Synthesis,pyrolytic and bioassay studies of complexes Ni(II), Cu(II) and Zn(II) bromides with a chelating ligand of N,N donor sites

Coordination complexes of modified hydrazine are prepared with Ni(II), Cu(II), and Zn(II) metal ions. The ligand is synthesized by removing the methoxy moiety of methyl anthranilate with nitrogen of hydrazine hydrate, creating new coordination site. The coordination complexes are synthesized by reacting the ABH ligand with dehydrated M(II) [Cu²⁺, Zn²⁺ and Ni²⁺] bromide in an inert environment. The structures of the coordination complexes are elucidated basing on the physical measurements including elemental analysis, NMR, IR, UV–Vis spectra, magnetic and conductance measurements. These results reflect the M(ABH)Br₂ composition of the corresponding complexes. Thermal studies show the Irving William trend for the stability of complexes. Antibacterial activities and antifungal studies are also carried out in order to investigate the biological activity upon complexation.     

A Tris(3-pyridyl)stannane as a Building Block for Heterobimetallic Coordination Polymers and Supramolecular Cages

The systematic assembly of supramolecular arrangements is a persistent challenge in modern coordination chemistry, especially where further aspects of complexity are concerned, as in the case of large molecular mixed-metal arrangements. One targeted approach to such heterometallic complexes is to engineer metal-based donor ligands of the correct geometry to build 3D arrangements upon coordination to other metals. This simple idea has, however, only rarely been applied to main group metal-based ligand systems. Here, we show that the new, bench-stable tris(3-pyridyl)stannane ligand PhSn(3-Py)₃ (3-Py=3-pyridyl) provides simple access to a range of heterometallic Sn^IV/transition metal complexes, and that the presence of weakly coordinating counter anions can be used to build discrete molecular arrangements involving anion encapsulation. This work therefore provides a building strategy in this area, which parallels that of supramolecular transition metal chemistry.     

Metal–Organic Coordination Strategy for Obtaining Metal-Decorated Mo-Based Complexes: Multi-dimensional Structural Evolution and High-Rate Lithium-Ion Battery Applications

Multi-dimensional metal oxides have attracted great attention in diverse applications due to their intriguing performances. However, their structural design remains challenging, particularly that based on organic chelation chemistry. Although metal–organic complexes with different architectures have been reported, their structure formation mechanisms are not well understood because of the complex chelation processes. Herein, we introduce a new metal–organic coordination strategy to construct metal-decorated (Ni, Co, Mn) Mo-based complexes ranging from 2D nanopetals to 3D microflowers. The chelating process of the metal–organic complex can be tuned by a surfactant, giving rise to different structures, and then a further metal can be appended. Thus, different metal (oxide)-decorated MoO₂/C-N structures were designed, enabling an extremely high lithium storage capability of 1018 mA h g⁻¹ and rate capacities of up to 10 A g⁻¹ over 1000 cycles. Relationships between electrochemical behavior and structure have been analyzed kinetically. A high-rate lithium-ion battery has been assembled from Ni-MoO₂/C-N and an Ni-rich layered oxide as the anode and cathode, respectively. We believe that this general metal–organic coordination strategy should be applicable to other multi-functional materials with superior capabilities.     

The Metaphosphite (PO2−) Anion as a Ligand

The utilization of monomeric, lower phosphorous oxides and oxoanions, such as metaphosphite (PO₂⁻), which is the heavier homologue of the common nitrite anion but previously only observed in the gas phase and by matrix isolation, requires new synthetic strategies. Herein, a series of rhenium(I–III) complexes with PO₂⁻ as ligand is reported. Synthetic access was enabled by selective oxygenation of a terminal phosphide complex. Spectroscopic and computational examination revealed slightly stronger σ-donor and comparable π-acceptor properties of PO₂⁻ compared to homologous NO₂⁻, which is one of the archetypal ligands in coordination chemistry.     

