A Dimeric Chromium(II) Pincer as an Electron Shuttle for N=N Bond Scission

Reduction of the bis-pyrazolyl pyridine complex [CrL]₂ with 4 KC₈, followed by addition of one azobenzene (overall mole ratio 1:4:1), PhNNPh, transfers reducing equivalents to three azobenzenes, to form [K₃Cr(PhNNPh)₃]. This has three κ² PhNNPh²⁻ ligands and K⁺ bound to nitrogen atoms of azobenzene. When the stoichiometry is modified to 1:4:3, the product is changed to [K₂CrL(PhNNPh)₂], which has C₂ symmetry except for the intimate ion pairing of two K⁺ ions to reduced azobenzene nitrogen atoms, and to pyrazolate and phenyl rings. The origin of the observed delivery of reducing equivalents to several, not to a single N=N bond, is traced to the resistance of the one-electron-reduced substrate to receiving a second electron, and is thus a general phenomenon. [CrL]₂ alone is shown to be a two-electron reductant towards benzo[c]cinnoline (BCC) resulting in a product of formula [Cr₂L₂(BCC)], in which the reducing equivalents originate purely from Cr^II. An analogous study of the reaction of [CrL]₂ with azobenzene yields [Cr₂L₂(PhNNPh)(THF)], an adduct in which one THF has displaced one of four hydrazide nitrogen/Cr bonds. Together these illustrate different modes for the Cr₂L₂ unit to bind and reduce the N=N bond. Collectively, these results show that two divalent Cr, without added K⁰, have the ability to reduce the N=N bond. Further KC₈ reduction of preformed Cr₂L₂(RNNR) inevitably gives products in which K⁺ stabilizes the charge in the increasingly electron-rich nitrogen atoms, in a phenomenon which mimics proton coupled electron transfer: K⁺ performs the role of H⁺. A least-squares fit of the two singly reduced DFT structures shows that the only major change is a re-orientation of one of the two phenyl rings in order to avoid repulsion with potassium but to still allow interaction of that phenyl π system with K⁺. This shows both the impact of K⁺, being modest to nitrogen/chromium interactions, but nevertheless accommodating some π donation of phenyl to potassium. Finally, delivering increasing equivalents of KC₈ leads to complete cleavage of the N=N bond, and both N bind to three Cr^II. The varied impacts of the K⁺ electrophile on NN multiple bond reduction is discussed.     

Saccharified Uranyl Ions: Self-Assembly of UO22+ into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases

The reaction of UO₂(OAc)₂ ⋅ 2H₂O with the biologically inspired ligand 2-salicylidene glucosamine (H₂ L¹ ) results in the formation of the anionic trinuclear uranyl complex [(UO₂)₃(μ₃-O)( L¹ )₃]²⁻ ( 1 ²⁻), which was isolated in good yield as its Cs-salt, [Cs]₂ 1 . Recrystallization of [Cs]₂ 1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)]₂ 1 , which was also obtained for the alkali metal ions Rb⁺ and K⁺ (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H₂ L² ) in a similar procedure with Cs⁺ gave the corresponding complex [Cs(18-crown-6)]₂[(UO₂)₃(μ₃-O)( L² )₃ ([Cs(18-crown-6)]₂ 2 ). From X-ray investigations, the [(UO₂)₃O( Lⁿ )₃]²⁻ anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H₂ L¹ and H₂ L² towards UO₂²⁺ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 1 ²⁻ and 2 ²⁻dianions in solution.     

Komplexe des Chroms mit 1,5,9-Triazacyclododecan: Darstellung,Magnetismus und Kristallstruktur von Tri-μ-hydroxo-bis[(1,5,9-triazacyclododecan)chrom(III)] tribromid Dihydrat; Kinetik und Mechanismus der Brückenspaltung mit Hydroxidionen

Complexes of Chromium Containing 1,5,9-Triazacyclododecane: Synthesis, Magnetism, and Crystal Structure of Tri-μ-hydroxo-bis[(1,5,9-triazacyclododecane) chromium (III)] tribromide · Dihydrate; Kinetic and Mechanism of its Bridge-cleavage with Hydroxide The oxidative decarbonylation of LCr(CO)₃ (L = 1,5,9-triazacyclododecane) with bromine yields green LCrBr₃. Base hydrolysis affords red [LCr(μ-OH)₃CrL]³⁺, whereas in the presence of acetate ions [L₂Cr₂(μ-OH)₂(CH₃CO₂)]³⁺ is formed. [LCr(μ-OH)₃CrL]Br₃· 2 H₂O crystallizes in the orthorhombic space group P2₁2₁2₁ with 8 formula units per unit cell. Two Cr^III centers are connected via three OH^? bridges; the spins of d³-electronic configuration are coupled intramolecularly, antiferromagnetically (2J = ?96 cm^?1). With excess OH^? but not with protons the tri-μ-hydroxo species is cleaved to give [L₂Cr₂(OH)₂(μ-OH)₂]²⁺. The kinetics of this reaction have been measured using the stopped flow technique. The mechanism is discussed.     

