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This review article presents a comprehensive analysis of metal complexes featuring ortho‐aminophenol based non‐innocent ligands in various oxidation states, including dianion/o‐amidophenolate, monoanion/o‐iminosemiquinonato, and o‐iminoquinonato forms. We focus extensively on the reactivity and catalytic properties of these metal complexes, offering insights into their potential applications and behavior in different chemical environments. The ligands are meticulously categorized based on their denticity, providing a clear framework for understanding their coordination chemistry. Correspondingly, the metal complexes are systematically organized according to the sequence of ligands, ensuring a coherent and logical presentation of the data. The structural approach not only highlights the intricate relationships between ligands and metal centers but also facilitates a deeper understanding of their roles in various catalytic processes. [ABSTRACT FROM AUTHOR]

Spin-crossover (SCO) and single-ion magnets (SIMs), or their mixed SCO-SIM derivatives, are a convenient solution in the evolution from molecular magnetism toward molecular spintronics and quantum computing. Herein, we report on the current trends and future directions on the use of mononuclear six-coordinate CoII SCO-SIM complexes with potential opto-, electro-, or chemo-active 2,6-pyridinediimine (PDI)- and 2,2′:6′,2′-terpyridine (TERPY)-type ligands as archetypical examples of multifunctional and multiresponsive magnetic devices for applications in molecular spintronics and quantum computing technologies. This unique class of spin-crossover cobalt(II) molecular nanomagnets is particularly well suited for addressing and scaling on different supports, like metal molecular junctions or carbon nanomaterials (CNMs) and metal–organic frameworks (MOFs) or metal-covalent organic frameworks (MCOFs), in order to measure the single-molecule electron transport and quantum coherence properties, which are two major challenges in single-molecule spintronics (SMS) and quantum information processing (QIP). [ABSTRACT FROM AUTHOR]

Spin-crossover (SCO) and single-ion magnets (SIMs), or their mixed SCO-SIM derivatives, are a convenient solution in the evolution from molecular magnetism toward molecular spintronics and quantum computing. Herein, we report on the current trends and future directions on the use of mononuclear six-coordinate CoII SCO-SIM complexes with potential opto-, electro-, or chemo-active 2,6-pyridinediimine (PDI)- and 2,2′:6′,2′-terpyridine (TERPY)-type ligands as archetypical examples of multifunctional and multiresponsive magnetic devices for applications in molecular spintronics and quantum computing technologies. This unique class of spin-crossover cobalt(II) molecular nanomagnets is particularly well suited for addressing and scaling on different supports, like metal molecular junctions or carbon nanomaterials (CNMs) and metal–organic frameworks (MOFs) or metal-covalent organic frameworks (MCOFs), in order to measure the single-molecule electron transport and quantum coherence properties, which are two major challenges in single-molecule spintronics (SMS) and quantum information processing (QIP).

We report on the synthesis and characterization of a series of (mostly) air‐stable diorganyl bis(pyridylimino) isoindolide (BPI) aluminum complexes and their chemistry upon visible‐light excitation. The redox non‐innocent BPI pincer ligand allows for efficient charge transfer homolytic processes of the title compounds. This makes them a universal platform for the generation of carbon‐centered radicals. The photo‐induced homolytic cleavage of the Al−C bonds was investigated by means of stationary and transient UV/Vis spectroscopy, spin trapping experiments, as well as EPR and NMR spectroscopy. The experimental findings were supported by quantum chemical calculations. Reactivity studies enabled the utilization of the aluminum complexes as reactants in tin‐free Giese‐type reactions and carbonyl alkylations under ambient conditions, which both indicated radical‐polar crossover behavior. A deeper understanding of the physical fundamentals and photochemical process was provided, furnishing in turn a new strategy to control the reactivity of bench‐stable aluminum organometallics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Non‐innocent ligands (NILs) like bis(pyridylimino)isoindolide (BPI) play crucial roles in coordination chemistry, biosciences, catalysis and material sciences. Investigating the isolated redox states of NILs is inevitable for understanding their redox‐activity and fine‐tuning the properties of corresponding metal complexes. The limited number of fundamental studies on the coordination behavior and redox chemistry of reduced BPI species is suggested to hamper further applications of the title compounds. This work describes for the first time the isolation of alkali metal complexes of BPI and Me2BPI in three different oxidation states and their characterization by means of NMR or EPR spectroscopy, DFT calculations, and SC‐XRD studies. The latter revealed the connection between bond orders in the ligand scaffold and its oxidation state. The paramagnetic compound Me2BPI‐K2 was isolated as a coordination copolymer with 18‐crown‐6, which enabled the characterization of the dianionic BPI radical. Furthermore, the so‐far unknown trianionic state of BPI was reported by the isolation of BPI‐K3. This divulges an unprecedented bis(amidinato)isoindolide coordination mode. [ABSTRACT FROM AUTHOR]

