Hydrolytic ring opening reactions of anhydrides for first row transition metal dicarboxylate complexes

Ring opening reactions of 2,3-pyridine dicarboxylic anhydride are studied with hydrated salts of cobalt, nickel and zinc. The hydrated metal salts preferentially hydrolyze 2,3-pyridine dicarboxylic anhydride rather than causing esterification in methanol medium. Hydrolytic opening of 2,3-pyridine dicarboxylic anhydride by hydrated cobalt(II) acetate and nickel(II) acetate resulted in the corresponding chelate complexes of monodeprotonated 2,3-pyridine dicarboxylic acid. The reaction of copper acetate with pyromellitic dianhydride in the presence of 1,10-phenanthroline gives a dinuclear copper complex whereas a similar reaction with copper(II) chloride gives a mononuclear copper complex.     

Cobaltocenium Carboxylate Transition Metal Complexes: Synthesis,Structure, Reactivity,and Cytotoxicity

Cobaltocenium carboxylate is an unusual betaine that functions as a formally neutral carboxylate ligand with late transition metal centers comprising Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Rh⁺. Structurally, a rich coordination chemistry is observed – from simple monomeric homoleptic complexes to heteroleptic dimeric, trimeric, and polymeric compounds, as shown by X‐ray diffraction of 11 compounds. Chemically, thermal decarboxylation was investigated aiming at the formation of cobaltocenium‐carbene transition metal complexes, in analogy to such chemistry of imidazolium carboxylate betaines. Cytotoxicity studies of cobaltocenium carboxylate transition metal complexes were performed to evaluate the medicinal bioorganometallic potential of these compounds. While cobaltocenium carboxylate was inactive, its complexes with Ag⁺, Cd²⁺, and Hg²⁺ triggered significant cytotoxic effects.     

Electrocyclic Ring Opening Reactions of Ethylene Oxides

Substituents capable of stabilizing negative charge endow ethylene oxides with the ability to undergo electrocyclic ring opening at the CC bond; heating or irradiation generates small equilibrium concentrations of carbonyl ylides which can engage in 1,3-dipolar cycloadditions. Apart from the normal conrotatory mode of ring opening, predicted by the Woodward-Hoffmann rules, the disrotatory process, forbidden by orbital symmetry, also appears to occur in the case of α-cyano-cis-stilbene oxide. Kinetic studies on α-cyano-trans -and -cis-stilbene oxide permit construction of the energy profile for electrocyclic ring opening to give the stereoisomeric carbonyl ylides and for their recyclization and rotation.     

Synthesis and Structural Characterization of Divalent Transition Metal Alkynylamidinate Complexes

A series of new alkynylamidinate complexes of selected first and second row transition metals has been synthesized and fully characterized. Treatment of MCl₂ precursors (M=Mn, Fe, Co) with 2 equiv. of the lithium alkynylamidinates Li[c-C₃H₅−C≡C−C(NR′)₂] ⋅ THF (R′=ⁱPr (2), Cy (cyclohexyl) ( 2 )) afforded a series of binuclear complexes of the type M₂[c-C₃H₅−C≡C−C(NR)₂-κN:κN′]₂[c-C₃H₅−C≡C−C(NR)₂-κ²N,N′]₂ ( 3 : M=Mn, R=Cy; 4 a : M=Fe, R=ⁱPr; 4 b : M=Fe, R=Cy; 5 : M=Co, R=ⁱPr) with no significant metal-metal bonding. In marked contrast, a similar reaction of CrCl₂ with 2 equiv. of 1 afforded the homoleptic dinuclear chromium(II) complex Cr₂[c-C₃H₅−C≡C−C(NⁱPr)₂-κN:κN′]₄ ( 6 ) which supposedly comprises a Cr−Cr quadruple bond. Complex 6 could also be prepared in a more rational way and in better yield (61 %) by using dichromium(II) tetraacetate, Cr₂(OAc)₄, as starting material. Related reactions employing dimolybdenum(II) tetraacetate, Mo₂(OAc)₄, and 2 or 3 equiv. of 1 afforded the mixed-ligand paddle wheel-type complexes trans-Mo₂(OAc-κO:κO′)₂([c-C₃H₅−C≡C−C(NⁱPr)₂-κN:κN′]₂ ( 7 ) and Mo₂(OAc-κO:κO′)([c-C₃H₅−C≡C−C(NⁱPr)₂-κN:κN′]₃ ( 8 ). All title compounds were structurally characterized through single-crystal X-ray diffraction and spectroscopic techniques (NMR, IR, Raman).     

