Donor-Stabilised [SbF4]+: SbF5 as a Fluoride-Ion Donor

Antimony pentafluoride is a strong Lewis acid and fluoride-ion acceptor that has not previously demonstrated any discreet fluoride-ion donor properties. The first donor-stabilised [SbF₄]⁺ cations were prepared from the autoionisation of SbF₅ in the presence of bidentate N-donor ligands 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) as their [SbF₆]⁻ salts. The [SbF₄(N−N)][Sb₂F₁₁] (N−N=bipy, phen) salts were synthesised by the addition of one equivalent of SbF₅⋅SO₂ to [SbF₄(N−N)][SbF₆] in liquid SO_2. The salts show remarkable stability and were characterised by Raman spectroscopy and multinuclear NMR spectroscopy. The crystal structures of [SbF₄(phen)][SbF₆] ⋅ 3CH₃CN and [SbF₄(phen)][SbF₆] ⋅ 2SO₂ were determined, showing distorted octahedral cations. DFT calculations and NBO analyses reveal that significant degree of electron-pair donation from N to Sb stabilizes [SbF₄]⁺ with the Sb−N bond strength being approximately two thirds of that of the Sb−F bonds in these cations and the cationic charge being primarily ligand-centred.     

Spin Crossover Behavior of FeII Complexes Bridged by Thiophene-Functionalized Triazole Ligands with Different Sizes and Rigidities

Four thiophene functionalized triazole ligands (L1=4-(thenyl)-1,2,4-triazole, L2=4-(thiophene ethyl)-1,2,4-triazole, L3=N-Thiophenylidene-4H-1,2,4-triazole-4-amine, and L4=(4-[(E)-2-(5-sulfothiophene)vinyl]-1,2,4-triazole) were synthesized. These ligands have different lengths and rigidities, while ligand L4 has a sulfonic acid group that can form a hydrogen bond. Five 1D Fe^II chain complexes were synthesized: [Fe(L1)₃](X)₂ ⋅ nH₂O [X=BF₄⁻, n=1.5 ( C1 ); X=ClO₄⁻, n=1 ( C2 )], [Fe(L2)₃](BF₄)₂ ⋅ 1.5H₂O ( C3 ); [Fe(L3)₃](X)₂ ⋅ nH₂O [X=BF₄⁻, n=2 ( C4 ); X=ClO₄⁻, n=2.5 ( C5 )]. The results of temperature-dependent magnetic susceptibility reveal that complexes C1 , C2 , and C3 experienced the transition between two spin states. And C4 and C5 maintain high spin states at all temperature ranges. Binuclear complex [Fe₂(L3)₅(SCN)₄] ( C6 ) and mononuclear material [Fe(L4)₂(H₂O)₄] ⋅ 2H₂O ( C7 ), these two zero-dimensional molecules were also synthesized. They all display weak antiferromagnetic exchange coupling and a high spin state in the whole process.     

Study on Cd2+ Determination Using Bud-like Poly-L-Tyrosine/Bi Composite Film Modified Glassy Carbon Electrode Combined with Eliminating of Cu2+ Interference by Electrodeposition

A bud-like poly-L-tyrosine/Bi modified glassy carbon electrode (p-Tyr/Bi/GC) was prepared by CV and in situ Bi plating, whose conductivity and membrane morphology were characterized by CV, EIS and SEM, respectively. The p-Tyr membrane can effectively promote the enrichment of Cd²⁺. The optimal Tyr concentration and scanning number for p-Tyr/GC preparation were 2.0 mmol ⋅ L⁻¹ and 35, while the optimal Bi³⁺ concentration, pH and Cd²⁺ accumulation potential in test medium were 3.0 μmol ⋅ L⁻¹, 6.5 and −1.3 V, respectively. The linear equation of p-Tyr/Bi/GC's response to Cd²⁺ (1.0 nmol ⋅ L⁻¹ to 2.0 μmol ⋅ L⁻¹) was i_p (μA) = −0.6809 + 100.2c (μmol ⋅ L⁻¹) (R² = 0.9985) with a detection limit of 0.11 nmol ⋅ L⁻¹ (3S/N). The elimination of interference caused by Cu²⁺ in sample was studied by electrodeposition. The p-Tyr/Bi/GC electrode was successfully used for detecting Cd in rice samples with good reliability and accuracy. The developed Cd²⁺ sensor exhibits high sensitivity, wide linear range and low detection limit, especially the designed method of eliminating Cu²⁺ interference has the characteristics of high selectivity, simple operation and wide application range.     

