System with Potential Dual Modes of Metal–Ligand Cooperation: Highly Catalytically Active Pyridine‐Based PNNH–Ru Pincer Complexes

Metal–ligand cooperation (MLC) plays an important role in catalysis. Systems reported so far are generally based on a single mode of MLC. We report here a system with potential for MLC by both amine–amide and aromatization–dearomatization ligand transformations, based on a new class of phosphino–pyridyl ruthenium pincer complexes, bearing sec‐amine coordination. These pincer complexes are effective catalysts under unprecedented mild conditions for acceptorless dehydrogenative coupling of alcohols to esters at 35 °C and hydrogenation of esters at room temperature and 5 atm H₂. The likely actual catalyst, a novel, crystallographically characterized monoanionic de‐aromatized enamido–Ru^II complex, was obtained by deprotonation of both the N?H and the methylene proton of the N‐arm of the pincer ligand.     

Synthesis and Applications of a New Polysiloxane-Immobilized Macrocyclic Ligand System

Abstract

Insoluble porous solid, macrocyclic 22-membered ring, 1-oxa-6,9,12,15,18-pentaaza-2,22-disilacyclododocosane polysiloxane ligand system has been prepared by the reaction of a macro-silane agent with tetraethylorthosilicate. The macro-silane agent was prepared by the reaction of imino-bis(N-2-aminoethylacetamide) ligand with 3-iodopropyltrimethoxysilane in 1:3 molar ratio. The new prepared polysiloxane system exhibits variable potentials for the extraction of metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺, and Pb²⁺) from aqueous solutions. The ligand system shows high capacity to extract silver, lead, and mercury. Chemisorption of the metal ions by the ligand system at the optimum conditions was found in the order Ag ⁺ > Pb²⁺ > Hg²⁺ > Cu²⁺ > Ni²⁺ > Fe³⁺ > Co²⁺ > Cd²⁺ > Zn²⁺.     

Exploring Coordination Modes: Late Transition Metal Complexes with a Methylene‐bridged Macrocyclic Tetra‐NHC Ligand

A tetranuclear silver(I) N‐heterocyclic carbene (NHC) complex bearing a macrocyclic, exclusively methylene‐bridged, tetracarbene ligand was synthesized and employed as transmetalation agent for the synthesis of nickel(II), palladium(II), platinum(II), and gold(I) derivatives. The transition metal complexes exhibit different coordination geometries, the coinage metals being bound in a linear fashion forming molecular box‐type complexes, whereas the group 10 metals adapt an almost ideal square planar coordination geometry within the ligand's cavity, resulting in saddle‐shaped complexes. Both the Ag^I and the Au^I complexes show ligand‐induced metal–metal contacts, causing photoluminescence in the blue region for the gold complex. Distinct metal‐dependent differences of the coordination behavior between the group 10 transition metals were elucidated by low‐temperature NMR spectroscopy and DFT calculations.     

A PCP Pincer Ligand for Coordination Polymers with Versatile Chemical Reactivity: Selective Activation of CO2 Gas over CO Gas in the Solid State

A tetra(carboxylated) PCP pincer ligand has been synthesized as a building block for porous coordination polymers (PCPs). The air‐ and moisture‐stable PCP metalloligands are rigid tetratopic linkers that are geometrically akin to ligands used in the synthesis of robust metal–organic frameworks (MOFs). Here, the design principle is demonstrated by cyclometalation with Pd^IICl and subsequent use of the metalloligand to prepare a crystalline 3D MOF by direct reaction with Co^II ions and structural resolution by single crystal X‐ray diffraction. The Pd?Cl groups inside the pores are accessible to post‐synthetic modifications that facilitate chemical reactions previously unobserved in MOFs: a Pd?CH₃ activated material undergoes rapid insertion of CO₂ gas to give Pd?OC(O)CH₃ at 1 atm and 298 K. However, since the material is highly selective for the adsorption of CO₂ over CO, a Pd?N₃ modified version resists CO insertion under the same conditions.     

