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212 results on '"Manor, Brian C."'

1. Electronic structure studies reveal 4f/5d mixing and its effect on bonding characteristics in Ce-imido and -oxo complexes

Author

Moreau, Liane M, Lapsheva, Ekaterina, Amaro-Estrada, Jorge I, Gau, Michael R, Carroll, Patrick J, Manor, Brian C, Qiao, Yusen, Yang, Qiaomu, Lukens, Wayne W, Sokaras, Dimosthenis, Schelter, Eric J, Maron, Laurent, and Booth, Corwin H

Subjects
Inorganic Chemistry, Chemical Sciences, Chemical sciences
Abstract

This study presents the role of 5d orbitals in the bonding, and electronic and magnetic structure of Ce imido and oxo complexes synthesized with a tris(hydroxylaminato) [((2- t BuNO)C6H4CH2)3N]3- (TriNO x 3-) ligand framework, including the reported synthesis and characterization of two new alkali metal-capped Ce oxo species. X-ray spectroscopy measurements reveal that the imido and oxo materials exhibit an intermediate valent ground state of the Ce, displaying hallmark features in the Ce LIII absorption of partial f-orbital occupancy that are relatively constant for all measured compounds. These spectra feature a double peak consistent with other formal Ce(iv) compounds. Magnetic susceptibility measurements reveal enhanced levels of temperature-independent paramagnetism (TIP). In contrast to systems with direct bonding to an aromatic ligand, no clear correlation between the level of TIP and f-orbital occupancy is observed. CASSCF calculations defy a conventional van Vleck explanation of the TIP, indicating a single-reference ground state with no low-lying triplet excited state, despite accurately predicting the measured values of f-orbital occupancy. The calculations do, however, predict strong 4f/5d hybridization. In fact, within these complexes, despite having similar f-orbital occupancies and therefore levels of 4f/5d hybridization, the d-state distributions vary depending on the bonding motif (Ce[double bond, length as m-dash]O vs. Ce[double bond, length as m-dash]N) of the complex, and can also be fine-tuned based on varying alkali metal cation capping species. This system therefore provides a platform for understanding the characteristic nature of Ce multiple bonds and potential impact that the associated d-state distribution may have on resulting reactivity.

Published
2022

2. Cerium( iv ) complexes with guanidinate ligands: intense colors and anomalous electronic structures

Author

Qiao, Yusen, Yin, Haolin, Moreau, Liane M, Feng, Rulin, Higgins, Robert F, Manor, Brian C, Carroll, Patrick J, Booth, Corwin H, Autschbach, Jochen, and Schelter, Eric J

Subjects
Inorganic Chemistry, Chemical Sciences, Affordable and Clean Energy, Chemical sciences
Abstract

A series of cerium(iv) mixed-ligand guanidinate-amide complexes, {[(Me3Si)2NC(N i Pr)2] x CeIV[N(SiMe3)2]3-x }+ (x = 0-3), was prepared by chemical oxidation of the corresponding cerium(iii) complexes, where x = 1 and 2 represent novel complexes. The Ce(iv) complexes exhibited a range of intense colors, including red, black, cyan, and green. Notably, increasing the number of the guanidinate ligands from zero to three resulted in significant redshift of the absorption bands from 503 nm (2.48 eV) to 785 nm (1.58 eV) in THF. X-ray absorption near edge structure (XANES) spectra indicated increasing f occupancy (n f) with more guanidinate ligands, and revealed the multiconfigurational ground states for all Ce(iv) complexes. Cyclic voltammetry experiments demonstrated less stabilization of the Ce(iv) oxidation state with more guanidinate ligands. Moreover, the Ce(iv) tris(guanidinate) complex exhibited temperature independent paramagnetism (TIP) arising from the small energy gap between the ground- and excited states with considerable magnetic moments. Computational analysis suggested that the origin of the low energy absorption bands was a charge transfer between guanidinate π orbitals that were close in energy to the unoccupied Ce 4f orbitals. However, the incorporation of sterically hindered guanidinate ligands inhibited optimal overlaps between Ce 5d and ligand N 2p orbitals. As a result, there was an overall decrease of ligand-to-metal donation and a less stabilized Ce(iv) oxidation state, while at the same time, more of the donated electron density ended up in the 4f shell. The results indicate that incorporating guanidinate ligands into Ce(iv) complexes gives rise to intense charge transfer bands and noteworthy electronic structures, providing insights into the stabilization of tetravalent lanthanide oxidation states.

