Well-defined phosphate yttrium dialkyl complexes for catalytic stereo-controllable 1,4-polymerization of isoprene

Oxygen ligation is envisioned to provide a stable and distinctive coordination environment to the strongly oxophilic rare-earth metals. However, the well-defined dialkyl complexes bearing oxyanion ancillary ligand had been rarely addressed for the instability of the complexes and the shortage of easily available ligands. Herein, we report the synthesis of phosphate ligated dialkyl yttrium complexes（PYR2） featuring a high stability and a tunable ligand. Treated with the borate reagent, the phosph...     

Syntheses,crystal structures,and magnetic properties of three one-dimensional metal–nitroxide complexes linked by 1,4-cyclohexanedicarboxylate ligands

Three one-dimensional metal–nitroxide complexes [Cu(NIT4Py)₂(1,4-chdc)] _n (1), {[Cu(IM4Py)₂(1,4-chdc)(H₂O)]·H₂O} _n (2) and {[Zn(IM4Py)₂(1,4-chdc)(H₂O)₂]·H₂O} _n (3) (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and 1,4-chdc = 1,4-cyclohexanedicarboxylate anion) have been synthesized and characterized structurally as well as magnetically. All three complexes crystallize in neutral one-dimensional chains in which the nitroxide–metal–nitroxide units are linked by linear 1,4-cyclohexanedicarboxylate anions. The 1,4-chdc ligands only present the e,e-trans-configuration in these complexes, although there are both cis- and trans-isomers in the free ligand. Magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the copper atoms and nitroxide radicals.     

Rapid access to 3-(N-substituted)-aminoquinolin-2(1H)-ones using palladium-catalyzed C-N bond coupling reaction

A series of 3-(N-substituted)-aminoquinolin-2(1H)-ones have been synthesized by the palladium-catalyzed C-N coupling reaction starting from 3-bromoquinolin-2-(1H)-ones. Various nucleophiles including amines, amides, sulfonamides, carbamates and ureas have been used successfully. In all the cases, the reactions take place rapidly in 1,4-dioxane and proceed in good to excellent yield using palladium acetate as a catalyst, Xantphos as a ligand and Cs₂CO₃ as a base.     

Isotype 1D polymers of cobalt(II) or zinc(II) constructed with square-planar tetraaqua-metal(2+) units and the bis-zwitterionic form of the μ2-O,O′-trans-1,4-dihydrogen-cyclohexanediaminotetraacetate(2−) ligand

An uncompleted reaction between equimolar amounts of Co₂CO₃(OH)₂·2H₂O and trans-1,4-H₄cyclohexanediaminotetraacetic acid in water affords the ‘acid’ complex {[Co^II(trans-1,4-H₂CDTA)(H₂O)₄]·6H₂O}_n (1). Its IR spectrum does not show the expected ν(CO) band of carboxylic groups. Reactions in aqueous solution between Na(trans-1,4-H₃CDTA) and Zn(AcO)₂·2H₂O or Na₂(trans-1,4-H₂CDTA) and Zn(NO₃)₂·6H₂O yield {[Zn(trans-1,4-H₂CDTA)(H₂O)₄]·6H₂O}_n (2) and {[Zn₂(trans-1,4-CDTA)(H₂O)₂]·H₂O}_n (3) respectively. Crystal structures of compounds 1-3 and that of the trans-1,4-H₄CDTA·2H₂O acid are reported. For steric reasons, in the four reported structures the 1,4-CDTA ligand has the two iminodiacetate moieties as equatorial groups in the 1,4-cyclohexanedi-yl chair. Compounds 1 and 2 are isotype 1D polymers constructed by square planar M^II(H₂O)₄²⁺ knots (M^II = Co^II or Zn^II) linked to bis-zwitterionic trans-1,4-H₂CDTA²⁻ ligands that play a typical μ₂-O,O′-dicarboxylate bridging role. These 1D polymeric structures seem to be favoured by the H-bonded intra-stabilization of the bis-zwitterionic trans-1,4-H₂CDTA²⁻ ligand. In the neutral complex (3), the trans-1,4-CDTA acts as a bridging bis-chelating ligand as well as a syn-anti carboxylate building a polymer where the zinc(II) centres exhibit a rough bipyramidal trigonal coordination.     

