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A series of iridium‐polymer complexes containing bipyridonate moieties were synthesized. The high catalytic performance of the iridium‐polymer complex for the dehydrogenative oxidation of alcohols was demonstrated. Notably, the bipyridonate moiety in the polymer structure acts as a chemically non‐innocent "functional ligand", realizing the enhancement of dehydrogenation process. While numerous metal‐polymer catalysts have been reported so far, to our knowledge, introducing a "functional ligand" into a polymer chain that can operate cooperatively with transition metals by changing their structures during the catalytic processes is rare. The iridium‐polymer complex could be easily separated from the product and recovered by precipitation upon the addition of methanol after the catalytic reaction. Furthermore, the recovered catalyst could be reused without loss of catalytic efficiency at least ten times. [ABSTRACT FROM AUTHOR]

A complete theoretical analysis using first the simple Hückel model followed by more sophisticated multi‐reference calculations on a trinuclear Ni(II) complex (Tp#Ni3HHTP), bearing the non‐innocent bridging ligand HHTP3−, is carried out. The three semiquinone moieties of HHTP3− couple antiferromagnetically and lead to a single unpaired electron localized on one of the moieties. The calculated exchange coupling integrals together with the zero‐field parameters allow, when varied within a certain range, reproducing the experimental data. These results are generalized for two similar other trinuclear complexes containing Ni(II) and Cu(II). The electronic structure of HHTP3− turns out to be independent of both the chemical nature and the geometry of the metal ions. We also establish a direct correlation between the geometrical and the electronic structures of the non‐innocent ligand that is consistent with the results of calculations. It allows experimentalists to get insight into the magnetic behavior of this type of complexes by an analysis of their X‐ray structure. [ABSTRACT FROM AUTHOR]

We report two novel three‐dimensional copper‐benzoquinoid metal–organic frameworks (MOFs), [Cu4L3]n and [Cu4L3 ⋅ Cu(iq)3]n (LH4=1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed‐valence metal and redox‐non‐innocent ligand L, which promotes through‐bond charge transfer between Cu metal sites, allows better metal‐ligand orbital overlap of the d‐π conjugation, leading to strong long‐range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly‐covalent Cu(III), non‐innocent ligand, and pore environments of these bench stable Cu(III)‐containing frameworks on multielectron transfer and electrochemical properties. [ABSTRACT FROM AUTHOR]

Two complexes, related to the active site of [FeFe]-hydrogenases, [Fe2(CO)4(κ2-pma)(µ-bdt)] (1) and [Fe2(CO)4(κ2-pma)(µ-pdt)] (2) (bdt = benzene-1,2-dithiolate, pdt = propane-1,2-dithiolate) featuring the diaza chelate ligand trans-N-(2-pyridylmethylene)aniline (pma) were prepared, in order to study the influence of such a redox ligand, potentially non-innocent, on their redox behaviours. Both complexes were synthesized by photolysis in moderate yields, and they were characterized by IR, 1H and 13C{1H} NMR spectroscopies, elemental analyses and X-ray diffraction. Their electrochemical study by cyclic voltammetry, in the presence and in the absence of protons, revealed different behaviours depending on the aliphatic or aromatic nature of the dithiolate bridge. Density functional theory (DFT) calculations showed the role of the pma ligand as an electron reservoir, allowing the rationalization of the proton reduction process of complex 1. [ABSTRACT FROM AUTHOR]

The syntheses of new neutral square-planar pyridine di-imine rhodium and iridium complexes with O- and S-donor (OH, OR, SH, SMe and SPh) ligands along with analogous cationic compounds are reported. Their crystal and electronic structures are investigated in detail with a focus on the non-innocence/innocence of the PDI ligand. The oxidation states of the metal centers were analyzed by a variety of experimental (XPS and XAS) and theoretical (LOBA, EOS and OSLO) methods. The dπ-pπ interaction between the metal centers and the π-donor ligands was investigated by theoretical methods and revealed the partial multiple-bond character of the M-O,S bonds. Experimental support is provided by a sizable barrier for the rotation about the Ir-S bond in the methyl thiolato complex and confirmed by DFT and LNO-CCSD(T) calculations. This was corroborated by the high Ir-O and Ir-S bond dissociation enthalpies calculated at the PNO-CCSD(T) level. [ABSTRACT FROM AUTHOR]