Nestlike Silver(I) Thiolate Clusters with Tunable Emission Color Templated by Heteroanions

Four silver thiolate clusters, [H₃O][(Ag₃S₃)(BF₄)@Ag₂₇(tBuS)₁₈(hfac)₆H₂O] ⋅ H₂O ( 1 ; hfac = hexafluoroacetylacetone), [(Ag₃S₃)(CF₃CO₂)@Ag₃₀(tBuS)₁₆(CF₃CO₂)₉(CH₃CN)₄] ⋅ CF₃CO₂ ⋅ 4 CH₃CN ( 2 ), [(Ag₃S₃)(MoO₄)@Ag₃₀(tBuS)₁₆(CF₃CO₂)₉(CH₃CN)₄] ⋅ 2 CH₃CN ( 3 ), and [(Ag₃S₃)(CrO₄)@Ag₃₀(tBuS)₁₆(CF₃CO₂)₉(CH₃CN)₄] ⋅ 4 CH₃CN ( 4 ), were isolated. They have similar nestlike structures assembled by an [Ag₃S₃]³⁻ template together with one of the BF₄⁻, CF₃CO₂⁻, MoO₄²⁻, or CrO₄²⁻ anions. Interestingly, the solid-state emissions of 2 – 4 are dependent on the templating anions and are tunable from green to orange and then to red by changing the template from CF₃CO₂⁻ to MoO₄²⁻ and to CrO₄²⁻, and this may be correlated to the charge transfer between these templates to metal atoms. This work helps to understand the templating role of heteroanions and the relationship between structure and properties.     

Enhanced and Heteromolecular Guest Encapsulation in Nonporous Crystals of a Perfluorinated Triketonato Dinuclear Copper Complex

The flexible host framework of a perfluorinated mononuclear copper complex, [Cu(L¹)₂] ( 1 , HL¹=3-hydroxy-1,3-bis(pentafluorophenyl)-2-propen-1-one), with a CuO₄ core reversibly encapsulated several organic guest molecules through electrostatic interactions in its crystals. Hence, the corresponding dinuclear complex, [Cu₂(L²)₂] ( 2 , H₂L²=1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one), was prepared to enhance guest recognition and the ability to separate molecular mixtures. Complex 2 comprises a Cu₂O₆ core and four pentafluorophenyl groups. In crystal 2 , cavities are formed on the axial sites of the metal core that are surrounded by pentafluorophenyl groups. The crystal of 2 encapsulates various guest molecules, that is, benzene ( 3 ), toluene ( 4 ), xylene ( 5 ), mesitylene ( 6 ), durene ( 7 ), and anisole ( 8 ). X-ray crystallographic and thermogravimetric (TG) studies show that three guest molecules are present in the crystal cavities. The number of guest molecules found in complex 2 was higher than that in complex 1 , for example, ( 2 )₃ ⋅ ( 6 )₁₀> 1⋅ ( 6 )₂, ( 2 )₂ ⋅ ( 7 )₇> 1⋅7 , or 2⋅ ( 8 )₃> 1⋅ ( 8 )₂. Naphthalene ( 9 ), was encapsulated in 2 to give 2⋅ ( 9 )₃, but not in 1 . In the crystal of complex 2 , heteromolecular guest encapsulation was confirmed, designated as 2⋅ ( 3 )₂ ⋅9 . TG analysis indicates that the thermal stability of the guest-included crystals of 2 is higher than that of 1 .     

