Komplexe der Alkalimetalltetraphenylborate mit makrocyclischen Kronenethern

Complexes of the Alkali Metal Tetraphenylborates with Macrocyclic Crown Ethers Alkali metal tetraphenylborates, MB(C₆H₅)₄ (M = Li to Cs), react in tetrahydrofuran with macrocyclic crown ethers to give complexes of the general formula MB(C₆H₅)₄(crown)_m(THF)_n. Suitable single crystals for X‐ray structure analysis were grown from a solvent mixture of tetrahydrofuran and n‐hexane. The salt like complexes [Li(12‐crown‐4)(thf)][B(C₆H₅)₄] ( 1 ), [Na(15‐crown‐5)(thf)][B(C₆H₅)₄] ( 2 ), and [Cs(18‐crown‐6)₂][B(C₆H₅)₄] · THF ( 6 ), the mononuclear molecular complexes [KB(C₆H₅)₄(18‐crown‐6)(thf)] ( 3 ), [RbB(C₆H₅)₄(18‐crown‐6)] ( 4 ), and [CsB(C₆H₅)₄(18‐crown‐6)] · THF ( 5 ), and the compound [CsB(C₆H₅)₄(18‐crown‐6)]₂[Cs(18‐crown‐6)₂][B(C₆H₅)₄] ( 7 ), which contains a binuclear molecule ([CsB(C₆H₅)₄(18‐crown‐6)]₂) beside a [Cs(18‐crown‐6)₂]⁺ cation and a [B(C₆H₅)₄]^? anion, are described. All compounds are charactarized by infrared spectra, elemental analysis, NMR‐spectroscopy, and X‐ray single crystal structure analysis.     

Strukturen von polaren Magnesiumorganylen: Synthese und Struktur von Basen‐Addukten des Bis(cyclopentadienyl)magnesiums

Structures of Polar Magnesium Organyls: Synthesis and Structure of Base Adducts of Bis(cyclopentadienyl)magnesium Eight donor‐acceptor complexes of bis(cyclopentadienyl)magnesium ( 1 ) with N‐ and O‐donor Lewis bases have been synthesized and characterized by X‐ray structure analysis. With acetonitrile, dimethoxyethane, diethyleneglycoldimethylether, dioxane, and tetramethylethylenediamine simple 1:1 adducts are formed ( 2 – 6 ). In some cases a change of the hapticity of one cyclopentadienylring from η⁵ to η² or η¹ is observed ( 4 – 6 ). In the adduct with pentamethyldiethylenetriamine ( 7 ) one C₅H₅‐ring is removed from the magnesium atom forming the cation [Mg(C₅H₅)(PMDTA)]⁺ and an uncoordinated five‐ring anion. With the crown ether 15‐crown‐5 the two ionic Mg compounds 8 and 9 are formed which have a [Mg(15‐crown‐5)L₂]²⁺‐cation [L = pyridine, THF] and two uncoordinated cyclopentadienyl anions. Cyclopentadienyl‐methyl‐magnesium reacts with 15‐crown‐5 to the salt [Mg(CH₃)(15‐crown‐5)]⁺ C₅H₅^? ( 10 ) which has also a free cyclopentadienyl anion.     

Propane‐1,3‐diaminium tetrachloridozincate(II) 18‐crown‐6 clathrate

The reaction of propane‐1,3‐diamine hydrochloride, 18‐crown‐6 and zinc(II) chloride in methanol solution yields the title complex salt [systematic name: propane‐1,3‐diaminium tetrachloridozincate(II)–1,4,7,10,13,16‐hexaoxacyclooctadecane (1/1)], (C₃H₁₂N₂)[ZnCl₄]·C₁₂H₂₄O₆, with an unusual supramolecular structure. The diprotonated propane‐1,3‐diaminium cation forms an unexpected 1:1 supramolecular rotator–stator complex with the crown ether, viz. [C₃H₁₂N₂(18‐crown‐6)]²⁺, in which one of the –NH₃⁺ substituents nests in the crown and interacts through N—H...O hydrogen bonding. The other –NH₃⁺ group interacts with the [ZnCl₄]²⁻ anion via N—H...Cl hydrogen bonding, forming cation–crown–anion ribbons parallel to [010].     

