Search

This study investigates post-synthetic ligand exchange in a series of copper(II) and chromium(II) cuboctahedral cages of the formula M24(R-bdc)24 through solvent-free mechanochemistry for the preparation of mixed-ligand cages. While solvent-based ligand exchange does not proceed when the cages are insoluble or when they are dissolved in non-coordinating solvents, solvent-free mechanochemistry can be used to prepare a number of mixed-ligand cages featuring a variety of functional groups regardless of cage solubility. We further extend this strategy to intercage ligand exchange reactions where the solid-state reaction of cages proceeds in just ten minutes while corresponding solvent-based reactions require more than one week of reaction time. The results highlight mechanochemically-facilitated ligand exchange as an exceptionally facile and efficient method for the production of mixed-ligand cuboctahedral cages. [ABSTRACT FROM AUTHOR]

Ligand‐exchange reactions on a mangana(II)cyclopentasilane complex that contains two THF ligands with aryl isocyanides led to the formation of manganese(0) bis(η2‐disilene) complexes via a retrocyclization. In stark contrast, ligand‐exchange reactions with CNtBu, an N‐heterocyclic carbene, or pyridine‐based ligands furnished manganese(II) complexes wherein the manganacyclopentasilane framework remained intact. The thermolysis of the obtained bis(η2‐disilene) complex in the presence of mesityl isocyanide led to the formation of a cyclotetrasilane via the formal dimerization of the two η2‐disilene moieties. The insertion of a mesityl isocyanide into the Mn−Siβ bond results in the formation of a manganese(II) complex supported by a [SiCSi]‐type tridentate ligand scaffold. [ABSTRACT FROM AUTHOR]

Ligand‐exchange reactions on a mangana(II)cyclopentasilane complex that contains two THF ligands with aryl isocyanides led to the formation of manganese(0) bis(η2‐disilene) complexes via a retrocyclization. In stark contrast, ligand‐exchange reactions with CNtBu, an N‐heterocyclic carbene, or pyridine‐based ligands furnished manganese(II) complexes wherein the manganacyclopentasilane framework remained intact. The thermolysis of the obtained bis(η2‐disilene) complex in the presence of mesityl isocyanide led to the formation of a cyclotetrasilane via the formal dimerization of the two η2‐disilene moieties. The insertion of a mesityl isocyanide into the Mn−Siβ bond results in the formation of a manganese(II) complex supported by a [SiCSi]‐type tridentate ligand scaffold. [ABSTRACT FROM AUTHOR]

Quantum‐chemical (DFT) calculations on hitherto unknown base(carbene)‐stabilized gallium monoiodides (LB→GaI) suggest that these systems feature one lone pair of electrons and a formally vacant p‐orbital – both centered at the central gallium atom – and exhibit metallomimetic behavior. The calculated reaction free energies as well as bond dissociation energies suggest that these LB→GaI systems are capable of forming stable donor‐acceptor complexes with group 13 trichlorides. Examination of the ligand exchange reactions with iron and nickel complexes indicates their potential use as ligands in transition metal chemistry. In addition, it is found that the title compounds are also able to activate various enthalpically robust bonds. Further, a detailed mechanistic investigation of these small molecule activation processes reveals the non‐innocent behavior of the carbene (base) moiety attached to the GaI fragment, thereby indicating the cooperative nature of these bond activation processes. The energy decomposition analysis (EDA) and activation strain model (ASM) of reactivity were also employed to quantitatively understand and rationalize the different activation processes. [ABSTRACT FROM AUTHOR]

The versatile coordinating nature of N,S bidentate ligands is of great importance in medicinal chemistry imparting stability and enhancing biological properties of the metal complexes. Phenylthiocarbamide‐based N,S donor Schiff bases converted into RuII/OsII(cymene) complexes and characterized by spectroscopic techniques and elemental analysis. The hydrolytic stability of metal complexes to undergo metal‐halide ligand exchange reaction was confirmed both by the DFT and NMR experimentation. The ONIOM (QM/MM) study confirmed the histone protein targeting nature of aqua/hydroxido complex 2 aH with an excellent binding energy of −103.19 kcal/mol. The antiproliferative activity against a panel of cancer cells A549, MCF‐7, PC‐3, and HepG2 revealed that ruthenium complexes 1 a–3 a were more cytotoxic than osmium complexes and their respective ligands 1‐3 as well. Among these ruthenium cymene complex bearing sulfonamide moiety 2 a proved a strong cytotoxic agent and showed excellent correlation of cellular accumulation, lipophilicity, and drug‐likeness to the anticancer activity. Moreover, the favorable physiochemical properties such as bioavailability and gastrointestinal absorption of ligand 2 also supported the development of Ru complex 2 a as an orally active anticancer metallodrug. [ABSTRACT FROM AUTHOR]

The kinetics of the ligand exchange reaction between aquapentacyanoruthenate(II) [Ru(CN)5OH2]3− ion and naphthalene substituted ligands [α‐nitroso‐β‐naphthol (αNβN), and nitroso‐R‐salt (NRS)] has been studied in aqueous salt solutions of sodium chloride (NaCl) or tetrapropylammonium bromide (Pr4NBr) salt. The kinetics was monitored spectrophotometrically at 525 nm corresponding to the λmax of reddish‐brown‐colored substituted products, [Ru(CN)5(αNβN)]3− or [Ru(CN)5(NRS)]3−. Increasing the ionic strength of the reaction mixture using NaCl, exerted a negative salt effect on the rate of formation of naphthalene‐substituted products. At the same time, an increment in the concentration of Pr4NBr imparted a positive salt effect on the reaction. The observed rate constant (kobs) exhibits linear increment with respect to the concentration of NRS or αNβN while remaining invariant with variation in [Ru(CN)5OH2]3−. The computed activation parameters for NRS (∆H# = 24.55 kJ mol−1, Ea = 27.03 kJ mol−1, ∆G# = 87.83 kJ mol−1, and ∆S# = – 212.5 J K−1 mol−1) and αNβN ((∆H# = 17.33 kJ mol−1, Ea = 19.81 kJ mol−1, ∆G# = 87.87 kJ mol−1, and ∆S# = – 236.7 J K−1 mol−1) also support the proposed mechanism. [ABSTRACT FROM AUTHOR]

Thermoplastic polymers obtained from resins such as Elium® combine desirable properties, including recyclability/reusability and excellent thermomechanical performances, at a relatively affordable cost. Nevertheless, their polymerization often requires a high amount of energy and/or involves hazardous chemical compounds. To address this last point, a series of bio-based captodative ligands was designed and synthesized in order to replace controversial phosphine oxides commonly used in low-energy initiating systems but suffering from toxicity issues. By using these captodative ligands, the curing time required for the polymerization of Elium® could be reduced from more than one hour to a mere 10 minutes. To gain a deeper insight into the redox mechanism involved during the polymerization process, the redox properties of a series of manganese(III) complexes containing different captodative ligands have been investigated employing cyclic voltammetry. It has been demonstrated that ligand exchange reactions induced by using the captodative (or push–pull) ligands possessing both electron-donating and electron-withdrawing groups had a significant impact on the reduction potential of the manganese(III) complexes. The reduction potential significantly changed depending on the type of heteroatom atom (X = O, S) and substituent included in the scaffold of the captodative ligands. [ABSTRACT FROM AUTHOR]