Syntheses and Properties of (Nitronyl nitroxide)-substituted Tri-phenylamine ortho-Bridged by Two Oxygen and Sulfur Atoms

A nitronyl nitroxide unit ( NN ) was linked with a triphenylamine-based condensed polycyclic skeleton DOTT to form a radical substituted donor NN - DOTT . X-ray crystal structure analysis demonstrated a flat bowl shape of the DOTT unit. EPR spectra showed the localization of electron spin on the NN unit. Chemical oxidation of the DOTT unit produced radical-substituted radical cation salts NN - DOTT ⁺ ⋅ SbF₆⁻ and NN - DOTT ⁺ ⋅ FeBr₄⁻ that are stable under ambient conditions. The magnetic behavior of NN - DOTT ⁺ ⋅ SbF₆⁻ is characterized by the strong intramolecular ferromagnetic interaction between NN and DOTT ⁺. The X-ray structural analysis of NN - DOTT ⁺ ⋅ FeBr₄⁻ shows planar structure of DOTT and 1D mixed-stack column of NN-DOTT ⁺ and FeBr₄⁻. Magnetic measurements established that NN - DOTT ⁺ ⋅ FeBr₄⁻ undergoes magnetic phase transition into a weak ferromagnet at 7 K.     

Synthesis of Functionalized Heteroleptic Germylene Alkoxides

N-coordinated Ge(II) alkoxides L¹(tBuO)Ge ( 1 ), L²(tBuO)Ge ( 2 ) and [L²(OtBu)Ge ⋅ BH₃] ( 4 ) were prepared. Effect of either chelating ligands L¹ and L² or Ge→B interaction on strength of the Ge−OtBu bond was studied by insertion reaction of PhNCO. As a result, the Ge(II) carbamate L²{[(tBuO)OC](Ph)N}Ge ( 3 ) was isolated. Alcoholysis exchange reactions of 1 and 2 with substituted phenols were studied to find an easy synthetic protocol for a synthesis of functionalized Ge(II) alkoxides. Reactions yielded Ge(II) alkoxides L^1,2(2-Br−C₆H₄O)Ge ( 5 for L¹, 8 for L²), L^1,2(2-MeNH−C₆H₄O)Ge ( 6 for L¹, 9 for L²), L^1,2(2-Ph₂P−C₆H₄O)Ge ( 7 for L¹, 10 for L²), L²(2-Br-3-OH−C₆H₃O)Ge ( 11 ) and L²(2-NC₅H₄O)Ge ( 12 ) containing the additional polar groups Y (Y=Br, MeNH, PPh₂, OH or N). Finally, phosphane decorated Ge(II) alkoxides 7 and 10 were tested as suitable ligands in reactions with (COD)W(CO)₄ and BH₃. As a consequence, new complexes [(κ²- 7 )W(CO)₄] ( 13 ) and [L¹(2-Ph₂P ⋅ {BH₃}-C₆H₄O)Ge ⋅ {BH₃}] ( 14 ) were isolated. All compounds were characterized by NMR and IR spectroscopy, and compounds 3 , 4 , 9 and 11 were additionally characterized by X-ray diffraction analysis.     

Structural Transformations and Spin-Crossover in [FeL2]2+ Salts (L=4-{tert-Butylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine): The Influence of Bulky Ligand Substituents

4-(tert-Butylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine (L) was obtained in low yield from a one-pot reaction of 2,4,6-trifluoropyridine with 2-methylpropane-2-thiolate and sodium pyrazolate in a 1:1:2 ratio. The materials [FeL₂][BF₄]₂⋅solv ( 1[BF₄]₂ ⋅solv) and [FeL₂][ClO₄]₂⋅solv ( 1[ClO₄]₂ ⋅solv; solv=MeNO₂, MeCN or Me₂CO) exhibit a variety of structures and spin-state behaviors including thermal spin-crossover (SCO). Solvent loss on heating 1[BF₄]₂ ⋅x MeNO₂ (x≈2.3) occurs in two steps. The intermediate phase exhibits hysteretic SCO around 250 K, involving a “reverse-SCO” step in its warming cycle at a scan rate of 5 K min⁻¹. The reverse-SCO is not observed in a slower 1 K min⁻¹ measurement, however, confirming its kinetic nature. The final product [FeL₂][BF₄]₂⋅0.75 MeNO₂ was crystallographically characterized, and shows abrupt but incomplete SCO at 172 K which correlates with disorder of an L ligand. The asymmetric unit of 1[BF₄]₂ ⋅y Me₂CO (y≈1.6) contains five unique complex molecules, four of which undergo gradual SCO in at least two discrete steps. Low-spin 1[ClO₄]₂ ⋅0.5 Me₂CO is not isostructural with its BF₄⁻ congener, and undergoes single-crystal-to-single-crystal solvent loss with a tripling of the crystallographic unit cell volume, while retaining the P space group. Three other solvate salts undergo gradual thermal SCO. Two of these are isomorphous at room temperature, but transform to different low-temperature phases when the materials are fully low-spin.     