A novel PtII–dibenzo‐18‐crown‐6 (DB18C6) complex

The novel Pt^II–dibenzo‐18‐crown‐6 (DB18C6) title complex, μ‐[tetrakis­(thio­cyanato‐S)­platinum(II)]‐N:N′‐bis{[2,5,8,­15,18,21‐hexa­oxa­tri­cyclo­[20.4.0.1^9,14]­hexa­cosa‐1(22),9(14),10,12,23,25‐hexaene‐κ⁶O]­potassium(I)}, [K(C₂₀H₂₄O₆)]₂[Pt(SCN)₄], has been isolated and characterized by X‐ray diffraction analysis. The structure analysis shows that the complex displays a quasi‐one‐dimensional infinite chain of two [K(DB18C6)]⁺ complex cations and a [Pt(SCN)₄]^2? anion, bridged by K⁺?π interactions between adjacent [K(DB18C6)]⁺ units.     

Chiral η6‐Arene/N‐Tosylethylenediamine–Ruthenium(II) Complexes: Solution Behavior and Catalytic Activity for Asymmetric Hydrogenation

Aromatic ketones are enantioseletively hydrogenated in alcohols containing [RuX{(S,S)‐Tsdpen}(η⁶‐p‐cymene)] (Tsdpen=TsNCH(C₆H₅)CH(C₆H₅)NH₂; X=TfO, Cl) as precatalysts. The corresponding Ru hydride (X=H) acts as a reducing species. The solution structures and complete spectral assignment of these complexes have been determined using 2D NMR (¹H‐¹H DQF‐COSY, ¹H‐¹³C HMQC, ¹H‐¹⁵N HSQC, and ¹H‐¹⁹F HOESY). Depending on the nature of the solvents and conditions, the precatalysts exist as a covalently bound complex, tight ion pair of [Ru⁺(Tsdpen)(cymene)] and X^?, solvent‐separated ion pair, or discrete free ions. Solvent effects on the NH₂ chemical shifts of the Ru complexes and the hydrodynamic radius and volume of the Ru⁺ and TfO^? ions elucidate the process of precatalyst activation for hydrogenation. Most notably, the Ru triflate possessing a high ionizability, substantiated by cyclic voltammetry, exists in alcoholic solvents largely as a solvent‐separated ion pair and/or free ions. Accordingly, its diffusion‐derived data in CD₃OD reflect the independent motion of [Ru⁺(Tsdpen)(cymene)] and TfO^?. In CDCl₃, the complex largely retains the covalent structure showing similar diffusion data for the cation and anion. The Ru triflate and chloride show similar but distinct solution behavior in various solvents. Conductivity measurements and catalytic behavior demonstrate that both complexes ionize in CH₃OH to generate a common [Ru⁺(Tsdpen)(cymene)] and X^?, although the extent is significantly greater for X=TfO^?. The activation of [RuX(Tsdpen)(cymene)] during catalytic hydrogenation in alcoholic solvent occurs by simple ionization to generate [Ru⁺(Tsdpen)(cymene)]. The catalytic activity is thus significantly influenced by the reaction conditions.     

Trichloropalladate(II) Complexes with Pyridine Ligands – Molecular Structure and Conformational Analysis of [K(18C6)][PdCl3(py)]

[K(18C6)]₂[Pd₂Cl₆] ( 1 ) (18C6 = 18‐crown‐6) was found to react with pyridines in a strictly stoichiometric ratio 1 : 2 in methylene chloride or nitromethane to yield trichloropalladate(II) complexes [K(18C6)][PdCl₃(py*)] (py* = py, 2a ; 4‐Bnpy, 2b ; 4‐tBupy, 2c ; Bn = benzyl; tBu = tert‐butyl). The reaction of 1 with pyrimidine (pyrm) in a 1 : 1 ratio led to the formation of the pyrimidine‐bridged bis(trichloropalladate) complex [K(18C6)]₂[(PdCl₃)₂(μ‐pyrm)] ( 3 ). The identities of the complexes were confirmed by means of NMR spectroscopy (¹H, ¹³C) and microanalysis. The X‐ray structure analysis of 2a reveals square‐planar coordination of the Pd atom in the [PdCl₃(py)]^? anion. The pyridine plane forms with the complex plane an angle of 55.8(2)°. In the [K(18C6)]⁺ cation the K⁺ lies outside the mean plane of the crown ether (defined by the 6 O atoms) by 0.816(1) Å. There are tight K···Cl contacts between the cation and the anion (K···Cl1 3.340(2) Å, K···Cl2 3.166(2) Å). To gain an insight into the conformation of the [PdCl₃(py)]^? anion, DFT calculations were performed showing that the equilibrium structure ( 6eq ) has an angle between the pyridine ligand and the complex plane of 35.3°. Rotation of the pyridine ligand around the Pd–N vector exhibited two transition states where the pyridine ligand lies either in the complex plane ( 6TS _pla, 0.87 kcal/mol above 6eq ) or is perpendicular to it ( 6TS _per, 3.76 kcal/mol above 6eq ). Based on an energy decomposition analysis the conformation of the anion is discussed in terms of repulsive steric interactions and of stabilizing σ and π orbital interactions between the PdCl₃^? moiety and the pyridine ligand.     