The cationic complex [Ni(H)(OH)]+ was previously found to activate dioxygen and methane in gas phase under single collision conditions. These remarkable reactivities were thought to originate from a non‐classical electronic structure, where the Ni‐center adopts a Ni(II), instead of the classically expected Ni(III) oxidation state by formally accepting an electron from the hydroxo ligand, which formally becomes a hydroxyl radical in the process. Such radicaloid oxygen moieties are envisioned to easily react with otherwise inert substrates, mimicking familiar reactivities of free radicals. In this study, the reductive activation of dioxygen by [Ni(H)(OH)]+ to afford the hydroperoxo species was investigated using coupled cluster, multireference ab initio and density functional theory calculations. Orbital and wave function analyses indicate that O2 binding tranforms the aforementioned non‐classical electronic structure to a classical Ni(III)‐hydroxyl system, before O2 reduction takes place. Remarkably, we found no evidence for a direct involvement of the radicaloid hydroxyl in the reaction with O2, as is often assumed. The function of the redox non‐innocent character of the activator complex is to protect the reactive electronic structure until the complex engages O2, upon which a dramatic electronic reorganization releases internal energy and drives the chemical reaction to completion. [ABSTRACT FROM AUTHOR]

The cationic complex [Ni(H)(OH)]+ was previously found to activate dioxygen and methane in gas phase under single collision conditions. These remarkable reactivities were thought to originate from a non‐classical electronic structure, where the Ni‐center adopts a Ni(II), instead of the classically expected Ni(III) oxidation state by formally accepting an electron from the hydroxo ligand, which formally becomes a hydroxyl radical in the process. Such radicaloid oxygen moieties are envisioned to easily react with otherwise inert substrates, mimicking familiar reactivities of free radicals. In this study, the reductive activation of dioxygen by [Ni(H)(OH)]+ to afford the hydroperoxo species was investigated using coupled cluster, multireference ab initio and density functional theory calculations. Orbital and wave function analyses indicate that O2 binding tranforms the aforementioned non‐classical electronic structure to a classical Ni(III)‐hydroxyl system, before O2 reduction takes place. Remarkably, we found no evidence for a direct involvement of the radicaloid hydroxyl in the reaction with O2, as is often assumed. The function of the redox non‐innocent character of the activator complex is to protect the reactive electronic structure until the complex engages O2, upon which a dramatic electronic reorganization releases internal energy and drives the chemical reaction to completion. [ABSTRACT FROM AUTHOR]

The prominence of binuclear, bimetallic catalysts underlines the need for the design and development of diverse bifunctional ligand frameworks that exhibit tunable electronic and structural properties. Such strategies enable metal-metal and ligand-metal cooperation towards catalytic applications, improve catalytic activity, and are essential for advancing multi-electron transfers for catalytic application. In this work we present the synthesis, crystal structure, and photocatalytic properties of a binuclear Ni(II) complex, [Ni 2 (1,10-phenanthroline) 2 (2-sulfidophenolate) 2 ] (1). Complex 1 crystallizes in the centrosymmetric triclinic system (P-1) showing extensive intra- and inter- non-coordinated interactions. 1 is employed as a catalyst for light driven hydrogen evolution. Its catalytic efficiency in a noble-metal-free photo-driven system using fluorescein as photosensitizer and triethanolamine as the electron donor, reaches TON 2900, threefold the efficiency of the corresponding homoleptic mononuclear complex [Ni(2-sulfidophenolate) 2 ]. Efficiency rises up to 9000 TONs when thioglycolic-coated CdTe quantum dots are used as photosensitizers in the presence of ascorbic acid at pH 4.5. UV-Vis spectroscopy, dynamic light scattering techniques, and Hg-poisoning measurements reveal that 1 maintains its molecular structure during catalysis. Electrochemical studies in DMF with TFA as the proton source were also performed for the elucidation of the mechanism of its catalytic action and its stability, suggesting that the proximity of two nickel ions plays a part in the increased catalytic activity, facilitating hydrogen evolution., (© 2025 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Fulfilment of energy demand by utilizing renewable energy sources that do not contribute to the production of greenhouse gases is a step forward in mitigating global warming. However, with the energy sources being intermittent in nature, renewable energy needs to be stored effectively on a grid scale. In this context, the development of redox-flow batteries has emerged as a promising technology where charging and discharging processes are accomplished by the redox shuttling of the electrolytes, namely anolytes and catholytes. This report describes the synthesis and characterization of a six-coordinate vanadyl complex (complex 1) with H 4 L SCH2(AP/AP) ligand comprising two redox-active (non-innocent) 2-aminophenol moieties. The metal ion-coordinated deprotonated ligand, which was in {[L SCH2(AP/ISQ) ] 3- } form, encountered one-electron reversible oxidation at 0.46 V vs Ag/AgCl where the 2-amidophenolate ([AP] 2- ) unit was being oxidized to [ISQ]⋅ - radical. Using this redox phenomenon, a static H-cell was constructed in a 1 : 1 CH 3 CN : CH 2 Cl 2 solvent mixture where galvanostatic charge/discharge cycles, in the potential range 0 to +0.8 V vs Ag/AgCl, were performed for 54 hours without noticeable degradation of the complex. GCD experiment provided a columbic efficiency (CE) of 97 % and energy efficiency (EE) of 71 %., (© 2025 Wiley-VCH GmbH.)

