Synthesis and Reactivity of an Anionic Diazoolefin

Bent (hetero)allenes such as carbodicarbenes and carbodiphosphoranes can act as neutral C-donor ligands, and diverse applications in coordination chemistry have been reported. N-Heterocyclic diazoolefins are heterocumulenes, which can function in a similar fashion as L-type ligands. Herein, we describe the synthesis and the reactivity of an anionic diazoolefin. This compound displays distinct reactivity compared to neutral diazoolefins, as evidenced by the preparation of diazo compounds via protonation, alkylation, or silylation. The anionic diazoolefin can be employed as an ambidentate, X-type ligand in salt metathesis reactions with metal halide complexes. Extrusion of dinitrogen was observed in a reaction with PCl(NiPr₂)₂, resulting in a stable phosphinocarbene.     

Hydrothermal Synthesis of Two Mixed‐Valence Copper Complexes with Mixed Ligands

Hydrothermal reactions of copper salts with fumaric acid, 1, 10‐phenanthroline or 2, 2‐bipyridine in basic aqueous solution gave rise to two mixed‐valence copper complexes [Cu₄(ophen)₄(fum)] ( 1 ) and [Cu₄(obipy)₄(fum)]·6H₂O ( 2 ) (fum = fumarate dianion, Hophen = 2‐hydroxy‐1, 10‐phenanthroline and Hobpy = 6‐hydroxy‐2, 2′‐bipyridine), which were characterized by single crystal X‐ray analysis. [Cu₄(ophen)₄(fum)] (1) crystallizes in the monoclinic space group P2₁/n, with a = 10.4749(8), b = 13.4210(9), c = 15.1090(10)Å, β = 103.811(3)° Z = 2; [Cu₄(obipy)₄(fum)]·6H₂O ( 2 ) has the triclinic space group P1¯, with a = 10.1302(11), b = 10.4406(12), c = 11.4450(13)Å, α = 84.384(2)°, β = 79.064(2)°, g = 67.734(2)° and Z = 1. The fumaric acid ligand acts as a multi‐dentate bridging ligand in both compounds, 1 and 2 , to link copper atoms into dumbbell structure. During the reactions, 1, 10‐phenanthroline and 2, 2′‐bipyridine ligands are all hydroxylated into ophen and obipy, which provide useful structural evidence for the study on the Gillard mechanism.     

Chemoselective Caging of Carboxyl Groups for On-Demand Protein Activation with Small Molecules

Tools for on-demand protein activation enable impactful gain-of-function studies in biological settings. Thus far, however, proteins have been chemically caged at primarily Lys, Tyr, and Sec, typically through the genetic encoding of unnatural amino acids. Herein, we report that the preferential reactivity of diazo compounds with protonated acids can be used to expand this toolbox to solvent-accessible carboxyl groups with an elevated pK_a value. As a model protein, we employed lysozyme (Lyz), which has an active-site Glu35 residue with a pK_a value of 6.2. A diazo compound with a bioorthogonal self-immolative handle esterified Glu35 selectively, inactivating Lyz. The hydrolytic activity of the caged Lyz on bacterial cell walls was restored with two small-molecule triggers. The decaging was more efficient by small molecules than by esterases. This simple chemical strategy was also applied to a hemeprotein and an aspartyl protease, setting the stage for broad applicability.     

Copper(I) Complexes of Anionic Tridentate CNC Pincer Ligands

New monoanionic CNC pincer ligands, [N{SiMe₂CH₂(RIm)}₂]^– (R = tBu, iPr, Ph) featuring three different N-heterocyclic carbenes and a disilylamido moiety is reported. Treatment of the lithium salt of [N{SiMe₂CH₂(RIm)}₂]^– with Cu^IOTf afforded the corresponding copper complexes [N{SiMe₂CH₂(RIm)}₂]Cu in 41–56 % yield. X-ray crystal structures of [N{SiMe₂CH₂(RIm)}₂]Cu show that they are monomeric and feature three-coordinate, pseudo T-shaped copper(I) sites. The X-ray crystal structure of one of the precursor lithium complexes, [N{SiMe₂CH₂(tBuIm)}₂]Li is also presented.     