We report a facile synthetic method for accessing rare T‐shaped Ni0 species, stabilised by low‐coordinate cationic germylene and stannylene ligands which behave as Z‐type ligands toward Ni0. An in‐depth computational analysis indicates significant Nid→Ep donation (E=Ge, Sn), with essentially no E→Ni donation. The tetrylene ligand's Lewis acidity can be modulated in situ through the addition of a donor ligand, which selectively binds at the Lewis acidic tetrylene site. This switches this binding centre from a Z‐type to a classical L‐type ligand, with a concomitant geometry switch at Ni0 from T‐shaped to trigonal planar. Exploring the effects of this geometry switch in catalysis, isolated T‐shaped complexes 3 a–c and 4 a–c are capable of the hydrogenation of alkenes under mild conditions, whilst the closely related trigonal planar and tetrahedral Ni0 complexes 5, D, and E, which feature L‐type chloro‐ or cationic‐tetrylene ligands, are inactive under these conditions. Further, addition of small amounts of N‐bases to the catalytic systems involving T‐shaped complexes significantly reduces turnover rates, giving evidence for the in situ modulation of ligand electronics for catalytic switching. [ABSTRACT FROM AUTHOR]

We report the synthesis, characterization, and electronic structure studies of a series of thorium(IV) and uranium(IV) bis-tetramethyltetraazaannulene complexes. These sandwich complexes show remarkable stability towards air and moisture, even at elevated temperatures. Electrochemical studies show the uranium complex to be stable in three different oxidation states; isolation of the oxidized species reveals a rare case of a non-innocent tetramethyltetraazaannulene (TMTAA) ligand.

Developing high-activity and long-term stable electrocatalysts for electrochemical CO 2 reduction reaction (eCO 2 RR) to valuable products is still a challenge. An in-depth understanding of reaction mechanisms and the structure-function relationship is required for the development of an advanced catalytic eCO 2 RR system. Herein, a coordination polymer of indium(III) and benzenehexathiol (BHT) was developed as an electrocatalyst (In-BHT) for eCO 2 RR to HCOO - , which displayed an outstanding catalytic performance over the entire pH range. However, experimental results revealed significantly different catalytic pathways in the acid and neutral/alkaline solutions, which are attributed to the influence of redox non-innocent ligands on the rate-determining step (RDS). In the acid solution, the RDS is the formation of *OCOH intermediate through the proton transfer that originates from H 2 O in the solution, leading to relatively sluggish kinetics. But in the neutral or alkaline solution, the thiolate groups could be protonated during the catalytic process, and such proton can attack on carbon of absorbed CO 2 via an intramolecular proton transfer, promoting the formation of *OCHO intermediate, resulting in faster kinetics. Our findings revealed the pivotal roles of the redox non-innocent ligands of metal active sites for eCO 2 RR, providing a new idea for designing highly efficient electrocatalysts., (© 2025 Wiley-VCH GmbH.)

We present herein the synthesis of a nearly square‐pyramidal chlorophosphorane supported by the tetradentate bis(amidophenolate) ligand, N,N′‐bis(3,5‐di‐tert‐butyl‐2‐phenoxy)‐1,2‐phenylenediamide. After chloride abstraction the resulting phosphonium cation efficiently promotes the disproportionation of 1,2‐diphenylhydrazine to aniline and azobenzene. Mechanistic studies, spectroscopic analyses and theoretical calculations suggest that this unprecedented reactivity mode for PV‐centres is induced by the high electrophilicity at the cationic PV‐center, which originates from the geometry constraints imposed by the rigid pincer ligand, combined with the ability of the o‐amidophenolate moieties to act as electron reservoir. This study illustrates the promising role of cooperativity between redox‐active ligands and phosphorus for the design of organocatalysts able to promote redox processes. [ABSTRACT FROM AUTHOR]

Herein, we report two newly synthesized salen‐type ligands, 2,3‐bis((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)thio)maleonitrile (H2L1) and 2,3‐bis((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)amino)malenonitrile (H4L2), bearing different coordination sites (sulfur vs amine) at maleonitrile tethered moiety to investigate metal mediated non‐innocence chemistry of these ligands. Upon metallation, ligand H2L1 did not yield simple metal‐ligand complex, rather ligand was split into two organic fragments, dithiolene moiety (mnt)2− and phenol moiety via C−S bond cleavage wherein (mnt)2− formed a stable metal complex [M(mnt)2]2−. The C−S bond cleavage was interpreted in terms of strong p(π) ... d(π) interaction between metal and dithiolene moiety in H2L1 ligand that invoked the intramolecular rearrangement facilitating C−S bond cleavage. Interestingly, the phenol moiety further transformed to either unprecedented 2,4‐di‐tert‐butyl‐6‐methylenecyclohexa‐2,4‐dienone (i. e. spiro compound; 5) or 2,4‐di‐tert‐butyl‐6‐(hydroxymethyl)phenol (6) depending on the temperature of reaction and type of metal ion used which was further predicted using DFT calculation. On the other hand, combined experimental and DFT studies explained that upon metallation, ligand H4L2 yielded non‐cleavage [M(H2L2)] (3 for M=Cu(II) and 4 for M=Ni(II)) complex, which slowly oxidized at −NH−CH2‐(amine) region to −N=CH− (imine) in H2L2 ligand under aerobic environment via C−H bond activation, yielding [CuII(L3)] (1) (or [NiII(L3)] (2) complex (H2L3=oxidatively dehydrogenated product of H4L2 ligand. [ABSTRACT FROM AUTHOR]