Bis(adamantan‐1‐aminium) tetrachloridozincate(II) 18‐crown‐6 monohydrate clathrate

The structure of the title compound [systematic name: bis(adamantan‐1‐aminium) tetrachloridozincate(II)–1,4,7,10,13,16‐hexaoxacyclooctadecane–water (1/1/1)], (C₁₀H₁₈N)₂[ZnCl₄]·C₁₂H₂₄O₆·H₂O, consists of supramolecular rotator–stator assemblies and ribbons of hydrogen bonds parallel to [010]. The assemblies are composed of one protonated adamantan‐1‐aminium cation and one crown ether molecule (1,4,7,10,13,16‐hexaoxacyclooctadecane) to give an overall [(C₁₀H₁₈N)(18‐crown‐6)]⁺ cation. The –NH₃⁺ group of the cation nests in the crown and links to the crown‐ether O atoms through N—H...O hydrogen bonds. The 18‐crown‐6 ring adopts a pseudo‐C_3v conformation. The second adamantan‐1‐aminium forms part of ribbons of adamantan‐1‐aminium–water–tetrachloridozincate units which are interconnected by O—H...Cl, N—H...O and N—H...Cl hydrogen bonds via three different continuous rings with R₅⁴(12), R₄³(10) and R₃³(8) motifs.     

Ion Pairing and Salt Structure in Organic Salts through Diffusion,Overhauser, DFT and X‐ray Methods

Pulsed gradient spin‐echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a – f [ a : X=BF₄^?; b : X=PF₆^?; c : X=MeSO₃^?, d : X=CF₃SO₃^?; e : X=BArF^?; f : X=PtCl₃(C₂H₄)^?], b) 4‐tert‐butyl‐N‐benzyl analogue, 7 and c) the aryl carbocations (p‐R‐C₆H₄)₂CH 9 a (R=CH₃O) and 9 b (R=(CH₃)₂N), (p‐CH₃O‐C₆H₄)_xCPh_3?x⁺ 10 a – c (x=1–3, respectively) and (p‐R‐C₆H₄)₃C⁺ 11 (R=(CH₃)₂N) and 12 (R=H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl₃, intermediate ion pairing in CD₂Cl₂ and little ion pairing in [D₆]acetone. ¹H, ¹⁹F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6 and 7 reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9 – 12 , (all as BF₄^? salts) based on the NOE results, one finds marked changes in the relative positions of the BF₄^? anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p‐substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid‐state structures for 6 c and the novel Zeise's salt derivative, [brucinium][PtCl₃(C₂H₄)], 6 f , are reported. Analysis of ¹⁹⁵Pt NMR and other NMR measurements suggest that the η²‐C₂H₄ bonding to the platinum centre in 6 f is very similar to that found in K[PtCl₃(C₂H₄)]. Field dependent T₁ measurements on [brucinium][PtCl₃(C₂H₄)] and K[PtCl₃(C₂H₄)], are reported and suggested to be useful in recognizing aggregation effects.     

Univalent Gallium Complexes of Simple and ansa‐Arene Ligands: Effects on the Polymerization of Isobutylene

Using [Ga(C₆H₅F)₂]⁺[Al(OR^F)₄]^?( 1 ) (R^F=C(CF₃)₃) as starting material, we isolated bis‐ and tris‐η⁶‐coordinated gallium(I) arene complex salts of p‐xylene (1,4‐Me₂C₆H₄), hexamethylbenzene (C₆Me₆), diphenylethane (PhC₂H₄Ph), and m‐terphenyl (1,3‐Ph₂C₆H₄): [Ga(1,4‐Me₂C₆H₄)_2.5]⁺ ( 2⁺ ), [Ga(C₆Me₆)₂]⁺ ( 3⁺ ), [Ga(PhC₂H₄Ph)]⁺ ( 4⁺ ) and [(C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺ ( 5²⁺ ). 4⁺ is the first structurally characterized ansa‐like bent sandwich chelate of univalent gallium and 5²⁺ the first binuclear gallium(I) complex without a Ga?Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI‐BP86/SV(P) level), [Ga(PhC₂H₄Ph)]⁺[Al(OR^F)₄]^?( 4 ) and [(C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺{[Al(OR^F)₄] ^?}₂ ( 5 ), featuring ansa‐arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR‐PIB). In comparison to the recently published 1 and the [Ga(1,3,5‐Me₃C₆H₃)₂]⁺[Al(OR^F)₄]^? salt ( 6 ) (1,3,5‐Me₃C₆H₃=mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR‐PIB with high contents of terminal olefinic double bonds (α‐contents=84–93 %), low molecular weights (M_n=1000–3000 g mol^?1) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6 , the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.     