Iron(III) chloride and its coordination chemistry

Abstract

The coordination chemistry of FeCl₃ is distinctly different to that of the other 3d metal halides. It has a distinct preference for O-donor ligands. Although it primarily forms six-coordinate complexes, it has some distinctive features that set it apart from metals like Mn(II), Co(II), and Ni(II), such as the self-ionized complexes [FeL₄Cl₂]⁺ [FeCl₄]^?. There are a number of examples where very small changes in the coordination sphere tilt the balance between isomeric structures. Chloride has a significant steric effect in the coordination sphere as well as a greater trans-influence than water.     

Sterically and Electronically Flexible Pyridylidene Amine Dinitrogen Ligands at Palladium: Hemilabile cis/trans Coordination and Application in Dehydrogenation Catalysis

Ligand design is crucial for the development of new catalysts and materials with new properties. Herein, the synthesis and unique hemilabile coordination properties of new bis-pyridylidene amine (bis-PYE) ligands to palladium, and preliminary catalytic activity of these complexes in formic acid dehydrogenation are described. The synthetic pathway to form cationic complexes [Pd(bis-PYE)Cl(L)]X with a cis-coordinated N,N-bidentate bis-PYE ligand is flexible and provides access to a diversity of Pd^II complexes with different ancillary ligands (L=pyridine, DMAP, PPh₃, Cl, P(OMe)₃). The ¹H NMR chemical shift of the trans-positioned PYE N−CH₃ unit is identified as a convenient and diagnostic handle to probe the donor properties of these ancillary ligands and demonstrates the electronic flexibility of the PYE ligand sites. In the presence of a base, the originally cis-coordinated bis-PYE ligand adopts a N,N,N-tridentate coordination mode with the two PYE units in mutual trans position. This cis–trans isomerization is reverted in presence of an acid, demonstrating a unique structural and steric flexibility of the bis-PYE ligand at palladium in addition to its electronic adaptability. The palladium complexes are active in formic acid dehydrogenation to H₂ and CO₂. The catalytic performance is directly dependent on the ligand bonding mode, the nature of the ancillary ligand, the counteranion, and additives. The most active system features a bidentate bis-PYE ligand, PPh₃ as ancillary ligand and accomplishes turnover frequencies up to 525 h⁻¹ in the first hour and turnover numbers of nearly 1000, which is the highest activity reported for palladium-based catalysts to date.     

Expanding the Chemistry of Cationic N‐Heterocyclic Carbenes: Alternative Synthesis,Reactivity, and Coordination Chemistry

A new synthetic route to complexes of the cationic N‐heterocyclic carbene ligand 2 has been developed by the attachment of a cationic pentamethylcyclopentadienylruthenium ([RuCp*]⁺) fragment to a metal‐coordinated benzimidazol‐2‐ylidene ligand. The coordination chemistry and the steric and electronic properties of the cationic carbene were investigated in detail by experimental and theoretical methods. X‐ray structures of three carbene–metal complexes were determined. The cationic ligand 2 is a poorer overall electron donor relative to the related neutral carbene, which is evident from cyclic voltammetry (CV) and IR measurements.     

The preparation of multimetallic complexes using sterically bulky N-centred tripodal dialkyl phosphino ligands

