Evidence for Charge Delocalization in Diazafluorene Ligands Supporting Low-Valent [Cp*Rh] Complexes

Ligands based upon the 4,5-diazafluorene core are an important class of emerging ligands in organometallic chemistry, but the structure and electronic properties of these ligands have received less attention than they deserve. Here, we show that 9,9′-dimethyl-4,5-diazafluorene (Me2daf) can stabilize low-valent complexes through charge delocalization into its conjugated π-system. Using a new platform of [Cp*Rh] complexes with three accessible formal oxidation states (+III, +II, and +I), we show that the methylation in Me2daf is protective, blocking Brønsted acid-base chemistry commonly encountered with other daf-based ligands. Electronic absorption spectroscopy and single-crystal X-ray diffraction analysis of a family of eleven new compounds, including the unusual Cp*Rh(Me2daf), reveal features consistent with charge delocalization driven by π-backbonding into the LUMO of Me2daf, reminiscent of behavior displayed by the workhorse 2,2′-bipyridyl ligand. Taken together with spectrochemical data demonstrating clean conversion between oxidation states, our findings show that 9,9′-dialkylated daf-type ligands are promising building blocks for applications in reductive chemistry and catalysis.

Download Full-text

Axially Chiral Bis(α-amino Acid)s and Their Deamino Analogues. Synthesis and Configurational Assignment

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19980211 ◽

1998 ◽

Vol 63 (2) ◽

pp. 211-221 ◽

Cited By ~ 5

Author(s):

Miloš Tichý ◽

Luděk Ridvan ◽

Miloš Buděšínský ◽

Jiří Závada ◽

Jaroslav Podlaha ◽

...

Keyword(s):

Amino Acid ◽

Nmr Spectra ◽

Building Blocks ◽

X Ray Diffraction ◽

Amino Groups ◽

X Ray ◽

Configurational Assignment ◽

Symmetry Properties ◽

Axially Chiral ◽

Polymeric Structures

The axially chiral bis(α-amino acid)s cis-2 and trans-2 as possible building blocks for polymeric structures of novel type of helicity were prepared. Their configuration has been determined by NMR spectroscopy and, in the case of the trans-isomer, confirmed by single-crystal X-ray diffraction. Analogous pair of stereoisomeric diacids cis-3 and trans-3, devoid of the amino groups, was also prepared and their configuration assigned. The observed differences in the NMR spectra of cis- and trans-isomers of 2 and 3 are discussed from the viewpoint of their different symmetry properties.

Download Full-text

A New POM-Based Supramolecular Compound: Synthesis, Structure and Adsorptive Property of [Cu(phen)2]3[W6O19]

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.919-921.2013 ◽

2014 ◽

Vol 919-921 ◽

pp. 2013-2016 ◽

Cited By ~ 2

Author(s):

Ya Bing Liu ◽

Hong Jie Wang ◽

Hong Kai Zhao

Keyword(s):

Three Dimensional ◽

Building Blocks ◽

Monoclinic Space Group ◽

X Ray Diffraction ◽

Hybrid Compound ◽

Adsorptive Property ◽

X Ray ◽

Hydrogen Bonding Interactions ◽

Compound Synthesis ◽

Metal Organic

A POM - based organice - inorganic hybrid compound with the chemical formula of[Cu (phen)2]3[W6O19] (phen = 1,10-phenanthroline) (1) has been hydrothermally synthesized andstructurally characterized by the elemental analysis, and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space groupC2/c witha=18.319(4) Å,b= 17.311(4) Å,c= 22.248(4) Å,β= 112.40(3) o,V= 6523(2) Å3,Z= 4, R1= 0.0448, andwR2=0.1218. Compound 1 consists of the [W6O19]3-building blocks and [Cu (phen)2]+metal organic cationic moieties, which are packed together via the extensive hydrogen-bonding interactions to form a three-dimensional supramolecular framework. The adsorption of methylene blue (MB) under UV irradiation with 1 as the heterogeneous adsorbent has been investigated, showing a good adsorptive property of 1 for MB degradation.

Download Full-text

An Intramolecular Boron Nitrogen Lewis Acid Base Pair on a Rigid Naphthyl Backbone

Zeitschrift für Naturforschung B ◽

10.5560/znb.2012-0091 ◽

2012 ◽

Vol 67 (6) ◽

pp. 589-593 ◽

Cited By ~ 4

Author(s):

Daniel Winkelhaus ◽

Beate Neumann ◽

Norbert W. Mitzel

Keyword(s):

Nmr Spectroscopy ◽

Single Crystal ◽

Lewis Acid ◽

Elemental Analysis ◽

Base Pair ◽

Ring System ◽

X Ray Diffraction ◽

Acid Base ◽

X Ray ◽

Boron Nitrogen

The reaction of (C6F5)2BCl with 8-lithio-N,N-dimethyl-1-naphthylamine (1) afforded the fivemembered ring system 8-bis(pentafluorophenyl)boryl-N,N-dimethyl-1-naphthylamine (2) with an intramolecular dative B-N bond. The compound was characterised by elemental analysis, NMR spectroscopy and single-crystal X-ray diffraction.