Ring‐Opening Reactions of 3‐Aryl‐1‐benzylaziridine‐2‐carboxylates and Application to the Asymmetric Synthesis of an Amphetamine‐Type Compound

Nucleophilic ring‐opening reactions of 3‐aryl‐1‐benzylaziridine‐2‐carboxylates were examined by using O‐nucleophiles and aromatic C‐nucleophiles. The stereospecificity was found to depend on substrates and conditions used. Configuration inversion at C(3) was observed with O‐nucleophiles as a major reaction path in the ring‐opening reactions of aziridines carrying an electron‐poor aromatic moiety, whereas mixtures containing preferentially the syn‐diastereoisomer were generally obtained when electron‐rich aziridines were used (Tables 1–3). In the reactions of electron‐rich aziridines with C‐nucleophiles, S_N2 reactions yielding anti‐type products were observed (Table 4). Reductive ring‐opening reaction by catalytic hydrogenation of (+)‐trans‐(2S,3R)‐3‐(1,3‐benzodioxol‐5‐yl)aziridine‐2‐carboxylate (+)‐trans‐ 3c afforded the corresponding α‐amino acid derivative, which was smoothly transformed into (+)‐tert‐butyl [(1R)‐2‐(1,3‐benzodioxol‐5‐yl)‐1‐methylethyl]carbamate((+)‐ 14 ) with high retention of optical purity (Scheme 6).     

Electrochemical Studies of Eight New Divalent Transition Metal Benzenesulphonate Ternary Complexes with 1,10-Phenanthroline

The electrochemical properties of eight new divalent transition metal benzenesulphonate complexes with 1, 10-phenanthroline in different solvents and supporting electrolytes were investigated by means of cyclic voltammetry(CV). Based on the CV data the influences of various coordination modes on the electrochemical behavior of the complexes were discussed. The diffusion coefficient Dc and rate constant k, of those complexes in DMF systems were estimated according to CV and the results show that these processes were all quasi-reversible.     

Clamshell Opening in the Mixed‐Metal Supramolecular Aggregates Formed by Fourfold Reduced Corannulene for Maximizing Intercalated Metal Content

The first members of a new class of supramolecular organometallic compounds with mixed‐alkali‐metal cluster cores, LiK₅ and Li₃K₃, sandwiched between two four‐fold reduced corannulene decks are prepared and fully characterized. The triple‐decker supramolecular anions, [(C₂₀H₁₀^4?)(LiK₅)⁶⁺(C₂₀H₁₀^4?)]^2? and [(C₂₀H₁₀^4?)(Li₃K₃)⁶⁺(C₂₀H₁₀^4?)]^2?, illustrate a record ability of bowl‐shaped and highly charged corannulene to provide all its sites, five benzene rings fused to a central five‐membered ring, for binding of six alkali‐metal ions. The previously unseen engagement of the hub‐site of C₂₀H₁₀^4? in lithium binding is accompanied by unprecedented shifts up to ?24 ppm in ⁷Li NMR spectra. The discussion of product formation mechanism, augmented by calculations, is provided.     

Three Polymorphic CdII Coordination Polymers Obtained from the Solution and Mechanochemical Reactions of 3‐Cyanopentane‐2,4‐dione with CdII Acetate

We previously reported that monomeric and polymeric metal complexes are obtained from solution and mechanochemical reactions of 3‐cyano‐pentane‐2,4‐dione (CNacacH) with 3d metal acetates (M=Mn^II, Fe^II, Co^II, Ni^II, Cu^II, and Zn^II). A common feature found in all complexes was that their structural base is trans‐[M(CNacac)₂]. Here, we report that the reactions of CNacacH with Cd^II acetate in the solution and solid states afford different coordination polymers composed of trans‐[Cd(CNacac)₂] and cis‐[Cd(CNacac)₂] units, respectively. From a methanol solution containing CNacacH (L) and Cd(OAc)₂ ? 2 H₂O (M), a coordination polymer ( Cd‐1 ) in which trans‐[Cd(CNacac)₂] units are three‐dimensionally linked was obtained. In contrast, two different coordination polymers, Cd‐2 and Cd‐3 , were obtained from mechanochemical reactions of CNacacH with Cd(OAc)₂ ? 2 H₂O at M/L ratios of 1:1 and 1:2, respectively. In Cd‐2 , cis‐[Cd(CNacac)₂] units are two‐dimensionally linked, whereas the units are linked three‐dimensionally in Cd‐3 . Furthermore, Cd‐1 and Cd‐2 converted to Cd‐3 by applying an annealing treatment and grinding with a small amount of liquid, respectively, in spite of the polymeric structures. These phenomena, 1) different structures are formed from solution and mechanochemical reactions, 2) two polymorphs are formed depending on the M/L ratio, and 3) structural transformation of resulting polymeric structures, indicate the usability of mechanochemical method in the syntheses of coordination polymers as well as the peculiar structural flexibility of cadmium‐CNacac polymers.     