Sterically bulky monodentate and bidentate phosphines have been widely used as ligands for metal complexation and catalyst formation. Bulky tridentate phosphine ligands are however much rarer and have not been widely investigated even though they may be considered attractive ligands for coordination chemistry studies and catalysis. Here we report the synthesis of two new N-centred tripodal phosphine ligands bearing bulky cyclohexyl and tert-butyl groups. The coordination chemistry of the cyclohexyl triphosphine ligand N(CH₂PCy₂)₃ (4) was investigated and found to react with Mo and W hexacarbonyls preferentially forming bidentate metal tetracarbonyl complexes [Mo(CO)₄{N(CH₂PCy₂)₃-κ²P}] (6) and [W(CO)₄{N(CH₂PCy₂)₃-κ²P}] (7) over the expected facial capping tridentate complexes. The steric bulk of the cyclohexyl groups on the phosphorus atoms is sufficient to prevent the third arm of the ligand from coordinating and adopting the required geometry for facial coordination. This ‘steric control’ at the metal centre results in the third arm remaining freely available for further metal coordination. The coordination chemistry of this free phosphine arm on complexes 6 and 7 was investigated further and used to prepare a series of gold, platinum and silver multimetallic complexes. The X-ray crystal structures of the resulting mixed bi and trimetallic complexes [W(CO)₄{N(CH₂PCy₂)₃-κ²P}AuCl] (8), [[Mo(CO)₄{N(CH₂PCy₂)₃-κ²P}]₂(μ-PtCl₂)] (9) and [[W(CO)₄{N(CH₂PCy₂)₃-κ²P}]₂(μ-Ag)]ClO₄ (11) are reported.     

Tuning the Excited State of Water‐Soluble IrIII‐Based DNA Intercalators that are Isostructural with [RuII(NN)2(dppz)] Light‐Switch Complexes

The synthesis of two new Ir^III complexes which are effectively isostructural with well‐established [Ru(NN)₂(dppz)]²⁺ systems is reported (dppz=dipyridophenazine; NN=2,2′‐bipyridyl, or 1,10‐phenanthroline). One of these Ir^III complexes is tricationic and has a conventional N₆ coordination sphere. The second dicationic complex has a N₅C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their Ru^II analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)‐based systems and are comparable with Ru^II(dppz) analogues.     

Microwave synthesis,spectral studies,antimicrobial approach,and coordination behavior of antimony(III) and bismuth(III) compounds with benzothiazoline

The reaction of 2-hydroxy-N-phenylbenzamide with 2-aminobenzenethiol yielded 2-hydroxy-N-phenylbenzamidebenzothiazoline (H₂-Saly · BTZ/HO⋂N⋂SH). The reaction of H₂-Saly · BTZ with PhSbCl₂, SbCl₃, and BiCl₃ under varied reaction conditions (microwave, as well as conventional method) gave corresponding antimony( III) and bismuth(III) Schiff base compounds (substitution along with addition) in different coordination environments. These complexes were characterized by elemental analysis, IR and NMR (¹H and ¹³C) spectral studies. The ligand was found to bifunctional tridentate, as well as monodentate for different starting materials of metal (Sb/Bi), as well as for different reaction conditions, hence, suitable coordination environments and pseudotrigonal bipyramidal geometry for the antimony and bismuth complexes have been proposed. Their biological activities have also been checked against many fungi and bacteria. The complexes were found to be more toxic than the corresponding ligand. The article is published in the original. The article is published in the original.     

Divergent Coordination Chemistry: Parallel Synthesis of [2×2] Iron(II) Grid‐Complex Tauto‐Conformers

The coordination of iron(II) ions by a homoditopic ligand L with two tridentate chelates leads to the tautomerism‐driven emergence of complexity, with isomeric tetramers and trimers as the coordination products. The structures of the two dominant [Fe^II₄ L ₄]⁸⁺ complexes were determined by X‐ray diffraction, and the distinctness of the products was confirmed by ion‐mobility mass spectrometry. Moreover, these two isomers display contrasting magnetic properties (Fe^II spin crossover vs. a blocked Fe^II high‐spin state). These results demonstrate how the coordination of a metal ion to a ligand that can undergo tautomerization can increase, at a higher hierarchical level, complexity, here expressed by the formation of isomeric molecular assemblies with distinct physical properties. Such results are of importance for improving our understanding of the emergence of complexity in chemistry and biology.     

