Magnesium and Nickel Complexes with Bis(p-iminoquinone) Redox-Active Ligand

Poorly soluble in the most part of organic solvents dimeric complexes $${\text{M}}{{{\text{g}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF (I) and $${\text{N}}{{{\text{i}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF (II) (L is 4,4'-(1,4-phenylenebis(azanylylidene))bis(3,6-di-tert-butyl-2-hydroxycyclohexa-2,5-dien-1-one dianion)) are synthesized by the reactions of magnesium and nickel acetates with the ditopic redox-active ligand of the hydroxy-para-iminoquinone type in a DMF solution. The molecular and crystal structures of the synthesized compounds are determined by X-ray diffraction analysis (CIF files CCDC nos. 2045665 (I) and 2045666 (II·3DMF)). The thermal stability is studied by thermogravimetry. The redox-active character of the organic bridging ligand in the dimeric complexes $${\text{M}}{{{\text{g}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF and $${\text{N}}{{{\text{i}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF is confirmed by the data of solid-phase electrochemistry.

Actinide Arene-Metalates: Ion Pairing Effects on the Electronic Structure of Unsupported Uranium-Arene Sandwich Complexes

Chatt reaction methods were employed to synthesize the first well characterized actinide-arene sandwich complexes. Namely, addition of [UI₂(THF)₃(μ-OMe)]₂⸱THF (<b>2⸱THF</b>) to THF solutions containing 6 equiv. of K[C₁₄H₁₀] generates the dimeric complexes [K(18-crown-6)(THF)₂]₂[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂⸱4THF (<b>118C6</b>⸱4THF) and {[K(THF)₃][U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]}₂ (<b>1THF</b>) upon crystallization of the products in THF in the presence or absence of 18-crown-6, respectively. Both <b>118C6</b>⸱4THF and <b>1THF</b> are thermally stable in the solid-state at room temperature; however, after crystallization, they become insoluble in THF or DME solutions and instead gradually decompose upon standing. X-ray diffraction analysis reveals <b>118C6</b>⸱4THF and <b>1THF</b> to be structurally similar, possessing uranium centers sandwiched between anthracene ligands of mixed tetrahapto and hexahapto ligation modes. Yet, the two complexes are distinguished by the close contact potassium-arene ion pairing that is seen in <b>1THF</b> but absent in <b>118C6</b>⸱4THF, which is observed to have a significant effect on the electronic characteristics of the two complexes. Structural analysis, SQUID magnetometry data, XANES spectral characterization, and computational analyses are generally consistent with U(IV) formal assignments for the metal centers in both <b>118C6</b>⸱4THF and 1THF, though noticeable differences are detected between the two species. For instance, the effective magnetic moment of <b>1THF</b> (3.74 µB) is significantly lower than that of <b>118C6</b>⸱4THF (4.40 µB) at 300 K. Furthermore, the XANES data shows the U LIII-edge absorption energy for 1THF to be 0.9 eV higher than that of <b>118C6</b>⸱4THF, suggestive of more oxidized metal centers in the former. Of note, CASSCF calculations on the model complex {[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂}^2- (<b>1*</b>) shows highly polarized uranium-arene interactions defined by π-type bonds where the metal contributions are primarily comprised by the 6d-orbitals (7.3± 0.6%) with minor participation from the 5f-orbitals (1.5 ± 0.5%). These unique complexes provide new insights into actinide-arene bonding interactions and show the sensitivity of the electronic structures of the uranium atoms to coordination sphere effects.<br>

Actinide Arene-Metalates: Ion Pairing Effects on the Electronic Structure of Unsupported Uranium-Arene Sandwich Complexes

Chatt reaction methods were employed to synthesize the first well characterized actinide-arene sandwich complexes. Namely, addition of [UI₂(THF)₃(μ-OMe)]₂⸱THF (<b>2⸱THF</b>) to THF solutions containing 6 equiv. of K[C₁₄H₁₀] generates the dimeric complexes [K(18-crown-6)(THF)₂]₂[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂⸱4THF (<b>118C6</b>⸱4THF) and {[K(THF)₃][U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]}₂ (<b>1THF</b>) upon crystallization of the products in THF in the presence or absence of 18-crown-6, respectively. Both <b>118C6</b>⸱4THF and <b>1THF</b> are thermally stable in the solid-state at room temperature; however, after crystallization, they become insoluble in THF or DME solutions and instead gradually decompose upon standing. X-ray diffraction analysis reveals <b>118C6</b>⸱4THF and <b>1THF</b> to be structurally similar, possessing uranium centers sandwiched between anthracene ligands of mixed tetrahapto and hexahapto ligation modes. Yet, the two complexes are distinguished by the close contact potassium-arene ion pairing that is seen in <b>1THF</b> but absent in <b>118C6</b>⸱4THF, which is observed to have a significant effect on the electronic characteristics of the two complexes. Structural analysis, SQUID magnetometry data, XANES spectral characterization, and computational analyses are generally consistent with U(IV) formal assignments for the metal centers in both <b>118C6</b>⸱4THF and 1THF, though noticeable differences are detected between the two species. For instance, the effective magnetic moment of <b>1THF</b> (3.74 µB) is significantly lower than that of <b>118C6</b>⸱4THF (4.40 µB) at 300 K. Furthermore, the XANES data shows the U LIII-edge absorption energy for 1THF to be 0.9 eV higher than that of <b>118C6</b>⸱4THF, suggestive of more oxidized metal centers in the former. Of note, CASSCF calculations on the model complex {[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂}^2- (<b>1*</b>) shows highly polarized uranium-arene interactions defined by π-type bonds where the metal contributions are primarily comprised by the 6d-orbitals (7.3± 0.6%) with minor participation from the 5f-orbitals (1.5 ± 0.5%). These unique complexes provide new insights into actinide-arene bonding interactions and show the sensitivity of the electronic structures of the uranium atoms to coordination sphere effects.<br>

