Heterodinuclear Complexes Research Articles

The Steric Effect in Preparations of Vanadium(II)/(III) Dinitrogen Complexes of Triamidoamine Ligands Bearing Bulky Substituents.

The reactions of newly designed lithiated triamidoamines Li3LR (R = iPr, Pen, and Cy2) with VCl3(THF)3 under N2 yielded dinitrogen–divanadium complexes with a μ-N2 between vanadium atoms [{V(LR)}2(μ-N2)] (R = iPr (1) and Pen (2)) for the former two, while not dinitrogen–divanadium complexes but a mononuclear vanadium complex with a vacant site, [V(LCy2)] (R = Cy2 (3)), were obtained for the third ligand. The V–NN2 and N–N distances were 1.7655(18) and 1.219(4) Å for 1 and 1.7935(14) and 1.226(3) Å for 2, respectively. The ν(14N–14N) stretching vibrations of 1 and 2, as measured using resonance Raman spectroscopy, were detected at 1436 and 1412 cm–1, respectively. Complex 3 reacted with potassium metal in the presence of 18-crown-6-ether under N2 to give a hetero-dinuclear vanadium complex with μ-N2 between vanadium and potassium, [VK(LCy2)(μ-N2)(18-crown-6)] (4). The N–N distance and ν(14N–14N) stretching for 4 were 1.152(3) Å and 1818 cm−1, respectively, suggesting that 4 is more activated than complexes 1 and 2. The complexes 1, 2, 3, and 4 reacted with HOTf and K[C10H8] to give NH3 and N2H4. The yields of NH3 and N2H4 (per V atom) were 47 and 11% for 1, 38 and 16% for 2, 77 and 7% for 3, and 80 and 5% for 4, respectively, and 3 and 4, which have a ligand LCy2, showed higher reactivity than 1 and 2.

Quantum correlations in a mixed spin-(1/2,1) Heisenberg dimer

In this article, we consider the heterodinuclear complex [Ni(dpt)(H2O)Cu(pba)] ⋅ 2H2O [pba =1,3-propylenebis(oxamato) and dpt = bis-(3-aminopropyl)amine] realized through the theoretical model of mixed spin-(1/2,1) coupled via Heisenberg interaction. We study the behaviors of thermal quantum correlations of the above material via Measurement-Induced Nonlocality (MIN) based on Hilbert–Schmidt norm and fidelity. We observe that the quantum correlation measures increase with the magnetic field in an unconventional way. The role of system parameters is also brought out at thermal equilibrium. The highlight of the results is that we are able to show the existence of room temperature quantum correlation using fidelity based MIN whereas the entanglement ceases to exist at 141K.

Pyrimidoquinazolinophenanthroline Opens Next Chapter in Design of Bridging Ligands for Artificial Photosynthesis.

The synthesis and detailed characterization of a new Ru polypyridine complex containing a heteroditopic bridging ligand with previously unexplored metal‐metal distances is presented. Due to the twisted geometry of the novel ligand, the resultant division of the ligand in two distinct subunits leads to steady state as well as excited state properties of the corresponding mononuclear Ru(II) polypyridine complex resembling those of prototype [Ru(bpy)3]2+ (bpy=2,2'‐bipyridine). The localization of the initially optically excited and the nature of the long‐lived excited states on the Ru‐facing ligand spheres is evaluated by resonance Raman and fs‐TA spectroscopy, respectively, and supported by DFT and TDDFT calculations. Coordination of a second metal (Zn or Rh) to the available bis‐pyrimidyl‐like coordination sphere strongly influences the frontier orbitals, apparent by, for example, luminescence quenching. Thus, the new bridging ligand motif offers electronic properties, which can be adjusted by the nature of the second metal center. Using the heterodinuclear Ru−Rh complex, visible light‐driven reduction of NAD+ to NADH was achieved, highlighting the potential of this system for photocatalytic applications.

Cyclometalated Rhodium and Iridium Complexes Containing Masked Catecholates: Synthesis, Structure, Electrochemistry, and Luminescence Properties.