Platinum (II) N‐heterocyclic carbene complexes: Synthesis,characterization and cytotoxic properties

Platinum (II) complexes bearing N‐heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of this type of complexes. A series of [PtCl₂(NHC)(PEt₃)] complexes were synthesized. The structures of all compounds were characterized by ¹H‐NMR, ¹³C‐NMR, IR and elemental analysis techniques, which supported the proposed structures. The single crystal structures of complexes 1a and 1e were determined. The title complexes show slightly distorted square‐planar coordination around the platinum (II) metal center. The cytotoxic properties of the platinum (II)–NHC complexes have been assessed in various human cancer lines, including cisplatin‐sensitive and resistant cells. IC₅₀ values of these four complexes were determined by the MTS‐based assay on three human cell lines—brain (SHSY5Y), colon (HTC116) and liver (HEP3B). These complexes have been highlighted cancer therapeutic agent with unique structures and functions.     

3‐(Arylhydrazono)pentane‐2, 4‐diones and their Complexes with Copper(II) and Nickel(II) — Synthesis and Crystal Structures

A series of new 3‐(arylhydrazono)pentane‐2, 4‐diones ( 1 ‐ 6 ) synthesized from pentane‐2, 4‐dione and diazonium salts of respective anilines using the procedure of Japp‐Klingemann are described. Complexes with Cu^II and Ni^II salts are prepared ( 7 ‐ 10 , respectively). Spectroscopic properties of these compounds have been studied and X‐ray crystal structures of selected hydrazones ( 3 , 4 , 6 ) and of the hydrazone complexes ( 7 ‐ 10 ) are reported. The structures of the uncomplexed hydrazones feature an intramolecular N‐H···O interaction to yield a six‐membered H‐bond ring reflecting preference of the hydrazone tautomeric structure. All the complexes are mononuclear 2:1 (L:M) structures of six‐membered chelate type involving N₂O₂ binding sites that are quadratic arranged but differ in the entire coordination environment dependent on the metal and the ligand substitution including distorted octahedral and quadratic pyramidal coordination geometries in the Cu^II complexes 7 and 8 or nearly regular square planar coordination geometry in the Ni^II complexes 9 and 10 , respectively. In the crystal packings, strong and weak H‐bond interactions cause supramolecular network structures.     

Fulleride-metal η5 sandwich and multi-decker sandwich complexes: A DFT prediction

The (C₆₀CN)⁻ formed by the reaction of CN⁻ with fullerene shows high electron rich character, very similar to C₆₀˙⁻, and it behaves as a large anion. Similar to Cp⁻, the bulky anion, (C₆₀CN)⁻, acts as a strong η⁵ ligand towards transition metal centers. Previous studies on η⁵ coordination of fullerene cage are reported for pseudo fullerenes whereas the present study deals with sandwich complexes of (C₆₀CN)⁻ with Fe(II), Ru(II), Cr(II), Mo(II), and Ni(II) and multi-decker sandwich complexes of CN–fullerides with Fe(II). The structural parameters of these complexes and the corresponding Cp⁻ complexes showed very close resemblance. Analysis of the metal-to-carbon bonding molecular orbitals showed that sandwich complex [Fe(η⁵-(C₆₀CN)⁻)₂] exhibit bonding features very similar to that of ferrocene. Also, a 6-fold decrease in the band gap energy is observed for [Fe(η⁵-(C₆₀CN)⁻)₂] compared to ferrocene. The energy of dissociation (ΔE) of the ligand (C₆₀CN)⁻ from [Fe(η⁵-(C₆₀CN)⁻)₂] is slightly lower than the ΔE of a Cp* ligand from a ferrocene derivative wherein each cyclopentadienyl unit is substituted with four tertiary butyl groups. The (C₆₀CN)⁻ ligand behaved as one of the bulkiest ligands in the chemistry of sandwich complexes. Further, the coordinating ability of the dianion, (C₆₀(CN)₂)²⁻ is evaluated which showed strong coordination ability simultaneously with two metal centers leading to the formation of multi-decker sandwich and pearl-necklace type polymeric structures.     