Two crown‐ether‐coordinated caesium halogen salts

The crystal structures of two crown‐ether‐coordinated caesium halogen salt hydrates, namely di‐μ‐bromido‐bis[aqua(1,4,7,10,13,16‐hexaoxacyclooctadecane)caesium(I)] dihydrate, [Cs₂Br₂(C₁₂H₂₄O₆)₂(H₂O)₂]·2H₂O, (I), and poly[[diaquadi‐μ‐chlorido‐μ‐(1,4,7,10,13,16‐hexaoxacyclooctadecane)dicaesium(I)] dihydrate], {[Cs₂Cl₂(C₁₂H₂₄O₆)(H₂O)₂]·2H₂O}_n, (II), are reported. In (I), all atoms are located on general positions. In (II), the Cs⁺ cation is located on a mirror plane perpendicular to the a axis, the chloride anion is located on a mirror plane perpendicular to the c axis and the crown‐ether ring is located around a special position with site symmetry 2/m, with two opposite O atoms exactly on the mirror plane perpendicular to the a axis; of one water molecule, only the O atom is located on a mirror plane perpendicular on the a axis, while the other water molecule is completely located on a mirror plane perpendicular to the c axis. Whereas in (I), hydrogen bonds between bromide ligands and water molecules lead to one‐dimensional chains running along the b axis, in (II) two‐dimensional sheets of water molecules and chloride ligands are formed which combine with the polymeric caesium–crown polymer to give a three‐dimensional network. Although both compounds have a similar composition, i.e. a Cs⁺ cation with a halogen, an 18‐crown‐6 ether and a water ligand, the crystal structures are rather different. On the other hand, it is remarkable that (I) is isomorphous with the already published iodide compound.     

Stabilization of Substituted Triazenide Oxides: Synthesis and X‐ray Structural Features of Polymeric Potassium 3‐(4‐carboxylatophenyl)‐1‐methyltriazene N‐oxide‐hydrate, {K[O2C‐C6H4‐N(H)NN(CH3)O]·4H2O}n

3‐(4‐carboxyphenyl)‐1‐methyltriazene N‐oxide reacts with KOH in methanol/pyridine to give {K[O₂C‐C₆H₄‐N(H)NN(CH₃)O]·4H₂O}_n, Potassium‐3‐(4‐carboxylatophenyl)‐1‐methyltriazene N‐oxide). The terminal carboxylato group of the anion does not interact with the cation. In the crystal lattice of {K(C₈H₈N₃O₃)·4H₂O}_n each three of the four water molecules interact with two potassium cations, every K⁺ ion being the centre of six bridging K···O interactions. Potassium cations interact further with the terminal N‐oxigen atom of single [C₈H₈N₃O₃]^? anions achieving two parallel {C₈H₈N₃O₃^?K⁺}_n chains, which are linked through water molecules. The resulting polymeric, one‐dimensional chain, is operated by a screw axis 2₁ parallel to the crystallographic direction [010], along and equidistant to the K⁺ centres. The coordination of the K⁺ centres involves a distortion of the boat conformation of elementary sulfur (S₈) with the ideal C_2v symmetry.     

Thermodynamic and Kinetic Study of Scandium(III) Complexes of DTPA and DOTA: A Step Toward Scandium Radiopharmaceuticals

Diethylenetriamine‐N,N,N′,N′′,N′′‐pentaacetic acid (DTPA) and 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) scandium(III) complexes were investigated in the solution and solid state. Three ⁴⁵Sc NMR spectroscopic references suitable for aqueous solutions were suggested: 0.1 M Sc(ClO₄)₃ in 1 M aq. HClO₄ (δ_Sc=0.0 ppm), 0.1 M ScCl₃ in 1 M aq. HCl (δ_Sc=1.75 ppm) and 0.01 M [Sc(ox)₄]^5? (ox^2?=oxalato) in 1 M aq. K₂C₂O₄ (δ_Sc=8.31 ppm). In solution, [Sc(dtpa)]^2? complex (δ_Sc=83 ppm, ?ν=770 Hz) has a rather symmetric ligand field unlike highly unsymmetrical donor atom arrangement in [Sc(dota)]^? anion (δ_Sc=100 ppm, ?ν=4300 Hz). The solid‐state structure of K₈[Sc₂(ox)₇] ? 13 H₂O contains two [Sc(ox)₃]^3? units bridged by twice “side‐on” coordinated oxalate anion with Sc³⁺ ion in a dodecahedral O₈ arrangement. Structures of [Sc(dtpa)]^2? and [Sc(dota)]^? in [(Hguanidine)]₂[Sc(dtpa)] ? 3 H₂O and K[Sc(dota)][H₆dota]Cl₂ ? 4 H₂O, respectively, are analogous to those of trivalent lanthanide complexes with the same ligands. The [Sc(dota)]^? unit exhibits twisted square‐antiprismatic arrangement without an axial ligand (TSA′ isomer) and [Sc(dota)]^? and (H₆dota)²⁺ units are bridged by a K⁺ cation. A surprisingly high value of the last DOTA dissociation constant (pK_a=12.9) was determined by potentiometry and confirmed by using NMR spectroscopy. Stability constants of scandium(III) complexes (log K_ScL 27.43 and 30.79 for DTPA and DOTA, respectively) were determined from potentiometric and ⁴⁵Sc NMR spectroscopic data. Both complexes are fully formed even below pH 2. Complexation of DOTA with the Sc³⁺ ion is much faster than with trivalent lanthanides. Proton‐assisted decomplexation of the [Sc(dota)]^? complex (τ_1/2=45 h; 1 M aq. HCl, 25 °C) is much slower than that for [Ln(dota)]^? complexes. Therefore, DOTA and its derivatives seem to be very suitable ligands for scandium radioisotopes.     

Why Do Five Ga+ Cations Form a Ligand‐Stabilized [Ga5]5+ Pentagon and How Does a 5:1 Salt Pack in the Solid State?

The reaction of the Ga⁺ source [Ga(PhF)₂]⁺[Al(OR^F)₄]^? with the neutral σ‐donor ligand dmap (4‐Me₂N‐C₆H₄N) produces the unexpectedly large and fivefold positively charged cluster cation salt [Ga₅(dmap)₁₀]⁵⁺([Al(OR^F)₄]^?)₅. It includes a regular and planar Ga₅ pentagon with strong metal–metal bonding. Additionally, the compound represents the first salt in which an ionic 1:5 packing is realized. We discuss the nature of this structure which results from the conversion of the non‐bonding 4s² lone‐pair orbitals into fully Ga‐Ga‐bonding orbitals and the solid‐state arrangement of the ions constituting the lattice as an almost orthohexagonal AX₅ lattice, possibly the aristotype of any 5:1 salt.     

Hydrogen Storage in a Potassium‐Ion‐Bound Metal–Organic Framework Incorporating Crown Ether Struts as Specific Cation Binding Sites

To develop a metal–organic framework (MOF) for hydrogen storage, SNU‐200 incorporating a 18‐crown‐6 ether moiety as a specific binding site for selected cations has been synthesized. SNU‐200 binds K⁺, NH₄⁺, and methyl viologen(MV²⁺) through single‐crystal to single‐crystal transformations. It exhibits characteristic gas‐sorption properties depending on the bound cation. SNU‐200 activated with supercritical CO₂ shows a higher isosteric heat (Q_st) of H₂ adsorption (7.70 kJ mol^?1) than other zinc‐based MOFs. Among the cation inclusions, K⁺ is the best for enhancing the isosteric heat of the H₂ adsorption (9.92 kJ mol^?1) as a result of the accessible open metal sites on the K⁺ ion.     

The first crystal structure of an alkaline metal salt of thioglucose: potassium 1‐thio‐β‐D‐glucoside monohydrate

In the crystal structure of the title hydrated salt, poly[(μ₂‐aqua)(μ₄‐1‐sulfido‐β‐D‐glucoside)potassium], [K(C₆H₁₁O₅S)(H₂O)]_n or K⁺·C₆H₁₁O₅S⁻·H₂O, each thioglucoside anion coordinates to four K⁺ cations through three of its four hydroxy groups, forming a three‐dimensional polymeric structure. The negatively charged thiolate group in each anion does not form an efficient coordination bond with a K⁺ cation, but forms intermolecular hydrogen bonds with four hydroxy groups, which appears to sustain the polymeric structure. The Cremer–Pople parameters for the thioglucoside ligand (Q = 0.575, θ = 8.233° and ϕ = 353.773°) indicate a slight distortion of the pyranose ring.     

