Critical Role of Nonrigid Unit and Spiral Acoustical Modes in Designing Colossal Negative Thermal Expansion.

Exploring the relationship between thermal expansion and structural complexity is a challenging topic in the study of modern materials where volume stability is required. This work reports a new family of negative thermal expansion (NTE) materials, AM(CN) with A = Li and Na and M = B, Al, Ga, and In. Here, the compounds of LiB(CN) and NaB(CN) were only synthesized; others were purely computationally studied.

Nickel(II) Cyanoborates and Cyanoborate-Ligated Nickel(II) Complexes.

Nickel(II) cyanoborates Ni[BH(CN)]·HO (·HO), Ni[BH(CN)]·0.5HO (·0.5HO), and Ni[B(CN)]·0.

Synthesis of Partially Fluorinated Alkyl Triflates by Electrochemical Fluorination (Simons Process).

A scalable straightforward synthesis of monofluoro- and difluoromethyl triflate CF SO OCH F (M ) and CF SO OCHF (M ) through electrochemical fluorination (ECF, Simons process) of methyl triflate M in anhydrous hydrogen fluoride at nickel anodes is presented. The ECF method is also feasible for the preparation of the deuterated analogues CF SO OCD F (M ) and CF SO OCDF (M ). Surprisingly, no H/D exchange occurs during ECF of CF SO OCD (M ); this provides further evidence for a NiF /NiF -mediated ECF mechanism.

Alkylcyanoborate Anions: Building Blocks for Fluorine-Free Low-Viscosity, Electrochemically and Thermally Stable Ionic Liquids.

A set of mixed-substituted potassium alkylcyano- and alkylcyanofluoroborates has been synthesized using easily accessible starting compounds and characterized by elemental analysis, NMR and vibrational spectroscopy, and mass spectrometry. In addition, single-crystal structures of salts of the cyanoborate anions have been derived from X-ray diffraction experiments. The 1-ethyl-3-methylimidazolium room temperature ionic liquids ([EMIm] -RTILs) with the new borate anions have been synthesized and their physicochemical properties, that is, high thermal and electrochemical stability, low viscosity, and high conductivity, have been compared to the properties of related [EMIm] -RTILs.

Insights into structure-property relationships in ionic liquids using cyclic perfluoroalkylsulfonylimides.

Room temperature ionic liquids of cyclic sulfonimide anions cPFSI (ring size: = 4-6) with the cations [EMIm] (1-ethyl-3-methylimidazolium), [BMIm] (1-butyl-3-methylimidazolium) and [BMPL] (BMPL = 1-butyl-1-methylpyrrolidinium) have been synthesized. Their solid-state structures have been elucidated by single-crystal X-ray diffraction and their physicochemical properties (thermal behaviour and stability, dynamic viscosity and specific conductivity) have been assessed. In addition, the ion diffusion was studied by pulsed field gradient stimulated echo (PFGSTE) NMR spectroscopy.

Cyano(fluoro)borate and cyano(hydrido)borate ionic liquids: low-viscosity ionic media for electrochemical applications.

The synthesis and detailed characterization of low-viscosity room-temperature ionic liquids (RTILs) and [BnPhP] salts with the cyano(fluoro)borate anions [BF(CN)] (MFB), [BF(CN)] (DFB), and [BF(CN)] as well as the new mixed-substituted anion [BFH(CN)] (FHB) is described. The RTILs with [EMIm] or [BMPL] as countercations were obtained in yields of up to 98% from readily available alkali metal salts and in high purities that allow application in electrochemical devices. Trends in thermal stability, melting and freezing behavior, density, electrochemical stability, dynamic viscosity, specific conductivity and ion diffusivity have been assessed and compared to those of the related tetracyanoborate- and cyano(hydrido)borate-RTILs.

Ethyl-, vinyl- and ethynylcyanoborates: room temperature borate ionic liquids with saturated and unsaturated hydrocarbon chains.

Ethyl-, vinyl- and ethynyltricyano and dicyanofluoroborates were prepared on a gram scale from commercially available potassium trifluoroborates and trimethylsilylcyanide. Salt metathesis resulted in the corresponding EMIm-salts that are hydrophobic room-temperature ionic liquids (RTILs). The new RTILs exhibit unprecedented large electrochemical windows in combination with high thermal stabilities, low dynamic viscosities and high specific conductivities.