A New Approach for the Voltammetric Determination of Amoxicillin in the Dosage Form Using Azo Coupling Reaction with Sulphanilamide

The novel method of amoxicillin (AM) determination has been developed using single-sweep polarography. The proposed method is based on the obtaining of yellow coloured azo compound due to azo coupling reaction of previous diazotized sulphanilamide (SA) (in the medium of 0.6 M hydrochloric acid) with amoxicillin at pH=9.0 with the further reduction of the formed analytical form on a dropping mercury electrode. Voltammetric determination of amoxicillin is carried out due to the reduction peak of azo group of the obtained azo compound in the presence of 0.05 mol ⋅ L⁻¹ Na₂B₄O₇ as a background electrolyte at the potential E_c^p2=−0.55 V and potential sweep rate of 2.5 V ⋅ s⁻¹. The developed voltammetric method has two linear ranges of the determined concentrations (0.05–2.0) ⋅ 10⁻⁵ mol ⋅ L⁻¹ and (0.2–1.0) ⋅ 10⁻⁴ mol ⋅ L⁻¹ and the high sensitivity: LOD without the removing of unreacted sodium nitrite is 1.1 ⋅ 10⁻⁶ mol ⋅ L⁻¹, and 7.2 ⋅ 10⁻⁷ mol ⋅ L⁻¹, when NaNO₂ excess is removed using urea. The developed voltammetric technique of AM determination has been approved during the analyses of tablets and oral suspension.     

Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren‐9‐olato− Anions and Indium(III) Phthalocyanine Bromide Radical Anions

Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu₄N⁺)₂[M^III(HFl−O⁻)(Pc^.3−)]^.−(Br⁻) ⋅ 1.5 C₆H₄Cl₂ [M=Al ( 1 ), Ga ( 2 ); HFl−O⁻=fluoren‐9‐olato⁻ anion; Pc=phthalocyanine] and (Bu₄N⁺) [In^IIIBr(Pc^.3−)]^.− ⋅ 0.875 C₆H₄Cl₂ ⋅ 0.125 C₆H₁₄ ( 3 ). The salts were found to contain Pc^.3− radical anions with negatively charged phthalocyanine macrocycles, as evidenced by the presence of intense bands of Pc^.3− in the near‐IR region and a noticeable blueshift in both the Q and Soret bands of phthalocyanine. The metal(III) atoms coordinate HFl−O⁻ anions in 1 and 2 with short Al−O and Ga−O bond lengths of 1.749(2) and 1.836(6) Å, respectively. The C−O bonds [1.402(3) and 1.391(11) Å in 1 and 2 , respectively] in the HFl−O⁻ anions are longer than the same bond in the fluorenone ketyl (1.27–1.31 Å). Salts 1 – 3 show effective magnetic moments of 1.72, 1.66, and 1.79 μ_B at 300 K, respectively, owing to the presence of unpaired S= 1/2 spins on Pc^.3−. These spins are coupled antiferromagnetically with Weiss temperatures of −22, −14, and −30 K for 1 – 3 , respectively. Coupling can occur in the corrugated two‐dimensional phthalocyanine layers of 1 and 2 with an exchange interaction of J /k _B=−0.9 and −1.1 K, respectively, and in the π‐stacking {[In^IIIBr(Pc^.3−)]^.−}₂ dimers of 3 with an exchange interaction of J /k _B=−10.8 K. The salts show intense electron paramagnetic resonance (EPR) signals attributed to Pc^.3−. It was found that increasing the size of the central metal atom strongly broadened these EPR signals.     