Synthesis and crystal structure of cyclopentadienyl(1,4-dimethyl-1,4-dibora-2,5-cyclohexadiene)cobalt

The synthesis of the organometallic derivative cyclopentadienyl(1,4-dimethyl-1,4-diboracyclohexa-2,5-diene)cobalt is described. This complex, [(CH₃BC₄H₄BCH₃)Co(η-C₅H₅)], forms red-oranged monoclinic crystals, space group P2₁/a with Z = 4 in a unit cell of dimensions a 11.362(7), b, 7.467(7), c 13.290(12) Å, β 103.76(6)°. The structure has been elucidated by heavy-atom methods from 1732 reflections (I > 2σ(I)) measured on a Syntex P2₁ four-circle diffractometer and refined to R = 0.055. In the coordination complex all six atoms of the cyclohexadiene ring are within bonding distance of the metal atom, but the two boron atoms bend away from the metal atom, and the ring elongates slightly in the B---B direction. As a standard of comparison the known geometry of the free ligand [1,4-difluoro-1,4-dibora-2,3,5,6-tetramethylcyclohexa-2,5-diene] is used. The terminal methyl groups on the boron atoms, by contrast, bend slightly back towards the metal atom. The cyclopentadienyl ring remains planar but is positionally disordered.     

Inhibition of two Cu(II) and Mn(II) coordination polymers on the surgical site infections by inhibiting the bacterial biofilm formation

Within this work, two novel Cu(II) and Mn(II)-based coordination polymers (CPs) along with chemical compositions of {[Cu₂(L¹)(1,4-NDC)₂]·3H₂O}_n (1, 1,4-H₂NDC = Naphthalene-1,4-dicarboxylic acid, L¹ ​= ​di(1H-imidazole-1-yl)methane) and [Mn₃(L²)₂(H₂O)₂(1,4-NDC)₂]_n (2, L² ​= ​1,4-di(1H-imidazole-1-yl)benzene) have been completed in success via related metal salts reaction with 1,4-H₂NDC ligand in existence of various N-donor co-ligands. We discovered its application values on the surgical site infections (SSI) along with corresponding mechanism in the interim. We evaluated inflammatory cytokines released into the urine through ELISA detection kit after compound treatment. Then, we discovered the inhibitory effect of compound on the bacterial biofilm formation via real time RT-PCR.     

Vibrational Spectroscopic Studies on the Dicycloheptylaminecobalt(II) Tetracyanonickellate(II) Host–Aromatic Guest Systems

Co(cycloheptylamine)₂Ni(CN)₄ host complex has been prepared in powder form and its vibrational spectra are investigated. The vibrational assignment of the cycloheptylamine in various phases (gas, solution, liquid and complex) are facilitated by means of DFT calculations performed on the free ligand molecule. The spectral data suggest that the prepared complex is similar in structure to the Hofmann-dma-type hosts. The sorption processes of some aromatic guests (benzene, toluene, o-, m-, p-xylene, 1,2-, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,4-dibromobenzene and naphthalene) in this host complex have also been examined at room temperature by gravimetric and spectroscopic measurements. The desorption of the benzene guest against time has been measured. The structure of the Co(cycloheptylamine)₂Ni(CN)₄ host changes on inclusion of the guest molecule and recovers after liberation.     

A novel C2-symmetric bisphosphane ligand with a chiral cyclopropane backbone: synthesis and application in the Rh(I)-catalyzed asymmetric 1,4-addition of arylboronic acids

The synthesis of a novel C₂-symmetric bisphosphane ligand was accomplished starting from trans-(2R,3R)-bis(3′,5′-diphenylphenyl)cyclopropane-1,1-dimethanol as a key intermediate. This ligand was tested in the asymmetric rhodium(I)-catalyzed 1,4-addition to cyclic enones. We also compared the new ligand with a similar phosphane ligand with a less bulky cyclopropane backbone. Good yields (up to 99%) and enantioselectivities (up to 89% ee) were observed. We demonstrated that the presence of a more bulky cyclopropane backbone resulted in a less effective ligand.     

