DFT calculations predict for many cobalt(III) corroles a broken-symmetry open-shell ground state, while CASSCF provides a more nuanced description where the weights of different closed- and open-shell configurations can be obtained. The S−T gap depends on the ligand field produced by the apical ligands and the ease of oxidation of the corroles.

Abstract

Cobalt(III) corroles are the most commonly studied types of metallocorroles, yet the details of their electronic structure, ground spin states and place of redox events are not always straightforward. Corroles are redox active, potentially non-innocent ligands, and it has been found through various experimental and computational techniques, that the innocent or non-innocent behavior is modulated by the apical ligands bound to the cobalt center. In this work, we aim to analyze the effect of corrole substituents and number and type of apical ligands on the electronic structure of cobalt corroles through density functional and wavefunction theories, and to determine the relative energies between closed- and open-shell states. We further perform preliminary analyses on the place of electron abstraction upon oxidation and on the effect of the corrole and apical ligands on the cobalt ligand field splittings. We find that both ligand field and electron-donating or withdrawing effects determine the relative energies of open-shell and closed shell singlet states.

Ammonia synthesis activity was improved by high crystallinity CeO₂ covered by low crystallinity CeO₂. However, too much low crystallinity CeO₂ affects ammonia synthesis negatively.

Abstract

Ruthenium (Ru) catalysts supported on cerium oxide (CeO₂), which was composed of high crystallinity (HC) CeO₂ covered by low crystallinity (LC) CeO₂ were investigated. The ammonia synthesis activities of a series of Ru/CeO₂(LC)/CeO₂(HC), having different LC/HC ratios were evaluated, and various characterizations, such as N₂ adsorption, X-ray diffraction, hydrogen temperature-programmed reduction (H₂-TPR), and hydrogen temperature-programmed desorption (H₂-TPD), were performed. Ru/CeO₂(LC)/CeO₂(HC) (0.1) demonstrated higher activity. H₂-TPR revealed that H₂ consumption increased as the LC/HC ratio increased. This indicates that the larger the amount of low crystallinity CeO₂, the higher the reducibility. However, the results of H₂-TPD imply that the larger the amount of low crystallinity CeO₂, the higher the interaction between adsorbed H₂ and the catalyst surface. These results indicate that the balance of reducibility and hydrogen adsorption strength plays an important role in increasing the ammonia synthesis activity.

Three novel mononuclear Fe(III) complexes based on 4-vinylpyridine coordinated with bis(salicylicdeneaminopropyl)amine and its derivatives exhibited different one-step spin crossover behaviour due to the chemical modification of the pentadentate Schiff base ligands.

Abstract

Three novel mononuclear 4-vinylpyridine-based Fe(III) complexes [FeL(4-VP)]BPh₄ (4-VP=4-vinylpyridine; H₂L=bis(salicylicdeneaminopropyl)amine, H₂salten, 1; H₂L=bis(salicylicdeneaminopropyl)methylamine, H₂salten^Me, 2; H₂L=bis(3-methoxysalicylideneaminopropyl)methylamine, ^3-OMeH₂salten^Me, 3) were synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that 1–3 both present the mononuclear structure based on 4-VP coordinated with bis(salicylicdeneaminopropyl)amine and its derivatives, which give 2D architectures by various interactions among cations and counter-ions. Magnetic studies showed that both 1 and 2 exhibit one-step complete spin-crossover (SCO) behaviours with critical transition temperatures (T _1/2) of 178 and 87 K respectively, while 3 exhibits one-step incomplete spin crossover behaviour (T _1/2,3=93 K). The introduction of methyl groups on the amine nitrogen of the Schiff base ligands in 2 and 3 give the bigger repulsive effect, further decrease the cooperation of spin centres, resulting in their spin transition occurring at lower temperatures. In addition, the presence of C−H⋯O weak interactions in 1 and 3 with synergistic effect, led to their spin transition temperatures being higher than that of 2.

The novel long-range “cis-spanning” PP ligand L_PP coordinates AuCl and Pt(CNC) in a highly selective manner. Subsequent halide abstraction gives rise to the formation of a Au−Pt bond. While the “cis-spanning” PN ligand L_PN does not allow for the generation of heterodinuclear complexes with a metal–metal bond, its potential to serve as a ditopic ligand has been shown in the present work.

