycle transfer sequence for synthesis of an alkynylated, selenophene-annulated PAH. The new PAHs are excellent synthons for macrocyclic conjugated nanocarbons. As a proof of concept, four were subjected to alkyne metathesis catalysis to afford large, PAH-containing arylene ethylene macrocycles, which possess a range of cavity sizes reaching well into the nanometer regime. Notably, these high-yielding macrocyclizations establish that synthetically convenient pentynyl groups can be effective for metathesis since the 4-octyne byproduct is sequestered by 5 A MS. Most importantly, this work is a demonstration of how site-selective reactions can be harnessed to rapidly build up structural complexity in a practical, scalable fashion.
- Published
- 2020
49. Site-Selective [2+2+n] Cycloadditions for Rapid, Scalable Access to Alkynylated Polycyclic Aromatic Hydrocarbons
- Author
-
Gavin R. Kiel, Harrison Bergman, and T. Don Tilley
- Abstract
Polycyclic aromatic hydrocarbons (PAHs) are attractive synthetic building blocks for more complex conjugated nanocarbons, but their use for this purpose requires appreciable quantities of a PAH with reactive functional groups. Despite tremendous recent advances, most synthetic methods cannot satisfy these demands. Here we present a general and scalable [2+2+n] (n = 1 or 2) cycloaddition strategy to access PAHs that are decorated with synthetically versatile alkynyl groups and its application to seven structurally diverse PAH ring systems (thirteen new alkynylated PAHs in total). The critical discovery is the site-selectivity of an Ir-catalyzed [2+2+2] cycloaddition, which preferentially cyclizes tethered diyne units with preservation of other (peripheral) alkynyl groups. The potential for generalization of the site-selectivity to other [2+2+n] reactions is demonstrated by identification of a Cp2Zr-mediated [2+2+1] / metallacycle transfer sequence for synthesis of an alkynylated, selenophene-annulated PAH. The new PAHs are excellent synthons for macrocyclic conjugated nanocarbons. As a proof of concept, four were subjected to Mo catalysis to afford large, PAH-containing arylene ethylene macrocycles, which possess a range of cavity sizes reaching well into the nanometer regime. More generally, this work is a demonstration of how site-selective reactions can be harnessed to rapidly build up structural complexity in a practical, scalable fashion.
- Published
- 2019
50. Dicopper Alkyl Complexes: Synthesis, Structure, and Unexpected Persistence
- Author
-
T. Don Tilley, Micah S. Ziegler, Hasan Celik, Amélie Nicolay, Daniel S. Levine, and Nicole A. Torquato
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Organic Chemistry ,Cationic polymerization ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,Medicinal chemistry ,Copper ,0104 chemical sciences ,Inorganic Chemistry ,chemistry ,Reagent ,Physical and Theoretical Chemistry ,Alkyl - Abstract
Cationic μ-alkyl dicopper complexes [Cu2(μ-η1:η1-R)DPFN]NTf2 (R = CH3, CH2CH3, CH2C(CH3)3; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine NTf2– = N(SO2CF3)2–) were synthesized by treatment of the acetonitrile-bridged dicopper complex [Cu2(μ-η1:η1-NCCH3)DPFN](NTf2)2 with LiR or MgR2. Structural characterization by X-ray crystallography and NMR spectroscopy revealed that the alkyl ligands symmetrically bridge the two copper centers, and the complexes persist in room-temperature solution. Notably, the μ-methyl complex showed less than 20% decomposition after 34 days in room-temperature THF solution. Treatment of the μ-methyl complex with acids allows installation of a range of monoanionic bridging ligands. However, surprisingly insertion into the dicopper–carbon bond was not observed upon addition of a variety of reagents, suggesting that these complexes exhibit a fundamentally new reactivity profile for alkylcopper species. Electrochemical characterization revealed oxidation–reduction events t...
- Published
- 2018
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