Download Full-text

Two types of Ln2Cu2 hydroxo-trimethylacetate complexes with 0D and 1D motifs: synthetic features, structural differences, and slow magnetic relaxation

Dalton Transactions ◽

10.1039/d1dt01161h ◽

2021 ◽

Author(s):

Anna Bovkunova ◽

Evgeniya S. Bazhina ◽

Igor Evstifeev ◽

Yulia V. Nelyubina ◽

Maxim Shmelev ◽

...

Keyword(s):

Magnetic Relaxation ◽

X Ray Diffraction ◽

Metal Core ◽

X Ray ◽

Trimethylacetate Complexes ◽

Structural Differences ◽

Slow Magnetic Relaxation ◽

New Compounds

Two series of heterometallic LnIII−CuII compounds containing a butterfly-like tetranuclear metal core were synthesized and characterized by X-ray diffraction and magnetometry. The structures of the new compounds were shown to...

Download Full-text

Synthese und Kristallstrukturen einiger Tetramethylstibonium-Hydrogendicarboxylate / Synthesis and Crystal Structures of Some Tetramethylstibonium Hydrogendicarboxylates

Zeitschrift für Naturforschung B ◽

10.1515/znb-1982-1106 ◽

1982 ◽

Vol 37 (11) ◽

pp. 1393-1401 ◽

Cited By ~ 12

Author(s):

Beatrix Milewski-Mahrla ◽

Hubert Schmidbaur

Keyword(s):

Hydrogen Bonds ◽

Crystal Structures ◽

Spectroscopic Data ◽

Molar Ratio ◽

Ionic Structure ◽

X Ray Diffraction ◽

X Ray ◽

Carboxylate Oxygen ◽

Donor Acceptor ◽

New Compounds

Reactions of pentamethylantimony (CH3)5Sb with carboxylic acids in the molar ratio 1:2 afford one equivalent of methane and essentially quantitative yields of crystalline tetramothylstibonium hydrogendicarboxylates. Six new compounds of this series have been synthesized using benzoic, o-phthalic, salicylic, 4-ethoxy-salicylic, oxalic, and malic acid, and characterized by analytical and spectroscopic data. An ionic structure with strong hydrogen bonds in the anionic components is proposed.The crystal structures of the hydrogen-dibenzoato (1), hydrogen-ortho-plithalato (2) and 4-ethoxy-hydrogen-salicylate (3) were determined by single crystal X-ray diffraction. The compounds can be described as having ionic lattices with some donor-acceptor interactions between the stibonium centers and the carboxylate oxygen atoms. The anions are characterized by strong hydrogen bonds O...H...O. Thus, the (CH3)4Sb-tetrahedron in 1 is distorted by two benzoate oxygon atoms (at 304(2) and 340(2) pin). The cation in 2 is largely undistorted and the anion has a hydrogenphthalate hydrogen bond of d(O...H...O) = 232 pm. The cation-anion contact in 3 is as short as d(Sb-O) = 289 pm rendering the Sb atom pentacoordinate.

Download Full-text

Selective Crystallization of Four Bis(phthalocyaninato)neodymium(III) Polymorphs

10.26434/chemrxiv.12646655.v1 ◽

2020 ◽

Author(s):

Maegan Dailey ◽

Claire Besson

Keyword(s):

Crystal Packing ◽

Detailed Comparison ◽

Protonated Form ◽

Slow Evaporation ◽

X Ray Diffraction ◽

Acid Base ◽

Initial Oxidation ◽

X Ray ◽

Secondary Interactions ◽

Selective Crystallization

Four polymorphs of bis(phthalocyaninato)neodymium(III) were reproducibly and selectively crystallized by the slow evaporation of saturated solutions. The obtained phase depended on the initial oxidation state of the NdPc2 molecule and the choice of solvent. Single-crystal X-ray diffraction studies were used to correct previous mis-identifications and provide missing coordinates for the γ-phase as well as a detailed comparison of molecular structure and crystal packing in all NdPc2 polymorphs. The primary feature in all phases is columnar stacking based on parallel π π interactions, with a variety of slip angles within those stacks as well as secondary interactions between them. Chemical redox and acid-base titrations, performed on re-dissolved crystals demonstrate that NdPc2+ and NdPc2- are easily obtained through weak oxidizing and reducing agents, respectively. Additionally, we show that the protonated form of the NdPc2- complex has a nearly identical UV-Vis spectra to that of neutral NdPc2, explaining some of the confusion over chemical composition in previously published literature.