Two neutral cyclometalated rhodium and iridium coordination assemblies [(F2ppy)2M(η-Cat)], M = Rh, (2) and M = Ir, (3) (F2ppy: 2,4-difluorophenylpyridine), displaying a masked catecholate (η-Cat = η-O∧O) are described. The catecholate ligand is π-bonded to an organometallic Cp*Ru(II) moiety. The latter brings stability to the whole system in solution and suppresses the formation of the related paramagnetic semiquinone complex. The determination of the molecular structure of the iridium complex [(F2ppy)2Ir(η-Cat)] (3) corroborates the formation of the target compound and reveals the generation of a rare two-dimensional (2D) honeycomb supramolecular architecture in the solid state, in which the Δ-enantiomer self-assembles with the Λ-enantiomer through encoded π-π interactions among individual units. The electrochemistry of complexes 2 and 3 was investigated and showed that reduction occurs at very negative potentials (∼-2.2 V versus saturated calomel electrode (SCE)), while oxidation of the cyclometalated Rh and Ir centers occurs at 0.8 and 0.86 V. In contrast to complexes with 1,2-dioxolene chelates, which are nonemissive, the heterodinuclear diamagnetic complexes 2 and 3 were found to be emissive at room temperature both in solution and in the solid state. Moreover, at 77 K in a solid state, both compounds display opposite emission behavior, for instance, complex 3 displays a blue-shifted emission, while rhodium compound 2 exhibits red-shifted emission to lower energy.

Rigidified Derivative of the Non-macrocyclic Ligand H4OCTAPA for Stable Lanthanide(III) Complexation.

The stability constants of lanthanide complexes with the potentially octadentate ligand CHXOCTAPA4–, which contains a rigid 1,2-diaminocyclohexane scaffold functionalized with two acetate and two picolinate pendant arms, reveal the formation of stable complexes [log KLaL = 17.82(1) and log KYbL = 19.65(1)]. Luminescence studies on the Eu3+ and Tb3+ analogues evidenced rather high emission quantum yields of 3.4 and 11%, respectively. The emission lifetimes recorded in H2O and D2O solutions indicate the presence of a water molecule coordinated to the metal ion. 1H nuclear magnetic relaxation dispersion profiles and 17O NMR chemical shift and relaxation measurements point to a rather low water exchange rate of the coordinated water molecule (kex298 = 1.58 × 106 s–1) and relatively high relaxivities of 5.6 and 4.5 mM–1 s–1 at 20 MHz and 25 and 37 °C, respectively. Density functional theory calculations and analysis of the paramagnetic shifts induced by Yb3+ indicate that the complexes adopt an unprecedented cis geometry with the two picolinate groups situated on the same side of the coordination sphere. Dissociation kinetics experiments were conducted by investigating the exchange reactions of LuL occurring with Cu2+. The results confirmed the beneficial effect of the rigid cyclohexyl group on the inertness of the Lu3+ complex. Complex dissociation occurs following proton- and metal-assisted pathways. The latter is relatively efficient at neutral pH, thanks to the formation of a heterodinuclear hydroxo complex.

Heterodinuclear Mg(II)M(II) (M=Cr, Mn, Fe, Co, Ni, Cu and Zn) Complexes for the Ring Opening Copolymerization of Carbon Dioxide/Epoxide and Anhydride/Epoxide.

The catalysed ring opening copolymerizations (ROCOP) of carbon dioxide/epoxide or anhydride/epoxide are controlled polymerizations that access useful polycarbonates and polyesters. Here, a systematic investigation of a series of heterodinuclear Mg(II)M(II) complexes reveals which metal combinations are most effective. The complexes combine different first row transition metals (M(II)) from Cr(II) to Zn(II), with Mg(II); all complexes are coordinated by the same macrocyclic ancillary ligand and by two acetate co‐ligands. The complex syntheses and characterization data, as well as the polymerization data, for both carbon dioxide/cyclohexene oxide (CHO) and endo‐norbornene anhydride (NA)/cyclohexene oxide, are reported. The fastest catalyst for both polymerizations is Mg(II)Co(II) which shows propagation rate constants (k p) of 34.7 mM−1 s−1 (CO2) and 75.3 mM−1 s−1 (NA) (100 °C). The Mg(II)Fe(II) catalyst also shows excellent performances with equivalent rates for CO2/CHO ROCOP (k p=34.7 mM−1 s−1) and may be preferable in terms of metallic abundance, low cost and low toxicity. Polymerization kinetics analyses reveal that the two lead catalysts show overall second order rate laws, with zeroth order dependencies in CO2 or anhydride concentrations and first order dependencies in both catalyst and epoxide concentrations. Compared to the homodinuclear Mg(II)Mg(II) complex, nearly all the transition metal heterodinuclear complexes show synergic rate enhancements whilst maintaining high selectivity and polymerization control. These findings are relevant to the future design and optimization of copolymerization catalysts and should stimulate broader investigations of synergic heterodinuclear main group/transition metal catalysts.