Gallium “Shears” for C=N and C=O Bonds of Isocyanates

Digallane [L¹Ga−GaL¹] ( 1 , L¹=dpp-bian=1,2-[(2,6-iPr₂C₆H₃)NC]₂C₁₂H₆) reacts with RN=C=O (R=Ph or Tos) by [2+4] cycloaddition of the isocyanate C=N bonds across both of its C=C−N−Ga fragments to afford [L¹(O=C−NR)Ga−Ga(RN−C=O)L¹] (R=Ph, 3 ; R=Tos, 4 ). The reactions with both isocyanates result in new C−C and N−Ga single bonds. In the case of allyl isocyanate, the [2+4] cycloaddition across one C=C−N−Ga fragment of 1 is accompanied by insertion of a second allyl isocyanate molecule into the Ga−N bond of the same fragment to afford compound [L¹Ga−Ga(AllN− C=O)₂L¹] ( 5 ) (All=allyl). In the presence of Na metal, the related digallane [L²Ga−GaL²] ( 2 ; L²=dpp-dad=[(2,6-iPr₂C₆H₃)NC(CH₃)]₂) is converted into the gallium(I) carbene analogue [L²Ga:]⁻ ( 2 A ), which undergoes a variety of reactions with isocyanate substrates. These include the cycloaddition of ethyl isocyanate to 2 A affording [Na₂(THF)₅]{L²Ga[EtN−C(O)]₂GaL²} ( 6 ), cleavage of the N=C bond with release of 1 equiv. of CO to give [Na(THF)₂]₂[L²Ga(p-MeC₆H₄)(N−C(O))₂−N(p-MeC₆H₄)]₂ ( 7 ), cleavage of the C=O bond to yield the di-O-bridged digallium compound [Na(THF)₃]₂[L²Ga-(μ-O)₂-GaL²] ( 8 ), and generation of the further addition product [Na₂(THF)₅][L²Ga(CyNCO₂)]₂ ( 9 ). Complexes 3 – 9 have been characterized by NMR (¹H, ¹³C), IR spectroscopy, elemental analysis, and X-ray diffraction analysis. Their electronic structures have been examined by DFT calculations.     

A bis-Pyrazolate Pincer on Reduced Cr Deoxygenates CO2: Selective Capture of the Derived Oxide by CrII

Reduction of the bis-(pyrazolyl)pyridine complex [LCr]₂ with stoichiometric KC₈ in THF produces a species that is reactive with CO₂ to produce an aggregate composed of paramagnetic K₂L₂Cr₂(CO₃) linked by KCl into a product of formula [K₂L₂Cr₂(CO₃)]₄⋅2KCl. X-ray diffraction reveals a pincer hydrocarbon exterior and an inorganic interior composed of K⁺, Cl⁻ and carbonate oxygens. Every Cr is five coordinate and square pyramidal, with the axial N donor weakly bonded to Cr due to the Jahn–Teller effect of a high spin d⁴ configuration. Reaction with ¹³CO₂ confirms that carbonate here is derived from CO₂, that oxide is derived from CO₂, and that CO is indeed released, since it is not a competent ligand to Cr^II. Guiding principles for selectivity in CO₂ reduction are deduced from the diverse successful molecular constructs to date.     

Structural and Oxidation State Alternatives in Platinum and Palladium Complexes of a Redox-Active Amidinato Ligand