DAB-Cy as an inexpensive and effective ligand for palladium-catalyzed homocoupling reaction of aryl halides

A novel catalytic system of PdCl₂(CH₃CN)₂ with N,N′-dicyclohexyl-1,4-diazabutadiene (DAB-Cy) ligand was successfully used in reductive coupling of aryl halides.     

Etude de la complexation des lanthanides trivalents par les isomères de l'acide diaminocyclohexanetétraacétique: Partie 2. Les Constantes d'Acidité et les Constantes de Formation des Complexes 1:1 avec l'Acide trans-1,4-Diaminocyclohexane-N,N,N′,N′-Tétraacétique

(Study of the complexation of trivalent lanthanides by the six isomers of diaminocyclohexanetetraacetic acid. Part 2. Acidity constants and formation constants of the 1:1 complexes of trans-1,4-diaminocyclohexane-N,N,N′,N′-tetraacetic acid)Potentiometric measurements of the acidity constants of trans-1,4-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (trans-1,4-DCTA) and of the stability constants of its 1:1 complexes with the trivalent lanthanides are reported for an ionic strength of 1 (KCl) at 25°C. The behaviour of this ligand is similar to that of monoaminodiacetic acids, suggesting that only one N(CH₂COO^?)₂ group participates in chelation. The selectivity of trans-1,4-DCTA for the lanthanides is better than that reported for the monoaminodiacetic acids.     

Syntheses and characterization of heterobimetallic complexes (dppf)Pt(dithiolate) (dppf: bis(diphenylphosphino)ferrocene); X-ray crystal structures of (dppf)PtL where L=dmit,phdt and i-mnt

Heterobimetallic complexes of the type (dppf)PtL (dppf=1,1′-bis(diphenylphosphino)ferrocene; L=dmit (1,3-dithiole-2-thione-4,5-dithiolate), dddt (5,6-dihydro-1,4-dithiin-2,3-dithiolate), phdt (6-hydro-5-phenyl-1,4-dithiin-2,3-dithiolate), dphdt (5,6-diphenyl-1,4-dithiin-2,3-dithiolate), mtdt (1,2-bis(methylthio)ethylene-1,2-dithiolate), i-mnt (2,2-dicyano-1,1-ethylenedithiolate)) have been synthesized and studied by a high-resolution FAB-MS, cyclic voltammetry and ³¹P NMR. (Dppf)Pt(i-mnt) exhibits one reversible redox peak at E_1/2=1.225 V and a strong Pt–P coupling constant (J_Pt–P=3237 Hz) due to the electron-accepting property of i-mnt ligand. On the contrary, (dppf)Pt(mtdt) shows three reversible redox peaks corresponding to [dppf]^0/+ (E_1/2¹=0.470 V), [Pt(mtdt)]^0/+ (E_1/2²=1.050 V) and [Pt(mtdt)]^+/2+ (E_1/2³=1.405 V) processes and a weak Pt–P coupling constant (J_Pt–P=2962 Hz) due to relatively strong electron-donor property of mtdt ligand. X-ray structural analyses were performed for the three complexes: (dppf)PtL where L=dmit, phdt and i-mnt. The P₂PtS₂ core shows a distorted square planar geometry for the three complexes with P(1)–Pt–P(2) bite angle being larger than 96°. The S(1)–Pt–S(2) bite angle of the i-mnt complex is the smallest (74.42°) because of the formation of the four-membered ring.     

Naphthalene complexes: V. Arene exchange reactions in naphthalenechromium complexes