Ligand Modifications Produce Two-Step Magnetic Switching in a Cobalt(dioxolene) Complex

Mononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) Co^III(cat²⁻) and high spin (h.s.) Co^II(sq⋅⁻) forms (cat²⁻=catecholato, and sq⋅⁻=seminquinonato forms of 3,5−di−^tBu-1,2-dioxolene), which reversibly interconvert via temperature-dependent intramolecular electron transfer. Typically, the remaining four coordination sites on cobalt are supported by a tetradentate ligand whose properties influence the temperature at which VT occurs. We report that replacing one chelating pyridyl arm of tris(2-pyridylmethyl)amine (tpa) with a weaker field ortho-anisole moiety facilitates access to a third magnetic state, and examine a series of related complexes. Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies support that this third state is consistent with l.s. Co^II(sq⋅⁻). Thus, our ligand modifications not only provide access to the VT transition from l.s. Co^III(cat²⁻) to l.s. Co^II(sq⋅⁻), but at higher temperatures, the complex undergoes spin crossover from l.s. Co^II(sq⋅⁻) to h.s. Co^II(sq⋅⁻), representing the first example of two-step magnetic switching in a mononuclear monodioxolene cobalt complex. We hypothesize that ligand dynamicity may facilitate access to the rarely observed l.s. Co^II(sq⋅⁻) intermediate state, suggesting a new design criterion in the development of stimulus-responsive multi-state molecular switches.     

Protonation versus Oxonium Salt Formation: Basicity and Stability Tuning of Cyanoborate Anions

Anhydrous H[BH₂(CN)₂] crystallizes from acidic aqueous solutions of the dicyanodihydridoborate anion. The formation of H[BH₂(CN)₂] is surprising as the protonation of nitriles requires strongly acidic and anhydrous conditions but it can be rationalized based on theoretical data. In contrast, [BX(CN)₃]⁻ (X=H, F) gives the expected oxonium salts (H₃O)[BX(CN)₃] while (H₃O)[BF₂(CN)₂]/H[BF₂(CN)₂] is unstable. H[BH₂(CN)₂] forms chains via N−H⋅⋅⋅N bonds in the solid state and melts at 54 °C. Solutions of H[BH₂(CN)₂] in the room‐temperature ionic liquid [EMIm][BH₂(CN)₂] contain the [(NC)H₂BCN−H⋅⋅⋅NCBH₂(CN)]⁻ anion and are unusually stable, which enabled the study of selected spectroscopic and physical properties. [(NC)H₂BCN−H⋅⋅⋅NCBH₂(CN)]⁻ slowly gives H₂ and [(NC)H₂BCN−BH(CN)₂]⁻. The latter compound is a source of the free Lewis acid BH(CN)₂, as shown by the generation of [BHF(CN)₂]⁻ and BH(CN)₂⋅py.     

A sensitive DNA biosensor based on the distance dependent quenching of Silica@Ru(bpy)32+-chitosan-GO electrochemiluminescence by Ferrocene@Gold nanoparticles

A sensitive electrochemiluminescence (ECL) biosensor for the specific DNA sequence of hepatitis C virus (HCV) was developed based on the efficient quenching effect of the ferrocene cluster functionalized gold nanoparticles (Fc@AuNPs) on the ECL of electrodeposited silica@Ru(bpy)₃²⁺-chitosan-graphene oxide nanocomposite (SiO₂@Ru−CS−GO). Graphene oxide (GO) can accelerate electron transfer rate, thus improving the ECL of Ru(bpy)₃²⁺ on electrode surface. The molecular beacons (MB) was fixed to SiO₂@Ru−CS−GO by glutaraldehyde (GA) using the Schiff reaction between amino groups of chitosan (CS) and MB. The ECL of SiO₂@Ru−CS−GO was depressed greatly by the Fc@AuNPs labelled at the end of MB, then, a stronger ECL was observed when the distance between Fc@AuNPs and SiO₂@Ru−CS−GO increased after the hybridization of target DNA with MB. Under optimum conditions, the restored ECL intensity increased linearly with the target DNA concentration in the range of 1.0×10⁻¹⁶∼1.0×10⁻¹⁰ mol ⋅ L⁻¹, and the limit of detection (LOD) is 1.4×10⁻¹⁷ mol ⋅ L⁻¹. The proposed method exhibits acceptable stability and reproducibility. In general, the constructed HCV biosensor can be used for the sensitive detection of HCV in human serum, suggesting potential application prospects in bioanalysis.     

Field-Induced SMM Behaviour of Tetranuclear Coordination Clusters with a Cubane [Ni4O4] Core

Two tetranuclear Ni(II) complexes: [Ni₄(HL¹)₄] ⋅ H₂O ( 1 ) and [Ni₄(HL²)₄] ⋅ 1.5 dmf ( 2 ) where dmf=dimethylformamide, H₃L¹=4-(tert-butyl)-2-(((2-hydroxy-5-nitrophenyl)imino)methyl)-6-(hydroxymethyl)phenol and H₃L²=4-(tert-butyl)-2-(hydroxymethyl)-6-(((2-hydroxyphenyl)-imino)methyl)phenol, have been prepared and characterized by single crystal X-Ray diffraction, elemental analysis and FT-IR spectroscopy. The solid-state structures reveal the formation of highly symmetric and asymmetric [Ni₄O₄] cubane cores in complexes 1 and 2 , respectively. Extensive magnetic studies show that both complexes present ferromagnetic exchange interactions between the Ni(II) ions within the cubane core with g=2.113(3), J₁=−7.89(8) cm⁻¹, J₂=13.3(1) cm⁻¹ and |D|=11.3(4) cm⁻¹ (for 1 ) and g=2.206(4), J₁=1.0(1) cm⁻¹, J₂=7.8(1) cm⁻¹ and |D|=8.7(2) cm⁻¹ (for 2 ). The large anisotropy, high ground spin state (arising from the ferromagnetic coupling) and the good isolation of the clusters provided by the Schiff base ligands, give rise to the first examples of field-induced single-molecule magnets (FI−SMM) in Ni₄O₄ clusters and to the highest energy barrier reported to date in a Ni₄O₄ cluster.     

Syntheses,Structures, and Bonding of NgF2⋅CrOF4, NgF2⋅2CrOF4 (Ng=Kr,Xe), and (CrOF4)∞

The noble-gas difluoride adducts, NgF₂ ⋅ CrOF₄ and NgF₂ ⋅ 2CrOF₄ (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single-crystal X-ray diffraction. The low fluoride ion affinity of CrOF₄ renders it incapable of inducing fluoride ion transfer from NgF₂ (Ng=Kr and Xe) to form ion-paired salts of the [NgF]⁺ cations having either the [CrOF₅]⁻ or [Cr₂O₂F₉]⁻ anions. The crystal structures show the NgF₂ ⋅ CrOF₄ adducts are comprised of F_t−Ng−F_b- - -Cr(O)F₄ structural units in which NgF₂ is weakly coordinated to CrOF₄ by means of a fluorine bridge, F_b, in which Ng−F_b is elongated relative to the terminal Ng−F_t bond. In contrast with XeF₂ ⋅ 2MOF₄ (M=Mo or W) and KrF₂ ⋅ 2MoOF₄, in which the Lewis acidic, F₄(O)M- - -F_b- - -M(O)F₃ moiety coordinates to Ng through a single M- - -F_b−Ng bridge, both fluorine ligands of NgF₂ coordinate to CrOF₄ molecules to form F₄(O)Cr- - -F_b−Ng−F_b- - -Cr(O)F₄ adducts in which both Ng−F_b bonds are only marginally elongated relative to the Ng−F bonds of free NgF₂. Quantum-chemical calculations show that the Cr−F_b bonds of NgF₂ ⋅ CrOF₄ and NgF₂ ⋅ 2CrOF₄ are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr- - -F_b−Ng bridge angles and staggered O−Cr- - -F_b−Ng−F_t dihedral angles. The crystal structures and Raman spectra of two CrOF₄ polymorphs have also been obtained. Both are comprised of fluorine-bridged chains that are cis- and trans-fluorine-bridged with respect to oxygen.     

C−H Activation by Iron-Vanadium Bimetallic Oxide Cluster Anions FeV3O10− and FeV5O15−: A Comparison with Scandium-Vanadium Oxide Clusters

Late transition metal-bonded atomic oxygen radicals (LTM−O⋅⁻) have been frequently proposed as important active sites to selectively activate and transform inert alkane molecules. However, it is extremely challenging to characterize the LTM−O⋅⁻-mediated elementary reactions for clarifying the underlying mechanisms limited by the low activity of LTM−O⋅⁻ radicals that is inaccessible by the traditional experimental methods. Herein, benefiting from our newly-designed ship-lock type reactor, the reactivity of iron-vanadium bimetallic oxide cluster anions FeV₃O₁₀⁻ and FeV₅O₁₅⁻ featuring with Fe−O⋅⁻ radicals to abstract a hydrogen atom from C₂−C₄ alkanes has been experimentally characterized at 298 K, and the rate constants are determined in the orders of magnitude of 10⁻¹⁴ to 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹, which are four orders of magnitude slower than the values of counterpart ScV₃O₁₀⁻ and ScV₅O₁₅⁻ clusters bearing Sc−O⋅⁻ radicals. Theoretical results reveal that the rearrangements of the electronic and geometric structures during the reaction process function to modulate the activity of Fe−O⋅⁻. This study not only quantitatively characterizes the elementary reactions of LTM−O⋅⁻ radicals with alkanes, but also provides new insights into structure-activity relationship of M−O⋅⁻ radicals.     

Gallium “Shears” for C=N and C=O Bonds of Isocyanates

Digallane [L¹Ga−GaL¹] ( 1 , L¹=dpp-bian=1,2-[(2,6-iPr₂C₆H₃)NC]₂C₁₂H₆) reacts with RN=C=O (R=Ph or Tos) by [2+4] cycloaddition of the isocyanate C=N bonds across both of its C=C−N−Ga fragments to afford [L¹(O=C−NR)Ga−Ga(RN−C=O)L¹] (R=Ph, 3 ; R=Tos, 4 ). The reactions with both isocyanates result in new C−C and N−Ga single bonds. In the case of allyl isocyanate, the [2+4] cycloaddition across one C=C−N−Ga fragment of 1 is accompanied by insertion of a second allyl isocyanate molecule into the Ga−N bond of the same fragment to afford compound [L¹Ga−Ga(AllN− C=O)₂L¹] ( 5 ) (All=allyl). In the presence of Na metal, the related digallane [L²Ga−GaL²] ( 2 ; L²=dpp-dad=[(2,6-iPr₂C₆H₃)NC(CH₃)]₂) is converted into the gallium(I) carbene analogue [L²Ga:]⁻ ( 2 A ), which undergoes a variety of reactions with isocyanate substrates. These include the cycloaddition of ethyl isocyanate to 2 A affording [Na₂(THF)₅]{L²Ga[EtN−C(O)]₂GaL²} ( 6 ), cleavage of the N=C bond with release of 1 equiv. of CO to give [Na(THF)₂]₂[L²Ga(p-MeC₆H₄)(N−C(O))₂−N(p-MeC₆H₄)]₂ ( 7 ), cleavage of the C=O bond to yield the di-O-bridged digallium compound [Na(THF)₃]₂[L²Ga-(μ-O)₂-GaL²] ( 8 ), and generation of the further addition product [Na₂(THF)₅][L²Ga(CyNCO₂)]₂ ( 9 ). Complexes 3 – 9 have been characterized by NMR (¹H, ¹³C), IR spectroscopy, elemental analysis, and X-ray diffraction analysis. Their electronic structures have been examined by DFT calculations.     

