Ferrocene-dichalcogenolate-bridged complexes, [Fe2(CO)6{μ-E(η5-C5H4)Fe(η5-C5H4)E}] (E = S, Se), are [FeFe]-hydrogenase biomimics, in which the two redox-active centres lie in close proximity. Here we report the syntheses and electrochemical studies of phosphine-substituted derivatives, which allows tuning of the oxidation chemistry of the Fe2 centre, while (effectively) leaving that of the ferrocene centre unchanged. Mono-substituted [Fe2(CO)5{μ-Se(η5-C5H4)Fe(η5-C5H4)Se}(Ph2P-p-tolyl)], chelated [Fe2(CO)4{μ-E(η5-C5H4)Fe(η5-C5H4)E}(κ2-dppv)] and bridged [Fe2(CO)4{μ-E(η5-C5H4)Fe(η5-C5H4)E}(μ-dppf)] complexes have been prepared under carefully controlled reaction conditions, the selenium derivative giving higher yields. Crystal structures of [Fe2(CO)4{μ-Se(η5-C5H4)Fe(η5-C5H4)Se}(κ2-dppv)] and [Fe2(CO)4{μ-Se(η5-C5H4)Fe(η5-C5H4)Se}(μ-dppf)] have been determined, which contain three closely located iron redox centres. Cyclic voltammetry (CV) and IR spectroelectrochemistry (IR SEC) have been used to understand changes occurring upon oxidation. Upon successive replacement of carbonyl(s), the oxidation potential of the Fe2 centre is lowered and in the dppv and dppf complexes it occurs prior to oxidation of the remote Fe(II) centre in the ferrocene-dithiolate bridge, as confirmed by IR SEC experiments. Dppf complexes contain three different iron oxidation centres, and three separate oxidation waves are identified in the CV of [Fe2(CO)4{μ-Se(η5-C5H4)Fe(η5-C5H4)Se}(μ-dppf)]. DFT calculations have been used to better understand the likely structures of the oxidised species. They suggest that oxidation of the Fe2 centre results in a structural rearrangement to give a semi-bridging carbonyl, but no such species are observed by IR SEC, possibly due to the high rearrangement energies. IR SEC studies also suggest that for the dppf complexes, oxidation may be delocalised over several sites.

Herein we report an electronic structure investigation of neutral and oxidized Ru complexes containing a redox noninnocent N2S2 ligand derived from o-phenylenediamide (L1). UV-vis spectroelectrochemistry (SEC) studies were conducted on the square pyramidal complex [RuII(L1)(PPh3)] (1) and the six-coordinate complexes [RuII(μ-BH3)(L1)(PPh3)] (2) - which has BH3 bound in a metal-ligand cooperative (MLC) fashion across Ru and L1 - and [RuII(L1)(PPh3)(MeCN)] (3). The SEC results yielded spectra assigned to singly and doubly oxidized 1 and 3, revealing electronic structure changes as a function of oxidation state and in response to the presence and absence of bound MeCN. By contrast, the SEC results of 2 showed that it rapidly loses MLC-bound BH3 upon oxidation. The SEC results for 1 and 3 were compared to single-crystal XRD data and UV-vis, EPR, and P K-edge, S K-edge, and Ru L3-edge X-ray absorption spectroscopy (XAS) data collected on isolated samples of chemically oxidized 3. The data revealed that the first two oxidations are primarily localized on the ligand, which was supported by DFT and TDDFT calculations. DFT calculations for the doubly oxidized species revealed a singlet ground state with a singlet-triplet gap of 8.9 kcal/mol. CASPT2 calculations corroborated the DFT calculations and further revealed that the singlet ground state is multiconfigurational with 21% radical character. Collectively, the results establish redox formalisms and the underlying electronic structure of Ru complexes containing a noninnocent tetradentate ligand in different oxidation states.

Stable anions based on classical N-heterocyclic carbenes (NHCs) can be prepared by KC8-reduction of the corresponding NHC radicals as reported by Diego M. Andrada, Rajendra S. Ghadwal et al. in their Research Article (e202215244). The key to the stability of these anions is the delocalization of the electron lone pair over the C2-biphenyl substituent. In the solid state, the anions form a hexameric tubular structure with biphenyl substituents pointing inwards, as a result of intriguing cation–π interactions. The spider weaves its web.