Reaction of [Pt(DMSO)₂Cl₂] or [Pd(MeCN)₂Cl₂] with the electron-rich LH=N,N’-bis(4-dimethylaminophenyl)ethanimidamide yielded mononuclear [PtL₂] ( 1 ) but dinuclear [Pd₂L₄] ( 2 ), a paddle-wheel complex. The neutral compounds were characterized through experiments (crystal structures, electrochemistry, UV-vis-NIR spectroscopy, magnetic resonance) and TD-DFT calculations as metal(II) species with noninnocent ligands L⁻. The reversibly accessible cations [PtL₂]⁺ and [Pd₂L₄]⁺ were also studied, the latter as [Pd₂L₄][B{3,5-(CF₃)₂C₆H₃}₄] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [Pt^II(L⁻)₂] or [Pt^.(L )₂], [Pt^II(L^0.5−)₂]⁺ or [Pt^III(L⁻)₂]⁺, [(Pd^II)₂(μ-L⁻)₄] or [(Pd^1.5)₂(μ-L^0.75−)₄], and [(Pd^2.5)₂(μ-L⁻)₄]⁺ or [(Pd^II)₂(μ-L^0.75−)₄]⁺. In each case, the first alternative was shown to be most appropriate. Remarkable results include the preference of platinum for mononuclear planar [PtL₂] with an N-Pt-N bite angle of 62.8(2)° in contrast to [Pd₂L₄], and the dimetal (Pd₂⁴⁺→Pd₂⁵⁺) instead of ligand (L⁻→L ) oxidation of the dinuclear palladium compound.     

Synthesis and crystal structure of [Et<Subscript>4</Subscript>N] [Cr(PzTp)Cl<Subscript>3</Subscript>] [PzTp<Superscript>−</Superscript> = Tetra(pyrazolyl) Borate]

Treatment of CrCl₃(THF)₃ with KPzTp in THF affords of the compound K[Cr(PzTp)Cl₃], and the K⁺ in this complex can be replaced by Et₄N⁺ in CH₂Cl₂. Well-defined green crystals of [Et₄N]r(PzTp)Cl₃] (I) suitable for X-ray diffraction are obtained at −₂0°C. In the anion the metal center shows a distorted octahedral geometry with the tetra(pyrazolyl) borate bonded as three N-donor tripod ligands and three chloride atoms completing the coordination sphere.     

Preparation and Characterization of Dinuclear Chromium(III) Complexes of a Hexadentate Tetraaza‐Dithiophenolate Ligand

The ability of the tetraaza‐dithiophenolate ligand H₂L² (H₂L² = N,N′‐Bis‐[2‐thio‐3‐aminomethyl‐5‐tert‐butyl‐benzyl]propane‐1,3‐diamine) to form dinuclear chromium(III) complexes has been examined. Reaction of Cr^IICl₂ with H₂L² in methanol in the presence of base followed by air‐oxidation afforded cis,cis‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1a ) and trans,trans‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1b ). Both compounds contain a confacial bioctahedral N₂ClCr^III(μ‐SR)₂(μ‐OH)Cr^IIIClN₂ core. The isomers differ in the mutual orientation of the coligands and the conformation of the supporting ligand. In 1a both Cl^? ligands are cis to the bridging OH function. In 1b they are in trans‐positions. Reaction of the hydroxo‐bridged complexes with HCl yielded the chloro‐bridged cations cis,cis‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]⁺ ( 2a ) and trans,trans‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]Cl ( 2b ), respectively. These bridge substitutions proceed with retention of the structures of the parent complexes 1a and 1b .     

A Benzodiphosphaborolediide

The first example of a diphosphaborolediide, the benzo-fused [C₆H₄P₂BPh]²⁻ ( 1²⁻ ), is prepared from ortho-bis(phosphino)benzene (C₆H₄{PH₂}) and dichlorophenylborane, via a sequential lithiation approach. The dilithio-salt can be obtained as an oligomeric THF solvate or discrete TMEDA adduct, both of which are fully characterized, including by X-ray diffraction. Alongside NICS calculations, data strongly suggest some aromaticity within 1²⁻ , which is further supported by preliminary coordination studies that demonstrate η⁵-coordination to a zerovalent molybdenum center, as observed crystallographically for the oligomeric [{Mo(CO)₃(η⁵- 1 )}{μ-η¹-Mo(CO)₃(TMEDA)}₂] ⋅ [μ-Li(THF)][μ-Li(TMEDA)].     