Published
2021

3. Cerium(iv) complexes with guanidinate ligands: intense colors and anomalous electronic structures.

Author

Qiao, Yusen, Yin, Haolin, Moreau, Liane M, Feng, Rulin, Higgins, Robert F, Manor, Brian C, Carroll, Patrick J, Booth, Corwin H, Autschbach, Jochen, and Schelter, Eric J

Subjects
Chemical Sciences
Abstract

A series of cerium(iv) mixed-ligand guanidinate-amide complexes, {[(Me3Si)2NC(N i Pr)2] x CeIV[N(SiMe3)2]3-x }+ (x = 0-3), was prepared by chemical oxidation of the corresponding cerium(iii) complexes, where x = 1 and 2 represent novel complexes. The Ce(iv) complexes exhibited a range of intense colors, including red, black, cyan, and green. Notably, increasing the number of the guanidinate ligands from zero to three resulted in significant redshift of the absorption bands from 503 nm (2.48 eV) to 785 nm (1.58 eV) in THF. X-ray absorption near edge structure (XANES) spectra indicated increasing f occupancy (n f) with more guanidinate ligands, and revealed the multiconfigurational ground states for all Ce(iv) complexes. Cyclic voltammetry experiments demonstrated less stabilization of the Ce(iv) oxidation state with more guanidinate ligands. Moreover, the Ce(iv) tris(guanidinate) complex exhibited temperature independent paramagnetism (TIP) arising from the small energy gap between the ground- and excited states with considerable magnetic moments. Computational analysis suggested that the origin of the low energy absorption bands was a charge transfer between guanidinate π orbitals that were close in energy to the unoccupied Ce 4f orbitals. However, the incorporation of sterically hindered guanidinate ligands inhibited optimal overlaps between Ce 5d and ligand N 2p orbitals. As a result, there was an overall decrease of ligand-to-metal donation and a less stabilized Ce(iv) oxidation state, while at the same time, more of the donated electron density ended up in the 4f shell. The results indicate that incorporating guanidinate ligands into Ce(iv) complexes gives rise to intense charge transfer bands and noteworthy electronic structures, providing insights into the stabilization of tetravalent lanthanide oxidation states.

Published
2020

12. N−H Bond Formation at a Diiron Bridging Nitride

Author

Zhang, Shaoguang, primary, Cui, Peng, additional, Liu, Tianchang, additional, Wang, Qiuran, additional, Longo, Thomas J., additional, Thierer, Laura M., additional, Manor, Brian C., additional, Gau, Michael R., additional, Carroll, Patrick J., additional, Papaefthymiou, Georgia C., additional, and Tomson, Neil C., additional

Published
2020
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15. Molecular titanium nitrides: nucleophiles unleashed† †Electronic supplementary information (ESI) available. CCDC 1490138–1490143. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc03422e Click here for additional data file. Click here for additional data file

Author

Grant, Lauren N., Pinter, Balazs, Kurogi, Takashi, Carroll, Maria E., Wu, Gang, Manor, Brian C., Carroll, Patrick J., and Mindiola, Daniel J.

Subjects
Chemistry
Abstract

Reactivity studies of a rare example of a molecular titanium nitride are presented. A combination of theory and NMR spectroscopy provide a description of the bonding in the these nitrides, the role of the counter cation, K+, as well as the origin of their highly downfield 15N NMR spectroscopic shifts., In this contribution we present reactivity studies of a rare example of a titanium salt, in the form of [μ2-K(OEt2)]2[(PN)2Ti 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 N]2 (1) (PN– = N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) to produce a series of imide moieties including rare examples such as methylimido, borylimido, phosphonylimido, and a parent imido. For the latter, using various weak acids allowed us to narrow the pK a range of the NH group in (PN)2TiNH to be between 26–36. Complex 1 could be produced by a reductively promoted elimination of N2 from the azide precursor (PN)2TiN3, whereas reductive splitting of N2 could not be achieved using the complex (PN)2Ti 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 NNTi(PN)2 (2) and a strong reductant. Complete N-atom transfer reactions could also be observed when 1 was treated with ClC(O)tBu and OCCPh2 to form NCtBu and KNCCPh2, respectively, along with the terminal oxo complex (PN)2TiO, which was also characterized. A combination of solid state 15N NMR (MAS) and theoretical studies allowed us to understand the shielding effect of the counter cation in dimer 1, the monomer [K(18-crown-6)][(PN)2TiN], and the discrete salt [K(2,2,2-Kryptofix)][(PN)2TiN] as well as the origin of the highly downfield 15N NMR resonance when shifting from dimer to monomer to a terminal nitride (discrete salt). The upfield shift of 15Nnitride resonance in the 15N NMR spectrum was found to be linked to the K+ induced electronic structural change of the titanium-nitride functionality by using a combination of MO analysis and quantum chemical analysis of the corresponding shielding tensors.

Published
2016

16. 13C NMR Shifts as an Indicator of U−C Bond Covalency in Uranium(VI) Acetylide Complexes: An Experimental and Computational Study

Author

Mullane, Kimberly C., Hrobarik, Peter, Cheisson, Thibault, Manor, Brian C., Carroll, Patrick J., and Schelter, Eric J.

Abstract

A series of uranium(VI)−acetylide complexes of the generalformula UVI(O)(CC-C6H4-R)[N(SiMe3)2]3, with variation of the parasubstituent (R = NMe2, OMe, Me, Ph, H, Cl) on the aryl(acetylide) ring, wasprepared. These compounds were analyzed by 13C NMR spectroscopy, whichshowed that the acetylide carbon bound to the uranium(VI) center, U-CC-Ar, was shifted strongly downfield, withδ(13C) values ranging from 392.1to 409.7 ppm for Cl and NMe2 substituted complexes, respectively. Theseextreme high-frequency13C resonances are attributed to large negativeparamagnetic (σpara) and relativistic spin−orbit (σSO) shielding contributions,associated with extensive U(5f) and C(2s) orbital contributions to the U−Cbonding in title complexes. The trend in the 13C chemicalshift of the terminalacetylide carbon is opposite that observed in the series of parent(aryl)acetylenes, due to shielding effects of the para substituent. The 13Cchemical shifts of the acetylide carbon instead correlate with DFT computedU−C bond lengths and corresponding QTAIM delocalization indices or Wiberg bond orders. SQUID magnetic susceptibilitymeasurements were indicative of the Van Vleck temperature independent paramagnetism (TIP) of the uranium(VI) complexes,suggesting a magnetic field-induced mixing of the singlet ground-state (f0) of the U(VI) ion with low-lying (thermallyinaccessible) paramagnetic excited states (involved also in the perturbation-theoretical treatment of the unusually largeparamagnetic and SO contributions to the 13C shifts). Thus, together with reported data, we demonstrate that the sensitive 13CNMR shifts serve as a direct, simple, and accessible measure of uranium(VI)-carbon bond covalency.

Published
2018

24. Magnetic Field Directed Rare‐Earth Separations.

Author

Higgins, Robert F., Cheisson, Thibault, Cole, Bren E., Manor, Brian C., Carroll, Patrick J., and Schelter, Eric J.

Subjects
MAGNETIC fields, RARE earth metals, ION bombardment, MAGNETICS, MAGNETIC properties, BINARY mixtures, RARE earth ions
Abstract

The separation of rare‐earth ions from one another is challenging due to their chemical and physical similarities. Nearly all rare‐earth separations rely upon small changes in ionic radii to direct speciation or reactivity. Herein, we show that the intrinsic magnetic properties of the rare‐earth ions impact the separations of light/heavy and selected heavy/heavy binary mixtures. Using TriNOx3− ([{(2‐tBuNO)C6H4CH2}3N]3−) rare‐earth complexes, we efficiently and selectively crystallized heavy rare earths (Tb–Yb) from a mixture with light rare earths (La and Nd) in the presence of an external Fe14Nd2B magnet, concomitant with the introduction of a concentration gradient (decrease in temperature). The optimal separation was observed for an equimolar mixture of La:Dy, which gave an enrichment factor of EFLa:Dy=297±31 for the solid fraction, compared to EFLa:Dy=159±22 in the absence of the field, and achieving a 99.7 % pure Dy sample in one step. These results indicate that the application of a magnetic field can improve performance in a molecular separation system for paramagnetic rare‐earth cations. [ABSTRACT FROM AUTHOR]

