Dihapto Coordination of Aromatic Molecules by the Asymmetric π-Bases {TpRe(CO)(L)} (Tp = hydridotris(pyrazolyl)borate; L = t BuNC, PMe3, pyridine, 1-methylimidazole, or NH3)

A variety of rhenium asymmetric π-basic dearomatization agents of the general formula TpRe(CO)(L)(Lπ) (Tp = hydridotris(pyrazolyl)borate; L = t BuNC, pyridine, PMe3, 1-methylimidazole, or NH3; Lπ = dihapto-coordinated ligand) have been synthesized via three different routes. By varying the ligand, L, the steric and electronic properties of these complexes can be tuned, and thus the stability and selectivity of the η2-aromatic systems can be adjusted. Comparisons among the various rhenium complexes are presented as well as comparisons to the established pentaammineosmium(II) system.