Structural Variety of Niobium(V) Polyoxo Clusters Obtained from the Reaction with Aromatic Monocarboxylic Acids: Isolation of {Nb2O}, {Nb4O4} and {Nb8O12} Cores

The reactivity of aryl monocarboxylic acids (benzoic, 1- or 2-naphtoic, 4’-methylbiphenyl-4-carboxylic, and anthracene-9-carboxylic acids) as complexing agents for the ethoxide niobium(V) (Nb(OEt)₅ precursor has been investigated. A total of eight coordination complexes were isolated with distinct niobium(V) nuclearities as well as carboxylate complexation states. The use of benzoic acid gives a tetranuclear core Nb₄(μ₂-O)₄(L)₄(OEt)₈] (L=benzoate ( 1 )) with four Nb−(μ₂-O)−Nb linkages in a square plane configuration. A similar tetramer, 7 , was obtained with 2-naphtoic acid by using a 55 % humid atmosphere synthetic route. Two types of dinuclear brick were identified with one central Nb−(μ₂-O)−Nb linkage; they differ in their complexation state, with one bridging carboxylate ([Nb₂(μ₂-O)(μ₂-OEt)(L)(OEt)₆], with L=1-naphtoate ( 3 ) or anthracene-9-carboxylate ( 5 )) or two bridging carboxylate groups ([Nb₂(μ₂-O)(L)₂(OEt)₆], with L=4’-methylbiphenyl-4-carboxylic ( 4 ) or anthracene-9-carboxylate ( 6 )). An octanuclear moiety [Nb₈(μ₂-O)₁₂(L)₈(η₁-L)_4−x(OEt)_4+x] (with L=2-naphtoate, x=0 or 2; 8 ) was obtained by using a solvothermal route in acetonitrile; it has a cubic configuration with niobium centers at each node, linked by 12 μ₂-O groups. The formation of the niobium oxo clusters was characterized by infrared and liquid ¹H NMR spectroscopy in order to analyze the esterification reaction, which induces the release of water molecules that further react through oxolation with niobium atoms, in different {Nb₂O}, {Nb₄O₄} and {Nb₈O₁₂} nuclearities.     

CS2 Reductive Coupling to Acetylenedithiolate by a Dinuclear Ytterbium(II) Complex

The activation of CS₂ is of interest in a broad range of fields and, more particularly, in the context of creating new C−C bonds. The reaction of the dinuclear ytterbium(II) complex [Yb₂L₄], 1 , [L=(OtBu)₃SiO⁻] with carbon disulfide led to the isolation of unprecedented reduction products. In particular, the crystallographic characterization of complex [Yb₂L₄(μ-C₂S₂)], 2 , provided the first example of an acetylenedithiolate ligand formed from metal reduction of CS₂. Computational studies indicated that this unprecedented reactivity can be ascribed to the unusual binding mode of CS₂²⁻ in the isolated “key intermediate” [Yb₂L₄(μ-CS₂)], 3 , which results from the dinuclear nature of 1 .     

Trinuclear Cyanido-Bridged [Cr2Fe] Complexes: To Be or not to Be a Single-Molecule Magnet,a Matter of Straightness

Trinuclear systems of formula [{Cr(L^N3O2Ph)(CN)₂}₂M(H₂L^N3O2R)] (M=Mn^II and Fe^II, L^N3O2R stands for pentadentate ligands) were prepared in order to assess the influence of the bending of the apical M−N≡C linkages on the magnetic anisotropy of the Fe^II derivatives and in turn on their Single-Molecule Magnet (SMM) behaviors. The cyanido-bridged [Cr₂M] derivatives were obtained by assembling trans-dicyanido Cr^III complex [Cr(L^N3O2Ph)(CN)₂]⁻ and divalent pentagonal bipyramid complexes [M^II(H₂L^N3O2R)]²⁺ with various R substituents (R=NH₂, cyclohexyl, S,S-mandelic) imparting different steric demand to the central moiety of the complexes. A comparative examination of the structural and magnetic properties showed an obvious effect of the deviation from straightness of the M−N≡C alignment on the slow relaxation of the magnetization exhibited by the [Cr₂Fe] complexes. Theoretical calculations have highlighted important effects of the bending of the apical C−N−Fe linkages on both the magnetic anisotropy of the Fe^II center and the exchange interactions with the Cr^III units.     

New d heterometallic coordination polymers based on compartmental Schiff-base ligands. Synthesis, structure and luminescence

The self-assembly processes between binuclear [Zn₂Lⁿ]²⁺ complex cations and complex anions, [M(CN)₂]⁻ [M(I) = Ag(I), Au(I)], generate new one-dimensional (1-D) coordination polymers: ¹_∞[{L¹Zn₂(μ₃-OH)}₂(H₂O){μ-[Ag(CN)₂]}](ClO₄)₃ THF 0.5MeOH 1, ¹_∞[{L¹Zn₂(μ₃-OH)}₂(H₂O){μ-[Au(CN)₂]}](ClO₄)₃ THF H₂O 2, ¹_∞[{L²Zn₂(μ-OH)}{μ-[Ag(CN)₂]}][Ag(CN)₂] H₂O 3 (H₂Lⁿ are bicompartmental Schiff-base ligands resulting from condensation reactions between 2,6-diformyl-p-cresol with 2-aminomethyl-pyridine, and 2-aminoethyl-pyridine, respectively). The luminescence properties of the new heterometallic complexes have been investigated.     