Intramolecular electronic communication between electrochemically active groups connected by a bridging moiety can be modified through small changes in the spatial disposition of the redox active moieties and/or by the nature of the central core. In this study, chiral bio-based compounds, namely isomannide and isosorbide, were employed as cheap and easy-to-functionalize chiral scaffolds to bridge two ferrocenyl electroactive moieties. The crystal structures of both bis-ferrocenyl diester complexes were studied and they showed that the chirality of the bridge results in an open or tight helical crystal packing. The electron communication between the two electroactive units in the mixed valent monocations was also investigated using electrochemistry (cyclic voltammetry and differential pulsed voltammetry), and spectroelectrochemistry in the UV-Vis NIR. A computational study through time-dependent DFT was also employed to gain greater insight into the results obtained.

Cooperativity at the crossroad: The two copper centers in the dinuclear copper(II) dimethylglyoxime complex work in concert to facilitate ligand hydrolysis that yields butane-2,3-dione monoxime and NH2OH. The fate of NH2OH depends on the solvent used, in CH3CN, for example, NH2OH is oxidized to N2O yielding [Cu(CH3CN)4]+ as reduced species. In ethanol, however, NH2OH is reduced to NH4+, which in turn yields acetaldehyde as oxidized species. More information can be found in the Research Article by S. Becker and co-workers (DOI: 10.1002/chem.202203438).

Stable anions based on classical N-heterocyclic carbenes (NHCs) can be prepared by KC8 reduction of the corresponding NHC radicals as reported by Diego M. Andrada, Rajendra S. Ghadwal, and co-workers in their Research Article (e202215244). The key to the stability of these anions is the delocalization of the electron lone pair over the C2-biphenyl substituent. In the solid state, the anions form a hexameric tubular structure with biphenyl substituents pointing inwards, as a result of intriguing cation–π interactions. The spider weaves its web.

Controlling the pairing strength of nucleobases in DNA through reactions with compounds found inside the cell is a formidable challenge. Here we report how a thiazolyl substituent turns a strongly pairing ethynylpyridone C-nucleoside into a reactive residue in oligonucleotides. The thiazolyl-bearing pyridone reacts with soft nucleophiles, such as glutathione, but not with hard nucleophiles like hydroxide or carbonate. The addition products pair much more weakly with adenine in a complementary strand than the starting material, and also change their fluorescence. This makes oligonucleotides containing the new deoxynucleoside interesting for controlled release. Due to its reactivity toward N, P, S, and Se-nucleophiles, and the visual signal accompanying chemical conversion, the fluorescent nucleotide reported here may also have applications in chemical biology, sensing and diagnostics.

In this report, we present the dinuclear copper(II) dimethylglyoxime (H2 dmg) complex [Cu2 (H2 dmg)(Hdmg)(dmg)]+ (1), which, in contrast to its mononuclear analogue [Cu(Hdmg)2 ] (2), is subject to a cooperativity-driven hydrolysis. The combined Lewis acidity of both copper centers increases the electrophilicity of the carbon atom in the bridging μ2 -O-N=C-group of H2 dmg and thus, facilitates the nucleophilic attack of H2 O. This hydrolysis yields butane-2,3-dione monoxime (3) and NH2 OH that, depending on the solvent, is then either oxidized or reduced. In ethanol, NH2 OH is reduced to NH4+ , yielding acetaldehyde as the oxidation product. In contrast, in CH3 CN, NH2 OH is oxidized by CuII to form N2 O and [Cu(CH3 CN)4 ]+ . Herein are presented the combined synthetic, theoretical, spectroscopic and spectrometric methods that indicate and establish the reaction pathway of this solvent-dependent reaction.

Organometallic complexes are frequently deposited on solid surfaces, but little is known about how the resulting complex-solid interactions alter their properties. Here, a series of complexes of the type Cu(dppf)(Lx)+ (dppf = 1,1'-bis(diphenylphosphino)ferrocene, Lx = mono- and bidentate ligands) were synthesized, physisorbed, ion-exchanged, or covalently immobilized on solid surfaces and investigated by 31P MAS NMR spectroscopy. Complexes adsorbed on silica interacted weakly and were stable, while adsorption on acidic γ-Al2O3 resulted in slow complex decomposition. Ion exchange into mesoporous Na-[Al]SBA-15 resulted in magnetic inequivalence of 31P nuclei verified by 31P-31P RFDR and 1H-31P FSLG HETCOR. DFT calculations verified that a MeCN ligand dissociates upon ion exchange. Covalent immobilization via organic linkers as well as ion exchange with bidentate ligands both lead to rigidly bound complexes that cause broad 31P CSA tensors. We thus demonstrate how the interactions between complexes and functional surfaces determine and alter the stability of complexes. The applied Cu(dppf)(Lx)+ complex family members are identified as suitable solid-state NMR probes for investigating the influence of support surfaces on deposited inorganic complexes.

