G3 Global Minima for CH4BX Structural Isomers X =Li to Br

The energetic and structural relationships of various CH4BX (X = Li to Br) isomers were elucidated at HF/6-311+G**, B3LYP/6-311+G**, and G3 levels of theory. The relative stabilities of bisected, eclipsed, bridged, and cyclic XCH2BH2 species, as well as their global minima, are determined by the electronegativity and the basicity of X. Alternatively, CH3BHX structural isomers are the global minima when X is a methyl group or an element with at least one lone-pair. Eclipsed BX rather than BH CH3BHX conformers are generally preferred, but the energy differences are small.