New Energetic Copper(II) Complexes With Pyrazolyl Type Ligands

Nine Cu^II complexes ( I – IX ) containing the azide ion and bis‐2,6‐(pyrazol‐1‐yl)pyridine (pp), bis‐2,6‐(pyrazol‐1‐yl)pyridine (dmpp), and 2‐(pyrazol‐1‐yl)‐6‐(3,5‐dimethylpyrazol‐1‐yl)pyridine (mpp), which are derivatives of pyrazolylpyridine, were prepared in nonaqueous medium. These complexes were characterized by elemental analyses and IR spectroscopy. Crystals of one of these complexes [CumppClN₃ ( VII )] were prepared in suitable size, and a molecular structure of this complex was obtained with X‐ray diffraction method. Complexes were examined by thermogravimetry and differential scanning calorimetry methods. Thermal decomposition was observed in complexes including two azide groups similar to that seen in explosives. In the complexes containing one azide group, formation of the Cu^I complexes was observed after thermal decomposition of the azide group.     

Novel Copper(I) Complexes and Clusters with Phosphorus-Sulfur and Sulfur-Sulfur Containing Ligands

Abstract

The synthesis and coordination chemistry of ligands bearing PS donor groups in complexes with copper(I) halides, in particular thiophosphites, thiophosphonites, and thiophosphinites, are described.     

First Copper(I) and Silver(I) Complexes Containing Phosphanylphosphido Ligands

Three new complexes with phosphanylphosphido ligands, [Cu₄{μ₂‐P(SiMe₃)‐PtBu}₄] ( 1 ), [Ag₄{μ₂‐P(SiMe₃)‐PtBu₂}₄] ( 2 ) and [Cu{η¹‐P(SiMe₃)‐PiPr₂}₂]^–[Li(Diglyme)₂]⁺ ( 3 ) were synthesized and structurally characterized by X‐ray diffraction, NMR spectroscopy, and elemental analysis. Complexes 1 and 2 were obtained in the reactions of lithium derivative of diphosphane tBu₂P‐P(SiMe₃)Li · 2.7THF with CuCl and [iBu₃PAgCl]₄, respectively. The X‐ray diffraction analysis revealed that the complexes 1 and 2 present macrocyclic, tetrameric form with Cu₄P₄ and Ag₄P₄ core. Complex 3 was prepared in the reaction of CuCl with a different derivative of lithiated diphosphane iPr₂P‐P(SiMe₃)Li · 2(Diglyme). Surprisingly, the X‐ray analysis of 3 revealed that in this reaction instead of the tetramer the monomeric form, ionic complex [Cu{η¹‐P(SiMe₃)‐PiPr₂}₂]^–[Li(Diglyme)₂]⁺ was formed.     

Characterization of Two New Copper(II) Complexes with Saccharinate and Benzimidazole as Ligands

The crystal structure of the complexes [Cu(sac)₂(bzim)₂(H₂O)] ( 1 ) and [Cu(sac)₂(bzim)(H₂O)(EtOH)] · 2 EtOH ( 2 ) (sac = saccharinate anion; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X‐ray diffractometry. Complex 1 crystallizes in the monoclinic C2/c space group with Z = 8 whereas complex 2 belongs to the triclinic P1 space group with Z = 2. Room temperature magnetic susceptibilities as well as electronic and IR spectra of both complexes were discussed. Their thermal behaviour was investigated by means of TG and DTA methods.     