This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo‐copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2O or Cu2S nanoparticles. Use of sub‐stoichiometric quantities of protonated ligand (pro‐ligand; 0.1–0.2 equivalents vs. [CuMes]z) allows saturation of surface coordination sites but avoids excess pro‐ligand contaminating the nanoparticle solutions. The pro‐ligands are nonanoic acid (HO2CR1), 2‐[2‐(2‐methoxyethoxy)ethoxy]acetic acid (HO2CR2) or di(thio)nonanoic acid, (HS2CR1), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2O is preferentially coordinated by carboxylate ligands and Cu2S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well‐defined nanoparticles and the need for appropriate ligand selection. [ABSTRACT FROM AUTHOR]

Cu(I) 4H‐imidazolate complexes are rare examples of Cu(I) complexes with chelating anionic ligands and are potent photosensitizers with unique absorption and photoredox properties. In this contribution, five novel heteroleptic Cu(I) complexes with monodentate triphenylphosphine co‐ligands are investigated. As a consequence of the anionic 4H‐imidazolate ligand and in contrast to comparable complexes with neutral ligands, these complexes are more stable than their homoleptic bis(4H‐imidazolato)Cu(I) congeners. Here, the ligand exchange reactivity was studied by 31P‐,19F‐, and variable temperature NMR and the ground state structural and electronic properties by X‐ray diffraction, absorption spectroscopy, and cyclic voltammetry. The excited‐state dynamics were investigated by femto‐ and nanosecond transient absorption spectroscopy. The observed differences, with respect to chelating bisphosphine bearing congeners, are often due to the increased geometric flexibility of the triphenylphosphines. These observations render the investigated complexes interesting candidates for photo(redox)reactions not accessible with chelating bisphosphine ligands. [ABSTRACT FROM AUTHOR]

The synthesis and the crystal structure of the double cluster compound [Nb6Cl14(MeCN)4][Nb6Cl14(pyz)4]·6CH3CN are described. The synthesis is based on a partial ligand exchange reaction, which proceeds upon dissolving [Nb6Cl14(pyz)4]·2CH2Cl2 in acetonitrile. The compound is built up of two discrete neutral cluster units, which consist of octahedra of Nb6 atoms coordinated by 12 edge-bridging chlorido and two terminal chlorido ligands, and four acetonitrile ligands on one and four pyrazine ligands on the other cluster unit. Co-crystallized acetonitrile molecules are also present. The single-crystal structure determination has revealed a cluster arrangement in which the [Nb6Cl14(pyz)4] units are connected by (halogen) lone-pair–(pyrazine) π interactions. These lead to chains of [Nb6Cl14(pyz)4] clusters. These chains are further connected to cluster layers by (nitrile-halogen) dipole–dipole interactions, in which the [Nb6Cl14(MeCN)4] and co-crystallized MeCN molecules are also involved. These cluster layers are arranged parallel to the crystallographic {011} plane. [ABSTRACT FROM AUTHOR]

Although multitargeted PtIV anticancer prodrugs have shown significant activities in reducing drug resistance, the types of bioactive ligands and drugs that can be conjugated to the Pt center remain limited to O‐donors. Herein, we report the synthesis of PtIV complexes bearing axial pyridines via ligand exchange reactions. Unexpectedly, the axial pyridines are quickly released after reduction, indicating their potential to be utilized as axial leaving groups. We further expand our synthetic approach to obtaining two multitargeted PtIV prodrugs containing bioactive pyridinyl ligands: a PARP inhibitor and an EGFR tyrosine kinase inhibitor; these conjugates exhibit great potential for overcoming drug resistance, and the latter conjugate inhibits the growth of Pt‐resistant tumor in vivo. This research adds to the array of synthetic methods for accessing PtIV prodrugs and significantly increases the types of bioactive axial ligands that can be conjugated to a PtIV center. [ABSTRACT FROM AUTHOR]

Although multitargeted PtIV anticancer prodrugs have shown significant activities in reducing drug resistance, the types of bioactive ligands and drugs that can be conjugated to the Pt center remain limited to O‐donors. Herein, we report the synthesis of PtIV complexes bearing axial pyridines via ligand exchange reactions. Unexpectedly, the axial pyridines are quickly released after reduction, indicating their potential to be utilized as axial leaving groups. We further expand our synthetic approach to obtaining two multitargeted PtIV prodrugs containing bioactive pyridinyl ligands: a PARP inhibitor and an EGFR tyrosine kinase inhibitor; these conjugates exhibit great potential for overcoming drug resistance, and the latter conjugate inhibits the growth of Pt‐resistant tumor in vivo. This research adds to the array of synthetic methods for accessing PtIV prodrugs and significantly increases the types of bioactive axial ligands that can be conjugated to a PtIV center. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis and structural characterization of a series of new ruthenium(II) complexes 1–7, with the general formula mer-[RuL3(N–N)Cl]Cl, where L is 2,2′:6′,2′′-terpyridine (tpy) or 4′-(4-chlorophenyl)-2,2′:6′,2′′-terpyridine (Cl-Ph-tpy) and N–N is o-benzoquinonediimine (o-bqdi), 2,3-naphthoquinonediimine (nqdi), 4,4′-dimethyl-2,2′-bipyridine (dmbpy) or 2,2′-bipyridine-4,4′-dicarboxylic acid (dcbpy). The kinetic results showed that the ligand substitution reactions of new Ru(II)-polypyridyl complexes with biomolecules were affected by different substituents and the aromaticity of meridional tridentate and bidentate spectator ligands as well as by the nature of the entering nucleophile. The reactivity of the complexes increases in the order: dmbpy < dcbipy < nqdi < o-bqdi. In addition, quantum chemical calculations were performed to support the interpretation and discussion of the experimental data. Furthermore, combining ethidium bromide (EB) and Hoechst 33258 (2-(4-hydroxyphenyl)-5-[5-(4-methylpiperazine-1-yl)benzimidazo-2-yl]-benzimidazole) fluorescence assay results implied that 1–7 might interact with calf thymus DNA through partial intercalation and/or minor groove binding. The human serum albumin (HAS)-fluorescence binding studies involving the site markers, eosin Y, as a marker for site I of subdomain IIA, and ibuprofen, as a marker for site II of subdomain IIIA, showed that Ru(II) compounds bind to both sites with moderately strong affinity (Kb = 104–106 M−1). Moreover, these DNA/HSA experimental results were confirmed by molecular docking. Complexes 2, 5 and 6 exerted good to strong and highly selective cytotoxic activity against breast adenocarcinoma (MDA-MB 231), colorectal carcinoma (HCT116) and cervix adenocarcinoma (HeLa). Depending on their structure and cell line, the complexes acted differently in terms of their influence on autophagy, the cell cycle and the engaged apoptotic pathway. [ABSTRACT FROM AUTHOR]