Synthesis and comparison study of electrochemiluminescence from mononuclear and corresponding heterodinuclear Ir-Ru complexes via an amide bond as a bridge.

A mononuclear iridium-based complex with a primary amine group (named Ir-NH2), a mononuclear ruthenium-based complex with a butanoic acid group (named Ru-COOH) and the corresponding heterodinuclear complex containing an iridium and ruthenium center via an amide bond bridge (named Ir-Ru) were designed and successfully synthesized in this study. The photophysical and electrochemical properties and ECL performances of these three metal complexes under various experimental conditions were well characterized. For the first time, the insights from this comprehensive comparison study indicate that the two metal-based subunits with comparable luminescent properties are significant in the design of bimetallic-based multicolor luminophores at the molecular level, which helps us to further understand the emission performances of bimetallic complexes and to rationally design more efficient corresponding organometallic luminophores with multicolor emission for wide applications in the future.

A bio-inspired heterodinuclear hydrogenase CoFe complex.

Herein, a new heterobimetallic CoFe complex is reported with the aim of comparing its performance in terms of H2 production within a series of related MFe complexes (M = Ni, Fe). The fully oxidized [(LN2S2)CoII(CO)FeIICp]+ complex (CoIIFeII, LN2S2 2- = 2,2'-(2,2'-bipyridine-6,6'-diyl)bis(1,1'-diphenylethanethiolate), Cp- = cyclopentadienyl anion) can be (electro)chemically reduced to its CoIFeII form, and both complexes have been isolated and fully characterized by means of classic spectroscopic techniques and theoretical calculations. The redox properties of CoIIFeII have been investigated in DMF, revealing that this complex is the easiest to reduce by one-electron among the analogous MFe complexes (M = Ni, Fe, Co). Nevertheless, it displays no electrocatalytic activity for H2 production, contrary to the FeFe and NiFe analogs, which have proven remarkable performance.

Sorting Phenomena and Chirality Transfer in Fluoride-Bridged Macrocyclic Rare Earth Complexes.

The reaction of fluoride anions with mononuclear lanthanide(III) and yttrium(III) hexaaza-macrocyclic complexes results in the formation of dinuclear fluoride-bridged complexes. As indicated by X-ray crystal structures, in these complexes two metal ions bound by the macrocycles are linked by two or three bridging fluoride anions, depending on the type of the macrocycle. In the case of the chiral hexaaza-macrocycle L1 derived from trans-1,2-diaminocyclohexane, the formation of these μ2-fluorido dinuclear complexes is accompanied by enantiomeric self-recognition of macrocyclic units. In contrast, this kind of recognition is not observed in the case of complexes of the chiral macrocycle L2 derived from 1,2-diphenylethylenediamine. The reaction of fluoride with a mixture of mononuclear complexes of L1 and L2, containing two different Ln(III) ions, results in narcissistic sorting of macrocyclic units. Conversely, a similar reaction involving mononuclear complexes of L1 and complexes of achiral macrocycle L3 based on ethylenediamine results in sociable sorting of macrocyclic units and preferable formation of heterodinuclear complexes. In addition, formation of these heterodinuclear complexes is accompanied by chirality transfer from the chiral macrocycle L1 to the achiral macrocycle L3 as indicated by CPL and CD spectra.

Heterodinuclear Cu–Gd (3d-4f) complex with di-compartmental Schiff base ligand in biological activity: Synthesis, crystal structure, catecholase activity and DNA & BSA-binding studies

A dinuclear CuII-GdIII Schiff base complex (a di-compartmental Schiff base ligand derived from o-vanillin) nominated as: 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol) (H2valpn) was synthesized in two steps. To characterize the compounds, single-crystal X-ray crystallography, UV–Vis spectroscopy, IR spectroscopy, and elemental analyses were used. The crystalline sample of the heterodinuclear complex revealed the structure of general formula [(valpn) (H2O) CuII GdIII (NO3)3], with the copper ion located in a square pyramidal section (with an axial aqua ligand) and the gadolinium (III) ion located in the open compartment, in which 10 oxygen atoms from three chelating nitrate ions and a Schiff base ligand surrounded it. To study the applications of the complex, the binding affinity of the complex with FS-DNA was studied by UV–Vis spectroscopy, fluorescence spectroscopy, viscosity measurements, cyclic voltammetry (CV) and circular dichroism (CD). From all of these methods, intercalation was suggested as the main mode of binding. The complex was also checked in interaction with Bovine serum albumin (BSA) by using UV–Vis and fluorescence spectroscopy. Cytotoxicity was tested by MTT assay toward HeLa, LNCaP, and MCF-7 cancer cell lines. Moreover, the docking calculation was performed and these results confirmed the experimental results. The mechanism and kinetics of the catalytic activity of the complex in the oxidation reaction of 3,5-di-tert-butylcatechol, was studied at 298 K.