Insertion of (Bioactive) Equatorial Ligands into Platinum(IV) Complexes

Platinum(IV) prodrugs are highly interesting alternatives to platinum(II) anticancer therapeutics due to their increased tumor selectivity and reduced side effects. In contrast to the established theory, we recently observed that the equatorial ligand(s) of e.g. oxaliplatin(IV) complexes can be hydrolyzed with formation of [(DACH)Pt(OH_eq)₂(OAc_ax)₂]. In the work presented here, we investigated the reactivity and synthetic usability of this complex to be exploited as a precursor for the development of novel platinum(IV) complexes, not able to be synthesized by conventional protocols. Indeed, we could substitute the equatorial hydroxido ligand(s) e.g. by one or two monodentate biotin ligands (which would be oxidized under standard methods). The formed complexes turned out to be very stable with slow ligand release after reduction, ideal for long-circulating tumor-targeting strategies. Therefore, two platinum(IV) complexes with equatorial maleimides, capable of exploiting serum albumin as a natural nanocarrier, were synthesized as well. The complexes showed massively prolonged plasma half-life and distinctly improved anticancer activity in vivo compared to oxaliplatin. Taken together, the newly developed synthetic platform allows the simple and specific insertion of equatorial ligands into platinum(IV) complexes. This will enable the attachment of three different (bioactive) moieties generating targeted triple-action platinum(IV) prodrugs within one single platinum complex.     

Copper(II) Complexes with Asymmetrical Schiff Base Ligands Derived from 2‐Acetylpyrazine

New copper(II) complexes of asymmetrical tetradentate Schiff bases containing pyrazine have been prepared and thoroughly characterised by elemental analysis, IR and electronic spectroscopy, mass spectrometry and magnetic measurements. Two alternative methods were used in the isolation of the complexes: template synthesis in the preparation of Cu(SalDpyz)ClO₄ (HSalDPyz = derived from the condensation of salicylaldehyde, acetylpyrazine and 1,2‐ethylendiamine, 2‐methyl‐1,2‐propylendiamine, 1,2‐phenylendiamine) and direct interaction between copper perchlorate and the corresponding Schiff base, as in the isolation of Cu(AEPyz)(ClO₄) (HAEPyz = (Z)‐4‐[2‐{[2‐{[(E)‐1‐(pyrazinyl)ethylidene]amino} ethyl)amino]‐3‐penten‐2‐one)]. [Cu(SalEn)(py)(OClO₃)][Cu(SalEn)(py)]ClO₄ ( 1 ) (SalEn = 4‐(2‐hydroxyphenyl)‐3‐aza‐3‐buten‐1‐amino, py = pyridine), metal precursor in the preparation of Cu(SalEnpyz)(ClO₄) (HSalEnpyz = 2‐{E(2‐{[(E)‐1‐(2‐pyrazinyl)ethylidene]amino}ethyl)imino]methyl}phenol), was crystallographically characterised. The crystal structure of [Cu(AEpyz)]ClO₄ ( 2 ) is also reported.     

Syntheses and Crystal Structures of Two One-Dimensional Chain Copper Benzoylacetone Complexes Bridged Through Azobispyridine Ligands

Two copper complexes [Cu(bzac)₂(4,4′-azpy)]·H₂O (1) and [Cu(bzac)₂(3,3′-azpy)] (2) (bzac = benzoylacetone, 4,4′-azpy = 4,4′-azobispyridine, 3,3′-azpy = 3,3′-azobispyridine) have been synthesized and characterized. The crystal structures were determined by X-ray diffraction analysis. In crystals of Complexes 1 and 2, the copper atoms have distorted octahedral symmetry. The two compounds possess very similar one-dimensional linear chains linked through the rod-like 4,4′-azpy or 3,3′-azpy ligands.     

Copper Complexes of Dicarboxy‐Functionalized Tetramethylcyclam. Crystal Structures of Complexes with the Axial Ligands Perchlorate,Chloride, and Iodide

6,13‐Dicarboxy‐1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane‐copper(II) perchlorate ( 2 a ) was synthesized via one‐step cyclocondensation from bis(N,N′‐dimethyl‐ ethylenediamine‐copper(II) perchlorate, formaldehyde and malonic acid. Anion exchange yielded the analogous copper(II) chloride ( 2 b ) and iodide ( 2 c ) complexes. Crystal structures of 2 a – 2 c show a square‐planar N₄‐co‐ordination of the copper(II) ion with RRSS configuration of the nitrogens and perchlorate, chloride or iodide ions weakly co‐ordinated axially. Relating to the macroring, the carboxy groups are in trans‐position. In 2 a , the packing is typical of parallel strands of complex subunits effected by dimerization of the carboxy groups, while in 2 b and 2 c formation of the supramolecular strands involve hydrogen bond interactions between carboxy groups and halide anions.     

