Measurement of boron trihalide electron affinities: correlation with boron-nitrogen adduct strengths

Abstract

The adiabatic electron affinities of several boron trihalides have been measured from the determination of threshold kinetic energies for the reaction Cs + BX3 + C s ' + BX). A crossed-molecular-beam apparatus was used. The electron affinities are <O.O, 0.33, 0.69,0.94, and 0.82 eV for BF,, BC13, BClZBr, BCIBr2, and BBr3, respectively, with an error estimate of about 4~0.2 eV. These electron affinities are used to obtain B-N bond energies for adducts of boron trihalides with Me3,N by using an ionic energy cycle. Values are compared to direct measurements and to those estimated from N M R shift measurements.

The vibrational spectra of molecular ions isolated in solid neon. XII. HCl+, (HCl)+2, ClHCl−, and O2⋅⋅HCl+

“…The adiabatic electron affinity of CO 2 in the gas phase is Ϫ0.6 eV, 60,61 and that of BF 3 is also slightly negative. [62][63][64] No absorption with a photodetachment threshold suitably low for assignment to HCl Ϫ has been detected in the present experiments.…”

Energetics of hydride and electron pair attachment to EX30/+ (E=B, C, Al, Si and X=F, Cl, Br, I) and the study of bonding trends among EX30/+, EX32−/−, and EX3H−/0 by use of ELF and NBO analyses

“…While spectroscopic studies of the relative Lewis acidities of boron trihalide donor-acceptor adducts have been extensive [33,34], experimental thermodynamic data are sparse for BX 3 adducts [35][36][37] and nonexistent for CX 3 + analogues. Gas-phase calorimetric measurements of TMAÁBX 3 (TMA = trimethylamine) show that the interaction energy is 3.9 kcal mol À1 lower for BCl 3 than for BF 3 [37] and the heats of reaction for BX 3 (X = F, Cl, Br) with pyridine and nitromethane show that the bond strengths increase in the order BF 3 < BCl 3 < BBr 3 [35]. Photoelectron studies have shown that the donor-acceptor interaction is stronger in the TMAÁBCl 3 and TMAÁBBr 3 adducts than in the BF 3 adduct [36].…”

Matrix isolation study of the interaction of excited neon atoms with BF3: Infrared spectra of BF2, BF+2, BF+3, and BF−3

“…Gas-phase studies 62-64 of electron capture by BF 3 yielded thresholds for anion production somewhat higher than 10 eV, with F Ϫ the principal product and F 2 Ϫ and BF 2 Ϫ formed in much lower concentration. Studies of crossed beams of Cs and BF 3 by Rothe and co-workers 65,66 gave F Ϫ as the only product anion. These workers concluded that, with an uncertainty of 0.2 eV, the electron affinity of BF 3 is less than zero.…”