The behaviour of triazolylidene ligands coordinated at a {Fe2(CO)5(µ-dithiolate)} core related to the active site of [FeFe]-hydrogenases have been considered to determine whether such carbenes may act as redox electron-reservoirs, with innocent or non-innocent properties. A novel complex featuring a mesoionic carbene (MIC) [Fe2(CO)5(Pmpt)(µ-pdt)] (1; Pmpt = 1-phenyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene; pdt = propanedithiolate) was synthesized and characterized by IR, 1H, 13C{1H} NMR spectroscopies, elemental analyses, X-ray diffraction, and cyclic voltammetry. Comparison with the spectroscopic characteristics of its analogue [Fe2(CO)5(Pmbt)(µ-pdt)] (2; Pmbt = 1-phenyl-3-methyl-4-butyl-1,2,3-triazol-5-ylidene) showed the effect of the replacement of a n-butyl by a phenyl group in the 1,2,3-triazole heterocycle. A DFT study was performed to rationalize the electronic behaviour of 1, 2 upon the transfer of two electrons and showed that such carbenes do not behave as redox ligands. With highly perfluorinated carbenes, electronic communication between the di-iron site and the triazole cycle is still limited, suggesting low redox properties of MIC ligands used in this study. Finally, although the catalytic performances of 2 towards proton reduction are weak, the protonation process after a two-electron reduction of 2 was examined by DFT and revealed that the protonation process is favoured by S-protonation but the stabilized diprotonated intermediate featuring a {Fe-H⋯H-S} interaction does not facilitate the release of H2 and may explain low efficiency towards HER (Hydrogen Evolution Reaction). [ABSTRACT FROM AUTHOR]

The title compound, bis(1,2-diphenyl-2-sulfanylideneethanethiolato-κ2S,S′)(1,3,5-triaza-7-phosphaadamantane-κP)cobalt(II) dichloromethane hemisolvate, [Co(pdt)2(PTA)]·0.5C2H4Cl2 or [Co(C14H10S2)2(C6H12N3P)]·0.5C2H4Cl2, contains two phenyldithiolene (pdt) ligands and a 1,3,5-triaza-7-phosphaadamantane (PTA) ligand bound to cobalt with the solvent 1,2-dichloroethane molecule located on an inversion center. The cobalt core exhibits an approximately square-pyramidal geometry with partially reduced thienyl radical monoanionic ligands. The supramolecular network is consolidated by hydrogen-bonding interactions primarily with nitrogen, sulfur and chlorine atoms, as well as parallel displaced π-stacking of the aryl rings. The UV–vis, IR, and CV data are also consistent with monoanionic dithiolene ligands and an overall CoII oxidation state.

Exceptionally electron‐rich, nearly trigonal‐planar tricyanidometalate anions [Fe(CN)3]7− and [Ru(CN)3]7− were stabilized in LiSr3[Fe(CN)3] and AE3.5[M(CN)3] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of −IV. Microcrystalline powders were obtained by a solid‐state route, single crystals from alkali metal flux. While LiSr3[Fe(CN)3] crystallizes in P63/m, the polar space group P63 with three‐fold cell volume for AE3.5[M(CN)3] is confirmed by second harmonic generation. X‐ray diffraction, IR and Raman spectroscopy reveal longer C−N distances (124–128 pm) and much lower stretching frequencies (1484–1634 cm−1) than in classical cyanidometalates. Weak C−N bonds in combination with strong M−C π‐bonding is a scheme also known for carbonylmetalates. Instead of the formal notation [Fe−IV(CN−)3]7−, quantum chemical calculations reveal non‐innocent intermediate‐valent CN1.67− ligands and a closed‐shell d10 configuration for Fe, that is, Fe2−. [ABSTRACT FROM AUTHOR]

