Terpene dispersion energy donor ligands in borane complexes.

Structural characterization of the complex [B(β-pinane) 3 ] (1) reveals non-covalent H⋯H contacts that are consistent with the generation of London dispersion energies involving the β-pinane ligand frameworks. The homolytic fragmentations of 1 , and camphane and sabinane analogues ([B(camphane) 3 ] (2) and [B(sabinane) 3 ] (3)) were studied computationally. Isodesmic exchange results showed that London dispersion interactions are highly dependent on the terpene's stereochemistry, with the β-pinane framework providing the greatest dispersion free energy (Δ G = -7.9 kcal mol -1 ) with Grimme's dispersion correction (D3BJ) employed. PMe 3 was used to coordinate to [B(β-pinane) 3 ], giving the complex [Me 3 P-B(β-pinane) 3 ] ( 4 ), which displayed a dynamic coordination equilibrium in solution. The association process was found to be slightly endergonic at 302 K (Δ G = +0.29 kcal mol -1 ).