High‐resolution X‐ray diffraction experiments, theoretical calculations and atom‐specific X‐ray absorption experiments were used to investigate two nickel complexes, (MePh3P)2[NiII(bdtCl2)2]·2(CH3)2SO [complex (1)] and (MePh3P)[NiIII(bdtCl2)2] [complex (2)]. Combining the techniques of nickel K‐ and sulfur K‐edge X‐ray absorption spectroscopy with high‐resolution X‐ray charge density modeling, together with theoretical calculations, the actual oxidation states of the central Ni atoms in these two complexes are investigated. Ni ions in two complexes are clearly in different oxidation states: the Ni ion of complex (1) is formally NiII; that of complex (2) should be formally NiIII, yet it is best described as a combination of Ni2+ and Ni3+, due to the involvement of the non‐innocent ligand in the Ni—L bond. A detailed description of Ni—S bond character (σ,π) is presented. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of complexes [Fe2(CO)4(κ2‐phen)(μ‐xdt)] (phen=1,10‐phenanthroline; xdt=pdt (1), adtiPr (2)) in MeCN‐[Bu4N][PF6] 0.2 m is described as a two‐reduction process. DFT calculations show that 1 and its monoreduced form 1− display metal‐ and phenanthroline‐centered frontier orbitals (LUMO and SOMO) indicating the non‐innocence of the phenanthroline ligand. Two energetically close geometries were found for the doubly reduced species suggesting an intriguing influence of the phenanthroline ligand leading to the cleavage of a Fe−S bond as proposed generally for this type of complex or retaining the electron density and avoiding Fe−S cleavage. Extension of calculations to other complexes with edt, adtiPr bridge and even virtual species [Fe2(CO)4(κ2‐phen)(μ‐adtR)] (R=CH(CF3)2, H) or [Fe2(CO)4(κ2‐phen)(μ‐pdtR)] (R=CH(CF3)2, iPr) showed that the relative stability between both two‐electron‐reduced isomers depends on the nature of the bridge and the possibility to establish a remote anagostic interaction between the iron center {Fe(CO)3} and the group carried by the bridged‐head atom of the dithiolate group. [ABSTRACT FROM AUTHOR]

The use of cyclopentadienyl ligands in organometallic chemistry and catalysis is ubiquitous, mostly due to their robust spectator role. Nonetheless, increasing examples of non‐innocent behaviour are being documented. Here, we provide evidence for reversible intramolecular C−H activation at one methyl terminus of C5Me5 in [(η‐C5Me5)Rh(PMe3)2] to form a new Rh−H bond, a process so far restricted to early transition metals. Experimental evidence was acquired from bimetallic rhodium/gold structures in which the gold center binds either to the rhodium atom or to the activated Cp* ring. Reversibility of the C−H activation event regenerates the RhI and AuI monometallic precursors, whose cooperative reactivity towards polar E−H bonds (E=O, N), including the N−H bonds in ammonia, can be understood in terms of bimetallic frustration. [ABSTRACT FROM AUTHOR]

Platinum(IV) complexes are extensively studied for their activity against cancer cells as potential substitutes for the widely used platinum(II) drugs. PtIV complexes are kinetically inert and need to be reduced to PtII species to play their pharmacological action, thus acting as prodrugs. The mechanism of the reduction step inside the cell is however still largely unknown. Gas‐phase activation of deprotonated platinum(IV) prodrugs was found to generate products in which platinum has a formal +3 oxidation state. IR multiple photon dissociation spectroscopy is thus used to obtain structural information helping to define the nature of both the platinum atom and the ligands. In particular, comparison of calculations at DFT, MP2 and CCSD levels with experimental results demonstrates that the localization of the radical is about equally shared between the dxz orbital of platinum and the pz of nitrogen on the amino group, the latter acting as a non‐innocent ligand. [ABSTRACT FROM AUTHOR]

The first example of ferrocene analogues with two transition‐metal metallole ligands of the general formula (η5‐C4R4M)2Fe in a sandwich structure are reported. Specifically, dinickelaferrocene 2, a type of dimetallametallocene, is efficiently synthesized from the reaction of dilithionickelole 1 with FeBr2 or FeCl2, presumably via a redox process, and is subjected to detailed experimental (single‐crystal X‐ray structural analysis, ICP‐OES, magnetometry, 57Fe Mössbauer, XPS) and theoretical (MOs, CDA, NICS, ICSS, and AICD) characterizations. Unlike ferrocene and its Cp ligands, the aromaticity of dinickelaferrocene and its nickelole ligands is accomplished by electron back‐donation from the Fe 3d orbitals to the π* orbitals of nickelole. Taken together, this work describes a new class of metallaferrocene sandwich complexes and provides a novel approach to effect aromaticity that will contribute to further development of metallocene chemistry. [ABSTRACT FROM AUTHOR]

The diphosphine, N‐heterocyclic phosphenium/phosphido (NHP+)/(NHP–)‐containing ligand (PPP+/–) has been coordinated to rhodium to study the coordination chemistry of group 9 metals and NHP+/– fragments. Addition of the chlorophosphine ligand PPClP to [Rh(COD)Cl]2 produces the complex (PPClP)RhCl (2), which can be reduced to form (PPP)Rh(PMePh2) (3), the asymmetric dimer [(PPP)Rh]2 (4), and the asymmetric dimer [(PPP)Rh(CNtBu)]2 (5). Analysis of the solid‐state structures and computational studies have provided insight into the electronic structure and bonding in 3–5, revealing that the NHP+/– fragments in 3, 4, and 5 are best described using an NHP–/RhI description. Both 3 and 5 were found to be reactive towards the S–H bond of thiophenol, generating (PPP)RhSPh (6) and (PPP)Rh(SPh)(CNtBu) (7), respectively. [ABSTRACT FROM AUTHOR]