Download Full-text

In situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated Ce(IV)-based Metal-Organic Frameworks with UiO-66 and MIL-140 architectures

10.26434/chemrxiv.13252544 ◽

2020 ◽

Author(s):

Stephen Shearan ◽

Jannick Jacobsen ◽

Ferdinando Costantino ◽

Roberto D’Amato ◽

Dmitri Novikov ◽

...

Keyword(s):

Crystal Growth ◽

Metal Organic Frameworks ◽

Building Blocks ◽

Nucleation And Growth ◽

X Ray Diffraction ◽

X Ray ◽

Rate Determining Step ◽

Wide Range ◽

Metal Organic

We report on the results of a thorough in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated Ce(IV)-based metal-organic frameworks (MOFs), analogues of the already well investigated Zr(IV)-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as building blocks, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds in situ in a wide range of conditions, varying parameters such as temperature, amount of the protonation modulator nitric acid (HNO3) and amount of the coordination modulator acetic acid (AcOH). When only HNO3 is present in the reaction environment, F4_MIL-140A(Ce) is obtained as a pure phase. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C, whereas the modulator influences nucleation and crystal growth to a similar extent. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products, consisting of F4_MIL-140A(Ce) and F4_UiO-66(Ce), are obtained. In these conditions, F4_UiO-66(Ce) is always formed faster and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate determining step. An increase in the amount of HNO3 slows down both nucleation and growth rates for F4_MIL-140A(Ce), whereas nucleation is mainly affected for F4_UiO-66(Ce). In addition, a higher amount HNO3 favours the formation of F4_MIL-140A(Ce). Similarly, increasing the amount of AcOH leads to slowing down of the nucleation and growth rate, but favours the formation of F4_UiO-66(Ce). The pure F4_UiO-66(Ce) phase could also be obtained when using larger amounts of AcOH in the presence of minimal HNO3. Based on these in situ results, a new optimised route to achieving a pure, high quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified.

Download Full-text

Cobalt(II) chloride adducts with acetonitrile, propan-2-ol and tetrahydrofuran: considerations on nuclearity, reactivity and synthetic applications

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229617000705 ◽

2017 ◽

Vol 73 (2) ◽

pp. 104-114 ◽

Cited By ~ 1

Author(s):

Danilo Stinghen ◽

André Luis Rüdiger ◽

Siddhartha O. K. Giese ◽

Giovana G. Nunes ◽

Jaísa F. Soares ◽

...

Keyword(s):

Single Molecule ◽

Building Blocks ◽

Direct Reaction ◽

X Ray Diffraction ◽

Single Molecule Magnets ◽

X Ray ◽

Ft Ir ◽

Bond Network ◽

Solvent Molecules ◽

Intramolecular Hydrogen

High-spin cobalt(II) complexes are considered useful building blocks for the synthesis of single-molecule magnets (SMM) because of their intrinsic magnetic anisotropy. In this work, three new cobalt(II) chloride adducts with labile ligands have been synthesized from anhydrous CoCl2, to be subsequently employed as starting materials for heterobimetallic compounds. The products were characterized by elemental, spectroscopic (EPR and FT–IR) and single-crystal X-ray diffraction analyses.trans-Tetrakis(acetonitrile-κN)bis(tetrahydrofuran-κO)cobalt(II) bis[(acetonitrile-κN)trichloridocobaltate(II)], [Co(C2H3N)4(C4H8O)2][CoCl3(C2H3N)]2, (1), comprises mononuclear ions and contains both acetonitrile and tetrahydrofuran (thf) ligands, The coordination polymercatena-poly[[tetrakis(propan-2-ol-κO)cobalt(II)]-μ-chlorido-[dichloridocobalt(II)]-μ-chlorido], [Co2Cl4(C3H8O)4], (2′), was prepared by direct reaction between anhydrous CoCl2and propan-2-ol in an attempt to rationalize the formation of the CoCl2–alcohol adduct (2), probably CoCl2(HOiPr)m. The binuclear complex di-μ-chlorido-1:2κ4Cl:Cl-dichlorido-2κ2Cl-tetrakis(tetrahydrofuran-1κO)dicobalt(II), [Co2Cl4(C4H8O)4], (3), was obtained from (2) after recrystallization from tetrahydrofuran. All three products present cobalt(II) centres in both octahedral and tetrahedral environments, the former usually less distorted than the latter, regardless of the nature of the neutral ligand. Product (2′) is stabilized by an intramolecular hydrogen-bond network that appears to favour atransarrangement of the chloride ligands in the octahedral moiety; this differs from thecisdisposition found in (3). The expected easy displacement of the bound solvent molecules from the metal coordination sphere makes the three compounds good candidates for suitable starting materials in a number of synthetic applications.