An initial investigation on the employment of targeted structural alterations, achieved through the post‐synthesis modification method, for modulation of the thermometric properties of metal–organic frameworks (MOFs) is reported. The MOF Eu0.05Tb0.95‐NBDC (NBDC = 2‐amino‐1,4‐benzenedicarboxylate) is chosen as pristine material, and its terminal N,N‐dimethylformamide (DMF) molecules are exchanged by various terminal and chelating ligands through a single‐crystal‐to‐single‐crystal coordinating solvent exchange reaction. Temperature‐dependence luminescence studies reveal that all samples are highly sensitive in the medium range with a maximum relative sensitivity of 2.6% K−1 at 190 K for Eu0.05Tb0.95‐NBDC. In addition, a shift of 50 K of the operating temperature range is evidenced for the exchanged analogs. This is attributed to the occurrence of different deactivation pathways in the exchanged analogs due to the presence of N‐donor terminal or N/O‐donor chelating aromatic ancillary ligands in the place of DMF terminal ligands in the pristine material. Overall, this work provides insights into the role of terminal and chelating ligands on the thermometric properties of mixed Eu–Tb MOFs and proposes a promising strategy to control and modulate their thermometric performances. [ABSTRACT FROM AUTHOR]

Cation exchange by post-synthetic modification of inorganic nanoparticles (NPs) is commonly monitored by probing alterations to the NP core, and not much is known about the ability of surface capping ligands to probe these reactions. This work systematically investigates the infrared (IR) absorption spectra of surface capping ligand 1-thioglycerol (1-TG) in ZnS or Zn(Tb)S NPs post-synthetically modified with Mn+ (Pb2+, Hg2+, Cd2+, Ca2+, Mg2+, Na+, and K+) individually, with [NPs] : [Mn+] = 1 : 1. An exchange of Zn2+ is observed in NPs with [NPs] : [Pb2+]/[Hg2+]/[Cd2+] = 1 : 1. Cation exchange in these NPs is associated with structural reorganization of (a) the H-bonding network and (b) the backbone structure of 1-TG, and this effect is found to be unperturbed by dopants. The spectral characteristics of [NPs] : [Mn+] = 1 : 10−2 NPs were also examined, which identified that the observed tuning of IR spectral properties is indeed a reflection of cation exchange and is not influenced merely by the chemical identity of the post-synthetically added cation. To the best of our knowledge, this work is the first experimental demonstration of surface capping ligands' usefulness for probing cation exchange reactions in inorganic NPs, and should open an additional sensing perspective for tracking such reactions. [ABSTRACT FROM AUTHOR]

Alkali‐metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6‐iPr2‐C6H3). Influenced by the large steric demands imposed by this amide, transamination of [NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic [Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ (1) resulting from the exchange of just one HMDS group. An alternative co‐complexation approach, combining the homometallic metal amides [NaN(SiMe3)Dipp] and [Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric [NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 (2). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic [Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ (4). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide [(py)Fe{N(SiMe3)Dipp}(HMDS)] (5), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. [ABSTRACT FROM AUTHOR]

This mini-review describes a broad spectrum of synthetic strategies to access mono- and polycyclic azaphosphiridines; properties and theoretical calculations of free and metal-ligated are discussed. These species are characterized by a highly strained (saturated) CPN ring with three differently polarized endocyclic bonds. The latter causes a high reactivity of aza-phosphiridine complexes towards ring expansion and exchange reactions. Increasing the ring strain leads to masked FLP behaviour, i.e., small molecule activation was observed. New perspectives in homogenous catalysis are also offered, e.g., a pool of novel chiral P-heterocyclic ligands, ready to be explored, if the challenge to unligate them is solved. [ABSTRACT FROM AUTHOR]

A study of the adsorption of different axial ligands on Fe porphyrin (FeP), both isolated and adsorbed on Cu(001), was performed by means of Density Functional Theory. The electronic and magnetic properties of the adsorbed FeP resulted to be strongly influenced by the axial ligands considered, Cl and O. Cl induces an enhancement of the overall molecular magnetic moment of 3.0 μB while O or O2 leave the spin state of the molecule unchanged. The influence of the Cl in the electronic states was moreover studied by means of theoretical NEXAFS N K-edge, where the spectra of isolated FeP and FeP with Cl ligand were calculated. The adsorption of the FeP molecules on Cu(001) leads in case of Cl to a further increase of the magnetic moment due to strong deformation of the Fe-N bond. [ABSTRACT FROM AUTHOR]

• Rapid Hg isotope exchange is observed in various environmental matrices. • Exchange reactions alter distributions and bioavailability of Hg isotopes. • Predictions of Hg biogeochemical transformations could be biased if isotope exchange is not considered. Enriched mercury (Hg) stable isotopes have been widely used as tracers in field and laboratory investigations of Hg(II) biogeochemical transformations such as methylation and demethylation. Few studies, however, have considered concurrent isotope exchange reactions between newly spiked and pre-existing Hg(II) in environmental matrices, which may alter redistribution and thus transformation of the spiked and pre-existing Hg(II). Using enriched 198Hg [as mercuric Hg(II) or HgCl n species], this study investigated isotope exchange between 198Hg and pre-existing Hg(II) bound to metacinnabar (β-HgS), sediments, low-molecular-weight (LMW) thiols, and dissolved organic matter (DOM). The impact of isotope exchange on methylmercury production in the presence of organic ligands was also evaluated with an iron-reducing bacterium Geobacter sulfurreducens PCA in a phosphate buffered solution (pH 7.4). We found that spiked 198Hg readily exchanged with mineral-bound ambient Hg(II) despite concurrent Hg(II) adsorption and immobilization on the solids. Rapid exchange (<3 min) was also observed between spiked 198Hg and 200Hg pre-equilibrated with LMW thiols and DOM in solution. While the exchange did not cause net changes in Hg(II) chemical speciation, it resulted in redistribution of Hg(II) isotopes bound to the ligands and thus an apparently similar methylation rate and magnitude of the spiked 198Hg and pre-existing 200Hg by PCA cells when 198Hg and 200Hg were added at 1:1 ratio. These observations underscore the importance of isotope exchange when an enriched Hg isotope is applied in environmental matrices, as the exchange could potentially lead to biased rate calculations of Hg(II) transformation and bioaccumulation and thus risk assessments of new Hg(II) input to the natural ecosystems. [ABSTRACT FROM AUTHOR]