Large-Scale Synthesis of a Niche Olefin Metathesis Catalyst Bearing an Unsymmetrical N-Heterocyclic Carbene (NHC) Ligand and its Application in a Green Pharmaceutical Context

A large-scale synthesis of known Ru olefin metathesis catalyst VII featuring an unsymmetrical N-heterocyclic carbene (NHC) ligand with one 2,5-diisopropylphenyl (DIPP) and one thiophenylmethylene N-substituent is reported. The optimised procedure does not require column chromatography in any step and allows for preparation of up to 0.5 kg batches of the catalyst from simple precursors. The application profile of the obtained catalyst was studied in environmentally friendly dimethyl carbonate (DMC). Although VII exhibited low efficiency in cross-metathesis (CM) with electron-deficient partners, good to excellent results were noted for substrates featuring easy to isomerise C−C double bonds. This includes polyfunctional substrates of medicinal chemistry interest, such as analogues of psychoactive 5F-PB-22 and NM-2201 and two PDE5 inhibitors—Sildenafil and Vardenafil. Finally, a larger scale ring-closing metathesis (RCM) of a Vardenafil derivative was conducted in DMC, allowing for straightforward isolation of the expected product (23 g) in high yield and with low Ru contamination level (7.7 ppm).     

大环多胺配体BDBPH的设计合成及其晶体结构

用Pb(SN)₂作模板,2,6-二甲酰基对甲苯酚与二亚乙基三胺通过[2+2]缩合反应,经NaBH₄还原、脱Pb²⁺、酸化等操作,得晶体BDBPH·6HBr·4H₂O.晶体属单斜晶系,P2_1/c空间群,晶体学参数:a=1.4441(5)nm,b=1.1482(4)nm,c=1.2090(6)nm,α=90°,β=96.92°,γ=90°,V=1.9900nm³大环分子采取椅式构型,6个Br-和4个H₂O分子对称分布于大环两侧.该大环配体结构新颖,可用于多种金属配合物的研究,对进一步了解金属酶活性中心的结构及其催化作用机理具有重要价值.     

An NHC–Silyl–NHC Pincer Ligand for the Oxidative Addition of C−H,N−H,and O−H Bonds to Cobalt(I) Complexes

N‐Heterocyclic carbene based pincer ligands bearing a central silyl donor, [CSiC]⁻, have been envisioned as a class of strongly σ‐donating ligands that can be used for synthesizing electron‐rich transition‐metal complexes for the activation of inert bonds. However, this type of pincer ligand and complexes thereof have remained elusive owing to their challenging synthesis. We herein describe the first synthesis of a CSiC pincer ligand scaffold through the coupling of a silyl–NHC chelate with a benzyl–NHC chelate induced by one‐electron oxidation in the coordination sphere of a cobalt complex. The monoanionic CSiC ligand stabilizes the Co^I dinitrogen complex [(CSiC)Co(N₂)] with an unusual coordination geometry and enables the challenging oxidative addition of E−H bonds (E=C, N, O) to Co^I to form Co^III complexes. The structure and reactivity of the cobalt(I) complex are ascribed to the unique electronic properties of the CSiC pincer ligand, which provides a strong trans effect and pronounced σ‐donation.     

Intramolecular Nitrene Insertion into Saturated C−H-Bond-Mediated C−N Bond Cleavage of a Coordinated NHC Ligand

Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The Ru^III–amido intermediates have been characterized by ¹H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism.     

Synthesis and Catalytic Study of Ruthenium Carbene Catalyst Containing a Zn‐Porphyrin Ligand

A ruthenium carbene complex containing a Zn‐porphyrin ligand has been developed. The complex was characterized by ¹H NMR, IR, HRMS and elemental analysis. The catalytic activity of the ruthenium carbene complex for olefin metathesis reactions was also investigated. The complex exhibited excellent performance for both ring‐closing and cross metathesis reactions at 35°C.     

基于配合物配体策略的Cu-Cd异核配位聚合物的合成与晶体结构

利用小分子配合物[Cu(2-mpac)₂(H₂O)]•3H₂O (1)作为配合物配体, 以其两侧未配位的羰基氧原子与金属配位合成了一个Cu-Cd异核配位聚合物[Cu(2-mpac)₂(H₂O)₂Cd(H₂O)₄(NO₃)₂]_n (2) (2-mpac＝5-methyl-2-pyrazinecarboxylic acid), 并利用元素分析、红外光谱以及X射线单晶衍射法对标题化合物进行了表征. 晶体学数据: 三斜晶系, P-1空间群, a＝0.7654(7) nm, b＝0.8903(8) nm, c＝0.9745(9) nm, α＝116.116(1)°, β＝98.408(1)°, γ＝90.335(1)°, V＝0.5880(9) nm³, Z＝1, S＝1.053, 最终残差因子[I＞2σ(I)] R₁＝0.0280, wR₂＝0.0718, 对于全部数据R₁＝0.0305, wR₂＝0.0741.     