Synthesis and Cu(I)/Mo(VI) Reactivity of a Bifunctional Heterodinucleating Ligand on a Xanthene Platform.

In an effort to probe the feasibility of a model of Mo-Cu CODH (CODH = carbon monoxide dehydrogenase) lacking a bridging sulfido group, the new heterodinucleating ligand LH2 was designed and its Cu(I)/Mo(VI) reactivity was investigated. LH2 ((E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol) features two different chelating positions bridged by a xanthene linker: bis(pyridyl)amine for Cu(I) and catecholate for Mo(VI). LH2 was synthesized via the initial protection of one of the amine positions, followed by two consecutive alkylations of the second position, deprotection, and condensation to attach the catechol functionality. LH2 was found to exhibit dynamic cooperativity between two reactive sites mediated by H-bonding of the catechol protons. In the free ligand, catechol protons exhibit H-bonding with imine (intramolecular) and with pyridine (intermolecular in the solid state). The reaction of LH2 with [Cu(NCMe)4]+ led to the tetradentate coordination of Cu(I) via all nitrogen donors of the ligand, including the imine. Cu(I) complexes were characterized by multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), X-ray crystallography, and DFT calculations. Cu(I) coordination to the imine disrupted H-bonding and caused rotation away from the catechol arm. The reaction of the Cu(I) complex [Cu(LH2)]+ with a variety of monodentate ligands X (PPh3, Cl-, SCN-, CN-) released the metal from coordination to the imine, thereby restoring imine H-bonding with the catechol proton. The second catechol proton engages in H-bonding with Cu-X (X = Cl, CN, SCN), which can be intermolecular (XRD) or intramolecular (DFT). The reaction of LH2 with molybdate [MoO4]2- led to incorporation of [MoVIO3] at the catecholate position, producing [MoO3(L)]2-. Similarly, the reaction of [Cu(LH2)]+ with [MoO4]2- formed the heterodinuclear complex [CuMoO3(L)]-. Both complexes were characterized by multinuclear NMR, UV-vis, and HRMS. HRMS in both cases confirmed the constitution of the complexes, containing molecular ions with the expected isotopic distribution.

Structural Characterization of Heterodinuclear ZnII-LnIII Complexes (Ln\u2009=\u2009Pr, Nd) with a Ring-Contracted H2valdien-Derived Schiff Base Ligand

Synthesis and structural characterization of two heterodinuclear ZnII-LnIII complexes with the formula [ZnLn(HL)(µ-OAc)(NO3)2(H2O)x(MeOH)1-x]NO3 · n H2O · n MeOH [Ln = Pr (1), Nd (2)] and the crystal and molecular structure of [ZnNd(HL)(µ-OAc)(NO3)2(H2O)] [ZnNd(HL)(OAc)(NO3)2(H2O)](NO3)2 · n H2O · n MeOH (3) are reported. The asymmetrical compartmental ligand (E)-2-(1-(2-((2-hydroxy-3-methoxybenzylidene)amino)-ethyl)imidazolidin-2-yl)-6-methoxyphenol (H2L) is formed from N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2valdien) through intramolecular aminal formation, resulting in a peripheral imidazoline ring. The structures of 1–3 were revealed by X-ray crystallography. The smaller ZnII ion occupies the inner N2O2 compartment of the ligand, whereas the larger and more oxophilic LnIII ions are found in the outer O2O2’ site.Graphic Synthesis and structural characterization of two heterodinuclear ZnII-LnIII complexes (Ln = Pr, Nd) bearing an asymmetrical compartmental ligand formed in situ from N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2valdien) through intramolecular aminal formation are reported.