Three mononuclear heteroleptic nickel complexes bearing the non-innocent o-aminobenzenethiolate (2-amnt) ligand and different diamine ligands, namely, [Ni(2-amnt)(o-phen)] (o-phen = o-phenylenediamine) (1), [Ni(2-amnt)(3,4-daba)] (3,4-daba = 3, 4-diamino benzoic acid) (2) and [Ni(2-amnt)(dmnt)] (dmnt = diaminomaleonitrile) (3), were synthesized and characterized. Complexes 1 – 3 are active homogeneous proton reduction electrocatalysts in dimethylformamide with trifluoroacetic acid as a proton source. All the three complexes are tested in light-driven hydrogen evolution reaction, indicating different catalytic efficiencies. Thus, although complex 3 indicates no catalytic action, both complexes 1 and 2 catalyze H 2 evolution in water-dimethylformamide solutions using fluorescein (Fl) as a photosensitizer. Complex 2 acts as a homogeneous catalyst reached 834 turnovers (TON); whereas 1, d espite being active in hydrogen evolution reaction (HER), decomposes to form nanomaterials. DFT calculations combined with electrochemical and spectroscopic data were employed to investigate the catalytic mechanism for H 2 formation as well as to unravel the key factors that influence the relative catalytic efficiencies. The proposed catalytic pathway involves ligand-based reduction and protonation steps followed by the formation of a nickel-hydride intermediate that reacts with a solution proton to generate H 2 via a very low energy transition state. [Display omitted] • Three heteroleptic Ni(II)-diamine-aminobenzethiolate complexes were synthesized. • They act as proton reduction electrocatalysts and light-driven catalysts. • Their catalytic efficiency depends on the nature of the ligands. • DFT and experimental data reveals the key factors of hydrogen evolution mechanism. [ABSTRACT FROM AUTHOR]

In this article, we report Mn(II), Fe(II) and Cu(I) complexes (BIP-Mn, BIP-Fe and BIP-Cu) bearing a non-innocent, NNN pincer ligand, 4-aminoantipyrine tethered 2,6-bis(iminoantipyrine)pyridine (BIP) and structural diversity. The complexes were characterized by different spectroscopic and single-crystal X-ray analysis. Superoxide dismutase (SOD) activity has been evaluated for BIP and complexes BIP-Mn, BIP-Fe and BIP-Cu. It was observed that the sevencoordinate BIP-Mn complex showed preeminent SOD activity on comparing to BIP-Fe and BIP-Cu complexes. Besides, preliminary in vitro anticancer properties of BIP-Mn, BIP-Fe and BIP-Cu have been studied. Again, BIP-Mn complex showed stronger anticancer activity compared to ligand, BIP-Fe and BIP-Cu complexes. [ABSTRACT FROM AUTHOR]

Alkyne complexes with vicinal substitution by a Lewis acid and a Lewis base at the coordinated alkyne are prospective frustrated Lewis pairs exhibiting a particular mutual distance and, hence, a specific activation potential. In this contribution, investigations on the generation of a WII alkyne complex bearing a phosphine as Lewis base and a carbenium group as Lewis acid are presented. Independently on potential substrates added, an intramolecular cyclisation product was always isolated. A subsequent deprotonation step led to an unprecedented side‐on λ5‐phosphinyne complex, which is interpreted as highly zwitterionic according to visible absorption spectroscopy supported by TD‐DFT. Low‐temperature 31P NMR and EPR spectroscopic measurements combined with time‐dependent IR‐spectroscopic monitoring provided insights in the mechanism of the cyclisation reaction. Decomposition of the multicomponent IR spectra by multivariate curve resolution and a kinetic hard‐modelling approach allowed the derivation of kinetic parameters. Assignment of the individual IR spectra to potential intermediates was provided by DFT calculations. [ABSTRACT FROM AUTHOR]

The title compound, bis(1,2-diphenyl-2-sulfanylideneethanethiolato-π2S,S')- (1,3,5-triaza-7-phosphaadamantane-πP)cobalt(II) dichloromethane hemisolvate, [Co(pdt)2(PTA)]·0.5C2H4Cl2 or [Co(C14H10S2)2(C6H12N3P)]·0.5C2H4Cl2, contains two phenyldithiolene (pdt) ligands and a 1,3,5-triaza-7-phosphaadamantane (PTA) ligand bound to cobalt with the solvent 1,2-dichloroethane molecule located on an inversion center. The cobalt core exhibits an approximately square-pyramidal geometry with partially reduced thienyl radical monoanionic ligands. The supramolecular network is consolidated by hydrogenbonding interactions primarily with nitrogen, sulfur and chlorine atoms, as well as parallel displaced π-stacking of the aryl rings. The UV-vis, IR, and CV data are also consistent with monoanionic dithiolene ligands and an overall CoII oxidation state. [ABSTRACT FROM AUTHOR]

• The role of the transition metal centre in stabilising the inter-ligand delocalization is examined. • PIO analysis is used to visualize the relevant orbitals and quantify their contributions. • Early and late transition metal centres use different orbitals in the stabilisation. • The importance of matching orbital symmetry is well illustrated. Non-innocent ligands are a class of ligands that gains attention in organometallic chemistry in recent years, and many remarkable coordination complexes with multiple non-innocent ligands have been synthesised. These complexes admit special electronic configurations that could be rationalised by "inter-ligand delocalisation". In this work, we make use of the Principal Interacting Orbital analysis we developed to examine the role of metal centre in these cases. We found that the metal orbitals used in such kind of stabilisation can differ between early and late transition metals, and the geometry of the complex is also influenced by symmetry factors. These analyses not only complement the earlier understanding of "inter-ligand delocalisation", but also give hint to the controversial roles of transition metal p orbitals in coordination chemistry. [ABSTRACT FROM AUTHOR]