Download Full-text

Alkin-Komplexe des Rheniums in hohen Oxidationsstufen / Alkyne Complexes of Rhenium in High Oxidation States

Zeitschrift für Naturforschung B ◽

10.1515/znb-1990-0620 ◽

1990 ◽

Vol 45 (6) ◽

pp. 876-886 ◽

Cited By ~ 11

Author(s):

Wolfgang A. Herrmann ◽

Josef K. Felixberger ◽

Josef G. Kuchler ◽

Eberhardt Herdtweck

Keyword(s):

Diffraction Study ◽

Scale Up ◽

Oxidation States ◽

X Ray Diffraction ◽

X Ray ◽

Reducing Conditions ◽

Molar Amount ◽

High Oxidation ◽

Alkyne Complexes ◽

Type 3

The class of π-alkyne complexes of metals in medium and high oxidation states has been extended by the type CH3ReO2(RC≡CR′) (3a—i). Exchange of alkyne for oxo ligands under reducing conditions has been employed as a new general synthesis. Compounds 3 are thus obtained by reaction of methyltrioxorhenium(VII) (1) with the alkynes 2a—i in the presence of a ca. 1.1-fold molar amount of polymer-bound triphenylphosphane as reducing agent (desoxygenation). The structural characterization was carried out for the example of the tolan complex 3 e by virtue of a single-crystal X-ray diffraction study at —80 °C, according to which the description of compounds 3 as “rhenacyclopropenes” seems justified. Evidence from NMR investigations of 3 a and 3 c shows that no fast rotation of the respective alkyne ligand around the axis to the metal atom occurs on the NMR time scale up to at least 105 °C. A minimal rotation barrier of approximately 20 kcal/mol is thus to be estimated. Reaction of type 3 compounds (R = R′ = CH3, b; R = R′ = C2H5, c) with polymer-bound triphenylphosphane under more drastic conditions (boiling toluene) for two days effects further reduction, with the dinuclear, diamagnetic rhenium(IV) complexes 4b and 4c, resp., being formed. Sterically demanding alkynes (e.g., R = R′ = Si(CH3)3, C6H5) seem to prevent this type of reaction. According to an X-ray diffraction study, 4b has an equilateral Re2O-triangular core geometry, with the ligands O, CH3, and butyne(2) arranged in such a way that C2-symmetry results. The alkyne complexes reported here are the first ones of tetra- and pentavalent rhenium.

Download Full-text

Synthesis and characterization of the new tin borate SnB8O11(OH)4

Zeitschrift für Naturforschung B ◽

10.1515/znb-2018-0035 ◽

2018 ◽

Vol 73 (5) ◽

pp. 337-348 ◽

Cited By ~ 2

Author(s):

Sandra Schönegger ◽

Klaus Wurst ◽

Gunter Heymann ◽

Andreas Schaur ◽

Andreas Saxer ◽

...

Keyword(s):

Hydrothermal Process ◽

Building Blocks ◽

Membered Ring ◽

Monoclinic Space Group ◽

X Ray Diffraction ◽

X Ray ◽

Thermoanalytical Investigations ◽

Hydrogen Bond Interactions ◽

Simple Hydrothermal Process

AbstractA new tin(II) borate with the composition SnB8O11(OH)4 was synthesized by a simple hydrothermal process. It crystallizes in the centrosymmetric monoclinic space group P21/n (no. 14) with the lattice parameters a=790.1(1), b=1402.2(2), c=994.8(1) pm, and β=90.40(5)° (Z=4). The new compound SnB8O11(OH)4 is isotypic to PbB8O11(OH)4 and isostructural to BaB8O11(OH)4. The borate layers are built up from fundamental building blocks (FBBs) with the composition [B8O11(OH)4]2−. Four of these FBBs form a nine-membered ring wherein the Sn2+ cations are located. These boron-oxygen layers are further connected by O–H···O hydrogen bond interactions. The characterization of SnB8O11(OH)4 is based on single-crystal X-ray diffraction data, vibrational spectroscopy, DFT calculations, and thermoanalytical investigations including high temperature powder XRD.

Download Full-text