Synthesis and Properties of Copper Trimesinate Complexes with Polypyridine Ligands

Russian Journal of General Chemistry - Copper trimesinate complexes Cu3(BTC)2L3 and Cu3(BTC)2L with polypyridine ligands, such as 2,2′-bipyridyl, 1,10-phenanthroline, and...     

Nitrite and Nitric Oxide Interconversion at Mononuclear Copper(II): Insight into the Role of the Red Copper Site in Denitrification

Nitrite (NO₂⁻) and nitric oxide (NO) interconversion is crucial for maintaining optimum NO flux in mammalian physiology. Herein we demonstrate that [ L ₂Cu^II(nitrite)]⁺ moieties (in 2 a and 2 b ; where, L = Me₂PzPy and Me₂PzQu ) with distorted octahedral geometry undergo facile reduction to provide tetrahedral [ L ₂Cu^I]⁺ (in 3 a and 3 b ) and NO in the presence of biologically relevant reductants, such as 4-methoxy-2,6-di-tert-butylphenol (4-MeO-2,6-DTBP, a tyrosine model) and N-benzyl-1,4-dihydronicotinamide (BNAH, a NAD(P)H model). Interestingly, the reaction of excess NO gas with [ L ₂Cu^II(MeCN)₂]²⁺ (in 1 a ) provides a putative {CuNO}¹⁰ species, which is effective in mediating the nitrosation of various nucleophiles, such as thiol and amine. Generation of the transient {CuNO}¹⁰ species in wet acetonitrile leads to NO₂⁻ as assessed by Griess assay and ¹⁴N/¹⁵N-FTIR analyses. A detailed study reveals that the bidirectional NO_x-reactivity, namely, nitrite reductase (NIR) and NO oxidase (NOO), at a common Cu^II site, is governed by the geometric-preference-driven facile Cu^II/Cu^I redox process. Of broader interest, this study not only highlights potential strategies for the design of copper-based catalysts for nitrite reduction, but also strengthens the previous postulates regarding the involvement of red copper proteins in denitrification.     

Crystal and Molecular Structures of Mononuclear Coordinated Copper(I) Complexes with Thio-triazole and Thio-triazine based Schiff base Ligands

Reaction of 4-amino-5-methyl-1,2,4-triazol-3(2H)-thione (AMTT) and 4-amino-6-methyl-3-thio-3,4-dihydro-1,2,4-triazin-5(2H)-one (AMTTO) with 2-hydroxybenzaldehyde led to the synthesis of corresponding Schiff base ligands [(Z)-4-((2-hydroxybenzylidene)amino)-3-methyl-1H-1,2,4-triazole-5(4H)-thione ( L1 ) and (Z)-4-((2-hydroxybenzylidene)amino)-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one ( L2 )]. Treatment of synthesized Schiff base ligands with CuCl provided the complexes [Cu(L1)₃Cl] ( 1 ) and [Cu(L2)₂Cl] ( 2 ). Synthesized complexes were characterized by elemental analyses, IR spectroscopy and X-ray diffraction studies. Complex 1 consists of a metal ion coordinated with one chloride ion and three Schiff base ligands via sulfur atoms in a distorted tetrahedral environment, whereas 2 consists of a metal ion coordinated with one chloride ion and two sulfur atoms from two different Schiff base ligands in a trigonal planar arrangement. Crystal data for 1 at –153 °C revealed an orthorhombic space group Fdd2, a = 34.8088(7), b = 33.8156(8), c = 11.6142(2) Å, Z = 16, R₁ = 0.0357; for 2 at –178 °C the symmetry was triclinic, space group P1 , a = 7.27520(10), b = 15.4620(2), c = 23.7985(4) Å, α = 72.1964(13), β = 86.5208(12), γ = 89.8597(11)°, Z = 4, R₁ = 0.0359.     