The synthesis and electrochemical properties of nickel, palladium and platinum mesoionic carbenes complexes is presented and investigated. The study shows that in such mono-MIC systems, ligand oxidation is favored over metal oxidation giving access to unique ligand radical complexes, supported by a N -heterocyclic / mesoionic carbene moiety. [Display omitted] • Synthesis of an isostructural series of group 10 MIC complexes. • Investigation of electrochemical properties and the structural, crystalline isolation of all oxidized products. • EPR spectroscopy of all compounds and theoretical calculations on the electronic structure. We present the synthesis of an isostructural series of group 10 mesoionic carbene complexes with the general formula [M(MIC)Py] (with M = Ni (1), Pd (2) and Pt (3), Py = pyridine and MIC = bis-phenolate triazolylidene). Their electrochemical properties are investigated, revealing two quasi-reversible oxidations for all compounds, while no reductions are observed. Isolation of the oxidized species has been achieved using either silver triflate or nitrosonium tetrafluoroborate for the nickel and the platinum complex yielding the corresponding mono-cationic complexes [1] X and [3] X (X = OTf or BF 4). For the palladium complex, oxidation reactions yielded different products 4 and 5 in which the pyridine and/or the phenol(oxy) donors were found to be labile compared to Ni and Pt. Additionally, for Pt the electron transfer reaction was found to be quite slow and short reaction times led to the isolation of an unusual heterobimetallic silver-platinum complex 6. The location of the redox event has been investigated using EPR spectroscopy and computational methods, which suggest, that the oxidation is mostly centered on one of the phenolate anchors. [ABSTRACT FROM AUTHOR]

β‐Diketonates, such as acetylacetonate, are amongst the most common bidentate ligands towards elements across the entire periodic table and are considered wholly redox‐inactive in their complexes. Herein we show that complexation of 1,1,1,5,5,5‐hexafluoroacetylacetonate (hfac−) to CrII spontaneously affords CrIII and a reduced β‐diketonate radical ligand scaffold, as evidenced by crystallographic analysis, magnetic measurements, optical spectroscopy, reactivity studies, and DFT calculations. The possibility of harnessing β‐diketonates as electron reservoirs opens up possibilities for new metal–ligand concerted reactivity in the ubiquitous β‐diketonate coordination chemistry. [ABSTRACT FROM AUTHOR]

Ruthenium complexes containing catecholamines and catechol as ligands with general formula [Ru(NH3)4(catecholamine)]Cl, where "catecholamine" is isoproterenol (in complex 1), dopamine (in complex 2), noradrenaline (in complex 3), catechol (in complex 4), or adrenaline (in complex 5), were synthesized. The complexes were characterized by vibrational and NMR spectroscopies, mass spectrometry, cyclic voltammetry, and spectroeletrochemistry. The electronic and electrochemical features were analyzed in terms of the electronic density, which is affected by ruthenium complexation and different substituent groups on the aromatic ring. Resonance Raman spectra displayed bands assigned to the Ru(II)-semiquinone stretching frequencies, which agreed with the charge transfer band. Theoretical calculations helped to evaluate the metal-non-innocent ligand orbital mixing. All the results suggested that Ru(II)-semiquinone complexes are formed, and that the unpaired electron is delocalized between the metal ion and the non-innocent ligand. [ABSTRACT FROM AUTHOR]

A titanium(IV) alkoxido complex, (dpp‐bian)Ti(OBn)2 (2), as well as alkoxido chlorido complexes (dpp‐bian)TiCl(OCH2CH2OMe) (3) and (dpp‐bian)TiCl2OBn (4), were synthesized from the titanium(IV) dichloride precursor [(dpp‐bian)TiCl2]2 (1) by exchange with corresponding sodium salts (comps. 2 and 3) or by the alcoholysis with BnOH (comp. 4). The compounds 2–4 were fully characterized by elemental analysis, NMR or EPR, and IR spectroscopy. Molecular structures of the metal complexes in the solid state have been determined by single‐crystal XRD analysis. Compounds 2–4 were tested as catalysts in the ROP of L‐lactide in a toluene medium. Whereas complexes 2 and 3 produce cyclic PLAs with broad dispersities and unpredictable molecular weights, complex 4 acts as an efficient ROP catalyst which polymerizes the monomer in a highly controllable manner. It produces BnO‐capped PLAs with narrow molecular weight distributions as well as linear dependence of Mns on monomer conversion. [ABSTRACT FROM AUTHOR]