A charge-separation-type ionic solid composed of hexanuclear complexes with a macrocyclic tetragold(I) metalloligand

The reaction of Na[Co^III(d -ebp)] (d -H₄ebp = N,N′-ethylenebis[d -penicillamine]) with [(Au^ICl)₂(dppe)] (dppe = 1,2-bis[diphenylphosphino]ethane) gave a cationic Au^I₄Co^III₂ hexanuclear complex, [Co^III₂(L^Au4)]²⁺ ([ 1 ]²⁺), where [L^Au4]⁴⁻ is a cyclic tetragold(I) metalloligand with a 32-membered ring, [Au^I₄(dppe)₂(d -ebp)₂]⁴⁻. Complex [ 1 ]²⁺ crystallized with NO₃⁻ to produce a charge-separation (CS)-type ionic solid of [ 1 ](NO₃)₂. In [ 1 ](NO₃)₂, the complex cations are assembled to form cationic supramolecular hexamers of {[ 1 ]²⁺}₆, which are closely packed in a face-centered cubic (fcc) lattice structure. The nitrate anions of [ 1 ](NO₃)₂ were accommodated in hydrophilic and hydrophobic tetrahedral interstices of the fcc structure to form tetrameric and hexameric nitrate clusters of {NO₃⁻}₄ and {NO₃⁻}₆, respectively. An analogous CS-type ionic solid formulated as [Ni^IICo^III(L^Au4)](NO₃) ([ 2 ](NO₃)) was obtained when a 1:1 mixture of Na[Co^III(d -ebp)] and [Ni^II(d -H₂ebp)] was reacted with [(Au^ICl)₂(dppe)], accompanied by the conversion of the diamagnetic, square-planar [Ni^II(d -H₂ebp)] to the paramagnetic, octahedral [Ni^II(d -ebp)]²⁻. While the overall fcc structure in [ 2 ](NO₃) was similar to that of [ 1 ](NO₃)₂, none of the nitrate anions were accommodated in any hydrophobic tetrahedral interstice, reflecting the difference in the complex charges between [ 1 ]²⁺ and [ 2 ]⁺.     

Solvent-Polarity-Induced Assembly of Calixarene-Capped Titanium-Oxo Clusters with Catalytic Activity in the Oxygenation of Sulfides

Four calixarene-coordinated titanium-oxo clusters, namely, [Ti₄(C6A)₂(μ₃-O)₂(DMF)₂] ( CIAC-258 ), [Ti₈(H₃C6A)₄(C₆H₅PO₃)₈(μ₂-O)₄]⁴⁻ ( CIAC-259 ), [Ti₆(TC4A)₃(μ₂-O)₃ (OiPr)₆] ( CIAC-260 ) and [Ti₆(H₂TC4A)₄(C₆H₅PO₃)₄(μ₂-O)₅(DMF)₂]²⁻ ( CIAC-261 ) were obtained, which feature sandwich-like, windmill-like, triangular, and tetrahedral structures, respectively. The polarity of the solvent determines the involvement of the auxiliary ligand phenylphosphonic acid in the formation of the products and their structures. Compounds CIAC-258 and CIAC-261 exhibit good catalytic performance in the selective oxidation of sulfides to sulfoxides with H₂O₂ as the oxidant, which can be attributed to the Ti active sites coordinated by exchangeable DMF molecules. Moreover, density functional theory (DFT) calculations revealed that the Ti-hydroperoxo species formed by the interaction of the Ti active site in CIAC-258 or CIAC-261 and H₂O₂ is the most likely catalytic active component during the catalytic sulfoxidation process.     

A Heterobimetallic Superoxide Complex formed through O2 Activation between Chromium(II) and a Lithium Cation

The reaction of 1,1,3,3‐tetraphenyl‐1,3‐disiloxandiol (LH₂) with n‐butyllithium and CrCl₂ results in a mononuclear chromium(II) complex ( 1 ) that further reacts with O₂ at low temperatures to yield a mononuclear chromium(III) superoxide complex [L₂CrO₂(THF)][Li₂(THF)₃] ( 2 ). The crystal structure revealed that the chromium superoxido entity is stabilized by the coordination to an adjacent lithium cation. Complex 2 thus contains an unprecedented heterobimetallic [Cr^III(μ‐O₂)Li⁺] core; beyond this it is the first chromium superoxide for which a temperature‐dependent magnetic characterization could be achieved, and the first structurally characterized representative with chromium in an exclusive O‐donor environment.     