BNB-doped phenalenyls - aromaticity switch upon one-electron reduction.

Fully aromatic, luminescent, and highly robust BNB-doped phenalenyls have been prepared, which are isoelectronic to the phenalenyl cation. B-Fluoromesityl-substitution leads to fluorescence in an extremely narrow range and significant increase in the reduction potential. Detailed theoretical investigations revealed an intramolecular aromaticity switch upon one-electron reduction.

Statistic Replacement of Lanthanide Ions in Bis-salicylatoborate Coordination Polymers for the Deliberate Control of the Luminescence Chromaticity.

Based on the strand-like coordination polymer (CP) type [Ln(BSB) (py) ], [BSB] =bis-salicylatoborate anion, mixed Eu/Tb-containing compounds of the constitution [Eu Tb (BSB) (py) ] were synthesised ionothermally for a phase width of (x=0.25-0.75) and characterized regarding structure and optical properties.

Innovative Syntheses of Cyano(fluoro)borates: Catalytic Cyanation, Electrochemical and Electrophilic Fluorination.

Different types of high-yield, easily scalable syntheses for cyano(fluoro)borates Kt[BF (CN) ] (n=0-2) (Kt=cation), which are versatile building blocks for materials applications and chemical synthesis, have been developed. Tetrafluoroborates react with trimethylsilyl cyanide in the presence of metal-free Brønsted or Lewis acid catalysts under unprecedentedly mild conditions to give tricyanofluoroborates or tetracyanoborates. Analogously, pentafluoroethyltrifluoroborates are converted into pentafluoroethyltricyanoborates.

Thermal Decomposition and Hypergolic Reaction of a Dicyanoborohydride Ionic Liquid.

In this study, in situ infrared spectroscopy techniques and thermogravimetric analysis coupled with mass spectrometry (TGA-MS) are employed to characterize the reactivity of the ionic liquid, 1-butyl-3-methylimidazolium dicyanoborohydride (BMIMDCBH), in comparison to the well-characterized 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA) ionic liquid. TGA measurements determined the enthalpy of vaporization (Δ) to be 112.7 ± 12.

Hydroxytricyanoborate Anion: Synthetic Aspects and Structural, Chemical, and Spectroscopic Properties.

In recent years, salts of the hydridotricyanoborate anion [BH(CN)] () have become readily available. In spite of the unusually high stability of the anion, it can be used as a valuable starting material for the preparation of selected tricyanoborates, for example, the boron-centered nucleophile B(CN). A further unprecedented example is the hydroxytricyanoborate anion [B(OH)(CN)] that is accessible by oxidation of (HO) with elemental bromine in water.

Cyanohydridoborate Anions: Synthesis, Salts, and Low-Viscosity Ionic Liquids.

High-yield syntheses up to molar scales for salts of [BH(CN) ] (2) and [BH (CN) ] (3) starting from commercially available Na[BH ] (Na5), Na[BH (CN)] (Na4), BCl , (CH ) SiCN, and KCN were developed. Direct conversion of Na5 into K2 was accomplished with (CH ) SiCN and (CH ) SiCl as a catalyst in an autoclave. Alternatively, Na5 is converted into Na[BH{OC(O)R} ] (R=alkyl) that is more reactive towards (CH ) SiCN and thus provides an easy access to salts of 2.

Oxidation of a Levitated 1-Butyl-3-methylimidazolium Dicyanoborate Droplet by Nitrogen Dioxide.

To develop the next generation of hypergolic, ionic-liquid-based fuels, it is important to understand the fundamental reaction mechanisms for the oxidation of ionic liquids (ILs). We consequently studied the oxidation of a levitated 1-butyl-3-methylimidazolium dicyanoborate ([BMIM][DCBH]) droplet by nitrogen dioxide (NO). The properties of [BMIM][DCBH], including short ignition-delay times, low viscosities, and a wide liquid temperature range, make the ionic liquid especially suitable as a component of a hypergolic fuel.

The Role of [BF ] and [B(CN) ] Anions in the Ionothermal Synthesis of Chalcogenidometalates.

