The electronic stability decrease in the BF4 - n(R)n- anions (R = CH3, C2H5; n = 0-4)

- The BF4 − n(R)n- anions (R = CH3, C2H5; n = 1-4) were studied at the OVGF level of theory.
- All BF4 − n(CH3)n- and BF4 − n(C2H5)n- anions were found to be thermodynamically stable.
- The VDE values calculated for the BF4 − n(R)n- anions exceed 4 eV in all cases.
- The smallest VDEs were found for the B(C2H5)4- (4.27 eV) and B(CH3)4- (4.42 eV).

The properties of the BF4 − n(R)n- anions (where R = CH3, C2H5 and n = 1-4) were investigated at the ab initio OVGF/6-311++G(3df,3pd)//MP2/6-311++G(d,p) level of theory. It is shown that subsequent replacement of the fluorine ligands with alkyl groups in the BF4- superhalogen anion results in a substantial electronic stability decrease (by 1.13-3.42 eV), however, even the fully substituted B(CH3)4- and B(C2H5)4- anions remain stable and relatively strongly bound (by ca. 4.3-4.4 eV) negatively charged systems. The presence of four substituents bound to the boron atom is identified as the most important factor that enables the existence and stability of the BF4−n(R)n- anions.