In this article, the synthesis and characterization of new palladium(η2‐olefin) complexes bearing isocyanides as spectator ligands are described. These derivatives have been tested on olefin exchange reactions, allowing to define a scale of strength of the palladium(0)‐olefin bond. In this way we have proved that dimethyl fumarate can be released by the metal center much more easily than the other olefins and that (Z)‐1,2‐ditosylethene is by far the most firmly anchored to palladium. When the sterically encumbered tetramethylethene‐1,1,2,2‐tetracarboxylate (tmetc) is involved in the olefin exchange, the reaction kinetics can be monitored by UV‐Vis spectrophotometry, showing that the process follows a second‐order rate law. This response indicates that the reaction mechanism is associative, as is also confirmed by a DFT study. [ABSTRACT FROM AUTHOR]

The interaction of heterometallic compounds [Co2La(Piv)6(NO3)(MeCN)2] (1) and [Co2La(Piv)6(NO3)(Py)2] (2) (Piv‐pivalate, Py‐pyridine) with triphenylphosphine was studied. It was shown that labile terminal molecules of MeCN in complex 1 were substituted by triphenylphosphine that led to the formation of complex [Co2La(Piv)6(NO3)(Ph3P)2] (3), whereas compound 2 in similar conditions did not undergo ligand substitution reaction. Molecular structure of compound 3 was determined by means single crystal X‐ray diffraction. The temperature dependence of the magnetic susceptibility of 3 was simulated with a model which implied only zero‐field splitting of Co(II) ions. It was found that ZFS parameters (D) for Co(II) ions in 3 were close to D value in 1. The field‐induced slow magnetic relaxation was observed for compound 3 on the result of magnetic susceptibility measurements in alternating current magnetic field. [ABSTRACT FROM AUTHOR]

Bimetallic carbon-supported PdBi catalysts were prepared by grafting. To do so a soluble complex of bismuth with exchangeable O-donor ligands was selected, and the carbon support was functionalized to increase the number of surface functions. The grafting procedure was carried out by contacting the various supports with solutions of Pd and/or Bi complexes, to allow ligand exchange reactions to take place between the complexes and the surface O-groups. The grafted fragments were then activated into carbon-supported nanoparticles, which were characterized to unravel the impact of grafting experimental variables on the physico-chemical characteristics of the materials obtained. The PdBi/C catalysts were finally tested in the archetypal glucose selective oxidation reaction, to assess the impact of those characteristics on the catalytic performance. It was found that simultaneous grafting gave larger nanoparticles than consecutive grafting, while higher number of stable surface functions allowed to obtain small and nicely distributed bimetallic nanoparticles. However, the surface functions were found to be deleterious for the catalytic activity, and the placement of the Bi promoter with respect to Pd active phase was identified as another key parameter for the activity, with grafting allowing to compare neatly samples where Bi is underneath, above or beside Pd. [ABSTRACT FROM AUTHOR]

The Hoveyda–Grubbs (HG) second-generation catalyst (HG-II), a Ru complex with a 2-isopropoxybenzylidene ligand, is extensively used for olefin metathesis, the rearrangement of carbon–carbon double bonds. A well-known strategy to control its complex reactivity is to modify the phenyl ring in the ligand, thereby directly influencing the coordination of the phenolic oxygen to the metal center. We, herein, report that a functional group attached to the phenolic moiety in the 2-alkoxybenzylidene ligand can indirectly affect the reactivities of HG-type complexes. In this work, the ligand exchange reactions between HG-II and phenolic moiety-modified 2-alkoxybenzylidene ligands are useful for evaluating the structural effects of the ligands. Specifically, an ethylene amide or an ester group at the terminal phenolic moiety in the benzylidene ligand was found to influence the relative stabilities of HG-type complexes compared to that of the HG-II complex. The structural analyses proved that the observed effects of the functional groups on the complex stabilities originate from the interactions with a chlorido ligand in HG-type complexes without changes in coordination fashions at the metal centers. It was found that the outer-sphere interactions also influence the catalytic activities of HG-type complexes, namely, the properties of HG-type complexes can be controlled by outer-sphere structural factors toward the metal center (i.e., "the second-coordination sphere effect"). In the design of functionalized HG-type complexes, the outer-sphere structural effects need to be considered in addition to the optimization of the metal coordination site. [ABSTRACT FROM AUTHOR]

Tetramethylaluminato/halogenido(X) ligand exchange reactions in half‐sandwich complexes [CpRLa(AlMe4)2] are feasible in non‐coordinating solvents and provide access to large coordination clusters of the type [CpRLaX2]x. Incomplete exchange reactions generate the hexalanthanum clusters [CpR6La6X8(AlMe4)4] (CpR=Cp*=C5Me5, X=I; CpR=Cp′=C5H4SiMe3, X=Br, I). Treatment of [Cp*La(AlMe4)2] with two equivalents Me3SiI gave the nonalanthanum cluster [Cp*LaI2]9, while the exhaustive reaction of [Cp′La(AlMe4)2] with the halogenido transfer reagents Me3GeX and Me3SiX (X=I, Br, Cl) produced a series of monocyclopentadienyl rare‐earth‐metal clusters with distinct nuclearity. Depending on the halogenido ion size the homometallic clusters [Cp′LaCl2]10 and [Cp′LaX2]12 (X=Br, I) could be isolated, whereas different crystallization techniques led to the aggregation of clusters of distinct structural motifs, including the desilylated cyclopentadienyl‐bridged cluster [(μ‐Cp)2Cp′8La8I14] and the heteroaluminato derivative [Cp′10La10Br18(AlBr2Me2)2]. The use of the Cp′ ancillary ligand facilitates cluster characterization by means of NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The exchange reaction of anhydrous YbCl3 with [1,3-C6H4{NC(Ph)N(SiMe3)}2Li2(THF)2]2 (I) (4 : 3 molar ratio, THF) gave ansa-bis(amidinate) ytterbium complex [1,3-C6H4{NC(Ph)N(SiMe3)}2]3Yb2 (II) in which three bis(amidinate) ligands form µ-bridges between two Yb3+ ions. An X-ray diffraction study (CIF file CCDC no. 1964848) showed that the dimeric structure of II is formed upon simultaneous coordination of κ2-N,N-chelating moieties of three ligands to two ytterbium atoms. [ABSTRACT FROM AUTHOR]

The exchange reactions of equimolar amounts of potassium penta(benzyl)cyclopentadienide CpBn5K (CpBn5 = C5(CH2Ph)5) and SmI2(THF)2 or YCl3 afforded the corresponding half-sandwich derivatives [CpBn5Sm(DME)(μ-I)]2 (1) and [CpBn5YCl2(THF)]2[KCl(THF)2] (2). According to the X-ray diffraction data, the metal ions in complexes 1 and 2 are coordinated by CpBn5 ligands in a η5-fashion. The difference is that there is a short contact between the SmII cation and one benzyl group of the cyclopentadienyl ligand in structure 1, whereas such interaction is absent in structure 2. [ABSTRACT FROM AUTHOR]