Rare-Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox-Switchable Single-Molecule Magnets

Using the redox-active tetrathiafulvalene tetrabenzoate (TTFTB⁴⁻) as the linker, a series of stable and porous rare-earth metal–organic frameworks (RE-MOFs), [RE₉(μ₃-OH)₁₃(μ₃-O)(H₂O)₉(TTFTB)₃] ( 1-RE , where RE=Y, Sm, Gd, Tb, Dy, Ho, and Er) were constructed. The RE₉(μ₃-OH)₁₃(μ₃-O) (H₂O)₉](CO₂)₁₂ clusters within 1-RE act as segregated single-molecule magnets (SMMs) displaying slow relaxation. Interestingly, upon oxidation by I₂, the S=0 TTFTB⁴⁻ linkers of 1-RE were converted into S= TTFTB^.3− radical linkers which introduced exchange-coupling between SMMs and modulated the relaxation. Furthermore, the SMM property can be restored by reduction in N,N-dimethylformamide. These results highlight the advantage of MOFs in the construction of redox-switchable SMMs.     

A Chromium(III)‐Superoxo Complex as a Three‐Electron Oxidant with a Large Tunneling Effect in Multi‐Electron Oxidation of NADH Analogues

Metal‐superoxo species are involved in a variety of enzymatic oxidation reactions, and multi‐electron oxidation of substrates is frequently observed in those enzymatic reactions. A Cr^III‐superoxo complex, [Cr^III(O₂)(TMC)(Cl)]⁺ ( 1 ; TMC=1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane), is described that acts as a novel three‐electron oxidant in the oxidation of dihydronicotinamide adenine dinucleotide (NADH) analogues. In the reactions of 1 with NADH analogues, a Cr^IV‐oxo complex, [Cr^IV(O)(TMC)(Cl)]⁺ ( 2 ), is formed by a heterolytic O−O bond cleavage of a putative Cr^II‐hydroperoxo complex, [Cr^II(OOH)(TMC)(Cl)], which is generated by hydride transfer from NADH analogues to 1 . The comparison of the reactivity of NADH analogues with 1 and p ‐chloranil (Cl₄Q) indicates that oxidation of NADH analogues by 1 proceeds by proton‐coupled electron transfer with a very large tunneling effect (for example, with a kinetic isotope effect of 470 at 233 K), followed by rapid electron transfer.     

Chemical design of heterometallic carboxylate structures with Fe3+ and Ag+ ions as a rational synthetic approach

Solid phase thermolysis of pivalate complex [Fe₃O(Piv)₆(HPiv)₃]Piv generates the [Fe₃O(Piv)₆]⁺ complex cation due to a deficiency of ligands in the coordination sphere of the metal ions. Crystallization of [Fe₃O(Piv)₆]⁺ from THF–EtOH leads to the heteroleptic complex [Fe₃O(Piv)₆(THF)(EtOH)(OH)] · 0.5 THF · 0.5 H₂O in 69% yield, while the reaction of [Fe₃O(Piv)₆]⁺ with AgNO₃ in toluene results in the complex [Fe₄Ag₄O₂(Piv)₁₂] · 2 PhMe with a rare combination of Fe^III and Ag^I atoms. Crystal structures of the two new complexes have been established.     

Synthesis and Characterization of Two Uranyl-Aryl “Ate” Complexes

Reaction of [UO₂Cl₂(THF)₃] with 3 equivalents of LiC₆Cl₅ in Et₂O resulted in the formation of first uranyl aryl complex [Li(Et₂O)₂(THF)][UO₂(C₆Cl₅)₃] ([Li][ 1 ]) in good yields. Subsequent dissolution of [Li][ 1 ] in THF resulted in conversion into [Li(THF)₄][UO₂(C₆Cl₅)₃(THF)] ([Li][ 2 ]), also in good yields. DFT calculations reveal that the U−C bonds in [Li][ 1 ] and [Li][ 2 ] exhibit appreciable covalency. Additionally, the ¹³C NMR chemical shifts for their C_ipso environments are strongly affected by spin-orbit coupling—a consequence of 5f orbital participation in the U−C bonds.