We present the synthesis of the tridentate Schiff base 2-(1-((pyridine-2-ylmethyl)imino)ethyl)naphtalen-1-ol (LH) providing a NNO coordination environment. Two new Ni(II) and Cu(II) complexes with a ligand to metal stoichiometric ratio of 1:1 and 2:1, respectively, were synthesized from LH. The Cu(II) complex of general formula [Cu(L)(MeOH)](ClO4)·MeOH (2) has a square planar geometry in the central ion completed by a MeOH molecule. In the case of the mononuclear Ni(II) complex [NiL2]·MeOH (3) the central ion has a distorted octahedral geometry. These new compounds were structurally, spectroscopically and electrochemically characterized using X-ray diffraction, UV-vis, IR, 1H NMR, 13C NMR spectroscopies, and cyclic voltammetry. LH is electroactive in the potential window of −1.0 to 1.0 V with one irreversible oxidation at 0.44 V, a quasi-reversible oxidation at 0.60 V, and one irreversible reduction at 0.24 V. For 2, there is a quasi-reversible oxidation at 0.43 V and one irreversible oxidation at 0.64 V. Complex 3 has two quasi-reversible oxidations at 0.19 V and at 0.58 V, one irreversible oxidation at 0.37 V, and one irreversible reduction at 0.38 V. DFT calculations were undertaken to obtain optimized structures and relative stability for 2 and 3 and their intermediates. [ABSTRACT FROM AUTHOR]

Copper complexes of corroles have recently been a subject of keen interest due to their ligand non‐innocent character and unique redox properties. Here we investigated bis‐copper complex of a triply‐linked corrole dimer that serves as a pair of divalent metal ligands but can be reduced to a pair of trivalent metal ligands. Reaction of triply‐linked corrole dimer 2 with Cu(acac)2 (acac=acetylacetonate) gave bis‐copper(II) complex 2Cu as a highly planar molecule with a mean‐plane deviation value of 0.020 Å, where the two copper ions were revealed to be divalent by ESR, SQUID, and XPS methods. Oxidation of 2Cu with two equivalents of AgBF4 gave complex 3Cu, which was characterized as a bis‐copper(II) complex of a dicationic triply‐linked corrole dimer not as the corresponding bis‐copper(III) complex. In accord with this assignment, the structural parameters around the copper ions were revealed to be quite similar for 2Cu and 3Cu. Importantly, the magnetic spin–spin interaction differs depending on the redox‐state of the ligand, being weak ferromagnetic in 2Cu and antiferromagnetic in 3Cu. [ABSTRACT FROM AUTHOR]

Highlights • Terpyridines are treated as Pincer ligand and/or non-innocent ligand. • With low-lying LUMO of pyridine rings and geometrical/steric advantages, terpyridines enhance the stability and reactivity of low-valent metal centers. • By forming stable and linear "closed-shell" octahedral complexes, terpyridines have been widely employed in supramolecular chemistry. • Different and multilayer terpyridine-based supramolecular structures have been achieved, such as Sierpiński triangles, hexagonal gasket and supramolecular rosettes. Abstract As an NNN-tridentate ligand, the 2,2′:6′,2″-terpyridine plays an important role in coordination chemistry. With three coordination sites and low LUMO, terpyridine and its derivatives are one of the typical Pincer ligand and/or non-innocent ligands in transition metal catalysis. Interesting catalytic reactivities have been obtained with these tpy-metal complexes targeting some challenging transformations, such as C–C bond formation and hydrofunctionalization. On the other hand, terpyridine ligands can form "closed-shell" octahedral complexes, which provide a linear and stable linkage in supramolecular chemistry. Numerous supramolecular architectures have been achieved using modified terpyridine ligands including Sierpiński triangles, hexagonal gasket and supramolecular rosettes. This review presents a summary of recent progress regarding transition metal-terpyridine complexes with the focus on their applications in catalysis and supramolecular structure construction. Facile synthesis of terpyridine derivatives is also described. We hope this article can serve to provide some general perspectives of the terpyridine ligand and their applications in coordination chemistry. [ABSTRACT FROM AUTHOR]

Three catecholato copper(II) complexes, [Cu(catCl4)(L1′)], [Cu(catBr4)(L1′)], and [Cu(catCl4)(L1H)], supported by sterically hindered neutral and anionic N3 type ligands: tris(3,5-diisopropyl-1-pyrazolyl)methane (referred to as L1′) and hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (referred to as L1−), are synthesized and characterized in detail. Their X-ray structures reveal that both [Cu(catCl4)(L1′)] and [Cu(catBr4)(L1′)] complexes have a five-coordinate square-pyramidal geometry and [Cu(catCl4)(L1H)] complex has a four-coordinate square-planar geometry. The L1H is unusual protonated ligand that controls its overall charge. For the three catecholato copper(II) complexes, the oxidation state of copper is divalent, and catechol exists in catecholate as two minus anion. This difference in coordination geometry affects their d-d and CT transitions energy and ESR parameters.