正八面体过渡金属化合物能谱计算的程序设计

本文对正八面体过渡金属化合物的价电子体系实现了(et_2)~*组态能谱计算的程序化,包括Hamilton算子矩阵元的计算以及各种分子多数的分子轨道计算。     

Formation and Structural Characterization of Metal Complexes derived from Thiosalicylic Acid

The formation and structural aspects of some metal complexes of thiosalicylic acid (TSA) were studied. The μ‐bridging tetra‐coordinated Ru complex, [Ru(C₆H₄(CO₂)(μ‐S)(H₂O)]₂ ( 1 ) was formed by hydrothermal reaction of TSA with RuCl₃. The complexes [M(dtdb)(phen)(H₂O)]_n ( 2 – 4 ) (M = Zn^II, Co^II, Ni^II, dtdb = 2,2′‐dithiodibenzoate anion, phen = 1,10‐phenanthroline) were obtained by the slow diffusion technique and the in situ S–S bond formation was confirmed by elemental, spectral and X‐ray analysis. Reaction of TSA with CuCl₂ and 2,2′‐bipyridine (bipy) under the slow diffusion technique yielded the dimer [Cu(tdb)(bipy)] ( 5 ) (tdb = thiodibenzoic acid), where the in situ generation of 2,2′‐thiodibenzoic acid was observed.     

Three New cpt‐Metal Complexes Displaying 0D, 1D,and 3D Topology Structures

Three new cpt‐metal complexes of different topology structures were synthesized by solvothermal methods [Hcpt = 4‐(4‐carboxyphenyl)‐1,2,4‐triazole]. The structure of [Mn(cpt)₂ · 2H₂O] ( 1 ) is essentially 0D monomeric, but extended into a 2D supramolecular network through cross‐linking hydrogen bonds. In [Cu(cpt)(OH) · 2H₂O] · 2H₂O ( 2 ), the hydroxo groups as well as cpt ligands join the copper ions into an infinite polymeric [Cu(μ‐cpt)(μ‐OH)] chain, which is interconnected into a 3D supramolecular network with different oriented channels by 1D water chains. The complex [Zn(cpt)₂] · 0.5DMF · CH₃CH₂OH ( 3 ), which crystallizes in a 3D open framework with fourfold interpenetrated diamondoid network topology, represents the first 3D structure based on cpt anions. The structure differences demonstrate that the reaction metal ions have an important effect on the structures of these complexes.     

Reactions of Titanocene with Triazines and Dicyandiamide: Formation of Novel Di‐ and Trinuclear Metallacyclic Complexes

The titanocene bis(trimethylsilyl)acetylene complex Cp₂Ti(η²‐Me₃SiC₂SiMe₃) ( 1 ) reacts with different triazines to give trinuclear titanocene compounds. Cleavage of the heterocyclic unit takes place in the reaction with cyanuric chloride, which furnishes a trinuclear cyanide bridged titanocene complex [Cp₂Ti(CN)]₃ ( 2 ). Reaction with cyanuric acid yields the paramagnetic ate complex (Cp₂Ti)₃(C₃N₃O₃) ( 3 ). With melamine the structurally similar amide species (Cp₂Ti)₃[C₃N₃(NH)₃] ( 4 ) is formed. A dinuclear, paramagnetic complex 5 is obtained in the reaction of 1 with dicyandiamide. Complexes 2 , 4 , and 5 were characterized by X‐ray analyses.     