Ho(III)希夫碱大环配合物的合成、晶体结构及对DNA的切割活性

本文合成一个新的希夫碱大环配体硝酸Ho(III)配合物 [Ho(H2L)(NO3)2](NO3) (H2L表示大环配体Fig. 1),并进行了系统的物理表征. 晶体结构研究表明: 配合物晶体结构属六方晶系,P 3(1)21空间群,晶胞参数a=1.47213(7) nm,c=2.8998(3) nm,α=90°,γ=120°,V=5.4424(7) nm 3,Z=6,R＝0.0331, wR＝0.0928。中心离子Ho3+位于隔室大环配体的一侧并于希夫碱大环上的两个酚基氧原子和三个氮原子配位,两个双齿配位硝酸根分别从希夫碱大环平面的两侧与中心离子配位使中心离子形成扭曲的九配位三冠三棱柱配位构型。并通过凝胶电泳实验初步研究了该配合物对pBR322质粒DNA的切割作用。     

The Synthesis of a Bis(thiosemicarbazone) Macrocyclic Ligand and the Mn(II), Co(II), Zn(II) and 68Ga(III) Complexes

A 1,4,7,10-tetraazacyclododecane (cyclen) variant bearing two thiosemicarbazone pendant groups has been prepared. The ligand forms complexes with Mn²⁺, Co²⁺ and Zn²⁺. X-ray crystallography of the Mn²⁺, Co²⁺ and Zn²⁺ complexes showed that the ligand provides a six-coordinate environment for the metal ions. The Mn²⁺ and Zn²⁺ complexes exist in the solid state as racemic mixtures of the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,λ)/Λ(δ,δ,δ,δ) diastereomers, and the Co²⁺ complex exists as the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,δ)/Λ(δ,δ,δ,λ) diastereomers. Density functional theory calculations indicated that the relative energies of the diastereomers are within 10 kJ mol⁻¹. Magnetic susceptibility of the complexes indicated that both the Mn²⁺ and Co²⁺ ions are high spin. The ligand was radiolabelled with gallium-68, in the interest of developing new positron emission tomography imaging agents, which produced a single species in high radiochemical purity (>95%) at 90 °C for 10 min.     

Crystal Structure and Solution Behavior of a Novel Enantiopure Helical Coordination Polymer Based on Binaphthyl-bisbipyridine Ligand

An enantiopure helical coordination polymer AgPF6·(R)-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand(R)-6,6'-di[6-(2,2'-bipyridyl)]-2,2'-diethoxyl-1,1'-binaphthalene [(R)-3] and Ag+ ion.The single crystal structural analysis indicates that this polymer exhibits an infinite cylindric single-stranded M-helical structure with local Λ configuration at each tetrahedral metal center.However,the extended structure is dissociated into some oligomeric fragments in solution.The 1H NMR spectra of complex AgPF6·(R)-3 show that the ligand possesses a good C2 symmetry,and the chemical shifts of the protons depend on the concentration and temperature.In addition,there are rapid dynamic exchanges among some oligonuclear fragments in the solution of AgPF6·(R)-3.     

Ring Opening and Bidentate Coordination of Amidinate Germylenes and Silylenes on Carbonyl Dicobalt Complexes: The Importance of a Slight Difference in Ligand Volume