Rational design of a molecular catalyst for a hydrogen evolution reaction (HER) with both high rates and low overpotential remains a challenge. Here we report a series of Ni‐based catalysts incorporating non‐innocent ligands and aimed at reduction of the overpotential by reserving electrons in the ligand, which could decouple the correlation between metal center reduction and metal hydride formation. The third‐order rate constant of our catalysts can be increased by 2 orders of magnitude without increase of overpotential by altering the substituents in the imide since the electronic effect of substituents can change the kinetics of metal hydride formation dramatically. Furthermore, constructing a proton shuttle in the ligand further improves the activity. The catalyst with both of these features can catalyze HER at a turnover frequency of 2572 s–1 with low concentrations of acid and an extremely high third‐order rate constant of 2.7×106 M–2·s–1 at a low overpotential. Regulation of metal center reduction and metal hydride formation for HER — lower overpotentials and faster reaction rates. [ABSTRACT FROM AUTHOR]

One‐pot reaction of 2,6‐iPr2‐aniline (DIPP‐NH2) with (Me2SiO)3 and Sr[N(SiMe3)2]2 (SrN′′2) gave a tetranuclear cluster consisting of four dianions [OSiMe2N‐DIPP]2– and four Sr2+ ions solvated each by one THF ligand. The general applicability of this method was investigated by variation of amine and metal. Anilines with smaller substituents led to insoluble uncharacterized coordination polymers, whereas bulkier anilines gave soluble product mixtures that could not be purified. Primary alkylamines neither led to isolable products. Introduction of a tBu group in para‐position of DIPP‐NH2, however, gave an isostructural cluster with increased solubility. Similar clusters could be obtained with barium. Both, the Sr and Ba clusters, were found to be active catalysts for a wide range of transformations: intramolecular alkene hydroamination, alkene hydrophoshination, pyridine hydroboration, pyridine hydrosilylation, and alkene hydrosilylation. The Ba catalysts were generally more active than the Sr catalysts. The tBu‐substituent in para‐position also had an accelerating effect, which is likely due to improved solubility. [ABSTRACT FROM AUTHOR]

Three monomeric complexes of chromium(III) containing the redox-active ligand derived from bis(3,5-di- tert -butyl-2-phenol)amine, [ONO cat ]H 3 , were prepared and fully characterized. The potassium salt of [ONO q ] 1− reacted with CrCl 3 (THF) 3 to afford [ONO q ]CrCl 2 (THF) ( 1 ); whereas, the trilithium salt of [ONO cat ] 3− reacted with CrCl 3 (THF) 3 in the presence of pyridine to afford [ONO cat ]Cr(py) 3 ( 3 ). The three electron series was completed by reacting 1 with K[bpy ] to afford [ONO sq ]CrCl(bpy) ( 2 ). All three members of the series were characterized by structural, spectroscopic, and electrochemical methods. Attempts to effect the two-electron reduction of 1 resulted in the formation of a bimetallic chromium complex, {[ONO cat ]Cr(py) 2 } 2 ( 4 ), which was also structurally characterized. The reaction of 1 with aryl transfer reagents resulted in a mixture of one- and two-electron reactivity, comprising the expulsion of either phenyl radical or biphenyl from the chromium coordination sphere. [ABSTRACT FROM AUTHOR]

The sodium salt of heteroleptic molybdenum complex with nitrilotris(methylenephosphonic) acid (NTP), hydroxylamine, and nitrogen(II) oxide Na[Mo(NO)(NHO){N(CHPO)H}]· 8HO was synthesized, isolated, and studied (space group P2/ c, Z = 4, a = 9.7385(2), b = 10.2542(2), c =21.6517(3) Å, β = 93.7060(10)°). The nitrilotris(methylenephosphonate) ion is monoprotonated at the PO group. The nitrogen atom is deprotonated and coordinates the Mo atom; the NTP denticity is 4. Hydroxylamine is ionized according to the acid type and is bidentate. The Mo-NO group is almost linear (176.31(19)° angle; Mo-N, 1.7599(13) Å; ν(N-O), 1756 cm), the electron density distribution attests to the formation of an Mo-N π-bond. The Mo coordination polyhedron is a distorted pentagonal bipyramid. Two Na ions are coordinated at the vertices of a distorted octahedron and the third one forms a distorted tetrahedral geometry. (CIF file CCDC no. 1543700.) [ABSTRACT FROM AUTHOR]