Published
2020
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39. Palladium-Catalyzed Enantioselective Arylation of Aryl Sulfenate Anions: A Combined Experimental and Computational Study

Author

Jia, Tiezheng, primary, Zhang, Mengnan, additional, McCollom, Samuel P., additional, Bellomo, Ana, additional, Montel, Sonia, additional, Mao, Jianyou, additional, Dreher, Spencer D., additional, Welch, Christopher J., additional, Regalado, Erik L., additional, Williamson, R. Thomas, additional, Manor, Brian C., additional, Tomson, Neil C., additional, and Walsh, Patrick J., additional

Published
2017
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43. Molecular titanium nitrides: nucleophiles unleashed

Author

Grant, Lauren N., primary, Pinter, Balazs, additional, Kurogi, Takashi, additional, Carroll, Maria E., additional, Wu, Gang, additional, Manor, Brian C., additional, Carroll, Patrick J., additional, and Mindiola, Daniel J., additional

Published
2017
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46. Interdependent Metal–Metal Bonding and Ligand Redox-Activity in a Series of Dinuclear Macrocyclic Complexes of Iron, Cobalt, and Nickel

Author

Wang, Qiuran, Zhang, Shaoguang, Cui, Peng, Weberg, Alexander B., Thierer, Laura M., Manor, Brian C., Gau, Michael R., Carroll, Patrick J., and Tomson, Neil C.

Abstract

This report describes an isostructural series of dinuclear iron, cobalt, and nickel complexes bound by a redox-active macrocyclic ligand. The series spans five redox levels (34–38 e–/cluster core), allowing for a detailed investigation into both the degree of metal–metal interaction and the extent of ligand-based redox-activity. Magnetometry, electrochemistry, UV–vis–NIR absorption spectroscopy, and crystallography were used in conjunction with DFT computational analyses to extract the electronic structures of the six homodinuclear complexes. The isoelectronic, 34 e–species [(3PDI2)Fe2(PMe3)2(μ-Cl)](OTf) and [(3PDI2)Co2(PMe3)2(μ-Cl)](OTf)3exhibit metal–metal single bonds, with varying amounts of electron density delocalization into the ligand as a function of the effective nuclear charge of the metal ions. One- and two-electron reductions of [(3PDI2)Co2(PMe3)2(μ-Cl)](OTf)3lead to isolable products, which show successive increases in both the Co–Co distances and the extent of reduction of the ligand manifold. This trend results from reduction of a Co–Co σ* orbital, which was found to be heavily mixed with the redox-active manifold of the 3PDI2ligand. A similar trend was observed in the 37 and 38 e–dinickel complexes [(3PDI2)Ni2(PMe3)2(μ-Cl)](OTf)2and [(3PDI2)Ni2(PMe3)2(μ-Cl)](OTf); however, their higher electron counts lead to high-spin ground states that result from occupation of a high-lying δ/δ* manifold with significant Ni–NPDIσ* character. This change in ground state configuration reforms a M–M bonding interaction in the 37 e–complex, but formation of the 38 e–species again disrupts the M–M bond alongside the transfer of electron density to the ligand.

Published
2020
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47. Redox-Driven Chelation and Kinetic Separation of Select Rare Earths Using a Tripodal Nitroxide Proligand

Author

Cole, Bren E., Cheisson, Thibault, Higgins, Robert F., Nakamaru-Ogiso, Eiko, Manor, Brian C., Carroll, Patrick J., and Schelter, Eric J.

Abstract

Separation of the rare-earth (RE) elements (Sc, Y, La–Lu) is challenging because of their similar chemical properties, but is necessary for their applications in renewable energy and electronic device technologies. The development of separation processes driven by kinetic factors represents a new area for this field. Herein, we disclose a novel method of separating select rare earths by reacting RE cyclopentadienides with the triradical species tris(2-tert-butylnitroxyl)benzylamine (1). The key proligand 1was characterized using a variety of techniques including X-ray crystallography, magnetometry, and EPR spectroscopy. When applied to an equimolar mixture of La:Y cyclopentadienide complexes, different rates of chelation of these organometallic precursors by 1were observed, affording a separation factor of 26 under the reported conditions.

Published
2020
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