The reactions of [Co₂(CO)₈] with one equiv of the benzamidinate (R₂bzam) group‐14 tetrylenes [M(R₂bzam)(HMDS)] (HMDS=N(SiMe₃)₂; 1 : M=Ge, R=iPr; 2 : M=Si, R=tBu; 3 : M=Ge, R=tBu) at 20 °C led to the monosubstituted complexes [Co₂{κ¹M?M(R₂bzam)(HMDS)}(CO)₇] ( 4 : M=Ge, R=iPr; 5 : M=Si, R=tBu; 6 : M=Ge, R=tBu), which contain a terminal κ¹M–tetrylene ligand. Whereas the Co₂Si and Co₂Ge tert‐butyl derivatives 5 and 6 are stable at 20 °C, the Co₂Ge isopropyl derivative 4 evolved to the ligand‐bridged derivative [Co₂{μ‐κ²Ge,N‐Ge(iPr₂bzam)(HMDS)}(μ‐CO)(CO)₅] ( 7 ), in which the Ge atom spans the Co?Co bond and one arm of the amidinate fragment is attached to a Co atom. The mechanism of this reaction has been modeled with the help of DFT calculations, which have also demonstrated that the transformation of amidinate‐tetrylene ligands on the dicobalt framework is negligibly influenced by the nature of the group‐14 metal atom (Si or Ge) but is strongly dependent upon the volume of the amidinate N?R groups. The disubstituted derivatives [Co₂{κ¹M?M(R₂bzam)(HMDS)}₂(CO)₆] ( 8 : M=Ge, R=iPr; 9 : M=Si, R=tBu; 10 : M=Ge, R=tBu), which contain two terminal κ¹M–tetrylene ligands, have been prepared by treating [Co₂(CO)₈] with two equiv of 1 – 3 at 20 °C. The IR spectra of 8 – 10 have shown that the basicity of germylenes 1 and 3 is very high (comparable to that of trialkylphosphanes and 1,3‐diarylimidazol‐2‐ylidenes), whereas that of silylene 2 is even higher.     

The Synthesis of a New Macrocyclic Dinucleating Ligand,3,6,9,17,20,23-Hexaaza-29,30-Dihydroxy-13,27-Dimethyl-Tricyclo[23,3,1,1~(11,15)]Triaconta-1(28),11,13, 15(30),25,26-Hexaene

Thecoordinationchemistryofbinuclearmetalcomplexeshasbeenasubjectofextensiveinvestigationrelatingtothesynthesisofmodelcompoundsforthemetal-bindingsitesofmetal1oproteinsthatrequirethepresenceoftWometalcentersl.Duringthe1astdecade,anumberofsyntheticstructuraImodeIsfortheseproteinswiththeuseofseveraltypesofligandshavebeenreportedinIiterature2-4.ForIigandswithanappropriatedispositionofdonoratoms,ithasbeenpossibletoshowthepresenceofhydroxo,imidazolato,azido,andthiocyanatobridgesbetweenmetalions5.T…     

手性氮磷配体与钌的配位过程的研究—原位变温 31P核磁及分子模拟计算

用原位变温 ³¹P NMR和分子模拟研究了手性氮磷配体与金属钌的配位过程。首先确定了配体及其与金属的配合物的化学位移信号分别在δ=-13.0ppm和δ=48.2ppm。配位过程在293～343K温度范围内,相继生成四配位和五配位中间体。四配位体在 ³¹P NMR上对应于30.8ppm和-15.0ppm的两个信号;五配位中间体对应于35.1ppm和-16.5ppm的两个信号;最后在343K,产物中只有六配位的配合物存在,其信号出现在48.2ppm。为了得到各种中间体的结构,用分子模拟方法进行了结构优化计算,并比较了它们的构象能。计算结果表明,四配位中间体有两种构象,能量相差9kcal·mol^-1,它们可能同时存在于平衡状态。而五配位中间体只有一种绝对优势构象,尚有一个磷原子未参与配位。六配位的钌金属配合物的结构优化结果显示,两个氯原子分别位于PNNP原子所构成平面的两侧。其构象能为162.0kcal·mol^-1,其中键角能的贡献是112.5kcal·mol^-1,而非键静电作用是-41.4kcal·mol^-1,这表明分子内的静电吸引力对于形成完全配位产物是十分有利的,但是收敛的配体分子却承受了较大的键角张力。     

Osmium(III) and Osmium(V) Complexes Bearing a Macrocyclic Ligand: A Simple and Efficient Catalytic System for cis‐Dihydroxylation of Alkenes with Hydrogen Peroxide

A simple protocol that uses [Os^III(OH)(H₂O)(L ‐N₄Me₂)](PF₆)₂ ( 1 ; L ‐N₄Me₂=N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane) as a catalyst and H₂O₂ as a terminal oxidant for efficient cis‐1,2‐dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron‐withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46–99 %). In the catalytic reactions, the stoichiometry of alkene:H₂O₂ is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os^V(O)(OH) species ( 2 ), which is formed via the hydroperoxide adduct, an Os^III(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized.