Stabilization of methyl anions by first-row substituents. The superiority of diffuse function-augmented basis sets for anion calculations

✍ Scribed by Günther W. Spitznagel; Timothy Clark; Jayaraman Chandrasekhar; Paul Von Ragué Schleyer

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 758 KB
• Volume: 3
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540030311

✦ Synopsis

The entire set of methyl anions, XCH,, substituted by first-row substituents, Li, BeH, BH2, CH3, NH2, OH, and F, was examined a t various ab initio levels. Diffuse orbital-augmented basis sets, such as 4-31+G and 6-31+~*, are needed to describe the energies of these anions adequately. Estimates of proton affinities are further improved by second-order Mgller-Plesset (MP2) electron correlation corrections, but relative energies are less affected. The methyl group in the ethyl anion is destabilizing, the amino substituent is borderline, but all other groups are stabilizing. Very large T effects are exhibited by BH2 and BeH groups; inductive stabilization by the electronegative F and OH groups is less effective. Lithium also is stabilizing, but the best singlet geometry of CH2Li-is not planar. A planar CH2Litriplet with a r1 configuration may be lower in energy.