Di-η⁶-naphthalenechromium(0) (1) reacts at 150°C with benzene to yield (η⁶-naphthalene)(η⁶-benzene)chromium(0) (3) in 76% yield. In the presence of THF, 1 undergoes Lewis base catalyzed arene exchange at 80°C. Reactions of 1 with substituted arenes yield the mixed sandwich complexes 4 and 6–10 (arene = 1,4-C₆H₄Me₂, 1,3,5-C₆H₃Me₃, C₆Me₆, 1,4-C₆H₄(OMe)₂, 1,4-C₆H₄F₂ and 1,4-C₁₀H₆Me₂). In all but one case (with 1,4-dimethylnaphthalene) exchange of a single naphthalene ligand is observed. In marked contrast to the lability of 1, dimesitylenechromium(0) (5) is inert to arene displacement in benzene up to 240°C. The molecular structure of 3 has been determined by X-ray crystallography. The crystal data are as follows: a 7.784(1), b 13.411(2), c 22.772(5) Å, Z = 8, space group Pbca. The structure was refined to a R_w value of 0.043. The naphthalene ligand in 3 is nearly planar and parallel to the approximately eclipsed benzene ring. Metal atom-ring distances are 1.631(9) and 1.611(4) Å for naphthalene and benzene, respectively. Catalyzed and uncatalyzed naphthalene exchanges in the sandwich complex are compared to the analogous reactions with the Cr(CO)₃ complex 2. Naphthalene exchange in 2 in benzene is 10³ to 10⁴ times faster than arene exchange in other arenetricarbonylchromium compounds. The mild conditions for Lewis base catalyzed naphthalene exchange make 2 a good precursor of other arenetricarbonylchromium compounds. Examples include the Cr(CO)₃ complexes of styrene, benzocyclobutene, 1-ethoxybenzocyclobutene, 1,8-dimethoxy-9,10-dihydroanthracene and 1,4-dimethylnaphthalene.     

Synthesis, crystal structure and properties of the Cu complex of a tetradentate imidazole-functionalized diazamesocyclic ligand, 1,4-bis(N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane

A new potential tetradentate ligand, 1,4-bis(N-1-methylimidazol-2-ylmethyl)-1,4-diazacycloheptane (l), together with its Cu^II complex [CulCl]ClO₄ (1), has been reported. The crystal structure of 1, determined by single-crystal X-ray analysis, shows that it is in chiral P2₁2₁2₁ space group. The Cu^II centre is penta-coordinated in square pyramidal geometry and the diazacycloheptane (DACH) ring adopts normal boat configuration. The most striking feature of this complex is the formation of a 3D network bridged through the C-H?Cl hydrogen bonds with the perchlorate anions in the cavities, and stabilized via π-π stacking interactions along the a-direction. The solution behaviour of 1 has been further investigated by UV/Vis and ESR techniques.     

Synthesis and study of copper(II), nickel(II), and cobalt(II) complex compounds with dihydrobenzoxazine derivatives

Complex compounds ML₂ of copper(II), nickel(II), and cobalt(II) with 2-(2-hydroxy-5-nitrophenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-benzoxazine and 2-(2-hydroxyphenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-benzoxazine (HL) were prepared by electrochemical and chemical syntheses. The complex formation involves the azomethine form of the ligand and gives a six-membered chelate cycle comprising deprotonated phenol and azomethine groups. The coordination entity has a planar structure with trans arrangement of the nitrogen and oxygen atoms.     

η4-endo-(17α,21-dihydroxypregna-1,4-diene-3,11,20-trione)-(η5-cyclopentadienyl)rhodium(I)

η⁴-endo-(17α,21-dihydroxypregna-1,4-diene-3,11,20-trione)-(η⁵-cyclopentadienyl)rhodium(I) was synthesized by successive treatment of 17α,21-dihydroxypregna-1,4-diene-3,11,20-trione with [(C₂H₄)₂RhCl]₂ and CpT1 in a yield of 54%.¹H NMR studies demonstrated that coordination of the organometallic moiety occurs from the side opposite to the 19-CH₃ group. Upon coordination, ringA of the prednisone ligand is fixed to adopt a boat conformation, and the basicity of the 3-CO group increases substantially.     

Synthesis, crystal structure, and thermal stability of 1D coordination polymer [Zn(BDOA)(Py)2(H2O)] n

A new coordination polymer, [Zn(BDOA)(Py)₂(H₂O)] _n (I) (BDOA = benzene-1,4-dioxylacetate, Py = pyridine), has been prepared via self-assembly of benzene-1,4-dioxylacetate with zinc nitrate under mild conditions and characterized by IR spectra, elemental analysis and X-ray diffraction single-crystal analysis. The complex crystallizes in the monoclinic system, space group C2/c with a = 15.5751(9), b = 6.0898(4), c = 21.7133(13) Å, V = 1991.9(2) ų, β = 104.719(1)°, Z = 4. The zinc atoms are bridged by BDOA ligand, forming a one-dimensional chain along the z axis. A two-dimensional layer structure is formed by the intermolecular hydrogen bonds. The thermal decomposition profile of the complex is reported as well.     