We report a series of organometallic nickel and palladium complexes containing iminophosphine ligands R2PCH2C(Ph) = N-Dipp (Dipp = 2,6-diisopropylphenyl; R = iPr, La; R = Ph, Lb; and R = o-C6H4OMe, Lc), synthesized by ligand exchange or oxidative addition reactions, and we investigate the capacity of such ligands to undergo reversible deprotonation to the corresponding phosphinoenaminato species. In the attempted ligand exchange reaction of the nickel bis(trimethylsilyl)methyl precursor [Ni(CH2SiMe3)2Py2] with Lb, the iminophosphine acts as a weak acid rather than a neutral ligand, cleaving one of the Ni–C bonds, to afford the phosphinoenaminato complex [Ni(CH2SiMe3)(L′b)(Py)] (L′b = conjugate base of Lb). We disclose a general method for the syntheses of complexes [Ni(CH2SiMe3)(L)(Py)]+ (L = La, Lb or Lc), and demonstrate that iminophosphine deprotonation is a general feature and occurs reversibly in the coordination sphere of the metal. By studying proton exchange reactions of the cation [Ni(CH2SiMe3)(Lb)(Py)]+ with bases of different strength we show that the conjugate phosphinoenaminato ligand in [Ni(CH2SiMe3)(L′b)(Py)] is a base with strength comparable to DBU in THF. The acyl group in the functionalized aryl complex [Ni(p-C6H4COCH3)(Br)(La)] does not interfere in the iminophosphine deprotonation with NaH. The latter reaction affords the unusual anionic hydroxide species [Ni(p-C6H4COCH3)(OH)(L′a)]−Na+, which was isolated and fully characterized. [ABSTRACT FROM AUTHOR]

New bis-p-iminobenzoquinone ligands, in which two hydroxy-p-iminobenzoquinone moieties are bridged by various functionalized linkers, were synthesized by 1,4-addition of aromatic diamines to 3,6-di-tert-butyl-o-benzoquinone. The exchange reaction between potassium salts of new ligands and ethylmercury(ii) chloride produces the corresponding mono- and binuclear metal complexes. In these complexes, the mercury atoms exhibit T-shaped trigonal geometry characteristic of three-coordinate mercury(ii) derivatives. The structures of the new ligands and the mercury complexes with these ligands were determined by IR, UV, and NMR spectroscopy and X-ray diffraction. [ABSTRACT FROM AUTHOR]

Herein we report the transformation of [Au25(SR)18]0 into Au28(SR)21 induced by ligand exchange reaction. In contrast to other reported cluster transformations, which proceed at elevated temperature and large excess of incoming ligands, the transformation reported here occurs under mild conditions (room temperature, very low thiol excess) with a chiral ligand. A difference of one methyl group between incoming and leaving thiol is sufficient to induce the transformation. To the best of our knowledge the Au28(SR)21 cluster has not been isolated before. [ABSTRACT FROM AUTHOR]

The attempted synthesis of bis(diphenylphosphinomethyl) phenylarsane and tris(diphenylphosphinomethyl) arsane through condensation of chloro arsanes and diphenyl (trimethylsilylmethyl) phosphane yielded a number of side products originating from migratory and redox-reactions in addition to the targeted ligands. An unexpected, 1,3,4-phosphadiarssolan-1-ium salt was obtained and crystallographically characterized as an A-shaped chlorido adduct. [ABSTRACT FROM AUTHOR]

A structural study of ligand exchange on chalcogen‐passivated copper nanoclusters is far less developed. Herein, we report the synthesis of polyhydrido copper nanoclusters [Cu20H11{Se2P(OiBu)2}9] (2) passivated by Se‐donor ligands via ligand replacement reaction on [Cu20H11{S2P(OiPr)2}9] (1) with NH4[Se2P(OiBu)2]. In parallel to the synthesis of 2, cluster [Cu20H11{S2P(CH2CH2Ph)2}9] (4) was produced by the ligand exchange reaction on a new derivative of 1, that is [Cu20H11{S2P(OnPr)2}9] (3). Solid state structures of both clusters 2 and 4 were unequivocally established by single‐crystal X‐ray diffraction studies and cluster 4 epitomizes exceptional case to preserve both the shape and size of the nanocluster during the course of ligand exchange. Structurally precise cluster 2 is the second example where the copper hydride nanocluster is stabilized by Se‐donor ligands. The anatomy of 2 can be visualized as a twisted cuboctahedral Cu13 core, two triangular faces of which are capped by a Cu6 cupola and a single Cu atom along the C3 rotational axis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Complexes [Re(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 κ- P }{Ph 2 P(S)NP(S)Ph 2 κ2- S,S ́}], E = O, S, Se were straightforwardly prepared upon chalcogenation of complex [Re(CO) 3 {Ph 2 PCH 2 PPh 2 -κ- P }{Ph 2 P(S)NP(S)Ph 2 -κ2- S,S ́}]. • [Re(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 κ-P}{Ph 2 P(S)NP(S)Ph 2 κ2- S,S ́}], E = O, S, Se in the presence of ReBr(CO) 5 triggered redistribution reactions affording [ReBr(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 -κ2- P,E }], E = O, S, Se. • It has been established that the ligand [Ph 2 P(S)NP(S)Ph 2 ]¯ is prone to undergo redistribution processes within the Re and Mn carbonyls' realm. • BPMO Ph 2 PCH 2 P(O)Ph 2 was efficiently de-coordinated from [ReBr(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 -κ2- P,O }]. Chalcogenation of complex [Re(CO) 3 {Ph 2 PCH 2 PPh 2 -κ- P }{Ph 2 P(S)NP(S)Ph 2 -κ2- S,Ś }] (1) led to complexes [Re(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 -κ- P }{Ph 2 P(S)NP(S)Ph 2 -κ2- S,Ś }], E = O, S, and Se (1a , 1b , 1c , respectively). Redistribution reactions between 1a and 1c and ReBr(CO) 5 afforded complexes 2a – 2c , [ReBr(CO) 3 {Ph 2 PCH 2 P(E)Ph 2 -κ2- P , E }], E = O, S, and Se, respectively. The BPMO Ph 2 PCH 2 P(O)Ph 2 was obtained from complex 2a. [ABSTRACT FROM AUTHOR]

