Surfactant Quaternary Ammonium Hydrotris(1-pyrazolyl)borates

Abstract

Quaternary ammonium surfactants with the hydrotris(1-pyrazolyl)borate anion as an unusual counterion were prepared and characterized. Dodecyl- (1a), tetradecyl- (1b), and hexadecyltrimethylammonium hydrotris(1-pyrazolyl)borate (1c), as well as didodecyldimethylammonium hydrotris(1-pyrazolyl)borate (2), were prepared by metathesis reactions with the corresponding quaternary ammonium bromides and potassium hydrotris(1-pyrazolyl)borate (4). Although the surfactants have limited stabilities in water at 23 degrees C, they were characterized by measurement of their Krafft temperatures and critical aggregation concentrations. (1)H NMR spectroscopy suggested that the single-chain surfactants 1 form small aggregates in water and revealed an association of the quaternary ammonium and hydrotris(1-pyrazolyl)borate ions above their critical aggregation concentrations. Cryo-etch high-resolution scanning electron microscopy indicated that 1a and 1b most likely form segregation patterns upon plunge-freezing and cryo-etching of their aqueous solutions, and a single-crystal X-ray diffraction study of 1a was performed.

Covalently Bound Tetracoordinated Organoborons as Superhalogens: A Combined Negative Ion Photoelectron Spectroscopy and Theoretical Study

“…The B–C and B–N bond lengths in each compound are identical. These calculated bond lengths are comparable to the structural data of molecular crystals deposited in the Cambridge Crystallographic Data Center (CCDC, ) from original literature − (also listed in Table ). By removing a single electron out from the closed-shell singlet anion, the neutral radical is in the doublet electronic state.…”

“… a The reported bond lengths for the anions in the CCDC are listed for comparison. b CCDC crystal structure of [N 4 C(C 6 H 5 ) 3 ] + ·[ B(C C 6 H 5 ) 4 ] − (CCDC 896474) (from ref ). c CCDC crystal structure of [Au(dppb) 2 ] + ·[ B(C 6 H 4 F) 4 ] − (CCDC 777274) (from ref ). d CCDC crystal structure of Li + [B(bim) 4 ] − (CCDC 734221) (from ref ). e Crystal structure of [N(CH 3 ) 3 (C 12 H 25 ] + ·[ BH(C 3 H 3 N 2 ) 3 ] − (from ref ). …”