Abstract

The novel bidentate PP and PN ligands o-(Ph₂P)−C₆H₄−C≡C−PPh₂ (L_PP) and o-(Ph₂P)−C₆H₄−4−(C₅H₉N−Me) (L_PN), respectively, have been designed as long-range “cis-spanning“ ligands for the stabilization of heterodinuclear complexes containing two metal atoms in close proximity. The synthesis of heterodinuclear, formal Au^IPt^II complexes with the ligand L_PP is straightforward. In the course of a one-pot reaction, a surprisingly high selectivity for the coordination of AuCl and Pt(CNC) (CNC=2,6-diphenylpyridine-o,o’-diate) to the phenyl-bound and the alkyne-bound PPh₂ sites of L_PP is observed, respectively. Chloride abstraction from the resulting heterodinuclear complex [(ClAu)(o-Ph₂P)−C₆H₄−C≡C−PPh₂(Pt{CNC})] with Ag[SbF₆] causes metal–metal bond formation and the generation of the cationic complex [L_PPAuPt(CNC)][SbF₆]. The high site selectivity for the coordination of the two metals to L_PP was investigated by stoichiometric reactions of the ligand with one equivalent of the corresponding precursors. While analogous complexation experiments with L_PN have not been successful, the synthesis of the heterodinuclear complex [(ClAu)(o-Ph₂P)−C₆H₄−4-(C₅H₉N−Me)(PtCl₂{dmso})] and of [L_PN(AuCl)₂] confirm the ability of L_PN to serve as a ditopic ligand. In this context, it is noteworthy that [L_PN(AuCl)₂] constitutes the first amine–AuCl complex featuring a tertiary amine.

The Front Cover shows the almost magical site-selective coordination of AuCl and [Pt(CNC)] to the novel long-range “cis-spanning” ligand L_PP in a one-pot reaction, followed by metal−metal bond-formation through chloride abstraction. L_PP is easily obtained in a one-pot process by double-deprotonation of phenyl acetylene followed by the addition of chlorodiphenylphosphine. The coordination of the gold and the platinum complexes to the phenylic and to the alkinylic phosphine sites of L_PP is highly selective, but a metal−metal interaction is not realized immediately. Subsequent chloride abstraction, however, gives rise to the selective formation of a metal−metal bond. Even mythical creatures might be attracted by these elegant processes. More information can be found in the Research Article by B. Butschke and co-workers.

The contribution reports the first hafnium-based coordination adaptable network (Hf−CooAn-10), based on carboxylate/carboxylic acid exchange, and kinetico-mechanistic studies of the exchange in the molecular [Hf₆O₄(OH)₄(O₂CMe)₁₂]₂/MeCOOH model system, which demonstrates the operationally associative exchange and qualifies the material as a coordination vitrimer.

Abstract

A hafnium-based coordination vitrimer (Hf−CooAN-10) has been prepared by carboxylate ligand exchange from [Hf₆O₄(OH)₄(O₂CMe)₁₂]₂ and poly-((ethylhexyl methacylate)-co-(carboxyethyl acrylate)) (M_n = 14.4 kg mol⁻¹, Đ = 2.2, 90 : 10 comonomer molar ratio), using a 10 % molar Hf loading with respect to the polymer maximum crosslinking capacity. The material shows high insoluble fraction and expected properties for a 3D network and has been reshaped three times at 50 °C under a 3-ton pressure without significant property alteration. The Hf−CooAN-10 thermomechanical and rheological properties are very similar to those previously reported for the analogous Zr−CooAN-10. The associative nature of carboxylate exchange between the [Hf₆O₄(OH)₄(O₂CR)₁₂] crosslinks and the polymer matrix free −COOH functions is suggested by parallel ¹H NMR line-broadening kinetic investigations of acetate exchange in the [Hf₆O₄(OH)₄(O₂CMe)₁₂]₂ precursor with free MeCOOH, the rate of which has a zero-order dependence on [MeCOOH], and by DFT calculations on a [Hf(μ-O₂CMe)(O₂CMe)₂(OH)(H₂O)]₂ model. The results of these investigations, including the activation parameters for the exchange of both chelating and bridging ligands, are very similar to those of the previously investigated zirconium system and suggest partial acetate dissociation assisted by H-bond formation with a (μ₃-OH) ligand as the rate-determining step, followed by acid coordination and intramolecular proton transfer.