The role of borate anions in ionothermal syntheses of crystalline chalcogenidometalates was shown by the directed ionothermal synthesis of seven new selenidostannates in ionic liquids with either [BF ] or [B(CN) ] anions. Single crystal structures are presented of four compounds, (C C C Im) [Sn Se ][BF ] (1, Im=imidazolium), (DMMPH) [Sn Se ] (2, DMMP=2,6-dimethylmorpholine), (C C Im) (DMMPH) [Sn Se ] (3), and K [Sn Se ] (4), and how the chosen ionic liquid anion, and the reaction temperature, influences the product spectrum is discussed: Notably, 1 contains an entire formula unit of the ionic liquid, (C C C Im)[BF ], while 4 contains neither the cation nor the anion of the ionic liquid-both observations being very uncommon for ionothermal syntheses. Three further compounds were obtained that exhibit strong disorder in the crystal structures (I-III), for which only their anionic substructures are discussed herein.

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

Anhydrous H[BH (CN) ] crystallizes from acidic aqueous solutions of the dicyanodihydridoborate anion. The formation of H[BH (CN) ] 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) ] (X=H, F) gives the expected oxonium salts (H O)[BX(CN) ] while (H O)[BF (CN) ]/H[BF (CN) ] is unstable.

Formation of a Trifluorophosphane Platinum(II) Complex by P-F Bond Activation of Phosphorus Pentafluoride with a Pt Complex.

The reaction of PF with [(Cy P) Pt] gave the PF complex trans-[(Cy P) PtF(PF )][PF ], which was characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy, and elemental analysis. To the best of our knowledge, this reaction is the first example of the oxidative addition of a P-F bond to a transition metal and is a rare example of an activation of a main-group-element-fluorine bond by a metal. Relativistic DFT calculations showed that the formation of the Lewis pair [(Cy P) Pt→PF ], which was not observed even at low temperatures, represents the initial step of the reaction.

The hexacyanodiborane(6) dianion [B2(CN)6](2-).

Diborane(6) dianions with substituents that are bonded to boron via carbon are very reactive and therefore only a few examples are known. Diborane(6) derivatives are the simplest catenated boron compounds with an electron-precise B-B σ-bond that are of fundamental interest and of relevance for material applications. The homoleptic hexacyanodiborane(6) dianion [B2 (CN)6 ](2-) that is chemically very robust is reported.

Syntheses of tricyanofluoroborates M[BF(CN)3] (M = Na, K): (CH3)3SiCl catalysis, countercation effect, and reaction intermediates.

Potassium tricyanofluoroborate, K[BF(CN)3], which is the starting material for tricyanofluoroborate room-temperature ionic liquids [N. Ignat'ev et al. J.

Convenient access to the tricyanoborate dianion B(CN)₃²⁻ and selected reactions as a boron-centred nucleophile.

Alkali metal tricyanoborates M2B(CN)3 (M = Na, K) are accessible by the reaction of tricyanofluoroborates with alkali metals (i) in liquid NH3 or (ii) in THF-naphthalene. The M2B(CN)3 are versatile starting materials for the synthesis of K[RB(CN)3] (R = Et, C6F5, CH2=CHCH2).

Salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB11X11]- (X = H, F, Cl, Br, I).

The caesium and tetraethylammonium salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB(11)X(11)](-) (X = H, F, Cl, Br, I) were synthesized from CsLi[closo-1-CB(11)X(11)] and phenylcyanate. All anions are stable against aqueous acids and bases, except for the fluorinated anion [1-NC-closo-1-CB(11)F(11)](-) that immediately reacts with water. The Cs(+) and [Et(4)N](+) salts of the anions were characterized by IR, Raman and multinuclear NMR spectroscopy as well as by MALDI and ESI mass spectrometry.

Anionic gold(I) complexes-twelve- and ten-vertex monocarba-closo-borate anions with carbon-gold sigma bonds.

The anionic gold(I) complexes [1-(Ph(3)PAu)-closo-1-CB(11)H(11)](-) (1), [1-(Ph(3)PAu)-closo-1-CB(9)H(9)](-) (2), and [2-(Ph(3)PAu)-closo-2-CB(9)H(9)](-) (3) with gold-carbon 2c-2e sigma bonds have been prepared from [AuCl(PPh(3))] and the respective carba-closo-borate dianion. The anions have been isolated as their Cs(+) salts and the corresponding [Et(4)N](+) salts were obtained by salt metathesis reactions. The salt Cs-3 isomerizes in the solid state and in solution at elevated temperatures to Cs-2 with DeltaH(iso)=(-75+/-5) kJ mol(-1) (solid state) and DeltaH( not equal)=(118+/-10) kJ mol(-1) (solution).