Front Cover: (p‐(Diphenylarsino)phenyl)diphenylphosphine as a Novel Template for Heterodinuclear Complexes (2/2021)

The Front Cover shows characteristic features of (p-(diphenylarsino)phenyl)diphenylphosphine, in which the phosphorus atom preferentially coordinates to Lewis acids such as borane and metals (Au and Pt). The tilted balances represent about its asymmetric coordination behavior. This kind of molecule can be utilized as a template ligand to precisely arrange various Lewis acids, particularly transition metals. More information can be found in the Full Paper by Hiroaki Imoto, Kensuke Naka et al.

Hydrogen peroxide production from oxygen and formic acid by homogeneous Ir-Ni catalyst.

Hydrogen peroxide was directly produced from oxygen and formic acid, catalysed by a hetero-dinuclear Ir-Ni complex with two adjacent sites, at ambient temperature. Synergistic catalysis derived from the hetero-dinuclear Ir and Ni centres was demonstrated by comparing its activity to those of the component mononuclear Ir and Ni complexes. A reaction intermediate of Ir-hydrido was detected by UV-vis, ESI-TOF-MS, and 1H NMR spectroscopies. It was revealed that the Ir moiety serves as an active species of Ir-hydrido, reacting with oxygen to afford an Ir-hydroperoxide species through O2 insertion, which is the rate-determining step for H2O2 production. Meanwhile, the Ni moiety promotes H2O2 formation by activating solvents as proton sources. We also found that H2O2 production is strongly affected by the solvent dielectric constants (DE); the highest H2O2 concentration was obtained in ethylene glycol with a moderate DE. The catalytic mechanism of H2O2 production by the Ir-Ni complex was discussed, based on kinetic analysis, isotope labelling experiments, and theoretical DFT calculations.

(p‐(Diphenylarsino)phenyl)diphenylphosphine as a Novel Template for Heterodinuclear Complexes

AbstractPhosphorus and arsenic have different coordination ability to Lewis acids, though they belong to 15 group. Utilizing the difference, we designed a novel ligand, (p‐(diphenylarsino)phenyl)diphenylphosphine, in which diphenylphosphine and diphenylarsine units are combined through a p‐phenylene linker, as a template to arrange Lewis acids. The phosphorus atom exhibited superior coordination ability to the arsenic one. NMR studies revealed that BH3, AuCl, and PtCl2 were preferentially coordinated by the phosphorus atom. Sequential addition of these Lewis acids realized precise arrangement on the template ligand.

From antiferromagnetic to ferromagnetic exchange in a family of phenoxido-bridged heterodinuclear Cu(II)-Mn(II) complexes: A magneto-structural theoretical study

Density functional theory with a broken symmetry approach was performed on phenoxido-bridged heterodinuclear complexes [LCuMn(NO3)2], for which magneto-structural correlations were developed. Satisfactory results were obtained at the B3LYP*/TZV level, and the calculated J value of the magnetic coupling constant was − 35.24 cm−1, which is consistent with the experimental result of − 35.80 cm−1. The analysis of spin populations indicated that the paramagnetic centers Cu(II) and Mn(II) exhibit a spin delocalization mechanism. The study of magneto-structural correlations indicated that the magnetic coupling constant J value shows a linear correlation with the bond angle (θ) of Cu–O-Mn; for θ < 97.20°, the magnetic coupling effect between Cu(II) and Mn(II) transformed from an anti-ferromagnetic to a ferromagnetic interaction.

Unconventional strengthening of the bipartite entanglement of a mixed spin-(1/2,1) Heisenberg dimer achieved through Zeeman splitting

The bipartite quantum and thermal entanglement is quantified within pure and mixed states of a mixed spin-(1/2,1) Heisenberg dimer with the help of negativity. It is shown that the negativity, which may serve as a measure of the bipartite entanglement at zero as well as nonzero temperatures, strongly depends on intrinsic parameters as for instance exchange and uniaxial single-ion anisotropy in addition to extrinsic parameters such as temperature and magnetic field. It turns out that a rising magnetic field unexpectedly reinforces the bipartite entanglement due to the Zeeman splitting of energy levels, which lifts a two-fold degeneracy of the quantum ferrimagnetic ground state. The maximal bipartite entanglement is thus reached within a quantum ferrimagnetic phase at sufficiently low but nonzero magnetic fields on assumption that the gyromagnetic g-factors of the spin-1/2 and spin-1 magnetic ions are equal and the uniaxial single-ion anisotropy is a half of the exchange constant. It is suggested that the heterodinuclear complex [Ni(dpt)(H$_2$O)Cu(pba)]$\cdot$2H$_2$O (pba=1,3-propylenebis(oxamato) and dpt=bis-(3-aminopropyl)amine), which affords an experimental realization of the mixed spin-(1/2,1) Heisenberg dimer, remains strongly entangled up to relatively high temperatures (about 140~K) and magnetic fields (about 140~T) being comparable with the relevant exchange constant.