Palladium(II)-Imidoyl Complexes: A New Piece in the Puzzle of Organopalladium Anticancer Agents. The library of organopalladium compounds with anticancer properties was expanded. The new class of Pd-imidoyl complexes bearing PTA, DAPTA and dppf phosphines showed promising results against ovarian cancer in terms of selectivity and apoptosis induction.

Abstract

Our search of new organopalladium compounds able to promote an effective antiproliferative action towards ovarian cancer cells continues. In this paper we have examined for the first time the anticancer activity of palladium imidoyl complexes, for which two different types of phosphines have been chosen as ancillary ligands: i) PTA and DAPTA to take advantage from their solubility in aqueous environment, and ii) dppf for combining the action of the Pd-imidoyl fragment with that, well-known, of ferrocene. The synthetic protocols as well as the exhaustive characterisation of the complexes through spectroscopic and diffractometric methods are described. In vitro tests carried out to assess the cytotoxicity of the new compounds towards two ovarian cancer cell lines (one cisplatin sensitive and the other cisplatin resistant) have revealed an interesting effect of the halide coordinated to the palladium centre (halogen effect). Moreover, all complexes have shown the same activity against the cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) cell lines, suggesting a different mode of action with respect to the “classical” platinum-based drugs. Finally, a selection of the most active compounds has shown an interesting selectivity towards ovarian cancer cells.

Synthesis of latent Grubbs-type ruthenium complex bearing a tridentate anionic bisfluoroalkoxy-carbene and unexpected formation of new complex formed upon coordination of the substrate and occurrence of only first olefin metathesis step; triggering its activity in olefin metathesis reactions by addition of HCl.

Abstract

A Grubbs-type ruthenium complex bearing a tridentate anionic bisfluoroalkoxy-carbene was synthesised and fully characterised. Under standard conditions, it proved to be inactive in olefin metathesis reactions, but the addition of HCl triggers its activity and allows the synthesis of a series of cyclic olefins and ethers as well as a stereoregular polynorbornene with an unexpectedly high content of trans-configured double bonds, as found in commercially available polynorbornene (Norsorex®). Detailed structural studies and DFT calculations showed that the complex enters the catalytic cycle, but instead of performing a full turnover, it is caught as a stable intermediate that does not undergo further reactions. The addition of HCl causes dissociation of the fluoroalkoxy units, resulting in a compound that behaves similarly to standard Grubbs-type complexes. To further understand this phenomenon, the corresponding Hoveyda-Grubbs complex was also obtained and studied in detail; due to the absence of the phosphine ligand, its behaviour was different from that of its Grubbs-type counterpart.

Copper(I) and copper (II) complexes with (^tBu)₂(ⁿPrSO₃)Htacn were synthesized and characterized. Focused on the reaction of Cu(II) complexes with H₂O₂ kinetic investigations in protic solvents were performed.

Abstract

Related to environmentally friendly productions in the industry, the synthesis of catalysts with designed ligands for solubility in protic solvents and reactivity under mild conditions becomes important. Thus, copper complexes were synthesized with a ligand system that was designed for better solubility in protic solvents. The reactivity of copper complexes with hydrogen peroxide under ambient conditions was investigated in water and in methanol. The formation of a μ-η² : η²-peroxide copper complex with a stability of a few minutes was observed in contrast to most related complexes reported in the literature. A kinetic analysis was performed, leading to activation parameters of ΔH ^≠: 66±4 kJ ⋅ mol⁻¹ and ΔS ^≠: −5±12 J ⋅ K⁻¹ ⋅ mol⁻¹ (in water), a strong indication of an interchange mechanism.

The Front Cover shows our rare earth corrosion inhibitor work. Corrosion is a significant burden to infrastructure, including bridges, and we have shown that incorporation of steric bulk about heteroatoms on the ligands bound to rare earth atoms (right figure) affects the ability to inhibit corrosion, compared to when we have open access to these heteroatoms (left figure). The artwork for the cover was done by Vidushi Vithana. More information can be found in the Research Article by P. C. Junk and co-workers.