Cis‐trans Isomerism in Copper(II) Complexes with N‐acyl Thiourea Ligands

The N‐acyl thiourea complexes bis[N,N‐diethyl‐N′‐(p‐nitrobenzoyl)‐thioureato]copper(II) ( 1a,1b ) and bis(N,N‐diphenyl‐N′‐benzoylthioureato)copper(II) ( 2a,2b ) crystallize in each case in two modifications. X‐ray structural analysis shows that 1a and 1b are cis‐trans isomers. This is very unusual for N‐acyl thioureato complexes because with exception of one platinum(II) complex up to now only cis complexes have been found. In contrast X‐ray structural analysis of both forms 2a and 2b of the other complex shows no cis‐trans pair. Both modifications are cis complexes. In solution both isomers of the copper(II) complexes are observable by EPR spectroscopy.     

Transition Metal Complexes with Organoazide Ligands: Synthesis,Structural Chemistry,and Reactivity

A drastically enhanced stability is observed for organoazides (RN₃) in the presence of Cu²⁺ or Pd²⁺ when the azido group is included in a ligand system chelating the transition metal ions. X-ray structure analysis of such complexes (the structure of a cyclohexaneazide palladium complex is depicted) confirms that the alkylated nitrogen atom of the N₃ moiety is coordinated to the transition metal center.     

Copper (I)-BOX Catalyzed Asymmetric 3-Component Reaction for the Synthesis of Trifluoromethylated Propargylic Ethers and Anilines**

An asymmetric 3-component reaction between EthynylBenziodoXoles (EBXs), 2,2,2-trifluorodiazoethane and nucleophiles catalyzed by a Cu^I-BOX (Bisoxazoline) catalyst is described. This protocol gives access to chiral trifluoromethylated propargyl ethers and anilines, which are valuable building blocks in synthetic and medicinal chemistry. The reaction proceeds with high enantioselectivity and yield with different nucleophiles such as primary, secondary and tertiary alcohols, as well as both electron-rich and electron-poor anilines. Aryl-, alkyl- and silyl-substituted alkynes can be successfully introduced as electrophiles. In case of chiral substrates, high catalyst control was observed, leading to good diastereoselectivity.     

基于含有硫醚基团的吡啶烷基酰胺配体的铜配合物的合成和结构表征

合成和表征了含有硫醚基团的吡啶烷基酰胺配体2-(甲硫基)-N-[2-(2-吡啶)甲基]乙酰胺(HL1)和2-(甲硫基)-N-[2-(2-吡啶)乙基]乙酰胺(HL2)及其3个铜的配合物,{[Cu(L1)(CH₃OH)](OTf)}_n(1)(Otf=三氟甲磺酸根),{[Cu(L2)(OTf)]·CH₃OH}_n(2)和[Cu(HL2)(CH₃OH)Cl](3),并通过X-射线单晶衍射分析确定了其晶体结构。配合物1和2均为含有铜的一维配位聚合物,而配合物3为单核铜配合物。分析了配合物中铜离子的配位特点及可能的形成原因。     

Syntheses,Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

The complexes [Cu(L¹)(H₂O)₂](BF₄)₂ · 2H₂O ( 1 ) [L¹ = 5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] and 0.5[Cu(L²)(NO₃)₂][Cu(L²)](NO₃)₂ ( 2 ) [L² = dibenzyl‐5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] were synthesized and characterized by single crystal X‐ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans‐III conformation. The Cu–N distances [1.999(7)–2.095(7) Å] are typical for such complexes, but the axial ligands are weakly coordinating Cu–OH₂ bonds [2.693(3) Å] and Cu–ONO₂ bonds [2.873(7) Å] due to the combination of the pseudo Jahn–Teller effect and strong in‐plane ligand field. The crystals are stabilized by a three‐dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF₄^–, and oxygen atoms of NO₃^–. The electronic absorption and IR spectroscopic properties are also discussed.