Model, Mixed and Non-mixed Oxide Catalysts for the Fischer–Trøpsch Reaction Derived from [M1M2(dba)2]: M1 = Co, Ni; M2 = Co, Ni and [M1M2(daaen)]: M1 = Cu; M2 = Co. Part 1: Supported on Non-porous Powder (Cab-O-Sil™)

Homo and hetero-dinuclear metal complexes were used as precursors to model, supported, mixed and non-mixed metal oxide catalysts. These metal complexes contained either Co(II) pairs, Ni(II) pairs, or the mixed pair: Co(II)–Ni(II) having the (dba) ligands. Another mixed pair, Cu(II)–Co(II) was prepared having the (daaen) ligand. Calcination and reduction of precursor supported on silica (Cab-O-Sil™) yielded catalysts that were active for the Fischer–Tropsch reaction. In a batch reactor, both Ni2(dba)2/SiO2 and NiCo(dba)2/SiO2 catalyst gave CH4 as the major product; whereas, the CuCo(daaen)/SiO2 catalyst produced carbon nanotubes as the major product. The Co2(dba)2/SiO2 catalyst was the most stable and active one towards the production of hydrocarbons in a batch reactor. Subsequent testing in a flow reactor revealed that the cobalt catalysts showed 99% CO conversion and 67% liquid hydrocarbon selectivity.

Homo- and Hetero-dinuclear Arene-Linked Osmium(II) and Ruthenium(II) Organometallics: Probing the Impact of Metal Variation on Reactivity and Biological Activity.

Dinuclear metallodrugs offer much potential in the development of novel anticancer chemotherapeutics as a result of the distinct interactions possible with bio-macromolecular targets and the unique biological activity that can result. Herein, we describe the development of isostructural homo-dinuclear OsII -OsII and hetero-dinuclear OsII -RuII organometallic complexes formed from linking the arene ligands of [M(η6 -arene)(C2 O4 )(PTA)] units (M=Os/Ru; PTA=1,3,5-triaza-7-phosphaadamantane). Using these complexes together with the known RuII -RuII analogue, a chromatin-modifying agent, we probed the impact of varying the metal ions on the structure, reactivity and biological activity of these complexes. The complexes were structurally characterised by X-ray diffraction experiments, their stability and reactivity were examined by using 1 H and 31 P NMR spectroscopy, and their biological activity was assessed, alongside that of mononuclear analogues, through MTT assays and cell-cycle analysis (HT-29 cell line). The results revealed high antiproliferative activity in each case, with cell-cycle profiles of the dinuclear complexes found to be similar to that for untreated cells, and similar but distinct profiles for the mononuclear complexes. These results indicate these complexes impact on cell viability predominantly through a non-DNA-damaging mechanism of action. The new OsII -OsII and OsII -RuII complexes reported here are further examples of a family of compounds operating via mechanisms of action atypical of the majority of metallodrugs, and which have potential as tools in chromatin research.

Esterification of Tertiary Amides: Remarkable Additive Effects of Potassium Alkoxides for Generating Hetero Manganese-Potassium Dinuclear Active Species.

A catalyst system of mononuclear manganese precursor 3 combined with potassium alkoxide served as a superior catalyst compared with our previously reported manganese homodinuclear catalyst 2 a for esterification of not only tertiary aryl amides, but also tertiary aliphatic amides. On the basis of stoichiometric reactions of 3 and potassium alkoxide salt, kinetic studies, and density functional theory (DFT) calculations, we clarified a plausible reaction mechanism in which in situ generated manganese–potassium heterodinuclear species cooperatively activates the carbonyl moiety of the amide and the OH moiety of the alcohols. We also revealed details of the reaction mechanism of our previous manganese homodinuclear system 2 a, and we found that the activation free energy (ΔG ≠) for the manganese–potassium heterodinuclear complex catalyzed esterification of amides is lower than that for the manganese homodinuclear system, which was consistent with the experimental results. We further applied our catalyst system to deprotect the acetyl moiety of primary and secondary amines.