• Metal coordination affects the redox behavior of dye chromophores. • Electron transfer sites may involve the metal and/or the dye ligand. • Variable coordination patterns are observed for metal complexes of indigo. • Radical formation and mixed valency may occur in oligonuclear complexes. • Long wavelength absorptions are common in metal complexes of dyes. The chromophores of several classes of well-established dyes, e.g., indigo, 9,10-anthraquinones, formazanes, diketopyrrolopyrroles (DPPs), or certain azo compounds, are not only responsible for intense low-energy absorptions but are also suited for dye ligand-based electron transfer and for (multiple) metal chelate coordination at N and O donor centers, after due deprotonation. Coupling with the redox activity of bonded transition metals such as ruthenium can lead to intricate electronic structures with variable oxidation state combinations, especially when the non-innocent dye-derived ligands are bridging two or more metal centers. Employing an array of experimental methods such as crystal structure determination, voltammetry, EPR, IR and UV–vis-NIR spectroelectrochemistry, and using supporting DFT calculations, it has been possible to analyze the geometrical and electronic situations in compounds such as [L x Run(µ-BL)RumL x ]k, involving radical formation of the bridging chromophore and/or metal-metal mixed valency (BL: bridging ligand derived from dye). Among the prominent suitable examples for BL components are deprotonated indigo with variable ligand oxidation states and coordination patterns (N,O; N,N′; O,O′; N,O:N′,O′; N,N′:O,O′), the non-innocent nindigo ligands with indigo-O replaced by NR, the widely employed 9,10-anthraquinones with additional O or NR donor substituents at various chelate-forming positions, bidirectionally non-innocent formazanato ligands, the DPP(diketopyrrolopyrrole) π system used for technical pigments, heterocyclic quinones, and selected bis-chelating azo compounds with strong and potentially useful NIR absorbance. The deprotonated bridging ligands can adopt several oxidation states such as. BL0, BL −, BL2−, BL 3− and BL4− for the indigo and anthraquinone examples. With the increasing application of classical dye chromophores in information technology systems based on optical and electronic properties, their hitherto neglected potential for metal coordination, including metal-metal bridging and coordination-enhanced electron transfer reactivity, awaits to be exploited – the scope of such capability is illustrated in this article. [ABSTRACT FROM AUTHOR]

Herein, we present the realization of a class of unprecedented aromatic structures 2: metalla‐aromatics with two independent and perpendicular aromatic rings spiro‐fused by a transition‐metal spiro atom, of which their corresponding organic analogues are impossible. Tetralithio spiro manganacycles 2 are readily synthesized from 1,4‐dilithio‐1,3‐butadienes 1 and MnCl2 in the presence of lithium. The aromaticity of 2 is supported by experimental measurements (X‐ray structural analysis, NMR) and theoretical analyses (NICS, ACID, MOs). The spiro atom Mn in 2 uses its 3dxz and 3dxy orbitals to form the two perpendicular manganacycles, which are two independent 6π aromatic systems. Theoretical analyses reveal that the Li cations play an indispensable role in governing their geometric and electronic structures and hence their aromaticity. Therefore, this work contributes not only to enrich the concept of aromaticity, but also to deepen the understanding of the fundamental chemical bonding. [ABSTRACT FROM AUTHOR]

New soluble and intensely near-IR-absorbing transition metal (Ti, Zr, V, Ni) complexes were synthesized using a redox non-innocent N,N’-bis(3,5-di-tertbutyl-2-hydroxy-phenyl) -1,2-phenylenediamine (H4L) as a ligand precursor. In all the complexes, ([Ti(Lox)2, [Zr(Lox)2], [V(Lsq1)(HLox)] and [Ni(HLox)2], two organic molecules coordinate to the metal center as tri- or tetradentate ligands. The solid-state structures of the complexes were determined using single crystal XRD, and the compounds were further characterized with Electrospray Ionisation Mass Spectrometry (ESI-MS). Thermoanalytical measurements indicated the thermal stabilities of the complexes. All compounds absorb strongly in the near-IR region and show very interesting magnetic and electrochemical properties. Moreover, it was shown that the V and Ni complexes can also convert absorbed near-IR photons to (un)paired electrons, which indicates great promise in photovoltaic applications.

Controlled ligand‐based redox‐activity and chemical non‐innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand‐to‐substrate single‐electron transfer as a relatively new mode of operation to exploit ligand‐centered reactivity and catalysis based thereon. Deposit or withdrawal? Controlled ligand‐based redox activity and chemical non‐innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand‐to‐substrate single‐electron transfer as a relatively new mode of operation to exploit ligand‐centered reactivity and catalysis based thereon. [ABSTRACT FROM AUTHOR]

Storage of electricity produced intermittently by renewable energy sources is a societal issue. Besides the use of batteries and supercapacitors, conversion of excess electricity into chemical energy is also actively investigated. The conversion of CO2 to fuel or fuel precursors is an option that requires the use of a catalyst to overcome the high activation energy barrier. Of molecular catalysts, metal complexes with polypyridyl ligands are well represented, among which the [Cp*Rh(bpy)Cl]+ and [M(bpy)(CO)3X] (M = Re, Mn) complexes. As redox non‐innocent ligand, the bipyridine ligand is generally involved in the reduction mechanisms. It is thus tempting to replace it by other redox non‐innocent ligands such as vacant polyoxometalates (POMs). We have thus prepared [α‐H2PW11O39{RhIIICp*(OH2)}]3– which is closely related to [Cp*RhIII(bpy)Cl]+ by substitution of the monovacant [PW11O39]7– Keggin‐type POM for the bipyridine ligand. Its activity towards CO2 reduction has been assessed in acetonitrile in the presence of water. Compared to [Cp*Rh(bpy)Cl]+ that produces formate selectively over CO and H2, the POM derived catalyst favors proton reduction over CO2 reduction. [α‐H2PW11O39{RhIIICp*(OH2)}]3– was prepared by reaction between the monovacant Keggin‐type [α‐H2PW11O39]5– and [Cp*Rh(CH3CN)3]2+. It is closely related to the CO2 reduction electrocatalyst [Cp*RhIII(bpy)Cl]+ by changing the bpy ligand by the polyoxometalate, both acting as redox non‐innocent bidentate ligands. The selectivity of the CO2 reduction was altered from the production of formate to dihydrogen. [ABSTRACT FROM AUTHOR]