While ZrO2 is known to have a large effect on the activity and selectivity of the Cu/ZrO2 catalyst for methanol synthesis, its role in this process is poorly understood. Surface defects such as oxygen vacancies could play a role in the strong metal-support interaction (SMSI) between Cu and ZrO2. However, due to the complexity of the surfaces, the exact molecular nature of this interaction is not at present known. Here, we make well-defined models of both reduced and coordinatively unsaturated surface oxygen vacancies on ZrO2 using the molecular precursor [Cp2ZrCl](2)(mu(2)-O) (1). Complex 1 can be reduced to form a complex (2) containing one Zr(III) center and a bridging hydride ligand (according to EPR and IR spectroscopy) derived from C-H activation of either thf or the Cp ring. Complex 2 reacts with CO2 to largely produce CO, suggesting that surface defects with similar structures probably do not play a role in the industrial catalyst. Halide abstraction from complex 1 results in the Lewis acidic species 3, which has similar Lewis acid properties to acidic defects on the ZrO2 surface. Similarities of both of these model species to real surface oxygen vacancies and their role in the catalytic reaction are discussed.

AbstractDie ersten stabilen Anionen K[SIPrBp] (4 a‐K) und K[IPrBp] (4 b‐K) (SIPrBp=BpC{N(Dipp)CH2}2, IPrBp=BpC{N(Dipp)CH}2; Bp=4‐PhC6H4; Dipp=2,6‐iPr2C6H3), die von klassischen N‐heterocyclischen Carbenen (NHCs) abgeleitet sind (d. h. SIPr und IPr), wurden als violette kristalline Feststoffe isoliert.4 a‐Kund4 b‐Kwurden durch die Reduktion der neutralen Radikale [SIPrBp] (3 a) bzw. [IPrBp] (3 b) mit KC8hergestellt. Die Radikale3 aund3 bsowie [Me‐IPrBp] (3 c) (Me−IPrBp=BpC{N(Dipp)CMe}2) liegen als kristalline Feststoffe vor, wenn die entsprechenden 1,3‐Imidazoli(ni)umbromide (SIPrBp)Br (2 a), (IPrBp)Br (2 b) und (Me‐IPrBp)Br (2 c) mit KC8umgesetzt werden. Die Cyclovoltammogramme von2 a–2 czeigen zwei reversible Ein‐Elektronen‐Redoxprozesse im Bereich von −0.5 bis −2.5 V, die den Radikalen3 a–3 cund den Anionen (4 a–4 c)−entsprechen. Quantenchemische Berechnungen deuten auf einen geschlossenschaligen Singulett‐Grundzustand für (4 a–4 c)−mit einer Singulett‐Triplett‐Energielücke von 17–24 kcal mol−1hin.

Herein, the first stable anions K[SIPrBp] (4 a-K) and K[IPrBp] (4 b-K) (SIPrBp=BpC{N(Dipp)CH2}(2), IPrBp=BpC{N(Dipp)CH}(2); Bp=4-PhC6H4; Dipp=2,6-iPr(2)C(6)H(3)) derived from classical N-heterocyclic carbenes (NHCs) (i.e. SIPr and IPr) have been isolated as violet crystalline solids. 4 a-K and 4 b-K are prepared by KC8 reduction of the neutral radicals [SIPrBp] (3 a) and [IPrBp] (3 b), respectively. The radicals 3 a and 3 b as well as [Me-IPrBp] 3 c (Me-IPrBp=BpC{N(Dipp)CMe}(2)) are accessible as crystalline solids on treatment of the respective 1,3-imidazoli(ni)um bromides (SIPrBp)Br (2 a), (IPrBp)Br (2 b), and (Me-IPrBp)Br (2 c) with KC8. The cyclic voltammograms of 2 a-2 c exhibit two one-electron reversible redox processes in -0.5 to -2.5 V region that correspond to the radicals 3 a-3 c and the anions (4 a-4 c)(-). Computational calculations suggest a closed-shell singlet ground state for (4 a-4 c)(-) with the singlet-triplet energy gap of 17-24 kcal mol(-1).