Treatment of 1,3-bis(2,6-diisopropylphenyl)imidazoline-2-tellone 1 with Tf2O in CH2Cl2 resulted in the formation of dicationic ditelluride salt 22+ 2 (OTf)− as air-stable green crystals in 88% yield. The anion exchange reaction of 22+ 2 (OTf)− with Na[B(C6F5)4] proceeded in CH3CN at room temperature giving the corresponding borate salt 22+ 2 [B(C6F5)4]− as blue crystals in 40% yield. The structures of these dicationic ditelluride derivatives were fully characterized on the basis of their NMR spectroscopic data and X-ray crystallography. In the crystalline state of 22+ 2 (OTf)−, two NHC ligands are entirely perpendicular to the central Te–Te bond with a Te–Te–C–N torsion angle of 89.93(19)°. In sharp contrast, X-ray analysis of 22+ 2 [B(C6F5)4]− revealed that two NHC ligands and the central Te–Te moiety are essentially coplanar with a Te–Te–C–N torsion angle of 7.99(17)°. In the DFT calculation for the model compound 32+, NBO orbitals around the Te–Te moiety in Ci symmetry consist of a Te–Te σ-bonding orbital, a Te–C σ-bonding orbital, a lone pair orbital on the Te atom (mainly s-character), and a lone pair orbital on the Te atom (pure p-character). [ABSTRACT FROM AUTHOR]

The major limitation of classic biphasic ionic liquid (IL) catalysis is the heavy use of solvent ILs, which not only violates green chemistry principles but also even worsens catalytic efficiency. So it has always been a challenge finding ways to use ILs more efficiently, economically, and greenly to construct highly effective and long term stable IL catalytic systems. In this work, we synthesized a class of room temperature phosphine-functionalized polyether guanidinium ionic liquids (RTP-PolyGILs) by a convenient ion exchange reaction of polyether guanidinium ionic liquids (PolyGILs) with phosphine-sulfonate ligands based on the concept of the integration of both the phosphine ligand and IL. The resulting RTP-PolyGILs existed as liquids at room temperature and possessed dual functions of both the phosphine ligand and solvent IL; therefore they could both form catalysts by complexing with transition metals and act as catalyst carriers, thus achieving the integration of phosphine ligands with ILs both in structure and properties. Based on the unique properties of these multi-functional integrated RTP-PolyGILs, we constructed a highly effective homogeneous catalysis-biphasic separation (HCBS) system for Rh-catalyzed hydroformylation of higher olefins using only a catalytic amount of RTP-PolyGILs (equivalent to 0.025–0.4 mol% of 1-alkenes). Our HCBS system could be flexibly regulated with regard to catalytic performance (activity and linear selectivity) by changing the structure or type of the sulfonated ligand anion on RTP-PolyGILs. Specifically, it presented a TOF value of 3000–26 000 h−1 and a linear selectivity of 68%–98% (corresponding to the l/b ratio of 2.2–37.5) with a total turnover number (TTON) of 11 000–45 000 and an extremely low Rh leaching of only 0.02–0.4 ppm. Therefore, the HCBS system can effectively combine the advantages of both homogeneous (high activity and good selectivity) and biphasic catalysis (easy catalyst separation). We additionally extended the application of the HCBS system to the hydrogenation of olefins to demonstrate the universality of the RTP-PolyGILs in catalytic reactions. [ABSTRACT FROM AUTHOR]

Dinuclear copper(I) complexes have been prepared starting from bis(diphenylphosphanyl)acetylene (dppa), [Cu(CH3CN)4](BF4) and various 1,10‐phenanthroline ligands (NN), namely 1,10‐phenanthroline (phen), neocuproine (dmp), bathophenanthroline (Bphen), bathocuproine (Bdmp) and 2‐phenyl‐1,10‐phenanthroline (mpp). The resulting [Cu2(µ‐dppa)2(NN)2](BF4)2 complexes have been thus obtained in excellent yields (88 to 94 %). X‐ray crystal structure analysis of four complexes revealed that the 10‐membered dimetallacycle adopts a chair‐like conformation in the solid state. Detailed variable temperature NMR investigations have evidenced dynamic coordination/decoordination of the NN ligands as well as ligand exchange reactions. At high temperature (100 °C), entropic effects tend to destabilize the dinuclear heteroleptic complexes. As a result, homoleptic mononuclear complexes, i.e. [Cu(NN)2]+ and undefined dppa copper(I) complexes, start to appear in solution. In contrast, the heteroleptic coordination scenario is almost exclusively favored at lower temperatures. For most of the dinuclear complexes, the 10‐membered dimetallacycle remains flexible and chair‐to‐chair interconversion occurs faster than the NMR timescale even at –70 °C. In the particular case of the mpp derivative, the bulky phenyl substituent prevents the isomerization of the metallacycle and thus contributes to rigidify the structure. This rigidification has a dramatic effect on the emission properties of this particular compound. The emission quantum yield of [Cu2(µ‐dppa)2(mpp)2](BF4)2 is effectively one order of magnitude higher when compared to all the other complexes in this series (20 % vs. 0.3–1.7 % in the solid state). [ABSTRACT FROM AUTHOR]

Heteroleptic copper(I) complexes combining phenanthroline derivatives (NN) and chelating bisphosphine ligands (PP) are an important class of luminescent materials for various applications. Although thermodynamically stable, [Cu(NN)(PP)]+ derivatives are also kinetically unstable. As a result, a dynamic ligand‐exchange reaction is often observed in solution, leading to a dynamic mixture of heteroleptic and homoleptic complexes. To prevent the formation of the homoleptic species, macrocyclic phenanthroline ligands have been used for the preparation of [Cu(NN)(PP)]+ pseudorotaxanes. The topological constraint resulting from the macrocyclic structure of the NN ligand drives the thermodynamic equilibrium towards the exclusive formation of the heteroleptic complex as long as the macrocycle is large and flexible enough to allow for the threading of the PP ligand. Conversely, when the threading is prevented by steric constraints, unprecedented copper(I) complexes with a trigonal coordination geometry are obtained. These results are summarized in the present concept article. Macrocyclic phenanthroline ligands have been used for the preparation of [Cu(NN)(PP)]+ pseudorotaxanes (NN=phenantroline derivative; PP=bisphosphine). Topological constraint drives the thermodynamic equilibrium towards the exclusive formation of the heteroleptic complex as long as the macrocycle is large and flexible enough to allow for the threading of the PP ligand. Conversely, when the threading is prevented by steric constraints, unprecedented copper(I) complexes are obtained. [ABSTRACT FROM AUTHOR]

A closed metallomolecular cage based on the tris(saloph) framework, in which its aperture can be opened by disulfide exchange, was designed. At the apertures of the molecular cage, bridging diamine ligands having a disulfide bond were introduced to close the cage structure. These bridging ligands efficiently blocked the uptake of a guest, Cs+, but the presence of a thiolate anion significantly accelerated the guest uptake. This clearly means that this cage complex became open by the addition of the thiolate anion, because the cage closure becomes more dynamic due to the disulfide exchange reaction. A closed metallomolecular cage based on the tris(saloph) framework, in which its aperture can be opened by disulfide exchange, was designed. At the apertures of the molecular cage, bridging diamine ligands having a disulfide bond were introduced to close the cage structure. These bridging ligands efficiently blocked the uptake of a guest, Cs+, but the presence of a thiolate anion significantly accelerated the guest uptake. [ABSTRACT FROM AUTHOR]