Although, the investigation of the interactions of Mo VI ion with the “non-innocent” phenols/hydroquinones is essential for the understanding of the role of molybdenum in the biological systems, the Mo VI complexes of phenolate/hydroquinonate and their functionalized variants remain mainly unexplored. Reaction of Na 2 Mo VI O 4 with tripod iminodiacetate phenol/hydroquinone ligands in aqueous solutions resulted in the synthesis of mononuclear phenolate/hydroquinonate and dinuclear bridged-hydroquinonate cis -Mo VI O 2 2+ complexes. The new complexes were isolated and characterized in solid state by X-ray crystallography. The 1 H, 13 C and 95 Mo NMR spectra of the aqueous solutions of the complexes show that they retain their structure at the pD range 2–4, with the dinuclear bridged-hydroquinonate cis -Mo VI O 2 2+ to form two isomers which are in dynamic equilibrium. At pDs 4–7 the Mo VI -O phenolate bond of the cis -Mo VI O 2 2+ compounds hydrolyzes to form Mo VI O 3 -iminodiacetate species. Variable temperature (VT) and 2D { 1 H} EXSY NMR spectroscopies where employed for the determination of the thermodynamic and activation parameters of the isomerization reaction between the dinuclear bridged-hydroquinonate cis -Mo VI O 2 2+ isomers. The exchange mechanism between cis -Mo VI O 2 2+ and the Mo VI O 3 species were also investigated by 2D { 1 H} EXSY NMR spectroscopy. Despite of the higher strength of the Mo VI -O phenolate bond, it is more labile than the Mo VI -O carboxylate bond. The rate determining step of the above exchange reactions was found to be the dissociation of the phenolate/hydroquinonate oxygen atom from Mo VI ion. [ABSTRACT FROM AUTHOR]

The new titanium(IV) coordinative compound (dpp-bian)TiCl 2 ( 2 ) was obtained by metathesis of the disodium salt (dpp-bian)Na 2 ( 1 ) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with TiCl 4 . It was shown that the chlorido ligands can be exchanged for chelating dpp-bian ligands, or tert -butoxy groups, with the formation of (dpp-bian) 2 Ti ( 3 ) and (dpp-bian)Ti(O t Bu) 2 ( 4 ), respectively. Complexes 2 – 4 were isolated and fully characterized. It was demonstrated that dpp-bian is in the reduced dianionic form and acts as a σ 2 π-donor ligand. [ABSTRACT FROM AUTHOR]

Pincer complexes attract considerable attention both as interesting objects for fundamental studies and efficient catalysts. This review describes a relatively new offshoot of the field – namely, the chemistry of iridium complexes with aliphatic PC sp3 P non-innocent pincer ligands. High flexibility, often combined with possibility to activate internal C–H bonds, offers several new patterns of metal-ligand cooperation; some of them were successfully used in catalysis of acceptorless alcohol dehydrogenation, olefin hydroformylation and deuterium exchange, others opened up for remarkable stoichiometric reactions. [ABSTRACT FROM AUTHOR]

Abstract: A dinuclear CoII complex, [Co2(tphz)(tpy)2]n+ (n=4, 3 or 2; tphz: tetrapyridophenazine; tpy: terpyridine), has been assembled using the redox‐active and strongly complexing tphz bridging ligand. The magnetic properties of this complex can be tuned from spin‐crossover with T1/2≈470 K for the pristine compound (n=4) to single‐molecule magnet with an ST=5/2 spin ground state when once reduced (n=3) to finally a diamagnetic species when twice reduced (n=2). The two successive and reversible reductions are concomitant with an increase of the spin delocalization within the complex, promoting remarkably large magnetic exchange couplings and high‐spin species even at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: A newly developed dihydrazonopyrrole ligand and corresponding Ni complexes have been synthesized and thoroughly characterized. Electrochemical studies and chemical reactivity tests show that these complexes can reversibly store both electrons and protons, or equivalently H‐atoms, via ligand‐based events. The stored H‐atom equivalent can be transferred to small molecules such as acetonitrile or oxygen. Furthermore, this series of complexes can adopt a variety of different coordination modes. In addition to one e− reactivity, the two e− electrophilic oxidation of phosphines is also demonstrated. Taken together, these results show that dihydrazonopyrrole complexes represent a geometrically and electronically flexible scaffold for controlling the flow of both electrons and protons. [ABSTRACT FROM AUTHOR]

Phosphasalen ligands can be viewed as the phosphorus analogues of salen, in which the imine functions were replaced by iminophosphoranes (P=N). Their divergent stereoelectronic properties compared to salen, namely larger electron‐donation, higher flexibility, and larger steric hindrance due to the presence of two substituents on the tetrahedral phosphorus atoms, were exploited in coordination chemistry and catalysis. They were proven to be able to stabilize metals in unusual oxidation states; square planar copper(III) and nickel(III) complexes were isolated. Because of the redox non‐innocent character of these ligands, the electronic structure of the one‐electron oxidized complexes was studied in depth to determine the metallic vs. ligand contribution in the overall delocalization. In addition, the catalytic activity of different phosphasalen complexes was proven for the ring opening polymerization of lactide, and rare‐earth phosphasalen complexes were shown to be powerful, rapid, controlled, and stereoselective initiators. Importantly, the stereochemical outcome of the reaction can be tuned by changing the ligand structure or the metal. In particular, efficient iso‐selective initiators were developed. [ABSTRACT FROM AUTHOR]

