Dihapto coordination of aromatic molecules by the asymmetric pi-bases {TpRe(CO)(L)} (Tp = hydridotris(pyrazolyl)borate; L = (BuNC)-Bu-t, PMe3, pyridine, 1-methylimidazole, or NH3)

A variety of rhenium asymmetric T-basic dearomatization agents of the gener al formula TpRe(CO)(L)(L-pi) (Tp = hydridotris(pyrazolyl)borate; L = (BuNC) -Bu-t, pyridine, PMe3, 1-methylimidazole, or NH3; L-pi = dihapto-coordinate d ligand) have been synthesized via three different routes. By varying the ligand, L, the steric and electronic properties of these complexes can be t uned, and thus the stability and selectivity of the eta (2)-aromatic system s can be adjusted. Comparisons among the various rhenium complexes are pres ented as well as comparisons to the established pentaammineosmium(II) syste m.