The coordination chemistry of a rigid tetradentate polypyridyl ligand has been developed with first-row transition metals Mn(ii), Fe(ii), Co(ii), Ni(ii), and Zn(ii). The polyaromatic ligand, 2,2′-di([2,2′-bipyridin]-6-yl)-1,1′-biphenyl (5, bpbb), is comprised of 2,2′-bipyridine donors positioned at the 2 and 2′ carbons of a biphenyl backbone. Notably, coordination of the typical strong field bipyridine fragments is constrained, weakening the octahedral ligand fields around manganese, iron, and cobalt to give high-spin electronic states. Solution magnetic susceptibility measurements were conducted across the series using the Evans method and variable-temperature solid-state SQUID magnetometry was performed on two Fe(ii) compounds, including a bis(thiocyanato) species. Spin crossover behavior was not observed as the compounds remained high-spin over the entire temperature range. The impact of the biphenyl bridge on M–N bond distances and redox potentials has also been assessed by comparison to relevant first-row metal bis- and tris-bipyridine compounds from the literature. [ABSTRACT FROM AUTHOR]

Azocarboxamides occupy a special place among azo ligands owing to their versatility for metal coordination. Herein ruthenium complexes with two different azocarboxamide ligands that differ in the presence (or not) of a coordinating pyridyl heterocycle are presented. By making full use of the O,N(amide), N(azo), and N(pyridyl) coordinating sites, the first diruthenium complex that is bridged by an azo ligand containing two different binding pockets was obtained. Moreover, it was conclusively proven that, in the mononuclear complexes, oxidation at the ruthenium center leads to a complete change of coordination at the chelating binding pocket. The complexes were characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. Additionally, the mechanism of the aforementioned redox‐triggered change in the chelating binding pocket and the electronic structures of all the complexes were investigated by a combination of electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, and DFT calculations. This is first instance in which a redox‐driven change in the complete chelating binding pocket has been observed in a ruthenium complex as well as with azo‐based ligands. These results thus show the potential of these versatile azocarboxamide ligands to act as redox‐driven switches with possible relevance to electrocatalysis. Join at the tip: Ruthenium complexes of azocarboxamide ligands with and without a coordinating pyridyl heterocycle were synthesized. By making full use of the O,N(amide), N(azo), and N(pyridyl) coordinating sites, the first diruthenium complex bridged by an azo ligand containing two different binding pockets was obtained. Moreover, in the mononuclear complexes, oxidation at the Ru center leads to a change in the coordination mode at the chelating binding pocket (see scheme). [ABSTRACT FROM AUTHOR]

Abstract: A series of silver alkynyl cages were synthesized using ligand 3,5-di-tert-butyl-phenylethynide and were structurally characterized. Reaction with [Ag(ArC≡C)]n polymer and (nBu4N)X (X = F, Cl, Br) gave compounds incorporating different halogen anions (F−, Cl−, Br−) and a hollow compound, namely [Ag14(ArC≡C)12(MeCN)6](OTf)2 · 4MeCN (I), [Ag14(ArC≡C)12(EtOH)2F]F · EtOH (II), [Ag14(ArC≡C)12(THF)2Cl]OH · THF (III) and [Ag14(ArC≡C)12(MeCN)4Br]OH (IV) (ArC≡C = 3,5-di-tert-butyl-phenylethynide). Direct synthesis of anion containing cages and indirect synthesis from the hollow cage were achieved. Structural studies (CCDC nos. 1831128 (I), 1831129 (II), 1831130 (III), and 1831131 (IV)) revealed that the incorporation of anions reduced the mean Ag−Ag bond length and therefore the cage size, giving the order of F@Ag14 ≈ Cl@Ag14 < Br@Ag14 < halogen-free. The cage size was larger than those of similar Ag14 clusters reported previously, which is likely due to the use of bulky alkynyl ligands. [ABSTRACT FROM AUTHOR]

Four new Zn(ii)/Cd(ii)-based metal–organic frameworks (MOFs), namely {[Cd(tmdb)(bib)0.5]·solvents}n (YZ-7, YZ stands for the initials of the author Yong-Zheng Zhang), {[Cd(tmdb)(bmib)0.5]·solvents}n (YZ-8), {[Zn2(tmdb)2(bmib)]·solvents}n (YZ-9) and {[Zn2(tmdb)2(bmip)2]·solvents}n (YZ-10) have been solvothermally synthesized by using a semi-rigid ligand, 4,4′-(H-1,2,4-triazol-1-yl)methylene-dibenzoic acid (H2tmdb), and a series of secondary bis-imidazole ligands (bib = 1,4-bis(1H-imidazol-1-yl)benzene, bmib = 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene, and bmip = 1,3-bis(2-methyl-1H-imidazol-1-yl)propane). By tuning the flexibility of the auxiliary ligands, these MOFs could be modulated from unstable (YZ-7–YZ-9) to stable (YZ-10) frameworks. Therefore, the gas adsorption properties of YZ-10 are further studied. Interestingly, it shows excellent CO2 selective uptake over CH4 and N2. At 298 K, both selectivities of CO2/CH4 and CO2/N2 show increasing trends and significantly reach 133.2 and 19.9 at 1 atm, respectively. Also, YZ-10 shows uncommon H2 selective uptake over N2 at 77 K. Moreover, the luminescence properties of YZ-8–YZ-10 were studied in the solid state at room temperature. [ABSTRACT FROM AUTHOR]

Alkaline earth metal ion organic frameworks (AEMOFs) represent a relatively underexplored subcategory of MOFs. Two new MOFs [Ca 6 (bpdc-(NH 2 ) 2 ) 5 (μ 3 -HCO 2 ) 2 (H 2 O) 2.5 (DMF) 0.5 ]·0.5H 2 O·2.5DMF ( 1 ) and [Sr 4 (bpdc-(NH 2 ) 4 )(μ 2 -DMF) 2 (DMF) 1/3 ]·2/3(DMF) ( 2 ) [H 2 bpdc-(NH 2 ) 2  = 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylic acid); DMF = N,N-dimethylformamide] are presented here. These MOFs display structural variety with diverse topologies and new structural features. Luminescence studies revealed that both MOFs display ligand based fluorescence with small differences in emission profiles possibly attributable to the difference in charge density of the metal ions combined with the different conformation adopted by the ligand in the crystal structures of 1 and 2 . Furthermore, initial sensing studies reveal that both MOFs can potentially function as fluorescent sensors for gas phase aldehydes. [ABSTRACT FROM AUTHOR]

Here, we have achieved the target switching fluorescence imaging and photodynamic activity of hydrosoluble AuNCs from lysosomes to mitochondria through ligand exchange. This work unveils the ligand-regulated subcellular distribution of AuNCs by which new strategies to improve their bio-applications such as precise nanotheranostics could be realized. [ABSTRACT FROM AUTHOR]