Three mononuclear metal complexes of Co 2+ , Ni 2+ and Cu 2+ with the Salen type ligand (( 2,2′ -[( 1-methyl-1,2 - ethanediyl ) bis ( nitriloethylidyne )] bis ( 1-naphthalenol )), H 2 Naphpren or L ) were synthesized and structurally characterized. All metal complexes have square planar geometries and crystallize in the P2 1 /c space group. Structural characterization of the ligand shows contribution of the bis(ketone) tautomer in the crystalline phase, in agreement with density functional theory (DFT) computations. However, according to the UV-vis spectrum, there is a stronger influence of the bis(phenol) tautomer in solution. Cyclic voltammetry experiments showed that the ligand undergoes a single irreversible oxidation process at 0.434 V (vs Fc/Fc + ) while the complexes with Co 2+ , Ni 2+ and Cu 2+ suffer electroxidative process on the surface of the working electrode in addition to solution-assigned redox processes. The CoL oxidation is localized on the metal center, however, the CuL and NiL oxidations are considered as metal-ligand based processes. DFT calculations confirmed our experimental findings. The UV-vis spectra of the complexes illustrate ligand characteristic bands: in the case of the Cu 2+ complex, the metal-to-ligand charge transfer (MLCT) band is present at 385 nm, while in the case of Co 2+ complex this same type of MLCT band appears at 377 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] We report the synthesis, the magnetic, electronic and spatial characterization of the novel compound [Dy(HDPA) 2 (H 2 DPA)]·1.5 H 2 O (H 2 DPA = dipicolinic acid), 1. The reaction yields ca. 76 % of a nonacoordinated formally Dy3+ compound possessing a rare tricapped trigonal prismatic geometry whose spectroscopic analyses by X-ray crystallography, 1H NMR, UV–Vis, and ESR are presented herein. The bond distances and angles coincide with most Dy3+ reports. DFT description of 1 suggests a non-innocent Dy3+ coordinated to a radical anion ligand, and other 2 non radical ligands and CASSCF/CASPT2 description support this description. Specifically, ESR confirms the presence of such a free radical system. At low temperatures (T ≈ 2 K), the ESR spectrum shows a similar free radical signal with a g value of 2.006, suggesting the delocalization of the electron in the π system. Moreover, the comparison of results with the equivalent Dy3+ with no free radical interaction is also included as a Dy3+ counterpart, [Dy3+(HDPA) 3 ] 2. [ABSTRACT FROM AUTHOR]

Abstract: Recently it was reported that copper bicarbonate/carbonate complexes are good electro‐catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3−2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2−2n solution. The results enable the evaluation of E°[(CuIII/II(CO3)n)aq]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single‐electron transfer from CuIII(CO3)n3−2n to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to CuIII results in the formation of C2O62− by means of a second‐order reaction of CuIII(CO3)n3−2n. The results point out that carbonate stabilizes transition‐metal cations at high oxidation states, not only as a good sigma donor, but also as a non‐innocent ligand. [ABSTRACT FROM AUTHOR]

Non-innocent ligands render the determination of the electronic structure in metal complexes difficult. As such, a combination of experimental techniques and quantum chemistry are required to correctly elucidate them. This paper deals with the one-electron oxidation of copper(II) and nickel(II) complexes featuring a phosphasalen ligand (Psalen), which differs from salen analogues by the presence of iminophosphorane groups (P=N) instead of imines. Various experimental techniques (X-ray diffraction, cyclic voltammetry, NMR, EPR, and UV/Vis spectroscopies, and magnetic measurements) as well as quantum chemical calculations were used to define the electronic structure of the oxidized complexes. These can be modified by a small change in the ligand structure, that is, the replacement of a tert-butyl group by a methoxy on the phenoxide ring. The different techniques have allowed quantifying the amount of spin density located on the metal center and on the Psalen ligands. All complexes were found to possess a multi-configurational ground state, in which the ratio of the +II versus +III oxidation state of the metal center, and therefore the phenolate versus phenoxyl radical ligand character, varies upon the substituents. The tert-butyl group favors a strong localization on the metal center whereas with the methoxy group the metallic configurations decrease and the ligand configurations increase. The importance of the geometrical considerations compared with the electronic substituent effect is highlighted by the differences observed between the solid-state (EPR, magnetic measurements) and solution characterizations (EPR and NMR data). [ABSTRACT FROM AUTHOR]

Cp*Rh(III) complexes 1a and 1b (Cp* = 1, 2, 3, 4, 5-pentamethylcyclopentadienyl) having functional N,O chelate ligands have been synthesized and characterized by 1 H, 13 C{ 1 H} NMR spectroscopy, elemental analysis, IR spectroscopy and X-ray diffraction. Reactivity of these complexes has been investigated towards dehydrogenation of alcohols and hydrogenation of ketones. It was found that these compounds are precursors to the formation of Rh nanoparticles which serve as catalysts, as evidenced by mercury poisoning of the catalysis and direct observation of the particles by TEM, EDX, and XRD. [ABSTRACT FROM AUTHOR]