Preparation, spectroscopic properties of 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) lanthanide complexes and the supramolecular structure of [Nd2L2(NO3)6(H2O)2]·H2O

The reaction of lanthanide nitrate with 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) yields six novel Ln(III) complexes ([Ln₂L₂(NO₃)₆(H₂O)₂]·H₂O) which are characterized by elemental analysis, thermogravimetric analysis (TGA), conductivity measurements, IR, electronic and ¹H NMR spectroscopies. A new quinoxalinedione-based ligand is used as antenna ligand to sensitize the emission of lanthanide cations. The lowest triplet state energy level of the ligand in the nitrate complex matches better to the resonance level of Eu(III) and Sm(III) than Tb(III) and Dy(III) ion. The f-f fluorescence is induced in the Eu³⁺ and Sm³⁺ complexes by exciting into the π-π* absorptions of the ligand in the UV. Furthermore, the crystal structures of a novel binuclear complex [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O has been determined by single-crystal X-ray diffraction. The binuclear [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O complex units are linked by the intermolecular hydrogen bonds and π-π interactions to form a two-dimensional (2-D) layer supramolecule.     

Copper-catalyzed one-pot N-alkenylation and N-alkylation of amides: an efficient synthesis of substituted 2,3-dihydropyrroles

A novel copper-catalyzed synthesis of substituted 2,3-dihydropyrroles via one-pot N-alkenylation and N-alkylation of amides with 1,4-diiodobut-1-ene derivatives has been developed. The reactions proceed in good to high yields using CuI as the catalyst, K₂CO₃ as the base, and rac-trans-N,N′-dimethylcyclohexane-1,2-diamine as the ligand.     

Coordination modes of 1,2,3,4-tetrahydro-1,4-diphenyl-1,4-benzodiphosphinine (bedip) to Pt and Pd metal ions: Synthesis and structural characterization of mono- and bi-nuclear complexes

Within this study, coordination properties of the cyclic diphosphine 1,2,3,4-tetrahydro-1,4-diphenyl-1,4-benzodiphosphinine (bedip) are investigated, through the preparation of neutral and cationic Pt(II), Pt(IV) and Pd(II) complexes. The diphosphine acts as bridging ligand in the neutral Pt(II) and Pd(II) complexes, affording [MX(CH₃)(μ-bedip)]₂ (X = Cl, Br, I, CH₃) species. Chelation is observed in all the remaining complexes. The molecular structures of [PtX(CH₃)(μ-bedip)]₂ (X = Br, I) and [PtI(CH₃)₃(bedip)] are also determined.     

Synthesis, characterization, and SAMs electroactivity of ruthenium complexes with sulfur containing ligands

The vibrational and ¹H NMR data hints that the coordination of the 2,2′-dithiodipyridine (2-pySS) ligand to the [Ru(CN)₅]³⁻ metal center occurs through the sulfur atom instead of the nitrogen atoms which is usually observed for N-heterocyclic ligands. Electrochemical results show that this coordination mode implies an additional thermodynamic stabilization of the Ru^II over Ru^III oxidation state due to a relative stronger π-back-bonding interaction with the empty low-lying dπ orbitals of the sulfur atom. Computational data reinforce the experimental results showing that the 2-pySS Lewis base centers are located on the sulfur atoms. Ligands containing only sulfur atoms as coordination sites (2,2′-dithiodipyridine N-oxide (2-pySSNO), 1,4-dithiane (1,4-dt), and 2,6-dithiaspiro[3.3]heptane (asp)) were also coordinated to the [Ru(CN)₅]³⁻ metal center to undoubtedly correlate the electrochemical results with the ligand coordination atom. Among the synthesized compounds, the [Ru(CN)₅(1,4-dt)]³⁻ and [Ru(CN)₅(asp)]³⁻ complexes showed to be able to form self-assembled monolayers (SAMs) on gold. These SAMs, which were characterized by SERS (surface-enhanced Raman scattering) spectroscopy, successfully assessed the heterogeneous electron transfer reaction of the cytochrome c metalloprotein in physiological medium.