Role of the (Pseudo)Halido Ligand in Ruthenium(II) p-Cymene α-Amino Acid Complexes on Speciation, Protein Reactivity and Cytotoxicity

The reactions of the dimeric complexes [RuX2(η6-p-cymene)]2 (X = Br, I, SCN) with ʟ-proline (ProH) and trans-4-hydroxy-ʟ-proline (HypH), in methanol in the presence of NaOH, afforded [RuX(κ2N,O-Pro)(η6-p-cymene)] (X = Br,...

Actinide arene-metalates: Ion pairing effects on the electronic structure of unsupported uranium-arenide sandwich complexes

Addition of [UI2(THF)3(μ-OMe)]2⸱THF (2⸱THF) to THF solutions containing 6 equiv. of K[C14H10] generates the heteroleptic dimeric complexes [K(18-crown-6)(THF)2]2[U(η6-C14H10)(η4-C14H10)(μ-OMe)]2⸱4THF (118C6⸱4THF) and {[K(THF)3][U(η6-C14H10)(η4-C14H10)(μ-OMe)]}2 (1THF) upon crystallization of the products in THF in...

Structural diversity of salts of terpyridine derivatives with europium(III) located in both, cation and anion, in comparison to molecular complexes

Three salts of the common composition [EuCl2(X-tpy)2][EuCl4(X-tpy)]·nMeCN were obtained from EuCl3·6H2O and the respective organic ligands (X-tpy = 4′-phenyl-2,2′:6′,2″-terpyridine ptpy, 4′-(pyridin-4-yl)-2,2′:6′,2″-terpyridine 4-pytpy, and 4′-(pyridin-3-yl)-2,2′:6′,2″-terpyridine 3-pytpy). These ionic complexes are examples of salts, in which both cation and anion contain Eu3+ with the same organic ligands and chlorine atoms coordinated. As side reaction, acetonitrile transforms into acetamide resulting in the crystallization of the complex [EuCl3(ptpy)(acetamide)] (4). Salts [EuCl2(ptpy)2][EuCl4(ptpy)]·2.34MeCN (1), [EuCl2(4-pytpy)2][EuCl4(4-pytpy)]·0.11MeCN (2), and [EuCl2(3-pytpy)2][EuCl4(3-pytpy)]·MeCN (3) crystallize in different structures (varying in space group and crystal packing) due to variation of the rear atom of the ligand to a coordinative site. Additionally, we show and compare structural variability through the dimeric complexes [Eu2Cl6(ptpy)2(N,N′-spacer)]·N,N′-spacer (5, 6, 7) obtained from [EuCl3(ptpy)(py)] by exchanging the end-on ligand pyridine with several bipyridines (4,4′-bipyridine bipy, 1,2-bis(4-pyridyl)ethane bpa, and 1,2-bis(2-pyridyl)ethylene bpe). In addition, photophysical (photoluminescence) and thermal properties are presented.

Anion influences on the structures of pyridyl-iminosulfonate copper(II) complexes and their reactivity in Chan–Lam couplings

Reaction of pyridylcarbaldehyde with taurine or orthanilic acid in the presence of copper salts provided copper complexes (PyC(H)N-CxHy-SO3)CuX with X = chloride, nitrate, acetate, or triflate and CxHy = o-C6H4 or C2H4. All complexes were characterized by single crystal X-ray diffraction and formed either mononuclear water adducts, dimeric complexes, or one-dimensional coordination polymers. Activities in the Chan–Lam coupling of aniline with phenylboronic acid varied by less than a factor of two between catalysts with various anions, supporting previous mechanistic claims that the anion does not participate in the formation of copper–boron intermediates. There is no difference in the performance of a catalyst with an alkyl backbone, indicating that sulfonate dissociation is not part of the catalytic cycle.

Emergence of non-monotonic deep cavity cavitand assembly with increasing portal methylation

Using molecular simulations, we examine the emergence of non-monotonic deep-cavity cavitand assembly patterns into monomeric and dimeric complexes with alkanes of increasing length.