Metal dithiolene complexes have increasingly developed over the last fifteen years due to their peculiar electronic structures that makes them very important units for magnetic, conducting and optical molecular materials. This review deals with the different families of chiral metal dithiolenes reported to date in the literature, with the objective of underlining the role of chirality on the resulting materials, in order to disclose possible directions for future developments. Chirality in such materials has been introduced through two strategies, via chiral cations in combination with anionic complexes or using pre-synthesized chiral dithiolene ligands. The corresponding materials resulting from both strategies are thoroughly discussed, with a special focus on the solid state architectures largely influenced by the chiral information. Chiral dithiolene ligands have generally provided homoleptic Ni(II) and Au(III) anionic and neutral bis(dithiolene) complexes, while heteroleptic complex have been described with Ni(II) and Mo(II). The neutral Au(III) complexes are especially interesting in the context of chiral single component conductors. [ABSTRACT FROM AUTHOR]

Assembly of the triangular, organic radical-bridged complexes Cp*6Ln3(μ3-HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*2Ln(BPh4) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three LnIII centers through the HAN3−. radical ligand. Thorough investigation of the DyIII congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of Ueff=51 cm−1. Magnetic coupling in the DyIII complex enables a large remnant magnetization at temperatures up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero-field up to 3.5 K. [ABSTRACT FROM AUTHOR]

The synthesis of the divinylamido PNP nickel(II) complex [NiBr{N(CHCHP tBu2)2}] is reported. This compound exhibits reversible, ligand-centered oxidation and protonation reactions. The resulting pincer chemical non-innocence can be utilized for benzylic C−H hydrogen atom abstraction. The thermochemistry and kinetics of hydrogen atom transfer were examined. [ABSTRACT FROM AUTHOR]

Copper(II) chloride complexes with nitrogen-containing ligands (amines, amides, heterocycles) were studied as catalysts of selective oxidation of thiols to disulfides. This process has an important biochemical analogue – the formation of disulfide bridge in proteins [Wang C, Wesener SR, Zhang H, Cheng Y-Q. An FAD-dependent pyridine nucleotide-disulfide oxidoreductase is involved in disulfide bond formation in FK228 anticancer depsipeptide. Chem and Biol. 2009;16:585–593]; which affects their activity [Zhang L, Chou CP, Moo-Young M. Disulfide bond formation and its impact on the biological activity and stability of recombinant therapeutic proteins produced by Escherichia coli expression system. Biotech Adv. 2011;29:923–929]. Also, thiol oxidation is an important process of oil sweetening. The search for effective and stable catalysts for this reaction is still topical [Ganguly SK, Das G, Kumar S, Sain B, Garg MO. Mechanistic kinetics of catalytic oxidation of 1-butanethiol in light oil sweetening. Catal Tod. 2012;198:246–251]. This article describes a mechanistic study of thiol oxidation and non-innocent ligands transformations during this reaction. The studied ligands are capable of oxidizing thiols, the reaction being followed by reoxidation of the reduced forms of the ligands with air oxygen. The oxidative activity of the ligand correlates with catalyst activity for thiol oxidation. [ABSTRACT FROM PUBLISHER]

Owing to their unique topologies and abilities to self-assemble into a variety of extended and aggregated structures, the binary platinum carbonyl clusters [Pt3(CO)6] n2− ('Chini clusters') continue to draw significant interest. Herein, we report the isolation and structural characterization of the trinuclear electron-transfer series [Pt3(μ-CO)3(CNArDipp2)3] n− ( n=0, 1, 2), which represents a unique set of monomeric Pt3 clusters supported by π-acidic ligands. Spectroscopic, computational, and synthetic investigations demonstrate that the highest-occupied molecular orbitals of the mono- and dianionic clusters consist of a combined π*-framework of the CO and CNArDipp2 ligands, with negligible Pt character. Accordingly, this study provides precedent for an ensemble of carbonyl and isocyanide ligands to function in a redox non-innocent manner. [ABSTRACT FROM AUTHOR]

Biomimetic diiron complexes bearing redox non-innocent ligands are discussed in this review. The complexes are synthesized to model the active site of [FeFe] hydrogenase in order to elucidate the catalytic mechanism of H2 evolution and design superior artificial catalysts. Employment of the redox active ligands serves an important factor to modulate electronic structure of the Fe2 core as the similar functionality exerted by the [4Fe4S] cofactor within the H-cluster. Different types of redox active ligands are summarized. The influence of their ligation is observable in spectroscopy as well as cyclic voltammetry, and studied by theoretical calculation. [ABSTRACT FROM AUTHOR]

Reducing hexaazatrinaphthylene (HAN) with potassium in the presence of 18-c-6 produces [{K(18-c-6)}HAN], which contains the S=1/2 radical [HAN].−. The [HAN].− radical can be transferred to the cobalt(II) amide [Co{N(SiMe3)2}2], forming [K(18-c-6)][(HAN){Co(N′′)2}3]; magnetic measurements on this compound reveal an S=4 spin system with strong cobalt-ligand antiferromagnetic exchange and J≈−290 cm−1 (−2 J formalism). In contrast, the CoII centres in the unreduced analogue [(HAN){Co(N′′)2}3] are weakly coupled (J≈−4.4 cm−1). The finding that [HAN].− can be synthesized as a stable salt and transferred to cobalt introduces potential new routes to magnetic materials based on strongly coupled, triangular HAN building blocks. [ABSTRACT FROM AUTHOR]