Evaluation of Donor and Steric Properties of Anionic Ligands on High Valent Transition Metals

DiFranco, Stephen A.; Maciulis, Nicholas A.; Staples, Richard J.; Batrice, Rami J.; Odom, Aaron L.

doi:10.1021/ic202524r

Cited by 62 publications

(73 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, the ligand donor strengths are ordered N < Cl < O, based on our data as well as ligand parameters. 19,20,24,25 The d orbital that experiences the greatest net ligand donation becomes the HOMO that gives the oxidation enhancement effect; Table 2 shows the resulting pattern.…”

Section: Resultsmentioning

confidence: 99%

“…This ligand was designed to incorporate a number of relevant properties. First, it contains a highly σ and π electron-donating alkoxide arm, 19,20 which not only allows it to stabilize high oxidation states, but also enhances water solubility and permits reversible protonation and hydrogen bonding. Second, this alkoxide is protected from oxidative degradation by the geminal dimethyl substitution, allowing it to survive the harsh reaction conditions required for water oxidation or formation of high-valent metal complexes.…”

Section: Introductionmentioning

confidence: 99%

“…Simple treatments, such as Lever parametrization, 19,20,24–26 cannot account for differences due to isomerism. This geometry effect was indeed noted by Lever, 24 but only for strong acceptor ligands (CO, NO + ).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A full set of iridium(iv) pyridine-alkoxide stereoisomers: highly geometry-dependent redox properties

et al. 2017

View full text Add to dashboard Cite

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A full set of iridium(iv) pyridine-alkoxide stereoisomers: highly geometry-dependent redox properties

et al. 2017

View full text Add to dashboard Cite

show abstract

“…These include Tolman’s cone angle and electronic parameter (TEP: the symmetric carbonyl stretching frequency of the complex LNi(CO) 3 ) [16, 17, 18]; Lever’s electronic parameter (LEP: the redox potential for reduction of L n Ru III to L n Ru II ) [19]; Odom’s amide rotation parameter in NCr( i Pr 2 N) 2 X complexes [20]; and other less-used tools [21, 22, 23, 24, 25, 26]. Interestingly, our measured and calculated ring flip barriers have poor correlation to these systems.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, structure, and conformational dynamics of rhodium and iridium complexes of dimethylbis(2-pyridyl)borate

et al. 2014

View full text Add to dashboard Cite

Rhodium(I) and Iridium(I) borate complexes of the structure [Me2B(2-py)2]ML2 (L2 = (tBuNC)2, (CO)2, (C2H4)2, cod, dppe) were prepared and structurally characterized (cod = 1,5-cyclooctadiene; dppe = 1,2-diphenylphosphinoethane). Each contains a boat-configured chelate ring that participates in a boat-to-boat ring flip. Computational evidence shows that the ring flip proceeds through a transition state that is near planarity about the chelate ring. We observe an empirical, quantitative correlation between the barrier of this ring flip and the π acceptor ability of the ancillary ligand groups on the metal. The ring flip barrier correlates weakly to the Tolman and Lever ligand parameterization schemes, apparently because these combine both σ and π effects while we propose that the ring flip barrier is dominated by π bonding. This observation is consistent with metal-ligand π interactions becoming temporarily available only in the near-planar transition state of the chelate ring flip and not the boat-configured ground state. Thus, this is a first-of-class observation of metal-ligand π bonding governing conformational dynamics.

show abstract

“…11 Making the catalyst more electron-rich should diminish the protonolysis rate and increase the relative abundance of intermediate B, allowing insertion of a second equiv of isonitrile. The catalyst was prepared (eq 7) from 2,3-dimethylindole (HInd Me2 ).…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

Titanium-Catalyzed Multicomponent Couplings: Efficient One-Pot Syntheses of Nitrogen Heterocycles

2015

Self Cite

View full text Add to dashboard Cite

Nitrogen-based heterocycles are important frameworks for pharmaceuticals, natural products, organic dyes for solar cells, and many other applications. Catalysis for the formation of heterocyclic scaffolds, like many C-C and C-N bond-forming reactions, has focused on the use of rare, late transition metals like palladium and gold. Our group is interested in the use of Earth-abundant catalysts based on titanium to generate heterocycles using multicomponent coupling strategies, often in one-pot reactions. To be of maximal utility, the catalysts need to be easily prepared from inexpensive reagents, and that has been one guiding principle in the research. For this purpose, a series of easily prepared pyrrole-based ligands has been developed. Titanium imido complexes are known to catalyze the hydroamination of alkynes, and this reaction has been used to advantage in the production of α,β-unsaturated imines from 1,3-enynes and pyrroles from 1,4-diynes. Likewise, catalyst design can be used to find complexes applicable to hydrohydrazination, coupling of a hydrazine and alkyne, which is a method for the production of hydrazones. Many of the hydrazones synthesized are converted to indoles through Fischer cyclization by addition of a Lewis acid. However, more complex products are available in a single catalytic cycle through coupling of isonitriles, primary amines, and alkynes to give tautomers of 1,3-diimines, iminoamination (IA). The products of IA are useful intermediates for the one-pot synthesis of pyrazoles, pyrimidines, isoxazoles, quinolines, and 2-amino-3-cyanopyridines. The regioselectivity of the reactions is elucidated in some detail for some of these heterocycles. The 2-amino-3-cyanopyridines are synthesized through isolable intermediates, 1,2-dihydro-2-iminopyridines, which undergo Dimroth rearrangement driven by aromatization of the pyridine ring; the proposed mechanism of the reaction is discussed. The IA-based heterocyclic syntheses can be accomplished start to finish (catalyst generation to heterocyclic synthesis) in a single vessel. The catalyst can be formed in situ from commercially available Ti(NMe2)4 and the protonated form of the ligand. Then, the primary amine, alkyne, and isonitrile are added to the flask, and the IA product is synthesized. The volatiles are removed (if necessary), and the next reagent is added. A brief video showing the process for the simple heterocycle 4-phenylpyrazole from phenylacetylene, cyclohexylamine, tert-butylisonitrile, and hydrazine hydrate is included. Further development in this field will unlock new, efficient reactions for the production of carbon-carbon and carbon-nitrogen bonds. As an example of such a process recently discovered, a catalyst for the regioselective production of pyrazoles in a single step from terminal alkynes, hydrazines, and cyclohexylisonitrile is discussed. Using titanium catalysis, many heterocyclic cores can be accessed easily and efficiently. Further, the early metal chemistry described is often orthogonal to late metal-based reactions, whi...

show abstract

Evaluation of Donor and Steric Properties of Anionic Ligands on High Valent Transition Metals

Cited by 62 publications

References 72 publications

A full set of iridium(iv) pyridine-alkoxide stereoisomers: highly geometry-dependent redox properties

A full set of iridium(iv) pyridine-alkoxide stereoisomers: highly geometry-dependent redox properties

Synthesis, structure, and conformational dynamics of rhodium and iridium complexes of dimethylbis(2-pyridyl)borate

Titanium-Catalyzed Multicomponent Couplings: Efficient One-Pot Syntheses of Nitrogen Heterocycles

Contact Info

Product

Resources

About