Self-Assembled,Highly Positively Charged,Allyl–Pd Crowns: Cavity-Pocket-Driven Interactions of Fluoroanions

A series of dodecanuclear highly positively charged homo- and heterometallamacrocycles [{Pd(η³-2-Me-C₃H₄)}₆(4-PPh₂py)₁₂{M₂(tpbz)}₃]¹⁸⁺ (M=Pd, Pt; tpbz=1,2,4,5-tetrakis(diphenylphosphanyl)benzene were synthesized by the quantitative self-assembly of {Pd(η³-2-Me-C₃H₄)}⁺, {M₂(tpbz)}⁴⁺ and 4-PPh₂py moieties in 2:1:4 molar ratio. The cationic assemblies were obtained as salts of different fluorinated anions with diverse sizes and electronic properties, namely BF₄⁻, PF₆⁻, SbF₆⁻ and CF₃SO₃⁻. The new crown-like metallamacrocycles showed remarkable differences in their NMR spectra due to the presence of the different counteranions. On the basis of the observed variations, the metallacycles have been tested as catalytic precursors in allylic alkylation reactions. The anion-dependent activity and selectivity has been analysed and compared with that of the corresponding monometallic allylic corners [Pd(η³-2-Me-C₃H₄)(4-PPh₂py)₂]X (X=BF₄⁻, PF₆⁻, SbF₆⁻, CF₃SO₃⁻). DFT calculations have been employed in order to help to the interpretation of the experimental data and to model the anion–crown interactions.     

Room-Temperature Solid-State Transformation of Na4SnS4 ⋅ 14H2O into Na4Sn2S6 ⋅ 5H2O: An Unusual Epitaxial Reaction Including Bond Formation,Mass Transport,and Ionic Conductivity

A highly unusual solid-state epitaxy-induced phase transformation of Na₄SnS₄ ⋅ 14H₂O ( I ) into Na₄Sn₂S₆ ⋅ 5H₂O ( II ) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS₃SH]³⁻ which condensates to [Sn₂S₆]⁴⁻. The reaction involves a complex sequence of O−H bond cleavage, S²⁻ protonation, Sn−S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn₂S₆]⁴⁻. DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ ¹H NMR demonstrate a transformation within several days and yield a reaction turnover of ≈0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na)=6×10⁻¹⁴ m² s⁻¹ at T=300 K with values increasing by three orders of magnitude from −20 to +25 °C.     

Cyclopolymerization of 3-phenyl[5]ferrocenophane-1,5-dimethylene: Synthesis and electronic properties of a polyferrocenophane

Radical cyclopolymerization of 3-phenyl[5]ferrocenophane-1,5-dimethylene ( 2 ) and copolymerization with styrene gave polymers ( 3 and 4 ) with [3]ferrocenophane moieties pendant to the backbone. Cyclic voltammetry (CV) on polymer 3 in CH₂Cl₂ showed two oxidation waves at −0.13 and +0.05 V (versus ferrocene/ferrocenium) and CV on copolymer 4 showed one oxidation potential at −0.03 V. CV on 3 in dimethylacetamide showed only one oxidation potential at −0.10 V. Near-IR spectroscopy of partially oxidized 3 showed a broad intervalence band at ca. 2000 nm, indicative of low-energy barriers to electron hopping. Conductivity measurements on 3 and poly(vinylferrocene) (PVFc) oxidatively doped with iodine vapors under an argon atmosphere showed a maximum conductivity ca. 5 × 10⁻⁵ S/cm before the samples cracked, while 4 exhibited a maximum conductivity of 1.6 × 10⁻⁶ S/cm. On iodine doping under ambient conditions, polymers 3 , 4 , and PVFc showed maximum conductivities of 7.6 × 10⁻⁴, 9.5 × 10⁻⁵, and 5.5 × 10⁻⁵ S/cm, respectively. Conductivity measurement were also performed on samples of 3 ⁺BF₄⁻ with oxidation levels ranging from 8 to 56%. Conductivities of these samples ranged from ca. 10⁻¹⁰ to 10⁻⁹ S/cm under vacuum and ca. 10⁻⁶ S/cm under ambient conditions, indicating that atmospheric moisture has a strong effect on the conductivity. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3365–3376, 1997