Effect of bridging anions on the structure and stability of phenoxide bridged zinc dipicolylamine coordination complexes

A series of four related phenol derivatives, with 2,2′-dipicolylamine substituents at the ortho positions, were prepared and their Zn²⁺ coordination complexes studied by spectroscopic methods. X-ray crystal diffraction analysis of a dinuclear zinc complex with two bridging acetate anions showed a ternary structure with highly charged interior and lipophilic exterior, which helps explain why this class of water-soluble complexes can effectively diffuse through cell membranes. The stability of the dinuclear zinc complexes in aqueous solution was found to be strongly anion dependent; that is, bridging oxyanions, such as acetate and pyrophosphate, lock the two Zn²⁺ cations to the surrounding ligand and greatly enhance ligand/zinc affinity. Overall, the results provide new insight into the structural and mechanistic factors that control the recognition and chemosensing performance of phenoxide bridged dipicolylamine molecular probes.     

Chemistry of Stannylene‐Based Lewis Pairs: Dynamic Tin Coordination Switching Between Donor and Acceptor Character

The coordination chemistry of cyclic stannylene‐based intramolecular Lewis pairs is presented. The P→Sn adducts were treated with [Ni(COD)₂] and [Pd(PCy₃)₂] (COD=1,5‐cyclooctadiene, PCy₃=tricyclohexylphosphine). In the isolated coordination compounds the stannylene moiety acts either as an acceptor or a donor ligand. Examples of a dynamic switch between these two coordination modes of the P?Sn ligand are illustrated and the structures in the solid state together with heteronuclear NMR spectroscopic findings are discussed. In the case of a Ni⁰ complex, ¹¹⁹Sn Mössbauer spectroscopy of the uncoordinated and coordinated phosphastannirane ligand is presented.     

Synthesis, spectroscopic, and thermal studies of some Hg(II) and Cd(II) coordination compounds of N,N-bis[(E)-3-(phenylprop)-2-enylidene]propanediamine

Some new coordination compounds of cadmium(II) and mercury(II) with N,N-bis[(E)-3-(phenylprop)-2-enylidene]propanediamine (L) as a new bidentate Schiff base ligand with general formula MLX₂ (X = Cl^?, Br^?, I^?, SCN^?, and N₃ ^?) have been prepared. They were characterized by elemental analysis, FT-infrared (FT-IR) and Ultraviolet–Visible spectra, ¹H- and ¹³C-NMR spectra. The reasonable shifts of FT-IR and NMR spectral signals of the complexes with respect to the free ligand confirm well coordination of ligand and anions(X-) in inner sphere coordination mode. The thermal behavior of the complexes from room temperature to 800 °C shows weight loss by decomposition of the anions and ligand segments in the subsequent steps. The results showed that cadmium complexes have no water molecules (neither as lattice nor as coordinated water) and are decomposed in two temperature steps except about cadmium thiocyanate complex that is decomposed in three steps. Final residual contents of cadmium complexes are suggested to be cadmium oxide or sulfide. Mercury complexes were decomposed in three to four temperature steps. Mercury bromide and azide complexes leave out a little amount of mercury oxide in final, while mercury chloride, iodide, and thiocyanate complexes were found to be completely decomposed without any residual matter.     

A New Sulfur‐containing Schiff‐Base Ligand and Binding to Copper(II) and Cobalt(II)

A new Schiff‐base ligand having a potentially coordinating thioether group (2‐quinoline‐N‐(2′‐methylthiophenyl)methyleneimine, qmtpm ) has been prepared. The synthesis, structure, UV‐Vis and EPR studies of one copper(II) and two cobalt(II) complexes from this ligand is reported. The X‐ray structures of the Cu^II and Co^II chlorido complexes 1 and 2 reveal the metal atoms in highly distorted square‐pyramidal environments constituted of one tridentate ligand and two anions. On the other hand, the thiocyanato Co^II compound 3 exhibits a distorted trigonal‐bipyramidal structure. These structural variations are apparently due to the different counter‐ions which leads to distinct lattice interactions. The spectroscopic data obtained by EPR and UV‐Vis investigations are in agreement with the solid‐state structures of the coordination compounds.     

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

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