Synthesis and characterization of tetramethylammonium trifluorosulfate

[Me₄N]⁺[SO₂F₃]^?, the first example of a [SO₂F₃]^? salt, has been prepared from Me₄NF and SO₂F₂. The colorless, microcrystalline solid was characterized by its infrared and Raman spectra. The trigonal bipyramidal structure of C_2v symmetry of the [SO₂F₃]^? anion is predicted by ab initio calculations. Two oxygen atoms with d(SO)=143.2 pm and one fluorine atom with d(SF)=157.9 pm occupy the equatorial plane. The two fluorine atoms in the axial position with d(SF)=168.5 pm are repulsed by the two oxygen atoms forming a bent axis with ?(F_axSF_ax)=165.2°.     

Crystal Structures of the Potassium and Silver Salts of Nitroform

The solid state structures of three nitroformate (NF) salts were determined using single crystal X‐ray crystallography. The NF anion was found to be a non‐planar moiety which adopts either the commonly observed C_2v conformation or distorted propeller conformation (D₃) in the case of the silver salts, or, a C₂ conformation in the case of the potassium salt. This latter C₂ conformation has been uniquely observed for potassium nitroformate. All structures exhibit cation‐anion interactions that influence the structure of the anion. The ¹³C and ¹⁴N NMR spectra of the NF anion show broad singlets, which indicates the equivalence of the nitro groups in solution within the NMR time‐scale. In addition, the vibrational and mass spectra of potassium nitroformate and silver nitroformate monohydrate were recorded. Furthermore, the gaseous decomposition products of potassium nitroformate at 25 °C were detected using IR spectroscopy and mass spectrometry.     

Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

Bis(6‐thioxo‐1,6‐dihydro­purinium) tetra­chloro­zincate(II)

The title salt, (C₅H₅N₄S)₂[ZnCl₄], consists of two 6‐thioxo‐1,6‐dihydro­purinium (6mpH₂⁺) cations (A and B) and a tetra­chloro­zincate anion, which are held together by N—H⋯Cl and C—H⋯Cl inter­actions. There is an anion–π inter­action between one Cl atom of the [ZnCl₄]⁻ anion and the pyrimidine ring of the 6mpH₂⁺(B) cation. Inter­molecular π–π stacking inter­actions allow 6mpH₂⁺(A) cations to form anti­parallel pairs. One inter­esting structural feature is the double N—H⋯N inter­molecular hydrogen bonds between two 6mpH₂⁺(A) cations. This kind of inter­action, mimicking that of natural nucleobases, can be very valuable in designing new therapeutic purine derivatives.     

Designing and Constructing a High‐Temperature Molecular Ferroelectric by Anion and Cation Replacement in a Simple Crown Ether Clathrate

Molecular ferroelectrics have displayed a promising future since they are light‐weight, flexible, environmentally friendly and easily synthesized, compared to traditional inorganic ferroelectrics. However, how to precisely design a molecular ferroelectric from a non‐ferroelectric phase transition molecular system is still a great challenge. Here we designed and constructed a molecular ferroelectric by double regulation of the anion and cation in a simple crown ether clathrate, 4 , [K(18‐crown‐6)]⁺[PF₆]^?. By replacing K⁺ and PF₆^? with H₃O⁺ and [FeCl₄]^? respectively, we obtained a new molecular ferroelectric [H₃O(18‐crown‐6)]⁺[FeCl₄]^?, 1 . Compound 1 undergoes a para‐ferroelectric phase transition near 350 K with symmetry change from P21/n to the Pmc21 space group. X‐ray single‐crystal diffraction analysis suggests that the phase transition was mainly triggered by the displacement motion of H₃O⁺ and [FeCl₄]^? ions and twist motion of 18‐crown‐6 molecule. Strikingly, compound 1 shows high a Curie temperature (350 K), ultra‐strong second harmonic generation signals (nearly 8 times of KDP), remarkable dielectric switching effect and large spontaneous polarization. We believe that this research will pave the way to design and build high‐quality molecular ferroelectrics as well as their application in smart materials.