An alternative approach to replacing the isothiocyantate ligands of the N3 photosensitizer with light-harvesting bidentate ligands is investigated for application in dye-sensitized solar cells (DSSCs). An in-depth theoretical analysis has been applied to investigate the optical and redox properties of four non-innocent ligand platforms, which is then corroborated with experiment. Taking advantage of the 5- and 7-positions of 8-oxyquinolate, or the carboxyaryl ring system of the N-arylcarboxy-8-amidoquinolate ligand, fluorinated aryl substituents are demonstrated as an effective means of tuning complex redox potentials and light-harvesting properties. The non-innocent character, resulting from mixing of both the central metal-dπ and ligand-π manifolds, generates hybrid metal-ligand frontier orbitals. These play a major role by contributing to the redox properties and visible electronic transitions, and promoting an improved power conversion efficiency in a Ru DSSC device featuring non-innocent ligands. [ABSTRACT FROM AUTHOR]

Oxidative addition of Br to [Mn(CO)] leads to the formation of [(CO)MnBr], followed by the ligand exchange of bromide to [S,Se-CH-4-Me] to form complex (CO)Mn ( µ- ŋ -SCH-4-(CH)Se-SeCH-4-(CH)S)Mn(CO) ( 1). A new five-coordinate complex [(CO)Mn(-S,-Se-CH-4-CH)] ( 2) can be synthesized through two different routes: (a) oxidative addition of diselenide [HS,Se-CH-4-Me] to the [Mn(CO)] followed by deprotonation and ligand dissociation to generate complex 2; (b) reduction of diselenide bonds of complex 1 by [BH] to produce 2. Drop-wise addition of HBF·OEt at 0 °C results in the formation of complex 1. The X-ray analysis shows that complex 2 has relative short Mn-Se and Mn-S bond distances compare to the published structures of cis-[(CO)Mn(EPh)] (E = S and Se; Liaw et al. in J. Chin. Chem. Soc. 43:427-431, 1996; Liaw et al. in Inorg. Chem. 35:2530, 1996). Interestingly, exposure of the coordinated unsaturated complex 2 under CO atmosphere resulted in complex cis-[(CO)Mn(-S,-Se-CH-4-Me)] ( 3) being formed. After purging the solution of complex 3 with N, it was reconverted completely back to complex 2; this observation was characterized by FTIR. The cyclic voltammetry scan of complex 2 shows a quasi-reversible redox couple with E = −1.94 V and I / I = 0.68. Ligand [HS, Se-CH-4-CH] and complexes 1 and 2 are all characterized by IR, UV-Vis, NMR, EA and X-ray single crystal diffraction. [ABSTRACT FROM AUTHOR]

We report the synthesis of a gallium complex incorporating redox-active pyridyl nitroxide ligands. The (pyNO−)2GaCl complex was prepared in 85% yield via a salt metathesis route and was characterized by 1H and 13C NMR spectroscopies, X-ray diffraction, and theory. UV–Vis absorption spectroscopy and electrochemistry were used to access the optical and electrochemical properties of the complex, respectively. Our discussion focuses primarily on a comparison of the gallium complex to the corresponding aluminum derivative and shows that although the complexes are very similar, small differences in the electronic structure of the complexes can be correlated to the identity of the metal.

Coupling reactions are staples in the synthetic world and their efficiency relies on well-defined, mostly bis-electronic, elementary catalytic steps. An area of great interest currently lies in the taming of radical species and their efficient introduction in catalytic cycles. Among these species bearing radical character, redox-active ligands hold much potential and can be used to sustain synthetically relevant couplings by introducing ligand-based electronic contribution. This minireview aims at presenting the current state of this promising field. [ABSTRACT FROM AUTHOR]

Single-electron oxidation of a diiron-sulfur complex [Cp*Fe( μ-bdt)FeCp*] ( 1, Cp*= η5-C5Me5; bdt=benzene-1,2-dithiolate) to [Cp*Fe( μ-bdt)FeCp*]+ ( 2) has been experimentally conducted. The bdt ligand with redox-active character has been computationally proposed to be a dianion (bdt2−) rather than previously proposed monoanion (bdt·−) radical in 1 though it has un-equidistant aromatic CC bond lengths. The ground state of 1 is predicted to be two low-spin ferrous ions ( SFe=0) and 2 has a medium-spin ferric ion ( SFe=1/2) and a low-spin ferrous center ( SFe=0), and the oxidation of 1 to 2 is calculated to be a single-metal-based process. Both complexes have no significant antiferromagnetic coupling character. [ABSTRACT FROM AUTHOR]

