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.

Pentafluoroethylaluminates: A Combined Synthetic, Spectroscopic, and Structural Study.

Salts of the tetrakis(pentafluoroethyl)aluminate anion [Al(C F ) ] were obtained from AlCl and LiC F . They were isolated with different counter-cations and characterized by NMR and vibrational spectroscopy and mass spectrometry. Degradation of the [Al(C F ) ] ion was found to proceed via 1,2-fluorine shifts and stepwise loss of CF(CF ) under formation of [(C F ) AlF ] (n=1-4) as assessed by NMR spectroscopy and mass spectrometry and supported by results of DFT calculations.

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.

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.