Ultrasmall (<2 nm) ligand-protected metal nanoclusters (NCs) have been an emerging class of functional materials with rich coordination chemistry, finding increasing acceptance in both basic and applied research owing to their atomic precision, well-defined molecular structure, and intriguing molecular-like properties. The presence of ligands on metal NCs is crucial not only for maintaining their atomic precision and well-defined structure, but also for their rich coordination chemistry with noble metals, influencing the synthesis, and physicochemical and catalytic properties of metal NCs. In this review, we discuss the important roles of ligands to metal NCs, taking water-soluble gold nanoclusters (Au NCs) as an example. The review covers the fundamental understandings (and advances) on the roles of ligands to water-soluble Au NCs in the synthesis ( e.g., influencing the size and formation rate, and revealing the growth mechanisms), physicochemical properties ( e.g., geometrical structure, chirality, stability, solubility, and electronic, photoluminescence and biological properties) and catalytic applications ( e.g., accessibility, activity, selectivity, and coordination of catalytic mechanism of quasi-homogeneous catalysts and immobilization of heterogeneous catalysts). The review also highlights some challenging issues on how ligands and ligand engineering could expand the scope of metal NCs in the synthesis, physicochemical properties, and catalytic application. [ABSTRACT FROM AUTHOR]

The interaction of manganese phthalocyanine with F4‐TCNQ is accompanied by the transformation of the acceptor molecule into a new organic ligand, the 4‐(dicyanomethanido)tetra‐fluorobenzoate dianion, resulting in the formation of a unique MnIII charge‐transfer complex, in which two Mn phthalocyanine moieties are bridged by the dianion, with parallel arrangement of all aromatic fragments and an interplanar distance of 3.30 Å. The formation of the complex takes place in a 2:1 ratio, with the two electrons transferring from two donor molecules to an acceptor molecule. Magnetic measurements reveal that MnIII ions in the studied complex occur in the high‐spin state S = 2 and are coupled antiferromagnetically, presumably by the superexchange mechanism through the 4‐(dicyanomethanido)tetrafluorobenzoate dianion bridge, with an interaction constant of J = 5 cm–1 (7 K). According to the electrochemical data, the new complex appears to have unusual redox properties and might be described as an electronic reservoir with strong acceptor ability, being able to take seven electrons. Notably, all of the reduction–oxidation steps are reversible, proceeding without structural changes. [ABSTRACT FROM AUTHOR]

Two novel Schiff base ligands (La and Lb) were prepared from the condensation of quinoline 2‐aldehyde with 2‐aminopyridine (ligand La) and from the condensation of oxamide with furfural (ligand Lb). Mixed ligand complexes of the type M+2La/b Lc were prepared, where (La and Lb) the primary ligands and Lc was 2,6‐pyridinedicarboxylic acid as secondary ligand. Metal ions used were Fe(II), Co(II), Ni(II) and Zn(II) for mixed ligands La Lc and Fe(II), Co(II), Ni(II), Cu(II), Hg(II) and Zn(II) for LbLc mixed ligands. La and Lb Schiff base ligands were both characterized using elemental analyses, molar conductance, IR, 1H and 13C NMR. Mass spectra for Lb, [Zn(La)LcCl]Cl and [Cu(Lb)LcCl]Cl were also studied. ESR spectrum of the [Cu(Lb) LcCl]Cl complex was also recorded The metal complexes were synthesized and characterized using elemental analyses, spectroscopic (IR, 1H NMR, UV‐visible, diffused reflectance), molar conductance, magnetic moment and thermal studies. The IR and 1H NMR spectral data revealed that 2,6‐pyridinedicarboxalic acid ligand coordinated to the metal ions via pyridyl N and carboxylate O without proton displacement. In addition, the IR data showed that La and Lb ligands behaved as neutral bidentate ligands with N2 donation sites (quinoline N and azomethine N for La and two azomethine N for Lb). Based on spectroscopic studies, an octahedral geometry was proposed for the complexes. The thermal stability and degradation of the metal complexes were investigated by thermogravimetric analysis. The binding modes and affinities of La, Lb and Zn(II) complexes towards receptors of crystal structure of E. coli (PDB ID: 3 t88) and mutant oxidoreductase of breast cancer (PDB ID: 3 hb5) receptors were also studied. The antimicrobial activity against two species of Gram positive, Gram negative bacteria and fungi were tested for the Schiff base ligands, 2,6‐pyridinedicarboxylic acid and the mixed ligand complexes and revealed that the synthesized mixed ligand complexes exhibited higher antimicrobial activity than their free Schiff base ligands. [ABSTRACT FROM AUTHOR]

To realize the molecular design of new functional silver(I) clusters, a new synthetic approach has been proposed, by which the weakly coordinating ligands NO3- in a Ag20 thiolate cluster precursor can be substituted by carboxylic ligands while keeping its inner core intact. By rational design, novel atom-precise carboxylic or amino acid protected 20-core Ag(I)-thiolate clusters have been demonstrated for the first time. The fluorescence and electrochemical activity of the post-modified Ag20 clusters can be modulated by alrestatin or ferrocenecarboxylic acid substitution. More strikingly, when chiral amino acids were used as postmodified ligands, CD-activity was observed for the Ag20 clusters, unveiling an efficient way to obtain atom-precise chiral silver(I) clusters. [ABSTRACT FROM AUTHOR]

Abstract: Colloidal coordination compounds in the sub‐micrometer range were synthesized from a chloro gold(I) carbene complex via the anti‐solvent procedure and stabilized by a surfactant shell of Tween 20. This compound was successfully applied as model system to monitor heterogeneous multiphase ligand substitution reactions at the solid–liquid interface. [ABSTRACT FROM AUTHOR]

[1′-(Diphenylphosphino)ferrocenyl]methylamine ( 1 ) reacts with Ph 2 PH/(CH 2 O) x or [Ph 2 P(CH 2 OH) 2 ]Cl to give mixtures of Ph 2 PfcCH 2 NHCH 2 PPh 2 and Ph 2 PfcCH 2 N(CH 2 PPh 2 ) 2 in which the triphosphine dominates (fc = ferrocene-1,1′-diyl). To avoid unwanted two-fold phosphinomethylation, the amine group in 1 was alkylated. As expected, the reaction of the N -methyl analogue Ph 2 PfcCH 2 NHMe ( 5 ), obtained by reductive methylation of the aldehyde Ph 2 PfcCHO, with [Ph 2 P(CH 2 OH) 2 ]Cl, only led to the diphosphine Ph 2 PfcCH 2 N(Me)CH 2 PPh 2 ( 6 ). The diphosphine was structurally characterized and further reacted with [PdCl 2 (MeCN) 2 ] and [PdCl(Me)(cod)] (cod = η 2 :η 2 -cycloocta-1,5-diene), affording the respective trans -chelate complexes [PdCl(X){Ph 2 PfcCH 2 N(Me)CH 2 PPh 2 -κ 2 P , P ′}] ( 7a : X = Cl; 7b : X = Me), which were also structurally authenticated by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]