The bdt-bridged diiron-amide complex [Cp ∗ Fe( μ - η 2 : η 2 -bdt)( μ -NH 2 )FeCp ∗ ][BF 4 ] 2 ( 1[BF 4 ] 2 , Cp ∗ = η 5 -C 5 Me 5 ; bdt = benzene-1,2-dithiolate) and its reduction products [Cp ∗ Fe( μ - η 2 : η 2 -bdt)( μ -NH 2 )FeCp ∗ ][BF 4 ] ( 2[BF 4 ] ) and [Cp ∗ Fe( μ - η 2 : η 1 -bdt)( μ -NH 2 )FeCp ∗ ] ( 3 ) have been synthesized. DFT calculations suggest that the sequential reduction of 1[BF 4 ] 2 to 2[BF 4 ] and further to 3 is a bimetal and single-metal based process, respectively. The ground state of 1[BF 4 ] 2 is predicted to be quartet. 2[BF 4 ] has an antiferromagnetic coupling BS(1,1) ground state, and the ground state of 3 is proposed to be BS(1,0). The bdt ligand in these three complexes is better viewed as a dianion ligand rather than a monoanionic radical. [ABSTRACT FROM AUTHOR]

We report the synthesis of aluminum complexes of pyridyl nitroxide ( R pyNO − ) ligands. The dimeric complexes {(μ-pyNO − )Al(CH 3 ) 2 } 2 ( 1 ) and {(μ- CH 3 pyNO − )Al(CH 3 ) 2 } 2 ( 2 ) were prepared through the 1:1 reaction between the pyridyl hydroxylamine ligand precursors R pyNOH and trimethylaluminum. Both compounds were characterized by 1 H and 13 C NMR spectroscopies. X-ray structural analysis revealed that 1 and 2 are isostructural, with the dimer structure resulting from an Al 2 O 2 core. Reaction of pyNOH with two equivalents of trimethylaluminum yielded the aluminum complex (pyNO − )AlMe 2 ·AlMe 3 ( 3 ), which was also characterized by 1 H and 13 C NMR spectroscopies and single-molecule X-ray diffraction. The electronic structure of the {(μ-pyNO − )Al(CH 3 ) 2 } 2 and {(μ- CH 3 pyNO − )Al(CH 3 ) 2 } 2 complexes were interrogated using UV–Vis electronic absorption spectroscopy and electrochemistry. The cyclic voltammograms of the complexes show two separate oxidation processes, the potentials of which are both dependent on the substitution pattern of the R pyNO − ligands. [ABSTRACT FROM AUTHOR]

Facile access to univalent Ga+and In+salts of the perfluorinated [Al(ORF)4]−anion (RF= C(CF3)3) allowed, for the first time, an investigation of the coordination chemistry of these simple cations. After investigating phosphanes, ethers, N-heterocyclic carbenes as well as bulky 2,6-tBu2-pyridine or pyrazine as ligands, the application of the classical 2,2'-bipyridine (bipy) ligand gave very unexpected results: bipy triggers a disproportionation of the univalent gallium salt [Ga(C6H5F)2]+[Al(ORF)4]−. In the resultant monomeric and paramagnetic [Ga(bipy)3]2+complex, the gallium cation is coordinated in a distorted octahedral fashion by three bipy ligands. Electron paramagnetic resonance showed the ligand to be non-innocent, and the radical is the ligand centered with a GaIIIcation. By contrast, upon changing to [In(C6H5F)2]+[Al(ORF)4]−, highly charged triangular and rhombic In3- and In4-clusters are formed, i.e. [In3(bipy)6]3+, [In3(bipy)5]3+, and [In3(bipy)6]4+. These clusters are formed by an unusual cationic cluster formation mechanism that is induced by the high lattice energies of the resulting AB3and AB4salts as well as charge transfer from bipy ligand to In+cation. [ABSTRACT FROM AUTHOR]

Relativistic quantum chemistry investigations are carried out to tackle the puzzling oxidation state problem in a series of MO trioxide anions of all d- and f-block elements with five valence electrons. We have shown here that while the oxidation states of V, Nb, Ta, Db, Pa are, as usual, all +V with divalent oxygen O(-II) in MO anions, the lanthanide elements Pr and Gd cannot adopt such high +V oxidation state in similar trioxide anions. Instead, lanthanide element Gd retains its usual +III oxidation state, while Pr retains a +IV oxidation state, thus forcing oxygen into a non-innocent ligand with an uncommon monovalent radical (O) of oxidation state -I. A unique Pr - (O) biradical with highly delocalized unpairing electron density on Pr(IV) and three O atoms is found to be responsible for stabilizing the monovalent-oxygen species in PrO ion, while GdO ion is in fact an OGd(O ) complex with Gd(III). These results show that a naïve assignment of oxidation state of a chemical element without electronic structure analysis can lead to erroneous conclusions. [ABSTRACT FROM AUTHOR]