The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH3PO Isomers and Their Cr(CO)5 Complexes

Opening gambit : A high‐level theoretical study on the relative stabilities of oxaphosphirane isomers and their Cr(CO)₅ complexes is reported (see picture). Furthermore, thermodynamics and kinetics of possible ring‐opening reactions of these complexes in the presence of a {Cp₂Ti^IIICl} fragment are theoretically investigated. The C? O bond cleavage is predicted to be the most efficient pathway, thus leading to reactive intermediates that are attractive for synthetic applications.

     

Syntheses,Structures, and Magnetism of Trinuclear Zn2Ln Complexes with 2,6‐Dipicolinoylbis(N,N‐diethylthiourea)

The bifunctional ligand 2,6‐dipicolinoylbis(N,N‐diethylthiourea) (H₂L) readily reacts with mixtures of Zn(CH₃COO)₂ and LnCl₃ in MeOH at ambient temperature with formation of trinuclear heterobimetallic complexes [Zn₂Ln(L)₂(OAc)₃] ( 1a – 1f ) (Ln = Ce, Nd, Sm, Gd, Dy, Er). The X‐ray single‐crystal diffraction and structural studies of the complexes revealed their isostructural nature, in which two doubly‐charged ligands {L^2–} bind two Zn²⁺ ions with the terminal acylthiourea sites and one Ln³⁺ ion with the central 2,6‐pyridinedicarboxamide site. In the complexes, the coordination numbers of Ln^III and Zn^II ions are 9 and 5, respectively. Magnetic properties of the complexes were studied by temperature‐dependent dc magnetic measurements. The observed μ_eff values at room temperature are all closed to the calculated values. Fitting χ_M and M data of [Zn₂Gd(L)₂(OAc)₃] ( 1d ) shows a g_iso value of 1.94.     

Direct In Situ Investigation of Milling Reactions Using Combined X‐ray Diffraction and Raman Spectroscopy

The combination of two analytical methods including time‐resolved in situ X‐ray diffraction (XRD) and Raman spectroscopy provides a new opportunity for a detailed analysis of the key mechanisms of milling reactions. To prove the general applicability of our setup, we investigated the mechanochemical synthesis of four archetypical model compounds, ranging from 3D frameworks through layered structures to organic molecular compounds. The reaction mechanism for each model compound could be elucidated. The results clearly show the unique advantage of the combination of XRD and Raman spectroscopy because of the different information content and dynamic range of both individual methods. The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structures and thus obtaining reliable data for mechanistic studies.     

Haloperoxidase‐like Compounds: Synthesis,Structure and Properties of Two New Oxidovanadium‐Poly(pyrazolyl)borate‐Carboxylate Complexes

Two new oxidovanadium (IV) complexes: TpVO(L₁) ( 1 ) and Tp*VO(pzH*)(L₂) ( 2 ) [Tp = hydrotris(pyrazolyl)borate, HL₁ = 5‐methyl‐1H‐pyrazole‐3‐carboxylic acid, Tp* = hydrotris(3,5‐dimethylpyrazolyl)borate, pzH* = 3,5‐dimethylpyrazole, HL₂ = 5‐phenyl‐1H‐pyrazole‐3‐carboxylic acid] have been synthesized and characterized by elemental analysis and IR spectroscopy. The single‐crystal structures of the complexes shows that the vanadium ion is in a distorted octahedral environment with a N₄O₂ donor set in each complex. Additionally, hydrogen bonding interaction exits in both complexes. Interestingly, the molecules of 1 are held together to form a 1D hydrogen bonded polymer along the b axis, whereas complex 2 is a hydrogen bonded dimer. In addition, the catalytic activities of complexes 1 and 2 in bromination reactions in phosphate buffer with phenol red as a trap were evaluated primary by UV/Vis spectroscopy. Furthermore, ab initio calculations of complexes 1 and 2 were performed.     

Isomorphous Substitution of Iron and Nickel into Analcime Zeolite

Studies on the effects of iron and nickel incorporation into the hydrothermal synthesis of ANA zeolite were carried out. The presented work reveals that pure Fe‐Al analcime is synthesized by using starting composition with a higher iron(III) content than reported in previous publications. Furthermore, the iron(III) and nickel(II) contents play important roles in the framework of the synthesized zeolite. XRD, FT‐IR spectroscopy, diffuse reflectance UV/Vis spectroscopy, nitrogen adsorption and SEM were used to characterize the synthesized zeolites. These investigations showed that loading of iron and nickel ions in ANA zeolite changes the pore size and morphology of analcime zeolite.