AbstractWir berichten über die Synthese und die Reaktivität mesoionischer Imine (MIIs) des 1,2,3‐Triazolin‐5‐imin Typs. Die MIIs sind über eine Basen‐mediierte Cycloaddition eines substituierten Acetonitrils mit einem aromatischen Azid, Methylierung nach etablierten Methylierungsrouten und anschließender Deprotonierung zugänglich. C=O‐Streckschwingungen in MII−CO2− und −Rh(CO)2Cl‐Komplexen wurden bemüht um die Gesamtdonorstärke zu bestimmen. Die MIIs sind stärkere Donoren als N‐Heterocyclische Imine (NHIs). MIIs sind exzellente Liganden für Hauptgruppenelemente und Übergangsmetalle, in welchen sie Substituenten‐induzierte Fluor‐spezifische Wechselwirkungen zeigen oder C−H‐Aktvierungen eingehen. DFT‐Berechnungen haben Einblicke in die Grenzorbitale der MIIs gegeben. Die Rechnungen sagen im Vergleich zu verwandten Liganden eine relative kleine HOMO–LUMO Lücke vorraus. MIIs können potentiell sowohl als π‐Donor‐ als auch π‐Akzeptorliganden wirken. Dieser Bericht demonstiert das Potential von MIIs spannende Eigenschaften mit einem gewaltigen Zukunftspotential zu entwickeln.

The ligands N-phenylcamphoriminoquinone 1 and N-(2-thiomethylphenyl)camphoriminoquinone 2 were reacted with copper(I) and copper(II) precursors to yield structurally characterized compounds with N-, O,N-, N,Sand O,N,S-coordination: [Cu-I(1-kappa O-2,N)(dppf)](PF6) 3(PF6), [Cu-I(2- kappa N-2,S)(dppf)](PF6) 4(PF6), [Cu-II(1- kappa N)(NO3- kappa O)(2)] and [Cu-II(1-kappa O-2,N)(NO3-kappa O)(2)] 5, and [Cu-II(2-kappa O-3,N,S)(NO3-kappa O)(2)] 7 where dppf is 1,1'-bis (diphenylphosphino) ferrocene. Spectroelectrochemistry reveals that the cations 3(+) and 4(+) exhibit ferrocene-based oxidation and camphoriminoquinone-centered reduction. The copper(II) compounds 5 and 7 exhibit coordinative variety with monodentate and bidentate coordination of the ligand 1 for two different molecules in 5, and with O,N,S-tridentate coordination for 2 in 7.

Using bis(3-methyl-2-pyridyl)-1,2,4,5-tetrazine 1, 3-(2-pyrimidyl)-6-methyl-1,2,4,5-tetrazine 2 and bis(2-pyrimidyl)-1,2,4,5-tetrazine=bmtz as ligands, the complexes 3=[Ru(acac)(2)(1)], 4={[Ru(acac)(2)](2)(1)], 5={[Ru(acac)(2)](2)(bmtz)], and 6={[Ru(acac)(2)](2)(2)] were prepared and identified by structure analysis of crystallized material. The one-electron oxidized form 6(PF6) was also studied structurally, suggesting a Class II mixed-valent situation. The neutral dinuclear systems exhibit two reversible oxidation processes with comproportionation constants 10(9.2)<K-c<10(14.1) and one reduction which were analyzed UV/vis/NIR and EPR spectroscopically. Oxidation produces largely metal-based mixed-valent cations with very weak intervalence absorptions in the near IR whereas the electron uptake occurs at the tetrazine acceptor.

[[CpNi(dRpf)](+) (dRpf=1,1'-bis(di-R-phosphino)ferrocene, R=phenyl (dppf) [1](+), iso-propyl (dippf) [2](+), and cyclohexyl (dcpf) [3](+)), CpNi(dRpf)](+)(dRpf=1,1'-bis(di-R-phosphino)ferrocene, R=phenyl (dppf) [1](+), iso-propyl (dippf) [2](+), and cyclohexyl (dcpf) [3](+)), showed two reversible electrochemical processes, one cathodic and one anodic in the cyclic voltammogram. CpNiI was generated in the cathodic processes for all three complexes, while spectroscopic data and dft analysis for the anodic process suggested contributions from the ferrocene, there was some degree of delocalization onto the Ni ion.

The electrochemistry and spectroelectrochemistry (SEC) of the three [ReCl(CO)(3)(N N)], N N=3-(pyrid-2-yl)-1,2,4,5-tetrazine [1], 3-(pyrid-2-yl)-4-ferrocenyl-4,5-dihydropyridazine [1H(2)Fc], and 3-(pyrid-2-yl)-4-ferrocenyl-pyridazine [1Fc], are reported. The ligand's conjugation affects the reduction potentials as well as intramolecular charge transfers observed in the UV-vis-NIR spectrum. The spectroscopic observations were further supported by DFT calculations.

AbstractMolekülchemie: Calcium bändigt Distickstoff, niedervalente Verbindungen in ungewöhnlichen Oxidationsstufen bestimmen das Geschehen, Koordinationsgeometrien kratzen an bisher für unmöglich Gehaltenem. Nebengruppen‐ und Koordinationschemie: aktivierter Distickstoff und die erste Reihe der Übergangsmetalle als Photosensibilisatoren.